JP4819524B2 - IMAGING DEVICE AND IMAGING DEVICE CONTROL METHOD - Google Patents

Description

  The present invention relates to an exposure control technique using both an electronic shutter function for controlling the timing of charge accumulation start or readout in an image sensor and a mechanical shutter function for shielding a light receiving surface of the image sensor with a light shielding blade.

  9 and 10 are sectional views showing a schematic configuration of a single-plate digital single-lens reflex camera. FIG. 9 shows a state when an object image is observed using an optical viewfinder, and FIG. 10 shows a state when an object image is observed using a rear liquid crystal monitor.

  Reference numeral 101 denotes a camera body, and reference numeral 102 denotes an interchangeable lens device that can be attached to and detached from the camera body 101. Reference numeral 102 denotes an interchangeable lens device that is electrically and mechanically connected to the camera body 101 via a known mount mechanism. By changing the type of the interchangeable lens device 102, it is possible to obtain captured images having different angles of view. The interchangeable lens device 102 adjusts the in-focus state by moving the internal imaging optical system 103 along the direction of the optical axis L1. The imaging optical system 103 is also formed with an infrared cut filter.

  Reference numeral 106 denotes a CMOS process compatible sensor (hereinafter referred to as a CMOS sensor) which is one of the amplification type solid-state imaging devices housed in the package 124. The CMOS sensor is capable of random access to arbitrary pixels, is easy to perform thinning readout for generating a display image on the display device 107 described later, and can perform image readout at a high frame rate.

  Reference numeral 156 denotes an optical low-pass filter provided in the optical path from the imaging optical system 103 to the image sensor 106, and is configured so that an unnecessarily high spatial frequency component is not transmitted from the subject onto the image sensor 106.

  Reference numeral 107 denotes a display device including a liquid crystal monitor provided on the back surface of the camera body 101, and the image data of the subject captured by the image sensor 106 is displayed on the display device 107.

  Reference numeral 111 denotes a movable half mirror that splits a light beam from the imaging optical system 103 and guides a part thereof to the optical viewfinder. Reference numeral 105 denotes a focusing screen disposed on the planned image formation plane of the subject, and 112 denotes a pentaprism.

  Reference numeral 109 denotes a lens for observing the image of the subject projected on the focusing screen 105. The focusing screen 105, the pentaprism 112, and the lens 109 constitute a finder optical system. A movable sub-mirror 122 is provided behind the half mirror 111, and deflects a light beam close to the optical axis among the light beams transmitted through the half mirror 111 to the focus detection device 121. The focus detection apparatus 121 of the present embodiment performs focus detection using a phase difference detection method.

  The optical path splitting means composed of the half mirror 111 and the sub mirror 122 can selectively take one of the two states of the first state shown in FIG. 9 and the second state shown in FIG. The optical path dividing means divides the light beam from the imaging optical system 103 in the first state, guides one to the finder optical system, and guides the other to the focus detection device 121. In the second state, the light beam from the imaging optical system 103 is guided to the image sensor 106 as it is.

  A mirror drive mechanism comprising an electromagnetic motor and a gear train (not shown) changes the positions of the half mirror 111 and the sub mirror 122, and switches between the first state and the second state of the optical path dividing means constituted by these. The first state is set when a subject image is observed using an optical viewfinder. The second state is set when observing a subject on the display device 107, when performing a focus detection operation or photometry operation using the image sensor 106, or when shooting a moving image.

  Reference numeral 113 denotes a focal plane shutter as a light shielding unit, and 119 denotes a main switch for switching the power of the camera body on and off. Reference numeral 123 denotes a finder mode switching switch for switching between using the optical finder or the display device 107 to observe the subject. Hereinafter, the setting for observing the subject using the optical finder is referred to as an optical finder mode, and the setting for observing the subject using the display device 107 is referred to as an electronic finder mode. Reference numeral 180 denotes an optical finder information display device for displaying photographing parameters such as a shutter speed and an aperture value when an object is observed using an optical finder.

  Many kinds of shutter devices can be applied to a digital camera having an electronic viewfinder function as compared with a camera having only an optical viewfinder function.

  For example, a form in which a focal plane shutter device having a front curtain and a rear curtain used in a silver halide camera is applied can be considered.

  The focal plane shutter device has two sets of blade units pivotally supported on a shutter substrate. This blade unit forms a parallel link by holding a plurality of divided light shielding blade groups rotatably by two arms. One blade unit acts as a leading blade (also referred to as a leading curtain) that shifts the shutter opening from the shielded state to the open state during exposure. The other blade unit acts as a rear blade (also referred to as a rear curtain) that shifts the shutter opening from the open state to the shield state during exposure. The blade units constituting the leading blade and the trailing blade are respectively connected to a driving member having a driving source such as a spring that applies a biasing force in a predetermined direction and an armature that is attracted and held by the control magnet.

  The blade unit constituting the leading blade is held by a charge lever (not shown) before being photographed to the photographing preparation position where the armature of the driving member contacts the yoke attracting surface of the control magnet, and the shutter opening is shielded. . The blade unit constituting the rear blade is held by the charge lever (not shown) to the shooting preparation position where the armature of the driving member contacts the yoke attracting surface of the control magnet before shooting, and the shutter opening is opened before shooting. The

  By operating a shutter switch (not shown), the charge lever is retracted from the position where the blade unit is held on the yoke suction surface. Each blade unit is held in a state where the armature is attracted to the yoke attracting surface of the control magnet by the magnetic force of the control magnet energized in the dedicated coil. Then, energization of the control magnet corresponding to the blade unit constituting the leading blade is cut off first, and the leading blade opens the shutter opening. After a predetermined time set based on the shutter speed, the control magnet corresponding to the blade unit constituting the rear blade is de-energized and the rear blade blocks the shutter opening. Thus, the imaging surface is exposed. After the travel of these rear blade units is completed, each blade unit is again moved to the shooting preparation position by a charge lever (not shown) and waits for the next shooting.

  FIG. 11 shows the accumulation operation of the image sensor in this camera and the traveling timing of the front and rear blades of the shutter device. The horizontal axis represents time, and the vertical axis represents the position in the vertical direction of the imaging region of the image sensor, that is, the position of the blade in the traveling direction. M101 indicates the position of the last slit forming end of the leading blade that functions as the exposure start position, and M201 indicates the position of the foremost slit forming end of the trailing blade that functions as the light shielding start position. E101 indicates the timing of the reset operation for starting the accumulation of the image sensor, and E201 indicates the timing of the read operation for obtaining a signal corresponding to the charge accumulated in the image sensor. The image sensor starts the accumulation operation before the front blade of the shutter device starts traveling, and performs the reading operation of the image sensor after both the front blade and the rear blade complete the travel. That is, the period during which the image sensor performs the accumulation operation includes the period during which both the leading blades and the trailing blades travel.

  When an electronic finder mode is to be implemented with a camera having such a configuration, the front blade needs to be retracted from the shutter opening in order to capture the subject image with the image sensor during the period when the subject is observed on the display device 107. There is.

  To retract the front blade from the shutter opening, the charge lever is retracted from the position where the blade unit is held on the yoke suction surface, the energization of the coil for the control magnet of the front blade is released, and the front blade is caused to travel. . At this time, energization of the coil for the control magnet of the rear blade is continued, and the rear blade is held at a position retracted from the shutter opening.

  During the electronic finder mode, the yoke attracting surface of the control magnet for the leading blade is exposed, and this exposed state continues until photographing is finished and the blade unit is moved to the photographing preparation position again. If it takes time for the photographer to decide the composition, the time that the yoke attracting surface of the control magnet is exposed becomes longer. Therefore, there is a high possibility that dust will enter the suction surface of the yoke of the control magnet, and the shutter time accuracy will deteriorate due to poor suction of the leading blade caused by this dust, or the armature itself cannot be held due to poor suction. Inconvenience may occur.

  Therefore, it is conceivable to provide a shutter device disclosed in Japanese Patent Laid-Open No. 11-41523 as a configuration that does not cause such a problem.

  This shutter device includes only a blade unit as a rear blade, and controls the exposure time of the image sensor by matching the charge accumulation start of the XY address type image sensor with the running characteristics of the rear blade.

  FIG. 12 shows the accumulation operation of the image sensor in this camera, the travel timing and travel characteristics of the rear blades of the shutter device. M202 indicates the position of the front slit forming end of the rear blade that functions as a light shielding start position. E102 indicates the timing of the reset operation for starting the accumulation of the image sensor, and E202 indicates the timing of the read operation for obtaining a signal corresponding to the electric charge accumulated in the image sensor. The image pickup device starts an accumulation operation according to the set shutter speed, a predetermined time before the trailing blade of the shutter device starts running. The start timing of this accumulation operation is controlled for each line of the image sensor so that the exposure amount is uniform in all regions in accordance with the traveling characteristics of the rear blades that travel while accelerating. The imaging device reads the accumulated charges after the travel of the blade unit as the rear blade is completed.

  According to this configuration, a blade unit as a leading blade is not required, moving image shooting without smearing can be performed, and still image shooting can be performed with a sufficiently accurate shutter operation. Further, there is no inconvenience that the shutter blade accuracy is not deteriorated due to the suction failure of the leading blade, and the armature itself cannot be held due to the suction failure.

  However, the vane unit changes its running characteristics due to changes in the camera body's attitude and operating environment temperature.If these effects are ignored, the exposure time will be reduced especially when a high shutter speed is set. The effect of unevenness increases. When both the front blade and the rear blade are configured with mechanical blade units, they are likely to have an equal effect on both blade units. There is no problem. However, when controlling the timing to start exposure by the reset operation of the image sensor, the extent to which the use environment temperature affects the reset operation and the rear blade may differ greatly, and this effect should be ignored. I can't.

  On the other hand, in Japanese Patent Application Laid-Open No. 2001-235777, a difference in running characteristics between a blade unit as a leading blade and a blade unit as a trailing blade is detected using a photo reflector, and this is reflected in driving of the next blade unit. It is disclosed.

Japanese Patent Application Laid-Open No. 2005-159418 discloses that the traveling characteristics of the blade unit of the leading blade are detected, and the timing at which exposure is started by the reset operation is controlled using the detection result. This configuration can estimate the traveling characteristics of the traveling unit as a rear blade to be traveled immediately before photographing, and thus is highly likely to reduce variations in exposure time of the entire screen.
Japanese Patent Laid-Open No. 11-41523 JP 2001-235777 A JP 2005-159418 A

  However, in the configuration disclosed in Japanese Patent Laid-Open No. 2001-23579, the travel characteristics of the blade unit cannot be detected unless the blade unit as the rear blade actually travels. Therefore, even if the difference between the start timing of the accumulation operation and the traveling characteristics of the blade unit is obtained, this result is reflected in the next and subsequent shootings. If the next and subsequent shootings are performed under the same conditions as when the traveling characteristics of the blade unit are detected, a highly accurate exposure time can be ensured, but this is not necessarily the case. This is because a number of factors such as camera posture, operating environment temperature, humidity, power supply state, number of operations, shooting interval, etc. may affect the running characteristics of the blade unit.

  Further, in the configuration disclosed in Japanese Patent Application Laid-Open No. 2005-159418, the front blade for detecting the travel characteristics, although the exposure time is controlled by the time from the reset operation to the travel of the rear blade. The blade unit is essential.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to more appropriately compensate for variations and deviations in exposure time that occur in each area of the image sensor.

In order to solve the above-described problems, one of the inventions according to the present application is an imaging device that accumulates electric charge according to a received light amount, a light shielding unit that travels a light shielding blade that shields a light receiving surface of the imaging device, and the imaging Control means for controlling the timing of scanning for starting charge accumulation for each element region, setting means for setting a target exposure time of the image sensor, and a position where the traveling direction of the light shielding blades is different Detecting means having a plurality of detecting portions for detecting that the end of the light shielding blade on the traveling direction side has passed, and the charge determined based on the detection result of the detecting means for each region of the image sensor . calculation means from the start of the accumulation for calculating the ratio of the target value corresponding to the target exposure time set by said setting means and the exposure time to be shielded by the light shielding blade, said operation means Ri using the correction value based on the calculated ratio, it is an image pickup apparatus characterized by having a correction means for performing luminance correction on the image data based on the charge stored in said imaging element .

Similarly, in order to solve the above-described problem, one of the inventions according to the present application is an image sensor that accumulates electric charge according to the amount of received light, a light shielding unit that travels a light shielding blade that shields the light receiving surface of the image sensor, Control means for controlling the scanning timing for starting charge accumulation for each area of the image sensor and the traveling direction end of the light shielding blade provided at a different position in the traveling direction of the light shielding blade pass. A detection unit having a plurality of detection units for detecting the detection, a setting step of setting a target exposure time of the image sensor, and the detection for each area of the image sensor eyes corresponding to the target exposure time set in the setting step and the exposure time to be shielded by the light shielding blade from the start of the accumulation means of the detection result the charge that is determined based on A calculating step of calculating a ratio of the value using the correction value based on the ratio calculated in the calculating step, a correction step of performing brightness correction on the image data based on the charge stored in said imaging element, It is characterized by having.

  Further, the present invention is a program characterized by including a program code for causing a computer to execute the above-described image image data correction method.

  According to the present invention, it is possible to obtain image data that compensates for variations and deviations in exposure time that occur in each region of the image sensor.

  The best mode for carrying out the present invention will be described below with reference to the drawings. In the following, a digital single lens reflex camera will be described as an example, but the present invention is not limited to this. As long as the imaging device includes an imaging device that outputs image data as an electrical signal and has a configuration that controls the exposure time of the imaging device by using a blade unit as a light shielding member, an imaging device having another configuration can also be used. It is possible to apply the present invention.

  The schematic configuration of the digital single-lens reflex camera according to the present embodiment is the same as that shown in FIGS. 9 and 10 described as the prior art. In other words, the optical path splitting unit including the half mirror 111 and the sub mirror 122 is provided, and a configuration capable of selectively taking either the first state shown in FIG. 9 or the second state shown in FIG. is doing. Further, there is a configuration in which an optical finder mode that is a setting for observing a subject using an optical finder and an electronic finder mode that is a setting for observing a subject using a display device 107 are switched.

  FIG. 1 shows a block diagram of a circuit of a digital single-lens reflex camera 200 according to the present embodiment.

  Reference numeral 201 denotes a lens unit including the imaging optical system 103, and 202 denotes a lens driving device. When the lens driving device 202 moves a zoom optical system (not shown) and the imaging optical system 103 included in the lens unit 201, zoom control, focus control, and the like are performed. Reference numeral 203 denotes a shutter device as a light shielding unit, and in this embodiment, a shutter unit corresponding to a rear blade of a so-called focal plane type shutter device used in a single-lens reflex camera is provided. Reference numeral 204 denotes a shutter drive device for driving the shutter device 203, which is composed of the above-described charge lever and control magnet.

  FIG. 2 shows a schematic configuration of the shutter device 203. Reference numeral 301 denotes a shutter base plate, and reference numeral 301a denotes a shutter opening formed in the shutter base plate 301 so as to allow the light beam reflected by the subject to pass therethrough. Reference numeral 302 denotes a first arm, and reference numeral 303 denotes a second arm, which are rotatably attached around an axis provided on the shutter base plate 301. Reference numerals 311 to 314 denote rear blades, which are rotatably supported by the dowels provided on the first arm and the dowels provided on the second arm. A blade unit in which parallel links are formed by the first arm 302, the second arm 303, and the rear blades 311 to 314 as light shielding blades is formed.

  The coil for the control magnet of the shutter driving device 204 is turned off from the state shown in FIG. 2 moved to the shooting preparation position by the charge lever. Then, the shutter opening 301a starts to be covered in the order of the rear blade 311, the rear blade 312, the rear blade 313, and the rear blade 314. Reference numeral 311a denotes a slit forming end at the leading end of the trailing blade 311. Charge accumulation is started by the image sensor 205 described later, and the time until the light is shielded by the slit forming end 311a is the area of the image sensor. Exposure time.

  The shutter device 203 shown in FIG. 2 and FIG. 6 to be described later is described in a direction in which the rear blade is located below FIG. 2 at the shooting preparation position, and the blade unit moves upward in FIG. Has been. For convenience of explanation, in FIGS. 11 and 12 described above and FIGS. 7 and 8 described later, the rear blade is described as moving from the upper side to the lower side in the drawing.

  Returning to FIG. 1, reference numeral 205 denotes an image sensor that receives a light beam from a subject, accumulates electric charge according to the amount of light, and generates image data of the subject based on the charge. It corresponds to the element 106. An image signal processing circuit 206 amplifies an analog signal of image data output from the image sensor 205. The image signal processing circuit 206 performs A / D conversion processing for converting image data from analog signals to digital signals, performs various correction processing on the image data after A / D conversion, and performs compression processing on the image data. Or give.

  A timing generation unit 207 outputs a timing signal to the solid-state imaging device 205 and the imaging signal processing circuit 206, and a memory unit 208 temporarily stores image data. Reference numeral 209 denotes a control circuit that controls the overall operation of the image pickup apparatus and calculates a correction parameter for image capturing parameters and image data. Reference numeral 210 denotes a recording medium control interface unit for recording image data on the recording medium 211 or reading image data from the recording medium 211. 211 is a removable recording medium such as a semiconductor memory for recording or reading image data, and 212 is an external interface unit for communicating with an external computer or the like.

  Reference numeral 213 denotes a photometric device that is disposed in the vicinity of the pentaprism 112 and measures the luminance of a subject using a light beam that has entered the optical finder in the optical finder mode. Reference numeral 214 denotes a focus detection device that detects the focus state of the subject using light beams reflected by the half mirror 111 and the sub mirror 122 in the optical finder mode, and corresponds to the focus detection device 121 in FIGS. 9 and 10. Reference numeral 215 denotes an attitude detection device that detects the orientation of the camera body using a gravity sensor. Reference numeral 216 denotes a display device for displaying the subject as a moving image or displaying a captured image in the electronic viewfinder mode, and corresponds to the display device 107 in FIGS.

  Next, a scanning method of the XY address type image sensor will be described. A scan (hereinafter referred to as a reset operation) for removing unnecessary charges accumulated for each pixel of the image sensor or for each line is executed. Then, the accumulation operation is completed by performing scanning for reading out signal charges for each pixel or for each line. Such a function of performing reset scanning and readout scanning with a time difference for each area of the image sensor is hereinafter referred to as a rolling electronic shutter.

  Next, the structure and driving method of the XY address type image sensor will be described with reference to FIGS. 3 and 4, and the rolling electronic shutter operation will be described.

  FIG. 3 shows a configuration of an image sensor that employs an XY address type scanning method. Reference numeral 401 denotes a unit pixel. Reference numeral 402 denotes a photodiode (hereinafter referred to as PD) that converts light into electric charges. Reference numeral 403 denotes a transfer switch that transfers charges generated in the PD by the transfer pulse φTX to an FD described later. Reference numeral 404 denotes a charge detection unit (hereinafter referred to as FD) that temporarily accumulates charges, and reference numeral 405 denotes an amplification MOS amplifier that functions as a source follower. Reference numeral 406 denotes a selection switch for selecting a pixel by a selection pulse φSELV, and reference numeral 407 denotes a reset switch for removing charges accumulated in the FD by a reset pulse φRES. The FD 404, the amplification MOS amplifier 405, and the constant current source 409 described later constitute a floating diffusion amplifier. Then, the charge of the pixel selected by the selection switch 406 is converted into a voltage and output to the readout circuit 413 through the signal output line 408. Reference numeral 409 denotes a constant current source serving as a load of the amplification MOS amplifier 405.

  Reference numeral 410 denotes a selection switch that selects an output signal from the readout circuit 413 and is driven by the horizontal scanning circuit 414. Reference numeral 412 denotes a vertical scanning circuit for selecting the switches 403, 406, and 407.

  The nth scanning line selected by the vertical scanning circuit 412 in each of φTX, φRES, and φSELV is assumed to be φTXn, φRESn, and φSELVn.

  FIG. 4 shows a driving pulse and an operation sequence in the conventional rolling electronic shutter operation. In FIG. 4, the description is made with respect to the n line to the n + 3 line selected by the vertical scanning circuit 412.

  In the rolling electronic shutter operation, a pulse is first applied to φRESn and φTXn from time t41 to t42 on the n line, and the transfer switch 403 and the reset switch 407 are turned on. Then, a reset operation for removing unnecessary charges accumulated in the PD 402 and the FD 404 in the nth line is performed.

  When the reset operation is performed, the transfer switch 403 is turned off at time t42, and an accumulation operation for accumulating the photocharge generated in the PD is started. Next, at time t <b> 44, a pulse is applied to φTXn to turn on the transfer switch 403, and a transfer operation for transferring the photocharge accumulated in the PD 402 to the FD 404 is performed. The reset switch 407 needs to be turned off prior to the transfer operation, and in this figure, the reset switch 407 is turned off simultaneously with the transfer switch 403 at time t42. Here, the accumulation time is from time t42 to time t44.

  After the transfer operation for the nth line is completed, a pulse is applied to φSELVn and the selection switch 406 is turned on, whereby the charge held in the FD 404 is converted into a voltage and output to the reading circuit 413. The signals temporarily held by the reading circuit 413 are sequentially output from the time t46 by the horizontal scanning circuit 412. The time from the start of transfer at time t44 to the end of reading at time t47 is T4read on the n line, and the time from time t41 to time t43 is T4wait on the n + 1 line. Similarly, for other lines, the time from the start of transfer to the end of reading is T4read, and the time from the start of resetting a certain line to the start of resetting the next line is T4wait.

  As described above, in the rolling electronic shutter operation, the timing of accumulation in the upper and lower regions of the image sensor is different, but the time required for each accumulation can be made equal in the upper and lower regions of the image sensor.

  Here, in the present embodiment, the exposure time of the image sensor is controlled by changing the time from the start of the charge accumulation operation by the reset operation to the light shielding by the blade unit.

  In this configuration, since the exposure time of the image pickup device is substantially from when the image pickup device is reset to when it is shielded by the blade unit, it is not necessary to equalize the time required for accumulation in the upper and lower regions of the image pickup device. In the present embodiment, the reset operation of the PD and FD of the image sensor is not performed at equal intervals for each line, but this reset operation needs to be matched to the running characteristics of the rear blades. Here, the traveling characteristic of the rear blade is a characteristic indicating the traveling position of the rear blade with respect to the passage of time when the rear blade is traveling.

  FIG. 5 shows a driving pulse and an operation sequence of the image sensor in the rolling electronic shutter operation of the present embodiment. Similar to FIG. 4, FIG. 5 also describes n lines to n + 3 lines selected by the vertical scanning circuit 412.

  In the electronic front curtain shutter, at time n51 to time t52, first, a pulse is applied to φRESn and φTXn to turn on the transfer switch 403 and the reset switch 407. As a result, a reset operation for removing unnecessary charges accumulated in the PD 402 and the FD 404 in the nth line is performed.

  At time t52, the transfer switch 403 is turned off, and an accumulation operation for accumulating photoelectric charges generated in the PD is started. Next, at time t <b> 54, a pulse is applied to φTXn to turn on the transfer switch 403, and a transfer operation for transferring the photocharge accumulated in the PD 402 to the FD 404 is performed. Note that the reset switch 407 needs to be turned off prior to the transfer operation. In this figure, the reset switch 407 is turned off simultaneously with the transfer switch 403 at time t52. Here, the accumulation time of n lines is from time t52 to time t54.

  After the transfer operation for the nth line is completed, a pulse is applied to φSELVn and the selection switch 406 is turned on, whereby the charge held in the FD 404 is converted into a voltage and output to the reading circuit 413. The signals temporarily held by the reading circuit 413 are sequentially output from the time t56 by the horizontal scanning circuit 412. The time from the start of transfer at time t54 to the end of reading at time t57 is T5read, and the time from time t51 to time t53 is T5wait. At this time t53, the accumulation operation on the (n + 1) th line starts. Similarly, in the other lines, the time from the start of transfer to the end of reading is T5read, but the time T5wait from the start of resetting PD and FD on one line to the start of resetting PD and FD on the next line is equal. It is not an interval. The time T5wait from the start of resetting PD and FD on one line to the start of resetting PD and FD on the next line is such that the time until the running characteristics of the trailing blades pass is almost the same for all lines. In addition, the timing is controlled so as to follow the running characteristics of the rear blade.

  However, even though the trailing blade running characteristics can be predicted to some extent, the image pickup device reset operation is delayed since it changes depending on many factors such as the camera posture, operating environment temperature, humidity, power supply status, number of operations, and shooting interval. It is difficult to match the running characteristics of the blades.

  In view of this, in the present embodiment, processing for reducing variations and deviations in exposure time for each region of the image sensor is performed by a method described later.

  Here, an operation at the time of shooting of the digital single lens reflex camera in the present embodiment will be described. Here, a case where the optical finder mode is set as the finder mode will be described as an example.

  When the main switch 119 is operated and the power is turned on, the power of the imaging system circuits such as the image signal processing circuit 206 and the timing generator 207 is turned on.

  When a release button (not shown) is pressed by one step and instructed to enter a shooting preparation operation, the control circuit 209 causes the photometric device 213 to perform photometry to determine subject brightness. The control circuit 209 determines an appropriate shutter speed (hereinafter referred to as a target exposure time) and an aperture value in accordance with the determined subject brightness. Further, the control circuit 209 extracts the high frequency component of the subject based on the signal output from the focus detection device 214 and calculates the distance to the subject.

  The lens driving device 202 is caused to adjust the position of the lens unit 201 so that the target determined to be the main subject by driving the lens unit is in a focused state. When the main subject is in focus, the user is notified of this by a method such as lighting a sound or a focus detection frame.

  Then, using the correction table storing a plurality of factors such as the camera posture, operating environment temperature, humidity, power supply state, number of operations, shooting interval, etc., the traveling characteristics of the blade unit, which is the rear blade, are estimated, and the imaging device 205 Calculate the reset operation timing for each line.

  When a release button (not shown) is pressed one more step and instructed to start photographing, the control circuit 209 jumps up the optical path dividing means composed of the half mirror 111 and the sub mirror 122 to the state shown in FIG.

  The reset operation of the image sensor 205 is started, and after the time corresponding to the determined target exposure time has elapsed, the travel of the blade unit as the rear blade is started. Note that the timing of starting the travel of the blade unit also takes into account the time from when the shutter drive device 204 outputs a signal for starting the travel of the blade unit until the slit forming end of the rear blade 311 covers the image sensor 205. To be determined.

  Then, after the travel of the blade unit is completed and the shutter opening 301a is completely covered by the rear blades 311 to 314, the image sensor 205 performs a reading scan of the accumulated charges for each line.

  When the electronic finder mode is set as the finder mode, the optical path dividing means composed of the half mirror 111 and the sub mirror 122 is flipped up before the release button is pushed one step to the state shown in FIG. The image sensor 205 periodically performs a reading operation, and continuously displays the subject image on the display device 216. Then, an appropriate shutter speed and aperture value are determined based on the image data obtained from the image sensor 205, and the position of the lens unit 201 is adjusted to the lens driving device 202 so that the target determined as the main subject is in focus. Let Then, the reset operation of the image sensor 205 is performed in accordance with the timing when the release button is further pushed one step, and the blade unit is caused to travel.

  When the photographing operation ends, the image data output from the image sensor 205 is amplified by the image signal processing circuit 206, further A / D converted, and written to the memory unit 208 by the control circuit 209.

  After that, the image data stored in the memory unit 208 is subjected to gain correction, which will be described later, by the control circuit 209, and the corrected image data is recorded on the removable recording medium 211 via the recording medium control interface unit 210. .

  Here, in the present embodiment, as shown in FIG. 6, blade detection means 321 and 322 are provided at a position where the slit forming end 311 a of the rear blade 311 begins to cover the imaging region of the image sensor 205 and a position where the covering ends. ing. The blade detection means 321 and 322 detect the timing at which the slit forming end 311a of the rear blade 311 passes at each position. For example, a photo interrupter may be used for the blade detection units 321 and 322.

  The control circuit 209 calculates a difference between the timing of the reset operation in the line superimposed on the detection position of each of the blade detection units 321 and 322 and the timing of passage of the slit forming end 311a detected by each of the blade detection units 321 and 322. Ask. The obtained two difference values are the actual exposure times in the blade detection means 321 and 322.

  The actual exposure time and the target exposure time are compared, and the control circuit 209 performs gain correction on the image data obtained by the shooting at that time according to the comparison result. If the target exposure time is equal to the actual exposure time obtained by the blade detection means 321, 322, gain correction by the control circuit 209 is not necessary. However, if at least one of the actual exposure time obtained by the blade detection unit 321 and the actual exposure time obtained by the blade detection unit 322 is different from the target exposure time, the gain correction differs for each region of the image data. To correct the brightness of the image data.

  FIG. 7 shows the accumulation operation of the image sensor and the travel timing of the rear blades of the shutter device in this embodiment. M21 indicates an ideal position of the front slit forming end of the rear blade that functions as a light shielding start position, and M22 indicates an actual position of the front slit forming end of the rear blade. E11 indicates the timing of the reset operation for starting the accumulation of the image sensor, and E21 indicates the timing of the read operation for obtaining a signal corresponding to the electric charge accumulated in the image sensor. The blade detection means 321 detects the passage of the rear blade 311 through the slit forming end 311a at the uppermost line of the image pickup device of FIG. 7 and the blade detection means 322 detects the lowermost line of the image pickup device of FIG.

  The target value from when the reset operation of the image sensor is started from the top line until the image sensor starts to be covered by the blade unit is t01, and the actual time required is tA. The target value from when the reset operation of the image sensor is started at the lowest line until the image sensor is completely covered by the blade unit is t02, and the actual time required is tB.

First, since the value of tA with respect to t01 is considered to be a shift in the actual start timing of the blade unit with respect to the target value, it can be considered that the exposure time has changed by the following expression with respect to the entire image data. .
tA / t01 (1)

Next, the deviation of the shape of the actual traveling characteristic from the shape of the traveling characteristic that is the target value of the blade unit is obtained by the following equation for each line by approximating the traveling characteristic of the blade unit to a linear function.
(TB−tA) / (t02−t01) × n / V (2)
Here, V is the total number of lines of the image sensor, and n is the number of lines from the top of FIG.

The exposure time is shifted from the target value in each line of the image sensor by the amount expressed by the equations (1) and (2). Therefore, if the gain correction represented by the following formula with the reciprocal number taken into consideration is performed on the pixels corresponding to each line, image data corresponding to the image data when the exposure time is matched with the target value can be obtained. Can do.
1 / {(tA / t01) × (tB−tA) / (t02−t01) × n / V} × Y (3)
However, Y represents the value of the luminance signal of the pixel that is the target for gain correction of the image data.

  FIG. 8 shows the concept of gain correction represented by the equation (3). Luminance by gain correction, taking into account the deviation of the travel start timing of the blade unit and the deviation of the actual running characteristic shape from the target value approximated by the linear expression with respect to the luminance signal of the image data obtained by shooting This shows that correction is being performed.

  Note that the method for compensating for the difference between the actual exposure time and the target exposure time is not limited to this.

  For example, Equation (2) is obtained as a linear function, but it may be obtained as a function of a quadratic or higher in consideration of the determined shutter speed. Also, instead of the equation (3), gain correction values are stored in advance in the correction table, and the gain correction values are selectively read out according to the combination of the target exposure time, t01, t02, tA and tB values. Also good. Further, another blade detection unit may be arranged between the blade detection units 321 and 322, and more accurate traveling characteristics of the blade unit may be calculated using outputs of more blade detection units.

  Furthermore, the present invention can be applied not only to the rear blade but also to the case where the front blade that defines the start timing of the exposure time is configured by the blade unit of the shutter device. Similar to the blade unit as the rear blade, by detecting the passage timing of the blade unit as the leading blade, the difference between the target values of the travel intervals of the two blade units is obtained. Furthermore, the difference of the running characteristics of the two blade units is also obtained by obtaining in the same manner as the above-described equation (2). By applying gain correction that takes these differences into account for the captured image, it is possible to appropriately compensate for variations in exposure time that occur in each area of the image sensor, as in the case of using the electronic shutter function of the image sensor as the leading blade. Can do.

  Further, the traveling characteristics of the blade unit can be detected without using the above-described blade detection means. For example, the reset operation of the image sensor is started for a subject having uniform brightness, and after the appropriate time has elapsed, the travel of the blade unit as the rear blade is started. If the timing for performing the reset operation of the image sensor coincides with the traveling characteristics of the blade unit, the brightness of the image data obtained at this time should be uniform in the traveling direction of the rear blade. If the brightness is not uniform and variation occurs, it is possible to determine the deviation of the travel characteristics of the blade unit with respect to the timing of the reset operation from the variation. According to this method, the travel characteristics of the blade unit can be obtained only by using the output of the image sensor without providing a dedicated sensor for detecting the movement of the blade unit.

  Note that the brightness correction process described above may be performed on a device other than the camera that has taken the image. Values corresponding to the target exposure time, t01, t02, tA, and tB are stored in a recording medium in association with image data obtained by photographing, and the above-described gain correction is performed by the image processing apparatus that has read the image data. It is also possible. In other words, if there is information indicating the timing of the reset operation for each area of the image sensor when the image data is obtained and information indicating the running characteristics of the blade unit, the image data is generated from the comparison result of these differences and the like. Luminance correction can be performed by an image processing device different from the imaging device. At this time, a program having a program code read by a computer included in the image processing apparatus in order to achieve the above function is also included in the present invention.

It is a block diagram of the circuit of the digital single-lens reflex camera concerning this embodiment. It is a figure which shows schematic structure of the shutter apparatus concerning this embodiment. It is a figure which shows the structure of the image pick-up element which takes the XY address type scanning method. It is a figure which shows the drive pulse and operation | movement sequence in the conventional rolling electronic shutter operation | movement. It is a figure which shows the drive pulse and operation | movement sequence of an image pick-up element in the rolling electronic shutter operation | movement of this embodiment. It is a figure for demonstrating the arrangement position of the blade | wing detection means of the shutter apparatus in this embodiment. It is a figure which shows the accumulation | storage operation | movement of the image pick-up element in this embodiment, and the driving | running | working timing of the rear blade | wing of a shutter apparatus. It is a figure which shows the concept of the gain correction in this embodiment. It is sectional drawing which shows schematic structure of the single plate type digital single-lens reflex camera with which the optical finder mode was set. It is sectional drawing which shows schematic structure of the single plate type digital single-lens reflex camera with which electronic finder mode was set. It is a figure which shows the accumulation | storage operation | movement of the image pick-up element in the conventional camera, and the driving | running | working timing of the front blade | wing and rear blade | wing using a blade | wing unit. It is a figure which shows the accumulation | storage operation | movement of another image pick-up element in the conventional camera, the timing of the reset operation | movement of the front blade | wing using an electronic shutter function, and the travel timing of the back blade | wing using a blade | wing unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 200 Digital single-lens reflex camera 201 Lens part 202 Lens drive device 203 Shutter apparatus 204 Shutter drive apparatus 205 Imaging device 206 Image signal processing apparatus 207 Timing generation part 208 Memory part 209 Control circuit 210 Recording medium control interface part 211 Recording medium 212 External interface part 213 Photometry device 214 Focus detection device 215 Attitude detection device 216 Display device 301 Shutter base plate 302 First arm 303 Second arm 311, 312, 313, 314 Lead blade 321, 322 Blade detection means

Claims (4)

An image sensor that accumulates charges according to the amount of light received;
A light shielding means that travels a light shielding blade that shields the light receiving surface of the imaging element;
Control means for controlling the timing of scanning for starting charge accumulation for each region of the image sensor;
Setting means for setting a target exposure time of the image sensor;
Detection means having a plurality of detection units that are provided at different positions in the traveling direction of the light shielding blade and detect that the end of the light shielding blade on the traveling direction side has passed,
The exposure time from the start of the accumulation of the electric charge determined based on the detection result of the detection means for each area of the image sensor until the light is shielded by the light shielding blade and the target set by the setting means A calculation means for calculating a ratio with a target value corresponding to the exposure time ;
An image pickup apparatus comprising: correction means for performing luminance correction on image data based on charges accumulated in the image pickup device using a correction value based on a ratio calculated by the calculation means . Having luminance acquisition means for acquiring subject luminance;
The imaging apparatus according to claim 1, wherein the setting unit sets the target exposure time based on the subject luminance acquired by the luminance acquisition unit.   The imaging apparatus according to claim 1, wherein the correction unit performs the luminance correction by performing different gain correction for each region of the image data. An image sensor that accumulates charges according to the amount of light received, a light shielding means that travels a light shielding blade that shields the light receiving surface of the image sensor, and a scanning timing for starting accumulation of charges for each region of the image sensor And a detection unit having a plurality of detection units that are provided at different positions in the traveling direction of the light shielding blade and detect that the end of the light shielding blade on the traveling direction side has passed. An apparatus control method comprising:
A setting step for setting a target exposure time of the image sensor;
The exposure time from the start of accumulation of the electric charge determined based on the detection result of the detection means for each area of the image sensor until the light is shielded by the light shielding blade and the target set in the setting step A calculation step for calculating a ratio with a target value corresponding to the exposure time ;
A correction step of performing luminance correction on image data based on the electric charge accumulated in the image sensor using a correction value based on the ratio calculated in the calculation step. Method.

Images