This article aims to solve the problem of indoor calibration technology for star sensors, and conducts research on a digital micro mirror (DMD) based star simulator spectral simulation system. It designs and constructs a digital micro mirror based star simulator spectral modulation system, mainly composed of a dynamic star simulator spectral modulation system based on DMD and a dynamic star simulator LCOS high contrast splicing display system, In conjunction with the basic components of the collimating optical system for projection and other star simulators, the output of star maps containing simulations of stars with different color temperatures has been achieved. At the same time, an experimental device for dynamic star simulator spectral modulation system based on DMD was built to verify the main technical indicators of the star simulator spectral system based on digital micro mirrors (DMD).
As a ground calibration equipment for star sensors, the dynamic star simulator mainly aims to verify the star point centroid extraction algorithm, star map recognition algorithm, and star map spectral matching algorithm for star sensors. According to the requirements of star sensors for star point characteristics, dynamic star simulators should have the following three functions.
① Navigation star map display
In response to the requirement of a large field of view for star sensor lens imaging, LCoS splicing is used to achieve a large field of view and high contrast display of the navigation star map.
② Simulation of star point spectra
Star point spectral simulation mainly calibrates the star sensor star map spectral matching algorithm. Therefore, the spectral information of star points is added through an optical system.
③ Star point distance simulation
The simulation of star point distance is mainly aimed at simulating the infinite light emitted by stars. Therefore, the imaging optical system of the dynamic star simulator adopts a collimating optical system for projection, and the spatial light modulator LCOS is placed at the focal plane of the optical system to achieve the simulation of parallel light.
The composition of the splicing LCoS dynamic star simulator includes a spectral modulation system based on DMD, a dual LCoS high contrast splicing display system, a collimating optical system for projection, a mechanical system, and a star map display control system. As shown in Figure 2.5.
Among them, a spectral modulation system based on DMD is used to simulate different spectral color temperature curves; The dual LCoS high contrast splicing display system is used to achieve the splicing of two LCoS pieces to expand the effective field of view; A collimating optical system for projection is used to emit star maps on two LCoS images in the form of parallel light, achieving distance simulation of infinite star maps; The mechanical system is used for the connection of spectral modulation systems based on DMD, dual LCoS high contrast splicing display systems, and collimating optical systems for projection, ensuring that their design indicators are achieved; The star map display control system is used to control the star map display on two LCoS chips, and can generate real-time star map simulation according to the requirements of the star sensor.
During operation, the dynamic star simulator uses a spectral modulation system based on DMD to emit light within a certain wavelength range that meets the simulation of a specific spectral color temperature curve, illuminating the dual LCoS; Under the action of a high contrast stitching display system, the dual LCoS achieves high-precision stitching and maintains consistent contrast. At the same time, the dual LCoS is controlled by the star map display control system to display the real-time star map required by the star sensor; The projection uses a collimating optical system to image the dual LCoS after being processed by a high contrast stitching display system, and emit it in the form of parallel light.
The DMD based star simulator spectral simulation system mainly consists of a dynamic star simulator spectral modulation system based on DMD, a dynamic star simulator LCOS high contrast stitching display system, and a collimating optical system for projection.
(1) Dynamic Star Simulator Spectral Modulation System Based on DMD
The spectral modulation system based on DMD dynamic star simulator consists of a xenon lamp fiber light source, a Czerny Turner type optical path containing reflective gratings and DMD, and a spectral coupling module. Its main function is to fit the star color temperature curve of a specific color temperature, and achieve the technical specifications of the spectral modulation system in the overall design.
(2) Dynamic Star Simulator LCoS High Contrast Mosaic Display System
The dynamic star simulator LCoS high contrast stitching display system consists of a polarizing beam splitter prism (PBS) and two silicon-based liquid crystals (LCoS). Its main function is to achieve high contrast display of navigation star maps and achieve the LCoS high contrast stitching display system star level simulation technical indicators in the overall design.
(3) Collimating optical system for projection
According to the light projection principle of the star simulator, the space light modulator (LCoS) is placed on the focal plane of the collimating optical system. After receiving the star map display command sent by the upper computer, the modulated incident light casts parallel light through the collimating optical system to simulate the star point position in the infinite star sky for star sensor to identify the star map. Implement the optical technical specifications of the collimating optical system for projection in the overall design. This article mainly focuses on the calibration of star map spectral matching algorithms for star sensors. Therefore, the focus is on studying the dynamic star simulator spectral modulation system based on DMD and the dynamic star simulator LCOS high contrast stitching display system based on DMD. For the collimating optical system used for projection, only the design results are provided.
The DMD based star simulator spectral simulation system mainly consists of three parts, namely the dynamic star simulator spectral modulation system based on DMD, the dynamic star simulator LCOS high contrast stitching display system, and the collimating optical system for projection. Figure 2.7 shows the overall structure of the DMD based star simulator spectral simulation system.
This chapter clarifies the main information to be included in the star point navigation map of a dynamic star simulator by introducing the basic theory of star navigation. Based on the requirements of star sensors for star point characteristics, determine the main indicators of the dynamic star simulator spectral simulation system for research. Based on the main technical indicators, a simulation scheme for the color temperature curve of stars was determined. Based on this scheme, the overall scheme design of a DMD based star simulator spectral simulation system was completed. The overall scheme includes a dynamic star simulator spectral modulation system based on DMD that needs to be studied, a LCoS high contrast splicing display system for dynamic star simulators, and a collimating optical system for projection that only provides results.
Send us a message,we will answer your email shortly!
TY-Space Technology (Beijing) Ltd. is professional focusing on advanced attitude optical sensors, especially Star Trackers for space industry.
