This invention relates, in general, to an optical device for LED lighting appliances designed for ordinary and/or emergency lighting applications. More specifically, the invention relates to a lens for LED lighting appliances, that is, an optical device comprising a hybrid system which exploits a light guide to bring the light to a zone of the lens where it is possible to extract it in a controlled manner, thanks to specific geometries, in order to obtain a photometric solid designed for ordinary lighting and emergency lighting applications and in order to have an illuminated surface which is large and such as to reduce glare.

A correct ordinary and emergency lighting must guarantee, in the field of vision, sufficiently high and rationally distributed lighting to allow the perception of important areas; in particular, the emergency lamps must guarantee a sufficient luminous flux to allow an easy and fast identification of the escape routes, especially in the case of danger.

On the other hand, a correct ordinary lighting must reduce glare as much as possible with adequate illumination and uniformity in the field of view. Amongst the various embodiments used for LED lighting, a first type of LED lighting appliances are still known, which have a continuous panel of LEDs for direct light diffusion, and a second type of LED lighting appliances, which are equipped with a series of lenses positioned in a substantially central area of the appliance.

Although the first type of appliances has the advantage of having a very low luminance and therefore a minimum glare, further drawbacks are determined by the yellowing of the surface, the low thermal dissipation of the LED diodes and the constructive complexity of the structure.

On the other hand, LED lighting appliances equipped with central lenses, despite a simple construction of the structure, an excellent thermal dissipation of the LED diodes and the absence of yellowing phenomena, have a high luminance and, therefore, glare phenomena due to the exposed LEDs.

The aim of the invention is therefore to make an LED lighting appliance, which is able to achieve a minimum luminance, in order to limit glare phenomena, whilst maintaining, at the same time, an excellent thermal dissipation of the LEDs and avoiding yellowing phenomena of the surface and/or of the structure.

Within the context of the above-mentioned aim, the purpose of the invention is to make a compact optical system, which is able to produce a photometric solid designed to satisfy the standards regarding ordinary and emergency lighting with a good visual comfort, therefore with a reduced luminance, starting from a spot or linear light source.

A further aim of the invention is to make an optical device which can be incorporated in an LED lighting appliance and which has a relatively simple, safe and reliable construction, using substantially known technologies and relatively inexpensive components.

These and other aims according to the invention are achieved by making an optical device or lens, designed to be mounted in an ordinary and/or emergency LED lighting appliance, according to appended claim 1 .

Further aims and advantages of an optical device for LED lighting appliances according to the invention will more fully emerge from the description which follows, of a non-limiting example, referred to the accompanying schematic drawings in which:

- Figure 1 is a perspective view of a preferred but non-limiting embodiment of an optical device used in the LED lighting appliance according to the invention;

- Figure 2 is a side view of the optical device of Figure 1 , according to the invention;

- Figure 3 is a plan view from above of the optical device of Figures 1 and 2, according to the invention;

- Figure 4 is a schematic cross-sectional view through the line IV-IV of Figure 2 of the optical device of Figures 1 and 2, according to the invention;

- Figure 5 shows the enlarged detail indicated by A in Figure 2, according to the invention;

- Figure 6 shows the enlarged detail indicated by B in Figure 4, according to the invention. With reference to the above-mentioned drawings, the LED lighting appliance, which is the object of the invention, comprises an optical device

10, advantageously of a hybrid type and having a central zone 11 , with a flat base where the LED light source is located, and peripheral elongated portions 12, specular with respect to the central zone 10, inside of which a light guide 13 is positioned, designed to bring the light coming from the light source to zones of the optical device 10 where it is possible to extract it in a controlled manner, thanks to specific geometries of the device 10; in this way, a photometric solid designed for ordinary lighting and emergency lighting applications is obtained, with the further advantage of a large illuminated surface such as to reduce glare.

The light extraction geometries for controlling the light in terms of photometric distribution are designed in order to have control in two perpendicular planes.

In particular, the optical device 10 allows the result to be obtained according to which substantially 100% of the light emitted by the LED light source is guided by total internal reflection inside the elongated portions 12 and there is no refracted direct light component.

In this way, the LED light source is never directly visible from the outside and the control is carried out entirely by the upper and lower structures of the elongated portions 12; this means that the structure of the optical device 10 allows the photometric distribution to be controlled on both the XZ and YZ planes.

More specifically, the optical device 10 consists of a central light input zone

11 , in which the LED light source is positioned, whose direct light emission has a direction of emission coinciding with the axis indicated with Z in Figure 1 , and a light guide 13, which, placed inside each elongated portion 12 and thanks to a curved profile, carries the light emission, coming from the LED light source (arrows F of Figure 2), towards the peripheral elongated portions 12, from where it can exit from the guide 13, in the plane XZ, at predetermined emission surfaces 15, having an internal structure with a well-defined geometry.

According to preferred embodiments of the invention, each internal structure of the respective elongated portion 12 has, at and along the entire length of the emission surface 15, a series of structural elements 16, with a preferably triangular shape, such as prisms and/or triangular tetrahedrons, placed in succession with each other and on opposite sides with respect to the emission surface 15.

Still preferably, the structural elements 16 have at least two sides, which form respective angles a, b predetermined and, advantageously, equal respectively to about 10° and 46°, with respect to the axis Z which is orthogonal to the surface 15; each of these angles a and b may however vary from 1 °to 89°.

Perpendicularly to the above-mentioned structural elements 16 and on the opposite side with respect to the light guide 13 (that is, in contact with each emission surface 15) there are further structural elements 17, preferably having a triangular cross-section, such as prisms and/or triangular tetrahedrons, placed in succession along the entire emission surface 15. Advantageously, the structural elements 17 have at least two sides, which form respective angles g, d which are predetermined and, advantageously, equal to each other and equal to about 76°, with respect to the axis Z which is orthogonal to the surface 15; each of the angles y and d may however vary from 1 °to 89°.

The control of the photometric distribution occurs, therefore, both on the plane YZ through the structural elements 17 of the surface 15, and on the plane XZ through the structural elements 16 formed on the opposite side with respect to the surface 15.

Consequently, the structured areas corresponding to the emitting surfaces 15 of the optical device 10 are illuminated with a medium-low glare light emission; in other words, by directly viewing the surfaces 15, the direct brightness of the LED source is not seen, as is the case with traditional appliances, since the emitting surface is in a more distant area (because the light is guided by the guide 13) and much larger than the surface of the LED source; thus, luminance is reduced.

In practice, the optical structures with variable geometry present on the elongated ends 12 of the optical device 10 are configured in such a way as to extract the light guided by the guide 13 and to emit it outside the optical device 10 according to suitable directions, which allow a suitable photometric solid to be formed, designed to produce the desired advantages.

The residual light, which is not extracted from the geometrical structures described above, is used to illuminate the ends or lateral zones 14, from which indirect light is emitted, that is, light having a direction facing the hemisphere behind the emission direction of the LED source (according to the direction of the axis -Z).

This contribution is important in order to ensure a quantity of ambient light designed to reduce the existing contrast with respect to the light extracted directly at the emission surfaces 15.

The optical device 10 thus achieves a direct light contribution and, at the same time, an indirect light contribution with medium-low glare. Lastly, the optical device 10 may have a length which is variable and dependent on the length of the light source.

It has been found in practice that the LED lighting appliance according to the invention is particularly innovative and advantageous and achieves the intended aims and advantages; in particular, amongst the above-mentioned advantages, the following should be noted:

- medium-low luminance to avoid glare;

- excellent LED dissipation;

- no yellowing of the structure;

- constructive simplicity.

The characteristics of the LED lighting appliance, according to the invention, clearly emerge from the description, as do the advantages thereof.

Lastly, it is clear that numerous other variants might be made to the LED lighting appliance in question, without thereby departing from the scope of the invention as expressed in the accompanying claims.