JP2002365524A - Autofocus device and imaging device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology by which a focal point is maintained at a correct focal position. SOLUTION: The autofocus device includes an imaging element, which converts an optical image having an imaged object into a video signal, an evaluation value calculating means for calculating focus evaluation value, which indicates the sharpness of the optical image the object imaged on the imaging element, on the basis of the video signal obtained by the imaging element, and a focus adjustment means which adjusts the focal point of a lens on the basis of the focus evaluation value and images the optical image of the object on the imaging element; and the imaging element is inclined with respect to a plane orthogonal to the optical axis of incident light. The evaluation value calculation means is provided with an evaluation value calculating means for calculating focus evaluation value for each pixel area divided, bordering on the line of intersection between the orthogonal plane and the imaging element. The focus adjustment means is provided with a comparison means for comparir the respective focus evaluation values of each divided pixel area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus device, and more particularly to an autofocus device which is effective when applied to an autofocus device provided in an imaging device such as a television camera in which a distance between a subject and a television camera changes frequently. It is about technology.

[0002]

2. Description of the Related Art A conventional autofocus device provided in a television camera uses a high-frequency component of an image picked up by an image pickup element as an in-focus evaluation value, and moves a focal position slightly back and forth based on the result of shooting. Calculate the direction of lens movement,
The so-called hill-climbing method was used.

In the autofocus control based on the hill-climbing method, for example, a first focus, which is a focus evaluation value obtained from a high-frequency component of an image from a photographic element at a first focus position which is a current focus position, is used. An evaluation value is calculated, and then a second focus evaluation value, which is a focus evaluation value obtained from a high-frequency component of an image from the imaging element at a second focus position slightly shifted from the first focus position. Calculate the value. Next, the first focus evaluation value and the second focus evaluation value are compared, and the direction of the focus position having the larger focus evaluation value is set as the direction of the focus position, and the lens is driven to move the focus position. Had a configuration. As described above, in the autofocus control based on the hill-climbing method, based on the focus evaluation values at the first focus position and the second focus position,
The moving direction of the focal position, that is, the driving direction of the lens is determined, and the operation of driving the lens in that direction is sequentially repeated to move the focal position in the direction of the focusing position.

As a focus evaluation value, for example, a luminance signal separated from a video signal obtained from an image sensor is input to a high-pass filter, and first, a high-frequency component is extracted. Next, the absolute value of the extracted high-frequency component is calculated, and the calculated value is integrated by integrating the obtained value over the entire imaging region of the imaging device or over a predetermined evaluation region.

[0005]

SUMMARY OF THE INVENTION As a result of studying the above prior art, the present inventor has found the following problems.

[0006] Like a TV camera or a video camera,
In order to always focus on the subject during a long shooting period, the conventional auto-focusing device using the hill-climbing method had to constantly change the focus position to continue detection and maintain the focus position. . At this time, in the conventional autofocus apparatus, as described above, when calculating the driving direction of the lens from the focus evaluation value of the image captured by the imaging element, the current position is set to the first focus position, It was necessary to capture an image in which the position where the lens was slightly driven from the position was the second focal position. That is, in the conventional autofocus device using the hill-climbing method, it is necessary to capture images at at least two different focal positions,
Since the image at this time is captured by the imaging element, even if the current position (first focus position) is the in-focus position, the image is slightly moved to the second focus position during the imaging period. However, there has been a problem that the focus position cannot be maintained at an accurate focus position.

Further, as described above, in the conventional autofocus device, at least two images are required, so that the image at the first focus position and the image at the second focus position have at least two fields. Time interval is required. That is, in the conventional autofocus device, it takes at least two fields to determine the driving direction of the lens. Therefore, in the case of a moving subject, the image at the first focus position and the image at the second focus position There is a time difference of two fields between the image and the image. For this reason, the autofocus device using the hill-climbing method has a problem that the detection sensitivity is lowered or the focusing operation becomes unstable.

An object of the present invention is to provide a technique capable of maintaining a focus position at an accurate focus position.
Another object of the present invention is to provide a technique capable of setting a focus position at a focus position even for a moving subject. The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0009]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

(1) An image sensor for converting an optical image of a captured object into a video signal, and sharpness of an optical image of the object formed on the image sensor based on a video signal obtained by the image sensor. Evaluation value calculation means for calculating a focus evaluation value, and focus adjustment means for adjusting a focal position of a lens based on the focus evaluation value and forming an optical image of the subject on the image sensor. In the autofocus device, the image sensor is disposed so as to be inclined with respect to an orthogonal plane orthogonal to an optical axis of incident light, and the evaluation value calculation unit is divided by an intersection of the orthogonal plane and the image sensor as a boundary. And an evaluation value calculation unit for calculating a focus evaluation value for each of the divided pixel regions, and the focus adjustment unit includes a comparison unit for comparing the focus evaluation values for each of the divided pixel regions.

(2) An auto-focus image sensor for converting an optical image of a captured object into a video signal, and forming an image on the auto-focus image sensor based on a video signal obtained by the auto-focus image sensor. Evaluation value calculating means for calculating a focus evaluation value indicating the sharpness of the optical image of the subject, and adjusting the focal position of the lens based on the focus evaluation value, and then, the imaging device for photographing the optical image of the subject An imaging device having an autofocus device comprising a focus adjustment unit that forms an image of the object, wherein the imaging device for autofocus is arranged to be inclined with respect to a plane orthogonal to an optical axis of incident light, and the evaluation value calculation unit is provided. Means for calculating a focus evaluation value for each divided pixel area divided by an intersection of the orthogonal plane and the autofocus image sensor, and Is provided with a comparing means for comparing the focus evaluation value of the divided pixel each region.

According to the above-described means, since the image pickup device is arranged to be inclined with respect to the orthogonal plane orthogonal to the optical axis of the incident light, it is divided at the intersection of the orthogonal plane and the image pickup element as a boundary. One of the divided pixel regions is closer to the lens, and the other divided pixel region is farther from the lens. Therefore, by using this image pickup device as an image pickup device for autofocus, an image when the focal position is moved by a very small amount can be obtained by one image pickup device. As a result, when the focus position has a focus position, the focus position can be maintained. In addition, since images at two different focus positions can be obtained by one imaging, the focus position can be set at the in-focus position even for a moving subject.

Here, the evaluation value calculation means calculates a focus evaluation value for each of the divided pixel areas divided by the intersection of the orthogonal plane and the image pickup device for autofocus as a boundary, and calculates the obtained focus evaluation value. Since the comparison is equivalent to comparing the focus evaluation values when the focal position is moved by a very small amount, the focus adjustment unit adjusts the focal position of the lens based on the comparison result. Accordingly, it is possible to form an optical image of the subject on the image sensor.

Therefore, in the image pickup apparatus equipped with this autofocus device, when the focus position is set to the in-focus position, the focus position of the image picked up by the image pickup device for obtaining the video output of the subject is automatically adjusted. Since the object is not moved even during the focus operation, a high-quality subject image can be obtained. In addition, since the autofocus operation can be performed by one imaging operation, the focus position can be quickly moved to the in-focus position even for a moving subject.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings together with embodiments (examples) of the invention. In all the drawings for describing the embodiments of the present invention, components having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

FIG. 1 is a diagram for explaining a schematic configuration of an autofocus apparatus according to an embodiment of the present invention.
In particular, FIG. 1A is a diagram for explaining the basic principle of the autofocus device according to the present embodiment, and FIG. 1B is a diagram illustrating the autofocus image sensor and the photographing device according to the present embodiment. FIG. 4 is a diagram for describing an example of division of a region in an imaging element. However, in this embodiment, the optical system such as the lens 101 and the autofocus image sensor 10 except for the arrangement positions of the autofocus image sensor 102 and the photographing image sensor 103 and the configuration of the focus determination unit 104
2 and a scanning drive pulse system for controlling the operations of the imaging element 103, and an image processing system for processing video signals from the auto-focus imaging element 102 and the imaging element 103 have a known configuration. Therefore, in the following description, the arrangement positions of the autofocus image sensor 102 and the image sensor 103 for the autofocus apparatus according to the present invention, and the focus control by the focus determination unit 104 will be described in detail.

In FIG. 1, 101 is a lens, 102 is an image sensor for autofocus, 103 is an image sensor for photographing, 104 is focus determining means, 105 is lens driving means,
Reference numeral 106 denotes an optical axis, 107 denotes a first area, and 108 denotes a second area.

As shown in FIG. 1A, an image sensor for autofocus (hereinafter, referred to as an AF image sensor) 10
2 and the image pickup device 103 are the optical axis 1 of the lens 101
06. The outputs from the AF image sensor 102 and the photographing image sensor 103 are as follows:
Each is connected to the focus determination unit 104. That is,
Image (subject image) captured by the AF image sensor 102
And an image (subject image) picked up by the image pickup device 103 are output to the focus determination unit 104. The drive output from the focus determining means 104 is output to the lens driving means 105, and the lens driving means 10
Reference numeral 5 denotes a structure for driving a focus mechanism (not shown) of the lens 101 to change the focus position.

The focus judging means 104 includes, for example, a well-known high-pass filter (hereinafter referred to as "HPF") that extracts only high-frequency components from an image picked up by the AF image pickup element 102 and the image pickup image pickup element 103, that is, a luminance signal in a video signal. ") And well-known absolute value calculating means for calculating the absolute values of the high frequency components passed through the HPF. Also, the focus determination unit 104 calculates the value output from the absolute value calculation unit for each of predetermined divided pixel regions in each image sensor, that is, the first region 107 and the second region 107 shown in FIG.
And a well-known adding means for adding the absolute values of the high-frequency components to obtain a focus evaluation value. Further, the focus determination unit 104 includes the imaging image sensor 103.
Based on the focus evaluation values of the first area 107 and the second area 108 in the first area 1 in the AF image sensor 102.
07 and the correction means for correcting the focus evaluation values of the second area 108, and the focus evaluation value of the first area 107 and the focus evaluation value of the second area in the AF image sensor 102 after the correction. And a known determining means for determining (determining) the driving direction of the lens, that is, the moving direction of the focal position, based on the comparison result. As described above, the focus determination unit 104 according to the present embodiment divides the image from the imaging sensor 103 into the first area 107 and the second area 108, and performs focus evaluation for each area. The drive output is obtained by calculating the respective values and comparing the focus evaluation value by the hill-climbing method. However, A corrected by the correction means
Without using the focus evaluation value of the first area 107 and the focus evaluation value of the second area 108 in the F image sensor 102,
The lens drive direction may be determined by comparing the focus evaluation value of the first area 107 and the focus evaluation value of the second area 108 in the AF image sensor 102 before correction. With such a configuration, the calculation for the correction by the correction unit is not required, so that the time required from image capturing to driving of the lens can be reduced.

The lens driving means 105 includes the focus determining means 1
This is a well-known lens driving unit that drives a focusing mechanism (not shown) of the lens 101 by a predetermined amount based on the driving direction determination output from the lens unit 04 to move the focal position. Therefore, in the present embodiment, the determining means and the lens driving means 105 operate as a focus adjusting means.

The image pickup device 103 is, similarly to the conventional image pickup device, perpendicular to the optical axis 106, or to such an extent that the image picked up by the image pickup device 103 is not distorted beyond a specified value. Are arranged vertically with an error of.
On the other hand, the AF image pickup device 102 is different from the image pickup device 103 as shown in FIG.
06, that is, not perpendicular to
3 are arranged so as not to be parallel. Therefore, in the present embodiment, the AF image pickup device 102 is arranged to be inclined at a predetermined inclination angle with respect to the photographing image pickup device 103.

However, as is apparent from FIG. 1A, in the autofocus device of the present embodiment, the optical axis 1
06 and the imaging image sensor 10 based on the position of the intersection of the AF 06 with the incident surface of the AF image sensor 102.
3 is inclined. In particular, a pixel direction (not shown) arranged in the horizontal direction arranged on the AF image sensor 102 is defined as an X-axis direction, and a pixel direction (not shown) arranged in the vertical direction is defined as a Y-axis direction. X-axis and Y having the point of intersection with the incident surface of 102 as the origin
When the axis is set, the AF image sensor 102 according to the present embodiment is configured to be inclined along the X axis.

At this time, as shown in FIG.
In the light receiving area of the imaging element 102 for F, the area above the optical axis 106, that is, the X axis which is the boundary is defined as the second area 10
8, when the area below the X axis is the first area 107, in the present embodiment, the AF imaging element 102
06 is located at the center of the light receiving surface,
The light receiving areas of the first region 107 and the second region 108 are set to be the same. Thus, A along the X axis
By inclining the F image sensor 102, the calculation of the focus evaluation value corresponding to the second area 108 is performed in the first area 1
Since it is possible to perform the calculation while the image signal is being read from 07 (during capture), the focus evaluation value can be calculated and compared quickly, and the focus responsiveness can be improved. .

The first region 107 and the second region 10
Although the light receiving area with 8 is not limited to the same area,
In this case, when the focus evaluation value is calculated by the focus determination unit 104, the image captured by the imaging element 103 according to the area ratio between the first area 107 and the second area 108 is also evaluated by the focus evaluation. You need to calculate the value. Further, the inclination of the AF image sensor 102 is not limited to the X axis, and
The inclination may be along the Y-axis with the origin at the intersection of the incident surface 6 and the incident surface of the AF image sensor 102, or may be along another straight line on the entrance surface passing through the intersection.

Next, FIG. 2 is a diagram for explaining the focusing operation in the automatic focusing apparatus according to the present embodiment.
Hereinafter, the operation of the autofocus device according to the present embodiment will be described with reference to FIG. However, FIG. 2A is a diagram for explaining the relationship between the focus evaluation value of the first area and the focus evaluation value of the second area before focusing, and FIG. Is the focusing evaluation value of the first area after focusing and the second
FIG. 9 is a diagram for explaining a relationship between a region and a focus evaluation value.

In the autofocus operation according to the present embodiment, the AF image pickup element 102 and the photographing image pickup element 103
Only high-frequency components are extracted from the luminance signals of the respective images picked up by the HPF, and the obtained high-frequency components are output to the next-stage HPF. HP at this time
The processing of F is performed by, for example, the AF image sensor 102 and the photographing image sensor 1 using a CCD type or CMOS type image pickup device.
A high-pass filter process is sequentially performed on a luminance signal obtained from a video signal sequentially output in the scanning line direction from 03. The HPF may be either digital processing or analog processing.

Next, the absolute values of the respective high frequency components extracted by the HPF are calculated by absolute value calculating means, and the absolute values are output to the adding means. The adding means sequentially adds the absolute values (the absolute values of the high-frequency components) output from the absolute value calculating means for each image sensor in the order of input. Here, when the absolute value from the absolute value calculating means reaches the end of the second area 108, that is, when the addition in the second area 108 is completed, the adding means sets the respective added values to the second area 108. 10
The value is output to the correction means as the focus evaluation value of 8, and the added value is reset. Thereafter, the adding means sequentially adds the next absolute value, that is, the absolute value in the first area 107, and when the absolute value from the absolute value calculating means reaches the end of the first area 107, the addition is performed. By outputting the value to the correcting unit as the focus evaluation value of the first area 107, the focus evaluation value of the first area 107 is calculated following the focus evaluation value of the second area 108.

In the correcting means, when the focus evaluation values of the first areas 107 corresponding to the AF image sensor 102 and the photographing image sensor 103 are input, first, the first image in the photographing image sensor 103 is input. For example, based on the ratio between the focus evaluation value of the area 107 and the focus evaluation value of the second area 108, for example, AF
The focus evaluation value of the second area 108 in the AF image sensor 102 is corrected based on the focus evaluation value of the first area in the image sensor 102 for AF. Next, the corrected focus evaluation value of the second area and the reference focus evaluation value of the first area in the AF image sensor 102 which is the reference are output to the determination unit.

In the determination means, the AF image pickup device 102 output from the correction means, that is, corrected by the correction means,
Is compared with the focus evaluation value of the first area 107 in the second area 108 in the AF image sensor 102,
The moving direction of the focal position, that is, the driving direction of the lens 101 is determined and output to the lens driving unit 105. However, the correction process and the determination process at this time are performed by the AF imaging device 10.
The focus evaluation value is corrected such that the ratio of the focus evaluation values of the first and second areas in the second image pickup device 2 becomes the same as the focus evaluation value ratio of the first and second areas in the imaging element 103 for photographing. The moving direction of the focus position is determined by comparing the corrected focus evaluation values.

For example, the focus evaluation value of the first area 107 in the AF image sensor 102 is a, the focus evaluation value of the second area 107 is b, and the first area in the photographing image sensor 103 is When the focus evaluation value of is c and the focus evaluation value of the second area is d, the following correction processing and determination processing are performed. As described above, the first area 10 in the AF image sensor 102
In the case where the focus evaluation value a of 7 is used as a reference, the focus of the second area 108 in the AF image sensor 102 is adjusted to d / c, which is the ratio of the focus evaluation value in the image pickup device 103. By multiplying the evaluation value b, a corrected focus evaluation value b × d / c of the second area 108 is obtained. Next, the determination means determines the focus evaluation value a of the first area 107 and the corrected second area 10
8 is compared with the focus evaluation value b × d / c. If the comparison result is a = b × d / c, the current focus position becomes the focus position. An instruction to maintain the position is issued to the lens driving unit 105. As a result, the lens driving unit 105 maintains the current focal position, so that the image obtained by the imaging element 103 for photographing is at the in-focus position. Needless to say, when a = b × d / c, the determination unit may not be configured to give a movement instruction to the lens driving unit 105. Further, the case where a = b × d / c is set as the current focus position, but when the range of the focus position is specified in advance by measurement or the like, the determination unit uses a = b × d / c. The current focus position is set to be the focus position in a range where a ≒ b × d / c including d / c. As an example of the range of the focus position at this time, the depth of focus of the optical system including the lens 101 for reproducing the spatial information of the subject (not shown) on the imaging element 103 for photographing, the value obtained by multiplying the focal depth by a coefficient, and the like are given. There is a range used as a reference.

When the comparison result by the judging means is a <b × d / c, it is compared with the focus evaluation value a of the first area 107 in the AF image pickup device 102, and Since the corrected focus evaluation value b × d / c of the second area 108 is larger, the determination unit performs the second
The lens driving unit 105 is instructed to move the focus evaluation value of the area 108 in the direction of decreasing the focus evaluation value, that is, the direction in which the focus position approaches the lens 101. On the other hand, when the comparison result by the determination means is a> b × d / c, the AF imaging device 10
2 and the corrected focus evaluation value b × d /
c, the first area 1 in the AF image sensor 102
07 is larger than the focus evaluation value a,
By instructing the lens driving unit 105 to move the focus evaluation value of the first area in the image pickup device 102 in the direction of decreasing the focus evaluation value, that is, in the direction of moving the focus position away from the lens 101, the current focus position is changed to the focus position. The focal position is moved so as to move in the direction of. As a comparison method in the determination means, for example, a known method such as a determination based on whether the subtraction result is positive or negative or a determination based on the division result is used.

As a determination method by division, for example, when dividing b / a, which is the ratio of the AF image sensor 102, by d / c, which is the ratio of the photographing image sensor 103, the division result is 1 In the case of (2), the current focal position becomes the in-focus position, and thus the determining unit issues an instruction to maintain the current focal position to the lens driving unit 105. As a result, the lens driving means 10
5 keeps the current focus position, so
The image obtained at 03 is at the in-focus position. However, when the division result is 1, the current focus position is determined as the in-focus position. For example, when the range of the in-focus position is specified in advance by measurement or the like, the determination unit determines the range including 1 as the division result. Is set so that the current focus position is the focus position. As an example of the range of the focus position at this time, the depth of focus of the optical system including the lens 101 for reproducing the spatial information of the subject (not shown) on the imaging element 103 for photographing, the value obtained by multiplying the focal depth by a coefficient, and the like are given. There is a reference range.

When the result of the division by the judging means is larger than 1, the focus evaluation value of the second area of the AF image sensor 102 is compared with the ratio of the focus evaluation value of the image pickup device 103. Is larger, the determination means is the AF image sensor 102
The lens driving unit 105 is instructed to move the focus evaluation value of the second area in the direction described above in the direction in which the focus position is reduced, that is, in the direction in which the focal position approaches the lens 101. On the other hand, when the result of the division by the determination means is less than 1, the focus evaluation value of the first area in the AF imaging element 102 is compared with the ratio of the focus evaluation value in the imaging element 103. Is large, the determination unit instructs the lens driving unit 105 to move the focus evaluation value of the first area in the AF image sensor 102 in a direction of decreasing the focus evaluation value, that is, in a direction of moving the focal position away from the lens 101. The focal position is moved so that the division result is 1, that is, the current focal position becomes the in-focus position.

When the ratio between the focus evaluation value c of the first area 107 and the focus evaluation value d of the second area 108 in the image pickup device 103 is equal or can be regarded as equal, It is sufficient to simply compare the focus evaluation value a of the first area 107 with the focus evaluation value b of the second area in the AF image sensor 102. Accordingly, as shown in FIG. 2A, for example, when the focus evaluation value of the second area 108 in the AF imaging device 102 is larger than the focus evaluation value of the first area 107, The magnitude of the focus evaluation value in each area is determined by subtracting the focus evaluation value of the first area 107 from the focus evaluation value of the second area 108, and the current focus position is determined based on the result. , Ie, the direction in which the lens is driven, and outputs an instruction to the lens driving means 105. However, as shown in FIG. 2B, when the difference between the focus evaluation values is 0 (zero) or within a preset value, the current focus position becomes the focus position. Sends an instruction to the lens driving unit 105 to maintain the current focal position. As a result, the lens driving unit 105 maintains the current focal position, so that the image obtained by the imaging element 103 for photographing is at the in-focus position.

As described above, when the ratio between the focus evaluation value c of the first area 107 and the focus evaluation value d of the second area 108 in the image pickup device 103 is equal or can be regarded as equal, Alternatively, when the determination process is performed only with the focus evaluation values a and b of the AF imaging element 102, the correction unit is not required, and the moving direction of the focal position can be determined only by subtraction by the determination unit. Can be further reduced. As a result, even when combined with another evaluation method, the time required from acquisition of one image (or one frame image) to movement of the focal position can be reduced.

However, an image pickup device for taking a moving image such as a television camera or a video camera provided with the above-described autofocus device and an image pickup device for taking a still image such as a digital camera as shown in FIG. It is difficult to arrange the AF image sensor 102 and the photographing image sensor 103 at the same position on the optical axis 106 of the same lens 101 at the same time. Using two sets (or more) of shooting lenses corresponding to the number of image sensors for shooting and
Alternatively, it is necessary to separate the optical path of light incident on one set of photographing lenses in the middle, and to impinge on the respective image pickup devices for AF and for photographing.

FIG. 3 is a diagram for explaining an example of the arrangement of the AF image sensor and the photographing image sensor in the autofocus apparatus according to the present embodiment. In particular, FIG. 3A is a diagram for explaining a schematic configuration of an autofocus apparatus in which an AF image sensor and a photographing image sensor are arranged using a plurality of lenses, and FIG. FIG. 3 is a diagram for explaining a schematic configuration of an autofocus device in which an optical path is separated behind a lens and an AF image sensor and a photographing image sensor are arranged.

In the auto-focusing device shown in FIG. 3A, a photographing lens 301 for reproducing spatial information of a subject (not shown) to the photographing image sensor 103 and a spatial information of the subject are transmitted to the AF image sensor 102. The configuration is such that an autofocus lens 302 for reproduction is provided separately. That is, a camera unit for photographing including the photographing lens 301 and the photographing image sensor 103 and a camera unit for autofocus including the autofocus lens 302 and the AF image sensor 102 are separately configured. It is a television camera equipped with an autofocus device.

In this configuration, the focus movement between the photographing lens 301 and the autofocus lens 302 is linked, and when the focus position of the autofocus lens 302 is moved to the focus position of the lens 302, the photographing is performed. The characteristics of the photographing lens 301 and the autofocus lens 302 are set so that the focal position of the lens 301 is also at the focal position of the lens 301, and the photographing image sensor 103 corresponding to each lens is AF image sensor 1
02 is arranged.

In the autofocus device shown in FIG. 3B, the photographing lens 3 forming the optical system of the television camera is used.
The optical path of the light beam (image) emitted from the imaging lens 301 is separated by the semi-transmissive mirror 303 disposed between the imaging device 103 and the imaging device 103. In this configuration, the light beam is made incident and the other light beam is made incident on the AF image sensor 102. In other words, the television camera is provided with an autofocus device having a relatively large and heavy optical system as one system.

In this configuration, for example, the semi-transmissive mirror 303
The distance that the light reaches the incident surface of the AF imaging device 102 after being reflected by the
The AF image sensor 102 and the photographing image sensor 103 are arranged so as to be equal to the distance to the incident surface of No. 3.

The spatial information of the object reproduced by the AF image sensor 102, that is, the image, and the image sensor 1
With respect to the spatial information of the subject reproduced in 03, that is, the image, the top and bottom are reversed and reproduced. Therefore, in the present embodiment, for example, the upper part of the spatial information of the subject is A
The image pickup device 103 and the image pickup device 103 are set so that the read start positions of the image pickup device 102 for F and
The F image sensor 102 is arranged.

It should be noted that the imaging element 10 for photographing described above
3 and the AF image sensor 102, that is, a shift in the rotation direction about the optical axis as the rotation center, and the respective image sensors 102, 1
Needless to say, the shift in the direction parallel to the imaging surface of No. 03 can be corrected by well-known image correction or the like.

FIG. 4 is a diagram for explaining the detection range of the focus evaluation value in the automatic focusing apparatus according to the present embodiment. However, FIG. 4A is a diagram (side view) for explaining the positional relationship between the auto-focus image sensor and the photographing image sensor, and FIG. 4B is a diagram illustrating the auto-focus image sensor and the photographing device. FIG. 3 is a diagram (front view) for describing a detectable region of focus evaluation in an imaging element.

In FIG. 4, dn indicates the near-subject-side focal depth from the in-focus position, and df indicates the far-subject-side focal depth. In the following description, a position where the circle of confusion determined by the F value of the lens, the focal length, and the subject distance is equivalent to the image size of the image sensor is defined as the depth of focus.

As shown in FIG. 4A, when the angle between the AF image pickup device 102 and the photographing image pickup device 103 is α, the difference between the high-frequency components of the image is within the depth of focus. Therefore, no focus evaluation value can be obtained.
Therefore, the range in which the focus evaluation value can be detected is a region that is separated from the position of the intersection of the AF imaging element 102 and the imaging imaging element 103 by the depth of focus or more. Since the depth of focus in the first area 107 is Ln = dn / tanα, the area 402 excluding the area 401 from the intersection point of the imaging devices 102 and 103 to the depth of focus Ln shown in FIG. This is the detection range of the focus evaluation value in the area 107 of No. 1. Similarly, since the depth of focus in the second area 108 is Lf = df / tanα, FIG.
The area 404 excluding the area 403 from the intersection point of the imaging elements 102 and 103 to the depth of focus Lf shown in (2) is the detection range of the focus evaluation value in the second area 108.

As described above, in the image pickup apparatus using the autofocus apparatus according to the present embodiment, the image pickup device that converts an optical image of a subject into a video signal includes A
The F image sensor 102 is arranged to be inclined with respect to the incident light, that is, the optical axis 106 of the lens 101. In particular, the optical axis 106
Imaging device 1 arranged in parallel with an orthogonal plane orthogonal to.
03, the AF image sensor 102 is arranged obliquely, so that the orthogonal plane at the position where the input surface of the AF image sensor 102 and the optical axis 106 intersect, and the line of intersection of the AF image sensor 106 With the AF as a boundary
Each pixel of No. 6 is divided into any one of two regions (a divided pixel region including a first region 107 and a second region 108). At this time, if the lower end of the AF image sensor 106 is inclined so as to be closer to the lens 101, the first area 107 of the AF image sensor 102 is closer to the lens 101 and the second area 108 is It is far from 101. When the tilt direction of the AF image sensor 102 is opposite,
It goes without saying that the relationship between the first and second regions 107 and 108 and the lens 101 is also reversed.

Therefore, even when one frame of the subject image is picked up by the AF image pickup device 102, the first position is centered on the position where the input surface of the AF image pickup device 102 and the optical axis 106 intersect. In the area 107, an image having the same effect as when the focal position is moved to the lens 101 side by a small amount is obtained, and in the second area, the focal position is set to a small amount by the lens 10.
An image having the same effect as when the image is moved to the side farther from 1 is obtained. As a result, even when the focal position is at the in-focus position, images at two different focal positions can be obtained without moving the focal position of the lens 101.
The focus position can be maintained in the imaging element 103 for photographing, and the movement of the focus position from the focus position due to the autofocus control can be prevented. Further, since images at two different focus positions can be obtained by one image pickup, the focus position can be quickly set to the in-focus position even for a moving subject.

In the present embodiment, the reading of the video signal from the photographing image sensor 103 and the AF image sensor 102 is controlled so that they are read in the same period. However, the present invention is not limited to this. A configuration in which a video signal is read from the AF imaging element 102 following reading of a video signal from the imaging imaging element 103, or vice versa. The configuration may be such that the video signals are read out in order. With such a configuration, in addition to the above-described effects, the HPF, the absolute value calculation unit, the correction unit, and the addition unit that constitute the focus determination unit 104 include: Since the image pickup device 103 for photographing and the image pickup device for AF can be shared, the circuit scale is reduced when the focus determination unit 104 is configured by hardware. Rukoto is possible. On the other hand, when the focus determination unit 104 is realized by a program that operates on a known information processing device such as a microcomputer, a relatively inexpensive information processing device can be used because the load on the information processing device can be reduced. it can.

Further, in this embodiment, the case has been described in which the AF image pickup element 102 and the photographing image pickup element 103 use image pickup elements having the same size and the same image pitch. However, the present invention is not limited to this. For example, by using an imaging element having the same number of pixels as the imaging element 103 and a small pixel pitch for the AF imaging element 102 which does not affect the quality of image output, the AF imaging element 102 and the AF imaging element are used. Since it is possible to reduce the size of the optical system related to 102, it is possible to reduce the size of the autofocus device. In addition, by using the small-sized AF image sensor 102 and the optical system, the manufacturing cost can be reduced. Further, it goes without saying that image pickup devices having incident areas of different sizes may be used. For example, when a focus area smaller than the imaging area of the imaging element 103 is set in advance, the AF imaging element 103 having an imaging area sufficient to capture an image of the focus area is used. The size of the optical system relating to the AF imaging element 102 as well as the AF imaging element 102 can be reduced, so that the autofocus device can be reduced in size. In addition, by using the small-sized AF image sensor 102 and the optical system, the manufacturing cost can be reduced.

Further, in the present embodiment, the image pickup device 10 for photographing is formed by inclining the image pickup device 102 for AF.
3, the image in which the focal position is moved to the side of the lens 101 by a small distance, and the focal position
Although it is configured to capture an image moved to a position distant from the first region 10, the present invention is not limited thereto.
It is needless to say that the above-described effect can be obtained even when two or more image sensors are provided, each of which has an image pickup area 7 and the second area 108.

Further, in the present embodiment, the lens driving unit 105 drives the focusing mechanism of the lens 101 based on the driving direction judgment output from the focusing judging unit 104 to set the focal position by a predetermined amount. However, the present invention is not limited to this. For example, a means for calculating the difference between the focus evaluation values of the first and second areas 107 and 108 is provided in the focus determination means 104, and the first and second areas are calculated.
A moving amount storing means for storing the moving amount of the lens 101 according to the difference between the focus evaluation values of the areas 107 and 108 is provided. A movement amount corresponding to the difference between the focus evaluation values is searched from the movement amount storage means, and the searched movement amount and the focus determination means 1 are searched.
By moving the lens 101 in the moving direction from the direction 04, the focal point movement of the lens 101 can be performed accurately and efficiently, so that the time required for focusing is reduced and an efficient focusing operation is realized. it can. However, it goes without saying that the movement amount of the lens 101 according to the difference between the focus evaluation values of the first and second regions 107 and 108 may be calculated each time the focus evaluation value is obtained. Furthermore, lens 1
By calculating the moving amount of the lens 101 in consideration of the F-number of 01, the focal length, the subject distance, and the like, the lens 101
Can be moved more accurately and more efficiently, and an efficient focusing operation in which the time required for focusing is further reduced can be realized.

As described above, the invention made by the present inventor is:
Although specifically described based on the embodiments of the present invention, the present invention is not limited to the embodiments of the present invention, and it is needless to say that various modifications can be made without departing from the gist of the present invention. .

[0054]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows. (1) Since the AF image pickup device is arranged to be inclined with respect to an orthogonal plane orthogonal to the optical axis of the incident light, an image when the focal position is moved by a very small amount with one image pickup device. Can be obtained by one imaging. As a result, even if there is a focus position at the in-focus position, the autofocus operation can be performed without moving the focus position. (2) Since the autofocus operation can be performed with a simple configuration having only one AF image sensor, the configuration of the autofocus device can be simplified. As a result, the size and cost of the device can be reduced. (3) Even when the conventional hill-climbing method is used for the autofocus control, the autofocus operation based on the image at one focal position can be performed. (4) Since the autofocus operation can be performed from one image, the processing related to the autofocus operation can be performed without any time loss. As a result, even if the subject is moving, the focus position can be quickly moved to the focus position.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a schematic configuration of an autofocus device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a focusing operation in the autofocus device of the present embodiment.

FIG. 3 is a diagram for explaining an example of the arrangement of an AF image sensor and a photographing image sensor in the autofocus device according to the present embodiment.

FIG. 4 is a diagram illustrating a detection range of a focus evaluation value in the autofocus device according to the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 ... Lens 102 ... Autofocus image sensor 103 ... Photographing image sensor 104 ... Focusing determination means 105 ... Lens driving means 106 ... Optical axis 107 ... First area 108 ... Second area 301 ... Shooting lens 302 ... Autofocus lens 303: semi-transmissive mirror 401: depth of focus area in first area 402, 404: detectable range of focus evaluation value 403: depth of focus area in third area

Continued on the front page F term (reference) 2H011 AA03 BA33 BA38 BB02 BB04 CA28 2H051 AA08 BA45 BA47 BA53 CB22 CB27 CD01 CD30 CE14 DA05 FA48 5C022 AB27 AC54 AC74

Claims (6)

[Claims] An image sensor that converts an optical image of a captured object into a video signal; and a sharpness of an optical image of the object formed on the image sensor based on a video signal obtained by the image sensor. An autofocusing device having an evaluation value calculating means for calculating a focus evaluation value to be indicated, and a focus adjusting means for adjusting a focal position of a lens based on the focus evaluation value and forming an optical image of the object on the image sensor. In the focusing device, the image sensor is disposed so as to be inclined with respect to an orthogonal plane orthogonal to the optical axis of the incident light, and the evaluation value calculation unit is divided by an intersection of the orthogonal plane and the image sensor as a boundary. An autofocus apparatus comprising: evaluation value calculation means for calculating a focus evaluation value for each divided pixel area; and said focus adjustment means includes comparison means for comparing the focus evaluation value for each divided pixel area. . 2. The auto-focusing device according to claim 1, further comprising: a photographing image pickup device that converts an optical image of the subject into a video signal, wherein the evaluation value calculating unit sets a pixel area of the photographing image pickup device to the image area. A unit that divides the image into a region corresponding to the divided pixel region of the imaging element, and calculates a focus evaluation value for each divided pixel region of the imaging unit for imaging; and for each of the divided pixel regions calculated from the imaging element for imaging. Correction means for correcting a focus evaluation value for each of the divided pixel regions of the image sensor based on the focus evaluation value, the focus adjustment means based on the corrected focus evaluation value of the image sensor, An autofocus apparatus, wherein a focal position of the lens is adjusted. 3. The auto-focusing device according to claim 1, wherein an image sensor is disposed in each of divided areas divided by an intersection line between the orthogonal plane and the image sensor. Focus device. 4. The auto-focusing device according to claim 3, wherein the image pickup devices arranged in the divided areas have image pickup surfaces arranged perpendicular to the optical axis and are connected to the respective image pickup devices. An auto-focus device, wherein the focus positions of optical images to be formed are different from each other. 5. An auto-focus image sensor for converting a captured optical image of a subject into a video signal, and forming an image on the auto-focus image sensor based on a video signal obtained by the auto-focus image device. Evaluation value calculation means for calculating a focus evaluation value indicating the sharpness of the optical image of the subject; adjusting a focal position of a lens based on the focus evaluation value; In an imaging apparatus having an autofocus device including a focus adjustment unit that forms an image, the imaging device for autofocus is disposed to be inclined with respect to a plane orthogonal to an optical axis of incident light, and the evaluation value calculation unit is Means for calculating a focus evaluation value for each divided pixel area divided by an intersection of the orthogonal plane and the autofocus image sensor, and wherein the focus adjustment means is Imaging apparatus characterized by comprising a comparison means for comparing the focus evaluation value of the serial divided pixel each region. 6. The imaging apparatus according to claim 5, wherein the evaluation value calculation unit divides a pixel area of the imaging element for photography into an area corresponding to a divided pixel area of the imaging element for autofocus, and Means for calculating a focus evaluation value for each divided pixel area of the imaging means for imaging, and dividing the auto-focus imaging element based on the focus evaluation value for each divided pixel area calculated from the imaging element for photographing. Correction means for correcting the focus evaluation value for each pixel region, wherein the focus adjustment means adjusts the focus position of the lens based on the corrected focus evaluation value of the auto-focus imaging device. Characteristic imaging device.