laser accordingly while the unit being replaced has a very high power 3 watt laser it has been surprisingly found that replacing the water cooled laser with an air cooled high power laser of from about 300 mw up to the maximum 500 mw actually surprisingly still works as a light source for a microplate reader when replacing it from the standard water cooled laser it has also been discovered that a more homogeneous lighting can be achieved by filtering the light or passing the light from the air cooled laser through a filter or aperture of some kind these embodiments provide a more even lighting on the bottom of a microplate during reading and thus when tested results in a coefficient of variation cv of 0 6 or about the same as a water cooled laser one skilled in the art and understanding the problems described herein can vary the choice of air cooled lasers and filters or apertures to optimize the light source in view of the disclosure herein the air cooled laser needs to be held in relative fixed relationship so that light emanating from the air cooled laser remains constant within the beam produced the stand or mounting bracket or the like can keep the relative position of the air cooled laser constant but must be able to be adjusted when in place.