Apparatus and method using non-contact light sensing with selective field of view, low input impedance, current-mode amplification and/or adjustable switching level

An apparatus for detecting light, said apparatus comprising:

• a light detector having a selective viewport, generating a current signal, based on the light received through the selective viewport;
• said selective viewport including an elongated hollow member having at least one light trap member disposed therein;
• a current amplifier coupled to receive the current signal from the light detector, generating an amplified current signal based on the current signal;
• a switch coupled to receive the amplified current signal from the current amplifier, generating an output signal based on the amplified current signal;
• wherein the light detector includes a photodiode mounted at a first end of the elongated, hollow member, the photodiode capable of generating the current signal based on the light received through the current signal based on the light received through a second end of the selective viewport;
• and,
• wherein the elongated, hollow member is formed to include an annular recess at the first end, the annular recess receiving the photodiode.

An apparatus for detecting light, said apparatus comprising:

• a light detector having a selective viewport, generating a current signal, based on the light received through the selective viewport;
• said selective viewport including an elongated hollow member having at least one light trap member disposed therein;
• a current amplifier coupled to receive the current signal from the light detector, generating an amplified current signal based on the current signal;
• a switch coupled to receive the amplified current signal from the current amplifier, generating an output signal based on the amplified current signal;
• wherein the light detector includes an optical fiber having first and second ends, the first end of the optical fiber being mounted in a first end of the elongated, hollow member, and a photodiode arranged in proximity to the second end of the optical fiber, capable of generating the current signal based on the light received through a second end of the selective viewport.

An apparatus for detecting light, said apparatus comprising:

• a light detector having a selective viewport, generating a current signal, based on the light received through the selective viewport;
• said selective viewport including an elongated hollow member having at least one light trap member disposed therein;
• a current amplifier coupled to receive the current signal from the light detector, generating an amplified current signal based on the current signal;
• a switch coupled to receive the amplified current signal from the current amplifier, generating an output signal based on the amplified current signal;
• wherein the current amplifier includes a multiple transistor circuit having a high-gain configuration, and wherein said multiple transistor circuit includes a Darlington pair of transistors.

An apparatus for detecting light, said apparatus comprising:

• a light detector having a selective viewport, generating a current signal, based on the light received through the selective viewport;
• said selective viewport including an elongated hollow member having at least one light trap member disposed therein;
• a current amplifier coupled to receive the current signal from the light detector, generating an amplified current signal based on the current signal;
• a switch coupled to receive the amplified current signal from the current amplifier, generating an output signal based on the amplified current signal;
• and,
• wherein the output signal is a predetermined logic level signal.

An apparatus receiving first and second predetermined voltage levels, said apparatus for detecting a light, said apparatus comprising:

• a first resistor having a first end coupled to the first predetermined voltage level, and a second end;
• a photodiode arranged to receive the light, having a cathode coupled to the second end of the first resistor, and an anode;
• a first NPN transistor having a base coupled to the anode of the photodiode, a collector and an emitter;
• a second NPN transistor having a base coupled to the emitter of the first NPN transistor, an emitter coupled to second predetermined voltage level and a collector coupled to the collector of the first NPN transistor;
• a second resistor having a first end coupled to the collectors of the first and second NPN transistors, and second end;
• a third resistor having a first end coupled to the second end of the second resistor, and a second end coupled to the first predetermined voltage level;
• a PNP transistor having an emitter coupled to the second end of the third transistor, a base coupled to the first end of the third transistor, and a collector;
• a fourth resistor having a first end couple to the collector of the PNP transistor, and a second end coupled to the second predetermined voltage level;
• and,
• an optical fiber having a first end receiving the light and a second end arranged in proximity to the photodiode, to guide the light to the photodiode.

An apparatus receiving first and second predetermined voltage levels, said apparatus for detecting a light, said apparatus comprising:

• a first resistor having a first end coupled to the first predetermined voltage level, and a second end;
• a photodiode arranged to receive the light, having a cathode coupled to the second end of the first resistor, and an anode;
• a first NPN transistor having a base coupled to the anode of the photodiode, a collector and an emitter;
• a second NPN transistor having a base coupled to the emitter of the first NPN transistor, an emitter coupled to second predetermined voltage level and a collector coupled to the collector of the first NPN transistor;
• a second resistor having a first end coupled to the collectors of the first and second NPN transistors, and second end;
• a third resistor having a first end coupled to the second end of the second resistor, and a second end coupled to the first predetermined voltage level;
• a PNP transistor having an emitter coupled to the second end of the third transistor, a base coupled to the first end of the third transistor, and a collector;
• a fourth resistor having a first end couple to the collector of the PNP transistor, and a second end coupled to the second predetermined voltage level;
• a hollow, elongated member having a first end receiving the light from a direction determined by alignment of the hollow, elongated member, and having a second end housing the photodiode;
• a first lead coupled between the cathode of the photodiode and the second end of the first resistor;
• a second lead coupled between the anode of the photodiode and the base of the first NPN transistor;
• and,
• a covering to house at least a part of the first and second leads.

A method comprising the steps of:

• a) selectively viewing light from a light source;
• b) converting at least part of the light selectively viewed in said step (a), into a current signal;
• c) amplifying the current signal to generate an amplified current signal;
• and
• d) switching an output signal between first and second logic levels, based on the amplified current signal;
• e) guiding the light received in the step (a), to a photodiode performing said step (b);
• before performing said steps (a)-(d) aligning a selective viewport for performing said step (a) so that the selective viewport is tilted downward to reduce blockage of the selective viewport by dust.