GB2307736A - Method and device for area illumination - Google Patents

Method and device for area illumination Download PDF

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Publication number
GB2307736A
GB2307736A GB9524633A GB9524633A GB2307736A GB 2307736 A GB2307736 A GB 2307736A GB 9524633 A GB9524633 A GB 9524633A GB 9524633 A GB9524633 A GB 9524633A GB 2307736 A GB2307736 A GB 2307736A
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Prior art keywords
light
deflector
disseminator
perceptor
radiation
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GB9524633A
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GB9524633D0 (en
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Leslie Adrian Alfred Woolard
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Leslie Adrian Alfred Woolard
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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21VFUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V17/00Fastening of component parts of lighting devices, e.g. shades, globes, refractors, reflectors, filters, screens, grids or protective cages
    • F21V17/02Fastening of component parts of lighting devices, e.g. shades, globes, refractors, reflectors, filters, screens, grids or protective cages with provision for adjustment
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21SNON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
    • F21S10/00Lighting devices or systems producing a varying lighting effect
    • F21S10/06Lighting devices or systems producing a varying lighting effect flashing, e.g. with rotating reflector or light source
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21VFUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V15/00Protecting lighting devices from damage
    • F21V15/01Housings, e.g. material or assembling of housing parts
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21VFUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V31/00Gas-tight or water-tight arrangements
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21VFUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V5/00Refractors for light sources
    • F21V5/04Refractors for light sources of lens shape
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21VFUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V7/00Reflectors for light sources
    • F21V7/0008Reflectors for light sources providing for indirect lighting

Abstract

A perceptor (eg a human eye) is furnished with apparently-continuous illumination over an extended area, which at any instant is only partly illuminated, by focusing a beam 5 from a source 1 onto a rotating deflector 6 which scans the beam repeatedly over the area such that every part thereof is repeatedly and intermittently illuminated by discontinuous flashes at a time interval not less than the decay period of the response of the perceptor to the radiation (eg at least twice every 1/10 sec.). A pair of back-to-back mirrors may be used, optionally curved to spread or condense the beam (Fig 4). Alternatively a rotating conical multi-sided mirror may be used (Fig 8) mounted above an annular fluorescent tube so as to provide multiple beam scanning.

Description

AN ILLUMINATION METHOD AND DEVICE This invention concerns an illumination method and device.

Broadly-speaking the invention relates to a method whereby the bright illumination provided by a concentrated, narrow beam of light or other electromagnetic radiation can apparently be disseminated, with comparable intensity, over a much wider area. The invention moreover also concerns a light disseminator device which is a combination of light deflector(s) with other means ar & which is able, in co-operation with a light source, to provide relatively high-intensity apparent illumination over a widespread target area, that is to say wide-arc illumination apparently more intense than could be spread over the same target area by the light source unaided by the device.

It is a commonplace that light emanating from a light source will normally be radiated therefrom broadcast in all directions, with correspondingly low intensity in any one direction. It is however also one of the most basic achievements of optics that light emanating from such a light source can be concentrated and directed by means of a suitable reflector (thus a mirror or system of mirrors) and/or refractor (thus a lens or system of lenses) into a narrow beam, which casts illumination of relatively much greater intensity in a chosen direction than would otherwise have been broadcast in that direction - but of course at the expense of diminishing or denying illumination in other directions.It seems that one is faced with an apparently inescapable choice - between relatively lowintensity illumination over a wide area on the one hand, or relatively high-intensity illumination over a narrow area on the other. And this is indeed the inescapable choice, when the intensity of illumination is perceived entirely objectively - there is no avoiding the laws of science, and one does not get something for nothing.

The present invention however springs originally from a realization that the perceived intensity of illumination is in certain circumstances not objective but can be quite subjective. In the most obvious case, when observed by the human eye and brain, the perceived illumination is dependent upon not only the actual light but also the imperfect response of the retina of the eye to light incident thereon.

Instantaneously stimulated by a flash of light, the retina of the human eye continues to respond to that stimulus for a fraction of a second longer than the stimulus itself before its response decays. This is a recognised imperfection of the human eye, referred to as persistence of vision. At the heart of the present invention is the realization that in appropriate circumstances it is possible to take advantage of the persistence of vision in the eye of an human (or animal) perceptor to induce an illusion of wide-arc, relatively high-intensity apparent illumination if a narrow, concentrated beam of such relatively high-intensity illumination is intermittently but repeatedly swept at sufficiently hort time-intervals across a wide target area.

This may seem improbable, but it has been tested and confirmed when observation is made with the eye of an human perceptor. Moreover a phenomenon in the visible light range occasioned by persistence of vision in the human (or other animal) eye must be reproducible even in a non-animal (eg. electrical and/or electronic) context, and indeed then even in the non-visible electromagnetic radiation ranges, whenever the observation is made using a perceptor instrument responsive to the electromagnetic radiation employed but with an imperfect, non-instantaneous persistence of response to that illumination. And again, this has received confirmation in preliminary testing, although its implications have yet to be fully explored.

According to this invention, in its broadest aspect, there is therefore provided a method of furnishing a perceptor with apparently-continuous illumination over an extended target area with electromagnetic radiation to which the perceptor is responsive, in which at any instant only part of said area is illuminated with said radiation but every part thereof is intermittently and repeatedly illuminated by discontinuous flashes of said electromagnetic radiation, said flashes being as regards any one part of said target area repeated at time intervals not less than the decay-period of the response of the perceptor to that radiation.

Dependent perhaps on the equipment employed in the method (to generate and otherwise handle the illumination) there seems to be no absolute limit on the range of electromagnetic radiation that can be used. At present however it seems unlikely that either gammaPrays and x-rays on the one hand or microwaves on the other will find much use in the method. It is therefore currently envisaged that the electromagnetic radiation employed will be in the ultraviolet, visible and/or infrared ranges, thus corresponding to wavelengths of say from lnm up to about 5mm.For the purposes at present contemplated it will be preferable to use visible light with wavelengths in the range of from about 380nm up to about 780nm, and/or actinic radiation ie. light in the violet and ultra-violet regions of the spectrum which will bring about chemical or photochemical changes, and may be regarded as corresponding to wavelengths of from 4 to 600nm. Of course the term "ultra-violet (or UV) radiation" refers to the non-visible part of actinic radiation, and may be regarded as corresponding to wavelengths of from 4 to 400nm., and more especially 325-365nm.Thus overall the preferred visible and actinic radiation for use in the method of the invention corresponds to wavelengths in the range of from 4nm up to 780nm. The electromagnetic radiation employed may be coherent, subject to the normal considerations governing its generation and use, but as currently envisaged will usually be normal, incoherent radiation.

Where the context so allows, the term "perceptor" as used herein includes not only the human (or other animal! eye responsive in the visible light range but also non- & imal (e.g. electric and/or electronic) perceptor instruments responsive in the visible and/or the non-visible radiation ranges. It moreover also includes part-human (or other animal) and partinstrumental perceptors, as for instance when nonvisible radiation is perceived initially by an instrument responsive thereto but then converted within that instrument into a secondary image in the visible light range and thus perceptible by the human (or other animal) eye of an ultimate observer.

The decay of the response of any perceptor will generally be exponential, and of course the term "decay-period" is not here used in an extreme theoretical sense which could include almost infinite periods as the response approaches zero but in its practical sense which embraces only perceptor-responses that are useful for their intended purpose. On an admittedly arbitrary basis the outside limit of the relevant decay-period can be defined as that over which the response of the perceptor falls to 30% of the maximum response of the perceptor to stimulation by that radiation. For all currently-envisaged purposes the decay-period should be set at that during which the perceptor-response falls to no less than 50% of maximum, and it is believed that the best results will be achieved when the relevant decay-period is set to end at a level of 80% or even 90% of maximum response.

In order to reduce or avoid any sensation in the perceptor of flickering in the perceived illumination it is quite desirable that the flashes of illumination should be repeated as regards any one part of the target area at least twice during the decay period, and (within experience so far) it is best if they are repeated substantially three times during that period.

When the illumination is in the visible range and the intended perceptor is the human eye these preferences correspond roughly with the flashes of visible light being desirably repeated at least twice every one-tenth of one second, and best repeated substantially three times every one-tenth of one second.

The method is conveniently performed by shifting a relatively-narrow beam of the radiation from one point to another on the relatively-wider target area. The narrow beam can most conveniently be shifted from one point to another on the target area by means of a light deflector interposed in the beam. The light deflector will usually and most conveniently be a rotating reflector.

According to another preferred aspect of this invention there is also provided a light disseminator, for use in carrying out the method herein disclosed, which comprises means operable to direct a beam of light so that it impinges upon a rotatably-mounted light-deflector, said light-deflector being arranged and disposed so that dependent upon its rotational position it will deflect the light-beam to one point or another around an arcuate target area centred upon the rotatable deflector, and means operable to rotate the light-deflector so that it sweeps the deflected beam around said arcuate target area, at a rotational rate such that any given part of the arcuate target area is intermittently but repeatedly illuminated by discontinuous flashes of light provided by the deflected light-beam at time-intervals of not more than one-tenth of one second.

In this case, the perceptor is to be the human eye, and the time-intervals should preferably be not more than one-thirtieth of one second, and possibly or even desirably still less.

Of course, the beam-directing means will desirably be so disposed and arranged as normally to direct a beam of substantially parallel light to impinge upon the rotatably-mounted mirror, but it is for some enduses advantageous also to provide means for adjusting the arrangement out of its normal disposition so as either to converge or to diverge the otherwise substantially parallel light-beam.

The beam-directing means preferably will comprise means for mounting a light-source, and a concave reflector mounted adjacent to said light-source on its side remote from the light-deflector so as to assist in directing the desired parallel light-beam to impinge upon the light-deflector(s).

Alternatively or in addition the beam-directing means may comprise means for mounting a light-source, and a convex lens or lens system mounted between said light-source and the light-deflector so as to assist in directing the desired parallel light-beam to impinge upon the light-deflector(s).

The light-disseminator will normally include an electrically-operable incandescent light-source supported in the mounting means, and there provided with electrical connections adapted under control to operate the incandescent light-source. The lightsource advantageously is or includes a single-filament incandescent light bulb so supported in the mounting as to dispose the filament with its axis normally vertical.

The light-deflector may be a refractor, eg. a multi-sided-prism, but experience so far suggests that it is advantageously a rotatably-mounted reflector, usually indeed a multi-faceted reflector. For the purposes currently envisaged the rotational axis of the light-deflector(s) should in normal use be disposed vertically.

In the simplest arrangement the multi-faceted reflector will advantageously be a double-side plane mirror. With such an arrangement, and in an ideal setup wherein a beam of truly parallel light from a truly linear source is incident upon a plane mirror of the same depth as the beam, then the reflected beam will be neither divergent nor convergent, and thus will have the same depth as the incident beam. Therefore on rotation of the mirror the reflected beam will be swept around a substantially 360arc, creating at any given instant a corresponding small patch of high-intensity illumination, (having the same depth as both the incident beam and the linear source) at one particular point on the 3600-arc centred on the rotating mirror.

In practice it is however effectively impossible to achieve such an ideal set-up, and there is an inevitable tendency for the beam incident on the mirror to include some stray, non-parallel light - and in that event the beam even when reflected from a plane mirror will to some extent be slightly divergent.

Nevertheless when using a beam of parallel light and a plane mirror most of the light is concentrated in the previously-mentioned small patch, and due to persistence of vision in an human observer's retina it will be perceived as a fairly thin, flat "band" of illumination around the rotating mirror, so-to-speak in a sort of horizontal disc.

Dependent upon requirements, it is possible either to accentuate the tendency for the beam to diverge or to try to counteract it.

Thus, in order to promote a wider band of illumination the light-deflector can be so constructed and arranged that it encourages the substantiallyparallel light-beam impingent thereon to become divergent in the vertical planes containing the rotational axis of the light-deflector, eg. by making the light-deflector a slightly-convex mirror.

Conversely, if it should be wished to concentrate the illumination into a still narrower band, then the light-deflector can be so constructed and arranged that it counters any tendency for the substantially-parallel light-beams impingent thereon to become divergent, or indeed even forces it to become convergent, eg. by making the light-reflector a slightly-concave mirror.

The transverse dimensions of the light-deflector in the plane normal to the impingent light-beam will desirably exceed the width of that light-beam, so as to ensure that the full width of the light-beam is deflected thereby for so much as possible of its rotation. On the other hand the light-deflector would have to be of infinite width if it were to be capable of deflecting the full width of the incident light beam throughout its entire rotation, which of course is absurdly impossible.

Balancing these considerations, it currently appears that for practical purposes the width of the light-deflector (normal to the incident beam, and in the plane normal to its rotational axis) should conveniently be in the range of from about 1.12 to about 2.24 times the width of that beam. On a somewhat arbitrary basis, it is currently thought best if the width of the light-deflector is substantially 1.4 times the width of the beam.

The light disseminator of this invention may be embodied in various ways according to the end-use envisaged. Possible uses seem very extensive, and have not yet been fully explored, but fall broadly into two categories. In one category of end-use the ultimate observer carries the device himself or for instance upon a vehicle, and thus requires wide-arc but still partly-directional illumination ahead of him, eg. in the manner of a hand-held torch or a vehicle-mounted headlamp. In another category of end-use the ultimate observer wishes to set up the device to provide high intensity all-round illumination, either temporarily as for instance at the scene of an accident or other emergency or on a more permanent basis as for instance in sporting arenas or other public concourse areas.

In order that the invention may be well understood various simple eibodiments thereof will now be described in more detail, though only by way of illustration, with reference to the accompanying schematic duawingsn which so far as possible the same reference numerals have been used for the same parts in all the various figures) as follows:: Figure 1 is a perspective view of the basic elements of a light-disseminator arrangement in accordance with this invention, laid out diagrammatically in a manner intended to facilitate understanding of its principle of operation rather than as it would be actually embodied in a commercial construction; Figure 2 is a plan view of a slightly more elaborate but basically similar arrangement to that shown in Figure 1 mentioned above; Figure 3 is a diagram also in plan view which indicates how rotation of the light-deflector sweeps the deflected light beam and thus the patch of instantaneous illumination around an arc of substantially 3600 centred upon the rotational axis of the light-deflector;; Figure 4 is a diagrammatic and exaggerated representation of an alternative and sometimes desirable double-sided light deflector for use in the arrangement of Figures 1 to 3, which in place of plane mirrors uses semi-convex mirrors, je. mirrors which ae convex in the vertical plane through their rotational axis but planar radially thereof; Figure 5 is a still-diagrammatic, partly cut-away, perspective and part-exploded view of a more practical embodiment of the basic light disseminator illustrated in Figures 1 to 4, intended to direct illumination over a wide but not full 3600 arc, rather in the manner of a hand-held torch or car headlight;; Figure 6 is a simplified, plan view of the embodiment of Figure 5, with the respective lightsource and spinning light-deflector compartments juxtaposed (rather than exploded) and with their transverse dimensions more realistically adjusted relative to each other; Figure 7 is a similar plan view of the embodiment of Figures 5 and 6, when mounted within a transparent housing, as they might be in an hand-held torch or, more especially, in a single car-headlight which affords wide-anglejbright, but still partly-directional illumination ahead and to each side of the observer carrying the torch or seated in the vehicle; and Figure 8 is a side-elevation, partly in crosssection, of an alternative embodiment of combined light source and rotatable light deflector, intended to provide illumination around a full 3600 arc.

Referring first to the schematic lay-out illustrted in Figures 1 to 3, an electric light-source generally indicated 1 has a vertically-disposed, substantially linear incandescent filament 2, and is interchangeably supported in suitable fittings (not shown) and supplied with power via electric leads 3.

The light-source 1 is positioned with the vertical axis of filament 2 at the focus of a semi-parabolic reflector 4, that is to say one which is parabolic in the horizontal plane but planar in all vertical planes, and directs a narrow but deep beam of substantially parallel light, approximately rectangular in crosssection, in the direction of arrow 5 onto a doublesided reflector generally-indicated 6, mounted on a rotatable, vertical spindle 7.

In the slightly more elaborate embodiment illustrated in Figure 2, the arrangement also includes a centrally-planar but peripherally convex lens 17 positioned between the light source 1 and the rotatable light deflector 6, the convex periphery of which tends to collect stray, non-parallel light emergent from the parabolic mirror 4 and converge it into parallel beam 5.

The top and bottom ends of spindle 7 are rotatably supported in journals 8a and 8K, and the spindle 7 is provided with a driven pulley-wheel 9 interconnected by belt 10 with the drive pulley-wheel 11 of an electric motor 12 supplied with power via leads 13.

When power is connected to light-source leads 3 and motor leads 13 the light generated by the filament 2 is concentrated into a narrow beam which is directed onto the rotating double-sided mirror 6 and there deflected, eg. in the direction of arrow 14, but as the spindle-mounted mirrors 6 are rotated the deflected beam is swept around in a substantially 3600 arc, partially indicated 15.

At any given instant the beam of light 14 will illuminate only a small patch eg. as indicated at 16, that patch being illuminated at that instant with the full intensity of which the particular arrangement is capable - but the illuminated patch will sweep around arc 15 at a rotational speed directly related to that imparted to the spindle 7 by the driven pulley-wheel 9, drive belt 10, drive pulley-wheel 11 and motor 12.

When the reflector employed is double-sided (as in all of Figures 1 to 7) the sweep-rate will be twice the rotational speed of the spindle.

The retina of the eye of the observer will perceive the patch 16 at its full illumination no matter where it finds itself, and due to persistence of vision will continue to respond to that level of illumination for about 1/10th of a second. Provided therefore that the patch 16 is re-illuminated by the rotating beam at least every l/lOth of a second the retina of the eye will perceive patch 16 as if it were steadily illuminat2d at the full level of which the arrangement is capable, and this no matter where the patch 16 under discussion is located around the 3600 arc centred on the rotating spindle 7.

Thus by driving motor 12 at such a speed as to sweep the beam around the arc at least once every onetenth of one second the illustrated arrangement can persuade the eye of an observer to perceive the fulllevel illumination of a narrow beam as if it extended all the time around the full 3600 arc. With the double-sided mirror arrangement of Figures 1 to 3 this requires the motor 12 to rotate the spindle 7 at a rate of at least 300 revolutions per minute (r.p.m) in order to achieve a sweep-rate of at least 600 r.p.m.

Figure 4 illustrates (in an exaggerated manner) a modification of the twin-mirror arrangement shown in Figures 1 to 3, in which the spindle-mounted, doublesided plane mirrors 6 there shown are here replaced by semi-convex mirrors, so that the impinging beam 5 is diverged thereby into a broader band of illumination.

Referring now to Figure 5, this shows (still rather schematically) a more practical embodiment in which as before a vertically-disposed linear light source 2 is supported between sockets 18 and 18k in alignment with the focus of the semi-parabolic reflector 4. By means of the sockets 18 and 18b the light source is thereby connected to electric leads 3.

Unlike the previously-described arrangement this lightsource assembly is provided with a transparent front cover-plate 19, formed of glass or "Perspex" (Registered Trade Mark) or some similar rigid transparent material.

The double-sided planar light-deflector 6 is, as in the previous embodiment, mounted on vertical spindle 7 rotatably supported between upper journal 8 and a lower journal (not shown). The lower end of spindle 7 is provided with a circular metal disc 19, whose function will be explained below. The light-deflector assembly comprising double-sided mirror 6, spindle 7, journals 8a and 8 > (not shown) and the metal disc 19 is however, unlike previously-described arrangements, housed within a transparent, evacuated housing 20, again formed of glass or "Perspex" (Registered Trade Mark) or some other rigid transparent plastics material.

Evacuation of the housing 20, even if less than total, . reduces air-resistance to the rotation of the spindle and the double-sided mirror mounted thereon but of course introduces difficulties in driving rotation of this light-deflector assembly 6. In this embodiment however the metal disc 19 within the housing 20 serves as the rotor member of an electrical induction motor, the stator 21 of which is mounted beneath the rotor 19 but outside the housing 20. The stator member 21 is powered via electrical leads 3.

Obviously using such an induction motor solves the problem of rotating the light-deflector assembly within housing 20, but necessitates supplying alternating current (a.c.) via leads 3 to the stator member 21.

For certain purposes (eg. in small light-disseminators akin to a hand-held torch or lantern) the need for the use of a.c. is a complication which may be undesirable - but it can be solved even when the electric power supply is derived from a d.c. source such as a battery by interposing an inverter (not shown) between the power source and the stator member 21.

The kind of arrangement described and illustrated with reference to Figure 5 above is basically advantageous because it enables the light-deflector assembly to be housed within an evacuated enclosure thus reducing air-resistance to the rotation of the double-sided mirror 6 and thereby reducing power consumption and/or increasing the speed of rotation of the deflected light beam. This construction moreover facilitates exchange of either the light-source assembly or the light-deflector assembly, when either of them becomes defunct and in need of replacement.

Figure 6 shows the assemblage of the light-source and the light-deflector into an unit, the relevant dimensions being approximately correct. It will be seen that the width of the twin-mirrors is about 1:4 times the width of the beam emergent from the lightsource aperture, so that when the mirrors 6 are at an angle of about 450 the full beam-width is still accommodated within the available width of the mirrors.

Figure 7 shows the assemblage of Figure 6 mounted with a transparent housing 22, such as might serve as a single, possible roof-mounted headlight for a motor vehicle, providing excellent illumination not only ahead of the vehicle (not shown) but also to both sides of it over a wide arc, as for instance shown by arrows 23.

A quite different embodiment of lightdisseminator, specifically intended to provide allround illumination, is shown in Figure 8. Here the light source 2 is an annular fluorescent tube mounted at the focus of an annular parabolic mirror 4, the annular light source 2 and parabolic mirror 4 being arranged around the vertical spindle 7 supported in a journal 8 driven by bevel-gear 24 which in turn is driven by meshing bevel-gear 25 driven by electric motor 12 powered via leads 13.

The light from source 2 is directed upwardly by parabolic mirror 4 to impinge upon a multi-faceted mirror 26, each facet being disposed at a suitable angle (eg. 450) to the vertical. Thus the parallel light directed upwardly from light source 2 and parabolic mirror 4 is reflected by the off-vertical mirror facets 26 into approximately horizontal beams as indicated by arrows 27. Although for simplicity of illustration this is not shown in Figure 8, it should be noted that each of the mirror facets 26 can advantageously be fluted.

It should at this point be observed that the embodiment of Figure 8 results in creation of not just one patch of reflected light but as many different patches of reflected light as correspond to the number of facets 26 on the rotating mirror assembly.

It will be appreciated that to achieve the illusion of wide-arc high intensity illumination what is necessary is that any given part of the target to be illuminated shall be thereby repeatedly illuminated at intervals not greater than l/lOth second, and when a single reflector is rotated to sweep a single beam around a 3600 arc the rate of revolution of that single reflector must therefore be at least 600 revolutions per minutes (r.p.m.) - but the requirement relates to the frequency with which any given patch of the target area is illuminated, and is not necessarily directly dependent on the rate of revolution of the spindle. In the case of the embodiment of Figure 8, if the multifaceted mirror has X facets then the minimum rate of revolution of the mirror assembly needed to achieve the illusion is 600/x revolutions per minute.

Claims (32)

1. A method of furnishing a perceptor with apparently-continuous illumination over an extended target area with electromagnetic radiation to which the perceptor is responsive, in which at any instant only part of said area is illuminated with said radiation but every part thereof is intermittently and repeatedly illuminated by discontinuous flashes of said radiation, said flashes being as regards any one part of said target area repeated at time intervals not less than the decay-period of the response of the percepzor to that radiation.
2. A method as claimed in claim 1, in which the electromagnetic radiation employed has a wavelength in the range of from lnm up to 5mm.
3. A method as claimed in claim 1 or claim 2, in which the radiation employed has a wavelength in the range of from 4nm to 780nm.
4. A method as claimed in any of the preceding claims, in which normal, incoherent electromagnetic radiation is used.
5. A method as claimed in any of the preceding claims, in which the radiation employed lies in the visible range with a wavelength of from 380nm to 780nm, and the perceptor is or includes the eye of an human observer.
6. A method as claimed in any of the preceding claims, in which the perceptor-response decay-period is that over which the response of the perceptor falls to 30% of the maximum response of said perceptor to stimulation by the incident radiation.
7. A method as claimed in claim 6, in which the decay-period is that over which the perceptor-response falls to 50%.
8. A method as claimed in claim 6 or claim 7, in which the decay-period is that over which the perceptor-response falls to 90%.
9. A method as claimed in any of the preceding claims, in which the flashes are repeated as regards any one part of the target area at least twice during the decay period.
10. A method as claimed in claim 9, in which the flashes are repeated substantially three times during the decay period.
11. A method as claimed in claims 5 and 9,in which the flashes of visible radiation are repeated at least twice every one-tenth of a second.
12. A method as claimed in claims 5 and 10, in which the flashes of visible radiation are repeated substantially three times every one-tenth of a second.
13. A method as claimed in any of the preceding claims, in which a relatively narrow beam of radiation is shifted from one point to another on a relatively-wider target area.
14. A method as claimed in claim 13, in which the narrow beam is shifted from one point to another on the target area by means of a light deflector interposed in the beam.
15. A method as claimed in claim 14, in which the light deflector is a rotating reflector.
16. A method as claimed in any of the preceding claims and substantially as herein described.
17. A light disseminator for carrying out the method claimed in any of the preceding claims, which comprises means operable to direct a beam of light so that it impinges upon a rotatably-mounted light-deflector, said light-deflector being arranged and disposed so that dependent upon its rotational position it will deflect the light-beam to one point or another around an arcuate target area centred upon the rotatable deflector, and means operable to rotate the lightdeflector so that it sweeps the deflected beam around said arcuate target area at such a rotational rate that any given part of the arcuate target area is intermittently but repeatedly illuminated by discontinuous flashes of light provided by the deflected light-beam at time-intervals of not more than one tenth of a second.
18. A light disseminator as claimed in claim 17, in which the beam-directing means are so disposed and arranged as normally to direct a beam of substantially parallel light to impinge upon the rotatably mounted light-deflector.
19. A light-disseminator as claimed in claim 18, which also comprises means for adjusting the arrangement out of its normal disposition so as either to converge or to diverge the otherwise substantially parallel light-beam.
20. A light disseminator as claimed in any of claims 17 to 19, in which the beam-directing means comprise a mounting for a light-source, and a concave reflector mounted adjacent to said light-source on its side remote from the light-deflector so as to assist in directing the desired normally parallel light-beam to impinge upon the light-deflector.
21. A light disseminator as claimed in any of claims 17 to 20, in which the beam-directing means comprise means for mounting a light-source and a convex lens or lens system mounted between said light-source and the light-deflector so as to assist in directing the desired normally parallel light-beam to impinge upon the light-deflector.
22. A light disseminator as claimed in claim 20 or claim 21, which includes an electrically-operabia incandescent light-source supported in the mounting, and there provided with electrical connections adapted under control to operate the incandescent light-source.
23. A light disseminator as claimed in claim 22, in which the light-source is or includes a single-filament incandescent light bulb so supported in the mounting as normally to dispose the filament thereof with its axis vertical.
24. A light disseminator as claimed in any of claims 17 to 23, in which the light-deflector is a rotatablymounted double-sided reflector.
25. A light disseminator as claimed in any of claims 17 to 24, in which the rotational axis of said lightdeflector is normally disposed vertically.
26. A light disseminator as claimed in any of claims 17 to 25, in which the light-deflector is so constructed and arranged that it encourages the substantially-parallel light-beam impingent thereon to become divergent in any plane containing the rotational axis of the light-deflector.
27. A light disseminator as claimed in any of claims 17 to 25, in which the light-deflector is so constructed and arranged that it counters any tendency for the substantially-parallel light-beams impingent thereon to become divergent in the plane normal to the rotational axis of the light-deflector.
28. A light disseminator as claimed in any of claims 17 to 27, in which the transverse dimension of the light-deflector in the plane normal to its rotational axis exceeds the width of the beam in that plane by a factor in the range of from 1.12 to 2.24.
29. A light disseminator as claimed in claim 28, in which the transverse dimension of the light-deflector is substantially 1.4 times the width of the beam.
30. A light disseminator as claimed in any of claims 17 to 29, and substantially as herein described.
31. A light disseminator substantially as herein described with reference to and/or as shown in any of Figures 1 to 7 of the accompanying drawings.
32. A light disseminator substantially as herein described with reference to and/or as shown in Figure 8 of the accompanying drawings.
GB9524633A 1995-12-01 1995-12-01 Method and device for area illumination Withdrawn GB2307736A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9524633A GB2307736A (en) 1995-12-01 1995-12-01 Method and device for area illumination

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9524633A GB2307736A (en) 1995-12-01 1995-12-01 Method and device for area illumination

Publications (2)

Publication Number Publication Date
GB9524633D0 GB9524633D0 (en) 1996-01-31
GB2307736A true GB2307736A (en) 1997-06-04

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB9524633A Withdrawn GB2307736A (en) 1995-12-01 1995-12-01 Method and device for area illumination

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GB (1) GB2307736A (en)

Cited By (2)

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Publication number Priority date Publication date Assignee Title
WO1998055797A1 (en) * 1997-06-03 1998-12-10 Leslie Adrian Alfred Woolard An illumination method and device
WO2010064984A1 (en) 2008-12-04 2010-06-10 Skäret Ab Fixture for emulation of omnidirectional or directed continuous lightning

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GB488616A (en) * 1937-01-07 1938-07-07 Stanley Edward Grubb Improvements relating to searchlights
GB520079A (en) * 1938-09-12 1940-04-15 Guglielmo Riccomagno Improvements in and relating to spotlights or projectors
GB558828A (en) * 1942-08-28 1944-01-24 Joseph Garfield Brough Revolving high-speed search-light for military and naval purposes
GB694357A (en) * 1948-08-28 1953-07-22 Guglielmo Riccomagno Improvements in or relating to illumination apparatus
GB951604A (en) * 1959-03-03 1964-03-04 Meiners Optical Devices Ltd Improvements in or relating to lamps
GB1083492A (en) * 1964-07-31 1967-09-13 Maldon Cavendish Harley Rotary lamps
US3865790A (en) * 1972-11-24 1975-02-11 Shane Harold P Du Persistence of vision, subliminal spot light
GB1486406A (en) * 1976-04-21 1977-09-21 Chambaret J Special lighting effect generating laser device usable as accessory for theatrical equipment
US4153926A (en) * 1977-02-28 1979-05-08 Hurt Jackson D Cyclic illumination device
GB2075653A (en) * 1980-05-05 1981-11-18 Wagner Electric Corp Scan-synthesized-beam headlamp
US5408389A (en) * 1993-09-07 1995-04-18 Burlingame; Glen E. Interrupted light source

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB488616A (en) * 1937-01-07 1938-07-07 Stanley Edward Grubb Improvements relating to searchlights
GB520079A (en) * 1938-09-12 1940-04-15 Guglielmo Riccomagno Improvements in and relating to spotlights or projectors
GB558828A (en) * 1942-08-28 1944-01-24 Joseph Garfield Brough Revolving high-speed search-light for military and naval purposes
GB694357A (en) * 1948-08-28 1953-07-22 Guglielmo Riccomagno Improvements in or relating to illumination apparatus
GB951604A (en) * 1959-03-03 1964-03-04 Meiners Optical Devices Ltd Improvements in or relating to lamps
GB1083492A (en) * 1964-07-31 1967-09-13 Maldon Cavendish Harley Rotary lamps
US3865790A (en) * 1972-11-24 1975-02-11 Shane Harold P Du Persistence of vision, subliminal spot light
GB1486406A (en) * 1976-04-21 1977-09-21 Chambaret J Special lighting effect generating laser device usable as accessory for theatrical equipment
US4153926A (en) * 1977-02-28 1979-05-08 Hurt Jackson D Cyclic illumination device
GB2075653A (en) * 1980-05-05 1981-11-18 Wagner Electric Corp Scan-synthesized-beam headlamp
US5408389A (en) * 1993-09-07 1995-04-18 Burlingame; Glen E. Interrupted light source

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998055797A1 (en) * 1997-06-03 1998-12-10 Leslie Adrian Alfred Woolard An illumination method and device
US6352357B1 (en) 1997-06-03 2002-03-05 Leslie Adrian Alfred Woolard Illumination method and device
GB2321955B (en) * 1997-06-03 2002-06-19 Leslie Adrian Alfred Woolard An illumination method and device
WO2010064984A1 (en) 2008-12-04 2010-06-10 Skäret Ab Fixture for emulation of omnidirectional or directed continuous lightning
EP2401545A1 (en) * 2008-12-04 2012-01-04 Skäret Ab Fixture for emulation of omnidirectional or directed continuous lightning
EP2401545A4 (en) * 2008-12-04 2013-12-18 Skaeret Ab Fixture for emulation of omnidirectional or directed continuous lightning

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