PURPOSE: To perform a high-speed, precise analysis by setting the thickness in focus depth direction of the area where a sample solution is carried in a sheath flow larger than the focus depth, and selecting a clear image signal from a plurality of images taken in a fixed direction to form a composite image.
CONSTITUTION: A sample solution containing particles is circumferentially enclosed by a sheath solution to form a sheath flow at a fixed speed. The thickness of the area where the sample solution is carried is set larger than the focus depth, so that a large quantity of the sample solution can be carried in a short time. A plurality of images are taken in a fixed direction by a CCD camera, and the image signal is divided every area by an image dividing circuit 33. In a visibility extracting circuit 34, the visibility showing the degree of obscureness of image is calculated every local point in each area. A selecting composite circuit 35 receives the divided image signals and the arithmetic result of visibility, and extracts the clearest part from each area to compose one particle image. In this case, every part in the image surface, the visibility of the corresponding part of the image in each area is mutually compared to select the optimum area, and the image signal is taken out to compose the image.
TSUZUKI KOICHI
MIYAKE AKIRA
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