Browse Prior Art Database

Reflectance Meter

IP.com Disclosure Number: IPCOM000092211D
Original Publication Date: 1968-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Baxter, DW: AUTHOR [+3]

Abstract

It is often desired to determine in advance whether a particular type of printing ink has a sufficiently low reflectance, relative to a document background, to render it visible to an optical reader having a given spectral response. This device is a portable reflectance meter capable of simulating the optical characteristics of a reading machine.

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Reflectance Meter

It is often desired to determine in advance whether a particular type of printing ink has a sufficiently low reflectance, relative to a document background, to render it visible to an optical reader having a given spectral response. This device is a portable reflectance meter capable of simulating the optical characteristics of a reading machine.

Drawing A shows light pipe 10 which contains the entire optical system of the meter. High-intensity lamp 11 is contained in central bore 12 having opaque lining 18. Aperture 13 in disk 14 defines the object spot size to be projected down bore 12. Light from lamp 11 next passes through aperture 15 in stop 16, being then demagnified and focussed onto an object plane by lens 17. Diffused reflected light from the object plane is collected at distal end 19 of pipe 10.

End 19 has a paraboloidal shape for directing the collected light through transparent material 22 nearly parallel to side walls 20.

The latter have reflective coatings 21 to decrease losses, although the paraboloidal shape of end 19 insures that most of the collected rays are not reflected more than once or twice. Collected rays next transverse gelatin filter 24, chosen to match the overall spectral response of the optical reader to be simulated. Photomultiplier 25 converts the filtered light to an electrical signal by meter 30 connected to anode 31 as in drawing B. Photocathode 26 and dynodes 27 are connected to power supply 28 by voltage divi...