In Popular Photography, June 1976, there's an article by Bob Schwalberg on an invention by Melrose R. Cole, of MA, which he called CPA (Concurrent Photon Amplification) and took six years to develop. It requires a camera with focal plane shutter to be modified to have a number of small light bulbs put into the dark chamber, which gives a correct dose of uniform non-image light on the film. At the time Cole charged $750 for the conversion.
The Photography How-To Guide, summer 1978, also has an article by Gerry Kopelow, not only as a follow-up, but also details the method of constructing your own, using components available off-the-shelf at the time.
The original Cole design used filament lamps which have to take moment to warm up to the correct output level, so a mechanical arrangement was made to fit over the shutter release button; you press it down to activate the bulbs, and further pressure hits the shutter release. The Kopelow version employed LEDs which give instantaneous response.
With the availability of smaller and more power-efficient parts, I feel that an updated design can make a lot of sense, now, who is ready to rise to the challenge?