Lens plate and lighting device having a lens plate - Patents.com

Abstract

The lens plate has an array of convex lenses, each having a top forming a light input surface for facing the light source and a base forming a light output surface. Each convex lens has a height H and a diameter D at the base, where H / D>0.85. The lens plate has a height from base to apex of the convex lens that is, for example, in the range of 1.5 mm to 5 mm.

Description

[Technical Field]

[0001] The present invention relates to a lens plate, for example as part of a lighting fixture, for shaping the light output from an array of LEDs. [Background technology]

[0002] For some lighting fixtures, it is desirable to produce uniform illumination, i.e. illumination that has a relatively constant light intensity over an area in a (horizontal) plane below the lighting fixture.

[0003] This requires light output intensity to be a function of emission angle, such that light from larger emission angles has greater light intensity because the light must travel further to the illumination plane. An example of a desirable light output intensity distribution is a so-called batwing intensity distribution.

[0004] It is known to use lenses or lens plates to convert the output light intensity distribution from a light source, such as the Lambertian light intensity distribution of an LED light source, into a desired bat-wing shaped intensity distribution.

[0005] Currently, concave and convex lenses are used to generate large beam angles for such uniform illumination.

[0006] A typical concave-convex lens and its ray trace diagram are shown in FIG.

[0007] 1 shows an LED light source 10 with a lens 20 over its light output surface. The lens 20 has a concave light input surface 22 and a convex light output surface 24. This type of lens is typically used with a one-to-one correspondence between the LED chips and the lens, or there may be a pair of LED chips underneath the lens. If this correspondence between the lens and the LEDs is not achieved, it is difficult to achieve the desired optical performance.

[0008] Figure 2 shows an alternative design of lens plate 30 formed as an array of convex spherical microlenses 32. This type of lens design can tolerate different alignments between the lens plate and the light source due to the small size of the microlenses. It also achieves better color uniformity, but the output beam angle does not differ significantly from the native light source.

[0009] Figure 2 shows the light trajectories of the three LED light sources 10. It can be seen that the desired wide beam light output is not achieved, and the output beam width matches the input beam width. The focal point FP1 of the microlens is on the opposite side of the lens plate from the LED light sources, and is approximately the same distance from the lens surface as the LED light sources. Summary of the Invention [Problem to be solved by the invention]

[0010] There remains a need for a lens structure that is suitable for multiple types of LED light sources, that is independent of the relative position of the light source with respect to the lens structure, and that achieves a desired broad beam output, e.g., a bat-wing shaped light intensity distribution. [Means for solving the problem]

[0011] The invention is defined by the claims.

[0012] According to an example according to one aspect of the present invention, there is provided a lens plate, the lens plate comprising: an array of convex lenses, each convex lens having an apex forming a light input surface for facing a light source and a base forming a light output surface, the base being disposed on or defining a substrate common to the array; A lens plate is provided in which each convex lens has a height H and a diameter D at its base, where H / D>0.85. The lens plate has a height from the base to the apex of the convex lens in the range of, for example, 1.5 mm to 5 mm. The height H of the convex lens is preferably in the range of 1 mm to 4 mm.

[0013] The convex lenses of this lens plate have a long, narrow bullet shape as a result of their height-to-diameter ratio. Therefore, the convex lenses are aspherical and have a very short focal length. For a lens plate with spherical lenses, i.e., H / D=0.5, the output beam angle does not differ significantly from the source beam (paraxial rays remain paraxial). A bullet-shaped lens with H / D>0.85 results in a focal point located inside the lens body, which means that the paraxial rays diverge very significantly. Off-axis rays also remain off-axis, resulting in a bat-wing shaped light output intensity that can be obtained from a Lambertian output of an LED light source.

[0014] The lens plate allows the light output characteristics to be independent of the position of the lens plate above the light source, e.g., an LED array. The same lens structure is suitable for different light source designs.

[0015] Each convex lens preferably has a focal point between its apex and its base, so that the apex of each lens converges to a focal point at a very short focal length, such that the focal point is within the lens body, resulting in a large convergence angle and therefore a post-focus divergence, meaning that off-axis rays are emitted from the base at a large angle.

[0016] The lens plate may further comprise a microstructure formed in a central region of each apex.

[0017] Each of the convex lenses and microstructures in the array further disperses the light emitted from the light source. The central microstructure at the convex apex of each convex lens diffuses small angle light rays from the light source.

[0018] Each microstructure is preferably diffusive or scattering, which provides the desired dispersion of light rays at small angles from the light source.

[0019] Each microstructure is an array of microlenses, embossed patterns, or It may also comprise an array of embedded particles.

[0020] Thus, there are a variety of possible designs for the microstructures.

[0021] The base of each convex lens and the common substrate are preferably flat, so that the optical function is in this case entirely defined by the top surface facing the light source, and the lens plate is simple to manufacture without the need for alignment between the top and bottom surfaces.

[0022] The apex of each convex lens forms, for example, a protrusion that is rotationally symmetric about the optical axis.

[0023] The lenses of the convex lens array preferably completely fill the active area of ​​the lens plate. By filling the active area of ​​the lens plate, all light to be processed passes through the lenses. The active area is the area of ​​the lens plate intended to beam shape the light output from the light source.

[0024] The lenses may have a pitch in the range of, for example, 0.5 mm to 5 mm, which provides a small lens pitch that helps make the light output less dependent on the alignment between the lens plate and the light source.

[0025] The bases of the convex lenses are preferably mated together, which allows the active area of ​​the lens plate to be completely covered as described above, and allows for a small pitch array of the apexes.

[0026] Each convex lens is Elliptical lines, Bezier curves, Parabola, or It may have partial curves including polynomial aspherical curves.

[0027] The lens plate preferably comprises a molded part.

[0028] The present invention also provides a lighting device comprising: An array of LEDs, and a lens plate as defined above, wherein the light output surface of each LED of the array of LEDs faces the apex of a convex lens of the lens plate.

[0029] The LED array has a pitch between the LEDs that is, for example, in the range of 0.5 mm to 3 mm.

[0030] The distance along the optical axis between the light output surface of the LED and the top of the convex lens is, for example, in the range of 3 mm to 7 mm, which allows the thermal conditions to be met.

[0031] When the lens plate includes a microstructure formed in a central region of each apex (as described above), the microstructure may extend along the optical axis of the associated convex lens over an area corresponding to a half angle ranging from 10 to 15 degrees from a point on the plane of the output face of the LED.

[0032] When the corresponding angle of incidence is greater than this half angle (e.g., 12 degrees), the angle of the departure ray increases sharply: the incident ray from the neighboring LED strikes the side of the convex lens away from the microstructure (again, at an angle of incidence greater than this half angle), which results in a departure angle of, e.g., 60-80 degrees.

[0033] The lighting device Less than 15% of the light from the LED array is emitted at angles ranging from 0 to 30 degrees. Over 70% of the light from the LED array is emitted at angles between 30 and 70 degrees. It may be sufficient that 5% to 20% of the light from the LED is emitted at an angle in the range of 70 to 90 degrees.

[0034] Thus, the light output distribution takes on a bat-wing shape with maximum light intensity in the range of 30-60 degrees.

[0035] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief explanation of the drawings]

[0036] For a better understanding of the present invention, and to show more clearly how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Figure 1] FIG. 1 shows a typical concave-convex lens and a ray trace diagram. [Figure 2] 10A-10C show alternative designs of lens plates formed as an array of convex spherical microlenses. [Figure 3] 1A and 1B show lens plates according to examples of the present invention. [Figure 4] FIG. 4 shows the same lens plate as FIG. 3, but with light rays passing through other parts of the convex lens. [Figure 5] FIG. 10 shows the optical performance of a convex lens design without microstructures for small angle incident beams. [Figure 6] FIG. 10 shows the optical performance of a convex lens design without microstructures for large angle incident beams. [Figure 7] FIG. 10 illustrates how input light from a light source with a larger angle of incidence to the lens plate is reconverted into output light with a larger beam angle. [Figure 8] 1A and 1B are diagrams used to explain possible designs of convex lenses. [Figure 9] FIG. 1 shows an example of an LED array comprising concentric rings of LEDs. [Figure 10] FIG. 1 shows an example of a convex lens array comprising a square grid of lenses. [Figure 11] FIG. 2 shows a perspective view of the top surface of the lens plate. [Figure 12] FIG. 10 shows a polar intensity diagram of a simulation of the performance of a lens plate over an array of medium power LEDs. DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention will now be described with reference to the figures.

[0038] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the devices, systems, and methods, are for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the devices, systems, and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the figures are schematic only and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to indicate the same or similar parts.

[0039] The present invention provides a lens plate having an array of convex lenses, each having a top forming a light input surface for facing a light source and a base forming a light output surface, each convex lens having a height H and a diameter D at the base, where H / D>0.85.

[0040] 3 shows a lens plate 40 according to an example of the present invention. The lens plate comprises an array 42 of convex lenses 44. Each convex lens 44 has a top 44a forming a light input surface facing the light source, and a base 44b forming a light output surface. The bases are flat and are mounted on or integrally formed with a common flat substrate 48. The light source is an array of LEDs 10, with the light output surface of each LED in the LED array facing the top 44a of a convex lens in the lens plate.

[0041] Thus, the convex lens has a beam-shaping surface on only one side (the side facing the light source 10), making it easier to manufacture, for example by injection molding. The convex lens has an aspheric surface. In particular, the curvature of the apex 44a corresponds to a shape having a height H and a diameter D at the base (H / D>0.85).

[0042] As shown in Figure 3 and described in more detail below, the convex lenses may be joined together at their bases. In such cases, the diameter D is defined by extrapolating the remaining convex lens surface area. Alternatively, the convex lenses may be separated from one another (either spaced apart or tangentially touching), in which case the diameter is the actual diameter at the base. When the individual lenses are separated, they are preferably spaced apart by less than 0.1 mm to minimize the size of the flat gap between the lenses.

[0043] The extrapolation is a smooth extension of the remaining convex lens surface area, i.e., the apex 44a of the lens. Curve extrapolation methods are well known for deriving the general general overall shape of a convex lens from the apex 44a. From this extrapolation, the diameter D can be defined.

[0044] The extrapolation takes into account the type of lens shape. For example, the partial curve of a convex lens is e.g. Elliptical lines, Bezier curves, Parabola, or Includes polynomial aspheric curves.

[0045] For these lens shapes, the generatrix is ​​a parabola, a Bezier curve, a circular arc, a hyperbola, or a combination thereof.

[0046] When the lens bases are joined together, the convex lenses of the array of convex lenses completely occupy the active area of ​​the lens plate. In particular, the lens bases are joined together to define a solid plate with no gaps. This avoids air gaps between the lenses, which would otherwise function as a flat plate. Furthermore, the joined bases mean that the lenses do not have vertical cylindrical sidewalls, which are undesirable for the intended light deflection. The convex lenses form, for example, a square grid. The apex of each convex lens forms a protrusion that is rotationally symmetrical about the optical axis of the lens, and this protrusion extends from the joined base toward the light source.

[0047] The lenses may alternatively be formed as a hexagonal grid.

[0048] Thus, convex lenses are tall and thin as a result of their height-to-diameter ratio. This allows them to have very short focal lengths, especially with the focal point located inside the lens body. This means that the divergence of paraxial rays is very large, as shown by the rays in Figure 3.

[0049] Off-axis rays remain off-axis, so that a bat-wing shaped output intensity can be obtained from the Lambertian output of the LED light source.

[0050] 3 shows an optional additional design feature of microstructures 46 formed in the central region of each apex 44a. Each microstructure 46 is diffusive or scattering. Any suitable structure may be used, such as an array of microlenses, an embossed pattern, or an array of embedded particles.

[0051] Both the convex lens design and the microstructures result in a more diffused light emitted from the light source. The microstructures diffuse the small angle light rays from the light source 10, while other portions of the convex surface of the convex lens are used to control the large angle light rays to achieve the desired target wide angle. Thus, the structure enhances the large angle light rays and reduces the central small angle light from the light source 10.

[0052] The total height of the entire lens plate (H and the thickness of the substrate 48) is, for example, in the range of 1.5 mm to 5 mm, e.g., about 3 mm. The height H of the convex lens is preferably in the range of 1 mm to 4 mm. The vertical distance d between the LED light source 10 and the top of the convex lens 44 is, for example, in the range of 3 mm to 7 mm, e.g., about 5 mm. This is preferable in order to satisfy the thermal conditions of the lens.

[0053] 3 shows schematically that the LED pitch does not have to be the same as the convex lens pitch. In fact, the lens plate may be used with different light source configurations having different LED pitches, and the relative alignment between the lens plate and the light source is not important.

[0054] Figure 3 shows a light ray passing through a microstructured region. The diagram shows that the light ray is focused within the body of the convex lens (whether or not there is a microstructure) so that the light exits the lens with a wide beam angle. Thus, small angle light rays are refracted to form large angle light rays.

[0055] Figure 4 shows the same lens plate, but with rays passing through other parts of the convex lens. This applies to light from a source that already has large ray angles (relative to the perpendicular optical axis). These large angle rays are also refracted to form larger beam angles.

[0056] Thus, the structure achieves a wide beam angle light distribution suitable for uniform illumination.

[0057] 5-7 show the optical performance of the convex lens design without microstructures.

[0058] FIG. 5 shows how input light from a light source having three different incident beam angles but centered on the optical axis is converted in each case into output light with a larger beam angle in the same way as described above.

[0059] FIG. 5 shows that the convex lens is designed such that the focal point FP2 is within the lens body, i.e., at a distance along the optical axis from the lens surface that is less than the lens height. Therefore, the focal point is within the lens plate. While the lens focal point is defined based on the incident parallel beam, the relatively large spacing relative to the display panel means that light from each LED 10, treated as a point source, is focused at a focal point within the lens body. This contrasts with the conventional lens design of FIG. 2, in which the focal point FP1 is below the lens plate and outside the lens body. The lens design of the present invention, as explained above, results in a large divergence of paraxial light rays. Light converges before the focal point and diverges after the focal point. The short focal length provided by the convex lens of the present invention results in a larger deflection of paraxial light rays.

[0060] FIG. 6 shows how input light from a light source, with a large angle of incidence to the lens plate, is reconverted into output light with a larger beam angle in the same manner as described above.

[0061] FIG. 7 shows how input light from a light source with a larger angle of incidence to the lens plate is reconverted into output light with a larger beam angle, which can result in some total internal reflection from the bottom surface of the substrate as shown.

[0062] FIG. 8 is used to illustrate a possible design of the convex lens, showing more clearly the dimensions D, H and d mentioned above.

[0063] Additionally, the optical axis of the light output from the light output surface 10a of the light source 10 is shown.

[0064] The microstructure extends from the plane of the output surface 10a of the LED 10 over an area corresponding to a half angle (θ) in the range of 10 to 15 degrees around the optical axis.

[0065] When the incident light is at an angle greater than this half angle, e.g., 12 degrees, the angle of the light rays exiting the base of the lens increases rapidly, resulting in exiting light rays having angles in the range of, e.g., 60 to 80 degrees relative to the optical axis.

[0066] In the case of illumination with a Lambertian light intensity distribution of an LED array, the resulting optical performance is e.g. Less than 15% of the light from the LED array is emitted at angles ranging from 0 to 30 degrees. Over 70% of the light from the LED array is emitted at angles between 30 and 70 degrees. This means that 5% to 20% of the light from the LED is emitted at an angle in the range of 70 to 90 degrees.

[0067] 9 shows an example of an LED array comprising concentric rings of LEDs 10. The spacing between the LEDs is, for example, about 1 mm in both width and height to provide thermal isolation.

[0068] 10 shows an example of an array of convex lenses comprising a square grid of lenses 40. Thus, the lens array of the lens plate does not need to be designed to match the design of the LED array, and the same lens plate may be used with different light sources.

[0069] The pitch of the LED array and the lens plate do not need to match, and alignment between the two is not critical.

[0070] The lenses of the array of convex lenses have, for example, a pitch in the range of 0.5 mm to 5 mm and a base diameter D in the range of 0.5 mm to 5 mm. The LED array has, for example, a pitch in the range of 0.5 mm to 3 mm.

[0071] Thus, the lens plate is suitable for a large number of possible LED configurations: there are many convex lenses due to the small pitch and the way they meet at the base to fill the active area.

[0072] 11 shows a perspective view of the top surface of lens plate 40. The figure shows a square grid structure with microstructures 46 on the apex of the convex lenses.

[0073] Figure 12 shows a simulation of the performance of a lens plate placed over an array of medium-power LEDs, showing polar intensity diagrams that demonstrate that the desired bat-wing shaped intensity distribution can be achieved.

[0074] The microstructure is optional. In the example above, it is provided on the top surface of each convex lens. However, instead, there may be a microstructure on a common substrate, or there may be microstructures on both surfaces.

[0075] Variations to the disclosed embodiments can be understood by those skilled in the art, from a study of the drawings, the disclosure, and the appended claims, and can be implemented in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0076] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0077] When the term "adapted to" is used in the claims or detailed description, the term "adapted to" is meant to be equivalent to the term "configured to."

[0078] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. 1. A lighting device comprising: an array of LEDs; a lens plate, the lens plate comprising: an array of convex lenses, each convex lens having an apex forming a light input surface for facing a light source and a base forming a light output surface, said base being disposed on or defining a substrate common to said array; each convex lens has a diameter D at the base and a height H from the base to its apex, H / D>0.85, and the height is in the range of 1 mm to 4 mm; a light output surface of each LED of the array of LEDs facing the apex of the convex lens of the lens plate; the LED array has a pitch between the LEDs ranging from 0.5 mm to 3 mm; and / or the distance (d) along the optical axis between the light output surface of the LED and the apex of the convex lens is in the range of 3 mm to 7 mm; Lighting device.

2. 10. The lighting device of claim 1, wherein each convex lens has a focal point between the apex and the base.

3. 3. The lighting device of claim 1, wherein the lens plate has a thickness in the range of 1.5 mm to 5 mm, the thickness of the lens plate including the height H of the convex lenses and the thickness of the substrate.

4. 3. The lighting device of claim 1, further comprising a microstructure formed in a central region of each apex.

5. 5. The lighting device of claim 4, wherein each microstructure is diffusive or scattering.

6. Each microstructure is an array of microlenses, embossed patterns, or 6. The lighting device of claim 5, comprising an array of embedded particles.

7. 3. A lighting device according to claim 1 or 2, wherein the base of each convex lens and the common substrate are flat.

8. 3. An illumination device according to claim 1 or 2, wherein the apex of each convex lens forms a protrusion that is rotationally symmetric about the optical axis.

9. 3. A lighting device as claimed in claim 1 or 2, wherein the lenses of the array of convex lenses completely occupy an active area of ​​the lens plate, the lenses having a pitch in the range of 0.5 mm to 5 mm, the active area being the area of ​​the lens plate intended to beam-shape the light output from a light source.

10. 3. The lighting device according to claim 1 or 2, wherein the bases of the convex lenses fit together.

11. Each convex lens is Elliptical lines, Bezier curves, Parabola, or 3. A lighting device according to claim 1, comprising a partial curve that includes a polynomial aspherical curve.

12. 3. The lighting device of claim 1, wherein the lens plate comprises a microstructure formed in a central region of each apex, the microstructure extending along the optical axis of the associated convex lens over an area corresponding to a half angle (θ) ranging from 10 to 15 degrees from a point on the plane of the output face of the LED.

13. less than 15% of the light from the LED array is emitted at an angle in the range of 0 to 30 degrees; greater than 70% of the light from the LED array is emitted at an angle in the range of 30 to 70 degrees; 5% to 20% of the light from the LED is emitted at an angle ranging from 70 to 90 degrees; 3. A lighting device according to claim 1 or 2.

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