Device for optically detecting the presence or absence of an object on an optical path including a variable I-V characteristic circuit to effect in a positive feedback relationship between the radiation source and the radiation detector

Claim 3

A device for optically detecting the presence or absence of an object according to claim 1, wherein said variable I-V characteristic means includes a photosensitive resistor which also constitutes said radiation detector.

Claim 4

A device for optically detecting the presence or absence of an object according to claim 1, wherein said variable I-V characteristic means includes a parallel connection of a first current path and a second current path, and wherein said second current path includes an active element having I-V characteristic changed by a bias applied thereto.

Claim 5

A device for optically detecting the presence or absence of an object according to claim 3, wherein said first current path includes a constant voltage element or a resistor.

Claim 6

A device for optically detecting the presence or absence of an object according to claim 3, wherein said first current path includes a constant voltage element a current through which abruptly increases when the voltage across said constant voltage element exceeds a predetermined voltage value, and wherein said second current path includes a three-terminal active element, and said three-terminal active element receives the output of said radiation detector circuit and assumes such a low impedance value that the voltage across said first and second terminals thereof may become smaller than said predetermined voltage value when said active element is driven.

Claim 7

A device for optically detecting the presence or absence of an object according to claim 5, wherein said constant voltage element includes at least one diode.

Claim 8

A device for optically detecting the presence or absence of an object according to claim 5, wherein said constant voltage element comprises at least one Zener diode.

Claim 9

A device for optically detecting the presence or absence of an object according to claim 5, wherein said three-terminal active element comprises at least one bipolar junction transistor.

Claim 10

A device for optically detecting the presence or absence of an object according to claim 5, wherein said three-terminal active element comprises at least one field effect transistor.

Claim 11

A device for optically detecting the presence or absence of an object according to claim 5, wherein said radiation detector circuit is connected between the control terminal of said three-terminal active element and one of said first or second terminals.

Claim 12

A combination comprising: a pair of power supply terminals; a series connection of a radiation source section and a bias section connected between said pair of power supply terminals, said radiation source section including a radiation source element, the quantity of light radiated by said radiation source element increasing with the current and the voltage drop across said radiation source element being nearly constant irrespective of the current, said bias section producing a voltage drop exceeding a predetermined level in response to a passage current exceeding a predetermined level; a short-circuit path for by-passing said bias section, said short-circuit path including an active element; and a radiation detector section for supplying the output current to said short-circuit path, said radiation detector section including a radiation detector element for receiving the radiation from said radiation source element, whereby when the radiation from the radiation source element is applied to the radiation detector element, said active element in the short-circuit path becomes more conductive and thereby the quantity of light radiated by said radiation source element increases to sufficiently turn on said active element by positive feedback, whereas when the radiation from said radiation source element is interrupted from said radiation detector element, said active element turns off and the current flowing through said radiation source section flows through said bias section.

Claim 13

A combination comprising: a pair of power supply terminals; a series connection of a radiation source section and a bias section connected between said pair of power supply terminals, said radiation source section including a radiation source element, the quantity of light radiated by said radiation source element increasing with the current and the voltage drop across said radiation source element being nearly constant irrespective of the current, said bias section producing a voltage drop exceeding a predetermined level in response to a passage current exceeding a predetermined level; a short-circuit path for by-passing said bias section, said short-circuit path including an active element; and a radiation detector section for supplying the output current to said short-circuit path, said radiation detector section including a radiation detector element for receiving the radiation from said radiation source element, whereby when the radiation from the radiation source element is applied to the radiation detector element, said active element in the short-circuit path becomes more conductive and thereby the quantity of light radiated by said radiation source element increases to sufficiently turn on said active element by positive feedback, whereas when the radiation from said radiation source element is interrupted from said radiation detector element, said active element turns off and the current flowing through said radiation source section flows through said bias section.

Claim 14

A combination according to claim 11, wherein said bias section comprises a constant voltage circuit.

Claim 15

A combination according to claim 12, wherein said constant voltage circuit includes a Zener diode.

Claim 16

A combination according to claim 12, wherein said constant voltage circuit includes a plurality of diodes connected in series.

Claim 17

A combination according to claim 11, wherein said bias section, said short-circuit section, and said radiation detector section are integrated on a single substrate.

Claim 18

Electronic components adapted to be used in a device for optically detecting the presence or absence of an object on an optical path, comprising: a radiation source element having two electrodes for passing the main current therethrough and being capable of emitting a light ray along an optical path, the quantity of light radiated by said radiation source element being increased with an increase of the current level flowing therethrough; and variable current-voltage (I-V) characteristic means having two terminals for passing the main current therethrough, one of said two terminals being connected to one of said two electrodes of said radiation source element, the I-V characteristic of said variable I-V characteristic means being changed in response to a control signal which decreases in magnitude when an object traverse the optical path, in such a positive feed-back manner that the main current is decreased by the traverse of the object.

Claim 19

Electronic components adapted to be used in a device for optically detecting the presence or absence of an object on an optical path, comprising: a radiation source element having two electrodes for passing the main current therethrough and being capable of emitting a light ray along an optical path, the quantity of light radiated by said radiation source element being increased with an increase of the current level flowing therethrough; and variable current-voltage (I-V) characteristic means having two terminals for passing the main current therethrough, one of said two terminals being connected to one of said two electrodes of said radiation source element, the I-V characteristic of said variable I-V characteristic means being changed in response to a control signal which decreases in magnitude when an object traverse the optical path, in such a positive feed-back manner that the main current is decreased by the traverse of the object.

Claim 20

Electronic components according to claim 16, wherein said control signal is an optical signal, and said variable I-V characteristic means comprises a photosensitive element which reduces its resistance when it receives radiation from said radiation source element.

Claim 21

Electronic components according to claim 16, further comprising a radiation detector circuit which generates said control signal, and said variable I-V characteristic means further including a control terminal adapted to receive said control signal.

Claim 22

Electronic components according to claim 18, wherein said variable I-V characteristic means includes a parallel connection of an active circuit including a pair of current terminals as well as said control terminal and a load having a pair of current terminals.

Claim 23

Electronic components according to claim 19, wherein said load has constant voltage characteristics.

Claim 24

A device for optically detecting the presence or absence of an object according to claim 1, wherein when said control signal results in higher or lower current through said variable I-V characteristic means the radiation source has an increase or decrease in light emission, respectively.

Claim 25

A device for optically detecting the presence or absence of an object according to claim 1, wherein said radiation source circuit and said radiation detector circuit are coupled so as to have a positive feedback operating relationship.