Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2000-10-30
2002-06-11
Ben, Loha (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S291000, C359S293000, C359S224200, C359S230000, C359S254000, C359S846000, C348S771000, C427S162000
Reexamination Certificate
active
06404534
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a micro-mirror device and an associated method, the device adapted so as to change the reflection path of an incident light beam by pivoting a micro-mirror using electrostatic attraction forces. More particularly, the present invention relates to a micro-mirror device and an associated method, the device having an improved structure for restoring the micro-mirror skewed by electrostatic attraction forces to its original position.
2. Description of the Related Art
A general micro-mirror device array is an array in which a plurality of micro-mirrors are installed so as to be pivoted by electrostatic attraction forces, and to reflect incident light beams at different reflection angles depending on pivoting angles or directions. Applications of micro-mirror device arrays include an image displaying apparatus of a projection television and various laser scanning devices such as a scanner, copier, or facsimile machine. In particular, when a micro-mirror device array is employed in an image displaying apparatus, in the micro-mirror device array, micro-mirrors
1
corresponding to the number of required pixels are arranged in an array in a two-dimensional plane, as shown in FIG.
1
. The micro-mirrors
1
arranged in an array, so as to correspond to respective pixels as described above are independently pivoted according to an image signal, decide respective reflection angles of incident light beams, and, therefore, can form an image.
Such micro-mirror devices are disclosed in, for example, U.S. Pat. No. 5,331,454 entitled “LOW RESET VOLTAGE PROCESS FOR DMD” issued Jul. 19, 1994 and assigned to Texas Instruments Incorporated, and U.S. Pat. No. 5,535,047 entitled “ACTIVE YOKE HIDDEN HINGE DIGITAL MICROMIRROR DEVICE” issued Jul. 9, 1996 and assigned to Texas Instruments Incorporated.
Briefly, as shown in
FIG. 2
, each of the disclosed micro-mirror devices comprises a substrate
11
, first and second address electrodes
13
and
14
provided on the substrate
11
, and a micro-mirror disposed to be spaced from and facing the first and second address electrodes
13
and
14
.
In the disclosed micro-mirror devices, the micro-mirror
15
is installed on the substrate
11
by means of at least one elastically deformable hinge or post so as to be pivotable, and is maintained in a horizontal position by an elastic restoring force. As the structure of such a hinge or post is described in the above-mentioned inventions, a detailed description thereof is omitted.
In the micro-mirror device having the structure as described above, when respective voltages are applied to the first and second address electrodes
13
and
14
and the micro-mirror
15
, the micro-mirror
15
is inclined by electrostatic attraction forces formed according to the differences in electric potentials between the first address electrode
13
and the micro-mirror
15
and between the second address electrode
14
and the micro-mirror
15
to the side having the larger electric potential difference. However, the electrostatic attraction forces must overcome the strength of the hinge or post which tends to keep the micro-mirror in the horizontal position.
That is, as shown in
FIG. 3
, when voltages V
1
and V
2
applied to the first and second address electrodes
13
and
14
, and voltage V
3
applied to the micro-mirror
15
all are zero (0), the micro-mirror
15
is maintained in a horizontal position. Therefore, the distance r
1
between the first electrode
13
and the micro-mirror
15
and the distance r
2
between the second electrode
14
and the micro-mirror
15
are the same.
On the other hand, when voltages V
1
, V
2
, and V
3
applied to the first and second address electrodes
13
and
14
and the micro-mirror
15
, respectively, have the relationship of V
1
<V
2
<V
3
, the electrostatic force F
1
acting between the first address electrode
13
and the micro-mirror
15
is greater than the electrostatic force F
2
acting between the second address electrode
14
and the micro-mirror
15
, as shown in FIG.
4
. Accordingly, the micro-mirror
15
is pivoted toward the first address electrode
13
side of the substrate
11
, and is inclined to a position where the electrostatic force F
1
is balanced by the sum of the electrostatic force F
2
and a restoring force of the hinge or post, such that the condition of r
1
<r
2
is satisfied.
The position of the micro-mirror can also be changed from the position shown in
FIG. 4
to the position shown in
FIG. 3
, or to a position where the micro-mirror is inclined to a direction opposite to the position shown in FIG.
4
. These operations of the micro-mirror device are described as follows.
First, when voltages V
1
, V
2
, and V
3
which all are zero (0) are applied to the first and second address electrodes
13
and
14
, and the micro-mirror
15
, the position of the micro-mirror
15
changes to the position shown in
FIG. 3
under the restoring force of the hinge or post which tends to maintain. the micro-mirror in a horizontal position. In this case, since the dimensions of the hinge or post are on the order of □m, the strength of the hinge is relatively weak with respect to torque, and the restoring force of the hinge is very weak. Therefore, the time required to change the position of the micro-mirror is longer than the desired time for driving the micro-mirror device, creating a problem in that the micro-mirror device cannot be driven at high speed.
Next, when voltages V
1
, V
2
, and V
3
which have the relationship of V
2
<V
1
<V
3
are applied to the first and second address electrodes
13
and
14
and the micro-mirror
15
, respectively, and the micro-mirror
15
is driven to be inclined in the opposite direction, the position of the micro-mirror
15
is changed by the restoring force of the hinge or post and electrostatic forces. In this case, when electrostatic forces F
1
and F
2
are compared to each other, the fact that the difference between voltages V
2
and V
3
exceeds the difference between voltages V
2
and V
3
does not always mean that the electrostatic force F
2
is greater than the electrostatic force F
1
. The reason is that the electrostatic forces F
1
and F
2
are inversely proportional to respective squares of distances r
1
and r
2
between the first and second address electrodes
13
and
14
and the micro-mirror
15
. Therefore, in this case, until distances r
1
and r
2
become similar to each other due to the restoring force of the hinge, the effect of reducing the time required to change the position of the micro-mirror
15
by applying voltages having reversed values is insignificant.
Therefore, the micro-mirror device having the structure as described above requires a relatively long time to change the position of a micro-mirror by forming electrostatic attraction forces. Consequently, the driving speed of the micro-mirrors is limited.
SUMMARY OF THE INVENTION
To solve the above problem, it is an objective of the present invention to provide a micro-mirror device and an associated method, the device having improved electrode structures, so that the time required to change the position of a micro-mirror, for example, to change from an inclined position of the micro-mirror to an initial position of the micro-mirror, or to an oppositely inclined position of the micro-mirror, can be reduced.
Accordingly, to achieve the above objective, the present invention provides a micro-mirror device including a substrate, address electrodes being provided on the substrate, and a micro-mirror facing the substrate and spaced a predetermined distance from the substrate. The micro-mirror is adapted so that the slope of the micro-mirror can be adjusted by electrostatic attraction forces between the address electrodes and the micro-mirror. The micro-mirror device includes auxiliary electrodes that are formed on and projected from the substrate and the upper portions of which are disposed in the vicinity of the micro-mirror so that restoring force
Chin Dae-je
Lee Sang-hun
Shin Hyung-jae
Ben Loha
Samsung Electronics Co,. Ltd.
LandOfFree
Micro-mirror device and driving method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Micro-mirror device and driving method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Micro-mirror device and driving method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2971949