Tools and Diagnostics for Projection Display Metrology
Paul A. Boynton
Electronic projection display specifications are often based on measurements made in ideal darkroom conditions and assume ideal measurement instrumentation. However, not everyone has access to such a facility, and not always will the light-measuring devices necessarily provide accurate information. In many environments, ambient light from other sources in the room illuminates the screen. This includes room lights directly illuminating the screen and the reflection of these light sources off of walls, floors, furniture, and other objects. Additionally, back-reflections arising from the image on the projection screen must be considered. These stray light components contribute to the measured values and give rise to inaccurate measurement of the projector light output. Thus, these and other conditions may make the task of adequately comparing and evaluating different projection systems difficult. We can better verify whether the projector is operating according to its specifications or compare its performance with other projectors by compensating for stray light and testing the measurement instrumentation. Simple tools and diagnostics will be discussed that address some of these concerns.