Abstract: A particle detection system uses illumination incident at an angle to detect particles in a liquid such as water. By using illumination incident at an angle, the scattered light can be measured through a range of angles that are greater than the measured range of angles produced when the illumination is incident at a normal angle, when using the same detector. For example, the light can be measured through an angle that is twice that produced with illumination incident at a normal angle.

Abstract: A particle detection system uses illumination incident at an angle to detect particles in a liquid such as water. By using illumination incident at an angle, the scattered light can be measured through a range of angles that are greater than the measured range of angles produced when the illumination is incident at a normal angle, when using the same detector. For example, the light can be measured through an angle that is twice that produced with illumination incident at a normal angle.

Abstract: A method and apparatus are provided for testing a photodetector (20) that has a narrow field of view (A) and an alignment surface (50), to determine whether the field of view and the axis (52) of the field of view are precisely what is expected or deviates therefrom. While the photodetector views a region or zone (102), a narrow spot of light (82) is moved into and out of the zone and across the zone, while the output of the photodetector is monitored. The narrow spot of light is generated by focusing a small spot of light onto a surface. The small spot of light can be a spot of light on an oscilloscope monitor (80) which scans the spot back and forth in a raster pattern. To create a very small spot, the image on the oscilloscope monitor is focused to a greatly reduced size spot image (124) onto the surface that the photodetector views.