Headlamp with stepped lens and variable distance between light source and reflector

The invention relates to a Fresnel lens spotlight, with adjustable aperture angle of the emergent light bundle, with a reflector, a lamp and at least one Fresnel lens.

The light-relevant parts in common Fresnel spotlights generally comprise a lamp, a Fresnel lens (Fresnel lens) and a spherical Auxiliary reflector. Conventionally, there is the lamp filament essentially unchanging in the center of the sphere spherical reflector. Thereby, a part of of the Lamp emitted light reflected back into this and the light output supported in the forward hemisphere. This front-facing light is the Fresnel lens bundled. The degree of light-condensing However, the distance between the Fresnel lens and the Lamp depends. the lamp filament is located in Focal point of the Fresnel lens, the result is the tightest Light collection. This is a quasi-parallel Beam, also called spot obtained. shortening the distance between the Fresnel lens and the lamp is the aperture angle of the emergent light beam steadily enlarged. This is a divergent beam, which also Flood is called, receive.

A disadvantage of such headlights, however, the poor light output, particularly in the spot position, since only a relatively small solid angle range the lamp is detected by the Fresnel lens. Also acts it is disadvantageous that the spherical of the Reflector light reflected to a large extent the Lamp filament itself meets again, it is absorbed and the lamp filament heats up additionally.

From DE 39 19 643 A1 is a headlamp with a Reflector, a diaphragm and a Fresnel lens known. With the headlamp is an adjustment of the Light source changes the illumination. This is a Change in brightness of the light effect. A Distance regulation between the apex and the reflector and between the aperture and the reflector is used to Brightness control.

From DE 34 13 310 A1 is a headlamp with a Lamp and a reflector or a lamp and a Collecting lens known. The headlamp further includes a Lens or a mirror, both of the angles are positioned at 45 °. Through the mirror, the light and deflected through the lens, the light scattered. By shifting the lens generates different light beam emission angles.

The DE 101 13 385 C1 describes a Fresnel lens spotlight, wherein the Fresnel lens is a Converging lens whose light-source-side focal point in the spot position approximately in reflectorless distant focal point of ellipsoidal reflector is. Thus, adding the Distances of the focal points of the reflector, the focal length of Reflector and the focal length of the Fresnel lens to Minimum length of such a Fresnel lens spotlight.

However, the invention is a Fresnel lens spotlight be created, which has a more compact design and consequently both space-saving and lighter than the conventional Fresnel lens spotlights is.

This object is achieved in a surprisingly simple manner with a Fresnel lens spotlight according to claim 1 and a lighting kit solved according to claim 19th

By using a Fresnel lens with a negative Focal length, achieves an extremely compact design be that, for example, in the spot position of the Fresnel lens spotlight essentially only the Length of the reflector together with the thickness of each Fresnel lens used corresponds.

is The inventive Fresnels a significantly improved light efficiency, in particular in Spot, but also achieved in flood position.

At the same time, the uniformity is the Illuminance in the entire light field obtained as this as an example in Figure 7 both for the spot is also shown for a flood position.

According to the invention is an ellipsoidal reflector with large Aperture provided. The spot position is set so that the lamp filament of a Black body radiator, in particular a halogen lamp or the discharge arc of a discharge lamp in reflector-side focal point of the ellipsoid is and reflectorless distant second focus of the ellipsoid in about negative or virtual focal point of the reflector remote Fresnel lens is arranged.

The light is reflected by the reflector before entry in the negative lens almost completely on the reflector distant focal point of the ellipsoid focused. The in the reflector-side focal point located Lamp filament or the discharge arc is after Passing through the Fresnel lens in the infinite ready and its light is thus in an almost parallel beam converted.

The reflected light is no longer true substantially the lamp filament or the discharge arc. The virtual negative focal point of the Fresnel lens coincides with the reflector distant focal point of the reflector together and hereby provides an extremely compact design.

With more appropriate choice of Aperturwinklels of reflector and the Fresnel lens is reflected by the reflector Light almost completely covered by the Fresnel lens and emitted as a narrow spot beam forward.

The light output is therefore considerably higher than in a conventional Fresnel lens spotlight.

The opening angle of light emerging from the Fresnel lens Beam may in a first embodiment almost be arbitrarily increased by the lamp in position With respect to the reflector on the one hand and the distance between the Fresnel lens to the reflector on the other hand suitably is changed.

Thus, the good properties of conventional Fresnel lens spotlight in relation to the uniformity remain the illuminance, this should Distance changes by a suitably chosen Compulsory coupling done.

An embodiment of the invention is that the Ellipsoid of a metallic or transparent material. Preference is given to glass and polymeric materials or plastics are used, which advantageously with a metal such as aluminum, may be coated.

Alternatively or additionally, one is used for preparing reflective surface be one of the two or both surfaces of the reflector with a system optically thin layers provided. Thereby reflected advantageously visible radiation components and the invisible components, in particular Thermal radiation components, passed.

A further preferred embodiment of the invention comprises a metallic coating on one or both Major surfaces of the reflector.

In another alternative configuration, the reflector a metallic reflector which both uncoated as well dielectric or metallic may be coated to provide the desired spectral and provide corrosion properties.

A preferred embodiment of the invention comprises a Fresnel lens spotlight, wherein the light-reflecting surface of the reflector light scattering is structured and none, one or two surfaces of the Fresnel lens are structured to scatter light. hereby there is a fixed share of the superposition scattered light to geometrically-optically imaged Light, which has a picture of the lamp in the light field avoids. Preferably, the reflector has this Partial surfaces or facets, which make it possible defined to calculate the light scattering portions and finished.

With increasing miniaturization of the light source, such as on the important field of digital projection or However, high-intensity discharge lamps, a more more pronounced medium dark area occur which stray facilities within the Reflector not or only with large light losses can be compensated. The conventional, to Avoid imaging of the emission center of create light source used scattering bodies here only limited, if any remedy, since this in every position of the Fresnel lens spotlight least illuminated the dark central aperture cone homogeneously must become. but precisely in this way it is particularly important in the spot position to large light losses, since only a present dark area with very small aperture but scattering of the conventional Fresnel lens with Facilities yet the full face of the Fresnel lens to Scattering of the light field is used.

The inventors have found that these high avoiding light losses in a surprisingly simple manner can be. It is particularly advantageous if the Fresnel lens comprises a diffuser, which in particularly preferably circular and only arranged still in the center of the Fresnel lens.

In this embodiment, in each position of the Fresnel lens spotlight the dark areas in the middle the illumination field are very effectively prevented, but it does not come to the high losses of light in the Spot position of the reflector.

Surprisingly, it appears that the geometrical-optical beam path of the out of the reflector emerging light at the location of the Fresnel lens precisely then a smaller area illuminates when the proportion required to scattered light is increased.

This effect, the inventors have made use to with the invention, an automatic or adaptive to provide light mixing system which synchronously with the Adjustment of the Fresnel lens spotlight only those Stray light to geometrically-optically imaged light mixed added which is required for this position.

This light mixing ratio, which almost perfectly to the respectively required light distributions are adapted can, is hereinafter abbreviated merely as Mixing ratio refers.

This automatic light mixing system is in Essentially for every position of the reflector, the correct Mixing ratio and thus always a very homogeneously illuminated light field created without this However unnecessary wastage occur.

Here, by the choice of the diameter of integrated diffusing screen in relation to the remaining Surface of the Fresnel lens, the mixing ratio of the whole area illuminated Fresnel lens can be defined and, by the scattering properties of the negative lens of the opening angle the scattered light can be defined.

Further, on the integrated diffusing screen itself the vary scattering effect, so that for example in the Center of the lens strongly scattering regions and to whose edge located less strongly scattering regions are. In this way, a more focused Ray beam additionally widened and let then extremely realize wide illumination angle.

Alternatively, the edge of the lens can not only abruptly ending be configured but can this in its scattering effect decreases continuously be designed extend and still below or above the Fresnel lens. This can be further adjustments to the making position-dependent mixing ratios.

With reference to the filed on the same day Application of the same applicant entitled "Optical Arrangement with fresnel lens ", the disclosure of which by Referring completely also the disclosure of the the present application is made.

According to the invention the use of the headlamp is for Architecture, medicine, film, stage, studio and photography and provided in a flashlight.

The lens may in preferred embodiments on both the light entry and at the be located light exit side. Furthermore, there is advantageous possibility of spreading discs at the Light entry and to be arranged on the light exit side. In this latter embodiment can also different scattering, for example, different locally scattering, spreading discs are used.

The invention is based on preferred embodiments and with reference to the accompanying drawings described in more detail.

Show it:<dl tsize="6" compact="compact"><dt>Fig. 1</dt><dd>an embodiment of the Fresnel lens spotlight in Spot position, the reflector distant focus the reflector in approximately the right side superimposed virtual focal point of the Fresnel lens is,</dd><dt>FIG. 2</dt><dd>the embodiment shown in Fig. 1 of Fresnel lens spotlight in a first Flood position, wherein the reflector far Focus of the reflector approximately in a close to the reflector surface of the Fresnel lens is arranged,</dd><dt>Fig. 3</dt><dd>the embodiment shown in Fig. 1 of Fresnel lens spotlight in a second Flood position with a larger opening angle, reflectorless distant focus of the reflector in front reflectorless distant surface of the Fresnel lens is imaged by the Fresnel lens,</dd><dt>Fig. 4</dt><dd>the embodiment shown in Fig. 1 of Fresnel lens spotlight in a third Flood position with even greater Opening angle than in the second flood position, wherein the reflector distant focal point of Reflector before the reflector surface of the distant Fresnel lens is imaged by the Fresnel lens and the light source from the close to the reflector Focal point moves out to the reflector is,</dd><dt>Fig. 5</dt><dd>the embodiment shown in Fig. 1 of Fresnel lens spotlight in the second Flood position with a larger opening angle, means of an auxiliary reflector another part the light first in the reflector and of this is directed into the Fresnel lens,</dd><dt>Fig. 6</dt><dd>a negative Fresnel lens with a centrally located Lens,</dd><dt>Fig. 7</dt><dd>an opening angle-dependent logarithmic Representation of the intensity of Fresnel lens spotlight in the spot and in one of its Flood positions.</dd><dt>Fig. 8</dt><dd>a characteristic curve for the forced coupling between the sizes A and B, wherein the parameters of Fresnel lens, an elliptical reflector and Illuminant are selected by way of example.</dd></dl>

Detailed description of preferred embodiments

is in the following detailed description assumed that like reference characters designate the same or equivalent elements in the various Embodiments described.

Reference is now made to FIG. 1, reference, which has a Embodiment of the Fresnel lens spotlight in Spot position shows. The Fresnel lens spotlight contains Essentially an ellipsoidal reflector 1, a lamp 2, which a halogen lamp or a discharge lamp may be, and a Fresnel lens 3, which lens one with negative refractive power, preferably a biconcave Fresnel lens is.

In Fig. 1 is the reflector distant focal point F2 of the ellipsoidal reflector 1 in approximately the right side virtual or negative focal point F 3 of the Fresnel lens 3 superimposed.

The light emerging from the headlamp light beam 4 is in the figures only schematically by its outer Marginal rays indicated.

The distances between a Fresnel lens 3 and the leading edge Reflector 1 and B between the lamp 2 and the apex of the Reflector 1 are also shown in Fig. 1.

The spot position is set by the fact that the Lamp filament or the discharge arc of the lamp 2 in Substantially in the reflector-side focal point F1 of the is reflector ellipsoid 1 arranged.

The light reflected from the reflector 1 is in light of this Position almost completely reflector on the remote Focus directed F2 of the ellipsoid. 1 The right side negative or virtual focal point F3 of the Fresnel lens 3fällt then approximately with the focal point F2 of the Reflector ellipsoid 1 together.

It can also be seen in Fig. 1 in the near field, such as the Opening 5 inside the reflector 1 in parallel Beam path of the light field 4 as a dark area 6 effect.

Within the Fresnel lens 3 is a circular, centrally arranged diffusing glass 7 is provided, which you defined scattered light ratio and a defined generates opening angle of the scattered light. hereby is a defined mixing ratio of the scattered light relative to the Fresnel lens 3 geometrical optics Light depicted provided.

As an alternative to this embodiment, the lens 7 changes at a further embodiment, the scattering effect along the radius of the lens 7 on continuous manner, so that in the middle of the lens 7 stronger scattering regions and to their abruptly-ending Border less strongly scattering regions are arranged.

In yet another alternative embodiment, the Edge of the lens 7 not only ends abruptly, but it this is in its scattering effect decreases continuously, formed and can this also under or above the Fresnel lens extending.

This will depend on the system, further adjustments to the made position-dependent mixing ratios, so that the expert is always an optimum mixing ratio for a homogeneously illuminated light field or even for Light fields with defined generated locally higher can provide intensities.

It is known from Fig. 1 also be seen that in the Spot position only a small portion of the total light, passes through the diffusing disc 7th

By the diffusion plate 7, there is a very homogeneous Illumination, as shown in Fig. 7, which is a Aperture-dependent logarithmic representation of the Intensity of the Fresnel lens spotlight shows for Spot position is represented with the line. 8

Fig. 2 shows the embodiment shown in Fig. 1 of Fresnel lens spotlight in a first flood position, wherein the reflector distant focal point F2 of the reflector 1 approximately in a close to the reflector surface of the Fresnel lens 3 is arranged.

Here, the value of the shift a relative to the is Spot position defined by a mechanical guide changed.

The structure is basically the same in Fig. 1 -described structure of the stepped lens spotlight.

However, 2 of FIG. Can be clearly seen that both the Opening angle of the outgoing light beam 4 and has increased that of the dark region. 6

Since in this position, however, a very high proportion of Light only on a very small area in the center of the Diffusing glass 7, just this region can so be designed so that its forward scattering lobe approximately the dark area 6 in the far field or remote area in desirably compensated. It is also to FIG. 7 directed that the light conditions with the line 9 exemplified are for a flood position.

Reference is now made to FIG. 3 reference, which in the Fig. 1 of the illustrated embodiment Fresnel lens spotlight in a second flood position with even larger opening angle than in Fig. 2, wherein the reflector distant focal point F2 of the reflector 1 front reflectorless distant surface of the Fresnel lens 3 by the Fresnel lens 3 is ready.

Here, a larger area of ​​the lens 7 as rayed in FIG. 2 and can its entire Scattering behavior to the circumstances of this flood position be adjusted.

A repeated widening of the beam 4 is obtained as shown in Fig. 4 as an alternative or in addition to the Flood position of FIG. 3 by changing the distance b Lamp 2 to the reflector 1. By shifting the lamp 2 to Reflector 1 towards is the leaving the reflector Light bundle bundled once more and it comes after emerging from the Fresnel lens 3 to elevated Exit angles.

The change of the distance a and the distance b For example, in other embodiments of Manual, mechanical, electrical, electronic or in done combination, for which purpose a Axial guidance of the optical components are used can.

To obtain the uniformity of the illuminance remains, the distance changes occur at a particularly preferred embodiment, however, by a expediently chosen positive coupling which the change of a and b is in a defined ratio.

The defined over the forced coupling ratio of Sizes A and B is used by the parameter of Fresnel lens, scattering disc, elliptical Reflector and lamp determined. The parameters include while the dimensions, geometry, structure and optical Properties of the individual components.

Specifically, the covers for the Fresnel lens whose optical diameter whose focal length, the curvature, whose light-scattering structure and their arrangement on the Upstream and / or back of the Fresnel lens; for those in the Fresnel lens inbuilt wide panel whose optical Diameter, whose light-scattering structure and their Arrangement; optical for the elliptical reflector whose Diameter, its curvature, whose focal length whose Surface structure, the distance between the two focal points and the diameter of the air duct and for the Luminous body whose shape, dimensions, location and the type of Filament, for example as a metal vapor discharge lamp, Halogen lamp or CDM lamp. More Influences are not explicitly named parameters here possible.

As example of this, Fig. 8 is a characteristic curve for the Compulsory coupling is between the magnitudes of a and b. The Parameters used by the Fresnel lens, elliptical Reflector and lamp are chosen by way of example: <b>Fresnel lens:</b> 160 mm optical diameter and 108.7 mm a negative focal length, inbuilt wide panel with 28 mm Diameter in the center (Honeycomb: diagonal 3.4 mm, Radius 4 mm, 3 ° twisted), back with light-diffusing texture; <b>Elliptic reflector:</b> with 160 mm diameter optical and 35 mm focal length, 160 mm distance between the two Foci, lamp guiding with 30 mm diameter; <b>Illuminant:</b> Cylinder in the axial position, etwa7.2 mm long, Diameter about 2.6 mm.

A change in the parameter results in a change of the defined over the forced coupling ratio of Variables a and b. This results in a change in the functional relationship of the forced coupling characterizing characteristic.

A further preferred embodiment is shown in FIG. 5. In this embodiment, the additional exception of a Auxiliary reflector 18 is substantially above the -Described embodiments corresponds to is determined by the Auxiliary reflector 18 light from the lamp 2, which in FIG. 5 would spread to the right and the reflector 1 no longer would reach by reflection into the reflector. 1 In this way, both the light which merely exemplary is represented by the beam path 19 and without the Auxiliary reflector would not contribute to illumination be used but it can also be the otherwise directly in the Fresnel lens 3 entering part of the light for better the desired light distribution can be used.

The shape of the auxiliary reflector 18 is advantageously selected so, that this reflected light does not return to the Lighting of the lamp 2, for example a filament or A discharge zone, and this additional unnecessary heated.

Alternatively, the auxiliary reflector 18 on the inner and applied or outer side of the glass body of the lamp 2 be. For this purpose, the glass of the lamp body can accordingly be shaped to the desired directivity for the to achieve reflected light.

Fig. 6 shows an example of a Fresnel lens 3 with Diffusing glass 7, as these are used by the invention becomes. The Fresnel lens 3 has a transparent Base 10 and a Fresnel lens ring system 11 with annular lens portions 11, 12, 13, within which the circular diffusion plate 7 is arranged.

The diffusion plate 7 is defined structured or has exactly on facets 15, 16, 17 in wide ranges definable scattering behavior, which in German Patent Application DE 103 43 630.8 of the same applicant described entitled "Lens", which on 19th filed September at the German Patent and Trademark Office has been. The disclosure of this application is Referring also fully into the disclosure of this application made.

However, the invention is not limited to these above- Embodiments of lenses is limited.

Particularly advantageously, the above described will Fresnels its use in a Lighting along with an over the prior Technology significantly reduced electrical power supply or Ballast. This power supply can in relation to the Prior art the same usable light output both electrically and mechanically made smaller to be there the inventive Fresnels a much more light features. Thus less Weight required and lower transport and storage Storage space claimed.

but this shall also, particularly when using Cold light reflectors, the entire thermal load of illuminated people and objects reduced.

In addition, the Fresnel lens spotlight according to the invention can to increase the light yield advantageous also in Flashlights are used, in which the available electrical energy is in principle more limited.

LIST OF REFERENCE NUMBERS

<dl tsize="2" compact="compact"><dt>1</dt><dd>reflector</dd><dt>2</dt><dd>lamp</dd><dt>3</dt><dd>fresnel lens</dd><dt>4</dt><dd>outgoing light beam</dd><dt>5</dt><dd>Opening in the reflector 1</dd><dt>6</dt><dd>dark area</dd><dt>7</dt><dd>Lens</dd><dt>8th</dt><dd>Intensity distribution in the spot position</dd><dt>9</dt><dd>Intensity distribution in flood position</dd><dt>10</dt><dd>basic body</dd><dt>11</dt><dd>Fresnel lens ring system</dd><dt>12</dt><dd>annular lens sections</dd><dt>13</dt><dd>dto.</dd><dt>14</dt><dd>dto.</dd><dt>15</dt><dd>facet</dd><dt>16</dt><dd>dto.</dd><dt>17</dt><dd>dto.</dd><dt>18</dt><dd>auxiliary reflector</dd><dt>19</dt><dd>by auxiliary reflector reflected beam path</dd></dl>