Particle sizing by optical diffraction

A particle-sizing instrument comprising:

• a sample cell for receiving a sample comprising a plurality of particles;
• a light source configured to illuminate the sample with a light beam to produce scattered light by the interaction of the light beam with the particles;
• a first optical system comprising a first and second optical element respectively configured to split a portion of the scattered light into a first and second portion of scattered light;
• a second optical system configured to receive the first and second portion of scattered light from the first optical system, and to recombine the first and second portion of scattered light to produce an interference signal at a detection location;
• a detector configured to detect the interference signal at the detection location;
• and
• a processor configured to receive measurement data from the detector indicative of the interference signal at the detection location, and to determine a particle size and/or a particle size distribution from the measurement data.