Imaging system including a beam guiding element having high solatization resistance in the visible spectral range

Abstract

To provide an imaging system including a beam guide element having high solarization resistance in a visible spectral range, in particular, in a blue spectral range, and not only suitable for a projector but also for material processing applications.SOLUTION: The imaging system comprises: at least one laser light source with a wavelength in visible spectral range; and a beam guide element having high solarization resistance at high beam power density. In an example embodiment of a DLP projector, three colors, blue, green and red (arrow 5) generated by the laser light source 1 reach the beam guide element 2, the beam guide element 2 deflects the light toward an imaging chip 3, (arrow 6), an image generated by the imaging chip 3 then reaches the beam guide element 2 (arrow 7), and then the beam guide element 2 causes a synthetic color image to reach a projection optical system 4 (arrow 8).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an imaging system including at least one laser light source having a wavelength in the visible spectrum range and a beam guiding element having high solrization resistance at a high beam output density. The present invention also relates to a method of using the imaging system, particularly in projectors and material processing.

Background Art

[0002] Light sources for projectors are currently undergoing a transition from xenon to laser fluorescent devices and pure RGB laser light sources with steadily increasing beam and power densities. For example, in today's cinema projectors equipped with laser light sources, beam fluxes up to 75,000 lumens and areal power densities of up to 50 W / cm 2 or more are achieved. With the increasing beam and power densities, the thermal load on the optical components increases, thereby degrading the projection quality and long-term stability. The optical system of a cinema projector typically consists of a large-volume prism array and a projection lens. In particular, the prism array is exposed to a high thermal load. Therefore, the requirements for optical glass with low absorption losses, i.e., maximum transmittance and low solrization tendency, i.e., low induced absorption losses during application, are constantly increasing.

[0003] Conventional xenon-based cinema projectors have a maximum beam flux of 45,000 lumens. However, in the latest laser-based projectors, beam fluxes up to 75,000 lumens and areal power densities of up to 50 W / cm 2 or more are achieved. The strong blue laser excites the emission of yellow light in the converter. The green and yellow channels are extracted from the yellow light using dichroic filters. A part of the blue light is used for the blue channel. Then, all three channels are used for projection.

[0004] Projection systems often consist of complex prism arrays that route individual color channels to a DLP chip and mix the signals for image generation. The optical path length may exceed 100 - 200 mm. Any light absorption within the prism array leads to temperature gradients and thermal lens effects. Therefore, the prism glass needs to have as high a transmittance as possible within the visible wavelength range. A further effect that becomes increasingly important with the increasing beam power of projectors is the glass solarization effect. The generation of defect centers due to absorption within the prism glass can lead to a decrease in transmittance, which is also associated with the thermal lens effect.

[0005] However, such solarization effects are not only relevant to the optical systems of the latest projectors. This type of phenomenon is also becoming increasingly important in materials processing applications.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, an object of the present invention is to provide an imaging system with a beam guiding element that has high solarization resistance in the visible spectrum range, particularly in the blue spectrum range, and can therefore be used not only in projectors but also in materials processing applications.

[0007] The imaging system is, in particular, a system comprising at least one light source and at least one beam guiding element, in particular a lens, prism, aspherical and / or optical waveguide. Such an optical waveguide utilizes total internal reflection at the glass-air interface and typically has a length not exceeding 300 mm. Such an imaging system is used, for example, in projectors, in particular in cinema projectors. In this context, the imaging system results in the generation of a recognizable image for the observer, for example on a screen, by means of the intended beam guiding of the light from the light source. The maximum power density usually occurs within the prism, in particular within the prism that causes the mixing of the color channels. Therefore, it is particularly important to provide such a prism beam guiding element made of a material that can withstand these power densities without causing a relevant solarization effect. The imaging system is also used in the case of material processing. By means of the intended beam guiding, the light from the light source can be focused onto the material to be processed so that the energy input of the light beam can be used for material processing.

Means for Solving the Problem

[0008] This problem is solved by the aspects of the claims. In particular, this problem is an imaging system comprising a) at least one laser light source selected from the group consisting of a laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less, B a laser light source G having a wavelength λ in the spectral range of more than 490 nm and 585 nm or less, G a laser light source R having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less, and R b) a beam guiding element, wherein the laser light source is suitable for generating an average area power density exceeding 10 W / cm² at at least one point of the beam guiding element, and the beam guiding element has a quality factor F(436 nm) = S(436 nm) × (Ext (436 nm)+Ext 2 at 0 (436 nm)+Ext 1It is solved by an imaging system composed of glass having F(436nm) / k and F(436nm) < 700 ppm / W.

[0009] The imaging system according to the present invention can include further components, such as an imaging chip (especially a DLP chip) and / or a projection optical system.

[0010] The imaging system according to the present invention can include a laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less. B Preferably, this imaging system has a wavelength λ in the spectral range of 400 nm or more and 480 nm or less, more preferably 420 nm or more and 470 nm or less, more preferably 425 nm or more and 460 nm or less, more preferably 430 nm or more and 450 nm or less. B It includes a laser light source B.

[0011] The imaging system according to the present invention can include a laser light source G having a wavelength λ in the spectral range of more than 490 nm and 585 nm or less. G Preferably, this imaging system has a wavelength λ in the spectral range of 510 nm or more and 580 nm or less, more preferably 520 nm or more and 570 nm or less, more preferably 530 nm or more and 560 nm or less, more preferably 540 nm or more and 550 nm or less. G It includes a laser light source G.

[0012] The imaging system according to the present invention can include a laser light source R having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less. R This imaging system preferably has a wavelength λ in the spectral range of 600 nm or more and 720 nm or less, more preferably 610 nm or more and 700 nm or less, more preferably 620 nm or more and 680 nm or less, more preferably 630 nm or more and 660 nm or less, more preferably 640 nm or more and 650 nm or less. R It includes a laser light source R.

[0013] The imaging system according to the present invention has a wavelength λ in the spectral range of 380 nm or more and 490 nm or less B a laser light source B having a wavelength λ in the spectral range of more than 490 nm and 585 nm or less G a laser light source G having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less R a laser light source R having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less, and can include exactly one laser light source selected from the group consisting of. According to the present invention, for example, only the laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less B or only the laser light source G having a wavelength λ in the spectral range of more than 490 nm and 585 nm or less G or only the laser light source R having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less. The imaging system includes R

[0014] In other embodiments, the imaging system according to the present invention has a wavelength λ in the spectral range of 380 nm or more and 490 nm or less B a laser light source B having a wavelength λ in the spectral range of more than 490 nm and 585 nm or less G a laser light source G having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less R a laser light source R having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less, and can include exactly two laser light sources selected from the group consisting of. According to the present invention, for example, exactly one laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less B and exactly one laser light source G having a wavelength λ in the spectral range of more than 490 nm and 585 nm or less, but does not include the laser light source R having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less. The imaging system according to the present invention has exactly one laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less G and exactly one laser light source R having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less, but has a wavelength λ in the spectral range of more than 490 nm and 585 nm or less R does not include the laser light source R having the same. According to the present invention, exactly one laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less B and exactly one laser light source R having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less, but has a wavelength λ in the spectral range of more than 490 nm and 585 nm or less R does not include the laser light source R having the same​G The imaging system also does not include a laser light source G having [the relevant property]. According to the present invention, the wavelength λ in the spectral range exceeding 585 nm and not exceeding 750 nm R exactly one laser light source R having a wavelength λ in the spectral range exceeding 490 nm and not exceeding 585 nm, and G exactly one laser light source G having a wavelength λ in the spectral range exceeding 490 nm and not exceeding 585 nm, but does not include a laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less. B is also an imaging system.

[0015] Particularly preferably, the imaging system according to the present invention includes exactly three laser light sources selected from the group consisting of a laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less, a laser light source G having a wavelength λ in the spectral range exceeding 490 nm and not exceeding 585 nm, and a laser light source R having a wavelength λ in the spectral range exceeding 585 nm and not exceeding 750 nm. Most preferably, the imaging system according to the present invention includes a laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less, a laser light source G having a wavelength λ in the spectral range exceeding 490 nm and not exceeding 585 nm, and a laser light source R having a wavelength λ in the spectral range exceeding 585 nm and not exceeding 750 nm. B A laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less, a laser light source G having a wavelength λ in the spectral range exceeding 490 nm and not exceeding 585 nm, and G a laser light source R having a wavelength λ in the spectral range exceeding 585 nm and not exceeding 750 nm. R The laser light source (particularly, a laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less, a laser light source G having a wavelength λ in the spectral range exceeding 490 nm and not exceeding 585 nm, and / or a laser light source R having a wavelength λ in the spectral range exceeding 585 nm and not exceeding 750 nm) is preferably at least 0.1 cm, more preferably at least 0.5 cm, and even more preferably at least 1 cm at at least one point of the beam guiding element. B A laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less, a laser light source G having a wavelength λ in the spectral range exceeding 490 nm and not exceeding 585 nm, and G a laser light source R having a wavelength λ in the spectral range exceeding 585 nm and not exceeding 750 nm. R is included.

[0016] The laser light source (particularly, a laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less, a laser light source G having a wavelength λ in the spectral range exceeding 490 nm and not exceeding 585 nm, and / or a laser light source R having a wavelength λ in the spectral range exceeding 585 nm and not exceeding 750 nm) is preferably at least 0.1 cm, more preferably at least 0.5 cm, and even more preferably at least 1 cm at at least one point of the beam guiding element. B A laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less, a laser light source G having a wavelength λ in the spectral range exceeding 490 nm and not exceeding 585 nm, and G a laser light source G having a wavelength λ in the spectral range exceeding 490 nm and not exceeding 585 nm and / or a laser light source R having a wavelength λ in the spectral range exceeding 585 nm and not exceeding 750 nm R is preferably at least 0.1 cm, more preferably at least 0.5 cm, and even more preferably at least 1 cm at at least one point of the beam guiding element. 2 More preferably at least 0.5 cm 2 Even more preferably at least 1 cm 2, more preferably at least 2 cm 2 , more preferably at least 3 cm 2 , more preferably at least 5 cm 2 , more preferably at least 7 cm 2 , more preferably at least 9 cm 2 on an area of, is suitable for generating an average areal power density exceeding 10 W / cm 2 A laser light source (particularly, a laser light source B having a wavelength λ in the spectral range of 380 nm or more and 490 nm or less, a laser light source G having a wavelength λ in the spectral range of more than 490 nm and 585 nm or less, and / or a laser light source R having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less) is, at at least one point of the beam guiding element, preferably at least 0.1 cm of the beam guiding element B , a laser light source B having a wavelength λ in the spectral range of more than 490 nm and 585 nm or less, a laser light source G having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less G and / or a laser light source R having a wavelength λ in the spectral range of more than 585 nm and 750 nm or less R at at least one point of the beam guiding element, preferably at least 0.1 cm of the beam guiding element 2 , more preferably at least 0.5 cm 2 , more preferably at least 1 cm 2 , more preferably at least 2 cm 2 , more preferably at least 3 cm 2 , more preferably at least 5 cm 2 , more preferably at least 7 cm 2 , more preferably at least 9 cm 2 on an area of, is suitable for generating an average areal power density exceeding 10 W / cm 2 and not exceeding 75 W / cm, more preferably not less than 15 W / cm 2 and not exceeding 60 W / cm, more preferably not less than 20 W / cm 2 and not exceeding 50 W / cm, more preferably not less than 25 W / cm 2 and not exceeding 45 W / cm, for example, not less than 30 W / cm 2 and not exceeding 40 W / cm, is suitable for generating an average areal power density as follows. 2 For example, not less than 25 W / cm 2 and not exceeding 45 W / cm 2 or not less than 30 W / cm 2 and not exceeding 40 W / cm 2

[0017] The laser light source B is preferably, at at least one point of the beam guiding element, preferably at least 0.1 cm of the beam guiding element2 and more preferably at least 0.5 cm 2 and more preferably at least 1 cm 2 and more preferably at least 2 cm 2 and more preferably at least 3 cm 2 and more preferably at least 5 cm 2 and more preferably at least 7 cm 2 and more preferably at least 9 cm 2 is suitable for generating an average areal power density exceeding 10 W / cm 2 Furthermore, preferably, the laser light source B has, at at least one point of the beam guiding element, preferably at least 0.1 cm of the beam guiding element 2 and more preferably at least 0.5 cm 2 and more preferably at least 1 cm 2 and more preferably at least 2 cm 2 and more preferably at least 3 cm 2 and more preferably at least 5 cm 2 and more preferably at least 7 cm 2 and more preferably at least 9 cm 2 on an area of, 10 W / cm 2 exceeding 75 W / cm 2 and below, more preferably 15 W / cm 2 and above 60 W / cm 2 and below, more preferably 20 W / cm 2 and above 50 W / cm 2 and below, for example 25 W / cm 2 and above 45 W / cm 2 and below, or 30 W / cm 2 and above 40 W / cm 2 and below, and is suitable for generating an average areal power density as described above.

[0018] The laser light source G preferably has, at at least one point of the beam guiding element, preferably at least 0.1 cm of the beam guiding element 2 and more preferably at least 0.5 cm 2 and more preferably at least 1 cm 2 and more preferably at least 2 cm2 and more preferably at least 3 cm 2 and more preferably at least 5 cm 2 and more preferably at least 7 cm 2 and more preferably at least 9 cm 2 is suitable for generating an average areal power density exceeding 10 W / cm 2 Furthermore, preferably, at at least one point of the beam guiding element, preferably at least 0.1 cm of the beam guiding element 2 and more preferably at least 0.5 cm 2 and more preferably at least 1 cm 2 and more preferably at least 2 cm 2 and more preferably at least 3 cm 2 and more preferably at least 5 cm 2 and more preferably at least 7 cm 2 and more preferably at least 9 cm 2 on the area of, 10 W / cm 2 exceeding 75 W / cm 2 or less, more preferably 15 W / cm 2 or more and 60 W / cm 2 or less, more preferably 20 W / cm 2 or more and 50 W / cm 2 or less, for example 25 W / cm 2 or more and 45 W / cm 2 or less, or 30 W / cm 2 or more and 40 W / cm 2 or less, and is suitable for generating an average areal power density as described above.

[0019] The laser light source R is preferably at at least one point of the beam guiding element, preferably at least 0.1 cm of the beam guiding element 2 and more preferably at least 0.5 cm 2 and more preferably at least 1 cm 2 and more preferably at least 2 cm 2 and more preferably at least 3 cm 2 and more preferably at least 5 cm 2 and more preferably at least 7 cm2 and more preferably at least 9 cm 2 on an area of, to generate an average areal power density exceeding 10 W / cm 2 is suitable. More preferably, the laser light source R, at at least one point of the beam guiding element, preferably at least 0.1 cm of the beam guiding element 2 and more preferably at least 0.5 cm 2 and more preferably at least 1 cm 2 and more preferably at least 2 cm 2 and more preferably at least 3 cm 2 and more preferably at least 5 cm 2 and more preferably at least 7 cm 2 and more preferably at least 9 cm 2 on an area of, 10 W / cm 2 exceeding 75 W / cm 2 or less, more preferably 15 W / cm 2 or more and 60 W / cm 2 or less, more preferably 20 W / cm 2 or more and 50 W / cm 2 or less, for example 25 W / cm 2 or more and 45 W / cm 2 or less, or 30 W / cm 2 or more and 40 W / cm 2 or less is suitable for generating an average areal power density.

[0020] The laser light source B, the laser light source G, and the laser light source R are preferably, at at least one point of the beam guiding element, preferably at least 0.1 cm of the beam guiding element 2 and more preferably at least 0.5 cm 2 and more preferably at least 1 cm 2 and more preferably at least 2 cm 2 and more preferably at least 3 cm 2 and more preferably at least 5 cm 2 and more preferably at least 7 cm 2 and more preferably at least 9 cm 2 on an area of 10 W / cm 2is suitable for generating an average areal power density exceeding. More preferably, the laser light source B, the laser light source G, and the laser light source R are, at at least one point of the beam guiding element, preferably at least 0.1 cm 2 , more preferably at least 0.5 cm 2 , more preferably at least 1 cm 2 , more preferably at least 2 cm 2 , more preferably at least 3 cm 2 , more preferably at least 5 cm 2 , more preferably at least 7 cm 2 , more preferably at least 9 cm 2 on an area of, an average areal power density of more than 10 W / cm 2 and not exceeding 75 W / cm 2 , more preferably more than 15 W / cm 2 and not exceeding 60 W / cm 2 , more preferably more than 20 W / cm 2 and not exceeding 50 W / cm 2 , for example more than 25 W / cm 2 and not exceeding 45 W / cm 2 , or more than 30 W / cm 2 and not exceeding 40 W / cm 2 is suitable for generating.

[0021] The imaging system according to the invention comprises a beam guiding element made of glass having a figure of merit F(436 nm)=S(436 nm)×(Ext 0 (436 nm)+Ext 1 (436 nm)) / k and F(436 nm)<700 ppm / W.

[0022] When a high-energy photon irradiates in the UV range, defects are induced in the material, leading to a change in spectral transmittance. If these are within the visible spectral range, this is accompanied by an undesired color change. This phenomenon is particularly undesirable in the case of optical components made of glass. Surprisingly, it has now been shown that in the case of a high laser output density, defect centers can be induced within the visible spectral range, for example at 450 nm, which are only found in the case of irradiation with UV / NUV in conventional light sources (= solarization). Without being limited to a particular explanation, it is assumed in the present invention that the occurrence of the solarization effect when irradiated with visible light is particularly due to a non-linear effect associated with a high power density. In the case of excitation at a sufficient power density, two-photon absorption may occur, which corresponds to the energy of a photon with a half wavelength (for example 450 nm / 2 = 225 nm) and thus approximately corresponds to UV absorption. In contrast to conventional UV solarization, this effect generally does not occur only in the glass volume near the surface facing the light source, but rather can occur over the entire optical path length. The formed defect centers induce new absorption bands that reduce the transmission intensity.

[0023] The induced absorption bands are accompanied by a temperature increase in the optical material / glass. This is because the refractive index and the geometric path change with temperature. Here, wavefront delay and undesired imaging errors occur.

[0024] As a result, there is a particularly high requirement for the material of the beam guiding element used in an imaging system that includes a laser light source suitable for generating an average areal power density exceeding 10 W / cm 2 at at least one point of the beam guiding element. Therefore, one object of the present invention is to provide an imaging system that avoids or at least significantly reduces undesired imaging errors.

[0025] FIG. 1 schematically shows an exemplary embodiment of the imaging system of the present invention. According to this embodiment, the imaging system is a DLP projector. The expression "DLP" is an abbreviation of the term "Digital Light Processing" in English notation. The imaging system according to the present invention shown in FIG. 1 includes a laser light source 1 and a beam guide element 2. According to the present invention, this imaging system has a wavelength λ in the spectral range of 380 nm or more and 490 nm or less B a laser light source B having, a wavelength λ in the spectral range of more than 490 nm and 585 nm or less G a laser light source G having, a wavelength λ in the spectral range of more than 585 nm and 750 nm or less R a laser light source R having, and includes at least one laser light source selected from the group consisting of. Therefore, it is also possible that two or more of the plurality of laser light sources mentioned, particularly one blue laser light source, one green laser light source, and one red laser light source, are present in the imaging system according to the present invention. The laser light source 1 shown as a simplified single box in FIG. 1 can represent, for example, three different color diode lasers, particularly a blue diode laser, a green diode laser, and a red diode laser. There may also be only a single laser light source, for example, a blue laser light source. In some embodiments, a converter, particularly a ceramic converter, can be used to convert the blue light emitted by the blue laser light source into light of a higher wavelength, for example, yellow, green, red, and / or yellow-green light, through luminescence.

[0026] In the DLP projector shown in FIG. 1, the laser light source 1 emits light of blue, green, and red (indicated by arrow 5). This can be achieved, for example, by the laser light source 1 representing the presence of blue, green, and red diode lasers. It is also possible that only the blue laser is present and the additional emitted green and red light is generated by the use of conversion materials. The three colors 5 emitted by the laser light source 1 reach the beam guiding element 2 after leaving the laser light source 1. This beam guiding element 2 includes at least one prism, but can also represent, for example, a prism array including a plurality of prisms. The prism array can consist of, for example, two or three prisms. Arrow 6 shows that the beam guiding element 2 deflects the light of the three colors emitted from the laser light source 1 onto the imaging chip 3. Preferably, the light of each of the three colors (blue, green, and red) is deflected onto one imaging chip 3 respectively. For reasons of simplification, only a single box representing the imaging chip 3 is shown in FIG. 1. Preferably, the imaging chip 3 is a DLP chip 3. Preferably, the imaging system includes one imaging chip 3 for each color channel. That is, the box shown in FIG. 1 preferably represents three imaging chips 3 (one each for blue, green, and red), in particular three DLP chips 3.

[0027] Next, the images generated by the DLP chip 3 (in particular, one blue, green, and red image each) reach the beam guiding element 2, in particular the prism 2 or the prism array 2. This is indicated by arrow 7.

[0028] Subsequently, the beam guiding element 2 causes the composite color image to reach the projection optical system 4. This is indicated by arrow 8.

[0029] Particularly in the region of the beam guiding element 2, a very high area power density can occur. Therefore, it is important that the beam guiding element 2 is made of glass having a quality factor according to the present invention.

[0030] This problem is solved, in particular, by the fact that the beam guiding element consists of a glass having a figure of merit F(436 nm)=S(436 nm)×(Ext 0 (436 nm)+Ext 1 (436 nm)) / k and F(436 nm)<700 ppm / W.

[0031] The figure of merit F takes into account various factors that lead to a reduction in imaging errors in the combinations found in this specification. In doing so, both wavelength-dependent and wavelength-independent factors are considered. The figure of merit F(436 nm) at a wavelength of 436 nm represents the properties of the glass in the spectral range from 380 nm to 490 nm. This range also represents the properties of the glass over the entire visible spectral range. According to the present invention, F(436 nm)<700 ppm / W is applied.

[0032] The properties of the glass at wavelengths outside the range from 380 nm to 490 nm can contribute to imaging errors in some cases, although to a lesser extent. The figure of merit F(436 nm) is, in principle, sufficient to represent the quality of the glass. However, in certain cases, in addition to the properties of the glass at a wavelength of 436 nm, it may also be significant to take into account the properties at a wavelength of 546 nm, which represents the wavelength range from above 490 nm to 585 nm, and / or the properties at a wavelength of 644 nm, which represents the wavelength range from above 585 nm to 750 nm. Preferably, the beam guiding element consists of a glass having a figure of merit F(546 nm)=S(546 nm)×(Ext 0 (546 nm)+Ext 1 (546 nm)) / k and F(546 nm)<215 ppm / W and / or a glass having a figure of merit F(644 nm)=S(644 nm)×(Ext 0 (644 nm)+Ext 1 (644 nm)) / k and F(644 nm)<85 ppm / W.

[0033] The quality factor F(RGB) can be determined from the properties of the glass at 436 nm, 546 nm, and 644 nm. Preferably, the beam guide element consists of glass having a quality factor F(RGB)=F(436 nm)+F(546 nm)+F(644 nm)=S(436 nm)×(Ext 0 (436 nm)+Ext 1 (436 nm)) / k+S(546 nm)×(Ext 0 (546 nm)+Ext 1 (546 nm)) / k+S(644 nm)×(Ext 0 (644 nm)+Ext 1 (644 nm)) / k and F(RGB)<1000 ppm / W.

[0034] The quality factor F takes into account the thermal property S(λ), the non-induced absorbance Ext 0 (λ), the induced absorbance Ext 1 (λ), and the thermal conductivity k of the glass. The thermal property, non-induced absorbance, and induced absorbance are parameters that depend on the wavelength. The thermal conductivity does not depend on the wavelength. The non-induced absorbance Ext 0 (λ) can be used as a measure of the absorbance in the as-received state or before the intended use. The induced absorbance Ext 1 (λ) can be used as a measure of the absorbance potentially induced by appropriate operation.

[0035] According to the present invention, F(436nm) < 700 ppm / W is applied. Preferably, F(436nm) is at most 600 ppm / W, more preferably at most 500 ppm / W, still more preferably at most 400 ppm / W, still more preferably at most 350 ppm / W, still more preferably at most 300 ppm / W, still more preferably at most 275 ppm / W, still more preferably at most 250 ppm / , still more preferably at most 225 ppm / W, still more preferably at most 210 ppm / W, still more preferably at most 200 ppm / W, still more preferably at most 150 ppm / W, still more preferably at most 100 ppm / W, still more preferably at most 75 ppm / W, still more preferably at most 50 ppm / W, still more preferably at most 25 ppm / W, still more preferably at most 20 ppm / W, still more preferably at most 15 ppm / W, still more preferably at most 10 ppm / W. In some embodiments, F(436nm) is at least 0.1 ppm / W, at least 0.5 ppm / W, at least 1 ppm / W, or at least 2 ppm / W.

[0036] Preferably, F(546nm) < 215 ppm / W is applied. More preferably, F(546nm) is at most 200 ppm / W, still more preferably at most 175 ppm / W, still more preferably at most 150 ppm / W, still more preferably at most 125 ppm / W, still more preferably at most 100 ppm / W, still more preferably at most 90 ppm / W, still more preferably at most 80 ppm / W, still more preferably at most 70 ppm / W, still more preferably at most 60 ppm / W, still more preferably at most 50 ppm / W, still more preferably at most 40 ppm / W, still more preferably at most 30 ppm / W, still more preferably at most 20 ppm / W, still more preferably at most 15 ppm / W, still more preferably at most 10 ppm / W, still more preferably at most 8 ppm / W, still more preferably at most 6 ppm / W, still more preferably at most 5 ppm / W. In some embodiments, F(546nm) is at least 0.001 ppm / W, at least 0.005 ppm / W, at least 0.01 ppm / W, at least 0.02 ppm / W, at least 0.1 ppm / W, at least 0.5 ppm / W or at least 1 ppm / W.

[0037] Preferably, F(644 nm) < 85 ppm / W is applied. More preferably, F(644 nm) is at most 80 ppm / W, more preferably at most 75 ppm / W, more preferably at most 70 ppm / W, more preferably at most 65 ppm / W, more preferably at most 60 ppm / W, more preferably at most 55 ppm / W, more preferably at most 50 ppm / W, more preferably at most 45 ppm / W, more preferably at most 40 ppm / W, more preferably at most 35 ppm / W, more preferably at most 30 ppm / W, more preferably at most 25 ppm / W, more preferably at most 20 ppm / W, more preferably at most 15 ppm / W, more preferably at most 10 ppm / W, more preferably at most 8 ppm / W, more preferably at most 6 ppm / W, more preferably at most 5 ppm / W. In some embodiments, F(546 nm) is at least 0.001 ppm / W, at least 0.005 ppm / W, at least 0.01 ppm / W, or at least 0.02 ppm / W, at least 0.1 ppm / W, at least 0.5 ppm / W, or at least 1 ppm / W.

[0038] Therefore, preferably, the beam guiding element has a quality factor F(RGB) = F(436 nm) + F(546 nm) + F(644 nm) = S(436 nm) × (Ext 0 (436 nm) + Ext 1 (436 nm)) / k + S(546 nm) × (Ext 0 (546 nm) + Ext 1 (546 nm)) / k + S(644 nm) × (Ext 0 (644 nm) + Ext 1It is made of glass having (644 nm)) / k and F(RGB) < 1000 ppm / W. Preferably, F(RGB) is at most 900 ppm / W, more preferably at most 800 ppm / W, still more preferably at most 700 ppm / W, still more preferably at most 600 ppm / W, still more preferably at most 500 ppm / W, still more preferably at most 400 ppm / W, still more preferably at most 350 ppm / W, still more preferably at most 300 ppm / W, still more preferably at most 250 ppm / W, still more preferably at most 200 ppm / W, still more preferably at most 150 ppm / W, still more preferably at most 100 ppm / W, still more preferably at most 80 ppm / W, still more preferably at most 60 ppm / W, still more preferably at most 50 ppm / W, still more preferably at most 40 ppm / W, still more preferably at most 30 ppm / W, still more preferably at most 25 ppm / W, still more preferably at most 20 ppm / W. In some embodiments, F(RGB) is at least 0.5 ppm / W, at least 1 ppm / W, at least 2 ppm / W, or at least 5 ppm / W.

[0039] One variable that has a large impact on the quality factor F is the wavelength-dependent thermal property S(λ). This thermal property represents the relative change between the optical path s = (n - 1)×d and the temperature T, where n is the refractive index and d is the sample thickness. Here, the relationship S = 1 / s×ds / dT holds. Since d = d(T) and n = n(T), the relationship S = 1 / s×(dn / dT×d+(n - 1)dd / dT) holds. Therefore, S = 1 / (n - 1)×dn / dT + 1 / d×dd / dT = 1 / (n - 1)×dn / dT + CTE holds. This CTE is the coefficient of thermal expansion or the thermal expansion coefficient (English notation: “coefficient of thermal expansion”).

[0040] The coefficient of thermal expansion is preferably determined as described in DIN 51045-1:2005-08 and DIN ISO 7991 1998-02. In this case, a glass sample of a defined length is prepared and the relative length change (ΔL / L) for each temperature interval (ΔT) is measured with a dilatometer. For the calculation of the thermal property S(λ), preferably the average coefficient of thermal expansion in the temperature interval from -30 °C to +70 °C is used. In particular, in the temperature range from -30 °C to +70 °C (CTE(-30 / 70)), a low coefficient of thermal expansion is advantageous. Preferably, CTE(-30 / 70) is in the range of 3.0 ppm / K to 14.0 ppm / K, in particular 4.0 ppm / K to 10.0 ppm / K, 4.5 ppm / K to 9.5 ppm / K, 5.0 ppm / K to 8.0 ppm / K and / or 5.5 ppm / K to 7.5 ppm / K, for example 5.6 ppm / K to 7.3 ppm / K, or 5.7 ppm / K to 7.2 ppm / K.

[0041] The determination of dn / dT can be carried out using a prism spectrometer in a temperature chamber (using the entire prism). The measurement is advantageous in the case of a configuration where the total deflection angle is minimal. This is because thereby the refractive index can be calculated from the deflection angle and the known prism angle only.

[0042] However, the determination of dn / dT is preferably performed using the half prism method. For this purpose, the sample is brought into a temperature-controlled sample chamber in the form of a half prism. The prism is irradiated with light of different wavelengths, and the deflection angle is determined for each. At this time, the temperature in the chamber changes. As a result, the refractive index value is obtained as a function of wavelength and temperature. For the calculation of the thermal property S(λ), preferably, the average dn / dT within the temperature range of +20°C or higher and +40°C or lower is used. In order to suppress the degree of the thermal lens effect as low as possible, it is advantageous that the change in refractive index with temperature (dn / dT) is particularly small within the temperature range of 20°C or higher and 40°C or lower. Preferably, the average dn / dT at wavelengths of 436 nm, 546 nm, and / or 644 nm within the temperature range of 20°C or higher and 40°C or lower is in the range of 0.1 ppm / K or higher and 8.0 ppm / K or lower, particularly 0.2 ppm / K or higher and 7.0 ppm / K or lower, 0.3 ppm / K or higher and 6.0 ppm / K or lower, and / or 0.4 ppm / K or higher and 5.0 ppm / K or lower. In this case, this information is related to the absolute value (magnitude) of the average dn / dT.

[0043] As described above, since the temperature rise in the glass is accompanied by an induced absorption band, when the refractive index and the geometric path change with temperature, wavefront delay and undesired imaging errors occur. Therefore, it is advantageous that the change in the optical path due to temperature (thermal property S) is small. In this way, even if an induced absorption band occurs, the imaging error can be minimized.

[0044] Preferably, S(436 nm) is at most 50 ppm / K, more preferably at most 30 ppm / K, even more preferably at most 25 ppm / K, even more preferably at most 20 ppm / K, even more preferably at most 15 ppm / K, even more preferably at most 10 ppm / K. In some embodiments, S(436 nm) is at least 0.1 ppm / K, at least 0.5 ppm / K, at least 1 ppm / K, or at least 2 ppm / K.

[0045] Preferably, S(546nm) is at most 50 ppm / K, more preferably at most 30 ppm / K, still more preferably at most 25 ppm / K, still more preferably at most 20 ppm / K, still more preferably at most 15 ppm / K, still more preferably at most 10 ppm / K. In some embodiments, S(546nm) is at least 0.1 ppm / K, at least 0.5 ppm / K, at least 1 ppm / K, or at least 2 ppm / K.

[0046] Preferably, S(644nm) is at most 50 ppm / K, more preferably at most 30 ppm / K, still more preferably at most 25 ppm / K, still more preferably at most 20 ppm / K, still more preferably at most 15 ppm / K, still more preferably at most 10 ppm / K. In some embodiments, S(644nm) is at least 0.1 ppm / K, at least 0.5 ppm / K, at least 1 ppm / K, or at least 2 ppm / K.

[0047] Preferably, S(436nm), S(546nm) and S(644nm) are at most 50 ppm / K, more preferably at most 30 ppm / K, still more preferably at most 25 ppm / K, still more preferably at most 20 ppm / K, still more preferably at most 15 ppm / K, still more preferably at most 10 ppm / K. In some embodiments, S(436nm), S(546nm) and S(644nm) are at least 0.1 ppm / K, at least 0.5 ppm / K, at least 1 ppm / K, or at least 2 ppm / K.

[0048] A further important parameter is the non-induced absorbance Ext 0 and the induced absorbance Ext 1 is. Ext 1 (λ) represents the additional absorbance per cm at wavelength λ after irradiation of the sample (in comparison with Ext 0 (λ)). The induced absorbance Ext 1depends, inter alia, on the specifications of the irradiation source. To evaluate the material with respect to its solarization stability, tests using a high-pressure mercury lamp (HOK4) have proven to be advantageous. The induced absorbance Ext 1 (λ) represents, according to the invention, the additional absorbance per centimeter at wavelength λ of a sample having a sample thickness d of 10 mm after irradiation with the HOK4 lamp for 15 hours (in comparison with Ext 0 (λ)). In contrast, the non-induced absorbance Ext 0 (λ) represents the absorbance per centimeter at wavelength λ of a sample having a sample thickness d of 10 mm before irradiation.

[0049] Preferably, an HOK4 / 120 lamp manufactured by Philips is used. The spectrum of this HOK4 / 120 lamp is shown in FIG. 2. The distance between the lamp and the sample is preferably 7 cm. The power density is preferably 25 mW / cm 2 . The sample size is preferably 20 mm × 30 mm × 10 mm. In this case, as already mentioned above, the 10 mm dimension is also referred to as the sample thickness d.

[0050] Here, it is advantageous if Ext 0 and Ext 1 are low. Thus, both values contribute to the quality factor F in total.

[0051] A low non-induced absorbance Ext 0 is advantageous because it results in a similarly low initial absorbance without pre-irradiation with the HOK4 lamp.

[0052] A low induced absorbance Ext 1 is also advantageous. This indicates that excessive absorbance does not occur even after irradiation and is thus a measure of the solarization resistance.

[0053] The absorbance Ext(λ) is the incident beam I at wavelength λ as the dividend 0and the natural logarithm of the quotient of the exit beam I and the sample thickness d as the divisor, i.e., Ext(λ)=ln(I 0 In this way, Ext 0 Ext 1 As already mentioned above, the sample thickness d is according to the invention 10 mm.

[0054] Preferably, Ext 0 (436 nm) is less than 0.01 / cm, more preferably at most 0.008 / cm, more preferably at most 0.005 / cm, more preferably at most 0.004 / cm, more preferably at most 0.003 / cm, and even more preferably at most 0.002 / cm. In some embodiments, Ext 0 (436 nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0055] Preferably, Ext 0 (546 nm) is less than 0.01 / cm, more preferably at most 0.008 / cm, more preferably at most 0.005 / cm, more preferably at most 0.004 / cm, more preferably at most 0.003 / cm, more preferably at most 0.002 / cm, more preferably less than 0.0015 / cm, and even more preferably less than 0.001 / cm. 0 (546 nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0056] Preferably, Ext 0 (644 nm) is less than 0.01 / cm, more preferably at most 0.008 / cm, more preferably at most 0.005 / cm, more preferably at most 0.004 / cm, more preferably at most 0.003 / cm, more preferably at most 0.002 / cm, and even more preferably at most 0.0015 / cm. In some embodiments, Ext 0(644 nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0057] Preferably, Ext 0 (436 nm), Ext 0 (546 nm), Ext 0 (644 nm) is less than 0.01 / cm, more preferably at most 0.008 / cm, more preferably at most 0.005 / cm, more preferably at most 0.004 / cm, more preferably at most 0.003 / cm, more preferably at most 0.002 / cm. In some embodiments, Ext 0 (436 nm), Ext 0 (546 nm), Ext 0 (644 nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0058] Preferably, Ext 1 (436 nm) is less than 0.3 / cm, more preferably at most 0.2 / cm, more preferably at most 0.1 / cm, more preferably at most 0.08 / cm, more preferably at most 0.06 / cm, more preferably at most 0.04 / cm, more preferably at most 0.02 / cm, more preferably at most 0.01 / cm, more preferably at most 0.009 / cm, more preferably at most 0.008 / cm, more preferably at most 0.007 / cm, more preferably at most 0.006 / cm. In some embodiments, Ext 1 (436 nm) is at least 0.0005 / cm, at least 0.001 / cm, at least 0.0015 / cm, or at least 0.02 / cm.

[0059] Preferably, Ext 1(546 nm) is less than 0.3 / cm, more preferably at most 0.2 / cm, even more preferably at most 0.1 / cm, even more preferably at most 0.08 / cm, even more preferably at most 0.06 / cm, even more preferably at most 0.04 / cm, even more preferably at most 0.02 / cm, even more preferably at most 0.01 / cm, even more preferably at most 0.009 / cm, even more preferably at most 0.008 / cm, even more preferably at most 0.007 / cm, even more preferably at most 0.006 / cm, even more preferably at most 0.005 / cm, even more preferably at most 0.004 / cm, even more preferably at most 0.003 / cm. In some embodiments, Ext 1 (546 nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0060] Preferably, Ext 1 (644 nm) is less than 0.3 / cm, more preferably at most 0.2 / cm, even more preferably at most 0.1 / cm, even more preferably at most 0.08 / cm, even more preferably at most 0.06 / cm, even more preferably at most 0.04 / cm, even more preferably at most 0.02 / cm, even more preferably at most 0.01 / cm, even more preferably at most 0.009 / cm, even more preferably at most 0.008 / cm, even more preferably at most 0.007 / cm, even more preferably at most 0.006 / cm, even more preferably at most 0.005 / cm, even more preferably at most 0.004 / cm, even more preferably at most 0.003 / cm. In some embodiments, Ext 1 (644 nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0061] Preferably, Ext 1 (436 nm), Ext 1 (546 nm), Ext 1(644 nm) is less than 0.3 / cm, more preferably at most 0.2 / cm, even more preferably at most 0.1 / cm, even more preferably at most 0.08 / cm, even more preferably at most 0.06 / cm, even more preferably at most 0.04 / cm, even more preferably at most 0.02 / cm, even more preferably at most 0.01 / cm, even more preferably at most 0.009 / cm, even more preferably at most 0.008 / cm, even more preferably at most 0.007 / cm, even more preferably at most 0.006 / cm. In some embodiments, Ext 1 (436 nm), Ext 1 (546 nm), Ext 1 (644 nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0062] A further important parameter is the thermal conductivity k. This thermal conductivity is the product of the density, specific heat capacity and thermal diffusivity. The determination of the density is preferably carried out according to Archimedes' principle (especially ASTM C693:1993). To determine the temperature dependence of the density, the expansion characteristics are preferably determined using dilatometry as described in DIN 51045-1:2005-08 and DIN ISO 7991:1998-02. The specific heat capacity is preferably determined using DSC (differential scanning calorimetry) according to DIN 51007:2019-04. The thermal diffusivity is preferably determined using flash analysis according to ASTM E1461:2013.

[0063] A high thermal conductivity k limits the steady-state temperature rise of the optical glass within the beam path. The thermal conductivity k is preferably greater than 0.005 W / (cm×K), more preferably at least 0.006 W / (cm×K), still more preferably at least 0.007 W / (cm×K), still more preferably at least 0.008 W / (cm×K), for example at least 0.009 W / (cm×K) or at least 0.010 W / (cm×K). In some embodiments, the thermal conductivity k is at most 0.050 W / (cm×K), at most 0.040 W / (cm×K), at most 0.030 W / (cm×K), at most 0.020 W / (cm×K), or at most 0.015 W / (cm×K).

[0064] As described above, the beam guiding element is made of glass that is particularly resistant to solarization, especially in the blue spectral range. This is advantageous for corresponding applications in projectors and material processing because it significantly reduces the occurrence of the thermal lens effect. Further aspects can additionally contribute to the reduction of the thermal lens effect. For example, for a given local deposited heat output (due to absorption of laser light), the steadily occurring temperature difference decreases with increasing thermal conductivity, and thus the imaging errors induced by temperature also decrease. Therefore, a high thermal conductivity k is advantageous.

[0065] Depending on the field of application, the refractive index can also be important. Preferably, the refractive index is in the range of 1.45 or more and 1.65 or less at wavelengths of 436 nm, 546 nm, and / or 644 nm.

[0066] It has been shown that various glass families can be used to obtain a glass having a quality factor according to the present invention. The glass is preferably selected from the group consisting of fluorophosphate glass, silicate glass, borosilicate glass, niobium phosphate, and aluminoborosilicate glass. The refining agents used are particularly relevant as described below.

[0067] Preferably, the beam guide element is made of glass containing the following components in the indicated percentages (by weight). That is, [Table 1]

[0068] The glass of the present invention may be, for example, fluorophosphate glass. A particularly preferred fluorophosphate glass of the present invention contains the following components in the indicated percentages (by weight). That is, [Table 2]

[0069] The fluorophosphate glass according to the present invention contains SiO 2 , B 2 O 3 , Li 2 O, Na 2 O, K 2 O, ZnO, TiO 2 , ZrO 2 , La 2 O 3 , Sb 2 O 3 , As 2 O 3 and SnO 2 each of the components of preferably less than 0.3% by weight, more preferably at most 0.2% by weight, even more preferably at most 0.1% by weight, or particularly preferably does not contain these components.

[0070] Preferably, the fluorophosphate glass contains Al 2 O 3 in a proportion of 7.5% by weight or more and 22.5% by weight or less, more preferably 10% by weight or more and 20% by weight or less, even more preferably 14% by weight or more and 19% by weight or less.

[0071] Preferably, the fluorophosphate glass contains MgO in a proportion of 1.5% by weight or more and 7.5% by weight or less, more preferably 2% by weight or more and 5% by weight or less, even more preferably 2.5% by weight or more and 3.5% by weight or less.

[0072] Preferably, the fluorophosphate glass contains CaO in a proportion of 7.5% by weight or more and 15% by weight or less, more preferably 9% by weight or more and 14% by weight or less, and still more preferably 10% by weight or more and 13% by weight or less.

[0073] Preferably, the fluorophosphate glass contains BaO in a proportion of 11% by weight or more and 25% by weight or less, more preferably 12% by weight or more and 20% by weight or less, and still more preferably 13% by weight or more and 17% by weight or less.

[0074] Preferably, the fluorophosphate glass contains SrO in a proportion of 15% by weight or more and 24% by weight or less, more preferably 16% by weight or more and 23% by weight or less, and still more preferably 16.5% by weight or more and 22% by weight or less.

[0075] Preferably, the fluorophosphate glass contains P 2 O 5 in a proportion of 6% by weight or more and 12% by weight or less, more preferably 7% by weight or more and 11% by weight or less, and still more preferably 8% by weight or more and 10% by weight or less.

[0076] Preferably, the fluorophosphate glass contains F in a proportion of 20% by weight or more and 40% by weight or less, more preferably 25% by weight or more and 35% by weight or less, and still more preferably 27.5% by weight or more and 32.5% by weight or less.

[0077] The glass of the present invention may be, for example, a silicate glass. A particularly preferred silicate glass of the present invention contains the following components in the indicated proportions (by weight). That is,

Table 3

[0078] The silicate glass according to the present invention contains B 2 O 3 , Al 2 O 3 , MgO, CaO, SrO, TiO 2 , P 2 O 5 , F, Sb 2 O3 and As 2 O 3 Each of the components of is preferably included in an amount of less than 0.3% by weight, more preferably at most 0.2% by weight, even more preferably at most 0.1% by weight, or particularly preferably not included at all.

[0079] Preferably, the silicate glass contains SiO in a proportion of 35% to 50% by weight, more preferably 37.5% to 47.5% by weight, even more preferably 40% to 45% by weight. 2 containing

[0080] Preferably, the silicate glass contains LiO in a proportion of 0.2% to 4% by weight, more preferably 0.4% to 2% by weight, even more preferably 0.5% to 1.5% by weight. 2 containing

[0081] Preferably, the silicate glass contains NaO in a proportion of 2% to 15% by weight, more preferably 3% to 10% by weight, even more preferably 4% to 7.5% by weight. 2 containing

[0082] Preferably, the silicate glass contains KO in a proportion of 1% to 10% by weight, more preferably 1.5% to 7.5% by weight, even more preferably 2% to 5% by weight. 2 containing

[0083] Preferably, the total proportion of alkali metal oxides (RO) in the silicate glass is in the range of 1% to 20% by weight, more preferably 2% to 15% by weight, even more preferably 5% to 12.5% by weight. This glass preferably does not contain additional alkali metal oxides other than LiO, NaO and / or KO. 2 O 2 O 2 O and / or 2 O

[0084] Preferably, the silicate glass contains BaO in a proportion of 2% by weight or more and 25% by weight or less, more preferably 5% by weight or more and 20% by weight or less, still more preferably 7.5% by weight or more and 15% by weight or less.

[0085] Preferably, the silicate glass contains ZnO in a proportion of 5% by weight or more and 30% by weight or less, more preferably 10% by weight or more and 27.5% by weight or less, still more preferably 15% by weight or more and 25% by weight or less.

[0086] Preferably, the silicate glass contains ZrO 2 in a proportion of 1.5% by weight or more and 10% by weight or less, more preferably 2% by weight or more and 8.5% by weight or less, still more preferably 3% by weight or more and 7% by weight or less.

[0087] Preferably, the silicate glass contains La 2 O 3 in a proportion of 2% by weight or more and 20% by weight or less, more preferably 5% by weight or more and 15% by weight or less, still more preferably 7.5% by weight or more and 12.5% by weight or less.

[0088] Preferably, the silicate glass contains SnO 2 in a proportion of 0.05% by weight or more and 0.4% by weight or less, more preferably 0.1% by weight or more and 0.35% by weight or less, still more preferably 0.15% by weight or more and 0.25% by weight or less.

[0089] The glass of the present invention may be, for example, borosilicate glass. A particularly preferred borosilicate glass of the present invention contains the following components in the indicated proportions (by weight). That is

Table 4

[0090] The borosilicate glass according to the present invention contains Al 2 O 3 , Li 2 O, MgO, ZnO, SrO, ZrO 2 , La 2 O 3 , P 2 O 5, As 2 O 3 and SnO 2 Each of these components is preferably included at less than 0.3% by weight, more preferably at most 0.2% by weight, even more preferably at most 0.1% by weight, or particularly preferably not included at all.

[0091] Preferably, the borosilicate glass contains SiO 2 in a proportion of 52.5% to 77.5% by weight, more preferably 55% to 75% by weight, even more preferably 57.5% to 72.5% by weight.

[0092] Preferably, the borosilicate glass contains B 2 O 3 in a proportion of 5% to 25% by weight, more preferably 7.5% to 20% by weight, even more preferably 9% to 19% by weight.

[0093] Preferably, the borosilicate glass contains Na 2 O in a proportion of 0% to 17.5% by weight, more preferably 0% to 15% by weight, even more preferably 0% to 12.5% by weight. In certain embodiments, the glass contains at least 2% by weight, at least 5% by weight of Na 2 O, or may even contain at least 8% by weight of Na 2 O.

[0094] Preferably, the borosilicate glass contains K 2 O in a proportion of 2% to 24% by weight, more preferably 4% to 23% by weight, even more preferably 6% to 22% by weight.

[0095] Preferably, the total proportion of alkali metal oxides (R 2 O) in the borosilicate glass is in the range of 5% to 30% by weight, more preferably 10% to 25% by weight, even more preferably 15% to 22% by weight. This glass preferably contains Na 2 O and / or K 2It does not contain any additional alkali metal oxides other than O.

[0096] Preferably, the borosilicate glass contains CaO in a proportion of 0 wt% or more and 5 wt% or less, more preferably 0 wt% or more and 2 wt% or less, and even more preferably 0 wt% or more and 1 wt%. In certain embodiments, the glass contains at least 0.1 wt% or at least 0.2 wt% of CaO.

[0097] Preferably, the borosilicate glass contains BaO in a proportion of 0 wt% or more and 5 wt% or less, more preferably 0 wt% or more and 3.5 wt% or less, and even more preferably 0 wt% or more and 2 wt%. In certain embodiments, the glass contains at least 0.1 wt% of BaO.

[0098] Preferably, the borosilicate glass contains TiO 2 in a proportion of 0 wt% or more and 2 wt% or less, more preferably 0 wt% or more and 1 wt% or less, and even more preferably 0 wt% or more and 0.5 wt%. In certain embodiments, the glass contains at least 0.1 wt% of TiO 2 Including.

[0099] Preferably, the borosilicate glass contains F in a proportion of 0 wt% or more and 15 wt% or less, more preferably 0 wt% or more and 12.5 wt% or less, and even more preferably 0 wt% or more and 10 wt%. In certain embodiments, the glass contains at least 1 wt%, at least 2 wt% of F, or even at least 5 wt% of F.

[0100] Preferably, the borosilicate glass contains Sb 2 O 3 in a proportion of 0.01 wt% or more and 0.45 wt% or less, more preferably 0.01 wt% or more and 0.4 wt% or less, and even more preferably 0.01 wt% or more and 0.35 wt%.

[0101] The glass of the present invention may be, for example, aluminoborosilicate glass. A particularly preferred aluminoborosilicate glass of the present invention contains the following components in the indicated proportions (wt%). That is,

Table 5

[0102] The aluminoborosilicate glass according to the present invention contains Li 2 O, MgO, CaO, SrO, TiO 2 , ZrO 2 , La 2 O 3 , P 2 O 5 , As 2 O 3 and SnO 2 each of the components of preferably less than 0.3% by weight, more preferably at most 0.2% by weight, even more preferably at most 0.1% by weight, or particularly preferably does not contain these components.

[0103] Preferably, the aluminoborosilicate glass contains SiO 2 in a proportion of 62.5% by weight or more and 77.5% by weight or less, more preferably 65% by weight or more and 75% by weight or less, even more preferably 67.5% by weight or more and 72.5% by weight or less.

[0104] Preferably, the aluminoborosilicate glass contains B 2 O 3 in a proportion of 7.5% by weight or more and 25% by weight or less, more preferably 10% by weight or more and 20% by weight or less, even more preferably 12.5% by weight or more and 17.5% by weight or less.

[0105] Preferably, the aluminoborosilicate glass contains Na 2 O in a proportion of 0.2% by weight or more and 10% by weight or less, more preferably 0.5% by weight or more and 5% by weight or less, even more preferably 1% by weight or more and 3% by weight or less.

[0106] Preferably, the aluminoborosilicate glass contains K 2 O in a proportion of 2% by weight or more and 17.5% by weight or less, more preferably 5% by weight or more and 15% by weight or less, even more preferably 10% by weight or more and 14% by weight or less.

[0107] Preferably, the total proportion of alkali metal oxides (R 2 O) in the aluminosilicate glass is in the range of 2% by weight or more and 25% by weight or less, more preferably 5% by weight or more and 20% by weight or less, and even more preferably 10% by weight or more and 15% by weight or less. This glass preferably does not contain additional alkali metal oxides other than Na 2 O and / or K 2 O.

[0108] Preferably, the aluminosilicate glass contains BaO in a proportion of 0.02% by weight or more and 5% by weight or less, more preferably 0.05% by weight or more and 2% by weight or less, and even more preferably 0.1% by weight or more and 1% by weight or less.

[0109] Preferably, the aluminosilicate glass contains ZnO in a proportion of 0.05% by weight or more and 5% by weight or less, more preferably 0.1% by weight or more and 2% by weight or less, and even more preferably 0.15% by weight or more and 1% by weight or less.

[0110] Preferably, the aluminosilicate glass contains F in a proportion of 0.1% by weight or more and 5% by weight or less, more preferably 0.2% by weight or more and 2% by weight or less, and even more preferably 0.5% by weight or more and 1.5% by weight or less.

[0111] Preferably, the aluminosilicate glass contains Sb 2 O 3 in a proportion of 0.02% by weight or more and 0.45% by weight or less, more preferably 0.05% by weight or more and 0.4% by weight or less, and even more preferably 0.1% by weight or more and 0.35% by weight or less.

[0112] The refining agent used, as well as CeO2 and Fe 2 O 3 is not particularly relevant without depending specifically on the glass system used. Therefore, the following information is valid for all glass families.

[0113] Preferably, the glass contains CeO 2 and Fe 2 O 3is not included. As a result, a particularly low Ext 0 value can be achieved.

[0114] Preferably, the proportion of As 2 O 3 in the glass according to the present invention is less than 0.3% by weight, preferably at most 0.2% by weight, more preferably at most 0.1% by weight. Even more preferably, the glass does not contain As 2 O 3 . As a result, a particularly low Ext 1 value can be achieved.

[0115] Preferably, the proportion of Sb 2 O 3 in the glass according to the present invention is at most 0.5% by weight, preferably at most 0.4% by weight, more preferably at most 0.3% by weight, for example at most 0.2% by weight, or at most 0.1% by weight. This glass may even not contain Sb 2 O 3 . As a result, a particularly low Ext 1 value can be achieved.

[0116] Preferably, the proportion of SnO 2 in the glass according to the present invention is at most 0.5% by weight, preferably at most 0.4% by weight, more preferably at most 0.3% by weight, for example at most 0.2% by weight, or at most 0.1% by weight. This glass may even not contain SnO 2 . As a result, a particularly low Ext 1 value can be achieved.

[0117] Preferably, the total proportion of As 2 O 3 +Sb 2 O 3 +SnO 2 is at most 0.5% by weight, preferably at most 0.4% by weight, more preferably at most 0.3% by weight, for example at most 0.2% by weight, or at most 0.1% by weight. This glass does not contain As 2 O 3 , Sb 2 O3 and SnO 2 may even not contain it. Thereby, an extremely low Ext 1 value can be achieved.

[0118] This glass can contain F, for example, at a ratio of 0 wt% or more and 45 wt% or less, particularly 0.5 wt% or more and 42.5 wt% or less, or 5 wt% or more and 40 wt% or less. Thereby, an extremely low Ext 1 value can be achieved.

[0119] This glass can also contain Cl, particularly based on Cl purification. The ratio is preferably less than 2 wt%, preferably less than 1.5 wt%, and particularly preferably less than 1 wt%. If the Cl ratio is excessively high, this may lead to undesired salt precipitation on the glass.

[0120] In this description, when it is stated that the glass does not contain one component or does not contain a specific component, this means that this component may be present in the glass as long as it is at most of the order of impurities. That is, this means that it is not added in large amounts. According to the present invention, the amounts that are not large are, respectively, less than 500 ppm, preferably less than 300 ppm, preferably less than 100 ppm, particularly preferably less than 50 ppm, and most preferably less than 10 ppm, on a weight basis.

[0121] Preferably, the beam guide element is a lens, an optical waveguide, a prism, or an aspherical surface, and particularly preferably a prism.

[0122] The present invention also relates to a glass having a quality factor according to the present invention.

[0123] The present invention also relates to the use of the imaging system according to the present invention, particularly in a projector or material processing.

[0124] The present invention also relates to a projector including the imaging system according to the present invention, particularly a DLP projector.

Brief Description of the Drawings

[0125]

Figure 1

Figure 2

Figure 3

Examples

[0126] Samples of five glass Examples 1 to 5 according to the present invention and a sample of Comparative Example A not according to the present invention had a sample thickness of 10 mm and were irradiated using an HOK4 lamp for 15 hours each. Here, a Philips HOK4 / 120 lamp was used. The spectrum of this HOK4 / 120 lamp is shown in FIG. 2. The distance between the lamp and the sample was 7 cm. The power density was 25 mW / cm 2 . The sample size was 20 mm × 30 mm × 10 mm. The composition of the glass is shown in Table 1 below (weight%).

Table 6

[0127] The quality factors F(436nm), F(546nm), F(644nm), and F(RGB) were calculated according to the above equations. For this purpose, the corresponding values of the thermal property S, non-induced absorbance Ext 0 , induced absorbance Ext 1 at wavelengths 436nm, 546nm, and 644nm, as well as the thermal conductivity k of the glass were determined. These results are shown in Figure 3. Table 2 below summarizes these measured values and calculations.

Table 7

[0128] It is clear that glasses 1 to 5 according to the present invention have a quality factor F(436nm) < 700 ppm / W, a quality factor F(546nm) < 215 ppm / W, a quality factor F(644nm) < 85 ppm / W, and a quality factor F(RGB) < 1000 ppm / W, in contrast to Comparative Example A.

[0129] Glass Example 3 has a very similar composition to Comparative Example A and is substantially different in that Comparative Example A contains a relevant proportion of As 2 O 3 . The results show that the performance of Example 3 has been improved in various aspects. Surprisingly, this effect can be achieved with glasses consisting of various glass families. Therefore, Example 1 and Example 5 are borosilicate glasses, Example 2 is an aluminoborosilicate glass, Example 3 is a silicate glass, and Example 4 is a fluorophosphate glass.

Explanation of Reference Numerals

[0130] 1 Laser light source 2 Beam guide element 3 Imaging chip 4 Projection optical system 5 Light reaching the beam guide element from the laser light source 6 Light deflected from the beam guide element to the imaging chip system 7 Image generated by the imaging chip and reaching the beam guide element Composite color image reaching the projection optical system

Claims

1. An imaging system, wherein the imaging system comprises: a) a wavelength λ in a spectral range of 380 nm or more and 490 nm or less Ｂ a laser light source B having a wavelength λ in a spectral range of more than 490 nm and 585 nm or less Ｇ a laser light source G having a wavelength λ in a spectral range of more than 585 nm and 750 nm or less Ｒ at least one laser light source selected from the group consisting of a laser light source R having a wavelength λ b) a beam guiding element; and the beam guiding element contains SiO₂ at a ratio of 50 wt% or more and 80 wt% or less; The laser light source is suitable for generating an average areal power density exceeding 10 W / cm ２ at at least one point of the beam guiding element, The beam guide element has a quality factor F(436 nm) = S(436 nm) × (Ext ０ (436 nm) + Ext １ (436 nm)) / k, S(436 nm) is the thermal property at a wavelength of 436 nm; S = 1 / (n - 1) × dn / dT + CTE holds, where n is the refractive index, T is the temperature, dn / dT is the change in refractive index due to temperature, and CTE is the coefficient of thermal expansion; Ext １ (436 nm) is the additional absorbance at wavelength 436 nm of a sample having a thickness of 10 mm after irradiation with a HOK4 lamp for 15 hours in comparison with Ext ０ (436 nm), and Ext ０ (436 nm) is the absorbance at a wavelength of 436 nm of a sample having a thickness of 10 mm without irradiation using a HOK4 lamp, k is the thermal conductivity [W / (cm×K)]; made of glass with F(436 nm) < 700 ppm / W; imaging system.

2. The beam guiding element contains SiO₂ at a ratio of 60 wt% or more and 80 wt% or less. The imaging system according to Claim 1.

3. An imaging system, wherein the imaging system comprises: a) at least one laser light source selected from the group consisting of a laser light source B having a wavelength λB in the spectral range of 380 nm or more and 490 nm or less, a laser light source G having a wavelength λG in the spectral range of more than 490 nm and 585 nm or less, and a laser light source R having a wavelength λR in the spectral range of more than 585 nm and 750 nm or less; b) a beam guiding element; and the beam guiding element contains SiO₂ at a ratio of 35 wt% or more and 50 wt% or less, ZnO at a ratio of 10 wt% or more and 27.5 wt% or less, and La₂O₃ at a ratio of 5 wt% or more and 15 wt% or less; the laser light source is suitable for generating an average areal power density exceeding 10 W / cm² at at least one point of the beam guiding element; the beam guiding element has a quality factor F(436 nm) = S(436 nm) × (Ext₀(436 nm) + Ext₁(436 nm)) / k; S(436 nm) is the thermal property at a wavelength of 436 nm; S = 1 / (n - 1) × dn / dT + CTE holds, where n is the refractive index, T is the temperature, dn / dT is the change in refractive index due to temperature, and CTE is the coefficient of thermal expansion; Ext₁(436 nm) is the additional absorbance at a wavelength of 436 nm of a sample having a thickness of 10 mm after irradiation with a HOK4 lamp for 15 hours in comparison with Ext₀(436 nm); Ext₀(436 nm) is the absorbance at a wavelength of 436 nm of a sample having a thickness of 10 mm without irradiation with a HOK4 lamp; k is the thermal conductivity [W / (cm×K)], a imaging system made of glass with F(436 nm) < 700 ppm / W. Imaging system. **Claim 4**: The beam guiding element contains SiO₂ at a ratio of 40 wt% or more and 45 wt% or less and / or ZnO at a ratio of 15 wt% or more and 25 wt% or less and / or La₂O₃ at a ratio of 7.5 wt% or more and 12.5 wt% or less. The imaging system according to claim 3. **Claim 5**: An imaging system, wherein the imaging system a) at least one laser light source selected from the group consisting of a laser light source B having a wavelength λB in the spectral range of 380 nm or more and 490 nm or less, a laser light source G having a wavelength λG in the spectral range of more than 490 nm and 585 nm or less, and a laser light source R having a wavelength λR in the spectral range of more than 585 nm and 750 nm or less; b) a beam guiding element; and includes the beam guiding element contains at most 5 wt% of SiO₂, at least 15 wt% of F, and at least 5 wt% of P₂O₅; the laser light source is suitable for generating an average areal power density exceeding 10 W / cm² at at least one point of the beam guiding element; the beam guiding element has a quality factor F(436 nm) = S(436 nm)×(Ext₀(436 nm) + Ext₁(436 nm)) / k; S(436 nm) is the thermal property at a wavelength of 436 nm; S = 1 / (n - 1)×dn / dT + CTE holds, where n is the refractive index, T is the temperature, dn / dT is the change in refractive index due to temperature, and CTE is the coefficient of thermal expansion; Ext₁(436 nm) is the additional absorbance at a wavelength of 436 nm of a sample having a thickness of 10 mm after being irradiated with a HOK4 lamp for 15 hours in comparison with Ext₀(436 nm); Ext₀(436 nm) is the absorbance at a wavelength of 436 nm of a sample having a thickness of 10 mm without irradiation with a HOK4 lamp; k is the thermal conductivity [W / (cm×K)], a imaging system made of glass with F(436 nm) < 700 ppm / W. Imaging system. **Claim 6** The imaging system has a laser light source B having a wavelength λ in a spectral range of 380 nm or more and 490 nm or less Ｂ a laser light source G having a wavelength λ in a spectral range of more than 490 nm and 585 nm or less Ｇ a laser light source R having a wavelength λ in a spectral range of more than 585 nm and 750 nm or less Ｒ and includes The laser light source B, the laser light source G, and the laser light source R are suitable for generating an average areal power density exceeding 10 W / cm ２ at at least one point of the beam guiding element, The beam guide element has a quality factor F(RGB) = F(436 nm) + F(546 nm) + F(644 nm) = S(436 nm) × (Ext ０ (436 nm) + Ext １ (436 nm)) / k + S(546 nm) × (Ext ０ (546 nm) + Ext １ (546 nm)) / k + S(644 nm) × (Ext ０ (644 nm) + Ext １ (644 nm)) / k, and is made of glass with F(RGB) < 1000 ppm / W, The imaging system according to any one of claims 1 to 5. **Claim 7** F(RGB) is at most 800 ppm / W. The imaging system according to claim 6. **Claim 8** The laser light source is a diode laser. The imaging system according to any one of claims 1 to 7.

9. The beam guide element is a prism. The imaging system according to any one of claims 1 to 8.

10. The laser light source is suitable for generating an average areal power density of 15 W / cm ２ or more and 60 W / cm ２ or less at at least one point of the beam guiding element. The imaging system according to any one of claims 1 to 9.

11. S (436 nm), S (546 nm), and S (644 nm) are at most 50 ppm / K. The imaging system according to claim 6 or 7.

12. Ext ０ (436 nm), Ext ０ (546 nm) and Ext ０ (644 nm) are less than 0.01 / cm, The imaging system according to claim 6 or 7.

13. Ext １ (436 nm), Ext １ (546 nm) and Ext １ (644 nm) are less than 0.3 / cm, The imaging system according to claim 6 or 7.

14. The thermal conductivity k exceeds 0.005 W / (cm×K). The imaging system according to any one of claims 1 to 13.

15. The average dn / dT at wavelengths of 436 nm, 546 nm, and / or 644 nm within a temperature range of 20°C or higher and 40°C or lower is in the range of 0.1 ppm / K or higher and 8.0 ppm / K or lower, where n is the refractive index, T is the temperature, and dn / dT is the change in refractive index due to temperature. The imaging system according to any one of claims 1 to 14.

16. A projector including the imaging system according to any one of claims 1 to 15.

Images