ITMI20082215A1 - LED LIGHTING DEVICE FOR LUMINOUS COLLIMATED HEADLAMPS AND DISTRIBUTION OF UNIFORM LIGHT - Google Patents

Description

LED LIGHTING DEVICE FOR DENTAL LAMPS WITH COLLIMATED BEAM AND UNIFORM LIGHT DISTRIBUTION

The present invention relates to a LED lighting device for dental lamps with a collimated light beam and uniform light distribution.

LED (light emitting diode) lighting devices are currently widely used in the lighting of environments or work areas which require luminance values lower than a predetermined threshold, for emission angles greater than a limit angle. These requirements are particularly relevant in the use of LED lighting devices in dental lamps as it is important to illuminate the area relating to the patient's mouth without however disturbing his eyes.

LED lighting devices for dental lamps generally include one or more light sources and an optical module which has the function of collecting and redistributing the light emitted by them so that the light rays are emitted by the lighting body at an angle of emission within a certain range.

Disadvantageously, the optical modules used in known LED lighting devices for dental lamps, in addition to being achievable only by complex and costly processes, can cause, as a side effect of the deviation of the light rays, a considerable decrease in the overall luminous flux emitted by the body. illuminating.

For example, some LED lighting devices for dental lamps are currently known in which the collimation of the light beam is obtained by passing the light of an LED source through a system of spherical polycarbonate lenses.

In order to obtain the desired collimation effect, these lenses have a considerable thickness. This makes obtaining them particularly complicated and expensive; in particular it is complicated to ensure an effective correspondence of the molded product with the imprint on the mold, generally obtaining optical modules with geometric imperfections. Such imperfections are often the cause of anomalous deviations of the light rays such as those shown in figures 5a-5c.

Furthermore, the large thickness causes a significant absorption of the light emissions from the source, thus considerably reducing the overall luminous flux emitted by the device.

Last but not least, in the case of several light sources, the spherical lenses are not able to make the light emission uniform, from which the emission bulbs clearly appear, separated by dark areas.

Another known LED lighting device for dental lamps is constituted by the emission of the direct light of a single source on a plurality of reflectors, which deflect the light in a suitable way.

In order to obtain the desired light emission, it is necessary to create perfectly calculated reflectors and surface treated by vacuum metallization so that they are able to deflect the light rays in the desired positions.

There is also a decrease in luminous performance due to the absorption of light by the metallization.

The purpose of the present invention is to obviate the aforementioned drawbacks and in particular to devise a LED lighting device for dental lamps which guarantees a good quantity of transmitted light and at the same time good effectiveness in controlling the photometric distribution.

Another object of the present invention is to provide a LED lighting device for dental lamps that allows to collimate the light rays emitted in a wide angular range, also guaranteeing a reduction in the amount of anomalous deviations, thus substantially eliminating unwanted glare effects. .

Not least object of the present invention is to provide a LED lighting device for dental lamps which can be made with simple processes and reduced costs.

These and other purposes according to the present invention are achieved by realizing an LED lighting device for dental lamps as set forth in claim 1.

Further characteristics of the LED lighting device for dental lamps are the subject of the dependent claims.

The characteristics and advantages of an LED lighting device for dental lamps according to the present invention will become more evident from the following description, which is exemplary and not limiting, referring to the attached schematic drawings in which:

Figure 1 is a sectional view of an embodiment of the LED lighting device for dental lamps according to the present invention;

Figure 2 is a perspective view in cut-away of a dental light using a LED lighting device according to the present invention; - figure 3 is a first partial schematic view of a LED lighting device for dental lamps according to the present intention;

Figure 4 is a second partial schematic view of a LED lighting device for dental lamps according to the present intention;

- figures 5a, 5b and 5c are a schematic representation of the anomalous deviations of the light rays generated by optical modules with geometry imperfections;

figures 6a, 6b and 6c are respectively a sectional view, a plan view and a perspective view of the internal lens of the LED lighting device for dental lamps according to the present intention; And

- figure 7 is a schematic representation of the deviation of the light rays emitted by the LED source due to the optical module of the LED lighting device for dental lamps according to the present invention;

Figure 8 is a schematic view of a cross-section of the internal lens in section of the LED lighting device for dental lamps according to the present intention.

With reference to the figures, a LED lighting device for dental lamps is shown, indicated as a whole with 10.

The LED lighting device 10 for dental lamps comprises a plurality of light sources s1, s2, â € ¦, s6a LEDs arranged aligned associated with an optical module 11 adapted to collect and redistribute the light emitted by the plurality of light sources s1, s2 , â € ¦, s6 in such a way that the light rays are emitted by the LED lighting device 10 with an emission angle included in a certain range.

The lighting device 10 has an elongated conformation, characteristic of dental lamps, having a main development direction A along which the light sources s1, s2, â € ¦, s6 are arranged aligned.

The lighting device 10 is preferably housed in a lamp body 20, as shown in Figure 2, in which there is also a dissipating element 21 placed in contact with at least one light source s1, s2, â € ¦, s6.

The optical module 11 comprises a pair of lenses L1, L2 of which a first internal lens L1Ã is made up of a plurality of flat elements 12a, 12b, 12c arranged inclined to each other on whose output surface 13 of the light rays there are prisms 14 constituting a Fresnel lens.

The flat elements 12a, 12b, 12c of the internal lens L1 are arranged inclined to each other at different angles so as to be oriented towards the focal length of the second external lens L2.

In particular, in a preferential embodiment in which six light sources positioned at a fixed distance D are used, the central elements 12a and the intermediate elements 12b, adjacent to them, are inclined to each other by a first angle γ1, while the outermost elements 12c are inclined with respect to the intermediate elements by a second angle γ2.

Each light source s1, s2, â € ¦, s6Ã is placed at a distance d1 from the input surface 15 of the light rays of the internal lens L1 and oriented in such a way that the nominal emission cone / -Î ± of this source s1, s2, â € ¦, if it is oriented towards the focal length of the L2 external lens.

Therefore, as shown in Figure 3, the resting surface 19 of the light sources s1, s2, â € ¦, s6a LED follows the development of the internal lens L1, also being made up of portions 19a, 19b, 19c inclined to each other.

In particular, the central portion 19a and the intermediate portions 19b are inclined to each other by the first angle γ1, while the outermost portions 19c are inclined with respect to the intermediate portions of the second angle γ2.

On the internal lens L1 the dimensions of each flat element 12a, 12b, 12c on which a Fresnel lens is made, of the first and second angle γ1e γ2 of relative inclination between these elements, of the angles of the Fresnel prisms 14 and of the distance d1 between the light sources s1, s2, â € ¦, s6 and the internal lens L1 are linked to the quantity of light that you want to intercept. The greater the distance between sources s1, s2, â € ¦, s6 and the internal lens L1, the greater the quantity of light intercepted by this lens.

However, in this case, in order to appropriately intercept and direct the entire light cone it is necessary to have a flat element 12a, 12b, 12c of larger dimensions on which a Fresnel lens with sufficiently large prisms is made, thus requiring similar thicknesses. to those of the known art and subject to the same disadvantages.

In fact, a limit to this increase is defined by the exit angles of the mold with which the internal lens L1 is produced in order to avoid geometric imperfections in the shape of the lens.

In the preferred embodiment illustrated, in which the square flat elements have dimensions that can vary between 20 and 35 mm on each side, the first and second angle of inclination γ1 and γ2 have dimensions between 2 ° -4 ° and 6 ° -8 ° respectively. and the distance d1 between the light sources s1, s2, â € ¦, s6 and the internal lens L1à is between 13-17 mm, most of the emission of the plurality of light sources s1, s2, â € ¦, s6 is collected and uniformly and collimated by the first lens L1 towards the second lens L2, as shown in figure 7, while ensuring an optimal realization of the internal lens L1.

In this configuration it is in fact possible to define the prisms 14 of the internal lens L1 in such a way as to optimize its efficiency, compatibly with the nominal efficiency of the plurality of light sources s1, s2, â € ¦, s6.

According to the present invention, the geometric shape of the single prisms 14 derives from a mathematical calculation which correlates the angle Î ± 1, Î ± 2 of incidence of the light ray 22 on the surface 15 of the incoming light rays of the internal lens L1, the refractive index n of the material, the focal distance d1, as well as the angle β between the light ray 23 exiting the internal lens L1 and the exit surface 13 of this lens L1, wanting to obtain a light ray 23 in outlet orthogonal to the inlet surface 15 of the internal lens L1.

Considering that the angle Î ± 1, Î ± 2 of incidence of the incoming light ray 22 varies with the distance between the C axis of the corresponding plane element 12a, 12b, 12c and the E axis of the single source s1, .., s6, inclinations of the output surface 13 of the internal lens L1 are obtained which vary from one prism 14 to the other.

The external lens L2 has a curved conformation and is characterized by an entrance surface 16 for the light rays having a first main development curve C1 on which cylindrical optics 17 are made, and by an exit surface 18 for the light rays having a second curve of main development C2.

Preferably, this external lens L2 has the radii of curvature of the first and second main development curves C1, C2 respectively comprised in the intervals 270 mm <C1 <280 mm and 280 mm <C2 <290 mm. The correlation between these two curves C1 and C2 allows to obtain a more or less accentuated closure of the light beam 24 exiting in the direction perpendicular B to the main development direction A of the lighting device 10.

The optics 17 of the second lens L2 have a cylindrical shape and a constant pitch.

In the preferred embodiment, the radius R of the cylindrical optics 17 varies between 17 mm and 20 mm, and the pitch varies between 2 mm and 3.5 mm. The correlation between these two quantities allows to obtain a more or less accentuated closure along the main development direction A of the lighting device 10.

Due to the effect of the cylindrical optics 17 present on the entrance surface 16 of the light rays and of the particular main curves C1, C2 of their development, it is able to refract and direct the beam while keeping it within the required angular interval. The relative positioning of the two internal and external lenses L1, L2 also allows to generate a uniform beam even in the presence of sources s1, s2, â € ¦, s6 point-like and discrete as they are separated from each other by a fixed distance D.

This positioning is crucial in order to give sharpness, uniformity and geometric characterization to the resulting luminous shape.

The law that regulates the relative distance between the two lenses L1 and L2 is of inverse proportionality to the magnitude of the relative inclination angles γ1 and γ2 between the flat elements 12a, 12b, 12c of the internal lens L1. In particular, decreasing the distance between L1 and L2 increases the sharpness and focus of the resulting total image.

In the illustrated embodiment, in the center (source s3), in which the relative inclination is zero, this central element being taken as a reference, the relative distance between the two lenses L1 and L2 is preferably between 10-18 mm, while at the extremes, in which the second angle of inclination γ2à ̈ between 6 ° -8 ° (source s1) the distance between the two internal and external lenses L1e L2à preferably between 4-10 mm.

Along the main development direction A of the illuminating device 10, the positioning is calibrated so that the cusps of the prisms 14 coincide with all the junctions of the flat elements 12a, 12b, 12c constituting the internal lens L1, as shown in figure 6b.

In the preferred embodiment in which six light sources s1, s2, â € ¦, s6 are used, these sources consist of LEDs with direct emission of light similar to "white light" characterized by a color degree K higher than 5500. The flat elements 12a, 12b, 12c associated with each LED source s1, s2, â € ¦, s6 can be combined into a single plastic element constituting the internal lens L1 on which a Fresnel lens is made in correspondence with each light source s1, s2, â € ¦, s6.

Said internal lens L1 can be obtained by single molding thanks to the particular conformation of the individual Fresnel lenses made on their own output surface 13 of the light rays which have both a concentric development of the prisms 14 and appropriate critical extraction angles from the mold.

In particular, Fresnel lenses consist of a series of blocks with slightly ovalized optical steps, the geometries of which are performed according to a turning with a diamond tool, also taking into account the variations necessary for the mold exit.

The printing elements, in particular the Fresnel dowels, are built with tools of nanometric geometry that allow to directly obtain prismatic elements having mirror polished surfaces with connecting edges between 0.01 and 0.03 mm and preferably equal to 0, 02 mm.

The ovalization of some sectors of the Fresnel optic prism 14 is obtained through the synchronized angular variation of the tool, of the rotation axis of the piece to be machined.

The L1Ã lens is obtained by means of a vacuum injection-compression molding which allows to obtain an optimal filling of the edges of the mold. In this way prismatic elements are obtained free of deformations, lack of filling and / or suction shown in figures 5a-5c. It is thus possible to eliminate the deviations of the light rays due to such geometric inaccuracies.

Preferably, for the realization of the lenses L1, L2 a material with a particularly high degree of fluidity and with characteristics such as to preserve the optical properties over time is used, such as for example a polymethylmethacrylate (PMMA).

From the above description the characteristics of the device object of the present invention are clear, as well as the relative advantages. The LED lighting device for dental lamps according to the present invention guarantees a good efficacy in controlling the photometric distribution while also maintaining a good quantity of transmitted light due to the reduced thickness of the internal lens obtainable thanks to the particular shape of the optical module.

Last but not least, this conformation allows the use of lenses with a particular geometry which can be made quickly and reliably.

Finally, it is clear that the device thus conceived is susceptible of numerous modifications and variations, all falling within the scope of the invention; furthermore, all the details can be replaced by technically equivalent elements. In practice, the materials used, as well as the dimensions, can be any according to the technical requirements.

Claims (10)

CLAIMS 1) LED lighting device (10) for dental lamps presenting an elongated development with main development direction (A) characterized by the fact that it comprises a plurality of LED light sources (s1, s2, â € ¦, s6) arranged aligned along said main development direction (A), and an optical module (11) adapted to collect and redistribute the light emitted by said plurality of light sources (s1, s2, â € ¦, s6), said optical module (11) comprising a pair of lenses (L1, L2), of which an internal lens (L1) of said pair of lenses (L1, L2) consists of a plurality of flat elements (12a, 12b, 12c) each associated with a light source of said plurality of light sources (s1, s2, â € ¦, s6), on an output surface (13) of the light rays of each of said flat elements (12a, 12b, 12c) being made of prisms (14) constituting a Fresnel lens, said flat elements (12a, 12b, 12c) being arranged inclined to each other in such a way as to be oriented towards the focal length of an external lens (L2) of said pair of lenses (L1, L2). 2) LED lighting device (10) for dental lamps according to claim 1 characterized in that the emission cone (+/- Î ±) of each of said light sources (s1, s2, â € ¦, s6) à It is oriented towards the focal length of said external lens (L2). 3) LED lighting device (10) for dental lamps according to claim 1 or 2 characterized in that each light source of said plurality of light sources (s1, s2, â € ¦, s6) is spaced from each other the other of a first fixed distance (D) and is placed at the same second fixed distance (d1) from an inlet surface (15) of the light rays of said internal lens (L1). 4) LED lighting device (10) for dental lamps according to any one of the preceding claims characterized by the fact that said plurality of light sources (s1, s2, â € ¦, s6) is arranged on a supporting surface (19) consisting of a plurality of surface portions (19a, 19b, 19c), said surface portions (19a, 19b, 19c) being arranged inclined to each other in such a way as to be oriented towards the focal length of said external lens (L2). 5) LED lighting device (10) for dental lamps according to any one of the preceding claims characterized in that the inclination (β) of said prisms (14) with respect to said inlet (15) of the light rays depends on the angle (Î ± 1, Î ± 2) of incidence of a light ray (22) on said surface (15) of entry of the light rays of said internal lens (L1), from the refractive index (n) of the material said internal lens (L1) and from said fixed distance (d1), wanting to obtain an output light beam (23) orthogonal to said inlet surface (15) of said internal lens (L1). 6) LED lighting device (10) for dental lamps according to any one of the preceding claims, characterized in that said prisms (14) constituting a Fresnel lens are ovalized. 7) LED lighting device (10) for dental lamps according to any one of the preceding claims characterized in that said second lens (L2) of said pair of lenses (L1, L2) is a curved lens having an entrance surface ( 16) of the light rays with a first main development curve (C1) and an exit surface (18) of the light rays with a second main development curve (C2), on said entrance surface (16) of the light rays being made a plurality of cylindrical optics (17) arranged at a constant pitch. 8) LED lighting device (10) for dental lamps according to any one of the preceding claims characterized by the fact that said internal lens (L1) and said external lens (L2) are mutually spaced according to a law of inverse proportionality to the magnitude of the angles of relative inclination (γ1, γ2) between said flat elements (12a, 12b, 12c) of said internal lens (L1). 9) LED lighting device (10) for dental lamps according to any one of the preceding claims characterized by the fact that said flat elements (12a, 12b, 12c) are combined in a single plastic element constituting said internal lens (L1), the cusps of said prisms (14) collimating with the junctions of said flat elements (12a, 12b, 12c). 10) Dental lamps comprising a lamp body (20) in which at least one lighting device is mounted, characterized in that said at least one lighting device is a LED lighting device (10) according to any one of the preceding claims.