WEB DETECTION WITH GRADIENT-INDEXED OPTICS

摘要

A device (10) for detecting a web (18), the device (10) including a light source (22) adapted to emit light generally in the direction of the web (18); a lens (26) spaced apart from the light source (22) and adapted to receive light originating from the light source (12), the lens (16) having a radial index of refraction gradient; and an image sensor (30) aligned with the lens (26), the image sensor (30) adapted to receive light from the lens (26) and to convert the light to a signal. Also, a method for detecting a web, the method including emitting light from a light source; capturing light reflected by the web (18) with a lens having a radial index of refraction gradient; focusing the captured light on an image sensor; and converting the focused light to a signal. Also, a method for aligning two webs, wherein each web has a position, and a method for detecting an object.