JP2003114377A - camera - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce a time lag at the time of shooting in a camera that performs a focusing operation by a contrast method. A lens driving range is divided into a predetermined number, a scan is started from a close range, a lens is stopped when scanning of the small division range where a peak is found ends, and the lens is immediately moved to the detected peak. Move to shoot.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera that performs a focusing operation by a contrast method using an image pickup signal of an image pickup device.

[0002]

2. Description of the Related Art Conventionally, there is a method called a contrast method as an AF method for cameras. With this method,
An image of a subject is picked up by an image pickup device such as a CCD, and the in-focus position is determined using an image pickup signal in the focus detection area. The image pickup signal in the area is passed through a bandpass filter (BPF) to extract a component of a predetermined spatial frequency band. Then, by integrating these absolute values within the area, the focus evaluation value for performing the focusing operation is obtained. The focus evaluation value represents the magnitude of contrast, and the highest focus is at the peak of the focus evaluation value. That is, the peak position is the in-focus position. When looking for this peak,
A conventionally known mountain climbing focusing operation is performed to find the peak. As an example of the peak detection method in such a mountain climbing method, first, while monitoring the change in the evaluation value while moving the focusing lens,
If the direction of change changes more than a predetermined range considering noise and flicker, the focusing lens is reversed and the degree of change in the evaluation value is monitored again.If it is determined that the change is sufficiently small, change it there. Judge as peak.

With such a method, it takes time to focus when the brightness of the subject is low or the contrast is low, and the time lag from when the photographer presses the shutter button until the actual photographing is possible. Will become bigger. On the other hand, a method for shortening the focusing time in a commercial video camera is disclosed in Japanese Patent Laid-Open No. 10-213843.
There, the moving range of the focusing lens is divided into a plurality of sections in advance, and each time the focusing lens moves in the divided section, it is determined whether or not there is a jaspin within that period. It is shown that the focusing time is shortened by moving the focusing lens to the just-in-spin position without driving the focusing lens over the entire area.

[0004]

However, the above disclosed method is premised on AF in a commercial video camera which continuously focuses a moving image, and the position of the focusing lens at the start of focusing is indefinite. Is. for that reason,
If you want to detect the peak in the small section to which the current focusing lens position belongs, first move the focusing lens in any direction, detect the end point of that section, and then move the focusing lens in that direction. Is reversed and the other end points are detected, and then scanning in the entire area within the divided section is completed.

In this method, since the divided small section is scanned once or more, the efficiency is low. Therefore, when the focusing lens reaches the end point, the small section before that is scanned unless the end point is a physical end point. It is more efficient to do so. In any case, it is detected that the driving of one divided section is completed only after the end points at both ends of the divided section are detected twice. Further, depending on the relationship between the distance to the subject and the first detected divisional section, the same section where the peak is not detected is driven twice before being driven to the next section, and finally the peak is detected there. In some cases, it is difficult to say that the lens movement is efficient.

An object of the present invention is to provide a focusing lens in a camera which performs a focusing operation by a contrast method using an image pickup signal of an image pickup element, and always drives a focusing lens from one end of its driving range when a shutter button is operated. After the start of the evaluation value peak is confirmed, the operation to search for the peak is stopped after a predetermined drive stop point, and the focusing lens is immediately returned to the above-mentioned peak position for shooting, and after release, until shooting. To provide a camera with less time lag.

[0007]

In order to solve the above problems, the invention of claim 1 provides an image pickup device for picking up a subject image through a photographing lens, and a lens for driving the photographing lens within a predetermined driving range. Drive means, an evaluation value calculation means for calculating a focus evaluation value based on an image pickup signal output from the image pickup device, and the lens drive means after starting driving the photographing lens from one end of the predetermined drive range, The deciding means for deciding on the basis of the evaluation value computing means whether the driving by the driving means is stopped at a predetermined stop point before reaching the other end of the predetermined driving range, and the photographing lens And a peak value detecting means for detecting a peak of the focus evaluation value output from the evaluation value calculating means when moving between the one end of the drive range and the stop point. Therefore, if the peak is once detected without scanning the entire area, it is possible to immediately drive the photographing lens to a position corresponding to the peak without performing scanning after the predetermined stop point, and it is possible to perform photographing at the time of photographing. The time lag is shortened.

According to a second aspect of the present invention, the lens driving means further comprises a driving start point changing means for changing one end of the predetermined driving range according to photographing conditions.
That is, in claim 3, the driving start end point has a first shooting mode suitable for shooting a subject at a relatively short distance and a second shooting mode suitable for shooting a subject at a long distance. The changing means changes the driving start end point of the photographing lens from the lens closest end in the first photographing mode to the lens infinite end in the second photographing mode. Further, in claim 4, the first shooting mode includes at least one of a normal shooting mode, a portrait shooting mode, and a close-up shooting mode.
The shooting mode is characterized by including at least a landscape shooting mode.

According to a fifth aspect of the present invention, the deciding means includes stop point changing means for changing the number of the stop points according to the photographing condition. In the invention of the sixth aspect, the photographing condition is The stop point changing unit has a first shooting mode suitable for shooting a subject at a relatively short distance and a second shooting mode suitable for shooting a subject at a long distance.
The number of stop points is changed to be smaller in the second mode than in the first shooting mode. And in Claim 7, the said 1st
The image capturing mode includes at least one of a normal image capturing mode, a portrait image capturing mode, and a close-up image capturing mode, and the second image capturing mode includes at least a landscape image capturing mode.

According to an eighth aspect of the invention, when the peak value detecting means detects a plurality of peak values, the lens driving means drives the photographing lens to a position corresponding to a peak value which is closer to the peak value. Since it is characterized by, it is possible to prioritize shooting at the near side where the main subject is likely to exist. In the invention according to claim 9, the lens driving means drives the photographing lens to a position corresponding to the maximum peak value when the peak value detecting means detects a plurality of peak values, In this case, the subject having the highest contrast within the predetermined drive range can be preferentially photographed.

According to a tenth aspect of the present invention, the evaluation value computing means has means for outputting the evaluation values to a plurality of distance measuring areas in the image pickup device, and the peak value detecting means has a plurality of means. For each of the table value for the area, having a means for detecting the peak of the focus evaluation place, when the peak value detecting means detects a plurality of peak values, at the position corresponding to the closest peak value 12. The photographing lens is driven, and the closest subject can be photographed among a plurality of peaks detected from a plurality of areas. While having means for respectively outputting the evaluation value to a plurality of distance measuring areas in the element, the peak value detecting means is for the value of the table value for the plurality of areas. Each has a means for detecting the peak of the focus evaluation place, and when the peak value detecting means detects a plurality of peak values, the photographing lens is driven to a position corresponding to the maximum peak value. With this feature, it is possible to preferentially shoot a subject having the highest contrast among a plurality of peaks detected from a plurality of areas.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram of an AF (autofocus) digital camera according to an embodiment of the present invention. The taking lens 101 is a zoom lens and is driven by the driver 113 in the optical axis direction. Here, the driver 113 includes a zoom drive mechanism of a zoom lens and a drive circuit thereof, and a focus drive mechanism of a focusing lens and a drive circuit thereof, each of which is a CPU.
Controlled by 112.

The taking lens 101 forms a subject image on the image pickup surface of the image pickup element 103. The image pickup element 103 is a photoelectric conversion image pickup element that outputs an electric signal according to the light intensity of the subject image formed on the image pickup surface, and a CCD type or MOS type solid state image pickup element is used. The image sensor 103 is driven by a driver 115 that controls the timing of signal extraction. A diaphragm 102 is provided between the taking lens 101 and the image sensor 103. The diaphragm 102 is driven by a driver 114 including a diaphragm mechanism and a drive circuit thereof. The image pickup signal from the solid-state image pickup device 103 is input to the analog signal processing circuit 104, and the analog signal processing circuit 104 performs correlated double sampling processing (CDS).
Etc. are processed. The image pickup signal processed by the analog signal processing circuit 104 is converted from an analog signal to a digital signal by the A / D converter 135.

The A / D converted signal is subjected to various image processing such as contour compensation and gamma correction in the digital signal processing circuit 106. The digital signal processing circuit also includes a luminance / color difference signal generation circuit for recording. The buffer memory 105 is a frame memory that can store data for a plurality of frames captured by the image sensor 103, and the A / D converted signal is temporarily stored in the buffer memory 105. Digital signal processing circuit 106
Then, the data stored in the buffer memory 105 is read and each processing described above is performed, and the processed data is stored again in the buffer memory 105.

The CPU 112 is a digital signal processing circuit 10.
6 and drivers 113 to 115, etc., and performs sequence control of camera operation. The AE calculation unit 1121 of the CPU 112 performs automatic exposure calculation based on the image signal from the image sensor, and the AWB calculation unit 1122 performs calculation of white balance adjustment. Bandpass filter (B
The PF) 1124 extracts a high frequency component in a predetermined band based on the image pickup signal in the focus detection area provided in the image pickup area. When a plurality of focus detection areas are set, the signals in each area are sequentially read, and the extraction processing for each area is performed by the bandpass filter (BPF) 11
24.

The output of the BPF 1124 is input to the next evaluation value calculator 1125, where the absolute value of the high frequency component is integrated and calculated as a focus evaluation value. The AF calculation unit 1126 uses the contrast method to calculate A based on these focus evaluation values.
F calculation is performed. The CPU 112 adjusts the focusing lens of the taking lens 101 by using the calculation result of the AF calculation unit 1126 to perform the focusing operation. For the operation unit 116 connected to the CPU 112, a power switch 1161 for turning on / off the power of the camera, a full-push switch 1162 and a half-push switch 1163 that are turned on / off in conjunction with a release button, a shooting mode, and the like are selected and interlocked with them. Setting button 116 for setting the number of divisions of the driving range of the present invention.
4. A selection button 1165 is provided for selecting an image signal recorded in the buffer memory 105 at the time of continuous shooting and finally recording it in the external memory. When these switches or buttons are operated, a signal corresponding to the operation is input to the CPU 112.

The CPU 112 also has a storage unit for storing various data, and the peak value of the evaluation value and the corresponding lens position, etc. are stored therein. The image data that has been subjected to various kinds of processing by the digital signal processing circuit 106 is temporarily stored in the buffer memory 105, and then recorded in the external storage medium 111 such as a memory card via the recording / reproducing signal processing circuit 110. When recording image data in the storage medium 111, generally, a predetermined compression format, for example, JP
Data compression is performed by the EG method. The recording / playback signal processing circuit 110 performs data compression when recording image data in the external storage medium 111 and data decompression processing when reading compressed image data from the storage medium 111. The recording / reproducing signal processing circuit 110 also includes an interface for performing data communication with the storage medium 111.

The monitor 109 is a liquid crystal display device for displaying a picked-up subject image, and is also used when reproducing and displaying image data recorded in the storage medium 111. When displaying an image on the monitor 109, the image data stored in the buffer memory 105 is read out, and D /
The A converter 108 converts the digital image data into an analog video signal. Then, an image is displayed on the monitor 109 using the analog video signal.

In the contrast method, there is a correlation between the degree of blurring of an image and the contrast, and the contrast of the image is maximized when there is a focus. The size of the contrast can be evaluated by the size of the high frequency component of the image pickup signal. That is, BPF1
A high-frequency component of the image pickup signal is extracted by 124, and the evaluation value calculation unit 1125 integrates the absolute value of the high-frequency component to obtain a focus evaluation value. As described above, the AF calculation unit 1126 performs AF calculation based on this focus evaluation value. CPU11
Reference numeral 2 adjusts the focusing lens position of the photographing lens 101 using the calculation result of the AF calculation unit 1126 to perform the focusing operation.

Next, one embodiment of the operation of the camera according to the present invention will be described based on the flowcharts of FIGS. 2 and 3 and the evaluation value variation diagram with respect to the lens position of FIG. In this embodiment, as shown in (1) to (4) of FIG. 4, the drive range of the entire focusing lens is set by the button 1
It is divided into four small ranges by 164. The power switch 1161 of FIG. 1 is turned on, and the processing of the flow shown in FIG. 2 is started. First, when the halfway press switch 1163 is turned on in step S100, the taking lens is moved to the initial position in step S101. As the initial position, either the infinity side extreme end position or the close-up side extreme end position is selected according to the above-described shooting mode. In the present embodiment, the case where the close-up side extreme end position is selected will be described. To go.

Steps S102 to S1 in FIG.
In the processing up to 05, the focus evaluation value is sampled in the entire divided lens drive range. First,
In step S102, the focusing lens of the taking lens 101 starts moving from the closest end of the small division range (1) in FIG. Almost at the same time as the lens movement in step S102, the image pickup signal is read from the CCD 103 in step S103, and the A / D converter 135 performs A / D conversion of the image pickup signal. In step S104, the evaluation value calculation unit 1125 calculates the in-area integration by the signal processed by the BPF 1124 for the image pickup signal in the predetermined focus detection area.
Done in. The results are stored in the storage unit 1123 as a pair with the lens position at the time of sampling.

In step S105, it is determined whether or not the lens position has reached the other end position of the selected small division range (1). If it is determined in step S105 that the other end point position has been reached, it is determined in step S106 in FIG. 3 whether or not there is a peak in (1) in the sub-division section that has just been scanned. If it is confirmed that there is a peak, the focusing lens is stopped in the next step S107. If it is determined in step S106 that there is no peak, the process proceeds to the next step S108, and it is determined whether or not the scans for all the small division sections (1) to (4) are completed. If it is determined in step S108 that the scanning of all the small sections has not been completed,
In step S109, the scanning of the small section adjacent to the small section just scanned is started, the process returns to step S103, the evaluation value in the new small section is calculated, and the value is stored in the memory 1123. If it is determined in step S108 that the scanning of the final section (the small division section (4) in this embodiment) has been completed, this completes the scanning of all of the focusing lens from the closest end to the infinite end. Nevertheless, no peak is found, it is determined that the subject has low contrast, the focusing lens is driven to a predetermined position in step S110, and the full-press switch 1162 is pressed in step S113. Wait for

If it is determined in step S106 that there is a peak in the subdivided section, the focusing lens is immediately stopped in step S107. If a plurality of peaks are detected, the closest peak is determined in step S1.
11, the driving direction is reversed in step S112, and the focusing lens is driven to the peak position selected in step S111 described above.
In step 3, it waits until the full-press switch 1162 is pressed. In step S113, the full-press switch 1162 is fully pressed,
If the subject has been photographed, the image pickup signal is written in the buffer memory in the next step S114, the above-mentioned various processes are performed thereafter, and further compressed and stored in the external storage medium 111.

The description of the case of FIG. 4 will be supplemented. First, since a peak is not recognized in the evaluation value at the time when the small division section (1) is scanned, the next small division section (2) is subsequently scanned. Then, when the scan of the small division section (2) is completed, the peak (P) is found in this section, so the scan is stopped there, and the focusing lens is immediately driven to the lens position corresponding to P. Therefore, since the focusing lens is not driven up to that point in the subdivided sections (3) and (4), the fluctuation portion of the evaluation value indicated by the broken line is not actually measured. In this way, when the main subject is on the near side, the driving range of the focusing lens can be small, so the time lag after pressing the shutter button is reduced. Also,
Even if there is a new peak in the subdivision section (3) or (4), the subject in the close range will be prioritized. There is no difference.

Further, as a method of selecting a peak in step S111, as described above, if a plurality of peaks are detected as a result of scanning a small division section, the nearest peak may be selected. Even if a plurality of peaks are detected from a plurality of focus detection areas, the closest peak may be selected. That is, the closest peak should always be selected.

Other examples of such a main subject on the near side include a person photographing mode and a close-up mode. On the other hand, in the landscape shooting mode or the like, step S1
In 01, the end position on the infinity side may be set as the initial lens position, and the scan may start from the small division section (4) to which the position belongs. In selecting the peak position in step S111, there is a method of giving priority to the magnitude of the contrast of the subject. In that case, the maximum peak may be selected from the plurality of peaks detected in step S106. In addition to the four divisions described here, the number of divisions may be changed according to the photographing mode, for example, the number of divisions may be increased during still image photography or close-up photography, and decreased during landscape mode. Furthermore, a method of narrowing the width of division on the near side and widening on the infinite side is also conceivable.

In the above-described embodiments, the digital camera has been described as an example, but the present invention can be applied to a silver halide film camera as long as the object is imaged by the image sensor and AF is performed by the contrast method.

[0028]

As described above, according to the present invention, the taking lens is driven only in the small division section, the peaks of a plurality of focus evaluation values are detected by the contrast method, and the predetermined peak positions are selected to deal with them. Shooting was done at the lens position. As a result, it is possible to shorten the time lag from when the shutter button is pressed until the actual photographing is performed.

[Brief description of drawings]

FIG. 1 is a functional block diagram of an AF digital camera according to the present invention.

FIG. 2 is a flowchart showing the operation of the camera according to the present invention.

FIG. 3 is a flowchart showing a process following the flowchart of FIG.

FIG. 4 is an explanatory diagram of changes in evaluation values when the lens driving range is divided into four.

[Explanation of symbols]

101 shooting lens 102 aperture 103 CCD 104 Analog signal processing circuit 105 buffer memory 106 digital signal processing circuit 112 CPU 113-115 driver 116 Operation part 135 A / D converter 1161 power switch 1162 full-press switch 1163 Half-press switch 1164 setting button 1165 selection button 1123 storage unit 1124 bandpass filter 1125 Evaluation value calculation unit 1126 AF calculation unit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideomi Hibino             Marunouchi 3 2-3 No. 3 shares, Chiyoda-ku, Tokyo             Ceremony Company Nikon (72) Inventor Toshiaki Maeda             Marunouchi 3 2-3 No. 3 shares, Chiyoda-ku, Tokyo             Ceremony Company Nikon (72) Inventor Masaru Ota             Tokyo Stock Exchange 1-325, Futaba 1-32             Company Nikon technical workshop (72) Inventor Masahide Tanaka             Tokyo Stock Exchange 1-325, Futaba 1-32             Company Nikon technical workshop F term (reference) 2H011 BA35 BB03 CA24                 2H051 BA47 BA66 CE16 DA03 DA22                       EA10                 5C022 AA13 AB02 AB12 AB29 AB40                       AC32 AC42 AC74

Claims (11)

[Claims] 1. A focus evaluation value is calculated based on an image pickup device for picking up a subject image through a taking lens, a lens driving means for driving the taking lens within a predetermined driving range, and an image pickup signal output from the image pickup device. Evaluation value calculation means for
After the lens driving means starts driving the photographing lens from one end of the predetermined driving range, the driving by the driving means can be stopped at a predetermined stop point before reaching the other end of the predetermined driving range. Determining means for determining movement based on the evaluation value calculating means; and the focus output from the evaluation value calculating means when the photographing lens moves between the one end of the predetermined drive range and the stop point. A camera comprising: a peak value detecting means for detecting a peak of an evaluation value. 2. The camera according to claim 1, wherein the lens driving means further comprises a driving start point changing means for changing one end of the predetermined driving range according to photographing conditions. 3. The photographing conditions include a first photographing mode suitable for photographing a subject at a relatively short distance and a second photographing mode suitable for photographing a subject at a long distance. The drive start end point changing means changes the drive start end point of the photographing lens from the lens closest end in the first photographing mode to the lens infinite end in the second photographing mode. The camera according to claim 2. 4. The first shooting mode includes at least one of a normal shooting mode, a portrait shooting mode, and a close-up shooting mode, and the second shooting mode includes at least a landscape shooting mode. The camera according to claim 3. 5. The camera according to claim 1, wherein the deciding means comprises a stop point changing means for changing the number of the stop points according to a photographing condition. 6. The photographing conditions include a first photographing mode suitable for photographing a subject at a relatively short distance and a second photographing mode suitable for photographing a subject at a long distance. 6. The camera according to claim 5, wherein the stop point changing unit changes the number of stop points in the second mode to be smaller than that in the first shooting mode. 7. The first shooting mode includes at least one of a normal shooting mode, a portrait shooting mode, and a close-up shooting mode, and the second shooting mode includes at least a landscape shooting mode. The camera according to claim 6. 8. The lens driving means drives the photographing lens to a position corresponding to the closest peak value when the peak value detecting means detects a plurality of peak values. The camera described in 1. 9. The lens driving means drives the photographing lens to a position corresponding to the maximum peak value when the peak value detecting means detects a plurality of peak values. The camera described in. 10. The evaluation value calculating means has means for outputting the evaluation values to a plurality of distance measuring areas in the image pickup device, respectively, and the peak value detecting means has a table value for the plurality of areas. Each has a means for detecting the peak of the focus evaluation place, and when the peak value detecting means detects a plurality of peak values, the photographing lens is driven to a position corresponding to a closer peak value. The camera according to claim 1, wherein: 11. The evaluation value calculating means has means for outputting the evaluation values to a plurality of distance measuring areas in the image pickup device, respectively, and the peak value detecting means has a surface value for the plurality of areas. Each has a means for detecting the peak of the focus evaluation place, and when the peak value detecting means detects a plurality of peak values, driving the photographing lens to a position corresponding to the maximum peak value. The camera according to claim 1, wherein: