MACHINE AND METHOD FOR MEASURING A CHARACTERISTIC OF AN OPTICAL SIGNAL

Abstract

A machine and methods measure a characteristic of an optical signal incident upon a detector characterized by one or more dynamic response parameters. One method receives an output signal from the detector and compares that output signal and a computationally determined response of the detector to a known optical signal incident upon the detector. The response is based on said one or more dynamic parameters. The method determines the characteristic based on a relationship between the output signal and the computationally determined response. Another method observes an output signal from an optical detector detecting one or more optical signals, accesses a characteristic curve of detector response, compares the observed output signal to the characteristic curve, and calculates at least one characteristic of one or more optical signals based on a relationship of the observed output signal and the characteristic curve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a laser, detector, and optical meter according to one embodiment.

FIG. 2 is a functional block diagram of the components shown in FIG. 1.

FIG. 3 is a more detailed block diagram of the optical meter in FIGS. 1 and 2.

FIG. 4 is a flowchart of a method according to one embodiment.

FIG. 5 is a flowchart of one version of one step of the method of FIG. 4.

FIGS. 6 and 7 are graphs illustrating operation of one version of the method of FIGS. 4 and 5 from a signal-based perspective.

FIGS. 8, 9, 10, 11, and 12 are graphs of simulation-based experiments of the method of FIGS. 4 and 5.

Claims

1. A method for measuring a characteristic of an optical signal incident upon a detector characterized by one or more dynamic response parameters, the method comprising: receiving an output signal from the detector;comparing the output signal and a computationally determined response of the detector to a known optical signal incident upon the detector, wherein the response is based on said one or more dynamic parameters; anddetermining the characteristic based on a relationship between the output signal and the computationally determined response.

2. A method as set forth in claim 1, wherein the characteristic is power.

3. A method as set forth in claim 1, wherein the characteristic is energy.

4. A method as set forth in claim 1, wherein the optical signal is an optical pulse.

5. A method as set forth in claim 1, wherein the optical signal is a train of optical pulses.

6. A method as set forth in claim 1, wherein the optical signal is a laser beam.

7. A method as set forth in claim 1, wherein the detector is a pyroelectric detector.

8. A method as set forth in claim 1, wherein the detector is a thermopile detector.

9. A method as set forth in claim 1, wherein said one or more dynamic parameters are selected from the group consisting of gain, cutoff frequency, rise time, fall time, settling time, overshoot, break frequency, natural frequency, resonant frequency, damping ratio, pole, zero, coefficient, and nonlinear term.

10. A method as set forth in claim 1, further comprising: computationally determining, on the basis of said one or more dynamic parameters, the computationally determined response of the detector.

11. A method as set forth in claim 1, further comprising: retrieving from a memory the computationally determined response of the detector.

12. A method as set forth in claim 1, wherein the optical signal comprises a series of laser pulses occurring at a pulse repetition rate, the method further comprising: computationally determining, on the basis of said one or more dynamic parameters, a single-pulse response of the detector to a single laser pulse having a known energy; andsuperimposing time-shifted versions of the single-pulse response, wherein the time-shift between versions equals the pulse repetition rate.

13. A method as set forth in claim 12, wherein the pulses have a known pulse width, and wherein the step of computationally determining a single-pulse response comprises: computationally convolving an impulse response of the detector with a mathematical representation of the single optical pulse.

14. A method as set forth in claim 13, further comprising: receiving input comprising said one or more dynamic parameters; anddetermining the impulse response on the basis of said one or more dynamic parameters.

15. A method as set forth in claim 12, wherein the pulse repetition rate is greater than about 2 kHz.

16. A method as set forth in claim 12, further comprising: measuring the pulse repetition rate.

17. A machine for measuring a characteristic of an optical signal incident upon a detector characterized by one or more dynamic response parameters, the detector producing an output signal in response to the optical signal being incident upon the detector, the machine comprising: an interface to the detector for receipt of the output signal;a memory in which are stored data related to said one or more dynamic parameters; anda processor connected to the memory and to the interface, the processor being configured to compare the output signal from the detector to a response of the detector to a known signal, the processor further being configured to determine, on the basis of the comparison, the characteristic.

18. A machine as set forth in claim 17, wherein the characteristic is power.

19. A machine as set forth in claim 17, wherein the characteristic is energy.

20. A machine as set forth in claim 17, wherein the optical signal is a laser beam.

21. A machine as set forth in claim 17, wherein the detector is a pyroelectric detector.

22. A machine as set forth in claim 17, wherein the detector is a thermopile detector.

23. A machine as set forth in claim 17 further comprising: the detector.

24. A machine as set forth in claim 17, wherein said one or more dynamic parameters are selected from the group consisting of gain, cutoff frequency, rise time, fall time, settling time, overshoot, break frequency, natural frequency, resonant frequency, damping ratio, pole, zero, coefficient, and nonlinear term.

25. A machine as set forth in claim 17, wherein the interface comprises: a data acquisition module connected to the detector, the data acquisition module generating digital samples of the output signal; anda memory, connected to the data acquisition module, in which are stored the digital samples generated by the data acquisition module.

26. A machine as set forth in claim 25, wherein the data acquisition module operates at a sampling rate, and wherein the sampling rate is unrelated to said one or more dynamic response parameters.

27. A machine as set forth in claim 17, further comprising: an input device into which a user can enter input data.

28. A machine as set forth in claim 17, further comprising: a display on which the characteristic is displayed.

29. A computer-readable medium for use with a machine for measuring a characteristic of an optical signal incident upon a detector characterized by one or more dynamic response parameters, the detector producing an output signal in response to the optical signal being incident upon the detector, the machine comprising an interface to the detector for receipt of the output signal, a memory in which are stored data related to said one or more dynamic parameters, and a processor connected to the memory and to the interface, the processor operating according to program instructions embedded on the computer-readable medium, the instructions comprising: instructions to compare the output signal from the detector to a calculated response of the detector to a known signal; andinstructions to determine, on the basis of the comparison, the characteristic.

30. A system for measuring a characteristic of an optical signal incident upon a detector characterized by one or more dynamic response parameters, the system comprising: a means for receiving an output signal from the detector;a means for comparing the output signal and a computationally determined response of the detector to a known optical signal incident upon the detector, wherein the response is based on said one or more dynamic parameters; anda means for determining the characteristic based on a relationship between the output signal and the computationally determined response.

31. A method comprising: observing an output signal from an optical detector detecting one or more optical signals;accessing a characteristic curve of detector response;comparing the observed output signal from the detector to the characteristic curve of detector response; andcalculating at least one characteristic of one or more optical signals based on a relationship of the observed output signal from the detector and the characteristic curve of detector response.

32. The method of claim 31, wherein the characteristic is energy.

33. The method of claim 31, wherein the characteristic is power.

34. The method of claim 31, wherein the accessing step comprises: receiving the characteristic curve.

35. The method of claim 35, wherein the characteristic curve is provided by the detector.

36. The method of claim 31, wherein the output signal is received by an optical meter in communication with the detector.

37. The method of claim 36, wherein the meter compares the output signal of the detector to the characteristic curve of detector response.

38. The method of claim 37, wherein the meter calculates the characteristic curve based on data received from the detector.

39. The method of claim 38, wherein the data is selected from the group consisting of gain, cutoff frequency, rise time, fall time, settling time, overshoot, break frequency, natural frequency, resonant frequency, damping ratio, pole, zero, coefficient, and nonlinear term.

40. The method of claim 31, wherein the accessing step comprises: calculating the characteristic curve.

41. The method of claim 40, wherein the characteristic curve is calculated based on information provided by a user.

42. The method of claim 41, wherein the information is selected from the group consisting of gain, cutoff frequency, rise time, fall time, settling time, overshoot, break frequency, natural frequency, resonant frequency, damping ratio, pole, zero, coefficient, and nonlinear term.

43. A machine for measuring a characteristic of one or more optical pulses incident upon an optical detector characterized by one or more dynamic response parameters, the pulses having a known pulse repetition rate, the machine comprising: an input connection for receiving an output signal from the detector, the output signal resulting from the pulses being incident upon the detector;a memory in which are stored data related to said one or more dynamic parameters;a processor operatively connected to the memory and to the input connection, the processor being configured to calculate, on the basis of the stored data, a response of the detector to a train of optical pulses having the known pulse repetition rate and a known energy, the processor being further configured to compare the output signal from the detector to the calculated response and to measure the characteristic on the basis of that comparison.

44. A machine as set forth in claim 43, wherein the processor calculates the response by determining on the basis of the stored data an impulse response for the detector, computationally convolving the impulse response with a mathematical representation of a single optical pulse having the known energy to thereby determine a single-pulse response of the detector, and superimposing time-shifted versions of the single-pulse response wherein the time-shift between versions equals the known pulse repetition rate.

45. A machine as set forth in claim 43, wherein the pulse repetition rate is known a priori.

46. A machine as set forth in claim 43, further comprising: a pulse rate measuring circuit to determine the pulse repetition rate.