GB2464345A - Monitoring physiological movement using mirrors - Google Patents

Abstract

Physiological movement of a subject, for example breathing, heart rate or general body movement, is monitored using a number of small rigid lightweight mirrors 4 placed on the subject's bedding 3 or clothing. The mirrors 4 may be placed individually 4 or as regular arrays on a flexible membrane (figs. 2 and 3). Movement of the subject (e.g. a child 1) results in movement of the mirrors and this causes changes in their reflected images, and these image changes can be viewed (directly or via video) to monitor movement. Changes in reflected light patterns (e.g. on a wall) may be monitored instead of reflected images (fig. 4). Ambient light may be used or light sources (16, fig, 4; 25, fig. 6) may be provided. Alternatively a mirror 21 is mounted on a first end of a lightweight beam 18 which is pivoted 19 on a support stand 20. The second end of the beam rests lightly in contact with the subject, and any motion of the subject causes corresponding beam inclination which can be detected using the mirror.

Description

Improvements in Physiological Movement Monitoring This invention relates to the monitoring or detection of movement of a human or animal subject in a sleeping, resting or reclining condition said movement including breathing, heart beat, limb and general body movement.

Existing physiological movement monitoring systems are either non-contacting or contacting. The former include an optically based method using infra red or visible radiation from an extended diffuse radiant source and one or more radiation detectors located on the opposite side of the subject to be monitored. Movement of a subject will generally influence the fraction of radiated power reaching a detector the output of which when electronically processed can produce data relating to the location, the frequency and the amplitude of movement. See Fothergill patent GB 2325519 13.

Other radiation based non contacting methods exploit ultrasonic time of flight or pulse echo processes involving directing an ultrasonic pulse onto a subject and deducing any movement from the delay between transmission and reception of the pulse. See patent FR 2571955. A disadvantage of ultrasonic radiation is that it is potentially vulnerable to the adverse effect of stray reflections from local objects as well as temperature variations arising from draughts for example.

As an alternative to ultrasonic radiation low power microwave radiation has been exploited for physiological movement monitoring and involves transmitting a continuous wave microwave beam towards a subject to be monitored and deducing any movement from say breathing for example, by measuring phase shift between transmitted and received signals. See Patent US 495 863A.

In general the above radiation based systems and others are relatively costly due to their technical sophistication and complexity and are generally unsuitable for most domestic applications such as reassurance monjtoring of sleeping babies or young children.

As an alternative to totally non-contacting breathing and other physiological movement monitoring systems there exist a number of contacting systems. These include those employing sensors located directly onto a subject's body or clothing typically in the thoracic or abdominal regions and generally secured in position using a lightweight strap. One common system employs hail effect sensors but requires signal leads to be routed to a remote processing unit under or around the monitored subject frequently producing false alarms from local disturbance as well as possible discomfort of the subject.

Another frequently used method exploits sensors incorporated in pads located under a cot mattress and detects subject movement induced stresses transmitted through the mattress. However such methods can be insensitive and or vulnerable to false alarms as a result of high attenuation of movement induced stresses through a mattress thereby confining applications to specialised types of mattresses.

According to one aspect of this invention there is provided a method for monitoring physiological movement of a human or animal subject by locating one or more small, lightweight mirrors directly onto a subject to be monitored or on their clothing or other covering or secured to a lightweight flexible membrane for placement on the subject or secured to a lightweight beam supported or pivoted at or towards one end with a section of the beam's length displaced from the support or pivot placeable lightly on that region of the subject to be monitored with any subject movement inducing corresponding changes in the inclination of said beam hence an attached mirror or in the planes of one or more minors placed more directly on said subject with said mirror inclinations producing lateral shifts in the images within said mirrors of local objects or optical features or lateral shifts in secondary images on a local diffuse reflector produced from mirror reflections of at least partially specular light with any said physiological movement induced lateral shifts in images being directly detectable by viewing or by means of video monitoring or the like and in the case of said beam's movement induced inclinational changes these may also be detectable using a displacement sensor close to or at said support or pivot point with said sensor output being electronically processed to facilitate recording and or display of physiological movement data.

The principle objective of this invention is to provide a physiological movement monitoring method which is essentially passive and simple to apply making it cost effective in its basic form but with the option to automate using displacement sensors with associated signal processing or video facilities. The method can be applied to humans and animals typically when asleep or reclining with detectable movement modes including breathing, heart beat, limb movement or body repositioning with the former two modes generating relatively low amplitude regular movements and the latter relatively high amplitude transient movements.

The method is applicable to all human age groups from paediatrics to the elderly as well as to animals and consists in its most basic form of locating either temporarily or permanently one or more small lightweight mirrors or mirror arrays directly or indirectly on the subject to be monitored. Suitable mirrors would be preferably of plane geometry and manufactured from rigid plastics.

The mirror arrays may be secured to a lightweight flexible rubber or fabric membrane typically with a linear or two dimensional geometry for direct placement on a subject's thoracic or abdominal regions for breathing and or heartbeat monitoring or other appropriate regions for referred breathing or heartbeat movement monitoring or for monitoring other movement modes. A mirror supporting membrane wilt be sufficiently limp to conform to the local geometry of the subject's contact area which may be clothing, night wear or bedding as appropriate or indeed directly on the skin or in the case of an animal, on its coat.

Physiological movement of the monitored region will generally induce angular shifts in one or more or possibly all mirror planes in an array. Direct viewing of the mirrors, or mirror array, will reveal reflections from local objects such as cot rails, cot sides or mobiles for infant subjects or walls ceilings or other optical features for older children or adult subjects.

For applications in dark or subdued light conditions such as would typically exist for sleeping subjects suitable optical features may be produced from regular arrays of low intensity light emitting diodes or a two dimensional array of apertures in a light box with either system located and stably secured over a subject's cot or bed as appropriate either free standing or secured to said cot or bed or the like.

For monitoring young infants in cots or children in beds illuminated cartoon characters again located and supported over a cot or bed may constitute a suitable optical feature or set of features to be viewed in one or more of the mirrors.

Physiological movement from relatively regular heartbeat or breathing or other more transient bodily movements will generally produce angular shifts in the plane of one or more contacting mirrors thereby creating corresponding lateral shifts in mirror images of the above optical features or patterns. In natural normal lighting conditions including artificial lighting the above regular optical pattern or array facilities could be deployed satisfactorily by either increasing the light intensity which may be implemented automatically or indeed switching off any energising current to relevant light sources which in the case of a light box in particular would result in a regular array of black apertures from approximately black body conditions.

According to a second aspect of this invention there is provided apparatus for monitoring physiological movement of a human or animal subject comprising one or more small lightweight minors placeable directly on the region of a subject to be monitored or secured to a lightweight flexible membrane means for placement on a subject's region to be monitored or secured to a lightweight beam supported or pivoted at or towards one end with a section of the beam's length displaced from the support or pivot placeable lightly on that region of the subject to be monitored with movement of said beam or mirrors contact regions inducing corresponding changes in the inclination of said beam hence attached mirror or in the planes of one or more mirrors placed more directly on said subject with said mirror inclinations producing lateral shifts in the images within said mirrors of local objects or optical features or lateral shifts in secondary images on a local diffuse reflector means produced from mirror reflections of at least partially specular light produced from a local source means with any said physiological movement induced lateral shifts in said images being directly detectable by viewing or by means of video monitoring or the like and in the case of said beams movement induced inclinational changes these may also be detectable using a displacement sensor means close to or at said support or pivot point with said sensor output being processed by electronic processing means to facilitate recording and or display of physiological movement data.

For applications using one or more small individual mirrors located directly on a subject to be monitored these mirrors may be unattached to said subject's outer covering but advantageously possess good frictional properties on the mirror and subject's contacting areas to prevent slippage during monitoring. Alternatively temporary attachment of said mirrors may be facilitated using hook and loop fastening.

The same or similar procedures for un-attaching or temporarily attaching individual mirrors may be applied to mirror arrays secured to limp flexible membrane supports.

For permanent attachment of individual mirrors or mirror arrays to a subject's outer covering these could be secured by sewing individual mirrors with peripheral perforations to a subject's outer covering or alternatively gluing using a preferably flexible adhesive. A flexible membrane supporting a mirror array may be permanently secured to a subject's outer covering by sewing or gluing to this covering.

For applications using said lightweight beam supporting a mirror and supported or pivoted externally from a subject to be monitored any large amplitude movements such as may result from said subject's repositioning or limb movement could possibly cause the beam to lose contact temporarily with the subject but with contact being restored when said large amplitude movement ceased. In order to maintain low contact pressures on a subject from a pivoted beam it may prove necessary to provide a degree of counterbalancing. Further to avoid any possible discomfort to a monitored subject a suitable beam may be produced from lightweight flexible foam rubber strip though sufficiently stiff to reliably transmit any subject movement at the region of contact to the pivot or support in order to ensure adequate corresponding inclinational movement of a mirror secured at or close to said support or pivot. Alternatively a beam may be produced from a relatively thin strip of plastics or metal with a soft covering at least over the contact area using for example foam rubber or hollow fibre insulating material contained within a cloth or polythene or the like sleeve.

A further application of the method exists for child safety restrainers such as push chair or pram harnesses as well as children's car safety harnesses. In these cases or similar ones one or more lightweight mirrors would be secured to a harness strap or other resilient restraint and movement of a subject typically while sleeping would be readily detectable from corresponding lateral shifts in reflected images of local objects or optical features illuminated by natural or artificial light.

This invention may be performed in various ways and some specific embodiments with possible modifications will now be described by way of example with reference to the accompanying drawings.

Fig. 1 shows a plan elevation of an infant in an infant's sleeping bag fitted with individual mirrors over the thoracic and abdominal regions.

Fig.2 shows a linear array of four mirrors mounted on a flexible membrane support.

Fig.3 shows a two dimensional array of nine mirrors mounted on a flexible membrane support.

Fig.4 shows a perspective of a subject in a bed with a linear array of mirrors mounted on bedding and illuminated by a locally supported specular light source.

Fig.5 shows a section through a human subject lying on a bed with a pivotally supported lightweight beam resting on the subject's bedding and with an illuminated mirror mounted close to the beam's pivot point.

Fig.6 shows a light box with a 7 X 6 regular two dimensional array of apertures.

Fig.7 shows an infant subject in a cot with a two dimensional mirror array positioned on bedding with a light box mounted on a horizontal cot rail and positioned over the subject.

Referring now to the drawings. Fig. I shows an infant subject I lying horizontally on a cot or bed mattress or the like 2 and wearing an infant's sleeping bag 3 with four individual mirrors 4 secured to or located on the sleeping bag 3. Direct viewing of one or more of the mirrors 4 will generally reveal images of local objects such as cot rails or sides or more remote optical features on a wall or ceiling. The mirrors 4 in Fig. I are positioned over the thoracic and abdominal regions 5 and 6 of the subject 1.

Breathing and heart beat induced movements will produce corresponding angular shifts in the mirror 4 planes hence associated lateral shifts in said images of local objects or optical features or the like thereby providing by direct viewing in the mirrors 4 confirmation or otherwise of subjects breathing or heartbeat. The former will generally have a lower frequency than the latter but both will be relatively regular.

In contrast any movement from body repositioning for example will induce substantially higher amplitude transient lateral shifts in mirror images. To prevent slippage of individual mirrors 4 their contacting undersides may be provided with a high friction surface such as rubber or thin felt. Such an arrangement would be suitable for monitoring immobile subjects including premature or new born babies too young to move independently in their cot or incubator as appropriate. In addition temporary monitoring of older sleeping or reclining subjects can be carried out using the above said unattached mirrors with potential applications in domestic as well as clinical environments with mirrors being located on a subject only when monitoring is required.

Where a subject becomes more mobile which would occur for babies several months old and older infants or adults mirrors may be secured to the outer surface of bedding using for example hook and loop attachments which would enable convenient removal of mirrors to facilitate washing of bedding. As well as locating individual mirrors 4 to bedding they may be secured or located temporarily directly onto a subject's sleeping garments such as an all in one sleep suit commonly known as Babygro' for babies where such garments are visible to an observer as might be the case for a baby in an incubator in a clinical environment.

In order to increase the sensitivity to small amplitude physiological movements e.g. breathing and heartbeat multiple mirror arrangements may be implemented in the form of linear or two dimensional regular arrays of mirrors. In such cases mirrors, preferably though not essentially plane, would be secured to highly flexible, limp lightweight fabric or rubber membranes or the like such that on placing an array on a subject's region to be monitored it would conform to the local geometry of the contacting surface.

Fig.2 shows a linear array 7 of four mirrors 8 secured to a flexible membrane 9 using for example a flexible adhesive. In general the contacting surface will be non planar over the length of the array 7 with the individual planes of each of the four mirrors 8 being inclined to each other.

Fig.3 shows a 3 X 3 two dimensional array 10 of mirrors 11 secured to a square supporting flexible membrane 12 which again when placed upon a subject's region to be monitored will conform to the local geometry with mirror 11 plane inclinations typically being different. Because of a larger contacting surface area associated with said linear and two dimensional array mirror sets 7 and 10 the associated membrane supports 9 and 12 respectively will tend to lie more stably on a monitored surface than for individual mirrors 4 particularly if mirror support membranes 9 and 12 have good frictional properties which would generally be the case for natural or synthetic rubber membranes 9 and 12.

Any physiological movement of a subject will generally induce corresponding angular shifts in the planes of the individual mirrors forming the arrays which will produce associated lateral shifts in the reflected images of local objects these angular hence lateral shifts typically differing from mirror to mirror but recurring at the frequency of the inducing physiological movement.

Application of the method so far has involved detecting physiological movement by direct viewing of mirrors located on a subject though remote observations may be carried out using video systems or the like.

However instead of viewing mirrors directly either visually or through cameras, mirrors or preferably mirror arrays, they may be illuminated by a local at least partially specular light source such as a torch or light emitting diode which would only need to have a low intensity in dark or subdued light conditions. This would be shone onto mirrors with reflections from individual mirrors generating secondary images on a local diffuse reflector such as a ceiling or wall. Different relative inclinations of mirror planes in a set would induce corresponding secondary image displacements as indicated in Fig.4. This Figure shows a linear array of mirrors 13 located on a subject's 14 bedding 15 with a divergent light source 16 directed towards the mirror arrayl3. The individual mirrors in the arrayl3 will generally reflect incident light 17 from the source 16 at different angles generating images of each of the illuminated mirrors on a local reflector and separated to an extent dependent upon the incident and reflected angles of the illuminating light source on the mirrors 13.

Movement induced changes in mirror inclination will generate corresponding lateral shifts in the said secondary images which will be readily visible from a remote observation position.

In order to prevent spurious secondary image shifts arising from any movement of an illuminating specular light source it is necessary to mechanically stabilise the source.

This may be readily achieved using a free standing support system or a support system mounted for example on a bed's head board or in the case of an infant's cot a light source may be secured to cot sides, rails or head board. In the case of divan beds a suitable mechanically stable support facility for a light source could deploy a stand with a tapered or sprung foot which would be pushed under the base of the bed where it would be trapped between the floor and base. Alternatively a suitable support facility could be implemented using a rigid flat plate possibly of plastics construction inserted between the upper surface of a bed base and underside of a mattress with a vertical member either integral with the plate or secured to it and extending beyond the upper surface of the subject's bedding with a light source being secured to the member towards its uppermost end. In all cases a light source itself should be capable of adjustment in both horizontal and vertical planes to ensure exposure of mirror arrays.

In circumstances where a subject may be restless during for example sleep -which is typical of many children -bedding such as a duvet may be kicked off or significantly displaced thereby displacing any mirror or mirror array from the illuminated region on a subject or bedding as appropriate with the resultant disappearance of secondary images on a local diffuse reflector. To avoid any such duvet slippage a commercially available duvet securing facility can be implemented see Fothergill patent GB 2278274 which will ensure positional stability of any mirrors or mirror arrays despite any repositioning of a sleeping subject. Any physiological movement will be detectable by resultant secondary image shifts produced by breathing, heartbeat or other movements being transmitted through bedding to its upper regions upon which mirrors or mirror arrays reside.

Fig.5 shows an alternative to location of mirrors or mirror arrays on a subject's bedding 15 or other outer covering. In the Figure a lightweight preferably though not essentially padded beam or arm 18 pivoted 19 towards one end may be deployed with the unsupported region resting lightly on a subject's 14 bedding 15 or outer covering.

The pivot 19 is secured or integral with a mechanically stable stand 20 and close but not coincident with the pivot 19 is a mirror 21 which may be illuminated by an at least partially specular light source 22 secured towards the upper end of the stand 20.

Any movement of the subject 14 in a vertical direction from for example breathing or heartbeat will deflect the beam in a vertical plane thereby generating an equal angular deflection of the mirror 21 and hence a corresponding angular shift in reflected light 23 from the mirror 21 and hence a lateral shift in any secondary image on an intercepting diffuse reflector -not shown. In order to minimise contact pressures to negligible undetectable levels on the subject 14 a small counter weight -not shown -may be applied to the pivoted beam 18. However the turning moment of the beam 18 about the pivot 19 must remain anti clockwise in the illustration to ensure that any vertical movement including large amplitude repositioning of the subject 14 will maintain contact with the beam 18 throughout any such movement.

The position of the mirror 21 on the opposite side of the pivot 19 to the subject 14 will ensure that a sleeping or horizontally reclining subject is unable to visually intercept light incident upon or reflected from the mirror 21 thereby enabling the use of relatively high intensity light from the source 22 this latter possibly being a low power laser diode or focussed light emitting diode. However the lightweight beam 18 facility in Fig.5 may also be deployed in the absence of the light source 22 in which case subject movement would be detectable by direct viewing of the mirror 21 which would reveal lateral shifts of images in the mirror of local objects or optical features.

Instead of positioning the mirror 21 on the right hand side of the pivot 19 in Fig.5 it could alternatively be positioned on the left hand side with subject movement induced lateral changes in images of local objects or optical features detected by direct viewing of secondary images resulting from reflections of specular light from said mirror onto a diffuse reflector. However this latter mirror positioning may increase the possibility of a subject being visually exposed to incident or reflected light from a source or mirror respectively thus limiting such an arrangement to relatively low intensity light from said source in order to avoid the possibility of visual disturbance.

The mirror or mirror arrays described above with reference to Figs. 1, 2 and 3 all involved direct viewing of mirror images of local objects or optical features. However instead of relying upon the presence of these local objects or optical features to provide mirror images which would require external illumination from sources of natural or artificial light and which may be undesirable for a sleeping subject a suitable set of optical features could be deployed in the form of a regular array of energised light emitting diodes or a regular array of apertures in a light box those arrays being located and supported over a subject's bed or cot as appropriate.

Fig.6 shows a perspective of a light box 24 with a two dimensional regular array of apertures 25. Within such a box there would be fitted one or more light sources which may be incandescent or light emitting diodes or the like. In either case energisation could be from internal batteries or from an externally located power supply. To promote reasonable uniformity of illumination from each of the apertures the internal surfaces of the light box would be highly reflective and essentially diffuse.

In application the subject would have located on their outer covering a mirror array in which images of illuminated apertures would be visible by direct viewing of the mirrors by a local observer which may be a parent or a clinical professional for

example.

Fig 7 shows an infant subject 26 in a cot 27 with a two dimensional mirror array 28 located on a duvet 29 over the thoracic or abdominal region of the subject 26. A light box 30 is located over the mirror array 28 and supported by means of a member 31 secured to a cot bar 32 though other locations on a cot could be deployed.

Alternatively the light box could be supported externally from a cot or bed using a free standing support facility or the like.

The embodiments discussed above are examples only exploiting the underlying principles of the invention with numerous variations and adaptations possible yet still falling within the scope of the invention. For example a principle domestic application would be for reassurance monitoring of infants in a cot or bed in which case a mirror array could be lowered onto a subject's bedding by means of a supporting facility which could be manually operated or automatically operated using for example a remote control. Support of a mirror array could involve a lightweight beam similar to that discussed herein but supporting a mirror array at its un-pivoted end and counterbalanced to possess two stable states -one involving contacting with a subject's monitoring zone e.g. over the thorax or abdomen and the other with the supporting beam angled away from the subject to remove contact with the subject possibly stably secured using a magnetic catch or the like when not in use.

Clinical applications would include general ward monitoring of sleeping or otherwise unconscious patients as well as intensive care patient monitoring with breathing, heartbeat or other movements being detected by direct viewing of mirrors or mirror arrays located on a subject or viewing of secondary images on for example a ceiling or remote viewing of video transmitted data to some patient monitoring including recording facility. Failure of any movement induced lateral shifts in images would constitute an alarm situation which could be immediately investigated to assess the significance of any medical implications.

In applications involving illumination of mirrors or mirror arrays located directly on a sleeping or reclining subject's bedding, sleep wear or clothing as appropriate an optical shield may be located close to the source of illumination to prevent direct viewing of the light source by the subject to avoid any possibility of visual disturbance to the subject such a light shield however not intercepting light from the source directed towards said mirrors or mirror arrays.

Claims (1)

1. CLAIMS1. A method for monitoring physiological movement of a human or animal subject by locating one or more small, lightweight mirrors directly onto a subject to be monitored or on their clothing or other covering or secured to a lightweight flexible membrane for placement on the subject or secured to a lightweight beam supported or pivoted at or towards one end with a section of the beam's length displaced from the support or pivot placeable lightly on that region of the subject to be monitored with any subject movement inducing corresponding changes in the inclination of said beam hence an attached mirror or in the planes of one or more mirrors placed more directly on said subject with said mirror inclinations producing lateral shifts in the images within said mirrors of local objects or optical features or lateral shifts in secondary images on a local diffuse reflector produced from mirror reflections of at least partially specular light with any said physiological movement induced lateral shifts in images being directly detectable by viewing or by means of video monitoring or the like and in the case of said beam's movement induced inclinational changes these may also be detectable using a displacement sensor close to or at said support or pivot point with said sensor output being * : :: : electronically processed to facilitate recording and or display of physiological movement data.

   *** . . . . . *,. 2. A method accordmg to claim 1 whereby it can be applied passively in * * . its most basic form or automated using displacement sensors or the like with *: associated signal processing or video and data recording facilities.

   * : 3. A method according to claims 1 and 2 wherein subjects to be monitored may be of any age group ranging from infants to the elderly in domestic as well as clinical environments.

   4. A method according to claims 1 -3 wherein subjects may be monitored when asleep or reclining with detectable physiological movement modes including breathing, heart beat, limb movement or body repositioning.

   5. A method according to claims 1 -4 wherein mirrors may preferably though not essentially be plane.

   6. A method according to claims 1 -5 wherein one or more mirrors may be secured to a limp flexible membrane which when placed upon a subjects region to be monitored will conform to the local geometry and will possess good frictional properties to ensure positional stability.

   7. A method according to claim 6 wherein mirrors may be arranged in linear or two dimensional symmetrical arrays.

   8. A method according to claims 1 -7 wherein one or more mirrors may be located directly on a subject or on their outer covering at a position to be monitored using a manual or automatic mirror placement facility with possible remote control for the latter. * * SS *S.. * S *se.

   9. A method according to claim 8 wherein one or more mirrors may be **** . . . . attached to a subject's sleepmg garments mcludrng mfants all m one sleep suits and baby grows. ** S

   10. A method according to claim 8 wherein one or more mirrors may be * located upon or attached to a subject's outer covering such as the upper surface of bedding including duvets and clothing.

   11. A method according to claim 10 wherein duvets may be employed and secured in position by fasteners to maintain positional stability of attached mirrors.

   12. A method according to claims 6 -11 wherein permanent attachment of a mirror or mirrors to a subject's covering may be through sewing individual mirrors with peripheral perforations to said covers or securing said mirrors to said covering using a flexible adhesive or sewing or glueing said mirrors to a limp flexible support membrane and securing this by sewing or using a flexible adhesive to a subject's covering.

   13. A method according to claims 6 -11 wherein one or more mirrors may be temporarily secured to a subject's covering using hook and loop fastening.

   14. A method according to any of the claims 1 -13 wherein physiological movement of a subject may be deduced from lateral shifts in mirror images of local objects which may include cot rails, cot sides or mobiles for infant subjects or walls, ceilings or other optical features for older subjects.

   15. A method according to any of the claims 1 -13 wherein a subject's physiological movement may be monitored by direct viewing or indirect viewing through video or the like facilities of images in mirrors of a light box or an * : : : illuminated optical pattern or cartoon features, or a regular array of light emitting diodes secured over a bed, cot or incubator with a stable support being secured to a bed, cot or incubator member or on an external free standing facility. ** .* * * S...

   * : * 16. A method according to any of the previous claims wherein physiologically induced inclinational changes in mirrors may be deduced from lateral shifts in secondary images on a local diffuse reflector produced from at least partially * specular light generated by a torch or light emitting diode or the like stably secured to a bed, cot or incubator member or a free standing facility and directed towards said mirror or mirror array.

   17. A method according to claim 16 wherein a support for a light source provides adjustment in both horizontal and vertical planes.

   18. A method according to claim 16 wherein said light source possesses a manual or automatic intensity control.

   19. A method according to claims 1 -5 wherein a mirror is located on a lightweight beam at a position on or close to the beam's pivot or support.

   20. A method according to claims 1 -5 wherein a mirror is located on a lightweight beam towards the unsupported end of the beam.

   21. A method according to claim 19 wherein a beam may possess a counterbalancing facility to minimise contact pressures with a monitored subject.

   22. A method according to any of the claims 1 -18 wherein an optical shield may be employed to prevent possible visual disturbance of a monitored subject from direct or reflected light emitted from said source but not intercepting incident light on a mirror or mirrors from said source.

   23. A method according to claim 19 wherein a relatively high intensity at * least partially specular light source may be deployed to illuminate a mirror said source possibly comprising a torch, a focussed light emitting diode or a low power laser diode, said source being stably supported on or by a bed, cot or incubator member or * ::: : on a free standing member. *

   *****S * * 24. A method according to claims 1 -8 and 12 -14 wherein one or more * s lightweight mirrors may be secured to a child's safety restraints such as pushchair or * * pram harnesses as well as car safety harnesses or other resilient restraints or covers.

   25. Apparatus for monitoring physiological movement of a human or animal subject comprising one or more small lightweight mirrors placeable directly on the region of a subject to be monitored or secured to a lightweight flexible membrane means for placement on a subject's region to be monitored or secured to a lightweight beam supported or pivoted at or towards one end with a section of the beam's length displaced from the support or pivot placeable lightly on that region of the subject to be monitored with movement of said beam or mirrors contact regions inducing corresponding changes in the inclination of said beam hence attached mirror or in the planes of one or more minors placed more directly on said subject with said mirror inclinations producing lateral shifts in the images within said mirrors of local objects or optical features or lateral shifts in secondary images on a local diffuse reflector means produced from mirror reflections of at least partially specular light produced from a local source means with any said physiological movement induced lateral shifts in said images being directly detectable by viewing or by means of video monitoring or the like and in the case of said beams movement induced inclinational changes these may also be detectable using a displacement sensor means close to or at said support or pivot point with said sensor output being processed by electronic processing means to facilitate recording and or display of physiological movement data. * * * ** . * *

   26. Apparatus accordmg to claim 25 wherem means are provided m its **** . . . . . . basic form to facilitate passive momtormg but by deploying displacement sensor * * means or the like with associated signal processing or video and data recording means monitoring may be automated.

   * : 27. Apparatus according to claim 25 comprising means for monitoring sleeping or reclining subjects including physiological movement data collection and processing means for detecting and characterising movement modes including heart beat, breathing, limb movement and body repositioning.

   28. Apparatus according to claim 25 wherein lightweight mirrors may be manufactured from rigid plastics.

   29. Apparatus according to claims 25 and 28 wherein means for supporting lightweight mirrors comprises a lightweight limp flexible membrane which may be produced from rubber or fabric with good frictional properties.

   30. Apparatus according to claims 28 and 29 comprising linear or two dimensional symmetrical mirror arrays secured to support membranes by flexible adhesive means or sewing means this latter by means of peripheral holes in individual mirrors.

   31. Apparatus according to claims 25 -30 comprising one or more mirrors or mirror arrays secured temporarily or permanently through adhesive or sewing means to a subject's garment or covering.

   32. Apparatus according to claim 31 comprising hook and ioop means for temporary attachment of mirrors to a subject's garment or covering.

   33. Apparatus according to claims 25 -32 comprising an illuminated optical feature means which may consist of a light box, an array of light emitting * * *. diodes, illuminated cartoon features or optical pattern. * * * ** * S...

   34. Apparatus according to claim 33 comprising an unlit light box * providing a regular array of black apertures.S *.... * S

   . : Apparatus according to claims 33 and 34 comprising means to stably * * support an illuminated or un-illuminated optical feature means on a bed, cot or * : incubator or free standing facility.

   36. Apparatus according to claim 25 comprising an at least partially specular light source means for generating secondary images from mirror reflections.

   37. Apparatus according to claim 36 comprising a diffuse reflector such as a ceiling, wall or other diffusely reflecting surface for intercepting at least partially specular light reflected from mirrors.

   38. Apparatus according to claim 36 comprising means for supporting and angularly adjusting an at least partially specular light source.

   39. Apparatus according to claims 33 -38 comprising means for manually or automatically adjusting light intensity levels.

   40. Apparatus according to claim 25 comprising a lightweight beam means pivoted or otherwise secured at one end on a structural member associated with a subject's bed or the like and supporting a mirror.

   41. Apparatus according to claim 40 comprising means to facilitate contact between said beam and monitored subject and means to lift and secure said beam in a non contacting state using a magnetic catch or the like.

   42. Apparatus according to claims 40 and 41 wherein said beam is formed * from plastics or metal strip means preferably softly padded or formed from relatively * stiff sponge rubber strip. *S.S * *

   . : 43. Apparatus according to any of the claims 40, 41 or 42 comprising * counterbalancing means to minimise contact pressures on a subject. *�*** * *

   44. Apparatus according to claims 40-43 when a mirror is mounted on or close to a beam's pivot or support comprising a relatively high intensity at least partially specular light source means stably supported over said mirror preferably on a subject's sleeping or reclining support facility.

   45. Apparatus according to claim 44 when said light source means comprises a torch.

   46. Apparatus according to claim 44 wherein said light source means comprises a focussed light emitting diode.

   47. Apparatus according to claim 44 wherein said light source means comprises a low power laser diode.

   48. Apparatus according to claims 25, 26, 28 -32 comprising child security means on which one or more mirrors may be secured.

   49. Apparatus according to claim 48 wherein child security means comprises a push chair or pram harness or a car seat belt harness.

   50. Apparatus according to claims 25 -39 wherein an optical shield may be deployed and mounted at a position to allow incident light from a source to pass unimpeded to a mirror or mirror array but to prevent visual exposure to a monitored subject.

   * :: 51. Apparatus substantially as herein before described with reference to any one of the accompanying drawings.

   52. A method substantially as herein before described with reference to ***** . * * any one of the accompanying drawings.