CN111562007A - Free-form surface spectrometer optical system and design method - Google Patents
Free-form surface spectrometer optical system and design method Download PDFInfo
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- CN111562007A CN111562007A CN202010441702.9A CN202010441702A CN111562007A CN 111562007 A CN111562007 A CN 111562007A CN 202010441702 A CN202010441702 A CN 202010441702A CN 111562007 A CN111562007 A CN 111562007A
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- 230000003287 optical effect Effects 0.000 title claims abstract description 39
- 238000000034 method Methods 0.000 title claims abstract description 9
- 238000013461 design Methods 0.000 title abstract description 16
- 238000012937 correction Methods 0.000 claims abstract description 8
- 230000003595 spectral effect Effects 0.000 claims abstract description 5
- 238000005457 optimization Methods 0.000 claims description 3
- 230000000007 visual effect Effects 0.000 claims 1
- 230000004075 alteration Effects 0.000 abstract description 3
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 238000009434 installation Methods 0.000 abstract 1
- 238000012545 processing Methods 0.000 description 6
- 238000001514 detection method Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229910003460 diamond Inorganic materials 0.000 description 2
- 239000010432 diamond Substances 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 238000007514 turning Methods 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000007516 diamond turning Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 210000001747 pupil Anatomy 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
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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
- G01J3/0208—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
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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
- G01J3/12—Generating the spectrum; Monochromators
- G01J3/18—Generating the spectrum; Monochromators using diffraction elements, e.g. grating
- G01J3/1804—Plane gratings
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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
- G01J2003/2866—Markers; Calibrating of scan
Abstract
The invention discloses an optical system of a free-form surface spectrometer and a design method thereof. Wherein the converging mirror comprises two free-form surface mirrors and a correcting lens. Light from an object space starts from a field diaphragm, reaches a grating after being reflected by a collimating mirror, is reflected by a first free-form surface of a converging mirror after being diffracted by the grating, is reflected by a second free-form surface of the converging mirror, is refracted by a correcting lens, then reaches a Dewar window and an optical filter, and finally reaches an image surface. The combination of the free-form surface reflector and the correction lens is beneficial to further correcting spectral distortion and image quality. The invention has the advantages that: the optical path layout is convenient, the distortion is low, the aberration correction capability is strong, the image plane inclination is small, the optical path layout can also meet the design requirements of a long slit and a small F number, optical axes of optical elements with focal power are parallel, and the installation and adjustment are easy.
Description
Technical Field
The invention relates to an optical system and an optical design, in particular to an optical system of a free-form surface spectrometer and a design method thereof.
Background
The design of the optical system of a spectrometer used in an imaging spectrometer needs to take into account the control of image quality, pupil position, distortion, etc. The spectrograph optical system using the curved surface grating for light splitting has better control on image quality and distortion, but the curved surface grating has higher requirement on ultra-precise manufacturing and higher manufacturing cost. Due to the development of modern ultra-precision machining technology, the machining and manufacturing of the high-precision free-form surface become easy to realize, so that a planar grating spectrometer based on a free-form surface and other complex surface types is also an optional high-performance scheme.
The main problems of the prior art are as follows: compared with a plane grating, the curved surface grating has higher development difficulty and cost; the optical system of the existing free-form surface spectrometer has weak F number and field adaptability, large residual aberration and distortion, large rise difference between a free-form surface and the nearest rotating surface, and is not beneficial to processing, or a certain inclination exists between each optical element, and is not beneficial to structural design and adjustment; for a multi-channel spectrometer sharing a telescope and a spectrometer on the same side of an object image, the space at a slit is not convenient for the layout of a detector, and the light path needs to be folded.
Disclosure of Invention
The invention aims to make up the defects of the prior art and provides an optical system of a free-form surface spectrometer and a design method.
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, the optical system of the spectrometer is composed of a field diaphragm 1, a free-form surface collimator lens 2, a plane grating 3, a converging lens 4, a detector window 5 and an optical filter 6, and the converging lens 4 is composed of a first free-form surface lens 4.1, a second free-form surface lens 4.2 and a correcting lens 4.3.
Light from an object space starts from the field diaphragm 1, is reflected by the free-form surface collimating mirror 2 and then reaches the plane grating 3, is diffracted and then reflected by the first free-form surface mirror 4.1 of the converging mirror 4, is reflected by the second free-form surface mirror 4.2, is refracted by the correcting lens 4.3, then reaches the detector window 5 and the optical filter 6, and finally reaches the image surface.
The origin of coordinates in the invention is at the vertex of the free-form surface collimating mirror 2, and the other elements have a certain off-axis amount relative to the origin of coordinates. The optical axis of the free-form surface collimating mirror 2, the plane grating 3, the first free-form surface mirror 4.1, the second free-form surface mirror 4.2, the correcting lens 4.3, the detector window 5 and the optical filter 6 is parallel and not inclined, and only has a midnight-direction off-axis.
The free-form surface collimating mirror 2, the first free-form surface mirror 4.1 and the second free-form surface mirror 4.2, the surface type is a smooth surface symmetrical about the y axis, and can be expressed by an expansion polynomial. The mirror is made of aluminum or silicon as a substrate material, is processed by adopting a diamond single-point turning and polishing technology, and adopts CGH holographic detection.
The design method of the optical system comprises the following steps: according to technical indexes of the system, calculating initial parameters including initial spherical curvature of a free-form surface collimating mirror 2 and a first free-form surface mirror 4.1 of a converging mirror 4, parameters of a plane grating 3, element intervals and the like, and establishing a model of the Carlnie-Terner spectrometer; the reflector surface type is set to be a free-form surface, and collimation, image quality, element interference and the like of emergent light rays behind the collimating mirror are controlled to be optimized; adding a correction lens 4.3, increasing and controlling spectral curvature and 8-color distortion, and optimizing; and a second free-form surface mirror 4.2 is added to convert the light path for optimization.
Due to the use of the technical scheme, the optical system of the free-form surface spectrometer has the advantages that: the second free-form surface mirror 4.2 is added in the system, the aberration correction capability is strong, and the distortion correction capability is strong due to the addition of the correction lens, so that the system can meet the design requirements of a small F number and a long slit; the second free-form surface mirror 4.2 with weak focal power is added in the converging mirror to turn the image surface, so that the problem that the detector is difficult to place when the object image is on the same side is avoided, and particularly in the design of an infrared spectrum band and a multi-channel imaging spectrometer sharing a main optical telescope, the layout space of the detector behind can be effectively widened; the rise deviation of the free curved surface and the nearest rotating curved surface is small, the method is more suitable for diamond single-point turning, the processing difficulty is close to that of an aspheric surface when the CGH is used for detection in processing; the optical axes of all the optical elements with focal power are parallel, the positive axis of the optical elements is processed, the structural processing precision of the mirror piece is well controlled, and the structural design and the optical adjustment are relatively easy to realize relative to an off-axis system.
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 free-form surface collimating lens; 3 is a plane grating; 4 is a converging mirror, 4.1 is a first free-form surface mirror, and 4.2 is a second free-form surface mirror; 5 is a detector window; and 6 is a filter.
Detailed Description
A preferred embodiment of the invention is described in detail below with reference to FIG. 1:
a short-medium wave infrared free-form surface spectrometer is designed, the size of a detector area array is 512 yuan multiplied by 320 yuan, the size of a pixel 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 |
| 1.0-3.4μm | 3.0 | -1× | 12.8mm | 8.0mm |
The design data is listed in table 2.
TABLE 2
The design result is as follows: the spectrometer is telecentric on the object side. The spectrometer normalizes the 0 field, 0.707 field and 1 field, representing spot patterns rms diameters of wavelengths 1.0 μm, 2.2 μm and 3.4 μm less than 5.6 μm and less than the pixel size 25 μm. At a nyquist cut-off frequency of 20pl/mm, the spectrometer normalizes the 0, 0.707 and 1 fields of view, representing MTFs at wavelengths of 1.0, 2.2 and 3.4 μm close to the diffraction limit, all better than 0.72. The spectral bend of the spectrometer is below 1 μm and the color distortion is below 4 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.
Claims (3)
1. The utility model provides a free-form surface spectrometer optical system comprises visual field diaphragm (1), free-form surface collimating mirror (2), plane grating (3), convergent mirror (4), detector window (5) and light filter (6), and convergent mirror (4) comprise first free-form surface mirror (4.1), second free-form surface mirror (4.2) and correction lens (4.3), its characterized in that:
light from an object space starts from a field diaphragm (1), is reflected by a free-form surface collimating mirror (2) and then reaches a plane grating (3), is diffracted and then reflected by a first free-form surface mirror (4.1) of a converging mirror (4), is reflected by a second free-form surface mirror (4.2), is refracted by a correcting lens (4.3), then reaches a detector window (5) and an optical filter (6), and finally reaches an image surface;
the free-form surface collimating mirror (2), the first free-form surface mirror (4.1), the second free-form surface mirror (4.2), the correcting lens (4.3), the detector window (5) and the optical filter (6) are arranged in an off-axis mode in the meridian direction of the optical system, and the optical axes of the free-form surface collimating mirror, the first free-form surface mirror and the second free-form surface mirror are parallel to the optical axis of the optical system.
2. The free-form surface spectrometer optical system according to claim 1, wherein:
the free-form surface collimating mirror (2), the first free-form surface mirror (4.1) and the second free-form surface mirror (4.2) are smooth surfaces which are symmetrical about a y axis.
3. A method for designing the optical system of a free-form surface spectrometer as claimed in claim 1, characterized in that the method comprises:
according to technical indexes of the system, calculating initial parameters including initial spherical curvature of a first free-form surface mirror (4.1) of a free-form surface collimating mirror (2) and a converging mirror (4), parameters of a plane grating (3), element intervals and the like, and establishing a Kernel-Terner spectrometer model; the reflector surface type is set to be a free-form surface, and collimation, image quality, element interference and the like of emergent light rays behind the collimating mirror are controlled to be optimized; a correction lens (4.3) is added to increase and control the spectral curvature and color distortion for optimization; and a second free-form surface mirror (4.2) is added to fold the light path for optimization.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010441702.9A CN111562007A (en) | 2020-05-22 | 2020-05-22 | Free-form surface spectrometer optical system and design method |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010441702.9A CN111562007A (en) | 2020-05-22 | 2020-05-22 | Free-form surface spectrometer optical system and design method |
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| CN111562007A true CN111562007A (en) | 2020-08-21 |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102109379A (en) * | 2010-12-14 | 2011-06-29 | 中国科学院长春光学精密机械与物理研究所 | Optical device for wide waveband plane grating dispersion type imaging spectrometer |
| US20130182250A1 (en) * | 2012-01-13 | 2013-07-18 | Roper Scientific, Inc. | Anastigmatic imaging spectrograph |
| CN108106729A (en) * | 2017-12-01 | 2018-06-01 | 中国科学院长春光学精密机械与物理研究所 | A kind of common CCD spectrometers of double grating |
-
2020
- 2020-05-22 CN CN202010441702.9A patent/CN111562007A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102109379A (en) * | 2010-12-14 | 2011-06-29 | 中国科学院长春光学精密机械与物理研究所 | Optical device for wide waveband plane grating dispersion type imaging spectrometer |
| US20130182250A1 (en) * | 2012-01-13 | 2013-07-18 | Roper Scientific, Inc. | Anastigmatic imaging spectrograph |
| CN108106729A (en) * | 2017-12-01 | 2018-06-01 | 中国科学院长春光学精密机械与物理研究所 | A kind of common CCD spectrometers of double grating |
Non-Patent Citations (1)
| Title |
|---|
| 袁立银 等: "紧凑型红外成像光谱仪光学设计", 《红外与激光工程》 * |
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Application publication date: 20200821 |