JPH03148041A - Particle counter used in liquid - Google Patents

Abstract

PURPOSE:To make it possible to increase the amount of sampling without changing detecting sensitivity by providing a high-sensitivity multi-channel photodetector at a means for measuring scattered light from liquid to be measured that is illuminated with light. CONSTITUTION:A laser generating device 2 is provided at a right angle with a cell 1 wherein fluid to be measured flows at a constant speed. A cylindrical lens 8 for flattening a beam and a laser-light condenser lens 3 for the liquid are arranged between the cell 1 and the device 2. A first image forming lens 5, a visual field stop 6, a second image forming lens 9 and a high-sensitivity multichannel photodetector 10 IMD are provided on an optical axis l2 which is orthogonal to the laser projecting direction l1. The scattering measuring part of particles 4 is illuminated with the linear laser beam. The scattering is inputted into the IMD and processed. Finally, the electric charge corresponding to the incident light is outputted. Thus, the amount of samplings can be increased without impairing sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to an in-liquid particle counter for counting particles of 0.1 μm or smaller in pure water or other fluids.

"Prior Art" Generally, when fine particles of submicron size are irradiated with strong light such as a laser, scattered light is generated depending on the particle size. This is generally called Rayleigh scattering. When the particle size of the scattering object is small, the degree of side scattering tends to be strong. Usually, in the case of a highly sensitive particle counter, measurements are performed in this region where side scattering is strong.

Figure 7 shows PMT (photomultiplier tube) (
7) is a conventional particle counter with 90° side scattering. In the figure, a laser such as an Ar laser from a laser generator (2) is irradiated through a condenser lens (3) perpendicularly to the water flow in the cell (1). The presence of fine particles (4) in the liquid causes Rayleigh scattering. This scattered light is passed through an imaging lens (5) and a field stop (6) to a PM
T (7) By performing photon counting by focusing an image on the particle, in other words, by detecting a pulse composed of multiple photons for one particle, the size of the particle and by counting the number of pulses, the number of particles is determined. was being measured.

The count value N detected by photon counting is expressed by the following equation.

N=P・σs・ω・T−QE・δ Here, σS = Scattering cross section of fine particles P = Incident light beam intensity ω = Light reception efficiency T = Transmittance of optical system QE = Quantum efficiency δ = Collection effect “Invention The count value N is the parameter that determines the particle size, but in reality, the background scene N is determined by the device.

The value of N+N,=N', is determined. Background light amount N. Most of this is due to the Rayleigh scattered light of the solution itself, which is determined by the field of view of the device, as will be described later. In other words, the Rayleigh scattered light of the particles used to measure the particles present in the solution is relatively weakened by the Rayleigh scattered light of the solution itself. For this reason, limiting the field of view at the detection unit is an important point.

Detailed explanation of field of view limitations. In Figure 8,
(a) shows the case where the ratio of unnecessary field of view (hereinafter referred to as background) (B) that captures the scattered light of water to the light scattered by particles (P) is large, and (b) shows the case where the ratio of the field of view (B) is large. This shows the case where the ratio of is small. (,) from (b
) has relatively higher sensitivity. Theoretically, the background (B) is the scattered light of particles (P
), the maximum sensitivity is achieved, but this must be determined in relation to the sampling amount, which will be described later.

4- When measuring particles, there is a big difference between the flow rate flowing through the cell and the flow rate actually being measured. Here, we need to consider the following quantities.

Sampling amount 2 The flow rate actually measured within a unit time.

If the field of view is made smaller in order to increase the detection sensitivity, the amount of sampling will decrease in proportion to this, making measurement time-consuming in actual use, which is impractical. For example, in order to measure ice, it is necessary to continue flowing many times the number of non-measurable objects, resulting in a lot of waste. The size of the field of view is determined by the relationship between the measured particle size and the sampling amount.

However, as shown in Fig. 7, in the case of measurement using PMT (7), the sampling amount and the restriction of the field of view (increasing the detection sensitivity) are contradictory, and it is impossible to satisfy both at the same time. Met.

The present invention allows the sampling site to be improved without changing the detection sensitivity.
The purpose is to obtain a device that can be lifted.

"Means for Solving the Problems" The present invention irradiates a liquid to be measured with light and measures particles in the liquid based on scattered light scattered in a direction different from the direction of irradiation of the light, wherein the scattered light The device is equipped with a highly sensitive multi-channel photodetector as a measuring means.

"Operation" A liquid is irradiated with light such as a laser beam, and scattered light scattered in a direction different from the direction of irradiation of the light is detected by a highly sensitive multichannel photodetector (IMD). This IMD is I
Since it is composed of an optical amplifier and a photodiode array, the detected light is amplified by the optical amplifier, and then
Photoelectric conversion is performed by the photodiode, the resulting charge is transferred to adjacent photodiodes, and the photodiode at the end outputs the charge corresponding to the incident light in series. Therefore, the amount of sampling can be increased without changing the detection sensitivity.

``Example'' An example of the present invention will be described below with reference to FIG. 1 and the following drawings. The same parts as in FIG. 7 are given the same reference numerals.

In FIG. 1, (1) is a cell, into 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 installed in a direction perpendicular to the direction in which the liquid flows, and a perfect circular laser beam is emitted into a long and thin flat beam between the laser generator (2) and the cell (1). A cylindrical lens (8) as a flattening means for forming a laser beam and a condensing lens (3) for focusing the laser beam onto a liquid are provided.

In order to measure the side scattering of the plurality of particles (4) irradiated with the elongated flat laser beam, the optical axis (Q2) is shifted by 90° with respect to the laser irradiation direction (Ql).
), the first imaging lens (5), the field diaphragm (6), the second
An imaging lens (9) and a highly sensitive multi-channel photodetector (hereinafter referred to as IMD) (10) are provided.

As shown in Figure 2, this IMD (10) consists of an II (image intensifier) (1, 1) as an optical amplifier that converts an input optical signal into photoelectrons and then multiplies it, and this multiplication. A POD (plasma coupled device) (12) as a photodiode array that converts the photoelectronic signal into an optical signal and then photoelectrically converts it into a time-series electrical signal output, and an optical coupling that couples these. This device consists of a fiber plate (17). That is, I I (11) as the optical amplifier
is a photocathode (13) that converts light into photoelectrons on the inside of the optical glass (33) on the light incidence surface, an internal electron lens (14),
It consists of an MCP (microchannel plate) (15), an output side fluorescent screen (16), and an external variable high voltage power supply (16a). Moreover, P as the photodiode array
CD (12) is a device in which extremely small photodiodes are arranged in a straight line, and the photoelectrically converted charge is transferred to adjacent photodiodes, and the photodiode at the end serially outputs a charge corresponding to the light incident on each photodiode. , a PCD drive circuit (12a), an amplifier circuit, etc.

In the above configuration, a laser beam is irradiated in a direction perpendicular to the direction in which the liquid 7- in the cell (1) flows. This laser beam is emitted from a laser generator M (2), converted into a flat beam by a cylindrical lens (8), and then condensed at the position of the liquid by a condensing lens (3). This will make the laser intensity uniform in a narrow strip against the background.

The measurement location of particle scattering is irradiated with a long and thin linear laser beam. The scattering of particles (4) at these measurement points is transmitted through the first imaging lens (5), the field diaphragm (6), and the second imaging lens (9) to the IMD.
(10).

In this I M D (10), a weak one-dimensional optical image due to particle scattering is generated on the photocathode (1
3) and is converted into a photoelectron image. This photoelectron image is
An image is formed on the input surface of an MCP (microchannel plate) (15) by an electron lens (4), and this MCP
After being intensified at (15), the light collides with the fluorescent screen (16) where it is converted into an optical image again. The optical image thus incident is intensified tens of thousands of times by I I (11). The intensified optical image is guided to the PCD (12) with high efficiency by coupling the fiber plate (18-7).

The linear photodiode of this P CD (12) performs photoelectric conversion, and the resulting charge is transferred to adjacent photodiodes, and the photodiode at the final end outputs a charge corresponding to the incident light. This output signal is 4CL per channel.
It is extracted as an independent time-series electrical signal at a transfer rate of K.

Next, the memory circuit of the IMD (10) is configured as shown in Fig. 3, and stores the data of 256 channels 128 times, and stores the Nth and N+1st Kch and the channels before and after it (6C in total). This is a circuit that adds and outputs to the computer. I will explain in more detail.

The clock of IMD (10) is IMHz, 5
Five clocks of 00,333°250.200 KHz can be selected. I M D (1
, 0) is output from O to -1, OV through the amplifier (I8) and the sample and hold circuit M (19).
d. This is converted into a 12-bit A/D conversion circuit (
After conversion in step 21), the upper 8 bits are sent to two first and second memories (22) and (23). An address selector (24) causes the first memory (22) to store even-numbered data, and the second memory (23) to store odd-numbered data. This is repeated up to 128 times as shown in Figure 4 (
1st and 2nd memory (22) (23) 64 times each)
Once this is repeated, the addition circuit (25) moves on to addition of 6 channels. That is, in FIG. 3, the Och data of the first and second memories (22) and (23) is taken into the first latch (26). Next, the lch data is taken into the second latch (27), and the 2ch data is taken into the third latch (28).

The six 8-bit data are added by an adder circuit (25) and stored in the main memory (29). Next, the data of 3ch is loaded into the first latch (26) and the data of 1, 2, and 3ch are stored in the main memory (29). This is 256c
Do this for 128 times.

When the storage in the main memory (29) is completed, a completion signal is sent to the computer (32) via the data selector (30) and interface (31), and the raw data and addition data are sent to the computer (32) by the data selector (30). ) and import the data into the computer (32).

The signal processing of the IMD (10) may be affected by positional errors due to crosstalk of the MCP (15) (for example, even if true data is received only on channel 3, the signal actually appears on channels 2 and 4). It is necessary to take into account deviations and time lags. An example of data processing for this purpose will be described below.

Example: The data measured at the nth nch is the data measured at the nth nch.
(n-1)ch, nch, (n+1)chn+1st (n-1)ch, nch, (n+1)ch
The sum of the total of 6 channels is assumed to be the data measured on the n-th channel.

This data is arranged on an X-Y (Xj time series, Yjch) matrix as shown in FIG. 5, and peak detection is performed. At this time, since each piece of data is the sum of six pieces of data, a signal group is created on the x-y matrix where particles are present. Signal processing is performed using the largest peak in this signal group as a parameter. In addition, with IMD, more data can be determined by the number of measurement channels than with PMT in the same measurement time.Separately, the threshold level according to the particle size is measured using standard latex, and the peaks between the levels are measured. 11- Detect the number of blocks.

In the above embodiment using the IMD, the signal amount is treated as an analog amount, but the MCP (15) inside the IMD
It is also possible to handle the signal as photo counting by making it multi-stage.

IMD (10) in FIG. 1 is the photocathode (
13) is covered with optical glass (33).

To provide a field of view restriction on the photocathode (13), the incident light is
Field stop (6) installed in front of M D (10)
is imaged by the first imaging lens (5), which is further imaged by the second imaging lens (9) on the photocathode (10) of the IMD (10).
13) Need to be imaged on. On the other hand, as shown in FIG. Since the second imaging lens can be provided above, the second imaging lens becomes unnecessary, and the optical adjustment is significantly reduced.

In the front embodiment, the scattering direction of the scattered light to be detected or the optical axis <'Q2) on which the high-sensitivity multichannel photodetector (10) is arranged is 2-90 degrees with respect to the direction of the light beam (Q□). However, the present invention is not limited to this, and the angle does not matter unless the high-sensitivity multi-channel photodetector (10) is in the direction of the irradiation light, that is, the irradiation light is not directly incident.

In the embodiment described above, a photodiode array is used as the P CD (12), but a CCD that operates in the same manner, a MOS diode array that differs only in the method of reading out charges, etc. may also be used. In addition, two-dimensional versions of these CODs and MOSs are also commercially available, but these have a large number of 1-dimensional elements in the vertical direction.
Considering that a dimensional diode array is arranged, if these are used, it is possible to cope with the case where the liquid scattering part is two-dimensional.

"Effects of the Invention" As described above, the present invention uses a highly sensitive multi-channel photodetector, so the amount of sampling relative to the background can be increased without impairing sensitivity. In addition, by using a fiber plate input type IMD as a photodiode array, the field stop can be installed on the fiber plate, thus reducing the number of imaging lenses and S
/N ratio can be improved and optical axis adjustment of the measurement system can be facilitated.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the submerged particle counter according to the present invention, and FIG. 2 is an explanatory diagram showing an embodiment of the submerged particle counter according to the present invention.
Figure 3 is a block diagram of the IMD memory circuit.
Fig. 4 is an explanatory diagram of the storage order in the memory, Fig. 5 is an explanatory diagram of the data peak detection state, Fig. 6 is an explanatory diagram of another embodiment of the present invention, and Fig. 7 is an explanatory diagram of the conventional device. , FIG. 8 is an explanatory diagram of the background and sampling amount. (1)...Cell, (2)...Laser generator, (3
)..., (4)... Fine particles, (5)... First imaging lens, (6)... Field stop, (7)... PMT,
(8)...Cylindrical lens, (9)...Second
Imaging lens, (10)...IMD, (11)...image intensifier, (12)...PCD (plasma coupled device), (12a)...PCD
[Dynamic circuit, (13)...Photocathode, (14)...Electronic lens, (15)...MCP (microchannel plate), (16)...Phosphor screen (16a)...Variable High voltage power supply. Hamamatsu Photonics Co., Ltd. Unexamined Publication No. 3 148041 (6) -11 yen - 1110

Claims (5)

[Claims] (1) In a device that irradiates a liquid to be measured with light and measures particles in the liquid based on scattered light scattered in a direction different from the light irradiation direction, a high-sensitivity multi-channel light is used as a means for measuring the scattered light. A liquid particle counter comprising a detector. (2) The high-sensitivity multichannel photodetector includes an optical amplifier,
2. The liquid particle counter according to claim 1, further comprising a photodiode array for individually detecting each portion of the output of the optical amplifier. (3) The submerged particle counter according to claim (2), wherein the optical amplifier comprises an image intensifier. (4) Claim (2) or (3) wherein the optical amplifier and the photodiode array are coupled by optical coupling means.
) Liquid particle counter described. (5) Claim (4) wherein a fiber plate and a field diaphragm are provided outside the photocathode of the optical amplifier, and the scattered light of the particles is imaged on the light incident surface side of the fiber plate within the field diaphragm. The liquid particle counter described.