Apparatus and method for detecting an object using digitally encoded optical signals

• US 5,902,998 A
• Filed: 06/16/1997
• Issued: 05/11/1999
• Est. Priority Date: 02/04/1997
• Status: Expired due to Term

• Current Assignee: Control Products Incorporated (Emerson Electric Company)
• Original Assignee: Control Products Incorporated (Emerson Electric Company)
• Inventors: Olson, Gary R L, Pichotta, Andrew J., Ham, Eardley L.
• Primary Examiner(s): ALLEN, STEPHONE B
• Application Number:
  US08/876,303
• Time in Patent Office: 694 Days
• Field of Search: 250/221, 250/222.1, 250/559.4, 250/214 B, 250/214 C, 340/555-557, 340/583, 356/375, 356/376
• US Class Current: 235/472.01
• CPC Class Codes: G01S 17/04 Systems determining the presence of a target

Abstract

A proximity detection apparatus for detecting objects within a predetermined region. The apparatus comprises a transmitter, a receiver, a microcontroller, and a power supply that provides electrical potential to the transmitter, the receiver, and the microcontroller. The microcontroller produces transmitted data bursts to the transmitter, the transmitter emits optical data bursts toward the predetermined region where, if the object is present, the optical data bursts reflect off of the object as return optical bursts. The receiver detects the return optical bursts and transmits received data bursts to the microcontroller. The microcontroller compares the received data bursts against the transmitted data bursts to verify that the object is present in the predetermined region. The microcontroller produces an output signal to control equipment based the object being present or absent from the predetermined region.

Claims

1. A proximity detection apparatus for detecting objects within a predetermined region, comprising:

(a) a transmitter having an axis of projection oriented toward said predetermined region;

(b) a receiver having an axis of reception oriented to intersect said axis of reception in said predetermined region;

(c) a microcontroller electrically connected to said transmitter and to said receiver; and

(d) means for providing electrical power to said microcontroller, said transmitter, and said receiver,

wherein said microcontroller electrically produces transmitted data bursts to said transmitter, said transmitter receives said transmitted data bursts and emits corresponding optical bursts toward said predetermined region, said optical bursts reflect off of said object as return optical bursts if said object is within said predetermined region, said receiver detects said return optical bursts and electrically transmits corresponding received data bursts to said microcontroller, and said microcontroller compares said transmitted data bursts to said received data bursts and verifies that said object is within said predetermined region.

2. The proximity detection apparatus of claim 1, wherein said transmitted data bursts are produced asynchronously.

3. The proximity detection apparatus of claim 2, wherein a time interval between successive transmitted data bursts is gradually increased during a predetermined periodic time band.

4. The proximity detection apparatus of claim 2, wherein a time interval between successive transmitted data bursts is random.

5. The proximity detection apparatus of claim 1, wherein said transmitter includes one or more light emitting diodes that emit said corresponding optical bursts and said receiver includes one or more photo transistors that detect said return optical bursts and electrically transmit said received data bursts corresponding to said return optical bursts.

6. The proximity detection apparatus of claim 5, wherein said receiver includes an amplifier for converting low level signals received from said photo transistors to high level signals.

7. The proximity detection apparatus of claim 5, wherein said receiver includes a comparator having an adjustable threshold, said comparator receiving variable-level data and driving an output line at logic levels, said output line being electrically connected to said microcontroller.

8. The proximity detection apparatus of claim 1, wherein a remote sensor unit functions as said transmitter and said receiver, said sensor unit being electrically connected to said microcontroller and being capable of asynchronously and bidirectionally communicating with said microcontroller, said sensor unit including:

(a) a light emitting diode functioning as said transmitter;

(b) a high speed receiver switch controlling said light emitting diode;

(c) two photo transistors functioning as said receiver;

(d) an amplifier converting low-level signals produced by said photo transistors into higher level signals; and

(e) a comparator having a lower threshold, said comparator receiving variable-level data from said amplifier and driving an output data line at logic levels, said output line being electrically connected to said microcontroller.

9. The proximity detection apparatus of claim 1, further comprising a software program operating within said microcontroller, wherein said software program produces said transmitted data burst, reads said received data burst, and verifies said received data burst against said transmitted data burst.

10. The proximity detection apparatus of claim 9, wherein said software program is designed to manage steps performed by said software program for each of said transmitted data bursts while operating in said scan sensor module, said steps including:

(a) building a data byte comprised of eight bits;

(b) serially shifting said data byte one bit at a time from a suitable output port of said microcontroller, said shifting of said data byte occurring at a predetermined data rate;

(c) serially reading said received digital data bursts on a bit by bit basis from a suitable input port of said microcontroller; and

(d) verifying said received digital data bursts against said transmitted digital data bursts.

11. The proximity detection apparatus of claim 10, wherein said step of building an data byte includes the steps of retrieving a four-bit segment from a memory location and appending the complement of said four-bit segment to said four-bit segment.

12. The proximity detection apparatus of claim 11, wherein said data byte and the complement of said data byte are alternately transmitted as said electrically transmitted data bursts.

13. The proximity detection apparatus of claim 10, wherein said step of building a data byte includes the step of retrieving said data byte from a memory location.

14. The proximity detection apparatus of claim 10, wherein said step of building an data byte includes the step of rotating said bits of said data byte.

15. The proximity detection apparatus of claim 10, wherein said software program asynchronously adjusts time intervals between transmissions of said digital data bursts.

16. The proximity detection apparatus of claim 15, wherein said software program gradually increases said time intervals while sweeping a predetermined time band.

17. The proximity detection apparatus of claim 15, wherein said software program randomly adjusts said time intervals.

18. The proximity detection apparatus of claim 9, wherein said software program verifies said received data burst against said transmitted data burst by initializing an eight-bit counter to zero before each transmission and incrementing said counter for each valid reception, whereby said received digital data burst is verified against said transmitted eight-bit data byte only if said counter equals eight.

19. The proximity detection apparatus of claim 9, wherein said software program has a latch module, said software program changes from operating in said scan sensor module to said latch module when said software program detects said object by verifying said received data bursts against said transmitted data bursts, said latch module differing from said scan sensor module in that said program transmits a steady state signal rather than said transmitted data burst causing said transmitter to emit a continuous optical beam rather than said optical burst.

20. The proximity detection apparatus of claim 19, wherein said software program operating in said latch module farther performs steps to identify whether said object is absent or present and whether said receiver is detecting optical noise, said steps including:

(a) comparing a received signal to said steady state transmitted signal when said transmitted signal is on, whereby said object is absent if said received signal is off in which case said software program enters said scan sensor module; and

(b) comparing said received signal to said steady state transmitted signal when said transmitted signal is switched on, off and on again, whereby said receiver is detecting optical noise if said received signal is on when said transmitted signal is switched off in which case said software program enters said scan sensor module, and said object is present if said receiver signal is on whenever said transmitted signal is on and said received signal is off whenever said transmitted signal is off in which case said software remains in said latch module.

21. The proximity detection apparatus of claim 1, further comprising a second receiver electrically connected to said microcontroller, said second receiver having an axis of reception intersecting said axis of projection of said transmitter, wherein said second receiver is positioned and arranged with respect to said transmitter and said receiver to create a larger predetermined region in which to detect said object.

22. The proximity detection apparatus of claim 1, wherein said receiver and said transmitter have a line driver, said line driver allowing said receiver and said transmitter to be positioned further from said microcontroller than without said line driver.

23. The proximity detection apparatus of claim 1, further including an interface circuit designed to control equipment, wherein said microcontroller emits output signals to said interface circuit, and said interface circuit emits output signals to said equipment based upon whether said object is detected within said predetermined region.

24. The proximity detection apparatus of claim 23, wherein said interface circuit includes load relays.

25. The proximity detection apparatus of claim 1, wherein a microprocessor replaces said microcontroller.

26. A proximity detection apparatus for detecting objects within a predetermined region, comprising:

(a) a transmitter having an axis of projection oriented toward said predetermined region, said transmitter including one or more light emitting diodes;

(b) a receiver having an axis of reception oriented to intersect said axis of reception in said predetermined region, said receiver including one or more photo transistors;

(c) a microcontroller electrically connected to said transmitter and to said receiver; and

(d) means for providing electrical power to said microcontroller, said transmitter, and said receiver;

(e) a software program operating within said microcontroller; and

(f) an interface circuit designed to control equipment,

wherein, said software program operating within said microcontroller asynchronously produces transmitted data bursts to said transmitter, said transmitter receives said transmitted data bursts and emits corresponding optical bursts toward said predetermined region, said optical bursts reflect off of said object as return optical bursts if said object is within said predetermined region, said receiver detects said return optical bursts and electrically transmits corresponding received data bursts to said microcontroller, said software program within said microcontroller reads and compares said received data bursts to said transmitted data bursts and verifies that said object is within said predetermined region, and emits an output signal to said interface circuit upon verifying said object is within said predetermined region.

27. A computer program operating within a proximity detection apparatus for detecting objects within a predetermined region, said program having a searching module in which said program performs steps to probe said predetermined region for said object, said steps comprising:

(a) asynchronously producing digitally encoded transmitted data bursts to a transmitter, said transmitter emitting optical data bursts corresponding to said transmitted data bursts toward said predetermined region, said optical data bursts reflect off of said object as return optical data bursts toward a receiver if said object is present in said predetermined region, said receiver transmitting received data bursts corresponding to said return optical data and to said transmitted data bursts;

(b) reading said received data bursts; and

(c) verifying that said received data bursts exactly duplicate said transmitted data bursts.

28. The computer program of claim 27, wherein said step of asynchronously producing data bursts includes the steps of resetting a predetermined time interval between said transmitted data bursts and gradually increasing said time interval while sweeping a predetermined periodic time band.

29. The computer program of claim 27, wherein said step of asynchronously producing data bursts includes the step of generating a random time interval using a randomizing function derived by a cyclical redundancy check on constantly varying data.

30. The computer program of claim 27, further comprising a latch module which, upon said program verifying said object is within said predetermined region, transmits a steady-state signal rather than said transmitted data bursts, toggles said steady-state signal on and off, reads a received signal resulting from the toggled steady-state signal, and compares said received signal against said steady-state signal to determined if said object is present or absent from said predetermined region or if said receiver is detecting optical noise.

31. A method for detecting objects within a predetermined region, said method comprising the steps of:

(a) asynchronously producing digitally encoded transmitted data bursts;

(b) converting said transmitted data bursts into optical data bursts corresponding to said transmitted data bursts;

(c) emitting said optical data bursts to said predetermined region;

(d) detecting return optical data bursts that reflect off of said object if said object is in said predetermined region;

(e) converting said return optical data bursts into received data bursts;

(f) reading said received data bursts; and

(g) verifying said received data bursts against said transmitted data bursts,

wherein said object is present in said predetermined region if said received data bursts exactly duplicate said digitally encoded transmitted data bursts.

32. The method for detecting objects within a predetermined region of claim 31, wherein the step of asynchronously producing digitally encoded transmitted data bursts includes the steps of resetting a predetermined time interval between said transmitted data bursts and gradually increasing said time interval while sweeping a predetermined periodic time band.

33. The method for detecting objects within a predetermined region of claim 31, wherein the step of asynchronously producing digitally encoded transmitted data bursts includes the steps of generating a random time interval using a randomizing function based on a cyclical redundancy check on constantly varying data.

34. The method for detecting objects within a predetermined region of claim 31, further including, upon detecting said object in said predetermined region, the steps of:

(a) ceasing to produce said digitally encoded transmitted data bursts;

(b) transmitting a steady-state signal and a corresponding optical signal;

(c) toggling said steady state signal and said corresponding optical signal on and off; and

(d) determining whether said object is absent or present or whether said receiver is detecting noise by comparing received signals against said steady-state signals.