Abstract A light meter for measuring the light reflected from a large area. A point source of light is reflected onto a high gain beaded reflective sheeting screen having the property of reflecting most of the light directly back to the source of the light. A reflecting mirror for the light is of the type that passes substantially half of the light and reflects substantially half of the light and is arranged at an angle so that part of the returning light from the reflecting screen will pass through the mirror to a photo electric cell positioned to correspond to the position of the light. The partially opaque object is laid on the reflective screen and the remaining portion of the reflecting screen is covered with a mask. The light is adjustable in intensity and is adjusted so that the photocell meter reads one hundred after the mask is in position but before the object is placed thereon. The reading after the object is placed thereon will give a percentage of clear area with respect to opaque area.
Inventors
👤 Dwin R Graig
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-30 14:22
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/84; G01N21/86
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
165 words
A large area retro-transmitting light meter for instantaneously measuring the percent opaque area versus the percent transparent area of the total area of a sample, comprising a generally flat high gain beaded reflective sheeting screen for reflecting most of the light falling thereon directly back to the source of the light and for supporting a stationary sample not larger than said screen and having opaque and transparent areas, a light source approximating a point source of light positioned adjacent said screen, a mirror positioned to reflect rays from said light source through the transparent areas of the sample to said screen, said mirror reflecting a portion of the light and transmitting the remainder of the light falling thereon, a photocell positioned to receive light reflected from said screen back through the transparent areas of the sample, a meter to measure and indicate the total light reaching said photocell and hand controlled means for varying the intensity of the light source to calibrate said light meter.
Claim 2
Dependent Claim
165 words
A large area retro-transmitting light meter for instantaneously measuring the percent opaque area versus the percent transparent area of the total area of a sample, comprising a generally flat high gain beaded reflective sheeting screen for reflecting most of the light falling thereon directly back to the source of the light and for supporting a stationary sample not larger than said screen and having opaque and transparent areas, a light source approximating a point source of light positioned adjacent said screen, a mirror positioned to reflect rays from said light source through the transparent areas of the sample to said screen, said mirror reflecting a portion of the light and transmitting the remainder of the light falling thereon, a photocell positioned to receive light reflected from said screen back through the transparent areas of the sample, a meter to measure and indicate the total light reaching said photocell and hand controlled means for varying the intensity of the light source to calibrate said light meter.
Claim 3
Dependent Claim
25 words
A device as claimed in claim 1 wherein the distance between said light and said mirror and said photocell and said mirror is substantially equal.
Claim 4
Dependent Claim
26 words
A device as claimed in claim 1 wherein an adjustable mask is positioned on said screen to mask out a portion of the light reflected therefrom.
Claim 5
Dependent Claim
29 words
A device as claimed in claim 1 wherein said mirror reflects substantially 50 percent of the light falling thereon and transmits substantially 50 percent of the light falling thereon.