Light detecting apparatus and fluid measuring apparatus
A light detecting apparatus includes: a first photoelectric conversion element unit ( 110 ) and a second photoelectric conversion element unit ( 120 ) each of which converts input light to an electric current and output it; an optical current transducer unit ( 100 ) for outputting, as a detected current, a differential current between an electric current outputted by the first photoelectric conversion element unit and an electric current outputted by the second photoelectric conversion element unit; and a first current/voltage converting unit ( 200 ) for amplifying the detected current outputted from the optical current transducer unit, converting it to a voltage signal, and outputting the voltage signal.
1. A light detecting apparatus for detecting a signal light component included in input light, said light detecting apparatus comprising:
an optical current transducer unit which includes first and second photoelectric conversion element units each converting the input light to an electric current and outputting it, and which outputs a differential current between an electric current outputted by the first photoelectric conversion element unit and an electric current outputted by the second photoelectric conversion element unit as a detected current; and
a first current/voltage converting unit which amplifies the detected current outputted from said optical current transducer unit, converts it to a voltage signal, and outputs the voltage signal, wherein
the first and second photoelectric conversion element units are connected in series such that cathodes thereof or anode thereof are connected to each other, and
a connection point between the first and second photoelectric conversion element units connected in series is floating.
2. The light detecting apparatus according to claim 1 , wherein
said optical current transducer unit has first and second terminals which are connected to both ends of the first and second photoelectric conversion element units, respectively, and
said first current/voltage converting unit has:
a fully differential amplifier having a positive input terminal connected to the first terminal, a negative input terminal connected to the second terminal, a negative output terminal for inverting, amplifying, and outputting a signal inputted to the positive input terminal, and a positive output terminal for inverting, amplifying, and outputting a signal inputted to the negative input terminal;
a first negative feedback resistor connected between the positive input terminal and the negative output terminal;
a second negative feedback resistor connected between the negative input terminal and the positive output terminal; and
an amplifier for amplifying a difference between a signal outputted from the positive output terminal and a signal outputted from the negative output terminal and for outputting it as a voltage signal.
3. A fluid measuring apparatus comprising:
an irradiating unit for irradiating a test object with light;
said light detecting apparatus according to claim 1 , to which light from the test object due to the irradiated light is inputted as the input light; and
a calculating unit for calculating fluid information about a fluid in the test object on the basis of the voltage signal outputted by said first current/voltage converting unit.
4. A fluid measuring apparatus comprising:
an irradiating unit for irradiating a test object with light;
said light detecting apparatus according to claim 2 , to which light from the test object due to the irradiated light is inputted as the input light; and
a calculating unit for calculating fluid information about a fluid in the test object on the basis of the voltage signal outputted by said first current/voltage converting unit.
5. A light detecting apparatus for detecting a signal light component included in input light, said light detecting apparatus comprising:
an optical current transducer unit which includes first and second photoelectric conversion element units each converting the input light to an electric current and outputting it, and which outputs a differential current between an electric current outputted by the first photoelectric conversion element unit and an electric current outputted by the second photoelectric conversion element unit as a detected current; and
a first current/voltage converting unit which amplifies the detected current outputted from said optical current transducer unit, converts it to a voltage signal, and outputs the voltage signal, wherein
the first and second photoelectric conversion element units are connected in series such that cathodes thereof or anode thereof are connected to each other,
said light detecting apparatus further comprises a bias voltage applying device which is connected between the first and second photoelectric conversion element units connected in series and which can apply a bias voltage to each of the first and second photoelectric conversion element units, and
said optical current transducer unit outputs each of the electric current outputted by the first photoelectric conversion element unit and the electric current outputted by the second photoelectric conversion element unit if the bias voltage is applied to each of the first and second photoelectric conversion element units by said bias voltage applying device.
6. The light detecting apparatus according to claim 5 , wherein
said optical current transducer unit has first and second terminals which are connected to both ends of the first and second photoelectric conversion element units, respectively, and
said first current/voltage converting unit has:
a fully differential amplifier having a positive input terminal connected to the first terminal, a negative input terminal connected to the second terminal, a negative output terminal for inverting, amplifying, and outputting a signal inputted to the positive input terminal, and a positive output terminal for inverting, amplifying, and outputting a signal inputted to the negative input terminal;
a first negative feedback resistor connected between the positive input terminal and the negative output terminal;
a second negative feedback resistor connected between the negative input terminal and the positive output terminal; and
an amplifier for amplifying a difference between a signal outputted from the positive output terminal and a signal outputted from the negative output terminal and for outputting it as a voltage signal.
7. A fluid measuring apparatus comprising:
an irradiating unit for irradiating a test object with light;
said light detecting apparatus according to claim 5 , to which light from the test object due to the irradiated light is inputted as the input light; and
a calculating unit for calculating fluid information about a fluid in the test object on the basis of the voltage signal outputted by said first current/voltage converting unit.
8. A light detecting apparatus for detecting a signal light component included in input light, said light detecting apparatus comprising:
an optical current transducer unit which includes first and second photoelectric conversion element units each converting the input light to an electric current and outputting it, and which outputs a differential current between an electric current outputted by the first photoelectric conversion element unit and an electric current outputted by the second photoelectric conversion element unit as a detected current;
a first current/voltage converting unit which amplifies the detected current outputted from said optical current transducer unit, converts it to a voltage signal, and outputs the voltage signal;
a third photoelectric conversion element unit for converting the input light to an electric current and outputting it; and
a second current/voltage converting unit for amplifying the electric current outputted from said third photoelectric conversion element unit and converting it to a voltage signal, wherein
an AC signal, which is an output of said first current/voltage converting unit, is standardized by a DC signal, which is an output of said second current/voltage converting unit.
9. The light detecting apparatus according to claim 8 , wherein
said optical current transducer unit has first and second terminals which are connected to both ends of the first and second photoelectric conversion element units, respectively, and
said first current/voltage converting unit has:
a fully differential amplifier having a positive input terminal connected to the first terminal, a negative input terminal connected to the second terminal, a negative output terminal for inverting, amplifying, and outputting a signal inputted to the positive input terminal, and a positive output terminal for inverting, amplifying, and outputting a signal inputted to the negative input terminal;
a first negative feedback resistor connected between the positive input terminal and the negative output terminal;
a second negative feedback resistor connected between the negative input terminal and the positive output terminal; and
an amplifier for amplifying a difference between a signal outputted from the positive output terminal and a signal outputted from the negative output terminal and for outputting it as a voltage signal.
10. A fluid measuring apparatus comprising:
an irradiating unit for irradiating a test object with light;
said light detecting apparatus according to claim 8 , to which light from the test object due to the irradiated light is inputted as the input light; and
a calculating unit for calculating fluid information about a fluid in the test object on the basis of the voltage signal outputted by said first current/voltage converting unit.