Pattern Recognition Vol. 14. Nos. I 6, pp. 283-288, 1981. Printed in Great Britain. 0031 3203/81/070283-06 $02,00/0 Pergamon Press Ltd. Pattern Recognition Society AN INFRA-RED SOURCE CLASSIFICATION SYSTEM* L. F. PAUI"and M. M. Y. EL NAHAS Department of Electronics and Physics, Ecole Nationale Supdrieure des Tel6communications, 46 rue Barrault, F 75634 Paris Cedex 13, France (Received 9 January 1980; in revisedform 3 June 1980; receivedfor publication 22 December 1980) Abstract - A passive system for the classification of isolated infra-red signatures is described along with the extraction of contour, spectral and emittance features, obtained in parallel from a starring non-image- forming mosaic with radial structure. Infra-red pictures Mosa'icsensors Non-parametric statistics Contour coding I. INTRODUCTION The successes in applying infra-red technology to remote sensing and target acquisition are. based on the joint development of high performance detectors, of infra-red optics and of signal processing hardware.~l.6.14) In particular the tendency has recently been towards high density detector mosa'ics (starring or with paral- lel-serial readout), as well as towards evolved analog and digital signal processing concepts incorporating pattern recognition35"7'*"d9'1°) These two parallel trends lead to prospective designs of infra-red source classification systems combining detector technology and signal classification for the purpose of target cueing and classification, rather than plain detec- tion3 ~'sl This functional task has emerged from a number of present or future passive surveillance requirements, where the same equipment should be able to screen a scene for different types of targets, to discriminate among them (e.g. types of vehicles, or targets/chaff), before other systems are activated based on this real-time classification outcome (e.g. for gui- dance, reconfiguration or warning purposes). It is essential that the classification circuitry de- veloped is properly integrated with the detector geo- metry and characteristics, which is the main idea behind this paper. The next idea to be developed is that if autonomous small size source classification equip- ment is considered, acceptable classification scores can be achieved with non-image forming mosa'ics designed to enhance the acquisition of good classification features (also called signatures). Very little has ap- peared in the literature along these lines ; see however the survey papers in ZissisY*~ This paper will report on continued work on a passive, non-image-forming infra-red source classifi- *(~3 French Government. ~Correspondence to: L. F. Pau, 2129 Wyoming Avenue N.W., Washington, DC 20008, U.S.A. cation system, with special starring detector geometry, the purpose of which is to analyze and classify the emission radiated from an isolated source in the 8- 13 ,am region. Although the source is assumed to drift slowly within the field of view, we will not cover tracking considerations here. Neither will attention be given to detector technology,~7)scene segmentation, t9) scanning ~6) or multi-frame and sliding window classification, t3) An overall system description is given in Section 1. The non-image forming detector geometry is studied in Section 2, while Section 3 deals with the hardware extraction of classification features. Finally, Section 4 discusses the initial steps of the signal processing and classification, which is microprocessor based. 2. SYSTEMDESCRIPTION 2.1. Subsystems The system consists of the following parts. (a) An optical head. (b) A mosa'/c detector (discussed in Section 3). (c) Analog and digital pre-processing circuitry (pre- sented in Section 4). (d) A microprocessor, on which are implemented the software algorithms introduced in Section 5. The requirements are for an autonomous system, of low volume and basically without special cooling devices. Presently only laboratory set-ups have been used. 2.2. Optical head The main components will be listed, as encountered during the propagation of the infra-red emission. (a) An optical collector, which consists of several coated and anti-reflection processed lenses made of germanium ; the guaranteed resolution in the 8-13 pm window is of 3 x 10- 3 rd. The alternate design is a thin-optics zooming collector with fields of view between 10° and 30°. In both cases, the spectral range of the collector is 3-13 ,urn. 283