To further isolate the scattered light 112 of a specific particle from the scattered light of a different particle, a pin hole device 116 can be used. The pin hole device 116 prevents unfocused light from other particles from entering the second plane 118, thus isolating a desired, focused image of one particle 110 of the sample 106. In one embodiment, the pin hole 116 has a size of several microns. At the second plane 118, a traditional imaging detection device 120 detects the defocused light. The position of the second image plane 118 is chosen for good angular resolution of the scattered light 112, and at the same time gives enough light for the imaging detection device 120 to obtain a sufficient reading.