Flat-Format Lens-Free Imaging Using an Organic Sensor With Guided Illumination and Application to Fingerprints

The cheap basis of organic sensors likely to be soon available for large areas (over 25 cm
²
) opens novel opportunities for flat capture photonic schemes. We investigate one such scheme whereby a thin coverslip-type glass above an organic sensor is used as an illumination medium. To preserve sufficient resolution of the order of 50 μm in spite of the nonimaging optics of considerable numerical aperture ~1.5, a design frame for directional filters is given. The response of various kinds of filters to the bandwidth and polarization of the illumination source, typically an LED, is discussed. Illustrations for fingerprint detections are provided. A possible layout for cheap, dense, parallel detection of scattering by nanosized systems is finally suggested.