Patent ID: 8184175

Claim:
A system for detecting an optical device, comprising: an illumination system for illuminating a target area; an image acquisition system comprising a camera for capturing a first short-exposure image of the target area from a first position and for capturing a second long-exposure image of the target area from the first position; and a processor and computer readable media having computer code for causing the processor to identify retro-reflections in the target area by analyzing the first short-exposure image and the second long-exposure image, wherein the computer code for causing the processor to identify retro-reflections in the target area by analyzing the first short-exposure image and the second long-exposure image comprises: identifying a local maximum having a well-defined peak of bright pixels surrounded by darker pixels in the first short-exposure image; determining if the identified local maximum has a size that is less than a threshold size in the first short-exposure image; and upon determining that the identified local maximum has a size that is less than a threshold size in the first short-exposure image, selecting the identified local maximum as a candidate local maximum in the first short-exposure image; identifying a local maximum having a well-defined peak of bright pixels surrounded by darker pixels in the second long-exposure image; determining a size of the identified local maximum in the second long-exposure image; determining if the identified local maximum has a size that is less than a threshold size in the second long-exposure image; and upon determining that the identified local maximum has a size that is less than a threshold size in the second long-exposure image, selecting the identified local maximum as a candidate local maximum in the second long-exposure image; determining if the candidate local maximum in the first short-exposure image and the candidate local maximum in the second long-exposure image are reflections from the same optical device by comparing the first short-exposure image and the second long-exposure image; and upon determining that the candidate local maximum in the first short-exposure image and the candidate local maximum in the second long-exposure image are reflections from the same optical device, indicating that the optical device has been detected.