Patent ID: 7686988

Claim:
A method of forming a die surface onto a producing die to produce an optical element, wherein the die surface transfers an optical surface onto the produced optical element, the method comprising the steps of: bringing a cutting tool to come in contact with a material so as to cut the material; and moving the material relatively to the cutting tool so as to form the die surface having a diameter of 5 mm or less with a curvature on the material; wherein the material is one of a ceramic and a tungsten carbide cobalt alloy and has a hardness not smaller than Rockwell hardness HRA 80 or Vickers hardness Hv 1000 and the cutting step is conducted to cut the material with a cutting-in depth of 1 μm or less, and wherein the cutting tool has a cutting edge capable of coming in contact with the material, the cutting edge comprises a diamond and the cutting step is conducted while the cutting tool is set such that a single point of the cutting edge comes in contact with the material as a cutting point, the cutting point of the cutting edge is fixed at the single point, and a (110) surface of the diamond is used as a rake face at the cutting point.