Design of Infrared Optical System for Uncooled Thermographic Camera

Abstract

The ability of thermal cameras to produce a crisp image even in total darkness and to measure objects temperature by special calibration in a non-contact mode makes them extremely suitable for a wide variety of applications. The objective of this thesis is to design high performance, simple structure, and low cost IR optical system (IR lenses) to work compatible with IR113 thermal detector module in order to obtain high quality thermal images, followed by thermal images processing software to build thermographic camera suitable for many civilian applications (early detection of breast cancer as medical application). ZEMAX optical design program was used to design, optimize, and meet the targeted criterion (lower MTF value at cutoff frequency = 0.583348, and maximum value of spot diameter = 8.805µm) of an IR optical system which consists of 3 germanium lens with one aspheric surface, and it was characterized by diameter of 40mm, length of 58.5mm, and weight of 70g. The manufacturing of this optical system was done in company specializing in production of IR optical systems at reasonable cost. 6061 aluminum alloy was used to manufacture special mechanical case to assemble (carry and align) the optical system with thermal detector module and build handheld thermal camera. This camera (IR optical system+ thermal detector module) was tested in field by taken several thermal images. MATLAB computer software was used to create PC thermal image processing software to convert the thermal gray images to flash color images and read the object temperature from its image. The thermographic camera was tested by read temperature of objects from its images and compared them with known in advance temperatures and we get acceptable results.