A cassette reader for detecting the status of stained samples is provided. The colorimeter includes one or more high power emitting diodes as the source of illuminating the sample. An elliptical mirror, with a central aperture to permit the light to penetrate on to the sample, directs the scattered light on to its focal point at a detector. The colorimeter includes a microprocessor which compares an output signal for the percent ratio value of the detected values of a sample and a standard sample. The colorimeter housing provides position sensors which allow the identification of the well being examined. Finally, the system is modified to measure cell motility by determining the ratio of motile sperms to total cell concentration.