Patent ID: 7171028

Claim:
A method for determining a rate of relative motion between a moving target and a pixel-based imaging device, the method comprising: acquiring a first digital image of the moving target with the pixel-based imaging device; selecting a first pixel set from the first digital image having at least one particular data value representing at least a portion of the moving target, and determining the pixel count of the first pixel set; using the pixel count for the first pixel set to determine a first distance separating the pixel-based imaging device and the moving target when the first digital image was acquired; acquiring a second digital image of the moving target with the pixel-based imaging device after expiration of a time interval; selecting a second pixel set from the second digital image having at least one particular data value representing at least a portion of the moving target, and determining the pixel count of the second pixel set; using the pixel count for the second pixel set to determine a second distance separating the pixel-based imaging device and the moving target when the second digital image was acquired; using the difference between the first and second distances in the first and second digital images and the time interval to determine a rate of relative motion between the pixel-based imaging device and the moving target.