WO2006136147A2

WO2006136147A2 - Device for particle detection in a diffuser with a limited depth

Info

Publication number: WO2006136147A2
Application number: PCT/DE2006/001073
Authority: WO
Inventors: Jan Schulz
Original assignee: Stiftung Alfred-Wegener-Institut Für Polar- Und Meeresforschung
Priority date: 2005-06-19
Filing date: 2006-06-18
Publication date: 2006-12-28
Also published as: DE102005028893B4; DE102005028893A1; WO2006136147A3

Abstract

Known devices for detecting particles in an optically limited measuring volume operate either according to the scattered light principle or use an imaging video camera that only resolves two-dimensional surfaces. The depth dimension of the measuring volume remains unconsidered. The inventive device is embodied as a mobile or fixed plankton video recorder for counting and identifying plankton in marine waters. To this end, the optically limited measuring volume (MV) is embodied as a three-dimensional diffuser (LS), the depth thereof being limited by a linear light source (LQ), and the thickness (d) thereof being determined by rectangular aperture diaphragms (AB1, AB2) in the diaphragm system, and rod lenses (SL1, SL2, SL3) in the focussing lens system (LN). The rectangular aperture diaphragms (AB1, AB2) and rod lenses (SL1, SL2, SL3) are arranged in such a way that the axes thereof are congruent with the axis of the linear light source (LQ), and the focussing line (FL) of the rod lenses (SL1, SL2, SL3) lies in front of the measuring volume (MV). A video camera (VK) used as a recording system (AS) is arranged orthogonally in relation to the diffuser (LS). The depth of the focussing range of the video camera (VK) is determined by direct illumination. The illuminated particles are only to be seen in the illuminated measuring volume.

Description

Device for particle detection in a depth-limited lens

description

The invention relates to a device for particle detection in a flowing fluid in an optically limited measurement volume with an illumination device comprising a light source, a diaphragm system and a focusing lens system and with an optical evaluation unit with further diaphragms and lenses and a recording system aligned with the measurement volume.

A central goal of marine ecology is the understanding of the distribution of planktonic organisms in the ocean and their regulatory processes. Of particular interest here are abundance and diversity of small plankers, which represent one of the largest sources of animal protein in the sea due to their numbers of individuals. This gives them an important role in the biological material circulation system. The unexplained impact of anthropogenic and climatic changes on marine ecosystems has been the focus of attention in recent years and decades

Science advised. It is now widely accepted that the abundance and diversity of various planktonic organisms are correlated, inter alia, with the physical parameters of the environment. The hydrodynamic processes in the water body can lead to both a dispersion of Plankter as well as to increased occurrence. These regulating processes of zooplankton distribution in time and space are central to understanding relationships with biotic and abiotic changes and to making statements about the ecosystem. For this purpose, methods are needed to dissolve these distributions over a large area on spatially and temporally small scales. The traditional method of sampling with nets is very time consuming and allows only one limited resolution in the small scale range. For this reason, a number of new methods and approaches have been developed in the past to expand the understanding of systemic ecology. In addition to the acoustic, the field of imaging techniques is of particular interest. The devices used here are referred to as VPR video plankton recorders, and they also provide the advantage of being able to study in situ fragile species, such as gelatinous plankton, and obtain information about the biology of these agents using classical methods during the sampling process, images of these species in the natural habitat allow conclusions about behavior, distribution and interactions.

State of the art

From the prior art, various VPRs for a mobile towing operation are known. The VPR of the company SEASCAN, Inc. Falmouth, MA, USA, for example, from the publication I "Autonomous Vertically Profiling Plankton Observatory" (Coastal Ocean Institute WHOI, available from the Internet at the web address http://4dgeo.whoi.edu/ vpr / vpr_overview.html, as of 08.06.2005), the publication "Video Plankton Recorder on CTD" (NOAA Arctic Research Office, available on the Internet at the web address http://www.arctic.noaa.gov/aro/russian- american / cruisel O-ctd-rosette.htm, as of 08.06.2005) or from the Globec Newsletter Vol.8, no. 2, October 2002, pp. 20-21, under the publication of "Möllmann et al.," Video Plankton Recorder reveals environmental problems of marine copepod, which is towed behind a ship for profiling plankton detection with a video camera system The diaphragm and lens system used and the design of the light source are not known However, relatively complex and space-consuming construction promotes disturbances in operation and in handling and problems in the evaluation. In addition, the device can not work independently without major effort or modifications stationary. A similar device from Canada is an optical plankton counter. However, this device does not provide images, but only measures particle size distributions, which can only be assigned to individual species with some uncertainty. Newer models use a laser light source for improved size resolution.

All known VPRs use punctiform light sources and individual spherical lenses for collimation. In the large scale range, strong halogen systems and Fresnel lenses are also used. However, the known devices have the problem that no sharp optical limit of the measuring volume can be generated and the depth of field in the measuring volume is adjusted by software, which in the small-scale range of

Plankton observation leads to high inaccuracies in volume estimation.

In the general field of particle detection, other various devices are known. From DD 232 552 A1 is a device for

Counting and classifying dispersed particles in liquids, e.g. Colors, with one of a measuring cell spatially limited measurement volume known. A laser beam is used to illuminate the measuring volume, whereby the beam focus lies in the middle of the measuring volume so that the detected measuring volume is reduced to one point. For detection, the

Scattered light intensity of each particle measured. It is assumed that the intensity of the scattered light at small angles is a function of the particle volume. The measuring volume is narrowed by the formation of the measuring cell so that there is always only one particle in the light focus, the scattering of which is measured in the laser light. The liquids are with a Injection syringe injected into the measuring chamber, a detection and

Determination of particles in a free flowing fluid is not possible with the known device. Furthermore, only relatively large particles can be detected, which can be singulated in the measuring cell. DD 221 861 A1 describes a lighting device for generating a two-dimensional light strip for pattern recognition and identification of workpieces in an industrial environment. For this purpose, a linear light source is used whose rays are directed through a louvre diaphragm and bundled by a cylindrical lens on the object to be detected. In contrast, a sharp black-and-white image of the respective illuminated strip is generated and analyzed by contrast adjustment in the recording system. A reflector can be mounted behind the light source for a higher light output. The objects are illuminated at an acute angle and the camera is located vertically above it. Quantity and type of parts can be determined depending on the resolution of the camera. To limit the viewing space, a solid background is required. Furthermore, from DE 298 13 109 U1 a lighting device for producing a long, narrow light band with two-dimensional expression is known in which the light of a number of lamps in a narrow housing with a first own and a second common lens to a narrow beam Focus is generated on a line of selectable distance. The light output corresponds approximately to the beam angle and is therefore very low. DE 197 36 172 B4 describes a device for analyzing particles dispersed in a flowing fluid, which works with diaphragms whose edges are curved in a hyperbolic manner and thus define a three-dimensional measuring volume with a known depth of field which is formed in a truncated cone with curved edges. In the associated method, particles with a defined transit time are evaluated in the measuring volume. The shape of the optically demarcated measurement volume allows particles of different speeds to be measured at a constant given transit time in the measurement volume take into account, whereby by the defined depth of focus, a three-dimensional measuring volume is detected by the detector. Preferably, particles with sizes in the micrometer range are considered. The illumination device is arranged parallel to the detector, the detection signal is deflected by a prism from the measurement volume.

Publication IV "Particle size distribution analysis by scattered light measurements using optically defined measuring volume" (H. Umhauer, J.Aerosol. Sci. Vol.14, No.6, 1983, pp. 765-770), of which the present invention As the closest prior art, describes a particle counter for flowing fluids on the principle of scattered light measurement of the particles to be solved in particular the Randzonenproblem that arises from particles that only partially detected at the edge of the measurement volume and consequently by the reduced scattered light than It is intended to determine particle distributions of solids in gases or liquids, but also of liquid droplets in gases and other liquids with very small dimensions in the micrometer range by means of particle separation and their serial detection. a shutter and lens system with circular dimensions for the optical definition of a three-dimensional measuring volume with cube-shaped dimensions in a flow channel. The focus of the light source is in the middle of the measurement volume, the goal of this focal position is the required separation of the particles for better scattered light detection, but this is not guaranteed, especially with the smallest particles. The detection takes place in an optical evaluation unit with further diaphragms and lenses and a recording system, wherein the evaluation unit is aligned in the form of a photomultikanalverstärkers parallel to the illumination device, so that there is a spatially compact design, and the optical Detection signal is detected by a 90 ° beam deflection from the measurement volume.

Task and solution according to the invention

Starting from the closest publication, the object of the present invention is to provide a device of the generic type described above, which reliably and accurately detects all particles occurring in a given measuring volume in a flowing fluid in real time. The device should be simple and robust design and handling even under adverse environmental conditions and allow flexible use. The solution according to the invention for this task can be found in the main claim. Advantageous developments of the device according to the invention are shown in the subclaims and are explained in more detail below in connection with the invention.

The device according to the invention is characterized in that the optically determined measurement volume is also limited in depth and is designed as a three-dimensional light disk which is deeply delimited by a linear light source and whose thickness is determined by rectangular aperture diaphragms and rod lenses. These are arranged on the same axis as the linear reflector lamp so that their longitudinal axes run parallel. The focus line of the rod lenses lies in front of the measurement volume. Focusing takes place deliberately outside the measuring volume, whereby uniform illumination of the measuring volume without light convergence or divergence is achieved. For example, if the focus line is set approximately 30 cm from the lens of a video camera as a recording system, a strip of approximately 0.5 cm should be placed in front of and behind the plane of the lens most sharply detected by the recording system be illuminated so that the lens has a total thickness of about 1 cm. Thicknesses between 0.5 cm and 3 cm are conceivable, the choice of thickness also depends on the type of particles to be detected. The widening of the beam path to the front is almost negligible or can be computationally well detected. The determination of the recorded measurement volume is of essential importance in order to provide a concentration indication of the measured water body with regard to the abundance and diversity of the planets in the corresponding area. The rod lenses may preferably be embodied as plano-convex or concave-convex rod lenses (or else cylindrical lenses), in particular with an aspherical design of the lens curvature, in order to achieve optimum linear focusing of the light beams emitted by the linear light source, which are linear in one plane but in the orthogonal plane spread out in a circle to reach.

The recording system of the device according to the invention is an orthogonal to the lens arranged video camera, which may be followed by a pattern recognition system. The device thus operates with an imaging system and does not use the principle of scattered light measurement for particle detection. When using a video camera as a recording system can be described on the resolution of only the two dimensions of orthogonal to the video camera oriented surface of the measuring volume. With a uniform illumination and appropriate lighting conditions, the picture thus has a theoretically infinite depth dimension. By specifying the lens with a defined depth limitation in the device according to the invention, the depth dimension is now determined exactly. The depth of the focus area for the recording system is thus resolved by direct illumination. Only particles in the illuminated measuring volume can be seen. Disturbances from outside the measuring volume are minimal and can be tolerated become. This represents a method in underwater measurement, which is used in this form so far of any optical plankton recorder.

Thus, a device is provided with the device according to the invention, for example, as a video plankton recorder (VPR) video and still images of planktem in natural environment in a visually narrow and well-defined measurement volume, for example, of about 4 cm ³ size, can absorb in flowing relative to the device water, which can then be reliably evaluated by the evaluation. But there are also other applications with the requirement of particle detection, for example in clarifiers or in chemical columns, possible. The range of uses is very broad. The fast, high-resolution image acquisition and storage with the aid of an evaluation software enables particle counting as well as particle identification, for example for recognizing important plankton species. In combination with relevant ship data such as position, speed and time as well as other locally measured, in particular hydrographic environmental parameters, a three-dimensional image of the plankton distribution can thus be determined relatively quickly. Thus, with the device according to the invention, an intelligent scientific system is created that can be used worldwide by research institutes, environmental organizations and environmental authorities. Due to the compact design of the device as VPR this can be used both as a towed device in ship missions, but also as anchorable or permanently mountable unit for a stationary operation and make continuous recordings of a defined volume of the water column. In this case, the low power consumption caused by the components used is favorable, since thereby an autonomous use of the VPR in stationary operation is possible. The planters contained in the water column are cut out of the total images as regions of interest (ROI) of interest, with the local physical ones Parameters associated and classified by the pattern recognition system as part of the evaluation. Contrary to the traditional plankton sampling, the device according to the invention is characterized by a significantly lower processing cost of the data obtained and allows easy-to-obtain, high-resolution and large-scale time series studies. By being able to connect environmental sensors such as salinity, depth, temperature, fluorescence or oxygen probes to the device according to the invention, environmental parameters are associated with each captured image. As a result, each planktic representative is also assigned the physical parameters of his direct environment. An investigation of the correlation of occurrence with hydrographic phenomena such as fronts, klines, etc., is thereby realized. The device according to the invention thus offers the possibility of determining the abundance and diversity of individual planktonic organisms groups on a small scale. In addition to the high spatial resolution of the vertical distribution on the centimeter scale, zooplankton variabilities can also be quantified quickly at a corresponding sampling frequency on small time scales. The resulting data should help to complete the understanding of biological-physical relationships, provide new in-situ insights into the ecology of individual organisms, and provide an important contribution to other time-series studies.

The VPR can open up new possibilities in plankton research, which are not provided in this way by any other plankton recorder system. Particular emphasis is placed on modularity and scalability so that individual components are easy to modify and allow for refinement even after construction. In general, the VPR can be used wherever determining the abundance and diversity of plankton is of interest. There is no limit to whether it is estimates for food chain analyzes or annuell Clarification of variability, the daily vertical migration, the

Colonization succession or emergence of meroplanktischen larvae. In all cases, the occurrence can be recorded with the physical parameters. An increase in pressure stability far beyond the 100 bar limit also opens up the possibility of penetrating not only the neritic but also far into the depths of the oceanic province, which has so far been predominantly sampled by classical methods and thus represents completely new territory for VPR systems. In the case of use in an anchorage, a continuous sampling can be carried out in near real time, which is possible without further effort. After the installation and the securing of the energy supply, as well as the data transmission, a multitude of questions could be dealt with with this VPR, without the need for time-consuming sampling with ships, nets and a large number of persons depending on the weather. Questions about meroplanktischen larvae can be processed in more detail by the small-scale plankton consideration in the water body.

Because each focus on a very small measurement volume, it is crucial to make a high number of video recordings in a short period of time. With a measuring volume of eg 10x10x10 mm 1000 images are needed until a water volume of one liter is equivalent sampled. At a hypothetical frequency of 24 frames per second, about 42 s pass. Between two images, it must be ensured that the measuring volume is 100% exchanged. If this is not the case, there is the possibility that a planter appears on two images and falsifies the statistics. Of greater importance than in the shelf area, this can be in the open ocean, where the average abundance of individual species is extremely low. Accordingly, the relative distance between two images must correspond at least to the diagonal (maximum value when incident parallel to the illumination) of the recorded image of the camera. in the Example 14.1 mm. At 24 frames per second, corresponding to 339.4 mm / s =

0,3394 m / s = 1, 222 km / h = 0,65 Kn. The speed of 0.65 knots can be provided relatively safely in operation mode aboard a ship. For fixed moorings, however, care must be taken to ensure that this flow velocity is also ensured.

The individual planks which enter the lens and simultaneously into the field of view of the video camera are detected by a CCD video camera in a normal recording cycle. To keep motion artifacts small, the video camera requires a very short exposure time as well as a

Triggering with a shutter during stroboscopic use. A telephoto or macro lens is set in front of the video camera with the help of extender rings, which ensures a resolution of about 10 μm per pixel. The quality of the images is influenced by other parameters such as suspended matter and the like. To keep the quality of the statement high relative to the spatial scale, the video camera must have a high resolution (e.g., 2000 x 2000 pixels corresponding to 20 x 20 mm). A plankter of 2 x 1.5 mm would deliver uncompressed at 8-bit color depth corresponding to 200 x 150 x 8 "30 kBit of pure image information. The magnification level should be as constant as possible in order to always provide the same parameters for the evaluation. The accuracy of the abundance calculations increases with the sampled volume per time and thus also with a higher resolution, which increases the scanned volume per image at the same μm / pixel value.

An evaluation module ensures the ROI extraction and the linkage with the parameters and can take place on a computer in the underwater unit. The data can then be sent, for example, online via the Internet or LAN to another computer in the network or on board, which performs the evaluation, if possible in real time. It is expected that on every second to eighth image organisms and particles occur. Attention must be paid to the Fact that individual structures may not always appear coherent (see below). In some areas, however, the number of ROIs per recording can increase significantly. The ROIs are stored along with metadata such as cruise name, date, time, latitude, longitude, and physical parameters such as CTD data and water volume. In the event that the energy supply is interrupted unexpectedly, it must be ensured that the data collected so far are preserved. For the same reason, in this case, as in all other follow-up modules, a high system stability is to be ensured. The pictures must be stored unchanged, so that a later

Evaluation of other factors, such as alignment of the organisms (e.g., overwintering stages at klines) and the like is possible.

In one embodiment of the device according to the invention, referred to below as VPR for short, two rectangular aperture diaphragms may be provided, wherein the second rectangular aperture diaphragm is narrower than the first rectangular aperture diaphragm and the focus line lies between the two rectangular aperture diaphragms. The rectangular panels together with the rod lenses ensure the rectangular appearance of the lens. As a result of the rectangular aperture diaphragms becoming smaller in the direction of the measuring volume, an increase in the illuminance in the direction of the measuring volume is achieved in the sense of concentration. A rectangular field of view aperture arranged in the region of the focal line with respect to the axis ensures reliable suppression of stray light in the part of the water body outside the illuminated measuring volume and thus for improved video detection of the particles. To achieve a special compactness of the VPR, the recording system can furthermore be aligned parallel to the illumination device, with the lens then being deflected at right angles via a 90 ° beam deflection in order to ensure that the recording direction of the Video camera stands orthogonally on the lens. For other applications, other deflection, multiple deflections or a design without deflection may be considered. It is important only that the recording axis is aligned perpendicular to the lens.

For optimal illumination of the lens, it is also advantageous if the linear light source has an emission angle of less than 70 ° and a maximum light output. This can be achieved if the linear light source is designed as a reflector lamp, which has a combined reflector of an elliptically extended and a spherically extended mirror with a central aperture and arranged in the focal line of the reflector, linear lighting means. This may be, for example, a strong flash / halogen / xenon lamp or a high-efficiency LED field, in particular in the embodiment as a series of several adjacent light-emitting diodes. In this case, the reflector may have reflector regions assigned to the individual light-emitting diodes. By using a plurality of aligned light-emitting diodes in the focal line of the first rod lens, a higher overall light output is achieved because it is not focused as in spherical lenses from two spatial directions punctiform on a focal point, but only from one direction. As a result, each point within the lens (except for the edge areas) is illuminated by several neighboring LEDs. It is advantageous here that particles which are illuminated in the lens have only a reduced shadow and thus do not distort the detection.

The light beams are combined via the optical aperture and diaphragm structure, directed, deflected and projected into the water as a light band parallel to the trailing or Fierrichtung. The first panel determines the width of the lens. An advantage of this lighting method is that not the entire body of water is illuminated and thus Background noise is reduced during recording. About the

Adjusting the aperture (0.5 - 3.0 cm), the width of the lens can be varied, to which the video camera is directed at right angles. The contrast and iris settings can be used to hide as much as possible organisms that are in front of or behind the illuminated measurement volume. The captured volume of water can be determined via the section of the video camera recorded horizontally and vertically in the surface and the thickness of the lens as a depth limit.

Another modification of the VPR provides that at least the light source and the video camera are arranged in a pressure-resistant and aerodynamically shaped housing. Furthermore, the rectangular aperture stops, the rectangular field stop and the rod lenses can be arranged in the housing, wherein this on its inside a

Has mirroring. An aspired flat design of the VPR makes it possible to design the housing as streamlined as possible. The VPR is therefore a device which, due to its design, builds up a low dynamic pressure. This prevents small planks from being washed around the sampling site and avoiding the evaluation. On the other hand, the number of less abundant species is sometimes underestimated by the method of sampling or they are not recorded at all. To prevent this, a high sampling rate must be achieved as well as an exact determination of the measuring volume. It must be as undisturbed as possible at the moment of recording. The VPR must be oriented in the direction of the tow or furrow so that turbulence and dynamic pressure are kept as low as possible. Finally, the individual environmental probes must be located near the focus area of the video camera, or on the same horizontal plane. The mirroring on the inside of the housing can also light be captured outside the central axis by multiple reflection and directed to the measurement volume, resulting in an increase in intensity of the light. Finally, in a further modification, the linear reflector lamp, the rectangular aperture diaphragms, the rectangular face panel diaphragm and the rod lenses can be connected to one another via the four side edges of a cuboid forming threaded rods and arranged to be adjustable. This results in a compact design with a good stabilization by the threaded rods, which serve simultaneously the parallel adjustment and fixation of the individual panels and rod lenses. Further structural details of the device according to the invention can be found in the following special description part.

embodiments

Embodiments of the device according to the invention are explained in more detail below for their further understanding with reference to the schematic figures. It shows

Figure 1 shows an embodiment as VPR in the side view in

Longitudinal section, Figure 2 shows an embodiment as VPR in the plan view with a

silvering,

Figure 3 shows an embodiment as VPR in the perspective side view without housing and

4 shows the illumination device with a linear

Reflector lamp in plan view.

In Figure 1, the device in the embodiment of a video plankton recorder VPR is shown in which a lighting device BE and an evaluation AW in a pressure-resistant housing DG with two pressure-tight in the housing wall fitted windows FE1, FE2 are arranged. Such a video plankton recorder can also be aptly called "Lightframe On-Sight Keyspecies Investigation" with the acronym "LOKI". The optical illumination device BE behind the window FE1 comprises a linear light source LQ and two rod lenses SL1, SL2 of a focusing lens system LN. In this case, the rod lenses SL1, SL2 in the selected exemplary embodiment are plano-convexly formed with an aspherical lens curvature. To the evaluation unit AW behind the window FE2 includes a video camera VK as a recording system AS and other screens and lenses and means for data processing, such as a pattern recognition system, and storage, but not shown in Figure 1. The rod lenses used SL1, SL2 are commercially available components. The focal lengths are selected to be high at 8 cm and 6 cm in the exemplary embodiment in order to ensure flat angles with respect to the optical axis of the video plankton recorder VPR, which reduces aberrations. Suitable are rod lenses made of glass with a higher refractive index (glass type SF6). The option to use the rod lens SL1 with more than 3 cm height is eliminated because the focus line FL moves farther away from the rod lens SL1, because with a required higher rounding of the convex side physical limitations according to the formula: Cylinder radius = focal length x (Refractive index - 1) is subject. In addition, this would make the angle between the perpendicular on the plane lens side and the deviation of the light beam LT from the optical axis in the edge region too large, which would also reduce the light intensity.

The video plankton recorder VPR generates for particle detection in a flowing fluid, an optically limited measurement volume MV, which is designed as a thin, depth-limited lens LS. The measuring volume MV is flowed through freely by the water, the flow direction is perpendicular to Drawing level, so that the measuring volume MV continuously fills and empties and always new volumes of water can be detected. The flameproof housing DG can be provided streamlined in the flow direction, so that no disturbing the detection results vortex arise in the flow through the water. The lens LS is generated by the light source LQ whose light beam LT is parallelized by means of the first rod lens SL1 and focused by the second rod lens SL2 on a focus line FL. In this case, due to the linear light source LQ used linear focus line FL is outside the flameproof housing DG and in front of the lens LS. The width B1 of the light beam LT is set by a first rectangular aperture stop AB1 in the pressure-resistant housing DG, which is arranged between the two rod lenses SL1, SL2. Behind the focus line FL, the focused light beam LT is parallelized again outside the pressure-resistant housing DG by a third rod lens SL3, which likewise has a plano-convex design with an aspherical lens curvature in the selected exemplary embodiment. At the same time, a second rectangular aperture diaphragm AB2 behind the focus line FL outside the pressure-resistant housing DG, which is narrower than the first rectangular aperture diaphragm AB1, intensifies the intensity of the light beam LT by narrowing the light beam LT to a width B2, through which the Thickness d of the lens LS is set as the depth limit of the measuring volume MV. In the area of the focus line FL, a rectangular field stop GB is arranged on the axis congruent to reduce scattered light. Behind the second rectangular aperture AB2 a deflecting mirror US is arranged, which deflects the concentrated light beam at right angles. Thus, the light beam enters the recording light beam AF of the video camera VK, which is bounded by a further diaphragm WB and is perpendicular to the light beam LT, so that the width B2 of the light beam LT now corresponds to the thickness d of the lens LS. All of these components are slidably mounted on threaded rods GS, thus they can in their distance from each other set and then fixed. The described arrangement and equipment of the illustrated video plankton recorder VPR with lenses and diaphragms is only an example and may, if necessary, look different.

FIG. 2 shows a top plan view of a video plankton recorder VPR in which all components are arranged in a pressure-resistant housing DG (reference numerals not explained here, see FIG. 1). In order to increase the luminous efficiency, in this embodiment variant, a reflective coating VS is provided on the inside of the pressure-resistant housing DG. Shown is an exemplary beam path along the optical axis of the system.

FIG. 3 shows a perspective side view of the video plankton recorder VPR without pressure-resistant housing DG. The linear

Light source LQ consists of a series of individual light-emitting diodes LED, which are surrounded by a common rectangular reflector RF. Light emitting diode LEDs are commercially available on the market - even with a beam angle of 70 ° or less - bright and durable (3 W - 5 W, 100,000 operating hours). In this case, the reflector RF the individual

Light emitting diode LED associated reflector areas RB on. These reflector regions RB can have an expression, as will be explained in more detail in FIG. At the four corners of the reflector RF a threaded rod GS is provided in each case. Between the four threaded rods GS, the optical components of the video plankton recorder VPR are stored and fixed (reference numerals not explained here, see FIG. 1). In this case, the support frame TR are all the same for the components with one exception. The exception is the support frame TR for the deflection mirror US, which lacks a longitudinal frame section. The existing longitudinal frame section LA has a 45 ° bevel, in which the deflection mirror US, which is larger than the support frame TR, can be inserted.

FIG. 4 shows a linear light source LQ as a linear reflector light RL with a combined reflector KR with a central aperture ZA. The combined reflector KR has an elliptical mirror SE in the form of an expanded rotational ellipsoid RE and a spherical mirror SS in the form of an extended spherical shell KS. The linear light source LQ is arranged in the first focal line BL1 of the elliptical mirror SE. The spherical mirror SS is also arranged with its center line in the first focal line BL1 of the elliptical mirror SE, its central aperture ZA is located exactly in the second focal line BL2 of the elliptical mirror SE. The luminous efficacy of such combined reflectors KR is particularly high, since all light rays that do not exit directly through the central aperture ZA are reflected by the spherical mirror S2 onto the elliptical mirror SE and are reflected from there to the central aperture ZA. Only in the edge regions of a linearly extended combined reflector KR occur losses.

LIST OF REFERENCE NUMBERS

AB rectangular aperture stop

AF recording beam

AS recording system

AW evaluation unit

B Width of the light beam

BE lighting device

BL focal line d thickness of the lens

DG flameproof housing

FE window

FL focus line

GB rectangular field of view

GS threaded rod

KR combined reflector

KS ball cup

LA longitudinal frame section

LED light emitting diode

LN lens system

LQ linear light source

LS lens

LT light beam

MV optically limited measuring volume

RB reflector area

RE rotational ellipsoid

RF rectangular reflector

RL reflector lamp

SE elliptical mirror

SL rod lens SS spherical mirror

TR supporting frame

US deflecting mirror

VK video camera

VPR Video Plankton Recorder

VS mirroring

WB more aperture

ZA central aperture

Claims

claims

1. Device for particle detection in a flowing fluid in an optically limited measurement volume with an illumination device comprising a light source, a diaphragm system and a focusing lens system and with an optical evaluation unit with further diaphragms and lenses and a recording system aligned with the measurement volume, characterized in that optically limited measurement volume (MV) as a three-dimensional, of a linear light source (LQ) depth-limited lens (LS) is formed whose thickness (d) by rectangular aperture (AB1, AB2) in the diaphragm system and rod lenses (SL1, SL2, SL3) in focusing Lens system (LN) is fixed, wherein the rectangular aperture (AB1, AB2) and rod lenses (SL1, SL2, SL3) are arranged on the axis congruent to the linear light source (LQ) and the focus line (FL) of the rod lenses (SL1, SL2, SL3) in front of the measurement volume (MV), and that the recording system (AS) is orthogonal to the lens (LS) a subordinate video camera (VK) is.

2. Apparatus according to claim 1, characterized in that the rod lenses (SL1, SL2, SL3) are formed plano-convex or concave-convex.

3. A device according to claim 2, characterized in that the lens curvature is formed aspherical.

4. Device according to one of claims 1 to 3, characterized in that the receiving system (AS) comprises a pattern recognition system.

5. Device according to one of claims 1 to 4, characterized in that two rectangular aperture diaphragms (AB1, AB2) are provided, wherein the second rectangular aperture diaphragm (AB2) is narrower than the first rectangular aperture diaphragm (AB1) and the focus line (FL ) lies between the two rectangular aperture stops (AB1, AB2).

6. Device according to one of claims 1 to 5, characterized in that in the region of the focus line (FL) achsenkongruent to a rectangular field stop (GB) is arranged.

7. Device according to one of claims 1 to 6, characterized in that the receiving system (AS) aligned parallel to the illumination device (BE) and the lens (LS) via a 90 ° beam deflection (US) is deflected at right angles.

8. Device according to one of claims 1 to 7, characterized in that the linear light source (LQ) has a radiation angle of less than 70 ° and a maximum light output.

9. The device according to claim 8, characterized in that the linear light source (LQ) is designed as a reflector lamp (RL) comprising a combined reflector (KR) of an elliptical mirror (SE) and a spherical mirror (SS) with a central aperture (ZA), where the linear Light source (LQ) in the focal line (BL1) of the elliptical mirror (SE) is arranged.

10. The device according to claim 9, characterized in that the linear light source (LQ) as a series of a plurality of adjacent light emitting diodes (LED) is formed and the combined reflector (KR) the individual light-emitting diodes (LED) associated reflector areas (RB).

11. Device according to one of claims 1 to 10, characterized in that at least the linear light source (LQ) and the video camera (VK) are arranged in a pressure-resistant and aerodynamically shaped housing (DG).

12. Device according to one of claims 1 to 11, characterized in that the rectangular aperture diaphragms (AB1, AB2), the rectangular field of view diaphragm (GB) and the rod lenses (SL1, SL2, SL3) in the pressure-resistant housing (DG) are arranged , which has on its inside a mirror coating (VS).

13. Device according to one of claims 1 to 12, characterized in that the linear light source (LQ) _1, the rectangular aperture (AB1, AB2), the rectangular field stop (GB) and the rod lenses (SL1, SL2, SL3) on the four Side edges of a cuboid forming threaded rods (GS) connected to each other and arranged to be adjustable.