Abstract: Apparatus (100) for measuring particle size distribution by light scattering comprises a blue LED (102) and a 633 nm helium neon laser (104). Light output from the LED and laser is separately passed or reflected by a dichroic element (116) onto a common path through a sample cell (122) containing a sample, the particle size distribution of which is to be measured. Light scattered from the sample cell is detected by one or more detectors (112B-H). Light transmitted by the sample cell is detected by detectors 112A, 112J. Output signals from one or more of the detectors are passed to a computation unit (114) which calculates particle size distribution. A small percentage of light from the blue LED is reflected by the dichroic element to a detector (110). Similarly, a small percentage of light from the laser is passed by the dichroic element to the detector. Output signals from the detector are fed back to control units (106, 108) to stabilize the output power of the LED and laser.

Abstract: Apparatus (100) for measuring particle size distribution by light scattering comprises a blue LED (102) and a 633 nm helium neon laser (104). Light output from the LED and laser is separately passed or reflected by a dichroic element (116) onto a common path through a sample cell (122) containing a sample, the particle size distribution of which is to be measured. Light scattered from the sample cell is detected by one or more detectors (112B-H). Light transmitted by the sample cell is detected by detectors 112A, 112J. Output signals from one or more of the detectors are passed to a computation unit (114) which calculates particle size distribution. A small percentage of light from the blue LED is reflected by the dichroic element to a detector (110). Similarly, a small percentage of light from the laser is passed by the dichroic element to the detector. Output signals from the detector are fed back to control units (106, 108) to stabilise the output power of the LED and laser.