Varying temperatures influence the figure errors of freeform metal mirrors by thermal expansion. Furthermore, different materials lead to thermo-elastic bending effects. The article presents a derivation of a compensation approach for general static loads. Utilizing perturbation theory this approach works for shape compensation of substrates which operate in various temperature environments. Verification is made using a finite element analysis which is further used to produce manufacturable CAD models. The remaining low spatial frequency errors are deterministically correctable using diamond turning or polishing techniques.

Theoretical compensation of static deformations of freeform multi mirror substrates

The invention provides a deep low temperature grading refrigeration and heat insulation system for a space infrared remote sensor, comprising a light shield (1), a lens assembly, a heat insulation rod, a focal plane refrigerator (7), a multi-layer heat insulation assembly (8), a cold shield assembly (9), a cold shield refrigerator (10), a lens refrigerator (11), a heat insulation ring (12), a focal plane detector (13), a detector support structure (14), and a bearing cylinder (15). The lens refrigerator and the cold shield refrigerator respectively cool the lens assembly and the cold shield assembly enveloping the outside of the lens assembly to finally cool the optical lens to a deep low temperature. The focal plane refrigerator cools the focal plane detector assembly to cool the focal plane device to a deep low temperature. Compared with the prior art, the deep low temperature grading refrigeration and heat insulation system for the space infrared remote sensor realizes the deep lowtemperature grading refrigeration and heat insulation of all-optical system of the space infrared remote sensor, and effectively reduces the background noise of the system. The system can be widely applied to the detection of weak targets and the imaging of large temperature range and has good use value.

Deep low temperature grading refrigeration and heat insulation system for space infrared remote sensor

Low-temperature interferometer

Cryogenic optical systems are often mounted in vacuum cryostat. An interesting concern in the mechanical design is how to maintain the stability of the line of sight (LOS) of the cryogenic optical system when it is cooled down to very low temperature. To investigate this problem an experimental cryogenic optical system, its mounting structure, and a cryostat were designed and fabricated. After assembling them together, a test experiment for measuring the LOS drift was carried out. Finally, the test results will be presented in this paper.

Stabilization of the line of sight of a cryogenic optical system

The invention discloses a secondary mirror light shield used for a space large aperture camera. The light shield comprises a louver cover, a cone cover and a bracket. The bracket is a hollow column-shaped frame body, and the louver cover is glued to the outer side of the bracket and used for shielding interference beams between the main mirror and the secondary mirror of the space large aperture camera. The cone cover is glued to the inner side of the bracket and used for shielding and absorbing the diffuse reflection stray light generated by the internal structure of the space large aperturecamera. According to the invention, by gluing the louver cover and the cone cover on both sides of the bracket, the overall structure of the secondary mirror light shield is optimized and the defect that rigidity of the traditional secondary mirror light shield is weak is overcome; and by designing the configuration of the louver cover and the bracket, the shielding ratio of the secondary mirror light shield is reduced, and the problems that the conventional secondary mirror light shield is easily damaged and the processing precision is low are solved.

Secondary mirror light shield used for space large aperture camera

The utility model relates to a low temperature infrared optical system, which belongs to the technical field of a Lacasitan optical system. The utility model is characterized in that the bottom of a concave primary mirror is an elastic bottom edge, a basal plate is grid-shaped, a convex secondary mirror is fixed on a plane which is determined by at least three support rods of a bracket, the plane is parallel with the basal plate; the natural frequency of the bracket is larger than the excitation frequency of the environment, and the components and optical elements of the utility model are made of same aluminium alloy. The utility model has the advantages of large caliber, light weight, etc., and the utility model can conduct high-speed refrigeration to achieve temperature balance and can achieve the imaging quality of diffraction limit under a low temperature.

Low-temp. infrared optical system

The utility model relates to an ultra-short optical system light shield, which belongs to the improvement of a low temperature infrared optical system light shield. The utility model is characterized in that at least three radial blades are uniformly ranged and fixedly connected between the circumference of a main light shield and the circumference of a secondary light shield, the center of which is arranged behind a secondary mirror, in the radial direction. The utility model can reduce one time scattering generated by visual field light ray which directly radiates a primary mirror, doesn't influence the signal acceptance of an optical system and reduces the constructional dimension of the light shield, and besides, the utility model has the advantages of simple structure, light weight and strong applicability.

Super-shortened optic system lens hood

Cryogenic optical system undergoes wide temperature change; therefore it must be athermal. That means when the system is cooled down to very low temperature, its imaging property should be kept as good as at room temperature. One way to achieve athermal optical system requires that all optical and mechanical parts in the system be made from same material. An all-reflective cryogenic optical system was thus developed in IOECAS, in which aluminum alloy was utilized to make such a system. This paper describes the key techniques for manufacturing this cryogenic optical system: material selection, forging process of the aluminum alloy blanks, initial machining, heat treatments, and final figuring. The cryogenic test of the developed system proved the validity of the manufacturing process.

Manufacturing of optical elements of a cryogenic optical system

An all aluminum reflective optical system was tested to evaluate its optical performances at near liquid nitrogen temperature. A special cryogenic dewar was designed and fabricated with an optical window made of quartz glass on the front wall of the dewar. The optical system under test and a reference plane mirror, which were mounted into the dewar and cooled by liquid nitrogen, formed a double pass interferometric test schema together with a He-Ne interferometer of Fizeau type outside the dewar. The test results showed that there was little differences between the wavefront errors before and after the optical system is cooled, and in both cases the optical system had a diffraction limited imaging quality.

Liao Sheng

Papers

Low-temp. infrared optical system

Super-shortened optic system lens hood

Manufacturing of optical elements of a cryogenic optical system

Cryogenic test of an all-aluminum infrared optical system