Spectral confocal displacement measuring head based on refractive-diffractive mixing principle

Abstract

The invention discloses a spectral confocal displacement measuring head based on a refractive-diffractive mixing principle, which belongs to the technical field of optical measurement and comprises a lens barrel, an optical fiber interface, a refractive-diffractive mixing lens, an optical fiber and a diaphragm, the optical fiber interface is arranged at one end of the lens barrel, and the refractive-diffractive mixing lens is mounted in the lens barrel and located at the other end opposite to the optical fiber interface. The first surface of the refractive and diffractive mixed lens is an aspheric surface and the second surface is a diffractive surface along the optical axis from left to right and is used for focusing and dispersing light beams; the polychromatic light is introduced into the lens barrel through the optical fiber and is subjected to dispersion focusing after passing through the aspheric surface and the diffraction surface of the refraction and diffraction mixed lens, and the focus of the polychromatic light is linearly distributed on the optical axis along with the wavelength. Compared with a traditional refraction type spectrum confocal measuring head, the measuring head has the advantages of being good in dispersion linearity, simple in structure, easy to install and adjust, small in size, light in weight and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of optical measurement and relates to a spectral confocal displacement probe based on the refraction-diffraction mixing principle. Background Art

[0002] Spectral confocal displacement measurement technology is a non-contact displacement measurement technology based on the confocal optical principle. The measured displacement is modulated into peak wavelength change information through a dispersive objective lens, and the peak wavelength is obtained by a spectrometer in combination with the corresponding relationship with the axial distance to calculate the position information of the measured object. The measurement resolution of the spectral confocal displacement sensor can reach nanometers, the measurement frequency can reach tens of thousands of hertz, the detection slope range is large, and the focal spot is small. It can be used for displacement, roughness, thickness and three-dimensional surface scanning measurement.

[0003] Traditional spectral confocal displacement probes use a dispersion lens group to focus the white light dispersion to achieve axial measurement. Generally, a combination of refractive lenses made of multiple Abbe number materials is used to control the dispersion range and reduce nonlinear dispersion. The combination structure of multiple refractive lenses increases the size and weight of the spectral confocal displacement probe, and also makes the installation and adjustment complicated. Summary of the invention

[0004] In response to the demand for improvement of the prior art, the present invention proposes a spectral confocal displacement probe based on the refraction-diffraction mixing principle.

[0005] To achieve the above-mentioned purpose, the present invention proposes a spectral confocal displacement probe based on the principle of refractive-diffractive mixing, which includes: a lens barrel, an optical fiber interface, a refractive-diffractive hybrid lens, an aspheric surface, a diffractive surface, an optical fiber, and an aperture. A fiber optic interface is provided at one end of the lens barrel for installing the optical fiber. The refractive-diffractive hybrid lens is installed inside the lens barrel at the other end opposite to the optical fiber interface. The first surface of the refractive-diffractive hybrid lens from left to right along the optical axis is an aspheric surface, and the second surface is a diffractive surface, which is used for light beam focusing and dispersion. An aperture is provided at the other end of the lens barrel, wherein complex color light is introduced into the lens barrel by the optical fiber, and dispersed and focused after passing through the aspheric surface and the diffractive surface of the refractive-diffractive hybrid lens, and its focus is linearly distributed with the wavelength on the optical axis.

[0006] Furthermore, the first surface, ie, the aspherical surface, of the refractive-diffractive hybrid lens is coated with an anti-reflection film to improve spectral transmittance.

[0007] Furthermore, the diffractive surface of the refractive-diffractive hybrid lens is a ring-shaped step-shaped microstructure.

[0008] Compared with the traditional spectral confocal probe, the technical solution proposed by the present invention has the following beneficial effects: 1. The spectral confocal probe based on the principle of refractive-diffractive hybrid uses the aspheric surface and the diffractive surface to share the focal length, so that the refractive-diffractive hybrid lens obtains a larger image-side numerical aperture, which is beneficial to improving the optical resolution of the spectral confocal probe.

[0009] 2. The spectral confocal probe based on the principle of refraction-diffraction mixing can use one lens to achieve the function of the traditional refractive lens group, reducing the size, weight and complexity of the spectral confocal probe.

[0010] 3. The spectral confocal probe based on the principle of refraction-diffraction mixing has a diffraction surface, which makes the focus position of the light beam only related to the wavelength, thus improving the dispersion linearity of the spectral confocal probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the structure of a spectral confocal displacement probe based on the refraction-diffraction mixing principle proposed by the present invention; Figure 2 Schematic diagram showing the annular step-shaped microstructure; Figure 3 is a graph showing the relationship between focus and wavelength of a specific example proposed by the present invention; Figure 4 is a focus-wavelength relationship diagram after linear fitting of a specific example proposed by the present invention; Explanation of the reference numerals: 1, lens barrel; 2, optical fiber interface; 3, refractive-diffractive hybrid lens; 4, aspheric surface; 5, diffractive surface; 6, optical fiber; 7, aperture. DETAILED DESCRIPTION

[0012] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms, and the present invention should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0013] See also Figure 1 The present invention proposes a spectral confocal displacement probe based on the principle of refractive-diffractive mixing. The spectral confocal displacement probe based on the principle of refractive-diffractive mixing has a lens barrel 1, which has a black coating inside to reduce stray light. One end of the lens barrel is provided with an optical fiber interface 2 for installing an optical fiber 6. A refractive-diffractive hybrid lens 3 is installed inside the lens barrel 1, located at the other end opposite to the optical fiber interface 2. The first surface of the refractive-diffractive hybrid lens 3 from left to right along the optical axis is an aspheric surface 4, and the second surface is a diffractive surface 5, which is used for light beam focusing and dispersion. An aperture 7 is provided at the other end of the lens barrel 1. The edge of the aperture blocks the marginal light passing through the refractive-diffractive hybrid lens, which is used to constrain the aperture of the outgoing light beam. The complex light is introduced into the lens barrel by the optical fiber 6, and is dispersed and focused after passing through the aspheric surface 4 and the diffractive surface 5 of the refractive-diffractive hybrid lens 3. The focus is linearly distributed with the wavelength on the optical axis.

[0014] In one embodiment, after the optical fiber 6 is installed in the optical fiber interface 2, the distance between the optical fiber head and the first surface of the refractive-diffractive hybrid lens 3 is 70 mm.

[0015] In one embodiment, the aspheric surface 4 is coated with a magnesium fluoride anti-reflection film to improve the transmittance of the spectrum. The aspheric surface 4 can be an odd-order aspheric surface, an even-order aspheric surface, or an extended aspheric surface.

[0016] In one embodiment, the surface of the diffractive surface 5 of the refractive-diffractive hybrid lens is a ring-shaped step-shaped microstructure. Figure 2 As shown, the annular step-shaped microstructure means that the diffraction surface has a certain number of concentric annular regions, and the phase difference between each region to the incident light is 2π. The ideal diffraction surface shape of each annular region is continuously changing, and it can actually be processed into a discrete step-shaped microstructure.

[0017] Furthermore, the diameter of the refractive-diffractive hybrid lens 3 is 15 mm.

[0018] Furthermore, the material of the refractive-diffractive hybrid lens 3 is fused quartz, and the refractive-diffractive hybrid lens 3 is a 4-step periodic annular structure, and the theoretical diffraction efficiency is 81%.

[0019] Figure 1 In , and Refers to the maximum operating wavelength, minimum operating wavelength and focal length of the center wavelength.

[0020] See also Figure 3 The central wavelength of the diffractive surface 5 of the refractive-diffractive hybrid lens 3 is 588 nm, the shortest working wavelength of the refractive-diffractive hybrid lens 3 is 500 nm, and the longest working wavelength is 700 nm.

[0021] See also Figure 4 , the dispersion range of the refractive-diffractive hybrid lens 3 on the optical axis is In the figure, y=-403.6*x+700 represents the wavelength-focus displacement linear fitting equation, where x is the focus displacement and y is the wavelength.

[0022] The aspheric surface 4 and the diffractive surface 5 of the refractive-diffractive hybrid lens 3 share the focusing and dispersion functions. The linear determination coefficient of the actual peak wavelength-displacement fitting line of the refractive-diffractive hybrid lens is: The aspheric surface has a higher numerical aperture, which brings high resolution, and the diffractive surface can improve the dispersion linearity.

[0023] The present invention can realize the function of a spectral confocal probe by using only a single refractive-diffractive hybrid lens, has a high numerical aperture, and has a high optical resolution. Due to the combination of the refractive dispersion and diffractive dispersion principles, the dispersion linearity can be adjusted to achieve high linear dispersion. According to the technical solution of the present invention, the optical resolution is high, the dispersion linearity is good, the volume is small, the weight is light, the assembly is convenient, and the practicability is strong.

[0024] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A spectral confocal displacement probe based on the principle of refraction-diffraction mixing, characterized in that: include: A lens barrel (1), an optical fiber interface (2), a refractive-diffractive hybrid lens (3), an aspheric surface (4), a diffractive surface (5), an optical fiber (6), and an aperture (7). One end of the lens barrel (1) is provided with an optical fiber interface (2) for installing the optical fiber (6). The refractive-diffractive hybrid lens (3) is installed inside the lens barrel (1) at the other end opposite to the optical fiber interface (2). The first surface of the refractive-diffractive hybrid lens (3) from left to right along the optical axis is an aspheric surface (4), and the second surface is a diffractive surface (5) for light beam focusing and dispersion. The other end of the lens barrel (1) is provided with an aperture (7). Complex color light is introduced into the lens barrel by the optical fiber (6), and dispersed and focused after passing through the aspheric surface (4) and the diffractive surface (5) of the refractive-diffractive hybrid lens (3). The focus is linearly distributed along the optical axis with the wavelength.

2. The spectral confocal displacement probe based on the refractive-diffractive mixing principle according to claim 1 is characterized in that: The first surface, ie, the aspherical surface, of the refractive-diffractive hybrid lens is coated with an anti-reflection film to improve spectral transmittance.

3. The spectral confocal displacement probe based on the refractive-diffractive hybrid principle according to claim 2 is characterized in that: The diffraction surface of the refractive-diffractive hybrid lens is an annular step-shaped microstructure.

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