Infrared obstacle detection in the presence of sunlight
First Claim
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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.
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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.
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Citations
24 Claims
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1. An optical object sensing apparatus having ambient light cancellation capabilities comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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.
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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.
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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.
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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.
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6. The apparatus of claim 4 further comprising:
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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 output and said, second digital output.
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7. The apparatus of claim 6 wherein said controller is adapted to execute an algorithm comprising the following steps:
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(a) initialize OFFSET and COMP parameters;
(b) read said second digital output;
(c) compare the value of said second digital output against a saturation value;
(d) if the value of said second digital output exceeds said saturation value proceed to step (a);
(e) else, compute a value for OFFSET using said value of said second digital output in an offset algorithm;
(f) add said values of OFFSET and COMP and output said control signal based on said added values;
(g) read said digital output;
(h) compute a value for COMP using said value of said digital output in a camp algorithm;
(i) add said values of OFFSET and COMP and output said control signal based on said added values; and
(j) proceed to step (b).
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8. The apparatus of claim 7 wherein a digital-to-resistance converter is utilized to change said gain.
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9. The apparatus of claim 2 wherein said controller is adapted to determine whether said level output exceeds a predetermined limit and adjusts a gain of said preamplifier if said predetermined limit is exceeded.
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10. The apparatus of claim 1 wherein said optical signal is an infrared optical signal.
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11. The apparatus of claim 10 further comprising a filtering agent disposed on said optical detector, said filtering agent for screening non-infrared energy.
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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.
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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.
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14. The apparatus of claim 1 wherein said controller is adapted to execute an algorithm comprised of the following steps;
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(a) reset parameters OFFSET and COMP;
(b) receive said digital output;
(c) test the value of said digital output against &
saturation value;
(d) if said digital value is less than said saturation value, proceed to step (g);
(e) else, test said OFFSET parameter value against a maximum sand if said OFFSET parameter value is equal to said maximum, go to step (b), otherwise increment said OFFSET parameter value;
(f) add said OFFSET parameter value to said COMP parameter value, output a control signal based on the result, and proceed two step (b);
(g) use said value of said digital output in an algorithm to compute a new COMP parameter value; and
(h) proceed to step (f).
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15. The apparatus of claim 1 wherein said controller is adapted to execute an algorithm comprised of the following steps;
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(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 output value is less than said saturation value, proceed to step (g);
(e) test said OFFSET parameter value against a maximum and if said OFFSET parameter value is equal to said maximum, proceed to step (b), otherwise increment said OFFSET parameter value;
(f) add said OFFSET parameter value to said COMP parameter value, output a control signal based on the result and proceed to step (b);
(g) test said digital output value against an undershoot value;
(h) if said, digital output value is less than said undershoot value, decrement said OFFSET parameter value and proceed to step (f);
(i) else, use said digital output value in an algorithm to compute a new value for said COMP parameter; and
(h) proceed to step (f).
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16. An optical object sensing apparatus capable of compensating for the effect of ambient light, comprising:
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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 received optical signal, said optical detector providing a detector output signal indicative of one characteristic of said received optical signal;
a conditioning circuit for 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. - View Dependent Claims (17, 18, 19, 20)
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.
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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.
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19. The of claim 16 wherein said controller is adapted to execute an algorithm comprised of the following steps:
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(a) read the value of said second digital output and set a parameter LITE to that value;
(b) turn on said optical source;
(c) test said value of LITE against a blanking intensity value and if said value of LITE is greater than said blanking intensity value, proceed to step (1);
(d) read the value of said first digital output;
(e) test said value of LITE against a maximum darkness value, and if said of LITE is less than said maximum darkness value, proceed to step (k);
(f) test said value of LITE against a constant effect value and, if said value of LITE is greater than said constant effect value, proceed to step (j);
(g) use the value of LITE as a variable in an algorithm to set a value for a variable COMP;
(h) subtract;
said value of COMP from said first digital output and set a value for a variable INTOUT equal to the result;
(i) stop;
(j) set said value of LITE equal to said constant effect value and proceed to step (g);
(k) set said value of LITE equal to said maximum darkness value an 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 said window to retract; and
(m) set INTOUT to a null value and proceed to step (i).
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20. The apparatus of claim 19, wherein said controller is further adapted to said algorithm by starting 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.
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21. A for canceling the effect of ambient light in an optical object sensing apparatus comprising:
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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 output from said conditioning circuit at a controller;
determining by raid 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. - View Dependent Claims (22)
modifying a 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.
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23. A method for canceling the effect of ambient light on an optical object sensing system comprising:
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optically coup ing 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. - View Dependent Claims (24)
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.
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Specification