Infrared image system and image guide for infrared image transfer

Abstract

The invention relates to an infrared image system (1), comprising: a lens (10) for generating an image of a motif having at least two different temperatures T1 and T2; an image guide (20) for image transfer, the image guide (20) being associated with the lens (10) at a distal end; a detector unit (40) for image capture, the detector unit (40) being associated with a proximal end of the image guide (20), wherein the ratio of the shared thermal resolution (NETD) of the image guide (20) and the detector unit (40) to the thermal resolution (NETD) of the detector unit is less than 10, preferably less than 5, particularly preferably less than 2.

Description

[0001] Infrared imaging system and image guide for infrared image transmission

[0002] Infrared imaging can be used for a variety of applications to provide information or auxiliary data that cannot be derived with the naked eye or conventional imaging devices.

[0003] In this case, it is sometimes desirable to separate the imaging device, especially the sensor, from the light-collecting lens to enable space- and application-optimized usability, especially in small and hazardous environments. Using a suitable image guide, the IR light image captured by the lens can be transmitted to the sensor over a desired distance.

[0004] Expanding the light spectrum can enable earlier prevention, performance optimization and / or risk reduction regarding material defects, for example in industrial applications.

[0005] Separating the electro-optical imaging device from the object being observed using IR-guided extensions can also enable monitoring of environments characterized by a high risk of failure and the inability of conventional IR imaging devices due to, for example, space-related, thermal, magnetic, and / or other electro-optical blockages. An extension thus enables greater positioning flexibility.

[0006] Through appropriate placement for the localization of hazard and risk areas (best-case prevention) and the identification of material effects occurring there through a broader wavelength spectrum, the use of IR image guides achieves dedicated local risk minimization and better performance in terms of damage prevention and reduction of the service life of electro-optical imaging devices. This applies particularly to small and hazardous environments, e.g., in industry and aviation. Further application areas for infrared imaging can include, for example, preventive maintenance of casings and insulation in confined and / or difficult-to-access environments, engine and power room monitoring, possibly even during operation, monitoring and inspection of turbine chambers, such as blade inspection, e.g.,in terms of weight, space and avionics balance, fire protection, firefighting, spark detection, for example in industrial infrastructure, in production, e.g. in relation to material supply or exhaust lines, within chambers, furnaces or control cabinets, measurement applications and scientific applications, e.g. in the field of chemical and / or physical processes, for example under magnetic or vacuum conditions, in the field of printed circuit boards, wafers and the like. In this case, the use of IR image guides can enable suitable, e.g. unobtrusive, placement of the infrared imaging system, even around corners or obstacles, due to the spatial separation from a detector unit.

[0007] In many applications it is also possible to gain indirect insight, i.e. states or events can be recorded or observed in or from a housing or room.

[0008] In general, optical systems that can detect temperature differences between an object and its surroundings (thermal imaging technology) are sometimes desirable. The aspect of an image transmission element (image guide) comes into play when direct illumination or direct observation, for example, via an IR camera, is not possible or not preferred, or in other words, when remote imaging is required, for example, in challenging environments or hard-to-reach places, assemblies, or similar areas, e.g., around a corner, through small openings, or between assemblies, etc. This is sometimes also the case in medical fields for imaging into, from, or inside a body.

[0009] An image guide can enable remote imaging, with the distal end kept away from the detector.

[0010] IR cameras and IR detector image chips are generally not comparable to those in the visible range. The pixel size is often larger due to adaptation to the wavelength range to be detected, and consequently the resolution is usually rather low. The development of highly sensitive and higher-resolution sensors and detectors has therefore been of increasing interest for some time, partly with regard to relatively specific applications. In contrast, further developments for image transmission elements in this context have so far received less attention. In particular, image guides that are better tailored to the respective system would be desirable. It should also be considered that in the IR range, many bodies can themselves function as IR transmitters and thus overlay a target signal.

[0011] It is therefore an object of the invention to provide a system for IR remote imaging that enables, above all, a spatial separation of the lens and sensor from the object to be observed by means of an image guide, wherein the components of the system, in particular the lens, image guide, sensor, and / or other optical components, are coordinated with one another. One aspect of the object of the invention is to increase image quality and optimize IR systems for practical application, while optimally utilizing and maintaining the performance of the downstream components, in particular the IR camera or the IR chip.

[0012] The invention relates to an infrared imaging system comprising a lens for image generation of one or more objects or motifs, an image guide for image transmission, wherein the image guide is assigned to the lens at a distal end, and a detector unit for image acquisition, wherein the detector unit is assigned or assignable to a proximal end of the image guide. The motif has, in particular, at least two different temperatures T1 and T2, e.g., T2 = 10°C to 25°C as a background or subsurface and T1 > T2 as an object in front of the background or subsurface.

[0013] Particularly preferably, the ratio of the joint thermal resolution (NETDB - NETD: Noise Equivalent Temperature Difference) of the image guide and the detector unit to the thermal resolution (NETDD) of the detector unit is less than 10, preferably less than 5, particularly preferably less than 2.

[0014] Furthermore, the ratio of the combined thermal resolution of the image guide and the detector unit to the thermal resolution of the detector unit is preferably greater than 1.00, particularly preferably greater than 1.05, and even more preferably greater than 1.1. Thus, for example, a value in the range from 1.01 to 10 or also a value in the range from 1.05 to 5 can be provided for said ratio.

[0015] The detector unit preferably comprises an IR-sensitive sensor and, if appropriate, one or more additional optical components, e.g., a dedicated optics system and / or a housing. The NETD value preferably refers to the entire detector unit. However, it should not be ruled out that the NETD value also refers to the sensor alone, as in the case of a detector unit consisting of only one sensor.

[0016] Alternatively or in addition to the above-mentioned ratio, it can be provided that the detector unit has a thermal resolution (NETD) that is less than 300 mK, preferably less than 200 mK, particularly preferably less than 100 mK, and even more preferably less than 50 mK. Alternatively or additionally, the image guide and the detector unit can also have a common thermal resolution (NETD) that is less than 400 mK, preferably less than 300 mK, and particularly preferably less than 200 mK.

[0017] The aforementioned properties advantageously enable better coordination of the image guide with the other components of the infrared imaging system, e.g., the detector unit. This allows for better coordination of the image guide with the infrared imaging system, and vice versa.

[0018] Advantageously, it can be provided or achieved that NETD (Noise Equivalent Temperature Difference) and / or MRTD (Minimum Resolvable Temperature Difference) of the detector is not significantly restricted.

[0019] A formula for determining the NETD value is given below. In certain cases, this can be used as a basis for the combined thermal resolution (NETD) of the image guide and detector unit. Below, some additional properties related to the detector unit are listed, which can also be used to determine a minimum resolvable temperature difference (MRTD) of the detector unit.

[0020] For example, it can be provided that the detector unit has a defectivity of at least 10 for a wavelength in the infrared range, in particular in the range from 0.8 pm to 14 pm. 8 cm Hz 1 / 2 W' 1 preferably of at least 10 9 cm Hz 1 / 2 W' 1particularly preferably at least 10 9 cm Hz 1 / 2 W' 1 more preferably at least 10 10 cm Hz 1 / 2 W' 1 more preferably at least 10 11 cm Hz 1 / 2 W' 1 e.g. between one of the values ​​mentioned and 10 13 cm Hz 1 / 2 W' 1 in particular between one of the above values ​​and 10 12 cm Hz 1 / 2 W' 1 has

[0021] The detector unit can have a resolution of at least 20 line pairs / mm, preferably of at least 50 line pairs / mm, particularly preferably of at least 150 line pairs / mm.

[0022] The detector unit may have an area of ​​at least 0.1 square centimeters, preferably of at least 0.5 square centimeters, particularly preferably of at least 5 square centimeters.

[0023] In a further development, the infrared imaging system can further comprise an optical element arranged between the proximal end of the image guide and the detector unit. In a specific embodiment, the detector unit can also be designed as a screen, in particular an "IR-sensitive" screen, which converts wavelengths from the infrared (IR) to visible light (VIS) using wavelength-converting material or a coating of this type, and the optical element can be designed for image projection onto the screen.

[0024] The image guide of the infrared imaging system can be designed, in particular, according to the following embodiments. The invention also relates, in particular, to an image guide for image transmission from a distal end to a proximal end, comprising a plurality of structural elements, each extending from the distal end to the proximal end, wherein at least two different types of structural elements are included, namely a first type with a first refractive index n1 and a second type with a second refractive index n2.

[0025] The ratio of the refractive indices n1 / n2 between the structural elements of the first type and the structural elements of the second type can, for example, be between 0.5 and 0.999, particularly preferably between 0.6 and 0.992, and even more preferably between 0.75 and 0.992. It is also possible for n1 / n2 to be between 0.8 and 0.999.

[0026] Furthermore, it can be provided that the first refractive index of the structural elements of the first type and the second refractive index of the structural elements of the second type differ by at least 0.05, by at least 0.075, in particular by at least 0.1, in particular by at least 0.2, in particular by at least 0.3, in particular by at least 0.4.

[0027] The structural elements can, for example, form a bundle of optical fibers, wherein the fibers each comprise a core and a cladding, wherein the cladding is in each case designed as a structural element of the first type and the core is in each case designed as a structural element of the second type.

[0028] However, it can also be provided that the structural elements form a base body with a plurality of, preferably filled, cavities, wherein the base body is designed as a structural element of the first type and the, preferably filled, cavities are designed as structural elements of the second type. Such an image guide can, for example, be designed similarly to or as a photonic crystal fiber (PCF).

[0029] Preferably, at least one structural element is designed to be transmissive for a wavelength in the infrared range, in particular in the range from 0.8 pm to 14 pm. The image guide can have a resolution of at least 25 line pairs / mm, preferably a resolution of at least 30 line pairs / mm, particularly preferably a resolution of at least 40 line pairs / mm.

[0030] The image guide may have a length of at least 50 cm, preferably a length of at least 100 cm, particularly preferably a length of at least 300 cm.

[0031] The image guide can be designed as a flexible body at least in sections and / or as a rigid body at least in sections.

[0032] Preferably, at least one core, one jacket, one base body, one filled cavity and / or one structural element comprises a material which has an attenuation of less than 50 dB / m, in particular less than 10 dB / m, in particular less than 1 dB / m, for a wavelength in the infrared range, in particular in the sensitivity or detection range of the detector unit or the emission range of a body or motif to be observed, and in particular in the range from 0.8 pm to 14 pm.

[0033] With regard to crosstalk, it can be provided that between the cores of the fibers and / or the structural elements of the second type, for a wavelength in the infrared range, in particular in the range from 0.8 pm to 14 pm, in particular in the range from 5 pm to 8 pm, a crosstalk (X-talk) of less than 0.4 occurs, preferably of less than 0.3 occurs, particularly preferably of less than 0.2 occurs, or of less than 0.1 occurs, or of less than 0.05 occurs.

[0034] The image guide preferably has a plurality of structural elements. The number of fibers and / or structural elements of the second type per mm 2The cross-sectional area of ​​the image guide can be at least 100, preferably at least 1000, particularly preferably at least 10000. The cores of the fibers and / or the structural elements of the second type can have a diameter between 5 pm and 200 pm, preferably between 5 pm and 100 pm, particularly preferably between 10 pm and 50 pm.

[0035] The sheaths of the fibers and / or the structural elements of the first type can have a diameter between 6 pm and 250 pm, preferably between 6 pm and 150 pm, particularly preferably between 10 pm and 70 pm.

[0036] The ratio of core to cladding diameters can be between 0.5 and 0.95.

[0037] The smallest distance between the centers of two cores and / or two structural elements of the second type may be less than 50 pm, preferably less than 20 pm, particularly preferably less than 15 pm.

[0038] Alternatively or additionally, the average distance between the centers of the cores and / or the structural elements of the second type may be less than 50 pm, preferably less than 20 pm, particularly preferably less than 15 pm.

[0039] A core, a cladding, a base body, a filled cavity, and / or a structural element can generally comprise or consist of glass. It is also possible for a core, a cladding, a base body, a filled cavity, and / or a structural element to comprise or consist of quartz.

[0040] A core, a shell, a base body, a filled cavity and / or a structural element can comprise a chalcogenide, in particular comprising at least one element from the group oxygen, sulfur, selenium and tellurium, and at least one element from the group arsenic, germanium, phosphorus, antimony, lead, boron, aluminum, gallium, indium, titanium, sodium.

[0041] Multicomponent glasses can also be used for the core, cladding, or base body, as can quartz glass, especially doped quartz glass. This is important insofar as they are compatible with each other and / or with chalcogenides or GLS materials, particularly with regard to chemical and / or thermomechanical properties, e.g., with regard to thermal expansion coefficient and / or their viscosity curve over temperature. This means, for example, that they can be processed or machined, particularly in thermal processes, so that, in particular, a waveguide can be produced using conventional methods for manufacturing fiber optic components.

[0042] GLS stands for a gallium lanthanum sulfide glass, whereby a core, a cladding, a base body, a filled cavity and / or a structural element can comprise such a gallium lanthanum sulfide glass (GLS).

[0043] The image guide preferably has a transmission of at least 30%, preferably of at least 50%, and particularly preferably of at least 60%, for a wavelength in the infrared range, in particular in the range from 0.8 pm to 14 pm. Furthermore, the image guide can have a transmission of at least 30%, preferably of at least 50%, and particularly preferably of at least 60%, for a wavelength in the range from 5 pm to 8 pm.

[0044] In a further advantageous embodiment, image guides with higher resolution can be provided based on the wave phenomenon of transverse Anderson localization (TAL). This takes advantage of the fact that a random distribution of refractive indices across the cross-section of the image guide, with simultaneous invariance of the refractive indices along the length of the image guide, leads to a limitation of the coupled-in light in the cross-section due to destructive interference. In practice, for example, a large number of individual glass fibers with different refractive indices can be combined to form a random fiber bundle. If a light beam is coupled into such a waveguide, it propagates along the length of the image guide with a transverse extension limited in the cross-section.

[0045] In a further embodiment, such image guides particularly advantageously comprise at least two different types of structural elements, namely a first type with a first refractive index and a second type with a second refractive index. The comprised plurality of structural elements can therefore comprise at least one structural element of the first type and one or more structural elements of the second type, or conversely one or more structural elements of the first type and one structural element of the second type, or even comprise both a plurality of structural elements of the first type and a plurality of structural elements of the second type. Of course, more than two different types, e.g. three different types of structural elements, can also be comprised.The structural elements each extend along the transport direction of the electromagnetic radiation through the image guide and proportionally across the cross-section of the waveguide, such that a plurality of cross-sectional regions is defined in the cross-section of the waveguide, each corresponding to the cross-section of an individual structural element. The structural elements therefore run next to one another, in particular parallel to one another, along the transport direction of the waveguide or image guide, and their cross-sections each occupy a planar portion of the cross-section of the waveguide and therefore each define a cross-sectional region of the cross-section of the waveguide. The cross-sectional regions therefore correspond in particular to the surface areas formed by the structural elements when looking at a cross-sectional area of ​​the waveguide, for example the light entry or exit area.

[0046] An image guide can therefore comprise a plurality of structural elements of the first type and a plurality of structural elements of the second type, wherein the structural elements of the first type are designed as bodies, in particular rod-shaped or tubular, with or made of a first medium, wherein the first medium has the first refractive index, and wherein the structural elements of the second type are designed as bodies, in particular rod-shaped or tubular, with or made of a second medium, wherein the second medium has the second refractive index, or wherein the structural elements of the second type are designed as cavities in the structural elements of the first type, wherein the cavities preferably form the second refractive index or are filled with a second medium, wherein the second medium has the second refractive index.

[0047] An image guide can therefore further define a longitudinal direction and a cross-section extending transversely to the longitudinal direction, wherein the structural elements extend over the cross-section of the image guide in such a way that a plurality of cross-sectional regions is defined in the cross-section of the image guide, each corresponding to the cross-section of an individual structural element, and / or wherein the structural elements, in particular their cross-sectional regions, are arranged unevenly to effect transverse Anderson localization transversely to the longitudinal direction. The uneven arrangement of the structural elements, in particular their cross-sectional regions, can in particular be random and / or uneven but determined by a predetermined rule, wherein the uneven arrangement is preferably formed:

[0048] (a) as a periodic positioning of structural elements, in particular their cross-sectional regions, wherein the periodically positioned structural elements have a variation among themselves which is random and / or irregular but clearly determined by a predetermined rule, wherein the variation of the periodically positioned structural elements among themselves is preferably formed as a variation of the type of structural elements, the refractive index of the structural elements and / or the geometry, e.g. the shape, the diameter and / or the substructure, of the structural elements,

[0049] (b) as an aperiodic positioning of structural elements, in particular their cross-sectional regions, wherein the aperiodic positions of the structural elements are random and / or uneven but clearly defined by a predetermined rule, wherein optionally the structural elements also have a variation among themselves which is random and / or uneven but clearly defined by a predetermined rule, and / or (c) as a positioning of structural elements, in particular their cross-sectional regions, on periodic positions, wherein some of the periodic positions are occupied and some of the periodic positions are unoccupied and the occupancy is random and / or uneven but clearly defined by a predetermined rule, wherein optionally the structural elements also have a variation among themselves which is random and / or uneven but clearly defined by a predetermined rule,is trained.,

[0050] According to a further development, the structural elements, in particular their cross-sectional regions, can be formed non-uniformly, but clearly defined by a predetermined rule. The structural elements therefore have an irregularity in relation to one another, i.e. they are formed non-uniformly, for example they are arranged non-uniformly, shaped non-uniformly and / or have an uneven nature. The non-uniformity is not located in the individual structural elements themselves, but in the structural elements as a whole, and there is therefore in particular a physical disorder, i.e. a deviation from one or more symmetry. On the other hand, the non-uniformly formed structural elements are formed in a predetermined manner, i.e. they are not formed randomly.The property that the structural elements exhibit irregularity or disorder with respect to one another is thus contrasted by a regularity, in particular in the sense that the irregularity or disorder follows a defined rule and not randomly. In particular, the irregularity or disorder is therefore clearly predetermined or specified by a rule or is characterized or characterizable by a rule. The irregularity of the structural elements, in particular of their cross-sectional regions, can be expressed in various ways. For example, the cross-sectional regions of the structural elements can have an irregular, in particular aperiodic, arrangement which is clearly defined by the predetermined rule. For example, the cross-sectional regions can be arranged deviating from a periodic lattice.However, the cross-sectional regions can also be distributed non-uniformly on a periodic lattice, for example. Alternatively or additionally, the cross-sectional regions of the structural elements can have non-uniform, in particular deviating, geometries, for example, non-uniform diameters, which are clearly defined by the predetermined rule. However, the geometries of the cross-sectional regions can also be similar but rotated relative to one another, particularly in the case of cross-sectional regions that have a non-circular shape. Furthermore, the structural elements can alternatively or additionally have non-uniform, in particular deviating, refractive indices, which are clearly defined by the predetermined rule.Such image guides enable resolutions that are even higher than the aforementioned resolutions of image guides based on the principle of waveguiding by total internal reflection. Furthermore, the characteristics regarding materials and mechanical construction, such as number, areas, and geometries, as well as manufacturing methods, are essentially also applied or applicable to such waveguides or image guides based on the wave phenomenon of transverse Anderson localization (TAL).

[0051] Embodiments of the invention are described in more detail below with reference to the figures.

[0052] Fig. 1 shows an infrared imaging system with a lens, an image guide and a detector unit,

[0053] Fig. 2 schematically shows an image guide designed as a fiber bundle with a plurality of first and second structural elements.

[0054] Fig. 3 schematic perspective views of two image guides with (a) two types of structural elements whose cross-sectional areas are arranged unevenly distributed on a grating and (b) a plurality of structural elements of uneven refractive indices (multiplicity of types) and / or uneven geometries (diameter),

[0055] Fig. 4 schematic illustration of various possibilities for image guides with unevenly arranged structural elements or their cross-sectional regions,

[0056] Fig. 5 schematic illustration of various aspects for variations among structural elements or their cross-sectional regions and possibilities for combinations of these aspects,

[0057] Fig. 6 schematic illustration of various further possibilities for waveguides with irregularly arranged structural elements or their cross-sectional regions, wherein the waveguides each comprise a structural element of a first type and a plurality of structural elements of a second type,

[0058] Fig. 1 shows an infrared imaging system 1 configured as an IR observation system, which has at least one lens 10 configured as an optical element or lens system for capturing images of an object 60 at temperature T1 against a background or in an environment 70 at temperature T2. The lens is constructed with or from an infrared-transmissive material, particularly in the wavelength range of the radiation to be detected.

[0059] Furthermore, the infrared imaging system 1 comprises an infrared image guide 20 and a further optical element 30 for image transmission to / onto a detector unit 40 or for projection onto a screen. The image guide 20 can be partially or partially rigid and / or partially or partially flexible. Furthermore, the image guide 20 can also be partially or partially semi-rigid.

[0060] The ratio of the combined thermal resolution (NETD) of the image guide (20) and the detector unit (40) to the thermal resolution (NETD) of the detector unit alone is less than 3, particularly at the temperature difference AT = T1 - T2.

[0061] Fig. 2 shows an image guide 20, which is designed as a fiber optic image guide and allows, for example, image transmission in the IR wavelength range between 1 pm and 14 pm. The image guide has two different types of structural elements, namely a first type 100a with a first refractive index and a second type 100b with a second refractive index, wherein the structural elements of the first type 100a each form the cladding of a fiber and the structural elements of the second type 100b each form the core of a fiber.

[0062] The structural elements of the first type 100a can be connected to one another in a form-fitting and / or material-fitting manner, e.g. by fusing, in such a fiber-optic image guide or fiber bundle, particularly if the latter is at least partially or sectionally rigid. In this case, essentially hexagonal superstructures often form and a denser packing of the image points can be achieved. This can be advantageous, for example, in order to fix the proximal and / or distal end and to connect it to other components of the IR imaging system in sleeves or connecting means, which can also involve a spatial fixation of the image points. In the case of purely rigid image guides, these can also be bent partially or sectionally, once or multiple times, and / or have their cross-sectional geometry changed, as well as having a twist.The latter means that the proximal and distal ends are oriented relative to one another by a certain angle of rotation (twisted image guide). The cross-sectional geometry of the distal and proximal ends is preferably essentially congruent to one another, i.e., except for manufacturing-related deviations or tolerances, to enable correct imaging of the subject. However, these can have different sizes, dimensions, e.g., diameters; for example, a rigid image guide can be tapered. This can be advantageous on both the distal and proximal sides of the image guide to adapt the dimensions to the subject to be captured or the detector.

[0063] Fig. 3 shows two further examples of image guides 20. The image guides 20 in turn comprise a plurality of structural elements 100, which each extend from a first front end 2 to a second front end 4 of the image guide 20 along the transport direction 5 and are, for example, rod-shaped.

[0064] The image guide shown in Fig. 3 (a) comprises a plurality of structural elements of a first type 100a and a plurality of structural elements of a second type 100b. In this example, the cross-sectional regions of the structural elements are arranged on a periodic lattice. However, the structural elements have a non-uniform arrangement in that the structural elements of the first type 100a and the second type 100b, and thus the refractive indices, are unevenly arranged and / or distributed and / or there is a non-uniform occupancy at periodic positions. It is possible for the structural elements 100a to comprise infrared-transmissive material. It is also possible for the structural elements 100b to comprise infrared-transmissive material.Furthermore, both the structural element 100a and the structural elements 100b may comprise infrared-transmissive material, wherein preferably different infrared-transmissive materials are provided for the two types.

[0065] The image guide shown in Fig. 3 (b) again has a plurality of structural elements 100 arranged on a periodic grating, wherein in this example the cross-sectional regions of the structural elements have non-uniform geometries. The geometries can differ in particular in that the diameters of the structural elements or their cross-sectional regions differ from one another. Furthermore, the structural elements 100 can have a non-uniformity in that the refractive indices of the structural elements differ from one another. In this case, a discrete number of different refractive indices, e.g., two, three, four, etc., can be provided, but in principle also a continuous variation of the refractive index is possible. In this variant, at least some of the structural elements 100 have infrared-transmissive material. Fig. 4 uses a tree diagram to show various possibilities for implementing a non-uniform arrangement. In Fig.Figure 4a shows a structural element 100a as a starting point, which can be formed, for example, as a matrix material (it is also possible for the structural element 100a to be formed as air or to be absent). Figure 4b shows a further starting point derived therefrom, with the structural element 100a and a plurality of periodic positions P for occupying structural elements, which then have a periodic positioning. Figure 4d shows a further starting point derived from Figure 4a, with the structural element 100a and a plurality of aperiodic positions P for occupying structural elements in order to achieve aperiodic positioning. Starting from the starting points shown in Figures 4b and 4d, image guides are produced by occupying the positions P with structural elements, as described in more detail below.

[0066] Starting from Fig. 4b, Fig. 4c shows an image guide 20 with structural elements 100b, 100c whose cross-sectional regions have a periodic positioning and / or are located at periodic positions. The image guide shown in Fig. 4c has three types of structural elements 100a, 100b, 100c, each of which may have a different refractive index. For example, structural element 100a may be formed as a matrix material, and structural elements 100b and 100c may be cavities in the matrix material filled with materials of different refractive indices.

[0067] However, it is also possible that one of the materials of structural elements 100b and 100c corresponds to the matrix material of structural element 100a, or that the (filled) cavities corresponding to these structural elements are missing in the matrix material (see Fig. 6a below). It is also possible that structural element 100a is formed as air or is absent, and structural elements 100b and 100c are adjacent to one another (see Fig. 3a).

[0068] The image guide 20 shown in Fig. 4c has structural elements 100b, 100c with a periodic positioning. However, the structural elements 100b, 100c are of different types, and the allocation of the different types on the regular grid is non-uniform. In particular, the variation of the structural elements 100b, 100c among each other is thus non-uniform. Fig. 4c thus shows a case of an image guide 20 in which the structural elements or their cross-sectional regions have a non-uniform arrangement. The term "arrangement" is to be understood here to mean that the selection or allocation of the different types of structural elements 100b, 100c at the respective periodic positions is non-uniform.

[0069] It is also possible that the structural elements 100b, 100c do not differ in their refractive indices, e.g., they have the same refractive index or are made of the same material, but differ in other aspects (see Fig. 5 below). It is also possible that the structural elements 100b, 100c differ both in their refractive indices and in other aspects.

[0070] In particular, the structural element 100a may comprise infrared-transmissive material and / or the structural elements 100b and / or 100c may comprise infrared-transmissive material or another infrared-transmissive material.

[0071] Starting from Fig. 4d, Fig. 4e shows an image guide 20 with two types of structural elements, namely the structural element 100a, which can be formed, for example, as a matrix material, and a plurality of structural elements 100b, which can be formed, for example, as, in particular, filled, cavities in the matrix material. The cross-sectional regions of the structural elements 100b are positioned aperiodically in this case. The positioning of the structural elements 100b can now represent a non-uniformity. In particular, the structural elements 100b of the second type can have non-uniform positions. Fig. 4e thus shows a case of an image guide 20, wherein the structural elements or their cross-sectional regions have a non-uniform arrangement. The term arrangement is to be understood here to mean that the or some of the structural elements or their cross-sectional regions are positioned aperiodically. In the case of Fig.4e, it is particularly provided that the structural elements 100b of the second type have a uniform refractive index, have uniform geometries, and / or are uniformly configured with respect to other aspects, in particular are identically configured. In this case, one can speak of a uniform occupancy of the aperiodic positions. The structural element 100a can comprise infrared-transmissive material and / or the

[0072] Structural elements 100b Infrared transmissive material or other infrared transmissive

[0073] material.

[0074] In contrast, Fig. 4f, starting from Fig. 4d, shows an image guide 20 in which an aperiodic positioning of structural elements with simultaneously different types of structural elements 100b, 100c is provided. In this case, the irregularity of the arrangement can lie in the aperiodic positioning of the structural elements 100b, 100c or in the occupancy, i.e., the variation of the structural elements 100b, 100c among each other, or in both the positioning and the occupancy.

[0075] The structural element 100a may comprise infrared transmissive material and / or the structural elements 100b and / or 100c may comprise infrared transmissive material or another infrared transmissive material.

[0076] Fig. 5 shows various possible variations that structural elements can exhibit among themselves (middle row) as well as exemplary, non-exhaustive, possible combinations of the variations (lower targets). The variations shown can be used in particular for occupying positions with structural elements that are non-uniformly formed. Structural elements whose cross-sectional regions are located at periodic or aperiodic positions, e.g., within a matrix material, can, for example, vary among themselves with regard to their shape, their type or refractive index, their substructure, and / or their rotation (and / or local position).

[0077] For example, variations in the geometries of the structural elements, in particular their cross-sectional regions, can be formed as variations in shape (number of corners, diameter). Variations in the geometry can also be formed as variations in the substructure. A substructure can in particular consist in a structural element, in particular its cross-sectional region, having at least two different regions with different refractive indices, in particular a core and a surrounding cladding (core-cladding system). In combination, for example, a first type of structural element can have a polygonal cladding and / or a polygonal core, and a second type of structural element can have a round cladding and a polygonal core (bottom row, first column). These two types of structural elements can then serve, for example, to occupy periodic or aperiodic positions.

[0078] Furthermore, for example, a first type of structural element can have a first refractive index and a first diameter and a second type of structural element can have a second refractive index and a second diameter (bottom row, second column); or a first type of structural element can have a core-cladding system with a core having a first diameter and a second type of structural element can have a core-cladding system with a core having a second diameter (bottom row, third column); or a first type of structural element can have a core-cladding system with a core having a first refractive index and a second type of structural element can have a core-cladding system with a core having a second refractive index (bottom row, fourth column);or a first type of structural element has a first diameter and a rotation about a pivot point outside the structural element and a second type of structural element has a second diameter and a rotation about a pivot point outside the structural element (bottom row, fifth column), or a first type of structural element is a core-shell system with a centered core and a second type of structural element is a core-shell system with a core with a rotation about a pivot point outside the core (bottom row, sixth column), and the like.;

[0079] Fig. 6a shows an image guide 20 which is comparable in some aspects to the image guide from Fig. 4c. The image guide has a first structural element 100a which can be formed, for example, as a matrix material. Furthermore, the image guide has a plurality of structural elements 100b which can be formed, for example, as cavities in the matrix material. The structural elements 100b are located at periodic locations, but not all periodic locations are occupied by a structural element. Fig. 6a thus shows a case of an image guide 20 wherein the structural elements or their cross-sectional regions have a non-uniform arrangement which is clearly defined by a predetermined rule. The term arrangement is to be understood here to mean that the or some of the structural elements or their cross-sectional regions are located at periodic locations, wherein some of the periodic locations are occupied and some of the periodic locations are unoccupied.It is possible for the structural element 100a to comprise infrared-transmissive material. It is also possible for the structural elements 100b to comprise infrared-transmissive material, particularly if these structural elements are formed as filled cavities. Furthermore, both the structural element 100a and the structural elements 100b can comprise infrared-transmissive material, with different infrared-transmissive materials preferably being provided for the two types.

[0080] Fig. 6b shows an image guide which is comparable in some aspects to the image guides from Fig. 4f. The image guide has a first structural element 100a, which can be formed, for example, as a matrix material. Furthermore, the image guide has a plurality of structural elements 100b with a first diameter and a plurality of structural elements 100c with a second diameter. The structural elements are positioned aperiodically in this example. Fig. 6b thus shows a case of an image guide 20, wherein the structural elements or their cross-sectional regions have a non-uniform arrangement. The term "arrangement" is to be understood here to mean that the or some of the structural elements or their cross-sectional regions are positioned aperiodically and / or wherein the structural elements have a variation among one another which is non-uniform, wherein the variation is formed as two types of structural elements, e.g.with different diameters. It is possible for the structural element 100a to comprise infrared-transmissive material. It is also possible for the structural elements 100b and / or 100c to comprise infrared-transmissive material, particularly if these structural elements are formed as filled cavities. Furthermore, both the structural element 100a and the structural elements 100b and / or 100c can comprise infrared-transmissive material, with different infrared-transmissive materials preferably being provided for the different types.

[0081] Regardless of the specific embodiment, at least one structural element of an image guide 20 is thus transmissive for a wavelength in the infrared range, e.g., for a wavelength in the range from 1 pm to 14 pm. The image guide 20 can have an attenuation in the IR wavelength range between at least 1 pm and 14 pm of, for example, less than 3 dB / m.

[0082] For the optical element(s) and / or structural elements of the image guide, materials containing or made of heavy metal oxides or chalcogenide glasses are used. In the near IR range, glasses, such as multi-component glasses, or quartz glass may also be used. Quartz glass here refers not only to materials consisting of pure SiO2, but also to its modifications, such as fluorine-doped variants, which have a lower refractive index than the pure variant. The IR materials can include crystals or ceramics. The choice of material classes depends in particular on the temperature difference T1 - T2 and the IR wavelength range, as well as compatibility in or for a manufacturing process for at least parts of an image guide.

[0083] The invention makes it possible, in particular, to use an image guide within an IR system, thereby achieving better coordination of the image guide with an IR system and thermal imaging technology, e.g., detector units or infrared cameras. The image guide can consist of a plurality of optical fibers that are compatible with thermal imaging technology. While conventional IR cameras, in which the subject is located directly in front of the camera lens, use lenses or lens arrangements to transmit the signal from the subject to the detector, the invention can be used to capture IR images located in any position, e.g., behind a corner, inside a body or machine, within a hazardous environment, generally in or at locations, sites, or components that are difficult or unsafe to access, etc.In some cases, this can also be achieved through an obstacle that is only translucent or even opaque in the visible range (VIS), such as a housing.

[0084] The NETD value (Net Equivalent Temperature Difference) can also be defined as the temperature difference of the object or within a subject required to generate an electrical signal in or at a detector or detector unit that is at least equal to the mean square noise of the detector or its image acquisition chips and / or associated electronics. In some cases, it can be expressed using the following equation. where the variables f# (optics number or f-number), Af (electronics bandpass, noise equivalent electrical bandwidth), A (detector area), and M* refer to the specifications of the detector or optical system, including their wavelength-dependent sensitivity. In contrast, top is the percentage of transmission through the system's optics (e.g., lenses and fiber bundles). High transmission through the fiber bundle can thus contribute to a low NETD, which allows small temperature differences to be detected or still to be detected, or can be used to specify the smallest, meaningfully detectable temperature difference of the IR imaging system.

[0085] Regarding the image resolution of an optical system, one approach is to measure the modulation transfer function (MTF), which measures the value of the contrast that the system can resolve. This value is typically measured using images of black and white lines, and the contrast value is expressed in line pairs / mm. Knowing this value can also be used to determine, for example, an MRTD value.

[0086] The contrast value M of an observed scene or the captured image can be defined as follows: where Imax denotes the highest signal intensity and Imin denotes the lowest signal intensity. The MTF at a given line frequency is the ratio between the theoretical contrast (M-meoreticai) between the object and the background and the contrast observed in the image acquired with the optical system (M age): The influence of an optical fiber bundle and a detector on the MTF can sometimes be strong and can be approximately characterized using simple geometric considerations. Both detectors and fiber bundles can be characterized by a two-dimensional pattern in which the elements are spaced at a specific distance from each other, also known as the pitch, i.e., the distance from center to center. For example, if one considers a detector with a pixel pitch of 15 pm, it is generally not capable of detecting contrasts at a smaller scale or distance relative to the detector than 15 pm. The resolution R of a detector can be specified as follows:

[0087] 1000 which, in the example above, would result in a resolution of 33 ip / mm. In practice, it is desirable that the size and / or spacing of the fibers in the bundle match the detector as closely as possible to optimize system performance.

[0088] Using the MTF value at a specific line frequency or resolution (e.g. at 33 Ip / mm), an MRTD value (Minimum Resolvable Temperature Difference) can be calculated, for example, as follows:

[0089] NETD

[0090] MRTD =

[0091] MTF

[0092] In other words, based on the minimum temperature difference that a signal can generate and the system's ability to maintain contrast with a certain efficiency, a minimum temperature difference that can actually be observed in the acquired image can be calculated.

[0093] The NETD value can also be thought of as the temperature difference between background and target that results in a signal-to-noise ratio of 1, or simply put, as the minimum temperature difference that can be distinguished between the background and the target. The MRTD value, related to the NETD value, can also be thought of as the minimum temperature difference between two objects that can be observed.

[0094] It should also be noted that the NETD value can depend on parameters that are independent of the image guide. For example, atmospheric conditions and signal strength are external factors that depend on the scene, object, or motif and are not controllable. The pixel size and specific defectivity depend on the quality of the detector; the spatial resolution depends on the wavelength; the aperture size can be predetermined by the detector or by a detector unit and can determine the depth of field.

[0095] The image guide can influence the signal strength, e.g., through signal absorption in or by its material, i.e., signal attenuation in or by the image guide or the materials it contains, and / or through the pixel size, e.g., if the pixels in the fiber optic bundle differ from the position and / or size and / or geometry of the detector pixels. This is especially true if the size of the pixels in the fiber optic bundle is larger than or even equal to the size of the detector pixels. A pixel-precise arrangement.

[0096] Alignment or imaging, for example by upstream optics or optical element, of the pixels of the light guide with respect to the pixels of the detector is preferred. This means that with pixels of the same or similar size in both elements, an essentially 1:1 alignment, arrangement or coverage is aimed for, so that ideally the pixels are congruent in terms of their position or coverage to one another, for example opposite one another. Typically, the pixels of an image guide are essentially round or, if necessary, embedded in a hexagonal superstructure, are essentially round. In contrast, the pixels of a detector are often rectangular, in particular square, so that the size of a pixel of the image guide preferably corresponds to the diameter of the smallest circle, or at least is not larger, that can be inscribed in such a rectangle, or possibly even in several adjacent pixels. This corresponds, for example, to the incircle of a square pixel of the detector.

[0097] Overdetermining the number of pixels in the image guide compared to the number of pixels in the detector can be advantageous, but can also be disadvantageous if the overdetermined pixels in the image guide display significantly different information, for example in terms of contrast, so that a pixel in the detector averages this information, possibly creating blur. A similar situation can also occur if one or more pixels in the image guide reach multiple pixels in the detector, for example those which, or whose edges, are in the immediate vicinity of the pixel addressed by the pixel(s) of the image guide. The properties of the detector can vary depending on the detector and manufacturer. For example, to detect an object 100 m away, a small aperture can be selected. With a weak signal, a large aperture can improve the quality of the image because more signal reaches the detector.Adapting the image guide to other components of the system is therefore advantageous.

[0098] The transmission efficiency or the transmission of light through an image guide can be inversely proportional to the NETD or MRTD. It is therefore advantageous to use low-loss materials, i.e. materials with high transmission or low attenuation in the relevant wavelength range, for the image guide. This aspect depends, particularly for IR-transmissive materials or in the IR wavelength range, on the purity of the materials or the glasses used. In the infrared range, moisture and metal oxides in particular can be causes of signal loss or high or undesired attenuation. Impurities in the raw materials, such as unwanted metals, metal compounds and other elements, can also have a negative influence on attenuation. Oxygen can play a special role here and can also have a particularly positive effect. To minimize optical losses, the selection of raw materials from which the materials, especially glasses, are made, e.g.are melted, with a low content of impurities. For example, raw materials with a purity of 99.999% can be selected. Sometimes such raw materials are further purified. In order to maintain the purity of the raw materials or to control their changes, e.g. with regard to their oxidation states or the formation of undesirable compounds, during the melting process, glass can be further produced under specifically adjusted melting conditions, e.g. by setting a certain atmosphere during or in the melting process of, for example, multi-component glasses or quartz glass, particularly in the case of chalcogenic glasses or GLS glasses in a sealed ampoule, sometimes under vacuum or inert gas. In this way, for example,The amount of oxygen and moisture that comes into contact with the raw materials before and during the glass melting process, and also undesirable redox states of certain raw materials or compounds formed in the melt from them, can be minimized or at least controlled. Similar considerations can be applied, in addition to a suitable selection of thermal (e.g., drawing temperature) and / or mechanical (e.g., drawing speed) process parameters, to the materials or material combinations from which an image guide is to be or can be manufactured. This means that even in a drawing process for the production of corresponding optical fibers or existing fiber-optic components, such as rigid image guides made up of several image-guiding elements, the adjustment of atmospheres can be useful and necessary in order to adjust or maintain the properties of the fiber or image guide.

[0099] As described, it is advantageous if the pixel size and the spacing between the pixels of the image guide or fiber bundle and the detector are essentially the same. However, the proximity of the fibers to one another and, in particular, the spacing of the cores (pitch) in the bundle can also play a role, which can be disadvantageous, for example, if the choice of materials is not appropriate, e.g., their difference in refractive index. In particular, it can happen that the signal passing through one of the cores of the bundle is not optically well defined due to the difference in refractive index and / or diameter of the cladding compared to the cladding, i.e., ultimately the distance between neighboring cores. This can lead to signals crosstalk between two or more cores, even though there is a physical barrier between them, namely the cladding. This effect is also referred to as crosstalk (X-talk).Crosstalk between pixels of the image guide can therefore contribute to a deterioration in image transmission. Firstly, parts of the signal intended to be transmitted via a pixel are no longer contained in this pixel at the distal end and can therefore be displayed or transmitted to the detector with less intensity. Secondly, these signal components can be transmitted to neighboring pixels and overlay the signal intended to be transmitted via this pixel or the associated image guide element. This can attenuate the overall signal (image) to be transmitted and reduce its contrast and sharpness.

[0100] As mentioned previously, crosstalk can be influenced and / or minimized, for example, by choosing materials for the core and cladding with their difference in refractive index. This can be used, for example, to achieve a high packing density of the image-guiding elements or to increase the fiber density in the bundle and thus the surface area of ​​the distal end face of the fiber bundle or image guide that can be used for imaging or to at least predetermine it and / or adapt it to a detector or its pixel size and spacing. With regard to crosstalk, there are basically several ways of describing the crosstalk in a bundle of optical fibers, although the special features of thermal imaging are generally not discussed.

[0101] An image guide with the properties described above can be manufactured, for example, from a first chalcogenide glass with a refractive index n1 of approximately 2.42 as the core and a cladding made of a second chalcogenide glass that is modified compared to the first, e.g., in its composition, so that its refractive index n2, at approximately 2.39, is smaller than the refractive index n1. Larger differences in refractive index can be achieved if, for example, a multi-component glass is used as the cladding material, which has sufficient thermomechanical and / or chemical compatibility with the core glass, so that an image guide can be manufactured from it in a corresponding process, as is known from the manufacture of fiber optic components.

[0102] The selection of the initial geometries, particularly the diameter of the core rod and the cladding tube and its wall thickness, as well as the assembly of several or a large number of such core-cladding combinations into a preform, allows the further parameters of the image guide to be predetermined within relatively wide limits and, for example, to be displayed depending on the process temperature (drawing temperature) and drawing speed, and possibly the number of consecutive drawing processes, so-called multi- or multi-multi-drawing. This makes it possible to adjust the number of pixels of the image guide, their size and spacing, etc., so that they are adapted to or for a detector unit as described above.

Claims

1. Infrared imaging system comprising: a lens (10) for generating an image of a subject with at least two different temperatures T1 and T2, an image conductor (20) for image transmission, wherein the image conductor (20) is associated with the lens (10) at a distal end, a detector unit (40) for image acquisition, wherein the detector unit (40) is associated with a proximal end of the image conductor (20), wherein the ratio of the common thermal resolution (NETD) of the image conductor (20) and the detector unit (40) to the thermal resolution (NETD) of the detector unit is less than 10, preferably less than 5, and particularly preferably less than 2.

2. Infrared imaging system (1) according to the preceding claim, wherein the detector unit (40) has a thermal resolution (NETD) which is less than 300 mK, preferably less than 200 mK, particularly preferably less than 100 mK, and / or wherein the image guide (20) and the detector unit (40) have a common thermal resolution (NETD) which is less than 400 mK, preferably less than 300 mK, particularly preferably less than 200 mK.

3. Infrared imaging system (1) according to one of the preceding claims, wherein the detector unit for a wavelength in the infrared range, in particular in the range from 0.8 pm to 14 pm, has a defectivity of at least 10 8 cm Hz 1 / 2 W' 1 exhibits, preferably of at least 10 9 cm Hz 1 / 2 W' 1 exhibits, particularly preferably of at least 10 9 cm Hz 1 / 2 W' 1 exhibits, again preferred by at least 10 10 cm Hz1 / 2 W' 1 exhibits, again preferred by at least 10 11 cm Hz 1 / 2 W- 1 exhibits, for example, between one of the mentioned values ​​and 10 13 cm Hz 1 / 2 W- 1 exhibits, in particular between one of the aforementioned values ​​and 10 12 cm Hz 1 / 2 W- 1 has, and / or wherein the detector unit has a resolution of at least 20 line pairs / mm, preferably at least 50 line pairs / mm, especially preferably having at least 150 line pairs / mm, and / or wherein the detector unit has an area of ​​at least 0.1 square centimeters, preferably at least 0.5 square centimeters, and particularly preferably at least 5 square centimeters. Infrared imaging system (1) according to one of the preceding claims, further comprising an optical element (30) arranged between the proximal end of the image guide (20) and the detector unit (40), and / or wherein the detector unit (40) is configured as a screen and the optical element (30) is configured for image projection onto the screen, and / or wherein the image guide (20) of the infrared imaging system (1) is configured according to one of the following claims. Image guide (20) for image transmission from a distal end to a proximal end, comprising a plurality of structural elements (100) each extending from the distal end to the proximal end,comprising at least two different types of structural elements, namely a first type (100a) with a first refractive index n1 and a second type (100b) with a second refractive index n2, in particular such that the structural elements form a bundle of optical fibers, wherein the fibers each comprise a core and a cladding, wherein the cladding is configured as a structural element of the first type and the core is configured as a structural element of the second type, or in particular such that the structural elements form a base body with a plurality of, preferably filled, cavities, wherein the base body is configured as a structural element of the first type and the, preferably filled, cavities are configured as structural elements of the second type, wherein at least one structural element is configured for a wavelength in the infrared range, in particular in the range from 0.8 pm to 14 pm.is transmissive and wherein the ratio n1 / n2 preferably lies between 0.5 and 0.999, particularly preferably between 0.6 and 0.992, and even more preferably between 0.75 and 0.

992. Image guide (20) according to the preceding claim, wherein the image guide (20) defines a longitudinal direction (5) and a cross-section extending transversely to the longitudinal direction (5), and wherein the structural elements extend over the cross-section of the image guide (20) such that a plurality of cross-sectional regions are defined in the cross-section of the image guide (20), each corresponding to the cross-section of a single structural element, and / or wherein the structural elements, in particular their cross-sectional regions, are arranged non-uniformly to effect transverse Anderson localization transversely to the longitudinal direction. Image guide (20) according to any one of the preceding claims, wherein the image guide (20) has a resolution of at least 25 line pairs / mm, preferably a resolution of at least 30 line pairs / mm, and particularly preferably a resolution of at least 40 line pairs / mm.Image conductor (20) according to any one of the preceding claims, wherein the image conductor (20) has a length of at least 50 cm, preferably a length of at least 100 cm, and particularly preferably a length of at least 300 cm. Image conductor (20) according to any one of the preceding claims, wherein the image conductor (20) is configured at least partially as a flexible body and / or wherein the image conductor (20) is configured at least partially as a rigid body. Image conductor (20) according to any one of the preceding claims, wherein a core, a sheath, a base body, a filled cavity, and / or a structural element comprises a material which exhibits an attenuation of less than 50 dB / m for a wavelength in the infrared range, particularly in the range of 0.8 pm to 14 pm. exhibits, in particular, a noise level of less than 10 dB / m, in particular a noise level of less than 1 dB / m. Image conductor (20) according to one of the preceding claims, wherein the number per mm 2The cross-sectional area of ​​the image conductor (20) of the fibers and / or the structural elements of the second type is at least 100, preferably at least 1000, and particularly preferably at least 10000. Image conductor (20) according to one of the preceding claims, wherein the cores of the fibers and / or the structural elements of the second type have a diameter between 5 pm and 200 pm, preferably between 5 pm and 100 pm, and particularly preferably between 10 pm and 50 pm, and / or wherein the claddings of the fibers and / or the structural elements of the first type have a diameter between 6 pm and 250 pm, preferably between 6 pm and 150 pm, and particularly preferably between 10 pm and 70 pm, and / or wherein the ratio of the core to cladding diameters is between 0.5 and 0.95.Image conductor (20) according to one of the preceding claims, wherein the smallest distance between the centers of two cores and / or two structural elements of the second type is less than 50 pm, preferably less than 20 pm, and particularly preferably less than 15 pm, and / or wherein the average distance between the centers of the cores and / or the structural elements of the second type is less than 50 pm, preferably less than 20 pm, and particularly preferably less than 15 pm. Image conductor (20) according to one of the preceding claims, wherein a core, a sheath, a base body, a filled cavity, and / or a structural element comprises a chalcogenide, in particular comprising at least one element from the group consisting of oxygen, sulfur, selenium, and tellurium, and at least one. Element from the group consisting of arsenic, germanium, phosphorus, antimony, lead, boron, aluminum, gallium, indium, titanium, sodium, and / or wherein a core, a sheath, a base body, a filled cavity, and / or a structural element comprises a gallium lanthanum sulfide (GLS) glass, and / or wherein a core, a sheath, a base body, a filled cavity, and / or a structural element comprises glasses, preferably multicomponent glasses, and / or wherein a core, a sheath, a base body, a filled cavity, and / or a structural element comprises fused silica.

15. Image guide (20) according to one of the preceding claims, wherein the image guide has a transmission of at least 30%, preferably at least 50%, and particularly preferably at least 60% for a wavelength in the infrared range, in particular in the range of 0.8 pm to 14 pm, and / or wherein the image guide has a transmission of at least 30%, preferably at least 50%, and particularly preferably at least 60% for a wavelength in the range of 5 pm to 8 pm. exhibiting a transmission of at least 30%, preferably at least 50%, and particularly preferably at least 60%.

Images