JP2014209744A - Image correction circuit, imaging device and image correction program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image correction circuit, an imaging device and an image correction program, which inhibit variations in an exposure amount caused by operating characteristics of a mechanical shutter.SOLUTION: An imaging device comprises: a mechanical shutter 13 for controlling exposure termination time of a plurality of photoelectric conversion elements arranged in an area image sensor 15 by shifting a light-shielding film; an image data creation section 20 for acquiring an obtained image; and an exposure amount correction section 20a for correcting a gradation value of the exposure amount of each pixel in the image data on the basis of operating characteristics of the mechanical shutter 13 with reference to an LUT (Look Up Table) 53a recorded in a ROM 53.

Description

  The present invention relates to a technique for correcting an image captured by controlling an exposure time with a mechanical shutter.

  2. Description of the Related Art Conventionally, there has been proposed an imaging apparatus that controls the timing of starting exposure in a plurality of photoelectric conversion elements by an electronic shutter and controls the timing of ending exposure by a mechanical shutter (see Patent Documents 1 to 3). In such an imaging apparatus, the exposure time for each photoelectric conversion element is made uniform by controlling the timing at which the electronic shutter starts exposure so that the mechanical shutter follows the timing at which exposure ends. It was. In general, the electronic shutter controls the timing at which exposure is started in units of lines in which a plurality of photoelectric conversion elements are linearly arranged.

Japanese Patent Laid-Open No. 11-41523 JP 2006-101492 A JP 2008-147799 A

However, the timing at which the mechanical shutter ends the exposure depends on the motion of the light-shielding curtain and has non-linear characteristics. Therefore, the timing at which the electronic shutter starts the exposure is controlled so as to follow the timing at which the mechanical shutter ends the exposure. It becomes difficult. That is, there is a problem that the electronic shutter must be operated at a timing having nonlinear characteristics, and the processing load of the electronic shutter control circuit during the electronic shutter operation increases. Further, when the mechanical shutter forms the boundary of the light shielding region so as to intersect the line on the element surface where the photoelectric conversion elements are arranged, the exposure time varies between the photoelectric conversion elements belonging to the line. In such a case, even if the timing at which the electronic shutter starts exposure on a line basis is controlled, it is not possible to suppress variations in exposure amount due to variations in exposure time between photoelectric conversion elements belonging to the line. was there.
The present invention has been made in view of the above problems, and an object of the present invention is to suppress variations in exposure amount caused by operating characteristics of a mechanical shutter.

  In order to achieve the above object, in the present invention, the image acquisition unit acquires an image photographed using a mechanical shutter that controls the exposure time in the plurality of photoelectric conversion elements. The correction unit corrects the image based on the operating characteristics of the mechanical shutter. As a result, it is possible to suppress variations in the exposure amount caused by the operating characteristics of the mechanical shutter by correcting the image after shooting. In the image correction, the image can be corrected without being restricted by the line direction of the photoelectric conversion element. Further, the correction can be performed after the image is taken, and it is not necessary to control the operation timing of the electronic shutter in a complicated manner during the electronic shutter operation.

  Here, the image acquisition unit only needs to acquire an image whose exposure time is controlled by at least a mechanical shutter, and the image correction circuit may be provided in an imaging device provided with the mechanical shutter. It may be provided in another device. In the latter case, when performing correction based on the operating characteristics of the mechanical shutter, the correction unit may acquire information indicating the operating characteristics of the mechanical shutter by, for example, attached information of an image or communication with a photographing apparatus. Furthermore, the photographing apparatus may be an apparatus having not only a function of photographing an image but also other functions such as a camera-equipped mobile phone or a camera-equipped personal computer. Further, the information indicating the operating characteristics of the mechanical shutter may directly indicate the operating characteristics, or may indicate the model of the photographing apparatus, the mechanical shutter mechanism, and the like. The correction unit may generate an image correction rule based on the operating characteristics of the mechanical shutter, or may acquire a correction rule created based on the operating characteristics of the mechanical shutter in advance. This correction rule may be, for example, a LUT (Look Up Table) that defines a correction amount for each pixel position in the image, or may be a function that gives a correction amount using the pixel position in the image as a variable.

Variations in exposure time among a plurality of photoelectric conversion elements can be noticeably generated in an image photographed by the electronic front curtain-mechanical rear curtain shutter system.
The electronic front curtain-mechanical rear curtain shutter system is as follows. First, the timing for starting exposure to a plurality of photoelectric conversion elements is controlled by an electronic shutter. Specifically, exposure is started by starting the accumulation of electric charges in the photoelectric conversion element. Then, by moving the light shielding part by the mechanical shutter, the boundaries of the light shielding regions are moved on the element surfaces of the plurality of photoelectric conversion elements to shield the plurality of photoelectric conversion elements, thereby exposing the plurality of photoelectric conversion elements. Control the timing of termination. Note that in this specification, exposure means a state in which photographing light reaches the photoelectric conversion element and the photoelectric conversion element accumulates electric charge according to the amount of the photographing light.

  In such an electronic front curtain-mechanical rear curtain shutter system, the start and end of exposure in each photoelectric conversion element are realized by different mechanisms. In other words, the operating characteristics of the electronic shutter and the operating characteristics of the mechanical shutter are different, and the difference can be a main factor causing variations in the exposure amount. Therefore, by performing correction based on the difference between the operating characteristics of the electronic shutter and the operating characteristics of the mechanical shutter, it is possible to effectively suppress the variation in the exposure amount.

  As an example of operation characteristics that cause variations in exposure amount, there is a timing characteristic that causes each photoelectric conversion element to start and end exposure. Since the end of exposure by the mechanical shutter is realized by mechanically moving the light shielding portion, the characteristic of the timing of completion of exposure by the mechanical shutter depends on the acceleration motion characteristic of the light shielding portion. On the other hand, since the exposure start timing by the electronic shutter does not depend on the motion characteristic of the light shielding portion, it differs from the timing characteristic at which the mechanical shutter ends the exposure of each photoelectric conversion element. When the characteristics of the timing when the electronic shutter starts exposure of each photoelectric conversion element and the characteristics of the timing when the mechanical shutter ends exposure of each photoelectric conversion element, the exposure time that is the period from the start to the end of exposure This is because each of the photoelectric conversion elements varies. Since the exposure amount increases as the exposure time increases, the exposure amount varies if the exposure time varies. Therefore, based on the difference between the timing characteristics of the electronic shutter and the timing characteristics of the mechanical shutter, the variation in the exposure amount is suppressed by performing a correction that increases the exposure amount as the photoelectric conversion element has a shorter exposure time. Is desirable.

  By the way, the exposure time can be made uniform by controlling the timing at which the electronic shutter starts the exposure so that the mechanical shutter follows the timing at which the exposure is ended as in the prior art. However, the boundary of the light shielding region formed by the light shielding portion of the mechanical shutter on the element surface of the photoelectric conversion element intersects a line in which a plurality of photoelectric conversion elements having a common wiring for starting charge accumulation are arranged in a straight line. In this case, the exposure time cannot be made uniform by the conventional technique. When the boundary of the light shielding region intersects the line, the exposure time varies between photoelectric conversion elements belonging to a single line, and the exposure time between photoelectric conversion elements is controlled even if the timing of starting exposure is controlled in line units. This is because the influence of variations in the number cannot be suppressed. Even in such a case, it is possible to perform correction that suppresses the influence of variations in exposure time among a plurality of photoelectric conversion elements belonging to a single line by performing different corrections on at least two photoelectric conversion elements in the line. It is. Note that the correction unit may correct the image in units of pixels, or may correct the image in units of blocks configured by a predetermined number of pixels.

Examples of the shutter mechanism of a mechanical shutter that can cross the boundary of a light shielding area with a line, for example, a shutter mechanism in which a light shielding portion rotates around a predetermined rotation axis, or a shutter that narrows a non-light-shielded area to one point on the element surface In the mechanism and the like, since the direction of the boundary of the light shielding region is not constant, the boundary of the light shielding region intersects the line.
As in the prior art, the correction of the image may be performed by controlling the timing at which the electronic shutter starts the exposure so that the mechanical shutter follows the timing at which the exposure ends.

  In the case of an electronic shutter, the exposure state of each photoelectric conversion element is controlled by directly electronically controlling the photoelectric conversion elements arranged on the element surface. That is, the electronic shutter controls the exposure state of each photoelectric conversion element by substantially shielding the photographing light on the element surface. On the other hand, the mechanical shutter shields the photographing light by the light shielding portion, but the position in the optical axis direction where the light shielding portion shields the photographing light is not usually on the element surface. This is because it is necessary to prevent the generation of frictional resistance between the light shielding portion and the element surface, or to prevent the photoelectric conversion element on the element surface from being damaged. The mechanical shutter that shields the photographing light at a position different from the element surface shields the photographing light that is not condensed on the photoelectric conversion element on the element surface. That is, in shielding the photographing light condensed on a certain photoelectric conversion element, the mechanical shutter shields the light flux of the photographing light having a certain width. Therefore, by the operation of the mechanical shutter, the photographing light condensed on a certain photoelectric conversion element is gradually narrowed down, and finally the photographing light condensed on the photoelectric conversion element is completely blocked. The exposure of the photoelectric conversion element is completed. Here, the amount of exposure per unit time is smaller in the narrowed-down period than in the period in which the luminous flux of the photographing light condensed on each photoelectric conversion element is not narrowed down by the mechanical shutter. Therefore, if the length of the period during which the light beam of the photographing light condensed on each photoelectric conversion element is gradually narrowed by the mechanical shutter varies, the exposure amount in each photoelectric conversion element also varies. The period during which the luminous flux of the photographing light is gradually narrowed by the light shielding portion of the mechanical shutter depends on the width of the light flux at the position of the light shielding portion, and the width of the light flux depends on the distance between the light shielding portion and the element surface in the optical axis direction. For this reason, it is desirable that the correction unit suppresses the variation in exposure amount by correction according to the distance between the light shielding unit and the element surface.

  By the way, the operating characteristics of the mechanical shutter depend on the operating history and operating environment at the time of shooting. For example, when the light-shielding part is operated by a spring force, the light is shielded by heating of the electromagnet or magnetization of the light-shielding part according to the period during which the electromagnet is held against the spring force before the light-shielding part is operated. The speed characteristics and acceleration characteristics of the part change. Furthermore, since the mechanical characteristics of the spring change depending on the use of the mechanical shutter and the passage of time, the operating characteristics of the mechanical shutter will be different even when the number of mechanical shutter operations and the manufacturing time are different. Therefore, it is desirable that the correction unit corrects the image in accordance with the operation history information of the mechanical shutter indicating the length of the past operation period, the number of operations, the elapsed time from the manufacturing time, and the like. Furthermore, the operating characteristics of the mechanical shutter change depending on the temperature and humidity of the mechanical shutter at the time of shooting. Therefore, it is desirable that the correction unit corrects the image according to the operating environment information indicating the temperature, humidity, and the like of the mechanical shutter.

  When the waiting time from the end of exposure to the reading of the exposure amount varies for each photoelectric conversion element, the longer the waiting time, the smaller the exposure amount corresponding to the waiting time may be corrected. . Thereby, the influence of the electric charge by the dark current slightly accumulate | stored in a photoelectric conversion element in standby time can be suppressed.

  The image correction circuit of the present invention is not limited to being realized as a single device, and each unit included in the image correction circuit of the present invention may be included in the photographing apparatus. Further, the function of each means described in the claims is realized by a hardware resource whose function is specified by the configuration itself, a hardware resource whose function is specified by a program, or a combination thereof. The functions of these means are not limited to those realized by hardware resources that are physically independent of each other. Furthermore, the present invention is also established as a recording medium for an image correction program. Of course, the recording medium for the computer program may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium developed in the future.

It is a block diagram which shows a digital camera. It is a schematic diagram of an area image sensor. It is a graph which shows the timing of exposure. It is a graph which shows the timing of exposure. It is the schematic diagram and graph which show a mode that a light beam is restrict | squeezed. It is a schematic diagram of an area image sensor and a light-shielding curtain. It is a graph which shows the timing of exposure. It is a graph which shows the timing which reads imaging data.

Hereinafter, embodiments of the present invention will be described in the following order with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the corresponding component in each figure, and the overlapping description is abbreviate | omitted.
(1) Configuration of photographing apparatus:
(2) LUT configuration:
(3) Modification 1:
(4) Modification 2:
(5) Modification 3:
(6) Modification 4:
(7) Modification 5:
(8) Modification 6:
(9) Modification 7:
(10) Modification 8:

(1) Configuration of photographing apparatus:
FIG. 1 shows a photographing apparatus 1 including an image correction circuit according to an embodiment of the present invention. The photographing apparatus 1 according to the present embodiment is a mirrorless digital camera provided with an EVF (Electronic View Finder). The photographing apparatus 1 includes an optical system 10, an area image sensor 15, an ASIC 200, a timing generator 30, a display unit 40, a CPU 50, an SD-RAM 52, a ROM 53, a RAM 54, an operation unit 55, and a removal memory 56. The CPU 50 executes the program recorded in the ROM 53 using the SD-RAM 52 and the RAM 54 as appropriate. With the function of the program, the CPU 50 executes a function of generating image data indicating a subject photographed by the area image sensor 15 in response to an operation on the operation unit 55. The operation unit 55 includes a shutter button and a dial switch for setting an exposure time (shutter speed).

  The optical system 10 includes a lens 11, a diaphragm 12, a mechanical shutter 13, and a low-pass filter 14. The lens 11 collects the photographing light and forms an image of the subject on the area image sensor 15. The diaphragm 12 adjusts the photographing light amount by narrowing the luminous flux of the photographing light. The exposure time is set depending on the setting of the aperture 12 in the case of aperture priority, in addition to the operation on the dial switch. The lens 11 and the diaphragm 12 are provided in an interchangeable lens unit, and the interchangeable lens unit is attached to the casing of the photographing apparatus 1 in a replaceable manner. The low-pass filter 14 prevents moiré in the photographed image by blocking the spatial high frequency component in the area image sensor 15 of the photographed light.

  FIG. 2A is a schematic diagram showing a part of the element surface of the area image sensor 15 as viewed from the front. The area image sensor 15 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (CCD) in which a color filter arranged in a Bayer arrangement and a plurality of photoelectric conversion elements that accumulate charges according to the exposure amount are arranged on a predetermined element surface. Charge Coupled Device) A solid-state imaging device such as an image sensor. In the present embodiment, a case where a CMOS image sensor is used will be described as an example. In FIG. 2, each photoelectric conversion element is shown as a square, and the color of the color filter provided corresponding to each photoelectric conversion element (3 channels: R (red), G (green), B (blue)) inside the square Indicates. The arrangement position of the plurality of photoelectric conversion elements on the element surface of the area image sensor 15 is defined by orthogonal coordinates, and a line is constituted by a plurality of photoelectric conversion elements arranged in a direction parallel to one coordinate axis, and the plurality of lines is the other of the other. They are arranged in a direction parallel to the coordinate axis. In this specification, a direction parallel to the line is called a horizontal direction, and a direction perpendicular to the line is called a vertical direction.

  In the area image sensor 15 in the present embodiment, the charge accumulated in the photoelectric conversion element can be reset (discharged) in units of lines. That is, charges are simultaneously reset in a plurality of photoelectric conversion elements belonging to the same line, and charge accumulation starts simultaneously with the reset release operation. The start of charge accumulation in the photoelectric conversion element means the start of exposure in the photoelectric conversion element. For example, each photoelectric conversion element includes a reset field effect transistor that discharges electric charges by conduction between the source and the drain, and in each photoelectric conversion element belonging to the same line, a voltage is applied to the gate of the reset field effect transistor. Wiring for sharing is common. The area image sensor 15 reads out the electric charges accumulated in the photoelectric conversion elements in units of lines. Note that the area image sensor 15 can perform intermittent reading without reading from all lines according to the required image quality and speed. The charge is also reset when the photoelectric conversion element reads out the charge. The area image sensor 15 performs A / D conversion on the gradation value of the exposure amount corresponding to the read charge by an A / D converter or the like, and generates imaging data associated with each pixel. This imaging data corresponds to an image of the present invention. The pixel of the imaging data uniquely corresponds to the photoelectric conversion element. The imaging data read from the area image sensor 15 is buffered in the SD-RAM 52, and various image processing is performed on the imaging data by the ASIC 200 described later.

FIG. 2B is a schematic diagram showing the entire element surface of the area image sensor 15 as viewed from the front. Each line is given a line number L (1 to L _max ) that increases by 1 as it goes upward in the vertical direction, and a vertical line that is orthogonal to the line has a column number that increases by 1 as it goes to the right in the horizontal direction. C (1 to C _max ) is attached. The line number L of the center line in the vertical direction is represented as L _mid, and the column in the center in the horizontal direction is represented as C _mid . The mechanical shutter 13 includes a light-shielding curtain (shown by hatching in FIG. 1) as a planar plate-shaped light-shielding portion that is substantially parallel to the element surface of the area image sensor 15 in which a plurality of photoelectric conversion elements are arranged. By this light shielding curtain, an exposure region R1 and a light shielding region R2 are formed on the element surface of the area image sensor 15 in which a plurality of photoelectric conversion elements are arranged. That is, the shade of the light shielding curtain on the element surface of the area image sensor 15 forms the light shielding region R2. The mechanical shutter 13 operates the light shielding curtain as follows.

  The mechanical shutter 13 of the present embodiment is a normally open type, and when the power of the photographing apparatus 1 is turned off, the light shielding curtain is locked by a locking lever and held by suction with a permanent magnet. The light-shielding curtain resists the spring force of the spring that attracts the light-shielding curtain at a position where the entire photographing light is shielded, and is locked outside the optical path of the photographing light by the locking lever and the permanent magnet. Then, when the photographing apparatus 1 is powered on, the light shielding curtain is unlocked by the locking lever. Even when the locking of the light-shielding curtain by the locking lever is released, the light-shielding curtain is attracted and held by the permanent magnet, and the light-shielding curtain is held against the spring force. When the shutter button is pressed, the electronic shutter control unit 30a1 starts exposure in each photoelectric conversion element, and when a period corresponding to the exposure time has elapsed from the start of exposure, the magnetic force of the permanent magnet that attracts the light shielding curtain. An electric current is supplied to the electromagnet that generates a magnetic force that cancels the magnetic field, and the adsorption and holding of the light shielding curtain by the permanent magnet is released. Thereby, the light shielding curtain is moved by the spring force, and the light shielding curtain is moved to a position where the entire photographing light is shielded.

  FIG. 2B schematically shows a state in which the boundary B between the exposure region R1 and the light shielding region R2 moves on the element surface of the area image sensor 15 when the mechanical shutter 13 moves the light shielding curtain by a spring force. Yes. In the present embodiment, the spring attracts the light-shielding curtain upward, so that the boundary B between the exposure region R1 and the light-shielding region R2 moves upward (in the direction of the dashed arrow) when the shutter closes. To do. When the boundary B reaches the photoelectric conversion element due to the movement of the light shielding curtain, the exposure of the photoelectric conversion element is completed. In the mechanical shutter 13 of the present embodiment, a light-shielding curtain is supported so as to be rotatable about a rotation shaft (not shown) provided on the right side of the element surface of the area image sensor 15. In the present embodiment, when the boundary B reaches the center line in the vertical direction, the boundary B and the line are parallel to each other. Until the boundary B reaches the center line in the vertical direction, the boundary B is inclined to the right and gradually approaches the line. When the boundary B arrives at the center line in the vertical direction, the boundary B gradually increases the inclination angle of the lower right shoulder. That is, the direction of the boundary B on the element surface of the area image sensor 15 is not constant, and basically the boundary B intersects the line. If the rotation axis of the light-shielding curtain is provided at a position sufficiently far from the element surface of the area image sensor 15, each line and the boundary B can be regarded as parallel. However, in this embodiment, the photographing apparatus 1 can be reduced in size or machine. The rotation axis of the light-shielding curtain is provided at a position where the boundary B can intersect the line in response to a request for speeding up the operation of the shutter 13.

  The timing generator 30 includes a sensor control unit 30a and a display control unit 30b, and the sensor control unit 30a includes an electronic shutter control unit 30a1. The sensor control unit 30 a generates signals for controlling various operation timings of the photoelectric conversion elements in the liquid crystal panel 42 and outputs the signals to the area image sensor 15. The display control unit 30 b generates a signal for controlling the display timing of each display pixel of the liquid crystal panel 42 and outputs the signal to the liquid crystal panel driver 41.

  When the shutter button is pressed by the operation unit 55, the electronic shutter control unit 30a1 opens the electronic shutter. Note that opening the electronic shutter means that the charge in all the photoelectric conversion elements of the area image sensor 15 is once reset, the charge accumulation is restarted, and the exposure is started. As described above, in this embodiment, charges accumulated in a plurality of photoelectric conversion elements can be reset in units of lines, and all charges can be reset and start to be accumulated for all lines in order. Accumulation of the photoelectric conversion elements is started. Note that the electronic shutter control unit 30a1 may cause the charge reset to be simultaneously performed for all the lines, and thereafter the charge accumulation may be sequentially started in units of lines. In either case, the timing at which exposure of the photoelectric conversion element starts varies from line to line.

  The display unit 40 is an EVF, displays a so-called live view moving image generated by reading out exposure amount data detected by each photoelectric conversion element of the area image sensor 15 by intermittent line reading, and displays a photographed subject. The still image of is displayed. The display unit 40 includes an interface circuit (not shown), a liquid crystal panel driver 41, a liquid crystal panel 42, an eyepiece (not shown), and the like. The liquid crystal panel driver 41 applies a voltage to each subpixel and outputs a signal for driving the liquid crystal to the liquid crystal panel 42.

  The ASIC 200 includes an image data generation unit 20. The image data generation unit 20 uses a line buffer or a frame buffer reserved in advance in the SD-RAM 52, and executes various image processes on the image data captured by the area image sensor 15 by pipeline processing. The ASIC 200 may be an image processing DSP (Digital Signal Processor). The image data generation unit 20 includes an exposure amount correction unit 20a, a pixel interpolation unit 20b, a color reproduction processing unit 20c, a filter processing unit 20d, a gamma correction unit 20e, and a resizing processing unit 20f.

  The image data generation unit 20 constitutes an image acquisition unit that acquires imaging data captured by the area image sensor 15. The exposure amount correction unit 20a constitutes a correction unit that corrects imaging data so as to suppress variations in exposure amount among a plurality of photoelectric conversion elements. That is, the exposure amount correction unit 20a refers to the LUT 53a recorded in the ROM 53 and corrects the gradation value of the exposure amount in the imaging data for each pixel. The LUT 53a is data in which information for correcting the gain of the exposure amount to be multiplied for each one or a plurality of photoelectric conversion elements provided in the area image sensor 15 is defined, and is created in advance for each exposure time. The The exposure amount correction unit 20a acquires an exposure time set at the time of shooting, and refers to the LUT 53a corresponding to the exposure time. Since each pixel of the imaging data uniquely corresponds to the plurality of photoelectric conversion elements of the area image sensor 15, the exposure amount correction unit 20 a can specify by correcting the gain of the exposure amount to be multiplied for each pixel.

  The pixel interpolation unit 20b performs an interpolation process using gradation values of peripheral pixels, thereby obtaining gradation values of two channel colors different from the color of the color filter provided in the photoelectric conversion element corresponding to each pixel. calculate. As a result, imaging data in which gradation values of three channels are associated with each pixel is generated. The color reproduction processing unit 20c performs color conversion processing for color matching by performing a 3 × 3 matrix operation on the gradation value of each pixel of the imaging data for which pixel interpolation has been completed. The filter processing unit 20d performs sharpness adjustment, noise removal processing, and the like on the captured image data by filter processing. The gamma correction unit 20e performs gamma correction that compensates for a characteristic difference between the color indicated by the gradation value of the photographic data of the area image sensor 15 and the color indicated by the gradation value of the image data handled by the display unit 40 or the like. The resize processing unit 20f performs interpolation calculation processing by sequentially referring to the data recorded in the line buffer, and specifies the gradation value of each channel at a position between pixels, for example, resizing to a recording size. Do. When resizing is completed in the resizing processing unit 20f, image data in which each image processing in the image data generating unit 20 is completed can be generated. The image data is buffered in the SD-RAM 52, displayed on the display unit 40, and recorded in the removal memory 56. The exposure correction unit 20a may be provided before or after any of the circuits 20b to 20f of the image data generation unit 20. The exposure amount correction by the exposure amount correction unit 20a may be performed before the pixel interpolation by the pixel interpolation unit 20b or after the pixel interpolation by the pixel interpolation unit 20b.

(2) LUT configuration:
The left graphs in FIGS. 3A and 3B are graphs showing the exposure timing in the area image sensor 15. The left graph in FIG. 3A shows a case where the set exposure time TE is 1/125 seconds, and the left graph in FIG. 3B shows a case where the set exposure time TE is 1/60 seconds. In the left graphs of FIGS. 3A and 3B, the horizontal axis indicates time, and the vertical axis indicates line number L. The left broken line in the left graphs of FIGS. 3A and 3B indicates the timing at which exposure of the photoelectric conversion elements of each line of the area image sensor 15 starts, and the timing (time) is given by the function X (L) of the line number L. The curves on the right side of the left graphs of FIGS. 3A and 3B indicate the timing when the exposure ends, and the timing (time) is given by the function Y (L, C) of the line number L and the column number C of each photoelectric conversion element. Hereinafter, when there is no need to indicate a specific line number L and column number C, the notation of variables (L, C), (L), etc. in each function may be omitted. In addition, since exposure starts by simultaneously starting accumulation of charges of all the photoelectric conversion elements belonging to the line, the timing X (L) does not become a function of the column number C. Here, the left broken line in the left graphs of FIGS. 3A and 3B indicates the operating characteristics of the electronic shutter, and the right timing indicates the operating characteristics of the mechanical shutter. The characteristic of the electronic shutter is a characteristic of a three-stage broken line here, but it need not be a three-stage broken line, and may be a straight line that is not a three-stage broken line to several tens of stages or more.

  As described above, since exposure in the photoelectric conversion element is started by resetting the charge by the electronic shutter control unit 30a1 and starting accumulation of the charge, the exposure start timing X corresponds to the operation characteristic of the electronic shutter. On the other hand, the exposure in the photoelectric conversion element is terminated when the boundary B between the exposure region R1 and the light shielding region R2 reaches the photoelectric conversion device due to the movement of the light shielding curtain of the mechanical shutter 13, and therefore, the exposure end timing Y is the mechanical shutter. This corresponds to 13 operating characteristics. The actual exposure time AE (L, C) in each photoelectric conversion element is a period from the start of exposure by the electronic shutter to the end of exposure by the mechanical shutter 13, and the difference between the timing X and the timing Y in the horizontal axis direction. {Y (L, C) -X (L)} means the actual exposure time AE (L, C) of the photoelectric conversion element.

  Here, the light-shielding curtain of the mechanical shutter 13 operates under the influence of a spring force, a frictional force, and the like. In this case, the position in the vertical direction of the boundary B between the exposure region R1 and the light shielding region R2 changes in a parabolic shape that gradually increases in inclination. Therefore, as indicated by the timing Y, the line number at which the exposure of the photoelectric conversion element is completed increases in a parabolic shape with the passage of time. That is, the timing Y is an inverse function of a quadratic function.

In the present embodiment, the timing X of the electronic shutter is a polygonal line shape that follows the timing Y of the mechanical shutter 13 in order to make the exposure time uniform in the photoelectric conversion elements belonging to each line. Specifically, the timing X of the electronic shutter is created as follows. First, the timing Y (L, C _mid ) at which the boundary B reaches each photoelectric conversion element belonging to the horizontal center column (column number C _mid ) is specified based on the motion equation of the light-shielding curtain. Then, an offset curve Z (shown by a broken line) is created by offsetting the timing Y (L, C _mid ) to the earlier time by the set exposure time TE. Next, tangent lines that contact the offset curve Z at line numbers L ₁ , L ₂ , and L _max are created. Note that 1 <L ₁ <L ₂ <L _max . Then, the intersection of two tangents that touch the offset curve Z at the line numbers L ₁ and L ₂ and the intersection of the two tangents that touch the offset curve at the line numbers L ₂ and L _max are the bending points 3 A stepped broken line is created, and the three stepped broken line is set as the electronic shutter timing X. Since the timing X of the electronic shutter follows a parabola that gradually increases in inclination, the inclination of the first-stage line is smaller than that of the second-stage line, counting from below, and the inclination of the second-stage line is the third-stage line. It becomes smaller than the broken line. The number of broken lines is not limited to three.

The electronic shutter control unit 30a1 performs a rolling shutter operation that causes the photoelectric conversion elements to start exposure in ascending order of the line numbers, and corresponds to the inclination of the timing X of the three-stage broken line between the exposure start timing intervals between adjacent lines. It is assumed to be the length. That is, the exposure start timing interval between adjacent lines of the line number corresponding to the nth (n is a natural number of 3 or less) line number is constant, and the adjacent line number corresponding to the (n + 1) th line. It is ensured longer than the exposure start timing interval between the two lines. When the shutter button is pressed, first, the electronic shutter control unit 30a1 starts accumulating the charge of the photoelectric conversion element from the lowermost line, and after waiting for a predetermined period from the start timing, the mechanical shutter 13 is moved to the electromagnet. Is supplied with a current to release the adsorption of the light shielding curtain by the permanent magnet, and the light shielding curtain is moved by the spring force. The predetermined period is substantially equal to the set exposure time TE, and among the photoelectric conversion elements of the lines with line numbers L ₁ , L ₂ , and L _max , photoelectrics belonging to the horizontal center column (column number C _mid ). A period in which the actual exposure time AE (L, C _mid ) of the conversion element is equal to the set exposure time TE.

As described above, the electronic shutter control unit 30a1 controls the timing at which the photoelectric conversion elements belonging to the respective lines start exposure so as to follow the timing Y (L, C _mid ) of the mechanical shutter 13, whereby the horizontal direction The actual exposure time AE (L, C _mid ) in each photoelectric conversion element belonging to the center column can be approximated to the set exposure time TE. However, the timing X (polygonal line) of the electronic shutter cannot completely follow the timing Y (L, C _mid ) (parabola) of the mechanical shutter 13, and as shown in the middle graphs of FIGS. 3A and 3B, The actual exposure time AE (L, C _mid ) = {Y (L, C _mid ) −X (L)} in each photoelectric conversion element belonging to the center column in the direction is not constant, and the actual exposure with respect to the exposure time TE is performed. An error of time AE (L, C _mid ) (shown by hatching) occurs. The magnitude of this error depends on the vertical position of each photoelectric conversion element. Next, the actual exposure time AE (L, C) in each photoelectric conversion element belonging to a column other than the central column in the horizontal direction will be considered.

FIG. 4 is a graph showing the exposure timing in the photoelectric conversion elements belonging to each column of the area image sensor 15. In the figure, the timing Y (L, C _mid ) at which the exposure of each photoelectric conversion element belonging to the central column in the horizontal direction ends is indicated by a solid line, and the exposure of each photoelectric conversion element belonging to the left end and right end columns ends. Timings Y (L, C ₁ ) and Y (L, C _max ) are indicated by a one-dot chain line and a two-dot chain line, respectively. As shown in FIG. 2B, since the boundary B between the exposure region R1 and the light shielding region R2 moves while changing its direction, the timing Y (L, C) differs for each column number C. That is, until the boundary B reaches the center line in the vertical direction (line number L _mid ), the boundary B rises to the right. Therefore, exposure is completed earlier as the photoelectric conversion element is closer to the right end. Therefore, until the boundary B reaches the vertical center of the line, the timing Y (L, C _max) precedes the timing Y (L, C _mid), timing Y (L, C _mid) timing Y (L , C ₁ ). On the other hand, after the boundary B reaches the center line in the vertical direction, the boundary B falls to the right. Therefore, exposure is completed earlier as the photoelectric conversion element is closer to the left end. Accordingly, after the boundary B reaches the vertical center of the line, the timing Y (L, C ₁₎ precedes the timing Y (L, C _mid), timing Y (L, C _mid) timing Y (L , C _max ). Further, the exposure of the photoelectric conversion elements belonging to the center line in the vertical direction (line number L _mid ) is all finished at the same time, and the timings Y (L _mid , C ₁ ), Y (L _mid , C _mid ) for the line number L _mid , Y (L _mid , C _max ) match.

As described above, the timings Y (L, C ₁ ), Y (L, C _mid ), and Y (L, C _max ) at which the exposure ends are different according to the horizontal position of the photoelectric conversion element. On the other hand, the exposure of the photoelectric conversion elements belonging to all the columns is started by the timing X (L) following the timing Y (L, C _mid ) for the photoelectric conversion elements in the central column in the light horizontal direction. The actual exposure times AE (L, C ₁ ) and AE (L, C _max ) for the photoelectric conversion elements belonging to columns other than the horizontal central column are the actual exposure times for the photoelectric conversion elements belonging to the horizontal central column. The exposure time AE varies more than the exposure time AE (L, C _mid ). Note that the timing X at which exposure is started cannot be controlled for each column of photoelectric conversion elements due to restrictions on wiring for resetting charges. That is, as long as the boundary B intersects the line, no matter how the exposure start timing X is adjusted, variations in the exposure time depending on the horizontal position of the photoelectric conversion element cannot be prevented.

  In the present embodiment, the computer for creating the LUT 53a predicts the movement of the light shielding curtain, and further predicts the transition of the boundary B between the exposure region R1 and the light shielding region R2 on the element surface by the light ray prediction of the photographing light, The actual exposure time AE (L, C) for all the photoelectric conversion elements is calculated. Then, as shown in the right graphs of FIGS. 3A and 3B, the gain GE (L, C) is calculated by dividing the set exposure time TE by the actual exposure time AE (L, C). 3A, 3B, and FIG. 4, the timing Y for the photoelectric conversion elements belonging to the columns in the horizontal left end, the center, and the right end is illustrated, but the timing Y for the photoelectric conversion elements belonging to all the columns is predicted, Gain GE is calculated. Further, the gain GE is associated with each photoelectric conversion element and stored in the LUT 53a.

  Here, the gain GE (L, C) for the photoelectric conversion element that is smaller than the exposure time TE for which the actual exposure time AE (L, C) is set is greater than 1, and conversely, the actual exposure time AE (L , C) has a gain GE (L, C) smaller than 1 for a photoelectric conversion element longer than the set exposure time TE. However, it is desirable that the value of the gain GE is designed to be always 1 or more. By setting the value of the gain GE to 1 or more, it is possible to suppress unevenness in the light amount and color unevenness of the image that occurs when the maximum saturation value of the corrected exposure amount is below a certain value. Further, as the absolute value of the error between the actual exposure time AE (L, C) and the set exposure time TE increases, the gain GE (L, C) becomes a value that greatly differs from 1. 3A and 3B, the magnitude of the error between the actual exposure time AE (L, C) and the set exposure time TE does not depend on the set exposure time TE. It is constant. This is because even if the set exposure time TE changes, the light-shielding curtain moves in the same manner due to the spring force. Therefore, the longer the set exposure time TE, the smaller the contribution of the error between the actual exposure time AE (L, C) and the set exposure time TE to the gain GE (L, C). The gain GE (L, C) is a value close to 1. As described above, since the gain GE depends on the set exposure time TE, the computer creates the LUT 53a for each set exposure time TE, or creates an LUT corresponding to a typical exposure time and sets other exposures. In the case of time TE, conversion is performed based on this LUT, and gain GE (L, C) corresponding to the exposure time at the time of photographing is calculated. Note that the gain GE may be calculated for some photoelectric conversion elements, and the gain GE for other photoelectric conversion elements may be calculated by interpolation based on the positional relationship of the photoelectric conversion elements on the element surface.

The exposure amount correction unit 20a refers to the LUT 53a corresponding to the exposure time at the time of shooting and multiplies the gradation value of the exposure amount of each pixel in the imaging data by the gain GE of the photoelectric conversion element corresponding to each pixel. In this way, by multiplying the gradation value of the exposure amount by the gain GE, the exposure amount for the photoelectric conversion element having a short actual exposure time AE (L, C) is increased, and the actual exposure time AE (L, L, C) is increased. The exposure amount for a photoelectric conversion element having a long C) can be reduced, and the influence of exposure time variation on the exposure amount can be suppressed. According to the LUT 53a, the gain GE can be defined in units of pixels, that is, in units of photoelectric conversion elements, so that it is possible to suppress the influence of variations in exposure time that vary depending on both the vertical position and the horizontal position of the photoelectric conversion elements. In particular, the variation in exposure time in the horizontal direction caused by the boundary B between the exposure region R1 and the light shielding region R2 intersecting with the line temporarily changes the timing X of the electronic shutter to the timing Y (L, C _mid ) of the mechanical shutter 13. Although it cannot be solved even when the tracking is completely followed, the influence of the variation in the exposure time in the horizontal direction can be suppressed by performing correction using the LUT 53a. In this embodiment, it is assumed that the exposure time and the exposure amount are in a proportional relationship, and correction is performed by multiplying the gain GE. However, when the nonlinearity between the exposure time and the exposure amount is considered, the gain is taken into account. The exposure amount may be corrected after nonlinear conversion of GE.

(3) Modification 1:
In the above, the example of creating the LUT 53a that suppresses the influence of the variation in the exposure time due to the difference in the timing characteristics of the electronic shutter and the mechanical shutter 13 has been described. However, paying attention to other operating characteristics of the mechanical shutter 13 You may create LUT53a which suppresses the dispersion | variation in exposure amount. For example, the LUT 53a may be created in consideration of the narrowing characteristic of the luminous flux of the photographing light by the electronic shutter and the narrowing characteristic of the luminous flux of the photographing light by the mechanical shutter 13.

  FIG. 5A is a schematic diagram illustrating a state of a luminous flux of photographing light shielded by the light shielding curtain of the mechanical shutter 13. In FIG. 5A, the light shielding curtain of the lens 11, the mechanical shutter 13, and the area image sensor 15 are shown as viewed from a direction perpendicular to the central optical axis of the photographing light and the moving direction of the light shielding curtain. In this modification, the boundary B between the exposure region R1 and the light shielding region R2 is always considered to be parallel to the line for the sake of simplicity of explanation. Further, it is assumed that the timing X of the electronic shutter completely follows the timing Y of the mechanical shutter 13. That is, it is assumed that the actual exposure time AE in all the photoelectric conversion elements is equal to the set exposure time TE.

Here, the following time t and upper end position y of the light shielding curtain are defined. First, at times t ₀ and t ₁ , exposure of photoelectric conversion elements belonging to the lowermost and uppermost lines (line numbers 1 and L _max ) in the area image sensor 15 is started. Then, the light shielding curtain of the mechanical shutter 13 starts to rise, and at the time t ₂ when the upper end position y of the light shielding curtain reaches y ₂ , the lowermost end of the light beam condensed on the photoelectric conversion element belonging to the lowermost line is Shaded. Next, the upper end position y of the light-blocking curtain lowermost end of the light flux is converged on the photoelectric conversion elements which belong to the uppermost line is blocked at time t ₃ when became y _3. Upper end position y of the light-blocking curtain uppermost end of the light flux is converged on the photoelectric conversion elements belonging to the lowermost line is blocked at time t ₄ when became y _4. Further, the upper end position y of the light-blocking curtain uppermost end of the light flux is converged on the photoelectric conversion elements which belong to the uppermost line is blocked at time t ₅ became y _5. At time t ₄ , the photographing light condensed on the photoelectric conversion elements belonging to the lowermost line is completely blocked, and the exposure of the photoelectric conversion elements belonging to the lowermost line is completed. That is, the boundary B between the light shielding region R2 and the exposure region R1 at time t ₄ reaches the lowermost line. Similarly, at time t ₅ the boundary B between the exposure region R1 and the light shielding region R2 reaches the uppermost line, the exposure of the photoelectric conversion elements belonging to the line ends.

FIG. 5B is a graph showing the exposure amount of the photoelectric conversion elements belonging to the lowermost line. The vertical axis in FIG. 5B indicates the exposure amount, and the horizontal axis indicates time. As shown in the figure, the exposure amount of the photoelectric conversion element belonging to the lowermost line increases linearly with a predetermined inclination from time t ₀ when the photoelectric conversion element belonging to the line starts exposure. When the time t ₂ to the lowermost end of the light beam is converged on the photoelectric conversion elements belonging to the lowermost line is blocked elapses, the exposure amount will light beam is focused is gradually narrowed down to the photoelectric conversion element The slope of increasing will decrease. Further, when the time t ₄ when the uppermost end of the light beam is converged on the photoelectric conversion elements belonging to the lowermost line is blocked has elapsed, exposure is ended in the photoelectric conversion element, eventually exposure amount is not increased . By reading and quantizing the charge corresponding to the exposure amount, a gradation value indicating the exposure amount of each pixel of the imaging data is determined.

As shown in FIG. 5B, the lower the exposure time FT from the time t _{2 at} which the light beam of the photographing light focused on the lowermost photoelectric conversion element starts to be reduced to the time t ₄ when the exposure ends, the lower the lower the exposure time FT is. The exposure amount of the photoelectric conversion element becomes small. In this modification, the timing X of the electronic shutter is made to completely follow the timing Y of the mechanical shutter 13, so that the actual exposure time AE (t _{0 to} t ₄ ) from the start to the end of exposure of each line. Is the same for all photoelectric conversion elements. However, the length of the narrow-down exposure time FT varies for each photoelectric conversion element.

FIG. 5C is a graph showing a relationship between the upper end position y of the light shielding curtain and the narrowed exposure time FT. In the figure, the horizontal axis indicates time t, and the vertical axis indicates the upper end position y. The upper end position y of the light shielding curtain changes in a parabolic shape due to the uniform acceleration motion of the light shielding curtain. The narrowed exposure time FT for the lowermost line and the uppermost line is a period (t _{2 to} t ₄ ) and a period (t _{3 to} t ₅ ), respectively, and the upper end position y is an interval (y _{2 to} y ₄ ). This corresponds to a period passing through the section (y _{3 to} y ₅ ). As shown in FIG. 5A, since the lowermost line and the uppermost line are vertically symmetrical with respect to the central optical axis, the length of the section (y _{2 to} y ₄ ) and the length of the section (y _{3 to} y ₅ ) Equal to each other. However, since the rate of the shielding curtain is increasing linearly, towards the period of passing through the interval (y ₃ ~y ₅₎ in the traveling direction downstream side of the shielding curtain (t ₃ ~t ₅₎ is, the interval (y ₂ ~y ₄₎ is shorter than the period for passing (t ₂ ~t _4). That is, the narrowed exposure time FT for the uppermost line is shorter than the narrowed exposure time FT for the lowermost line. Therefore, the exposure amount is larger in the uppermost line having a shorter narrowed exposure time FT. That is, the exposure amount varies depending on the position of the photoelectric conversion element in the vertical direction due to the narrowing characteristic of the photographing light.

As described above, the narrowing exposure time FT is in the sections (y _{2 to} y ₄ ) and (y _{3 to} y ₅ ) of the upper end position y of the light-shielding curtain where the luminous flux of the photographing light condensed on the photoelectric conversion element is narrowed. It changes depending on. The lengths and positions of the sections (y _{2 to} y ₄ ) and (y _{3 to} y ₅ ) in the traveling direction of the light shielding curtain are based on the positional relationship among the lens 11, the light shielding curtain, and the area image sensor 15 shown in FIG. It can be specified geometrically. Therefore, it is desirable to suppress variation in exposure amount by correction based on the position in the optical axis direction where the light shielding curtain of the mechanical shutter 13 shields the photographing light. For example, as the distance between the light shielding curtain and the area image sensor 15 is longer, the light shielding curtain narrows the luminous flux of the photographing light in the longer sections (y _{2 to} y ₄ ) and (y _{3 to} y ₅ ). The narrowed exposure time FT for the conversion element becomes longer. Therefore, for the mechanical shutter 13 having a long distance between the light-shielding curtain and the area image sensor 15, the LUT 53a having a large gain GE value may be created. The LUT 53a for correcting the variation in the exposure amount described above may be created by calculation based on the position in the optical axis direction where the light shielding curtain of the mechanical shutter 13 blocks the photographing light, but as follows. The LUT 53a may be created.

  In this modification, a subject having a uniform color (for example, white) is photographed with the entire angle of view of the optical system 10 while irradiating the subject with a uniform light source. Then, the computer that creates the LUT 53a acquires imaging data from the area image sensor 15. The computer acquires the gradation value of the exposure amount corresponding to a predetermined photoelectric conversion element in the imaging data for each of the RGB channels, and uses the gradation value as a reference gradation value. Here, the predetermined photoelectric conversion element is preferably a photoelectric conversion element having the shortest exposure time in the area image sensor 15 so that the gain GE is 1 or more. Then, the exposure amount ratio obtained by dividing the gradation value of each pixel of the imaging data by the reference gradation value with the matching channel is calculated, and the reciprocal of the exposure amount ratio is used as the gain GE for the photoelectric conversion element corresponding to each pixel. The correspondence relationship between the photoelectric conversion element and the gain GE is stored in the LUT 53a. As described above, the aperture exposure time FT for which the light beam is focused and exposed depends on the position of the light-shielding curtain in the optical axis direction. Therefore, by creating the LUT 53a for each airframe of the photographing apparatus 1, It is possible to absorb the influence of variations in operating characteristics caused by variations in the position of the light shielding curtain and manufacturing errors of the mechanical shutter. For example, the LUT 53 a may be created when the photographing apparatus 1 is manufactured and stored in the ROM 53. According to this method, it is possible to suppress variations in exposure amount due to variations in exposure time described in the embodiment. According to the correction of this modification, both the start and end of exposure are performed by a mechanical shutter, and even when the positions of the mechanical shutter in the optical axis direction are different from each other, the exposure in the optical axis direction of the light shielding curtain is different. Variation in exposure amount due to a difference in position (difference in narrowing characteristics) can be suppressed. In addition, by periodically creating the LUT 53a, it is possible to absorb the influence of deterioration over time of the photographing apparatus 1.

(4) Modification 2:
In the above, attention has been paid to the operating characteristics of the mechanical shutter 13 when actually taking a picture. However, the operating characteristics of the mechanical shutter 13 may change depending on the operating history of the mechanical shutter 13 before taking a picture. It is done. Unlike the mechanical shutter 13 of the above-described embodiment, the mechanical shutter of this modification operates as follows. In other words, the mechanical shutter 13 of the above embodiment maintains the adsorption and holding of the light shielding curtain by the permanent magnet when the light shielding curtain is unlocked by the locking lever. In this modification, the mechanical shutter 13 is engaged by the locking lever. When releasing the stop, an electric current is supplied to the electromagnet, and the holding of the light shielding curtain against the spring force is continued by the magnetic force of the electromagnet. Then, when a period corresponding to the exposure time TE elapses from the start of exposure, the current supply to the electromagnet is stopped, and the holding of the light shielding curtain by the electromagnet is released. Thereby, the light shielding curtain is moved by the spring force, and the light shielding curtain is moved to a position where the entire photographing light is shielded, and the exposure of each photoelectric conversion element is completed. Usually, in a period before photographing, a live-view moving image photographed by the area image sensor 15 is viewed on an EVF (display unit 40) or the like, and a shutter chance is viewed. In the mechanical shutter of this modification, during the period when the live view moving image is displayed, the light shielding curtain is unlocked by the locking lever and the light shielding curtain is attracted and held by the electromagnet. In such a mechanical shutter, the longer the period during which the live view moving image is displayed, the higher the electromagnet becomes. Here, the responsiveness of the mechanical shutter 13 decreases due to the high temperature of the electromagnet. When the responsiveness decreases, the time from when the current supply to the electromagnet is stopped to when the light-shielding curtain is driven becomes longer. Accordingly, the longer the period during which the live view moving image is displayed, the longer the exposure end. Therefore, a correction error occurs when the exposure amount correction unit 20a corrects the gradation value of the exposure amount with reference to the same LUT 53a regardless of the period during which the live view moving image is displayed.

  Therefore, in the present modification, the exposure correction unit 20a acquires operation history information indicating the length of the period during which the live view moving image was displayed before the shutter button was pressed from the CPU 50. Then, the exposure amount correction unit 20a refers to the LUT 53a corresponding to the length of the period during which the live view moving image is displayed based on the operation history information, and the exposure amount correction unit 20a determines the gradation value of the exposure amount. to correct. Note that in this modification as well, the LUT 53a may be created for each display period of a plurality of live view moving images based on the imaging data of a uniform color subject as in the first modification. Of course, the gain GE specified in the LUT 53a may be corrected according to the period during which the live view moving image is displayed, and then the correction based on the gain GE may be performed. Note that the exposure amount may be corrected based on the time when the current is supplied to any of the electromagnets involved in the operation of the light-shielding curtain. For example, in a mechanical shutter that requires current supply to an electromagnet in a shutter preparation operation (for example, an operation when the shutter button is half-pressed), the exposure amount may be corrected based on the period of the shutter preparation operation.

(5) Modification 3:
As described above, the quick response of the mechanical shutter 13 is reduced due to the high temperature of the electromagnet due to the long-term display of the live view moving image. The responsiveness of 13 is reduced. Further, when the photographing apparatus 1 is used at a high temperature, a change occurs not only in the electromagnet but also in the characteristics of the spring that attracts the light-shielding curtain. Furthermore, the characteristics of the spring change with humidity. When the spring characteristics change, the movement of the light-shielding curtain changes and the exposure time error shown in the middle graphs of FIGS. 3A and 3B increases. Furthermore, the characteristics of the spring also change depending on the number of expansions and contractions (fatigue) and aging of the spring. For example, as the number of expansions / contractions increases, the longer the time after manufacture, the lower the acceleration of the light-shielding curtain due to the deterioration of the elastic force of the spring, and the longer the exposure time. Therefore, the exposure amount correction unit 20a of the present modification obtains operating environment information indicating the temperature and humidity of the mechanical shutter 13 when the shutter button is pressed from a sensor (not shown), and the manufacturing time and machine of the photographing apparatus 1 Operation history information indicating the number of operations of the shutter 13 is acquired from the CPU 50. Then, the exposure amount correction unit 20a specifies the temperature and humidity of the mechanical shutter 13, the manufacturing time of the photographing apparatus 1, and the number of operations of the mechanical shutter 13 based on the operation environment information and the operation history information, and a combination thereof. The gradation value of the exposure amount is corrected with reference to the LUT 53a corresponding to. In the present modification as well, as in the first modification, the temperature and humidity of the mechanical shutter 13, the manufacturing time of the photographing apparatus 1, and the number of operations of the mechanical shutter 13 are determined based on the imaging data of the subject of uniform color. An LUT 53a may be created for each combination.

(6) Modification 4:
FIG. 6 is a schematic diagram showing the light-shielding curtain of the mechanical shutter 13 and the area image sensor 15 according to this modification. In this modification, the mechanical shutter 13 employs a diaphragm shutter system in which the light-shielding curtain is constituted by five diaphragm blades, and the five diaphragm blades are driven so as to narrow the optical path toward the central optical axis. The light shielding curtain of the mechanical shutter 13 may be provided between the area image sensor 15 and the lens 11, or may be provided on the upstream side of the optical path from the lens 11. In such an aperture shutter system, the boundary B between the exposure region R1 and the light shielding region R2 forms a circumscribed pentagon of a circle centered on the central optical axis, and each side of the circumscribed pentagon is a line ( Crossed with a broken line arrow). Further, such an aperture shutter system has a characteristic that the closer to the center of the optical axis, the slower the arrival of the boundary B between the exposure region R1 and the light-shielding region R2 and the later the timing at which the exposure ends. On the other hand, since the direction of the line of the area image sensor 15 is the horizontal direction, the timing of the mechanical shutter 13 cannot be tracked even if the timing at which the photoelectric conversion element starts exposure in units of lines. Even in such a case, it is possible to suppress variations in the exposure amount by correcting the gradation value of the exposure amount in the imaging data in accordance with the position of the photoelectric conversion element.

(7) Modification 5:
The left graph in FIG. 7 is a graph showing the exposure timing in the area image sensor 15 of the present modification. In this modification, the electronic shutter control unit 30a1 does not cause the timing X of the electronic shutter to follow the timing Y of the mechanical shutter 13. That is, as shown in the left graph of FIG. 7, by simultaneously resetting charges in all photoelectric conversion elements belonging to all lines and simultaneously starting charge accumulation in all photoelectric conversion elements (performing global shutter). , Exposure in all photoelectric conversion elements is started simultaneously. In the example of the left graph in FIG. 7, the actual exposure time TE (L _max , C _mid ) in the horizontal center photoelectric conversion element of the uppermost line (line number L _max ) matches the set exposure time TE. Let In this case, especially in the lower line, the timing X of the electronic shutter and the timing Y of the mechanical shutter 13 are greatly different, so that the actual exposure time TE set as shown in the middle graph of FIG. The exposure time AE varies greatly. In particular, in the lower line, the actual exposure time AE becomes significantly shorter than the set exposure time TE.

  Also in this modification, the gain GE is obtained by dividing the exposure time TE set as shown in the right graph of FIG. 7 by the actual exposure time AE. Then, the gain GE is stored in the LUT 53a in association with each photoelectric conversion element, and the exposure amount correction unit 20a refers to the LUT 53a to convert the exposure amount gradation value of each pixel in the imaging data into a photoelectric conversion corresponding to each pixel. Multiply the element gain GE. In this modification, a line is generated in which the actual exposure time AE is significantly shorter than the set exposure time TE. By multiplying such a line by a gain GE significantly larger than 1, Although noise is amplified, variation in exposure can be suppressed. That is, if correction is performed by multiplying the gradation value indicating the exposure amount by the gain GE as in the present invention, variations in the exposure amount can be suppressed without accurately controlling the timing X of the electronic shutter. Therefore, the circuit scale of the electronic shutter control unit 30a1 can be reduced without significantly degrading the image quality of the captured image.

(8) Modification 6:
FIG. 8 is a graph showing the timing of exposure and readout of imaging data in the photoelectric conversion elements of each line. In the example of FIG. 8, the timing X of the electronic shutter is made to completely follow the timing Y of the mechanical shutter 13 as in the first modification. Accordingly, the actual exposure time AE in each photoelectric conversion element coincides with the set exposure time TE. In FIG. 8, the timing P (L) indicating the timing for reading the imaging data for each line is indicated by a broken line. Since there are a large number of photoelectric conversion elements in each line, the period required to read out the imaging data for each line is longer than the period in which the boundary B passes through each line by the mechanical shutter 13. Accordingly, the timing P (L) at which the imaging data is read has a gentler slope than the timings X and Y at which the photoelectric conversion elements of each line start and end exposure. Accordingly, the standby period WT (L) from the end of exposure by the photoelectric conversion element to the readout of the imaging data becomes longer as the line number increases. In the standby period WT (L), the light shielding curtain of the mechanical shutter 13 shields the photoelectric conversion elements, but as the standby period WT (L) is longer, the charge accumulation amount N (due to the dark current noise of the area image sensor 15 is increased. L) increases. That is, the exposure amount in each photoelectric conversion element varies due to non-uniformity of the standby period WT (L) caused by the difference between the timing Y of the mechanical shutter 13 and the readout timing P (L) of the imaging data. Will occur. In this modification, since the exposure amount for the dark current increases toward the upper line, the standby period is reduced by subtracting the value N (L) at which the noise amount increases toward the upper line from the gradation value of the exposure amount. Variation in exposure amount due to non-uniformity of WT (L) is suppressed.

(9) Modification 7:
In the above, the example in which the image is corrected by the photographing apparatus 1 has been described, but the image may be corrected by an apparatus other than the photographing apparatus 1. For example, the image capturing apparatus 1 includes a mode in which image data captured by the area image sensor 15 is recorded in the removal memory 56 as it is without performing various image processing by the image data generating unit 20. Further, the photographing apparatus 1 attaches attached information specifying the model of the photographing apparatus 1 and the exposure time (shutter speed) at the time of photographing to the imaging data. In this modification, the exposure amount is corrected by a computer that can read the above-described imaging data from the removal memory 56. The timing Y of the mechanical shutter 13 is greatly different for each model of the photographing apparatus 1 having physically different shutter mechanisms. Therefore, in this modification, an LUT 53a is created in advance for each model of the photographing apparatus 1 and recorded in the computer. When the computer reads the imaging data, the computer refers to the LUT 53a corresponding to the model of the imaging apparatus 1 specified by the attached information attached to the imaging data, and sets the exposure amount associated with each pixel of the imaging data. Correct tone values. In addition, you may attach LUT itself according to the exposure time (shutter speed) at the time of imaging | photography. In this case, unlike the case where no LUT is attached, the gradation value of the exposure amount associated with each pixel of the imaging data is corrected with reference to the LUT.

(10) Modification 8:
As compared with the middle graphs of FIGS. 3A and 3B, the longer the set exposure time TE, the smaller the influence of the error between the actual exposure time AE and the set exposure time TE on the exposure amount. The gain GE for suppressing the influence of the error is a value close to 1. Further, when the set exposure time TE is increased, the variation in exposure amount due to an error between the actual exposure time AE and the set exposure time TE is not felt when the image is viewed. Therefore, when the set exposure time TE is longer than the predetermined threshold value, the correction by the exposure amount correction unit 20a may not be performed. For example, when the relative ratio of the maximum absolute value of the error between the actual exposure time AE and the set exposure time TE with respect to the set exposure time TE is a predetermined threshold (for example, 1/50, etc.). On the other hand, correction may not be performed because it is difficult to perceive variations in the exposure amount.
Specific embodiments of the present invention are not limited to the above-described embodiments and modifications, and may be a combination of the embodiments and modifications, and do not depart from the technical idea of the present invention. The deformation may be performed with

  DESCRIPTION OF SYMBOLS 1 ... Imaging device, 10 ... Optical system, 11 ... Lens, 12 ... Aperture, 13 ... Mechanical shutter, 14 ... Low pass filter, 15 ... Area image sensor, 20 ... Image data generation part, 20a ... Exposure amount correction part, 20b ... Pixel interpolation unit, 20c ... color reproduction processing unit, 20d ... filter processing unit, 20e ... gamma correction unit, 20f ... resizing processing unit, 30 ... timing generator, 30a ... sensor control unit, 30a1 ... electronic shutter control unit, 30b ... display Control unit 40 ... Display unit 41 ... Liquid crystal panel driver 42 ... Liquid crystal panel 55 ... Operation unit 56 ... Removal memory

Claims (8)

An image acquisition unit that acquires an image captured using a mechanical shutter that controls the exposure time of the plurality of photoelectric conversion elements;
And a correction unit that corrects the image based on an operating characteristic of the mechanical shutter.   The image acquisition unit mechanically operates an electronic shutter that controls the start of exposure by starting accumulation of electric charges in the plurality of photoelectric conversion elements, and a plurality of photoelectric conversion elements. The image correction circuit according to claim 1, wherein an image captured using the mechanical shutter that forms a light-shielding region shielded by the light-shielding unit on an arrayed element surface is acquired.   The correction unit is based on a difference between a characteristic of timing at which the electronic shutter starts exposure to the plurality of photoelectric conversion elements and a characteristic of timing at which the mechanical shutter ends exposure to the plurality of photoelectric conversion elements. The image correction circuit according to claim 2, wherein the correction is performed such that the exposure amount of the photoelectric conversion element that shortens the exposure time is increased. The electronic shutter starts exposure in units of lines in which the plurality of photoelectric conversion elements having a common wiring for starting charge accumulation are arranged linearly on the element surface, and
The boundary of the light shielding area intersects the line,
The image correction circuit according to claim 3, wherein the correction unit performs different corrections on at least two photoelectric conversion elements in the line.   The image correction circuit according to claim 1, wherein the correction unit performs correction according to a distance between the light shielding unit and the element surface in an optical axis direction of photographing light.   The correction unit acquires at least one of the operation history information and the operation environment information of the mechanical shutter when the image is captured, and the image is displayed according to at least one of the operation history information and the operation environment information. The image correction circuit according to claim 1, wherein correction is performed.   An imaging device comprising the image correction circuit according to any one of claims 1 to 6. An image acquisition function for acquiring an image captured using a mechanical shutter that controls the exposure time of a plurality of photoelectric conversion elements;
An image correction program for causing a computer to execute a correction function for correcting the image based on operating characteristics of the mechanical shutter.

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