JP2014059405A - Imaging apparatus, focusing position detecting method, and focusing position detecting program - Google Patents

Abstract

An imaging apparatus, an in-focus position detection method, and an in-focus position detection program capable of further speeding up an AF operation in accordance with shooting conditions and improving operation responsiveness are provided.
An AF start position determination unit that acquires an AF evaluation value from image data while moving a focus lens in a first direction, and determines an AF start position based on the acquired AF evaluation value; AF processing for acquiring an AF evaluation value from image data while moving the focus lens from the start position in a second direction opposite to the first direction, and detecting a focus position based on the acquired AF evaluation value The AF start position determination unit detects the peak of the AF evaluation value until the focus lens moves to the target position, and detects the peak of the AF evaluation value when a predetermined condition is satisfied. The position of the focus lens is regarded as the focus position, and the detection of the focus position by the AF processing unit is cancelled.
[Selection] Figure 10

Description

  The present invention relates to an imaging apparatus having an autofocus function for automatically focusing on a subject, a focus position detection method, and a focus position detection program.

  An imaging apparatus such as a digital still camera generally has an autofocus (hereinafter referred to as “AF”) function that automatically focuses on a subject. As a control method of the AF operation, hill-climbing AF control is widely known (for example, see Patent Document 1). In this hill-climbing AF control, an integrated value of the luminance difference of the neighboring pixels is obtained from the image data output from the imaging unit, and this integrated value of the luminance difference is used as an AF evaluation value indicating the degree of focus. When the subject is in focus, the outline of the subject is clear and the brightness difference between adjacent pixels increases, so the AF evaluation value increases. On the other hand, in the out-of-focus state, the contour portion of the subject is blurred and the luminance difference between pixels becomes small, so the AF evaluation value becomes small. When performing the AF operation, the AF evaluation value is acquired from the image data output from the imaging unit at a predetermined timing or at a fixed time interval while moving the lens, and the AF evaluation value is the largest. In other words, the peak position is detected as the in-focus position, the lens is moved to the in-focus position and stopped, and the subject is automatically focused.

  In the conventional general hill-climbing AF control method, the lens is temporarily moved over the entire moving range of the lens, and the lens position at which the maximum AF evaluation value is obtained during that time is specified, and the lens is moved to this specified position. It has become. More specifically, for example, a position (hereinafter referred to as “AF start position”) at which the movement of the lens is started in order to detect the in-focus position is set to the center position of the lens driving range, and this AF start is started. Move the lens to the position, move the lens from this AF start position to a certain direction, for example, toward the closest focusing position, then reversely move the lens toward the infinite focusing position, The focus position where the maximum AF evaluation value is obtained is detected. For this reason, the AF operation takes a long time, and a photo opportunity may be missed.

  Therefore, when performing an AF operation, an AF evaluation value is acquired even while the lens is moved to a temporarily determined AF start position, and an AF for actually detecting the in-focus position based on the acquired AF evaluation value There has been proposed a technique for speeding up the AF operation by determining the start position, acquiring the AF evaluation value while reversing the lens from the AF start position, and detecting the focus position (for example, patents). Reference 2).

  By using the technique disclosed in Patent Document 2, it is possible to focus on the subject with high accuracy while speeding up the AF operation particularly in an imaging apparatus having a wide lens driving range. However, in situations where it is desired to immediately photograph a moving subject, it may be desirable to prioritize operation responsiveness over focus position accuracy. In other words, it is desirable to further increase the AF operation speed so that the photographer can find a subject to be photographed and then quickly turn on the power of the imaging apparatus to photograph the subject. In addition, the photographer may intentionally press down the release switch during the AF operation, and high responsiveness is required for such an operation.

  The present invention has been made in view of the above, and an imaging apparatus, a focus position detection method, and a focus position detection that can further increase the speed of an AF operation and improve the responsiveness of an operation according to a shooting situation. The purpose is to provide a program.

  In order to solve the above-described problems and achieve the object, an imaging apparatus according to the present invention includes a lens, an imaging unit that outputs a subject image captured using the lens as image data, and the lens as a first. An AF evaluation value is acquired from the image data while being moved in the direction, an AF start position determination unit that determines an AF start position based on the acquired AF evaluation value, and the lens from the AF start position to the first An AF processing unit that acquires the AF evaluation value from the image data while moving in a second direction that is opposite to the direction, and detects an in-focus position based on the acquired AF evaluation value; The AF start position determination unit detects a peak of the AF evaluation value until the lens moves to a predetermined position, and detects a peak of the AF evaluation value when a predetermined condition is satisfied. The position of the serial lens is regarded as the focus position, characterized in that to cancel the detection of the focus position by the AF processing unit.

  The focus position detection method according to the present invention is a focus position detection method executed by an imaging device including a lens and an imaging unit that outputs a subject image captured using the lens as image data. An AF start position step of acquiring an AF evaluation value from the image data while moving the lens in a first direction and determining an AF start position based on the acquired AF evaluation value; and AF processing for acquiring the AF evaluation value from the image data while moving from a position in a second direction opposite to the first direction, and detecting a focus position based on the acquired AF evaluation value In the AF start position determination step, when the peak of the AF evaluation value is detected before the lens moves to a predetermined position and a predetermined condition is satisfied, The position of the lens where the peak of the AF evaluation value is detected is regarded as the focus position, characterized in that it does not perform detection of the focusing position in the AF process.

  In addition, the in-focus position detection program according to the present invention moves the lens in the first direction to an imaging apparatus that includes a lens and an imaging unit that outputs a subject image captured using the lens as image data. While acquiring an AF evaluation value from the image data and determining an AF start position based on the acquired AF evaluation value, the lens is moved in a direction opposite to the first direction from the AF start position. A focus position detection program for acquiring the AF evaluation value from the image data while moving in the direction of 2 and detecting a focus position based on the acquired AF evaluation value, The function of determining the AF start position is such that the peak of the AF evaluation value is detected when the peak of the AF evaluation value is detected before the lens moves to the predetermined position and the predetermined condition is satisfied. Click is regarded as the focusing position detected position of the said lens, characterized in that for canceling the detection of the focusing position.

  According to the present invention, the AF start position determination unit detects the peak of the AF evaluation value until the lens moves to the predetermined position, and detects the peak of the AF evaluation value when the predetermined condition is satisfied. Since the position of the lens is regarded as the in-focus position and the detection of the in-focus position by the AF processing unit is cancelled, the AF operation can be further accelerated according to the shooting situation, and the responsiveness of the operation can be improved. Play.

FIG. 1 is a top view of a digital still camera. FIG. 2 is a front view of the digital still camera. FIG. 3 is a rear view of the digital still camera. FIG. 4 is a block diagram illustrating a configuration example of a control system of the digital still camera. FIG. 5 is a diagram for explaining an example of the AF processing area. FIG. 6 is a timing chart showing an example of the VD signal, the focus lens drive timing, the electronic shutter charge sweep pulse timing, and the exposure timing at the time of capturing image data. FIG. 7 is a flowchart showing a flow of a series of processes in the AF operation. FIG. 8 is a flowchart illustrating an example of the start scan process. FIG. 9 is a flowchart illustrating an example of the start position determination process. FIG. 10 is a flowchart illustrating an example of the start position determination process. FIG. 11 is a diagram for explaining the scan direction difference. FIG. 12 is a diagram illustrating an example of a waveform representing a change in the AF evaluation value at the time of peak detection and at the far side determination. FIG. 13 is a diagram illustrating an example of a waveform representing a change in the smooth differential value at the time of peak detection and at the time of determination on the far side. FIG. 14 is a flowchart illustrating an example of AF scan processing. FIG. 15 is a diagram illustrating an example of a waveform representing a change in AF evaluation value acquired in the AF scan process. FIG. 16 is a diagram illustrating an example of a waveform representing a change in the smooth differential value calculated in the AF scan process. FIG. 17 is a flowchart illustrating another example of the start position determination process.

  Exemplary embodiments of an imaging apparatus, a focus position detection method, and a focus position detection program according to the present invention will be described below in detail with reference to the accompanying drawings. Although an example in which the present invention is applied to a digital still camera will be described below, the present invention can be widely applied to any type of imaging apparatus having an AF function.

(First embodiment)
1 to 3 are views showing the appearance of the digital still camera according to the present embodiment. FIG. 1 is a top view of the digital still camera, FIG. 2 is a front view of the digital still camera, and FIG. It is a rear view of a still camera. As shown in FIG. 1, a strobe light emitting unit 3, an objective surface of an optical viewfinder 4, a remote control light receiving unit 6, and a lens barrel unit 7 are arranged on the front surface of a camera body CB that is a housing of a digital still camera. . A memory card loading chamber and a battery loading chamber lid 2 are provided on one side surface of the camera body CB.

  As shown in FIG. 2, a release button (switch) SW1, a mode dial SW2, and a sub liquid crystal display (sub LCD) (hereinafter, “liquid crystal display” is referred to as “LCD”) 1 are arranged on the upper surface of the camera body CB. Has been. The release button (switch) SW1 has two states and is configured to detect a half-pressed state (hereinafter referred to as “half-press”) and a fully-pressed state (hereinafter referred to as “full-press”). Has been.

  As shown in FIG. 3, on the back of the camera body CB, there are an eyepiece part of the optical finder 4, an AF light emitting diode (hereinafter referred to as “LED”) 8, a strobe LED 9, an LCD monitor 10, and a power switch. 13, wide-angle zoom switch SW3, telephoto zoom switch SW4, self-timer setting and release switch SW5, menu switch SW6, upward movement and strobe set switch SW7, right movement switch SW8, display switch SW9, downward movement and macro switch SW10 The left shift and image confirmation switch SW11, the OK switch SW12, and the quick access switch SW13 are arranged.

  Next, a configuration example of a control system of the digital still camera according to the present embodiment will be described with reference to FIG. FIG. 4 is a block diagram illustrating a configuration example of a control system of the digital still camera. Various operations (processing) of the digital still camera according to the present embodiment are controlled by a digital still camera processor (hereinafter simply referred to as “processor”) 104 configured as a digital signal processing IC (integrated circuit) or the like. The processor 104 includes a first CCD (charge coupled device) signal processing block 104-1, a second CCD signal processing block 104-2, a CPU (central processing unit) block 104-3, a local SRAM (SRAM: static random access). Memory) 104-4, USB (Universal Serial Bus) block 104-5, serial block 104-6, JPEG codec (CODEC) block 104-7, resize (RESIZE) block 104-8, TV signal display block 104-9, And a memory card controller block 104-10. Each of these blocks is connected to each other via a bus line.

  Outside the processor 104, an SDRAM (Synchronous Random Access Memory) 103 for storing RAW-RGB image data, YUV image data, and JPEG image data, a RAM 107, a built-in memory 120, and a ROM 108 in which a control program is stored. These are connected to the processor 104 via a bus line.

  The control program stored in the ROM 108 is written in a code readable by the CPU block 104-3, and is loaded from the ROM 108 into the main memory such as the SDRAM 103 or the RAM 107 when the power of the digital still camera is turned on. Various functions of the digital still camera are realized by the CPU block 1043 controlling the operation of each unit in accordance with the control program. This control program includes a program for realizing the AF function. The control program for realizing the AF function includes a start scan processing unit (AF start position determination unit) 108-1, an AF scan processing unit (AF processing unit) 108-2, a focus position determination processing unit 108-3, and a focus. The module configuration includes a position movement processing unit 108-4, and the CPU block 1043 executes this control program, whereby the start scan processing unit 108-1, the AF scan processing unit 108-2, and the in-focus position determination process. The processing units of the unit 108-3 and the in-focus position movement processing unit 108-4 are generated in the digital still camera, and the AF function in the digital still camera is realized.

  The lens barrel unit 7 includes a zoom optical system 7-1 having a zoom lens 7-1a, a focus optical system 7-2 having a focus lens 7-2a, an aperture unit 7-3 having an aperture 7-3a, and a mechanical shutter 7-. A mechanical shutter unit 7-4 having 4a is provided. The zoom optical system 7-1, the focus optical system 7-2, the aperture unit 7-3, and the mechanical shutter unit 7-4 are respectively a zoom (ZOOM) motor 7-1b, a focus (FOCUS) motor 7-2b, and an aperture motor. 7-3b and mechanical shutter motor 7-4b. These ZOOM motor 7-1b, FOCUS motor 7-2b, aperture motor 7-3b, and mechanical shutter motor 7-4b are driven by a motor driver 7-5, and the motor driver 7-5 is a CPU of the processor 104. Operation is controlled by block 104-3.

  The zoom lens 7-1a and the focus lens 7-2a of the lens barrel unit 7 constitute an imaging lens for forming a subject optical image on the imaging surface of the CCD 101 as an imaging element. The CCD 101 converts a subject optical image that has passed through the imaging lens into an electrical image signal and inputs it to an F / E-IC (front end IC) 102. The F / E-IC 102 includes a CDS (correlated double sampling unit) 102-1, an AGC (automatic gain control unit) 102-2, and an A / D (analog-digital) conversion unit 102-3. Each of the input image signals is subjected to predetermined processing, converted into a digital signal, and input to the first CCD signal processing block 104-1 of the processor 104. These signal processing operations are controlled by a VD / HD (vertical drive / horizontal drive) signal output from the first CCD signal processing block 104-1 of the processor 104 via a TG (timing generator) 102-4. The The first CCD signal processing block 104-1 performs signal processing such as white balance adjustment and γ adjustment on the digital image data input from the CCD 101 via the F / E-IC 102, as well as VD signals and Output HD signal.

  The CPU block 104-3 of the processor 104 controls the sound recording operation by the sound recording circuit 115-1. The voice recording circuit 115-1 records the voice signal converted by the microphone 115-3 and amplified by the microphone amplifier 115-2 in accordance with a command from the CPU block 104-3. The CPU block 104-3 also controls the operation of the audio reproduction circuit 116-1. The audio reproduction circuit 116-1 amplifies the audio signal recorded in the memory by the audio amplifier 116-2 and inputs the audio signal to the speaker 116-3 in response to an instruction from the CPU block 104-3. Reproduce. Further, the CPU block 104-3 controls the strobe circuit 114 to operate, thereby causing the strobe light emitting unit 3 to emit illumination light. The CPU block 104-3 also controls the operation of the distance measuring unit 5 that measures the subject distance.

  Note that the digital still camera according to the present embodiment performs AF control based on digital image data input from the CCD 101 to the processor 104 via the F / E-IC 102 as described later. Measurement of the subject distance by the distance unit 5 is not necessarily performed, and the distance measurement unit 5 may be omitted. Further, by providing the distance measuring unit 5, subject distance measurement information may be used for strobe light emission control in the strobe circuit 114. Further, the subject distance measurement information by the distance measuring unit 5 may be used in an auxiliary manner for focusing control based on image data.

  Further, the CPU block 104-3 is also coupled to a sub CPU 109 disposed outside the processor 104. The sub CPU 109 controls display on the sub LCD 1 via the LCD driver 111. The sub CPU 109 is also coupled to the AF LED 8, the strobe LED 9, the remote control light receiving unit 6, the operation key unit including the switches SW1 to SW13, and the buzzer 113, respectively.

  Further, as described above, the CPU block 104-3 implements various functions in the digital still camera by executing the control program loaded from the ROM 108 to the main memory.

  The USB block 104-5 is coupled to the USB connector 122, and the serial block 104-6 is coupled to the RS-232C connector 123-2 via the serial driver circuit 123-1. The TV signal display block 104-9 is coupled to the LCD monitor 10 via the LCD driver 117, and the TV signal display block 104-9 is also coupled to the video jack 119 via the video amplifier 118. . The memory card controller block 104-10 is coupled to the card contact of the memory card slot 121. When the memory card is loaded in the memory card slot 121, the memory card controller block 104-10 contacts and is electrically connected to the contact of the memory card. .

  Next, the operation of the digital still camera configured as described above will be described. The digital still camera is activated in the recording mode by setting the mode dial SW2 shown in FIGS. 1 to 3 to the recording mode. The recording mode setting by the mode dial SW2 is detected by the CPU block 104-3 via the sub CPU 109 that the state of the mode dial SW2 included in the operation key units (SW1 to SW13) in FIG. Is done by. The CPU block 104-3 controls the motor driver 7-5 to move the lens barrel unit 7 to a position where it can be imaged. Further, the power is turned on to the respective parts such as the CCD 101, the F / E-IC 102, and the LCD monitor 10 to start the operation. When the power of each part is turned on, the operation in the finder mode is started.

  In the finder mode, a subject image is formed on the light receiving surface of the CCD 101 by light from the subject incident on the CCD 101 which is an imaging element through the imaging lens of the lens barrel unit 7. The subject image is converted into an electrical signal, input to the CDS 102-1 as an RGB analog signal, and sent to the A / D conversion unit 102-3 via the AGC 102-2. The R, G, and B signals converted into digital signals by the A / D conversion unit 102-3 are converted into YUV image data by the YUV conversion means provided in the second CCD signal processing block 104-2 in the processor 104. It is converted and recorded in the SDRAM 103 as a frame memory. The second CCD signal processing block 104-2 performs appropriate processing such as filtering processing on the RGB image data to convert it into YUV image data. The YUV image data is read by the CPU block 104-3, sent to the LCD driver 117 via the TV signal display block 104-9, and an image is displayed on the LCD monitor 10 by driving the LCD driver 117. Alternatively, the YUV data read by the CPU block 104-3 is sent to the external monitor via the video amplifier 118 and the video jack 119, and an image is displayed on the external monitor. This processing is performed at intervals of 1/30 seconds, and the display is performed in the finder mode updated every 1/30 seconds.

  When the release button SW1 of the operation key unit is half-pressed in the finder mode, the degree of focus in a predetermined at least part of the screen from the digital RGB image data captured in the first CCD signal processing block 104-1 An AF evaluation value indicating AE and an AE evaluation value indicating the exposure state are calculated. The AF evaluation value is read as feature data to the CPU block 104-3 and used for the AF operation.

  Since the edge of the subject in focus is clear, the high frequency component of the spatial frequency included in the image data is the highest. The AF evaluation value calculated using the image data of the subject is set to be a value that reflects the height of the high-frequency component, for example, a differential value with respect to the displacement amount. Therefore, this AF evaluation value is a maximum value. The position of the focus lens 7-2a that acquired the image data becomes the in-focus position. That is, the focus position can be specified by detecting the peak position from the AF evaluation value, and the operation of detecting the focus position and adjusting the position of the focus lens 7-2a to the focus position is the AF operation. is there. In the AF operation, taking into consideration that a plurality of maximum points of the AF evaluation value appear, when there are a plurality of maximum points, the magnitude of the AF evaluation value at the peak position and the AF evaluation values at the peripheral positions Considering the degree of descent or ascending, the maximum point that is estimated to be most reliable is set as the in-focus position.

  The AF evaluation value can be calculated from a specific range (AF processing area) in the digital RGB image data. FIG. 5 is a diagram for explaining an example of the AF processing area, and shows an example of the position and size of the AF processing area on the screen displayed on the LCD monitor 10 in the finder mode. In FIG. 5, the frame displayed at the center of the LCD monitor 10 is an AF processing area in the digital still camera. In this example, the range of 40% in the horizontal direction and 30% in the vertical direction in the center of the screen of digital RGB image data is set as the AF processing area.

  Next, the relationship between the drive timing of the focus lens 7-2a and the AF evaluation value acquisition timing during the AF operation will be described. The focus lens 7-2a is driven by a predetermined lens driving amount corresponding to one VD signal. For example, when the focus motor 7-2b is a pulse motor, the lens drive amount corresponds to the number of drive pulses. By driving the focus lens 7-2a by a predetermined number of drive pulses at a predetermined pulse rate corresponding to the fall of the VD signal pulse, one lens drive is completed. Next, predetermined lens driving is performed again in response to the fall of the output VD signal pulse. Such lens driving is performed in synchronization with the VD signal (that is, the frame period).

  FIG. 6 is a timing chart showing the VD signal, the drive timing of the focus lens 7-2a, the charge sweep pulse (SUB) timing at the electronic shutter, and the exposure timing when image data is captured at a frame rate of 30 fps. is there. In FIG. 6, when one VD signal is generated (see FIG. 6A), two pulses are generated to drive the focus lens 7-2a using the VD signal as a trigger (see FIG. 6D). The focus lens 7-2a is driven and moved by a drive amount corresponding to the drive pulse. In addition, a predetermined number of charge sweep pulses (SUB) are generated using the VD signal as a trigger (see FIG. 6B), and the charge charged in the CCD 101 is swept out according to the number of SUBs. In addition, after the charge sweeping process is completed, an exposure process is performed (see FIG. 6C). By exposure processing, an optical image of the subject is captured as image data, and an AF evaluation value is acquired using this image data. The number of drive pulses is variable and changes according to the focal length, the drive range of the focus lens 7-2a, and the like. As described above, the AF operation in the present embodiment is performed within the drive range of the focus lens 7-2a in synchronization with the VD signal.

  Thereafter, when the release button SW1 is fully pressed in a state where the AF operation is completed, shooting of a still image or a moving image is started, and the image data of the shot still image or moving image is stored in the built-in memory 120 or the memory card slot 121. Recorded on a memory card or the like. Here, in particular, in the digital still camera according to the present embodiment, the photographer immediately captures a still image or a moving image, such as immediately after the digital still camera is turned on or when the release button SW1 is fully pressed before the AF operation ends. When it is presumed that it is desired to start shooting, a part of the AF operation can be omitted or shortened to speed up the AF operation so that the image intended by the photographer can be properly shot. I have to.

  Next, a specific example of the AF operation in the digital still camera according to the present embodiment will be described. The AF operation described below is performed by the CPU block 104-3 of the processor 104 executing a control program for realizing the AF function loaded from the ROM 108 to the main memory.

  FIG. 7 is a flowchart showing a flow of a series of processes in the AF operation of the present embodiment. A series of processing of the AF operation shown in the flowchart of FIG. 7 is repeatedly executed in the finder mode. First, it is determined whether or not the release button SW1 is pressed (whether half-pressed or fully pressed) during the finder mode (step S101). If the release button SW1 is not pressed as a result of this determination (step S101: No), the AF operation is terminated. On the other hand, when the release button SW1 is pressed (step S101: Yes), the start scan processing by the start scan processing unit (AF start position determining unit) 108-1 is performed (step S102).

  Here, details of the start scan processing performed in step S102 of FIG. 7 will be described with reference to FIG. FIG. 8 is a flowchart illustrating an example of the start scan process. When the start scan processing is started, the start scan processing unit 108-1 first performs target position setting processing (step S201). The target position is a temporary position in the previous stage for determining the actual AF start position when performing AF processing. When performing the AF process later, it is desirable that the moving direction of the focus lens 7-2a is a direction that does not affect backlash or a direction that does not require removal of backlash. The focus lens 7-2a in the present embodiment is not affected by backlash when moved in the direction from the short distance side toward infinity, or it is not necessary to remove the backlash. In this case, the driving direction of the focus lens 7-2a is the short distance side → the infinity side direction. Therefore, it is desirable to set the target position on the closest side. In the present embodiment, the position of the focus lens 7-2a that focuses on the subject at the 30 cm position that is the closest position is set as the target position.

  Next, the start scan processing unit 108-1 starts lens driving and moves the focus lens 7-2a toward the target position set in step S201 (step S202). The start scan processing unit 108-1 then waits for the VD signal after starting lens driving (step S203), and acquires an AF evaluation value from image data input for each VD signal (step S204). Accordingly, the focus lens 7-2a is moved in the first direction toward the target position in synchronization with the VD signal, and the AF evaluation value and the position of the focus lens 7-2a when the AF evaluation value is acquired correspond to each other. So that you can In this way, when the AF start position is determined later, the position to move the focus lens 7-2a can be specified.

  Next, the start scan processing unit 108-1 performs start position determination processing (step S205). Details of the start position determination process performed in step S205 in FIG. 8 will be described with reference to FIG. FIG. 9 is a flowchart illustrating an example of the start position determination process. When the start position determination process is started, the start scan processing unit 108-1 first determines whether or not the evaluation value count number, which is a value obtained by counting the number of acquired AF evaluation values, is greater than “2”. (Step S301). This is because “3” is necessary at the minimum for the number of evaluation values required for the subsequent smooth differential calculation. If the evaluation value count number is less than “3” as a result of this determination (S301: No), the start scan processing unit 108-1 adds “1” to the evaluation value count number (step S306) and starts. The position determination process ends. On the other hand, when the evaluation value count is larger than “2” (step S301: Yes), the start can processing unit 108-1 performs smooth differentiation using the acquired AF evaluation value (step S302).

The smooth differentiation operation is performed as follows, for example. The AF evaluation value acquired based on the image data of the subject captured at a predetermined timing from the moving focus lens 7-2a is assumed to be X [0], and the AF evaluation value acquired a before the X [0]. X [−a], AF evaluation value acquired a after X [0] is X [a], and the weight coefficients for each AF evaluation value are b1, b2,. [0] is
Y [0] = Σ [i = 0 → a] (X [i] −X [−i]) × bi
Can be obtained.

A specific example will be described. When obtaining the smooth differential value Y [0] using three evaluation values before and after the current AF evaluation value (X [0]),
Y [0] = (X [1] −X [−1]) × 1 + (X [2] −X [−2]) × 2 + (X [3] −X [−3]) × 3
It becomes. Here, the weighting coefficient (bi = 1, 2, 3...) Is a distant AF evaluation value (for example, X [1]) close to the current AF evaluation value X [0]. For example, let X [3]) be a larger coefficient. That is, the smaller the degree of correlation with the current value (X [0]), the larger the value. The specific coefficient value is not limited to the above example.

  The start scan processing unit 108-1 obtains the above smooth differential value based on the correlation of the AF evaluation values acquired in response to the movement of the focus lens 7-2a in this way, whereby the extreme value of the AF evaluation value is obtained. Is identified. The above arithmetic expression performs a smooth differential calculation using three AF evaluation values before and after, but the number of AF evaluation values used for the calculation is not limited to this.

  Since a plurality of AF evaluation values are required to obtain the smooth differential value, the smooth differential calculation is performed immediately after the start of the start scanning process or at the acquisition timing of the AF evaluation value immediately before the focus lens 7-2a reaches the target position. Can not be done. Therefore, the start scan processing unit 108-1 waits until the number of AF evaluation values that can start the smooth differential calculation after the start scan process is started, and then performs the smooth differential calculation process. Alternatively, the smooth differential calculation process is performed by estimating and interpolating the AF evaluation value necessary for the smooth differential calculation process using the already acquired AF evaluation value.

  Next, the start scan processing unit 108-1 determines whether or not the smooth differential value is above “0” (step S303), and if the smooth differential value is above “0” (step S303). S303: Yes), it is determined that the smooth differential value is rising, the rising flag is turned on (step S304), and the falling count is reset to “0” (step S305).

  On the other hand, when the smooth differential value is “0” or less (step S303: No), the start scan processing unit 108-1 adds “1” to the descending count (step S307), and then the ascending flag is turned on. It is determined whether or not (step S308). When the rising flag is ON (step S308: Yes), the start scan processing unit 108-1 determines whether or not the descending count is larger than “2” (step S309). If it is larger than “2” (step S309: Yes), the peak detection flag is turned ON (step S310). The waveform of the smooth differential value at this time is as shown in the example of FIG. 13A, and the sign of the smooth differential value when the peak is detected is inverted from plus to minus.

  On the other hand, when the increase flag is not ON (step S308: No), the start scan processing unit 108-1 determines whether or not the decrease count is greater than “4” (step S312), and the decrease count is If it is greater than “4” (step S312: Yes), it is determined that the subject has already passed the in-focus position, and the far side determination flag is turned ON (step S313). As shown in FIG. 13B, this determination is based on the property that the smooth differential value after the position where the subject is focused is always negative.

  Next, the start scan processing unit 108-1 performs start position determination processing based on whether peak detection or far-side determination is performed (step S311). When the start position determination processing ends, the evaluation value count number is set to “1”. "Is added (step S306), and the start position determination process is terminated.

  Here, details of the start position determination process performed in step S311 of FIG. 9 will be described with reference to FIG. FIG. 10 is a flowchart illustrating an example of the start position determination process. When the start position determination process is started, the start scan processing unit 108-1 first determines whether or not the peak detection flag is ON (whether or not it is a peak detection time) (step S401). As a result of this determination, if the peak detection flag is ON (step S401: Yes), the start scan processing unit 108-1 has elapsed from when the digital still camera is turned on until the release button SW1 is pressed. It is determined whether or not the time is shorter than a predetermined time (for example, 5 seconds) (step S402). If the elapsed time since the power is turned on is shorter than the predetermined time (step S402: Yes), the start scan is performed. The peak position detected by the process is set as the in-focus position (step S403), the AF scan process cancel flag is turned on (step S404), and the start position determination process is terminated.

  The peak position detected by the start scan process can be specified as the position where the smooth differential value of the AF evaluation value is inverted from the plus side to the minus side. However, in the start scan process, the backlash must be removed. Since the focus lens 7-2a is moved in the direction, the actual peak position is slightly shifted from the position where the smooth differential value of the AF evaluation value is reversed from the plus side to the minus side, as shown in FIG. (Hereinafter, this deviation is referred to as “scan direction difference”). Therefore, as the in-focus position set in step S403, a position shifted by the difference in the scanning direction is set with respect to the position where the smooth differential value of the AF evaluation value is reversed from the plus side to the minus side. This difference in scan direction may vary depending on the body of the digital still camera and may have a value adjusted in the manufacturing stage, but in this embodiment, it is uniformly +2 pulses.

  On the other hand, if the result of determination in step S402 is that the elapsed time since the power was turned on is equal to or longer than the predetermined time (step S402: No), the start scan processing unit 108-1 determines the current position of the focus lens 7-2a The position before the “1” evaluation value, that is, the position from which the previous AF evaluation value was acquired (hereinafter, this position is referred to as “peak detection start position”) is determined as the AF start position (step S405). Then, the start position determination process ends.

  When the peak detection flag is OFF as a result of the determination in step S401 (step S401: No), the start scan processing unit 108-1 determines whether or not the far side determination flag is ON (far side determination). It is determined whether or not it is time (step S406). If the far-side determination flag is ON (step S406: Yes), the start scan processing unit 108-1 is a position “2” before the evaluation value from the current position of the focus lens 7-2a, that is, two before. The position at which the AF evaluation value is acquired (hereinafter, this position is referred to as “far-side determination start position”) is determined as the AF start position (step S407), and the start position determination process ends. On the other hand, when the far-side determination flag is OFF (step S406: No), the start scan processing unit 108-1 ends the start position determination process without determining the AF start position.

  FIG. 12 is a diagram illustrating an example of a waveform representing a change in AF evaluation value at the time of peak detection and at the time of far-side determination (during monotonous descent), where the vertical axis indicates the magnitude of the AF evaluation value, and the horizontal axis indicates the focus lens 7. -2a position. FIG. 13 is a diagram showing an example of a waveform representing a change in the smooth differential value at the time of peak detection and at the far side determination (during monotonic descent), where the vertical axis indicates the magnitude of the smooth differential value and the horizontal axis indicates the focus. The position of the lens 7-2a is shown. 12 (a) and 13 (a) show the waveforms at the time of peak detection, respectively, and FIGS. 12 (b) and 13 (b) show the waveforms at the time of far-side determination (during monotonic descent), respectively. Yes.

  When the peak is detected, if the elapsed time from when the power of the digital still camera is turned on until the release button SW1 is pressed is equal to or longer than a predetermined time (for example, 5 seconds), FIG. 12 (a) and FIG. 13 (a). As shown in FIG. 6, the evaluation value indicated by the previous white circle is acquired from the AF evaluation value acquired last, that is, the smooth differential value indicated by the previous white circle is calculated from the last calculated smooth differential value. The position of the focus lens 7-2a at this time is the peak detection start position, and this position is set as the AF start position. In the subsequent AF scan process, the focus position is detected while moving the focus lens 7-2a from the AF start position in the direction opposite to the movement direction in the start scan process (second direction). On the other hand, if the elapsed time from when the digital still camera is turned on to when the release button SW1 is pressed is shorter than a predetermined time (for example, 5 seconds) at the time of peak detection, the smooth differential value shown in FIG. The position of the focus lens 7-2a shifted by the difference in the scanning direction from the position where the lens is inverted from the plus to the minus side is set as the in-focus position, and the AF scan process for detecting the in-focus position is omitted.

  In the far side determination, as shown in FIG. 12B and FIG. 13B, an evaluation value indicated by a white circle two before is acquired from the last acquired AF evaluation value, that is, calculated last. The position of the focus lens 7-2a when the smooth differential value indicated by the previous white circle is calculated from the smooth differential value is the far side determination start position, and this position is set as the AF start position. In the subsequent AF scan process, the focus lens 7-2a is moved from the AF start position in the opposite direction (second direction) to the movement direction (first direction) in the start scan process. Is detected.

  Since the first direction in which the focus lens 7-2a is moved in the start scan process is a direction affected by backlash or a direction in which the backlash needs to be removed, the focus position is determined in the start scan process. This often causes a problem as the accuracy of the in-focus position. Therefore, in a situation where the release button SW1 is pressed after a predetermined time (for example, 5 seconds) has elapsed since the power of the digital still camera is turned on, the start scan process is the start position of the AF scan process, which is the next process. Only the AF start position is determined, and then AF scan processing is further performed so that the in-focus position can be detected with high accuracy. On the other hand, if the elapsed time from when the digital still camera is turned on until the release button SW1 is pressed is shorter than a predetermined time (for example, 5 seconds), the photographer wants to take a picture immediately. Since it is estimated that the situation is highly likely, the peak position with the difference in scan direction is regarded as the in-focus position, and the subsequent AF scan processing is omitted, so that the AF operation is further speeded up and the image is immediately displayed. To be able to shoot. The elapsed time from when the power of the digital still camera is turned on until the release button SW1 is pressed can be measured, for example, by counting the elapsed time with a timer provided inside the digital still camera.

  Returning to FIG. 8, when the start position determination process in step S205 is completed, the start scan processing unit 108-1 determines whether or not the AF start position is determined in the start position determination process in step S205 (step S206). If the AF start position is determined (step S206: Yes), the start scan processing unit 108-1 moves the focus lens 7-2a to the determined AF start position (step S207), and starts. The scan process ends. On the other hand, when the AF start position has not been determined (step S206: No), the start scan processing unit 108-1 determines whether or not the current position of the focus lens 7-2a has reached the target position set in step S201. (Step S208), and if the current position of the focus lens 7-2a has not reached the target position (step S208: No), the process returns to step S203 and the subsequent processing is repeated. On the other hand, when the current position of the focus lens 7-2a has reached the target position (step S208: Yes), the start scan processing unit 108-1 is set in the current position of the focus lens 7-2a, that is, step S201. The start scan process is terminated with the target position thus set as the AF start position.

  Returning to FIG. 7, when the start scan process in step S102 is completed, an AF scan process is performed by the AF scan processing unit (AF processing unit) 108-2 (step S103). Here, details of the AF scan processing performed in step S103 of FIG. 7 will be described with reference to FIG. FIG. 14 is a flowchart illustrating an example of AF scan processing. When the AF scan process is started, the AF scan processing unit 108-2 first determines whether or not the AF scan process cancel flag is OFF (step S501). If the AF scan process cancel flag is ON (step S501: No), since the in-focus position has already been set, the AF scan processing unit 108-2 ends the AF scan process.

  On the other hand, when the AF scan processing cancel flag is OFF (step S501: Yes), the AF scan processing unit 108-2 waits until it detects the falling edge of the VD signal (step S502), and the rising edge of the VD signal. After detecting the fall, the focus motor 7-2b is driven according to a predetermined number of pulses, and the focus lens 7-2a is moved from the AF start position by a predetermined amount in the second direction (step S503). Then, the AF scan processing unit 108-2 acquires an AF evaluation value from image data input after the focus lens 7-2a is moved (step S504), and performs a smooth differential calculation process from the AF evaluation value ( Step S505).

  Next, the AF scan processing unit 108-2 performs processing for detecting a peak position based on the smooth differential value calculated in step S505 (step S506). This is a process of detecting the position of the focus lens 7-2a where the sign of the smooth differential value is inverted. Then, the AF scan processing unit 108-2 determines whether or not the peak position is detected in the process of step S506 (step S507). If the peak position is detected (step S507: Yes), the AF scan process is performed. Exit. On the other hand, when the peak position is not detected (step S507: No), the AF scan processing unit 108-2 determines whether or not the current position of the focus lens 7-2a has reached the end position of the AF scan process ( If the current position of the focus lens 7-2a has not reached the end position (step S508: No), the process returns to step S502 and the subsequent processing is repeated. On the other hand, when the current position of the focus lens 7-2a has reached the end position (step S508: Yes), the AF scan processing unit 108-2 ends the AF scan process.

  FIG. 15 is a diagram illustrating an example of a waveform representing a change in the AF evaluation value acquired in step S504 in the AF scan process. FIG. 15A shows the waveform of the AF evaluation value when the subject brightness is LV10, and FIG. 15B shows the waveform of the AF evaluation value when the subject brightness is LV8. The vertical axis indicates the AF evaluation value. The horizontal axis represents the position of the focus lens 7-2a. The example shown in FIG. 15B is a waveform of an AF evaluation value acquired in an environment where the amount of light is smaller (darker) than the example shown in FIG. 15A, and the luminance difference between adjacent pixels is very small. The influence of noise is large, the AF evaluation value varies, and a plurality of peak positions appear. If the peak position (maximum value) of the AF evaluation value is one as shown in FIG. 15A, it may be set as the in-focus position. However, as shown in FIG. If there is a position, it cannot be simply determined which position is the in-focus position.

  FIG. 16 is a diagram illustrating an example of a waveform representing a change in the smooth differential value calculated in step S505 in the AF scan process. 16A shows a waveform of a smooth differential value calculated based on the AF evaluation value shown in FIG. 15A, and FIG. 16B shows the AF evaluation value shown in FIG. 15B. 4 shows the waveform of the calculated smooth differential value, where the vertical axis represents the magnitude of the smooth differential value and the horizontal axis represents the position of the focus lens 7-2a. As shown in FIGS. 16A and 16B, the smooth differential value is not calculated until a predetermined number of AF evaluation values are acquired. The smooth differential value calculated after the predetermined number of AF evaluation values are acquired is displaced with the movement of the focus lens 7-2a, and the sign is inverted at a certain point. This inversion point corresponds to the maximum value of the AF evaluation value, and the position of the focus lens 7-2a at that time is the peak position. That is, the position where the sign of the smooth differential value calculated by the above-described arithmetic expression is inverted, that is, the position where the smooth differential value is zero is the maximum point of the AF evaluation value. In this way, by specifying the position of the focus lens 7-2a from which the AF evaluation value at which the sign of the smooth differential value is inverted is specified, the position is set as the in-focus position, and the subject is in focus. Can be taken.

  Returning to FIG. 7, when the AF scan process in step S103 is completed, a focus position determination process is performed by the focus position determination processing unit 108-3 (step S104). When the peak position is detected in the AF scan process of step S103, the focus position determination processing unit 108-3 determines the peak position as the focus position. Further, when the peak position is not detected in the AF scan process, the focus position determination processing unit 108-3 determines the NG position as the focus position as AFNG. The NG position here is the position of the focus lens 7-2a that focuses on a subject about 2.5 m away. Note that when the in-focus position is set in the start scan process in step S102 and the AF scan process in step S103 is omitted, the in-focus position is not determined by the in-focus position determination processing unit 108-3.

  When the in-focus position determination process in step S104 is completed, the in-focus position movement process is finally performed by the in-focus position movement processing unit 108-4 (step S105). This in-focus position moving process is a process of moving the focus lens 7-2a to the in-focus position determined in the in-focus position determining process in step S104 or the in-focus position set in the start scan process in step S102. is there.

  As described above in detail with specific examples, according to the digital still camera according to the present embodiment, the focus lens 7-2a is at the target position in the start scan processing by the start scan processing unit 108-1. When the peak of the AF evaluation value is detected before moving, and the elapsed time from when the digital still camera is turned on until the release button SW1 is pressed is shorter than a predetermined time (for example, 5 seconds) Considers the position of the focus lens 7-2a from which the peak of the AF evaluation value is detected as the in-focus position, and cancels the AF scan processing by the AF scan processing unit 108-2. In a desired situation, the AF operation can be further speeded up and the response of the operation can be improved.

  Further, according to the digital still camera according to the present embodiment, in the start scan processing by the start scan processing unit 108-1, if the elapsed time from turning on the power of the digital still camera is equal to or longer than a predetermined time, AF evaluation is performed. Since the subject state is confirmed based on the value and an appropriate AF start position is determined according to the subject state, the subject can be focused with high accuracy while speeding up the AF operation.

  Further, according to the digital still camera according to the present embodiment, in the start scan processing by the start scan processing unit 108-1, the smooth differential value is calculated from the AF evaluation value, and the peak of the AF evaluation value is obtained from the change of the smooth differential value. Since the detection is performed, the peak can be detected with high accuracy. Further, according to the digital still camera according to the present embodiment, even in the AF scan processing by the AF scan processing unit 108-2, the smooth differential value is calculated from the AF evaluation value, and the peak of the AF evaluation value is calculated from the change of the smooth differential value. Is detected, so that the peak can be detected with high accuracy.

  In the present embodiment, 5 seconds is exemplified as the predetermined time to be compared with the elapsed time from when the power of the digital still camera is turned on until the release button SW1 is pressed, but the length of the predetermined time is However, the length may be set in consideration of the activation time of the digital still camera, or the length of the predetermined time may be variable. Further, a mode in which the photographer sets the length of the predetermined time may be provided.

(Second Embodiment)
Next, a second embodiment will be described. The second embodiment is different from the first embodiment described above in the contents of the start position determination process (step S311 in FIG. 9) in the start scan process by the start scan processing unit 108-1. That is, in the start position determination process of the first embodiment, the elapsed time from when the peak detection flag is ON and when the release button SW1 is pressed after the digital still camera is turned on is less than a predetermined time (eg, 5 seconds). If the peak position is shorter, the detected peak position is set to the in-focus position, and the AF scan process cancel flag is turned ON. In contrast, in the start position determination process of the second embodiment, when the peak detection flag is ON and the release button SW1 is fully pressed, the detected peak position is set as the in-focus position, Set the AF scan processing cancel flag to ON. Further, in the start position determination process of the first embodiment, when the peak detection flag is OFF and the far side determination flag is OFF, the start scan process is continued without determining the AF start position. On the other hand, in the start position determination process of the second embodiment, even when the peak detection flag is OFF and the far side determination flag is OFF, the release button SW1 is fully pressed and the evaluation value When the count number exceeds the predetermined number, the current position of the focus lens 7-2a is set as the AF start position, and the start scan process is terminated. In addition, since processes other than the configuration of the digital still camera of the second embodiment and the start position determination process in the AF operation are the same as those of the first embodiment described above, the first embodiment will be described below. Only a different start position determination process will be described, and a description overlapping that of the first embodiment will be omitted.

  FIG. 17 is a flowchart illustrating an example of a start position determination process according to the second embodiment. When the start position determination process of the second embodiment is started, the start scan processing unit 108-1 first determines whether or not the peak detection flag is ON (whether or not it is during peak detection) ( Step S601). As a result of this determination, when the peak detection flag is ON (step S601: Yes), the start scan processing unit 108-1 determines whether or not the release button SW1 is fully pressed (step S602), and the release button. When SW1 is fully pressed (step S602: Yes), the peak position detected by the start scan process is set as the focus position (step S603), the AF scan process cancel flag is turned ON (step S604), and the process starts. The position determination process ends.

  As in the first embodiment, the peak position set as the in-focus position in step S604 is a position shifted by a difference in the scanning direction with respect to the position where the smooth differential value of the AF evaluation value is reversed from the plus side to the minus side. . Regarding this difference in scan direction, there may be a difference depending on the body of the digital still camera, and there may be a value adjusted in the manufacturing stage. However, in this embodiment as well, the same as in the first embodiment. Uniform +2 pulses.

  On the other hand, if the result of determination in step S602 is that the release button SW1 has been pressed halfway (step S602: No), the start scan processing unit 108-1 evaluates “1” from the current position of the focus lens 7-2a. The peak detection start position before the value is determined as the AF start position, and the start position determination process ends.

  When the peak detection flag is OFF as a result of the determination in step S601 (step S601: No), the start scan processing unit 108-1 determines whether the far side determination flag is ON (far side determination). It is determined whether or not it is time (step S606). If the far-side determination flag is ON (step S606: Yes), the start scan processing unit 108-1 is the far-side determination start position that is “2” evaluation value before the current position of the focus lens 7-2a. Is determined as the AF start position (step S607), and the start position determination process ends.

  On the other hand, if the far side determination flag is OFF (step S606: No), the start scan processing unit 108-1 next determines whether or not the release button SW1 is fully pressed (step S608). If the release button SW1 is fully pressed (step S608: Yes), it is determined whether or not the AF evaluation value count is greater than a predetermined number (eg, “10”) (step S609). If the count value of the AF evaluation value is greater than the predetermined number (step S609: Yes), it is determined that the peak position cannot be detected even if the start scan process is continued further, and the current position of the focus lens 7-2a is determined. The AF start position is determined (step S610), and the start position determination process ends.

  On the other hand, if it is determined in step S608 that the release button SW1 is half pressed (step S608: No), or if it is determined in step S609 that the AF evaluation value count is equal to or less than a predetermined number, start. The scan processing unit 108-1 ends the start position determination process without determining the AF start position.

  As described above, in the present embodiment, when the release button SW1 is fully pressed during the start scan process, or when the release button SW1 that serves as a trigger for starting the AF operation is not half-pressed but fully pressed. In situations where there is a high possibility that the photographer wants to take an image immediately, such as when the peak position is detected in the start scan process, the peak position is regarded as the in-focus position, and the subsequent AF scan process By omitting, the AF operation is further speeded up so that an image can be taken immediately. In the present embodiment, when peak detection or far-side determination is not performed in a state where AF evaluation values are acquired to some extent in the start scan processing, the focus lens 7-2a is moved in the first direction toward the target position. If it is determined that it is difficult to detect the peak or the far side even if the lens is further moved, and the release button SW1 is fully pressed, priority is given to responsiveness and the current position of the focus lens 7-2a is set to AF. The AF operation is further speeded up by determining the start position and proceeding to AF scan processing immediately.

  As described above, according to the digital still camera according to the present embodiment, in the start scan processing by the start scan processing unit 108-1, the AF evaluation value is measured before the focus lens 7-2a moves to the target position. When the peak is detected and the release button SW1 is fully pressed, the position of the focus lens 7-2a where the peak of the AF evaluation value is detected is regarded as the in-focus position, and the AF scan processing unit 108-2 Since the AF scanning process is canceled, the AF operation can be further speeded up and the responsiveness of the operation can be improved in a situation where the photographer wants to take a picture immediately.

  Moreover, according to the digital still camera according to the present embodiment, in the start scan processing by the start scan processing unit 108-1, peak detection or far-side determination is not performed in a state where the AF evaluation value is acquired to some extent, When the release button SW1 is fully pressed, since the current position of the focus lens 7-2a is determined as the AF start position and the process immediately shifts to AF scan processing, the AF operation is further accelerated and operated. Can increase the responsiveness.

  Also, with the digital still camera according to the present embodiment, in the start scan processing by the start scan processing unit 108-1, if the release button SW1 remains half pressed, the subject state is confirmed based on the AF evaluation value. Since an appropriate AF start position is determined according to the subject state, it is possible to focus on the subject with high accuracy while speeding up the AF operation.

  In this embodiment, 10 is exemplified as the threshold value of the evaluation value count number, which is a criterion for determining whether or not the AF evaluation value is acquired to some extent. The threshold value of the evaluation value count number is not limited to this, and an optimal value may be set as appropriate.

  In the first embodiment and the second embodiment described above, the time elapsed since the power of the digital still camera was turned on as a condition for further speeding up the AF operation by giving priority to responsiveness. The condition that is shorter than a predetermined time (for example, 5 seconds) and the condition that the release button SW1 is fully pressed are illustrated, but these two conditions may be used in combination, or other than the above two conditions It may be used in combination with other conditions.

  Note that the AF function characteristic of the digital still camera according to the first embodiment and the second embodiment described above is realized by a control program executed by the CPU block 104-3 of the processor 104 as an example, as described above. Is done. A control program for realizing the AF function is provided by being incorporated in advance in the ROM 108 of the digital still camera, for example. Also, a control program for realizing the AF function is read in a computer such as a CD-ROM, a flexible disk (FD), a CD-R, a DVD (Digital Versatile Disc) in a file in an installable or executable format. You may comprise so that it may record on a possible recording medium and provide. Furthermore, a program for realizing the AF function may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Further, a program for realizing the AF function may be provided or distributed via a network such as the Internet.

  The control program for realizing the AF function in the digital still camera according to the present embodiment includes the above-described start scan processing unit 108-1, AF scan processing unit 108-2, in-focus position determination processing unit 108-3, and focusing program. The module configuration includes each processing function of the focal position movement processing unit 108-4. As actual hardware, the CPU block 104-3 reads out and executes the control program from the ROM 108, so that each processing described above is performed. The functions are loaded on a main memory (for example, SDRAM 103 or RAM 107), and each processing function is generated on the main memory.

  Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments as they are, and is embodied by adding various modifications without departing from the scope of the invention in the implementation stage. can do. In other words, the configuration and operation of the digital still camera described above are merely specific examples, and various modifications can be made according to the application and purpose.

7-2a Focus lens 101 CCD
102 F / E-IC
104 Digital Still Camera Processor 104-3 CPU Block 108-1 Start Scan Processing Unit 108-2 AF Scan Processing Unit SW1 Release Button

Japanese Examined Patent Publication No. 39-5265 JP 2011-138103 A

Claims (8)

A lens,
An imaging unit that outputs a subject image captured using the lens as image data;
An AF start position determination unit that acquires an AF evaluation value from the image data while moving the lens in a first direction, and determines an AF start position based on the acquired AF evaluation value;
The AF evaluation value is acquired from the image data while moving the lens from the AF start position in a second direction that is opposite to the first direction, and focusing is performed based on the acquired AF evaluation value. An AF processing unit for detecting a position,
The AF start position determination unit detects the peak of the AF evaluation value until the lens moves to a predetermined position, and the peak of the AF evaluation value is detected when a predetermined condition is satisfied. An imaging apparatus, wherein the position of the lens is regarded as the in-focus position, and the detection of the in-focus position by the AF processing unit is canceled.   The imaging apparatus according to claim 1, wherein the predetermined condition is a condition that an elapsed time since the power of the imaging apparatus is turned on is within a predetermined time. With a switch to instruct the start of still image or video shooting,
The imaging apparatus according to claim 1, wherein the predetermined condition is a condition that the switch is operated. With a switch to instruct the start of still image or video shooting,
The AF start position determination unit operates when the switch is operated in a state where the peak of the AF evaluation value is not detected and the number of times the AF evaluation value is acquired exceeds a predetermined number. The imaging apparatus according to claim 1, wherein a position is determined as the AF start position.   The imaging apparatus according to claim 1, wherein the AF start position determination unit determines the AF start position based on a smooth differential value calculated from a plurality of AF evaluation values.   The imaging apparatus according to claim 1, wherein the AF processing unit detects the in-focus position based on a smooth differential value calculated from a plurality of AF evaluation values. A focus position detection method executed by an imaging apparatus including a lens and an imaging unit that outputs a subject image captured using the lens as image data,
An AF start position determining step of acquiring an AF evaluation value from the image data while moving the lens in a first direction, and determining an AF start position based on the acquired AF evaluation value;
The AF evaluation value is acquired from the image data while moving the lens from the AF start position in a second direction that is opposite to the first direction, and focusing is performed based on the acquired AF evaluation value. AF processing step for detecting the position,
In the AF start position determining step, the peak of the AF evaluation value is detected before the lens moves to a predetermined position, and the peak of the AF evaluation value is detected when a predetermined condition is satisfied. An in-focus position detecting method, wherein the position of the lens is regarded as the in-focus position, and the in-focus position is not detected in the AF processing step. An imaging apparatus including a lens and an imaging unit that outputs a subject image captured using the lens as image data.
A function of acquiring an AF evaluation value from the image data while moving the lens in a first direction, and determining an AF start position based on the acquired AF evaluation value;
The AF evaluation value is acquired from the image data while moving the lens from the AF start position in a second direction that is opposite to the first direction, and focusing is performed based on the acquired AF evaluation value. A position detection program for realizing a position detection function,
The function of determining the AF start position is such that the peak of the AF evaluation value is detected before the lens moves to the predetermined position, and the peak of the AF evaluation value is detected when a predetermined condition is satisfied. Further, the focus position detection program cancels the detection of the focus position by regarding the position of the lens as the focus position.

Images