Optical: systems and elements – Lens
Reexamination Certificate
2001-08-21
2004-12-14
Lester, Evelyn A. (Department: 2873)
Optical: systems and elements
Lens
C359S355000, C359S661000, C359S719000, C359S743000, C359S803000, C359S819000, C369S112230, C369S112250
Reexamination Certificate
active
06831790
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical element, a method for producing the same, and an optical pickup comprising the optical element.
2. Description of the Related Art
Recently, it is demanded to make an optical disc storage with medium high density. Therefore, in optical disc apparatuses, research and development have been underway for shortening the wavelength of a light source and for enlarging the numerical aperture (NA) of a reproduction optical disc system. Further, it is desired to increase the transfer rate of data in such the reproduction optical disc systems.
When shortening the wavelength of the light source and enlarging the NA of the reproduction optical disc system, in addition to the fact that the size of an optical spot becomes small, the focal depth becomes shallower, so it is desired to reduce the focus servo error. Further, a data recording width (track width) of the optical disc storage medium becomes narrower, so it is desired to reduce the tracking servo error.
For increasing the data transfer rate, it is desired to make the bandwidth of an actuator used for the focus servo and tracking servo higher. As a result, two improvements are desired for servo characteristics: reduction of the remaining amount of error and raising the bandwidth. An actuator can be improved in its servo characteristics by reducing the weight of the actuator.
FIG. 1A
is a sectional view illustrating an optical element as a related art and
FIG. 1B
is a plane view of the optical element in FIG.
1
A.
This optical element
10
has a substrate
14
A formed by an optical material and having a thickness t
1
. The substrate
14
A has a convex part
11
configuring a convex lens and a flat part
12
positioned around the convex part
11
.
The optical element
10
can be formed by heat treating a circular mask layer with a Radius R formed on the front surface of a planar optical material to form it into a lens shape by surface tension, then etching the planar optical material so that the lens shape is transferred to the optical material.
At the outer circumference of the convex part
11
is formed a groove
19
called a “trench” formed when transferring the shape by the etching. The groove
19
clearly separates the convex part
11
and the flat part
12
.
In the optical element
10
in
FIGS. 1A and 1B
, parts other than the convex part
11
are etched away to give a thin planar shape.
When using this optical element
10
in combination with other optical elements, care must be taken that an optical path in other combined optical elements is maintained.
FIGS. 2A and 2B
are sectional views of the optical element
10
in
FIGS. 1A and 1B
and a lens holder thereof.
FIG. 2A
shows a case when clamping the circumferential edge of the flat part
12
of the optical element
10
by a lens holder
10
A.
FIG. 2B
shows a case when clamping an upper surface of the flat part
12
of the optical element
10
by a lens holder
10
B.
As shown in
FIGS. 2A and 2B
, it is necessary to enlarge the flat part
12
in order to mount the optical element
10
in
FIGS. 1A and 1B
on the lens holders
10
A and
10
B.
Further, considering deviation of position at the time of bonding and a squeezing out of excess adhesive, it is necessary to enlarge the flat part
12
not only in the case when using the optical element
10
in combination with other optical elements. For example, when the convex part
11
has an effective diameter (diameter) of a convex lens of about 200 &mgr;m and has a radius of curvature of the convex lens of about 150 &mgr;m, the thickness of the flat part
12
becomes about 50 &mgr;m or less. If assuming the sum of tolerance of the positioning accuracy in the bonding process and the amount of the adhesive squeezed out to be about 500 &mgr;m, the convex lens ends up being positioned on a thin plate of about 50 &mgr;m thickness and about 500 &mgr;m length.
Therefore, improvement of mechanical strength is desired for the optical element as shown in
FIGS. 1A and 1B
. Further, because the flat part
12
is thin, resonance due to vibration in a thickness direction easily occurs. Therefore, it is desired to make the structure difficult to resonate.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical element having a substrate formed by an optical material, with the improved mechanical strength and free from a critical resonance.
Another object of the present invention is to provide an optical pickup having the optical element.
Still another object of the present invention is to provide a method for producing the optical element with efficiency and at a high accuracy.
According to a first aspect of the present invention, there is provided an optical element having a substrate formed by an optical material, wherein the substrate has a convex part functioning as a convex lens, a flat part positioned around the convex part, and an outer circumference part positioned around the flat part, the thickness of the outer circumference part being greater than that of the flat part.
Preferably, the thickness of the outer circumference part is thicker than that of the convex part.
Preferably, the substrate has a first groove formed at a boundary between the convex part and the flat part, for defining a region of the convex part.
Preferably, the substrate has a second groove formed at a boundary between said flat part and said outer circumference part, for defining a region of said flat part.
Preferably, the optical material comprises fused silica.
Preferably, the surface of the outer circumference part is flat or approximately flat.
Preferably, a plurality of steps are formed at the outer circumference part, and the thickness of the substrate at an outer side step is thicker than that of the substrate at an inner side step.
According to the first aspect of the present invention, there is provided an optical element having a substrate formed by an optical material, wherein the substrate has a convex part functioning as a convex lens, a flat part positioned around the convex part, an outer circumference part positioned around the flat part, a first groove formed at a boundary between the convex part and the flat part, for defining a region of the convex part, and a second groove formed at a boundary between the flat part and the outer circumference part, for defining a region of the flat part, wherein a thickness of the outer circumference part is greater than that of the flat part, both the flat part and the outer circumference part have flat shapes in the thickness direction, and the convex part, the flat part, and the outer circumference part are integrated in a unit by the substrate.
According to the first aspect of the present invention, there is provided an optical element having a substrate formed by an optical material, wherein the substrate has a convex part functioning as a convex lens, a flat part positioned around the convex part, an outer circumference part positioned around the flat part, and a groove formed at a boundary between the convex part and the flat part, for defining a region of the convex part, wherein a thickness of the outer circumference part is greater than that of the convex part, both the flat part and the outer circumference part have flat shapes in the thickness direction, and the convex part, the flat part, and the outer circumference part are integrated in a unit by the substrate.
According to the first aspect of the present invention, there is provided an optical element having a substrate formed by an optical material, wherein the substrate has a convex part functioning as a convex lens, a flat part positioned around the convex part, a first outer circumference part positioned around the flat part, a second outer circumference part positioned around the first outer circumference part, a third groove formed at a boundary between the convex part and the flat part, for defining a region of the convex part, and a fourth groove formed at a boundary between the flat part and the first o
Kishima Koichiro
Kouchiyama Akira
Kananen Ronald P.
Lester Evelyn A.
Rader & Fishman & Grauer, PLLC
Sony Corporation
LandOfFree
Optical element, method for producing the same, and optical... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical element, method for producing the same, and optical..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical element, method for producing the same, and optical... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3333976