IR optical system design of uncooled thermal imaging camera in long band (8—12µm)

Abstract

For 384×288 pixel uncooled micro bolometer (a-Si) focal plane array (FPA) detector an infrared optical system (lenses) has been designed in this paper for work in long wavelength infrared region (LWIR) 8-12 µm. the design results show that the optimum optical performance can be obtained by our proposed approach, so the modulation transfer function (MTF) at Nyquist frequency above 0.5 and closed to diffraction limit, and diameter of geometrical blur image less than detector unit cell (pixel) and concentrated on it. The main advantages of this design beside quality of it optically, it's simple in structure (consists of one conic surface-ellipse; and five spherical surfaces), lightweight (about 77.59g), small volume (entrance pupil diameter=40mm), and short length (total track=58.5mm). These mechanical parameters in addition to chosen tolerance level for manufacture of lenses have a positive affect on the cost of production for this designed system. So the designed optical system should good enough to meets the technical performance requirements for: high image quality, small size, light weight, and low cost thermal camera. This system can be applied in many civilian applications, and short range military applications.