RU2442229C1 - Lighting panel with frontal input of light emission (options) - Google Patents

Abstract

FIELD: electrical lighting. ^ SUBSTANCE: invention relates to lighting panels with a frontal input of light emission and allows to get economical, eye comforting, homogeneous on the radiant surface light panels with LEDs light source to illuminate accommodation and technical premises and to be applied to demonstrational sign-boards, information directories, luminous advertising, medical lighting devices and other lighting devices; the technical result is attained thanks to the lighting panel with a frontal input of the light emission which has a lightguiding panel element and the light emitting source, at that the lightguiding panel element represents a lightguide executed in the shape of a triangular prism, one lateral side of the prism is smaller than the others, at that the emitting light source is located in front of the smaller side of the prism. ^ EFFECT: enhancement of the cross-sectional evenness of brightness of emerging light beams providing a high coefficient of efficiency upon input-output luminous radiation and securing of the specified direction of emerging beams of light. ^ 6 cl, 5 dwg.

Description

The invention relates to light panels with an end input of radiation and allows to obtain cost-effective, light-emitting surface panels with an LED light source for illuminating residential, technological and technical rooms, uniform on the emitting surface, that can be used in demonstration signs, indexes of various information, light advertisements , lighting devices for medical applications and other lighting devices.

Known lighting panels with an end radiation input, for example, RU 95886, necessarily include three main structural elements shown in Fig. 1, namely, a light guide element 11 (for example, a flat waveguide), light-scattering elements 12, which can be made as additional layers applied to the light guide element 11, and in the form of any changes on the surface (US 2010014318), and the radiation source 13. Sources supply light for illumination, light guide elements provide light delivery along the panel from the source nicks to the light-scattering elements, and light-scattering elements - the output of light outward from the panel. In this case, optimal lighting conditions must be ensured. Light panels may also contain various additional elements, such as reflective coatings. The optical fiber elements (optical fibers) used in the known panels by themselves practically do not bring the radiation out: the transmission efficiency of the radiation through the optical fibers exceeds 95%. This is because, firstly, the radiation from the sources is introduced by the optical fibers at an angle exceeding the angle of total internal reflection. And, secondly, the shape of the optical fibers is such that the propagating radiation at any point in the optical fiber (without scattering elements) experiences a full internal reflection.

Under optimal conditions, the light panel forms from the light beams of the sources one or more beams of a given direction and cross section with the most uniform distribution of light intensity (brightness) over the cross section of the output beams, with the greatest possible (possibly close to 1) efficiency for outputting light radiation. The latter is determined by the ratio of the total power of light from sources to the total power of light output from the panel. To ensure lighting, the absolute output power of the light radiation of the panel must be sufficiently high (comparable to the power of light from incandescent lamps). The characteristic transverse dimensions of the light beam emerging from the panel are much larger (several times) than the transverse dimensions of the beam emanating from sources, provided that the cross section of the corresponding beams is measured at the same distance from the source and from the panel. The shape of the outgoing light beam coincides, as a rule, with the shape of the working (output) surfaces of the panel.

Thus, the objective of the present invention is to create a light panel with an end input of radiation, which provides the following requirements:

1) the conversion of light beams from sources into one or more outgoing light beams of a larger cross section;

2) ensuring a more uniform brightness of the outgoing beams over the cross section;

3) ensuring high efficiency in input-output of light radiation;

4) providing a given direction (directions) of the emerging beams.

The need for high efficiency in input / output of light radiation is one of the differences between lighting panels and screen panels (for example, computer monitors, US 7554626). In the latter, if the uniformity of illumination of the working surface (screen) is necessary, a high (i.e., comparable to the power necessary for lighting) output power and, accordingly, the efficiency of the panel-screens for input-output radiation may not be high.

A disadvantage of the known lighting panels (for example, RU 95886 is their complex device, since the transmission of radiation from sources along the panel and the output of radiation from the panel and the formation of the output light beam occur in different structural elements: in optical fibers and light-scattering elements, respectively. This increases the number of structural elements Another drawback is the incomplete solution of the panel tasks (low quality of lighting), in particular, the uniform brightness of radiation over the cross section of the output light guide about the beam and providing the specified direction of the beam. In the present invention, these disadvantages are eliminated by combining the functions of transmitting radiation from sources along the panel and the function of outputting radiation from the panel and forming the output light beam in a single structural element.

The proposed light panel is a wedge-shaped light guide or a prism (Figure 2) of a transparent material (for example, glass) with flat or curved (Figure 5) working surfaces 21 - large surfaces of the wedge. Sources of radiation 22 (for example, LEDs) are placed at the end (smaller) surface of a given fiber. As can be seen in Figure 2, there are no special light-scattering elements, and light scattering occurs during the propagation of radiation along the fiber due to its wedge-shaped shape.

The principle of operation of the proposed light panel is also illustrated in FIG. 2, which describes the radiation transfer and output from the proposed wedge-shaped light panel, where φ _* is the angle of total internal reflection, α is the angle at the apex of the wedge-shaped fiber, θ is the angle at which the beam from the source 22 falls on the end surface of the fiber, φ ₁ , φ ₂ , ..., φ _k are the angles at which 1, 2, ..., k-oe reflections occur inside the fiber.

< φ_*=arcsin(1/n) - угла полного внутреннего отражения для материала световода с показателем преломления n. При отражении k_* и последующих свет начнет выходить из световода наружу. Таким образом, на начальном этапе распространения света при k < k_*(θ) происходит его перенос вдоль панели без выхода наружу, а затем при k ≥ k_*(θ) - и перенос и выход излучения наружу. Лучи источника с большим углом (относительно оси световода будут выходить ближе к входного торцу световода, а лучи с меньшим θ - дальше от торца. Таким образом обеспечивают равномерность выхода излучения с боковой поверхности световода. Принцип работы световой панели с неплоскими (искривленными) рабочими поверхностями аналогичен изложенному выше, изменится лишь выражение для φ_k.For simplicity, we consider a wedge-shaped light guide with flat working surfaces. The beam from the source, having an angle relative to the axis of the fiber, experiences the first reflection at an angle φ ₁ = π / 2-θ-α / 2, from the left working surface of the fiber and passes further. After the second reflection (reflection from the right working surface) φ ₂ = π / 2-θ-3α / 2, after the k-th - φ _k = π / 2-θ-α (k-1/2), i.e. φ _k decreases with each reflection. Thus, with some reflection k _* (θ) (in Fig. 2 k _* (θ) = 2) it turns out that

<φ _* = arcsin (1 / n) is the angle of total internal reflection for the fiber material with a refractive index n. Upon reflection of k _* and subsequent light starts to go out of the fiber. Thus, at the initial stage of the propagation of light for k <k _* (θ), it is transported along the panel without going outside, and then for k ≥ k _* (θ), the radiation is transferred and released to the outside. The rays of the source with a large angle (relative to the axis of the fiber will go closer to the input end of the fiber, and rays with a smaller θ - further from the end. This ensures uniform output of radiation from the side surface of the fiber. The principle of operation of the light panel with non-planar (curved) working surfaces is similar above, only the expression for φ _k will change.

Figure 3 shows a set of fictitious radiation sources - images of a source located at the end (input) surface of the panel. When calculating the provisions of fictitious sources, for simplicity, it was assumed that the present source was placed in the material of the fiber. Fictitious sources give the same lighting as this light panel (wedge-shaped light panel with flat work surfaces). The numbers 0, 1, 2 ... correspond to the number of light reflection of the source from the working surfaces of the panel. Bold dotted arrows show the directions of the total light beams from the right and left working surfaces of the panel.

Thus, the light panel is equivalent to replacing radiation from the input source with radiation from a larger number of fictitious image sources. Such a replacement of one source by several leads to a more uniform distribution of brightness over the section of the output beam of the panel than the distribution of brightness of the original source. Figure 3 also shows that from a unidirectional source beam, the panel forms light beams in two directions. Directivity patterns with two directions of propagation of light beams are practically necessary, for example, for outdoor lighting devices. In Fig. 3, part of the fictitious sources (see the source lying below the horizontal line) emits in the direction opposite to the direction of light (from top to bottom) from the original source. Such fictitious sources correspond to reflected radiation; they determine the efficiency of a given light panel. For small angles (the backward reflection occurs after the light in the panel has experienced a sufficiently large number of forward reflections. For example, for the angle α in Figure 3, the backward reflection occurs after 5 reflections. Thus, for small α, the backward reflection loss is small, and the efficiency of the panel exceeds 90%. For a given angular distribution of the input source, the properties and characteristics of the panel with flat working surfaces are determined by the angle α at the wedge tip and the refractive index n of the panel material. single light beams and the ratio of the brightness of light beams can be changed due to the curvature of the working surfaces of the panel.

An analysis of the position of fictitious sources (images) for a real source located outside the fiber shows that its images are “smeared” and are short luminous filaments located in the same place as the point images of the source and directed along the radii of circles in Fig. 3.

Figure 4 shows a wedge-shaped optical fiber with curved working surfaces. In this example, the surface of the panel is selected in such a way as to provide output radiation, mainly only on one side of the panel. On the other hand, radiation is practically not output, despite the fact that there are no separate reflective elements (mirror coatings) on this side of the panel. The absence of reflective elements simplifies the design and increases the reliability of the panel, because it does not contain mirror elements, such as metallized coatings susceptible to corrosion. The principle of constructing a light panel with a curved coating, where radiation is provided, mainly on the one hand, is explained using Figure 4. The arrows in Figure 4 indicate the directions of the propagation of rays in the panel and outside it.

между крайним лучом 42 от источника и нормалью к плоскому элементу 43 поверхности, от которого совершается первое отражение, должен быть равен углу θ_*=arcsin(1/n) полного внутреннего отражения для материала панели с показателем преломления n. Например, для панели из стекла с n=1.536 на Фиг.4 θ_*=40.6°. Все лучи, лежащие между крайними лучами 42 и 44 источника, будут испытывать полное внутреннее отражение от элемента 43 поверхности, так как соответствующие этим лучам углы падения θ⁽¹⁾:

, где

- угол падения крайнего луча 44 от источника, здесь и далее верхний индекс в скобках соответствует номеру отражения. Таким образом, при первом отражении излучение от источника не выходит за пределы панели. Свет источника, полностью отраженный от элемента поверхности 43 внутрь световой пластины, доходит затем до плоского элемента 45 ее боковой поверхности 4100. Элемент 45 повернут относительно элемента 43 (вертикального на Фиг.4) против часовой стрелки на угол γ, поэтому углы падения θ⁽²⁾ лучей от источника на элемент 45

т.е. все лучи от источника, за исключением самого крайнего луча с углом падения

при отражении от элемента 45 частично выходят наружу. После частичного отражения от элемента 45 свет от источника доходит до плоского элемента 46 поверхности 4200, который повернут относительно элемента 45 на угол γ, т.е. на угол 2γ относительно вертикали. Так же, как и для элемента 44, все лучи от источника будут испытывать полное внутреннее отражение от элемента 46 и, следовательно, не будут выходить наружу из панели. Затем лучи, отраженные от элемента 46, доходят до элемента 47 поверхности 4100, элемент 47 повернут относительно элемента 46 на угол γ (т.е. на угол 3γ относительно вертикали) против часовой стрелки, поэтому, также как и для элемента 45, ни один из лучей источника (кроме самого крайнего) не будет испытывать полного внутреннего отражения от элемента 47, и все они будут частично выходить через элемент 47 наружу. Аналогичным образом строятся остальные элементы панели, при этом используются построение изображений источника как, например, изображения 48, 49, 410 на Фиг.4. Из Фиг.4 видно, что после достаточно большого числа отражений часть света начнет выходить через поверхность 4200: там показаны направления 411 выхода света из поверхности 2400 4-м отражении от нее.There is a point light source 41 with an aperture of radiation with an angular divergence γ, formed, for example, by a lens or aperture. For the case of FIG. 4, γ = 12 °. The spatial configuration of the side surfaces of the panel 4100 (left) and 4200 (right) and the direction of the maximum radiation of the source are selected so that the radiation from the source, for a certain number of reflections in the panel, experiences total internal reflection from the surface 4200 and does not go out, but does not experience complete internal reflection from the surface 4100 and, therefore, partially exits through this surface to the outside at each reflection. The corresponding shape of the surfaces 4100 and 4200 can be determined, for example, according to the following algorithm. The radiation from the source hits the surface of the panel 4200 and experiences the first total internal reflection there: for this, the angle of incidence

between the extreme beam 42 from the source and the normal to the flat surface element 43 from which the first reflection occurs, should be equal to the angle θ _* = arcsin (1 / n) of total internal reflection for the panel material with a refractive index n. For example, for a glass panel with n = 1.536 in FIG. 4, θ _* = 40.6 °. All rays lying between the extreme rays 42 and 44 of the source will experience total internal reflection from the surface element 43, since the angles of incidence θ ⁽¹⁾ corresponding to these rays:

where

- the angle of incidence of the extreme beam 44 from the source, hereinafter, the superscript in parentheses corresponds to the reflection number. Thus, during the first reflection, the radiation from the source does not extend beyond the panel. The source light, which is completely reflected from the surface element 43 inside the light plate, then reaches the flat element 45 of its side surface 4100. The element 45 is rotated relative to the element 43 (vertical in FIG. 4) counterclockwise by an angle γ, therefore, the angles of incidence θ ^{(2 )} rays from the source to the element 45

those. all rays from the source, except for the most extreme ray with an angle of incidence

when reflected from the element 45 partially go outside. After partial reflection from the element 45, the light from the source reaches the flat element 46 of the surface 4200, which is rotated relative to the element 45 by an angle γ, i.e. at an angle of 2γ relative to the vertical. As with element 44, all rays from the source will experience total internal reflection from element 46 and, therefore, will not go out of the panel. Then, the rays reflected from the element 46 reach the element 47 of the surface 4100, the element 47 is rotated relative to the element 46 by an angle γ (i.e., by an angle 3γ relative to the vertical) counterclockwise, therefore, as with element 45, none from the rays of the source (except the most extreme) will not experience complete internal reflection from the element 47, and all of them will partially go out through the element 47. Similarly, the remaining elements of the panel are constructed, using the construction of source images such as, for example, images 48, 49, 410 in Figure 4. Figure 4 shows that after a sufficiently large number of reflections, part of the light will begin to exit through the surface 4200: there are shown directions 411 of light exit from the surface 2400 of the 4th reflection from it.

The effectiveness of this panel in this way should be characterized, incl. the relative fraction of the radiation energy of the source exiting through the surface 4100. The mentioned efficiency of the light panel can be estimated using the well-known expressions for the amplitude reflection coefficients

light wave fields of various (normal and parallel to the plane of incidence of the beam) polarizations. Here θ, θ 'are the angles of incidence of the light ray in the panel and its continuation outside the panel, respectively, nsinθ = sinθ'. Using the energy conservation law for the incident, transmitted, and reflected from the interface media radiation in the form ncosθ = T _{||, ⊥} (θ) + nr ² _{|, ⊥} (θ) cos (θ), we can obtain the transmission coefficients T _{||, ⊥} (θ) in intensity (brightness) of the radiation. To assess the brightness of radiation emitted from the panel, it is enough to take the average transmission coefficient of the field and the angle of incidence

Using the last formula, it can be found that in the case of Fig. 4, after the first reflection from the panel surface 4100, T _av = 0.701 will come out of it, i.e. 70% of the radiation, after the second -T _av (1-T _av ) ₂ = 0.209-21%, and after the third -T ^av (1-T _av ) ² = 0.062-6%.

Thus, the efficiency of this panel for outputting radiation through the surface of 4200 is at least 70 + 21 + 6 = 97%. The rest of the source radiation can partially exit through the opposite surface 4100. By changing the aperture of the source, another distribution of the energy of the output radiation after reflections can be obtained. For example, estimates for a smaller aperture γ = 4 ° than in Figure 4 give that after the first, second, and third reflections, 56%, 25%, and 11% of the radiation energy will leave the panel, respectively, and the panel efficiency will be 92%.

This construction and an example of the conversion of panel radiation due to the curvature of its surface are not the only ones possible. This panel can be optimized, including by selecting its optimal thickness - depending on the aperture of the source. The working surfaces of the panel may have straightened corners. A more general case of a source with a wider aperture (limited, for example, by beam 412 in FIG. 4) can be realized so that the rays of only part of the aperture exit the panel, and the rays of the other part experience total internal reflection both on surface 4100 and on surface 4200. In this case, the power radiated by the panel in different areas can be controlled by tilting the surface of the corresponding area, for example, so that the part of the source aperture containing the light coming out of the panel increases with increasing reflection number. This will allow you to distribute the radiated power on the surface of the panel. The data on the implementation of the light panel is somewhat more complex than that indicated in Figure 4, in principle, do not differ from the example presented in Figure 4. Other examples of panels with curved surfaces can be implemented to meet customer needs. For example, due to surface curvature, a panel can form several light beams of different directions. For example, figure 5 presents a panel with cylindrical surfaces, the generators of which are circles of radii R _w and R _d , the centers of the circles are offset by a distance Δ. In this case, the radiation output from the side of the lower (radius R _d <R _w ) surface of the panel practically does not occur due to the effect of total internal reflection, the entire radiation output occurs only from the side of the upper (radius R _w ) surface.

Claims (6)

1. A light panel with an end input of radiation, comprising a light guide panel element and a radiation source, characterized in that the light guide panel element is a light guide made in the form of a trihedral prism, one side face of which is smaller than the other two side faces, the radiation source being placed in front of said smaller side face. 2. The panel according to claim 1, characterized in that the said two other side faces are made with flat surfaces. 3. The panel according to claim 1, characterized in that the said two other side faces are made with non-planar surfaces. 4. The light panel with the end input of radiation, containing the light guide panel element and the radiation source, characterized in that the light guide panel element is a light guide made in the form of a multifaceted prism, while the radiation source is placed in front of one of the aforementioned side faces of the said light guide, and others said lateral faces form a convex polyhedral surface for outputting radiation from said radiation source and a concave polyhedral surface for reflecting radiation from said of said radiation source, respectively. 5. The panel according to claim 4, characterized in that the side faces of said polyhedral surfaces are flat surfaces. 6. The panel according to claim 4, characterized in that the side faces of said polyhedral surfaces are non-planar surfaces.

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