JP2009272735A - Imaging apparatus, photometric value correction method and photometric value correction program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique of an imaging apparatus, capable of surely setting a correction value relating to a photometric value from a photometric sensor which changed, accompanying the exchange of a transparent member, without exerting a load on a user. <P>SOLUTION: The imaging apparatus includes an imaging element and the photometric sensor for receiving the object light which has passed through a focus plate (transparent member) provided exchangeably and performing photometry, and set exposure values and the photometric values for the photometric sensor are compared to execute exposure control. In the state where the exposure control is executed, the photometry is executed, on the basis of image signals obtained in the imaging element, and whether a difference value between the photometric value and the exposure value becomes a threshold α or more is determined (ST9-10). Here, when the difference value becomes the threshold α or larger, it is defined that the focus plate is to be replaced, and the difference value is set as a correction value, relating to the photometric value of the photometric sensor (ST11). As a result, the correction value relating to the photometric value of the photometric sensor changed, accompanying the exchange of the focus plate is surely set without exerting a load on the user. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique of an imaging apparatus including a photometric sensor and an imaging sensor.

  An imaging apparatus such as a single-lens reflex digital camera (digital single-lens reflex camera) has a replaceable focusing screen (focus screen) in a finder optical system that guides subject light that has passed through a photographing lens to a finder window. There is something.

  Here, when the focusing screen is replaced with an optional product with different optical characteristics such as transmittance and diffusion characteristics, it is detected by the photometric sensor that receives the subject light that has passed through the focusing screen (translucent member). The photometric value (photometric level) may change and an error may occur. If exposure control is performed based on a photometric value that is shifted from an accurate photometric value in this way, appropriate exposure control cannot be performed.

  For example, there is a technique disclosed in Patent Document 1 as a method for improving the defect after the replacement of the focusing screen. According to this technique, when exchanging the focusing screen, the user sets a correction value corresponding to the above error on the basis of the index shown on the holding member that holds the focusing screen, thereby enabling appropriate exposure control. Yes.

Japanese Patent Laid-Open No. 11-44906

  However, in the technique of the above-mentioned Patent Document 1, although the user recognizes the above-described index, the necessity of setting a correction value for the photometric value detected by the photometric sensor and the appropriate correction value can be grasped. The correction value setting operation is a burden on the user. Further, since the correction value setting is left to the user, the setting is not surely performed. For example, when the user forgets to set the correction value or does not understand the setting method, the correction value is not set, so that it is difficult to shoot in an appropriate exposure state.

  The present invention has been made in view of the above problems, and is an imaging apparatus that can reliably set a correction value related to a photometric value of a photometric sensor that has changed with the replacement of a translucent member without placing a burden on the user. The purpose is to provide technology.

  One aspect of the present invention is an imaging apparatus, which receives an object light guided from a photographic lens along a predetermined optical path and generates an image signal related to the object, and on the predetermined optical path A photometric sensor that receives subject light that has passed through a translucent member provided in a place that is not replaceable, performs photometry to obtain a first photometric value, and setting means for setting a target value for exposure control; Based on an exposure control means for performing the exposure control by comparing a measurement value based on the first photometric value and the target value, and an image signal acquired by imaging by the imaging sensor in the state where the exposure control is performed. Metering means for obtaining a second photometric value by performing photometry, wherein the exposure control means determines whether or not the translucent member has been replaced based on a difference value relating to the target value and the second photometric value. To determine When it is determined by the determining means and the determining means that the translucent member has been exchanged, a correction value based on the difference value is set, and the first photometric value is corrected by the correction value to perform the measurement. Photometric value correcting means for generating a value.

  According to the present invention, the translucent member is based on the difference value between the target value related to the exposure control and the second photometric value based on the image signal acquired by the imaging sensor in the state where the exposure control is performed. When it is determined whether or not the translucent member has been replaced, a correction value based on the difference value is set, and the first photometric value acquired by the photometric sensor based on the correction value is determined. to correct. As a result, the correction value relating to the photometric value of the photometric sensor that has changed with the replacement of the translucent member can be set reliably without imposing a burden on the user.

<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 part 301 to which the interchangeable lens 2 is mounted at the front center and a lens exchange button 302 arranged on the right side of the mount part 301 can be gripped. A grip portion 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, an optical finder 316 disposed above the LCD 311, an eye cup 321 surrounding the optical finder 316, and a main switch 317 disposed on the left side of the optical finder 316. And are provided. Furthermore, the camera body 10 has an exposure correction button 323 and an AE lock button 324 disposed on the right side of the optical viewfinder 316 on the back side, a flash unit 318 and a connection terminal portion disposed above the optical viewfinder 316. 319.

  The mount 301 is provided with a connector Ec (see FIG. 6) for electrical connection with the mounted interchangeable lens 2 and a coupler 75 (see FIG. 6) 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. 6) is housed in the battery compartment as a power source for the camera, and a memory card 67 (see FIG. 6) 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 shootings 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.

  Here, when the automatic exposure control mode is set by the mode setting dial 305, for example, 10 EV (Exposure Value) is set as an appropriate exposure value in the exposure control, and the aperture 23 is set so that photographing can be performed in an appropriate exposure state. Aperture value and shutter speed of the image sensor 101 are set. On the other hand, when the manual exposure mode is set by the mode setting dial 305, the user can arbitrarily set the exposure value, and shooting can be performed in an exposure state where the eyes are slightly over or under.

  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 shooting operation (the image sensor 101 (see FIG. 3) is exposed, a predetermined image processing is performed on an image signal obtained by the exposure, and the result is recorded on a memory card or the like. Is performed).

  The LCD 311 includes a color liquid crystal panel capable of displaying an image. The LCD 311 displays an image picked up by the image pickup device 101 (see FIG. 3), reproduces and displays a recorded image, and is mounted on the image pickup apparatus 1. Function and mode setting screen. 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. 6) in the wide direction or the tele direction), frame-by-frame feeding of a recorded image to be reproduced on the LCD 311 or the like, and shooting conditions (aperture value , Shutter speed, presence / absence of flash emission, etc.) for inputting instructions.

  The optical viewfinder 316 optically displays a range where a subject is photographed. In other words, the subject image from the interchangeable lens 2 is guided to the optical finder 316, and the user can visually recognize the subject actually captured by the image sensor 101 by looking into the optical finder 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 light shielding properties and suppresses intrusion of external light into the optical viewfinder 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. 6). The lens group 21 includes a focus lens 211 (see FIG. 6) for adjusting the focal point and a zoom lens 212 (see FIG. 6) 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 included in the interchangeable lens 2 when the interchangeable lens 2 is attached to the camera body 10. . 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 viewfinder unit 102 includes a pentaprism 105, an eyepiece lens 106, and an optical viewfinder 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 upright by the pentaprism 105 to the outside of the optical viewfinder 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.

  A focusing screen 77 is disposed below the pentaprism 106 in the finder unit 102, and a photometric sensor 78 is disposed along the upper surface of the pentaprism 106.

  The focusing screen 77 is configured as a translucent member that can be exchanged at a place that is not on a predetermined optical path, and the subject light that is reflected by the main mirror 1031 and whose path is changed upward is imaged.

  The photometric sensor 78 is configured as a photometric element, receives subject light that has entered the pentaprism 105 through the focusing screen 77, and performs photometry to obtain a photometric value (first photometric value) related to the subject. A photometric area Et (parallel oblique line portion) that can be measured by the photometric sensor 78 is a partial area included in the imaging range Es of the imaging element 101, and includes a large number of divided areas Eh that are divided in a honeycomb shape. (FIG. 5). In the photometric sensor 78 having such a structure, for example, an average value of photometric values detected in each divided area Eh is output.

  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 with the optical viewfinder 316 during shooting standby, the 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. The phase difference AF module 107 can perform so-called multipoint AF (multipoint distance measurement) in order to realize highly accurate phase difference AF.

  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.

<Electrical Configuration of Imaging Device 1>
FIG. 6 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, a focus lens 211 and a zoom lens 212, and a diaphragm 23 for adjusting the amount of light incident on the image sensor 101 provided in the camera body 10 are arranged in the lens barrel 22 with an optical axis LT (FIG. 3). ), And captures an optical image of the subject and forms it on the image sensor 101. 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, 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, the image signal generated by the image sensor 101 can be amplified in a variable amplification factor (gain), and the ISO sensitivity corresponding to the silver salt film can be changed by changing the 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 control 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 control circuit 612 identifies a portion that is originally estimated to be white based on luminance, saturation data, and the like in the photographic subject based on the WB adjustment data provided from the main control unit 62, and R, G of that portion. , B, the average of the respective color components, the G / R ratio and the G / B ratio are obtained, and the levels are corrected as R and B correction 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 includes a CPU 62a that functions as a computer, a flash ROM 62b that stores a control program, and a RAM (not shown) that temporarily stores data, and controls the operation of each unit of the imaging apparatus 1. Is. The flash ROM 62b stores a photometric value correction program PG that is executed by the CPU 62a to correct photometric values, which will be described later. The program data such as the photometric value correction program PG recorded in the memory card 67 is installed in the flash ROM 62b, so that the program can be reflected in the operation of the imaging apparatus 1.

  The main control unit 62 includes an exposure setting unit 621, an exposure control unit 622, and a photometry unit 623 that are realized by executing a control program by the CPU 62a.

  The exposure setting unit 621 is a part for setting an exposure value (target value) related to exposure control in the automatic exposure control mode or the manual exposure mode.

  The exposure control unit 622 performs exposure control by comparing the measured value based on the photometric value (first photometric value) obtained by the photometric sensor 78 with the exposure value set as the control target value by the exposure setting unit 621. It is a part.

  The photometry unit 623 is a part that obtains a photometric value (second photometric value) by performing photometry based on an image signal of a subject acquired by imaging with the imaging device 101 in a state where exposure control is performed.

  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 primary battery such as an alkaline battery or a secondary battery such as a nickel metal hydride 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.

<Response when the focusing screen 77 is replaced>
In the imaging apparatus 1 having the above-described configuration, when the focusing screen 77 is replaced with one having a different optical characteristic, the photometric value detected by the photometric sensor 78 may change and erroneous detection may be performed. There is. For example, when the user who owns the imaging device 1 replaces the focusing screen 77 attached at the time of purchase of the imaging device 1 with a light transmittance that is low, the photometric value output from the photometric sensor 78 Will fall. Thus, if the photometric value is erroneously detected by the photometric sensor 78, the exposure control will be adversely affected.

  Therefore, in the imaging apparatus 1 of the present embodiment, the photometric value is acquired by the photometric unit 623 from the captured image acquired by the imaging element 101 during the main imaging, and the photometric value of the photometric sensor 78 is corrected based on the photometric value. It will be reflected in the exposure control in the next and subsequent main shooting. Here, for obtaining a photometric value using the image sensor 101, an area corresponding to the photometric area Et (FIG. 5) of the photometric sensor 78 in the imaging range Es is extracted from the photographed image, and the photometric sensor is extracted in this extracted area. Similarly to the above, a divided area Eh (FIG. 5) is set. Then, LV (Light Value) as a photometric value is obtained by calculating a photometric value in each divided area Eh and obtaining an average of them.

  Hereinafter, a method for correcting the photometric value detected by the photometric sensor 78 will be described with reference to three specific cases (1) to (3).

(1) Case in which automatic exposure control mode is set and standard focus plate 77 is mounted In this case, it is not necessary to correct the photometric value of photometric sensor 78 because of standard standard focus plate 77 .

  That is, as shown in FIG. 3, when subject light enters the photometric sensor 78 via the focusing screen 77, the exposure control unit 622 performs exposure control based on the photometric value detected by the photometric sensor 78 so that the appropriate exposure value EV10 is obtained. Do. Next, when the shutter button 307 is fully pressed, the actual photographing operation is performed, and a photographed image is acquired by the image sensor 101. The photometric value calculated by the photometric unit 623 from this photographed image is LV10. Thus, when there is no difference in the photometric value (exposure value) between EV10 and LV10, it can be determined that a standard focusing screen 77 that does not need to correct the photometric value of photometric sensor 78 is mounted.

(2) Case in which the automatic exposure control mode is set and the optional focusing screen 77 is mounted In this case, since the optional focusing screen 77 having a low light transmittance is mounted, for example, the photometric sensor 78 is installed. It is necessary to correct the photometric value.

  That is, as shown in FIG. 3, when subject light enters the photometric sensor 78 through the focusing screen 77, the exposure control unit 622 exposes the exposure value EV10 to an appropriate exposure value EV10 based on an erroneous photometric value detected by the photometric sensor 78. Control will be performed. Next, when the shutter button 307 is fully pressed, a captured image is acquired by the image sensor 101. However, since exposure control based on an erroneous photometric value is performed, a photometric value calculated from the captured image is For example, LV11 is used instead of the original LV10. Here, since LV11 is subtracted from EV10 to “−1”, the exposure control unit 622 is equipped with an optional focusing plate 77 that requires “+1” correction of the photometric value of the photometric sensor 78. Is determined. In the next and subsequent shootings, if the correction value of “+1” level is added to the photometric value detected by the photometric sensor 78 to correct it, the proper exposure can be achieved even when the optional focusing screen 77 is attached. Shooting in the state becomes possible. The above correction value is stored in the flash ROM 62b, for example, so that it can be used for the next shooting.

(3) Case where manual exposure mode is set and optional focus plate 77 is mounted In this case, a non-standard optional focus plate 77 is mounted, so the photometric sensor is the same as in case (2) above. The photometric value from 78 must be corrected. However, in the correction of the photometric value, it is necessary to consider that the exposure value desired by the user (for example, the exposure value increased by “+0.5” with respect to the appropriate exposure) is set in the manual exposure mode. is there.

  That is, when subject light enters the photometric sensor 78 through the focusing screen 77 as shown in FIG. 3, the exposure control unit 622 sets the photographer in the exposure control unit 622 based on an erroneous photometric value detected by the photometric sensor 78. The exposure control is performed so that the exposure value EV10.5 including “+0.5” is obtained. Next, when the shutter button 307 is fully pressed, a captured image is acquired by the image sensor 101. However, since exposure control based on an erroneous photometric value is performed, a photometric value calculated from the captured image is For example, LV11.5, which is not the original LV10.5. Here, since LV11.5 is subtracted from EV10.5 to be “−1”, the exposure control unit 622 has an optional focusing plate 77 that requires correction of “+1” level for the photometric value of the photometric sensor 78. It is determined that it is installed. Then, in the next and subsequent shootings, if the photometric value detected by the photometric sensor 78 is corrected by adding a correction value of “+1” level, the photographer can be taken even if the optional focusing plate 77 is attached. Can be photographed in the desired exposure state.

  Hereinafter, a specific operation of the imaging apparatus 1 will be described.

<Operation of Imaging Device 1>
FIG. 7 is a flowchart showing the basic operation of the imaging apparatus 1. This operation particularly shows a photometric value correction operation for correcting the photometric value of the photometric sensor 78 in the photographing mode. The photometric value correction program PG is executed by the CPU 62a of the main control unit 62.

  In step ST1, it is determined whether or not the automatic exposure control mode is set in the mode setting dial 305. If the automatic exposure control mode is set, the process proceeds to step ST2. If the manual exposure mode is set instead of the automatic exposure control mode, the process proceeds to step ST3.

  In step ST2, the exposure setting unit 621 sets the exposure to an appropriate exposure value (for example, EV10).

  In step ST3, the exposure setting unit 621 performs exposure setting to the exposure value manually set by the user.

  In step ST4, photometry is performed by the photometric sensor 78 to obtain a photometric value.

  In step ST5, it is determined whether correction of the photometric value detected by the photometric sensor 78 is necessary. For example, whether or not correction is necessary is determined according to whether or not correction value information about the photometric value of the photometric sensor 78 is stored in the flash ROM 62b. If correction of the photometric value is necessary, the process proceeds to step ST6. If correction is not necessary, the process proceeds to step ST7.

  In step ST6, the exposure value is controlled by adding a correction value to the photometric value obtained by the photometric sensor 78. That is, since the optional focusing screen 78 is attached, the correction value stored in the flash ROM 62b in step ST11 described later is read from the flash ROM 62b and added to the photometric value detected by the photometric sensor 78 for exposure control. Use.

  In step ST7, exposure control is performed based on the photometric value obtained by the photometric sensor 78. That is, since it is determined that the standard focusing screen 77 is attached, the photometric value detected by the photometric sensor 78 is used for exposure control.

  In step ST <b> 8, actual photographing is performed and the subject image is acquired by the image sensor 101.

  In step ST9, photometry is performed based on the image signal of the subject image obtained by the image sensor 101 by the photometry unit 623. Here, as shown in FIG. 5, if the photometric value is calculated based on the image signal belonging to the area corresponding to the photometric area Et that can be measured by the photometric sensor 78 in the imaging range Es of the image sensor 101, the photometric sensor 78 What corresponds to the photometric value can be detected with high accuracy.

  In step ST10, it is determined whether the difference value between the exposure value set in step ST2 or step ST3 and the photometric value obtained by the image sensor 101 in step ST9 is greater than or equal to the threshold value α. That is, it is determined whether or not the focusing screen 77 has been replaced by comparing the difference value relating to the set exposure value and the photometric value obtained by the image sensor 101 with the threshold value α. Note that the threshold value α may be set to a value that is a minimum unit of photometric value calculation in the imaging apparatus, for example, 0.125 EV.

  In step ST10, if the amount of the difference value is equal to or larger than the threshold value α, it is determined that the optional focusing plate 77 is attached, and the process proceeds to step ST11. Assuming that the plate 77 is attached, the process returns to step ST1.

  In step ST11, the difference value is set as a correction value related to the photometric value of the photometric sensor 78, and information on the correction value is stored in the flash ROM 62b. That is, if it is determined in step ST10 that the difference value is equal to or greater than the threshold value α and the focusing screen 77 has been replaced, a correction value based on the difference value is set in step ST11, and the photometry of the photometric sensor 78 is performed based on this correction value. The measured value related to exposure control is generated in step ST6 by correcting the value.

  Through the operation of the imaging apparatus 1 as described above, it is determined that the focusing screen 77 has been replaced based on the difference value between the exposure value set in the automatic exposure control mode or the manual exposure mode and the photometric value obtained by the imaging element 101. In this case, a correction value based on the difference value is set for the photometric value of the photometric sensor 78. As a result, the correction value relating to the photometric value of the photometric sensor 78 that has changed along with the replacement of the focusing screen 77 can be set reliably without imposing a burden on the user.

<Modification>
In the above embodiment, it is not essential to determine that the focusing screen 77 has been replaced if the difference value is equal to or greater than the threshold value α in step ST10 shown in FIG. If the threshold value α is not less than a plurality of times, it may not be determined that the focusing screen 77 has been replaced. Thus, if it is determined that the focusing screen 77 has been replaced when each difference value obtained by imaging a predetermined number of times (for example, two times or three times) by the imaging element 101 is equal to or greater than the threshold value α, a photometric error or the like may occur. It is possible to improve reliability by eliminating the erroneous determination caused.

  In the above embodiment, it is not essential to perform photometry based on the image signal acquired by the image sensor 101 during the main shooting, and the live view image signal acquired by the image sensor 101 during the live view display before the main shooting. The photometric value (second photometric value) may be obtained by performing photometry based on the above. In this case, a subject image with an appropriate exposure state can be obtained even in the first actual photographing after the replacement of the focusing screen 77.

  In the image sensor 101 in the above-described embodiment, it is not essential to perform photometry based on the image signal of the area corresponding to the photometry area Et of the photometry sensor 78, and the photometry is performed based on the image signal of the entire captured image or the central portion. May be. In this case, although the accuracy is slightly lowered compared to the photometry in the area corresponding to the photometry area Et, photometry can be easily performed.

  -It is not essential to correct the photometric value of the photometric sensor 78 in the above embodiment when the focusing screen is replaced, and a translucent member (for example, a focus position) provided separately from the focusing screen. It may be carried out when the screen on which the target mark indicating etc. is displayed is exchanged.

1 is a diagram illustrating an external configuration of an imaging apparatus 1 according to an embodiment of the present invention. 1 is a diagram illustrating an external configuration of an imaging apparatus 1. FIG. 1 is a longitudinal sectional view of an imaging apparatus 1. FIG. It is a figure which shows the state of the mirror up in the mirror part. It is a figure for demonstrating the photometry area Et in the photometry sensor 78. FIG. 2 is a block diagram illustrating an electrical configuration of the imaging apparatus 1. FIG. 3 is a flowchart showing a basic operation of the imaging apparatus 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Interchangeable lens 10 Camera body 62 Main control part 62a CPU
62b Flash ROM
67 Memory Card 77 Focusing Plate 78 Photometric Sensor 101 Image Sensor 103 Mirror Unit 307 Shutter Button 621 Exposure Setting Unit 622 Exposure Control Unit 623 Photometric Unit Et Photometric Area PG Photometric Value Correction Program

Claims (5)

An imaging sensor that receives subject light guided from the photographing lens along a predetermined optical path and generates an image signal related to the subject; and
A photometric sensor that receives subject light that has passed through a translucent member that is replaceably provided at a location that is not on the predetermined optical path, and performs photometry to obtain a first photometric value;
Setting means for setting a target value for exposure control;
Exposure control means for performing the exposure control by comparing the measured value based on the first photometric value and the target value;
Photometric means for performing photometry based on an image signal acquired by imaging by the imaging sensor in a state where the exposure control is performed, and acquiring a second photometric value;
With
The exposure control means includes
Determination means for determining whether or not the translucent member has been replaced based on a difference value between the target value and the second photometric value;
When the determination means determines that the translucent member has been replaced, a correction value based on the difference value is set, and the first photometry value is corrected by the correction value to generate the measurement value. Photometric value correction means;
An imaging apparatus having   The imaging apparatus according to claim 1, wherein the determination unit determines that the translucent member has been replaced when each of the difference values obtained by imaging a predetermined number of times or more by the imaging sensor is a predetermined threshold value or more. .   The imaging apparatus according to claim 1, wherein the photometric unit acquires the second photometric value based on an image signal belonging to an area corresponding to a photometric area that can be measured by the photometric sensor in an imaging range of the imaging sensor. An imaging step of generating an image signal related to the subject by an imaging sensor that receives the subject light guided from the photographing lens along a predetermined optical path;
A first photometric step of obtaining a first photometric value by performing photometry with a photometric sensor that receives subject light that has passed through a translucent member provided interchangeably at a location not on the predetermined optical path;
A setting step for setting a target value for exposure control;
An exposure control step for performing the exposure control by comparing the measured value based on the first photometric value and the target value;
A second photometric step of obtaining a second photometric value by performing photometry based on an image signal acquired by imaging by the imaging sensor in the state in which the exposure control is performed;
With
The exposure control step includes
A determination step of determining whether or not the translucent member has been replaced based on a difference value related to the target value and the second photometric value;
When it is determined in the determination step that the translucent member has been replaced, a correction value based on the difference value is set, and the first photometric value is corrected by the correction value to generate the measurement value. A photometric correction process;
A photometric value correction method comprising: In the computer built into the imaging device,
An imaging step of generating an image signal related to the subject by an imaging sensor that receives the subject light guided from the photographing lens along a predetermined optical path;
A first photometric step of obtaining a first photometric value by performing photometry with a photometric sensor that receives subject light that has passed through a translucent member provided interchangeably at a location not on the predetermined optical path;
A setting step for setting a target value for exposure control;
An exposure control step for performing the exposure control by comparing the measured value based on the first photometric value and the target value;
A second photometric step of obtaining a second photometric value by performing photometry based on an image signal acquired by imaging by the imaging sensor in the state in which the exposure control is performed;
And execute
The exposure control step includes
A determination step of determining whether or not the translucent member has been replaced based on a difference value related to the target value and the second photometric value;
If it is determined in the determination step that the translucent member has been replaced, a correction value based on the difference value is set, and the first photometric value is corrected by the correction value to generate the measurement value. A photometric correction process;
A photometric value correction program.

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