JP2003057531A - Method and device for phase difference detection, range finder, and image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress complicated processing and deterioration in detection precision as much as possible as to a phase difference detecting device which detects the phase difference between pictures imaged on a couple of optical sensor arrays. SOLUTION: A correlation arithmetic part 5e extracts partial picture data groups from a couple of picture data arrays corresponding to the outputs of the couple of optical sensor arrays 3a and 3b, generates a plurality of combinations of the couple of partial picture data groups having different relative positions on the couple of optical sensor arrays 3a and 3b, and obtain correlativity by the combinations, and a right-left difference correction acquisition part 5i obtains a correction value corresponding to the data difference between the couple of partial picture data groups showing the maximum correlativity among obtained correlativity values; and a correlation arithmetic part 5j corrects a partial picture data group as an object of correlation operation with the obtained correction value to obtain correlativity and a phase difference detection part 5n detects the phase difference between pictures imaged on the couple of optical sensor arrays 3a and 3b according to the couple of partial picture data group showing the maximum correlativity among correlativity values obtained by the correlation arithmetic part 5j.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase difference detecting method, a phase difference detecting device, a distance measuring device and an image pickup device.

[0002]

2. Description of the Related Art Conventionally, in an autofocus camera, when a subject is focused by a so-called passive method, a non-TT
In the case of the L camera, the position of the photographing lens is controlled according to the detected subject distance after detecting the subject distance using the subject image that has not passed through the photographing lens.
In the case of a camera, the amount of deviation from the in-focus state is detected using a subject image obtained by passing through the photographing lens, and then the position of the photographing lens is controlled according to the detected amount of deviation.
Hereinafter, the operation principle described above will be described with reference to FIG.

In the figure, a pair of lenses 1a and 1b are arranged apart from each other by a predetermined base line length b, and a pair of lenses 1a and 1b are arranged apart from the pair of lenses 1a and 1b by a focal length f. Images of the target 2 are formed on the optical sensor arrays 3a and 3b through different optical paths A and B, respectively. Target 2 is 1
It is assumed that the pair of lenses 1a and 1b are present at a position separated by a distance L in the front direction.

The center of the image formed on the pair of photosensor arrays 3a and 3b when the object 2 is located at infinity is the reference corresponding to the optical axes of the lenses 1a and 1b on the photosensor arrays 3a and 3b. The image is formed at the positions (3a1, 3b1), but when the object 2 approaches the infinity position, the image is formed at a position deviated from the reference positions (3a1, 3b1) by α. From the principle of triangulation, the distance L to the target 2 is L = bf
/ Α. Since the base line length b and the focal length f are constants, the distance L can be measured by detecting the shift amount α. This is the principle of passive distance measurement (so-called external light triangulation) used in non-TTL cameras. In a non-TTL camera, instead of using the distance L as the output value of the distance measuring device, the shift amount α may be used as it is. In the present application, this shift amount α is referred to as a phase difference.

In the case of the TTL camera, the light passing through the image pickup lens (not shown) is given to the pair of lenses 1a and 1b to detect the phase difference α between the left and right image pairs as described above.
In this case, the center of the image in the focused state is the reference position on each of the photosensor arrays 3a and 3b. Therefore, whether the phase difference α is positive or negative is the front focus state or the rear focus state, and the absolute value thereof indicates the degree of deviation from the focus.

In both of these, an image of an object is formed on a pair of photosensor arrays by an optical system, and a relative position shift of a pair of video signals output by the pair of photosensor arrays,
That is, the phase difference is detected by performing the correlation calculation on the partial video data groups (see FIG. 3B) extracted from the pair of video signals. Note that such phase difference detection is not limited to the autofocus camera, and can be used in various distance measuring devices, focus detection devices, and the like.

In such a method for detecting a phase difference, as a method for reducing deterioration of detection accuracy due to stray light such as flare that occurs when a strong light source such as the sun exists in the background of the subject, for example, Japanese Patent Laid-Open No. There is one disclosed in Japanese Patent Laid-Open No. 8-166237. Specifically, three technologies are disclosed, and the first technology is a technology for correcting an average value of a pair of sensor data output by a pair of optical sensors so that there is no difference between the two sensor data. The second technique is a technique for correcting each combination of partial image data groups extracted from a pair of sensor data so that there is no difference in the representative value between both partial image data groups, and the third technique is a pair of sensor data. Is a technique for correcting so that each data value of is replaced with a differential approximation value related to the data variable number.

[0008]

However, in the case of the above-mentioned first technique, that is, when the average value of the pair of sensor data output by the pair of optical sensors is corrected so that there is no difference between the two sensor data, The partial video data group used when performing the correlation calculation is affected by the error between the sensor data not included in the partial video data group. Therefore, for example, the combination of partial image data groups having the highest correlation in the uncorrected state is not affected by flare,
When other parts are affected by flare, there is a problem that the phase difference detection accuracy after correction becomes worse than before correction.

Further, in the case of the above-mentioned second technique, that is, in the case of correcting so that there is no difference in the representative value between the partial video data groups for each combination of the partial video data groups extracted from a pair of sensor data, the partial video data There is a problem that a correction amount must be calculated for each combination of groups, and the processing operation increases as the number of combinations of partial video data groups increases.

In the third technique, that is, when correcting each data value of a pair of sensor data by replacing it with a differential approximation value relating to a data variable number, a complicated differential approximation value replacement process is performed for each data. Is required.

It is an object of the present invention to provide a phase difference detecting method, a phase difference detecting device, a distance measuring device and an image pickup device capable of suppressing complicated processing and deterioration of detection accuracy as much as possible.

[0012]

According to a first aspect of the present invention, a pair of video data strings composed of a plurality of video data corresponding to the outputs of a pair of photosensor arrays on which an image from a measurement object is formed is relative. Correlation degree obtaining step for obtaining a correlation degree for each combination of the pair of partial video data groups by extracting partial video data groups at different positions and forming a plurality of combinations of the pair of partial video data groups, and the correlation Between the correction value acquisition step of obtaining a correction value according to the data difference between the pair of partial video data groups showing the maximum degree of correlation, and at least a part of each of the pair of video data strings. A correction step of correcting the data difference based on the correction value, and a phase difference detection step of detecting a phase difference between the images formed on the pair of sensor arrays based on the corrected image data. Including phase difference detection method It is. According to the method including such steps, the phase difference between the images formed on the pair of sensor arrays is detected by the correction value according to the difference between the pair of partial image data groups showing the maximum correlation. Since the data difference between the video data used for the correction is corrected, the correction can be performed based on the difference between the pair of partial video data groups having a high correlation originally, and the influence of the data not having a high correlation is reduced. Therefore, it is possible to prevent the troublesome processing of obtaining the correction amount for each combination of the partial video data groups, and to eliminate the complicated differential approximation value replacement processing for each data.

A second invention comprises a pair of sensor arrays on which an image from a measurement object is formed, and a pair of image data strings consisting of a plurality of image data corresponding to the outputs of the pair of sensor arrays. A correlation degree acquisition unit that extracts partial video data groups having different relative positions to form a plurality of combinations of a pair of partial video data groups, and obtains a correlation degree for each combination of the pair of partial video data groups; Between the correction value acquisition unit for obtaining a correction value according to the data difference between the pair of partial video data groups, in which the correlation degree acquisition unit shows the maximum correlation degree, and at least a part of each of the pair of video data strings Correction unit for correcting the data difference between the pair of sensor arrays based on the image data corrected by the correction unit, and a phase difference for detecting the phase difference between the images formed on the pair of sensor arrays. Phase difference detection including phase difference detector It is a device. According to such a configuration, the phase difference between the images formed on the pair of sensor arrays is detected by the correction value corresponding to the difference between the pair of partial image data groups showing the maximum correlation. Since the data difference between the video data used is corrected, correction can be performed based on the difference between a pair of partial video data groups that originally have a high degree of correlation, and it is possible to reduce the influence of data that originally has a low degree of correlation. It is possible to prevent the troublesome process of obtaining the correction amount for each combination of the image data groups, and to eliminate the complicated differential approximation value replacement process for each data.

According to a third aspect of the present invention, there is provided a distance measuring device comprising the phase difference detecting device and a distance detecting section for obtaining distance data corresponding to the distance to the object to be measured based on the phase difference detected by the phase difference detecting device. It is a device. According to such a configuration, in addition to the above effects, the accuracy of the distance data is improved, so that it is possible to prevent a decrease in the distance measurement accuracy.

According to a fourth aspect of the present invention, the phase difference detecting device, the objective lens, an image forming section on which an object image passing through the objective lens is formed, and the phase difference obtained by the phase difference detecting device are obtained. Accordingly, the imaging apparatus includes a focusing control unit that performs a focusing operation between the objective lens and the image forming unit. According to this configuration, in addition to the above effects, the focusing accuracy of the objective lens is improved, so that the image quality of the captured image can be improved.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 shows an example in which the present invention is applied to an image pickup apparatus. In addition, in FIG.
The same components as those in FIG.

In FIG. 1, the pair of lenses 1a and 1b are used to form the image of the object 2 into the pair of photosensor arrays 3 as described above.
Images are formed on a and 3b, respectively. Optical sensor array 3
Each of a and 3b has 162 pixels (photoelectric conversion elements) arranged on a line, and each pixel outputs an electric signal corresponding to the light amount of the image of the object 2 imaged on the pixel. . The number of pixels of the pair of photosensor arrays 3a and 3b can be changed as appropriate. The output unit 4 outputs the outputs of the pair of photosensor arrays 3a and 3b to the CPU 5. C
The PU 5 processes the input outputs of the pair of photosensor arrays 3a and 3b based on various operation programs and various data stored in the memory section 6 as described below. The focus control unit 7 is controlled by the CPU 5, moves the objective lens 8 in the direction of the double-headed arrow X, and performs the focusing operation between the objective lens 8 and the image forming unit 9. The image forming unit 9 may be a silver salt film or a solid-state image sensor having a photoelectric conversion element such as a so-called CCD sensor or CMOS sensor.

Next, focusing on the function of the CPU 5, FIG.
The operation will be described with reference to. In FIG. 1, a functional block diagram is adopted in the CPU 5 in order to explain the functions of the CPU 5.

When a release switch (not shown) is operated, the pair of photosensor arrays 3a and 3b start operating (step 3a). As described above, the pair of optical sensor arrays 3a and 3b are provided with the pair of lenses 1a and 1b, respectively.
Images are formed respectively via different optical paths A and B, and an electric signal corresponding to the light amount of the formed images is output from the pair of photosensor arrays 3a and 3b.

The A / D conversion section 5a A / D converts the outputs of the pair of photosensor arrays 3a and 3b input through the output section 4.
Convert. The memory section 5b outputs the output of the pair of A / D converted photosensor arrays 3a and 3b to the pair of video data strings (I
L, IR) are stored in the pair of memory areas 5bL, 5bR. In this example, the A / D converted optical sensor array 3a
Is stored in the memory area 5bL and the A / D converted output of the photosensor array 3b is stored in the memory area 5bR. Further, in this example, since the number of pixels of each of the pair of photosensor arrays 3a and 3b is 162, the video data string (IL,
Each IR has 162 data (IL (1 to 16)
2), IR (1-162)).

The left / right difference determining section 5c reads out a pair of video data strings (IL, IR) stored in the memory areas 5bL, 5bR in the memory section 5b (step 3b), and calculates the difference or maximum value of their average values. Is calculated, and it is determined whether the calculated value is greater than or equal to a predetermined value A (step 3c). That is, the difference between the pair of video data strings (IL, IR) is taken as the left-right difference, and it is determined whether or not the left-right difference is equal to or larger than the predetermined value A.

The left / right difference correction unit 5d has a left / right difference determination unit 5c.
When it is determined that the difference between the average values or the maximum values of the pair of video data strings (IL, IR) is equal to or larger than the predetermined value A, that is, 1
When it is determined that the difference between the pair of video data strings (IL, IR) is not less than the predetermined value A (step 3c), the difference between the average value or the maximum value of the pair of video data strings (IL, IR) is predetermined. All the data of the video data string is corrected by a uniform correction amount so as to be smaller than the value A, and the corrected data is stored in the memory areas 5bL and 5bR, and a pair of video data strings (I
L, IR) is updated (step 3d). The correction by the left / right difference correction unit 5d is almost the same as the first technique already described as the conventional technique.

When the difference between the pair of video data strings (IL, IR) is smaller than the predetermined value A in step 3c or when the process in step 3d is completed, the correlation calculation unit 5e as the correlation degree acquisition unit performs the correlation calculation. (Step 3e). As a specific process, a partial video data group (iL, IR) is generated from a pair of video data strings (IL, IR).
iR) are extracted so that their relative positions on the optical sensor array are different, and each extracted partial image data group (iL,
The correlation degree is calculated for the combination of iR). In this example, the number of data of the partial video data group is 26, the partial video data group (iL) extracted from the video data string (IL) is fixed, and the video data string (IR) is fixed as shown in FIG. 3B. The method of shifting the partial video data group (iR) extracted from each one by one is adopted. Specifically, the correlation calculation is performed based on the following equation (1).

[0024]

[Equation 1]

When the correlation calculation in step 3e is completed, the maximum correlation degree detecting section 5f executes the equation (1) calculated by the correlation calculating section 5e.
The minimum value of S (l) based on the calculation result of
Let S (x) shown in (b). ) That is, the maximum correlation is detected, and the detected S (x) and the correlation calculation function S (l)
And (l = 1 to 137) are stored in the memory unit 5g (step 3f).

When the storage in the memory unit 5g is completed, the maximum correlation degree determining unit 5h determines whether the minimum value S (x) obtained by the maximum correlation degree detecting unit 5f is within the predetermined value B or more and the predetermined value C or less. Then, it is determined whether the pair of partial image data groups is not affected by stray light such as flare (step 3g).

In step 3g, the minimum value S (x) is not included in the range from the predetermined value B to the predetermined value C and the pair of partial image data groups (IL, IR) is affected by stray light such as flare. If it is determined that there is a high possibility that there is a high probability, the left / right difference correction amount acquisition unit 5i as the correction value acquisition unit divides the minimum value S (x) by the number of data pieces (26 pieces) of the partial video data group and the error per data The amount is calculated and used as the left-right difference correction value (step 3h).

When the left-right difference correction value is obtained, the correlation calculation unit 5j as a correction unit makes the relative positions of the partial video data groups (iL, iR) different from each other from the pair of video data strings (IL, IR). Each of the extracted partial video data groups (iL, iR) is corrected with the left / right difference correction value obtained by the left / right difference correction amount acquisition unit 5i (step 3i). As an example of the correction, for example, the sum of each data of the partial video data group (iLx, iRx) indicating the minimum value S (x) is obtained, and the magnitude relation of the total is determined to determine the partial video data group (i
Lx) is large, the partial video data group (iL)
Correction is performed by subtracting the left-right difference correction value from each data included in the partial video data group (iL), and the total sum of the partial video data group (iLx) is less than the total sum of the partial video data group (iRx). If it is small, the partial video data group (iL) is extracted when the partial video data group (iL) is extracted.
The correction is performed by adding the left-right difference correction value from each data included in. Using the partial video data group (iL) after such correction, the correlation calculation unit 5j performs the correlation calculation of the above-mentioned formula (1) (step 3j).

In this way, the pair of partial video data groups is corrected for each combination of the partial video data groups by the correction value according to the difference between the pair of partial video data groups showing the maximum correlation,
Since the correlation calculation is performed again for each combination of the corrected pair of partial image data groups, the correlation degree is obtained, so that the correction is performed based on the difference between the pair of partial image data groups having a high correlation degree before the correction. It is possible to reduce the influence of data that is not originally high in correlation during correction, prevent the troublesome processing of calculating the correction amount for each combination of partial image data groups, and perform complicated differentiation on individual data. It is possible to eliminate the approximate value replacement process.

When the correlation calculation in step 3j is completed, the maximum correlation degree detection unit 5k determines the minimum value of S (l) (S (x ')), that is, the maximum correlation, based on the calculation result performed by the correlation calculation unit 5j. Detect the degree. When S (x ′) is detected by the maximum correlation degree detection unit 5k, the comparison determination unit 5k
For l, the magnitude of S (x) stored in the memory unit 5g and S (x ') detected by the maximum correlation degree detection unit 5k are compared (step 3k). Supplementing this operation, it is considered that stray light may change intricately depending on the shape of the strong light source that is the source of stray light and the positional relationship between the light source and the target 2, and the effect of stray light is reduced by the above-mentioned correction depending on the situation of stray light. There may be cases where it is done and cases where it is not done. Therefore, step 3k is executed to confirm whether the influence of stray light is reduced by the above-described correction.

The comparison / decision unit 5l uses the smaller one of S (x) and S (x '), that is, the one with a higher degree of correlation as valid data (steps 3l, 3m). Specifically, S (x) is S
If it is smaller than (x ′), S (x) before correction in step 3i and the correlation calculation function S (l) (an integer of 1 = 1 to 137) are read from the memory unit 5g and output to the interpolation calculation unit 5m. If (x ′) is smaller than S (x), S after correction in step 3i used by the maximum correlation degree detection unit 5k
(X ′) and its correlation calculation function S (l) (l = 1 to 137
Is output to the interpolation calculation unit 5m.

As described above, the maximum correlation before correction and the maximum correlation after correction are compared, and when the maximum correlation deteriorates due to the correction, the maximum correlation before correction is used as valid data, which is complicated. If the effect of stray light cannot be removed by the correction, the correction can be invalidated. Therefore, it is possible to prevent the deterioration of the phase difference detection accuracy due to the ineffective correction.

The interpolation calculation unit 5m inputs the minimum value (S
(X ') or S (x)) and the correlation operation function values (S (x'-1) and S (x' + 1)) before and after it or S (x-).
X'or x is corrected by the interpolation method using 1) and S (x + 1)) (step 3n). Since this interpolation calculation is a known technique, detailed description will be omitted.

When x'or x is corrected by the interpolation calculation, the phase difference detecting section 5n causes the corrected x'or x to have a reference position (for example, non-TTL) set on the optical sensor 3b side.
In the case of external light triangulation such as a camera, it is set to a position corresponding to the center position of the target image at the infinity position in the measurement direction, and in the case of a focus detection device used in a TTL camera or the like, the taking lens is in focus The position corresponds to the center position of the target image at a given time. ), That is, a phase difference is detected (step 3o).

The focus control section 7 controls the position of the objective lens 8 based on the phase difference detected by the phase difference detection section 5n, and performs the focus operation between the objective lens 8 and the image forming section 9. In addition, non-T
In the case of a TL camera, the distance detection unit 5o obtains the distance data to the object 2 based on the phase difference detected by the phase difference detection unit 5n, and the focusing control unit 7 causes the objective lens 8 to operate based on the distance data. The position may be controlled to perform the focusing operation between the objective lens 8 and the image forming unit 9.

In the above description, when performing the correlation calculation, one partial video data group (iL) is fixed and the other partial video data group (iR) is shifted one by one.
The correlation calculation method is not limited to the above, and can be changed as appropriate. For example, as disclosed in Japanese Unexamined Patent Publication No. 8-166237, which is shown as a conventional technique, both partial video data groups may be sequentially shifted so that their relative positions are different.

Further, in the above, each video data string (IL, I
The number of data of R) is 162 and the number of data of the partial video data group is 26, but these can be changed appropriately.

Further, although the example in which the present invention is applied to the image pickup apparatus has been shown above, the invention is not limited to the image pickup apparatus. For example, it can be used for various distance measuring devices, focus detection devices, and the like.

[0039]

According to the present invention, the phase difference between the images formed on the pair of sensor arrays is detected by the correction value according to the difference between the pair of partial image data groups showing the maximum correlation. Since it corrects the data difference between the video data used to
It is possible to perform correction based on the difference between a pair of partial video data groups that originally have a high degree of correlation, reduce the influence of data that is not originally high in correlation, and obtain a correction amount for each combination of partial image data groups. It is possible to prevent troublesome processing and eliminate complicated differential approximation value replacement processing for individual data.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of FIG.

FIG. 3 is an explanatory diagram for explaining the operation of FIG. 1.

[Explanation of symbols]

3a Optical sensor array 3b optical sensor array 5e Correlation degree acquisition unit 5i Correction value acquisition unit 5j Correction unit 5n Phase difference detector 5o Distance detector 7 Focus control section 8 Objective lens 9 Imaging unit

Claims (4)

[Claims] 1. A partial image data group having a different relative position is extracted from a pair of image data strings consisting of a plurality of image data corresponding to the outputs of a pair of photosensor arrays on which an image from a measurement object is formed. A plurality of combinations of a pair of partial video data groups, and a correlation degree acquisition step of obtaining a correlation degree for each combination of the pair of partial video data groups; and showing the maximum correlation degree among the correlation degrees. A correction value acquisition step of obtaining a correction value according to a data difference between a pair of partial video data groups, and at least a data difference between a part of each of the pair of video data strings is corrected based on the correction value. A phase difference detection method comprising: a correction step; and a phase difference detection step of detecting a phase difference between images formed on the pair of sensor arrays based on the corrected image data. . 2. A relative position is different from a pair of sensor arrays on which an image from a measurement target is formed and a pair of image data rows composed of a plurality of image data corresponding to outputs of the pair of sensor arrays. A correlation degree acquisition unit for extracting a partial video data group to create a plurality of combinations of a pair of partial video data groups and obtaining a correlation degree for each combination of the pair of partial video data groups; Is a maximum correlation, and a correction value acquisition unit that obtains a correction value according to a data difference between the pair of partial video data groups, and a data difference between at least a part of each of the pair of video data strings. A correction unit that corrects based on the correction value, and a phase difference detection unit that detects a phase difference between the images formed on the pair of sensor arrays based on the image data corrected by the correction unit. A position characterized by including Difference detection device. 3. The phase difference detection device according to claim 2, and a distance detection unit that obtains distance data according to the distance to the measurement target based on the phase difference detected by the phase difference detection device. Distance measuring device characterized by. 4. The phase difference detecting device according to claim 2, an objective lens, an image forming section on which an object image passing through the objective lens is formed, and the phase difference obtained by the phase difference detecting device. An image pickup apparatus comprising: a focusing control unit that performs a focusing operation between the objective lens and the image forming unit according to the above.