PURPOSE: To secure the uniformity of an area coated with adhesive and to improve the flatness of a platen glass by injecting the adhesive into a groove, and putting the platen glass on the groove injected the adhesive.

CONSTITUTION: After attaching a photodetector array 3, a LED array 4 and a 'Selfoc(R)' lens 5 which are an optical part to a enclosure 1, the adhesive such as a silicone resin is injected into the groove 9 of the box 1 by a needle and the like, a platen glass 2 is put on the enclosure 1, and an adhesion is executed by applying pressure on the above mentioned platen glass in the direction of an arrow 10. At this work, by making the quantity of the adhesive appropriate, the drip and the swell of the adhesive are evaded. Therefore, by applying pressure in the case of the adhesion, the platen glass 2 is adhered closely to the putting part of the enclosure 1. Thus, the platen glass is adhered to the enclosure 1 uniformly and the flatness of the platen glass is improved.