NL2007701C2

NL2007701C2 - Beacon light optic.

Info

Publication number: NL2007701C2
Application number: NL2007701A
Authority: NL
Inventors: Thomas Leeuwangh; Pieter Gerardus Goedknegt
Original assignee: Orga Holding B V
Priority date: 2011-11-02
Filing date: 2011-11-02
Publication date: 2013-05-07
Also published as: WO2013066180A1

Description

Title: Beacon light optic

Field of the invention

The present invention relates to a beacon light used to mark obstructions that may present a hazard to, for example, aircraft or marine vessel navigation.

5

Background

Conventional beacon light optics are typically either of the lens-type or the reflector-type. Seen in a direction along its optical axis, a beacon light optic of the lens-type includes a light emitting element juxtaposed to a lens, 10 whereas a beacon light optic of the reflector-type typically includes a light emitting element juxtaposed to a reflector. The lens and the reflector, respectively, serve to both collect light emitted by the light emitting element, and to redirect the light into the desired directions. An aviation beacon light that is mounted on top of an obstruction, for example, may emit light outward 15 over a 360° angular distribution in the horizontal plane to provide an obstruction warning in all directions. The beam spread - i.e. the angle of the beam measured in a vertical plane over which the intensity of the emitted light is greater than 50% of the peak intensity of the emitted light - of the light may typically be on the order of several degrees, e.g. 3 degrees. Collecting the light 20 from the light emitting element of the beacon light optic, and effecting therefrom a beam of light with the desired properties is the purpose of the lens or reflector.

US 7,758,210 (Peck) discloses both a beacon light with optics of the lens-type and a beacon light with optics of the reflector type.

25

Summary of the invention A drawback of conventional beacon light optics, such as those disclosed by US’210, is that the single optical element, i.e. the lens or the reflector, fulfills two functions: light collection, and light redirection.

2

Optimizing the configuration of the optical element for one of these functions may lead to concessions in the implementation of other. Such concessions can only be avoided in part by increasing the complexity of the optical element’s design, and hence its manufacturing costs.

5 It is an object of the present invention to provide for an alternative beacon light optic that is structurally simple, compact, economically manufacturable, and energy efficient in the sense that light losses within the optic are minimized.

To this end, a first aspect of the present invention is directed to a 10 beacon light optic. The beacon light optic includes a light transmitting element having an optical axis, a first linear extrusion axis perpendicular to the optical axis, a front surface, and a back surface that is disposed opposite said front surface. The front surface defines a slot having a semi-circular cross-sectional portion that is projected along the first linear extrusion axis. The back surface 15 has a parabolic cross-sectional portion that is projected along the first linear extrusion axis, which parabolic cross-sectional portion has a focus line that substantially coincides with a center line of the semi-circular cross-sectional portion of the slot. The beacon light optic further includes a light reflective coating that is provided over substantially the entire back surface of the light-20 transmitting element. In addition, the beacon light optic includes at least one light emitting element that is disposed in front of the light transmitting element such that a light emitting surface of the light emitting element faces the semi-circular cross-sectional portion of the slot.

The beacon light optic according to the present invention employs a 25 very compact, dual optic, including both a lens, i.e. the light transmitting element, and a reflector, i.e. the light reflective coating. In use, light from the light emitting element is first collected by the front surface of the lens, and then guided towards the back surface of the lens where the reflector redirects the light, at least by generally reversing its direction of propagation. 30 Subsequently, the light is guided back towards the front surface of the lens, 3 which eventually refracts and emits the light according to the desired light distribution. In the presently disclosed dual optic, it is the interplay between the lens and the reflector that determines both the amount of light that is collected and eventually emitted, and the directions in which the light is 5 emitted.

It may in particular be noted that the optionally anti-reflectively coated slot in the front surface of the lens may arc over the light emitting element, so as to ensure optimum capture of light. In addition, the dual nature of the single-piece optic eliminates the dependence on total internal reflection 10 at the lens’s surfaces to redirect the light. More specifically, since a light reflective coating is provided on the back surface of the light transmitting element, light will be reflected at the back surface, within the light transmitting element and to a degree irrespective of its angle of incidence relative to the back surface. The light reflection within the light transmitting 15 element thus prevents light losses associated with optical interface transitions, and mimics the efficiency of total internal reflection. Yet, the use of the light reflective coating enables greater control over the shapes of the surfaces of the light transmitting element, and hence over the amount of light that can be collected and the directions in which the collected light is eventually 20 distributed.

A second aspect of the present invention is directed to a beacon light for marking obstructions that present a hazard to aircraft or marine vessel navigation. The beacon light comprises a plurality of beacon light optics according to the first aspect of the invention. The optics are arranged in 25 juxtaposition, such that the first extrusion axes (z) of adjacent optics are angled relative to each other at non-zero angles, while their front surfaces face outward and away from each other.

In one embodiment, the optics of said plurality of beacon light optics are arranged such that, in use, light is emitted outward over at least a 90° 30 angular distribution in a plane defined by the optical axis (x) and the first 4 extrusion axis (z), or a plane parallel thereto. Beacon lights with a 90° angular distribution in the horizontal plane are particularly useful for marking obstructions that include walls defining inward and outward comers; a straight inward corner may, for example, be fitted with a beacon light with an 5 angular distribution of 90°, while a (straight) wall may be fitted with a beacon light with an angular distribution of 180°, and a straight outward comer may be fitted with a beacon light with an angular distribution of about 270°.

In another embodiment, the beacon light may include a first and a second plurality of beacon light optics according to the first aspect of the 10 invention. The respective optics of the first and second pluralities may be arranged in juxtaposition, such that the first extrusion axes of adjacent optics are angled relative to each other at non-zero angles, while their front surfaces face outward and away from each other. In addition, the optics of the second plurality may be stacked on top of the optics of said first plurality. Accordingly, 15 multiple (partial) rings of outwardly radiating optics may be placed on top of each other within a single beacon light, so as to increase that beacon light’s available light power.

These and other features and advantages of the invention will be more fully understood from the following detailed description of certain 20 embodiments of the invention, taken together with the accompanying drawings, which are meant to illustrate and not to limit the invention.

Brief description of the drawings

Fig. 1 schematically illustrates an exemplary embodiment of a 25 beacon light according to the present invention, including two stacked rings of optics;

Fig. 2 is a schematic perspective view of an isolated beacon light optic as used in the beacon light of Fig. 1;

Fig. 3 is a schematic front view of the beacon light optic shown in 30 Fig. 2; 5

Fig. 4 is a schematic side view of the beacon light optic shown in Fig.

2;

Fig. 5 is a schematic top view of the beacon light optic shown in Fig.

2; and 5 Fig. 6 is a schematic perspective view of the beacon light optic of

Figs. 2-5, illustrating the paths of light rays emanating from the light emitting surface of the middle light emitting element.

Detailed description 10 Fig. 1 schematically illustrates an exemplary embodiment of a beacon light 1 according to the present invention. The beacon light 1 may include a housing 2, having a base 4 on top of which a substantially cylindrical compartment, circumferentially bounded by a cylinder jacket-shaped transparent shield 3, is positioned. Within the cylindrical compartment, the 15 housing 2 may accommodate a plurality of beacon light optics 10, which may be arranged in one or more stacked rings 8, 8’ each including a plurality - in the embodiment of Fig.1 : seven - optics 10. As will more fully understood from the description below, the optics 10 within each ring 8, 8’ may be arranged in a regular polygon, e.g. a heptagon, with their front surfaces facing outwards, and 20 the z- or first extrusion axes of adjacent optics 10 angled relative to each other at non-zero angles, so as to be able to emit light outward over a 360° angular distribution in the horizontal plane to provide an obstruction warning in all directions. The housing 2 may further accommodate a power supply/ transformer and/or control logic (not shown), which on the one hand may be 25 electrically connected to the beacon light optics 10, and on the other hand to an external electrical connector 6 via which power may be supplied to beacon light 1. The beacon light 1 may be attached to, especially mounted on top of, a structure to be marked by means of the base 4.

Figs. 2-5 schematically illustrate an isolated beacon light optic 10 as 30 used in the beacon light 1 of Fig. 1 in a perspective view, a front view, a side 6 view and a top view, respectively. To enable a clear exposition, each Figure 2-5 further indicates a right-handed Cartesian coordinate system including an x-axis, a y-axis and a z-axis, which may be considered to be fixedly connected to the geometrical center of the optic 10. The construction of the optic 10 will now 5 be illustrated with reference to Figs. 2-5.

The beacon light optic 10 may include a light transmitting element 12. The light transmitting element 12 may be made of any material that transmits light at the wavelengths at which the light emitting elements 32 (to be discussed infra) are configured to emit light, including glass, optical grade 10 acrylics such as polymethylmethacrylate (PMMA), and polycarbonate. The element 12 may define a front surface 14, a back surface 22, two side surfaces 30, 30’, and a bottom and a top surface 32, 32’. The front and back surfaces 14, 22 may typically be the largest of the surfaces 14, 22, 30, 30’, 32, 32’ in terms of surface area. The front surface 14 may be disposed substantially opposite 15 the back surface 22, while the two side surfaces 30, 30’ and the bottom and top surfaces 32, 32’, respectively, may be disposed opposite to each other. Each of the side surfaces 30, 30’ and the bottom and top surfaces 32, 32’ may interconnect the front and back surfaces 14, 22 along a portion of their respective circumferential edges.

20 Near the corners of the beacon light optic 10, where the front and back surfaces 14, 22 meet with one of the side surfaces 30, 30’ and one of the bottom and top surface 32, 32’, the light transmitting element 12 may be fitted with a mounting provision 40. In the depicted embodiment, there are four identical mounting provisions 40 in the form of a flat plate-like protrusion 25 fitted with a through-hole, one near each corner. The mounting provisions 40 may preferably be integrally formed with the body of the light transmitting element 12 to facilitate the manufacture of the optic 10. It is understood, however, that in other embodiments the optic 10 may be fitted with fewer or more, possibly differently shaped mounting provisions 40 that may be disposed 30 at different positions at the outer surfaces of the light transmitting element 12.

7

The front surface 14 of the light transmitting element 12 may define a slot 16 that runs substantially the entire width of the light transmitting element 12, or at least a substantial portion thereof, e.g. at least 10%, and preferably at least 80% of the width. In some embodiments, the slot 16 may 5 include multiple sub-slots; i.e. the ‘main’ slot may not be continuous, but -seen along its length - define multiple sub-slots. The slot 16 may have a semicircular cross-sectional portion 18 that is projected along the z- or first linear extrusion axis. The semi-circular cross-sectional portion of the slot 16 may preferably be symmetrical relative to the a plane xz-plane, or a plane parallel 10 thereto. To optimize the light-capturing capability of the slot 16, its surface, and in particular its semi-circular cross-sectional portion 18, may be provided with an anti-reflection coating. The slot 16 may be disposed anywhere along the height of the front surface 14, and preferably at about halfway the height thereof, such that the front surface 14 may define both a first and a second 15 light-exiting surface portion 14a, 14b on opposite sides of the slot 16. As far as their surface area and curvature are concerned, the first and second light-exiting surface portions 14a, 14b may be identical. This is the case in the depicted embodiment, where both the first and second light-exiting surfaces 14a, 14b have a cross-section that is projected along the y- or second linear 20 extrusion axis. I.e. one of the principle radii of curvature of either surface 14a, 14b is infinite; the other principle radius of curvature may preferably be at least 125 mm, so as to limit the curvature thereof to a maximum considered suitable for beacon light optics. In alternative embodiments the first and second light exiting surfaces 14a, 14b may differ in surface area and/or 25 curvature. For instance, in one embodiment, the first light-exiting surface 14a may be twice the size of the second light-exiting surface 14b, and be doubly curved while the second light-exiting surface 14b may be only singly curved.

The back surface 22 of the light transmitting element 12 may be disposed substantially opposite the front surface 14, such that the x- or optical 30 axis of the light transmitting element 12 extends through both said surfaces 8 14, 22. In addition, each of the front and back surfaces 14, 22 may preferably be symmetrical with respect to the optical axis. The back surface 22 may include a substantially parabolic cross-sectional portion 24 that, like the slot 16, is projected along the z- or first linear extrusion axis. A focus line 26 of the 5 parabolic cross-sectional portion may run parallel to, and substantially coincide with, a center line 20 of the semi-circular cross-sectional portion 18 of the slot 16.

The back surface 22 may be provided with a single- or multilayer light reflective coating 28, which may extend over substantially the entire 10 surface area thereof. The light reflective coating 28 may be made of any suitable material(s), including in particular aluminum and silver, and preferably have a reflectivity of at least 80%, and more preferably at least 90%, at the wavelengths at which the light emitting elements 32 (to be discussed infra) are configured to emit light. The reflective coating 28 may generally 15 have a thickness smaller than about 5 pm, and be applied to the back surface 22 by, for example, physical or chemical vapor deposition (PVD, CVD), dip coating, spraying etc.

To prevent light travelling through the light transmitting element 12 from disadvantageously escaping, the side surfaces 30, 30’ and/or the 20 bottom and top surfaces 32, 32’ of the light transmitting element 12 may also be coated with a light reflective coating, just like the back surface 22.

The beacon light optic 10 may further include at least one light emitting element 34. The at least one light emitting element 34 may include one or more (approximate) point sources, e.g. LEDs, or elongate line sources, 25 e.g. a xenon discharge tube, a fluorescent tube or an LED strip. Compared to point sources, a line source may increase the amount of produced/available light (lumen) per optic 10 so as to enable the beacon light 1 with a certain light output to be built more compactly. The at least one light emitting element 34 may include a light emitting surface 36, having a light emitting axis 38 that 30 extends substantially perpendicular thereto. The light emitting element 34 9 may be disposed in front of the light transmitting element 12, such that its light emitting surface 36 faces the semi-circular cross-sectional portion 18 of the slot 16, and preferably such that the light emitting axis 36 extends in alignment or in parallel with the x- or optical axis of the light transmitting 5 element 12. In a preferred embodiment, the light emitting surface 36 may be disposed at or near the center line 20 of the semi-circular cross-sectional portion 18 of the slot 16, preferably within a distance of about 0.5 mm thereof. In the depicted embodiment, the optic includes a plurality, namely five, light emitting elements 34 in the form of high-power LEDs. The LEDs 34 are 10 regularly spaced apart along the 2-axis, in a configuration that is symmetric with respect to the middle of the slot 16, and disposed in front of the light transmitting element 12 such that their light emitting surfaces 36 are positioned substantially at the center line 20 of the semi-circular cross-sectional portion 18 of the slot 16, and hence at the focus line of the parabolic 15 cross-sectional portion 24 of the back surface 22.

Now that the construction of the beacon light optic has been described in some detail, attention is invited to its operation. For this purpose, Fig. 6 shows a schematic perspective view of the beacon light optic 10 of Figs. 2-5, now including the paths of a number of imaginary light rays emanating 20 from the light emitting surface 36 of the middle light emitting element 34. For clarity, the paths of the light rays are shown only in the horizontal xz-plane and in the vertical ry-plane.

Referring first to the light rays in the horizontal x2-plane, which are marked with an open arrow head. Light rays emanating from the light 25 emitting surface 36 of the light emitting element 34 will first strike the front surface 14 of the light transmitting element 12 at the linearly extruded slot 16. As they pass the interface, the diverging light rays will be refracted towards the x- or optical axis of the optic 10. That is, the linearly extruded interface acts to collect as much light from the light emitting element 34 as possible, and 30 to direct the collected light towards the back surface 22 of the light 10 transmitting element. Light rays that are insufficiently refracted to be immediately redirected towards the back surface 22 may be reflected towards the back surface through reflections at the side surfaces 30, 30’. Light rays that subsequently impinge on the back surface 22 are reflected by the light 5 reflective coating 28 provided thereon, and transmitted back towards the front surface 14, more particularly towards the linearly extruded interface of the slot 16 thereof. Back at that interface, the light rays are refracted away from the x- or optical axis as they leave the light transmitting element 12. The result is a strongly diverging light beam in the horizontal X2-plane.

10 Referring now to the light rays in the vertical xy-plane, which are marked with a closed arrow head. Light rays emanating from the light emitting surface 36 of the light emitting element 34 will first strike the front surface 14 of the light transmitting element 12 at the semi-circular cross-sectional portion of the slot 16. As the light emitting surface 36 of the light 15 emitting element 34 is disposed at the center line of the semi-circular cross-sectional portion 18, the light rays will pass into the light transmitting element 12 substantially without being refracted. Furthermore, since the center line 20 of the semi-circular cross-sectional portion 18 of the slot 16 coincides with the focus line 26 of the parabolic cross-sectional portion 24 of 20 the back surface 22, the light rays will be reflected at the back surface 22 to form an approximately collimated beam that propagates back towards the front surface 14, and more particularly towards the light-exiting surface portions 14a, 14b thereof. Because the light-exiting surface portions 14a, 14b have a cross-section that is symmetrical relative to the xy-plane, the reflected 25 light rays travelling in the vertical xy-plane will leave the light transmitting element 12 via the light-exiting surface portion 14a, 14b substantially without being refracted.

One skilled in the art will appreciate that although the light emitting element 34 may be approximated by a point source that is disposed 30 on the center line 20 of the semi-circular cross-sectional portion 18 of the slot 11 16, it is in fact not. Consequently, light rays travelling into and out of the light transmitting element 12 via the front surface 14, within the ry-plane, may undergo some refraction which may eventually cause the light beam exiting the light transmitting element 12 to be imperfectly collimated. By 5 intentionally deviating the position of the light emitting surface 26 from the center line 20, e.g. by a few tenths of a millimeter, a light beam having a certain defined beam spread may be created.

It will be clear that light rays emanating from the light source 34 and not bound to the xy- or xz-planes will travel paths that are 10 (vector)componentwise similar to those of the light rays discussed above with reference to Fig. 6.

In this text relative terms such as for example ‘horizontal’, ‘vertical’, ‘left’, ‘right’, ‘top’, ‘bottom’, ‘back’ and ‘front’ as well as adjectival and adverbial derivatives thereof (e.g. ‘horizontally’, ‘upwardly’, etc.) should be construed to 15 refer to the particular orientation as then described or shown in the drawing or figure under discussion. Relative terms are employed to clarify the exposition and may reflect a typical orientation, e.g. an orientation typical for the intended use or execution of the present invention. However, unless expressly stated otherwise, relative terms are not intended to limit the scope of the 20 invention to any particular orientation.

Although illustrative embodiments of the present invention have been described above, in part with reference to the accompanying drawings, it is to be understood that the invention is not limited to these embodiments. Variations to the disclosed embodiments can be understood and effected by 25 those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. 30 Thus, the appearances of the phrases "in one embodiment" or "in an 12 embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, it is noted that particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner to form new, not explicitly described 5 embodiments.

13

List of elements 1 beacon light 2 housing 3 transparent shield 5 4 base 6 connector 8 ring of beacon light optics 10 beacon light optic 12 light transmitting element 10 14 front surface 14a first light-exiting surface portion 14b second light-exiting surface portion 16 slot in front surface of light transmitting element 18 semi-circular cross-sectional portion of slot 15 20 center line of semi-circular cross-sectional portion of slot 22 back surface 24 parabolic cross-sectional portion of back surface 26 focus line of parabolic cross-sectional portion 28 light reflective coating on back surface 20 30, 30’ left/right side surface 32, 32’ bottom/top surface 34 light emitting element 36 light emitting surface 38 light emitting axis 25 40 mounting provision x optical axis (depth) y second linear extrusion axis (height) ^ first linear extrusion axis (width)

Claims

A beacon light optic (10), comprising: - a light-transmitting element (12) with an optical axis (x), a first linear extrusion axis (2) extending perpendicular to the optical axis (x), a front surface (14) ), and a rear surface (22) arranged opposite said front surface; wherein said front surface (14) defines a slot (16) with a semicircular cross-sectional portion (18) projected along the first linear extrusion axis (x); wherein said rear surface (22) has a parabolic cross-sectional part (24) projected along the first linear extrusion axis (2), said parabolic cross-sectional part having a focus line (26) substantially coinciding with a centerline (20) of the semicircular cross-sectional portion (18) of the slot (16); - a light-reflecting coating (28) applied to substantially the entire rear surface (22) of the light-transmitting element (12); and - at least one light emitting element (12) provided in front of the light emitting element (12) such that a light emitting surface (34) of the light emitting element (32) faces the semicircular cross-sectional portion (18) from the slot (16).

The beacon light optic according to claim 1, wherein the light emitting surface (34) of the at least one light emitting element (32) is provided at the center line (20) of said slot (20).

3. The beacon light optic according to claim 1 or 2, wherein the light emitting element (32) has a light emitting axis (36) perpendicular to its light emitting surface (34), and parallel to the optical axis (x) of the light transmitting element (12).

The beacon light optic according to any of claims 1-3, wherein the front surface (14) of the light-transmitting (12) comprises a first light-emitting surface part (14a) provided on a first side of the slot (16), and a second light-emitting surface portion (14b) provided on a second, opposite side of the slot (16).

The beacon light optic according to claim 4, wherein at least one of the first and second light-emitting surface parts (14a, 14b) is convex.

The beacon light optic according to claim 5, wherein the at least one of the first and second light-emitting surface parts has a principal radius of curvature of at least 125 mm.

The beacon light optic according to any of claims 4-6, wherein the at least one of the first and second light-emitting surface parts (14a, 14b) is double-curved.

The beacon light optic according to any of claims 4-6, wherein the light transmitting element (12) further has a second linear extrusion axis (v) perpendicular to both the optical axis (x) and the first linear extrusion axis ( z) 15, and wherein at least one of the first and second light-emitting surface portions (14a, 14b) has a cross-sectional area projected along a portion of the second linear extrusion axis.

9. The beacon light optic according to any of claims 1-8, wherein the light-emitting surface (36) of the at least one light-emitting element (34), measured along the optical axis (x), is within 1 mm, and preferably within 0.5 mm, of the focus line (26) of the parabolic cross-sectional portion (24) of the rear surface.

10. The beacon light optic according to any of claims 1-9, wherein the at least one light-emitting element comprises a plurality of light-emitting elements.

The beacon light optic according to any of claims 1-10, wherein the light reflecting coating has a reflectivity of at least 80%.

12. The beacon light optic according to any of claims 1-11, wherein the light-reflecting coating (28) is at least partially made of aluminum or silver.

The beacon light optic according to any of claims 1 to 12, wherein the light transmitting element (12) is at least partially made from polymethyl methacrylate or polycarbonate.

The beacon light optic according to any of claims 1-13, arranged such that light emitted by the optic (10) has a beam spread of less than 5 degrees in a plane defined by the optical axis (x) and the second extrusion axis (y).

The beacon light optic according to any of claims 1-14, arranged such that light emitted by the optic (10) has a beam spread 10 of at least 10 degrees in a plane defined by the optical axis (x) and the first extrusion axis (z)

16. A beacon light (1) for marking obstacles that pose a danger to air or shipping navigation, comprising: - a first plurality (8) of beacon light optics (10) according to any of claims 1-15; said optics (10) of said first plurality being placed side by side such that the first extrusion axes (z) of adjacent optics are not mutually aligned and enclose an angle, while their front surfaces (14) are outward and apart have turned away.

A beacon light (1) according to claim 16, wherein said optics of said first plurality are arranged such that, in use, light is radiated outward over an angular range of at least 90 ° in a plane defined by the optical axis (x ) and the first extrusion axis (z), or a plane parallel thereto.

A beacon light (1) according to any of claims 16-17, further comprising: - a second plurality (8 ') of beacon light optics (10) according to any of claims 1-15; said optics (10) of said second plurality being placed side by side such that the first extrusion axes (z) of adjacent optics are not mutually aligned and enclose an angle, while their front surfaces (14) extend outwardly and out of are turned away from each other, and wherein said optics of said second plurality (8 ') are stacked on top of the optics of said first plurality (8).