Calibration pattern light projection device

Abstract

To reduce labor for measuring the distortion aberration of a lens and measure the distortion aberration precisely.SOLUTION: A pattern light generation unit 10 of a correction pattern light projector 1 has a movable unit 21 for adjusting the distance to a half mirror 11, and generates a correction pattern light and projects the light to the half mirror 11. The half mirror 11 makes the correction pattern light projected from the pattern light generation unit 10 reflected and projected to an arbitrary object 104. Reflection light reflected by the surface of the arbitrary object 104 thus passes through the half mirror 11 and forms an image on a focus point surface 111 through a measurement target lens 110. A user takes an image of the arbitrary object 104 by changing the distance between a camera 102 and the arbitrary object 104 before an initial measurement before measurement of the distortion error, and moves the mobile unit 21 into a moving direction D so that the size of the image forming pattern is not changed by the imaging distance.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus for projecting a calibration pattern light for measuring the distortion aberration of a lens. [Background technology]

[0002] Conventionally, a method is known in which a calibration pattern on which a specific pattern is printed is used to measure the distortion aberration of a lens.

[0003] 14 is a diagram illustrating a conventional method for measuring lens distortion using a calibration pattern. In the conventional method, a calibration pattern 101 in which a specific pattern (e.g., a checkerboard pattern) is printed on a flat surface is used, and a user photographs the calibration pattern 101 using a camera 102 with a lens 110 to be measured attached to a housing 112.

[0004] The distortion aberration measuring device 103 inputs the image of the calibration pattern 101 obtained on the focal plane 111 of the camera 102, measures the distortion aberration of the measurement target lens 110 based on the image of the calibration pattern 101, and outputs this as a distortion aberration parameter.

[0005] For example, the distortion aberration measuring device 103 determines the position of the center of gravity of each pattern element constituting the calibration pattern 101 from the image of the calibration pattern 101, and determines the distortion aberration based on the position of the center of gravity of each pattern element.

[0006] There is also a known method of irradiating a collimated thin laser beam from the subject side onto a lens to be measured, and measuring various aberrations including distortion from the imaging state (imaging position and blur state).

[0007] Furthermore, a weak calibration method is known in which the same subject is photographed multiple times while changing the relative position between the camera and the subject, and camera calibration parameters including distortion aberration are measured based on the multiple images (see, for example, Patent Document 1).

[0008] This weak calibration method extracts multiple characteristic image patterns (feature points) from multiple images obtained by shooting, matches the feature points between the multiple images, and measures distortion aberrations and the like from the multiple image coordinate pairs obtained as a result (see paragraphs 56 to 67 of Patent Document 1). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 4372328 Publication Summary of the Invention [Problem to be solved by the invention]

[0010] 14, it is necessary that the calibration pattern 101 be captured so as to fit just within the angle of view α of the camera 102. In addition, it is preferable that the calibration pattern 101 be perpendicular to the optical axis β of the lens 110 to be measured.

[0011] In a method using such calibration pattern 101, for example, the wider the angle of measurement target lens 110 and the longer the distance between camera 102 and calibration pattern 101, the larger the area of ​​the calibration pattern 101 must be. This can easily lead to difficulties in installing or handling calibration pattern 101. Furthermore, when the area of ​​calibration pattern 101 becomes larger, it becomes difficult to maintain its planarity, resulting in a problem of deterioration in the measurement accuracy of distortion aberration.

[0012] In addition, the above-mentioned method using laser light involves attaching a dedicated measuring device to the camera and directing laser light at a strictly calibrated position and angle to the lens to be measured. With this method, during construction, the camera is brought to a location where the dedicated measuring device is located, and the dedicated measuring device is attached to the camera to measure distortion aberration and the like. Then, during operation, the camera needs to be moved from the location where the dedicated measuring device is located to the operation location, and there is a possibility that distortion aberration and the like may deviate from the state at the time of calibration due to vibrations or temperature changes during transportation.

[0013] In addition, according to the aforementioned weak calibration method, a specific calibration pattern is not required, but it is necessary to prepare a subject whose feature points can be sufficiently acquired, and then acquire multiple images while changing the relative position between the camera and the subject.

[0014] The subject needs to be large enough to fully cover the angle of view of the camera. The wider the angle of the lens being measured and the longer the distance between the camera and the subject, the larger the subject needs to be.

[0015] When the camera is moved to change the relative position, the camera parameters may be shifted due to the effects of vibration, etc. On the other hand, when the subject is moved to change the relative position, the subject may be distorted, particularly if the subject is large, which may result in an error in the distortion aberration.

[0016] Therefore, the present invention has been made to solve the above-mentioned problems, and its object is to provide a calibration pattern light projection device that reduces the effort required to measure lens distortion aberration and is capable of measuring distortion aberration with high precision. [Means for solving the problem]

[0017] In order to solve the above problem, the calibration pattern light projection device of claim 1 is a calibration pattern light projection device that projects calibration pattern light for measuring distortion aberration of a lens attached to a camera onto a predetermined object, and is equipped with a pattern light generating unit that generates the calibration pattern light using a light source, and a half mirror that reflects the calibration pattern light generated by the pattern light generating unit and projects it onto the predetermined object, wherein an optical path length from the light source to the predetermined object via the half mirror is equal to an optical path length from a first principal point of the lens to the predetermined object via the half mirror, and when the calibration pattern light is projected onto the predetermined object, the reflected light reflected on the surface of the predetermined object passes through the half mirror and is imaged on the focal plane of the camera via the lens.

[0018] The calibration pattern light projection device of claim 2 is characterized in that, in the calibration pattern light projection device of claim 1, the pattern light generating unit is provided with a movable unit capable of moving the light source in the optical axis direction between the light source and the half mirror.

[0019] The calibration pattern light projection device of claim 3 is characterized in that, in the calibration pattern light projection device of claim 1 or 2, it further comprises a device movable part that moves the calibration pattern light projection device relative to the camera in the optical axis direction between a first principal point of the lens and the half mirror while keeping the position of the light source relative to the half mirror fixed.

[0020] The calibration pattern light projection device of claim 4 is the calibration pattern light projection device of any one of claims 1 to 3, characterized in that the pattern light generating unit includes a mask having a plurality of transmitting portions and a plurality of light-shielding portions for forming a pattern of the calibration pattern light, and generates the calibration pattern light in a solid angle with the light source as a vertex by using the mask.

[0021] The calibration pattern light projection device of claim 5 is characterized in that, in the calibration pattern light projection device according to any one of claims 1 to 3, the pattern light generating unit includes a scanning mechanism that scans the light beam emitted by the light source, and generates the calibration pattern light in a solid angle with the light source as a vertex by using the scanning mechanism. Effect of the Invention

[0022] As described above, according to the present invention, it is possible to reduce the time and effort required for measuring the distortion of a lens, and to measure the distortion with high accuracy. [Brief description of the drawings]

[0023] [Figure 1] 1 is a configuration diagram showing an example of an entire system including a calibration pattern light projection device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a configuration diagram showing a first example of a pattern light generating unit. [Diagram 3] 1A is a diagram illustrating a mask for a sequence of dots, and FIG. 1B is a diagram illustrating a mask for a checkerboard pattern. [Figure 4] (a) is a diagram illustrating a mask using a lens array, (b) is a diagram illustrating an example of a mask cross section (A-A' plane), and (c) is a diagram illustrating another example of a mask cross section (A-A' plane). [Diagram 5] FIG. 13 is a configuration diagram showing a second example of the pattern light generating unit. [Figure 6] FIG. 13 is a configuration diagram showing a third example of the pattern light generating unit. [Figure 7] 11A and 11B are diagrams illustrating the optical path length when the calibration pattern light projection device according to the embodiment of the present invention is used. [Figure 8] FIG. 1A is a diagram illustrating an example of imaging when an object is close to the camera, and FIG. 1B is a diagram illustrating an example of imaging when the object is far away, when the distance between the light source and the half mirror is appropriate. [Figure 9] FIG. 1A is a diagram illustrating an example of imaging when an object is close to the camera, and FIG. 1B is a diagram illustrating an example of imaging when the light source is far from the half mirror. [Figure 10] FIG. 1A is a diagram for explaining an example of imaging when an object is close to the camera in the case where the light source is close to the half mirror, and FIG. 1B is a diagram for explaining an example of imaging when the object is far away. [Figure 11] FIG. 13A is a diagram illustrating an example of imaging when there is no distortion when a point sequence mask is used, and FIG. 13B is a diagram illustrating an example of imaging when there is distortion. [Figure 12] FIG. 1A is a diagram illustrating an example of imaging when there is no distortion when a checkerboard pattern mask is used, and FIG. 1B is a diagram illustrating an example of imaging when there is distortion. [Figure 13] 1A and 1B are diagrams for explaining blurring of an image caused by unevenness on the surface of an arbitrary object. [Figure 14] 1A and 1B are diagrams illustrating a conventional method for measuring lens distortion using a calibration pattern. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. [Overall system] 1 is a configuration diagram showing an example of an entire system including a calibration pattern light projection device according to an embodiment of the present invention. This system is configured with a calibration pattern light projection device 1, a camera 102, a distortion aberration measurement device 103, and an arbitrary object 104, and measures the distortion aberration of a measurement target lens 110 based on an image formed by projecting the calibration pattern light onto the arbitrary object 104.

[0025] The calibration pattern light projection device 1 generates a calibration pattern light of a predetermined pattern for measuring the distortion aberration of the measurement target lens 110, and projects the calibration pattern light onto an arbitrary object 104.

[0026] A measurement target lens 110 is attached to the camera 102. The camera 102 is configured to include the measurement target lens 110 and a housing 112, and the housing 112 supports the measurement target lens 110.

[0027] The camera 102 captures an image of the arbitrary object 104 and forms an image of the arbitrary object 104 on a focal plane 111. Specifically, the calibration pattern light projected by the calibration pattern light projection device 1 is irradiated onto the arbitrary object 104, so that reflected light from the arbitrary object 104 is incident on the focal plane 111 via the measurement target lens 110, and an image of the arbitrary object 104 is formed on the focal plane 111.

[0028] Distortion aberration measuring device 103 inputs data on the image of an arbitrary object 104 formed on focal plane 111 of camera 102 in a state in which a predetermined optical path length has been adjusted by a user in an initial adjustment described below. Then, distortion aberration measuring device 103 determines the position of the center of gravity of each pattern element constituting the image, and measures the distortion aberration of measurement target lens 110 based on the position of the center of gravity of each pattern element. Then, distortion aberration measuring device 103 outputs this as a distortion aberration parameter.

[0029] [Calibration pattern light projection device 1] Next, a calibration pattern light projection device 1 according to an embodiment of the present invention will be described. The calibration pattern light projection device 1 is attached to a camera 102 on the side of an arbitrary object 104 with respect to a measurement target lens 110 attached to the camera 102, as shown in FIG.

[0030] The calibration pattern light projector 1 includes a pattern light generating unit 10, a half mirror 11, and a housing 12.

[0031] The pattern light generating unit 10 generates a calibration pattern light having a predetermined solid angle (for example, spreading in a cone shape) with the light source as the apex, and projects the calibration pattern light onto the half mirror 11. The pattern light generating unit 10 in Fig. 1 shows a first example in Fig. 2, which will be described later, that includes a movable unit 21, a light source 22, and a mask 23. The pattern light generating unit 10 will be described in detail later.

[0032] The half mirror 11 reflects the calibration pattern light generated by the pattern light generating unit 10, and projects the reflected calibration pattern light onto an arbitrary object 104. The half mirror 11 is disposed obliquely relative to the lens 110 under measurement.

[0033] Preferably, the half mirror 11 is positioned so that when an axis J passing through the center of the mask 23 from the light source 22 provided in the pattern light generating unit 10 is moved symmetrically with respect to the surface normal n of the half mirror 11, the axis coincides with the optical axis β1 of the lens 110 to be measured.

[0034] The reflectance and transmittance of the half mirror 11 are arbitrary. For example, when the calibration pattern light projection device 1 is attached to the camera 102 only when the distortion aberration is measured, the reflectance may be set to about 0.5, i.e., reflectance=transmittance=0.5. When the calibration pattern light projection device 1 is attached not only when the distortion aberration is measured but also during normal operation of the camera 102, the reflectance may be set to a small value (for example, reflectance=0.1, transmittance=0.9, etc.). FIG. 1 shows an example of an arrangement in which the angle between the half mirror 11 and the optical axis β1 from the half mirror 11 to the measurement target lens 110 is 45 degrees.

[0035] The housing 12 supports the pattern light generating unit 10 so that the pattern light generating unit 10 (movable unit 21) moves in a moving direction D during initial adjustment, which will be described later, and has openings on both the camera 102 side and the arbitrary object 104 side. The calibration pattern light projector 1 is attached to the camera 102 by inserting an opening of a housing 112 provided on the camera 102 into the opening on the camera 102 side of the housing 12.

[0036] (First example of the pattern light generating unit 10) Next, a detailed description will be given of a configuration example of the pattern light generating unit 10 shown in Fig. 1. Fig. 2 is a configuration diagram showing a first example of the pattern light generating unit 10. This pattern light generating unit 10-1 is configured to include a movable unit 21, a light source 22, and a mask 23, and is supported so as to move in a moving direction D with respect to the housing 12.

[0037] A recess 40 is formed in the movable part 21, the light source 22 is fixed to the bottom surface of the recess 40, and the mask 23 is fixed to the opening of the recess 40. The movable part 21 is movable in a movement direction D relative to the housing 12. Therefore, the light source 22 and the mask 23 are also movable in the movement direction D relative to the housing 12. The movement direction D is the direction of the optical axis (axis J shown in FIG. 1) between the light source 22 and the half mirror 11 (point B shown in FIG. 7 described later).

[0038] Movable part 21 may have a structure that simply slides in movement direction D, or may have a structure that uses, for example, a helicoid to convert rotational motion into linear motion in movement direction D. Movable part 21 is operated by the user during initial adjustment, which will be described later, and its position is adjusted.

[0039] When the movable part 21 moves in the moving direction D, the light source 22 fixed to the movable part 21 also moves in the moving direction D, and the distance from the light source 22 to the arbitrary object 104 via the half mirror 11 can be changed (see FIG. 1). In other words, the optical path length L2 of the optical axis β2 (see FIG. 7 described later) from the light source 22 to the arbitrary object 104 via the half mirror 11 can be changed.

[0040] The light source 22 is fixed to the bottom surface of the recess 40 of the movable part 21. The light source 22 is preferably a point light source, but may be one whose area is narrowed down sufficiently (for example, a diameter of 2 mm or less) by an aperture plate, a diffusion plate, a lens, a reflector, or the like. The directionality of the light emitted by the light source 22 is set to optically cover the opening in the recess 40 of the movable part 21 to which the mask 23 described later is fixed.

[0041] The mask 23 includes a plurality of transmitting portions and a plurality of light-shielding portions for generating a predetermined calibration pattern light from the light emitted by the light source 22. The plurality of transmitting portions included in the mask 23 transmit the light from the light source 22, and the plurality of light-shielding portions block the light.

[0042] As a result, the light from the light source 22 transmitted through multiple transmission sections provided on the mask 23 of the pattern light generating unit 10-1 is generated as a calibration pattern light of a certain pattern and projected onto the arbitrary object 104 via the half mirror 11.

[0043] 3(a) is a diagram illustrating an example of a dot array mask 23. This mask 23-1 has a transmission portion and a light-shielding portion of a pinhole array arranged in a two-dimensional lattice. The white portions are the transmission portions and the black portions are the light-shielding portions. The light emitted by the light source 22 is transmitted through the transmission portions of the pinhole array to generate a calibration pattern light.

[0044] Fig. 3(b) is a diagram illustrating an example of a checkerboard pattern mask 23. This mask 23-2 has a checkerboard pattern of transmissive and light-shielding parts. As in Fig. 3(a), the white parts are transmissive parts and the black parts are light-shielding parts. The light emitted by the light source 22 is transmitted through the transmissive parts of the checkerboard pattern to generate a calibration pattern light.

[0045] Fig. 4(a) is a diagram for explaining an example of a mask 23 using a lens array. This mask 23-3 has a transmission portion and a light-shielding portion of a lens array consisting of a plurality of microlenses 30. As in Figs. 3(a) and (b), the plurality of microlenses 30 in the white areas are the transmission portions, and the black areas are the light-shielding portions. The light emitted by the light source 22 passes through the transmission portions of the lens array to generate a calibration pattern light.

[0046] Fig. 4(b) is a diagram illustrating an example of a mask cross section (A-A' plane) of the mask 23-3 of Fig. 4(a). In the cross section of the mask 23-3 shown in Fig. 4(b), the lens array is arranged in a straight line. This mask 23-3 is formed in a planar shape as a whole, and a plurality of micro lenses 30 are arranged on the plane.

[0047] Fig. 4(c) is a diagram for explaining another example of the mask cross section (A-A' plane) of the mask 23-3 of Fig. 4(a). In the cross section of the mask 23-3 shown in Fig. 4(c), the lens array is arranged in a curved shape. This mask 23-3 is formed in a curved shape as a whole, and has a structure in which a square portion is cut out from a spherical surface centered on the light source 22. Note that the mask 23-3 may have a structure in which a square portion is cut out from a surface of any curved shape, such as a cylindrical shape.

[0048] 4(b) and (c), the optical axis of the microlenses 30 constituting the lens array passes through the center of the light emission of the light source 22. The focal length of each microlens 30 is equal to the distance from the principal point of the microlens 30 on the light source 22 side to the center of the light emission of the light source 22.

[0049] When multiple micro lenses 30 are arranged on a plane, such as the mask 23-3 shown in FIG. 4(b), the focal length of the micro lenses 30 near the center of the mask 23-3 is shorter than the focal length of the surrounding micro lenses 30.

[0050] Furthermore, when multiple microlenses 30 are arranged on a spherical surface centered on the center of light emission of the light source 22, as in the mask 23-3 shown in Figure 4(c), the focal length of the microlenses 30 will coincide with the radius of the spherical surface.

[0051] Furthermore, as long as the optical axis of each microlens 30 passes through the center of the light emission of the light source 22 and its focal length is the distance from the principal point of the microlens 30 on the light source 22 side to the center of the light emission of the light source 22, the three-dimensional arrangement of each microlens 30 is arbitrary.

[0052] In this manner, by using the mask 23-1 shown in Fig. 3(a), the mask 23-2 shown in Fig. 3(b), and the mask 23-3 shown in Fig. 4(a), a certain pattern of calibration pattern light is generated from the light emitted by the light source 22. The calibration pattern light generated by the pattern light generating unit 10-1 is reflected by the half mirror 11 and projected onto the arbitrary object 104.

[0053] 2 shows a configuration in which the light source 22 and the mask 23 move together with the movable part 21, but the mask 23 may be fixed to the half mirror 11. For example, the mask 23 is fixed to a predetermined position of the housing 12 that does not interfere with the movement of the movable part 21. In this case, the pattern light generating unit 10-1 is configured to include the pattern light generating unit 10 having the movable part 21 and the light source 22, the mask 23, the half mirror 11, and the housing 12, and only the light source 22 moves together with the movement of the movable part 21.

[0054] (Second Example of Pattern Light Generator 10) Next, a second example of the pattern light generating unit 10 shown in Fig. 1 will be described. Fig. 5 is a configuration diagram showing the second example of the pattern light generating unit 10. This pattern light generating unit 10-2 is configured to include a movable unit 21, a scanning mechanism 24, and a light source 25, and is supported so as to move in a moving direction D relative to the housing 12.

[0055] A recess 40 is formed in the movable part 21, similar to the pattern light generating part 10-1 shown in Fig. 2. A scanning mechanism 24 is provided on the bottom surface of the recess 40. The movable part 21 is movable in a movement direction D relative to the housing 12. Since a light source 25 is provided in the scanning mechanism 24 as described later, the scanning mechanism 24 and the light source 25 are also movable in the movement direction D relative to the housing 12.

[0056] When the movable part 21 moves in the movement direction D, the light source 25 also moves in the movement direction D, and the distance (optical path length) from the light source 25 to the arbitrary object 104 via the half mirror 11 can be changed.

[0057] The scanning mechanism 24 is a swivel mechanism installed on the bottom surface of the recess 40 of the movable part 21. A light source 25 is disposed in the scanning mechanism 24. The scanning mechanism 24 scans the light beam emitted from the light source 25 by using the swivel mechanism. The scanning mechanism 24 may be capable of scanning in a plurality of axes (for example, by changing the elevation angle and azimuth angle) to realize planar scanning.

[0058] The light source 25 generates a light beam (narrowed collimated light γ1) that is sufficiently narrowed (for example, the diameter of the light emitting part is 2 mm or less) and sufficiently parallelized (for example, the spread of the light beam is 5 arc minutes or less). As the light source 25, for example, a combination of a laser and a collimating lens can be used.

[0059] The pattern light generating unit 10-2 also includes a control unit (not shown), which controls the scanning of the scanning mechanism 24 and the blinking (presence or absence of light emission) or the degree of light emission of the light source 25 according to a predetermined control pattern. For example, the control unit scans the scanning mechanism 24 and blinks the light source 25 so as to generate a calibration pattern light corresponding to the dot sequence mask 23-1 in FIG. 3(a). For example, the control unit also causes the scanning mechanism 24 to scan while the light source 25 is turned on, so as to generate a calibration pattern light of lattice lines. For example, the control unit also causes the scanning mechanism 24 to scan while the light source 25 is turned on, so as to generate one or more circular calibration pattern lights.

[0060] In this way, the scanning mechanism 24 operates according to a control pattern by a control unit (not shown), thereby controlling the direction of the collimated light γ1 from the light source 25 and the lighting or blinking of the light source 25, and a certain pattern of calibration pattern light is generated. Then, the calibration pattern light generated by the pattern light generating unit 10-2 is projected onto the arbitrary object 104 via the half mirror 11.

[0061] (Third Example of Pattern Light Generator 10) Next, a third example of the pattern light generating unit 10 shown in Fig. 1 will be described. Fig. 6 is a configuration diagram showing the third example of the pattern light generating unit 10. This pattern light generating unit 10-3 is configured to include a movable unit 21, a galvanometer mirror 26, and a light source 27, and is supported so as to move in a moving direction D with respect to the housing 12.

[0062] 2 and 5, a recess 40 is formed in the movable part 21. A galvanometer mirror 26 is provided on the bottom surface of the recess 40. The movable part 21 is movable in a movement direction D relative to the housing 12.

[0063] As the movable part 21 moves in the movement direction D, the galvanometer mirror 26 fixed to the movable part 21 also moves in the movement direction D, thereby changing the distance (optical path length) from the light source 27 to the arbitrary object 104 via the galvanometer mirror 26 and the half mirror 11.

[0064] The galvanometer mirror 26 is a movable reflecting mirror installed on the bottom surface of the recess 40 of the movable part 21, which reflects the light beam from the light source 27 and projects the reflected light γ2 in the direction of the half mirror 11 (downward in FIG. 6). In other words, the galvanometer mirror 26 scans the reflected light γ2 of the light beam emitted by the light source 27.

[0065] The light source 27 is fixedly installed at a predetermined location in the recess 40 of the movable part 21, and similar to the light source 25 shown in Figure 5, generates a light beam that is sufficiently narrowed and sufficiently parallelized (narrowed collimated light γ1).

[0066] The pattern light generating unit 10-3 also includes a control unit (not shown), which controls the scanning of the galvanometer mirror 26 and the degree of blinking or light emission of the light source 27 according to a predetermined control pattern.

[0067] In this way, the galvanometer mirror 26 operates according to the control pattern by the control unit, whereby it is possible to control the direction of the reflected light γ2 of the collimated light γ1 emitted by the light source 27 and the lighting or blinking of the light source 27, and a certain pattern of calibration pattern light is generated. Then, the calibration pattern light generated by the pattern light generating unit 10-3 is projected onto the arbitrary object 104 via the half mirror 11.

[0068] The pattern light generating unit 10-3 may include a polygon mirror attached to an actuator, instead of the galvanometer mirror 26. The galvanometer mirror 26 may be configured to perform planar scanning by combining two or more movable reflecting mirrors.

[0069] Furthermore, the pattern light generating unit 10-3 may further include a scanning mechanism (equivalent to the scanning mechanism 24 shown in FIG. 5) that scans the collimated light γ1 emitted by the light source 27. In this case, the light source 27 is not provided at a predetermined location in the recess 40 of the movable part 21, but is provided at the scanning mechanism, which is provided at a predetermined location in the recess 40 of the movable part 21. In this way, by combining the scanning mechanism with a scanning mechanism using the movable reflecting mirror of the galvanometer mirror 26, planar scanning can be realized.

[0070] [Distance between the light source 22 and the half mirror 11 and image size when the pattern light generating unit 10-1 is used] 8 to 10, the distance between the light source 22 and the half mirror 11 when the pattern light generating unit 10-1 is used and the size of the image pattern formed on the focal plane 111 will be described. The same applies to the cases when the pattern light generating units 10-2 and 10-3 are used.

[0071] 1, a portion of the calibration pattern light generated by the calibration pattern light projector 1 is reflected by a half mirror 11 and projected onto an arbitrary object 104. The calibration pattern light projected onto the arbitrary object 104 is reflected by the surface of the arbitrary object 104 (hereinafter, only the diffuse reflection component is considered).

[0072] The light reflected by the pattern portion of the calibration pattern light projected onto the surface of the arbitrary object 104 (for example, when the mask 23-1 of the dot sequence shown in FIG. 3(a) is used, the point projected onto the arbitrary object 104 by any bright point of the dot sequence) is diffused and passes through the half mirror 11. Then, the reflected light from the arbitrary object 104 that passes through the half mirror 11 is imaged (possibly with defocus) on the focal plane 111 via the measurement target lens 110.

[0073] Fig. 7 is a diagram for explaining the optical path length when the calibration pattern light projector 1 shown in Fig. 1 is used. As shown in Fig. 7, the distance (optical path length) of the optical axis β1 from the first principal point M of the measurement target lens 110 to the arbitrary object 104 is defined as L1, and the distance (optical path length) of the optical axis β2 from the light source 22 to the arbitrary object 104 via the half mirror 11 is defined as L2. Also, the position (transmission point) of the optical axis β1 on the half mirror 11 through which the reflected light from the arbitrary object 104 transmits and the position (reflection point) of the optical axis β2 on the half mirror 11 through which the light emitted by the light source 22 is reflected is defined as point B.

[0074] In addition, the optical axial distance (optical path length) from the first principal point M of the lens 110 to be measured to point B of the half mirror 11 is defined as L11, and the optical axial distance (optical path length) from the light source 22 to point B of the half mirror 11 is defined as L22.

[0075] The size of the imaged pattern imaged on the focal plane 111 changes depending on the relationship between the optical path lengths L1 and L2 (optical path lengths L11 and L22). For example, assume that the optical path lengths L1 and L2 match due to an initial adjustment described later (optical path lengths L11 and L22 match), that is, the distance between the light source 22 and the half mirror 11 is appropriate. In this case, as shown in FIG. 8 described later, the size of the imaged pattern remains unchanged regardless of the distance between the camera 102 and the arbitrary object 104. Hereinafter, a detailed description will be given with reference to FIG. 8 to FIG. 10.

[0076] 8A is a diagram for explaining an example of imaging when an arbitrary object 104 is close to the camera 102, and FIG. 8B is a diagram for explaining an example of imaging when the distance between the light source 22 and the half mirror 11 is appropriate. FIG. 8 and FIG. 9 and FIG. 10 described later show examples of imaging when the mask 23-1 of the point sequence shown in FIG. 3A is used.

[0077] Figures 8(a) and (b) show the case where the distance between the light source 22 and the half mirror 11 is appropriately adjusted by the initial adjustment described later, that is, the case where the movable part 21 of the pattern light generation unit 10 is appropriately adjusted.

[0078] As described above, the case of appropriate adjustment means the case where, in FIG. 7, the optical path length L1 and the optical path length L2 match (when the virtual image of the first principal point M of the lens 110 to be measured coincides with the position of the light source 22 with respect to the half mirror 11). That is, it is the case where L1 = L2 (L11 = L22).

[0079] In this case, the size and distortion of the imaging pattern on the focal plane 111 are invariant regardless of the distance between the camera 102 and the arbitrary object 104, as shown in FIGS. 8(a) and (b). Note that the blurring degree of the imaging pattern may change. Also, although the arrangement of the imaging pattern may be geometrically distorted, the degree of distortion is invariant regardless of the distance.

[0080] FIG. 9 is a diagram for explaining an example of imaging when the light source 22 is far from the half mirror 11. (a) is a diagram for explaining an example of imaging when the arbitrary object 104 is close to the camera 102, and (b) is a diagram for explaining an example of imaging when it is far.

[0081] FIGS. 9(a) and (b) show the case where the light source 22 is farther from the half mirror 11 than the appropriate position, that is, the case where L1 < L2 (L11 < L22) in FIG. 7.

[0082] As shown in FIGS. 9(a) and (b), the size of the imaging pattern on the focal plane 111 becomes smaller as the arbitrary object 104 is farther from the camera 102.

[0083] FIG. 10 is a diagram for explaining an example of imaging when the light source 22 is close to the half mirror 11. (a) is a diagram for explaining an example of imaging when the arbitrary object 104 is close to the camera 102, and (b) is a diagram for explaining an example of imaging when it is far.

[0084] 10(a) and (b) show a case where the light source 22 is closer to the half mirror 11 than the appropriate position, that is, a case where L1>L2 (L11>L22) in FIG.

[0085] The size of the image pattern on the focal plane 111 becomes larger as the object 104 becomes farther away from the camera 102, as shown in FIGS. 10(a) and (b).

[0086] [Procedure for measuring distortion aberration of the measurement target lens 110 / initial adjustment] Next, a procedure for measuring the distortion aberration of the measurement target lens 110 using the calibration pattern light projector 1 will be described.

[0087] 8 to 10, an initial adjustment is performed before actual measurement so as to obtain the property shown in FIG. 8 when the distance between the light source 22 and the half mirror 11 is appropriate. As the initial adjustment, the user first photographs the arbitrary object 104 while changing the optical path length L1 from the camera 102 to the arbitrary object 104. Then, the user adjusts the position of the movable part 21 by moving the movable part 21 in the moving direction D so that the size of the image formation pattern does not change depending on the shooting distance.

[0088] As a result, the optical path length L1 from the first principal point M of the measurement target lens 110 to the arbitrary object 104 via the half mirror 11 and the optical path length L2 from the light source 22 to the arbitrary object 104 via the half mirror 11 are equal (L1=L2 (L11=L22)). In other words, as shown in Figures 8(a) and (b), the size and distortion of the imaging pattern are invariant regardless of the optical path length L1 between the camera 102 and the arbitrary object 104, and it is possible to establish the projection of the calibration pattern light that is not dependent on the shooting distance to the arbitrary object 104.

[0089] After such initial adjustment, calibration pattern light is projected from the calibration pattern light projection device 1 onto some arbitrary object 104, and data on the image formed on the focal plane 111 is input to the distortion aberration measurement device 103. Then, the distortion aberration measurement device 103 measures the distortion aberration of the measurement target lens 110 based on the image formation data.

[0090] [Image formed on focal plane 111] Next, the image formed on the focal plane 111 will be described. The image formed on the focal plane 111 is an image that directly reflects the distortion aberration of the measurement target lens 110. In addition, the image may be blurred due to defocus, but this does not affect the degree of distortion or the size of the image pattern. Since the size and shape of this image pattern do not depend on the shooting distance between the camera 102 and the arbitrary object 104, the arbitrary object 104 may have any shape and may be at any shooting distance. In addition, the arbitrary object 104 does not need to be a rigid body.

[0091] Figure 11(a) is a diagram illustrating an example of imaging when there is no distortion aberration, and (b) is a diagram illustrating an example of imaging when there is distortion aberration, when the dot sequence mask 23-1 shown in Figure 3(a) is used.

[0092] When there is no distortion as shown in Fig. 11(a), the arrangement of the centers of gravity of the points constituting the point array is similar to the arrangement of the pinhole array of the mask 23-1 at a certain ratio. When there is distortion as shown in Fig. 11(b), the distortion is barrel distortion.

[0093] The degree of blur in the image varies depending on the location of the image. In Figures 11(a) and (b) and Figures 12(a) and (b) described later, the upper part of the image has a higher degree of blur.

[0094] Fig. 13 is a diagram for explaining blurring of an image caused by unevenness on the surface of the arbitrary object 104. In Fig. 13, it is assumed that reflected light m1, m2, etc. from a position C1 on the surface of the arbitrary object 104 forms an image at a position R2 on the focal plane 111, and reflected light n1, n2, etc. from the position C2 forms an image at a position R1 on the focal plane 111. It is also assumed that the distance from the camera 102 to the position C1 of the arbitrary object 104 is shorter than the distance from the camera 102 to the position C2 of the arbitrary object 104.

[0095] In this case, an image without blur is formed at the location R2 on the focal plane 111, but an image with blur is formed at the location R1 on the focal plane 111.

[0096] In this way, when the reflective surface of the arbitrary object 104 is uneven and the distance from the camera 102 varies depending on the location on the reflective surface, the degree of blur in the formed image will differ from location to location, as shown in Figures 11(a) and (b). However, even if the distance from the camera 102 varies depending on the location on the reflective surface due to the unevenness of the reflective surface of the arbitrary object 104, the arrangement of the centers of gravity in the sequence of points of the formed image formed on the focal plane 111 will not change regardless of the presence or absence of distortion.

[0097] The calibration pattern light projection device 1 inputs imaging data such as that shown in Figure 11(a) or (b), determines the center of gravity of each point that constitutes the point sequence based on the imaging data, and measures the distortion aberration of the measurement target lens 110 based on each center of gravity position.

[0098] Figure 12(a) is a diagram illustrating an example of an imaging pattern when there is no distortion aberration, and (b) is a diagram illustrating an example of an imaging pattern when there is distortion aberration, when the checkerboard pattern mask 23-2 shown in Figure 3(b) is used.

[0099] When there is no distortion as shown in Fig. 12(a), the degree of blurring differs from place to place, but the arrangement of the centers of gravity of the elements that make up the checkerboard pattern is similar to the checkerboard pattern arrangement of mask 23-2 at a certain ratio. When there is distortion as shown in Fig. 12(b), the distortion is barrel distortion.

[0100] 12(a) or 12(b) is input to the calibration pattern light projection device 1. Then, the calibration pattern light projection device 1 obtains the center of gravity of each element constituting the checkerboard pattern based on the imaging data, and measures the distortion aberration of the measurement target lens 110 based on each center of gravity position.

[0101] As described above, according to the calibration pattern light projection device 1 of the embodiment of the present invention, the pattern light generation unit 10 includes the movable unit 21 for adjusting the distance to the half mirror 11, generates the calibration pattern light, and projects the calibration pattern light onto the half mirror 11. The half mirror 11 is disposed obliquely with respect to the measurement target lens 110, and reflects the calibration pattern light projected from the pattern light generation unit 10 and projects it onto the arbitrary object 104.

[0102] Before the distortion error of the measurement target lens 110 is measured by the distortion aberration measuring device 103, the user performs an initial adjustment to move the movable part 21 provided in the pattern light generating unit 10 to an appropriate position.

[0103] In the initial adjustment, the user photographs the arbitrary object 104 while changing the distance from the camera 102 to the arbitrary object 104. Then, the user adjusts the position of the movable part 21 by moving the movable part 21 in the moving direction D so that the size of the imaging pattern does not change depending on the shooting distance.

[0104] 7, it is possible to make the optical path length L1 from the first principal point M of the measurement target lens 110 to the arbitrary object 104 coincide with the optical path length L2 from the light source 22 to the arbitrary object 104 via the half mirror 11. In this case, the optical path length L11 from the first principal point M of the measurement target lens 110 to point B of the half mirror 11 coincides with the optical path length L22 from the light source 22 to point B of the half mirror 11.

[0105] When the calibration pattern light is projected onto the arbitrary object 104 with these distances being consistent, the light reflected from the surface of the arbitrary object 104 passes through the half mirror 11 and forms an image on the focal plane 111 via the measurement target lens 110. The size and distortion of this imaged pattern are invariant regardless of the distance from the camera 102 to the arbitrary object 104, the degree of unevenness on the surface of the arbitrary object 104, and the angle of view of the measurement target lens 110.

[0106] As a result, the measurement of the distortion aberration inherent to the measurement target lens 110 can be performed by using an arbitrary object 104 of an arbitrary shape as a projection target of the calibration pattern light. In other words, the arbitrary object 104 can be a projection target regardless of whether the surface of the arbitrary object 104 has irregularities or not, and regardless of whether the arbitrary object 104 is a rigid body or not. For example, the arbitrary object 104 may be any object that can diffusely reflect light, such as a studio wall, a curtain, an animal, a living thing, etc.

[0107] Therefore, by using the calibration pattern light projector 1, the effort required for measuring the distortion aberration of the measurement target lens 110 can be reduced, and the distortion aberration can be measured with high accuracy.

[0108] Furthermore, as a conventional technique, there is a technique in which the measurement target lens 110 is removed from the camera 102 and the distortion aberration is measured for the measurement target lens 110 alone using laser light or the like. In the embodiment of the present invention, the distortion aberration can be measured in a state in which the measurement target lens 110 is attached to the camera 102, and therefore, compared to the above-mentioned conventional technique, the distortion aberration caused by the backlash or bending of the measurement target lens 110 when attached can also be measured.

[0109] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the technical concept thereof.

[0110] For example, in the above embodiment, the pattern light generating unit 10 of the calibration pattern light projector 1 is provided with a movable unit 21 that is movable in the movement direction D, but instead of the movable unit 21, it may be provided with a fixed unit that does not move (that is, is fixedly installed relative to the housing 12).

[0111] This fixing portion is fixed to the housing 12 so that the optical path length L1 and the optical path length L2 shown in Fig. 7 match (so that the optical path length L11 and the optical path length L22 match). In this case, initial adjustment by the user is not required.

[0112] In addition, in the above embodiment, the movable part 21 of the pattern light generating unit 10 of the calibration pattern light projector 1 is structured to move in a moving direction D, which is the direction of the optical axis of the light source 22, so as to move the light source 22 toward and away from the half mirror 11.

[0113] This makes it possible to change the optical path length L22 from the light source 22 to point B of the half mirror 11 while keeping the optical path length L11 from the first principal point M of the lens 110 to be measured to point B of the half mirror 11 fixed, thereby making it possible to match the two distances.

[0114] In contrast to this, the calibration pattern light projection device 1 may be provided with a device movable part that moves the entire calibration pattern light projection device 1 relative to the camera 102 while the positions of the light source 22 and the mask 23 relative to the half mirror 11 are fixed. The movement direction of the entire calibration pattern light projection device 1 is the direction of the optical axis β1 shown in Fig. 7. In this case, the pattern light generation unit 10 of the calibration pattern light projection device 1 includes the above-mentioned fixed part instead of the movable part 21.

[0115] This makes it possible to change the optical path length L11 from the first principal point M of the lens 110 to be measured to point B of the half mirror 11, and to make the two distances equal while keeping the optical path length L22 from the light source 22 to point B of the half mirror 11 fixed.

[0116] Furthermore, the calibration pattern light projection device 1 may include the movable part 21 that moves the light source 22, and may also include the above-mentioned device movable part that moves the entire calibration pattern light projection device 1. [Explanation of symbols]

[0117] 1 Calibration pattern light projection device 10, 10-1, 10-2, 10-3 Pattern light generating unit 11 Half Mirror 12,112 units 21 Moving parts 22,25,27 light source 23, 23-1, 23-2, 23-3 Mask 24 Scanning mechanism 26 Galvano Mirror 30 Microlenses 40 Recess 101 Calibration Pattern 102 Camera 103 Distortion aberration measuring device 104 Arbitrary object 110 Measurement target lens 111 Focal plane α Angle of View β,β1,β2 optical axis γ1 Collimated light γ2,m1,m2,n1,n2 Reflected light J axis M first principal point Point B D Moving direction L1,L2,L11,L22 Optical path length C1, C2, R1, R2 Location

Claims

1. A calibration pattern light projection device that projects a calibration pattern light for measuring distortion aberration of a lens attached to a camera onto a predetermined object, comprising: a pattern light generating unit that generates the calibration pattern light using a light source; a half mirror that reflects the calibration pattern light generated by the pattern light generating unit and projects the calibration pattern light onto the predetermined object, an optical path length from the light source to the predetermined object via the half mirror is equal to an optical path length from a first principal point of the lens to the predetermined object via the half mirror; a calibration pattern light projection device characterized in that, when the calibration pattern light is projected onto the specified object, the reflected light reflected from the surface of the specified object passes through the half mirror and is imaged on the focal plane of the camera via the lens.

2. 2. The calibration pattern light projection device according to claim 1, The pattern light generating unit includes: a movable portion for moving the light source in an optical axis direction between the light source and the half mirror;

3. 3. The calibration pattern light projection device according to claim 1, The calibration pattern light projection device further comprises a device movable part that moves the calibration pattern light projection device relative to the camera in the optical axis direction between a first principal point of the lens and the half mirror while keeping the position of the light source relative to the half mirror fixed.

4. 4. The calibration pattern light projection device according to claim 1, The pattern light generating unit includes: a calibration pattern light projection device comprising: a mask having a plurality of transmitting portions and a plurality of light-shielding portions for forming a pattern of the calibration pattern light, and using the mask, generating the calibration pattern light in a solid angle with the light source as a vertex.

5. 4. The calibration pattern light projection device according to claim 1, The pattern light generating unit includes: a scanning mechanism for scanning a light beam emitted by the light source, and using the scanning mechanism, generating the calibration pattern light in a solid angle with the light source as a vertex.

Images