The camera lucida is an optical component that fits into the optical train of the light microscope in such a manner that when observing the specimen through the eyepiece you can simultaneously see your piece of paper and pencil and the drawing you are doing.
Artists use macroscopic versions of this device - and David Hockney in his book Secret Knowledge uses a Camera lucida to replicate the rapid and accurate sketching style of Ingres drawings - http://www.koopfilms.com/hockney/articles.html).
Using a camera lucida is not a tracing task nor just copying - it requires an ability to choose which details are most important to record to make an accurate record of the specimen. It does not use hardware and the image recording medium is paper and pencil (or pen).
The field of paleontology still makes heavy use of camera lucida drawings to illustrate research papers - they have found that photographic reproduction of a faint impression on a dark background does not reveal the detail that they can see with the human eye through a stereo microscope.
Interestingly one of the most famous paleontological stories of the past 30 years - the re-discovery of the Burgess Shale fossils - was facilitated by camera lucida drawings - here is the lead academic Harry Whittington reflecting on it;
"I soon realised, in my work on Burgess Shale fossils, that explanatory drawings would be needed as well as photographs, to describe these fossils. This is where Dr Wollaston enters the scene - a late 18th to early 19th Century physician, who practised in London for many years, and made valuable contributions to chemistry and optics. He had a cracked shaving mirror, but instead of throwing it away he puzzled over the refractions and reflections of light caused by the cracks.
This led to his realising that by inserting a prism into a microscope tube, the image could be directed laterally, then down on to paper beside the microscope, and provide a way to draw an accurate picture. In much refined form this is his invention, the camera lucida, which I used to make my drawings."
Here is a camera lucida drawing of an anomalocaris fossil trilobite from http://www.trilobites.info/species.html
