JP4334784B2 - Autofocus device and imaging device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an autofocus device, and more particularly to a technique effective when applied to an autofocus device provided in an imaging device such as a television camera in which the distance between a subject and the television camera changes frequently.
[0002]
[Prior art]
A conventional TV camera has an autofocus device that uses the high-frequency component of the image captured by the imaging element as the focus evaluation value and moves the focal position slightly back and forth based on the result of shooting. The so-called hill-climbing method is used.
[0003]
In the autofocus control by the hill-climbing method, for example, the first focus evaluation value that is a focus evaluation value obtained from the high frequency component of the image from the imaging element at the first focus position that is the current focus position is obtained. And then calculating a second focus evaluation value, which is a focus evaluation value obtained from the high frequency component of the image from the imaging element at the second focus position shifted slightly from the first focus position. To do. Next, the first focus evaluation value and the second focus evaluation value are compared, and the lens is driven to move the focus position with the direction of the focus position having the large focus evaluation value as the direction of the focus position. It was a composition. As described above, in the autofocus control by the hill-climbing method, the moving direction of the focal position, that is, the lens driving direction is determined based on the focus evaluation values at the first focal position and the second focal position, and in that direction. The focus position is moved in the in-focus position direction by sequentially repeating the operation of driving the lens.
[0004]
As the 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 obtained value is calculated by integrating within the entire imaging region of the image sensor or a preset evaluation region.
[0005]
[Problems to be solved by the invention]
As a result of examining the prior art, the present inventor has found the following problems.
[0006]
When the focus always follows the subject over a long shooting period, such as a TV camera or a video camera, the conventional autofocus device using the hill-climbing method always changes the focus position slightly and continues detection. It was necessary to keep the in-focus position. At this time, in the conventional autofocus device, as described above, when calculating the lens driving direction from the focus evaluation value of the image captured by the imaging element, the current position is set as the first focus position, and this current position is determined. It was necessary to capture an image with the second focus position at the position where the lens was finely driven from the 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, and the images at this time are captured by the imaging element, so the current position ( Even when the first focus position) is the in-focus position, there is a problem that the focus position cannot be maintained at the correct in-focus position because it is slightly moved to the second focus position during the photographing period.
[0007]
Further, as described above, since the conventional autofocus device requires at least two images, the time interval for at least two fields between the image at the first focus position and the image at the second focus position. Is required. That is, in the conventional autofocus device, it takes time for at least two fields to determine the lens driving direction. Therefore, in a moving subject, the image at the first focal position and the second focal position are used. There was a time difference of two fields from the image. For this reason, the autofocus device using the hill-climbing method has a problem that the detection sensitivity becomes low or the focusing operation becomes unstable.
[0008]
An object of the present invention is to provide a technique capable of maintaining a focal position at an accurate in-focus position.
Another object of the present invention is to provide a technique capable of setting a focal position at a focus position even for a moving subject.
The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.
[0009]
[Means for Solving the Problems]
Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
[0010]
(1) Convert an optical image of a captured subject into a video signal For auto focus An imaging device; For auto focus Based on the video signal obtained by the imaging device, For auto focus An evaluation value calculating means for calculating a focus evaluation value indicating the sharpness of the optical image of the subject imaged on the image sensor, and adjusting the focal position of the lens based on the focus evaluation value; For imaging In an autofocus device having a focus adjustment unit that forms an optical image of the subject on an image sensor, For auto focus The image sensor is arranged to be inclined with respect to an orthogonal plane orthogonal to the optical axis of the incident light, and the evaluation value calculation means is At the position where the input surface of the image sensor for autofocus and the optical axis intersect Orthogonal plane and said For auto focus Evaluation value calculation means for calculating a focus evaluation value for each divided pixel region divided with the intersection line with the image sensor as a boundary When And the focus adjustment means includes comparison means for comparing focus evaluation values for the divided pixel areas. The evaluation value calculation means divides the pixel area of the imaging element for imaging into areas corresponding to the divided pixel areas of the imaging element for autofocus, and sets a focus evaluation value for each divided pixel area of the imaging element for imaging. Means for calculating, and correction means for correcting the focus evaluation value for each of the divided pixel areas of the image sensor for autofocus based on the focus evaluation value for each of the divided pixel areas calculated from the imaging element for photographing. And the focus adjustment means adjusts the focal position of the lens based on the corrected focus evaluation value of the image sensor for autofocus. .
[0011]
(2) An autofocus image sensor that converts an optical image of a captured subject into a video signal, and the subject that forms an image on the autofocus image sensor based on a video signal obtained by the autofocus image sensor An evaluation value calculation means for calculating a focus evaluation value indicating the sharpness of the optical image, and adjusting a focal position of the lens based on the focus evaluation value, thereby forming an optical image of the subject on the image sensor for photographing. In the imaging apparatus having an autofocus device including the focus adjustment unit, the autofocus imaging element is disposed to be inclined with respect to an orthogonal plane orthogonal to the optical axis of incident light, and the evaluation value calculation unit is At the position where the input surface of the image sensor for autofocus and the optical axis intersect Means for calculating a focus evaluation value for each divided pixel region that is divided with an intersecting line between the orthogonal plane and the image sensor for autofocus as a boundary, and the focus adjustment unit performs focus evaluation for each divided pixel region. Comparing means for comparing values The evaluation value calculation means divides the pixel area of the imaging element for imaging into areas corresponding to the divided pixel areas of the imaging element for autofocus, and sets a focus evaluation value for each divided pixel area of the imaging element for imaging. Means for calculating, and correction means for correcting the focus evaluation value for each of the divided pixel areas of the image sensor for autofocus based on the focus evaluation value for each of the divided pixel areas calculated from the imaging element for photographing. And the focus adjustment means adjusts the focal position of the lens based on the corrected focus evaluation value of the image sensor for autofocus. .
[0012]
According to the above-described means, since the imaging device is arranged to be inclined with respect to the orthogonal plane orthogonal to the optical axis of the incident light, each divided pixel is divided with the intersection line between the orthogonal plane and the imaging device as a boundary. One of the regions is close to the lens, and the other divided pixel region is far from the lens. Therefore, by using this image sensor as an autofocus image sensor, an image when the focal position is moved by a minute amount with one image sensor can be obtained by one imaging. As a result, when the focus position is at the focus position, the focus position can be maintained. Further, since images at two different focal positions can be obtained by one imaging, the focal position can be set at the in-focus position even for a moving subject.
[0013]
Here, the evaluation value calculation means calculates a focus evaluation value for each divided pixel area divided by using the intersecting line between the orthogonal plane and the autofocus imaging device as a boundary, and compares the obtained focus evaluation values. Is equivalent to comparing the focus evaluation values when the focal position is moved by a minute amount. Therefore, the focus adjustment unit adjusts the focal position of the lens based on the comparison result, thereby obtaining an image. An optical image of a subject can be formed on the element.
[0014]
Therefore, in the imaging apparatus including the autofocus device, when the focus position is set to the in-focus position, the focus position of the image captured by the imaging image sensor that obtains the video output of the subject is in the autofocus operation. However, since it is not moved, a high-quality subject image can be obtained. In addition, since the autofocus operation can be performed with one imaging, the focus position can be quickly moved to the in-focus position even for a moving subject.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings together with embodiments (examples) of the invention.
Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment of the invention, and the repetitive description thereof is omitted.
[0016]
FIG. 1 is a diagram for explaining a schematic configuration of an autofocus device 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 an autofocus image sensor and photographing device according to the present embodiment. It is a figure for demonstrating an example of the division | segmentation of the area | region in an image sensor. However, in the present embodiment, the optical system such as the lens 101, the autofocus image sensor 102, and the image capturing device are excluded, except for the arrangement positions of the autofocus image sensor 102 and the image sensor 103 and the configuration of the focus determination unit 104. The scanning drive pulse system that controls the operation of the image sensor 103 and the video processing system that processes the video signals from the autofocus image sensor 102 and the image sensor 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 photographing and the focus control in the focus determination unit 104 according to the autofocus device of the present invention will be described in detail.
[0017]
In FIG. 1, 101 is a lens, 102 is an image sensor for autofocus, 103 is an image sensor for photographing, 104 is a focusing determination unit, 105 is a lens driving unit, 106 is an optical axis, 107 is a first region, and 108 is A second region is shown.
[0018]
As shown in FIG. 1A, an autofocus imaging device (hereinafter referred to as an AF imaging device) 102 and a photographing imaging device 103 are arranged on an optical axis 106 of a lens 101. It has become. Outputs from the AF image sensor 102 and the image sensor 103 are connected to the focus determination unit 104, respectively. In other words, the image (subject image) captured by the AF image sensor 102 and the image (subject image) captured by the image sensor 103 are each output to the focus determination unit 104. . The drive output from the focus determination means 104 is output to the lens drive means 105, and the lens drive means 105 drives a focus mechanism (not shown) of the lens 101 to change the focus position.
[0019]
The focus determination unit 104 is a well-known high-pass filter (hereinafter, referred to as “HPF”) that extracts only high-frequency components from luminance signals in images captured by the AF image sensor 102 and the image sensor 103, that is, video signals, for example. ) And known absolute value calculation means for calculating the absolute values of the high-frequency components that have passed through the HPF. Further, the focus determination unit 104 outputs the value output from the absolute value calculation unit for each predetermined divided pixel region in each image sensor, that is, the first region 107 and the second region shown in FIG. And a known adding means for adding the absolute values of the high frequency components to obtain the focus evaluation value. Further, the focus determination unit 104 determines the first area 107 and the AF area 102 based on the focus evaluation values of the first area 107 and the second area 108 in the imaging element 103. The correction means for correcting the focus evaluation value 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 correction are compared. And a known determination 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 element 103 for imaging into the images of the first area 107 and the second area 108, and performs the focus evaluation for each area. Each value is calculated, and the drive output is obtained by comparing the in-focus evaluation value by the hill-climbing method. However, the AF image sensor 102 before correction is not used without using 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 corrected by the correction unit. The in-focus evaluation value of the first area 107 and the in-focus evaluation value of the second area 108 may be compared to determine the lens driving direction. By adopting such a configuration, it is not necessary to perform a correction operation in the correction unit, so that it is possible to reduce the time taken from image capturing to lens driving.
[0020]
The lens driving unit 105 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 focusing determination unit 104 to move the focal position. is there. Therefore, in the present embodiment, the determination unit and the lens driving unit 105 operate as a focus adjustment unit.
[0021]
In addition, like the conventional image sensor for photographing, the image sensor for photographing 103 is an error that is perpendicular to the optical axis 106 or does not cause distortion exceeding a specified value in an image captured by the image sensor for photographing 103. It is arranged vertically. On the other hand, as is clear from FIG. 1A, the AF image sensor 102 is not orthogonal to the optical axis 106, that is, not parallel to the image sensor 103, unlike the image sensor 103. Is arranged. Therefore, in the present embodiment, the AF image sensor 102 is inclined with a predetermined tilt angle with respect to the imaging image sensor 103.
[0022]
However, as is clear from FIG. 1A, in the autofocus device according to the present embodiment, the AF image sensor 102 is mounted on the basis of the intersection position between the optical axis 106 and the incident surface of the AF image sensor 102. It is configured to be inclined with respect to the imaging element 103 for imaging. In particular, a pixel direction (not shown) arranged in the lateral direction arranged in the AF image sensor 102 is an X axis direction, and a pixel direction (not shown) arranged in the vertical direction is a Y axis direction, and the optical axis 106 and the AF image sensor. When the X-axis and the Y-axis having the origin at the intersection point with the incident surface 102 are set, the AF image sensor 102 of the present embodiment is configured to be inclined along the X-axis.
[0023]
At this time, as shown in FIG. 1 (b), in the light receiving area of the AF image sensor 102, the area above the optical axis 106, that is, the X axis serving as the boundary, is defined as the second area 108 and the X axis. In this embodiment, when the lower region is the first region 107, the AF imaging element 102 is arranged so that the optical axis 106 is at the center of the light receiving surface. The light receiving area of the second region 108 is set to be the same. By tilting the AF image sensor 102 along the X axis in this way, the calculation of the focus evaluation value corresponding to the second area 108 is being read (captured) from the first area 107. Therefore, the focus evaluation value can be quickly calculated and compared, and the focus responsiveness can be improved.
[0024]
The light receiving areas of the first region 107 and the second region 108 are not limited to the same area, but in that case, when the focus evaluation unit 104 calculates the focus evaluation value, It is necessary to calculate a focus evaluation value for an image captured by the imaging element 103 in accordance with the area ratio between the first region 107 and the second region 108. Further, the inclination of the AF image sensor 102 is not limited to the X axis, and the inclination along the Y axis with the intersection point between the optical axis 106 and the incident surface of the AF image sensor 102 as the origin, or this intersection point. It is good also as the inclination along the other straight line on the entrance plane passing through a position.
[0025]
Next, FIG. 2 shows a diagram for explaining the focusing operation in the autofocus device of the present embodiment. Hereinafter, the operation of the autofocus device of the present embodiment will be described based on FIG. However, FIG. 2A is a diagram for explaining the relationship between the focus evaluation value of the first region and the focus evaluation value of the second region before focusing, and FIG. FIG. 10 is a diagram for explaining the relationship between the focus evaluation value of the first region and the focus evaluation value of the second region after focusing.
[0026]
In the autofocus operation according to the present embodiment, only high frequency components are extracted by the HPF from the luminance signals of the respective images picked up by the AF image pickup device 102 and the image pickup image pickup device 103, and the obtained high frequency components are To the HPF of the stage. The HPF processing at this time is performed on the luminance signal obtained from the image signal sequentially output in the scanning line direction from the AF imaging element 102 and the imaging imaging element 103 using, for example, a CCD type or CMOS type imaging device. The high-pass filter process is sequentially performed. The HPF may be either digital processing or analog processing.
[0027]
Each high-frequency component extracted by the HPF is then calculated by the absolute value calculation means, and the absolute value is output to the addition means. The adding means sequentially adds the respective absolute values (absolute values of high frequency components) output from the absolute value calculating means in the order of input for each image sensor. 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 assigns each added value to the second area 108. The in-focus evaluation value 108 is output to the correction means, 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 the addition is performed when the absolute value from the absolute value calculating means reaches the end of the first area 107. By outputting the value as a focus evaluation value of the first region 107 to the correction unit, the focus evaluation value of the first region 107 is calculated following the focus evaluation value of the second region 108.
[0028]
When the focus evaluation values of the first areas 107 corresponding to the AF image sensor 102 and the imaging image sensor 103 are input to the correction unit, first, the first area 107 of the imaging image sensor 103 is input. Based on the ratio between the in-focus evaluation value of the first area and the in-focus evaluation value of the second area 108, for example, the AF image sensor 102 uses the focus evaluation value of the first area in the AF image sensor 102 as a reference. The focus evaluation value of the second area 108 is corrected. 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 are output to the determination unit.
[0029]
In the determination unit, the focus evaluation value of the first area 107 in the AF image sensor 102 output from the correction unit, that is, corrected by the correction unit, and the second area 108 in the AF image sensor 102 are matched. The focus evaluation value is compared, and the moving direction of the focal position, that is, the driving direction of the lens 101 is determined, and is output to the lens driving means 105. However, the correction process and the determination process at this time are such that the ratio of the focus evaluation values of the first and second areas in the AF image sensor 102 is the same between the first and second areas in the image sensor 103. The focus evaluation value is corrected so as to be the same as the focus evaluation value ratio, and the movement direction of the focal position is determined by comparing the corrected focus evaluation values.
[0030]
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 is b, and the focus of the first area in the image sensor 103 is When the evaluation value is c and the focus evaluation value of the second region is d, the following correction processing and determination processing are performed. As described above, when the focus evaluation value a of the first region 107 in the AF imaging element 102 is used as a reference, the focus evaluation value ratio in the imaging image sensor 103 is d / c. By multiplying the focus evaluation value b of the second region 108 in the AF image sensor 102, the focus evaluation value b × d / c of the second region 108 after correction is obtained. Next, the determination unit compares the focus evaluation value a of the first region 107 with the focus evaluation value b × d / c of the corrected second region 108, and the comparison result is a = b ×. In the case of d / c, since the current focal position is the in-focus position, the determination unit instructs 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 photographing imaging element 103 is the in-focus position. Needless to say, when a = b × d / c, the determination unit may not give a movement instruction to the lens driving unit 105. Further, although the current focal position is set to the in-focus position when a = b × d / c, for example, when the range of the in-focus position is specified in advance by measurement or the like, the determination unit determines that a = b × The current focus position is set to be the in-focus position within a range including a / b * d / c including d / c. As an example of the range of the focus position at this time, the focal depth of the optical system including the lens 101 that reproduces the spatial information of the subject (not shown) on the photographing image sensor 103, a value obtained by multiplying the focal depth by a coefficient, and the like. There are standard ranges.
[0031]
When the comparison result in the determination unit is a <b × d / c, the second evaluation result in the AF image sensor 102 is compared with the focus evaluation value a in the first area 107 in the AF image sensor 102. Since the in-focus evaluation value b × d / c after correction of the area 108 is larger, the determination unit determines the direction in which the in-focus evaluation value of the second area 108 in the AF image sensor 102 is reduced, that is, the focal position as the lens. The lens driving unit 105 is instructed to move in a direction closer to the lens 101. On the other hand, when the comparison result by the determination unit is a> b × d / c, the AF evaluation result is compared with the corrected focus evaluation value b × d / c of the second area 108 in the AF image sensor 102. Since the focus evaluation value a of the first area 107 in the image pickup device 102 is larger, the determination means determines the direction in which the focus evaluation value of the first area in the AF image pickup device 102 is decreased, that is, the focal position. By instructing the lens driving means 105 to move in a direction away from the lens 101, the focal position is moved so that the current focal position moves in the direction of the in-focus position. As a comparison method in the determination means, for example, a known method such as determination based on positive / negative of a subtraction result or determination based on a division result is used.
[0032]
As a determination method by division, for example, when b / a which is a ratio in the AF image sensor 102 is divided by d / c which is a ratio in the imaging image sensor 103, the current result is obtained when the division result is 1. Therefore, the determination unit instructs 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 photographing imaging element 103 is the in-focus position. However, when the division result is 1, the current focal position is the in-focus position. However, for example, when the range of the in-focus position is specified in advance by measurement or the like, the determination unit includes a range including 1 as the division result. To set the current focus position as the in-focus position. As an example of the range of the focus position at this time, the focal depth of the optical system including the lens 101 that reproduces the spatial information of the subject (not shown) on the photographing image sensor 103, a value obtained by multiplying the focal depth by a coefficient, and the like. There are standard ranges.
[0033]
When the result of division by the determination means is larger than 1, the focus evaluation value of the second area in the AF image sensor 102 is more compared to the ratio of the focus evaluation value in the image sensor 103. Since it is large, the determination unit instructs the lens driving unit 105 to move the focus evaluation value in the second region of the AF image sensor 102 in a direction that decreases the focus evaluation value, that is, in the direction that brings the focal position closer to the lens 101. On the other hand, when the result of division by the determination unit is less than 1, the focus evaluation value of the first area in the AF image sensor 102 is compared with the ratio of the focus evaluation value in the image sensor 103. Therefore, the determination unit instructs the lens driving unit 105 to move the focus evaluation value in the direction to decrease the focus evaluation value of the first area in the AF image sensor 102, that is, the direction away from the lens 101, to the lens driving unit 105. The focus position is moved so that the division result is 1, that is, the current focus position becomes the focus position.
[0034]
When the ratio of 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 image sensor 103 can be regarded as equal or equal, the AF imaging is performed. It is sufficient to compare the focus evaluation value a of the first region 107 and the focus evaluation value b of the second region at the element 102. Therefore, for example, as shown in FIG. 2A, when the focus evaluation value of the second area 108 in the AF image sensor 102 is larger than the focus evaluation value of the first area 107, The focus evaluation value of the first region 107 is subtracted from the focus evaluation value of the second region 108 to determine the magnitude of the focus evaluation value in each region. Based on the result, the current focus position is determined. The moving direction from the lens, that is, the lens driving direction is determined, and the instruction is output 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. Instructs the lens driving means 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 photographing imaging element 103 is the in-focus position.
[0035]
As described above, when the ratio of the focus evaluation value c of the first region 107 and the focus evaluation value d of the second region 108 in the imaging image sensor 103 can be regarded as equal or equal, or for AF When the determination process is performed only with the focus evaluation values a and b of the image sensor 102, the correction unit is unnecessary, and the moving direction of the focal position can be determined only by subtraction by the determination unit, so that the time required for the determination can be further reduced. can do. As a result, even when combined with other evaluation methods, the time required from the acquisition of one image (or an image for one frame) to the movement of the focal position can be reduced.
[0036]
However, in the imaging apparatus for capturing a moving image such as a television camera or a video camera provided with the above-described autofocus apparatus and the imaging apparatus for capturing a still image such as a digital camera, as shown in FIG. Since it is difficult to arrange the image pickup element 102 and the image pickup image pickup element 103 at the same position on the optical axis 106 of the same lens 101, in the actual image pickup element arrangement, as described later, for AF and for image pickup Use two sets (or more) of photographic lenses corresponding to the number of each image sensor, or separate the optical path of light incident on one set of photographic lenses, It is necessary to enter each imaging element.
[0037]
FIG. 3 is a diagram for explaining an example of the arrangement of the AF image sensor and the image sensor for photographing in the autofocus device 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 imaging element and a photographing imaging element 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 image sensor and a photographing image sensor are arranged by separating an optical path behind a lens.
[0038]
In the autofocus device shown in FIG. 3A, an imaging lens 301 that reproduces the spatial information of a subject (not shown) on the imaging sensor 103 and an auto that reproduces the spatial information of the subject on the AF imaging element 102. The focusing lens 302 is provided separately. In other words, the camera unit for shooting composed of the photographing lens 301 and the image sensor for photographing 103 and the camera unit for autofocus composed of the autofocus lens 302 and the image sensor for AF 102 are configured separately. It is a TV camera equipped with an autofocus device.
[0039]
In this configuration, the focal movements of the photographing lens 301 and the autofocus lens 302 are interlocked. When the focal position of the autofocus lens 302 is moved to the in-focus position of the lens 302, the photographing lens 301 is used. The characteristics of the photographic lens 301 and the autofocus lens 302 are set so that the focal position of the lens 301 is also the in-focus position of the lens 301, and the photographic imaging element 103 and AF imaging corresponding to each lens are set. The element 102 is arranged.
[0040]
In the autofocus device shown in FIG. 3B, the light is emitted from the photographing lens 301 by the semi-transmissive mirror 303 disposed between the photographing lens 301 and the photographing image sensor 103 that form the optical system of the television camera. In this configuration, the optical path of the separated light beam (image) is separated, one separated light beam is incident on the image sensor for photographing 103, and the other light beam is incident on the image sensor for AF 102. That is, the television camera is provided with an autofocus device that uses a single optical system that is relatively large and heavy.
[0041]
In this configuration, for example, the distance that is reflected by the semi-transmissive mirror 303 and reaches the incident surface of the AF image sensor 102 is equal to the distance that passes through the semi-transmissive mirror 303 and reaches the incident surface of the image sensor 103. In addition, an AF imaging element 102 and a photographing imaging element 103 are arranged.
[0042]
In addition, the spatial information of the subject reproduced on the AF imaging element 102, that is, the image, and the spatial information of the subject reproduced on the imaging imaging element 103, that is, the image, are reproduced with the top and bottom reversed. . Therefore, in the present embodiment, for example, the imaging image sensor 103 and the AF imaging element 102 are arranged such that the upper part of the spatial information of the subject is the reading start position of the AF imaging element 102 and the imaging image sensor 103. Is placed.
[0043]
It should be noted that the above-described deviation between the imaging element 103 for imaging and the imaging element 102 for AF, that is, a deviation in the rotational direction around the optical axis and a deviation in a direction parallel to the imaging surface of each of the imaging elements 102 and 103. On the other hand, it goes without saying that the image can be corrected by a known image correction or the like.
[0044]
FIG. 4 is a diagram for explaining the detection range of the focus evaluation value in the autofocus device according to the present embodiment. However, FIG. 4A is a diagram (side view) for explaining the positional relationship between the autofocus imaging device and the imaging sensor, and FIG. 4B is an autofocus imaging device and imaging. It is a figure (front view) for demonstrating the detection possible area | region of the focus evaluation in an image sensor.
[0045]
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, the depth of focus is a position where a 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.
[0046]
As shown in FIG. 4A, when the angle formed by the AF image sensor 102 and the image sensor 103 is α, there is no difference in the high frequency component of the image inside the depth of focus. In-focus evaluation values cannot be obtained. Therefore, the range in which the focus evaluation value can be detected is a region that is separated from the intersection position between the AF image sensor 102 and the image sensor 103 by a focal depth or more. Since the focal depth in the first region 107 is Ln = dn / tanα, the region 402 excluding the region 401 from the intersection position of the imaging elements 102 and 103 to the focal depth Ln shown in FIG. This is the detection range of the focus evaluation value in the first area 107. Similarly, since the depth of focus in the second region 108 is Lf = df / tanα, the region 404 excluding the region 403 from the intersection position of the imaging elements 102 and 103 shown in FIG. 4B to the depth of focus Lf. Is the detection range of the focus evaluation value in the second region 108.
[0047]
As described above, in the imaging device using the autofocus device of the present embodiment, the AF imaging device 102 is incident light, that is, a lens, among the imaging devices that convert an optical image of a subject to a video signal. 101 is inclined with respect to the optical axis 106. In particular, by arranging the AF image sensor 102 to be inclined with respect to the image sensor 103 for imaging arranged in parallel with the orthogonal plane orthogonal to the optical axis 106, the input surface and the optical axis of the AF image sensor 102 are arranged. Each pixel of the AF image sensor 106 is divided into two regions (a first region 107 and a second region 108), with the intersecting line between the orthogonal plane at the position where the image sensor 106 intersects and the AF image sensor 106 as a boundary. Divided pixel area). At this time, in the case where the lower end of the AF image sensor 106 is inclined so as to be close to the lens 101, the first area 107 of the AF image sensor 102 is close to the lens 101, and the second area 108 is the lens. It is far from 101. Needless to say, when the tilt direction of the AF image sensor 102 is reversed, the relationship between the first and second regions 107 and 108 and the lens 101 is also reversed.
[0048]
Therefore, even when a subject image for one frame is captured by the AF image sensor 102, the first area 107 is centered on the position where the input surface of the AF image sensor 102 and the optical axis 106 intersect. An image with the same effect as when the focal position is moved to the lens 101 side by a minute amount is obtained, and the same effect as when the focal position is moved far from the lens 101 by a minute amount in the second region. An image is obtained. As a result, even when the focus position is at the focus position, images at two different focus positions can be obtained without moving the focus position of the lens 101. Can be maintained, and the movement of the focal position from the in-focus position associated with the autofocus control can be prevented. Further, since images at two different focal positions can be obtained by one imaging, the focal position can be quickly set to the in-focus position even for a moving subject.
[0049]
Note that in this embodiment, the readout of video signals from the imaging imaging element 103 and the AF imaging element 102 is controlled so as to be read out in the same period, thereby shortening the calculation time required for focusing. However, the present invention is not limited to this, and the video signal is read from the AF image sensor 102 following the reading of the video signal from the image sensor 103, or vice versa. The signal may be read out. 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 can be used for imaging. Since the element 103 and the AF image sensor can be shared, the circuit scale can be reduced when the focus determination means 104 is configured by hardware. To become. 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, the burden on the information processing device can be reduced, so a relatively inexpensive information processing device is used. it can.
[0050]
In the present embodiment, the case where the AF imaging element 102 and the imaging imaging element 103 use the same size and the same image pitch is described. However, the present invention is not limited to this. By using an image sensor having the same number of pixels as that of the image sensor 103 and a small pixel pitch for the AF image sensor 102 that does not affect the output quality, the AF image sensor 102 and the AF image sensor 102 are related. Since the optical system can be miniaturized, the autofocus device can be miniaturized. In addition, the manufacturing cost can be reduced by using the small AF image sensor 102 and the optical system. Furthermore, it goes without saying that imaging elements having different incident areas may be used. For example, when a focus area smaller than the imaging area of the imaging element 103 is set in advance, by using the AF imaging element 103 having an imaging area sufficient to capture an image of the focus area, AF Since not only the image pickup element 102 but also the optical system related to the AF image pickup element 102 can be downsized, the autofocus device can be downsized. In addition, the manufacturing cost can be reduced by using the small AF image sensor 102 and the optical system.
[0051]
Further, in the present embodiment, by tilting the AF image sensor 102, an image in which the focal position is moved to the lens 101 side by a minute distance with respect to the photographing image sensor 103, and the focal position is a minute distance. However, the present invention is not limited to this, and the first area 107 and the second area 108 are set as two imaging areas, respectively. It goes without saying that the above-described effects can be obtained even in a configuration in which more image sensors are provided.
[0052]
Furthermore, in the present embodiment, the lens driving unit 105 drives the focus mechanism of the lens 101 based on the drive direction determination output from the focus determination unit 104 and moves the focus position by a preset amount. Although configured, it is not limited to this. For example, the focus determination means 104 is provided with means for calculating the difference between the focus evaluation values of the first and second areas 107 and 108 and the difference between the focus evaluation values of the first and second areas 107 and 108. A moving amount storing means for storing the moving amount of the lens 101 in accordance with the focusing amount, and the focusing mechanism determines the difference in the focusing evaluation value from the moving amount storing means based on the difference in the focusing evaluation value from the focusing determining means 104. By searching for the corresponding movement amount and moving the lens 101 in the movement direction from the searched movement amount and the in-focus determination means 104, the focal point of the lens 101 can be accurately and efficiently moved. Therefore, it is possible to shorten the time required for focusing and realize an efficient focusing operation. 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 every time the focus evaluation value is obtained. Furthermore, by calculating the movement amount of the lens 101 in consideration of the F value, focal length, subject distance, etc. of the lens 101, the focal point movement of the lens 101 can be performed more accurately and efficiently. It is possible to realize an efficient focusing operation that further shortens the time required for focusing.
[0053]
The invention made by the present inventor has been specifically described based on the embodiment of the invention, but the invention is not limited to the embodiment of the invention and does not depart from the gist of the invention. Of course, various changes can be made.
[0054]
【The invention's effect】
The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
(1) Since the image sensor for AF is inclined with respect to the orthogonal plane orthogonal to the optical axis of the incident light, an image when the focal position is moved by a minute amount with one image sensor. Can be obtained by one imaging. As a result, even when the focus position is at the 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 of only one AF image sensor, the configuration of the autofocus device can be simplified. As a result, the apparatus can be reduced in size and cost.
(3) Even when the conventional hill-climbing method is used for autofocus control, an autofocus operation based on an 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 time loss. As a result, even for a moving subject, the focal position can be quickly moved to the in-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 according to the present embodiment;
FIG. 3 is a diagram for explaining an example of an arrangement of an AF image sensor and a shooting image sensor in the autofocus device according to the present embodiment;
FIG. 4 is a diagram for explaining a focus evaluation value detection range in the autofocus device according to the present embodiment;
[Explanation of symbols]
101 ... Lens 102 ... Autofocus imaging device
103 ... Image sensor for photographing 104 ... Focus determination means
105 ... Lens driving means 106 ... Optical axis
107 ... first region 108 ... second region
301 ... Lens for photographing 302 ... Lens for autofocus
303: Transflective mirror 401 ... Depth of focus area in the first area
402, 404 ... detectable range of focus evaluation value
403: Depth of focus area in the third area

Claims (2)

And autofocus imaging device for converting an optical image of the imaged object in a video signal, based on the image signal obtained by the autofocus imaging device, an optical image of the object to be imaged on the autofocus imaging element An evaluation value calculating means for calculating a focus evaluation value indicating the sharpness of the image, and a focus adjustment for adjusting the focal position of the lens based on the focus evaluation value and forming an optical image of the subject on the image pickup device for imaging An autofocus device having means,
The image sensor for autofocus is disposed to be inclined with respect to an orthogonal plane orthogonal to the optical axis of incident light, and the evaluation value calculating means is at a position where the input surface of the image sensor for autofocus and the optical axis intersect. and a evaluation value calculating means for calculating an orthogonal plane to the focus evaluation value of the divided pixel each region where the intersection of the autofocus image sensor is divided as a boundary, the focus adjusting means of the divided pixel each region Comparing means for comparing the focus evaluation values ,
The evaluation value calculation unit divides the pixel area of the imaging element for imaging into areas corresponding to the divided pixel areas of the imaging element for autofocus, and calculates a focus evaluation value for each divided pixel area of the imaging element for imaging. And means for correcting the focus evaluation value for each of the divided pixel regions of the image sensor for autofocus based on the focus evaluation value for each of the divided pixel regions calculated from the image pickup device for photographing. And the focus adjusting means adjusts the focal position of the lens based on the corrected focus evaluation value of the image sensor for autofocus. An autofocus imaging device that converts a captured optical image of a subject into a video signal, and an optical image of the subject that forms an image on the autofocus imaging device based on a video signal obtained by the autofocus imaging device An evaluation value calculation means for calculating a focus evaluation value indicating the sharpness of the image, and a focus adjustment for adjusting the focal position of the lens based on the focus evaluation value and forming an optical image of the subject on the image pickup device for photographing In an imaging device having an autofocus device comprising:
The image sensor for autofocus is disposed to be inclined with respect to an orthogonal plane orthogonal to the optical axis of incident light, and the evaluation value calculating means is at a position where the input surface of the image sensor for autofocus and the optical axis intersect. Means for calculating a focus evaluation value for each divided pixel region that is divided with an intersecting line between the orthogonal plane and the image sensor for autofocus as a boundary, and the focus adjustment unit performs focus evaluation for each divided pixel region. Comparing means for comparing values ,
The evaluation value calculation unit divides the pixel area of the imaging element for imaging into areas corresponding to the divided pixel areas of the imaging element for autofocus, and calculates a focus evaluation value for each divided pixel area of the imaging element for imaging. And means for correcting the focus evaluation value for each of the divided pixel regions of the image sensor for autofocus based on the focus evaluation value for each of the divided pixel regions calculated from the image pickup device for photographing. And the focus adjusting means adjusts the focal position of the lens based on the corrected focus evaluation value of the image sensor for autofocus .

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