Optics: measuring and testing – Photometers – Photoelectric
Patent
1994-06-27
1996-01-23
Warden, Robert J.
Optics: measuring and testing
Photometers
Photoelectric
352141, 356227, G01J 142
Patent
active
054869145
ABSTRACT:
In a handheld incident light meter instrument, a custom LCD panel provides both a digital readout and a bar graph array which simulates an analog meter but uses no moving mechanical parts and which may be operated in a choice of modes: bar, floating zone or dedicated. Unusual accuracy and stability over a wide dynamic range, from 0.1 to over 50,000 footcandles, are achieved in a novel analog photo-amplifier portion having a linear autoranging preamplifier, an averaging integrator and a temperature-compensated log converter, driving an IC analog-to-digital converter connected to a microprocessor programmed to operate in a choice of modes to operate the LCD via a driver to display light readings according to commands entered via a set of ergonomic user controls. Battery condition is displayed continuously. The digital readout may be backlit for low ambient light level. Two versions each provide special operating modes in addition to a regular illuminance mode in which incident light readings are displayed in a choice of footcandles or lux with up to 5 sequential readings storable on display. A first version, the "Cinemeter II", directed particularly to cinematography, accepts user-entered data such as film speed, shutter speed, shutter angle and lens filters, and displays movie camera f-stop settings automatically calculated from the light reading. A second version, the "Lighting Director", for evaluating illuminance in various environments including movie-making, stage lighting, general photography and architectural illumination, etc., can display light readings as +/- deviation from a preset target value, with optional audible indication.
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Blowers William L.
Denove Thomas F.
GDB Enterprises, Inc.
McTaggart J. E.
Thornton Krisanne M.
Warden Robert J.
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