Georgia Tech has invented a system that can find and neutralize digital cameras:
Abowd's system locates the offending device, then neutralizes it. Every digital camera has an image sensor known as a CCD, which is retroreflective and sends light back directly to its original source rather than scattering it. Retroreflections make it fairly easy to detect and identify digital cameras because they emit either a visible or an invisible beam of light. Once identified, the anti-camera system would beam an invisible infrared laser into the camera's lens, in effect overexposing the photo and rendering it useless. Low levels of energy neutralize cameras but are neither a health danger to operators nor a physical risk to cameras.