Detection and recognition of space objects with ground-based photoelectric systems is one of the major technical ways for space situational awareness. During the past thirty years, there has been significant development of optical telescopes dedicated to wide-field surveys of time-dependent deep space phenomena, slow-moving near-earth objects (NEOs) and fast-moving earth-orbiting space debris. While telescope fields of view have gradually increased, a single technical approach has not emerged as the dominant design. To design an effective wide-field telescope for sky survey or space surveillance, It is necessary to carefully match the characteristics of the optical system (layout, aperture, focal ratio and modulation transfer function) with those of the observing site (sky brightness, transparency, seeing and elevation), the detector (pixel pitch, quantum efficiency, read rate and read noise), and the observing program (target brightness, target motion, observing strategy and feature extraction software). In this paper, we design a telescope with wide field of view (≥2.5°×3.5°) and large aperture (1.1m). The focal length of the system is 1.5m, F/# is 1.36. Because of the small Fnumber and wide field of view, we choose the prime focus corrector structure which has single mirrors with refractive prime focus correctors. Moreover, the especial requirements of the Modulation Transfer Function (MTF), spot, energy concentration, and distortion etc. are all satisfied.
Since the concept of wavefront coding was proposed, many types of phase masks have been reported to extend the depth-of-field of imaging system. Unfortunately there exist some unpleasant image artifacts in the final decoded images, especially for asymmetric phas1 e masks. In this paper, we illustrate a technique that involve shifting a phase mask laterally in pupil plane to introduce axial defocus to an imaging system, which can further be used to determine the defocus map according to the amount of image artifacts. This eventually enables recovery of extended depth-of-filed, artifacts-free decoded images together with a range map. Theoretical analyses and experimental results indicate the effectiveness of this method. Keywords: wavefront coding,
A kind of high accuracy Photo-electric auto-collimator based on PSD was designed. The integral structure composed of light source, optical lens group, Position Sensitive Detector (PSD) sensor, and its hardware and software processing system constituted. Telephoto objective optical type is chosen during the designing process, which effectively reduces the length, weight and volume of the optical system, as well as develops simulation-based design and analysis of the auto-collimator optical system. The technical indicators of auto-collimator presented by this paper are: measuring resolution less than 0.05″; a field of view is 2ω=0.4° × 0.4°; measuring range is ±5′; error of whole range measurement is less than 0.2″. Measuring distance is 10m, which are applicable to minor-angle precise measuring environment. Aberration analysis indicates that the MTF close to the diffraction limit, the spot in the spot diagram is much smaller than the Airy disk. The total length of the telephoto lens is only 450mm by the design of the optical machine structure optimization. The autocollimator’s dimension get compact obviously under the condition of the image quality is guaranteed.
The laser tracker is composed of a mechanical structure and a servo control system. And the characteristics of them all affect the error and stability of the laser tracker measurement system. In the dynamic characteristics, the mechanical structure has its natural frequency and the servo control system has servo bandwidth. If the natural frequency closes to the servo bandwidth, the noise produced by system will have an influence on the stability and measure precision of the turntable. In order to make a laser tracker take a good performance, the natural frequency has to stay away from the range of the servo bandwidth. Based on this relationship between the natural frequency and servo bandwidth, construct and simplify a 3D model, analyze the influence of material stiffness, friction and rotary inertia on the natural frequency of a self-developed laser tracker turntable. Analysis shows that the natural frequency augments with the increase of material stiffness and reduction of rotary inertia and has nothing to do with friction. And factors of the structure material influence the different orders of natural frequency differently. These conclusions show that the kind of material with low density and high stiffness is more fitted to the turntable and provide references for optimization design of precision laser tracking turntable.
A kind of space target acquisition optical system with small F-number was designed. The system had a working wavelength range of 0.45~0.85μm, an effective focal length of 240 mm, a field of view is 2ω=3°, and an F-Number of F/2. The system characteristic is that the structure is simple. And the especial requirements of the spot, energy concentration, distortion and lateral color etc. are all satisfied. The primary and secondary mirrors are all spheres, so the difficulty and cost of machining are reduced. Moreover, the temperature characteristic of the system is analyzed. The temperature request is satisfied.
Proc. SPIE. 9142, Selected Papers from Conferences of the Photoelectronic Technology Committee of the Chinese Society of Astronautics: Optical Imaging, Remote Sensing, and Laser-Matter Interaction 2013
The photoelectric rotary and angle encoder is a digital angle measuring device, which is integrated with optics, mechanics and electrics. Because of its simple structure, high resolution, and high accuracy, it has been widely used in precision measurement of angle, digital control and digital display system. With the needs of fast tracking and accurate orientation on the horizon and air targets, putting forward higher requirements on accuracy of angle measurement and resolution of photoelectric rotary and angle encoder. Influences of manufacturing, electronics segmentation, optical and mechanical structure and eccentric shaft to photoelectric encoder precision and reducing methods are introduced. Focusing on the eccentricity error, building up an error correction model to improve the resolution of angle encoder and the model was verified by test.
With the development of space technology, more and more Rendezvous and Docking (RVD) mission require more precise measurement of relative position and attitude between tracking spacecraft and target spacecraft. In the procedure of docking between near spacecraft , the optical retroreflector on the target Spacecraft were tracked by the laser tracking and ranging device on the tracking spacecraft , the distance data were provided by laser ranging system, and the azimuth data were provided by tracking gimbal, Synthesized the distance data and azimuth data, the relative position information between two spacecraft were provided to the target spacecraft. Furthermore, through tracking more than three point on the target spacecraft ,the complete information of relative position and attitude between two spacecraft were calculated rapidly by the measurement system，which were presented to the control system during the whole RVD operating stage. The laser tracking technology guaranteed continuous measurement and supplied accurate azimuth information, and the laser ranging technology ensured high accuracy of distance information. In addition, the untouched measure mode give no disturbance to the docking operation, moreover, the monochromaticity of laser make the tracking and ranging procedure avoiding to be disturbed by parasitic light of space, thus there will be a effective measurement accompanying the whole docking operating procedure and affording valid data to the control system of docking.