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Retroluminometer |
| T987003 |
Retroluminometer
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| Patent Drawings: | |
| Inventor: |
Johnson, et al. |
| Date Issued: |
October 2, 1979 |
| Application: |
05/929,299 |
| Filed: |
July 31, 1978 |
| Inventors: |
Johnson; Norbert L. (Oakdale, MN)
Knowd; Michael J. (New Brighton, MN)
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| Assignee: |
Minnesota Mining and Manufacturing Company (St. Paul, MN) |
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| U.S. Class: |
356/445; 356/447 |
| Field Of Search: |
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| International Class: |
G01N 21/55 |
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| Abstract: |
a retroluminometer for measuring retroreflectivity of signs or markings at their actual point of use comprises (1) a source of alternating light; (2) optical means for both directing the alternating light onto a sign or marking that is to be tested and for transmitting light retroreflected by the sign or marking onto a panel within the retroluminometer; (3) a matrix of light-transmitting means arranged on the face of the panel; (4) photosensing means optically connected to the light-transmitting means and adjustable to sense and measure the light from different ones of the light-transmitting means, thereby measuring retroreflection at different angles of deviation from the axis of the light beam incident on the sign or marking; and (5) electric circuitry for presenting the photosensed light as a visually-readable measurement. The electric circuitry includes filtering circuitry for filtering out signals having a frequency different from that of the alternating source so as to eliminate the effect of ambient or extraneous light. |
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