Illumination – Plural light sources
Reexamination Certificate
1999-02-23
2001-10-09
Sember, Thomas M. (Department: 2875)
Illumination
Plural light sources
C362S231000, C362S800000
Reexamination Certificate
active
06299329
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to illumination sources. More particularly, this invention relates to the use of solid state lamps in an illumination source.
BACKGROUND OF THE INVENTION
Fluorescent lamps have been used to provide illumination for scanners. As an illumination source, fluorescent lamps provide the advantage of low operating temperatures. However, fluorescent lamps have several disadvantages. Typically, the visible light spectrum generated by a fluorescent lamp includes spikes (locations in the spectrum of emitted light for which the energy is above the desired nominal level) and holes (locations in the spectrum of emitted light for which the energy is below the desired nominal level). Furthermore, the spectral content of the light generated by fluorescent lamps shifts over time. In addition, the illumination intensity tends to vary over time. As a result, the scanner must frequently undergo calibration cycles to compensate for shifts in the spectral content of the lamp and the lamp intensity. Fluorescent lamps are generally the scanner component having the highest failure rate. As a result, replacement of the fluorescent lamp during the operating life of the scanner may be required.
Because the illumination characteristics of fluorescent lamps are temperature dependent, a warm up time in the range of one minute is generally required before use on both cold cathode fluorescent lights and hot cathode fluorescent lights. In some scanner applications, the time required from the initiation of scanning the first unit of media to completion is an important performance parameter. In order to reduce the time required for scanning the first unit of media, several techniques have been employed. In one technique, the fluorescent lamp is driven at higher than normal operating power in order to accelerate the warming of the lamp. In another technique, the lamp is continuously illuminated in order to eliminate the delay associated with the warming of the lamp. However, both of these techniques reduce the life of the fluorescent lamp, thereby worsening fluorescent lamp reliability problems. A need exists for an illumination source that improves upon these performance and reliability limitations.
SUMMARY OF THE INVENTION
Accordingly, an illumination source for use in a scanner to illuminate an object for scanning includes a plurality of solid state lamps. The plurality of the solid state lamps is configured to generate light having a substantially uniform energy spectrum over a range of visible light frequencies for illuminating the object when power is supplied to the plurality of the solid state lamps.
A scanner for scanning images formed on an object to be scanned, includes a scanning mechanism including a sensor for measuring light reflected from the object to be scanned. The scanner further includes an illumination source for illuminating the object to be scanned. The illumination source includes a plurality of the solid state lamps configured to generate the light having a substantially uniform energy spectrum over a range of visible light frequencies. The light is generated when power is supplied to the plurality of the solid state lamps.
In an illumination source, including a plurality of solid state lamps, used in a scanner configured to scan an object, a method for using the illumination source includes applying power to each of the plurality of the solid state lamps to generate light. The method further includes guiding the light to illuminate the surface of the object with the light having a substantially uniform energy spectrum over a range of visible light frequencies.
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CIS Technology/CIS Advantages; ScanVision Inc.; 1998; Web Design by COPTECH WEST.
HP Introduces White LEDs with Color-Temperature Grading; Hewlett-Packard Web Page; Mar. 23, 1999; pp. 1-3.
Andersen Eric L.
Miller Craig L.
Mui Paul K.
DelGizzi Ronald E.
Hewlett--Packard Company
Sember Thomas M.
Wisdom Gregg W.
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