Proceedings Article | 24 November 2021
KEYWORDS: Stars, Signal to noise ratio, Star sensors, Diffraction, Optical design, Sensors, Diffractive optical elements, Aspheric lenses, Distortion, Lenses
In order to improve the measurement accuracy and detection ability of the star sensor, this paper uses a double Gauss structure with conic aspheric surface and hybrid refractive-diffractive to design an optical system with large field of view of 25°and large relative aperture of 1/1.156, and only 6 lenses are used. First, According to the selected CMOS APS sensor performance parameters, the entrance pupil diameter, field of view, focal length and wavelength range are determined. The field of view is 25°, F number is 1.156, focal length is 52mm, entrance pupil diameter is 45mm, the wavelength range is 500-800nm. The detection of 6 magnitude stars is realized, the probability of capturing 5 navigation stars is 100%, and autonomous navigation recognition is realized. Then, the glass material selection and structure optimization of the optical system are conducted, the optical system is optimized by introducing two conic aspheric surfaces and a diffractive surface. Finally, the influence of the diffraction efficiency of the diffractive optical element on the signal-to-noise ratio is analyzed. After analysis of image quality, the shape of diffuse spot in each field of view is approximately circular, the energy is close to Gaussian distribution, more than 90% of the energy is concentrated in 3×3 pixels, lateral color is less than 1.06μm, and relative distortion is less than 0.87%. The optical system only uses six lenses, the imaging quality meets the imaging requirements of the star sensor, and is beneficial to improve the accuracy and detection capability of the star sensor.
