Spectrometer light path structure based on photoacoustic composite film thickness detection, mechanical device and assembling and adjusting method thereof

Abstract

The invention discloses a spectrometer optical path structure based on photoacoustic composite film thickness detection, a mechanical device and an adjustment method thereof, and relates to the technical field of optical coherence tomography. The light path structure comprises a collimating lens group used for collimating an incident light beam into parallel light; the reflecting element is obliquely arranged and is used for reflecting the collimated light beam; and the grating element is used for splitting the reflected light beam. An achromatic collimating lens group, a high-diffraction-efficiency body phase holographic grating and a glass material with an extremely low dispersion coefficient are used as focusing lenses to build a light path structure, through precise optical design, the RMS radius of a light spot with a single wavelength is optimized to be close to a diffraction limit, more than 95% of light energy is concentrated in a tiny area, and the light path structure is optimized to be uniform. The extremely high energy concentration ratio effectively reduces the requirement for the pixel size of the camera, the overall signal-to-noise ratio and spectral resolution of the system are remarkably improved, and the inherent disadvantages that an infrared indium gallium arsenic camera is small in pixel and low in signal-to-noise ratio are successfully overcome.

Description

Technical Field

[0001] This invention belongs to the field of optical coherence tomography technology, specifically a spectrometer optical path structure, mechanical device and its assembly and adjustment method based on photoacoustic composite film thickness detection. Background Technology

[0002] Optical coherence tomography (OCT) technology is widely used in biomedical and industrial inspection fields due to its high resolution, non-destructive, and real-time imaging characteristics.

[0003] In recent years, high-intensity focused ultrasound transducers (HIFUs) fabricated using the photoacoustic effect have shown potential in fields such as intravascular imaging. Their core component is a photoacoustic composite membrane based on polymer materials (such as PDMS). In the fabrication process of these photoacoustic composite membranes, the precise, non-destructive, and online detection of the micron-level light-absorbing layer thickness has become a key bottleneck restricting their industrial application. Precise control of the light-absorbing layer thickness is a challenge in PDMS thin film fabrication, primarily because the thickness cannot be measured non-destructively while simultaneously and accurately in both areas using traditional film thickness and 3D morphology detection equipment. This makes quantification and monitoring of the thin film fabrication process difficult. Therefore, the inability to establish highly repeatable and consistent film fabrication process parameters fundamentally limits the widespread commercial application of this technology.

[0004] If OCT technology can be used to detect morphological parameters such as film thickness of polymer photoacoustic composite films, monitoring film quality in the PDMS film preparation process will no longer be a challenge. This will significantly reduce the preparation cost of photoacoustic materials and make mass production easier, enabling the widespread clinical application of high-intensity focused ultrasound imaging technology. Currently, there is no research on infrared spectral domain optical coherence tomography systems for detecting the film thickness and three-dimensional morphological quality of polymer photoacoustic composite films, either domestically or internationally.

[0005] In existing technologies, frequency-domain OCT (Optical Characteristic Transmission) techniques are divided into two types: one is SDOCT, which uses a supercontinuum laser diode (SLD) with a center wavelength of 840-950 nm as the light source and a spectrometer as the detector; the other is SSOCT, which uses a swept-frequency laser in the 1060 nm and 1310 nm bands as the light source and a balanced detector and a high-speed data acquisition card as the detector. Therefore, 1310 nm OCT systems are all implemented using SS-OCT technology. However, when applied to polymer thin film detection, SS-OCT is limited by the high cost of swept-frequency light sources, poor k-phase stability, unavoidable self-coherent horizontal line noise, low longitudinal resolution, and difficulty in identifying short-cavity interference periods. Therefore, SSOCT cannot accurately measure the thickness of films on the micrometer scale. Compared to the swept-frequency principle of SSOCT, SDOCT uses a spectrometer for spectral dispersion, achieving higher resolution, better phase stability, and less self-coherent noise. Furthermore, SDOCT uses an SLD as the light source, eliminating the problem of multiple interference periods caused by short-cavity light sources. Therefore, SDOCT is theoretically more suitable for detecting morphological parameters such as film thickness. Given this, obtaining an infrared-band SDOCT and OCT spectrometer is a key technology for accurately measuring the morphological parameters of photoacoustic composite films, such as film thickness. The infrared-band SD-OCT system not only ensures the wavelength's penetration capability but also achieves higher longitudinal resolution.

[0006] The current technical challenge limiting the application of infrared light in SD-OCT technology lies in whether a corresponding OCT spectrometer can be developed. The core components of an OCT spectrometer are an ultra-high line density grating and a high-speed linear array camera. As is well known, infrared linear array CMOS cameras primarily use indium gallium arsenide (IGaAs) as the photodetector. Most commercially available infrared cameras are characterized by low signal-to-noise ratio, low pixel count, and small pixel size. This undoubtedly increases the difficulty of optical design, optomechanical assembly, and image quality enhancement for using infrared cameras in OCT spectrometers. This is the main reason why there are currently no commercially available infrared SD-OCT systems.

[0007] In summary, existing film thickness detection technologies face the following challenges:

[0008] (1) The visible light band (400-700nm) used by traditional detection methods such as white light interferometers cannot effectively penetrate the polymer photoacoustic composite film, resulting in the inability to perform non-destructive measurement of the internal film thickness and morphology.

[0009] (2) Currently, OCT systems based on the 1310nm infrared band mainly employ the swept-frequency light source OCT (SS-OCT) scheme. However, SS-OCT has inherent defects when detecting micron-sized thin films: the swept-frequency light source is expensive, has relatively poor phase stability, contains self-coherent noise that is difficult to eliminate, and its interference signal may contain multi-period interference artifacts caused by short-cavity lasers. These factors make it difficult for the SS-OCT system to clearly and accurately distinguish the weak reflection signals at the upper and lower interfaces of the thin film from noise and artifacts, resulting in inaccurate film thickness measurements.

[0010] (3) Theoretical analysis shows that spectral domain OCT (SD-OCT) technology using a low-coherence broadband light source and spectrometer has advantages in phase stability, signal-to-noise ratio and longitudinal resolution, and is more suitable for the precise measurement of micron-scale thin films. Therefore, developing an infrared SD-OCT system is an ideal technical approach to solve the problem of photoacoustic composite film detection.

[0011] (4) The core of realizing an infrared SD-OCT system lies in its spectrometer. High-speed linear array cameras in the infrared band (especially around 1310nm) mainly use indium gallium arsenide (InGaAs) materials, which generally suffer from problems such as a small number of pixels, small size, low full-well capacity, and relatively poor signal-to-noise ratio (SNR). This requires that the optical design and mechanical assembly of the infrared OCT spectrometer must maximize the utilization of light energy and the stability of the system to compensate for the inherent shortcomings of the detector. At present, there is a lack of mature commercial high-precision OCT spectrometers optimized for this band and complete SD-OCT systems on the market.

[0012] In summary, there is an urgent need to invent a spectrometer optical path and SD-OCT system that is specifically optimized for the infrared band, has a compact structure, is easy to assemble and adjust, and has stable performance, so as to achieve high-precision, non-destructive testing of the thickness and morphology of special materials such as photoacoustic composite films.

[0013] The information disclosed above in this background section is only for enhancing the understanding of the background section of this invention, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0014] The purpose of this invention is to provide a spectrometer optical path structure, mechanical device, and assembly and adjustment method based on photoacoustic composite membrane thickness detection, so as to solve the problems in the prior art.

[0015] To achieve the above objectives, the present invention provides the following technical solution: an optical path structure for a spectrometer based on photoacoustic composite film thickness detection, comprising:

[0016] Collimating lens group is used to collimate an incident beam into parallel light;

[0017] The reflective element is tilted to reflect the collimated light beam.

[0018] A grating element, tilted, is used to split the reflected light beam;

[0019] A focusing lens group is used to focus a beam of light that has been split.

[0020] Camera components used to receive focused spectral signals;

[0021] The reflective element and the grating element are both mounted at an angle of 51.813°, so that the beam of the center wavelength is emitted with a diffraction angle of 51.813°.

[0022] The light beam is transmitted to the collimating lens group and collimated. The collimated light beam is transmitted to a reflective element at a certain tilt angle. After reflection, it illuminates the tilted grating element at a certain angle, which splits the light beam and emits it according to the diffraction angle. The light beam is transmitted to the focusing lens group, which consists of a first biconvex lens, a second biconvex lens, and a plano-convex lens. The light beam is focused and reaches the camera element.

[0023] Preferably, the grating element is a transmissive volume phase holographic grating with a grating density of 1200 l / mm.

[0024] Preferably, the camera element is an infrared array indium gallium arsenide CMOS camera with a pixel size of 10µm wide × 125µm high and a total number of camera pixels of 1024 or 2048.

[0025] The focusing lens group includes a biconvex lens one, a biconvex lens two, and a plano lens arranged sequentially along the optical path. The lenses are made of low-dispersion glass material.

[0026] The present invention also provides a spectrometer mechanical device based on photoacoustic composite membrane thickness detection, including the above-mentioned spectrometer optical path structure.

[0027] Preferred options also include:

[0028] Collimator-lens integrated mount, used to mount collimating lens group;

[0029] Mounting brackets are used to install reflective elements and grating elements;

[0030] Mounting bracket for mounting the focusing lens assembly;

[0031] The base plate is used to integrate and mount all optical and mechanical components.

[0032] Preferably, the lens body on the collimator-lens integrated mount is an F60 cemented doublet lens, and the lens body is mounted on the collimator-lens integrated mount through a lens sleeve; the reflecting element is mounted on the top surface of the mounting base through a reflecting mirror retaining ring; one end of the mounting base is provided with a lens retaining ring one, and the other end is provided with a lens retaining ring two; the camera element is mounted on the base plate through a camera mounting plate.

[0033] This invention also provides a method for assembling and adjusting the mechanical device of a spectrometer based on photoacoustic composite film thickness detection as described above, comprising the following steps:

[0034] Step 1: Fiber Optic Collimator Collimation Adjustment

[0035] A 1310nm LD light source is introduced into the optical fiber. By adjusting the distance between the collimating lens group and the optical fiber adapter, the fringes of the shearing interferometer are observed to be parallel to the reference line, which indicates that the adjustment is in place. The top screw of the lens group needs to be fixed.

[0036] Step 2: Installation

[0037] Install the adjusted fiber collimation module into the main structure of the spectrometer, and install all mechanical and optical components of the spectrometer in place;

[0038] Step 3: Adjusting the direction of the grating lines

[0039] Make the direction of the grating lines perpendicular to the camera pixels to ensure that the spectral band is coaxial with the camera pixels and has the strongest energy.

[0040] Step 4: Focusing lens adjustment

[0041] By adjusting the distance between the focusing lens group barrel and the camera image plane, observe the interference fringes acquired by the camera until the brightness and contrast are at their maximum. Once this is achieved, secure the top screw of the lens barrel.

[0042] The present invention also provides a spectral domain optical coherence tomography imaging system, including the spectrometer optical path structure as described above.

[0043] Preferably, the system operates in the 1270nm-1350nm band with a center wavelength of 1310nm, and is suitable for measuring the thickness of polymer film that can only penetrate the infrared band.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. This invention uses an achromatic collimating lens group, a high diffraction efficiency volume phase holographic grating, and a glass material with an extremely low dispersion coefficient as a focusing lens to build the optical path structure. Through precise optical design, the RMS radius of a single wavelength spot is optimized to be close to the diffraction limit, and more than 95% of the light energy is concentrated in a tiny area. This extremely high energy concentration effectively reduces the requirements for camera pixel size, significantly improves the overall signal-to-noise ratio and spectral resolution of the system, and successfully overcomes the inherent disadvantages of small pixels and low signal-to-noise ratio of infrared indium gallium arsenide cameras.

[0046] 2. The core spectroscopic device of the infrared OCT spectrometer of this invention employs a high-density transmission volume phase holographic grating with a grating of 1200 l / mm. This grating exhibits high diffraction efficiency and low polarization sensitivity within the target wavelength range, ensuring uniform and efficient utilization of light energy over a wide spectral range, thus laying the foundation for obtaining high-contrast OCT interference signals.

[0047] 3. This invention integrates all optical and mechanical components with high precision through a precise mechanical structure design, ensuring long-term stability of the optical path and resistance to environmental interference. It also proposes a four-step assembly and adjustment method based on shearing interferometer fringe alignment and camera interference fringe optimization. The steps are clear and the criteria are well-defined, which greatly reduces the assembly and adjustment difficulty and technical threshold of infrared spectrometers and improves production and maintenance efficiency.

[0048] 4. This invention not only discloses the optical path of the core spectrometer, but also provides a complete spectral domain optical coherence tomography imaging system including the spectrometer and its assembly and adjustment method. This system realizes for the first time film thickness detection based on the SD-OCT principle in the 1310nm infrared band. It provides a practical and high-performance technical solution to solve the industry problem that special materials such as polymer photoacoustic composite films cannot be measured non-destructively and accurately using traditional methods, and has important industrial application value. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0050] Figure 1 This is a schematic diagram of the optical path structure of the spectrometer of the present invention;

[0051] Figure 2 This is a point diagram of the optical path structure of the spectrometer of the present invention;

[0052] Figure 3 This is a schematic diagram of the diffraction energy in the Y direction of the present invention;

[0053] Figure 4 This is a schematic diagram of the exploded structure of the spectral domain optical coherence tomography imaging system of the present invention. Figure 1 ;

[0054] Figure 5 This is a schematic diagram of the exploded structure of the spectral domain optical coherence tomography imaging system of the present invention. Figure 2 .

[0055] In the picture:

[0056] 1. Collimating lens group; 11. Collimator-lens integrated mount; 12. Lens sleeve; 13. Lens body;

[0057] 21. Mounting base; 22. Reflecting element; 23. Reflecting mirror retaining ring; 24. Grating element;

[0058] 3. Focusing lens group; 31. Mounting base; 32. Lens retaining ring one; 33. Lens retaining ring two; 34. Biconvex lens one; 35. Biconvex lens two; 36. Plano-convex lens;

[0059] 41. Camera components; 42. Camera mounting plate;

[0060] 5. Base plate. Detailed Implementation

[0061] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0062] Example 1:

[0063] Please see Figure 1 An optical path structure for a spectrometer based on photoacoustic composite film thickness detection is disclosed, comprising a collimating lens group 1, a reflecting element 22, a grating element 24, a focusing lens group 3, and a camera element 41. The collimating lens group 1 collimates the incident beam into parallel light; the reflecting element 22 reflects the collimated beam; the grating element 24 splits the reflected beam; the focusing lens group 3 focuses the split beam; and the camera element 41 receives the focused spectral signal.

[0064] The optical fiber transmits light into the air through the optical fiber adapter 10. The light beam is transmitted to the collimating lens group 1 and collimated. The collimated light beam is transmitted to the reflective element 22 with an installation tilt angle of 51.813°. After reflection, it illuminates the grating element 24 with an installation tilt angle of 51.813° at a certain angle. The grating element 24 and the reflective element 22 cooperate to split the light beam and exit it with a diffraction angle of 51.813°. The light beam is transmitted to the focusing lens group 3, which consists of a first biconvex lens 34, a second biconvex lens 35, and a plano-convex lens 36. After being focused, the light beam reaches the camera element 41.

[0065] Specifically, the grating element 24 employs a transmission-type volume-phase holographic grating with a line density of 1200 l / mm. This grating boasts high diffraction efficiency (up to 99% diffraction efficiency per wavelength under Bragg conditions), low polarization sensitivity (consistent diffraction efficiency for p- and S-beams), extremely low stray light (no ghost lines, more than 10 times lower than that of a scribed grating), high dispersion capability (line density up to 4000 lines / mm), robustness, scratch resistance, ease of handling, and easy cleaning, along with excellent directional and temperature stability. Its use in OCT applications, optimized within the desired wavelength range, allows the spectrometer to achieve optimal performance.

[0066] To illustrate the actual performance of the grating element, a set of measured data (corresponding to grating serial number 8259A-01-25) is cited: the spatial frequency of the grating is 1200 l / mm, and the center wavelength (CWL) is 840 nm. Under the conditions of a measurement wavelength of 850 nm and an incident angle of 30.2 degrees, its measured diffraction efficiency is as follows: for P-polarized light, the first-order diffraction efficiency reaches 85%, and the 0th-order diffraction efficiency is 9%; for S-polarized light, the first-order diffraction efficiency reaches 88%, and the 0th-order diffraction efficiency is 6%. The above grating exhibits high diffraction efficiency and considerable polarization selectivity near the target wavelength, ensuring efficient utilization of the system's optical energy.

[0067] Specifically, camera element 41 employs an infrared array indium gallium arsenide CMOS camera. Its camera pixels feature a narrow, elongated design, measuring 10µm wide × 125µm high. This design aims to increase the photosensitive area of ​​a single pixel in the spectral defocusing direction (Y direction), thereby effectively improving the photon collection capability and dynamic range of a single channel within a limited total number of pixels, compensating for the relatively low full-well capacity of the indium gallium arsenide detector. The total number of camera pixels is 1024 or 2048, corresponding to different requirements for system cost and resolution, respectively. When the total number of camera pixels is 2048, the system spectral resolution reaches 0.039nm; when the total number of pixels is 1024, the spectral resolution reaches 0.078nm.

[0068] The optical structure of the OCT spectrometer employs a collimating lens-VPH transmission grating-focusing lens (LGL) configuration, with an infrared array indium gallium arsenide CMOS camera serving as the detector. Multicolor light enters the spectrometer through an entrance pinhole, generating a diverging beam. Then, a collimating lens is used to generate parallel rays. The subsequent transmission diffraction grating, the core component of the spectrometer, changes the beam's direction according to its wavelength (i.e., color). Finally, the focusing lens converges the beam onto the detector. Each wavelength of light converges at a different position on the detector; by measuring the intensity as a function of this position, the spectrum of the light can be obtained.

[0069] Example 2:

[0070] Please see Figures 4-5 A spectrometer mechanical device based on photoacoustic composite film thickness detection, comprising the above-mentioned spectrometer optical path structure, and further comprising:

[0071] Collimator-lens integrated mount 11, used to mount collimating lens group 1;

[0072] Mounting bracket 21 is used to mount reflective element 22 and grating element 24;

[0073] Mounting base 31 is used to mount focusing lens group 3;

[0074] Base plate 5 is used for the integrated mounting of all optical and mechanical components.

[0075] The lens body 13 on the collimator-lens integrated mount 11 is an F60 cemented doublet lens. The lens body 13 is mounted on the collimator-lens integrated mount 11 through the lens sleeve 12. The reflecting element 22 is mounted on the top surface of the mounting base 21 through the reflecting mirror retaining ring 23. One end of the mounting base 31 is provided with a lens retaining ring 32, and the other end is provided with a lens retaining ring 33. The camera element 41 is mounted on the base plate 5 through the camera mounting plate 42.

[0076] The assembly and adjustment method of the spectrometer's mechanical components includes the following steps:

[0077] Step 1: Fiber Optic Collimator Collimation Adjustment

[0078] A 1310nm LD light source is introduced into the optical fiber. By adjusting the distance between the collimating lens group 1 and the optical fiber adapter 10, the fringes of the shearing interferometer are observed to be parallel to the reference line, which indicates that the adjustment is in place. The top screw of the lens tube needs to be fixed.

[0079] Step 2: Installation

[0080] Install the adjusted fiber collimation module into the main structure of the spectrometer, and install all mechanical and optical components of the spectrometer in place;

[0081] Step 3: Adjusting the direction of the grating lines

[0082] Make the direction of the grating lines perpendicular to the camera pixels to ensure that the spectral band is coaxial with the camera pixels and has the strongest energy.

[0083] Step 4: Focusing lens adjustment

[0084] By adjusting the distance between the focusing lens group 3 and the camera image plane, observe the interference fringes acquired by the camera to find that the brightness is at its maximum and the contrast is at its strongest. Once this is achieved, fix the top screw of the lens group.

[0085] The spectrometer bandwidth was set between 1270 nm and 1350 nm, a band that possesses very strong penetration capabilities for both biological and industrial samples. This band lies within the absorption window of water, allowing for deep penetration into biological tissues; simultaneously, it exhibits good penetration and low scattering for many polymer molecules, making it an ideal choice for detecting internal membrane structures. Through optical software simulation optimization, under this optical path structure, the Airy disk radius of the beam with a center wavelength of 1310 nm is 10.51 μm, and the root mean square radius (RMS Radius) of the dot plot is 11.509 μm (e.g., ...). Figure 2 This indicates that the aberrations of the system are well corrected. For example... Figure 3 As shown, in the spectral defocusing direction (Y direction), over 95% of the diffraction energy is concentrated within a circular spot with a diameter of approximately 5µm. This means the system has high energy concentration and a high tolerance for camera pixel size, enabling the acquisition of signals with high signal-to-noise ratio and high spectral resolution even when using infrared cameras with smaller pixel sizes. The system exhibits a sensitivity roll-off of less than 12dB at an imaging depth of 8mm.

[0086] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0087] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0088] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. An optical path structure for a spectrometer based on photoacoustic composite membrane thickness detection, characterized in that, include: Collimating lens group (1) is used to collimate the incident beam into parallel light; The reflective element (22) is tilted and used to reflect the collimated beam. The grating element (24) is tilted and used to split the reflected light beam; The focusing lens group (3) is used to focus the beam after it has been split; Camera element (41) is used to receive the focused spectral signal; The reflective element (22) and the grating element (24) are both tilted at an angle of 51.813°, so that the beam of the center wavelength is emitted at a diffraction angle of 51.813°.

2. The optical path structure of a spectrometer based on photoacoustic composite film thickness detection according to claim 1, characterized in that: The grating element (24) is a transmissive volume phase holographic grating with a grating density of 1200 l / mm.

3. The optical path structure of a spectrometer based on photoacoustic composite film thickness detection according to claim 1, characterized in that: The camera element (41) is an infrared array indium gallium arsenide CMOS camera with a pixel size of 10µm wide × 125µm high and a total number of camera pixels of 1024 or 2048.

4. The optical path structure of a spectrometer based on photoacoustic composite film thickness detection according to claim 1, characterized in that: The focusing lens group (3) includes a biconvex lens one (34), a biconvex lens two (35), and a plano lens (36) arranged sequentially along the optical path. The lenses are made of low-dispersion glass material.

5. A spectrometer mechanical device based on photoacoustic composite membrane thickness detection, characterized in that, Includes the spectrometer optical path structure as described in any one of claims 1-4.

6. The spectrometer mechanical device based on photoacoustic composite film thickness detection according to claim 5, characterized in that, Also includes: Collimator-lens integrated mount (11) is used to mount the collimating lens group (1); Mounting bracket (21) for mounting reflective element (22) and grating element (24); Mounting bracket (31) is used to mount the focusing lens group (3); The base plate (5) is used to integrate and mount all optical and mechanical components.

7. The spectrometer mechanical device based on photoacoustic composite film thickness detection according to claim 6, characterized in that: The lens body (13) on the collimator-lens integrated mount (11) is an F60 cemented doublet lens, and the lens body (13) is mounted on the collimator-lens integrated mount (11) through the lens sleeve (12); the reflective element (22) is mounted on the top surface of the fixed base (21) through the reflective mirror retaining ring (23); one end of the mounting base (31) is provided with a lens retaining ring one (32), and the other end is provided with a lens retaining ring two (33); the camera element (41) is mounted on the base plate (5) through the camera fixing plate (42).

8. The assembly and adjustment method of the spectrometer mechanical device based on photoacoustic composite film thickness detection as described in any one of claims 5-7, characterized in that, Includes the following steps: Step 1: Fiber optic collimator collimation adjustment A 1310nm LD light source is introduced into the optical fiber. By adjusting the distance between the collimating lens group (1), the lens barrel, and the optical fiber adapter (10), the fringes of the shearing interferometer are observed to be parallel to the reference line. This indicates that the adjustment is in place, and the top screw of the lens barrel needs to be fixed. Step 2: Installation Install the adjusted fiber collimation module into the main structure of the spectrometer, and install all mechanical and optical components of the spectrometer in place; Step 3: Adjusting the direction of the grating lines Make the direction of the grating lines perpendicular to the camera pixels to ensure that the spectral band is coaxial with the camera pixels and has the strongest energy. Step 4: Focusing lens adjustment By adjusting the distance between the focusing lens group (3) and the camera image plane, observe the interference fringes collected by the camera to find the maximum brightness and the strongest contrast. Once the adjustment is complete, fix the top screw of the lens tube.

9. A spectral-domain optical coherence tomography system, characterized in that, Includes the spectrometer optical path structure as described in any one of claims 1-4.

10. The spectral domain optical coherence tomography system according to claim 9, characterized in that: The system operates in the 1270nm-1350nm band, with a center wavelength of 1310nm. The system is suitable for measuring the thickness of polymer film that can only penetrate the infrared band.

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