JPH1020182A - Focus detector and image pickup device provided with focus detecting function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a lowering of focus detecting accuracy caused by an attaching error of a focus detection part and an image pickup part by directly noticing the actual focusing state of a photographic image plane without through a virtual surface such as a primary image-formation surface in order to detect the focusing state of an image pickup surface. SOLUTION: An optical element 1 is arranged on the image space side of a photographing optical system Z and deflects light passing a part of the image space by using reflecting and refracting action. The direction of the image space of the optical system Z is partially changed by the element 1 and the image space is divided. Image pickup elements 2a and 2b are arranged individually in every image space so as to pick up an optical image. A part of a luminous flux group is distributed through the element 1 while keeping perfect luminous flux shape. The luminous flux group is converged in every divided image space and forms the partial image of the optical image. Meanwhile, the remaining luminous flux group is the one that luminous flux cross section extends over the divided part of the image space and a part of the luminous flux cross section is deflected by the element 1. As a result, the luminous flux group converged at one light spot is distributed in the image space and a boundary part is formed as an overlapped area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detection device for detecting a focus adjustment state of a photographing optical system, and an imaging device having an imaging function in addition to the focus detection function.
In particular, the difference from the conventional phase difference detection method is that focus detection is performed directly on the imaging surface without providing a virtual surface for focus detection (such as a primary imaging surface) separately from the imaging surface. It is.

[0002]

2. Description of the Related Art Conventionally, cameras and other optical devices are equipped with a phase difference detection type focus detection device for detecting a focus adjustment state. FIG. 20 is a diagram showing an electronic camera equipped with this type of focus detection device. 20, a lens barrel 62 is attached to the front of a camera body 61, and a photographing optical system 63 is arranged inside the lens barrel 62.

A main mirror 64 and a sub-mirror 65 are sequentially arranged on the optical axis of the photographing optical system 63, and a mat surface, a pentaprism, and the like are arranged along the reflection direction of the main mirror 64. On the other hand, a focus detection unit 66 is disposed in the reflection direction of the sub mirror 65, and the focus detection unit 66
Is connected to a microprocessor 68 via an A / D converter 67.

A CCD is provided behind the sub mirror 65.
An image pickup unit 70 including an image pickup device is arranged, and the image pickup unit 7 is provided.
0 captures a subject image in the mirror-up state. FIG. 21 is an exploded perspective view showing the internal configuration of the focus detection unit 66. 21, a lens holder 71 is provided on the upper surface of the focus detection unit 66, and the lens holder 7 is provided.
1 is fitted with a condenser lens 72.

[0005] On the upper surface of the condenser lens 72, a field mask 73 for limiting the field of view and an infrared cut filter 74 for blocking infrared light are arranged. A mirror 75 is disposed obliquely directly below the condenser lens 72, and an aperture plate 77, a lens plate 78, and an image sensor 79 are sequentially disposed along the reflection axis of the mirror 75. The output of the image sensor 79 is connected to the microprocessor 68 via the A / D converter 67.

The aperture plate 77 is provided with aperture masks 77a and 77b each having a symmetrical opening, and the lens plate 78 is provided with separator lenses 78a and 78b each having a symmetrical imaging lens. Are integrally formed. Hereinafter, a conventional focus detection operation will be described with reference to these drawings. First, in the mirror-down state, the focus detection unit 66 receives light reflected by the sub-mirror 65.

The received light beam forms an image once near a virtual plane optically equivalent to the imaging plane (hereinafter, this plane is referred to as a “primary imaging plane”). The field mask 73 shields an unnecessary portion of the light image and extracts only the light image in the focus detection area. The light image in this focus detection area passes through the primary imaging plane, is dispersed again, and reaches the aperture masks 77a and 77b via the condenser lens 72.

In the stop masks 77a and 77b, these light beams are pupil-divided to form symmetrical split light beams. These split light beams are individually tilt-formed via the separator lenses 78a and 78b, and form a set of light images on the light receiving surface of the image sensor 79.

Here, the image sensor 79 photoelectrically converts the set of light images. The microprocessor 68
The photoelectric output of the image sensor 79 is captured. The microprocessor 68 performs a well-known correlation operation on the photoelectric output to detect an image interval between a pair of light images. Based on this image interval, the amount of deviation between the primary image plane and the optical image is calculated.

The microprocessor 68 indirectly calculates a shift amount (hereinafter, referred to as "defocus amount") between the imaging surface and the optical image by multiplying the shift amount by a conversion coefficient. On the other hand, when the release button (not shown) is fully pressed, the main mirror 64 and the sub mirror 65 are flipped up,
The light beam passing through the imaging optical system 63 directly reaches the imaging surface of the imaging unit 70, and forms a subject image.

The imaging section 70 performs photoelectric conversion of the subject image and outputs an image signal to an image recording section and a display section (not shown).

[0012]

By the way, in the conventional focus detecting device, the primary image forming plane for focus detection is set separately from the photographing optical path. The conventional focus detection device indirectly detects a focus adjustment state (for example, a defocus amount or the like) on the imaging surface by performing focus detection on the primary imaging surface.

For this reason, if a mounting error of the focus detecting unit 66 or the imaging unit 70 or an aging of the mounting position occurs and the positional relationship between the imaging surface and the primary image forming surface is slightly shifted, the focus detection accuracy is reduced. There has been a problem that it is greatly reduced. Further, the conventional focus detection device cannot receive the photographing light beam when the mirror is raised. For this reason, there is a problem that the focus adjustment state at the moment when the photographing is performed cannot be directly detected.

As a result, there is a problem that the focus state shifts during the release time lag. In a general electronic camera, 1/2 to 1
An image sensor of about ／ inch is used. Such an electronic camera has a photographing screen several times smaller than a 35 mm silver halide camera and the like, and has a fine pixel pitch of about 10 μm or less. Therefore, it is necessary to reduce the diameter of an allowable circle of confusion on the imaging surface. .

Therefore, if the focus detection unit for a 35 mm camera is used as it is in the optical system of such an electronic camera, there is a problem that the focus detection accuracy becomes insufficient and the focus accuracy becomes insufficient. Therefore, an object of the present invention is to provide a focus detection device capable of directly detecting a focus adjustment state on an imaging surface in order to solve the above-described problem.

A second object of the present invention is to provide a focus detecting device capable of detecting a focus adjustment state more accurately, in addition to the object of the first embodiment. A third object of the present invention is to provide a focus adjustment device capable of detecting a focus adjustment state of a specific subject, in addition to the object of the first embodiment. A fourth object of the present invention is to provide a focus adjusting device capable of arbitrarily selecting an object to be detected of a focus adjusting state, in addition to the object of the third object.

A fifth object of the present invention is to provide a focus adjustment device suitable for using a color image pickup device, in addition to the object of the first embodiment. According to a sixth aspect of the present invention, in addition to the object of the fifth aspect, it is possible to provide a focus detection device capable of detecting a focus adjustment state with higher accuracy when a color imaging element is used. Aim.

According to a seventh aspect of the present invention, in addition to the object of the first aspect, a focus detection device capable of detecting a focus adjustment state with higher accuracy with substantially no chromatic aberration when dividing an image space. The purpose is to provide. An eighth aspect of the present invention is to provide a focus detection device using a prism as an optical element for dividing an image space, in addition to the object of the first aspect.

A further object of the present invention is to provide a focus detecting device using an eccentric lens as an optical element for dividing an image space, in addition to the object of the first aspect. An object of the invention according to claim 10 is to provide an image pickup apparatus that can easily realize a large photographic screen, in addition to the object of claim 1.

[0020]

FIG. 1 is a diagram for explaining the first aspect of the present invention. Hereinafter, in association with FIG.
Means for solving the problem will be described.

According to a first aspect of the present invention, there is provided an optical system which is disposed on the image space side of the photographing optical system Z, deflects light passing through a partial range of the image space by reflection or refraction, and divides the image space into a plurality. A device 1; a plurality of image sensors 2a and 2b which are individually arranged for each of the plurality of image spaces divided by the optical device 1 and capture an optical image divided and formed for each image space; and a plurality of image sensors 2a and 2b And a focus detecting means 4 for detecting a focus adjustment state of the photographing optical system Z based on the displacement detected by the displacement detecting means 3. Wherein the displacement detecting means 3 detects a displacement between the corresponding light images in an overlapping area of the light images formed in the divided part of the image space.

According to a second aspect of the present invention, in the focus detection device according to the first aspect, the displacement detecting means 3 performs gain correction on the image information for each overlapping area in accordance with a division ratio of a light beam, and the corrected image information is corrected. It is characterized in that displacement is detected for image information. According to a third aspect of the present invention, in the focus detection device according to the first aspect, the displacement detection means 3 detects a displacement of image information by limiting a detection range to a focus detection area provided in an overlapping area. It is characterized by the following.

According to a fourth aspect of the present invention, there is provided the focus detecting device according to the third aspect, further comprising an operation means for selecting, moving, or reducing or enlarging the focus detection area by an external input. The invention according to claim 5 is
In the focus detection device according to claim 1, the imaging device includes:
A color filter in a predetermined color system is mixedly arranged for each pixel of the light receiving surface, and the displacement detecting means 3 extracts a predetermined color component of the image information and detects a displacement of the color component. It is characterized by.

According to a sixth aspect of the present invention, in the focus detection device according to the fifth aspect, the image pickup device is configured such that at least one color of a color filter is continuously arranged in a vertical direction, a horizontal direction, or an oblique direction. The displacement detecting means 3 detects a displacement of image information along a continuous direction of one color. According to a seventh aspect of the present invention, in the focus detection device according to the first aspect, the optical element 1 is provided with an imaging optical system Z.
And a reflecting member that reflects light passing through a partial range and partially reflects the image space.

According to an eighth aspect of the present invention, in the focus detection apparatus according to the first aspect, the optical element 1 is provided with a photographing optical system Z.
And a prism that refracts light passing through a partial range and divides the image space into a plurality of parts. According to a ninth aspect of the present invention, in the focus detection device according to the first aspect, the optical element 1 has a lens principal point outside the optical axis of the photographing optical system Z, and tilts transmitted light in a partial range. It is an eccentric lens that forms an image and divides an image space into a plurality of parts.

According to a tenth aspect of the present invention, there is provided an image pickup apparatus comprising the focus detection device according to any one of the first to ninth aspects, wherein the image information photoelectrically converted by the plurality of image pickup elements is converted into The image processing apparatus further includes an image synthesizing unit that obtains image information of a subject image by synthesizing the image in accordance with the positional relationship in the image space before the division.

(Function) In the focus detecting device according to the first aspect, the optical element 1 is arranged on the image space side of the photographing optical system Z. The optical element 1 deflects light that passes through a part of the image space by using a reflecting action or a refracting action. Due to the optical action of the optical element 1, the image space of the photographing optical system Z partially changes its direction, and the image space is divided into a plurality.

The image sensors 2a and 2b are individually arranged for each of a plurality of divided image spaces, and pick up an optical image divided and formed for each image space. Here, a light beam group converging on each point of the light image is considered. A part of such a light beam group is distributed via the optical element 1 while keeping a complete light beam shape. These light flux groups converge for each divided image space to form a partial image of the light image.

On the other hand, the remaining light beam group is a light beam group whose light beam cross section extends over a divided portion of the image space. In these light beam groups, a part of the light beam cross section is deflected by the optical element 1. As a result, a light flux group that should originally converge to one light spot is distributed to a plurality of image spaces. Therefore, in the divided image space, the overlapping area of the optical images is formed such that the boundary portions of the optical images protrude from each other.

FIGS. 2 to 4 are views showing point images of the overlapping area in each focus adjustment state. In the in-focus state, FIG.
As shown in (c), a light beam to be converged at one point is distributed to overlapping areas β and β ′ via the optical element 1. In these overlapping areas β and β ′, the light flux after distribution converges to each other, so that a point image is formed. In the back focus state, FIG.
As shown in (a) to (c), a light beam to form a perfect circular blurred image is distributed to overlapping areas β and β ′ via the optical element 1. In these overlapping regions β and β ′, since the cross section of the light beam after distribution appears as a blurred image, a semicircular blurred image is formed.

Further, in the front focus state, FIGS.
As shown in (c), a light beam to form a perfect circular blurred image is distributed via the optical element 1 to the overlapping areas β and β ′. In these overlapping regions β and β ′, since the cross section of the light beam after distribution appears as a blurred image, a semicircular blurred image is formed. In the front focus state, the light flux temporarily converges before reaching the imaging devices 2a and 2b, and the left and right (or up and down) of the blurred image is inverted. An image is formed.

FIG. 5 is a diagram illustrating these blur shapes for each focus adjustment state. In the focused state, FIG.
As shown in (1), since the optical images in the overlapping areas β and β ′ are formed, the relative displacement of the optical images becomes zero. Further, in the rear focus state, as shown in FIG. 5B, a semicircular blurred image is formed in each of the overlapping areas β and β ′, so that the displacement of the center of gravity of the optical image (φ in FIG. 5) ) Occurs.

Further, in the front focus state, as shown in FIG. 5C, a semi-circular blurred image is formed in each of the overlapping areas β and β ′, so that the displacement of the center of gravity of the optical image (FIG. -Φ). Here, in the back focus state and the front focus state, the direction of the blur shape is opposite, so that the center of gravity displacement of the optical image has a positive and negative value.

The displacement detecting means 3 detects such a displacement of the light image. The focus detecting means 4 can determine whether the camera is in the rear focus state or the front focus state based on the sign of the displacement. In addition, the amount of displacement (for example, the amount of defocus) from the in-focus state can be detected from the magnitude of the displacement. According to the operation described above, the present invention directly detects the focus adjustment state of the imaging surface (the light receiving surfaces of the imaging elements 2a and 2b).

Accordingly, since there is no error factor such as a mounting error between the focus detection unit and the imaging unit, a high focus detection accuracy can be obtained. When a mirror box is arranged in front of the imaging surface, if a light transmission portion is provided in a part of the main mirror as in the related art, focus detection can be performed while the mirror is in the down state.

Further, even in the mirror-up state, since the photographic light beam can be received on the imaging surface which is the focus detection surface, the focus adjustment state at the moment when the imaging is performed can be directly detected. Further, since the image information for focus detection is taken in at the resolution of the imaging elements 2a and 2b, the focus adjustment state can be detected with appropriate accuracy.

In the focus detecting device according to the second aspect, the displacement detecting means 3 performs gain correction on the image information for each overlapping area according to the division ratio of the light beam. As shown in FIGS. 2A to 2C, in the overlapping areas β and β ′, the division ratio of the light beam changes according to the position of the point image. Due to such a change in the division ratio, the luminance level of the overlapping area changes in the focused state.

Here, when the detection range is limited to the center of the overlapping areas β and β ′, the division ratio of the light beam is equally divided as shown in FIG. There is no particular problem. However, when the detection range is widened, the detection of the displacement of the center of gravity is biased because the split ratio of the light beam is biased as shown in FIGS.

Therefore, the displacement detecting means 3 corrects the luminance level of the overlapping area according to the division ratio of the light beam,
The deviation of the displacement of the center of gravity as described above is prevented. In the focus detection device according to the third aspect, the displacement detection means 3 detects the displacement of the image information by limiting the detection range to the focus detection area provided in the overlapping area. By such an operation, a specific subject can be narrowed down as a focus detection target without making the entire overlap area a focus detection target. Therefore, focus detection can be performed strictly in a narrow range.

The focus detecting device according to the fourth aspect is provided with operating means for selecting, moving or reducing / enlarging the focus detecting area. By such an operation, even when the photographing target is out of the center of the screen, the target subject can be the focus detection target by appropriately selecting or moving the focus detection area.

The width of the overlapping area changes depending on the open F value of the photographing optical system Z. Therefore, an appropriate focus detection area can always be ensured by reducing and expanding the focus detection area in response to an external input of the open F value. In the focus detecting device according to the fifth aspect, a predetermined color system (for example, an RGB color system,
Color filters of YIQ color system, complementary color system, etc.) are mixedly arranged in pixel units.

In such a case, the displacement of the light image cannot be detected by comparing different color components. Thus, the displacement detecting means 3 extracts a specific color component and generates image information for focus detection. Since this image information is a luminance pattern composed of a single color, the displacement of the optical image can be reliably detected.

In the focus detecting device according to the sixth aspect, at least one color of the color filters is continuously arranged in a vertical direction, a horizontal direction, or an oblique direction. By arranging the color filters in this manner, a line sensor is equivalently configured in the continuous direction of one color. The displacement detecting means 3 detects the displacement of the image information along the continuous direction.

With such an operation, it is possible to accurately detect the displacement of the image information with the accuracy of the pixel density in the continuous direction. In the focus detection device according to the seventh aspect, a reflection member is used as the optical element 1. The reflection member is arranged on the image space side of the imaging optical system Z, and divides the image space by reflecting passing light in a partial range.

Normally, when chromatic aberration occurs in the optical element 1, the imaging performance deteriorates and the displacement of image information cannot be detected with high accuracy. However, in the focus detection device of claim 7,
Since the optical element 1 uses a reflection action, chromatic aberration hardly occurs. Therefore, while improving the imaging performance,
Displacement of image information can be detected with high accuracy.

In the focus detecting device according to the eighth aspect, a prism is used as the optical element 1. This prism is
It is arranged on the image space side of the photographing optical system Z, and refracts passing light in a partial range to divide the image space. In the focus detecting device according to the ninth aspect, an eccentric lens is used as the optical element 1. The eccentric lens is arranged on the image space side of the photographing optical system Z, and divides the image space by tilting the transmitted light in a partial range.

According to a tenth aspect of the present invention, there is provided an imaging apparatus including the focus detecting device according to any one of the first to ninth aspects, and an image synthesizing unit. This image combining means
Photoelectric outputs are taken from a plurality of image sensors in the focus detection device. The image combining means combines these pieces of image information according to the positional relationship in the image space before division, and combines the image information of the subject image.

With such a configuration, an imaging device having a focus detection function can be easily realized.

[0049]

Embodiments of the present invention will be described below with reference to the drawings. FIG.
It is a figure which shows embodiment corresponding to 10.

FIG. 7 shows the reflecting member 14 in this embodiment.
FIG. 3 is an explanatory diagram showing the configuration of FIG. In these drawings, a photographing optical system 12 is attached to an imaging device 11, and an aperture 13 and a reflecting member 14 are sequentially arranged on the optical axis of the photographing optical system 12. The reflecting member 14 includes a rectangular parallelepiped transparent block 14s made of optical glass, transparent resin, or the like, and a mirror surface 14a obliquely crossing the left half inside the transparent block 14s.

The reflecting member 14 is manufactured, for example, as follows. First, the transparent member 14s is formed by being divided into “obliquely divided shapes”. afterwards,
A mirrored surface 14a is formed on half of one cross section, and both cross sections are bonded together. The reflecting member 14 thus formed
The image sensor 15a is arranged in the reflection direction, and the image sensor 15b is arranged in the transmission direction. These imaging devices 15a,
A release button 11a is connected to 15b.

These image sensors 15a and 15b are arranged so as to satisfy the following positional relationship. (1) The light receiving surface of the image sensor 15b is arranged on a virtual shooting screen preset on the shooting optical axis, and the right end of the light receiving surface coincides with the right frame of the shooting screen. On the other hand, the left end of the light receiving surface reaches “a position where the exit pupil of the imaging optical system 12 in the open aperture state is completely hidden by the mirror surface 14a”.

(2) The "image pickup device 15" by the mirror surface 14a
The mirror image of the “light receiving surface a” is located on the above-described photographing screen, and the left end of the mirror image coincides with the left frame of the photographing screen. On the other hand, the right end of the mirror image reaches “a position where the above-described exit pupil is not hidden by the mirror surface 14a”. Image sensor 1 arranged in this way
The output of the image synthesizing unit 1 is output via the first storage unit 16a.
7, and the output of one image sensor 15b is connected to the image synthesizing unit 17 via the second storage unit 16b.

The output of the image synthesizing unit 17 is connected to an output control unit 18 via a synthesized image storage unit 17a, and the output of the output control unit 18 is connected to a display unit 19 and an image output terminal 20. Further, the first storage unit 16a and the second storage unit 1
The output of 6b is connected to a focus detection calculation unit 22 via an image shift calculation unit 21. The output of the focus detection calculation unit 22 is connected to the display unit 19 and the image synthesis unit 17 and to a focus drive unit that performs focus control.

An area selection button 21 which is an operation member for manually selecting a focus detection area is provided on the housing of the imaging device 11.
The output of the area selection button 21a is connected to the display unit 19 and the image shift calculation unit 21. In addition,
Regarding the correspondence between the invention described in claims 1 to 7 and the present embodiment, a partial range of the image space corresponds to the mirror surface 14a,
The optical element 1 corresponds to the reflection member 14, the plurality of imaging elements correspond to the imaging elements 15a and 15b, the displacement detecting means 3 corresponds to the image shift calculating section 21, and the focus detecting means 4 corresponds to the focus detecting calculating section 22. Corresponding.

As for the correspondence between the invention described in claim 10 and the present embodiment, in addition to the above-mentioned correspondence, an image combining means corresponds to the image combining section 17. FIG. 8 is a flowchart showing the operation of the present embodiment. Hereinafter, the operation of the first embodiment will be described based on these drawings. First, when the release button 11a is pressed (step S1), the image sensor 1
At 5a and 15b, accumulation of photocharge is started (step S2).

In this state, when a predetermined exposure time has elapsed (step S3), photocharges are sequentially transferred from the image pickup devices 15a and 15b, and are stored in the first storage unit 16a and the second storage unit 16b, respectively (step S3). Step S4). Here, since the optical image of the image sensor 15a is a mirror image, the first storage unit 16a stores the image information by reversing the left and right of the image information (step S5).

Next, the image shift calculation section 21 takes in the output of the area selection button 21a and detects the manually selected focus detection area. FIG. 9 is a diagram illustrating an example of the arrangement of the focus detection areas. In this arrangement example, three focus detection areas P
1 to P3 are arranged in the vertical direction in the overlapping areas β and β ′ of the divided light images.

The image shift operation section 21 stores the image information in the selected focus detection area in the first storage section 16a and the second storage section 16a.
The data is individually fetched from the storage unit 16b (step S6). Here, in the light images in the overlapping areas β and β ′, a luminance variation as shown in FIG. 10 occurs according to the division ratio of the light flux. Therefore,
The image shift operation unit 21 performs gain correction on the captured set of image information in accordance with the division ratio of the light beam (step S7).

Next, the image shift calculator 21 extracts a specific color component from a set of image information (step S8). This extraction method is determined as follows according to the color filter arrangement of the imaging elements 15a and 15b. For example, FIG.
In (a) and (b), specific color components are continuously arranged. The image shift calculator 21 extracts the pixel values in the continuous direction as they are. By such an extraction operation, a color component can be extracted with the accuracy of the pixel density of the imaging devices 15a and 15b.

However, in this case, in order to make the arrangement direction of the specific color component coincide with the direction of the image shift due to defocus, for example, it is necessary to specify the direction orthogonal to the direction of the boundary line of the split pupil in FIG. Need to be arranged. FIG. 11C shows a case where specific color components are arranged at regular intervals in the image shift direction due to defocus. The image shift calculator 21 extracts the specific color component by thinning it out at regular intervals.

Further, in FIG. 11D, the color filter array is divided into 2 × 2 small blocks, and the color components (the same color components or different color components) in the small blocks are mixed to specify the color filter array. Is extracted. FIG.
In (e), a specific color component is extracted by dividing the color filter array into 4 × 2 small blocks and mixing the color components (the same color component or different color components) in the small block.

Further, in FIG. 12F, the color filter array is divided into 2 × 2 small blocks. At this time, the small block is divided so as to overlap the left and right small blocks by half. A specific color component is extracted by mixing the color components (the same color component or different color components) in the small block. By such an operation, a pixel row can be extracted at a high density, and the focus detection accuracy can be improved.

In FIG. 12G, the color filter array is divided into 4 × 2 small blocks. At this time, the small block is divided so as to overlap the left and right small blocks by half.
A specific color component is extracted by mixing the color components (the same color component or different color components) in the small block. By such an operation, a pixel row can be extracted at a high density, and the focus detection accuracy can be improved.

FIG. 13 is a diagram showing a set of image information preprocessed as described above. Here, the image shift operation unit 2
1 performs, for example, the following correlation operation on the set of image information. First, one image information is shifted left and right by a predetermined interval, a difference from the other image information is obtained, and a sum of absolute values of the difference is obtained.

By calculating the value of the predetermined interval that minimizes the sum, the center-of-gravity displacement φ of one set of image information is calculated (step S9). The focus detection calculation unit 22 can determine the focus position based on the sign of the center-of-gravity displacement φ as follows. That is, when the center-of-gravity displacement φ has a positive sign, as shown in FIG.

When the displacement φ of the center of gravity becomes zero, it can be determined that the object is in focus, as shown in FIG. Further, when the center-of-gravity displacement φ has a negative sign, it can be determined that the front focus state has been reached, as shown in FIG. Next, the focus detection calculation unit 22 calculates DF = φ / K (1) according to the center-of-gravity displacement φ to obtain the defocus amount DF (step S1).
0).

Here, the value of the coefficient K is K ≒ 1 / θ when an angle at which the center of gravity of the split pupil (the center of gravity O, O ′ in FIG. 14) is viewed from the center of the focus detection area is θ. -(2) This is a value represented by equation (2). However, the actual value of K is determined based on actual measurement. Since the exact value of K is a function of the center of gravity displacement φ, it is determined by a table process or the like.

In this state, when the defocus amount DF exceeds a predetermined threshold value (step S11), the focusing drive unit moves the photographing optical system 12 back and forth based on the defocus amount DF to execute focus control. (Step S12).
On the other hand, when the defocus amount DF is equal to or smaller than the predetermined threshold (step S11), the image synthesizing unit 17 determines that the image is in focus and starts the image information synthesizing process.

FIG. 15 is a diagram showing image information obtained by divisional imaging. FIG. 16 is a diagram illustrating image composition. Hereinafter, the operation of the image synthesizing unit 17 will be described with reference to these drawings. As shown in FIG. 15, the image information captured by the image sensor 15a and the image sensor 15b includes areas α and γ where the split light images do not overlap, and areas β and γ where the split light images overlap.
β '.

First, the image synthesizing unit 17 includes a storage unit 16a,
16 (b), the pixels in the sections α and γ are read out, and C (i, j) = A (i, j) (1 ≦ i ≦ 6, 1 ≦ j ≦ 4) (6) C (i, j) , j + 4) = B (i, j) (where 1 ≦ i ≦ 6, 3 ≦ j ≦ 6) (7) The pixels are rearranged in accordance with the following equation (7) and stored in the combined image storage unit 17a ( Step S13).

Next, the pixels in the overlapping areas β and β 'are read out and C (i, j) = A (i, j) + B (i, j-4) (where 1≤i≤6,5≤j≤ 6) Add according to (8) and store in the combined image storage unit 17a (step S14). The output control unit 18 controls the combined image storage unit 1
The combined image information is read from 7a and sequentially output to the outside (step S15).

According to the operation described above, in the present embodiment, the defocus amount on the imaging surface of the imaging elements 15a and 15b can be directly detected. Therefore,
High focus detection accuracy can be obtained without any conventional error factors such as mounting errors of the focus detection unit and the imaging unit and aging of the mounting position.

Further, since the focus adjustment state at the moment of photographing can be directly detected, it is possible to surely eliminate the problem that the focus state is lost during the release time lag. Further, the imaging devices 15a and 15b
Since the image information for focus detection is taken in according to the resolution of (1), the focus adjustment state can be detected with appropriate accuracy according to the image quality.

Further, since the displacement of the center of gravity is detected for the image information from which the luminance fluctuation has been removed, the displacement of the center of gravity can be accurately detected without bias. Further, since the focus detection area is selected by an external operation, even when the shooting target is out of the center of the screen, it is possible to focus on the target subject.

Further, since a specific color component is extracted to generate image information for focus detection, displacement of a color image can be reliably detected. In addition, since imaging is performed by dividing the photographing screen into left and right, the chip size of each of the imaging elements 15a and 15b can be reduced. Therefore,
It is not necessary to use a large-sized image sensor alone, and the cost of parts for the image sensor can be significantly reduced.

Further, since a single photographing screen is photographed by combining a plurality of image pickup devices 15a and 15b, the resolution of the photographing screen can be easily increased. Therefore,
The imaging device 11 that outputs high-definition image information can be easily realized. In the above-described embodiment, the combined image storage unit 17a is provided to temporarily store image information being combined, but the present invention is not limited to this configuration. For example, the image information being combined may be directly stored in a memory card or another external storage medium without the combined image storage unit 17a.

Further, in the above-described embodiment, the description has been given of the still image capturing, but the present invention is not limited to this. In particular, the image information synthesizing process according to the present invention is a simple process including the image information transfer process and the addition process, so that the synthesizing process can be performed in real time. Therefore, by performing image synthesis in real time, a moving image can be captured.

In the above embodiment, the image space is 2
Although the case of division has been described, the present invention is not limited to this. The image space may be divided into three or more parts and focus detection may be performed on at least one overlapping area. In the above-described embodiment, the reflection member 14 is used as the optical element 1 for image space division, but the present invention is not limited to this configuration. Generally, any optical element that divides a part of the image space by reflection or refraction may be used.

In the following, another example of the configuration of the optical element 1 for image space division will be listed. FIG. 17 is a diagram illustrating a configuration example of the reflection member 34. The reflection member 34 includes a transparent block 34s made of optical glass, transparent resin, or the like, and a reflection surface 34a disposed on the lower surface side of the transparent block 34s.
34b. Two mirror surfaces 34a, 34b
The imaging devices 35a and 35b are arranged to face each other in the reflection direction of.

The mirror surfaces 34a and 34b need not be mirror-finished if the cross section of the transparent block 34s satisfies the condition of total reflection. In the reflecting member 34 having such a configuration, the optical paths after the division are symmetrically arranged, so that the optical actions until reaching the individual imaging elements 35a and 35b can be equalized. Therefore, optical characteristics such as brightness and image magnification can be aligned with high precision in each piece of image information obtained by divisional imaging.

FIG. 18 shows a prism 4 according to the eighth aspect.
3 is a diagram illustrating a configuration example of FIG. The prism 43 is formed of an optical glass or transparent resin in a gable roof shape, and the concave surface thereof is disposed toward the photographing optical system 42. This prism 43
The image sensors 44a and 44b are arranged side by side. Also in the prism 43 having such a configuration, the optical paths after division are arranged symmetrically, so that the individual imaging elements 44a and 44
The optical action up to the point b can be equalized. Therefore, optical characteristics such as brightness and image magnification can be aligned with high precision in each piece of image information obtained by divisional imaging.

FIG. 19 is a view showing eccentric lenses 56a and 56b according to the ninth aspect. This eccentric lens 56
Reference numerals a and 56b denote compound lenses having principal points disposed at symmetric positions with respect to the optical axis of the photographing optical system 55. Behind these eccentric lenses 56a and 56b, image sensors 57a and 5
7b are juxtaposed.

The eccentric lenses 56a, 56 having such a configuration
Also in b, since the optical paths after division are arranged symmetrically,
It is possible to equalize the optical action until reaching the individual imaging elements 57a and 57b. Therefore, optical characteristics such as brightness and image magnification can be aligned with high precision in each piece of image information obtained by divisional imaging.

[0085]

As described above, according to the first aspect of the present invention, the focus adjustment state of the imaging surface (the light receiving surfaces of the plurality of imaging elements) is detected.

Therefore, it is possible to directly know the actual focus adjustment state of the photographing screen without going through a virtual plane such as a primary imaging plane. Since the focus detection is performed on the imaging surface in this manner, the conventional disadvantage that the focus detection accuracy is reduced due to the mounting error of the focus detection unit and the imaging unit can be completely solved.

Further, it is possible to avoid the problem that the focus detection accuracy is gradually reduced due to the aging of the mounting position of the focus detection unit and the imaging unit. Therefore, in the present invention, high focus detection accuracy can be stably obtained over a long period of time. In particular, it is possible to directly know the focus adjustment state at the moment when shooting is performed. for that reason,
By performing the focus control based on the focus detection value at the moment when the photographing is performed, it is possible to completely eliminate the problem that the focus state is lost during the release time lag.

Further, since the image information for focus detection is taken in according to the resolution of the image pickup device, the focus adjustment state can be detected with appropriate accuracy according to the image quality of the photographed image. Therefore, there is no need to change the design of the focus detection unit according to the chip size of the image sensor.

According to the second aspect of the present invention, the image information for each overlapping area is gain-corrected to remove the luminance fluctuation in the overlapping area. Since the displacement is detected with respect to the image information from which the luminance fluctuation has been removed, the detected value of the displacement is not biased. Therefore, the focus adjustment state can be detected more accurately.

According to the third aspect of the present invention, since the focus detection area is provided in the overlapping area, the focus can be detected for a specific subject. Therefore, it is possible to strictly perform focus detection while aiming at a narrow range such as a part of a subject. According to the fourth aspect of the present invention, since the focus detection area can be appropriately selected, moved, or reduced / enlarged, the target object can be reliably recognized as a focus detection target.

The width of the overlapping area changes depending on the open F value of the photographing optical system Z and the like. Therefore, it is possible to always secure an appropriate size of the focus detection area by reducing and expanding the focus detection area in response to an external input of the open F value. In the invention according to claim 5,
By extracting a specific color component, image information for focus detection is generated. Therefore, when using a color image sensor, displacement of an optical image can be reliably detected.

According to the sixth aspect of the present invention, a monochromatic line sensor is equivalently configured by arranging at least one color of a color filter continuously. Since the displacement of the image information is detected along the continuous direction, it is possible to detect the displacement of the image information with the accuracy of the pixel density in the continuous direction. According to the seventh aspect of the present invention, since the reflecting member is used as the optical element, chromatic aberration hardly occurs. Therefore,
The focus detection accuracy can be improved while improving the imaging performance of the subject image.

According to the eighth aspect of the present invention, since the prism is used as the optical element, the image information is not mirrored, and the processing of inverting the image information left and right can be omitted at all. According to the ninth aspect of the present invention, since an eccentric lens is used as the optical element, the image information is not reflected, and processing such as inverting the image information from side to side can be omitted at all.

According to the tenth aspect, image information captured by a plurality of image sensors is synthesized. Therefore, the chip size of each image sensor can be reduced. Usually, when the chip size is reduced to １ ／, the production yield is increased. Therefore, it is easy to secure the required number of image sensors, and the cost of parts required for the image sensors can be significantly reduced.

Further, by combining a plurality of image pickup devices,
Since one photographing screen is configured, the enlargement of the photographing screen can be easily realized. Further, as compared with a case where a single image sensor is used, a plurality of image sensors are combined, so that the resolution of a shooting screen can be easily increased. Therefore, it is possible to easily realize an imaging device that outputs large-screen and high-definition image information.

As described above, in the electronic camera system to which the present invention is applied, it is possible to directly detect the focus adjustment state on the imaging surface. Therefore, it is possible to easily realize a camera system that performs close focusing control immediately in response to an actual subject image to be captured.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the invention described in claim 1;

FIG. 2 is a diagram showing a point image of an overlapping area in a focused state.

FIG. 3 is a diagram illustrating a point image of an overlapping area in a back focus state.

FIG. 4 is a diagram showing a point image of an overlapping area in a front focus state.

FIG. 5 is a diagram illustrating a blur shape in an overlapping area.

FIG. 6 is a diagram showing an embodiment corresponding to claims 1 to 7 and 10;

FIG. 7 is an explanatory diagram illustrating a configuration of a reflection member 14 in the present embodiment.

FIG. 8 is a flowchart showing the operation of the present embodiment.

FIG. 9 is a diagram illustrating an example of an arrangement of a focus detection area.

FIG. 10 is an explanatory diagram showing luminance fluctuation in a focus detection area and gain correction thereof.

FIG. 11 is a diagram illustrating selection of a color component.

FIG. 12 is a diagram illustrating selection of a color component.

FIG. 13 is a diagram showing a set of image information extracted for focus detection.

FIG. 14 is a diagram showing the center-of-gravity opening θ of the split pupil.

FIG. 15 is a diagram showing image information obtained by divisional imaging.

FIG. 16 is a diagram illustrating image composition.

FIG. 17 is an explanatory diagram illustrating a configuration example of a reflection member.

FIG. 18 is an explanatory diagram showing a configuration example (corresponding to claim 8) of a prism.

FIG. 19 shows a configuration example of an eccentric lens (corresponding to claim 9).
FIG.

FIG. 20 is a diagram showing a conventional example.

FIG. 21 is an exploded perspective view showing a conventional focus detection unit 66.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical element 2a, 2b Imaging element 3 Displacement detection means 4 Focus detection means 11 Imaging device 11a Release button 12 Imaging optical system 13 Aperture 14 Reflection member 14a Mirror surface 14s Transparent block 15a Image sensor 15b Image sensor 16a 1st storage part 16b Second storage unit 17 Image synthesis unit 17a Synthetic image storage unit 18 Output control unit 19 Display unit 20 Image output terminal 21 Image shift operation unit 21a Area selection button 22 Focus detection operation unit 34 Reflecting members 34a, 34b Mirror surface 34s Transparent block 42 imaging optical system 43 prism 44a, 44b imaging device 55 imaging optical system 56a, 56b eccentric lens 57a, 57b imaging device 61 camera body 62 lens barrel 63 shooting optical system 64 main mirror 65 sub mirror 66 focus detection unit 67 A / D conversion unit 68 Microprocessor Reference Signs List 70 imaging unit 71 lens holder unit 72 condenser lens 73 field mask 74 infrared cut filter 75 mirror 77 aperture plate 77a, 77b aperture mask 78 lens plate 78a, 78b separator lens 79 image sensor

Claims (10)

[Claims] 1. An optical element disposed on an image space side of a photographing optical system and deflecting light passing through a partial range of the image space by reflection or refraction to divide the image space into a plurality of optical elements; A plurality of image sensors that are individually arranged for each of the plurality of divided image spaces, and capture an optical image that is divided and formed for each image space, and capture image information of the plurality of image sensors. A displacement detecting unit that detects a displacement; and a focus detecting unit that detects a focus adjustment state of the imaging optical system based on the displacement detected by the displacement detecting unit. In the overlapping area of the light image formed in the part,
A focus detection device for detecting a displacement between corresponding light images. 2. The focus detection device according to claim 1, wherein the displacement detection unit performs gain correction on the image information for each of the overlapping areas in accordance with a division ratio of a light beam, and detects a displacement on the corrected image information. A focus detection device. 3. The focus detection device according to claim 1, wherein the displacement detection unit detects a displacement of the image information by limiting a detection range to a focus detection area provided in the overlapping area. A focus detection device. 4. The focus detection device according to claim 3, further comprising an operation unit for selecting, moving, or reducing or enlarging the focus detection area by an external input. 5. The focus detection device according to claim 1, wherein the image pickup device is configured by mixing and arranging color filters in a predetermined color system for each pixel on a light receiving surface. A focus detection device for extracting a predetermined color component of the image information and detecting a displacement of the color component. 6. The focus detection device according to claim 5, wherein the image pickup device has at least one color of the color filter continuously arranged in a vertical direction, a horizontal direction, or an oblique direction. The focus detection device detects a displacement of the image information along the continuous direction of the one color. 7. The focus detection device according to claim 1, wherein the optical element is disposed in an image space of the photographing optical system, and reflects light passing through the partial range to partially cover the image space. A focus detection device, which is a reflection member for reflecting. 8. The focus detection device according to claim 1, wherein the optical element is disposed in an image space of the photographing optical system, and refracts light passing through the partial range to divide the image space into a plurality. A focus detection device, comprising: 9. The focus detection device according to claim 1, wherein the optical element has a lens principal point outside an optical axis of the imaging optical system, and forms a tilt image of the light passing through the partial range. And a decentering lens for dividing an image space into a plurality of parts. 10. An imaging device comprising the focus detection device according to claim 1, wherein the image information photoelectrically converted by the plurality of imaging elements is
An image pickup apparatus, comprising: an image synthesizing unit that synthesizes images according to a positional relationship in an image space before division to obtain image information of a subject image.