Satellite-borne laser radar and optical remote sensing camera transceiver integrated optical system

Abstract

The present application relates to a kind of spaceborne lidar and optical remote sensing camera transceiver integrated optical system, it is related to space remote sensing technical field.The optical system includes: main reflector, secondary reflector, first light path folding mirror, double cemented lens group, dichroic mirror;The focal point of main reflector and secondary reflector coincides;Further include: lidar transmitting unit, laser signal receiving system and optical imaging system.The spaceborne lidar and optical remote sensing camera transceiver integrated optical system of the present application uses off-axis two-reflection afocal telescope as common-aperture optical antenna, makes the far-field spot position of laser beam and the center of receiving field of view accurate alignment, fundamentally eliminates the transmission axis matching error.Therefore, without additional configuration optical axis monitoring camera, laser footprint camera and angle adjustment mechanism are carried out transmission matching, simplify system structure, improve system integration.

Description

Technical Field

[0001] This invention relates to the field of aerospace remote sensing technology, and in particular to an integrated optical system that combines a spaceborne lidar and an optical remote sensing camera. Background Technology

[0002] Traditional optical remote sensing cameras excel at providing two-dimensional multispectral imagery of the Earth's surface, but they suffer from limitations such as reliance on sunlight, time constraints, and limited ability to acquire elevation information of ground features. Spaceborne lidar can accurately detect the three-dimensional structure of space targets, but struggles to obtain detailed spectral information about ground objects. By combining spaceborne lidar with optical remote sensing cameras, it is possible to simultaneously acquire the structural, three-dimensional, and spectral characteristics of target objects. This multimodal information fusion provides a solid foundation for in-depth data analysis and accurate interpretation, contributing to improved effectiveness and comparability of remote sensing imaging data.

[0003] Currently, the "Jumang" terrestrial ecosystem carbon monitoring satellite has successfully applied the above technologies. Its onboard multi-beam lidar is the first in the world to combine lasers with cameras, acquiring ground vegetation height information while simultaneously obtaining high-resolution multispectral ground images. The payload emits a directional laser beam to the ground via a lidar transmitting system, using an optical axis monitoring camera to monitor the laser's emission axis, ensuring the far-field laser spot is within the receiving system's field of view. The receiving system simultaneously receives the reflected laser signal and ground object light signals.

[0004] The "Jumang" terrestrial ecosystem carbon monitoring satellite, as the first truly integrated active and passive remote sensing system, has played a significant role in my country's large-scale survey of forestry resources and carbon sink monitoring. However, its main drawback is that the lidar transmitting and receiving systems are designed separately. The matching of laser signal transmission and reception is achieved through a laser footprint camera, an optical axis monitoring camera, and an offset angle adjustment mechanism. This separate design increases the system's complexity and puts considerable pressure on the satellite's size and weight. Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art and make full use of the limited space of the satellite platform, the present invention provides an integrated optical system for transmitting and receiving spaceborne lidar and optical remote sensing camera.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] An integrated optical system for satellite-borne lidar and optical remote sensing camera includes, in sequence along the optical path: a primary reflector, a secondary reflector, a first optical path folding reflector, a cemented doublet lens group, and a dichroic mirror; the primary reflector and the secondary reflector have coincident focal points.

[0008] The optical system also includes: a lidar transmitting unit, a laser signal receiving system, and an optical imaging system; wherein:

[0009] The lidar transmitting unit includes: a laser;

[0010] The laser signal receiving system includes, in sequence along the optical path, a third lens, a field stop, a second optical path folding mirror, a fourth lens, a narrowband filter, a fifth lens, and a photodetector.

[0011] The optical imaging system includes, in sequence along the optical path, a third optical path folding reflector and an image sensor; the image sensor is used to receive visible light ground object information and generate a two-dimensional image of the target;

[0012] The laser beam emitted by the laser is reflected sequentially by the secondary mirror and the primary mirror, which expands the beam waist radius, reduces the divergence angle, and then shines towards the ground.

[0013] Dichroic mirrors are used to separate laser signals from visible light bands, causing the laser signal to be refracted and reflected onto the third lens, while visible light is focused onto the image sensor through the dichroic mirror and the third optical path folding mirror.

[0014] After being reflected, the ground laser signal is received by the laser signal receiving system. It then passes through the primary reflector, secondary reflector, first optical path folding reflector, cemented doublet lens group, dichroic mirror, third lens, field stop, second optical path folding reflector, fourth lens, narrowband filter, and fifth lens before being received by the photoelectric detection device.

[0015] In the above technical solution, the reflector surface of the main reflector is a free-form surface characterized by an XY polynomial with a parabolic base, and the reflector surface has a diameter of 260mm×360mm and a radius of curvature of -720mm.

[0016] In the above technical solution, the secondary reflector is a free-form surface characterized by an XY polynomial based on a parabolic surface, and the diameter of the reflector surface is a rectangle of 32mm×44mm with a radius of curvature of -72mm.

[0017] In the above technical solution, the laser is a semiconductor-pumped Nd:YAG pulsed laser that emits a 1064nm wavelength laser beam, with a pulse energy of 1.5mJ, a pulse width of 2ns, a repetition frequency of 10kHz, a spot size of 2mm, and a divergence angle of 0.68mrad.

[0018] In the above technical solution, the double-cemented lens group includes, in sequence, a first lens and a second lens in the optical path direction;

[0019] The center thickness of the first lens is 6mm, and the center thickness of the second lens is 3mm.

[0020] In the above technical solution, the dichroic mirror is an optical glass with a dichroic film coated on its surface.

[0021] In the above technical solution, the image sensor is a CMOS sensor, which is located on the imaging side of the optical imaging system.

[0022] In the above technical solution, the visible light band is 400-750nm.

[0023] In the above technical solution, the laser ground footprint is located at the center of the receiving field of view of the laser signal receiving system.

[0024] The present invention has the following beneficial effects:

[0025] The spaceborne lidar and optical remote sensing camera integrated optical system of this invention uses a common aperture design for the optical remote sensing camera, lidar transmitting system, and receiving system, avoiding the transmission and reception matching problems caused by the separate design of the laser transmitting system and receiving system. At the same time, the system integrates the active and passive detection capabilities of the spaceborne lidar and optical remote sensing camera, ensuring the spatiotemporal consistency of multi-source remote sensing images.

[0026] The spaceborne lidar and optical remote sensing camera integrated transceiver optical system of this invention uses an off-axis dual-mirror afocal telescope as a common aperture optical antenna, which ensures that the far-field spot position of the laser beam is precisely aligned with the center of the receiving field of view, fundamentally eliminating transceiver axis matching errors. Therefore, there is no need to configure additional optical axis monitoring cameras, laser footprint cameras, and offset angle adjustment mechanisms for transceiver matching, simplifying the system structure and improving the system integration.

[0027] The spaceborne lidar and optical remote sensing camera transceiver integrated optical system of the present invention uses a primary reflector and a secondary reflector for three channels: optical remote sensing, laser emission, and laser reception. This greatly improves the system's integration, reduces the size, weight, and cost of the equipment, adapts to the aerospace remote sensing imaging environment, avoids the problem of satellite platform installation size limitations, and extends the operating time of remote sensing satellites.

[0028] The spaceborne lidar and optical remote sensing camera transceiver integrated optical system of this invention employs multiple optical path folding mirrors to achieve an optimized balance between system size and performance. Its overall envelope dimensions are 490mm (length) × 260mm (width) × 420mm (height), and its mass is ≤15kg. At a satellite orbital altitude of 500km, the system can achieve a ground pixel resolution of 1m for optical remote sensing (MTF@Nyquist>0.2) and a range resolution of 0.3m for lidar. Attached Figure Description

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] Figure 1 This is a schematic diagram of the integrated optical system for satellite-borne lidar and optical remote sensing camera of the present invention.

[0031] Figure 2 This is a schematic diagram of the structure of the laser radar transmitting unit of the integrated optical system for spaceborne laser radar and optical remote sensing camera of the present invention.

[0032] Figure 3 This is a schematic diagram of the laser signal receiving system of the integrated optical system for spaceborne lidar and optical remote sensing camera of the present invention.

[0033] Figure 4 This is a schematic diagram of the optical imaging system of the integrated optical system for spaceborne lidar and optical remote sensing camera of the present invention.

[0034] Figure 5 This is a schematic diagram of the double cemented lens assembly of the integrated optical system for spaceborne lidar and optical remote sensing camera of the present invention.

[0035] Figure 6 This is a light spot diffusion diagram of the laser radar transmitting unit of the integrated optical system for spaceborne laser radar and optical remote sensing camera of the present invention.

[0036] Figure 7 This is a light spot diffusion diagram of the laser signal receiving system of the integrated optical system for spaceborne lidar and optical remote sensing camera transceiver of the present invention.

[0037] Figure 8 This is a light spot diffusion diagram of the optical imaging system of the spaceborne lidar and optical remote sensing camera integrated transceiver optical system of the present invention.

[0038] Figure 9 This is the MTF diagram of the optical imaging system of the integrated optical system for spaceborne lidar and optical remote sensing camera of the present invention.

[0039] The reference numerals in the figure are:

[0040] 1-Primary reflector; 2-Secondary reflector; 3-Laser; 4-First optical path folding reflector; 5-Cemented doublet lens group; 5.1-First lens; 5.2-Second lens; 6-Dichroic mirror;

[0041] 7-Third optical path folding mirror; 8-Image sensor; 9-Third lens; 10-Field stop; 11-Second optical path folding mirror; 12-Fourth lens; 13-Narrow band filter; 14-Fifth lens; 15-Photodetector.

[0042] 16 - First surface of the cemented doublet lens group; 17 - Second surface of the cemented doublet lens group; 18 - Third surface of the cemented doublet lens group. Detailed Implementation

[0043] The inventive concept of this invention is as follows:

[0044] To make the most of the limited space on the satellite platform, the spaceborne lidar and optical remote sensing camera integrated optical system of the present invention has a laser footprint that is always located at the center of the receiving field of view, so there is no need to adjust the offset angle mechanism to match the transmission and reception of the laser signal.

[0045] The spaceborne lidar and optical remote sensing camera integrated transceiver optical system of this invention adopts a shared primary and secondary mirror approach, integrating the lidar transmitting system, laser signal receiving system, and optical remote sensing camera into a single transceiver design. This solves the problems of high complexity, high resource consumption, and low application efficiency caused by the separate design of the spaceborne lidar transceiver system and optical remote sensing camera system in existing remote sensing technologies. The primary and secondary mirrors serve as laser beam expanders for the lidar transmitting system, compressing the divergence angle of the laser beam emitted from the laser; simultaneously, they act as receiving antennas for both the laser signal receiving system and the optical remote sensing camera, enabling simultaneous detection of spectral information of ground objects and the three-dimensional structure of targets.

[0046] The spaceborne lidar and optical remote sensing camera integrated transceiver optical system of this invention mainly includes: a lidar transmitting unit, a laser signal receiving system, and an optical imaging system. The lidar transmitting unit includes: a laser beam expander system composed of a primary reflector and a secondary reflector, and a laser. The laser beam emitted by the laser is reflected sequentially by the secondary reflector and the primary reflector, expanding the beam waist radius to 10 times its original size and reducing the divergence angle to 1 / 10 of its original size before being directed towards the ground. The laser signal receiving system receives the reflected laser signal, which then passes sequentially through the primary reflector, secondary reflector, first optical path folding reflector, first lens, second lens, dichroic mirror, third lens, field stop, second optical path folding reflector, fourth lens, narrowband filter, and fifth lens. Finally, it is converted into an electrical signal output by a photoelectric detection device. The laser signal receiving system operates at a wavelength of 1064 nm, a focal length of 1600 mm, an F-number of 6.4, and a receiving field of view of 0. The optical imaging system receives ground object spectral information sequentially through a primary mirror, secondary mirror, first optical path folding mirror, first lens, second lens, dichroic mirror, and third optical path folding mirror before being received by the image sensor. The optical imaging system operates at a wavelength of 400-750 nm, a focal length of 3500 mm, an F-number of 14, and a full field of view of 0.294°. At an orbital altitude of 500 km, the corresponding swath width is 2.6 km, the ground pixel resolution is 1 m, the Airy disk radius is 10 μm, the image-side diffuse spot RMS radius is less than 4 μm, and the modulation transfer function of each field of view is greater than 0.2 at the Nyquist frequency (72 lp / mm).

[0047] The spaceborne lidar and optical remote sensing camera integrated optical system of the present invention has a three-dimensional size of approximately 490mm×260mm×420mm. Both the on-axis and off-axis fields of view achieve diffraction-limited image quality, realizing a compact design that integrates the lidar transmitting system, lidar receiving system and optical imaging system.

[0048] The present invention will now be described in detail with reference to the accompanying drawings.

[0049] like Figure 1-5 As shown, the spaceborne lidar and optical remote sensing camera transceiver integrated optical system of the present invention includes: a lidar transmitting unit, a laser signal receiving system, and an optical imaging system.

[0050] in:

[0051] The lidar transmitting unit includes: a primary reflector 1, a secondary reflector 2, and a laser 3;

[0052] The laser signal receiving system includes: a primary reflector 1, a secondary reflector 2, a first optical path folding reflector 4, a cemented doublet lens group 5, a dichroic mirror 6, a third lens 9, a field stop 10, a second optical path folding reflector 11, a fourth lens 12, a narrowband filter 13, a fifth lens 14, and a photodetector 15; the dichroic mirror 6, which transmits visible light and reflects laser light, is a beam splitting unit; the cemented doublet lens group 5 includes, in sequence along the optical path, a first lens 5.1 and a second lens 5.2;

[0053] The optical imaging system includes: a primary mirror 1, a secondary mirror 2, a first optical path folding mirror 4, a cemented doublet lens group 5, a dichroic mirror 6, a third optical path folding mirror 7, and an image sensor 8.

[0054] In the integrated optical system of spaceborne lidar and optical remote sensing camera of the present invention, the primary reflector 1, secondary reflector 2, first optical path folding reflector 4, cemented doublet lens group 5, and dichroic mirror 6 are shared in the lidar transmitting unit, the laser signal receiving system, and the optical imaging system, respectively.

[0055] like Figure 5 As shown, the cemented doublet lens group in the transceiver integrated optical system of the spaceborne lidar and optical remote sensing camera of the present invention includes: a first surface 16 of the cemented doublet lens group, a second surface 17 of the cemented doublet lens group, and a third surface 18 of the cemented doublet lens group.

[0056] like Figure 6-9 As shown, the optical performance evaluation of the spaceborne lidar and optical remote sensing camera integrated optical system of the present invention includes: the spot diffusion map of the lidar transmitting unit, the spot diffusion map of the laser signal receiving system, the spot diffusion map of the optical imaging system, and the MTF map of the optical imaging system.

[0057] in:

[0058] The spot dispersion pattern of the lidar transmitting unit shows the diffraction limit of the outgoing beam RMS angle deviation and the outgoing beam angle error. Figure 6 The solid coil represents the diffraction limit of the outgoing beam angle error, and the blue spot represents the actual angle deviation of the outgoing beam. It can be seen that the angle deviation of the outgoing beam is much smaller than the diffraction limit, and the quality of the outgoing beam is excellent.

[0059] The spot diffusion diagram of the laser signal receiving system shows the size of the diffuse spot and the Airy disk size at the image plane of the laser signal receiving system. Figure 7 The solid coil represents the size of the Airy disk, and the blue spot represents the degree of diffusion of the actual spot. It can be seen that the radius of the Airy disk is 7.78μm, and the RMS radius of the actual diffuse spot is less than 7μm, indicating excellent imaging quality.

[0060] The diffusion pattern of an optical imaging system shows the size of the diffuse spot and the Airy disk at the image plane of the optical imaging system. Figure 8 The solid coil represents the size of the Airy disk, and the colored spot represents the degree of diffusion of the actual spot. It can be seen that the radius of the Airy disk is 10μm, and the RMS radius of the actual diffuse spot is less than 4μm, resulting in excellent imaging quality.

[0061] The MTF plot of an optical imaging system shows the modulation transfer function curves for each field of view. Figure 9 As can be seen, the modulation transfer function of each field of view of the optical imaging system exceeds 0.2 at the Nyquist frequency (72 lp / mm), indicating that the optical system has excellent performance.

[0062] Specifically:

[0063] The lidar transmitting unit includes: a primary reflector 1, a secondary reflector 2, and a laser 3. The primary reflector 1 has a reflective surface characterized by an XY polynomial based on a parabolic surface. The reflective surface is rectangular with an aperture of 260mm × 360mm and a radius of curvature of -720mm. The substrate material is aluminum-based silicon carbide, and the surface is coated with anti-reflection films for the 400nm-750nm wavelength band and the 1064nm wavelength band. The secondary reflector 2 has a reflective surface characterized by an XY polynomial based on a parabolic surface. The reflective surface is rectangular with an aperture of 32mm × 44mm. The laser has a radius of curvature of -72 mm, and its substrate material is aluminum-based silicon carbide. The surface is coated with anti-reflective films for the 400nm-750nm wavelength band and a 1064nm wavelength band. The primary reflector 1 and secondary reflector 2 have coincident focal points, forming an off-axis, two-reflector, afocalless system that serves as the laser beam expander for the lidar transmitting unit. Laser 3 is a semiconductor-pumped Nd:YAG pulsed laser capable of emitting a 1064nm wavelength laser beam, with a pulse energy of 1.5 mJ, a pulse width of 2 ns, a repetition frequency of 10 kHz, a spot size of 2 mm, and a divergence angle of 0.68 mrad. The laser beam emitted by laser 3 is reflected sequentially by secondary reflector 2 and primary reflector 1, expanding its beam waist radius to 20 mm and reducing its divergence angle to 0.068 mrad before being directed towards the ground. The laser ground footprint of the satellite at an orbital altitude of 500 km has a spot diameter of 35 m. Simulation results show that the angular deviation of the emitted beam from the lidar transmitting unit is much smaller than the diffraction limit, indicating excellent beam quality.

[0064] The dichroic mirror 6, which transmits visible light and reflects laser light, is a beam splitting unit located on the common channel of the laser signal receiving system and the optical imaging system. It is an optical glass with a dichroic film coated on its surface, used to separate the 1064nm wavelength laser signal from the visible light band, so that the laser signal is refracted 90° and reflected onto the third lens 9. Visible light in the 400-750nm band passes through the dichroic mirror 6 and converges to the image sensor 8.

[0065] The receiving field of view of the laser signal receiving system is 0.1 mrad. The laser ground footprint is located at the center of the receiving field of view of the laser signal receiving system. After the ground laser signal is reflected, it is received by the laser signal receiving system. It passes through the primary reflector 1, secondary reflector 2, first optical path folding reflector 4, cemented doublet lens group 5, dichroic mirror 6, third lens 9, field stop 10, second optical path folding reflector 11, fourth lens 12, narrowband filter 13 and fifth lens 14 in sequence before being received by the photoelectric detection device 15. The primary reflector 1 and the secondary reflector 2 together form the optical receiving antenna of the laser signal receiving system. The first optical path folding reflector 4 is located 340mm behind the secondary reflector 2 along the optical axis, with an aperture of 44mm × 52mm. Its surface is coated with anti-reflective coatings for the 400nm-750nm wavelength band and the 1064nm wavelength band. Its function is to fold the optical path by 90°, reducing the system size. The cemented doublet lens group 5 includes a first lens 5.1 and a second lens 5.2, located 100mm behind the first optical path folding reflector 4 along the optical axis. Its function is to converge the light. The first lens 5.1 is made of calcium fluoride, and the second lens 5.2 is made of Chengdu Guangming's H-LAK7A flint glass. These two materials effectively correct the chromatic aberration of the optical system and improve the image quality. The first surface 16 of the cemented doublet lens group 5 is the front surface of the first lens 5.1, with an even-order aspherical shape and a radius of curvature of -1979.706 mm. The second surface 17 is the rear surface of the first lens 5.1, with a spherical shape and a radius of curvature of -64.796 mm. The third surface 18 is the rear surface of the second lens 5.2, with an even-order aspherical shape and a radius of curvature of -98.223 mm. The center thickness of the first lens 5.1 is 6 mm, and the center thickness of the second lens 5.2 is 3 mm. The dichroic mirror 6 is located 200 mm behind the optical axis of the cemented doublet lens group 5. The third optical path folding mirror 7 is located 60 mm behind the dichroic mirror 6 along the optical axis, and its surface is coated with an anti-reflective coating in the 400 nm-750 nm band. Its function is to fold the optical path by 90° and reduce the system size. The third lens 9 is located 20 mm behind the dichroic mirror 6 along the optical axis (at this time, the optical axis of the laser signal receiving system has been rotated 90°). The material of the third lens 9 is fused silica glass (F-SILICA) with high transmittance in the near-infrared region. The front surface of the third lens 9 is spherical with a radius of curvature of 40.527 mm, the rear surface is spherical with a radius of curvature of 341.323 mm, and the center thickness is 4 mm. The field stop 10 is located 54.5 mm behind the third lens 9 along the optical axis (the location of the primary imaging plane of the laser signal receiving system). The diameter of its central hole is approximately 0.15 mm, which serves to limit the off-axis field of view and filter stray light with a field of view angle greater than 0.1 mrad in the laser signal receiving channel. The second optical path folding reflector 11 is located 9 mm behind the field stop 10 along the optical axis.At a position 2mm, a 1064nm wavelength anti-reflective coating is deposited on the surface, which folds the optical path by 90° to reduce the system size. The fourth lens 12 is located 20mm behind the second optical path folding mirror 11 along the optical axis. Its function is to converge the diverging beam into parallel light, facilitating precise filtering by the narrowband filter. The material of the fourth lens 12 is fused silica glass (F-SILICA). The front surface of the fourth lens 12 is spherical with a radius of curvature of 29.609mm, and the rear surface is an even-order aspherical with a radius of curvature of -23.477mm. The center thickness is 3mm. The narrowband filter 13 is located 2mm behind the fourth lens 12 along the optical axis, allowing infrared signals with wavelengths in the range of 1064±0.4nm to pass through, reducing the background light generated by the sun. To reduce noise and improve the signal-to-noise ratio of lidar signal acquisition, the fifth lens 14 is located 2 mm behind the narrow-band filter 13 along the optical axis. Its function is to focus parallel light onto the photodetector. The material of the fifth lens 14 is fused silica glass (F-SILICA). The front surface of the fifth lens 14 is an even-order aspherical surface with a radius of curvature of 36.964 mm, the rear surface has a radius of curvature of -21.775 mm, and the center thickness is 3 mm. The photodetector 15 is an InGaAs-APD (indium gallium arsenide avalanche photodiode), located 29.167 mm behind the fifth lens 14 along the optical axis (the imaging side of the laser signal receiving system). It is used to receive the 1064 nm wavelength laser signal transmitted through the fifth lens 14 and generate three-dimensional information of the target. The InGaAs-APD uses InGaAs (indium gallium arsenide) as the absorber layer and InP (indium phosphide) as the multiplication layer. It operates in the 800nm–1750nm wavelength range and exhibits high quantum efficiency for 1064nm lasers. Simulations show that the Airy disk radius of the laser signal receiving system is 7.78μm, and the RMS radius of the actual diffuse spot is less than 7μm, resulting in excellent imaging quality.

[0066] The optical imaging system comprises, in sequence from the object plane to the image plane: a primary mirror 1, a secondary mirror 2, a first optical path folding mirror 4, a cemented doublet lens group 5, a dichroic mirror 6, a third optical path folding mirror 7, and an image sensor 8. The primary mirror 1 and secondary mirror 2 together form the optical receiving antenna of the optical imaging system. The image sensor 8, employing a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor, is located on the imaging side of the optical imaging system and is used to receive visible light ground object information in the 400-750nm wavelength band to generate a two-dimensional image of the target. The sensor size is 18.2 × 6.1 mm, and the pixel size is 7 μm. Simulation results show that the Airy disk radius of the optical imaging system is 10 μm, and the RMS radius of the actual diffuse spot is less than 4 μm, indicating excellent imaging quality. The modulation transfer function of each field of view of the optical imaging system exceeds 0.2 at the Nyquist frequency (72 lp / mm), demonstrating excellent optical system performance.

[0067] In the above embodiments, the present invention designs the primary reflector 1 and secondary reflector 2 of the integrated optical system of spaceborne lidar and optical remote sensing camera as freeform surfaces to increase more degrees of freedom for optimization. To address the asymmetry of the system in the sagittal direction, a freeform surface characterized by XY polynomials is used to correct aberrations. The surface profile of this freeform surface is defined by superimposing Taylor polynomials on a quadratic basis.

[0068]

[0069] Where k is the conic coefficient; c is the reciprocal of the vertex radius of curvature; N is the total number of polynomial coefficients in the series; A i Let X be the coefficient of the i-th XY polynomial.

[0070] The XY polynomial freeform surface parameters of the primary reflector in the above embodiments are shown in Table 1 (normalized radius is 100):

[0071] Table 1. XY polynomial freeform surface parameters of the primary reflector in the above embodiments.

[0072] <![CDATA[X 1 AND 0 ]]> -0.102 <![CDATA[X 3 AND 1 ]]> 0 <![CDATA[X 0 AND 1 ]]> 0.044 <![CDATA[X 2 AND 2 ]]> -3.859E-005 <![CDATA[X 2 AND 0 ]]> 0.027 <![CDATA[X 1 AND 3 ]]> 0 <![CDATA[X 1 AND 1 ]]> 0 <![CDATA[X 0 AND 4 ]]> 0 <![CDATA[X 0 AND 2 ]]> 0.017 <![CDATA[X 5 AND 0 ]]> 0 <![CDATA[X 3 AND 0 ]]> -1.115E-03 <![CDATA[X 4 AND 1 ]]> -7.979E-007 <![CDATA[X 2 AND 1 ]]> 1.539E-005 <![CDATA[X 3 AND 2 ]]> 0 <![CDATA[X 1 AND 2 ]]> -1.116E-003 <![CDATA[X 2 AND 3 ]]> 4.416E-006 <![CDATA[X 0 AND 3 ]]> -9.831E-005 <![CDATA[X 1 AND 4 ]]> 0 <![CDATA[X 4 AND 0 ]]> 0 <![CDATA[X 0 AND 5 ]]> 0

[0073] The XY polynomial freeform surface parameters of the secondary reflector in the above embodiments are shown in Table 2 (normalized radius is taken as 100):

[0074] Table 2 shows the XY polynomial freeform surface parameters of the secondary reflector in the above embodiments.

[0075] <![CDATA[X 1 AND 0 ]]> -0.402 <![CDATA[X 3 AND 1 ]]> 0 <![CDATA[X 0 AND 1 ]]> 0.439 <![CDATA[X 2 AND 2 ]]> 0 <![CDATA[X 2 AND 0 ]]> 2.689 <![CDATA[X 1 AND 3 ]]> 0 <![CDATA[X 1 AND 1 ]]> 0 <![CDATA[X 0 AND 4 ]]> 0 <![CDATA[X 0 AND 2 ]]> 1.695 <![CDATA[X 5 AND 0 ]]> 0 <![CDATA[X 3 AND 0 ]]> 0 <![CDATA[X 4 AND 1 ]]> 0 <![CDATA[X 2 AND 1 ]]> 0.221 <![CDATA[X 3 AND 2 ]]> 0 <![CDATA[X 1 AND 2 ]]> 0 <![CDATA[X 2 AND 3 ]]> 0 <![CDATA[X 0 AND 3 ]]> 0.220 <![CDATA[X 1 AND 4 ]]> 0 <![CDATA[X 4 AND 0 ]]> -0.019 <![CDATA[X 0 AND 5 ]]> 0

[0076] In the above embodiments, the present invention designs the first surface 16, the third surface 18, the rear surface of the fourth lens 12, and the front surface of the fifth lens 14 of the cemented doublet lens group in the integrated optical system of spaceborne lidar and optical remote sensing camera transceiver as even-order aspherical surfaces, thereby effectively correcting spherical aberration and improving the imaging quality of the system. The surface shape and height are described as follows:

[0077]

[0078] Where k is the conic coefficient; c is the reciprocal of the vertex radius of curvature; and r is the radial coordinate in lens units. α4, α6, α8, α 10 These are higher-order aspherical coefficients.

[0079] The even-order aspherical parameters used in the above embodiments are listed in Table 3 below:

[0080] Table 3 List of even-order aspherical parameters in the above embodiments

[0081]

[0082] Simulation results show that the integrated optical system of spaceborne lidar and optical remote sensing camera of the present invention is practical and effective.

[0083] The spaceborne lidar and optical remote sensing camera integrated optical system of this invention uses a common aperture design for the optical remote sensing camera, lidar transmitting system, and receiving system, avoiding the transmission and reception matching problems caused by the separate design of the laser transmitting system and receiving system. At the same time, the system integrates the active and passive detection capabilities of the spaceborne lidar and optical remote sensing camera, ensuring the spatiotemporal consistency of multi-source remote sensing images.

[0084] Existing spaceborne lidar systems generally employ a separate transmitting and receiving optical system. Transmitter-receiver matching is achieved through an optical axis monitoring camera, a laser footprint camera, and an offset angle adjustment mechanism to ensure the laser footprint is centered in the receiving field of view, thereby maximizing the reception efficiency of the target scattered signal. However, this design increases the system's complexity, size, and weight, hindering optimized integration into the spaceborne platform. The spaceborne lidar and optical remote sensing camera integrated transceiver optical system of this invention uses an off-axis dual-mirror afocal telescope as a common-aperture optical antenna, ensuring precise alignment of the laser beam's far-field spot with the center of the receiving field of view, fundamentally eliminating transceiver axis matching errors. Therefore, there is no need for additional optical axis monitoring cameras, laser footprint cameras, and offset angle adjustment mechanisms for transceiver matching, simplifying the system structure and improving system integration.

[0085] The spaceborne lidar and optical remote sensing camera transceiver integrated optical system of the present invention uses a primary reflector and a secondary reflector for three channels: optical remote sensing, laser emission, and laser reception. This greatly improves the system's integration, reduces the size, weight, and cost of the equipment, adapts to the aerospace remote sensing imaging environment, avoids the problem of satellite platform installation size limitations, and extends the operating time of remote sensing satellites.

[0086] The spaceborne lidar and optical remote sensing camera transceiver integrated optical system of this invention employs multiple optical path folding mirrors to achieve an optimized balance between system size and performance. Its overall envelope dimensions are 490mm (length) × 260mm (width) × 420mm (height), and its mass is ≤15kg. At a satellite orbital altitude of 500km, the system can achieve a ground pixel resolution of 1m for optical remote sensing (MTF@Nyquist>0.2) and a range resolution of 0.3m for lidar.

[0087] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An integrated optical system for satellite-borne lidar and optical remote sensing camera, characterized in that, The following components are arranged sequentially along the optical path: a primary reflector (1), a secondary reflector (2), a first optical path folding reflector (4), a cemented doublet lens group (5), and a dichroic mirror (6); the focal points of the primary reflector (1) and the secondary reflector (2) coincide. The optical system also includes: a lidar transmitting unit, a laser signal receiving system, and an optical imaging system; wherein: The lidar transmitting unit includes: a laser (3); The laser signal receiving system includes, in sequence along the optical path, a third lens (9), a field stop (10), a second optical path folding mirror (11), a fourth lens (12), a narrowband filter (13), a fifth lens (14), and a photodetector (15); The optical imaging system includes a third optical path folding mirror (7) and an image sensor (8) arranged sequentially in the optical path direction; the image sensor (8) is used to receive visible light ground object information and generate a two-dimensional image of the target; The laser beam emitted by the laser (3) is reflected by the secondary reflector (2) and the primary reflector (1) in sequence, and then the beam waist radius is expanded, the divergence angle is reduced, and the beam is directed toward the ground. The dichroic mirror (6) is used to separate the laser signal from the visible light band, so that the laser signal is refracted and reflected onto the third lens (9), and the visible light is converged to the image sensor (8) through the dichroic mirror (6) and the third optical path folding mirror (7). After being reflected, the ground laser signal is received by the laser signal receiving system. It passes through the primary reflector (1), secondary reflector (2), first optical path folding reflector (4), doublet lens group (5), dichroic mirror (6), third lens (9), field stop (10), second optical path folding reflector (11), fourth lens (12), narrowband filter (13) and fifth lens (14) before being received by the photoelectric detection device (15).

2. The integrated optical system for spaceborne lidar and optical remote sensing camera as described in claim 1, characterized in that, The mirror surface of the main mirror (1) is a free-form surface characterized by an XY polynomial based on a parabolic surface. The diameter of the mirror surface is a rectangle of 260mm×360mm and the radius of curvature is -720mm.

3. The integrated optical system for satellite-borne lidar and optical remote sensing camera as described in claim 1, characterized in that, The secondary reflector (2) has a reflective surface that is a free-form surface characterized by an XY polynomial based on a parabolic surface. The reflective surface has a diameter of 32mm × 44mm and a radius of curvature of -72mm.

4. The integrated optical system for spaceborne lidar and optical remote sensing camera as described in claim 1, characterized in that, The laser (3) is a semiconductor-pumped Nd:YAG pulsed laser that emits a 1064nm wavelength laser beam. The pulse energy is 1.5mJ, the pulse width is 2ns, the repetition frequency is 10kHz, the spot size is 2mm, and the divergence angle is 0.68mrad.

5. The integrated optical system for satellite-borne lidar and optical remote sensing camera as described in claim 1, characterized in that, The cemented doublet lens group (5) includes, in sequence, a first lens (5.1) and a second lens (5.2) in the optical path direction; The center thickness of the first lens (5.1) is 6 mm, and the center thickness of the second lens (5.2) is 3 mm.

6. The integrated optical system for spaceborne lidar and optical remote sensing camera as described in claim 1, characterized in that, The dichroic mirror (6) is an optical glass with a dichroic film coated on its surface.

7. The integrated optical system for spaceborne lidar and optical remote sensing camera as described in claim 1, characterized in that, The image sensor (8) is a CMOS sensor and is located on the imaging side of the optical imaging system.

8. The integrated optical system for spaceborne lidar and optical remote sensing camera according to any one of claims 1-7, characterized in that, The visible light band is 400-750nm.

9. The integrated optical system for spaceborne lidar and optical remote sensing camera according to any one of claims 1-7, characterized in that, The laser ground footprint is located at the center of the receiving field of view of the laser signal receiving system.

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