Browse Prior Art Database

Optical Measurement System

IP.com Disclosure Number: IPCOM000082186D
Original Publication Date: 1974-Oct-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Goetz, WE: AUTHOR [+3]

Abstract

Described is an apparatus for performing photometric light measurement for a light-emitting diode product.

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Optical Measurement System

Described is an apparatus for performing photometric light measurement for a light-emitting diode product.

The figure shows the light-emitting diode (LED) 1, upon which is focused the objective lens 2 of the apparatus. A current pulse energizes the light-emitting diode 1, which emits a pulse of light which is directed through the objective lens 2 to the beam-splitting prism 3. This prism passes a sufficient amount of light to the eye piece 4, for visual observation and alignment of the LED 1.

The predominant portion of the light from the objective lens is transmitted through the beam-splitting prism 3, through the phototube 5 and through the exit pupil 7 of the eye piece 6. The active area of the photodetector 8 is placed in the plane of the exit pupil 7 such that if a small light source such as the LED 1, is moved across the object field, no motion is evident in the exit pupil 7. The detector 8 is a silicon photodiode chosen to provide a flat response over a broad spectral range.

The transduced electric pulse from the detector 8 is amplified in the preamplifier 9 and further amplified in the DC amplifier 10, so as to obtain a high- gain current-to-voltage conversion to amplify the linear current output characteristic of the photodetector 8. The positioning of the detector 8 at the exit pupil 7 serves to reduce errors caused by the across surface nonlinearity of large-area detectors.

The flat response of the diode-amplifier combination...