JP4343753B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus that switches between a first state in which a light beam from a photographing lens is guided to a finder optical system and a second state in which the light beam reaches an image sensor.

  In a single-lens reflex camera that is one of the imaging devices, when observing an object image using an optical finder, the light beam emitted from the photographing lens is reflected by a reflecting mirror disposed on the image plane side with respect to the photographing lens, It leads to an optical viewfinder including a pentaprism. Thereby, the photographer can view the object image formed by the photographing lens as a normal image. At this time, the reflection mirror is provided obliquely on the photographing optical path.

  On the other hand, when photographing an object image, the reflecting mirror is retracted from the photographing optical path so that the light flux from the photographing lens reaches the imaging medium (imaging device such as a film or a CCD). When the photographing operation is completed, the reflecting mirror is obliquely installed on the photographing optical path.

  Here, some single-lens reflex digital cameras can manually select focus adjustment by a phase difference detection method and focus adjustment by a contrast detection method (for example, see Patent Document 1). When the reflecting mirror is obliquely arranged on the photographing optical path, focus adjustment is performed by the phase difference detection method, and when the reflecting mirror is retracted from the photographing optical path, the focus by the contrast detection method is used using the output of the image sensor. Some perform adjustment (see, for example, Patent Document 2). In the camera of Patent Document 2, it is possible to perform focus adjustment by a contrast detection method while displaying (electronically displaying) an image read from the image sensor on a display unit. It is also possible to measure subject luminance using the output of the image sensor.

  In general, the focus adjustment by the contrast detection method has a problem that it takes time to reach an in-focus state because the evaluation function value is obtained while slightly moving the imaging lens in the optical axis direction. In the focus adjustment by the phase difference detection method, the photographing lens is only moved by the detected defocus amount, so that the time until the in-focus state is achieved is shorter than that in the contrast detection method.

  Therefore, even when an object image is observed using an electronic display, the camera can be configured as described below in order to perform high-speed focus adjustment by the phase difference detection method.

  The main mirror, which is a full-surface half mirror provided in the camera, and a sub mirror that reflects the light transmitted from the main mirror are operated independently, and the EVF (Electric View Finder) state and the OVF (Optical View Finder) state are set. The positions of the main mirror and the sub mirror are changed accordingly. That is, in the OVF state, the light beam from the photographic lens is reflected by the main mirror and guided to the optical viewfinder, and the transmitted light of the main mirror is reflected by the sub mirror and guided to the focus detection unit. Further, in the EVF state, the sub mirror is retracted from the imaging optical path, the position of the main mirror is changed to reflect the light beam from the imaging lens and guided to the focus detection unit, and the transmitted light of the main mirror reaches the image sensor. To.

  With the above-described configuration, the focus detection unit can perform focus detection by the phase difference detection method in the OVF state and the EVF state, and high-speed focus adjustment can be performed.

On the other hand, in a single-lens reflex camera, a photometric unit for measuring subject luminance is usually disposed in the vicinity of the finder optical system and captures a part of the light beam passing through the finder optical system (for example, (See Patent Document 3). This is because a photometric unit is preferably provided in the vicinity of the finder optical system in order to perform TTL (Through The Lens) photometry using a light beam from the photographing lens.
JP 2001-275033 A (paragraph numbers 0053 to 0057, FIG. 5) JP 2001-125173 A (paragraph numbers 0062 to 0067, FIGS. 8 and 9) JP-A-10-312009 (FIG. 1 etc.)

  However, in the camera configured to change the positions of the main mirror and the sub mirror according to the OVF state and the EVF state described above, since the photographing light beam is not guided to the finder optical system in the EVF state, the photometric unit disposed in the finder optical system Metering cannot be performed using.

  Further, when the camera is in the OVF state and the photographer takes a picture as a subject, for example, when performing remote photography or self-timer photography, the photographer moves the eyepiece of the finder optical system. It will not be excluded. For this reason, light outside the camera may enter the camera via the eyepiece and reach the focus detection unit, the image sensor, or the photometry unit.

  Light that enters from the eyepiece (finder back-incident light) is not used for photographing, and thus becomes ghost light. When the finder back-incident light reaches the focus detection unit, an error occurs in focus detection, and when it reaches the image sensor, the image obtained by the imaging operation is deteriorated. Furthermore, when the finder reverse incident light reaches the photometry unit, an error occurs in photometry detection.

An imaging apparatus according to the present invention includes an imaging element that photoelectrically converts a subject image formed by a light beam from a photographing lens, a finder optical system that enables optical observation of the subject image by the light beam, and an optical path of the light beam. switching driven to a second state for transmitting to the first state, the light beam is located on the optical path towards the imaging device for reflecting the finder optical system the light beam is located a mirror unit, and photometric means for performing photometry using the reflected light beam from the mirror unit, when the mirror unit is in said first state performs photometry using the output signal from said light measuring means, when in the second state is characterized by a control means for performing photometry using the output signal from the imaging device.

  According to the present invention, the signal used for performing photometry among the output signals of the photometry means and the image sensor is changed according to the state of the mirror unit, so that the mirror unit is in either the first state or the second state. Metering can be performed even in the state of.

  Examples of the present invention will be described below.

  Hereinafter, a camera that is Embodiment 1 of the present invention will be described with reference to FIGS.

  FIG. 6 is a schematic diagram showing the configuration of the camera system in the present embodiment. This camera system has a camera body and a lens device that is detachably attached to the camera body.

  The camera is a single-plate digital color camera using an image sensor such as a CCD or CMOS sensor, and obtains an image signal representing a moving image or a still image by driving the image sensor continuously or once. Here, the imaging element is an area sensor of a type that converts the exposed light into an electrical signal for each pixel, accumulates charges according to the amount of received light, and reads the accumulated charges.

  In FIG. 6, reference numeral 101 denotes a camera body, and reference numeral 102 denotes a lens device that can be detached from the camera body 101. A photographing optical system is provided in the lens device 102. The lens device 102 is electrically and mechanically connected to the camera body 101 via a known mount mechanism. Then, by attaching the lens device 102 having different focal lengths to the camera body 101, it is possible to obtain shooting screens having various angles of view.

  In the lens device 102, a focusing lens, which is a part of the photographing optical system 103, is moved in the direction of the optical axis L1 via a driving mechanism (not shown), or the focusing lens is moved to a flexible transparent elastic member or liquid. It is composed of a lens, and the focus of the photographic optical system is adjusted by changing the refractive power by changing the interface shape.

  Reference numeral 106 denotes an image sensor housed in a package 124. In the optical path from the photographic optical system 103 to the image sensor 106, the cutoff frequency of the photographic optical system 103 is limited so that a spatial frequency component higher than necessary of the object image (optical image) is not transmitted to the image sensor 106. An optical low-pass filter 156 is provided. The photographing optical system 103 is formed with an infrared cut filter (not shown).

  The signal read from the image sensor 106 is displayed on the display unit 107 as image data after being subjected to predetermined processing as will be described later. The display unit 107 is attached to the back of the camera body 101 so that the user can directly observe the display on the display unit 107.

  If the display unit 107 is composed of an organic EL spatial modulation element, a liquid crystal spatial modulation element, a spatial modulation element using fine particle electrophoresis, or the like, the power consumption can be reduced and the display unit 107 can be made thin. . Thereby, the power saving and size reduction of the camera body 1 can be achieved.

  Specifically, the image sensor 106 is a CMOS process compatible sensor (hereinafter abbreviated as a CMOS sensor) which is one of the amplification type solid-state image sensors. One of the features of the CMOS sensor is that the MOS transistors in the area sensor and the peripheral circuits such as the image sensor drive circuit, AD converter circuit, and image processing circuit can be formed in the same process. It can be greatly reduced. In addition, it has a feature that random access to an arbitrary pixel is possible, reading out for a display is easy, and real-time display can be performed at a high display rate on the display unit 107.

  The image sensor 106 uses the above-described features to perform a display image output operation (reading in a region where a part of the light receiving region of the image sensor 106 is thinned) and a high-definition image output operation (reading in the entire light receiving region). Do.

  Reference numeral 111 denotes a movable half mirror (first mirror member) that reflects a part of the light flux from the photographing optical system 103 and transmits the remaining part. The half mirror 111 has a refractive index of about 1.5 and a thickness of 0.5 mm. Reference numeral 105 denotes a focusing screen arranged on a predetermined image plane of an object image formed by the photographing optical system 103, and 112 denotes a pentaprism.

  Reference numeral 109 denotes a finder lens for observing an object image formed on the focusing screen, and actually includes three finder lenses (109-1, 109-2, 109-3 in FIG. 1). . The focusing screen 105, the pentaprism 112, and the finder lens 109 constitute a finder optical system.

  In the finder optical system, a photometric sensor (photometric means) 144 for measuring the subject brightness and a photometric lens 145 for forming an image of the light flux of the picked-up image displayed on the focusing screen 105 on the light receiving surface of the photometric sensor 144. Is provided.

  A movable sub-mirror (second mirror member) 122 is provided behind the half mirror 111 (on the image plane side), and reflects the light beam close to the optical axis L1 out of the light beam transmitted through the half mirror 111, thereby the focus detection unit. (Focus detection means) 121. The sub mirror 122 rotates around a rotation shaft 125 (see FIG. 1 and the like) described later, and is housed in the lower part of the mirror box according to the movement of the half mirror 111. That is, the sub mirror 122 does not operate integrally with the half mirror, and can advance and retreat independently with respect to the photographing optical path.

  The focus detection unit 121 receives the light beam from the sub-mirror 122 and performs focus detection by the phase difference detection method.

  The optical path splitting system composed of the half mirror 111 and the sub mirror 122 can be switched between the first to third optical path splitting states as will be described later. In the first optical path division state (first state), the light beam from the photographing optical system 103 is reflected by the half mirror 111 and guided to the finder optical system, and the light beam transmitted through the half mirror 111 is reflected by the sub mirror 122. To the focus detection unit 121.

  In the first optical path division state, the object image formed by the light beam can be observed through the finder lens 109 and the focus detection unit 121 can perform focus detection. In addition, in FIG. 6, the 1st optical path division | segmentation state is shown.

In the second optical path division state (transmission / reflection state : second state ), the light beam from the photographing optical system 103 passes through the half mirror 111 and passes through the open focal plane shutter 113, and the image sensor 106. And is reflected by the half mirror 111 and guided to the focus detection unit 121. In the second optical path division state, captured image data can be displayed in real time on the display unit 107, or high-speed continuous shooting can be performed. Here, in the second optical path division state, since it is possible to perform imaging with the image sensor 106 without operating the optical path division system, high-speed continuous shooting is performed by speeding up the operation in the signal processing system. Can do.

  In the second optical path division state, the focus detection unit 121 can perform focus detection. For this reason, it is possible to perform high-speed focus adjustment by the phase difference detection method even during monitoring by the display unit 107.

In the third optical path division state (retracted state), the focal plane shutter 113 is opened, so that the light flux from the photographing optical system 103 is directly guided to the image sensor 106. In this state, the half mirror 111 and the sub mirror 122 are retracted from the photographing optical path. The third optical path division state is used to generate a high-definition image suitable for large prints and the like. In this state, optical path division by the half mirror 111 and the sub mirror 122 is not actually performed, but in this embodiment, this state is referred to as a third optical path division state.

  The optical path splitting system is driven by a mirror driving mechanism 150 having an electromagnetic motor and a gear train (not shown). By changing the positions of the half mirror 111 and the sub mirror 122, the first to third optical path splitting states are changed. Can be switched between. The drive control of the mirror drive mechanism 150 is performed by the camera system control circuit 135.

  Here, in order to switch the above-described three optical path division states at high speed, the half mirror 111 is formed of a transparent resin to reduce the weight. A polymer thin film having birefringence is attached to the back surface of the half mirror 111 (the surface on the sub mirror 122 side in FIG. 6). This is because a stronger low-pass effect is provided in correspondence with the case where the image is not captured using all the pixels of the image sensor 106 as in the case of monitoring an image (real-time display) or when performing high-speed continuous shooting.

  In addition, by forming a fine pyramid-like periodic structure having a pitch smaller than the wavelength of visible light on the surface of the half mirror 111 and acting as a so-called photonic crystal, light caused by a difference in refractive index between air and resin It is also possible to reduce the surface reflection of the light and increase the light utilization efficiency. If comprised in this way, it can prevent that a ghost generate | occur | produces by the multiple reflection of the light in the back surface and the surface of the half mirror 111 in a 2nd optical path division | segmentation state.

  Reference numeral 104 denotes a movable flash light emitting unit, which is movable between a storage position stored in the camera main body 101 and a light emission position protruding from the camera main body 101. Reference numeral 113 denotes a focal plane shutter for adjusting the amount of light incident on the image plane, and reference numeral 119 denotes a main switch for starting the camera body 101.

Reference numeral 120 denotes a release button that is pressed in two steps. A shooting preparation operation (photometry operation, focus adjustment operation, etc.) is started by a half-press operation (SW1 ON), and a shooting operation is performed by a full-press operation (SW2 ON). ( Image recording operation: recording of image data read from the image sensor 106 on a recording medium) is started.

  Reference numeral 123 denotes a mode changeover switch (operation means), which is operated to switch between the OVF mode and the EVF mode. The finder mode changeover switch 123 is a slide-type switch, and is configured to be able to hold this position when moved to a set position in the OVF mode or EVF mode.

  Reference numeral 180 denotes an information display unit in the optical viewfinder for displaying specific information on the focusing screen 105.

  Next, a photometric optical system having the photometric lens 145 and the photometric sensor 144 will be described.

  In the first optical path division state, the photographing light beam that has passed through the photographing lens 103 is reflected by the half mirror 111 and forms an image on the upper surface of the focusing screen 105 (the surface on the pentaprism 112 side). The upper surface of the focusing screen 105 is matted to diffuse the photographing light flux. For this reason, when a photographing light beam forms an image on the upper surface of the focusing screen 105, the photographer can observe a clear photographed image through the finder optical system. Only photographed images that are blurred due to diffused light flux can be seen. Since the upper surface of the focusing screen 105 is disposed at a position optically equivalent to the imaging position of the image sensor 106, the photographer can use the diffusion action on the upper surface of the focusing screen 105 to focus the photographing optical system. The state can be grasped.

  The light beam diffused on the upper surface of the focusing screen 105 has many components parallel to the optical axis (finder optical axis), and the component having an angle with respect to the optical axis decreases as the angle increases. As shown in FIG. 3, the photometric optical system is disposed at a position where the upper surface of the focusing screen 105 can be observed from an angle inclined by approximately 6 degrees with respect to the optical axis. That is, since a component having a not-so-large angle with respect to the optical axis is incident on the photometric optical system, the light beam reflected by the half mirror 111 in the first optical path division state (FIG. 3) is converted into a viewfinder lens. 109 and the light metering optical system.

  The light beam reaching the photometric optical system is imaged on the light receiving surface of the photometric sensor 144 by the photometric lens 145. Here, the light receiving surface of the photometric sensor 144 is divided into 35 (7 × 5), and subject luminance is measured in each of the 35 divided photometric areas. The light receiving surface of the photometric sensor 144 is provided at a position optically equivalent to the imaging surface (light receiving surface) of the image sensor 106.

  FIG. 7 is a block diagram showing an electrical configuration of the camera system in the present embodiment. Here, the same reference numerals are used for the same members as those described in FIG. First, an explanation will be given from the part related to the imaging and recording of object images.

  The camera system has an imaging system, an image processing system, a recording / reproducing system, and a control system. The imaging system has a photographing optical system 103 and an imaging element 106, and the image processing system has an A / D converter 130, an RGB image processing circuit 131, and a YC processing circuit 132. The recording / reproducing system includes a recording processing circuit 133 and a reproducing processing circuit 134. The control system includes a camera system control circuit (control means) 135, an operation detection circuit 136, an image sensor driving circuit 137, and a photometry control circuit 143. Have.

  Reference numeral 138 denotes a connection terminal that is connected to an external computer or the like and is standardized to transmit and receive data. The electric circuit described above is driven by receiving power from a small fuel cell (not shown).

  The imaging system is an optical processing system that forms an image of light from an object on the imaging surface of the imaging element 106 via the imaging optical system 103. By controlling the driving of a diaphragm (not shown) provided in the photographing optical system 103 and controlling the driving of the focal plane shutter 113 as necessary, the image sensor 106 receives an appropriate amount of object light. Can do.

  As the image sensor 106, an image sensor having a total of about 10 million pixels in which 3700 square pixels are arranged in the long side direction and 2800 in the short side direction is used. In addition, R (red), G (green), and B (blue) color filters are alternately arranged in each pixel to form a so-called Bayer array in which four pixels form a set.

  In the Bayer array, the overall image performance is improved by arranging more G pixels that are easily felt when an observer views the image than the R and B pixels. In general, in image processing using this type of image sensor, a luminance signal is generated mainly from G, and a color signal is generated from R, G, and B.

  The signal read from the image sensor 106 is supplied to the image processing system via the A / D converter 130. Image data is generated by image processing in this image processing system.

  The A / D converter 130 is a signal conversion circuit that converts, for example, an output signal of the image sensor 106 into a 10-bit digital signal and outputs the signal according to the amplitude of the signal read from each pixel of the image sensor 106. The subsequent image processing is executed by digital processing.

  The image processing system is a signal processing circuit that obtains an image signal in a desired format from R, G, and B digital signals. The R, G, and B color signals are converted into a luminance signal Y and a color difference signal (R−Y), ( B-Y) and the like are converted into a YC signal.

  The RGB image processing circuit 131 is a signal processing circuit that processes the output signal of the A / D converter 130, and includes a white balance circuit, a gamma correction circuit, and an interpolation calculation circuit that performs high resolution by interpolation calculation.

  The YC processing circuit 132 is a signal processing circuit that generates a luminance signal Y and color difference signals RY and BY. The YC processing circuit 132 generates a high-frequency luminance signal generation circuit that generates a high-frequency luminance signal YH, a low-frequency luminance signal generation circuit that generates a low-frequency luminance signal YL, and color difference signals RY and BY. It has a color difference signal generation circuit. The luminance signal Y is formed by combining the high frequency luminance signal YH and the low frequency luminance signal YL.

  The recording / reproducing system is a processing system that outputs an image signal to a memory (not shown) and outputs an image signal to the display unit 107. The recording processing circuit 133 performs writing processing and reading processing of the image signal to the memory, and the reproduction processing circuit 134 reproduces the image signal read from the memory and outputs it to the display unit 107.

  The recording processing circuit 133 includes a compression / expansion circuit that compresses the YC signal representing still image data and moving image data in a predetermined compression format and expands the compressed data. The compression / decompression circuit has a frame memory or the like for signal processing. The frame memory stores the YC signal from the image processing system for each frame, and the signals accumulated from each block among a plurality of blocks. Read and compression encode. The compression encoding is performed, for example, by subjecting the image signal for each block to two-dimensional orthogonal transformation, normalization, and Huffman encoding.

  The reproduction processing circuit 134 is a circuit that converts the luminance signal Y and the color difference signals RY and BY into a matrix signal, for example, an RGB signal. The signal converted by the reproduction processing circuit 134 is output to the display unit 107 and displayed (reproduced) as a visible image. The reproduction processing circuit 134 and the display unit 107 may be connected via wireless communication such as Bluetooth. With such a configuration, an image captured by this camera can be monitored from a remote location.

  On the other hand, the operation detection circuit 136 in the control system detects the operation of the main switch 119, the release button 120, the viewfinder mode switch 123, the shooting mode setting switch 126, etc. (other switches are not shown in FIG. 7). The detection result is output to the camera system control circuit 135.

  Here, the shooting mode setting switch 126 is a switch operated to select and set one of a plurality of shooting modes that can be set in the camera. Examples of the shooting mode include a shutter priority shooting mode, an aperture priority shooting mode, a remote shooting mode described later, and a self-timer shooting mode.

  The camera system control circuit 135 receives the detection signal from the operation detection circuit 136 and performs an operation according to the detection result. Further, the camera system control circuit 135 generates a timing signal for performing an imaging operation and outputs the timing signal to the imaging element driving circuit 137.

  The image sensor drive circuit 137 receives the control signal from the camera system control circuit 135 and generates a drive signal for driving the image sensor 106. The information display circuit 142 receives a control signal from the camera system control circuit 135 and controls driving of the information display unit 180 in the optical viewfinder.

  The photometry control circuit 143 controls driving of the photometry sensor 144 based on the output from the camera system control circuit 135. The eyepiece shutter driving mechanism 151 causes the eyepiece shutter 163 to enter or retreat from the optical path of the finder optical system under the control of the camera system control circuit 135.

  The control system controls driving in the imaging system, image processing system, and recording / reproducing system in accordance with the operation of various switches provided in the camera body 101. For example, when SW2 is turned ON by operating the release button 120, the control system (camera system control circuit 135) performs driving of the image sensor 106, operation of the RGB image processing circuit 131, compression processing of the recording processing circuit 133, and the like. Control. Further, the control system controls the display of the information display unit 180 in the optical viewfinder via the information display circuit 142 to change the display in the optical viewfinder (display segment state).

  Next, the focus adjustment operation of the photographic optical system 103 will be described.

  The camera system control circuit 135 is connected to the AF control circuit 140. Further, by attaching the lens device 102 to the camera body 101, the camera system control circuit 135 is connected to the lens system control circuit 141 in the lens device 102 via the mount contacts 101a and 102a. The AF control circuit 140, the lens system control circuit 141, and the camera system control circuit 135 communicate data required for specific processing with each other.

  The focus detection unit 121 outputs a detection signal in a focus detection area provided at a predetermined position in the shooting screen to the AF control circuit 140. The AF control circuit 140 generates a focus detection signal based on the output signal from the focus detection unit 121, and detects the focus adjustment state (defocus amount) of the photographing optical system 103. Then, the AF control circuit 140 converts the detected defocus amount into a driving amount of a focusing lens, which is a part of the photographing optical system 103, and transmits data related to the focusing lens driving amount via the camera system control circuit 135. To the lens system control circuit 141.

  Here, when focus adjustment is performed on a moving object, the AF control circuit 140 takes into account the time lag from when the release button 120 is fully pressed until the actual imaging control is started. Predict an appropriate stop position. Then, data regarding the driving amount of the focusing lens to the predicted stop position is transmitted to the lens system control circuit 141.

  On the other hand, when the camera system control circuit 135 determines that the brightness of the object is low and sufficient focus detection accuracy cannot be obtained based on the output signal of the image sensor 106, the flash light emitting unit 104 or the camera body 101 is provided. The object is illuminated by driving a white LED or a fluorescent tube (not shown).

  When the lens system control circuit 141 receives data relating to the driving amount of the focusing lens, it drives the driving mechanism (not shown) in the lens apparatus 102 to move the focusing lens in the direction of the optical axis L1. As described above, when the focusing lens is composed of a liquid lens or the like, the interface shape is changed. Thereby, the focus adjustment operation of the photographing optical system 103 is performed.

  When the AF control circuit 140 detects that the object is in focus, this information is transmitted to the camera system control circuit 135. At this time, if SW2 is turned on by a full press operation of the release button 120, the photographing operation is performed by the imaging system, the image processing system, and the recording / reproducing system as described above.

  Next, a photometric operation using the photometric sensor 144 will be described.

  When the light beam that has passed through the photometric lens 145 is received by the light receiving surface of the photometric sensor 144 divided into 35, a detection current is generated in the photometric sensor 144. The photometry control circuit 143 converts the detection current of each of the 35 photometry areas into a voltage and sends it to the camera system control circuit 135 as a detection signal.

  The camera system control circuit 135 A / D converts the detection voltage of each photometry area sent from the photometry control circuit 143 to obtain luminance information in each photometry area. Then, the camera system control circuit 135 weights the luminance in each photometric area according to the photometric method selected by the photographer, and determines the luminance used for the final exposure calculation.

  The above metering methods include, for example, an evaluation metering method for performing metering in all metering areas to obtain an optimal exposure for the subject, a partial partial metering method for metering the center area of the screen, and an emphasis on the screen center area. There is a center-weighted average metering method that averages the entire screen while placing The photographer can select the above-mentioned photometric method by operating a switch (not shown) provided in the camera while viewing the display content on the display unit 107.

  1 to 5 are sectional views of the camera system in this embodiment. In these drawings, a part of the lens device 102 is shown. The same members as those described in FIG.

  Here, FIG. 1 is a cross-sectional view of the camera system in the second optical path division state, and FIG. 2 is a camera system in the middle of switching between the first optical path division state and the second optical path division state. FIG. FIG. 3 is a cross-sectional view of the camera system in the first optical path split state, and FIG. 4 is a cross-sectional view of the camera system in a state where the camera system is in the middle of switching between the first optical path split state and the third optical path split state. FIG. 5 is a cross-sectional view of the camera system in the third optical path division state.

  Hereinafter, the configuration of the camera system will be described with reference to FIG. 3 (FIG. 3) when the optical path splitting system constituted by the half mirror 111 and the sub mirror 122 is in the first optical path splitting state described above.

  In FIG. 3, 101 is a camera body, and 102 is a lens device. The lens device 102 is attached to the camera side mount 101b via the lens side mount 102b. Reference numeral 103a denotes a photographing lens positioned closest to the image plane among a plurality of lenses constituting the photographing optical system 103, and reference numeral 105 denotes a focusing screen of the finder optical system. Reference numeral 107 denotes a display unit, and 163 denotes an eyepiece shutter (finder shutter).

Reference numeral 164 denotes a condenser lens that serves as a light beam capturing window in the focus detection unit 121, and reference numeral 165 denotes a reflecting mirror that reflects the light flux from the condenser lens 164. Reference numeral 166 denotes a re-imaging lens for forming an image of the light beam reflected by the reflection mirror 165 on the focus detection sensor 122, and 167 denotes a focus detection sensor.

  Reference numeral 111 denotes a movable half mirror, which is held by a half mirror receiving plate (not shown). Pins 173 are provided on both side edge portions (backward direction and front side of the paper surface) of the half mirror receiving plate, and pins 174 are provided on one side edge portion (backward direction on the paper surface). Here, the half mirror 111 and the pins 173 and 174 move integrally.

  Reference numeral 170 denotes a half mirror drive lever, and 171 denotes a half mirror support arm. The half mirror drive lever 170 is rotatably supported with respect to a rotation shaft 170 a fixed to the camera body 101, and the half mirror support arm 171 is supported to be rotatable with respect to a rotation shaft 171 a fixed to the camera body 101. ing.

  Further, the half mirror support arm 171 is connected to a structure having substantially the same shape provided on the opposite wall surface side of the mirror box via the connection portion 171b. Pins 173 provided on both sides of a half mirror receiving plate (not shown) are engaged with a through-hole portion 171 c provided at the tip of the half mirror support arm 171. Thereby, the half mirror 111 can be rotated centering on the through-hole part 171c via the half mirror receiving plate.

  The half mirror backing plate is biased in the direction of arrow A by a torsion spring (not shown) at an intermediate position between the pins 173 and 174, and the biasing force of the torsion spring is also applied to the half mirror 111 via the half mirror backing plate. is working.

  In the first optical path split state, the mirror stoppers 160 and 161 are in a state where they enter the moving area of the half mirror 111, so that the half mirror 111 receives the urging force of the torsion spring and hits the mirror stoppers 160 and 161. It touches. At this time, there is a slight gap between the pin 173 and the first cam surface 170b of the half mirror drive lever 170 and between the pin 174 and the second cam surface 170c of the half mirror drive lever 170. Thereby, the half mirror 111 is positioned in the state shown in FIG.

  Note that the mirror stoppers 160 and 161 can enter or retreat into the moving region of the half mirror 111 by driving the mirror driving mechanism 150. In addition, the mirror stoppers 160 and 161 are located outside the photographing optical path (positions that do not affect the photographing light flux) regardless of whether the mirror stoppers 160 and 161 are inside or outside the moving region of the half mirror 111. Further, mirror stoppers 175 and 176, which will be described later, are similarly located outside the photographing optical path.

  On the other hand, the sub mirror 122 is rotatable about the rotation axis 125. In the first optical path split state, the transmitted light from the half mirror 111 is transmitted to the focus detection unit 121 (condenser lens 164) side as shown in FIG. It is held at the position where it is reflected.

  In the first optical path division state, a part of the light beam from the photographing optical system 103 is reflected by the half mirror 111 and guided to the finder optical system, and the remaining light beam is transmitted through the half mirror 111 and reflected by the sub mirror 122. Then, it is guided to the focus detection unit 121.

  When the mirror stoppers 160 and 161 in the state shown in FIG. 3 are retracted from the moving area of the half mirror 111, the half mirror 111 receives the urging force in the direction of arrow A by a torsion spring (not shown) and enters the state shown in FIG. . At this time, the pin 173 contacts the first cam surface 170b of the half mirror drive lever 170 and the pin 174 contacts the second cam surface 170c of the half mirror drive lever 170 by the biasing force of the torsion spring.

  And according to rotation of the half mirror drive lever 170, the pins 173 and 174 slide along the first cam surface 170b and the second cam surface 170c, respectively, and the posture of the half mirror 111 changes. That is, the half mirror support arm 171 rotates with the rotation of the half mirror drive lever 170 and is connected to the half mirror drive lever 170 and the half mirror support arm 171 via the pins 173 and 174. The mirror receiving plate and the half mirror 111 operate integrally.

  As the half mirror drive lever 170 and the half mirror support arm 171 rotate counterclockwise in FIG. 3, the half mirror 111 contacts the mirror stoppers 175 and 176 as shown in FIG. At this time, since the half mirror 111 receives a biasing force in the direction of arrow A by a torsion spring (not shown), the half mirror 111 is held in the state shown in FIG. 1, that is, the second optical path split state.

  Here, when the half mirror 111 shifts from the first optical path split state to the second optical path split state, the sub mirror 122 rotates clockwise about the rotation shaft 125 to the lower part of the mirror box. Moving. That is, before the half mirror 111 shifts from the first optical path split state to the second optical path split state, the sub mirror 122 moves to the lower part of the mirror box to avoid the half mirror 111 from colliding with the sub mirror 122. ing.

  In the second optical path division state, as shown in FIG. 1, a part of the light flux from the photographing lens 103a is reflected by the half mirror 111 and guided to the focus detection unit 121, and the remaining light flux is half mirror 111. , And reaches the image sensor 106.

  On the other hand, when transitioning from the first optical path split state (FIG. 3) to the third optical path split state (FIG. 5), the half mirror 111 is caused by the half mirror drive lever 170 rotating clockwise in FIG. Is retracted above the camera body 101 (to the focusing screen 105 side) with respect to the imaging optical path. Further, by rotating the sub mirror 122 in the clockwise direction in FIG. 3 about the rotation axis 125, the sub mirror 122 is retracted to the lower side of the camera body 101 with respect to the photographing optical path.

  In the third optical path division state, the light beam from the photographing lens 103a reaches the image sensor 106 as shown in FIG.

  Next, a case where subject luminance is measured (photometric) using the output of the image sensor 106 in the second optical path division state will be described.

  As described above, in the second optical path division state, the photographic light beam is not guided to the finder optical system, and thus photometry cannot be performed using the photometric sensor 144. On the other hand, the object light emitted from the photographing lens 103 a passes through the half mirror 111 and reaches the image sensor 106. For this reason, in the second optical path division state, subject luminance is measured using a signal generated by photoelectric conversion in the image sensor 106 with respect to the transmitted light.

  In the second optical path state, an imaging operation is performed at a frame rate of 60 Hz, and the obtained image is displayed on the display unit 107 in real time. In order to realize a frame rate of 60 Hz, the image sensor 106 performs thinned readout. As described above, the image sensor 106 is composed of a CMOS, and can randomly access any pixel. Therefore, the image sensor 106 can perform readout thinned for real-time display.

  The image signal read out by being thinned out from the image sensor 106 is converted into a 10-bit digital signal corresponding to the amplitude of the signal at each pixel by the A / D converter 130. The R, G, and B image signals converted into 10-bit digital signals are converted into luminance signals Y and color difference signals RY and BY by processing in an image processing system.

  Here, when photometry is performed using the output signal of the image sensor 106, the subject luminance is determined based on the intensity distribution of the luminance signal Y. Then, the intensity distribution of the luminance signal Y is weighted according to the photometry method selected by the photographer, and the luminance used for the final exposure calculation is determined.

  A shooting sequence in the camera system having the above-described configuration will be described with reference to FIG. The operation shown in FIG. 8 is performed in the camera system control circuit 135.

  In step S100, it is determined whether or not the main switch 119 is on. If the main switch 119 is on, the process proceeds to step S101. In step S101, the camera system is activated by supplying power to an electric circuit in the camera system.

  In step S200, a finder mode switching subroutine is executed. Details of this operation will be described later.

  In step S102, based on the output of the operation detection circuit 136, it is determined whether or not the finder finder mode changeover switch 123 has been operated. When the operation of the finder mode changeover switch 123 is detected, a finder mode changeover operation is executed in step S200. On the other hand, when the operation of the finder mode changeover switch 123 is not detected, the process proceeds to step S103.

  In step S103, it is determined by operating the shooting mode setting switch 126 whether the remote shooting mode or the self-timer shooting mode is set. Here, the remote shooting mode is a mode in which a shooting preparation operation (SW1 on) and a shooting operation (SW2 on) are started by an operation from a remote control device separate from the camera body 101. In many cases, it is used. The self-timer shooting mode is a mode in which a shooting operation is started after a predetermined time has elapsed after the release button 120 is fully pressed, and this mode is also used when the photographer himself / herself becomes a subject. There are many.

  If it is determined in step S103 that the remote shooting mode or the self-timer shooting mode is set, the process proceeds to step S119. In step S119, the camera system control circuit 135 causes the eyepiece shutter 163 to enter the optical path of the finder optical system via the eyepiece shutter drive mechanism 151 (closed state).

  In the remote shooting mode and the self-timer shooting mode, since the photographer does not look into the eyepiece portion of the optical viewfinder, the finder back-incident light easily enters the camera body 101 from the eyepiece portion. Here, since the photometric sensor 144 is disposed in the finder optical system and is close to the eyepiece, the finder reverse incident light is highly likely to reach the photometric sensor 144.

  When the finder back-incident light reaches the photometric sensor 144, it may cause a photometric detection error, and high-precision photometry may not be performed. Further, when the finder back-incident light reaches the focus detection unit 121, it may cause a focus detection error, and high-precision focus detection may not be performed.

  For this reason, the eyepiece shutter 163 is closed in step S119 so that highly accurate photometric operation and focus detection operation can be performed. After the eyepiece shutter 163 is closed, the process proceeds to step S104.

  If it is determined in step S103 that the remote shooting mode or the self-timer shooting mode is not set, the process proceeds to step S104.

  In step S104, it is determined whether or not the mode selected by the finder mode changeover switch 123 is the EVF mode via the operation detection circuit 136. If the OVF mode is selected, the process proceeds to step S105, and photometry is performed using the photometric sensor 144 provided in the viewfinder optical system. On the other hand, if the EVF mode is selected, the process proceeds to step S106, and photometry is performed using the output of the image sensor 106.

  In the OVF mode (first optical path division state), a part of the photographing light beam is reflected by the half mirror 111 and guided to the finder optical system, and the remaining light beam is transmitted through the half mirror 111 and reflected by the sub mirror 121. The light is guided to the focus detection unit 121 and used as a light beam for focus detection. For this reason, the imaging light flux does not reach the image sensor 106, and photometry cannot be performed using the output of the image sensor 106. Therefore, by performing photometry with the photometric sensor 144 using the reflected light of the half mirror 111 diffused by the focusing screen 105, it is possible to calculate the exposure suitable for photographing.

  On the other hand, in the EVF mode (second optical path division state), a part of the photographing light beam is reflected by the half mirror 111 and guided to the focus detection unit 121, and the remaining light beam passes through the half mirror 111 and passes through the image sensor 106. Therefore, the photographing light flux is not guided to the finder optical system (photometric sensor 144). For this reason, photometry cannot be performed using the photometric sensor 144 provided in the finder optical system. Therefore, in this embodiment, photometry is performed using the luminance signal Y obtained from the output signal of the image sensor 106 that receives the light transmitted through the half mirror 111. Thereby, even in the EVF mode, it is possible to perform exposure calculation suitable for photographing.

  In step S107, it is determined whether or not SW1 is turned on by a half-press operation of the release button 120. If SW1 is not on, the process returns to S102 to determine again whether or not the finder mode changeover switch 123 has been operated. On the other hand, if SW1 is on, the process proceeds to step S108.

  In step S <b> 108, the camera system control circuit 135 causes the focus detection sensor 167 to start a focus detection operation by sending an AF start signal to the AF control circuit 140. As described above, the lens system control circuit 141 adjusts the focus of the photographing optical system by driving the focus lens of the photographing optical system 130 by the amount of lens driving obtained by the AF control circuit 140.

  In step S109, it is determined whether or not the mode selected by the finder mode changeover switch 123 is the EVF mode. If the OVF mode is selected, the process proceeds to step S110, and photometry is performed using the photometric sensor 144 provided in the viewfinder optical system. On the other hand, if the EVF mode is selected, the process proceeds to step S111, and photometry is performed using the output of the image sensor 106.

  In the OVF mode (first optical path division state), a part of the photographing light beam is reflected by the half mirror 111 and guided to the finder optical system, and the remaining light beam is transmitted through the half mirror 111 and reflected by the sub mirror 121. The light is guided to the focus detection unit 121 and used as a light beam for focus detection. For this reason, the imaging light flux does not reach the image sensor 106, and photometry cannot be performed using the output of the image sensor 106. Therefore, by performing photometry with the photometric sensor 144 using the reflected light of the half mirror 111 diffused by the focusing screen 105, it is possible to calculate the exposure suitable for photographing.

  On the other hand, in the EVF mode (second optical path division state), a part of the photographing light beam is reflected by the half mirror 111 and guided to the focus detection unit 121, and the remaining light beam passes through the half mirror 111 and passes through the image sensor 106. Therefore, the photographing light flux is not guided to the finder optical system (photometric sensor 144). For this reason, photometry cannot be performed using the photometric sensor 144 provided in the finder optical system. Therefore, in this embodiment, photometry is performed using the luminance signal Y obtained from the output signal of the image sensor 106 that receives the light transmitted through the half mirror 111. Thereby, even in the EVF mode, it is possible to perform exposure calculation suitable for photographing.

  Then, using the photometric result in step S110 or step S111, an exposure value (shutter speed and aperture value) when performing an imaging operation in step S115 described later is determined.

  In step S112, it is determined whether or not SW2 is ON by a full pressing operation of the release button 120. If SW2 is not on, the process returns to S104, and the finder mode (OVF mode / EVF mode) is determined again. On the other hand, if SW2 is on, the process proceeds to step S113.

  In step S113, the eyepiece shutter 163 provided in the viewfinder optical system is closed. Here, when the eyepiece shutter 163 is closed in advance in step S119, the operation in this step is not performed.

  In step S114, the camera system control circuit 135 sends a mirror drive start signal to the mirror drive mechanism 150, changes the positions of the half mirror 111 and the sub mirror 122, and sets the third optical path split state (FIG. 5). In the third optical path division state, the half mirror 111 and the sub mirror 122 are retracted from the imaging optical path, so that the light flux from the imaging optical system 103 can directly reach the image sensor 106.

  In step S115, the camera system control circuit 135 controls driving of a diaphragm (not shown) provided in the lens device 102 via the lens system control circuit 141, and drives the focal plane shutter 113 as necessary. Control. As a result, an appropriate amount of object light is imaged on the imaging surface of the imaging element 106 via the imaging optical system 103. The exposure amount at this time is the exposure amount determined based on the photometric result obtained in step S110 or step S111.

  In addition, the camera system control circuit 135 sends an imaging start signal to the imaging element driving circuit 137 to cause the imaging element 106 to perform an imaging operation (charge accumulation and readout of accumulated charges).

  In step S116, the image signal read from the image sensor 106 is sent to the RGB image processing circuit 131 via the A / D converter 130, and subjected to white balance processing, gamma correction, and interpolation calculation processing. Further, the YC processing is performed by the YC processing circuit 132, and the image processing is completed. In photographing in the third optical path division state, since the light beam from the photographing lens 103a reaches the image sensor 106 directly, high-definition images can be captured.

  In step S117, the image data after image processing is sent to the recording processing circuit 133, compressed in a predetermined compression format, and then recorded on a recording medium (built in the camera body 101 or detachably attached to the camera body 101). To record).

  In step S118, the image data after image processing is also sent to the reproduction processing circuit 134, and the image data captured on the display 107 is displayed (preview display). After the preview display, the process returns to the finder mode switching subroutine (S200), and the optical path division state corresponding to the operation state of the finder mode switching switch 123 is set.

  In this embodiment, as described above, the photometric operation can be performed in both the OVF mode and the EVF mode, and the finder back-incident light is prevented from entering the camera body 101 when performing the photographing operation. Can do.

  Next, the finder mode switching subroutine (S200) will be described with reference to FIG.

  In step S <b> 201, the camera system control circuit 135 determines the state of the finder mode changeover switch 123 based on the output from the operation detection circuit 136. If the EVF mode is set, the process proceeds to step S202. If the OVF mode is set, the process proceeds to step S220.

  Here, the process after step S202 shows the process when switching from the OVF mode to the EVF mode, and the process after step S220 shows the process when switching from the EVF mode to the OVF mode.

In step S202, the eyepiece shutter 163 provided in the finder optical system is closed. In step S203, the driving of the information display circuit 142 is controlled to stop the information display unit 180 in the optical viewfinder. Thereby, the information display in the viewfinder field is not displayed. Here, since the eyepiece shutter 163 has already been closed by the process in step S202, even if specific information is displayed in the viewfinder field, the photographer cannot see the information. Therefore, by stopping driving of the information display unit 180 in the optical viewfinder, unnecessary power consumption in the camera system can be suppressed, and battery consumption can be delayed.

  In step S204, in order to move the half mirror 111 to the second optical path split state, first, the sub mirror 122 is moved to the lower part of the mirror box and retracted from the photographing optical path.

  In step S <b> 205, the mirror stoppers 160 and 161 are retracted from the moving region of the half mirror 111 by controlling the driving of the mirror driving mechanism 150. After retracting the mirror stoppers 160 and 161, when the half mirror driving lever 170 is rotated counterclockwise in FIG. 3 in step S206, the half mirror 111 is biased by a spring (not shown) (force indicated by arrow A). By being received, it is driven to the second optical path division state (FIG. 1) through the state shown in FIG.

  As a result, a part of the light beam emitted from the photographing lens 103a is reflected by the half mirror 111 and guided to the focus detection unit 121, and the remaining light beam passes through the half mirror 111 and proceeds to the image plane side. .

  In the second optical path split state (FIG. 1), between the pin 173 and the first cam surface 170b of the half mirror drive lever 170 and between the pin 174 and the second cam surface 170c of the half mirror drive lever 170. There is a slight gap, and the half mirror 111 is positioned in contact with the mirror stopper 175 and the mirror stopper 176.

  The position of the reflection surface of the half mirror 111 in the second optical path division state is substantially equal to the position of the reflection surface of the sub mirror 122 in the first optical path division state. With this configuration, it is possible to prevent the position of the light beam incident on the focus detection unit 121 from being shifted between the first optical path split state and the second optical path split state.

  In the second optical path division state, the light beam from the photographing lens 103 a passes through the half mirror 111 and reaches the image sensor 106, so that the focus position of the object image formed on the image sensor 106 by the light beam transmitted through the half mirror 111 is reached. Is slightly different from the case of reaching the image sensor 106 without passing through the half mirror 111.

  For this reason, in step S207, the focus correction mode is activated to correct the above-described shift of the focus position.

  In the present embodiment, the focus detection signal output from the focus detection unit 121 indicates a focus state when the light beam from the photographing lens 103a directly reaches the image sensor 106 in the third optical path division state. . In contrast, when the focus correction mode is set in the second optical path split state, the focus state when the light beam from the photographing lens 103a passes through the half mirror 111 and reaches the image sensor 106 is shown. The focus detection signal is corrected. For this reason, the focus position of the focus lens in the photographing optical system 103 in the second optical path division state is shifted by the amount of correction of the focus detection signal with respect to the focus positions in the first and third optical path division states. It will be.

  Therefore, when performing shooting operation with SW2 turned on in the EVF mode, that is, when switching the optical path splitting system from the second optical path splitting state to the third optical path splitting state, the front curtain drive mechanism of the focal plane shutter 113 With the above charging, the position of the focus lens is corrected by the amount of deviation described above. That is, the focus lens is moved from the in-focus position in the second optical path division state to the in-focus position in the third optical path division state. Thereafter, the focal plane shutter 113 is opened for a predetermined time to perform an imaging operation by the imaging element 106.

  By configuring as described above, in the EVF mode (second optical path division state), a focused image can be confirmed on the display unit 107, and when shooting is performed in the third optical path division state. It is possible to obtain a photographed image that is in focus.

  In step S208, only the front curtain of the focal plane shutter 113 is caused to travel to the bulb exposure state so that the object light that has passed through the photographing optical system 103 reaches the image sensor 106 continuously, and an image is displayed on the display unit 107. It is assumed that it is possible to capture an image for displaying.

  In step S209, the display unit 107 is powered on. In step S <b> 210, an image pickup operation by the image pickup device 106 is continuously performed on the object image formed by the shooting optical system 103, and image data read from the image pickup device 106 and subjected to image processing is displayed on the display unit 107 in real time. Display. Then, the switching operation from the OVF mode to the EVF mode is completed.

  Here, in the second optical path division state that is the EVF mode, the light beam from the photographing lens 103 a reaches the image sensor 106 after being refracted by the half mirror 111. For this reason, as shown in FIG. 12, the light receiving area 190 of the image sensor 106 in the second optical path division state is in the vertical direction ( There may be a slight deviation in the vertical direction in FIG. That is, an image displayed in real time on the display unit 107 in the second optical path division state may be shifted without matching with an image photographed in the third optical path division state.

  Here, an area 190 a that does not overlap the area 191 in the area 190 is an area that is displayed in real time on the display unit 107 but is not included in an image obtained by imaging in the third optical path division state.

  In the camera of the present embodiment, as shown in FIG. 13, the region 192 corresponding to the region 190a is blacked out of the image region displayed in real time on the display unit 107 so that the entire region 190 is not displayed. . This process is performed in the reproduction processing circuit 134.

  As a result, it is possible to avoid a problem such that an image actually displayed on the display unit 107 is not included in the actually captured image.

  Next, a case where it is determined in step S201 in FIG. 9 that the OVF mode is set will be described. That is, an operation when the camera is switched from the EVF mode to the OVF mode will be described.

  In step S220, the driving of the display unit 107 is stopped and the imaging operation by the imaging element 106 is stopped.

  In step S221, the rear curtain of the focal plane shutter 113 is moved to close the shutter, and the driving mechanism for the front curtain and the rear curtain is charged in preparation for shooting. In step S222, the mirror stoppers 160 and 161 are retracted from the movement region of the half mirror 111 in order to enable the movement of the half mirror 111 performed in a later step.

  In step S223, the half mirror drive lever 170 is rotated clockwise in FIG. 1, and only the half mirror 111 is moved in the order of the state of FIG. 2, the state of FIG. 3, the state of FIG. 4, and the state of FIG. At this time, the half mirror 111 enters the third optical path division state (FIG. 5) through the first optical path division state (FIG. 3).

  In step S224, the mirror stoppers 160 and 161 are moved into the moving area of the half mirror 111 and moved to a predetermined position for positioning the half mirror 111.

  As described above, after the mirror stoppers 160 and 161 are retracted from the moving region of the half mirror 111, the half mirror 111 is moved to the third optical path split state, and then the mirror stoppers 160 and 161 are moved within the moving region of the half mirror 111. Therefore, when the half mirror 111 moves, it does not collide with the mirror stoppers 160 and 161. Thereby, the mechanical reliability at the time of switching from the OVF mode to the EVF mode can be increased.

  In step S225, the half mirror drive lever 170 is rotated counterclockwise in FIG. 5, and the half mirror 111 is changed from the third optical path division state (state of FIG. 5) to the first optical path division through the state of FIG. Move to the state (state of FIG. 3). Here, the half mirror 111 comes into contact with the mirror stoppers 160 and 161 by receiving a biasing force (a force indicated by an arrow A in FIG. 3) of a spring (not shown) in the mirror driving mechanism 150.

  In step S226, the eyepiece shutter 163 provided in the viewfinder optical system is opened.

  In step S227, the camera system control circuit 135 determines whether or not the manual focus mode is set based on the operating state of an AF / MF selector switch (not shown) provided in the camera system. If the manual focus mode is set, the process proceeds to step S205. If the manual focus mode is not set and the auto focus mode is set, the process proceeds to step S228.

  When the manual focus mode is set, it is not necessary to operate the focus detection unit 121, and the background (subject image) can be more accurately grasped by using the EVF than by using the OVF. it can. Therefore, when the manual focus mode is set, the process proceeds to step S205 in order to perform real-time display on the display unit 107.

  Here, when the process proceeds to step S205, the eyepiece shutter 163 is closed. Thereby, in the manual focus mode, it is possible to prioritize subject observation using EVF, and it is possible to suppress adversely affecting the image displayed in real time from the back incident light from the finder optical system.

  In step S 228, the sub mirror 122 is caused to enter the photographing optical path, and the object light transmitted through the half mirror 111 is set at a predetermined position for guiding it to the focus detection unit 121. Here, during the processing from step S220 to step S227, the sub mirror 122 is in the position in the second optical path division state (FIG. 1), that is, the position retracted from the photographing optical path, and operates when the process proceeds to step S228. Will do.

  In step S229, the camera system control circuit 135 drives the optical viewfinder information display unit 180 to light the viewfinder information display. Then, the switching operation from the EVF mode to the OVF mode is completed.

  In this embodiment, when the captured image is displayed on the display unit 107, that is, in the EVF mode, the optical path division system having the half mirror 111 and the sub mirror 122 is in the second optical path division state (FIG. 1). The light beam from the photographic lens 103 a is guided to the focus detection unit 121. Thereby, even in the EVF mode, a high-speed focus adjustment operation can be performed based on the focus detection by the focus detection unit 121 using the phase difference detection method.

  Next, signal processing for focus detection in the focus detection unit 121 will be described.

  The light beam (object light) emitted from the photographic lens 103a is reflected by the half mirror 111 in the second optical path division state, reflected by the sub mirror 122 in the first optical path division state, and then a condenser provided at the lower part of the mirror box. The light enters the lens 164. The light beam incident on the condenser lens 164 is deflected by the reflection mirror 165 and forms a secondary image of the object on the focus detection sensor 167 by the action of the re-imaging lens 166.

  The focus detection sensor 167 includes at least two pixel columns. When the signal waveforms output from the two pixel columns are compared, a relatively laterally shifted state is observed according to the imaging state of the object image formed by the photographing optical system 103 on the focus detection region. . The focus state is based on whether the imaging state is the front pin or the rear pin, and the shift direction of the output signal waveform is reversed, and the shift direction and shift amount (phase difference) are detected using a method such as correlation calculation. It is.

  10 and 11 are diagrams showing output signal waveforms of the focus detection sensor 167 input to the AF control circuit 140. FIG. The horizontal axis indicates the arrangement of pixels, and the vertical axis indicates the output value of the focus detection sensor 167. FIG. 10 shows an output signal waveform when the object image is not in focus, and FIG. 11 shows an output signal waveform when the object image is in focus.

  In general, the light beam used for focus detection is not the same as the imaging light beam in the fully open state, but is a part of the imaging light beam. That is, when performing focus detection, a dark F-number light beam is used. Further, in consideration of the error of the mechanism in the camera, the position of the image sensor 106 and the position of the focus detection sensor 167 are not optically conjugate in a strict sense.

  Therefore, even when the object image is in focus, a slight initial phase difference Δ remains between the two output signal waveforms as shown in FIG. The initial phase difference Δ is different from that used in the correction for the focus detection signal in the above-described focus correction mode (see step S207 in FIG. 9).

  Here, since the true phase difference can be obtained by subtracting the initial phase difference Δ from the phase difference detected by the correlation calculation of the two images, the presence of the initial phase difference Δ is not usually a problem.

  In the present embodiment, as described above, the light beam used for focus detection may be guided from the sub mirror 122 in the first optical path split state or may be guided from the half mirror 111 in the second optical path split state. In this case, the reflection surface position of the sub-mirror 122 in the first optical path division state (FIG. 3) and the reflection surface position of the half mirror 111 in the second optical path division state (FIG. 1) are completely in terms of mechanism accuracy. The values of the initial phase difference Δ differ depending on the optical path division state. For this reason, the true phase difference in the first and second optical path division states cannot be known only by subtracting a certain initial phase difference Δ from the phase difference detected by the correlation calculation.

  With normal component processing accuracy, there is a possibility that the positions of the two reflecting surfaces are shifted by approximately 30 μm in the direction perpendicular to the reflecting surfaces. Here, if it is attempted to mechanically reduce the displacement of the reflecting surface position, the cost for processing the parts becomes extremely high.

  Therefore, in the present embodiment, the initial phase difference Δ is set for each of the first optical path split state and the second optical path split state, and the initial phase difference Δ corresponding to the optical path split state is used, whereby the focus detection sensor 167 The output signal is corrected. As a result, the true phase difference according to the optical path division state can be known, and accurate focus detection can be performed based on the phase difference.

  As described above, it is possible to determine whether or not the photographing optical system is in a focused state by determining the identity of a set of signals in consideration of the initial phase difference. Further, the defocus amount can be obtained by detecting a phase difference using a known method using correlation calculation, for example, a method disclosed in Japanese Patent Publication No. 5-88445. Then, if the obtained defocus amount is converted into the driving amount of the focusing lens of the photographing optical system 103 and the focusing lens is driven by the driving amount, the focus adjustment of the photographing optical system can be automatically performed.

  In the phase difference detection method, since the driving amount of the focusing lens can be known in advance, the lens driving to the in-focus position is usually performed only once, and extremely fast focus adjustment is possible.

  According to the present embodiment, since the photometry is performed by using the output of the image sensor 106 or the output of the photometric sensor 144 according to the first and second optical path division states, the optical path division system is the first. Photometry can be performed regardless of which of the first and second optical path split states.

  In addition to observing an object image using a finder optical system (in the case of the OVF mode), the focus detection unit 121 also performs a position in the case of displaying the object image in real time on the display unit 107 (in the case of the EVF mode). Focus detection by the phase difference detection method can be performed, and the focus adjustment operation of the photographing optical system can be performed at high speed. Further, if continuous shooting or moving image shooting is performed in the second optical path division state (FIG. 1), high-speed focus adjustment operation can be performed in these shootings. Furthermore, since it is not necessary to provide two focus detection units as in the prior art, there is no increase in cost.

  In this embodiment, in the second optical path division state (FIG. 1), the light beam from the photographing lens 103a is guided to the focus detection unit 121, and the focus detection unit 121 performs focus detection by the phase difference detection method. Since the light beam from the photographing lens 103a reaches the image sensor 106 in the optical path division state, focus adjustment by a contrast detection method may be performed based on the output of the image sensor 106. That is, after the focus lens is driven based on the focus detection result by the phase difference detection method, the focus lens can be accurately moved to the in-focus position by performing focus adjustment by the contrast detection method.

  Here, the focus adjustment by the contrast detection method is obtained by evaluating the sharpness of the object image formed by the imaging optical system 103 by a predetermined function with respect to the output of the imaging element 106, and the function value is an extreme value. The position of the focus lens on the optical axis is adjusted so that

  As an evaluation function, an absolute value of a difference between adjacent luminance signals is added within the focus detection area, a square of the difference between adjacent luminance signals is added within the focus detection area, or R, G, B Among these image signals, there is one that processes the difference between adjacent signals in the same manner as described above.

  On the other hand, in the EVF mode (second optical path division state), since the eyepiece shutter 163 is in the closed state, it is possible to prevent the finder reverse incident light from entering the camera body 101. Further, by closing the eyepiece shutter 163 when performing remote shooting or self-timer shooting, it is possible to prevent the viewfinder back-incident light from entering the camera body 101 from the eyepiece of the viewfinder optical system.

  Thereby, the finder back-incident light does not reach the focus detection unit 121 and the photometric sensor 144, and the focus detection accuracy and photometry accuracy can be improved.

Sectional drawing of the camera in a 2nd optical path division | segmentation state. Sectional drawing of the camera in the middle of switching from a 1st optical path division | segmentation state to a 2nd optical path division | segmentation state. Sectional drawing of the camera in a 1st optical path division | segmentation state. Sectional drawing of the camera in the middle of switching from a 1st optical path division | segmentation state to a 3rd optical path division | segmentation state. Sectional drawing of the camera in a 3rd optical path division | segmentation state. 1 is a schematic diagram illustrating a configuration of a camera system according to Embodiment 1. FIG. 1 is a block diagram illustrating a circuit configuration of a camera system according to Embodiment 1. FIG. 5 is a flowchart illustrating a shooting operation of the camera according to the first embodiment. The flowchart which shows operation | movement of a mode switching subroutine. The figure showing the output signal waveform of a focus detection sensor when an imaging optical system is not in focus. The figure showing the output signal waveform of a focus detection sensor when an imaging optical system is in an in-focus state. The figure showing the relationship between the image range which can be output to a display unit, and an imaging range. The figure showing the relationship between the image range which can be output to a display unit, and an imaging range.

Explanation of symbols

103: Imaging optical system 105 ... Focusing screen 106 ... Image sensor 107 ... Display unit 109 ... Finder lens 111 ... Half mirror 121 ... Focus detection unit 122 ... Sub mirror 123 ... Mode selector switch 135 ... Camera system control circuit 144 ... Photometric sensor 145 ... Photometric lens

Claims (7)

An image sensor that photoelectrically converts a subject image formed by a light beam from a photographing lens;
A finder optical system that enables optical observation of a subject image by the luminous flux;
A first state that is disposed in the optical path of the light beam and reflects the light beam toward the finder optical system; and a second state that is disposed in the optical path and transmits the light beam toward the image sensor. A mirror unit that is driven to switch to
Photometric means for performing photometry using a reflected light beam from the mirror unit;
Control that performs photometry using the output signal from the photometry means when the mirror unit is in the first state, and performs photometry using the output signal from the image sensor when in the second state And an imaging device. Operating means for instructing switching between the first and second states;
Whether the control unit drives the mirror unit based on a signal from the operation unit and performs photometry using an output signal from the photometry unit or photometry using an output signal from the image sensor The imaging apparatus according to claim 1, wherein: A finder shutter for opening and closing the optical path of the finder optical system;
Driving means for opening and closing the finder shutter,
3. The image pickup apparatus according to claim 1, wherein the control unit drives the driving unit to close the finder shutter when the mirror unit is driven to the second state. 4. A focus detection unit that detects a focus state of the photographing lens using the light beam;
The first state is a state in which the light beam is reflected toward the finder optical system and the focus detection means, and the second state is a state in which the light beam is transmitted toward the image sensor and the focus detection is performed. The imaging apparatus according to any one of claims 1 to 3, wherein the imaging apparatus is in a state of reflecting toward the means. The mirror unit includes a first mirror member that reflects a part of the light beam and transmits the remainder, and a second mirror member that reflects the light beam transmitted through the first mirror member,
Wherein the first state is disposed in said first and second mirror member before Symbol optical path, wherein the second state the second with the first mirror member is disposed on the optical path mirror member is retracted from the previous SL optical path,
The imaging apparatus according to claim 4, wherein the first and second mirror members are retracted from the optical path during an image recording operation.   The imaging apparatus includes mode setting means capable of setting a plurality of shooting modes including a remote shooting mode and a self-timer shooting mode, and the control means includes at least one of the remote shooting mode and the self-timer shooting mode. The imaging apparatus according to claim 3, wherein the viewfinder shutter is closed in response to one of the settings. The imaging device according to any one of claims 1 to 6,
An imaging system comprising an imaging lens attached to the imaging apparatus.

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