Interferometer Calibration Methods and Apparatus
First Claim
1. A method for calibrating an interferometer having first and second reflecting surfaces and an optical gap between the first and second reflecting surfaces, the method comprising the steps of:
- a) providing an actuator adapted to control the optical gap in response to application of an electrical signal;
b) illuminating the interferometer with a beam of substantially monochromatic light having a predetermined wavelength, the beam being oriented at a first predetermined angle of incidence to at least one of the first and second reflecting surfaces; and
c) detecting light reflected from the interferometer at a second predetermined angle to the at least one of the first and second reflecting surfaces while varying an electrical signal applied to the actuator, thereby establishing a calibrated relationship between the applied electrical signal and an optical path length of the interferometer.
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Abstract
A Fabry-Perot (FP) interferometer includes substantially parallel first and second reflecting surfaces spaced apart by an optical gap between the first and second reflecting surfaces. The FP interferometer also has a mechanism for controlling the optical gap. The mechanism includes a plurality of electrostatic control plates. Each electrostatic control plate has a fixed control-plate area. Each control plate is adapted to control the optical gap by application of a control-plate voltage. The control-plate areas are related by integral ratios.
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Citations
50 Claims
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1. A method for calibrating an interferometer having first and second reflecting surfaces and an optical gap between the first and second reflecting surfaces, the method comprising the steps of:
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a) providing an actuator adapted to control the optical gap in response to application of an electrical signal;
b) illuminating the interferometer with a beam of substantially monochromatic light having a predetermined wavelength, the beam being oriented at a first predetermined angle of incidence to at least one of the first and second reflecting surfaces; and
c) detecting light reflected from the interferometer at a second predetermined angle to the at least one of the first and second reflecting surfaces while varying an electrical signal applied to the actuator, thereby establishing a calibrated relationship between the applied electrical signal and an optical path length of the interferometer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method for calibrating an interferometer having first and second reflecting surfaces and an optical gap between the first and second reflecting surfaces, the method comprising the steps of:
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a) providing an actuator adapted to control the optical gap in response to application of an electrical signal;
b) illuminating the interferometer with a beam of substantially monochromatic light having a predetermined wavelength, the beam being oriented at a first predetermined angle of incidence to at least one of the first and second reflecting surfaces;
c) varying the electrical signal applied to the actuator in a series of discrete steps, while detecting light reflected from the interferometer at a second predetermined angle to the at least one of the first and second reflecting surfaces with a photosensor having an analog photosensor output;
d) converting the analog photosensor output to a digital photosensor signal;
e) storing a digital value of a digital photosensor signal corresponding to each discrete step of the electrical signal applied to the actuator; and
f) calculating an optical path length corresponding to each discrete step of the applied electrical signal, thereby establishing a calibrated relationship between the applied electrical signal and optical path length of the interferometer. - View Dependent Claims (24)
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25. A method for calibrating an interferometer having first and second reflecting surfaces and an optical gap between the first and second reflecting surfaces, the method comprising the steps of:
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a) providing an electrostatic actuator having a plurality of control plates, each control plate having a fixed control-plate area and each control plate being adapted to control the optical gap by application of a control-plate voltage;
b) illuminating the interferometer with substantially monochromatic light; and
c) detecting light reflected from the interferometer while selectively applying a fixed voltage to each control plate of the plurality of control plates, thereby establishing a calibrated relationship between the applied control-plate voltage and an optical path length of the interferometer. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
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42. A method for calibrating an interferometer having first and second reflecting surfaces and an optical gap between the first and second reflecting surfaces, the method comprising the steps of:
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a) providing an electrostatic actuator having a number N of control plates, each control plate having a fixed control-plate area and each control plate being adapted to control the optical gap by application of a control-plate voltage, the N control plates having fixed control-plate areas related by integral ratios of 1, 2, 4, . . . , 2N−
1.b) illuminating the interferometer with substantially monochromatic light; and
c) detecting light reflected from the interferometer while selectively applying a fixed voltage to each control plate of the N control plates, thereby establishing a calibrated relationship between the applied control-plate voltage and an optical path length of the interferometer.
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43. A Fabry-Perot interferometer, comprising:
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a) substantially parallel first and second reflecting surfaces spaced apart by an optical gap between the first and second reflecting surfaces; and
b) means for controlling the optical gap, including a plurality of electrostatic control plates, each electrostatic control plate having a fixed control-plate area and each control plate being adapted to control the optical gap by application of a control-plate voltage, the control-plate areas being related by integral ratios. - View Dependent Claims (44, 45, 46, 47, 48, 49)
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50. A method of using an electrostatic actuator having a plurality of control plates for calibrating an interferometer having first and second reflecting surfaces and having an optical gap between the first and second reflecting surfaces, the method comprising the steps of:
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a) illuminating the interferometer with substantially monochromatic light, b) controlling the optical gap by selectively applying a fixed voltage to each control plate of the plurality of control plates, and c) detecting light reflected from the interferometer, thereby establishing a calibrated relationship between the applied control-plate voltage and an optical path length of the interferometer.
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Specification