A method of modulating data having a basic data length of m bits, to a variable-length code having a basic code length of n bits. The light source emits an illumination beam to the macula. The treated surfaces are brought into contact. The protruding part protrudes nearly perpendicularly from the side face which is perpendicular to the peripheral face of the developing sleeve, so as to cover the regions of the peripheral face of the developing sleeve from the base part to the portion facing the doctor blade. The second interlocking member has an attachment region that is facing away from the web. Furthermore, a protective transmission line is provided, and a protective-signal light switch for selecting a combination of the protective transmission line, the wave multiplexer, and the wave demultiplexer is provided.