CN112229516A - Spectroscopic imaging system for snapshot type imaging spectrometer and imaging method thereof - Google Patents

Spectroscopic imaging system for snapshot type imaging spectrometer and imaging method thereof Download PDF

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CN112229516A
CN112229516A CN202011204846.9A CN202011204846A CN112229516A CN 112229516 A CN112229516 A CN 112229516A CN 202011204846 A CN202011204846 A CN 202011204846A CN 112229516 A CN112229516 A CN 112229516A
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light
incident
lens
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季轶群
谭奋利
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Suzhou University
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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
    • G01J3/12—Generating the spectrum; Monochromators
    • 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
    • G01J3/14—Generating the spectrum; Monochromators using refracting elements, e.g. prisms
    • 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
    • G01J2003/1208—Prism and grating

Abstract

The invention relates to a spectroscopic imaging system for a snapshot type imaging spectrometer and an imaging method thereof. The light splitting imaging system is of a coaxial symmetrical structure and comprises a light splitting element, and a collimating lens group and a focusing lens group which are symmetrically arranged on two sides of the light splitting element. The imaging method includes that incident light rays pass through a collimating lens group to obtain compound-color parallel light beams parallel to an optical axis, the compound-color parallel light beams are incident to a light splitting element, after the light is split by the light splitting element formed by combining a holographic grating and a prism, single-color parallel light beams with different wavelengths parallel to the optical axis are emitted and incident to a focusing lens group, and the single-color parallel light beams are focused and imaged at a detector. The spectral imaging system provided by the invention has the characteristics of large relative aperture, high spectral resolution, high light energy utilization rate, simple and compact structure and the like, and has wide application prospect.

Description

Spectroscopic imaging system for snapshot type imaging spectrometer and imaging method thereof
Technical Field
The invention relates to the technical field of imaging spectrometer spectral imaging systems, in particular to a spectral imaging system for a snapshot-type imaging spectrometer.
Background
The spectral imaging technology is a novel multidimensional information acquisition technology combining the imaging technology and the spectral technology, and can simultaneously acquire two-dimensional space information and one-dimensional spectral information of a measured target. Based on the characteristics, researchers can accurately identify, detect and analyze the target object according to the spectral fingerprint characteristics of the target object, so that the technology has wide application prospects in the fields of production and life, scientific research, military reconnaissance and the like.
The existing spectral imaging technology mostly adopts a slit to perform field segmentation to obtain a spectral image of a line field of view and obtains a full-field spectral image by scanning and imaging a target.
The snapshot type spectral imaging technology is a novel spectral imaging technology, two-dimensional spatial information and spectral information of a target object can be obtained within the integral time of a detector without push-scanning, and the practical requirements of applications needing to obtain the spatial information and the spectral information in real time can be met.
Referring to fig. 1, which is a schematic diagram of the overall structure of a snapshot type spectral imaging system provided in the prior art, according to the light transmission direction, there are an aperture diaphragm 1, a pre-objective 2, a micro-lens array 3, a collimating lens group 4, a beam splitting element 5, a focusing lens group 6 and a CCD detector 7 in sequence; the collimating lens group 4, the beam splitting element 5 and the focusing lens group 6 form a beam splitting imaging system, incident light is transmitted to a front objective lens through an aperture diaphragm 1 positioned at an object space focal plane of the front objective lens 2, and the front objective lens images a distant scene at a primary image surface; the micro lens array 3 positioned at the primary image surface divides and scales the image surface and forms a pupil image array at the focal plane of the micro lens array image; light rays emitted by the pupil images enter the collimating lens group 4 to obtain polychromatic parallel light beams, the polychromatic parallel light beams are emitted to monochromatic parallel light beams with different wavelengths after passing through the combined light splitting element 5 and enter the focusing lens group 6, and the light beams are focused by the focusing lens group to obtain monochromatic pupil image arrays with different wavelengths at the CCD detector 7, so that the imaging process is completed. The spectroscopic imaging system is used as a core component of a snapshot type imaging spectrometer, and the imaging quality of the spectroscopic imaging system determines the spectral resolution and the imaging performance of the system.
The common light splitting modes in the prior art mainly comprise prisms, gratings and the like, the prisms are low in dispersion rate and poor in light splitting capability, and the relief gratings are low in diffraction efficiency and low in light energy utilization rate. Common grating spectral imaging systems, such as Offner grating type, Czerny-Turner grating type, and the like, all of which are off-axis structures, have the defects of large volume, difficult assembly and adjustment, poor stability, and the like.
The chinese invention patent CN 110081976 a discloses a large field of view grating prism spectral imaging system, which comprises a slit, a spherical mirror and a planar mirror, a grating prism module, a focusing mirror group consisting of 8 lenses, an optical filter and a detector. The working wave band of the system is 420-1000 nm, the length of the slit is 29.4mm, and the F number is 2.4; the optical system adopts a reflection type structure as a collimating objective and adopts a transmission type structure as a focusing lens group, thereby realizing spectral imaging of wide band, large relative aperture and long slit and achieving the design purpose; however, it has the following disadvantages: the first is that the spherical reflector and the plane mirror form an off-axis collimation group, and the spectral imaging system belongs to an off-axis system, so that the installation and adjustment are difficult and the system stability is poor; secondly, the spectral imaging system adopts the slit to divide the field of view, the light energy utilization rate of the system is low, and the acquisition of the full-field spectral image can be realized only by scanning.
Therefore, the spectral imaging system for the snapshot type imaging spectrometer is designed to solve the problems of most of the existing spectral imaging systems, and has great practical significance for popularization and application of the spectral imaging technology.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a direct-view spectral imaging system and an imaging method thereof, wherein the direct-view spectral imaging system has the advantages of high spectral resolution, good imaging quality, simple and compact structure and easiness in processing, assembly and adjustment.
The technical scheme adopted by the invention is to provide a light splitting imaging system for a snapshot type imaging spectrometer, which is of a coaxial symmetrical structure and comprises a light splitting element, and a collimating lens group and a focusing lens group which are symmetrically arranged at two sides of the light splitting element; the collimating lens group and the focusing lens group have the same structure and respectively comprise five refracting lenses; the light splitting element comprises a volume holographic grating and a prism; according to the incident direction of light rays, the optical elements of the spectroscopic imaging system are as follows in sequence: the lens comprises a first meniscus lens, a first biconvex lens, a second meniscus lens, a second biconvex lens, a first biconcave lens, a volume holographic grating, a prism, a second biconcave lens, a third biconvex lens, a third meniscus lens, a fourth biconvex lens and a second meniscus lens, wherein the first biconcave lens and the second biconcave lens form a double-cemented lens group, and the second biconcave lens and the third biconvex lens form another double-cemented lens group.
The invention provides a light splitting imaging system for a snapshot type imaging spectrometer, the numeric area of the working F number of the system is more than or equal to 2.4 and less than or equal to F/#andless than or equal to 2.65, the object space field of view is phi more than 3mm, the magnification is minus 1 x, the distortion is less than 0.2 percent, and the total length L of the system is more than or equal to 85mm and less than or equal to L and less than or equal to 90 mm.
One preferred embodiment of the present invention is: the first surface of the prism has an included angle beta with the vertical direction of the optical axis1，0°＜β1Less than 90 DEG, and the second surface of the prism forms an angle beta with the perpendicular direction of the optical axis2，0°＜β2< 90 DEG and beta1And beta2The conditions are satisfied: emergent rays of the main wavelength rays incident in parallel to the optical axis and split by the light splitting element are still parallel to the optical axis; a more excellent effect is as follows: beta is1The main wavelength light incident parallel to the optical axis satisfies the grating Bragg condition.
The technical scheme of the invention also comprises an imaging method of the spectroscopic imaging system for the snapshot type imaging spectrometer, which comprises the following steps:
(1) incident light rays pass through the collimating lens group to obtain a complex-color parallel light beam parallel to an optical axis;
(2) the compound color parallel light obtained in the step (1) is incident to a light splitting element, and after light splitting is carried out by a combined light splitting element, single color parallel light beams with different wavelengths parallel to an optical axis are emitted; the light splitting element comprises a volume holographic grating and a prism, and the included angle between the first surface of the prism and the vertical direction of the optical axis enables the main wavelength light incident parallel to the optical axis to meet the grating Bragg condition;
(3) and (3) enabling the monochromatic parallel light beams with different wavelengths obtained in the step (2) to be incident to a focusing lens group, and imaging the incident light rays at a detector after focusing.
In the step (2), the principal ray of the central wavelength incident in parallel to the optical axis is in theta1Incident on the grating substrate, refracted inside the grating substrate and at an angle theta2Incident on the grating and at a diffraction angle theta3Is emitted from the grating and then enters a prism3=θ2After refraction inside the prism at an angle theta4Incident on the rear surface of the prism at an angle theta5Emerging from the light-splitting element, [ theta ]5=β2To realize the straight-in and straight-out of the light, wherein theta1、θ2、θ3、θ4And theta5Respectively the angle between the light and the normal of the incident or emergent surface.
The snapshot spectral imaging system provided by the invention has the advantages that through the coaxial symmetric structural design, the relative aperture of the system is increased, the light collecting capacity and the system resolution of the system can be improved, and the application range of the spectral imaging system is enlarged.
Compared with the prior art, the invention has the beneficial effects that:
1. the collimating lens group and the focusing lens group of the spectroscopic imaging system are designed into the same structure, so that the processing cost is saved; through reasonable selection of glass materials and design, the relative aperture of the optical lens is increased while aberration correction and balance are realized, so that the light collecting capacity and the resolution of the system are obviously improved.
2. The spectral imaging method provided by the invention uses the volume holographic transmission grating with higher diffraction efficiency and the prism as a spectral element after being glued, and controls the included angle beta between the first surface of the prism and the direction vertical to the optical axis1The incident angle of the light with the central wavelength parallel to the optical axis meets the grating Bragg condition, the energy utilization rate of the system is improved, and the light splitting performance is better; by controlling the included angle between the second surface of the prism and the direction vertical to the optical axis to be beta2Make the centerLight rays with wavelengths incident parallel to the optical axis exit parallel to the optical axis. Therefore, the light splitting imaging system is a coaxial optical system, has compact structure, smaller volume, easy processing, adjustment and strong stability, and is beneficial to the miniaturization and portability development of the imaging spectrometer.
3. The spectral imaging system provided by the invention simultaneously meets the requirements of object-side telecentric and image-side telecentric structures, has higher telecentricity, and is beneficial to improving the measurement precision of spatial position information, and both the object-side telecentricity and the image-side telecentricity are less than 0.03 degrees.
4. According to the spectral imaging system provided by the invention, the optical lens is only composed of ten spherical refraction lenses, and all the lenses are made of domestic glass materials, so that the processing difficulty and the processing cost of the lens are reduced, and the spectral imaging system has practical application value.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a snapshot-type spectral imaging system provided in the prior art;
FIG. 2 is a schematic structural diagram of a spectroscopic imaging system provided by an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a light-splitting element according to an embodiment of the present invention;
FIG. 4 is a distortion plot of a spectroscopic imaging system provided by an embodiment of the present invention;
FIG. 5 is a graph of field curvature and astigmatism for a spectroscopic imaging system according to an embodiment of the present invention;
FIG. 6 is a ray tracing point diagram of a spectroscopic imaging system according to an embodiment of the present invention;
FIG. 7 is a graph of a transfer function curve MTF of a spectroscopic imaging system according to an embodiment of the present invention;
FIG. 8 is an energy concentration curve for a spectroscopic imaging system according to an embodiment of the present invention;
in the figure: 1. an aperture diaphragm; 2. a front objective lens; 3. a microlens array; 4. a collimating lens group; 5. a light-splitting element; 6. a focusing lens group; 7. an image plane; 41. a first meniscus lens; 42. a first sheet of lenticular lens; 43. a second meniscus lens; 44. a second sheet of lenticular lens; 45. a first biconcave lens; 510. glass substrate front surface (stop); 51. a volume holographic grating; 511. a glass substrate; 512. a grating; 513. protecting glass; 52. a prism; 61. a second biconcave lens; 62. a third sheet of lenticular lens; 63. a third meniscus lens; 64. a fourth sheet of lenticular lens; 65. and a fourth meniscus lens.
Detailed description of the preferred embodiments
The following further describes the embodiments of the present invention with reference to the drawings and examples.
Embodiment 1 the technical solution of this embodiment is to provide a spectroscopic imaging system for a snapshot imaging spectrometer. The optical lens consists of a volume holographic transmission grating, a prism combined light splitting element and 10 refracting spherical lenses, wherein the focal length F of an optical system is =17mm, the F number is F/# =2.6, the object space field phi is =3mm, and the working wavelength is 400-700 nm.
Referring to fig. 2, it is a schematic structural diagram of the spectroscopic imaging system provided in this embodiment, and it is composed of a collimating lens group 4 and a focusing lens group 6 symmetrically disposed on both sides of a spectroscopic element 5, where each of the two lens groups includes five refractive lenses, and the optical element is a first meniscus lens 41 in turn according to the incident direction of light; a first sheet of lenticular lenses 42; a second meniscus lens 43; a second sheet of lenticular lenses 44; a first biconcave lens 45; a light-splitting element 5; a second piece of biconcave lens 61; a third sheet of lenticular lenses 62; a second meniscus lens 63; a fourth sheet of biconvex lens 64; a fourth meniscus lens 65. Among them, the first meniscus lens 42, it is crooked to the incident direction of the light; a second meniscus lens 43 bent toward the incident direction of light; the second biconvex lens 43 and the first biconcave lens 44 form a double cemented lens group; the second biconcave lens 61 and the third biconvex lens 62 form a double cemented lens group; a third meniscus lens 63, curved away from the direction of light incidence; a fourth meniscus lens 65, which is curved in the direction of light incidence. When the spectral imaging system is used for imaging, incident light is collimated into a polychromatic parallel beam through the collimating lens group 4, the polychromatic parallel beam is dispersed by the light splitting element 5 and then is emitted as monochromatic parallel beams with different wavelengths, and the light splitting element mainly comprises a volume holographic grating 51 and a prism 52; and then the monochromatic parallel light beams with different wavelengths are focused by the focusing lens group 6 and imaged at a detector, thereby completing the imaging process.
Referring to fig. 3, it is a schematic structural diagram of the light splitting element provided in this embodiment, the light splitting element mainly includes a volume holographic grating 51 and a prism 52, wherein a system diaphragm 512 is disposed at a front surface 510 of a glass substrate, and the glass substrate 511, a protective glass 513 and the prism 52 are made of the same material; the first surface of the prism of the light splitting element has an included angle beta with the direction vertical to the optical axis OO1The second surface of the prism forms an included angle beta with the direction vertical to the optical axis OO2。β1，0°＜β1＜90°，0°＜β2< 90 DEG and beta1And beta2The conditions are satisfied: the outgoing light ray of the main wavelength light ray incident parallel to the optical axis passing through the light splitting element 5 is still parallel to the optical axis.
Chief rays of central wavelength incident parallel to the optical axis OO' are at θ1Incident on the grating substrate, refracted inside the grating substrate and at an angle theta2Incident on the grating and at a diffraction angle theta3（θ3=θ2) The light beam is emitted from the grating and enters the prism, refracted inside the prism and forms an angle theta4Incident on the rear surface of the prism and finally at an angle theta5（θ5=β2) The light is emitted from the light splitting element to realize the straight-in and straight-out of the light, wherein theta1、θ2、θ3、θ4And theta5Is the angle between the light ray and the normal of the incident (or emergent) surface. In order to obtain high diffraction efficiency, the incident angle of light incident on the holographic grating should satisfy the Bragg condition, i.e. the diffraction angle is equal to the incident angle,
Figure 495999DEST_PATH_IMAGE002
wherein the content of the first and second substances,
Figure 147560DEST_PATH_IMAGE004
is the center wavelength, d is the grating constant, nGIs the refractive index of the grating material. While the angle of incidence of the central wavelength on the grating substrate can be determined from the law of refraction, i.e.
Figure 599401DEST_PATH_IMAGE006
Wherein n isPThe refractive index of the grating substrate is determined, and the included angle between the front surface of the prism and the direction perpendicular to the optical axis is determined so that the light incident on the grating substrate satisfies the Bragg condition
Figure 525769DEST_PATH_IMAGE008
。
To realize the straight-in and straight-out characteristics of the central wavelength, the included angle of the back surface of the prism satisfies the following relation
Figure 74562DEST_PATH_IMAGE010
Figure 569128DEST_PATH_IMAGE012
Figure 570582DEST_PATH_IMAGE014
The included angle between the rear surface of the prism and the direction perpendicular to the optical axis can be obtained by simultaneous solution of the above formulas
Figure DEST_PATH_IMAGE015
As shown below
Figure DEST_PATH_IMAGE017
In this embodiment, an included angle β between the first surface of the prism and the vertical direction of the optical axis1=1.57 °, and the angle between the second surface of the prism and the direction perpendicular to the optical axis is β2=5.9 °, the volume hologram grating groove density was 100 lines/mm, and the parameters of each optical element of this example are shown in table 1.
Table 1:
Figure DEST_PATH_IMAGE019
。
the imaging method of the spectroscopic imaging system for the snapshot type imaging spectrometer comprises the following steps:
(1) incident light rays pass through the collimating lens group to obtain a complex-color parallel light beam parallel to an optical axis;
(2) the compound color parallel light obtained in the step (1) is incident to a light splitting element, and after light splitting is carried out by a combined light splitting element, single color parallel light beams with different wavelengths parallel to an optical axis are emitted;
(3) and (3) enabling the monochromatic parallel light beams with different wavelengths obtained in the step (2) to be incident to a focusing lens group, and imaging the incident light rays at a detector after focusing.
Referring to fig. 4, which is a distortion curve diagram of the spectroscopic imaging system provided in this embodiment, the abscissa of the graph represents a distortion value (unit%) with respect to the image plane, and the ordinate represents a normalized field of view, and it can be known from the result of fig. 4 that the distortion aberration of the spectroscopic imaging system has been sufficiently corrected, and the distortion rate has been obtained to be less than 0.2%.
Referring to fig. 5, which is a graph of field curvature and astigmatism of the spectroscopic imaging system provided in this embodiment, the abscissa of the graph indicates the field curvature astigmatism value, and the ordinate of the graph indicates the normalized field of view, and the two curves in the graph, the dashed curve and the solid curve in the graph indicate the field curvatures in the sagittal plane and the meridional plane, respectively, as can be seen from the results of fig. 5, the spectroscopic imaging system effectively corrects the astigmatism and the field curvature so that the difference between the two curves, i.e., the astigmatism value, is within the aberration tolerance range.
Referring to fig. 6, it is a light tracing point diagram of the spectroscopic imaging system provided by this embodiment, in the diagram, the root mean square radius of the point diagram of each field of view corresponding to three wavelengths is less than 2 μm, the geometric radius of the point diagram is less than 3 μm, the imaging quality is good, and the system use requirements are met.
Referring to fig. 7, it is a transfer function MTF curve on the image plane corresponding to each field of view of the spectroscopic imaging system provided in this embodiment. As can be seen from FIG. 7, the MTF value of each field under 70lp/mm is greater than 0.7, which is close to the diffraction limit, the curve is smooth and compact, which indicates that the lens imaging is clear and uniform, and the system has good imaging quality in the full-band full-field.
Referring to fig. 8, which is an energy concentration curve of the spectroscopic imaging system according to the present embodiment, it can be seen from fig. 8 that more than 80% of the energy is concentrated at a point within the Airy spot range.
The light splitting imaging system for snapshot type spectral imaging provided by the technical scheme of the invention only comprises ten lenses, and the light collecting capacity and the system resolution of the system are increased by improving the relative aperture of the lens imaging, so that an image with uniform illuminance distribution, concentrated energy and high resolution can be obtained.
The spectroscopic imaging system and the imaging method thereof provided by the technical scheme of the invention have the characteristics of large relative aperture, good imaging quality, high spectral resolution, high light energy utilization rate, simple and compact structure, easy processing, assembly and adjustment, strong stability and the like through strict aberration correction, can be used in the field of spectral imaging, and have wide application prospect.

Claims (6)

1. A spectroscopic imaging system for a snapshot imaging spectrometer, characterized by: the optical fiber laser is of a coaxial symmetrical structure and comprises a light splitting element (5), and a collimating lens group (4) and a focusing lens group (6) which are symmetrically arranged on two sides of the light splitting element (5); the collimating lens group (4) and the focusing lens group (6) have the same structure and respectively comprise five refracting lenses; the light splitting element (5) comprises a volume holographic grating (51) and a prism (52); according to the incident direction of light rays, the optical elements of the spectroscopic imaging system are as follows in sequence: the lens comprises a first meniscus lens (41) bent back to the incident direction of light, a first biconvex lens (42), a second meniscus lens (43) bent to the incident direction of light, a second biconvex lens (44), a first biconcave lens (45), a volume holographic grating (51), a prism (52), a second biconcave lens (61), a third biconvex lens (62), a third meniscus lens (63) bent back to the incident direction of light, a fourth biconvex lens (64) and a second meniscus lens (65) bent to the incident direction of light, wherein the second biconvex lens (44) and the first biconcave lens (45) form a double-lens combination, and the second biconcave lens (61) and the third biconvex lens (62) form another double-lens combination.
2. The spectroscopic imaging system of claim 1 for a snapshot imaging spectrometer, wherein: the value range of the working F number is more than or equal to 2.4 and less than or equal to 2.65, the object space field phi is more than 3mm, the magnification is minus 1 x, the distortion is less than 0.2 percent, and the total length L of the system is more than or equal to 85mm and less than or equal to 90 mm.
3. The spectroscopic imaging system of claim 1 for a snapshot imaging spectrometer, wherein: the first surface of the prism (52) forms an angle beta with the perpendicular direction of the optical axis1，0°＜β1< 90 DEG, the second surface of the prism (52) making an angle beta with the direction perpendicular to the optical axis2，0°＜β2< 90 DEG and beta1And beta2The conditions are satisfied: the outgoing light beam split by the light splitting element (5) of the main wavelength light beam incident in parallel to the optical axis is still parallel to the optical axis.
4. A spectroscopic imaging system for a snapshot imaging spectrometer as in claim 3 wherein: beta is1The main wavelength light incident parallel to the optical axis satisfies the grating Bragg condition.
5. An imaging method for a spectroscopic imaging system of a snapshot imaging spectrometer, comprising the steps of:
(1) incident light rays pass through the collimating lens group (4) to obtain a compound-color parallel light beam parallel to an optical axis;
(2) the compound color parallel light obtained in the step (1) is incident to a light splitting element (5), and after being split by a combined light splitting element, single color parallel light beams with different wavelengths parallel to an optical axis are emitted; the light splitting element (5) comprises a volume holographic grating (51) and a prism (52), and an included angle between a first surface of the prism (52) and the vertical direction of an optical axis enables a dominant wavelength light ray incident in parallel to the optical axis to meet a grating Bragg condition;
(3) and (3) enabling the monochromatic parallel light beams with different wavelengths obtained in the step (2) to enter a focusing lens group (6), and imaging the incident light rays at a detector after focusing.
6. The imaging method of the spectroscopic imaging system for a snapshot imaging spectrometer of claim 5, wherein: in the step (2), the principal ray of the central wavelength incident in parallel to the optical axis is in theta1Incident on the grating substrate, refracted inside the grating substrate and at an angle theta2Incident on the grating and at a diffraction angle theta3Is emitted from the grating and then enters a prism3=θ2After refraction inside the prism at an angle theta4Incident on the rear surface of the prism at an angle theta5Emerging from the light-splitting element, [ theta ]5=β2To realize the straight-in and straight-out of the light, wherein theta1、θ2、θ3、θ4And theta5Respectively the angle between the light and the normal of the incident or emergent surface.
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CN114137735A (en) * 2021-12-13 2022-03-04 北京航空航天大学 Large-aperture long-intercept IMS spectral imaging system collimating lens
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CN112925087A (en) * 2021-02-25 2021-06-08 福建海创光电有限公司 Large-numerical-aperture color separation double-telecentric optical system
CN112925087B (en) * 2021-02-25 2023-02-28 福建海创光电技术股份有限公司 Large-numerical-aperture color separation double-telecentric optical system
CN114137735A (en) * 2021-12-13 2022-03-04 北京航空航天大学 Large-aperture long-intercept IMS spectral imaging system collimating lens
CN114137735B (en) * 2021-12-13 2022-11-25 北京航空航天大学 Large-aperture long-intercept IMS spectral imaging system collimating lens
CN115655467A (en) * 2022-11-11 2023-01-31 中国科学院长春光学精密机械与物理研究所 Imaging spectrometer

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