Research On Multi-spectral And Multi-axis Collimation

In modern military optoelectronic systems, in spite of military weapons and equipments with a single spectrum, a multispectral application combining with visible light, laser and infrared has been formed. Therefore, the consistency of multi-optical axis such as Television sight axis, Infrared sight axis, Laser emission axis has play a important rule in the accuracy of the target detection and information acquisition. In order to achieve fast and accurate calibration of the consistency of the multi-axis in a multispectral photoelectric tracking device, a calibration system is designed based on the consistency of optical axis of Cassegrain.The system use a halogen lamp as visible light source, a blackbody as infrared light source, a star-point reticle with ZnS glass substrate provides infinity target, the system aperture being200mm, focal length being1500mm, Parallel to the axis point better than the outgoing light10",just meet the needs of multi-spectral detection in multi-axis consistency requirements1’.1. For the characteristics of the optical collimation system, the paper designs an achromatic reflective collimator.By analyzing the traditional reflective collimator, a collimated optical system based on Cassegrain is designed. Using ZEMAX optical design software to resolve and conduct optimized design of the original structure of the optical systems, ultimately a coaxial Cassegrain optical system consisting of a hyperbolic primary mirror and a hyperbolic secondary mirror is designed, with its diameter being200mm, focal length being1500mm. type.The system selects MTF as a way of qualitative evaluation, making the result more reliable and objective.Evaluation results show that the image quality is even, Visible close to0.8at40line pairs at the MTF value,while at15lines of mid-infrared at0.4MTF, the system resolution meets the detecting requirements of the detector parts.2. According to the structural parameters after the optimization of the optical design, plus the size design of the existing instrument, the system gives a structural size and begin the modeling of collimation system with Solidworks. The shell is cylindrical. Taking into account of the high strength to be standed by the device, wire-electrode cutting technique is used to process integrally both the inner and outer ribs. The diameter of primary mirror is200mm with center thickness being25mm, the diameter of secondary mirror is44mm with center thickness being4.5mm. The distance between primary and secondary mirror is234mm and this relative position of the two lenses can be fine-tuned through a washer. the secondary mirror holder takes the shape of three blades.In the reticle part, theexperiments use a highly bright and clear hole-type reticle which is easy to capture images.At infinity target generator design part, the uniformity of the light source also enhances by using a fly-eye lens groups, all those bring convenience to the later image acquisition.3. The paper realized the spot centroid algorithm based on CCD technology, through analysis and comparison of various types of centroid algorithm, ultimately raise the centroid method to handle the collected spot image, which is accurate and easy to use.Detection can be automated and the impact of human factors can also be reduced. Lumenera’s Lul30CCD is used in the experiment, the pixel is1392×1040, pixel size4.65x4.65um. In the position of the CCD detector,there placed a conjugate partition target system, through CCD, it collects images emitted by the infinity generator. After reading the target and background, adjusting the gray scale values, filtering noise, marking connected domain, extracting spot position, the coordinates of spot center can be obtained, and then come to the deviation of optical axis consistency of the system.Experimental results verifies the feasibility of the method and reliability of the instrument.