Optical: systems and elements – Lens – With support
Reexamination Certificate
2000-06-28
2001-04-17
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With support
C359S719000, C359S718000, C264S001100
Reexamination Certificate
active
06219191
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a plastic lens, in particular a pickup lens which is a component of an optical head for optical disks, magnetooptical disks and the like.
The drive unit of optical disks, magnetooptical disks and the like (which are hereunder collectively referred to as “optical disks”) is equipped with an optical head for reading out the information recorded on the optical disks.
The optical head has a pickup lens (objective lens) fixed on a lens holder in the moving part of an actuator and when an electric current is applied to the coil of the actuator, the moving part is driven in two independent directions, one being parallel to the optical axis of the pickup lens and the other being along the radius of the optical disk, so as to perform focusing and tracking control.
The pickup lens is typically manufactured by injection molding of plastic materials. The gate or channel through which a molten plastic material is injected into a mold is located on a lateral side of a cavity (molding space) which conforms to the shape of the pickup lens to be molded and, hence, the produced pickup lens has a corresponding projection (gate portion) formed as an integral part of the periphery.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a plastic lens from which unnecessary gate portion is at least partially removed, to thereby facilitate mounting of the plastic lens to a lens holder with accuracy and ease.
Another object of the present invention is to provide a plastic lens from which unnecessary gate portion is at least partially removed without any adverse effect on the optical characteristic of the lens.
To achieve the above-noted and other objects, the present invention provides the followings:
(1) A plastic lens injection-molded with a plastic material, the plastic lens comprising:
a lens portion which functions effectively as a lens; and
an ineffective area which does not function as a lens, the ineffective area being located radially outward of the lens portion and continuous with the lens portion, the ineffective area having a generally flat area substantially oriented radially outward of the lens portion and being formed as a consequence of removing a portion of the ineffective area.
(2) A plastic lens according to (1), wherein the ineffective area includes a gate portion corresponding to a channel through which a molten plastic material was injected during molding, and the generally flat area is formed as a consequence of cutting off a portion of the gate portion.
(3) A plastic lens according to (2), wherein the portion of the gate portion is cut off by relatively moving a pair of cutting blades toward each other in a direction substantially parallel to an optical axis of the lens portion.
(4) A plastic lens according to (3), wherein the ineffective area further includes an annular rim circumscribing the lens portion entirely, the gate portion projecting from the annular rim radially outward and continuous with the lens portion through the annular rim.
(5) A plastic lens according to (4), wherein the annular rim defines a reference plane orthogonal to the optical axis of the lens portion, and the generally flat area is located entirely on one side in a direction parallel to the optical axis with respect to the reference plane.
(6) A plastic lens according to (1), wherein the ineffective area includes an annular rim circumscribing the lens portion entirely, and the generally flat area is formed as a consequence of cutting off a portion of the annular rim together with a gate portion corresponding to a channel through which a molten plastic material was injected during molding.
(7) A plastic lens according to (6), wherein the annular rim can be distinguished from the lens portion visually or tangibly.
(8) A plastic lens according to (6), wherein the ineffective area has a maximum thickness smaller than a minimal thickness of the lens portion.
(9) A plastic lens according to (6), wherein the generally flat area is located radially inward relative to an outermost circumference of the plastic lens.
(10) A plastic lens according to (6), wherein the generally flat area does not traverse the lens portion.
REFERENCES:
patent: 5257145 (1993-10-01), Kanazawa et al.
patent: 5555480 (1996-09-01), Tanaka et al.
patent: 5642235 (1997-06-01), Ichikawa
patent: 5975882 (1999-11-01), Nomura et al.
patent: 6055111 (2000-04-01), Nomura et al.
patent: 58-69811 (1983-05-01), None
patent: 59-188601 (1984-10-01), None
Iwaki Makoto
Ohashi Haruyuki
Asahi Kogaku Kogyo Kabushiki Kaisha
Epps Georgia
Greenblum & Bernstein P.L.C.
Thompson Tim
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