PURPOSE: To reduce fatigue and to improve operability of an observer by enabling displaying coordinates of an observation image being observed at present within the scope of a visual field of a microscope or at a part of a screen of a TV device.

CONSTITUTION: A photomask 1 having a mask pattern 1a is fixed on an XY table 2 and displayed by enlarging as the observation image within the scope of the visual field by the microscope 3 incorporated with a light source 4, a condenser lens 5, an objective lens 6, half mirrors 7, 8, a prism 9 and an ocular lens 10 in a lens-barrel 11. Further, a length measuring machine 12 utilizing laser light or the like is arranged at one end of the table 2 and a detected XY coordinates signal is inputted to a control circuit 13 to make a digital numerical display on a coordinates display 14. Further, a numerical image displayed on the display 14 is synthesized in the observation image of a pattern image by a coordinates optical system 19 consisting of a light source 15, lenses 16, 17, a half mirror 18, etc.