JP2010148045A - Imaging device and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a brightness uniformly in an imaging surface, and to vary a depth of field in an imaging surface. <P>SOLUTION: When controlling linearly operating reset scanning so that an exposure time becomes short gradually for the vertical position of the imaging surface, an aperture is stepped down (F-number is made large) in an area with the long exposure time to correct to make uniform the brightness in the imaging surface, and the aperture is controlled to release the aperture gradually (F-number is made small), as the exposure time becomes short. The brightness in the imaging surface becomes uniform approximately by controlling the aperture. Additionally, the depth of field becomes the deepest by making an F-number large in an area with the long exposure time, and the depth of field becomes shallow gradually by making the F-number small as the exposure time becomes short. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus and an image pickup method for picking up images having different depths of field within an image pickup surface.

  In recent years, an imaging apparatus such as a single-lens reflex type digital camera (hereinafter, appropriately referred to as a digital single-lens reflex camera) is equipped with a live view function and a monitoring mode for displaying an image obtained by capturing a subject in a moving image. Products have been commercialized.

  For example, a focal plane shutter is used as the shutter of such an imaging apparatus. The focal plane shutter is composed of two curtains called a front curtain and a rear curtain. By opening and closing the front curtain and the rear curtain, the exposure operation for an image sensor such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor provided in the image pickup apparatus is controlled.

  Specifically, before the release button provided on the imaging apparatus is pressed, the front curtain is in a closed state and the rear curtain is in an open state. When shooting is started by pressing the release button, the front curtain opens and an exposure operation for the image sensor is performed. Then, the rear curtain is closed according to a preset shutter speed and exposure time, and the exposure operation is completed. At this time, the time difference through which the leading edge positions of the front curtain and the rear curtain pass is the exposure time for the image sensor. Further, the length of the exposure time is determined by the shutter speed.

  By the way, when the live view function or the monitoring mode is used, since it is necessary to shoot in a moving image, the front curtain of the focal plane shutter is normally open. Here, in the case of the focal plane shutter using the front curtain by the curtain body, when shooting is started by pressing the release button, it is necessary to once close the opened front curtain and then open the front curtain again. For this reason, there is a time lag from when the release button is pressed until the actual shooting is started.

  Therefore, recently, the operation of the front curtain of the focal plane shutter is performed by electronically controlling the exposure operation of the image sensor instead of the curtain of the curtain. For example, in Patent Document 1 below, the front curtain of the focal plane shutter is provided by sequentially supplying a reset signal for causing each pixel of the image sensor to perform a reset operation in units of pixel lines and starting the exposure operation of the image sensor. A technique for electronic control is described.

Japanese Patent No. 3988215

  By the way, in the conventional focal plane shutter using two curtains as the front curtain and the rear curtain, the operations of the front curtain and the rear curtain are substantially the same. Therefore, as shown in FIG. 10A, the exposure time in the captured image is constant. Therefore, the exposure amount in the captured image is substantially uniform.

  On the other hand, when the electronic front curtain is used, for example, when the reset signal is supplied at a constant timing for each pixel line and the front curtain is operated at a constant speed, the operation of the front curtain is captured. It is linear with respect to the vertical position of the surface. The rear curtain operates in an accelerating manner with respect to the vertical position of the imaging surface as in the conventional case.

  In this case, since the operations of the front curtain and the rear curtain do not match, the exposure times in the captured image are different as shown in FIG. 10B. Therefore, the exposure amount in the captured image is different, and the brightness is not uniform. Further, as shown in FIG. 10C, the difference in exposure time becomes more conspicuous as the shutter speed becomes shorter.

  As a method of uniformly correcting the brightness in the captured image, for example, a method of adjusting a difference in exposure amount by gain conversion or an operation of the front curtain is not linear, and is indicated by a dotted line in FIGS. 10B and 10C. In this way, a method of controlling to approach the operation of the rear curtain can be considered.

  However, the conventional correction method can obtain the effect of making the brightness uniform in the captured image, but cannot obtain the other effects.

  Accordingly, an object of the present invention is to provide an imaging apparatus and an imaging method capable of correcting the brightness in a captured image uniformly and varying the depth of field in the captured image.

In order to solve the above-described problem, the first invention starts exposure by sequentially storing charges obtained by photoelectric conversion in which a plurality of pixels are arranged in a matrix and the irradiated light is sequentially stored for each line. An image sensor that outputs an image signal;
Shutter means that operates to shield the image sensor;
A diaphragm means for adjusting an exposure amount for the image sensor;
Control means for controlling the imaging element and the diaphragm means,
The control means
Control the exposure start timing by the image sensor so that an exposure time difference occurs for each line with respect to the exposure time determined based on the exposure start timing by the image sensor and the light shielding timing by the shutter means,
The imaging apparatus controls the diaphragm means so that the exposure amount for each line becomes substantially uniform according to the exposure time difference.

In the second aspect of the invention, a plurality of pixels are arranged in a matrix, and exposure is started by sequentially accumulating charges, which are converted by photoelectric conversion of the irradiated light for each line, and output as an imaging signal. The exposure start timing by the image sensor is controlled so that there is a difference in exposure time for each line with respect to the exposure time determined based on the exposure start timing by the element and the light shielding timing by the shutter means that operates to shield the image sensor. And
In this imaging method, the diaphragm means for adjusting the exposure amount for the image sensor is controlled so that the exposure amount for each line becomes substantially uniform in accordance with the exposure time difference.

  As described above, in the first and second inventions, a plurality of pixels are arranged in a matrix, and exposure is started by sequentially accumulating charges, which are converted by photoelectric conversion, for each line, for each line, The image sensor so that an exposure time difference is generated for each line with respect to the exposure time determined based on the exposure start timing by the image sensor output as an image signal and the light shielding timing by the shutter means that operates to shield the image sensor. Since the exposure start timing is controlled and the aperture means for adjusting the exposure amount for the image sensor is controlled so that the exposure amount for each line becomes substantially uniform according to the exposure time difference, the exposure in the captured image is controlled. The amount can be made substantially uniform, and the depth of field in the captured image can be varied.

  The present invention controls an exposure start timing by an image sensor so that an exposure time difference is generated for each line, and adjusts an exposure amount for the image sensor so that the exposure amount for each line becomes substantially uniform according to the exposure time difference. The means is controlled. Therefore, there is an effect that the brightness in the captured image can be made substantially uniform and the depth of field in the captured image can be varied.

Embodiments of the present invention will be described below. The description will be given in the following order.
1. 1. First embodiment of the present invention Second embodiment of the present invention

<1. First Embodiment of the Invention>
A first embodiment of the present invention will be described with reference to the drawings. In the first embodiment of the present invention, a front curtain that controls the exposure operation of the image sensor is applied as the front curtain of the focal plane shutter. Then, the difference in exposure amount in the captured image that occurs when the front curtain is linearly controlled is corrected by controlling the aperture. By doing so, the brightness in the captured image can be corrected uniformly, and images with different depths of field can be captured in the captured image.

[Configuration of imaging device]
A configuration of the imaging apparatus applicable to the first embodiment of the present invention will be described. FIG. 1 shows a configuration of an example of an imaging apparatus 1 applicable to the first embodiment of the present invention. The imaging apparatus 1 includes a camera unit 10, an image signal processing unit 11, a display unit 12, a control unit 13, an operation unit 14, a memory controller 15, and an SDRAM (Synchronous Dynamic Random Access Memory) 16.

  The camera unit 10 includes an optical system 21, an iris (aperture) 22, an image sensor 23, a lens driving unit 25, an aperture driving unit 26, and a timing generation circuit (TG; Timing Generator) 27.

  The optical system 21 includes a lens, a focus mechanism, a zoom mechanism, and the like. The focus mechanism and the zoom mechanism are driven by a drive signal output from the lens drive unit 25 based on the control of the control unit 13 described later, and focus, zoom / wide, and the like are adjusted. The iris 22 has an aperture adjustment mechanism, and is driven by a drive signal output from the aperture drive unit 26 based on the control of the control unit 13 to adjust the amount of light. A subject image incident from the outside passes through the optical system 21 and the iris 22 and is formed on the image sensor 23.

  The image sensor 23 is composed of an image sensor such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor, for example, converts irradiated light into an electrical signal by photoelectric conversion, and outputs it as an image signal. Further, the image sensor 23 is driven in accordance with a timing signal output from the timing generation circuit 27 based on the control of the control unit 13.

  Although not shown, the rear curtain of the focal plane shutter is provided between the optical system 21 and the image sensor 23. The rear curtain operates such that the tip thereof moves from the lower part to the upper part of the image sensor 23 so as to shield the image sensor 23 from light. The image sensor 23 is inverted and arranged so that the upper part is positioned below the image pickup apparatus 1. This is because the top and bottom and the left and right of the image formed on the imaging surface of the imaging device 23 via the lens are inverted.

  The lens driving unit 25 generates a driving signal for operating the lens 21 based on the control of the control unit 13. The aperture drive unit 26 generates a drive signal for operating the iris 22 based on the control of the control unit 13. The timing generation circuit 27 generates various timing signals for operating the image sensor 23 based on the control of the control unit 13.

  The image signal processing unit 11 uses the SDRAM 16 as a buffer as necessary, and converts the digital image pickup signal output from the image pickup element 23 into image data including, for example, a luminance signal and a color difference signal. The image signal processing unit 11 also performs various types of processing such as image quality adjustment such as γ (gamma) correction and white balance correction, color tone correction, and sharpness correction.

  The display unit 12 is composed of, for example, an LCD, converts the image data generated by the image signal processing unit 11 into a displayable format, and displays the converted image data, which is used as a viewfinder. The captured image displayed on the display unit 12 is displayed so that the upper part of the imaging surface of the image sensor 23 is positioned above the display unit 12.

  The operation unit 14 is provided with various operators used to operate the imaging apparatus 1 and outputs a control signal corresponding to an operation on each operator. For example, a power key for switching power ON / OFF, a mode switching key for switching an operation mode in the imaging apparatus 1 such as a shooting mode and a playback mode, a shooting mode switching key for switching shooting condition settings, a key for moving a cursor, etc. Is provided. Further, the operation unit 14 operates a release button used when taking a still image with the imaging apparatus 1, and controls the focus, aperture, zoom, and the like of the optical system 21 and the iris 22 when shooting a moving image or a still image. An operator for performing the operation is also provided.

  The control unit 13 uses a RAM (Random Access Memory) 18 as a work memory, and controls the entire operation of the imaging apparatus 1 according to a program stored in advance in a ROM (Read Only Memory) 17. Further, the control unit 13 generates control signals for controlling the optical system 21, the iris 22, and the image sensor 23 based on the control signal corresponding to the operation on the operation unit 14, and the lens driving unit 25 and the diaphragm driving unit. 26 and the timing generation circuit 27. It should be noted that the ROM 17 also stores in advance parameters used for various signal processing on the digital imaging signal in the image signal processing unit 11.

  The memory controller 15 is connected to the recording medium 20, and performs recording control of data on the recording medium 20 and reproduction control of data recorded on the recording medium 20. As the recording medium 20, for example, a removable nonvolatile memory such as a memory card can be used. Also, a recordable optical disc can be used as the recording medium 20. Furthermore, a removable hard disk or a built-in hard disk in the imaging apparatus 1 can be used as the recording medium 20.

  FIG. 2 shows an exemplary configuration of the image sensor 23. The image sensor 23 is an XY address type image sensor, and includes pixels 31, 31,..., Column ADC (Analog Digital Converter) units 32, 32,..., Horizontal switches 33, 33,. A scanning circuit 35 and a horizontal scanning circuit 36 are provided. In this example, a column AD (Analog / Digital) system that performs parallel processing for each pixel column, converts an analog signal output from the pixels 31, 31,... Into a digital signal and outputs the digital signal is used. Will be described. Further, in this example, only the pixel group of 4 lines × 4 columns is shown for easy explanation.

  In the image sensor 23, a plurality of pixels 31, 31,... Are arranged in a matrix. The outputs from the pixels 31, 31,... For each column are connected in common by a vertical signal line, and are connected to a column ADC unit 32 provided for each column.

  A vertical scanning line connected to the vertical scanning circuit 35 is connected in common to the pixels 31, 31,... For each pixel line. Further, the column ADC unit 32 and the horizontal switch 33 are provided for each column.

  The pixels 31, 31,... Include a photodiode 41, an amplifying element 42, a vertical selection switch 43, and a reset switch (not shown). The photodiode 41 accumulates the irradiated light as a charge by photoelectric conversion. The amplifying element 42 converts the electric charge accumulated in the photodiode 41 into a pixel signal, and amplifies and outputs the pixel signal.

  The vertical selection switch 43 is controlled to be turned ON / OFF by a vertical scanning signal supplied via a vertical scanning line based on control of a vertical scanning circuit 35 described later. When the vertical selection switch 43 is turned on, the charge (pixel signal) accumulated in the photodiode 41 is output.

  Although not shown, the reset switch is controlled to be turned on / off by a reset signal. When the reset switch is turned on, the charge (pixel signal) accumulated in the photodiode 41 is discharged.

  The column ADC unit 32 includes a comparator 44, a counter 45, and a latch circuit 46, converts the analog pixel signal output from the pixel 31 into a digital pixel signal, and outputs the digital pixel signal. The comparator 44 compares the voltage of the pixel signal output from the pixel 31 with the reference voltage, and outputs the comparison result to the counter 45. The counter 45 counts the comparison result from the comparator 44 and outputs it to the latch circuit 46. The latch circuit 46 latches the signal output from the counter 45.

  The horizontal switch 33 is controlled to be turned on / off based on the control of a horizontal scanning circuit 36 to be described later. When the horizontal switch 33 is turned on, a digital pixel signal output from the column ADC unit 32 is output.

  The vertical scanning circuit 35 outputs a vertical scanning signal for controlling the vertical selection switch 43 via a vertical scanning line provided for each pixel line, and outputs it to each pixel 31, 31,. Control to output the accumulated charge.

  The horizontal scanning circuit 36 outputs a control signal for controlling the horizontal switch 33 for each column, and performs control so as to extract a pixel signal output from the column ADC unit 32 provided for each column.

  The method of the image sensor 23 is not limited to the column AD method, and other methods such as a column CDS (Correlated Double Sampling) method using a correlated double sampling method for removing an offset signal for each pixel are applied. May be.

[Operation of imaging device]
Next, the operation of the image pickup apparatus 1 according to the first embodiment of the present invention will be described. When a shutter speed is set by a user operation on the operation unit 14 and shooting is started by operating the release button, a reset signal is output at a timing corresponding to the set shutter speed. At this time, the reset signal is sequentially output for each pixel line from the pixel line side located above the image sensor 23. The output timing of this reset signal is the exposure start timing for the pixel 31.

  Next, the reset switch provided in the pixel 31 is turned ON by the reset signal, and the charge accumulated in the photodiode 41 until then is discharged. After the charge accumulated in the photodiode 41 is discharged, the reset switch is turned off, and the accumulation of the charge by the light irradiated on the photodiode 41 is started. Such an operation corresponds to the operation of the front curtain of the focal plane shutter.

  In the following description, the operation in which the reset switch is turned on by the reset signal, the electric charge accumulated in the photodiode 41 is discharged, the reset switch is turned off, and the exposure is started is described as “reset scanning”. explain.

  Next, after a lapse of a predetermined time, the rear curtain of the focal plane shutter is operated, and the light applied to the photodiode 41 of each pixel 31 is cut off sequentially from the upper part to the lower part of the image sensor 23. The exposure time is the time difference between the leading and trailing curtains passing through a predetermined position by reset scanning at this time.

  When the rear curtain operates to block light to the photodiode 41, the horizontal switch 33 is turned on by the control of the horizontal scanning circuit 36, and a vertical scanning signal is received from the vertical scanning circuit 35 according to the operation of the rear curtain. Output is sequentially performed for each pixel line, and the vertical selection switch 43 is turned ON. Then, the charge (pixel signal) accumulated in the photodiode 41 is read out, A / D converted in the column ADC unit 32, and output. Then, the output pixel signal is supplied to the image signal processing unit 11 as an imaging signal, and predetermined signal processing is performed.

  As described above, since the image pickup device 23 is arranged upside down and left and right, when viewed from the image pickup apparatus 1, the reset scanning and the rear curtain are performed as shown in FIG. It moves so as to move from the lower part to the upper part with respect to the imaging surface. That is, when viewed from the image pickup device 23 side, the reset scanning and the rear curtain operate from the upper part to the lower part with respect to the image pickup surface. Further, the reset scanning position and the leading edge position of the rear curtain move so as to be substantially parallel.

[Brightness correction method]
Next, a method for uniformly correcting the brightness in the imaging surface will be described. As described above, in the first embodiment of the present invention, the front curtain of the focal plane shutter is operated by reset scanning of the image sensor 23. The operation of the front curtain by reset scanning is determined by the output timing of the reset signal. For example, when a reset signal is output at regular time intervals for each pixel line, the leading curtain by reset scanning operates so that the relationship between the time and the vertical position of the imaging surface is linear.

  On the other hand, since the rear curtain is mechanically controlled as in the conventional case, the rear curtain operates so as to accelerate the relationship between the time and the position of the imaging surface in the vertical direction. Therefore, when the operation of the front curtain is controlled to be linear, the trajectories of the front curtain and the rear curtain are different, so that the exposure time in the imaging surface is different and the brightness in the imaging surface is uniform. It will disappear.

  Here, for example, as shown in FIG. 4A, when reset scanning (corresponding to the front curtain of the focal plane shutter) that operates linearly is controlled so that the exposure time gradually decreases with respect to the vertical position of the imaging surface. think about. In this case, since the exposure time is gradually shortened according to the vertical position of the imaging surface, the exposure amount in the imaging surface is not uniform. Therefore, as shown in FIG. 4B, the captured image when the operation of the front curtain is controlled in this way is an image that is brighter in the upper part and becomes darker toward the lower part along the shutter direction.

  Therefore, in the first embodiment of the present invention, the iris (iris) is controlled in accordance with the exposure time in order to correct the brightness within the imaging surface to be uniform. Specifically, as shown in FIG. 5A, for example, in a region where the exposure time is long, the aperture is stopped (F-number (Focal number) is increased), and the aperture is gradually opened as the exposure time becomes shorter. The aperture is controlled so that it is reduced (F value is decreased).

  Since the exposure amount is reduced by reducing the aperture, and the exposure amount is increased by opening the aperture, the brightness is substantially reduced as shown in FIG. 5B by making the exposure amount uniform by controlling the aperture. A uniform captured image can be captured.

  4B and 5B show the case where the image is viewed from the image pickup element 23 side, and therefore, the case where the reset scanning and the rear curtain operate from the upper part to the lower part is shown.

  In general, it is known that when the aperture is changed, the depth of field of the captured image changes according to the aperture. Specifically, when the aperture is opened (F value is reduced), the depth of field becomes shallow, and when the aperture is reduced (F value is increased), the depth of field is increased. . For this reason, the depth of field in the imaging plane can be varied by controlling the aperture to uniformly correct the brightness in the imaging plane.

  That is, in the example shown in FIG. 5B, the depth of field is deepest by increasing the F value at the upper part of the imaging surface, and the depth of field is gradually decreased by gradually decreasing the F value toward the lower part. A captured image that becomes shallower can be taken.

  In this way, by shooting images with different depths of field within the imaging surface, for example, when shooting portraits, a distant landscape or a face of a nearby person is focused, It is possible to take an image that the surroundings are blurred.

  The aperture shown in FIG. 5B operates so that the F value up to a predetermined time is constant, the F value is linearly reduced from the predetermined time, and the F value is constant from another predetermined time. However, this is not limited to this example. For example, you may make it operate | move so that F value may become linearly always small.

[Display shooting guide]
As described above, when shooting an image in a mode in which the depth of field is different on the imaging surface (hereinafter referred to as a depth-of-field changing mode as appropriate), the focused area and the blurred area in the same captured image And exist. For this reason, if an image is taken without knowing that the depth of field varies depending on the region in the captured image, it is possible that the image assumed by the user cannot be taken. Therefore, in the first embodiment of the present invention, when shooting is performed in the depth-of-field change mode, a shooting guide indicating that the depth of field varies depending on the area in the captured image is displayed on the display unit 12. It is displayed to the user and is made clear to the user.

  For example, as shown in FIG. 6A, the display unit 12 displays a boundary line 50 indicating a boundary between a region with a deep depth of field and a region with a shallow depth of field as a photographing guide. The region above the boundary line 50 is a region where the depth of field is deep and the focus can be adjusted as a whole. The area below the boundary line 50 is an area where the depth of field is shallow and the area around the focused part is blurred. Therefore, by photographing so that the subject is contained in the area below the boundary line 50, it is possible to focus on the subject and photograph the subject to be blurred.

  In this example, the boundary line 50 as a photographing guide is set so as to be positioned approximately in the center with respect to the vertical direction of the captured image, but this is not limited to this example. In the first embodiment of the present invention, since the depth of field in the captured image is continuously changed from a deep region to a shallow region, for example, the boundary line 50 with respect to the vertical direction of the captured image The display position may be changed according to the depth of the depth of field.

  Further, for example, as shown in FIG. 6B, a contour line 50 ′ of a subject (for example, a person) or the like may be displayed on the display unit 12 as a photographing guide instead of the boundary line 50. In this case, since the subject does not necessarily need to be within the outline 50 ′, it is more preferable to display information indicating that on the display unit 12.

  In this way, by displaying the shooting guide, for example, when shooting a portrait, it is possible to easily set in which area the subject is stored and in which area the landscape is stored.

  Further, as shown in FIGS. 6A and 6B, the display unit 12 displays information indicating that the shooting mode is the depth-of-field change mode. In this way, the user can be notified that the current shooting mode is a special mode. Furthermore, it is more preferable that information indicating that it is possible to start photographing in the depth-of-field changing mode is displayed on the display unit 12.

[Imaging method]
The processing flow of the imaging method according to the first embodiment of the present invention will be described with reference to the flowchart shown in FIG. Note that the following processing is performed under the control of the control unit 13 unless otherwise specified. In this example, only the imaging method in the depth-of-field change mode will be described, and the description of the imaging method in the normal shooting mode will be omitted.

  When a power key provided on the operation unit 14 is turned on, a series of processing is started, and a shooting mode is set by an operation on the operation unit 14 by the user. In step S1, it is determined whether or not the shooting mode is a depth-of-field change mode. If it is determined that the shooting mode set by the user is the depth-of-field change mode, the process proceeds to step S2, and the shutter speed, exposure amount, peripheral light amount, and the like set in advance by the user are determined. Various settings such as exposure are performed. Then, the set value is stored in the RAM 18, for example. In step S3, the currently set shooting mode (depth-of-field changing mode) and shooting guide are displayed on the display unit 12.

  In step S4, it is determined whether to shoot in the depth-of-field change mode. If it is determined to shoot in the depth-of-field change mode, the process proceeds to step S5. In step S5, it is determined whether or not the release button provided on the operation unit 14 is half-pressed. If it is determined that the release button has been pressed halfway, the process proceeds to step S6. On the other hand, if it is determined that the release button is not half-pressed, the process returns to step S2.

  In step S6, when the release button is pressed halfway in step S5, the aperture is opened, and the subject in the photographing guide displayed on the display unit 12 is focused. In step S7, it is used in the depth-of-field change mode based on the set value based on the shutter speed, exposure amount, peripheral light amount, etc. stored in the RAM 18 in step S2, the adjustment range of the lens diaphragm, and the like. Various parameters are calculated. This parameter indicates, for example, the aperture F value at a predetermined time. In step S8, information indicating that shooting in the depth-of-field change mode is possible is displayed on the display unit 12.

  In step S9, it is determined whether or not the release button has been pressed deeply. If it is determined that the release button has been pressed deeply, shooting in the depth-of-field change mode is started, the process proceeds to step S10, and shooting of the subject is performed according to the various parameters calculated in step S7. . In step S11, the captured image is displayed on the display unit 12, and the process returns to step S2. If it is determined in step S9 that the release button has not been pressed deeply, the process returns to step S6.

  On the other hand, if it is determined in step S1 that the shooting mode is not the depth-of-field change mode, the process proceeds to step S12. In step S12, it is determined whether or not to change the shooting mode to the depth of field change mode. If it is determined that the shooting mode is changed to the depth-of-field change mode, the process proceeds to step S13, and the shooting mode is changed to the depth-of-field change mode based on an operation on the operation unit 14 by the user. Then, the process proceeds to step S2.

  If it is determined in step S4 that shooting is not performed in the depth of field change mode, or if it is determined in step S12 that the shooting mode is not changed to depth of field change mode, the shooting mode is set in step S14. The mode is changed to the normal shooting mode, and a series of processing ends. In addition, description is abbreviate | omitted about the imaging | photography method by normal imaging | photography mode in step S14.

<2. Second Embodiment of the Invention>
A second embodiment of the present invention will be described. In the first embodiment described above, the brightness within the imaging surface is uniformly corrected by controlling the diaphragm. However, there may be a case where the brightness in the imaging surface cannot be sufficiently corrected only by controlling the aperture.

  Therefore, in the second embodiment, in addition to controlling the diaphragm, ISO (International Organization for Standardization) sensitivity is controlled to uniformly correct the brightness in the imaging surface.

  The ISO sensitivity can be changed, for example, by controlling a gain circuit (not shown) provided in the image signal processing unit 11 based on the control of the control unit 13 and adjusting the gain for the imaging signal.

  When the front curtain that operates linearly is controlled so that the exposure time gradually decreases with respect to the vertical position of the imaging surface, and the ISO sensitivity is controlled to uniformly correct the brightness in the imaging surface Think. For example, as shown in FIG. 8A, in a region where the exposure time is long, the ISO sensitivity is set low, and the ISO sensitivity is controlled to be gradually increased as the exposure time becomes shorter. Since the exposure amount decreases by lowering the ISO sensitivity, and the exposure amount increases by increasing the ISO sensitivity, the ISO sensitivity is controlled together with the aperture control to make the exposure amount uniform, as shown in FIG. 8B. As described above, it is possible to capture a captured image with substantially uniform brightness.

  Note that when the ISO sensitivity is increased, not only the imaging signal but also noise is amplified, so that not only the brightness but also the noise level may be different within the imaging surface. For this reason, it is preferable that the brightness control based on the ISO sensitivity is used as an auxiliary role for the aperture control.

  As described above, according to the first and second embodiments of the present invention, when the reset scanning and the rear curtain operate so that the exposure time differs with respect to the vertical position of the imaging surface, Alternatively, the ISO sensitivity is controlled to uniformly correct the brightness of the captured image. Therefore, captured images with different depths of field can be captured within the imaging surface.

  Although the first embodiment and the second embodiment of the present invention have been described above, the present invention is not limited to the first embodiment and the second embodiment of the present invention described above. Various modifications and applications are possible without departing from the scope of the present invention. In the embodiment of the present invention, the case where a mechanical rear curtain is used as the rear curtain of the focal plane shutter has been described, but this is not limited to this example. For example, in the image sensor 23, if it is possible to perform an operation from reading out charges from the pixels 31, 31,... You may make it control electronically using.

  For example, as shown in FIG. 9A, when the front curtain and rear curtain that operate linearly are controlled so that the exposure time is gradually increased with respect to the vertical position of the imaging surface, the F value is set in a region where the exposure time is short. The aperture is controlled so that the F value increases as the exposure time increases. By so doing, the brightness in the imaging surface can be corrected uniformly, and a captured image with a shallow depth of field at the top of the imaging surface and a deep depth of field at the bottom can be taken.

  For example, as shown in FIG. 9B, when the front curtain and the rear curtain that operate linearly are controlled so that the exposure time is gradually shortened with respect to the vertical position of the imaging surface, The aperture is controlled so that the value is increased and the F value is decreased as the exposure time is shortened. By so doing, the brightness in the imaging surface can be corrected uniformly, and a captured image with a deep depth of field at the top of the imaging surface and a shallow depth of field at the bottom can be taken.

  Further, for example, when the operation of the front curtain and the rear curtain is controlled to change stepwise, the F value is controlled to change stepwise according to the operation of the front curtain and the rear curtain. It is also possible to change the depth of field stepwise in the plane.

1 is a block diagram illustrating a configuration of an example of an imaging apparatus applicable to a first embodiment of the present invention. It is a block diagram which shows the structure of an example of an image pick-up element. It is a basic diagram for demonstrating reset scanning and operation | movement of a trailing curtain. It is a basic diagram for demonstrating the brightness in an imaging surface. It is a basic diagram for demonstrating an example of the method of correct | amending the brightness in an imaging surface. It is a basic diagram which shows an example of the display at the time of imaging | photography by the depth-of-field change mode. It is a flowchart for demonstrating the flow of a process of an example of the imaging method by 1st Embodiment of this invention. It is a basic diagram for demonstrating the brightness correction by the 2nd Embodiment of this invention. It is a basic diagram for demonstrating an example of the method of controlling the depth of field in an imaging surface. It is a basic diagram for demonstrating the exposure time based on operation | movement of a front curtain and a rear curtain.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 10 Camera part 11 Image signal processing part 12 Display part 13 Control part 14 Operation part 20 Recording medium 21 Optical system 22 Iris 23 Imaging element 25 Lens drive part 26 Aperture drive part 27 Timing generation circuit 31 Pixel 32 Column ADC part 33 Horizontal switch 35 Vertical scanning circuit 36 Horizontal scanning circuit 41 Photodiode 42 Amplifying element 43 Vertical selection switch 50 Boundary line 50 'Outline line

Claims (6)

An image sensor in which a plurality of pixels are arranged in a matrix, and exposure is started by sequentially accumulating charges, which are converted by photoelectric conversion of irradiated light, for each line;
Shutter means that operates to shield the image sensor;
A diaphragm means for adjusting an exposure amount for the image sensor;
Control means for controlling the imaging device and the diaphragm means,
The control means includes
Controlling the exposure start timing by the image sensor so that an exposure time difference occurs for each line with respect to the exposure time determined based on the exposure start timing by the image sensor and the light shielding timing by the shutter means;
An imaging apparatus that controls the aperture means so that the exposure amount for each line becomes substantially uniform in accordance with the exposure time difference. The control means includes
Control the exposure start timing by the image sensor so that the exposure time for each line gradually decreases,
The imaging apparatus according to claim 1, wherein the aperture unit is controlled to be gradually opened as the exposure time for each line gradually decreases. An amplifying unit for adjusting an amplification amount for the imaging signal output from the imaging element;
The control means includes
The imaging apparatus according to claim 1, wherein the diaphragm unit and the amplification unit are controlled so that an exposure amount for each line becomes substantially uniform according to the exposure time difference. And further comprising display means for displaying a captured image based on the imaging signal output from the imaging element,
The display means is
The imaging apparatus according to claim 1, wherein a guide indicating a boundary between different depths of field in the captured image is displayed.   The imaging apparatus according to claim 1, wherein the imaging element is a CMOS image sensor. A plurality of pixels are arranged in a matrix, and exposure is started by sequentially accumulating charges, which are converted by photoelectric conversion of irradiated light, for each line, and the exposure start timing by the image sensor that outputs as an imaging signal, Controlling the exposure start timing by the image sensor so that an exposure time difference is generated for each line with respect to the exposure time determined based on the light shielding timing by the shutter means that operates to shield the image sensor;
An imaging method for controlling a diaphragm unit that adjusts an exposure amount for the image sensor so that an exposure amount for each line becomes substantially uniform according to the exposure time difference.

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