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In this chapter, a new optical design of two reflected lens with compressed optical path for reflecting four times is described. We have designed this novel system with a longer focal length and a shorter physical length. It will fabricate inexpensively and reduce the difficulty of the test. The system is designed at the focal length of 850 mm, F-number of 3.6 and the pixel size of 30 μm × 30 μm with the field of view 3° × 3° with the uncooled M/LWIR microbolometer array detector. In the design process, it is used four times reflection to reduce the length of system. The result shows that the system can be utilized efficiently and the system is compact and image quality is favorable.

Additive manufacturing (AM) enable new and innovative design forms that cannot be produced by conventional manufacturing methods. Space optical instruments are precision systems that require high resolution, light weight, low cost and short schedule. Metal AM technology is more adept to the fabrication of mirror blanks and support structures with complex shapes. In this study, selective laser melting (SLM) technology were utilized to create workpieces. The AlSi10Mg mirror blanks were fabricated with metallic powder bed fusion. After forming, post annealing process at 300 ℃ for 2 h was performed to relieve internal stresses. The microstructure of AlSi10Mg produced by SLM is compact, and the mechanical properties are much higher than the alloy formed by conventional casting. The single point diamond turning (SPDT) was been applied to deliver optical quality mirror. The surface characteristics of AM components have been measured. The turning surface meets the 8~11nm RMS and 1.05λ PV. This research can be used for the manufacturing of lightweight space optical mirrors and improve overall process efficiency.

To reduce the alignment difficulty and achieve high diffraction efficiency, a self-aligned method for fabricating large-aperture multi-level Fresnel membrane optic is proposed. Using this method, the rigorous alignment is avoided during fabrication process and high diffraction efficiency is achieved. A 4-level Fresnel diffractive polyimide membrane optic in 200 mm diameter and 20 μm thickness was manufactured by this method, which exhibits about 63% diffraction efficiency into the +1 order. The thickness variation of the membrane has a RMS of 30 nm.

To reduce the cost and achieve high diffraction efficiency, a modified moire technique for fabricating a large-aperture multi-level Fresnel membrane optic by a novel design of alignment marks is proposed. The modified moire fringes vary more sensitively with the actual misalignment. Hence, the alignment accuracy is significantly improved. Using the proposed method, a 20 μm thick, four-level Fresnel diffractive polyimide membrane optic with a 200 mm diameter is made, which exhibits over 62% diffraction efficiency into the +1 order, and an efficiency root mean square of 0.051.

Diffractive membrane imaging can be widely used in infrared band due to its longer minimum linewidth and loose requirement of RMS to fabricate more easily and reduce production period and manufacturing cost than used in visible band. A deployable infrared diffractive membrane imaging system was designed, consisting of Φ200mm imaging aperture (actual aperture is Φ500mm) and deployable structure that supports the infrared membrane under tension. Its spectral band width is >1.2μm, field of view is >1°, and diffractive efficiency can be >60%. Stowed size is 150mm×150mm×400mm. Research result of this project can promote the application of diffractive membrane imaging in infrared band and provide an effective and feasible means for achieving extremely large optical primary mirror from compact, lightweight payload.

Diffractive optical imaging is a new method to realize high-resolution imaging from geostationary orbit(GEO). Technical advantages of diffractive optical imaging is analyzed in the field of space optics. For application of super large diameter space optical system, the system scheme and a new achromatic method is proposed. An imaging system is developed and tested, the result of optical system wavefront is 0.169λ(RMS), optical system MTF is 0.85, and the imaging system MTF is 0.19. Test results show the new achromatic method is feasible. The above conclusions have reference significance for the development of super large diameter diffractive optical imaging system.

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 μmthick, 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.

Transmissive diffractive membrane optic can be used in space optical telescope to reduce the size and mass of imaging system. Based on the international research results about transmissive diffractive membrane, a 4-level diffractive substrate with 100mm apertures was designed and transmissive diffractive membrane was fabricated by spin coating. High-precision support structure for diffractive membrane with surface precision 0.12λ RMS (λ=632.8nm) was introduced, and that can meet the diffractive imaging requirements. Diffraction efficiency of the diffractive membrane supported by support structure was tested, and the test results showed that diffraction efficiency was >50%. The step figure test results illustrated the etched deep precision was less the 10nm. The imaging wavefront test result demonstrated a wavefront error of about 38 nm RMS. The transmissive diffractive membrane optic can be very useful for large aperture imaging system to realize low mass and low cost.

High-resolution earth observation from geostationary orbit (GEO) is a good way to satisfy the increased time resolution for resource, environment and disaster monitor. Earth observation from geostationary orbit will require optical remote sensor with ultra-large aperture. Given size, weight and launch ability constraints, as well as cost consideration, the traditional monolithic aperture optical system couldn’t satisfy the need. This paper gives a new method, the diffractive imaging system. Diffract ive imaging system is a feasible way to realize high-resolution earth observation from geostationary orbit. The principle of diffract ive imaging system is introduced firstly, then, the primary design of remote sensor with 1m resolution from geostationary orbit using diffractive imaging system is analyzed. Finally, the key technologies are analyzed and feasible solutions are given.