Optical axis calibration device and optical axis calibration method

Abstract

The application discloses an optical axis calibration device and an optical axis calibration method. The optical axis calibration device comprises a tested target, a light splitting element, an off-axis parabolic mirror and a calibration target. The tested target is located on the focal plane of the off-axis parabolic mirror and is used for emitting a calibration light beam. The calibration light beam comprises a visible light beam and an infrared light beam. The light splitting element is located at the focal point of the off-axis parabolic mirror. The calibration light beam is split by the light splitting element to form a transmitted light beam and a reflected light beam. The reflected light beam is reflected by the off-axis parabolic mirror to form a parallel light beam. The test area of the optical axis calibration device is located on the propagation path of the parallel light beam, and the test area is used for placing a camera to be calibrated. The optical axis calibration device and method provided by the application realize the calibration of the optical axes of the visible light lens and the thermal imaging lens of the camera to be calibrated, thereby ensuring the cooperative working quality of the visible light lens and the thermal imaging lens in the camera to be calibrated.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of optical equipment, in particular to an optical axis calibration device and an optical axis calibration method. BACKGROUND

[0002] The camera for security monitoring usually integrates a visible light lens and a thermal imaging lens, and the visible light lens and the thermal imaging lens work cooperatively, so that the optical axis centers of the visible light lens and the thermal imaging lens need to be parallel. Only when the optical axis centers of the visible light lens and the thermal imaging lens are parallel, the details of the target area captured by the visible light lens are consistent with the target area monitored by the thermal imaging lens.

[0003] Therefore, the optical axis calibration device is needed to calibrate the optical axes of the visible light lens and the thermal imaging lens. SUMMARY

[0004] The present application provides an optical axis calibration device and an optical axis calibration method to calibrate the optical axes of the visible light lens and the thermal imaging lens.

[0005] In the first aspect, the embodiment of the present application provides an optical axis calibration device for optical axis calibration of a to-be-calibrated camera, and the optical axis calibration device comprises:

[0006] a tested target, a light splitting element, an off-axis parabolic mirror and a calibration target;

[0007] The tested target is located on the focal plane of the off-axis parabolic mirror, and the tested target is used for emitting a calibration light beam, and the calibration light beam comprises a visible light beam and an infrared light beam;

[0008] The light splitting element is located on the propagation path of the calibration light beam, and the light splitting element is located at the focal point position of the off-axis parabolic mirror;

[0009] The calibration light beam is split by the light splitting element to form a transmitted light beam and a reflected light beam;

[0010] The off-axis parabolic mirror is located on the propagation path of the reflected light beam, and the calibration target is located on the propagation path of the transmitted light beam;

[0011] The reflected light beam is reflected by the off-axis parabolic mirror to form a parallel light beam, and a test area of the optical axis calibration device is located on the propagation path of the parallel light beam, and the test area is used for placing the to-be-calibrated camera.

[0012] Optionally, a heating mark is arranged on the tested target, and the heating mark is used for emitting the calibration light beam.

[0013] The heating mark includes a center heating mark located at a center position of the tested target;

[0014] The calibration target includes a through hole corresponding to the center heating mark;

[0015] The tested target is further provided with a light compensation calibration pattern, a geometric center of the light compensation calibration pattern overlaps with a geometric center of the center heating mark.

[0016] Optionally, the heating mark further includes at least one edge heating mark located at an edge of an effective area of the tested target.

[0017] Optionally, the optical axis calibration device further includes a first displacement adjustment support, a second displacement adjustment support and a third displacement adjustment support;

[0018] The first displacement adjustment support is connected with the light splitting element to adjust a position of the light splitting element;

[0019] The second displacement adjustment support is connected with the tested target to adjust a position of the tested target;

[0020] The third displacement adjustment support is connected with the calibration target to adjust a position of the calibration target.

[0021] Optionally, the heating mark includes a heating resistance wire.

[0022] Optionally, the light splitting element includes a half mirror or a prism.

[0023] In a second aspect, the embodiments of the present application further provide an optical axis calibration method applied to any optical axis calibration device in the first aspect, and the method includes:

[0024] Placing a camera to be calibrated in a test area;

[0025] Adjusting a focal length of a thermal imaging lens of the camera to be calibrated to a preset focal length, adjusting a position of the thermal imaging lens, so that the thermal imaging lens captures a thermal imaging image of a center heating mark on a tested target, and the thermal imaging image of the center heating mark is located at a field center of the thermal imaging lens, the thermal imaging lens is calibrated, and the thermal imaging lens is fixed;

[0026] Adjusting a focal length of a visible light lens of the camera to be calibrated to a preset focal length, adjusting a position of the visible light lens, so that the visible light lens captures a visible light image of the center heating mark on the tested target, and the visible light image of the center heating mark is located at a field center of the visible light lens, the visible light lens is calibrated, and the visible light lens is fixed.

[0027] Optionally, before adjusting the camera to be calibrated, further comprising:

[0028] The tested target is powered to heat;

[0029] The position of the light splitting element is adjusted so that the light splitting element is located at the focal point of the off-axis parabolic mirror;

[0030] The positions of the tested target and the calibration target are adjusted so that the central heating mark on the tested target corresponds to the position of the through hole of the calibration target.

[0031] Optionally, the tested target is further provided with a light compensation calibration pattern, and a geometric center of the light compensation calibration pattern overlaps with a geometric center of the central heating mark;

[0032] After the visible light lens optical axis is calibrated and the visible light lens is fixed, further comprising:

[0033] The light compensation lamp of the camera to be calibrated is adjusted to a preset angle, and the position of the light compensation lamp of the camera to be calibrated is adjusted so that the light spot of the light compensation lamp on the tested target is located in the light compensation calibration pattern.

[0034] Optionally, the heating mark further comprises at least one edge heating mark, and the edge heating mark is located at the edge of the effective area of the tested target.

[0035] After the visible light lens optical axis is calibrated and the visible light lens is fixed, and the thermal imaging lens optical axis is calibrated and the thermal imaging lens is fixed, further comprising:

[0036] The visible light image of the edge heating mark obtained through the visible light lens is a first calibration image;

[0037] The thermal imaging image of the edge heating mark obtained through the thermal imaging lens is a second calibration image;

[0038] According to the first calibration image and the second calibration image, the visible light image output by the visible light lens and the thermal imaging image output by the thermal imaging lens are calibrated.

[0039] The optical axis calibration device and the optical axis calibration method provided by the embodiment of the present application can emit calibration light beams including visible light beams and infrared light beams through the setting of the tested target, the calibration light beams are reflected by the light splitting element and the off-axis parabolic mirror to form parallel light beams, so that the thermal imaging lens and the visible light lens of the camera to be calibrated in the test area can all acquire the image of the tested target, and whether the optical axes of the thermal imaging lens and the visible light lens are parallel is judged by observing the image of the tested target through the thermal imaging lens and the visible light lens, so that the optical axis calibration of the thermal imaging lens and the visible light lens is realized. Meanwhile, the calibration target is set on the propagation path of the transmitted light beams, so that part of the calibration light beams is transmitted to the calibration target through the light splitting element, the self-calibration of the optical axis calibration device is realized, and the calibration accuracy of the optical axis calibration device is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A structural schematic diagram of an optical axis calibration device provided by the embodiment of the present application is shown in

[0041] Figure 2 A structural schematic diagram of a camera to be calibrated provided by the embodiment of the present application is shown in

[0042] Figure 3 An optical path schematic diagram of an off-axis parabolic mirror in a two-dimensional coordinate system provided by the embodiment of the present application is shown in

[0043] Figure 4 A flow schematic diagram of an optical axis calibration method provided by the embodiment of the present application is shown in

[0044] Figure 5 A structural schematic diagram of an optical axis calibration method provided by the embodiment of the present application is shown in DETAILED DESCRIPTION

[0045] The present application will be further described below in conjunction with the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application. In addition, it should be noted that, for the convenience of description, only the parts related to the present application are shown in the drawings, but not all the structures.

[0046] Figure 1 A structural schematic diagram of an optical axis calibration device provided by the embodiment of the present application is shown in Figure 1As shown, the optical axis calibration device provided by the embodiment of the present application is used for optical axis calibration of the camera to be calibrated, and the device comprises a tested target 10, a light splitting element 11, an off-axis parabolic mirror 12 and a calibration target 13. The tested target 10 is located on the focal plane of the off-axis parabolic mirror 12, and the tested target 10 is used for emitting a calibration light beam 20, which comprises a visible light beam and an infrared light beam. The light splitting element 11 is located on the propagation path of the calibration light beam 20 and is located at the focal point position of the off-axis parabolic mirror 12. The calibration light beam 20 is split by the light splitting element 11 to form a transmitted light beam 21 and a reflected light beam 22. The off-axis parabolic mirror 12 is located on the propagation path of the reflected light beam 22, and the calibration target 13 is located on the propagation path of the transmitted light beam 21. The reflected light beam 22 is reflected by the off-axis parabolic mirror 12 to form a parallel light beam 23. A test area 30 of the optical axis calibration device is located on the propagation path of the parallel light beam 23, and the test area 30 is used for placing the camera to be calibrated 40.

[0047] As shown, the optical axis calibration device provided by the embodiment of the present application is used for optical axis calibration of the camera to be calibrated 40, and the purpose of the optical axis calibration is to make the optical axes of the visible light lens, the thermal imaging lens and the fill light and other optical components in the camera to be calibrated 40 parallel. The camera to be calibrated 40 can be a monitoring camera or other types of cameras, and the embodiment of the present application does not limit this.

[0048] As shown, Figure 2 A structural schematic diagram of the camera to be calibrated provided by the embodiment of the present application is shown in FIG. 1. Figure 1 As shown, Figure 2 As shown, the camera to be calibrated 40 can comprise a thermal imaging lens 41, a visible light lens 42 and a fill light 43.

[0049] As shown,

[0050] 1) The thermal imaging lens 41 is used for monitoring the surface thermal radiation change of a target area, so as to achieve the purpose of early warning, such as fire early warning and unknown object intrusion early warning of the border line of the sea and land.

[0051] 2) After the thermal imaging lens 41 monitors the thermal radiation change of the target area, the visible light lens 42 zooms in to enlarge the target area, captures the detail information and outputs the color / monochrome image in real time to the management personnel for distinguishing and making a judgment.

[0052] 3) The fill light 43 works in the night environment, and the fill light 43 emits near-infrared light to illuminate the visible light lens 42, so that the visible light lens 42 outputs the monochrome image in real time for the management personnel to view the detail information of the monitored target area.

[0053] As can be seen from the above working mode, the thermal imaging lens 41, the visible light lens 42 and the fill light 43 need to work cooperatively, and therefore the optical axis centers of the thermal imaging lens 41, the visible light lens 42 and the fill light 43 need to be ensured to be parallel, so that the detail information of the target area captured by the visible light lens 42 is consistent with the target area monitored by the thermal imaging lens 41, and the area irradiated by the near-infrared light emitted by the fill light 43 is consistent with the target area captured by the visible light lens 42.

[0054] It should be noted that, Figure 2 In the illustrated to-be-calibrated camera 40, the to-be-calibrated camera 40 includes the three optical components of the thermal imaging lens 41, the visible light lens 42 and the fill light 43, but is not limited thereto, and in other embodiments, the to-be-calibrated camera 40 can also include two optical components, for example, the to-be-calibrated camera 40 only includes the thermal imaging lens 41 and the visible light lens 42, or the to-be-calibrated camera 40 only includes the visible light lens 42 and the fill light 43, or the to-be-calibrated camera 40 includes more optical components, and the embodiments of the present application do not limit this.

[0055] In addition, Figure 2 In the illustrated to-be-calibrated camera 40, the thermal imaging lens 41, the visible light lens 42 and the fill light 43 are arranged in parallel, but are not limited thereto, and in other embodiments, the thermal imaging lens 41, the visible light lens 42 and the fill light 43 in the to-be-calibrated camera 40 can also be irregularly arranged, and the embodiments of the present application do not limit this.

[0056] With reference to Figure 1 The optical axis calibration device provided by the embodiments of the present application includes a tested target 10, a light splitting element 11, an off-axis parabolic mirror 12 and a calibration target 13.

[0057] The tested target 10 is used to emit a calibration light beam 20, and the tested target 10 is used to emit the calibration light beam 20, and the calibration light beam 20 includes a visible light beam and an infrared light beam.

[0058] For example, Figure 1 As shown in the figure, the side of the tested target 10 away from the propagation direction of the calibration light beam 20 can be provided with an illumination light source (not shown in the figure), and the light emitted by the illumination light source transmits through the tested target 10 to form the visible light beam, and at the same time, the tested target 10 can also be heated to output the infrared light beam, thereby forming the calibration light beam 20. The calibration light beam 20 is reflected by the light splitting element 11 and the off-axis parabolic mirror 12 in turn to form a parallel light beam 23, and the visible light lens 42 in the to-be-calibrated camera 40 receives the parallel light beam 23, so that the visible light image of the tested target 10 can be obtained; the thermal imaging lens 41 in the to-be-calibrated camera 40 receives the parallel light beam 23, so that the thermal imaging image of the tested target 10 can be obtained.

[0059] Figure 3 A light path schematic diagram of an off-axis parabolic mirror in a two-dimensional coordinate system is provided for an embodiment of the present application, as shown in Figure 1 and Figure 3 Optionally, the surface type of the reflecting surface of the off-axis parabolic mirror 12 can be a part of a rotating parabolic mirror, wherein the entire parabolic mirror can be formed by rotating a parabola y(x) around a symmetry axis, and the expression of the parabola y(x) can be represented as: Figure 3

[0060] y(x) 2 =2px

[0061] wherein the coordinates of the focus F of the parabolic mirror are (p / 2, 0), and the directrix is x = -p / 2.

[0062] Continuing to refer to Figure 1 , the tested target 10 is located on the focal plane of the off-axis parabolic mirror 12, and the light splitting element 11 is located on the propagation path of the calibration light beam 20, and part of the calibration light beam 20 is reflected to the off-axis parabolic mirror 12 through the light splitting element 11, wherein the light splitting element 11 is located at the focal point position of the off-axis parabolic mirror 12, and according to the characteristics of the parabolic mirror and the above formula, it can be known that the light emitted at the focus F will form parallel light after being reflected by the off-axis parabolic mirror 12, and therefore, as shown in Figure 1 , the reflected light beam 22 will form a parallel light beam 23 after being reflected by the off-axis parabolic mirror 12, and the test area 30 of the optical axis calibration device is located on the propagation path of the parallel light beam 23, and the camera to be calibrated 40 is placed in the test area 30, and the camera to be calibrated 40 is equivalent to observing the tested target 10 at an infinite distance, so that the image information of the tested target 10 can be captured and finally processed.

[0063] wherein by placing the tested target 10 on the focal plane of the off-axis parabolic mirror 12 and setting the light splitting element 11 at the focal point position of the off-axis parabolic mirror 12 to form the parallel light beam 23, the camera to be calibrated 40 in the test area 30 can obtain the image of the tested target 10 at an infinite distance without placing the tested target 10 at a far distance, so that the test space of the optical axis calibration device can be greatly reduced, the mass production operation is facilitated, and the calibration efficiency is improved.

[0064] Further, as shown in Figure 1 , part of the calibration light beam 20 is transmitted to the calibration target 13 through the light splitting element 11 for self-calibration of the optical axis calibration device, so as to ensure the calibration accuracy of the optical axis calibration device.

[0065] The use process of the optical axis calibration device provided by the embodiment of the present application can be as follows:

[0066] ​The to-be-calibrated camera 40 is placed in the test area 30, wherein the front end surface of the to-be-calibrated camera 40 is parallel to the directrix x = -p / 2 of the off-axis parabolic mirror 12.

[0067] The thermal imaging lens 41 of the to-be-calibrated camera 40 captures a thermal imaging image of the tested target 10, and calibrates the optical axis of the thermal imaging lens 41 according to the thermal imaging image.

[0068] The visible light lens 42 of the to-be-calibrated camera 40 simultaneously captures a visible light image of the tested target 10, and calibrates the optical axis of the visible light lens 42 according to the visible light image.

[0069] In summary, the optical axis calibration device provided by the embodiment of the present application comprises a main optical path composed of the tested target 10, the light splitting element 11, the off-axis parabolic mirror 12 and the calibration target 13, wherein the tested target 10 can emit a calibration light beam 20 comprising a visible light beam and an infrared light beam. By setting the calibration light beam 20 to be reflected by the light splitting element 11 and the off-axis parabolic mirror 12 to form parallel light beams, the thermal imaging lens 41 and the visible light lens 42 of the to-be-calibrated camera 40 in the test area 30 can both obtain the image of the tested target 10. By observing the image of the tested target 10 through the thermal imaging lens 41 and the visible light lens 42, it can be determined whether the optical axes of the thermal imaging lens 41 and the visible light lens 42 are parallel, thereby realizing the optical axis calibration of the thermal imaging lens 41 and the visible light lens 42. At the same time, by setting the calibration target 13 to be located on the propagation path of the transmitted light beam 21, part of the calibration light beam 20 is transmitted to the calibration target 13 through the light splitting element 11, thereby realizing the self-calibration of the optical axis calibration device, and further ensuring the calibration accuracy of the optical axis calibration device.

[0070] With reference to the foregoing description, the tested target 10 is a circular plate, and the center of the tested target 10 is the center of the circle. Figure 1 Optionally, the tested target 10 is provided with a heating mark 14, the heating mark 14 is used to emit the calibration light beam 20, and the heating mark 14 comprises a center heating mark 141 located at the center of the tested target 10. The calibration target 13 comprises a through hole 131 corresponding to the center heating mark 141.

[0071] The heating mark 14 can be heated to generate thermal radiation, so as to emit the visible light beam and the infrared light beam at the same time, form the calibration light beam 20, and then the calibration light beam 20 is reflected by the light splitting element 11 and the off-axis parabolic mirror 12 in sequence to form a parallel light beam 23. The thermal imaging lens 41 of the to-be-calibrated camera 40 receives the parallel light beam 23, and can obtain the thermal imaging image of the heating mark 14. The visible light lens 42 of the to-be-calibrated camera 40 receives the parallel light beam 23, and can obtain the visible light image of the heating mark 14.

[0072] The heating mark 14 includes a center heating mark 141 located at the center of the tested target 10, so that whether the optical axes of the optical components are parallel can be determined by observing whether the image of the center heating mark 141 falls in the center of the field of view of each optical component.

[0073] The shape of the heating mark 14 can include a cross, a circle or a square, etc. Figure 1 In the embodiment, the shape of the heating mark 14 is only taken as an example of the cross, and the embodiment is not limited to this.

[0074] Continuing to refer to Figure 1 Optionally, the calibration target 13 includes a through hole 131 corresponding to the center heating mark 141.

[0075] For example, as shown in the figure, Figure 1 The through hole 131 can be located at the center of the calibration target 13, and the through hole 131 can be a circular hole, which is in the same height and coaxial with the center heating mark 141 of the tested target 10, and the diameter of the through hole 131 is consistent with the diameter of the circumscribed circle of the center heating mark 141.

[0076] When the optical axis calibration device performs self-calibration, the positions of the tested target 10 and the calibration target 13 are adjusted so that the center heating mark 141 at the center of the tested target 10 is inscribed in the through hole 131 at the center of the calibration target 13, so as to ensure that the calibration light beam 20 is reflected by the light splitting element 11 at the focal point position of the off-axis parabolic mirror 12, thereby ensuring the calibration accuracy of the optical axis calibration device.

[0077] The through hole 131 can be a circular hole, a cross-shaped hole or a square hole, Figure 1 In the embodiment, the through hole 131 is only taken as an example of the circular hole, and the embodiment is not limited to this.

[0078] The use process of the optical axis calibration device provided by the embodiment can be as follows:

[0079] The camera to be calibrated 40 is placed in the test area 30, and the front end surface of the camera to be calibrated 40 is parallel to the directrix x = -p / 2 of the off-axis parabolic mirror 12.

[0080] The thermal imaging lens 41 of the camera to be calibrated 40 captures the thermal imaging image of the center heating mark 141 at the center of the tested target 10, and in the calibration process, the thermal imaging image of the center heating mark 141 is ensured to be at the center position of the output image of the thermal imaging lens 41, that is, the thermal imaging image of the center heating mark 141 is at the center of the field of view of the thermal imaging lens 41.

[0081] The visible light lens 42 of the camera to be calibrated 40 captures a visible light image of the center heating mark 141 of the center position of the test target 10, and the visible light image of the center heating mark 141 is ensured to be in the center position of the output image of the visible light lens 42 in the calibration process, that is, the visible light image of the center heating mark 141 is in the center of the field of view of the visible light lens 42.

[0082] Wherein, by adjusting the positions of the thermal imaging lens 41 and the visible light lens 42, so that the image of the center heating mark 141 is located in the center of the field of view of the thermal imaging lens 41 and the center of the field of view of the visible light lens 42 at the same time, then the optical axes of the thermal imaging lens 41 and the visible light lens 42 are parallel, thereby realizing the calibration of the optical axes of the thermal imaging lens 41 and the visible light lens 42.

[0083] With reference to the foregoing Figure 1 Optionally, the test target 10 is further provided with a light supplement calibration pattern 15, and the geometric center of the light supplement calibration pattern 15 overlaps with the geometric center of the center heating mark 141.

[0084] Wherein, the light supplement calibration pattern 15 is used to calibrate the center axis of the light spot emitted by the light supplement lamp 43 to be parallel to the optical axis of the visible light lens 42.

[0085] For example, as Figure 1 shown in the figure, the light supplement calibration pattern 15 can be a circular ring drawn in the effective area of the test target 10, and the diameter of the circular ring can be consistent with the diameter of the circular light spot formed by the light beam emitted by the light supplement lamp 43 under the condition of the minimum light emission angle.

[0086] It should be noted that the effective area refers to the area corresponding to the image of the test target 10 obtained by the camera to be calibrated 40, for example, when the camera to be calibrated 40 photographs the test target 10, it can only obtain part of the image of the test target 10, and the area of this part of the test target 10 is the effective area of the test target 10.

[0087] When calibrating the optical axes of the light supplement lamp 43 and the visible light lens 42, the visible light image of the center heating mark 141 is in the center of the field of view of the visible light lens 42, the light supplement lamp 43 emits near-infrared light, according to the principle of light path reversibility, when a parallel light beam enters the off-axis parabolic mirror 12, it converges at the focal point F position, therefore, the near-infrared light is focused on the surface of the light splitting element 11 after being reflected by the off-axis parabolic mirror 12, part of the near-infrared light is reflected by the light splitting element 11, and finally irradiates on the test target 10 to form a light spot, by adjusting the position of the light supplement lamp 43, the light spot formed by the light supplement lamp 43 on the test target 10 is located in the circular ring, then the optical axes of the light supplement lamp 43 and the visible light lens 42 are parallel.

[0088] Wherein, the shape of the light supplement calibration pattern 15 can beFigure 1 The shape of the light compensation calibration pattern 15 is not limited to the circular shape shown in the figures, and in other embodiments, the shape of the light compensation calibration pattern 15 can be square or the like, and embodiments of the present application are not limited in this regard.

[0089] With reference to the figures Figure 1 Optionally, the heating mark 14 further comprises at least one edge heating mark 142, which is located at the edge of the effective area of the tested target 10.

[0090] The edge heating mark 142 is used for image calibration of different wavelengths, specifically calibration of the output image of the visible light lens 42 and the output image of the thermal imaging lens 41, thereby facilitating accurate fusion of the output image of the visible light lens 42 and the output image of the thermal imaging lens 41.

[0091] For example, as shown in the figures Figure 1 The edge heating mark 142 is arranged at the edge of the effective area of the tested target 10, so that the thermal imaging lens 41 can acquire a thermal imaging image of the edge heating mark 142, and at the same time, the visible light lens 42 can also acquire a visible light image of the edge heating mark 142. Capturing and calibrating the thermal imaging image and the visible light image of the edge heating mark 142 helps to improve the fusion quality of the output image of the thermal imaging lens 41 and the output image of the visible light lens 42.

[0092] By arranging the edge heating mark 142 at the edge of the effective area of the tested target 10, the distance between the edge heating mark 142 and the center heating mark 141 is far, which helps to improve the fusion quality of the output image of the thermal imaging lens 41 and the output image of the visible light lens 42.

[0093] It should be noted that the shape, number and position of the edge heating mark 142 can be set according to actual needs, Figure 1 In the figures, only four edge heating marks 142 in the shape of a cross are arranged at the edge positions of the four corners of the effective area of the tested target 10, but embodiments of the present application are not limited in this regard.

[0094] With reference to the figures Figure 1 Optionally, the optical axis calibration device provided by embodiments of the present application further comprises a first displacement adjustment support 16, a second displacement adjustment support 17 and a third displacement adjustment support 18. The first displacement adjustment support 16 is connected with the light splitting element 11 to adjust the position of the light splitting element 11; the second displacement adjustment support 17 is connected with the tested target 10 to adjust the position of the tested target 10; and the third displacement adjustment support 18 is connected with the calibration target 13 to adjust the position of the calibration target 13.

[0095] The light splitting element 11 is fixedly installed on the first displacement adjusting support 16, so as to adjust the position of the light splitting element 11 by the first displacement adjusting support 16, and make the light splitting element 11 located at the focal point position of the off-axis parabolic mirror 12.

[0096] Optionally, as shown in Figure 1 , the angle between the light splitting element 11 and the horizontal direction is 45°, and the position of the light splitting element 11 can be fine-tuned by the first displacement adjusting support 16.

[0097] Continuing to refer to Figure 1 , the tested target 10 is fixedly installed on the second displacement adjusting support 17, so as to adjust the position of the tested target 10 by the second displacement adjusting support 17, and make the tested target 10 located at the focal plane position of the off-axis parabolic mirror 12.

[0098] Continuing to refer to Figure 4 , the calibration target 13 is fixedly installed on the third displacement adjusting support 18, so as to adjust the position of the calibration target 13 by the third displacement adjusting support 18, and realize the self-calibration of the optical axis calibration device itself.

[0099] Among them, the first displacement adjusting support 16, the second displacement adjusting support 17 and the third displacement adjusting support 18 can adopt a six-dimensional adjusting support to realize multi-dimensional position adjustment and improve the calibration accuracy, but are not limited thereto.

[0100] Meanwhile, the driving mode of the first displacement adjusting support 16, the second displacement adjusting support 17 and the third displacement adjusting support 18 can be manual to reduce the cost, and in other embodiments, the driving mode of the first displacement adjusting support 16, the second displacement adjusting support 17 and the third displacement adjusting support 18 can also be electric, thereby saving manpower.

[0101] Optionally, the heating mark 14 includes a heating resistance wire.

[0102] Among them, by setting the heating mark 14 to adopt a heating resistance wire, the heating resistance wire can be energized to heat, thereby realizing that the heating mark 14 emits heat radiation to form an infrared light beam, and the structure is simple and easy to realize.

[0103] Exemplarily, as shown in Figure 4As shown, the heating resistance wire can be used to form a cross shape at the center position of the tested target 10 to form a center heating mark 141, and the heating resistance wire can be used to form a cross shape at the edge position of the effective area of the tested target 10 to form an edge heating mark 142. After the heating resistance wire is powered and heated, the infrared light beam is emitted, so that the thermal imaging lens 41 can capture the thermal imaging images of the center heating mark 141 and the edge heating mark 142, and at the same time, the visible light lens 42 can also capture the visible light images of the center heating mark 141 and the edge heating mark 142.

[0104] In other embodiments, other ways of arranging the heating mark 14 can also be used as long as the heating mark 14 can be heated to emit the infrared light beam.

[0105] Optionally, the light splitting element 11 includes a half-mirror or a prism.

[0106] Specifically, the light splitting element 11 can be a half-mirror or a prism to achieve the light splitting function. Figure 5 For example, the light splitting element 11 is a half-mirror, but is not limited thereto.

[0107] The transmittance of the half-mirror is 50%, and the reflectance is 50%, so that 50% of the calibration light beam 20 is transmitted to the calibration target 13 for self-calibration of the optical axis calibration device, and 50% of the calibration light beam 20 is reflected to the surface of the off-axis parabolic mirror 12.

[0108] In other embodiments, the light splitting ratio of the light splitting element 11 can also be adjusted according to actual needs, and the embodiments of the present application are not limited thereto.

[0109] It should be noted that the material of the light splitting element 11 can be one or more of glass, PC, PMMA and multi-spectrum zinc sulfide, and the embodiments of the present application are not limited thereto.

[0110] In summary, the optical axis calibration device provided by the embodiments of the present application can realize the optical axis calibration of the three optical components, i.e., the thermal imaging lens 41, the visible light lens 42 and the fill light 43, by designing the pattern of the tested target 10, and can also be compatible with the combination scheme of the two optical components, i.e., the thermal imaging lens 41 and the visible light lens 42, or the combination scheme of the two components, i.e., the visible light lens 42 and the fill light 43. At the same time, the image calibration of the thermal imaging lens 41 and the visible light lens 42 can also be realized, so that the image fusion function of the thermal imaging lens 41 and the visible light lens 42 can be realized, and a dedicated calibration device does not need to be additionally designed, the production tooling is reduced, the management is facilitated, and the production efficiency is improved.

[0111] Based on the same inventive concept, the embodiment of the present application also provides a light axis calibration method, which is applied to any light axis calibration device provided by the above-mentioned embodiments, and the same or corresponding structures and explanations of terms are not described here again. Figure 5 The flowchart of the light axis calibration method provided by the embodiment of the present application is shown in Figure 5 The method comprises the following steps:

[0112] S110, placing the camera to be calibrated in the test area.

[0113] Among them, Figure 5 The structural diagram of the light axis calibration method provided by the embodiment of the present application is shown in Figure 5 The camera to be calibrated 40 is placed at a predetermined position in the test area 30, so that the camera to be calibrated 40 can receive the parallel light beam 23.

[0114] S120, adjusting the focal length of the thermal imaging lens of the camera to be calibrated to a preset focal length, adjusting the position of the thermal imaging lens, so that the thermal imaging lens captures the thermal imaging image of the center heating mark on the test target, and the thermal imaging image of the center heating mark is located at the center of the field of view of the thermal imaging lens, the thermal imaging lens is calibrated, and the thermal imaging lens is fixed.

[0115] With reference to Figure 5 , for example, the focal length of the thermal imaging lens of the camera to be calibrated can be adjusted to a preset focal length first, so that the thermal imaging lens 41 of the camera to be calibrated 40 is zoomed to the maximum and focused clearly. If the thermal imaging lens 41 is a fixed focus lens, it can be focused clearly. The position of the thermal imaging lens 41 in the camera to be calibrated 40 is adjusted, so that the thermal imaging image of the center heating mark 141 in the center area of the test target 10 is located at the center position of the output image of the thermal imaging lens 41, that is, the thermal imaging image of the center heating mark 141 is located at the center of the field of view of the thermal imaging lens 41. After the adjustment is completed, the thermal imaging lens 41 is fixed.

[0116] S130, adjusting the focal length of the visible light lens of the camera to be calibrated to a preset focal length, adjusting the position of the visible light lens, so that the visible light lens captures the visible light image of the center heating mark on the test target, and the visible light image of the center heating mark is located at the center of the field of view of the visible light lens, the visible light lens is calibrated, and the visible light lens is fixed.

[0117] With reference to Figure 5For example, the focal length of the thermal imaging lens of the camera to be calibrated is adjusted to a preset focal length, the visible light lens 42 of the camera to be calibrated 40 is zoomed to the maximum magnification and focused clearly, if the visible light lens 42 is a fixed focus lens, the focusing is clear, the position of the visible light lens 42 in the camera to be calibrated 40 is adjusted so that the visible light image of the central heating mark 141 of the central region of the test target 10 is located at the center position of the output image of the visible light lens 42, that is, the visible light image of the central heating mark 141 is located at the center of the field of view of the thermal imaging lens 41, and after the adjustment is completed, the visible light lens 42 is fixed.

[0118] At this time, the image of the central heating mark 141 is located at the center of the field of view of the thermal imaging lens 41 and the center of the field of view of the visible light lens 42, and it can be considered that the optical axes of the thermal imaging lens 41 and the visible light lens 42 are parallel, and the optical axis calibration of the thermal imaging lens 41 and the visible light lens 42 of the camera to be calibrated 40 is completed.

[0119] Optionally, before adjusting the camera to be calibrated, the method further comprises:

[0120] The test target is powered and heated.

[0121] The position of the light splitting element is adjusted so that the light splitting element is located at the focal point position of the off-axis parabolic mirror.

[0122] The positions of the test target and the calibration target are adjusted so that the central heating mark on the test target corresponds to the through hole position of the calibration target.

[0123] Optionally, before the optical axis calibration device is used to perform the batch calibration of the optical axes of the cameras to be calibrated, the optical axis of the optical axis calibration device is calibrated first to ensure the calibration accuracy of the optical axis calibration device.

[0124] For example, as shown in Figure 5 The off-axis parabolic mirror 12 is first fixed, and the camera to be calibrated 40 is placed at a predetermined position in the test area 30. Among them, before the camera is shipped, a batch of cameras to be calibrated 40 will be calibrated at this time, and the camera to be calibrated 40 placed at a predetermined position in the test area 30 can be the first camera to be calibrated 40 that needs to be calibrated.

[0125] When the heating mark 14 of the test target 10 is a heating resistance wire, the heating mark 14 of the test target 10 is powered and heated to make the central heating mark 141 emit calibration light 20.

[0126] Continuing to refer to Figure 5Optionally, the optical axis calibration device further comprises a first displacement adjusting support 16, a second displacement adjusting support 17 and a third displacement adjusting support 18. The first displacement adjusting support 16 is connected with the light splitting element 11 to adjust the position of the light splitting element 11. The second displacement adjusting support 17 is connected with the target under test 10 to adjust the position of the target under test 10. The third displacement adjusting support 18 is connected with the calibration target 13 to adjust the position of the calibration target 13. The first displacement adjusting support 16, the second displacement adjusting support 17 and the third displacement adjusting support 18 can be six-dimensional adjusting supports to realize multi-dimensional position adjustment.

[0127] With reference to the foregoing description Figure 5 After the heating mark 14 in the effective area of the target under test 10 is heated by power, the first displacement adjusting support 16 is adjusted so that the light splitting element 11 is located at the focal point of the off-axis parabolic mirror 12.

[0128] Then, the second displacement adjusting support 17 and the third displacement adjusting support 18 are adjusted so that the central heating mark 141 in the central region of the target under test 10 is inscribed in the through hole 131 in the central region of the calibration target 13. The central heating mark 141 inscribed in the through hole 131 of the calibration target 13 means that, as viewed from the through hole 131 of the calibration target 13 to the central heating mark 141, the image of the central heating mark 141 at the through hole 131 is inscribed in the edge of the through hole 131 of the calibration target 13.

[0129] Further, the first displacement adjusting support 16 is finely adjusted so that the light reflected by the surface of the light splitting element 11 forms parallel light after being reflected by the off-axis parabolic mirror 12 again, and the parallel light is captured by the thermal imaging lens 41 of the camera under calibration 40, and the thermal imaging image of the central heating mark 141 in the central region of the target under test 10 is located at the center of the output image of the thermal imaging lens 41, i.e. the thermal imaging image of the central heating mark 141 is located at the center of the field of view of the thermal imaging lens 41.

[0130] At this point, the self optical axis calibration of the optical axis calibration device is completed.

[0131] With reference to the foregoing description Figure 5 Optionally, the target under test 10 is further provided with a light supplement calibration pattern 15, and the geometric center of the light supplement calibration pattern 15 overlaps with the geometric center of the central heating mark 141.

[0132] After the optical axis of the visible light lens 42 is calibrated and the visible light lens 42 is fixed, the method further comprises:

[0133] The light supplement lamp 43 of the camera under calibration 40 is adjusted to a preset angle, and the position of the light supplement lamp 43 is adjusted so that the light spot of the light supplement lamp 43 on the target under test 10 is located in the light supplement calibration pattern 15.

[0134] As shown in ​ As shown in

[0135] The visible light image of the test target 10 can be acquired through the visible light lens 42 to determine whether the light spot of the fill light 43 on the test target 10 is within the range of the fill light calibration pattern 15.

[0136] At this point, it can be considered that the optical axes of the visible light lens 42 and the fill light 43 are parallel, and the optical axis calibration of the visible light lens 42 and the fill light 43 of the to-be-calibrated camera 40 is completed.

[0137] With reference to ​ Optionally, the heating mark 14 further comprises at least one edge heating mark 142, and the edge heating mark 142 is located at the edge of the effective area of the test target 10.

[0138] After the optical axis calibration of the visible light lens 42 is completed, the visible light lens 42 is fixed, and after the optical axis calibration of the thermal imaging lens 41 is completed, the thermal imaging lens 41 is fixed, the method further comprises:

[0139] The visible light image of the edge heating mark 142 acquired through the visible light lens 42 is a first calibration image.

[0140] The thermal imaging image of the edge heating mark 142 acquired through the thermal imaging lens 41 is a second calibration image.

[0141] The visible light image output by the visible light lens and the thermal imaging image output by the thermal imaging lens are calibrated according to the first calibration image and the second calibration image.

[0142] After the optical axis calibration of the thermal imaging lens 41 and the visible light lens 42 of the camera 40 to be calibrated is completed, there may still be a slight angle between the optical axes of the thermal imaging lens 41 and the visible light lens 42. This results in a difference between the position of the image of the same target in space on the thermal imaging lens 41 relative to the optical axis of the thermal imaging lens 41 and the position of the same target in space on the visible light lens 42 relative to the optical axis of the visible light lens. Therefore, the relative positions of the same target in space are different in the thermal imaging image and the visible light image, that is, there is an image coordinate offset between the two, making it impossible to accurately fuse the thermal imaging image and the visible light image of the same target.

[0143] In this embodiment, the edge heating mark 142 is used to achieve image calibration of different wavelengths. Specifically, the image calibration of different wavelengths refers to the calibration of the visible light image output by the visible light lens 42 and the thermal imaging image output by the thermal imaging lens 41, which is beneficial to the accurate fusion of the visible light image output by the visible light lens 42 and the thermal imaging image output by the thermal imaging lens 41.

[0144] For example, such as ​ As shown, the visible light lens 42 in the camera to be calibrated captures a visible light image of the edge heating mark 142 at the edge of the effective area of ​​the target 10 under test as the first calibration image. The thermal imaging lens 41 in the camera to be calibrated captures a thermal imaging image of the edge heating mark 142 at the edge of the effective area of ​​the target 10 under test as the second calibration image. By comparing the first calibration image and the second calibration image, the position of the visible light image of the edge heating mark 142 in the output image of the visible light lens 42, and the offset between the position of the thermal imaging image of the edge heating mark 142 in the output image of the thermal imaging lens 41, are determined to achieve calibration of the visible light image output by the visible light lens 42 and the thermal imaging image output by the thermal imaging lens 41. Subsequently, image algorithm technology can be used to compensate for the offset, thereby achieving accurate fusion of the visible light image output by the visible light lens 42 and the thermal imaging image output by the thermal imaging lens 41.

[0145] In summary, the optical axis calibration method provided by this invention can calibrate the optical axis parallelism of three optical components inside the camera to be calibrated: the thermal imaging lens, the visible light lens, and the supplementary light. It is also compatible with combinations of two components: the thermal imaging lens and the visible light lens, as well as combinations of the visible light lens and the supplementary light. Simultaneously, it can calibrate the visible light image output by the visible light lens and the thermal image output by the thermal imaging lens, thereby facilitating the accurate fusion of these two images. This method offers high precision, excellent optical axis calibration, and high image calibration accuracy, resulting in cameras produced using this method exhibiting superior overall performance.

[0146] Note that the above merely describes preferred embodiments of the application and the principles of the technology applied. Those skilled in the art will understand that the application is not limited to the specific embodiments described herein, and that various obvious changes, modifications, combinations and substitutions can be made thereto without departing from the scope of the application. Therefore, although the application has been described in detail by the above embodiments, the application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the application, and the scope of the application is determined by the appended claims.

Claims

1. An optical axis calibration device for optical axis calibration of a camera to be calibrated, characterized in that Comprising: a tested target, a light splitting element, an off-axis parabolic mirror and a calibration target; the tested target is located on the focal plane of the off-axis parabolic mirror, and the tested target is used to emit a calibration light beam, the calibration light beam comprises a visible light beam and an infrared light beam; the light splitting element is located on the propagation path of the calibration light beam, and the light splitting element is located at the focal point of the off-axis parabolic mirror; the calibration light beam is split by the light splitting element to form a transmitted light beam and a reflected light beam; the off-axis parabolic mirror is located on the propagation path of the reflected light beam, and the calibration target is located on the propagation path of the transmitted light beam for receiving the transmitted light beam to realize self-calibration of the optical axis calibration device; the tested target is provided with a heating mark for emitting the calibration light beam, the heating mark comprises a center heating mark located at the center of the tested target, and the calibration target comprises a through hole corresponding to the center heating mark; the reflected light beam is reflected by the off-axis parabolic mirror to form a parallel light beam, and a test area of the optical axis calibration device is located on the propagation path of the parallel light beam, and the test area is used to place the camera to be calibrated; the camera to be calibrated comprises a thermal imaging lens and a visible light lens, the visible light lens receives the parallel light beam to obtain a visible light image of the tested target, and the thermal imaging lens receives the parallel light beam to obtain a thermal imaging image of the tested target.

2. The optical axis calibration device according to claim 1, wherein: a light supplement calibration pattern is further arranged on the tested target, and the geometric center of the light supplement calibration pattern overlaps with the geometric center of the center heating mark.

3. The optical axis calibration device according to claim 1, wherein: the heating mark further comprises at least one edge heating mark located at the edge of the effective area of the tested target.

4. The optical axis calibration device according to claim 1, wherein: the optical axis calibration device further comprises a first displacement adjusting support, a second displacement adjusting support and a third displacement adjusting support; the first displacement adjusting support is connected with the light splitting element to adjust the position of the light splitting element; the second displacement adjusting support is connected with the tested target to adjust the position of the tested target; the third displacement adjusting support is connected with the calibration target to adjust the position of the calibration target.

5. The optical axis calibration device according to claim 1, wherein: the heating mark comprises a heating resistance wire.

6. The optical axis calibration device according to claim 1, wherein: the light splitting element comprises a half-mirror or a prism.

7. A method of optical axis alignment, applied to the optical axis alignment device according to any one of claims 1 to 6, characterized in that, Comprising: placing the camera to be calibrated on the test area; adjusting the focal length of the thermal imaging lens of the camera to be calibrated to a preset focal length, adjusting the position of the thermal imaging lens to make the thermal imaging lens capture a thermal imaging image of the center heating mark on the tested target, and the thermal imaging image of the center heating mark is located at the center of the field of view of the thermal imaging lens, the optical axis calibration of the thermal imaging lens is completed, and the thermal imaging lens is fixed. Adjusting the focal length of the visible light lens of the camera to be calibrated to a preset focal length, adjusting the position of the visible light lens, so that the visible light lens captures a visible light image of the center heating mark on the test target, and the visible light image of the center heating mark is located at the center of the field of view of the visible light lens, the optical axis of the visible light lens is calibrated, and the visible light lens is fixed.

8. The optical axis calibration method of claim 7, wherein, before adjusting the camera to be calibrated, the method further comprises: The test target is powered and heated; Adjusting the position of the light splitting element so that the light splitting element is located at the focal point position of the off-axis parabolic mirror; Adjusting the positions of the test target and the calibration target so that the center heating mark on the test target corresponds to the through hole position of the calibration target.

9. The optical axis calibration method of claim 7, wherein, the test target is further provided with a light supplement calibration pattern, the geometric center of the light supplement calibration pattern overlaps with the geometric center of the center heating mark; after the optical axis of the visible light lens is calibrated and the visible light lens is fixed, the method further comprises: Adjusting the light emitting angle of the light supplement lamp of the camera to be calibrated to a preset angle, adjusting the position of the light supplement lamp of the camera to be calibrated, so that the light spot of the light supplement lamp on the test target is located in the light supplement calibration pattern. Further comprising: The heating mark further comprises at least one edge heating mark, and the edge heating mark is located at the edge of the effective area of the test target; After the optical axis of the visible light lens is calibrated and the visible light lens is fixed, and the optical axis of the thermal imaging lens is calibrated and the thermal imaging lens is fixed, the method further comprises:

10. The optical axis calibration method of claim 7, wherein, Obtaining a visible light image of the edge heating mark through the visible light lens as a first calibration image; Obtaining a thermal imaging image of the edge heating mark through the thermal imaging lens as a second calibration image; Calibrating the visible light image output by the visible light lens and the thermal imaging image output by the thermal imaging lens according to the first calibration image and the second calibration image. ​ ​ ​

Images