DE2810209C2 - Filter combination for use in a fiber optic light guide system - Google Patents

Description

35

The present invention relates to a light guide system with a first color filter between the light source and the radiation end of the light guide, as well as a second color filter between the light source and this first color filter.

The use of fiber optics enables the diverse « Design of new lighting systems, such as B. Signal display devices for various forms of traffic (signal display devices are described, for example, in DE-AS 24 37 580 and DE-OS 21 26 672). The use of very bright light sources (halogen lamps) and the strong focus of the light on the Above all, however, the entry surface of the light guide brings in the case of colored signals there is the difficulty that the absorption of the rays not allowed through by the filter leads to its heating the stop glasses used for red and yellow signal lights, this leads to an impermissible shift exercise of the color location as well as an undesirable reduction in the light intensity, especially since the standards regarding Color locus and luminous intensity for narrow traffic signals Set limits. A filter for the red and yellow spectral range that has these negative properties does not have, is not known and, with the current state of the art, cannot be produced or can only be produced with great effort.

The aforementioned tarnish glasses are to be understood as filter glasses in which there is no color carrier. dene submicroscopic particles are to be considered, the optical effect of which is decisive not only on their composition, but also on their size is influenced. These particles usually only reach their effective size through a subsequent temperature treatment of the initially practically colorless glass.

The coloring is caused, for example, by sulfur (light yellow). Cadmium sulfide (yellow). Cadmium selenide (orange-red). Gold (pink to ruby). The shape of the The transmission curve is similar to an absorption edge that separates the long-wave area of high transmission from the shorter-wave area of lower transmission. If the glass thickness is low, it remains in the short-wave areas still noticeable permeability. It is therefore advisable to use tempered glasses with a glass thickness of at least 2 mm to be used. The wide range of options is particularly valuable. The absorption edge layer can be varied in the range between approx. 400 and 800 nm by guiding the start-up process.

One way to solve the above problem would be to cool the filter. However, this measure separates because of the high effort and the associated costs.

The interposition of heat absorption or Reflective filters are only possible with a few specific color filters (e.g. green or blue) where the thermal radiation absorbs most of that from the filter Radiation.

From DE-OS 21 09 639 a Liditleitsystem is with known two filters between the light source and the irradiating end of the light guide. One filter serves to create color effects and that other filters have the task of keeping the heat from the light source away from the light guide.

To isolate limited wavelength ranges from a spectrum, see »Colored and filter glass for Science and technology". Jenaer Glaswerk Schott & Gen, Mainz. 1959. p. 9. Filter combinations suggested. It is also pointed out that If the filter glasses are exposed to high temperatures, reversible changes in the transmission curves occur, which, especially in the case of the ani jf glasses, result in a shift towards longer wavelengths.

The object of the present invention is to provide a filter combination which, when exposed to light, shifts the absorption edge of a Start-up filter avoids.

The present invention is based on the idea that one. since the infrared radiation the red and yellow starter glasses happened largely unhindered, would have to try to absorb the filter and in Heat-converted, shorter-wave part of the radiation emanating from the light source used intercept the filter.

The task is solved with a filter combination, in which the first filter is a start-up filter and the second filter is a filter, which is largely only that of this first filter does not let through the absorbed spectral range and all other light that incites the Filters conducts, reflects or absorbs.

Like the first filter, this second filter can also consist of a tarnish glass, the * absorption edge of which is shifted into the short-wave range to such an extent that it The absorption edge of the main filter is not reached despite heating.

It should be noted that by spatial distance heating of the main filter by convection or heat conduction is avoided between the two filters.

According to one embodiment, this is the second

Color filter an absorption filter, its absorption edge lies in the shorter-wave region of the spectrum with respect to the absorption edge of this first filter, and whose temperature dependence of the absorption is such that its absorption edge is also at the maximum temperature that occurs during operation of this light guide system does not exceed the absorption edge this first filter wanders out.

According to a particular embodiment of the invention this second filter can consist of a reflection or color division filter, which only the desired Spectral range lets through, but atles other Light that would cause the main filter to heat up is reflected. For this purpose z. B. glasses with dielectric Multiple layers can be used.

F i g. 1 shows the arrangement of a filter combination according to the invention:

Ti The light emanating from the light source is turned on

jg the end of the light guide focused. In the beam path of this arrangement, the jf erfindungsgemä- U is initially SSE second filter 2, and behind the actual H ERß color filter. 3

§> Below are two examples of the spectral

|! Given the design of the filter according to the invention Sj (see also Fig. 2 and Fig. 3):

t! In these figures the transparency against the

Uj length plotted.

f: B eis ρ ie I 1

'{i filter combination with absorption filter

! "· (According to FIG. 2, a main filter 5 (e.g.

| i Schott OG 590) with a stop glass 7 (e.g.

ψ. Schott OG 550) with shifted to the short-wave

: Combined with an absorption edge. Curve 8 shows the

ι} Displacement of this aniaufgias when heated.

Example 2

; '" Filter combination with a color division filter

3 shows the combination of a main filter 6 (e.g. Schott OG 550) with a color division filter 9 (e.g. Schott DICHROIT filter type 312). A shift the absorption edge as with the tempered glasses does not need to be taken into account here.

For this purpose 2 sheets of drawings

30th

60

65

Claims (4)

Patent claims: 1. Light guide system with a first color filter between the light source and the irradiation end of the Light guide, as well as a second color filter between the light source and this first color filter, characterized in that this first filter is a start-up filter and this second filter is a Filter is. which largely only the spectral range not absorbed by this first filter lets through and reflects or absorbs all other light that leads to the heating of the filter. 2. Light guide system according to claim 1, characterized in that this second color filter is an Ab- i> sorption filter is. its absorption edge in the shorter-wave region of the spectrum with reference to the absorption edge of this first filter lies and its temperature dependence of the absorption is such. that its absorption edge even at the maximum temperature that occurs when operating this Lichtieiisy stems does not exceed the Absorption edge of this first filter wanders out. 3. Light guide system according to claim i. characterized in that this second color filter is a reflection filter. which essentially includes all light rays of the shorter-wave spectral range Reflected with respect to the absorption edge of this first filter. 4. light guide system according to claim 2. characterized: .. that this second color filter is a start-up filter.