During my school days in the 1960s and 1970s, the teacher would occasionally wheel out a monstrosity known as the opaque projector. It would project the image of an opaque object, such as the page of a book, onto a screen. Apparently, the models of that era had about a 1000 watt lamp inside, and their size was due in part to the fact that they required a big fan to keep it cool. The process also required a lens that was quite large.
The projector was rarely used. Instead, it was much more common to copy the desired image onto a transparency, which was projected with the much more common overhead projector.
75 years ago this month, the September 1943 issue of Popular Science showed how to make an opaque projector. The article doesn’t seem to specify the wattage of the bulbs, but since ordinary household bulbs are shown, I assume that they would be 100 watts. The lens is made from one, or preferably two, magnifying glasses mounted in a tube.
