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Mark Sensing With Transmitted Light

IP.com Disclosure Number: IPCOM000098823D
Original Publication Date: 1958-Jun-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Hammer, JP: AUTHOR [+2]

Abstract

The basic idea is that of detecting marks on tabulating machine cards by transmitted light.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

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Mark Sensing With Transmitted Light

The basic idea is that of detecting marks on tabulating machine cards by transmitted light.

The standard card stock as used in the majority of tabulating machine card manufacture transmits light to some degree. By placing a light detector, such as a photocell, on one side of the card, and a standard source of illumination, such as an electric lamp, on the other side of the card, a mark on the card can be detected by the light detector as the mark passes between the light source and the light detector. The mark could be any mark which interrupts the transmission of light through the card to the light detector.

A pencil mark on the card would be sufficient to interrupt the light. The operation of an opaque object interrupting the light between a source of light and a light detector is well known.

If light detectors such as cadmium or lead sulphide cells are used, the signal to noise ratio is very good.

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