LENS FOR USE IN A DETECTOR

Abstract

A lens (200) for detecting light waves (110) is provided. The lens comprises a first part (210) configured to receive light waves, wherein the first part (210) has the form of a spherical cap of a first sphere with a first radius. The lens also comprises a second part (220) in the form of a spherical segment of a second sphere (220) with a second radius. The radius of the second sphere is equal to or larger than the radius of the first sphere, and the centers of the first and second spheres coincide in a point on the optical axis of the lens (200). In a base side that faces away from the first part (210), the second part (220) comprises a plurality of concentric sections 230), each having a first surface (230a) that faces away from the optical axis of the lens (200) and that has the form of a spherical zone of a third sphere with a center coinciding with the centers of the first and second spheres. The lens (200) is configured to focus light waves from different angles of incidence onto a common focal plane.

Claims

1. A lens having an optical axis, the lens comprising: a first part in the form of a spherical cap of a first sphere with a first radius (r.sub.0), and a second part in the form of a spherical segment of a second sphere with a second radius (r.sub.j), wherein r.sub.j is equal to or larger than r.sub.0, and wherein the centers of the first sphere and the second sphere coincide in a point on the optical axis, wherein the second part has a top side facing towards the first part and a base side facing away from the first part, wherein the base side comprises a plurality of concentric sections, each section having a first surface that faces away from the optical axis and a second surface that faces towards the optical axis, wherein each first surface has the form of a spherical zone of a third sphere with a center that coincides with the point, wherein, for each section, the first surface and the second surface have a common circular base edge located in a first plane at the base side of the second part, and wherein the second part is configured to transmit at least one light wave of the light waves received by the first part and to project the at least one light wave via the plurality of concentric sections onto a second plane parallel to the first plane.

2. The lens according to claim 1, wherein the spherical zone of at least one first surface has a third radius (r.sub.i) corresponding to the third sphere, and wherein r.sub.i<r.sub.0.

3. The lens according to claim 1, wherein the first part has a spherical surface, and wherein the spherical surface is provided with an anti-reflection layer.

4. The lens according to claim 1, wherein the lens comprises a polymer.

5. The lens according to claim 1, wherein the lens comprises a glass with a refractive index (n), wherein n>1.5.

6. The lens according to claim 1, wherein the first part is a hemisphere.

7. The lens according claim 1, wherein the first part is configured to receive light waves at angles of incidence up to at least 50 degrees with respect to the optical axis.

8. The lens according claim 1, wherein r.sub.0<r.sub.j so that the top side of the second part defines a rim around the first part, and wherein the rim is opaque.

9. A detector for detecting light waves comprising: a lens according claim 1, and a photodetector comprising a plurality of segments arranged in the second plane, wherein each segment of the plurality of segments is arranged to receive at least one light wave of the light waves transmitted by the lens.

10. The detector according to claim 9, wherein the lens and the photodetector are separated by a volume of air.

11. The detector according to claim 9, wherein the volume is enclosed by a cylindrical opaque cover, and wherein the cylindrical opaque cover is arranged at least partially around the second part.

12. The detector according to claim 9, wherein the cylindrical opaque cover is light absorbing.

13. The detector according to claim 9, wherein each segment of the plurality of segments comprises a hexagonal form, and wherein the segments of the plurality of segments are arranged adjacent to each other.

14. A detector arrangement comprising: a Universal Serial Bus (USB) device, and a detector according claim 9, wherein the detector is communicatively connected to the USB device.

15. A detector system, comprising: a detector according to claim 9, and at least one emitter configured to emit light waves detectable by the detector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0053] FIG. 1 schematically shows a cross-sectional view of a lens;

[0054] FIG. 2 schematically shows a cross-sectional view of a detector;

[0055] FIG. 3 schematically shows a perspective view of a detector comprising a lens and a photodetector;

[0056] FIG. 4 shows a top view of a photodetector;

[0057] FIG. 5 schematically shows a perspective view of a detector;

[0058] FIGS. 6a-6d show multiple perspective views of a lens;

[0059] FIGS. 7a-7b show a side view and a perspective view of a lens, respectively; and

[0060] FIG. 8 shows a view of a system comprising a detector and emitters emitting light waves.

[0061] As illustrated in the figures, the sizes of layers and regions are exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of embodiments of the present invention. Like reference numerals refer to like elements throughout.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0062] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

[0063] FIG. 1 shows a cross-sectional view of a lens 200 with an optical axis A. The lens 200 comprises a first part 210 configured to receive light waves 110. The first part 210 has the form of a spherical cap of a first sphere with a center located in point P on the optical axis A. The first sphere has a first radius r.sub.0.

[0064] The lens 200 further comprises a second part 220 adjacently arranged to the first part 210. The second part 220 has the form of a spherical segment of a second sphere with a second radius r.sub.j. The center of the second sphere coincides with the center of the first sphere in point P on the optical axis A.

[0065] The second part 220 has a top side that is facing towards the first part 210 and a base side that is facing away from the first part 210. The base side of the second part 220 comprises a plurality of concentric sections 230. Each section 230 comprises a first surface 230a that is facing away from the optical axis A and a second surface 230b that faces towards the optical axis A.

[0066] For each section, the first surface 230a and the second surface 230b have a common circular base edge located in a first plane K perpendicular to the optical axis A.

[0067] Each first surface 230a has the form of a spherical zone of a third sphere with a center coinciding with the point P on the optical axis A.

[0068] FIG. 1 further shows a second plane H parallel to the first plane K. The second part 220 is configured to transmit at least one light wave of the light waves 110 received by the first part 210 and to project the at least one light wave via the plurality of sections 230 onto the second plane H. In FIG. 1, the first part 210 has the form of a spherical cap of a first sphere with a first radius r.sub.c, and a center in point P on the optical axis A. The second part 220 has the form of a spherical segment of a second sphere with a second radius r.sub.j and a center in point P on the optical axis. The second radius r.sub.j of the second sphere can be equal to or larger than the first radius r.sub.c, of the first sphere. In the lens illustrated in FIG. 1, the second radius r.sub.j is larger than the first radius r.sub.0, which results in a rim 221 on the top side of the second part 220 that surrounds the first part 210.

[0069] For each section 230, the first surface 230a has the form of a spherical zone of a third sphere with a center in the point P on the optical axis. For each first surface 230a, the third sphere associated with the spherical zone has a third radius r.sub.i, wherein i=1, 2, . . . ,N, and wherein N is the number of sections 230. It is understood that the radii r.sub.i and r.sub.c, illustrated in FIG. 1 are exemplary radii and that the radius r.sub.i can be smaller than r.sub.0. The difference between the two radii may also be different in different embodiments, and the skilled person would understand that there are many ways to choose the different radii.

[0070] The refractive index of the first part 210 may differ from the refractive index of the second part 220. Furthermore, the refractive index of the first part 210 and the second part 220 may be the same.

[0071] Furthermore, in FIG. 1 focal lengths f.sub.i and f.sub.i+1 are shown to end up at the second plane H. Each section 230 will, together with the first part 210 and the second part 220, have a respective focal length. This is partly due to the different third radii associated with the sections 230. The angle between one of these focal lengths f.sub.i and the subsequent focal length f.sub.i+1 is illustrated in FIG. 1 as α.sub.i. The spacing between the sections 230 may be determined by for example choosing an equal spacing in angle α.sub.i. The spacing between the sections 230 may also be different and not include equal spacing in angle α.sub.i. A focal length f.sub.i of the lens may depend on r.sub.i, the refractive index n of the lens 200, and the angle α.sub.i, according to the following formula:

[00001]$f_i=\frac{r_{i}n}{2\left(n-1\right)\cos {\alpha }_i}$

[0072] FIG. 2 shows a cross-sectional view of a detector 100. The detector 100 comprises a lens that corresponds to the lens 200 of FIG. 1, and it is referred to FIG. 1 for the associated text for an increased understanding.

[0073] The detector 100 of FIG. 2 further comprises a photodetector 120 extending along a plane that coincides with plane H as illustrated in FIG. 1, perpendicular to the optical axis A. The light waves 110 have an angle of incidence Φ. The photodetector 120 is configured to receive the light waves 110 transmitted by the plurality of sections 230. The photodetector 120 comprises a plurality of segments (not shown in FIG. 2). Each segment is configured to receive at least one light wave of the light waves 110 depending on the angle of incidence. The light waves 110 may for example be modulated light waves configured to carry information. Such modulated light waves may be used with the detector 100 in a LiFi-system for achieving an Internet or data connection.

[0074] Furthermore, the detector 100 of FIG. 2 comprises a volume 150 defined by the separation between the lens 200 and the photodetector 120. The volume 150 can be air. It is to be understood that the volume 150 may be a different transparent medium such as glass or plastic.

[0075] The volume 150 is enclosed by a cylindrical opaque cover 300 that is also arranged around the second part 220 of the lens 200. The cylindrical opaque cover 300 is configured to shield the second part 220 and/or the photodetector 120 from stray light. An example of stray light can be ambient light that is of no interest for detection. The cylindrical opaque cover 300 may have different shapes depending on the lens 200 and the photodetector 120 than that is shown in FIG. 2. Yet another example, the cylindrical opaque cover 300 may comprise multiple (sub) elements and may comprise a coating covering the second part 220 of the lens 200. For example, the coating can be a paint that absorbs light or metal coating that reflects light.

[0076] The rim 221 is also opaque such that unwanted ambient light does not enter the detector 100 directly through the second part 220 of the lens 200 without first passing through the first part 210. The rim 221 may have a coating that absorbs or reflects ambient light.

[0077] FIG. 3 shows a perspective view of a detector 100 extending along an optical axis, A. The detector 100 of FIG. 3 corresponds to the detector 100 of FIG. 2, and it is referred to FIG. 2 and the associated text for an increased understanding. The detector 100 of FIG. 3 comprises a lens 200 comprising a first part 210 and a second part 220. The first part 210 is configured to receive light waves. The first part 210 has a hemispherical shape, allowing the first part to receive light waves from a relatively large range of angles of incidence. The second part 220 comprises a plurality of concentric sections 230 in a base side that faces away from the first part 210, and it is configured to transmit the light waves received by the first part 210 on to the photodetector 120 depending on the angle of incidence of light. The base side of the second part 220 has a portion 310 extending in a first plane K. The photodetector 120 extends in a second plane H. The photodetector 120 comprises multiple segments 130 (not shown in FIG. 3) configured to receive the light waves received by the first part 210 and transmitted by the second part 220. In FIG. 3, the first plane K, and the second plane H extend parallel to each other. The area of the photodetector 120 may be equal, smaller, or larger than the area of the portion 310 of the second part 220.

[0078] FIG. 4 schematically shows an example of a photodetector 120 that may be used in the detector 100 described herein. The photodetector 120 comprises a plurality of segments 130. The segments 130 are placed adjacently to each other and each has a hexagonal shape, placed in a so-called honeycomb pattern. The exemplified honeycomb pattern provides an efficient manner to organize individually functioning photodetector segments, in order to optimize area and/or material usage of the photodetector 120. It is to be understood that the number of segments 130 and the shape of the segments 130 may differ. For example, the photodetector 120 may comprise fewer segments 130, which furthermore may be rectangular. Each of the segments 130 are configured to function independently of each other. By the term “function independently”, it is meant that each segment 130 may detect light waves and generate a signal independently from the functioning of any other segment 130. Furthermore, the signal generated by each of the segment 130 may be distinguishable from one another. Instead of hexagonal, the shapes of the segments 130 may be square, rectangular, triangular, or any other geometric shape. The segments 130 may also have different shapes, meaning that one (first) segment 130 of the photodetector 120 has a certain shape, and another (second) segment 130 of the photodetector 120 has a different shape.

[0079] FIG. 5 shows a perspective view of the detector 100 as described in FIGS. 2 and 3. In this embodiment, the detector 100 further comprises a cylindrical opaque cover 300 configured to hinder or mitigate light from entering the detector 100 without first passing through the first part 210 of the lens 200. The cylindrical opaque cover 300 may be a rim extending radially around the second part 220 of the lens 200 of the detector 100.

[0080] FIGS. 6a-6d show different views of the lens 200 according to the invention. For example, the lens 200 can be used in the detector 100 of one or more of the embodiments disclosed in the application.

[0081] The lens 200 comprises a first part 210 configured to receive light waves. In FIGS. 6a-6d, the first part 210 is shaped as a hemisphere of a first sphere with a first radius and a center in a point P on the optical axis of the lens 200. The hemispherical shape is configured to provide a relatively large viewing angle for the lens 200.

[0082] The lens 200 further comprises a second part 220 configured to transmit the light waves received by the first part 210. The second part 220 has the form of a spherical segment of a second sphere whose center coincides with the center of the first sphere in point P on the optical axis of the lens 200.

[0083] The base side of the second part 220 comprises a plurality of concentric sections 230. Each of the sections 230 comprises a first surface facing away from the optical axis of the lens and having the form of a spherical zone of a third sphere with a center that coincides with the centers of the first and the second spheres in point P on the optical axis of the lens 200.

[0084] The radius of the second sphere associated with the second part 220 is larger than the radius of the first sphere associated with the first part 210, which is visualized as the rim 221 that surrounds the first part 210 in FIGS. 6a-6c. The cylindrical opaque cover 300 described in FIG. 5 may also be configured to shield this rim 221 from incoming stray light, such as ambient light that is of no interest for detection.

[0085] The second part 220 in FIGS. 6a-6d further comprises a plurality of concentric sections 230, each having a first surface facing away from the optical axis of the lens 200 and having the form of a spherical zone of a third sphere with a center in point P on the optical axis, some of which have radii smaller than the radius of the first sphere associated with the hemispherical top part 210. The distance between the sections 230 may vary depending on use.

[0086] FIGS. 7a-7b show two different views of a lens 200 that can be used in the detector 100 of the embodiments disclosed in the application. The lens 200 is similar to the one described in FIGS. 6a-6d with the difference that the second radius of the second sphere associated with the second part 220 is substantially equal to the first radius of the first sphere associated with the hemispherical first part 210. Therefore, the transition from the first part 210 and the second part 220 is smoother in this example.

[0087] It is to be understood that the number of concentric sections 230 may differ, as long as there are two or more sections 230, having first surfaces facing away from the optical axis of the lens and having the form of spherical zones of spheres with different radii.

[0088] FIG. 8 shows a system comprising a detector 100. The system further comprises a plurality of emitters 400 emitting light waves 110. The detector 100 is configured to detect the light waves 110. The plurality of emitters 400 may, for example, be LED lights emitting light waves in the visible or infrared spectrum. It should be noted that the emitters 400 in FIG. 8 are indicated schematically. For example, the emitters 400 may be point sources directly in the ceiling or integrated into the luminaire. The emitters 400 may be configured to emit modulated light waves to create a LiFi-system and supply downlink information for establishing an Internet or data connection.

[0089] A system as shown in FIG. 8 may further comprise a transmitter for emitting modulated light waves in connection with the detector 100. The transmitter for emitting modulated light waves may be able to send information for establishing an internet or data connection. The individual segments of the photodetector in the detector 100 may receive the incoming modulated light waves 110 guided by the lens of the detector 100. This depends on the angles of incidence of the incoming modulated light waves 110. Relative intensity variation measured through the segments of the photodetector will allow determination of the closest emitter and as well as the relative direction of the emitters. This creates the possibility to only establish a connection with a specific emitter 400 with the highest intensity for the best possible connection.

[0090] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.

[0091] The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage. The various aspects discussed above can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that two or more embodiments may be combined.