PATTERNING OF MULTILAYER DIELECTRIC OPTICAL COATINGS FOR MULTISPECTRAL CCDS

The development of optical sensors for spacecraft applications require s that al components be as lightweight as possible. One method to redu ce the weight of a multispectral optical system is to eliminate beamsp litting optics and multiple detectors by patterning a filter array dir ectly onto a CCD. However, techniques commonly used in the production of these filter arrays result in decreased image resolutions. This can greatly impact the performance of sensors used for applications such as planetary probes. To address this issue, we have studied the patter ning of multilayer dielectric optical coatings in a small scale, two d imensional array, which will allow development of a four color sensor with a resolution one-half that of monochromatic sensors (compared to one-fourth or less for a four color striped array). We have developed ion milling techniques for the preparation of optical filter arrays wh ich are patterned on a scale as small as 7.5 mu m, enabling each pixel of a CCD to have its own associated filter. This paper presents detai ls of the fabrication of these multispectral arrays, and discusses pro blems associated with pixel-sized filters.