Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Reexamination Certificate
1999-08-11
2002-02-05
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
C315S156000, C327S514000
Reexamination Certificate
active
06344641
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to displays, and, more particularly, to a system and method for the on-chip calibration of illumination sources for an integrated circuit display.
BACKGROUND OF THE INVENTION
A new integrated circuit micro-display uses illumination sources that are directed toward a reflective imaging element to provide high quality image reproduction. A typical color micro-display has red, green and blue light-emitting diode (LED) light sources, although other illumination sources are possible. Often, each color source is composed of multiple LEDs generating light of the same nominal wavelength, spatially arrayed to produce a uniform illumination field. Commercially-available LEDs, which are nominally manufactured to the same specifications, typically exhibit a significant amount of mismatch relative to each other, regarding both turn-on voltage and intensity vs. current characteristics. Furthermore, the light output of LEDs manufactured to the same specifications may vary due to factors such as aging of the device and the temperature at which the device is stored and operated.
Unfortunately, this mismatch requires that the illumination sources of each micro-display module be calibrated at the time of manufacture. The illumination sources may be calibrated by, for example, trimming the circuit driving each LED, or programming a non-volatile memory associated with the display. These “per unit” adjustments add significantly to the manufacturing cost of each micro-display. Furthermore, calibration at the time of manufacture fails to address the problem of long term LED mismatch due to aging and/or temperature variations.
Therefore, it would be desirable to incorporate continuous, automatic calibration of the illumination sources directly onto the device that forms the imaging element of the micro-display.
SUMMARY OF THE INVENTION
The invention provides a system and method for the on-chip calibration of illumination sources for an integrated circuit micro-display.
The invention can be conceptualized as a method for calibrating an illumination source, the method comprising the following steps: providing an integrated circuit including at least one photo-detector and an intensity sense and control circuit; illuminating the one photo-detector using the illumination source; measuring an intensity of the illumination source using the photo-detector; communicating the intensity to the intensity sense and control circuit; and adjusting the illumination source to a predetermined level using the intensity sense and control circuit.
In architecture, the invention provides a system for calibrating an illumination source, comprising: an integrated circuit including an imaging array and a photo-detector; an illumination source optically coupled to the imaging array; and circuitry resident on the integrated circuit, the circuitry including intensity sense circuitry coupled to the photo-detector and control circuitry coupled to the illumination source.
The invention has numerous advantages, a few which are delineated below merely as examples.
An advantage of the invention is that it allows for the on-chip calibration of the illumination sources for a micro-display.
Another advantage of the invention is that it allows an illumination source to compensate for ambient light variations that may affect a micro-display.
Another advantage of the invention is that it significantly reduces manufacturing cost of a micro-display.
Another advantage of the invention is that it allows a fully integrated illumination source driver to reside on the same device as a micro-display.
Another advantage of the invention is that it helps reduce the effects of aging on an illumination source.
Another advantage of the invention is that it improves image quality in a micro-display.
Another advantage of the invention is that it is simple in design and easily implemented on a mass scale for commercial production.
Other features and advantages of the invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description. These additional features and advantages are intended to be included herein within the scope of the invention.
REFERENCES:
patent: 4352013 (1982-09-01), Fasig et al.
patent: 5769384 (1998-06-01), Baumgartner et al.
patent: 5977717 (1999-11-01), Dean
patent: 6207943 (2001-03-01), Smelker
Blalock Travis N.
Nishimura Ken A.
Agilent Technologie,s Inc.
Allen Stephone B.
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