Optical: systems and elements – Deflection using a moving element – By moving a reflective element
Reexamination Certificate
2003-02-07
2004-04-27
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
By moving a reflective element
C359S223100, C359S227000
Reexamination Certificate
active
06728018
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a light control device configured to switch an optical path or limit it (i.e., to control the quantity of light) by displacement of a moving plate and consequently a mirror or light shielding plate mounted thereon.
FIG. 1A
shows the construction of an optical switch which is an example of a conventional light control device of this kind. The illustrated optical switch is a 2-by-2 optical switch for switching optical paths of two incoming rays B
1
and B
2
parallel to each other but opposite in direction.
On a moving plate
11
there are mounted four mirrors
12
as light control means. The mirrors
12
are disposed at an angle of 45 degrees with respect to the incoming rays B
1
and B
2
, respectively, as depicted in FIG.
1
A.
The moving plate
11
is supported by two support beams
13
in a manner to be displaceable in a direction vertical to the surface of the moving plate
11
itself. The support beams
13
are projected from a pair of opposed sides of the moving plate
11
of a square plate configuration, and are respectively extended around it along its three sides. The extended ends of the support beams
13
are fixedly coupled to stationary parts
15
on a frame
14
surrounding the moving plate
11
.
Under the moving plate
11
is located a fixed electrode
16
at a predetermined spacing as shown in
FIG. 1B
, and a base
17
with which the fixed electrode
16
is formed integrally has its marginal portion joined to the frame
14
. The moving plate
11
opposed to the fixed electrode
16
functions as a moving electrode.
In the optical switch of the above configuration, upon voltage application across the moving plate
11
and the fixed electrode
16
, the moving plate
11
is attracted down by electrostatic power toward the fixed electrode
16
, and upon removing the voltage, the moving plate returns to its initial position.
Accordingly, the optical switch is able to switch the optical paths by the mirrors
12
which undergo displacement as the moving plate
11
moves up and down. That is, when the moving plate
11
lies at the position indicated in
FIG. 1B
, the incoming rays B
1
and B
2
are reflected by the mirrors
12
to travel as indicated by the solid lines marked with the arrows, whereas when the moving plate
11
is at its lowered position, the mirrors
12
go out of the optical paths, allowing the incoming rays B
1
and B
2
to traveling in straight lines without being reflected by the mirrors
12
.
FIGS. 2 and 3
show a sequence of steps involved in the manufacture of the above optical switch. The optical switch is manufactured using two base plates or substrates. Steps S
1
to S
4
in
FIG. 2
show steps of processing the upper substrate, and steps S
5
to S
7
in
FIG. 3
show steps of processing the lower substrate.
The upper substrate is, in this example, a multi-layered SOI (Silicon On Insulator) substrate
24
with a SiO
2
layer
21
sandwiched between silicon (Si) layers
22
and
23
as depicted in FIG.
2
. The manufacturing process will be described below step by step.
Step S
1
: The SOI substrate
24
are coated all over its top and bottom surfaces with thermally oxidized films
25
and
26
, respectively.
Step S
2
: Patterns for the moving plate, the support beams and the stationary parts are formed by photolithography over the thermally oxidized film
25
on part of the top surface, then the thermally oxidized film
25
is selectively etched away as patterned, and the Si layer
22
is selectively etched away using the thermally oxidized film pattern as a mask. On the other hand, a frame pattern is formed by photolithography over the thermally oxidized layer
26
, and the thermally oxidized film
26
is selectively etched away as patterned.
Step S
3
: The thermally oxidized film
25
remaining on the part of the top surface is etched away, and a thick resist film is coated over the entire area of the top surface and patterned to form mirror bodies, which are coated all over its surface area with an Au film to form the mirrors
12
.
Step S
4
: The Si layer
23
on the side of the bottom surface is selectively etched away, and the SiO
2
layer
21
is selectively etched away to form the frame
14
. As a result, two stationary parts
15
are positioned on the SiO
2
layer of the frame
14
composed of the Si layer
2
and the SiO
2
layer
21
, and the moving plate
11
carrying the mirrors
12
is supported by the stationary parts
15
through the support beams
13
.
On the other hand, an Si substrate
27
is used as the lower substrate. Referring to
FIG. 3
, the manufacturing process will be described below step by step.
Step S
5
: The Si substrate
27
is coated all over its top and bottom surfaces with thermally oxidized films
28
and
29
, respectively.
Step S
6
: A fixed electrode pattern is formed by photolithography over the thermally oxidized film
28
, and the thermally oxidized film
28
is selectively etched away as patterned.
Step S
7
: The substrate
27
is etched away as predetermined using the pattern of the thermally oxidized film
26
as a mask, after which the thermally oxidized film
28
are etched away. As a result, the upwardly protruded fixed electrode
16
is formed on the base
17
.
The Si substrate
27
and the SOI substrate
24
thus obtained are integrated into a single-piece structure with the frame
14
fixedly mounted on the base
17
by bonding, for instance. In this way, the optical switch shown in
FIGS. 1A and 1B
is manufactured.
In such a conventional a light control device as the above-described optical switch of the construction in which the moving plate is used as a moving electrode and displaced by electrostatic driving to switch or limit optical paths by displacement of the mirrors or light shielding plates mounted on the moving plate, the moving plate is drive in its widthwise direction, that is, in the direction vertical to the plate surface.
Accordingly, the fixed electrode for electrostatic driving of the moving plate needs to be disposed opposite the moving plate surface, but it is difficult to obtain from one substrate the moving plate (the moving electrode) and the fixed electrode bearing such a positional relationship to each other. On this account, it is conventional to produce them separately using two substrates and integrate them as by bonding.
Hence, the prior art manufacturing method involves patterning by photolithography and etching for each of the two substrate and necessitates their integration (by bonding) into a unitary structure; hence, these works inevitably increase the number of man-hours, making the manufacture of the light control device complicated and time-consuming.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a light control device that can be manufactured with a smaller number of man-hours and with high accuracy.
The light control device according to the present invention comprises:
side beams;
a moving plate having opposed side surfaces;
at least one pair of support beams extended in opposite directions from said opposed side surfaces of said moving plate in parallel relation to said moving plate and having its tip ends fixed to said side beams, respectively, to support said moving plate in a manner to be elastically displaceable in a plane in which the plate surface of said moving plate lies;
drive means for driving said moving plate relative to said side beams in said plane in which said plate surface lies; and
light control means mounted on said moving plate, for controlling incident optical beams in accordance with the displacement of said moving plate by said drive means;
wherein said moving plate, said support beams, said side beams and said drive means are formed by etching one substrate.
Said drive means may be formed moving planar electrodes extended from sad side surfaces of said moving plate and a fixed planar electrode disposed opposite said moving comblike electrodes in common to them.
Alternatively, said drive means may be formed by moving comblike el
Gallagher & Lathrop
Japan Aviation Electronics Industry Limited
Lathrop, Esq. David N.
Phan James
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