Importance

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Abstract

The invention relates to a device (1) for shortening hairs (3), in particular growing from human skin (5). The device (1) has a laser source (7) for generating a laser beam (9) during a predetermined pulse time, an optical system (15) for focusing the laser beam into a focal spot (25), and a laser beam manipulator (17) for positioning the focal spot in a target position. According to the invention, a dimension of the focal spot (25) and a power of the generated laser beam (9) are such that, in the focal spot (25), the laser beam has a power density which is above a characteristic threshold value for hair tissue above which, for the predetermined pulse time, a laser induced optical breakdown (LIOB) phenomenon occurs in the hair tissue. The LIOB phenomenon results in a number of mechanical effects in the hair tissue, such as cavitation and the generation of shock waves, which damage the hair (3) in positions surrounding the position in which the LIOB phenomenon occurs. From experiments it appeared that, with a sufficient amount of total energy of the laser source (7), the LIOB phenomenon can be used to completely break and thus to shorten a hair. An advantage of the device (1) according to the invention is that the amount of total energy, which is necessary to completely break a hair (3), is at such a level that irritation and damage of the skin tissue surrounding the hair are limited to an acceptable level or even completely prevented.

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First Claim