Lens thickness measuring device and method

Abstract

The invention provides a device and a method for measuring the thickness of a lens. The measuring device comprises two independent zooming thickness measuring optical systems, the two thickness measuring optical systems can be focused on the upper surface and the lower surface of a to-be-measured lens respectively, each thickness measuring optical system is provided with an illumination optical assembly, a zooming optical assembly and an imaging optical assembly, the illumination optical assembly provides illumination light, and the zooming optical assembly provides zooming light; illumination light is converged on the surface of a to-be-measured lens after passing through the zoom optical assembly and is reflected to form measurement light, and the measurement light is analyzed after passing through the imaging optical assembly to form a measurement signal; wherein the illumination light has a continuous spectrum, the illumination light can be focused on zero-position focal planes with different heights through zooming of the zooming optical assembly, and each zero-position focal plane can map a corresponding thickness measuring range based on the continuous spectrum. According to the measuring device, the thickness measuring range of the thickness measuring optical system can be increased, and the contradiction between the measuring range and the measuring precision of a spectrum confocal sensor is overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of optical measurement, and particularly to a device and a method for measuring the thickness of a lens. Background Art

[0002] Lens thickness measurement equipment has a very wide range of applications in modern optical processing and testing. For example, in the manufacturing process of high-precision optical systems, a test accuracy of 1 micron or less is required. Existing optical lens thickness tests are usually carried out through a mechanical contact method for long-stroke tests, and then accurate thickness values are obtained through high-precision position measurement. However, contact measurement has a risk of damaging the lens surface, so lens manufacturers prefer to use optical non-contact measurement methods to measure the lens thickness.

[0003] A spectral confocal sensor is a new type of optical thickness measurement device. It obtains the position information of the lens surface through dispersion and spectral measurement. Compared with traditional laser triangulation, it has a higher signal-to-noise ratio and measurement accuracy. Compared with traditional thickness measurement, it has the characteristics of a large measurement range and strong material adaptability. Therefore, spectral confocal sensors have been very popular in the industrial production field. However, the measurement range and measurement accuracy of spectral confocal sensors are usually contradictory. The measurement range of high-precision spectral confocal sensors is only a few millimeters, which is not applicable to lens thickness measurement. Summary of the Invention

[0004] Based on this, the present invention aims to provide an improved device and method for measuring the thickness of a lens to solve at least one of the above problems.

[0005] In a first aspect, the present application provides a device for measuring the thickness of a lens, including: two independently zoomable thickness measurement optical systems, which can respectively focus on the upper and lower surfaces of the lens to be measured, and each of the thickness measurement optical systems has an illumination optical component, a zoom optical component, and an imaging optical component. The illumination optical component provides illumination light, the illumination light converges on the surface of the lens to be measured and is reflected to form measurement light after passing through the zoom optical component, and the measurement light is resolved into a measurement signal after passing through the imaging optical component.

[0006] Wherein, the illumination light has a continuous spectrum, and the illumination light can be focused on zero-position focal planes at different heights after zooming through the zoom optical component. Each zero-position focal plane can map a corresponding thickness measurement range based on the continuous spectrum.

[0007] The above-mentioned measuring device for the lens thickness can form zero-position focal planes at different heights by setting a zoom optical component. Each zero-position focal plane can map a corresponding thickness measurement range based on the continuous spectrum of the illumination light. This is beneficial to increasing the thickness measurement range of the thickness measurement optical system and overcoming the contradiction between the measurement range and the measurement accuracy of the spectral confocal sensor.

[0008] In one embodiment, during measurement, an illumination optical path and a measurement optical path are formed in the thickness measurement optical system. Among them, the illumination optical component is located in the illumination optical path, the zoom optical component is shared by the illumination optical path and the measurement optical path, and the imaging optical component is located in the measurement optical path.

[0009] In one embodiment, the illumination optical component includes a measurement light source, an illumination diaphragm, and a light source collimating lens group; the zoom optical component includes a zoom optical lens group and a light source converging lens group; the imaging optical component includes an imaging converging lens group, an imaging diaphragm, an imaging lens group, and an image detector; the measurement device is further provided with a beam splitting component, and the beam splitting component is configured to redirect a part of the illumination light emitted from the light source collimating lens group to enter the zoom optical lens group, and make a part of the measurement light emitted from the zoom optical lens group in the reverse direction enter the imaging converging lens group.

[0010] In one embodiment, the measurement light source is a white light source.

[0011] In one embodiment, the surface of the lens to be measured is conjugate to the detection surface of the image detector.

[0012] In one embodiment, the plane where the illumination diaphragm is located is conjugate to the plane where the imaging diaphragm is located.

[0013] In one embodiment, the illumination diaphragm, the light source collimating lens group, the imaging converging lens group, and the imaging diaphragm form a 4f optical system, and the plane where the illumination diaphragm is located coincides with the front focal plane of the light source collimating lens group, and the plane where the imaging diaphragm is located coincides with the rear focal plane of the imaging converging lens group.

[0014] In one embodiment, the zoom type of the zoom optical lens group includes one or more of mechanical zoom, liquid zoom, spatial light modulator zoom, and acousto-optic modulator zoom.

[0015] Second aspect, the present application provides a method for measuring the thickness of a lens, which is measured by using the measuring device described in any of the foregoing embodiments. The method includes: calibrating the accuracy of the measuring device by using a standard body with a known thickness, so that the zero-position focal planes of the two thickness-measuring optical systems of the measuring device coincide with the upper and lower surfaces of the standard body respectively; replacing the standard body with the lens to be measured; determining the height information of the upper and lower surfaces of the lens according to the spectra of the light rays reflected back from the upper and lower surfaces of the lens to be measured; and determining the thickness of the lens to be measured according to the known thickness of the standard body and the obtained height information.

[0016] The above method for measuring the thickness of a lens overcomes the disadvantage of the short measuring range of the spectral confocal system, and can increase the measuring range without using moving parts, so as to achieve fast and accurate measurement, and can adapt to the on-line measurement scenarios with high requirements for measuring range, measuring accuracy, system stability and measuring speed.

[0017] In one of the embodiments, the determining the height information of the upper and lower surfaces of the lens according to the spectra of the light rays reflected back from the upper and lower surfaces of the lens to be measured includes: obtaining the readings of each thickness-measuring optical system; wherein, the readings are determined by the thickness-measuring optical system based on the spectra of the light rays reflected back from the surface of the lens to be measured, and a positive reading indicates that the surface of the lens to be measured is closer to the center of the lens relative to the zero-position focal plane, a reading of 0 indicates that the surface of the lens to be measured is at the same height as the zero-position focal plane, and a negative reading indicates that the surface of the lens to be measured is farther from the center of the lens relative to the zero-position focal plane.

[0018] Correspondingly, the determining the thickness of the lens to be measured according to the known thickness of the standard body and the obtained height information includes: determining the thickness of the lens to be measured according to the relational expression h = D - d1 - d2; wherein, h represents the thickness of the lens to be measured, D represents the known thickness of the standard body, d1 represents the reading of the thickness-measuring optical system for measuring the height of the upper surface of the lens to be measured, and d2 represents the reading of the thickness-measuring optical system for measuring the height of the lower surface of the lens to be measured. Description of the Drawings

[0019] In order to more clearly illustrate the embodiments of the present specification or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present specification. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 Schematic diagram of the composition of the measuring device according to an embodiment of the present application;

[0021] Figure 2 Schematic diagram of the composition of the thickness measurement optical system according to an embodiment of the present application;

[0022] Figure 3 Schematic diagram of the lens thickness measurement method according to an embodiment of the present application;

[0023] Figure 4 Schematic diagram of the lens thickness measurement method according to another embodiment of the present application;

[0024] Figure 5 Schematic flow diagram of the lens thickness measurement steps according to an embodiment of the present application. Detailed implementation manners

[0025] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation manners of the present invention with reference to the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0026] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0027] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0028] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for illustrative purposes and do not represent the only implementation.

[0029] The embodiment of the present application provides a measuring device for the thickness of a lens. By setting a zoom optical component, the thickness measurement optical system can form zero-position focal planes at different heights. Each zero-position focal plane can map a corresponding thickness measurement range based on the continuous spectrum of the illumination light. This is beneficial to increasing the thickness measurement range of the thickness measurement optical system and solving the contradiction between the measurement range and the measurement accuracy of the spectral confocal sensor.

[0030] In some embodiments of the present application, such as Figure 1 and Figure 2 As shown, the lens thickness measuring device 10 includes: two independently zoomable thickness measurement optical systems 100. The two thickness measurement optical systems 100 can respectively focus on the upper and lower surfaces of the lens 20 to be measured. Each thickness measurement optical system 100 has an illumination optical component 110, a zoom optical component 120, and an imaging optical component 130. The illumination optical component 110 provides illumination light S1 (black solid line). The illumination light S1 converges on the surface of the lens to be measured and is reflected to form measurement light S2 (red solid line) after passing through the zoom optical component 120. The measurement light S2 is analyzed by the imaging optical component 130 to form a measurement signal. Among them, the illumination light S1 has a continuous spectrum. The illumination light S1 can be focused on zero-position focal planes at different heights after being zoomed by the zoom optical component 120. Each zero-position focal plane can map a corresponding thickness measurement range based on the continuous spectrum.

[0031] Exemplarily, the thickness measurement optical system used in the embodiment of the present application can be a spectral confocal sensor, which can measure the lens thickness using the dispersion of light. The light source of the spectral confocal sensor is white light, which contains a continuous spectrum. Light rays of different wavelengths can be focused on focal planes at different heights. As Figure 2 shown, the thickness measurement optical system 100 can focus on focal plane A with a focal length of f1, focal plane B with a focal length of f2, and focal plane C with a focal length of f3. When the surface of the lens to be measured is at a certain height, the thickness measurement optical system can inversely deduce the height information of the surface of the lens to be measured according to the spectrum of the light reflected from the surface of the lens to be measured.

[0032] Exemplarily, continue to refer to Figure 2 , the zero-position focal plane of the thickness measurement optical system 100 can be considered as Figure 2The focal plane with a focal length of f2. At this time, if the focal plane with a focal length of f1 and the focal plane with a focal length of f3 are respectively the highest focal plane and the lowest focal plane of the thickness measurement optical system 100, then the height difference range between the focal length f1 and the focal length f3 is the measurement range of the thickness measurement optical system. The measurement range of the thickness measurement optical system is mainly based on the magnitude of the dispersion of the illumination light S1, and the thickness measurement range of the thickness measurement optical system 100 can be increased by changing the position of the zero focal plane of the thickness measurement optical system 100 by using a zoom optical component.

[0033] Exemplarily, the measurement signal can form a detection reading of the thickness measurement optical system for the surface of the lens to be measured, and this reading reflects the height difference between the surface of the lens to be measured and the zero focal plane. Optionally, when the reading is positive, it means that the surface of the lens to be measured is closer to the center of the lens relative to the zero focal plane. When the reading is 0, it means that the surface of the lens to be measured is at the same height as the zero focal plane. When the reading is negative, it means that the surface of the lens to be measured is farther from the center of the lens relative to the zero focal plane.

[0034] Exemplarily, referring to Figure 3 , two thickness measurement optical systems 100 are respectively configured to detect the height of the upper surface and the lower surface of the lens 20. During the detection, as Figure 3 shown, the zero position calibration of the thickness measurement optical system 100 can be first performed using a standard body 30 (such as a flat crystal with a known thickness of D). It can be seen that at this time, the zero focal planes of the upper and lower thickness measurement optical systems 100 are respectively calibrated on the plane with a focal length of f01 and the plane with a focal length of f02. Then, the standard body 30 is replaced with the lens 20 to be measured to form a measurement scenario as Figure 1 shown. At this time, if the readings of the two thickness measurement optical systems 100 are d1 and d2 respectively, then the thickness h of the middle lens can be expressed as h = D - d1 - d2.

[0035] Optionally, when the surface of the lens to be measured is closer to the center of the lens 20 relative to the corresponding zero focal plane, the reading is positive. When the upper surface of the lens to be measured is farther from the center of the lens 20 relative to the corresponding zero focal plane, the reading is negative. Defined in this way, the measurement formula for the lens thickness will not be affected by the change in the thickness of different standard bodies. As Figure 4 shown, if the standard body 30' with a thickness of D' (D' < D) is used to calibrate the thickness measurement optical system 100, the zero focal planes of the upper and lower thickness measurement optical systems 100 can be respectively calibrated on the plane with a focal length of f03 and the plane with a focal length of f04. Correspondingly, at this time, if the readings of the two thickness measurement optical systems 100 are d1' and d2' respectively, then both d1' and d2' are negative. Then, the thickness of the lens to be measured can be accurately calculated through the aforementioned lens thickness measurement formula.

[0036] In some embodiments of the present application, as Figure 2As shown, an illumination optical path and a measurement optical path are formed in the thickness measurement optical system 100. Among them, the illumination optical component 110 is located in the illumination optical path, the zoom optical component 120 is shared by the illumination optical path and the measurement optical path, and the imaging optical component is located in the measurement optical path. Optionally, continue to refer to Figure 2 , the illumination optical component 110 sequentially includes a measurement light source 111, an illumination diaphragm 112, and a light source collimating lens group 113 along the light propagation direction; the zoom optical component 120 sequentially includes a zoom optical lens group 121 and a light source converging lens group 122 along the light propagation direction; the imaging optical component 130 sequentially includes an imaging converging lens group 131, an imaging diaphragm 132, an imaging lens group 133, and an image detector 134 along the light propagation direction; the measuring device 10 is further provided with a beam splitting component 140, and the beam splitting component 140 is configured to redirect a part of the illumination light S1 emitted from the light source collimating lens group 113 to be incident on the zoom optical lens group 121, and make a part of the measurement light S2 emitted in the reverse direction from the zoom optical lens group 121 incident on the imaging converging lens group 131.

[0037] In some embodiments of the present application, continue to refer to Figure 2 , the surface of the lens to be measured is conjugate to the detection surface of the image detector 134, which is beneficial to improving the imaging clarity. Optionally, the plane where the illumination diaphragm is located is conjugate to the plane where the imaging diaphragm is located. The illumination diaphragm 112, the light source collimating lens group 113, the imaging converging lens group 131, and the imaging diaphragm 132 form a 4f optical system, and the plane where the illumination diaphragm 112 is located coincides with the front focal plane of the light source collimating lens group 113, and the plane where the imaging diaphragm 132 is located coincides with the rear focal plane of the imaging converging lens group 131.

[0038] In some embodiments of the present application, the zoom type of the zoom optical lens group 121 includes one or more of mechanical zoom, liquid zoom, spatial light modulator zoom, and acousto-optic modulator zoom. When mechanical zoom is adopted, a motor can be used to drive the zoom optical lens group 121 to move the focal position; when liquid zoom, spatial light modulator zoom, or acousto-optic zoom is adopted, no movable components need to be provided inside the thickness measurement optical system, and the zoom optical lens group 121 can move the focal position by itself through lens expansion and contraction, which is beneficial to improving the stability and measurement speed of the system on the basis of increasing the thickness measurement range. It should be noted that the movable components need to measure the accurate position during the measurement process, so the use cost is likely to increase.

[0039] The embodiment of the present application also provides a method for measuring the thickness of a lens, which is measured by using the measuring device described in any of the previous embodiments. As Figure 5 shown, the measurement method includes:

[0040] S100. Calibrate the accuracy of the measuring device using a standard body with a known thickness, so that the zero focal planes of the two thickness measuring optical systems of the measuring device coincide with the upper and lower surfaces of the standard body respectively;

[0041] S200. Replace the standard body with the lens to be measured;

[0042] S300. Determine the height information of the upper and lower surfaces of the lens according to the spectra of the light rays reflected back from the upper and lower surfaces of the lens to be measured;

[0043] S400. Determine the thickness of the lens to be measured according to the known thickness of the standard body and the obtained height information.

[0044] The above method for measuring the lens thickness overcomes the shortcoming of the short measuring range of the spectral confocal system, and can increase the measuring range without using moving parts, so as to achieve fast and accurate measurement, and can adapt to the on-line measurement scenarios with high requirements for measuring range, measuring accuracy, system stability and measuring speed.

[0045] Exemplarily, step S300 may include: obtaining the readings of each thickness measuring optical system; wherein, the readings are determined by the thickness measuring optical system based on the spectra of the light rays reflected back from the surface of the lens to be measured, and a positive reading indicates that the surface of the lens to be measured is closer to the center of the lens relative to the zero focal plane, a reading of 0 indicates that the surface of the lens to be measured is at the same height as the zero focal plane, and a negative reading indicates that the surface of the lens to be measured is farther from the center of the lens relative to the zero focal plane; correspondingly, step S400 may include: determining the thickness of the lens to be measured according to the relationship h = D - d1 - d2; wherein, h represents the thickness of the lens to be measured, D represents the known thickness of the standard body, d1 represents the reading of the thickness measuring optical system for measuring the height of the upper surface of the lens to be measured, and d2 represents the reading of the thickness measuring optical system for measuring the height of the lower surface of the lens to be measured.

[0046] Next, it will be combined with Figure 1 and Figure 2 Specifically elaborate on the measurement process of the lens thickness.

[0047] The measuring device 10 is provided with a thickness measuring optical system 100 located on the upper and lower sides of the lens 20 to be measured. Among them, the measuring light source 111 emits parallel light (illumination light ray S1), which is spatially filtered by the illumination diaphragm 112 and then incident on the light source collimating lens group 113. After being emitted by the light source collimating lens group 113, it becomes parallel light. After part of the parallel light passes through the beam splitting component 140 and is incident on the zoom optical lens group 121 and the light source converging lens group 122, the light rays converge on the surface of the lens to be measured and are reflected by the surface of the lens to form the measuring light ray S2. After the measuring light ray S2 passes through the light source converging lens group 122, the zoom optical lens group 121 and the beam splitting component 140 again, it is converged by the imaging converging lens group 131 on the plane where the imaging diaphragm 132 is located. After passing through the imaging lens group 133, it forms an image on the focal plane of the image detector 134, and finally the position information of the surface of the lens to be measured is analyzed. Among them, the position calibration between the image detector 134 and the optical surface to be measured (i.e., the surface of the lens to be measured) has been completed, that is, the height of the image detector 134 is related to the optical surface to be measured, and each pixel corresponds one-to-one to different height positions.

[0048] It should be noted that the numbers representing quantity or property used to describe and claim certain embodiments of the present application should be understood as being modified by the terms "substantially", "about", "approximate" or "essentially" in certain cases. For example, unless otherwise specified, "substantially", "about", "approximate" or "essentially" may indicate a ±20% variation of the value they describe. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, and such approximate values may change according to the characteristics required by individual embodiments. In some embodiments, the numerical parameters should consider the specified significant digits and adopt the method of retaining general digits. Although the numerical ranges and parameters used to confirm the scope breadth in some embodiments of the present application are approximate values, in specific embodiments, such numerical settings are made as precise as possible within the feasible range.

[0049] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0050] The above-described embodiments merely represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A device for measuring lens thickness, characterized in that: include: Two independent zoom thickness measuring optical systems, the two thickness measuring optical systems can focus on the upper and lower surfaces of the lens to be measured respectively, and each of the thickness measuring optical systems has an illumination optical component, a zoom optical component and an imaging optical component, the illumination optical component provides illumination light, the illumination light converges on the surface of the lens to be measured after passing through the zoom optical component and is reflected to form a measurement light, and the measurement light is analyzed after passing through the imaging optical component to form a measurement signal; in, The illumination light has a continuous spectrum, and the illumination light can be focused on zero focal planes at different heights after being zoomed by the zoom optical component. Each of the zero focal planes can be mapped to a corresponding thickness measurement range based on the continuous spectrum.

2. The measuring device according to claim 1, characterized in that During measurement, an illumination optical path and a measurement optical path are formed in the thickness measuring optical system, wherein the illumination optical component is located in the illumination optical path, the zoom optical component is shared by the illumination optical path and the measurement optical path, and the imaging optical component is located in the measurement optical path.

3. The measuring device according to claim 2, characterized in that The illumination optical assembly includes a measuring light source, an illumination aperture, and a light source collimating lens group; The zoom optical assembly includes a zoom optical lens group and a light source convergence lens group; The imaging optical assembly includes an imaging converging lens group, an imaging aperture, an imaging lens group, and an image detector; The measuring device is also provided with a spectroscopic component, which is configured to redirect part of the illumination light emitted through the light source collimating lens group to be incident on the zoom optical lens group, and to make part of the measurement light reversely emitted through the zoom optical lens group be incident on the imaging converging lens group.

4. The measuring device according to claim 3, characterized in that The measuring light source is a white light source.

5. The measuring device according to claim 3, characterized in that The surface of the lens to be tested is conjugate with the detection surface of the image detector.

6. The measuring device according to claim 3, characterized in that The plane where the illumination aperture is located is conjugate with the plane where the imaging aperture is located.

7. The measuring device according to claim 6, characterized in that The illumination aperture, the light source collimating lens group, the imaging converging lens group and the imaging aperture form a 4f optical system, and the plane where the illumination aperture is located coincides with the front focal plane of the light source collimating lens group, and the plane where the imaging aperture is located coincides with the rear focal plane of the imaging converging lens group.

8. The measuring device according to claim 3, characterized in that The zoom type of the zoom optical lens assembly includes one or more of mechanical zoom, liquid zoom, spatial light modulator zoom, and acousto-optic modulator zoom.

9. A method for measuring lens thickness, using the measuring device as claimed in any one of claims 1 to 8, characterized in that: The method comprises: Using a standard body of known thickness to calibrate the accuracy of the measuring device, so that the zero focal planes of the two thickness measuring optical systems of the measuring device coincide with the upper and lower surfaces of the standard body respectively; Substituting the standard body with the lens to be tested; Determine the height information of the upper and lower surfaces of the lens according to the spectrum of the light reflected back from the upper and lower surfaces of the lens to be tested; The thickness of the lens to be tested is determined according to the known thickness of the standard body and the obtained height information.

10. The measuring method according to claim 9, characterized in that: The step of determining the height information of the upper and lower surfaces of the lens according to the spectrum of the light reflected from the upper and lower surfaces of the lens to be tested comprises: Obtaining readings of each thickness measuring optical system; wherein the readings are determined by the thickness measuring optical system based on the spectrum of the light reflected from the surface of the lens to be measured, and a positive reading indicates that the surface of the lens to be measured is closer to the center of the lens relative to the zero focal plane, a reading of 0 indicates that the surface of the lens to be measured is at the same height as the zero focal plane, and a negative reading indicates that the surface of the lens to be measured is farther away from the center of the lens relative to the zero focal plane; Accordingly, The step of determining the thickness of the lens to be tested according to the known thickness of the standard body and the obtained height information comprises: The thickness of the lens to be tested is determined according to the relationship h=D-d1-d2; wherein h represents the thickness of the lens to be tested, D represents the known thickness of the standard body, d1 represents the reading of the thickness measuring optical system used to measure the height of the upper surface of the lens to be tested, and d2 represents the reading of the thickness measuring optical system used to measure the height of the lower surface of the lens to be tested.

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