Photoelectronic apparatus

Claim 2

Photoelectronic apparatus having photoelectric convertor means including a first operational photoelectric convertor which in operation is adapted to receive a light beam from a source, a processing circuit adapted to process an output from the photoelectric convertor means to generate a control signal in response to an obstruction of the light beam, and protective means adapted to prevent the photoelectronic apparatus from failing to recognize the obstruction in the presence of unwanted stray light, the protective means comprising a second auxiliary photoelectric convertor disposed in the immediate vicinity of the first operational photoelectric convertor, and circuit means for forming a weighted difference signal between the outputs of the first operational photoconvertor and the second auxiliary photoconvertor, the last mentioned means determining a predtermined threshold for stray light below which the photoelectric convertor will always deliver the control signal in the presence of the obstruction irrespective of the level of stray light and above which as a safety measure the control signal will always be delivered irrespective of whether the beam is obstructed or not.

Claim 3

Photoelectronic apparatus according to claim 1 wherein the auxiliary photoelectric convertor comprises at least two individual photoelectric convertors connected in parallel and disposed on either side of the operational convertor.

Claim 4

Photoelectronic light barrier apparatus comprising: light source means for producing an operational light beam; light receiving means including an operational photoelectric convertor disposed in fixed disposition with respect to said light source means to receive said operational light beam, and an auxiliary photoelectric convertor arranged in the immediate vicinity of said operational photoelectric convertor and positioned outside the light beam so as to receive substantially no light from said light source means but so as to receive stray light incident on said light receiving means; an electronic processing circuit; circuit means operatively coupled with the convertors for forming a weighted difference signal from the outputs of the auxiliary convertor and of the operational photoelectric convertor and for passing the weighted difference signal to the electronic processing circuit; the electronic processing circuit including means defining a threshold and adapted to produce a first signal when said weighted difference signal exceeds said threshold and a second signal when said weighted difference is less than said threshold, one of said first and second signals indicating the presence of an obstruction in said light beam and the other being indicative of the absence of an obstruction in said light beam; the circuit means applying a level of weighting in forming said weighted difference signal which defines a threshold for stray light below which the photoelectric light barrier apparatus is compensated for the effects of stray light to reliably indicate the presence of an obstruction and above which the light barrier apparatus will always indicate the presence of an obstruction irrespective of whether or not an obstruction is actually present.

Claim 5

Photoelectronic light barrier apparatus comprising: light source means for producing an operational light beam; light receiving means including an operational photoelectric convertor disposed in fixed disposition with respect to said light source means to receive said operational light beam, and an auxiliary photoelectric convertor arranged in the immediate vicinity of said operational photoelectric convertor and positioned outside the light beam so as to receive substantially no light from said light source means but so as to receive stray light incident on said light receiving means; an electronic processing circuit; circuit means operatively coupled with the convertors for forming a weighted difference signal from the outputs of the auxiliary convertor and of the operational photoelectric convertor and for passing the weighted difference signal to the electronic processing circuit; the electronic processing circuit including means defining a threshold and adapted to produce a first signal when said weighted difference signal exceeds said threshold and a second signal when said weighted difference is less than said threshold, one of said first and second signals indicating the presence of an obstruction in said light beam and the other being indicative of the absence of an obstruction in said light beam; the circuit means applying a level of weighting in forming said weighted difference signal which defines a threshold for stray light below which the photoelectric light barrier apparatus is compensated for the effects of stray light to reliably indicate the presence of an obstruction and above which the light barrier apparatus will always indicate the presence of an obstruction irrespective of whether or not an obstruction is actually present.

Claim 6

Photoelectronic apparatus in accordance with claim 3 wherein the auxiliary photoelectric convertor directly borders on the operational photoelectric convertor.

Claim 7

Photoelectronic apparatus according to claim 3 wherein the auxiliary photoelectric convertor surrounds the operational convertor.

Claim 8

Photoelectronic apparatus according to claim 3 wherein the auxiliary photoelectric convertor comprises at least two individual photoelectric convertors connected in parallel and disposed on either side of the operational convertor.

Claim 9

Photoelectronic apparatus according to claim 3 wherein the operational and auxiliary photoelectric convertors are connected directly together in parallel across a resistor at the input to the processing circuit.

Claim 10

Photoelectronic apparatus according to claim 3 wherein the said operational and auxiliary photoelectric convertors are so connected together opposition in that the effect of the auxiliary convertor is greater than that of the operational convertor.

Claim 11

Photoelectronic apparatus according to claim 8 wherein two series connected resistors are provided at the input side of the processing circuit, and wherein the operational photoelectric convertor is connected across one of the resistors and the auxiliary photoelectric convertor is connected with reversed polarity across both said resistors.

Claim 12

Photoelectronic apparatus according to claim 8 wherein the auxiliary photoelectric convertor is connected via an amplifier in opposition to the operational photoelectric convertor.

Claim 13

Photoelectronic apparatus according to claim 3 wherein the processing circuit comprises a circuit having a threshold value.

Claim 14

Photoelectronic apparatus according to claim 9 wherein the auxiliary photoelectric convertor is connected via an amplifier in opposition to the operational photoelectric convertor.