| 摘要 |
1. A fingerprint sensor delivering an electrical signal corresponding to the papillary pattern of the skin of a finger (2) to be examined, comprising an elastic contact surface (20) designed on one side of a transparent body (18) for impression by the finger (2), wherein the respectively impressed papillary pattern produces a corresponding topographic relief by elastic deformation, which relief can be illuminated by a light beam (9) supplied to the contact surface through the transparent body (18) and reflected from the illuminated relief, where the reflected light beam is modulated in accordance with the illuminated relief and supplied to a light-sensitive field (28) of an opto-electric detector device (30) for detecting the distribution of the light intensity incident upon the field (28), which device (30) produces an electrical signal (a) which corresponds to the topographic relief and simultaneously corresponds to the impressed papillary pattern, characterised in that the light beam (9) supplied to the contact surface (20) through the transparent body (18) is supplied to the contact surface (20) through a partially-reflective surface (12) of a beam-splitter (10), which is arranged at an angle of 45 degrees to said contact surface, in such a manner that it is vertically incident upon the contact surface (20) and illuminates the relief, and that in the light beam (21) reflected from the illuminated relief and supplied to the light-sensitive field (28) by means of reflection on the partially-reflective surface there are arranged both a focussing optical system (24) for focussing a real image of the illuminated relief on the light-sensitive field (28) and a spatial frequency filter device (26) which allows the predominant spatial frequencies in the relief to pass through to the light sensitive field (28), but greatly suppresses residual spatial frequencies. |
