When the projector has a fixed lens, the size of the image on the reflective screen is constant.
The intensity of the light was increased by a combination of a dioptric fixed lens and catoptric mirrors.
Coolpix A is a fixed lens, point-and-shoot camera.
In terms of single-lens cameras, he could look at the Yashica T3, which has a fixed 35-millimeter lens and a water-resistant exterior.
It is easier to make fixed focal lenses than to include them in a variable focus lens.
(He uses a Pentax 67II with only two fixed lenses.)
The original apparatus was an oil burner with a catadioptric fixed lens and light intensity of 600 cd.
Their major drawback is a lack of versatility; most have a single, fixed lens, and none allow the user to adjust exposure manually.
Again, I would say consider an SLR and a couple of basic fixed lenses for the same price.
It also has a fixed lens and a beam splitting prism instead of a moving mirror.