PURPOSE: To convert an image of a cathode-ray tube to a three dimensional stereo image by placing a mirror oscillates the image on the cathode-ray tube and a semitransparent mirror between them by inclining to about 45°.

CONSTITUTION: A mirror 3 is placed in parallel on the fluorescent screen of a cathode-ray tube 1, and between them a semitransparent mirror 2 is placed by inclining to about 45°. When the mirror 3 is oscillated to the surface itself in the vertical direction, the image due to the mirror 3 of the cathode-ray tube surface oscillates an area 4, and further, an image due to the semitransparent mirror 2 oscillates an area 5. This can be observed from a position 6. Here, when a display pattern, etc., on the cathode-ray tube are changed in accordance with the position of the mirror 3, a three dimensional image can be freely drawn at an area 5.