Optics: measuring and testing – For optical fiber or waveguide inspection
Patent
1996-01-23
1998-04-14
Font, Frank G.
Optics: measuring and testing
For optical fiber or waveguide inspection
356336, 356338, 356343, 356341, 356364, G01N 1502, G01N 2100, G01J 400
Patent
active
057399026
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a liquid flow cytometer for counting and classification of particles such as biological cells or other microscopic particles in liquids, where the cytometer includes an optical system for irradiation and detection in a metering zone, thus enabling optical dispersion and fluorescence caused by the particles to be simultaneously detected when the particles pass the metering zone.
2. The Prior Art
The use of cytometers based on optical dispersion is known in the prior art for counting and classification of microscopic particles in a liquid. This prior art is illustrated schematically in FIGS. 1-3, where FIG. 1 shows the flow system with a flow cell, FIG. 2 shows a hydrodynamic focusing device assigned to the flow cell, and FIG. 3 shows the detector device for optical dispersion caused by particles in the flow cell. In FIG. 1 the sample is fed into a flow cell together with a transport liquid in the form of filtered water which is pumped into the flow cell from a container. The transport liquid and the sample, i.e., those particles which have to be counted and classified pass through the flow cell, a pump system and a filter which removes particles, after which the transport liquid, i.e., filtered water, is passed back to the container. In the flow cell there is provided a hydrodynamic focusing device in flow connection with the actual flow cell which is composed of a capillary tube. The hydrodynamic focusing device is in the form of a conical nozzle which tapers towards and leads into the capillary tube. The sample is passed into the nozzle through a thin tube in the centre of the nozzle and is carried along with the transport water in such a manner that the sample is accelerated towards the mouth of the nozzle and the capillary tube. By directing a focused beam of preferably monochromatic, coherent light onto the flow cell, the particles in the liquid will cause a scattering or dispersion of the light. The scattered light is focused by a lens device on to a photodetector and the intensity of the detected, scattered light will be a measure of the degree of dispersion which in turn is related to the number of particles in the metering zone and their size. In order to prevent the light from the laser beam from entering the detector there is positioned between the flow cell and the focusing device a beam stop which forms a shield against the direct radiation from the laser, but which substantially does not impair the scattered light.
A cytometer which is substantially based on the above-mentioned principles and is suitable for detection, counting and classification of biological cells and other microscopic particles in liquids is known from Norwegian patent application No. 91 427, which hereby is incorporated as reference.
There are also known cytometers and similar instruments for the detection of particles based on the use of fluorescence which is emitted by the particles when they are irradiated with light from a light source. One example of a detector of this kind is known from EP-A1-0539 743, in which there is disclosed a collimator in the form of a parabolic reflector 40 which permits a more efficient use of bandpass filters in order to block scattered radiation during detection.
U.S. Pat. No. 4,662,742 discloses a flow cytometry apparatus including an optical path with a beam splitter to transmit fluorescence and reflect scatter. EP-A-0538551 discloses a flow cytometer for the detection of fluorescence above.
The need for stable, reliable and sensitive analytical instruments for the determination of microbial and cellular content in liquids such as water, beverages, oils and bodily fluids is constantly increasing.
By means of liquid flow cytometry biological particles which are in suspension can be counted and classified in a rapid and reliable manner. As mentioned above, according to this method the particle sample is fed along with a transport liquid and care is normally taken to ensure that the particles pass substantially on
REFERENCES:
patent: 4281924 (1981-08-01), Auer et al.
patent: 4662742 (1987-05-01), Chupp
patent: 5030002 (1991-07-01), North, Jr.
patent: 5040890 (1991-08-01), North, Jr.
patent: 5179026 (1993-01-01), Matsuda et al.
International Pub. No. WO 93/07471 to W. Kaye entitled, "Detecting A Radiation Signal," dated 15 Apr. 1993.
Gjelsnes Oddbj.o slashed.rn
Tangen Reidar
Font Frank G.
Stafira Michael P.
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