EP0127244A1
Expired / Lapsed
EP
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Arrangement for measuring the velocity and/or the length of moving objects
Assignee: Koninklijke Philips NV
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Filing: 1984-05-25
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Granted: —
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Expires: 2004-05-25
Abstract
Abstract The invention relates to a method of and an arrangement for measuring the velocity and/or length of moving objects in accordance with the Doppler principle. …<??>If the velocity of objects must be measured over a wide range then the problem is encountered that stringent requirements must be imposed on the bandwidth of the electronics which must process the Doppler shift. The method according to the invention has for its object to measure velocity and/or length accurately using simple, narrow-band processing electronics by imparting a pre-shift to the frequency of the electromagnetic wave directed towards the object to be measured, which pre-shift is opposite to the Doppler shift generated by the movement of the object. The pre-shift can be realized by imaging a light beam originating from a laser on the object via a rotating phase grating. The rate of rotation of the phase grating is controlled so that the total Doppler shift measured is always constant.
Inventors
- 👤 Marten Pieter Weistra
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-23 09:49
CPC Classifications
G; G01; G01S; G01S17/00; G01S17/02; G01S17/50; G01S17/58
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
119 words
A method of measuring the velocity and/or length of moving objects in accordance with the Doppler-principle, characterized in that the method comprises the following steps: (1) an electromagnetic wave is pre-shifted to an adjustable degree to obtain at least one frequency-shifted or phase-modulated wave; (2) the pre-shifted electromagnetic wave is directed towards the moving object; (3) the Doppler shift of the electromagnetic wave reflected from the object is adjusted or substantially adjusted to a predetermined fixed frequency value by influencing the pre-shift of the electromagnetic wave in the opposite sense of the Doppler-shift produced by the motion of the object; the velocity and/or the length of the object is determined from the difference between the Doppler-shift and the pre-shift.
Claim 2
Independent Claim
119 words
A method of measuring the velocity and/or length of moving objects in accordance with the Doppler-principle, characterized in that the method comprises the following steps: (1) an electromagnetic wave is pre-shifted to an adjustable degree to obtain at least one frequency-shifted or phase-modulated wave; (2) the pre-shifted electromagnetic wave is directed towards the moving object; (3) the Doppler shift of the electromagnetic wave reflected from the object is adjusted or substantially adjusted to a predetermined fixed frequency value by influencing the pre-shift of the electromagnetic wave in the opposite sense of the Doppler-shift produced by the motion of the object; the velocity and/or the length of the object is determined from the difference between the Doppler-shift and the pre-shift.
Claim 3
Dependent Claim
29 words
A method as claimed in Claim 1, characterized in that the pre-shifted electromagnetic wave comprises two sub-waves which are in a fixed phase or frequency relationship to each other.
Claim 4
Dependent Claim
79 words
An arrangement for performing a method as claimed in either of the preceding Claims, characterized in that the arrangement comprises a source for generating electro- magnetic waves, pre-shifting means for generating at least one pre-shifted wave from the electromagnetic waves originating from the source, means for imaging the pre-shifted electromagnetic waves on the object, a detector for detecting at least a portion of the electromagnetic waves reflected from the object and a signal processing unit connected to the detector.
Claim 5
Dependent Claim
27 words
An arrangement as claimed in Claim 3, characterized in that the source of electromangetic waves is a laser, spectral lamp, gas discharge lamp or solid state radiator.
Claim 6
Dependent Claim
41 words
An arrangement as claimed in Claim 3 or 4, characterized in that the means for generating pre-shifted electromagnetic waves comprises a rotatable grating and means for rotating the grating, the rate of rotation of the grating by said means being adjustable.
Claim 7
Dependent Claim
32 words
An arrangement as claimed in Claim 5, characterized in that the rotatable grating is a phase grating which in operation generates two subwaves of the first order (1+ and 1- order, respectively).
Claim 8
Dependent Claim
29 words
An arrangement as claimed in Claim 3, characterized in that at least a portion of the waves reflected from the object are focused onto the detector by a collector.
Claim 9
Dependent Claim
18 words
An arrangement as claimed in Claim 7, characterized in that the collector comprises at least one Fresnel lens.
Claim 10
Dependent Claim
103 words
An arrangement as claimed in Claim 3, characterized in that the signal processing unit comprises a comparator unit and a frequency standard unit for determining a difference signal which is indicative of the difference between the frequency of the detector signal and the fixed frequency value of the frequency standard unit, in that the comparator unit is coupled to the pre- shifting means for adjusting the value of the pre-shifting frequency, and in that the signal processing unit further comprises a measuring unit for measuring the velocity and/or the length from the difference between the Doppler-shift and the pre-shift of the electro-magnetic waves.
Claim 11
Dependent Claim
102 words
An arrangement as claimed in Claim 9, characterized in that the signal processing unit comprises a filter which is coupled to the detector for extracting the desired signal, in that the comparator unit comprises a phase/frequency detector and the frequency standard unit comprises a voltage-controlled oscillator (VCO), in that an output of the filter and an output of the VCO are coupled to the phase/frequency detector to determine the difference frequency, and in that the measuring unit comprises an up/down counter whose up-counting input is coupled to the output of the VCO and whose down-counting input is coupled to the pre-shifting means.
Claim 12
Dependent Claim
162 words
An arrangement as claimed in Claim 3, characterized in that the signal processing unit comprises a d.c. voltage generating device, a voltage-controlled oscillator, a measuring unit and a difference producer, in that the d.c. voltage generating device generates a d.c. voltage signal which is proportional to the frequency of the detected signal, in that an output of the d.c. voltage generating device is conndcted to both the control input of the voltage-controlled oscillator and to a first input of the difference producer, in that a reference value is applied to a second input of the difference producer, in that an output of the difference producer is coupled to the pre-shifting means, and in that an output of the voltage-controlled oscillator and an output of the pre-shifting means are coupled to the measuring unit for determining the velocity and/or the length of the object from the difference between the frequency of the voltage-controlled oscillator and the pre - shift of the electro-magnetic waves.
Claim 13
Dependent Claim
115 words
An arrangement as claimed in Claim 11, characterized in that the d.c. voltage generating device comprises a filter which is coupled to the detector for filtering out the desired signal and in that the d.c. voltage generating device further comprises the following units: an amplifier, a limiter, a trigger pulse-shaping circuit, a monostable multivibrator, a switch and an integrator, which units are arranged in cascade and are connected to an output of the filter, and in that the d.c. voltage generating device further comprises an amplitude detector coupled to the output of the filter for opening the switch if the amplitude of the output signal of the filter does not exceed a predetermined threshold value.
References Cited (Backward Citations)
FR2118874A1
Cited
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