Recently, many types of computer-generated stereograms (CGSs), i.e. various works of art produced by using computer
are published for hobby and entertainment. It is said that activation of brain, improvement of visual eye sight, decrease of
mental stress, effect of healing, etc. are expected when properly appreciating a kind of CGS as the stereoscopic view.
There is a lot of information on the internet web site concerning all aspects of stereogram history, science, social
organization, various types of stereograms, and free software for generating CGS. Generally, the CGS is classified into
nine types: (1) stereo pair type, (2) anaglyph type, (3) repeated pattern type, (4) embedded type, (5) random dot
stereogram (RDS), (6) single image stereogram (SIS), (7) united stereogram, (8) synthesized stereogram, and (9) mixed
or multiple type stereogram. Each stereogram has advantages and disadvantages when viewing directly the stereogram
with two eyes by training with a little patience.
In this study, the characteristics of united, synthesized and mixed type stereograms, the role and composition of depth
map image (DMI) called hidden image or picture, and the effect of irregular shift of texture pattern image called wall
paper are discussed from the viewpoint of psychophysical estimation of 3D virtual depth and visual quality of virtual
image by means of simultaneous observation in the case of the parallel viewing method.