In this paper, an integrated hyperspectral imaging sensor array technology by using arrayed diffractive micro-optics elements for driving infrared beams with chosen wavelength into designated subsensors is proposed. The diffractive optical element, which can be treated as a functioned microlens here, collect the incident Gaussian beam or other types of infrared beams out-from targets and then concentrate the incident light into desired monochromatic point pattern or arbitrary distinct hyperspectral image at the imaging plane based on phase transformation and diffraction propagation process. For the incident infrared beams with different wavelengths, the arrayed diffractive micro-optics elements is designed based on the diffractive integral theory, and the weighted iterative phase retrieval algorithm is modeled so as to obtain the needed phase distribution, and therefore the frequency spectrum of the incident beams can be separated locally in different locations over the focal plane according to designated wavelength. We can then achieve beam-splitting imaging by placing sensor array (4×4 pixels per subsensor) on the focal plane at locations that correspond to different wavelengths. Simulation results demonstrate that the designed elements can successfully implement both the functions of demultiplexing different wavelength beams and focusing each component at a pre-designated position simultaneously.
A design method of diffractive micro-optics elements based on the diffractive integral theory for simulating and representing the turbulent wavefront in infrared wavelength region, and the fabrication technologies mainly consisted of electron beam photolithography and low-cost anisotropic wet etching, are developed in this paper. We simulate the diffraction propagation process according to the Rayleigh-Sommerfeld (RS) diffractive theory or the angular spectrum diffraction theory. The modified Gerchberg-Saxton (GS) algorithm for modeling and simulation so as to easily realize the iterative transmission process from the input plane to the output, which is employed as the design optimization algorithm of diffractive micro-optics elements, is investigated. Several elements are fabricated quickly through a low cost semiconductor technological process. Infrared diffractive optical elements produced by the method are mainly used to form complex far field patterns related with atmospheric flow such as typical turbulence. The elements can transfer common Gaussian beams into desired patterns correspondent to atmospheric turbulence through creating fine phase microstructures with needed size and depth or height over the surface of the elements. The fine surface morphologies of the elements, which originate from the simple planar patterns in photomask and further etched into the wafer, are created by the software based on the phase distribution designed. The diffractive micro-optics elements for generating several typical light field patterns have been fabricated quickly. Experiments show that the method can achieve several special light field simulations. Future work will mainly include a more realistic model for light field generation in atmospheric turbulence.
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