Optical system design with variable working distance for monitoring of environmental contamination in infrared region

Abstract

The project is dedicated to a research and development of a compact optical system for an identification of dangerous substances in a surrounding environment using a spectrum of scattered laser radiation. There is a whole class of tasks for diagnostics of environments and substances which are solved by mobile systems on distances of 0.5 – 10 m from the object. The key feature of an optical system in this case is having the highest functionality, to meet this demands it should be able to work on variable distances and provide the minimal light spot. The purpose of the work is a research of the best possible initial system parameters and its components, designing of an optical system with minimum possible number of elements providing acceptable quality of the image in the required dimensions. An image quality criterion for such systems is the size of the light spot, which defines an operation speed of the system. Using the beam diameter and allowable system dimensions as initial parameters of the two components system, relations were found which helps to define optimal component parameters for future design. To provide the possibility of working on various distances the thickness between the components can be varied. An example of a two component system consisted of three lenses with spherical surfaces is presented. The system works with a laser with the wavelength of 0.785 μm and provides the light spot less than 2.3 mm for all working distances within the range of 2 – 5 m.