JPH07109403B2 - Liquid particle counter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention relates to the case where 0.
The present invention relates to an in-liquid particle counter for counting fine particles (particles) of 1 μm or less.

“Prior Art” Generally, when intense light such as a laser is applied to fine particles of submicron or less, scattered light corresponding to the particle diameter is generated. This is generally called Rayleigh scattering. When the particle size of the fine particles is small, the degree of side scattering tends to be strong. Usually, in the case of a highly sensitive particle counter, measurement is performed in this region where side scattering is strong.

FIG. 7 shows a conventional 90 ° side-scattering particle counter using a PMT (photomultiplier tube) 7. In this figure, perpendicular to the water flow in cell 1,
A laser such as an Ar laser from the laser generator 2 is emitted through the condenser lens 3. If there are fine particles p in the particle detection region 4 in the liquid, Rayleigh scattering occurs. The scattered light is imaged on the PMT 7 through the imaging lens 5 and the field stop 6 to perform photon counting, that is, by detecting a pulse composed of a plurality of photons for one fine particle p, The number of fine particles p was measured by counting the size and the number of this pulse.

In the case of a particle counter using PMT7, its S / N ratio is expressed by the following equation.

Here, P = incident light beam intensity σs = scattering cross-sectional area of fine particles N = field-of-view area that becomes background light “Problems to be solved by the invention” However, the particle size of the fine particles p that are scattered objects is small (for example, If it becomes less than a micron), the scattered light becomes weak, so in order to extract the particle scattered light, the volume of the particle detection area must be reduced to weaken the background light, and this background light is converted into an electrical signal by photoelectric conversion. Had a problem that a large fluctuation component appeared and the S / N ratio deteriorated. That is,
Since most of the background light amount is due to the Rayleigh scattered light of the solution itself determined by the size of the field of view of the device, the Rayleigh scattered light of the fine particles p for measuring the fine particles p existing in the solution is due to the Rayleigh scattered light of the solution itself. It was weakened relatively and the S / N ratio was deteriorated.

On the other hand, if the field of view is reduced to improve the S / N ratio, the sampling rate will be reduced in proportion to it, and in actual use, there is a problem that measurement takes time and it is not practical. . This is because, for example, to measure 1 cc, it is necessary to keep flowing a ratio measurement object that is many times as much as that, so that there is much waste. Here, the sampling rate is expressed by the following equation.

Here, the sampling amount represents the flow rate actually measured within the unit time.

However, as shown in Fig. 7, in the case of measurement using PMT7, the sampling amount and the field of view limitation (improving the S / N ratio) are contradictory, and it is impossible to satisfy both at the same time. It was

The present invention has been made in view of the above problems, and an object of the present invention is to obtain an in-liquid particle counter capable of improving the S / N ratio without changing the sampling rate.

"Means for Solving the Problems" The present invention counts the fine particles in the liquid by irradiating the liquid flowing in a predetermined direction with light and measuring the scattered light scattered in a direction different from the light irradiation direction. In the submerged particle counter, the high-sensitivity multi-channel photodetector for individually detecting scattered light from a plurality of particle detection regions along the flow direction in the liquid, and the same fine particles as the plurality of particle detection regions A detection data sequential addition means for sequentially capturing and adding detection data of the corresponding area from the high-sensitivity multi-channel photodetection means when passing through each area of the plurality of particle detection areas in the liquid. It is characterized in that they are arranged in the same direction as the light irradiation direction.

"Operation" The liquid is irradiated with light such as a laser beam, and scattered light scattered in a direction different from the light irradiation direction is detected by a high-sensitivity multichannel photodetector (IMD). The IMD is composed of an optical amplifier such as II (Image Intensifier) and a photodiode array, and individually detects scattered light from a plurality of particle detection regions along the flow direction in the liquid. Then, the detection data sequential addition means sequentially acquires and adds the detection data of the corresponding region from the IMD when the same fine particle passes through each of the plurality of particle detection regions in the liquid. Therefore, for the same particle, signals can be fetched and cumulatively added by the number of a plurality of particle detecting means (for example, the number of photodiode arrays) with the same S / N ratio. Therefore, the S / N ratio can be improved by the square root times the number of particle detection regions without changing the sampling rate.

Moreover, since the plurality of particle detection regions along the flow direction in the liquid are arranged in the same direction as the light irradiation direction, the fine particles travel on the same line as the light traveling direction. Therefore, it is possible to increase the number of particle detection regions and increase the number of detection data from the same particles without limiting the light scattering time of the particles. Further, since the light has a substantially uniform intensity in the traveling direction, it is possible to make the intensity of scattered light from the same fine particle in a plurality of particle detection regions uniform.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings starting from FIG. The same parts as those in FIG. 7 are designated by the same reference numerals.

In FIG. 1, reference numeral 1 is a cell in which a liquid to be measured such as pure water is flowed at a constant speed. A laser generator 2 such as an Ar laser is provided in the same direction as the liquid flowing direction, and a condenser lens 3 for condensing the laser on the liquid is provided between the laser generator 2 and the cell 1. Has been.

A region along the direction of flow of the liquid in the cell 1, condensing region and nearby regions of the laser, a plurality of particle detection region _{4 1, 4 2, 4 3} , ..., 4 n , and the detection to The liquid containing the fine particles p to be passed through. Irradiated with the laser beam of the laser generator 2, the particle detection regions 4 ₁ , 4 ₂ , 4 ₃ ,
, For measuring the scattered light laterally scattered by the fine particles p within 4 _n , the imaging lens 5 is placed on the optical axis (l ₂ ) which is shifted by 90 ° with respect to the laser irradiation direction (l ₁ ). And a high sensitivity multi-channel photodetector (hereinafter referred to as IMD) 10 is provided. The field stop 6 is fixed to the input surface of the IMD 10, and the fiber plate 34 is joined to the outside of the photocathode 13.
A detection data sequential addition circuit 9 is coupled to the output side of the IMD 10.

As shown in FIG. 2, the IMD 10 converts the input optical signal into photoelectrons and then multiplies them by an II (image intensifier) 11 as an optical amplifier, and the multiplied photoelectron signals into optical signals again. PCD as a photodiode array that performs photoelectric conversion and time-series electric signal output after conversion
(Plasma Coupled Device) 12 and a fiber plate 17 as an optical coupling for coupling them. That is, II11 as the optical amplifier
Is a field stop 6 fixed to the light incident surface, a fiber plate 34 provided inside the field stop 6, a photocathode 13 for converting light into photoelectrons, an internal electronic lens 14, an MCP (microchannel plate) 15, It comprises a phosphor screen 16 on the output side and an external variable high voltage power supply 16a. Further, in the PCD12 as the photodiode array, extremely small photodiodes are arranged on a straight line, photoelectrically converted charges are transferred to adjacent photodiodes, and charges corresponding to light incident on each photodiode in series from the end photodiode are transferred. In addition, it is provided with a PCD drive circuit 12a, an amplifier circuit and the like.

The detection data sequentially adding circuit 9, the particles detection region 4 ₁ riding multiple or the same particles of liquid flow singular,
When passing through each of the areas 4 ₂ , 4 ₃ , ..., 4 _n ,
It is a circuit for sequentially fetching and adding detection data of the corresponding area from the IMD 10, and is configured as shown in FIG. 3, for example. That is, an amplifier that amplifies the output of the n region (for example, n = 1024) output from the PCD 12 of the IMD 10 in series.
18, a sample hold circuit 19, an A / D conversion circuit 21 and a CPU (central processing control circuit) 22 which are sequentially coupled to the output side of the amplifier 18, and a RAM 23, a ROM 24 coupled to the CPU 22.
The same particles p as the timer 25 and the scanning counter 26
There the particle detecting region 4 _1, 4 _2, 4 _3, ..., and set the time T that passes between regions at the time when passing through each region of 4 _n,
It comprises an inter-region passing time setting unit 27 that outputs the setting signal to the CPU 22, and a display unit 28 is coupled to the output side of the CPU 22. The RAM 23 includes a first memory for storing detection data and a second memory for storing display data.
And a memory. The CPU 22 achieves the following functions based on the program stored in the ROM 24. That is, a storage control unit that sequentially captures the detection data from the IMD 10 at the interval of the transit time T set by the inter-region transit time setting unit 27 and stores the data in the first memory in the RAM 23, and in the first memory in the RAM 23. When n pieces of data corresponding to the detection output when the same fine particle p exists in each of the particle detection areas 4 ₁ , 4 ₂ , 4 ₃ , ..., 4 _n are accumulated in a predetermined storage area of It has read control means for reading n pieces of data from this storage area, and operation control means for sequentially adding the read data and transferring it to the second memory in the RAM 23.

In the above configuration, the laser generator 2
The laser beam is applied in the same direction as the flowing direction of the liquid in the cell 1. The laser beam particle detecting region 4 ₁ of liquid by the condenser lens 3, 4 _2, 4 _3, ..., is condensed to 4 _n.
Then, these particles detection region 4 _1, 4 _2, 4 _3, ..., the scattered light of the microparticle p is the 4 _n enters the IMD10 through the imaging lens 5, a field stop 6.

In this IMD 10, a weak one-dimensional optical image due to particle scattering is incident on the photocathode 13 of II11 and converted into a photoelectron image. This photoelectron image is formed on the input surface of the MCP (micro channel plate) 15 by the electron lens 14, and this MCP 15
After being enhanced by, the light impinges on the phosphor screen 16 and is converted into an optical image again. The optical image thus entered is enhanced tens of thousands of times by II11. The enhanced optical image is efficiently guided to the PCD 12 by the coupling of the fiber plate 17. Then, photoelectric conversion is performed by the linear photodiode of this PCD12, and the charge is transferred to the adjacent photodiode,
The photodiode corresponding to the incident light is output from the photodiode at the final end. This output signal is taken out as an independent time-series electric signal at a transfer rate of 4 CLK per channel and is input to the detection data sequential addition circuit 9.

The detection data sequential addition circuit 9 operates as follows.

(A) First, it is determined whether or not to enter the measurement mode depending on whether or not the measurement flag is on.

(B) If the measurement flag is on, the contents of the scanning number counter 26 are set to 1, and the timer 25 is set to the inter-region passing time T.

(C) Next, at T _1, the first scan is performed, and the detection data of the IMD 10 is fetched by this scan and stored in a predetermined area in the first memory for writing in the RAM 23. That is,
Ch1,2,3 of PCD12 of IMD 10, ..., n, as shown in FIG. 5, the particle detection region 4 _1, 4 _2, 4 _3, ..., so 4 _n of the scattered light is detected outputs , T ₁ stores the detection data of ch 1 in the area M ₁ in the first memory. Therefore, the first
As shown in the figure, if it is assumed that there is fine p to T ₁ at the particle detection region 4 _1, the detection data of ch1 (hatched portion) contains data of the light scattered by fine particles p.

(D) Next, when the inter-region passing time T has elapsed, it is determined whether the number of scans is n or more. Scan count counter if not
1 is added to the contents of 26, and the transit time T between areas is added to the timer 25.
Set.

(E) Next, at the time of T _2, the second scanning is performed, and the detection data of the IMD 10 is fetched by this scanning and stored in a predetermined area in the first memory for writing in the RAM 23. That is,
T ₂ times the detection data ch1,2 area in the first memory
Stored in M ₂ and M ₁ . Therefore, as shown in FIG. 5, T ₁
Located at the particle detection region 4 there microparticles p is T ₂ times the particle detection region 4 in ₂ in _1, the detection data of ch2 contains data of the scattered light by fine particles p, the data shown in FIG. 5 Are stored in the area M ₁ . Further, in time the T _2, detection data becomes data only by background light that is stored in the region M ₂ if the new fine p does not flow into the particle detection region 4 in _1, a new particle p inflow If so, the detection data stored in the area M ₂ includes the data of the scattered light due to the fine particles p.

(F) In the same manner, the fetched detection data and the storage in a predetermined area in the first memory are repeated in the same manner, and when the number of scans reaches n, n pieces of data are stored in the area M ₁ in the first memory. Since the data is accumulated, the read control means reads out n pieces of data in the area M ₁ , the arithmetic control means adds these data, and the added data is transferred to the second memory for display in the RAM 23 to display the data. Display at 28.

(G) When the number of scans reaches n + 1, n pieces of data are accumulated in the area M ₂ in the first memory. Therefore, the reading control means reads the n pieces of data in the area M ₂ , and the arithmetic control means Add these data and add the data
The data is transferred to the second display memory in the RAM 23 and displayed on the display unit 28.

In the above embodiment using the IMD, the signal amount is treated as an analog amount, but it is also possible to treat the signal as photocounting by making the MCP 15 in the IMD multistage.

In the IMD 10 shown in FIG. 1, by bonding the fiber plate 34 to the outside of the photocathode 13, the field of view is directly provided on the fiber plate 34, and only one imaging lens is required, and the optical adjustment is performed. Although it is made simple, the present invention is not limited to this. Instead of joining the fiber plate 34 to the outside of the photocathode 13, the field stop 6 may be replaced.
May be disposed at a position separated from the front surface of the IMD 10 by a predetermined distance, and a second imaging lens may be provided between the field stop 6 and the IMD 10.

Although the photodiode array is used as the PCD 12 in the above-described embodiment, a CCD that operates in the same manner, a MOS diode array that is different only in the method of reading charges, or the like may be used. Two-dimensional CCDs and MOSs are also available on the market, but these are considered to have a large number of one-dimensional diode arrays arranged in the vertical direction. If it is

[Advantages of the Invention] The submerged particle counter according to the present invention is, as described above, a high-sensitivity multi-channel light detection unit that individually detects scattered light from a plurality of particle detection regions along the flow direction in the liquid, Since the same fine particles are provided with detection data sequential addition means for sequentially capturing and adding detection data of corresponding areas from the high-sensitivity multi-channel photodetection means when passing through each area of a plurality of particle detection areas,
With respect to the same particle, with the same S / N ratio, signals can be fetched and accumulated and added by the number of a plurality of particle detection regions (for example, the number of photodiode arrays). Therefore, the S / N ratio can be improved by the square root times the number of particle detection regions without changing the sampling rate.
That is, as shown in the equation (1), the S / N ratio is proportional to the scattering cross-sectional area σs of the fine particles, and the visual field area N that becomes the background light.
Since it is inversely proportional to the square root of, the S / N ratio in the conventional example in which the number of particle detection areas is ₁ is represented by (S / N) _1.
N) ₁ When the S / N ratio in the present invention in which the number of particle detection regions is _n is represented by (S / N) _n , this (S / N) _n is Becomes S / N ratio is It has been improved twice. In other words, as shown in FIG. 6, the component proportional to the scattering cross section σs of the fine particles is n times as large as the component proportional to the visual field area N as the background light. Because it will be doubled.

Moreover, since a plurality of particle detection regions along the flow direction in the liquid are provided in the same direction as the light irradiation direction so that the fine particles travel on the same line as the traveling direction of light, the light scattering time of the fine particles is limited. Of course, it is possible to increase the number of particle detection regions (correspondingly, increase the number of photodetectors of the high-sensitivity multi-channel photodetection means) and increase the number of detection data from the same particle. That is, the number of n can be increased to further improve the S / N ratio. Also,
Since the light has a substantially uniform intensity in the traveling direction, the scattered light intensity from the same fine particle in a plurality of particle detection regions can be made uniform.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a submerged particle counter according to the present invention, FIG. 2 is an explanatory diagram of an IMD used in the present invention, and FIG. 3 is a block of a detection data sequential addition circuit of FIG. 4 and 5 are flow charts for explaining the operation of the detection data sequential addition circuit of FIG. 3, and FIG. 5 is an explanatory view for explaining the operation of taking the detection data by the storage control means and storing it in the first memory in the RAM. Fig. 6 shows the S / N ratio FIG. 7 is an explanatory diagram for explaining that it is doubled, and FIG. 7 is an explanatory diagram of a conventional device. 1 ...... cell, 2 ...... laser generator, 3 ...... condenser lens, 4, 4 ₁ to 4 _n ...... particle detection region, 5 ...... first imaging lens, 6 ...... field stop, 7 ...... PMT, 9 ... Detection data sequential addition circuit, 10 ... IMD (high-sensitivity mar-channel photodetector), 11 ... II (image intensifier), 12 ...
… PCD (Plasma Coupled Device), 12a …… PCD drive circuit, 13 …… Photocathode, 14 …… Electron lens, 15 …… MCP
(Micro channel plate), 16 ... Phosphor screen, 16a
...... Variable high-voltage power supply, p ... fine particles.

Front Page Continuation (72) Inventor Keisuke Masuda 1 Hamamatsu Photonics Co., Ltd., 1126 Nomachi, Hamamatsu City, Shizuoka Prefecture (72) Inventor Fumihiko Shimomura 1 126 1 Nomachi, Hamamatsu, Shizuoka Prefecture Hamamatsu Photonics Co., Ltd. (72) Inventor Hirano Isuke, 1126, Nomachi, Hamamatsu City, Shizuoka Prefecture, 1126, Hamamatsu Photonics Co., Ltd. (72) Inventor, Kiyoshi Koike, 1126, Nomachi, Hamamatsu City, Shizuoka Prefecture, Hamamatsu Photonics Co., Ltd. (56) Reference References JP-A 2-161336 (JP, A) JP-A 60-231133 (JP, A) JP-A 58-111576 (JP, A) JP-A 56-102053 (JP, A)

Claims (2)

[Claims] 1. A submerged particle counter for counting fine particles in a liquid by irradiating a liquid flowing in a predetermined direction with light and measuring scattered light scattered in a direction different from the light irradiation direction. A high-sensitivity multi-channel light detection means for individually detecting scattered light from a plurality of particle detection regions along the flow direction in the liquid, and the same fine particles when passing through each of the plurality of particle detection regions And a detection data sequential addition means for sequentially acquiring and adding detection data of corresponding areas from the high-sensitivity multi-channel light detection means, and a plurality of particle detection areas in the liquid in the same direction as the light irradiation direction. An in-liquid particle counter characterized by being arranged. 2. The high-sensitivity multi-channel light detecting means individually detects an optical amplifier that amplifies scattered light from a plurality of particle detection regions along the flow direction of the liquid, and each part of the output of this optical amplifier. The submerged particle counter according to claim 1, comprising a photodiode array.