Patent Description:
Flight obstruction illuminators or "lights" are lighting apparatuses attached to high buildings or the like for preventing aircraft from colliding with the structures. The lights increase the visibility of high structures and they are mainly used in the night time, but they are also used during the day, if necessary. Typically the lights are continuously-lit or blinking red lights or white blinking lights. The type, application, lighting, method, intensity and several other aspects are determined by national and international air traffic regulations, such as those by ICAO and FAA.

The advantages of LED lighting are long service intervals, good reliability and long service life. Thus they are especially well suited for use in places with difficult access either due to structural reasons or long distances.

The light beams of flight obstruction lights are constructed to meet the requirements of very precise regulations. Such requirements include, among others, the light power and the width of the beam. In a horizontally omnidirectional light the intensity of the light beam should be as even as possible along the whole circle lit by the light beam. In LED lights the widely emitted light of the light source is controlled by means of lenses. For example, a beam with a vertical extension of three degrees and having a good efficiency requires a large lens. The horizontal light distribution of e.g. a fresnel lens is about <NUM> degress.

Because the intensity of the light emitted from the lens is reduced towards the edges of the light, an area having a lower intensity is formed between two lenses. In order to produce an even light beam ring along the circumference of the circle, a number of lenses, such as eight lenses with <NUM> degree distances, have been installed on a circumference, whereby their light beams partly overlap. This allows producing a good and consistent omnidirectional ring of light, but the lenses form a large circle. Simultaneously the cost effectiveness, weight and ease of handling during installation are decreased.

An advanced obstruction illuminator is disclosed in <CIT> featuring several Fresnel lenses arranged on different supplementary angles.

In addition, <CIT> discloses a multi-LED setup with a concave reflector for illuminating certain sections of the road. <CIT> discloses a discloses an illuminating system for producing navigational light signals with three planar faces, whereon a single-LED illuminators have been mounted. <CIT> discloses an aircraft landing light with multiple LEDs covered by a lens with a flat optical entry surface.

There remains, however, a long standing need to achieve a simplified illuminator construction for achieving a good horizontal coverage of, for example, <NUM> degrees.

It is herein proposed a novel omnidirectional illuminating system, wherein three obstruction or aviation illuminators are arranged at supplementing angles in respect to each other such that angular coverage of the light output of the illuminators covers <NUM> degrees in one dimension. The illuminator features an artificial light source with a plurality of light emitting elements and a lens covering them. The light emitting elements are arranged only along the first Cartesian dimension. The lens has an optical portion which has a first optical surface and a second optical surface that define a thickness there between. The lens has a length in a first Cartesian dimension, a height in a second Cartesian dimension, and a depth in a third Cartesian dimension. The thickness of the optical portion is non-uniform along the first Cartesian dimension and along the third Cartesian dimension. The first optical surface is concave, when viewed in the second dimension from the point of view of the at least one artificial light source. The first optical surface is cylindrical with the cylinder axis extending in the third dimension.

The novel lens geometry provides considerable benefits. The lens design enables an illuminator to be constructed as a planar device that is able to produce an output light pattern with a horizontal coverage of <NUM> degrees. Accordingly, an omnidirectional illuminating system may be constructed from three such illuminators arranged in a triangle. The ability to install light emitting elements and lenses on a planar device as opposed to a multifaceted device considerably simplifies the design and manufacturing.

In the following certain exemplary embodiments are discussed in greater detail with reference to the accompanying drawings in which:.

<FIG> shows an exemplary lens <NUM> in a perspective view with three Cartesian dimensions X, Y, and Z shown for establishing a frame of reference which is to be used throughout this description. The lens <NUM> has two major portions, firstly an optical portion <NUM> for modifying and controlling the passage of light through the lens <NUM> and secondly a mounting portion <NUM> for mounting the lens <NUM> to an illuminator (omitted from <FIG>) and over a light source (omitted from <FIG>). The mounting portion <NUM> has a flange or other suitable shape which is suited to precisely affixing the lens <NUM> to the illuminator. A planar mounting portion <NUM> is preferred because the planar shape ensures correct attitude of the lens <NUM>. The mounting portion <NUM> may include mounting points, such as feet <NUM> shown in the FIGURES, simple through holes, or marked points for indicating drilling locations, etc. The two portions <NUM>, <NUM> are preferably manufactured as integral parts by injection molding, for example. The optical portion <NUM> and the mounting portion <NUM> connect and morph to each other through a side surface <NUM> on the side of the lens <NUM> and at the extreme of the optical portion <NUM>. In this context, the optical portion is the part of the lens <NUM> that produces the visible light pattern when the lens <NUM> is used in its appropriate setting, i.e. mounted to an illuminator.

It may be seen from <FIG> that the optical portion <NUM> is elongated in the first dimension X, relatively flat in the second dimension Y, and relatively narrow in and curved around the third dimension Z. Generally speaking the shape of the optical portion <NUM> is semi-toroidal. When viewed in the third dimension Z, the optical portion <NUM> exhibits a generally annular shape that does not form a complete circle or other non-circular closed profile. In particular, the optical portion <NUM> is penannular when viewed in the third Cartesian dimension Z, i.e. in side elevation. It is to be noticed that the term semi-toroidal may be understood in a non-rigidly mathematical meaning but as a characterization of a shape that curved in one dimension and rounded in another. For example, the second optical surface <NUM> may not exhibit a perfect circle when viewed in the third dimension Z. Instead, and as shall transpire here after, the second optical surface <NUM> is curved with a non-uniform radius.

<FIG> shows the lens <NUM> in a side elevation view along the third dimension Z. The horizontal of <FIG> is aligned with the first dimension X with the vertical aligned with the second dimension Y, whereby the third dimension Z extends up from the shown plane X, Y. In other words the plane view X, Y reveals the largest extension of the optical portion <NUM>. <FIG> also demonstrates how the optical portion <NUM> is curved around the third dimension Z. The length of the optical portion <NUM> is shown as an extension in the first dimension X and the height in the second dimension Y. The width of the optical portion <NUM> is not expressed in <FIG> but may observed in <FIG>, <FIG>, and <FIG> which show the third dimension Z.

An artificial light source <NUM> is sketched in <FIG>. The light source <NUM> may be an LED or a plurality of LEDs arranged in a formation, such as a queue extending in the first dimension X. In the example of <FIG>, the light source <NUM> has three light emitting elements <NUM>, <NUM>, <NUM>, e.g. LEDs, arranged successively in the first dimension X. In other words, the light emitting elements <NUM> - <NUM> are spread along the greatest extension of the optical portion <NUM>. The light emitting elements <NUM> - <NUM> are preferably arranged in the same plane. The light source <NUM> has a main emission direction which in the shown example extends in the second dimension Y, i.e. vertically in the illustration. The main emission direction forms a zero angle which acts as a point of reference to the light pattern produced. The light source <NUM> and the lens <NUM> form an illuminating unit which may form part of a larger illuminator.

The light source <NUM> is placed under a first optical surface <NUM> which in this context is referred to as the optical inlet surface for emphasizing the point of entry of the light emitted by the light source <NUM>. The optical portion <NUM> has a thickness defined by the distance between the optical inlet surface <NUM> and a second surface <NUM>. More specifically, the thickness is observed along a line drawn between a focal point of the optical inlet surface <NUM> and the second optical surface <NUM>, when viewed in the third dimension Z. The second optical surface <NUM> is in this context referred as the optical outlet surface for emphasizing the point of exit of the light emitted by the light source <NUM>. In respect to the light source <NUM> the optical inlet surface <NUM> is the inner surface of the lens <NUM> and the optical outlet surface <NUM> is the outer surface of the lens <NUM>.

<FIG> shows that the optical portion <NUM> of the lens <NUM> has a first axis of symmetry AS1 extending in the second dimension Y at the center point of the optical portion <NUM> along the extension in the first dimension X. While the complete lens <NUM> could share the first axis of symmetry AS1, such symmetry is not required. In fact, the mounting portion <NUM> may be non-symmetrical by including, for example, one chamfered corner and three rounded corners (<FIG>) for orienting the lens <NUM>. The first axis of symmetry AS1 is preferably aligned with the zero angle of the light source <NUM> or a focal point of the optical inlet surface <NUM>.

The optical inlet surface <NUM> is concave when viewed below in the second dimension Y or from the point of view of the light source <NUM>. As shown in <FIG>, the optical inlet surface <NUM> may be arranged in a curved shape around the light source <NUM>. More particularly, the optical inlet surface <NUM> is curved around the third dimension Z. It is preferable that the light source is placed in the focal point of the optical inlet surface <NUM>. It should be pointed out that the entire lens <NUM> may not comprise a single focal point. Rather, there may be several efficient points for the light emitting elements to emit light to produce the light pattern. If, as illustrated in the FIGURES, the optical inlet surface <NUM> has several focal points along a shape, such as a line, it is preferable that the plurality emitting elements of the light source are positioned along that shape. Accordingly, the optical inlet surface <NUM> may be cylindrical. The cylindrical shape may have its axis aligned with the light source <NUM>, particularly with the focal point of the light source. The axis of the cylindrical shape extends in the third dimension Z.

The lens <NUM> has a variable or non-uniform thickness. In view of <FIG>, one way of observing the variable thickness is to study the thickness across the optical portion <NUM> as a function of angular deviation from the zero line or the first axis of symmetry AS <NUM>. Near the first axis of symmetry AS <NUM> the optical portion <NUM> has a thickness t1. As the angle between the first axis of symmetry AS1 and a line connecting the optical outlet surface <NUM> and the focal point of the optical inlet surface <NUM> increases about the third dimension Z or focal point of the optical inlet surface <NUM>, the thickness of the optical portion <NUM> increases. Farther from the first axis of symmetry AS1 the optical portion <NUM> has a thickness t2 which is greater than the thickness t1 nearer the zero line or the first axis of symmetry AS1. It may be stated that the thickness of the extension of the optical portion <NUM> in the first dimension X varies. It may alternatively be stated that the thickness of the extension of the optical portion <NUM> in the first dimension X reaches its maximum at the extreme points in the first dimension X and minimum between the extreme points in the first dimension X, such in the middle. It may alternatively be stated that the thickness of the extension of the optical portion <NUM> in the first dimension X increases from the zero angle or first axis of symmetry AS1 towards the plane defined by the first and third dimension X, Z. In other words the second optical surface <NUM> is curved with a non-uniform radius.

Because the optical portion <NUM> is thicker at the ends and slimmer in the middle of the extension in the first dimension X, a ray of light originating from the light source <NUM> and passing through the optical portion <NUM> travels a longer distance at an end of the optical portion <NUM> than at the middle of the optical portion <NUM>.

Let us turn now to <FIG> which shows a side elevation view of the lens <NUM> in the first dimension X. <FIG> shows that the optical portion <NUM> of the lens <NUM> has a second axis of symmetry AS2 extending in the second dimension Y at the center point of the optical portion <NUM> along the extension in the third dimension Z. The second axis of symmetry AS2 is aligned with the zero angle of the light source <NUM> or a focal point of the optical inlet surface.

The lens <NUM> has a variable or non-uniform thickness in the third dimension Z. In view of <FIG>, one way of observing the variable thickness is to study the thickness across the optical portion <NUM> as a function of angular deviation from the zero line or the second axis of symmetry AS2 which are aligned and therefore herein used interchangeably. Near the second axis of symmetry AS2 the optical portion <NUM> has a thickness t3. As the angle between the second axis of symmetry AS2 and a line connecting the optical outlet surface <NUM> and the focal point of the optical inlet surface <NUM> increases about the first dimension X or focal point of the optical inlet surface <NUM>, the thickness of the optical portion <NUM> decreases. Farther from the first axis of symmetry AS1 the optical portion <NUM> has a thickness t4 which is smaller than the thickness t3 nearer the zero line or the first axis of symmetry AS1. It may be stated that the thickness of the extension of the optical portion <NUM> in the third dimension Z varies. It may alternatively be stated that the thickness of the extension of the optical portion <NUM> in the third dimension Z reaches its minimum at the extreme points in the third dimension Z and maximum between the extreme points in the third dimension Z, such in the middle. It may alternatively be stated that the thickness of the extension of the optical portion <NUM> in the first dimension X decreases from the zero angle or second axis of symmetry AS2 towards the plane defined by the first and third dimension X, Z.

<FIG> shows the lens <NUM> in top elevation view along the second dimension Y which extends up from the shown plane formed by the first and third dimension X, Z. <FIG> shows the third axis of symmetry AS3 of the optical portion <NUM>. The third axis of symmetry AS3 extends along the first dimension X in the middle of the optical portion <NUM> along the third dimension Z.

<FIG> also shows the fourth axis of symmetry AS4 of the optical portion <NUM>. The fourth axis of symmetry AS4 extends along the third dimension Z in the middle of the optical portion <NUM> along the first dimension X.

<FIG> shows a side elevation view of a modified version of the lens <NUM> shown in <FIG>. As may be seen, the periphery <NUM> of the optical outlet surface <NUM> exhibits less draft than the embodiment of <FIG>. Periphery in this context refers to the zone of the optical outlet surface at the transfer between the optical portion <NUM> and the mounting portion <NUM>. The embodiment of <FIG> exhibits a positive draft of <NUM> degrees in respect to the second dimension Y. The embodiment of <FIG> exhibits zero draft in respect to the second dimension Y.

<FIG> shows a side elevation view of a modified version of the lens <NUM> shown in <FIG>. As may be seen, the periphery <NUM> of the optical outlet surface <NUM> exhibits less draft than the embodiment of <FIG>. The embodiment of <FIG> exhibits a negative draft of <NUM> degrees in respect to the second dimension Y. While the embodiment of <FIG> is foreseen, a positive draft, such as that shown in <FIG>, is preferred for manufacturing purposes.

The draft of the periphery <NUM>, be it negative or positive, provides the effect that light rays emitted to the extreme of the optical portion <NUM> will be reflected, which may be utilized to enhance output at the extreme of the light pattern, particularly at <NUM> degrees. The phenomenon is illustrated in <FIG> which shows the output light pattern achieved with the lens <NUM> described above. <FIG> shows the light intensity as a function of radiation angle in the horizontal. As can be seen, the light pattern extends across an angular range of approximately <NUM> degrees. The light reflected off the periphery <NUM> of the optical portion <NUM> of the lens may be seen as a peak at approximately <NUM> degrees rather symmetrically in respect to zero angle. The area is highlighted in <FIG> with a dashed circle. <FIG> shows three different peaks that represent three different draft angles used in experimentation. The benefit is particularly useful for mitigating the effect of a planar transparent cover over the lens. As the lenses may be arranged in a planar setup, also the cover may be planar. Such a cover, despite being made of optically effective material, may due to the angle of the light source, decrease the output of the light source above approximately <NUM> degrees, particularly at approximately <NUM> degrees. With the drafted periphery, the lens <NUM> is able to counteract the dip caused by the cover.

The lens <NUM> as described in connection with any of the embodiments is preferably constructed to produce a light pattern which extends across <NUM> degrees or more in one dimension. The light pattern may be expressed in FWHM or it may be a square wave pattern. In another dimension, the light pattern preferably only extends across <NUM> degrees or less, more preferably five degrees or less, most preferably three degrees or less, such as <NUM> degrees. Such a flat oval light pattern is very desirable in obstruction illuminator applications. In the context of <FIG>, the light pattern is wide in the plane formed by the first and second dimension X, Y, e.g. the horizontal, and narrow in the plane formed by the second and third dimension Y, Z, e.g. the vertical.

According to another embodiment the lens is constructed to produce a light pattern which extends across <NUM> or more but less than <NUM> degrees in the dimension exhibiting the widest angular coverage. Such a lens may be used for augmenting the output of an illuminator pursuing a total light pattern produced with several lenses producing <NUM> degrees or more. The augmenting lens may take the form of a Fresnel lens.

Let us now turn to <FIG> and <FIG>, which show an illuminator provided with a plurality of lenses <NUM> according to the embodiment of <FIG>. <FIG> shows an illuminator <NUM> in plan view along the second dimension. The illuminator <NUM>, when installed, is configured to produce a horizontal light pattern. The perspective of <FIG> is horizontal. The illuminator <NUM> has a frame <NUM> which houses a mounting plate <NUM>. The mounting plate <NUM> supports a plurality of primary illuminating units, which may feature lenses <NUM> described above with reference to <FIG>, and optionally secondary illuminating units, which feature augmenting lenses <NUM>. The augmenting lenses <NUM> are Fresnel lenses that are able to produce a relatively narrow light pattern but with good efficiency. The exemplary illuminator <NUM> has <NUM> primary illuminating units arranged in a five by four matrix pattern and <NUM> augmenting lenses arranged in a five by four matrix pattern that is mixed with that of the primary illuminating units. The illuminating units are installed in the same plane on the mounting plate <NUM>. Such planar installation facilitates manufacturing and optics design. Also, compared to traditional V- or C-shaped mounting plates, the planar installation is able to effectively exploit the light output of the light emitting elements. A practical application of such an illuminator could be a high intensity aviation illuminator for tall structures, such as buildings, bridges, etc. In this context high intensity means an output of <NUM><NUM> effective candela or more.

<FIG> shows the output light pattern achieved with the illuminator <NUM> described above. <FIG> shows the light intensity as a function of radiation angle in the horizontal. As can be seen, the light pattern extends across an angular range of approximately <NUM> degrees. Compared to the output of an individual lens <NUM>, it may be seen that the augmenting lenses <NUM> supplement the light output between the pronounced extremes at approximately <NUM> degrees and at the region of zero angle to achieve a relatively even pattern across the angular coverage in the horizontal.

<FIG> shows the illuminator <NUM> of <FIG> being applied to form an omnidirectional illuminating system <NUM>. <FIG> shows the omnidirectional illuminating system <NUM> in top elevation view, wherein the plane of the FIGURE is horizontal. The omnidirectional illuminating system <NUM> features a triangular frame <NUM> with three illuminators <NUM> mounted to each face. As each of the three covers <NUM> degrees, the summed output of the omnidirectional illuminating system <NUM> is <NUM> degrees in the horizontal. The mounting plates <NUM> of the three illuminators <NUM> are successively turned by <NUM> degrees to each other. That way the illuminators <NUM> are arranged at supplementing angles in respect to each other, whereby the angular coverage of the light output of the illuminators <NUM> covers <NUM> degrees in the horizontal. Simultaneously, the produced light pattern extends across a relatively small angular coverage in the vertical. The vertical angular coverage of the light output may be <NUM> degrees or less, more preferably five degrees or less, most preferably three degrees or less.

Claim 1:
An omnidirectional illuminating system (<NUM>) comprising three obstruction or aviation illuminators (<NUM>) arranged at supplementing angles in respect to each other such that angular coverage of the light output of the illuminators (<NUM>) covers <NUM> degrees in one dimension, such as the horizontal, wherein each illuminator (<NUM>) comprises:
- at least one artificial light source (<NUM>) which comprises a plurality of light emitting elements (<NUM>, <NUM>, <NUM>), wherein the light emitting elements (<NUM>, <NUM>, <NUM>) are arranged only along the first Cartesian dimension (X) and
- a lens (<NUM>) for an obstruction illuminator or an aviation illuminator, the lens (<NUM>) comprising an optical portion (<NUM>) which:
• comprises a first optical surface (<NUM>) and a second optical surface (<NUM>) defining a thickness there between,
• has a length in a first Cartesian dimension (X),
• has a height in a second Cartesian dimension (Y),
• has a depth in a third Cartesian dimension (Z), and which
• covers the plurality of light emitting elements (<NUM>, <NUM>, <NUM>) of the at least one artificial light source (<NUM>),
wherein:
- the thickness of the optical portion (<NUM>) is non-uniform along the first Cartesian dimension (X) and along the third Cartesian dimension (Z),
- the first optical surface (<NUM>) is concave, when viewed in the second dimension (Y) from the point of view of the at least one artificial light source (<NUM>), and in that
- the first optical surface (<NUM>) is cylindrical with the cylinder axis extending in the third dimension (Z).