Apparatus for optically directly recording skin prints for mobile applications

An apparatus for direct optical recording of a skin print, the apparatus comprising:

• a layer body comprising a placement surface formed by a terminating layer of the layer body, and a combination of a display and a sensor layer, the sensor layer having light-sensitive elements arranged in a sensor grid;
• a light source unit arranged below the display, the light source unit being formed as a light guide layer and having an LED light in-coupling at a narrow side of the light guide layer;
• the light guide layer having light out-coupling structures, the light out-coupling structures permitting directed coupling out of light from the light guide layer at a defined angle in a direction of a terminating layer based on an inclination angle c of the light out-coupling structures and on differences of refractive indices between neighboring layers of the light guide layer, wherein total internal reflection (TIR) of the light at an air interface of the placement surface has a divergence angle range of ≤±15° after the light passes through all of the layers up to the terminating layer to achieve a high spatial resolution of the skin print to be recorded, the display having a defined transparency of at least 1% of the light guide layer in a direction of the placement surface;
• and
• a first adhesion layer disposed between the display and the light guide layer, and a sec-ond adhesion layer disposed between the light guide layer and the sensor layer;
• wherein the first adhesion layer and the second adhesion layer have a refractive index of the same magnitude being at least from 1% to 30% lower than refractive indices of the light guide layer, the display and the sensor layer, the refractive indices of the light guide layer, the display and the sensor layer being between 1.45 and 2.0.