1. An optical system of an integrated field-of-view spectrometer with high sampling efficiency is characterized by comprising a slit module (1), a narrow-band filter module (2), a collimation module (3) and a dispersion module (4) which are sequentially arranged along the transmission direction of an optical path; the angle between the normal of the collimation module (3) and the normal of the dispersion module (4) is equal to the incident angle of the dispersion module (4) in use, the angle between the normal of the dispersion module (4) and the normal of the imaging module (5) is equal to the diffraction angle of the dispersion module (4) in use, and the imaging module (5) and the reflection detector module (6) are linearly arranged.

2. The optical system of the high-sampling-efficiency integrated field-of-view spectrometer according to claim 1, wherein the slit module (1) comprises a plurality of slit units (1-1) arranged in parallel, each slit unit (1-1) comprises a first slit mechanism (1-2) and a second slit mechanism (1-3), a 30mm interval (1-4) is arranged between the first slit mechanism (1-2) and the second slit mechanism (1-3), and each first slit mechanism (1-2) and each second slit mechanism (1-3) are composed of the same number of optical fibers (1-5).

3. The high sampling efficiency integrated field spectrometer optical system according to claim 2, wherein each of the first slit mechanism (1-2) and the second slit mechanism (1-3) comprises 500 optical fibers (1-5) arranged at intervals of 120 μm, and the length of each of the first slit mechanism (1-2) and the second slit mechanism (1-3) is 60 mm; the first slit mechanism (1-2), the interval (1-4) and the second slit mechanism (1-3) are on the same straight line.

4. The high sampling efficiency integrating field of view spectrometer optical system as claimed in claim 1 wherein said narrowband filter module (2) is a narrowband filter.

5. The optical system of the high-sampling-efficiency integrating field-of-view spectrometer as claimed in claim 1, wherein the collimating module (3) comprises a first lens (3-1), a second lens (3-2), a third lens (3-3), a fourth lens (3-4), a fifth lens (3-5) and a sixth lens (3-6) which are arranged in sequence along the transmission direction of the optical path; the materials of the first lens (3-1), the second lens (3-2), the third lens (3-3), the fourth lens (3-4), the fifth lens (3-5) and the sixth lens (3-6) are sequentially H-ZK6, H-K9L, H-K3, H-F51, FCD100 and LAF 3.

6. The high sampling efficiency integrating field of view spectrometer optical system as claimed in claim 1, wherein said dispersive module (4) is a scribed reflective grating.

7. The optical system of the high-sampling-efficiency integrating field-of-view spectrometer as claimed in claim 1, wherein the imaging module (5) comprises a seventh lens (5-1), an eighth lens (5-2), a ninth lens (5-3), a tenth lens (5-4), an eleventh lens (5-5) and a twelfth lens (5-6) which are arranged in sequence along the diffraction direction of the optical path; the seventh lens (5-1), the eighth lens (5-2), the ninth lens (5-3), the tenth lens (5-4), the eleventh lens (5-5) and the twelfth lens (5-6) are made of H-LAK11, H-LAK11, ZF52, Fused silica, ZF52 and ZF52 in sequence.

8. The high sampling efficiency integrating field of view spectrometer optical system as claimed in claim 1, wherein said reflective detector module (6) comprises a plane mirror (6-1) and a detector, said detector comprises a first detector (6-2) and a second detector (6-3), the plane mirror (6-1) is placed between the detector and the imaging module (5); the first detector (6-2) and the twelfth lens (5-6) are arranged in parallel, and an image of the first slit mechanism (1-2) in the slit unit (1-1) is emitted from the twelfth lens (5-6) and then directly irradiated and imaged on the first detector (6-2); the second detector (6-3) is arranged below the plane reflector (6-1), the plane reflector (6-1) is arranged between the second detector (6-3) and the twelfth lens (5-6) and forms 45 degrees with the second detector (6-3) and the twelfth lens (5-6), and an image of the second slit mechanism (1-3) in the slit unit (1-1) is emitted from the twelfth lens (5-6), reflected by the plane reflector (6-1) and irradiated on the second detector (6-3) to be imaged.

9. A method for designing an optical system of a high sampling efficiency integrating field of view spectrometer as claimed in claim 1, comprising the steps of:

step 1, determining grating parameters:

the grating equation is:

d(sinα+sinβ)＝mλ (1)

in the formula, m is diffraction order, lambda is wavelength, d is grating constant, alpha is reflection grating incident angle, beta is diffraction angle, the same sign of alpha and beta represents that the incident angle and the diffraction angle are on the same side of the grating normal, and different signs represent that the incident angle and the diffraction angle are on two sides of the grating normal respectively; the spectrometer resolution expression is as follows:

where Δ β is the angle at which the two wavelengths λ and λ + Δ λ are separated by diffraction. Then the focal length fs of the imaging system corresponding to the separation distance s between λ and λ + Δ λ on the spectrometer detector is:

fs＝s/Δβ (3)

the focal length fc of the collimating system before the grating is:

fc＝fs/M (4)

wherein M is the magnification of the spectrometer system, which is determined by the size D of the target surface of the detector, the number N of optical fibers to be imaged on the detector and the arrangement interval L of the optical fibers, and the expression is as follows:

M＝D/(N×L) (5)

the size of the grating used in the spectrometer is related to the focal ratio Fin of the incident light, Lg is the length of the grating ruling direction, and Wg is the length of the grating dispersion direction:

Lg＝fc/Fin (6)

Wg＝Lg/cosα (7)

in the design of a spectrometer, the spatial arrangement direction of an integrated Field of view Unit (IFU) exit end optical fiber array and the dispersion direction of each optical fiber are vertical on a detector; the overall resolving power of the spectrometer is determined by a number of factors, including: resolution of the grating, width of the slit, size of the detector and size of the diffuse spot; in order to realize the spectral resolution index designed by the spectrometer, in the dispersion direction, the separation distance s between two wavelengths of lambda and lambda + delta lambda on the detector is at least more than or equal to the size of the imaging of one optical fiber on the detector along the dispersion direction; formula (5) is the magnification of the spectrometer in the fiber space direction; the expression of the magnification M' of the spectrometer in the dispersion direction is as follows:

M'＝M cosα/cosβ (8)

the size O' of the image of the core diameter of each fiber on the detector along the dispersion direction is:

O'＝M'×O (9)

wherein O is the diameter of the optical fiber core; the spectral design is to satisfy the following relations:

in the formula, eta is the size of a single pixel of the detector;

calculating and analyzing spectrometer design parameters according to formulas (1) to (10) based on detector parameters, slit length and spectrometer resolution capability requirements, and selecting and determining grating parameter size, reticle density and blaze wavelength in a spectrometer;

step 2, determining the number of the slits in the slit module (1)

The number of slits of the multi-slit integral field-of-view spectrometer is related to many parameters, such as the size of a target surface of a detector, the spectral resolution, the bandwidth of an observation waveband and the like; each sub-slit is subjected to chromatic dispersion by a spectrometer system and then imaged on a target surface of a detector, and the size Nsi occupied along the chromatic dispersion direction is as follows:

Nsi＝s·(τ₀+τ₁+τ₂)/Δλ (11)

in the formula tau₀、τ₁、τ₂Respectively representing the central observation waveband width of the narrow-band filter and the waveband widths corresponding to the rising edge and the falling edge of the narrow-band filter; on the detector, the spectrums dispersed by the plurality of slits cannot be overlapped, and the number Ns of the slits at the incident end that can be accommodated on the detector is:

ns is less than or equal to an integer (D/(Nsi + delta D)) (12)

In the formula, delta d is the size of a dark space between two adjacent slits which are subjected to dispersion and imaged on a detector along the dispersion direction;

as is clear from equations (11) and (12), τ is the narrow band filter₀、τ₁、τ₂The smaller the size, the larger the number of slits observed at one time, so that it is necessary to ensure τ as much as possible when customizing the filter₁、τ₂Small, namely the rising edge and the falling edge of the transmittance of the narrow-band filter changing along with the wavelength are steep;

step 3, adopting a refraction type optical design: due to the design of the multi-slit integral field spectrometer, the size of the object plane of the spectrometer formed by the multi-slit integral field spectrometer is too large, and the two-dimensional large field design is difficult to realize by a reflection type structure under the condition of no shielding; for the design of a 7-slit integrated field spectrometer, the size of an object plane reaches 60mm multiplied by 150mm, and the requirement is provided for the glass material of optical design, because the size of a lens blank of a common optical material is 160mm in caliber; but considering that the observation wave band range is not large, the glass materials used in the optical design are all selected from a Chengdu Guangming glass library;

and 4, considering that the use of the integral view field unit is required to realize the spectral imaging of the observed object, the image needs to be reconstructed, so that the light energy loss of each optical fiber needs to be consistent, the spectrometer system adopts an object space telecentric optical path design in the design, and the grating is arranged at the exit pupil of the collimation system.

Background

In recent years, with the rapid development of astronomy technology, many astronomical telescopes in China and internationally use IFU to replace a slit in a general spectrometer to link a telescope and a spectrometer system to form an optical fiber imaging spectrometer. The traditional spectrometer observation is to obtain spectral information, and to obtain two-dimensional spatial information, a slit is required to perform spatial scanning to obtain the two-dimensional information, and the method has the defect of low time resolution. The IFU is composed of a micro-lens array end and a pseudo-slit end, the micro-lens array end divides a two-dimensional space image, then the pseudo-slit formed by the rearrangement of the output end is arranged at the incident end of the spectrometer for dispersion through optical fiber transmission, and therefore two-dimensional space information and one-dimensional spectrum information can be obtained simultaneously, and the possibility is provided for observation with high time resolution. However, the number of optical fibers needed for observing by using the integral view field unit is large to obtain large two-dimensional view field information, so that the development of the integral view field spectrometer with high sampling efficiency is an important guarantee for guaranteeing high-time resolution ratio spectral imaging observation. For example, for a large-scale coronal mass spectrometer in China in the future, a single IFU comprises more than ten thousand spatial sampling points, and twenty or more than ten thousand optical fibers are needed due to the adoption of paired IFU technology, so that the great number of optical fibers provides an urgent need for an integral field-of-view spectrometer with high sampling efficiency.

At present, there is no high-sampling-efficiency integrated field-of-view spectrometer (or high-sampling-efficiency fiber spectrometer) capable of simultaneously performing spectral dispersion on thousands of optical fibers.

Disclosure of Invention

The invention discloses an optical system of an integral field spectrometer with high sampling efficiency and a design method thereof, aiming at the requirement of the integral field spectrometer with high sampling efficiency. The method disclosed by the invention is used for developing a high-sampling-efficiency integral field spectrometer capable of accommodating 7000 optical fibers for simultaneous dispersion, and the method is also used for the high-sampling-efficiency integral field spectrometer of a large-scale coronagraph terminal in China in the future.

In order to solve the technical problem, the invention discloses an optical system of an integrating field-of-view spectrometer with high sampling efficiency, which comprises a slit module, a narrow-band filter module, a collimation module and a dispersion module which are sequentially arranged along the transmission direction of an optical path; the angle between the normal of the collimation module and the normal of the dispersion module is equal to the incident angle of the dispersion module in use, the angle between the normal of the dispersion module and the normal of the imaging module is equal to the diffraction angle of the dispersion module in dispersion use, and the imaging module and the reflection detector module are linearly arranged.

Optionally, the slit module includes a plurality of slit units arranged in parallel, each slit unit includes a first slit mechanism and a second slit mechanism, a 30mm interval is provided between the first slit mechanism and the second slit mechanism, and each of the first slit mechanism and the second slit mechanism is composed of the same number of optical fibers.

Optionally, each of the first slit mechanism and the second slit mechanism comprises 500 optical fibers arranged at intervals of 120 μm, and the length of each of the first slit mechanism and the second slit mechanism is 60 mm; the first slit mechanism, the spacer and the second slit mechanism are collinear.

Optionally, the narrowband filter module is a narrowband filter.

Optionally, the collimating module includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens, which are sequentially disposed along the transmission direction of the light path; the materials of the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are sequentially H-ZK6, H-K9L, H-K3, H-F51, FCD100 and LAF 3.

Optionally, the dispersive module is a scribed reflective grating.

Optionally, the imaging module includes a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, and a twelfth lens, which are sequentially disposed along the diffraction direction of the optical path; the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens and the twelfth lens are made of H-LAK11, H-LAK11, ZF52, Fused silica, ZF52 and ZF52 in sequence.

Optionally, the reflection detector module includes a plane mirror and a detector, the detector includes a first detector and a second detector, and the plane mirror is disposed between the detector and the imaging module; the first detector and the twelfth lens are arranged in parallel, and an image of the first slit mechanism in the slit unit is emitted from the twelfth lens and then directly irradiated on the first detector to be imaged; the second detector is arranged below the plane reflector, the plane reflector is arranged between the second detector and the twelfth lens and forms a 45-degree angle with the second detector and the twelfth lens (5-6), and an image of a second slit mechanism in the slit unit is emitted from the twelfth lens, reflected by the plane reflector and then irradiated on the second detector to be imaged.

The invention also discloses a design method of the optical system of the high-sampling-efficiency integral field spectrometer, which comprises the following steps:

step 1, determining grating parameters:

the grating equation is:

d(sinα+sinβ)＝mλ (1)

in the formula, m is diffraction order, lambda is wavelength, d is grating constant, alpha is reflection grating incident angle, beta is diffraction angle, the same sign of alpha and beta represents that the incident angle and the diffraction angle are on the same side of the grating normal, and different signs represent that the incident angle and the diffraction angle are respectively on two sides of the grating normal; the spectrometer resolution expression is as follows:

where Δ β is the angle at which the two wavelengths λ and λ + Δ λ are separated by diffraction. Then the focal length fs of the imaging system corresponding to the separation distance s between λ and λ + Δ λ on the spectrometer detector is:

fs＝s/Δβ (3)

the focal length fc of the collimating system before the grating is:

fc＝fs/M (4)

wherein M is the magnification of the spectrometer system, which is determined by the size D of the target surface of the detector, the number N of optical fibers to be imaged on the detector and the arrangement interval L of the optical fibers, and the expression is as follows:

M＝D/(N×L) (5)

the size of the grating used in the spectrometer is related to the focal ratio Fin of incident light, Lg is the length of the grating ruling direction, and Wg is the length of the grating dispersion direction:

Lg＝fc/Fin (6)

Wg＝Lg/cosα (7)

in the design of a spectrometer, the spatial arrangement direction of an integrated Field of view Unit (IFU) exit end optical fiber array and the dispersion direction of each optical fiber are vertical on a detector; the overall resolving power of the spectrometer is determined by a number of factors, including: resolution of the grating, width of the slit, size of the detector and size of the diffuse spot; in order to realize the spectral resolution index of the spectrometer design, in the dispersion direction, the separation distance s between two wavelengths of lambda and lambda + delta lambda on the detector is at least more than or equal to the size of the imaging of one optical fiber on the detector along the dispersion direction; formula (5) is the magnification of the spectrometer in the fiber space direction; the expression of the magnification M' of the spectrometer in the dispersion direction is as follows:

M'＝Mcosα/cosβ (8)

the size O' of the image of the core diameter of each fiber on the detector along the dispersion direction is:

O'＝M'×O (9)

wherein O is the diameter of the optical fiber core; the spectral design is to satisfy the following relations:

in the formula, eta is the size of a single pixel of the detector;

calculating and analyzing spectrometer design parameters according to formulas (1) to (10) based on detector parameters, slit length and spectrometer resolution capability requirements, and selecting and determining grating parameter size, linear density and blazed wavelength in a spectrometer;

step 2, determining the number of slits in the slit module 1

The number of slits of the multi-slit integrated field-of-view spectrometer is related to many parameters, such as the size of the target surface of the detector, the spectral resolution, the observation wave band and other factors; each sub-slit is subjected to dispersion by a spectrometer system and then imaged on a detector target surface, and the size Nsi occupied along the dispersion direction is as follows:

Nsi＝s·(τ₀+τ₁+τ₂)/Δλ (11)

in the formula tau₀、τ₁、τ₂Respectively representing the central observation waveband width of the narrow-band filter and the waveband widths corresponding to the rising edge and the falling edge of the narrow-band filter; on the detector, the spectrums dispersed by the plurality of slits cannot be overlapped, and the number Ns of the slits at the incident end that can be accommodated on the detector is:

ns is less than or equal to an integer (D/(Nsi + delta D)) (12)

In the formula, delta d is the size of a dark space between two adjacent slits which are subjected to dispersion and imaged on a detector along the dispersion direction;

as is clear from equations (11) and (12), τ is the narrow band filter₀、τ₁、τ₂The smaller the size, the larger the number of slits observed at one time, so that it is necessary to ensure τ as much as possible when customizing the filter₁、τ₂Small, namely the rising edge and the falling edge of the transmittance of the narrow-band filter changing along with the wavelength are steep;

step 3, adopting a refraction type optical design: due to the design of the multi-slit integral field spectrometer, the size of the object plane of the spectrometer formed by the multi-slit integral field spectrometer is too large, and the two-dimensional large field design is difficult to realize by a reflection type structure under the condition of no shielding; for the design of a 7-slit integrated field spectrometer, the size of an object plane reaches 60mm multiplied by 150mm, and the requirement is provided for the glass material of optical design, because the size of a lens blank of a common optical material is 160mm in caliber; but considering that the observation wave band range is not large, the glass materials used in the optical design are all selected from Chengdu Guangming glass libraries;

and 4, considering that the use of the integral view field unit is required to realize the spectral imaging of the observed object, the image needs to be reconstructed, so that the light energy loss of each optical fiber needs to be consistent, the spectrometer system adopts an object-side telecentric optical path design in the design, and the grating is arranged at the exit pupil of the collimation system.

Compared with the prior art, the invention can obtain the following technical effects:

1) the high-sampling-efficiency integral field-of-view spectrometer provided by the invention can obviously reduce the number of observation telescope terminal spectrometers using IFU equipment, or improve the observation field size (namely the number of optical fibers) under the condition that the number of the spectrometers is certain.

2) The invention adopts the core technical scheme of combining a multi-slit unit and two slits, realizes high sampling efficiency spectrum observation by matching a band-pass filter and a front reflector of a detector, realizes that an integral view field spectrometer can simultaneously obtain two-dimensional space information and one-dimensional spectrum information of a larger view field, and further realizes the purpose of measuring the spectral information of an object (for example: sun) high time resolution observation.

3) For telescope equipment which needs a large number of optical fibers for observation at the same time, such as a large-scale coronagraph in China in the future, the high-sampling-efficiency integral field spectrometer can obviously reduce the number of terminal spectrometers of the observation telescope and the volume of the terminal equipment.

Of course, it is not necessary for any one product to practice the invention to achieve all of the above-described technical results simultaneously.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention without limiting the invention to the best mode contemplated. In the drawings:

FIG. 1 is a schematic structural diagram of an optical system of a high sampling efficiency integrating field-of-view spectrometer according to the present invention;

FIG. 2 is an enlarged view of A of FIG. 1 in accordance with the present invention;

FIG. 3 is a schematic structural diagram of a slot module of the present invention;

FIG. 4 is an enlarged view of B of FIG. 1 in accordance with the present invention;

FIG. 5 is a chart of an image particle column at a wavelength of 519.85nm on a detector of an optical system of a high sampling efficiency integrated field of view spectrometer provided by the present invention; wherein, the black circle represents the Airy spot size;

FIG. 6 is a chart of an image particle column at a wavelength of 525.15nm on a detector of an optical system of a high sampling efficiency integrated field of view spectrometer provided by the present invention; wherein, the black circle represents the Airy spot size;

FIG. 7 is a chart of an image particle column at a wavelength of 530.45nm on a detector of an optical system of a high sampling efficiency integrated field of view spectrometer provided by the present invention; wherein, the black circle represents the Airy spot size;

fig. 8 is a spectrum resolution present pilot diagram of the optical system of the high sampling efficiency integrated field-of-view spectrometer provided by the present invention (satisfying R5800 @530 nm).

Detailed Description

The following embodiments are described in detail with reference to the accompanying drawings, so that how to implement the present invention by applying technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented.

The invention provides an optical system of an integral field-of-view spectrometer with high sampling efficiency, which is a technical scheme combining a plurality of slits and two sections of slits, and is matched with a band-pass filter and a front reflector of a detector at the same time to improve the sampling efficiency of the spectrometer from two dimensions of the dispersion direction and the space direction of the spectrometer, as shown in figure 1, the optical system comprises a slit module 1, a narrow-band filter module 2, a collimation module 3 and a dispersion module 4 which are arranged in sequence along the transmission direction of an optical path; the angle between the normal of the collimating module 3 and the normal of the dispersive module 4 is equal to the corresponding incident angle (α in equation (1)) of the grating in the dispersive module 4 when in use; the angle between the normal of the dispersion module 4 and the normal of the imaging module 5 is equal to the diffraction angle (beta in formula (1)) corresponding to the grating in the dispersion module 4 in use, and the imaging module 5 and the reflection detector module 6 are arranged in a straight line.

The slit module 1 comprises a plurality of slit units 1-1 which are arranged in parallel, each slit unit 1-1 comprises a first slit mechanism 1-2 and a second slit mechanism 1-3, a 30mm interval 1-4 is arranged between the first slit mechanism 1-2 and the second slit mechanism 1-3, and each first slit mechanism 1-2 and each second slit mechanism 1-3 are composed of optical fibers 1-5 with the same number.

The slit module 1 adopts a technical scheme of combining a plurality of slits and two slits, a plurality of slit units are arranged in parallel at intervals, and each single slit is divided into two sub-slits (a first slit mechanism 1-2 and a second slit mechanism 1-3) with the interval of 30mm to realize the improvement of the sampling efficiency of the spectrometer from two dimensions of the dispersion direction and the space direction of the spectrometer.

The narrow-band filter module 2 is a narrow-band filter, the rising edge and the falling edge of the transmittance of the narrow-band filter changing along with the wavelength are as steep as possible, and the narrow-band filter is arranged between the slit module 1 and the collimation module 3.

All the slits pass through the same narrow-band filter, so that the spectrums dispersed by the slits are prevented from being overlapped on the detector, and the validity of spectrum data is guaranteed.

The collimation module 3 comprises a first lens 3-1, a second lens 3-2, a third lens 3-3, a fourth lens 3-4, a fifth lens 3-5 and a sixth lens 3-6 which are sequentially arranged along the spectrum transmission direction; the materials of the first lens 3-1, the second lens 3-2, the third lens 3-3, the fourth lens 3-4, the fifth lens 3-5 and the sixth lens 3-6 sequentially adopt H-ZK6, H-K9L, H-K3, H-F51, FCD100 and LAF 3; the collimating module 3 is placed behind the narrowband filter module 2.

A collimation module: the light emitted by all the slit sections is collimated into parallel light by the same collimation system and then irradiates on the same reflection grating.

The dispersion module 4 is a reflective grating, the light beam incident from the slit module 1 is collimated by the collimation module 3 and then irradiates the reflective grating in the dispersion module 4 for dispersion, and the light beam diffracted by the grating enters the imaging module 5.

The imaging module 5 comprises a seventh lens 5-1, an eighth lens 5-2, a ninth lens 5-3, a tenth lens 5-4, an eleventh lens 5-5 and a twelfth lens 5-6 which are sequentially arranged along the diffraction direction of the light path; the seventh lens 5-1, the eighth lens 5-2, the ninth lens 5-3, the tenth lens 5-4, the eleventh lens 5-5 and the twelfth lens 5-6 are made of H-LAK11, H-LAK11, ZF52, Fused silica, ZF52 and ZF52 in sequence; the imaging system module 5 is positioned in the light path of the exit direction of the diffracted light of the dispersion module 4, and converges and images the diffracted light on the detector in the reflective detector module 6.

The reflection detector module 6 comprises a plane reflector 6-1 and a detector, the detector comprises a first detector 6-2 and a second detector 6-3, and the plane reflector 6-1 is arranged between the detector and the imaging module 5; the first detector 6-2 and the twelfth lens 5-6 are arranged in parallel, and an image of the first slit mechanism 1-2 in the slit unit 1-1 is emitted from the twelfth lens 5-6 and then directly irradiated and imaged on the first detector 6-2; the second detector 6-3 is arranged below the plane reflector 6-1, the plane reflector 6-1 is arranged between the second detector 6-3 and the twelfth lens 5-6 and forms a 45-degree angle with the second detector 6-3 and the twelfth lens 5-6, and an image of the second slit mechanism 1-3 in the slit unit 1-1 is emitted from the twelfth lens 5-6, reflected by the plane reflector 6-1 and then irradiated to be imaged on the second detector 6-3.

Wherein the reflective detector module: a plane mirror 6-1 is used to separately image the sub-slits (the first slit mechanism 1-2 and the second slit mechanism 1-3) divided into two sections on the first detector 6-2 and the second detector 6-3.

The slit module 1 of the optical system adopts a plurality of slit units 1-1 arranged side by side to be combined with the narrow-band optical filter 2 for use, so that the spectrum dispersed by each slit is not overlapped on the detector, the plane mirror 6-1 arranged in front of the final end detector separately images the diffraction imaging light of two sections of slits (the first slit mechanism 1-2 and the second slit mechanism 1-3) on the first detector 6-2 and the second detector 6-3, and the sampling efficiency of the spectrometer is improved from two dimensions of the dispersion direction and the space direction of the spectrometer. Slits of all incident ends in the spectrograph are collimated by the same set of collimating system 3, then the slits irradiate on the reflection grating 4 to be diffracted, and diffracted light beams are imaged by the same set of imaging system 5. It should be noted that, because the front slit adopts a scheme of combining a multi-slit and two-segment slits, the grating in the scheme cannot work under the Littrow condition, that is, incident light and diffracted light of the grating cannot share one set of optical system, and a double-pass structure cannot be adopted.

The invention also discloses a design method of the optical system of the high-sampling-efficiency integral field spectrometer, which comprises the following steps:

step 1, an incident end (slit module 1) of a spectrometer adopts a technical scheme of combining a plurality of slit units 1-1 and two sections of slit first slit mechanisms 1-2 and two sections of slit second slit mechanisms 1-3, the plurality of slit units 1-1 are arranged in parallel at intervals along a dispersion direction of the spectrometer to improve sampling efficiency, and each slit unit 1-1 is divided into a first slit mechanism 1-2 and a second slit mechanism 1-3 at intervals of 30mm along a spatial direction of the slit to improve sampling efficiency; the arrangement of the slits at the entrance end of the spectrometer is schematically shown in FIG. 3.

And 2, combining the slit module 1 with the narrow-band filter module 2 for use, wherein the front end of the spectrometer adopts a multi-slit design, and a proper narrow-band-pass filter needs to be matched, so that the spectrums dispersed by the slits are not overlapped on a detector, the validity of spectrum data is ensured, and the sampling efficiency of the spectrometer is improved from the dispersion direction of the spectrometer. The number of the slits of the spectrometer is related to the size of the target surface of the detector, the resolution power of the detector and the observation bandwidth, and the specific relations are shown in formulas (11) to (12).

And 3, dividing each slit into two sections (a first slit mechanism 1-2 and a second slit mechanism 1-3 in the graph 3) and combining with a front plane reflecting mirror 6-1 of the detector for use, so as to ensure that the spectrums dispersed by the two segmented slits enter two different detectors (a first detector 6-2 and a second detector 6-3) respectively. The incident light of all slits at the incident end of the whole spectrograph passes through the same set of narrow-band filter module 2, the collimation module 3, the dispersion module 4 and the imaging system 5, so that the function of two spectrometers by one spectrograph is realized in the real sense, and the number and the size of the spectrometers are greatly reduced; the sampling efficiency of the spectrometer is improved along the spatial direction of the spectrometer.

And 4, the scheme is suitable for adopting a refraction structure and is not suitable for utilizing a reflection structure, namely, optical elements of the collimation system and the imaging system adopt the optical design of a lens refraction structure. This is because the spectrometer adopts the core technology of combining multiple slits and two-section slits, because with this structure, the entrance end of the spectrometer is not a conventional single slit, or a plurality of slits are arranged in a line, but a two-dimensional object plane. If a reflection type structure is adopted, in order to avoid the shielding of light rays in a spectrometer system, an off-axis reflection structure is necessarily adopted, and the off-axis reflection structure is not favorable for imaging a large-size two-dimensional object plane, so that a collimation system and an imaging system adopt a refraction type structure in the aspect of design.

Example 1

The embodiment of the invention adopts the high-sampling-efficiency integral field spectrometer optical system, mainly aims at the solar coronagar observation wave band of 519.85nm-530.45nm, has abundant solar chromatophore and photosphere spectral lines in the wave band range, can realize the observation of the solar chromatophore and the chromatophore, is installed at the rear end of a FASOT-1B telescope of an astronomical observation station of Tailijiang astronomical of Yunnan of Chinese academy of sciences after being successfully developed, can improve the observation field of view of the existing telescope by nearly 30 times, and is used for deeply researching and understanding solar activities and solving the sun physical core problems of severe atmospheric activity mechanism, solar wind acceleration, coronage heating and the like. In addition, the optical system of the high-sampling-efficiency integrated field-of-view spectrometer is the first high-sampling-efficiency integrated field-of-view spectrometer model which is developed by the 1.2-meter global maximum refraction coronagraph in our country and meets the requirements in the future. The high-sampling-efficiency integral field spectrometer mainly aims at coronagary spectral lines to observe, and the spectral resolution power meets [email protected] in order to avoid too long exposure time considering that coronagary energy is weak; the observation wave band is: 519.85nm-530.45 nm.

The invention adopts a method of combining a plurality of slits and two sections of slits, and firstly selects a proper grating to finish the design of an optical system of a high-sampling-efficiency integral field-of-view spectrometer, wherein the grating is used as a core element of the spectrometer (namely the optical system of the high-sampling-efficiency integral field-of-view spectrometer, the same applies below). The grating equation is:

d(sinα+sinβ)＝mλ (1)

in the formula, m is diffraction order, lambda is wavelength, d is grating constant, alpha is reflection grating incident angle, beta is diffraction angle, the same sign of alpha and beta represents that the incident angle and the diffraction angle are on the same side of the grating normal line, and different signs represent that the incident angle and the diffraction angle are respectively on two sides of the grating normal line. The spectrometer resolution expression is as follows:

where Δ β is the angle at which the two wavelengths λ and λ + Δ λ are separated by diffraction. Then the focal length fs of the imaging system corresponding to the separation distance s between λ and λ + Δ λ on the spectrometer detector is:

fs＝s/Δβ (3)

the focal length fc of the collimating system before the grating is:

fc＝fs/M (4)

wherein M is the magnification of the spectrometer system, which is determined by the size D of the target surface of the detector, the number N of optical fibers to be imaged on the detector and the arrangement interval L of the optical fibers, and the expression is as follows:

M＝D/(N×L) (5)

the size of the grating used in the spectrometer is related to the focal ratio Fin of the incident light, Lg is the length of the grating ruling direction, and Wg is the length of the grating dispersion direction:

Lg＝fc/Fin (6)

Wg＝Lg/cosα (7)

in the design of the spectrometer, the spatial arrangement direction of the fiber array at the exit end of the IFU and the dispersion direction of each fiber are vertical on the detector. The overall resolving power of the spectrometer is determined by a number of factors, including: the resolving power of the grating, the width of the slit, the size of the detector and the size of the diffuse spot. In order to realize the spectral resolution index of the spectrometer design, in the dispersion direction, the separation distance s between the two wavelengths λ and λ + Δ λ on the detector is at least equal to or greater than the size of an optical fiber on the detector along the dispersion direction. Equation (5) is the magnification of the spectrometer in the fiber space direction. Due to the particularity of the grating, the magnification of the spectrometer in the dispersion direction of the optical fiber is different from the spatial direction of the optical fiber, and the magnification M' expression of the spectrometer in the dispersion direction is as follows:

M'＝Mcosα/cosβ (8)

the size O' of the image of the core diameter of each fiber on the detector along the dispersion direction is:

O'＝M'×O (9)

wherein O is the diameter of the optical fiber core. The four factors that affect the resolving power of the spectrometer mentioned above, the one with the lowest resolution, which is generally the square root of the sum of the squares of the four factors, are decisive. Because the resolving power of the grating is high, the resolving power of the spectrometer is not limited, so the spectrum design satisfies the following relation:

in the formula, η is the size of a single pixel of the detector. The most reasonable design is that these factors match each other, especially not because the detector affects the original resolving power.

For an optical system of the high-sampling-efficiency integrated field-of-view spectrometer, the detector selects the SCOMS camera with the largest target surface in China at present, the chip is 6144pixels multiplied by 6144pixels, the size of a single pixel is 10 mu m/pixel, and the size of the target surface of the detector is 61.44 mm. The total heights of the slits at the incident end 1-2, 1-3 and 1-4 are 150mm, wherein the lengths of 1-2 and 1-3 are respectively 60mm (corresponding to 500 optical fibers arranged at intervals of 120 μ M), the optical fibers are respectively imaged on two detectors, the system magnification M is 61.44/60 or 1.024 in the arrangement space direction of the optical fibers, a part of dark space is left around the target surface of the detector in consideration of spectral line bending, and the magnification M is 0.95. The two wavelengths λ and λ + Δ λ that satisfy the spectral resolution R5800 @530nm are separated by a distance s on the detector of the order of 37 μm, and the spectrometer system incident angle ratio Fin/5. Based on the detector parameters, the slit length, the spectrometer resolving power and other parameters, the commercial Richardson grating, model 53-260, is selected according to the design calculation and analysis formulas (1) - (10) of the spectrometer. Other optical system specific parameters are as follows: 1) collimation system focal length fc is 720mm, imaging system focal length fs is 685mm, 2) grating incident angle: α is 22 °, diffraction angle: β -3.245(530 nm). 3) The size of the grating: lg is 144mm, and Wg is 155 mm. 4) The magnification M' in the dispersion direction is 0.88.

Secondly, calculating the number of slits which can be accommodated by the spectrometer, wherein each sub-slit is subjected to dispersion by a spectrometer system and then imaged on a target surface of a detector, and the size Nsi occupied along the dispersion direction is as follows:

Nsi＝s·(τ₀+τ₁+τ₂)/Δλ (11)

in the formula tau₀、τ₁、τ₂Respectively representing the central observation waveband width of the narrow-band filter and the waveband widths corresponding to the rising edge and the falling edge of the narrow-band filter. On the detector, the spectrums dispersed by the plurality of slits cannot be overlapped, and the number Ns of the slits at the incident end that can be accommodated on the detector is:

ns is less than or equal to integer ((D + (tau)₁+τ₁)/Δλ)/(Nsi+Δd)) (12)

Wherein, deltad is the dimension of the dark space between the two adjacent slits which are subjected to dispersion and imaged on the detector along the dispersion direction.

As can be seen from the equations (11) and (12), τ is the narrow band filter₀、τ₁、τ₂The smaller the number of slits observable at one time, the greater the number of slits observable at one time, so that it is necessary to ensure τ as much as possible when customizing the filter₁、τ₂Small, i.e. steep, rising and falling edges of the transmittance of the narrowband filter as a function of wavelength. At present, the transmittance of the domestic optical filter at the rising edge and the falling edge reaches 10^－5Tmax, corresponding to τ₁And τ₂Is 5 nm. Observation band τ₀The wavelength is 10.6nm, 20pixels on a detector are taken as delta d, Ns is less than or equal to 7.3 through formulas (11) to (12), and the integer Ns is 7. Therefore, the optical system of the high-sampling-efficiency integrated field-of-view spectrometer has 7 slits, each slit is divided into two sections, and the optical fibers can be accommodated in the optical system, wherein the number of the optical fibers is 7 multiplied by 500 multiplied by 2 to 7000 optical fibers.

The observation requirement in the later stage of the optical system of the high-sampling-efficiency integral field-of-view spectrometer is considered, the high-sampling-efficiency integral field-of-view spectrometer can be matched with different telescopes for observation, the spectrometer is required to be conveniently moved, the structure is compact, and the size is not large easily. In addition, the size of the object plane of the spectrometer composed of 7 slits is too large, and the reflecting structure is difficult to realize the 4.8 degree multiplied by 11.8 degree large field design under the condition of no shielding. Based on the above two points, the optical design of the project adopts a refraction type optical design. Because the size of the object plane is 60mm multiplied by 150mm, the requirement of the glass material of optical design is provided, because the size of the lens blank of the general optical material is 160mm caliber. But the observation wave band range is not large, and the possibility of using a refraction type optical design is provided, and the glass materials used by the optical design are all selected from a glass library with great brightness. In addition, considering that the use of the integral view field unit is used to realize the spectral imaging of the observed object, an image needs to be reconstructed, which requires that the optical energy loss of each optical fiber is consistent, in the design, the spectrometer system adopts an object space telecentric optical path design, and the grating is arranged at the exit pupil of the collimation system.

The design of the optical system of the high-sampling-efficiency integrated field-of-view spectrometer of the embodiment of the invention is shown in figure 1. In fig. 1, the slit 1 is a pseudo slit (as shown in fig. 3) composed of 7000 optical fibers arranged at an interval of 120 μm, and the slit employs 7 slit units, each slit unit is divided into two segments, two sub-slits (the first slit mechanism 1-2 and the second slit mechanism 1-3) are spaced by 30mm, and can accommodate 7000 optical fibers altogether. Light incident from 7 slits in the slit module 1 passes through the band-pass filter 2, is collimated by the collimating module 3 composed of 6 large lenses, and then irradiates the dispersion module 4 for dispersion, and a spectrum after dispersion is imaged on a detector in the reflection detector module 6 by the imaging module 5 composed of 6 large lenses. At the distance of 150mm from the front end of the reflection detector module 6, a reflecting mirror 6-1 is placed, and the diffracted imaging light of the sub-slit with the incident end divided into two sections is separately imaged on two different detectors 6-2 and 6-3. The effect that one spectrometer works as two spectrometers is achieved.

FIGS. 5-7 are diagrams of image particle columns on the detector of the high sampling efficiency integrated field of view spectrometer optical system, showing the spot columns of the 1 st, 4 th and 7 th slits in slit 1 at the wavelengths of 519.85nm, 525.15nm and 530.45nm, where only the image quality map on one detector is shown, the other is consistent with it. The black circle in the diagram shows the size of Airy spot under the diffraction limit condition, the point sequence diagram designed by the optical system of the spectrometer is basically within the Airy spot, the imaging is close to the diffraction limit, and the image quality of the optical system is good.

With respect to the system resolution of [email protected], that is, after a light beam emitted from an optical fiber at any position of a slit is subjected to grating dispersion, an optical fiber image with a wavelength of 530nm (λ) is distinguishable from an optical fiber image with a wavelength of 530.091379nm (λ + d λ) at a detector, wherein the optical fiber image is a single-wavelength optical fiber with a wavelength of 530+ 530/5800. FIG. 8 is a diagram showing the resolving power of the spectrometer, wherein each cell corresponds to 10 μm, and three wavelengths of 530nm (λ), 530.091379nm (λ + d λ) and 529.908621nm (λ -d λ) emitted from a point on the slit are separated at 36 μm intervals on the detector. The size of the imaging point diffuse spot diameter (RMS value) is 4.5 μm at most, the size of the ideal imaging (point object imaging point imaging) of the fiber core diameter of 35 μm on the detector along the dispersion direction is 30 μm, so the size of the lambda wavelength (530nm) corresponding to the fiber core diameter of 35 μm on the detector (along the dispersion direction) is(the distance separating λ from λ + d λ on the detector). Therefore, the three wavelengths of 530nm, 530.091379nm and 529.908621nm emitted by the same optical fiber can be separated on the detector, and the design requirement of the field of resolution of R5800 @530nm is met.

The embodiment can accommodate the optical system of the high-sampling-efficiency integral field-of-view spectrometer which is capable of simultaneously sampling 7000 optical fibers arranged at intervals of 120 mu m, the optical system of the high-sampling-efficiency integral field-of-view spectrometer is already put into engineering processing, and meanwhile, the developed high-sampling-efficiency integral field-of-view spectrometer can solve the core technology of a future 1.2 m global maximum refraction type coronagraph and provide technical support for the high-sampling-efficiency spectrometer required by the terminal of the high-sampling-efficiency integral field-of-view spectrometer.

While the foregoing description shows and describes several preferred embodiments of the invention, it is to be understood, as noted above, that the invention is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the inventive concept as expressed herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.