JPS63233352A - Particle analyser - Google Patents

Abstract

PURPOSE:To perform measurement generating no error, by periodically sampling an input signal at a time other than a time when a pulse is generated by the passage of a particle to be inspected to extract a base line value and calculating the difference between the base line value and the input signal from the light detector. CONSTITUTION:The output (a) of a beam detector 1 to which laser beam is incident is branched into two and both outputs are respectively supplied to HPF 2 and a delay circuit 3. The output (b) of HPF 2 is inputted to a comparing circuit 4 along with reference voltage VO to be compared with said voltage VO and, as a result, the passing timing pulse (c) of a particle to be inspected is obtained. This pulse (c) is supplied to an AND circuit 6 along with a clock pulse CLK through a sampling prohibiting circuit 5. Next, OR of the pulse (c) and the pulse CLK is claculated in the circuit 6 and a sampling clock pulse (e) is inputted to a sample holding circuit 8. The output (f) of the circuit 3 is inputted to a differential circuit 7 and the circuit 8 and the output of the circuit 8 is inputted to the differential circuit 7 as a signal (g) through LPE 9 and the difference between the signals (g), (f) is calculated in the circuit 7 to display an output (h) having good accuracy on a display part 11 through a processing part 10.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a particle analysis device called a so-called flow cytometer that analyzes the properties of test particles by detecting scattered light from the test particles.

[Conventional technology]

A flow cytometer is a cell suspension solution that flows at high speed.
In other words, it is a device that irradiates a sample liquid with, for example, a laser beam, detects a photoelectric signal from the scattered light and fluorescence, and elucidates the properties and structure of cells, and is used in cytochemistry, immunology, hematology, oncology, genetics, etc. used in the field of In the conventional particle analysis device used in this flow cytometer, for example, 200 ILmX
Inside the flow section with a minute rectangular cross section of 200 lm,
A light beam such as a laser beam is irradiated onto test particles such as blood cells passing through the sheath fluid, and the resulting pulsed forward and side scattered light is used to determine the shape, size, and shape of the test particles. It is possible to obtain particle-like properties such as refractive index. In addition, for test particles that can be stained with fluorescent agents, important information for analyzing the test particles can be obtained by detecting the fluorescence of the test particles from side scattering light in a direction almost perpendicular to the irradiation light. can be found. Scattered light and fluorescence obtained when the test particles cross the laser beam are collected by an optical system such as a lens (not shown) and are incident on a photodetector. Therefore, the output signal a converted into an electrical signal contains a pulse-like signal corresponding to the test particle as shown in Fig. 2 (1), and includes the scattered light from the edge of the blow cell, the Fluorescence caused by fluorescent substances melted in the sample liquid other than those deposited on particles is superimposed as an external noise component in the form of direct current or as a low frequency component. As a result, this appears as a mismatch between the baseline a' and the zero level, or as a fluctuation in the baseline a'. In conventional signal processing circuits that calculate the peak value of a pulse signal or the area integral value of a pulse, it is necessary to remove low frequency components such as DC components and noise caused by the above-mentioned external light, etc. This problem is solved using the adjustment circuit shown in Japanese Patent No. 153545/1982. However, as the frequency of passage of test particles increases, that is, as the repetition frequency of the pulse increases, the baseline will drop below the zero level when using the /X pass filter, and the peak value of the pulse will decrease. An error will occur. Furthermore, even when the above-mentioned adjustment circuit is used, the extracted baseline value becomes larger than the actual value, and the final output after the differential circuit has a baseline lower than the zero level, resulting in an error, as in the former case. [Objective of the Invention] An object of the present invention is to extract a baseline value by periodically sampling the input signal at a time other than when a pulse is generated due to the passage of a test particle, and to extract a baseline value from the input signal by a photodetector. By calculating the difference between the input signal from the base line and the input signal, the baseline value and zero level will match even if the pulse repetition frequency increases. The object of the present invention is to provide a particle analysis device that enables error-free measurement. [Summary of the Invention] The gist of the present invention to achieve the above-mentioned object is to irradiate a light beam onto a test particle, receive pulsed scattered light from the test particle, and analyze the test particle. The apparatus includes means for extracting a baseline value of an output signal from a photodetector that receives scattered light at a time other than when a pulse is generated, and a means for extracting a baseline value obtained by the extraction means as an output of the photodetector. A particle analysis device characterized by comprising: means for subtracting from a signal. [Embodiments of the Invention] The present invention will be described in detail based on illustrated embodiments. The output a of the photodetector 1 into which the laser beam is incident is divided into two branches,
It is connected to a bypass filter 2 and a delay circuit 3. The output of the bypass filter 2 is inputted to the comparison circuit 4 along with the reference voltage vO, and the output C of the comparison circuit 4 is sent to the AND circuit 6 via the sampling prohibition circuit 5 as a clock pulse CL.
Connected with K. The output f of the delay circuit 3 is branched into two branches and connected to a differential circuit 7 and a sample-and-hold circuit 8.
Further, the output e of the AND circuit 6 is connected to the sample hold circuit 8 together with the output f of the delay circuit 3, and the output of the sample hold circuit 8 is connected to the differential circuit 7 as a signal f through a low pass filter 9. The output of 7 is the processing part 1.
0 to the display section 11. The output signal a of the photodetector l shown in FIG. 2(1) is first passed through a bypass filter 2 and then input to a comparator circuit 4 in order to recognize the passage of test particles. Bypass filter 2
As shown in FIG. 2 (2), when the frequency of arrival of pulses increases, the baseline b' is slightly lower than the zero level. down. The comparator circuit 4 compares this signal with the reference value vO, and as a result, the passage timing pulse C of the test particle shown in FIG. 2 (3) is obtained, and this timing pulse C is input to the sampling prohibition circuit 5. be done. In order to prohibit sampling of the falling portion lower than the reference value vO shown in FIG. 2 (2) in the sampling prohibition circuit 5, a passing timing pulse is applied to its output d as shown in FIG. 2 (4). The sampling prohibition period d° is set longer than C. Furthermore, the AND circuit 6 calculates the AND with the sampling clock pulse CLK, and finally the AND circuit 6 obtains the sampling clock pulse e shown in FIG. 2 (5), which is input to the sample hold circuit 8. Ru. On the other hand, the output signal a from the photodetector l is also input to the delay circuit 3, and the output signal f from the delay circuit 3 shown in FIG. 2(6) is input to the sample and hold circuit 8. Then, the output signal f is sampled according to the sampling clock pulse e, and by passing it through the delay circuit 3, it is possible to prevent the sampling of the rising part below the reference value vO, and in the end, it is possible to prevent the sampling of the rising part below the reference value vO. It becomes possible to sample only lines. 5 more
The output signal of the sample-and-hold circuit 8 is passed through a low-pass filter 9 to obtain a smooth baseline signal g shown in FIG. 2 (7). By determining the difference between this baseline signal g and the output f of the delay circuit 3, the final result is that there is no fluctuation in the baseline a' and that the baseline a' coincides with the zero level as shown in Fig. 2 (8). ) It is possible to obtain the highly accurate pulse signal shown in (). This signal is input to a processing section 10, where peak values, area integral values, etc. are detected, subjected to statistical processing, and sent as data such as a histogram to a display section 11 for necessary display. When the scattered light from the edge of the flow cell is small, the fluctuation value due to a 50 Hz or 60 Hz commercial power source superimposed on the baseline a' is extremely small. In this case,
It is sufficient to cut only the DC component, and sampling of the baseline a' is not done periodically, but once between pulses.
For example, it suffices to sample once immediately after the pulse. In addition, if the pulse interval at that time is long and a voltage drop due to leakage current of the capacitor of the sample-and-hold circuit 8 becomes a problem, the baseline value immediately after the pulse is converted from analog to digital and -H latched. It is also possible to perform digital-to-analog conversion to obtain the difference between the output signal a and the output signal a of the photodetector 1. [Effects of the Invention] As explained above, the particle analysis device according to the present invention extracts the baseline value by periodically sampling only the baseline value of the output signal of the photodetector other than when a pulse is generated, By taking the difference from the output signal, fluctuations in the baseline value can be removed and an accurate baseline cut signal in which the baseline value coincides with the zero level can be obtained. This makes it easy to perform signal processing such as detecting a peak value of a pulse with high accuracy or detecting an integral value of an area, regardless of the pulse repetition frequency.

[Brief explanation of drawings]

The drawings show an embodiment of the particle analysis apparatus according to the present invention, with FIG. 1 being a block circuit configuration diagram and FIG. 2 being an output waveform diagram of the main parts. Symbol l is a photodetector, 2 is a bypass filter, 3 is a delay circuit, 4 is a comparison circuit, 5 is a sampling prohibition circuit, 6 is an AND circuit, 7 is a differential circuit, 8 is a sample and hold circuit,
9 is a low-pass filter, 10 is a processing section, and 11 is a display section.

Claims (1)

[Scope of Claims] 1. An apparatus for analyzing the test particles by irradiating the test particles with a light beam and receiving pulsed scattered light from the test particles, the apparatus comprising: a light beam that receives the scattered light; It is characterized by comprising means for extracting the baseline value of the output signal from the detector at a time other than when a pulse is generated, and means for subtracting the baseline value obtained by the extraction means from the output signal of the photodetector. Particle analysis device. 2. The particle analysis device according to claim 1, wherein the baseline value is extracted by periodically sampling. 3. The particle analysis device according to claim 1, wherein the baseline value is extracted by sampling immediately after pulse generation. 4. The particle analysis device according to claim 1, wherein the extracted baseline value is converted into a digital value.