CN114166347A - Medium-wave infrared hyperspectral spectral imaging unit - Google Patents

Medium-wave infrared hyperspectral spectral imaging unit Download PDF

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Publication number
CN114166347A
CN114166347A CN202111482165.3A CN202111482165A CN114166347A CN 114166347 A CN114166347 A CN 114166347A CN 202111482165 A CN202111482165 A CN 202111482165A CN 114166347 A CN114166347 A CN 114166347A
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lens
blazed grating
slit
plane
collimating
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王健
韩希珍
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Suzhou Oriental Croto Photoelectric Technology Co ltd
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Suzhou Oriental Croto Photoelectric Technology Co ltd
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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
    • 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
    • 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
    • G01J3/0243—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows having a through-hole enabling the optical element to fulfil an additional optical function, e.g. a mirror or grating having a throughhole for a light collecting or light injecting optical fiber
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light

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  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
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  • Spectrometry And Color Measurement (AREA)

Abstract

The invention relates to a medium-wave infrared hyperspectral split imaging unit, which comprises a slit, a collimating lens consisting of a first lens, a second lens and a third lens, and a plane blazed grating, wherein the first lens is arranged on the slit; the light transmitted by the slit is collimated by the collimating lens, then enters the plane blazed grating, is split by the plane blazed grating and then returns to the collimating lens; the returned light passes through the collimating lens and then is imaged on an area array detector arranged on a front focal plane of the collimating lens; the first lens is a biconvex lens; the second lens is a meniscus negative lens, one side of the second lens facing the slit is a concave surface, and one side of the second lens facing the plane blazed grating is a convex surface; the third lens is a meniscus positive lens, one side of the meniscus positive lens facing the slit is a concave surface, and one side of the meniscus positive lens facing the planar blazed grating is a convex surface. The invention avoids the use of high-cost convex blazed gratings and concave blazed gratings, reduces the difficulty of installation and adjustment, and leads the imaging spectrometer to have more compact structure and good imaging effect.

Description

Medium-wave infrared hyperspectral spectral imaging unit
Technical Field
The invention belongs to the technical field of infrared hyperspectrum, and relates to a medium wave infrared hyperspectral light splitting and imaging unit of a telecentric auto-collimation structure based on a planar blazed grating with high integration degree.
Background
The medium-wave infrared hyperspectral imaging equipment can simultaneously acquire image information and spectral information of a detected ground object, and can distinguish substance types and components through fingerprint spectral information of a ground object target, so that the medium-wave infrared hyperspectral imaging equipment has important application value in the aspects of mineral exploration, gas component analysis, forest fire detection and the like.
The spectral imaging unit is a core component of the hyperspectral imaging equipment. The imaging spectrometer is classified according to a light splitting mode, and is divided into a dispersion type spectrometer and an interference type spectrometer, wherein the market distribution of the dispersion type spectrometer taking blazed gratings as light splitting elements is the widest. In order to miniaturize the hyperspectral imaging device, the combination design of collimation, light splitting and focusing is generally carried out, wherein the most widely used design forms are Offner imaging spectrometer and Dyson imaging spectrometer. However, the two mainstream design forms of the spectral gratings adopt curved surface gratings, the Offner structure adopts convex surface gratings, the Dyson structure adopts concave surface blazed gratings, the curved surface gratings are difficult to process, the price is high, and the reflecting surfaces are more and the assembly difficulty is high. The spectrometer structure based on the plane grating structure comprises three parts of collimation, light splitting and focusing, and the structure is difficult to miniaturize.
The invention content is as follows:
the invention aims to solve the technical problem of providing a medium wave infrared hyperspectral split-beam imaging unit, which solves the problems of processing difficulty and high price caused by curved surface blazed gratings and multi-reflector structures in the traditional medium wave infrared hyperspectral imaging equipment based on blazed gratings, realizes the dispersion split-beam imaging of slits in a medium infrared band by utilizing a plane blazed grating and a telecentric autocollimator, and has good imaging quality and compact structure.
In order to solve the technical problem, the medium-wave infrared hyperspectral split imaging unit comprises a slit, a collimating lens consisting of a first lens, a second lens and a third lens, and a plane blazed grating; the slit is arranged on the front focal plane of the collimating mirror, and the length direction of the opening of the slit is vertical to the optical axis and is parallel to the tangent line of a circle taking the optical axis as the axis; the center of the plane blazed grating is positioned on the back focal plane of the collimating mirror, and the angle of the plane blazed grating can be adjusted according to the wavelength range of incident light; the light transmitted by the slit is collimated by the collimating lens, then enters the plane blazed grating, is split by the plane blazed grating and then returns to the collimating lens; the returned light passes through the collimating lens and then is imaged on an area array detector arranged on a front focal plane of the collimating lens; the first lens is a biconvex lens; the second lens is a meniscus negative lens, one side of the second lens facing the slit is a concave surface, and one side of the second lens facing the plane blazed grating is a convex surface; the third lens is a meniscus positive lens, one side of the meniscus positive lens facing the slit is a concave surface, and one side of the meniscus positive lens facing the planar blazed grating is a convex surface.
Setting the wavelength range of incident light as lambda 1-lambda 3, and setting the included angle between the principal ray and the optical axis of the incident light emitted by the collimating mirror and incident on the plane blazed grating as theta; the grating constant of the plane blazed grating is d, and the effective diffraction order during working is m; the focal length of the collimating mirror is f; the vertical distance h from the center of the slit to the optical axis satisfies formula (1), and the included angle alpha between the normal of the planar blazed grating and the optical axis satisfies formula (2);
Figure BDA0003395697580000021
2dsinαcosθ＝mλ1 (2)
the technical parameters and materials of the first lens, the second lens and the third lens are shown in table 1, wherein t is the thickness of the lens, and d is the distance between the rear surface of the optical element and the front surface of the next optical element;
TABLE 1
Figure BDA0003395697580000022
Advantageous effects
The invention adopts a light splitting mode that the center of the plane blazed grating is arranged on the back focal plane of the collimating mirror, incident light is collimated by the transmission type collimating mirror and returned light is imaged on the area array detector, thereby realizing the dispersion light splitting and imaging of the slit in the imaging spectrometer, avoiding the use of high-cost convex blazed grating and concave blazed grating, reducing the installation and adjustment difficulty and enabling the imaging spectrometer to have a more compact structure; the high-spectrum imaging of the spectrometer is realized through the parameter configuration of telecentric auto-collimation, and the imaging effect is good.
Drawings
Fig. 1 is a schematic structural view of the present invention.
In the figure, 1, a slit, 21, a first lens, 22, a second lens, 23, a third lens, 3, a plane blazed grating, 4, an area array detector, 5, a front focal plane of a collimating mirror, and 6, a rear focal plane of the collimating mirror.
Fig. 2, fig. 3 and fig. 4 are diagrams of imaging points of the spectroscopic imaging unit for three operating wavelengths λ 1, λ 2 and λ 3. The circles in the figure indicate airy spots corresponding to diffraction limits.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and examples, it being understood that the specific embodiments described herein are illustrative of the invention only and are not limiting. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other suitable relationship. The specific meanings of the above terms in the present invention can be specifically understood in specific cases by those of ordinary skill in the art.
In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," or "beneath" a second feature includes the first feature being directly under or obliquely below the second feature, or simply means that the first feature is at a lesser elevation than the second feature.
In the description of the present embodiment, the terms "upper", "lower", "left", "right", and the like are used in the orientation or positional relationship shown in the drawings only for convenience of description and simplicity of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used only for descriptive purposes and are not intended to have a special meaning.
As shown in fig. 1, the medium-wave infrared hyperspectral split imaging unit of the invention comprises a slit 1, a collimating lens consisting of a first lens 21, a second lens 22 and a third lens 23, and a plane blazed grating 3; the slit is arranged on the front focal plane 5 of the collimating mirror, and the length direction of the opening of the slit is vertical to the optical axis and is parallel to the tangent line of a circle taking the optical axis as the axis; the center of the plane blazed grating 3 is positioned on the back focal plane 6 of the collimating mirror, and the angle of the plane blazed grating can be adjusted according to the wavelength range of incident light; the light transmitted by the slit 1 is collimated by the collimating mirror, then enters the plane blazed grating 3, is split by the plane blazed grating and then returns to the collimating mirror; the returned light rays pass through the collimating lens and then are imaged on an area array detector 4 arranged on a front focal plane 5 of the collimating lens; the slit 1 and the area array detector 4 are respectively positioned at two sides of the optical axis.
The centers of the first lens 21, the second lens 22, the third lens 23, and the plane blazed grating 3 are located on the same optical axis.
The first lens 21 is a biconvex lens; the second lens 22 is a meniscus negative lens, and one side of the second lens facing the slit is a concave surface and one side of the second lens facing the planar blazed grating 3 is a convex surface; the third lens 23 is a meniscus positive lens, and its side facing the slit is a concave surface and its side facing the planar blazed grating 3 is a convex surface.
Setting the wavelength range of incident light as lambda 1-lambda 3, and setting the included angle between the principal ray and the optical axis of the incident light emitted by the collimating mirror and incident on the plane blazed grating as theta; the grating constant of the plane blazed grating is d, and the effective diffraction order during working is m; the focal length of the collimating mirror is f; the vertical distance h from the center of the slit to the optical axis satisfies formula (1), and the included angle alpha between the normal of the planar blazed grating and the optical axis satisfies formula (2);
Figure BDA0003395697580000041
2dsinαcosθ＝mλ1 (2)
the chief ray of the light beam emitted by the slit 1 is incident to a collimating mirror consisting of a first lens 21, a second lens 22 and a third lens 23; and the light is emitted through the third lens 23 and then is directed to the center of the plane blazed grating 3. The light is reflected by the planar blazed grating 3 and returns to the collimating mirror, and is imaged to the area array detector 4 through the collimating mirror.
The technical parameters and materials of the first lens 21, the second lens 22 and the third lens 23 are shown in table 1, wherein t is the thickness of the lens, and d is the distance between the rear surface of the optical element and the front surface of the next optical element.
TABLE 1
Figure BDA0003395697580000051
When the lambda 1 is 3700nm and the lambda 3 is 4800nm, the distance from the center of the corresponding slit 1 to the optical axis is 10mm, the distance from the center of the area array detector 4 to the axis is also 10mm, and the theta angle is 20.46 degrees.
As can be seen from FIGS. 2, 3 and 4, the imaging light spot root mean square diameter of 3700nm wavelength in the full slit range is less than 7 μm, the imaging light spot root mean square diameter of 4250nm wavelength in the full slit range is less than 2 μm, and the imaging light spot root mean square diameter of 4800nm wavelength in the full slit range is less than 3 μm, both of which are less than airy spot diameter.

Claims (3)

1. A medium wave infrared high spectrum spectral imaging unit is characterized in that: the light splitting imaging unit comprises a slit, a collimating lens consisting of a first lens, a second lens and a third lens, and a plane blazed grating; the slit is arranged on the front focal plane of the collimating mirror, and the length direction of the opening of the slit is vertical to the optical axis and is parallel to the tangent line of a circle taking the optical axis as the axis; the center of the plane blazed grating is positioned on the back focal plane of the collimating mirror, and the angle of the plane blazed grating can be adjusted according to the wavelength range of incident light; the light transmitted by the slit is collimated by the collimating lens, then enters the plane blazed grating, is split by the plane blazed grating and then returns to the collimating lens; the returned light passes through the collimating lens and then is imaged on an area array detector arranged on a front focal plane of the collimating lens; the first lens is a biconvex lens; the second lens is a meniscus negative lens, one side of the second lens facing the slit is a concave surface, and one side of the second lens facing the plane blazed grating is a convex surface; the third lens is a meniscus positive lens, one side of the meniscus positive lens facing the slit is a concave surface, and one side of the meniscus positive lens facing the planar blazed grating is a convex surface.
2. The medium wave infrared hyperspectral spectroscopic imaging unit of claim 1, wherein: setting the wavelength range of incident light as lambda 1-lambda 3, and setting the included angle between the principal ray and the optical axis of the incident light emitted by the collimating mirror and incident on the plane blazed grating as theta; the grating constant of the plane blazed grating is d, and the effective diffraction order during working is m; the focal length of the collimating mirror is f; the vertical distance h from the center of the slit to the optical axis satisfies formula (1), and the included angle alpha between the normal of the planar blazed grating and the optical axis satisfies formula (2);
Figure FDA0003395697570000011
2d sinαcosθ＝mλ1 (2) 。
3. the medium wave infrared hyperspectral spectroscopic imaging unit of claim 1, wherein: the technical parameters and materials of the first lens, the second lens and the third lens are shown in table 1, wherein t is the thickness of the lens, and d is the distance between the rear surface of the optical element and the front surface of the next optical element;
TABLE 1
Figure FDA0003395697570000021
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104019910A (en) * 2014-06-23 2014-09-03 山东科技大学 Blazed grating-based fabry-perot THz wavelength measurement instrument and measurement method thereof
CN203828901U (en) * 2014-02-07 2014-09-17 中国科学院上海光学精密机械研究所 Spectrometer for frequency domain OCT system
CN110375856A (en) * 2019-07-18 2019-10-25 中国科学院西安光学精密机械研究所 Spectrum imaging system and method based on glittering plane reflection gratings double before partial wave
CN213067938U (en) * 2020-09-09 2021-04-27 河北先河环保科技股份有限公司 Large-aperture push-broom type imaging spectrometer system
US20210318170A1 (en) * 2019-09-17 2021-10-14 Huazhong University Of Science And Technology Spectral resolution enhancement device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN203828901U (en) * 2014-02-07 2014-09-17 中国科学院上海光学精密机械研究所 Spectrometer for frequency domain OCT system
CN104019910A (en) * 2014-06-23 2014-09-03 山东科技大学 Blazed grating-based fabry-perot THz wavelength measurement instrument and measurement method thereof
CN110375856A (en) * 2019-07-18 2019-10-25 中国科学院西安光学精密机械研究所 Spectrum imaging system and method based on glittering plane reflection gratings double before partial wave
US20210318170A1 (en) * 2019-09-17 2021-10-14 Huazhong University Of Science And Technology Spectral resolution enhancement device
CN213067938U (en) * 2020-09-09 2021-04-27 河北先河环保科技股份有限公司 Large-aperture push-broom type imaging spectrometer system

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王秋萍等: "《制版工程光学》", 30 November 1991, 上海交通大学出版社, pages: 214 - 216 *

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Application publication date: 20220311