A method and an arrangement for recording intensity patterns occurring on
a contact surface by frustrated total reflection, particularly for
low-distortion recording of relatively large-area fingerprints,
handprints or footprints or other parts of the skin. It is an object of
the invention to find a novel possibility for recording intensity
patterns occurring on a support surface according to the principle of
frustrated total reflection which achieves a high-resolution,
low-distortion image of the intensity pattern using simple optical
arrangements. This object is met, according to the invention, in that a
support surface for the measurement object is illuminated homogeneously
by a light source at an angle of total reflection, an image of the
support surface is imaged on the image sensor as an intensity pattern
only by of an imaging optical system, so that the image is imaged on the
image sensor so as to be distorted but sharp in all parts of the image,
and light from the light source which is totally reflected at the support
surface enters parallel to the axis of the optical system, the image of
the support surface is scanned by the image sensor with substantially
more image elements (pixels) than those required for the desired
resolution in the output-side final image of the intensity pattern, and
the optoelectronically converted, trapezoidally distorted image is
rectified by displacement, interpolation and averaging operations based
on the generation of combined pixel data from a data surplus occurring as
a result of the increased quantity of recorded pixels compared to the
necessary quantity of pixels in the final image.