DE3930642C2 - Highly sensitive particle size detector with noise suppression - Google Patents

Description

The invention relates to a particle measuring device for the detection of parts size, in particular for the detection of particle sizes using of light scattering.

Devices for determining particle sizes are generally known and also that laser beams can be used to target particles size measurements. See, for example, U.S. Patent No. 3,406,289. Au In addition, US Pat. No. 4,571,079 describes and describes a particle size measurement an open cavity laser (active) and U.S. Patent 4,594,715 a measurement with passive cavity; both patents became the current applicant Splits.

So far there has been a linear array of detectors along with parallel Processing of the electrical signals used by each detector Data acquisition can be generated. See, for example, U.S. Patent 3,941,982 to current applicant.

In DE 37 12 665 A1, which represents the closest prior art represents, a particle measuring device for particle size detection is described with a first device which enables a particle-containing Me dium is guided through a certain measuring range, and a second device device, which illuminates the measuring range, so that the particles in the measuring range Cause light scattering, the particle measuring device following components comprises: a detector field which receives the light scattered in the measuring range and detected and has a plurality of detector elements which are arranged such that certain detector elements that of certain sections of the measuring range Scattered light received, the certain sections of the measuring range too are arranged away from each other and each detector element is a noisy one Output signal that the detected light emitted by the particles in be agreed section of the measuring range has been scattered, contains, as well as a Processor.

Known particle measuring devices have so far been used for various purposes used, including determining the presence or size of part  in various gases, including air. With special regard to air carried particles made tolerance limits and the effects of the Verunreini Macroparticles from the environment require an effective treatment cleaning control to introduce the manufacture of many now used Allow devices. In particular, for example, the precision Manufacture of microelectronic systems largely through development and the use of dust-free cleanrooms.

For many years, the dust-free clean rooms were class 100 or class 1000 more than sufficient for practically all electronic devices used chatting. However, when the current generation of microcomputers was introduced the need for microelectronic components such as memory chips from large capacity, the development of devices during manufacture are extremely susceptible to contamination.

Macro particle contamination during manufacture Devices causes the yield of usable products very min is changed. Depending on their nature, the contaminating particles can, for example affect the completeness of lithographic images or depending on their Nature to open or short-circuited circuits and spoiled districts to lead. Now, manufacturing microchips seems the most critical job to be in the electronic manufacturing industry by contamination by Macro particle is disturbed.

The semiconductor industry for VLSI (Very Large Scale Integrated Circuit = very highly integrated ICs) also has the state of the art in counters for air particles driven forward, which are used to test dust-free cleanrooms. The need for much stricter clean room classes arises from the requirements of the manufacturers of VLSI circuits and improvements in the fil that reach much smaller levels of contamination.

Most known aerosol meters have a sample throughput of 0.028 m ³ / min (one cubic foot / min (cfm)). However, to get useful statistical values in the class 1 range, many cubic meters of air must be collected for the sample if the sensitivity is limited to 0.5 microns (0.5 × 10 ^-6 m). As the number of particles increases with decreasing size, most manufacturers of air particle counters decided to determine the size of smaller particles in order to be able to develop the correct statistical base more easily.

For example, the distribution of the average particle size in a dust-free clean room at 0.1 × 10 ^-6 m is almost a hundred times the particle counts at <0.1 × 10 ^-6 m compared to counts at <0.5 × 10 ^-6 m . The more sensitive the particle counter is, the less time is required for the certification of the clean room class.

In addition, the manufacturers produce devices whose shape design has structures that are smaller than 0.5 × 10 ^-6 m. In addition to generating a statistical basis in a very short time, a higher sensitivity gives better information about the particle size for possibly defective devices.

With the introduction of lasers, the size measurement of particles up to 0.1 × 10 ^-6 m via light scattering became easy, since the entire energy of the laser beams can be bundled with high intensity to a small size. Various devices now on the market provide a sensitivity of 0.1 × 10 ^-6 m, but none of them can collect samples with a throughput of 0.028 m ³ / min (1 cfm). In most cases, with a sensitivity of 0.1 × 10 ^-6 m, only a throughput below 0.0028 m ³ / min (0.1 cfm) can be achieved.

For various processes, the manufacturers of semiconductors also need gases of high purity with low contaminants with macro particles. This is necessary in order to be able to carry out the measurements at line pressure (often up to 1 × 10 ⁶ Pa (150 PSI)). Some of these gases are also high molecular weight gases that scatter light more than air (e.g. a mixture mainly of oxygen and nitrogen), so the molecular scatter must be reduced even if flow rates are less than 0.028 m ³ / min (1 cfm) are sufficient.

The possible statistical advantage with a smaller particle size is thus in High molecular scatter environments partially lost.

It is an object of the present invention to provide a particle measuring device To create particle size detection, even in applications with high moles Specular scattering achieved high sensitivity.

This object is achieved by the invention defined in claim 1. Advantageous further developments are characterized in the subclaims.

The invention provides noise suppression in a particle detector, especially high sensitivity noise suppression in an environment with strong molecular scattering.

Background noise due to molecular scatter is reduced, with the noise reduction is effected by several linear detectors, one of which each scans a section of the entire measuring range that at the intersection of the Flow path of a mixture of gas and particles as well as a laser beam is ordered and an electrical output signal for the sampled or measured NEN particles generated, the output signals of the detectors with the off output signals of those detectors which are not adjacent sections of the Monitor measuring range, be processed in parallel by using noise suppressors are combined.

The drawings show a complete embodiment of the invention according to the best kind so far for the practical application of the basics of Invention was developed:

. Figure 1 shows a distribution curve for particle sizes after the classifi cation system and the areas of the size concentration, as published currently in U.S. Federal Standard 209 (FS209);

Fig. 2 is a representation of a distribution curve for particle sizes after the proposed revision of FS209;

Fig. 3 is an illustration showing a distribution curve of particle sizes, which clear the data in the Istzählung currently built dust-free pressure for the semiconductor production of very highly integrated IC's (VLSI);

4A is a partial schematic view showing the cross section of a circular flow, which serves to build up a measurement range.

Figure 4B is a partial schematic view showing a rectangular-shaped flow cross-section which serves to build up a measurement range.

Figure 5 is a schematic representation of a simplified Seitenschnit tes a particle size measuring device with an open cavity laser, the invention being used with this;

Fig. 6 is a simplified side elevation showing the arrangement of the detector unit for monitoring the measuring range via an image device or an imager according to an embodiment of the invention;

Fig. 7 is a simplified electronic block diagram showing the electronic signal processing according to an embodiment of the invention;

FIG. 8 is a simplified block diagram showing the use according to an embodiment of the invention of the noise reduction circuit in connection with the parallel processing device of FIG. 7;

Fig. 9 is a simplified electronic diagram illustrating the cancellation circuit of Fig. 8.

Current particle control in electronic manufacturing rooms is based primarily on the application of US Federal Standard 209 (FS209), VDI 2083 or similar standards. Fig. 1 shows the current classification system and the size concentration ranges used in FS209. The left vertical column of FIG. 1 (as well as FIGS . 2 and 3) shows the total amount of particles / cubic feet which, as shown, are equal to or larger than the specified particle size. Counts below 10 particles / cubic foot (0.35 part chen / l) are unreliable (and therefore shown in dashed lines), except for a large number of samples. The smallest particle that has to be measured has a diameter of 0.5 µ, the maximum prescribed purity level being 100 particles / cubic foot.

However, these standards for dust-free cleanrooms have existed for several years and the current requirements for electronic products showed that the detected level for an appropriate production of microelectronic devices  directions is unsatisfactory because of the requirements of particle control have become stricter now. The need for revised definitions of the Levels of contamination by particles are thus evident and therefore will be Plans developed to modify FS209 to take measurements on smaller particles and to be able to perform cleaner levels.

Although a revision of FS209 is now being carried out under the leadership of the Institute of Environmental Science, this revision has not yet been completed. One of the main objectives of this revision is to define a room or area, the level or level of cleanliness of the air at the level of class 10 , and to enable the measurement of particles smaller than 0.5 µ in diameter to adequately to get statistical definitions at the lower levels. Standards expected to be used in other industrialized countries are also expected to be revised soon, and the FS209 revision is only the first in a series of new standards. In fact, class 1 levels can currently be reached and must also be included in the near future.

Since the particle concentration increases sharply as the particle size decreases, the recommendation of measurements of smaller particles seems to be expedient. Therefore, the plans for the revised FS209 include measurements of 0.3 × 10 ^-6 m and for clean rooms 0.1 × 10 ^-6 m. Fig. 2 shows the currently planned classification format, which allows measurements of sizes below 0.5 × 10 ^-6 m. However, it should be noted that the slope of the classification curves of FIG. 2 is based on the slope of the current FS209.

A change in the slope of the classification curves is contemplated based on newer data obtained in less dust-free VSLI rooms in the United States. A laser counter was used for measurements from 0.1 × 10 ^-6 m upwards; the data are shown in FIG. 3. It appears that the particle size distribution in dust-free cleanrooms has a much steeper increase below 0.1 × 10 ^-6 m than would be expected from the current classification curves according to FS209, with one more possibility to interpret the increase even steeper than in Fig. 3.

If the classification ^{curves are} extended in the size range of 0.1 × 10 ^-6 m, the time and effort required to obtain valid data for rooms of class 100 and better are reduced, regardless of whether FS209 is simply extra-polished or according to the newer data is revised according to FIG. 3.

The development of a device that has a sensitivity of 0.1 µm in in an environment with high molecular scattering, as by the Erfin was not easy to achieve. With a view to reverse Exercise with molecular scattering due to high throughputs of up to or more than one Cubic feet / min are relatively large flow cross-sections due to the sensitive volume an optical measuring device required.

Even at the speed of sound, it is impossible to achieve a cross-section of 1.8 mm ² and full speed of sound through conventional vacuum layers. Thus, the more normal flow velocities are 1/3 to ½ the speed of sound, and the flow cross-sections are increased to 4 to 5 mm ² at 0.028 m ³ / min (1 cfm) in normal instruments. This large flow cross-section must be illuminated evenly if the particles are to be measured exactly in size.

Thus, the illuminated area cannot be near a narrowly focused area of a laser beam, but usually must be arranged in an elongated laser beam if the flow cross-section is circular as in Fig. 4A or if it extends along the beam axis if the flow cross-section according to FIG. 4B is designed rectangular. Therefore, the best possible construction, as used in the invention, has a flow cross section of 1 × 10 mm ² , and the converging lenses are designed like those of US Pat. Nos. 4,571,079 and 4,594,715.

The laser beam itself must generate approximately 1 W of power within the measuring range in order to achieve a sensitivity of 0.1 × 10 ^-6 m. A HeNe laser resonator at 633 nm is the most convenient method to generate the required power, although any 1 W light laser can be used (e.g., argon ion laser). Since light sources can be developed that provide a sufficient energy density to measure small particles such as 0.1 × 10 ^-6 m and allow cross sections for 1 cfm, the problem appears to be easily solvable.

This would be the case if the particles were the only source of light scattering in the measuring range. Scattered light can be effectively excluded by careful construction. However, there are inevitably approximately 10 ¹⁶ air molecules / mm ³ that accompany the airborne particles as they pass the laser beam. Calculations show that such an air volume scatters over 100 times more energy than a normal particle with 0.1 × 10 ^-6 m dimensions (see RG Knollenberg: "The Measurement of Particle Sizes Below 0.1 Micrometers", in The Journal of Environmental Sciences, January-February 1985). This large accumulation of molecular scattering media is always present, where this signal source mainly provides a constant component.

However, there are also fluctuations (alternating components) in the molecular scatter signal (alternating component noise), which cover the desired particle signal at 0.1 × 10 ^-6 m. The noise itself is proportional to the molecular stray DC signal. However, the noise is higher for laser sources than calculated from Shott's noise assumption, and the laser cavity is easily statically modulated by gas flow (creating noise). In such cases, the AC component noise is proportional to the DC component instead of its square root. Measurements show that the molecular scattering noise in most systems at 1 cfm is 5 to 10 times stronger than that of a particle of 0.1 × 10 ^-6 m, making detection and measurement with the known devices impossible.

For environments or a background with high molecular scatter For example, this noise can be a hundred times greater than that Scattering by 0.1 µm particles. This high molecular scatter arises not only when the gas volume under consideration is large, as is the case for high throughput sentences is required, but also, for example, due to high molecular weight  density (high pressures above ambient pressure) or due to the presence of large gas molecules. Whenever a background with high molecular scatter is found, the device according to an embodiment of the invention used to allow high sensitivity in An presence of the background is achieved with strong molecular scattering.

The invention uses an illuminating device to illuminate a measuring area or a measuring volume through which a gas (mostly air), of which the particles are to be measured, has to flow. The illuminating device is preferably like that shown in FIG. 5, in which a illuminating device 10 with a laser beam according to US Pat. No. 4,571,079 or 4,594,715 is used.

As shown in FIG. 5, access to the laser cavity 12 can be achieved by closing a plasma tube 14 at one end with a Brewster window 16 . A curved mirror 18 (with a radius of, for example, r = 100 cm) is arranged at the other end of the tube 14 . A photodetector 20 and a pre-amplifier 22 are arranged in a conventional manner on the laser beam axis outside of the mirror 18 to provide a measure of the relative intensity of the lighting.

For the measurement of the particle size, the particles, the size of which is to be measured, are let into a particle beam 24 so that they pass through the laser beam 25 between the Brewster window 16 and an external laser mirror 26 (for example r = 70 cm) .

As shown in FIG. 5, the block 28 is arranged for optical scanning on the particle beam 24 , with light-collecting optical elements or an image generator 29 being positioned in the block 28 , which can have two lenses 30 and 31 above and close to the particle beam.

A photodetector 33 with a plurality of detector elements 34 (FIGS . 6 and 7) is arranged next to the block 28 so that it lies in the focal plane of the lenses 30 and 31 . The electrical output signals of the photodetector 33 are present on the parallel processor 35 . The output of the parallel processor 35 can be passed through an analyzer 36 to produce a low resolution display output and a converter 37 which provides a high resolution digital display output for the particle size. In addition, the converter 37 outputs a display output signal for overwriting a minimum size.

Photodetector 39 and preamplifier 40 can optionally be arranged on the other side of mirror 26 on the laser beam axis for reference measurement, as are photodetector 20 and preamplifier 22 .

In this invention, the noise is reduced in that an imaging device or an imaging device with detector reduce the background light from the molecular scattering to easy-to-use levels. As FIG. 6 shows, the detector 33 has a row of rectangular individual elements or detector elements 34 (eleven of which are shown in FIG. 6 for the purpose of explanation). This row or array of detector elements connected to the parallel processor for two-dimensional data acquisition is described in US Pat. No. 3,941,982.

This field of individual elements (which can be photodiodes according to FIG. 7) "see" corresponding partial volumes (ie a section of the total measuring volume) within the laser beam. The light scattered by a particle is imaged on a single element as a bright image together with a background of diffuse molecular scattering, which is generated by all air molecules in the monitored partial volume.

This makes the molecular background scatter by the number of elements decreased that were selected for the field. For light noise sources that are not can be described by Shott noise, there is a reduction of noise, which is proportional to the number of elements in the field. For shott Noise sources is the reduction in noise proportional to the square root the number of elements in the field.

If, according to one embodiment of the invention, N independent detector elements are used, the electrical output signal of each detector element must be interrogated in order to determine when a particle image was "observed" by an element. Fig. 7 shows a plurality of detector elements 34 which form the detector device 33, wherein each detector element is connected to another Si gnalverarbeitungskreis 41 of the parallel processor 35th In particular, each detector element 34 in each signal processing circuit 41 is connected to a preamplifier 42 (each of which has a feedback resistor 43 connected between the output and the negative input). Each of the signal processing circuit 41 also has a comparison circuit 44 and a storage element for the peak voltages (holding circuit) 46 .

Each preamplifier 42 generates an amplified electrical signal of the noise and the particle-based signal and passes it to the associated comparison circuit 44 . The threshold level of each comparison circuit is set to the peak amplitude of the signal for the minimum recognizable particle size. The output signals of all comparison circuits are combined in the logic control unit 48 in an OR circuit, the logic control circuit 48 emitting a pulse for the passage time of a particle for clocking purposes and an indication of when a particle of the minimum recognizable size is scanned.

For dimensions larger than the minimum recognizable size, the recognizability of the size depends on the desired resolution. For example, if a simple count of all particles <0.1 x 10 ^-6 m in a single size channel is desired, the signal processing circuits 41 can be easily used with the logic controller 48 .

For multi-channel applications with high resolution (e.g. if a resolution of 0.01 × 10 ^-6 m with 10 channels between 0.1 × 10 ^-6 m and 0.2 × 10 ^-6 m is required), the peak amplitudes of each detector element are stored individually before processing. For this high resolution (if, for example, the second threshold level is 0.11 × 10 ^-6 m), the output signal of each preamplifier 42 is fed to its associated peak voltage memory (holding circuit) 46 , which stores the peak amplitude. The peak amplitudes stored in the holding circuits 46 are then individually read out by the converter 37 , which has the logic control unit 48 and a scanning analog-digital converter 49 ( FIG. 7).

For multi-channel applications with low resolution, it is sufficient to sum all the output signals from the amplifiers 42 by each output signal via an associated resistor 50 to a summing amplifier 52 (whose feedback resistor 43 is connected between the output and the negative input) of the analyzer 36 , which also has a conventional pulse height analyzer 54 to which the output signals of the amplifier 52 are applied. Such a low resolution application assumes that the second threshold level used is sufficiently higher than the first so that the added noise is still less than the peak amplitudes that exceed the second threshold level. For example, if the second threshold level is 0.2 × 10 ^-6 m, it would be approximately 40 times larger than the threshold level of 0.1 × 10 ^-6 m, with the added noise being much less than such a high threshold level.

Each signal processing circuit thus determines together with its De tector element, when a particle is detected and the size of the scattering event ses that can lie between two elements if the picture is on the border or is slightly out of focus.

A further improvement in the detection can be achieved by installing a noise suppression circuit in the parallel processor circuit of FIG. 7.

As shown in FIG. 8, the noise suppression device 58 consists of a plurality of noise suppression circuits 60 (designated as 60 a and 60 b in FIG. 8), to which the output signals of the detector elements are applied, which monitor spaced or non-adjacent sections of the entire measuring range which is swept by the detector.

As shown in Fig. 6, the detector 33 has a plurality of detector elements 34 which are connected such that each area monitored by a detector element 34 is a partial section of the entire measuring range, each partial section having adjacent partial sections and the rest of the partial sections being removed or not adjacent is beard.

According to Fig. 8 34 monitors detector element a part section of the adjacent by the detector element 34 b, however, the c is not removed from the adjacent detector element 34 or. In the same way, detector element 34 b monitors an area which is adjacent to that of detector element 34 c, but which is distant or not adjacent to that of detector element 34 d, and finally, detector element 34 c monitors an area adjacent to detector element 34 d.

Although only four detector elements are shown in FIG. 8, it is obvious that this circuit pattern can be carried out with all common detector elements and that pairs or groups of detector elements which monitor sections which are distant or not adjacent to one another can easily be selected for noise suppression.

Fig. 8 also shows that the output signal of the detector element 34 a via a preamplifier 42 a with feedback resistor 43 a is applied to the noise suppression circuit 60 a, while the output signal of the detector element 37 c (ie the detector element, one of which is monitored by the detector element 34 a Section not adjacent section monitored) ge via a preamplifier 42 c with feedback resistor 43 c to the noise suppression circuit 60 a. Likewise, the output signal of the detector element 34 is b a b Before amplifier 42 to the noise reduction circuit 60 b and the output signal of the detector element 34 d (that is, the detector element, the one to the Detek gate element 34 b monitored area not recorded on adjacent region) through a preamplifier 42 d to the noise suppression circuit 60 b (it should be noted that the number of suppression circuits is normally half the number of detector elements used).

After noise reduction in the noise reduction circuits, the signal goes to particle detection circuits. According to Fig. 8 the off is output signal of the noise suppression circuit 60 a thus at a comparison circuit 44 a, to a holding amplifier 46 a and a resistor 50 a to ei nem analyzer 36, while the output signal of the noise reduction circuit 60 b to a comparison circuit 44 b, a holding amplifier 46 b and via a resistor 50 b to the analyzer 36 (all of these components have been described with reference to FIG. 7).

Fig. 9 shows the special circuit diagram of the noise reduction circuit 60 a (it should be noted that the other noise reduction circuits 60 are identical to this). As shown, the output signal of the Detektorele passes ments 34 a via the preamplifier 42 a to the resistor 62 of the Rauschunterdrüc kung circuit 60 a, while the output signal of the detector element c 34 c through the preamplifier 42 to the inverter 64 of the noise suppression circuit 60 a to is, the output signal of the Inverter 64 reaches resistor 66 . The resistors 62 and 66 are connected to each other and sum the output signals of the detector elements, the sum output signal of the summing connection 68 to the comparison circuit 44 a, the holding amplifier 46 a and via the resistor 50 a to the analyzer 36 .

Fig. 9 also shows that if the output signal A (of the detector element 34 a) has both noise and a useful signal and if the output signal B (of the detector element 34 c) contains only noise, the noise of the inverted output signal B ( B of FIG. 9) suppresses the noise in the output signal A when both signals are summed by the noise suppression circuit (ie A + B = 0).

Common mode disturbances correlate at points that are very far apart on a beam (ie more than a few mm). Although this applies to all illuminating beams, the difficulty is greatest with multimode lasers operating in higher order modes where the coherence length is short. Since the degree of correlation is related to the spatial phase coherence along the radiation axis, the coherence is greatly improved and the noise is correlated when samples are taken at short spatial distances. Therefore, if an arrangement of detector elements 34 is used for sampling short distances, and then the output signal of a pair of detector elements is inverted, noise suppression is achieved according to one embodiment of the invention (it being noted that the detector elements monitoring the adjacent subsections are not arranged in pairs because the images of two neighboring detector elements have to be used together).

In operation, a laser beam is passed through the measuring area, and a gas with particles is allowed to flow through the measuring area with throughputs which have at least a throughput of approximately 1 cfm. Particles within the measuring range cause light scattering, light scattering due to particles whose diameter is at least 0.1 × 10 ^-6 m can be detected with the detector field. Each detector element of the field monitors a certain Teilvo lumen of the measuring volume, measures the visible light scatter within the monitored section and generates an electrical output signal for the scanned light scattering (together with the signals resulting from the background noise). In order to achieve high-resolution readings, the stored peak amplitudes are then read out individually and converted into a digital output signal.

In one embodiment of the invention, a sensitivity of particle sizes of 0.1 µm could be achieved in an environment with high molecular scattering, with a throughput of 0.02832 m ³ / min (1 cfm).

The invention thus provides an improved particle measurement device for a particle size detector that has high sensitivity in an environment with high molecular scatter by using an array of detector has elements that have the required reduction in molecular scattering allow background noise caused.

Claims (10)

1. Particle measuring device for particle size detection with a first device which enables a medium containing particles to be guided through a specific measuring range and a second device which illuminates the measuring range so that the particles in the measuring range cause light scattering, which particle measuring device ( 10 ) has the following components:
a detector field ( 33 ) which receives and detects the light scattered in the measuring area ( 25 ) and has a plurality of detector elements ( 34 ) which are arranged in such a way that certain detector elements ( 34 a, b, c) sections of the measuring area from certain sub-parts ( 25 ) receive scattered light, the specific sections of the measuring range ( 25 ) being arranged at a distance from one another and each detector element ( 34 a, b, c, d) emitting a noisy output signal which reflects the light detected by the particles in the respective section of the measuring range ( 25 ) has been scattered, contains, and a processor ( 35 ) with a noise suppression arrangement ( 58 ), which is connected to the individual detector elements ( 34 a, b, c, d) and causes the noise components of the Output signals of the individual detector elements ( 34 a, b, c, d) are deleted as possible, so that the output signals of the processor ( 35 ) practically only by particles in the measuring range ( 25 ) Show direct light scatter. 2. Particle measuring device according to claim 1, characterized in that the detector field ( 33 ) and the processor ( 35 ) for effective detection and processing of the light, which is scattered by particles in the measuring area ( 25 ), are formed so that particles with Diameters of at least 0.1 µm are detected. 3. Particle measuring device according to one of the preceding claims, characterized in that the detector field ( 33 ) and the processor ( 35 ) are designed for effective detection and processing of the light scattered by the particles in the measuring region ( 25 ) so that the flow of the medium with the particles Chen through the measuring range ( 25 ) with a throughput of at least 0.028 m ³ / min. 4. Particle measuring device according to one of the preceding claims, characterized in that the processor ( 35 ) is a parallel processor which has a plurality of processing circuits ( 41 ), each of which is connected to a different one of the detector elements ( 34 a, b, c, d) in order to process the outputs thereof separately and that the outputs of the processing circuits ( 41 ) are connected to the noise suppression arrangement ( 58 ). 5. Particle measuring device according to one of the preceding claims, characterized in that the noise suppression arrangement ( 58 ) has a plurality of noise suppression circuits ( 60 a, b), each of which with two be detector elements ( 34 a + 34 c; 34 b + 34 d) connected is. 6. Particle measuring device according to claim 5, characterized in that each noise suppression circuit ( 60 a, b) has a summing element ( 62 , 66 ) and egg nen signal inverter ( 64 ) connected to one ( 34 c) of the certain detector elements ( 34 ) is to invert its output signal before feeding into the summing elements ( 62 , 66 ). 7. Particle measuring device according to one of the preceding claims, characterized in that the detector field ( 33 ) is divided into first and second predetermined detector elements ( 34 a, 34 d) which receive light from first and second sections of the measuring range ( 25 ), wherein the second sections are arranged at a distance from one another and with the respective first sections of the measuring range ( 25 ) are adjacent, and that the processor ( 35 ) has a second noise suppression arrangement ( 60 b) which with the second detector elements ( 34 a, 34 d) is connected to cause noise suppression in their output signals. 8. Particle measuring device according to claim 7, characterized in that the detector field ( 33 ) receives and detects the light scattered over the substantially entire measuring range ( 25 ), the specific first and second sections of the measuring range ( 25 ) alternating. 9. Particle measuring device according to claim 7 or 8, characterized in that the noise suppression arrangement ( 58 ) has a plurality of noise suppression circuits ( 60 a, b), the number of which is equal to the number of detector elements ( 34 a, b, c, d). 10. Particle measuring device according to one of the preceding claims, characterized in that the processor ( 35 ) has amplifiers ( 42 , 44 ) which are connected between the detector elements ( 34 a, b, c, d) and the noise suppression arrangement ( 58 ) .