Communications – electrical: acoustic wave systems and devices – Echo systems – Returned signal used for control
Patent
1981-10-20
1984-08-07
Farley, Richard A.
Communications, electrical: acoustic wave systems and devices
Echo systems
Returned signal used for control
367108, 367112, 367900, 367103, G01S 1514, G01S 752
Patent
active
044647387
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a distance sensing apparatus.
There is a need for a device which is simple to use for sensing when an object is within a predetermined distance, for example, as an aide when reversing large lorries. There is also a need for a device which can sense the distance to an object rapidly and provide an indication of this distance, for example, when measuring the dimensions of a room. The present invention seeks to provide apparatus for carrying out such functions.
According to the invention there is provided distance sensing apparatus comprising a generator for radiating pulsed sonic or ultrasonic measurement signals along a measurement path, a receiver for converting into electrical signals reflections of measurement signals from a remote surface back along the measurement path, a time measurement device for determining the time lapse between radiation of a measurement signal pulse and receipt of a reflected signal, thereby to provide a distance signal which will be representative of the path distance between the apparatus and said surface, and an amplifier for increasing the amplification of said electrical signal as a function of the time elapsed from radiation of a measurement signal pulse.
By including the amplifier for increasing the amplification as a function of time elapsed from the radiation of a measurement signal pulse the apparatus is compensated for the attenuation, of the reflected sonic or ultrasonic signal, which increases with path distance between the generator and the remote surface.
Display means will ideally be provided that is responsive to the distance signal and is calibrated in distance markings to provide a direct indication of the path distance. The distance can then be determined rapidly by reading the display.
In the preferred embodiment the generator comprises a transducer which is responsive to exciting means and ideally this transducer also acts as the receiver for reflected signals. A piezoelectric transducer is preferred. Where the apparatus is to be used for measuring substantial distances (say 30 meters or more) it is great advantage to provide a sound lens or sound horn adjacent to the generator to create a narrow directional beam sonic or ultrasonic signal. Such a feature is particularly suitable for use with a piezoelectric transducer so that distance measurement of up to 50 to 60 meters is possible with a fair degree of certainty and the device can still be made to operate well beyond that range. For long range purposes it is desirable to restrict the projection angle of the beam by means of the sound lens or the sound horn to about 3.degree. or less. If the apparatus is to be used for measuring nearby objects then a narrow projection angle is not necessary and thus a sound lens or sound horn producing a projection angle of up to 20.degree. (with respect to the axis of projection) or more may be suitable for these cases.
The apparatus will preferably include display means responsive to the distance signal which is calibrated to provide a direct indication of said path distance. In this case the time measurement device may include a counter arranged to count pulses from a clock generator in the interval between radiation and reception of a measurement signal pulse, which pulse is arranged to drive the display means. It is preferred that there should also be means for blanking the counter display during radiation of a burst of measurement signal and to retain the display in the blanked condition in the absence of a distance signal. The apparatus can also carry a viewing device enabling the apparatus to be aimed at an object whose distance is to be sensed.
The means for increasing the amplification of the electrical signal as a function of time can be provided by an attenuator connected in series with the amplifier together with means for reducing the attenuation of the attenuator as a function of time elapsed from the radiation of a measurement signal pulse. The attenuator can be an electronic attentuator connected for control by a voltage derived f
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patent: 3234502 (1966-02-01), Sicuranza
patent: 3372576 (1968-03-01), Dory
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patent: 3624596 (1971-11-01), Dickenson et al.
patent: 3696326 (1972-10-01), McAlpin
patent: 3733582 (1973-05-01), Eck et al.
patent: 3787803 (1974-01-01), Beebe
patent: 4200921 (1980-04-01), Buckley
Farley Richard A.
Sonic Tape Public Limited Company
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