PURPOSE: To make a fine adjustment of diopters and also to make a focus adjustment of a lens easily by superposing an interchangeable frame on the front- side surface of a main frame, and moving back and forth receiving bodies and sliding levers for adjustment and then fixing them.

CONSTITUTION: Sliding levers 16 and 16 formed at lugs 15 and 15 of the interchangeable frame 2 are inserted into front opening parts 11a and 11a of receiving bodies 9 and 9 fixed to lugs 5 and 5 of the main frame 1, and the sliding levers 16 and 16 are slid back and forth to allow support frames 3 and 3 to come closer to and leave lens frames 13 and 13, thus adjusting the positions of the lens frame 13 and 13 according to eyesight. Then, screws 12 and 12 are engaged threadably with through holes 10 and 10 bored in top surfaces of the receiving bodies 9 and 9 and the sliding levers 16 and 16 are fixed and held with tips of the screws 12 and 12 so that they can be disengaged.