Experimental program is designed to analyze the radiation and absorption characteristic of the sky background at near-infrared Oxygen A absorption band of passive ranging based on Oxygen spectral absorption; an acousto-optic tunable hyper spectral imaging spectrometer is used as the measuring device. Under the condition of sunny, cloudy, and snowy weather, the sky background spectral distribution is collected using the acousto-optic tunable hyper spectral imaging spectrometer. Then the Oxygen absorption rate is calculated according to the principle of Oxygen spectrum absorption passive ranging. The measurement result shows: absorption lines exist in the sky background spectral distribution at the Oxygen A absorption band, and the absorption rates are different at different weather conditions. The Oxygen absorption rates are the biggest under snowy weather, bigger under cloudy weather, and the smallest under sunny weather. The general change pattern of Oxygen absorption rate under different weather conditions is obtained and the result has laid solid foundation for suppressing the interference of the background and extracting target spectral accurately in subsequent passive ranging researching.
An approach of in-situ measuring the complex response of a scene spatial light modulator which working in differential
state was presented by using an image of Ronchi grating substituted for a concrete one. Its principle and testing method
have been studied and a typical XGA2L11 spatial light modulator has been characterized. The scene image under
complicated background has been edge enhanced by mapping the measurement results, and the correlation results
showed that scene spatial modulator with the differential state can increase the SNR and PCE of correlation peak. The
way could be wholly applied in Vander Lugt Correlator and has very strong practicability and effectiveness.
A method for measuring refractive index of plate glass by joint transform correlative technique is given. In the one of two correlative light beams passing through the two correlative images of certain separation in input plane, a unknown refractive index and known thickness plate glass is inserted with a certainty angle (θ). Joint transform power spectrum (JPS) is recorded separately at the back focal plane of the lens by a CCD detector when Θ = 90° or Θ = 45°, the JPS is sent to the LCD on the input plane by the computer. Then two groups of correlative points will be recorded separately by the CCD detector. On the basis of the interval difference value between two groups of altered correlative points, the refractive index is calculated. Theory analysis and examination result are given.
Multiple synthetic discriminant function (SDF) filters has been verified to be a better strategy for distortion invariant optical pattern recognition, especially for the in-plane rotation invariant ones. However, how to select the training sets is very crucial for the filter’s validity. In this paper, referring to the Rayleigh criteria, the distortion tolerance of a single matched spatial filter (MSF) has been tested by using a digital-optical hybrid 4f correlation system. Experimental results are ±5° and ±8% for the rotation and scaling distortion tolerance, respectively. According to the results, an equal correlation peak phase-only SDF algorithm has been adopted to synthesize two SDF filters, in which the training set images have been correspondingly selected with 5° and 10° intervals. The SDF filter constructed with 10° interval training sets has demonstrated as good performance as that one with 5° interval, but with the advantage of reduction by half of the number of multiple SDF filters for 360° full-rotation, which indicated that the double of distortion tolerance selected as the interval of training images is more suitable for real-time correlator recognitions.