JP4541808B2 - Imaging apparatus and imaging system - Google Patents

Description

  The present invention relates to an image pickup apparatus in which a taking lens can be attached and detached, for example, a digital single lens reflex camera.

In a digital single-lens reflex camera with interchangeable lenses, photometry is performed via a focusing screen 17 and a pentaprism 18 by a photometric unit 20 shown in FIG. 8, as in a conventional single-lens reflex camera for a silver salt film . It has been broken .

However, in a digital single-lens reflex camera with interchangeable lenses, the photometric means is disposed above the pentaprism 18 and away from the optical axis of the photographic lens 1 as shown in FIG. The photometry is performed using a light beam different from the light beam reaching the beam 11. For this reason, appropriate exposure may not be obtained.

  An object of the present invention is to provide an imaging device capable of optimal exposure setting.

In order to achieve the above object, according to the present invention, there is provided an imaging device having an imaging element that can attach and detach a photographic lens, receives a subject image formed by the photographic lens, and photoelectrically converts the subject image. Each time the photometric lens is replaced , and the exposure amount detection means for detecting the exposure amount received by the image sensor, and each time the photographic lens is replaced, each time a plurality of shootings are performed with different exposure values. The exposure value is detected using the exposure amount detection means , and the exposure value obtained by using the photometry means is corrected from the exposure value for the optimum exposure amount of the exposure amount detected for each photographing. And means for obtaining correction information for the purpose.

According to the present invention, each time a photographic lens is replaced, a plurality of times of shooting with different exposure values are detected, and an exposure amount is detected using the exposure amount detection means for each of the shoots. Correction information for correcting the exposure value obtained by using the photometry means is obtained from the exposure value corresponding to the exposure value that is the optimum exposure among the exposure values. Accordingly, Ki out to determine the correction information corresponding to the imaging lens to be mounted, to each imaging lens, it is possible to optimum exposure settings using the photometric means.

  First, the prerequisite technology of the present invention will be described.

  FIG. 1 shows the configuration of a digital single-lens reflex camera system, which is the first prerequisite technology of the present invention. This camera system includes a photographic lens 1 and a digital single-lens reflex camera (imaging device: hereinafter referred to as a camera body) 8 in which the photographic lens 1 can be attached and detached.

In FIG. 1, a photographing lens 1 houses a photographing optical system 2 as an objective lens. The photographic optical system 2 is composed of one or a plurality of lens groups, and the focal length can be changed or the focus can be adjusted by moving all or a part of them.

Reference numeral 3 denotes a focus drive unit that drives the focus adjustment lens (2a) in the photographing optical system 2 for focus adjustment, and reference numeral 4 denotes a focus position detector 4 for detecting the position of the focus adjustment lens 2a.

Reference numeral 6 denotes a storage circuit including a ROM and the like. Reference numeral 5 denotes a CPU that controls the entire photographing lens 1.
This is a lens control circuit 5 made up of and the like.

Although not shown in the drawing, in the taking lens 1, a zoom drive unit and a diaphragm unit (not shown) for driving a zoom lens (not shown) in the taking optical system 2 for zooming,
A zoom lens and a detector for detecting the aperture position are accommodated.

Here, as the focus position detector 4, for example, an encoder electrode provided on a lens barrel that rotates or moves to move the focus adjustment lens 2 a in the optical axis direction, and a detection electrode that contacts the encoder electrode Are used to output signals corresponding to the amount of movement from the position or reference position of the focus adjustment lens 2a. However, the focus position detector 4 is not limited to this, and various detectors such as an optical type and a magnetic type can 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, and 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,
A pentaprism 18 and an eyepiece 19 for inverting the subject image formed on the focusing screen 17
And a finder optical system consisting of

Further, on the back side of the main mirror 9, a sub mirror 10 that guides the light beam transmitted through the half mirror portion of the main mirror 9 downward is provided along with the main mirror 9 so as 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. An image sensor 11 such as a CCD or CMOS sensor 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 2 a in the photographic optical system 2 is at the in-focus position. A focus determination unit 16 for determining whether or not, an arithmetic circuit 14 for calculating a difference between an output from the focus determination unit 16 and an output from the focus detection unit 12, and a difference amount calculated by the arithmetic circuit 14 Memory circuit 1 such as an EEPROM for storing correction information
5 are 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 as defined in the claims.

Reference numeral 7 denotes a communication contact provided in the photographic lens 1 and the camera body 8, and exchanges various information and supplies power from the camera body 8 side to the photographic lens 1 side through the communication contact 7 while being attached to each other. Is called. The camera body 8 also has a switch (not shown) for setting a calibration mode for calculating and storing the correction information described above.

FIG. 2 shows the configuration of the optical system portion of the focus detection unit 12 shown in FIG. In the figure, reference numeral 27 denotes a light beam on the optical axis of the photographic optical system 2, and the main mirror 9 extends from the photographic optical system 2.
And reaches the imaging surface 11a of the imaging device 11. Reference numeral 21 denotes an imaging surface 18 by the sub-mirror 10.
, A paraxial image plane 22, 22 is a reflecting mirror. Reference numeral 23 denotes an infrared cut filter.

A diaphragm 24 has two openings 24-1 and 24-2. A secondary imaging optical system 25 has two lenses 25-1 and 25-2 arranged corresponding to the two openings 24-1 and 24-2 of the stop 24. Reference numeral 36 denotes a reflecting mirror, and 26 denotes a photoelectric conversion element (sensor). The photoelectric conversion element 26 includes two area sensors 26-1 and 26-2.
have.

Here, the sub mirror 10 has a curvature, and the two openings 24-1 and 24-2 of the diaphragm 24.
Has a convergent power (refractive power: reciprocal of focal length) to project near the exit pupil of the photographing optical system 2.

Also. The sub-mirror 10 has a metal film such as aluminum or silver deposited on the surface of the glass substrate so that only a necessary region reflects light, and also serves as a field mask that limits the focus detection range. .

Further, in the other reflecting mirrors 22 and 36, in order to reduce the stray light incident on the photoelectric conversion element 26, a metal film such as aluminum or silver is deposited only in the minimum necessary region.
Note that a light-absorbing paint or the like is preferably applied to a region that does not function as a reflecting surface of each reflecting mirror.

FIG. 3 is a view of the diaphragm 24 shown in FIG. 2 as viewed from the light incident direction. The diaphragm 24 has a configuration in which two horizontally long openings 24-1 and 24-2 are arranged in a direction in which the opening width is narrow. The dotted lines in the figure indicate the lenses 25-1, 25-2 of the secondary imaging system 25 disposed on the light exit side corresponding to the openings 24-1, 24-2 of the stop 24, respectively. 25-2.

FIG. 4 is a view of the photoelectric conversion element 26 shown in FIG. 2 as viewed from the light incident direction. Each of the two area sensors 26-1 and 26-2 is a sensor in which pixels are two-dimensionally arranged as shown in the drawing, and two area sensors 26-1 and 26-2 are arranged side by side.

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 mirror surfaces of the main mirror 19 as shown in FIG. 2. , And is reflected by the sub mirror 10 in a direction substantially along the inclination of the main mirror 19, is turned rearward by the reflecting mirror 22, and then passes through the infrared cut filter 23 to each of the two apertures of the diaphragm 24. It passes through the sections 24-1 and 24-2.

The light beams that have passed through the two openings 24-1 and 24-2 of the diaphragm 24 are collected by the lenses 25-1 and 25-2 of the secondary imaging system 25 and directed downward by the reflecting mirror 36, respectively. To reach the area sensors 26-1 and 26-2 on the photoelectric conversion element 26, respectively.

The light beams 27-1 and 27-2 in FIG. 2 are light beams that form an image at the center of the imaging surface 11a.
A light beam that forms an image at another position also reaches the photoelectric conversion element 26 through a similar path, and the light intensity distributions of the two areas related to the subject image corresponding to a predetermined two-dimensional area on the image sensor 11 as a whole are photoelectrically converted. It is formed on each area sensor 26-1, 26-2 of the element 26.

The focus detection unit 12 uses the phase difference detection method for the light quantity distributions related to the two subject images obtained as described above in accordance with the detection principle of the phase difference detection method, that is, the two shown in FIG. By detecting the relative positional relationship in the vertical direction on the 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 detected. (Hereinafter referred to as focus detection) is performed, and the result is output as a defocus amount (defocus amount) D.

  In the first prerequisite technology, the driving position for obtaining the focus of the focus adjustment 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. The lens-side storage circuit 6 stores in advance the design correction value of the lens model, and the camera body side uses this to use the best imaging position and the imaging surface 11a at the time of shooting. Perform correction to match.

However, since the correction value stored in the storage circuit 6 on the lens side does not include the individual difference for each photographing lens or the individual difference of the focus detection unit 12 even for the same model, it is stored in the storage circuit 6. Even if the designed correction value is used as it is, it is difficult to obtain a truly accurate in-focus state.

  Therefore, in the first prerequisite technology, 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 the focus drive position of the lens based on the defocus amount D detected by the focus detection unit 12), first, the focus adjustment lens 2 a is moved in the optical axis direction by the focus drive unit 3. , 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.

Then, the arithmetic circuit 14 calculates the difference amount 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, and this difference amount is actually mounted. The information is stored in the storage circuit 15 on the camera body side as correction information unique to the taking lens 1 that has been used. 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 performing the calibration will be described with reference to the flowchart shown in FIG. In the first prerequisite technology, when the photographic lens 1 is newly attached to or replaced with the camera body 8, 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 501).

First, the camera control circuit 13 sends a signal to the lens control circuit 5 to move the focus adjustment lens 2a to a predetermined position through the focus drive unit 3 (step 502). next,
The focus determination unit 16 is made to detect the contrast of the image signal obtained from the image sensor 11 (step 503). Then, the minute movement (wobbling) of the focus adjustment lens 2a in step 502 and contrast detection in step 503 are repeatedly performed until step 503 reaches the predetermined number N (step 503a).

The focus determination unit 16 determines the position of the focus adjustment lens 2a from which the image signal with 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 504).

Subsequently, the camera control circuit 13 causes the focus detection unit 12 to perform focus detection by the phase difference detection method, and a detection result at that time, that is, an out-of-focus amount (defocus amount) in the in-focus direction of the focus adjustment lens 2a. The value converted into the driving amount is added to the position information from the focus position detector 4 to create in-focus position information (step 505).

The camera control circuit 13 is a focus that is a difference between the focus position information obtained when the focus is determined by the focus determination unit 16 and the focus position information obtained from the detection result of the first focus detection unit 12. The position correction value is calculated by the arithmetic circuit 14 (step 506).

Then, the focus position correction value calculated by the arithmetic circuit 14 is stored in the storage circuit 15 (step 507). This completes the calibration.

Here, if there is a time lag between step 504 and step 505, an error may occur due to movement of the subject or the like. Therefore, it is more desirable that step 504 and step 505 be performed substantially simultaneously.

Also, if you try to calibrate using a general subject as described above,
Since errors may occur due to movement of the subject etc., a calibration chart is built in the camera, calibration using this chart,
A method of projecting a chart on a PC screen by connecting to a personal computer and performing calibration using this chart may be adopted.

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.

  In the first prerequisite technique, the focus determination unit 16 is the same as the focus detection device of the contrast detection type used in the conventional video camera, but the camera body 8 is provided with a mechanical shutter. If you are using an image sensor that is not capable of electronic shuttering and you cannot perform focus detection using the conventional contrast detection method, take multiple images and detect the contrast of these images. It may be.

Regarding the storage of the focus position correction value, only the focus position correction value may be stored in the storage circuit 14 provided in the camera body 8, or the correction value C in the above formula (1).
You may memorize | store as a numerical value containing the value of.

Further, the in-focus position correction value may be stored by rewriting the correction value C in the storage circuit 6 provided in the photographing lens 1, or may be stored as a correction value different from the correction value C. Also good.

Further, if the calibration operation as described above is performed for each subject distance and the in-focus position correction value is stored in the storage circuit 14 or the like in association with each subject distance, a high-precision alignment is possible regardless of the subject distance. Focus control can be performed.

Further, the calibration operation as described above may be performed for each model of the photographing lens, and the focus position correction value may be stored in the storage circuit 14 or the like for each identification information for identifying the lens model.

  Furthermore, in the calibration operation of the first prerequisite technology, focus detection is performed by the focus detection unit 12 after the focus position information is generated using the focus determination unit 16, but the focus detection using the focus determination unit 16 is performed. By performing focus detection by the focus detection unit 12 before generating the focus position information, the range in which the focus adjustment lens 2a is driven in step 502 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 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 with reference to the flowchart of FIG.

Here, the focus position correction value is stored in the storage circuit 15 in the camera body 8 separately from the correction value C.
It is assumed that it is stored in

When the shutter button of the camera body 8 is operated halfway by the first stroke operation (step 601), the camera control circuit 13 causes the focus detection unit 12 to perform focus detection by the phase difference detection method (step 602).

Next, the camera control circuit 13 detects the focus drive amount of the focus adjustment lens 2 a calculated based on the focus detection result (defocus amount) by the focus detection unit 12 and the current focus adjustment detected by the focus position detector 4. From the position information of the lens 2a, focus position information (focus control information) that becomes a focus target position of the focus adjustment lens 2a is created. Correction is performed using the correction value C and the in-focus position correction value created in the calibration mode (step 603).

Next, the camera control circuit 13 determines the lens control circuit 5 based on the corrected focus position information.
The drive command is communicated to. The lens control circuit 5 drives the focus adjustment lens through the focus drive unit 3 until the position corresponding to the corrected focus position information is detected by the focus position detector 4 to complete the focus operation (step 604). ).

Thereafter, the shutter button is operated for the second stroke to be fully pressed (step 605), and photographing is performed (step 606).

  As described above, in the first base technology, in the calibration mode, the focus detection unit 12 that performs focus detection using the phase difference detection method and the focus determination unit 16 that performs focus determination using the contrast detection method are obtained. Since the focus position difference (correction information) is stored, and the focus control information obtained by using the focus detection unit 12 at the time of shooting is corrected by the stored correction information, high-speed performance by the phase difference detection method is achieved. While maintaining the above, it is possible to perform focusing control with high accuracy.

Further, as described above, the in-focus position correction value is stored in the storage circuit 15 in the camera body 8 as a numerical value including the correction value C, so that the correction value C is obtained between the photographing lens 1 and the camera body 8. It is no longer necessary to communicate between each other, and focusing control at higher speed becomes possible.

  Next, the second prerequisite technology of the present invention will be described.

FIG. 7 shows a flowchart of the calibration operation in the digital single-lens reflex camera system which is the second premise technique of the present invention. The configuration of the camera system is the same as that of the first prerequisite technology. For this reason, the same reference numerals as those in the first prerequisite technology are assigned to the components common to the first prerequisite technology. In the second base technology, the focus position correction value is automatically calculated without setting the calibration mode.

When calibration starts (step 701), first, the camera control circuit 1
3 causes the focus detection unit 12 to perform focus detection by the phase difference detection method, and creates in-focus position information as in the first prerequisite technology (step 702). Next, based on this focus position information, the focus adjustment lens 2a is driven through the lens control circuit 5 and the focus drive unit 3, and a focus operation is performed (step 703).

Next, the camera control circuit 13 causes the focus driving unit 3 to move the focus adjustment lens 2a at the position driven in Step 703 by a minute amount (Step 704).

In this state, the camera control circuit 13 causes the focus determination unit 16 to perform contrast detection (step 705), and after repeating step 704 and step 705 for a predetermined N times (step 705a), the most of the detected contrasts are detected. Focus position information is created from the position of the focus adjustment lens 2a (position detected by the focus position detector 4) when an image signal with high contrast is obtained (step 706).

Next, an in-focus position correction value that is a difference between the in-focus position information obtained in step 706 and the in-focus position information obtained in step 702 using the focus detection unit 12 is calculated by the arithmetic circuit 14 ( Step 707).

Then, the calculated in-focus position correction value is stored in the storage circuit 15 (step 708).
The calibration is completed by the above operation.

Here, the timing for starting the calibration can be performed in a situation where the photographer does not touch the shutter button, and the calibration can be interrupted when the photographer operates the shutter button for the first stroke. Also, during actual shooting, take multiple shots (with different in-focus conditions) while moving the focus adjustment lens 2a at a shutter speed that is 1/2 or less of the set shutter speed, and select the one that is most in focus. Alternatively, a method may be used in which brightness is corrected by image processing after the end of shooting so that a shot image equivalent to shooting at a set shutter speed can be obtained.

The actual photographing operation using the in-focus position correction value created by the calibration is the same as that described in the first base technology.

Example 1
Next, embodiments of the present invention will be described in detail with reference to the drawings.

  In addition to the calibration related to the in-focus position described in the first and second prerequisite technologies described above, calibration related to exposure may be performed.

FIG. 8 shows the configuration of a digital single-lens reflex camera system that is Embodiment 1 of the present invention. In addition, the same code | symbol as 1st base technology is used for the component which is common in 1st base technology. However, the components related to the calibration of the in-focus position described in the first and second prerequisite technologies are omitted in FIG.

In this embodiment, the photometry unit 20 and the exposure control circuit 2 that controls the exposure of the image sensor 11.
1, an exposure amount detection circuit 22 for detecting the exposure amount of the image sensor 11, a camera control circuit 13 ′ also serving as an arithmetic circuit, and a storage circuit 24 are added to the camera body 8 of the first prerequisite technology. Yes.

Next, exposure calibration will be described with reference to the flowchart of FIG.
When the calibration mode is entered by the photographer's switch operation (step 901), the camera control circuit 13 ′ causes the photometry unit 20 to perform photometry (step 902). Then, set the exposure on the basis of the photometry result of the photometry unit 12 (step 903), it performs photographing in the exposure that has been set (exposure value) (step 904).

Then, the exposure (exposure value) set in step 903 is changed by a predetermined value (step 905), and photographing is performed with this changed exposure (exposure value) (step 906). Thus, after repeating step 905 and step 906 for a predetermined N times (step 906a), the exposure amount detection circuit 22 detects the exposure amount of the N images taken in step 904 and step 906 (step 907). .

Next, among the detected exposure amount, calculates the exposure value for the exposure amount of optimum exposure is obtained as an optimum exposure value (Step 907). Next, the camera control circuit 13 ′ as an arithmetic circuit calculates a difference between the optimum exposure value and the exposure (exposure value) set in step 903 (step 908). The camera control circuit 13 ′ stores the calculated difference in the storage circuit 24 as an exposure correction value (step 909). This completes the exposure calibration.

Here, the exposure calibration may be performed by performing image capturing while changing the exposure at the same time during a plurality of image capturing operations performed during the above-described calibration of the in-focus position.

Next, an operation for performing photographing using the exposure correction value calculated by exposure calibration will be described with reference to the flowchart of FIG.

When the photographer operates the shutter button for the first stroke and is half-pressed (step 1001), the camera control circuit 13 ′ causes the photometry unit 20 to perform photometry (step 1002).

Then, the exposure value obtained based on the photometric result by the photometric unit 20 is stored in the storage circuit 2.
4 is corrected using the exposure correction value stored in 4 (step 1003). Further, based on the corrected result, exposure setting at the time of shooting is performed (step 1004).

Thereafter, when the shutter button is operated for the second stroke to be fully pressed, the camera control circuit 13 ′ performs photographing (step 1005).

As described above, optimal exposure can be set by performing exposure correction at the time of shooting using the exposure correction value obtained by exposure calibration.

Here, it is desirable that the in-focus position calibration described in the first and second prerequisite technologies and the exposure calibration described in the present embodiment be performed every time the photographing lens 1 is replaced. If the in-focus position correction value and the exposure correction value corresponding to the photographing lens 1 attached to the camera are not stored in the storage circuit of the camera body 8, it is desirable to warn the photographer by sound or display. .

  Further, the focus position correction value and the exposure correction value are stored in the storage circuit provided in the camera body 8 in the first and second premise techniques and the present embodiment, but the photographing lens The conventional correction value stored in the memory circuit provided in 1 may be rewritten.

It is a figure which shows the structure of the camera system which is the 1st premise technique of this invention. It is a figure which shows the structure of the principal part of the focus detection unit which comprises the said camera system. 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. It is a flowchart which shows the focusing position calibration operation | movement in the said camera system. It is a flowchart which shows operation | movement of the camera at the time of imaging | photography using the correction value calculated by the said focus position calibration. It is a flowchart of the focus position calibration operation | movement in the camera system which is the 2nd premise technique of this invention. It is a figure which shows the structure of the camera system which is Example 1 of this invention. It is a flowchart which shows the exposure calibration operation | movement in the said Example 1. FIG. It is a flowchart which shows operation | movement of the camera at the time of imaging | photography using the correction value calculated by the said exposure correction calibration.

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 body 9 Main mirror
DESCRIPTION OF SYMBOLS 10 Submirror 11 Image pick-up element 12 Focus detection unit 13, 13 'Camera control circuit 14 Arithmetic circuit 15 Memory circuit 16 Focus determination unit 17 Focus plate 18 Pentaprism 19 Eyepiece optical system 20 Photometry unit 21 Exposure control circuit 22 Exposure amount detection circuit 24 Memory circuit

Claims (2)

An imaging device having an imaging element that can be attached and detached with a photographic lens, receives a subject image formed by the photographic lens, and photoelectrically converts the subject image,
Photometric means for performing photometry using light from the photographing lens;
Exposure amount detecting means for detecting an exposure amount received by the image sensor;
Each time the photographic lens is replaced, a plurality of photographings with different exposure values and the exposure amount detection using the exposure amount detecting means for each photographing are performed, and the exposure detected for each photographing. An image pickup apparatus comprising: means for obtaining correction information for correcting an exposure value obtained by using the photometry means from the exposure value with respect to an exposure amount that is an optimum exposure among the amounts . An imaging system comprising: the imaging apparatus according to claim 1; and a photographing lens that can be attached to and detached from the imaging apparatus.

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