All-optical athermalization of infrared imaging systems using thermally dependent binary phase masks

Abstract

Lenses used in many infrared (IR) imaging systems are temperature sensitive. One of the most popular IR optical materials for lens fabrication is germanium; nevertheless, it exhibits a strong temperature dependent refractive index, causing significant thermal focal shift which in turn results in image blur. An all-optical solution for IR lens athermalization with no moving parts based on a thermally dependent binary phase mask is hereby proposed and analyzed. It allows high quality imaging to be obtained for a wide range of temperature variations, with minimal performance degradation at nominal temperature conditions.

Effect of point spread function position bias in wavefront coding infrared imaging system

“…They have strict requirements for size, weight and stability. Additionally, infrared imaging systems are sensitive to environmental temperature, which causes significant thermal defocus aberration and degrades imaging quality [1][2][3]. Conventional athermalization approaches such as the active mechanical [4], passive mechanical [5] and passive optical measures [6], have their disadvantages in size, weight and stability.…”

Experimental validation of hybrid optical–digital imaging system for extended depth-of-field based on co-optimized binary phase masks

“…Among the many possible phase mask struc-tures, binary annular phase masks have the advantage of being easier to manufacture than nonrotationally symmetric masks, such as cubic phase masks. 15 They have been implemented in practice and have shown good performance on specific applications in infrared 16,17 and visible imaging systems [18][19][20][21] . A systematic study of their theoretical performance and of their robustness to aberrations has been done in a previous work 11 where we addressed in particular the fundamental questions of the maximum DoF reachable with these masks and of the minimum number of rings necessary to reach a given level of performance.…”

A wide-FoV athermalized infrared imaging system with a two-element lens

“…Among wavefront coding techniques, this approach using a binary phase mask [10,11] as a coding mask was validated by simulation over a temperature range of 40°C. Decoded images by this approach [12] are serious in noise.…”