JP2002090619A - Focus detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always obtain a high-contrast subject image and to realize proper focus detection. SOLUTION: This focus detector is provided with a light-receiving means for receiving at least a pair of images using different optical systems, an arithmetic means calculating focus information based on a signal from the light- receiving means and an optical filter arranged at the prestage of the light- receiving means. Then, the optical separating direction (shown by arrow) of a pair of images and the same color (R, G and B) direction of the optical filter are made the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a focus detection device provided in a camera or the like.

[0002]

2. Description of the Related Art Conventionally, a technique for optically measuring a distance to an object existing in a plurality of directions has been disclosed in Japanese Patent Publication No. 4-676.
No. 07, for example. According to this technique, distance distribution information and defocus distribution information of an object existing in the object scene can be obtained, and it is possible to recognize an object arrangement state of the object scene from the distribution information.

In this method, a known correlation operation is performed between parallax images based on a pair of images with parallax obtained by photographing with a stereo camera or the like using a CCD image pickup device or the like. According to the principle, it is possible to measure the distance to the object and the defocus for each calculation area.
By performing these calculations for each area of the captured image in the same manner, distance and defocus distribution information can be obtained.

As another method, conventionally, as a focus detecting device of a TTL camera, the relative displacement of a plurality of subject images in which light beams coming from regions having different pupil positions of the photographing optical system are generated, based on the relative displacement of the photographing optical system. 2. Description of the Related Art A so-called pupil division type automatic focus detection device that detects a focus adjustment state is known. For example, this type of automatic focusing device is disclosed, which is constituted by a pair array of a lens array arranged near a primary image plane and a light receiving element array arranged immediately after the lens array. Further, a field lens arranged on the primary image plane, two re-imaging lenses for re-imaging an image formed on the primary image plane on the secondary image plane, and two image sensors arranged on the secondary image plane An autofocus device of this type, composed of an array, is disclosed.

A conventional technique will be described with reference to FIG.

In FIG. 1, reference numeral 101 denotes a photographing lens;
2 is a quick return mirror, 103 is a sub mirror, 1
04 is a field lens, 701 is an aperture, 702 is a secondary imaging lens, 703 is an area sensor, 704 is a focus detection unit, 705 is a focus output unit, 112 is a focus lens,
113 is a pentaprism, 114 is an eyepiece, 115
Is a photographer's eye, 116 is a shutter curtain, and 117 is a film surface.

A part of the light beam that has passed through the taking lens 101 is
The click return mirror 102 and the sub-mirror 103 form an image on the area sensor 703 via the field lens 104, the aperture 701, and the secondary imaging lens 702.
Here, a detailed configuration of the focus detection system will be described with reference to FIG.

[0008] Two imaging screens 70 of the area sensor 703
Light beams are guided from different pupil positions of the photographing lens 101 to the field lenses 1a and 3b, respectively.
04, re-imaging is performed at an imaging magnification determined by the secondary imaging lens 702. The area sensor 703 is located at a position optically equivalent to the photographic film surface with respect to the photographic lens 101, and the imaging screens 703a and 703b each have a part of the imaging screen or a field of view equal to the imaging screen. The aperture 701 has a function of an infrared cut filter as well as the function of the aperture to remove unnecessary light.

With the above arrangement, the imaging screens 703a and 703b having different parallaxes of the pupil position of the predetermined photographing lens.
Is obtained. When a well-known correlation operation is performed on the imaging screen having the parallax between the signals in the opposing blocks by the focus detection unit 704 in FIG. 7, the distance to the object in the previous block and the defocus are measured. Can do things. At this time,
The image is preferably a high-contrast image because a correlation operation is performed to detect a shift amount of the image. If the contrast is low, the correlation calculation cannot be performed correctly, and the focus cannot be detected. By performing this measurement on a predetermined block, distance information or defocus information can be obtained, and the result is output from the focus output unit 705. Then, by driving the photographing lens 101 based on the output result and adjusting the focal position, automatic focusing can be realized.

The remaining light beam passing through the photographing lens 101 has its optical axis bent by the quick return mirror 102, and the focus lens 112 and the pentaprism 11
3. The image is guided to the photographer's eye 115 via the eyepiece 114, and is recognized as a photographing visual field image.

Thereafter, when the photographer presses the shutter button, the quick return mirror 102, the sub mirror 103, and the shutter 116 are retracted, and the film 11 is retracted.
Exposure, that is, photographing, is performed on.

[0012]

The conventional focus detection area sensor has a sensitivity characteristic that has sensitivity over the entire visible region. For this reason, it is impossible to identify the color, and although the color differs depending on the subject, there is an inconvenience that the contrast cannot be obtained in the sensor output.
That is, in the conventional example, there is a disadvantage that even if the color of the subject is different, contrast cannot be obtained, and a phenomenon that the focus cannot be detected occurs.

Further, a color subject image cannot be obtained at the same time, and a separate image pickup device is required to provide an electronic display function.

(Object of the Invention) A first object of the present invention is to provide a focus detection device which can always obtain a high-contrast subject image and can always perform good focus detection. is there.

A second object of the present invention is to provide a focus detection device which has an electronic display function and can always perform good focus detection at low cost.

[0016]

In order to achieve the first object, according to the present invention, there is provided a light receiving means for receiving at least a pair of images having different optical systems, and a signal from the light receiving means. Computing means for calculating focus information based on the optical filter, and an optical filter disposed in front of the light receiving means, wherein the optical separation direction of the pair of images and the same color direction of the optical filter are the same. It is a focus detection device.

Similarly, in order to achieve the first object,
The invention according to claim 2 is an imaging unit that receives at least a pair of images having different imaging optical systems and electronically captures the images, an arithmetic unit that calculates focus information based on a signal from the imaging unit, An optical filter disposed upstream of the imaging means, wherein the optical separation direction of the pair of images and the same color direction of the optical filter are the same.

Further, in order to achieve the second object,
According to a third aspect of the present invention, there is provided a means for receiving at least a pair of images different from each other by an imaging optical system and electronically imaging them to obtain a signal used for focus detection and a signal used for image display for observation. Image processing means, a display processing means for generating a color image signal suitable for a display means for observation display based on a signal from the image processing means, and an optical element arranged in front of the image processing means And a dynamic filter,
According to another aspect of the present invention, there is provided a focus detection apparatus in which the optical separation direction of the pair of images is the same as the color direction of the optical filter.

Similarly, in order to achieve the second object,
According to a fourth aspect of the present invention, at least a pair of images having different imaging optical systems are received and electronically imaged, and a signal used for focus detection and a signal used for displaying or storing the captured image are obtained. Imaging processing means also used as means,
A display unit or a storage unit that displays a captured image based on a signal from the imaging processing unit, and an optical filter that is arranged at a stage preceding the imaging processing unit, and an optical separation direction of the pair of images and According to another aspect of the present invention, there is provided a focus detection device in which the same color direction of the optical filter is the same.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments.

(First Embodiment) FIG. 1 is a block diagram showing the entire structure of a single-lens reflex camera according to a first embodiment of the present invention. The same parts as those in FIG. The description is omitted.

In FIG. 1, reference numeral 105 denotes a stop, 106 denotes a secondary imaging lens, 107 denotes an area sensor, 108 denotes a first focus detection unit, 109 denotes a second focus detection unit, and 110 denotes a focus output unit.

A part of the light beam that has passed through the taking lens 101 is
The optical axis is bent by the click return mirror 102 and the sub mirror 103, and the field lens 104 and the aperture 10
5. Area sensor 107 via secondary imaging lens 106
Is imaged. The images having different pupil positions formed on the area sensor 107 are subjected to a known correlation operation by the first focus detection unit 108, and the distance to the subject and defocus information are calculated. The result is output to the focus processing output unit 11
Input to 0. Similarly, the second focus detection unit 109 obtains information on the distance to the subject and defocus information from other images having different pupil positions, and the results are input to the focus processing output unit 110. The focus processing output unit 110 determines whether the information is appropriate from the information from the first focus detection unit 108 and the information from the second focus detection unit 109, and outputs the result as a focus detection result if appropriate. I do. Thereafter, as in the conventional example, the photographing lens 601 is used based on the focus detection result.
Is driven to focus.

The focus detection system at this time will be further described with reference to FIG.

In FIG. 2, reference numeral 101 denotes a photographing lens, and four light beams having different pupil positions of the photographing lens 101 are shown. Light beams with different pupil positions are imaged by the aperture 105 at the pupil position via the field lens 104 at the primary image plane position. An aperture 105 has a function of restricting a light beam at a pupil position of the photographing lens 101, and has a function of dividing the light beam into four light beams in FIG. And
107 is formed on the sensor 107 by the secondary imaging lens 106.
a, 107b, 107c, 107d shooting lens 101
Images corresponding to the four pupil positions are formed.
By this, 107a, 107b, 107c, 10
The four obtained images 7d are four images having different pupil positions.

FIG. 3 shows the state of these four images.

The four images have different pupil positions, respectively.
07a and 107b have different pupil positions in the horizontal direction,
Focus detection can be performed by performing a correlation operation using the two as a pair. At this time, the axial direction in which the correlation is obtained needs to be the same as the axial direction having a different pupil position. And 1
Optical filters are arranged in stripes in the same horizontal direction as the shift direction of the pupil position with respect to 07a and 107b. In the drawing, as an example, an optical filter that periodically repeats three primary colors of light, red (R), green (G), and blue (B), is used. May be used as the optical filter. And
One cycle includes at least the entire visible light range.

By arranging the optical filters in this manner, 1
The shift amount can be obtained in the same color image in the same direction as the shift direction of the pupil positions of 07a and 107b, and as a result, focus detection becomes possible. This is the first focus detection unit 10 in FIG.
8 is processed.

Similarly, the pupil positions of 107c and 107d are shifted in the vertical direction, and the focus detection can be performed in the same manner by performing the correlation operation of the vertical stripe images of the same color. This is processed by the second focus detection unit 109. In the figure, since the filters are separated by three colors, it is possible to perform focus detection with the wavelength component for each of the three colors.

As described above, by using a plurality of focus detecting means provided with at least two or more types of stripe-shaped (in the same horizontal direction as the direction in which the pupil position shifts) color filters that repeat periodically, the conventional example can be used. Thus, even for a subject for which focus detection cannot be performed, good focus detection can be performed.

Further, as described above, the optical filter for changing the shift direction of the pupil position for calculating the shift amount and the sensitivity characteristic of the sensor is formed in a stripe shape in the same direction, so that a plurality of sensors having different sensitivity characteristics are configured identically. It becomes easy to do.

In FIG. 3, RGB is described in a rough and easy-to-understand manner, but by making the lines finer, the focus detection position can be selected more freely. Also, the description has been made with respect to the two shift directions, horizontal and vertical, but this is not a limitation, and either one may be used.

(Second Embodiment) FIG. 4 is a structural view showing a main part of a single-lens reflex camera according to a second embodiment of the present invention, and the same parts as those in FIGS. 1 and 7 have the same reference numerals. With
The description is omitted.

In the second embodiment, both an area sensor for focus detection and an area sensor as an electronic viewfinder are used.

In the figure, reference numeral 401 denotes an imaging processing unit;
2 is an image output unit to the outside, 403 is a focus detection unit, 404
Denotes a display processing unit for displaying a captured image or a subject;
Reference numeral 5 denotes the display.

Images having different pupil positions are processed by the imaging processing unit 401, and required image data is output to the focus detection unit 403, the display processing unit 404, and the image output unit 402. The focus detection unit 403 performs the same processing as in the first embodiment, and outputs the result to the focus output unit 110. At this time, an example in which focus detection is performed using a plurality of sensitivity characteristics has been described in the first embodiment, but the present invention is not limited to this, and focus detection using one sensitivity characteristic is sufficient in the second embodiment. FIG. 4 shows an example of this.

The display processing unit 404 performs image processing from the output image of the sensor so as to match the resolution of the display unit 405, and can output a color image. The display 405 displays the obtained subject image and functions as an electronic viewfinder. The image output unit 402 is used for outputting a subject image or the like to an external monitor, storing the image in an external storage device, or the like.

As described above, high-precision focus detection and color monitoring of a subject can be simultaneously realized by one sensor. As a result, this can be realized without using a plurality of expensive sensors, and the cost can be significantly reduced.

(Third Embodiment) FIG. 5 is a structural view showing a main part of a single-lens reflex camera according to a third embodiment of the present invention, and the same parts as those in FIGS. Numbers are assigned, and description thereof is omitted.

The third embodiment is an example in which the present invention is applied to a digital camera or the like, and differs from the first and second embodiments in the manner in which the pupil position is shifted.

In the figure, reference numeral 501 denotes one pixel for two pixels of the sensor.
A microlens array in which one is arranged, and 502 is an area sensor. FIG. 6 shows the state of the micro lens array 501 and the area sensor 502.

Since one microlens is arranged in each of the two pixels a and b of the area sensor, light beams having different pupil positions of the photographing lens 101 are incident on the respective pixels a and b.
Therefore, an image composed of only pixels corresponding to pixel a of the area sensor and an image composed of pixels corresponding to pixel b are images having different pupil positions. At this time, the first of the implementation
Similarly to the second embodiment, by arranging optical filters of the same color in the same direction as the separation direction of each pixel a and b, the same effect can be obtained by the same operation.

By this operation, a focus detection method having a higher correlation is selected, and it is possible to always obtain a stable and good focus detection result with high focus detection accuracy.

In each of the above-described embodiments, the pupil position shift has been described. However, the same applies to a parallax image, and similar effects can be obtained.

According to each of the above embodiments, there is provided means for capturing an image having at least a pair of phase differences, and the phase difference direction is set to be the same as the color direction of the optical filter of the image sensor. By doing so, it is possible to realize good focus detection and detection capability with one image sensor, and it is also possible to have a color viewfinder function and a function of displaying or storing a subject image.

[0046]

As described above, according to the first or second aspect of the present invention, it is possible to always obtain a high-contrast subject image and always perform a good focus detection. Can be provided.

According to the third or fourth aspect of the present invention, it is possible to provide a focus detection device which has an electronic display function and can always perform good focus detection at low cost. It is.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an entire single-lens reflex camera according to a first embodiment of the present invention.

FIG. 2 is a perspective view illustrating a configuration of a focus detection optical system that performs pupil division in FIG.

FIG. 3 is a diagram for describing a configuration of an area sensor and a filter in FIG. 1;

FIG. 4 is a configuration diagram showing a main part of a single-lens reflex camera according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a main part of a single-lens reflex camera according to a third embodiment of the present invention.

FIG. 6 is a side view showing a configuration of a focus detection optical system that performs pupil division shown in FIG.

FIG. 7 is a configuration diagram showing an entire conventional single-lens reflex camera.

8 is a perspective view illustrating a configuration of a focus detection optical system that performs pupil division in FIG.

[Explanation of symbols]

 Reference Signs List 101 shooting lens 105 aperture 106 secondary imaging lens 107, 502 area sensor 108 first focus detection unit 109 second focus detection unit 110 focus output unit 401 imaging processing unit 403 focus detection unit 404 display processing unit 405 display 501 Micro lens array

Claims (7)

[Claims] 1. A light receiving means for receiving at least a pair of images having different optical systems, a calculating means for calculating focus information based on a signal from the light receiving means, and an optical filter arranged in front of the light receiving means Wherein the optical separation direction of the pair of images and the same color direction of the optical filter are the same. 2. An image pickup means for receiving at least a pair of images having different image pickup optical systems and electronically picking up an image, calculating means for calculating focus information based on a signal from the image pickup means, and a preceding stage of the image pickup means Wherein the optical separation direction of the pair of images and the same color direction of the optical filter are the same. 3. An image pickup optical system that receives at least a pair of images different from each other and electronically captures the images, and is also used as a means for obtaining a signal for focus detection and a signal for image display for observation. The image processing apparatus includes: an image processing unit; a display processing unit that generates a color image signal suitable for a display unit for observation based on a signal from the image processing unit; and an optical filter disposed at a stage preceding the image processing unit. A focus detection device, wherein an optical separation direction of the pair of images is the same as a same color direction of the optical filter. 4. An image pickup optical system which receives at least a pair of images different from each other and electronically picks up the images, and is also used as a means for obtaining a signal used for focus detection and a signal used for displaying or storing a picked-up image. Image processing means, display means or storage means for displaying a captured image based on a signal from the image processing means, and an optical filter arranged in a preceding stage of the image processing means. Wherein the optical separation direction is the same as the color direction of the optical filter. 5. The focus detection device according to claim 1, wherein the optical filter is at least two or more types of stripe-shaped color filters that repeat periodically. 6. The focus detection device according to claim 5, wherein the optical filter includes at least the entire visible light region in one cycle. 7. The focus detection device according to claim 5, wherein the optical filter includes at least three primary color filters of light.