Patent ID: 7609372

Claim:
A system for measuring a total track length of a telescopic lens, the telescopic lens and an image sensor received in a holder, the telescopic lens being movable relative to the image sensor, the system comprising: a testing chart having a frame pattern and a plurality of line pair patterns arranged in the frame pattern, each of the line pair patterns including a plurality of black and white line pairs, the testing chart facing the holder; a light source for illuminating the testing chart; the testing chart being configured for facing and aligning with the image sensor for allowing the image sensor to capture an image of the line pair patterns of the testing chart; a processor configured for analyzing the line pair patterns of the testing chart of the image generated by the image sensor, so as to obtain a modulation transfer function value representative of a precision focal position of the lens; a display screen configured for displaying the image generated by the image sensor and the modulation transfer function value thereon; and a range finder configured for measuring a first distance between the image sensor and the range finder, a second distance between the lens and the range finder, and calculating a distance difference between the first distance and the second distance to obtain the total track length of the lens.