Characteristics of the reflection of infrared signals in the 0.8–0.96 μm band in a mine working

Abstract

The development of systems for the automation and monitoring of production processes of underground mine production requires contact-free methods for analysis of the properties of the surrounding medium.One of the promising methods of this analysis is the method of optical scanning, which can be used in laser location systems [i]. Poller [2] conducts preliminary analysis of the use of reflected optical signals for the monitoring of underground objects.In our study, we investigate the method and results of experimental evaluation of the reflection characteristics of infrared signals.In principles, the use of fiber-optic light guides and couplers for measurement, which significantly simplify the latter, especially under. subsurfaceconditions, is a new concept.In contrast to [3], where the reflection characteristics are reduced for especially ground rock specimens, the measurements were conducted for nonmachined natural surfaces.The measurements themselves were taken at the large-scale Sibiri Mine in workings opened through rock and high-grade ore, and in workings with sprayed-plaster/concrete bracing.Some of the reflection characteristics were recorded under laboratory conditions for rock specimens from the same mine.The method of measurements was based on the use of an optical OT-6 tester with a fiberoptic module for evaluating the level of the reflected optical signal [4]. The measurement scheme is shown in Fig. i. A fiber-optic coupler fabricated in the Mining Institute, Siberian Branch of the Academy of Sciences of the USSR was used for the measurements on the specimens. For statistical evaluation of the reflection characteristics of surface segments, the dimensions of a segment were selected as approximately 10 • 10 cm, and the measurements were at no less than 50 different points over this same area at a distance of more than 1 cm between adjacent points.The distance s between the end of the light guide and the surface was varied from 2 to 8 mm for measurements in the mine, and was 1-2 nan for measurements on the specimens.A Schacter luminnaire with a radiation spectrum in the 0.4-1.2 pm region and the source of the OT-6 optical tester were used as the source of the light flux rThe photodetector of the OT-6 optical tester has a maximum spectral sensitivity in the 0.85-~m region, and the radiation source in the OT-6 tester has a wavelength in the 0.81-0.89-~um region.The field of view ~fv is determined by the aperature of the light guide employed (-0.2); then =fv = 23~The end area of the light guide is -2.2"10 -9 m 2, and the area S is approximately 2 n~m 2 when s = 5 mm, and about 0.4 mm 2 when s = nml.Control measurements of the reflection characteristics from a mirror surface were also taken to obtain comparative characteristics.The following theoretical premises were employed in interpreting the experimental results obtained.In illuminating a heterogeneous surface, where the dimensions of the heterogeneities are many times the wavelengths of the radiation, the reflection is complex in nature, and the refle...