Laser three-dimensional imaging system with real-time wavefront compensation function
Technical field
This patent is related to the aberration active compensation techniques, in particular to one kind of satellite borne laser three-dimensional imaging receiving optics
Large aperture telescope is compensated since gravity or thermal deformation cause the scheme form of multinomial aberration using progressive thickness plane deformation mirror.
Background technique
Laser three-dimensional imaging radar is a kind of for accurately and fast obtaining the master on ground and ground target three-dimensional spatial information
Dynamic formula the radar exploration technique system is round-the-clock sensor, small with being interfered by earth background, sky background, and has Gao Ding
The advantages that position precision and highly sensitive, laser pulse are not influenced vulnerable to shade and sun angle, adopts to substantially increase data
The quality of collection.These features enable it to meet the scouting of High-precision high-frequency degree quick environment, the especially hidden mesh of military target monitoring
Mark the application requirement of detection.
In terms of the development trend of domestic and international space camera, laser terrain following radar MOLA, GLAS of the transmitting of the states such as America and Europe etc. exist
Technique preparation is done in terms of heavy caliber and high-resolution.In order to realize ground imaging resolution better than 4m, altimetry precision better than 0.5m
The development of spaceborne three-dimensional laser imaging radar, Image-forming instrument include operating temperature range and crucial mirror temperature to thermal control technology
The requirement of the indexs such as gradient is very strict, challenges for existing thermal control technology very big.It is defended simultaneously for microminiature
For star, volume, weight and power consumption have stringent limitation, and the permission weight for distributing to heat control system is extremely limited, this is wanted
It asks and substantially increases the difficulty of thermal control design.Equally, heavy caliber three-dimensional radar after transmitting track operation during, due to ground
Different from the environment of space, mirror surface must endure as the release deformation of gravity caused by in-orbit microgravity environment, and this deformation can only be
Ground applies stress and carrys out stimulated microgravity, but simulated conditions have differences with truth, lead to instrument in orbit
Imaging characteristics are inconsistent with ground tests.
Current Airborne Lidar examining system in order to solve these problems, be using passively inhibit error source method come
Realize the imaging of high quality.The method that plane turning mirror is focused is inserted into generally in radar optical path to become to reduce mirror temperature
Influence of the shape to optical system picture element.This method can only solve the problems, such as defocus, spherical aberration, intelligent caused by deforming to mirror temperature
The higher order aberratons such as difference, astigmatism then seem helpless.Control the error that different error sources generate need using different technology and
Method, and interact and compromise and error is maintained to certain level with optical design, structure design.Radar is in orbit
When, other than focus adjusting mechanism can compensate for certain defocus and spherical aberration, these passively technology and methods to being likely to occur
Other aberration compensation effects are unobvious.From the perspective of optical system imaging, error caused by power, thermal environment factor is finally all
The wave front aberration of optical system is shown as, high-order spherical aberration, coma and astigmatism etc. can be generated.Therefore, active deformation mirror technology is from control
Error source processed is set out, and directly can be inhibited and be compensated for imaging wave front aberration.It is adopted in laser three-dimensional imaging radar
It is enhancing space camera to power, the adaptability of thermal environment with active deformation mirror technology, simplifies camera structure, reduce camera power consumption and mention
New method is supplied, also the space camera for more heavy caliber, more long-focus provides technological approaches.
Summary of the invention
In conclusion how active deformation mirror technology to be combined with large aperture telescope to solve space environment adaptability
The problem of, a kind of new technological means is provided for Study of Laser three-dimensional imaging radar.For this purpose, the purpose of this patent is to provide one kind
Plane deformation mirror technology based on progressive thickness.
This patent be the laser three-dimensional imaging system with real-time wavefront compensation function, including telescope imaging system 1, point
Beam mirror 2, Hartmann sensor 3, plane deformation mirror 4 and imaging CCD camera 5.
400-800nm wavelength imaging beam and 1064nm wavelength detecting light beam from atural object pass through telescope imaging respectively
System 1 converges to beam splitter 2,1064nm wavelength detecting light beam after the transmission of beam splitter 2 on Hartmann sensor 3, Hartmann
The 1 wavefront distortion information of telescope imaging system in detection light beam is analyzed and obtained to sensor 3, and wavefront distortion result is fed back to
The control system of plane deformation mirror 4 produces plane deformation mirror 4 by the piezoelectricity PZT sensor of control system driving plane deformation mirror 4
Raw surface deformation carrys out the wavefront distortion of real-time correction telescope imaging system 1;The atural object imaging beam of 400-800nm wavelength simultaneously
Plane deformation mirror 4 is reflexed to by beam splitter 2, image deformation wavefront is imaged onto imaging CCD camera after the compensation of plane deformation mirror 4
On 5.
The telescope imaging system 1 is a Cassegrain telescope, is formed by two-mirror reflection is aspherical, face shape is equal
For quadratic surface.
The beam splitter 2 is a quartz material optical filter, by system wave front acquisition wavelength 1064nm and imaging wavelength
Both 400-900nm are separated.
The plane deformation mirror 4 is a plane aluminium reflector, at before telescopic system focal plane 50 to 100mm,
Mirror surface bore 100mm has progressive thickness t variation as follows with half bore x relationship: T=8.09514+0.24526x-
0.04266x2+0.00174x3-2.90602E-5x4+1.73128E-7x5.Plane deformation mirror 4 is driven using piezoelectricity PZT sensor
Surface deformation is generated, there is attaching clamp in plane deformation mirror central area, and mirror edges circumferential plane is that sensor reinforces region, pressure
Electric PZT sensor generates displacement and then causes to deform to mirror edges.It is right according to the wavefront variation that Hartmann sensor 3 measures
Wavefront carries out data processing, obtains spherical aberration, coma and astigmatism data;According to this data, controls 4 face shape of plane deformation mirror and reversely produce
Raw aberration, to realize the compensation to telescope imaging system spherical aberration, coma and astigmatism wavefront distortion.
The plane deformation mirror in heavy caliber high-resolution laser three-dimensional imaging radar optical path is worked according to this patent, will be passed
System focusing lens are modified to active deformation mirror, it will be apparent that improve the ability of system balance aberration.The advantages of this patent system, is as follows:
1. applying in heavy caliber high-resolution laser three-dimensional imaging radar, receiving telescope primary mirror bore is greater than
500mm, imaging instantaneous field of view are better than 5 μ rad.
2. the thickness of active deformation mirror is gradual change form with bore variation, this form makes shape behind mirror surface flexible deformation
It is small to generate high-order residual error, residual error is only 10E-6mm when plane aperture of mirror is 100mm, overcomes uniform thickness mirror surface and generates high-order picture
Difference influences the problem of optical system imaging quality.
3. active deformation mirror can generate the Curvature varying or astigmatism of needs using single-point drive scheme, drive scheme is simple
It is easy.
4. active deformation mirror can compensate the spherical aberration or astigmatism variation of low order or high-order, it is suitable for space environment gravity deformation
With the correction of temperature deformation.
Detailed description of the invention
Fig. 1 is index path of the plane deformation mirror in laser three-dimensional imaging radar telescope;Wherein: 1- telescope imaging system
CCD camera is imaged in system, 2- beam splitter, 3- Hartmann sensor, 4- plane deformation mirror, 5-.
Specific embodiment
The main technical characteristics of laser three-dimensional imaging system and compensation method with real-time wavefront compensation function are as follows:
1. telescope imaging system: primary mirror bore 500mm, 5 μ rad of imaging space resolution ratio.
2. plane deformation mirror: bore 100mm has progressive thickness curve, can compensate for spherical aberration, coma and the astigmatism of system,
Residual aberration is less than 10E-6mm.Planar thickness t variation is T=8.09514+0.24526x-0.04266x with half bore x relationship2
+0.00174x3-2.90602E-5x4+1.73128E-7x5。
3. plane deformation mirror drive: reinforcing mode using center built-in edge, when driving moment is 200N, generate
Spherical aberration, surface deformation amount are 1.15mm;When vertical mirror surface both direction reinforces 105N and 5N respectively, astigmatism is generated, astigmatism becomes
Shape amount is 0.55mm.
4. system uses closed-loop measuring and control mode, the wave of telescope imaging system is first measured by Hartmann sensor
Preceding variation, then plane deformation mirror is driven to generate opposite aberration, to realize aberration compensation.
5. Hartmann sensor unit contains information collection and data processing module, before advanced traveling wave after information collection, then
The aberration of wavefront is obtained by processing module as a result, providing foundation for aberration correction.