Two wavelength optical sensor and sensing system
First Claim
1. A sensor for use in a two-wavelength, referenced optical sensing system, for determining a value of a measurand, the sensor comprising:
- wavelength sensitive beamsplitting means for receiving an optical input signal having first and second wavelength bands, and for forming therefrom first and second beams, the first beam containing a major portion of the optical input signal in the first wavelength band, and the second beam containing a major portion of the optical input signal in the second wavelength band;
an encoder, the encoder including means for modulating the intensity of light by an amount that varies as the value of the measurand varies;
wavelength sensitive modulation means for preferentially modulating the intensity of light in the first wavelength band in comparison to light in the second wavelength band; and
optical path means for forming signal and reference paths for the respective first and second beams such that the first beam is modulated by the encoder to form a modulated first beam, and such that the second beam is modulated by the wavelength sensitive modulation means to form a modulated second beam, whereby the relative intensity of the modulated first beam with respect to the modulated second beam provides a measure of the value of the measurand.
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Accused Products
Abstract
A sensor for determining the value of a measurand, such as the rotational position of a shaft (32). The sensor includes a wavelength sensitive beamsplitter (44), an encoder (30), and a wavelength sensitive modulator (48). A beamsplitter receives an optic input signal (60) having first (80) and second (82) wavelength bands, and forms the input signal into first (62) and second (64) beams corresponding to the wavelength bands. The encoder includes a track (36). The modulator preferentially modulates the intensity of light in the first wavelength band in comparison to light in the second wavelength band. The first beam is modulated by the encoder to form a modulated first beam (66), and the second beam is modulated by the modulator to form a modulated second beam (68). A differential embodiment is also provided in which the encoder comprises a pair of mechanically coupled tracks, one track modulating each beam.
38 Citations
18 Claims
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1. A sensor for use in a two-wavelength, referenced optical sensing system, for determining a value of a measurand, the sensor comprising:
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wavelength sensitive beamsplitting means for receiving an optical input signal having first and second wavelength bands, and for forming therefrom first and second beams, the first beam containing a major portion of the optical input signal in the first wavelength band, and the second beam containing a major portion of the optical input signal in the second wavelength band; an encoder, the encoder including means for modulating the intensity of light by an amount that varies as the value of the measurand varies; wavelength sensitive modulation means for preferentially modulating the intensity of light in the first wavelength band in comparison to light in the second wavelength band; and optical path means for forming signal and reference paths for the respective first and second beams such that the first beam is modulated by the encoder to form a modulated first beam, and such that the second beam is modulated by the wavelength sensitive modulation means to form a modulated second beam, whereby the relative intensity of the modulated first beam with respect to the modulated second beam provides a measure of the value of the measurand. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A two-wavelength reference optical sensing system for determining a value of a measurand, the sensor comprising:
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means for producing an optical input signal having first and second wavelength bands; wavelength sensitive beamsplitting means for receiving the optical input signals and for forming therefrom first and second beams, the first beam containing a major portion of the optical input signal in the first wavelength band, and the second beam containing a major portion of the optical input signal in the second wavelength band; an encoder, the encoder including means for modulating the intensity of light by an amount that varies as the value of the measured varies; wavelength sensitive modulation means for preferentially modulating the intensity of light in the first wavelength band in comparison to light in the second wavelength band; optical path means for forming signal and reference paths for the respective first and second beams such that the first beam is modulated by the encoder to form a modulated first beam, and such that the second beam is modulated by the wavelength sensitive modulation means to form a modulated second beam, whereby the relative intensity of the modulated first beam with respect to the modulated second beam provides a measure of the value of the measurand; combining means for combining the modulated first and second beams into a single optical output signal; and detection means including means for receiving the optical output signal, and means for determining the relative intensity of light in the first wavelength band with respect to light in the second wavelength band to thereby providing a measure of the value of the measurand.
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Specification