While the Camera Lucida was not patented until 1807 by William Hyde Wollaston, there is some evidence that it is nothing but a re-envisioned device that was found to be clearly described by Johannes Kepler in 1611, but Keplers work had practically vanished my the 19th century so Wollaston was never challenged, the name itself, was made by Wollaston, “lucida” meaning “light” in Latin rather than Camera Obscura’s “dark room”.
In 2001 David Hockney’s book Secret Knowledge was met with mixed reviews as it challenged some of the pasts greatest artists; Ingres, Van Eyck and Caravaggio, theorizing that they used a Camera Lucida or other image acquisition devices to create their masterpieces.
In the simplest form of camera lucida, the artist looks down at the drawing surface through a half-silvered mirror tilted at 45 degrees. This superimposes a direct view of the drawing surface beneath, and a reflected view of a scene horizontally in front of the artist. This design produces an inverted image which is right-left reversed when turned the right way up. Also, light is lost in the imperfect reflection. Wollaston’s design used a prism with four optical faces to produce two successive reflections (see illustration), thus producing an image that is not inverted or reversed.