Cylindrical sample space imaging and material BRDF performance measurement

In the field of space exploration, it is often necessary to detect and identify the target under specific light source illumination and different observation angle conditions. Due to different shapes of the sample at different wavelengths of illumination source and geometry measurement conditions, the appearance of the obtained sample images are very different, and there are great differences between the apparent scale of the image and the inherent dimensions of the actual object. Using a standard reflector to calibrate the imaging system, the image or data can be corrected. In this paper, cylindrical sample is selected as the research object, a beam of 680nm parallel monochromatic light source is used for illumination, and the digital camera is used to photograph at a certain angular interval in the range of observation angle (0-75°), and the geometric dimension of the image pixel is calibrated. Through the calibration of image pixel geometry and the calculation of image gray value, the relationship between the gray value changes and the geometrical dimensions of the images captured under different imaging geometry conditions is studied. With the same wavelength light source lighting conditions, a bi-directional reflection distribution function (BRDF) calibration device was used to measure BRDF under multiple geometric conditions for the same material flat material. The BRDFs of material was used to study the appearance of the target sample, and the relationship between the image of the target sample and the corresponding BRDF of the material under different geometric conditions was analyzed and compared. A series of image processing data and methods for cylindrical samples are given in this paper, which has certain practical significance for the study of material properties and target imaging.