GB2112244A - Improvements in or relating to monitoring apparatus - Google Patents

Abstract

Monitoring apparatus for detecting the direction from which light is incident comprises a plurality of light guides (1, 2, 3, 4) arranged to receive light from different respective directions and feed it to detector means (5), the light guides being of different lengths so as to impose different respective time delays on transmission of light to the detector means indicative of the respective direction from which the light was incident. The apparatus can be used for example in a military vehicle to detect a single light pulse from a laser range finder. Other embodiments involving more than one detector are also described. <IMAGE>

Description

SPECIFICATION Improvements in or relating to monitoring apparatus This invention concerns improvements in or relating to monitoring apparatus and relates more particularly to monitoring apparatus for detecting the direction from which light is incident on the apparatus.

In some circumstances, and particularly in military situations, there is a requirement for detecting when and from where light is directed towards you. For example, a laser range finder may be directed at a military vehicle, such as an aircraft or a tank, as a preparatory step to attacking that vehicle. Detection of the direction from which the laser light is incident on the vehicle can enable evasive or aggressive action appropriate to the direction of the attacker to be taken. Initiation of such counter measures can be triggered directly from the detection system or via the vehicle commander.

In some cases the incident laser light may consist of a single pulse, for example with a duration of about 20 nanoseconds, which renders detection of its direction more difficult. Thus a mechanically scanning detection system would generally be unable to detect a pulse of such short duration except by chance. There have been proposals for systems employing a multiplicity of detectors each of which effectively monitors a solid angle, for example as described in British Patent Specification No. 1,355,975, but such systems tend to be complex and expensive and can occupy considerable space especially when a large field is to be monitored with a high degree of directional precision.

Broadly according to the present invention there is provided monitoring apparatus comprising light guide means, and detection means for receiving light transmitted by the light guide means, in which the light guide means are arranged to provide light paths of different lengths which impose different time delays on transmission of light to the detector means, and the different time delays indicate different respective directions from which light is incident on the apparatus.

The term 'light' when used herein is not to be construed as necessarily limited to visible electromagnetic radiation but may be invisible such as infra-red or ultra-violet radiation.

More particularly according to the present invention there is provided monitoring apparatus for detecting the direction from which light is incident on the apparatus, comprising a plurality of light guides of different lengths such that light takes different times to travel along the respective guides, the guides being respectively arranged to receive light incident on the apparatus from different directions, detector means for detecting light incident on the apparatus from any of the directions and for responsively producing a reference signal and for detecting such light after transmission along one of the guides and for responsibly producing a delayed signal, the time interval between the reference signal and the delayed signal being dependent on which of the guides the light is transmitted along and hence indicative of the direction from which the light is incident on the apparatus, and timing means effective to discriminate between the different time intervals corresponding to transmission of the light along the respective different length guides.

By such discrimination the apparatus can effectively identify the light guide along which the light was transmitted and hence the direction from which the light was incident. This can be achieved even when the incident light consists of a single pulse. When the incident light is of more prolonged duration, or a series of pulses, then the apparatus can effectively operate on the commencement of incidence, or on the first pulse of the series, i.e. can respond to the commencement of, or first, reference and delayed signals between which there will be the requisite time interval. The apparatus may comprise display means effective to display in a convenient manner the identified direction from which the light was incident.

It is to be understood that references to light incident from a direction are not to be construed as limited to a precise single direction and that in practice each guide can effectively monitor an angular field covering a general direction. It will further be understood that the apparatus can have a sensitivity adapted to the ambient light conditions such that it reacts only to directional incident light of greater intensity than ambient.

Further, as explained more fully later, the reference signal need not necessarily precede the delayed signal. Thus, the time interval between the reference signal and the delayed signal may be the time interval from the delayed signal to a further delayed reference signal. This may be achieved by having associated with each light guide of different length another light guide of greater length which receives light incident from the same direction and transmits the light to provide the further delayed reference signal, the difference in length between the associated guides providing a time interval indicative of the direction of incidence.

The light guides may be arranged each with one end facing towards the respective direction of incidence monitored by that guide and with the other end in communicating relationship with the detector means, which may comprise a single detector common to all the guides for producing the delayed signal. Thus the guides may be arranged in a basically fan-like formation with their spread ends facing in the different respective directions and their other ends closely together in communicating relationship with the detector means. There may be light directing means, such as a lens, for directing, e.g. collecting or focussing, light from said other ends of the guides on to the detector means.There may be light directing means, such as a lens, for directing light on to said one end of each guide, e.g. to collect or focus light incident over an angular field covering the general direction monitored by that guide. The light directing means may comprise diffractive optics, such as a diffraction grating or hologram, e.g. to direct a specific laser wavelength to one end of a guide over a determined angle range. As a further example, the light directing means may comprise integrated optics waveguides which may be used, e.g. to combine the light output from a number of guides on to a single detector.

Said one end of each guide need not necessarily face towards the respective direction of incidence monitored by that guide but light incident from that direction could be directed to said one end of the guide by light directing means, such as one or more mirrors or prisms, arranged to receive light incident from that direction.

The detector means may comprise a single detector or a plurality of detectors. Thus there may be separate detectors for producing the reference signal and the delayed signal respectively, or a single detector may produce both the reference signal and the delayed signal.

The apparatus may comprise wide angle light directing means, such as one or more 'fish-eye' lenses, effective to receive light incident from any of the directions monitored by the guides and to direct such light on to the detector means to produce the reference signal.

The guide lengths may differ by regular amounts so as to provide regular time differences for transmission of light along the guides. The different time intervals between the reference signal and the delayed signal can then be multiples of a regular time period corresponding to the shortest such time interval, and the timing means may comprise a counter effective to count the number of such regular time periods in the time interval between the reference signal and the delayed signal.

There may be some overlap between angular fields effectively monitored by adjacent guides. In this case when light is incident from a direction within the area of overlap there may be more than one delayed signal, e.g. within the field of overlap between two guides there may be two delayed signals resulting from transmission of the light along the two guides with a time difference between the delayed signals because of the different lengths of the guides. The timing means may be arranged to respond to the two (or more) delayed signals effectively to identify the two (or more) guides along which the light was transmitted and hence to indicate that the light was incident from a direction within the area of overlap of those two (or more) guides.

The light guides may be optical fibres and may be coiled to reduce space occupation.

The apparatus may comprise a plurality of groups of light guides, each group comprising a plurality of guides of different lengths and associated detector means, and means to discriminate between delayed signals produced by the respective detector means of the different groups. Thus the different groups may monitor different fields so that such discrimination effectively identifies the field from which light is incident, and the timing means effectively identifies the direction within that field. There may be a separate timing means associated with each group or a common timing means may operate for a number or all of the groups. A reference signal may be produced by the detector means associated with each respective group or may be produced by a detector common to a number or all of the groups.Provision of groups of guides can have the advantage of requiring a smaller total guide length for a given number of separate guides since the guides within a group may have similar lengths to the guides within another group.

Apparatus in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings in which Figure 1 is a schematic representation of a first embodiment, Figure 2 is a schematic representation of a second embodiment, Figure 3 is a schematic representation of a third embodiment, and Figure 4 is a diagrammatic representation of a binary system, Figure 5 is a schematic representation of a fourth embodiment, and Figure 6 is a perspective view with part cut away of a mechanical arrangement.

Figure 1 schematically shows for purposes of illustration and explanation a highly simplified arrangement comprising four optical fibres 1, 2, 3 and 4 of the same light transmitting material but of different lengths, and an associated photodetector 5. The fibre 1 is of one unit's length and has one end facing North and the other end facing the detector 5. The fibre 2 is of two unit's length and has one end facing East and the other end facing the detector 5. The fibre 3 is of three unit's length and has one end facing south and the other end facing the detector 5. The fibre 4 is of four unit's length and has one end facing West and the other end facing the detector 5. The fibres 1, 2, 3 and 4 thus constitute light guides providing light paths of different lengths which impose different time delays on transmission of light to the detector 5.

If light transmitted along the fibre 1 is considered to take unit time to travel from one end to the other, then light will take twice that time to travel from one end to the other of fibre 2, three times that time for fibre 3 and four times that time for fibre 4. Thus, the time of receipt of light by the detector 5 will depend on which fibre has transmitted the light to the detector, and hence the direction from which the light is incident. The different time delays thus indicate different respective directions from which light is incident on the apparatus.

The detector 5 is capable of receiving not only light transmitted along the fibres 1, 2, 3 and 4 but also light transmitted through air and incident from any of the directions. The speed of light through air is greater than that through the fibre material. Hence, if a light pulse is incident on the apparatus from any of the directions North, East, South or West the detector 5 will first receive it transmitted through air, and produce a reference (or effectively zero-time) signal, and will then receive it after transmission through the fibre which is facing in the direction from which it is incident, and produce a delayed signal. The time interval between the reference signal and the delayed signal is dependent upon the particular fibre which transmitted the pulse and hence indicative of the direction from which it came.

The electrical reference and delayed signals emitted by the photo-detector 5 are passed to an electronic timing device 6 effective to discriminate between the different time intervals.

The timing device 6 is connected to a display device 7 which gives a visual display of the directional information in convenient manner, e.g.

in the arrangement of Figure 1 provides a display of 'N', 'E', 'S' or 'W'.

In the highly simplified arrangement shown in Figure 1 it is assumed that each fibre monitors a 900 field, i.e. the fibre 1 monitors North which is considered to extend from North West to North East, fibre 2 monitors East which is considered to extend from North East to South East etc. If desired the apparatus may be arranged so that, instead of contiguous fields, there is an overlap of the fields monitored by adjacent fibres. With such arrangement a light pulse incident from the area of overlap may be received by more than one fibre. Thus, for example, referring again to Figure 1, a light pulse incident from the North East could be received both by the fibre 1 and by the fibre 2.

The detector 5 would then emit two delayed signals, one responsive to transmission of the pulse along the fibre 1 and the other responsive to transmission of the pulse along the fibre 2. Since the fibre 2 is twice the length of the fibre 1 the second delayed signal would occur a corresponding time after the first, and the timing device 6 may be arranged to respond to both delayed signals thereby identifying the direction from which the pulse was incident as being within the area of overlap of the identified fibres.

It is preferable that the difference in length of the fibres should be regular so that the respective time intervals between the reference signal and the delayed signal follow a regular pattern. In particular, if such time intervals are multiples of a time period corresponding to the shortest such time interval, then the timing device 6 can conveniently comprise a counting device which counts the number of regular time periods between the reference signal and the delayed signal. Thus, with the arrangement of Figure 1 a count of one regular time period indicates a light pulse incident from the North and transmitted along fibre 1 while a count of four regular time periods indicates incidence from the West and transmission along fibre 4.

It will be seen that, at least in principle, one of the directional fibres could be omitted so that, when a light pulse is incident from that direction, the detector 5 emits only a reference signal and no delayed signal, the absence of any delayed signal itself indicating the direction. For example, if the fibre 4 were omitted from the Figure 1 arrangement having a counting device as mentioned above, a count of one from the reference signal to the delayed signal would indicate incidence from the North, two from the East, three from the South, and, if there has been no delayed signal up to and including a count of three, incidence from the West.

As will be apparent and as mentioned above, the arrangement shown in Figure 1 is a highly simplified one for purposes of illustration and explanation. In practice the apparatus would normally have a much greater number of fibres than four. For example, each fibre may monitor a field angle of say about 100 so that a 1800 two dimensional overall field would require eighteen fibres. The fibres may be arranged in a basically fan-like formation, as schematically illustrated in Figure 2, with their spread ends facing in the different respective directions and their other ends collected together and facing towards the detector 5. A lens 8 may be associated with the outward end of each fibre to collect or focus incident light within the field to be monitored by that fibre on to its end.One lens may in practice serve a plurality of fibres, the lens being such as to direct light incident from different directions on to different fibres. The ends of the fibres need not necessarily face directly towards the directions of incidence to be monitored but one could, if desired, direct light on to a fibre end by means of, for example, one or more mirrors and/or prisms.

The inward ends of the fibres may have an associated lens 9 which collects or focusses light on to the detector 5.

If desired there may be a reference detector 10, separate from the detector 5, arranged to receive light from any direction, i.e. all directions, monitored by the fibres and to emit the reference signal to the timing device 6. There may be associated with the reference detector 10 one or more very wide angle 'fish eye' lenses 11, or other suitable light directing means, effective to collect or focus light from the overall monitored field on to the reference detector.

It will be understood that a large number of fibres having a reasonable length difference can involve a large total length of fibre. If, for example, a time interval of one nanosecond is taken as suitable for discrimination by the timing device 6, then about one foot represents a reasonable length difference for the fibres. In order to reduce space and distance occupation, the fibres may be coiled, coiled fibres being schematically indicated in Figure 3.

The total length of fibre required for a given number of fibres may be reduced by employing groups of fibres, each group comprising a plurality of fibres of different lengths, and a detector associated with each group. This is schematically illustrated in Figure 3 which shows a first group of fibres 12 with associated detector 5A and a second group of fibres 13 with associated detector 5B. The group of fibres 12 collectively monitor an overall field A while the group of fibres 13 collectively monitor an overall field B. The detectors 5A and 5B are connected to the timing device 6 via a discriminator 14 effective to discriminate between signals from the detector 5A and signals from the detector 5B.The detectors 5A and 5B may each be arranged to emit a reference signal on receipt of a pulse of light incident (by transmission through air) from the field A or B respectively, or there may be a separate reference detector 10 (or detectors) arranged to emit a reference signal on receipt of a light pulse from either of the fields A and B. In operation when a pulse of light is incident on the apparatus, after emission of a reference signal as described above, a delayed signal is emitted by the detector 5A or the detector 5B depending on whether the light pulse is incident from field A or field B.The discriminator 14 effectively identifies which field and the timing device 6 effectively identifies which fibre of those monitoring that field transmitted the pulse to the respective detector, and hence the direction from which the pulse was incident within the respective field. If desired, separate timing devices could be provided in association with the respective detectors 5A and 5B.

The grouping arrangement reduces the total fibre length required for a given number of fibres since the fibres of group 12 need not be of different lengths from the fibres of group 13.

Thus, for example, if there are eight groups each of sixteen fibres, then (assuming a one foot length difference between fibres) a total fibre length of 1,088 ft. is required. This compares favourably with the 8,256 ft. total length which would be required with 128 fibres all of different lengths feeding a single detector. When the fibres are grouped and a plurality of detectors employed, such detectors may take the form of one or more linear detector arrays whose linear characteristics can assist the electronic or micro processing.

The directional discrimination with a given number of fibres can be increased by having overlap between the solid angles effectively viewed by the fibres, as previously mentioned, with extra logic in the associated electronic circuitry or in the software for a microprocessor.

Maximum use of the overlap possibility (and employing the previously mentioned no delayed signal option for one direction) provides a binary system so that 'n' fibres to a single detector allows discrimination of 2" directions. Thus a four fibre system can, with the extra complexity of light directing means, such as mirrors or prisms, to direct light to the fibres in a manner such as to provide all possible overlap permutations and logic to discriminate between the permutations, discriminate sixteen directions. The principle is illustrated in the diagram of Figure 4 which shows a full circle divided into sixteen directional segments, the reference numerals in each segment indicating which of the individual fibres 1, 2, 3 and 4 receive light incident from that direction.At the centre of the diagram are concentric circles with shaded portions indicative of the respective arcuate 'fields of view of the fibres. The fibre 1 has a continuous 1 800 angular field of view represented in the innermost circle, and the fibre 2 has a continuous 1800 angular field of the view represented in the next circle and displaced by 900 from and hence providing 900 of overlap with, that of the fibre 1. The fibre 3 has a total angular field of view of 1 800 but split into two opposed equi-spaced 900 portions each disposed with an overlap of 450 with the field of the fibre 2. The fibre 4 has a total angular field of view of 1800 (represented in the outermost circle) split into four equi-spaced 450 portions disposed so that two of them overlap centrally with respective portions of the field of view of the fibre 3.

As a further example, a binary system with seven fibres can discriminate 128 directions employing (assuming a one foot length difference between fibres) a total length of 28 feet of fibre.

This is only 0.34% of the 8,256 ft. total fibre length which would be required if there were 128 fibres all of different lengths each monitoring a respective one of the 1 28 directions.

It will be understood that the display device 7, which may for example be a cathode ray tube or a liquid crystal display, is arranged to provide a visual display of directional information having a precision corresponding to the capability of the apparatus. Thus, whereas it is suggested above that with the highly simplified system of Figure 1 the display could simply indicate 'N', 'E', 'S' or 'W' these representing the four distinguishable directions, with a system capable of distinguishing a greater number of more specific directions the display is adapted accordingly, e.g.

could indicate a more precise compass bearing. It will further be understood that instead of or in addition to a display, the output of the timing device 6 could be fed to a control system which, for example, automatically orients a device, e.g.

trains a gun to the direction from which the light pulse is detected as incident.

Figure 5 schematically illustrates a further embodiment in highly simplified form in similar fashion to Figure 1. However, in the Figure 5 arrangement there are two fibres facing in each of the four shown directions. The additional fibres 1 5, 1 6, 1 7 and 18 relative to Figure 1 are all of the same five unit length. A light pulse incident from the North will be transmitted both along the fibre 1 and along the associated fibre 1 5. The detector 5 will thus emit a first delayed signal responsive to transmission through the fibre 1 and then a second delayed signal responsive to transmission along the fibre 1 5. The time interval between these two signals will be four time units (corresponding to the four unit length difference between the fibres 1 and 15).Similarly, a light pulse incident from the East will produce two signals separated by a time interval of three time units (corresponding to the three unit length difference between the fibres 2 and 16). Likewise a light pulse incident from the south will produce signals separated by a two time unit interval, and a light pulse incident from the West will produce two signals separated by a one time unit interval.

The timing device 6 can effectively identify the direction from which the pulse was incident by the length of the time interval between the two signals. With this arrangement it is unnecessary for the detector 5 to receive the light pulse transmitted through air in order to produce a reference signal, since transmission of the pulse along the fibre 15, 16, 17 or 18 provides the reference signal. The difference from the operation of the Figure 1 arrangement is that with the Figure 5 arrangement the delayed signal (from transmission along the fibre 1, 2, 3 or 4) precedes the reference signal. The timing device 6 nevertheless effectively detects the time interval between the reference signal and the delayed signal, i.e. the time interval from the delayed signal to the (further delayed) reference signal.

Figures 1 to 5 schematically illustrate arrangements in two dimensions which can effectively monitor an area. It will be understood that in practice the apparatus may be arranged in three dimensions to monitor a volume. For example, the basically fan-like two dimensional formation of the fibres schematically shown in Figures 2 and 3 could in three dimensions take a form similar to a hedge-hog's back. Likewise, the two dimensional four directions highly simplified arrangements of Figures 1 and 5 could be supplemented in three dimensions by two further fibres (or in Figure 5 pairs of fibres) aligned with the detector 5 and arranged orthogonally to the plane of the drawing with one facing rearwardly and the other facing forwardly from that plane, to provide a six directions arrangement.It will be appreciated that a two dimensional system may be arranged to monitor all or any desired part of a full 3600 field, i.e. a full circle, and a three dimensional system may be arranged to monitor all or any desired part of a full sphere.

The mechanical arrangement of apparatus in accordance with the invention may be as shown in Figure 6. This illustrates a generally cylindrical housing 1 9 having a series of peripheral windows 20. Each window 20 contains a lens which collects or images light incident on the apparatus from the general direction towards which that window faces, onto an array 21 of fibre ends.

The array and lens are such that light is focussed on to a particular fibre of the array dependent on the particular direction of incidence within the general field monitored by that window. The fibres 22 are coiled on spools 23 suitably disposed within the housing 1 9. The detectors may also be mounted within the housing 1 9 and connections may pass down a tubular shaft 24 to a required location. For example, the housing 19 may be mounted on the top of a vehicle, such as a tank, with the shaft 24 leading to the inside of the vehicle.

It will be understood that the sensitivity of the apparatus, and in particular of the detector(s), is such as to suit the ambient light conditions under which the apparatus is to operate so that it reacts only to incident light having an intensity greater than ambient which it is required to detect, for example laser light e.g. from a laser range-finder.

Preferably the apparatus, and notably the detector(s), can be adjusted for sensitivity to suit different ambient light conditions, e.g. day and night conditions, for example by the provision of suitable filters. It will be further understood that the apparatus, although particularly suitable for detecting laser light, may be arranged to respond to other light sources, e.g. a lightning flash, and indicate their direction, the processing electronics, and/or the inclusion of a narrow band filter or filters in the optical system, being adapted accordingly. Also the system may be arranged to detect not only visible radiation but also or alternatively invisible electromagnetic radiation such as infra-red or ultra-violet radiation.

In the foregoing description with reference to the drawings the incident light has been considered as a single pulse. It will be appreciated that incident light of more prolonged duration, or consisting of a series of pulses, can also be detected, the timing device 6 being arranged to react to the commencement of incidence, or the first pulse, by responding to the commencement of, or the first, reference and delayed signals.

It will further be understood that the particular arrangements shown and described are by way of illustration and example and that other variations are possible. Notably, whereas in the specific embodiments described above, the light directing means comprise refractive lenses, other forms of light directing means may be employed. Thus reflective means such as mirrors could be used, as could diffractive optics which act in a diffractive rather than a reflective or refractive way. For example a diffraction grating or hologram may be arranged to direct a specific laser wavelength to one fibre over a determined angle range. As a further example, integrated optics waveguides could be used e.g. to combine the light output from a number of fibres on to a single detector.

Claims (17)

Claims

1. Monitoring apparatus comprising light guide means, and detection means for receiving light transmitted by the light guide means, in which the light guide means are arranged to provide light paths of different lengths which impose different time delays on transmission of light to the detector means, and the different time delays indicate different respective directions from which light is incident on the apparatus.

2. Monitoring apparatus for detecting the direction from which light is incident on the apparatus, comprising a plurality of light guides of different lengths such that light takes different times to travel along the respective guides, the guides being respectively arranged to receive light incident on the apparatus from different directions, detector means for detecting light incident on the apparatus from any of the directions and for responsively producing a reference signal and for detecting such light after transmission along one of the guides and for responsively producing a delayed signal, the time interval between the reference signal and the delayed signal being dependent on which of the guides the light is transmitted along and hence indicative of the direction from which the light is incident on the apparatus, and timing means effective to discriminate between the different time intervals corresponding to transmission of the light along the respective different length guides.

3. Monitoring apparatus according to Claim 2 comprising display means to display the identified direction from which light was incident.

4. Monitoring apparatus according to Claim 2 or Claim 3 in which the light guides are arranged with one end facing towards the respective direction of incidence and with the other end in communicating relationship with the detector means.

5. Monitoring apparatus according to any of Claims 2 to 4 comprising a single detector common to all the guides for producing the delayed signal.

6. Monitoring apparatus according to Claim 4 or Claim 5 in which the light guides are arranged in a basically fan-like formation with their spread ends facing in the different respective directions and their other ends closely together in communicating relationship with the detector means.

7. Monitoring apparatus according to any of Claims 2 to 6 comprising light directing means for directing light from the guides onto the detector means.

8. Monitoring apparatus according to any of Claims 2 to 7 comprising light directing means for directing incident light onto an end of a guide.

9. Monitoring apparatus according to Claim 8 in which the light directing means collects or focusses light incident over an angular field covering the general direction monitored by that guide.

10. Monitoring apparatus according to any of Claims 2 to 9 in which the detector means comprises separate detectors for producing the reference signal and the delayed signal respectively.

11. Monitoring apparatus according to any of Claims 2 to 10 comprising wide angle light directing means effective to receive light incident from any of the directions monitored by the guides and to direct such light onto the detector means to produce the reference signal.

12. Monitoring apparatus according to any of Claims 2 to 11 in which the guide lengths differ by regular amounts so as to provide regular time differences for transmission of light along the guides.

13. Monitoring apparatus according to Claim 12 in which the timing means comprises a counter effective to count the number of regular time periods in the time interval between the reference signal and the delayed signal.

14. Monitoring apparatus according to any of Claims 2 to 13 arranged so that there is overlap between angular fields effectively monitored by adjacent guides, and in which the timing means is arranged to respond to a plurality of delayed signals effectively to identify the plurality of guides along which the light was transmitted and hence to indicate that the light was incident from a direction within the area of overlap of that plurality of guides.

15. Monitoring apparatus according to any of Claims 2 to 14 in which the light guides are optical fibres.

16. Monitoring apparatus according to any of Claims 2 to 15 comprising a plurality of groups of light guides, each group comprising a plurality of guides of different lengths and associated detector means, and means to discriminate between delayed signals produced by the respective detector means of the different groups.

17. Monitoring apparatus according to Claim 16 comprising common timing means for a plurality of the groups.

1 8. Monitoring apparatus according to Claim 1 6 or Claim 1 7 comprising a detector common to a plurality of the groups to produce a reference signal.

1 9. Monitoring apparatus substantially as described herein with reference to any of the figures of the accompanying drawings.