Infrared occupant position detection system and method for a motor vehicle

• US 6,298,311 B1
• Filed: 03/01/1999
• Issued: 10/02/2001
• Est. Priority Date: 03/01/1999
• Status: Expired due to Fees

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Wu, Cunkai, Thayer, Peter Alan, Griffin, Dennis Palmer, Fultz, William W., Perisho, Robert Allan Jr.
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): Bui, Bryan
• Application Number:
  US09/260,224
• Time in Patent Office: 946 Days
• Field of Search: 702/150-155, 702/159, 280/730.1, 280/734, 280/735, 180/268-269, 180/271, 701/45-46, 701/49, 356/375-376, 356/614, 356/621-622
• US Class Current: 702/150
• CPC Class Codes: B60R 21/01534 using electromagneticwaves, e.g. infrared
• CPC Class Codes: B60R 21/01542 detecting passenger motion
• CPC Class Codes: G01S 17/04 Systems determining the presence of a target
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: G01S 7/4814 of transmitters alone
• CPC Class Codes: G01S 7/4868 Controlling received signal intensity or exposure of sensor
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection
• CPC Class Codes: G06V 10/143 Sensing or illuminating at different wavelengths
• CPC Class Codes: G06V 20/59 inside of a vehicle, e.g. relating to seat occupancy, driver state or inner lighting conditions
• CPC Class Codes: G06V 40/10 Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands

Abstract

An improved IR occupant position detection system that provides accurate and reliable classification and position information at a speed sufficient to timely inhibit or otherwise control deployment of occupant restraints. A two-dimensional array of IR emitters is selectively activated to periodically illuminate two or more of predetermined viewing planes in the vicinity of a passenger seating area, and the reflected IR energy is detected by a photo-sensitive receiver and analyzed to detect the presence of an occupant, to classify the occupant, and to identify and dynamically track the position of the occupant'"'"'s head/torso relative to predefined zones of the passenger compartment. Modulating the intensity of the emitted IR beams with a known carrier frequency, band-pass filtering the received signal, and synchronously detecting the filtered signal distinguishes the reflected IR energy from other signals picked up by the IR receiver. Additionally, a two stage adaptive control mechanism compensates for the variation in intensity of the reflected energy with distance between the emitter and the occupant. The emitter is implemented with orthogonal anode and cathode power rails with individual IR LED elements placed at each anode-cathode intersection. Optical dispersion within the package is greatly reduced by an opaque cover layer that effectively forms a well for each LED element.

Claims

1. A system for detecting a position of an occupant of a motor vehicle including an IR transmitter for emitting a beam of IR light through an optical lens for reflection off the occupant, an IR receiver for receiving the reflected IR light and forming an occupant range related input signal therefrom, and a controller coupled to said IR transmitter and IR receiver for determining the position of the occupant from said input signal, an improvement wherein:

the IR transmitter includes an IR light emitting diode for emitting said beam of IR light, and a current source effective when enabled to activate said light emitting diode with a sinusoidal current of predetermined frequency so that the emitted beam of IR light has an intensity that is modulated at said predetermined frequency;

the IR receiver includes a photo-sensitive device that generates a current signal having an occupant range related component at said predetermined frequency and representing the range of said occupant, and a band-pass filter for extracting said occupant range related component from said current signal to form said input signal.

2. The improvement of claim 1, wherein:

the IR receiver includes a peak following circuit for tracking an instantaneous peak value of said input signal when enabled by said controller; and

the controller includes means for enabling said peak following circuit so as to detect said occupant range related component in synchronism with peak values of said sinusoidal current to form said input signal.

3. The improvement of claim 1, wherein said photo-sensitive device generates first and second current signals, each having an occupant range related component at said predetermined frequency, and said IR receiver includes first and second band-pass filters for coupled to said first and second current signals for respectively extracting first and second range related components therefrom to form first and second input signals for said controller.

4. The improvement of claim 3, wherein

the IR receiver includes first and second peak following circuits for tracking instantaneous values of said first and second range related components when enabled by said controller;

and

the controller includes means for enabling said first and second peak following circuits so as to detect peak values of said first and second range related components in synchronism with peak values of said sinusoidal current to form said first and second input signals.

5. A system for detecting a position of an occupant of a motor vehicle including an IR transmitter for emitting a beam of IR light through an optical lens for reflection off the occupant, an IR receiver for receiving the reflected IR light and forming an occupant range related input signal therefrom, and a controller coupled to said IR transmitter and IR receiver for determining a range of the occupant from said input signal, an improvement wherein:

the IR receiver includes a photo-sensitive device that generates a current signal having an occupant range related component representing the range of said occupant, a circuit for extracting such component from said current signal, and a programmable gain amplifier for amplifying the extracted component to form said input signal; and

the controller receives the input signal at an input port thereof, and adjusts the gain of said programmable gain amplifier based on a magnitude of the received input signal so as to drive said input signal into a desired input range of said input port.

6. The improvement of claim 5, wherein:

the controller includes a microprocessor, and the input port is an analog-to-digital input port of the microprocessor.

7. The improvement of claim 5, wherein:

the controller increases the gain of the programmable gain amplifier if the received input signal is lower than said desired input range, and decreases the gain of the programmable gain amplifier if the received input signal is higher than said desired input range.

8. The improvement of claim 5, wherein:

said photo-sensitive device generates first and second current signals, each having an occupant range related component, and said IR receiver includes first and second circuits for respectively extracting the first and second components from said first and second current signals, and first and second programmable gain amplifiers for amplifying the extracted first and second components to form first and second input signals for said controller; and

said controller receives the first and second occupant range related input signals at said input port, and individually adjusts the gain of said first and second programmable gain amplifiers based on respective magnitudes of the received first and second input signals so as to drive the first and second input signals into a desired input range of said input port.

9. A system for detecting a position of an occupant of a motor vehicle including an IR transmitter for emitting a beam of IR light through an optical lens for reflection off the occupant, an IR receiver for receiving the reflected IR light and forming first and second occupant range related input signals therefrom, and a controller coupled to said IR transmitter and IR receiver for determining a range of the occupant from said input signals, an improvement wherein:

the IR receiver includes a photo-sensitive device that produces first and second currents used to form said first and second input signals;

the IR transmitter includes an IR light emitting diode for emitting said beam of IR light, and a current source effective when enabled to activate said light emitting diode with an activation current having a selectable magnitude, the first and second currents produced by said photo-sensitive device of said IR receiver having magnitudes that vary in relation to the selected magnitude of said activation current; and

the controller receives the first and second occupant range related input signals, determines a range of the occupant based on a ratio of such received first and second input signals, and selects the magnitude of said current source based on a magnitude of the received first and second input signals so as to limit a range in magnitude of the first and second currents.

10. The improvement of claim 9, wherein:

the controller selects an increased magnitude of said current source if the received first or second input signals are lower than a first predetermined threshold, and selects a decreased magnitude of said current source if the received first or second input signals are higher than a second predetermined threshold, said first and second predetermined thresholds corresponding to a desired range in variation of said first and second currents.

11. A system for detecting a position of an occupant of a motor vehicle including an IR transmitter for emitting a beam of IR light through an optical lens for reflection off the occupant, an IR receiver for receiving the reflected IR light and developing an occupant range related input signal therefrom, and a controller coupled to said IR transmitter and IR receiver for determining the position of the occupant from said input signal, an improvement wherein:

the IR transmitter includes an array of IR light emitters that are individually and selectively activated to emit beams of IR light corresponding to respective positions of the activated IR light emitters in said array;

the controller includes;

a microprocessor for requesting activation of a selected IR light emitter, receiving the input signal corresponding to the selected IR light emitter, and determining the occupant position based on a plurality of said input signals; and

a state machine that operates in response to a requested activation of a selected IR light emitter to enable activation of the selected IR light emitter by the IR transmitter and reception of the reflected IR light by the IR receiver, and to signal the microprocessor that the input signal corresponding to the selected IR light emitter is ready to be received.

12. The improvement of claim 11, wherein:

the IR transmitter activates the selected IR light emitter so as to modulate the emitted beam of IR light at a predetermined frequency;

the IR receiver includes a sensor and circuit for producing a range related oscillatory signal at said predetermined frequency, and a detection circuit for detecting an instantaneous value of said oscillatory signal to form said input signal; and

the state machine enables said detection circuit to detect the value of said oscillatory signal in synchronism with the modulation of the emitted beam of IR light.

13. The improvement of claim 11, wherein:

the IR receiver develops a range related signal, and includes a sampling circuit effective when enabled to sample and average one or more values of said range related signal;

the microprocessor determines a specified number of times that said range related signal should be sampled; and

the state machine enables said sampling circuit said specified number of times before signaling the microprocessor that the an input signal corresponding to the selected IR light emitter is ready to be received.

14. A system for detecting a position of an occupant of a motor vehicle including an IR transmitter for emitting a beam of IR light through an optical lens for reflection off the occupant, an IR receiver for receiving the reflected IR light and developing an occupant range related input signal therefrom, and a controller coupled to said IR transmitter and IR receiver for determining the position of the occupant from the input signal, an improvement wherein:

the IR transmitter includes a two-dimensional array of IR light emitting diodes that are individually and selectively activated to emit a beam of IR light corresponding to a position of the activated IR light emitting diode in said array, said array including a first plurality of parallel conductor segments defining columns of said array and a second plurality of parallel conductor segments oriented perpendicular to said first plurality of segments and defining rows of said array, each of said IR light emitting diodes being positioned at a unique intersection of a row and column of said array, and activated when the conductor segments defining such row and column are coupled to a current source.

15. The improvement of claim 14, wherein:

each of the IR light emitting diodes has a first terminal mounted on a column conductor segment, and a second terminal that is wire-bonded to a row conductor segment adjacent said column conductor segment.

16. The improvement of claim 14, wherein:

said array includes a plurality of insulator segments disposed between said first and second plurality of conductor segments at least at the intersections thereof so as to electrically isolate said first and second plurality of conductor segments.

17. The improvement of claim 14, wherein:

the array includes a cover layer of opaque material substantially covering said first and second pluralities of conductor segments except in proximity to the row and column intersections of said array, thereby defining cavities in which said IR light emitting diodes are positioned.

18. The improvement of claim 17, wherein said cover layer has a thickness sufficient to substantially prevent dispersion of IR light emitted by said IR light emitting diodes.

19. A system for detecting a position of an occupant of a motor vehicle including an IR transmitter for emitting a beam of IR light through an optical lens for reflection off the occupant, an IR receiver for receiving the reflected IR light and developing an occupant range related input signal therefrom, and a controller coupled to said IR transmitter and IR receiver for determining the position of the occupant relative to a predefined zone of the vehicle, an improvement wherein:

the IR transmitter includes a two-dimensional array of IR light emitters that are individually and selectively activated to emit a beam of IR light corresponding to a position of the activated IR light emitter in said array;

the controller selectively and repeatedly activates each of the IR light emitters in a determined sequence and receives corresponding input signals to identify an emitter array position corresponding to a beam of IR light illuminating a head/torso of the occupant, and to indicate when the identified emitter array position corresponds to a beam of emitted light passing through said predefined zone.

20. The improvement of claim 19, wherein:

the controller is mounted on a portion of said vehicle which is higher than the occupant; and

the array position corresponding to a minimum detected occupant range is identified as the position that illuminates the head/torso of the occupant.

21. The improvement of claim 19, wherein:

the controller forms a grouping of array positions contiguous with said identified position, and indicates when any position in the grouping corresponds to a beam of emitted light passing through said predefined zone.

22. The improvement of claim 21, wherein:

the controller compares range information corresponding to the contiguous positions of said grouping, and confirms that said positions correspond to beams of IR light illuminating the head/torso of the occupant when a variation of said compared range information is less than a predetermined amount.

23. The improvement of claim 21, wherein:

the controller activates the IR light emitters corresponding to the grouping of positions of said array at a repetition rate that is higher than for other positions of said array.

24. The improvement of claim 19, wherein:

the controller activates the IR light emitter corresponding to the identified position of said array at a repetition rate that is higher than for other positions of said array.