An ultra-high precision spectral confocal measurement lens and spectral confocal displacement sensor

Abstract

The present invention relates to the field of optical measurement technology, and discloses an ultra-high precision spectral confocal measurement lens and a spectral confocal displacement sensor, wherein the ultra-high precision spectral confocal measurement lens comprises a front lens group and a rear lens group coaxially arranged in sequence from the object side to the image side along the path of light incidence; the front lens group comprises a first lens, a second lens, and a third lens coaxially arranged in sequence along the path of light incidence, and the rear lens group comprises a fourth lens and a fifth lens coaxially arranged in sequence along the path of light incidence. The light beam emitted by the light source is incident on the first lens and emitted by the fifth lens to form dispersed light. The spectral confocal displacement sensor comprises a white light source, a spectrometer, a Y-type optical fiber, and the ultra-high precision spectral confocal measurement lens, wherein the white light source, the spectral confocal measurement lens, and the spectrometer are connected via a Y-type optical fiber. The lens realizes a two-fold reduction from the object height to the image height, which can significantly improve the resolution and measurement accuracy of the system.

Description

Technical Field

[0001] The present application relates to the field of optical measurement technology, and in particular to an ultra-high precision spectral confocal measurement lens and a spectral confocal displacement sensor. Background Art

[0002] The spectral confocal displacement sensor is a high-precision photoelectric measurement device that establishes a clear correspondence between the focal position and the wavelength by utilizing the optical dispersion characteristics. It can not only measure the displacement of objects and the thickness of transparent materials, but also achieve more complex functions through the combination of multiple probes, with significant advantages of non-destructive testing, non-contact operation and high-speed measurement.

[0003] As the core component of the sensor, the performance of the spectral confocal measurement lens directly determines the capabilities of the system. The axial dispersion range of the lens affects the measurement range, the object numerical aperture determines the maximum acceptable measurement inclination angle, and the size of the spot is closely related to the resolution of the sensor. In industrial measurement, different application scenarios and objects have different requirements for measurement range and working distance. However, the resolution and accuracy of most spectral confocal measurement lenses currently cannot meet higher requirements. Therefore, how to achieve a good balance between measurement range, working distance and resolution is still an important challenge in the design of spectral confocal lenses. Summary of the invention

[0004] In view of this, the embodiment of the present application provides an ultra-high precision spectral confocal measurement lens and spectral confocal displacement sensor, which take into account the requirements of measurement range and working distance, and at the same time significantly improve the resolution and measurement accuracy of the sensor by correcting aberrations and achieving a two-fold reduction from object height to image height. The lens is simple and compact in design, easy to assemble, and has high practical value and applicability.

[0005] According to a first aspect of an embodiment of the present application, there is provided an ultra-high precision spectral confocal measurement lens, comprising a front lens group and a rear lens group coaxially arranged in sequence from the object side to the image side along a light incident path;

[0006] The front lens group includes a first lens, a second lens, and a third lens coaxially arranged in sequence along the path of incident light, wherein the second lens and the third lens form a first doublet lens;

[0007] The rear lens group includes a fourth lens and a fifth lens coaxially arranged in sequence along the path of incident light, wherein the fourth lens and the fifth lens form a second doublet lens;

[0008] The light beam emitted by the light source is incident on the first lens and exits from the fifth lens, where: the first lens is a positive focal length lens, the incident surface is concave, -330 mm < r < -320 mm, the exit surface is convex, -35 mm < r < -25 mm; the second lens is a positive focal length lens, the incident surface is convex, 10 mm < r < 20 mm, the exit surface is concave, 35 mm < r < 45 mm; the third lens is a negative focal length lens, the incident surface is convex, 35 mm < r < 45 mm, the exit surface is concave, 330 mm < r < -320 mm; the fourth lens is a positive focal length lens, the incident surface is convex, 5 mm < r < 15 mm, the exit surface is concave, 50 mm < r < 60 mm; the fifth lens is a positive focal length lens, the incident surface is convex, 50 mm < r < 60 mm, the exit surface is concave, 15 mm < r < 25 mm; where r is the radius of curvature.

[0009] Optionally, the radius of curvature of the incident surface of the first lens is -325.9 mm, and the radius of curvature of the exit surface is -31.3 mm; the radius of curvature of the incident surface of the second lens is 16.7 mm, and the radius of curvature of the exit surface is 39 mm; the radius of curvature of the incident surface of the third lens is 39 mm, and the radius of curvature of the exit surface is 8.7 mm; the radius of curvature of the incident surface of the fourth lens is 10 mm, and the radius of curvature of the exit surface is 52.8 mm; the radius of curvature of the incident surface of the fifth lens is 52.8 mm, and the radius of curvature of the exit surface is 17.5 mm.

[0010] Optionally, the glass material of the first lens: 1.9 < n < 2.1, 20 < Vd < 30; the glass material of the second lens: 1.8 < n < 2, 10 < Vd < 20; the glass material of the third lens: 1.75 < n < 1.95, 40 < Vd < 50; the glass material of the fourth lens: 1.9 < n < 2.1, 20 < Vd < 30; the glass material of the fifth lens: 1.6 < n < 1.8, 50 < Vd < 60; where n is the refractive index and Vd is the Abbe number.

[0011] Optionally, the first lens and the fourth lens are made of the same glass material.

[0012] Optionally, the distance between the first lens and the second lens is 0 mm, and the distance between the first doublet lens and the second doublet lens is 2 mm.

[0013] According to the second aspect of the embodiments of the present application, a spectral confocal displacement sensor is provided, including a white light source, a spectrometer, a Y-shaped optical fiber, and the ultra-high-precision spectral confocal measurement lens described in the first aspect, and the white light source, the spectral confocal measurement lens, and the spectrometer are connected by the Y-shaped optical fiber.

[0014] The technical solutions provided by the embodiments of the present application may include the following beneficial effects:

[0015] It can be seen from the above embodiments that the light beam emitted by the light source first passes through the front lens group, and after the convergence of the first lens, it passes through the second lens and the third lens in turn to achieve beam expansion and preliminary dispersion processing; then it passes through the rear lens group, and further corrects the chromatic aberration and achieves the second axial dispersion through the fourth lens and the fifth lens. Finally, the dispersed light beam output by the fifth lens irradiates the target object to form a single-wavelength reflected light, and returns along the original path through the fifth lens and the first lens. The spectral confocal measurement lens effectively corrects the aberration under the condition of achieving an object height to image height ratio of 2:1, and the working distance reaches 14.5mm. At the same time, the measurement range is significantly expanded to 3mm through two axial dispersions, and the numerical aperture (NA) of the object side is fully utilized. The entire design has the characteristics of compact structure and easy assembly. It can be efficiently applied to a variety of industrial measurement scenarios and has a wide range of practicality.

[0016] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0018] Figure 1 1 is an optical structure diagram of a spectral confocal measurement lens provided in one embodiment of the present invention.

[0019] Figure 2 The figure is a schematic diagram of the composition structure of a spectral confocal measurement lens in a spectral confocal sensor provided by an embodiment of the present invention.

[0020] Figure 3 4 is a graph showing the relationship between the focus position and wavelength of a spectral confocal measurement lens provided in one embodiment of the present invention.

[0021] Figure 4 This is a spot diagram of a spectral confocal measurement lens provided by an embodiment of the present invention at a wavelength of 500 nm.

[0022] Figure 5 This is a spot diagram of a spectral confocal measurement lens provided by an embodiment of the present invention at a wavelength of 585 nm.

[0023] Figure 6 1 is a point diagram of a spectral confocal measurement lens provided by an embodiment of the present invention at a wavelength of 700 nm.

[0024] Figure 7 This is a light trace diagram of a spectral confocal measurement lens at a wavelength of 500 nm provided by an embodiment of the present invention.

[0025] Figure 8 This is a light trace diagram of a spectral confocal measurement lens at a wavelength of 585 nm provided by an embodiment of the present invention.

[0026] Fig. 9 This is a light trace diagram of a spectral confocal measurement lens at a wavelength of 700 nm provided by an embodiment of the present invention.

[0027] In the figure:

[0028] L1, first lens; L2, second lens; L3, third lens; L4, fourth lens; L5, fifth lens;

[0029] 21. White light source; 22. Spectrometer; 23. Y-type optical fiber; 24. Spectral confocal measurement lens. DETAILED DESCRIPTION

[0030] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0031] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0032] It should be understood that although the terms first, second, third, etc. may be used in the present application to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0033] refer to Figure 1As shown in the figure, an embodiment of the present invention provides an ultra-high-precision spectral confocal measurement lens. The measurement lens has a positive telephoto structure and includes a front group of lenses and a rear group of lenses coaxially arranged in sequence from the object side to the image side along the light incident path. The front group of lenses includes a first lens L1, a second lens L2, and a third lens L3 coaxially arranged in sequence along the light incident path. Among them, the second lens L2 and the third lens L3 form a first doublet lens. The rear group of lenses includes a fourth lens L4 and a fifth lens L5 coaxially arranged in sequence along the light incident path. Among them, the fourth lens L4 and the fifth lens L5 form a second doublet lens.

[0034] In one embodiment, the light beam emitted by the light source is incident on the first lens L1 and exits from the fifth lens L5, where: the first lens L1 is a positive focal length lens, the incident surface is concave, -330mm < r < -320mm, the exit surface is convex, -35mm < r < -25mm; the second lens L2 is a positive focal length lens, the incident surface is convex, 10mm < r < 20mm, the exit surface is concave, 35mm < r < 45mm; the third lens L3 is a negative focal length lens, the incident surface is convex, 35mm < r < 45mm, the exit surface is concave, 5mm < r < 15mm; the fourth lens L4 is a positive focal length lens, the incident surface is convex, 5mm < r < 15mm, the exit surface is concave, 50mm < r < 60mm; the fifth lens L5 is a positive focal length lens, the incident surface is convex, 50mm < r < 60mm, the exit surface is concave, 15mm < r < 25mm. Among them, r is the radius of curvature. Through the reasonable combination of the positive focal length lens and the negative focal length lens, the aberration of the system is greatly reduced, and the measurement accuracy is improved.

[0035] In one embodiment, the radius of curvature of the incident surface of the first lens L1 is -330mm, and the radius of curvature of the exit surface is -35mm; the radius of curvature of the incident surface of the second lens L2 is 10mm, and the radius of curvature of the exit surface is 35mm; the radius of curvature of the incident surface of the third lens L3 is 35mm, and the radius of curvature of the exit surface is 5mm; the radius of curvature of the incident surface of the fourth lens L4 is 5mm, and the radius of curvature of the exit surface is 50mm; the radius of curvature of the incident surface of the fifth lens L5 is 50mm, and the radius of curvature of the exit surface is 15mm.

[0036] In another embodiment, the radius of curvature of the incident surface of the first lens L1 is -320 mm, and the radius of curvature of the exit surface is -25 mm; the radius of curvature of the incident surface of the second lens L2 is 20 mm, and the radius of curvature of the exit surface is 45 mm; the radius of curvature of the incident surface of the third lens L3 is 45 mm, and the radius of curvature of the exit surface is 15 mm; the radius of curvature of the incident surface of the fourth lens L4 is 15 mm, and the radius of curvature of the exit surface is 60 mm; the radius of curvature of the incident surface of the fifth lens L5 is 60 mm, and the radius of curvature of the exit surface is 25 mm.

[0037] In a preferred embodiment, the radius of curvature of the incident surface of the first lens L1 is -325.9 mm, and the radius of curvature of the exit surface is -31.3 mm; the radius of curvature of the incident surface of the second lens L2 is 16.7 mm, and the radius of curvature of the exit surface is 39 mm; the radius of curvature of the incident surface of the third lens L3 is 39 mm, and the radius of curvature of the exit surface is 8.7 mm; the radius of curvature of the incident surface of the fourth lens L4 is 10 mm, and the radius of curvature of the exit surface is 52.8 mm; the radius of curvature of the incident surface of the fifth lens L5 is 52.8 mm, and the radius of curvature of the exit surface is 17.5 mm.

[0038] In an embodiment, the glass material of the first lens L1: 1.9 < n < 2.1, 20 < Vd < 30; the glass material of the second lens L2: 1.8 < n < 2, 10 < Vd < 20; the glass material of the third lens L3: 1.75 < n < 1.95, 40 < Vd < 50; the glass material of the fourth lens L4: 1.9 < n < 2.1, 20 < Vd < 30; the glass material of the fifth lens L5: 1.6 < n < 1.8, 50 < Vd < 60; where n is the refractive index and Vd is the Abbe number. By reasonably selecting the lens glass materials, spherical aberration, coma aberration and other aberrations of the system are greatly reduced, thereby improving the measurement accuracy of the system.

[0039] In an embodiment, the first lens L1 and the fourth lens L4 adopt the same kind of glass material. By optimizing the structure and material selection, the manufacturing process is effectively simplified, the production cost is reduced, and at the same time, the chromatic aberration caused by material differences and the influence of temperature changes on the optical performance are significantly reduced.

[0040] In an embodiment, the distance between the first lens L1 and the second lens L2 is 0 mm, and the distance between the first doublet lens and the second doublet lens is 2 mm. This design not only realizes the compactness of the lens structure, but also fully takes into account the requirements of high-quality imaging, achieving a perfect balance between performance and structural optimization, thereby endowing the system with higher application adaptability and flexibility.

[0041] Table 1 Parameters of the lens group:

[0042] surface Radius of curvature (unit / mm) Semi-diameter (unit / mm) The first lens L1 incident surface -325.9 6.5 The first lens L1 exit surface -31.3 6.5 The second lens L2 incident surface 16.7 6.5 The second lens L2 exit surface 39 6.5 The incident surface of the third lens L3 39 4.577 The third lens L3 exit surface 8.7 6.5 The incident surface of the fourth lens L4 10 6.5 The fourth lens L4 exit surface 52.8 6.5 Fifth lens L5 incident surface 52.8 6.5 Fifth lens L5 exit surface 17.5 3.604

[0043] In one embodiment, Table 1 gives the parameters of the spectral confocal measurement lens group. Figure 2 , the composition structure of the spectral confocal measurement lens in the spectral confocal sensor is given, and the white light source 21, the spectral confocal measurement lens 24 and the spectrometer 22 are connected by a Y-type optical fiber. After the light beam emitted by the white light source 21 is converged by the first lens L1, it is successively expanded and initially dispersed by the second lens L2 and the third lens L3; then, the chromatic aberration is further corrected and the second axial dispersion is achieved by the fourth lens L4 and the fifth lens L5. Finally, the dispersed light beam output by the fifth lens L5 irradiates the target object, forming a single-wavelength reflected light, and returns along the original path through the fifth lens L5 and the first lens L1, and enters the spectrometer 22.

[0044] See also Figure 3 From the focus position and wavelength relationship diagram of the spectral confocal measurement lens provided in this embodiment, it can be seen that the lens achieves a dispersion range of 3mm in the wavelength range of 500nm~700nm, and the working distance reaches 14.5mm.

[0045] See also Figure 4 The spot diagram of the spectral confocal measurement lens provided in this embodiment at a wavelength of 500nm, Figure 5 The spot diagram of the spectral confocal measurement lens provided in this embodiment at a wavelength of 585nm, Figure 6 The spot diagram of the spectral confocal measurement lens provided for this embodiment at a wavelength of 700nm. The spot diagram shows that the spot size of each field of view is close to the Airy disk, indicating that the system is close to the diffraction limit. Figure 7 , Figure 8 , Fig. 9 The light trace diagrams of the spectral confocal measurement lens at wavelengths of 500nm, 585nm and 700nm are shown respectively. The object height of the system is 100μm, and the light trace diagram shows that the image height of the system is 50μm, so the spectral confocal measurement lens achieves an object height to image height ratio of 2:1, which can significantly improve the resolution and measurement accuracy, and effectively correct the aberration.

[0046] It can be seen from the above embodiments that the present application provides an ultra-high precision spectral confocal measurement lens, which is composed of five lenses and has a simple and compact structure. The lens effectively corrects aberrations and achieves a 2:1 ratio of object height to image height, which can significantly improve the resolution and measurement accuracy of the system. The lens achieves a 3mm dispersion range in the wavelength range of 500nm~700nm, and the working distance reaches 14.5mm. At the same time, the NA of the object side is also fully utilized.

[0047] refer to Figure 2The embodiment of the present invention further provides a spectral confocal displacement sensor, comprising a white light source 21, a spectrometer 22, a Y-type optical fiber 23 and the above-mentioned ultra-high precision spectral confocal measurement lens 24, wherein the white light source 21, the spectral confocal measurement lens 24 and the spectrometer 22 are connected via the Y-type optical fiber 23. The structure of the ultra-high precision spectral confocal measurement lens has been described in detail above and will not be repeated here.

[0048] Those skilled in the art will readily appreciate other embodiments of the present application after considering the description and practicing the contents disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The description and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the claims.

[0049] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. An ultra-high precision spectral confocal measurement lens, characterized in that: It includes a front group lens and a rear group lens that are coaxially arranged in sequence from the object side to the image side along the path of light incidence; The front group lens includes a first lens, a second lens, and a third lens that are coaxially arranged in sequence along the path of light incidence. Among them, the second lens and the third lens form a first doublet lens; The rear group lens includes a fourth lens and a fifth lens that are coaxially arranged in sequence along the path of light incidence. Among them, the fourth lens and the fifth lens form a second doublet lens; The light beam emitted by the light source is incident on the first lens and exits from the fifth lens. Among them: the first lens is a positive focal length lens, the incident surface is concave, -330mm < r < -320mm, the exit surface is convex, -35mm < r < -25mm; the second lens is a positive focal length lens, the incident surface is convex, 10mm < r < 20mm, the exit surface is concave, 35mm < r < 45mm; the third lens is a negative focal length lens, the incident surface is convex, 35mm < r < 45mm, the exit surface is concave, -330mm < r < -320mm; the fourth lens is a positive focal length lens, the incident surface is convex, 5mm < r < 15mm, the exit surface is concave, 50mm < r < 60mm; the fifth lens is a positive focal length lens, the incident surface is convex, 50mm < r < 60mm, the exit surface is concave, 15mm < r < 25mm; where r is the radius of curvature; The distance between the first lens and the second lens is 0mm, and the distance between the first doublet lens and the second doublet lens is 2mm; The optical components with focal power in the front group lens and the rear group lens are only the above five lenses.

2. The ultra-high precision spectral confocal measurement lens according to claim 1, characterized in that: The radius of curvature of the incident surface of the first lens is -325.9mm, and the radius of curvature of the exit surface is -31.3mm; the radius of curvature of the incident surface of the second lens is 16.7mm, and the radius of curvature of the exit surface is 39mm; the radius of curvature of the incident surface of the third lens is 39mm, and the radius of curvature of the exit surface is 8.7mm; the radius of curvature of the incident surface of the fourth lens is 10mm, and the radius of curvature of the exit surface is 52.8mm; the radius of curvature of the incident surface of the fifth lens is 52.8mm, and the radius of curvature of the exit surface is 17.5mm.

3. The ultra-high precision spectral confocal measurement lens according to claim 1, characterized in that: The glass material of the first lens: 1.9 < n < 2.1, 20 < Vd < 30; the glass material of the second lens: 1.8 < n < 2, 10 < Vd < 20; the glass material of the third lens: 1.75 < n < 1.95, 40 < Vd < 50; the glass material of the fourth lens: 1.9 < n < 2.1, 20 < Vd < 30; the glass material of the fifth lens: 1.6 < n < 1.8, 50 < Vd < 60; where n is the refractive index and Vd is the Abbe number.

4. The ultra-high precision spectral confocal measurement lens according to claim 1, characterized in that: The first lens and the fourth lens are made of the same glass material.

5. A spectral confocal displacement sensor, characterized in that: It includes a white light source, a spectrometer, a Y-shaped optical fiber, and the ultra-high-precision spectral confocal measurement lens according to any one of claims 1-4. The white light source, the spectral confocal measurement lens, and the spectrometer are connected by the Y-shaped optical fiber.

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