Imaging device and parallax displacement correction method

Abstract

To provide an imaging apparatus and a parallax deviation correction method which can correctly correct a parallax deviation even in a case where there is a chart installation deviation.SOLUTION: An imaging apparatus 10 comprises: a first imaging unit 11 and a second imaging unit 12 which are arranged at positions that are apart from each other at a certain distance; a first parallax calculation unit 13 which calculates a first parallax on the basis of an image of a first pattern 21 captured by the first imaging unit 11 and an image of the first pattern 21 captured by the second imaging unit 12; a second parallax calculation unit 14 which calculates a second parallax on the basis of the image of the first pattern 21 captured by the first imaging unit 11 and the image of the second pattern 22 captured by the second imaging unit 12; and a correction unit 15 which corrects a parallax deviation between the first imaging unit 11 and the second imaging unit 12 on the basis of the first parallax and the second parallax.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an imaging device and a parallax displacement correction method. [Background technology]

[0002] As an imaging device, for example, an in-vehicle stereo camera mounted on a vehicle is known. In-vehicle stereo cameras perform image processing using corresponding calibration parameters, acquire parallax images, and can measure the distance to a subject using the acquired parallax images. Therefore, they are widely used in driving assistance systems such as collision damage mitigation brakes.

[0003] In-vehicle stereo cameras are installed inside the vehicle so that they can capture images of the vehicle's surroundings through the windshield, which causes parallax misalignment due to the influence of windshield distortion. This parallax misalignment can prevent the distance to the subject from being measured correctly, which could result in the driver assistance system not functioning properly. For this reason, in order to generate accurate parallax images, the optical axis must be calibrated (in other words, the parallax misalignment must be corrected) after the stereo camera is installed in the vehicle. Calibration can be broadly divided into two types: one is calibration performed in a static environment by placing a chart in front of the stereo camera; and the other is calibration performed in a dynamic environment, such as while driving on a public road.

[0004] Calibration performed in a static environment involves placing a chart in front of the vehicle (i.e., in front of the stereo camera) and correcting the difference between the ideal parallax value calculated from the chart installation distance and the value of the parallax image captured by the stereo camera to obtain a correct parallax value. As a related technique, for example, Patent Document 1 discloses a method for correctly correcting parallax deviation caused by distortion of the windshield by comparing images captured with a chart placed in front of the vehicle with and without the windshield. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-169583 Summary of the Invention [Problem to be solved by the invention]

[0006] However, if there is an error in the installation distance of the chart (i.e., the distance from the stereo camera to the chart) (in other words, if there is a misalignment in the chart installation), the above correction method will not be able to correctly correct the parallax displacement.

[0007] The present invention has been made to solve these technical problems, and has as its object to provide an imaging device and a parallax displacement correction method that can correctly correct parallax displacement even when there is a displacement in the chart installation. [Means for solving the problem]

[0008] The imaging device of the present invention is an imaging device that captures an image of a chart that is positioned at a known distance and has a first pattern and a second pattern, and corrects parallax shift, and is characterized by comprising: a first imaging unit; a second imaging unit that is positioned at a certain distance from the first imaging unit; a first parallax calculation unit that calculates a first parallax based on an image of the first pattern captured by the first imaging unit and an image of the first pattern captured by the second imaging unit; a second parallax calculation unit that calculates a second parallax based on the image of the first pattern captured by the first imaging unit and an image of the second pattern captured by the second imaging unit; and a correction unit that corrects parallax shift between the first imaging unit and the second imaging unit based on the first parallax calculated by the first parallax calculation unit and the second parallax calculated by the second parallax calculation unit.

[0009] In the imaging device according to the present invention, the correction unit corrects the parallax shift between the first imaging unit and the second imaging unit based on the first parallax calculated by the first parallax calculation unit and the second parallax calculated by the second parallax calculation unit, so even if there is a misalignment of the chart, it is possible to correct the parallax shift without being affected by the misalignment of the chart. As a result, even if there is a misalignment of the chart, it is possible to correctly correct the parallax shift. [Effects of the Invention]

[0010] According to the present invention, even if there is a displacement in the chart installation, the parallax displacement can be corrected correctly. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a diagram for explaining the principle of distance measurement of a stereo camera. [Figure 2] 1 is a block diagram showing an imaging apparatus according to an embodiment; [Figure 3] FIG. 10 is a diagram showing an example of a chart used for correcting parallax displacement. [Figure 4] 10A to 10C are process diagrams illustrating a parallax displacement correction method using an imaging device. [Figure 5] FIG. 10 is an image diagram for explaining calculation of a first parallax. [Figure 6] FIG. 10 is an image diagram for explaining calculation of a second parallax. [Figure 7] 10A and 10B are diagrams illustrating the relationship between the amount of parallax displacement and the amount of displacement of the chart installation. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of an imaging device and a parallax displacement correction method according to the present invention will be described with reference to the drawings. In the following description, left and right directions and positions, and horizontal directions and horizontal positions are those seen from a vehicle on which the imaging device is mounted.

[0013] The imaging device 10 of this embodiment is equipped with a stereo camera placed in the cabin of an automobile, for example, and is a device that captures images of an object to be recognized in front of the vehicle through the windshield using a pair of left and right cameras placed a certain distance apart, and measures the distance to the object based on the captured images. Here, the distance measurement principle of the stereo camera will be explained with reference to Figure 1.

[0014] As shown in Figure 1, if the distance between the pair of left and right cameras that make up the stereo camera (so-called baseline length) is B (mm), the focal length of the lenses of the pair of left and right cameras is f (mm), the pixel pitch of the image sensor (e.g., CMOS sensor) is δ (mm / pixel), the horizontal position of the center of the captured image is cx (pixel), and the horizontal positions of the recognized object (i.e., subject) P(X,Z) in front of the camera when projected onto the CMOS surface of each of the pair of cameras are xl (pixel) and xr (pixel), respectively, xl and xr can be expressed by the following equations.

[0015]

number

[0016] The difference between the left and right projection positions (xl-xr) is called the disparity d (pixel). Therefore, the disparity d can be calculated using the following equation (3).

[0017]

number

[0018] Then, the distance Z (mm) to the recognition object P can be calculated using the following equation (4).

[0019]

number

[0020] 2 is a block diagram showing an imaging device according to an embodiment. The imaging device 10 of this embodiment includes a pair of left and right imaging units (a first imaging unit 11 and a second imaging unit 12), a first parallax calculation unit 13, a second parallax calculation unit 14, and a correction unit 15. The first imaging unit 11 and the second imaging unit 12 are arranged apart in the horizontal direction by a distance equal to the base length, and each is composed of an imaging element such as a CMOS element.

[0021] The first parallax calculation unit 13 calculates the first parallax based on the image captured by the first imaging unit 11 and the image captured by the second imaging unit. Specifically, the first parallax calculation unit 13 uses the image captured by the first imaging unit 11 as a reference image and extracts feature points with changes in shading. Next, the first parallax calculation unit 13 searches for the position where the same subject is reflected in the reference image, using the image captured by the other imaging unit, the second imaging unit 12, as the reference image, for the extracted feature points. For example, template matching such as SAD (Sum of Absolute Difference) can be used for the search. The first parallax calculation unit 13 then calculates the difference between the extracted feature points and the reflected positions in the reference image as the first parallax.

[0022] The second parallax calculation unit 14 calculates the second parallax based on the image captured by the first imaging unit 11 and the image captured by the second imaging unit 12. Specifically, the second parallax calculation unit 14 uses the image captured by the first imaging unit 11 as a reference image and extracts feature points with changes in shading. Next, the second parallax calculation unit 14 uses the image captured by the other imaging unit, the second imaging unit 12, as a reference image and searches for a position in the reference image where, for example, an object with the same pattern but at a different position is reflected, for the extracted feature points. For example, template matching such as SAD can be used for the search. The second parallax calculation unit 14 then calculates the difference between the extracted feature points and the reflected positions in the reference image as the second parallax.

[0023] The correction unit 15 corrects the parallax shift between the first imaging unit 11 and the second imaging unit 12 based on the first parallax calculated by the first parallax calculation unit 13 and the second parallax calculated by the second parallax calculation unit 14.

[0024] The imaging device 10 having such a structure images a chart placed at a known distance and having a first pattern and a second pattern using the first imaging unit 11 and the second imaging unit 12, and corrects the parallax shift between the first imaging unit 11 and the second imaging unit 12 in the baseline length direction (i.e., the left-right direction) based on the captured image.

[0025] Fig. 3 is a diagram showing an example of a chart used for correcting parallax displacement. In Fig. 3, the left side is a plan view of the chart, and the right side is a front view of the chart. As shown in Fig. 3, the chart 20 is, for example, a flat plate having a certain thickness, and is installed at a position that is a known distance Z away from the imaging device 10. If there is no installation displacement of the chart 20, the installation distance of the chart 20 relative to the imaging device 10 (i.e., the distance from the imaging device 10 to the chart 20) is equal to the known distance Z.

[0026] A predetermined pattern (here, a checkerboard pattern) is provided on the main surface of the chart 20 facing the imaging device 10. Adjacent black squares are defined as a first pattern 21 and a second pattern 22, respectively, and the distance between the first pattern 21 and the second pattern 22 in the horizontal direction is defined as ΔX. Note that the pattern provided on the chart 20 is not limited to a checkerboard pattern, and may be a circle or the like as long as it allows feature points to be detected.

[0027] A parallax displacement correction method using the imaging device 10 will be described below with reference to Fig. 4. The parallax displacement correction method of this embodiment includes a chart imaging step S1, a first parallax calculation step S2, a second parallax calculation step S3, an installation displacement amount calculation step S4, an installation distance calculation step S5, and a parallax displacement correction step S6. Note that installation displacement amount calculation step S4, installation distance calculation step S5, and parallax displacement correction step S6 constitute the "correction step" set forth in the claims.

[0028] In the chart imaging step S1, the first imaging section 11 and the second imaging section 12 capture an image of the chart 20 placed in front of the imaging device 10.

[0029] In the first parallax calculation step S2, the first parallax calculation unit 13 calculates the first parallax based on the image of the first pattern 21 captured by the first imaging unit 11 and the image of the first pattern 21 captured by the second imaging unit 12.

[0030] At this time, the first parallax calculation unit 13 calculates the first parallax by template matching, using the image of the first pattern 21 captured by the first imaging unit 11 as a base image and the image of the first pattern 21 captured by the second imaging unit 12 as a reference image. Specifically, as shown in Fig. 5, the first parallax calculation unit 13 calculates the difference in the base length direction (i.e., the left-right direction) between the position of the first pattern 21 on the image captured by the first imaging unit 11 and the position of the first pattern 21 on the image captured by the second imaging unit 12 as the first parallax.

[0031] In second parallax calculation step S3, second parallax calculation unit 14 calculates second parallax based on the image of first pattern 21 captured by first imaging unit 11 and the image of second pattern 22 captured by second imaging unit 12. That is, unlike first parallax calculation unit 13, second parallax calculation unit 14 uses captured images of different patterns to calculate parallax.

[0032] As shown in FIG. 3, since the first pattern 21 and the second pattern 22 have the same design, the second parallax calculation unit 14 uses the image of the first pattern 21 captured by the first imaging unit 11 as a base image and the image of the second pattern 22 captured by the second imaging unit 12 as a reference image, and calculates the second parallax by template matching.

[0033] Specifically, as shown in Fig. 6, the second parallax calculation unit 14 calculates the difference in the base line length direction (i.e., the left-right direction) between the position of the first pattern 21 on the image captured by the first imaging unit 11 and the position of the second pattern 22 on the image captured by the second imaging unit 12 as the second parallax. When calculating the second parallax, the above formula (2) becomes formula (5), and the above formula (3) becomes formula (6). From formula (6), it can be seen that the second parallax is the parallax of the base line length (B+ΔX) (in other words, the parallax when the base line length is shifted by ΔX).

[0034]

number

[0035] As described above, ΔX is the distance between the first pattern 21 and the second pattern 22 in the chart. Since the second parallax is calculated by template matching, a detection error is introduced. From the viewpoint of reducing the influence of this detection error, it is desirable that the value of ΔX is large.

[0036] In the installation deviation calculation step S4, the correction unit 15 uses the first parallax and the second parallax to calculate the installation deviation of the chart 20. For the above formula (3), if an installation deviation ΔZ occurs in the installation distance of the chart 20, for example, a parallax deviation Δd occurs as shown in the following formula (7).

[0037]

number

[0038] When the installation distance of the chart 20 is a constant value (for example, a known distance Z), the relationship between the installation displacement amount (ΔZ) of the chart 20 and the parallax displacement amount (Δd) between the first imaging unit 11 and the second imaging unit 12 is as shown in Fig. 7. Fig. 7 is a diagram showing the relationship between the parallax displacement amount and the installation displacement amount of the chart. In Fig. 7, the horizontal axis represents the installation displacement amount of the chart 20, and the vertical axis represents the parallax displacement amount between the first imaging unit 11 and the second imaging unit 12.

[0039] As shown in FIG. 7, when the installation displacement amount is the same, comparing the baseline length B with the baseline length (B+ΔX), it can be seen that the parallax displacement amount varies depending on the length of the baseline. The difference D in FIG. 7 is the difference between the baseline length (B+ΔX) and the baseline length B, and the magnitude of the value of the difference D varies depending on the installation displacement amount. Therefore, the difference D is calculated using the first parallax and the second parallax, and the installation displacement amount can be found based on the calculated difference D. Then, when the installation distance of the chart 20 is determined as a constant value (i.e., a known distance), the installation displacement amount can be easily found by previously setting a conversion table or a linear approximation formula so that the value of the difference D becomes the input value and the installation displacement amount becomes the output value.

[0040] The difference D is the difference between the parallax shift amount when the baseline length is B (hereinafter simply referred to as the "parallax shift amount for baseline length B") and the parallax shift amount when the baseline length is (B+ΔX) (hereinafter simply referred to as the "parallax shift amount for baseline length (B+ΔX)"). The parallax shift amount for baseline length B is the difference between the parallax obtained by substituting the installation distance (known distance) of the chart 20 into equation (3) and the first parallax calculated in step S2 (in other words, the first parallax calculated by the first parallax calculation unit 13 (see FIG. 5)). On the other hand, the parallax shift amount for baseline length (B+ΔX) is the difference between the parallax obtained by substituting the installation distance (known distance) of the chart 20 into equation (6) and the second parallax calculated in step S3 (in other words, the second parallax calculated by the second parallax calculation unit 14 (see FIG. 6)).

[0041] Then, once the difference D is known, the correction unit 15 calculates the installation displacement amount of the chart 20 based on the difference D, using the relationship between the installation displacement amount and the parallax displacement amount shown in FIG. 7, or a preset conversion table or a first-order approximation formula, as described above.

[0042] In installation distance calculation step S5, correction unit 15 calculates the installation distance of chart 20. Specifically, correction unit 15 calculates the installation distance of chart 20 by adding the installation deviation amount calculated in step S4 to the installation distance of chart 20 (known distance).

[0043] In the parallax shift correction step S6, the correction unit 15 first calculates an ideal parallax at the installation distance that takes into account the installation shift amount, based on the installation distance of the chart 20 calculated in step S5 and the above formula (4). Next, the correction unit 15 calculates the amount of parallax shift between the first imaging unit 11 and the second imaging unit 12, based on the calculated ideal parallax and the first parallax calculated in step S2. Next, the correction unit 15 corrects the parallax shift between the first imaging unit 11 and the second imaging unit 12, based on the calculated amount of parallax shift.

[0044] In the imaging device 10 of this embodiment, the correction unit 15 corrects the parallax shift between the first imaging unit 11 and the second imaging unit 12 based on the first parallax calculated by the first parallax calculation unit 13 and the second parallax calculated by the second parallax calculation unit 14, so even if there is a misalignment in the installation of the chart 20, it is possible to correct the parallax shift without being affected by the misalignment in the installation of the chart 20. As a result, even if there is a misalignment in the installation of the chart 20, it is possible to correctly correct the parallax shift.

[0045] Furthermore, according to the parallax displacement correction method using the imaging device 10, even if the chart 20 is misaligned in placement, the parallax displacement can be corrected correctly.

[0046] In the above-described step S3, an example has been described in which the first pattern 21 and the second pattern 22 have the same pattern. However, the first pattern 21 and the second pattern 22 may have different patterns. When the first pattern 21 and the second pattern 22 have different patterns, the second parallax calculation unit 14 first uses a prepared template image of the first pattern 21 as a base image and an image of the first pattern 21 captured by the first imaging unit 11 as a reference image, and detects the position (e.g., coordinate position) of the first pattern 21 on the image by template matching. Next, the second parallax calculation unit 14 uses a prepared template image of the second pattern 22 as a base image and an image of the second pattern 22 captured by the second imaging unit 12 as a reference image, and detects the position (e.g., coordinate position) of the second pattern 22 on the image by template matching. Next, the second parallax calculation unit 14 calculates the difference between the detected position of the first pattern 21 on the image and the detected position of the second pattern 22 on the image as the second parallax. In this way, the second parallax can be calculated using the first pattern 21 and the second pattern 22 that have different designs.

[0047] Furthermore, in the above embodiment, an example was described in which the imaging device 10 is placed inside a vehicle and images the chart 20 through the windshield, but the imaging device 10 can also be applied to cases in which images of the chart 20 are captured without passing through a transparent body such as a windshield.

[0048] Furthermore, in the above embodiment, when the correction unit 15 calculates the amount of parallax shift between the first imaging unit 11 and the second imaging unit 12, the imaging device 10 may be further configured to have an alarm function for informing the operator of the amount of parallax shift.

[0049] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as set forth in the claims. [Explanation of symbols]

[0050] 10: imaging device, 11: first imaging unit, 12: second imaging unit, 13: first parallax calculation unit, 14: second parallax calculation unit, 15: correction unit, 20: chart, 21: first pattern, 22: second pattern

Claims

1. An imaging device that captures an image of a chart that is placed at a known distance and has a first pattern and a second pattern through a windshield, and corrects parallax displacement due to distortion of the windshield, a first imaging unit; a second imaging unit disposed at a position spaced a predetermined distance from the first imaging unit; a first parallax calculation unit that calculates a first parallax based on an image of the first pattern captured by the first imaging unit and an image of the first pattern captured by the second imaging unit; a second parallax calculation unit that calculates a second parallax based on an image of the first pattern captured by the first imaging unit and an image of the second pattern captured by the second imaging unit; a correction unit that corrects a parallax shift between the first imaging unit and the second imaging unit due to an influence of distortion of a windshield, based on the first parallax calculated by the first parallax calculation unit and the second parallax calculated by the second parallax calculation unit; and An imaging device comprising:

2. 2. The imaging device according to claim 1, wherein the correction unit calculates an installation shift amount of the chart based on the first parallax calculated by the first parallax calculation unit, the second parallax calculated by the second parallax calculation unit, and the parallax calculated based on the known distance, calculates an installation distance of the chart based on the calculated installation shift amount of the chart and the known distance, and corrects the parallax shift between the first imaging unit and the second imaging unit based on the calculated installation distance of the chart.

3. the correction unit calculates a difference in parallax shift amount based on the first parallax calculated by the first parallax calculation unit, the second parallax calculated by the second parallax calculation unit, and the parallax calculated based on the known distance, and calculates an installation displacement amount of the chart based on the calculated difference in parallax shift amount and a relationship between a preset parallax shift amount and an installation displacement amount of the chart; The difference in the parallax shift amount is the difference between the parallax shift amount of the base line length B and the parallax shift amount of the base line length (B+ΔX), The parallax shift amount of the base line length B is a difference between the parallax d obtained by the following formula (3) and the first parallax calculated by the first parallax calculation unit, In formula (3), base length B is the distance in the horizontal direction between the first imaging unit and the second imaging unit, f is the focal length of the lenses of the first imaging unit and the second imaging unit, Z is the known distance, and δ is the pixel pitch of the image pickup elements of the first imaging unit and the second imaging unit, The parallax shift amount of the base line length (B+ΔX) is a difference between the parallax d obtained by the following formula (6) and the second parallax calculated by the second parallax calculation unit, 3. The imaging device according to claim 2, wherein, in equation (6), base length B is the horizontal distance between the first imaging unit and the second imaging unit, ΔX is the horizontal distance between the first pattern and the second pattern within the chart, f is a focal length of lenses of the first imaging unit and the second imaging unit, Z is the known distance, and δ is a pixel pitch of image sensors of the first imaging unit and the second imaging unit.

4. 3. The imaging device according to claim 2, wherein the correction unit calculates a parallax shift amount between the first imaging unit and the second imaging unit based on the calculated installation distance of the chart and the first parallax calculated by the first parallax calculation unit, and corrects the parallax shift between the first imaging unit and the second imaging unit based on the calculated parallax shift amount.

5. 2. The imaging device according to claim 1, wherein the first parallax calculation unit calculates the first parallax by template matching using an image of the first pattern captured by the first imaging unit as a base image and an image of the first pattern captured by the second imaging unit as a reference image.

6. When the first pattern and the second pattern are the same design, 2. The imaging device according to claim 1, wherein the second parallax calculation unit calculates the second parallax by template matching using an image of the first pattern captured by the first imaging unit as a base image and an image of the second pattern captured by the second imaging unit as a reference image.

7. When the first pattern and the second pattern are different patterns, The second parallax calculation unit a template image of the first pattern prepared in advance is used as a base image, and the image of the first pattern captured by the first imaging unit is used as a reference image, and a position of the first pattern on the image is detected by template matching; a template image of the second pattern prepared in advance is used as a base image, and the image of the second pattern captured by the second imaging unit is used as a reference image, and a position of the second pattern on the image is detected by template matching; The imaging device according to claim 1 , wherein a difference between a position of the detected first pattern on the image and a position of the detected second pattern on the image is calculated as the second parallax.

8. A parallax displacement correction method for correcting parallax displacement of an imaging device caused by distortion of a windshield, using a chart that is placed at a known distance and has a first pattern and a second pattern, comprising: a chart imaging step of imaging the chart through a windshield using a first imaging unit and a second imaging unit that are disposed at positions separated by a predetermined distance from the imaging device; a first parallax calculation step of calculating a first parallax based on an image of the first pattern captured by the first imaging unit and an image of the first pattern captured by the second imaging unit; a second parallax calculation step of calculating a second parallax based on an image of the first pattern captured by the first imaging unit and an image of the second pattern captured by the second imaging unit; a correction step of correcting a parallax shift between the first imaging unit and the second imaging unit due to an influence of distortion of a windshield, based on the first parallax calculated in the first parallax calculation step and the second parallax calculated in the second parallax calculation step; A parallax displacement correction method comprising:

9. The correction step includes: an installation displacement amount calculation step of calculating an installation displacement amount of the chart based on the first parallax calculated in the first parallax calculation step, the second parallax calculated in the second parallax calculation step, and the parallax calculated based on the known distance; an installation distance calculation step of calculating an installation distance of the chart based on the installation deviation amount of the chart calculated in the installation deviation amount calculation step and the known distance; a parallax displacement correcting step of correcting parallax displacement between the first imaging unit and the second imaging unit based on the installation distance of the chart calculated in the installation distance calculating step; The parallax displacement correction method according to claim 8 , further comprising:

10. in the installation displacement amount calculation step, a difference in parallax displacement amount is calculated based on the first parallax calculated in the first parallax calculation step, the second parallax calculated in the second parallax calculation step, and a parallax calculated based on the known distance, and an installation displacement amount of the chart is calculated based on the calculated difference in parallax displacement amount and a relationship between a preset parallax displacement amount and an installation displacement amount of the chart; The difference in the parallax shift amount is the difference between the parallax shift amount of the base line length B and the parallax shift amount of the base line length (B+ΔX), The parallax shift amount of the base line length B is a difference between the parallax d obtained by the following formula (3) and the first parallax calculated in the first parallax calculation step, In formula (3), base length B is the distance in the horizontal direction between the first imaging unit and the second imaging unit, f is the focal length of the lenses of the first imaging unit and the second imaging unit, Z is the known distance, and δ is the pixel pitch of the image pickup elements of the first imaging unit and the second imaging unit, The parallax shift amount of the base line length (B+ΔX) is a difference between the parallax d obtained by the following formula (6) and the second parallax calculated in the second parallax calculation step, 10. The parallax displacement correction method according to claim 9, wherein, in equation (6), base length B is the horizontal distance between the first image capturing unit and the second image capturing unit, ΔX is the horizontal distance between the first pattern and the second pattern within the chart, f is a focal length of lenses of the first image capturing unit and the second image capturing unit, Z is the known distance, and δ is a pixel pitch of image capturing elements of the first image capturing unit and the second image capturing unit.

11. 10. The parallax displacement correction method according to claim 9, wherein in the parallax displacement correction step, an amount of parallax displacement between the first image capture unit and the second image capture unit is calculated based on the installation distance of the chart calculated in the installation distance calculation step and the first parallax calculated in the first parallax calculation step, and the parallax displacement between the first image capture unit and the second image capture unit is corrected based on the calculated amount of parallax displacement.

12. 9. The parallax displacement correction method according to claim 8, wherein in the first parallax calculation step, the image of the first pattern captured by the first imaging unit is used as a base image, and the image of the first pattern captured by the second imaging unit is used as a reference image, and the first parallax is calculated by template matching.

13. When the first pattern and the second pattern are the same design, 9. The parallax displacement correction method according to claim 8, wherein in the second parallax calculation step, the image of the first pattern captured by the first imaging unit is used as a base image, and the image of the second pattern captured by the second imaging unit is used as a reference image, and the second parallax is calculated by template matching.

14. When the first pattern and the second pattern are different patterns, In the second parallax calculation step, a template image of the first pattern prepared in advance is used as a base image, and the image of the first pattern captured by the first imaging unit is used as a reference image, and a position of the first pattern on the image is detected by template matching; a template image of the second pattern prepared in advance is used as a base image, and the image of the second pattern captured by the second imaging unit is used as a reference image, and a position of the second pattern on the image is detected by template matching; The parallax displacement correcting method according to claim 8 , further comprising calculating, as the second parallax, a difference between the detected position of the first pattern on the image and the detected position of the second pattern on the image.

Images