A lens focal length measurement method and device based on measuring light spot

Abstract

The present application discloses a lens focal length measurement method and device based on measuring light spots, and relates to the field of lens focal length measurement technology. The device comprises: a slidingly connected focal length measurement sub-device and a base; the focal length measurement sub-device arrangement comprises a parallel light generating component, a measured lens, a movable image receiving component and a computer arranged in sequence. The present application adopts the principle of projection method to measure focal length, and collects the light spot images of at least two measuring points before or after the initial focus and the distance between the measuring points. High-precision measurement of focal length can be achieved without knowing the position of the principal point of the measured lens, and the focal length value can be obtained by only moving the CCD detector forward and backward once during measurement, and the measurement process is simple and fast.

Description

Technical Field

[0001] The present application relates to the technical field of lens focal length measurement, and in particular to a lens focal length measurement method and device based on measuring light spots. Background Art

[0002] With the rapid development of optoelectronic science, people are increasingly using optical lenses. Optical lenses are involved in everything from distant deep space exploration to the glasses we wear every day. The focal length of a lens is an important parameter that determines the image quality, field of view, and perspective effect. Therefore, the measurement of the focal length of a lens is an important research topic in the field of optics. By measuring the focal length of a lens, we can evaluate and detect the accuracy, distortion, aberration and other indicators of the lens, thereby improving the design and production process of the lens. In the design and optimization of optical systems, accurate focal length data is crucial to ensure image quality and system performance.

[0003] Domestic and foreign scholars have conducted a lot of research on the measurement methods of lens focal length, and a variety of measurement methods have emerged. They can be roughly divided into imaging methods and non-imaging methods. Imaging focal length measurement methods include autocollimation method, conjugate method, object distance image distance method, magnification method, knife-edge target imaging, etc. Non-imaging measurement methods are mostly based on the theory of interference and diffraction with precise equipment to measure the lens focal length.

[0004] The lens focal length measurement method has gone through a long development from the early simple measurement to the modern high-precision instrument measurement. In the early stage of optical research, the measurement of lens focal length relied on simple imaging principles and experiments, and the focal length value was obtained by geometric methods. Early focal length measurement methods included autocollimation method, conjugate method and object distance image distance method; and with the emergence of various optical instruments and new technologies, new focal length measurement methods have also emerged: with the emergence of image sensors and the increasing maturity of computer simulation and image processing technology, image sensors have been widely used as image receiving devices in focal length measurement research. This makes focal length measurement not limited to traditional physical experiments.

[0005] By analyzing the image through a computer program, the optical parameters of the lens can be determined more accurately. This method reduces human errors and improves the repeatability and accuracy of the measurement, such as the magnification method, knife-edge target imaging, etc. The knife-edge target imaging method uses a knife-edge target to form an image, and the image is processed by the detector using image processing technology to obtain the focal length of the lens; laser is used as a measurement light source because of its good directionality and strong coherence. Based on this, focal length measurement methods based on interference theory have emerged, such as the Taber-Mohr method and laser differential interferometry. Through interference pattern analysis, the focal length and other optical parameters of the lens can be accurately measured. This method is suitable for the production and detection of high-precision optical components. In addition, there are measurement methods based on diffraction theory, such as the method of measuring the focal length of the lens based on Fresnel diffraction of phase step light.

[0006] In general, lens focal length measurement methods have undergone significant development from the initial simple geometric measurement to today's high-precision instrument measurement system. These advances have not only improved the accuracy of measurement, but also promoted the development of optical technology and applications.

[0007] However, the commonly used methods for measuring focal length, such as displacement method, autocollimation method, parallel light method, interference method, Talber-Mohr method and the later laser differential confocal interferometry, have the following defects:

[0008] The displacement method and the autocollimation method are the most primitive geometric optical measurement methods. They have a simple structure but relatively low accuracy. The parallel light method initially used manual readings, so the measurement results were affected by the subjectivity of the observer and the depth of focus, and had large errors. Although microscopic readings and CCD imaging readings were later used, although the measurement accuracy was high, the machine interpretation and processing of the image was relatively troublesome, and the presence of aberrations in the measurement system itself made the error relatively large and the measurement time long. For the interference method, the Taber-Mohr method, and the laser differential confocal interferometry method, these methods are all based on the principle of interference. These methods have the characteristics of high accuracy and can measure multiple parameters of optical lenses. However, the measurement principle is relatively complicated and easily interfered by the outside world, difficult to debug, and relatively costly.

[0009] That is, most of the currently used methods involve complex theoretical analysis or cumbersome measurement procedures, and are unable to achieve simple, efficient, and high-precision measurement of the lens focal length. Summary of the invention

[0010] The purpose of this application is to provide a lens focal length measurement method and device based on measuring light spots, which can simplify the lens focal length measurement procedure and realize simple, efficient and high-precision measurement of the lens focal length.

[0011] To achieve the above objectives, this application provides the following solutions:

[0012] In a first aspect, the present application provides a lens focal length measurement device based on measuring light spots, comprising: a focal length measurement sub-device and a base;

[0013] The focal length measurement sub-device is slidably connected to the base;

[0014] The focal length measurement sub-device arrangement specifically includes:

[0015] A parallel light generating component, a lens to be tested, a movable image receiving component and a computer are arranged in sequence;

[0016] The parallel light generating assembly is used to generate beam-expanded parallel laser light;

[0017] The lens under test is used to converge the beam-expanded parallel laser to obtain converged laser;

[0018] The movable image receiving component is used to collect spot images of at least two different measuring points, wherein the positions of the measuring points refer to positions within a preset range of an initial focus position, and the initial focus position is a focus position calibrated by moving the movable image receiving component to an initial position;

[0019] The computer is connected to the movable image receiving assembly, and is used to control the movable image receiving assembly to move on the base, and calculate the focal length of the measured lens according to the spot images of at least two different measuring points and the distances between the measuring points.

[0020] In a second aspect, the present application provides a lens focal length measurement method based on a measuring light spot, wherein the lens focal length measurement method based on a measuring light spot is implemented using the lens focal length measurement device based on a measuring light spot described in the first aspect, and the lens focal length measurement method based on a measuring light spot includes:

[0021] Acquire the spot images corresponding to at least two different measuring points and the distances between the measuring points, wherein the positions of the measuring points refer to positions within a preset range of an initial focus position, and the initial focus position is a focus position calibrated by moving the movable image receiving component to an initial position;

[0022] The focal length of the measured lens is calculated according to the distance between the light spot image and the measuring point.

[0023] According to the specific embodiments provided in this application, this application has the following technical effects:

[0024] The present application provides a lens focal length measurement method and device based on measuring light spots, the device comprising: a slidingly connected focal length measurement sub-device and a base; the focal length measurement sub-device arrangement comprises a parallel light generating component, a measured lens, a movable image receiving component and a computer arranged in sequence. The present application adopts the principle of projection method to measure focal length, and by collecting the light spot images of at least two measuring points before or after the initial focus and the distance between the measuring points, high-precision measurement of focal length can be achieved without knowing the position of the principal point of the measured lens, and during measurement, the focal length value can be obtained by only moving the CCD detector forward and backward once, and the measurement process is simple and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic structural diagram of a focal length measurement sub-device provided in Example 1 of the present application;

[0027] Figure 2 This is a schematic diagram of the principle of selecting two measurement points before and after the focus to measure the focal length in Example 1 of the present application;

[0028] Figure 3 This is a schematic diagram of the principle of selecting the first two measurement points of the focus to measure the focal length in Example 1 of the present application.

[0029] Reference numerals:

[0030] 1-Laser; 2-Collimation and beam expansion assembly; 3-Energy attenuation subassembly; 4-Measured lens; 5-Moveable image receiving assembly; 6-Computer. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0033] Example 1

[0034] The measurement method of lens focal length has also been rapidly developed with the improvement of scientific and technological level. Many new technologies and testing instruments have been introduced into the measurement system, which has continuously enriched the measurement means and improved the measurement accuracy.

[0035] In recent years, with the advancement of automation and intelligent technology, focal length measurement methods have also moved towards de-manualization, automation, and efficiency. The automated focal length measurement system that combines computer vision technology with automation technology can accurately and quickly measure the focal length of the lens, which not only improves the measurement speed, but also reduces the intervention of operators, making the measurement process more stable and reliable.

[0036] Most of the focal length measurement methods currently used have complex theoretical analysis or cumbersome measurement procedures, which cannot achieve simple, efficient and high-precision measurement of lens focal length. In addition, manual inspection and human eye interpretation are still used in lens processing inspection, which is not suitable for large-scale inspection.

[0037] This embodiment proposes a projection method for rapid measurement of lens focal length, which uses beam expansion parallel laser to measure focal length, and uses CCD detector to collect light spots and machine interpret images, avoiding the subjectivity of human readings, and making it easy to process the resulting images. The lens focal length measurement device is composed of a focal length measurement sub-device and a base, and the focal length measurement sub-device includes a parallel light generating component that can realize beam expansion laser and energy attenuation functions, a lens to be measured, a movable image receiving component and a computer. The measurement device has a simple structure, good stability and low cost.

[0038] The lens focal length measurement device based on measuring light spots provided in this embodiment includes: a focal length measurement sub-device and a base.

[0039] The focal length measuring sub-device is slidably connected to the base.

[0040] The focal length measurement sub-device arrangement specifically includes: a parallel light generating component, a measured lens, a movable image receiving component and a computer arranged in sequence.

[0041] The parallel light generating component is used to generate expanded beam parallel laser.

[0042] The parallel light generating component specifically comprises: a parallel light generating sub-component and an energy attenuation sub-component arranged in sequence;

[0043] The parallel light generating subassembly is used to generate a first beam-expanding parallel laser.

[0044] The energy attenuation subassembly is used to attenuate the energy of the first beam-expanded parallel laser to obtain the energy-attenuated beam-expanded parallel laser, and the energy-attenuated beam-expanded parallel laser is the beam-expanded parallel laser.

[0045] The parallel light generating subassembly specifically includes a laser and a collimating beam expanding assembly;

[0046] The laser is used to generate laser light;

[0047] The collimating and beam expanding component is used to perform collimating and beam expanding processing on the laser to obtain the first beam expanded parallel laser.

[0048] The collimating and beam expanding assembly specifically comprises: a concave lens and a convex lens arranged in sequence; the focus of the concave lens coincides with the focus of the convex lens.

[0049] The energy attenuation subassembly specifically includes: two polarizers arranged in sequence.

[0050] The measured lens is used to converge the beam-expanded parallel laser to obtain converged laser.

[0051] The movable image receiving component is used to collect spot images of at least two different measuring points, wherein the position of the measuring point refers to a position within a preset range of an initial focus position, and the initial focus position is a focus position calibrated by moving the movable image receiving component to an initial position.

[0052] The movable image receiving component specifically includes: a CCD detector and a motor.

[0053] The CCD detector and the motor are both connected to the computer.

[0054] The CCD detector is connected to the motor.

[0055] The CCD detector is slidably connected to the base.

[0056] The motor is used to drive the CCD detector to move on the base.

[0057] The CCD detector is used to collect light spot images corresponding to at least two different measuring points.

[0058] The computer is connected to the movable image receiving assembly, and is used to control the movable image receiving assembly to move on the base, and calculate the focal length of the measured lens according to the spot images of at least two different measuring points and the distances between the measuring points.

[0059] like Figure 1The lens focal length measurement sub-device of a specific structure shown in the figure is composed of a laser 1, a collimating and expanding assembly 2, an energy attenuation sub-assembly 3, a lens to be measured 4, a movable image receiving assembly 5 and a computer 6. The laser emitted by the laser is expanded and collimated to obtain parallel laser light required for measurement. The energy of the parallel laser light is then attenuated by the energy attenuation sub-assembly, and the attenuated parallel laser light is converged by the lens to be measured 4, and the converged light spot (i.e., the defocused light spot) is received by the CCD detector in the movable image receiving assembly 5. During measurement, the light spot images of different measurement points are received by moving the CCD detector, and the displacement size is recorded.

[0060] In the collimating beam expansion component 2, the focus of the first lens is overlapped with the focus of the second lens, so that the laser emitted by the laser 1 is expanded by a concave lens and a convex lens to obtain the parallel laser required for measurement. The energy attenuation subassembly attenuates the laser energy in the form of dual polarizer attenuation, and the purpose of accurately controlling the intensity of the transmitted light is achieved by controlling the angle between the polarization directions of the two polarizers. The light intensity passing through the two polarizers conforms to Malus's law. When measuring, the polarization direction of one polarizer is fixed and the other polarizer is rotated, so that the light intensity is attenuated from strong to weak, so that the CCD detector will not be saturated.

[0061] The movable image receiving component 5 is composed of a CCD detector and a motor thereunder. When measuring, the CCD detector position is first reset to zero to move it to the initial position, then the CCD detector is set for exposure time, and then the CCD detector is smoothly moved from the initial point to the final point after the focus, and the moving distance between the measurement points is recorded. The CCD detector then transmits the collected spot image to the computer for image processing, and the focal length value is obtained by solving or fitting.

[0062] The focal length measurement principle adopted in this embodiment, that is, the projection method, is based on the convergence effect of the lens on the light beam. It is not necessary to know the position of the principal point of the lens to be measured. The parallel light generated after the light beam is collimated and expanded is incident on the lens to be measured, and then converged by the lens to be measured and focused on the focal plane. The focal length value is obtained by measuring the size of the defocused light spot and the displacement between the two points before and after the focus, the two points before the focus, or the two points after the focus. If the two points before and after the focus are selected for focal length measurement, the measurement principle diagram is as follows: Figure 2 shown.

[0063] The light beam converges to Point, when measuring The position of the point is calibrated and Take two points before and after the point and , the size of the defocused light spot at these two points is and , the angle between the converging light and the optical axis is Due to the focal depth of the optical system, when the CCD detector receives the defocused light spot, due to the limitation of the resolution of the CCD detector and the influence of aberration, the number of pixels lit by the CCD detector is the same within a certain distance before and after the focus, and the observed light spot size does not change. Therefore, the position of the focus cannot be determined during measurement, so The position of the point is inaccurate. Therefore, when measuring, you cannot choose the distance between the two selected measurement points and the focus. You should choose to measure the distance between the two points. Set the distance between the two points before and after the focus. , The distance between , Click to The distance is , is the laser aperture size after collimation and beam expansion. From the similarity of triangles, we can conclude that:

[0064] (1);

[0065] Also because

[0066] (2);

[0067] From this, the measurement formula for focal length can be derived as follows:

[0068] (3).

[0069] When measuring two points in front of or behind the focus, simply calibrate the focus position before measuring. Select two measurement points before and , use CCD detector to measure the defocused spots at these two points. , The distance between two points is , and The sizes of the two light spots are and , the measurement principle diagram is as follows Figure 3 shown.

[0070] From the trigonometric relationship, we can get

[0071] (4);

[0072] Therefore, the formula for measuring focal length when selecting the first two points of the focus is as follows:

[0073] (5).

[0074] From the above two measurement principles, it can be seen that when measuring focal length, the convergence and position of the focal spot will not affect the focal length measurement in theory, because when measuring, we only need to know the relative position between the measuring point and the focal point, and the focal length value can be obtained by measuring the size of the defocused light spot and the distance between the two measuring points. In addition, due to the existence of a lens when using a CCD detector for measurement, the formula must be deduced forward, assuming that the magnification of the lens is Then the above formula (3) and formula (5) are transformed into the following formula (6) and formula (7) respectively.

[0075] (6);

[0076] (7).

[0077] In addition, the focal length can also be obtained by fitting, that is, the defocused spot is measured multiple times before or after the focus, and the distance from each measurement point to the selected edge point is recorded, and the linear fitting method is used to obtain the straight line and The intercept of the axis is the focal length of the lens being tested.

[0078] The entire focal length measurement sub-assembly is arranged on an optical bench or a movable guide rail, which is conducive to adjusting the axis consistency of the focal length measurement sub-assembly. The parallel laser generating sub-assembly can be designed as follows: Figure 1 The structure of the laser 1 and the collimating beam expansion component 2 shown, that is, the dot laser is matched with a set of Galilean beam expanders, or the dot laser with a collimating beam expansion component is directly used to realize the collimating beam expansion function, which can directly emit a highly parallel beam expansion laser. During the debugging process, a CCD detector can be used to receive the generated parallel laser, record the size of the defocused spot, and move forward or backward for a distance to record the size of the laser spot again. The generated parallel laser can be judged by comparing the size of the defocused spot twice before and after. When designing the energy attenuation subcomponent 3, the polarization attenuation method can be selected or the filter can be used to attenuate the beam energy. In the movable image receiving component, the CCD detector is fixed on the slider, and the slider is driven by the servo motor to move forward and backward to realize the forward and backward movement of the CCD detector. The computer is connected to the servo motor through the USB to serial port or the motor is controlled by wireless transceiver. Finally, the CCD detector is connected to the computer and the exposure time is set to perform subsequent measurements.

[0079] From the measurement principle, we know that we need to measure the distance between the two selected measurement points, followed by the size of the defocused light spot; for the moving distance between the measurement points, we can read it manually through the scale on the optical bench or rail. We can also calculate it through the rotation of the servo motor, that is, calculate the moving distance between the measurement points through the rotation angle and rotation number of the motor at different measurement points.

[0080] For the measurement of the defocused light spot, before the measurement, the CCD detector is moved to the initial position along the optical axis direction, and the focus position is simply calibrated. Then the measurement method is selected, and two points are taken before or after the focus for measurement, or the fitting method is used to set the detector exposure time.

[0081] The spot image of the measuring point collected by the CCD detector is transmitted to the computer, and the MTLAB software is used for image processing. First, the brightness of the spot image needs to be adjusted. Since the original spot image often has uneven internal light intensity distribution, the image is dark and the contrast is poor, this will directly affect the subsequent processing and edge detection of the image. Then the image is threshold segmented to separate the image and the background, and the grayscale image is converted into a binary image. Using the difference in grayscale between the target object to be extracted and the background in the image, a suitable threshold is selected. By judging whether the characteristic attributes of each pixel in the image meet the threshold requirements, it is determined whether the pixel in the image belongs to the target area or the background area, thereby generating a binary image. The selection of the threshold becomes the key to correct segmentation, and the processing results of different thresholds are very different. If the threshold is selected too high, too many background pixels will be misclassified as targets; on the contrary, if the threshold is selected too low, too many target pixels will be misclassified as background.

[0082] Then, the pulse interference and image scanning noise are filtered out by median filtering. The median filter sorts the grayscale of all pixels in a small window centered on a certain pixel from small to large, and takes the middle value of the sorting result as the grayscale value of the pixel. After nonlinear stretching, the grayscale value of the background interference is very different from that of its adjacent pixels. Therefore, the result of taking the median after sorting is to force this interference to become the same as the grayscale value of its adjacent pixels, so as to achieve the purpose of removing interference. Since the edge of the binary image still contains some large noise, it is necessary to use morphological methods to remove this noise to smooth the edge of the spot. Mathematical morphology consists of a set of morphological algebraic operators, including 4 basic operations: dilation, erosion, opening and closing. Since the information processed by the opening and closing operations is related to the convex and concave parts of the image, they are unilateral operators themselves, and the opening and closing operations can be used to remove the noise of the image. Finally, the image edge is contour tracked and circle fitted to obtain the coordinates and diameter of the center of the circle, and then the size of the defocused spot is determined.

[0083] For the focal length of an optical lens, it is necessary to determine the position of its principal point, and the focal length is obtained by measuring the distance from the focus to the principal point. However, since the principal point of the lens is generally inside the lens and is uncertain, it can be seen from the measurement principle that when using the measuring device of this embodiment, it is not necessary to know the position of the principal point, and the focal length value can be obtained by measuring the spot size; and during measurement, the focal length value can be obtained by only moving the CCD detector back and forth once, and the measurement process is fast.

[0084] This embodiment proposes a lens focal length measuring device that can be used for automatic focal length measurement. The lens measuring device uses laser as a light source, expands and attenuates the beam to obtain parallel laser light, which is incident on the lens to be measured. The motor drives the CCD detector to move to receive the defocused light spot, which is then transmitted to the computer for image processing using image processing technology. The focal length value is obtained by measuring the size of the defocused light spot. The measurement speed is fast, the principle is simple and the accuracy is high, and it is suitable for large-scale, automated lens processing and detection scenarios.

[0085] Example 2

[0086] This embodiment provides a lens focal length measurement method based on a measuring light spot, and the lens focal length measurement method based on a measuring light spot is implemented using the lens focal length measurement device based on a measuring light spot described in Embodiment 1. The lens focal length measurement method based on a measuring light spot includes:

[0087] S1: Obtaining the spot images corresponding to at least two different measuring points and the distances between the measuring points, wherein the positions of the measuring points refer to positions within a preset range of an initial focus position, and the initial focus position is a focus position calibrated by moving the movable image receiving component 5 to the initial position.

[0088] S2: Calculating the focal length of the measured lens according to the distance between the light spot image and the measuring point.

[0089] S21: Calculating the sizes of the defocused light spots corresponding to the different measuring points according to the light spot image.

[0090] S22: Calculating the focal length according to the sizes of the different defocused light spots and the distances between the measuring points.

[0091] The process of obtaining the distance between the measuring points specifically includes:

[0092] The positions of the different measuring points are determined according to the scale on the base; and the distances between the measuring points are calculated according to the positions of the different measuring points.

[0093] Alternatively, the rotation angle and the number of rotations of the motor at different measuring points are obtained; and the distance between the measuring points is calculated according to the rotation angle and the number of rotations.

[0094] The measurement principle of this embodiment is consistent with the measurement principle in Embodiment 1. Please refer to the definition of the measurement principle in Embodiment 1, which will not be repeated here.

[0095] The present embodiment provides a method for measuring the focal length of a lens, which can realize rapid measurement of the focal length of the lens, has a simple structure, is easy to operate, and has high detection efficiency. The lens focal length measuring device adopts the principle of projection method to measure the focal length, and a highly parallel expanded beam laser is incident on the lens to be measured. Based on the convergence effect of the lens, a CCD detector is used to measure the radius of the light spot of the measuring point before and after the focal plane, and the focal length value of the lens is obtained by measurement or fitting according to the relative position distance between the measuring points. Therefore, when measuring, it is only necessary to move the CCD from the front of the focus to the back of the focus to obtain the focal length of the lens to be measured. This method has the advantages of fast measurement speed, simple principle and high precision, and is suitable for large-scale, automated lens processing and detection scenarios.

[0096] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above 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.

[0097] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A lens focal length measuring device based on measuring light spot, characterized in that: The lens focal length measuring device based on measuring light spots comprises: a focal length measuring sub-device and a base; The focal length measurement sub-device is slidably connected to the base; The focal length measurement sub-device specifically comprises: a parallel light generating component, a lens to be measured, a movable image receiving component and a computer arranged in sequence; The parallel light generating assembly is used to generate beam-expanded parallel laser light; The lens under test is used to converge the beam-expanded parallel laser to obtain converged laser; The movable image receiving component is used to collect spot images of at least two different measuring points, wherein the positions of the measuring points refer to positions within a preset range of an initial focus position, and the initial focus position is a focus position calibrated by moving the movable image receiving component to an initial position; The computer is connected to the movable image receiving assembly, and is used to control the movable image receiving assembly to move on the base, and calculate the focal length of the measured lens according to the spot images of at least two different measuring points and the distance between the measuring points; When the measuring points are two points before and after the focus, the focal length of the lens under test is equal to the laser aperture size after collimation and expansion multiplied by the distance between the measuring points, and then divided by the sum of the light spots, wherein the sum of the light spots refers to the sum of the defocused light spot sizes of the measuring points, and the size of the defocused light spot is calculated based on the light spot image.

2. The lens focal length measuring device based on measuring light spot according to claim 1, characterized in that: The parallel light generating component specifically comprises: a parallel light generating sub-component and an energy attenuation sub-component arranged in sequence; The parallel light generating subassembly is used to generate a first beam-expanding parallel laser; The energy attenuation subassembly is used to attenuate the energy of the first beam-expanded parallel laser to obtain the energy-attenuated beam-expanded parallel laser, and the energy-attenuated beam-expanded parallel laser is the beam-expanded parallel laser.

3. The lens focal length measuring device based on measuring light spot according to claim 2, characterized in that: The parallel light generating subassembly specifically includes a laser and a collimating beam expanding assembly; The laser is used to generate laser light; The collimating and beam expanding component is used to perform collimating and beam expanding processing on the laser to obtain the first beam expanded parallel laser.

4. The lens focal length measuring device based on measuring light spot according to claim 3, characterized in that: The collimating and beam expanding assembly specifically comprises: a concave lens and a convex lens arranged in sequence; the focus of the concave lens coincides with the focus of the convex lens.

5. The lens focal length measuring device based on measuring light spot according to claim 2, characterized in that: The energy attenuation subassembly specifically includes: two polarizers arranged in sequence.

6. The lens focal length measuring device based on measuring light spot according to claim 1, characterized in that: The movable image receiving component specifically includes: a CCD detector and a motor; The CCD detector and the motor are both connected to the computer; The CCD detector is connected to the motor; The CCD detector is slidably connected to the base; The motor is used to drive the CCD detector to move on the base; The CCD detector is used to collect light spot images corresponding to at least two different measuring points.

7. A lens focal length measurement method based on measuring light spots, characterized in that: The lens focal length measurement method based on the measuring light spot is implemented by using the lens focal length measurement device based on the measuring light spot according to any one of claims 1 to 6, and the lens focal length measurement method based on the measuring light spot comprises: Acquire the spot images corresponding to at least two different measuring points and the distances between the measuring points, wherein the positions of the measuring points refer to positions within a preset range of an initial focus position, and the initial focus position is a focus position calibrated by moving the movable image receiving component to an initial position; Calculating the sizes of the defocused light spots corresponding to different measuring points according to the light spot image; The focal length of the measured lens is calculated according to the size of the defocused light spot, the distance between the measuring points and the laser aperture size after collimation and beam expansion.

8. The lens focal length measurement method based on measuring light spot according to claim 7, characterized in that: Calculating the focal length of the measured lens according to the distance between the light spot image and the measuring point specifically includes: Calculating the sizes of the defocused light spots corresponding to the different measuring points according to the light spot images; The focal length is calculated according to the sizes of the different defocused light spots and the distances between the measuring points.

9. The lens focal length measurement method based on measuring light spot according to claim 7, characterized in that: The process of obtaining the distance between the measuring points specifically includes: Determine the positions of the different measuring points according to the scale on the base; The distance between the measuring points is calculated according to the positions of the different measuring points.

10. The lens focal length measurement method based on measuring light spot according to claim 7, characterized in that: The process of obtaining the distance between the measuring points specifically includes: Obtain the rotation angle and rotation times of the motor at different measurement points; The distance between the measurement points is calculated according to the rotation angle and the number of rotations.

Images