Diffractive optical system can be a favorable choice for large-aperture space telescope to reduce the mass and size of image system. To meet the demand of large-aperture, high efficiency, lightweight diffractive optic for high resolution remote sensing, a 200 mm diameter, 20 <i>μm</i>thick, 4-level diffractive membrane fabricated is shown to have over 62% diffraction efficiency into the +1 order, with 0.051 efficiency RMS. Over 66% diffraction efficiency is achieved for a 100 mm aperture membrane, with 0.023 efficiency RMS. The membrane thickness uniformity control is discussed and 8 nm wave front error RMS is achieved in 100 mm diameter.
This paper presents the impact of the light source expanded width on the detection sensitivity in an optical readout
uncooled infrared system, which consists of a focal-plane array (FPA) containing bi-material cantilever pixels and
reflectors. The relationship between the light source expanded width and the detection sensitivity is discussed based on
four different curvatures of reflectors(R=8mm,11mm,25mm,∞). The analysis indicates that the detection sensitivity
decreases with the light source expanded width's increment. For the flat reflectors , the detection sensitivity decreases to
90% when the light source expanded width is about 0.64mm. Compared with the flat ones, when the curvatures of
reflectors are smaller, the requirement of light source expanded width becomes lower for the sensitivity. The experiment
intuitively shows that the image quality by using the light source with 0.05mm size is better than the one with 1mm size,
which confirms the first conclusion.