GB1604304A

GB1604304A - Apparatus for indicating the prescence of an object

Info

Publication number: GB1604304A
Application number: GB2333478A
Authority: GB
Original assignee: Heyes A D
Current assignee: Heyes A D
Priority date: 1978-05-26
Filing date: 1978-05-26
Publication date: 1981-12-09

Description

(54) APPARATUS FOR INDICATING THE PRESENCE OF AN OBJECT (71) I, ANTHONY DAVID HEYES, a British Subject of 15 Arleston Drive, Woollaton, Nottingham, do hereby declare the invention for which I pray that a patent may be granted to me and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to apparatus for indicating the presence of an object which is not visible to the user of the apparatus. The invention is therefore particularly suitable for indicating the approximate location of obstacles in the path of intended movement to blind persons but is also suitable for other uses for example as a reversing aid to drivers of large vehicles.

According to the present invention there is provided apparatus for indicating the presence of an object, said apparatus comprising means for transmitting pulses of ultrasonic energy, means for receiving the pulses on reflection from an object located in the transmitting path, the receiving means comprising a first receiver transducer which faces in a forward direction and further receiver transducers facing in other directions, means presenting successively a predetermined number of output stages subsequent to the transmission of each pulse during which stages the receiving means is operable, and means operable in response to a reflected pulse being received by the receiving means to maintain the stage then being presented and activate means for displaying a signal which is representative of the stage being maintained so as to indicate the distance between the transmision means and the object causing the reflected pulse, means being provided for electronically switching the receiving means and the signal displaying means together so as to provide a desired relationship between each input of the receiving means and outputs of the signal displaying means, and the stage maintaining means, in response to an input at said first receiver transducer, being operable to discontinue the electronic switching of the receiving means and the signal displaying means and to repeat activation of the latter while a signal continues to be received by said first receiver transducer.

Preferably the stage presenting means comprises a gated multivibrator circuit which transmits signals at predetermined time intervals to a counter, the outputs of the latter defining said predetermined number of stages and being presented successively to the signal displaying means in accordance with successive signals from the gated multivibrator circuit.

Preferably also the signal displaying means comprises an oscillator arrangement, the output frequency of which is divided a different predetermined number of times in accordance with each of the stages presented so as to be capable, when the signal displaying means is activated, of presenting individual output display signals indicative of the distance between the transmission means and the object causing the reflected pulse.

The counter may be a decade counter which presents eight outputs to the signal displaying means, the output display signals from the latter being audible and corresponding to the notes of a musical scale with the end note of the scale representing the nearest distance.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a perspective view showing one form of a blind aid apparatus according to the invention; Figure 2 is a block diagram of the circuitry for the apparatus; and Figures 3 to 10 are circuit diagrams of respective parts of the circuitry shown in Figure 2.

Referring to the drawings an apparatus for indicating the presence of an object, for use by a blind person in detecting objects in the intended path of movement, comprises a head-set in the form of a spectacle frame 10 connected by leads to a pocket sized casing 11 for the circuitry. The frame 10 mounts, along its top frame member 12, a housing 14 within which is located means for transmitting pulses of ultrasonic energy. The transmitting means may be in the form of a single wide beam transmitter transducer or as shown in the form of two transmitter transducers 16, 18 which are arranged to transmit pulses in convergent paths and for this purpose are directed at angles of 10 to the forward direction.Also located in the housing 14 is means for receiving the pulses on reflection from an object located in the transmitting path, the receiving means being in the form of three receiver transducers 20, 22 and 24, the transducer 22 being positioned between the transmitter transducers 16, 18 and facing in a forward direction and the transducers 20, 24 being located at respective sides of the transmitter transducers 16, 18 and being splayed divergently at angles of 30 to the forward direction. Means for displaying an audible signal as hereinbefore described is provided in the head-set and is in the form of two ear pieces 26, 28 each mounted on a respective leg 30 of the spectacle frame 10 in close proximity to, but not actually in physical contact with, the ears of the user.

The circuitry for controlling the apparatus is shown in block diagram form in Figure 2 and comprises a main timing control in the form of a gated clock (Figure 3) which includes a free running multivibrator arrangement having two complementary metal oxide substrate (CMOS) gates 30, a resistor 32 for reducing the frequency dependence of the arrangement on supply voltage, and a diode 34 producing a mark to space ratio of approximately 100:1. A Capacitor 36 and a variable resistor 38 define the timing components for the multivibrator and are adjusted to give a frequency of 666 Hz. This provides an output pulse at intervals of 1.5 milli-seconds.A capacitor 40, in conjunction with the output impedance of the multivibrator, provides some integration and rounds off the edges of the pulses from the clock so as to lessen the chances of the receiver transducers being triggered by electrical pick-up. The output of the clock is gated by a CMOS NOR gate 42.

The output pulses from the gated clock are transmitted to a range counter (Figure 4) including a CMOS decade counter 44. The incoming clock pulses cause a logic 1' to be incremented from one output pin of the counter 44 to the next, the outputs being identified '0' to 9' for simplicity. The range counter arrangement is selfcycling. As sound travels in air at a speed of 330 metres per second each count in the counter 44 is representative of a distance of approximately 250 mm.

On the count of '0' the transmitter transducers 16, 18 are enabled and at the same time the receiver transducers 20-24 are disabled as hereinafter described. The range counter includes a NOR gate 46 which provides an inhibit input to an echo triggered monostable arrangement as hereinafter described so that the latter cannot be activated during the count of '0' or 9' in the counter 44. During counts '1' to '8' successive outputs or stages are presented to a display circuit as hereinafter described. On the count of '9' the counter 44 is disabled for a period of some 20 milliseconds by the action of an integrating circuit consisting of a capacitor 48 and a resistor 50 connecting the output '9' to a clock enable input of the counter 44.This introduces a pause in the sequence and reduces the transmitter repetition rate so that all echoes from one transmitter pulse have died away before the next pulse is initiated.

The count continues on the next incoming pulse from the clock after the clock enable input has returned to logic '0'. It should be noted that the counter 44 is "level" rather than "edge" triggered and will increment when the clock enable input becomes logic '0' if the clock input is already at logic 1. Thus if the clock were to have a 1:1 mark to space ratio the period for which the range counter was at zero would vary randomly from 100% to 50% of the inter-clock pulse period.

This instability is removed by using a clock of low mark to space ratio as hereinbefore described.

The transmitter circuit (Figure 5) utilises half of a dual CMOS integrated monostable trigger circuit 52 to provide a 1 millisecond pulse which is triggered on the count '0' in the counter 44. The pulse length is determined by capacitor 54 and resistor 56 and is used to gate a high frequency oscillator formed from a CMOS inverter 58 and a NOR gate 60. A resistor 62 is included in the transmission arrangement between the integrated circuit 52 and the oscillator such that a test point 64 can be shorted to earth enabling the oscillator to run continuously without however overloading the output of the integrated circuit 52. A resistor 66 reduces the effect of supply voltage change on the oscillator the frequency of which is determined by a capacitor 68 and a variable resistor 70.The oscillator which is adjusted to run at 40KHz is coupled by a respective secondary winding of a transformer 72 to each of the transmitter transducers 16, 18 which operate simultaneously.

The circuit for the receiver arrangement (Figure 6) includes a quad operable amplifier in which signals picked up by any of the receiver transducers 224 are amplified by three stages 74 thereof, the fourth stage 76 acting as a comparator to transmit only above threshold signals to the echo triggered monostable arrangement.

The associated components of the amplifier provide for a limited band width centred on 40 KHz, the signal being envelope detected after amplification by means of diodes 78, 80. A number of control lines are used to modify the action of the receiver. A transistor 82 shorts the input to ground during the period of count '0' in the counter 44. The time constant of a swept gain circuit defined by resistor 84 and capacitor 86 determines the time dependency of the impedance across the transistor 82. This action has two purposes, firstly it introduces a dead time sufficiently long so that the receiver is not triggered directly by the transmitter, i.e. by cross-talk, and secondly it sweeps the gain of the receiver and so modifies the effective beam width. The amplifier stage 76 acting as the threshold detector is inhibited during count '0' on the counter 44 by virtue of the diode 88 and is also inhibited during the period when the display circuit is enabled by the echo triggered monostable by means of diode 90 thus preventing further triggering of the echo triggered monostable circuit by electrical transients internally generated in the apparatus. The resistor 92 and the capacitor 94 ensure that the threshold detector is inhi bited for a sufficiently long time after enabling of the display circuit that the echo triggered monostable circuit can only be operated once each transmission pulse.

The echo triggered monostable circuit (Figure 7) utilises the other half of the dual CMOS integrated monostable trigger circuit 52 and has timing components in the form of a capacitor 96 and resistor 98 to give an output signal in the form of a pulse of 4s50 milliseconds which is transmitted to the display circuit. The inherent retriggerable nature of the monostable circuit is defeated by feeding the output back via a resistor 100 into the input of the echo triggered monostable arrangement. A diode 102 isolates the feedback circuit from the receiver. As hereinbefore described the echo triggered monostable arrangement is disabled during counts '0' and '9' of the counter 44 which prevents operation by out-of-range echoes.Further outputs are used to gate the clock in order that the range counter pauses for 40 milliseconds at the count number appropriate to the distance of the object, to disable the receiver, and to enable the display circuit as hereinbefore described.

As the incoming clock pulses to the counter 44 are timed at 1.5 millisecond intervals and each causes an increment from one output pin to the next in the counter 44, the count at which the range counter pauses due to the output signal from the echo triggered monostable arrangement, which in turn is due to a reflected pulse being received at one of the receiver transducers, determines the range of the object producing the deflected pulse.

The circuitry for the display arrangement (Figure 8) comprises a master oscillator having a NOR gate 104,. an inverter 106 and associated components i.e. resistor 108. variable resistor 110 and capacitor 112. A resistor 114 is included in the input line in order that the oscillator may be enabled continuously by shorting test point 116 to earth. During setting up procedure the resistor 110 is adjusted so that the oscillator has a frequency of approximately 105 KHz. A feedback enable l.ne includes a diode 118 so that the output of a CMOS inverter 126 of the display outpt always "stops" low. The output frequency of the oscillator is divided by a switchable divider 120 (Figure 9) comprising a tens decade counter 122 and a unit decade counter 124 in series.The particular count presented by the counter 44 at the time when the range counter pauses due to an output signal from the echo triggered monostable arrangement causes the output frequency of the master oscillator to be divided a predetermined number of times and produces an audible display output at a respective earpiece 26,28, in the form of a note of the lonian or Major musical scale.

The number of times the output frequency has to be divided for each note can be determined from Figure 9, the display output being tken from the count '2' output of the tens counter 122 and passed through a further CMOS inverter 127 and the inverter 126 in series. A capacitor 128 is included to suppress low frequency switching transients and variable resistor (not shown) provides a volume control for operation by the user.

An azimuth counter (Figure 10) comprises an integrated circuit 138 in the form of a binary divide. The input is taken from the transmitter enable input i.e. '0' count in the counter 44 and outputs A and B are used to control a dual four way analogue gate in the form of CMOS integrated circuit 140. In accordance with the following table the receiver transducers 20-24 are electronically switched with the output display in a time division multiplexer, so that receiver transducer 20 is firstly enabled followed by receiver transducer 22, then receiver transducer 24, receiver transducer 22 again, and receiver transducer 20 again to begin another cycle.The apparatus therefore in effect "looks" to the right, the centre, the left, the centre, the right etc. with the output display being switched in turn as shown in the table to the right ear, both ears, the left ear, both ears, the right ear etc.

Switching Table A B INPUT LEAR REAR 0 0 RIGHT GND 0 O CENTRE - - 0 1 LEFT - GND CENTRE - Because the detection of objects straight ahead of the user is more important than the detection of objects either side, the existence of an above threshold echo in the centre receiver transducer 22 is used to inhibit the time division multiplexer, so that azimuth scanning ceases and only information received by the centre receiver transducer 22 is displayed to the user till such time that the object is negotiated.This is achieved by the centre target detector circuitry (Figure 10) wherein diodes 142 and 144 form an AND gate which produces a reset pulse for the integrated circuit 138, the length of which is determined by a capacitor 146 and a resistor 148, at the end of an output display period occasioned by a signal received by the receiver transducer 22, i.e. when the time division multiplexer is switched to the "centre". The effect of the reset pulse is to return outputs A and B to their low condition which is equivalent to the apparatus "looking" right.

However the transmission pulse which follows immediately causes the time division multiplexer to then count to the state wherein the receiver transducer 22 is again enabled. During such a period it will be appreciated that the display repetition rate is increased to four times that for side information.

The apparatus as hereinbefore described therefore has a prime function to detect and indicate the distance of any object which lies directly in the path of the user and in the absence of any object directly ahead the apparatus reverts to its secondary function of indicating the presence and distance of objects to the left and to the right of the travel path. In the interests of achieving simplicity at the display the apparatus represents target distance in terms of one of the eight notes of the musical scale. The lowest note of the scale represents a target within the range of zero to 500 mm with subsequent notes being assigned to successive 250 mm zones up to a maximum range of 2.25 metres.

It will be appreciated that it is possible to use any other type of display but it is considered that the notes of the musical scale are preferable in order to make their relationship between distance and output as meaningful as possible.

An apparatus as hereinbefore described has the following advantages: (1) relevant information is provided in a form that is simple to understand; (2) the apparatus responds only to objects which lie within a defined range thus reducing the amount of information reaching the user; (3) the apparatus incorporates a display which is silent in the absence of an object within a defined range; (4) the apparatus responds only to the nearest object; (5) the apparatus displays information about an object lying to a side of the use by means of the ear on that side alone while for objects lying directly ahead both ears are used; (6) the apparatus enables the user to move parallel to a fixture such as a wall or a hedge by keeping the musical tone in one ear constant;; (7) the apparatus in the presence of a central object stops giving information about objects lying to the side thus selecting the relevant information for the user; (8) the apparatus provides a display repetition rate increased fourfold in the presence of a central object thus emphasising the presence of a hazard; (9) the device is relatively inexpensive to manufacture; (10) the device is pocket sized and easy to use; (11) the apparatus can use as a power source a re-chargeable battery such as requiring an overnight recharge once every two weeks It is to be appreciated that the invention can be applied to an apparatus of more simplified form which has a single transmitter transducer and a single receiver transducer so as to detect and indicate objects on one direction only, for example a forward direction.With such a modified apparatus it will be appreciated that there will be no requirement for an azimuth counter providing for the receiver and the display arrangements being time division multiplexed nor will there be a requirement for a centre target detector. Such a modified apparatus can also be formed as a spectacle frame or a hand held device preferably having an output socket which in cludes an internal switch so that, ifan ear piece is used, a variable resistor providing a volume control is in series with the output. If the ear piece plug is removed an internal speaker may be driven by an out-of-phase voltage from inverters and is unaffected by the setting of the variable resistor.

Various other modifications may be made without departing from the invention. For example it will be appreciated that a switch arrangement can be provided for operation by the user.

It is also appreciated that the invention can be used in applications other than aids for blind persons. For example an apparatus according to the invention may be used as a reversing aid for drivers of large vehicles, the transmitters and receivers being positioned where appropriate on the vehicle and the display being available in the cab of the vehicle for the driver. Also the invention may be used as a detecting apparatus for divers in muddy waters, or for firemen in smoke filled rooms.

WHAT I CLAIM IS: 1. Apparatus for indicating the presence of an object, said apparatus comprising means for transmitting pulses of ultrasonic energy, means for receiving the pulses on reflection from an object located in the transmitting path, the receiving means comprising a first receiver transducer which faces in a forward direction and further receiver transducers facing in other directions, means presenting successively a predetermined number of output stages subsequent to the transmission of each pulse during which stages the receiving means is operable, and means operable in response to a reflected pulse being received by the receiving means to maintain the stage then being presented and activate means for displaying a signal which is representative of the stage being maintained so as to indicate the distance between the transmission means and the object causing the reflected pulse, means being provided for electronically switching the receiving means and the signal displaying means together so as to provide a desired relationship between each input of the receiving means and outputs of the signal displaying means, and the stage maintaining means, in response to an input at said first receiver transducer, being operable to discontinue the electron switching of the receiving means and the signal displaying means and to repeat activation of the latter while a signal continues to be received by said first receiver transducer.

2. Apparatus according to Claim 1, wherein the stage presenting means comprises a gated multivibrator circuit which transmits signals at predetermined time intervals to a counter, the outputs of the latter defining said predetermined number of stages and being presented successively to the signal displaying means in accordance with successive signals from the gated multivibrator circuit.

3. Apparatus according to Claim 2, wherein the counter is self-cycling, a first output of the counter enabling the transmitting means and disabling of the receiving means. and the first and last outputs of the counter inhibiting operation of the stage maintaining means.

4. Apparatus according to Claim 3, wherein the receiving means includes means which short the input to ground on presentation of the first

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

eight notes of the musical scale. The lowest note of the scale represents a target within the range of zero to 500 mm with subsequent notes being assigned to successive 250 mm zones up to a maximum range of 2.25 metres.

It will be appreciated that it is possible to use any other type of display but it is considered that the notes of the musical scale are preferable in order to make their relationship between distance and output as meaningful as possible.

An apparatus as hereinbefore described has the following advantages: (1) relevant information is provided in a form that is simple to understand; (2) the apparatus responds only to objects which lie within a defined range thus reducing the amount of information reaching the user; (3) the apparatus incorporates a display which is silent in the absence of an object within a defined range; (4) the apparatus responds only to the nearest object; (5) the apparatus displays information about an object lying to a side of the use by means of the ear on that side alone while for objects lying directly ahead both ears are used; (6) the apparatus enables the user to move parallel to a fixture such as a wall or a hedge by keeping the musical tone in one ear constant;; (7) the apparatus in the presence of a central object stops giving information about objects lying to the side thus selecting the relevant information for the user; (8) the apparatus provides a display repetition rate increased fourfold in the presence of a central object thus emphasising the presence of a hazard; (9) the device is relatively inexpensive to manufacture; (10) the device is pocket sized and easy to use; (11) the apparatus can use as a power source a re-chargeable battery such as requiring an overnight recharge once every two weeks It is to be appreciated that the invention can be applied to an apparatus of more simplified form which has a single transmitter transducer and a single receiver transducer so as to detect and indicate objects on one direction only, for example a forward direction.With such a modified apparatus it will be appreciated that there will be no requirement for an azimuth counter providing for the receiver and the display arrangements being time division multiplexed nor will there be a requirement for a centre target detector. Such a modified apparatus can also be formed as a spectacle frame or a hand held device preferably having an output socket which in cludes an internal switch so that, ifan ear piece is used, a variable resistor providing a volume control is in series with the output. If the ear piece plug is removed an internal speaker may be driven by an out-of-phase voltage from inverters and is unaffected by the setting of the variable resistor.

Various other modifications may be made without departing from the invention. For example it will be appreciated that a switch arrangement can be provided for operation by the user.

It is also appreciated that the invention can be used in applications other than aids for blind persons. For example an apparatus according to the invention may be used as a reversing aid for drivers of large vehicles, the transmitters and receivers being positioned where appropriate on the vehicle and the display being available in the cab of the vehicle for the driver. Also the invention may be used as a detecting apparatus for divers in muddy waters, or for firemen in smoke filled rooms.

WHAT I CLAIM IS: 1. Apparatus for indicating the presence of an object, said apparatus comprising means for transmitting pulses of ultrasonic energy, means for receiving the pulses on reflection from an object located in the transmitting path, the receiving means comprising a first receiver transducer which faces in a forward direction and further receiver transducers facing in other directions, means presenting successively a predetermined number of output stages subsequent to the transmission of each pulse during which stages the receiving means is operable, and means operable in response to a reflected pulse being received by the receiving means to maintain the stage then being presented and activate means for displaying a signal which is representative of the stage being maintained so as to indicate the distance between the transmission means and the object causing the reflected pulse, means being provided for electronically switching the receiving means and the signal displaying means together so as to provide a desired relationship between each input of the receiving means and outputs of the signal displaying means, and the stage maintaining means, in response to an input at said first receiver transducer, being operable to discontinue the electron switching of the receiving means and the signal displaying means and to repeat activation of the latter while a signal continues to be received by said first receiver transducer.
2. Apparatus according to Claim 1, wherein the stage presenting means comprises a gated multivibrator circuit which transmits signals at predetermined time intervals to a counter, the outputs of the latter defining said predetermined number of stages and being presented successively to the signal displaying means in accordance with successive signals from the gated multivibrator circuit.
3. Apparatus according to Claim 2, wherein the counter is self-cycling, a first output of the counter enabling the transmitting means and disabling of the receiving means. and the first and last outputs of the counter inhibiting operation of the stage maintaining means.
4. Apparatus according to Claim 3, wherein the receiving means includes means which short the input to ground on presentation of the first

output of the counter, and a threshold detecting arrangement which is inhibited when the first output of the counter is presented and when the stage maintaining means is operative.
5. Apparatus according to any of the preceding claims, wherein the signal displaying means comprises an oscillator arrangement, the output frequency of which is divided a different predetermined number of times in accordance with each of the stages presented so as to be capable, when the signal displaying means is activated, of presenting individual output display signals indicative of the distance between the transmission means and the object causing the reflected pulse.
6. Apparatus according to Claim 5, when dependent on any of Claims 2 to 4, wherein the counter is a decade counter which presents eight outputs to the signal display means, the output display signals from the latter being audible and corresponding to the notes of a musical scale with the end note of the scale representing the nearest distance.
7. Apparatus according to any of the preceding Claims, wherein said further receiver transducers comprise a second transducer which faces in a direction to the right of said first forward facing transducer, and a third which faces in a direction to the left thereof.
8. Apparatus according to Claim 7, wherein the apparatus is mounted in a head-set which has legs for fitting on the ears of the wearer and the signal displaying means comprises two outputs which are provided on the respective legs of the head-set.
9. Apparatus according to any of the preceding claims wherein the transmitting means comprises two transmitter transducers which face convergently in a forward direction.
10. Apparatus for indicating the presence of an object substantially as hereinbefore described with reference to the accompanying drawings.