GB2578683A

GB2578683A - Object detection device

Info

Publication number: GB2578683A
Application number: GB1913522.7A
Authority: GB
Inventors: Manzouri Shahamat; John Callaway Patrick
Original assignee: BAE Systems PLC
Current assignee: BAE Systems PLC
Priority date: 2018-09-24
Filing date: 2019-09-19
Publication date: 2020-05-20
Anticipated expiration: 2039-09-19
Also published as: GB2578683B; GB201815544D0; GB201913522D0

Abstract

A wearable or manually portable object detection device 10 for visually impaired operators comprises a ranging device 2 operable to transmit an outward signal S and to receive a return signal representative of the object and the range. The device also includes a processor 4 for converting the return signal into a vibration signal, the frequency of which is selected according to the range at which the object has been detected, wherein the frequency of the vibration signal varies monotonically and increasingly as the range gets shorter. A transducer 6 generates human-interpretable vibrations from the vibration signal. Also provided is a method of representing the range of an object comprising dividing the environment into consecutive range gates and providing a look-up table associating each range gate with a human-interpretable vibration at a unique frequency. Each range gate may be divided into a plurality of angular sectors, each sector having a defining characteristic.

Description

OBJECT DETECTION DEVICE

According to the following invention there is provided a wearable or manually portable object-detection device and a method of representing to a visually impaired operator, the range of an object.

People who are blind or who have impaired vision may find it difficult to navigate an environment safely. To improve safety, it is known to provide a walking cane comprising an ultrasound transceiver configured to provide a vibration to the user as proximate objects are detected.

According to a first aspect of the invention there is provided a wearable or manually portable object-detection device for visually impaired operators comprising: a ranging device operable to transmit an outward signal for propagating onto an object, and operable to receive a return signal representative of the object and the range; a processor for converting the return signal into a vibration signal, the frequency of which is selected according to the range at which the object has been detected; and a transducer for generating human-interpretable vibrations from the vibration signal, wherein the processor is operable such that the frequency of the selected vibration signal varies monotonically and increasingly as the range gets shorter.

Such a provision can provide a signal which the applicant has found to be readily appreciable to an operator, who may wish to have greater sensitivity to range at shorter ranges.

The device may be operable to: define a set of range gates; and wherein the processor converts the return signal into the vibration signal such that for each range gate there is assigned a human-interpretable vibration having a unique frequency.

Such a provision can make it easier for the operator to learn the range gates and their associated frequencies, thereby building the operator's -2 -confidence in the device and their ability to perceive the environment using the device.

The unique frequency of the human-interpretable vibration may be an audible frequency corresponding to a note on a predetermined musical scale.

By utilising a set of frequencies which the operator may already be familiar with, familiarity with the device can tend to develop quicker.

Consecutive range gates may have assigned to them consecutive notes on the musical scale.

By utilising a set of frequencies which the operator may already be 10 familiar with and which are arranged in what may be a familiar sequence, familiarity with the device can tend to develop even quicker.

The device may be operable to define: a first set of contiguous range gates having a first precision level; and a second set of contiguous range gates having a second precision level, the first precision level having more range gates per metre than the second precision level.

The first set of contiguous range gates may be at a closer range than the second set.

The device may be operable to define a third set of contiguous range gates having a third precision level, the third precision level having fewer range gates per metre than the second prevision level, the third set being at a greater range than the second set.

By thus compartmentalising the volume which the device illuminates, there can tend to be established a readily learnable framework.

Each range gate may be divided into a plurality of angular sectors, each sector having a defining characteristic.

Such a provision can enable the operator to perceive space as well as range. For example where in the azimuth or elevation an object may be.

For angular sectors, the defining characteristic may be such that return signals from a first angular sector in a given range gate are converted into -3 -human-interpretable vibrations in a first octave, and returns from a second angular sector in the given range gate are converted into human-interpretable vibrations in a second octave.

Such a provision can minimise the informational load experienced by the operator insofar as the relationship between one sector and another can be perceived. Should the operator be familiar with the use of octaves in wester musical scales, and should the vibrations from one sector to another correspond to equivalent notes in different octaves, the familiarisation can tend to be accelerated.

o The transducer may comprise a first and second transducer, one for each of the operator's ears and wherein the defining characteristic of each angular sector is such that return signals from sectors on the left of the operator are converted into human-interpretable vibrations at the respective ear, and return signals from sectors on the right of the operators are converted into human-interpretable vibrations at the other ear.

Such a provision may tend to provide an intuitive set of signals to the user by which to interpret the environment, insofar as they may mimic binaural hearing.

The device may comprise a plurality of ranging devices, with boresights inclined to one another, to thereby divide each range gate into a number of sectors.

The ranging device may comprise a pulsed ranging device.

The ranging device may be for transmitting and receiving inaudible sound waves and the range gates extend no further than 4m.

Such waves (which may for example be ultrasound waves) used in such a range can provide a suitable compromise such that an operator can be updated suitably regularly about suitably proximate items.

The wearable object detection device may be provided within a housing that can be mounted on the operator's head such that the device remains fixed in position relative to the operator's head as the operator moves their head. -4 -

Such a provision can enable the operator to scan the environment in an intuitive way.

According to a second embodiment of the invention there is provided a method of representing to a visually impaired operator, the range of an object, the method comprising: providing a range detecting device and processor for dividing an environment into a plurality of consecutive range gates; providing a look up table associating each range gate with a human-interpretable vibration at a unique frequency; determining by the range detecting device and processor that a range gate is occupied by an object; selecting from the look-up table the human-interpretable vibration associated with that range gate; and using a transducer to expose the operator to that human-interpretable vibration, wherein the range gates vary such that a closer range gate is shorter than a farther range gate.

So that the invention may be understood, at least one example embodiment thereof will now be described with reference to the following Figures, of which: Figure 1 shows a side elevation of a first embodiment of the invention, as worn by a user; Figure 2 shows a plot of human-interpretable vibration signals for corresponding to range gates in an example embodiment; Figure 3 shows a plan elevation of a further embodiment of the invention, as worn by a user; and Figures 4a, 4b and 4c show plots of human-interpretable vibration signals for corresponding with range gates in the further embodiment.

Referring to Figure 1, there is shown an object detection device 10 worn by a user. The object detection device has the general form of a pair of glasses at least insofar as it comprises firstly a front section which rests on the user's nose such that the front section is generally in front of the eyes, and secondly a -5 -pair of arms, each extending from the front section to rest on an ear. Accordingly, the object detection device 10 moves with the user's head.

The object detection device 10 comprises a ranging device 2, a processor 4, and interface 5, and a transducer 6. The processor 4 is operably 5 connected to the ranging device 2 and the transducer 6.

The ranging device 2 is configured to generate and transmit a physical signal into the ambient environment. Further, the ranging device 2 is configured to receive return signals from the ambient environment, created for example as the transmitted physical signal reflects off of objects in the ambient environment and back to the device 10.

In the present embodiment, the physical signal transmitted into the ambient environment is an acoustic wave S which has an inaudible ultrasonic frequency. This ultrasonic signal is transmitted as a pulse, repeated at a constant and predetermined interval (the Pulse Repetition Frequency -PRF). In the present embodiment, in order to receive signal returns from a range of 0 to 3 m, the PRF is set at between 10 to 60Hz, more particularly between 15 and 25Hz and still more particularly 20 Hz.

The ranging device 2 is configured to radiate the acoustic wave S along a major axis, or bore sight 8.

As shown in Figure 1, the object detection device 10 is arranged such that when worn, the physical signal, here an ultrasonic pulse, is transmitted generally downwards (e.g. so that if the operator defines a direction of gaze, the pulse is transmitted through a boresight 8 inclined at 20° rather than in alignment with the direction of gaze). This tends to comfortably direct the pulse to areas which are of concern to the operator.

In alternative embodiments, the ranging device 2 can be mounted at the object detection device 10 such that the boresight 8 is generally aligned with the direction the user's face is facing.

As the user moves their head, the section of the ambient environment 30 illuminated by the acoustic wave S moves correspondingly. Various -6 -characteristics for the radiation pattern illuminating the volume are contemplated here; however an exemplary pattern would give an effective beam angle relative to the boresight of ±30° azimuth and ±30° elevation. The radiation pattern may be configured to match the field of view of a standard human.

The ranging device 2 is provided with a sensor for detecting return signals from the ambient environment. The sensor is configured to convert the acoustic vibrations from the return signal into an electrical representation of those returns. Electrical representations of the acoustic vibrations are referred to here as the electrical return signal.

The ranging device 2 is operably connected to the processor 4 such that the electrical return signal can be input to the processor 4. An analogue to digital converter (ADC) may be provided between the ranging device 2 sensor and the processor 4 in order to arrange the electrical return signal in a suitable format for the processor 4.

At the processor 4, the electrical return signal is analysed to determine a range for the object which is inferred to have given rise to the return signal.

Further, the processor 4 is configured to define a set of predetermined range gates in the ambient environment, each range gate corresponding to a section of the volume. For example and with reference to Figure 1, a first range gate, AB, is defined at nodes Al, Bl, al and All (where Al and Al both sit on a line of constant range, and where B1 and BM sit on a line of constant range), a second range gate, BC, is defined at nodes B1, C2, Cl and B'1, and so on until the most distant range gate, GH, defined at G1, H1, H'1, and G'1. As shown in Figure 1, in the present embodiment, seven range gates are defined in this manner.

Moreover, the range gates are not all of the same range-interval (i.e. width between lines of constant range). The four closest-range range gates have the same short range-interval, the next two range gates have the same intermediate range-interval, and the furthest-range range gate has a long range-interval. As such, the processor 4 rasterises the ambient environment such that -7 -there are more range gates close to the ranging device 2 than there are at longer range.

With the range of the object determined, and the ambient volume divided into range gates, the processor 4 is configured to identify which range gate the object is present in.

Still further, the processor 4 is configured to, for each of the range gates, assign a unique vibration signal such that this vibration signal can be output by the processor if an object is determined as being present in that range gate. This assignment or mapping operation may be carried out with reference to a look-up table, or could be performed according to a simple algorithm. Figure 2 shows diagrammatically the relationship used to map the range gates from Figure 1 to unique vibration signals.

In particular, returns from the closest range gate AB (with a range of between 0 and 25cm) are assigned a vibration signal with a 1000 Hz signal; returns from the second closest range gate BC (between 25cm and 50cm) are assigned a vibration signal with a 870Hz signal; returns from the third closest range gate CD (between 50cm and 75cm) are assigned a vibration signal with a 730Hz signal; returns from the fourth closest range gate DE (between 75cm and 100cm) are assigned a vibration signal with a 580Hz signal; returns from the fifth closest range gate EF (between 100cm and 150cm) are assigned a vibration signal with a 420Hz signal; returns from the sixth closest range gate FG (between 150cm and 200cm) are assigned a vibration signal with a 250Hz signal; returns from the seventh closest GH (i.e. furthest) range gate (between 200cm and 300cm) are assigned a vibration signal with a 100Hz signal. Thus each of the vibration signals has a frequency corresponding to a soundwave in the audible range.

As such, the device is configured so that: the nearest four range gates have the same range interval (25cm) and occupy a combined range gate extending over range R; the next two nearest range gates have the same range 3o interval (50cm) which is greater than the range interval for the nearest four range gates and occupy a combined range gate extending from range R to -8 -range 2R; and the farthest range gate has a range interval extending from range 2R to range 3R. Range gates are contiguous. The frequency change between adjacent range gates is approximately constant (varying between 130Hz and 170Hz in the example of Figure 2).

With the range gate in which the object 0 is present having been detected, and with reference to the mapping algorithm, the processor 4 is operable to output a suitably selected vibration signal.

The processor 4 is operably connected to the transducer 6, which in the present example is a bone conducting headphone mounted on a bone structure close to the ear (e.g. the jaw), for issuing audible signals. In alternative embodiments there is provided an in-ear speaker which may be more colloquially referred to as an ear bud or a headphone. The transducer 6 is configured to receive the vibration signal from the processor 4 (a digital to analogue converter may be provided between) and convert the vibration signal into a human-interpretable soundwave/vibration signal. The human-interpretable soundwave/vibration signal has the same frequency as its corresponding vibration signal.

The transducer 6 may comprise, or further comprise, a haptic' transducer (i.e. an actuator for issuing a touch signal to the user) which may act in combination or as an alternative to the audible transducer. Certain range gates may be associated with the transducer providing a haptic vibration signal, in addition or as an alternative to the audible vibration signal. For example the closest range gate AB may, in addition or as an alternative to an audible 1000Hz signal, provide a haptic signal at that frequency.

By varying the range interval from range gate to range gate like this, whilst keeping constant the frequency change from range gate to range gate, and passing that to the operator as a human-interpretable vibration, the vibration frequency changes monotonically (e.g. as shown here it keeps going up as the range shortens) and the vibration frequency changes increasingly (i.e. for a given range interval, the difference in frequency across that range interval -9 -at a closer range will be greater than the difference in frequency across that range interval at a farther range).

In a particular approach to the mapping of ranges onto frequencies, the vibration frequency may vary exponentially with range. For example there may be an exponential decay in frequency with range such as a negative exponential relationship where plotting the range given by mid-point of the range gates against the frequency of the range gates yields a set of points along the line where f n-R (where f = frequency, n = a constant, R = range).

Alternatively, the monotonic and increasing relationship may be such that there is an inverse relationship between the frequency and the range, so that plotting the range given by mid-point of the range gates against the frequency of the range gates yields a set of points along the line where f a IR (where f = frequency, R = range).

In operation a user wearing the object-detection device may find 15 themselves in an environment where there is, for example, an object 0 present (as shown in Figure 1).

With the device 10 activated, the ranging device 2 will transmit an ultrasonic pulse S into the environment which will then propagate in the direction in which the user is facing.

On the illumination of an object 0 by the pulse S, an acoustic return signal will be generated, a component of which propagates back to the ranging device 2.

This acoustic/pulse return is received at the sensor of the ranging device 2, converted into an electrical return signal and relayed to the processor 4 (perhaps via an ADC). Time of pulse arrival information, relating to the acoustic/pulse return, may be determined at the ranging device 2 and incorporated into the electrical return signal, or may be inferred at the processor 4 from the time of arrival of the electrical return signal.

At the processor 4, the electrical return signal is analysed to determine the range of the object, then the corresponding range gate, and then the corresponding vibration signal for sending to the in-ear speaker 6.

The processor 4 may also perform a change detection operation by referring to a memory at the processor to determine whether the previously transmitted pulse S gave rise to the same finding. If performing a change-detection operation, the analysed returns from each pulse should be stored in the memory at least until the next pulse has been analysed and compared thereto.

Having determined the vibration signal to relay to the transducer 6, this signal is relayed and the transducer 6 outputs an audible waveform at the selected frequency. In the present embodiment, the audible waveform is in the form of a number of pulses at the relevant frequency.

Thus the user will appreciate not only that there is an object present in front of them, but also will be able to infer the range of the object from the frequency of the sound.

Whilst there is no innate association in the mind of the user between the frequency of a sound and the range of an object, the applicant has found that over time the user can build up that association, particularly if a consistent 20 mapping of range gates to frequencies is used.

Moreover, if there is something recognisable about the choice of frequencies, a user can more readily adapt to the system. Thus, in alternative embodiments of the present invention, the frequencies chosen correspond to notes from a recognisable musical scale (for example C Major, western standard scale) where consecutive notes of that scale corresponded with consecutive range gates.

The object-detection device 10 may operable in different modes: An 'internal walk' mode where the sonar pulse is configured to give a maximum range of 2 m, and the human interpretable vibration is in the form of 30 two audible pulses at the relevant frequency per range-gate change detected; An 'external walk' mode where the maximum range is 3m, and the human interpretable vibration is in the form of three audible pulses at the relevant frequency per range-gate change detected; A 'static/work' mode which is as per the 'internal walk' mode but any detections from the closest 0.5 m lead to no either human-interpretable vibration, or a secondary form of human-interpretable vibration (e.g. as may issue from a haptic transducer instead of an audible-signal speaker); and A 'constant' mode which is as per the 'external walk' mode regarding range but where the human-interpretable pulses are audible pulses repeated continuously at 0.5 Hz, the operator thereby receiving the audible signal irrespective of whether there has been a change in a range gate.

The user may switch between these modes using the interface 5 provided (e.g. buttons on the device, voice activation, gesture recognition) which communicates with the processor 4.

In other embodiments, the device 10 may be provided with an external communications module for interfacing with environmental transponders (e.g. GPS, locally placed RF beacons, Bluetooth Tm stations or WiFiTM stations) which may prompt the device 10 to switch to a particular mode. For example, where the external communications module is for GPS geo-location, the processor be configured to associated a specific location with a specific mode, so that on arriving at a designated static/work area (for example at a cashpoint/ATM) the static/work mode may be prompted.

Referring to Figure 3, a further embodiment of the wearable object detection device 20 is provided. This object detection device 20 is similar to the first embodiment at least in so far as there is an overall device 20 having the general form of glasses, which comprise a processor 24 operably connected between a transducer 27, and a central ranging device 22.

However, the object detection device 20 further comprises a port-side ranging device 21 and a starboard-side ranging device 23. Still further, the object detection device 20 comprises a further transducer 26 for the user's other ear.

As with the first embodiment, the central ranging device 22 is substantially aligned with the direction in which the user faces, and has a boresight shown at C. The port-side ranging device 21 is inclined in the azimuth to the central ranging device 22 by approximately +45°. The port-side ranging device 22 defines a boresight shown at axis L, which is accordingly inclined to the central boresight 8 by +45° in Figure 3.

The starboard-side ranging device 23 is inclined in the azimuth to the central ranging device 22 by approximately -45°. The starboard-side ranging device 23 defines a boresight shown at axis R, which is accordingly inclined to the central boresight 8 by -45° in Figure 3.

Each ranging device 21, 22, 23, is operable to transmit a respective ultrasound pulse T, U, V along its respective boresight L, 8, R. In the present example, the pulses T, U and V have different pulse 15 frequencies to one another, each has the same PRF of the first embodiment (e.g. 20Hz), and the pulses are emitted in phase with one another.

Given that the radiation patterns of each ranging device are adjacent to one another, each ranging device is configured such that the beam intensity defined by the radiation pattern drops off sharply once it is closer to another ranging device's boresight than its own. Thus the radiation pattern for the central ranging device 22 is substantially contained within the guidelines A2, B2, C2 and D2 and A3, B3, C3 and D3 (C1, C2, D1 and D2 are not shown in Figure 3 but can be inferred from Figure 1).

Each ranging device 21, 22, 23 comprises a sensor for detecting returns from its respective ultrasound pulse T, U, V, and generating a respective electrical return signal. Where each pulse has a distinct frequency, returns from one pulse can be readily distinguished from returns from other pulses.

Each of the ranging devices 21, 22, and 23 are operably connected to the processor 24 so that electrical return signals can be analysed to determine 30 the range of the object and the ranging device which has detected it. (As shown in Figure 3, an object P is located in view of the star-board ranging device 23, pulse V is shown to have propagated beyond object P and so returns from pulse P (not shown) will have been propagating back to the ranging device 23).

Moreover, to exploit the provision of ranging devices 21, 22, 23 which address a different azimuthal sector of the environment, the processor is configured to compartmentalise/rasterise the environment into range gates that are defined not only by range intervals but also by the azimuthal sectors associated with the respective range detectors. Thus, as can be seen in Figure 3, the processor defines a series of range gates such as those defined by: nodes A1, B1, B2, A2 (AB12); nodes A2, B2, B3, A3 (AB23); or nodes A3, B3, B4, A4 (AB34).

Once the environment is compartmentalised/rasterised according to such a predetermined scheme, the processor 4 can map each range gate onto a predetermined and unique vibration signal, and output the vibration signal associated with the range gate which is determined to have the object within it.

In the present embodiment the vibration signal is output from the processor to the dual transducers 26, 27 such that each transducer receives the same signal.

Figures 4a, 4b, and 4c illustrate how the first three range gates are 20 mapped to a frequency for each sector.

In particular, for the central ranging device 22 as shown in Figure 4b: the first (AB23) range gate, in the range interval 0 to R/2, corresponds to a frequency of 2f; the second range gate (not shown in Figure 3), in the range interval R/2 to R, corresponds to a frequency of nf; and the third range gate (not shown in Figure 3), in the range interval R to 2R corresponds to a frequency of mf. 2f > nf > mf > f.

Meanwhile, the range gates (AB12, etc.) associated with the port-side ranging device 21 have the same mapping to vibration signals as in the central ranging device 22 but with the frequency doubled (i.e. in the octave above).

Meanwhile, the range gates (AB34, etc.) associated with the starboard-side ranging device 23 have the same mapping to vibration signals as in the central ranging device 22 but with the frequency halved (i.e. in the octave below).

Thus, if an object moves across the user's field of regard from left/port to right/starboard, whilst remaining in the same range interval (e.g. AB), then three notes will be delivered to the user which are in harmony and have the impression of an ascending scale. In embodiments where the frequencies are chosen to represent the notes of a musical scale, these notes will be from an adjacent octave (e.g. C 523Hz, middle C 262 Hz and C 130Hz).

Further, if two objects are present, this can be indicated to the user by providing both of the relevant vibration signals at the same time.

Due to the selection of notes in adjacent octaves for adjacent azimuth sectors, there may prove to be fewer frequencies available to the user as compared with the single-sector ranging device 10 in the Figure 1 embodiment. Therefore the further embodiment may provide larger range gates (i.e. range gates having a greater range interval) and/or a shorter maximum range.

The further embodiment may be operable in a plurality of different modes.

The first mode may be as already described, where all three of the ranging devices 21, 22, 23 are activated and the volume is compartmentalised additionally into azimuthal sectors.

The second mode may be where only the central ranging device 22 is activated, and the further embodiment therefore operates in a mode equivalent to the first embodiment of the object detection device 10.

In order to facilitate switching between modes, the object detection 25 device 20 may be provided with a toggle switch 25, operably connected to the processor 24, to selectively activate the port and starboard ranging devices 21 and 23.

In alternative embodiments, the object-detection device may be provided with upper and lower range detectors which would provide for further compartmentalisation/rasterization of the volume into elevation sectors.

In alternative embodiments, a single ranging device may be provided which is capable of separately scanning in an azimuth or elevation direction to compartmentalise the volume. For example, the ranging device may be a phased array stepping through boresights in sequence, or a single ranging device mounted on a tip and/or tilt gimbal.

In alternative embodiments, the azimuth sector in which the object is detected could be indicated using a surround sound effect such that: objects associated with the central ranging device 22 could have a common vibration signal sent to each of the transducers 26, 27; objects associated with the port-side ranging device 21 would have a vibration signal sent only or predominantly to the left ear transducer 26; and objects associated with the starboard-side ranging device 23 would have a vibration signal sent only or predominantly to the right ear transducer 27.

In alternative embodiments, the object-detection device could be 15 provided as part of another head-wearable item such as a hat, headband, or mask.

In alternative embodiments, the ranging device may make use of LIDAR instead or in combination with the ultrasound acoustic device described above.

In alternative embodiments of the multi-sector / multi-ranging device configuration, returns from ranging devices could be differentiated by firing each ranging device at a separate time, that is to say sufficiently out of phase such that returns from one ranging device are unlikely to lead to significant intensity returns at a further ranging device whilst that further ranging device is operating to receive returns from its particular pulse.

Typically, the transducer has the form of an earpiece for exciting the air within the operator's ear canal; however in an alternative arrangement, the transducer would be one configured for sending vibrations through the operator's skeletal system to the ear bones, or configured as a haptic device.

In some embodiments, the ranging device may be operable in an 'object delineate' mode configured for determining the precise location of an object (e.g. a wallet or smartphone) adjacent to (e.g. lying on) another object (e.g. a table). In an 'object delineate' mode, a narrow ultrasonic pulse/beam is emitted, the volume is not compartmentalised into range gates (other than as limited by the ranging device 2), and an 'object delineate' audible signal is continually issued to the operator.

The 'object delineate' audible signals are not selected from a register of particular musical notes or predefined scales: it is a continuous mapping of the frequency range to the displacement ranges. The 'object delineate' mode can provide a monotonic and increasing interrelationship between range and frequency.

Whilst using the device 10 in the 'object delineate' mode. the user may for instance be directing the narrow pulses towards a table whilst aiming to locate a wallet lying somewhere on the table.

In order to perceive the range, a continuous audible waveform signal is issued to the operator. Thus as the operator sweeps their head back and forth, variations in the range of the object (e.g. variations in the displacement from the table top) will be converted into varying audible signals. Such audible variations will be smoothly changing as the head is swept over a smooth surface such as an uncluttered table; however if an object such as a wallet lying on the table represents a step-change in range, there will be a clear step step-change in the frequency of the audible signal. Thus the operator will be able to perceive a precise location where a step change in range occurs, and hence infer from this that there is a separate object there. The frequency change of the step-change will also suggest the height off of the table surface which that object stands.

In an alternative device, there is additionally provided a directional sensor for determining the temperature of certain areas of the environment.

This directional temperature sensor is operably connected to the processor, and the processor is operable connected to a warning device. The processor can be configured to, if certain temperature criteria are met, activate the warning device to issue a distinct signal to the operator.

In particular the directional sensor could be a non-contact temperature sensor, operating at Infra-Red wavelengths (e.g. a laser temperature sensor).

The directional sensor could be mounted to the device 10 at particular position and orientation, so that it senses along a known line of sight and the operator can learn and remember which region of the environment is being analysed. The directional sensor could alternatively be detachable from the device (whilst remaining operably connected to the processor e.g. by RF signalling standards such as standardised under IEEE 802.15.1) and manually pointed to enable the operator to understand their environment in finer detail and/or without swivelling their head.

In particular, the warning device could be the in-ear speaker 6 configured to issue voice signals such as "Warning! Temperature Hazard!".

In particular, the temperature criteria could be the detection of a temperature exceeding a maximum limit. In such cases, the warning device, embodied as an in-ear speaker could issue voice signals such as "Warning! Hot!" or "Warning! [read out measured temperature]!'.

Such an alternative device could facilitate the safe navigation of environments where harmful temperatures may be encountered, or where unpleasant temperatures may be encountered. For example: when in a kitchen, when operating a kettle, or when waiting for a hot beverage to cool to a suitable temperature.

Other temperature sensing devices may be provided as a stand alone device, that is to say as a device 10 without the ranging device 2 and its associated object ranging capability.

Claims

-18-CLAIMS 1. A wearable or manually portable object-detection device for visually impaired operators comprising: A ranging device operable to transmit an outward signal for propagating onto an object, and operable to receive a return signal representative of the object and the range; A processor for converting the return signal into a vibration signal, the frequency of which is selected according to the range at which the object has 10 been detected; and A transducer for generating human-interpretable vibrations from the vibration signal, wherein the processor is operable such that the frequency of the selected vibration signal varies monotonically and increasingly as the range gets shorter.
2. A device according to claim 1 operable to: define a set of range gates; and wherein the processor converts the return signal into the vibration signal such that for each range gate there is assigned a human-interpretable vibration having a unique frequency.
3. A device according to claim 2 wherein the unique frequency of the human-interpretable vibration is an audible frequency corresponding to a note on a predetermined musical scale.
4. A device according to claim 3 wherein consecutive range gates have assigned to them consecutive notes on the musical scale.
5. A device according to any one of claims 2 to 4 operable to define: a first set of contiguous range gates having a first precision level; and a second set of contiguous range gates having a second precision level, the first precision level having more range gates per metre than the second precision level.
6. A device according to claim 5 wherein the first set of contiguous range gates are at a closer range than the second set.
7. A device according to claim 5 or 6 operable to define a third set of contiguous range gates having a third precision level, the third precision level having fewer range gates per metre than the second prevision level, the third set being at a greater range than the second set.
8. A device according to any of claims 2 to 7 wherein each range gate is divided into a plurality of angular sectors, each sector having a defining characteristic.
9. A device according to claim 8 wherein the defining characteristic is such that return signals from a first angular sector in a given range gate are converted into human-interpretable vibrations in a first octave, and returns from a second angular sector in the given range gate are converted into human-interpretable vibrations in a second octave.
10. A device according to claim 8 or 9 wherein the transducer comprises a first and second transducer, one for each of the operator's ears and wherein -20 -the defining characteristic of each angular sector is such that return signals from sectors on the left of the operator are converted into human-interpretable vibrations at the respective ear, and return signals from sectors on the right of the operators are converted into human-interpretable vibrations at the other ear.
11. A device according to any of claims 8 to 10 comprising a plurality of ranging devices, with boresights inclined to one another, to thereby divide each range gate into a number of sectors.
12. A device according to any of the preceding claims wherein the ranging device comprises a pulsed ranging device.
13. A device according to any of the previous claims wherein the ranging device is for transmitting and receiving inaudible sound waves and the range 15 gates extend no further than 4m.
14. A device according to any of the preceding claims wherein the wearable object detection device is provided within a housing that can be mounted on the operator's head such that the device remains fixed in position relative to the operator's head as the operator moves their head.
15. A method of representing to a visually impaired operator, the range of an object, the method comprising: Providing a range detecting device and processor for dividing an environment into a plurality of consecutive range gates; Providing a look up table associating each range gate with a human-interpretable vibration at a unique frequency; Determining by the range detecting device and processor that a range gate is occupied by an object; -21 -Selecting from the look-up table the human-interpretable vibration associated with that range gate; and Using a transducer to expose the operator to that human-interpretable vibration, wherein the range gates vary such that a closer range gate is shorter than a farther range gate.