Focusing aid and procedure for setting up an optical system

Abstract

Focusing aid (300) for setting up an optical system (106), comprising the focusing aid (300): a light module (310) comprising a light-emitting layer (312); and a mask structure (320) which is arranged on the light-emitting layer (312), wherein the mask structure (320) has an opaque layer (322) with a plurality of recesses (322a) and is arranged such that a plurality of sections (312a) of the light-emitting layer (312) are exposed and light can be emitted through the plurality of recesses (322a), and that one or more sections (312b) of the light-emitting layer (312) are covered and can form an optical contrast to the plurality of exposed sections (312a) of the light-emitting layer (312) to form a self-illuminating optical contrast pattern (300m), wherein the light module (310) comprises one or more organic light-emitting diodes or wherein the light module (310) is an organic light-emitting diode module, and wherein the opaque layer (322) has a layer thickness of less than 1 mm.

Description

[0001] Various embodiments relate to a focusing aid and a method for setting up an optical system by means of a focusing aid.

[0002] Some technical systems use, among other things, particle-containing fluids (also known as aerosols) and / or are created as a result of a process used. Such aerosols can, for example, occur in a variety of forms (gaseous / liquid; gaseous / solid; liquid / solid; liquid / liquid). In most cases, the aerosols influence a technical process, e.g., the atomization of particles for coating surfaces. For some processes, it can therefore be helpful to obtain as precise information as possible about the particle properties or the properties of the particle-containing fluid. To examine the particles or the particle-containing fluid, scattered light particle measuring devices or laser diffraction measuring devices are usually used in technical applications. EP 2 233 913 A1 and US 6 635 487 B1 show known focusing aids for setting up an optical system.DE 10 2005 049 364 A1 shows a calibration device for characterizing a luminescence measuring system.

[0003] According to various embodiments, a measuring system is provided by means of which, for example, a particle-containing fluid can be examined. For this purpose, the measuring system has an optical system so that measurements can be taken non-invasively. It can be helpful to focus the optical system on a predefined spatial region within a fluid guide that is at least partially transparent. In this case, the object plane (also referred to as the adjustment plane) of the optical system is clearly brought into a predefined position within the fluid guide. This can be done by positioning the optical system and / or by changing an optics (e.g., by changing the focal length) of the optical system.

[0004] This allows, for example, particles of the particle-containing fluid that lie on the object plane to be imaged sharply. Particles in front of or behind the particle plane are also imaged, provided they are still within the depth of field, but less sharply than in the object plane. The depth of field is defined, for example, by the distance between the near point of the optical system and the far point of the optical system and can be calculated and / or measured accordingly.

[0005] According to various embodiments, the optical system can have a shallow depth of field compared to the aperture of the fluid guide (e.g., the depth of field can be less than one-hundredth of the aperture of the fluid guide, e.g., less than 100 µm or less than 50 µm), so that precise adjustment of the optical system may be necessary or at least helpful in examining the particles of the particle-containing fluid as precisely as possible. Examining the particles can, for example, include determining their size and / or shape, determining their trajectory, determining their angular momentum, etc.

[0006] Various embodiments relate to a focusing aid that enables focusing of an optical system such that the object plane lies within an at least partially transparent fluid guide. The optical system can, for example, be part of a measuring system by means of which one or more characteristic variables of a particle-containing fluid can be determined. Characteristic variables of a particle-containing fluid can be, for example, the flow velocity or the flow velocity profile, the particle concentration in the particle-containing fluid, the trajectory of the particles, or properties of the particles themselves, e.g., the shape and size of the particles, etc.

[0007] Precise focusing of the optical system enables in-situ measurement of a fluid flow within the fluid guide, which can offer corresponding advantages. For example, the particle-containing fluid can be examined without affecting the flow behavior. Furthermore, flows of any temperature can be investigated.

[0008] According to various embodiments, a focusing aid can be used to set up an optical system. The focusing aid can, for example, comprise at least one radiation source configured such that at least a first portion of the focusing aid can emit electromagnetic radiation generated by the at least one radiation source, and wherein at least a second portion of the focusing aid is configured such that it can form an optical contrast with the at least one first portion to form an optical contrast pattern.

[0009] Illustratively, the focusing aid can have at least one radiation source and be configured such that a self-luminous optical contrast pattern can be generated by the focusing aid. The optical contrast of the contrast pattern can, for example, be a light-dark contrast and / or a color contrast. The optical contrast or the contrast pattern can be defined by a brightness difference, which is generated in at least one exposed surface area of ​​the focusing aid by activating the at least one radiation source of the focusing aid.

[0010] According to various embodiments, a method for setting up an optical system may comprise the following: arranging a focusing aid in a fluid guide, wherein the fluid guide is at least partially transparent, and wherein the optical system is arranged outside the fluid guide; activating the at least one radiation source of the focusing aid; and setting up the optical system by means of the focusing aid based on at least one image of the optical contrast pattern of the focusing aid by means of the optical system.

[0011] According to various embodiments, a method for setting up an optical system can comprise the following: introducing a focusing aid into a fluid guide, wherein the fluid guide is at least partially transparent; irradiating a spatial region within the fluid guide by means of electromagnetic radiation, wherein the electromagnetic radiation is generated by means of a measuring radiation source arranged outside the fluid guide; aligning the focusing aid in the spatial region; activating the at least one radiation source of the focusing aid; and setting up an optical system, which is arranged outside the fluid guide, by means of the focusing aid based on at least one image of the optical contrast pattern of the focusing aid by means of the optical system.

[0012] According to various embodiments, a method for setting up an optical system and for determining a characteristic size of a particle-containing fluid can comprise the following: introducing a focusing aid into a fluid guide, wherein the fluid guide is at least partially transparent; irradiating a spatial region within the fluid guide using electromagnetic radiation, wherein the electromagnetic radiation is generated by a measuring radiation source arranged outside the fluid guide; aligning the focusing aid in the spatial region; activating the at least one radiation source of the focusing aid; setting up an optical system, which is arranged outside the fluid guide, using the focusing aid based on at least one image of the optical contrast pattern of the focusing aid using the optical system;and, after setting up the optical system, guiding a particle-containing fluid within the fluid guide; and determining a characteristic size of the particle-containing fluid. Determining the characteristic size of the particle-containing fluid can, for example, comprise the following: generating at least one image of the spatial region using the optical system, wherein particles of the particle-containing fluid that are irradiated in the spatial region by the electromagnetic radiation of the measuring radiation source are imaged in the at least one generated image; and determining the characteristic size of the particle-containing fluid based on the particles imaged in the at least one image.

[0013] According to various embodiments, the optical system can be configured such that the largest possible section or one or more predefined sections of the surface area of ​​the focusing aid is / are imaged in a focused manner in an image.

[0014] Examples of embodiments are shown in the figures and are explained in more detail below.

[0015] It shows Fig. 1 a measuring system in a schematic view, according to various embodiments; Fig. 2A and Fig. 2B each shows a schematic flow diagram of a method for setting up an optical system, according to various embodiments; Fig. 2C is a schematic flow diagram of a method for setting up an optical system and determining a characteristic size of a particle-containing fluid, according to various embodiments; Fig. 3A and Fig. 3B each shows a focusing aid in a schematic view, according to various embodiments; Fig. 4 shows a measurement setup in a schematic view, according to various embodiments; and Fig. 5A to 5D show a correction of optical distortions on a pipe in a schematic view, according to various embodiments.

[0016] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. It is to be understood that the features of the various exemplary embodiments described herein may be combined with one another unless specifically stated otherwise. The following description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0017] Various embodiments relate to a method for image focusing. According to various embodiments, a setting plane of an optical system can be or will be focused, for example, within a round quartz glass tube for recording an image of a spatial region within the quartz glass tube. Within the quartz glass tube, for example, a fluid in the high-temperature range can be or will be guided, e.g. a fluid with a temperature of more than 800°C, e.g. temperatures up to 1000°C or more than 1000°C. Flowing fluids in general can be of great importance for a variety of technical systems. This flow, regardless of whether it is in the gaseous, liquid or solid state, can be essential, for example, for the operation of power plants (e.g. as a transport medium for heat transport). The three-dimensional flow behavior can, for example, have an influence on the efficiency of heat transport.Changes in flow behavior, e.g., caused by load changes in an upstream heat source, can affect the three-dimensional flow behavior (or the flow profile). Restrictions in the flow guidance, for example, can lead to local flow turbulence, which can cause vibrations in individual pipe segments and even damage the entire system. In order to capture and understand influences and their effects on flow profiles, it can be helpful to precisely examine such a flow three-dimensionally using a measuring system at a defined local location within the flow.

[0018] Traditionally, sensors are inserted into such a flow in order to obtain information about the local flow velocity or other flow properties. However, sensors that are inserted into the fluid can influence the flow field to be described, for example by changing the flow field and thus falsifying the measured variable or the measurement signal. Furthermore, due to their operating principle and their own design, such sensors cannot generally be used in a temperature range above 800°C, for example. In order to still be able to carry out measurements in such a temperature range (above the limit temperature of, for example, metal-encapsulated sensors), a portion of the flow that is used for flow characterization in a separate area (lower temperatures, slower flow, less aggressive environment) can be diverted via a bypass.However, this generally limits the precise measurement of flow profile properties, for example, due to the fluid being extracted from the main flow. One reason for this may be the inability to reproducibly adjust the mixing ratio between the main and secondary flows.

[0019] To prevent physical interference with a flow and to enable measurements in a high-temperature range, an optical and non-invasive measurement system can be used, for example, primarily in research and development. Furthermore, systems that enable the optical and non-invasive measurement of particle properties and / or particle flow properties are increasingly becoming established for commercial and industrial applications.

[0020] Due to their high resolution and cost-effectiveness, particle image velocimetry (PIV) systems are primarily used to study particle flows. Non-invasive data acquisition is achieved using, for example, a pulsed laser that illuminates microscopic particles in the flow in a stroboscopic manner. These particles are present as contaminants in every industrial application. A camera (e.g., a CCD camera) positioned to the laser beam (e.g., at a 90° angle) can capture images of the illuminated particles at microsecond intervals. With appropriate analysis software, the movement of individual particles can be reconstructed from the captured images, allowing, for example, precise conclusions to be drawn about the three-dimensional flow profile.This can also be done, for example, by evaluating the particle shape as well as the axial behavior between two images and the recorded total concentration of individual particles.

[0021] The fluid guide (e.g., a flow-conducting pipe) can have a transparent section (e.g., the flow-conducting pipe can have a translucent pipe segment), e.g., made of quartz glass. Compared to conventional sight glasses, quartz glass offers the advantage of a low thermal expansion coefficient and high resistance to thermal shock. Furthermore, heated quartz glass, for example, offers the advantage that thermophoretically driven particle deposits cannot form at the viewing points due to the low temperature gradient (hot flow / heated quartz glass).

[0022] Fig. 1 illustrates a measuring system 100 in a schematic view, according to various embodiments. The measuring system 100 illustrates a possible configuration for non-invasively / optically determining (e.g., measuring, estimating, e.g., based on a model, etc.) one or more characteristic properties of a particle-containing fluid or one or more characteristic properties of particles of the particle-containing fluid. It is understood that other configurations of the measuring system 100 are possible, which may also be useful.

[0023] The measuring system 100 can, for example, have a fluid guide 102. This can be configured to guide a particle-containing fluid 112 (in other words, an aerosol). The particle-containing fluid 112 can, for example, be a gas or gas mixture with liquid and / or solid particles. The particle-containing fluid 112 can furthermore be a liquid or a liquid mixture with solid particles. The particle-containing fluid 112 can furthermore be a liquid or a liquid mixture with liquid particles (illustratively not miscible with the liquid or liquid mixture). The particle-containing fluid 112 can also have only solid particles (e.g., sand or the like). The particles can, for example, have an average particle size in a range from 100 nm to 100 µm.

[0024] According to various embodiments, the fluid guide 102 may, for example, have a diameter of 50 mm and the resulting spatial area 122 may be substantially completely captured by the optical system 106.

[0025] The measuring system 100 may further comprise, for example, a measuring radiation source 104. The measuring radiation source 104 may be configured to emit electromagnetic radiation 114, e.g., into a spatial region 122 within the fluid guide 102. Furthermore, the measuring system 100 may comprise an optical system 106. The optical system may be configured to capture an image of the spatial region 122 within the fluid guide 102 and thus image particles 112p of the particle-containing fluid 112.

[0026] The fluid guide 102 has, for example, a wall 102w, which can be completely or at least partially transparent, e.g., such that the spatial region 122 within the fluid guide 102 can be irradiated by electromagnetic radiation (e.g., by means of the electromagnetic radiation 114 emitted by the measuring radiation source 104). According to various embodiments, the fluid guide 102 can be designed to be transparent such that an image of the spatial region 122 inside the fluid guide 102 can be recorded (e.g., by means of the optical system 106). The term "transparent" can, for example, be understood to mean that more than 50% or more than 66% of the electromagnetic radiation (e.g., emitted by the measuring radiation source 104) impinging on the wall 102w (e.g., from outside) is transmitted, i.e., reaches the interior of the fluid guide 102.Furthermore, the term transparent can be understood, for example, in such a way that more than 50% or more than 66% of the electromagnetic radiation impinging on the wall 102w (e.g. from the inside) (e.g. emitted or reflected by particles 112p of the particle-containing fluid 112) is transmitted, ie escapes from the fluid guide 102.

[0027] The fluid guide 102 can, for example, have one or more wall sections made of glass (e.g., quartz glass) or be made entirely of glass (e.g., quartz glass). According to various embodiments, the fluid guide 102 can be configured to connect two process areas of a processing system. Clearly, the fluid flow 112s in the fluid guide 102 can be the main flow to be analyzed, rather than branching off from a main flow to be analyzed.

[0028] According to various embodiments, the measuring radiation source 104 can be configured to irradiate the spatial region 122 within the fluid guide 102 using electromagnetic radiation 114. The measuring radiation source 104 clearly generates a spatial radiation intensity distribution of the electromagnetic radiation 114 in the spatial region 122. The spatial region 122 in the fluid guide 102 irradiated by the measuring radiation source 104 can also be referred to, for example, as a laser section or laser light section if the measuring radiation source 104 is a laser beam source and clearly emits a fanned-out laser beam.

[0029] According to various embodiments, the optical system 106 can be configured to generate an image 106b of the spatial region 122. For example, particles 112p of the particle-containing fluid 102 that are irradiated by the electromagnetic radiation 114 in the spatial region 122 or in an effective spatial region within the spatial region 122 can be or become imaged in the generated image 106b. Particles 112p of the particle-containing fluid 102 that are not in the spatial region 122 and thus are not irradiated by the electromagnetic radiation 114 of the measuring radiation source 104 can not be or become imaged in the generated image 106b.

[0030] Particles 112p of the particle-containing fluid 102 that are irradiated in the spatial region 122 by the electromagnetic radiation 114, but the electromagnetic radiation 114 has too low a radiation intensity, may not be or become imaged in the generated image 106b. Therefore, it may be helpful to determine an effective spatial region in which the radiation intensity of the electromagnetic radiation 114 is sufficiently high to image the particles 112p accordingly in the generated image 106b.

[0031] According to various embodiments, the measuring system 100 may comprise at least one processor 108 (e.g., one or more processors) (e.g., as part of a computer system or the like) configured to determine one or more characteristic variables 110 of the particles 112p or the particle-containing fluid 112 (e.g., to measure, to estimate based on a model, etc.).

[0032] The at least one processor 108 may, for example, be configured to process a number, N P , of particles 116p depicted in the generated image 106b. Furthermore, the at least one processor 108 can be configured to determine a particle concentration, P P , the particles 112p of the particle-containing fluid 112 in the spatial area 122 or the effective spatial area to be determined based on the determined number, N P , of particles 116p depicted in the generated image 106b and a determined volume of the spatial region 122 or a determined volume of the effective spatial region.

[0033] The at least one processor 108 may, for example, be configured to determine the shape and / or size of the particles 112p of the particle-containing fluid 112 in the spatial region 122 based on the particles 116p depicted in the generated image 106b.

[0034] The at least one processor 108 may, for example, be configured to determine a trajectory of one or more particles 112p of the particle-containing fluid 112 in the spatial region 122 based on one or more particles 116p depicted in an image sequence comprising a plurality of images 106b.

[0035] According to various embodiments, the electromagnetic radiation 114 emitted by the measuring radiation source 104 can be laser radiation, e.g., with a wavelength of approximately 532 nm. This can enable precise measurement within the fluid guide 102 through a quartz glass wall section. The electromagnetic radiation 114 can, for example, be provided in a pulsed manner by the measuring radiation source 104. For example, a laser beam source can be operated in a pulsed manner for pulsed irradiation of the spatial region 122 within the fluid guide 102 using laser radiation.

[0036] According to various embodiments, the optical system 106 may include or be a CCD (charge-coupled device) camera. The CCD camera may include a CCD sensor and corresponding optics for imaging the particles 112p of the fluid stream 112s irradiated in the spatial region 122.

[0037] According to various embodiments, an optical axis 106o of the optical system 106 can be aligned substantially perpendicular to a main emission direction 114h of the electromagnetic radiation 114. The main emission direction 114h of the electromagnetic radiation 114 can be defined by the measurement radiation source 104; for example, the main emission direction 114h can be the direction along which the electromagnetic radiation 114 is emitted with the greatest intensity.

[0038] Fig. Figure 2A illustrates a schematic flow diagram of a method 200a for setting up an optical system, according to various embodiments. The optical system can, for example, be part of the measuring system 100. It is understood that any other optical system can also be set up in the same or similar manner.

[0039] The method 200a for setting up an optical system may, for example, comprise the following: in 210a, arranging a focusing aid in a fluid guide, wherein the fluid guide is at least partially transparent, and wherein the optical system is arranged outside the fluid guide; in 220a, activating at least one radiation source of the focusing aid to form an optical contrast pattern; and, in 230a, setting up the optical system by means of the focusing aid based on at least one image of the contrast pattern of the focusing aid by means of the optical system.

[0040] According to various embodiments, the focusing aid can be self-luminous, e.g. it can have an OLED film or the like.

[0041] Fig. Figure 2B illustrates a schematic flow diagram of a method 200b for setting up an optical system, according to various embodiments. The optical system can, for example, be part of the measuring system 100. It is understood that any other optical system can also be set up in the same or similar manner.

[0042] The method 200b for setting up an optical system can, for example, comprise the following: in 210b, introducing a focusing aid into a fluid guide, wherein the fluid guide is at least partially transparent; in 220b, irradiating a spatial region within the fluid guide by means of electromagnetic radiation, wherein the electromagnetic radiation is generated by means of a measuring radiation source arranged outside the fluid guide; in 230b, aligning the focusing aid in the spatial region; in 240b, activating at least one radiation source of the focusing aid to form an optical contrast pattern; and, in 250b, setting up an optical system, which is arranged outside the fluid guide, by means of the focusing aid based on at least one image of the optical contrast pattern of the focusing aid by means of the optical system.

[0043] Fig. Figure 2C illustrates a schematic flow diagram of a method 200c for setting up an optical system and for determining a characteristic variable of a particle-containing fluid, according to various embodiments. The optical system can, for example, be part of the measuring system 100. It is understood that any other optical system can also be set up in the same or similar manner.

[0044] The method 200c for setting up an optical system and for determining a characteristic size of a particle-containing fluid may, for example, comprise the following: in 210c, setting up the optical system according to method 200b; and, after setting up the optical system, in 220c, guiding a particle-containing fluid within the fluid guide; and, in 230c, determining a characteristic size of the particle-containing fluid.

[0045] For example, if the optical system 106 of the measuring system 100 is to be set up, see for example Fig. 1 and Fig. 4, and the measuring system 100 is to be used to determine the characteristic size of the particle-containing fluid, the determination of the characteristic size of the particle-containing fluid can, for example, comprise the following: generating at least one image 106b of the spatial region 122 by means of the optical system 106, wherein one or more particles 112p of the particle-containing fluid 112, which are irradiated in the spatial region 122 by means of the electromagnetic radiation 114 of the measuring radiation source 104, are imaged in the at least one generated image 106b; and determining the characteristic size of the particle-containing fluid 112 based on the one or more particles 116p imaged in the at least one image 106b.

[0046] Fig. 3A and Fig. 3B each illustrate a focusing aid 300 in various schematic views, according to various embodiments.

[0047] According to various embodiments, the focusing aid 300 can be used accordingly to set up an optical system 106. For example, the optical system 106 can be adjusted such that a contrast pattern 300m formed by the focusing aid 300 is sharply imaged. The contrast pattern 300m can, for example, be provided in a plane, wherein this plane is set as the object plane during imaging by means of the optical system 106.

[0048] According to various embodiments, the focusing aid 300 can be designed such that the contrast pattern 300m is or will be formed from one or more radiation-emitting sections 302 of the focusing aid 300 and one or more non-radiation-emitting sections 304 of the focusing aid 300. Fig. 3A clearly shows a top view of the contrast pattern 300m of the focusing aid 300. It is understood that the contrast pattern 300m is or will be formed in a surface region of the focusing aid 300 that is exposed, so that the contrast pattern 300m can be detected by the optical system 106. According to various embodiments, the focusing of the optical system 106 can be performed manually based on the contrast pattern 300m or by means of an autofocus function, e.g., by means of a contrast autofocus function, of the optical system 106.

[0049] According to various embodiments, the focusing aid 300 may comprise at least one radiation source (e.g., a light module 310, as shown in Fig. 3B is illustrated in a schematic cross-sectional view). The focusing aid 300 can, for example, be configured such that at least a first section 302 can emit electromagnetic radiation, which is generated by means of the at least one radiation source of the focusing aid 300, and that at least a second section 304 of the focusing aid 300 is configured such that it forms or can form an optical contrast to the at least one first section 302, e.g., when the radiation source of the focusing aid 300 is activated.

[0050] The respective first section 302 of the focusing aid 300 can, for example, be a light-emitting region of a lighting module. The respective second section 304 of the focusing aid 300 can, for example, be part of a mask structure. The respective second section 304 can, for example, be a matte black section of a layer that can be applied to a light-emitting region of a lighting module to generate the contrast pattern 300m.

[0051] Fig. 3B illustrates a focusing aid 300 in a schematic cross-sectional view, according to various embodiments.

[0052] The focusing aid 300 can, for example, comprise a lighting module 310. The lighting module 310 can, for example, comprise at least one light-emitting layer 312. The lighting module 310 can, for example, comprise an organic light-emitting diode (OLED) or multiple organic light-emitting diodes. The lighting module 310 can, for example, be an OLED module.

[0053] According to various embodiments, the lighting module 310 can be configured, for example, as a surface light source. A surface light source (like any other surface radiation source) can, for example, emit light like a Lambertian radiator. For example, the radiation source of the focusing aid 300 (e.g., the lighting module 310 or the light-emitting layer 312 of the lighting module 310) can be configured such that the luminance is spatially homogeneously distributed with respect to the radiation surface and is equally distributed in all radiation directions.

[0054] Furthermore, the focusing aid 300 can, for example, have a mask structure 320. The mask structure 320 can, for example, be arranged on the lighting module 310, e.g., directly on the light-emitting layer 312 or above the light-emitting layer 312.

[0055] According to various embodiments, the mask structure 320 may be configured such that the light-emitting layer 312 of the lighting module 310 is partially exposed and partially covered, such that an optical contrast is formed between exposed, light-emitting regions 312a and covered, non-light-emitting regions 312b.

[0056] According to various embodiments, the mask structure 320 may include an opaque layer 322, wherein a plurality of cutouts 322a are provided in the opaque layer 322. The plurality of cutouts 322a may, for example, be provided such that light can be emitted through them by the light-emitting layer 312 of the lighting module 310. Illustratively, however, only light from the exposed regions 312a of the light-emitting layer 312 can actually be emitted, and not from the covered regions 312b of the light-emitting layer 312.

[0057] According to various embodiments, the opaque layer 322 may have a layer thickness (thickness) of, for example, less than 1 mm. Thus, for example, precise focusing can be achieved at an edge of the opaque layer 322.

[0058] It is understood that other possible embodiments of the focusing aid 300 arise in a similar manner, in which light is emitted at least in sections to generate a self-luminous contrast pattern 300m, which can then be used to focus an optical system.

[0059] Also in Fig. The contrast pattern 300m shown in Figure 3A (formed from the regions 302, 304) is for illustrative purposes only. In principle, any simple pattern (e.g., with only two regions 302, 304) or even more complex patterns (e.g., where varying sizes and / or shapes are used for the respective regions 302, 304) are suitable for focusing an optical system. For example, the contrast pattern can comprise or be a line pattern, a grid pattern, an arrangement of circles, etc.

[0060] According to various embodiments, the recesses 322a in the opaque layer 322 can be circular cutouts. These can be precisely cut out, for example, using a laser cutting process. For example, in order to be able to perform reference measurements using the focusing aid 300, e.g., for image correction or the like, the mask structure 320 can be measured. For example, the opaque layer 322 can be measured after the recesses 322a have been cut out. The opaque layer 322 can be, for example, a film that can be adhesively bonded to the lighting module 310.

[0061] According to various embodiments, the term opaque can be understood such that less than 50% or less than 25% or even less than 1% of the electromagnetic radiation emitted by the radiation source of the focusing aid 300 is transmitted.

[0062] Fig. 4 illustrates a measurement setup 400 with an optical system, which, according to various embodiments, can be set up using a focusing aid 300. Setting up the optical system using the focusing aid 300 can be carried out, for example, according to one of the methods 200a, 200b. The measurement setup 400 can be configured in the same or similar manner as described for the measurement system 100. For example, the measurement setup 400 can have a fluid guide 102, wherein the fluid guide 102 is at least partially transparent, and furthermore an optical system 106, which is arranged outside the fluid guide 102.

[0063] A focusing aid 300 can be arranged within the fluid guide 102, e.g., in the spatial region 122 that is irradiated with electromagnetic radiation 114 by a measuring radiation source 104. The fluid guide 102 is, for example, transparent at least in sections, and the optical system 106 can thus be arranged outside the fluid guide 102.

[0064] According to various embodiments, the optical system 106 can be focused on a surface area of ​​the focusing aid 300. In other words, the focusing aid 300 can define an object plane 411, which is sharply imaged by the optical system 106. The contrast pattern 300m is also formed in the surface area of ​​the focusing aid 300.

[0065] It is understood that other possible configurations of the measurement setup 400 or the measurement system 100 arise in a similar manner. When using a PIV system, for example as an optical measurement system, it may be useful to ensure in advance (e.g., within a setup or during maintenance or calibration work) that the measurement system can be adjusted to a reproducible and fixed point in the flow with regard to the focal length and image focusing. It is also apparent, for example, that arranging an optical system 106 (e.g., an optical camera) outside the fluid guide 102 for imaging an area within the fluid guide 102 can lead to problems in image representation. Light refraction at the fluid guide 102 (e.g., in an area with a round or oval cross-section) can, for example, make it difficult to obtain an exact overall image of the vertical pipe cross-section.The fluid guide 102 can be or comprise, for example, a quartz glass tube.

[0066] By modifying the fluid guide 102, the image representation could be partially improved. For example, a pipe segment in the shape of a square profile could be used as the fluid guide 102. Since such pipe segments can be significantly more expensive to manufacture than, for example, cylindrical pipe segments, they are generally not used very often. Also not to be neglected is the newly introduced measurement inaccuracy due to the change in flow behavior (e.g., during a transition from a cylindrical pipe section to a prismatic pipe section and / or vice versa). In order to nevertheless compensate for refraction across the entire cross-section, for example, in a cylindrical pipe (e.g., in a cylindrical quartz glass tube), the following points can be considered: Introducing the electromagnetic radiation 114 (e.g. a laser beam) of the measuring radiation source 104 over the end face of the tube so that it is not fanned out in the tube; Precise adjustment of the image focus by varying the focal length of the optical system 106; Alignment of the image focus of the optical system 106 to the laser cross-section; Compensation of refraction in the edge area of ​​the tube by a suitable device with its own scale.

[0067] In order to be able to capture a usable image across the entire spatial area 122 of a cross-section of the fluid guide 102 (illustratively, essentially across the full height of the interior of the fluid guide 102), a suitable focusing aid 300 can be used. By using the focusing aid 300, it may be possible to precisely align the camera image within the spatial area (illustratively, within the measurement illumination area) 122 of the laser cut.

[0068] The focusing of the optical system 106 can be achieved with the aid of a focusing aid (e.g., in the form of a self-luminous target), wherein the focusing aid 300 can be or can be incorporated into the fluid guide 102 during a calibration of the measuring system 100 or the measuring setup 400. In process systems, this can be done during system setup or during maintenance work. The focusing aid can, for example, have an actively luminous OLED film as a light source. An opaque film (e.g., a few µm thick) can be or can be glued to the surface of the actively luminous OLED film. The opaque film can have through-holes (i.e., clearly designed as a mask structure 320), e.g., circular cutouts with a varying diameter. The cutouts in the opaque film can, for example, be created using a cutting laser. Due to the low thickness of the opaque film (e.g.,By applying a black film, a sharp edge of a circle can be created on the luminous OLED film as a contrast for the camera. This allows the camera image to be focused precisely in the lateral plane using the sharp edge. This can ensure precise image focusing of the camera (down to the microscopic level) on the surface of the focusing aid.

[0069] Thus, for example, it can be ensured that particles 112p in the fluid flow that pass through the spatial region 122 and are illuminated are now also detected with sharp edges by the optical system 106. This method can be performed non-invasively, e.g., independently of exothermic reactions in the gas flow.

[0070] Furthermore, a further advantage can be seen in the fact that transmission losses of the quartz glass of the fluid guide 102 can be compensated, e.g., due to the active illumination of the focusing aid. For example, the OLED film can have a predefined luminosity (e.g., a luminance in a range of approximately 1 cd / m 2 up to approximately 10000 cd / m 2 or e.g. a specific light emission in a range of approximately 10 lm / m 2 up to approximately 30000 lm / m 2 ), so that these can be used as a reference to determine the transmission losses. These losses can be caused, for example, by light refraction on the round quartz glass tube, by impurities in the quartz glass tube, or by reflections from the quartz glass itself.

[0071] If the cutouts in the opaque film are provided essentially over the entire surface, they can be imaged in the entire cross-section of the tube by means of the optical system 106. Due to the refraction of light in the edge region of the quartz glass tube, distortions of the circular structure can occur during image recording (e.g., round circles are displayed as oval circles), as exemplified in Fig. 5A is illustrated.

[0072] Such structural distortions 500v can result from refraction of light at the wall of the fluid guide 102. When considering refractions in a pipe, for example, a refraction of a plane perpendicular to the pipe axis can occur, as in Fig. 5B (left in a plan view of the pipe and right in a cross-sectional view of the pipe).

[0073] The refraction also takes place in the plane parallel to the tube axis, as in Fig. 5C. This increases the 2D distortion of the entire field of view.

[0074] According to various embodiments, while compensating for the known refraction, the structural distortions 500v, see for example Fig. 5A, of the real image. As a result, the real overall image 500r can be made available for further processing, as shown for example in Fig. 5D is shown.

[0075] According to various embodiments, structural distortions 500v of a circular structure can be converted back into round circular structures using evaluation software, since in addition to the predefined light intensity, the circular structure on the surface of the focusing aid 300 can also be predefined. This can also have a positive effect on the particles 112p to be recorded in the flow 112, since they can now be imaged and evaluated in an undistorted form. This form of representation, even in the edge region, thus enables conclusions to be drawn about the entire flow profile and its flow behavior.

[0076] Various examples are described below which relate to what is described herein and shown in the figures.

[0077] Example 1 is a focusing aid (e.g. for setting up an optical system), the focusing aid comprising: at least one radiation source which is set up such that at least a first section of the focusing aid can emit electromagnetic radiation which is generated by means of the at least one radiation source, and wherein at least a second section of the focusing aid is set up such that it can form an optical contrast to the at least one first section for forming an optical contrast pattern.

[0078] In Example 2, the focusing aid according to Example 1 may further comprise that the at least one radiation source is a surface radiation source.

[0079] In Example 3, the focusing aid according to Example 2 may further comprise that the at least one first section of the focusing aid is at least one section of a radiation emission layer of the surface radiation source.

[0080] In Example 4, the focusing aid according to any one of Examples 1 to 3 may further comprise: a mask structure arranged on or above the radiation source. During setup of the optical system, the mask structure may be arranged between the radiation source of the focusing aid and the optical system.

[0081] In Example 5, the focusing aid according to Example 4 may further comprise that the at least one second section of the focusing aid is formed by the mask structure.

[0082] In Example 6, the focusing aid according to Example 4 or 5 may further comprise that the mask structure has a radiation-absorbing layer and at least one recess. The radiation-absorbing layer and the at least one recess may be configured such that electromagnetic radiation emitted by the radiation source of the focusing aid can be radiated through the at least one recess.

[0083] In Example 7, the focusing aid according to Example 6 may further comprise that the at least one recess has an opening width in a range of approximately 10 µm to approximately 10 mm.

[0084] In Example 8, the focusing aid according to any one of Examples 1 to 7 can further comprise that the at least one second section of the focusing aid is formed by a light-absorbing and / or opaque layer. A light-absorbing layer can, for example, reflect less than 50%, less than 25%, or less than 1% of the incident electromagnetic radiation (e.g., in the visible wavelength range, ie, light).

[0085] In Example 9, the focusing aid according to any one of Examples 1 to 8 may further comprise that the radiation source of the focusing aid is a light source which emits the electromagnetic radiation in the visible wavelength range.

[0086] In Example 10, the focusing aid according to any one of Examples 1 to 9 may further comprise that the radiation source comprises or consists of one or more organic light-emitting diodes.

[0087] Example 11 is a focusing aid (e.g., for setting up an optical system), the focusing aid comprising: a light source comprising a light-emitting layer; and a mask structure arranged on the light-emitting layer, wherein the mask structure comprises an opaque layer having a plurality of recesses and is configured such that a plurality of portions of the light-emitting layer are exposed and light can be emitted through the plurality of recesses, and that one or more portions of the light-emitting layer are covered and can form an optical contrast with the plurality of exposed portions of the light-emitting layer to form an optical contrast pattern.

[0088] Example 12 is a method (e.g., for setting up an optical system), the method comprising: arranging a focusing aid according to any one of examples 1 to 11 in a fluid guide, wherein the fluid guide is at least partially transparent, and wherein the optical system is arranged outside the fluid guide; activating the at least one radiation source of the focusing aid to form the optical contrast pattern; imaging the optical contrast pattern of the focusing aid by means of the optical system in at least one image; and setting up the optical system by means of the focusing aid based on the optical contrast pattern of the focusing aid imaged in the at least one image.

[0089] Example 13 is a method (e.g., for setting up an optical system and / or for determining a characteristic size of a particle-containing fluid), the method comprising: introducing a focusing aid into a fluid guide, wherein the fluid guide is at least partially transparent; irradiating a spatial region within the fluid guide by means of electromagnetic radiation, wherein the electromagnetic radiation is generated by means of a measuring radiation source arranged outside the fluid guide; aligning the focusing aid in the spatial region; activating the at least one radiation source of the focusing aid; and setting up an optical system, which is arranged outside the fluid guide, by means of the focusing aid based on at least one image of the optical contrast pattern of the focusing aid by means of the optical system.

[0090] In Example 14, the method according to Example 13 may further comprise that the focusing aid is configured according to any one of Examples 1 to 11.

[0091] In Example 15, the method according to any one of Examples 12 to 14 may further comprise: after setting up the optical system, removing the focusing aid from the fluid guide.

[0092] In Example 16, the method according to any one of Examples 12 to 15 may further comprise: after setting up the optical system, guiding a particle-containing fluid within the fluid guide; and determining a characteristic size of the particle-containing fluid.

[0093] In Example 17, the method according to Example 16 may further comprise determining the characteristic size of the particle-containing fluid comprising: generating at least one image of the spatial region by means of the optical system, wherein particles of the particle-containing fluid which are irradiated in the spatial region by means of the electromagnetic radiation of the measuring radiation source are imaged in the at least one generated image; and determining the characteristic size of the particle-containing fluid based on the particles imaged in the at least one image.

[0094] In example 18, the method according to example 16 or 17 may further comprise that the characteristic variable is at least one of the following characteristic variables: a particle number in the spatial region, a particle concentration in the spatial region, a flow velocity of the particle-containing fluid, a size of at least one particle of the particle-containing fluid, a shape of at least one particle of the particle-containing fluid, a trajectory of at least one particle of the particle-containing fluid in the fluid guide.

[0095] In Example 19, the method according to any one of Examples 13 to 18 may further comprise that the electromagnetic radiation emitted by the measuring radiation source is laser radiation, preferably laser radiation having a wavelength of approximately 532 nm.

[0096] In Example 20, the method according to any one of Examples 13 to 19 may further comprise that the measuring radiation source is a laser, wherein the laser is operated in a pulsed manner for pulsed irradiation of the spatial region within the fluid guide by means of laser radiation.

[0097] In Example 21, the method according to any one of Examples 12 to 20 may further include that the optical system comprises or is a camera. The camera may, for example, be a charge-coupled device camera comprising a CCD sensor and a camera lens.

[0098] In Example 22, the method according to any one of Examples 12 to 21 may further comprise that the fluid guide comprises or consists of quartz glass for irradiating the spatial region within the fluid guide by means of the electromagnetic radiation through the quartz glass and for generating the image of the spatial region by means of the optical system through the quartz glass.

[0099] In Example 23, the method according to any one of Examples 13 to 22 may further comprise that an optical axis of the optical system is aligned substantially perpendicular to a main emission direction of the electromagnetic radiation emitted by the measuring radiation source.

[0100] In Example 24, the method according to any one of Examples 12 to 23 may further comprise that setting up the optical system comprises: aligning an object plane of the optical system with the focusing aid such that the focusing aid is imaged in partial or complete focus by means of the optical system.

[0101] In Example 25, the method according to any one of Examples 12 to 24 may further comprise that setting up the optical system comprises: imaging the contrast pattern of the focusing aid by means of the optical system in at least one image; determining at least one parameter which characterizes an actual imaging of the contrast pattern in the at least one image; determining at least one reference parameter which represents a desired imaging of the contrast pattern in the at least one image; and determining at least one image correction parameter based on a deviation of the at least one parameter from the at least one reference parameter.

[0102] In Example 26, the method according to Example 25 may further comprise: generating at least one corrected image from at least one image generated by the optical system based on the at least one image correction parameter.

[0103] In Example 27, the method according to Example 26 may further comprise: using the at least one corrected image to determine the characteristic size of the particle-containing fluid based on the particles represented in the at least one corrected image

[0104] Example 28 is a measuring system comprising: a fluid guide for guiding a particle-containing fluid within the fluid guide; a radiation source for irradiating a spatial region within the fluid guide by means of electromagnetic radiation; an optical system for generating at least one image of the spatial region by means of the optical system, wherein the optical system and the fluid guide are configured such that particles of the particle-containing fluid which are irradiated in the spatial region by means of the electromagnetic radiation can be imaged in the at least one image generated by the optical system; one or more processors configured to determine a characteristic size of particles of the particle-containing fluid or the particle-containing fluid based on particles imaged in the at least one generated image.

[0105] Example 29 is a use of a focusing aid according to any one of Examples 1 to 11 for implementing an optical system. According to various embodiments, implementing the optical system may include changing one or more operating parameters of the optical system (e.g., the focal length) and / or changing a position of the optical system or a part of the optical system relative to the focusing aid. According to various embodiments, the object plane of the optical system may be adjusted by adjusting to an (exposed) surface area of ​​the focusing aid in which the contrast pattern is generated.

[0106] It is understood that functions, algorithms, etc. described herein with reference to a method (e.g., the method 200a, 200b, 200c) may also be implemented in the same or similar manner in a device (e.g., the measurement system 100 and / or the measurement setup 400) and vice versa.

Claims

[1] Focusing aid (300) for setting up an optical system (106), the focusing aid (300) comprising: a light-emitting module (310) comprising a light-emitting layer (312); and a mask structure (320) arranged on the light-emitting layer (312), wherein the mask structure (320) has an opaque layer (322) with a plurality of cutouts (322a) and is configured such that a plurality of sections (312a) of the light-emitting layer (312) are exposed and light can be emitted through the plurality of cutouts (322a), and that one or more sections (312b) of the light-emitting layer (312) are covered and can form an optical contrast to the plurality of exposed sections (312a) of the light-emitting layer (312) to form a self-luminous optical contrast pattern (300m), wherein the lighting module (310) comprises one or more organic light-emitting diodes or wherein the lighting module (310) is an organic light-emitting diode module, and wherein the opaque layer (322) has a layer thickness of less than 1 mm. [2] Focusing aid (300) according to claim 1, wherein the self-luminous optical contrast pattern (300m) comprises or is a line pattern, a grid pattern, or an arrangement of circles. [3] Focusing aid (300) according to claim 1 or 2, wherein the lighting module (310) is designed as a surface light source. [4] Focusing aid (300) according to one of claims 1 to 3, wherein the lighting module (310) or the light-emitting layer (312) of the lighting module (310) is configured such that the luminance is spatially homogeneously distributed with respect to the emission surface and is equally distributed in all emission directions. [5] Focusing aid (300) according to one of claims 1 to 4, wherein the mask structure (320) is arranged directly on the light-emitting layer (312). [6] Focusing aid (300) according to one of claims 1 to 5, wherein the opaque layer (322) is a film which is glued to the lighting module (310). [7] Focusing aid (300) according to one of claims 1 to 5, wherein the light-emitting layer (312) is an actively luminous organic light-emitting diode film, and wherein the opaque layer (322) is an opaque film which is glued to the surface of the actively luminous organic light-emitting diode film, wherein the opaque film further has circular cutouts with a varying diameter. [8] A method (200a) for setting up an optical system, the method comprising: Arranging a focusing aid (300) according to one of claims 1 to 7 in a fluid guide (102), wherein the fluid guide (102) is at least partially transparent, and wherein the optical system (106) is arranged outside the fluid guide (102); Activating the at least one light module (310) of the focusing aid (300) to form the optical contrast pattern (300m); imaging the optical contrast pattern (300m) of the focusing aid (300) by means of the optical system (106) in at least one image; and Setting up the optical system (106) by means of the focusing aid (300) based on the optical contrast pattern (300m) of the focusing aid (300) depicted in the at least one image. [9] Method (200b, 200c) for setting up an optical system (106) and / or for determining a characteristic size of a particle-containing fluid (112), the method comprising: Introducing a focusing aid (300) into a fluid guide (102), wherein the fluid guide (102) is at least partially transparent; Irradiating a spatial region (122) within the fluid guide (102) by means of electromagnetic radiation (114), wherein the electromagnetic radiation (114) is generated by means of a measuring radiation source (104) arranged outside the fluid guide (102); Aligning the focusing aid (300) in the spatial area (122); Activating the at least one radiation source (310) of the focusing aid (300); Setting up an optical system (106) which is arranged outside the fluid guide (102) by means of the focusing aid (300) based on at least one image of the optical contrast pattern (300m) of the focusing aid (300) by means of the optical system (106); after setting up the optical system (106), removing the focusing aid (300) from the fluid guide (102); and after setting up the optical system (106) and after removing the focusing aid (300) from the fluid guide (102), guiding a particle-containing fluid (112) within the fluid guide (102) and determining a characteristic size of the particle-containing fluid (112). [10] The method (200b, 200c) according to claim 9, wherein determining the characteristic size of the particle-containing fluid (112) comprises: Generating at least one image (106b) of the spatial region (122) by means of the optical system (106), wherein particles (112p) of the particle-containing fluid (112) which are irradiated in the spatial region (122) by means of the electromagnetic radiation (114) of the measuring radiation source (104) are imaged in the at least one generated image (106b); and Determining the characteristic size of the particle-containing fluid (112) based on the particles (116p) depicted in the at least one image (106b). [11] The method (200b, 200c) according to claim 10, wherein the characteristic quantity is at least one of the following characteristic quantities: a particle number in the spatial area (122), a particle concentration in the spatial area (122), a flow velocity of the particle-containing fluid (112), a size of at least one particle (112p) of the particle-containing fluid (112), a shape of at least one particle (112p) of the particle-containing fluid (112), a trajectory of at least one particle (112p) of the particle-containing fluid (112) in the fluid guide (102). [12] The method (200a, 200b, 200c) according to one of claims 8 to 11, wherein the optical system (106) comprises or is a camera, preferably a charge-coupled device camera. [13] The method (200a, 200b, 200c) according to any one of claims 8 to 12, wherein setting up the optical system (106) comprises: Aligning an object plane (411) of the optical system (106) with the focusing aid (300) such that the focusing aid (300) is imaged in partial or complete focus by means of the optical system (106). [14] The method (200a, 200b, 200c) according to any one of claims 8 to 13, wherein setting up the optical system (106) comprises: imaging the contrast pattern (300m) of the focusing aid (300) by means of the optical system (106) in at least one image (106b); Determining at least one parameter which characterizes an actual image of the contrast pattern (300m) in the at least one image (106b); Determining at least one reference parameter which represents a desired image of the contrast pattern (300m) in the at least one image (106b); and Determining at least one image correction parameter based on a deviation of the at least one parameter from the at least one reference parameter. [15] The method (200a, 200b, 200c) according to claim 14, further comprising: Generating at least one corrected image (500r) of at least one image (106b) generated by the optical system (106) based on the at least one image correction parameter, and Using the at least one corrected image (500r) to determine the characteristic size of the particle-containing fluid (112) based on the particles (116p) represented in the at least one corrected image (500r).

Images