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We have been engaged in the researches on the active lighting techniques for twenty years. At first, we proposed a method to measure the 3-D shape of the object by projecting multiple patterns of structured light, because it is much faster than the method with scanning slit of light, and dense range image can be measured. For this purpose, we made a projector which consists of mechanicallychangeable masks, but it was soon replaced by a speciallymade liquid crystal panel with many slit segments. From the fact, we can proudly declare that the projector is not a diverted device but exclusively developed as a part of projector-camera systems, and the projection target is originally not a planar screen but a real scene with varied depth. Actually, this infant device was successful and commercially enough practical for 3-D shape measurement, but unfortunately we had to wait for the evolution of panel display technology more than a decade, to make a step to the studies which utilizes full duality between cameras and projectors. In the middle of 1990s, many researchers started using video projectors. Since we were computer vision researchers, we used the flexibility of video projector not for a interaction technique but improving performance of 3-D measurement such as motion tracking. But we were also aware of its advantage as a visualization tool in a real scene. Alike to the other research activities, we have confirmed that the projector can change the seen color, texture and specular of the real object. In addition, faked shade projected on the object make it possible to change our interpretation of its shape. Furthermore, the traditional shape measurement method we had developed is seamlessly combined with the visualization technique. Therefore, we have a common view to the possibility of intuitive interface systems with realistic visualization for communicating, training and designing works, so now is a good time to look-ing back on the history of projector-camera systems for our community. Of course you are already familiar with most researches in this field, but we regret our less presence if you are not aware of our research activities. Therefore, in this paper, we summarize the history and progress on light projection methodologies in our laboratory.