Athermalization of infrared annular folded lens based on wavefront coding.

• A wavefront coding annular folded lens is presented in this paper which can achieve athermalization within the 100 °C range. • The relationship between obscuration radio and phase plate parameter is derived, which can be seen from the mathematical model that increased obscuration radio reduces PSF consistency. • A synthesized PSF is constructed using the genetic algorithm. High-quality image restoration over a wide temperature range with a single filter is enabled by the synthesized PSF. The annular folded lens (AFL) achieves miniaturization and integration of optical systems by single-element design. When over a wide temperature range, the AFL cannot be athermalized with one substrate material. In order to reduce the impact of temperature on imaging quality of the AFL, wavefront coding (WFC) technology is introduced. The WFC-AFL design principle is studied, the relationship between the obstruction ratio and the phase plate parameter is deduced, and the model of the obstruction ratio and the point spread function (PSF) consistency is established. In the digital decoding section, the image restoration effect of the PSF under different weights is studied, and the model of synthesized PSF is constructed using the genetic algorithm (GA). According to theory analysis, the infrared WFC-AFL with IRG26 is designed in the long-wave infrared 8 ∼ 12 μ m. The focal length is 50 mm, the total length is 18 mm, the F-number is 1 and the full field of view is 11° Image restoration with a single filter is achieved by using the synthetic PSF. For the restored images at -40 °C and 60 °C, the average SSIM values are improved by 0.0397 and 0.0141 respectively, the average PSNR values are improved by 1.9540db and 1.1077db respectively compared with common methods. The design provides a new idea for the athermalization of integrated and miniaturized optical systems. [ABSTRACT FROM AUTHOR]