Display based optical communication system

• US 6,118,490 A
• Filed: 05/01/1997
• Issued: 09/12/2000
• Est. Priority Date: 05/01/1997
• Status: Expired due to Fees

• Current Assignee: International Learning Group, Inc.
• Original Assignee: Interactive Learning Group Incorporated
• Inventors: Voss, Robert C., Meyer, Michael F., Moore, Kevin B.
• Primary Examiner(s): Kostak, Victor R.
• Application Number:
  US08/847,100
• Time in Patent Office: 1,230 Days
• Field of Search: 348/473, 348/476, 348/478, 348/465, 348/468, 348/553, 348/552, 348/189, 348/12, 348/13
• US Class Current: 348/473
• CPC Class Codes: H04N 5/44 Receiver circuitry for the reception of television signals according to analogue transmission standards H04N5/14 takes precedence
• CPC Class Codes: H04N 7/0255 Display systems therefor
• CPC Class Codes: H04N 7/08 Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band , e.g. by time division H04N7/007 takes precedence

Abstract

A communication system for transmitting information by digital binary signaling over an optical channel as a series of light pulses each beginning with a minimum duration and thereafter being variable to represent different binary states. Transmission is between an optical transmitter based on a portion of a display screen in a display device and a photodetector in a signal processing system. Information is recovered by finding averaged sample values, and is evaluated by comparing it against an accumulated averaged sample based threshold derived from the optical signal at a selected intensity. The information received can be used to verify user inputs to the signal processing system.

Claims

1. A communication system for transmitting information by digital binary signaling over an optical channel, said system comprising:

an optical transmitter provided by a selected portion of a visual display in a display device which can provide light at selected intensities to thereby provide sequences of light pulses in said optical channel such that durations of said light pulses therein represent binary logic states in accord with digital data provided to said optical transmitter from a data source to thereby form a binary pulse duration modulated optical signal in said optical channel, said light pulses in said sequences of said optical signal each having a minimum duration after such pulse begins;

a photodetector positioned across from said selected portion of said visual display to receive said optical signal from said optical channel and provide at an output thereof corresponding electrical signals serving as photodetector output signals; and

a signal processor having an input electrically connected to said photodetector output to receive said photodetector output signals, said signal processor being capable of determining substantially when individual ones of said light pulses began and ended relative to neighboring said light pulses in said sequences thereof.

2. The apparatus of claim 1 wherein said sequences of light pulses are grouped into packets each having a start light pulse to begin each packet followed by further said light pulses to form that packet.

3. The apparatus of claim 1 wherein said photodetector is a photoconductor.

4. The apparatus of claim 1 wherein said photodetector is provided in an at least partially hollow stem of a suction cup that is suitable for mounting to a surface of a transparent material across from said selected portion of said visual display to be held there by relative air pressure differences between front and back sides of said suction cup, said photodetector being set back from said surface of said suction cup that is against said surface of said transparent material by at least one-eighth inch.

5. The apparatus of claim 1 wherein said signal processor has a capacitor connected to said input thereof and a switch connected to said input thereof and to a controller, said switch also having a discharge resistor and a signal input of a magnitude comparator electrically connected thereto to thereby be capable of being directed to electrically connect said capacitor alternatively to said discharge resistor and to said comparator under direction of said controller, said comparator having also an output and an input so as to be capable of having an output signal on said output thereof in one logic state for a signal magnitude on said input thereof going beyond a threshold value and in an opposite logic state for a signal magnitude on said input thereof that fails to reach said threshold value.

6. The apparatus of claim 1 wherein said display device comprises a selected one of a television receiver and a display monitor.

7. The apparatus of claim 2 wherein said signal processor has a capacitor connected to said input thereof and a switch connected to said input thereof and to a controller, said switch also having a discharge resistor and a signal input of a magnitude comparator electrically connected thereto to thereby be capable of being directed to electrically connect said capacitor alternatively to said discharge resistor and to said comparator input under direction of said controller, said comparator having also an output so as to be capable of having an output signal on said output thereof in one logic state for a signal magnitude on said input thereof going beyond a threshold value and in an opposite logic state for a signal magnitude on said input failing to reach said threshold value.

8. The apparatus of claim 3 wherein said photoconductor is formed of cadmium sulfide.

9. The apparatus of claim 4 wherein said suction cup is substantially opaque to light passing therethrough.

10. The apparatus of claim 5 wherein said switch is directed by said controller to repeatedly connect said capacitor between said comparator input and said resistor following a transition from relatively more light to relatively less light at an ending of a light pulse until a transition from relatively less light to relatively more light is found to occur.

11. The apparatus of claim 5 wherein said switch is directed by said controller to repeatedly connect said capacitor between said comparator input and said resistor after a predetermined amount of time following a transition from relatively less light to relatively more light that begins a light pulse.

12. The apparatus of claim 5 wherein a digital counter is provided having an output and having a clock input, said digital counter being capable of counting pulses in clocking signals provided at said clock input thereof by said controller and terminating such counting as controlled by said controller.

13. The apparatus of claim 6 wherein said data source comprises a selected one of a broadcast station, a video tape player, a video disk player and a computer.

14. The apparatus of claim 7 wherein said switch is directed by said controller to repeatedly connect said capacitor between said comparator input and said resistor following a transition from relatively more light to relatively less light at an ending of a light pulse until a transition from relatively less light to relatively more light is found to occur, and wherein said switch is directed by said controller to repeatedly connect said capacitor between said comparator input and said resistor after a predetermined amount of time following a transition from relatively less light to relatively more light that begins a light pulse.

15. The apparatus of claim 10 wherein said switch is directed by said controller, in repeatedly connecting said capacitor between said comparator input and said resistor, to switch from connecting said capacitor to said comparator input to connecting said capacitor to said resistor following a signal on said comparator input going beyond said threshold value.

16. The apparatus of claim 11 wherein said switch is directed by said controller, in repeatedly connecting said capacitor between said comparator input and said resistor, to switch from connecting said capacitor to said comparator input to connecting said capacitor to said resistor following a signal on said comparator input going beyond said threshold value.

17. The apparatus of claim 12 wherein a digital accumulator is provided having an output and having an input electrically connected to said digital counter output to receive counts therefrom for summing and temporary storage of resulting sums in said digital accumulator.

18. The apparatus of claim 14 wherein that number of light pulses in a packet is counted following a start light pulse to determine if a complete packet of light pulses has been received.

19. The apparatus of claim 17 wherein said switch is directed by said controller at selected times to repeatedly connect said capacitor between said comparator input and said resistor with each connection to said comparator input being of sufficient duration to cause said comparator to change output states to thereby enable said digital counter to provide a count for each such duration having a value proportional to that duration which counts are summed in said digital accumulator to provide a corresponding accumulation of such counts, there being one such accumulation provided for each said selected time.

20. The apparatus of claim 19 wherein a digital comparator having a signal input is electrically connected to said digital accumulator output to compare said accumulation to a threshold value, said threshold value being determined from a fraction of an accumulation based on said optical transmitter providing light of a selected intensity.

21. An optical signal receiving system for coupling to an optical channel to receive therefrom optical signals provided as sequences of light pulses representing binary states, said system comprising:

a photodetector for coupling to said optical channel to receive said optical signals therefrom and provide at an output thereof corresponding electrical signals serving as photodetector output signals; and

a signal processor having an input electrically connected to said photodetector output to receive said photodetector output signals, said signal processor being capable of initiating a sequence of repeated measurements of said photodetector output signal magnitude to thereby provide a corresponding sequence of magnitude representations which are summed to provide a corresponding accumulation of those said magnitude representations, including a calibration accumulation based on said optical signal being of a selected light intensity and bit detection accumulations based on optical intensities occurring in connection with said light pulses, said signal processor providing said calibration accumulation after a selected modification thereto as a threshold magnitude against which magnitudes of bit detection accumulations are compared in determining which binary states are represented by said light pulses.

22. The apparatus of claim 21 wherein said modification of said calibration accumulation is providing a fraction thereof resulting from addition of other fractions of said calibration accumulation.

23. A method for transmitting information by digital binary signaling over an optical channel, said system comprising:

transmitting an optical signal provided by a selected portion of a visual display in a display device, serving as an optical transmitter, which can selectively provide light to thereby provide sequences of light pulses in said channel as said optical signal with durations of said light pulses therein representing binary logic states in accord with digital data provided to said optical transmitter by a data source to thereby form a binary pulse duration modulated optical signal in said channel, said light pulses in said sequences of said optical signal each having a minimum duration after their beginning;

converting said optical signal to a corresponding electrical signal in a photodetector positioned across from said selected portion of said visual display to receive said optical signal from said channel, including converting first and second portions of said optical signal, representing corresponding first and second datums from said data source, to first and second portions of said electrical signal, said electrical signal and first and second portions thereof serving as a photodetector output signal and portions thereof;

acquiring said photodetector output signal first portion in a signal processor capable of determining substantially when individual ones of said light pulses began and ended relative to neighboring said light pulses in said sequences thereof; and

evaluating said photodetector output signal first portion with a processor signal representing a third datum to determine whether a selected relationship is present between said first datum and said third datum if said processor signal, acquired from a source other than said photodetector, is presented for such evaluation within a selected time duration of said acquiring of said photodetector output signal first portion and before any acquiring of said photodetector output signal second portion.

24. The method of claim 23 wherein a fourth datum is subsequently represented by another processor signal acquired from a source other than said photodetector before any acquiring of said photodetector output signal second portion, and further comprising evaluating said photodetector output signal first portion with said other processor signal representing said fourth datum to determine whether a selected relationship is present between said first datum and said fourth datum.

25. The method of claim 23 wherein said processor signal representing a third datum is acquired from a timer.

26. The method of claim 24 where in said other processor signal representing said fourth datum is acquired from a timer.

27. The method of claim 24 wherein said evaluating of said photodetector output signal first portion with said other process or signal representing said fourth datum occurs even if said evaluating of said photodetector output signal first portion with said processor signal representing said third datum does not occur because said processor signal representing said third datum is not presented within a selected time duration of acquiring said photodetector output first signal portion and before acquiring of said photodetector signal output portion.

28. The method of claim 26 wherein said processor signal representing said third datum is acquired from a further timer.