Web detection with gradient-indexed optics

A device for detecting the position of an edge of a web, the device comprising:

• a light source adapted to emit light generally in the direction of the web, wherein a portion of the light is reflected by the web;
• an image sensor adapted to receive the portion of light and to convert the portion to a signal;
• and
• a signal processor adapted to process the signal using a cross correlation to determine the edge position web with sub-pixel resolution.

A method for detecting a web, the method comprising:

• emitting light from a light source;
• capturing light reflected by the web 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.

A method for aligning two webs, wherein each web has a position, the method comprising:

• emitting light from a first light source;
• capturing light from the first light source reflected by the first web with a first lens having a radial index of refraction gradient;
• focusing the captured light from the first light source on a first image sensor;
• converting the focused light from the first light source to a first signal;
• emitting light from a second light source;
• capturing light from the second light source reflected by the second web with a second lens;
• focusing the captured light from the second light source on a second image sensor;
• converting the focused light from the second light source to a second signal;
• comparing the first signal with the second signal to determine if the webs are aligned;
• and
• adjusting the position of at least one of the webs until the webs are aligned.

A method for detecting an object, comprising:

• emitting light from a light source;
• capturing light reflected by the object 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.

A web detection system comprising:

• a light source adapted to emit light generally in the direction of the web;
• a means for focusing light reflected by the web using a radial index of refraction gradient;
• and
• an image sensor adapted to receive focused light and to convert the focused light to a signal.

A device for aligning two webs, wherein each web has a position, the device comprising:

• a first light source adapted to emit light generally in the direction of the first web;
• a first lens spaced apart from the first light source and adapted to receive light originating from the first light source, the first lens having a radial index of refraction gradient;
• a first image sensor aligned with the first lens, the first image sensor adapted to receive light from the first lens and to convert the light to a first signal;
• a first signal processor coupled to the first image sensor, the first signal processor receiving the first signal;
• a second light source adapted to emit light generally in the direction of the second web;
• a second lens spaced apart from the second light source and adapted to receive light originating from the second light source;
• a second image sensor aligned with the second lens, the second image sensor adapted to receive light from the second lens and to convert the light to a second signal;
• and
• a second signal processor coupled to the second image sensor, the second signal processor receiving the second signal.

A device for detecting an edge of a web, the device comprising:

• a light source adapted to emit light generally in the direction of the web;
• a lens spaced apart from the light source and adapted to receive light that originates from the light source and is reflected by the web, the lens being an array of lenses each having a radial index of a refraction gradient, wherein the lens has at least one focus point and an acceptance angle, and wherein the light source is positioned to emit light at an angle to the lens greater than the acceptance angle;
• an image sensor aligned with the lens and positioned substantially at the focus point, the image sensor being a CMOS image sensor adapted to receive light from the lens and convert the light to a signal;
• and
• a signal processor coupled to the image sensor, wherein the signal processor receives the signal, and wherein the signal processor uses a cross correlation to process the signal to determine the edge with sub-pixel resolution.