Polychromic light source for the realization of multispectral processing method of skin malignant lesions images

When diagnosing oncological skin diseases, the problem of untimely detection of pathologies remains relevant. Modern diagnostic methods have a number of disadvantages associated with the limited capabilities of human vision, high requirements for non-invasive studies and digital representation of the results obtained for their transmission over communication channels. The most important tasks of early binary diagnostics of skin neoplasms can be solved using bioradiophotonics methods. The paper considers the author's multispectral method for processing images of skin areas using a new specialized polychrome light source with software control of the radiation wavelength. The principle of operation of such a source is analyzed and the use of a set of LEDs with a special arrangement is justified which makes it possible to direct a beam of light of any wavelength in one direction. The choice of the wavelength ranges used for LEDs is confirmed, the first version of the layout of such a light source is described, and its optical and structural diagrams are given. It is shown that the optimal way of the wavelength programmable control is its coarse tuning by switching LEDs and fine tuning by acousto-optic tunable filters installed at the source output. A number of test images of a pigment spot on the skin with a size of 40 × 30 mm with wavelengths ranging from near ultraviolet to near infrared ranges using a black and white camera are presented. With digital processing, received monochromatic images, histogram equalization and median filtering of images were carried out to expand the dynamic range of brightness levels and minimize distortion caused by the unevenness of the skin area under study and the presence of shadow illumination. Graphs of the amplitude intensity distribution in the original and filtered images are obtained for the selected wavelengths of the LEDs. It is shown that the presence of a skin neoplasm can be judged by the dips in the light intensity distribution curve. The radial arrangement of LEDs on the board is justified to minimize shadow illumination when illuminating the skin. The conducted studies of multispectral image processing using a realized polychrome light source contribute to the development of new methods for the early diagnosis of skin neoplasms based on photonics and optoelectronics and can find practical application in medical technologies.