Surface metrology system based on bidirectional microdisplays
Typical optical metrology systems for surface and shape characterization are based on a separated camera and projection unit, yielding to a limitation concerning the miniaturization of the sensor. We present a compact, highly integrated optical distance sensor applying the inverse confocal principle using a bidirectional OLED microdisplay (BiMiD). This microdisplay combines light emitting device (AM-OLED microdisplay) and photo sensitive detectors (photodiode matrix) on one single chip based on OLED-on-CMOS-technology. Comparable to conventional confocal sensors, the object is shifted through the focal plane (±?z) and the back reflected/scattered light is collected via an special designed optic and detected by the photo sensitive detector elements. The detected photocurrent depends on movement (?z) of the measurement plane. In contrast to conventional confocal sensors, our inverse confocal sensor detects a minimum of reflected/scattered light if the object is positioned in the focal plane. We present a novel sensor concept as well as system and optical simulations that demonstrate the principle of the novel inverse confocal sensor setup.