Passive optical velocity measurement device and method
First Claim
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1. A velocity sensing apparatus for sensing the velocity of a wheeled vehicle comprising:
- a first sensor receiving light from the vehicle along a first optical path having a first optical path length, the light having a predetermined intensity spatial frequency component associated with a selected feature of the vehicle, the first sensor comprising;
a first grating having a line frequency selected such that the first grating passes light from the vehicle at the spatial frequency associated with the selected feature of the vehicle,a first detector receiving light passed by the first grating and generating a first signal indicative of motion of the vehicle;
a second sensor receiving the light from the vehicle along a second optical path having a second optical path length, a differential optical path length being defined by a difference between the first and second optical path lengths, the second sensor comprising;
a second grating having the line frequency selected such that the second grating passes light from the vehicle at the spatial frequency associated with the selected feature of the vehicle,a second detector receiving light passed by the second grating and generating a second signal indicative of motion of the vehicle; and
a processor coupled to the first sensor and the second sensor, the processor receiving the first signal and generating therefrom a first angular velocity measurement for the vehicle, and receiving the second signal and generating therefrom a second angular velocity measurement for the vehicle, wherein the processor computes an absolute velocity of the vehicle using the differential optical path length and the first and second angular velocity measurements.
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Abstract
An optical velocity measuring device includes a pair of V/H sensors effectively located at two different distances from a moving object. Each sensor is used to determine an image velocity and a corresponding angular velocity of the object. The angular velocity measurements and the difference in distance or optical path length of the individual sensors are used to determine the absolute linear tangential speed of the object without determining the absolute distance to the object.
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Citations
13 Claims
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1. A velocity sensing apparatus for sensing the velocity of a wheeled vehicle comprising:
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a first sensor receiving light from the vehicle along a first optical path having a first optical path length, the light having a predetermined intensity spatial frequency component associated with a selected feature of the vehicle, the first sensor comprising; a first grating having a line frequency selected such that the first grating passes light from the vehicle at the spatial frequency associated with the selected feature of the vehicle, a first detector receiving light passed by the first grating and generating a first signal indicative of motion of the vehicle; a second sensor receiving the light from the vehicle along a second optical path having a second optical path length, a differential optical path length being defined by a difference between the first and second optical path lengths, the second sensor comprising; a second grating having the line frequency selected such that the second grating passes light from the vehicle at the spatial frequency associated with the selected feature of the vehicle, a second detector receiving light passed by the second grating and generating a second signal indicative of motion of the vehicle; and a processor coupled to the first sensor and the second sensor, the processor receiving the first signal and generating therefrom a first angular velocity measurement for the vehicle, and receiving the second signal and generating therefrom a second angular velocity measurement for the vehicle, wherein the processor computes an absolute velocity of the vehicle using the differential optical path length and the first and second angular velocity measurements. - View Dependent Claims (2, 3, 4)
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5. A method for sensing the velocity of a wheeled vehicle comprising:
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predetermining an intensity spatial frequency component of light associated with a selected feature of the vehicle; with a first sensor, receiving light from the vehicle along a first optical path having a first optical path length; providing a first grating having a line frequency selected such that the first grating passes light from the vehicle at the spatial frequency associated with the selected feature of the vehicle; with a first detector, receiving light passed by the first grating and generating a first signal indicative of motion of the vehicle; in a processor, receiving the first signal and generating a first angular velocity measurement for the vehicle; with a second sensor, receiving the light from the vehicle along a second optical path having a second optical path length; computing a differential optical path length, said differential optical path length being defined by a difference between the first and second optical path lengths; providing a second grating having the line frequency selected such that the second grating passes light from the vehicle at the spatial frequency associated with the selected feature of the vehicle; with a second detector, receiving light passed by the second grating and generating a second signal indicative of motion of the vehicle; in the processor, receiving the second signal and generating a second angular velocity measurement for the vehicle; and in the processor, computing an absolute velocity of the vehicle using the differential optical path length and the first and second angular velocity measurements.
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6. A velocity sensing apparatus for sensing the velocity of a wheeled vehicle comprising:
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a first sensor receiving light from the vehicle along a first optical path having a first optical path length, the light having an intensity spatial frequency component of about 0.04 cycles per inch associated with a selected feature of the vehicle, the first sensor comprising; a first grating having a line frequency selected such that the first grating passes light from the vehicle at the spatial frequency associated with the selected feature of the vehicle, a first detector receiving light passed by the first grating and generating a first signal indicative of motion of the vehicle, and a second sensor receiving the light from the vehicle along a second optical path having a second optical path length, a differential optical path length being defined by a difference between the first and second optical path lengths, the second sensor comprising; a second grating having the line frequency selected such that the second grating passes light from the vehicle at the spatial frequency associated with the selected feature of the vehicle, a second detector receiving light passed by the second grating and generating a second signal indicative of motion of the vehicle; and a processor coupled to the first sensor and the second sensor, the processor receiving the first signal and generating a first angular velocity measurement for the vehicle, and receiving the second signal and generating a second angular velocity measurement for the vehicle, wherein the processor computes an absolute velocity of the vehicle using the differential optical path length and the first and second angular velocity measurements. - View Dependent Claims (7, 8)
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9. A method for sensing the velocity of a wheeled vehicle comprising:
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selecting an intensity spatial frequency component of light at about 0.04 cycles per inch and associated with a selected feature of the vehicle; with a first sensor, receiving light from the vehicle along a first optical path having a first optical path length; providing a first grating having a line frequency selected such that the first grating passes light from the vehicle at the spatial frequency associated with the selected feature of the vehicle; with a first detector, receiving light passed by the first grating and generating a first signal indicative of motion of the vehicle; in a processor, receiving the first signal and generating a first angular velocity measurement for the vehicle; with a second sensor, receiving the light from the vehicle along a second optical path having a second optical path length; computing a differential optical path length, said differential optical path length being defined by a difference between the first and second optical path lengths; providing a second grating having the line frequency selected such that the second grating passes light from the vehicle at the spatial frequency associated with the selected feature of the vehicle; with a second detector, receiving light passed by the second grating and generating a second signal indicative of motion of the vehicle; in the processor, receiving the second signal and generating a second angular velocity measurement for the vehicle; and in the processor, computing an absolute velocity of the vehicle using the differential optical path length and the first and second angular velocity measurements.
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10. A velocity sensing apparatus for sensing the velocity of a wheeled vehicle comprising:
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a first sensor receiving light from the vehicle along a first optical path having a first optical path length, the light having an intensity spatial frequency component associated with a wheel well of the vehicle, the first sensor comprising; a first grating having a line frequency selected such that the first grating passes light from the vehicle at the spatial frequency associated with the wheel well of the vehicle, a first detector receiving light passed by the first grating and generating a first signal indicative of motion of the vehicle, and a second sensor receiving the light from the vehicle along a second optical path having a second optical path length, a differential optical path length being defined by a difference between the first and second optical path lengths, the second sensor comprising; a second grating having the line frequency selected such that the second grating passes light from the vehicle at the spatial frequency associated with wheel well of the vehicle, a second detector receiving light passed by the second grating and generating a second signal indicative of motion of the vehicle; and a processor coupled to the first sensor and the second sensor, the processor receiving the first signal and generates a first angular velocity measurement for the vehicle, and receiving the second signal and generating a second angular velocity measurement for the vehicle, wherein the processor computes an absolute velocity of the vehicle using the differential optical path length and the first and second angular velocity measurements. - View Dependent Claims (11, 12)
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13. A method for sensing the velocity of a wheeled vehicle comprising:
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with a first sensor, receiving light from the vehicle along a first optical path having a first optical path length, the light having an intensity spatial frequency component associated with a wheel well of the vehicle; providing a first grating having a line frequency selected such that the first grating passes light from the vehicle at the spatial frequency associated with the wheel well of the vehicle; with a first detector, receiving light passed by the first grating and generating a first signal indicative of motion of the vehicle; in a processor, receiving the first signal and generating a first angular velocity measurement for the vehicle; with a second sensor, receiving the light from the vehicle along a second optical path having a second optical path length; computing a differential optical path length, said differential optical path length being defined by a difference between the first and second optical path lengths; providing a second grating having the line frequency selected such that the second grating passes light from the vehicle at the spatial frequency associated with the wheel well of the vehicle; with a second detector, receiving light passed by the second grating and generating a second signal indicative of motion of the vehicle; in the processor, receiving the second signal and generating a second angular velocity measurement for the vehicle; and in the processor, computing an absolute velocity of the vehicle using the differential optical path length and the first and second angular velocity measurements.
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Specification