Canon Kabushiki Kaisha

Masaki Ohmori

Kiyoshi Yamamoto

Takeshi Nomura

Fumitaka Yoshimura

Isamu Shigyo

Tetsuo Kuwabara

Bunryo Sato

Masashi Mashige

An optical lens press-molded so that within at least the optically effective diameter thereof, the thickness thereof may become greater from the center of the optical axis thereof toward the marginal portion of the lens, characterized in that at least one of the both lens surfaces thereof is a spherical or aspherical concave lens continuous from a transferred surface formed so that in the area outside the optically effective diameter thereof, the thickness of the lens may be limited away from the extension of a curved surface of a radius of curvature setting the optically effective diameter toward the outer diameter of the lens, and forming the transferred surface up to at least the required outer diameter of the lens, and a free surface portion is left outside the outer diameter of the lens during molding.

Optical lens and mold for molding the same

A method for press-forming a glass preform includes the steps of applying positioning pressure to an upper mold as the temperature of the upper mold and a lower mold increase to set values, maintaining a first temperature difference between the upper and lower molds of at least 10.degree. C. and increasing the temperature of the glass preform to a value above its glass transition temperature. Additional steps include cooling the upper and lower molds at a rate of 30.degree. to 100.degree. C. per minute while maintaining a temperature difference between the upper and lower molds at at least the first temperature difference, applying pressure to the lower mold, and opening the upper and lower molds to release the formed optical element after the temperatures of the upper and lower molds decrease to below a set value and a temperature difference between the upper and lower molds becomes greater than the first temperature difference.

Press-forming method for optical element

A method of molding an optical element by pressing glass material uses a cavity composed of a pair of mold members and a side mold member. Either or both of the pair of mold members are rendered slidable along the axial direction of the optical element within the side mold member used during the pressurized molding operation, so that the pair of mold members move in close contact with the contracting glass along the axial direction in the side mold member, during the cooling subsequent to the pressurized molding due to adhesion between the contracting glass and either or both of the pair of mold members. The contraction of the glass during the cooling phase is limited by the adhesive force between the glass and the mold members when at least one of the pair of mold members traverses a gap and reaches a limit of travel; thus tension will be created in the glass.

Molding method for optical element

In a process for manufacturing an optical element, in which a molding material is put in molds and is heated and press-molded to manufacture an optical element, a preheating treatment of the molding material is performed before it is put in the molds at a reduced pressure and a temperature lower than a temperature during the press molding.

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Kawasaki, Japan

Masaki Ohmori