Phase sensitive beam tracking system

Patent metadata

Field	Value
Publication number	US-10277319-B2
Application number	US-201815889193-A
Country	US
Kind code	B2
Filing date	Feb 5, 2018
Priority date	May 25, 2016
Publication date	Apr 30, 2019
Grant date	Apr 30, 2019

Abstract

The method includes receiving axis signals from a multi-axis position sensing detector, generating a reference signal by summing the axis signals, determining a mirror position of a mirror directing the optical beam based on the beam position error of each axis of the multi-axis position sensing detector, and actuating the mirror to move to the mirror position. Each axis signal is indicative of a beam position of an optical beam incident on the multi-axis position sensing detector, each axis signal corresponding to an axis of the multi-axis position sensing detector. For each axis of the multi-axis position sensing detector, the method includes converting a phase of an axis to have a 90 degree phase difference from a signal of the axis, generating an axis-phasor signal by summing the axis signals, and comparing the axis-phasor signal and the reference signal to determine a phase difference.

First claim

What is claimed is:

1. A method comprising:
receiving, at signal processing hardware, axis signals from a position sensing detector, each axis signal indicative of a beam position of an optical beam incident on the position sensing detector;
for an axis of the position sensing detector:
converting, by the signal processing hardware, a phase of a first axis signal of the axis to have a 90 degree phase difference from a second axis signal of the axis, resulting in a phase converted first axis signal;
generating, by the signal processing hardware, an axis-phasor signal by summing the phase converted first axis signal and the second axis signal, the axis-phasor signal indicative of the beam position of the optical beam; and
comparing, by the signal processing hardware, the axis-phasor signal and a reference signal to determine a phase difference, the reference signal based on the axis signals, and the phase difference mapping to a beam position error along the corresponding axis on the multi-axis position sensing detector; and

determining, by the signal processing hardware, a mirror position of a mirror directing the optical beam based on the beam position error of the axis of the position sensing detector.

2. The method of claim 1 , further comprising:
receiving, at the signal processing hardware, photocurrents for the axis of the position sensing detector, each photocurrent having an amplitude dependent on a beam power and the beam position of the optical beam; and
converting, by at least one transimpedance amplifier of the signal processing hardware, the photocurrents to the corresponding axis signals, each axis signal being a voltage signal.

3. The method of claim 1 , further comprising high pass filtering each axis signal using at least one single or multi-pole filter of the signal processing hardware.

4. The method of claim 1 , further comprising low pass filtering the axis-phasor signal using at least one single or multi-pole filter of the signal processing hardware.

5. The method of claim 1 , further comprising modifying, by at least one limiting amplifier of the signal processing hardware, the axis-phasor signal and the reference signal to each represent a corresponding logarithmic gain.

6. The method of claim 5 , further comprising filtering, by at least one comparator of the signal processing hardware, the modified axis-phasor signal and the modified reference signal to perform an edge detection on the modified axis-phasor signal and the modified reference signal.

7. The method of claim 6 , further comprising synchronizing, by the signal processing hardware, the reference signal to a reference clock of the signal processing hardware.

8. The method of claim 7 , further comprising trimming a frequency of the reference signal using a digital potentiometer of the signal processing hardware.

9. The method of claim 1 , further comprising determining, by a controller of the signal processing hardware, the mirror position in consideration of a rate of change of the mirror position based on the beam position error of the axis of the position sensing detector.

10. The method of claim 1 , further comprising filtering, by a notch filter in communication with the controller, the mirror position to attenuate a target frequency.

11. An optical beam tracking system comprising:
a position sensitive detector configured to output a first axis signal and a second axis signal in relation to a beam position of an optical beam incident on the position sensitive detector, the second axis signal including an axis signal phase;
at least one phase shifter in communication with the position sensitive detector and configured to shift the axis signal phase of the second axis signal by 90 degrees;
at least one summing amplifier in communication with the position sensitive detector and the at least one phase shifter, the at least one summing amplifier configured to output a summed axis signal comprising a summation of the first axis signal and the shifted second axis signal; and
signal processing hardware in communication with the at least one summing amplifier and configured to determine a mirror position of a mirror directing the optical beam, the mirror position based on a signal difference between a reference signal and the summed axis signal.

12. The optical beam tracking system of claim 11 , wherein the first axis signal and the second axis signal are associated with a common axis of the position sensitive detector.

13. The optical beam tracking system of claim 11 , wherein the signal processing hardware is configured to actuate the mirror to move to the mirror position.

14. The optical beam tracking system of claim 11 , further comprising at least one single or multi-pole filter in communication with the position sensitive detector and configured to high-pass filter the first axis signal and the second axis signal.

15. The optical beam tracking system of claim 11 , further comprising at least one limiting amplifier in communication with the at least one summing amplifier, the at least one limiting amplifier configured to:
receive the summed axis signal and the reference signal;
modify the summed axis signal and the reference signal to each represent a logarithmic gain; and
output the modified summed axis signal and the modified reference signal, each modified signal proportional to a logarithm of the corresponding received signal.

16. The optical beam tracking system of claim 15 , further comprising at least one comparator in communication with the at least one limiting amplifier, the at least one comparator configured to perform an edge detection on each of the modified summed axis signal and the modified reference signal.

17. The optical beam tracking system of claim 16 , further comprising a digital potentiometer in communication with the at least one comparator, the digital potentiometer configured to trim a frequency of the reference signal.

18. The optical beam tracking system of claim 11 , wherein the signal processing hardware comprises a controller configured to determine the mirror position in consideration of a rate of change of the mirror position based on the signal difference between the reference signal and the summed axis signal.

19. The optical beam tracking system of claim 18 , further comprising a notch filter in communication with the controller, the notch filter configured to filter the mirror position to attenuate a target frequency.

20. The optical beam tracking system of claim 18 , further comprising a mirror scaling calculator in communication with the controller, the mirror scaling calculator configured to generate complimentary first and second mirror signals that rotate away from a mirror bias set point.

Assignees

• X Dev Llc

Inventors

• Steinkraus Robert
• Ulander Klaus

Classifications

• H04B10/11

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