Multi-spot spectral confocal lens

Abstract

The utility model provides a kind of multi-spot spectral confocal lens, from object side to image side sequentially include: light source, the first lens with negative optical power, positive optical power second lens, positive optical power third lens, negative optical power fourth lens, positive optical power fifth lens, positive optical power sixth lens and positive optical power seventh lens;Wherein, the object side surface and image side surface of the first lens are both convex to the object side spherical surface;The object side surface and image side surface of the second lens are both convex to the object side spherical surface;The object side surface and image side surface of the third lens are both convex to the object side spherical surface, the object side surface of the fourth lens is plane, image side surface is concave to the image side spherical surface, the object side surface of the fifth lens is plane, image side surface is convex to the image side spherical surface, the object side surface and image side surface of the sixth lens are both convex to the object side spherical surface, the object side surface and image side surface of the seventh lens are both concave to the image side spherical surface.

Description

Technical Field

[0001] This utility model relates to the field of precision glass thickness measurement technology, and in particular to a multi-spot spectral confocal lens. Background Technology

[0002] Spectral confocal measurement lenses are key components in displacement measurement systems. Traditional lenses, due to their large outer diameter and total length exceeding 90mm, result in bulky dimensions and optical interference when multiple lenses are placed side-by-side. While this can be mitigated by reducing the size of individual lenses, it comes at the cost of key performance aspects. For example, reducing the outer diameter leads to a decrease in numerical aperture and a deterioration in signal-to-noise ratio; shortening the overall lens length results in a narrower axial chromatic aberration range, limiting measurement depth; and simplifying the lens elements can increase the fluctuation of the working F#, reducing measurement consistency.

[0003] Therefore, it is necessary to design a multi-spot spectral confocal lens to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-point spectral confocal lens suitable for thin glass that can measure the thickness of multiple points at one time, so as to solve the problem of large size when using multiple spectral confocal sensors at the same time.

[0005] To achieve the above objectives, this utility model adopts the following technical solution: a multi-point spectral confocal lens, comprising, from the object side to the image side, a light source, a first lens with negative optical power, a second lens with positive optical power, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with positive optical power, and a seventh lens with positive optical power; wherein, the object-side and image-side surfaces of the first lens are both convex spherical surfaces facing the object side; the object-side and image-side surfaces of the second lens are both convex spherical surfaces facing the object side; the object-side and image-side surfaces of the third lens are both convex spherical surfaces facing the object side; the object-side surface of the fourth lens is a plane, and the image-side surface is a spherical surface concave towards the image side; the object-side surface of the fifth lens is a plane, and the image-side surface is a spherical surface convex towards the image side; the object-side and image-side surfaces of the sixth lens are both convex spherical surfaces facing the object side; and the object-side and image-side surfaces of the seventh lens are both concave spherical surfaces facing the image side.

[0006] As a further improvement of the present invention, the light source has multiple light spots, and the light rays emitted by the multiple light spots are parallel to each other and are focused at different positions on the image side after passing through the lens.

[0007] As a further improvement of the present invention, the refractive indices of the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens and seventh lens are 1.631~1.81.

[0008] As a further improvement of this utility model, the fourth lens is a cemented lens, and the cemented surface is a spherical surface convex to the object side.

[0009] As a further improvement of this utility model, the multi-spot spectral confocal lens has a measurement range of 0-7mm within the working wavelength range of 450nm to 660nm.

[0010] As a further improvement of this utility model, the maximum outer diameter of the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens and seventh lens is ≤33mm.

[0011] As a further improvement of this utility model, the total optical length of the multi-spot spectral confocal lens is ≤83mm.

[0012] As a further improvement of this utility model, the working F# of the multi-spot spectral confocal lens is 1.78-1.93.

[0013] As a further improvement of this utility model, the object-side numerical aperture of the multi-spot spectral confocal lens is 0.2.

[0014] As can be seen from the above technical solutions, the multi-spot spectral confocal lens of this utility model achieves precise linear dispersion control through a segmented design consisting of a collimating dispersion lens group (first and second lenses), an aberration correction lens group (third and fourth lenses), a spot shaping lens group (fifth and sixth lenses), and a back focusing lens group (seventh lens). This results in small focusing deviations for each wavelength during multi-spot measurements. The use of concave-convex-planar surfaces allows for layered correction of spherical aberration, chromatic aberration, and eccentricity, ensuring good consistency in the diameter of the multi-spot light spots and minimal difference in spot quality between edge and center spots, thus guaranteeing uniform measurement accuracy across the entire field of view. Furthermore, by adapting the surface shape to the glass parameters, the spatial distribution of the multi-spot light spots can be flexibly controlled to accommodate different measurement fields of view. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the optical path structure of a multi-spot spectral confocal lens according to an embodiment of the present invention; Figure 2 for Figure 1 A dot plot of a multi-spot spectral confocal lens at a working wavelength of 450 nm; Figure 3 for Figure 1 A dot plot of a multi-spot spectral confocal lens at a working wavelength of 550 nm; Figure 4 for Figure 1 A dot plot of a multi-spot spectral confocal lens at a working wavelength of 660 nm; Figure 5 for Figure 1 The system MTF diagram of a multi-spot spectral confocal lens at a working wavelength of 450 nm; Figure 6 for Figure 1 The system MTF diagram of a multi-spot spectral confocal lens at a working wavelength of 550 nm; Figure 7 for Figure 1 System MTF diagram of a multi-spot spectral confocal lens at a working wavelength of 660 nm; Figure 8 for Figure 1 Spherical aberration correction diagram of a multi-spot spectral confocal lens at a working wavelength of 450 nm; Figure 9 for Figure 1 Spherical aberration correction diagram of a multi-spot spectral confocal lens at a working wavelength of 550 nm; Figure 10 for Figure 1 Spherical aberration correction diagram of a multi-spot spectral confocal lens at a working wavelength of 660nm. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Please refer to Figure 1 As shown, this utility model provides a multi-point spectral confocal lens, which, from the object side to the image side, includes: a light source 1, a first lens 2 with negative optical power, a second lens 3 with positive optical power, a third lens 4 with positive optical power, a fourth lens 5 with negative optical power, a fifth lens 6 with positive optical power, a sixth lens 7 with positive optical power, and a seventh lens 8 with positive optical power. 9 is the focal position of the lens. The light path propagates from left to right. The light emitted from the object surface passes through the aforementioned lenses and finally forms an image at the focal position 9. The light source 1 includes multiple fiber optic points. These multiple fiber optic points pass through the lens to the focal position 9 and reflect information back from multiple points. Figure 1 For clarity, only the light path of one of the light spots is shown.

[0018] The first lens 2 has spherical surfaces on both the object and image sides that are curved towards the object side; the second lens 3 has spherical surfaces on both the object and image sides that are curved towards the object side; the third lens 4 has spherical surfaces on both the object and image sides that are curved towards the object side; the fourth lens 5 is a cemented doublet lens, wherein the first surface is a plane, the second surface is a spherical surface curved towards the object side, and the third surface is a spherical surface curved towards the image side; the fifth lens 6 has a plane on the object side and a spherical surface curved towards the image side on the image side; the sixth lens 7 has spherical surfaces on both the object and image sides that are curved towards the object side; the seventh lens 8 has spherical surfaces on both the object and image sides that are curved towards the image side.

[0019] Please refer to Table 1. The specific parameters of each optical element in the preferred multi-spot spectral confocal lens in this embodiment are as follows: Table 1. Parameters of Multi-Spot Spectral Confocal Lens

[0020] In Table 1, T represents the air gap or lens thickness of each optical element, Nd represents the refractive index of the material of each optical element at wavelength d, and Vd represents the Abbe number of the material of each optical element at wavelength d. The apertures of the first lens 2 to the seventh lens 8 are all less than 33mm, and the total lens length is no more than 83mm. This results in good imaging quality, convenient installation and use, and facilitates further reduction in the overall size of the testing equipment. The object-side working distance is 30.3mm, and the image-side working distance is 44.8mm. The system's working F# (working F / # is the ratio of focal length to entrance pupil diameter calculated based on the lens's actual conjugate surface and real light data, reflecting the lens's performance under actual working conditions) is 1.78-1.92, where F#=1.78@450nm and F#=1.93@660nm. The preferred working wavelengths are 450nm, 550nm, and 660nm, with a measurement range of 7mm@450-660nm. The object-side numerical aperture is 0.2.

[0021] Figures 2 to 10 The evaluation results for the imaging quality of the aforementioned multi-spot spectral confocal measurement lens are presented. Specifically, Figure 2 , Figure 3 and Figure 4 The image shows spot diagrams of the multi-spot spectral confocal measurement lens at operating wavelengths of 450nm, 550nm, and 660nm. Spot diagrams are used to study the imaging quality of the system by analyzing the concentration of light rays reaching the image plane. Figures 2-4 It is evident that the quality of the central field-of-view spot is superior to that at the edges across all three operating wavelengths, indicating that the lens's on-axis aberration correction is sufficient and suitable for "parallel measurement of the central region" in multi-spot arrays. Therefore, for thickness measurement of transparent materials (such as thin glass), a combination of 450nm (upper surface) + 660nm (lower surface) can be used. Leveraging the high precision of short wavelengths and the penetrability of long wavelengths, the thickness can be calculated through the "wavelength-object distance" correspondence of spectral confocal measurement. This set of point plots clearly demonstrates the lens's aberration characteristics and focusing capabilities at different wavelengths, providing direct evidence for "wavelength selection, field-of-view optimization, and error compensation" in multi-spot spectral confocal measurements, supporting the accuracy and reliability of multi-spot parallel measurements.

[0022] Figure 5 , Figure 6 and Figure 7 The MTF (Modulation Transfer Function) of the spectral confocal measurement lens is given for operating wavelengths of 450nm, 550nm, and 660nm, respectively. Figures 5-7It can be seen that the maximum value of RMSRADIUS is 0.872μm at the three wavelengths, which is less than the diffraction limit of 1.52μm. The MTF curve is flat across the entire frequency range, and the high-frequency band (>200cy / mm) decreases slowly. The separation between the tangential and sagittal curves is small, indicating that chromatic aberration, spherical aberration, and astigmatism are all adequately corrected. The spot quality is consistent across the entire field of view during multi-spot measurement, making it suitable for high-precision parallel measurement.

[0023] Figure 8 , Figure 9 and Figure 10 The images show the spherical aberration correction of the spectral confocal measurement lens at working wavelengths of 450nm, 550nm, and 660nm, respectively. The spherical aberration of the spectral confocal measurement lens is less than 0.014mm at wavelengths of 450nm, 550nm, and 660nm, demonstrating the lens's "object distance focusing consistency" at different wavelengths. This provides a key basis for wavelength selection, accuracy optimization, and error compensation in multi-spot spectral confocal measurement.

[0024] The terms used herein, such as "front" and "back," indicating spatial relative position, are for illustrative purposes to describe the relationship of one feature relative to another, as shown in the accompanying drawings. It is understood that, depending on the product's placement, these terms may be intended to include different orientations besides those shown in the figures, and should not be construed as limiting the claims.

[0025] Furthermore, the above embodiments are only used to illustrate the present utility model and are not intended to limit the technical solutions described in the present utility model. The understanding of this specification should be based on those skilled in the art. Although the present utility model has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still make modifications or equivalent substitutions to the present utility model. All technical solutions and improvements that do not depart from the spirit and scope of the present utility model should be covered within the scope of the claims of the present utility model.

Claims

1. A multi-spot spectral confocal lens, characterized in that, The lens comprises, in sequence from the object side to the image side: a light source, a first lens with negative optical power, a second lens with positive optical power, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with positive optical power, and a seventh lens with positive optical power; wherein, the object side and image side of the first lens are both convex spherical surfaces facing the object side; the object side and image side of the second lens are both convex spherical surfaces facing the object side; the object side and image side of the third lens are both convex spherical surfaces facing the object side; the object side of the fourth lens is a plane, and the image side is a spherical surface concave towards the image side; the object side of the fifth lens is a plane, and the image side is a spherical surface convex towards the image side; the object side and image side of the sixth lens are both convex spherical surfaces facing the object side; and the object side and image side of the seventh lens are both concave spherical surfaces facing the image side.

2. The multi-spot spectral confocal lens as described in claim 1, characterized in that: The light source has multiple light spots, and the light rays emitted from the multiple light spots are parallel to each other. After passing through the lens, they are focused at different positions on the image side.

3. The multi-spot spectral confocal lens as described in claim 1, characterized in that: The refractive indices of the first, second, third, fourth, fifth, sixth, and seventh lenses are 1.631 to 1.

81.

4. The multi-spot spectral confocal lens as described in claim 1, characterized in that: The fourth lens is a cemented lens, and the cemented surface is a spherical surface convex towards the object side.

5. The multi-spot spectral confocal lens as described in claim 1, characterized in that: Within the operating wavelength range of 450nm to 660nm, the measurement range of the multi-spot spectral confocal lens is 0-7mm.

6. The multi-spot spectral confocal lens as described in claim 1, characterized in that: The maximum outer diameter of the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens and seventh lens is ≤33mm.

7. The multi-spot spectral confocal lens as described in claim 1, characterized in that: The total optical length of the multi-spot spectral confocal lens is ≤83mm.

8. The multi-spot spectral confocal lens as described in claim 1, characterized in that: The working F# of the multi-spot spectral confocal lens is 1.78-1.

93.

9. The multi-spot spectral confocal lens as described in claim 1, characterized in that: The object-space numerical aperture of the multi-spot spectral confocal lens is 0.2.

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