Patent ID: 8531663

Claim:
A particle diameter distribution measurement device comprising a light irradiation part that irradiates light on a particle group that moves in a disperse medium, a light receiving part that receives scattered light emitted from the particle group on which the light is irradiated and that outputs a pulse signal in accordance with a photon number of the received light, a plurality of multibit counters that are arranged in parallel and each of which has a gate and receives the pulse signal while the gate is open and counts a pulse number, a correlator that obtains auto-correlation data from time series data of the pulse number obtained sequentially from each of the multibit counters, and a calculation part that calculates particle diameter distribution of the particle group based on the auto-correlation data obtained from the correlator, and further comprising a gate time changing part that changes gate time once or a plurality of times and a gate time judging part that compares mutually, at every time when the gate time is changed, the differences between the maximum value and the minimum value of the auto-correlation data output by the correlator at every time when the gate time is changed by the gate time changing part and judges the gate time corresponding to the maximum difference as a recommended value.