Infrared obstacle detection in the presence of sunlight

• US 20040056199A1
• Filed: 09/25/2002
• Published: 03/25/2004
• Est. Priority Date: 09/25/2002
• Status: Active Grant

• Current Assignee: Prospects Corp.
• Original Assignee: Prospects Corp.
• Inventors: OʼConnor, Christopher J., Hawley, Stephen A., Davis, James D. Jr., Vernaz, Todd R.
• Granted Patent: US 6,812,466 B2
• Time in Patent Office: Days
• US Class Current: 250/341.1
• CPC Class Codes: E05F 15/40 Safety devices, e.g. detection of obstructions or end positions
• CPC Class Codes: E05F 15/43 responsive to disruption of energy beams, e.g. light or sound
• CPC Class Codes: E05F 2015/434 with cameras or optical sensors
• CPC Class Codes: E05Y 2900/531 Doors
• CPC Class Codes: E05Y 2900/542 Roof panels
• CPC Class Codes: E05Y 2900/55 Windows
• CPC Class Codes: G01J 5/06 Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity for adjusting of solid angle of collected radiation G01J5/07; means for wavelength selection G01J5/0801
• CPC Class Codes: G01S 17/04 Systems determining the presence of a target
• 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: G01V 8/12 using one transmitter and one receiver

Abstract

In an infrared obstruction detection system, an apparatus is used to detect the presence of ambient light and initiate compensation to minimize the effects of the ambient light on the performance of the system. In one embodiment, the magnitude of the ambient light is measured and an offset proportional to that magnitude is fed to the obstruction detection system such that the data indicative of an obstacle are not obscured. In another embodiment, the apparatus continually monitors the effect of ambient light and adjusts the obstacle detection information during the changing states of the ambient light detected.

Claims

1. An optical object sensing apparatus having ambient light cancellation capabilities comprising:

an optical source and optical detector optically coupled for monitoring a target area that reflects at least a portion of an optical signal for detection as a received optical signal, said optical signal having temporal characteristics allowing said optical signal to be distinguished from ambient light, said optical detector providing a detector output signal indicative of the characteristics of said received optical signal;

a conditioning circuit for outputting a conditioned output indicative of one characteristic of said detector output signal and a level output indicative of a second characteristic of said detector output signal;

a sensing apparatus for using said conditioned output to sense the presence of an object in said target area; and

a controller for receiving said level output from said conditioning circuit, converting said level output to a digital output, determining the magnitude of an ambient light-induced signal in said digital level output and outputting a control signal to a second input of said conditioning circuit, wherein said control signal is used by said conditioning circuit as an error compensating offset.

2. The apparatus of claim 1 wherein said conditioning circuit comprises:

a summing junction having a plurality of inputs and a summed output, a first input of said summing junction being connected to said optical detector for receiving said detector output signal, and a second input of said summing junction being connected to said control signal;

a preamplifier connected to said summed output for receiving a summed signal and for providing said level output;

and further wherein said controller includes;

an analog-to-digital converter for receiving said level output and for outputting a digital output; and

a digital-to-analog converter for receiving a digital control signal from said controller and outputting an analog signal as said control signal to said second input of said summing junction.

3. The apparatus of claim 2 further comprising a digital-to-resistance converter having a variable resistance that is set based on an algorithm using said digital output, said variable resistance connected into a gain circuit of said preamplifier for controlling the transfer function of said preamplifier.

4. The apparatus of claim 2 further comprising an amplifier for receiving said level output and for amplifying said level output prior to it being received by said analog-to-digital converter, wherein said amplified level output is proportional to said summed signal.

5. The apparatus of claim 4 wherein said conditioned output is AC connected to the remainder of said optical object sensing apparatus and said level output is DC connected to said amplifier.

6. The apparatus of claim 4 further comprising:

a low-gain amplifier for receiving said summed output in parallel with said amplifier and for providing a reduced range output proportional to said summed output; and

a second analog-to-digital converter for receiving said reduced range output and for outputting a second digital output to said controller, wherein said controller outputs said control signal based on said digital signal and said second digital signal.

7. The apparatus of claim 6 wherein said controller is operative to execute the following steps comprising a loop:

a. initialize said offset and comp parameters

b. read said second digital output;

c. test the value of said second digital output against a saturation level;

d. if the value exceeds said saturation level proceed to step a;

e. compute an offset value using said value of said second digital output in an offset algorithm;

f. add said values of offset and comp, output a control signal based on said result;

g. read said digital output;

h. compute a comp value using said value of said digital output in a comp algorithm;

i. add said values of offset and comp, output a control signal based on the result; and

j. proceed to step b.

8. The apparatus of claim 7 wherein a digital-to-resistance converter is utilized to change said gain.

9. The apparatus of claim 2 wherein said controller determines whether said level output exceeds a predetermined limit and adjusts a gain of said preamplifier when the level is exceeded.

10. The apparatus of claim 1 wherein said optical signal is an infrared optical signal.

11. The apparatus of claim 10 further comprising a filtering agent disposed on said optical detector, said filtering agent for screening non-infrared energy.

12. The apparatus of claim 10 wherein said optical object sensing apparatus is operative in conjunction with a power window and wherein said window partially covering said target area filters said non-infrared component of said optical signal received by said optical detector.

13. The apparatus of claim 1 wherein said controller is selected from the group consisting of a microcontroller, a microprocessor and a programmable logic device.

14. The apparatus of claim 1 wherein said controller is operative to execute the following steps constituting a loop:

a. reset parameters offset and comp;

b. receive said digital output;

c. test a digital value of said digital output against a saturation value;

d. if said digital value is less than said saturation value, go to step g;

e. test said offset parameter against a maximum and if said offset parameter is equal to said maximum, go to step b, otherwise increment said offset parameter;

f. add said value of said offset parameter to said value of said comp parameter, and output a control signal based on the result and go to step b;

g. use said digital value in an algorithm to compute a new value for said comp parameter; and

h. proceed to step f.

15. The apparatus of claim 1 wherein said controller is operative to execute the following steps constituting a loop:

a. reset parameters offset and comp;

b. receive said digital output;

c. test the value of said digital output against a saturation value;

d. if said digital value is less than said saturation value, go to step g;

e. test said offset parameter against a maximum and if said offset parameter is equal to said maximum, go to step b, otherwise increment said offset parameter;

f. add said value of said offset parameter to said value of said comp parameter, output a control signal based on the result and go to step b;

g. test said digital value against an undershoot parameter;

h. if said digital value indicates an undershoot, decrement said offset parameter and proceed to step f;

i. use said digital value in an algorithm to compute a new value for said comp parameter; and

h. proceed to step f.

16. An optical object sensing apparatus capable of compensating for the effect of ambient light, comprising:

an optical source and detector optically coupled for monitoring a target area that reflects at least a portion of an optical signal for detection as a received optical signal, said optical detector providing a detector output signal indicative of one characteristic of said received optical signal;

a conditioning circuit outputting a first digital output representative of said detector output signal and a second digital output representative of an integrated output signal; and

a controller for receiving said first and second digital outputs, said controller adapted to determine an effect of said ambient light on said integrated output signal from said first and second digital outputs and adapted to output a detection output.

17. The apparatus of claim 16, wherein said conditioning circuit comprises:

a preamplifier for receiving said detector output signal and for providing a conditioned output;

a first analog-to-digital converter for receiving said conditioned output; and

a second analog-to-digital converter for receiving an integrated output signal from said optical object sensing system.

18. The apparatus of claim 16 further comprising a digital-to-resistance converter having a variable resistance that is set based on an algorithm using said first digital output, said variable resistance connected into a gain circuit of said preamplifier for controlling the transfer function of said preamplifier.

19. The apparatus of claim 16 wherein said controller is operative to execute the following steps:

a. read the value of said second digital output and set parameter LITE to that value;

b. turn on said optical source;

c. test LITE against a blanking intensity value and if LITE is brighter than said blanking intensity value, proceed to step 1;

d. read the value of said first digital output;

e. test LITE against a maximum darkness value, and if LITE is darker than said maximum darkness value, proceed to step k;

f. test LITE against a constant effect value and if LITE is brighter than said constant effect value, proceed to step j;

g. use the value of LITE as a variable in an algorithm to set a variable COMP;

h. subtract COMP from said first digital output to set a variable INTOUT;

i. pass variable INTOUT to said obstacle detection mechanism and stop;

j. set LITE equal to said constant effect value and proceed to step g;

k. set LITE equal to said maximum darkness value and proceed to step g;

l. test whether a window in the field of view of the optical detector is higher than a set position and if so, command window to retract; and

m. set INTOUT to a null value and proceed to step i.

20. The apparatus of claim 19 wherein said controller starts execution at step a when an express close command is received from a window control mechanism and when a monitor command is received from said obstacle detection mechanism.

21. A method for canceling the effect of ambient light in an optical object sensing apparatus comprising:

optically coupling an optical source and detector for monitoring a target area that reflects at least a portion of an optical signal for detection as a received optical signal, said optical detector providing a detector output signal indicative of one characteristic of said received optical signal;

outputting a digital output representative of said detector output signal from a conditioning circuit;

receiving said digital output from said conditioning circuit at a controller;

determining by said controller the magnitude of an ambient light-induced signal in said digital output;

outputting a control signal to said conditioning circuit; and

adjusting said digital output, by said conditioning circuit, to compensate for said ambient light-induced signal on the basis of said control signal.

22. The method of claim 21 further comprising:

modifying a gain of said conditioning circuit based on said digital output by controlling a digital-to-resistance converter using an algorithm using said digital output, the resistance of said digital-to-resistance converter incorporated into a gain portion of said conditioning circuit.

23. A method for canceling the effect of ambient light on an optical object sensing system comprising:

optically coupling an optical source and detector for monitoring a target area that reflects at least a portion of an optical signal for detection as a received optical signal, said optical detector providing a detector output signal indicative of one characteristic of said received optical signal;

receiving said detector output signal at a conditioning circuit;

outputting from said conditioning circuit a first digital output representative of said detector output signal and a second digital output representative of an integrated output signal; and

receiving said first and second digital outputs in a controller adapted to determine an effect of the ambient light on said integrated output signal and to output a detection output based upon said first and second digital outputs.

24. The method of claim 23 further comprising:

modifying a gain of said conditioning circuit based on said first digital output by controlling a digital-to-resistance converter using an algorithm using said first digital output, the resistance of said digital-to-resistance converter incorporated into a gain portion of said conditioning circuit.