Methods and devices to determine the wavelength of a laser beam
First Claim
1. A method for detection and wavelength discrimination of a monochromatic light beam with at least one detector pair consisting of a first photo detector and a second photodetector aligned with the first photo detector and a wavelength dependent variable attenuator on top of said second photo detector, the method comprising the steps of;
- measuring a first photo current generated in said first photo detector due to illumination of said monochromatic light beam;
measuring a second photo current generated in said photo detector due to illumination of said monochromatic light beam through said variable attenuator;
comparing value of said first photo current with a threshold value to detect if the intensity of Laid monochromatic light beam is sufficient for wavelength determination; and
obtaining a ratio between value of said second photo current'"'"'s value and said first photo current'"'"'s value; and
determining the wavelength of said light beam from said ratio.
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Abstract
Methods for wavelength determination of a monochromatic light beam are described. The methods involve a detector unit containing at least one pair of photo detectors. One of the detectors in each detector pair is covered with a variable attenuator and the other is not covered by the variable attenuator. The optical transmission coefficient of the variable attenuator is a monotonic function of wavelength. Under illumination of a monochromatic light, the photocurrents produced in the detectors with and without the variable attenuator are compared. The relative values of the photocurrents are used to determine the wavelength of the monochromatic light.
23 Citations
20 Claims
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1. A method for detection and wavelength discrimination of a monochromatic light beam with at least one detector pair consisting of a first photo detector and a second photodetector aligned with the first photo detector and a wavelength dependent variable attenuator on top of said second photo detector, the method comprising the steps of;
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measuring a first photo current generated in said first photo detector due to illumination of said monochromatic light beam; measuring a second photo current generated in said photo detector due to illumination of said monochromatic light beam through said variable attenuator; comparing value of said first photo current with a threshold value to detect if the intensity of Laid monochromatic light beam is sufficient for wavelength determination; and obtaining a ratio between value of said second photo current'"'"'s value and said first photo current'"'"'s value; and
determining the wavelength of said light beam from said ratio. - View Dependent Claims (2, 3, 4)
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5. A device for detection and wavelength discrimination of a monochromatic light beam comprising:
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at least one detector pair consisting of a first photo detector and a second photo detector aligned with the first photo detector and a wavelength dependent variable attenuator superimposed over said second photo detector, the device having means for measuring a first photo current generated in said first photo detector due to illumination by said monochromatic light beam; means for measuring a second photo current generated in said second photo detector due to illumination by said monochromatic light beam through said variable attenuator; means for obtaining a ratio between a value of said second photo current and a value of said first photo current; and means for determining the wavelength of said light beam from said ratio. - View Dependent Claims (6, 7, 8, 9, 10)
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11. A device for detecting and wavelength discriminating of a monochromatic light beam comprising:
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at least one detector pair consisting of a first photo detector and a second photo detector adjacent to each other on a single substrate, a thin film wavelength depend ent variable attenuator being superimposed on a surface of the second photo detector, the device having means for measuring a first photo current generated in said first photo detector due to illumination by said monochromatic light beam; means for measuring a second photo current generated in said second photo detector due to illumination by said monochromatic light beam through said variable filter; means for obtaining a ratio between said second photo current and said first photo current; and means for determining the wavelength of said light beam from said ratio. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification