DE20118502U1 - lighting device - Google Patents

Description

Lighting device

The invention relates to a lighting device with a light guide between a lamp and a light outlet.

Lighting devices of this type have been known in large numbers for a long time and are used primarily where operations, manipulation, inspection or monitoring are to be carried out in a confined, unlit environment, particularly in the field of medical technology or technical optical quality control or manipulation control.

Tasks of this kind are usually carried out with miniaturized endoscopes, both with conventional lens endoscopes and with fiber optic endoscopes. For illumination purposes, multifilament fiber optic light guides are used, which are arranged either independently of the endoscope or parallel to its longitudinal axis in the outer endoscope tube. These fiber optic light guides are exposed to light from different lamps at a light entry end on the eyepiece side. This light radiated into the light guides exits the light guide distally in the area of the endoscope lens and thus illuminates the observation area or operation area. If the optical axis of the endoscope lens is aligned coaxially to the optical transmission axis in the endoscope, the fiber optic lighting device is usually designed as a fiber sheath that envelops the optical transmission path of the endoscope and concentrically surrounds the endoscope lens in the distal front exit surface.

In viewing devices where the optical axis of the endoscope lens is not coaxial with the optical axis of the endoscope on the image transmission path, for example where both optical axes are aligned at right angles to each other, it is common practice to

to also redirect the light transmitted in the light guide of the lighting device so that it is emitted along an optical exit axis which is at least essentially aligned coaxially to the optical axis of the endoscope lens. Endoscopes for laryngoscopy in the medical field or for optical quality control of hidden soldering points when assembling printed circuit boards in the technical field are examples of endoscopes constructed in this way with lighting devices. While the deflection of the optical image axis in such viewers usually takes place on a separate component, usually on a deflection prism or a mirror, the light emerging from the illumination light guide can either be deflected in the same way, usually on the edge regions of the same mirror or prism on which the optical axis is also deflected, as is known for example from the German utility model DE 29806922 U1, or can be done more elegantly optically simply by arranging the optical fibers guiding the illumination light themselves bent by 90 °, as is known for example from the German utility model DE 7440701 U1.

Although these two known and common means of deflecting the illumination light from the long endoscope axis lead to optically satisfactory results, their design disadvantage is that they are incompatible with the further miniaturization demanded by users in a wide variety of application areas of such viewing devices equipped with an illumination device. Either the mirror or deflection prism must be made larger than required for the viewing optics, or additional space must be created in the endoscope tube for a minimum radius of curvature beyond which the conductor fibers of the illumination light guide can no longer be bent elastically without breaking.

Based on this prior art, the invention is based on the technical problem of designing a lighting device with a light guide between a lamp and a light exit, which enables the illumination light to be emitted at the light exit point on an optical axis that is no longer aligned coaxially with the axis of the light guide between the light entry section and the light exit section, with minimal space requirements.

The invention solves this problem in that a monofilament light guide is provided as the light guide with a flat front surface on the light exit side, which is aligned at an angle to the central axis of the light guide, i.e. is aligned neither perpendicular to it nor parallel to it.

Due to the inclination of the light-exit side face of the monofilament light guide, this face on the inside of the guide acts as an internal reflector to a greater or lesser extent, depending on the design of the external surface, the inclination of the face, the density of the light guide material and the optical parameters of the illumination light. If desired, total reflection of the illumination light introduced on the light entry side can also be set on this inner surface at any time. The easiest way to achieve this is to grind the inclined surface completely flat and then mirror it. The angle of inclination of the surface normal to the light guide axis set for the light-exit side face of the monofilament light guide primarily determines the position and direction of the optical axis of the deflected illumination light.

The cross-section of the monofilament light guide can in principle be designed as desired, in particular round, oval, rectangular or square. However, it must be ensured that in the area in which the illumination light exits the light guide exit, the configuration of the outer surface of the light guide determines the exit geometry of the light

For example, a more or less strong curvature of a glass surface leads to a more or less broad scattering of the light in the horizontal plane, while a flat exit surface, as occurs with a square or rectangular cross-section of the light guide, leads to a well-directed illuminating light beam.

Further embodiments of the invention are the subject of the subclaims.

The invention is explained in more detail below using an embodiment in conjunction with the drawing. The only figure, namely the

Figure 1 shows a schematic representation, not to scale, of the light exit end section of a monofilament light guide of the lighting device.

Figure 1 shows a schematic representation of the distal or “light exit side” section of a monofilament light guide 1 made of plastic.

At its outermost light-exit end, the light guide 1 has a flat front surface 2, the normal 4 of which is inclined by approximately 45° (angle 6) to the light guide axis 3.

The flat, ground, slanted front surface 2 of the monofilament light guide 1 is ground flat and mirrored in such a way that the reflective surface faces inwards into the light guide, while a matte back surface of the coating of the front surface 2 faces outwards. The illumination light incident in the direction of the light guide axis 3 is reflected on the flat front surface 2 of the light guide and emerges essentially perpendicular to the original direction in the direction of arrow 7, illuminating the surrounding area.

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In the radial plane, the monofilament light guide 1 has in particular and preferably a width extension 5-5 in the range from 0.1 mm to 2 mm. As can be seen from Figure 1, this range specification refers to the diameter of the light guide in the case of a circular cross-section of the monofilament light guide 1, whereas in the case of a square cross-section of the light guide 1, the edge length of the radial cross-sectional area of the light guide 1 can be in the specified range from 0.1 mm to 2 mm.

With a round cross-section, the emerging light 7 is spread out perpendicular to the plane of the drawing in Figure 1, thus providing excellent field illumination, while with the flat exit surface of a monofilament light guide 1 it can be used in the manner of a collimated beam. It is clear that, depending on the requirements of the individual application, illumination ranging from diffuse field light to point focusing can be generated by appropriately configuring the surface of the light guide casing 1 in the area of the light exit. Such configurations are at the discretion of the expert.

Claims (12)

1. Lighting device with a light guide between a lamp and a light exit, characterized by a monofilament light guide ( 1 ) with a flat front surface ( 2 ) at its light exit end, the normal ( 4 ) of which is inclined at an angle ( 6 ) in the range from > 0° to < 90° to the light guide axis ( 3 ). 2. Lighting device according to claim 1, characterized by a flat light exit-side end face ( 2 ) whose normal ( 4 ) is inclined at an angle ( 6 ) in the range from > 30° to < 60° to the light guide axis ( 3 ). 3. Lighting device according to one of claims 1 or 2, characterized by a flat light exit side end face ( 2 ) whose normal ( 4 ) is inclined at such an angle ( 6 ) to the light guide axis ( 3 ) that a light ( 3 ) radiated into the light guide on the light entry side is totally reflected at the flat light exit side end face ( 2 ). 4. Lighting device according to one of claims 1 to 3, characterized by a flat light exit side end face, the normal ( 4 ) of which is inclined at such an angle to the light guide axis ( 3 ) that light radiated into the light guide ( 1 ) on the light entry side is reflected on the flat light exit side end face ( 2 ) perpendicular ( 7 ) to the light guide axis ( 3 ). 5. Lighting device according to one of claims 1 to 4, characterized by a non-reflective or only moderately reflective flat surface of the light exit side end face ( 2 ). 6. Lighting device according to one of claims 1 to 5, characterized by a flat and polished surface of the light exit side end face ( 2 ). 7. Lighting device according to one of claims 1 to 6, characterized by a flat polished and mirrored surface of the light exit side end face ( 2 ). 8. Lighting device according to one of claims 1 to 7, characterized by a monofilament light guide ( 1 ) which is non-round in cross section. 9. Lighting device according to claim 8, characterized by a monofilament light guide ( 1 ) with an oval cross section. 10. Lighting device according to claim 8, characterized by a monofilament light guide ( 1 ) with a rectangular or square cross section and an edge length ( 5-5 ) measured perpendicular to the light guide axis ( 3 ) in the range of 0.1 mm to 2 mm. 11. Lighting device according to one of claims 1 to 7, characterized by a monofilament light guide ( 1 ) with a round cross section and a diameter ( 5-5 ) in the range of 0.1 mm to 2 mm. 12. Lighting device according to one of claims 1 to 10, characterized by a monofilament light guide ( 1 ) made of plastic.