Drop size detect circuit
AssigneeHewlett-Packard Company
InventorLowell Stewart
Life of this patent
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Abstract
An optical drop detect circuit for a thermal ink jet printer. The optical drop detect circuit includes an optical sensor for providing an electrical output indicative of a presence of an ink drop, a transconductance amplifier responsive to the output of said optical sensor, first and second cascaded bandpass amplifiers responsive to the transconductance amplifier, a first comparator circuit responsive to the output of the cascaded bandpass amplifiers for providing an output pursuant to optical sensing of a first minimum ink drop size, and a second comparator circuit responsive to the output of the cascaded bandpass amplifiers for providing an output pursuant to optical sensing of a second minimum ink drop size.
Claims5
An optical drop detect circuit comprising:
- an optical sensor for providing an output indicative of a presence of an ink drop in a light beam sensed by the optical sensor;
- amplifier means responsive to the output of said optical sensor for providing an amplified output;
- bandpass amplifier means responsive to said amplified output for providing a bandpass output;
- first comparator means responsive to said bandpass output for providing a first comparator output that is indicative of when said bandpass output decreases below a first predetermined threshold, said first comparator output being indicative of sensing of an ink drop having a size at least as large as a first minimum drop size;
- and
- second comparator means for providing a second comparator output indicative of when said bandpass output decreases below a second predetermined threshold, said second comparator output being indicative of sensing of an ink drop having a size at least as large as a second minimum drop size which is different from said first minimum drop size.
Dependencies are inferred from the claim text.