Redrawable glass, light guide element having said glass, and uses thereof

Abstract

A redrawable glass, in particular for light guide elements (1) such as glass fibres, is provided. In particular, highly transparent glasses, a method for producing same, and uses thereof. The glasses are preferably used as core glass in a light and/or image guide (1). A light and/or image guide (1) that includes the glass as core glass (2), and a cladding glass (3) is also provided. The use of such a glass in the fields of medical technology, in particular for endoscopic applications, imaging, projection, telecommunications, optical data transmission technology, mobile drive, laser technology and disinfection, and also optical elements or preforms of such optical elements.

Claims

1. Glass comprising: SiO.sub.2 and at least one of two components Gd.sub.2O.sub.3 and Y.sub.2O.sub.3, a ratio of a sum of the proportions by weight of Gd.sub.2O.sub.3 and Y.sub.2O.sub.3 to the proportion by weight of SiO.sub.2 is at least 0.01, wherein a proportion of Ta.sub.2O.sub.5 is at most 10 wt %, wherein a proportion of ZrO.sub.2 is at least 0.1 wt %, wherein the ratio of the proportion by weight of B.sub.2O.sub.3 to the proportion by weight of SiO.sub.2 is at most 0.50.

2. The glass as recited in claim 1 wherein the sum of the proportions by weight of Gd.sub.2O.sub.3 and Y.sub.2O.sub.3 is at least 0.2 wt %.

3. The glass as recited in claim 1 wherein a sum of the proportions by weight of BaO and La.sub.2O.sub.3 is at least 20 wt %.

4. The glass as recited in claim 1 wherein the following components are in the stated proportions (by weight): TABLE-US-00038 Component Min (wt %) Max (wt %) SiO.sub.2 10 55 B.sub.2O.sub.3 0 25 CaO 0 5.0 BaO 0 50 SrO 0 5.0 ZnO 0 30 La.sub.2O.sub.3 0 70 Gd.sub.2O.sub.3 0 15 Y.sub.2O.sub.3 0 15 ZrO.sub.2 0.1 10 Ta.sub.2O.sub.5 0 10 Nb.sub.2O.sub.5 0 10 R.sub.2O 0 10

5. The glass as recited in claim 1 wherein the proportion of Y.sub.2O.sub.3 and Gd.sub.2O.sub.3 is in each case at least 0.1 wt %, preferably in each case at least 0.2 wt %.

6. The glass as recited in claim 1 wherein the proportion by weight of Y.sub.2O.sub.3 is greater than the proportion by weight of Nb.sub.2O.sub.5.

7. The glass as recited in claim 1 wherein the proportion of La.sub.sO.sub.3 is at least 15 wt %.

8. The glass as recited in claim 7 wherein the proportion of La.sub.2O.sub.3 is at most 40 wt %.

9. The glass as recited in claim 1 wherein the ratio of the proportion by weight of La.sub.2O.sub.3 to the sum of the proportions by weight of Gd.sub.2O.sub.3 and Y.sub.2O.sub.3 is at most 10.

10. The glass as recited in claim 1 wherein the sum of the proportions of La.sub.2O.sub.3, Gd.sub.2O.sub.3 and Y.sub.2O.sub.3 is at least 10 wt %.

11. The glass as recited in claim 1 wherein a lower devitrification point is at least 650 C. when the glass is thermally treated for a retention time of 5 minutes in a gradient furnace with rising temperature control.

12. The glass as recited in claim 1 wherein a difference between a lower devitrification point and the softening point is at least 50 K.

13. The glass as recited in claim 1 wherein the proportion of ZrO.sub.2 is less than 10 wt %.

14. A light guide element comprising the glass as recited in claim 1 wherein the refractive index n.sub.d of the glass is in a range from 1.65 to 1.80.

15. The light guide element comprising the glass as recited in claim 1 as core glass and a cladding glass surrounding the core glass.

16. The light guide element as recited in claim 15 wherein the cladding glass consists of a borosilicate glass.

17. The light guide element as recited in claim 15 wherein the cladding glass includes the following components of compositions B1 or B2 TABLE-US-00039 Composition B1 B2 SiO.sub.2 60-75 60-75 B.sub.2O.sub.3 7-25 0.5-15 Na.sub.2O 0-8 1-15 K.sub.2O 0-8 0-15 Al.sub.2O.sub.3 5-17 3-10

18. The light guide element as recited in claim 14 having a numerical aperture of at least 0.82.

19. The light guide element as recited in claim 14 having a spectral attenuation in the near IR range at a wavelength of 800 nm of at most 0.3 dB/m.

20. A method for producing the glass as recited in claim 1, the method comprising the following steps: melting glass raw materials to obtain a glass melt, cooling a glass or glass article obtained from the glass melt, processing the glass melt.

21. A method comprising employing the glass as recited in claim 1 as core glass in a light or image guide.

22. A method comprising employing the light guide element as recited in claim 14 in endoscopic applications, in projection apparatuses, in optical data transmission technology, automotive applications, laser technology or disinfection applications.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0261] The invention is intended to be explained below on the basis of the figures. The figures are also exemplary embodiments,

and show

[0262] FIG. 1: a schematic depiction of a glass fibre,

[0263] FIG. 2: in a first line chart, the spectral attenuation of the glass fibre according to the invention compared to a conventional glass fibre, and

[0264] FIG. 3: in a second line chart, the measured intensity relative to the angle to the radiation axis of the glass fibre, for determining the angular aperture.

DETAILED DESCRIPTION

[0265] FIG. 1 schematically depicts a glass fibre in the form of a light guide element 1, the glass fibre having a core glass 2 and a cladding glass 3. The total diameter of this fibre produced in this way is 70 m. In the exemplary embodiment show, the glass from the above example 15 was used as core glass 2.

[0266] The cladding glass 3 consists of a borosilicate glass which was described above, in particular with compositions containing the components of groups B1 or B2, and is typically in the form of a glass tube.

[0267] FIG. 2 shows, in a first line chart 4, the results of spectral attenuation measurements for a conventional glass fibre 7 and the glass fibre 8 according to the invention, as described previously with respect to FIG. 1. The spectral attenuation 5 is plotted here relative to the wavelength 6 (in nm) of the transmitted light. To this end, what are referred to as measurement light guides of specific lengths, e.g. 1 m or 3 m long, were produced, and transmittance was measured taking into consideration reflection losses at the end faces. The length-independent spectral attenuation can then be calculated from the transmittance and the length of the light guide, and this is given on the chart in dB/km, from which the specification dB/m with 1000 dB/km=1 dB/m, which is relatively common for such fibre optic cables, can be derived.

[0268] It is particularly advantageous here that in particular the spectral attenuation 5 of the glass fibre 7 according to the invention in the near-infrared region (NIR), e.g. at 800 nm, wavelength 6, is lower than for a conventional glass fibre 8, as was for example described at the outset. In the example shown, this is 200 dB/km or 0.2 dB/m compared to approx. 350 dB/km or 0.35 dB/m in the conventional glass fibre. This is particularly advantageous in spectroscopic analysis in uses in medical technology, for example in endoscopes, since in particular tissue analyses in the NIR region enable an improved signal-to-noise ratio and thus e.g. imaging contrast can be increased in particular. In addition, any fluctuations in different melts have proven to be less pronounced at this wavelength range than in conventional glasses, which can in particular be ascribed to the composition according to the invention.

[0269] On the other hand, however, the first line chart 4 also shows that what is referred to as the UV edge or blue edge for the above-described glass fibre 8 according to the invention is shifted to considerably higher wavelengths than the conventional glass fibre 7; in other words, the spectral attenuation 5 in the blue wavelength region between 400 nm and 500 nm is considerably higher than in the conventional glass fibre 7. As described above, the position of the UV edge or blue edge can be adjusted by the Y.sub.2O.sub.3 or Gd.sub.2O.sub.3 content, or the combination thereof.

[0270] Somewhat higher spectral attenuation 5 in the blue region is then in particular not disadvantageous if such glass fibres are used in particular in endoscopic devices. Here, the typical usage lengths are at most 1 m to 2 m, and therefore the yellow shift, i.e. a colour shift towards yellow, is not particularly pronounced, which is in particular non-critical for single-use endoscopes which have typical usage lengths of <1 m. Advantageously, the slightly increased attenuation in the blue region can even be utilized if the light guide element, for example a glass fibre, is coupled to a light source which emits more strongly in the blue region, and/or if it is intended to examine tissue which is sensitive to blue light and thus reacts to higher-energy components of the spectrum.

[0271] FIG. 3 shows, in a second line chart 9, the results for determining the angular aperture of the glass fibres. To this end, a sensor is customarily used to measure the intensity 10 of the light radiated out by the light guide depending on the angle 11 relative to the radiation axis of the light guide, as is shown for a conventional glass fibre 7 and for the glass fibre 8 according to the invention, in accordance with the glass fibre described above and shown in FIG. 1. What is referred to as the 2 angular aperture then results, according to its definition, from the angles 11 at which the intensity 10 has dropped to 50% of the maximum value at 0.

[0272] As shown in FIG. 3, the two glass fibres 7, 8 have a virtually identical 2 angular aperture=2approx. 60=120, corresponding to a numerical aperture of NA=0.86, where NA=sin.sup.1(), and therefore both glass fibres can be referred to as wide-angle glass fibres, such as can advantageously be used in endoscopic applications in order to be able to illuminate the field of view of such cameras without shadows, according to the diagonal angular aperture of camera chips.

[0273] Further examinations of the glass fibre 8 according to the invention compared to the conventional glass fibre 7, both of which are wide-angle fibres and have a fibre diameter of 70 m, relate to the level of strength. To this end, 30 glass fibre samples each, of the same length, were tensioned in a tensile testing machine, and the strain at break of the fibres was measured. Accordingly, virtually identical tensile strengths around 1000 MPa strain at break were measured for both glass fibres 7 and 8, with the statistical fluctuation ranges overlapping to such an extent that it can be assumed they both have the same level of tensile strength.

REFERENCE SIGNS

[0274] 1 Glass article, light guide element [0275] 2 Core glass [0276] 3 Cladding glass [0277] 4 First Line chart [0278] 5 Spectral attenuation [0279] 6 Wavelength [0280] 7 Conventional glass fibre [0281] 8 Light guide element, glass fibre, according to the invention [0282] 9 Second Line chart [0283] 10 Intensity [0284] 11 Angle