Illumination – Supported by vehicle structure – Condition responsive
Patent
1990-03-06
1991-06-11
Ullah, Akm
Illumination
Supported by vehicle structure
Condition responsive
362 32, G02B 600, F21V 704
Patent
active
050227289
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a device composed of a light guide plate, in which light emitted from a light source is guided by components in a direction parallel to the main surfaces of the plate and issues from projections on a surface of the plate.
With a known device of this type (German Offenlegungsschrift 3,240,942), the projections are situated spaced out directly on the plate. No details are given on their size and spacing. For the exemplary embodiments i is assumed that these values are in the centimeter range. The reflection of the light from the surface of the plate is uneven because only the regions of the surface which have projections emit light.
The underlying object of the invention is to develop the known device further in such a way that the resulting density of surface illumination is even to the eye.
According to the invention this object is achieved by the fact that the smooth surface of the plate is coated with a continuous, transparent intermediate layer having on one side closely spaced projections with a height and width lying in a range between 0.5 mm and 0.001 mm.
Since, according to the invention, the sizes and spacing of the light regions in the form of the projections are of such a nature that their upper limits coincide approximately with the lower limit of the resolving power of the human eye (this resolving power is present when the distance between two points is greater than 0.2 mm when the points are located at a distance of 1 m from the eye, see Grimsehl, Lehrbuch der Physik, vol. 3, 1955, page 309), the main surface of the device according to the invention appears to be evenly luminous. The provision of the intermediate layer on the other hand enables the projections to be produced; without the intermediate layer the projections of the type according to the invention could not be created. The lower limit for the sizes of the projections is thus meaningful since smaller projections could hardly, if at all, be manufactured.
SUMMARY OF THE INVENTION
The advantage of the subject of the invention compared with several direct lighting units combined to form a surface-lighting unit lies in its cheaper manufacture, its lower energy consumption and its greater simplicity.
With regard to the projection or the layer, there are possibilities of variation in respect of the form of the projections, the manufacture and the material of the layer. By varying these values, the light can thus be controlled in that the intensity of the issuing light can be controlled along a line on the reflecting surface. For example, it can be achieved that the light issues over the entire surface with equal intensity everywhere, as it can also be achieved that the light in the vicinity of the light feed point is reflected with greater or lesser intensity than in regions at greater distances from the light source. Of course, this also concerns the bunching of the irradiated light or its degree of diffusion. Thus the less intense reflection mentioned can be achieved by the fact that the light is directed substantially parallel to the main surfaces, or also by the fact that the convexity of the projections is correspondingly altered along the line mentioned.
The device according to the invention is simple to manufacture. For example, a layer can be sprayed onto the plate; if the consistency of the material to be sprayed on is appropriate, the projections are formed in the specified shape. However, a foil or second plate can also be pulled onto the plate, which has the said projections on the side facing away from the first plate.
Accordingly, the projections are generally and preferably small elevations, the upper sides of which are generally curved outwards approximately in the shape of a cap, that is to say they are convex. However, they can also be concave, i.e. in the shape of a lens. In the plan view they are largely circular to oval.
It should be mentioned that it is already known (see Machine Design, Oct. 29, 1959, page 96, FIG. 2b), to provide a light guide plate with pro
REFERENCES:
patent: 3222515 (1965-12-01), Orr
patent: 3491245 (1970-01-01), Hardesty
patent: 4471412 (1984-09-01), Mori
patent: 4930863 (1990-06-01), Croitoriu et al.
patent: 4932749 (1990-06-01), Haidle et al.
Machine Design, Oct. 29, 1959, pp. 98-103.
Stone Mark P.
Ullah Akm
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