A duobinary optical transmission device provides duobinary optical transmission with improved quality by a technique that does not require an electrical low pass filter LPF. The system includes a module interface connected with the processor, a peripheral interface unit connected between the module interface and a peripheral component connected to the peripheral interface unit. An image of the subject formed by the image pickup optical system is converted into an electric signal. The position-limiting device is assembled in the interior of the machine seat for restricting and fixing the work-piece backing plate in position to prevent the work-piece backing plate from shifting bias in the course of processing, able to elevate processing precision. The transparent electrically-conductive film according to the present invention has especially excellent color feeling and mechanical property as well as excellent transmittance.