Patent Description:
As a background art in this technical field, PTL <NUM> is known. This literature states that a plurality of charts placed at different distances are photographed with a stereocamera to correct an optical distortion of the camera and to calibrate a translational shift of one camera with another camera as a reference.

PTL <NUM> states that "Provided is an stereocamera adjustment device that adjusts, by image processing, an optical distortion and a positional shift of the stereocamera by converting, using parameters, each of a pair of image data output from a pair of cameras constituting a stereocamera. This stereocamera adjustment device has a correction unit and a calibration unit. Here, targeting a pair of image data output by capturing a chart having a predetermined pattern with a stereocamera, the correction unit calculates correction parameter for converting the image data so that the pattern projected on an image plane defined by the image data approaches a predetermined pattern included in the chart. Here, this correction parameter corrects at least the distortion of the image data due to the optical distortion of the camera. The calibration unit calculates a calibration parameter for correcting the shift of the pair of image data due to the positional shift of the pair of cameras, using, as a constraint condition, the characteristics of the image related to the pair of image data converted by the calculated correction parameters.

PTL <NUM> states that a chart present at an infinite position is photographed using a collimator and a distance conversion parameter is corrected using parallax data and actual distance data. PTL <NUM> states that, for example, "A stereocamera calibrating device <NUM> includes a first camera <NUM>, a second camera <NUM>, and a camera stay <NUM>. A collimator unit <NUM> forms a light path which is equivalent to a case that a test chart <NUM> disposed at an interval from a stereocamera is disposed at an infinity position. A parallax calculating portion <NUM> calculates parallax data corresponding to different optical distances between the test chart <NUM> and the stereocamera from right and left images captured by the stereocamera. A parameter calculating portion <NUM> calculates a parallax offset b and a distance conversion parameter a which are ranging parameters of the stereocamera by using the parallax data calculated by the parallax calculating portion <NUM> and actual distance data to the test chart. PTL <NUM> states that "The collimator unit includes a diameter that can simultaneously generate an optical path equivalent to that where the reference object to the first camera and the second camera is placed at an infinity position".

Further background art is known from PTL <NUM> and PTL <NUM>.

A stereocamera measures the distance of a photographed object from images obtained by photographing with the left and right cameras. At this time, in order to use the relative positions of the object in the left and right images, it is necessary to correct external parameters such as the relative position and orientation of the camera and internal parameters such as the optical distortion of the lens.

These corrections are performed when the stereocamera is assembled. After that, if it is mounted on a vehicle, the light rays coming from the object change due to the influence of the windshield and the like, causing image translation (horizontal and vertical image shift) and rotation. Since these changes cause an error in the measurement distance by the stereocamera, further correction is required.

When using one chart placed at a predetermined distance at the time of correcting a stereocamera, it is necessary to adjust the position of the test camera with respect to the chart with high accuracy. However, it is difficult to adjust the installation with high accuracy in a state of being mounted on the vehicle, or it creates an unnecessary restriction.

In the case of placing two charts at different distances as in PTL <NUM>, high-accuracy installation of the test camera becomes unnecessary, but the installation accuracy of the charts becomes necessary according to the distance. The longer the distance from the stereocamera to the chart, the lower the required accuracy for chart installation, but on the other hand, a large footprint is required.

It is possible to optically make the chart appear to be far away as in PTL <NUM>, and well-known devices include a collimator. The collimator used for inspection of a single camera is known. If the test camera moves while photographing with each of the left and right cameras, a correction error will occur due to camera installation error. For this reason, it is stated that the diameter is increased so that the left and right cameras view the chart at the same time.

However, a large-diameter lens has the disadvantages that it is expensive and heavy, and that the device size increases according to the focal length. The above-mentioned optical device has a problem that it is difficult to cope with the rotation of an image because it is difficult to perform photographing with a wide angle of view.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to correct a stereocamera with high accuracy and at low cost.

The present invention is a method for correcting a stereocamera mounted on a vehicle, in which a first optical device that has a first chart having a predetermined pattern and a mirror surface having a diameter equal to or greater than a baseline length of the stereocamera generates a virtual image of the first chart, and the stereocamera uses images obtained by capturing the virtual image with a plurality of cameras to correct a parameter corresponding to the relative position of the images obtained by the cameras, characterized in that the first optical device includes either a reflecting telescope or a catadioptric telescope.

Therefore, the present invention can provide a chart of a plurality of distances in a space-saving manner at low cost, and can highly accurately perform correction of a stereocamera while relaxing the installation accuracy of a vehicle.

The detail of at least one embodiment of the subject matter disclosed in the present description will be mentioned in the accompanying drawings and the following description. Other features, aspects, and effects of the disclosed subject matter will become apparent from the following disclosure, drawings, and claims.

In the present embodiment, an example of the device for correcting the stereocamera and the method for correcting the stereocamera will be described.

<FIG> is an example of a configuration view of a device for correcting a stereocamera <NUM> of the present embodiment. In <FIG>, <NUM> is a vehicle mounted with a stereocamera, <NUM> is the stereocamera, <NUM> is an optical device that generates a virtual image of an infinite distance chart, and <NUM> is a two-dimensional planar finite distance chart placed at a predetermined distance. The correction device includes the optical device <NUM> and the finite distance chart <NUM>.

After the vehicle <NUM> is stopped at a predetermined position, the stereocamera <NUM> captures a virtual image of the infinite distance chart generated by the optical device <NUM> and an image of the finite distance chart <NUM>, and corrects a parameter for calculating parallax or distance using a captured image.

Here, the stereocamera <NUM> has completed geometric correction in advance, and in the present correction step, the optical distortion newly generated in the windshield of the vehicle <NUM> is corrected. The distortion generated in the windshield is rotation and shift of the image, and enlargement/reduction and flatness of the image are small enough for distance measurement to have no actual harm.

<FIG> is a view illustrating an example of an internal configuration of the optical device <NUM>. <NUM> is a housing, <NUM> is a light source, <NUM> is a transmissive infinite distance chart, <NUM> is a plane mirror that changes the direction of light ray, and <NUM> is a concave mirror.

In the optical device <NUM>, the concave mirror <NUM> is installed on the inner circumference of one end of the cylindrical housing <NUM>, and an opening end <NUM> is formed on the other end. An eyepiece portion is formed at a predetermined position on the side surface of the housing <NUM>, and the infinite distance chart <NUM> and the light source <NUM> are installed on the eyepiece portion.

The light ray that is incident from the light source <NUM>, transmitted through one point of the infinite distance chart <NUM>, and emitted is output as parallel light from the opening end <NUM> on the right side in the figure via the plane mirror <NUM> and the concave mirror <NUM>.

Therefore, when observing this output light from the opening end <NUM> side, it is possible to observe a virtual image of the infinite distance chart <NUM> at an infinite distance. The concave mirror <NUM> has a diameter equal to or greater than the baseline length of the stereocamera <NUM>, so that the left and right cameras of the stereocamera <NUM> can simultaneously capture a virtual image of the same infinite distance chart <NUM>.

<FIG> illustrates an example of the infinite distance chart <NUM>. The infinite distance chart <NUM> forms a transmissive cross pattern on a black background. The width of the cross line is determined so that the width of the image at the time of photographing with the stereocamera <NUM> becomes equal to or less than the size of the image sensor (pixel), and the infinite distance chart <NUM> is installed so that the inclination of the cross line after geometric correction is about <NUM> degrees with respect to the pixel arrangement of the image sensor.

These are for detecting the position on the image sensor at the point where the cross lines intersect. The contrast for ensuring a necessary detection accuracy is adjusted with the light source <NUM>. A diffuser plate may be inserted between the infinite distance chart <NUM> and the light source <NUM> in order to uniform the brightness of the cross lines.

By making an appropriate installation position of the infinite distance chart <NUM>, it is possible to make the virtual image of the light ray transmitted through the cross line appear to be an infinite distance. It is correct that the parallax at the intersection of the cross lines detected by the left camera and the right camera at this time becomes zero. Therefore, the relative positions of the left and right images are corrected so as to satisfy this condition.

The configuration of the optical device <NUM> is similar to that of the Newtonian reflecting telescope. The Maksutov-Newtonian or the epsilon reflecting telescope may be adopted. The usual method of using the Newtonian reflecting telescope is to collect, via the concave mirror <NUM> and the plane mirror <NUM>, parallel light rays emitted from a distant object, and to observe the image of the object through the eyepiece.

In the present invention, the infinite distance chart <NUM> is installed at the light collection point, and a virtual image of the infinite distance chart <NUM> is generated at a distance of substantially infinity via the plane mirror <NUM> and the concave mirror <NUM>.

That is, the present optical device <NUM> can be achieved at low cost by using a commercially available telescope. In this case, by installing a film camera not illustrated into a draw tube of the telescope (optical device <NUM>) and installing the infinite distance chart <NUM> on a film guide rail of the film camera, it is possible to easily install the infinite distance chart <NUM> at an appropriate position.

Therefore, it is convenient that the width of the infinite distance chart <NUM> has a film width of equal to or less than <NUM>. Even if a commercially available catadioptric telescope is used instead of the reflecting telescope, an inexpensive and highly accurate optical device can be achieved.

The light ray transmitted through the infinite distance chart <NUM> generates a virtual image at an infinite distance, but depending on the accuracy of the optical system, a perfectly parallel light rays can sometimes be obtained. Therefore, it is possible to tolerate a decrease in parallelism to an extent that it does not affect the calibration accuracy of the stereocamera <NUM> although not a perfectly parallel light ray. Therefore, the present embodiment assumes that the infinite distance includes substantially infinity.

<FIG> illustrates an example of a design of the finite distance chart <NUM> placed at a predetermined distance. The design of the finite distance chart <NUM> only needs to be able to associate the position on the image sensor with respect to the position on the chart. Therefore, the design is not limited to this, and a design in which a feature point is arranged as in the finite distance chart <NUM> of <FIG> may be used.

Alternatively, since it is sufficient that the left image and the right image can be associated with each other, the finite distance chart <NUM> may have a design in which a frequency in a predetermined range or a plurality of frequencies are superimposed. The stereocamera <NUM> photographs the design of the finite distance chart <NUM>, and corrects the rotation direction of the image so that the corresponding points of the left camera image and the right camera image are arranged on the epipolar line.

The finite distance chart <NUM> is formed of a rectangular flat plate and is placed at a predetermined distance in front of the vehicle <NUM>. More precisely, the finite distance chart <NUM> is installed so as to be at a predetermined distance from the camera <NUM> of the stereocamera <NUM> placed inside the windshield of the vehicle <NUM>.

<FIG> illustrates the finite distance chart <NUM> and the infinite distance chart <NUM> observed from the right camera of the stereocamera <NUM>.

The finite distance chart <NUM> uses the design of <FIG>, and the black circles on center right and center left indicate optical axes of the right camera (<NUM>-R) and the left camera (<NUM>-L), respectively. These black circles are shown for the sake of explanation, but needs not be present necessary in practice.

The upper solid circles in the figure of optical axis points (<NUM>-R and <NUM>-L) are two through holes <NUM>-L and <NUM>-R formed in the finite distance chart <NUM>, and the cross indicated inside (<NUM>-R) the solid circle on the right side is the infinite distance chart <NUM>. The circle shown by the dotted line in the figure indicates the shape on the opening end <NUM> side of the housing <NUM> of the optical device <NUM> placed on the back surface of the finite distance chart <NUM>, and is substantially equal to the diameter of the reflecting telescope.

The left and right through holes <NUM>-L and <NUM>-R are through holes of the finite distance chart <NUM> in which the centers of them are placed apart by the baseline length of the stereocamera <NUM>, and a virtual image of the infinite distance chart <NUM> of the optical device <NUM> placed on the back surface through the through holes is observed. In the following description, when the left and right of the through hole are not specified, the reference numeral "<NUM>", where the "-" and subsequent parts are omitted, is used. The same applies to the reference numeral s of other components.

From the right camera <NUM>-R of the stereocamera <NUM>, the cross on the right side can be visually recognized but the cross on the left side cannot be seen. Similarly, from the left camera <NUM>-L, the cross on the left side can be visually recognized but the cross on the right side cannot be seen.

Of the rays output from the optical device <NUM>, the only rays that contribute to generation of the image of the infinite distance chart <NUM> by the left and right cameras <NUM> are the rays that enter the entrance pupil of the camera <NUM>. Therefore, the size of the solid circle (through hole <NUM>) is determined by the installation error of the stereocamera <NUM>, i.e., the accuracy of the stop position of the vehicle <NUM>. Assuming that the entrance pupil diameter of the left and right cameras <NUM> is g and the installation error of the stereocamera <NUM> is ±h, the radius r of the solid circle (through hole <NUM>) is
<MAT>.

Here, the shape of the above two through holes <NUM> may be one oval through hole <NUM> including the two through holes <NUM>-L and <NUM>-R as shown in <FIG>. The circle shown by the dotted line in <FIG> indicates the opening end <NUM> side of the housing <NUM> of the optical device <NUM> placed on the back surface of the finite distance chart <NUM>, and is substantially equal to the diameter. Since the through hole <NUM> needs to be inside the housing <NUM> indicated by the dotted line circle in <FIG>, a diameter R of the optical device <NUM> is
<MAT> where the baseline length of the stereocamera <NUM> is L.

In <FIG>, the left and right through holes <NUM>-L and <NUM>-R are placed above the optical axes of the left and right cameras <NUM> because there is less influence even if the position shields the finite distance chart <NUM>.

When the finite distance chart <NUM> and the infinite distance chart <NUM> are photographed at the same time with the stereocamera <NUM>, it is not possible to photograph the finite distance chart <NUM> on the entire necessary angle of view, and it is not possible to photograph the finite distance chart <NUM> in the part where the infinite distance chart <NUM> overlaps.

Here, in the image of the stereocamera <NUM>, the area below the vanishing point is the area where the road surface and the object in front appear, which is an important area for object recognition, and the area above the vanishing point is the area where there are many objects that do not require accuracy such as signals, signs, and the sky.

Therefore, it is desirable to place the infinite distance chart <NUM> so as to appear above the vanishing point. On the other hand, in order to secure the recognition performance of a distant object, the stereocamera <NUM> is placed so that the vicinity of the optical axis of the lens having high resolution coincides with the vanishing point.

There is a concern that the detection error of the infinite distance chart <NUM> increases due to the influence of distortion or the like in the peripheral portion where the image height is high away from the optical axis of the camera <NUM>. Therefore, the left and right through holes <NUM> are placed in the vicinity of the optical axis of the left and right cameras <NUM> and above the optical axis or the vanishing point, where the left and right through holes <NUM> do not overlap the optical axis or the vanishing point. In <FIG>, the optical device <NUM> is installed at a position higher than an optical axis C of the stereocamera, and the optical axis of the optical device <NUM> faces the stereocamera <NUM> for the above reason.

Here, when the optical device <NUM> is fixed to the ceiling or the like independently of the finite distance chart <NUM> as in <FIG>, the bottom portion of the optical device <NUM> may be placed at a position higher than the top portion of the vehicle <NUM> so as not to hinder the movement of the vehicle <NUM> after photographing or correction.

In <FIG> and <FIG>, the peripheral edge of the finite distance chart <NUM> indicated by the through hole <NUM> is bordered with a color such as black, white, or red. This is for making it clear the boundary between the infinite distance chart <NUM> and the finite distance chart <NUM> to facilitate image processing.

As shown in <FIG>, the optical device <NUM> may have a structure of penetrating the finite distance chart <NUM>.

In this case, as shown in <FIG>, through holes <NUM>-L and <NUM>-R for viewing a virtual image of the infinite distance chart <NUM> from the above-described left and right cameras <NUM> may be formed on the opening end <NUM> side of the optical device <NUM> and a second finite distance chart <NUM> may be provided in an area other than the through hole <NUM>. A peripheral portion <NUM> of the outer periphery of the second finite distance chart <NUM> can be colored such as black, white, or red as described above to ensure image recognition accuracy.

Next, the correction procedure will be described. First, the configuration of the stereocamera <NUM>, which is the correction target of the present invention, will be described with reference to <FIG>.

<NUM>-R is the right camera having a lens and an image sensor, <NUM>-L is the left camera having a lens and an image sensor, <NUM> is an image processing unit that includes geometric correction, parallax detection, and distance detection, <NUM> is an object recognition unit, and <NUM> is a correction parameter memory.

The image data acquired by the camera <NUM>-R and the camera <NUM>-L are sent to the image processing unit <NUM>, and the image processing unit <NUM> geometrically transforms the sent image data using the information in the correction parameter memory <NUM>.

The correction parameter memory <NUM> stores correction information corrected at the time of manufacturing the stereocamera <NUM> before executing the correction of the present invention. The image processing unit <NUM> generates parallax image data and distance image data from the left and right geometric transformation image data, and sends the generated image data to the object recognition unit <NUM>. The object recognition unit <NUM> performs object recognition using the sent image data, and outputs the object recognition result to the outside as vehicle control information.

As described above, the stereocamera <NUM> by itself, targeted by the present invention, has completed the geometric correction and the correction of the relative positions of the left and right camera images. Therefore, when mounted on the vehicle <NUM>, the variation in the thickness of the windshield causes the rotation of the image and the shift in the image plane direction, and the parameter memory <NUM> is updated by correcting this. The enlargement/reduction and flatness of the image are small enough for distance measurement to have no actual harm.

The correction procedure in the device for correcting <FIG> will be described with reference to <FIG>. The vehicle <NUM> is stopped at a predetermined position (<NUM>). The stereocamera <NUM> captures an image of the infinite distance chart <NUM> (<NUM>).

From the captured left and right images, respective geometric transformation images are generated by the image processing unit <NUM> using the information in the correction parameter memory <NUM> (<NUM>). The image processing unit <NUM> corrects a relative rotation shift of the left and right images by using the finite distance chart <NUM> portion of the left and right images after geometric transformation (<NUM>).

The image processing unit <NUM> corrects a relative translational shift of the left and right images by using the portion of the infinite distance chart <NUM> of the left and right images after geometric transformation (<NUM>). The image processing unit <NUM> rewrites the data in the correction parameter memory <NUM> in consideration of the correction amount obtained in steps <NUM> and <NUM> above (<NUM>).

When the vehicle <NUM> is moved forward after the above procedure is finished, the finite distance chart <NUM> and the optical device <NUM> fixed to the finite distance chart <NUM> may be moved upward or left and right. In the case where the finite distance chart <NUM> and the optical device <NUM> are placed as shown in <FIG>, if the lowest point of the optical device <NUM> is placed at a position higher than the highest point of the vehicle, only the finite distance chart <NUM> may be moved.

As described above, the device for correcting the present embodiment can provide charts of a plurality of distances in a space-saving manner at low cost, and can highly accurately correct the stereocamera <NUM> while relaxing the installation accuracy of the vehicle <NUM>.

In the first embodiment, the correction device and the correction method when two charts are photographed at the same time are shown, but the infinite distance chart <NUM> and the finite distance chart <NUM> may be photographed independently.

In the present embodiment, an example in which the infinite distance chart <NUM> and the finite distance chart <NUM> are photographed in order will be described. <FIG> is an example of a configuration view of the device for correcting the stereocamera <NUM> of the present embodiment.

Since the components of the correction device are the same as those in <FIG> of the first embodiment, they will be omitted. The optical device <NUM> is fixed at a position higher than the total height of the vehicle <NUM> on the back surface of the finite distance chart <NUM>. The finite distance chart <NUM> has a mechanism that can move upward.

The procedure of correction of the stereocamera <NUM> using the correction device is shown in the flowchart of <FIG>. After stopping the vehicle <NUM> (<NUM>), the stereocamera <NUM> photographs the finite distance chart <NUM> (602b). At this time, the finite distance chart <NUM> is placed at the position shown in <FIG>, and the stereocamera <NUM> only photographs the finite distance chart <NUM>, and does not photograph the infinite distance chart <NUM>.

After finishing the photographing (602b), the finite distance chart <NUM> is moved upward and placed at a position where the infinite distance chart <NUM> is not interrupted (<NUM>). The stereocamera <NUM> photographs the infinite distance chart <NUM>. Since steps <NUM> to <NUM> are the same as those in the first embodiment, they will be omitted.

By placing the finite distance chart <NUM> and the infinite distance chart <NUM> of the optical device <NUM> as described above and performing photographing in order by the stereocamera <NUM>, it is possible to perform photographing without interrupting the chart of each other and to correct the entire chart.

By providing also the optical device <NUM> with a vertically moveable mechanism, it is possible to place the optical device <NUM> at the height of the optical axis C of the stereocamera <NUM> as shown in <FIG>.

The correction procedure in this case is shown in the flowchart of <FIG>. After stopping the vehicle (<NUM>), the stereocamera <NUM> photographs the finite distance chart <NUM> (602b). At this time, the finite distance chart <NUM> and the optical device <NUM> are placed at the position shown in <FIG>. Only the finite distance chart <NUM> is photographed, and the infinite distance chart <NUM> is not photographed.

After finishing the photographing (602b), the finite distance chart <NUM> is moved upward (or in the vehicle width direction) and placed at a position where the infinite distance chart <NUM> is not interrupted (<NUM>). The stereocamera <NUM> photographs the infinite distance chart <NUM> (602a). After finishing the photographing (602a), the optical device <NUM> is moved upward (<NUM>). Since steps <NUM> to <NUM> are the same as those in the first embodiment, they will be omitted. Here, the movement of the optical device <NUM> (<NUM>) may be performed after the data rewriting (<NUM>) because the movement of the optical device <NUM> only needs not to interfere with the movement of the vehicle <NUM>.

The optical device <NUM> may be placed in front of the finite distance chart <NUM>. It is convenient that the closer to the stereocamera <NUM> the optical device <NUM> is placed, the more the requirement for the installation angle is relaxed.

In the above-mentioned first embodiment and the second embodiment, the finite distance chart <NUM> is a two-dimensional plane chart placed at a finite distance, but the finite distance chart <NUM> may be a virtual image at an infinite distance similarly to the infinite distance chart <NUM>.

This configuration can correct the relative rotation shift of the left and right camera images by using both the infinite distance chart <NUM> and the finite distance chart <NUM> while correcting the relative translational shift of the both camera images from the image position of either the infinite distance chart <NUM> or the finite distance chart <NUM>.

In the present embodiment, an example in which the finite distance chart <NUM> is a virtual image of an infinite distance will be described. <FIG> is an example of a configuration view of the device for correcting the stereocamera <NUM> of the present embodiment. The components are the same as those in <FIG>, but an optical device 401A has the same configuration as that of the optical device <NUM>, and irradiates a virtual image of an infinite distance chart 401B of a cross pattern at an infinite distance.

Both the optical device <NUM> and the optical device 401A are fixed to the ceiling or the like and are placed at a position higher than the total height of the vehicle <NUM>.

<FIG> schematically illustrates images of the infinite distance chart <NUM> and the infinite distance chart 401B captured by the left and right cameras <NUM>. The right image is illustrated on the upper side, and the left image is illustrated on the lower side. In each of the left and right images, images of the infinite distance chart <NUM> and the infinite distance chart 401B and the optical device <NUM> and the optical device 401A that generate them respectively are formed at different positions.

It is convenient that the both images are farther apart in order to highly accurately correct the rotation shift. Since each of the infinite distance chart <NUM> and the infinite distance chart 401B appears to be at an infinite distance, the relative positions of the left and right images are equal, and on the other hand, each of the optical device <NUM> and the optical device 401A appears to be at a finite distance, and therefore the relative position of the left and right images appears to be shifted by the parallax.

The correction procedure is shown in the flowchart of <FIG>. After stopping the vehicle <NUM> (<NUM>), the stereocamera <NUM> captures images of the infinite distance charts <NUM> and 401B (<NUM>). The left and right cameras <NUM> captures images of the infinite distance chart <NUM> and the infinite distance chart 401B at the same time.

After finishing the photographing (<NUM>), from the captured left and right images, the image processing unit <NUM> generates respective geometric transformation images using the information in the correction parameter memory <NUM> of <FIG> (<NUM>).

The image processing unit <NUM> corrects the relative rotation shift of the left and right images by using the infinite distance chart <NUM> and the infinite distance chart 401B of the left and right images after geometric transformation (<NUM>). The image processing unit <NUM> corrects the relative translational shift of the left and right images by using the infinite distance chart <NUM> or the infinite distance chart 401B of the left and right images after geometric transformation (<NUM>). The infinite distance chart 401B rewrites the data in the correction parameter memory <NUM> illustrated in <FIG> in consideration of the correction amount obtained in steps <NUM> and <NUM> above (<NUM>).

By placing the two optical devices <NUM> and 4011A that irradiate the infinite distance charts <NUM> and 401B as described above to perform photographing with the stereocamera <NUM>, it is possible to correct the relative translation and rotation of the left and right images.

With the the method of claim <NUM>, it is possible to provide the finite distance chart <NUM> and the infinite distance chart <NUM> in a space-saving manner at low cost, and it is possible to highly accurately correct the stereocamera while relaxing the installation accuracy of the vehicle <NUM>.

With the method of claim <NUM>, it is possible to correct the relative position (translational shift) of the image.

with the method of claim <NUM>, it is possible to provide the optical device <NUM> at low cost.

with the method of claim <NUM>, it is possible to perform correction in the rotation direction of the camera from the image of the finite distance chart <NUM>.

With the method of claim <NUM>, the size of the through hole <NUM> is determined by the installation error of the stereocamera <NUM>, i.e., the accuracy of the stop position of the vehicle <NUM>. It is possible to highly accurately correct the stereocamera <NUM> while relaxing the installation accuracy of the vehicle <NUM> according to the size of the diameter of the through hole <NUM>.

with the method of claim <NUM>, the size of the through hole <NUM> is determined by the installation error of the stereocamera <NUM>, i.e., the accuracy of the stop position of the vehicle <NUM>. It is possible to highly accurately correct the stereocamera <NUM> while relaxing the installation accuracy of the vehicle <NUM> according to the size of the diameter of the through hole <NUM>. It is possible to install the optical device <NUM> on the back surface of the finite distance chart <NUM>, the virtual image of the infinite distance chart <NUM> can be transmitted through the through hole <NUM> and captured by the stereocamera <NUM>, and the correction device can be compactly configured.

With the method of claim <NUM>, it is possible to correct the stereocamera <NUM> by alternately capturing the virtual image from the optical device <NUM> and an image of the finite distance chart <NUM> with the correction device configured to be compact.

With the method of claim <NUM>, it is possible to correct the relative translation and rotation of the left and right images by placing the two optical devices <NUM> and 4011A that irradiate the infinite distance charts <NUM> and 401B and performing photographing with the stereocamera <NUM>.

With the method of claim <NUM>, in the image of the stereocamera <NUM>, the area below the vanishing point is the area where the road surface and the object in front appear, which is an important area for object recognition, and the area above the vanishing point is the area where there are many objects that do not require accuracy such as signals, signs, and the sky. Therefore, it is desirable to place the infinite distance chart <NUM> so as to appear above the vanishing point. On the other hand, in order to secure the recognition performance of a distant object, the stereocamera <NUM> can be placed so that the vicinity of the optical axis of the lens having high resolution coincides with the vanishing point.

with the method of claim <NUM>, it is possible to make it clear the boundary between the infinite distance chart <NUM> and the finite distance chart <NUM> and to facilitate image processing.

Claim 1:
A method for correcting a stereocamera (<NUM>) mounted on a vehicle (<NUM>), wherein
a first optical device (<NUM>) that has a first chart (<NUM>) having a predetermined pattern and a mirror surface (<NUM>) having a diameter equal to or greater than a baseline length (L) of the stereocamera (<NUM>) generates a virtual image of the first chart (<NUM>), and
the stereocamera (<NUM>) uses images obtained by capturing the virtual image with a plurality of cameras (<NUM>) to correct a parameter corresponding to the relative position of the images obtained by the cameras (<NUM>),
characterized in that the first optical device (<NUM>) includes either a reflecting telescope or a catadioptric telescope.