A small-aperture axially symmetric spectral confocal probe

Abstract

The present invention is a small-aperture axially symmetric spectral confocal probe, which includes a lens barrel. An axially symmetric fiber optic emission integrated module is provided inside the lens barrel. One end of the lens barrel introduces an optical fiber and is connected to the axially symmetric fiber optic emission integrated module. A dispersion lens group is provided inside the lens barrel and on the output optical path of the axially symmetric fiber optic emission integrated module, so that the axially symmetric fiber optic emission integrated module emits the composite light introduced by the optical fiber to the dispersion lens group. After the light beams of different wavelengths are dispersed, separated, refracted and focused by the dispersion lens group, their focal points are sequentially distributed on the optical axis with the change of wavelength, mapping the wavelength distribution of the composite light to the position information of the measured space, and realizing the monitoring of its spatial position by detecting the wavelength of the reflected light from the measured object. The structure of the present invention can ensure the high measurement accuracy of the probe while making the probe axially symmetrically arranged and having a small aperture, improving the integratability of the probe.

Description

Technical Field

[0001] The present invention relates to the field of detection technology, and particularly to a small-aperture axially symmetric spectral confocal probe. Background Art

[0002] In response to the increasingly widespread demand for high-precision non-contact precision measurement, the spectral confocal measurement method that uses a dispersive objective lens to map the wavelength distribution of a complex light wave to the spatial position has been favored by various precision measurement industries since its invention in 1955, and is widely used in fields such as biological tissue detection, precise control of chemical raw materials, mapping of cultural relics' shapes, and semiconductor process monitoring. With the gradual rise of the semiconductor and 3C industries of mobile phones, computers, etc., the demand for size measurement of small and micro parts has become increasingly strong, and small-aperture, well-integrated spectral confocal measurement probes have gradually become a hot topic in precision measurement research.

[0003] Traditional confocal measurement probes generally use optical fibers as the means of introducing a detection complex light source. According to the different shapes of their emission end faces, there are mainly two standards: vertical and inclined. The end-face vertical optical fiber can make the optical fiber connector coincide with the axis of the confocal measurement probe, ensuring that the radial size of the probe is controllable. However, this method will result in a relatively high measurement background signal due to the direct reflection at the interface between the optical fiber core and air. The inclined end-face method can significantly reduce the direct reflection of the end face, but it needs to be installed inclined. Due to the inherent volume of the optical fiber connector, this asymmetric method will inevitably increase the radial size of the probe, which is not conducive to the effective integration of the probe in the application scenario.

[0004] Moreover, to meet the small-size design of the probe's outer shape, its internal lens group also tends to be smaller and smaller. Due to the current lens processing technology and lens barrel processing level, there are inevitably inherent fitting gaps in the assembly of each lens. As the lens size becomes smaller, the relative proportion of the fitting gap to the lens size becomes larger, and the accumulated deviation of aberration caused by this becomes more obvious. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art, and provide a small-aperture axially symmetric spectral confocal probe, which is axially symmetrically arranged with a small aperture while ensuring high measurement accuracy of the probe, thereby improving the integratability of the probe.

[0006] To achieve the above technical purpose and reach the above technical effect, the present invention is realized through the following technical solutions:

[0007] A small-aperture axially symmetric spectral confocal probe head, comprising a lens barrel, wherein an axially symmetric optical fiber emission integration module is arranged in the lens barrel. One end of the lens barrel introduces an optical fiber and is communicated with the axially symmetric optical fiber emission integration module. A dispersion lens group is arranged in the lens barrel and on the output optical path of the axially symmetric optical fiber emission integration module, so that the axially symmetric optical fiber emission integration module emits the polychromatic light introduced by the optical fiber to the dispersion lens group. After the light beams of different wavelengths are dispersed, separated and refracted and focused by the dispersion lens group, their focal points are sequentially distributed on the optical axis with the change of wavelength, mapping the wavelength distribution of the polychromatic light to the position information of the measured space, and realizing the monitoring of its spatial position by detecting the wavelength of the reflected light of the measured object.

[0008] Further, the dispersion lens group includes a fixed dispersion lens group and an aberration compensation dispersion lens group. The fixed dispersion lens group and the aberration compensation dispersion lens group are arranged in the lens barrel and are sequentially arranged on the output optical path of the axially symmetric optical fiber emission integration module, and are respectively used for dispersion separation and refractive focusing to reduce the total aberration of the overall lens group.

[0009] Further, the fixed dispersion lens group and the aberration compensation dispersion lens group are composed of several single lenses, and both the fixed dispersion lens group and the aberration compensation dispersion lens group adopt a symmetric structure.

[0010] Further, the axially symmetric optical fiber emission integration module includes a beam diffuser head, a diffuser head fixing sleeve and a tightening diaphragm. The beam diffuser head is arranged in the diffuser head fixing sleeve. A fiber hole is arranged in the diffuser head fixing sleeve. The optical fiber penetrates into the fiber hole and is connected to one end of the beam diffuser head. The tightening diaphragm is located at the other end of the beam diffuser head and is screwed together with the diffuser head fixing sleeve through threads, and is used for pressing the beam diffuser head and restricting the beam aperture.

[0011] Further, the beam diffuser head is made of the same material as the core of the optical fiber, and the two are connected by high-energy laser melting, so that the light introduced by the optical fiber is transmitted to the beam diffuser head without loss through its end face, and after being diffused by the beam diffuser head, the direct reflection caused by the end face of the device is greatly reduced.

[0012] Further, a diaphragm through hole with an opening facing outwards is arranged in the middle of the tightening diaphragm for passing light, and the edge of the tightening diaphragm blocks the edge light of the beam diffuser head for restricting the beam aperture.

[0013] Further, a multi-layer dielectric antireflection film is evaporated on the end face of the beam diffuser head opposite to the tightening diaphragm for further reducing the end face reflection.

[0014] Furthermore, the beam diffusing head is integrally composed of a frustum section and a cylindrical section. The cylindrical section is connected to the lower bottom surface of the frustum section. The upper bottom surface of the frustum section is connected to the optical fiber, and the diameter of the cylindrical section is greater than the diameter of the lower bottom surface of the frustum section, forming a diffusive emission end face.

[0015] The beneficial effects of the present invention are as follows:

[0016] The present invention adopts a diffusive structure for the emission end face. While expanding the reflection area of the optical fiber end face, it is supplemented with a multi-layer dielectric antireflection film to effectively reduce the direct reflection of the optical fiber end face and ensure the coaxial configuration of the transmitting optical fiber, so as to reduce the overall aperture of the probe and enhance the applicability of the spectral confocal probe.

[0017] On the basis of fixing the dispersion lens group, the present invention adds an aberration compensation dispersion lens group. While ensuring the dispersion range of the spectral confocal probe, it reduces the total aberration of the overall lens group and improves the measurement performance of the probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a structural schematic diagram of the present invention;

[0019] Figure 2 is a structural diagram of the axisymmetric optical fiber emission integrated module in the present invention;

[0020] Figure 3 is a diagram of the aberration list of the fixed dispersion lens group and the aberration compensation dispersion lens group in the present invention.

[0021] Reference numeral description in the figures: 1. Axisymmetric optical fiber emission integrated module, 11. Beam diffusing head, 12. Diffusing head fixing sleeve, 13. Tightening diaphragm, 2. Fixed dispersion lens group, 3. Aberration compensation dispersion lens group, 4. Optical fiber, 5. Lens barrel. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The present invention will be described in detail below with reference to the drawings and in combination with embodiments.

[0023] As Figure 1 shown, a small-aperture axisymmetric spectral confocal probe includes a lens barrel 5. An axisymmetric optical fiber emission integrated module 1 is provided in the lens barrel 5. One end of the lens barrel 5 introduces an optical fiber 4 and is connected to the axisymmetric optical fiber emission integrated module 1. A dispersion lens group is provided in the lens barrel 5 and on the output optical path of the axisymmetric optical fiber emission integrated module 1, so that the axisymmetric optical fiber emission integrated module 1 emits the composite light introduced by the optical fiber 4 to the dispersion lens group. After the light beams of different wavelengths are dispersed, separated, refracted, and focused by the dispersion lens group, their focal points are sequentially distributed along the optical path axis with the change of wavelength, mapping the wavelength distribution of the composite light to the position information of the measured space, and realizing the monitoring of its spatial position by detecting the wavelength of the reflected light from the measured object.

[0024] The dispersion lens group includes a fixed dispersion lens group 2 and an aberration compensation dispersion lens group 3. The fixed dispersion lens group 2 and the aberration compensation dispersion lens group 3 are located in the lens barrel 5 and are sequentially arranged on the output optical path of the axially symmetric fiber optic emission integrated module 1, and are respectively used for dispersion separation and refractive focusing to reduce the total aberration of the overall lens group.

[0025] The fixed dispersion lens group 2 and the aberration compensation dispersion lens group 3 are composed of a plurality of single lenses, and both the fixed dispersion lens group 2 and the aberration compensation dispersion lens group 3 adopt a symmetric structure.

[0026] In this embodiment, the selected size of the dispersion lens group is restricted. The inner diameter D of the lens barrel 5 of the spectral confocal probe is 8 mm. Within its working wavelength band [λ1, λ2], λ1 and λ2 are respectively the short-wave and long-wave limits of the working wavelength band, so that the dispersion lens group satisfies: In the formula, 1 to n are the serial numbers of the single lenses through which the light rays starting from the emitting surface of the probe light source pass in sequence, D i is the effective clear aperture of the i-th single lens, is the optical power of the i-th single lens, v′ i is the relative Abbe number of the i-th single lens within the working wavelength band of the spectral confocal probe, and MR is the measurement range of the spectral confocal probe;

[0027] Among them, the Abbe number v′ i The calculation formula is: In the formula, n iF , n iC , are respectively the refractive indices corresponding to the F light, C light, and the wavelength limits of the working wavelength band of the spectral confocal probe for the i-th single lens;

[0028] At a specific wavelength λ0 within the working wavelength band [λ1,..., λ0,..., λ2] of the spectral confocal probe, its corresponding back focal length The absolute values of the differences between the back focal lengths corresponding to the short-wave limit λ1 and the long-wave limit λ2 are both 1.5 mm, that is:

[0029]

[0030]

[0031]

[0032] -Δ1 = Δ2 = 1.5;

[0033] At the focus of the light rays emitted by the spectral confocal probe at the wavelength λ0, as shown in Figure 1 In, the angle between the maximum aperture light ray and the optical axis:

[0034] As shown Figure 2 in the figure, the axisymmetric optical fiber emission integrated module 1 includes a beam diffuser head 11, a diffuser head fixing sleeve 12, and a tightening diaphragm 13. The beam diffuser head 11 is disposed within the diffuser head fixing sleeve 12. The diffuser head fixing sleeve 12 is provided with an optical fiber channel. The optical fiber 4 passes through the optical fiber channel and is connected to one end of the beam diffuser head 11. The tightening diaphragm 13 is located at the other end of the beam diffuser head 11 and is screwed together with the diffuser head fixing sleeve 12 by a thread, and then can be integrally fixed by dispensing glue, which is used to press the beam diffuser head 11 and limit the beam aperture.

[0035] The beam diffuser head 11 is made of the same core material as the optical fiber 4. In this embodiment, both are made of quartz material. The numerical aperture of the optical fiber 4 is 0.22 mm, and the two are connected by high-energy laser melting to ensure the smooth continuity of the quartz material in space, so that the light introduced by the optical fiber 4 is transmitted to the beam diffuser head 11 without loss from its end face. When the light diffuses to the end face S of the beam diffuser head 11, partial reflection occurs. The reflected light continues to diffuse in the reverse direction. Since the ratio of the optical fiber end face to the reverse diffusion face is extremely small, only a very small amount of light will directly return to the optical fiber 4, greatly reducing the direct reflection caused by the device end face. If the end face of the optical fiber 4 emits directly in free space, partial reflection will occur at the optical fiber end face due to the difference in refractive indices of the quartz material of the optical fiber core and air. Part of the reflected light is confined by the optical fiber cladding and returns completely, which will lead to the enhancement of the background signal. The structure of the present invention avoids the aforementioned problems.

[0036] The middle of the tightening diaphragm 13 is provided with a diaphragm through hole opening outward for passing light. The light continues to propagate through the beam diffuser head 11 to Figure 2 the end face S in it. The edge of the tightening diaphragm 13 blocks the marginal light of the beam diffuser head 11, restricting the initial numerical aperture of the beam na = n1sinθ0 = 0.22 to NA = n1sinθ1 = 0.1.

[0037] Within the working wavelength band [λ1, λ2] of the spectral confocal probe head, on the end face of the beam diffuser head 11 opposite to the tightening diaphragm 13 ( Figure 2 the end face S in it), a multi-layer dielectric antireflection film is deposited to reduce the degree of partial reflection. The intensity of the return light that the optical fiber 4 can receive is almost zero, its background signal is extremely low, and the signal-to-noise ratio is good.

[0038] The beam diffuser head 11 is integrally composed of a frustum section and a cylindrical section. The cylindrical section is connected to the lower bottom surface of the frustum section. The upper bottom surface of the frustum section is connected to the optical fiber 4, and the diameter of the cylindrical section is larger than the diameter of the lower bottom surface of the frustum section, forming a diffusive emission end face.

[0039] In addition, in this embodiment, regarding the selection of the specifications of the single lenses in the fixed dispersion lens group 2 and the aberration compensation dispersion lens group 3, reference can be directly made to Figure 3 the aberration list diagrams of the fixed dispersion lens group 2 and the aberration compensation dispersion lens group 3 therein; since both the fixed dispersion lens group 2 and the aberration compensation dispersion lens group 3 adopt a symmetric structure, according to the characteristics of the symmetric structure in this technical field, the lateral aberration of the fixed dispersion lens group 2 and the aberration compensation dispersion lens group 3:

[0040] Coma: ∑S II fix 、∑S II com ; Distortion: ∑S V fix 、∑S V com ; Lateral chromatic aberration: ∑C II fix 、∑C II com are all 0;

[0041] Optimization and correction are carried out so that the total axial aberration of the spectral confocal probe is as follows:

[0042] ∑S I sum =∑S I fix +∑S I com =0

[0043] ∑s III sum =∑s III fix +∑s III com =0

[0044] ∑S IV sum =∑s IV fix +∑S IV com =0

[0045] ∑C I sum =∑C I fix +∑c I com =MR;

[0046] When the axial aberration of the fixed dispersion lens group 2 has deviations ∑Δ(S I fix ), ∑Δ(S III fix ), ∑Δ(S IV fix ) due to actual processing errors, the relative distance between the aberration compensation dispersion lens group 3 and it can be adjusted to change the position where the light is projected onto it, so that it generates aberration deviations ∑Δ(S I com ), ∑Δ(S III com ), ∑Δ(S IV com ) with the same value but opposite signs to those of the fixed dispersion lens group 2 to offset the influence of the processing errors on the spectral confocal probe, that is:

[0047] ∑Δ(S I fix )+∑Δ(S I com )=0

[0048] ∑Δ(S III fix)+∑Δ(S III com )=0

[0049] ∑Δ(S IV fix )+∑Δ(S IV com )=0, since the adjustment displacement is small, the design symmetry of the two lens groups will not be destroyed, so the sum of the vertical axis aberrations remains 0. The above-mentioned symmetrical dispersion grouping structure and adjustment method can effectively offset the influence of the processing error on the aberration of the spectral confocal probe, ensuring the perfect measurement performance of the spectral confocal probe.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A small-aperture axially symmetric spectral confocal probe, comprising a lens barrel (5), characterized in that, An axially symmetric fiber optic emission integrated module (1) is provided inside the lens barrel (5). One end of the lens barrel (5) introduces an optical fiber (4) and is connected to the axially symmetric fiber optic emission integrated module (1). A dispersion lens group is provided inside the lens barrel (5) and on the output optical path of the axially symmetric fiber optic emission integrated module (1), such that the axially symmetric fiber optic emission integrated module (1) emits the composite light introduced by the optical fiber (4) to the dispersion lens group. After the light beams of different wavelengths are dispersed, separated, refracted, and focused by the dispersion lens group, their focal points are sequentially distributed along the optical axis with the change of wavelength, mapping the wavelength distribution of the composite light to the position information of the measured space, and realizing the monitoring of its spatial position by detecting the wavelength of the reflected light from the measured object; The dispersion lens group includes a fixed dispersion lens group (2) and an aberration compensation dispersion lens group (3). The fixed dispersion lens group (2) and the aberration compensation dispersion lens group (3) are located inside the lens barrel (5) and are sequentially arranged on the output optical path of the axially symmetric fiber optic emission integrated module (1), respectively used for dispersion separation and refractive focusing to reduce the total aberration of the overall lens group; Both the fixed dispersion lens group (2) and the aberration compensation dispersion lens group (3) adopt a symmetric structure; The axially symmetric fiber optic emission integrated module (1) includes a beam diffuser head (11), a diffuser head fixing sleeve (12), and a tightening diaphragm (13). The beam diffuser head (11) is arranged inside the diffuser head fixing sleeve (12). The diffuser head fixing sleeve (12) is provided with an optical fiber channel, and the optical fiber (4) penetrates into the optical fiber channel and is connected to one end of the beam diffuser head (11). The tightening diaphragm (13) is located at the other end of the beam diffuser head (11) and is screwed together with the diffuser head fixing sleeve (12) through threads, used to press the beam diffuser head (11) and limit the beam aperture; The beam diffuser head (11) is made of the same core material as the optical fiber (4), and the two are connected by high-energy laser melting, so that the light introduced by the optical fiber (4) is transmitted to the beam diffuser head (11) without loss from its end face, and the direct reflection caused by the device end face is greatly reduced after being diffused by the beam diffuser head (11); A multilayer dielectric antireflection film is deposited on the end face of the beam diffuser head (11) opposite to the tightening diaphragm (13) to further reduce the end face reflection.

2. The small-aperture axially symmetric spectral confocal probe according to claim 1, wherein The fixed dispersion lens group (2) and the aberration compensation dispersion lens group (3) are composed of several single lenses.

3. The small-aperture axially symmetric spectral confocal probe according to claim 1, characterized in that, The middle of the tightening diaphragm (13) is provided with a diaphragm through hole opening outward for passing light, and the edge of the tightening diaphragm (13) blocks the edge light of the beam diffuser head (11) to constrain the beam aperture.

4. The small-aperture axially symmetric spectral confocal probe according to claim 1, characterized in that The beam diffuser head (11) is integrally composed of a frustum section and a cylindrical section. The cylindrical section is connected to the lower bottom surface of the frustum section. The upper bottom surface of the frustum section is connected to the optical fiber (4), and the diameter of the cylindrical section is larger than the diameter of the lower bottom surface of the frustum section, forming a diffused emission end face.

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