Design Of Integrated Optical System For Detection And Recognition Based On Continuous Zoom Structure

With the exploration of space by human beings,the direction of future development will gradually change from earth to space.As the cornerstone of the development of space economy,the security of space field occupies a pivotal position.Efficient and continuous monitoring of space becomes even more important.Space debris is a major threat to spacecraft.It is necessary to collect the position and velocity information of a large amount of debris in real time,and to identify the type,shape of space debris.The spacecraft can effectively deal with the threat source.Optical detection system can track specific space debris and collect its geographic location information.The identification imaging system can obtain high-resolution target’s image information.Some researchers have integrated the two systems.However,most of these integrated systems are spectroscopic.It has low utilization of light energy.Due to the spectroscopic design,it is necessary to deploy two detectors,supporting circuits and mechanical structure for the detection channel and the identification channel.It will occupy a huge volume.As a space-based integrated system,it increases the cost of satellite’s launch.In order to realize the multi-functional tracking and monitoring of space debris,the detection system and the identification system are combined by zoom structure.Specific targets in space area are accurately detected and identified in detail.Improve the tracking and detection ability of small and dim targets.Improve the judgment accuracy of target’s category and behavior.Compared with the traditional integrated optical system solution,the traditional integrated optical system has weak detection ability and low signal-to-noise ratio of the imaging system.The lens group of each subsystem occupies a large volume of space.In this paper,another solution of detection and imaging integrated optical system is proposed and designed through the change of the relative position of components.It realizes the basic working mode of different relative positions corresponding to different focal lengths.The system is divided into long focus with small field state and short focus with large field state.The short focus position completes the detection of multiple targets,and the long focus position completes the identification of specific targets.This method solves the problem of uneven distribution of light energy.It reduces the detection difficulty of dim targets caused by low energy level.The design improves the imaging quality and limits the overall volume and weight of the system.In order to achieve the zoom integrated optical design,after determining the index of the optical system,select a reasonable acquisition method for detection and recognition.The optical design parameters of the integrated optical system are calculated by the detection sensitivity and target resolution,including focal length,field,effective aperture.Then,based on the principle of zoom amplification of non-focus optical path,zoom the traditional small zoom focus system.Complete the initial structure design of zoom optical system of long focus segment.The magnification of the afocal structure is 9 times.The focal range of the initial zoom structure is133.3mm～233.3mm,and the focal range of the final integrated optical structure is1200mm～2100mm.The afocal structure takes the form of objective lens+eyepiece with one image plane.The focal length of objective lens is 1800 mm with reflective structure.The focal length of the eyepiece is 200 mm.Both the eyepiece and zoom structure are lenses,and if the eyepiece is designed with the reflector part,a large amount of aberration is introduced into the eyepiece,so the eyepiece and the zoom structure are combined for design.Theoretically,it becomes a finite conjugate distance zoom design with magnification β= 0.667～1.1667.By calculating the initial structure parameters of zoom theory,we assign the degree of focus and the distance of each component.The computer automatically calculates the corresponding zoom position.The exit pupil of the reflector structure is the entrance pupil of the system.The reflector structure image height is the height of the system object.The aberration coefficient of each element is calculated by PW method,and a reasonable lens group is selected.Then,complete the initial scheme design of the zoom structure.Combine the reflector structure with the zoom structure.Although pupil matching was completed,the image quality will slightly reduce after combining the front and back groups.It needs to be optimized again to get the final structure of the system.After image quality evaluation and energy analysis of the detection envelope circle,80% of the energy of the detection part is located in the circle with diameter of 18.4.μm.The system can detect very dim targets in space.The image points in each field of the imaging system are within the diffraction limit.The modulation transfer function(MTF)of the edge field is greater than 0.26 at 108.7lp/mm Nyquist frequency,and the image quality is good.The energy concentration and MTF in the middle focal state varies steadily.After tolerance analysis,the imaging status has a strict tolerance for preanalysis.After tightening the strict tolerance,the 80% probability of MTF in meridiandirection(TAN)at 108.7lp/mm in edge field decreases to 0.221,and 80% the probability of MTF sagittal direction(RAD)at 108.7lp/mm in edge field decreases to0.231.Under the tolerance of imaging state,the 80% probability of encircle energy distribution in detection state is in a circle with a diameter of 18.4μm.The detection ability and imaging quality are at a high level.The design of integrated optical system for detection and recognition with zoom structure has the potential of processing and manufacturing.