Linear scan confocal spectral measurement structure

Abstract

This invention relates to the field of spectral measurement technology, and more particularly to a linear scan confocal spectral measurement structure, comprising: a light source for emitting polychromatic light; the polychromatic light undergoes axial dispersion via a dispersive lens assembly to form a probe light, which is incident on the object under test to form a return light, which exits after passing through the dispersive lens assembly; a slit is located in the transmission path of the return light emitted from the dispersive lens assembly, and the return light is filtered by the slit to form a signal light; a spectrometer assembly includes a beam splitter element, a plane reflection grating, an echelle grating, a first array detector, and a second array detector; the signal light is split into a first signal light and a second signal light by the beam splitter element; the first signal light is diffracted by the echelle grating and then incident on the first array detector, and the second signal light is diffracted by the plane reflection grating and then incident on the second array detector. This invention is advantageous for achieving high optical throughput, wide spectral bandwidth, and high resolution spectral measurements.

Description

Technical Field

[0001] This invention belongs to the field of spectral measurement technology, and particularly relates to a linear scan confocal spectral measurement structure. Background Technology

[0002] Spectroscopic confocal measurement is a non-contact, high-precision three-dimensional measurement technology. It uses the axial dispersion of the dispersive objective lens to encode the wavelength of light waves and the focal position, and uses a spectrometer to decode the wavelength to obtain the focal position information. It can realize the three-dimensional contour measurement of transparent samples and multi-layer structures, and provides a brand-new measurement method for surface morphology, working thickness, roughness, and deviation of target objects.

[0003] The measurement principle of the spectroscopic confocal measuring instrument is as follows: The polychromatic light emitted by the light source passes through the dispersive objective lens and forms a focal line arranged in wavelength order along the axial direction within the measurement range; when the sample surface is located at a certain focal plane, the light of the corresponding wavelength is reflected and enters the spectrometer through the slit. The spectrometer sends the wavelength corresponding to the light intensity peak to the computer. Based on the pre-calibrated "wavelength-displacement" curve, the wavelength data of all points on the entire contour line are converted into height values, realizing the scanning confocal measurement.

[0004] However, existing confocal spectral measuring instruments have the problem of low light throughput when using dispersive spectrometers. This problem can be solved by using a biaxial dispersive lens, but when a wide-band spectrum enters the dispersive spectrometer, the spectral resolution of the plane reflection grating will decrease, making it impossible to distinguish specific wavelengths, which limits the instrument's ability to detect multispectral characteristic signals. Summary of the Invention

[0005] In view of this, the present invention aims to provide a line-scan confocal spectral measurement structure, which is at least advantageous for achieving high light throughput, wide spectral band and high resolution spectral measurement.

[0006] To achieve the above objectives, the technical solution created by this invention is implemented as follows: This invention provides a line-scan confocal spectral measurement structure, comprising: a light source for emitting polychromatic light; a dispersive lens assembly, wherein the polychromatic light undergoes axial dispersion to form a probe light, which is incident on the object under test to form a return light, which is emitted after passing through the dispersive lens assembly; a slit located in the transmission path of the return light emitted from the dispersive lens assembly, wherein the return light is filtered by the slit to form a signal light; and a spectrometer assembly for receiving the signal light, comprising a beam splitter element, a plane reflection grating, an echelle grating, a first array detector, and a second array detector, wherein the signal light is split into a first signal light and a second signal light by the beam splitter element, the first signal light is incident on the echelle grating, and after diffraction by the echelle grating, it is incident on the first array detector, and the second signal light is incident on the plane reflection grating, and after diffraction by the plane reflection grating, it is incident on the second array detector.

[0007] Furthermore, the spectrometer assembly also includes a first prism, which is a triangular prism with a first side and a second side. The first side is in contact with the grating surface of the echelle grating. The first signal light passes through the first prism and enters the echelle grating. After being diffracted by the echelle grating, the first signal light passes through the first prism and enters the second array detector. The first signal light emitted from the beam splitter enters the first prism through the second side and then exits from the first side before heading towards the echelle grating. The first signal light diffracted by the echelle grating enters the first prism through the first side and then exits from the second side before heading towards the first array detector.

[0008] Furthermore, the echelle grating and the first prism constitute a combined element, which satisfies a first condition to realize the compensation of image plane curvature using the first prism. The first condition is as follows: the spectral line curvature generated by the first prism and the spectral line curvature generated by the echelle grating are equal in magnitude and opposite in direction.

[0009] Furthermore, the spectrometer assembly also includes a first collimating lens, a first imaging lens, and a second imaging lens. The first collimating lens is located between the slit and the beam splitter, the first imaging lens is located between the echelle grating and the first array detector, and the second imaging lens is located between the planar reflection grating and the second array detector.

[0010] Furthermore, the dispersive lens assembly includes a symmetrically arranged incident component and an exit component, with the object under test located on the axis of symmetry of the incident component and the exit component; the polychromatic light emitted by the light source undergoes axial dispersion through the incident component to form a probe light, which is incident on the object under test to form a return light, which passes through the exit component and is directed toward the slit.

[0011] Furthermore, the incident component includes a second collimating lens, a first PPG structure, and a first converging lens arranged sequentially along the transmission direction of the polychromatic light. The first PPG structure includes a second prism, a third prism, and a first grating arranged sequentially along the transmission direction of the polychromatic light. The polychromatic light passes through the second collimating lens, the second prism, the third prism, the first grating, and the first converging lens in sequence to form a probe light. The exit component includes a third collimating lens, a second PPG structure, and a second converging lens arranged sequentially along the transmission direction of the return light. The second PPG structure includes a second grating, a fourth prism, and a fifth prism arranged sequentially along the transmission direction of the return light. The return light passes through the third collimating lens, the second grating, the fourth prism, the fifth prism, and the second converging lens in sequence before being directed toward the slit.

[0012] Furthermore, the light source, dispersive lens assembly, object under test, slit, and spectrometer assembly are all located on the first plane.

[0013] Furthermore, the first direction is defined as the normal direction of the first plane. The first direction, the second direction, and the third direction are perpendicular to each other. The second direction is parallel to the axis of symmetry of the incident component and the exit component. The scribe line direction of the plane reflection grating is parallel to the first direction. The normal direction of the plane reflection grating is deflected relative to the second direction by the corresponding Littoral angle of the plane reflection grating. The scribe line direction of the echelle grating is parallel to the first direction. The normal direction of the echelle grating is deflected relative to the third direction by the corresponding Littoral angle of the echelle grating.

[0014] Furthermore, the second and fifth prisms have the same structure, the third and fourth prisms have the same structure, the first grating and the second grating have the same structure, the scribe lines of the first grating and the scribe lines of the second grating are both parallel to the first direction, and there is an angle between the normal direction of the first grating and the second direction.

[0015] Furthermore, both the second and third prisms are triangular prisms. In the cross-section of the first plane, the cross-sectional shape of both the second and third prisms is triangular. The first side of the second prism faces the light source, the second side of the second prism faces the third prism, the first side of the third prism faces the second prism, and the second side of the third prism faces the first grating. The second side of the second prism is in contact with the first side of the third prism, and the second side of the third prism is in contact with the grating surface of the first grating. The apex angles of the triangles corresponding to the cross-sectional shape of the second prism and the triangles corresponding to the cross-sectional shape of the third prism are located on different sides.

[0016] Compared with the prior art, the present invention can achieve the following beneficial effects: In the line-scanning confocal spectral measurement structure provided by the present invention, the dispersive lens assembly is a biaxial dispersive lens structure. Based on this, combined with the detection optical path where the echelle grating is located, line-spectral confocal measurement with high light throughput and high resolution is realized. In addition, since the dispersive lens assembly is a biaxial dispersive lens structure, if only the detection optical path where the plane reflection grating is located is relied upon, the broadband signal light transmitted by the dispersive lens assembly to the spectrometer assembly will result in too low spectral resolution. However, relying solely on the detection optical path where the echelle grating is located will produce order aliasing. Therefore, the spectrometer assembly provided by the present invention adopts a dual-arm structure, wherein one arm is the detection optical path where the echelle grating is located, and the other arm is the detection optical path where the plane reflection grating is located. The detection optical path where the plane reflection grating is located is used to realize order selection, and the detection optical path where the echelle grating is located is used to realize high resolution. In this way, the order aliasing problem can be solved, and line-spectral confocal measurement with high light throughput and high resolution can be realized. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the line-scan confocal spectral measurement structure described in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] refer to Figure 1 This invention provides a line-scan confocal spectral measurement structure, comprising: a light source 1 for emitting polychromatic light; a dispersive lens assembly, wherein the polychromatic light undergoes axial dispersion to form a probe light, which is incident on the object under test 5 to form a return light, which is emitted after passing through the dispersive lens assembly; a slit 9 located in the transmission optical path of the return light emitted from the dispersive lens assembly, wherein the return light is filtered by the slit 9 to form a signal light; and a spectrometer assembly for receiving the signal light, comprising a beam splitter 11, a plane reflection grating 12, an echelle grating 18, a first array detector 15, and a second array detector 14, wherein the signal light is split into a first signal light and a second signal light by the beam splitter 11, the first signal light is incident on the echelle grating 18, and after diffraction by the echelle grating 18, it is incident on the first array detector 15, and the second signal light is incident on the plane reflection grating 12, and after diffraction by the plane reflection grating 12, it is incident on the second array detector 14.

[0024] The function of slit 9 is to filter out stray light. Since the dispersive lens assembly disperses the polychromatic light axially to form the probe light, different wavelengths of light are focused at different positions along the optical axis. Not only the light focused on the object 5 will form return light, but other non-focused light will also enter the object 5 to form return light. However, the return light formed by other non-focused light is stray light. Therefore, slit 9 is needed to filter out this part of stray light.

[0025] It should be noted that although the planar reflection grating 12 has low resolution, it does not produce order overlap (or order aliasing). The echelle grating 18 can achieve high resolution but will produce order overlap. Therefore, the present invention uses the planar reflection grating 12 to achieve order selection and the echelle grating 18 to meet high resolution. This allows the line scan spectral confocal measurement structure to achieve a wide measurement range and high resolution while using a dual-axis dispersive lens structure to achieve high light throughput.

[0026] The first signal light and the second signal light must be exactly the same to ensure that the data obtained after signal processing based on the first signal light corresponds to the data obtained after signal processing based on the second signal light, thereby enabling order selection and high-resolution spectral measurement.

[0027] Furthermore, the spectrometer assembly also includes a first prism 17, which is a triangular prism with a first side and a second side. The first side is in contact with the grating surface of the echelle grating 18. The first signal light passes through the first prism 17 and then enters the echelle grating 18. After being diffracted by the echelle grating 18, the first signal light passes through the first prism 17 and then enters the second array detector 14. The first signal light emitted from the beam splitter 11 enters the first prism 17 through the second side and then exits from the first side before heading towards the echelle grating 18. The first signal light diffracted by the echelle grating 18 enters the first prism 17 through the first side and then exits from the second side before heading towards the first array detector 15.

[0028] Furthermore, the echelle grating 18 and the first prism 17 constitute a combined element. The combined element satisfies a first condition to realize the compensation of image plane curvature by using the first prism 17. The first condition is as follows: the spectral line curvature generated by the first prism 17 and the spectral line curvature generated by the echelle grating 18 are equal in magnitude and opposite in direction. ,in, The spectral line bending produced by the first prism 17 The focal length of the first imaging lens 16 The width of the operating band. This represents the change in the effective apex angle of the light rays on the first prism 17. This represents the wavelength of the signal light after it has passed through slit 9. The refractive index of prism 17 represents the refractive index of the first prism. Represents the angle of dispersion The change ,in, The spectral line bending produced by the echelle grating 18 Represents the angle of incidence The change The focal length of the first imaging lens 16 The width of the operating band. Angle of incidence Let be the diffraction angle, satisfying ,in, The grating constant is for an echelle grating of 18. This is the diffraction order of the echelle 18. This represents the wavelength of the signal light after it has been filtered through slit 9.

[0029] While achieving diffraction and spectral dispersion, the combined elements utilize the opposite bending directions of the image plane generated by the first prism 17 and the middle echelle grating 18 to make the magnitude of the image plane bending equal through calculation, thereby alleviating the bending of spectral lines.

[0030] Furthermore, the spectrometer assembly also includes a first collimating lens 10, a first imaging lens 16, and a second imaging lens 13. The first collimating lens 10 is located between the slit 9 and the beam splitter 11, the first imaging lens 16 is located between the echelle grating 18 and the first array detector 15, and the second imaging lens 13 is located between the planar reflection grating 12 and the second array detector 14.

[0031] After the signal light is incident on the spectrometer assembly, it is first collimated by the first collimating lens 10 and then incident on the beam splitting element 11. The beam splitting element 11 can be a beam splitting prism. The signal light is split into a first signal light and a second signal light by the beam splitting element 11. The first signal light and the second signal light are diffracted by the planar reflection grating 12 and the echelle grating 18 located on adjacent sides of the beam splitting element 11, respectively, and then directed to the first imaging lens 16 and the second imaging lens 13. Specifically, the first signal light, after being diffracted by the echelle grating 18, is imaged onto the first array detector 15 after passing through the first imaging lens 16, and the second signal light, after being diffracted by the planar reflection grating 12, is imaged onto the second array detector 14 after passing through the second imaging lens 13. The imaging of the first array detector 15 may have overlapping order, but the target order can be selected by using the imaging result of the second array detector 14.

[0032] Furthermore, the dispersive lens assembly includes an incident component and an exit component arranged symmetrically, with the object under test 5 located on the axis of symmetry of the incident component and the exit component; the polychromatic light emitted by the light source 1 undergoes axial dispersion through the incident component to form a probe light, which is incident on the object under test 5 to form a return light, and the return light passes through the exit component and is directed toward the slit 9.

[0033] Furthermore, the incident component includes a second collimating lens 2, a first PPG (Prism-Prism-Grating) structure, and a first converging lens 4 arranged sequentially along the transmission direction of the polychromatic light. The first PPG structure 3 includes a second prism 31, a third prism 32, and a first grating 33 arranged sequentially along the transmission direction of the polychromatic light. The polychromatic light passes sequentially through the second collimating lens 2, the second prism 31, the third prism 32, the first grating 33, and the first converging lens 4 to form a probe. The light metering assembly includes a third collimating lens 6, a second PPG (Prism-Prism-Grating) structure 7, and a second converging lens 8 arranged sequentially along the transmission direction of the returned light. The second PPG structure 7 includes a second grating 73, a fourth prism 72, and a fifth prism 71 arranged sequentially along the transmission direction of the returned light. The returned light passes through the third collimating lens 6, the second grating 73, the fourth prism 72, the fifth prism 71, and the second converging lens 8 in sequence before being directed toward the slit 9.

[0034] The second collimating lens 2 converts the polychromatic light from the point light source 1 into parallel polychromatic light. The parallel polychromatic light enters the first PPG structure 3, generates dispersion, and exits in parallel. It is then focused onto the object under test 5 by the first converging lens 4. The returning light enters the exiting assembly, is first collimated by the third collimating lens 6, and then enters the second PPG structure 7. After exiting the second PPG structure 7, it is converged by the second converging lens 8 and then enters the slit 9.

[0035] Furthermore, the light source 1, the dispersive lens assembly, the object under test 5, the slit 9, and the spectrometer assembly are all located on the first plane.

[0036] Furthermore, the first direction Y is defined as the normal direction of the first plane. The first direction Y, the second direction X, and the third direction Z are perpendicular to each other. The second direction X is parallel to the axis of symmetry of the incident component and the exit component. The scribe line direction of the planar reflection grating 12 is parallel to the first direction Y. The normal direction of the planar reflection grating 12 is deflected relative to the second direction X by the corresponding Littoral angle of the planar reflection grating 12. The scribe line direction of the echelle grating 18 is parallel to the first direction Y. The normal direction of the echelle grating 18 is deflected relative to the third direction Z by the corresponding Littoral angle of the echelle grating 18.

[0037] Furthermore, the second prism 31 and the fifth prism 71 have the same structure, the third prism 32 and the fourth prism 72 have the same structure, the first grating 33 and the second grating 73 have the same structure, the scribe lines of the first grating 33 and the scribe lines of the second grating 73 are both parallel to the first direction Y, and there is an angle between the normal direction of the first grating 33 and the second direction X, and there is the same angle between the normal direction of the second grating 73 and the second direction X.

[0038] Furthermore, both the second prism 31 and the third prism 32 are triangular prisms. On the cross-section of the first plane, the cross-sectional shape of both the second prism 31 and the third prism 32 is triangular. The first side of the second prism 31 faces the light source 1, the second side of the second prism 31 faces the third prism 32, the first side of the third prism 32 faces the second prism 31, and the second side of the third prism 32 faces the first grating 33. The second side of the second prism 31 is in contact with the first side of the third prism 32, and the second side of the third prism 32 is in contact with the grating surface of the first grating 33. The apex of the triangle corresponding to the cross-sectional shape of the second prism 31 (i.e., the apex of the second prism) and the apex of the triangle corresponding to the cross-sectional shape of the third prism 32 (i.e., the apex of the third prism) are located on different sides.

[0039] The PPG structure is used to alleviate spectral line bending and improve dispersion linearity. For the first PPG structure 3 in the dispersive lens assembly, it has the following characteristics: a spatial rectangular coordinate system is established, with the z-axis parallel to the normal direction of the first grating 33, the y-axis parallel to the grating line direction of the first grating 33, and the x-axis perpendicular to the grating line direction of the first grating 33. The angle between the edge ray of the beam passing through the second collimating lens 2 and the xy plane of the spatial rectangular coordinate system is... The angle between the central ray of the beam passing through the second collimating lens 2 and the normal to the first side surface of the second prism 31 is... The apex angle of the second prism 31 is The apex angle of the third prism 32 is According to the refraction theorem of a prism, we can obtain: This formula is derived from the law of refraction of the first refractive surface in the y-axis direction; This formula is derived from the law of refraction of the first refractive surface in the z-axis direction; ; in, Represents the refractive index of air. The refractive index of the second prism 31 is represented. Let N represent the assumed refractive index of the second prism 31 in the z-axis direction. This is because the common law of refraction in the y-axis direction cannot be used in the z-axis direction. For the sake of formal consistency, the expression on the right side of the equation is set to N1. The angle of incidence along the y-axis of the first refractive surface. The angular component of refraction along the y-axis represents the first refracting surface, which is the first side surface of the second prism 31. The incident angle component along the z-axis represents the first refracting surface. The component of the refraction angle along the z-axis represents the first refraction surface; Define the second side surface of the second prism 31 as the second refractive surface. From the second refractive surface, we can obtain: ; ; in, The incident angle component along the z-axis represents the second refracting surface. The incident angle component along the y-axis represents the second refracting surface; According to the law of refraction, we can obtain: ; ; ; in, The refractive index of the third prism 32 is represented. The refractive index of the material representing the first grating 33 The assumed refractive index of the third prism 32 along the z-axis is represented by . The component of the refraction angle of the second refraction surface in the y-axis direction. The component of the refraction angle of the second refraction surface in the z-axis direction; Define the second side surface of the third prism 32 as the third refractive surface. From the third refractive surface, we can obtain: ; ; ; ; ; in, This represents the assumed refractive index of the first grating 33 along the z-axis. The component of the refraction angle along the y-axis represents the third refraction surface. The component of the refraction angle along the z-axis represents the third refraction surface; On the grating surface of the first grating 33, or in other words, on the diffraction surface of the first grating 33, according to geometric relationships and the equation of conical diffraction, we can obtain: ; ; ; ; in, The y-axis component represents the emission angle of the diffraction surface of the first grating 33. This represents the incident angle component of the first grating 33 diffraction plane in the y-axis direction. This represents the incident angle component of the first grating 33 diffraction plane along the z-axis. Represents the diffraction order of the first grating 33. The grating constant representing the first grating 33, The wavelength represents light source 1.

[0040] In summary, the deflection angle of the light rays along the z-axis after passing through the first PPG structure 3 can be obtained. The expression is as follows: ; In other words, based on ( , , , , , , , , as well as )and ( , , , , , , The direction of light propagation emitted from the first PPG structure 3 can be determined.

[0041] When the length of slit 9 and the focal length of the second collimating lens 2 are determined, This is also determined accordingly, therefore, the amount of spectral line bending. It can be represented as: ; The positions of light rays of different wavelengths on the measured object 5 can be represented as follows: ; in, The focal length of the first converging lens 4, The angle of deflection in the dispersion direction of the light rays from the slit edge after passing through the first PPG structure 3. The angle of deviation in the dispersion direction of the light ray from the center of the slit after passing through the first PPG structure 3.

[0042] Take 3 wavelengths , and , , and The following relationship must be satisfied: That is, the three wavelengths are equally spaced, using To measure dispersion linearity, express and The dispersion width between and The quotient of the dispersion widths between them minus one, i.e. If the system dispersion is perfectly linear, then and The dispersion width between them should be equal to and The more linear the system dispersion, the greater the dispersion width between the two values. The closer it gets to zero.

[0043] In summary, when wavelength After determining the materials of the first converging lens 4, the second collimating lens 2, the prism, the first grating 33, the grating density, and the diffraction order of the first grating 33, and Only and The function that causes the spectral line bending amount Smaller and dispersion linearity When it is small, it can be determined and .

[0044] In some embodiments, Less than 20 micrometers When the value is less than 0.01, the PPG structure effectively alleviates spectral line bending and effectively improves dispersion linearity.

[0045] The line scan working mode refers to scanning the sample with a line extending along the first direction Y. Only light focused on the object under test 5 can pass through the slit 9.

[0046] The linear scanning confocal spectral measurement structure provided by this invention has advantages such as wide measurement band, high light flux, and high resolution. The spectrometer assembly provided by this invention uses a dual-arm spectrometer structure to replace the ordinary planar grating spectrometer used in traditional confocal spectral measurement instruments, improving the instrument's resolution while maintaining a wide measurement range. The dispersive lens assembly provided by this invention adopts a dual-axis dispersive lens to achieve a structural design that separates the illumination optical axis and the probe optical axis, significantly reducing the influence of stray light and defocused light, and significantly improving light energy utilization and signal-to-noise ratio. Secondly, it can achieve submicron-level axial and lateral resolution at a low numerical aperture, effectively suppressing multiple scattering, and has higher detection sensitivity for semi-transparent and porous materials. It also reduces the stringent requirements of lateral resolution on optical design, making it easier to achieve a larger working distance and measurement field of view. At the same time, it improves the system's light flux and overall performance parameters, making it perform better in high-speed, high-precision three-dimensional topography measurement.

[0047] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0048] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A linear scan confocal spectral measurement structure, characterized in that, include: Light source, the light source being used to emit polychromatic light; The dispersive lens assembly is a dual-axis dispersive lens structure. The polychromatic light undergoes axial dispersion through the dispersive lens assembly to form a probe light. The probe light is incident on the object under test to form a return light. The return light passes through the dispersive lens assembly and is then emitted. A slit is located in the transmission optical path of the returning light emitted from the dispersive lens assembly, and the returning light is filtered by the slit to form signal light; A spectrometer assembly for receiving the signal light includes a beam splitter, a plane reflection grating, an echelle grating, a first array detector, and a second array detector. The signal light is split into a first signal light and a second signal light by the beam splitter. The first signal light is incident on the echelle grating and, after diffraction by the echelle grating, is incident on the first array detector. The second signal light is incident on the plane reflection grating and, after diffraction by the plane reflection grating, is incident on the second array detector.

2. The linear scan confocal spectral measurement structure according to claim 1, characterized in that, The spectrometer assembly further includes a first prism, which is a triangular prism with a first side and a second side. The first side is in contact with the grating surface of the echelle grating. The first signal light passes through the first prism and then enters the echelle grating. After being diffracted by the echelle grating, the first signal light passes through the first prism and then enters the second array detector. The first signal light emitted by the beam splitter enters the first prism through the second side and then exits from the first side before being directed toward the echelle grating. The first signal light, after being diffracted by the echelle grating, enters the first prism through the first side and then exits from the second side before being directed toward the first array detector.

3. The linear scan confocal spectral measurement structure according to claim 2, characterized in that, The echelle grating and the first prism constitute a combined element. The combined element satisfies a first condition to realize the compensation of image plane curvature using the first prism. The first condition is as follows: the spectral line curvature generated by the first prism and the spectral line curvature generated by the echelle grating are equal in magnitude and opposite in direction.

4. The linear scan confocal spectral measurement structure according to claim 1, characterized in that, The spectrometer assembly further includes a first collimating lens, a first imaging lens, and a second imaging lens. The first collimating lens is located between the slit and the beam splitter, the first imaging lens is located between the echelle grating and the first area array detector, and the second imaging lens is located between the planar reflection grating and the second area array detector.

5. The linear scan confocal spectral measurement structure according to claim 1, characterized in that, The dispersive lens assembly includes an incident component and an exit component arranged symmetrically. The object under test is located on the axis of symmetry of the incident component and the exit component. The polychromatic light emitted by the light source undergoes axial dispersion through the incident component to form a probe light. The probe light is incident on the object under test to form a return light. The return light passes through the exit component and is directed toward the slit.

6. The linear scan confocal spectral measurement structure according to claim 5, characterized in that, The incident component includes a second collimating lens, a first PPG structure, and a first converging lens arranged sequentially along the transmission direction of the polychromatic light. The first PPG structure includes a second prism, a third prism, and a first grating arranged sequentially along the transmission direction of the polychromatic light. The polychromatic light passes through the second collimating lens, the second prism, the third prism, the first grating, and the first converging lens in sequence to form the probe light. The outgoing component includes a third collimating lens, a second PPG structure, and a second converging lens arranged sequentially along the transmission direction of the returned light. The second PPG structure includes a second grating, a fourth prism, and a fifth prism arranged sequentially along the transmission direction of the returned light. The returned light passes sequentially through the third collimating lens, the second grating, the fourth prism, the fifth prism, and the second converging lens before being directed toward the slit.

7. The linear scan confocal spectral measurement structure according to claim 6, characterized in that, The light source, the dispersive lens assembly, the object under test, the slit, and the spectrometer assembly are all located on the first plane.

8. The linear scan confocal spectral measurement structure according to claim 7, characterized in that, The first direction is defined as the normal direction of the first plane. The first direction, the second direction, and the third direction are perpendicular to each other. The second direction is parallel to the axis of symmetry of the incident component and the exit component. The scribe line direction of the planar reflection grating is parallel to the first direction, and the normal direction of the planar reflection grating is deflected relative to the second direction by the corresponding Littoral angle; the scribe line direction of the echelle grating is parallel to the first direction, and the normal direction of the echelle grating is deflected relative to the third direction by the corresponding Littoral angle.

9. The linear scan confocal spectral measurement structure according to claim 8, characterized in that, The second prism and the fifth prism have the same structure, the third prism and the fourth prism have the same structure, the first grating and the second grating have the same structure, the scribe line direction of the first grating and the scribe line direction of the second grating are both parallel to the first direction, and there is an angle between the normal direction of the first grating and the second direction.

10. The linear scan confocal spectral measurement structure according to claim 9, characterized in that, Both the second prism and the third prism are triangular prisms. On the cross-section of the first plane, the cross-sectional shape of the second prism and the cross-sectional shape of the third prism are both triangular. The first side of the second prism faces the light source, the second side of the second prism faces the third prism, the first side of the third prism faces the second prism, the second side of the third prism faces the first grating, and the second side of the second prism is in contact with the first side of the third prism and the second side of the third prism is in contact with the grating surface of the first grating. The apex angle of the triangle corresponding to the cross-sectional shape of the second prism is located on a different side from the apex angle of the triangle corresponding to the cross-sectional shape of the third prism.

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