Compact interference spectrum measurement device and method based on catadioptric angle cutter

Abstract

The invention discloses a compact interference spectrum measurement device and method based on a catadioptric angle cutter. The device comprises an optical fiber light source, a collimator objective, a composite dispersion prism, the catadioptric angle cutter, a cylindrical lens and a linear array detector which are sequentially arranged in the direction of an optical axis. Incident light is collimated to form parallel light, and the parallel light firstly passes through the composite dispersion prism; the composite dispersion prism is used for dispersing collimated light beams with different wavelengths into light beams with small angle difference, dispersion light enters the catadioptric angle clipper, and in the propagation process, due to different parity of reflection times, shearing inversion is generated in the direction of an emergent wave surface, dispersion directions are symmetrical, and equivalent spatial heterodyne interference modulation is realized; and the two beams of coherent light form interference fringes on the detector after being focused by the cylindrical lens. The device can achieve the spatial heterodyne effect through a single dispersion element, is compact in structure, easy and convenient to debug, high in light energy utilization rate and suitable for point spectrum high-resolution measurement scenes of Raman, fluorescence, absorption and other weak signals.

Description

Technical Field

[0001] The present invention belongs to the technical field of spectrum measurement, and in particular to a compact interference spectrum measurement device and method based on a catadioptric angle shearer. Background Art

[0002] As the application of high-resolution and high-sensitivity spectral detection in weak signal analysis scenarios such as Raman scattering, fluorescence imaging, and molecular absorption continues to deepen, spectral measurement systems are facing multiple challenges between resolution, stability, and compactness. In recent years, the rapidly developing spatial heterodyne structure uses symmetrically configured double gratings or double prisms to introduce angular dispersion shearing, so that the spectral signal forms spatially modulated interference fringes on the detection surface, realizing static interferometry without scanning. Although this solution has the advantages of non-scanning and high resolution, it still has the following key issues:

[0003] 1) The spatial heterodyne structure requires two dispersion elements with good consistency, and the placement positions must be strictly consistent, which makes the system development difficult.

[0004] 2) The spatial heterodyne structure uses two dispersion elements, which results in a larger system optical path volume.

[0005] 3) Gratings are often used as dispersion elements in spatial heterodyne structures, which results in significant limitations on light energy utilization.

[0006] Therefore, it is necessary to propose a spectral measurement device with a compact structure, independent of a double-plate symmetrical dispersion structure, high light flux and controllable spectral shearing to meet the high-resolution measurement requirements in point spectral scenarios. Summary of the Invention

[0007] The purpose of the present invention is to address the problems existing in the above-mentioned prior art and provide a compact interference spectroscopy measurement device and method for a fold-reflective angle shearer, which realizes stable and controllable wavefront shearing interference through a fold-reflective path configuration without relying on a bisymmetrical dispersion element.

[0008] The technical solution for achieving the purpose of the present invention is as follows: on the one hand, a compact interferometric spectroscopy measuring device based on a catadioptric angle shear is provided, the device comprising: a light source, a collimating objective lens, a compound dispersive prism, a catadioptric angle shear, a cylindrical lens, and a linear array detector, which are sequentially arranged along the optical axis;

[0009] Among them, the collimating objective lens is used to collimate the divergent light beam emitted by the light source into a parallel light beam propagating along the optical axis, and the compound dispersive prism is used to disperse the collimated light beams of different wavelengths into light beams with small angular differences; the folding angle shear is used to shear the dispersed light emitted by the compound dispersive prism into two coherent light beams with small angular deviations and spatial displacements; the cylindrical lens is used to focus the two coherent light beams emitted by the folding angle shear onto the linear array detector along an axial direction orthogonal to the shearing direction to form interference fringes containing spectral information; wherein, the degree of small angular deviation and spatial displacement is custom designed and adjusted.

[0010] Furthermore, the composite dispersive prism is a beam-splitting prism with a beam-splitting surface arranged along the optical axis direction, which is used to respectively emit the dispersed light emitted from the composite dispersive prism along the refraction-reflection-refraction path and the refraction-transmission-refraction path. There is an odd-even difference in the number of reflections of the two beams of light during the propagation process, causing the shear directions of the output wavefronts to be opposite and the dispersion directions to be symmetrical, thereby realizing wavelength-dependent optical path difference modulation equivalent to spatial heterodyne.

[0011] Furthermore, the composite dispersion prism is composed of two pieces of optical glass glued together, namely a low-dispersion crown glass at the front and a high-dispersion flint glass at the back; wherein,

[0012] The crown glass has a relatively low refractive index and a relatively high Abbe number, so as to improve dispersion linearity;

[0013] The flint glass has a relatively high refractive index and a relatively low Abbe number, which is used to enhance angular dispersion between different wavelengths.

[0014] Furthermore, for the compound dispersion prism, by optimizing the bonding interface position, dispersion vertex angle and geometric dimensions of the two optical glasses, the emission direction of the long-wavelength light beam is made close to the optical axis, and a certain angle θ is created between the output light of the compound dispersion prism and the beam splitting interface of the catadioptric angle shear.

[0015] Furthermore, the catadioptric angle shear has a symmetrical beam splitting structure for shearing an incident dispersed light beam in opposite directions into two coherent light beams with angular deviation and spatial offset, wherein:

[0016] The first part of the light enters through the first side incident surface of the catadioptric angle shear, is refracted, reflected at the beam splitting interface, and then refracted through the exit surface to exit;

[0017] The second part of the light enters through the incident surface on the other side of the catadioptric angle shear, is refracted in sequence, transmitted at the beam splitting interface, and then refracted through the exit surface to exit.

[0018] Furthermore, the light source adopts an optical fiber coupled output form.

[0019] In another aspect, a method for measuring angular shearing interferometry spectroscopy is provided, the method comprising:

[0020] Step 1, converting the divergent light beam output by the light source into a parallel light beam through a collimating objective lens;

[0021] Step 2, passing the parallel light beam through a compound dispersive prism to generate wavelength-dependent angular dispersion;

[0022] Step 3: The dispersed light beam passes through a beam splitting prism, whereby shearing in opposite directions is formed between the outgoing wavefronts, and a wavelength-related optical path difference is naturally formed in the propagation path;

[0023] Step 4: using a cylindrical lens to converge the two coherent light beams onto a linear array detector to form interference fringes containing target spectral information;

[0024] Step 5: perform wavelength calibration and non-uniform Fourier transform processing on the interference fringe signal to reconstruct and obtain high-resolution spectrum information of the sample to be tested.

[0025] Compared with the prior art, the present invention has the following significant advantages:

[0026] (1) The present invention only requires one composite dispersion prism to achieve the effect of spatial heterodyne, avoiding the reliance on the consistency of two dispersion elements in the traditional structure, significantly simplifying the system structure and reducing the difficulty of installation and adjustment.

[0027] (2) The present invention uses only a single dispersion prism and a folding angle shear, which effectively reduces the optical path volume and improves the compactness of the system.

[0028] (3) The dispersion element used in the present invention is a composite dispersion prism, which avoids the energy loss problem caused by multi-order diffraction of the grating and effectively utilizes the light energy.

[0029] (4) The device has the advantages of compact structure, easy installation and adjustment, high throughput, and high spectral resolution, and is suitable for high-sensitivity measurement tasks of point spectra of weak signals.

[0030] The present invention is further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of a compact interferometric spectroscopy measurement device based on a fold-reflective angle shear.

[0032] Figure 2 This is a structural diagram of the beam shearing process, showing how two beams of light exit the prism through the "refraction-reflection-refraction" and "refraction-transmission-refraction" paths, respectively, and form coherent shear wavefronts.

[0033] Figure 3The simulation results of interference fringes formed on the linear array detector by the device of the present invention under illumination of light sources of different wavelengths are shown in FIG. Figure 3 (a)-(c) are laser interference fringes of 780, 880, and 980 nm, respectively. Figure 3 (d) in the figure is the simulation result of the interference pattern under white light illumination with a spectral width of 100 nm. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described below are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0035] Furthermore, directional terms (e.g., "up," "down," "left," "right," "front," "back," etc.) used in the embodiments of the present invention are only used to describe the relative positions of components in the specific postures shown in the drawings. If the posture changes, the corresponding directional terms should also change accordingly.

[0036] Furthermore, if terms such as “first” and “second” appear in the present invention, they are only used to distinguish different features or steps and cannot be understood as indicating their priority, importance or quantitative limitation.

[0037] In addition, the technical features of different embodiments of the present invention can be arbitrarily combined under the premise that there is no conflict; however, if there is a contradiction between the technical features or the technology is not feasible, the combination shall be deemed invalid and shall not fall within the scope of protection of the present invention.

[0038] In one embodiment, combined Figure 1 , provides a compact interference spectroscopy measurement device based on a catadioptric angle shear, the device comprising: a light source 1, a collimating objective lens 2, a compound dispersion prism 3, a catadioptric angle shear 4, a cylindrical lens 5 and a linear array detector 6, which are arranged in sequence along the optical axis;

[0039] Among them, the collimating objective lens 2 is used to collimate the divergent light beam emitted by the light source 1 into a parallel light beam propagating along the optical axis, and the compound dispersive prism 3 is used to disperse the collimated light beams of different wavelengths into light beams with small angular differences; the folding angle shear 4 is used to shear the dispersed light emitted by the compound dispersive prism 3 into two coherent light beams with small angular deviations and spatial displacements; the cylindrical lens 5 is used to focus the two coherent light beams emitted by the folding angle shear 4 along an axial direction orthogonal to the shearing direction onto the linear array detector 6 to form interference fringes containing spectral information; wherein, the degree of small angular deviation and spatial displacement is custom designed and adjusted.

[0040] Furthermore, in one of the embodiments, the compound dispersive prism 3 is a beam splitting prism with a beam splitting surface arranged along the optical axis direction, which is used to respectively emit the dispersed light emitted from the compound dispersive prism 3 along the refraction-reflection-refraction path and the refraction-transmission-refraction path. There is an odd-even difference in the number of reflections of the two beams of light during the propagation process, causing the shear directions of the output wavefronts to be opposite and the dispersion directions to be symmetrical, thereby realizing wavelength-dependent optical path difference modulation equivalent to spatial heterodyne.

[0041] Preferably, in some embodiments, the composite dispersion prism 3 is formed by gluing two pieces of optical glass, namely, a low-dispersion crown glass at the front and a high-dispersion flint glass at the back, so as to achieve an angular dispersion output with good linearity in a compact structure; wherein,

[0042] The crown glass has a relatively low refractive index and a relatively high Abbe number, so as to improve dispersion linearity;

[0043] The flint glass has a relatively high refractive index and a relatively low Abbe number, which is used to enhance angular dispersion between different wavelengths.

[0044] Here, for the compound dispersion prism 3, by optimizing the bonding interface position, dispersion vertex angle and geometric dimensions of the two optical glasses, the emission direction of the long-wavelength light beam is made close to the optical axis, and a certain angle θ is present between the output light of the compound dispersion prism 3 and the beam splitting interface of the folding angle shear 4.

[0045] Furthermore, in one embodiment, the folding angle shear 4 has a symmetrical beam splitting structure for shearing the incident dispersed light beam into two coherent light beams with angular deviation and spatial offset in opposite directions; Figure 2 :

[0046] The first part of the light (red light) enters through the first side incident surface of the catadioptric angle shear 4, is refracted, reflected at the beam splitting interface, and then refracted through the exit surface;

[0047] The second part of light (blue light) enters through the incident surface on the other side of the folding-reflecting angle shear 4, is refracted in sequence, is transmitted at the beam splitting interface, and is refracted and emitted through the exit surface.

[0048] Because the two beams experience an odd or even number of reflections within the prism, they ultimately form opposite wavefront shear angles between the exiting wavefronts, with symmetrical dispersion directions. This angle introduces a wavelength-dependent optical path difference. This design enables equivalent spatial heterodyne modulation, simplifies structural alignment, and significantly improves system stability and practicality.

[0049] Preferably, in some embodiments, the light source 1 adopts a fiber-coupled output form and can be connected to a laser or a broadband white light source to provide a divergent light beam of the signal to be measured.

[0050] In one embodiment, a method for measuring angular shearing interferometry spectroscopy based on the above device is provided, the method comprising:

[0051] Step 1, converting the divergent light beam output by the light source into a parallel light beam through a collimating objective lens;

[0052] Step 2, passing the parallel light beam through a compound dispersive prism to generate wavelength-dependent angular dispersion;

[0053] Step 3: The dispersed light beam passes through a beam splitting prism, whereby shearing in opposite directions is formed between the outgoing wavefronts, and a wavelength-related optical path difference is naturally formed in the propagation path;

[0054] Step 4: using a cylindrical lens to converge the two coherent light beams onto a linear array detector to form interference fringes containing target spectral information;

[0055] Step 5: perform wavelength calibration and non-uniform Fourier transform processing on the interference fringe signal to reconstruct and obtain high-resolution spectrum information of the sample to be tested.

[0056] As a specific example, the present invention is further verified in one of the embodiments.

[0057] like Figure 3 As shown in FIG, the interference pattern simulation result of the device of the present invention in the MATLAB environment. Figure 3 (a)–(c) correspond to monochromatic laser illumination with wavelengths of 780nm, 880nm, and 980nm, respectively. Clear and uniform interference fringes can be observed on the linear array detector. As the wavelength increases, the fringe spacing increases, indicating that the optical path difference of the system is inversely proportional to the wavelength and the interferometric modulation characteristics are good. Figure 3 Middle (d) shows the fringe pattern under broadband white light illumination, which verifies that the system has the ability to effectively modulate the continuous spectrum and can provide a stable data basis for subsequent high-resolution spectral reconstruction.

[0058] In practical applications, this device can be configured with a 785nm laser as a Raman excitation source. By optimizing the vertex angle and material combination of the composite dispersion prism, angular dispersion control can be achieved across a wider wavelength range of 785–1000nm or even wider. The collected interference fringes are then subjected to wavelength calibration and non-uniform Fourier transform processing to obtain high-resolution spectral information of the target sample.

[0059] In summary, the present invention achieves stable spatial shearing interferometry through a refractive-reflective shearing structure, constructing a compact interferometric spectroscopy system with high stability and high resolution that does not require a bisymmetric dispersion element. It is suitable for a variety of weak signal point spectral measurement scenarios such as Raman, fluorescence, and molecular absorption.

[0060] The light path arrows in the figure indicate the direction of light propagation; all angles, dimensions, and proportions are schematic representations; actual structural parameters can be flexibly adjusted according to application requirements. The embodiments described in this invention are preferred examples only; any reasonable substitutions and improvements to the structural form, material selection, or signal processing method within the core concept of this invention shall be considered within the scope of protection of this invention.

[0061] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only illustrative of the principles of the present invention. Without departing from the spirit and scope of the present invention, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A compact interferometric spectroscopy measuring device based on a catadioptric angle shear, characterized in that: The device comprises: a light source (1), a collimating objective lens (2), a compound dispersion prism (3), a catadioptric angle shear (4), a cylindrical lens (5), and a linear array detector (6), which are arranged in sequence along the optical axis; The collimating objective lens (2) is used to collimate the divergent light beam emitted by the light source (1) into a parallel light beam propagating along the optical axis; the compound dispersive prism (3) is used to disperse the collimated light beams of different wavelengths into light beams with small angular differences; the folding angle shear (4) is used to shear the dispersed light emitted by the compound dispersive prism (3) into two coherent light beams with small angular deviations and spatial displacements; the cylindrical lens (5) is used to focus the two coherent light beams emitted by the folding angle shear (4) along an axial direction orthogonal to the shearing direction onto a linear array detector (6) to form interference fringes containing spectral information; wherein the degree of small angular deviation and spatial displacement is custom designed and adjusted.

2. The compact interferometric spectroscopy measuring device based on a catadioptric angle shearer according to claim 1, characterized in that: The composite dispersion prism (3) is a beam splitting prism with a beam splitting surface arranged along the optical axis direction, and is used for respectively emitting the dispersed light emitted from the composite dispersion prism (3) along a refraction-reflection-refraction path and a refraction-transmission-refraction path. The two beams of light have an odd-even difference in the number of reflections during the propagation process, causing the shear directions of the exiting wavefronts to be opposite and the dispersion directions to be symmetrical, thereby achieving wavelength-dependent optical path difference modulation equivalent to spatial heterodyning.

3. The compact interferometric spectroscopy measuring device based on a catadioptric angle shearer according to claim 1, characterized in that: The composite dispersion prism (3) is composed of two pieces of optical glass glued together, namely a low-dispersion crown glass at the front and a high-dispersion flint glass at the back; wherein, The crown glass has a relatively low refractive index and a relatively high Abbe number, so as to improve dispersion linearity; The flint glass has a relatively high refractive index and a relatively low Abbe number, which is used to enhance angular dispersion between different wavelengths.

4. The compact interferometric spectroscopy measuring device based on a catadioptric angle shearer according to claim 3, characterized in that: For the composite dispersion prism (3), by optimizing the bonding interface position, dispersion vertex angle and geometric dimensions of two optical glasses, the emission direction of the long-wavelength light beam is made close to the optical axis, and a certain angle θ is formed between the output light of the composite dispersion prism (3) and the beam splitting interface of the catadioptric angle shear (4).

5. The compact interferometric spectroscopy measuring device based on a catadioptric angle shearer according to claim 1, characterized in that: The catadioptric angle shear (4) has a symmetrical beam splitting structure and is used for shearing an incident dispersed light beam into two coherent light beams with an angular deviation and a spatial offset in opposite directions, wherein: After the first part of the light enters through the first side incident surface of the folding-reflecting angle shear (4), it is refracted, reflected at the beam splitting interface, and then refracted through the exit surface to exit; After entering through the incident surface on the other side of the folding and reflecting angle shear (4), the second part of the light is refracted, transmitted at the beam splitting interface, and then refracted through the exit surface to exit.

6. The compact interferometric spectroscopy measuring device based on a catadioptric angle shearer according to claim 1, characterized in that: The light source (1) adopts an optical fiber coupled output form.

7. The angular shearing interferometry spectroscopy measurement method based on the device according to any one of claims 1 to 6, characterized in that: The method comprises: Step 1, converting the divergent light beam output by the light source into a parallel light beam through a collimating objective lens; Step 2, passing the parallel light beam through a compound dispersive prism to generate wavelength-dependent angular dispersion; Step 3: The dispersed light beam passes through a beam splitting prism, whereby shearing in opposite directions is formed between the outgoing wavefronts, and a wavelength-related optical path difference is naturally formed in the propagation path; Step 4: using a cylindrical lens to converge the two coherent light beams onto a linear array detector to form interference fringes containing target spectral information; Step 5: perform wavelength calibration and non-uniform Fourier transform processing on the interference fringe signal to reconstruct and obtain high-resolution spectrum information of the sample to be tested.

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