DMD-based bloom control for intensified imaging systems

In most advanced imaging systems designed for low light level applications, the heart of the detection process is an image intensifier. While such imaging systems are ideal in low light, they are sensitive to sudden increases in brightness levels within the field of view. These sudden bright spots are caused by a variety of sources (both intentional and not) and can result in a loss of contrast, blinding of the imaging system and damage to the components. As a safety measure against this situation, most systems incorporate global methods for automatic protection against bright sources. Unfortunately, this results in loss of gain and image contrast over the entire field of view, even if the bright source occupies only a small portion of the image. Exposure control over individual segments of the image is required. We present initial results from a unique implementation of the Digital Micromirror Device (DMD(TM)) technology. Through proper placement of the DMD in the optical path and by providing an automatic feedback control loop from. the intensified digital imager, sections of the image plane can be automatically diverted from the optical path by controlling the mirror pixels in those affected areas. An innovative approach, the DMD-based Anti-Blooming System (DABS), has been developed. Using rapid digital processing, this control can be ultimately implemented between frames of the imager to both preserve the hardware and allow for seamless return to a high contrast image. Repeated polling of the image plane through the feedback loop will allow far active control of the intensified image. A system description of the DABS and successful results from initial closed loop operation are presented.