CN112284538A - Optical system of prism grating spectrometer and design method - Google Patents
Optical system of prism grating spectrometer and design method Download PDFInfo
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- CN112284538A CN112284538A CN202010966376.3A CN202010966376A CN112284538A CN 112284538 A CN112284538 A CN 112284538A CN 202010966376 A CN202010966376 A CN 202010966376A CN 112284538 A CN112284538 A CN 112284538A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/28—Investigating the spectrum
- G01J3/2823—Imaging spectrometer
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
- G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
- G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
- G01J3/021—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using plane or convex mirrors, parallel phase plates, or particular reflectors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
- G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
- G01J3/0216—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using light concentrators or collectors or condensers
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- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
- Diffracting Gratings Or Hologram Optical Elements (AREA)
Abstract
The invention discloses an optical system of a grid prism spectrometer and a design method thereof. The collimating lens is a free-form surface, the prism grating component is a combination of a plane reflection grating and a prism, the converging lens is a six-lens group, and the front surface of the first lens is a free-form surface. Light from an object space starts from a field diaphragm, reaches the turning mirror after being reflected by the collimating mirror, is reflected to the edge grating component, is converged by the converging mirror after being diffracted by the edge grating component, and finally reaches an image plane after passing through a detector window and the optical filter. The collimating mirror uses an off-axis free-form surface reflector to avoid center obscuration. And the free-form surface and the edge grating component are adopted, so that the compact size and the distortion correction are facilitated. The invention has the advantages that: the aberration correction capability is strong, the method is suitable for design with a small F number, the distortion is low, the optical path layout is compact, and the method is easy to install and adjust.
Description
Technical Field
The invention relates to an optical system and an optical design, in particular to a prism grating spectroscopic spectrometer optical system and a design method thereof.
Background
The imaging spectrometer is widely applied to various fields such as aerospace, scientific research, civil use and the like. The core component in the optical system is a light splitting component, and the technical modes of the component are various, wherein a dispersive grating or a prism accounts for the vast majority. Common dispersive light splitting elements include plane gratings, curved gratings, prisms, prism-grating assemblies, etc. In the patent, the invention discloses a prism-grating-prism spectrometer, which is already applied to the field of aerial high-resolution in China, and the invention is an upgrade and beneficial supplement to the invention.
The main problems of the prior art are as follows: the spectrometer uses a coaxial collimating lens, so that the system has a certain central barrier and the effective F number is increased; the F number of the system is about 3.5, and for a small pixel detector, the F number needs to be properly reduced in order to improve the signal-to-noise ratio; the prism-grating-prism assembly is relatively complex in structure and can be further simplified.
Disclosure of Invention
The invention aims to make up the defects of the prior art and provides an optical system of a prism grating spectrometer and a design method thereof.
In order to achieve the purpose, the technical scheme of the invention is as follows:
fig. 1 is a schematic diagram of the optical path of the spectrometer of the present invention, and the optical system of the spectrometer is composed of a field diaphragm 1, a collimating mirror 2, a turning mirror 3, a prism assembly 4, a converging mirror 5, a detector window 6 and an optical filter 7, wherein the prism assembly 4 is composed of a plane reflection grating 4.1 and a prism 4.2.
Light from an object space starts from the field diaphragm 1, is reflected by the collimating lens 2, reaches the turning lens 3, is reflected to the edge grating component 4, is diffracted, is converged by the converging lens 5, passes through the detector window 6 and the optical filter 7, and finally reaches the image surface.
The collimating mirror 2 uses a single concave reflecting mirror to improve the optical efficiency, and uses an off-axis free-form surface to avoid the central obstruction of the system, which is also beneficial to improving the optical efficiency. The free-form surface concave reflecting mirror used by the collimating mirror 2 has a surface type which is an extended polynomial surface symmetrical about a y axis.
The grating element 4 is a combination of a plane reflection grating 4.1 and a prism 4.2, and the prism 4.2 can be placed in front of or behind the plane reflection grating 4.1. For the sake of easy adjustment, the prism 4.2 is designed as a right-angle prism, the normal of the optical surface on the right-angle side is coaxial with the optical axis of the rear condenser 5.
The converging lens 5 is a six-piece lens group, and the lens material is a combination of calcium fluoride, quartz, high-refractive-index low-Abbe-number glass and low-refractive-index high-Abbe-number glass. The glass with short wave band can be selected from PK52, SF4 and SILICA. To further correct distortion and image quality, the front surface of the first lens is a free-form surface whose surface shape is an extended polynomial surface symmetrical about the y-axis. For the structural design and convenient adjustment, the angle of the turning mirror 3 and the plane grating 4.1 and the wedge angle of the prism 4.2 are controlled, and the optical axis of the condenser 5 is designed to be parallel to the optical axis of incident light.
The free-form surface mirror piece is made of aluminum or glass as a substrate material, is processed by adopting a diamond single-point turning and polishing technology, and adopts CGH holographic detection.
The optical filter 7 is a secondary spectrum filter and is divided into two regions, one region is coated with a cut-off film, the spectrum between 900nm is cut off before, and the spectrum near the anti-reflection range of 900nm to 1700nm is increased; the other area is coated with a cut-off film to cut off the spectrum between 1500nm before and increase the transmission from 1500nm to 2500 nm.
The design method of the optical system comprises the following steps: calculating initial parameters including the focal lengths of the collimating mirror 2 and the converging mirror 5 and the line number of the plane reflection grating 4.1 according to technical indexes of the system; modeling a lens group; modeling a collimating mirror; the system modeling is realized by setting a collimating mirror off-axis, setting a prism assembly, setting the front surface shapes of the collimating mirror and the first lens to be free-form surfaces, and controlling the collimation, the image quality, the element interference and the like of emergent rays behind the collimating mirror, so as to optimize.
Due to the use of the technical scheme, the prism grating spectrometer optical system has the advantages that: the collimating mirror uses an off-axis free-form surface reflector to avoid center obscuration. And the free-form surface and the edge grating component are adopted, so that the compact size and the distortion correction are facilitated. The invention has strong aberration correction capability, is suitable for design with smaller F number, has low distortion and compact optical path layout and is easy to install and adjust.
Drawings
FIG. 1 is a schematic diagram of the optical path of a spectrometer of the present invention.
In the figure: 1 is a field diaphragm; 2 is a collimating mirror; 3 is a turning mirror; 4 is a prism grating component, 4.1 is a plane reflection grating, and 4.2 is a prism; 5 is a converging mirror; 6 is a detector window; and 7 is a filter.
Detailed Description
A preferred embodiment of the invention is described in detail below with reference to FIG. 1:
a short-wave infrared edge grating spectrometer is designed, the area array scale of the detector is 640 yuan multiplied by 256 yuan, the pixel size is 25 mu m multiplied by 25 mu m, and the design index requirements are listed in Table 1.
TABLE 1
| Spectral range | F number | Lateral magnification | Length of slit | Width of dispersion |
| 1.0-2.5μm | 2.8 | -1× | 16.0mm | 2.8mm |
The design data is listed in table 2.
TABLE 2
The design result is as follows: the spectrometer entrance pupil is in front of the field of view diaphragm, 200mm from the field of view diaphragm. The spectrometer normalizes the 0 field, 0.707 field and 1 field, representing spot patterns rms diameters of wavelengths 0.9 μm, 1.7 μm and 2.5 μm less than 6.9 μm and less than the pixel size 25 μm. At a nyquist frequency of 20lp/mm, the spectrometer normalizes the 0, 0.707, and 1 fields of view, representing MTFs at wavelengths of 0.9, 1.7, and 2.5 μm close to the diffraction limit, all better than 0.78. The spectral bend of the spectrometer is lower than 2.1 μm and the color distortion is lower than 2.9 μm. The rise deviation of the secondary mirror region of the curved surface and the primary mirror closest to the rotating curved surface is less than 0.5mm, the single-point diamond turning and polishing technology is adopted for processing, the CGH holographic technology is matched for detection, and the processing detection and the adjustment feasibility are achieved. If a transmission objective lens matched with the pupil is arranged in front of the spectrometer, the whole imaging spectrometer is compact in volume and excellent in imaging quality.
Claims (5)
1. The utility model provides a grizzly spectrometer optical system, includes visual field diaphragm (1), collimating mirror (2), turning mirror (3), grizzly subassembly (4), convergent mirror (5), detector window (6) and light filter (7), its characterized in that:
light from an object space starts from the field diaphragm (1), is reflected by the collimating lens (2) and then reaches the turning lens (3), is reflected to the edge grating component (4), is diffracted and then converged by the converging lens (5), and finally reaches the image plane through the detector window (6) and the optical filter (7).
2. The optical system of a prism grating spectrometer as claimed in claim 1, wherein:
the collimating mirror (2) is a free-form surface concave reflecting mirror used in an off-axis mode, and the surface type of the collimating mirror is an extended polynomial surface which is symmetrical about a y axis.
3. The optical system of a prism grating spectrometer as claimed in claim 1, wherein:
the edge grating component (4) is an assembly of a plane reflection grating (4.1) and a prism (4.2), and the prism (4.2) is placed in front of or behind the plane reflection grating (4.1).
4. The optical system of a prism grating spectrometer as claimed in claim 1, wherein:
the converging lens (5) is a six-piece lens group, the front surface of the first lens is a free-form surface, and the surface type of the first lens is an extended polynomial surface which is symmetrical about the y axis.
5. A method of designing an optical system of a prism grating spectrometer as claimed in claim 1, characterized in that the method comprises:
according to technical indexes of the system, calculating initial parameters including focal lengths of a collimating mirror (2) and a converging mirror (5) and the number of lines of a plane reflection grating (4.1); modeling a lens group; modeling a collimating mirror; the system modeling is realized by setting a collimating mirror off-axis, setting a prism assembly, setting the front surface shapes of the collimating mirror and the first lens to be free-form surfaces, and controlling the collimation, the image quality, the element interference and the like of emergent rays behind the collimating mirror, so as to optimize.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010966376.3A CN112284538A (en) | 2020-09-15 | 2020-09-15 | Optical system of prism grating spectrometer and design method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010966376.3A CN112284538A (en) | 2020-09-15 | 2020-09-15 | Optical system of prism grating spectrometer and design method |
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| Publication Number | Publication Date |
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| CN112284538A true CN112284538A (en) | 2021-01-29 |
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| CN202010966376.3A Pending CN112284538A (en) | 2020-09-15 | 2020-09-15 | Optical system of prism grating spectrometer and design method |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102507001A (en) * | 2011-10-18 | 2012-06-20 | 中国科学院上海技术物理研究所 | Refraction-reflection type imaging spectrometer optical system based on prism-grating-prism decomposition |
| CN103900688A (en) * | 2014-03-28 | 2014-07-02 | 中国科学院上海技术物理研究所 | Imaging spectrometer beam splitting system based on free-form surface |
| US20160169741A1 (en) * | 2014-12-10 | 2016-06-16 | Meopta - Optika, S.R.O. | Optical system of a high-resolution imaging spectrograph for deep uv raman spectroscopy |
| US20170268927A1 (en) * | 2015-10-26 | 2017-09-21 | Burt J. Beardsley | Field lens corrected three mirror anastigmat spectrograph |
| WO2017157514A1 (en) * | 2016-03-14 | 2017-09-21 | Universität Stuttgart | Arrangement and method for raman spectroscopy |
| US20210131869A1 (en) * | 2017-08-16 | 2021-05-06 | University Of Rochester | Compact freeform echelle spectrometer |
-
2020
- 2020-09-15 CN CN202010966376.3A patent/CN112284538A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102507001A (en) * | 2011-10-18 | 2012-06-20 | 中国科学院上海技术物理研究所 | Refraction-reflection type imaging spectrometer optical system based on prism-grating-prism decomposition |
| CN103900688A (en) * | 2014-03-28 | 2014-07-02 | 中国科学院上海技术物理研究所 | Imaging spectrometer beam splitting system based on free-form surface |
| US20160169741A1 (en) * | 2014-12-10 | 2016-06-16 | Meopta - Optika, S.R.O. | Optical system of a high-resolution imaging spectrograph for deep uv raman spectroscopy |
| US20170268927A1 (en) * | 2015-10-26 | 2017-09-21 | Burt J. Beardsley | Field lens corrected three mirror anastigmat spectrograph |
| WO2017157514A1 (en) * | 2016-03-14 | 2017-09-21 | Universität Stuttgart | Arrangement and method for raman spectroscopy |
| US20210131869A1 (en) * | 2017-08-16 | 2021-05-06 | University Of Rochester | Compact freeform echelle spectrometer |
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