JP2011081306A - Imaging apparatus and photometric method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for an imaging apparatus capable of shortening time taken until appropriate subject luminance is detected in photometry using a linear output type photometric sensor. <P>SOLUTION: The imaging apparatus includes the linear output type photometric sensor which linearly amplifies charge signals generated in a plurality of pixels respectively by exposure by two different gains, and outputs two photometric values. A luminance domain concerning measured luminance is divided into a low luminance domain La, a high luminance domain Lc and a middle luminance domain Lb showing luminance between them, and one graph adopted as an extension digital value is decided out of two graphs Ha and Hc in the respective luminance domains La, Lb and Lc to generate an extension digital value EBx(i, j) of each pixel Px. By deriving an exposure condition set in next photometry based on the generated photometry data, the time taken until the appropriate subject luminance is detected can be shortened. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique of an imaging apparatus including a photometric sensor that linearly amplifies a charge signal generated by each of a plurality of photoelectric conversion units by exposure to generate a photometric value.

  Some imaging devices such as a digital single-lens reflex camera detect the luminance of a subject by a photometric sensor and use it for exposure control.

  As for the photometric sensor, there are, for example, a linear output type configured as a CCD and a logarithmic compression type configured as a LOG sensor. Here, the linear output type photometric sensor has an advantage that a highly accurate photometric output can be obtained and photometry can be performed even during flash emission. On the other hand, in the linear output type, since the dynamic range of photometry is a relatively narrow range (for example, about 6 EV) compared to the logarithmic compression type, subject brightness may deviate from this dynamic range and whiteout or blackout may occur. . In such a case, it is necessary to perform photometry again after changing the photometry conditions such as the integration time (exposure time), and the time until proper subject luminance is detected becomes long.

  As a technique for improving the drawbacks of this linear output type, for example, a technique disclosed in Patent Document 1 has been proposed. In this technology, the charge signal generated by the photoelectric conversion element by photoelectric conversion action is amplified with different gains (amplification factors), and multiple amplified signals are output from the sensor at the same time, thereby expanding the dynamic range. Is planned.

JP 2007-189537 A

  However, in the technique of Patent Document 1, a plurality of amplified signals multiplied by different gains are output from the sensor. However, if control for selecting an optimum signal from these amplified signals is not performed, an appropriate subject brightness is obtained. It is not obtained and the detection time is not shortened.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging device technique capable of shortening the time until proper subject luminance is detected in photometry using a linear output type photometry sensor. And

  One aspect of the present invention is an imaging apparatus, in which a charge signal generated by each of a plurality of photoelectric units having a predetermined photoelectric conversion cell by exposure is linearly amplified with a plurality of different gains, and a plurality of photometry is performed. A photometric sensor that generates a value and outputs the photometric values in a first dynamic range, and a photometric value that is output from the photometric sensor by photometry set in the first exposure condition and the gain Based on this, photometric data having a second dynamic range wider than the first dynamic range is generated, and set in the next photometry related to the photometry set in the first exposure condition based on the photometric data. And a photometric control means for deriving the second exposure condition.

  According to the present invention, a plurality of photometric values are generated by linearly amplifying a charge signal generated by each of a plurality of photoelectric units having a predetermined photoelectric conversion cell by exposure with a plurality of different gains. A photometric sensor that outputs a photometric value in a first dynamic range is provided, and a photometric sensor that is wider than the first dynamic range based on a plurality of photometric values and gains output from the photometric sensor by photometry set in the first exposure condition. Photometry data having a dynamic range of 2 is generated, and second exposure conditions set in the next photometry are derived based on the photometry data. As a result, it is possible to shorten the time until proper subject luminance is detected in photometry using a linear output type photometric sensor.

1 is a diagram illustrating an external configuration of an imaging apparatus according to an embodiment of the present invention. It is a figure which shows the external appearance structure of an imaging device. It is a longitudinal cross-sectional view of an imaging device. It is a figure for demonstrating the state of mirror up. It is a block diagram which shows the electrical structure of an imaging device. It is a figure for demonstrating the structure of a photometry sensor. It is a figure for demonstrating the structure of a photometry sensor. It is a figure for demonstrating operation | movement of a photometric sensor. It is a figure for demonstrating the photometry output from a photometry sensor. It is a figure for demonstrating the method of extending the dynamic range of photometry. It is a flowchart which shows the basic operation | movement of an imaging device. It is a flowchart which shows a photometry process. It is a figure for demonstrating the photometry output from a photometry sensor. It is a figure for demonstrating the method of extending the dynamic range of photometry. It is a figure for demonstrating the structure of the photometry sensor which concerns on the modification of this invention.

<Embodiment>
[Appearance configuration of imaging device]
1 and 2 are diagrams showing an external configuration of an imaging apparatus 1 according to the embodiment of the present invention. Here, FIGS. 1 and 2 show a front view and a rear view, respectively.

  The imaging device 1 is configured as, for example, a single-lens reflex digital still camera, and includes a camera body 10 and an interchangeable lens 2 as a photographic lens that can be attached to and detached from the camera body 10.

  In FIG. 1, on the front side of the camera body 10, a mount portion 301 to which the interchangeable lens 2 is mounted at the center of the front surface, a lens exchange button 302 disposed on the right side of the mount portion 301, and a gripper. The grip part 303 is provided. Further, the camera body 10 is provided with a mode setting dial 305 disposed at the upper left portion of the front surface, a control value setting dial 306 disposed at the upper right portion of the front surface, and a shutter button 307 disposed on the upper surface of the grip portion 303. It has been.

  In FIG. 2, on the rear side of the camera body 10, there are an LCD (Liquid Crystal Display) 311, a setting button group 312 arranged on the left side of the LCD 311, and a cross key 314 arranged on the right side of the LCD 311. And a push button 315 disposed in the center of the cross key 314. On the back side of the camera body 10, a finder window 316 disposed above the LCD 311, an eye cup 321 surrounding the finder window 316, and a main switch 317 disposed on the left side of the finder window 316. And are provided. Further, the camera body 10 has an exposure correction button 323 and an AE lock button 324 disposed on the right side of the finder window 316 on the back side, a flash unit 318 and a connection terminal unit disposed above the finder window 316. 319.

  The mount 301 is provided with a connector Ec (see FIG. 5) for electrical connection with the mounted interchangeable lens 2 and a coupler 75 (see FIG. 5) for mechanical connection.

  The lens exchange button 302 is a button that is pressed when the interchangeable lens 2 attached to the mount unit 301 is removed.

  The grip part 303 is a part where the user grips the imaging device 1 at the time of photographing, and is provided with surface irregularities that match the finger shape in order to improve fitting properties. Note that a battery storage chamber and a card storage chamber (not shown) are provided inside the grip portion 303. A battery 69B (see FIG. 5) is housed in the battery compartment as a power source for the camera, and a memory card 67 (see FIG. 5) for recording image data of the photographed image is detachably housed in the card compartment. It has come to be. The grip unit 303 may be provided with a grip sensor for detecting whether or not the user has gripped the grip unit 303.

  The mode setting dial 305 and the control value setting dial 306 are made of a substantially disk-shaped member that can rotate in a plane substantially parallel to the upper surface of the camera body 10. The mode setting dial 305 is used for various types of shooting such as an automatic exposure (AE) control mode, an autofocus (AF) control mode, a still image shooting mode for shooting a single still image, and a continuous shooting mode for continuous shooting. This mode is used to selectively select a mode and a function installed in the imaging apparatus 1, such as a mode and a reproduction mode for reproducing a recorded image. On the other hand, the control value setting dial 306 is for setting control values for various functions installed in the imaging apparatus 1.

  The shutter button 307 is a push switch that can be operated in a “half-pressed state” that is pressed halfway and further operated in a “full-pressed state”. When the shutter button 307 is pressed halfway in the still image shooting mode, a preparation operation (preparation operation such as setting of an exposure control value or focus detection) for shooting a still image of the subject is executed. Further, when the shutter button 307 is fully pressed, a photographing operation (image pickup device 101 (see FIG. 3) is exposed, predetermined image processing is performed on the image signal obtained by the exposure, and the result is recorded in the memory card 67 or the like. A series of operations) is executed.

  The LCD 311 includes a color liquid crystal panel that can display an image. The LCD 311 displays an image obtained by capturing an image of a subject using the image sensor 101 (see FIG. 3), reproduces and displays a recorded image, and the like. A function or mode setting screen mounted on the apparatus 1 is displayed. Note that an organic EL or a plasma display device may be used instead of the LCD 311.

  The setting button group 312 is a button for performing operations on various functions installed in the imaging apparatus 1. The setting button group 312 includes, for example, a selection confirmation switch for confirming the content selected on the menu screen displayed on the LCD 311, a selection cancel switch, a menu display switch for switching the content of the menu screen, a display on / off switch, A display enlargement switch is included.

  The cross key 314 has an annular member having a plurality of pressing portions (triangle marks in the figure) arranged at regular intervals in the circumferential direction, and is not shown and provided corresponding to each pressing portion. The pressing operation of the pressing portion is detected by the contact (switch). The push button 315 is arranged at the center of the cross key 314. The cross key 314 and the push button 315 are used to change the shooting magnification (movement of the zoom lens 212 (see FIG. 5) in the wide direction or the tele direction), frame-by-frame feeding of a recorded image to be reproduced on the LCD 311 and the like, and shooting conditions (aperture value). , Shutter speed, presence / absence of flash emission, etc.) for inputting instructions.

  The viewfinder window 316 optically displays a range where the subject is photographed. That is, the subject image from the interchangeable lens 2 is guided to the finder window 316, and the user can visually recognize the subject actually captured by the image sensor 101 by looking into the finder window 316. .

  The main switch 317 is a two-contact slide switch that slides to the left and right. When the switch is set to the left, the power of the imaging apparatus 1 is turned on, and when the switch is set to the right, the power is turned off.

  The flash unit 318 is configured as a pop-up built-in flash. On the other hand, when attaching an external flash or the like to the camera body 10, the connection is made using the connection terminal portion 319.

  The eye cup 321 is a “U” shaped light shielding member that has a light shielding property and suppresses intrusion of external light into the finder window 316.

  The exposure correction button 323 is a button for manually adjusting an exposure value (aperture value or shutter speed), and the AE lock button 324 is a button for fixing exposure.

  The interchangeable lens 2 functions as a lens window that captures light (light image) from a subject, and also functions as a photographing optical system that guides the subject light to the image sensor 101 disposed inside the camera body 10. It is. The interchangeable lens 2 can be detached from the camera body 10 by depressing the lens interchange button 302 described above.

  The interchangeable lens 2 includes a lens group 21 including a plurality of lenses arranged in series along the optical axis LT (see FIG. 5). The lens group 21 includes a focus lens 211 (see FIG. 5) for adjusting the focal point and a zoom lens 212 (see FIG. 5) for performing zooming. By driving in the direction (see FIG. 3), zooming and focus adjustment are performed. Further, the interchangeable lens 2 is provided with an operation ring that can rotate along the outer peripheral surface of the lens barrel at a suitable position on the outer periphery of the lens barrel. The zoom lens 212 can be operated by manual operation or automatic operation. It moves in the optical axis direction according to the rotation direction and rotation amount of the operation ring, and is set to a zoom magnification (imaging magnification) according to the position of the movement destination.

[Internal Configuration of Imaging Device 1]
Next, the internal configuration of the imaging apparatus 1 will be described. FIG. 3 is a longitudinal sectional view of the imaging apparatus 1. As shown in FIG. 3, the camera body 10 includes an image sensor 101, a finder unit 102 (finder optical system), a mirror unit 103, a phase difference AF module 107, and the like.

  The imaging element 101 is arranged in a direction perpendicular to the optical axis LT on the optical axis LT of the lens group 21 provided in the interchangeable lens 2 when the interchangeable lens 2 is attached to the camera body 10. Yes. As the image sensor 101, for example, a plurality of pixels configured with photodiodes are two-dimensionally arranged in a matrix, and R (red), G (green), for example, having different spectral characteristics on the light receiving surface of each pixel. , B (blue) color filters are arranged in a ratio of 1: 2: 1, and a Bayer array CMOS color area sensor (CMOS type image sensor) is used. The image sensor 101 converts the light image of the subject formed through the interchangeable lens 2 into analog electrical signals (image signals) of R (red), G (green), and B (blue) color components, and R , G, and B image signals.

  On the optical axis LT, a mirror unit 103 is disposed at a position where subject light is reflected toward the viewfinder unit 102. The subject light that has passed through the interchangeable lens 2 is reflected upward by a mirror unit 103 (a main mirror 1031 described later). Part of the subject light that has passed through the interchangeable lens 2 passes through the mirror unit 103.

  The finder unit 102 includes a pentaprism 105, an eyepiece lens 106, and a finder window 316. The pentaprism 105 has a pentagonal cross section, and is a prism for converting an object light image incident from the lower surface thereof into an upright image by changing the top and bottom of the light image by internal reflection. The eyepiece 106 guides the subject image that has been made an erect image by the pentaprism 105 to the outside of the finder window 316. With such a configuration, the finder unit 102 functions as a finder for confirming the subject during shooting standby before actual shooting.

  The mirror unit 103 includes a main mirror 1031 and a sub mirror 1032, and is provided on the back side of the main mirror 1031 so that the sub mirror 1032 is tilted toward the back of the main mirror 1031. Part of the subject light transmitted through the main mirror 1031 is reflected by the sub mirror 1032, and the reflected subject light enters the phase difference AF module 107.

  The mirror unit 103 is configured as a so-called quick return mirror, and during exposure (main photographing), as shown in FIG. 4, the mirror unit 103 jumps upward with a rotating shaft 1033 as a rotation fulcrum. At this time, the sub mirror 1032 is folded so as to be substantially parallel to the main mirror 1031 when the mirror unit 103 stops at a position below the pentaprism 105. Accordingly, the subject light guided from the interchangeable lens 2 along the optical path on the optical axis LT without being blocked by the mirror unit 103 is received by the image sensor (imaging sensor) 101. When the imaging operation in which the imaging element 101 is exposed is completed, the mirror unit 103 returns to the original position (position shown in FIG. 3).

  In addition, by setting the mirror unit 103 in the mirror-up state shown in FIG. 4 before the main shooting (shooting for image recording), the imaging device 1 can perform moving image processing based on image signals sequentially generated by the imaging device 101. In this manner, live view (preview) display in which the subject is displayed on the LCD 311 is possible. In other words, in the imaging apparatus 1 before the actual photographing, the composition of the subject can be determined by selecting the electronic viewfinder (live view mode) in which the live view display is performed or the optical viewfinder. Note that switching between the electronic viewfinder and the optical viewfinder is performed by operating the changeover switch 85 shown in FIG.

  In addition, a focusing screen 77 is disposed below the pentaprism 106 in the finder unit 102, and a photometric sensor 78 is disposed on the upper rear side of the pentaprism 106.

  On the focusing screen 77, the subject light reflected by the main mirror 1031 and having its path changed upward is imaged.

  The photometric sensor 78 is configured as a linear output type (linear integral type) photometric element that outputs a photometric value proportional to the amount of received light. The photometric sensor 78 detects subject light incident on the pentaprism 105 through the focusing screen 77. It receives light and obtains a photometric value related to the subject. The configuration and operation of the photometric sensor 78 will be described in detail later.

  The phase difference AF module 107 is configured as a so-called AF sensor including a distance measuring element that detects focus information of a subject. The phase difference AF module 107 is disposed at the bottom of the mirror unit 103 and detects a focus position by phase difference detection type focus detection (hereinafter also referred to as “phase difference AF”). That is, when the user checks the subject through the finder window 316 during shooting standby, light from the subject is guided to the phase difference AF module 107 with the main mirror 1031 and the sub mirror 1032 down as shown in FIG. It is burned. Then, based on the output from the phase difference AF module 107, the focus lens 211 in the interchangeable lens 2 is driven to perform focusing.

  A shutter unit 40 is disposed in front of the image sensor 101 in the optical axis direction. The shutter unit 40 includes a curtain body that moves in the vertical direction, and a mechanical focal plane that performs an optical path opening operation and an optical path blocking operation of subject light guided to the image sensor 101 along the optical axis LT by the opening operation and the closing operation. It is configured as a shutter. The shutter unit 40 can be omitted when the image sensor 101 is an image sensor capable of complete electronic shutter.

  In addition, the interchangeable lens 2 is provided with a diaphragm 23 for adjusting the amount of light incident on the image sensor 101 provided in the camera body 10.

[Electrical Configuration of Imaging Device 1]
FIG. 5 is a block diagram illustrating an electrical configuration of the imaging apparatus 1. Here, the same members and the like as those in FIGS. 1 to 4 are denoted by the same reference numerals. For convenience of explanation, the electrical configuration of the interchangeable lens 2 will be described first.

  The interchangeable lens 2 includes a lens driving mechanism 24, a lens position detection unit 25, a lens control unit 26, and a diaphragm driving mechanism 27 in addition to the lens group 21 described above.

  In the lens group 21, the focus lens 211, the zoom lens 212, and the diaphragm 23 are held in the direction of the optical axis LT (FIG. 3) in the lens barrel 22, and an optical image of the subject is captured and formed on the image sensor 101. Let In the AF control, focus adjustment is performed by driving the focus lens 211 in the optical axis LT direction by the AF actuator 71M in the interchangeable lens 2.

  The focus drive control unit 71A generates a drive control signal for the AF actuator 71M necessary for moving the focus lens 211 to the in-focus position based on the AF control signal given from the main control unit 62 via the lens control unit 26. Is to be generated. The AF actuator 71M is composed of a stepping motor or the like, and applies a lens driving force to the lens driving mechanism 24.

  The lens driving mechanism 24 includes, for example, a helicoid and a gear (not shown) that rotates the helicoid, and receives the driving force from the AF actuator 71M to drive the focus lens 211 and the like in a direction parallel to the optical axis LT. It is. Note that the movement direction and the movement amount of the focus lens 211 are in accordance with the rotation direction and the rotation speed of the AF actuator 71M, respectively.

  The lens position detection unit 25 moves integrally with the lens while being in sliding contact with the encode plate in which a plurality of code patterns are formed at a predetermined pitch in the optical axis LT direction within the movement range of the lens group 21. An encoder brush, and detects the amount of movement of the lens group 21 during focus adjustment. The lens position detected by the lens position detection unit 24 is output as the number of pulses, for example.

  The lens control unit 26 is composed of, for example, a microcomputer having a built-in memory such as a ROM that stores a control program and a flash memory that stores data related to status information.

  The lens control unit 26 has a communication function for performing communication with the main control unit 62 of the camera body 10 via the connector Ec. Thereby, for example, the state information data such as the focal length, the exit pupil position, the aperture value, the focusing distance, and the peripheral light amount state of the lens group 21 and the position information of the focus lens 211 detected by the lens position detection unit 25 are main-controlled. For example, the driving amount data of the focus lens 211 can be received from the main control unit 62.

  The aperture drive mechanism 27 receives the driving force from the aperture drive actuator 76M via the coupler 75 and changes the aperture diameter of the aperture 23.

  Next, the electrical configuration of the camera body 10 will be described. The camera body 10 includes an AFE (analog front end) 5 and an image processing unit 61, an image memory 614, a main control unit 62, a flash circuit 63, and an operation unit 64 in addition to the image sensor 101 and the shutter unit 40 described above. , A VRAM 65, a card I / F 66, and a memory card 67. The camera body 10 includes a communication I / F 68, a power supply circuit 69, a battery 69B, a mirror drive control unit 72A and a mirror drive actuator 72M, a shutter drive control unit 73A and a shutter drive actuator 73M, an aperture drive control unit 76A, and an aperture drive. An actuator 76M is provided.

  The image sensor 101 is composed of a CMOS color area sensor as described above, and the timing control circuit 51 described below starts (and ends) the exposure operation of the image sensor 101 and selects the output of each pixel included in the image sensor 101. The imaging operation such as readout of the pixel signal is controlled.

  The AFE 5 gives a timing pulse for causing the image sensor 101 to perform a predetermined operation, performs predetermined signal processing on the image signal of the subject output from the image sensor 101, converts the image signal into a digital signal, and converts the image signal into an image processing unit 61. Is output. The AFE 5 includes a timing control circuit 51, a signal processing unit 52, an A / D conversion unit 53, and the like.

  The timing control circuit 51 generates a predetermined timing pulse (a pulse for generating a vertical scanning pulse φVn, a horizontal scanning pulse φVm, a reset signal φVr, etc.) based on the reference clock output from the main control unit 62, and the imaging device 101. And the imaging operation of the image sensor 101 is controlled. In addition, the operation of the signal processing unit 52 and the A / D conversion unit 53 is controlled by outputting predetermined timing pulses to the signal processing unit 52 and the A / D conversion unit 53, respectively.

  The signal processing unit 52 performs predetermined analog signal processing on the analog image signal output from the image sensor 101, and includes a CDS (correlated double sampling) circuit, an AGC (auto gain control) circuit, a clamp circuit, and the like. It has been. In this AGC circuit, an image signal generated by the image sensor 101 can be amplified in a variable amplification factor (gain). In addition, the A / D converter 53 converts the analog R, G, and B image signals output from the signal processor 52 into a plurality of bits (for example, 12) based on the timing pulse output from the timing control circuit 51. Bit) to a digital image signal.

  The image processing unit 61 performs predetermined signal processing on the image data output from the AFE 5 to create an image file, and includes a black level correction circuit 611, a white balance correction circuit 612, a gamma correction circuit 613, and the like. Has been. The image data captured by the image processing unit 61 is temporarily written in the image memory 614 in synchronization with the reading of the image sensor 101. Thereafter, the image data written in the image memory 614 is accessed to access the image processing unit. Processing is performed in each of the 61 blocks.

  The black level correction circuit 611 corrects the black level of each of the R, G, and B digital image signals A / D converted by the A / D conversion unit 53 to a reference black level.

  The white balance correction circuit 612 performs level conversion (white balance (WB) adjustment) of digital signals of each color component of R (red), G (green), and B (blue) based on a white reference corresponding to the light source. Is what you do. That is, the white balance correction circuit 612 identifies a portion that is originally estimated to be white from the luminance and saturation data in the photographic subject, and integrates (or averages) each of the R, G, and B color components of that portion. Then, the G / R ratio and the G / B ratio are obtained, and the levels are corrected as R and B correction gains (white balance gains).

  The gamma correction circuit 613 corrects the gradation characteristics of the image data subjected to WB adjustment. Specifically, the gamma correction circuit 613 performs non-linear conversion and offset adjustment using a gamma correction table set in advance for each color component.

  The image memory 614 temporarily stores the image data output from the image processing unit 61 in the photographing mode, and is also used as a work area for performing predetermined processing on the image data by the main control unit 62. It is. In the playback mode, the image data read from the memory card 67 is temporarily stored.

  The main control unit 62 is configured as a microcomputer and mainly includes a CPU, a RAM, and a ROM. The main control unit 62 implements various functions in software by reading a program stored in the ROM and executing the program by the CPU. For example, the main control unit 62 performs a focus control operation for controlling the position of the focus lens 211 in cooperation with the phase difference AF module 107, the focus drive control unit 71A, and the like.

  Further, the main control unit 62 has a photometry control unit 621 that is realized by software. The photometry control unit 621 controls an operation of generating an extended digital value (photometry data) based on an output from the photometry sensor 78 and deriving an exposure time at the next photometry as will be described later. The ROM of the main control unit 62 stores a default value (for example, 1 ms) of the exposure time (integration time) in the photometric sensor 78.

  The flash circuit 63 controls the light emission amount of the external flash connected to the flash unit 318 or the connection terminal unit 319 to the light emission amount set by the main control unit 62 in the flash photographing mode.

  The operation unit 64 includes the mode setting dial 305, the control value setting dial 306, the shutter button 307, the setting button group 312, the cross key 314, the push button 315, the main switch 317, etc., and the operation information is sent to the main control unit 62. It is for input.

  The VRAM 65 has an image signal storage capacity corresponding to the number of pixels of the LCD 311 and is a buffer memory between the main control unit 62 and the LCD 311. The card I / F 66 is an interface for enabling transmission / reception of signals between the memory card 67 and the main control unit 62. The memory card 67 is a recording medium that stores image data generated by the main control unit 62. The communication I / F 68 is an interface for enabling transmission of image data and the like to a personal computer and other external devices.

  The power supply circuit 69 includes, for example, a constant voltage circuit, and generates a voltage for driving the entire imaging apparatus 1 such as a control unit such as the main control unit 62, the imaging element 101, and other various driving units. Note that energization control to the image sensor 101 is performed by a control signal supplied from the main control unit 62 to the power supply circuit 69. The battery 69B includes a secondary battery such as a nickel metal hydride rechargeable battery or a primary battery such as an alkaline battery, and is a power source that supplies power to the entire imaging apparatus 1.

  The mirror drive control unit 72A generates a drive signal for driving the mirror drive actuator 72M in accordance with the timing of the photographing operation. The mirror drive actuator 72M is an actuator that rotates the mirror unit 103 (quick return mirror) to a horizontal posture or an inclined posture.

  The shutter drive control unit 73A generates a drive control signal for the shutter drive actuator 73M based on a control signal given from the main control unit 62. The shutter drive actuator 73M is an actuator that performs opening / closing driving (opening / closing operation) of the shutter unit 40.

  The diaphragm drive control unit 76A generates a drive control signal for the diaphragm drive actuator 76M based on the control signal given from the main control unit 62. The aperture driving actuator 76M applies a driving force to the aperture driving mechanism 27 via the coupler 75.

[Configuration and Operation of Photometric Sensor 78]
6 and 7 are diagrams for explaining the configuration of the photometric sensor 78. FIG. 6 shows a light receiving surface of the photometric sensor 78, and FIG. 7 shows an electrical configuration of the photometric sensor 78. As shown in FIG. FIG. 8 is a diagram for explaining the operation of the photometric sensor 78, which is a time chart showing the passage of time from left to right.

  In the photometric sensor 78, as shown in FIG. 6, red (R), green (G) and blue (B) color filters Fr, Fg, Fb are arranged in a Bayer array, and each color filter Fr, Fg, A photodiode PD (FIG. 7) is provided below (behind) Fb. In the photometric sensor 78, a photoelectric unit (hereinafter also referred to as “pixel”) Px composed of four photodiodes PD adjacent in the vertical and horizontal directions is defined. As a result, each of a plurality of pixels (photoelectric units) Px arranged in the photometric sensor 78 obtains photometric data of each RGB color having sensitivity of each of the three primary colors, and luminance information (density) of each RGB color from one pixel Px. Information) can be acquired.

  Further, the photometric sensor 78 has an amplifier (amplifier) Ap in which a charge (amplification factor) α is set by the charge signal accumulated in the photodiode PD by the photoelectric conversion action passing through the horizontal shift register Rh and the vertical shift register Rv. And an amplifier Aq for which a gain β (where β <α) is set. Note that the gain α of the amplifier Ap is set to, for example, 8 times corresponding to 3EV with respect to the gain β of the amplifier Aq. With such a configuration, at the output terminal Bp and the output terminal Bq of the photometric sensor 78, a photometric value (hereinafter also referred to as “H output value”) multiplied by a gain (hereinafter also referred to as “H gain”) α by the amplifier Ap. ) And a photometric value (hereinafter also referred to as “L output value”) multiplied by a gain (hereinafter also referred to as “L gain”) β by the amplifier Aq. However, these photometric values are output from the photometric sensor 78 with a dynamic range of about 6 EV, for example.

  In the photometric sensor 78 having the above configuration, as shown in FIG. 8, after the charge signal is generated by the photodiode PD by the exposure operation (integration operation) for the exposure time Te, the charge signal in each photodiode PD is read. By executing this over the period Tp, the above-described H output value and L output value can be appropriately obtained from the output terminals Bp and Bq (FIG. 7).

  As described above, in the photometric sensor 78, the charge signal generated in each pixel (photoelectric unit) Px having the four photodiodes PD constituting the photoelectric conversion cells by exposure is linearly generated with two different gains α and β. Amplification generates two photometric values (H output value and L output value), and outputs these H / L output values within a predetermined dynamic range (signal range). In the following, photometric control that uses the photometric sensor 78 to accurately derive the exposure time Te at the next photometric measurement and to shorten the time until proper subject luminance is detected will be described in detail.

[About metering control]
FIG. 9 is a diagram for explaining the photometric output from the photometric sensor 78. In FIG. 9, the horizontal axis represents the measured luminance (EV) with respect to the subject, and the vertical axis represents the digital value when the photometric output of the photometric sensor 78 is converted by a 10-bit A / D converter.

  In FIG. 9, the H output value and the L output value from the photometric sensor 78 are represented by a graph Ga composed of a curved portion Ga1 and a straight portion Ga2, and a curved graph Gb. Here, in the graph Ga related to the H output value, the high luminance portion is saturated like the straight line portion Ga2, but this is because the photometric value (H output value) amplified with a relatively high gain α is over the range when the luminance is high. It is to do. The linear output type photometric sensor 78 has a linear characteristic in which the output value increases or decreases in proportion to the amount of light received (measured luminance), but only the horizontal axis is logarithmized as shown in FIG. In this case, the photometric output is represented by curved graphs Ga1 and Gb.

  Using the photometric sensor 78 capable of obtaining the H output value and the L output value such as the above graphs Ga and Gb, the exposure time Te at the next photometry is accurately derived, and the time until the appropriate subject brightness is detected is shortened. In order to achieve this, it is necessary to obtain an appropriate photometric value (photometric data) by one photometry (exposure of the photometric sensor 78). Here, in order to obtain appropriate photometric data by a single photometry, it is preferable that blackout and whiteout are not generated even for a low-luminance or high-luminance subject. Although such photometry can be realized by setting a wide dynamic range, the linear output type photometric sensor 78 has a relatively narrow dynamic range as compared with the logarithmic compression type as described above. Therefore, in the imaging apparatus 1 of the present embodiment, the dynamic range of photometry can be expanded in a pseudo manner by effectively using the H output value and the L output value from the photometric sensor 78. A method for extending the dynamic range will be described in detail below.

  FIG. 10 is a diagram for explaining a technique for extending the dynamic range of photometry. In FIG. 10, the horizontal axis represents the measured luminance (EV) with respect to the subject, and the vertical axis logarithmically converted a digital value (expanded digital value described later) of the photometric data obtained using the photometric sensor 78. Shows things.

  A polygonal line graph Ha and a straight line graph Hb composed of the straight line portion Ha1 and the straight line portion Ha2 are obtained by logarithmically compressing the graph Ga and the graph Gb shown in FIG. 9 in the vertical axis direction.

  The H output value from the photometric sensor 78 has a merit of reducing the possibility of black crushing on a low-luminance subject as shown in the graph Ha1, but is saturated like the straight line portion Ha2 in the high-luminance region Lc. As a result, appropriate metering data cannot be obtained. Therefore, a graph Hc in which each value on the graph Hb is multiplied by 8 (= gain α / β) is generated by the photometry control unit 621, and the saturated portion (straight line) of the graph Ha is measured by the photometric data of the high luminance region Lc in the graph Hc. The graphs Ha and Hc are synthesized so as to complement the part Ha2). Thereby, the dynamic range regarding the photometric data obtained based on the output of the photometric sensor 78 is virtually extended from 10 bits to 13 bits. The digital value of the photometric data expanded in this way is also referred to as “extended digital value” below.

  A specific operation of the imaging apparatus 1 capable of artificially extending the photometric dynamic range as described above will be described in detail below.

[Operation of Imaging Device 1]
FIG. 11 is a flowchart showing the basic operation of the imaging apparatus 1. This operation particularly shows the operation relating to photometry, and is mainly executed by the photometry control unit 621 of the main control unit 62.

  When the imaging apparatus 1 is turned on by a user operation on the main switch 317, it is determined whether the shutter button 307 is half-pressed by the user (step ST1). If the shutter button 307 is half-pressed, the process proceeds to step ST2, and if it is not half-pressed, step ST1 is continued.

  In step ST2, a shooting preparation operation such as an AF control operation accompanied by driving of the focus lens 211 is performed.

  In step ST3, photometric processing is performed based on the output from the photometric sensor 78 (detailed later).

  In step ST4, it is determined whether the shutter button 307 is half-pressed continuously. If the half-press is continued, the process returns to step ST2, and if the half-press is released, the process exits this flowchart.

  FIG. 12 is a flowchart corresponding to the above step ST3 and showing the photometric process.

  In step ST11, it is determined whether or not the first photometry is performed by the photometry sensor 78. This first photometry is the first photometry performed by the photometry sensor 78 immediately after the shutter button 307 is half-pressed. Here, if it is the first photometry, the process proceeds to step ST12, and if it is the second or later, the process proceeds to step ST13.

  In step ST12, the exposure time (integration time) of the photometric sensor 78 is set to a default value (for example, 1 ms). Here, a predetermined default value (for example, “256” as a digital value) is set as a target value (operating point) in the next (second and subsequent) photometry.

  In step ST13, exposure (photometric integration) of the photometric sensor 78 is performed with the set exposure time (first exposure condition).

  In step ST14, a photometric value based on the charge signal generated by the photometric sensor 78 by the exposure operation in step ST13 is read. The A / D converted photometric data is divided into an H output value and an L output value and stored in, for example, the RAM of the main control unit 62. Here, in the pixel Px at the pixel position (i, j) in the photometric sensor 78, the digital value of the photometric data obtained by the H / L output value for each RGB color is defined as follows.

Digital values related to red (R) H / L output values: LBrH (i, j) and LBrL (i, j)
Digital values related to green (G) H / L output values: LBgH (i, j) and LBgL (i, j)
Digital values related to H / L output value of blue (R): LBbH (i, j) and LBbL (i, j)
Each pixel Px includes two green color filters Fg as shown in FIG. 6, but is based on a charge signal from each photodiode PD that receives subject light via these two green color filters Fg. The averaged output value is set (substituted) in LBgH (i, j) and LBgL (i, j). In the following, LBrH (i, j), LBgH (i, j) and LBbH (i, j) are collectively referred to as LBxH (i, j), and LBrL (i, j), LBgL (i, j) j) and LBbL (i, j) may be collectively referred to as LBxL (i, j).

  The operations in the next steps ST15 to ST17 indicate processing of photometric values obtained using the photometric sensor 78. Each of these operations will be described in detail below.

  In step ST15, the digital value of the photometric data obtained from the photometric sensor 78 is converted into the above-described extended digital value. That is, as shown in FIG. 10, a graph Hc is newly generated by multiplying each value on the graph Hb by 8 times. Then, the photometry dynamic range is extended by supplementing the saturated portion (straight line portion Ha2) of the graph Ha with the photometry data of the high luminance region Lc in the graph Hc. Hereinafter, the conversion (generation) of the extended digital value will be specifically described.

  As shown in FIG. 10, the measured luminance is divided into a low luminance region La, a high luminance region Lc, and a medium luminance region Lb which is the luminance between them, and two graphs are shown as follows in each luminance region La, Lb, Lc. One graph to be adopted as the extended digital value of Ha and Hc is determined, and the extended digital value EBx (i, j) of each pixel Px is generated.

(i) Low luminance area La
As shown in FIG. 10, in the graph Hb representing the L output value, the graph Ha representing the H output value is adopted as the extended digital value in the measured luminance of the low luminance region La smaller than the threshold Th1 (for example, Th1 = 16). That is, when LBxL (i, j) <Th1, the extended digital value EBx (i, j) = LBxH (i, j).

(ii) Medium luminance region Lb
In the graph Hb representing the L output value as shown in FIG. 10, in the measured luminance of the middle luminance region Lb that is not less than the threshold Th1 (for example Th1 = 16) and not more than the threshold Th2 (for example Th2 = 128), the two graphs Ha and Hc The larger output value is adopted as the extended digital value. That is, when Th1 ≦ LBxL (i, j) ≦ Th2, the extended digital value EBx (i, j) = Max (LBxH (i, j), LBxL (i, j) × 8). The function Max (a, b,...) Is a function that outputs the maximum, that is, the larger one of the arguments a, b,. If the larger output value is set to the extended digital value in this way, the subject brightness can be detected higher, so that whiteout can be suppressed at the next photometry by the feedback control.

  Here, with respect to the graph adopted as the above-described extended digital value, a calculated value (= LBxH) obtained by multiplying the H output value LBxH (i, j) by the inverse of the magnification (= 8 times) of the gain α with respect to the gain β. (i, j) / 8) and the calculated value obtained by multiplying the L output value LBxL (i, j) by the reciprocal of the magnification (= 1 times) of itself (gain β) based on the gain β, It is possible to select an appropriate one from the two graphs Ha and Hc also by selecting a large calculation value.

(iii) High luminance region Lc
As shown in FIG. 10, in the graph Hb representing the L output value, the graph Hc obtained by multiplying the L output value by 8 is used as the extended digital value in the measured luminance of the high luminance region Lc larger than the threshold Th2 (for example, Th2 = 128). That is, when LBxL (i, j)> Th2, the extended digital value EBx (i, j) = LBxL (i, j) × 8.

  As described above, when the L output value (subject luminance) obtained by the photometric sensor 78 is smaller than the threshold (first threshold) Th1, the photometric value amplified with the maximum gain α out of the two gains α and β. When an extended digital value (photometric data) is generated based on (H output value) and the L output value is larger than the threshold value (second threshold value) Th2 larger than the threshold value Th1, the two gains α and β An extended digital value is generated based on the photometric value (L output value) amplified by the minimum gain β multiplied by 8. When the L output value is equal to or greater than the threshold Th1 and equal to or less than the threshold Th2, as described above, the reciprocals of the gains α and β relating to the two photometric values (H output value and L output value) are obtained as the photometric values. Each of the calculated values obtained by multiplying is compared to generate an extended digital value. As described above, by generating the extended digital value, photometric data having an appropriately expanded dynamic range can be obtained.

  In step ST16, a representative value is determined for each pixel Px. Specifically, in each pixel Px of the photometric sensor 78, the luminance representative value EBd (i, j) and the color information Ecol (i, j) of the representative value are set as follows.

Representative value of luminance: EBd (i, j) = Max (EBr (i, j), EBg (i, j), EBb (i, j))
Color information of representative value: Ecol (i, j) = EBd (i, j) color number (for example, 1 = R, 2 = G, 3 = B)
As described above, by making the maximum value among the extended digital values (photometric data) of each RGB color in each of all the pixels (photoelectric units) Px of the photometric sensor 78 as a representative value, step ST18 described later based on this representative value. By deriving the exposure time (second exposure condition) at the next photometry, it is possible to derive the exposure time based on appropriate photometry data.

  In step ST17, an intermediate parameter (hereinafter also referred to as “intermediate parameter”) regarding the photometric data is calculated to be used in the next step ST18. Specifically, the intermediate parameters EBmax, EBmin, and EBave regarding the maximum value, the minimum value, and the average value are set as follows.

Maximum value EBmax: Maximum value of EBd (i, j) at all pixels Px Minimum value EBmin: Minimum value of EBd (i, j) at all pixels Px Average value EBave: EBd (at all pixels Px ( i, j) average value In this way, the maximum value (maximum representative value) EBmax and the minimum value (minimum representative value) EBmin are extracted from all the representative values for each pixel (photoelectric unit) Px of the photometric sensor 78. At the same time, by calculating the average value EBave for all the representative values related to each pixel Px, the exposure time (second time) for the next photometry in step ST18 described later based on these intermediate parameters EBmax, EBmin, EBave. In this case, the exposure time can be derived based on accurate photometric information.

  In step ST18, the exposure time for the next photometry is calculated. Hereinafter, assuming that the exposure time set in the current photometry in step ST13 is Te1, a method for calculating the exposure time Te2 set in the next photometry will be specifically described.

(i) Case where whiteout occurs in the current photometry If the minimum intermediate parameter EBmin calculated in step ST17> Th3 (for example, Th3 = 7168), the following formula (1) is used for the next photometry. An exposure time Te2 is obtained.

Te2 = Te1 × (128 / EBmin) (1)
When the minimum intermediate parameter (minimum representative value) EBmin is larger than the threshold value Th3 in this way, the minimum intermediate parameter obtained by the next photometry is a predetermined value, that is, the right side of the above equation (1). By deriving the next exposure time (second exposure condition) Te2 so as to be “128”, it becomes possible to appropriately suppress whiteout at the next photometry.

(ii) Case in which black crushing occurs in the current photometry If the maximum intermediate parameter EBmax <Th1 (for example, Th1 = 16) calculated in step ST17, the following photometry is performed according to the following equation (2). An exposure time Te2 is obtained.

Te2 = Te1 × (896 / EBmax) (2)
Thus, when the maximum intermediate parameter (maximum representative value) EBmax is smaller than the threshold Th1, the maximum intermediate parameter obtained by the next photometry is a predetermined value, that is, the right side of the above equation (2). By deriving the next exposure time (second exposure condition) Te2 so as to be “896”, it is possible to appropriately suppress black crushing at the next photometry.

(iii) Cases where no whiteout or blackout occurs in this photometry If the above cases (i) and (ii) do not apply, the following cases (iii-a) and (iii-b) The exposure time Te2 for the next photometry is obtained by the following equation (3) using the operating point (= 256) set in step ST12. This makes it possible to control the average luminance at the next photometry to an appropriate value.

Te2 = Te1 × (256 / EBave) (3)
(iii-a) Case where the average brightness obtained by the current photometry is high For example, when the average parameter EBave> 1024 of the average value calculated in step ST17, the exposure time at the next photometry is calculated by the following equation (4). Find Te2. This makes it possible to control the minimum luminance at the next photometry to an appropriate value, that is, “16” on the right side of the following equation (4).

Te2 = Te1 × (16 / EBmin) (4)
(iii-b) Case where the average brightness obtained by the current photometry is low For example, when the average parameter EBave <16 of the average value calculated in step ST17, the exposure time at the next photometry is calculated by the following equation (5). Find Te2. This makes it possible to control the maximum brightness at the next photometry to an appropriate value, that is, “896” on the right side of the following equation (5).

Te2 = Te1 × (896 / EBmax) (5)
In step ST19, normalization of the photometric value is performed as preprocessing of the next step ST20. Specifically, Kr (i, j), Kg (i, j), and Kb (i, j) are set as correction values for the photometric data of each RGB color so that the same light intensity can be obtained even if the colors are different. Then, photometric values EBrc (i, j), EBgc (i, j) and EBbc (i, j) normalized by the following equations (6) to (8) are obtained. Here, for example, “1” is set as the correction value Kg (i, j).

EBrc (i, j) = Kr (i, j) × EBr (i, j) (6)
EBgc (i, j) = Kg (i, j) × EBg (i, j) (7)
EBbc (i, j) = Kb (i, j) × EBb (i, j) (8)
Note that the operation of step ST19 can be omitted in the case of a photometric sensor without a color sensitivity difference, instead of the photometric sensor 78 having a color sensitivity difference as shown in FIG.

  In step ST20, Y and averaging processes are performed. That is, the luminance value (Y value) of the subject is obtained using the photometric values EBrc (i, j), EBgc (i, j), and EBbc (i, j) normalized for each color in step ST19. Average. Specifically, first, the Y value EY (i, j) of each pixel Px is obtained by the following equation (9).

EY (i, j) = (5 × EBrc (i, j) + 9 × EBgc (i, j) + 2 × EBbc (i, j)) / 16 (9)
Then, the Y value EY (i, j) of each pixel Px calculated by the above equation (9) is averaged to obtain the average value EYave.

  In step ST21, an absolute luminance value related to the subject is calculated from the exposure conditions set in the current photometry in step ST13. Specifically, the aperture value (AV value) AVt related to the aperture 23 of the interchangeable lens 2, the exposure time (TV value) TVt during the current photometry, and the effective sensitivity (SV value) SVt related to the H output value of the photometric sensor 78 Based on the following equation (10), an absolute luminance value (BV value) BVz is obtained.

BVz = AVt + TVt-SVt (10)
Then, using the absolute luminance value BVz calculated by the above equation (10), the average luminance value EYave obtained in step ST20, and the operating point (= 256) set in step ST12, the following equation (11 ) To obtain the expected value BVc for exposure control.

BVc = BVz + log ₂ (EYave-256) (11)
In step ST22, an exposure calculation is performed based on the absolute luminance value BVz calculated in step ST21. That is, the exposure control value at the time of actual photographing, specifically the sensitivity (SV value) SVc, aperture value (AV value) AVc, shutter speed (TV value) TVc, and exposure value (EV value) EVc of the image sensor 101, It determines based on following Formula (12)-(14).

EVc = SVc + BVc (12)
AVc = EVc / 2 (13)
TVc = EVc−AVc (14)
However, the aperture value AVc and the shutter speed TVc calculated by the above equations (13) to (14) are limited by a predetermined limit value.

  By the operation of the imaging apparatus 1 as described above, two photometric values (H output value and L output value) output from the photometric sensor 78 by performing photometry according to the exposure time (first exposure condition) set in step ST13. ) And gains α and β, as shown in FIG. 10, an extended digital value (photometric data) having a second dynamic range wider than the dynamic range (first dynamic range) of the photometric sensor 78 is generated. Then, based on this extended digital value, an exposure time (second exposure condition) set in the next photometry related to the photometry in step ST13 is derived (step ST18). By generating and using an extended digital value in which the dynamic range of metering is expanded in this way, the possibility of black crushing or whiteout in the metering data is reduced, so one metering (for example, the first metering) This makes it possible to accurately grasp the subject brightness. As a result, it is possible to shorten the time until proper subject luminance is detected in photometry using the linear output type photometry sensor 78.

  In the imaging apparatus 1, it is not essential to use the photometric sensor 78 that outputs each photometric value amplified with two different gains α and β, and outputs each photometric value amplified with three or more different gains. An extended digital value may be generated using a photometric sensor. Hereinafter, the calculation of the extended digital value will be described by taking as an example a photometric sensor 78A (FIGS. 3 to 5) that outputs each photometric value multiplied by three different gains (H / M / L gain).

  FIG. 13 is a diagram for explaining the photometric output from the photometric sensor 78A. In FIG. 13, the horizontal axis represents the measured luminance (EV) with respect to the subject, and the vertical axis represents the digital value when the photometric output of the photometric sensor 78A is converted by a 12-bit A / D converter.

  The photometric sensor 78A has, for example, a configuration in which one amplifier is further added to the two amplifiers Ap and Aq in the photometric sensor 78 shown in FIG. As a result, photometric values (H / M / L output values) amplified with three different gains γa, γb, and γc can be obtained simultaneously from the three output terminals of the photometric sensor 78A. Each gain is set so that, for example, the relationship that the gain γa is 8 times the gain γb and the gain γb is 8 times the gain γc, that is, the relationship γa = 8 × γb = 64 × γc is established. .

  Regarding the H / M / L output value from the photometric sensor 78A, as shown in FIG. 13, a graph Gc composed of a curved line portion Gc1 and a saturated straight line portion Gc2, and a graph composed of a curved line portion Gd1 and a saturated straight line portion Gd2. It is represented by Gd and a curve graph Ge. Here, since the gain γa related to the H output value is 8 times the gain γb related to the M output value, the graph Gc saturates at a lower luminance than the graph Gd.

  FIG. 14 corresponds to FIG. 10 and is a diagram for explaining a technique for extending the dynamic range of photometry.

  A broken line graph Hd composed of the straight line portion Hd1 and the straight line portion Hd2, a broken line graph He composed of the straight line portion He1 and the straight line portion He2, and a straight line graph Hf are represented by the graph Gc and the graph Gd shown in FIG. The graph Ge is logarithmically compressed in the vertical axis direction. The graph Hg is obtained by multiplying each value on the graph Hd by 8 times, and the graph Hh is obtained by multiplying each value on the graph Hf by 64 times.

  Then, the measured luminance is divided into a low luminance region Ka, a medium luminance region Kb, and a high luminance region Kc. In the low luminance region Ka, the photometric data of the graph Hd is adopted as an extended digital value. Further, instead of the graph Hd in which appropriate photometric data cannot be obtained in the medium luminance region Kb, the photometric data in the graph Hg is adopted as an extended digital value, and the graph Hg () in which appropriate photometric data cannot be obtained in the high luminance region Kc. Instead of Hd), the photometric data of the graph Hh is adopted as an extended digital value. Thereby, the dynamic range of photometry is appropriately expanded from 12 bits to 18 bits.

  In the imaging apparatus that generates the extended digital value as described above, an operation similar to the flowcharts shown in FIGS. 11 and 12 is executed by the photometric control unit 621A (FIG. 5) of the main control unit 62. However, the conversion operation of the extended digital value in step ST15 of FIG. 12 is different, and this operation will be described in detail below.

  First, with respect to the pixel Px at the pixel position (i, j) in the photometric sensor 78A, the digital value of the photometric data obtained as the H / M / L output value for each RGB color is defined as follows.

-Red (R) H / M / L output values: LBrH (i, j), LBrM (i, j) and LBrL (i, j)
-Green (G) H / M / L output values: LBgH (i, j), LBgM (i, j) and LBgL (i, j)
-Blue (R) H / M / L output values: LBbH (i, j), LBbM (i, j) and LBbL (i, j)
Then, the digital value of the photometric data obtained from the photometric sensor 78A is converted into the above-described extended digital value. That is, as shown in FIG. 14, a graph Hg in which each value on the graph Hd is multiplied by 8 is newly generated and a graph Hh in which each value on the graph Hf is multiplied by 64 is newly generated. Then, the saturated portions (straight line portions Hd2, He2) of the graphs Hd and He are supplemented with the photometric data of the medium luminance region Kb in the graph Hg and the photometric data of the high luminance region Kc in the graph Hh. Hereinafter, the conversion (generation) of the extended digital value will be specifically described.

  In the low luminance region Ka, the medium luminance region Kb, and the high luminance region Kc shown in FIG. 14, one graph to be adopted as an extended digital value is determined from the three graphs Hd, Hg, and Hh as follows, and each pixel Px An extended digital value EBx (i, j) is generated.

(i) Low luminance area Ka
As shown in FIG. 14, in the graph He representing the M output value, the graph Hd representing the H output value is adopted as the extended digital value in the measured luminance of the low luminance region Ka smaller than the threshold value Tha (for example, Tha = 256). That is, when LBxM (i, j) <Tha, the extended digital value EBx (i, j) = LBxH (i, j).

(ii) Medium luminance area Kb
In the graph He representing the M output value as shown in FIG. 14, in the measured luminance of the middle luminance region Kb that is equal to or higher than the threshold value Tha (for example, Th1 = 256) and equal to or lower than the threshold value Thb (for example, Thb = 2048), Hg is adopted as an extended digital value. That is, when Tha ≦ LBxM (i, j) ≦ Thb, the extended digital value EBx (i, j) = LBxM (i, j) × 8.

(iii) High brightness area Kc
As shown in FIG. 14, in the graph He representing the M output value, the graph Hh obtained by multiplying the L output value by 64 is adopted as the extended digital value for the measured luminance in the high luminance region Kc larger than the threshold Thb (for example, Thb = 2048). That is, when LBxM (i, j)> Thb, the extended digital value EBx (i, j) = LBxL (i, j) × 64.

  As described above, if an extended digital value in which the dynamic range of metering is expanded based on the H / M / L output value from the metering sensor 78A is generated, the subject brightness can be accurately grasped by one metering, so that an appropriate value can be obtained. The time until the subject luminance is detected can be shortened.

<Modification>
In the photometric sensor in the above embodiment, it is not essential to arrange the color filters for each color of RGB in a Bayer arrangement as shown in FIG. 6, but may be arranged in a stripe arrangement as shown in FIG. In the color filter arrangement shown in FIG. 15, a set of red (R), green (G), and blue (B) color filters Fr, Fg, and Fb adjacent to the left and right (horizontal direction) is one pixel (photoelectric unit). ) Px.

  The photometric sensor 78 (78A) in the above embodiment is not necessarily provided in a single-lens reflex camera (imaging device), and may be provided in a compact camera. Moreover, it is not essential to provide in a digital camera, You may provide in the camera which uses a silver salt film.

  Although the present invention has been described in detail, the above description is illustrative in all aspects, and the present invention is not limited thereto. It is understood that countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Interchangeable lens 10 Camera body 62 Main control part 78, 78A Photometry sensor 101 Image pick-up element 621, 621A Photometry control part Ap, Aq Amplifier Ka, La Low brightness area Kb, Lb Middle brightness area Kc, Lc High brightness area PD Photodiode Px Pixel (photoelectric unit)

Claims (7)

A charge signal generated by each of a plurality of photoelectric units having a predetermined photoelectric conversion cell by exposure is linearly amplified with a plurality of different gains to generate a plurality of photometric values, and the plurality of photometric values are converted into the first photometric values. A photometric sensor that outputs in the dynamic range;
Based on a plurality of photometric values output from the photometric sensor by the photometry set to the first exposure condition and the gain, photometric data having a second dynamic range wider than the first dynamic range is generated. A photometric control means for deriving a second exposure condition set in the next photometry related to the photometry set in the first exposure condition based on the photometric data;
An imaging apparatus comprising: The photometric control means is
A first generation unit configured to generate the photometric data based on a photometric value amplified with a maximum gain among the plurality of gains when a subject luminance detected by the photometric sensor is smaller than a first threshold;
A second generation for generating the photometric data based on a photometric value amplified with a minimum gain among the plurality of gains when the subject brightness is higher than a second threshold value greater than the first threshold value; Means,
When the subject brightness is not less than the first threshold and not more than the second threshold, based on the calculated value obtained by multiplying the photometric value by the reciprocal of the gain related to each of the plurality of photometric values, Third generation means for generating the photometric data;
The imaging apparatus according to claim 1, comprising: From the photometric sensor, in each of the plurality of photoelectric units, photometric data of each color having the sensitivity of each of a plurality of colors is obtained,
The photometric control means is
Exposure condition deriving means for deriving a second exposure condition based on the representative photometric data among the photometric data of the respective colors in each of the plurality of photoelectric units;
The imaging apparatus according to claim 1, comprising: The exposure condition deriving means includes
Means for extracting a maximum representative value and a minimum representative value from all the representative values for each of the plurality of photoelectric units, and calculating an average value for all the representative values;
Means for deriving the second exposure condition based on the maximum representative value, the minimum representative value, and the average value;
The imaging apparatus according to claim 3, wherein: The photometric control means is
Means for deriving the second exposure condition so that the minimum representative value obtained by the next photometry is a predetermined value when the minimum representative value is larger than a predetermined threshold;
The imaging device according to claim 4, comprising: The photometric control means is
Means for deriving the second exposure condition so that the maximum representative value obtained by the next photometry is a specific value when the maximum representative value is smaller than a specific threshold;
The imaging device according to claim 4, comprising: A charge signal generated by each of a plurality of photoelectric units having a predetermined photoelectric conversion cell by exposure is linearly amplified with a plurality of different gains to generate a plurality of photometric values, and the plurality of photometric values are converted into the first photometric values. A photometric process that outputs in the dynamic range;
Based on a plurality of photometric values output in the photometric step and the gain by photometry set to the first exposure condition, photometric data having a second dynamic range wider than the first dynamic range is generated. A photometric control step of deriving a second exposure condition to be set in the next photometry relating to the photometry set to the first exposure condition based on the photometric data;
A photometric method comprising:

Images