an instrument attached to a microscope, etc to enable an observer to view simultaneously the image and a drawing surface to facilitate the sketching of the image
Word origin
New Latin: light chamber
camera lucida in American English
(ˈlusɪdə)
an optical instrument, containing a prism or an arrangement of mirrors, that appears to project the image of an object being viewed through it onto a surface, thereby allowing its outline to be traced: often used with a microscope