Patent ID: 7646934

Claim:
A method of detecting an image of a reflective object, comprising the steps of: capturing a first image by an image sensor while a light-emitting device is emitting light; down-sampling a first image signal outputted from the image sensor to a first digital signal by comparing a level of the first image signal with a predetermined first reference level; capturing a second image by the image sensor while the light-emitting device is not emitting light; down-sampling a second image signal outputted from the image sensor to a second digital signal by comparing a level of the second image signal with a predetermined second reference level; computing an image of difference between the first image and the second image by subtracting the second digital signal from the first digital signal; and specifying the image of the reflective object by locating a bright point remaining in the image of difference, wherein the first reference level is the same as the second reference level and the step of down-sampling the first image signal includes the steps of: lowering the level of the first image signal by a predetermined amount; and down-sampling the first image signal having the level lowered by comparing the level of the first image signal having the level lowered with the second reference level.