Optical: systems and elements – Lens – With support
Reexamination Certificate
2001-07-03
2004-01-06
Dang, Hung Xuan (Department: 2873)
Optical: systems and elements
Lens
With support
C359S811000, C396S526000, C362S455000, C353S100000
Reexamination Certificate
active
06674584
ABSTRACT:
BACKGROUND OF THE INVENTION
This application relates generally to optical systems, and more particularly to techniques and devices for mounting optical devices.
In virtually any optomechanical engineering application, it is necessary for optical elements to be mounted within the system with accurate alignment. This is especially the case for a variety of high-performance optical systems, such as may be used in fiber-optic telecommunications applications, among others. In the design and manufacture of such systems, optical components are typically mounted with a lens cell, with the optical axis of such optical components being aligned with respect to an axis of the lens cell. The lens cell may then be used within an assembly having multiple components, the alignment of the optical elements within the assembly being achieved through alignment of the lens-cell axis.
Examples of such a prior-art lens cell are illustrated in
FIGS. 1A-1F
.
FIG. 1A
shows a perspective drawing of a prior-art lens cell
100
in which optical elements are positioned within the lens cell
100
.
FIGS. 1B and 1C
respectively show a cutaway perspective drawing and a cross-sectional projection drawing of the same lens cell
100
in which other features of the lens cell
100
may be more apparent. An external cylindrically shaped body
104
is used to house the optical elements, which in
FIGS. 1A-1C
are shown as a pair of achromatic lens doublets
120
and
124
separated by a spacer
116
. The spacer
116
forms part of the interior of the lens cell
100
and is used for configurations in which a separation is desired between individual lens elements. The optical elements
120
and
124
are configured such that they share a common optical axis that is coincident with the central axis
102
of the cylindrical external body
104
.
The optical elements
120
and
124
are mounted within the lens cell
100
on their outside diameters, requiring machining of tight tolerances. The interior of the lens cell may be configured with different inside diameters at different points in order to accommodate differences in optical elements. For example, the lens cell illustrated in
FIGS. 1A-1C
is configured generally with an inside diameter ID(
1
) that is appropriate for housing the first lens doublet
120
. It also includes a notched portion with a larger inside diameter ID(
2
) at that point where the second lens doublet is mounted. After machining the lens cell
100
with tight tolerances, the optical elements are typically mounted within by filling any small space around a given lens element with an elastomeric material such as a room-temperature vulcanizing elastomer. The optical elements are additionally secured with a threaded retainer clamp
128
, which is secured within the lens cell
100
by threads
132
and perhaps also by staking. For the illustrated prior-art configuration, at least one end of the lens cell
100
is equipped with a shoulder
112
having a plurality of notches
108
that may assist in maintaining alignment of optical elements when the lens cell
100
is integrally connected with a subsequent component of the optical-system assembly.
FIGS. 1D
,
1
E, and
1
F show cross-sectional details of different optical elements that may be mounted. In these figures, reference numerals correspond generally to those structures in
FIGS. 1A-1C
, but include primes to designate structures that may be configured differently to accommodate differences in the optical elements.
In
FIG. 1D
, for example, a plano-concave lens
120
′ having flat surfaces is shown. The external body
104
′ provides a holding structure for the lens
120
′ having surfaces S
1
′ and S
2
′ in a nominally aligned condition relative to the axis
102
of the lens cell. The flat surfaces of the lens
120
′ are configured in contact with seat
134
′ and the retainer clamp
128
′. In
FIG. 1E
, an example of an optical element having only a single flat surface, in this instance a plano-convex lens
120
″ having surfaces S
1
″ and S
2
″, is shown. The lens
120
″ is mounted similarly to the external body
104
″, with the plano surface of the lens configured in contact with the seat
134
″, but a precision centering spacer
136
″ is additionally installed over the outer convex optical surface in contact with the retainer clamp
128
″. In
FIG. 1F
, a meniscus lens
120
′″ having surfaces S
1
′″ and S
2
′″ is shown. Although the lens
120
′″ has two curved surfaces, it includes a sag
156
′″ configured for contact with a precision centering spacer
136
′″. The lens
120
′″ is mounted to the external body
104
′″ by including a conical or spherical surface
158
′″ used to center the lens
120
′″ to the cell and by including a retainer clamp
128
′″.
Such prior-art lens-cell arrangements suffer from a number of disadvantages, including the need to satisfy tight tolerances to mount the optical elements on their outside diameters. Generally, the outside diameter of the lens must be controlled to the optical axis as well as the sag. The difficulty in achieving proper alignment is evident for all three of the mounting schemes shown in
FIGS. 1D-1F
. In general, the axis
152
of the lens
120
may be tilted with respect to the axis
102
of the lens cell
100
by an angle &phgr; and may be offset longitudinally by a distance &Dgr;z; in the figures, axis
150
shows the lens axis
152
after being rotated to be parallel to the cell axis
102
. Mounting of the lens
120
seeks to achieve (&phgr;=&Dgr;z=0.
Thus, with the arrangement of
FIG. 1D
, the tilt &phgr; of the lens axis
152
is established by the shoulder in contact with the seat
134
′ and by alignment of S
1
′ and S
2
′. Centration of lens
120
′ is established by the low-precision threaded retainer clamp
128
′. The arrangement of
FIG. 1E
is somewhat better. The precision centering spacer
136
″ is match-machined for mating to the inside diameter of the lens
120
″. Centration of the lens
120
″ to the cell
100
is therefore established by the carefully machined conical surface of the spacer
136
″. The tilt is controlled the same fashion as in FIG.
1
D. In the arrangement of
FIG. 1F
, in which the lens
120
′″ includes sag
156
′″, both the tilt and centration are controlled by the precision spacer
136
′″.
For these prior-art designs to be effective, it is necessary to control a number of physical parameters to very great precision, including: (i) the inside diameter of the external body
104
; (ii) the relative sizes of the outside and inside diameters of the external body
104
; (iii) the position of the conical or spherical seat position relative to the external body
104
; (iv) the outside diameter of the spacer
136
relative to the outside diameter of the external body
104
; (v) the orientation of the spacer
136
relative to the outside external body
104
; and (vi) the orientation of the lens sag
156
to the lens axis
152
. A deficiency in any one of these parameters may result in a poorly oriented lens in the lens cell. Accordingly, it is desirable to have another lens-cell arrangement that avoids these disadvantages.
SUMMARY OF THE INVENTION
Thus, embodiments of the invention are directed to an apparatus and method for housing an optical element. In one embodiment, a first optical component is configured with a ring having a symmetry that corresponds to that of the optical element. The ring is configured for bonding with the optical element on an optical surface at a periphery of the optical element.
In certain embodiments, the invention is directed to an optical-system assembly that includes the first optical component engaged with a second optical component. The first optical element may include a means for demountably engaging the r
Dang Hung Xuan
Martinez Joseph
PTS Corporation
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