Mark W Daniel

US Patent:

50308327, Jul 9, 1991

Filed:

Jun 8, 1989

Appl. No.:

7/364194

Inventors:

Richard E. Williams - Lake Mary FL
Mark L. Daniel - Deltona FL

Assignee:

Minnesota Mining and Manufacturing Company - St. Paul MN

International Classification:

G01N 2164

US Classification:

2504581

Abstract:

An apparatus for detecting the fluorescence of a luminescent material. Photo-diodes receiving the visible fluorescence from a target luminescent material and a luminescent reference are coupled "back-to-back" resulting in a single-channel detector inherently balanced and insensitive to variations in the excitation stimulus. The photo-diode output is sent through a second harmonic amplifier making available a phase detection of the fluorescence instead of an amplitude detection. The phase of the signal is compared with a known phase from the excitation power source. By adding signals that either reinforce or oppose, the phase information is converted back to amplitude information at a voltage level that can be easily detected. The detected amplitude is compared against the amplitude of the excitation stimulus to account for amplitude variations in such stimulus. The compared output then triggers an indicator producing an indication of the amount of fluorescence of the target luminescent material.

US Patent:

52607305, Nov 9, 1993

Filed:

Jan 25, 1993

Appl. No.:

8/008503

Inventors:

Richard E. Williams - Lake Mary FL
Ernest F. Clough - Lake Mary FL
Mark L. Daniel - Deltona FL

Assignee:

Numa Corporation - Lake Mary FL

International Classification:

G03B 2100

US Classification:

353122

Abstract:

A relatively small liquid-crystal display (LCD) device located well above the fresnel stage of an overhead projector produces large, sharp images with full color and motion. A focus-correcting lens moves with the overhead projector's optical head to maintain proper projection-focus and magnification. Spectrally-selective filters are interposed between the LCD device and fresnel stage to avoid LCD deterioration. A fan-actuated shutter or electrically-actuated shutter optionally provide still further protection. Optical collimation methods are employed to attain a large depth-of-field and image brightness.