JPS63233372A - Particle analyzer - Google Patents

Abstract

PURPOSE:To enable the highly precise detection of a peak value and an area integral value by a method wherein a base line value of an input signal before measurement is stored as a digital value and this value is subtracted from an output signal of a photodetector during the measurement. CONSTITUTION:An output signal (a) of photodetector 1 is passed through LPF 2, and thereby a direct-current component (b) is obtained. Simultaneusly with a rise signal at the beginning of measurement, a processing unit 7 delivers a conversion start signal (d) to an A/D converter 4. Next, simultaneously with the end of A/D conversion of the component (b), the processing unit 7 delivers a write signal (e) to a memory 5, and thereby a digital value b' of a base line at the beginning of the measurement is stored in the memory 5. Thereafter the content of the memory 5 are inputted to a D/A converter 5 during the measurement, and a value (f) obtained through D/A conversion of the component in the converter 6 is outputted as the ampli tude of the base line at the beginning of the measurement and inputted to a differential circuit 3. In this circuit 3 the value (f) is subtracted from the signal (a), so as to obtain an output signal (g) formed by separating the component (b) away from the signal (a). This signal (g) is inputted to the processing unit 7, and a peak value or the like is detected thereby and displayed as a signal (h) on a display unit 8.

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. It is something.

[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 conventional particle analysis devices used in flow cytometers, etc., the central part of the flow cell has a particle diameter of 200 gm
A beam of light such as a laser beam is irradiated onto test particles such as blood cells wrapped in a sheath liquid and passing through a flow section with a minute rectangular cross section of 0.00 gm, resulting in pulsed forward and side scattering. The light detects the shape and shape of the particles being tested.
It is possible to obtain particle properties such as size and 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.

Generally, the output signal converted into an electrical signal by a photodetector includes a pulse-like signal caused by the particles to be detected as shown in FIG. 2 (1), and this signal includes scattered light from the edge of the flow cell, Alternatively, fluorescence caused by a fluorescent substance that does not adhere to the test particles and is melted into the sample liquid is superimposed as an external noise component in a DC manner. In other words, the baseline a' of the input signal becomes greater than the zero level, and it is difficult to accurately detect the pulse height value, area integral value, etc. as it is, so it is necessary to remove this DC component.

In conventional signal processing circuits that detect the peak value of the pulse signal or the area integral value of the pulse, a bypass filter is conventionally used to remove DC components caused by external light, noise, etc.

I am also making offset adjustments to the circuit.

However, 1. For example, when passing through a bypass filter, as the frequency of passage of the test particle increases, that is, as the repetition frequency of the signal pulse increases, the baseline drops below the zero level, making it difficult to accurately detect the pulse peak value. I can't.

Furthermore, when performing offset adjustment, even though there is no such drawback, the user must perform offset adjustment of the processing circuit to match the baseline to the zero level, and this must be done periodically. The disadvantage is that it requires a lot of effort, such as having to repeat it.

[Object of the invention] The object of the invention is to obtain a baseline value of an input signal before measurement;
In other words, by storing the DC component as a digital value and subtracting this value from the photodetector output signal during measurement,
An object of the present invention is to provide a particle analysis device capable of obtaining a highly accurate pulse signal whose baseline coincides with the zero level.

[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 comprises means for storing a baseline value of an output signal from a photodetector that receives scattered light as a digital value before starting measurement, and means for converting the stored baseline value into an analog value during measurement. 1. A particle analysis apparatus characterized by comprising: means for subtracting from an output signal of a photodetector.

[Embodiments of the invention] The present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a block circuit configuration diagram, and FIG. 2 is a signal waveform diagram. The signal a obtained by the photodetector l is branched into two branches and connected to a low pass filter 2 and a differential circuit 3. The output of the low-pass filter 2 is sequentially connected to an analog/digital converter 4, a memory 5, a digital/analog converter 6, and a differential circuit 3, and the output g of the differential circuit 3 is connected to a processing section 7. ing. Furthermore, outputs e, d, and h of the processing section 7 are connected to an analog-to-digital converter 4, a memory 5, and a display section 8, respectively.

Scattered light obtained when the test particle crosses the laser beam is collected by an optical system such as a lens (not shown) and is incident on the photodetector 1. As mentioned above, this photodetector 1
As shown in Fig. 2 (1), the output signal from the DC component has a DC component superimposed on the baseline a'.
Alternatively, if the amount of scattered light from the edges of the flow cell is not extremely large, it is very small and can be ignored compared to the pulse signal from the target particles. Since the sample flow diameter and laser power inside are both constant, the DC component is also constant.

Therefore, by passing the output signal a through a low-pass filter 2, a DC component as shown in FIG. 2(2) is obtained. Then, along with the rising signal C of the measurement start in FIG. 2 (3),
The processing section 7 is connected to the analog/digital converter 4 as shown in Fig. 2 (4).
A conversion start signal d shown in is sent. At the same time as the analog-to-digital conversion of the DC component ends, the processing section 7 stores the memory 5.
A write signal e as shown in FIG. Thereafter, the contents of the memory 5 continue to be input to the digital-to-analog converter 6 throughout the measurement, and the output value shown in FIG. 2 (6) of the digital-to-analog converter 6, that is, the DC component is converted into Furthermore, the analog-converted value f is output as the magnitude of the baseline a' at the start of measurement,
Input to differential circuit 6. In the differential circuit 6, the baseline value f is subtracted from the output signal a of the photodetector 1 under measurement.
Figure 2 (7) shows the DC component finally cut from signal a.
) is obtained. This signal g
is input to the processing unit 7, where the peak value, area integral value, etc. are detected and subjected to statistical processing to form data such as a histogram, which is sent as a signal to the display unit 8 for necessary display.

In this example, the baseline value was extracted at the start of the measurement, but it is also possible to extract the baseline value at the point when the sample flow starts flowing before the measurement starts, or in some cases, only the sheath liquid can be used for scattered light. It is also possible to extract the baseline value while the message is being played, for example, some time after the power is turned on. Note that in the case of only the sheath liquid, it is not necessary to pass it through the low-pass filter 2, and the digital value is also used.

Although the memory 5 is provided to store the information, a simple latch circuit may be used.

[Effects of the Invention] As explained above, the particle analyzer according to the present invention stores the baseline value at the start of measurement as a digital value, and stores the base line value by converting the digital value from the output signal of the photodetector into an analog value until the end of the measurement. By subtracting the line value, a pulse signal whose baseline coincides with the zero level is obtained.

This ensures good accuracy regardless of the pulse repetition frequency. It has the advantage of being able to detect the % peak value and area integral value, and also omitting the effort of offset adjustment.

[Brief explanation of drawings]

The drawings show an embodiment of the particle analysis apparatus according to the present invention, in which FIG. 1 is a block circuit diagram of a signal processing section, and FIG. 2 is an output waveform diagram of the main part. 1 is a photodetector, 2 is a low-pass filter, 3 is a differential circuit, 4 is an analog-to-digital converter, 5 is a memory, 6 is a digital/e-analog converter, 7 is a processing section, and 8 is a display section. Patent applicant Canon Co., Ltd. Drawings Figure 1 Figure 2 (7). knee·

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; means for storing the baseline value of the output signal from the detector as a digital value before starting measurement; and means for converting the stored baseline value into analog and subtracting it from the output signal of the photodetector during measurement. A particle analysis device comprising: 2. The particle analysis device according to claim 1, wherein the means for converting the baseline value into a digital value converts the output signal of the photodetector into a digital value after passing it through a low-pass filter.