A MEMS-based tunable spectral imaging system, device and method

Abstract

The present application relates to the technical field of spectral imaging, and particularly relates to a tunable spectral imaging system, device and method based on MEMS, the system comprising an external large field of view module, an internal tunable module and an image sensor which are coaxially arranged in sequence along an optical axis; the external large field of view module is an image-side telecentric optical path, and an image-side focal plane thereof is coincident with an object-side focal plane of the internal tunable module; the internal tunable module comprises a first conjugate optical path, a MEMS spectral chip and a second conjugate optical path; the MEMS spectral chip is located between the first conjugate optical path and the second conjugate optical path, a light transmission aperture of the MEMS spectral chip serves as a diaphragm of the internal tunable module, the first conjugate optical path is object-side telecentric, and the second conjugate optical path is image-side telecentric. By setting the external large field of view module, the optical path thereof is set as image-side telecentric, so that the outgoing chief ray is perpendicular to the focal plane, is matched with the internal tunable module, the viewing angle range of the system is expanded, and the application requirements under different viewing angles are met.

Description

Technical Field

[0001] This invention relates to the field of spectral imaging technology, and specifically to a MEMS-based tunable spectral imaging system, device, and method. Background Technology

[0002] Spectral imaging, based on the principle of combining optical and spatial information, guides incident light to the surface of the object being observed. After interaction with the object, the reflected or transmitted light is decomposed using a spectrometer to obtain the object's spectral information at different wavelengths. It can simultaneously capture the spatial characteristics and nanometer-level spectral resolution information of the measured object. Its spectral brightness curve can directly reflect the chemical composition of the substance, providing a precise basis for material analysis. Hyperspectral imaging acquires high-resolution spectral information over a relatively wide wavelength range, forming a three-dimensional data cube containing both spatial and spectral dimensions for detailed spectral feature extraction. It has been widely used in scientific research, medicine, environmental monitoring, and other fields.

[0003] In imaging optics systems, Fabry-Pérot (FP) cavities, as high-precision wavelength selection and spectroscopic elements, are widely used in MEMS-FPI spectral chips. FP cavities achieve wavelength selection by adjusting the gap between two parallel plates with high reflectivity. Their filtering performance is highly dependent on the angle between the incident beam and the FP cavity plane. When the principal ray angle of the incident beam increases, polarization separation occurs between the P-polarization state and the S-polarization state of the beam, leading to a decrease in the cavity's filtering characteristics and a significant broadening of the full width at half maximum (FWHM). This phenomenon is fundamentally due to the close relationship between the FP cavity's filtering characteristics and the incident angle. When the incident angle exceeds a critical value, the cavity's wavelength selectivity decreases sharply, making it impossible to maintain high spectral resolution.

[0004] In practical applications, the introduction of off-axis optical paths is unavoidable to achieve a given imaging angle. Traditional MEMS spectral chips typically employ collimated optical path designs, confining all beams near the principal optical axis to avoid the uneven optical path difference introduced by off-axis beams. However, this design limits the system's field of view and cannot meet the demands for large field of view in industrial applications. Summary of the Invention

[0005] In practical applications, the introduction of off-axis optical paths is unavoidable to achieve a given imaging angle. Traditional MEMS spectral chips typically employ a collimated optical path design, confining all beams near the principal optical axis, thereby avoiding the problem of uneven optical path difference introduced by off-axis beams. However, this design limits the system's field of view (FOV) and cannot meet the demands for large FOVs in industrial applications.

[0006] To address the aforementioned problems, this invention provides a MEMS-based tunable spectral imaging system, comprising an external large field-of-view module, an internal tunable module, and an image sensor arranged coaxially along the optical axis; wherein, The external large field-of-view module is an image-side telecentric optical path, and its image-side focal plane coincides with the object-side focal plane of the internal tunable module. The internal tunable module includes a first conjugate optical path, a MEMS spectral chip, and a second conjugate optical path. The MEMS spectral chip is located between the first and second conjugate optical paths, and the aperture of the MEMS spectral chip serves as the aperture of the internal tunable module. The first conjugate optical path is object-side telecentric, and the second conjugate optical path is image-side telecentric.

[0007] Preferably, the first conjugate optical path and the second conjugate optical path are centrally symmetrical about the MEMS spectral chip, such that the object-side height and the image-side height of the internal tunable module are equal.

[0008] Based on the above scheme, the second conjugate optical path is configured such that the main light rays emitted to the image sensor are perpendicular to the photosensitive surface of the image sensor.

[0009] Specifically, the external wide field-of-view module includes a front lens group, an aperture, and a rear lens group arranged sequentially along the optical axis. The front lens group includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The fourth and fifth lenses form a first cemented doublet lens. The rear lens group includes a sixth lens, a seventh lens, an eighth lens, and a ninth lens. The seventh and eighth lenses form a second cemented doublet lens.

[0010] Furthermore, the external wide field of view module is composed of spherical and aspherical mirrors, the ratio of the focal length of the front lens group to the focal length of the external wide field of view module is 4.43, and the ratio of the focal length of the rear lens group to the focal length of the external wide field of view module is 2.665.

[0011] Preferably, the first conjugate optical path includes a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens, a fifteenth lens, and a sixteenth lens; the second conjugate optical path includes a seventeenth lens, an eighteenth lens, a nineteenth lens, a twentieth lens, a twenty-first lens, a twenty-second lens, and a twenty-third lens.

[0012] Based on the above scheme, the first conjugate optical path includes the following cemented doublet lenses: a third cemented doublet lens composed of a tenth lens and an eleventh lens, a fourth cemented doublet lens composed of a twelfth lens and a thirteenth lens, and a fifth cemented doublet lens composed of a fifteenth lens and a sixteenth lens.

[0013] Preferably, the ratios of the focal lengths of the third, fourth, fourteenth, and fifth cemented doublet lenses to the focal length of the first conjugate optical path are 1.108, -0.493, 0.592, and -6.723, respectively.

[0014] On the other hand, the present invention provides a spectral imaging camera, including the MEMS-based tunable spectral imaging system as described above, wherein the optical distortion of the external large field-of-view module is less than 0.5%, and the optical distortion of the internal tunable module is less than 0.1%.

[0015] Furthermore, the present invention also provides a MEMS-based tunable spectral imaging method, the method comprising: By using an external optical path that is telecentric to the image side, a scene with a large field of view is imaged onto its focal plane to form the first intermediate image; The first intermediate image is transmitted through the first conjugate optical path at the object side telecentricity, and the light beam is incident on the MEMS spectral chip for filtering. The filtered light beam is converged via a second conjugate optical path at the image side telecentric and transmitted to the image sensor for imaging, wherein the second conjugate optical path makes the outgoing principal ray perpendicular to the photosensitive surface of the image sensor.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention sets up an external large field of view module and sets its optical path to the image side telecentric so that the emitted principal ray is perpendicular to the focal plane, which matches the internal tunable module, expands the viewing angle range of the system, and makes it meet the application requirements under different viewing angles. 2. The first conjugate optical path of the internal tunable module is set to object-side telecentric, and the second conjugate optical path is set to image-side telecentric, which has extremely low distortion at different field of view angles and ensures excellent imaging quality. 3. The conjugate optical path in the internal tunable module is mirrored with the MEMS spectral chip, which enables the reuse of the mirror group and greatly saves costs; the image size is consistent and can be extended to many scenarios, while the internal tunable module can be directly used as a microscopic system. 4. The MEMS spectral chip serves as the aperture of the internal tunable module. Even with a limited aperture, it ensures that all light that can pass through the optical system reaches the MEMS spectral chip without additional energy loss, resulting in uniform illumination and better imaging quality. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the tunable system of the present invention; Figure 2 This is a schematic diagram of the optical path of the tunable system of the present invention; Figure 3This is a detailed structural diagram of the tunable system of the present invention; Figure 4 This is the optical path design diagram of the tunable system of the present invention; Figure 5 This is a dot diagram of the external large field-of-view optical path of the present invention; Figure 6 This is a TV distortion diagram of the external large field-of-view optical path of the present invention; Figure 7 This is a diagram showing the distribution of the principal ray angle under the normalized field of view of this invention; Figure 8 This is the MTF diagram of the external large field-of-view optical path of the present invention; Figure 9 This is a dot diagram of the internal tunable module of the present invention; Figure 10 This is a TV distortion diagram of the internal tunable module of the present invention; Figure 11 This is the MTF diagram of the internal tunable module of the present invention; Figure 12 This is the MTF diagram of the tunable system of the present invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings: 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 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.

[0019] The technical terms involved in this invention are explained as follows: FP cavity (Fabry-Perot interferometer cavity): It is an optical cavity composed of two parallel and partially transparent mirrors. Due to the interference effect, only light of a specific wavelength can resonate in the cavity, resulting in a series of spectral peaks that pass through and are suppressed.

[0020] Normalized field of view refers to the standardization or normalization of the field of view of an optical system.

[0021] Full width at half maximum (FWHM) is a core quantitative indicator in the field of spectroscopic optics for measuring the characteristics of spectral peaks and the resolution of spectroscopic instruments. Its definition, physical meaning, and application are all directly related to the intensity distribution characteristics of the spectrum.

[0022] Center wavelength (CWL) is a core parameter in the field of spectral optics that describes the position of spectral peaks and the center of the passband of optical devices.

[0023] Distortion refers to the deviation between the geometry of a straight line or planar object in a scene and its actual shape when the image is captured by a lens.

[0024] Airy disk, or Airy disk, is a concept in optics that refers to a specific pattern of light intensity distribution formed on the focal plane after a focused beam of light passes through an optical system (such as a lens or telescope) with a circular aperture. It determines the diffraction limit of the optical system.

[0025] A spot diagram is a tool used in optical design to evaluate and compare the performance of different optical systems. It shows how a beam of light passing through an optical system is focused at the focal plane and is typically used to analyze and optimize the design of lenses or mirrors.

[0026] The Modulation Transfer Function Graph (MTF) is an important tool for evaluating the imaging quality of imaging systems (such as camera lenses, telescopes, and microscopes). The MTF quantitatively describes the imaging system's ability to respond to details at different spatial frequencies, thereby assessing the system's imaging performance.

[0027] Spatial frequency refers to the frequency of detail changes in an image, usually measured in lines per millimeter (lp / mm) or cycles per degree.

[0028] MTF (Modulation Transfer Capability) refers to the modulation transfer capability of an imaging system to a specific spatial frequency, usually expressed as a percentage. Ideally, a perfect imaging system has an MTF of 100% for all spatial frequencies.

[0029] Principal ray: In each field of view, the ray that passes through the center of the aperture stop is called the principal ray.

[0030] CRA: Principal Ray Angle.

[0031] To address the technical shortcomings of existing architectures that cannot adapt to large field of view, this invention aims to realize a modular design for the beam splitting function of MEMS chips, so that output parameters can be flexibly adjusted simply by replacing the sensor with the same target surface specification; at the same time, it takes into account the high energy utilization rate of spectral imaging, fully explores the energy potential of the light transmission aperture of MEMS chips, and deconstructs and adapts to incident light with large field of view.

[0032] like Figure 1 and Figure 2 As shown, this invention provides a MEMS-based tunable spectral imaging system, comprising an external large field-of-view module, an internal tunable module, and an image sensor, all three being coaxial; wherein, An external wide field-of-view module and an internal tunable module are combined and configured. The external wide field-of-view module is an image-side telecentric optical path, and its image-side focal plane coincides with the object-side focal plane of the internal tunable module. The internal tunable module includes a first conjugate optical path, a MEMS spectral chip, and a second conjugate optical path. The MEMS spectral chip is located between the first and second conjugate optical paths, and the MEMS is positioned at the aperture stop. The aperture of the MEMS spectral chip serves as the aperture stop of the internal tunable module. The first conjugate optical path is object-side telecentric, and the second conjugate optical path is image-side telecentric.

[0033] This invention uses the light-transmitting aperture of the MEMS as an aperture stop. The exit pupil position of the first conjugate optical path coincides with the light-transmitting aperture of the MEMS spectral chip, and the entrance pupil position of the second conjugate optical path coincides with the light-transmitting aperture of the MEMS spectral chip. This can make full use of the light-transmitting aperture of the MEMS chip, effectively improve the light transmission energy of the entire spectral device, and ensure the imaging signal strength.

[0034] The size of the image sensor is adapted to the output image of the internal tunable system and is directly coupled to the internal tunable system.

[0035] According to the technical concept of the present invention, the light-transmitting aperture of the MEMS spectral chip is used as an aperture stop, which fundamentally suppresses the degradation of filtering performance caused by angle changes. According to the technical concept of the present invention, the external large field-of-view module is the image-side telecentric optical path, which is used for object-side adaptation with the first conjugate optical path of the internal tunable module. The external large field-of-view module is located at the front end of the system. By setting the external large field of view, the existing limited field of view range can be increased, and multiple detection angles can be compatible.

[0036] Example 1 This embodiment provides an external wide field-of-view module, such as... Figure 3 and Figure 4 As shown, the external wide field-of-view module includes a front lens group, an aperture, and a rear lens group arranged sequentially along the optical axis. The front lens group includes a first lens G1, a second lens G2, a third lens G3, a fourth lens G4, and a fifth lens G5. The rear lens group includes a sixth lens G6, a seventh lens G7, an eighth lens G8, and a ninth lens G9. The fourth lens G4 and the fifth lens G5 form a first cemented doublet, and the seventh lens and the eighth lens form a second cemented doublet.

[0037] Table 1 Optical characteristic parameters of external large field of view

[0038] Table 2. Coefficients of Aspherical Mirrors in External Wide Field of View

[0039] As shown in Tables 1 and 2, the external wide field-of-view module in this embodiment consists of spherical and aspherical mirrors. G1 and G9 are aspherical mirrors, and the rest are spherical mirrors. Specifically, the ratio of the focal length fq of the front lens group to the focal length of the lens (external wide field-of-view module) is 4.43; the ratio of the focal length f1 of the first lens to the focal length fq of the front lens group is -0.533; the ratio of the focal length f2 of the second lens to the focal length fq of the front lens group is -0.509; the ratio of the focal length f3 of the third lens to the focal length fq of the front lens group is -1.568; the ratio of the focal length f45 of the first cemented doublet lens to the focal length fq of the front lens group is 0.389; the ratio of the focal length fh of the rear lens group to the focal length f of the lens is 2.665; the ratio of the focal length f6 of the sixth lens to the focal length fh of the rear lens group is 1.716; the ratio of the focal length f78 of the second cemented doublet lens to the focal length fh of the rear lens group is -2.925; and the ratio of the focal length f9 of the ninth lens to the focal length fh of the rear lens group is 0.952.

[0040] The parameters described above in this embodiment are optimized data obtained by the inventors through multiple experiments. Based on the above parameter settings, the external wide field of view optical path parameters in this embodiment are as follows: maximum field of view is 80°, aperture number is 6, focal length is 6mm, working wavelength range is 486nm-656nm, image height of focal plane is 5mm, and the CRA of the incident image plane after the beam passes through the ninth lens of the external wide field of view module is <0.5°.

[0041] Based on the design described in this embodiment, the external wide field-of-view module, acting as an optical lens, can have its performance evaluated using the following tools. For example... Figure 5 As shown in the dot plot, the region formed by the Airy disk radius is displayed. All working wavelengths from different viewing angles converge within the Airy disk radius, thus the optical lens has excellent imaging quality.

[0042] Figure 6 Regarding the distortion distribution of the optical lens, when this external wide field-of-view module is used in a photographic system, the optical distortion is approximately 1%, which meets the requirement of less than 2% distortion. Figure 7 As shown, under normalized field of view, within an 80° field of view, the maximum angle CRA of the principal rays in each field of view is approximately 0.1°. The principal rays of all beams output from the external optical path and about to enter the internal tunable module are almost perfectly parallel to the optical axis, thus maximally suppressing center wavelength angular shift from the external optical path. The vertical axis of the MTF plot represents the MTF value, indicating the imaging system's modulation transmission capability for a specific spatial frequency, such as... Figure 8As shown, the MTF distribution of the imaging lens is close to the diffraction limit across the entire field of view, resulting in excellent contrast and sharpness in the image.

[0043] In other embodiments, based on satisfying the image-side telecentric setting, those skilled in the art can design the optical path according to actual needs to further expand the field of view beyond 80°, ensuring that the main light rays emitted to the internal tunable module are perpendicular to the imaging surface.

[0044] According to the present invention, the external large field-of-view module ensures that the light emitted to the internal tunable module is a parallel beam by setting the image side to telecentricity. Its object-side incident characteristics can be freely configured according to application requirements. It can be a large field-of-view camera objective system or a limited field-of-view microscope objective system, compatible with different field-of-view angles and meeting different application requirements.

[0045] Example 2 This embodiment provides an internally tunable module in which the first conjugate optical path and the second conjugate optical path are arranged in reverse image-object configuration and are centrally symmetrical with respect to the MEMS spectral chip.

[0046] The first conjugate optical path is set at the object-side telecentric, and the second conjugate optical path is set at the image-side telecentric. The two work together to form a dual telecentric conjugate optical system, ensuring that the principal ray angle of each field of view is perpendicular to the photosensitive surface of the image sensor.

[0047] like Figure 3 and Figure 4 As shown in the figure, this embodiment provides a specific structure of an internally tunable module. The first conjugate optical path includes a tenth lens G10, an eleventh lens G11, a twelfth lens G12, a thirteenth lens G13, a fourteenth lens G14, a fifteenth lens G15, and a sixteenth lens G16; the second conjugate optical path includes a seventeenth lens G17, an eighteenth lens G18, a nineteenth lens G19, a twentieth lens G20, a twenty-first lens G21, a twenty-second lens G22, and a twenty-third lens G23. The first and second conjugate optical paths are set in reverse phase with respect to the MEMS image, so the optical paths are centrally symmetrically distributed, and G10-G16 and G17-G23 are mirror images of each other.

[0048] Among them, G10 and G11 form the third cemented doublet lens G1011, G12 and G13 form the fourth cemented doublet lens G1213, G15 and G16 form the fifth cemented doublet lens G1516, symmetrically, G17 and G18 form the sixth cemented doublet lens G1718, G20 and G21 form the seventh cemented doublet lens G2021, and G22 and G23 form the eighth cemented doublet lens G2223.

[0049] Table 3 Optical characteristic parameters of each lens in the internal tunable module

[0050] Table 4 Aspherical Mirror Coefficients in Internal Tunable Module

[0051] As shown in Tables 3 and 4, the internal tunable module in this embodiment consists of spherical and aspherical mirrors. G14 and G19 are aspherical mirrors, and the rest are spherical mirrors. Since the aperture is perfectly mirrored before and after, only the parameters of one set of lenses need to be analyzed. The ratio of the focal length f1011 of G1011 to the focal length of the first conjugate system is -1.108, the ratio of the focal length f1213 of G1213 to the focal length f of the first conjugate system is -0.493, the ratio of the focal length f14 of G14 to the focal length f of the first conjugate system is 0.592, and the ratio of the focal length f1516 of G1516 to the focal length f of the first conjugate optical path is -6.723.

[0052] The parameters described above in this embodiment are optimized data obtained by the inventors through multiple experiments. Based on the lens parameters, the object-side cone angle of the internal tunable module is 4, the focal length is 131.386mm, the working wavelength range is 486nm~656nm, the image height of the focal plane is 10mm, and the object height is 10mm.

[0053] In this embodiment, the image-side exit angle (FOV) of the first conjugate optical path is ≤20°, the maximum incident field of view of the first conjugate optical path is ≤20°, and the internal tunable module can be modularly assembled with the MEMS and the mirror group through a pre-integration method.

[0054] like Figure 9 As shown in the dot plot, the region defined by the Airy disk radius of this optical lens is displayed. All operating wavelengths converge within the Airy disk radius, thus indicating excellent image quality of this optical lens; Figure 10 As shown, this illustrates the distortion distribution of the optical lens. When this internal tunable module is used in a photographic system, the optical distortion is less than 0.05%, meeting the requirement of less than 2% distortion. The vertical axis of the MTF plot represents the MTF value, indicating the imaging system's ability to modulate and transmit specific spatial frequencies. Figure 11 As shown, the MTF distribution of the imaging lens is close to the diffraction limit across the entire field of view, resulting in excellent contrast and sharpness. Based on the MTF distribution of this internal tunable module, this embodiment demonstrates superior imaging performance compared to existing imaging systems.

[0055] In this embodiment, the internal tunable module achieves lens reuse through a dual-Gaussian design, significantly reducing mold costs. Simultaneously, it exhibits extremely low distortion regardless of the field of view, ensuring excellent imaging performance. Compared to existing technologies, the light-passing aperture of the MEMS acts as an aperture stop, ensuring all light passes through it, thus resolving existing illumination unevenness issues and guaranteeing better image quality.

[0056] Those skilled in the art should understand that in other embodiments, the matching of the first conjugate optical path and the second conjugate optical path can also be achieved through two different sets of optical paths. Without using a strict double-Gaussian system, an approximate double-Gaussian system can be used, and the characteristics of the double telecentric optical path can still be maintained.

[0057] The external large field-of-view optical path in Embodiments 1 and 2 above is matched with the internal tunable module. Because the focal plane of the external large field-of-view module is located on the object plane of the internal tunable module, the system can be directly stitched together. The system parameters of the tunable spectral imaging system of the present invention are as follows: the image height of the CMOS image sensor is 10mm, the pixel size of the CMOS image sensor is 2.74um, the FOV of the system of the present invention is 80°, and the aperture of the MEMS is 1.8mm. Figure 12 The figure shows the MTF diagram of the tunable spectral imaging system. Based on the pixels of the CMOS image sensor, the Nyquist frequency of the system is approximately 180 lp / mm, which can meet the requirements of most application scenarios.

[0058] According to the present invention, different working distances and different fields of view can be matched by changing the external large field of view optical path; the image height of the internal tunable module is 10mm, which can meet the requirements of cameras with all target surfaces below the image height and be used in different scenarios.

[0059] Based on the above-mentioned inventive concept, the present invention also provides a spectral imaging camera, including the above-mentioned MEMS-based tunable spectral imaging system, wherein the optical distortion of the external large field-of-view module is less than 1%, and the optical distortion of the internal tunable module is less than 0.1%.

[0060] The spectral imaging camera specifically includes: An external wide field-of-view module, which is a telecentric optical path for the image side, is used to receive light from a wide field-of-view scene and form an intermediate image; The internal tunable module includes a first conjugate optical path, a MEMS spectral chip, and a second conjugate optical path arranged in sequence along the optical axis. The first conjugate optical path is a telecentric optical path in the object side, and the second conjugate optical path is a telecentric optical path in the image side. The first conjugate optical path and the second conjugate optical path constitute a dual telecentric conjugate optical system. An image sensor, located on the image side of the second conjugate optical path, is used to receive the filtered optical signal; The image-side focal plane of the external large field-of-view module coincides with the object-side focal plane of the internal tunable module, and the aperture of the MEMS spectral chip constitutes the aperture stop of the internal tunable module.

[0061] Based on the above-mentioned inventive concept, the present invention further provides a MEMS-based tunable spectral imaging method, the method comprising: The external wide field-of-view module, with its image-side telecentric design, images the wide field-of-view scene onto its focal plane, forming the first intermediate image; the external wide field-of-view module is configured to have optical distortion of less than 1% across its entire field of view. The first intermediate image is incident onto the MEMS spectral chip via the first conjugate optical path at the object side telecentricity for filtering; Specifically, the light beam is incident on a MEMS spectral chip for wavelength-selective filtering; wherein, the dual telecentric optical system formed by the first conjugate optical path and the subsequent optical path has an optical distortion of less than 0.1% across the entire field of view; The filtered light beam is converged via a second conjugate optical path at the image side telecentric and transmitted to the image sensor for imaging, wherein the second conjugate optical path makes the outgoing principal ray perpendicular to the photosensitive surface of the image sensor.

[0062] When the first conjugate optical path is mirrored with respect to the MEMS spectral chip and the second conjugate optical path, the image height is consistent during imaging; when the first conjugate optical path is not completely mirrored with respect to the MEMS spectral chip and the second conjugate optical path, the image height is inconsistent during imaging.

[0063] According to the present invention, a MEMS spectral chip is integrated into an internal tunable module. The internal tunable module has a dual telecentric optical path design, which provides excellent imaging performance. It can be used as a standalone product in microscopic scenarios and directly adapted to industrial cameras with corresponding target surfaces. It can also be used as a tunable module to match an external large field-of-view module to obtain images with a greater distance and a wider field of view.

[0064] The foregoing has shown and described the basic principles and main features of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments. Therefore, the embodiments should be considered as exemplary and not restrictive. The scope of the present invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the present invention.

[0065] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A MEMS-based tunable spectral imaging system, characterized in that, It includes an external large field-of-view module, an internal tunable module, and an image sensor, all arranged coaxially along the optical axis; among which, The external large field-of-view module is an image-side telecentric optical path, and its image-side focal plane coincides with the object-side focal plane of the internal tunable module. The internal tunable module includes a first conjugate optical path, a MEMS spectral chip, and a second conjugate optical path. The MEMS spectral chip is located between the first and second conjugate optical paths, and the aperture of the MEMS spectral chip serves as the aperture of the internal tunable module. The first conjugate optical path is object-side telecentric, and the second conjugate optical path is image-side telecentric.

2. The MEMS-based tunable spectral imaging system according to claim 1, characterized in that, The first conjugate optical path and the second conjugate optical path are centrally symmetrical about the MEMS spectral chip, so that the object height and image height of the internal tunable module are equal.

3. The MEMS-based tunable spectral imaging system according to claim 1, characterized in that, The second conjugate optical path is configured such that the main light rays emitted to the image sensor are perpendicular to the photosensitive surface of the image sensor.

4. The MEMS-based tunable spectral imaging system according to claim 3, characterized in that, The external wide field-of-view module includes a front lens group, an aperture, and a rear lens group arranged sequentially along the optical axis. The front lens group includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The fourth and fifth lenses form a first cemented doublet lens. The rear lens group includes a sixth lens, a seventh lens, an eighth lens, and a ninth lens. The seventh and eighth lenses form a second cemented doublet lens.

5. The MEMS-based tunable spectral imaging system according to claim 4, characterized in that, The external wide field-of-view module is composed of spherical and aspherical mirrors. The ratio of the focal length of the front lens group to the focal length of the external wide field-of-view module is 4.43, and the ratio of the focal length of the rear lens group to the focal length of the external wide field-of-view module is 2.

665.

6. The MEMS-based tunable spectral imaging system according to claim 2, characterized in that, The first conjugate optical path includes the tenth lens, the eleventh lens, the twelfth lens, the thirteenth lens, the fourteenth lens, the fifteenth lens, and the sixteenth lens; the second conjugate optical path includes the seventeenth lens, the eighteenth lens, the nineteenth lens, the twentieth lens, the twenty-first lens, the twenty-second lens, and the twenty-third lens.

7. The MEMS-based tunable spectral imaging system according to claim 6, characterized in that, The first conjugate optical path includes the following cemented doublet lenses: a third cemented doublet lens composed of a tenth lens and an eleventh lens, a fourth cemented doublet lens composed of a twelfth lens and a thirteenth lens, and a fifth cemented doublet lens composed of a fifteenth lens and a sixteenth lens.

8. The MEMS-based tunable spectral imaging system according to claim 7, characterized in that, The ratios of the focal lengths of the third, fourth, fourteenth, and fifth cemented doublet lenses to the focal length of the first conjugate optical path are 1.108, -0.493, 0.592, and -6.723, respectively.

9. A spectral imaging camera, characterized in that, The system includes a MEMS-based tunable spectral imaging system as described in any one of claims 1-6, wherein the optical distortion of the external large field-of-view module is less than 0.5%, and the optical distortion of the internal tunable module is less than 0.1%.

10. A MEMS-based tunable spectral imaging method, characterized in that, The method includes: By using an external optical path that is telecentric to the image side, a scene with a large field of view is imaged onto its focal plane to form the first intermediate image; The first intermediate image is transmitted through the first conjugate optical path at the object side telecentricity, and the light beam is incident on the MEMS spectral chip for filtering. The filtered light beam is converged via a second conjugate optical path at the image side telecentric and transmitted to the image sensor for imaging, wherein the second conjugate optical path makes the outgoing principal ray perpendicular to the photosensitive surface of the image sensor.

Images