Study On Alignment Method And Testing Technology Of Fiber Folded FOV, High Resolution Power Hyperspectal Imager

The imaging method, principle and component of wide FOV, high resolution, hyperspectal imager are key technologies of the field of space remote sensing. The high resolution, hyperspectal imager integrate with satellite platform constitute the various types of space remote sensor, which are widely used in aerospace industry. A primary problem is a relative narrow FOV of hyperspectal imager at the present stage, which correspondingly swath can’t satisfy the operational space application requirements. Consequently, expand the FOV of high resolution, hyperspectal imager, and develop the new conception, new technique has important application value and academic significance, become a focal point and frontier of future development of high resolution, hyperspectal imager technology.In our development of the“fiber folded FOV, high resolution hyperspectal imager”, put forward a new conception and new principle of high resolution hyperspectal imager, application of fiber image transmission technology, which can greatly expands the field of view (FOV) of hyperspectal imager. The new imaging method causes particularity and novelty of optical structure in the instrument. Therefore, there are new contents in imaging quality evaluation and system alignment field needs deeply discussion and research. The paper based on imaging principle of the prototype, study on the aligning method and evaluation technology of fiber folded FOV hyperspectal imager. The main contents and results of the article are as follows.1. Because conventional imaging spectrometer use fixed edge slit to achieve the separation of view field, and conventional slit is continuous spatial, therefore the coupling between detector and slit satisfied linear, space-invariant hypothesis. The fiber folded FOV imaging spectrometer use discrete sampling fiber-optic image bundles to achieve folding of FOV. The paper start with this character, from the theoretical model and experiment method focus on the using of coupled contrast transfer function as basis for evaluation, to alignment the pixel of detector and fiber array. Alignment test was done and followed with laboratory tests, outdoor spectral imaging test at last.2. Based on the engineering designing of fiber folded FOV imaging spectrometer prototype, study on the method of alignment, proposed the process of alignment of prototype. The paper summarized the assembly technology, mounting and evaluating methods for coaxial refraction optical system. Moreover, proposed the aligning methods for telescopic imaging lens, collimation lens of spectrometer, imaging lens of spectrometer in the prototype, and complete the alignment experiment. Through the test of key parameters, paper verified the feasibility of alignment method.3. The paper analysis the discrete sampling process of fiber-optic image bundles as the key component of the prototype. Study on the sampling and reconstruction process of fiber-optic image bundles to the input signal. According to the definition of the contrast, paper study on the expression of contrast transfer function for fiber-optic image bundles, under the square wave input. The paper deduced mathematical model of contrast transfer function of fiber-optic image bundles, and based of it to simulation the output character and cycles of fiber-optic image bundles under the square wave input.4. The paper study on the characters of contrast transfer function of fiber-optic image bundles. The research based on mathematical model to study on the effect law of fiber number, initial position, and frequency domain of input signal to CTF of fiber array. Conclusions are obtained as followed: At the Nyquist frequency and frequency-division, the CTF oscillation with initial position. At the frequency domain very close to Nyquist frequency and frequency-division, the CTF of fiber-optic image bundles convergent to a fixed value. The law of convergence is: With the smaller frequency deviation, the CTF convergent with the increasing of fiber number to a fixed value on slower rate. When the deviation of frequency more than 10%, simulation results show that, the fiber number and initial position little effect to CTF of fiber-optic image bundles. 5. According to the aligning error of pixel between fiber-optic image bundles and detector, the paper study on the responding character of coupled sampling imaging system, constituted by fiber-optic image bundles and detector, to square wave input. The mathematical model of coupled contrast transfer function is deduced as followed. And the definition of average initial position contrast transfer function, and average coupled contrast transfer function is described later. The paper simulates the effect law between initial position, character of input frequency domain, coupled error and coupled contrast transfer function. The results show that, at the frequency domain less than Nyquist frequency, coupled contrast transfer function and its initial position averaging oscillation cycle with the coupled error. The closer of frequency of input signal, the little number of fibers in the bundles, and the larger of initial position, the coupled contrast transfer function has greater amplitude with the coupled error. In addition, within this frequency domain, the average coupled contrast transfer function of coupled discrete sampling system dose not satisfied the cascade multiplication rule.