A filter transmittance measuring device and method based on a FOSC type astronomical spectrograph

Abstract

The application discloses a filter transmittance measuring device and method based on a FOSC astronomical spectrometer, and belongs to the field of astronomical observation instrument detection and calibration, and comprises a spectrometer body, a multi-hole template, a filter mounting mechanism, a light source module and a data processing unit; wherein the multi-hole template is arranged at a focal plane and is used for dividing an image plane into a plurality of sampling sub-beams; the filter mounting mechanism at least comprises a first mounting station arranged at a rear adjacent position of the multi-hole template and a second mounting station arranged in a collimating light path, and is respectively used for measuring spatial position transmittance distribution and incident angle transmittance response of a filter to be measured. The light source module comprises a line spectrum calibration light source and a continuous spectrum measuring light source. The device and method can realize in-situ characterization of the filter in a real working light path of the FOSC astronomical spectrometer, and are especially suitable for measuring spatial uniformity and angle response of a narrow-band filter under real working conditions.

Description

Technical Field

[0001] This invention relates to the field of astronomical observation instrument testing and calibration technology, and in particular to a filter transmittance measurement device and method based on a FOSC-type astronomical spectrometer. Background Technology

[0002] Optical filters are key optical components in astronomical observation systems. Their performance parameters, such as transmittance spectrum, peak transmittance, center wavelength, and full width at half maximum (FWHM), directly affect the system's light transmission efficiency, effective wavelength range, and the accuracy of scientific observation results. For narrowband filters, their film structure is typically sensitive to the angle of incidence, focal ratio, field of view position, and installation conditions. Therefore, in practical use, phenomena such as center wavelength drift, changes in peak transmittance, and performance inconsistencies between different locations are prone to occur.

[0003] Existing filter transmittance tests are typically conducted using independent spectrophotometers or offline laboratory testing platforms. These tests are mostly performed under conditions of near-normal incidence, ideal parallel light, or conditions outside the overall astronomical observation environment. Although they can obtain the nominal transmittance curve of the filter, they cannot accurately reflect its working condition in a real astronomical observation system.

[0004] Especially in FOSC-type astronomical spectrometers, the system optical path includes both a focal plane converging beam and a collimated beam. Filters at different installation positions correspond to different beam angle distributions and principal ray conditions. Offline test results are difficult to equivalently characterize the true performance of the filter in the whole instrument.

[0005] Furthermore, existing testing methods typically struggle to simultaneously perform the following two types of measurements on the same platform: firstly, the measurement of transmittance non-uniformity at different spatial locations of the filter; and secondly, the measurement of the filter's transmittance response under different incident angles. For narrowband filters, if spatial position effects and incident angle effects cannot be simultaneously examined in the optical path of a real instrument, it is difficult to accurately evaluate their actual observation performance.

[0006] Therefore, it is necessary to provide an in-situ transmittance measurement device and method that can utilize the optical path of a FOSC-type astronomical spectrometer to perform transmittance measurements of the spatial position and incident angle of a filter without deviating from actual working conditions. Summary of the Invention The purpose of this invention is to solve the problem that in the prior art, the transmittance test of filters usually relies on an independent test platform, which makes it difficult to reflect the true performance of the filter in the actual working optical path of the instrument.

[0007] To achieve the above objectives, the present invention employs the following technology: a filter transmittance measuring device based on a FOSC-type astronomical spectrometer, comprising a spectrometer body and a light source module adapted to provide calibration light and measurement light to the spectrometer body; The spectrometer body comprises, in sequence along the optical path, a focal plane, a collimating optical system, a dispersive element, an imaging optical system, and a detector; A porous template is provided at the focal plane, and the porous template is adapted to divide the light beam incident on the focal plane into multiple sampling sub-beams; The spectrometer body is provided with a filter mounting mechanism, which includes a first mounting station and a second mounting station. The first mounting station is located behind and adjacent to the porous template, and is used to allow multiple sampling sub-beams to pass through different local areas of the filter under test to measure the spatial transmittance distribution of the filter under test. The second mounting station is located in the collimated optical path formed by the collimating optical system, and is used to allow different principal ray directions corresponding to different sampling sub-beams to pass through the filter under test at different incident angles to measure the incident angle transmittance response of the filter under test. The measuring device also includes a data acquisition and processing unit, which is electrically connected to the detector. The data acquisition and processing unit is used to establish a one-to-one correspondence between each sampling sub-beam, each light-passing aperture, and the corresponding spectral trajectory on the detector. After dark field subtraction, background correction, bad pixel correction, exposure time normalization, and wavelength registration, the transmittance spectrum is calculated based on the ratio of the measured spectrum to the reference spectrum.

[0008] As a further description of the above technical solution: the first installation station includes a filter wheel disposed behind the porous template. The filter wheel is used to make the filter to be tested fit tightly against the rear surface of the porous template and can quickly switch between different filters. The second installation station is located at the filter wheel position in the collimating optical path, at the collimating beam position in front of the dispersive element.

[0009] As a further description of the above technical solution: the porous template is provided with multiple light-transmitting holes, and the multiple light-transmitting holes are arranged in a linear array, area array, ring array or non-uniform array. At least a portion of the multiple light-transmitting apertures have different off-axis amounts relative to the optical axis to form sampling sub-beams corresponding to different field-of-view positions.

[0010] As a further description of the above technical solution: the light source module includes a line spectrum calibration light source, a continuous spectrum measurement light source, and a switching component for switching between the line spectrum calibration light source and the continuous spectrum measurement light source, wherein the line spectrum calibration light source is used to perform wavelength calibration on the spectrometer body, and the continuous spectrum measurement light source is used to acquire the reference spectrum when there is no filter to be tested and the measurement spectrum after the filter to be tested is installed.

[0011] As a further description of the above technical solution: the line spectrum calibration light source is a spectral lamp with known characteristic spectral lines, including at least one of He lamp, Ne lamp, He-Ne combined spectral lamp, Hg-Ar spectral lamp and Ar spectral lamp; The continuous spectrum measurement light source is a light source capable of providing continuous or quasi-continuous spectrum radiation, including at least one of halogen lamps, halogen tungsten lamps, integrating spherical sources, diffuse surface sources, sky diffuse light, and lunar reflected light.

[0012] As a further description of the above technical solution: the filter mounting mechanism is provided with a positioning structure for repeated positioning and installation of the filter to be tested.

[0013] As a further description of the above technical solution: it also includes a light-blocking mechanism, which is used to block the incident light path during dark field acquisition.

[0014] A method for in-situ transmission measurement of a filter using the above-mentioned apparatus includes the following steps: S1. Place the porous template at the focal plane of the spectrometer body so that the incident light passes through the porous template to form multiple sampling sub-beams, and establish a one-to-one correspondence between each light-passing hole, each sampling sub-beam and the corresponding spectral trajectory on the detector. S2. Acquire dark field signals under shading conditions for subsequent dark field subtraction of calibration spectrum, reference spectrum and measurement spectrum; S3. A line spectrum calibration light source is used to collect the calibration spectrum corresponding to each sampling sub-beam through the porous template. Based on the correspondence between the wavelength of the known characteristic spectral lines and the position of the detector pixel, the wavelength calibration relationship corresponding to each sampling sub-beam is established. S4. Using a continuous spectrum measurement light source, the reference spectrum corresponding to each sampling sub-beam is collected without installing the filter to be measured; S5. While keeping the position of the porous template unchanged and ensuring that the instrument's optical path state, dispersive element state and detector operating parameters are consistent or calibrable, install the filter to be tested at the first or second installation position and collect the measurement spectrum corresponding to each sampling sub-beam. S6. Perform dark field subtraction, bad pixel correction, exposure time normalization and wavelength registration on the reference spectrum and the measured spectrum, and calculate the transmittance spectrum for each sampled sub-beam. S7. Based on the transmittance spectrum corresponding to each sampling sub-beam, extract the peak transmittance, center wavelength, and full width at half maximum (FWHM) parameters of the filter under test. S8. When the filter under test is installed at the first installation station, output the spatial transmittance distribution of the filter under test; when the filter under test is installed at the second installation station, output the transmittance response of the incident angle of the filter under test.

[0015] As a further description of the above technical solution: when the filter under test is installed at the first installation station, each sampling sub-beam corresponds to a different local area on the filter under test; by comparing the transmittance spectrum corresponding to different sampling sub-beams and the peak transmittance, center wavelength and half width at half maximum (WHM) parameters extracted from them, the transmittance consistency, center wavelength difference and WHM difference at different spatial positions of the filter under test are obtained.

[0016] As a further description of the above technical solution: when the filter under test is installed at the second installation station, the relationship between each sampling sub-beam and the corresponding incident angle is established according to the field position, off-axis position and / or principal ray direction corresponding to each sampling sub-beam; by comparing the transmittance spectrum corresponding to different incident angles and the peak transmittance, center wavelength and half width at half maximum (WWHM) parameters extracted from them, the center wavelength shift, peak transmittance change and WWHM change of the filter under test as a function of the incident angle are obtained.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This invention utilizes the actual working optical path of the FOSC astronomical spectrometer to measure the transmittance of the filter. It can be characterized without removing the filter from the overall optical environment of the instrument. Therefore, the measurement results can better reflect the working performance of the filter under actual observation conditions.

[0018] 2. By setting a porous template on the focal plane and maintaining its stable position during the measurement process, the present invention enables a stable one-to-one correspondence between the calibration spectrum, the reference spectrum, and the measurement spectrum among multiple sampling sub-beams, providing a reliable basis for subsequent quantitative ratio calculation, thereby helping to reduce systematic errors between different testing stages.

[0019] 3. By setting up a first installation station and a second installation station, the present invention enables the measurement of transmittance of the filter at different spatial positions and under different incident angles within the same platform. This allows for the joint characterization of the spatial uniformity and angular response of the filter, avoiding the problem in the prior art that usually requires the use of different test platforms to complete the two types of tests separately.

[0020] 4. This invention is particularly applicable to in-situ performance evaluation of narrowband filters under real working conditions. It can directly obtain key parameters such as center wavelength drift, peak transmittance change and full width at half maximum (FWHM) change, thereby providing a basis for filter selection, system assembly and calibration. Attached Figure Description

[0021] Fig. 1 A schematic diagram of the overall structure provided according to an embodiment of the present invention is shown; Fig. 2 A schematic diagram of a porous template structure provided according to an embodiment of the present invention is shown; Fig. 3 A flowchart of a measurement method provided according to an embodiment of the present invention is shown.

[0022] Legend: 1. Light source module; 2. Spectrometer body; M1. Porous template; F1. First mounting station; L1. Collimating optical system; F2. Second mounting station; G1. Dispersive element; L2. Imaging optical system; D1. Detector. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Reference Figs. 1-3 This embodiment provides a filter transmittance measurement device and method based on a FOSC-type astronomical spectrometer. The device is built on the optical path of the FOSC-type astronomical spectrometer and includes a spectrometer body 2 and a light source module 1 suitable for providing calibration light and measurement light to the spectrometer body 2. The spectrometer body 2 is a FOSC-type astronomical spectrometer. A detector D1 is used to record the spectral signals corresponding to each sampled sub-beam, and a data processing unit is used to complete wavelength calibration, spectral line correspondence, reference measurement, transmittance calculation, and parameter extraction.

[0025] The light source module 1 includes a line spectrum calibration light source and a continuous spectrum measurement light source, which are used in conjunction with the FOSC-type astronomical spectrometer body via a switching component. The line spectrum calibration light source is used to calibrate the wavelength of the spectrometer body 2, while the continuous spectrum measurement light source is used to acquire the reference spectrum without the filter under test and the measurement spectrum after the filter under test is installed.

[0026] Specifically, the line spectrum calibration light source is a spectral lamp with known characteristic spectral lines, including at least one of He lamp, Ne lamp, He-Ne combined spectral lamp, Hg-Ar spectral lamp and Ar spectral lamp; The continuous spectrum measurement light source is a light source capable of providing continuous or quasi-continuous spectrum radiation, including at least one of halogen lamps, halogen tungsten lamps, integrating spherical sources, diffuse surface sources, sky diffuse light, and lunar reflected light.

[0027] The device can also be equipped with a light-shielding mechanism to block the incident light path during dark field acquisition, thereby improving the convenience of measurement data processing.

[0028] The spectrometer body 2 includes, in sequence along the optical path, a focal plane, a collimating optical system L1, a dispersive element G1, an imaging optical system L2, and a detector D1.

[0029] The porous template M1 is installed at the focal plane of the FOSC-type astronomical spectrometer to select multiple discrete sampling regions at the image plane position and form multiple sampling sub-beams that can be identified separately on the detector. The porous template M1 can be configured as a linear array, area array, ring array, or other predetermined arrangement according to measurement requirements to correspond to different field-of-view positions or different regions to be measured. Preferably, the position of the porous template M1 is kept fixed throughout the wavelength calibration, reference measurement, and filter measurement processes to ensure the stable correspondence between the sampling sub-beams.

[0030] Multiple light-transmitting holes are provided on the porous template M1. The light-transmitting holes can be circular holes, slits, rectangular holes, or other equivalent light-transmitting structures. The multiple light-transmitting holes can be arranged in a linear array, area array, ring array, or non-uniform array, wherein at least some of the light-transmitting holes are located at different off-axis positions relative to the optical axis.

[0031] In one specific embodiment, the porous template M1 may adopt a structure in which two rows of circular holes are arranged in a V-shape in order to obtain sampling sub-beams at different off-axis positions. Fig. 2 An embodiment of the porous template M1 is given, wherein two rows of circular holes are arranged in a V-shape with an included angle of 90 degrees, the spacing between the circular holes is 2 mm, and the diameter of the circular holes is 0.1 mm.

[0032] The spectrometer body 2 is equipped with a filter mounting mechanism, which includes a first mounting station F1 and a second mounting station F2. The first mounting station F1 is located in the area adjacent to the rear of the porous template M1, and preferably adopts the form of a filter wheel to facilitate the switching of different filters to be tested. The second mounting station F2 is located in the collimated optical path, preferably at the position of the filter wheel or other collimated beam position in front of the dispersive element G1, so that different sampling sub-beams pass through the filter at this location with different principal ray directions.

[0033] Transmittance measurement at the spatial position under the first installation station F1: In this embodiment, the filter under test is installed at the first installation station F1, and the fixing device at the second installation station F2 is removed or the filter is rotated to an empty position to ensure that the light path is not blocked. Since the different light-transmitting holes on the porous template M1 correspond to different local areas on the filter under test, each sampling sub-beam passes through different positions of the filter, thereby obtaining the transmittance spectrum of different local areas of the filter under test.

[0034] Before measurement, the porous template M1 is first installed at the focal plane, and the system is adjusted to ensure that the sampling sub-beams formed by different apertures can be stably transmitted to the detector D1. Then, the dark field signal is acquired with the incident light source turned off or the incident light path blocked. After that, the line spectrum calibration light source is turned on, and the calibration spectrum corresponding to each sampling sub-beam is acquired through the porous template M1, and the wavelength calibration relationship is established.

[0035] After wavelength calibration, the light source is switched to a continuous spectrum measurement source, and the reference spectrum corresponding to each sampling sub-beam is acquired without the filter under test installed. Then, while keeping the position of the porous template M1 unchanged and ensuring that the system optical path state, the state of the dispersive element G1, and the operating parameters of the detector D1 are consistent or calibrable, the filter under test is installed in the first installation position F1, and the measurement spectrum corresponding to each sampling sub-beam is acquired again.

[0036] The data processing unit performs dark field subtraction, bad pixel correction, exposure time normalization, and wavelength registration on the reference and measured spectra, respectively. After processing, the transmittance spectrum is calculated for each sampling sub-beam, and parameters such as peak transmittance, center wavelength, and full width at half maximum (FWHM) are further extracted. By comparing the differences in the corresponding parameters of different sampling sub-beams, the spatial transmittance distribution of the filter under test, as well as the differences in center wavelength and FWHM between different locations, can be obtained.

[0037] Preferably, the distance between the first installation station F1 and the porous template M1 is controlled within a small range to reduce the beam spread and angle aliasing effects introduced by the additional propagation distance and improve the representativeness of the local area measurement.

[0038] Transmittance measurement at the incident angle under the second installation position: In this embodiment, the filter under test is installed at the second mounting position F2, which is located in the collimated optical path of the FOSC-type astronomical spectrometer. The fixing device at the first mounting position F1 is removed or the filter is rotated to an empty position to ensure that the optical path is not blocked. Since different light-passing holes of the porous template M1 correspond to beams at different field-of-view positions and different off-axis positions, different sampling sub-beams correspond to different principal ray directions in the collimation section. When the filter under test is located at the second mounting position F2, different sampling sub-beams pass through the filter at different incident angles, thereby obtaining the incident angle transmittance response of the filter under test.

[0039] The measurement process of this implementation is basically the same as that of the spatial transmittance measurement at the first installation station F1. First, wavelength calibration or wavelength verification is completed using a line spectrum calibration light source; then, without installing the filter to be tested, a reference spectrum is collected using a continuous spectrum measurement light source; after that, the filter to be tested is installed at the second installation station F2, and the measurement spectrum is collected under the condition that the remaining system conditions are consistent or under calibrable consistency.

[0040] The data processing unit calculates the transmittance spectrum for each sampling sub-beam and establishes the correspondence between the sampling sub-beam and the incident angle based on the aperture position, field of view position, off-axis position, and / or known optical path geometry. By comparing the transmittance spectra at different incident angles, the center wavelength shift, peak transmittance change, and full width at half maximum (FWHM) change of the filter under test can be obtained.

[0041] Wavelength calibration implementation method: In this embodiment, a line spectrum calibration light source is used to calibrate the wavelength of the system. Preferably, the line spectrum calibration light source is a He lamp, a Ne lamp, or a He-Ne combined spectral lamp; when it is necessary to expand the wavelength coverage or improve the multi-point calibration accuracy, an Hg-Ar spectral lamp, an Ar spectral lamp, or other spectral lamps with known emission lines can also be used.

[0042] During calibration, the line spectrum calibration light enters the FOSC-type astronomical spectrometer through the porous template M1, and the detector D1 records the calibration spectra corresponding to different sampled sub-beams. The data processing unit establishes a calibration function between pixel coordinates and wavelength based on the relationship between the center wavelength of a known spectral line and its corresponding pixel position. In some embodiments, a low-order polynomial can be used to describe the relationship between pixel coordinates and wavelength; in other embodiments, a piecewise function or other equivalent calibration model can be used depending on the instrument's spectral imaging characteristics.

[0043] Implementation methods for continuous spectrum reference measurement and transmittance calculation: In this embodiment, a continuous spectrum measurement light source is used to obtain the reference spectrum and the filter measurement spectrum. The continuous spectrum measurement light source can be a halogen lamp, a halogen tungsten lamp, an integrating spherical source, a diffuse surface source, or it can be diffuse sky light, lunar reflected light, or other light sources that can provide continuous or quasi-continuous spectrum radiation.

[0044] During measurement, a dark-field signal is first acquired under shaded conditions. Then, without the filter under test installed, a continuous spectrum measurement light source is used to acquire the reference spectrum corresponding to each sampling sub-beam through the porous template M1. Afterwards, while keeping the position of the porous template M1 unchanged and ensuring that the instrument's optical path state, the state of the dispersive element G1, and the operating parameters of the detector D1 are consistent or calibrable, the filter under test is installed at either the first mounting position F1 or the second mounting position F2, and the measurement spectrum corresponding to each sampling sub-beam is acquired again.

[0045] The data processing unit first extracts the one-dimensional spectrum based on the corresponding spectral trajectories of each sampling sub-beam on detector D1, and then performs dark field subtraction, background correction, bad pixel correction, exposure time normalization, and wavelength registration on the reference spectrum and the measured spectrum, respectively. After processing, for the i-th sampling sub-beam, its reference spectrum and measured spectrum can be expressed as:

[0046]

[0047] This yields the transmittance spectrum corresponding to the i-th sampled sub-beam:

[0048] in, This is the reference spectrum without the filter under test installed. The measured spectrum after installing the filter under test. and These are the dark-field correction terms corresponding to the reference spectrum and the measured spectrum, respectively. and These are the exposure times for the reference spectrum and the measured spectrum, respectively.

[0049] After obtaining the transmittance spectrum, the data processing unit further extracts parameters such as peak transmittance, center wavelength, and full width at half maximum (FWHM). Within the target spectral band, peak transmittance is defined as the maximum value of the transmittance spectrum; when the transmittance spectrum has two wavelengths at FWHM... and When the full width at half maximum (FWHM) is defined as:

[0050] The center wavelength is defined as:

[0051] In some implementations, the center wavelength can also be defined as the wavelength corresponding to the peak transmittance; preferably, a uniform center wavelength definition method is used in the same set of measurements to ensure the comparability of results between different sampling sub-beams.

[0052] When the filter under test is installed at the first mounting position, each sampling sub-beam corresponds to a different local area on the filter under test. Therefore, by comparing different local areas, the filter can be analyzed. The spatial transmittance distribution of the filter is obtained from the extracted parameters. When the filter under test is installed at the second installation position, each sampling sub-beam corresponds to a different principal ray direction and incident angle. Therefore, the transmittance distribution can be obtained by comparing different parameters. The transmittance response of the filter at the incident angle is obtained by extracting its parameters.

[0053] Preferred applications for narrowband filters: This invention is particularly suitable for in-situ performance measurement of narrowband filters. In this embodiment, the filter under test can be first installed at the first installation station F1 to obtain the transmittance spectrum and spatial uniformity distribution of different local regions; then it can be installed at the second installation station F2 to obtain its transmittance response under different incident angles. By jointly analyzing the two sets of results, it is possible to distinguish whether the filter performance change mainly originates from the spatial inhomogeneity of the film system or mainly from the angle change of the working beam.

[0054] For narrowband filters, this invention can directly obtain key parameters such as center wavelength drift, peak transmittance attenuation, and full width at half maximum (FWHM) variation under actual instrument optical path conditions, thereby providing a basis for filter selection, system assembly and adjustment, optimization of usage location, and subsequent observation calibration.

[0055] Based on the above, a method for in-situ transmittance measurement of filters using a FOSC-type astronomical spectrometer specifically includes the following steps: S1. Place the porous template at the focal plane of the spectrometer body 2 so that the incident light passes through the porous template M1 to form multiple sampling sub-beams, and establish a one-to-one correspondence between each light-passing hole, each sampling sub-beam and the corresponding spectral trajectory on the detector D1. S2. Acquire dark field signals under shading conditions for subsequent dark field subtraction of calibration spectrum, reference spectrum and measurement spectrum; S3. Using a line spectrum calibration light source, the calibration spectrum corresponding to each sampling sub-beam is collected through the porous template M1. Based on the correspondence between the wavelength of the known characteristic spectral lines and the pixel position of the detector D1, the wavelength calibration relationship corresponding to each sampling sub-beam is established. S4. Using a continuous spectrum measurement light source, the reference spectrum corresponding to each sampling sub-beam is collected without installing the filter to be measured; S5. While keeping the position of the porous template M1 unchanged, and ensuring that the optical path state of the instrument, the state of the dispersive element G1 and the working parameters of the detector D1 are consistent or calibrable, install the filter to be tested at the first installation station F1 or the second installation station F2, and collect the measurement spectrum corresponding to each sampling sub-beam. S6. Perform dark field subtraction, bad pixel correction, exposure time normalization and wavelength registration on the reference spectrum and the measured spectrum, and calculate the transmittance spectrum for each sampled sub-beam. S7. Based on the transmittance spectrum corresponding to each sampling sub-beam, extract the peak transmittance, center wavelength, and full width at half maximum (FWHM) parameters of the filter under test. S8. When the filter under test is installed at the first installation station F1, each sampling sub-beam corresponds to a different local area on the filter under test. By comparing the transmittance spectrum corresponding to different sampling sub-beams and the peak transmittance, center wavelength and half width at half maximum (WHM) parameters extracted from them, the transmittance consistency, center wavelength difference and WHM difference at different spatial positions of the filter under test are obtained. When the filter under test is installed at the second installation station F2, the transmittance response of the filter under test at the incident angle is output. Based on the field position, off-axis position and / or principal ray direction corresponding to each sampling sub-beam, the relationship between each sampling sub-beam and the corresponding incident angle is established. By comparing the transmittance spectrum corresponding to different incident angles and the peak transmittance, center wavelength and half width at half maximum (WWHM) parameters extracted from them, the center wavelength shift, peak transmittance change and WWHM change of the filter under test as the incident angle changes are obtained.

[0056] Without departing from the spirit of this invention, the aperture shape of the porous template M1 can be a circular aperture, a slit, a rectangular aperture, or other equivalent light-transmitting structure; the aperture array can be set as a regular array or an irregular array as needed. The specific mechanical structure of the first mounting station F1 and the second mounting station F2 can also be adjusted according to the layout of different FOSC-type astronomical spectrometers. The specific types of the line spectrum calibration light source and the continuous spectrum measurement light source can also be replaced according to the band requirements and the usage environment. The algorithm implementation in the data processing unit can be implemented by software, firmware, or hardware circuits; the above substitutions do not affect the basic concept of this invention.

[0057] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A filter transmittance measuring device based on a FOSC-type astronomical spectrometer, characterized in that, It includes a spectrometer body (2) and a light source module (1) adapted to provide calibration light and measurement light to the spectrometer body (2); The spectrometer body (2) includes, in sequence along the optical path, a focal plane, a collimating optical system (L1), a dispersive element (G1), an imaging optical system (L2), and a detector (D1). A porous template (M1) is provided at the focal plane, and the porous template (M1) is adapted to divide the light beam incident on the focal plane into multiple sampling sub-beams; The spectrometer body (2) is provided with a filter mounting mechanism, which includes a first mounting station (F1) and a second mounting station (F2). The first mounting station (F1) is located behind and adjacent to the porous template (M1) to allow multiple sampling sub-beams to pass through different local areas of the filter under test to measure the spatial transmittance distribution of the filter under test. The second mounting station (F2) is located in the collimated optical path formed by the collimating optical system (L1) to allow different principal ray directions corresponding to different sampling sub-beams to pass through the filter under test at different incident angles to measure the incident angle transmittance response of the filter under test. The measuring device also includes a data acquisition and processing unit, which is electrically connected to the detector (D1) and is used to establish a one-to-one correspondence between each sampling sub-beam, each light-passing aperture and the corresponding spectral trajectory on the detector (D1). After dark field subtraction, background correction, bad pixel correction, exposure time normalization and wavelength registration, the transmittance spectrum is calculated based on the ratio of the measured spectrum to the reference spectrum.

2. The filter transmittance measuring device based on a FOSC-type astronomical spectrometer according to claim 1, characterized in that, The first installation station (F1) includes a filter wheel disposed behind the porous template (M1). The filter wheel is used to make the filter to be tested fit tightly against the rear surface of the porous template (M1) and can quickly switch between different filters. The second installation station (F2) is located at the filter wheel position in the collimated optical path, in front of the collimated beam position of the dispersive element (G1).

3. The filter transmittance measuring device based on a FOSC-type astronomical spectrometer according to claim 1, characterized in that, The porous template (M1) is provided with multiple light-transmitting holes, which are arranged in a linear array, area array, ring array or non-uniform array. At least a portion of the multiple light-transmitting apertures have different off-axis amounts relative to the optical axis to form sampling sub-beams corresponding to different field-of-view positions.

4. The filter transmittance measuring device based on a FOSC-type astronomical spectrometer according to claim 1, characterized in that, The light source module (1) includes a line spectrum calibration light source, a continuous spectrum measurement light source, and a switching component for switching between the line spectrum calibration light source and the continuous spectrum measurement light source. The line spectrum calibration light source is used to perform wavelength calibration on the spectrometer body (2), and the continuous spectrum measurement light source is used to obtain the reference spectrum when there is no filter to be tested and the measurement spectrum after the filter to be tested is installed.

5. The filter transmittance measuring device based on a FOSC-type astronomical spectrometer according to claim 4, characterized in that, The line spectrum calibration light source is a spectral lamp with known characteristic spectral lines, including at least one of He lamp, Ne lamp, He-Ne combined spectral lamp, Hg-Ar spectral lamp, and Ar spectral lamp; The continuous spectrum measurement light source is a light source capable of providing continuous or quasi-continuous spectrum radiation, including at least one of halogen lamps, halogen tungsten lamps, integrating spherical sources, diffuse surface sources, sky diffuse light, and lunar reflected light.

6. The filter transmittance measuring device based on a FOSC-type astronomical spectrometer according to claim 1, characterized in that, The filter mounting mechanism is equipped with a positioning structure for repeated positioning and installation of the filter under test.

7. The filter transmittance measuring device based on a FOSC-type astronomical spectrometer according to claim 1, characterized in that, It also includes a light-blocking mechanism, which is used to block the incident light path during dark field acquisition.

8. A method for in-situ measurement of the transmittance of a filter using the apparatus according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Place the porous template at the focal plane of the spectrometer body (2) so that the incident light passes through the porous template (M1) to form multiple sampling sub-beams, and establish a one-to-one correspondence between each light-passing hole, each sampling sub-beam and the corresponding spectral trajectory on the detector (D1). S2. Acquire dark field signals under shading conditions for subsequent dark field subtraction of calibration spectrum, reference spectrum and measurement spectrum; S3. Using a line spectrum calibration light source, the calibration spectrum corresponding to each sampling sub-beam is collected through the porous template (M1). Based on the correspondence between the wavelength of the known characteristic spectral lines and the pixel position of the detector (D1), the wavelength calibration relationship corresponding to each sampling sub-beam is established. S4. Using a continuous spectrum measurement light source, the reference spectrum corresponding to each sampling sub-beam is collected without installing the filter to be measured; S5. While keeping the position of the porous template (M1) unchanged, and ensuring that the optical path state of the instrument, the state of the dispersive element (G1) and the working parameters of the detector (D1) are consistent or calibrable, install the filter to be tested at the first installation position (F1) or the second installation position (F2), and collect the measurement spectrum corresponding to each sampling sub-beam. S6. Perform dark field subtraction, bad pixel correction, exposure time normalization and wavelength registration on the reference spectrum and the measured spectrum, and calculate the transmittance spectrum for each sampled sub-beam. S7. Based on the transmittance spectrum corresponding to each sampling sub-beam, extract the peak transmittance, center wavelength, and half width at half maximum (WWHM) parameters of the filter under test. S8. When the filter under test is installed at the first installation station (F1), output the spatial transmittance distribution of the filter under test; when the filter under test is installed at the second installation station (F2), output the transmittance response of the incident angle of the filter under test.

9. The method for in-situ transmittance measurement of filters based on a FOSC-type astronomical spectrometer according to claim 8, characterized in that, When the filter under test is installed at the first installation station (F1), each sampling sub-beam corresponds to a different local area on the filter under test. By comparing the transmittance spectra corresponding to different sampling sub-beams and the peak transmittance, center wavelength and half width at half maximum (WHM) parameters extracted from them, the transmittance consistency, center wavelength difference and WHM difference at different spatial positions of the filter under test are obtained.

10. The method for in-situ transmittance measurement of filters based on a FOSC-type astronomical spectrometer according to claim 8, characterized in that, When the filter under test is installed at the second installation station (F2), the relationship between each sampling sub-beam and the corresponding incident angle is established according to the field position, off-axis position and / or principal ray direction of each sampling sub-beam; by comparing the transmittance spectrum corresponding to different incident angles and the peak transmittance, center wavelength and half width at half maximum (WWHM) parameters extracted from it, the center wavelength shift, peak transmittance change and WWHM change of the filter under test as the incident angle changes are obtained.

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