Illumination – Light source and modifier – Adjustable or repositionable modifier
Reexamination Certificate
2000-03-07
2002-03-05
O'Shea, Sandra (Department: 2875)
Illumination
Light source and modifier
Adjustable or repositionable modifier
C362S322000
Reexamination Certificate
active
06352357
ABSTRACT:
This invention concerns an illumination method and device.
Broadly-speaking the invention relates to a method whereby 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 and 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 low-intensity 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.
It is known, however, that the perceived intensity of illumination is in certain circumstances not objective but can be quite subjective. This phenomenon is called persistence of vision, and refers to how the human eye can be fooled into perceiving continuous illumination even if it is in fact discontinuous, i.e. rapidly repeated flashes of illumination. Therefore it is possible to produce in the eye of an human (or animal) perceptor 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 high frequency across a wide target area.
Various methods of overcoming the objective problem, which utilise this phenomenon, have been suggested, and the most pertinent of these have been outlined below.
U.S. Pat. Nos. 3,865,790 and 4,153,926 disclose methods and devices which have tried, with only partial success, to solve the problem by taking a device that produces a beam of light, and then rotating the entire assembly at high speed. Similarly British Patents No. 694,357 and No. 1,083,492 both also relate to devices where the light source and the beam concentrating means are rotated together.
Whilst fine in concept, this type of device is rather lacking in practical feasibility. For a start the beam produced tends to be a disc in overall configuration and this is not by any means ideal. The source will only cast light on a given point once (per beam that is produced) per revolution of the source. More importantly however, in devices of this general type, the light source can be one of relatively high power and therefore produce several beams, or it may be confined to producing one beam only and therefor require a less powerful source of light. Naturally when more beams than one are produced, and are able to scan across the target area, then the speed of rotation of the source can be reduced, but even so it will still be required to rotate at high speed. One is faced with the dilemma that if the amount of beams produced is increased, then the speed of rotation can be decreased but the size of the device that must be rotated is increased—whereas conversely the opposite of course is true in that the size of device can be kept down by using fewer beams, but then the speed at which the device must spin is dramatically increased.
These considerations mean that any design of this type must be fairly cumbersome to contain all the features required to rotate a large and complex object at high speed. For instance it requires fairly complex, and hence unreliable, wiring mechanisms to electrically link the rotating bulb to the power supply. Additionally the whole rotating part must be carefully balanced to prevent vibration and the problems associated with it.
The most important point is however that, during high speed rotation, the filament of the bulb can be forced out of alignment with the optics, due to the centrifugal forces. This is hard to avoid because a filament must by design be of narrow diameter and hence flexible.
In an attempt to overcome some of the problems associated with the above disclosed methods, devices wherein the light source was held stationary and the beam producing means were rotatable therearound were instead proposed. In British Patent No. 488,616 a device with lens arrays rotating about a light source was disclosed. Additionally in British Patent No. 520,079 a fixed light source with a set of rotating parabolic mirrors located around it was proposed. Both these devices suffer from the problem of having to rotate the beam means around the light source at high speed, but in close proximity to the bulb. This is especially a problem of the device of GB 520,079 which had at least two back-less parabolic reflectors joined around the light such that they projected at least two beams of light from the source. This has the effect of producing a weak source of light so that the overall lighting phenomenon is diminished.
Various other methods have been employed in an attempt to achieve the proposed objectives, and they have for example, involved a large rotating tower with complex internal reflectors as in GB 558,828; or they have used vibrating mirrors, light source and rotating prisms to scan light over a small area as in GB 951,604.
All the above have failed to effectively overcome the problems associated with attempting to achieve the objectives of the present invention, or indeed for that matter the objectives they set themselves. Indeed the very fact that none of them ever caught on, gives testament to their lack of effectiveness. The present invention, on the other hand, provides a convenient and effective means of achieving those objectives and overcoming the problems.
Therefore, according to this invention in its broadest aspect, there is provided a method of furnishing a perceptor with apparently-continuous illumination by electromagnetic radiation to which the perceptor is responsive over an extended target area, in which a rotatable reflector is used to deflect a relatively narrow beam of radiation from one point to another over a relatively wide target area, whereby 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 perceptor to that radiation.
The terms “radiation” and “reflector” used above, and hereinafter employed for convenience, refer respectively to any suitable electromagnetic radiation that may be efficiently reflected, and to a reflector capable of reflecting said radiation.
It is currently envisaged that the electromagnetic radiation employed will be in the ultraviolet, visible and/or infrared ranges, thus corresponding to wavelengths of say from 1 nm up to about 5 nm. For the purposes at present contemplated it will be preferable to use visible light with wavelengths in the range of from about 380 nm up to about 780 nm, and/or actinic radiation i.e. light in the violet and ultra-violet regions of the spectrum which will bring
O'Shea Sandra
Synnestvedt & Lechner LLP
Truong Bao
LandOfFree
Illumination method and device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Illumination method and device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Illumination method and device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2870382