JPH10161012A - Focus detector and image pickup device having focus detecting function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To directly detect a focusing state on an image pickup scene by providing a focus detecting means for detecting the focusing state of an image pickup optical system based on displacement detected by a displacement detecting means. SOLUTION: The image pickup optical system 1 forms light from a subject into an image. An optical element 2 is arranged on the image space side of the optical system 1 and divides the image space by dividing the light to transmitted light and reflected light in accordance with incident light. Plural image pickup means 3a and 3b are individually arranged in every image space divided into plural by the optical element 2, and an optical image divided and formed in every image space is picked up. The displacement detecting means 4 fetches image information from the means 3a and 3b and detects the displacement between the respective pieces of image information. The focus detecting means 5 detects the focusing state of the optical system 1 based on the displacement detected by the detecting means 4. Thus, the focusing state on the image pickup surfaces of the means 3a and 3b is directly detected.

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 pupil division 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 a point that is done.

[0002]

2. Description of the Related Art Conventionally, cameras and other optical apparatuses are equipped with a focus detection device of a pupil division phase difference detection system for detecting a focus adjustment state. FIG. 23 is a diagram showing an electronic camera equipped with this type of focus detection device. FIG.
In 3, a lens barrel 62 is attached to the front of a camera body 61, and a photographing optical system 63 is disposed 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. 24 is an exploded perspective view showing the internal configuration of the focus detection unit 66. In FIG. 24, a lens holder 71 is provided on the upper surface of the focus detector 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 tilted and imaged through the separator lenses 78a and 78b, and form a set of light images on the imaging surface of the image sensor 79. Here, the image sensor 79 photoelectrically converts the set of light images. The microprocessor 68 captures the photoelectric output of the image sensor 79.

The microprocessor 68 performs a well-known correlation operation on the photoelectric output to detect the image interval of a set 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 the amount of deviation between the imaging surface and the optical image (hereinafter, referred to as “defocus amount”) by multiplying the amount of deviation 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, and the light beam passing through the photographing optical system 63 directly reaches the image pickup surface of the image pickup section 70, and To form Imaging unit 70
Performs photoelectric conversion of the subject image and outputs an image signal to an image recording unit and a display unit (not shown).

[0011]

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. By performing focus detection on the primary imaging plane, a focus adjustment state (for example, a defocus amount or the like) on the imaging plane is indirectly estimated. Therefore, if a mounting error of the focus detection unit 66 or the imaging unit 70 or a secular change of the mounting position occurs and the positional relationship between the imaging surface and the primary imaging surface is slightly shifted, the focus detection accuracy is reduced. There was a problem that it would.

Further, the conventional focus detection device cannot receive the photographing light beam when the mirror is raised. for that reason,
There has been a problem that the focus adjustment state at the moment of photographing cannot be directly detected. As a result, there is a problem that the in-focus state shifts during the release time lag.

Further, in a general electronic camera, an image pickup device of about 1/2 to 1/3 inch is used as the image pickup section 70. Such an electronic camera has a photographing screen several times smaller than a 35 mm silver halide camera or the like, and has a small pixel pitch of about 10 μm or less, so that the diameter of the permissible circle of confusion on the imaging surface is small. Therefore, if a focus detection unit for a 35 mm camera is used as it is in the optical system of such an electronic camera, the focus detection accuracy may be insufficient and the focus accuracy may be insufficient.

In the conventional focus detection device, when performing focus detection for a plurality of focus detection areas, it is necessary to provide optical paths corresponding to the internal optical paths of the focus detection section 66 by the number of focus detection areas. Therefore, in this type of focus detection device, there is a problem that the size of the device is increased. Further, in the conventional focus detection device, the focus detection area is structurally fixed. Therefore, when continuously changing the position of the focus detection area, it was necessary to mechanically move the focus detection unit. In such an apparatus, a drive mechanism for the focus detection unit and the like must be separately provided, and there is a problem that the apparatus is increased in size. Further, there is also a problem that it is very difficult to keep the positional relationship between the imaging plane and the primary imaging plane constant when the focus detection unit moves.

Therefore, according to the first and second aspects of the present invention,
In order to solve the above-mentioned problems, it is an object of the present invention to provide a focus detection device capable of directly detecting a focus adjustment state on an imaging surface. A third aspect of the present invention is to provide a focus detection device capable of detecting a focus adjustment state at every corner of a shooting screen, in addition to the object of the first aspect.

A fourth object of the present invention is to provide, in addition to the object of the first embodiment, a focus detecting device capable of detecting a focus adjustment state of a specific subject.
A fifth object of the present invention is to provide a focus detecting device capable of freely changing a detection target of a focus adjustment state, in addition to the object of the fourth object. An object of the invention described in claim 6 is to provide a focus detection device suitable for using a color imaging element, in addition to the object of claim 1.

According to a seventh aspect of the present invention, in addition to the object of the sixth aspect, there is provided a focus detection device capable of detecting a focus adjustment state with higher accuracy when a color image pickup device is used. The purpose is to do. An object of the invention described in claim 8 is to provide a focus detection device suitable for using an image pickup device in which spatial pixels are shifted, in addition to the object of claim 1.

According to a ninth aspect of the present invention, in addition to the object of the first aspect, there is provided an imaging apparatus capable of easily realizing a high resolution, a high S / N, or a large screen of a photographing screen. The purpose is to: A further object of the present invention is to provide, in addition to the object of the ninth aspect, an imaging device capable of appropriately determining the charge accumulation time of the imaging device.

[0019]

FIG. 1 is a block diagram showing the principle corresponding to the first aspect of the present invention. Hereinafter, means for solving the problem will be described with reference to FIG. According to the first aspect of the present invention, a photographing optical system 1 for forming an image of light from a subject and an image space side of the photographing optical system 1 which divides light into transmitted light and reflected light according to an incident angle. An optical element 2 for dividing an image space, a plurality of image pickup means 3a and 3b individually arranged for each of the plurality of image spaces divided by the optical element 2, and for picking up an optical image divided and formed for each image space; A displacement detecting means 4 for taking in image information from the imaging means 3a and 3b and detecting a displacement between the image information, and a focusing state of the photographing optical system 1 based on the displacement detected by the displacement detecting means 4. And a focus detection means 5 for detecting.

FIG. 2 is a diagram for explaining the second aspect of the present invention. According to a second aspect of the present invention, in the imaging device according to the first aspect, the optical element 2 is an optical prism 6 having a gap 6c on an optical path of the photographing optical system 1, and the gap 6
c is a gap formed in the gap between the prism cross sections 6a and 6b inclined with respect to the optical path.

FIG. 3 is a diagram for explaining the third aspect of the present invention. According to a third aspect of the present invention, in the focus detection device according to the first or second aspect, the imaging optical system 1 is provided.
Is characterized in that the optical system is an optical system in which the image space side is substantially telecentric. The photographing optical system 1 here
Is not limited to an optical system that forms a telecentric system in a strict sense, and an imaging optical system whose exit pupil is sufficiently separated from the size of the imaging screen may be substantially used. For example, using a shooting lens for a 35 mm camera,
A case where an optical image is formed on an image sensor of about inches is also included.

According to a fourth aspect of the present invention, in the focus detection apparatus according to any one of the first to third aspects,
The displacement detection means 4 is characterized in that the detection range is limited to a focus detection area provided in the photographing screen of the imaging means 3a, 3b, and the displacement of the image information is detected. FIG. 4 is a diagram for explaining the invention described in claim 5.

According to a fifth aspect of the present invention, in the focus detecting apparatus of the fourth aspect, there is provided an operating means 7 for selecting, moving or reducing / enlarging the focus detection area by an external input. According to a sixth aspect of the present invention, in the focus detection device according to any one of the first to fifth aspects, a color filter in a predetermined color system is provided on the imaging surfaces of the imaging units 3a and 3b. The displacement detecting means 4 is characterized by extracting or synthesizing a predetermined color component of the image information and detecting the displacement of the color component.

According to a seventh aspect of the present invention, in the focus detection device of the sixth aspect, the image pickup means 3a and 3b are arranged such that at least one of the color filters is continuously arranged in a vertical direction, a horizontal direction, or an oblique direction. The displacement detecting means 4 detects the displacement of the image information along the continuous direction of one color. FIG. 5 is a principle block diagram corresponding to the invention described in claim 8.

According to a eighth aspect of the present invention, in the focus detection apparatus according to any one of the first to seventh aspects,
The plurality of imaging units 3a and 3b are configured such that spatial pixel shifting is performed on the pixel arrangement on the imaging surface, and the displacement detecting unit 4 corrects the positional shift of the image information due to the spatial pixel shifting by weighting addition in pixel units. It is characterized by comprising a pixel correcting means 4a and a detecting means 4b for detecting a displacement between the image information corrected by the pixel correcting means 4a.

FIG. 6 is a block diagram showing the principle corresponding to the ninth aspect of the present invention. According to a ninth aspect of the present invention, there is provided an imaging apparatus including the focus detection device according to any one of the first to eighth aspects, wherein the plurality of imaging means 3 are provided.
An image synthesizing means 8 for synthesizing image information photoelectrically converted by a and 3b in accordance with a positional relationship in an image space before division to obtain image information of a subject image is provided.

According to a tenth aspect of the present invention, in the imaging apparatus of the ninth aspect, the imaging means 3a, 3b is a charge accumulation time for accumulating photocharges in accordance with a state transition between focus detection and photographing. Is changed.

(Function) In the focus detecting device according to the first aspect, the optical element 2 is arranged on the image space side of the photographing optical system 1. The optical element 2 divides light into reflected light and transmitted light according to the incident angle of the light.

By the optical action of the optical element 2 as described above,
The image space of the photographing optical system 1 partially changes direction, and the image space is divided into a plurality. The imaging units 3a and 3b are individually arranged for each of a plurality of divided image spaces, and capture an optical image formed for each image space. Here, a group of light beams converging on each point on the photographing screen is considered. It is assumed that a part of such a light beam group is divided via the optical element 2 while maintaining a complete light beam shape. These light flux groups converge in one image space to which the light is to be distributed, and form a part of the light image as it is.

On the other hand, the other light beam group is a light beam group in which the light beam cross section is divided (pupil division) according to the incident angle. These light flux groups form a plurality of light images for each image space to which the light is to be distributed. Therefore, an optical image that should originally be one is formed over a plurality of image spaces. Hereinafter, the region where the optical images are formed so as to overlap is referred to as “overlap region”. (Although the case where the overlapping area is formed in a part of the shooting screen is described here, the entire area of the shooting screen may be the overlapping area in the present invention.) FIG. 3 is a diagram showing a point image of an overlapping area in each focus adjustment state.

In the focused state, as shown in FIGS. 7A to 7C, a light beam to be converged at one point is distributed to the overlapping areas β1 and β2 via the optical element 2. These overlapping areas β1,
At β2, the light flux after distribution converges on each, so that point images are individually formed. In the rear focus state, FIG.
As shown in (a) to (c), a light beam to form a circular blurred image is distributed to the overlapping areas β1 and β2 via the optical element 2. In these overlapping areas β1 and β2, 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 circular blurred image is distributed to overlapping areas β1 and β2 via the optical element 2. In these overlapping areas β1 and β2, 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 image pickup means 3a, 3
Before arriving at b, the light flux is once converged, and the left and right (or up and down) of the blurred image is reversed, so that a semicircular blurred image is formed in the opposite direction to the back focus state. FIG. 10 is a diagram illustrating these blur shapes for each focus adjustment state.
In the focused state, as shown in FIG.
Since the optical image is similarly formed at 1, β2, the relative displacement of the optical image becomes zero.

In the back focus state, as shown in FIG. 10B, a semicircular blurred image is formed in each of the overlapping areas β1 and β2, so that the displacement of the center of gravity of the light image (FIG. Ρ)
Occurs. Further, in the front focus state, as shown in FIG. 10C, a semicircular blurred image is formed in each of the overlapping areas β1 and β2, so that the displacement of the center of gravity of the optical image (− in FIG. 10).
ρ) occurs.

Here, in the rear focus state and the front focus state, since the direction of the blur shape is opposite, the displacement of the center of gravity of the optical image has the opposite value in the positive and negative directions. The displacement detecting means 4 detects such a displacement of the light image. The focus detecting means 5 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 from the in-focus state (for example, the amount of defocus) can be detected from the magnitude of the displacement.

According to the operation described above, the present invention makes it possible to directly detect the focus adjustment state of the imaging surfaces of the imaging means 3a and 3b. 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, the imaging light beam can be received on the imaging surface which is the focus detection surface, so that 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 means 3a, 3b, the focus adjustment state can be detected with appropriate accuracy.

In the focus detecting device according to the second aspect, an optical prism 6 having a gap 6c is arranged as the optical element 2. Here, assuming that the relative refractive index between the optical prism 6 and the medium in the gap 6c is nd, the critical angle φ of total reflection in the gap 6c is calculated by the following equation (1). Critical angle φ = sin ⁻¹ (1 / nd) (1) Light incident at an angle larger than this critical angle φ is totally reflected at prism cross section 6a (A in FIG. 2).

On the other hand, most of the light (for example, 96% or more) incident at an angle smaller than the critical angle φ is transmitted through the prism cross section 6a and becomes refracted light. This refracted light reaches the prism cross section 6b and is refracted in the opposite direction, and travels in the original traveling direction (B in FIG. 2). By such an optical action,
The optical prism 6 can divide light into reflected light and transmitted light with the critical angle φ as a boundary.

The condition for generating total reflection is that the relative refractive index nd is "1" or more, so that the medium in the gap 6c is not limited to air or vacuum. In the focus detecting device according to the third aspect, a telecentric system is formed substantially on the image space side by the optical action of the photographing optical system 1. Here, the substantially telecentric system is an optical system in which the principal ray (Pr in FIG. 3) of the emitted light beam is uniformly and substantially parallel on the image space side.

As such an optical system, it is sufficient that the exit pupil is sufficiently separated from the size of the photographing screen. For example, using an interchangeable lens for a 35 mm camera,
An optical system that forms an optical image on the small light receiving surface of the image sensor may be used. In such a photographing optical system 1, all the principal rays Pr reaching the photographing screen enter the optical element 2 at almost the same incident angle. Therefore, except for the effects of vignetting,
Pupil division by the optical element 2 occurs almost uniformly over the entire area of the photographing screen. As a result, as shown in FIG. 3, an overlapping area is formed over almost the entire area of the photographing screen.

Normally, in the structure of the first aspect, a part of the photographing screen is an overlapping area. Since focus detection can be performed in this overlapping area, the focus detection area is limited to a part of the shooting screen. However, in the configuration of the third aspect, by forming the telecentric system substantially on the image space side, the overlapping area is expanded to almost the entire area of the photographing screen. As a result, it is possible to detect the focus adjustment state all over the shooting screen.

In the focus detecting device according to the fourth aspect, the displacement detecting means 4 detects the displacement of the image information by limiting the detection range to the focus detecting 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, even when the overlapping area is widened, it is possible to strictly perform focus detection while aiming at a narrow range.

The focus detecting device according to the fifth aspect is provided with an operating means 7 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 varies depending on the type of the photographing optical system 1, the open F value, and the like. Therefore, it is possible to always secure an appropriate focus detection area by reducing and enlarging the focus detection area in response to an external input such as an open F value.

In the focus detecting device according to the sixth aspect, a predetermined color system (for example,
Color filters of an RGB color system, a YIQ color system, a complementary color system, etc.) are mixed and arranged in pixel units. In such a case,
The displacement of the light image cannot be detected by comparing different color components.

Accordingly, the displacement detecting means 4 extracts or combines specific color components to generate 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 detection device according to the seventh 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 way, a line sensor is equivalently constructed in the continuous direction of one color. The displacement detecting means 4 detects the displacement of the image information along this continuous direction. By 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 detecting device according to the eighth aspect, the pixel arrangement of the plurality of imaging means 3a and 3b is shifted by spatial pixels. On the other hand, the pixel correction means 4a corrects the positional shift of the image information due to the spatial pixel shift by weighted addition in pixel units. The detecting means 4b detects the displacement between the image information thus corrected.

Therefore, it is possible to perform focus detection irrespective of the positional shift of the image information due to the spatial pixel shift. In the imaging apparatus according to claim 9, claim 1 is
9. A focus detection device according to any one of (1) to (8), and an image synthesizing unit 8.

The image synthesizing means 8 takes in the photoelectric outputs from the plurality of imaging means 3a and 3b in the focus detecting device. The image synthesizing means 8 synthesizes these pieces of image information according to the positional relationship in the image space before division, and synthesizes image information of the subject image. With such a configuration, an imaging device having a focus detection function can be easily realized.

In the image pickup apparatus according to the tenth aspect, the image pickup means 3a and 3b change the charge accumulation time between the time of focus detection and the time of photographing. Normally, when the underexposure or underexposure occurs in the image information at the time of focus detection, it becomes impossible to determine the difference between the image patterns, and thus the focus detection is hindered. Also,
The charge accumulation time at the time of photographing should be manually or automatically determined according to the photographing intention, an appropriate exposure value, and the like.

In such a situation as described above, the method of determining the charge storage time is switched according to the state transition between the time of focus detection and the time of photographing, so that proper charge storage is performed in either state. It becomes possible.

[0054]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 11 is a diagram showing an embodiment corresponding to the first to ninth aspects. FIG. 12 is an explanatory diagram illustrating the configuration of the optical prism 14 according to the present embodiment. In these figures, a photographing lens 12 is attached to an image pickup apparatus 11, and an aperture 13 is arranged near an object-side focal point of the photographing lens 12. On the image space side of the taking lens 12, an optical prism 14 is arranged.

The optical prism 14 is made of optical glass having a shape obtained by diagonally dividing a cube. Between these optical glasses, a metal flake 1 having a thickness several times the visible wavelength or more is placed.
4d, the gap 1 between the prism cross sections
4c is formed. When a general borax crown glass (BK7) is used as the material of the optical glass, the gap 14
The relative refractive index nd with c is about 1.52. In this case, the critical angle φ of total reflection in the gap 14c is about 41 °.

The image sensor 15a is arranged in the direction of light reflection by the space 14c, and the image sensor 15b is arranged in the direction of light transmission. These imaging devices 15a and 15b
4c is disposed at a mirror-related position with respect to 4c. The ratio between the amount of transmitted light and the amount of reflected light can be freely adjusted by changing the critical angle φ and the inclination angle of the gap 14c. For example, when the transmitted light amount and the reflected light amount are made substantially equal, the “angle formed by the gap 14c and the main plane of the photographing lens 12” and the critical angle φ may be set to be equal. Thus, even when the inclination angle of the gap 14c is changed, the optical prism 14 is maintained so as to maintain the mirror relationship with the gap 14c interposed therebetween.
Are formed on the bottom and side surfaces, and the image sensor 1
What is necessary is just to arrange | position 5a, 15b.

The output of the image sensor 15a arranged as described above is connected to the pixel interpolation unit 17 and the area extraction unit 18 via the first storage unit 16a. Also, the image sensor 15b
Is connected to the pixel interpolation unit 17 and the area extraction unit 18 via the second storage unit 16b. The output of the pixel interpolation unit 17 is connected to the output control unit 21 via the image synthesis unit 19 and the image storage unit 20, and the output of the output control unit 21 is
It is connected to the image output terminal 22 and the display unit 23.

On the other hand, the output of the area extraction unit 18 is connected to a focus detection calculation unit 26 via a weighting addition unit 24 and an image shift calculation unit 25. An output of the focus detection calculation unit 26 is connected to a focus control unit 27 and a release control unit 30. The focus control unit 27 drives the photographing lens 12 and the aperture 13 forward and backward via a focus driving mechanism 28. When the focus control operation is completed, the focus control unit 27 turns on a focusing LED (not shown).

A release button 29 is provided on the housing of the imaging device 11, and a switch output of the release button 29 is connected to the area extraction unit 18 and the release control unit 30. The output of the release control unit 30 is
And the image sensor 15b. The release control unit 30 controls the imaging device 15 during focus detection.
The electronic shutters a and 15b are repeatedly driven. The charge storage time of these electronic shutters is sequentially controlled to a time that minimizes the loss of white and black of the image based on the image information of the previous time.

On the other hand, at the time of photographing, the charge accumulation time of the electronic shutter is determined according to the exposure value set manually or the exposure value automatically determined by an exposure control unit (not shown). The housing of the imaging device 11 is provided with an area selector 31 which is a pointing device for manually selecting a focus detection area.
Is connected to the area extracting unit 18.

Incidentally, as for the correspondence between the invention described in claim 1 and the present embodiment, the photographing optical system 1
2, the optical element 2 corresponds to the optical prism 14,
The imaging units 3a and 3b correspond to the imaging devices 15a and 15b and the release control unit 30, the displacement detection unit 4 corresponds to the image shift calculation unit 25, and the focus detection unit 5 corresponds to the focus detection calculation unit 26.

As for the correspondence between the invention described in claim 2 and the present embodiment, the optical prism 6 is
, And the gap 6c corresponds to the gap 14c. Claim 3
The imaging optical system 1 corresponds to the imaging lens 12 and the aperture 13.

The correspondence between the invention described in claim 4 and the present embodiment is as follows.
8 and the image shift calculator 25. Regarding the correspondence between the invention described in claim 5 and the present embodiment, the operation unit 7 corresponds to the area selection unit 31. Regarding the correspondence between the invention described in claims 6 and 7 and the present embodiment, the displacement detecting means 4 includes the area extracting section 18 and the image shift calculating section 2.
Corresponding to 5.

As for the correspondence between the invention described in claim 8 and the present embodiment, the pixel correction means 4a corresponds to the weighting addition section 24, and the detection means 4b corresponds to the image shift calculation section 25. Regarding the correspondence between the present invention described in claims 9 and 10 and the present embodiment, the image synthesizing means 8
7 and the image synthesizing unit 19.

FIGS. 13 and 14 are flowcharts showing the operation of the present embodiment. Hereinafter, the operation of the present embodiment will be described with reference to these drawings. The aperture 13 is arranged near the object-side focal point of the taking lens 12. Therefore, this aperture 13
All the principal rays of the light beam group passing through the (entrance pupil) pass through the object-side focal point of the photographing lens 12. When such a principal ray passes through the photographing lens 12, all the principal rays on the image space side are parallel.

By the above optical action, a telecentric system is formed on the image space side of the taking lens 12, as shown in FIG. In such a telecentric system, the light beam group reaches the air gap 14c at a uniform incident angle. The air gap 14c bisects these uniform light flux groups into reflected light and transmitted light with the total reflection angle φ (for example, 41 °) as a boundary.

Here, the reflected light reaches the image pickup surface of the image pickup device 15a to form a light image. The other transmitted light reaches the imaging surface of the imaging element 15b and forms an optical image. In this state, when the release button 29 is half-pressed (step S
1), the release control unit 30 includes the imaging devices 15a and 15b
Unnecessary photocharges on the imaging surface are once removed to start accumulation of photocharges (step S2).

Here, when the charge accumulation time at the time of focus detection has elapsed (step S3), the imaging devices 15a and 15b individually output a set of image information according to a command from the release control unit 30. Note that the charge accumulation time at the time of focus detection uses the initial setting value for the first time, and the second and subsequent times are sequentially controlled based on the image information for the previous time to a time at which no white or black loss occurs in the image. Is done.

Generally, since the division ratio of the light beam in the air gap 14c is not equal, the average luminance level of a set of image information is slightly shifted. Therefore, the first storage unit 16a and the second
The storage unit 16b performs gain correction on the deviation of the average luminance level according to the division ratio, and stores the corrected image information (step S4). In addition, when the inclination angle of the air gap 14c and the like are set appropriately and the division ratio of the light beam is set to be equal, the gain correction here can be omitted.

Further, in the first storage section 16a, the image information is reversed left and right in order to restore the image information captured in the mirror image state (step S5). Here, the area extracting unit 18 captures the output of the area selecting unit 31 and detects the manually selected focus detection area. FIG. 15 (a)
FIG. 4 is a diagram showing an example of the arrangement of focus detection areas. In this arrangement example, the focus detection areas (P in the figure) are arranged 5 × 3 in the photographing screen (S in the figure). One of these focus detection areas P is manually selected via the area selector 31.

The area extracting section 18 reads out the pixel rows (Q in the drawing) in the selected focus detection area P from the first storage section 16a and the second storage section 16b, respectively (step S6). The pixel row Q may be set so as to protrude from the focus detection area P as shown in FIG. Next, the area extracting unit 18 extracts a specific color component from these pixel rows (Step S7).

This extraction method is based on the image pickup devices 15a, 15b
For example, the following is determined according to the color filter arrangement of In FIGS. 16A and 16B, specific color components are continuously arranged. The image shift calculator 25 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 image shift due to defocus, the specific color component is arranged in parallel with the pupil division direction by the optical prism 14. Is preferred. FIG.
FIG. 6C shows a case where specific color components are arranged at regular intervals in the direction of image shift due to defocus. The image shift calculator 25 extracts the specific color component by thinning it out at regular intervals.

Further, in FIG. 16D, 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 combined to specify the color filter array. Is obtained. FIG. 17 (e)
Then, the color filter array is divided into 3 × 2 small blocks.
At this time, the small blocks are divided so as to overlap the left and right small blocks by half and to be arranged in a stepped manner. Color components in this small block (same color components or different color components)
Are combined to obtain a specific color component.

Next, the weighting and adding unit 24 performs weighting addition on the pixel columns in response to the case where the pixel positions of both pixel columns do not match (step S8). The method of such weighted addition is determined, for example, as follows according to the pixel arrangement of the imaging elements 15a and 15b. FIG.
In (α), the pixel arrangements of the imaging elements 15a and 15b match within an allowable range. Therefore, when the pixel row is composed of one row, as shown in FIG. 18 (β), the pixel row having the same pixel arrangement is selected as it is. When the pixel column is composed of a plurality of columns, uniform weighting is performed on each column as shown in FIG. In addition, the weight of the central row (c) is increased,
The weights of the peripheral portions (b) and (d) may be reduced.

In FIG. 19 (a), the image pickup devices 15a, 15
In order to apply a spatial pixel shift to b, the pixel arrangement is shifted by about 画素 pixel in the y direction. Therefore, when the pixel row is composed of one row, as shown in FIG. 19 (β), a pixel row with the least deviation in the y direction is selected. When the pixel column is composed of a plurality of columns, as shown in FIG.
Ｆf are added. As the coefficients a to f, for example, the following values are used.

A = 1/2 b = 1 c = 1/2 d = 1 e = 1 f = 0 In FIG. 20 (a), the pixel arrangements of the imaging elements 15 a and 15 b match within an allowable range, and The pupil division direction by the prism 14 is parallel to the oblique direction of the pixel arrangement. Therefore,
When the pixel row is composed of one row, as shown in FIG. 20 (β), the pixel row in the oblique direction is selected as it is. When the pixel column is composed of a plurality of columns, as shown in FIG. 20 (γ), appropriate weighting is performed on each column in the oblique direction.

Further, the pixel arrangement shown in FIG. 20 (α) may be weighted as shown in FIG. The image shift operation unit 25 performs, for example, the following correlation operation on a set of pixel rows subjected to such processing. First, while shifting one pixel row by a predetermined interval,
A difference from the other pixel row is obtained, and a sum of absolute values of the difference is obtained.

The value of the predetermined interval at which the sum is minimized is calculated by the interpolation method with an accuracy equal to or less than the sample pitch, thereby calculating the displacement ρ of the center of gravity of a set of pixel rows (step S9). The focus detection calculation section 26 can determine the focus position as follows based on the sign of the displacement ρ of the center of gravity. That is, as shown in FIG. 10B, when the displacement ρ of the center of gravity has a positive sign, it can be determined that the back focus state.

As shown in FIG. 10 (a), when the displacement ρ of the center of gravity becomes zero, it can be determined that the object is in focus.
Further, as shown in FIG. 10C, when the displacement ρ of the center of gravity is a negative sign, it can be determined that the front focus state. next,
The focus detection calculation unit 26 calculates DF = ρ · K (2) according to the center-of-gravity displacement amount ρ to obtain the defocus amount DF (step S1).
0).

Here, the value of the coefficient K is given by: K ≒ 1 / ω (3) where ω (radian) is the angle at which the center of gravity of the divided exit pupil is viewed from the center of the photographing screen. It is a value represented by an expression. However, the actual value of K is determined based on actual measurement, optical path simulation, and the like.

Further, the displacement ρ of the center of gravity of the divided exit pupil
Depends on the aperture amount of the taking lens 12 and the like. Therefore, when the aperture value or the like changes, an appropriate coefficient K according to the aperture value may be determined by preparing a table or an expression for determining the value of the coefficient K depending on the aperture value or the like in advance. Good.

Strictly speaking, the value of the coefficient K is a function of the displacement ρ of the center of gravity. Therefore, by diverting the operation formula in the known phase difference detection method, the coefficient K can be changed to the displacement ρ
May be corrected. Here, the defocus amount DF
Exceeds a predetermined threshold (step S11), the focus control unit 27 moves the photographing lens 12 forward and backward based on the defocus amount DF, and executes focus control (step S12). Such focus control is returned to step S2 and repeated.

On the other hand, when the defocus amount DF is equal to or smaller than the predetermined threshold value (step S11), the focus control section 27 turns on the focusing LED (step S13). In this state, when the release button 29 is fully pressed (step S14), the release control unit 30 once eliminates unnecessary photocharges on the imaging surfaces of the imaging elements 15a and 15b, and starts accumulation of photocharges. (Step S15).

Here, when the charge accumulation time during photographing has elapsed (step S16), the imaging devices 15a and 15b individually output a set of image information according to a command from the release control unit 30. The release control unit 30 determines the charge accumulation time at the time of photographing based on an exposure value set manually or an exposure value automatically set by the exposure control unit or the like.

Generally, since the division ratio of the light beam in the air gap 14c is not equal, the average luminance level of a set of image information is slightly shifted. Therefore, the first storage unit 16a and the second
The storage unit 16b performs gain correction on the deviation of the average luminance level according to the division ratio, and stores the corrected image information (step S17). Further, in the first storage unit 16a, in order to restore image information captured in a mirror image state,
The left and right of the image information is reversed (step S18).

In this state, the pixel interpolation unit 17 starts the process of synthesizing the image information as follows. FIG. 22 is a diagram illustrating the data flow of the combining process. Here, the operation of the combining process will be described on the assumption that spatial pixels are shifted in two directions in the vertical and horizontal directions. Note that the same processing as described below is performed for each primary color for the color image sensor.

First, the pixel interpolation unit 17 performs pixel interpolation by applying an interpolation operator to each of the pixels (a11 to a33) of one of the pieces of image information, and obtains a pixel (a) that is positioned vertically and horizontally and obliquely to each pixel. ). In addition, the pixel interpolation unit 17
Performs similar pixel interpolation for each pixel (b11 to b33) of the other image information, and obtains a pixel (b) vertically and horizontally and diagonally positioned for each pixel (step S19).

Next, the image synthesizing unit 19 adds the interpolated image information for each corresponding pixel, and stores it in the image storage unit 20 (step S20). The output control unit 21 reads out the combined image information from the image storage unit 20 and sequentially outputs it to the outside (Step S21). By the operation described above, an imaging device having a focus detection function and a focus adjustment function is realized.

Particularly, in the present embodiment, the image pickup device 1
The amount of defocus on the imaging surfaces 5a and 15b is 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. In addition, since the focus adjustment state at the moment of photographing can be directly detected, it is possible to reliably solve the problem that the focus state is lost during the release time lag.

Further, image information for focus detection is taken in according to the resolution of the imaging elements 15a and 15b.
The focus adjustment state can be detected with appropriate accuracy according to the image quality. In addition, since the focus detection area is selected by an external operation, it is possible to focus on the target subject even when the shooting target is out of the center of the screen.

Further, since a specific color component is extracted and image information for focus detection is generated, displacement of a color image can be reliably detected. In addition, a plurality of image sensors 15
Since one imaging screen is imaged by combining a and 15b, the resolution of the imaging 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 image storage unit 20 is provided to temporarily store the image information being combined, but the present invention is not limited to this configuration. For example, the image storage unit 20 may be omitted, and the image information being combined may be directly stored in a memory card or other external storage medium. In the above-described embodiment, air or vacuum is used as a medium in the gap 14c, but the present invention is not limited to this configuration. Generally, if the relative refractive index between the optical prism and the gap is “1” or more, total reflection occurs in the gap. Therefore, any medium that satisfies this condition can be placed in the gap.

Further, in the above-described embodiment, the gap 14
Although c is set at an angle of 45 °, the present invention is not limited to this configuration. For example, the angle between the main plane of the taking lens and the gap may be about 41 °. In such a configuration, the light can be almost equally divided into the reflected light and the transmitted light with the incident light parallel to the optical axis of the taking lens as a boundary. Also,
The inclination angle of the air gap 14c such that the amount of reflected light and the amount of transmitted light are equal may be determined based on actual measurement. With such a configuration, the average luminance levels of a set of image information can be equalized.

Further, in the above-described embodiment, the relative refractive index of the optical prism 14 is set to about 1.52, but the present invention is not limited to this configuration. For example, when the relative refractive index of the optical prism 14 is about 1.41, the critical angle φ of total reflection can be made exactly 45 °. In such a configuration, an incident light beam parallel to the optical axis of the photographing lens is used as a boundary.
Light can be divided equally into reflected light and transmitted light. Therefore, the average luminance levels of a set of image information can be equalized.

Further, in the above-described embodiment, the charge storage time of the imaging devices 15a and 15b is controlled by the electronic shutter. However, the present invention is not limited to this configuration. For example, the charge accumulation time may be controlled using a mechanical shutter or the like. Further, in the above-described embodiment, the focus priority mode (the photographing is started after the focus state is reached)
Is described, but the present invention is not limited to this configuration. For example, an operation of a shutter priority mode (detecting full release of the release and starting shooting regardless of focusing) may be performed, or both modes may be manually selected by an external selection member. Good.

[0098]

As described above, according to the first aspect of the present invention, the focus adjustment state of the imaging surface of the imaging means is directly detected. Therefore, it is possible to directly know the actual focus adjustment state of the shooting screen without going through a virtual plane such as a primary imaging plane. Since focus detection is performed on the imaging surface in this manner, it is possible to solve the conventional problem that focus detection accuracy is reduced due to an error in mounting the focus detection unit and the imaging unit.

Further, it is possible to solve the problem that the focus detection accuracy is gradually reduced due to aging of the mounting position of the focus detection unit and the imaging unit. In particular, it is possible to directly know the focus adjustment state at the moment when shooting is performed. Therefore, by performing the focus control based on the focus detection value at the moment when the photographing is performed, it is possible to solve 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 means, it is possible to detect the focus adjustment state with appropriate accuracy according to the image quality. Therefore, it is not particularly necessary to change the design of the focus detection unit according to the chip size of the imaging unit.
According to the second aspect of the present invention, an optical prism having an oblique gap is disposed as the optical element. By the optical action of this gap, incident light from the imaging optical system can be divided into reflected light or transmitted light according to the incident angle.

According to the third aspect of the present invention, since a substantially telecentric system is formed on the image space side, all principal rays on the image space side enter the optical element at substantially the same incident angle. Therefore, excluding the influence of vignetting and the like, pupil division by the optical element occurs almost uniformly over the entire area of the photographing screen. Therefore, by forming a substantially telecentric system on the image space side, the overlapping area can be extended to almost the entire area of the photographing screen. As a result, it is possible to detect the focus adjustment state at every corner of the shooting screen.

According to the fourth aspect of the present invention, since a part of the overlapping area is used as the focus detection area, focus detection can be performed 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 fifth aspect of the present invention, since the focus detection area can be appropriately selected, moved, or reduced / enlarged, the target subject can be freely captured as a focus detection target.

According to the fifth aspect of the present invention, the focus detection area can be set freely within the overlapping area. Therefore, unlike the conventional pupil division phase difference detection method, it is not particularly necessary to set the number of focus detection optical paths equal to the number of focus detection areas. Even when a large number of focus detection areas are provided, the apparatus may become large. There is almost no.

Further, the position of the focus detection area can be continuously moved within the overlapping area. Therefore, unlike the related art, it is not particularly necessary to provide a drive mechanism for mechanically moving the focus detection unit, and there is no possibility that the apparatus is increased in size. According to the invention described in claim 6, specific color components are extracted or combined to generate image information for focus detection. Therefore, even when the color image pickup device is used, the displacement of the light image can be reliably detected.

According to the seventh aspect of the present invention, a single-color line sensor is equivalently constructed 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 eighth aspect of the invention, the positional shift of the image information due to the spatial pixel shift is corrected by weighted addition in pixel units. For this reason, even when using an imaging unit in which the spatial pixels are shifted, the displacement of the optical image can be reliably detected.

According to the ninth aspect of the present invention, image information taken by a plurality of image pickup means is synthesized. Here, when a plurality of imaging units are shifted in spatial pixels, the resolution of a shooting screen can be increased as compared with a case where a single imaging unit is used. Further, when the plurality of imaging units are not subjected to the spatial pixel shift, when adding the image information for each corresponding pixel, the noise component generated in the plurality of imaging units in a non-correlation manner is reduced as compared with the signal component. Therefore, the S / N of the image information can be increased as compared with the case where a single imaging unit is used.

Further, when the overlapping area is limited to a part of the screen, the photographing screen can be enlarged right and left (or up and down) as compared with the case where a single image pickup means is used. According to the tenth aspect of the present invention, the charge accumulation time of the imaging unit is changed in accordance with the state transition between the time of focus detection and the time of shooting.

For example, the charge accumulation time at the time of focus detection is set to “the time during which no blackout or blackout occurs in the image information”, and the charge accumulation time at the time of photographing is determined by “photographing intention, proper exposure value, and the like. Time ". As in this example, it is possible to flexibly cope with different circumstances at the time of focus detection and at the time of shooting, and to appropriately carry out charge accumulation.

As described above, in an electronic camera system or the like to which the present invention is applied, it is possible to directly detect a focus adjustment state on an 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 principle block diagram corresponding to the invention described in claim 1;

FIG. 2 is a diagram for explaining the invention described in claim 2;

FIG. 3 is a diagram for explaining the invention described in claim 3;

FIG. 4 is a diagram for explaining the invention described in claim 5;

FIG. 5 is a principle block diagram corresponding to the invention described in claim 8;

FIG. 6 is a principle block diagram corresponding to the invention described in claim 9;

FIG. 7 is a diagram showing a point image of an overlapping area in a focused state.

FIG. 8 is a diagram illustrating a point image of an overlapping area in a back focus state.

FIG. 9 is a diagram showing a point image of an overlapping area in a front focus state.

FIG. 10 is a diagram illustrating a blur shape in an overlapping area.

FIG. 11 is a diagram showing an embodiment corresponding to claims 1 to 9;

FIG. 12 is a perspective view illustrating a configuration of an optical prism 14 according to the present embodiment.

FIG. 13 is a flowchart showing the operation of the present embodiment.

FIG. 14 is a flowchart (continued) showing the operation of the present embodiment.

FIG. 15 is a diagram illustrating an example of an arrangement of a focus detection area.

FIG. 16 is a diagram illustrating selection of a color component.

FIG. 17 is a diagram illustrating selection of a color component.

FIG. 18 is a diagram illustrating a calculation example of weighted addition according to a pixel arrangement.

FIG. 19 is a diagram illustrating a calculation example of weighted addition according to a pixel arrangement.

FIG. 20 is a diagram illustrating a calculation example of weighted addition according to a pixel arrangement.

FIG. 21 is a diagram illustrating a calculation example of weighted addition according to a pixel arrangement.

FIG. 22 is a diagram for explaining a data flow of a combining process.

FIG. 23 is a diagram showing a conventional example.

FIG. 24 is an exploded perspective view showing a conventional focus detection unit.

[Explanation of symbols]

 Reference Signs List 1 shooting optical system 2 optical element 3a, 3b imaging means 4 displacement detection means 4a pixel correction means 4b detection means 5 focus detection means 6 optical prism 6a, 6b prism section 6c air gap 7 operation means 8 image synthesis means 11 imaging device 12 imaging lens Reference Signs List 13 aperture 14 optical prism 14c air gap 14d metal thin film 15a imaging device 15b imaging device 16a first storage unit 16b second storage unit 17 pixel interpolation unit 18 area extraction unit 19 image synthesis unit 20 image storage unit 21 output control unit 22 image output terminal Reference Signs List 23 display unit 24 weighting addition unit 25 image shift calculation unit 26 focus detection calculation unit 27 focus control unit 28 focus drive mechanism 29 release button 30 release control unit 31 area selection unit

Claims (10)

[Claims] 1. An imaging optical system that forms an image of light from a subject, disposed on an image space side of the imaging optical system, and divides light into transmitted light and reflected light in accordance with an incident angle to form the image space. An optical element to be divided; a plurality of image pickup units which are individually arranged for each of the image spaces divided by the optical element, and which pick up an optical image divided and formed for each image space; and image information from the plurality of image pickup units. And a displacement detecting means for detecting a displacement between the image information, and a focus detecting means for detecting a focus adjustment state of the photographing optical system based on the displacement detected by the displacement detecting means. A focus detection device. 2. The imaging device according to claim 1, wherein the optical element is an optical prism having a gap on an optical path of the photographing optical system, and the gap has a prism cross section inclined with respect to the optical path. A focus detection device, characterized in that the space is formed in a gap. 3. An image pickup apparatus according to claim 1, wherein said photographing optical system is an optical system having an image space side substantially telecentric. 4. The focus detection device according to claim 1, wherein the displacement detection unit limits a detection range to a focus detection area provided in a shooting screen of the imaging unit. A focus detection device for detecting a displacement of the image information. 5. The focus detection device according to claim 4, further comprising an operation unit for selecting, moving, or reducing or enlarging the focus detection area by an external input. 6. The focus detection device according to claim 1, wherein the imaging unit is configured to mix a color filter in a predetermined color system for each pixel on an imaging surface. A focus detection device, wherein the displacement detection means extracts or synthesizes a predetermined color component of the image information and detects a displacement of the color component. 7. The focus detection device according to claim 6, wherein the imaging unit is configured such that at least one color of the color filter is continuously arranged in a vertical direction, a horizontal direction, or an oblique direction, and the displacement detection unit. The focus detection device detects a displacement of the image information along the continuous direction of the one color. 8. The focus detection device according to claim 1, wherein the plurality of imaging units are configured such that a pixel arrangement on an imaging surface is shifted by a spatial pixel, and the displacement is The detecting unit includes a pixel correcting unit that corrects a position shift of image information due to the spatial pixel shift by weighted addition in pixel units, and a detecting unit that detects a displacement between the image information corrected by the pixel correcting unit. A focus detection device, comprising: 9. An imaging device comprising the focus detection device according to claim 1, wherein the image information photoelectrically converted by the plurality of imaging units 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. 10. The imaging apparatus according to claim 9, wherein the imaging unit changes a charge accumulation time for accumulating photocharges in accordance with a state transition between focus detection and photographing. Imaging device.