GB1588927A - Creación de Inventos y Patentes con Inteligencia Artificial

GB1588927A – Sonic ranging systems
– Google Patents

GB1588927A – Sonic ranging systems
– Google Patents
Sonic ranging systems

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Publication number
GB1588927A

GB1588927A
GB39151/77A
GB3915177A
GB1588927A
GB 1588927 A
GB1588927 A
GB 1588927A
GB 39151/77 A
GB39151/77 A
GB 39151/77A
GB 3915177 A
GB3915177 A
GB 3915177A
GB 1588927 A
GB1588927 A
GB 1588927A
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GB
United Kingdom
Prior art keywords
filter
frequency
burst
varying
signal
Prior art date
1976-10-04
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Expired

Application number
GB39151/77A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Polaroid Corp

Original Assignee
Polaroid Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1976-10-04
Filing date
1977-09-20
Publication date
1981-04-29

1977-09-20
Application filed by Polaroid Corp
filed
Critical
Polaroid Corp

1981-04-29
Publication of GB1588927A
publication
Critical
patent/GB1588927A/en

Status
Expired
legal-status
Critical
Current

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Classifications

G—PHYSICS

G02—OPTICS

G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements

G02B7/28—Systems for automatic generation of focusing signals

G02B7/40—Systems for automatic generation of focusing signals using time delay of the reflected waves, e.g. of ultrasonic waves

G—PHYSICS

G01—MEASURING; TESTING

G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems

G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves

G01S15/06—Systems determining the position data of a target

G01S15/08—Systems for measuring distance only

G01S15/10—Systems for measuring distance only using transmission of interrupted, pulse-modulated waves

G01S15/102—Systems for measuring distance only using transmission of interrupted, pulse-modulated waves using transmission of pulses having some particular characteristics

G01S15/104—Systems for measuring distance only using transmission of interrupted, pulse-modulated waves using transmission of pulses having some particular characteristics wherein the transmitted pulses use a frequency- or phase-modulated carrier wave

Abstract

The rangefinder (11) for a camera (10) contains a transmitter (27), which emits the sound pulses (28, 31, 29) to the object (16) to be photographed, and a receiver (33) which receives the echo reflected by the object. Each pulse emitted contains a first portion, having frequencies which differ from one another, and a second portion with an essentially fixed frequency. On receiving the first portion of the echo, the receiver (33) processes the frequencies which differ from one another and, on receiving the second portion of the echo, it processes the fixed frequency. As a result, the disruptions of the echo, which cause blurred camera focusing, are avoided.

Description

(54) IMPROVEMENTS IN SONIC RANGING SYSTEMS
(71) We, POLAROID CORPORA
TION, a corporation organised under the laws of the State of Delaware, United States of America, of 549 Technology Square, Cambridge, Massachusetts, United States of
America, do hereby declare the invention, for which we pray that a patent may be granted to and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an ultrasonic ranging system, and to a camera into which such a system is incorporated.
Ultrasonic ranging systems for cameras are disclosed in U.S. Patent 3,522,764, German
Patent 864,048 and I.B.M. Technical Disclosure Bulletin, Volume 9, No. 7, December, 1966, pp. 744–745. In each of the systems, ultrasonic energy is transmitted toward a subject to be photographed, and the subject reflects energy back to the camera. Characteristics of the transmitted and received signals are compared necessitating separate sending and receiving transducers, and a control signal representative of subject distance is produced. The control signal is used to drive the lens mount of the camera to a position functionally related to subject distance whereby the subject will be in focus.
In the U.S. Patent No. 3,522,764, ultrasonic bursts are transmitted at 40kHz with a period no less than the time required for sound to travel twice the maximum subject distance for which the lens mount is to be adjusted. Echoes from the subject, with the same periodicity as the transmitted bursts, are received in the intervals between the transmitted bursts the time between transmission and reception of a burst being related to subject distance and used to establish the duty cycle of a first pulse generator. A second pulse generator, with the same frequency as the first, is associated with the lens mount, but the duty cycle of the second generator depends on the position of the lens mount.
Movement of the lens mount takes place until the duty cycles of the two pulse generators are equalized.
In the German patent and in the I.B.M.
publication, ultrasonic wave trains are frequency modulated with a period no less than the time required for sound to travel twice the maximum subject distance for which the lens mount is to be adjusted. The echoes from a subject are thus frequency modulated with the same periodicity as the transmitted energy, so that the subject range can be established by the instantaneous difference between the frequencies of the transmitted and received signals.
In addition to requiring two transducers, the known prior art systems have the disadvantage of requiring a considerable amount of time to establish subject range. At room temperature, sound travels at about 340 meters per second so that the time required for a burst to reach a target at 7 meters, which is the maximum distance for which focusing is usually required, is about 20 msec. Thus, each period of the above systems must be about 40 msec; and if ten periods are required to establish subject range, then about 0.5 seconds is consumed in achieving camera focus. Such elapsed time is relatively long with respect to human reflexes, with the result that this photography has to proceed in two successive and distinct steps: one involving focusing, and one involving shutter actuation.
For general ranging purposes, an ultrasonic pulse distance measuring device is disclosed in U.S. Patent No. 3,454,922 wherein separated fixed frequency bursts are transmitted by a transducer, and a reflected echo is received by the same transducer after a period of time related to target range.
When a fixed frequency ultrasonic sound is utilized it has been found that subjects within the acceptance angle of the transducer, and within the field of view of the camera, are often undetected. From experimental work, it appears that reflections from various points on the subject may interfere with each other thus cancelling or so weakening the echo at the receiver, that the latter cannot respond, and the subject remains undetected. This phenomenon is most notice able for subjects that are relatively close to the transducer.
In the context of photographing a subject, the latter is considered to be close to the camera when it is within 2 meters from
the camera. Since many photographs are taken with subjects at this relatively close range, the failure of the transponder to receive an echo from a relatively close subject would normally cause the lens mount to be improperly positioned.
The side lobes associated with the radiation pattern of ultrasonic transmission give rise to another problem. An off-axis target relatively close to the transducer, and located within an attenuated side lobe of the antenna pattern, may have a surface condition or other characteristic which produces an echo of a strength comparable to a subject located on-axis at a considerable distance from the transducer. In such case, the lens mount of the camera may be set in accordance with the distance to the off-axis target rather than the subject being photographed, and an unfocused exposure would result. While the transducer can be made more directional by increasing its area, this expedient increases the size of the ranging equipment associated with the camera, and neutralises one of the basic reasons for going to a single transducer which is to reduce the size and weight of the ranging equipment.
A sonic ranging system according to the present invention includes means actuable for transmitting a burst of sonic energy towards a subject, means for receiving and processing an echo from the subject and for producing a range signal related to the range of the subject, and further comprises means for controlling the transmitting means to produce a sonic frequency burst having a constant frequency for one portion of its duration and having at least one other frequency present for a smaller portion in the remainder of its duration, whereby the presence of at least two frequencies in the transmitted burst reduces the possibility of cancellation of echoes from near subjects and the presence of the sonic frequency of longer duration facilitates reception of echoes from more distant subjects. Advantageously, the constant frequency is maintained for a major portion of the burst.
In the preferred sonic ranging system embodying the invention the sonic burst varies in frequency for a portion of its duration; and a variable-Q filter in the receiver filters echo signals received and the Q increases and the bandwidth decreases during the predetermined time interval; this avoids the need to use a matched filter.
Such a sonic ranging system may easily be embodied in a photographic camera, which may include means responsive to the range signal for varying light-transmitting means within the camera to move the focus of image-carrying light rays from an object at the range represented by the value of the range signal towards the focal plane of the camera.
It has been found experimentally, that the strength of the return from close subjects is highly dependent on the frequency of the ultrasonic burst. If at one frequency the echo would be very small due to interference, there are other frequencies at which the echo would be large. On the other hand, the return from remote subjects is much less dependent on frequency.
The preferred form of the frequencymodulated burst is a leading half in the form of a chirp (using radar terminology) wherein the frequency decreases with time, and a trailing half in the form of a constant frequency equal to the lowest frequency of the chirp. Because of the chirp, energy at many different frequencies will be incident on a subject increasing the probability that some of the frequencies will be reflected back to the transducer by relatively close subjects even if other frequencies are lost because they set up cancelling interference patterns.
The preferred format of the burst is to be distinguished from the approach taken in
U.S. Patent No. 2,433,782 which shows a single burst, frequency-modulated ultrasonic ranging system without a constant frequency portion. In the present invention, the frequency values and their time-wise distribution are selected to minimize both the effects of absorption at all ranges and the cancellation of echoes at close range without adversely affecting the signal-to-noise ratio for long range echoes.
During the initial portion of the receiver ranging time in which any return will be from a relatively close subject and will likely
include many different frequencies in the chirp, the Q of the filter is made low ensue ing that the filter bandwidth will be wide enough to accommodate all of the chirp frequencies. The low Q allows more noise reception, however, the latter is offset by the strong signal from close subjects. During the final portion of the receiver ranging time in which any return will be from a relatively distant subject and will, due to absorption, probably exclude the higher chirp frequencies, the filter is altered to a higher Q with the bandwidth narrow and centered on the constant frequency. Thus the receiver has reduced sensitivity to the effects of cancellation with only a slight compromise in the signal-tonoise (S/N) ratio for remote subjects.
The lower value of Q of the filter during the initial portion of the receiver ranging time has the added benefit of decreasing the response time of the filter (more rapid rise in filter response) for echoes from subjects close to the camera as compared to subjects more remote therefrom. Consequently, the accuracy will be better for subjects that are close than for more remote subjects, an advantageous situation in photography where the focus is more sensitive to errors in the lens mount position for close subjects.
The admittance of the variable Q filter increases during the receiver ranging time causing the receiver, in effect, to amplify echo signals from remote subjects more than nearby subjects. This technique decreases the angula; sensitivity of the transducer and discriminates against echoes from nearby off-axis targets which result from side lobes of the angular field pattern of the transducer.
A receiver embodying the present invention may also include detector means responsive to the output of the filter for producing a range signal when the output exceeds a predetermined level. The time of detection measured from the keying pulse is representative of the subject distance.
In order that the invention may be better understood, a camera having a sonic ranging system embodying the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a block diagram of a general form of an ultrasonic ranging system according to the present invention showing the system incorporated into the camera;
Figure 2 is an idealised response diagram of a variable Q-filter;
Figure 3 is a detailed circuit diagram of a preferred form of the ranging system according to the present invention;
Figure 4 is a waveform diagram showing idealised waveforms occuring at various Iccations in the system of Figure 3;
Figure 5 is a circuit diagram of a voltage generator employed in the system of Figure 3;
Figure 6 is a block diagram of an alternative embodiment of the transducer drive shown in the ranging system of Figure 3; and
Figure 7 is a waveform diagram of the ultrasonic burst produced with the embodiment of Figure 6.
Referring now to Figure 1, reference numeral 10 designates a camera into which an ultrasonic ranging system 11 according to the present invention has been incorporated.
Camera 10, which is shown in schematic form, includes housing 12 within which film 13 is supported opposite lens mount 14 which is axially displaceable along the optical axis 15 between spaced terminal positions. At one terminal position, lens mount 14 is positioned to focus subject 16 onto the plane of film 13 when the subject is close to the camera, e.g., about 25cm away. At the other terminal position of lens mount 14, subject 16 will be in focus when it is located beyond say 7.5m from the camera. The position of lens mount 14 between the two terminal positions for bringing a subject into focus, is a predetermined function of the distance to the subject, such function being highly non-linear and being termed the lens/subject function.
In a manner to be described below, ultrasonic ranging system 11 produces a range pulse 17 that is delayed with respect to a keying pulse 18 by a period of time linearly related to the distance of subject 16 from the camera. Focusing mechanism 19 associated with the camera responds to the pulses 17 and 18 by moving the lens mount 14 to an axial position at which subject 16 will be in focus.
In the construction shown in the above noted cop enduing application, the focusing mechanism includes a logic circuit 20 which, in response to a range signal 21 generated by range pulse generator 22, produces a train of pulses whose number is representative of the axial position of the lens mount at which the subject will be in focus. Such pulses are gated into counter 23 and used for the purpose of driving motor 24 which is mechanically connected by means 25 to the lens mount
14. In addition means 25 is also connected to a feedback system such as an auxiliary pulse generator 26 so that rotation of motor 24 under the control of the contents of counter 23 causes auxiliary pulse generator 26 to produce a predetermined number of pulses for each unit displacement of lens mount 14. Logic means 20 responds to the output of auxiliary pulse generator 26 for the purpose of determining when lens mount 14 has been moved to the position determined by the contents of counter 23 thus bringing the subject into focus.
The ultrasonic ranging system of the present invention designated by reference numeral 11 includes ultrasonic transducer means 27 which may include an electrostatic transducer element of the Sell-type similar to that disclosed in the article: Geide, K: «Oscillation
Characteristics of Electroacoustic Transducers using the Sell Principle», Acustica, Vol. 10, pp. 295-303 (1960). The nature of the main and side lobes of the preferred form of element 27 depends on the output pattern of the backing plate (not shown) of the element.
For a transducer of given size driven at a given frequency, the narrowest beam is produced by a constant output across the transducer element. For example a transducer of the type disclosed in the above article, with a 3.5cm diameter active area driven at 50kHz, has a half power angle of 60 off-center. The first zero occurs at 130 and the first side lobe at 190. These angles are about inversely proportional to the diameter of the transducer and to the frequency; and the first side lobe may have a relative power of – 17.6dB for transmit and receive conditions; combined the relative power for the system is approximately – 33dB. Improved patterns would have slightly larger angles but smaller side lobes.
Transducer means 27 is physically located adjacent lens mount 14 and has a transmission pattern 28 with a main lobe 29 closely matching the field of view 30 of the lens mount. Associated with the main lobe of the pattern are side lobes 31, the precise form of the main and side lobes depending upon the specific design of the transducer element.
Ranging system 11 also includes control voltage generator 35, frequency modulator 32 for driving transducer means 27 and causing the latter to transmit a burst of ultrasonic energy towards subject 16 in response to a keying pulse 18 applied to generator 35, and receiver 33 for processing an echo signal 21 produced by the transducer in response to receipt of an echo from the subject within a predetermined interval of time (hereinafter termed the receiver ranging time) following the burst.
In operation, a manual input to the system, such as for example, the depression of a camera pushbutton (not shown), is converted, by leading edge detector 34, into keying pulse 18 which is applied to control voltage generator 35. The output of generator 35 controls frequency modulator 32 which causes transducer means 27 to produce a frequencymodulated burst. Generator 35 is effective to modulate the output voltage of modulator 32 such that, during half the transducer burst, the frequency changes between the limits of 65 to 50 kHz; and during the other half of the transducer burst the frequency remains constant at about SOkHz.
In view of experimental results showing that the return from a close subject is highly dependent on the frequency of the incident ultrasonic burst in the sense that cancellation of an echo can occur at certain frequencies, the provision of the chirp will insure the presence of many frequencies incident on the subject. At least some of the frequencies will be reflected back to the transducer without being cancelled. The provision of the 50kHz constant frequency during half of the burst minimizes the effects of absorption on ultrasonic energy thus insuring a return from a remote subject under adverse ambient conditions. It is known, for example, that the reflected signal power varies exponentially with the distance of the subject and approximately inversely with the fourth power of the distance to the subject. For example, an approximately 60dB variation in reflected signal power occurs when a subject is moved from 25cm to 5m using a SOkHz signal at 200C. It has been found from experiments that the absorption, and the variation of absorption, with temperature and humidity, increase rapidly with frequency. Generally speaking, the lower the frequency, the lower the absorption. For the frequencies of the preferred burst, the lowest absorption, for a given temperature and humidity, ocurs for the SOkHz signal.
Under adverse conditions of temperature and humidity, the higher frequencies in the burst are likely to be attenuated. Hence, they will be most effective for close subjects, which is precisely where interference is encountered were a single frequency used in the burst
The SOkHz portion of the burst is the leasl attenuated of all of the frequencies present and so is suitable for subjects remote from the camera.
When subject 16 is relatively close to transducer means 27, the frequencies in the return signal incident on the transducer element will contain most of the frequencies in the chirp except those frequencies which have been cancelled by reason of interference. When the subject 16 is located more remotely from transducer means 27, the return signal is most likely to contain those frequencies least attenuated by the environment, namely the frequencies close to the lower frequency of the chirp.
The 65 to 50kHz chirp portion and the SOkHz constant portion of the burst can be arranged in eight different combinations. Half of these involve step-type discontinuities at the transition between the two portions. For reasons relating to simplification of the electronics for developing the control voltage that drives the modulator, the latter discontinuous burst arrangements are not preferred.
Turning to the other four possible (continuous) burst arrangements, it should be noted that the chirp portion could rise or fall to the constant frequency and could precede or follow the constant frequency portion.
Now, at near distances, interference or socalled speckle is a problem while at far distances the signal-to-noise ratio is of most concern. Based upon the above, it is preferred to have the chirp first which provides the greater ranging accuracy of operating with the leading edge of the burst thereby permitting greater focusing accuracy desired for close subject distances. On the other hand, since lower frequencies are less absorbed, their use is preferable for far distances where signal-to-noise ratio is important. Consequently, a leading chirp which falls to a lower constant frequency was preferred with the frequency of the burst to start at 65kHz and drop to SOkHz in 0.5 msec, and then remain constant at SOkHz.
Referring again to FIG. 1, keying pulse 18, upon initiating the operation of control voltage generator 35 and the transmission of a frequency-modulated ultrasonic burst from transducer means 27, is also applied to blanking gate 36 of the receiver 33. Blanking gate 36 produces a level that is applied to the output of the receiver 33 so as to enable
the output approximately 0.4ms following the termination of the transducer burst, and then maintains the output in active operation for a predetermined period of time, termed the receiver ranging time, which is preferably about 40ms in duration. In this interval of time, sound at sea level at 200C travels from the transducer to a target located about 7.3m, and returns to the transducer. The 0.4ms delay in enabling the output provides sufficient time for the transducer element of transducer means 27 to stabilize following termination of the burst. As a result, the delay time defines the closest subject distance that can be accommodated by the ranging system, namely about 25cm. As shown in FIG. 1, the output of the blanking gate 36 may also be applied to a pre-amplifier 37 to enable the latter following the indicated delay.
An echo signal, produced by transducer means 27 on receipt of a return from subject
16, is applied via line 38 to the pre-amplifier
37 whose output is processed by filter network
39 which as later explained in detail with regards to FIG. 3 includes variable Q filter 40, and amplifier 41 whose gain is optionally variable. Level detector 42 produces a range pulse 17 when the output of variable gain amplifier 41 reaches a threshold level.
Associated with variable Q filter 40 is programmed Q control circuit 43 which is responsive to keying pulse 18 for increasing the Q of the filter during the receiver ranging time. The center frequency of the filter is the lowest frequency of the burst, namely 50kHz in the present situation. Control 43 may typically change the Q of the filter 40 from a value of 5 to a value of 70 during the receiver ranging time.
The admittance of Q filter 40 as a function of frequency is shown in FIG. 2 for different values of the parameter Q. When the Q of the filter 40 is low, as indicated by curve 44 in FIG. 2, the bandwidth of the filter -will be relatively wide, and in fact, will be sufficiently wide to pass all of the chirp frequencies. The Q of the filter 40 is relatively low during the initial portion of the receiver ranging time within which subjects close to the transceiver will supply an echo return to transducer means 27.
When the Q of the filter 40 is relatively high during the terminal portion of the receiver ranging time, the bandwidth of the filter will be relatively narrow and can be optimized with respect to signal-to-noise ratio.
The 50kHz portion of the burst will be most effective in reaching a subject remote from the transducer and will be strongly present in any return therefrom. Since the relatively narrow bandwidth of the filter occurs during the latter portion of the receiver ranging time, this is consistent with subjects remote from the camera.
As indicated in FIG. 2, the admittance of filter 40 when its Q is low will be significantly less than its admittance when the
Q filter is relatively high. Consequently, the impedance of filter 40 will be higher during the initial portion of the receiver ranging time than during the final portion thereof.
This has the effect of attenuating the output of pre-amplifier 37 for echo signals produced when a subject is close where the amplitude of the echo is likely to be large. The output of filter 40 thus tends to have a level independent of subject range.
In general, however, the gain of amplifier 41, which is a part of overall filter network 39, can be programmed using gain control circuit 46 associated with this amplifier. Control circuit 46 responds to the application of keying pulse 18 by producing a control signal which causes the gain of amplifier 41 to increase during the receiver ranging time. As a consequence of this operation relatively weak echo signals associated with objects relatively remote from the transducer will be amplified to a greater extent than relatively strong echo signals from a subject closer to the transducer.
The advantages of varying the gain of the overall filter network is explained in connection with the presence of side lobes 31 shown in FIG. 1, and the presence of target 16A within one of the side lobes. Since target
16A is out of the field of view of the objective lens of the camera, it is highly desirable for the ranging system to discriminate against target 16A in favor of subject 16 which is within the field of view. The variation in admittance of filter 40 alone, or together with the variation in gain of amplifier 41 if filter 40 is not sufficient, cooperates in achieving this discrimination as explained below.
The return from target 1 6A will reach transducer means 27 before the return from subject 16 which is more remote from the transducer than target 16A. Not only will the signal strength of the return from target 16A be relatively low by reason of the strength of the side lobe, but the operation of filter 40 and amplifier 41 will be such as to ensure that the signal reaching level detector 42 will be below the threshold of the detector. By the time the return from subject 16 reaches transducer means 27, the admittance of the filter will have increased (which means that the impedance of the filter 40 to the echo signal will have decreased) from its previous value presented to the return from target 16A. In addition, the gain of amplifier 41 will have increased from its previous value. Consequently, the output of amplifier 41 will exceed the threshold of detector 42 and cause range pulse 17 to be produced at a point in time corresponding to the range of subject 16 from the transducer.
In addition to the changes in Q of filter 40, which change the admittance of the filter in a way that beneficially decreases the angular sensitivity of the transducer and discriminates against off-axis targets, another beneficial result is achieved. Such result arises because the rise time of filter 40 is faster when the Q is relatively low than when the Q is higher.
The relatively faster rise time thus occurs in connection with echo signals associated with objects relatively close to the camera.
Since the rise time allows early detection of the leading edge of the echo, the more rapid rise time results in greater accuracy for the generation of range pulses associated with close subjects. This is consistent with the requirements for a camera since focus is more sensitive to errors at close range than to errors at distances more remote from the camera.
The preferred construction of an ultrasonic ranging system is shown in FIG. 3, and is designated by reference numeral 11A. System 11A includes ultrasonic transducer element 27A, modulator 50 for driving the element and causing it to transmit a frequencymodulated burst of ultrasonic energy toward a subject in response to the application of keying pulse 18 to the modulator, and receiver 33A, including filter 51, for processing an echo signal produced by element 27A in response to its receipt of an echo from a subject (not shown) within a predetermined time interval following the burst (i.e., within the ranging time of the system). Receiver 33A produces a range signal 17 delayed with respect to keying pulse 18 by a period of time z linearly related to the subject distance (i.e., twice the time for sound to travel between the transducer and the subject).
Turning again to FIG. 3, a modulator 50 includes gate generator 52, voltage generator 53, voltage controlled oscillator 54, amplifier 55, transformer 56, and decoupling diedes 57. A keying pulse 18 applied at (b) to the input of gate generator 52 causes the latter to produce a gate signal 58 at (c). A single shot multivibrator with automatic delay reset or an RC delay in combination with a Schmitt trigger circuit may be employed for the gate generator 52. As shown in FIG. 4(c), gate signal 58 has a duration of about 40 msec, corresponding to the time required for sound
to travel about 7 meters from the transponder
to a target and back again, such distance
corresponding to an infinity focus position
of the lens mount. For subjects beyond 7
meters, the lens mount is positioned at its
infinity focus, and this would cause the sub
ject to be in focus.
In response to the gate signal 58, voltage
generator 53 produces the time-variable voltage pulse 59 shown in FIG 4(d). An exemplary voltage generator is shown in FIG. 5 wherein a conventional pulse generator 98, for example, a single shot multivibrator with automatic delayed reset upon triggering by the gate generator 52 produces a 1.Oms input pulse (the length of the burst which is delivered to parallel circuit legs 100 and 102 ment and its sensitivity to echoes are simultaneously maximized. In addition, the Q of the output circuit, which depends in part on the capacitance of the transducer, should be relatively low in order for the chirp to be transmitted with a constant amplitude and with no significant dependence on the capacitance of the transducer. By maintaining a relatively low Q, the energy of the system dies rapidly at the termination of the drive voltage thus allowing the transducer element to quickly reach a quiesence condition at which it can receive echoes from relatively close subjects.
Decoupling diodes 57 function to decouple transformer secondary 61 from the transducer element during reception of an echo.
During transmission, the voltage drop of about 0.7 volts across the diodes is so small
with respect to -the 300 volt peak-to-peak
driving voltage, that the decoupling diodes
have no effect on transmission. During re
ception, however, echo signals produced by
element 27A are in the range of 2 1V to
20 mV; and the diodes are in effect an open
circuit to the echo signals.
An echo from a subject is symbolically
indicated at 64 in FIG. 3; and the resultant
echo signal produced by element 27A is pro
cessed by receiver 33A which includes pre
amplifier 65, filter 51 referred to previously,
means 66 for varying the Q of the filter
during the receiver ranging time, and de
tector means 67 for converting an echo signal
to range pulse 17. During the receiver rang
ing time, the dc voltage on element 27A
remains substantially at 1SOVdc. The input
impedance of pre-amplifier 65 is matched
to the transducer element impedance (about 12kQ). The output impedance of the pre
amplifier is selected to be compatible with
the highest Q of filter 51, which is about
70. The gain of the pre-amplifier is about 48dB.
Filter 51 is an LC filter comprising secon
dary 61 of transformer 51 which furnishes
the inductance of the filter, and capacitors
68, 69 between which the output of pre
amplifier 65 is connected. A tap 70 relatively
close to the ground connection of the secon
dary applies the output of the filter to input
71A of high-impedance output amplifier 71
through resistor 72 which has a value of
about 1KQ. Resistor 72, which is in parallel
with the LC circuit of the filter, is a part
of pre-programmed Q control means 66 for
varying the Q of the filter. Q control means
66 also includes current generator 73 and
dynamically variable resistance means 74 connected to resistor 72 and input 71A. Resis
tance means 74 comprises fixed resistors 75 (of about lMQ) in parallel with diode 76
arranged to conduct during the time that the
current generator 73 supplies current.
To provide the best signal-to-noise ratio for echo signals from subjects most remote from the camera (i.e. about 7 meters), the difference between the center frequency of the filter and the frequency at which the response power drops to half, Af, is related to the constant frequency pulse length as follows: 0.2/(constant frequency pulse length). In the preferred embodiment, the half-power bandwidth of the filter should be about 0.8kHz near the end of the receiver ranging time when echo signals from remote subjects are being processed. During the initial portion of the receiver ranging time, when echo signals from subjects close to the camera are being processed, the bandwidth of the filter must be such as to pass all of the frequencies of the chirp. Thus, the filter must initially have a half-power bandwidth of about 30kHz, the center frequency being about SOkHz. The required change in bandwidth is achieved by changing the Q of the filter from about 5 near the beginning of the ranging time to about 70 near the end.
For a typical LC circuit (with a capacitance of about 300pf), the resistance in parallel with the circuit must vary from about 1KQ to about 1MQ.
The resistance in parallel with the LC circuit of filter 51 is the effective resistance of resistor 72 in series with the parallel combination of resistor 75 and diode 76. The dynamic resistance of diode 76, for small ac signals supplied by pre-amplifier 65, is about inversely proportional to the dc current flow through the diode, and will be substantially independent of the exact diode characteristics.
When the dc current flow is relatively high, the dynamic resistance of the diode will be significantly smaller than the resistance of resistors 72 and 75, with the result that the effective resistance of filter 51 will depend substantially only on resistor 72. Consequently, the Q of the filter 51, under the condition of high current flow through diode 76, will depend on the value of resistor 72 which is selected, taking the inductance and capacitance of the filter 51 into account, to provide a Q which establishes the filter bandwidth such that all of the frequencies of the chirp are passed by the filter.
When the current through diode 76 is relatively low, the dynamic resistance of the diode will be of the same order of magnitude as the resistance of resistor 75 with the result that the effective resistance of filter 51 will depend essentially on the resistor 75. Consequently, the Q of the filter under the condition of low current flow through diode 76 will depend on the value of resistor 75 which is selected to establish a bandwidth matched as well as possible to the fixed frequency of the burst.
The time-wise variation in the current supplied to diode 76 by current generator 73 is such as to ensure a suitable variation in the effective value of the resistance in parallel with the LC circuit of filter 51. To this end, generator 73 is responsive to gating pulse 58 for producing a dc current that is initially high for a relatively short time at the beginning of the receiver ranging time, and monotonically decreases as indicated by curve 77 in FIG. 4(e). Curve 77 is of a type that can be produced by relatively simple components with more assurance of repeatability and stability as compared to a monotonically increasing curve. A suitable current generator may be provided by a network of RC circuits, each having different time constants thereby providing diminishing current. Curve 77 has three portions: a transitional portion 77A lasting about 4 msec during which the current rapidly drops to a substantially constant level, an initial portion 77B lasting about 6 msec during which the current remains substantially constant, and a terminal portion 77C during which the current decreases substantially linearly. During portion 77A, the effective resistance in parallel with the LC circuit increases, but the Q of the filter is primarily dependent on the value of resistor 72 and changes only slightly as indicated in FIG.
4(f). During portion 77B, the Q of the filter remains substantially constant. Thus, for objects within about 1.5m from the transducer element, the bandwidth and admittance of the filter are substantially constant. For objects beyond 1.5m, the bandwidth gradually decreases as the filter Q increases, and the filter admittance increases (see FIG. 4(g)).
The change in filter admittance can be thought of as changes in effective gain of the receiver, the effective gain being relatively low and substantially constant for objects up to about 1.5m from the transducer element, and increasing for subject distances beyond this point, which is in accordance with the principles set forth above.
Hence, the bandwidth remains essentially constant, at a relatively broad value for approximately 9 ms or approximately one-fifth to one-quarter of the predetermined range time of 42 ms and then gradually is narrowed
during the remainder of the range time.
Stated otherwise, the bandwidth and Q etc.
remain constant during the initial portion of the range time when echoes may be received from close up subjects (up to 1.5 meters from the camera) so as to ensure reception of all chirp frequencies and produce fast filter rise.
Then, the bandwidth is narrowed during the remainder of the range time to increase the signal-to-noise ratio.
The output of filter 51 is applied to input 71A of amplifier 71 which has a high input impedance to prevent loading the filter and lowering its Q. The back-to-back diodes of
Q control means 76 and the location of tap 70, limit the transmit pulse, but the amplifier 71 is still overdriven to some extent.
It is designed to recover rapidly, however, and can handle a filtered echo signal after about 0.3 msec following the transmit pulse.
The output impedance of this amplifier is low; and the gain is about 65dB.
The output of amplifier 71 is applied to detector network 67 which includes a conventional clamping circuit 80, an RC integrator 81 and a detector 82. Circuit 80 is driven by blanking generator 83 which produces a blanking pulse 84 in response to gate pulse 58 as shown in FIG 4(h). Pulse 84 lasts about 1.5 msec; and during this pulse, clamping circuit 80 is effective to clamp the detector input to ground.
Following the blanking pulse, an echo signal passed by filter 51 and amplified by amplifier 71 is rectified and correlated. The integrator 81 is constructed such that several cycles of an echo signal must be applied to the integrator within a given time span (say 0.2 msec) for the voltage to build up on the capacitor so as to reach the threshold of amplifier 84 which thereby forms a range pulse 17. While the correlation technique utilized does not improve the signal-to-noise ratio of the input signal, it does provide a filter for discriminating against single spikes such as may be present due to logic circuits associated with the mechanism for moving the lens mount of the camera.
As noted, the varied Q filter provides increasing gain during the transmit-receive time.
However, the gain of the amplifier 71 may also be varied during the transmit-receive time by means of a ramp generator 96 which in response to the gating pulse 58 of gate generator 52 applies continuously increased gain control to amplifier 71 during the predetermined transmit-receive time of approximately 42 msec thereby providing substantially continuously increasing amplifier gain as the interval progresses.
With only slight modification, the circuit described above is capable of operation in several different modes. As noted in the preferred mode, a single burst namely a single one msec duration transmit pulse, is utilized.
This arrangement without amplifier ramp gain permits detection of objects at a distance of from 25cm to about Sm, the total time needed to measure the distance being less than about 35 msec; the latter being extended to about 9m when amplifier ramp gain is employed. This mode is preferred with a snap-shot type camera since focusing can be effected and exposure completed with a single manual input.
In an alternative embodiment, the chirp portion of the burst may be digitally formed in a stepped arrangement as shown in FIG. 6 wherein in response to the 42 msec gate pulse 58 from gate generator 52, a stepped frequency pulse 120 is provided by means of a clock 122 and programmed divider 124. As shown in FIG. 7, the pulse 120 falls in a series of small steps from 65kHz to SOkHz.
In another mode of operation, several different pulses could be used, one for each of several different ranges. For example, a short pulse could be used for objects from 10cm to lm. A second and longer pulse could be used for longer distances. The Q of the filter would have to be adjusted to the pulse length, however; and the maximum Q would be different for different pulses. Since the signal-to-noise ratio is proportional to the square root of the pulse length, a change in pulse length would permit the range to be increased. If a system has a Sm range with a 0.5 msec pulse, a system with a maximum pulse length of 5 msec could provide range information for objects up to 6.5m.
The Q of the filter, however, would preferably be ten times higher.
The present invention is also capable of being used in a continuous pulsing mode suitable for use with a movie camera enabling the focus to be adjusted continuously during
the time the camera is running. Using a slow drive for moving the lens mount, an integration of the echoes would be achieved improving the signal-to-noise ratio.
The variation in filter Q in the preferred embodiment has many advantages when used in a ranging system for a camera. In most cases, the need for a separate ramp gain in the general form of the invention shown in FIG. 1 may be eliminated. Secondly, the need for a matched filter, which is required for reception of a chirp is eliminated, thereby simplifying the circuitry yet permitting the use of a chirp which reduces sensitivity to interference for close objects without significantly compromising the signal-to-noise ratio for remote objects. Thirdly, the filter
Q is low for near-by objects where absolute accuracy is most needed, and a low Q filter has a fast rise time ensuring good accuracy.
Finally, an electronic drift in output frequency, as compared to the filter frequency, or the frequency shift produced by the movement of the target (Doppler effect), affects only the far distance, where the consequences are less important for a photographic camera.
The larger the drift or frequency shift, the nearer will be the affected distance. This gradual influence has to be compared with the total disappearance of the echo at a certain drift at all distances for a constant Q system.
The selections of frequencies, pulse durations and the like are by way of example only, it being understood that these parameters are chosen in accordance with the use to which the ranging system of the present invention is applied. For example, the frequency of 50kHz was selected on the basis of the largest distance to be measured reliably in the presence of acoustic and thermal noise.
Other considerations are involved in frequency selection, such as transducer size, acceptance angle, etc.
Finally, the disclosed technique for varying the effective resistance of the filter is by way of example only. The resistance can be in series with the LC circuit instead of parallel; and this expedient would require different values of resistors. Alternative to the use of a current-controlled diode, an FET transistor operating in the depletion mode could be used, preferably with the transistor used in a parallel mode.
Ranging systems 11 and 11A have applicability more general than incorporation into cameras. For example, they are applicable to arrangements for assisting blind persons, or assisting in maintaining proper spacing between vehicles, or any operation requiring ranging information.
WHAT WE CLAIM IS: 1. A sonic ranging system including means actuable for transmitting a burst of sonic energy towards a subject, means for receiving and processing an echo from the subject and for producing a range signal related to the range of the subject, and further comprising means for controlling the transmitting means
to produce a sonic frequency burst having
a constant frequency for one portion of its duration and having at least one other fre
quency present for a smaller portion in the
remainder of its duration, whereby the pre
sence of at least two frequencies in the trans
mitted burst reduces the possibility of can
cellation of echoes from the near subjects
and the presence of the sonic frequency of
longer duration facilitates reception of echoes
from more distant subjects.
2. A sonic ranging system in accordance
with claim 1, wherein the constant frequency
is maintained for a major portion of the
burst.
3. A sonic ranging system in accordance
with claim 1 or 2, in which the sonic burst
varies in frequency for a portion of its
duration.
4. A system as defined in claim 3, wherein
a signal of varying frequency is transmitted
in an initial portion of the burst and there
after a signal of constant frequency is
transmitted.
5. A system as defined in claim 3 or 4,
wherein the frequency of the constantfrequency signal is substantially equal to or is less than the lowest frequency of the varying frequency portion of the burst.
6. A system as defined in claim 5, in which the varying-frequency portion of the burst, the frequency decreases progressively from an initial value to the value of the constant frequency.
7. A system as defined in claim 6, wherein the frequency of the said burst decreases
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (38)

**WARNING** start of CLMS field may overlap end of DESC **. shown in FIG. 7, the pulse 120 falls in a series of small steps from 65kHz to SOkHz. In another mode of operation, several different pulses could be used, one for each of several different ranges. For example, a short pulse could be used for objects from 10cm to lm. A second and longer pulse could be used for longer distances. The Q of the filter would have to be adjusted to the pulse length, however; and the maximum Q would be different for different pulses. Since the signal-to-noise ratio is proportional to the square root of the pulse length, a change in pulse length would permit the range to be increased. If a system has a Sm range with a 0.5 msec pulse, a system with a maximum pulse length of 5 msec could provide range information for objects up to 6.5m. The Q of the filter, however, would preferably be ten times higher. The present invention is also capable of being used in a continuous pulsing mode suitable for use with a movie camera enabling the focus to be adjusted continuously during the time the camera is running. Using a slow drive for moving the lens mount, an integration of the echoes would be achieved improving the signal-to-noise ratio. The variation in filter Q in the preferred embodiment has many advantages when used in a ranging system for a camera. In most cases, the need for a separate ramp gain in the general form of the invention shown in FIG. 1 may be eliminated. Secondly, the need for a matched filter, which is required for reception of a chirp is eliminated, thereby simplifying the circuitry yet permitting the use of a chirp which reduces sensitivity to interference for close objects without significantly compromising the signal-to-noise ratio for remote objects. Thirdly, the filter Q is low for near-by objects where absolute accuracy is most needed, and a low Q filter has a fast rise time ensuring good accuracy. Finally, an electronic drift in output frequency, as compared to the filter frequency, or the frequency shift produced by the movement of the target (Doppler effect), affects only the far distance, where the consequences are less important for a photographic camera. The larger the drift or frequency shift, the nearer will be the affected distance. This gradual influence has to be compared with the total disappearance of the echo at a certain drift at all distances for a constant Q system. The selections of frequencies, pulse durations and the like are by way of example only, it being understood that these parameters are chosen in accordance with the use to which the ranging system of the present invention is applied. For example, the frequency of 50kHz was selected on the basis of the largest distance to be measured reliably in the presence of acoustic and thermal noise. Other considerations are involved in frequency selection, such as transducer size, acceptance angle, etc. Finally, the disclosed technique for varying the effective resistance of the filter is by way of example only. The resistance can be in series with the LC circuit instead of parallel; and this expedient would require different values of resistors. Alternative to the use of a current-controlled diode, an FET transistor operating in the depletion mode could be used, preferably with the transistor used in a parallel mode. Ranging systems 11 and 11A have applicability more general than incorporation into cameras. For example, they are applicable to arrangements for assisting blind persons, or assisting in maintaining proper spacing between vehicles, or any operation requiring ranging information. WHAT WE CLAIM IS:

1. A sonic ranging system including means actuable for transmitting a burst of sonic energy towards a subject, means for receiving and processing an echo from the subject and for producing a range signal related to the range of the subject, and further comprising means for controlling the transmitting means
to produce a sonic frequency burst having
a constant frequency for one portion of its duration and having at least one other fre
quency present for a smaller portion in the
remainder of its duration, whereby the pre
sence of at least two frequencies in the trans
mitted burst reduces the possibility of can
cellation of echoes from the near subjects
and the presence of the sonic frequency of
longer duration facilitates reception of echoes
from more distant subjects.

2. A sonic ranging system in accordance
with claim 1, wherein the constant frequency
is maintained for a major portion of the
burst.

3. A sonic ranging system in accordance
with claim 1 or 2, in which the sonic burst
varies in frequency for a portion of its
duration.

4. A system as defined in claim 3, wherein
a signal of varying frequency is transmitted
in an initial portion of the burst and there
after a signal of constant frequency is
transmitted.

5. A system as defined in claim 3 or 4,
wherein the frequency of the constantfrequency signal is substantially equal to or is less than the lowest frequency of the varying frequency portion of the burst.

6. A system as defined in claim 5, in which the varying-frequency portion of the burst, the frequency decreases progressively from an initial value to the value of the constant frequency.

7. A system as defined in claim 6, wherein the frequency of the said burst decreases
during its initial portion from substantially 65 kllz to substantially 50 kHz and remains at the latter value for the remainder of the burst.

8. A system as defined in any one of the preceding claims, wherein the means for receiving and processing the echo includes a filter, and means for varying the bandwidth of the filter between first and second values during a predetermined interval following the transmission.

9. A system as defined in claim 8, wherein the bandwidth-varying means reduces the bandwidth of a filter from a first value to a second, narrower, value during the said predetermined time interval.

10. A system as defined in claim 8, wherein the bandwidth-varying means includes means for maintaining the bandwidth at a first value during one portion of the said interval and for reducing the bandwidth from the first value to a second value narrower than the first, for the other portion of the said interyal.

11. A system as defined in claims 6 and 8, wherein the bandwidth-varying means includes means for maintaining the bandwidth
substantially constant at a first value during
an initial portion of the said interval and for then progressively altering the bandwidth to a second value, narrower than the first, as the interval progresses, whereby all frequencies in the said burst may be received
in echoes from close-up subjects and the
signal-to-noise ratio for more distant subjects
is improved.

12. A system as defined in claim 11,
wherein the bandwidth is maintained at the
substantially constant first value during approximately the initial one-fifth of the said
interval.

13. A system as defined in any one of
claims 8 to 12, wherein the bandwidth of the
said filter is changed by changing its Q.

14. A system as defined is any one of
claims 1 to 7 wherein the means for receiving
and processing the echo includes a filter of
adjustable Q and means for varying the Q
of the said filter during a predetermined time
interval following the transmission.

15. A system according to claim 14, in
which the Q-varying means includes a pre
programmed Q-control circuit for increasing
the Q of the filter during the predetermined
interval.

16. A system as defined in claim 15, fur
ther including an amplifier for amplifying
the output of the filter and a preprogrammed
gain-control circuit for increasing the gain
of the amplifier during the said predetermined
interval.

17. A system as defined in any one of
claims 8 to 16, including, for varying the
bandwidth and the Q of the said filter, a
diode connected to the filter to form a part
of its resistance and means for varying the dynamic resistance of the diode during the said predetermined interval of time.

18. A system as defined in claim 17, wherein the means for varying the dynamic resistance of the diode includes a programmed current generator for supplying a time-varying dc current to the diode.

19. A system as defined in any one of claims 8 to 18, wherein the bandwidth of the filter is centred on the said substantially constant frequency and at the beginning of the said predetermined interval is wide enough to comprehend the frequencies in the varyingfrequency portion of the burst but decreases during the said predetermined interval, wherein the bandwidth of the filter for echoes from close subjects is wider than the bandwidth for echoes from more remote subjects.

20. A system as defined in claim 19, wherein the bandwidth of the filter is centred at substantially 50 kHz, and wherein the bandwidth is substantially 30 kHz at the beginning of the said predetermined interval and decreases thereafter.

21. A system according to claim 14, wherein the filter comprises an LC circuit defining a filter with a given centre frequency and in which the means for varying the Q includes a resistive element coupled with the said LC circuit and means for dynamically varying the resistance of the said resistive element to change the filter Q as a function of time.

22. A system as defined in any one of the preceding claims, in which the transmitting means includes means for producing a keying pulse, a sonic transducer, a modulator driving the transducer to cause the latter to transmit the said burst of sonic energy towards a subject in response to the application of the keying pulse to the modulator, and means for generating a time-varying control signal, the modulator being responsive to the said timevarying control signal to cause the frequency of the burst to vary during the initial portion thereof from a higher to a lower frequency and then to remain substantially constant during the remainder of the burst.

23. A system in accordance with claim 21, wherein the modulator includes a transformer whose secondary is connected to the transducer through a decoupler that decouples the said secondary from the transducer when the latter produces an echo signal, and a variable frequency oscillator connected to the primary of the transformer, and wherein the filter is an LC filter whose inductance is constituted by the secondary of the transformer, and a pre-amplifier shunts the decoupler and is connected to the capacitive side of the filter for applying echo signals to the filter.

24. A system according to claim 14, wherein the means for varying the Q of the said filter includes current-sensitive resistor means in the filter, and a current generator for pro viding a time-variable current to the resistor means during the said predetermined interval of time.

25. A system according to claim 24, wherein the resistor means includes a diode connected to fixed resistors, the current generator supplying the said time-variable current to the diode for changing its dynamic resistance.

26. A system according to any one of claims 8 to 21, including a detector responsive to the output of the filtei for producing an output signal when the level of the filter output is above a predetermined level, the output signal constituting the range signal.

27. A system as defined in any one of claims 3 to 13, wherein the frequency of the said signal during the varying-frequency portion of the burst is varied in discrete steps.

28. A system as defined in any one of the preceding claims wherein the duration of the said sonic burst is about one millisecond.

29. A system as defined in any one of claims 3 to 13, wherein the duration of the substantially constant-frequency signal is at least one quarter of the length of the said burst.

30. A photographic camera including a sonic ranging system in accordance with any one of the preceding claims.

31. A camera as defined in claim 30, including means responsive to the range signal for varying light-transmitting means within the camera to focus on the focal plane of the camera image-carrying light rays from an object at the said range.

32. A camera comprising means for controlling the transmission of image-carrying light rays to the focal plane from a subject to be photographed, means for automatically varying the said controlling means in accordance with a range signal related to the distance of the subject from the camera, and a sonic ranging system in accordance with claim 1 for providing the range signal, and wherein the frequency of the transmitted burst varies with time in the said remainder of the duration of the burst, whereby the frequencies existing in the said remainder of the duration of the burst facilitate the reception and processing of echoes from subjects at close distances and the said constant frequency facilitates the reception and processing of echoes from subjects at far distances,

33. A camera as defined in claim 32, wherein the constant frequency is approximately equal to the lowest of the said variable frequencies.

34. A camera as defined in claim 32 or 33 wherein the signal-producing means includes means for automatically varying the receiving means to attenuate the reception of the said varying frequency signal at a predetermined time following initiation of the burst, the said time corresponding to the earliest return of an echo from a subject at a distance of 7.5 metres.

35. A cinematographic camera having a sonic ranging system according to any one of claims 1 to 29, and in which bursts of sonic energy are transmitted in a continuous series while the camera is running, and further comprising means responsive to the range signal for varying a light-transmitting means within the camera so as to move the focus of image-carrying light rays from an object at the range represented by the said range signal towards the focal plane of the camera.

36. A cinematographic camera according to claim 35, in which the rate of repetition of the bursts and the response of the lensmoving means are such that an integration of successive range signals is achieved in the control of the lens-moving means.

37. A sonic ranging system substantially as herein described with reference to the accompanying drawings.

38. A photographic camera including a sonic ranging system substantially as herein described with reference to the accompanying drawings.

GB39151/77A
1976-10-04
1977-09-20
Sonic ranging systems

Expired

GB1588927A
(en)

Applications Claiming Priority (1)

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Priority Date
Filing Date
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US72939276A

1976-10-04
1976-10-04

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true

GB1588927A
(en)

1981-04-29

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ID=24930826
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GB39151/77A
Expired

GB1588927A
(en)

1976-10-04
1977-09-20
Sonic ranging systems

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(1)

JPS6045378B2
(en)

AT
(1)

AT370885B
(en)

CA
(1)

CA1120578A
(en)

CH
(1)

CH629312A5
(en)

DE
(1)

DE2744092C3
(en)

FR
(1)

FR2366582A1
(en)

GB
(1)

GB1588927A
(en)

IT
(1)

IT1087398B
(en)

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(en)

1985-04-11
1986-10-15
Frankie Wang
Automatic distance-off alarms for reversing vehicles

GB2352294A
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1996-09-11
2001-01-24
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Ultrasonic object detection system

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1978-01-12
1979-07-19
Agfa Gevaert Ag

DEVICE FOR FOCUSING THE LENS OF A PHOTOGRAPHIC OR KINEMATOGRAPHIC CAMERA

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1978-11-13
1982-02-16
Polaroid Corporation
Camera with auto ranging focusing and flash fire control

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1979-01-02
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Polaroid Corporation
Autofocus movie camera having pulsed terminal drive means

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1979-01-02
1980-12-16
Polaroid Corporation
Autofocus movie camera having improved focus response

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1979-07-30
1981-02-19
Dorian Ind Pty Ltd
Method and device for measuring distances

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1979-10-03
1983-09-20
John M. Reynard
Echo recognition system

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1980-06-03
1981-12-29
Polaroid Corporation
Auto focus camera with electronic lens disc pawl release arrangement

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1982-04-28
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West Electric Co Ltd
Ultrasonic distance measuring device

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2010-11-23
2012-05-30
比亚迪股份有限公司
Ultrasonic ranging method, ranging system and camera component with ranging system

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Zeiss Ikon Ag

Device for automatic distance adjustment of camera lenses

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Method for distance measurement according to the echo delay method

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1973-08-09
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1977

1977-07-06
CA
CA000282156A
patent/CA1120578A/en
not_active
Expired

1977-09-14
FR
FR7727772A
patent/FR2366582A1/en
active
Granted

1977-09-20
JP
JP52113184A
patent/JPS6045378B2/en
not_active
Expired

1977-09-20
GB
GB39151/77A
patent/GB1588927A/en
not_active
Expired

1977-09-27
IT
IT27949/77A
patent/IT1087398B/en
active

1977-09-30
DE
DE2744092A
patent/DE2744092C3/en
not_active
Expired

1977-10-03
CH
CH1205377A
patent/CH629312A5/en
not_active
IP Right Cessation

1977-10-04
AT
AT0706477A
patent/AT370885B/en
active

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Publication date
Assignee
Title

GB2173620A
(en)

1985-04-11
1986-10-15
Frankie Wang
Automatic distance-off alarms for reversing vehicles

GB2352294A
(en)

1996-09-11
2001-01-24
Michael William Hustwitt
Ultrasonic object detection system

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Publication number
Publication date

FR2366582B1
(en)

1980-07-25

AT370885B
(en)

1983-05-10

ATA706477A
(en)

1982-09-15

DE2744092C3
(en)

1980-10-09

FR2366582A1
(en)

1978-04-28

CH629312A5
(en)

1982-04-15

DE2744092A1
(en)

1978-04-06

JPS6045378B2
(en)

1985-10-09

IT1087398B
(en)

1985-06-04

CA1120578A
(en)

1982-03-23

JPS5345267A
(en)

1978-04-22

DE2744092B2
(en)

1980-02-21

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