The abbe number of diffractive optical element is negative, which is opposite to that of traditional refraction optical element. So diffractive optical element has unique advantages on achromatic and thermal compensation. Therefore, it can be applied to diffractive and refraction hybrid optical systems to simplify the optical structure and improve the imaging quality. However, the diffraction efficiency of the single-layer diffractive optical element depends on the wavelength mightily , However, the diffraction efficiency of the design order of the double-layer diffractive optical element in the whole working band is coincident basically and more than 90%, which can significantly suppress the stray light of the non-design order and advance the image contrast. Therefore, the double-layer diffractive optical elements are adopted in this long-wave infrared wide waveband optical system, and the design idea of superposing the diffractive surface on the aspheric surface is proposed. Only two lenses and two materials were used to realize the optimal design. By matching the microstructure parameters of the double-layer diffractive elements ,the diffraction efficiency of the whole working band reached more than 97%. Imaging quality analysis shows that the chromatic aberration of 8μm-14μm is well corrected. the secondary spectrum is well controlled also, and the MTF is close to the diffraction limit, which meets the design requirements.
The GZIII.18/18-ZQ is a spherical three generation image intensifier, whose cathodic sensitivity and signal-to-noise ratio index are significantly improved compared to the second generation, which can improve the night detection capability and observation effect of the microlight night vision. According to the spectra of three generation image intensifier spectral response, sensitivity, signal-to-noise ratio and other parameters, combined with the system requirements of the field of view, resolution and other technical indicators, a low level light system is designed with a focal length of 20.00mm, F number 1.29 and the field of view of 50 degrees. The system uses four lenses, the total length of the total objective is less than 60mm, and the weight is less than 100g. Using a free-surface prism to achieve optical circuit rotation, the performance is improved. Finally, we get the off-axis MTF curve in 40lp/mm greater than 0.5, the whole field of view distortion is less than 4% without vignetting , the transmission rate is greater than 83%.
Super-wide FOV lens has a short focal length, making the detection distance shorter. To suit the need of long detection distance, the inversed telephoto structure is used. In this paper, we designed a super-wide FOV camera system with a negative-positive inversed telephoto structure, whose FOV is 95°×71.25°.And optical aberration were analyzed detailedly, the structure of foreside and backside were made certain respectively, based on these, optical optimum design was accomplished.The result shows that in the entire field of view, the MTF at 60lp/mm is more than 0.4, the diameter RMS of spot diagram dispersion circle is less than 5 microns and the maximum distortion is less than 5%. The result shows that it meets the requirement of system well.
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