The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 16, 1992
Filed:
Nov. 21, 1990
Bryan A Santarelli, Haverhill, MA (US);
Marc T Thompson, Cambridge, MA (US);
Polaroid Corporation, Cambridge, MA (US);
Abstract
A laser driver circuit pulses of current to a laser diode to activate the diode to emit pulses of radiation suitable for operation of a laser printer. A field-effect transistor (FET) is serially connected with the laser diode and with a feedback resistor for applying the current pulses, the feedback resistor serving as a source of a feedback signal indicative of the magnitude of current flow. A photodetector senses radiation outputted by the laser diode and emits an optical feedback signal representative of radiated power of the laser diode. A combiner circuit, responsive to an input digital command signal, combines the current feedback signal and the optical feedback signal with the command signal to signal generate a drive signal for activating the FET. The combiner circuit includes an input section in which a current source powers a differential amplifier operating in a switching mode in response to the command signal, a drive section wherein a current source powers a differential amplifier operating in a linear mode and connecting between the input section and the FET, and a threshold section connected to the input section for establishing a threshold current level in the drive signal which activates the FET.