Photo-sensor cell suitable for IC chip

A photo-sensor cell, comprising:

• (a) a first optical flip-flop sensor for generating two different first binary level signals from a pulsed supply voltage when an intensity of light allowed to be incident thereupon rises beyond or drops below a first incident light threshold (L.sub.1), respectively;
• (b) a second optical flip-flop sensor for generating two different second binary level signals from a pulsed supply voltage when said intensity of light allowed to be incident thereupon rises beyond or drops below a second incident light threshold (L.sub.2) higher than said first threshold (L.sub.1), respectively;
• (c) a first logic cell responsive to said first optical flip-flop sensor, for latching said two different first binary level signals generated by said first optical flip-flop sensor as first latched signals and for generating two different binary level signals corresponding to said first latched signals and, when said first optical flip-flop sensor generates two of the same binary level signals simultaneously, said first logic cell keeping two preceding different binary level signals latched;
• (d) a second logic cell responsive to said second optical flip-flop sensor for latching said two different second binary level signals generated by said second optical flip-flop sensor as second latched signals and for generating two different binary level signals corresponding to said second latched signals and, when said second optical flip-flop sensor generates two of the same binary level signals simultaneously, said second logic cell keeping two preceding different binary level signals latched;
• and
• (e) an output logic cell responsive to said first and second logic cells for generating an output binary signal on the basis of said first and second latched signals of said first and second logic cells from a time when said intensity of light allowed to be incident upon said second optical flip-flop sensor rises beyond said second threshold (L.sub.2) to a time when said intensity of light allowed to be incident upon said first optical flip-flop sensor drops below said first threshold (L.sub.1), in such a way as to provide a hysteresis loop for said output binary signal with respect to said intensity of light for said photo-sensor cell.

A photo-sensor cell comprising:

• (a) a first optical flip-flop sensor for generating first and second binary signals "0" and "1" at first and second output terminals thereof, respectively, when an intensity of light allowed to be incident thereupon rises beyond a first light intensity threshold (L.sub.1), and second and first binary signals "1" and "0" at said first and second output terminals thereof, respectively, when said intensity of light allowed to be incident thereupon drops below said first light intensity threshold (L.sub.1), said first sensor being activated by a pulsed supply voltage;
• (b) a second optical flip-flop sensor for generating first and second binary signals "0" and "1" at first and second output terminals thereof, respectively, when an intensity of light allowed to be incident thereupon rises beyond a second light intensity threshold (L.sub.2) higher than said first light intensity threshold (L.sub.1) and second and first binary signals "1" and "0" at said first and second output terminals thereof, respectively, when said intensity of light allowed to be incident thereupon drops below said second light intensity threshold (L.sub.2), said second sensor being activated by said pulsed supply voltage;
• (c) a first logic cell connected to said first optical flip-flop sensor, for latching said binary signals generated from said first optical flip-flop sensor, and generated second and first binary signals "1" and "0" at first and second output terminals thereof, respectively, in response to said first and second binary signals "0" and "1" from said first and second terminals of said first optical flip-flop sensor and said first and second binary signals "0" and "1" from said first and second output terminals, respectively, in response to said second and first binary signals "1" and "0" of said first and second terminals of said first optical flip-flop sensor, when said first optical flip-flop sensor generates two of the same binary level signals "0" or "1", said first logic cell latching two preceding different binary level signals in response to said binary signals of said first optical flip-flop sensor;
• (d) a second logic cell connected to said second optical flip-flop sensor, for latching said binary signals generated by said second optical cell, and generating second and first binary signals "1" and "0" from first and second output terminals thereof, respectively, in response to said first and second binary signals "0" and "1" from said first and second terminals of said second optical flip-flop sensor and said first and second binary signals "0" and "1" from said first and second output terminals thereof, respectively, in response to said second and first terminals of said second optical flip-flop sensor, when said first optical flip-flop sensor generates two of the same binary level signals "0" and "1", said second logic cell latching two preceding different binary level signals in response to said binary signals from said second optical flip-flop sensor;
• and
• (e) an output logic cell connected to said first and second logic cells, for generating a second binary signal "0" in response to said second and first binary signals "1" and "1" of said first and second terminals of said first logic cell and said first and second terminals of said second logic cell, when said intensity of light rises beyond said second threshold L.sub.2 of said second optical flip-flop sensor and drops below said first threshold L.sub.1 of said first optical flip-flop sensor and a first binary signal "0" in response to said first and second binary signals "0" and "1" of said first and second terminals of said first logic cell and of said first and second terminals of said second logic cell when said intensity of light drops below said second threshold L.sub.2 of said second optical flip-flop sensor and also below said first threshold L.sub.1 of said first optical flip-flop sensor.