Scanner having cold-cathode-tube light source and method of controlling a drive signal for illuminating a cold-cathode-tube light source
AssigneeNEC Corporation
InventorsShinya Kubo, Tetsuichiro Yamamoto
Life of this patent
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Abstract
The scanner includes the switch 10 that is closed when a document is read, the boosted-voltage conversion circuit 12 that boosts a DC voltage of 12 volts (V) supplied from a power source (not shown) and then converts it into a high-frequency signal b of 50 KHz, the temperature detection circuit 20 formed of the thermistor 15 for ambient temperature detection and correction circuit 16, and the dimmer control circuit 13 that varies the high-frequency signal b from the boosted-voltage conversion circuit 12 according to a temperature detected by the thermistor 15 and produces a drive signal c to vary the luminance of the cold-cathode-tube light source 2.
Claims11
A sensor comprising:
- a cold-cathode-tube light source for illuminating a surface of a document;
- a photoelectric conversion element for receiving light reflected from the surface of said document and producing an image signal;
- a temperature detection circuit for detecting an ambient temperature at a location remote to the cold-cathode-tube light source;
- and
- a control circuit for controlling a drive signal according to detected ambient temperature, said drive signal causing said cold-cathode-tube light source to illuminate when said document is read.
A scanner comprising:
- a cold-cathode-tube light source for illuminating a surface of a document;
- a photoelectric conversion element for receiving light reflected from the surface of said document and producing an image signal;
- an impedance detection circuit for detecting an impedance between electrodes of said cold-cathode-tube light source;
- and
- a control circuit for controlling a drive signal according to detected impedance information, said drive signal causing said cold-cathode-tube light source to illuminate when said document is read.
A method of controlling a drive signal for causing a cold-cathode-tube light source to illuminate comprising the steps:
- detecting an ambient temperature at a location away from the cold-cathode-tube light source and
- controlling a drive signal based on said detected ambient temperature, said drive signal causing said cold-cathode-tube light source to illuminate when said document is read.
Dependencies are inferred from the claim text.