JP2013088759A - Imaging device and control program for imaging device - Google Patents

Abstract

[PROBLEMS] In continuous shooting, when the brightness of the subject environment becomes dark on the way, the charge accumulation time required by the photometric element becomes long, and the continuous shooting speed may drop rapidly during continuous shooting. there were.
An imaging apparatus includes: an imaging element; a photometric element; a calculation unit that calculates the brightness of a subject based on a photometric signal; and an imaging element that captures an image when the imaging element outputs an image signal continuously. When the photometric light-receiving time assigned during the light-receiving operation, which is the time for the photometric element to receive the subject image, is less than the preset allowable light-receiving time corresponding to the brightness of the subject environment, the calculation unit A control unit that performs imaging light receiving operation by applying the brightness of the subject calculated in advance.
[Selection] Figure 5

Description

  The present invention relates to an imaging apparatus and a control program for the imaging apparatus.

In general, an TTL imaging device that separately includes an imaging device that receives a subject image and outputs an image signal, and a photometric device that detects the brightness of the subject environment, exclusively transmits the subject luminous flux to each device. A movable mirror structure is provided. Accordingly, during continuous shooting in which the image sensor continuously outputs image signals, the brightness of the subject environment is detected by the photometric element by driving the movable mirror between the imaging light receiving operations by the image sensor. The imaging light receiving operation is controlled according to the exposure value determined based on the detected brightness of the subject environment.
[Prior art documents]
[Patent Literature]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2005-6217

  However, during continuous shooting, if the brightness of the subject environment becomes dark during the process, the charge accumulation time required by the metering element may become longer, and the continuous shooting speed may drop rapidly while shooting continues. It was. If the charge accumulation time is limited by giving priority to the continuous shooting speed, the readout gain of the photometric element increases, and an accurate exposure value cannot be calculated.

  An imaging device according to a first aspect of the present invention includes an imaging device that receives a subject image and outputs an image signal, a photometric device that receives the subject image and outputs a photometric signal, and brightness of the subject based on the photometric signal. And a photometric light receiving time that is a time during which the photometric element receives the subject image, which is assigned during the imaging light receiving operation by the image sensor when the image sensor outputs image signals continuously. A control unit that executes the imaging light receiving operation by applying the brightness of the subject calculated in advance by the calculation unit when it is less than the preset allowable light reception time corresponding to the brightness of the subject environment .

  An imaging apparatus control program according to a second aspect of the present invention controls an imaging apparatus including an imaging element that receives a subject image and outputs an image signal, and a photometric element that receives the subject image and outputs a photometric signal. When the imaging device outputs image signals continuously, a reference step for referring to an allowable light reception time set in advance corresponding to the brightness of the subject environment, and imaging as a result of reference by the reference step When the photometric light-receiving time, which is the time for the photometric element to receive the subject image, assigned during the imaging light-receiving operation by the element, is less than the allowable time, the subject brightness calculated in advance is applied. And causing the computer to execute an imaging step for performing the operation.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is principal part sectional drawing of the single-lens reflex camera which concerns on this embodiment. 1 is a block diagram schematically showing a system configuration of a single-lens reflex camera. It is a figure which shows the relationship between the charge storage time of a photometry element, and an output value. It is a figure which shows the relationship between EV value and electric charge accumulation time. It is a figure which shows the relationship between photometry light reception time and the calculated EV value. It is a figure which shows the AE lock | rock area | region and photometry follow-up area | region divided according to EV value and photometry satisfaction conditions. It is a timing chart which shows the operation transition of a main mirror, a photometry element, and an image sensor. It is a flowchart which mainly shows the process of the photometry operation | movement at the time of continuous shooting.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a cross-sectional view of a main part of a single-lens reflex camera 10 according to the present embodiment. The single-lens reflex camera 10 functions as an imaging device by combining the lens unit 20 and the camera unit 30.

  The lens unit 20 includes a lens group 21 arranged along the optical axis 11. The lens group 21 guides the incident subject luminous flux to the camera unit 30. The lens group 21 includes a focus lens, a zoom lens, and the like, and is configured to be movable in the optical axis direction in response to instructions for focus adjustment and field angle adjustment. The lens unit 20 includes a lens mount 22 at a connection portion with the camera unit 30, engages with a camera mount 54 included in the camera unit 30, and is integrated with the camera unit 30.

  The lens unit 20 includes a lens system control unit 23 that controls the operation and the like of the lens unit 20. The lens system control unit 23 communicates with the camera unit 30 via communication terminals provided on the lens mount 22 and the camera mount 54.

  The camera unit 30 includes a main mirror 31 that reflects the subject light beam incident from the lens unit 20 and a focus plate 35 on which the subject light beam reflected by the main mirror 31 forms an image. The main mirror 31 is held by the main mirror holding frame 32 and rotates around the main mirror rotation shaft 33 so that the main mirror 31 is obliquely installed in the subject light flux centered on the optical axis 11 and retracted from the subject light flux. The evacuation state to take can be taken.

  When the subject image is guided to the focus plate 35 side, the main mirror 31 is provided obliquely in the subject light flux. At this time, the back surface of the main mirror holding frame 32 comes into contact with the main mirror eccentric pin 34, and the oblique angle of the main mirror 31 is defined. The main mirror eccentric pin 34 can adjust the position where it abuts on the main mirror holding frame 32 by rotating, and the oblique angle of the main mirror 31 can be accurately set. The focus plate 35 is disposed at a position conjugate with the light receiving surface of the image sensor 48. The subject image formed on the focus plate 35 is converted into an erect image by the pentaprism 36 and is observed by the user via the eyepiece optical system 37.

  A photometric element 39 is disposed above the exit surface of the pentaprism 36, and an object image formed on the focusing plate 35 is formed on the light receiving surface of the photometric element 39 via the pentaprism 36 and the photometric optical system 38. The next image is formed. The photometric element 39 is an element that plays the role of an AE sensor that detects the luminance distribution of the subject environment, and is composed of two-dimensionally arranged photoelectric conversion elements.

  A finder display unit 40 composed of a liquid crystal element is disposed between the focus plate 35 and the pentaprism 36. The finder display unit 40 can display grid lines, focus adjustment regions, and the like, and the user can observe these images superimposed on the subject image formed on the focusing screen 35 via the eyepiece optical system 37. .

  A region near the optical axis 11 of the main mirror 31 in the oblique state is formed as a half mirror, and a part of the incident subject luminous flux is transmitted therethrough. The transmitted subject light flux is reflected by the sub mirror 41 held by the sub mirror holding frame 42 that rotates in conjunction with the main mirror 31, and is guided to the AF optical system 45. The subject light flux that has passed through the AF optical system 45 enters the AF sensor 46.

  The sub mirror holding frame 42 rotates around a sub mirror rotation shaft 43 provided on the main mirror holding frame 32. In the oblique installation state, the back surface of the sub mirror holding frame 42 abuts on the sub mirror eccentric pin 44, and the oblique installation angle of the sub mirror 41 is defined. The sub mirror eccentric pin 44 can adjust the position where it abuts on the sub mirror holding frame 42 by rotating, and the oblique angle of the sub mirror 41 can be set accurately.

  The AF sensor 46 is, for example, a plurality of photoelectric conversion element arrays that output phase difference signals from the received subject light flux. Specifically, the focus state, front pin state, and rear pin state can be detected in each of a plurality of focus adjustment regions provided corresponding to specific regions of the subject image. Is configured so that the amount of deviation from the in-focus state can also be detected. The sub mirror 41 retracts from the subject light beam in conjunction with the main mirror 31 when the main mirror 31 retracts from the subject light beam.

  A focal plane shutter 47 and an image sensor 48 are arranged along the optical axis 11 behind the oblique main mirror 31. The focal plane shutter 47 is in an open state when the subject light beam is guided to the image sensor 48 and is in a shielded state at other times. The imaging element 48 is a photoelectric conversion element such as a CMOS sensor, for example, and converts the subject image formed on the light receiving surface into an electrical signal.

  The electrical signal photoelectrically converted by the image sensor 48 is processed into image data by the image processing unit 55 which is a DSP mounted on the main board 49. In addition to the image processing unit 55, a camera system control unit 51 that is an MPU that integrally controls the system of the camera unit 30 is mounted on the main board 49. The camera system control unit 51 manages the camera sequence and performs input / output processing of each component. For example, the brightness of the subject environment is calculated from the luminance distribution of the subject image output from the photometric element 39. Then, the exposure value is determined from the calculated brightness and the program diagram. Further, focusing control is performed using the phase difference signal output from the AF sensor 46.

  A rear display unit 52 such as a liquid crystal monitor is disposed on the rear surface of the camera unit 30, and a subject image processed by the image processing unit 55 is displayed. The rear display unit 52 displays various menu information, shooting information, and the like as well as a still image after shooting. The camera unit 30 houses a detachable secondary battery 53, and supplies power to the lens unit 20 as well as the camera unit 30.

  FIG. 2 is a block diagram schematically showing the system configuration of the single-lens reflex camera 10. The system of the single-lens reflex camera 10 includes a lens control system centered on the lens system control unit 23 and a camera control system centered on the camera system control unit 51 corresponding to each of the lens unit 20 and the camera unit 30. Is done. The lens control system and the camera control system exchange various data and control signals with each other via a communication terminal connected by the lens mount 22 and the camera mount 54.

  The image processing unit 55 included in the camera control system processes the imaging signal photoelectrically converted by the imaging device 48 into image data in accordance with a command from the camera system control unit 51. The processed image data is sent to the display control unit 59 and displayed on the rear display unit 52 for a certain time after shooting, for example. In parallel with this, the processed image data is processed into a predetermined image format and recorded in the external memory via the external connection IF 56.

  The camera memory 57 is a non-volatile memory such as a flash memory, for example, and plays a role of storing a program for controlling the single-lens reflex camera 10, various parameters, and the like. The work memory 58 is a memory that can be accessed at high speed, such as a RAM, and has a role of temporarily storing image data being processed.

  The camera driving unit 60 drives the main mirror 31, the sub mirror 41, the focal plane shutter 47, and the like according to instructions from the camera system control unit 51. The operation input unit 61 detects that an operation member such as a release button, a shooting mode dial, and a photometry mode dial has been operated by the user, and outputs it to the camera system control unit 51. As described above, the camera system control unit 51 receives the output of the photometric element 39 and calculates the brightness of the subject environment.

  The lens system control unit 23 receives various control signals from the camera system control unit 51 and controls various operations. The lens memory 24 stores lens-specific information, a program executed by the lens system control unit 23, and the like.

  Next, the relationship between the charge accumulation time of the photometric element 39 and the output will be described. FIG. 3 is a diagram showing the relationship between the charge accumulation time of the photometric element 39 and the output value when light of the same intensity is received. The horizontal axis represents the passage of charge accumulation time, and the vertical axis represents the output value after AD conversion of the output signal of the photometric element 39 with a resolution of 10 bits. The charge accumulation time is a time during which light reception of the subject image is continued after each photoelectric conversion element of the photometry element 39 is reset.

When the object image having the same brightness is continuously received, the output voltage increases as the charge accumulation time increases. However, since each photoelectric conversion element has an upper limit of the amount of light that can be accepted, it eventually becomes saturated. When AD conversion of the output signal with a gain of 1 is performed, an analog voltage AD conversion value corresponding to the vicinity of the saturation charge amount may be set as the upper limit value of the AD converter. As shown in FIG. 3, when the charge accumulation is continued until time T ₀ with a gain of 1, the saturation output value K ₁ is reached. When the EV value is larger, that is, when the subject environment is brighter, the time T ₀ is shortened. Conversely, when the EV value is smaller, that is, when the subject environment is darker, the time T ₀ is longer. Therefore, targeted level K ₂ is slightly smaller than the saturation output value, by measuring the time T ₁ of the to reach this target level, to detect the EV value as brightness of an object environment it can.

When a subject image having the same brightness is received, if the gain, which is an amplification factor, is doubled, the target level is reached in approximately half the charge accumulation time compared to when the gain is doubled. In FIG. 3, the relationship 2T ₂ ≈T ₁ is established. Similarly, when the gain is quadrupled, the target level is reached in approximately one-fourth of the charge accumulation time compared to when the gain is doubled. In FIG. 3, the relationship 4T ₄ ≈T ₁ is established.

Therefore, if the gain is doubled when a subject image with half intensity is received, the charge accumulation time becomes T ₁ . Similarly, if four times the gain when receiving an object image of the intensity of 1/4, the charge accumulation time is also a T _1. Therefore, when the subject environment is dark, the charge accumulation time can be shortened by increasing the gain. In other words, if a certain amount of charge accumulation time can be ensured, by adopting a large gain, it is possible to detect even a dark EV as a subject environment, that is, a small EV. However, if the gain is increased too much, the S / N ratio deteriorates. Therefore, it is important to set an upper limit of the gain that can be adopted by, for example, prior experiments. In this embodiment, the maximum gain is four times.

  FIG. 4 is a diagram showing the relationship between the detected EV value and the charge accumulation time. The horizontal axis represents the EV value, and the vertical axis represents the charge accumulation time. Here, a case where EV0 to EV20 is described as an example of the detection capability of the photometric element 39.

In the region A where the subject environment is relatively bright, charge accumulation is performed while adjusting the charge accumulation time and gain so that the output of the photometric element 39 reaches the target level. In the figure, when the solid line is traced from the higher (brighter) side to the lower (darker) side of the subject, first, the gain is set to 1 and the minimum accumulation time T _min as the charge accumulation time. And EV20 correspond to each other. It can be seen that the EV value decreases as the charge accumulation time to reach the target level increases as the process proceeds along the line with a gain of 1.

If the gain switching upper limit time T _gu is reached while the gain is set to 1 time, the gain is switched to 2 times at the next photometry. At this time, the charge accumulation time is approximately halved. Then, it can be seen that the current EV value decreases as the charge accumulation time for reaching the target level increases as the current gain line advances. When the gain switching upper limit time T _gu is reached again, the gain is switched four times at the next photometry. At this time, the charge accumulation time is also halved. Similarly, when the process proceeds along a line with a gain of 4 times, it can be seen that the corresponding EV value becomes smaller as the charge accumulation time to reach the target level becomes longer until the maximum charge accumulation time _Tmax .

The maximum charge accumulation time T _max represents an upper limit time that can be allocated as the charge accumulation time by the camera system control unit 51. When the single-lens reflex camera 10 performs continuous shooting, if the charge accumulation time that is the photometric light receiving time of the photometric element 39 is set longer, the frame speed that is the number of shots per unit time decreases accordingly. In addition, the photometry cycle is lengthened, and the followability to the luminance change of the subject is also reduced. Furthermore, if the charge accumulation time is too long, the SN ratio of the output signal also deteriorates. Therefore, the maximum charge accumulation time T _max is set in advance as the upper limit time of the charge accumulation time from the viewpoint of ensuring the frame speed and photometry cycle and the reliability of the output signal.

In the region B where the subject environment is relatively dark, the line with a gain of 4 eventually reaches _Tmax , and the subsequent charge accumulation time reaches a peak at _Tmax . When the charge accumulation time is limited to a constant value _Tmax , the camera system control unit 51 calculates the EV value from the amount of charge accumulated during the certain time, that is, the AD conversion value corresponding thereto.

Note that a line indicated by a chain line in FIG. 4 indicates the relationship between the charge accumulation time and the EV value when the subject luminance changes from the low side to the high side. When the gain is set to 4 times and the gain switching lower limit time _Tgl is reached, the gain is switched to 2 times. At this time, the charge accumulation time is approximately doubled. When the gain is set to double and the gain switching lower limit time _Tgl is reached again, the gain is switched to 1 time. Also at this time, the charge accumulation time is approximately doubled. In this way, fluctuations in gain switching are avoided by providing hysteresis when the subject luminance changes from the high side to the low side and when the subject luminance changes from the low side to the high side.

In the solid line shown in FIG. 4, the hatched portion is not limited in T _max represents the charge storage time to reach the target level, the horizontal part being limited in T _max is the corresponding EV value when detecting accuracy It represents the required charge accumulation time. That is, the solid line shown in FIG. 4 represents an ideal charge accumulation time when the EV value is calculated. If the charge accumulation time and the photometric light receiving time for the photometry element 39 to receive the subject image are equal, ignoring errors due to the reset timing of the photoelectric conversion element, the charge accumulation time represented by the solid line in FIG. It can be seen as time.

As described above, the maximum charge accumulation time _Tmax is set as the upper limit time of the charge accumulation time from the viewpoint of securing the frame speed, etc., but in actual continuous shooting, a higher-speed shooting sequence is executed. There is. Therefore, when the image sensor 48 continuously outputs image signals, the photometric light reception time that the camera system control unit 51 allocates during the image light reception operation may be shorter than _Tmax . That is, the camera system control unit 51 may not be able to divide the time _Tmax as the photometric light receiving time between frames. In that case, the EV value must be calculated from the output signal in which charges are accumulated in the photometric light receiving time shorter than the target light receiving time. However, if the photometric light receiving time is too short, the accumulated charge is small and the calculation result is not stable. That is, the reliability of the calculated EV value is low and cannot be used for calculating the exposure value. Therefore, in this embodiment, an allowable light receiving time is introduced as a photometric light receiving time during which the calculated EV value can be determined to be correct.

  FIG. 5 is a diagram showing the relationship between the photometric light reception time and the calculated EV value. In particular, an area corresponding to the area B in FIG. 4 is shown. The horizontal axis represents photometric light reception time on a logarithmic scale, and the vertical axis represents the calculated EV value. This figure schematically shows the result of an experiment in which the subject environment adjusted to the luminance corresponding to each EV value is actually measured with the photometric element 39 while changing the photometric light receiving time.

  Each line represents the experimental results of EV0, EV1,... EV9 in order from the bottom. Each line becomes a curve in a region where the photometric light receiving time is short and becomes a horizontal straight line in a long region. In addition, the connection point between the curved line portion and the horizontal straight line portion appears at a shorter time point with respect to the photometric light receiving time as the EV value increases. The horizontal straight line portion of each line is in good agreement with the EV value corresponding to the actually adjusted luminance of the subject environment with reference to the calculated EV value on the vertical axis. For example, the horizontal straight line portion of the line obtained for the subject environment adjusted to the luminance corresponding to EV6 indicates EV6 as a calculation result. However, in the curve portion, the calculated EV value shows a large value with respect to the luminance of the subject environment actually adjusted. That is, when the photometric light receiving time is short, the calculated EV value is larger than the EV value with respect to the actual luminance of the subject environment.

  That is, it can be said that the calculated EV value and the EV value corresponding to the actual luminance of the subject environment coincide with each other in the region on the longer side than the photometric light receiving time corresponding to the connection point of each line. In other words, the calculated EV value is determined to be correct when the photometric light receiving time is in a region longer than the allowable light receiving time defined by connecting the vicinity of the connection point of each line. .

Therefore, the photometric light receiving time exists in the shaded area in FIG. 5 between the line of the target light receiving time (in FIG. 5, T _max corresponds to 100 msec) and the allowable light receiving time described with reference to FIG. If it is, it can be judged that the calculated EV value is accurate. On the contrary, if the photometric light receiving time exists in a region other than this region, it can be determined that the calculated EV value is not reliable. In this sense, the shaded area in FIG. 5 can be defined as a photometric area.

  The camera system control unit 51 receives an output signal measured by the photometric element 39 during the assigned photometric light receiving time, and calculates an EV value. Then, the assigned photometric light receiving time and the calculated EV value are applied to the graph of FIG. 5 to select the applicable line. Since the selected line is an experimental result for a specific EV value, as described above, the allowable light receiving time is defined near the connection point between the curved portion and the horizontal straight portion. The camera system control unit 51 determines whether or not the assigned photometric light-receiving time belongs to a photometric available area that is a horizontal straight line portion on the right side of the allowable light-receiving time. If it is determined that it belongs to the photometric area, the calculated EV value is adopted as an accurate value, and if it is determined that it does not belong, it is discarded as an unreliable value. In other words, the camera system control unit 51 adopts an accurate value if the calculated EV value matches the EV value of the selected line, and discards it as an unreliable value if they do not match. However, as will be described later, the allowable light receiving time and the target light receiving time determined from the line selected here are referred to when determining the photometric light receiving time in the next photometric operation.

  In FIG. 5, a line indicating the experimental result in increments of EV values is drawn, but of course, the experimental data may be acquired more finely. Then, a look-up table indicating a photometric area for each EV value is created from the data acquired through experiments or simulations as described above, and stored in the camera memory 57. The camera system control unit 51 determines whether or not to adopt the calculated EV value with reference to this lookup table when the assigned photometry time is short, such as during continuous shooting.

  As described above, the photometric light receiving time is particularly shortened during continuous shooting. If the subject is bright even during the shortened photometric light receiving time, the camera system control unit 51 can calculate an accurate EV value from the output of the photometric element 39. On the other hand, if the subject is dark, an accurate EV value cannot be calculated. Therefore, when the accurate EV value can be calculated, the camera system control unit 51 calculates the exposure value from the EV value between the frames even during continuous shooting, and images the next frame according to the exposure value. Reflect in control. That is, photometric tracking is executed. If an accurate EV value cannot be calculated, the EV value is discarded and the exposure value applied in the previous frame is applied to the shooting control of the next frame. That is, AE lock is executed. In the AE lock, an exposure value calculated in advance using, for example, an accurate EV value calculated prior to the imaging operation of the first frame is continuously applied.

  As described above, depending on whether or not the photometric light-receiving time exists in the photometric area, it may be determined whether to follow the photometry or to lock the AE, but the photometric satisfaction condition defined by the photometric light-receiving time / target light-receiving time A lookup table can also be generated according to the above. FIG. 6 illustrates a lookup table generated in this respect. More specifically, FIG. 6 shows an AE lock area and a photometric tracking area that are classified according to the EV value and the photometric satisfaction condition. The horizontal axis represents the calculated EV value, and the vertical axis represents the photometric satisfaction condition.

The boundary line between the photometry tracking area and the AE lock area in FIG. 6 is derived from the photometry possible area in FIG. In FIG. 5, in an area having a luminance higher than EV8, the allowable light reception time and the target light reception time are represented by parallel lines, so _RL in FIG. 6 is determined by this constant ratio. In the region below EV8, the target light reception time is constant (= T _max ), whereas the allowable light reception time increases at a constant rate as the EV value decreases. Therefore, the boundary line in this region in FIG. 6 shows a relationship in which the photometric satisfaction condition increases as the EV value decreases. Furthermore, in the area of less than EV1, since the allowable receiving time and the target light-receiving time is represented by parallel lines, R _U in FIG. 6 is also determined by this scale. Thus, if the boundary line between the photometric tracking area and the AE lock area is divided according to the photometric satisfaction condition, management as a lookup table is facilitated.

  When continuous shooting is performed in the single-lens reflex camera 10 according to the present embodiment as described above, the camera system control unit 51 is assigned during the imaging light receiving operation by the imaging element 48, and the photometric element 39 receives the subject image. The photometric light receiving time, which is the time to perform, is gradually increased. This will be specifically described below.

  When continuous shooting is performed with a conventional single-lens reflex camera, the system controller places the main mirror obliquely between the imaging light receiving operations of the image sensor, guides the subject light flux to the photometry element, and accumulates sufficient charge in the photometry element. I gave time to do photometry. By controlling in this way, it is possible to follow a change in the brightness of the subject environment that occurs during continuous shooting, and it is possible to execute a single image pickup light receiving operation with a more appropriate exposure value. However, for example, when the subject moves from the sun to the shade, and the brightness of the subject environment suddenly decreases, the charge accumulation time required by the photometric element increases rapidly. In this case, the frame speed rapidly decreases before and after the brightness change. That is, if too much emphasis is placed on tracking the change in brightness in photometry control for continuous shooting, the user feels uncomfortable with the rapid decrease in frame speed.

  Alternatively, when continuous shooting is performed with a conventional single-lens reflex camera, the system control unit fixes the exposure value used for the first image and performs AE lock applied to subsequent successive imaging light receiving operations. It was. In this case, since the frame speed is prioritized, a rapid decrease in the frame speed does not occur, but it cannot follow the change in brightness of the subject environment that occurs during continuous shooting. Therefore, all image data taken after the subject environment has become dark may be under.

  Therefore, in the present embodiment, the camera system control unit 51 takes into consideration the balance between the frame speed continuity and the follow-up performance with respect to changes in brightness, and the photometric light receiving time allocated to the photometric element 39 as described below. Are gradually increased during continuous shooting. FIG. 7 is a timing chart showing operation transitions of the main mirror 31, the photometric element 39, and the image sensor 48. In the figure, the horizontal axis represents the passage of time. The example shown in the figure represents a transition for three consecutive photographing operations from the nth image after the start of the continuous photographing operation so as to show a characteristic change.

  In the figure, in the vertical axis direction, the state of the main mirror 31, the charge accumulation state of the photometric element 39, and the charge accumulation state of the image sensor 48 are aligned in order from the top. As described above, the main mirror 31 takes the retracted state that is the UP state and the oblique state that is the DOWN state. When the camera system control unit 51 sends a release control signal to the camera driving unit 60, the camera driving unit 60 starts to drive the main mirror 31 from the DOWN state to the UP state. At this time, the sub mirror 41 is also displaced to the UP state in conjunction with the displacement of the main mirror 31. Since the mirror unit including the main mirror 31 and the sub mirror 41 is displaced at high speed by the camera driving unit 60, it takes time for the bounce to attenuate until it comes to rest even when it reaches the UP state.

  When the charge accumulation of the image sensor 48 is completed as will be described later, the camera system control unit 51 sends a control signal for driving the mirror unit to the DOWN state to the camera driving unit 60. The mirror unit is driven by the camera driving unit 60 and is displaced from the UP state to the DOWN state. Also in this case, it takes time for the bounce of the mirror part to attenuate until the mirror part stops in the DOWN state. In this way, the mirror unit repeats the UP state and the DOWN state while continuous shooting is performed.

  The photometric element 39 receives the subject image formed on the focus plate 35. Therefore, the period during which the photometric element 39 can receive the subject luminous flux and accumulate the charge is a stationary period in the DOWNNN state in which the main mirror 31 stably guides the subject luminous flux to the focus plate 35. The camera system control unit 51 performs control to adjust the length of this period.

  As shown in the middle part of FIG. 7, the photometric element 39 is controlled by the camera system control unit 51 so as to execute charge accumulation during the stationary period of the main mirror 31 in the DOWN state. The period during which the object luminous flux is actually received and the charge can be accumulated is defined as a photometric light receiving time. The camera system control unit 51 may detect the stationary time of the mirror unit with another sensor, or measure in advance the time from when the camera driving unit 60 starts to drive to the DOWN state until the bounce decays. It may be predicted by keeping it.

  The camera system control unit 51 does not change the photometric light receiving time abruptly in consideration of the continuity of the frame speed of the continuous shooting once started. Therefore, even if the subject environment becomes dark during continuous shooting and the target light reception time is extended, the camera system control unit 51 does not immediately assign the target light reception time as the photometric light reception time. Specifically, the camera system control unit 51 assigns the previous photometric light reception time when the photometric operation was correctly performed under a bright subject environment. Then, the camera system control unit 51 receives the output signal measured by the photometric element 39 during the photometric light receiving time, and calculates the EV value. In this case, since the subject environment is actually dark, as described with reference to FIG. 5, the assigned photometric light reception time does not reach the allowable light reception time determined by the selected line, and is calculated. The EV value is discarded. In this case, since the camera system control unit 51 cannot calculate an accurate EV value of the subject environment, the exposure value used in the previous (n−1) th imaging light receiving operation is used for successive imaging light receiving operations. Use as is. That is, the camera system control unit 51 executes the imaging light receiving operation with the AE lock. The camera system control unit 51 stores the current photometric light reception time and the target light reception time determined by the selected line in preparation for the next (n + 1) th image pickup light reception operation.

  The camera system control unit 51 drives the aperture of the lens unit 20 with the aperture value applied in the (n-1) th imaging light receiving operation as the nth imaging light receiving operation, and drives the focal plane shutter 47 at the shutter speed. The output signal of the image sensor 48 is amplified with ISO sensitivity. As shown in the lower part of FIG. 7, the image sensor 48 is in the charge accumulation state during the stationary period of the mirror unit in the UP state. The camera system control unit 51 moves the front curtain and the rear curtain of the focal plane shutter 47 within this period, and adjusts the period (shutter speed) during which the subject luminous flux reaches the image sensor 48.

  As described above, if the allowable light receiving time can be secured as the charge accumulation time, the photometric element 39 can output an accurate luminance distribution. In the present embodiment, the camera system control unit 51 gradually increases the photometric light reception time, and when the photometric light reception time exceeds the allowable light reception time, releases the AE lock and calculates a new exposure value.

  The camera system control unit 51 calculates the extension time using the stored n-th photometric light-receiving time and the target light-receiving time, and determines the n + 1-th photometric light-receiving time with reference to this. Specifically, by adding an extension time obtained by multiplying a deficiency time that is a difference between the target light reception time and the photometry light reception time in the nth sheet by a predetermined ratio to the nth photometry light reception time, n + 1 sheets Determine the photometric light reception time for the eyes. As shown in the middle part of FIG. 7, the (n + 1) th photometric light-receiving time is longer than the nth photometric light-receiving time by the amount of extension time added. Similarly to the n-th process, the camera system control unit 51 receives an output signal measured by the photometric element 39 during the photometric light receiving time, and calculates an EV value. Then, the line in FIG. 5 is selected from the photometric light receiving time and the calculated EV value, and the allowable light receiving time for the (n + 1) th sheet is determined. In the example in the figure, the photometric light receiving time is less than the newly set allowable light receiving time even for the (n + 1) th sheet. Accordingly, since the camera system control unit 51 cannot calculate an accurate EV value, the exposure value used in the previous (n-th) imaging light receiving operation is used as it is for successive imaging light receiving operations. That is, the camera system control unit 51 executes the imaging light receiving operation with the AE lock in the same manner as the nth imaging light receiving operation.

  Similarly, the camera system control unit 51 gradually increases the photometric light receiving time for the subsequent n + 2th sheet. In other words, the n + 2th photometric light-receiving time is added to the n + 1th photometric light-receiving time by adding an extension time obtained by multiplying a deficiency time that is the difference between the target light-receiving time and the photometric light-receiving time in the n + 1st photo by a predetermined ratio. Determine the light reception time. In the example shown in the figure, the photometric light receiving time of the (n + 2) th sheet is longer than the photometric light receiving time of the (n + 1) th sheet by the addition of the extension time, and as a result, exceeds the allowable light receiving time determined for the (n + 2) th sheet. ing. Therefore, the camera system control unit 51 calculates an EV value from the output of the photometric element 39, and executes an AE calculation that determines an exposure value according to the selected photographing mode. And the camera system control part 51 applies the exposure value determined by AE calculation with respect to continuous imaging light reception operation | movement. In addition, even when continuous shooting is continued continuously for the n + 3rd sheet, the n + 4th sheet, etc., the camera system control unit 51 sets the extended time obtained by multiplying the previous shortage time by a predetermined ratio to the previous time. The current photometric light reception time is determined by adding to the photometric light reception time. In this case, the photometric light receiving time is gradually increased until the target light receiving time is reached, and when the target light receiving time is exceeded, it is not further extended. In addition, as a result of gradually increasing the photometric light receiving time, if the photometric light receiving time exceeds the allowable light receiving time, the target light receiving time may not be extended even if the target light receiving time is not reached.

  Next, a flow of a series of processes will be described. FIG. 8 is a flowchart showing mainly photometric operation processing during continuous shooting. The flow starts when the single-lens reflex camera 10 is turned on and can receive a shooting preparation instruction from the user.

  In step S101, the camera system control unit 51 detects whether or not SW1 is turned on, which is turned on when a release button as one of the operation input units 61 is half-pressed by the user. If the camera system control unit 51 detects ON, the camera system control unit 51 proceeds to step S102 and starts a shooting preparation operation.

  In step S <b> 102, the camera system control unit 51 performs charge accumulation of the photometric element 39 using the target light receiving time as the photometric light receiving time. In step S103, the camera system control unit 51 performs a photometric calculation to calculate an EV value as luminance information of the subject, and calculates an exposure value based on the EV value and the set shooting mode. Note that the camera system control unit 51 may perform the charge accumulation operation in the shooting preparation stage not only once but several times.

  In step S104, the camera system control unit 51 waits for SW2, which is a shooting instruction, to be turned on until a preset timer time elapses. SW2 is turned on when the release button is fully pressed by the user.

  If the camera system control unit 51 determines that SW2 is turned on in step S104, the camera system control unit 51 proceeds to step S105 and starts the photographing operation. Specifically, the camera system control unit 51 shifts the mirror unit to the UP state via the camera driving unit 60, and sets the image sensor 48 to the charge accumulation state. In parallel, the aperture of the lens unit 20 is driven via the lens system control unit 23 according to the aperture value calculated in step S103. Furthermore, the camera system control unit 51 causes the focal plane shutter 47 to travel according to the shutter speed calculated in step S103 via the camera driving unit 60. The camera system control unit 51 reads out the image signal obtained by photoelectrically converting the subject image from the image sensor 48 in accordance with the ISO sensitivity calculated in step S103, performs AD conversion, and sends it to the work memory 58.

  The camera system control unit 51 sequentially transfers the image data temporarily stored in the work memory 58 to the image processing unit 55 and starts image processing. The image processing unit 55 performs image processing, filing processing, and the like according to the designated image format, and sends the generated image file to an external memory.

  After completing the shooting operation in step S105, the camera system control unit 51 can continuously move to the next shooting operation. When the first image capturing operation is completed, the camera system control unit 51 determines whether or not it is turned off in step S106. If it is determined that SW2 is turned off, it is determined that the shooting instruction has ended. If it is determined that SW2 remains on, it means that the user has fully pressed the release button, so the camera system control unit 51 determines that the user has instructed continuous shooting. .

The camera system control unit 51, SW2 is continuously in the step S106 proceeds to step S107 if it is determined that the ON state, assigns the photometric light receiving time T _g, to perform the charge accumulated in the metering device 39. Then, in step S108, the camera system controller 51, as described with reference to FIG. 5, once calculated the EV value from the output of the photometric device 39, the photometric light receiving time T _g is, based on the calculated EV value It is determined whether or not the allowable light receiving time T _p is less than the predetermined allowable light receiving time T _p . If the photometric light receiving time _{T g} is allowed photodetection time _{T p} above, the process proceeds to step S109, the camera system control unit 51 uses the EV value calculated from the charge storage results of the photometric device 39 in step S107, and step S103 Similarly, photometric calculation and exposure value calculation are performed. However, during the continuous shooting continue to demand to maintain the frame speed to high speed, since the photometric light receiving time The T _g assigned limited to a short time necessary and sufficient, the charge accumulation multiple times to be performed by the photometric element 39 Rather, it is once in principle. The camera system control unit 51 sets the calculated exposure value as an exposure value to be applied to the photographing operation executed in step S110.

In step S108, if it is determined that the photometric light receiving time T _g is below the allowable receiving time T _p, the camera system control unit 51 does not reflect the charge accumulation results of the photometric device 39. That is, the previous exposure value is set as it is as the exposure value applied to the photographing operation executed in step S110. For example, in the preparation stage for the second image capturing operation, the exposure value calculated in step S103 is set.

In step S110, the camera system control unit 51 executes a shooting operation according to the set exposure value, as in step S105. Further, the image processing unit 55 executes image processing. Then, the camera system controller 51 proceeds to step S111, and calculates the extension time as described with reference to FIG. 7, by adding the extension time in the photometric light receiving time T _g, the photometric light receiving time T _g Update. When the photometric light receiving time _Tg is updated, the process returns to step S106 again. If SW2 is kept on in step S106, continuous shooting is continued. At this time, in step S107, the updated photometric light receiving time _Tg is assigned.

  If SW1 is not turned on in step S101, SW2 is not turned on in step S104, or SW2 is turned off in step S106, the process proceeds to step S112, and the camera system control unit 51 It is determined whether or not is turned off. If it is determined that the power is not turned off, the process returns to step S101. If it is determined that it has been turned off, the series of processing ends.

Further, in the above-described processing in step S108, the camera system controller 51, if it is determined that the photometric light receiving time T _g is below the allowable receiving time T _p, it does not perform the photometric operation and the exposure value calculation. However, the photometry calculation itself and the exposure value calculation itself may be performed uniformly and the result may not be used.

In the above embodiment, the process in the case where the photometric light receiving time _Tg is gradually increased has been described assuming that the subject environment becomes dark. However, the subject environment may become bright just as it may become dark during continuous shooting. If made bright, relative to the photometric light receiving time The T _g is gradually increased until it, it is envisioned that the target light-receiving time is suddenly shortened. In this case, the followability to the change in brightness is not sacrificed, but in terms of continuity of the frame speed, it may suddenly become high speed, and the memory is unexpectedly consumed and the memory is unexpectedly consumed. There is a problem of end. Accordingly, the camera system controller 51, the photometric light receiving time T _g, the excess time is the difference between the target light receiving time T _t, and subtracts the shortened time multiplied by the shortening ratio determined in advance, the photometric light receiving time T _g Is gradually reduced. By executing such processing, the frame speed is gradually increased, so that the user's uncomfortable feeling can be alleviated and rapid memory consumption can be prevented. A result of the gradually decreasing the photometric light receiving time T _g, in the case of below the target light receiving time T _t, the camera system control unit 51 does not photometric light receiving time T _g is shortened more. Further, when the time is excessively shortened, the time may be gradually increased until the target light reception time T _t or the allowable light reception time T _p is reached.

  In the above embodiment, the photometry element 39 receives and outputs the subject image in step S107, that is, calculates the EV value from the photometry signal received and output during the assigned photometry reception time, and corresponds to the EV value. Tolerable time was determined. However, the single-lens reflex camera 10 may be provided with a sensor that detects the luminance of the surrounding environment, and the EV value may be calculated from the output of the sensor. If the photometric light-receiving time is very short, the EV value calculated from the accumulated charge may be far from the actual EV value. It can be expected to be decided.

  In the above embodiment, 4 times is adopted as the maximum amplification factor. Of course, a higher amplification factor can be adopted in consideration of the SN ratio. In this case, when the photometric signal is output with a predetermined maximum amplification factor, the imaging light receiving operation is executed based on the allowable light receiving time as in the above embodiment. At this time, if the photometric light receiving time is insufficient when the photometric signal is output with an amplification factor smaller than the maximum amplification factor, the amplification factor may be increased and the photometric tracking may be performed.

  Therefore, the imaging light receiving operation is executed based on the allowable light receiving time when the brightness of the subject is darker than the predetermined brightness. In other words, when the photometric light reception time is less than the target light reception time determined based on at least one of the brightness of the subject and the imaging cycle in which the image sensor outputs an image signal, based on the allowable light reception time An imaging light receiving operation is executed.

  In the above embodiment, the brightness of the subject environment has been described as uniformly corresponding to the EV value as the luminance. In the Apex calculation, the EV value is an exposure value, which is a control value represented by the sum of an aperture value (AV value) corresponding to the aperture value and an exposure time (TV value) corresponding to the shutter speed. The photometric element 39 directly calculates a luminance value (BV value), and a value obtained by adding a sensitivity value (SV value) corresponding to the ISO sensitivity to the luminance value is a light value (LV value). Appropriate exposure is obtained when the exposure calculation is performed so that the EV value and the LV value are equal. That is, in the above embodiment, it demonstrated on the assumption of appropriate exposure. Therefore, a BV value may be applied as a value calculated from the output of the photometric element 39, and a lookup table corresponding to FIG. 5 may be generated based on the LV value. Of course, if proper exposure is not assumed, adjustment between the EV value and the LV value may be performed based on the difference from the proper exposure.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

10 single lens reflex camera, 11 optical axis, 20 lens unit, 21 lens group, 22 lens mount, 23 lens system control unit, 24 lens memory, 30 camera unit, 31 main mirror, 32 main mirror holding frame, 33 main mirror rotation axis , 34 Main mirror eccentric pin, 35 Focus plate, 36 Penta prism, 37 Eyepiece optical system, 38 Photometric optical system, 39 Photometric element, 40 Viewfinder display unit, 41 Sub mirror, 42 Sub mirror holding frame, 43 Sub mirror rotation axis, 44 Sub mirror eccentric Pin, 45 AF optical system, 46 AF sensor, 47 Focal plane shutter, 48 Image sensor, 49 Main board, 51 Camera system control unit, 52 Rear display unit, 53 Secondary battery, 54 Camera mount, 55 Image processing unit, 56 Circumscribed IF, 57 camera memory, 58 a work memory, 59 display controller, 60 camera driver, 61 operation input unit

Claims (7)

An image sensor that receives a subject image and outputs an image signal;
A photometric element that receives the subject image and outputs a photometric signal;
A calculation unit that calculates the brightness of the subject based on the photometric signal;
When the image sensor continuously outputs the image signal, the photometric light receiving time, which is the time during which the photometric element receives the subject image, is allocated during the imaging light receiving operation by the image sensor. A controller that executes the imaging light reception operation by applying the brightness of the subject calculated in advance by the calculation unit when the allowable light reception time is less than a preset allowable light reception time corresponding to the brightness of Imaging device.   When the photometric light-receiving time is equal to or longer than the allowable light-receiving time, the control unit calculates the calculation unit based on the photometric signal output by the photometric element receiving the subject image during the photometric light-receiving time. The imaging apparatus according to claim 1, wherein the imaging light receiving operation is executed by applying the brightness of the subject.   The control unit determines the permissible time from the brightness of the subject calculated by the calculation unit based on the photometric signal output by the photometry element receiving and outputting the subject image during the photometric light receiving time. The imaging apparatus according to 1 or 2.   The said control part performs the said imaging light reception operation | movement based on the said permissible light reception time, when the said photometry signal is output by the predetermined maximum amplification factor. The imaging device described.   5. The imaging according to claim 1, wherein the control unit performs the imaging light receiving operation based on the allowable light receiving time when the brightness of the subject is darker than a predetermined brightness. 6. apparatus.   The control unit determines the photometric light receiving time based on at least one of brightness of the subject and an imaging cycle in which the imaging device outputs the image signal, and the photometric device receives the subject image. The imaging device according to any one of claims 1 to 5, wherein the imaging light receiving operation is executed based on the allowable light receiving time when it is less than a target light receiving time. A control program for an imaging apparatus comprising: an imaging device that receives a subject image and outputs an image signal; and a photometric device that receives the subject image and outputs a photometric signal,
A reference step of referring to an allowable light receiving time set in advance corresponding to the brightness of the subject environment when the image sensor continuously outputs the image signal;
As a result of the reference in the reference step, when the photometric light receiving time, which is the time during which the photometric element receives the subject image, which is allocated during the imaging light receiving operation by the image sensor, is less than the allowable time, in advance An imaging device control program that causes a computer to execute an imaging step of executing the imaging light receiving operation by applying the calculated brightness of the subject.

Images