Optical methods of measuring the hair diameter

When dealing with various tasks of medicine, in mathematical modelling of processes in the human body, it is necessary to know the physical parameters of biological tissues. In cosmetology and dermatology, these are the physical properties of hair − diameter, density, heat capacity, thermal conductivity, and optical parameters. Existing methods can solve the problem of measuring these parameters, but as a rule, they take a great deal of time and resources. Therefore, the purpose of this paper is to develop and study fast and cheap optical methods for measuring the diameter of a human hair using computer methods for processing the results of the experiment. Several methods for measuring the diameter of a human hair have been studied. The hair diameter was measured by analysing the pattern of laser scattering and using a microscope with a digital attachment and an eyepiece micrometer. Measurements by diffraction methods are consistent with each other within the limits of errors. Measurements using PAINT program are a little more accurate (the average error is 0.7 μm) than using MATHCAD program (the average error is 1.3 μm). Measurements using MATHCAD program are more complicated. Therefore, of the two remaining methods, the first one is preferable. Measurements using a microscope require more manual work; especially focus adjustment, which, with a large magnification of the lens (20x – 40x), is a time-consuming operation. The measurement error (1 μm) is comparable with the error of diffraction methods. Thus, of the four methods considered, the diffraction method with the processing results using PAINT program, which is included with all versions of Microsoft Windows system, has the greatest advantages, in contrast to the paid MATHCAD program, which has be installed on a computer.