ITVR20100153A1 - DIFFUSION LENS FOR SPREADING LIGHT EMITTED BY A PUNCTUAL SOURCE - Google Patents

Description

DIFFUSION LENS FOR DIFFUSING LIGHT EMITTED FROM A SOURCE

PUNCTIFORM

The present disclosure generally relates to lenses used to diffuse the light emitted by point light sources.

More particularly, the lens according to the present disclosure is suitable for being placed next to other identical lenses to form a multiple lens able to diffuse the light emitted by several sources organized in a rectangular array of rows and columns of point sources, uniformly on a rectangular area.

LEDs (acronym for Light Emitting Diode) are almost point-like light sources that emit most of the light energy according to a circular symmetry, typically in a conventional cone with a vertex angle of about 120 °. The light intensity is maximum along the axis of the cone and is reduced to about half along a direction inclined by 60 ° with respect to the direction of maximum intensity, i.e. at the edge of the light cone, beyond which it is further reduced for greater angles. until it vanishes completely at about 90 °. The light pattern is visible with reference to a characteristic curve A in Figure 3 of the figures attached to the present disclosure.

In lighting fixtures, the light generally generated by an array of LEDs must be distributed through lenses designed to determine an appreciable uniformity on the illuminated area and reduce the glare that intense point sources such as LEDs could cause.

A problem associated with the use of LED sources, as well as other point light sources such as optical fiber terminations and similar devices, lies in the fact that the solutions designed to produce an accentuated uniformity of illumination penalize the intensity of illumination on a target area, and vice versa.

Various LED lighting fixtures with light diffusion lenses with accentuated directivity characteristics are on the market to favor an adequate level of illumination over an area relatively distant from the LED source, as is typical for headlights and street lighting fixtures, for example. but to a good extent also for lighting environments such as porches, rooms and corridors. The manufacturers of LED street lights also tend to manufacture their own diffusion lenses to be placed in front of the individual LED array point sources that allow them to satisfy certain contractual technical specifications.

However, the results are often unsatisfactory as the lenses used are mostly elliptical in shape, consequently creating shadow areas due to an accentuated concentration of the light beam along the optical axis of the lens.

The rare cases where a more satisfactory optical solution has been implemented, this proved to be very complex to implement and very expensive.

It should also be noted that the legislation currently in force on the subject establishes precise conditions as regards street lighting, with a uniformity coefficient equal to 0.4, while as regards the illuminated area it must be: longitudinally of 3 , 7 times and 1, 5 times transversely the height of the support pole of the street light.

In order to obtain an approximately rectangular symmetrical flux, also suitable for the illumination of rooms, in the case of street projectors, relatively high and narrow lenses (even 4.15 cm thick) are currently built, mounted in metal frames that prevent the lateral light scattering. These lenses have a decent yield, but remain complicated and expensive to build.

The most common commercial elliptical lenses, arranged at different angles, have poor performance and are difficult to assemble with the other parts of the projector. In fact, to obtain a more homogeneous luminous flux on the illuminated area, an attempt is made to compensate for the lower flux at the edges of the illuminated rectangular area by tilting the LEDs outwards, but this penalizes the yield as the inclination on one side subtracts a part of the luminous flux otherwise destined for the central part of the illuminated area.

According to another technique, light conveying channels are created in the lens body, which is difficult to produce in lenses that can be manufactured at low cost, typically by injection molding of suitable transparent thermoplastic material.

More often the uniformity of illumination is peacefully sacrificed in order to use higher efficiency light sources, such as LEDs, to reduce energy consumption, using simple elliptical lenses that produce light spot lighting with a very annoying light / dark effect. , as well as dangerous for driving.

In the present context, the term "lens" means, from time to time, both the single optical structure of diffusion of the light emitted by a single point source, such as for example an LED, and, as commonly used in the industry of lighting fixtures illumination of relatively large areas distant from the luminaire, using arrays of numerous point light sources organized in rectangular rows and columns, a multiple lens including a rectangular monolithic structure, adapted to be arranged in front of a rectangular array of point sources, in the which are replicated, with the same array organization, single optical structures so that each optical structure (single lens) is perfectly aligned with a respective point light source of the underlying array.

A new lens has been found capable of diffusing the light generated by a point light source (for example an LED) with accentuated uniformity and almost rectangular symmetry, on a distant rectangular area to be illuminated, whose longer side can be even more twice the shorter side.

This result is achieved with a lens of suitable transparent optical material, a first face of which is substantially flat with the exception of at least one point or points in which there is a depression, or a circular recess, relatively shallow, which may have for for example a spherical or conical dome profile (forming a concave surface), and which is placed in front of a point light source (commonly an LED) which identifies the center and the optical axis of the lens of diffusion of the light emitted by the point source, and through the concave surface of which the luminous flux enters the optical material (medium) of the lens.

On the opposite face, and in correspondence with each circular inlet cavity of the luminous flux emitted by a point source, there is an optical structure in relief whose base imprint, on the plane from which it rises, can be inscribed in a rectangular envelope perimeter . The optical structure of the lens includes two identical salient lobes, preferably with rounded perimeter edge, mirrored together by a central saddle depression (saddle) whose central point of minimum elevation and minimum width with respect to the maximum elevation and width of the two identical lateral lobes, is located in correspondence with the optical axis of the point light source and the center of said circular recess for inlet of the light flux in the transparent medium of the lens.

A lens thus made has a bi-lobed shape with an accentuated central narrowing, which defines, on opposite sides or sides of the optical structure, two recesses or hollows or recesses.

Optionally, although preferably, on the flat face opposite to the face from which the raised optical structure of the lens rises, associated with the inlet hollow of the luminous flux emitted by the juxtaposed point source, there are two notches (claws) which can be almost parallel to each other and to the longitudinal symmetry axis with respect to the optical structure with imprint that can be inscribed in a rectangle, deeper than the circular cavity and practically tangent or secant to said less deep circular concavity.

In one embodiment, the profile of the footprint at the base of the central part of the salient structure in the form of a sheer joining the two salient lobes together, can overlap, in geometric projection, an arched edge of the steep inner side of said parallel notches "Claw", while an almost straight edge of the opposite side of the claw, rising from the bottom of the carving with a reduced inclination, can lie, in geometric projection, under the longest side of the envelope rectangle of the optical structure of the lens.

Said lateral notches can also have geometries different from that of a "claw". Alternatively, narrow straight "U" or "V" trenches can be formed along the opposite sides of the circular flow inlet concavity.

The salient structure of each individual lens therefore has a major or longitudinal axis of symmetry and a minor or transverse axis of symmetry, both passing through the point of minimum elevation and minimum width of the joining saddle between the two salient lobes with edge rounded and coincident with the optical axis of the circular recess and the point light source.

While the accentuated uniformity of the rectangular symmetrical flux produced by the diffusion lens associated with a point source is the result of the peculiar bi-lobed geometry with dividing saddle of the luminous flux, entering through the concave surface of the circular recess, towards the two lobes of the optical structure with rectangular development, the notches along diametrically opposite sides of the circular entrance concavity hinder the lateral diffusion of light in the optical medium of the lens, confining it and usefully conveying it towards the saddle crossed by the optical axis of the structure in relief on the opposite face of the lens. This helps to increase the yield by significantly reducing losses due to lateral scattering of light.

Therefore, a particularly preferred embodiment of the lens of the present disclosure also provides for the presence of such parallel notches, in order to improve the illumination yield.

The invention is defined in the attached claims.

Other advantages, characteristics and methods of use of the object of the present disclosure will become evident from the following detailed description of its preferred embodiments, given by way of example and not of limitation.

However, it is evident that each embodiment can have one or more of the advantages listed above; in any case, it is not however required that each embodiment have all the listed advantages simultaneously. It is also to be understood that, within the scope of the present disclosure, all the possible combinations of the previously indicated embodiments and those described with reference to the following detailed description fall within the scope of the present disclosure.

Reference will be made to the figures of the attached drawings, in which:

Figure 1 is a plan view of the optical structure of the lens according to a preferred exemplary embodiment, in which planes or lines of transverse and longitudinal section of the structure are identified.

- Figure 2A is a sectional view along the line A-A of Figure 1.

- Figure 2B is a sectional view along the line B-B of Figure 1.

- Figure 2C is a sectional view along the line C-C of Figure 1.

- Figure 2D is a sectional view along the line D-D of Figure 1.

- Figure 2E is a sectional view along the line E-E of Figure 1.

- Figure 2F is a sectional view along the line F-F of Figure 1.

- Figure 2G is a sectional view along the line G-G of Figure 1.

- Figure 2H is a sectional view along the line H-H of Figure 1.

- Figure 2J is a sectional view along the line J-J of Figure 1.

- Figure 2K is a sectional view along the line K-K of Figure 1.

- Figure 2L is a sectional view along the line L-L of Figure 1.

- Figure 2M is a sectional view along the line M-M of Figure 1.

- Figure 2N is a sectional view along the line N-N of Figure 1.

- Figure 2P is a sectional view along the line P-P of Figure 1.

- Figure 2R is a sectional view along the line R-R of Figure 1.

- Figure 2S is a sectional view along the line S-S of Figure 1.

- Figure 2T is a sectional view along the T-T line of Figure 1.

Figure 3 shows diagrams of the luminous flux produced by a single LED (characteristic curve A) and with a diffusion lens of the present invention (characteristic curves B and C).

Figures 4 and 5 are perspective views of a rectangular multiple lens for a projector using a rectangular array of individual LED sources on which the individual optical structures of the present disclosure are replicated functionally facing respective LEDs of the rectangular array.

With reference to the attached figures, figure 1 shows the layout of an exemplary embodiment on a plate of transparent optical material 1 of a lens for diffusing the light beam emitted by a point source which, in the continuation of this description, will also be defined as LED , while being aware that the invention is suitable and useful for use also with point sources of different types. The plate 1 has an optical structure in relief 2.

Figures 2A to 2T show series of parallel sections, respectively along orthogonal axes, in the section planes identified by pairs of letters on the layout of Figure 1.

In the layout view, the imprint of the base of the raised optical structure 2 on the plane of the surface facing the illuminated area of a plate 1 of transparent optical material, is inscribed in an almost rectangular envelope perimeter P and has a bi shape -lobata with an accentuated central narrowing, which defines lateral recesses 9 and 10.

In particular, the relief structure 2 includes two identical salient lobes with rounded edges 3 and 4 joined by the central saddle 5 and its spatial development can be inspected by observing the sequences of sections along the two orthogonal axes of rectangular symmetry of figures 2A to 2T.

In the layout view of Figure 1 and in the relevant orthogonal sections of Figures 2A to 2T, the depression or circular recess 6 present on the plane of the surface of the plate 1 facing towards the point light source (not shown in the Figures) can be observed and, in the preferred embodiment illustrated, there are also claw notches 7 and 8 substantially parallel to each other along opposite and deeper sides of the circular concavity 6 for the entry of the luminous flux. The notches can also be tangent, or even marginally secant, to the circumference of the edge of the circular concavity 6.

The width of the raised optical structure 2 of each individual light diffusion lens produced by a point light source, at the point of minimum width of the profile, at the base of the sheer 5 joining the two salient lobes with rounded edges, it can be between 65% and 75% of the smaller side of the envelope rectangle P of the base impression of the relief structure 2 of the lens.

The height of the raised optical structure 2 of each individual light diffusion lens produced by a point light source, with respect to the base plane of the plate 1 from which it rises, at the central point of the sheer 5 joining the two identical salient lobes 3 and 4, lying on the optical axis of the point source and of the circular concavity 6, can generally be between 80% and 90% of the maximum height of the two salient lobes 3 and 4.

The circular recess 6, which can be spherical or conical, present on the side of the lens facing the point light source, in axis with respect to the optical axis of the source, favors a widening of the light beam emitted by the point source, by diffraction, entering the optical medium of the lens.

If present, the two parallel and relatively deep notches 7 and 8, tangent, or even marginally secant, in diametrically opposite points of the circular depression or recess 6, can have, as in the example illustrated, the shape of "claws", whose side steep interior, respectively 7a and 8a, almost orthogonal to the plane of the lens, which reaches the bottom of the notch in the sheet of optical material of the lens, is arched, while on the contrary, the opposite side or external side of the claws, respectively 7b and 8b , gradually rises towards the flat surface of a flat plate of optical material from the face of which the optical structure 2 rises, up to a straight edge. The rectilinear edge of the external sides, 7b and 8b respectively, can coincide, in geometric projection, with the perimeter of the envelope rectangle P of the base impression of the raised optical structure 2 present on the opposite face of the flat plate of the lens, while the arched edge of the internal steep side, respectively 7a and 8a, of the claw notch coincides in geometric projection with the profile at the base of the saddle-shaped central part 5 of the relief optical structure 2.

The effect of the two parallel notches 7 and 8, along opposite sides of the circular recess 6, parallel to the longitudinal axis of symmetry of the optical structure 2 of the lens, is to reduce the lateral dispersion of light to increase the yield of the lens. diffusion, constituting surfaces reflecting the light towards the axis of maximum transmission intensity.

As can be seen in the diagram of Figure 3, the single light diffusion lens produced by a point light source of the present invention determines a light diffusion curve or lobe which in the direction of the longitudinal symmetry axis of the raised optical structure of the lens, has an extraordinary uniformity for an inclination with respect to the optical axis of 70 °, i.e. an excellent uniformity of distribution of the light intensity over an area inscribed in a cone of at least 135 ° (diagram or characteristic curve C) , while in the transverse direction, the diffusion uniformity narrows to a cone with a vertex angle of about 75 ° (diagram or characteristic curve B). The exceptional widening of the area illuminated by a single point light source in a significantly uniform way is exceptional considering that the single point light source, without the diffusion lens of the present invention, would hardly exceed the area intercepted by a cone with a vertex angle of about 60 ° (diagram or characteristic curve A).

Figures 4 and 5 are two perspective views of a multiple lens made according to the present description.

In the case of a multiple lens for the diffusion of light produced by numerous point sources arranged in a rectangular array by rows and columns of sources arranged, on a rectangular area, the "lens" takes the form of a flat plate L of transparent material with suitable optical characteristics, juxtaposed to the rectangular array of multiform sources ordered by rows and columns, on which the individual optical structures in relief 2 are made with a similar array organization, defined according to the geometric and functional characteristics of the present invention, each coincident, on the other side of the sheet, with a respective depression or circular concavity for the entry of the light flux, in axis with a respective point light source (LED) of the rectangular array. It should be noted that in figures 4 and 5 the notches 7 and 8, produced on the rear face of the plate L, along the sides of the inlet concavities of the luminous flux emitted by an LED source, are not however visible. The plate L is provided with holes 11 for fixing a lighting device not visible in the drawings to a casing.

Obviously how many point light sources are in the array, there are many individual optical structures in relief 2 of the present invention defined on the face of the rectangular plate L facing the area to be illuminated.

The longitudinal axes of symmetry of the individual optical structures in relief and of the optional notches on the flat face facing the array of point light sources, are preferably oriented parallel to the shorter sides of the array and of the rectangular plate L. In fact, in consideration of the accentuated diffusion uniform in a pre-eminently extended area along the direction of the major axis of rectangular symmetry of the optical structure of the lens, in the case of a multiple lens for rectangular array of point light sources, the orientation of the individual optical structures in relief of the individual lenses is preferably parallel to the shorter sides of the rectangular plate so as to accentuate the distribution yield of the luminous flux limited to the area to be illuminated, such as for example a roadway. The repetitiveness of several transverse rows of lenses spaced apart along the major axis of the rectangular plate (and of the array of the underlying point light sources) of the street lighting device, allows to achieve the degree of uniformity of illumination along the longitudinal axis greater than the illuminated area, obtained by designing the separation distance between the transverse rows of lenses for the entire longitudinal extension of the array of multiform sources and of the related rectangular multiple diffusion lens juxtaposed to the array of sources.

Following are lighting engineering tables for the same LED array street projector, equipped with common elliptical lenses (Table 1) for diffusion of the light emitted by the individual LEDs, and equipped with a multiple lens of the present invention (Table 2), as shown in figure 4 and 5.

TABLE 1

TABLE 2

As can be seen from the values of table "1" which uses a traditional elliptical lens, the light is concentrated under the lamp and scarce at the sides, while the values measured by table "2" which uses a lens according to this disclosure there is an illuminance with homogeneous values such as to eliminate Γ shadow effect.

The lenses of the invention can be completely manufactured by means of molding techniques of thermoplastic materials and therefore can be produced at low cost.

Optical materials that can be used are primarily for production with injection molds the resins of the PMMA and PC type, although different materials can also be used, such as: glass and derivatives with different types of processing.

The object of the present disclosure has been described up to now with reference to its preferred embodiments. It is to be understood that there may be other embodiments that pertain to the same inventive core, all falling within the scope of the claims annexed hereafter.

Claims (11)

CLAIMS 1. Lens for the diffusion of light produced by a point light source on a rectangular area to be illuminated comprising a plate (1) of transparent optical material on one face of which there is at least a depression, or a circular recess, (6) able to be juxtaposed and aligned with the point light source, and on the opposite face of which there is an optical structure in relief (2) including two salient lobes (3, 4), joined together specularly by a saddle (5), the central point of minimum elevation and minimum width of said sheer (5) with respect to a maximum elevation and maximum width of both said salient lobes (3, 4) being in correspondence with said at least one depression, or a circular hollow, (6) and in which said raised optical structure (2) has a base imprint which can be inscribed in a rectangular envelope perimeter (P). 2. Lens according to claim 1, in which the central point of minimum elevation and minimum width of said sheer (5) with respect to a maximum elevation and maximum width of both said salient lobes (3, 4) coincides with a central area of called at least a depression, or a circular recess, (6). Lens according to claim 1 or 2, in which the base impression of said raised optical structure (2) can be inscribed in an envelope rectangle (P) with a major axis of symmetry passing through said salient lobes (3, 4 ) and said sheer (5), and the minor axis of symmetry passing through said central point of minimum elevation and minimum sheer width (5). Lens according to claim 1, 2 or 3, further comprising two parallel notches (7, 8) in said first face, respectively on one side and on the opposite side, and deeper than said circular recess (6). 5. Lens according to claim 4, wherein said notches (7, 8) have the shape of claws, the edge of the steep inner side (7a, 8a) of which is arched and the edge of the outer side of which (7b, 8b) which gradually rises towards a surface of the sheet of optical material is rectilinear and coincides, in geometric projection, with the longer side of the rectangular envelope perimeter (P), called the arched edge of the internal steep side (7a, 8a) of the notches coinciding , in geometric projection, with the profile at the base of said sheer (5) of the optical structure in relief (2). Lens according to any one of the preceding claims, in which said salient lobes (3, 4) have a rounded edge. 7. Lens according to any of the preceding claims, in which the elevation in the central point lying on the optical axis of said saddle (5) is between 80% and 90% of the maximum elevation of said salient lobes (3, 4). Lens according to any one of the preceding claims, wherein the width at the central point of minimum width at the base of said saddle is between 65% and 75% of the width of said salient lobes (3, 4). 9. Lens for the diffusion of light produced by a rectangular array of point light sources organized by rows and columns on a rectangular area, comprising a plate (1) of rectangular transparent optical material juxtaposed to said rectangular array of point sources, including a plurality of said circular depressions or recesses (6) and a plurality of said raised optical structures (2) according to any one of the preceding claims 1 to 8. The lens of claim 9, wherein the major axes of symmetry of said raised optical structures (2) of the individual lenses for diffusion of the light produced by a point light source and pairs of parallel notches (7, 8) with each other according to claim 5, are oriented parallel to the shorter sides of the rectangular array of the optical structures and of the rectangular plate (1). 11. Lens according to claim 10, characterized in that transverse columns of single optical structures (2) are replicated at a separation distance fixed on the basis of design parameters of a luminaire, along the longitudinal extension of said rectangular plate (1).