Particle size distribution measuring apparatus and particle size distribution measuring method

A particle size distribution measuring method using a particle size distribution measuring apparatus comprising:

• a cell into which a portion of a sample including a medium and particles dispersed in the medium is successively introduced;
• a light source that emits measurement light;
• a photodetector that receives scattered light from particles irradiated with the measurement light and detects an intensity of the scattered light;
• a filter member that is arranged in a predetermined position in a light path of the measurement light from the light source to the cell or a light path of the scattered light from the cell to the photodetector and attenuates the measurement light or the scattered light;
• and a measurement part that on a basis of a fluctuation in the scattered light intensity detected by the photodetector and an attenuation level of the filter member, measures a particle size distribution of a portion of the sample in the cell, wherein:
• the measurement part, by measuring a particle size distribution every time a portion of the sample is introduced into the cell as well as combining particle size distributions obtained at a series of times of measurement, calculates a particle size distribution of measured portions, the portions being introduced at the multiple times of measurement, respectively;
• and
• the filter member is changed to one having a different attenuation level at every time of measurement or a part of the multiple times of measurement.