JP2014010089A - Range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a range value in a real time even when the positional deviation of a stereo camera occurs.SOLUTION: The range finger includes: a laser irradiation device 20 which emits a plurality of parallel beams 24 isolated with a predetermined interval to an object 41; a plurality of imaging lens 12 which image spot light by a plurality of beams respectively reflected on the object; a plurality of imaging means 13 which image a plurality of images related to the object including respective spot light imaged by the respective imaging lens; ranging means 31 which calculates a distance to the object on the basis of parallax information between the respective images; and distance correction means 33 which corrects the distance to the object calculated by the ranging means on the basis of a distance to the object to be calculated from an interval of the imaging positions of the respective spot light on at least one imaging means between the respective imaging means.

Description

  The present invention relates to a distance measuring device that performs distance measurement using parallax images acquired by a plurality of cameras, and more particularly to a distance measuring device that can correct a distance measurement error caused by a positional deviation of cameras in real time. is there.

Conventionally, a “stereo distance measurement” technique is known in which a measurement object is photographed by two cameras and distance information to the measurement object is obtained using the two obtained images. In stereo ranging, the depth distance is calculated based on the principle of triangulation using the parallax generated between two captured images.
In order to obtain parallax in stereo ranging, it is necessary to perform window matching to find corresponding points (corresponding points) in each image.

FIGS. 15 and 16 are diagrams illustrating the principle of a distance measuring method using the principle of triangulation used in “stereo distance measurement”. In stereo ranging, two cameras are configured by combining a pair of two-dimensional sensors and a pair of lenses, and the displacement (parallax) of the measurement object is detected and the principle of triangulation is used. Measure distance.
In the stereo camera device 106 shown in FIG. 15, consider a case where two cameras 102 a and 102 b having the same optical system are arranged and each camera 102 captures light from the measurement object 101.
Each camera 102 (102a, 102b) includes a lens 103 (103a, 103b) on which an optical image of the measurement object 101 is incident, and an optical image (measurement object image 104: 104a) of the measurement object 101 incident on each lens 103. , 104b), and a two-dimensional sensor 105 (105a, 105b).

The measurement object image 104a obtained through the lens 103a of the camera 102a and the measurement object image 104b obtained through the lens 103b of the camera 102b have the same point on the measurement object 101 shifted by the parallax Δ, and the two-dimensional sensor 105a, Each reaches 105b (FIG. 16) and is received by a plurality of light receiving elements (pixels) and converted into an electrical signal.
Here, the distance between the optical axes of the lenses 103a and 103b is called a baseline length. When the base line length is D, the distance between the lens 103 and the measurement object 101 is A, and the focal length of the lens 103 is f, the following equation holds when A >> f.
A = Df / Δ Expression (1)
As shown in FIG. 15, since the baseline length D and the focal length f of the lens are known, the distance A to the measurement object 101 can be calculated from the equation (1) by detecting the parallax Δ.

  In the above method, in order to detect the distance A with high accuracy, it is necessary to detect the parallax Δ with high accuracy. In particular, when a “translational deviation” occurs in which the lens 103 is displaced in the direction in which the parallax occurs (Y direction in FIG. 16), the translational deviation appears as it is as an error of the parallax Δ, and an accurate distance cannot be calculated. Generally, since it is necessary to detect the parallax with an accuracy of 1 pixel or less, the parallax must be detected with an accuracy of several μm or less. However, for example, in FIG. 15, when the lens 103a has a translational deviation of several μm, this becomes an error of the parallax Δ, and an accurate distance cannot be calculated.

Patent Documents 1 and 2 disclose a technique for solving the above problem by performing correction even when a positional deviation occurs in a stereo camera.
Patent Document 1 discloses a technique for correcting a positional shift of a stereo camera by performing geometric conversion on a stereo image. When adjusting the positional deviation, the correction value detection device is connected to the image correction device. Then, the angle of view difference, rotational deviation, or translational deviation of the stereo image obtained by imaging the adjustment pattern dedicated for correction is calculated, and the affine transformation parameters (image conversion values) corresponding to the calculated values are corrected. Set to device. By performing affine transformation on the image based on the affine parameters set in this way, the positional shift including the horizontal shift of the stereo camera is equivalently corrected by image processing.
Patent Document 2 discloses a technique for correcting a positional shift of a stereo camera in real time. The left and right lanes are detected from the photographed image shown in the stereo camera, the straight line extending in the distance direction is determined, and the vanishing point of the image is calculated from the intersection of the approximate straight lines. Correct distance measurement can be performed by correcting the image based on this vanishing point.

However, since the apparatus described in Patent Document 1 needs to be connected to an image correction apparatus or to capture a dedicated adjustment pattern, the distance cannot be corrected in real time. In Patent Document 2, the distance can be corrected in real time by calculating the vanishing point of the image. However, when the vanishing point of the image cannot be obtained, there is a problem that the distance cannot be corrected.
The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a novel distance measuring device that can correct a distance value in real time even when a stereo camera is displaced.

  In order to solve the above-described problem, the invention according to claim 1 is directed to an irradiation device that emits a plurality of parallel beams toward an object, and spot light generated by the plurality of beams reflected by the object. A plurality of imaging lenses for imaging a plurality of imaging means for imaging a plurality of images related to the object including the spot lights imaged by the imaging lenses, and parallax information between the images. A distance measuring means for calculating the distance to the object based on the distance to the object obtained from the interval between the imaging positions of the spot lights on at least one image pickup means of the image pickup means, Distance correction means for correcting the distance to the object calculated by the distance measurement means.

  In the present invention, the object is irradiated with a plurality of parallel beams whose beam intervals are kept constant. The spot light formed on the surface of the object is picked up by the image pickup means, and the distance to the object irradiated with the beam can be found by calculating the interval of the spot light on the image pickup means. In addition, the distance to the object is calculated from the parallax information between the plurality of images. By using the distance obtained from the spot light interval, the distance to the object calculated from the parallax information between the images is corrected, thereby enabling real-time correction.

It is the schematic diagram which showed the distance measuring device which concerns on 1st embodiment of this invention. It is a block diagram of the ranging apparatus shown in FIG. It is a figure for demonstrating the relationship between the parallel beam irradiated from a laser irradiation apparatus, and the image imaged with a stereo camera. It is a graph which shows the relationship between the distance from a stereo camera, and the pixel count of two spot space | intervals. It is a figure explaining the ranging method using the principle of triangulation. It is the graph which showed the relationship between the distance A to a target object, and the parallax amount (pixel) on an image pick-up element. It is a figure for demonstrating an example of the correction method of translational deviation. It is a schematic diagram of the laser irradiation apparatus applied to the ranging apparatus which concerns on 2nd embodiment of this invention. It is a schematic diagram of the laser irradiation apparatus applied to the ranging apparatus which concerns on 3rd embodiment of this invention. It is a schematic diagram of the laser irradiation apparatus which shows the modification of 3rd embodiment. (A), (b) is a figure for demonstrating operation | movement of the laser irradiation apparatus shown in FIG. It is a figure which shows the relationship between the rotation amount of the polarization by a polarization | polarized-light rotation element, the light radiate | emitted from a light splitting element, and the light intensity of 0th-order light. (A)-(c) is the figure which showed the relationship between an imaging range and the obstruction in an imaging range. It is the flowchart which showed an example of the process in the distance measuring device of this invention. It is a figure explaining the principle of the ranging method using the principle of triangulation. It is a figure explaining the principle of the ranging method using the principle of triangulation.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .
<First embodiment>
A distance measuring apparatus according to a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing a distance measuring apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram of the distance measuring apparatus shown in FIG. The distance measuring device according to the present embodiment calculates the distance (correction reference value) from a plurality of spot lights formed on the object to the object, and calculates the distance based on the parallax image using the correction reference value. It is characterized in that the distance to the object (range measurement value) is corrected.

As shown in FIGS. 1 and 2, the distance measuring device 1 includes a stereo camera 10 that captures two object images having parallax with each other, and two parallel objects separated by a predetermined distance L toward the object 41. A laser irradiation device 20 (irradiation device) that emits the beam 24 (24a, 24b), and a distance measurement unit 31 that calculates a distance (range value) from the image captured by the stereo camera 10 to the object 41 And a control unit 30 having
The stereo camera 10 forms a plurality of lenses 12 (12a, 12b: imaging) that forms an optical image of the object 41 including a plurality of spot lights 25 (25a, 25b) by a plurality of beams 24 reflected by the object 41, respectively. Lens) and a plurality of imaging elements 13 (13a, 13b: imaging means) that capture a plurality of images related to the object 41 including each spot light 25 imaged by each lens 12. Note that the image sensor 13 is a two-dimensional sensor such as a CCD or a CMOS.

  The control unit 30 includes a distance measuring unit 31 that calculates a distance to the object 41 based on parallax information between two images captured by each image sensor 13, and at least one image sensor 13 a of each image sensor 13. Based on the distance (correction reference value) to the target object 41 obtained from the interval between the imaging positions of the respective spot lights 25 above, the distance to the target object 41 (ranging value) calculated by the distance measuring means 31 is corrected. Distance correction means 32 and irradiation control means 33 for controlling the laser irradiation apparatus 20 are provided. The irradiation control means 33 also functions as means for controlling on / off of the semiconductor laser 21 described later.

The laser irradiation device 20 transmits a semiconductor laser 21 (light source) that emits laser light (illumination light), a coupling lens 22 that converts light emitted from the semiconductor laser 21 into parallel light, and part of the parallel light. And a light splitting element 23 provided with a light quantity splitting surface 23A (half mirror) that reflects part of the light and a total reflection face 23B that totally reflects parallel light transmitted through the light quantity splitting face 23A. The parallel light reflected by the light quantity dividing surface 23A and the total reflection surface 23B is emitted as parallel beams 24 (24a, 24b) with an interval L.
The stereo camera 10 has a horizontal angle of view of an angle α (see FIG. 3), and the emission directions of the two beams 24 are adjusted so as to fall within the imaging angle of view of the stereo camera 10.

The principle of the present invention will be described with reference to FIG. FIG. 3 is a diagram for explaining the relationship between the parallel beam irradiated from the laser irradiation apparatus and the image captured by the stereo camera.
The relationship between the horizontal angle of view α of the stereo camera 10 and the spot light 25 formed by a plurality of parallel beams 24 emitted from the laser irradiation device 20 will be described with reference to FIG. At the position where the distance from the stereo camera 10 is A1, the shooting range B1 in the horizontal direction (Y direction in FIG. 2) of the stereo camera 10 is expressed by the following equation.
B1 = 2 × A1 × tan (α / 2) (2)
When the parallel beam 24 is irradiated toward the object 41 (plane) whose distance from the stereo camera 10 is at the position A1, a plurality of spot lights 25 corresponding to each beam are formed on the object 41. Assuming that the interval L of the parallel beam 24 and the number of pixels of the imaging device of the stereo camera are VGA (640 × 480 pixels), the interval C1 (number of pixels) of the spot light 25 imaged on the imaging device is expressed by the following equation. The
C1 = (L / B1) × 640 (pixels)
= (L / 2 × A1 tan (α / 2)) × 640 (pixels) (3)

Similarly, when the distance from the stereo camera 10 changes to A2 and A3, the intervals C2 and C3 of the parallel beam 24 on the image sensor change as follows.
C2 = (L / 2 × A2 tan (α / 2)) × 640 (pixels) (4)
C3 = (L / 2 × A3 tan (α / 2)) × 640 (pixels) (5)
As shown in the equations (1) to (3), there is an inversely proportional relationship between the distance C and the distance A. If the horizontal angle of view α of the stereo camera 10 is 50 degrees and the interval L of the parallel beam 24 is L = 20 mm, the distance A from the stereo camera 10 and the interval C (pixels) of the spot light 25 detected on the image pickup device 13. When the number is graphed, it is expressed as shown in FIG. FIG. 4 is a graph showing the relationship between the distance from the stereo camera and the number of pixels at two spot intervals. In FIG. 4, the distance A is on the horizontal axis and the interval C is on the vertical axis.

As can be seen from FIG. 4, if the interval (number of pixels) of the spot light 25 on the image sensor can be detected, the distance A from the stereo camera 10 to the object 41 is uniquely determined. In particular, under this condition, when the distance A is 200 mm or less, the sensitivity is high, and even if the distance A is slightly changed, the interval (number of pixels) of the spot light 25 on the image sensor changes greatly. In other words, the distance A can be detected with high accuracy even if there is some error when detecting the interval (number of pixels) of the spot light 25 on the image sensor.
As described above, if the beam interval L, the horizontal angle of view α of the stereo camera, and the number of pixels of the image sensor 13 are known in advance, the distance can be obtained with high accuracy from the interval (number of pixels) of the spot light reflected on the image sensor. it can. Therefore, by referring to the distance obtained from the interval between the parallel beams 24, even if a positional deviation occurs in the stereo camera, it can be accurately corrected in real time.

Here, how a distance measurement error occurs due to a position shift (particularly a translation shift in the Y direction) generated in the stereo camera will be described.
FIG. 5 is a diagram for explaining a distance measuring method using the principle of triangulation used in “stereo distance measurement”. The stereo camera 10 includes a plurality of monocular cameras 11 (11a, 11b), and each camera 11 includes a plurality of lenses 12 (12a, 12b) on which an optical image of an object 41 is incident, And a plurality of imaging elements 13 (13a, 13b: imaging means) that capture a plurality of images of the object 41 imaged by the lens 12.
When the focal length of the lenses 12a and 12b is f, the distance between the optical axes (base line length) of the two lenses 12a and 12b is D, and the distance A to the object 41 is, the obtained parallax Δ is Δ = Df / A.・ Formula (6)
It is expressed. As an example, when the base line length D = 5 mm, the focal length f = 1.6 mm, and the distance A = 200 mm, the parallax Δ = 0.04 mm. If the size of one pixel of the image sensors 13a and 13b is 2 μm, parallax corresponding to 20 pixels (= 0.04 mm / 2 μm) is generated. FIG. 6 is a graph showing the relationship between the distance A to the object and the amount of parallax on the image sensor. The relationship between the distance A and the parallax Δ when the base line length D = 5 mm, the focal length f = 1.6 mm, and the size of one pixel is 2 μm is shown. As described above, the distance measuring unit 31 detects the parallax Δ to obtain the distance A.

In the stereo camera 10 having the above configuration, it is assumed that one lens 12b is displaced by 2 μm in the + Y direction as shown in FIG. At this time, the parallax is 0.042 mm, and a parallax equivalent to 21 pixels (= 0.042 mm / 2 μm) is generated. Since the distance A is expressed by “A = Df / Δ” as shown in Expression (1), when the parallax Δ is 0.042 mm, the distance measuring unit 31 calculates the distance A = 190.5 mm.
Thus, due to the slight translational deviation of one lens of the stereo camera, the distance measuring means 31 calculates the distance of 200 mm as 190.5 mm and generates an error of about 5%. For example, in the inspection process of a manufacturing factory, if an inspection is continued using a distance measuring device without noticing that a lens shift has occurred, an erroneous inspection value is output and a large number of “defective products” are generated. It will be. In this “defective product”, there is a possibility that a genuine defective product and a normal product determined as a defective product due to a ranging error caused by a lens shift of the distance measuring device may be mixed. In such a case, it is difficult to distinguish between a true defective product and a normal product determined to be defective. Therefore, it is desirable to correct the output value of the stereo camera in real time.

  As described above, if the interval (number of pixels) of the plurality of parallel beams 24 on at least one image sensor 13 can be detected, the distance A to the object 41 can be obtained. Since this method is not a method of detecting the distance using two cameras 11 as in the stereo camera 10, the calculated distance even when the lens 12 of one of the cameras 11 is displaced in the Y-axis direction in the figure. Does not affect. That is, even if one lens 12 is displaced in the Y-axis direction, the plurality of parallel beams 24 are imaged while maintaining an interval corresponding to the distance to the object 41. The distance between the lens 12 and the object 41 obtained by detection can be used as a correction reference value for correcting the distance measurement value.

A method of correcting the distance measurement value using the distance between the lens and the object obtained by detecting the interval between the parallel beams will be described with reference to FIG. FIG. 7 is a diagram for explaining an example of a translational deviation correction method used in the present invention.
The distance A ′ (correction reference value) between the lens 12 and the object 41 obtained by detecting the base line length D of the lens 12 and the distance between the spot lights 25, the focal length f of the lens 12, and the translational deviation of the lens 12 are as follows. It is assumed that the parallax Δ observed when it does not occur, the translational displacement p in the Y direction of the lens 12 (12a), and the parallax Δ ′ observed when the lens 12a undergoes a translational deviation.

If the base line length of the stereo camera 10 is (D + p) and the parallax Δ ″ is observed and the distance A between the lens 12 and the object 41 is obtained, the following equation (7) is established.
A ′ = (D + p) f / Δ ″ (7)
Here, when A ′ >> f and D >> p, it can be written as Δ≈Δ ″. When the translational deviation p occurs, the parallax Δ ′ observed on the image sensor 13 is the translational deviation p. Can be expressed as “Δ = Δ′−p”. Therefore, if equation (7) is modified,
A ′ = (D + p) f / (Δ′−p) (8)
Solving for p,
p = (A′Δ′−fD) / (f + A ′) (9)
Therefore, the accurate distance A can be obtained by the following equation (10) using the translational deviation p obtained from the equation (9) and the observed parallax Δ ′.
A = Df / (Δ′−p) (10)

  As described above, in the present embodiment, the stereo camera 10 captures an image of the object 41 irradiated with the plurality of parallel beams 24. The distance measuring means 31 calculates the distance (range value) to the target object 41 based on the parallax from the obtained plurality of images. Further, the distance correction unit 32 calculates the distance (correction reference value) to the object 41 based on the interval of the spot light 25 on the image sensor from any of the obtained images. The distance correction unit 32 compares the obtained distance measurement value with the correction reference value in real time. When the difference between the distance measurement value and the correction reference value becomes larger than a predetermined threshold value, the distance correction means 32 regards the correction reference value as a correct value and obtains the translational deviation amount by the equation (9). Further, the distance measurement value corrected by subtracting the translational deviation amount from the parallax observed by the equation (10) is output. In this way, the distance obtained from the stereo camera can always be kept accurate.

As described above, the distance to the object can be determined by calculating how many pixels the interval of the spot light based on the plurality of parallel beams corresponds to from the image captured by the stereo camera. Since the distance is not obtained from the parallax of images taken by the two cameras, it is not affected by the positional deviation of the stereo camera (especially translational deviation in the Y direction). Therefore, by comparing the distance obtained from the parallax and the distance obtained from the beam interval, it is possible to recognize an error caused by the positional deviation of the stereo camera.
Further, the distance measurement value is obtained based on the parallax from a plurality of images related to the object imaged in a state where the parallel beam is irradiated. In addition, the distance to the object is calculated based on the parallel beam using one of the captured images. In this way, the distance measurement value and the correction reference value can be calculated in parallel by one shooting. Therefore, the distance measurement value can be corrected in real time.

<Second Embodiment>
A distance measuring apparatus according to a second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a schematic diagram of a laser irradiation apparatus applied to the distance measuring apparatus according to the second embodiment of the present invention. The laser irradiation apparatus according to the present embodiment is characterized not only by irradiating the parallel beam for correcting the distance measurement value but also by irradiating the object with pattern light. Hereinafter, the same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
As described above, in distance measurement using a stereo camera (stereo distance measurement), parallax is calculated by window matching to obtain a distance. Therefore, it is necessary to find “corresponding points” in the pair of captured images. However, when the surface of the object is uniform and it is difficult for the luminance value to change, a “corresponding point” cannot be found, so that the parallax cannot be obtained and the distance cannot be obtained. For this reason, in the present embodiment, a predetermined pattern light is irradiated in order to enable distance measurement to an object where the luminance value hardly changes.

As shown in FIG. 8, the laser irradiation device 50 generates a diffraction pattern light by being arranged on one optical path of the split light and a light splitting element 51 that splits the parallel light transmitted through the coupling lens 22 into three parts. And a diffractive optical element 52.
The light splitting element 51 transmits two parts of incident parallel light and reflects part of the two light quantity splitting surfaces 23A and 23C, and a total reflection face 23B that totally reflects the parallel light that has passed through the light quantity splitting face 23C. ,have. As the light splitting surface, a polka dot in which a large number of minute openings are provided at predetermined intervals on the incident surface of a metal plate such as gold, and the transmittance is changed according to the area ratio between the opening and the shielding portion of the incident surface is used. be able to.
The diffractive optical element 52 is disposed on the optical path of the parallel light (beam 24c) reflected by the light amount dividing surface 23C disposed between the light amount dividing surface 23A and the total reflection surface 23B.
In the laser irradiation device 50, laser light having a wavelength λ is emitted from the semiconductor laser 21 and is converted into parallel light by the coupling lens 22. The parallel light is split into three parallel beams 24a, 24b, and 24c by the light splitting element 51. The diffractive optical element 52 is disposed in the optical path of the beam 24c, which is one of the three beams. The beam 24c incident on the diffractive optical element 52 becomes a predetermined pattern light 53 and is irradiated onto the object. The beams 24a and 24c that do not pass through the diffractive optical element 52 are irradiated on the object as they are and become spot light 25 (25a and 25b).

As described above, in this embodiment, the diffractive optical element is arranged in the optical path of one of the plurality of parallel beams. The beam incident on the diffractive optical element is converted into a beam having a predetermined pattern (pattern light) and irradiated onto the object. When a pattern is formed by pattern light on the surface of an object that hardly changes in luminance value, the luminance value changes on the surface of the object, and distance measurement can be performed using a stereo camera.
Therefore, according to the present embodiment, it is possible to accurately correct the distance in real time from the interval of the spot light based on the parallel beam reflected on the image sensor, and at the same time, to measure the distance to the object whose luminance value hardly changes. It becomes.

<Third embodiment>
A distance measuring apparatus according to a third embodiment of the present invention will be described with reference to FIG. FIG. 9 is a schematic diagram of a laser irradiation apparatus applied to the distance measuring apparatus according to the third embodiment of the present invention. The laser irradiation apparatus according to the present embodiment is characterized in that an object is irradiated with a parallel beam for obtaining distance correction data and pattern light using light divided into two by a light dividing element. Hereinafter, the same components as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted.
The light splitting element 23 constituting the laser irradiation apparatus 60 shown in FIG. 9 emits parallel light transmitted through the coupling lens 22 as two parallel beams 24a and 24b. A diffractive optical element 52 is disposed on the optical path of one beam 24b. The diffractive optical element 52 generates pattern light 53 obtained by diffracting the beam 24 b and irradiates the object 41. The beam 24a that does not pass through the diffractive optical element 52 is irradiated to the object 41 as it is.
The beam 24 b is diffracted by the diffractive optical element 52 to become a predetermined pattern light 53. At this time, the beam 24b incident on the diffractive optical element 52 is not necessarily 100% diffracted, and some light passes through (transmits) the diffractive optical element 52 without being diffracted. This light is generally called 0th order light (0th order diffracted light), and behaves the same as when the diffractive optical element 52 is not present. That is, the beam 24 a and the zero-order light 54 are parallel to each other, and form the spot lights 25 a and 25 c on the object 41. Therefore, the distance to the object 41 can be calculated by acquiring the imaging interval of the two spot lights 25 in the image sensor 13.

  Here, it is desirable that the beam 24a and the zero-order light 54 have appropriate and equivalent light intensities. The reason is that if the light intensity of the beam 24a and the 0th-order light 54 is stronger than the pattern light 53, the pattern light 53 is canceled out by the spot light 25, and distance measurement using the pattern light 53 cannot be performed accurately. . Conversely, if the intensity of the beam 24a and the zero-order light 54 is weaker than that of the pattern light 53, the spot light 25 is canceled out by the pattern light 53, and accurate distance correction cannot be performed.

  An example of a laser irradiation apparatus that solves the above problem will be described with reference to FIG. FIG. 10 is a schematic diagram of a laser irradiation apparatus showing a modification of the present embodiment. As shown in the figure, the laser irradiation device 70 includes a polarization rotation element 71 that rotates the polarization direction of the parallel light that has passed through the coupling lens 22, and a light splitting element 72 that splits the polarization light that has passed through the polarization rotation element 71 into two. It is equipped with. The light splitting element 72 includes a polarizing film 72A having a different reflectance depending on the polarization direction of incident light, and a total reflection surface 72B that reflects the light transmitted through the polarizing film 72A.

Hereinafter, a principle (method) for equalizing the intensities of the beam 24a and the 0th-order light 54 will be described with reference to FIGS. 11A and 11B are diagrams for explaining the operation of the laser irradiation apparatus shown in FIG. FIG. 12 is a diagram illustrating the relationship between the amount of polarization rotation by the polarization rotation element and the light intensity of the beam and the 0th-order light emitted from the light splitting element.
The light emitted from the semiconductor laser 21 is generally linearly polarized light. Hereinafter, an example in which the semiconductor laser 21 emits S-polarized light will be described. The polarizing film 72A of the light splitting element 72 has a property of reflecting 100% of S-polarized light and transmitting 100% of P-polarized light.
First, consider a case where the polarization rotation element 71 transmits incident S-polarized light as it is. As shown in FIG. 11A, the S-polarized light emitted from the semiconductor laser 21 is converted into parallel light by the coupling lens 22. The parallel light passes through the polarization rotation element 71 as S-polarized light and then enters the light splitting element 72. Since the polarizing film 72A reflects 100% of S-polarized light, the parallel light incident on the light splitting element 72 is reflected 100% by the polarizing film 72A to become a beam 24a. Since the parallel light is reflected 100% by the polarizing film 72A, it does not enter the diffractive optical element 52, and the zero-order light 54 and the pattern light 53 are not generated.

  Next, consider using the polarization rotation element 71 to rotate the polarization direction of linearly polarized light emitted from the semiconductor laser 21 by 90 °. As shown in FIG. 11B, the S-polarized light emitted from the semiconductor laser 21 is converted into parallel light by the coupling lens 22. The parallel light is converted from S-polarized light to P-polarized light by the polarization rotation element 71. The light that has become P-polarized light enters the light splitting element 72. Since the polarizing film 72A transmits 100% of the P-polarized light, the parallel light incident on the light splitting element 72 transmits 100% of the polarizing film 72A. Further, the parallel light is reflected 100% by the total reflection surface 72B and enters the diffractive optical element 52. The light incident on the diffractive optical element 52 is emitted as 0th-order light 54 and pattern light 53.

Thus, when the light incident on the light splitting element 72 is S-polarized light, the light intensity of the beam 24a is strong, and when the light is P-polarized light, the light intensity of the beam 24b is strong.
Incidentally, the relationship of the light intensity when the polarization direction of the light incident on the light splitting element 72 is rotated from the S-polarized light to the P-polarized light by the polarization rotating element 71 is as shown in FIG. As the light intensity of the beam 24b reflected by the total reflection surface 72B increases, the light intensity of the zero-order light 54 also increases. As shown in the figure, it is understood that the light intensities of the beam 24a and the 0th-order light 54 are equal when they are slightly closer to the P-polarized light than between the S-polarized light and the P-polarized light (45 ° direction).

Therefore, in the present invention, the polarization direction is adjusted by controlling the polarization rotation element 71 so that the light intensity of the beam 24a and the zero-order light 54 is equalized by the irradiation control means 33 (FIG. 10).
For example, when a half-wave plate is used as the polarization rotation element 71, the polarization direction can be rotated by mechanically rotating the half-wave plate by a driving source. If the half-wave plate is rotated so that it is slightly closer to the P-polarized light than the middle of the S-polarized light and the P-polarized light (45 ° direction), the light intensity of the beam 24a is equal to the light intensity of the zero-order light 54. can do.
It should be noted that what percentage of the beam 24b incident on the diffractive optical element 52 is emitted as the 0th-order light 54 can be designed by adjusting the shape and depth of the groove of the diffractive optical element 52. Therefore, the light intensity of the beam 24b and the 0th-order light 54 can be set to be optimal and equal by adjusting the rotation direction of the polarization rotating element 71 and processing the groove shape and depth of the diffractive optical element 52. is there.

  As described above, in the present embodiment, the diffractive optical element is arranged in the optical path of one of a plurality of parallel beams. The diffractive optical element converts the incident beam into a predetermined pattern light. At this time, light (0th order light) that passes through the diffractive optical element without being diffracted by the diffractive optical element is generated. Since the zero-order light and the other beams are parallel to each other with a constant interval, the correction reference value can be obtained by photographing the spot light formed on the surface of the object by the zero-order light and the beam. it can. In addition, since the diffraction pattern light and the beam that generates the 0th-order light (based on the beam) can be shared, the laser irradiation apparatus can be reduced in size and cost.

<About correction timing>
The distance measurement correction timing using the parallel beam described in the first to third embodiments will be described with reference to FIG. FIGS. 13A to 13C are diagrams illustrating the relationship between the imaging range and the obstacles in the imaging range.
When the distance measurement value is corrected, it is desirable that the entire imaging range of the stereo camera 10 is a plane that is equidistant from the stereo camera 10 (FIG. 13A). In such a case, the distance from the stereo camera 10 is uniform over the entire imaging range, and the distance from the stereo camera 10 to the two spot lights 25 is always the same. Therefore, the distance as the correction reference can be accurately obtained from the two spot lights 25 by the parallel beam 24.
Since the distance measuring devices shown in the above embodiments all include a stereo camera, the distance of the entire shooting screen can be obtained by the stereo camera. Thereby, the perspective distribution in the screen is known, and it is possible to detect whether or not the entire surface of the imaging screen is flat (the presence or absence of an obstacle in the imaging screen). When there are no obstacles and the entire screen is on the same plane, the target is irradiated with multiple parallel beams, and the spot light formed on the surface of the object is photographed to obtain an accurate correction reference value. Can be obtained.

On the other hand, let us consider a case where there are irregularities in the imaging range of the stereo camera 10. As shown in FIG. 13B, an obstacle 43 exists on the object 41. At this time, the distance from the stereo camera 10 to the obstacle 43 is A1, but the distance from the stereo camera 10 to the object 41 is A2.
If the spot light 25a is formed on the obstacle 43 and the spot light 25b is formed on the object 41, the spot light 25a forms an image closer to the end on the image sensor 13 than the spot light 25b. (See FIG. 3). This is caused by the camera principle that even if the object is the same size, it appears larger when it is in front. In such a case, the correction reference value cannot be obtained using the correlation between the interval (number of pixels) of the spot light 25 imaged on the image sensor 13 and the distance from the stereo camera 10 to the spot light. Therefore, accurate correction cannot be performed. Therefore, when photographing a plurality of parallel beams 24, at least the surface irradiated with the parallel beams needs to be a plane at the same distance from the stereo camera.

FIG. 13C shows a case where there are irregularities in the imaging range of the stereo camera 10, but the two spot lights are on the same plane. Thus, it is effective to take an image when there is no obstacle in the direction in which a plurality of parallel beams are arranged (Y direction in FIG. 13). In particular, if there are no obstacles in the entire shooting screen in the Y direction, not just the portion irradiated with a plurality of parallel beams, it is possible to acquire an accurate correction reference value and accurately correct the distance measurement value. .
Therefore, for example, when correcting the output of the distance measuring device provided in the inspection line of the manufacturing factory, it is parallel to the belt conveyor (object 41) in the gap between the sample flowing in the upward direction in the figure and the sample (obstacle 43). The correction reference value may be obtained by irradiating the beam 24 and photographing the spot light 25. With such a method, it is possible to correct almost in real time. In particular, when the sample flows on the belt conveyor at regular intervals, the spot light may be photographed in accordance with the timing at which the belt conveyor is exposed.
For example, in order to confirm that the plurality of spot lights 25 are on the same plane, the distances to the two spot lights 25 are calculated based on the parallax images, and the distances from the stereo camera 10 are the same. You can confirm. It may be confirmed that the distance from the stereo camera 10 is the same not only in the portion of each spot light 25 but also within a predetermined range including the two spot lights 25 or the entire screen. In the latter case, the distance measurement value can be corrected more accurately.
Even when translational shift occurs in the camera 11, the same parallax is generated for objects on the same plane. Therefore, it is possible to confirm that a desired portion of the imaging range is on the same plane.

An example of the processing flow of the distance measurement value correction method of the present invention will be described. FIG. 14 is a flowchart showing an example of processing in the distance measuring apparatus of the present invention. In this example, the distance measurement value is corrected by determining whether or not the spot light is irradiated on a plane suitable for obtaining the correction reference value.
First, the irradiation control means 33 turns on the semiconductor laser 21, and emits the parallel beam 24 from the laser irradiation apparatus 20 (step S1). Then, the spot light 25 is formed on the object 41 or the obstacle 43 that is within the imaging range of the stereo camera 10. Images including the spot light 25 are captured by the two cameras 11 of the stereo camera 10. From the two parallax images, the distance measuring means 31 calculates the distances (range values) to the two spot lights 25 (step S2).
The distance correction unit 32 compares the distance between the stereo camera 10 and the two spot lights 25. When the distance to the spot light 25a is different from the distance to the spot light 25b as a result of comparison (No in step S3: see FIG. 13B), the two spot lights 25 are not formed on the same plane. Judge. In this case, since an accurate correction reference value cannot be obtained and the distance measurement value cannot be corrected, the process returns to step S2 and the distance to the two spot lights 25 is calculated again.
When the distance to the two spot lights 25 is the same (Yes in step S3: see FIG. 13 (a) or (c)), the distance correcting unit 32 forms the spot light imaged on one image sensor 13. Based on the 25 interval (number of pixels), the distance to the object 41 is calculated (step S4).

The distance correction unit 32 compares the distance (correction reference value) calculated based on the interval (number of pixels) of the spot light 25 and the distance measurement value calculated by the distance measurement unit 31, and the difference between the two is a predetermined value. It is determined whether it is within the threshold value (step S5). If the difference between the two is within the threshold value (No in step S5), it is determined that there is no translational deviation in the lens 12 of the stereo camera 10, and it is determined that there is no need to correct the distance measurement value. And exit the flow.
If the difference between the two is not within the threshold value (Yes in step S5), it is determined that the distance measurement value needs to be corrected because a translational shift has occurred in the lens 12 of the stereo camera 10. Accordingly, the distance correction unit 32 calculates the translational displacement amount p of the lens from the equation (9), and sets the equation (10) as a distance measurement value correction equation (step S6). Thereafter, the distance measurement value is calculated from the amount of parallax obtained from the two cameras 11 using Equation (10).

  As described above, according to this embodiment, the distance measurement value is corrected after confirming that the beam is irradiated on the same plane, so that accurate correction is possible. In particular, if the parallax information obtained from the stereo camera is used to confirm that the beam is irradiated on the same plane, the distance measurement value can be automatically corrected at an appropriate timing.

  The distance measuring device having the stereo camera and the laser irradiation device described above can correct the distance in real time by obtaining the interval between the beams irradiated from the laser irradiation device. Accordingly, it is possible to always calculate an accurate distance measurement value when the distance measuring device is used on the inspection line of the manufacturing factory. This eliminates the need to stop the inspection line and perform periodic inspections and corrections, thereby improving productivity and realizing an accurate inspection.

  DESCRIPTION OF SYMBOLS 1 ... Distance measuring device, 10 ... Stereo camera, 11 ... Camera, 12 ... Lens, 13 ... Imaging element, 20 ... Laser irradiation apparatus, 21 ... Semiconductor laser, 22 ... Coupling lens, 23 ... Light splitting element, 23A ... Light quantity Dividing surface, 23B ... Total reflection surface, 23C ... Light quantity dividing surface, 24 ... Beam, 25 ... Spot light, 30 ... Control unit, 31 ... Distance measuring means, 32 ... Distance correcting means, 33 ... Irradiation controlling means, 41 ... Irradiation Surface: 41 ... Object, 43 ... Obstacle, 50 ... Laser irradiation device, 51 ... Light splitting element, 52 ... Diffraction optical element, 53 ... Pattern light, 54 ... Zero order light, 60 ... Laser irradiation device, 70 ... Laser Irradiation device 71 ... Polarization rotating element 72 ... Light splitting element 72A ... Polarizing film 72B ... Total reflection surface 101 ... Measurement object 102 ... Camera 103 ... Lens 104 ... Measurement object image 105 ... 2 Dimension Sa, 106 ... stereo camera device

Japanese Patent No. 3792932 Japanese Patent No. 457397

Claims (3)

An irradiation device for emitting a plurality of parallel beams toward the object;
A plurality of imaging lenses for imaging spot lights by the plurality of beams respectively reflected by the object;
A plurality of image pickup means for picking up a plurality of images related to the object including the spot lights imaged by the image pickup lenses;
Distance measuring means for calculating a distance to the object based on parallax information between the images;
The distance to the object calculated by the distance measuring means is corrected based on the distance to the object obtained from the interval between the image formation positions of the spot lights on at least one image pickup means of the image pickup means. Distance correction means;
A distance measuring device comprising:   2. The distance measuring apparatus according to claim 1, wherein a diffractive optical element that generates diffraction pattern light obtained by diffracting the beam is disposed in an optical path of at least one of the plurality of beams.   The distance measuring apparatus according to claim 2, wherein at least one of the plurality of spot lights is zero-order diffracted light included in the diffraction pattern light.

Images