A fish-eye lens dynamic measurement device and an optical axis detection method

Abstract

The present invention relates to a fish-eye lens dynamic measurement device and an optical axis detection method, including a robotic arm and a fish-eye lens. The number of the robotic arms is at least two, and at least two of the robotic arms and the fish-eye lens are rotatably arranged. The optical axis of the fish-eye lens coincides with the central axis of the robotic arm. A number of light sources with uniform light emission are spaced inside the robotic arm, and the distance between each light source and the fish-eye lens is the same. Test cards are respectively installed on the number of light sources for detecting the performance parameters of the fish-eye lens. The main purpose of the present invention is to provide a fish-eye lens dynamic measurement device and an optical axis detection method, which have a simple structure, are easy to implement, have a low production cost, are accurately measured, and have high efficiency.

Description

Technical Field

[0001] The present invention relates to the field of fish-eye lens detection, and particularly to a fish-eye lens dynamic measurement device and an optical axis detection method. Background Art

[0002] With the continuous development of optical technology, lenses with a field of view angle exceeding 180 degrees such as fish-eye lenses have received increasing attention and popularity, and their applications have become more and more widespread. To achieve the maximum field of view angle of the lens, the diameter of its front lens bulges forward in a parabolic shape. The field of view angle of a fish-eye lens can reach or even exceed the range that the human eye can see. Since the field of view angle of a fish-eye lens often reaches more than 180 degrees, in the production and detection process of fish-eye lenses, the plane test card used in conventional projection detection cannot detect angles above 160 degrees, so there are detection dead angles; to overcome this defect, a hemispherical test card has been specifically designed for such ultra-wide-angle lenses for shooting tests. However, the hemispherical test card not only has a complex manufacturing process, but also has high requirements for lighting technology because uniform lighting is required during testing, and it is not easy to implement. In addition, when testing different parameters, different test cards need to be sequentially replaced, and the process is quite time-consuming and laborious.

[0003] Regarding the optical axis detection and calibration method of the lens, after retrieval, Chinese Patent No. CN201611178375.2, with the authorization announcement date of February 26, 2019, and the invention creation name: An optical axis detection and calibration method for an ultra-wide-angle lens. This application case includes the following steps: obtaining a standard image obtained by imaging a chart by an ultra-wide-angle lens in an ideal state; clamping the ultra-wide-angle lens to be calibrated with a fixture, and adjusting the distance between the fixture and the chart to be d; calculating the angle between each elliptical image and the concentric circle image corresponding to the elliptical image in the standard image according to the distance between the original concentric circles on the chart and the distance between the concentric circle images in the standard image; rotating the imaging plane of the ultra-wide-angle lens to be calibrated in the reverse inclination direction by an inclination angle to obtain the inclined correction imaging plane of the ultra-wide-angle lens to be calibrated. This application case is not affected by the large distortion of the wide-angle lens and can accurately detect the inclination angle of the wide-angle lens; however, this application case is not applicable to a three-dimensional hemispherical chart, and the steps of detection and correction are complex and time-consuming, and further improvement is required. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a fish-eye lens dynamic measurement device with a simple structure, easy to implement, low production cost, accurate measurement, and high efficiency.

[0005] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0006] A fish-eye lens dynamic measurement device, comprising a robotic arm and a mounting platform. A fish-eye lens is detachably mounted on the mounting platform. The number of the robotic arms is at least two, and the robotic arms are rotatably arranged relative to the mounting platform. The optical axis of the fish-eye lens coincides with the central axis of the robotic arm. A number of light sources with uniform light emission are spaced inside the robotic arm, and the distance between each light source and the fish-eye lens is the same. Test cards are respectively mounted on the number of light sources.

[0007] Further, the light source is an LED light source with uniform light emission.

[0008] Further, the number of the robotic arms is 2 - 4.

[0009] Further, test cards for testing different performance parameters are respectively mounted on each of the robotic arms.

[0010] Further, each of the test cards is tangent to an arc centered on the fish-eye lens.

[0011] An optical axis detection method based on the fish-eye lens dynamic measurement device. A number of holes penetrating through the robotic arm are spaced on the robotic arm, and the centers of the number of holes are in the same plane. The number of holes and the number of light sources are arranged alternately. A point light source is correspondingly arranged at each hole, and the perpendicular distance from the point light source to the inner side surface of the robotic arm is greater than zero. The detection method includes starting the fish-eye lens to take a picture to obtain an image, and connecting a number of point light sources on the same robotic arm in the image to form a number of reference lines;

[0012] If the number of reference lines is the same as the number of robotic arms and all are straight lines, it indicates that the optical axis of the fish-eye lens coincides with the central axis of the robotic arm;

[0013] If the number of reference lines is the same as the number of robotic arms and there is an arc among the reference lines, it indicates that the optical axis of the fish-eye lens has a tilt angle relative to the central axis of the robotic arm but no offset;

[0014] If the number of reference lines is inconsistent with the number of robotic arms, it indicates that the optical axis of the fish-eye lens has an offset relative to the central axis of the robotic arm.

[0015] Further, the hole is a long and narrow slit.

[0016] Further, the point light source is located at the middle position of the long and narrow slit.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention solves the problems of difficult production of a hemispherical test card designed for a fish-eye lens and difficult realization of uniform lighting, and designs a brand-new test structure; adopting this structure, only an existing conventional planar test card can be used to complete the detection. Different test cards with different detection performances can be placed on different robotic arms at the same time. Moreover, due to the adoption of a dynamically rotatable structure, various parameters of multiple fields of view with different fields of view can be measured at one time for each test card; compared with the prior art, the structure is simplified, the manufacturing process is simple and easy to implement, and the measurement efficiency and measurement accuracy are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a three-dimensional structure diagram of a fish-eye lens dynamic measurement device of the present invention;

[0019] Figure 2 is a three-dimensional structure diagram of another perspective of a fish-eye lens dynamic measurement device of the present invention;

[0020] Figure 3 is a top view of a fish-eye lens dynamic measurement device of the present invention;

[0021] Figure 4 is a bottom view of a fish-eye lens dynamic measurement device of the present invention;

[0022] Figure 5 is a cross-sectional view of the front view when the number of robotic arms in a fish-eye lens dynamic measurement device of the present invention is one;

[0023] Figure 6 is a reference example diagram in a method for detecting the optical axis of the present invention;

[0024] Figure 7 is a schematic diagram of the installation method of a test card in a fish-eye lens dynamic measurement device of the present invention;

[0025] Wherein, 1, robotic arm; 2, installation platform; 3, fish-eye lens; 4, light source; 5, test card; 6, field of view; 7, point light source; 71, reference line; 8, hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0027] It should be noted that in the description of the technical solution of the present invention, in order to clearly describe the technical features of the present invention, some orientation words are used, such as "front", "rear", "upper", "lower", "top", "bottom", "inner", "outer", etc., which are all in terms of the orientation of the drawings of the present invention.

[0028] Embodiment

[0029] As Figure 1 , Figure 2 , Figure 3 and Figure 4 shown, a dynamic measurement device for a fish-eye lens according to this embodiment includes a robotic arm 1 and a mounting platform 2. A fish-eye lens 3 is detachably mounted on the mounting platform 2. The specific mounting method of the fish-eye lens 3 adopts a structure in the prior art, such as snap connection or embedding, etc. The robotic arm 1 is in an arch-shaped structure or a hemispherical structure, and several light sources 4 are provided at intervals inside. Specifically, in this embodiment, the robotic arm 1 adopts an arch-shaped structure, and the number of robotic arms 1 is at least two. Generally, it is preferably 2-4. Specifically, in this embodiment, the number of robotic arms 1 is preferably 3. The robotic arm 1 is relatively rotatably arranged with the mounting platform 2. Specifically, in this embodiment, the robotic arm 1 is fixedly arranged, and the specific fixing method is the prior art. The mounting platform 2 is rotatably arranged, and the specific rotation method is the prior art. The rotation speed of the mounting platform 2 is adjustable. When the mounting platform 2 rotates, it can drive the fish-eye lens 3 to rotate. The bottom of the mounting platform 2 is connected to a driving device. The driving device includes a driving motor and a speed reducer. The driving motor is connected to the speed reducer, and the speed reducer is connected to the bottom of the mounting platform 2. When the driving motor is started, it can drive the mounting platform 2 to rotate through the speed reducer, and the rotation speed of the mounting platform 2 can be adjusted by adjusting the rotation speed of the driving motor. In addition, the driving device of the mounting platform 2 is not limited to the structure described in this embodiment, and other structures in the prior art can also be adopted as long as the rotation and speed adjustment of the mounting platform 2 can be achieved.

[0030] In this embodiment, the optical axis of the fish-eye lens 3 coincides with the central axis of the robotic arm 1. A number of light sources 4 with uniform light emission are arranged at intervals inside the robotic arm 1. The specific number of the light sources 4 is determined according to specific test requirements. The light source 4 uses an LED light source with uniform light emission, which has a small volume, a long service life, no radiation, and can be recycled, belonging to a green lighting source. The distance between each light source 4 and the fish-eye lens 3 is the same. Test cards 5 are respectively installed on a number of the light sources 4 for detecting the performance parameters of the fish-eye lens 3. The test cards 5 on the same robotic arm 1 can detect the parameters of different fields of view 6. Each test card 5 is tangent to the arc centered on the fish-eye lens 3. The test card 5 can be a resolution test card, a contrast test card, an HDR high dynamic range test card, a uniformity test card, etc.; test cards 5 for testing different performance parameters are respectively installed on each robotic arm 1. For example, when it is necessary to test the resolution, contrast, and uniformity of the fish-eye lens 3, a resolution test card is respectively installed on a number of the LED light sources of the first robotic arm 1, a contrast test card is respectively installed on a number of the LED light sources of the second robotic arm 1, and a uniformity test card is respectively installed on a number of the LED light sources of the third robotic arm 1. In this way, the resolution, contrast, and uniformity parameters of different field angles can be tested simultaneously; and when the fish-eye lens 3 rotates one week, the resolution, contrast, and uniformity parameters of different fields of view of the fish-eye lens 3 can be tested. The specific test steps for testing the parameters of the lens using the test card 5 are prior art and will not be elaborated here. In this embodiment, according to the international standard ISO / FDIS 12233:1999(E), when testing the resolution of the fish-eye lens 3, the rectangular test card 5 is installed and placed at a 5-degree oblique angle (as Figure 7 shown).

[0031] A fish-eye lens dynamic measurement device in this embodiment solves the problems that it is difficult to manufacture a hemispherical test card designed for the fish-eye lens 3 and it is not easy to achieve uniform light illumination. A brand-new test structure is designed. In this structure, the number of the robotic arms 1 and the number of the light sources 4 on the robotic arm 1 are both determined according to specific test requirements. By adopting this structure, only the existing conventional planar test card can be used to complete the detection. With the planar test card and the flat-panel LED light source, uniform light illumination of the test card 5 can be realized; different test cards 5 for detecting different performances can be placed on different robotic arms 1 at the same time. Moreover, due to the adoption of a rotatable dynamic structure, when the installation platform 2 rotates one week at an angular velocity w and the fish-eye lens 3 takes pictures at hfps per second, each test card 5 will be photographed with images at an interval of w / h degrees. One week of rotation will take (360 / w)*h images; therefore, each type of test card 5 can measure the parameter values of different fields of view of multiple fields at one time. Compared with the prior art, the structure is simplified, the manufacturing cost is reduced, the manufacturing process is simple and easy to implement, and the measurement efficiency and measurement accuracy are significantly improved.

[0032] In addition, by adopting this dynamic structure, it can also be used to test the frame rate limit of the camera. Since different angular velocities w and different field of view 6 radii can make the test card 5 have different relative moving speeds, in this embodiment, taking one of the light sources 4 as an example, the specific detection is as follows: As Figure 5 shown, the installation platform 2 rotates at an angular velocity w. The distance between the light source 4 and the fisheye lens 3 is R. The angle between the line connecting the center of the test card 5 on the light source 4 and the optical axis of the fisheye lens 3 is θ. The vertical distance between the center of the test card 5 and the optical axis of the fisheye lens 3, that is, the radius of the field of view 6 corresponding to the test card 5 is R*sinθ. When taking the installation platform 2 as a reference object, the relative rotational moving speed of the center of the test card 5 is w*R*sinθ. When the frame rate of the fisheye lens 3 is f, the pixel is located at a position R away from the fisheye lens 3, and the center distance between adjacent pixels captured is p. If the frame rate f of the fisheye lens 3 is greater than (w*R*sinθ) / p, then there will be no afterimage (ghosting) in the captured adjacent pixels. As the rotational angular velocity w gradually increases, when there is an afterimage (ghosting) in the captured adjacent pixels, that is, when the frame rate f of the fisheye lens 3 starts to be less than (w*R*sinθ) / p, this is the frame rate limit of the fisheye lens 3 at this time.

[0033] As Figure 5 and Figure 6 shown, based on the above optical axis detection method of the fisheye lens dynamic measurement device, it is used to detect whether the optical axis of the fisheye lens 3 is offset or tilted relative to the central axis of the robotic arm 1. A number of holes 8 penetrating the robotic arm 1 are evenly distributed on each robotic arm 1. The centers of the number of holes 8 are in the same plane. The connection lines of the number of holes 8 on the same robotic arm 1 can form an arc with the same radian as the robotic arm 1. The number of holes 8 and the number of light sources 4 are arranged alternately. A point light source 7 is correspondingly arranged at each hole 8. The vertical distance from the point light source 7 to the inner side surface of the robotic arm 1 is greater than zero. The point light source 7 uses an LED light source. Specifically, in this embodiment, the point light source 7 is installed on the outer side surface of the robotic arm 1. This detection method includes starting the fisheye lens 3 to take pictures to obtain a picture, and connecting the number of point light sources 7 on the same robotic arm 1 on the picture to form a number of reference lines 71; since the offset or tilt of the optical axis of the fisheye lens 3 relative to the central axis of the robotic arm 1 is generally very small, the patterns presented on the picture are generally divided into the following several situations,

[0034] The first situation: If the number of reference lines 71 is the same as the number of robotic arms 1 and they are all straight lines (as Figure 6 shown in a), it means that the optical axis of the fisheye lens 3 coincides with the central axis of the robotic arm 1; no correction is required.

[0035] The second case: If the number of reference lines 71 is the same as the number of robotic arms 1 and one of the reference lines 71 is an arc (as shown in Figure 6 Figure b), it indicates that the optical axis of the fish-eye lens 3 has a tilt angle relative to the central axis of the robotic arm 1 but no offset; during calibration, first rotate the optical axis of the fish-eye lens 3 until one of the reference lines 71 is straight. At this time, the optical axis of the fish-eye lens 3 is tilted along the axis where the straight reference line 71 is located. Then, rotate the optical axis of the fish-eye lens 3 along the axis where the straight reference line 71 is located until all the reference lines 71 in the captured photo are straight.

[0036] The third case: If the number of reference lines 71 is different from the number of robotic arms 1, it indicates that the optical axis of the fish-eye lens 3 has an offset relative to the central axis of the robotic arm 1. Specifically, if there is only one straight reference line 71 in the photo (as shown in Figure 6 Figure c), it indicates that the optical axis of the fish-eye lens 3 has an offset relative to the central axis of the robotic arm 1, and the optical axis of the fish-eye lens 3 is offset along the axis where the reference line 71 is located. During calibration, move the optical axis of the fish-eye lens 3 along the axis where the reference line 71 is located until several reference lines 71 with the same number as the robotic arms 1 appear in the captured photo. Then, observe the several reference lines 71. If they are all straight, there is no need to continue calibration. If there are arcs, use the method in the second case above to continue calibration.

[0037] The fourth case: If there is no reference line 71 in the photo, it indicates that the optical axis of the fish-eye lens 3 has an offset relative to the central axis of the robotic arm 1, and the offset direction does not coincide with any of the robotic arms 1. At this time, first rotate the mounting platform 2 until at least one reference line 71 appears in the captured photo, which indicates that there is also a tilt. Then, continue calibration by referring to the method in the third case above; if rotating the fish-eye lens 3 or the robotic arm 1 can never make at least one reference line 71 appear in the captured photo, it indicates that there is no tilt. At this time, directly move the optical axis of the fish-eye lens 3 until all the reference lines 71 in the captured photo are straight, and the calibration is completed.

[0038] In addition, to better implement the above detection method, the hole 8 in this embodiment is a long strip-shaped slit, and the maximum width of the long strip-shaped slit does not exceed 1 / 5 of the thickness of the robotic arm 1. Preferably, the width of the long strip-shaped slit is 1 / 50 - 1 / 30 of the thickness of the robotic arm 1. With this width setting, when the optical axis of the fish-eye lens 3 is offset, the point light source 7 will be blocked by the long strip-shaped slit and thus cannot be photographed, which can improve the accuracy of detection. At the same time, the point light source 7 is located at the middle position of the long strip-shaped slit, so that it is possible to detect whether the fish-eye lens 3 has a vertical offset relative to the center of the hemispherical surface where the robotic arm 1 is located through the photographed picture. Specifically, if the fish-eye lens 3 is offset upward in the vertical direction, the position of the point light source 7 in the photographed picture will deviate from the middle position of the long strip-shaped slit and shift outward; conversely, if the fish-eye lens 3 is offset downward in the vertical direction, the position of the point light source 7 in the photographed picture will deviate from the middle position of the long strip-shaped slit and shift inward.

[0039] A method for detecting the optical axis of the present invention is used to detect whether the optical axis of the fish-eye lens 3 in the above fish-eye lens dynamic measurement device coincides with the central axis of the robotic arm 1. The detection method is intuitive and effective, the calibration steps are simple and convenient, the whole process saves time and effort, is easy to operate, has high detection efficiency and good accuracy, and can effectively ensure the measurement accuracy of the fish-eye lens dynamic measurement device.

[0040] For those skilled in the art, various corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all such changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A method for detecting the optical axis of a fisheye lens dynamic measurement device, characterized in that: The device includes a robotic arm (1) and a mounting platform (2). A fisheye lens (3) is detachably mounted on the mounting platform (2). The number of robotic arms (1) is at least two. The robotic arm (1) is rotatably arranged relative to the mounting platform (2). The optical axis of the fisheye lens (3) coincides with the central axis of the robotic arm (1). A number of uniformly illuminated light sources (4) are spaced inside the robotic arm (1). The distance between each light source (4) and the fisheye lens (3) is the same. Test cards (5) are respectively mounted on a number of the light sources (4). A number of holes (8) penetrating through the robotic arm (1) are spaced on the robotic arm (1). The holes (8) are long and narrow slits. The centers of a number of the holes (8) are in the same plane. A number of the holes (8) and a number of light sources (4) are arranged alternately. A point light source (7) is correspondingly arranged at each hole (8). The perpendicular distance from the point light source (7) to the inner side surface of the robotic arm (1) is greater than zero. This detection method includes starting the fisheye lens (3) to take pictures, and connecting a number of point light sources (7) belonging to the same robotic arm (1) on the pictures to form a number of reference lines (71). If the number of reference lines (71) is the same as the number of robotic arms (1) and all are straight lines, it indicates that the optical axis of the fisheye lens (3) coincides with the central axis of the robotic arm (1). If the number of reference lines (71) is the same as the number of robotic arms (1) and there is a reference line (71) that is an arc, it indicates that the optical axis of the fisheye lens (3) has a tilt angle relative to the central axis of the robotic arm (1) but no offset. If the number of reference lines (71) is inconsistent with the number of robotic arms (1), it indicates that the optical axis of the fisheye lens (3) has an offset relative to the central axis of the robotic arm (1).

2. The method for detecting the optical axis of a fisheye lens dynamic measurement device according to claim 1, characterized in that: The light source (4) is an LED light source with uniform illumination.

3. The method for detecting the optical axis of a fisheye lens dynamic measurement device according to claim 2, characterized in that: The number of robotic arms (1) is 2 - 4.

4. The method for detecting the optical axis of a fisheye lens dynamic measurement device according to claim 3, characterized in that: Test cards (5) for testing different performance parameters are respectively mounted on each robotic arm (1).

5. The method for detecting the optical axis of a fisheye lens dynamic measurement device according to claim 1 or 4, characterized in that: Each test card (5) is tangent to an arc centered on the fisheye lens (3).

6. The method for detecting the optical axis according to claim 1, characterized in that: The point light source (7) is located at the middle position of the long and narrow slit.

Images