Particle measuring device and particle measuring method

A particle measuring method comprising:

• detecting scattered light generated due to interaction between a particle contained in a liquid sample and light incident on the liquid sample, and converting the detected scattered light into a signal with a magnitude corresponding to intensity of the detected scattered light;
• performing a predetermined number of parallel processing on the signal to add a predetermined number of uncorrelated noises to the signal respectively and output resulting signals after the performing the predetermined number;
• binarizing the resulting signals after the addition using a binarization threshold set in accordance with the liquid sample, and outputting the binarized signals;
• calculating and outputting a value based on the binarized signals;
• passing a predetermined frequency component of the output in the calculating and outputting the value;
• determining that the particle is present when the output in the passing the predetermined frequency component exceeds a predetermined particle threshold determined in advance according to a minimum measurable particle size of a particle measuring device;
• and
• calculating the binarization threshold based on a characteristic amount of a scattered light component of the liquid sample,
• wherein, in the binarization, the resulting signals after the addition are binarized using the binarization threshold calculated by the binarization threshold calculation.

A non-transitory computer readable medium encoded with a signal processing program for measuring a particle included in a liquid sample, that is to be executed by a computer including a processor coupled to a memory storing instructions to permit the processor to function as:

• an addition unit that performs a predetermined number of parallel processing on a signal to add a predetermined number of uncorrelated noises to the signal respectively and outputs resulting signals after the addition, the signal having a magnitude corresponding to intensity of scattered light generated due to interaction between the particle and light incident on the liquid sample;
• a binarization unit that binarizes the resulting signals after the addition using a binarization threshold set in accordance with the liquid sample, and outputs the binarized signals;
• a calculation unit that calculates and outputs a value based on the binarized signals;
• a filter unit that passes a predetermined frequency component of the output of the calculation unit;
• a determination unit that determines that the particle is present when an output of the filter unit exceeds a predetermined particle threshold determined in advance according to a minimum measurable particle size of a particle measuring device;
• and
• a binarization threshold calculation unit that calculates the binarization threshold based on a characteristic amount of a scattered light component of the liquid sample,
• wherein the binarization unit binarizes the resulting signals after the addition using the binarization threshold calculated by the binarization threshold calculation unit.