JP2006215398A - Image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image pickup device of a lens interchangeable type with which focusing control of higher accuracy is made at a higher speed. <P>SOLUTION: The image pickup device has the photographic lens which is interchanged by being attached to and detached from a camera body and enables the focusing control, and an image pickup element which performs photographing by subjecting the subject image formed by the photographic lens to photoelectric conversion. The photographic lens has a memory means which transmits a signal to the camera body, and stores and holds the individual recognition information of the photographic lens together with the correction value on focusing of the photographic lens in the memory means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging apparatus capable of attaching and detaching a photographic lens such as a digital single-lens reflex camera.

In general, as a focus detection device of a digital single-lens reflex camera capable of exchanging lenses, a so-called phase difference detection type focus detection device is mainly used like a conventional single-lens reflex camera for a silver salt film.
In addition, a hybrid system that controls the focus of a photographing lens by combining a so-called contrast detection type focus detection apparatus and a phase difference detection type focus detection apparatus as used in a video camera has been proposed.
Here, the phase difference detection method divides a part of the photographing light beam into two parts, forms images of these two light beams on the line sensor, and detects the shift direction and shift amount of the two images on the line sensor. By doing so, the movement direction and amount of movement of the focus adjustment lens necessary for focusing on the planned focal plane (a plane conjugate with the imaging plane) are calculated. In such a phase difference detection method, since the moving direction and moving amount of the focus adjustment lens necessary for focusing can be directly calculated, focusing can be obtained quickly.
The contrast detection method extracts a high frequency component from a video signal generated based on a signal output from an image sensor for capturing a subject image, and observes the level of the high frequency component at a predetermined sampling interval. Then, the focus adjustment lens is driven in a direction in which the level of the high-frequency component is directed toward the peak, so that the focus is determined when the level of the high-frequency component finally reaches a predetermined peak range. In such a contrast detection method, since focus determination is performed using a video signal obtained based on an output signal from an image sensor that captures a subject image, it is possible to obtain focus on the subject with high accuracy. it can.
Japanese Patent Laid-Open No. 2003-295047 (Patent Document 1) proposes an interchangeable lens type imaging apparatus capable of performing focusing control at higher speed and higher accuracy.
JP 2003-295047 A

However, in a digital single-lens reflex camera capable of exchanging lenses, if only the phase difference detection type focus detection device is used, sufficient focusing accuracy may not be obtained. The main reason is that the light flux of the imaging optical system that forms an image to be observed or photographed is generally different from the light flux captured by the focus detection device.
Further, in a phase difference detection type focus detection apparatus, a focal position or an out-of-focus amount that should be originally determined by the amount of aberration in the longitudinal (optical axis) direction is converted into an image shift related to lateral aberration. Therefore, if there is an aberration in the photographing optical system, a difference may be caused between the two depending on the aberration correction state.
In order to solve such a problem, for example, a focus detection signal D representing an out-of-focus amount is obtained using a correction value C unique to each photographing lens.
DC = D-C (1)
A correction circuit for correcting the image is provided, and the whole or a part of the photographic optical system is driven based on the obtained corrected focus detection signal, and the lens is controlled so that the best imaging position coincides with the imaging surface. Yes.
However, this correction information has a different correction value for each product even for products having the same specifications. When there are a plurality of the same products, since the focus control is performed using the same correction value, accurate focus control becomes difficult.
SUMMARY OF THE INVENTION An object of the present invention is to provide an interchangeable lens type imaging apparatus capable of performing high-speed and high-precision focusing control.

In order to achieve the above object, an imaging apparatus according to a first aspect of the present invention includes a camera body,
A photographic lens capable of being attached to and detached from the camera body and capable of focusing control;
In an imaging device having an imaging element that performs imaging by subjecting a subject image formed by the imaging lens to photoelectric conversion,
The imaging lens has storage means that can be transmitted to the camera body, and stores and stores individual identification information of the photographing lens together with a correction value for focusing the photographing lens in the storage means.
Furthermore, in the imaging apparatus of the second aspect of the invention, the camera body includes a focus detection unit that detects a focused state of the imaging lens by a phase difference detection method using a light beam incident from the imaging lens,
In-focus determination means for determining an in-focus state of the photographic lens by the imaging element;
Correction means for correcting information indicating the in-focus state of the imaging lens detected by the focus detection unit based on information indicating the in-focus state of the imaging lens determined by the in-focus determination unit. And
In the imaging apparatus, information indicating the in-focus state corrected by the correction unit is stored and stored in the storage unit together with individual identification information of the imaging lens.
Furthermore, in the imaging apparatus according to a third aspect of the present invention, the correction unit includes in-focus position information indicating the in-focus state of the photographing lens detected by the focus detection unit, and the in-focus determination unit determines the in-focus position information. In the imaging apparatus, information indicating the in-focus state corrected by the correction unit is obtained based on a difference from in-focus position information indicating an in-focus state of the imaging lens.
Furthermore, in the imaging device of the fourth aspect of the present invention, the storage means H indicates information indicating the in-focus state corrected by the correction means, and indicates the in-focus state of the imaging lens detected by the focus detection means. If the design correction information for correcting the information shown is H ′,
The imaging apparatus stores and holds H + H ′ in the storage unit together with individual identification information of the photographing lens.
Furthermore, in the imaging device of the fifth aspect of the present invention, the correction unit corrects the information indicating the focused state in another state by approximation from the corrected information indicating the focused state measured at least once. It is the said imaging device which calculates | requires.
Furthermore, in the imaging device of the sixth aspect of the present invention, the correction means replaces more reliable data by several measurements.
Furthermore, the imaging device according to a seventh aspect of the present invention is the imaging device, wherein the focus determination unit performs in-focus determination multiple times while driving a focus adjustment lens included in the photographing lens.
Furthermore, an imaging apparatus according to an eighth aspect of the present invention is the imaging apparatus in which a calibration mode for performing an operation for obtaining the correction information can be set.

According to the imaging apparatus of the first aspect of the present invention, the imaging lens has storage means that can transmit to the camera body, and stores the individual identification information of the photographing lens together with a correction value for focusing the photographing lens. In order to store and hold the information in the means, the camera body holds the identification information of the photographing lens, and the focus control information is created using the design correction value suitable for each photographing lens, so that the defocus amount is corrected. Since the correction information can use a value suitable for each individual photographing lens, it is possible to perform focusing control with higher speed and higher accuracy.
Further, by storing the correction information on the camera body side, data transmission between the camera body and the taking lens can be shortened to the minimum, so that faster focusing is possible.
Further, according to the imaging apparatus of the second aspect of the present invention, the camera body includes a focus detection unit that detects a focusing state of the imaging lens by a phase difference detection method using a light beam incident from the imaging lens,
In-focus determination means for determining an in-focus state of the photographic lens by the imaging element;
Correction means for correcting information indicating the in-focus state of the imaging lens detected by the focus detection unit based on information indicating the in-focus state of the imaging lens determined by the in-focus determination unit. And
Information indicating the in-focus state corrected by the correction unit is stored in the storage unit together with the individual identification information of the imaging lens, and thus the detection accuracy is insufficient in the phase difference detection method excellent in high speed. Compared to the hybrid method, etc., by obtaining correction information to compensate for this based on information indicating the in-focus state using contrast detection of a captured image from an image sensor that can perform in-focus determination with high accuracy. Focus control by the phase difference detection method at higher speed and with sufficiently high accuracy is possible.
Further, the focus control information obtained by the correction means is stored and held on the camera body side together with the individual identification information of the photographing lens, thereby reducing the exchange of data between the camera body and the photographing lens, and quick focusing. Control becomes possible.
In this case, the storage means stores correction information in association with the individual identification information that each photographic lens has, and among the correction information stored in the storage means, the individual identification obtained from the attached photographic lens If the focus control information is corrected using the correction information corresponding to the information, it becomes possible to correct the detection result by the focus detection means using the correction information suitable for the optical characteristics unique to each photographing lens, and mounting It is possible to ensure the best level of accuracy regardless of the taking lens used.

  Hereinafter, the present invention will be described with reference to the drawings based on the embodiments.

With reference to FIG. 1, the configuration of a digital single-lens reflex camera according to a first embodiment of the present invention will be described.
A digital single-lens reflex camera according to Embodiment 1 of the present invention, which is an example of an imaging apparatus, includes a photographic lens 1 and a camera body 8 in which the photographic lens 1 can be attached and detached. In the photographing lens 1, a photographing optical system 2 as an objective lens is accommodated. The photographing optical system 2 is composed of one or a plurality of lens groups, and changes the focal length by moving all or a part of the lens group or performs focus adjustment. The focus drive unit 3 is a device that drives a focus adjustment lens (not shown) in the photographing optical system 2 for focus adjustment, and the focus position detector 4 is a device that detects the position of the focus adjustment lens. The storage circuit 6 includes a ROM or the like, and stores individual identification information of the photographing lens 1 and design focus correction information. The lens control circuit 5 is a control circuit including a CPU that controls the entire photographing lens 1.
In the photographing lens 1, a zoom driving unit (not shown) for driving a variable power lens (not shown) in the photographing optical system 2 for zooming, a diaphragm unit (not shown), a variable power lens and a diaphragm position are detected. A detector (not shown) is accommodated. Here, as the focus position detector 4, for example, an electrode for an encoder provided in a lens barrel that rotates or moves to move the focus adjustment lens in the optical axis direction, a detection electrode that contacts this, and the like A signal corresponding to the amount of movement from the position of the focus adjustment lens or the reference position is output. However, the focus position detector 4 is not limited to this, and various detectors such as an optical type and a magnetic type can also be used.

  On the other hand, in the camera body 8, a main mirror 9 that can be moved back and forth with respect to the photographing optical path, a focusing screen 17 on which a subject image is formed by light reflected upward by the main mirror 9 disposed in the photographing optical path, and a focal point A finder optical system including a pentaprism 18 and an eyepiece 19 for inverting the subject image formed on the plate 17 is accommodated. Further, on the back side of the main mirror 9, a sub mirror 10 formed of a half mirror that guides the light beam transmitted through the main mirror 9 downward is provided along with the main mirror 9 so as to be able to advance and retreat with respect to the photographing optical path. Further, in the camera body 8, the focus detection unit 12 to which the light beam reflected by the sub mirror 10 is guided, the camera control circuit 13 that controls all of the camera body 8, and the subject image formed by the photographing optical system 2 are photoelectrically recorded. The image sensor 11 such as a CCD or CMOS to be converted is accommodated. Further, in the camera body 8, the contrast of the photoelectric conversion image (captured image) is detected using the output signal from the image sensor 11, and whether or not the focus adjustment lens in the photographic optical system 2 is at the in-focus position. An in-focus determination unit 16 for calculating the difference between the output from the in-focus determination unit 16 and the output from the focus detection unit 12, and the difference amount calculated by the arithmetic circuit 14 and the lens. A storage circuit 15 such as an EEPROM for storing correction information on the design value transmitted from the side as correction information together with individual identification information of the lens is accommodated. The focus determination unit 16 is the same as that known as a focus detection device that performs automatic focus control of a photographing lens by a so-called contrast detection method. Further, the camera control circuit 13 and the arithmetic circuit 14 constitute correction means that is a component of the first aspect of the present invention. The communication contact 7 is interposed between the photographic lens 1 and the camera body 8, and exchanges various information via the communication contact 7 and the photographic lens 1 from the camera body 8 side with the photographic lens 1 and the camera body 8 attached to each other. Power is supplied to the side. Further, the camera body 8 has a switch (not shown) for setting a calibration mode for calculating and storing the correction information described above.

Next, the configuration of the optical system portion of the focus detection unit 12 shown in FIG. 1 will be described with reference to FIG.
The optical axis 27 passes through the main mirror 9 from the photographing optical system 2 and reaches the image pickup surface 11 a of the image pickup device 11. The paraxial imaging surface 20 is positioned conjugate to the imaging surface 18 of the sub-mirror 10 and includes a reflecting mirror 21 and an infrared cut filter 22. The diaphragm 23 has two openings 23-1 and 23-2, and the secondary imaging system 24 has two openings arranged corresponding to the two openings 23-1 and 23-2 of the diaphragm 23. It has lenses 24-1 and 24-2. Furthermore, it has a reflecting mirror 25 and a photoelectric conversion element (sensor) 26. The photoelectric conversion element 26 includes two area sensors 26-1 and 26-2. Here, the sub mirror 10 has a curvature, and has a convergent power (refractive power) for projecting the two openings 23-1 and 23-2 of the diaphragm 23 near the exit pupil of the photographing optical system 2.
The submirror 10 also serves as a field mask that limits the range of focus detection by depositing a metal film such as aluminum or silver on the surface of the glass substrate so that only a necessary region reflects light. Further, in the other reflecting mirrors 21 and 25, in order to reduce stray light incident on the photoelectric conversion element 26, a metal film such as aluminum or silver is deposited only in a necessary minimum region. In addition, it is preferable to apply a light-absorbing paint or the like to a region that does not function as a reflecting surface of each reflecting mirror.
The diaphragm 23 shown in FIG. 2 viewed from the light incident direction is configured by arranging two horizontally long openings 23-1 and 23-2 in a direction in which the opening width is narrow, as shown in FIG. 3. The lenses 24-1 and 24-2 indicated by dotted lines in the drawing of the secondary imaging system 24 are arranged on the light emission side corresponding to the openings 23-1 and 23-2 of the stop 23.
The photoelectric conversion element 26 shown in FIG. 2 as viewed from the light incident direction is composed of two area sensors 26-1 and 26-2 arranged side by side as shown in FIG. Pixels are arranged in the array.

In the focus detection unit 12 configured as described above and the optical system that guides light to the focus detection unit 12, the light beams 27-1 and 27-2 from the photographing optical system 2 are half mirrors of the main mirror 9 as shown in FIG. 2. After passing through the surface, the light is reflected by the sub-mirror 10 in a direction substantially along the inclination of the main mirror 9, is turned rearward by the reflecting mirror 21, passes through the infrared cut filter 22, and then has two openings of the diaphragm 23. It passes through the sections 23-1, 23-2. The light beams that have passed through the two openings 23-1 and 23-2 of the stop 23 are collected by the lenses 24-1 and 24-2 of the secondary imaging system 24, and can be turned downward by the reflecting mirror 25. As a result, the sensors reach the area sensors 26-1 and 26-2 on the photoelectric conversion element 26, respectively.
The light beams 27-1 and 27-2 shown in FIG. 2 are light beams that form an image at the center of the imaging surface 11 a, but the light beams that are imaged at other positions also pass through the same path to the photoelectric conversion element 26. As a whole, the light quantity distributions of the two areas related to the subject image corresponding to the predetermined two-dimensional area on the image sensor 11 are formed on the area sensors 26-1 and 26-2 of the photoelectric conversion element 26.
The focus detection unit 12 shows the separation direction and the separation amount of the subject image, that is, the amount of light distribution regarding the two subject images obtained as described above according to the detection principle of the phase difference detection method, that is, as shown in FIG. By calculating the relative positional relationship in the vertical direction on the two area sensors 26-1 and 26-2 at each position on the area sensors 26-1 and 26-2, the focus adjustment state of the photographing optical system 2 is calculated. Is detected (hereinafter referred to as focus detection), and the result is output as a defocus amount (defocus amount) D.
In the first embodiment of the present invention, the driving position for obtaining the focus of the focusing lens obtained according to the defocus amount D is a value for obtaining the focus with the highest possible accuracy for each model of the photographing lens 1. In this manner, the lens-side storage circuit 6 stores in advance the correction value in the design of the lens model, and the camera body side uses this to determine the best imaging position and the imaging surface 11a at the time of shooting. Perform correction to match. At this time, since the lens has individual identification information, it is possible to perform more accurate focusing control in consideration of individual differences even in the same model.
However, since the correction value stored in the storage circuit 6 on the lens side does not include individual differences of the focus detection unit 12 even if the same model, the design correction value stored in the storage circuit 6 is not changed. Even if it is used as it is, it is difficult to obtain a truly accurate in-focus state.
Therefore, in the first embodiment of the present invention, the design correction value stored in the storage circuit 6 on the lens side is set to a value for obtaining a focus with higher accuracy reflecting the individual differences (that is, In order to obtain a value for obtaining a focus with higher accuracy as a focus drive position of the lens based on the defocus amount D detected by the focus detection unit 12), first, the focus adjustment unit 3 moves the focus adjustment lens in the optical axis direction. , The contrast of the image signal obtained from the image sensor 11 is detected, and the focus determination unit 16 determines the focus position from this contrast state. A difference amount H between the in-focus position determined (detected) by the in-focus determination unit 16 and the in-focus position calculated using the focus detection unit 12 is calculated by the arithmetic circuit 14, and the difference amount and the lens are calculated. Is stored in the storage circuit 15 on the camera body side as correction information unique to the photographic lens 1 currently mounted. Here, a series of operations for obtaining correction information unique to the photographing lens 1 is referred to as calibration.

Here, the operation of the camera system for performing the calibration will be described with reference to the flowchart shown in FIG.
In Embodiment 1 of the present invention, when a photographic lens 1 is newly attached to the camera body 8 or replaced, the photographer turns on a calibration switch (not shown) provided on the camera body 8 to control the camera. The circuit 13 enters the calibration mode and executes the following flow.
After entering the calibration mode, the calibration operation starts automatically or when the photographer turns on the shutter switch (step 501).
First, lens identification information and lens design correction values are called to the camera side. (Step 502) In this method, all the correction information tables on the lens side are called.
Next, the camera control circuit 13 sends a signal to the lens control circuit 5 to move the focus adjustment lens to a predetermined position through the focus drive unit 3 (step 503).
Next, contrast detection is performed, and the focus determination unit 16 detects the contrast of the image signal obtained from the image sensor 11 (step 504).
Then, the fine movement (wobbling) of the focus adjustment lens in step 503 and the contrast detection in step 504 are repeatedly performed until step 505 reaches the predetermined number N.
The focus determination unit 16 determines the position of the focus adjustment lens from which the image signal having the highest contrast among the N contrast detection results is obtained as the focus position, and sends a signal to the camera control circuit 13. The camera control circuit 13 obtains position information from the focus position detector 4 at that time through the lens control circuit 5, and creates in-focus position information (step 506).
Next, the camera control circuit 13 causes the focus detection unit 12 to perform focus detection by the phase difference detection method, and the detection result at that time, that is, the amount of defocus (defocus amount) in the in-focus direction of the focus adjustment lens. The value converted into the drive amount is added to the position information from the focus position detector 4 to create in-focus position information (step 507).
Subsequently, the camera control circuit 13 calculates the difference between the in-focus position information when the in-focus determination is performed by the in-focus determination unit 16 and the in-focus position information obtained from the detection result by the first focus detection unit 12. A certain in-focus position correction value is calculated by the arithmetic circuit 14. (Step 508)
Then, a design correction value obtained by calling the in-focus position correction value calculated by the arithmetic circuit 14 from the lens side is added and stored together with the lens identification information in the storage circuit 15 (step 509). This completes the calibration.
Here, if there is a time lag between step 506 and step 507, an error may occur due to movement of the subject or the like. Therefore, it is more preferable that step 506 and step 507 are performed simultaneously.

As described above, if calibration is performed using a general subject, errors may occur due to movement of the subject, etc., so a calibration chart is built in the camera, and calibration is performed using this chart. It is also possible to adopt a method for performing calibration or projecting a chart on the screen of a PC by connection with a personal computer and performing calibration using this chart.
Further, if a method of performing calibration using pattern projection using auxiliary light or the like is used, it is possible to perform calibration with higher accuracy.
Furthermore, in the first embodiment of the present invention, the same focus determination unit 16 as that used in a conventional video camera is used as the focus determination unit 16, but a mechanical shutter is used in the camera body 8. If an image sensor that does not allow electronic shuttering is used and focus detection using the conventional contrast detection method cannot be performed, multiple images are captured and the contrast of these images is detected. It may be. Alternatively, a method in which the user determines the in-focus position may be used.
The in-focus position correction value is stored in the storage circuit 15 provided in the camera body 8 as a numerical value including the correction value C in the above formula (1) together with the lens identification information. .
Further, by performing these calibrations several times from the place where the calibration is once completed and sequentially storing higher contrast data in the storage circuit, it is possible to obtain more accurate focus correction information. .
Further, in the calibration operation according to the first embodiment of the present invention, focus detection is performed by the focus detection unit 12 after the creation of the focus position information using the focus determination unit 16, but the focus determination unit 16 is used. By performing focus detection by the focus detection unit 12 before generating focus position information, the range in which the focus adjustment lens is driven in step 503 is limited to the vicinity of the focus position detected by focus detection by the phase difference detection method. And the calibration can be completed more quickly.

Next, the configuration of the storage circuit 15 in the camera body 8 will be described with reference to FIG.
The storage circuit 15 is provided with a plurality of circuits for storing individual lens identification information and lens correction information. Specific examples of the lens individual identification information include a lens serial number. By storing such lens-specific information in the lens and storing it on the camera side, lens-specific design correction values can be used for the above corrections, and more accurate focus correction information can be created. become.
As a correction method, calibration is performed at least once at a certain focal length and a certain object distance, and the obtained correction information is proportionally multiplied to approximately calculate the correction information of other focal lengths. When the difference in focus position between the focus determination unit and the focus detection unit obtained at a certain focal length f1 is Δdef1, the difference Δdef2 at an arbitrary focal length is the FNo. Let F1 and F2 be
Δdef2 = (F2 / F1) Δdef1
... (1)
Can be approximated by The correction information at each focal length obtained from this equation is stored and held in the storage circuit 15 on the camera side in addition to the correction information on the lens design.
In general, the telephoto side is more sensitive than the wide side, so the focal length is set to a proportional constant.
Δdef2 = (f2 / f1) 2Δdef1
... (2)
A method of calculating correction information of an arbitrary focal length by the following equation may be used.
Further, the calibration operation as described above is performed for each model of the photographing lens, and the focus position correction value is stored in the storage circuit 15 or the like for each identification information for identifying the lens model.

Next, with reference to the flowchart of FIG. 7, the operation of the camera when actually taking a picture using the in-focus position correction value calculated and stored in the calibration mode will be described.
Here, it is assumed that the focus position correction value is stored in the storage circuit 15 in the camera body 8 together with the correction value C. When the shutter button of the camera body 8 is operated halfway by the first stroke operation (step 701), the camera control circuit 13 causes the focus detection unit 12 to perform focus detection by the phase difference detection method (step 702).
Next, the camera control circuit 13 uses the focus drive amount of the focus adjustment lens calculated based on the focus detection result (defocus amount) by the focus detection unit 12 and the current focus adjustment lens detected by the focus position detector 4. The focus position information (focus control information) that is the focus target position of the focusing lens is created from the position information of the focus adjustment lens, and the focus position correction value created in the calibration mode for this focus position information Is used for correction (step 703).
Next, the camera control circuit 13 communicates a drive command to the lens control circuit 5 on the basis of the corrected focus position information, and the focus adjustment unit is made to correspond to the corrected focus position information through the focus drive unit 3. Driving is performed until the position is detected by the focus position detector 4, and the focusing operation is completed (step 704).
Thereafter, the shutter button is operated for the second stroke to be fully pressed (step 705), and photographing is performed (step 706).
As described above, in the first embodiment of the present invention, in the calibration mode, the focus detection unit 12 that performs focus detection by the phase difference detection method and the focus determination unit 16 that performs focus determination by the contrast detection method are obtained. The in-focus position difference (correction information) is stored, and the focus control information obtained using the focus detection unit 12 at the time of shooting is corrected by the stored correction information. The focus control can be performed with high accuracy while maintaining the performance.

Next, referring to FIG. 8, the calibration operation in the second embodiment of the present invention will be described.
In Embodiment 2 of the present invention, when a photographing lens 1 is newly attached to the camera body 8 or replaced, the photographer turns on a calibration switch (not shown) provided in the camera body 8. The camera control circuit 13 enters the calibration mode and executes the following flow.
After entering the calibration mode, the calibration operation starts automatically or when the photographer turns on the shutter switch (step 801).
First, lens identification information and lens design correction values are called to the camera side. (Step 802) In this method, some correction information used by each lens is called and held on the camera side. This correction information has a different value for each lens, and when the lens has individual identification information, correction information suitable for each lens can be called.
Next, the camera control circuit 13 sends a signal to the lens control circuit 5 to move the focus adjustment lens to a predetermined position through the focus drive unit 3 (step 803).
Next, contrast detection is performed, and the focus determination unit 16 detects the contrast of the image signal obtained from the image sensor 11 (step 804). Then, the fine movement (wobbling) of the focus adjustment lens in step 803 and the contrast detection in step 804 are repeated until step 805 reaches the predetermined number N.
The focus determination unit 16 determines the position of the focus adjustment lens from which the image signal having the highest contrast among the N contrast detection results is obtained as the focus position, and sends a signal to the camera control circuit 13. The camera control circuit 13 obtains position information from the focus position detector 4 at that time through the lens control circuit 5, and creates in-focus position information (step 806).
Next, the camera control circuit 13 causes the focus detection unit 12 to perform focus detection by the phase difference detection method, and the detection result at that time, that is, the amount of defocus (defocus amount) in the in-focus direction of the focus adjustment lens. The value converted into the drive amount is added to the position information from the focus position detector 4 to create in-focus position information (step 807).
Subsequently, the camera control circuit 13 calculates the difference between the in-focus position information when the in-focus determination is performed by the in-focus determination unit 16 and the in-focus position information obtained from the detection result by the first focus detection unit 12. A certain in-focus position correction value is calculated by the arithmetic circuit 14. (Step 808)
Then, a design correction value obtained by calling the in-focus position correction value calculated by the arithmetic circuit 14 from the lens side is added and stored in the storage circuit 15 together with the lens identification information (step 809). This completes the calibration.
Here, if there is a time lag between step 806 and step 807, an error may occur due to movement of the subject or the like. Therefore, it is more preferable that step 806 and step 807 are performed simultaneously.

As described above, if calibration is performed using a general subject, errors may occur due to movement of the subject, etc., so a calibration chart is built in the camera, and calibration is performed using this chart. It is also possible to adopt a method for performing calibration or projecting a chart on the screen of a PC by connection with a personal computer and performing calibration using this chart.
Further, if a method of performing calibration using pattern projection using auxiliary light or the like is used, it is possible to perform calibration with higher accuracy.
Furthermore, in the second embodiment of the present invention, the same focus determination unit 16 as the focus detection device of the contrast detection method used in the conventional video camera is used, but the camera body 8 has a mechanical shutter. If an image sensor that does not have an electronic shutter can be used and focus detection using the conventional contrast detection method cannot be performed, multiple images are taken and the contrast of these images is detected. You may make it do. Alternatively, a method in which the user determines the in-focus position may be used.
The in-focus position correction value is stored in the storage circuit 15 provided in the camera body 8 as a numerical value including the correction value C in the above formula (1) together with the lens identification information. .
Further, calibration is performed from the position where calibration has been performed once, and data having the highest contrast is sequentially stored in the storage circuit. By repeating this several times, more accurate focus correction information can be obtained.
Furthermore, in the calibration operation of the present embodiment, focus detection is performed by the focus detection unit 12 after the creation of focus position information using the focus determination unit 16, but the focus position using the focus determination unit 16 is used. By performing focus detection by the focus detection unit 12 before creating information, the range in which the focus adjustment lens is driven in step 803 can be limited to the vicinity of the in-focus position detected by focus detection by the phase difference detection method. Calibration can be completed faster.
The actual photographing operation using the focus position correction value created by the calibration is the same as that described in the first embodiment of the present invention.

Next, a calibration operation in the digital single-lens reflex camera system according to the third embodiment of the present invention will be described with reference to the flowchart of FIG.
Since the configuration of the camera system is the same as that of the first embodiment of the present invention, components common to the first embodiment of the present invention will be described with the same reference numerals.
In Embodiment 3 of the present invention, the focus position correction value is automatically calculated without setting the calibration mode.
When calibration starts (step 901), the camera control circuit 13 first calls the lens identification information to the camera side together with the design correction value on the lens side (step 902). At this time, a method of calling all the correction information held by the lens side or a method of calling only a part of the correction information, that is, only the correction information unique to the lens may be used.
Next, the focus detection unit 12 is caused to perform focus detection by the phase difference detection method, and in-focus position information is created as in the first embodiment (step 903).
Next, based on this focus position information, the focus adjustment lens is driven through the lens control circuit 5 and the focus drive unit 3 to perform a focus operation (step 904).
Next, the camera control circuit 13 causes the focus drive unit 3 to move the focus adjustment lens at the position driven in step 903 by a minute amount (step 905).
In this state, the camera control circuit 13 causes the focus determination unit 16 to perform contrast detection (step 906), and after repeating steps 904 and 905 a predetermined N times (step 907), Focus position information is created from the position of the focus adjustment lens (position detected by the focus position detector 4) when an image signal with high contrast is obtained (step 908).
Next, an in-focus position correction value that is a difference between the in-focus position information obtained in step 908 and the in-focus position information obtained in step 904 using the focus detection unit 12 is calculated by the arithmetic circuit 14 ( Step 909).
Then, the calculated focus position correction value is added to the called design correction value and stored in the storage circuit 15 together with the lens identification information (step 910).
The calibration is completed by the above operation.
Here, the timing for starting the calibration is performed in a situation where the photographer does not touch the shutter button, and when the photographer operates the shutter button for the first stroke, the calibration is interrupted, or during actual photographing. Take multiple shots while moving the focus adjustment lens at a shutter speed that is 1/2 or less of the set shutter speed, and image processing that is equivalent to shooting at the set shutter speed is performed after image capture. You may use the method of making it obtain.
In addition, a method may be used in which these operations are performed several times and more accurate focus correction information is stored in the storage circuit.
The actual photographing operation using the focus position correction value created by the calibration is the same as that described in the first embodiment of the present invention.

1 is a configuration diagram of a digital single-lens reflex camera according to a first embodiment of the present invention. FIG. 1 is a diagram illustrating a configuration of a main part of a focus detection unit that constitutes a digital single-lens reflex camera according to Embodiment 1 of the present invention. FIG. FIG. 3 is a plan view of the diaphragm shown in FIG. 2. It is a top view of the photoelectric conversion element shown in FIG. 3 is a flowchart showing an in-focus position calibration operation in the digital single-lens reflex camera of Embodiment 1 of the present invention. 1 is a configuration diagram of a storage circuit in a digital single-lens reflex camera according to Embodiment 1 of the present invention. 6 is a flowchart illustrating the operation of the camera when shooting is performed using the correction value calculated by the in-focus position calibration of the digital single-lens reflex camera of Embodiment 1 of the present invention. It is a flowchart of the focusing position calibration operation | movement in the digital single-lens reflex camera of Example 2 of this invention. It is a flowchart of the focusing position calibration operation | movement in the digital single-lens reflex camera of Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shooting lens 2 Imaging optical system 3 Focus drive unit 4 Focus position detector 5 Lens control circuit 6 Memory circuit 7 Communication contact 8 Camera main body 9 Main mirror 10 Submirror 11 Image sensor 12 Focus detection unit 13 Camera control circuit 14 Arithmetic circuit 15 Storage Circuit 16 In-focus determination unit 17 Focusing plate 18 Pentaprism 19 Eyepiece optical system 20 Paraxial image plane conjugate to imaging surface 18 by sub-mirror 10 Reflector 22 Infrared cut mirror 23 Aperture 24 Secondary imaging system 25 Reflection Mirror 26 Photoelectric conversion element 27 Light beam focused on the center of the imaging surface 11a

Claims (8)

The camera body,
A photographic lens capable of being attached to and detached from the camera body and capable of focusing control;
In an imaging device having an imaging element that performs imaging by subjecting a subject image formed by the imaging lens to photoelectric conversion,
The imaging lens has storage means capable of transmitting to the camera body, and stores and holds individual identification information of the photographing lens in the storage means together with a correction value for focusing the photographing lens. Imaging device. The camera body includes a focus detection unit that detects a focused state of the imaging lens by a phase difference detection method using a light beam incident from the imaging lens;
In-focus determination means for determining an in-focus state of the photographic lens by the imaging element;
Correction means for correcting information indicating the in-focus state of the imaging lens detected by the focus detection unit based on information indicating the in-focus state of the imaging lens determined by the in-focus determination unit. And
The imaging apparatus according to claim 1, wherein information indicating the in-focus state corrected by the correction unit is stored and held in the storage unit together with individual identification information of the imaging lens. The correction means includes in-focus position information indicating the in-focus state of the photographing lens detected by the focus detection means, and in-focus position information indicating the in-focus state of the imaging lens determined by the in-focus determination means. The image pickup apparatus according to claim 1, wherein information indicating the in-focus state corrected by the correction unit is obtained based on a difference between the image pickup unit and the correction unit. The storage means is H for information indicating the focus state corrected by the correction means, and correction information for design for correcting information indicating the focus state of the imaging lens detected by the focus detection means. Is H ',
2. The imaging apparatus according to claim 1, wherein H + H ′ is stored and held in the storage unit together with individual identification information of the photographing lens. The imaging apparatus according to claim 1, wherein the correction unit obtains a correction value of information indicating the in-focus state in another state by approximation from information indicating the corrected in-focus state measured at least once. The imaging apparatus according to claim 1, wherein the correction unit replaces more reliable data by several measurements. The imaging apparatus according to claim 1, wherein the in-focus determination unit performs in-focus / in-focus determination a plurality of times while driving a focus adjustment lens included in the photographing lens. The imaging apparatus according to claim 1, wherein a calibration mode for performing an operation for obtaining the correction information can be set.

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