Offner-type light-splitting dual-band differential interference wind measurement system

Abstract

An Offner-type light-splitting dual-band differential interference wind measurement system relates to the technical field of optical systems of interferometers, and aims to solve the problems of complex structure and redundant elements of a conventional dual-band detection instrument. The system comprises a spectroscope, a front imaging lens group, an interference unit, an Offner-type imaging unit and a collimation light source; the gas glow enters the interference unit through the spectroscope and the front imaging lens group to form interference fringes, and the interference fringes are imaged through the Offner type imaging unit; when the system is calibrated, light emitted by the calibration light source is collimated by the collimating mirror and then enters the spectroscope and the front imaging lens group to enter the interference unit to form interference fringes, and the interference fringes are imaged by the Offner type imaging unit. The dual-band detection mode of the invention is realized by a convex grating in the Offner type imaging unit. The convex grating has an imaging function and a light splitting function. The surface type of the convex grating is a spherical surface, and the convex grating can be used as a spherical reflector in the Offner type imaging unit to correct aberration, can be used as a diffraction element to split light, and plays a role in stripping light in two wave bands of 557.7 nm and 630 nm.

Description

Technical Field

[0001] The invention relates to the technical field of optical systems of interferometers, and in particular to an Offner-type light-splitting dual-band differential interferometry wind measurement system. Background Art

[0002] Atmospheric wind field is an important parameter that characterizes the dynamic characteristics of the entire Earth's atmospheric system. It is also essential basic data for business work and scientific research in the fields of meteorological forecasting, space weather, climatology, etc. Passive optical remote sensing is one of the main technical means in the field of atmospheric wind field measurement.

[0003] The atmospheric light source radiation of the oxygen atom green line in the 557.7nm band and the oxygen atom red line in the 630nm band in the target area passes through the Doppler differential interferometer system, and the interference fringes formed are imaged on the detector. The spectral line Doppler frequency shift is obtained based on the phase information of the interference pattern, and finally the atmospheric wind field information is obtained.

[0004] See "Space Sci Rev.", Harlander et al. published a paper titled "Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI): Monolithic Interferometer Design and Test". The system uses transmissive dual-band detection imaging, achieves high-quality imaging by stacking lenses, and uses a dichroic mirror to achieve beam splitting. Due to the use of transmissive imaging, in order to meet the requirements of long-distance edge detection, the optical path is long and the volume is large. The dichroic mirror introduces additional aberrations and occupies additional volume in the imaging optical path. Using a dichroic mirror to split the light to achieve dual-band imaging increases the number of optical devices in the system and makes the structure complex. Summary of the invention

[0005] The invention aims to solve the problem of complex structure and redundant components of current dual-band detection instruments, and provides an Offner type spectroscopic dual-band differential interferometry wind measurement system.

[0006] The technical solution of the present invention is as follows:

[0007] An Offner-type spectroscopic dual-band differential interferometry wind measurement system, the system comprising a spectroscope, a front imaging lens group, an interference unit, an Offner-type imaging unit and a collimated light source;

[0008] The gas glow enters the interference unit through the beam splitter and the front imaging mirror group to form interference fringes and is imaged by the Offner type imaging unit;

[0009] The front surface of the beam splitter is coated with an anti-reflection film, and the rear surface is coated with an anti-reflection film;

[0010] The front imaging mirror group includes a front mirror group 1, a field diaphragm located at the primary image plane, and a front mirror group 2; the air glow light is incident on the front mirror group 1 through a beam splitter, enters the front mirror group 2 through the field diaphragm, and the air glow light is incident on the interference unit through the front mirror group 2;

[0011] The interference unit includes a beam splitter prism, a first field-of-view expanding prism, a second field-of-view expanding prism, a first echelle grating and a second echelle grating;

[0012] The light output by the front imaging lens group enters the beam splitter prism, and the beam splitter prism forms the first light beam by transmission and forms the second light beam by reflection.

[0013] The first light beam passes through the first field-expanding prism and reaches the first echelle grating to be diffracted and reflected. After being diffracted by the first echelle grating, the first light beam passes through the first field-expanding prism and enters the beam splitter prism again, and is reflected by the beam splitter prism.

[0014] The second light beam passes through the second field-expanding prism and reaches the second echelle grating to be diffracted and reflected. After being diffracted by the second echelle grating, the second light beam passes through the second field-expanding prism and enters the beam splitter prism again, and is transmitted through the beam splitter prism.

[0015] The first light beam reflected by the beam splitter prism and the second light beam transmitted by the beam splitter prism are superimposed and interfered before entering the Offner type imaging unit; the two light beams enter the Offner type imaging unit after superimposed and interfered; the interference fringe image is analyzed to obtain the wind speed information of the area corresponding to the airglow;

[0016] The collimated light source comprises a calibration light source and a collimating mirror;

[0017] When the system is calibrated, the light emitted by the calibration light source is collimated by the collimator and then incident on the beam splitter and the front imaging lens group to enter the interference unit to form interference fringes and is imaged by the Offner type imaging unit.

[0018] Beneficial effects of the present invention:

[0019] 1. The dual-band detection mode of the present invention is realized by the convex grating in the Offner type imaging unit. Compared with the dual-band detection using filters and dichroic mirrors, the convex grating in the present invention has imaging and spectroscopic functions. The convex grating has a spherical surface, which can correct aberrations as a spherical reflector in the Offner type imaging unit, and can be used for spectroscopic separation as a diffraction element, playing a role in stripping the two bands of 557.7nm and 630nm.

[0020] 2. The present invention uses an Offner imaging reflective mirror group to realize interferometer back-end imaging. Compared with the transmission imaging solution, the Offner imaging unit achieves the function of the transmission optical path with fewer components and has a simple structure under the same imaging conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure of an Offner-type dual-band wind field detection Doppler differential interferometry system of the present invention;

[0022] Figure 2 This is an interference fringe pattern formed on the detector in an embodiment of the present invention.

[0023] Wherein: 1-beam splitter; 2-front imaging mirror group, 21-front mirror group 1, 22-field diaphragm, 23-front mirror group 2; 3-interference unit, 31-beam splitter prism, 32-first field expansion prism, 33-second field expansion prism, 34-first middle step grating, 35-second middle step grating; 4-Offner type imaging unit, 41-Offner imaging mirror group, 411-primary mirror, 412-convex grating, 42-folding reflector, 43-detector; 431-first interference fringe pattern, 432-second interference fringe pattern; 5-collimated light source, 50-calibration light source, 51-collimating mirror. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0025] like Figure 1 As shown, an Offner-type spectroscopic dual-band differential interferometry wind measurement system includes a spectroscope 1, a front imaging lens group 2, an interference unit 3, an Offner-type imaging unit 4 and a collimated light source 5.

[0026] The gas glow light enters the interference unit 3 through the beam splitter 1 and the front imaging lens group 2 to form interference fringes and is imaged by the Offner type imaging unit 4;

[0027] The front surface of the beam splitter 1 is coated with an anti-reflection film, and the rear surface is coated with an anti-reflection film.

[0028] The front imaging lens group 2 includes a front lens group 1 21, a field stop 22 located at the primary image plane, and a front lens group 23. The air glow light is emitted to the front lens group 1 21 through the beam splitter 1, and enters the front lens group 23 through the field stop 22. The air glow light enters the interference unit 3 through the front lens group 23.

[0029] The interference unit 3 includes a beam splitter prism 31 , a first field-of-view expanding prism 32 , a second field-of-view expanding prism 33 , a first echelle grating 34 and a second echelle grating 35 .

[0030] The first echelle grating 34 and the second echelle grating 35 have the same specification parameters, and the number of grating lines is 64 lp / mm.

[0031] The light outputted by the front imaging lens group 2 enters the beam splitter prism 31 , and the beam splitter prism 31 forms the incident light into a first light beam by transmission, and forms the incident light into a second light beam by reflection.

[0032] The first light beam passes through the first field-of-view expansion prism 32 and reaches the first echelle grating 34 to be diffracted and reflected. After being diffracted by the first echelle grating 34 , the first light beam passes through the first field-of-view expansion prism 32 and enters the beam splitter prism 31 again, and is reflected by the beam splitter prism 31 .

[0033] The second light beam passes through the second field-expanding prism 33 and reaches the second echelle grating 35 to be diffracted and reflected. After being diffracted by the second echelle grating 35 , the second light beam passes through the second field-expanding prism 33 and enters the beam splitter prism 31 again, and is transmitted through the beam splitter prism 31 .

[0034] The first light beam reflected by the beam splitter prism 31 and the second light beam transmitted by the beam splitter prism 31 are superimposed and interfered before entering the Offner type imaging unit 4. After superimposed and interfered, the two light beams enter the Offner type imaging unit 4 for imaging, and the wind speed information of the area corresponding to the airglow is obtained by data analysis of the interference fringe image.

[0035] The Offner type imaging unit 4 includes an Offner imaging lens group 41 , a folding reflection mirror 42 and a detector 43 .

[0036] The Offner imaging lens assembly 41 includes a primary mirror 411 and a convex grating 412 .

[0037] The primary mirror 411 and the convex grating 412 satisfy the Rowland circle position relationship. The primary mirror 411 is a spherical mirror. The convex grating 412 has a spherical surface with a number of lines of 100 lp / mm. It serves as an imaging device and also has a spectroscopic function.

[0038] As a spherical reflector, the convex grating 412 has a curvature radius, which can play a role in high-quality imaging of airglow; as a diffraction device grating, it can use different diffraction orders to achieve the stripping of airglow in different bands.

[0039] The folding reflector 42 is located on the outgoing light path of the primary mirror 411, with an angle of 45° with the incident light, and is used to fold the light path to reduce the volume.

[0040] The outgoing light of the beam splitter prism 31 is reflected by the primary mirror 411 to the convex grating 412. The airglow light is diffracted and split at the convex grating 412 and reflected to the primary mirror 411, and then reaches the folding reflector 42 after being reflected by the primary mirror 411. After being reflected by the folding reflector 42, it enters the detector 43 and forms an image.

[0041] like Figure 2 The first interference fringe pattern 431 is an interference fringe pattern formed by a light signal with a wavelength of 557.7 nm on the detector 43 , and the second interference fringe pattern 432 is an interference fringe pattern formed by a light signal with a wavelength of 630 nm on the detector 43 .

[0042] The collimated light source 5 includes a calibration light source 50 and a collimating mirror 51 .

[0043] The collimated light source 5 is used for phase tracking. By calculating the phase information of the imaging of the calibration light source 50, the phase drift error caused by external factors can be removed, thereby achieving phase tracking.

[0044] The light emitted by the calibration light source 50 is collimated by the collimator 51 and reaches the beam splitter 1. After being reflected by the beam splitter 1, it enters the pre-imaging lens group 2 and then passes through the interference unit 3 and the Offner type imaging unit 4 in sequence to finally form an image.

[0045] The working process of an Offner type spectroscopic dual-band differential interferometry wind measurement system is as follows:

[0046] The airglow light is transmitted through the beam splitter 1 and enters the front imaging lens group 2. The light is converged to the field stop 22 through the front lens group 1 21, and then enters the interference unit 3 through the front lens group 23. The light is split by the beam splitter prism 31, and the two beams of light respectively pass through the first field expansion prism 32 and the second field expansion prism 33 to reach the first echelle grating 34 and the second echelle grating 35. The light passing through the first echelle grating 34 is diffracted and reflected along the original optical path to the beam splitter prism 31, and is reflected by the beam splitter prism 31 to enter the Offner type imaging unit 4. The light passing through the second echelle grating 35 is diffracted and reflected along the original optical path to the beam splitter prism 31, and is transmitted through the beam splitter prism 31 to enter the Offner type imaging unit 4. The two beams of light are combined and interfered before entering the Offner type imaging unit 4. The combined light is reflected by the mirror 411 to the convex grating 412, where it undergoes diffraction and splitting at two wavelengths of 557.7nm and 630nm and is reflected to the primary mirror 411. The light is reflected by the primary mirror 411 and passes through the folding reflector 42 to finally enter the detector 43 for imaging. The interference fringe image is analyzed for data to obtain wind speed information of the area corresponding to the airglow.

[0047] The emitted light of the calibration light source 50 of the collimated light source 5 is collimated by the collimator 51 and reaches the beam splitter 1, and is reflected by the beam splitter 1 and enters the front imaging lens group 2. The rest of the process is the same as the above-mentioned airglow.

Claims

1. An Offner type spectroscopic dual-band differential interferometry wind measurement system, characterized in that: The system comprises a beam splitter (1), a front imaging lens group (2), an interference unit (3), an Offner-type imaging unit (4) and a collimated light source (5); The gas glow light enters the interference unit (3) through the beam splitter (1) and the front imaging lens group (2) to form interference fringes and is imaged through the Offner type imaging unit (4); The front surface of the beam splitter (1) is coated with an anti-reflection film, and the rear surface is coated with an anti-reflection film; The front imaging lens group (2) comprises a front first lens group (21), a field diaphragm (22) located at a primary image plane, and a front second lens group (23); the gas glow light is incident on the front first lens group (21) via a beam splitter (1), enters the front second lens group (23) via the field diaphragm (22), and the gas glow light is incident on the interference unit (3) via the front second lens group (23); The interference unit (3) comprises a beam splitter prism (31), a first field-of-view expanding prism (32), a second field-of-view expanding prism (33), a first echelle grating (34) and a second echelle grating (35); The light output by the front imaging lens group (2) enters the beam splitter prism (31), and the beam splitter prism (31) forms a first light beam by transmission and forms a second light beam by reflection. The first light beam passes through the first field-expanding prism (32) and reaches the first echelle grating (34) to be diffracted and reflected. After being diffracted by the first echelle grating (34), the first light beam passes through the first field-expanding prism (32) and enters the beam splitting prism (31) again, and is reflected by the beam splitting prism (31). The second light beam passes through the second field-expanding prism (33) and reaches the second echelle grating (35) to be diffracted and reflected. After being diffracted by the second echelle grating (35), the second light beam passes through the second field-expanding prism (33) and enters the beam splitting prism (31) again, and is transmitted through the beam splitting prism (31). The first light beam reflected by the beam splitter prism (31) and the second light beam transmitted by the beam splitter prism (31) are superimposed and interfered before entering the Offner type imaging unit (4); the two light beams enter the Offner type imaging unit (4) for imaging after being superimposed and interfered; data analysis is performed on the interference fringe image to obtain wind speed information of the area to which the corresponding airglow belongs; The collimated light source (5) comprises a calibration light source (50) and a collimating mirror (51); When the system is calibrated, the light emitted by the calibration light source (50) is collimated by the collimator (51) and then incident on the beam splitter (1) and the front imaging lens group (2), enters the interference unit (3) to form interference fringes and is imaged by the Offner type imaging unit (4).

2. An Offner type spectroscopic dual-band differential interferometry wind measurement system, characterized in that: The first echelle grating (34) and the second echelle grating (35) have the same specification parameters, and the number of grating lines is 64 lp / mm.

3. An Offner type spectroscopic dual-band differential interferometry wind measurement system, characterized in that: The Offner type imaging unit (4) comprises an Offner imaging lens group (41), a folding reflector (42) and a detector (43); The Offner imaging mirror assembly (41) comprises a primary mirror (411) and a convex grating (412); The primary mirror (411) and the convex grating (412) satisfy the Rowland circle position relationship; the primary mirror (411) is a spherical mirror; the convex grating (412) has a spherical surface and a number of engraved lines of 100 lp / mm, and serves as an imaging device while also having a spectroscopic function; The folding reflector (42) is located on the outgoing light path of the primary mirror (411), with an angle of 45° with the incident light, and is used to fold the light path to reduce the volume; The outgoing light of the beam splitter prism (31) is reflected by the primary mirror (411) to the convex grating (412), the airglow light is diffracted and split at the convex grating (412) and reflected to the primary mirror (411), reaches the folding reflector (42) after being reflected by the primary mirror (411), and is incident on the detector (43) after being reflected by the folding reflector (42) to form an image.

4. An Offner type spectroscopic dual-band differential interferometry wind measurement system, characterized in that: The working process of the system is as follows: the gas glow light of two wavelength bands of 557.7 nm and 630 nm is transmitted through a beam splitter (1) into a front imaging lens group (2), the light is converged to a field stop (22) through a front first lens group (21), and then is incident into an interference unit (3) through a front second lens group (23), the light is split by a beam splitter prism (31), the two light beams respectively pass through a first field expansion prism (32) and a second field expansion prism (33) to reach a first echelle grating (34) and a second echelle grating (35), the light passing through the first echelle grating (34) is diffracted and reflected along the original optical path to the beam splitter prism (31), and is reflected by the beam splitter prism (31). The light beam is incident on an Offner type imaging unit (4); the light beam passing through the second middle step grating (35) is diffracted and reflected along the original light path to a beam splitting prism (31), and then transmitted through the beam splitting prism (31) to enter the Offner type imaging unit (4); the two light beams are combined and interfered before entering the Offner type imaging unit (4); the combined light beams are reflected through a mirror (411) to a convex grating (412); the light beams are diffracted and split into two wavelength bands of 557.7 nm and 630 nm at the convex grating (412), and then reflected to a primary mirror (411); the light beams are reflected through the primary mirror (411), pass through a folding reflector (42), and finally enter a detector (43) to form an image.

Images