Camera flange distance detection device

Abstract

The utility model discloses a camera flange distance detection device, which comprises a reference platform, a lens, a calibration plate and an image acquisition unit, and is characterized in that the reference platform comprises a shell and a Sensor plate arranged in the shell, the shell is provided with a first through hole penetrating along a first direction, and a photosensitive chip on the Sensor plate is arranged to directly face the first through hole; the shell has a standard flange distance in the first direction; the lens is coaxially connected with the first through hole; the calibration plate is located on one side of the lens away from the reference platform; and the image acquisition unit is electrically connected with the Sensor plate and is used for acquiring an MTF value of the lens through calibration of the lens by the calibration plate, and flange distance detection is carried out on the camera by replacing the reference platform as the camera during use. The device is simple to operate when camera flange distance detection is realized, and is high in detection precision, high in efficiency and low in cost.

Description

Technical Field

[0001] The utility model belongs to the technical field of lens detection, and in particular relates to a camera flange distance detection device. Background Art

[0002] The C-mount is a common camera mount with a fixed flange focal distance of 17.526mm. This ensures that light accurately converges on the camera chip when used with a C-mount lens, resulting in clear images. The flange focal distance, measuring the distance from the camera's mount's reference plane to the image plane, is a key parameter for measuring the compatibility between lens and camera. However, due to manufacturing and assembly tolerances of camera components, it's difficult to precisely control the flange focal distance within the required tolerance, requiring repeated adjustments to achieve the desired image clarity.

[0003] A lens's MTF curve quantitatively describes its image clarity. Back focal length, the distance between the last surface of the lens' optical system and the imaging sensor, primarily affects image clarity and focal plane position. For the same lens, varying back focal lengths can lead to significant differences in the MTF values ​​obtained by processing and calculating the line pairs captured by the image acquisition device.

[0004] A Chinese patent application with authorization announcement number CN218584314U proposes a lens flange focal length detection device, comprising a light source module, a target plate, a collimating lens, a beam splitter, a standard block, an imaging objective lens, and an imaging module. The lens to be tested is located between the beam splitter and the standard block. Light emitted by the light source module passes through the target plate and is collimated by the collimating lens. The resulting parallel light beam passes through the beam splitter and the lens to be tested, and is focused on the standard block. The light is reflected by the standard block and then returned. After being reflected by the beam splitter, it is imaged onto the imaging module through the imaging objective lens. A lens with a flange focal length that meets the tolerance range is placed in the detection system of the utility model. The distance between the standard block and the lens to be tested is adjusted to ensure the clearest image on the imaging module (at this time, the standard block is located at the optimal focal plane of the lens to be tested). Then, lenses from the same batch are placed in the corresponding position. If the image is blurred, the distance of the standard block relative to the lens to be tested is moved until it becomes clear again. The error of the lens flange focal length is obtained by the distance the standard block moves forward or backward. The detection device of the utility model can improve the error accuracy of the lens flange focal length to ±30μm. However, there are the following disadvantages: 1) A lens with a flange focal length that meets the tolerance range is used as the measurement benchmark. First of all, the flange focal length of the lens used as the benchmark itself has a tolerance, especially at the upper or lower limit of the tolerance. Judging other lenses of the same batch based on this benchmark will cause transmission errors, resulting in misjudgment and inaccurate measurement, which is not conducive to improving the accuracy of the test results; 2) After each inspection of other lenses of the same batch, when they are replaced, after the standard block is moved, the new lens with a flange focal length that meets the tolerance needs to be placed on the inspection table for calibration each time. The operation is not simple and the efficiency is low; 3) The structure of the detection equipment is complex, and the direction of the light is also complex, which can easily cause cumulative errors, thereby affecting the accurate measurement of the flange focal length of the lens. Utility Model Content

[0005] The purpose of the present invention is to solve the above problems and to provide a camera flange distance detection device, which has simple operation, high detection accuracy, high efficiency and low cost.

[0006] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0007] The present invention proposes a camera flange focal length detection device, comprising a reference platform, a lens, a calibration plate, and an image acquisition unit, wherein:

[0008] The reference platform includes a housing and a sensor board built into the housing. The housing is provided with a first through hole extending along a first direction. The photosensitive chip on the sensor board is arranged opposite the first through hole, so that the housing has a standard flange distance in the first direction.

[0009] a lens coaxially connected to the first through hole;

[0010] The calibration plate is located on the side of the lens away from the reference platform;

[0011] The image acquisition unit is electrically connected to the sensor board and calibrates the lens through the calibration board to collect the MTF value of the lens. When in use, the reference platform is replaced with the camera to detect the flange focal length of the camera.

[0012] Preferably, the camera flange distance detection device further includes a supporting platform, the reference platform or the camera is mounted on the supporting platform, and the axis of the first through hole is perpendicular to the outer bottom surface of the supporting platform.

[0013] Preferably, the camera is further connected to the lens via an adapter ring, and the adapter ring is a CS adapter ring.

[0014] Preferably, the reference platform further includes an FPC cable, IR glass and a bracket. The image acquisition unit and the sensor board are electrically connected via the FPC cable. The IR glass is connected to the sensor board via the bracket. The IR glass is located between the sensor board and the lens.

[0015] Preferably, the distance between the calibration plate and the lens is 40 cm to 60 cm.

[0016] Preferably, the standard flange distance is the C-port flange distance, that is, 17.526 mm.

[0017] Preferably, the image acquisition unit is an image acquisition box.

[0018] Preferably, the calibration board is a Chart board.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This application can utilize the correspondence between the MTF value and the mechanical back focus of the lens, effectively reducing the difficulty of processing and assembling the detection equipment. All data can be measured and read, and the operation is simple and convenient, with high precision. For example, the precision can reach more than ±20um, and the efficiency is greatly improved, ensuring production efficiency and the judgeability and accuracy of the detection results, and has a wide range of applications. The performance requirements for the jigs used in the detection process (such as the carrier, lens, and calibration plate) are not high, which is conducive to reducing costs while ensuring accuracy and is easy to implement and popularize. The flange distance of the camera can be adjusted during detection through the adapter ring to ensure that the flange distance of the camera is within a reasonable range, which is conducive to expanding product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic structural diagram of the camera flange distance detection device of the present invention;

[0022] Figure 2 This is an assembly cross-sectional view of the support platform, reference platform and lens of the utility model;

[0023] Figure 3 For this utility model Figure 2 A partial enlarged view of FIG1;

[0024] Figure 4 This is a schematic diagram of the structure of the camera flange distance detection of the utility model;

[0025] Figure 5 This is a graph showing the relationship between the MTF value and the mechanical back focus of the lens of the present invention.

[0026] Explanation of the accompanying symbols: 1. Carrying platform; 2. Reference platform; 3. Lens; 4. Calibration plate; 5. Image acquisition unit; 6. Camera; 7. Adapter ring; 21. Housing; 22. Sensor board; 23. FPC cable; 24. IR glass; 25. Bracket. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0028] It should be noted that when a component is referred to as being "connected" to another component, it may be directly connected to the other component or there may be an intermediate component. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art in the art of this application. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0029] like Figure 1-5 As shown, a camera flange focal length detection device includes a reference platform 2, a lens 3, a calibration plate 4 and an image acquisition unit 5, wherein:

[0030] The reference platform 2 includes a housing 21 and a sensor board 22 built into the housing 21. The housing 21 is provided with a first through hole extending along a first direction. The photosensitive chip on the sensor board 22 is arranged opposite the first through hole, so that the housing 21 has a standard flange distance in the first direction.

[0031] Lens 3, coaxially connected to the first through hole;

[0032] The calibration plate 4 is located on the side of the lens 3 away from the reference platform 2;

[0033] The image acquisition unit 5 is electrically connected to the sensor board 22 and calibrates the lens 3 through the calibration board 4 to collect the MTF value of the lens 3. When in use, the reference platform 2 is replaced with the camera 6 to detect the flange focal length of the camera 6.

[0034] The camera flange focal distance detection device includes a reference platform 2, a lens 3, a calibration plate 4, and an image acquisition unit 5. The reference platform 2 includes a housing 21 and a sensor board 22 built into the housing 21. The housing 21 can be of any structure, such as a high-precision hollow housing machined using a CNC (numerically controlled) machine. This housing is a standard housing, preferably capable of ensuring a C-mount flange focal distance of 17.526 mm. The sensor board 22 is internally mounted and is used to connect to the image acquisition unit 5 for information collection. The lens 3 (e.g., a C-mount lens) does not require any special performance (e.g., image quality) and any specification can be used. The lens 3 is screwed into the standard housing, and the calibration plate 4 is placed on the side of the lens 3 away from the reference platform 2. The sensor board 22 is connected to the image acquisition unit 5. By adjusting the lens 3, the MTF value of the lens 3 can be obtained through the image acquisition unit 5. Based on the correspondence between the MTF value and the mechanical back focus of the lens, the flange focal distance of the camera 6 can be detected with high accuracy and is convenient and fast.

[0035] In one embodiment, the camera flange distance detection device further includes a support platform 1, on which the reference platform 2 or the camera 6 is mounted, and the axis of the first through hole is perpendicular to the outer bottom surface of the support platform 1. The support platform 1 enables the standard housing to be vertically upward, which helps ensure measurement accuracy.

[0036] In one embodiment, the camera 6 is further connected to the lens 3 via an adapter ring 7, which is a CS adapter ring. The adapter ring 7 allows the flange focal distance of the camera 6 to be adjusted during testing to ensure that the flange focal distance of the camera 6 is within a reasonable range, thereby increasing product yield.

[0037] In one embodiment, the reference platform 2 further includes an FPC cable 23, an IR glass 24 and a bracket 25. The image acquisition unit 5 and the sensor board 22 are electrically connected through the FPC cable 23. The IR glass 24 is connected to the sensor board 22 through the bracket 25. The IR glass 24 is located between the sensor board 22 and the lens 3.

[0038] In one embodiment, the distance between the calibration plate 4 and the lens 3 is 40 cm to 60 cm, preferably 50 cm, which can achieve excellent imaging effects.

[0039] In one embodiment, the standard flange distance is the C-port flange distance, i.e., 17.526 mm. The standard flange distance can be adjusted to the required flange distance according to the actual application scenario.

[0040] In one embodiment, the image acquisition unit 5 is an image acquisition box, which is a prior art and is used to acquire MTF values. It is a technology well known to those skilled in the art and will not be described in detail here.

[0041] In one embodiment, the calibration plate 4 is a Chart plate, or may be other calibration plates well known to those skilled in the art.

[0042] Working principle:

[0043] After the camera flange focal length detection device is built, the lens 3 can be adjusted and the corresponding relationship between the MTF value and the mechanical back focus of the lens can be recorded. The image acquisition unit 5 reads the MTF value of the lens 3 to determine a reasonable MTF range. For example, by adjusting the lens 3, the mechanical back focus at the maximum MTF value (MAX-MTF) is determined, and the MTF value (Right-MTF) of the preset mechanical back focus is increased or decreased (Left-MTF) relative to the mechanical back focus at the maximum MTF value within the required accuracy. Then the reasonable MTF range is between MAX-MTF and Right-MTF or between MAX-MTF and Left-MTF. The corresponding relationship between the MTF value and the mechanical back focus of the lens can be referred to as Figure 5 Then, the reference platform 2 is replaced with the camera 6, the lens 3 is screwed into the camera 6, and the current MTF value is read. When the current MTF value falls within a reasonable MTF range, it is considered that the flange focal length of the camera 6 is qualified, that is, the camera 6 meets the requirements. Otherwise, the camera 6 is a defective product. The adapter ring 7 can be further adjusted until the current MTF value falls within a reasonable MTF range. Then, the flange focal length of the camera 6 is considered to meet the requirements. Locking the adapter ring 7 of the camera 6 can ensure that the flange focal length of the camera 6 meets the requirements, and the camera 6 is calibrated to a good product, thereby increasing the product yield.

[0044] This application utilizes the correspondence between the MTF value and the mechanical back focus of the lens to effectively reduce the difficulty of processing and assembling the detection equipment. All data can be measured and read, and the operation is simple and convenient, with high precision, the precision can reach more than ±20um, and the efficiency is greatly improved, ensuring production efficiency and the judgeability and accuracy of the detection results, and has a wide range of applications; the requirements for the jigs used in the detection process (such as the carrier, lens, calibration plate) are not high, which is conducive to reducing costs while ensuring accuracy and is easy to implement and popularize; and the flange distance of the camera can be adjusted during detection through the adapter ring to ensure that the flange distance of the camera is within a reasonable range, which is conducive to expanding product yield.

[0045] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0046] The above-described embodiments merely represent specific and detailed examples of the present application and should not be construed as limiting the scope of the patent application. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A camera flange focal distance detection device, characterized by: The camera flange distance detection device comprises a reference platform (2), a lens (3), a calibration plate (4) and an image acquisition unit (5), wherein: The reference platform (2) comprises a housing (21) and a sensor board (22) built into the housing (21), wherein the housing (21) is provided with a first through hole extending along a first direction, and a photosensitive chip on the sensor board (22) is arranged facing the first through hole, so that the housing (21) has a standard flange distance in the first direction; The lens (3) is coaxially connected to the first through hole; The calibration plate (4) is located on a side of the lens (3) away from the reference platform (2); The image acquisition unit (5) is electrically connected to the sensor board (22), and calibrates the lens (3) through the calibration board (4) to acquire the MTF value of the lens (3). When in use, the reference platform (2) is replaced with a camera (6) to perform flange focal length detection on the camera (6).

2. The camera flange focal distance detection device according to claim 1, wherein: The camera flange distance detection device further comprises a carrier platform (1), the reference platform (2) or the camera (6) is mounted on the carrier platform (1), and the axis of the first through hole is perpendicular to the outer bottom surface of the carrier platform (1).

3. The camera flange focal distance detection device according to claim 1, wherein: The camera (6) is also connected to the lens (3) via an adapter ring (7), and the adapter ring (7) is a CS adapter ring.

4. The camera flange focal distance detection device according to claim 1, wherein: The reference platform (2) further comprises an FPC cable (23), an IR glass (24) and a bracket (25); the image acquisition unit (5) and the sensor board (22) are electrically connected via the FPC cable (23); the IR glass (24) is connected to the sensor board (22) via the bracket (25); and the IR glass (24) is located between the sensor board (22) and the lens (3).

5. The camera flange focal distance detection device according to claim 1, wherein: The distance between the calibration plate (4) and the lens (3) is 40 cm to 60 cm.

6. The camera flange focal distance detection device according to claim 1, wherein: The standard flange distance is the C-port flange distance, which is 17.526 mm.

7. The camera flange focal distance detection device according to claim 1, wherein: The image acquisition unit (5) is an image acquisition box.

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