Lamp control scheme for rapid warmup of fluorescent lamp in office equipment
First Claim
1. An image scanning apparatus, comprising:
- a fluorescent lamp for generating illumination light for illuminating an image to be scanned and captured electronically;
a lamp drive circuit for generating electrical drive signals to operate the lamp;
a photosensitive array of light sensitive pixels responsive to illumination light for producing electrical signals representative of a light intensity at pixel locations;
a controller for controlling the lamp drive circuit, said controller adapted to operate in a cold start mode to cause the lamp drive circuit to over-drive the lamp for up to a predetermined time limit to accelerate lamp warmup, the controller responsive to signals from the photosensitive array indicating the intensity of the light produced by the lamp along a lamp longitudinal extent during the cold start mode, said controller adapted to determine when a light output from said lamp exceeds a predetermined minimum output level and when an intensity profile along the lamp longitudinal extent has stabilized, the controller activating image scanning operations only when said light output exceeds said predetermined minimum output level and said intensity profile has stabilized.
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Accused Products
Abstract
A lamp control scheme for rapid warmup of a cold cathode fluorescent lamp, to minimize the warmup time while maintaining long lamp service light. The lamp is over-driven with high current for up to a predetermined time limit to accelerate mercury vaporization. The drive current is then reduced to a normal level. The scanner light output is monitored by a sensor circuit, and the system waits until the light output exceeds a minimum output and the light profile is sufficiently stable. The scanner is then calibrated to a white reference, and the closed loop control of the signal level is activated. The scan or copy process is now performed, and the light level control is deactivated as needed. Thereafter, between uses the lower lamp current is 40% of normal level to keep the lamp warm while extending the life of the product. If the product has not been used in a long time, the lamp is turned off.
194 Citations
20 Claims
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1. An image scanning apparatus, comprising:
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a fluorescent lamp for generating illumination light for illuminating an image to be scanned and captured electronically; a lamp drive circuit for generating electrical drive signals to operate the lamp; a photosensitive array of light sensitive pixels responsive to illumination light for producing electrical signals representative of a light intensity at pixel locations; a controller for controlling the lamp drive circuit, said controller adapted to operate in a cold start mode to cause the lamp drive circuit to over-drive the lamp for up to a predetermined time limit to accelerate lamp warmup, the controller responsive to signals from the photosensitive array indicating the intensity of the light produced by the lamp along a lamp longitudinal extent during the cold start mode, said controller adapted to determine when a light output from said lamp exceeds a predetermined minimum output level and when an intensity profile along the lamp longitudinal extent has stabilized, the controller activating image scanning operations only when said light output exceeds said predetermined minimum output level and said intensity profile has stabilized. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for rapid warmup of a fluorescent lamp used as a light source in an image scanning apparatus, comprising a sequence of the following steps:
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overdriving the lamp with high current for up to a predetermined time limit to accelerate warmup, and then reducing the current drive; monitoring the lamp light output with a sensor circuit; determining from the sensor circuit when a light output intensity exceeds a predetermined minimum output and a light intensity profile along a longitudinal extent of the lamp has stabilized; using the warmed up lamp in image scanning operations. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification