Field of the disclosure

The disclosure relates generally to illumination engineering. More particularly, the disclosure relates to an optical device for modifying a distribution of light produced by a light source that may comprise, for example but not necessarily, one or more light emitting diodes “LED”. Furthermore, the disclosure relates to light fixture comprising a light source and an optical device configured to modify a distribution of light produced by the light source.

Background

Distribution of light produced by a light source can be important or even critical in some applications. The light source may comprise, for example but not necessarily, one or more light emitting diodes “LED”, one or more filament lamps, or one or more gas-discharge lamps. The distribution of light produced by a light source can be modified with optical devices such as lenses, reflectors, and combined lens-reflector devices that comprise sections which act as lenses and sections which act as reflectors. Figure 1 shows a section view of an exemplifying light fixture that comprises a light source 102 and an optical device 101 according to the prior art. The optical device 101 is configured to modify a distribution of light emitted by the light source 102. Exemplifying light beams are depicted with dashed line arrows. The optical device 101 can be for example rotationally symmetric with respect to the y-axis of a coordinate system 199. In this exemplifying case, the light source 102 is a light emitting diode “LED” that comprises a semiconductor part 130 emitting blue light and yellow phosphorus 131 that converts the blue light into white light having a plurality of wavelengths.

In many cases, a light emitting surface “LES” of the light source 102 may have for example a square shape when seen along the y-axis of the coordinate system 199, but it is not wanted that the square shape of the light emitting surface is visible on a light distribution pattern created by the light fixture. The undesired effect of the shape of the light emitting surface can be mitigated for example with textures and/or roughening on the light ingress surface 104 and/or on the light egress surface 105 of a center lens 103 of the optical device 101. Drawbacks of the textures and roughening is that they reduce the efficiency of the optical device 101 by reflecting light backwards towards the light source 102. Furthermore, the textures and roughening may scatter light to undesired directions, and this may in turn cause glare.

Summary

The following presents a simplified summary to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments.

In this document, the word “geometric” when used as a prefix means a geometric concept that is not necessarily a part of any physical object. The geometric concept can be for example a geometric point, a geometric line, a geometric curve, a geometric plane, a non-planar geometric surface, a geometric space, or any other geometric entity that is zero, one, two, or three dimensional.

In accordance with the invention, there is provided a new optical device for modifying a distribution of light produced by a light source.

An optical device according to the invention is made of transparent material, and the optical device comprises a lens having a light ingress surface and a light egress surface. The light ingress surface of the lens comprises a center ingress surface and an outer ingress surface that rims the center ingress surface, wherein the center ingress surface is shaped to constitute a concave lens surface and the outer ingress surface is shaped to constitute a convex lens surface.

In conjunction with the present invention, it has been noticed that a center part of a lens plays a significant role in unwanted projection of a shape of a light emitting surface on a light distribution pattern especially in conjunction with optical devices whose purpose is to produce a narrow and spot-like light distribution pattern wherein collimation is important.

The concavity of the center ingress surface of the optical device according to the invention eliminates or at least reduces an undesired effect of a shape of a light emitting surface of a light source on a light distribution pattern which is generated by a light fixture that comprises the light source and the optical device. Furthermore, as the center ingress surface and the outer ingress surface can be smooth, i.e. free from textures and roughening, reduction in the efficiency of the optical device can be avoided as well as scatter of light to undesired directions and thereby glare can be avoided, too.

In accordance with the invention, there is also provided a new light fixture that comprises:

- a light source, and

- an optical device according to the invention and configured to modify a distribution of light emitted by the light source.

A light emitting surface of the light source is located symmetrically with respect to the center ingress surface of the lens of the optical device. The light source may comprise for example one or more light emitting diodes “LED”.

In accordance with the invention, there is also provided a new mold having a form suitable for manufacturing, by mold casting, a piece of transparent material, e.g. plastic, having a shape of an optical device according to the invention.

Various exemplifying and non-limiting embodiments are described in accompanied dependent claims.

Exemplifying and non-limiting embodiments both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments when read in conjunction with the accompanying drawings. The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features.

The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated.

Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.

Brief description of the figures

Exemplifying and non-limiting embodiments and their advantages are explained in greater detail below with reference to the accompanying drawings, in which: figure 1 illustrates a light fixture that comprises a light source and an optical device according to the prior art for modifying a light distribution, figure 2 illustrates a light fixture that comprises a light source and an optical device according to an exemplifying and non-limiting embodiment for modifying a light distribution, figure 3 illustrates an optical device not constituting a part of the invention, and figure 4 illustrates an optical device not constituting a part of the invention.

Figure 1 has already been explained in the Background-section of this document.

Description of exemplifying and non-limiting embodiments

The specific examples provided in the description given below should not be construed as limiting the scope and/or the applicability of the appended claims. Lists and groups of examples provided in the description given below are not exhaustive unless otherwise explicitly stated.

Figure 2 illustrates an optical device 201 according to an exemplifying and nonlimiting embodiment. The optical device 201 is configured to modify a distribution of light emitted by a light source 202. The light source 202 can be for example a light emitting diode “LED” that comprises a semiconductor part emitting blue light and yellow phosphorus that converts the blue light into white light having a plurality of wavelengths. In figure 2, exemplifying light beams are depicted with dashed line arrows.

In figure 2, the optical device 201 is shown as a section view so that the geometric section plane is parallel with the xy-plane of a coordinate system 299. In this exemplifying case, the optical device 201 is rotationally symmetric with respect to the y-axis of the coordinate system 299. For another example, an optical device according to an embodiment of the invention can be an elongated element so that a section of the kind shown in figure 2 is a cross-section of the optical device and the cross-section is the same over a longitudinal length perpendicular to the geometric section plane. The optical device 201 is a single piece of transparent material whose refractive index is greater than one. The transparent material can be for example acrylic plastic, polycarbonate, optical silicone, or glass. A method of manufacture of the optical device 201 can be for example mold casting. It is however also possible that an optical device according to an embodiment of the invention comprises elements attached to each other or otherwise mechanically supported with respect to each other.

The optical device 201 comprises a lens 203 that has a light ingress surface 204 and a light egress surface 205. The light ingress surface 204 comprises a center ingress surface 206 and an outer ingress surface 207 that rims the center ingress surface 206. The center ingress surface 206 is shaped to constitute a concave lens surface. In the exemplifying optical device 201 , the center ingress surface 206 has a shape of a spherical dome surface. In figure 2, the radius of curvature the spherical dome surface is depicted with an arrow R. The outer ingress surface 207 is shaped to constitute a convex lens surface. In this exemplifying case, the light egress surface 205 of the lens 203 is planar. In an optical device according to an exemplifying and non-limiting embodiment, the surface area of the center ingress surface 206 can be for example from 5 % to 50 % of the surface area of the whole light ingress surface 204.

The concavity of the center ingress surface 206 can be defined for example so that a geometric line segment which connects two geometric points on the center ingress surface 206 to each other is outside the transparent material of the optical device 201 . Correspondingly, the convexity of the outer ingress surface 207 can be defined for example so that a geometric line segment which connects two geometric points on the outer ingress surface 207 to each other and which does not across the center ingress surface 206 is inside the transparent material.

The concavity of the center ingress surface 206 eliminates or at least reduces an undesired effect of a shape of a light emitting surface “LES” 220 on a light distribution pattern generated by the light fixture. Furthermore, in the exemplifying optical device 201 , the center ingress surface 206 and the outer ingress surface 207 are smooth so that the center ingress surface 206 is free from corners inside the center ingress surface and correspondingly the outer ingress surface 207 is free from corners inside the outer ingress surface. Thus, scatter of light to undesired directions and thereby glare can be avoided.

The exemplifying optical device 201 illustrated in figure 2 comprises a reflector section 208 bordering the lens 203. The reflector section 208 comprises a light ingress surface 209 that surrounds the light ingress surface 204 of the lens 203 and a reflector surface 210 for reflecting light arrived through the light ingress surface 209 so that total internal reflections “TIR” take place on the reflector surface 210. The reflector section 208 further comprises a light egress surface 211. In the exemplifying optical device 201 , the light egress surface 211 has a shape of a truncated cone.

The optical device 201 and the light source 202 constitute a light fixture according to an exemplifying and non-limiting embodiment. The light source 202 is mechanically supported with respect to the optical device 201 so that the light emitting surface 220 of the light source 202 is located symmetrically with respect to the center ingress surface 206 of the lens 203 of the optical device 201 .

In a light fixture according to an exemplifying and non-limiting embodiment, the diameter D of the center ingress surface 206 of the lens 203 is in a range from 25 % to 125 % of a diameter of the smallest geometric circle capable of surrounding the light emitting surface 220 of the light source 202. In a light fixture according to an exemplifying and non-limiting embodiment, the light emitting surface 220 of the light source 202 has substantially a square shape when seen along the y-axis of the coordinate system 299.

Figure 3 shows a section view of an optical device 301 not constituting a part of the invention. The geometric section plane is parallel with the xy-plane of a coordinate system 399. Exemplifying light beams are depicted with dashed line arrows. The optical device 301 is made of transparent material whose refractive index is greater than one, and the optical device 301 is rotationally symmetric with respect to the y- axis of the coordinate system 399. The optical device 301 comprises a lens 303 that has a light ingress surface 304 and a light egress surface 305. The light ingress surface 304 comprises a center ingress surface 306 and an outer ingress surface 307 that rims the center ingress surface 306. The center ingress surface 306 is shaped to constitute a concave lens surface, and the outer ingress surface 307 is shaped to constitute a convex lens surface. In this exemplifying case, the light egress surface 305 of the lens 303 is planar. The concavity of the center ingress surface 306 eliminates or at least reduces an undesired effect of a shape of a light emitting surface “LES” 320 on a light distribution pattern modified by the optical device 301 .

The exemplifying optical device 301 illustrated in figure 3 comprises a reflector section 308 bordering the lens 303. The reflector section 308 comprises a light ingress surface and a reflector surface for reflecting light arrived through the light ingress surface so that total internal reflections “TIR” take place on the reflector surface. In this exemplifying optical device 301 , the reflector section has nested subsections each of which comprises a subsection-specific part of the light ingress surface of the reflector section 308 and a subsection-specific part of the reflector surface of the reflector section 308 so that the subsection-specific parts of the light ingress surface and the subsection-specific parts of the reflector surface constitute a saw-tooth profile where the subsection-specific parts of the light ingress surface and the subsection-specific parts of the reflector surface are alternately. In figure 3, two of the nested subsections are denoted with references 312 and 313, a part of the light ingress surface of the reflector section 308 belonging to the subsection 312 is denoted with a reference 314, a part of the light ingress surface of the reflector section 308 belonging to the subsection 313 is denoted with a reference 315, a part of the reflector surface belonging to the subsection 312 is denoted with a reference 316, and a part of the reflector surface belonging to the subsection 313 is denoted with a reference 317. Figure 4 shows a section view of an optical device 401 not constituting a part of the invention. The geometric section plane is parallel with the xy-plane of a coordinate system 499. The optical device 401 is made of transparent material whose refractive index is greater than one. The optical device 401 comprises a lens 403 that has a light ingress surface 404 and a light egress surface 405. The light ingress surface 404 comprises a center ingress surface 406 and an outer ingress surface 407 that rims the center ingress surface 406. The center ingress surface 406 is shaped to constitute a concave lens surface, and the outer ingress surface 407 is shaped to constitute a convex lens surface. In this exemplifying case, the light egress surface 405 of the lens 403 is planar. The specific examples provided in the description given above should not be construed as limiting the scope and/or the applicability of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.