PURPOSE: To stably and inexpensively supply a high-performance diffraction grating by working the surface of a quartz glass base plate to the shape of the diffraction grating, forming a noble metal thin film on this base plate, using this base plate as a mold and pressing the mold to a thermally softened glass member, thereby transferring the shape of the diffraction grating to the surface of a glass member.
CONSTITUTION: The shape of the diffraction grating is formed on the surface of the quartz glass base plate 3. As a result, the shape specifications as the mold for molding of the diffraction grating having the shape featuring sufficiently high surface roughness and high accuracy are sufficiently satisfied. Fusion arises with the glass blank in a stage of press forming in this state when such base plate is softened by heating in the case of using the base plate as the mold for glass forming and, therefore, the noble metal thin film 4 having a mold parting effect to the glass is previously formed on the surface of the glass base plate formed with the diffraction grating in order to deal with such fusion. The shape of the diffraction grating is transferred in reversal onto the glass blank by press forming the thermally softened glass blank by using the quartz glass mold subjected to such treatment.
TAKASE HIROTSUGU
TAKIZAWA HIDEKI
