Reduction of artefacts and noise for a wavefront coding athermalized infrared imaging system

Abstract

Because of obvious drawbacks including serious artefacts and noise in a decoded image, the existing wavefront coding infrared imaging systems are seriously restricted in application. The proposed ultra-precision diamond machining technique manufactures an optical phase mask with a form manufacturing errors of approximately 770 nm and a surface roughness value Ra of 5.44 nm. The proposed decoding method outperforms the classical Wiener filtering method in three indices of mean square errors, mean structural similarity index and noise equivalent temperature difference. Based on the results mentioned above and a basic principle of wavefront coding technique, this paper further develops a wavefront coding infrared imaging system. Experimental results prove that our wavefront coding infrared imaging system yields a decoded image with good quality over a temperature range from −40°C to +70°C.

110 °C range athermalization of wavefront coding infrared imaging systems

“…This experiment with athermalization range of 100°C is only target observation in laboratory and its decoded images at high-low temperature are serious in artefacts. Our previous works report thermal effect [8], design and manufacture of optical phase masks [2,9], a proposed decoding method based on shrinkage function [10], and a developed wavevfront coding athermalized infrared imaging [9]. This paper will further make a quantitative validation of our wavefront coding athermalized infrared imaging system in three aspects of athermalization temperature range, extension of focal depth, approximation to with in-focus image.…”

“…Form measurements of our cubic phase mask are previously reported [9]. The measurement consists of form manufacturing error and surface roughness.…”

“…As one of the two key elements (including optical coding and digital decoding), our decoding method using shrinkage functions and a simulated point spread function (PSF) is previously reported [9]. For a visual comparison of image quality, those two infrared imaging systems adopt the same data-mapped method by which the images are mapped from 16 bits to 8 bits.…”

A Wide-FoV Athermalized Infrared Imaging System with a Two-Piece Lens

“…This technique firstly was used to extend field depth of a microscope [8] and then researchers explored this technique athermalized an infrared imaging systems [5] . This technique mainly includes two stages of optical coding and digital decoding.…”

“…We further developed wavefront coding athermalized infrared imaging systems with a narrow-medium FoV [1,5] .…”