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Browse Prior Art Database

Timing Mark Sensor Element

IP.com Disclosure Number: IPCOM000083139D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Bealle, FJ: AUTHOR

Abstract

Described is a device which eliminates the need for the exact alignment of phototransistors and which promotes symmetry of a phototransistor sensitivity pattern, particularly in regard to the Shark timing mark sensor. PN2449740.

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Timing Mark Sensor Element

Described is a device which eliminates the need for the exact alignment of phototransistors and which promotes symmetry of a phototransistor sensitivity pattern, particularly in regard to the Shark timing mark sensor. PN2449740.

The device illustrated is a large nonsensitive phototransistor or simple solar cell, which replaces the Sharp phototransistors. A provision is provided for illumination of the object by a hole drilled through the solar cell for the lens tip.

It may be observed from the figure that if the phototransistors are replaced by the solar cell the light-sensitive area of the assembly is increased by a large factor, and it has been shown that the sensitivity per unit area of the phototransistors to the solar cells is a factor of lesser magnitude. The result is that the use of the solar cells results in a significant net improvement in sensitivity. Finally, it has been demonstrated that solar cells are easier to align and cost less than phototransistors.

For example, the light-sensitive area of two miniature phototransistors might be 0.0007 inch square on a Shark timing mark sensor, PN2449740, whereas the light-sensitive area of a solar cell of the design shown would be approximately
0.084 inch square, thereby increasing the light-sensitive area by a factor of 120. The sensitivity per unit area is reduced by a factor of 30 at worst, resulting in a net improvement factor of 4 in sensitivity.

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