Visible-terahertz low-frequency double-spectrum radiation synchronous measurement optical system

Abstract

The invention relates to the technical field of radiation measurement, in particular to a visible-terahertz low-frequency-band bispectral radiation synchronous measurement optical system, which comprises a main reflector which is a double-conical-surface reflector, is provided with different curvature radiuses and cone coefficients in the meridian direction and the sagittal direction, and is used for receiving wide-spectrum radiation; forming a primary light spot comprising a short wave band and a long wave band; the double-plane auxiliary reflecting mirror is used for carrying out amplitude separation on the light beams of the short-wave band and the long-wave band in the initial light spots according to the space direction; and the final reflecting mirror is also a double-conical-surface reflecting mirror and is used for carrying out refocusing and aberration correction on the short-wave-band light beam and the long-wave-band light beam respectively and guiding the light beams to different areas which are spatially isolated on the focal plane detector. According to the system and system disclosed by the embodiment of the invention, synchronous imaging of two wavebands in the same view field and area is realized, a space registration error is effectively avoided, and data space consistency and time synchronization of multiband radiation measurement are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of radiation measurement, and particularly relates to a dual-spectral-band radiation synchronous measurement optical system in the visible-terahertz low-frequency band. BACKGROUND

[0002] The wave band range of terahertz waves is 30-3000 micrometers (μm), and the 0.4-50 μm wave band radiation covers the range from visible light to the low-frequency band of terahertz waves, belongs to the key energy interval of solar radiation and earth thermal radiation, and the radiation in this wave band is an important observation wave band in the fields of climate monitoring, atmospheric research and land surface temperature inversion.

[0003] In the related art, independent optical systems and detectors are often used to measure the two wave bands of 0.4-5 μm and 5-50 μm, respectively, which leads to the difficulty in completely coinciding the fields of view, the asynchronization of observation time, the existence of spatial offset and registration error, and the influence on the data fusion and quantitative analysis effect. Therefore, how to realize the synchronous and same-field-of-view measurement of the dual-spectral-band in the visible-terahertz low-frequency band (i.e. 0.4-50 μm) to improve the time-space consistency and physical analysis precision of the radiation data has become a problem to be solved. SUMMARY

[0004] In view of this, the present disclosure provides a dual-spectral-band radiation synchronous measurement optical system in the visible-terahertz low-frequency band to solve the problem of how to realize the synchronous and same-field-of-view measurement of the dual-spectral-band in the visible-terahertz low-frequency band (i.e. 0.4-50 μm) to improve the time-space consistency and physical analysis precision of the radiation data.

[0005] The present disclosure provides a dual-spectral-band radiation synchronous measurement optical system in the visible-terahertz low-frequency band, which comprises a primary mirror, a double-plane secondary mirror, a final mirror and a focal plane detector, wherein: the primary mirror is a double-cone mirror, which is provided with different radii of curvature and conic coefficients in the meridional direction and the sagittal direction, respectively, is used to receive 0.4-50 μm wide-spectrum radiation in the same spatial field of view, and forms a preliminary imaging spot containing a 0.4-5 μm short wave band and a 5-50 μm long wave band; the double-plane secondary mirror is composed of a first plane secondary mirror and a second plane secondary mirror, is used to split the light beams in the short wave band and the long wave band in the preliminary imaging spot in the spatial direction, and keep the dual optical paths consistent; the final mirror is also a double-cone mirror, which is also provided with different radii of curvature and conic coefficients in the meridional direction and the sagittal direction, respectively, is used to refocus and correct the aberration of the light beams in the short wave band and the long wave band, respectively, and guide the light beams to different regions on the focal plane detector; and the focal plane detector is a microbolometer array, which is integrated with a wide-spectrum filter array composed of SILICA and KRS5 base materials at the front end, and is used to form a dual-spectrum non-aliasing image.

[0006] In a possible implementation, the curvature radius of the primary mirror in the meridional direction and the sagittal direction is 160 mm and 100 mm respectively, and the conic coefficients in the meridional direction and the sagittal direction are -1.3 and -0.9 respectively.

[0007] In a possible implementation, the first plane sub-mirror and the second plane sub-mirror in the double-plane sub-mirror are symmetrically arranged in the sagittal direction, and the angle between the mirror normal of the first plane sub-mirror and the mirror normal of the second plane sub-mirror is 10 degrees.

[0008] The first plane sub-mirror and the second plane sub-mirror are configured to direct the separated short-wave band light beam and the long-wave band light beam to the final mirror.

[0009] In a possible implementation, the curvature radius of the final mirror in the meridional direction and the sagittal direction is 130 mm and 80 mm respectively, and the conic coefficients in the meridional direction and the sagittal direction are -1.2 and -1.0 respectively.

[0010] In a possible implementation, the inclination angle of the primary mirror relative to the horizontal plane is 12 degrees, the inclination angle of the final mirror relative to the horizontal plane is 15 degrees, and the angle between the optical axis of the first plane sub-mirror and the optical axis of the second plane sub-mirror is 5 degrees.

[0011] In a possible implementation, the thickness of the SILICA and KRS5 substrate materials constituting the wide-spectrum filter array of the focal plane detector is 1 mm; and the wide-spectrum filter array is arranged 1 mm in front of the focal plane detector.

[0012] In a possible implementation, the spatial field of view range is 10 degrees x 10 degrees.

[0013] By using the above-mentioned embodiment of the present disclosure, the dual-spectrum synchronous radiation measurement optical system applicable to the 0.4-50 μm wave band is realized. By using the common optical path design and the amplitude splitting and imaging technology, the synchronous imaging of the two wave bands in the same field of view and observation area is realized, the spatial registration error caused by the optical axis deviation and the imaging time difference is effectively avoided, the data spatial consistency and time synchronization of the multi-wave band radiation measurement are significantly improved, and the accuracy and reliability of the subsequent radiation data fusion, quantitative inversion and physical modeling are improved.

[0014] In addition, by using the biconical mirror to construct the wide-spectrum optical path without transmission elements, the complex design of the cylindrical mirror or the multi-lens structure required for realizing the dual-focal-length imaging in the related art is avoided. By using the double-plane mirror to realize the amplitude splitting and imaging, and in combination with the focal plane filter array integrated in front of the detector, the visible-terahertz low-frequency band (i.e., 0.4-50 μm) ultra-wide wave band is efficiently covered. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the specific embodiments or the related art of the present disclosure, the accompanying drawings required to be used in the description of the specific embodiments or the related art will be briefly introduced. Obviously, the accompanying drawings in the following description are some embodiments of the present disclosure, and other drawings can also be obtained by those skilled in the art without any creative work on the premise of not paying any creative work.

[0016] Figure 1 is a structural schematic diagram of a visible-terahertz low-frequency dual-spectral-band radiation synchronous measurement optical system provided by an embodiment of the present disclosure;

[0017] Figure 2 is a focal plane detector receiving surface schematic diagram of a visible-terahertz low-frequency dual-spectral-band radiation synchronous measurement optical system provided by an embodiment of the present disclosure;

[0018] Figure 3 is an imaging principle diagram of a visible-terahertz low-frequency dual-spectral-band radiation synchronous measurement optical system provided by an embodiment of the present disclosure;

[0019] Figure 4 is a 0.4-5 μm wave band MTF curve diagram of a visible-terahertz low-frequency dual-spectral-band radiation synchronous measurement optical system provided by an embodiment of the present disclosure;

[0020] Figure 5 is a 5-50 μm wave band MTF curve diagram of a visible-terahertz low-frequency dual-spectral-band radiation synchronous measurement optical system provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0021] It is one of the key requirements in modern radiation detection technology to simultaneously realize 0.4-5 μm and 5-50 μm dual-spectral-band spectral sub-band radiation synchronous measurement in the range of 0.4-50 μm. Realizing high consistency measurement of dual-spectral-band in the same field of view and observation area is not only a basic requirement to improve the physical consistency and accuracy of data, but also can ensure the reliability of quantitative analysis of radiation energy.

[0022] The 0.4-5 μm wave band covers the visible light and near-infrared region, which is the most concentrated interval of solar radiation energy, accounting for more than 95% of the total solar radiation energy, so it plays an irreplaceable basic role in studying the energy balance of the earth, global climate change, and atmospheric radiation transmission. The 5-50 μm wave band covers the low-frequency range of the terahertz wave (here, the low-frequency range of the terahertz wave specifically refers to the range of 30-50 μm), which is the main wave band of thermal radiation of the earth and various low-temperature objects (such as clouds, ice and snow, vegetation, ground, and urban infrastructure), and plays a core role in the inversion of ground temperature, the observation of atmospheric window, and the analysis of infrared radiation balance.

[0023] However, the observed target physical properties of the two wave bands are different, the radiation mechanisms are different, and the spatial and temporal consistency of the measurement data is particularly important for subsequent physical modeling, parameter inversion and data fusion. If two wave bands are measured by independent systems or separate field of view, it inevitably introduces view angle difference, time mismatch, spatial offset and registration error, thereby significantly reducing the physical consistency and quantitative accuracy of radiation measurement. In particular, in the study of earth system science, multi-source radiation inversion and atmosphere-surface energy coupling, different wave band data of the same observation area must have strict field of view coincidence and synchronization in order to achieve high confidence physical quantity inversion and cross-wave band energy balance analysis. Therefore, the realization of double spectral band co-optical path, same field of view and synchronous radiation measurement in the 0.4-50 μm wave band can promote high-precision thermal infrared radiation calibration, earth system observation and energy closure analysis.

[0024] At present, the mainstream method in the related art is to observe 0.4-5 μm and 5-50 μm as two independent wave bands, and an independent optical system and a detector module need to be equipped respectively.

[0025] However, the method of "double system side-by-side arrangement" in the related art often has the following problems:

[0026] 1. The field of view is difficult to accurately coincide, resulting in spatial offset of the observation results of the same target area under two wave bands;

[0027] 2. The observation time of the two systems is often asynchronous, which is difficult to meet the demand of instantaneous synchronous measurement;

[0028] 3. Spatial registration error and imaging inconsistency seriously affect the physical consistency and quantitative analysis accuracy of subsequent radiation data;

[0029] 4. The traditional beam splitting element is difficult to efficiently cover the ultra-wide wave band of 0.4-50 μm, which is limited by factors such as material transmission range, manufacturing precision and energy loss, and it is difficult to realize efficient, low-loss wide spectral band beam splitting imaging.

[0030] To solve the above problems, the visible-terahertz low-frequency dual-band radiation synchronous measurement optical system is provided in various embodiments of the present disclosure, and the system comprises a main mirror, a double-plane sub-mirror, a final mirror and a focal plane detector, wherein: the main mirror is a double-cone mirror, which is provided with different radii of curvature and conic coefficients in the meridional direction and the sagittal direction respectively, is used for receiving 0.4-50-micron wide spectrum radiation in the same spatial field of view, and forms a preliminary imaging spot containing a 0.4-5-micron short-wave band and a 5-50-micron long-wave band; the double-plane sub-mirror is composed of a first plane sub-mirror and a second plane sub-mirror, is used for separating the light beams in the short-wave band and the long-wave band in the preliminary imaging spot in the spatial direction in amplitude, and keeping the double light paths consistent; the final mirror is also a double-cone mirror, which is also provided with different radii of curvature and conic coefficients in the meridional direction and the sagittal direction respectively, is used for respectively refocusing and aberration correcting the short-wave band light beam and the long-wave band light beam, and guiding the light beams to different regions on the focal plane detector which are spatially isolated; the focal plane detector is a microbolometer array, which is integrated at the front end with a wide spectrum filter array composed of SILICA and KRS5 base materials, and is used for forming a double-spectrum non-aliasing image.

[0031] To make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are some but not all of the embodiments of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present disclosure.

[0032] Please refer to Figure 1 , Figure 1 is a structural schematic diagram of the visible-terahertz low-frequency dual-band radiation synchronous measurement optical system provided by the embodiments of the present disclosure. The structure of the system can include:

[0033] The main mirror is a double-cone mirror, which is provided with different radii of curvature and conic coefficients in the meridional direction and the sagittal direction respectively, is used for receiving 0.4-50-micron wide spectrum radiation in the same spatial field of view, and forms a preliminary imaging spot containing a 0.4-5-micron short-wave band and a 5-50-micron long-wave band.

[0034] In the present embodiment, the main mirror can be the first mirror of the optical system in the present embodiment, and can be used for focusing the wide spectrum radiation from the same spatial field of view into a preliminary imaging spot.

[0035] Specifically, the main mirror (denoted as M1 below) is a double-cone mirror, wherein the double-cone mirror refers to a non-spherical mirror with different radii of curvature and conic coefficients in two orthogonal directions (i.e. the meridional direction and the sagittal direction).

[0036] Here, the meridional direction refers to the direction of the vertical tangent plane passing through the principal optical axis, and the sagittal direction refers to the direction perpendicular to the meridional plane.

[0037] For example, in a three-dimensional rectangular coordinate system with the optical axis as the reference axis (Z axis), the meridional direction can be the plane direction containing the principal optical axis and the incident light, i.e., the meridional direction can be represented by the XZ plane; the sagittal direction can be represented by the YZ plane.

[0038] Further, the double-tapered mirror can be represented by the following formula (1):

[0039]

[0040] where R x is the radius of curvature in the meridional direction, R y is the radius of curvature in the sagittal direction; k x is the conic coefficient in the meridional direction, and k y is the conic coefficient in the sagittal direction.

[0041] Here, the radius of curvature represents the curvature of the mirror surface in the meridional and sagittal directions; the greater the curvature, the flatter (or the more gentle) the mirror surface, and vice versa.

[0042] The conic coefficient represents the degree of deviation of the mirror surface from a spherical surface; when the conic coefficient is 0, the mirror surface is spherical; when the conic coefficient is less than 0, the mirror surface is ellipsoidal or parabolic; and when the conic coefficient is greater than 0, the mirror surface is hyperbolic.

[0043] Further, M1 is used to receive 0.4-50 μm wide-spectrum radiation of the same spatial field of view and form a preliminary imaging spot containing a short-wave band of 0.4-5 μm and a long-wave band of 5-50 μm.

[0044] Here, the range of the wide-spectrum radiation received by M1 can be set arbitrarily within the interval [0.4, 50] according to actual measurement requirements. For example, M1 can be used to receive wide-spectrum radiation in the range [0.4, 33] and form a preliminary imaging spot containing a short-wave band of 0.4-5 μm and a long-wave band of 33-50 μm.

[0045] Specifically, M1 is used to receive 0.4-50 μm wide-spectrum radiation from the same spatial field of view of 10°x10°, and by setting different radii of curvature and conic settings in the meridional and sagittal directions, different directions of light are subjected to differential deflection, forming a rectangular preliminary imaging spot containing a short-wave band of 0.4-5 μm and a long-wave band of 5-50 μm. That is, R x >R y , and k x <k y .

[0046] Here, 10°x10° is the range of the spatial field of view, i.e. the spatial range that M1 can collect the target from the imaging center to the periphery; specifically, the horizontal direction system of M1 can see a range of 10°, and the vertical direction can also see a range of 10°, which is equivalent to expanding an angular cone view area with the detector as the center.

[0047] The rectangular preliminary imaging spot can be a rectangular focal spot of 6.56mmx2.19mm.

[0048] In one possible implementation, M1 is used to realize aberration correction and preliminary imaging under the spatial field of view of 10°x10° by regulating the surface shape of the biconical mirror.

[0049] The double-plane sub-mirror is composed of a first plane sub-mirror and a second plane sub-mirror, and is used to separate the light beams of the short-wave band and the long-wave band in the preliminary imaging spot in the spatial direction in an amplitude-dividing manner, and keep the double light paths consistent.

[0050] In the embodiment, the first plane sub-mirror is denoted as M21, and the second plane sub-mirror is denoted as M22; the double-plane sub-mirror is composed of M21 and M22.

[0051] Here, M21 and M22 in the double-plane sub-mirror are arranged in high-precision parallel, can receive the rectangular preliminary imaging spot reflected by M1, reflect the light beams of the short-wave band and the long-wave band in different inclination angles, and make the light paths of the short-wave band and the long-wave band completely consistent when reaching the final mirror.

[0052] For example, M21 can be used to reflect the light beam of the short-wave band, and M22 can be used to reflect the light beam of the long-wave band; or M21 can be used to reflect the light beam of the long-wave band, and M22 can be used to reflect the light beam of the short-wave band.

[0053] The amplitude-dividing separation of M21 and M22 to the light beams of the short-wave band and the long-wave band can mean that the two light beams of different wavelengths are separated from the rectangular focal spot in a geometric path.

[0054] The final mirror is also a biconical mirror, and different curvature radii and conic coefficients are respectively arranged in the meridian direction and the sagittal direction, which are used to respectively perform refocusing and aberration correction on the light beams of the short-wave band and the long-wave band, and guide the light beams to different regions on the focal plane detector.

[0055] In the embodiment, the final mirror is denoted as M3. M3 is also a biconical mirror, and different curvature radii and conic coefficients are respectively arranged in the meridian direction and the sagittal direction.

[0056] Here, M3 can also be expressed by the above formula (1). The double-cone mirror of M3 also satisfies R x >R y , and k x <k y .

[0057] M3 further differentiates the short-wavelength light beam and the long-wavelength light beam by the different curvature radii and conic coefficients in the meridional direction and the sagittal direction.

[0058] Specifically, the short-wavelength light beam is reflected by M21 or M22 and then enters the upper half region of M3, M3 delays the convergence in the horizontal direction by the long focal length in the meridional direction, and simultaneously compresses the light beam in the vertical direction by the short focal length in the sagittal direction, and finally focuses on the region above the focal plane; the long-wavelength light beam is reflected by M22 or M21 and then enters the lower half region of M3, M3 matches the horizontal propagation path of the long-wavelength light beam by the long focal length in the meridional direction, and simultaneously converges the long-wavelength light beam in the vertical direction to the region below the focal plane by the short focal length in the sagittal direction.

[0059] Further, the conic coefficient of M3 in the meridional direction can eliminate the spherical aberration of the short-wavelength light beam, and the conic coefficient of M3 in the sagittal direction can eliminate the coma of the long-wavelength light beam.

[0060] Still further, M3 guides the light beams after refocusing and eliminating aberration to different regions isolated in space on the focal plane detector.

[0061] The focal plane detector is a microbolometer array, and a wide-spectrum filter array composed of SILICA and KRS5 substrate materials is integrated at the front end of the focal plane detector, and is used to form a double-spectrum non-aliasing image.

[0062] In the embodiment, the microbolometer array is used to realize signal acquisition by detecting the temperature change caused by radiation to cause resistance change.

[0063] SILICA is silicon dioxide, which has excellent ultraviolet to near-infrared transmittance, can be applied to high transmittance of 0.4-5 μm, and cuts off long-wave radiation; KRS5 is thallium bromoiodide, which has excellent transmittance in the 5-50 μm medium and long wave infrared band, and cuts off short-wave radiation.

[0064] Further, the wide-spectrum filter array is composed of SILICA and KRS5 arranged in an array form, and is integrated at the front end of the focal plane detector, and can be used to selectively transmit or cut off light of different wavebands.

[0065] M3 projects the short-wavelength light beam to the SILICA region of the wide-spectrum filter array of the focal plane detector and projects the long-wavelength light beam to the KRS5 region of the wide-spectrum filter array of the focal plane detector by refocusing and eliminating aberration of the short-wavelength light beam and the long-wavelength light beam.

[0066] Here, M1 and M3 focus the dual-band light beams to different regions on the surface of the detector by the design of the radius of curvature and the conic constant, to achieve spatial isolation; the wide-spectrum filter array further filters the wavelengths to ensure that each pixel only receives radiation of a single band; each pixel in the microbolometer array corresponds to a filter unit, independently collects the radiation signal of a single band, and forms a dual-spectrum image after circuit processing, avoiding interference from two bands received by the same pixel at the same time.

[0067] The above-mentioned embodiment of the present disclosure is applicable to a 0.4-50-micron dual-spectrum synchronous radiation measurement optical system, which realizes synchronous imaging of two bands in a completely consistent field of view and observation area through common optical path design and amplitude splitting imaging technology, effectively avoids spatial registration errors caused by optical axis deviation and imaging time sequence difference, significantly improves the data spatial consistency and time synchronization of multi-band radiation measurement, and improves the accuracy and reliability of subsequent radiation data fusion, quantitative inversion and physical modeling. By using a biconical mirror to construct a full-reflection, non-transmissive element wide-spectrum optical path, the complex design of a cylindrical mirror or a multi-lens structure required for realizing dual-focal-length imaging in related technologies is avoided. By using a double-plane mirror to realize amplitude splitting imaging, and combining a focal plane filter array integrated in the front end of the detector, a 0.4-50-micron ultra-wide band is efficiently covered. By using SILICA and KRS5 as the base material to form a wide-spectrum filter array, efficient light splitting in the full spectrum is realized, solving the problem that traditional light splitting elements in related technologies cannot efficiently cover the 0.4-50-micron ultra-wide band.

[0068] In one possible implementation of the above-mentioned embodiment, the radii of curvature of the main mirror in the meridional direction and the sagittal direction are 160 mm and 100 mm, respectively, and the conic constants in the meridional direction and the sagittal direction are -1.3 and -0.9, respectively.

[0069] In the present embodiment, the radius of curvature R x of M1 in the meridional direction is 160 mm, the radius of curvature R y in the sagittal direction is 100 mm, the conic constant k x in the meridional direction is -1.3, and the conic constant k y in the sagittal direction is -0.9.

[0070] Since the wavelength of the short-wave band light beam is short and sensitive to mirror curvature, the 100-mm radius of curvature set in the sagittal direction can enhance the focusing ability of the short-wave band light beam in the sagittal direction with smaller sagittal curvature; since the wavelength of the long-wave band light beam is long, the 160-mm radius of curvature set in the meridional direction can enhance the focusing ability of the long-wave band light beam in the meridional direction with larger meridional curvature.

[0071] Further, the conic coefficient of the meridional direction is -1.3 corresponding to a hyperboloid, and the hyperboloid characteristic can effectively correct the spherical aberration of the long-wave band light beam, so that the divergent long-wave band light beam is focused at the focal point after reflection, avoiding energy dispersion. The conic coefficient of the sagittal direction is -0.9 close to a paraboloid, and the paraboloid characteristic can have ideal focusing ability for the short-wave band light beam, which can reduce the focusing deviation of the short-wave band light beam in the sagittal direction.

[0072] Through the above-mentioned embodiment of the present disclosure, the optical system suitable for 0.4-50 μm dual-band synchrotron radiation measurement can eliminate the meridional-sagittal surface optical path difference caused by the wavelength difference through the asymmetric parameter design of "large curvature radius + hyperboloid conic coefficient" in the meridional direction of M1 and "small curvature radius + paraboloid-like conic coefficient" in the sagittal direction, so as to ensure the focusing accuracy of 0.4-50 μm wide spectrum radiation in the same optical path.

[0073] In one possible implementation of the above-mentioned embodiment, the first plane sub-reflector and the second plane sub-reflector in the dual-plane sub-reflector are symmetrically arranged in the sagittal direction, and the included angle between the mirror normals of the first plane sub-reflector and the second plane sub-reflector is 10 degrees.

[0074] The first plane sub-reflector and the second plane sub-reflector are used to reflect the separated short-wave band light beam and long-wave band light beam to the final reflector.

[0075] In the embodiment, M21 and M22 in the dual-plane sub-reflector are symmetrically arranged in the sagittal direction, so that the wavefront phase distribution of the short-wave band light beam and the long-wave band light beam in the sagittal plane remains symmetrical after reflection, avoiding the introduction of additional aberration due to asymmetric reflection, and providing low-aberration light beam conditions for the subsequent refocusing of M3.

[0076] Here, the included angle between the mirror normals of M21 and M22 is 10°, so that the short-wave band light beam is reflected by M21 to M3 at a first angle, and the long-wave band light beam is reflected by M22 to M3 at a second angle deviating from the first angle by 10°, thereby realizing the pre-separation of the light beams in the spatial angle.

[0077] It can be understood that M21 can reflect the short-wave band light beam or the long-wave band light beam; correspondingly, if M21 reflects the short-wave band light beam, M22 reflects the long-wave band light beam; if M21 reflects the long-wave band light beam, M22 reflects the short-wave band light beam.

[0078] The optical system of the embodiment of the present disclosure is applicable to the dual-band synchronous radiation measurement optical system in the wave band of 0.4-50 microns. The symmetry of M21 and M22 makes the optical path difference in the meridional direction of the short wave band and the long wave band cancel each other out in the reflection process, avoids introducing additional aberration due to asymmetric reflection, and improves the subsequent focusing accuracy. Since the plane mirror only changes the propagation direction of the light beam and does not introduce focusing or divergence, the two separated wave bands can be guided to M3 without affecting the focusing characteristics of the light beam, thereby shortening the physical length of the entire optical system and reducing the energy loss and aberration accumulation caused by the curved mirror. In addition, the angle deflection characteristics of the plane mirror make the short wave band and the long wave band be incident on the final mirror at an angle difference of 10 degrees, which further improves the spatial separation effect corresponding to the different curvature regions of the meridional direction and the sagittal direction of the final mirror.

[0079] In one possible implementation of the above embodiment, the curvature radii of the final mirror in the meridional direction and the sagittal direction are 130 mm and 80 mm respectively, and the conic coefficients in the meridional direction and the sagittal direction are -1.2 and -1.0 respectively.

[0080] In the embodiment, the curvature radius R x of M3 in the meridional direction is 130 mm, the curvature radius R y in the sagittal direction is 80 mm, the conic coefficient k x in the meridional direction is -1.2, and the conic coefficient k y in the sagittal direction is -1.0.

[0081] Here, the curvature radii of M3 in the meridional direction and the sagittal direction form an asymmetric surface that is relatively slow in the meridional direction and relatively steep in the sagittal direction. When the long wave band is incident on the meridional plane at a specific angle, the curvature radius of 130 mm can reduce the long wave band diffraction loss, and when the short wave band is incident on the sagittal plane at a specific angle, the curvature radius of 80 mm can enhance the focusing ability in the sagittal direction.

[0082] Further, the meridional direction corrects the spherical aberration of the long wave band through the characteristics of the hyperboloid (the conic coefficient k x is -1.2), that is, the residual divergence of the long wave band after being reflected by the hyperboloid of M1 can be further converged by the hyperboloid of the meridional plane of M3, so as to ensure that the long wave band is strictly focused on the long wave region of the focal plane detector and avoid imaging blur caused by energy dispersion.

[0083] The sagittal direction focuses the short wave band on a point without aberration through the characteristics of the paraboloid (the conic coefficient k y is -1.0), so as to realize high-resolution imaging of the short wave band.

[0084] By the above-mentioned embodiment of the application, the optical system for measuring the double spectral band of the 0.4-50 micron band of the synchrotron radiation is used, the two wave bands of light beams deflected by M21 / M22 are focused differently: the long wave is focused in the meridional plane slow bending mirror surface to reduce the loss and focus, the short wave is focused in the sagittal plane steep bending mirror surface to improve the focusing sharpness, and finally the residual astigmatism introduced by M1 and the double plane sub-mirror is eliminated to ensure the clearness of the focus surface imaging. In addition, M21 / M22 makes the two wave bands of light beams incident to M3 at an angle difference of 10 degrees, and M3 precisely focuses the angle-separated light beams to the spatially isolated areas of the detector by setting different curvature radii and conic coefficients in two directions, which fundamentally avoids the double spectral aliasing.

[0085] In a possible implementation of the above-mentioned embodiment, the angle of the main mirror relative to the horizontal plane is 12 degrees, the angle of the final stage mirror relative to the horizontal plane is 15 degrees, and the angle between the optical axis of the first plane sub-mirror and the optical axis of the second plane sub-mirror is 5 degrees.

[0086] In the embodiment, the incident wide spectrum light beam is folded to the working area of M21 / M22 by the 12-degree angle, avoiding the optical path interference caused by the direct horizontal propagation of the light beam.

[0087] Here, the angle can be coordinated with the curvature parameters of M1 to make the initial incident light cover the M1 mirror surface at the optimal angle, ensuring the uniform distribution of the long / short wave band light beam energy and reducing the vignetting loss of the edge light.

[0088] Further, the long / short wave light beams separated by M21 / M22 are incident to M3 at different angles, and the 15-degree angle makes the normal line of the M3 mirror surface form a reasonable angle with the average incident direction of the two light beams, which can ensure that the long wave band light beam is incident at an angle close to perpendicular to the meridional plane of M3, and the 130mm curvature radius is used to realize precise focusing; and the short wave band light beam is incident at an angle adapted to the 80mm curvature of the sagittal plane to avoid the increase of coma caused by the too large incident angle.

[0089] Further, the angle between the optical axes of M21 / M22 is 5 degrees, so that the short wave band light beam and the long wave band light beam produce a fixed angle difference through the geometric optical reflection law.

[0090] By the above-mentioned embodiment of the application, the optical system for measuring the double spectral band of the 0.4-50 micron band of the synchrotron radiation is used, the optical system for measuring the double spectral band of the 0.4-50 micron band of the synchrotron radiation is used, the initial direction regulation of the wide spectrum light beam and the efficient coupling of the double plane sub-mirror are realized through the 12-degree angle of M1. The focusing position offset and the aberration correction of the double wave band light beams are realized through the coordination of the 15-degree angle and the asymmetric curvature of M3. The angle differential propagation of the long / short wave light beams is realized through the 5-degree optical axis angle of M21 / M22.

[0091] In a possible implementation of the above embodiment, the air gap between the primary mirror and the first planar minor is 110 mm, and the air gap between the second planar minor and the final mirror is 95 mm.

[0092] In this embodiment, the specific values of 110 mm and 95 mm can be set based on the space planning of the entire optical system to ensure that the components do not interfere after installation, while meeting the needs of portability or integration.

[0093] Here, if the gap is too large, the energy of the light beam can be attenuated during propagation in the air, and if the gap is too small, the components can be difficult to install and debug due to the close spacing.

[0094] The above embodiment of the present disclosure is applicable to a dual-spectral band synchronous radiation measurement optical system in the 0.4-50 micrometer wave band. By using a biconical mirror to construct a wide-spectrum optical path without a transmission component, the system structure is compact, avoiding the complex design of a cylindrical mirror or a multi-lens structure required for traditional dual-focal-length imaging, reducing the overall structural complexity and manufacturing cost, and having good engineering realizability and remote sensing platform integration adaptability.

[0095] In a possible implementation of the above embodiment, the thickness of the SILICA and KRS5 substrate materials constituting the wide-spectrum filter array is 1 mm; and the wide-spectrum filter array is arranged 1 mm in front of the focal plane detector.

[0096] In this embodiment, the SILICA substrate thickness is controlled to be 1 mm, which can realize low-loss transmission and spectral accuracy in the visible-near infrared wave band, and provide pure spectral input for short-wave detection. The KSR5 substrate thickness is controlled to be 1 mm, which realizes the balance between high-efficiency transmission and substrate damage resistance in the medium-long wave infrared wave band, and adapts to the spectral response requirements of the long-wave detector.

[0097] As an example, refer to Figure 2 , Figure 2 is a focal plane detector receiving surface schematic diagram of a visible-terahertz low-frequency dual-spectral band radiation synchronous measurement optical system provided by the embodiment of the present disclosure. The first part of the receiving surface of the focal plane detector can be configured as a SILICA substrate material of a wide-spectrum filter array to receive the short-wave light beam incident by M3; and the second part of the receiving surface can be configured as a KRS5 substrate material of a wide-spectrum filter array to receive the long-wave light beam incident by M3.

[0098] As another example, refer to Figure 3 , Figure 3is the imaging schematic diagram of a visible-terahertz low frequency band dual spectral band radiation synchronous measurement optical system provided by the embodiment of the present disclosure, wherein the observation target is imaged by M1 and M21 / M22, and two spatially independent amplitude division images are generated; the amplitude division images are imaged by M3 and filtered by the filter, and an aliasing-free dual waveband image is generated.

[0099] As an example, for the above-mentioned embodiments of the present disclosure, structural modeling and performance simulation evaluation are carried out in combination with Zemax optical design software. Specifically, for the visible to near-infrared waveband (0.4-5 μm) and the mid-infrared to far-infrared waveband (5-50 μm), imaging performance evaluation is carried out respectively.

[0100] Among them, in the 0.4-5 μm waveband, please refer to Figure 4 , Figure 4 is the 0.4-5 μm waveband MTF curve diagram of the visible-terahertz low frequency band dual spectral band radiation synchronous measurement optical system provided by the embodiment of the present disclosure, as shown in Figure 4 , at a sampling frequency of 8.3 lp / mm, the modulation transfer function (Modulation Transfer Function, MTF) value is generally higher than 0.4, and part of the field point is close to 0.6, which fully meets the requirements of high image quality and wide field of view synchronous detection.

[0101] In the 5-50 μm waveband, please refer to Figure 5 , Figure 5 is the 5-50 μm waveband MTF curve diagram of the visible-terahertz low frequency band dual spectral band radiation synchronous measurement optical system provided by the embodiment of the present disclosure, as shown in Figure 5 , at a sampling frequency of 8.3 lp / mm, the MTF value is generally close to 0.3, and the MTF curve of each field position decays smoothly, which shows that the system has stable mid-infrared and far-infrared imaging capability and is suitable for high-precision radiation energy quantitative measurement.

[0102] Here, MTF is a core index for measuring the imaging quality of an optical system, which is used to represent the transmission ability of the system to different spatial frequency signals. Among them, if MTF=1, it means that the system perfectly transmits image details and contrast without attenuation; if MTF=0, it means that the system cannot distinguish the details of the spatial frequency.

[0103] The system shows excellent imaging quality at multiple field points in the meridional and sagittal directions in the full field of view. Simulation results show that at a sampling frequency of 8.3 lp / mm, the MTF value is generally higher than 0.4, and some field points are close to 0.6, fully meeting the requirements of high image quality and wide field of view synchronous detection. In the 5-50 μm waveband, although long-wave radiation poses higher challenges to optical diffraction control, the system still exhibits good imaging modulation. At a sampling frequency of 8.3 lp / mm, the MTF value is generally close to 0.3, and the MTF curve at each field position decays smoothly, showing that the system has stable mid-infrared imaging capability and is suitable for high-precision radiation energy quantitative measurement. In summary, the simulation results fully verify the imaging consistency and performance stability of the optical system in the full waveband and full field of view, and the system has excellent engineering implementability.

[0104] Although the embodiments of the present disclosure are described in conjunction with the drawings, various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the present disclosure, and such modifications and changes fall within the scope defined by the appended claims.

Claims

1. A dual-spectrum radiation synchronous measurement optical system in the visible-terahertz low-frequency band, characterized by: The system includes: a primary reflector, a double-plane secondary reflector, a final reflector and a focal plane detector, wherein: The primary reflector is a biconical reflector having different curvature radii and conic coefficients in the meridional and sagittal directions, respectively, for receiving 0.4 to 50 micron wide-spectrum radiation in the same spatial field of view and forming a preliminary imaging spot including a 0.4 to 5 micron short-wave band and a 5 to 50 micron long-wave band; The dual-plane sub-reflector is composed of a first plane sub-reflector and a second plane sub-reflector, and is used to separate the short-wavelength and long-wavelength light beams in the preliminary imaging spot according to the spatial direction and maintain the consistency of the two-path optical path; The final reflector is also a biconical reflector, and has different curvature radii and conic coefficients in the meridional and sagittal directions, respectively, for refocusing and aberration correction of the short-wavelength and long-wavelength beams, and guiding the beams to different spatially isolated areas on the focal plane detector; The focal plane detector is a microbolometer array, and a wide-spectrum filter array composed of SILICA and KRS5 substrate materials is integrated at the front end to form a dual-spectrum aliasing-free image.

2. The system according to claim 1, wherein: The curvature radii of the main reflector in the meridional and sagittal directions are 160 mm and 100 mm, respectively, and the conic coefficients in the meridional and sagittal directions are -1.3 and -0.9, respectively.

3. The system according to claim 1, wherein: The first plane secondary reflector and the second plane secondary reflector of the double plane secondary reflector are arranged symmetrically in the sagittal direction, and the angle between the mirror normals of the first plane secondary reflector and the second plane secondary reflector is 10 degrees; The first plane sub-reflector and the second plane sub-reflector are used to direct the separated short-wavelength light beam and long-wavelength light beam to the final reflector.

4. The system according to claim 1, wherein: The curvature radii of the final reflector in the meridional and sagittal directions are 130 mm and 80 mm, respectively, and the conic coefficients in the meridional and sagittal directions are -1.2 and -1.0, respectively.

5. The system according to any one of claims 1 to 4, characterized in that The inclination angle of the primary reflector relative to the horizontal plane is 12 degrees, the inclination angle of the final reflector relative to the horizontal plane is 15 degrees, and the angle between the optical axis of the first plane sub-reflector and the optical axis of the second plane sub-reflector is 5 degrees.

6. The system according to claim 5, characterized in that The air distance between the primary reflector and the first plane secondary reflector is 110 mm, and the air distance between the second plane secondary reflector and the final reflector is 95 mm.

7. The system according to claim 1, wherein: The thickness of the SILICA and KRS5 substrate materials constituting the broadband filter array of the focal plane detector is 1 mm; the broadband filter array is arranged 1 mm from the front end of the focal plane detector.

8. The system according to claim 1, wherein: The range of the spatial field of view is 10 degrees×10 degrees.

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