JP2006251065A - Hybrid af camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hybrid AF camera achieving higher-speed and more accurate focusing operation. <P>SOLUTION: The hybrid AF camera is equipped with a main mirror 4 and a sub mirror 5. The main mirror 4 and the sub mirror 5 are respectively movably constituted so as to be arranged in a photographing optical path on a condition that the mirrors fall down in a photography standby state, and made to retreat to the outside of the photographing optical path on a condition that the mirrors rise up in a photographing state. A focusing position is detected by a range-finding element 8 and an imaging element 7 when the mirrors fall down, and it is detected by the imaging element 7 when the mirrors rise up. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a single-lens reflex camera provided with a so-called hybrid AF having a plurality of in-focus position detecting means.

  In recent years, a subject image formed by a photographing optical system is photoelectrically converted into an electric signal using an image sensor such as a CCD or CMOS, and the image signal obtained thereby is recorded on a recording medium or the like. Digital cameras are widely used. Such a digital camera has a so-called contrast detection type focus detection unit that detects a focus state of a subject image based on a difference (contrast) in the amount of high-frequency components included in an imaging signal acquired by an imaging device.

  In general, an automatic focusing (AF) unit which is an automatic focusing adjustment unit configured to automatically adjust the focusing position of the photographing optical system based on the focus detection result by the focus detection unit is used. It has been put into practical use. This is because it is not necessary to provide a dedicated sensor or an optical system for focus detection, and AF is performed using the image pickup device itself, so that focusing accuracy is high.

  However, such contrast detection AF means (hereinafter referred to as contrast AF) captures image signals at a plurality of locations while driving the imaging optical system little by little in order to detect the contrast peak at the in-focus position. Since the contrast of each part must be compared, it takes time to focus. For this reason, there is a problem that the time lag until photographing increases and a photo opportunity is missed or a moving subject cannot be focused.

  Therefore, for single-lens reflex digital cameras that require continuous shooting performance and moving object tracking performance, phase difference detection AF means (hereinafter referred to as phase difference AF) employed in conventional single-lens reflex type silver salt film cameras are used. ) Is adopted.

  In the phase difference AF, one or more pairs of image detection sensors such as line sensors are arranged on a surface that is substantially equivalent to an imaging surface on which a silver salt film or an imaging device is arranged. Then, the light beams from different parts of the light transmitted through the photographing optical system are guided to different image detection sensors, and the focus of the subject image is based on the inter-image distance (phase difference) between the subject images output from the paired image detection sensors. The state is detected. From the direction and amount of displacement of the subject image on the paired image detection sensors, it is possible to immediately recognize how far the in-focus position is in which direction with respect to the film surface. For this reason, since the in-focus position can be obtained by driving the photographing optical system once, the in-focus time is fast.

  On the other hand, the image pickup element of a digital camera is considerably smaller than the size of a silver salt film, and the density of pixels has been increased, and some of them have millions of pixels. As the density of pixels in the image sensor increases, the pitch between the pixels decreases. For this reason, when a digital camera is configured using an image sensor in which a plurality of pixels are arranged at a higher density than in the past, the permissible circle of confusion is smaller than in the prior art, so that high focusing accuracy is required during AF. The

  In order to realize a highly accurate in-focus state by phase difference AF, it is necessary to increase the resolution of the image detection sensor. For this reason, the size of the image detection sensor must be increased, and the secondary imaging lens for guiding the light fluxes of different parts of the light transmitted through the photographing optical system to different image detection sensors must be increased in size. However, there is a problem that there is a limit to disposing in the camera and that the cost is increased due to the increase in size of the image detection sensor and the secondary imaging lens. Further, there may be a case where the focus position includes an error due to an attachment error of the image detection sensor. Therefore, there is a limit to the focusing accuracy in phase difference AF, and it is becoming impossible to perform AF with focusing accuracy corresponding to the pixel pitch as the number of pixels of the image sensor increases.

  In view of such a problem of focusing time and focusing accuracy, a hybrid AF having both AF methods of contrast AF and phase difference AF has been proposed in conventional digital cameras. For example, in the focusing operation, first, coarse adjustment is performed with phase difference AF, and then fine adjustment is performed with contrast AF (see Patent Document 1), or focus position information obtained with phase difference AF and contrast AF are obtained. A method is disclosed in which correction information is calculated on the basis of the difference from the in-focus position information and a focusing operation is performed by adding correction information after phase difference AF during actual shooting (see Patent Document 2). ing.

Japanese Unexamined Patent Publication No. 7-43605 (page 3, FIG. 6) JP 2003-295047 A (page 5, FIG. 6)

  However, since the hybrid AF described in Patent Document 1 performs the final focusing operation with contrast AF, it is necessary to drive the mechanical mechanism when switching from phase difference AF to contrast AF. After all, there is a problem that it cannot follow a moving subject and cannot focus.

  Further, the hybrid AF described in Patent Document 2 obtains correction information based on the difference between the focus position information of the phase difference AF and the contrast AF by calibration, and adds to the focus position information of the phase difference AF at the time of shooting. ing. However, since the focus position information changes depending on the contrast of the subject or the difference in the light source that illuminates the subject, the correction information may not be correct depending on the shooting situation. This problem can be avoided by performing calibration every time the shooting situation changes, but there are problems such as missing a photo opportunity while performing calibration and troublesome actions themselves.

  Accordingly, an object of the present invention is to provide a hybrid AF camera capable of performing a focusing operation with higher speed and higher accuracy.

  The hybrid AF camera according to the present invention includes a main mirror composed of a half mirror for dividing a photographing optical path into a plurality of optical paths, and an optical path for guiding one of the divided optical paths to an in-focus position determination element and the other to an imaging element. Each of the main mirror and the sub mirror is arranged in the imaging optical path by being mirrored down in the first state, and is mirrored up in the second state. In the first state, the in-focus position is detected by the in-focus position determining element and the image sensor, and in the second state, the in-focus position is detected by the image sensor. It is characterized in that position detection can be performed.

  Further, the hybrid AF camera according to the present invention guides one of the divided optical paths to the focusing position determination element and the other to the imaging element to divide the photographing optical path into a plurality of optical paths. Each of the main mirror and the sub-mirror is arranged in the imaging optical path after being mirrored down in the first state and mirror-up in the second state. Correction information storage that is configured to be movable so as to be retracted out of the imaging optical path, and that stores a difference in focus position information between the imaging elements in the first state and the second state Means for detecting the in-focus position by the imaging device in the first state and performing imaging when performing the mirror up operation of the main mirror and the sub mirror. Based on the correction information stored in the correction information storage means, drives the focus lens and corrects the focus position.

  In the hybrid AF camera of the present invention, the focus position detection by the focus position determination element is a phase difference detection method, and the focus position detection by the imaging element is a contrast detection method.

  In the hybrid AF camera of the present invention, any one of the phase difference detection method when the mirror is down, the contrast detection method when the mirror is up, and the phase difference and contrast detection method when the mirror is down is used as the in-focus position detection. The detection method can be selected.

  In the hybrid AF camera of the present invention, a shutter mechanism that is a light shielding means is provided on the subject side in the optical axis direction of the image sensor in the photographing optical path, and when the in-focus position is detected by the image sensor, the in-focus position is detected. The shutter mechanism is opened before position detection is started.

  In addition, according to the control method of the image pickup apparatus of the present invention, the main mirror composed of a half mirror for dividing the photographing optical path into a plurality of optical paths, and one of the divided optical paths is used as a focusing position determination element and the other as an image pickup element. A sub-mirror composed of a half mirror that divides into an optical path for guiding, and the main mirror and the sub-mirror are each disposed in the imaging optical path after being mirrored down in the first state, and in the second state An image pickup apparatus control method configured to be movable so as to be moved out of the image pickup optical path, wherein the image pickup device includes a combination of the image pickup device in the first state and the second state. The difference between the focal position information is memorized, and in the first state, when the imaging position is detected by the imaging element and the imaging is performed, during the mirror up operation of the main mirror and the sub mirror, Serial based on the stored correction information, and driving the focus lens and corrects the focus position.

  According to the first aspect of the present invention, since the in-focus position can be detected by the image sensor even in the mirror down position, a hybrid AF camera capable of performing a high-speed and high-precision in-focus operation can be realized.

  According to the second aspect of the present invention, the correction information storage means for storing the difference in focus position information by the image pickup device at the mirror up position and the mirror down position is provided. When shooting with the focus position detected by the image sensor at the mirror down position, the focus lens is driven and focused based on the correction information stored in the correction information storage means during the mirror up operation of the main mirror and the sub mirror. Correct the focal position. Thereby, a hybrid AF camera capable of performing a focusing operation with higher accuracy can be realized.

  According to the third aspect of the present invention, the focus position detection by the distance measuring element is performed by the phase difference detection method, and the focus position detection by the image pickup element is performed by the contrast detection method, so that a faster and more accurate focusing operation is performed. It is possible to realize a hybrid AF camera capable of performing the above.

  According to the invention of claim 4, the in-focus position is detected by any one of a phase difference detection method at the mirror down position, a contrast detection method at the mirror up position, and both a phase difference and contrast detection method at the mirror down position. Can be selected, it is possible to realize a hybrid AF camera capable of selecting an optimum in-focus position detection method at the time of shooting.

  According to the fifth aspect of the present invention, when the focus position is detected by the image sensor, the focus position can be detected by the image sensor by opening the shutter mechanism before the focus position detection is started. A simple hybrid AF camera can be realized.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a digital single-lens reflex camera according to the present embodiment.
Reference numeral 1 denotes a camera body, and 2 denotes a mount for making a photographic lens 3 to be described later attachable to and detachable from the camera body 1, and has a mount contact 2a that is an interface unit for communicating various signals and supplying drive power. . Reference numeral 3 denotes an interchangeable photographic lens, which has a focus lens group 3a and a zoom lens group 3b therein. Although each lens group is shown as a single lens for convenience, it is actually composed of a complex combination of lens groups with a large number of lenses.

  Reference numeral 4 denotes a main mirror composed of a half mirror, which can be rotated according to the operating state of the camera. When observing a subject with a viewfinder, the main mirror is obliquely installed in the photographing optical path, and the light beam from the photographing lens 2 is bent. Then, the light is guided to a finder optical system, which will be described later, and retracted from the photographic optical path during exposure to guide the light beam from the photographic lens 3 to the imaging element 7 described later. Reference numeral 5 denotes a sub-mirror that rotates together with the main mirror 4 and is composed of a half mirror. A focus detection device, which will be described later, is formed by bending a light beam that has passed through the main mirror 4 when the main mirror 4 is obliquely installed on the photographing optical path. The light beam is divided into a light beam that is guided to 8 and a light beam that is transmitted and guided to an image sensor 7 described later. Reference numeral 6 denotes a shutter, and 7 denotes an image sensor such as a CCD or a CMOS.

  Reference numeral 8 denotes a focus detection device that outputs a signal for determining the in-focus position, and includes a field lens 8a, reflection mirrors 8b and 8c, a secondary imaging lens 8e, an aperture 8d, and a plurality of CCDs arranged in the vicinity of the imaging surface. Area sensor 8f and the like. The focus detection device 8 is configured to be able to detect the focus by a known phase difference method for 45 regions of the subject.

  Reference numeral 9 denotes a focusing plate disposed on the primary image forming surface of the photographing lens 3, a Fresnel lens (condenser lens) is provided on the incident surface, and a subject image (finder image) is formed on the exit surface. . Reference numeral 10 denotes a finder field frame that forms a finder field area, and 11 is a pentaprism for changing the finder optical path, and corrects the subject image formed on the exit surface of the focusing plate 9 to an erect image. Reference numerals 12 and 13 are eyepieces, and 14 is a pupil for observing the viewfinder. An optical system constituted by the focus plate 9, the pentaprism 11, and the eyepieces 12 and 13 is referred to as a finder optical system. Reference numeral 15 denotes a liquid crystal monitor that displays a photographed image.

  16 is a focus drive motor for driving the focus lens group 3a, 17 is a focus drive member including a drive gear, 18 is a photocoupler, 19 is a pulse plate linked to the focus drive member 17, and 20 is in the photographing lens 3. Reference numeral 21 denotes an aperture driving device including an aperture driving circuit 62 described later.

FIG. 2 is a block diagram showing an electrical configuration built in the digital single-lens reflex camera having the configuration shown in FIG. 1, and the same components as those in FIG.
50 is a microcomputer (central processing unit; hereinafter referred to as MPU) that controls the camera unit and the entire camera, 51 is a memory controller that performs various controls of image data, and 52 is a setting / adjustment for performing various controls. An EEPROM storing data and the like.

  Reference numeral 53 denotes a focus detection circuit that determines the in-focus position, and performs accumulation control and readout control of the area sensor 8f in accordance with a signal from the MPU 50, and outputs pixel information of each ranging point to the MPU 50. The area sensor 8f includes 45 sets of line sensors CCD-01 to CCD-45 corresponding to a plurality of distance measuring points in the finder field frame 10. The MPU 50 performs focus detection by a known phase difference detection method on pixel information of each distance measuring point, and sends the detected focus detection information to a lens control circuit 60 described later to perform lens focus adjustment. A series of operations from the focus detection to the focus adjustment is referred to as an autofocus (hereinafter referred to as AF) operation.

  A motor drive circuit 54 controls a motor M155 that drives the main mirror 4 and a motor M256 that charges the shutter 6 in accordance with a signal from the MPU 50. Reference numeral 57 denotes a shutter driving time. In accordance with a signal from the MPU 50, the magnet MG-158 that travels the front curtain of the shutter 6 and the magnet MG-259 that travels the rear curtain of the shutter 6 are exposed to the image sensor 7 with a predetermined amount of light. To control.

  Reference numeral 60 denotes a lens control circuit, which controls a focus adjustment circuit 61 and a diaphragm drive circuit 62, which will be described later, based on a signal from the MPU 50 via the mount contact 2a. The focus adjustment circuit 61 drives the focus drive motor 16 by a predetermined amount on the basis of the rotation information of the pulse plate 19 detected by the photocoupler 18 and the information of the focus lens drive amount from the lens control circuit 60, and thereby the focus lens. The group 3a is moved to the in-focus position. The aperture driving circuit 62 drives the aperture 20 based on the aperture information from the lens control circuit 60. Reference numeral 63 denotes an operation SW for operating the camera or performing various settings for photographing.

  64 is a CDS (correlated double sampling) / AGC (automatic gain adjustment) circuit that samples and holds the image signal output from the image sensor 7 and automatically adjusts the gain, and 65 converts the analog output of the CDS / AGC circuit 64 into a digital signal. An A / D converter 66 is a TG (timing generation) circuit, which supplies a drive signal to the image sensor 7, a sample hold signal to the CDS / AGC circuit 64, and a sample clock signal to the A / D converter 65. . Here, it is possible for the memory controller 51 to receive the image signal output from the image sensor 7 via the CDS / AGC circuit 64 and the A / D converter 65 and to detect the focus of the subject image by the contrast detection method. .

  67 is an SDRAM for temporarily recording the image digitally converted by the A / D converter 65, and 68 performs Y / C (luminance signal / color difference signal) separation, white balance correction, γ correction, and the like. An image processing circuit 69 is an image compression / decompression circuit that compresses an image according to a format such as JPEG and decompresses the compressed image.

  Reference numeral 70 denotes a D / A converter that converts an image into an analog signal in order to display the image recorded on the SDRAM 67 or the medium 72 on the liquid crystal monitor 15. Reference numeral 71 denotes an I / F (interface) with the medium 72 for recording and storing images. Reference numeral 73 denotes a DC / DC converter that converts the voltage of the power source 74 into a voltage necessary for each circuit.

  FIG. 3 is a viewfinder field diagram of the camera, and a plurality of distance measuring points 201 to 245 are all inside the viewfinder field frame 10, that is, in the field frame, by a superimpose (hereinafter referred to as SI) device (not shown). SI is displayed. 4a represents the shape of the mask provided on the main mirror 4. Of the light beams reaching the main mirror 4, the light beams necessary for AF at a plurality of distance measuring points 201 to 245 are transmitted and unnecessary light beams are transmitted. The light is supplied to the viewfinder by reflecting the light without transmitting it. For the light beam that has passed through the mask 4 a, the light beam reflected by the sub-mirror 5 having a size slightly larger than the mask 4 a is guided to the focus detection device 8, and the transmitted light beam is guided to the image sensor 7.

  Here, since the finder field frame 10 has a size equivalent to the light receiving surface size of the image sensor 7, the same picture (field range) as the image obtained by the image sensor 7 can be confirmed by the finder (so-called finder field ratio). 100%). Therefore, FIG. 3 is a viewfinder view, which is equivalent to representing the size of the mask 4a of the main mirror 4 and the sub mirror 5 with respect to the image sensor 7. That is, the light beam that passes through the main mirror 4 and the sub mirror 5 and reaches the image sensor 7 is in the range of the mask 4 a on the image sensor 7.

Next, the operation of the camera will be described using the following flowchart.
FIG. 4 is a flowchart in the contrast AF mode in the digital single-lens reflex camera having the configuration shown in FIGS.
In S301, the photographer operates an AF mode switch (not shown) to select an AF mode. Here, it is assumed that the contrast AF mode is selected. This contrast AF mode is an accuracy priority mode that prioritizes the focusing accuracy of the subject.
In S302, the photographer presses a release button (not shown) halfway, and SW1 (not shown) is turned on.
In S303, when SW1 is turned on, the motor M155 is energized by the motor drive circuit 54, and the main mirror 4 is raised.

In S304, the shutter drive circuit 57 energizes the magnet MG-158 to open the front curtain of the shutter 6.
In S <b> 305, an image received by the image sensor 7 is read by the memory controller 51 and recorded in the SDRAM 67.

In S <b> 306, the memory controller 51 determines whether or not the focus peak position has been detected from the image recorded in the SDRAM 67 by contrast detection. If detected, the process proceeds to S308, and if not detected, the process proceeds to S307. In order to detect the focus peak position, at least three images corresponding to the three stop positions of the focus lens group 3a are required, so the routine from S305 to S307 is performed three times or more. Actually, when the in-focus position is not known at all, it is necessary to read the image and detect the peak position while driving the focus lens group 3a little by little from the infinite end or the closest end to the opposite side. For this reason, the peak position is rarely detected by three readings, and is often read many times.
In S307, the focus adjustment circuit 61 drives the focus lens group 3a by a predetermined amount, and the process returns to S306.

  In S308, the defocus amounts of the distance measuring points 201 to 245 are calculated based on the detected focus peak position, the focal length of the photographing lens 3, and the optical data such as the sensitivity of the focus lens group 3a. Then, the focus adjustment circuit 61 drives the focus lens group 3a to the in-focus position according to the defocus amount of the distance measuring point that measures the position determined as the main subject. There are various ways to determine the main subject, such as the subject closest to the camera or far away from the total defocus amount, or the subject located at the average value of all defocus amounts. It is done. If the photographer has previously selected a desired distance measuring point from the plurality of distance measuring points 201 to 245, it follows the defocus amount of the selected distance measuring point.

In S309, the luminance of the main subject and the entire shooting angle of view is calculated from the image received by the image sensor 7, and the MPU 50 determines the exposure value from the result.
In S310, when the photographer fully presses a release button (not shown) to turn on SW2 (not shown), the MPU 50 determines that the photographer accepts the current in-focus state and the photometric value.
In S 311, the diaphragm 20 is driven by the diaphragm driving circuit 62. The aperture value of the aperture 20 is determined from the exposure value determined in S309.

In S312, the shutter drive circuit 57 energizes the magnet MG-259 to close the rear curtain of the shutter 6.
In S313, an image received by the image sensor 7 immediately before closing the shutter 6 in S312 is recorded on the medium 72. At this time, the time for the image sensor 7 to capture an image is the shutter time determined from the exposure value determined in S309.
In S314, the motor drive circuit 54 energizes the motor M155 to perform mirror down.
In S315, the motor drive circuit 54 energizes the motor M256 to charge the shutter 6 to prepare for the next shooting.

  As described above, since the contrast AF mode requires time for AF, it is not suitable for shooting where continuous shooting performance or moving object tracking performance is required. However, since the imaging element 7 itself performs AF, the focusing accuracy is high. As a result, it is possible to perform shooting with priority on accuracy, such as landscapes and macro shooting that require in-focus accuracy.

  Although the explanation is omitted in the flowchart of FIG. 4, the main mirror 4 is raised during the photographing operation, and the optical path to the viewfinder is blocked. For this reason, by displaying the image received by the image sensor 7 on the liquid crystal monitor 15 in real time, the photographer can check the shooting angle of view.

FIG. 5 is a flowchart in the hybrid AF mode in the digital single-lens reflex camera having the configuration shown in FIGS.
In S321, the photographer operates an AF mode switch (not shown) to select the AF mode. Here, it is assumed that the hybrid AF mode is selected. This hybrid AF mode is a speed priority mode in which priority is given to shortening the release time lag.
In S322, the photographer presses a release button (not shown) halfway, and SW1 (not shown) is turned on.
In S323, the shutter drive circuit 57 energizes the magnet MG-158 to open the front curtain of the shutter 6.

In S324, when the MPU 50 detects that the SW1 is turned on, the MPU 50 causes the line sensors CCD-01 to CCD-45 to perform accumulation operation, calculates the correlation amount from the data, and calculates the correlation amount and the focal length of the photographing lens 3. Based on optical data such as the sensitivity of the focus lens group 3a, the defocus amounts (image shift amounts) of the distance measuring points 201 to 245 are calculated.
In S325, the focus lens group 3a is selected by the focus adjustment circuit 61 according to the defocus amount of the distance measuring point that is measuring the position determined as the main subject from the calculated defocus amounts of the distance measuring points 201 to 245. Drive is started with the focus position + α as a target. The method of determining the main subject is the same as in the contrast AF mode described above.
In S326, when the focus lens group 3a reaches a predetermined position, the image received by the image sensor 7 is read by the memory controller 51 and recorded in the SDRAM 67.

  In S327, the memory controller 51 determines whether or not the in-focus peak position has been detected from the image recorded in the SDRAM 67 by contrast detection. If detected, the process proceeds to S328, and if not detected, the process returns to S324. In order to detect the in-focus peak position, three images corresponding to the three stop positions of the focus lens group 3a are required. Therefore, the routine from S325 to S327 is performed three times.

  This will be described in detail. The timing at which the image is read in S326 is the timing at which the focus lens group 3a is in three positions of the focus position -α, the focus position, and the focus position + α. The vicinity of the in-focus position calculated by the phase difference AF is detected again in detail by the contrast AF. If the peak position cannot be detected, the process returns to S324 and the phase difference AF is performed. For example, when the subject is a moving object, the position can be detected by the phase difference AF even if the distance to the subject suddenly changes. Accordingly, the peak position can always be detected at three positions of the in-focus position and the in-focus position ± α, so that lens driving and image reading can be performed in the shortest without waste. Here, α is automatically set by the camera so that the in-focus position ± α is within the allowable depth of field with respect to the in-focus position based on the focal length of the photographing lens 3, FNo, the distance to the subject, and the like. Various methods such as setting the depth of field desired by the photographer can be considered.

In S328, the photometric circuit (not shown) measures the luminance of the main subject and the entire shooting angle of view determined from the focusing result using a photometric sensor (not shown), and the MPU 50 determines the exposure value based on the result.
In S329, when the photographer fully presses a release button (not shown) to turn on SW2 (not shown), the MPU 50 determines that the photographer accepts the current focus state and photometric value.
In S330, when SW2 is turned on, the motor M155 is energized by the motor drive circuit 54, and the main mirror 4 is raised.

  In S331, the contrast AF in S327 is performed with the light beam transmitted through the main mirror 4 and the sub mirror 5 because the mirror is in the mirror-down state. More precisely, since the in-focus position is shifted, a correction value for correcting the shift is read from the EEPROM 52, and the defocus amount is calculated. Here, the correction value varies depending on the incident angle of the light beam, so that the transmission distance through each mirror changes. Therefore, a correction value table corresponding to the shooting state is provided in the EEPROM 52 so that the correction value is an optimum correction value depending on the focal length, FNo, the selected distance measuring point, etc. Various methods are conceivable, such as storing the in-focus position difference during mirror up and mirror down in the EEPROM 52 according to the state (so-called calibration).

In S332, the focus lens group 3a is driven according to the defocus amount calculated in S331.
In step S <b> 333, the diaphragm drive circuit 62 drives the diaphragm 20. The aperture value of the aperture 20 is determined from the exposure value determined in S328. Actually, the sequence from S331 to S333 is simultaneously driven while the main mirror 4 is raised in S330.

In S334, the magnet MG-259 is energized by the shutter drive circuit 57, and the rear curtain of the shutter 6 is closed.
In S335, an image received by the image sensor 7 immediately before closing the shutter 6 in S334 is recorded on the medium 72. At this time, the time for the image sensor 7 to capture an image is the shutter time determined from the exposure value determined in S328.
In S336, the motor drive circuit 54 energizes the motor M155 to perform mirror down.
In S337, the motor M256 is energized by the motor drive circuit 54 to charge the shutter 6 to prepare for the next shooting.

  As described above, in the hybrid AF mode, the basic focus position detection is performed by the phase difference AF, and the AF state is shortened by performing contrast AF only in the vicinity of the focus position without changing the camera state. Improves focus accuracy. Further, the focus position shift caused by performing contrast AF with the transmitted light of each mirror is corrected without increasing the AF time by driving the focus lens group 3a during the up operation of the main mirror 4. As a result, speed-priority shooting that requires continuous shooting performance and moving object tracking performance is possible.

  Although the description is omitted in the flowchart of FIG. 5, it is possible to display an image received by the image sensor 7 on the liquid crystal monitor 15 in real time as in the contrast AF mode and take a picture while checking the subject. . Further, since the main mirror 4 is in a down state except when it is actually photographed, it is also possible to photograph while confirming the subject with the finder as in a normal single-lens reflex camera.

  In the present embodiment, AF can be performed in the entire area of the image sensor 7 in the contrast AF mode. However, in the hybrid AF mode, AF can be performed only in the area 4a on the image sensor 7 as shown in FIG. Even in the hybrid AF mode, it is possible to eliminate the mask 4a of the main mirror 4 in order to perform AF in the entire area of the image sensor 7. However, in that case, there is a problem that the amount of light to the viewfinder decreases. In addition, since the size of the sub mirror 5 is smaller than that of the main mirror 4, the light beam received by the imaging device 7 depending on the image height and the incident angle of the light beam is transmitted only through the main mirror 4, and the main mirror 4 and the sub mirror 5. There is a case in which both of them are transmitted, and the setting of the correction value becomes complicated.

  In the present embodiment, the two focus position detection modes of the contrast AF mode in FIG. 4 and the hybrid AF mode in FIG. 5 can be selected, but the phase difference AF mode by the focus detection device 8 at the mirror down position can also be selected. There is no problem.

  As described above, according to the present embodiment, the focus position can be detected by the image sensor 7 even in the mirror down position. Further, by providing an EEPROM 52 (correction information storage means) that stores a difference in focus position information by the image sensor 7 at the mirror-up position and the mirror-down position, high-precision focus by the image sensor 7 also at the mirror-down position. Position detection can be realized.

  Further, basic focus position detection is performed in advance by a phase difference detection method using the focus detection device 8 (ranging element), and subsequently focus position detection is performed using a contrast detection method using the image sensor 7 at the mirror down position. During the mirror up operation, the focus lens group 3a is driven and the focus position is corrected based on the correction information stored in the EEPROM 52, so that the focus operation can be performed at higher speed and with higher accuracy. A simple hybrid AF camera can be realized.

In addition, by selecting one of the phase difference AF mode at the mirror-down position, the contrast AF mode at the mirror-up position, and the hybrid AF mode at the mirror-down position, the optimum focus position detection mode can be selected during shooting. A possible hybrid AF camera can be realized.
Note that contrast AF can also be realized in a digital single-lens reflex camera by opening the shutter 6 before the focus position detection by the image sensor 7 is started.

It is a schematic sectional drawing of the digital single-lens reflex camera which concerns on embodiment of this invention. It is a block diagram which shows the electrical structure incorporated in the digital single-lens reflex camera which concerns on embodiment of this invention. It is a figure which shows the finder visual field of the digital single-lens reflex camera which concerns on embodiment of this invention. 6 is a flowchart in the contrast AF mode of the digital single-lens reflex camera according to the embodiment of the present invention. 6 is a flowchart in the hybrid AF mode of the digital single-lens reflex camera according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camera body, 3 Shooting lens, 3a Focus lens group, 3b Zoom lens group, 4 Main mirror, 5 Sub mirror, 6 Shutter, 7 Image sensor, 8 Focus detection apparatus, 9 Focus plate, 10 Viewfinder field frame, 11 Penta prism, 12, 13 eyepiece, 14 observation pupil, 15 liquid crystal monitor, 16 focus drive motor, 17 focus drive member, 18 photocoupler, 19 pulse plate, 20 aperture, 21 aperture drive, 50 microcomputer (MPU), 51 memory Controller, 52 EEPROM, 53 Focus detection circuit, 54 Motor drive circuit, 57 Shutter drive cycle, 60 Lens control circuit, 61 Focus adjustment circuit, 62 Aperture drive circuit, 63 Operation SW, 64 CDS / AGC circuit, 65 A / D conversion , 66 TG Timing generator) circuit, 67 SDRAM, 68 image processing circuit, 69 an image compression / decompression circuit, 70 D / A converter, 71 I / F (interface), 73 DC / DC converter.

Claims (6)

Consists of a main mirror composed of a half mirror to divide the imaging optical path into a plurality of optical paths, and a half mirror that divides one of the divided optical paths into an in-focus position determination element and an optical path for guiding the other to the image sensor. With a sub-mirror,
Each of the main mirror and the sub mirror is configured to be movable so as to be mirrored down in the first state and disposed in the imaging optical path, and mirrored up in the second state and retracted out of the imaging optical path.
In the first state, the in-focus position is detected by the in-focus position determining element and the imaging element, and in the second state, the in-focus position can be detected by the imaging element. AF camera. Consists of a main mirror composed of a half mirror to divide the imaging optical path into a plurality of optical paths, and a half mirror that divides one of the divided optical paths into an in-focus position determination element and an optical path for guiding the other to the image sensor. With a sub-mirror,
Each of the main mirror and the sub mirror is configured to be movable so as to be mirrored down in the first state and disposed in the imaging optical path, and mirrored up in the second state and retracted out of the imaging optical path.
Correction information storage means for storing a difference in in-focus position information by each of the imaging elements in the first state and the second state;
In the first state, when the imaging element detects the focus position and performs imaging, the correction information stored in the correction information storage means during the mirror up operation of the main mirror and the sub mirror is used. Then, a hybrid AF camera that corrects the in-focus position by driving a focus lens.   3. The hybrid AF camera according to claim 1, wherein in-focus position detection by the in-focus position determination element is a phase difference detection system, and in-focus position detection by the imaging element is a contrast detection system.   As a focus position detection, it is possible to select any one of a phase difference detection method when the mirror is down, a contrast detection method when the mirror is up, and a phase difference and contrast detection method when the mirror is down. The hybrid AF camera according to claim 1, wherein the hybrid AF camera is characterized in that:   In the photographing optical path, a shutter mechanism that is a light shielding unit is provided on the subject side in the optical axis direction of the image sensor, and when the focus position is detected by the image sensor, the shutter is detected before the focus position detection is started. The hybrid AF camera according to claim 1, wherein the mechanism is in an open state. Consists of a main mirror composed of a half mirror to divide the imaging optical path into a plurality of optical paths, and a half mirror that divides one of the divided optical paths into an in-focus position determination element and an optical path for guiding the other to the image sensor. The main mirror and the sub mirror are arranged in the imaging optical path by being mirrored down in the first state, and are raised in the second state and retracted out of the imaging optical path, respectively. A control method for an imaging apparatus configured to be movable,
Storing in-focus position information difference between the respective image sensors in the first state and the second state;
In the first state, when the imaging element detects the focus position and takes an image, the focus lens is adjusted based on the stored correction information during the mirror up operation of the main mirror and the sub mirror. A control method comprising driving and correcting a focus position.

Images