PURPOSE: To obtain a picture of good quality by protecting optical parts from dust containing floating toner essentially, by arranging a dust adsorption plate near the optical path surface of a light focusing glass fiber transmission body.

CONSTITUTION: An original image on original setting table 11 which can reciprocate to left and right is projected successively upon photoreceptor drum 2 via light source 12 and light focusing glass fiber transmission body 13. The rectangular bottom surface of transmission body 13 opposing to drum 2 adsorbs easily floating toner coming off a developing mechanism. To adsorb this floating toner, dust adsorption plate 4 made of a high molecular electret film is arranged near transmission body 13. Consequently, no dust sticks to transmission body 13, the functions of a lens are maintained for a long period, and pictures of good quality are obtained without causing a fogging phenomenon.