Modified method of laser triangulation

The measurement of the thickness of thin layers of biological tissue that are transparent to radiation in the visible range in the interval [0.01; 1] mm, in particular the corneal layer of the eye, is an actual and completely unsolved problem. The main difficulty lies in controlling the thickness of the residual corneal layers during ophthalmic operations for refractive correction of vision on the anterior tissues of the eye. The method of thickness measurement due to the specific task (in vivo - on the cornea) must satisfy a number of criteria: to be carried out in contact with the tissues under investigation (optical methods), in real time (a certain ratio of the processing speed to the volume of information obtained), safety of use should be considered (minimal risk of complications after use). In this paper, we consider various modifications and applications of the method of laser triangulation to the measurement of the thickness of thin transparent layers. We give an estimate of the limit of the smallest layer thickness, which can be measured by the proposed method and the results of experiments (0.23 mm). In addition, we propose an algorithm for computer processing of obtained images, which allows increasing the range of this method (up to 0.10 mm). We estimate the most optimal angles of viewing of laser radiation (0.88 rad), the position of the photodetector (0.17 rad) and the maximum permissible power density of the laser radiation used (10 mW/mm(2)).