Imaging system comprising beam directing element with high resistance to solarization

Abstract

The invention relates to an imaging system comprising at least one laser light source having a wavelength in the visible spectral range and a beam directing element having high resistance to sunlight at high beam power densities. The invention also relates to the use of the imaging system, in particular in projectors and material processing.

Description

[0001] This application is a divisional application of patent application 202110564050.2, filed on May 24, 2021, entitled "Imaging System Including a Beam Guiding Element with High Sunlight Resistance". Technical Field

[0002] This invention relates to an imaging system comprising at least one laser source having a wavelength in the visible spectrum and a beam guiding element having high resistance to sunlight at high beam power density. The invention also relates to applications of the imaging system, particularly in projectors and material handling. Background Technology

[0003] Currently, the light sources used in projectors are evolving from xenon gas to luminous laser materials and then to pure RGB laser light sources, with luminous flux and power density continuously increasing. Modern cinema projectors with laser light sources achieve, for example, luminous flux of up to 75,000 lumens and power density of up to 50 W / cm². 2 Or even higher surface power density. With increasing luminous flux and power density, the thermal load on optical components increases, thereby compromising projection quality and long-term stability. The optical system of a cinema projector typically consists of a large-volume arrangement of prisms and projection lenses. In particular, the arrangement of prisms is subject to high thermal loads. Therefore, there is a growing demand for optical glass with low absorption loss (i.e., maximum transmittance) and low solar exposure (i.e., low induced absorption loss in applications).

[0004] Traditional xenon-based cinema projectors have a maximum luminous flux of up to 45,000 lumens. However, the latest laser-based projectors have achieved a luminous flux of up to 75,000 lumens and a light output of up to 50 W / cm². 2 Or a higher surface power density. A strong blue laser excites the emission of yellow light in the converter. Using a dichroic filter, the green and yellow channels are extracted from the yellow light. A portion of the blue light is used for the blue channel. Then, all three channels are used for projection.

[0005] Projection systems typically consist of complex arrangements of prisms that guide monochromatic channels to a DLP chip and mix the signals to generate an image. The optical path length can be greater than 100 to 200 mm. Any light absorption within the prism arrangement leads to temperature gradients and thermal lensing effects. Therefore, the prism glass should have the highest possible transmittance in the visible light wavelength range. Another effect that becomes increasingly important with increasing projector luminous flux is the solar radiation effect in the glass. The generation of defect centers induced by absorption in the prism glass can lead to reduced transmittance, which in turn coexists with the thermal lensing effect.

[0006] However, this solar radiation effect is not only related to the optical systems of the latest projectors. It also plays an increasingly important role in materials processing applications. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide an imaging system with a beam guiding element, characterized by high resistance to sunlight in the visible spectrum, especially in the blue spectrum, so that it can be used not only excellently in projectors, but also in material handling applications.

[0008] Imaging systems, in particular, are systems having at least one light source and at least one beam guiding element, especially lenses, prisms, aspherical mirrors, and / or light guides. These light guides utilize total internal reflection at the interface glass / air and are typically no more than 300 mm in length. Such imaging systems are used, for example, in projectors, especially in cinema projectors. In this case, the imaging system is used to generate, for example, an image (guided by a targeted beam of light from the light source) on a screen, which is recognizable to the observer. Typically, the highest power density occurs in the prisms, especially those responsible for color channel mixing. Therefore, it is particularly important to provide such prism-beam guiding elements made of materials capable of withstanding these power densities without experiencing the associated solar radiation effects. Imaging systems are also used in material processing. By guiding the targeted beam, the light from the light source can be focused onto the material to be processed, allowing the energy input of the light radiation to be used for material processing.

[0009] This objective is achieved by the subject matter of the claims. In particular, this objective is achieved by an imaging system comprising: a) At least one laser source, selected from the spectral range of 380 nm to 490 nm, having a wavelength λ B Laser source B has a wavelength λ in the spectral range of >490nm to 585nm. G The laser source G and the wavelength λ in the spectral range of >585nm to 750nm. R The group consisting of laser light source R, and b) Beam guiding element, The laser source is adapted to generate a value greater than 10 W / cm² at at least one point of the beam guiding element. 2 The average surface power density is , and the beam guiding element is composed of glass with a quality factor F(436nm)=S(436nm)* (Ext0(436nm)+Ext1(436nm)) / k, where F(436nm)<700ppm / W.

[0010] The imaging system according to the invention may include other components, such as an image generation chip (especially a DLP chip) and / or projection optics.

[0011] The imaging system according to the present invention may include a wavelength λ in the spectral range of 380 nm to 490 nm. B The laser source B. Preferably, the imaging system includes a wavelength λ in the spectral range of 400nm to 480nm, more preferably 420nm to 470nm, more preferably 425nm to 460nm, and more preferably 430nm to 450nm. B Laser source B.

[0012] The imaging system according to the present invention may include a wavelength λ in the spectral range of >490 nm to 585 nm. G The laser source G. Preferably, the imaging system includes a wavelength λ in the spectral range of 510 nm to 580 nm, more preferably 520 nm to 570 nm, more preferably 530 nm to 560 nm, and more preferably 540 nm to 550 nm. G Laser source G.

[0013] The imaging system according to the present invention may include a wavelength λ in the spectral range of >585 nm to 750 nm. R The laser source R. Preferably, the imaging system includes a wavelength λ in the spectral range of 600 nm to 720 nm, more preferably 610 nm to 700 nm, more preferably 620 nm to 680 nm, more preferably 630 nm to 660 nm, and more preferably 640 nm to 650 nm. R The laser source R.

[0014] The imaging system according to the invention may include exactly one laser source having a wavelength λ selected in the spectral range of 380 nm to 490 nm. B Laser source B has a wavelength λ in the spectral range of >490nm to 585nm. G The laser source G and the wavelength λ in the spectral range of >585nm to 750nm. R A group consisting of laser light sources R. According to the invention, for example, an imaging system includes only one laser source having a wavelength λ in the spectral range of 380 nm to 490 nm. B Laser source B, or only one with a wavelength λ in the spectral range of >490nm to 585nm. G The laser source G, or only one with a wavelength λ in the spectral range of >585nm to 750nm. R The laser source R.

[0015] In other embodiments, the imaging system according to the invention may include exactly two laser sources selected from those having wavelengths λ in the spectral range of 380 nm to 490 nm. BLaser source B has a wavelength λ in the spectral range of >490nm to 585nm. G The laser source G and the wavelength λ in the spectral range of >585nm to 750nm R A group consisting of laser light sources R. According to the invention, for example, an imaging system includes a laser light source R having a wavelength λ in the spectral range of 380 nm to 490 nm. B The laser source B has a wavelength λ in the spectral range of >490nm to 585nm. G The laser source G, however, does not have a wavelength λ in the spectral range of >585nm to 750nm. R Laser source R. According to the present invention, the imaging system includes a wavelength λ in a spectral range of exactly 380 nm to 490 nm. B The laser source B has a wavelength λ in the spectral range of >585nm to 750nm. R The laser source R, however, does not have a wavelength λ in the spectral range of >490nm to 585nm. G Laser source G. According to the present invention, the imaging system comprises a wavelength λ in a spectral range of >585 nm to 750 nm. R The laser source R and the wavelength λ are exactly in the spectral range of >490nm to 585nm. G The laser source G, however, does not have a wavelength λ in the spectral range of 380 nm to 490 nm. B Laser source B.

[0016] Particularly preferably, the imaging system according to the invention comprises exactly three laser sources selected from the spectral range of 380 nm to 490 nm, each having a wavelength λ. B Laser source B has a wavelength λ in the spectral range of >490nm to 585nm. G The laser source G and the wavelength λ in the spectral range of >585nm to 750nm R The system comprises a group of laser light sources R. Particularly preferably, the imaging system according to the invention includes a wavelength λ in the spectral range of 380 nm to 490 nm. B Laser source B has a wavelength λ in the spectral range of >490nm to 585nm. G The laser source G and the wavelength λ in the spectral range of >585nm to 750nm R The laser source R.

[0017] Laser sources (especially those with wavelength λ in the spectral range of 380nm to 490nm) B Laser source B has a wavelength λ in the spectral range of >490nm to 585nm. GThe laser source G and / or has a wavelength λ in the spectral range of >585nm to 750nm. R The laser source R is suitable for placement at at least one point of the beam guiding element, preferably at least 0.1 cm above the beam guiding element. 2 More preferably at least 0.5cm 2 More preferably, at least 1cm 2 More preferably, at least 2cm 2 More preferably, at least 3cm 2 More preferably at least 5cm 2 More preferably at least 7cm 2 More preferably, at least 9cm 2 A region with a strength greater than 10 W / cm 2 The average surface power density. Preferably, the laser source (especially in the spectral range of 380 nm to 490 nm) has a wavelength λ. B Laser source B has a wavelength λ in the spectral range of >490nm to 585nm. G The laser source G and / or has a wavelength λ in the spectral range of >585nm to 750nm. R The laser source R is suitable for placement at at least one point of the beam guiding element, preferably at least 0.1 cm above the beam guiding element. 2 More preferably at least 0.5cm 2 More preferably, at least 1cm 2 More preferably, at least 2cm 2 More preferably, at least 3cm 2 More preferably at least 5cm 2 More preferably at least 7cm 2 More preferably at least 9 cm 2 A region with a strength greater than 10 W / cm 2 Up to 75W / cm 2 More preferably 15W / cm 2 Up to 60W / cm 2 More preferably 20W / cm 2 Up to 50W / cm 2 For example, 25W / cm 2 Up to 45W / cm 2 Or 30W / cm 2 Up to 40W / cm 2 The average surface power density.

[0018] Preferably, the laser source B is positioned at at least one point of the beam guiding element, preferably at least 0.1 cm from the beam guiding element. 2More preferably at least 0.5cm 2 More preferably, at least 1cm 2 More preferably, at least 2cm 2 More preferably, at least 3cm 2 More preferably at least 5cm 2 More preferably at least 7cm 2 More preferably, at least 9cm 2 A region with a strength greater than 10 W / cm 2 The average surface power density. More preferably, the laser source B is adapted to be at at least one point of the beam guiding element, preferably at least 0.1 cm from the beam guiding element. 2 More preferably at least 0.5cm 2 More preferably, at least 1cm 2 More preferably, at least 2cm 2 More preferably, at least 3cm 2 More preferably at least 5cm 2 More preferably at least 7cm 2 More preferably, at least 9cm 2 A region with a strength greater than 10 W / cm 2 Up to 75 W / cm 2 More preferably 15W / cm 2 Up to 60W / cm 2 More preferably 20W / cm 2 Up to 50W / cm 2 For example, 25W / cm 2 Up to 45W / cm 2 Or 30W / cm 2 Up to 40W / cm 2 The average surface power density.

[0019] Preferably, the laser source G is positioned at at least one point of the beam guiding element, preferably at least 0.1 cm from the beam guiding element. 2 More preferably at least 0.5cm 2 More preferably, at least 1cm 2 More preferably, at least 2cm 2 More preferably, at least 3cm 2 More preferably at least 5cm 2 More preferably at least 7cm 2 More preferably, at least 9cm 2 A region with a strength greater than 10 W / cm 2The average surface power density. More preferably, the laser source G is adapted to be at at least one point of the beam guiding element, preferably at least 0.1 cm above the beam guiding element. 2 More preferably at least 0.5cm 2 More preferably, at least 1cm 2 More preferably, at least 2cm 2 More preferably, at least 3cm 2 More preferably at least 5cm 2 More preferably at least 7cm 2 More preferably, at least 9cm 2 A region with a strength greater than 10 W / cm 2 Up to 75 W / cm 2 More preferably 15W / cm 2 Up to 60W / cm 2 More preferably 20W / cm 2 Up to 50W / cm 2 For example, 25W / cm 2 Up to 45W / cm 2 Or 30W / cm 2 Up to 40W / cm 2 The average surface power density.

[0020] Preferably, the laser source R is positioned at at least one point of the beam guiding element, preferably at least 0.1 cm from the beam guiding element. 2 More preferably at least 0.5cm 2 More preferably, at least 1cm 2 More preferably, at least 2cm 2 More preferably, at least 3cm 2 More preferably at least 5cm 2 More preferably at least 7cm 2 More preferably, at least 9cm 2 A region with a strength greater than 10 W / cm 2 The average surface power density. More preferably, the laser source R is adapted to be at at least one point of the beam guiding element, preferably at least 0.1 cm above the beam guiding element. 2 More preferably at least 0.5cm 2 More preferably, at least 1cm 2 More preferably, at least 2cm 2 More preferably, at least 3cm 2 More preferably at least 5cm 2 More preferably at least 7cm 2 More preferably, at least 9cm2 A region with a strength greater than 10 W / cm 2 Up to 75 W / cm 2 More preferably 15W / cm 2 Up to 60W / cm 2 More preferably 20W / cm 2 Up to 50W / cm 2 For example, 25W / cm 2 Up to 45W / cm 2 Or 30W / cm 2 Up to 40W / cm 2 The average surface power density.

[0021] Preferably, laser source B, laser source G, and laser source R are positioned at at least one point on the beam guiding element, preferably at least 0.1 cm from the beam guiding element. 2 More preferably at least 0.5cm 2 More preferably, at least 1cm 2 More preferably, at least 2cm 2 More preferably, at least 3cm 2 More preferably at least 5cm 2 More preferably at least 7cm 2 More preferably, at least 9cm 2 A region with a strength greater than 10 W / cm 2 The average surface power density. More preferably, laser source B, laser source G, and laser source R are adapted to be positioned at at least one point on the beam guiding element, preferably at least 0.1 cm from the beam guiding element. 2 More preferably at least 0.5cm 2 More preferably, at least 1cm 2 More preferably, at least 2cm 2 More preferably, at least 3cm 2 More preferably at least 5cm 2 More preferably at least 7cm 2 More preferably, at least 9cm 2 A region with a strength greater than 10 W / cm 2 Up to 75 W / cm 2 More preferably 15W / cm 2 Up to 60W / cm 2 More preferably 20W / cm 2 Up to 50W / cm 2 For example, 25W / cm 2 Up to 45W / cm 2 Or 30W / cm 2Up to 40W / cm 2 The average surface power density.

[0022] The imaging system according to the invention includes a beam guiding element composed of glass having a quality factor F(436nm)=S(436nm)*(Ext0(436nm)+Ext1(436nm)) / k, wherein F(436nm)<700ppm / W.

[0023] Under radiation with high-energy photons in the UV range, defects are induced in materials, leading to changes in spectral transmittance. When these defects are in the visible spectrum, this is accompanied by undesirable color changes. This phenomenon is particularly undesirable in the case of optical components made of glass. Unexpectedly, it has now been shown that, under high laser power densities, defect centers (=sunlighting) are induced also in the visible spectrum, for example at 450 nm, which is only observed when emitted in UV / NUV with conventional light sources. Without being limited to a specific interpretation, it is assumed here that the occurrence of the sunlighting effect under visible light radiation can be attributed in particular to a nonlinear effect, which is a complication of high power densities. When excitation with sufficient power density is performed, two-photon absorption may occur, corresponding to the energy of a photon with half the wavelength (e.g., 450 nm / 2 = 225 nm), thus similar to UV absorption. Unlike conventional UV sunlighting, this effect is generally not limited to the glass volume near the surface facing the light source but can occur along the entire optical path length. The formed defect centers induce new absorption bands, which reduce the transmission intensity.

[0024] Induced absorption bands are accompanied by an increase in internal temperature of the optical material / glass; as the refractive index and geometric path change with temperature, this leads to wavefront deceleration and undesirable aberrations.

[0025] This places particularly high demands on the materials used in beam guiding elements in imaging systems, requiring them to produce a strength greater than 10 W / cm² at at least one point within the beam guiding element. 2 The average surface power density. Therefore, one object of the present invention is to provide an imaging system that avoids or at least significantly reduces undesirable aberrations.

[0026] Figure 1 A schematic embodiment of the imaging system of the present invention is shown. According to this embodiment, the imaging system is a DLP projector. The phrase "DLP" is an abbreviation for the term "Digital Light Processing". Figure 1 The imaging system shown according to the present invention includes a laser source 1 and a beam guiding element 2. According to the present invention, the imaging system includes at least one laser source selected from those having a wavelength λ in the spectral range of 380 nm to 490 nm. BLaser source B has a wavelength λ in the spectral range of >490nm to 585nm. G The laser source G and the wavelength λ in the spectral range of >585nm to 750nm. R The group consists of laser light sources R. Therefore, it is also possible that more than one of the mentioned laser light sources, particularly blue, green, and red laser light sources, may be present in the imaging system according to the invention. Figure 1 The laser source 1, shown in a simplified manner as a single box, can, for example, represent three diode lasers of different colors, particularly a blue diode laser, a green diode laser, and a red diode laser. It is also possible that only one laser source, such as a blue laser source, exists. In some embodiments, it is possible, by means of a converter, particularly a ceramic converter, to convert the blue light emitted by the blue laser source into light with a longer wavelength, for example, into yellow, green, red, and / or yellow-green light.

[0027] exist Figure 1 In the DLP projector described, laser source 1 emits blue, green, and red light (indicated by arrow 5). This can be achieved, for example, by the fact that laser source 1 represents the presence of blue, green, and red diode lasers. It is also possible that only a blue laser is present, and additional emitted green and red light is generated using a conversion material. After leaving laser source 1, the three colors 5 emitted by laser source 1 reach beam guiding element 2. Beam guiding element 2 includes at least one prism, and for example, it can also represent a prism arrangement comprising several prisms. The prism arrangement can, for example, consist of two or three prisms. Arrow 6 illustrates that beam guiding element 2 redirects the three colors of light emitted by laser source 1 to image generating chip 3. Preferably, each of the three colors (blue, green, and red) is redirected to an image generating chip 3 respectively. For simplicity, Figure 1 Only a single frame representing the image generation chip 3 is shown. The preferred image generation chip 3 is a DLP chip 3. Preferably, the imaging system includes one image generation chip 3 for each color channel. Therefore, preferably, Figure 1 The boxes shown represent three image generation chips 3 (each for blue, green, and red, respectively), and specifically three DLP chips 3.

[0028] Then, the image generated by the DLP chip 3 (specifically, the image in blue, green, and red respectively) reaches the beam guiding element 2, specifically the prism 2 or an arrangement of prisms 2. This is indicated by arrow 7.

[0029] Then, the beam guiding element 2 ensures that the composite color image reaches the projection optics 4. This is indicated by arrow 8.

[0030] Especially in the region of beam guiding element 2, very high surface power density may occur. Therefore, it is important that beam guiding element 2 is composed of glass having the quality factors according to the present invention.

[0031] This objective is achieved, in particular, by the fact that the beam guiding element is composed of glass with a quality factor F(436nm) = S(436nm)*(Ext0(436nm)+Ext1(436nm)) / k, where F(436nm) < 700ppm / W.

[0032] The quality factor F takes into account various factors, and the combination found here results in a reduction in aberrations. Both wavelength-dependent and wavelength-independent factors are considered here. The quality factor F(436nm) at a wavelength of 436nm represents the behavior of the glass in the spectral range of 380nm to 490nm. This range further represents the behavior of the glass across the entire visible spectrum. According to the invention, the following condition is satisfied: F(436nm) < 700ppm / W.

[0033] In some cases, the behavior of glass outside the 380 nm to 490 nm range may cause aberrations, albeit to a lesser extent. In principle, the quality factor F (436 nm) is sufficient to describe the quality of the glass. However, in some cases, it may be reasonable to consider, in addition to the glass's behavior at 436 nm, the behavior at 546 nm, representing the wavelength range >490 nm to 585 nm, and / or the behavior at 644 nm, representing the wavelength range >585 nm to 750 nm. Preferably, the beam guiding element is composed of glass having a quality factor F(546nm)=S(546nm)*(Ext0(546nm)+Ext1(546nm) / k, wherein F(546nm)<215 ppm / W, and / or is composed of glass having a quality factor F(644nm)=S(644nm)*(Ext0(644 nm)+Ext1(644 nm)) / k, wherein F(644 nm)<85 ppm / W.

[0034] The quality factor F(RGB) can be determined from the behavior of the glass at 436 nm, 546 nm, and 644 nm. Preferably, the beam guiding element is composed of glass having a quality factor F(RGB) = F(436 nm) + F(546 nm) + F(644 nm) = S(436 nm)*(Ext0(436 nm) + Ext1(436 nm)) / k + S(546 nm)*(Ext0(546 nm) + Ext1(546 nm)) / k + S(644 nm)*(Ext0(644 nm) + Ext1(644 nm)) / k, wherein F(RGB) < 1000 ppm / W.

[0035] The quality factor F considers the glass's heat S(λ), non-induced absorbance Ext0(λ), induced absorbance Ext1(λ), ​​and thermal conductivity k. Heat, non-induced absorbance, and induced absorbance are wavelength-dependent parameters. Thermal conductivity is wavelength-independent. Depending on its intended purpose, non-induced absorbance Ext0(λ) can be used as a measure of absorbance under transfer conditions or before use. Induced absorbance Ext1(λ) can be used as a measure of absorbance potentially induced through proper operation.

[0036] According to the present invention, the following condition is satisfied: F(436nm) < 700ppm / W. Preferably, F(436nm) is at most 600ppm / W, more preferably at most 500ppm / W, more preferably at most 400ppm / W, more preferably at most 350ppm / W, more preferably at most 300ppm / W, more preferably at most 275ppm / W, more preferably at most 250ppm / W, more preferably at most 225ppm / W, more preferably at most 210ppm / W, more preferably at most 200ppm / W, more preferably at most 150ppm / W, more preferably at most 100ppm / W, more preferably at most 75ppm / W, more preferably at most 50ppm / W, more preferably at most 25ppm / W, more preferably at most 20ppm / W, more preferably at most 15ppm / W, more preferably at most 10ppm / W. In some embodiments, F (436nm) is at least 0.1ppm / W, at least 0.5ppm / W, at least 1ppm / W, or at least 2ppm / W.

[0037] Preferably, the following condition is met: F(546 nm) < 215 ppm / W. More preferably, F(546 nm) is at most 200 ppm / W, more preferably at most 175 ppm / W, more preferably at most 150 ppm / W, more preferably at most 125 ppm / W, more preferably at most 100 ppm / W, more preferably at most 90 ppm / W, more preferably at most 80 ppm / W, more preferably at most 70 ppm / W, more preferably at most 60 ppm / W, more preferably at most 50 ppm / W, more preferably at most 40 ppm / W, more preferably at most 30 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 (546nm) is at least 0.001ppm / W, at least 0.005ppm / W, at least 0.01ppm / W, at least 0.02ppm / W, at least 0.1ppm / W, at least 0.5ppm / W, or at least 1ppm / W.

[0038] Preferably, the following condition is met: F(644nm) < 85ppm / W. More preferably, F(644nm) is at most 80ppm / W, more preferably at most 75ppm / W, more preferably at most 70ppm / W, more preferably at most 65ppm / W, more preferably at most 60ppm / W, more preferably at most 55ppm / W, more preferably at most 50ppm / W, more preferably at most 45ppm / W, more preferably at most 40ppm / W, more preferably at most 35ppm / W, more preferably at most 30ppm / W, more preferably at most 25ppm / W, more preferably at most 20ppm / W, more preferably at most 15ppm / W, more preferably at most 10ppm / W, more preferably at most 8ppm / W, more preferably at most 6ppm / W, more preferably at most 5ppm / W. In some embodiments, F (644nm) is at least 0.001ppm / W, at least 0.005ppm / W, at least 0.01ppm / W, or at least 0.02ppm / W, at least 0.1ppm / W, at least 0.5ppm / W, or at least 1ppm / W.

[0039] Therefore, preferably, the beam guiding element is composed of glass with a quality factor F(RGB) = F(436nm) + F(546nm) + F(644nm) = S(436nm)*(Ext0(436nm) + Ext1(436nm)) / k + S(546nm)*(Ext0(546nm) + Ext1(546nm)) / k + S(644nm)*(Ext0(644nm) + Ext1(644nm)) / k, wherein F(RGB) < 1000ppm / W. Preferably, F(RGB) is at most 900 ppm / W, more preferably at most 800 ppm / W, more preferably at most 700 ppm / W, more preferably at most 600 ppm / W, more preferably at most 500 ppm / W, more preferably at most 400 ppm / W, more preferably at most 350 ppm / W, more preferably at most 300 ppm / W, more preferably at most 250 ppm / W, more preferably at most 200 ppm / W, more preferably at most 150 ppm / W, more preferably at most 100 ppm / W, more preferably at most 80 ppm / W, more preferably at most 60 ppm / W, more preferably at most 50 ppm / W, more preferably at most 40 ppm / W, more preferably at most 30 ppm / W, more preferably at most 25 ppm / W, 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.

[0040] The parameter that significantly affects the quality factor F is the wavelength-dependent heat S(λ). Heat describes the relative change of the optical path s = (n-1)*d with temperature T, where n is the refractive index and d is the sample thickness. The following condition must be satisfied: S = 1 / s*ds / dT. Since the following conditions also satisfy: d = d(T) and n = n(T), the following condition is also valid: S = 1 / s*(dn / dT*d + (n-1)dd / dT). Therefore, the following condition also satisfies: S = 1 / (n-1)*dn / dT + 1 / d*dd / dT = 1 / (n-1)*dn / dT + CTE. CTE is the coefficient of thermal expansion.

[0041] Preferably, the coefficient of thermal expansion is determined, for example, as described in DIN 51045-1:2005-08 and DIN ISO 7991 1998-02. Here, a glass sample of a defined length is prepared, and the relative change in length (DeltaL / L) / temperature range (DeltaT) is measured in a dilatometer. To calculate the heat S(λ), preferably, the average coefficient of thermal expansion over a temperature range of -30°C to +70°C is used. A low coefficient of thermal expansion is advantageous, particularly in the temperature range of -30°C to 70°C (CTE(-30 / 70)). Preferably, the CTE (-30 / 70) is in the range of 3.0 to 14.0 ppm / K, particularly 4.0 to 10.0 ppm / K, 4.5 to 9.5 ppm / K, 5.0 to 8.0 ppm / K and / or 5.5 to 7.5 ppm / K, for example 5.6 to 7.3 ppm / K or 5.7 to 7.2 ppm / K.

[0042] The determination of dn / dT can be achieved using a prism spectrometer (with the entire prism) located within a temperature chamber. Preferably, the measurement is performed in a configuration where the total deflection angle is minimized, since the refractive index can then be calculated using only the deflection angle and the known prism angle.

[0043] However, the determination of dn / dT is particularly preferably achieved by the semi-prism method. For this purpose, a sample in the form of a semi-prism is placed in a temperature-controlled sample chamber. The prism is irradiated with light of different wavelengths, and the deflection angle is determined separately. During this time, the temperature within the chamber changes. Therefore, the obtained reflected power is a function of wavelength and temperature. To calculate the heat S(λ), the average dn / dT over a temperature range of +20°C to +40°C is preferably used. To keep the degree of thermal lensing effect as small as possible, it is advantageous that the change in refractive index with temperature (dn / dT) be as small as possible, especially in the temperature range of 20°C to 40°C. Preferably, within a temperature range of 20°C to 40°C, the average dn / dT at wavelengths of 436 nm, 546 nm, and / or 644 nm is in the range of 0.1 to 8.0 ppm / K, particularly 0.2 to 7.0 ppm / K, 0.3 to 6.0 ppm / K, and / or 0.4 to 5.0 ppm / K, wherein this information relates to the absolute value (absolute amount) of the average dn / dT.

[0044] As described above, when the refractive index and geometric path change with temperature, induced absorption bands accompany the temperature increase within the glass, causing wavefront deceleration and undesirable aberrations. Therefore, preferably, the change in the optical path with temperature (heat S) is small. In this way, aberrations can be minimized even when induced absorption bands are present.

[0045] Preferably, S(436nm) is at most 50ppm / K, more preferably at most 30ppm / K, more preferably at most 25ppm / K, more preferably at most 20ppm / K, more preferably at most 15ppm / K, and more preferably at most 10ppm / K. In some embodiments, S(436nm) is at least 0.1ppm / K, at least 0.5ppm / K, at least 1ppm / K, or at least 2ppm / K.

[0046] Preferably, S(546nm) is at most 50ppm / K, more preferably at most 30ppm / K, more preferably at most 25ppm / K, more preferably at most 20ppm / K, more preferably at most 15ppm / K, and more preferably at most 10ppm / K. In some embodiments, S(546nm) is at least 0.1ppm / K, at least 0.5ppm / K, at least 1ppm / K, or at least 2ppm / K.

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

[0048] Preferably, S(436nm), S(546nm), and S(644nm) are at most 50 ppm / K, more preferably at most 30 ppm / K, more preferably at most 25 ppm / K, more preferably at most 20 ppm / K, more preferably at most 15 ppm / K, and 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.

[0049] Other important parameters are the non-induced absorbance Ext0 and the induced absorbance Ext1. Ext1(λ) describes (compared to Ext0(λ)) the additional absorbance per centimeter at wavelength λ after irradiating the sample. The induced absorbance Ext1 depends on the type of radiation source. Testing with a mercury high-pressure lamp (HOK 4) is advantageous for evaluating the material's resistance to sunlight. According to the present invention, the induced absorbance Ext1(λ) describes (compared to Ext0(λ)) the additional absorbance per centimeter at wavelength λ after irradiating a sample with a thickness d of 10 mm with HOK 4 for 15 hours. On the other hand, the non-induced absorbance Ext0(λ) describes the absorbance per centimeter at wavelength λ before irradiating a sample with a thickness d of 10 mm.

[0050] Preferably, a Philips HOK 4 / 120 lamp is used. The spectrum of the HOK 4 / 120 lamp is as follows: Figure 2 As shown. Preferably, the distance between the lamp and the sample is 7 cm. Preferably, the power density is 25 mW / cm². 2 Preferably, the sample size is 20mm × 30mm × 10mm. Here, for example, as already described above, the 10mm dimension is referred to as the sample thickness d.

[0051] This is advantageous when Ext0 and Ext1 are low. Therefore, the sum of the two values ​​contributes to the quality factor F.

[0052] The low non-induced absorbance Ext0 is advantageous because it provides a similarly low initial absorbance without prior irradiation with a HOK 4 lamp.

[0053] A low induced absorbance (Ext1) is also advantageous. This indicates that no excessive absorption occurs after irradiation, thus serving as a measure of sun resistance.

[0054] The absorbance Ext(λ) is described as the quotient of the natural logarithm of the quotient of the incident radiation I0 and the emitted radiation I at wavelength λ, divided by the sample thickness d: Ext(λ) = ln(I0 / I) / d. In this way, both Ext0 and Ext1 can be determined. As described above, according to the present invention, the sample thickness d is 10 mm.

[0055] Preferably, Ext0 (436nm) is less than 0.01 / cm, more preferably at most 0.008 / m, more preferably at most 0.005 / cm, more preferably at most 0.004 / cm, more preferably at most 0.003 / cm, and more preferably at most 0.002 / cm. In some embodiments, Ext0 (436nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0056] Preferably, Ext0 (546nm) 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 more preferably less than 0.001 / cm. In some embodiments, Ext0 (546nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0057] Preferably, Ext0 (644nm) 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 more preferably less than 0.001 / cm. In some embodiments, Ext0 (644nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0058] Preferably, Ext0 (436nm), Ext0 (546nm), and Ext0 (644nm) are 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 more preferably at most 0.002 / cm. In some embodiments, Ext0 (436nm), Ext0 (546nm), and Ext0 (644nm) are at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0059] Preferably, Ext1 (436nm) 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, Ext1 (436nm) is at least 0.0005 / cm, at least 0.001 / cm, at least 0.0015 / cm, or at least 0.02 / cm.

[0060] Preferably, Ext1 (546nm) 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, more preferably at most 0.005 / cm, more preferably at most 0.004 / cm, more preferably at most 0.003 / cm. In some embodiments, Ext1 (546nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0061] Preferably, Ext1 (644nm) 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, more preferably at most 0.005 / cm, more preferably at most 0.004 / cm, more preferably at most 0.003 / cm. In some embodiments, Ext1 (644nm) is at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0062] Preferably, Ext1 (436 nm), Ext1 (546 nm), and Ext1 (644 nm) are 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, and more preferably at most 0.006 / cm. In some embodiments, Ext1 (436 nm), Ext1 (546 nm), and Ext1 (644 nm) are at least 0.0001 / cm, at least 0.0002 / cm, at least 0.0003 / cm, or at least 0.0005 / cm.

[0063] Another important parameter is thermal conductivity k. Thermal conductivity is the product of density, specific heat capacity, and thermal conductivity at temperature. Preferably, density is determined according to Archimedes' theorem (especially ASTM C693:1993). To determine the temperature dependence of density, expansion behavior is preferably determined by a dilatometer, as described in, for example, DIN 51045-1:2005-08 and DIN ISO 7991:1998-02. Specific heat capacity is preferably determined by DSC (differential scanning calorimetry) according to DIN 51007:2019-04. Thermal conductivity is preferably determined by flash analysis according to ASTM E1461:2013.

[0064] A high thermal conductivity k limits the temperature rise of the optical glass within the beam path. Preferably, the thermal conductivity k is greater than 0.005 W / (cm*K), more preferably at least 0.006 W / (cm*K), more preferably at least 0.007 W / (cm*K), 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).

[0065] As mentioned above, the beam guiding element is made of glass, which is resistant to sunlight to a certain extent, particularly in the blue spectrum. This is advantageous for corresponding applications in projectors and material handling, as it significantly reduces the occurrence of thermal lensing effects. Further contributions can be made to reducing thermal lensing effects. For example, when a given localized residence heat power (through laser absorption) increases with thermal conductivity, the temperature difference, adjusted in a fixed manner, becomes smaller, and thus the temperature-induced aberrations become smaller. Therefore, a high thermal conductivity k is advantageous.

[0066] Depending on the application, the refractive index may also play a role. Preferably, the refractive index at wavelengths of 436 nm, 546 nm, and / or 644 nm is in the range of 1.45 to 1.65.

[0067] It has been shown that a number of different glass series can be used to obtain glass with the quality factors according to the invention. The glass is preferably selected from the group consisting of free fluorophosphate glass, silicate glass, borosilicate glass, niobium phosphate glass, and aluminoborosilicate glass. The refining agents used have specific relevance, as described below, for example.

[0068] Preferably, the beam guiding element is composed of glass, which comprises the following components (wt%).

[0069] For example, the glass of the present invention can be a fluorophosphate glass. A particularly preferred fluorophosphate glass of the present invention comprises the following components (wt%).

[0070] The fluorophosphate glass according to the invention preferably comprises less than 0.3% by weight, more preferably at most 0.2% by weight, more preferably at most 0.1% by weight of each of the components SiO2, B2O3, Li2O, Na2O, K2O, ZnO, TiO2, ZrO2, La2O3, Sb2O3, As2O3 and SnO2, or particularly preferably, even does not contain these components.

[0071] Preferably, the fluorophosphate glass comprises 7.5 to 22.5% by weight, more preferably 10 to 20% by weight, and even more preferably 14% to 19% by weight of Al2O3.

[0072] Preferably, the fluorophosphate glass comprises 1.5 to 7.5% by weight, more preferably 2 to 5% by weight, and more preferably 2.5 to 3.5% by weight of MgO.

[0073] Preferably, the fluorophosphate glass comprises 7.5 to 15% by weight, more preferably 9 to 14% by weight, and more preferably 10 to 13% by weight of CaO.

[0074] Preferably, the fluorophosphate glass comprises 11 to 25% by weight, more preferably 12 to 20% by weight, and even more preferably 13 to 17% by weight of BaO.

[0075] Preferably, the fluorophosphate glass comprises 15 to 24 wt%, more preferably 16 to 23 wt%, and even more preferably 16.5 to 22 wt% of SrO.

[0076] Preferably, the fluorophosphate glass comprises 6 to 12 wt%, more preferably 7 to 11 wt%, and even more preferably 8 to 10 wt% of P2O5.

[0077] Preferably, the fluorophosphate glass comprises 20 to 40 wt%, more preferably 25 to 35 wt%, and more preferably 27.5 to 32.5 wt% of F.

[0078] For example, the glass of the present invention can be a silicate glass. A particularly preferred silicate glass of the present invention comprises the following components (wt%).

[0079] The silicate glass according to the invention preferably comprises less than 0.3% by weight, more preferably up to 0.2% by weight, more preferably up to 0.1% by weight of each of the components B2O3, Al2O3, MgO, CaO, SrO, TiO2, P2O5, F, Sb2O3 and As2O3, or particularly preferably, even does not contain these components.

[0080] Preferably, the silicate glass comprises 35 to 50 wt%, more preferably 37.5 to 47.5 wt%, and more preferably 40 to 45 wt% of SiO2.

[0081] Preferably, the silicate glass comprises 0.2 to 4 wt%, more preferably 0.4 to 2 wt%, and more preferably 0.5 to 1.5 wt% of Li2O.

[0082] Preferably, the silicate glass comprises 2 to 15 wt%, more preferably 3 to 10 wt%, and more preferably 4 to 7.5 wt% Na2O.

[0083] Preferably, the silicate glass comprises 1 to 10 wt%, more preferably 1.5 to 7.5 wt%, and more preferably 2 to 5 wt% of K2O.

[0084] Preferably, the total amount of alkali metal oxides (R₂O) in the silicate glass is in the range of 1 to 20% by weight, more preferably 2 to 15% by weight, and even more preferably 5 to 12.5% ​​by weight. Preferably, the glass does not contain other alkali metal oxides except for Li₂O, Na₂O, and / or K₂O.

[0085] Preferably, the silicate glass comprises 2 to 25% by weight, more preferably 5 to 20% by weight, and more preferably 7.5 to 15% by weight of BaO.

[0086] Preferably, the silicate glass comprises 5 to 30 wt%, more preferably 10 to 27.5 wt%, and more preferably 15 to 25 wt% of ZnO.

[0087] Preferably, the silicate glass comprises 1.5 to 10 wt%, more preferably 2 to 8.5 wt%, and more preferably 3 to 7 wt% of ZrO2.

[0088] Preferably, the silicate glass comprises 2 to 20 wt%, more preferably 5 to 15 wt%, and more preferably 7.5 to 12.5 wt% of La2O3.

[0089] Preferably, the silicate glass comprises 0.05 to 0.4% by weight, more preferably 0.1 to 0.35% by weight, and more preferably 0.15 to 0.25% by weight of SnO2.

[0090] For example, the glass of the present invention can be borosilicate glass. A particularly preferred borosilicate glass of the present invention comprises the following components (wt%).

[0091] The borosilicate glass according to the invention preferably comprises less than 0.3% by weight, more preferably up to 0.2% by weight, more preferably up to 0.1% by weight of each of the components Al2O3, Li2O, MgO, ZnO, SrO, ZrO2, La2O3, P2O5, As2O3 and SnO2, or particularly preferably, even does not contain these components.

[0092] Preferably, the borosilicate glass comprises 52.5 to 77.5% by weight, more preferably 55 to 75% by weight, and even more preferably 57.5 to 72.5% by weight of SiO2.

[0093] Preferably, the borosilicate glass comprises 5 to 25% by weight, more preferably 7.5 to 20% by weight, and even more preferably 9 to 19% by weight of B2O3.

[0094] Preferably, the borosilicate glass comprises 0 to 17.5 wt%, more preferably 0 to 15 wt%, and even more preferably 0 to 12.5 wt% of Na₂O. In some embodiments, the glass comprises at least 2 wt%, at least 5 wt%, or even at least 8 wt% of Na₂O.

[0095] Preferably, the borosilicate glass comprises 2 to 24 wt%, more preferably 4 to 23 wt%, and even more preferably 6 to 22 wt% of K2O.

[0096] Preferably, the total amount of alkali metal oxides (R₂O) in the borosilicate glass is in the range of 5 to 30% by weight, more preferably 10 to 25% by weight, and even more preferably 15 to 22% by weight. Preferably, the glass does not contain other alkali metal oxides except for Na₂O and / or K₂O.

[0097] Preferably, the borosilicate glass comprises 0 to 5% by weight, more preferably 0 to 2% by weight, and even more preferably 0 to 1% by weight of CaO. In some embodiments, the glass comprises at least 0.1% by weight or at least 0.2% by weight of CaO.

[0098] Preferably, the borosilicate glass comprises 0 to 5% by weight, more preferably 0 to 3.5% by weight, and even more preferably 0 to 2% by weight of BaO. In some embodiments, the glass comprises at least 0.1% by weight of BaO.

[0099] Preferably, the borosilicate glass comprises 0 to 2% by weight, more preferably 0 to 1% by weight, and even more preferably 0 to 0.5% by weight of TiO2. In some embodiments, the glass comprises at least 0.1% by weight of TiO2.

[0100] Preferably, the borosilicate glass comprises 0 to 15 wt%, more preferably 0 to 12.5 wt%, and even more preferably 0 to 10 wt% of F. In some embodiments, the glass comprises at least 1 wt%, at least 2 wt%, or even at least 5 wt% of F.

[0101] Preferably, the borosilicate glass comprises 0.01 to 0.45 wt%, more preferably 0.01 to 0.4 wt%, and more preferably 0.01 to 0.35 wt% of Sb2O3.

[0102] For example, the glass of the present invention can be an aluminoborosilicate glass. Aluminoborosilicate glass particularly preferred by the present invention comprises the following components (wt%).

[0103] The aluminoborosilicate glass according to the invention preferably comprises less than 0.3% by weight, more preferably up to 0.2% by weight, more preferably up to 0.1% by weight of each of the components Li2O, MgO, CaO, SrO, TiO2, ZrO2, La2O3, P2O5, As2O3 and SnO2, or particularly preferably, even does not contain these components.

[0104] Preferably, the aluminoborosilicate glass comprises 62.5 to 77.5% by weight, more preferably 65 to 75% by weight, and even more preferably 67.5 to 72.5% by weight of SiO2.

[0105] Preferably, the aluminoborosilicate glass comprises 7.5 to 25% by weight, more preferably 10 to 20% by weight, and even more preferably 12.5 to 17.5% by weight of B2O3.

[0106] Preferably, the aluminoborosilicate glass comprises 0.2 to 10 wt%, more preferably 0.5 to 5 wt%, and more preferably 1 to 3 wt% Na2O.

[0107] Preferably, the aluminoborosilicate glass comprises 2 to 17.5% by weight, more preferably 5 to 15% by weight, and more preferably 10 to 14% by weight of K2O.

[0108] Preferably, the total amount of alkali metal oxides (R₂O) in the aluminoborosilicate glass is in the range of 2 to 25% by weight, more preferably 5 to 20% by weight, and even more preferably 10 to 15% by weight. Preferably, the glass does not contain other alkali metal oxides except for Na₂O and / or K₂O.

[0109] Preferably, the aluminoborosilicate glass comprises 0.02 to 5% by weight, more preferably 0.05 to 2% by weight, and more preferably 0.1 to 1% by weight of BaO.

[0110] Preferably, the aluminoborosilicate glass comprises 0.05 to 5% by weight, more preferably 0.1 to 2% by weight, and more preferably 0.15 to 1% by weight of ZnO.

[0111] Preferably, the aluminoborosilicate glass comprises 0.1 to 5 wt%, more preferably 0.2 to 2 wt%, and more preferably 0.5 to 1.5 wt% of F.

[0112] Preferably, the aluminoborosilicate glass comprises 0.02 to 0.45 wt%, more preferably 0.05 to 0.4 wt%, and more preferably 0.1 to 0.35 wt% of Sb2O3.

[0113] Of particular relevance are the refining agents used, as well as CeO2 and Fe2O3, which are independent of the glass system used. Therefore, the following information applies to all glass series.

[0114] Preferably, the glass is free of CeO2 and Fe2O3. Therefore, a particularly low Ext0 value can be achieved.

[0115] Preferably, the As₂O₃ content in the glass according to the invention is less than 0.3% by weight, preferably at most 0.2% by weight, and more preferably at most 0.1% by weight. Even more preferably, the glass is free of As₂O₃. Therefore, particularly low Ext1 values ​​can be achieved.

[0116] Preferably, the Sb₂O₃ content in the glass according to the 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. The glass may even be free of Sb₂O₃. Therefore, particularly low Ext1 values ​​can be achieved.

[0117] Preferably, the SnO2 content in the glass according to the 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. The glass may even be SnO2-free. Therefore, particularly low Ext1 values ​​can be achieved.

[0118] Preferably, the sum of As₂O₃ + Sb₂O₃ + SnO₂ is at most 0.5 wt%, preferably at most 0.4 wt%, more preferably at most 0.3 wt%, for example at most 0.2 wt% or at most 0.1 wt%. The glass may even be free of As₂O₃, Sb₂O₃, and SnO₂. Therefore, particularly low Ext1 values ​​can be achieved.

[0119] The glass may include, for example, 0 to 45 wt%, particularly 0.5 to 42.5 wt%, or 5 to 40 wt% F. Therefore, particularly low Ext1 values ​​can be achieved.

[0120] The glass may also contain Cl, especially due to Cl refining. Preferably, it is less than 2% by weight, more preferably less than 1.5% by weight, and particularly preferably less than 1% by weight. When the Cl content is too high, this may cause undesirable salt precipitation on the glass.

[0121] When the specification states that the glass contains no component or does not contain a certain component, it means that the component is only permitted to exist in the glass as an impurity. This means that it will not be added in large quantities. According to the invention, amounts 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 by weight are not considered large quantities.

[0122] Preferably, the beam guiding element is a lens, a light guide rod, a prism, or an aspherical mirror, and particularly preferably a prism.

[0123] The present invention also relates to glass having quality factors according to the present invention.

[0124] The present invention also relates to the use of the imaging system according to the invention, particularly in projectors or material handling.

[0125] The present invention also relates to a projector, particularly a DLP projector, that includes an imaging system according to the present invention. Attached Figure Description

[0126] Figure 1 An embodiment of the invention is illustrated schematically. An exemplary design of an imaging system as a DLP projector is shown. After leaving the laser source 1, the three colors blue, green, and red (arrow 5) generated by the laser source 1 reach the beam guiding element 2. The beam guiding element 2 redirects the light to the image generating chip 3 (arrow 6). Then, the image generated by the image generating chip 3 (specifically an image in blue, green, and red respectively) reaches the beam guiding element 2. This is shown by arrow 7. The beam guiding element 2 then ensures that the composite color image reaches the projection optics system 4, as shown by arrow 8.

[0127] Figure 2 The emission spectrum of the Phillips HOK 4 / 120 lamp is shown. The wavelength is shown in nm on the x-axis. The relative intensity is shown relative to the maximum intensity on the y-axis.

[0128] Figure 3 This is a bar chart showing the quality factor F (436 nm) and quality factor F (RGB) of the five embodiments 1-5 according to the present invention and the comparative example A not according to the present invention. Detailed Implementation

[0129] Five samples of example glass 1-5 according to the present invention and a comparative example A not according to the present invention, each with a sample thickness of 10 mm, were irradiated for 15 hours using a Philips HOK 4 / 120 lamp. The spectrum of the HOK 4 / 120 lamp is shown below. Figure 2 As shown. The distance between the lamp and the sample is 7 cm. The power density is 25 mW / cm². 2 The sample size is 20mm × 30mm × 10mm. The composition of the glass is shown in Table 1 below (wt%).

[0130] Table 1

[0131] The quality factors F(436nm), F(546nm), F(644nm), and F(RGB) were calculated using the above formulas. To this end, the corresponding values ​​of the thermal conductivity S, non-induced absorbance Ext0, and induced absorbance Ext1 for wavelengths of 436nm, 546nm, and 644nm, as well as the thermal conductivity k of the glass, were determined. The results are as follows... Figure 3 As shown in the figure. Table 2 below summarizes the measured values ​​and calculation results.

[0132] Table 2

[0133] As can be seen, compared with Comparative Example A, the quality factors of the glasses 1-5 according to the present invention are F(436nm) < 700ppm / W, F(546nm) < 215ppm / W, F(644nm) < 85 ppm / W and F(RGB) < 1000 ppm / W.

[0134] Example glass 3 and Comparative Example A have very similar compositions, and the essential difference between them lies in the presence of As₂O₃ in Comparative Example A. As a result, the performance of Example 3 is shown to be several times improved. It is noteworthy that this effect can be achieved using many different glass series. Therefore, Examples 1 and 5 are borosilicate glasses, Example 2 is an aluminoborosilicate glass, Example 3 is a silicate glass, and Example 4 is a fluorophosphate glass.

[0135] List of reference numerals 1. Laser source 2. Beam guiding element 3 Image generation chip 4. Projection Optical Components 5. Light from the laser source reaches the beam guiding element. 6. Light redirected from the beam guiding element to the image generation chip. 7. The image generated by the image generation chip reaches the beam guiding element. 8. The composite color image reaches the projection optics.

Claims

1. A glass having a quality factor F(436nm) = S(436nm)*(Ext0(436nm)+Ext1(436 nm)) / k, wherein, S(436nm) is the heat at wavelength 436nm, Ext1(436nm) is the additional absorbance at wavelength 436nm after irradiating a 10mm thick sample with a HOK 4 lamp for 15 hours compared to Ext0(436nm), Ext0(436nm) is the absorbance at wavelength 436nm of a 10mm thick sample without irradiation with a HOK 4 lamp, wherein F(436nm) < 700ppm / W, and the glass comprises the following components (wt%): 。 2. The glass according to claim 1, wherein the glass is a borosilicate glass comprising the following components (wt%): 。 3. The glass according to claim 1, wherein the glass is a silicate glass comprising the following components (wt%): 。 4. The glass according to claim 1, wherein the glass is a fluorophosphate glass comprising the following components (wt%): 。 5. A beam guiding element, said beam guiding element being composed of glass according to any one of claims 1 to 4.

6. The beam guiding element according to claim 5, wherein the beam guiding element is a prism.

7. An imaging system comprising a beam guiding element according to claim 5 or 6 and at least one laser source, said laser source being selected from a spectral range of 380 nm to 490 nm having a wavelength λ B Laser source B has a wavelength λ in the spectral range of >490nm to 585nm. G The laser source G and the wavelength λ in the spectral range of >585nm to 750nm. R A group consisting of laser light sources R, in, The laser source is adapted to produce a value greater than 10 W / cm² at at least one point of the beam guiding element. 2 The average surface power density, and the beam guiding element is composed of glass with a quality factor F(436nm) = S(436nm)*(Ext0(436nm)+Ext1(436nm)) / k, where S(436nm) is the heat at wavelength 436nm, Ext1(436nm) is the additional absorbance at wavelength 436nm after irradiating a 10mm thick sample with a HOK 4 lamp for 15 hours compared to Ext0(436nm), Ext0(436nm) is the absorbance at wavelength 436nm of a 10mm thick sample without irradiation with a HOK 4 lamp, k is the thermal conductivity, and where F(436nm) < 700 ppm / W.

8. The imaging system of claim 7, comprising having a wavelength λ in the spectral range of 380 nm to 490 nm. B Laser source B has a wavelength λ in the spectral range of >490nm to 585nm. G The laser source G and the wavelength λ in the spectral range of >585nm to 750nm. R The laser source R, wherein, The laser source B, laser source G, and laser source R are adapted to produce a beam density greater than 10 W / cm² at at least one point of the beam guiding element. 2 The average surface power density, and the beam guiding element is composed of glass having a quality factor F(RGB) = F(436nm) + F(546nm) + F(644nm) = S(436nm)*(Ext0(436nm) + Ext1(436nm)) / k + S(546nm)*(Ext0(546nm) + Ext1(546nm)) / k + S(644nm)*(Ext0(644nm) + Ext1(644nm)) / k, where F(RGB) < 1000 ppm / W, or where F(RGB) is at most 800 ppm / W.

9. The imaging system according to claim 7, wherein, The laser source is a diode laser.

10. The imaging system according to claim 7, wherein, The laser source is adapted to generate 15 to 60 W / cm² at at least one point of the beam guiding element. 2 The average surface power density.

11. The imaging system according to claim 7, wherein, S(436 nm), S(546 nm), and S(644 nm) are at most 50 ppm / K; or, Among them, Ext0 (436 nm), Ext0 (546 nm), and Ext0 (644 nm) are less than 0.01 / cm; or Among them, Ext0 (436nm), Ext0 (546nm), and Ext0 (644nm) are less than 0.3 / cm; or Among them, the thermal conductivity k is higher than 0.005 W / (cm*K).

12. The imaging system according to claim 7, wherein, The average dn / dT at wavelengths of 436 nm, 546 nm and / or 644 nm in the temperature range of 20 to 40 °C is in the range of 0.1 to 8.0 ppm / K, where dn / dT represents the change of refractive index with temperature.

13. A projector comprising an imaging system according to any one of claims 7 to 12.

Images