Method and device for measuring the angular velocity of a luminance transition zone and steering aid system for fixation and tracking a target comprising at least one such luminance transition zone
First Claim
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1. A method for measuring a time delay between two output signals measured by two adjacent optical sensors, the time delay resulting from a movement of an object moving in a given direction, the method comprising:
- carrying out a spatial filtering of the first and second signals delivered by a first and a second optical sensor, the optical axes of the first and the second optical sensors forming an inter-receptor angle containing the object;
calculating a first order derivative and carrying out a temporal low-pass filtering of the first and second signals delivered by the first and second optical sensors in order to obtain respectively a third and a fourth signals;
calculating the second order temporal derivative of the first and second signals delivered by the first and second sensors in order to obtain respectively a fifth and a sixth signals;
measuring the delay between the first and second signals delivered by the first and second optical sensors, the delay depending on the angular velocity of the luminance transition zone of the object;
wherein the step of measuring the delay is a feedback loop based on an estimated delay between the temporally filtered signals delivered by the first and second optical sensors, the feedback loop comprising the steps of;
estimating a time delay at a first instant between the third and fourth signals;
calculating the error at the first instant between the fourth signal at the first instant and third signal at the first instant delayed by the estimated time delay at the first instant; and
estimating whether the error at the first instant is different from 0, namely whether a delay error at the first instant exists;
if the error at the first instant is different from 0, estimating whether the delay error at the first instant is smaller or bigger than zero on the basis of the error at the first instant and the fifth and sixth signals;
calculating the evolution of the delay on the basis of the time delay at the first instant and the delay error at the first instant.
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Abstract
The present invention relates to a method for measuring a time delay between two output signals measured by two adjacent optical sensors, the time delay resulting from a movement of an object moving in a given direction. The method comprises the steps:
- carrying out a spatial filtering of the signals Ph1 and Ph2 delivered by a first and a second optical sensor;
- calculating a first order derivative and carrying out a temporal low-pass filtering of the signals;
- calculating the second order derivative of the signals;
- measuring the delay between the signals;
and is characterized in that the step of measuring the delay is a feedback loop based on an estimated delay between the temporally filtered signals.
Device and set of devices for measuring the angular velocity of a luminance transition zone and steering aid system for fixation and tracking a target comprising at least one such luminance transition zone.
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Citations
19 Claims
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1. A method for measuring a time delay between two output signals measured by two adjacent optical sensors, the time delay resulting from a movement of an object moving in a given direction, the method comprising:
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carrying out a spatial filtering of the first and second signals delivered by a first and a second optical sensor, the optical axes of the first and the second optical sensors forming an inter-receptor angle containing the object; calculating a first order derivative and carrying out a temporal low-pass filtering of the first and second signals delivered by the first and second optical sensors in order to obtain respectively a third and a fourth signals; calculating the second order temporal derivative of the first and second signals delivered by the first and second sensors in order to obtain respectively a fifth and a sixth signals; measuring the delay between the first and second signals delivered by the first and second optical sensors, the delay depending on the angular velocity of the luminance transition zone of the object; wherein the step of measuring the delay is a feedback loop based on an estimated delay between the temporally filtered signals delivered by the first and second optical sensors, the feedback loop comprising the steps of; estimating a time delay at a first instant between the third and fourth signals; calculating the error at the first instant between the fourth signal at the first instant and third signal at the first instant delayed by the estimated time delay at the first instant; and estimating whether the error at the first instant is different from 0, namely whether a delay error at the first instant exists; if the error at the first instant is different from 0, estimating whether the delay error at the first instant is smaller or bigger than zero on the basis of the error at the first instant and the fifth and sixth signals; calculating the evolution of the delay on the basis of the time delay at the first instant and the delay error at the first instant. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A device for measuring an angular velocity of a luminance transition zone of an object moving in a given direction, the device comprising at least:
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a first and a second optical sensor having each an optical axis that delimit an inter-receptor angle, the inter-receptor angle containing the object; and a lens in order to carry out a spatial filtering of the signals delivered by the first and second optical sensors the lens having an optical center, the first and second optical sensors being placed substantially in the image focal plane of this lens, the two lines linking the centers of the first and second optical sensors and the optical center of the lens being defined as average directions of observation of the first and second optical sensors; and a detection circuit connected to the first and second optical sensors and comprising a band-pass filter in order to carry out a band-pass temporal filtering of the signals delivered by the first and second optical sensors in order to obtain respectively a third and a fourth signals, a means for measuring the delay between the signals delivered by the first and the second optical sensors, the delay depending on the angular velocity of the light transition zone, and a calculator for calculating the angular velocity starting from the delay, the angular velocity being the ratio of the inter-receptor angle to the delay; wherein means for measuring the delay comprises; a means to sample the temporally filtered signals of the first and second optical sensors, this means following the band-pass filter; a means to estimate a time delay at a first instant between the third and fourth signals, a means to compute the error at the first instant between the fourth signal at the first instant and the third signal at the first instant and delayed by the estimated time delay at the first instant; and a means to compute the evolution of the estimated delay starting from the estimated time delay at the first instant and the delay error calculated at the first instant. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification