JP2003214846A - Ranging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ranging apparatus in which a release timing lag is reduced by shortening time for detecting subject distance, and at the same time accurately measuring the subject distance. <P>SOLUTION: A ranging apparatus 1 comprises a means 13 for extracting extraction images 20 having each specific size from two image data, correlation operation means 14 and 17 for calculating the correlation value of both the images while successively shifting the extraction image, an operation-controlling means 15 for controlling the operation of the correlation value, a reliability- judging means 16 for detecting the extremal value of the calculated correlation value, and a corresponding-position detecting means 18 for detecting a corresponding position. The operation-controlling means 15 suspends the calculation of the correlation value during the operation. The reliability-judging means 16 judges whether an extremal value has been already detected in the calculated correlation value during the interruption of the operation, and terminates the operation of the correlation value when the extremal value is detected, and detects the corresponding position. When the extremal value cannot be detected during suspension, the operation of the correlation value is resumed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a pair of image pickup devices, which receives a subject light and detects a subject distance based on an image obtained by each image pickup device. Regarding the device.

[0002]

2. Description of the Related Art Conventionally, in an external light passive distance measuring device, a part of a subject image obtained by each of a pair of image pickup devices is extracted, one image is compared with the other image, and the distance between the two images is compared. It is configured to detect the subject distance by calculating the shift amount.

That is, the conventional distance measuring device 70 is shown in FIG.
As shown in (a), a pair of objective lenses 71L, 71R
And a pair of image pickup elements 72L and 72R for photoelectrically converting subject light from the objective lenses 71L and 71R, and the image pickup element 72
Control unit 73 for processing image data from L and 72R
And have. The distance measuring device 70 is shown in FIG.
As shown in (b), the camera is mounted so that the detection range 72 of the image pickup device of the distance measuring optical system is arranged in the distance measuring area 81 provided in the photographing range 80 of the camera. Then, by framing the main subject 100 so as to fit within the distance measuring area 81, the detection range 72 of the image sensor is detected.
Overlaps the main subject 100, and an image data string relating to the brightness of the main subject can be detected.

The image data sequence relating to the brightness of the subject detected by the respective image pickup devices in this manner is sent to the control section 73. The control unit 73 includes extraction means 74 for extracting an extraction image of a predetermined size at an arbitrary position from the image data sent from each image sensor,
Correlation calculation means 7 for calculating a correlation value indicating the correlation value of both images while sequentially shifting at least one extracted image extracted by the extraction means 74 for each first predetermined number of pixels.
5, reliability determination means 76 for determining whether or not an extreme value has been detected in the correlation value calculation, corresponding position detection means 77 for detecting the corresponding position based on the correlation coefficient string output from the correlation calculation means, Distance detection means 78 for determining the subject distance based on the detection result of the position detection means 77. Each of these means functions as follows to detect the subject distance.

FIG. 12 is a diagram for explaining how a correlation value is calculated based on image data of a subject. First, the extraction unit 74 extracts the extraction image 100 of a predetermined size at an arbitrary position in the luminance distribution of the image data output from each of the right sensor 71R and the left sensor 71L. The correlation calculation means 75 compares one extracted image extracted by the extraction means 74 with the other extracted image, and calculates a correlation value indicating how much they match each other. Next, the correlation calculation means 75 calculates the correlation coefficient sequence to detect the corresponding position, which is the position showing the extreme value where the correlation value is the smallest, by sequentially shifting the extraction positions and switching the comparisons.

Specifically, first, the farthest extracted images 101L and 101R are compared (1), and then the extracted image 102R obtained by shifting the right image closer by one pixel to the left extracted image 102R. The image 101L is compared (2). Next, the image on the left is 1
Extracted image 102L and extracted image 10 that are shifted closer by the pixel
Compare with 2R (3). In this way, the correlation calculating means 75 calculates the correlation value by comparing both image data from the farthest to the latest while shifting each image data by one pixel (1).
(10), a correlation coefficient string as shown in FIG. 13 is created.

The corresponding position detecting means 76 detects the decimal corresponding position based on the correlation coefficient string as shown in FIG.
Specifically, since the correlation calculating means 75 calculates the correlation value while shifting the image data of both pixels by one pixel, the correlation value of FIG.
3 are discontinuous, such as white circles 90a to 90d. These are obtained by shifting the extracted image by position pixels, and in reality, there is a possibility that there is a true corresponding position (decimal corresponding position) having a shift of less than 1 pixel. In order to detect the true corresponding position, the corresponding position detecting means 76, in the vicinity of the integer corresponding position 90c having the lowest correlation value, has the lowest correlation value, which is the intersection of the rising portion and the falling portion of the correlation coefficient sequence, corresponding to the decimal. The corresponding position 90 m is calculated as the position.

However, as described above, the extracted images are compared in the entire range of the left and right image pickup devices, the correlation coefficient string is created, and the extreme value is calculated after calculating the correlation value in the entire range. It In this control, in reality, the corresponding positions should be obtained in the comparison of (5) in FIG. 12, but the comparisons (6) to (10) are virtually meaningless operations. Therefore, when the control is performed so that the comparison is performed in the entire range, there is a problem that the time for detecting the subject distance becomes long and the operability of the camera is impaired.

As described above, in order to solve the problem that the object distance detection time becomes long, a technique is disclosed in which the extraction ranges of the left and right extracted images are shifted by a plurality of pixels to reduce the number of comparison calculations. Has been done. That is, FIG.
As shown in FIG. 4, the extraction position of the extraction image 100 is shifted by a plurality of pixels, and only the odd comparisons (1), (3), and (5) in FIG. 12 are performed. The number of comparison operations is reduced. When the provisional corresponding positions 113L and 113R with the smallest correlation value are detected based on the result of comparison of the entire range while reducing the number of calculations, the extraction positions 116 and 117 around the temporary corresponding positions are compared and calculated. The values are replenished, and the decimal corresponding position, which is the extreme value, is calculated based on these correlation values in the same manner as above.

As described above, if the entire corresponding range is roughly compared and the temporary corresponding position having the smallest correlation value is obtained, and then the correlation values in the vicinity thereof are finely calculated, the number of comparison calculations is reduced. The time required to detect the subject distance is shortened. However, in such arithmetic control, there is a problem that the corresponding position may not be detected in a subject having a repeating pattern as described below.

That is, as shown in FIG. 15, the extracted image 120 which is a subject having a repeating pattern is
When the pixel is shifted pixel by pixel and a rough comparison operation is performed, it is actually 1
Consider a subject in which two corresponding positions of 21L, 121R and 122R, 122L are detected. When roughly comparing images for such subjects,
In some cases, as shown in FIG. 16, only the corresponding positions 122L and 122R are detected, and the corresponding positions 121L and 121R are skipped and are not detected. That is, the correlation values of the positions 121L and 121R are actually the positions 122R and 122L.
Even if it is lower than the correlation value of, the result of performing the comparison operation roughly is that the positions 121L and 121R are skipped and the comparison operation is performed, and it is detected that the positions 122R and 122L have the minimum correlation value. Therefore, this position 122
As a result of finely analyzing the periphery of R and 122L and calculating the subject distance, there are cases where a photograph in which the main subject existing in the vicinity of the positions 121L and 121R is properly focused cannot be obtained.

[0012]

SUMMARY OF THE INVENTION Therefore, the technical problem to be solved by the present invention is to shorten the calculation time by shortening the time until the detection of the object distance, thereby reducing the release time lag and the object distance. It is an object of the present invention to provide a distance measuring device that can accurately measure.

[0013]

In order to solve the above technical problems, the present invention provides a distance measuring device having the following structure.

The distance measuring device detects the subject distance from the image data obtained by the pair of image pickup elements that receive the subject light, and the extracting means extracts the extracted images of a predetermined size from the image data. And a correlation calculation means for calculating a correlation value indicating a correlation value of both images while sequentially shifting at least one of the extracted images extracted by the extraction means for each predetermined number of pixels, and a correlation value calculation by the correlation calculation means. Corresponding to the operation control means for controlling the start, end, and interruption of the, the reliability determination means for determining whether or not the extreme value has been detected in the correlation value operation, and the correlation coefficient sequence output by the correlation operation means. Corresponding position detecting means for detecting the position and distance detecting means for determining the subject distance based on the detection result of the corresponding position detecting means. Then, the calculation control means suspends the correlation value calculation of the correlation calculation means at an arbitrary stage, and the reliability determination means, while the correlation value calculation of the correlation calculation means by the calculation control means is suspended. It is determined whether or not an extreme value has been detected in the correlation value calculation that has already been performed. If the extreme value is detected during the interruption, the calculation control means terminates the correlation value calculation of the correlation calculation means. The corresponding position detecting means detects the corresponding position, and when the extreme value is not detected during the interruption, the calculation control means restarts the correlation value calculation of the correlation calculating means.

In the above structure, the distance measuring device is of a so-called external light passive type, and is provided with a pair of image pickup devices for receiving the subject light reflected by the subject. The pair of image pickup devices photoelectrically convert the subject light and output it as image data. The image data output from the pair of image pickup devices is processed by each means as follows.

First, the extracting means extracts an extracted image of a predetermined size at an arbitrary position of the image data output from each of the pair of image pickup devices. At this time, it is preferable to extract the extracted image from the far side. The correlation calculation means compares one of the extracted images extracted by the extracting means with the other extracted image, and calculates a correlation value indicating how much the two extracted images match. The correlation calculating means repeats the above comparison while sequentially shifting the extraction position by a predetermined number of pixels and switching the extraction position to create a correlation coefficient string. The shift amount of the extracted image is not particularly limited, but it is particularly preferable to make it as small as possible and to perform it for each pixel.

At an arbitrary stage of the correlation value calculation by the correlation calculation means, the calculation control means interrupts the correlation value calculation. The reliability determining means uses the correlation coefficient string until the interruption to detect the extreme value of the correlation coefficient string in order to detect the corresponding position where the correlation value is the smallest. Make a sex decision. If there is an extreme value in the correlation coefficient sequence before the interruption, the calculation control means ends the correlation value calculation of the correlation calculation means after the interruption.

If there is no extreme value in the correlation coefficient sequence until the interruption, the calculation control means restarts the continuation of the correlation value calculation. It should be noted that the number of interruptions of the correlation value calculation by the arithmetic control means and at which stage it is interrupted are not particularly limited. When the interruption is performed a plurality of times, it is determined whether or not the extreme value could be detected by using the correlation coefficient sequence performed after the interruption of the previous correlation value calculation by the calculation control means and before the interruption. It is preferable that such a decision be made.

Further, in the detection of the extreme value during the second and subsequent interruptions, the extreme value is detected using a correlation coefficient sequence including at least a part of the correlation coefficient sequence included in the correlation value calculation at the previous interruption. Preferably. In this way, by detecting the extreme value including a part of the previous correlation coefficient sequence, the extreme value can be accurately detected even when the correlation value immediately before the interruption is the extreme value. it can.

When the extreme value is detected in the correlation value calculation, the corresponding position detecting means detects the corresponding position (decimal corresponding position).
And the distance detection means determines the subject distance from the corresponding position.

According to the above configuration, the correlation value calculation is interrupted midway to detect the extreme value, and when the extreme value is found in the correlation coefficient sequence until the interruption, the correlation value calculation thereafter is not performed. To control. Therefore, by shortening the calculation time, it is possible to shorten the time until the detection of the subject distance and reduce the release time lag.

The distance measuring device of the present invention can be specifically configured in the following modes.

Preferably, the correlation calculation means starts the correlation value calculation sequentially from a long distance range of the image pickup device, and the calculation control means interrupts the correlation value calculation once at an intermediate stage thereof, and then in two stages. The correlation calculation means is controlled so as to be performed separately.

The distance measuring device having the above structure is constructed such that a normal camera can measure a distance from about 30 cm to infinity, and the corresponding position on the image sensor is on the far side of the image sensor. Based on being mostly present. That is, in the external light passive distance measuring device, since the distance is calculated based on the principle of triangulation, the change in the object distance in a distant object does not change much on the image sensor. When the subject distance changes for a close subject, the corresponding position changes remarkably. The image sensor of the distance measuring device is configured to have a long near area so that the distance can be measured for a subject that is very close. Therefore, when the comparison calculation is performed in two stages from the middle, the region farther than the center becomes the regular region, and the frequency of the corresponding position in the near region is lower than the frequency in the far region. Have.

Therefore, in the above structure, the correlation calculating means starts the correlation value calculation sequentially from the long range of the image pickup device, and interrupts the calculation processing in the vicinity of the intermediate stage of the correlation value calculation to generate the extreme value. Is detected, and the calculation processing of the short range is performed only when the extreme value does not exist in the long range.

According to the above construction, the feature that the distance to the object is measured based on the principle of the triangulation of the distance measuring device is utilized, the processing is frequently completed only by the calculation in the common area, and the distance to the object is more reliably achieved. The detection of can be shortened.

The present invention also provides a distance measuring device having the following configuration.

The distance measuring device detects the subject distance from the image data obtained by the pair of image pickup devices which receive the subject light, and extracts the extracted images of a predetermined size from the image data. Means, correlation calculating means for performing a correlation value calculation showing a correlation value of both images while sequentially shifting at least one of the extracted images extracted by the extracting means for each first predetermined number of pixels, and the correlation calculating means. Calculation control means for controlling the start, end, and interruption of the correlation value calculation by means of, reliability judgment means for judging whether or not an extreme value has been detected in the correlation value calculation, and a correlation coefficient string output by the correlation calculation means. Corresponding position detecting means for detecting the corresponding position on the basis of the detection result, and distance detecting means for determining the subject distance based on the detection result of the corresponding position detecting means. Then, the correlation calculation means performs the correlation value calculation in which at least one extracted image is sequentially shifted for each first predetermined number of pixels, and the reliability determination means detects a plurality of extreme values in the correlation value calculation. When the difference between the correlation values of the extreme values is less than or equal to a predetermined value, the calculation control means sets the extracted image to a first predetermined number of pixels in the vicinity of the plurality of extreme values detected by the correlation calculation means. The correlation value calculation is sequentially restarted for each second predetermined number of pixels, which is smaller than the above.

In the above structure, the distance measuring device is of the external light passive type, and is provided with a pair of image pickup elements for receiving the subject light reflected by the subject. The pair of image sensors are
Each subject light is photoelectrically converted and output as image data. The image data output from the pair of image pickup devices is processed by each means as follows.

First, the extracting means extracts an extracted image of a predetermined size at an arbitrary position of the image data output from the pair of image pickup devices. The correlation calculation means compares one of the extracted images extracted by the extracting means with the other extracted image, and calculates a correlation value indicating how much the two extracted images match. The correlation calculation means sequentially shifts the extraction positions for each of the plurality of first predetermined pixels for comparison, and compares the extraction positions to detect a corresponding position that is a position having an extreme value that minimizes the correlation value. To create.
That is, the correlation value calculation is roughly performed over the entire range to obtain a rough correlation coefficient string at all distances.

After that, the reliability determining means detects from the rough correlation coefficient sequence obtained by the correlation calculating means whether or not the correlation coefficient sequence has an extreme value in which the positive / negative of the inclination is reversed. Here, in the case where there are a plurality of extreme values, and the difference in the correlation value of the extreme values is less than or equal to a predetermined value, the calculation control means, in the vicinity where the plurality of extreme values are detected by the correlation calculation means. The correlation value calculation for sequentially shifting the extracted image for each second predetermined pixel number smaller than the first predetermined pixel number is controlled to be restarted. That is, in the vicinity where the extreme value is detected, by calculating the correlation value in detail for each fine pixel, the reliability determining means can detect the appropriate corresponding position. When there are a plurality of extreme values and the difference between the extreme values is equal to or more than a predetermined value, the correlation value calculation may be performed in detail only for the neighborhood of the smaller extreme value.

The corresponding position detecting means detects the corresponding position (decimal corresponding position) detected by the reliability determining means, and the distance detecting means determines the subject distance from the corresponding position.

According to the above construction, the correlation calculation means can first obtain a rough correlation coefficient sequence information by a comparison calculation in which at least one of the extracted images is sequentially shifted for each of a plurality of pixels, and at the same time, the reliability judgment is performed. The means detects an extreme value in the correlation value calculation. Then, when there are a plurality of extreme values and the difference between the correlation values is less than or equal to a predetermined value, an accurate corresponding position can be detected by obtaining the correlation values in detail in the vicinity of both extreme values. Therefore, it is possible to reduce the number of correlation value calculation processes.

Therefore, by shortening the calculation time, the time until the detection of the object distance can be shortened and the release time lag can be reduced.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION A distance measuring device according to each embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the structure of the distance measuring apparatus according to the first embodiment of the present invention. The distance measuring device 1 of the present embodiment is an external light passive distance measuring device that receives subject light reflected by a subject and measures the subject distance based on the principle of triangulation. That is, by extracting a part of the subject image obtained by each of the pair of image pickup devices and comparing one image with the other image to calculate the defocus amount between the two images, the subject distance can be detected. It is configured.

The distance measuring device 1 includes a pair of objective lenses 10L,
10R, a pair of image pickup devices 11L and 11R that photoelectrically convert subject light from the objective lenses 10L and 10R, and a control unit 12 that arithmetically processes image data from the image pickup devices 11L and 11R. Then, the distance measuring apparatus 1 uses the image pickup devices 11L and 11L through the objective lenses 10L and 10R.
The subject light is imaged on R, and the image data, which is the luminance distribution of the subject, is transmitted to the control unit 12.

The control section 12 is a section that is connected to a distance measuring device and performs processing and calculation that is sensitive to the detection of the subject distance, and includes the following means. The extracting unit 13 extracts an extracted image of a predetermined size at an arbitrary position from the image data sent from each of the image pickup devices 11L and 11R. First correlation calculation means 14 and second correlation calculation means 1
Reference numeral 7 performs a correlation value calculation for obtaining a correlation value which is the degree of coincidence between the two images while sequentially shifting at least one of the extracted images extracted by the extracting means 13 for each pixel.
The difference between the two is that the distance area in charge of the correlation value calculation is different, and the first correlation calculation means 14 calculates a long distance area, whereas the second correlation calculation means 17 calculates a short distance area. This will be described later in detail.

The calculation permission means 15 gives permission to start the calculation of the second correlation calculation means. The reliability determination means 16 is the first
Also, the extreme value is detected using the correlation coefficient string obtained as a result of the correlation value calculation by the second correlation calculation means 14 and 17. The corresponding position detecting means 18 detects the corresponding position (decimal corresponding position) with the smallest correlation value based on the correlation coefficient sequence output from the correlation calculating means. The distance detecting means 19 determines the subject distance based on the detection result of the corresponding position detecting means.

FIG. 2 is a flow chart of subject distance detection processing in the distance measuring device of FIG. 3 and 4 are diagrams for explaining the processing procedure of the correlation value calculation in the distance measuring apparatus of FIG. 1, and FIG. 3 is the processing procedure in the first correlation calculation means.
FIG. 4 shows a processing procedure in the second correlation calculation means.

As described above, the first correlation calculation means 13 and the second correlation calculation means 17 are different in the distance area in charge of the correlation value calculation. The first correlation calculation means 13 is in charge of the far side area side from the approximate center of the total correlation value calculation, and the second correlation calculation means 17 is in charge of the near side area from the approximate middle in the overall correlation value calculation.
The calculation areas of both may be slightly overlapped near the true center.

First, the right sensor 10R and the left sensor 10L
The extracted image 20 of a predetermined size is extracted by the extraction unit 12 at an arbitrary position in the luminance distribution of the image data output from each of the. First correlation calculation means 13
Compares one of the extracted images extracted by the extracting means 12 with the other extracted image, and calculates a correlation value indicating how much they match each other (# 11).

At this time, the first correlation calculating means 13 compares the images extracted from the farthest side. That is, the farthest extracted images 21L and 21R are compared (1), and then the extracted image 22R obtained by shifting the right image by one pixel to the near side and the left extracted image 21L are compared (2). ). Next, the image on the left is 1
Extracted image 22L and extracted image 22R that are shifted closer by the pixel
And are compared (3). In this way, the correlation calculation means 7
Reference numeral 5 indicates a correlation value by shifting both image data by one pixel and performing a comparison calculation on the far side regions (1) to (6) up to a substantially intermediate stage of all correlation value calculation (1) to (10). Then, the correlation value calculation is ended.

When the first correlation value calculation is completed, the reliability determining means 16 determines the reliability of the first coefficient (#
12). Here, the reliability is determined by the degree of matching between the left and right images,
Whether or not the contrast is ensured and the correlation coefficient sequence has a descending portion and an ascending portion, that is, whether or not it is considered that the decimal corresponding position having the lowest correlation value at the intersection is considered to be present. Specifically, a value obtained by dividing the extreme value obtained as a result of the correlation value calculation by the contrast value,
The contrast value itself, which is the sum of the absolute values of the differences between adjacent pixel data, is used. That is, when (extreme value / contrast value) is small and the contrast value is equal to or more than a predetermined value, it is determined that the reliability is high.

When it is judged in step 13 that the first correlation value calculation is reliable, the corresponding position detecting means 1
8 calculates the decimal point corresponding position from the first correlation coefficient sequence (# 14). In addition, the calculation of the decimal point corresponding position is performed by using
As shown in (4), the processing that has been widely performed in the past is used.

When it is determined in step 13 that the first correlation value calculation is not reliable, the calculation permission means 15
Permits the second correlation calculation means 17 to start the correlation value calculation. The second correlation calculation means 17, as shown in FIG.
Near-side area (7) -of all correlation value calculations (1)-(10)
The second correlation value calculation, which is the comparison of (10), is performed. (# 15) That is, the extracted image 24 of the left sensor
The correlation coefficient is calculated by comparing L and the extracted image 24R of the right sensor (7). Next, the extracted image of the right sensor is shifted toward the near side by one pixel, and the extracted image 24 of the left sensor is moved.
L is compared with the extracted image 25R of the right sensor (8). In this way, the extracted image of the closest region is compared and calculated, and the second correlation value calculation is completed.

When the second correlation value calculation is completed, the corresponding position detecting means 18 calculates the corresponding position (decimal corresponding position) from the second correlation coefficient sequence (# 16). When the second correlation value calculation is performed, since there is no decimal point corresponding position in the first correlation coefficient sequence, it is not necessary to determine the reliability unlike the first correlation value calculation. The calculation of the decimal-corresponding position in the second correlation coefficient string is performed by the same process as the calculation of the decimal-corresponding position in the first correlation coefficient string.

When the decimal corresponding position is detected from the first correlation coefficient sequence or the second correlation coefficient sequence, the distance detecting means 19
The subject distance is determined based on the detection result of the corresponding position detecting means 18.

The distance measuring apparatus according to the present embodiment divides all the correlation value calculations into two steps, and is controlled so as to start the calculation from the far side area, which is the normal area, so that the second value is calculated frequently. It is possible not to perform the correlation value calculation of. Therefore, the time required to detect the subject distance can be shortened, and the release time lag can be reduced.

FIG. 5 is a block diagram showing the structure of the distance measuring apparatus according to the second embodiment of the present invention. The distance measuring device 2 of the present embodiment is an external light passive distance measuring device that receives subject light reflected by the subject and measures the subject distance based on the principle of triangulation. The distance measuring device 2 includes a pair of objective lenses 30L and 30R and a pair of image pickup elements 31L and 31L.
It has an R and a control unit 32.

The control unit 32 includes the extracting unit 33, the first correlation calculating unit 34, the second correlation calculating unit 36, the repetition determining unit 35, the corresponding position detecting unit 37, and the distance detecting unit 38.
With. The extraction unit 33, the corresponding position detection unit 37, and the distance detection unit 38 of the control unit 32 have substantially the same functions as those provided in the control unit 12 of the distance measuring device 1 according to the first embodiment. Play.

The first correlation calculating means 34 and the second correlation calculating means 36 sequentially shift at least one of the extracted images extracted by the extracting means 33 by the first predetermined number of pixels and calculate the correlation value of both images. The correlation value calculation shown is performed. The difference between the two is that the distance area in charge of the correlation value calculation and the shift amount of the extracted image are different, and the first correlation calculation means 34.
While the extracted image is calculated over the entire area while shifting the extracted image by a plurality of pixels (2 pixels), the second correlation calculation means 36 makes a determination by the repeat determination means 35 while shifting the extracted image by one pixel. The calculated extreme value region is calculated.
This will be described later in detail.

The repetition determining means 35 detects the extreme value using the correlation coefficient string whose correlation value is roughly calculated by the first correlation calculating means 33. Then, in the vicinity of the detected extreme value, the second correlation calculation means 36 is permitted to start the comparison calculation. Although the details will be described later, when there are a plurality of extreme values and the difference is within a predetermined range, it is determined that the pattern is repetitive and the comparison calculation in the vicinity of both extreme values is permitted.
If the difference between the two is greater than or equal to a predetermined value, the comparison operation is instructed only in the vicinity of the minimum extremum.

Next, the flow of processing for detecting the object distance of the distance measuring apparatus according to this embodiment will be described. FIG. 6 is a processing flowchart of subject distance detection in the distance measuring device of FIG. FIG. 7 is a diagram for explaining the processing procedure of the correlation value calculation in the first correlation calculation means of the range finder of FIG.

First, the right sensor 30R and the left sensor 30L
The extracted image 40 of a predetermined size is extracted by the extraction unit 32 at an arbitrary position in the luminance distribution of the image data output from each of the. First correlation calculation means 33
Compares one of the extracted images extracted by the extracting means 32 with the other extracted image, and calculates a correlation value indicating how much they match each other.

At this time, the first correlation calculating means 33 compares the images extracted from the farthest side. That is, the farthest extracted images 41L and 41R are compared, then the right-side image and the left-side image are shifted closer by 2 pixels, and the right-side extracted image 42R and the left-side extracted image 42L are compared. To do. Similarly, the right-side image and the left-side image are shifted closer by a plurality of pixels, and the right-side extracted image 43R and the left-side extracted image 43L are compared. In this way, the correlation calculation means 75 calculates the correlation coefficient for the correlation value calculation in the entire range while shifting the image data of both pixels by a plurality of pixels, and the correlation value calculation in the first correlation calculation means 33 ends. (# 21).

FIG. 8 is a diagram showing a correlation coefficient sequence obtained by the first correlation calculating means 33. Black circle 5 in Figure 8
0 is the correlation value actually obtained by the first correlation calculation means 33, and the broken line circle 51 is the correlation value that has not been actually compared and calculated by shifting the extracted image by a plurality of pixels.

Next, the repeat determination means 35 makes a repeat determination (# 22). Specifically, first, based on each correlation value of the correlation coefficient string shown in FIG. 8, it is determined whether or not there is an extreme value at which the slope of successive correlation values is reversed from negative to positive. In FIG. 8, the black circles (A) and (B) are determined to be extreme values. Then, it is determined whether the difference H between the selected black circles (A) and (B) is less than or equal to a predetermined value. When there are a plurality of extreme values and the difference between them is less than or equal to a predetermined value, it is determined that the pattern is a repeating pattern (# 23).

When it is determined in step 23 that the pattern is a repetitive pattern, the second correlation calculating means 36 calculates the correlation value in the vicinity of the plurality of extreme values (A) and (B) (# 27). FIG. 9 is a diagram for explaining the processing procedure of the correlation value calculation in the second correlation calculation means 36. The second correlation calculation means 36 performs a comparison calculation on the left and right extracted images in the vicinity of the extreme value detected based on the correlation value calculated by the first correlation calculation means 33 to calculate the correlation value.
Specifically, as shown in FIG. 9, the extreme values are detected by comparing the extracted images calculated by the first first correlation calculating means 33 indicated by the broken line, and the extracted image 5 in the vicinity thereof is detected.
Comparison calculation is performed on 4L to 57L and 54R to 57R.

FIG. 10 is a diagram showing a correlation coefficient sequence obtained by the second correlation calculating means 36. As shown in FIG. 10, the hatched circle 5 is formed by the comparison calculation of the second correlation calculation means 36.
The correlation coefficients 2, 53 are added to the correlation coefficient string. Then, the corresponding position detecting means 37 determines which extreme value is the minimum based on this correlation coefficient sequence (# 2).
8) In FIG. 10, the correlation coefficient 52 not calculated in the first correlation value calculation shows a smaller correlation value, and that value is selected.

On the other hand, if it is determined in step 23 that the pattern is not a repetitive pattern, the second correlation calculating means 3
In step 6, the correlation value is calculated in the vicinity of the extremum having the smaller correlation value (# 24).

The corresponding position detecting means 37 detects the decimal corresponding position using the correlation coefficient string to which the stored correlation coefficient is added based on the extreme value determined in steps 24 and 27 (# 25). . This step is the process of detecting the corresponding position according to the first embodiment (step 14 in FIG. 2).
The procedure is similar to. Next, when the decimal fraction corresponding position is detected, the distance detecting means 38 determines the subject distance based on the detection result of the corresponding position detecting means 37.

In the distance measuring apparatus according to the present embodiment, all correlation value calculations are first roughly performed, and then detailed correlation value calculations are performed. Therefore, the number of correlation value calculation processes is reduced, and The distance can be detected quickly. Also, in determining the area for performing the detailed correlation value calculation thereafter, the extreme value of the correlation coefficient sequence is used for determination,
Since the difference between the correlation values is within a predetermined range,
In the ranging calculation of a repeated pattern or the like, it is possible to detect the true corresponding position skipped by the rough correlation value calculation without overlooking.

In this embodiment, the shift amount of the extracted image is 2 pixels in the first correlation value calculation and 1 pixel in the second correlation value calculation, but the shift amount can be changed appropriately. it can. For example, the first correlation value calculation may have four pixels, and the second correlation value calculation may have two pixels.

As described above, the distance measuring apparatus according to the present embodiment can shorten the time for detecting the object distance by reducing the number of times the correlation value is calculated, and can accurately grasp the object. .

The present invention is not limited to the above embodiment, but can be implemented in various other modes. For example, since the distance measuring device includes a pair of image pickup devices, it is possible to detect the distance to the subject only at one position in the shooting range. With the selection, it is possible to change the distance measuring area within the shooting range.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a distance measuring device according to a first embodiment of the present invention.

FIG. 2 is a flowchart of subject distance detection processing in the distance measuring device of FIG.

FIG. 3 is a diagram for explaining a processing procedure of a correlation value calculation in a first correlation calculation means of the distance measuring device of FIG.

FIG. 4 is a diagram for explaining a processing procedure of a correlation value calculation in a second correlation calculation means of the distance measuring apparatus of FIG.

FIG. 5 is a block diagram showing a configuration of a distance measuring device according to a second embodiment of the present invention.

6 is a processing flow chart of subject distance detection in the distance measuring apparatus of FIG.

FIG. 7 is a diagram for explaining a processing procedure of a correlation value calculation in the first correlation calculation means of the distance measuring device of FIG.

8 is a diagram showing a correlation coefficient string obtained by a first correlation calculating means of the distance measuring device of FIG.

9 is a diagram for explaining a processing procedure for calculating a correlation value in the second correlation calculating means of the distance measuring device in FIG. 5;

10 is a diagram showing a correlation coefficient sequence obtained by a second correlation calculating means of the distance measuring device of FIG.

11A and 11B are configuration diagrams of a conventional distance measuring device, FIG. 11A is a block diagram, and FIG. 11B is an explanatory diagram of arrangement of distance measuring areas in a shooting range.

FIG. 12 is a diagram for explaining a processing procedure of a correlation value calculation in a conventional distance measuring device.

FIG. 13 is a diagram illustrating a procedure in a process of obtaining a decimal-corresponding position from a correlation value sequence.

FIG. 14 is a diagram for explaining the processing procedure of another example of the correlation value calculation in the conventional distance measuring apparatus.

FIG. 15 is a diagram illustrating a processing procedure when correlation calculation is sequentially performed on a repetitive pattern.

16 is a diagram illustrating a case where a repeating pattern is performed in the processing procedure of the correlation value calculation of FIG. 14;

[Explanation of symbols]

1, 2 distance measuring device 10L, 10R, 30L, 30R objective lens 11L, 11R, 31L, 31R Image sensor 12, 32 Control unit 13,33 Extraction means 14,34 First correlation calculation means 15 Calculation permission means 16 Reliability judging means 17,36 Second correlation calculation means 18, 37 Corresponding position detecting means 19,38 Distance detecting means 35 Repeat determination means

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Claims (3)

[Claims] 1. A distance measuring device for detecting a subject distance from image data obtained by a pair of image pickup devices for receiving subject light, and extracting means for extracting an extracted image of a predetermined size from the image data. A correlation calculation unit that calculates a correlation value indicating a correlation value between the two images while sequentially shifting at least one extracted image extracted by the extraction unit for each predetermined number of pixels; and a correlation value calculation by the correlation calculation unit. Computation control means for controlling the start, end, and interruption of the correlation value, reliability determination means for determining whether or not an extreme value has been detected in the correlation value computation, and correspondence based on the correlation coefficient string output by the correlation computation means. The arithmetic control unit includes: a corresponding position detecting unit that detects a position; and a distance detecting unit that determines a subject distance based on a detection result of the corresponding position detecting unit. Is for interrupting the correlation value calculation of the correlation calculation means at an arbitrary stage, and the reliability determination means is for the correlation value calculation already performed while the correlation value calculation of the correlation calculation means by the calculation control means is interrupted. It is determined whether or not an extreme value is detected in the calculation, and when the extreme value is detected during the interruption, the calculation control means terminates the correlation value calculation of the correlation calculation means and the corresponding position detection means. Detects the corresponding position, and when the extreme value is not detected during the interruption, the calculation control means restarts the correlation value calculation of the correlation calculation means. 2. The correlation calculation means sequentially starts the correlation value calculation from a long distance range of the image sensor, and the calculation control means interrupts the correlation value calculation once at an intermediate stage thereof, and in two stages. 2. The distance measuring device according to claim 1, wherein the correlation calculation means is controlled so as to be performed separately. 3. A distance measuring device for detecting a subject distance from image data obtained by a pair of image pickup devices for receiving subject light, and extracting means for extracting an extracted image of a predetermined size from the image data. A correlation calculation unit that calculates a correlation value indicating a correlation value between the two images while sequentially shifting at least one extracted image extracted by the extraction unit for each predetermined number of pixels; and a correlation value calculation by the correlation calculation unit. Computation control means for controlling the start, end, and interruption of the correlation value, reliability determination means for determining whether or not an extreme value has been detected in the correlation value computation, and correspondence based on the correlation coefficient string output by the correlation computation means. The correlation calculating means includes: a corresponding position detecting means for detecting a position; and a distance detecting means for determining a subject distance based on a detection result of the corresponding position detecting means. Performs the correlation value calculation in which at least one extracted image is sequentially shifted for each first predetermined number of pixels, the reliability determination means detects a plurality of extreme values in the correlation value calculation, and the correlation of the extreme values is calculated. When the difference between the values is less than or equal to a predetermined value, the calculation control means first outputs the extracted image in the vicinity of the plurality of extreme values detected by the correlation calculation means.
The distance measuring device is controlled so as to restart the correlation value calculation for sequentially shifting for each second predetermined pixel number smaller than the predetermined pixel number.