Contact imaging: simulation and experiment

We report simulated and experimental image quality for contact imaging, a method for imaging objects close to the sensor surface without intervening optics. This technique preserves microscale resolution for applications that can not tolerate the size or weight of conventional optical elements. In order to assess image quality, we investigated the spatial resolution of contact imaging, which depends on the sensor size as well as the distance between objects and the sensor surface. We studied how this distance affects image quality using a commercial optical simulator. Simulation results show that the image quality degrades as objects move away from the sensor surface. To experimentally validate these results, an image sensor was designed and fabricated in a commercially available three metal, two poly, 0.5 [micro]m CMOS technology. Experiments with the contact imager corroborate the simulation results. Two specific applications of contact imaging are demonstrated. Index Terms--CMOS analog integrated circuits, contact imaging, geometrical optics, image resolution, image sensors, mixed signal analog-digital integrated circuits.