Adjustable X-Y stage

An adjustable X-Y stage (10) comprises a single monolithic member from which regions have been cut to define a central mounting portion (19), a peripheral frame portion (20) a plurality of moveable portions (21), each located between the central mounting portion and the peripheral frame portion, a plurality of first spring portions (22), each interconnecting one of the moveable portions to the central mounting portion, and a plurality of second spring portions (23), each being adjacent a moveable portion and each interconnecting the peripheral frame portion to the central mounting portion. A plurality of screws (12-15), each adapted to extend through the peripheral frame portion (20), engages one of the moveable portions (21) to permit adjustments of the central mounting portion (19) in transverse X and Y directions.

TECHNICAL FIELD 
This invention relates to X-Y stages and, more particularly, to adjustable 
X-Y stages with which microscopic adjustments can be made. 
BACKGROUND OF THE INVENTION 
As greater use of photonics devices is made for such purposes as optical 
communications and optical computing, there has developed a demand for 
components that can aid in the assembly of apparatus used in such systems. 
It has long been recognized that appropriate packaging apparatus must be 
developed which will aid in the assembly of photonics and optical 
components with relative alignments that are extremely precise. For 
example, it is not uncommon that lasers or laser arrays must be packaged 
with alignment tolerances that are accurate to within one or less than one 
micron. The copending application of Basavanhally et al., Ser. No. 
07/705,229, filed May 24, 1991, describes the need for accurately aligned 
optical fiber bundles. Photodetectors, photodetector arrays, lens arrays, 
mirrors, and other optical devices all perform various functions within 
optical systems and may require great precision in their alignment within 
packages. 
There is a great deal of literature concerning general adjustment of 
optical devices, but comparatively little concerning adjustments with 
tolerances in the micron or sub-micron range. When such high precision is 
required, friction between component elements usually leads to 
nonlinearities due to sticking and slipping motions, hysteresis, wear, and 
other factors. Flexture structures have been proposed for avoiding some of 
such nonlinearities, but such structures usually do not provide X 
direction motion that is completely independent of Y direction motion. 
Piezoelectric elements have been used to give small incremental movements, 
but it would often be useful for such small movements to be accurately 
deamplified. 
Accordingly, there is a continuing long-felt need for methods and apparatus 
that permit optical and photonics devices to be packaged within X-Y 
adjustment stages with X and Y direction alignment tolerances in the 
micron or sub-micron range, and which are relatively simple to use. 
SUMMARY OF THE INVENTION 
In accordance with an illustrative embodiment of the invention, an 
adjustable X-Y stage comprises a single monolithic member from which 
regions have been cut to define (1) a central mounting portion, (2) a 
peripheral frame portion, (3) a plurality of moveable portions, each 
located between the central mounting portion and the peripheral frame 
portion, (4) a plurality of first spring portions, each interconnecting 
one of the moveable portions to the central mounting portion, and (5) a 
plurality of second spring portions, each being adjacent a moveable 
portion and each interconnecting the peripheral frame portion to the 
central mounting portion. Illustratively, a plurality of screws, each 
adapted to extend through the peripheral frame portion, engages one of the 
moveable portions to permit adjustments of the central mounting portion in 
transverse directions. 
In the illustrative embodiment, the device contains four moveable portions 
symmetrically arranged with respect to the center of the central mounting 
portion, with four screws, each extending substantially radially with 
respect to the center of the central mounting portion. A device to be 
aligned is contained on the central mounting portion. Two first spring 
portions interconnect opposite sides of each moveable portion of the 
central mounting portion, and two second spring portions interconnect the 
central mounting portion to the peripheral frame portion on opposite sides 
of each moveable portion. Inward movement of a screw then compresses each 
of the first spring portions and tenses each of the second spring portions 
associated with that screw. Adjustment of two orthogonal screws gives 
orthogonal X-Y adjustments. After the adjustment has been made, the 
remaining two screws can be firmly abutted to adjacent moveable portions 
to lock the central mounting portion in place. An elastomeric material 
such as silicone can be used to fill the open regions of the monolithic 
member, either before or after the proper adjustment has been made, and 
thereafter the entire member may be used as part of a package for 
containing an optical device mounted on the central mounting portion. 
Because the X-Y stage is made from a single monolithic member, all 
movements result from flextures of part of the monolithic element, and 
such movements can easily be made to fall within the linear elastic range 
of the member. This avoids problems such as nonlinearities, hysteresis, 
and stick-slip motion encountered by conventional devices using, for 
example, conventional piezoelectric stages or mechanically driven stages. 
These and other objects, features, and benefits of the invention will be 
better understood from a consideration of the following detailed 
description taking in conjunction with the accompanying drawing.

DETAILED DESCRIPTION 
Referring now to FIGS. 1 and 2, there is shown an illustrative embodiment 
of the invention comprising an X-Y adjustable stage 10 upon which is 
mounted an array 11 of optical fibers. The purpose of the apparatus is to 
align the optical fiber array 11 by means of adjusting screws 12-15. The 
optical fiber array can be made by the method described in the 
aforementioned Basavanhally et al. patent application, which describes how 
the component optical fiber ends can be aligned in a matrix configuration 
to tolerances within micron or sub-micron dimensions. If the optical fiber 
matrix is to be used in a free-space photonics switch as was described in 
the application, it is necessary, not only to align the individual optical 
fibers of the array, but also to align the array with other optical 
apparatus, again to within micron or sub-micron tolerances. The X-Y stage 
10 constitutes apparatus for mounting the optical fiber array, allowing 
final fine adjustments in the X-Y position of the array to be made, and 
which thereafter may constitute a part of the permanent package within 
which the optical fiber array is utilized. 
In accordance with the invention, the stage 10 (except for the screws) is 
made from a single workpiece of linear elastic material such as spring 
steel or copper-beryllium. From this single monolithic structure is cut 
regions 17 to define a central mounting portion 19, a peripheral frame 
portion 20, a plurality of moveable portions 21, each located between the 
central mounting portion 19 and the frame portion 20, a plurality of first 
spring portions 22, each interconnecting one of the moveable portions to 
the central mounting portion, and a plurality of second spring portions 
23, each being adjacent a moveable portion and each interconnecting the 
peripheral frame portion to the central mounting portion. The regions 17 
are preferably removed from a single workpiece by electron discharging 
machining, a known process in which an electrical wire defines a line to 
be cut by forming an electrical discharge; see, e.g., "Nontraditional 
Manufacturing Processes," by G. F. Benedict, Marcel Dekker, Inc., New York 
and Basel, Switzerland, pp. 231-245. The workpiece is moved with respect 
to the electrical discharge such that the wire cuts the workpiece in the 
manner of a jigsaw. 
It should be noted that the cuts are made such that each first spring 
portion 22 nests within a second spring portion 23 with both of the spring 
portions being in the shape of an arc of a circle having a common center 
of curvature. After the electrical discharge machining, four threaded 
apertures for containing screws 12-15 are made in the peripheral frame 
portion 20, the openings being radially extending and located in 
quadrature as shown. As can be seen more clearly in FIG. 2, screws 12-15 
are then screwed into the apertures such that they can abut against one of 
the moveable portions 21. 
In using the X-Y stage 10 to align the optical fiber bundle 11, one may 
first back two of the screws such as screws 14 and 15 to be out of contact 
from their corresponding moveable portions 21. Then, screws 12 and 13 are 
moved in or out to give independent X and Y movement to the central 
mounting portion 19. For example, screwing screw 12 into the aperture 
causes downward or Y direction movement on the moveable portion 21 and 
also on the central portion 19. As the downward motion progresses, the 
first spring portions 22 associated with screw 12 are compressed, while 
the second spring portions 23 associated with that screw are placed in 
tension. As a consequence, the axial motion of the screw is translated 
through two sets of springs to give motion to the central mounting member 
19. The axial motion of the screw is thereby significantly and desirably 
deamplified or reduced. With spring steel thicknesses of thirteen to 
twenty-eight mils, the percent reduction in axial motion is typically 
between fourteen and twenty-three percent. 
After the Y direction adjustment, X direction adjustment may be made by 
screwing screw 13 in or out, such movement again being deamplified as 
described above. After adjustment in both directions, screws 14 and 15 may 
be screwed axially inwardly to abut against corresponding moveable 
portions 21 to give firm symmetrical support on all sides of the central 
mounting portion. Either before or after adjustment, the open regions 17 
can be filled with a damping material for reducing vibration during 
operation. The vibration damping material may be silicone or other 
rubber-like material. 
The X-Y stage shown in FIG. 1 has been made from stainless steel having 
dimensions 15/8 inch.times.15/8 inch.times.3/16 inches. It was found that 
microscopically small and accurate movements of less than one micron could 
be made by adjusting the screws and simultaneously observing them through 
a microscope. In the model that was made, the optical fiber bundle 11 was 
not mounted in the central mounting portion 19, but rather a spot on the 
central mounting portion was observed for experimental purposes. Movements 
of from a fraction of a micron to several microns easily fall within the 
linear elastic range of the stainless steel that was used. Since all of 
the elements are made of a single monolithic member, all movements result 
from flexture of portions of that member. This avoids problems such as 
nonlinearities, hysteresis, and relative motion of different parts, as are 
encountered by conventional devices. Adjustments in one direction do not 
affect alignment in the other direction; that is, the X and Y adjustments 
are independent of each other. 
The use of screws result in inherent problems of wear and "backlash" which 
can be avoided by using piezoelectric actuated elements instead of screws. 
This is illustrated in FIG. 3, in which a piezoelectric element 27 is used 
in place of screw 12. The piezoelectric element is expanded or contracted 
in the Y direction by an electronic control 28 which applies Y direction 
force on a plunger element 29 that bears against the moveable portion 22. 
Referring to FIG. 1, all four screws 12-15 are preferably replaced by 
piezoelectric elements as illustrated in FIG. 3. Alternately, only screws 
12 and 13 could be replaced by piezoelectric elements, since screws 14 and 
15 are used merely for providing mechanical support rather than for 
adjustment purposes. 
From the foregoing, it can be appreciated that the adjustable X-Y stage can 
be used for supporting photodetectors, photodetector arrays, lens arrays, 
mirrors, and other optical devices which may require great precision in 
their alignment within a package. After alignment has been performed, it 
is foreseen that the X-Y stage 10 would then constitute part of the 
package in which the mounted apparatus is to be used. Alternatively of 
course, the adjustable X-Y stage can be used for laboratory purposes or 
for whatever other purposes are required for obtaining extremely small 
adjustments of whatever devices may be under observation. These and other 
embodiments and modifications may be made by those skilled in the art 
without departing from the spirit and scope of the invention.