Optical: systems and elements – Mirror – With support
Reexamination Certificate
2002-12-26
2004-11-16
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Mirror
With support
C359S223100, C359S224200, C359S225100, C359S226200, C359S871000, C359S872000
Reexamination Certificate
active
06817725
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a micro mirror unit and a method of making it. The micro mirror unit is an element incorporated e.g. in an optical switching device which switches optical paths between a plurality of optical fibers, or in an optical disc drive which records data onto an optical disc and/or reproduces data recorded on it.
2. Description of the Related Art
In recent years, optical communications technology is utilized widely in a variety of fields. In the optical communications, optical fibers serve as a medium through which optical signals are passed. When the optical signal passing through a given optical fiber is switched to another optical fiber, so-called optical switching devices are used in general. In order to achieve high quality optical communications, the optical switching device must have high capacity, high speed and high reliability in switching action. In view of these, micro mirror units manufactured by micro-machining technology is attracting attention as a switching element to be incorporated in the optical switching device. The micro mirror units enable the switching operation without converting optical signals into electric signals between the optical paths on the input side and the output side of the optical switching device. This is advantageous to achieving the desired characteristics mentioned above.
Micro mirror units are disclosed e.g. in Japanese Patent Laid-Open No. 4-343318 and No. 11-52278. Further, optical switching devices which use micro mirror units manufactured by micro-machining technologies are disclosed in the article “
MEMS Components for WDM Transmission Systems”
(
Optical Fiber Communication
[OFC] 2002, pp.89-90 etc.
FIG. 21
outlines an ordinary optical switching device
500
. The optical switching device
500
includes a pair of micro mirror arrays
501
,
502
, an input fiber array
503
, an output fiber array
504
, and a plurality of micro lenses
505
,
506
. The input fiber array
503
includes a predetermined number of input fibers
503
a
. The micro mirror array
501
is provided with the same plurality of micro mirror units
501
a
each corresponding to one of the input fibers
503
a
. Likewise, the output fiber array
504
includes a predetermined number of input fibers
504
a
. The micro mirror array
502
is provided with the same plurality of micro mirror units
502
a
each corresponding to one of the output fibers
504
a
. Each of the micro mirror units
501
a
,
502
a
has a mirror surface for reflection of light. The orientation of the mirror surface is controllable. Each of the micro lenses
505
faces an end of a corresponding input fiber
503
a
. Likewise, each of the micro lenses
506
faces an end of a corresponding output fiber
504
a.
In transmitting optical signals, lights L
1
coming out of the output fibers
503
a
pass through the corresponding micro lenses
505
respectively, thereby becoming parallel to each other and proceeding to the micro mirror array
501
. The lights L
1
reflect on their corresponding micro mirror units
501
a
respectively, thereby deflected toward the micro mirror array
502
. At this point, the mirror surfaces of the micro mirror units
501
a
are oriented, in advance, in predetermined directions so as to direct the lights L
1
to enter their respective desired micro mirror units
502
a
. Then, the lights L
1
are reflected on the micro mirror units
502
a
, and thereby deflected toward the output fiber array
504
. At this point, the mirror surfaces of the micro mirror units
502
a
are oriented, in advance, in predetermined directions so as to direct the lights L
1
into their respective desired output fibers
504
a.
As described, according to the optical switching device
500
, the lights L
1
coming out of the input fibers
503
a
reach the desired output fibers
504
a
due to the deflection by the micro mirror arrays
501
,
502
. In other words, a given input fiber
503
a
is connected with an output fiber
504
a
in a one-to-one relationship. With this arrangement, by appropriately changing deflection angles of the micro mirror units
501
a
,
502
a
, switching can be performed and the lights L
1
can be deflected into different output fibers
504
a.
FIG. 22
outlines another ordinary optical switching device
600
. The optical switching device
600
includes a micro mirror array
601
, a fixed mirror
602
, an input-output fiber array
603
, and a plurality of micro lenses
604
. The input-output fiber array
603
includes a predetermined number of input fibers
603
a
and a predetermined number of output fibers
603
b
. The micro mirror array
601
includes the same plurality of micro mirror units
601
a
each corresponding to one of the fibers
603
a
,
603
b
. Each of the micro mirror units
601
a
has a mirror surface for reflection of light and orientation of the mirror surfaces is controllable. Each of the micro lenses
604
faces an end of a corresponding one of the fibers
603
a
,
603
b.
In transmitting optical signals, light L
2
coming out of the input fiber
603
a
passes through the corresponding micro lens
604
and is directed toward the micro mirror array
601
. The light L
2
is then reflected by a corresponding first micro mirror unit
601
a
, and thereby deflected toward the fixed mirror
602
, reflected by the fixed mirror
602
, and then enters a corresponding second micro mirror unit
601
a
. At this point, the mirror surface of the first micro mirror unit
601
a
is oriented, in advance, in a predetermined direction so as to direct the light L
2
to enter a predetermined one of the micro mirror units
601
a
. Then, the light L
2
is reflected on the second micro mirror unit
601
a
, and thereby deflected toward the input-output fiber array
603
. At this point, the mirror surface of the second micro mirror unit
601
a
is oriented, in advance, in a predetermined direction so as to direct the light L
2
to enter a predetermined one of the output fibers
603
b.
As described, according to the optical switching device
600
, the light L
2
coming out of the input fiber
603
a
reaches the desired output fiber
603
b
due to the deflection by the micro mirror array
601
and the fixed mirror
602
. In other words, a given input fiber
603
a
is connected with an output fiber
603
b
in a one-to-one relationship. With this arrangement, by appropriately changing deflection angles of the first and the second micro mirror units
601
a
, switching can be performed and the light L
2
can be deflected into different output fibers
603
b.
FIG. 23
is a perspective view, partly unillustrated, of a portion of a conventional micro mirror unit
700
for incorporation in such devices as the optical switching devices
500
,
600
. The micro mirror unit
700
includes a mirror-formed portion
710
having an upper surface provided with a mirror surface (not illustrated), an inner frame
720
and an outer frame
730
(partly unillustrated), each formed with come-like electrodes integrally therewith. Specifically, the mirror-formed portion
710
has ends facing away from each other, and a pair of comb-like electrodes
710
a
,
710
b
are formed respectively on these ends. In the inner frame
720
a pair of comb-like electrodes
720
a
,
720
b
extend inwardly, corresponding to the comb-like electrodes
710
a
,
710
b
. Also, a pair of comb-like electrodes
720
c
,
720
d
extend outwardly. In the outer frame
730
a pair of comb-like electrodes
730
a
,
730
b
extend inwardly, corresponding to the comb-like electrodes
720
c
,
720
d
. The mirror-formed portion
710
and the inner frame
720
are connected with each other by a pair of torsion bars
740
. The inner frame
720
and the outer frame
730
are connected with each other by a pair of torsion bars
750
. The pair of torsion bars
740
provides a pivotal axis for the mirror-formed portion
710
to pivot with respect to the inner frame
720
. The pair of torsion bars
750
provides a pivotal axis for the inner frame
720
, as wel
Kouma Norinao
Mizuno Yoshihiro
Okuda Hisao
Sawaki Ippei
Soneda Hiromitsu
Armstrong Kratz Quintos Hanson & Brooks, LLP
Sikder Mohammad
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