Photodetecting apparatus having intensity tuneable light irradiating unit
First Claim
1. A photodetecting apparatus comprising:
- intensity tuneable light irradiating means for generating light to irradiate a scattering and absorption medium, an intensity of said light being modulated by a modulating signal having an ac component with a predetermined frequency, an amount of modulation of generating light or a quantity of generating light being adjustable in accordance with an external instruction;
photodetecting means for detecting an optical signal having a component with said predetermined frequency emerging from said scattering and absorption medium after said optical signal is generated from said intensity tuneable light irradiating means, irradiates said scattering and absorption medium and propagates in said scattering and absorption medium;
feedback means for receiving an optically detected signal corresponding to the intensity of said optical signal emitted from said photodetecting means, sending an instruction to said intensity tuneable light irradiating means to increase the quantity of generating light or to increase the amount of modulation of generating light when the intensity of an ac component of said optically detected signal detected by said photodetecting means is smaller than a predetermined value, and sending an instruction to said intensity tuneable light irradiating means to decrease the quantity of generating light or to decrease the amount of modulation of generating light when the intensity of the ac component of said optically detected signal detected by said photodetecting means is larger than the predetermined value; and
processing means for receiving said modulating signal and said optically detected signal and obtaining one of a timing difference between said modulating signal and said optically detected signal, and a phase difference between said modulating signal and said optically detected signal.
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Accused Products
Abstract
Light the intensity of which is modulated to the initial intensity by a modulating signal having an ac component with a predetermined frequency and which is from the intensity tuneable light irradiating unit irradiates the scattering and absorption medium which is an object to be measured. The modulated light incident on the scattering and absorption medium propagates in the scattering and absorption medium, emerges therefrom and is incident to the photodetecting unit, and the photodetecting unit converts the incident light into an electric signal corresponding to the intensity of the incident light, and thereafter, outputs the electric signal as an optically detected signal. The feedback unit extracts the ac component from the input optically detected signal, and the intensity of the ac electric signal and the adjusting value are compared and the variation of the quantity of generating light is sent to the intensity tuneable light irradiating unit. Then, the phase difference detection is performed as the gain of the photodetecting means is fixed and the intensity of the ac component having a modulation frequency emitted from the photodetecting means is maintained so as to substantially match with the preset adjusting value.
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Citations
18 Claims
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1. A photodetecting apparatus comprising:
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intensity tuneable light irradiating means for generating light to irradiate a scattering and absorption medium, an intensity of said light being modulated by a modulating signal having an ac component with a predetermined frequency, an amount of modulation of generating light or a quantity of generating light being adjustable in accordance with an external instruction; photodetecting means for detecting an optical signal having a component with said predetermined frequency emerging from said scattering and absorption medium after said optical signal is generated from said intensity tuneable light irradiating means, irradiates said scattering and absorption medium and propagates in said scattering and absorption medium; feedback means for receiving an optically detected signal corresponding to the intensity of said optical signal emitted from said photodetecting means, sending an instruction to said intensity tuneable light irradiating means to increase the quantity of generating light or to increase the amount of modulation of generating light when the intensity of an ac component of said optically detected signal detected by said photodetecting means is smaller than a predetermined value, and sending an instruction to said intensity tuneable light irradiating means to decrease the quantity of generating light or to decrease the amount of modulation of generating light when the intensity of the ac component of said optically detected signal detected by said photodetecting means is larger than the predetermined value; and processing means for receiving said modulating signal and said optically detected signal and obtaining one of a timing difference between said modulating signal and said optically detected signal, and a phase difference between said modulating signal and said optically detected signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A photodetecting apparatus comprising:
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intensity tuneable light irradiating means for generating a first number of lights each having a different predetermined wavelength to irradiate a scattering and absorption medium, an intensity of each said light being modulated by a modulating signal having an ac component with a predetermined frequency, an amount of modulation of generating light or a quantity of generating light being adjustable in accordance with an external instruction; light branching means for receiving optical signals each having said predetermined frequency component emerging from said scattering and absorption medium after said optical signals are generated from said intensity tuneable light irradiating means, irradiate said scattering and absorption medium and propagate in said scattering and absorption medium, and branching said optical signals into said first number of lights each having said predetermined wavelength; photodetecting means comprising said first number of photodetecting units arranged for each said light having said predetermined wavelength, for detecting light emitted from said light branching means; feedback means for receiving an optically detected signal for each said predetermined wavelength corresponding to the intensity of said optical signal for each said predetermined wavelength emitted from said photodetecting means, sending an instruction to said intensity tuneable light irradiating means to increase the quantity of generating light having the respective wavelength or to increase the amount of modulation of generating light having the respective wavelength when the intensity of an ac component of said optically detected signal detected by said photodetecting means is smaller than a predetermined value, and sending an instruction to said intensity tuneable light irradiating means to decrease the quantity of generating light having the respective wavelength or to decrease the amount of modulation of generating light having the respective wavelength when the intensity of the ac component of said optically detected signal detected by said photodetecting means is larger than the predetermined value; and processing means for receiving said modulating signal and said optically detected signals and obtaining one of a timing difference between said modulating signal and said optically detected signal, and a phase difference between said modulating signal and said optically detected signal, for each said predetermined wavelength. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification