JP2008039976A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of enhancing the precision of a focus detection result by a phase difference detection system. <P>SOLUTION: The imaging apparatus includes: a first detection means (135) for detecting the focusing state of a photographing optical system by a contrast detection system by using the output of an imaging device (106); a second detection means (167) for detecting the focusing state of the photographing optical system by the phase difference detection system; light splitting means (111 and 122) for splitting the luminous flux from the photographing optical system and guiding the luminous flux to the imaging device and the second detection means; and a control means (135) for correcting the detection result of the second detection means based on the detection result of the first detection means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus that detects a focus adjustment state of a photographing optical system using two detection units and corrects the detection result of the other detection unit based on the detection result of one detection unit.

  Conventionally, a contrast detection method and a phase difference detection method are known as methods for detecting the focus adjustment state of the photographing optical system.

  The contrast detection method is the focus included in the photographic optical system so that the sharpness of the subject image formed by the photographic optical system is obtained by evaluating the output of the image sensor with a predetermined function, and the function value takes an extreme value. The lens position (position in the optical axis direction) is adjusted. Here, as an evaluation function, an absolute value of a difference between luminance signals in adjacent pixels is added in the focus detection area, a square of a difference in luminance signal in adjacent pixels is added in the focus detection area, Alternatively, there is one that processes the difference between adjacent signals in the same manner as described above for the output signals of the R, G, and B pixels.

  In general, the contrast detection method is characterized in that the sensor used for focus detection and the sensor used for imaging are the same, so that it is resistant to changes with time and the focus detection accuracy is high. However, since the evaluation function value is obtained while slightly moving the focus lens in the optical axis direction, it may take too much time to reach the in-focus state.

  On the other hand, the phase difference detection method is characterized in that the time required for focus adjustment of the photographing optical system is shorter than that of the contrast detection method. This phase difference detection method is a known technique as disclosed in Patent Document 1. In other words, the phase difference detection method detects the focus adjustment state of the photographing optical system based on the relative positional relationship between a pair of subject images formed by light beams that have passed through different exit pupil regions of the photographing optical system. is there.

  Here, in the phase difference detection method, since the shift amount and shift direction with respect to the in-focus position are known, it is only necessary to move the focus lens based on this amount and direction, and the focus lens is moved completely as in the contrast detection method. There is no need to move the range. In the contrast detection method, the evaluation function value is obtained every time the focus lens is moved. In the phase difference detection method, the focus adjustment state of the photographing optical system can be detected by one detection.

  However, in the phase difference detection method, the sensor used for focus detection is different from the sensor used for imaging, so that it is easily affected by changes over time, and there is a problem that the accuracy of focus detection is lower than that of the contrast detection method.

  In a single-lens reflex type camera, the light from the photographing optical system (subject light) is reflected by a half mirror and guided to a finder optical system (OVF, Optical View Finder) including a pentaprism, etc. It is possible to observe the subject image formed in step 1 as a normal image. The light transmitted through the half mirror is reflected by a sub-mirror located behind the half mirror and guided to a phase difference type focus detection unit. When the subject image is observed through the finder optical system, the half mirror is located in the photographing optical path, and the subject light is also guided to the focus detection unit.

  In the camera having the above-described configuration, the half mirror and the sub mirror are brought into predetermined positions (a first position retracted from the photographing optical path and a second position in the photographing optical path) by contact with a positioning member provided in the camera body. Positioned. In this configuration, the operation between the first position and the second position of the mirror is repeatedly performed, so that the contact surface with the positioning member is worn, and the positions of the half mirror and the sub mirror in the photographing optical path are changed. Sometimes.

  When the mirror position changes in this way, the incident angle of the light beam reflected by the half mirror with respect to the focus detection unit may change. In this case, the relationship between the focus position based on the focus detection result (phase difference detection method) of the focus detection unit and the focus position based on the focus detection result (contrast detection method) using the image sensor is the initial state. It will change with respect to the positional relationship. That is, an error occurs in the focus detection result obtained by the focus detection unit.

  Therefore, in order to suppress an error in the focus detection result by the phase difference detection method, it is conceivable to correct the detection result by the phase difference detection method using the detection result by the contrast detection method.

  Here, Patent Document 2 discloses a camera that can manually select a phase difference detection method and a contrast detection method. When the phase difference detection method is selected, the mirror is positioned in the photographing optical path, and the subject light is reflected by the mirror and guided to the focus detection unit. Thereby, the focus detection by the phase difference detection method is performed in the focus detection unit. On the other hand, when the contrast detection method is selected, the subject light is guided to the image sensor side by retracting the mirror from the photographing optical path. Thereby, focus detection by the contrast detection method is performed using the output of the image sensor.

  In the above-described camera configuration, the focus detection result by the phase difference detection method can be corrected using the focus detection result by the contrast detection method.

On the other hand, there is an imaging apparatus that can perform a phase difference detection method and a contrast detection method on the same subject at the same timing (see, for example, Patent Document 3). This imaging apparatus has an imaging device including a first photoelectric conversion unit group constituting a single photoelectric conversion unit and a second photoelectric conversion unit group constituting a photoelectric conversion unit divided into two. The focus state of the photographing optical system is detected based on the phase difference between the image signals output from the pair of photoelectric conversion units in the second photoelectric conversion unit group. And according to this structure, the focus detection by a contrast detection system can be performed using the output signal from a 1st photoelectric conversion part group or a 2nd photoelectric conversion part group.
Japanese Patent Laid-Open No. 05-127074 (paragraph number 0023, FIG. 1, etc.) JP 2001-275033 A (FIG. 2 etc.) JP 2000-292585 (paragraph number 0046-0077, FIG. 4 etc.)

  However, in the camera described in Patent Document 2, focus detection by the phase difference detection method can be performed only when the mirror is located in the photographing optical path, and contrast detection is performed when the mirror is retracted from the photographing optical path. Only focus detection by the method can be performed. In this case, the timing for performing the focus detection by the phase difference detection method and the timing for performing the focus detection by the contrast detection method are shifted.

  Therefore, the focus detection result by the phase difference detection method and the focus detection result by the contrast detection method are not the focus detection results for the same subject image in terms of time. For example, if the subject moves between the timings of focus detection by the phase difference detection method and the contrast detection method, or if the imaging device moves due to camera shake or the like, focus detection is performed on different subjects. . That is, the consistency of the focus detection results by the phase difference detection method and the contrast detection method cannot be achieved.

  Here, in the imaging device described in Patent Document 3, focus detection can be performed by the phase difference detection method and the contrast detection method at the same timing, but the following problems arise.

  In the configuration described in Patent Document 3, when the photoelectric conversion unit is divided into two, twice as many transfer gates are required to transfer charges accumulated in the photoelectric conversion unit to the vertical transfer path. In addition, a circuit for driving the transfer gate is required, and the structure of the image sensor is complicated. In order to realize such a complicated structure, a high degree of miniaturization is required, which increases the cost of the imaging apparatus.

  In addition, since the second photoelectric conversion unit group is different in shape from the first photoelectric conversion unit group, the sensitivity is different, and the degree of blur in the defocused state is also different. For this reason, it is difficult to generate a captured image using the image signal of the second photoelectric conversion unit group, and it is necessary to perform interpolation processing using the output signal of the first photoelectric conversion unit located in the vicinity.

  Furthermore, since the second photoelectric conversion unit group is located in the focus detection region, the following problems occur. That is, the photographer often aligns the important part of the subject with the focus detection area, and if the second photoelectric conversion unit group is located in the focus detection area, the important part of the subject must be interpolated. In this case, there is a possibility that the image quality of the photographed image is deteriorated.

  An imaging apparatus according to the present invention detects a focus adjustment state of an imaging optical system by a contrast detection method using an imaging element that photoelectrically converts a subject image formed by a light beam from the imaging optical system and an output of the imaging element. First detection means. Also, a second detection means for detecting the focus adjustment state of the photographic optical system by the phase difference detection method, and light for dividing the light beam from the photographic optical system and guiding it to the image sensor and the second detection means And dividing means. Furthermore, it has a control means which correct | amends the detection result of a 2nd detection means based on the detection result of a 1st detection means.

  Here, the control means can calculate a correction value for correcting the detection result of the second detection means based on the detection results of the first and second detection means. Then, the light splitting means can be operated between a state where the light splitting means is positioned in the photographing optical path and the light beam from the photographing optical system is guided to the image sensor and the second detecting means, and a state where the light splitting means is retracted from the photographing optical path. Here, the correction value can be calculated when the light dividing means is located in the photographing optical path. This correction value can be stored in the storage means.

  In addition, the detection operation by the first detection unit and the detection operation by the second detection unit can be performed at the same timing.

  Further, when the optical element that can advance and retreat with respect to the photographing optical path is used as the light splitting means and the optical element is located in the photographing optical path, a part of the light flux from the photographing optical system is secondly reflected. In addition to being guided to the detection means, other light beams can be guided to the image sensor.

  In addition, in the case of having a finder optical system for observing a subject using a light beam from the photographing optical system, the light dividing means can be switched between the first and second states. Here, the first state is a state in which the light beam from the photographing optical system is guided to the finder optical system and the second detection means, and the second state is a state in which the light beam from the photographing optical system is guided to the imaging element and the first element. This is a state of leading to the second detection means.

  In the light splitting means, first and second mirrors that can move independently of each other can be used. Here, when the light splitting means is in the first state, the first mirror reflects a part of the light beam from the photographing optical system to the finder optical system and transmits the other light beam. it can. And the light beam which permeate | transmitted the 1st mirror with the 2nd mirror can be reflected to a 2nd detection means.

  On the other hand, when the light splitting means is in the second state, the first mirror can reflect the part of the light flux to the second detecting means and allow the other light flux to pass therethrough. Then, the second mirror can be retracted from the photographing optical path.

  Further, when the light splitting means is in the first state, the second mirror reflects a part of the light flux transmitted through the first mirror to the second detection means, while allowing the other light flux to be reflected. The light can be transmitted to the image sensor.

  According to the present invention, since the light beam from the photographing optical system is guided to the image sensor and the second detection means by the light splitting means, the focus adjustment state of the photographing optical system by the contrast detection method and the phase difference detection method is substantially simultaneously. It can be carried out. Then, the accuracy of the detection result in the phase difference detection method can be improved by correcting the detection result in the phase difference detection method based on the detection result in the contrast detection method.

  Examples of the present invention will be described below.

  A camera system that is Embodiment 1 of the present invention will be described below with reference to FIGS.

  FIG. 1 is a schematic diagram showing the configuration of the camera system of the present embodiment. The camera in this embodiment is a single-plate digital color camera using an image sensor such as a CCD sensor or a CMOS sensor, and an image signal representing a moving image or a still image by driving the image sensor continuously or once. Can be obtained. Here, the image sensor is an area sensor of a type that photoelectrically converts received light into an electrical signal in each pixel, accumulates charges according to the amount of received light, and reads the charges.

  In FIG. 1, reference numeral 101 denotes a camera body, and reference numeral 102 denotes a lens apparatus that has a photographing optical system 103 and is detachable from the camera body 101. The lens device 102 is electrically and mechanically connected to the camera body 101 via a mount mechanism (not shown). Here, by replacing the lens devices 102 having different focal lengths, it is possible to obtain shooting screens having various angles of view.

  The lens device 102 has a drive mechanism (not shown) for moving the focus lens and zoom lens included in the photographing optical system 103 in the direction of the optical axis L1. In this embodiment, the focus of the photographing optical system 103 is adjusted by moving the focus lens in the direction of the optical axis L1, but the present invention is not limited to this. For example, the focus lens can also be adjusted by configuring the focus lens with a flexible transparent elastic member or a liquid lens and changing the interface shape (refractive power).

  Reference numeral 106 denotes an image sensor housed in the package 124. An optical low-pass filter 156 that limits the cutoff frequency of the photographing optical system 103 is provided on the light receiving surface side of the image sensor 106 so that a high-frequency component included in the subject light does not reach the image sensor 106. The photographing optical system 103 is also formed with an infrared cut filter.

  A subject image captured using the image sensor 106 is displayed on the display unit 107. The display unit 107 is attached to the back of the camera, and the user can directly observe the image displayed 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 microparticle electrophoresis, etc., the display unit 107 can be reduced in thickness while reducing power consumption.

  In this embodiment, a CMOS process compatible sensor (CMOS sensor), which is one of amplification type solid-state image sensors, is used as the image sensor 106. In a CMOS sensor, a peripheral circuit such as a MOS transistor in an area sensor unit and an image sensor driving circuit, an AD conversion circuit, and an image processing circuit can be formed in the same process. For this reason, the number of masks and the process steps can be greatly reduced as compared with the CCD sensor. In addition, the CMOS sensor allows random access to arbitrary pixels, and can read out thinned out for display. Thereby, real-time display can be performed at a high display rate.

  A half mirror 111 reflects a part of the light flux (subject light) from the photographing optical system 103 and guides it to the finder optical system, and transmits the other light flux. Reference numeral 105 denotes a focusing screen arranged on the planned image formation plane of the subject image. The position of the focusing screen 105 and the position of the image sensor 106 have an optically conjugate relationship.

  Reference numeral 112 denotes a pentaprism, which converts the light beam from the photographing optical system 103 into an erect image by reflecting the light beam a plurality of times. Reference numeral 109 denotes an eyepiece for observing a subject image (optical image), and actually includes three lenses (lenses 109a, 109b, and 109c in FIG. 3). The focusing screen 105, pentaprism 112, and lens 109 described above constitute a finder optical system.

  The half mirror 111 has a refractive index of approximately 1.5 and a thickness of 0.5 mm. A sub-mirror 122 is provided behind the half mirror 111, and reflects the light beam close to the optical axis among the light beams transmitted through the half mirror 111 toward the focus detection unit 121. The focus detection unit 121 performs focus detection by a phase difference detection method.

  An illumination unit 104 irradiates the subject with illumination light. The lighting unit 104 protrudes from the camera body 101 when in use, and is housed in the camera body 101 when not in use. Reference numeral 113 denotes a focal plane shutter (hereinafter referred to as a shutter) that controls the amount of light incident on the image sensor 106. The shutter 113 has a front curtain and a rear curtain composed of a plurality of light shielding blades.

  The shutter 113 covers the aperture serving as a light passage opening with the front curtain or the rear curtain when not photographing, and shields the photographing light flux. During photographing, the front curtain and the rear curtain travel while forming a slit to take the photographing light flux. Is passed to the image plane side. A main switch 119 is operated to operate the camera body 101.

  Reference numeral 118 denotes a calibration switch, which is operated when the photographer executes calibration. Reference numeral 120 denotes a release button, which is operated to instruct the start of a shooting preparation operation (including a focus adjustment operation and a photometry operation) and a shooting operation. Reference numeral 123 denotes a finder mode changeover switch, which can switch the setting of the optical finder mode (OVF mode) and the electronic finder mode (EVF mode). Here, in the OVF mode, an object image can be observed through the finder optical system, and in the EVF mode, the object image can be observed through the display unit 107.

  The photographing mode changeover switch 123 is a slide type switch. When the shooting mode changeover switch 123 is moved to a position corresponding to the OVF mode or EVF mode, this shooting mode is maintained. Reference numeral 180 denotes an information display unit that displays predetermined information (for example, photographing information) in the finder optical system. Thereby, the photographer can observe predetermined information together with the subject image by looking into the eyepiece lens 109.

  In the configuration described above, the half mirror 111 and the sub mirror 122 can selectively take three states from the first optical path state to the third optical path state, as will be described later. In the first optical path state (first state), the light from the photographing optical system 103 is guided to the finder optical system and the focus detection unit 121. In the second optical path state (second state), light from the photographing optical system 103 is guided to the image sensor 106 and the focus detection unit 121. In the third optical path state (third state), the light from the imaging optical system 103 reaches the image sensor 106 directly.

  Specifically, in the first optical path state, the half mirror 111 and the sub mirror 122 are obliquely installed in the photographing optical path. The light from the imaging optical system 103 is guided to the finder optical system by being reflected by the half mirror 111, and the light transmitted through the half mirror 111 is guided to the focus detection unit 121 by being reflected by the sub mirror 122. . Thereby, in the first optical path state, the object image can be observed through the eyepiece lens 109 and the focus detection unit 121 can perform focus detection.

  In the second optical path state, only the half mirror 111 remains obliquely installed in the photographing optical path. The light from the photographing optical system 103 is reflected by the half mirror 111 and guided to the focus detection unit 121, and the light transmitted through the half mirror 111 can reach the image sensor 106. Note that the sub mirror 122 is in a state of being retracted from the photographing optical path.

  As a result, in the second optical path state, a captured image can be displayed on the display unit 107 based on the output of the image sensor 106, or shooting (continuous shooting or movie shooting) can be performed, and the focus detection unit 121 can be used. Focus detection can be performed at.

  In the third optical path state, the half mirror 111 and the sub mirror 122 are retracted from the imaging optical path, and the light from the imaging optical system 103 can reach the image sensor 106 directly. As a result, in the third optical path state, a captured image can be displayed on the display unit 107 or photographed based on the output of the image sensor 106. This shooting can generate a high-definition image, and is suitable for enlarging the shot image and performing a large print.

  In order to switch the above-described three optical path states at high speed, the half mirror 111 is made of a transparent resin to reduce the weight. In addition, a polymer thin film having birefringence is attached to the back surface of the half mirror 111. For this reason, in the second optical path state, when a captured image is monitored by the display unit 107 or when high-speed continuous shooting is performed, a stronger low-pass is achieved in correspondence with the fact that all the pixels of the image sensor 106 are not used for imaging. Gives an effect.

  Note that a fine pyramid-shaped periodic structure having a pitch smaller than the wavelength of visible light can be formed on the surface of the half mirror 111 with a resin so as to act as a so-called photonic crystal. As a result, it is possible to reduce the surface reflection of light due to the difference in refractive index between air and resin, and to increase the light utilization efficiency. And in a 2nd optical path state, it can prevent that a ghost generate | occur | produces by the multiple reflection of the light in the front and back of the half mirror 111. FIG.

  A mirror driving mechanism including an electromagnetic motor (not shown) and a gear train changes the optical path state by changing the positions of the half mirror 111 and the sub mirror 122, and the first optical path state, the second optical path state, and the third optical path state described above. Switch according to the optical path condition.

  In imaging in the second optical path state, as will be described later, the half mirror 111 and the sub mirror 122 remain held at predetermined positions, and there is no need to operate the mirror drive mechanism. For this reason, it is possible to perform ultra high-speed continuous shooting by speeding up the image signal processing. Further, the focus adjustment can be performed even when an image is displayed on the display unit 107.

  FIG. 2 is a block diagram illustrating an electrical configuration of the camera system according to the present embodiment. This camera system has an imaging system, an image processing system, a recording / reproducing system, and a control system. First, an explanation will be given regarding imaging and recording of an object image. In FIG. 2, the same members as those described in FIG.

  The imaging system includes a photographing optical system 103 and an imaging element 106, and the image processing system includes 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, and the control system includes a camera system control circuit (control circuit) 135, an operation detection circuit 136, and an image sensor driving circuit 137.

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

  The imaging system is an optical processing system that forms an image of light from a subject on the imaging surface of the imaging element 106 via the imaging optical system 103. Then, the aperture (light quantity adjustment unit) 143 in the lens device 102 and the travel of the front curtain and rear curtain in the shutter 113 are adjusted as necessary, and the image sensor 106 is exposed to subject light having an appropriate light quantity.

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

  In the Bayer array, the overall image performance is improved by arranging more G pixels that are easily felt when the photographer looks at the image than the R and B pixels. In general, in image processing using this type of image sensor 106, a luminance signal is generated mainly from G, and a color signal is generated from R, G, and B.

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

  The image processing system is a signal processing system that obtains an image signal of a desired format from R, G, and B digital signals. The R, G, and B color signals are converted into luminance signals Y and color difference signals (R−Y), ( (B−Y) and the like. The RGB image processing circuit 131 is a signal processing circuit that processes an image signal of 3700 × 2800 pixels received from the image sensor 106 via the A / D converter 130, and is a white balance circuit, a gamma correction circuit, and an interpolation calculation high It has an interpolation operation circuit that performs resolution.

  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 includes 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 a color difference that generates color difference signals RY and BY. It consists of a 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 (recording medium, not shown) and outputs an image signal to the display unit 107. The recording processing circuit 133 performs a writing process and a reading process of the image signal to the memory. 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 also includes a compression / decompression circuit that compresses YC signals representing still images and moving images in a predetermined compression format (for example, JPEG format) and decompresses the compressed data when the compressed data is read out. Have. The compression / decompression circuit includes a frame memory for signal processing. The YC signal from the image processing system is stored in this frame memory for each frame, and is read and compressed for each of a plurality of blocks. 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 a visible image is displayed (reproduced). The reproduction processing circuit 134 and the display unit 107 can be connected via a wireless communication line such as Bluetooth. If comprised in this way, the image imaged with the camera can be monitored from the distant place.

  On the other hand, the operation detection circuit 136 which is a part of the control system detects operations of the release button 120, the finder mode changeover switch 123, and the like. The camera system control circuit 135 controls driving of each member in the camera including the half mirror 111 and the sub mirror 122 according to the detection signal of the operation detection circuit 136, and generates and outputs a timing signal at the time of imaging. To do.

  The image sensor drive circuit 137 generates a drive signal for driving the image sensor 106 under the control of the camera system control circuit 135. The information display circuit 142 controls driving of the information display unit 180.

  The control system controls driving of each circuit in the imaging system, the image processing system, and the recording / reproducing system in accordance with an external operation. For example, the control system detects that the release button 120 has been pressed, and controls the driving of the image sensor 106, the operation of the RGB image processing circuit 131, the compression processing of the recording processing circuit 133, and the like. The control system controls the state of each segment in the information displayed in the optical viewfinder by the information display circuit 142.

  Next, the focus adjustment will be described. An AF control circuit 140 and a lens system control circuit 141 are connected to the camera system control circuit 135. These control circuits 140 and 141 communicate with each other data necessary for each processing with the camera system control circuit 135 as a center.

  The AF control circuit 140 generates a focus detection signal by receiving a signal output of the focus detection sensor 167 corresponding to the focus detection area provided at a predetermined position on the shooting screen, and the focus state ( Defocus amount) is detected. When the defocus amount is detected, the defocus amount is converted into a drive amount of the focus lens in the photographing optical system 103 and transmitted to the lens system control circuit 141 via the camera system control circuit 135.

  For a moving object, the focus lens drive amount is determined based on the result of predicting an appropriate lens stop position, taking into account the time lag from when the release button 120 is operated until the actual shooting operation starts. Instruct. When the brightness of the subject is low and sufficient focus detection accuracy cannot be obtained, the object is illuminated by a white LED or a fluorescent tube (not shown) provided in the illumination unit 104 or the camera body 101. Here, the luminance of the subject can be detected by a luminance detection unit (not shown) provided in the camera body 101.

  When the lens system control circuit 141 receives the driving amount of the focus lens sent from the camera system control circuit 135, the lens system control circuit 141 performs an operation such as moving the focus lens in the direction of the optical axis L1 by a driving mechanism (not shown) in the lens device 102. And adjust the focus. When the AF control circuit 140 detects that the subject is in focus, this detection information is transmitted to the camera system control circuit 135. At this time, if the release button 120 is operated, the imaging control is performed by the imaging system, the image processing system, and the recording / reproducing system as described above.

  The diaphragm 143 adjusts the amount of subject light directed toward the image plane in accordance with a command from the lens system control circuit 141. The camera system control 135 and the lens system control circuit 141 are configured to be able to communicate via the electrical contact (communication unit) 144a of the mount unit on the lens device 102 side and the electrical contact 144b of the mount unit on the camera body 101 side. Has been.

  3 to 7 are longitudinal sectional views of the camera system according to the present embodiment. A part of the lens device 102 is shown. In these drawings, operations of the driving mechanisms (mirror driving mechanisms) of the half mirror 111 and the sub mirror 122 are mainly shown in time series. The same members as those described in FIGS. 1 and 2 are denoted by the same reference numerals.

  The configuration of the mirror drive mechanism will be described with reference to FIG. FIG. 5 shows a view when the camera is in the first optical path state described above.

  In FIG. 5, reference numeral 101 denotes a camera body, 102 denotes a lens device, 103a denotes a lens positioned closest to the image plane among a plurality of lenses constituting the photographing optical system, and 105 denotes a focusing screen of the finder optical system. Reference numeral 164 denotes a condenser lens that serves as a light beam capturing window in the focus detection unit 121, and 107 denotes a display unit. Reference numeral 163 denotes an eyepiece shutter (light-shielding member) that can advance and retract in the optical path of the finder optical system. This light shielding member is a member for avoiding an influence on imaging due to light from the eyepiece lens 109a side.

  The movable half mirror 111 is held by a half mirror receiving plate (not shown). The half mirror receiving plate is provided with pins 173 and 174, and the half mirror 111 and the pins 173 and 174 are movable together through the half mirror receiving plate. Reference numeral 170 denotes a half mirror drive lever, and 171 denotes a half mirror support arm. The half mirror drive lever 170 is supported to be rotatable with respect to the rotation shaft 170a, and the half mirror support arm 171 is supported to be rotatable with respect to the rotation shaft 171a.

  The half mirror drive lever 170 is connected to a drive source via a power transmission mechanism (not shown), and can rotate around the rotation shaft 170a by receiving a drive force from the drive source. Further, the half mirror support arm 171 is connected to a structure having substantially the same shape on the opposite wall surface side of the mirror box via the connection portion 171b.

  A pin 173 provided on a half mirror receiving plate (not shown) is slidably engaged with a through hole 171c provided at the tip of the half mirror support arm 171. Thereby, the half mirror 111 can be rotated centering on the through-hole 171c via the half mirror receiving plate. Further, an urging force in the direction of arrow A is applied to an intermediate position between the pin 173 and the pin 174 in the half mirror receiving plate by a torsion spring (not shown).

  In the first optical path state (FIG. 5), the mirror stoppers (stopper members) 160 and 161 are in the state of entering the movement locus of the half mirror 111 outside the imaging optical path. In this state, the half mirror 111 is positioned in contact with the mirror stoppers 160 and 161 by receiving a biasing force in the direction of arrow A by the torsion spring. As a result, the half mirror 111 is inclined on the photographing optical path.

  Here, the pin 173 does not contact the first cam surface 170b of the half mirror drive lever 170, and the pin 174 does not contact the second cam surface 170c of the half mirror drive lever 170. Further, the sub mirror 122 is located behind the half mirror 111 in a state in which the rotation around the rotation axis 125 is suppressed.

  In the first optical path state described above, the light beam reflected by the half mirror 111 out of the light beam emitted from the photographing optical system 103 is guided to the finder optical system. Then, the light beam transmitted through the half mirror 111 is reflected by the sub-mirror 122 behind the half mirror 111 and guided to the focus detection unit 121.

  When the mirror stoppers 160 and 161 are retracted from the movement locus of the half mirror 111 or when the half mirror drive lever 170 is rotated clockwise in FIG. 5, the pins 173 and 174 are moved in the direction of arrow A by a torsion spring (not shown). Receive a biasing force. Accordingly, 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.

  Then, the pins 173 and 174 move along the first cam surface 170b and the second cam surface 170c in accordance with the rotation amount of the half mirror drive lever 170, respectively. Thereby, the attitude | position (inclination with respect to the optical axis L1) of the half mirror 111 changes. That is, the half mirror support arm 171 rotates in conjunction with the rotation of the half mirror drive lever 170. Then, the half mirror receiving plate connected to the half mirror driving lever 170 and the half mirror supporting arm 171 via the pins 173 and 174 is operated, and the half mirror 111 is operated together with the half mirror receiving plate.

  3 to 7 are diagrams illustrating the operation of the half mirror 111 and the sub mirror 122. FIG. 3 shows the second optical path state described above, and FIG. 4 shows a transition process from the first optical path state to the second optical path state. FIG. 6 shows a transition process from the first optical path state to the third optical path state, and FIG. 7 shows the third optical path state described above.

  When in the first optical path state (FIG. 5), the half mirror 111 and the sub mirror 122 act so as to guide the subject light emitted from the imaging optical system 103 to the finder optical system and the focus detection unit 121 as described above. To do. Further, when in the second optical path state (FIG. 3), the half mirror 111 acts to guide the subject light emitted from the imaging optical system 103 to the imaging element 106 and the focus detection unit 121. In the second optical path state, it is possible to perform a high-speed focus adjustment operation using the focus detection result of the focus detection unit 121 while observing a subject image using the display unit 107. Further, when in the third optical path state (FIG. 7), the half mirror 111 and the sub mirror 122 are retracted from the photographing optical path.

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

  3 to 7, reference numeral 164 denotes a condenser lens, 165 denotes a reflecting mirror, 166 denotes a re-imaging lens, and 167 denotes a focus detection sensor.

  The light beam emitted from the photographing optical system 103 and reflected by the half mirror 111 (in the second optical path state) or the sub mirror 122 (in the first optical path state) is incident on the condenser lens 164 below the mirror box. Then, the light is deflected by the reflection mirror 165, and a secondary image of the object is formed 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. Between the output signal waveforms of the two pixel columns, 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 shift direction of the output signal waveform is reversed at the front and rear pins, and this phase difference (shift amount), including the shift direction, is detected using a method such as correlation calculation. ).

  8 and 9 are diagrams illustrating output signal waveforms of the focus detection sensor 167 input to the AF control circuit 140. FIG. The horizontal axis represents the pixel arrangement, and the vertical axis represents the output value. FIG. 8 shows an output signal waveform when the subject image is not in focus, and FIG. 9 shows an output signal waveform when the subject image is in focus.

  In general, the light beam for focus detection is not the same as the imaged light beam in the open aperture state, and focus detection is performed using a part of the imaged light beam. That is, a dark F-number light beam is used for focus detection. Further, in consideration of mechanism errors, the position of the image sensor 106 and the position of the focus detection sensor 167 are not optically conjugate in a strict sense. As a result, even if the subject image is in focus, a slight initial phase difference Δ remains between the two output signal waveforms (FIG. 9).

  This is different from the correction in the focus correction mode for sharpening the electronic image display focus described later (see step S207 in FIG. 11). The existence of the initial phase difference Δ is not usually a problem because the true phase difference can be known by subtracting this from the phase difference detected by the correlation calculation of the two images.

  However, there is a problem that the position of the reflecting surface of the sub-mirror 122 in the first optical path state and the position of the reflecting surface of the half mirror 111 in the second optical path state do not completely match in terms of mechanism accuracy, and the initial phase difference Δ is also slightly Different. With normal part processing accuracy, there is a possibility that the reflective surface is shifted in the normal direction of about 30 μm. If this amount is reduced, the cost for processing the part becomes extremely high.

  Therefore, the initial phase difference Δ is set for each of the first optical path state and the second optical path state, and the value of the initial phase difference Δ is changed according to the optical path state. For example, the initial phase difference Δ in the first optical path state and the second optical path state is stored in a memory 135 a provided in the camera system control circuit 135. Then, by detecting the position of the mirror (half mirror 111 and sub mirror 122) or detecting the finder mode (EVF mode and OVF mode), the initial phase difference in the first optical path state or the second optical path state Δ can be read out.

  With this configuration, focus detection can be performed with good accuracy in any optical path state.

  In this way, first, using the idea of the initial phase difference, it is possible to detect the in-focus state by determining the identity of a set of signals. 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. 05-088445. If the obtained defocus amount is converted into an amount by which the focus lens of the photographing optical system 103 should be driven, automatic focus adjustment is possible.

  In this method, the amount by which the focus lens is to be driven is known in advance, so that the focus lens is normally driven to the in-focus position only once, and extremely high speed focus adjustment is possible.

  Next, a shooting sequence in the camera system of the present embodiment will be described with reference to FIG.

  In step S100, the process waits until the main switch 119 is operated (ON state), and the operation proceeds to step S101. In step S101, current is supplied (started) to various electric circuits in the camera body 101. In step S200, a subroutine for finder mode switching processing is executed. Details of this processing will be described later.

  In step S102, it is determined whether or not the finder mode changeover switch 123 has been operated. When the operation of the finder mode changeover switch 123 is detected, the process returns to step S200, and the finder mode is switched. On the other hand, when the operation of the finder mode switch 123 is not detected, the process proceeds to step S103.

  In step S103, it is determined whether or not the remote shooting mode or the self-timer shooting mode is set. These shooting modes can be set by a setting switch (not shown) provided in the camera body 101.

  Here, the remote shooting mode is a mode in which a shooting operation is performed in the camera system by operating a remote control device separate from the camera body 101. The remote shooting mode is often set when the photographer himself / herself also becomes a subject. The self-timer shooting mode is a mode in which a shooting operation is performed after a predetermined time has elapsed since an operation for starting a shooting operation (for example, a full pressing operation of the release button 120) is performed. This self-timer shooting mode is also often set when the photographer himself is the subject.

  If the remote shooting mode or the self-timer shooting mode is set in step S103, the process proceeds to step S104. If not set, the process proceeds to step S105.

  In step S104, the eyepiece shutter 163 of the finder optical system is closed. Here, in the remote shooting mode and the self-timer shooting mode, since the photographer does not look into the eyepiece lens 109 of the finder optical system, light from outside may enter the camera body 101 through the finder optical system. is there. In this case, when back-entered light from the finder optical system reaches the focus detection unit 121, there is a possibility that a focus detection error may occur, and high-precision focus detection may not be performed. Therefore, in step S104, the eyepiece shutter 163 is closed to prevent reverse incident light from the viewfinder optical system from entering the camera body 101.

  In step S105, it is determined whether or not the calibration switch 118 has been operated (turned on). If the calibration switch 118 has been operated, the process proceeds to step S700, and a calibration mode subroutine is executed. The contents of this subroutine will be described later (FIG. 14). On the other hand, if the calibration switch 118 has not been operated, the process proceeds to step S106.

  In step S106, based on the output of the operation detection circuit 136, it is determined whether or not the release button 120 has been pressed halfway (in other words, whether or not SW1 is in an on state). If SW1 is on, the process proceeds to step S107. If SW1 is off, the process returns to step S102.

  In step S107, subject luminance is measured (photometric operation), and the focus detection unit 121 performs a focus detection operation using a phase difference detection method. These detection results are sent to the camera system control circuit 135, and an exposure value (shutter speed and aperture value) and a defocus amount are calculated. Here, the detection result of the focus detection unit 121 is a value corrected using the correction amount Δx obtained by EVF calibration (FIG. 15), as will be described later.

  Then, based on the calculated defocus amount, the focus lens of the photographing optical system is driven and focused under the control of the AF control circuit 140 and the lens system control circuit 141. Further, based on the calculated aperture value, the aperture 143 is driven to switch the opening area of the light passage opening. When the EVF mode is set, in other words, when the camera body 101 is in the second optical path state (FIG. 3), focus detection by the contrast detection method is performed based on the output of the image sensor 106. You can also

  In step S108, based on the output of the operation detection circuit 136, it is determined whether or not the release button 120 has been fully pressed (in other words, whether or not SW2 is in an ON state). If SW2 is on, the process proceeds to step S109. If SW2 is off, the process returns to step S106.

  In step S109, the eyepiece shutter 163 of the finder optical system is closed. In Step S110, the half mirror 111 and the sub mirror 122 are set to the third optical path state (FIG. 7) by driving the mirror driving mechanism. In step S111, the image sensor 106 is exposed by operating the shutter 113 based on the shutter speed calculated in step S107. As described above, the output signal from the image sensor 106 is input to the image processing system.

  In step S112, 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. In the YC processing circuit 132, YC processing is performed and image processing is completed. By these image processes, high-definition images can be captured.

  In step S113, the image-processed image is sent to the recording processing circuit 133, and is compressed and recorded in a predetermined compression format. In step S114, the image processed image is also sent to the reproduction processing circuit 134, and the captured image is displayed (preview display) on the display unit 107. After the process of step S114, the process returns to step S200.

  Next, the finder mode switching operation will be described.

  While the electric circuit in the camera is operating, the state of each operation switch is detected via the operation detection circuit 136. When it is detected that the finder mode changeover switch 123 is operated, the finder mode (OVF mode and EVF mode) is detected. The mode switching operation is immediately started (step S200 in FIG. 10).

  FIG. 11 is a flowchart for explaining the finder mode switching operation, which will be described along this flow.

  In step S201, when the current finder mode is detected and the finder mode changeover switch 123 is operated to switch from the OVF mode to the EVF mode, the process proceeds to step S202. On the other hand, when the EVF mode is switched to the OVF mode by operating the finder mode switch 123, the process proceeds to step S220.

  First, a case where the OVF mode is switched to the EVF mode will be described.

  In the OVF mode, the optical path splitting system composed of the half mirror 111 and the sub mirror 122 is in the first optical path state (FIG. 5). In the EVF mode, since no object light is guided to the optical viewfinder, first, in step S202, the camera system control circuit 135 drives the driving source (not shown) to close the eyepiece shutter 163. That is, the eyepiece shutter 163 is caused to enter the finder optical path between the lens 109b and the lens 109c.

  This is to prevent the photographer from misunderstanding that the subject image becomes invisible through the eyepiece lens 109 when the EVF mode is set, as a camera failure. Another reason for this is to prevent the occurrence of a ghost due to the back incident light from the optical viewfinder entering the image sensor 106.

  In step S203, the information display in the optical viewfinder is set to the non-display state by the drive control of the information display unit 180. This is because, since the eyepiece shutter 163 is already closed in step S202, the photographer cannot see this display even if information is displayed in the optical viewfinder. Thereby, power consumption can be reduced and consumption of the battery can be suppressed.

  In step S204, the sub mirror 122 is retracted to the lower part of the mirror box in preparation for moving the half mirror 111 to the second optical path state (FIG. 3) by operating the mirror driving mechanism (FIG. 3).

  In step S205, the mirror stoppers 160 and 161 are retracted from the movement locus of the half mirror 111. After the mirror stoppers 160 and 161 are retracted, in step S206, the half mirror drive lever 170 is rotated counterclockwise by the mirror drive mechanism. As a result, the half mirror 111 receives the urging force in the direction of arrow A by a torsion spring (not shown), and enters the second optical path state (FIG. 3) through the state shown in FIG.

  When the half mirror 111 is in the second optical path state, a part of the light beam from the photographing optical system 103 is reflected by the half mirror 111 and guided to the focus detection unit 121. Further, the remaining light flux passes through the half mirror 111 and travels toward the image sensor 106 side.

  In the second optical path state, the half mirror 111 is positioned in contact with the mirror stoppers 175 and 176 disposed outside the photographing optical path by receiving a biasing force in the direction of arrow A by the torsion spring. At this time, the pin 173 does not contact the first cam surface 170b of the half mirror drive lever 170, and the pin 174 does not contact the second cam surface 170c of the half mirror drive lever 170.

  The position of the reflecting surface of the half mirror 111 is substantially the same as the position where the reflecting surface of the sub mirror 122 is located in the first optical path state. With this configuration, the reflected light guided to the focus detection unit 121 by the sub mirror 122 (first optical path state), and the reflected light guided to the focus detection unit 121 by the half mirror 111 (second optical path state). It is possible to suppress the shift. Thereby, the position of the focus detection area can be hardly changed.

  Here, the focus position of the subject image formed by the light flux that has passed through the half mirror 111 formed on the image sensor 106 is slightly deviated from the focus position when the subject light does not pass through the half mirror 111. Sometimes. For this reason, in step S207, the focus correction mode is activated in order to correct the shift of the focus position.

  In the first optical path state, the focus detection unit 121 causes the object image to be sharply formed on the image sensor 106 when the half mirror 111 and the sub mirror 122 are retracted from the imaging optical path (third optical path state). A focus detection signal is output.

  On the other hand, when the focus correction mode is on in the second optical path state, the focus detection unit transmits the half mirror 111 and projects the subject image projected onto the image sensor 106 sharply. The focus detection signal 121 is corrected. As a result, when the focus correction mode is set in the second optical path state, the focus position of the focus lens in the second optical path state is the third amount corresponding to the correction of the focus detection signal of the focus detection unit 121. It shifts with respect to the focus position of the focus lens in the optical path state.

  Therefore, when the EVF mode is set, when the second optical path state is switched to the third optical path state in response to the start of the imaging operation, the front curtain drive mechanism of the shutter 113 is charged in synchronization with this. (Shutter 113 is closed). Further, the focus lens is returned to the original position (the in-focus position in the third optical path state) by the amount corresponding to the correction of the focus position of the object image in the focus correction mode. Thereafter, the shutter 113 is opened for a predetermined time, and the image sensor 106 performs imaging.

  With this configuration, the focus state is accurately confirmed based on the image displayed on the display unit 107 in the second optical path state, and then an image in focus in the third optical path state is captured. be able to.

  In step S <b> 208, only the front curtain of the shutter 113 is caused to travel so as to be in a bulb exposure state, and object light is continuously guided to the image sensor 116, thereby enabling imaging for displaying an image on the display unit 107.

  In step S300, EVF calibration is executed, and a correction amount for correcting the focus detection result of the phase difference detection method is obtained using the focus detection result of the contrast detection method. The specific contents of this EVF calibration will be described later (FIG. 15). In this embodiment, every time the EVF mode is set, a correction amount for correcting the focus detection result of the phase difference detection method is obtained. Thereby, the correction amount according to the change with time can be obtained, and the detection error of the phase difference detection method can be suppressed by using this correction amount. And the detection accuracy of a phase difference detection system can be improved.

  In step S209, the display unit 107 is powered on. In step S210, object images are continuously picked up by the image pickup device 106, real-time display is started on the display unit 107, and a series of viewfinder switching processes are ended.

  In the EVF mode (second optical path state), since the subject light emitted from the photographing optical system 103 is refracted by the half mirror 111, the electronic image of the subject displayed in real time on the display unit 107 is the third one. In the optical path state, the image is slightly shifted in the vertical direction as compared with the actually captured image.

  FIG. 12 is a diagram for explaining a difference between an image displayed on the display unit 107 in the second optical path state and an image actually captured in the third optical path state. In FIG. 12, reference numeral 190 denotes an imaging range (region surrounded by a thick line frame) that is imaged in the second optical path state. That is, it indicates the range of captured images that can be output to the display unit 107 during real-time display. Reference numeral 191 denotes an imaging range in which imaging is performed in the third optical path state.

  The imaging range 190 and the imaging range 191 have a relationship shifted in the vertical direction. As a result, the display unit 107 can output, but there is a region 190 a that is not imaged in the third optical path state, that is, a region that does not overlap the imaging range 191 in the imaging range 190.

  Therefore, the reproduction processing circuit 134 performs processing so that the area 192 corresponding to the area 190a in FIG. 12 is not displayed and the entire photographing range 190 is not displayed on the display unit 107 as shown in FIG. As a result, the display unit 107 displays a region looking into the region 192 in the imaging region 190. As a result, it is possible to eliminate the inconvenience that the image is not actually photographed despite being displayed on the display unit 107 in the EVF mode.

  Next, a case will be described in which the process proceeds to step S220 in order to switch from the EVF mode to the OVF mode by determining the finder mode in step S201.

  In the EVF mode in the initial state, the optical path division system composed of the half mirror 111 and the sub mirror 122 is in the second optical path state (FIG. 3), and real-time display is performed on the display unit 107 as described above.

  In step S220, the power of the display unit 107 is turned off and imaging by the image sensor 106 is stopped. In step S221, the rear curtain of the shutter 113 is moved to close the shutter 113, and the front curtain / rear curtain drive mechanism is charged in preparation for shooting.

  In step S <b> 222, the mirror stoppers 160 and 161 are retracted from the movement locus of the half mirror 111 in order to enable the movement of the half mirror 111. In step S223, the half mirror drive lever 170 is rotated clockwise in FIG. 3, so that the half mirror 111 and the sub mirror 122, which are optical path dividing systems, are in the state of FIG. 4, the state of FIG. 5, the state of FIG. To be in the state (third optical path state).

  When the half mirror drive lever 170 rotates in the clockwise direction, the pin 174 is pushed and moved into the second cam surface 170c, and the pin 173 is pushed and moved into the first cam surface 170b. As a result, the half mirror support arm 171 rotates clockwise about the rotation shaft 171a, and the half mirror 111 rotates clockwise about the pin 173.

  In step S224, the mirror stoppers 160 and 161 are inserted into the movement locus of the half mirror 111. Since the mirror stoppers 160 and 161 are inserted after the half mirror 111 is moved to the third optical path state, there is no collision with the half mirror 111 when the mirror stoppers 160 and 161 are inserted. The mechanical reliability when switching the position of the half mirror 111 (switching between the OVF mode and the EVF mode) can be increased.

  In this embodiment, the half mirror 111 is moved to the third optical path state. However, since the mirror stoppers 160 and 161 do not have to collide with the half mirror 111, the half mirror 111 corresponds to the third optical path state. You may move to the vicinity of the position to do.

  In Step S225, the half mirror 111 is rotated from the third optical path state (FIG. 7) to the first optical path state (FIG. 5) by rotating the half mirror drive lever 170 counterclockwise in FIG. ). At this time, the half mirror 111 receives a biasing force of a spring (not shown) in the mirror driving mechanism and is in contact with the mirror stoppers 160 and 161.

  In step S226, the eyepiece shutter 163 is opened. In step S227, based on the output from the operation detection circuit 136, it is determined whether or not the manual (M) focus mode is set. If the manual focus mode is selected, the process proceeds to step S208. If the manual focus mode is selected instead of the manual focus mode, the process proceeds to step 228.

  In the manual focus mode, it is not necessary to operate the focus detection unit 121, and the electronic image display can be more accurately understood than the optical viewfinder to grasp the background blur. For this reason, the process proceeds to step S208 for performing real-time display on the display unit 107.

  In step S228, the sub mirror 122 is set at a predetermined position so as to guide subject light to the focus detection unit 121. That is, the sub mirror 122 housed in the lower part of the mirror box (FIG. 7) is moved behind the half mirror 111 by rotating around the rotation shaft 125 (FIG. 5).

  In step S229, predetermined information is lit and displayed in the viewfinder by the drive control of the information display unit 180, and the series of viewfinder switching processes is terminated.

  Next, the calibration mode (step S700 in FIG. 10) will be described with reference to FIG.

  In step S701, it is determined whether or not the finder mode is the EVF mode. If the EVF mode is set, the process proceeds to step S300. If the EVF mode is not set, the process proceeds to step S702.

  In step S300, EVF calibration is executed, and a correction amount for correcting the focus detection result of the phase difference detection method is obtained using the focus detection result of the contrast detection method. The specific contents of this EVF calibration will be described later (FIG. 15). In this embodiment, every time the calibration switch 118 is operated, a correction amount for correcting the focus detection result of the phase difference detection method is obtained. Thereby, the correction amount according to the change with time can be obtained, and the detection error of the phase difference detection method can be suppressed by using this correction amount. And the detection accuracy of a phase difference detection system can be improved.

  In step S702, the eyepiece shutter 163 of the finder optical system is closed. In step S703, the sub mirror 122 is retracted to the lower part of the mirror box in preparation for moving the half mirror 111 to the second optical path state (FIG. 3) by operating the mirror driving mechanism (FIG. 3).

  In step S704, the mirror stoppers 160 and 161 are retracted from the movement locus of the half mirror 111. After the mirror stoppers 160 and 161 are retracted, in step S705, the half mirror drive lever 170 is rotated counterclockwise by the mirror drive mechanism. Thereby, the half mirror 111 is in the second optical path state (FIG. 3) through the state shown in FIG. 4 by receiving a biasing force in the direction of arrow A by a spring (not shown). As a result, the subject light is reflected by the half mirror 111 and guided to the focus detection unit 121.

  In step S <b> 706, only the front curtain of the shutter 113 is caused to travel so as to be in a bulb exposure state, and subject light is continuously guided to the image sensor 106 to enable imaging for displaying an image on the display unit 107. In step S300, EVF calibration described later is executed.

  In step S707, the rear curtain of the shutter 113 is moved to close the shutter 113, and the front curtain / rear curtain drive mechanism is charged in preparation for shooting. In step S <b> 708, the mirror stoppers 160 and 161 are retracted from the movement locus of the half mirror 111 in order to enable the movement of the half mirror 111.

  In step S709, by rotating the half mirror drive lever 170 clockwise in FIG. 3, the half mirror 111 and the sub mirror 122, which are optical path dividing systems, are in the state of FIG. 4, the state of FIG. 5, the state of FIG. 7 so as to be in the state 7 (third optical path state).

  In step S710, the mirror stoppers 160 and 161 are inserted into the movement locus of the half mirror 111. Since the mirror stoppers 160 and 161 are inserted after the half mirror 111 is moved to the third optical path state, there is no collision with the half mirror 111 when the mirror stoppers 160 and 161 are inserted. And the mechanical reliability at the time of switching the position of the half mirror 111 (switching between OVF mode and EVF mode) can be improved.

  In step S711, the half mirror 111 is rotated from the third optical path state (FIG. 7) to the first optical path state (FIG. 6) by rotating the half mirror drive lever 170 counterclockwise in FIG. 5). At this time, the half mirror 111 receives a biasing force of a spring (not shown) in the mirror driving mechanism and is in contact with the mirror stoppers 160 and 161.

  In step S712, the eyepiece shutter 163 of the viewfinder optical system is opened. In step S713, the sub mirror 122 is moved to a predetermined position (position shown in FIG. 5) so that subject light is guided to the focus detection unit 121.

  As described with reference to FIG. 14, in the present embodiment, EVF calibration is automatically executed only by operating the calibration switch 118 even when the EVF mode is not set. That is, regardless of whether the EVF mode or the OVF mode is set, the EVF calibration can be automatically executed only by operating the calibration switch 118. Therefore, when the OVF mode is set, it is not necessary to switch to the EVF mode by operating the finder mode changeover switch 123 in order to execute EVF calibration.

  Next, a subroutine for EVF calibration (step S300 in FIGS. 11 and 14) will be described with reference to FIG.

  In step S <b> 301, focus detection by the phase difference detection method is performed using the focus detection unit 121. In step S302, the focus lens of the photographing optical system 103 is driven in the optical axis direction based on the focus detection result obtained in step S301. Specifically, the focus lens is moved by a predetermined amount (an amount corresponding to the defocus amount) in the direction of deviation in the focus detection result. As a result, the focus lens stops at a position determined to be in focus in the phase difference detection method.

  In step S303, an initial value “1” is substituted into the lens extension stage number n indicating the position of the focus lens. In step S <b> 304, the camera system control circuit 135 outputs a control signal to the AF control circuit 140 to start the focus detection operation by the focus detection sensor 167. In step S305, the camera system control circuit 135 controls the driving of the image sensor 106 via the image sensor driving circuit 137, thereby acquiring the contrast value Cn of the subject image on the imaging surface. Specifically, the contrast value Cn of the imaging area corresponding to the focus detection area on the imaging surface of the imaging element 106 is acquired.

  Here, as described above, since the light beam reaching the image sensor 106 is refracted by the half mirror 111, the light beam reaching the image sensor 106 without passing through the half mirror 111 is compared with the imaging position of the light beam. It will shift up and down. For this reason, in the present embodiment, the imaging region used for focus detection in the contrast detection method is set at a position that takes the above-described deviation into consideration. As a result, even when contrast detection focus detection is performed using light transmitted through the half mirror 111, the focus detection area on the image sensor 106 may be shifted from the focus detection area on the focus detection sensor 167. Absent. That is, these focus detection areas can be maintained in an optically conjugate positional relationship.

  In this embodiment, the contrast value Cn is acquired by performing imaging at a high frame rate using the imaging element 106. In order to realize a high-speed frame rate, the image sensor 106 performs thinned readout. In this embodiment, since a CMOS sensor capable of random access to an arbitrary pixel is used as the image sensor 106, thinning-out readout for contrast acquisition can be performed.

  In the phase difference detection method in step S304, focus detection is performed using a component reflected by the half mirror 111 in the subject light. In the contrast detection method in step S305, focus detection is performed using a component of the subject light that has passed through the half mirror 111. That is, in steps S304 and S305, focus detection is performed using light from the same subject.

  Further, by performing each processing of step S304 and step S305 at substantially the same timing, focus detection can be performed on the same subject at substantially the same timing. Thereby, two focus detection results for the same subject can be obtained at substantially the same timing.

  In step S306, the camera system control circuit 135 drives the focus lens of the photographing optical system 103 via the lens system control circuit 141. Specifically, the focus lens is moved in one direction along the optical axis by one step. Here, one step at the time of driving the focus lens is a constant multiple of the permissible circle of confusion (δ) and the F number (F) of the photographing optical system 103. The permissible circle of confusion is an amount of blur that is assumed to be in focus but not to the human eye if the blur is smaller than this assuming a constant blur on the imaging surface. Even after the focus lens is step-driven, the focus lens is normally driven in steps of Fδ / 2 in order that the focus adjustment state of the photographing optical system 103 shows a blur amount smaller than the allowable circle of confusion.

  In step S307, the focus detection sensor 167 is driven again to perform focus detection by the phase difference detection method. In step S308, the contrast value Cn is acquired by driving the image sensor 106. Also in steps S307 and S308, focus detection is performed at substantially the same timing on the same subject after driving the focus lens.

  In step S309, the contrast value Cn obtained in step S305 is compared with the contrast value Cn + 1 obtained in step S308 to determine whether or not a contrast value peak has occurred. Here, there are several methods for determining whether or not a peak value has occurred. For example, if the contrast value at the current acquisition is lower than the contrast value at the previous acquisition, there is a method of determining the contrast value at the current acquisition as the peak value. There is also a method of determining that the peak value has been exceeded if the maximum contrast value at the time of past acquisition is continuously reduced three times. Further, there is a method of determining that the peak value has been exceeded when the contrast value has been below a predetermined value or more with respect to the maximum value of the past acquisition. The present invention is not limited to these methods.

  If it is determined in step S309 that no peak value has occurred, in step S312, the lens feed stage number “n” indicating the position of the focus lens is incremented, and the process returns to step 306. Then, the processes in steps S306 to S309 and step S312 are repeated until it is determined that a peak value has occurred. That is, in the processing from step S306 to step S309 and step S312, it is determined whether or not the photographing optical system 103 is in focus in the contrast detection method. On the other hand, if it is determined in step S309 that a peak value has occurred, the process proceeds to step S310.

  In step S310, the difference in optical path length until reaching the image sensor 106 is corrected in each of the second optical path state and the third optical path state. In the second optical path state (FIG. 3), since the subject light passes through the half mirror 111 and reaches the image sensor 106, the optical path length of the subject light in the third optical path state (FIG. 7) is different. Therefore, in step S310, the detection result (contrast values Cn, Cn + 1) obtained by the contrast method detection method is corrected by the difference in the optical path length.

  In step S311, a correction amount Δx, which is the difference between the focus detection result by the phase difference detection method and the focus detection result by the contrast detection method, is calculated. As will be described later, this correction amount Δx indicates the difference between the position of the focus lens that is determined to be in focus by the phase difference detection method and the position of the focus lens that is determined to be in focus by the contrast detection method. The correction amount Δx is used to correct the focus detection result by the phase difference detection method.

  A method of calculating the correction amount Δx will be described with reference to FIG. In FIG. 16A, the horizontal axis indicates the position of the focus lens corresponding to the lens extension stage number n, and the vertical axis indicates the contrast value Cn obtained from the image sensor 106. In FIG. 16B, the horizontal axis indicates the position of the focus lens corresponding to the lens extension stage number n, and the vertical axis indicates the detection result by the phase difference detection method (a pair of subject images in the focus detection sensor 167). Phase difference Pn) is shown.

  When the contrast value shown in FIG. 16A is obtained, it is determined in step S309 that the contrast value has reached the peak value when the lens extension number n is “4”. That is, in the contrast detection method, it is determined that the photographing optical system 103 is in focus at the contrast value C4. On the other hand, in the phase difference detection method, at the point where a straight line connecting a plurality of phase differences Pn (n = 1 to 7) shown in FIG. Is determined to be in focus.

  Here, in step S302 of FIG. 15, the focus lens is moved to the in-focus position (position corresponding to the phase difference P1) based on the detection result by the phase difference detection method in step S301. However, as shown in FIG. 16, the focus position by the phase difference detection method (position in the vicinity of the phase difference P1) and the focus position by the contrast detection method (position corresponding to the contrast value C4) are equivalent to Δx. It may be off.

  The reason why this difference Δx exists is mainly a mechanical error in the mirror driving mechanism. For example, if the tilt angle of the half mirror 111 with respect to the photographing optical axis L1 in the second optical path state (FIG. 3) changes due to changes over time, the incident angle of the light reflected by the half mirror 111 with respect to the focus detection unit 121 is changed. Will change. In this case, an error occurs in the focus detection result in the focus detection unit 121. And as shown in FIG. 16, the focus position by a phase difference detection system will shift | deviate by the amount of (DELTA) x with respect to the focus position by a contrast detection system.

  In this embodiment, the focus detection result by the phase difference detection method using the focus detection unit 121 is corrected using the focus detection result by the contrast detection method using the image sensor 106. That is, the correction amount Δx is calculated, and the focus detection result by the phase difference detection method is corrected based on the correction amount Δx. Thereby, the error of the focus detection result by a phase difference detection system can be suppressed.

  In this embodiment, the half mirror 111 is set to the second optical path state (FIG. 3) so that light from the same subject is simultaneously guided to the focus detection unit 121 and the image sensor 106. Then, focus detection by the phase difference detection method using the focus detection unit 121 and focus detection by the contrast detection method using the image sensor 106 are performed at substantially the same timing. In this case, focus detection by the phase difference detection method and the contrast detection method can be performed on the same subject at substantially the same timing, and the consistency of these focus detection results can be achieved.

  Here, as in Patent Document 2, when focus detection is performed by a phase difference detection method and a contrast detection method at different timings, these focus detection results may not be for the same subject. In this case, even if the focus detection result by the phase difference detection method is corrected based on the focus detection result by the contrast detection method, the accuracy of the focus detection result by the phase difference detection method cannot be ensured.

  In this embodiment, as described above, since two focus detection results can be obtained for the same subject at substantially the same timing, the accuracy of the focus detection result by the phase difference detection method can be improved. . Here, the difference (correction amount Δx) between the two focus detection results in the present embodiment is caused by the positional deviation of the half mirror 111, and is not caused by the focus detection operations performed at different timings. If the focus detection result by the phase difference detection method is corrected based on the correction amount Δx, the error of the focus detection result due to the positional deviation of the half mirror 111 can be corrected accurately.

  In step S312, the correction amount Δx calculated in step S311 is stored in the memory 135a in the camera system control circuit 135. This correction amount Δx is calculated every time the EVF calibration shown in FIG. 15 is executed, and stored in the memory 135a.

  Here, when EVF calibration shown in FIG. 15 is executed, there is a possibility that an erroneous focus detection result may be obtained because dust or the like is accidentally attached to the focus detection sensor 167 and the image sensor 106. In this case, the correction amount Δx also becomes an incorrect value. Therefore, in the present embodiment, as described above, each time EVF calibration is executed, the correction amount Δx is calculated, and the correction amount Δx is stored in the memory 135a so that the incorrect correction amount Δx is used. Can be prevented. That is, when there is a correction amount Δx that is clearly different from the other correction amount Δx in the memory 135a, the use of the other correction amount Δx is prohibited by prohibiting the use of the correction amount Δx, thereby detecting the phase difference. The correction accuracy of the focus detection result by the method can be improved.

  If a correction amount Δx that is clearly wrong among the plurality of correction amounts Δx stored in the memory 135a is included, this correction amount Δx can be deleted from the memory 135a. . For example, when a correction amount Δx that differs by a predetermined amount or more compared to another correction amount Δx is included, the correction amount Δx can be deleted.

  Here, in the present embodiment, focus detection by the phase difference detection method is performed using the focus detection unit 121 in step S107 of FIG. 10, and the correction amount Δx stored in the memory 135a is obtained for this detection result. Use to correct.

  According to the camera system of the present embodiment, the accuracy of the focus detection result can be improved by correcting the focus detection result by the phase difference detection method using the correction amount Δx obtained by EVF calibration. . Moreover, since the correction amount Δx is calculated every time EVF calibration is executed, the focus detection result by the phase difference detection method can be corrected using the latest correction amount Δx. That is, even when the correction amount Δx changes due to a change over time or the like, it is possible to cope with a change over time by using the latest correction amount Δx. The focus detection result by the phase difference detection method can be maintained with high accuracy.

  Further, in this embodiment, since it is not necessary to use a complicated image sensor that requires advanced miniaturization technology, an increase in cost can be suppressed. Furthermore, since the pixel column used for imaging and the pixel column used for focus detection do not coexist, it is not necessary to obtain a part of the subject image by interpolation processing, and a high-quality captured image can be obtained.

  The configuration of a camera system that is Embodiment 2 of the present invention will be described with reference to FIG. Here, the state shown in FIG. 17 corresponds to the first optical path state in the first embodiment (FIG. 5). In FIG. 17, the same members as those described in the first embodiment are denoted by the same reference numerals.

  In the first optical path state (FIG. 5), the sub mirror 122 according to the first embodiment is configured to reflect all the light beams that have passed through the half mirror 111. On the other hand, in this embodiment, a sub mirror 177 composed of a half mirror is used. For this reason, in the optical path state shown in FIG. 17 (first optical path state in the first embodiment), the subject light from the photographing optical system 103 is divided into three components described below by the half mirror 111 and the sub mirror 177. The

  The first component is a component that is reflected by the half mirror 111 and guided to the finder optical system. This first component is used for observing the subject image via the finder optical system. The second component is a component that is transmitted through the half mirror 111, reflected by the sub mirror 177, and guided to the focus detection unit 121. The second component is used for focus detection by the phase difference detection method in the focus detection unit 121. The third component is a component that passes through the half mirror 111 and the sub mirror 177 and travels toward the image sensor 106. This third component is used to display a captured image obtained from the output of the image sensor 106 on the display unit 107 or to be used for focus detection by a contrast detection method using the image sensor 106.

  As described above, in the camera system of this embodiment, it is possible to simultaneously perform focus detection by the phase difference detection method and focus detection by the contrast detection method while observing the subject image using the finder optical system. As in the first embodiment, the focus detection result by the phase difference detection method can be corrected using the focus detection result by the contrast detection method.

  Since the imaging sequence in the camera system of the present embodiment is the same as that in the camera system of Embodiment 1 (FIG. 10), description thereof is omitted. In the present embodiment, the contents of the subroutine of the finder mode switching process in the shooting sequence are different from those in the first embodiment. Hereinafter, the finder mode switching process of the present embodiment will be described with reference to FIG.

  In step S401, when the current finder mode is detected and the finder mode changeover switch 123 is operated to switch from the OVF mode to the EVF mode, the process proceeds to step S402. On the other hand, when the EVF mode is switched to the OVF mode by operating the finder mode switching switch 123, the process proceeds to step S420.

  Here, the processes in steps S402 to S408 in FIG. 18 are the same as the processes in steps S202 to S208 in the first embodiment (FIG. 11), and thus detailed description thereof is omitted.

  In step S300, EVF calibration is executed as described in the first embodiment (FIG. 15). That is, a correction amount Δx for correcting the focus detection result by the phase difference detection method is calculated based on the focus detection result by the phase difference detection method and the focus detection result by the contrast detection method. Also in this embodiment, EVF calibration is executed every time the EVF mode is set. Note that the specific processing in step S300 of the present embodiment is the same as the processing described in the first embodiment (see FIG. 15).

  After the process of step S300 is completed, the process proceeds to step S409. Here, the processes of steps S409 and S410 are the same as the processes of steps S209 and S210 in the first embodiment (FIG. 11), and thus detailed description thereof is omitted.

  On the other hand, when the EVF mode is switched to the OVF mode, the processes in steps S420 to S425 are the same as the processes in steps S220 to S225 in the first embodiment (FIG. 11), and thus detailed description thereof is omitted. .

  In step S500, OVF calibration is executed. This OVF calibration operation is the same as the EVF calibration operation in step S300. That is, a correction amount Δx for correcting the focus detection result by the phase difference detection method is calculated based on the focus detection result by the phase difference detection method and the focus detection result by the contrast detection method.

  Here, in the EVF calibration described in the first embodiment (FIG. 15), the contrast value is corrected based on the difference in optical path length between the light beam transmitted through the half mirror 111 and the light beam not transmitted through the half mirror 111. (Step S310 in FIG. 15). On the other hand, in this embodiment, in the optical path state shown in FIG. 17, subject light passes through the half mirror 111 and the sub mirror 117 and reaches the image sensor 106. Therefore, the contrast value is corrected based on the difference in optical path length between the light beam transmitted through the half mirror 111 and the sub mirror 117 and the light beam not transmitted through the half mirror 111 and the sub mirror 117 (light beam shown in FIG. 7). .

  After the process of step S500 is completed, the process proceeds to step S426. Here, the processing of each step S426 to S429 is the same as the processing of each step S226 to S229 in the first embodiment (FIG. 11), and thus detailed description thereof is omitted.

  Also in the camera system of the present embodiment, the same effect as that of the camera system of the first embodiment described above can be obtained. That is, since the focus detection result by the phase difference detection method is corrected using the correction amount Δx, the accuracy of the focus detection result can be improved. In addition, since the correction amount Δx is calculated every time the calibration mode (step S700 in FIG. 10) is executed, the focus detection result by the phase difference detection method can be corrected using the latest correction amount Δx. Thereby, the focus detection result by the phase difference detection method can be maintained with high accuracy.

  Here, in the present embodiment, EVF calibration and OVF calibration are executed every time the finder mode is switched, so that the correction amount Δx can be calculated in any finder mode.

  In this embodiment, since the correction amount Δx is calculated in both the EVF mode and the OVF mode, the number of correction amounts Δx stored in the memory 135a is increased, and the focus detection result of the phase difference detection method is calculated. Accuracy can be improved. That is, by increasing the number of correction amounts Δx, it is possible to prevent the focus detection result from being corrected by the phase difference detection method based on the correction amount Δx that is erroneously calculated.

  Further, since the correction amount Δx is calculated in the EVF mode and the OVF mode, the correction amount Δx is calculated in one of the set finder modes even when the EVF mode or the OVF mode is not set at all. Can do. Thereby, the focus detection result by the phase difference detection method can be corrected using the correction amount Δx.

  In this embodiment, the half mirror 111 and the sub mirror 177 can be operated between two states, a state shown in FIG. 17 and a state where the half mirror 111 and the sub mirror 177 are retracted from the photographing optical path (state shown in FIG. 7).

  A configuration of a camera system that is Embodiment 3 of the present invention will be described with reference to FIGS. 19 and 20. Here, the same reference numerals are used for the same members as those described in the first embodiment (FIGS. 3 to 7). Hereinafter, differences from the first embodiment will be described.

  In the camera system of this embodiment, no finder optical system is provided. Further, in this embodiment, the sub mirror described in the first embodiment is not provided, and only the half mirror 111 is used. Hereinafter, a specific configuration of the camera system of the present embodiment will be described.

  FIG. 19 is a diagram illustrating a first optical path state in the camera system of the present embodiment, and FIG. 20 is a diagram illustrating a second optical path state in the camera system of the present embodiment. The half mirror 111 is movable between a position obliquely provided in the photographing optical path (position shown in FIG. 19) and a position retracted from the photographing optical path (position shown in FIG. 20).

  When the half mirror 111 is located in the photographing optical path, some components of the subject light from the photographing optical system 103 are reflected by the half mirror 111 and guided to the focus detection unit 121. On the other hand, the remaining components are transmitted through the half mirror 111 and guided to the image sensor 106 side. For this reason, it is possible to perform high-speed focus adjustment based on the focus detection result by the phase difference detection method in the focus detection unit 121 while displaying the captured image obtained from the output of the image sensor 106 on the display unit 107. .

  On the other hand, when the half mirror 111 is retracted from the photographing optical path, the subject light from the photographing optical system 103 is directed directly toward the image sensor 106 as shown in FIG.

  Here, the drive mechanism of the half mirror 111 will be briefly described. The half mirror 111 is held by a half mirror receiving plate (not shown). This half mirror receiving plate is supported so as to be rotatable about a rotation shaft 178. The half mirror receiving plate is urged by a torsion spring (not shown). In other words, the torsion spring biases the half mirror 111 from the position shown in FIG. 20 toward the position shown in FIG. The half mirror receiving plate is held in the state shown in FIG. 19 by abutting against a mirror stopper (not shown) provided in the camera body 101.

  The half mirror receiving plate is connected to a drive source (not shown) via a power transmission mechanism (not shown), and is operable by receiving a drive force from the drive source. Here, when the half mirror 111 is moved from the first optical path state (FIG. 19) to the second optical path state (FIG. 20), the half mirror receiving plate is moved to the torsion spring by using the driving force of the driving source. Rotate against the urging force. The half mirror receiving plate is held in the state shown in FIG. 20 by abutting against a mirror stopper (not shown) provided in the camera body 101.

  On the other hand, when the half mirror 111 is moved from the second optical path state (FIG. 20) to the first optical path state (FIG. 19), the force against the biasing force of the torsion spring is released and the biasing force of the torsion spring is released. To rotate the half mirror 111. As a result, the half mirror receiving plate comes into contact with the mirror stopper and is held in the state shown in FIG.

  Next, a shooting sequence in the camera system of the present embodiment will be described with reference to FIG.

  In step S600, the process waits until the main switch 119 is operated (ON state), and the operation proceeds to step S601. In step S601, current is supplied (activated) to various electric circuits in the camera body 101.

  In step S602, the focus correction mode is operated. At the stage where the camera body 101 is activated, the half mirror 111 is in the state shown in FIG. Here, the imaging position on the image sensor 106 of the light beam that has passed through the half mirror 111 may be slightly shifted as compared with the case where it does not pass through the half mirror 111. Therefore, in step S602, the focus detection signal of the focus detection unit 121 is set so that the subject image projected through the half mirror 111 and projected onto the image sensor 106 is sharply formed by operating the focus correction mode. Correct.

  In step S300, EVF calibration is executed, and a correction amount Δx for correcting the focus detection result of the phase difference detection method is calculated based on the focus detection result of the contrast detection method and the focus detection result of the phase difference detection method. . Here, the EVF calibration process is the same as in the first embodiment (FIG. 15).

  In step S603, it is determined whether or not the calibration switch 118 has been operated (turned on). If the calibration switch 118 has been operated, the process proceeds to step S300. If the calibration switch 118 has not been operated, the process proceeds to step S604. Here, in step S300, EVF calibration is executed again.

  Each process from step S604 to step S606 is the same as step S106 to step S108 described in the first embodiment (FIG. 10). Here, the focus adjustment in step S605 is performed based on a result of correcting the focus adjustment result of the phase difference detection method using the correction amount Δx obtained by the EVF calibration in step S300.

  In step S607, the half mirror 111 is moved from the first optical path state (FIG. 19) to the second optical path state (FIG. 20) by driving the mirror driving mechanism. As a result, the subject light from the photographing optical system 103 goes directly to the image sensor 106 side. In step S608, an imaging operation is performed in the same manner as in step S111 of the first embodiment (FIG. 10).

  In step S609, the half mirror 111 is moved from the second optical path state to the first optical path state by driving the mirror driving mechanism. Each process of step S610 to step S612 is the same as each process of step S112 to step S114 described in the first embodiment (FIG. 10).

  According to the camera system of the present embodiment, the same effects as those of the first embodiment can be obtained. That is, by correcting the focus detection result by the phase difference detection method using the correction amount Δx, the accuracy of the focus detection result can be improved. In addition, since the correction amount Δx is calculated every time the camera system is activated, the focus detection result by the phase difference detection method can be corrected using the latest correction amount Δx. Thereby, the focus detection result by the phase difference detection method can be maintained with high accuracy.

  The configuration of a camera that is Embodiment 4 of the present invention will be described with reference to FIG. Here, FIG. 22 is a schematic diagram showing the configuration of the camera of the present embodiment.

  Reference numeral 201 denotes a camera body. Reference numeral 203 denotes a photographing optical system composed of a plurality of lenses (including a zoom lens and a focus lens), and 202 denotes a lens barrel that holds the photographing optical system 203. The lens barrel 202 moves the zoom lens and the focus lens in the optical axis direction by a driving mechanism (not shown). By changing the position of the zoom lens, the shooting angle of view is changed, and the position of the focus lens is changed, whereby the shooting optical system 203 can be brought into focus. The lens barrel 202 is fixed to the camera body 201.

  By configuring the lens barrel 202 and the camera body 201 as one body, the space through which the imaging light beam (subject light) passes can be maintained in a substantially sealed state. Here, if the lens barrel 202 is attached to the camera body 201 in a clean room with little dust and dirt, it is possible to prevent dust and dirt from entering the space through which the imaging light flux passes.

  Reference numeral 204 denotes an image sensor such as a CCD sensor or a CMOS sensor housed in a package. An optical low-pass filter 205 that limits the cutoff frequency of the imaging optical system 203 is provided on the imaging optical system 203 side with respect to the imaging element 204 so that a high-frequency component included in the subject light does not reach the imaging element 204. . The photographing optical system 203 is also formed with an infrared cut filter.

  A captured image obtained from the output of the image sensor 204 is displayed on the display unit 211. The display unit 211 is attached to the back surface of the camera body 201, and the user can directly observe the image displayed on the display unit 211.

  Reference numeral 206 denotes a beam splitter, which is movable between a state located in the photographing optical path and a state retracted from the photographing optical path as indicated by arrows in the drawing. Further, the beam splitter 206 divides the light from the photographing optical system 203 when located in the photographing optical path. The beam splitter 206 is configured by bonding a plurality of prisms, and a dichroic film 207 is deposited on the bonding surface. The dichroic film 207 is configured to transmit the light beam in the visible region and reflect the light beam in the near infrared region.

  The light beam reflected by the dichroic film 207 proceeds to the light incident surface (the surface on which light from the imaging optical system 203 first enters) of the beam splitter 206, but the incident angle with respect to this light incident surface is larger than the critical angle. Furthermore, the light is totally reflected at the light incident surface. Then, the totally reflected light beam exits from the end face (lower side in the figure) of the beam splitter 206 and is guided to the focus detection unit 208. The focus detection unit 208 detects the focus adjustment state of the photographing optical system 203 by a phase difference detection method. The sensor surface (light receiving surface) in the focus detection unit 208 is optically conjugate with the image capturing surface (light receiving surface) of the image sensor 204.

  In the configuration described above, when the beam splitter 206 is positioned in the imaging optical path, the light beam in the visible region passes through the dichroic film 207 and travels toward the image sensor 204. This light beam is used to display a captured image on the display unit 211 and to perform focus detection by a contrast detection method using the image sensor 204. On the other hand, the light beam in the near infrared region is reflected by the light incident surfaces of the dichroic film 207 and the beam splitter 206 and guided to the focus detection unit 208. This light beam is used for focus detection by a phase difference detection method.

  That is, in the first optical path state in which the beam splitter 206 is located in the photographing optical path, focus detection can be performed by the focus detection unit 208 while observing the subject image with the display unit 211. In the first optical path state, high-speed continuous shooting can be performed. In addition, if the signal processing system is speeded up, higher-speed continuous shooting can be performed. On the other hand, in the second state in which the beam splitter 206 is retracted from the photographing optical path, a high-definition photographed image suitable for large prints can be obtained.

  In the present embodiment, when the beam splitter 206 is positioned in the imaging optical path, focus detection of the phase difference detection method is performed using the reflected light of the beam splitter 206, and contrast detection is performed using the reflected light of the beam splitter 206. The focus detection is performed. Here, in the phase difference detection method and the contrast detection method, focus detection can be performed using a light beam from the same subject.

  Therefore, by executing the EVF calibration described in the first embodiment (FIG. 15), the correction amount Δx for correcting the focus detection result by the phase difference detection method can be calculated. Then, by correcting the focus detection result by the phase difference detection method using the correction amount Δx, the accuracy of the focus detection result can be improved. Here, in this embodiment, every time the camera is activated, the correction amount Δx is calculated.

  Next, the principle of focus detection in the focus detection unit 208 will be described. FIG. 23 is a diagram showing the relationship between the configuration of the focus detection unit 208 and the photographic optical system 203. In this figure, in order to make the explanation easy to understand, the photographing optical system 203 and the focus detection unit 208 are arranged on the same axis.

  Reference numeral 220 denotes a pupil of the photographing optical system 203. The light receiving surface of the focus detection unit 208 is disposed on the planned imaging surface of the photographing optical system 203. One pixel of the focus detection unit 208 is composed of two photoelectric conversion elements 209a and 209b. The microlens 210 disposed on the photographing optical system 203 side with respect to the photoelectric conversion elements 209a and 209b receives light beams transmitted through different positions of the pupil 220 of the photographing optical system 203 by the photoelectric conversion elements 209a and 209b. It is configured.

  In FIG. 23, the photoelectric conversion element 209a mainly receives a light beam transmitted through the lower part of the pupil 220 of the photographing optical system 203 in the figure, and the photoelectric conversion element 209b mainly transmits the upper part of the pupil 220 of the photographing optical system 203 in the figure. Receiving the luminous flux. FIG. 24 shows the pupil 220 of the photographing optical system 203 when viewed from the focus detection unit 208 side in the configuration shown in FIG. The light beam received by the photoelectric conversion element 209a passes through the pupil region 221a in the pupil 220, and the light beam received by the photoelectric conversion element 209b passes through a pupil region 221b different from the pupil region 221a.

  At the time of focus detection, the stored signals of the photoelectric conversion elements 209a and 209b are read, and based on the output from each pixel of the focus detection unit 208, an image signal is generated by a light beam that has passed through a different pupil position of the photographing optical system 203. The Then, focus detection is performed based on the relative positional relationship between the image signal based on the light beam that has passed through the pupil region 221a and the image signal based on the light beam that has passed through the pupil region 221b.

  FIG. 25 shows a pixel array of the focus detection unit 208. FIG. 25 is a diagram when the focus detection unit 208 is viewed from the photographing optical system 203 side. One microlens 210 (shown by a dotted line) is disposed on a region corresponding to the pair of photoelectric conversion units 209a and 209b. The pair of photoelectric conversion units 209a and 209b and the microlens 210 constitute one pixel in the focus detection unit 208.

  Here, when focus detection is performed, a pixel column in which a pair of photoelectric conversion units 209a and 209b are arranged is used as a pixel column for focus detection. Then, focus detection is performed by a phase difference detection method based on two image signals obtained from a pair of photoelectric conversion units in a pixel row for focus detection.

  The shooting sequence in the present embodiment is the same as that in the third embodiment (FIG. 21). However, the correction amount in the focus correction mode in step S602 is different. In the third embodiment, the difference between the image formation position on the image sensor 106 of the light beam transmitted through the half mirror 111 and the image formation position on the image sensor 106 of the light beam not transmitted through the half mirror 111 are corrected. It was. On the other hand, in this embodiment, the difference between the imaging position of the light beam that has passed through the beam splitter 206 on the image sensor 204 and the imaging position of the light beam that does not pass through the beam splitter 206 on the image sensor 204 is corrected. I have to. That is, in this embodiment, the focus detection signal of the focus detection unit 208 is corrected so that the subject image that has passed through the beam splitter 206 and is projected onto the image sensor 204 is sharply formed.

  As described above, the light beam for focus detection is a light beam in the near infrared region, and the light beam used for imaging is a light beam in the visible region. Since the refractive index when passing through the beam splitter 206 differs depending on the wavelength, the imaging position on the image sensor 204 and the imaging position on the focus detection unit 208 are not optically conjugate in a strict sense. As a result, even if the subject image is in focus, a slight initial phase difference Δ remains in the detection result of the focus detection unit 208 (see FIG. 9). Therefore, a true phase difference can be obtained by subtracting the initial phase difference Δ from the phase difference obtained by the focus detection unit 208. The initial phase difference Δ can be obtained in advance.

  Also in the camera of the present embodiment, the same effect as that of the camera system of the first embodiment can be obtained. That is, by correcting the focus detection result by the phase difference detection method using the correction amount Δx, the accuracy of the focus detection result can be improved. In addition, by calculating the correction amount Δx each time the camera is activated, the focus detection result by the phase difference detection method can be corrected using the latest correction amount Δx. Thereby, the focus detection result by the phase difference detection method can be maintained with high accuracy.

  In this embodiment, since the beam splitter 206 is merely moved with respect to the imaging optical path, the driving mechanism of the beam splitter 206 can be simplified.

It is the schematic which shows the structure of the camera system which is Example 1 of this invention. 1 is a schematic diagram illustrating a circuit configuration of a camera system according to Embodiment 1. FIG. It is a figure which shows the 2nd optical path state in the camera system of Example 1. FIG. It is a figure which shows the state between the 1st and 2nd optical path state in the camera system of Example 1. FIG. It is a figure which shows the 1st optical path state in the camera system of Example 1. FIG. It is a figure which shows the state between the 1st and 3rd optical path states in the camera system of Example 1. FIG. 6 is a diagram illustrating a third optical path state in the camera system of Embodiment 1. FIG. It is a figure which shows the waveform of the output signal of the sensor for focus detection. It is a figure which shows the waveform of the output signal of the sensor for focus detection. 3 is a flowchart illustrating a photographing operation in the camera system according to the first exemplary embodiment. 6 is a flowchart illustrating a finder mode switching operation according to the first exemplary embodiment. It is a figure showing the relationship between the visual field which can be output to an image display, and the visual field imaged. It is a figure showing the relationship between the visual field which can be output to an image display, and the visual field imaged. 6 is a flowchart illustrating processing in a calibration mode according to the first embodiment. 3 is a flowchart illustrating EVF calibration processing in the first embodiment. It is a figure which shows the relationship between the focus detection result (A) by a contrast detection system, and the focus detection result (B) by a phase difference detection system. It is a figure which shows the structure of the camera system which is Example 2 of this invention. 10 is a flowchart illustrating a finder mode switching operation according to the second exemplary embodiment. It is a figure which shows the structure of the camera system which is Example 3 of this invention. It is a figure which shows the structure of the camera system which is Example 3 of this invention. 10 is a flowchart illustrating a photographing operation in the camera system of Example 3. It is a figure which shows the structure of the camera which is Example 4 of this invention. It is a figure which shows the relationship between an imaging optical system and a focus detection unit. It is a figure which shows the pupil of an imaging optical system. FIG. 10 is a diagram illustrating a configuration of a focus detection unit in Embodiment 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101: Camera main body 102: Lens apparatus 103: Shooting optical system 106: Image pick-up element 111: Half mirror 121: Focus detection unit 122: Sub mirror 135: Camera system control circuit 135a: Memory

Claims (9)

An image sensor that photoelectrically converts a subject image formed by a light beam from a photographing optical system;
First detection means for detecting a focus adjustment state of the photographing optical system by a contrast detection method using an output of the image sensor;
Second detection means for detecting a focus adjustment state of the photographing optical system by a phase difference detection method;
A light splitting means for splitting a light beam from the photographing optical system and guiding it to the image sensor and the second detection means;
An imaging apparatus comprising: a control unit that corrects a detection result of the second detection unit based on a detection result of the first detection unit.   2. The control unit according to claim 1, wherein the control unit calculates a correction value for correcting the detection result of the second detection unit based on the detection results of the first and second detection units. Imaging device. The light splitting means is operable between a state where it is located in the photographing optical path and guides the light beam from the photographing optical system to the imaging device and the second detecting means, and a state where it is retracted from the photographing optical path. And
The imaging apparatus according to claim 2, wherein the control unit calculates the correction value when the light dividing unit is located in the photographing optical path.   The image pickup apparatus according to claim 2, further comprising a storage unit that stores the correction value.   5. The imaging apparatus according to claim 1, wherein the timing of the detection operation by the first detection unit is equal to the timing of the detection operation by the second detection unit. 6. The light splitting means has an optical element that can move forward and backward with respect to the photographing optical path,
When the optical element is located in the photographing optical path, a part of the light flux from the photographing optical system is guided to the second detection unit and another light flux is guided to the imaging element. The imaging apparatus according to any one of claims 1 to 5, wherein A viewfinder optical system for observing a subject using a light beam from the photographing optical system;
The light splitting means has a first state for guiding a light beam from the photographing optical system to the finder optical system and the second detection means, and a light beam from the photographing optical system to the imaging element and the second detection. The imaging apparatus according to claim 1, wherein the imaging apparatus switches between a second state leading to the means. The light splitting means has first and second mirrors movable independently of each other,
When the light splitting means is in the first state, the first mirror reflects a part of the light beam from the photographing optical system to the finder optical system and transmits the other light beam. , The second mirror reflects the light beam transmitted through the first mirror to the second detection means,
When the light splitting means is in the second state, the first mirror reflects the part of the light flux to the second detection means and transmits the other light flux, and the second mirror The imaging apparatus according to claim 7, wherein the imaging apparatus is retracted from the imaging optical path.   When the light splitting means is in the first state, the second mirror reflects a part of the light flux transmitted through the first mirror to the second detection means and The imaging apparatus according to claim 8, wherein a light beam is transmitted and guided to the imaging element.