Light path structure of light splitting spectrometer applied to OCT (optical coherence tomography) and OCT system

Abstract

The utility model provides a light path structure of a spectrophotometer applied to OCT (optical coherence tomography) and an OCT system. An optical fiber emits a broadband light source with a divergence angle; the collimating lens collimates the broadband light source emitted by the optical fiber to form a collimated light beam; the plane mirror reflects the collimated light beam formed by the collimating lens to form a reflected light beam; the transmission-type diffraction grating splits the reflected light beam formed by the plane mirror to form a split light beam; and the focusing lens focuses the split light beams formed by the transmission-type diffraction grating to the line-scan digital camera. The light path structure is simple, the light source energy loss is small, and most importantly, the resolution of the spectrophotometer can be high.

Description

Technical Field

[0001] The utility model relates to the technical field of optical structures, and in particular to an optical path structure of a spectrometer applied to OCT and an OCT system. Background Art

[0002] In optics, OCT stands for Optical Coherence Tomography, which is an advanced imaging technology that is particularly suitable for non-invasive, high-resolution imaging of biological tissues. The working principle of OCT is based on low-coherence light interferometer, which can perform cross-sectional scans of the microstructure of biological tissues and generate high-contrast three-dimensional images. The spectrometer is a component of the OCT test system, and its function is to separate the light emitted by the broadband light source in the OCT test system into interference light signals of different frequencies.

[0003] like Figure 1 As shown in the figure, the basic structure of the spectrometer is that the optical fiber (1") emits a broadband light source with a certain divergence angle, which is collimated by the achromatic collimating lens (2"), split by the diffraction grating (3"), and converged by the focusing lens (4") to the line array camera (5"), which collects the relevant interference spectrum signal and obtains the depth information of the object to be measured after Fourier transformation.

[0004] The spectral resolution of the spectrometer is one of the determining factors of the resolution of the OCT imaging system. The basic structure of the spectrometer is as follows: Figure 1 As shown in Figure 1, according to relevant theories, the spectral resolution of a spectrometer depends on its optical path design, hardware selection, and data acquisition. Currently, the spectral resolution of the spectrometers on the market is not high, making it difficult to achieve high-precision imaging measurements of OCT. Utility Model Content

[0005] Based on the above records, the utility model provides an optical path structure of a spectrometer applied to OCT and an OCT system, aiming to solve the technical problem in the prior art that the spectral resolution of the spectrometer is not high, making it difficult to achieve high-precision imaging of OCT.

[0006] An optical path structure of a spectrometer used in OCT, comprising an optical fiber, a collimating lens, a plane reflector, a transmission diffraction grating, a focusing lens and a linear array camera arranged in sequence along the optical path direction;

[0007] The optical fiber emits a broadband light source with a divergence angle;

[0008] The collimating lens collimates the broadband light source emitted by the optical fiber to form a collimated light beam;

[0009] The plane reflector reflects the collimated light beam formed by the collimating lens to form a reflected light beam;

[0010] The transmission diffraction grating splits the reflected light beam formed by the plane reflector to form a split light beam;

[0011] The focusing lens focuses the split light beam formed by the transmission diffraction grating onto the line scan camera.

[0012] Furthermore, the number of grating lines of the transmission diffraction grating is 1800 lines / mm, and the aperture is 45 mm.

[0013] Furthermore, the incident angle of the transmission diffraction grating is 49.1°.

[0014] Furthermore, the collimating lens is an achromatic plano-convex lens with a focal length of 80 mm.

[0015] Furthermore, the focusing lens adopts an achromatic plano-convex lens with a focal length of 150 mm.

[0016] Furthermore, the reflective surface of the plane reflector is silvered.

[0017] Furthermore, the diameter of the plane reflector is 50.8 mm.

[0018] Furthermore, the interface of the optical fiber is FC / APC, the type of the optical fiber is 780HP, and the numerical aperture of the optical fiber is 0.13.

[0019] Furthermore, the pixel size of the linear array camera is 4 microns × 4 microns.

[0020] An OCT system includes a spectrophotometer, wherein the spectrophotometer uses the aforementioned optical path structure of the spectrophotometer applied to OCT.

[0021] The beneficial technical effect of the utility model is that in the optical path structure adopted by the utility model, the diffraction grating adopts a transmission Littrow structure. This is because the efficiency of the transmission grating is greater than the reflection type, it will not produce glaring ghost lines due to surface reflection, and it is insensitive to the polarization state of light. The optical path structure is simple, the energy loss of the light source is small, and most importantly, the resolution of the spectral spectrometer can be high, and the resolution can be lower than 10pm. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the optical path structure of a spectrophotometer in the prior art;

[0023] Figure 2 This is a schematic diagram of the optical path structure of a spectrometer used in OCT according to the utility model;

[0024] Figure 3 The utility model is a schematic diagram of the size structure of the optical path structure of a spectrometer applied to OCT.

[0025] in,

[0026] 1- Fiber optic;

[0027] 2- Collimating lens;

[0028] 3- Transmission diffraction grating;

[0029] 4- Focusing lens;

[0030] 5-Line scan camera. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0032] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0034] See also Figure 2 The utility model provides an optical path structure of a spectrometer applied to OCT, comprising an optical fiber (1), a collimating lens (2), a plane reflector (6), a transmission diffraction grating (3), a focusing lens (4) and a linear array camera (5) arranged in sequence along the optical path direction;

[0035] The optical fiber (1) emits a broadband light source having a divergence angle;

[0036] The collimating lens (2) collimates the broadband light source emitted by the optical fiber (1) to form a collimated light beam;

[0037] The plane reflector (6) reflects the collimated light beam formed by the collimating lens (2) to form a reflected light beam;

[0038] The transmission diffraction grating (3) splits the reflected light beam formed by the plane reflector (6) to form a split light beam;

[0039] The focusing lens (4) focuses the split light beam formed by the transmission diffraction grating (3) onto the line array camera (5).

[0040] A broadband light source is a light source that can emit light in a wider spectrum range. Compared with a light source that only emits a single wavelength or a narrow band of light (such as a laser), it can provide continuous or nearly continuous light output in a wider wavelength range.

[0041] The linear array camera is a linear array CCD. A linear array CCD (Charge-Coupled Device) is a special charge-coupled device designed specifically for photoelectric signal conversion and detection in one-dimensional image or linear scanning applications. Unlike an area array CCD, a linear array CCD consists of a single array of photosensitive elements, which are usually arranged in a row and can capture continuous image data extending in one direction.

[0042] In the optical path structure adopted by the utility model, the diffraction grating adopts a transmission Littrow structure. This is because the efficiency of the transmission grating is greater than that of the reflection type, it will not produce glaring ghost lines due to surface reflection, and it is insensitive to the polarization state of light. The optical path structure is simple, the energy loss of the light source is small, and most importantly, the resolution of the spectral spectrometer can be high, and the resolution can be lower than 10pm.

[0043] Furthermore, the number of grating lines of the transmission diffraction grating (3) is 1800 lines / mm, and the aperture is 45 mm.

[0044] Furthermore, the incident angle of the transmission diffraction grating (3) is 49.1°.

[0045] A diffraction grating is an optical element with dense and equally spaced parallel lines (or grooves). Its main function is to disperse the incident polychromatic light (light containing multiple wavelengths) according to its wavelength. This process is called dispersion.

[0046] A transmission diffraction grating is an optical element whose basic structure is to make a series of transparent slits or grooves of equal spacing and width on a transparent substrate (such as glass or film). The size of these slits or grooves is very small, and their function is to use the diffraction and interference of light to disperse the incident light according to the wavelength to form a spectrum. Unlike reflection gratings, transmission gratings allow light to penetrate the grating material itself instead of reflecting from the surface.

[0047] Furthermore, the collimating lens (2) is an achromatic plano-convex lens with a focal length of 80 mm.

[0048] The main function of an achromatic collimating lens is to correct light and transform it into a parallel beam while ensuring that light of different wavelengths (colors) can converge at almost the same focal plane, thereby minimizing or eliminating chromatic aberration.

[0049] Furthermore, the focusing lens (4) is an achromatic plano-convex lens with a focal length of 150 mm.

[0050] The main function of the focusing lens is to converge the incident light or electron beam to a point or a narrow area, thereby forming a real image or enhancing the energy density.

[0051] Furthermore, the reflective surface of the plane reflector (6) is silver-plated.

[0052] Furthermore, the diameter of the plane reflector (6) is 50.8 mm.

[0053] The surface of the plane reflector (6) is silver-plated, the diameter is 50.8 mm, and it is used to fold the optical path and reduce the structural volume.

[0054] The diameter of a flat mirror refers to the linear distance of the circular edge of the mirror. If the mirror is square or other shapes, it refers to the maximum linear dimension of its corresponding size. The diameter is a key parameter in optical design and mirror selection because it directly affects the size of the beam that the mirror can collect and process, the light energy utilization of the system, and its adaptability in the optical layout.

[0055] Furthermore, the interface of the optical fiber (1) is FC / APC, the type of the optical fiber (1) is 780HP, and the numerical aperture of the optical fiber (1) is 0.13.

[0056] The fiber 1 interface is FC / APC: This indicates that the fiber connector type is FC, where APC stands for "Angled Physical Contact". The FC connector is a common fiber connector, known for its threaded locking mechanism and good repeatability. APC means that the end face has been polished at an angle of 8 degrees. This design can effectively reduce return loss (i.e. reflection) and is suitable for high-speed data transmission or sensitive measurement applications that require a low-reflection environment.

[0057] NA (Numerical Aperture) is a parameter that measures the ability of optical fiber to capture and transmit light. It is related to the diameter and refractive index of the optical fiber. The larger the numerical aperture, the wider the angle range of the optical fiber to receive light. In theory, it can capture more light, thereby improving the coupling efficiency of the optical signal.

[0058] The wavelength of the light source emitted by the optical fiber (1) is 840nm±50nm.

[0059] Furthermore, the pixel size of the linear array camera (5) is 4 microns×4 microns.

[0060] The pixel of a line scan camera refers to the most basic photosensitive unit on the sensor of a line scan camera, also known as a pixel or pixel point. In digital images, a pixel is the smallest unit that makes up an image. Each pixel corresponds to a specific physical position on the sensor and can capture and convert light intensity into an electrical signal.

[0061] The utility model also provides an OCT system, comprising a spectrophotometer, characterized in that the spectrophotometer uses the optical path structure of the spectrophotometer mentioned above.

[0062] For the projection diffraction grating (3), when the diameter of the parallel light beam incident on the surface of the diffraction grating (3) is D, in order to achieve a grating resolution of ≤10pm, the following should be true:

[0063] δλ g =λ0 / (mND / cosθ0)≤10pm;

[0064] Where λ0 is the central wavelength of the broadband light source, that is, the laser emitted by optical fiber 1 (central wavelength 840nm); N is the number of grating lines (lines / mm), N=1800lines / mm; the grating incident angle θ0=49.1°, m=1 is known, and substitution is: D≥30.55mm.

[0065] The spectral resolution required after passing through the diffraction grating (3) and being focused by the focusing lens (4) is:

[0066] δλ c =pdcosθ0 / f2m≤10pm;

[0067] Where p is the pixel size, the pixel size of the linear array camera (5) is 4 microns×4 microns, and by substituting p=4 microns and d=1 / 1800 mm (grating period), we obtain f2≥145.45 mm.

[0068] The spot diameter after being focused by the focusing lens (4) is:

[0069] 2ω≈4λ0f2 / πD(4)

[0070] The calculated value is 2ω≈4.2um, which is slightly larger than the pixel size and can meet the usage requirements.

[0071] like Figure 3 As shown, the aperture of the collimating lens 2 is 50.8 mm; the focal length is 80 mm; the numerical aperture of the optical fiber NA=0.13, and according to f=D / 2NA, D1 is approximately 20.8 mm.

[0072] The plane reflector angle is shown in FIG3 , so that the incident angle is 49.1°. After calculation, it can be obtained that the diameter of the light spot projected on the mirror surface is D2=32.67 mm. The transmission diffraction grating (3) is parallel to the plane reflector (6), and the diameter of the light spot on the surface of the transmission diffraction grating (3) is D3=D2=32.67 mm.

[0073] The light aperture D0 of the transmission diffraction grating (3) is 45 mm>32.672 mm, and D3=32.67 mm>design value 30.55 mm, meeting the design requirements.

[0074] The above are only preferred embodiments of the present invention, and do not limit the implementation mode and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. An optical path structure of a spectrometer used in OCT, characterized in that: It comprises an optical fiber (1), a collimating lens (2), a plane reflector (6), a transmission diffraction grating (3), a focusing lens (4) and a linear array camera (5) which are arranged in sequence along the optical path direction; The optical fiber (1) emits a broadband light source having a divergence angle; The collimating lens (2) collimates the broadband light source emitted by the optical fiber (1) to form a collimated light beam; The plane reflector (6) reflects the collimated light beam formed by the collimating lens (2) to form a reflected light beam; The transmission diffraction grating (3) splits the reflected light beam formed by the plane reflector (6) to form a split light beam; The focusing lens (4) focuses the split light beam formed by the transmission diffraction grating (3) onto the line array camera (5); The transmission type diffraction grating (3) adopts a transmission type Littrow structure.

2. The optical path structure of a spectrometer applied to OCT according to claim 1, characterized in that: The transmission diffraction grating (3) has a grating line count of 1800 lines / mm and a light aperture of 45 mm.

3. The optical path structure of a spectrometer applied to OCT according to claim 2, characterized in that: The incident angle of the transmission diffraction grating (3) is 49.1°.

4. The optical path structure of a spectrometer applied to OCT according to claim 1, characterized in that: The collimating lens (2) is an achromatic plano-convex lens with a focal length of 80 mm.

5. The optical path structure of a spectrometer applied to OCT according to claim 1, characterized in that: The focusing lens (4) is an achromatic plano-convex lens with a focal length of 150 mm.

6. The optical path structure of a spectrometer applied to OCT according to claim 1, characterized in that: The reflective surface of the plane reflector (6) is silver-plated.

7. The optical path structure of a spectrometer applied to OCT according to claim 1, characterized in that: The diameter of the plane reflector (6) is 50.8 mm.

8. The optical path structure of a spectrometer applied to OCT according to claim 1, characterized in that: The interface of the optical fiber (1) is FC / APC, the type of the optical fiber (1) is 780HP, and the numerical aperture of the optical fiber (1) is 0.

13.

9. The optical path structure of a spectrometer applied to OCT according to claim 1, characterized in that: The pixel size of the linear array camera (5) is 4 micrometers×4 micrometers.

10. An OCT system, comprising a spectrometer, characterized in that: The spectrometer uses the optical path structure of a spectrometer applied to OCT as described in any one of claims 1 to 9.

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