Dielectric micro-filters for locally resolving color sensors

Two different types of color sensors have been developed using dielectric micro-filters. One kind of sensor was developed for integral color evaluation. Interference filters were deposited directly on photoelectric cells, using a low temperature coating procedure. The spectral sensitivity of the photoelectric cells was modified according to the application requirements; losses due to absorption and scattered light were minimized. The geometric shape of the receiver cells was chosen to be adaptable to concentric micro-optical components making efficient use of the available sensitive area. For a local resolving color sensor, 19 identical hexagons each consisting of three different filters formed like rhombi have been arranged on one glass substrate. Identically patterned photoelectric cell arrays and dielectric filter arrays were aligned with each other and make it possible to distinguish and measure colors with a local resolution. The hexagonal arrangement of filters and receiver cells , a flexible optical sensor-setup, and smart data processing permit a fast adaptation to different industrial applications. In this paper the design and development of miniaturized interference filters are discussed, and different manufacturing procedures are depicted. The modular setup of sensor prototypes is outlined, all optical components are described, and the electronic parts are presented.