IMAGING SYSTEM INCLUDING BEAM GUIDING ELEMENT HAVING HIGH SOLARIZATION RESISTANCE IN THE BLUE SPECTRAL RANGE

Abstract

An imaging system, includes: a laser light source having a wavelength from 380 nm to 490 nm; and a beam guidance element, the laser light source configured for generating an average surface power density of more than 10 W/cm.sup.2, the beam guidance element including a glass which has a quality factor F(436 nm)=S(436 nm)*(Abs.sub.0(436 nm)+Abs.sub.1(436 nm))/k, wherein S(436 nm) is a thermality at a wavelength of 436 nm, Abs.sub.1(436 nm) is an additional absorbance in comparison to Abs.sub.0(436 nm) at a wavelength of 436 nm after an irradiation with a power density of 345 W/cm.sup.2 for 72 hours with a laser light having a wavelength of 455 nm, Abs.sub.0(436 nm) is an absorbance at a wavelength of 436 nm of a sample having a thickness of 100 mm without the irradiation, k is the thermal conductivity, and the quality factor F(436 nm) is <15 ppm/W.

Claims

1. An imaging system, comprising: at least one laser light source B having a wavelength λ.sub.B in a spectral range from 380 nm to 490 nm; and a beam guidance element, the at least one laser light source B being configured for generating, in at least one point of the beam guidance element, an average surface power density of more than 10 W/cm.sup.2, the beam guidance element including a glass which has a quality factor F(436 nm)=S(436 nm)*(Abs.sub.0(436 nm)+Abs.sub.1(436 nm))/k, wherein S(436 nm) is a thermality at a wavelength of 436 nm, Abs.sub.1(436 nm) is an additional absorbance in comparison to Abs.sub.0(436 nm) at a wavelength of 436 nm of a sample having a thickness of 100 mm after an irradiation with a power density of 345 W/cm.sup.2 for 72 hours with a laser light having a wavelength of 455 nm, Abs.sub.0(436 nm) is an absorbance at a wavelength of 436 nm of a sample having a thickness of 100 mm without the irradiation, k is the thermal conductivity, and the quality factor F(436 nm) is <15 ppm/W.

2. The imaging system according to claim 1, wherein the at least one laser light source B is a diode laser.

3. The imaging system according to claim 1, wherein the beam guidance element is a prism.

4. The imaging system according to claim 1, wherein the at least one laser light source is configured for generating, in the at least one point of the beam guidance element, an average surface power density of 20 W/cm.sup.2 to 300 W/cm.sup.2.

5. The imaging system according to claim 1, wherein S(436 nm), S(546 nm), and S(644 nm) are at most 50 ppm/K.

6. The imaging system according to claim 1, wherein Abs.sub.0(436 nm), Abs.sub.0(546 nm), and Abs.sub.0(644 nm) are less than 0.01/cm.

7. The imaging system according to claim 1, wherein Abs.sub.1(436 nm), Abs.sub.1(546 nm), and Abs.sub.1(644 nm) are less than 0.009/cm.

8. The imaging system according to claim 1, wherein the thermal conductivity k is more than 0.005 W/(cm*K).

9. The imaging system according to claim 1, wherein an average do/dT at a wavelength of at least one of 436 nm, 546 nm, and 644 nm in a temperature range from 20° C. to 40° C. is in a range from 0.1 to 8.0 ppm/K.

10. The imaging system according to claim 1, wherein the imaging system is configured for being used in a projector or in a materials processing.

11. An imaging system, comprising: at least one laser light source B having a wavelength λ.sub.B in a spectral range from 380 nm to 490 nm; at least one laser light source G having a wavelength λ.sub.G in a spectral range from >490 nm to 585 nm; at least one laser light source R having a wavelength λ.sub.R in a spectral range from >585 nm to 750 nm; and a beam guidance element, the laser light source B, the laser light source G, and the laser light source R being configured for generating, in at least one point of the beam guidance element, an average surface power density of more than 10 W/cm.sup.2, the beam guidance element including a glass which has an induced absorbance Abs.sub.1(RGB)=Abs.sub.1(436 nm)+Abs.sub.1(546 nm)+Abs.sub.1(644 nm), wherein Abs.sub.1(RGB) is <0.03/cm.

12. A beam guidance element, comprising: a glass which has at least one of the following properties: (a) a quality factor F(436 nm)=S(436 nm)*(Abs.sub.0(436 nm)+Abs.sub.1(436 nm))/k, wherein F(436 nm) is <15 ppm/W; (b) a quality factor F(RGB)=F(436 nm)+F(546 nm)+F(644 nm)=S(436 nm)*(Abs.sub.0(436 nm)+Abs.sub.1(436 nm))/k+S(546 nm)*(Abs.sub.0(546 nm)+Abs.sub.1(546 nm))/k+S(644 nm)*(Abs.sub.0(644 nm)+Abs.sub.1(644 nm))/k, wherein F(RGB) is <40 ppm/W; (c) an induced absorbance Abs.sub.1(436 nm)<0.01/cm; and (d) an induced absorbance Abs.sub.1(RGB)=Abs.sub.1(436 nm)+Abs.sub.1(546 nm)+Abs.sub.1(644 nm), wherein Abs.sub.1(RGB) is <0.03/cm.

13. The beam guidance element according to claim 12, wherein the beam guidance element is selected from at least one of lenses, prisms, aspheres, plane plates, freeforms, fast axis collimators, and light-guiding rods.

14. A glass, comprising: at least one of the following properties: (a) a quality factor F(436 nm)=S(436 nm)*(Abs.sub.0(436 nm)+Abs.sub.1(436 nm))/k, wherein F(436 nm) is <15 ppm/W; (b) a quality factor F(RGB)=F(436 nm)+F(546 nm)+F(644 nm)=S(436 nm)*(Abs.sub.0(436 nm)+Abs.sub.1(436 nm))/k+S(546 nm)*(Abs.sub.0(546 nm)+Abs.sub.1(546 nm))/k+S(644 nm)*(Abs.sub.0(644 nm)+Abs.sub.1(644 nm))/k, wherein F(RGB) is <40 ppm/W; (c) an induced absorbance Abs.sub.1(436 nm)<0.01/cm; and (d) an induced absorbance Abs.sub.1(RGB)=Abs.sub.1(436 nm)+Abs.sub.1(546 nm)+Abs.sub.1(644 nm), wherein Abs.sub.1(RGB) is <0.03/cm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0255] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0256] FIG. 1 is shows schematically one embodiment of the present invention;

[0257] FIG. 2 is a bar chart; and

[0258] FIG. 3 is a bar chart.

[0259] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0260] FIG. 1 shows schematically one embodiment of the present invention. An illustrative configuration of the imaging system as a DLP projector is shown. The three colors blue, green and red (arrow 5) generated by the laser light source(s) 1, after leaving the laser light source(s) 1, reach the beam guidance element 2. The beam guidance element 2 deflects the light onto image-generating chips 3 (arrow 6). The images generated by the image-generating chips 3 (in particular, one image each in blue, green and red) then reach the beam guidance element 2. This is shown by the arrow 7. The beam guidance element 2 then ensures that a composite color image reaches the projection optics 4. This is shown by the arrow 8.

[0261] FIG. 2 is a bar chart, which shows the quality factor F(436 nm) and the quality factor F(RGB) for the examples 1 to 8 of the invention and for the non-invention comparative example A. The numerical values shown on the y-axis are data in “ppm/W”.

[0262] FIG. 3 is a bar chart, which shows the induced absorbances Abs.sub.1(436 nm) and Abs.sub.1(RGB) for the examples 1 to 8 of the invention and for the non-invention comparative example A. The numerical values shown on the y-axis are data in “1/cm”.

Examples

[0263] Samples of the example glasses 1 to 8 of the invention and of the non-invention comparative example A with a sample thickness of 100 mm were each irradiated with a power density of 345 W/cm.sup.2 for 72 hours with laser light of a wavelength of 455 nm. In order to achieve both a high power density and a uniform irradiation of the sample, the sample prior to irradiation was polished on all sides and the laser light was irradiated onto the 4×4 mm.sup.2 entry face at the angle of total internal reflection (TIR). With a 55 W laser, irradiation was consequently achieved with a power density of 345 W/cm.sup.2. The power density in the volume was about 331 W/cm.sup.2.

[0264] The sample size was 100 mm×4 mm×4 mm.

[0265] The compositions of the glasses are shown in table 1 below (in wt %).

TABLE-US-00006 TABLE 1 Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. A SiO.sub.2 70 70 70 70 70 70 70 43 70 B.sub.2O3 11 11 11 11 11 11 11 11 Li.sub.2O 1 Na.sub.2O 10 10 10 10 10 10 10 5 10 K.sub.2O 7 7 7 7 7 7 7 3 7 CaO 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 BaO 1 1 1 1 1 1 1 10 1 ZnO 22 TiO.sub.2 0.1 0.05 0.05 0.1 ZrO.sub.2 5 La.sub.2O.sub.3 11 F Sb.sub.2O.sub.3 0.3 0.3 0.3 0.3 SnO.sub.2 0.3 0.3 0.3 0.3 0.2 Cl 0.34 0.35 0.35 0.34 0.35 0.34 0.34 0.33 CeO.sub.2 0.025 0.01 0.01 0.01 MnO.sub.2 0.1 ppm 0.7 ppm 0.1 ppm 0.1 ppm 0.1 ppm 0.1 ppm 0.1 ppm 0.1 ppm 1.1 ppm

[0266] The glasses differed as follows in terms of the MnO.sub.2 amount. The MnO.sub.2 amount in example 2 was 0.7 ppm (based on weight). In comparative example A, the MnO.sub.2 amount was 1.1 ppm (based on weight). For the rest of the example glasses 1 and 3 to 8, the MnO.sub.2 amount was in each case 0.1 ppm (based on weight).

[0267] The quality factor F(436 nm), the quality factor F(546 nm), the quality factor F(644 nm) and the quality factor F(RGB) were calculated according to the formulae indicated above. For this purpose the corresponding values of the thermality S, the noninduced absorbance Abs.sub.0 and of the induced absorbance Abs.sub.1 were determined for the wavelengths 436 nm, 546 nm and 644 nm, and the thermal conductivity k of the glass was determined as well. The results are shown in FIGS. 2 and 3. Table 2 below summarizes the measurement values and calculations.

TABLE-US-00007 TABLE 2 Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. A S (436 nm) 13.7 13.7 13.7 13.7 13.7 13.7 13.7 19.6 13.7 [ppm/K] S (546 nm) 12.9 12.9 12.9 12.9 12.9 12.9 12.9 18.0 12.9 [ppm/K] S (644 nm) 12.3 12.3 12.3 12.3 12.3 12.3 12.3 17.3 12.3 [ppm/K] Abs.sub.0 (436 nm) 0.0012 0.0015 0.0031 0.0032 0.0021 0.0011 0.0018 0.0013 0.0016 [1/cm] Abs.sub.0 (546 nm) 0.0012 0.0014 0.0020 0.0016 0.0013 0.0010 0.0015 0.0004 0.0008 [1/cm] Abs.sub.0 (644 nm) 0.0008 0.0005 0.0010 0.0016 0.0006 0.0005 0.0016 0.0006 0.0012 [1/cm] Abs.sub.1 (436 nm) 0.0035 0.0035 0.0033 0.0087 0.0026 0.0010 0.0016 0.0029 0.0115 [1/cm] Abs.sub.1 (546 nm) 0.0015 0.0079 0.0016 0.0057 0.0009 0.0006 0.0004 0.0015 0.0103 [1/cm] Abs.sub.1 (644 nm) 0.0011 0.0039 0.0008 0.0033 0.0007 0.0003 0.0003 0.0007 0.0092 [1/cm] Abs.sub.1 (RGB) 0.0061 0.0153 0.0057 0.0177 0.0042 0.0019 0.0023 0.0051 0.0310 [1/cm] k 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.0083 0.011 [W/(cm*K)] F (436 nm) 5.76 6.20 7.93 14.71 5.80 2.59 4.20 9.92 16.18 [ppm/W] F (546 nm) 3.09 10.74 4.12 8.50 2.54 1.85 2.20 4.12 12.84 [ppm/W] F (644 nm) 2.16 4.90 1.96 5.40 1.44 0.89 2.11 2.70 11.54 [ppm/W] F (RGB) 11.0 21.8 14.0 28.6 9.8 5.3 8.5 16.7 40.6 [ppm/W]

[0268] It is apparent that glasses 1 to 8 of the invention, in contrast to comparative example A, have a quality factor F(436 nm)<15 ppm/W, a quality factor F(546 nm)<12 ppm/W, a quality factor F(644 nm)<10 ppm/W and a quality factor F(RGB)<40 ppm/W. Moreover, glasses 1 to 8 of the invention, in contrast to comparative example A, have induced absorbances Abs.sub.1 such that Abs.sub.1(436 nm) is <0.01/cm, Abs.sub.1(546 nm) is <0.01/cm, Abs.sub.1(644 nm) is <0.009/cm and Abs.sub.1(RGB) is <0.03/cm.

[0269] In large parts the example glasses 1 to 7 and the comparative example A have a very similar composition. They are each borosilicate glasses. The principal differences are essentially that examples 1, 5 and 7, and comparative example A, were refined using Sb.sub.2O.sub.3, whereas examples 2, 3, 4 and 6 underwent Sn/Cl refining. Comparative example A was produced with conventional raw materials, resulting in a comparatively high MnO.sub.2 amount of more than 1.0 ppm. For examples 2, 3, 5 and 7, CeO.sub.2 was used. Examples 1, 4 and 7, and the comparative example A, additionally contained small amounts of TiO.sub.2. Example 8 is a silicate glass refined using SnO.sub.2.

[0270] Particularly good results were achieved with example 6, which is distinguished by Sn/Cl refining and the absence of TiO.sub.2.

LIST OF REFERENCE NUMERALS

[0271] 1 Laser light source(s) [0272] 2 Beam guidance element [0273] 3 Image-generating chips [0274] 4 Projection optics [0275] 5 Light from the laser light source(s) arrives at the beam guidance element [0276] 6 Light from the beam guidance element is redirected to the image-generating chips [0277] 7 The images generated by the image-generating chips reach the beam guidance element [0278] 8 A composite color image reaches the projection optics

[0279] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.