The present invention relates to hybrid rings and methods for manufacturing hybrid rings. The hybrid rings are configured to be used in optical systems, in particular in LiDAR systems.

Background of the invention

Light Detection And Ranging (LiDAR) or Laser Detection And Ranging (LaDAR) is a method for optical distance and velocity measurement using laser light, hereinafter referred to as LIDAR. For this purpose, LiDAR systems emit laser beams in the near infrared spectrum (NIR), i.e. la ser beams with wavelengths above 780 nm, which are reflected by objects in the environment and at least partially return to and are detected by the LiDAR system. By means of the pattern of the reflected beams, the LiDAR system can detect objects and by means of the time of flight of the laser beams, it can calculate the distance of these objects. Some LiDAR systems can also calculate the velocities of objects on the basis of phase relationships between the emitted and reflected beams.

LiDAR systems or LiDAR sensors currently represent an important technology for enabling au tonomous driving. Further applications and fields of use for LiDAR systems are for example ro botic taxis, robotic trucks, robotic flight taxis, industrial and logistic robots, ships, mining, con struction and mining machinery, space satellites as well as the generation of topology/land maps from the air, from land and underwater, the optimization of wind turbines, the measure ment of turbulence at airports, the determination of aircraft turbulence, etc.

All LiDAR systems require at least one optical window, which is located between the optoelec tronic components of the LiDAR system and the environment. The at least one optical window provides mechanical protection against environmental influences. The different LiDAR systems can be distinguished according to their design, more precisely with regard to the shape and construction of the windows used in the LiDAR systems. For example, some LiDAR systems are equipped with planar windows to separate the sensitive components of the system from the out side world. Other LiDAR systems have curved windows instead of planar windows. A very im portant type of LiDAR systems are so-called spinning LiDAR systems, in which the emitter and detector typically rotate in a stationary ring-shaped window.

However, prior art LiDAR windows often have disadvantages in terms of their durability and reli ability and often have a low and insufficient environmental stability. For example, many prior art LiDAR windows do not sufficiently protect sensitive components behind the LiDAR window against damaging external influences, such as moisture. Moreover, prior art LiDAR windows of ten degrade under the influence of weathering, for example due to deposits from the atmos phere (after a chemical reaction), which consequently reduces the signal strength of the LiDAR system.

It is an object of the present invention to provide an optical window for optical systems, in partic ular for LiDAR systems, more precisely for spinning LiDAR systems, which has improved char acteristics and overcomes at least some of the disadvantages of the prior art.

In particular, it is an object of the present invention to provide an optical window for optical sys tems, in particular for LiDAR systems, more precisely for spinning LiDAR systems, which has an optimal optical performance and provides an improved protection for sensitive optoelectronic components arranged behind the optical window.

These objects are achieved by the subject matter of the independent claims. Preferred embodi ments and preferred features are specified in the dependent claims and the following descrip tion.

Summary of the invention

According to an aspect, the present invention provides a hybrid ring for optical systems, in par ticular LiDAR-systems. More precisely, by means of its ring-shaped geometry the hybrid ring is suitable for being used in a spinning LiDAR system. The hybrid ring comprises an outer ring and an inner ring. One of the outer ring and the inner ring is a glass ring and the other one of the outer ring and the inner ring is a polymer ring.

The inner ring is arranged coaxially inside and in contact with the outer ring. The inner ring can be in direct contact with the outer ring, wherein an inner circumferential surface of the outer ring is in touch with or at least partially abuts an outer circumferential surface of the inner ring. Alter natively, the inner ring can be in indirect contact with the outer ring, wherein the inner circumfer ential surface of the outer ring is connected with the outer circumferential surface of the inner ring via at least one additional layer or component. A radius of the inner ring is less than a ra dius of the outer ring.

The hybrid ring has an average transmittance of less than 10 %, preferably less than 5 %, more preferably less than 1 % for visible light, i.e. for light with a wavelength between 400 nm and 700 nm. The hybrid ring has an average transmittance of 90 % or more at least for light with a working wavelength of typically 905 nm, 940 nm and/or 1550 nm, preferably at least for light with a working wavelength in the near infrared spectrum (NIR), i.e. between 780 nm and 3 pm. The hybrid ring can have an average transmittance of preferably 95 % or more, more preferably 98 % or more, at least for light with a working wavelength of typically 905 nm, 940 nm and/or 1550 nm, preferably at least for light with a working wavelength in the near infrared spectrum (NIR), i.e. between 780 nm and 3 pm. The low transmittance of visible light ensures that compo nents inside the hybrid ring cannot be viewed from the outside, which allows for a clean appear ance of the LiDAR system. Further, the low transmittance of visible light ensures that the elec tromechanical components and the detection as such are not negatively influenced by light not being in the range of the working wavelength/s. The high transmittance of light with a working wavelength ensures that light with the working wavelength/s is reliably and sufficiently emitted towards the object to be detected and reflected back through the hybrid ring to a detector inside the hybrid ring.

By means of the integrated glass ring and polymer ring, the hybrid ring according to the present invention combines advantages of a glass LiDAR window and a polymer LiDAR window. By means of the glass ring, the hybrid ring provides a reliable barrier that prevents diffusion of gas and moisture through the hybrid ring and can thus protect sensitive optoelectronic elements and components of the LiDAR system against damaging external influences. Thus, the hybrid ring can protect components surrounded by the hybrid ring against harmful environmental influ ences. With other words, the hybrid ring is resistant and durable against external and circumfer ential influences as it provides a hermetic seal between the optoelectronic components of the LiDAR system and the environment. Hence, by means of the hybrid ring according to the inven tion, the LiDAR system in which the hybrid ring is installed can have an increased lifetime com pared to prior art LiDAR systems with conventional polymer windows. At the same time, the hy brid ring can be easily provided with necessary optical characteristics by means of the inner pol ymer ring, in particular regarding the specific average low transmittance for visible light and the specific average high transmittance (transparency) for light with working wavelength/s. Moreo ver, the hybrid ring provides a cost efficient solution that can be easily assembled.

The outer ring and the inner ring can have a concentricity of 0.2 mm or less, preferably 0.1 mm or less, more preferably 0.075 mm or less, still more preferably 0.05 mm or less.

The hybrid ring, in particular the glass ring, can have an oxygen permeability of less than 10 cm ³ /(m ² d bar), preferably less than 1 cm ³ /(m ² d bar), more preferably less than 0.1 cm ³ /(m ² d bar), still more preferably less than 0.01 cm ³ /(m ² d bar), even more preferably less than 0.001 cm ³ /(m ² d bar). The oxygen permeability can be the oxygen permeability measured at 23 °C, with 85 % relative humidity, wherein 1 d = 24 h, preferably measured according to DIN 53380-3: 1998-07. The hybrid ring, in particular the glass ring, can have a water vapor permeability of less than 10 g/(m ² d), preferably less than 1 g/(m ² d), more preferably less than 0.1 g/(m ² d), still more preferably less than 0.01 g/(m ² d), even more preferably less than 0.001 g/(m ² d). The water vapor permeability can be the water vapor permeability measured at 23 °C, with 85 % relative humidity, wherein 1 d = 24 h, preferably measured according to DIN EN ISO 15106-3: 2005.

In an embodiment of the hybrid ring, the polymer ring can have an average transmittance of less than 10 %, preferably less than 5 %, more preferably less than 1 % for visible light, i.e. at least for light with a wavelength between 400 nm and 700 nm. Preferably, the polymer ring can be colored black by pigments in order to absorb visible light and achieve the aforementioned low average transmittance (i.e. opaqueness). The polymer ring can be colored in the bulk. In this embodiment, the intensity of the coloring of the polymer ring can depend on the thickness of the polymer ring. More precisely, the thinner the polymer ring is, the more intensely it can be colored, in order to achieve the intended low average transmittance. Thus, no bulk coloring or other coloring of glass is necessary, which simplifies the manufacturing process of the hybrid ring.

In an embodiment, the glass ring can have an average transmittance of less than 10 %, prefera bly less than 5 %, more preferably less than 1 % for visible light, i.e. at least for light with a wavelength between 400 nm and 700 nm. Preferably, the glass ring can be black glass which absorbs visible light and achieves the aforementioned low average transmittance (i.e. opaque ness). In this embodiment, the intensity of the coloring of the black glass can depend on the thickness of the glass ring. More precisely, the thinner the glass ring is, the more intensely it can be colored, in order to achieve the intended low average transmittance.

In an embodiment, the average transmittance of the hybrid ring of less than 10 %, preferably less than 5 %, more preferably less than 1 % for visible light, i.e. at least for light with a wave length between 400 nm and 700 nm, can be achieved by providing an outer circumferential sur face of the outer ring and/or an inner circumferential surface of the inner ring with a coating, a foil, etc. that has an average transmittance of the hybrid ring of less than 10 %, preferably less than 5 %, more preferably less than 1 % for visible light, i.e. at least for light with a wavelength between 400 nm and 700 nm.

In an embodiment, the average transmittance of the hybrid ring of less than 10 %, preferably less than 5 %, more preferably less than 1 % for visible light, i.e. at least for light with a wave length between 400 nm and 700 nm, can be achieved by providing a combination of the colored glass ring (with black glass) and/or a colored polymer ring and/or one or more additional foil/s, coating/s, etc. of the types described above. The difference, more precisely the absolute value of the difference, between a refractive index of the polymer ring and a refractive index of the glass ring can be less than 0.35, preferably less than 0.15, more preferably less than 0.07, still more preferably less than 0.05. By means of this particular maximum refractive index difference, a minimum reflection at the transition between the glass ring and the polymer ring can be achieved. The refractive index as used herein can relate to a refractive index for light with the working wavelength, in particular for light with a wavelength of 905 nm, 940 nm or 1550 nm. For example, the refractive index of the glass ring can be 1.46 (for borosilicate glass) or 1.46 (for fused silica). For example, the refractive index of the polymer ring can be 1.49 (for PMMA) or 1.585 (for PC).

In an embodiment of the hybrid ring, the outer ring is the glass ring (i.e. an outer glass ring) and the inner ring is the polymer ring (i.e. an inner polymer ring). By means of providing an outer glass ring, the hybrid ring has an improved mechanical resistance, durability and stability to wards the outside. Hence, the hybrid ring can have an increased lifetime. In particular, such a hybrid ring is scratch resistant towards the outside. Scratches in prior art LiDAR windows often occur during operation of the LiDAR system due to (a) environmental influences caused by small impacting particles (e.g. sand in the air or particles from cars in front), (b) mechanical cleaning of the windows and/or (c) hard material or sand that scratches over the window surface when using windscreen wipers and/or (d) other hard material that scratches over the LiDAR window during use of the system. Scratched surfaces, through which reflected and reflected light must pass, have an enormous impact on the optical performance and reliability of the sys tem, especially by removing light, misdirecting light to the wrong pixels, scattering and reducing the signal-to-noise ratio.

Alternatively, the outer ring can be the polymer ring and the inner ring can be the glass ring. In this case, the glass ring at least provides the hermetic seal between the optoelectronic compo nents of the LiDAR system and the environment.

According to an embodiment, the ratio between a coefficient of thermal expansion of the glass ring and a coefficient of thermal expansion of the polymer ring (CTE _g iass/CTEp ₀ iymer) is between 0.0025 and 0.2, preferably between 0.004 and 0.125, more preferably between 0.04 and 0.06, still more preferably about 0.05. The ratio between the coefficient of thermal expansion of the glass ring and the coefficient of thermal expansion of the polymer ring can be at least 0.0025, preferably at least 0.004, more preferably at least 0.04, still more preferably at least 0.05. The ratio between the coefficient of thermal expansion of the glass ring and the coefficient of thermal expansion of the polymer ring can be 0.2 or less, preferably 0.125 or less, more preferably 0.06 or less, still more preferably 0.05 or less. The ratio of the coefficients of thermal expansion ap plies for consideration at room temperature, in particular at 20°C. In other words, the specified ratio relates to a comparison of the coefficient of thermal expansion of the glass ring and the co efficient of thermal expansion of the polymer ring (CTE _g iass/CTEp ₀ iymer) at room temperature, in particular at 20 °C. This particular ratio of the coefficients of thermal expansion according to the invention ensures that the hybrid ring can be reliably utilized and is stable in all temperature ranges particularly relevant for LiDAR applications, more precisely at least in temperature ranges between -40 °C and 125 °C. The specified ratio of the coefficients of thermal expansion avoids an unwanted detachment of the glass ring and the polymer ring due to environmental temperature effects. Further, the specified ratio of the coefficients of thermal expansion can be advantageous with regard to assembling the hybrid ring.

The coefficient of thermal expansion of the glass ring can preferably be between 0.01 10 ⁶ K ¹ and 10 10 ⁶ K ¹ , preferably between 2.5 10 ⁶ K ¹ and 4 10 ⁶ K ¹ , more preferably between 3 10 ⁶ K ¹ and 3.5 10 ⁶ K ¹ . Here, the coefficient of thermal expansion of the glass ring is the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987.

The coefficient of thermal expansion of the polymer ring can preferably be between 50 10 ⁶ K ¹ and 200 10 ⁶ K ¹ , preferably between 55 10 ⁶ K ¹ and 130 - 1 O ⁶ K ¹ , more preferably between 60 10 ⁶ K ¹ and 80 10 ⁶ K ¹ . Here, the coefficient of thermal expansion is the coefficient of ther mal expansion at a temperature range of 20 °C.

In an embodiment, the hybrid ring can comprise an adhesive layer and/or a filling layer arranged between the outer ring and the inner ring. The adhesive layer and/or the filling layer can be in direct contact with the inner circumferential surface of the outer ring and can be in direct contact with the outer circumferential surface of the inner ring such that it connects the outer ring with the inner ring. Thus, in this embodiment the outer ring and the inner ring can be indirectly con nected via at least the adhesive layer and/or the filling layer. The adhesive layer can for exam ple comprise an acrylate adhesive. The filling layer can for example comprise oil. The additional adhesive layer and/or filling layer can improve the mechanical and/or optical connection be tween the outer ring and the inner ring and can thus serve to provide an even more stable hy brid ring. The adhesive layer and/or filling layer can compensate for the different thermal expan sions of the outer ring and the inner ring and can reliably maintain the connection between both rings. Moreover, the adhesive layer and/or filling layer can help to avoid small gaps between both rings. Providing the adhesive layer and/or the filling layer between the outer ring and the inner ring can prevent moisture from entering the hybrid ring (moisture intrusion). Thus, the ad hesive layer and/or the filling layer can help to prevent moisture from negatively affecting the optical characteristics and the mechanical structure of the hybrid ring. Finally, the adhesive layer is also advantageous in case of mechanical damage of the outer ring as it would hold back glass fragments.

The adhesive layer and/or the filling layer can have particular properties in order to be best suit able for use in a hybrid ring between the outer ring and the inner ring. In particular, the following preferred properties of the adhesive layer and/or the filling layer relate to a cured state or cured condition of the adhesive layer and/or the filling layer, unless otherwise specified, particularly to a state or condition in which the adhesive layer and/or the filling layer is installed in the hybrid ring.

A coefficient of thermal expansion of the adhesive layer and/or the filling layer can preferably be between 50 10 ⁶ K ¹ and 350 10 ⁶ K ¹ , preferably between 100 10 ⁶ K ¹ and 325 10 ⁶ K ¹ , more preferably between 150 10 ⁶ K ¹ and 300 10 ⁶ K ¹ , still more preferably between 225

10 ⁶ K ¹ and 275 10 ⁶ K ¹ . Here, the coefficient of thermal expansion is the coefficient of thermal expansion at room temperature, in particular at a temperature of 20 °C. A relatively high coeffi cient of thermal expansion of the adhesive layer and/or the filling layer is preferable as it in creases the contraction of the adhesive layer and/or the filling layer and thus achieves an im proved adaption and abutting to the polymer ring, in particular during cooling of the hybrid ring, when the polymer ring is the inner ring.

The adhesive layer and/or the filling layer can have an average transmittance between 85 % and 100 % for light with a wavelength between 400 nm and 700 nm, i.e. for visible light. The ad hesive layer and/or the filling layer can have an average transmittance between 85 % and 100 % at least for light with a working wavelength in the near infrared spectrum (NIR), particu larly for light with a working wavelength of 905 nm, 940 nm and/or 1550 nm, preferably a wave length from 780 nm to 3 pm. Thus, a minimum impact of the adhesive layer and/or the filling layer on the optical characteristics of the hybrid ring can be achieved so that the optical charac teristics of the hybrid ring, in particular the transmission and absorption of light with certain wavelengths, can be specifically adapted substantially by means of the outer glass ring and the inner polymer ring, and by means of adapting the adhesive layer to the specifically selected glass and polymer materials.

The adhesive layer and/or the filling layer can be striae-free (or streak-free). In other words, the adhesive layer and/or the filling layer can be striae class A or better. Striae are small scale inho mogeneities within the adhesive layer and/or the filling layer with a spatial gradient of the refrac tive index (refractive index ripples within the adhesive layer and/or the filling layer). The striae class of the adhesive layer and/or the filling layer can be measured by means of shadowgraph measurement. Shadowgraph measurement can be carried out according to the test method de scribed in the publically available publication by SCHOTT AG, “TIE-25: Striae in optical glass”, dated June 2006. The adhesive layer and/or the filling layer can have a high homogeneity. By providing a substantially stiae-free and/or homogeneous adhesive layer and/or filling layer, the impact of this layer on the optical characteristics of the hybrid ring can be minimized. Preferably, the glass ring and/or the polymer ring are also striae-free, i.e. striae class A or better.

The adhesive layer and/or the filling layer can have a shore hardness A of 70 or less, preferably 50 or less, more preferably 30 or less. Herein, it is referred to shore hardness scale A. By means of such a shore hardness, the adhesive layer and/or the filling layer can have a perma nent elastic behavior and can thus have a sufficient thermal stability at least from -40 °C to +125 °C.

The adhesive layer and/or the filling layer can have a viscosity of 3000 mPa-s or less, preferably 2000 or less, more preferably 1000 or less, at room temperature, measured by means of a rota tional viscometer, in particular according to ISO 2555:2018. This viscosity parameter refers to an uncured adhesive layer and/or the filling layer, i.e. to a state of the adhesive layer and/or the filling layer before it is applied to the hybrid ring. Such a viscosity allows for an optimal applica bility, castability and dispensability of the adhesive layer and/or the filling layer between the outer glass ring and the inner polymer ring.

The adhesive layer and/or the filling layer can have an elongation at break of at least 100 %, preferably at least 200 %, more preferably at least 300 %. This allows for a stable connection of the outer glass ring and the inner polymer ring by the adhesive layer and/or the filling layer, even under the application and impact of external forces, mechanical loads and/or circumferen tial influences such as variations in temperature.

The adhesive of the adhesive layer and/or the filler of the filling layer can be curable by light with a wavelength between 400 nm and 700 nm (by visible light). Providing an adhesive layer and/or filling layer that is curable by visible light enables use of UV-blocking material (glass) for the outer glass ring. Alternatively, the adhesive layer and/or the filling layer can be UV-curable, e.g. by light with a wavelength between 300 nm and 400 nm, preferably 365 nm. In this case, the outer glass ring must comprise UV-transparent glass. The adhesive layer and/or the filling layer can be fast curable, which means that it is curable within 2 min or less, preferably 1 min or less, more preferably 30 s or less. In some embodiments, the adhesive layer can comprise a two-component adhesive and/or a one-component adhesive. The curing of a one-component or a two-component adhesive can for example take one to several hours. The adhesive layer can be heat curable. The adhesive layer and/or the filling layer can have a transmission haze of 0.5 % or less, prefer ably 0.3 % or less, more preferably 0.1 % or less, for layer thickness of the adhesive layer of the filling layer of 1 mm according to ASTM D1003 (Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics). By providing an adhesive layer and/or filling layer with such a transmission haze, the impact of this layer on the optical characteristics of the hybrid ring can be minimized.

The adhesive layer and/or the filling layer can be substantially particle-free. In particular, sub stantially particle-free can define that the adhesive layer and/or the filling layer only contains particles with a diameter or an extension of 500 pm or less, preferably 300 pm or less, more preferably 150 pm or less, still more preferably 100 pm or less, even more preferably 50 pm or less. In other words, substantially particle-free can define that the adhesive layer and/or the fill ing layer does not contain any particles that have a diameter or an extension that is larger than the aforementioned value. By providing a particle-free adhesive layer and/or filling layer, the im pact of this layer on the optical characteristics of the hybrid ring can be minimized.

The adhesive layer and/or the filling layer can have a high UV-stability so that substantially no yellowing occurs during long-term use of the hybrid ring. More precisely, the adhesive layer and/or the filling layer can have a yellowing b of less than 5 (b < 5), preferably less than 4 (b < 4), more preferably less than 3 (b < 3), when measured according to the sun light test (using a Xe lamp), with a measurement time of t = 1000 hours and a thickness of the adhesive layer and/or the filling layer of d = 1 mm.

The adhesive layer and/or the filling layer can be substantially bubble-free. In particular, sub stantially bubble-free can define that the adhesive layer and/or the filling layer only contains bubbles with a diameter or an extension of 500 pm or less, preferably 300 pm or less, more preferably 150 pm or less, still more preferably 100 pm or less, even more preferably 50 pm or less. In other words, substantially bubble-free can define that the adhesive layer and/or the fill ing layer does not contain any bubbles that have a diameter or an extension that is larger than the aforementioned value. By providing a bubble-free adhesive layer and/or filling layer, the im pact of this layer on the optical characteristics of the hybrid ring can be minimized.

All refractive indices as used herein can relate to a refractive index for light with the working wavelength, respectively, in particular for light with a wavelength of 905 nm, 940 nm and/or 1550 nm.

In an embodiment, the adhesive layer and/or the filling layer can have a refractive index in the range of 1.33 to 1.74, preferably in the range of 1.43 to 1.63, more preferably in the range of 1.5 to 1.54. Thus, the reflection of the hybrid ring (more precisely the total reflection by all interfaces between the layers of the hybrid ring) can be reduced to 1 % or less, preferably to 0.3 % or less, more preferably to 0.1 % or less. This can apply in particular for an embodiment of the hybrid ring with an outer glass ring having a refractive index of 1.46 and an inner polymer layer having a refractive index of 1.59.

In an embodiment of the hybrid ring the following criteria can be fulfilled: wherein n _giaS s is the refractive index of the glass ring, ni _ay er is the refractive index of the adhesive layer and/or the filling layer, and n _p0iymer is the refractive index of the polymer ring. By means of these ratios or conditions, the optical characteristics of the hybrid ring can be optimized by mini mizing the reflection of the hybrid ring, more precisely the reflection at the interfaces between the glass ring and the adhesive/filling layer and between the adhesive/filling layer and the poly mer ring.

According to an embodiment of the hybrid ring, a length (axial extension) of the glass ring can be equal to a length or the polymer ring. Alternatively, the length of the glass ring can exceed the length or the polymer ring, preferably by at least 1 mm, more preferably at least 2.5 mm, still more preferably at least 5 mm. This embodiment enables an advantageous installability of the hybrid ring in a LiDAR system, i.e. an advantageous attachability of the hybrid ring to a housing of a LiDAR system via the glass ring. For example, the glass ring can have a total axial length between 15 mm and 200 mm, preferably between 40 mm and 120 mm, more preferably be tween 45 mm and 75 mm. In particular, the glass ring can have a total axial length of 15 mm or more, preferably 40 mm or more, more preferably 45 mm or more. In particular, the glass ring can have a total axial length of 200 mm or less, preferably 120 mm or less, more preferably 75 mm or less.

In an embodiment, the hybrid ring can have a total thickness of 6 mm or less, preferably 5 mm or less, more preferably 4 m or less, still more preferably 3 mm or less, even more preferably 2.6 mm or less. The total thickness can be the thickness of all layers of the hybrid ring. In other words, the total thickness of the hybrid ring can be i) the thickness of the outer ring plus the thickness of the inner ring, ii) the thickness of the outer ring plus the thickness of the adhesive layer and/or filling layer plus the thickness of the inner ring, iii) the thickness of the outer ring plus the thickness of the adhesive layer and/or filling layer plus the thickness of the inner ring plus the thickness of one or more additional glass ring, polymer ring, layer, foil, coating, etc.

The thickness of the glass ring can be 2 mm or less. The thickness of the polymer ring can be 2 mm or less, preferably 1.5 mm or less, more preferably 1 mm or less. The thickness of the ad hesive layer and/or filling layer can be 2 mm or less, preferably 1.5 mm or less, more preferably 1 mm or less, still more preferably 0.5 mm or less.

In an embodiment, an outer radius of the inner ring can be between 0.5 mm and 2 mm smaller than an inner radius of the outer ring, e.g. in an assembled state when glued together. Such a constrain of the outer radi/outer diameters simplifies the assembling of the hybrid ring.

The outer ring can have an outer radius between 25 mm and 200 mm, preferably between 44 mm and 180 mm, more preferably between 85 mm and 160 mm. The outer radius of the outer ring can be at least 25 mm, preferably at least 44 mm, more preferably at least 85 mm. The outer radius of the outer ring can be 200 mm or less, preferably 180 mm or less, more prefera bly 160 mm or less.

In an embodiment of the hybrid ring, the glass ring can have a fracture toughness K _|C of 0.8 MPa m ^1/2 or less, preferably 0.76 MPa m ^1/2 or less, more preferably 0.74 MPa m ^1/2 or less, still more preferably 0.7 MPa m ^1/2 or less, even more preferably 0.68 MPa m ^1/2 or less, in par ticular 0.66 MPa m ^1/2 or less. The fracture toughness K _|C can be measured in application of the standard test method according to ASTM-C-1421-16 (“Standard Test Methods for Determina tion of Fracture Toughness of Advanced Ceramics at Ambient Temperature”, with pre-cracked beam test specimen) . This significantly reduces the risk of hybrid ring damage during use due to external impacts, in particular when the glass ring is the outer ring.

According to an embodiment, the outer circumferential surface of the outer ring and/or the inner circumferential surface of the inner ring can be provided with an anti-reflection coating for light with the working wavelength. This further increases transparency of the hybrid ring for working wavelengths, i.e. especially for light with wavelengths in the near infrared (NIR) spectral range. In other words, the anti-reflection coating/s can reduce reflection losses for light in the working wavelength range at the air/glass interface and/or polymer/air or gas interface. As a result, transmission of light in the working wavelength range (e.g. laser beams) through the hybrid ring can be maximized, both in terms of emission to the outside and in terms of transmission of re flected light from the outside back to a detector inside the hybrid ring. The hybrid ring can com prise an anti-reflection (AR) layer system comprising several anti-reflection layers or coatings.

An AR layer system can cover wider wavelength ranges than individual AR layers.

Preferably, the outer circumferential surface of the inner ring can be free of any anti-reflection coating or layer. The inner circumferential surface of the outer ring can be free of any anti-re- flection coating or layer. This improves the mechanical and optical connectability of the inner ring to the outer ring, e.g. by an adhesive and/or filling layer.

The hybrid ring can be provided with an UV-coating (UV light blocking coating), preferably on the outer circumferential surface of the outer ring and/or on the inner circumferential surface of the inner ring. This allows protecting the components inside the hybrid ring, such as optoelec tronic components, against UV light. Further, when the UV-coating is provided on the outer cir cumferential surface of the outer ring also the inner ring can be protected against UV light.

In an embodiment of the hybrid ring, the glass ring can comprise borosilicate glass, soda-lime glass, fused silica and/or aluminosilicate glass.

The glass ring can be a UV-protective glass (UV light blocking glass). This allows protecting the components inside the hybrid ring, such as optoelectronic components, against UV light. Fur ther, when the glass ring is the outer ring also the inner polymer ring can be protected against UV light, which further increases the lifetime and prevents degradation of the hybrid ring.

The glass ring can comprise thin glass, in particular in an embodiment in which the glass ring is the inner ring. Thin glass can be glass with a thickness of 1.2 mm or less, preferably 0.75 mm or less, more preferably 0.5 mm or less. Thin glass can be glass with a thickness of at least 0.4 mm, more preferably at least 0.5 mm.

Preferable materials can have the following composition in percent by weight:

Table 1 Possible compositions are indicated in the below table:

Table 2

"R2O" means alkali metal oxides selected from U2O, Na ₂ 0 and K2O. "RO" means metal oxides selected from MgO, ZnO, CaO, BaO and SrO.

In an embodiment, the glass material of the glass ring can be borosilicate glass having the fol lowing composition in percent by weight (wt.-%):

Table 3

Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, Mhq2, T1O2, CuO, CeC>2, Cr2C>3, 0 - 2 wt.-% of AS2O3, Sb2C>3, Sn02, SO3, Cl, F and/or CeC>2 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total composition is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be between 3.0 10 ⁶ K ¹ and 9.1 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987.

Preferably, the borosilicate glass can have the following composition in percent by weight (wt- %):

Table 4

Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, Mhq2, T1O2, CuO, Ce02, Cr203, 0 - 2 wt.-% of AS2O3, Sb203, Sn02, SO3, Cl, F and/or Ce02 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total composition is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be between 2.8 10 ⁶ K ¹ and 7.5 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987. More preferably, the borosilicate glass can have the following composition in percent by weight (wt.-%):

Table 5

Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, Mhq2, TiC>2, CuO, Ce02, 0203, 0 - 2 wt.-% of AS2O3, Sb203, Sn02, SO3, Cl, F and/or Ce02 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total composition is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be between 3.1 10 ⁶ K ¹ and 7.5 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987.

In an embodiment, the glass material of the glass ring can be soda-lime glass having the following composition in percent by weight (wt.-%):

Table 6

Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, Mhq2, T1O2, CuO, Ce02, Cr203, 0 - 2 wt.-% of AS2O3, Sb203, Sn02, SO3, Cl, F and/or Ce02 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total composition is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be between 5.5 10 ⁶ K ¹ and 9.8 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987.

Preferably, the soda-lime glass can have the following composition in percent by weight (wt.-%):

Table 7

Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, Mhq2, T1O2, CuO, CeC>2, Cr2C>3, 0 - 2 wt.-% of AS2O3, Sb2C>3, Sn02, SO3, Cl, F and/or CeC>2 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total composition is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be between 4.9 10 ⁶ K ¹ and 10.3 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987.

More preferably, the soda-lime glass can have the following composition in percent by weight (wt.-%):

Table 8

Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, Mhq2, T1O2, CuO, Ce02, Cr203, 0 - 2 wt.-% of AS2O3, Sb203, Sn02, SO3, Cl, F and/or Ce02 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total composition is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be between 4.9 10 ⁶ K ¹ and 10.3 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987. In an embodiment, the glass material of the glass ring can be alkali metal aluminosilicate glass having the following composition in percent by weight (wt.-%):

Table 9

Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, Mhq2, TiC>2, CuO, Ce02, 0203, 0 - 2 wt.-% of AS2O3, Sb203, SnC>2, SO3, Cl, F and/or CeC>2 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total composition is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be between 3.3 10 ⁶ K ¹ and 10.0 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987.

Preferably, the alkali metal aluminosilicate glass can have the following composition in percent by weight (wt.-%):

Table 10

Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, Mhq2, T1O2, CuO, Ce02, Cr203, 0 - 2 wt.-% of AS2O3, Sb203, Sn02, SO3, Cl, F and/or Ce02 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total com position is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be be tween 3.9 10 ⁶ K ¹ and 10.3 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987.

More preferably, the alkali metal aluminosilicate glass can have the following composition in percent by weight (wt.-%):

Table 11 Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, Mhq2, TiC>2, CuO, Ce02, 0203, 0 - 2 wt.-% of AS2O3, Sb203, Sn02, SO3, Cl, F and/or CeC>2 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total composition is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be between 4.5 10 ⁶ K ¹ and 9.1 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987.

In an embodiment, the glass material of the glass ring can be aluminosilicate glass with a low alkali content having the following composition in percent by weight (wt.-%):

Table 12

Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, MnC>2, T1O2, CuO, CeC>2, Cr203, 0 - 2 wt.-% of AS2O3, Sb203, SnC>2, SO3, Cl, F and/or CeC>2 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total composition is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be between 2.8 10 ⁶ K ¹ and 6.5 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987. Preferably, the aluminosilicate glass with a low alkali content can have the following composition in percent by weight (wt.-%):

Table 13

Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, Mhq2, TiC>2, CuO, Ce02, 0203, 0 - 2 wt.-% of AS2O3, Sb203, SnC>2, SO3, Cl, F and/or Ce02 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total composition is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be between 2.8 10 ⁶ K ¹ and 6.5 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987.

More preferably, the aluminosilicate glass with a low alkali content can have the following composition in percent by weight (wt.-%):

Table 14

Optionally, coloring oxides can be added, such as Nd ₂ 0 ₃ , Fe ₂ 0 ₃ , CoO, NiO, V2O5, Mhq2, TiC>2, CuO, Ce02, Cr203, 0 - 2 wt.-% of AS2O3, Sb203, Sn02, SO3, Cl, F and/or Ce02 can be added as refining agents, and/or 0 - 5 wt.-% of rare earth oxides can be added to introduce magnetic, photon or optical functions into the glass material (glass ring). The total amount of the total composition is 100 wt.-%.

The coefficient of thermal expansion of a glass ring comprising this glass material can be between 2.8 10 ⁶ K ¹ and 6.5 10 ⁶ K ¹ . The coefficient of thermal expansion can describe the mean linear coefficient of thermal expansion in a temperature range from 20 °C to 300 °C. It can be determined according to DIN ISO 7991:1987.

The glass ring can comprise glass material with a PbO content of less than 1000 ppm.

The glass ring can be thermally or chemically toughened.

A chemical toughening under ion exchange can be carried out, for example, by immersion of the outer glass ring in a potassium-based molten salt. An aqueous potassium silicate solution, paste or dispersion can also be used, or ion exchange can be performed by vapor deposition or temperature-activated diffusion. Chemical toughening is characterized i.a. by the parameters compressive stress and penetration depth:

“Compressive stress” (CS) or “surface stress” can be understood as the stress resulting from the displacement effect on the glass network by the glass surface after an ion exchange, while no deformation occurs in the glass.

The "penetration depth" or "depth of ion exchanged layer" or “depth pf layer” or "depth of ion exchanged layer" can be understood as the thickness of the glass surface layer where ion exchange occurs and compressive stress is generated. The compressive stress CS and the penetration depth (DoL) can each be measured, for example, by the commercially available FSM6000 stress meter, based on optical principles.

Ion exchange therefore means that the glass is hardened or chemically toughened by ion exchange processes, a process that is well known to the skilled person in the field of glass refinement or processing. The typical salt used for chemical toughening is for example K ⁺ -containing molten salt or mixtures of salts. Commonly used salts include KNO3, KCI, K2SO4 or K2S12O5; additives such as NaOH, KOH and other sodium or potassium salts are also used to control the rate of ion exchange for chemical toughening.

In an embodiment, the glass ring can have a depth of layer (DoL) of a toughened layer between 10 pm and 100 pm, preferably between 25 pm and 75 pm, more preferably of about 50 pm. The compressive stress can be at least 100 MPa, preferably at least 200 MPa, preferably at least 300 MPa. The compressive stress can be below 1500 MPa, for example below 1000 MPa. The toughening can substantially increase the mechanical resistance of the outer glass ring.

Chemical tempering can be performed in particular by ion exchange of sodium ions by potassium ions or of lithium ions by sodium and/or potassium ions. The ion exchange can take place by treating the material with an appropriate salt at an elevated temperature, for example at 350 °C to 550 °C, e.g. from 400 °C to 480°C. Suitable salts can include nitrates and halides of the ions concerned, e.g. KNO3, KCI, NaNCh, NaCI and mixtures thereof. The duration of the treatment depends on the desired layer depth. The duration of the treatment can be at least 2 hours, at least 4 hours or at least 5 hours. Optionally, the duration is limited to a maximum of 16 hours, a maximum of 12 hours or a maximum of 8 hours.

In an embodiment, the polymer ring can comprise at least one polymer selected from the group consisting of polystyrene (PS), styrene-acrylonitrile copolymer, polyethylene terephthalate (PET), ethylene glycol modified polyethylene terephthalate (PETG), polyethylene-vinyl acetate (EVA), polycarbonate (PC), polyimide (PI), polyvinyl chloride (PVC), polyvinyl butyral (PVB), thermoplastic polyurethanes (TPU), polymethyl methacrylate (PMMA), polyethylene (PE), silicone polymer, sol-gel polymer, polyethersulphone, polyacrylate, inorganic silica/polymer hybrid, cycloolefin copolymer, polyolefin, a silicone resin, polypropylene, polypropylenepolyvinyl chloride, ethylene-vinyl acetate copolymer, polybutylene terephthalate, polyamide (PA), polyacetal, polyphenyleneoxide, polyphenylenesulfide, fluorinated polymer, a chlorinated polymer, eth- ylene-tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF), polyethylene naphthalate (PEN), terpolymer made of tetrafluroethylene, terpolymer made of hexafluoropropylene, terpolymer made of vinylidene fluoride (THV) or polyurethane, and mixtures thereof. The hybrid ring can be provided with one or more additional polymer ring/s and/or one or more additional glass ring/s. The additional ring/s can be arranged outside of and surrounding the outer ring and/or can be arranged inside of and surrounded by the inner ring. Preferably, the ad ditional glass ring/s can comprise thin glass.

According to another aspect, the present invention provides a method for manufacturing a hy brid ring, in particular a hybrid ring of the type described above. The method comprises the steps of providing an outer ring; arranging an inner ring coaxially inside the outer ring; and connecting the inner ring with the outer ring, wherein one of the outer ring and the inner ring is a glass ring and the other one of the outer ring and the inner ring is a polymer ring.

The hybrid ring has an average transmittance of less than 10 %, preferably less than 5 %, more preferably less than 1 % for visible light, i.e. for light with a wavelength between 400 nm and 700 nm. The hybrid ring has an average transmittance of 90 % or more at least for light with a working wavelength of typically 905 nm, 940 nm and/or 1550 nm, preferably at least for light with a working wavelength in the near infrared spectrum (NIR), i.e. between 780 nm and 3 pm. The hybrid ring can have an average transmittance of preferably 95 % or more, more preferably 98 % or more, at least for light with a working wavelength of typically 905 nm, 940 nm and/or 1550 nm, preferably at least for light with a working wavelength in the near infrared spectrum (NIR), i.e. between 780 nm and 3 pm. The low transmittance of visible light ensures that compo nents inside the hybrid ring cannot be viewed from the outside, which allows for a clean appear ance of the LiDAR system. Further, the low transmittance of visible light ensures that the elec tromechanical components and the detection as such are not negatively influenced by light not being in the range of the working wavelength/s. The high transmittance of light with a working wavelength ensures that light with the working wavelength/s is reliably and sufficiently emitted towards the object to be detected and reflected back through the hybrid ring to a detector inside the hybrid ring.

The specified transmittance of the hybrid ring can be achieved by means of the glass ring and/or by means of the polymer ring.

In an embodiment, the step of connecting the inner ring with the outer ring can comprise gluing the outer circumferential surface of the inner ring to the inner circumferential surface of the outer ring by an adhesive. More precisely, after arranging the inner ring coaxially inside the outer ring, fixing both rings relative to each other and closing one end of a gap formed between the outer ring and the inner ring, the adhesive can be dispensed into the gap. Dispensing the adhesive can be carried out quickly and evenly. After dispensing the adhesive into the gap, the adhesive can be cured, e.g. by means of visible light, UV-light and/or heat.

The step of connecting the inner ring with the outer ring can comprise press-fitting the inner ring into the outer ring, either with or without an adhesive layer and/or a filling layer between the outer ring and the inner ring.

Press-fitting the inner ring into the outer ring can comprise cooling the polymer ring to a cooling temperature before arranging the inner ring coaxially inside the outer ring. This applies in partic ular for a hybrid ring embodiment, in which the glass ring is the outer ring and the polymer ring is the inner ring. The glass ring can maintain non-cooled during the press-fitting step. The cool ing temperature can be between -60 °C and -20 °C, preferably between -50 °C and -30 °C, more preferably between -45 °C and -35°C, still more preferably about -40 °C. By cooling the polymer ring, it contracts due to its relatively large coefficient of thermal expansion. Press-fitting the inner ring into the outer ring can further comprise heating the polymer ring at least to room temperature, i.e. a temperature between 18 °C and 24 °C, after arrangement of the inner ring coaxially inside the outer ring. By heating the polymer ring, it expands due to its relatively large coefficient of thermal expansion. In case the press-fitting is carried out with an adhesive layer and/or a filling layer between the outer ring and the inner ring, respective filling material or the adhesive is provided between the outer circumferential surface of the inner ring and the inner circumferential surface of the outer ring at least before heating the polymer ring. Additional filling material and/or adhesive can avoid miniature gaps and moisture intrusion.

In an alternative method, in particular in a method for manufacturing a hybrid ring embodiment, in which the glass ring is the inner ring and the polymer ring is the outer ring, the press-fitting can comprise heating the polymer ring to an elevated temperature above room temperature be fore arranging the inner ring coaxially inside the outer ring. The glass ring can maintain non- heated during the press-fitting step. By heating the polymer ring, it expands due to its relatively large coefficient of thermal expansion. Press-fitting the inner ring into the outer ring can further comprise cooling the polymer ring at least to room temperature, i.e. a temperature between 18 °C and 24 °C, after arrangement of the inner ring coaxially inside the outer ring. By cooling the polymer ring, it contracts due to its relatively large coefficient of thermal expansion. In case the press-fitting is carried out with an adhesive layer and/or a filling layer between the outer ring and the inner ring, respective filling material or the adhesive is provided between the outer circum ferential surface of the inner ring and the inner circumferential surface of the outer ring at least before cooling the polymer ring. Additional filling material and/or adhesive can avoid miniature gaps and moisture intrusion.

The step of connecting the inner ring with the outer ring can comprise injection molding the pol ymer ring directly to the glass ring by providing the glass ring as a mold (part of a mold) or in side a mold. More precisely, in this embodiment, a polymer melt for forming the inner or outer ring is injected directly to the glass ring where it cools and hardens.

By means of the described embodiments of the method, the hybrid ring can be easily and cost- effectively assembled. Further, the press-fitting, gluing and/or injection does not involve any use of hazardous gases.

Another aspect relates to use of a hybrid ring according to the type described above for optical systems, in particular for LiDAR-systems.

The hybrid ring according to the present invention combines both advantageous from glass rings and polymer rings. The hybrid ring can thus have a smooth surface, i.e. minimal rough ness. Further, the hybrid ring has low hazard of delamination due to the hybrid ring’s inherent stiffness and environmental stability. Moreover, the hybrid ring has a good optical performance. As there is no gap between the outer glass ring and the inner polymer ring, the contamination risk is minimized.

Even though some of the features, functions, embodiments, technical effects and advantages have been described with regard to the hybrid ring or the method for manufacturing a hybrid ring, it will be understood that these features, functions, embodiments, technical effects and ad vantages can also apply accordingly to the method for manufacturing a hybrid ring and/or the hybrid ring. Particularly, all preferred embodiments for the hybrid ring apply also for the method of manufacturing the hybrid ring and the other way around unless specified otherwise.

Brief description of the drawings

For a better understanding of embodiments of the invention and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings in which like numerals designate corresponding elements or sections throughout.

In the accompanying drawings: Fig. 1 shows a schematic perspective view of a hybrid ring according to an embodiment of the invention.

Fig. 2 shows a schematic perspective view of an outer glass ring of the hybrid ring of Fig. 1. Fig. 3 shows a schematic perspective view of an inner polymer ring of the hybrid ring of Fig. 1. Fig. 4 shows a schematic top view of the hybrid ring of Fig. 1.

Fig. 5 shows a schematic top view of a hybrid ring according to another embodiment of the in vention.

Detailed description of the drawings

Various examples of embodiments of the present invention will be explained in more detail by virtue of the following embodiments illustrated in the figures and/or described below.

Figure 1 shows a perspective view of a hybrid ring 10 according to an embodiment of the inven tion. The hybrid ring 10 comprises an outer ring 12 which is a glass ring, i.e. an outer glass ring 12, and an inner ring 14 which is a polymer ring, i.e. an inner polymer ring 14. The outer glass ring 12 and the inner polymer ring 14 are firmly attached and are arranged coaxially to each other. In the shown embodiment, the outer glass ring 12 and the inner polymer ring 14 are in di rect contact with each other. The outer glass ring 12 and the inner polymer ring 14 are firmly at tached by means of press-fitting.

As can be seen in Figure 1, the axial extension of the outer glass ring 12 exceeds the axial ex tension of the inner polymer ring 14 and the lateral extension of the outer glass ring 12 exceeds the lateral extension of the inner polymer ring 14. The outer glass ring 12 has an axial extension of 45 mm. The inner polymer ring 14 has an axial extension of 42 mm. The outer glass ring 12 has an outer radius of 50 mm. The inner polymer ring 14 has an outer radius of 48 mm in an as sembled state at room temperature. The inner polymer ring 14 is press-fitted into the outer glass ring 12. Thus, the inner polymer ring 14 would have an outer radius of slightly more than 48 mm is an unassembled state.

Figure 1 is only a schematic drawing that does not show any thicknesses of the hybrid ring 10 components, i.e. of the outer glass ring 12 and the inner polymer ring 14. A schematic view of the hybrid ring 10 that shows the thicknesses of the outer glass ring 12 and the inner polymer ring 14 is provided in Figure 4. In the shown embodiment, the thickness of the outer glass ring 12 is 2 mm and the thickness of the inner polymer ring 14 is 1.5 mm. Thus, the hybrid ring 10 has a total thickness of 3.5 mm.

The outer glass ring 12, which is shown separately in Figure 2, comprises borosilicate glass.

The outer glass ring 12 has a coefficient of thermal expansion of 3.3 10 ⁶ K ¹ at least at 20 °C and has a refractive index of 1.46 for light with a wavelength of 905 nm, 940 nm and 1550 nm (working wavelength). The outer glass ring 12 is substantially transparent for visible light and for light in the near infrared spectrum (NIR).

The inner polymer ring 14, which is shown separately in Figure 3, comprises PC. The inner pol ymer ring 14 has a coefficient of thermal expansion of 65 10 ⁶ K ¹ at least at 20 °C and has a refractive index of 1.58 for light with a wavelength of 905 nm, 940 nm and 1550 nm (working wavelength). The inner polymer ring 14 is substantially transparent for light in the near infrared spectrum (NIR), in particular for light with the working wavelengths of 905 nm, 940 nm and 1550 nm, but has an average transmittance of less than 5 % for visible light, i.e. for light with a wave length between 400 nm and 700 nm. The inner polymer ring 14 has been colored black by pig ments in the bulk in order to absorb visible light and achieve the described low average trans mittance (i.e. opaqueness). Thus, no bulk coloring or other coloring of glass is necessary, which simplifies the manufacturing process of the hybrid ring.

By means of the individual characteristics of the connected inner polymer ring 14 and outer glass ring 12, the hybrid ring 10 has advantageous mechanical and optical characteristics. In particular, the hybrid ring 10 is scratch resistant towards the outside, is resistant and durable against other external and circumferential influences and can provide a hermetic seal between the optoelectronic components of the LiDAR system and the environment.

Further, the hybrid ring 10 blocks visible light but allows a substantially loss-free pass through of light of the working wavelengths and thus enables an optimal detection and function of a LiDAR system in which the hybrid ring is installed. The hybrid ring 10 has a difference between the re fractive index of the inner polymer ring and the refractive index of the outer glass ring of only about 0.12. The hybrid ring further has a ratio between the coefficient of thermal expansion of the outer glass ring 12 and the coefficient of thermal expansion of the inner polymer ring 14 (CTEgiass/CTEpoiymer) of only 0.05 (set in relation at a temperature of 20 °C), which makes the hy brid ring 10 particularly suitable for a stable and reliable use in a wide temperature range and thus for use in LiDAR systems. Figure 5 shows a schematic top view of a hybrid ring 20 according to another embodiment of the invention. Similar to hybrid ring 10 of Figures 1 to 4, hybrid ring 20 of Figure 5 also com prises an outer glass ring 22 and an inner polymer ring 24. However, different from the embodi ment of Figures 1 to 4, the hybrid ring 20 comprises an additional adhesive layer 26 arranged between the outer glass ring 22 and the inner polymer ring 24. Thus, in the embodiment of Fig ure 5, the outer glass ring 22 and the inner polymer ring 24 are indirectly connected to each other by the adhesive layer 26. In alternative embodiments, the adhesive layer 26 could also be or additionally comprise a filling layer.

The axial extension of the outer glass ring 22 exceeds the axial extension of the inner polymer ring 24 and the lateral extension of the outer glass ring 22 exceeds the lateral extension of the inner polymer ring 24 and of the adhesive layer 26, wherein the lateral extension of the adhe sive layer exceeds the lateral extension of the inner polymer ring 24. The axial extension of the adhesive layer 26 is equal to the axial extension of the inner polymer layer 24 in the present embodiment. The outer glass ring 22 has an axial extension of 45 mm. The inner polymer ring 24 and the adhesive layer 26 have an axial extension of 42 mm. The outer glass ring 22 has an outer radius of 50 mm. The inner polymer ring 24 has an outer radius of 47.5 mm in an assem bled state at room temperature. The adhesive layer 26 has an outer radius of 48 mm and an in ner radius of 47.5 mm in an assembled state at room temperature. The thickness of the outer glass ring 22 is 2 mm, the thickness of the adhesive layer 26 is 0.5 mm and the thickness of the inner polymer ring 24 is 1.5 mm. Thus, the hybrid ring 20 has a total thickness of 4 mm.

The outer glass ring 22 comprises borosilicate glass. The outer glass ring 22 has a coefficient of thermal expansion of 3.3 10 ⁶ K ¹ at least at 20 °C and has a refractive index of 1.46 for light with a wavelength of 905 nm, 940 nm and 1550 nm (working wavelength). The outer glass ring 22 is substantially transparent for visible light and for light in the near infrared spectrum (NIR).

The inner polymer ring 24 comprises PC. The inner polymer ring 24 has a coefficient of thermal expansion of 65 10 ⁶ K ¹ at least at 20 °C and has a refractive index of 1.58 for light with a wavelength of 905 nm, 940 nm and 1550 nm (working wavelength). The inner polymer ring 24 is substantially transparent for light in the near infrared spectrum (NIR), in particular for light with the working wavelengths of 905 nm, 940 nm and 1550 nm, but has an average transmittance of less than 5 % for visible light, i.e. for light with a wavelength between 400 nm and 700 nm. The inner polymer ring 24 has been colored black by pigments in the bulk in order to absorb visible light and achieve the described low average transmittance (i.e. opaqueness). The adhesive layer 26 comprises an acrylate adhesive. The adhesive layer 26 has a coefficient of thermal expansion of 250 10 ⁶ K ¹ and has a refractive index of 1.524 for light with a wave length of 905 nm, 940 nm and 1550 nm (working wavelength). The adhesive layer 26 is sub stantially transparent for visible light and for light in the near infrared spectrum (NIR).

By means of the individual characteristics of the connected inner polymer ring 24, the adhesive layer 26 and the outer glass ring 22, the hybrid ring 20 has advantageous mechanical and opti cal characteristics. In particular, the hybrid ring 20 is scratch resistant towards the outside, is re sistant against other external and circumferential influences and can provide a hermetic seal be tween the optoelectronic components of the LiDAR system and the environment. Further, the hybrid ring 20 blocks visible light but allows a substantially loss-free pass through of light of the working wavelengths and thus enables an optimal detection and function of a LiDAR system in which the hybrid ring is installed. In the hybrid ring 20, the following condition applies:

0.044 wherein n _giaS s is the refractive index of the outer glass ring, ni _ay er is the refractive index of the ad hesive layer and/or the filling layer, and n _p0iymer is the refractive index of the inner polymer ring. By means of these ratios, the hybrid ring 20 has optimal optical characteristics, i.e. has a mini mal reflection at the interfaces between the outer glass ring 22 and the adhesive layer 26 and between the adhesive layer 26 and the inner polymer ring 24.

The hybrid ring 20 further has a ratio between the coefficient of thermal expansion of the outer glass ring 22 and the coefficient of thermal expansion inner polymer ring 24 (CTEgi _aS s/CTEpoiymer) of only 0.05 (set in relation at a temperature of 20 °C), which makes the hybrid ring 20 particu larly suitable for stable and reliable use in a wide temperature range and thus for use in LiDAR systems. The adhesive layer 26 has an elongation at break of at least 100 % and has a shore hardness A of less than 70. Thus, the adhesive layer can sufficiently compensate for the differ ent thermal expansions of the outer glass ring 22 and the inner polymer ring 24, wherein the dif ference of thermal expansions is relatively low by means of the advantageous ratio of only 0.05 of the coefficients of thermal expansion of the glass ring and the polymer ring. List of reference signs

10 hybrid ring according to a first embodiment 12 outer glass ring of the first embodiment 14 inner polymer ring of the first embodiment 20 hybrid ring according to a second embodiment 22 outer glass ring of the second embodiment 24 inner polymer ring of the second embodiment

26 adhesive layer