Signal processing circuit and method using analog voltage signal to pulse width modulation conversion
AssigneeSilicon Light Machines Corporation
InventorDouglas A. Webb
Life of this patent
Estimating the term…
Abstract
A signal processor and processing method are provided for measuring current received from a photo-detector. Generally, the processor includes a transimpedance amplifier (TIA) to integrate a current received from a photo-detector in the optical navigation system to generate a voltage signal having a slope that is proportional to the received current, and a comparator having a first input coupled to an output of the TIA to receive the voltage signal, and a second, inverting, input coupled to a threshold voltage. The comparator is configured to compare the voltage signal to the threshold voltage and to generate an output pulse having a predetermined voltage and a duration or width that is a function of the received current.
Claims14
A signal processor for use with an optical navigation system, the signal processor comprising:
- a transimpedance amplifier (TIA) to integrate a current received from a photo-detector in the optical navigation system to generate a voltage signal having a slope that is proportional to the received current;
- a comparator having a first input coupled to an output of the TIA to receive the voltage signal, and a second, inverting, input coupled to a threshold voltage, the comparator configured to compare the voltage signal to the threshold voltage and to generate an output pulse having a predetermined voltage and a duration that is a function of the received current;
- and
- a sample and hold (S/H) circuit and a differential amplifier (Diff Amp) coupled between the TIA output and the first input of the comparator, wherein:
- the S/H circuit has an input coupled to the TIA output to sample and hold a voltage of the voltage signal at a first predetermined time following a reset of the signal processor;
- and
- the Diff Amp has a first input coupled to an output of the S/H circuit and a second input coupled to the TIA output to determine a difference between the voltage stored in the S/H circuit and a voltage of the voltage signal at the output of the TIA at a second predetermined time,
- whereby the voltage signal coupled to the first input of the comparator is independent of and substantially unaffected by reset noise from the TIA.
A signal processor for use with an optical navigation system, the signal processor comprising:
- a transimpedance amplifier (TIA) to integrate a current received from a photo-detector in the optical navigation system to generate a voltage signal having a slope that is proportional to the received current;
- a comparator having a first input coupled to an output of the TIA to receive the voltage signal, and a second, inverting, input coupled to a threshold voltage, the comparator configured to compare the voltage signal to the threshold voltage and to generate an output pulse having a predetermined voltage and a duration that is a function of the received current;
- and
- wherein the threshold voltage is defined by the following equation:
- Vt=(mt2+bt)/C
- where m is the slope of a linear response out from the signal processor in amps per second, t is time in seconds, b is the current at time zero, and C is the capacitance of an integrator in the TIA.
A method of measuring current received from a photo-detector using a signal processor, comprising steps of:
- integrating the current received from a photo-detector to generate a voltage signal having a slope that is proportional to the received current;
- comparing the voltage signal to a threshold voltage defined by the following equation:
- Vt=(mt2+bt)/C
- where m is the slope of a linear response out from the signal processor in amps per second, t is time in seconds, b is the current at time zero, and C is the capacitance of an integrator in a transimpedance amplifier (TIA) used to integrate the current received from the photo-detector;
- and
- generating an output pulse having a predetermined voltage and a duration that is a function of the received current.
Dependencies are inferred from the claim text.