EP2475926B1

EP2475926B1 - Light distribution array optical system

Info

Publication number: EP2475926B1
Application number: EP10724909.6A
Authority: EP
Inventors: Dariusz Litwin; Tadeusz Kryszczynski; Jacek Galas; Adam Czyzewski
Original assignee: Instytut Badawczy Drog I Mostow; Instytut Optyki Stosowanej
Current assignee: Instytut Badawczy Drog I Mostow; Instytut Optyki Stosowanej
Priority date: 2009-09-09
Filing date: 2010-04-12
Publication date: 2013-11-13
Anticipated expiration: 2030-04-12
Also published as: EP2475926A1; UA101080C2; PL388995A1; WO2011031170A1; PL216006B1

Description

The subject matter of the invention is a light distribution array optical system, in particular for the road signs of variable content, with the application of an array with LEDs as sources of light.
The EP 0930600 patent description discloses light distribution optical systems used in road signs of variable content, comprising individual optical systems provided with a light emitting diode (LED), a lens stop, a converging lens and a diverging lens located coaxially in a single housing. The distance between the lenses has been selected so that sunlight from the outside is maximally reduced either by the lens stop or the housing wall. This prevents the phantom phenomenon which manifests itself as apparent light caused by sunray reflecting from reflectors or other optical system elements. A disadvantage of individual optical systems is the occurrence of numerous optical elements of complicated geometry located in a separate housing, which aggravates installation and maintenance. Moreover, such a solution does not ensure good visibility of the content displayed from a greater distance.
There are also known sign boards optical systems provided with optical elements integrated with a LED array, which create a light beam. Such systems may be provided with optical filters, rod lenses, stepped lenses or other elements limiting and forming light penetrating the system. Additional optical elements make it possible to shape the light stream on the system output and eliminate the glare by the point source of light or the phantom effect.
Another system is proposed in patent application EP 0081361 A1 . This application discloses a lamp comprising a reflector which directs light emitted by a light bulb towards positive lens surfaces on one side of a lens plate which converges light rays towards respective light-transmitting interstices in an otherwise opaque or light-absorbing surface disposed on the opposite side of the plate. This arrangement serves to reduce the visibility of the internal components of the lamp when viewed from the front, and at the same time minimises the occurrence of "ghost" signals produced by external incident light. Althought the small size of the interstices substantially prevents external light from passing through, the light-absorbing surface of the plate is generally light-obstructing and only part of the light emitted by the bulb passes through the surface. The system is also not designed for LEDs.
The EP 1696171 patent description discloses a LED display device with plurality of LEDs and a first lens array, which comprises a plurality of lenses for collimating and/or focusing of the radiation emitted by the LEDs. A second lens array follows the first lens array in an emission direction of the LEDs. Between the lens arrays a diaphragm arrangement is arranged. One lens of the second lens array is associated in each case with one lens of the first lens array. The second lens array are curved convexly from the side of the LEDs. The lens of the first lens array in each case comprises an optical axis which is arranged offset relative to an optical axis of the associated lens of the second lens array. The incidental light from outside is deflected substantially onto absorbent regions of the diaphragm arrangement. A disadvantage of this solution is complicated geometry of the system and unique geometry of the lenses, especially TIR lenses proposed for the first lens array. Moreover the diaphragm arrangement partly limits the LEDs light distribution.
The EP 1091167 patent description discloses a traffic lights optical system with an arrangement of LEDs in which beams of light emitted by the diodes are formed by an internal board panel with converging lenses and Fresnel lenses and the system output features an optical material stop with its internal surface featuring elements limiting distribution of the light penetrating the system and preventing the phantom phenomenon.
The DE 102005002535 patent description discloses a LED array optical system of light distribution to road signs, in which the element limiting and forming the beam of light penetrating the system comprises an uniform flat board made of optical organic material or glass and a lens located between the board and the LED. The board internal and external surfaces are covered with an aperture surface created by perforated diaphragms with circular openings transmitting the light and located in the optical axis of each LED. In this solution only part of the light emitted by the LEDs passes through the circular openings in the stop, and the remaining part is stopped by the stop material.
The light distribution array optical system provided with an array of LEDs as light sources and internal and external board panels, which are located in parallel and are forming the light beams emitted by the LEDs, at least one of the board panels features as a surface limiting the volume of light penetrating the system, in accordance with the invention is characterised by the fact that the input surfase of the internal board panel situated on the side of the LEDs, is provided with focusing elements constituting convexities located in the optical axis of each LED, having an aspherical shape and a radius of curvature increasing towards base. The vertical radius R of convexity is from 0.3 to 0.5 of distance s between the optical axes of adjacent LEDs. The total thickness d of the internal board panel is from 1.58 to 2.08 of distance s. The external board panel has at least two breaking surfaces a concave surface and a spherical convex surface which have a common axis of symmetry and a square outline. The breaking surfaces in frontal projection cover a square array of four adjacent convexities from the internal board panel. The surface limiting the volume of light penetrating the system is the aperture surface and has a circular windows located in the optical axis of each LED, said aperture surface being situated on the internal board panel surface opposite the convexities.
It is advantageous if the internal board panel side length is the k-multiplicity of the s distance where k is a natural even number from 2 to 100.
It is also advantageous if the aperture surface of the internal board panel is created of perforated diaphragm adhering to the panel.
In another execution of the internal board panel the aperture surface of the internal board panel is a profiled surface comprising symmetrical convex segments in the shape of truncated cones, with circular windows constituting their frontal surfaces.
It is advantageous if the external board panel is made of a uniform board form of an outline matching the outline of the internal board panel, while the output surface is a spherical convex surface.
In another execution of the external board panel the breaking surfaces are located on separate board forms, the first and the second, of which the first one is located from the side of the internal board panel.
It is advantageous if the breaking surfaces are located from the side of the gap separating the board forms, and the other surfaces are flat. It is also advantageous if the output surface is a spherical convex surface and the concave surface is located on the first board form from the side of the internal board panel.
It is advantageous if the output surface is a concave surface and the spherical convex surface is located on the first board form from the side of the second board form.
Also advantageous is such an execution of the external board panel in which between the board forms there is a separating layer made of optical material transmitting light.
It is advantageous if the concave surface has the shape of a cone side surface of a vertical angle within the range from 140° to 175°.
It is also advantageous if the concave surface has the shape of a tetragonal pyramid of a vertical angle measured in the standard plane to the panel side within the range from 140° to 175°.
It is advantageous if the relation between the active diameter φ of the circular windows to diameter φ_e of convexity base amounts to 0.15 to 0.45.
A solution in accordance with the invention has a compact design obtained thanks to the integrated system of the LED array with the board panels. Within the system, the panels cover at least one square array of LEDs constituting sources of light. Thanks to the board panel geometry, beams of light emitted by the diodes are formed and adjusted by the external and the internal board panels and after that they spread in a direction parallel-like to the optical axis of the LEDs and the focusing elements, and the watching person sees all the diodes identically as points of light of identical brightness intensity. Light distribution array optical system design parameters result from the requirements pertaining to the visibility of road signs of variable content. Diode image obtained in a system in accordance with the invention is very well visible from large distances, and the system design as well as the application of aperture surface ensure elimination of the phantom phenomenon. Moreover, the panel design allows to produce them as board forms of dimensions adjusted to typical dimensions of road signs of variable content, which facilitates their production and maintenance and ensures greater durability during an extended period of operation.
The invention is shown in exemplary drawing in which fig. 1 shows a light distribution array optical system in cross-section, fig. 2 shows the internal board panel in front view, fig. 3 shows the board panels in cross-section, fig. 4 shows the external board panel made of a uniform board form in cross-section, fig. 5 shows another execution of the board panels in cross-section, fig. 6 shows another execution of the light distribution array optical system in side view, fig. 7 shows the internal board panel from fig. 6 in front view, fig. 8 shows the external board panel with a flat output surface in cross-section, fig. 9 shows the external board panel with a convex output surface in cross-section, fig. 10 shows the external board panel with a concave output surface in cross-section, fig. 11 shows the board form with a concave surface in the shape of a tetragonal pyramid in cross-section.
As shown in fig. 1, the light distribution array optical system is provided with an array of LEDS 1 constituting sources of light and two parallel board panels, internal 3 and external one, which form beams of light emitted by the LEDs 1. The internal board panel 3 input surface features, on the side of the LEDs 1, focusing elements constituting convexities 2 located in the optical axis of each LED 1. The convexities 2 have an aspherical shape and a radius of curvature increasing towards the base. The vertical radius R of convexity 2 amounts to 0.3 to 0.5 of the s distance between the optical axes of adjacent LEDs 1, and the total thickness d of the internal board panel 3 amounts to 1.58 to 2.08 of the s distance. The external board panel has at least two breaking surfaces of common axis of symmetry and square outline, a concave surface 7 and a spherical convex surface 8. In the frontal projection, the breaking surfaces cover a square array of four adjacent convexities 2 on the internal board panel 3. Moreover, the surface limiting the light penetrating the system is constituted by the aperture surface 4, 4' being the internal board panel 3 external surface. The aperture surface 4, 4' has circular windows 5 located in the optical axis of each LED 1. The internal board panel 3 side length is the k-multiplicity of the s distance where k is a natural even number from 2 to 100. The aperture surface 4 of the internal board panel 3 is formed of a perforated diaphragm.
The external board panel is made of an uniform board form 6 of an outline matching the outline of the internal board panel 3, subject to the output surface being a spherical convex surface 8 and the concave surface 7 having the shape of a cone side surface. In another execution of the uniform board form 6 shown in fig. 4, the concave surface 7' has the shape of tetragonal pyramid sides.
As shown in fig. 2 and fig. 3, the smallest design module realising a system in accordance with the invention features sides of the internal board panel 3 of a length equal to the double s distance between the optical axes of adjacent LEDs 1 and covers a square array of four adjacent convexities 2 formed on the input surface e from the side of the LED array. The same outline of the sides in front view is featured in the uniform board form 6 constituting part of the module.
As shown in fig. 5, in another execution of the external board panel the breaking surfaces are located on separate board forms 11 and 12, the first one located from the side of the internal board panel 3 and the second one with the output surface seen directly by the watching person. The panel's output surface is constituted by the aspherical convex surface 8 while the concave surface 7 is located on the first board form 11 from the side of the internal board panel 3. Between the board forms 11 and 12 there may be located a separating layer 10 made of optical material transmitting light.
As shown in fig. 6, in another execution the internal board panel 3 has a profiled aperture surface 4' comprising symmetrical convex segments 9 in the shape of truncated cones, the frontal surfaces of which are made of circular windows 5. In this system, the external board panel comprises separate board forms 11 and 12 subject to the breaking surfaces being located from the side of the gap separating both forms and the other surfaces being flat. The concave surface 7 is made on the first board form 11 while the spherical convex surface 8 is on the second form. The profiled aperture surface 4' facilitates the formation of a beam of light going out of the system and limits the volume of the external light penetrating the system thanks to reflection and dispersion on the profiled surface.
Fig. 7 shows the aperture surface 4' made of four symmetrical convex segments 9 shown in fig. 6. Frontal surfaces of the segments have circular windows 5 of geometrical axes located at a distance s equal to the s distance between the optical axes of adjacent LEDs 1 constituting part of the system.
The external board panel made of two separate board forms 11 and 12 with breaking surfaces forming the beams going out of the system towards the watching person may feature miscellaneous locations of the breaking surfaces with respect to each other.
In fig. 8, the external board panel surfaces are located in an order reverse to that in the external board panel shown in fig. 6. On the first board form 11 there is a spherical convex surface 8 and on the other board form 12 there is a concave surface 7.
In fig. 9, the external board panel output surface is a spherical convex surface 8 and the concave surface 7 is located on the opposite side of the panel, on the first board form 11.
In fig. 10, the external board panel output surface is a concave surface 7 and the spherical convex surface 8 is located on the first board form 11, from the side of the other board form 12.
fig. 11 shows another execution of the board form constituting part of the external board panel, on which there is a concave surface 7. In this case, the concave surface 7' is in the shape of the sides of a tetragonal pyramid due to which the external edges of the surface are on the same plane.
In the exemplary embodiment of the system in accordance with the invention, the internal board panel 3 and the external board panel forms are made of optical organic material of a refraction index from 1.49 to 1.55, determined at the wave length of 587.56 nm. The shape of convexity 2 is similar to a rotating paraboloid. The aspherical surface of convexity 2 arising from the extension of the conical curvatures has the base diameter φ_e, and its shape is determined by the ε eccentric. Circular windows 5 of aperture surface 4 and 4' have the active diameter φ.
Total thickness d of board panel 3 is measured along the optical axis. Distance g between circular windows 5 and the external board panel has been selected appropriately to the geometry of the system optical elements and does not exceed distance s between the optical axes of adjacent LEDs 1. Distance c between the frontal surface of each diode and the surface of convexity 2 is selected appropriately to the light distribution solid angle for a specific type of a diode, in particular of semi-spherical shape. Diodes may come in numerous colour versions, depending on requirements.
Engineering data of the embodiment of the system shown by way of example in accordance with the invention, with semi-spherical LEDs 1 of the diameter of 5 mm and light distribution angle of 15° were as follows:

R=3.0 mm
ε = 1,0
d=17.8mm
φ_e = 8.38 mm
φ = 2.0 mm
g = 4.0 mm
s = 10.0 mm.

concave surface

In a solution in accordance with the invention, internal board panel 3 may be formed by means of plastic moulding, injection or another method utilised in plastic processing. The system may comprise internal board panel 3 of the shape shown in fig. 1 or fig. 2, and any external panel of the shape shown in fig. 1, 4, 5, 6, 8, 9 and 10. Panel dimensions may be adjusted to typical optical system array configurations in this type of boards, with a square or rectangular outline. Panels may also be connected with their sides. Active surface of the aperture surface 4 and 4' is determined by the surface of circular windows 5 of the active diameter φ. The relation between the φ active diameter of circular windows 5 and the φ_e diameter of convexity 2 amounts to 0.15 to 0.45.
Flat aperture surface 4 may be executed in the form of a perforated diaphragm made of thin, blackened sheet metal, foil or other coating not transmitting light, placed on the panel. In the event of application of profiled aperture surface 4', the volume of light penetrating the system is limited due to retraction and dispersion of the light falling on conical surfaces around circular windows 5. The surfaces may be transparent, mat or covered with appropriate coating. A beam of sunlight which passes through circular windows 5 inside the system becomes weakened in the panel material as a result of dispersion and absorption, or leaves the system. Residual light which returns through circular windows 5 is not seen by the watching person and does not interfere with the sign content. Additionally, the external board panel output surface may be covered with an anti-reflective layer transmitting light.

Claims

A light distribution array optical system provided with an array of LEDs (1) as light sources and internal (3) and external board panels, which are located in parallel and are forming the light beams emitted by the LEDs, at least one of the board panels features as a surface limiting the volume of light penetrating the system, characterised in that the input surface of the internal board panel (3) situated on the side of the LEDs (1), is provided with focusing elements constituting convexities (2) located in the optical axis of each LED (1), having an aspherical shape and a radius of curvature increasing towards base, the vertical radius "R" of convexity (2) is from 0.3 to 0.5 of distance "s" between the optical axes of adjacent LEDs (1), and total thickness "d" of the internal board panel (3) is from 1.58 to 2.08 of distance "s"; and the external board panel has at least two breaking surfaces a concave surface (7, 7') and a spherical convex surface (8) which have a common axis of symmetry and a square outline, where the breaking surfaces in frontal projection cover a square array of four adjacent convexities (2) from the internal board panel (3); while the surface limiting the volume of light penetrating the system is the aperture surface (4, 4') and has a circular windows (5) located in the optical axis of each LED (1), said aperture surface being situated on the internal board panel (3) surface opposite the convexities (2).
A system as claimed in claim 1, wherein the internal board panel (3) side length is the k-multiplicity of the "s" distance where "k" is a natural even number from 2 to 100.
A system as claimed in claim 1, wherein the aperture surface (4) of the internal board panel (3) is created of perforated diaphragm adhering to the panel.
A system as claimed in claim 1, wherein the aperture surface (4') of the internal board panel (3) is a profiled surface comprising symmetrical convex segments (9) in the shape of truncated cones, with circular windows (5) constituting their frontal surfaces.
A system as claimed in claim 1 or 2, wherein the external board panel is made of a uniform board form (6) of an outline matching the outline of the internal board panel (3), while the output surface is a spherical convex surface (8).
A system as claimed in claim 1 or 2, wherein the breaking surfaces are located on separate board forms (11, 12), the first and the second, constituting the external board panel, of which the first one is located from the side of the internal board panel (3).
A system as claimed in claim 6, wherein the breaking surfaces are located from the side of the gap separating the board forms (11, 12), and the other surfaces are flat.
A system as claimed in claim 6, wherein the output surface is a spherical convex surface (8) and the concave surface (7) is located on the first board form (11) from the side of the internal board panel (3).
A system as claimed in claim 6, wherein the output surface is a concave surface (7) and the spherical convex surface (8) is located on the first board form (11) from the side of the second board form (12).
A system as claimed in claim 6, wherein between the board forms (11, 12) there is a separating layer (10) made of optical material transmitting light.
A system as claimed in claim 1, wherein the concave surface (7) has the shape of a cone side surface of a vertical angle within the range from 140° to 175°.
A system as claimed in claim 1, wherein the concave surface (7') has the shape of a tetragonal pyramid of a vertical angle measured in the standard plane to the panel side within the range from 140° to 175°.
A system as claimed in claim 1, wherein the relation between the active diameter "φ" of the circular windows (5) to diameter "φ_e" of convexity (2) base is from 0.15 to 0.45.