Photography – Having variable focal length of camera objective – Lens moves in or out of light path
Reexamination Certificate
2003-08-25
2004-12-07
Tamai, Karl (Department: 2834)
Photography
Having variable focal length of camera objective
Lens moves in or out of light path
C310S309000, C348S374000, C396S439000, C396S661000
Reexamination Certificate
active
06829433
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrostatic actuator driven by electrostatic force and a camera module using the electrostatic actuator.
2. Discussion of the Background
Heretofore, as an electrostatic actuator, there has been proposed a constitution of a type shown in, for example,
FIG. 26
(for example, refer to Japanese Patent Laid-Open No. 140367/1996). A conventional electrostatic actuator shown in
FIG. 26
is constituted by a slider (or movable section)
101
and two stators
102
and
103
sandwiching the slider
101
from above and from below. The respective stators
102
and
103
are arranged with two series of electrodes
102
a
,
102
b
,
103
a
and
103
b
and a total of four series of electrodes are provided by upper and lower sets of the stators. Further, the slider
101
is provided with electrode portions
101
a
and
101
b
formed in a projected shape to be opposed to the electrodes of the stators.
Further, pitches and electrode widths of the respective electrodes
102
a
,
102
b
,
103
a
and
103
b
provided at the stators
102
and
103
and the electrode portions
101
a
and
101
b
provided at the slider
101
are respectively the same. Further, in the stators
102
and
103
, the respective electrodes are arranged alternately such that two series of the electrodes respectively appear in turn in a predetermined direction. Further, the upper electrodes
102
a
and
102
b
of the stator
102
and the lower electrodes
103
a
and
103
b
of the stator
103
, are arranged such that phases of aligning pitches thereof are shifted from each other exactly by ½.
Here, when voltage is applied between the electrode
102
a
of the stator
102
and the slider
101
, by electrostatic force (Coulomb force) operated between the electrode
102
a
and the electrode portion
101
a
provided at the slider
101
, the slider
101
is attracted to the stator
102
(such that the electrode
102
a
and the electrode portion
101
a
overlap). Successively, when the applied voltage is switched to the electrode
103
a
of the stator
103
, by electrostatic force (Coulomb force) operated between the electrode
103
a
and the electrode
101
b
provided at the slider
101
, the slider
101
is attracted to the stator
103
(such that the electrode
103
a
and the electrode
101
b
overlap).
When the voltage applied to the electrodes on the stator side is successively switched such that the electrodes are activated in the order
102
a
→
103
a
→
102
b
→
103
b
, the slider
101
is driven macroscopically in the predetermined direction (right side in the drawing) of alternately arranged electrodes of the stators while vibrating upwardly and downwardly microscopically. When the order of applying the voltage to the electrodes of the stators is reversed such that the electrodes are activated in the order
102
a
→
103
b
→
102
b
→
103
a
, the slider
101
is driven in a reverse direction (left side in the drawing) to the predetermined direction of alternately arranged electrodes of the stator.
However, according to such an arrangement, the following problem is posed. According to the conventional electrostatic actuator, driving force is changed depending on its altitude by influence of gravitational force and therefore, a distance of advancing the slider
101
in one step is changed. For example, when a direction of driving the slider
101
coincides with a vertical direction, in order to drive the slider
101
upwardly in the vertical direction, in applying voltage to the electrode of the stator, it is necessary to repeat the same step a plurality of times (for example, at a step of the electrode
102
a
→
103
a
by a plurality of times). Therefore, in order to realize firm driving operation in correspondence with all the altitude, the actuator is driven under the severest condition and therefore, there poses a problem that voltage is applied more than necessary, moving speed is reduced and power consumption for driving is increased.
Further, in order to realize driving operation in the above-described predetermined direction, it is necessary to accurately control the phases in arranging the electrodes
102
a
and
102
b
provided at the stator
102
and the electrodes
103
a
and
103
b
provided at the stator
103
, further, it is necessary to accurately fabricate the electrode portions at two faces of the slider
101
opposed to the electrodes. Therefore, the cost is high owing to time and labor required for assembling, which poses a problem in realizing mass production.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an electrostatic actuator resolving such a problem, realizing efficient driving operation, easy to fabricate and excellent in mass production performance and provide a camera module for executing focal point adjusting operation by using the electrostatic actuator.
In order to resolve the above-described problem, according to an aspect of the embodiment of the invention, in an electrostatic actuator having first electrode portion and second electrode portion arranged at predetermined intervals, the electrode portions including respectively a plurality of series of electrodes arranging successively in a predetermined direction, a slider arranged in the intervals, having electrode portions at side faces opposed to the first electrode portion and the second electrode portion and movable in the predetermined direction, an electrostatic capacitance detecting circuit configured to detect electrostatic capacitances between the plurality of series of electrodes of the first electrode portion or the second electrode portion and the electrode portions of the slider, and a driving circuit configured to drive the slider in the predetermined direction by applying voltages alternately between the plurality of series of electrodes of the first electrode portion or the second electrode portion and the electrode portions of the slider, the plurality of series of electrodes respectively selected based on a detected result of the electrostatic capacitance detecting circuit.
Further, according to another aspect of the embodiment of the invention, in an electrostatic actuator having first electrode portion and second electrode portion arranged at predetermined intervals, the first electrode portion including three series or more of electrodes arranging successively in the predetermined direction and said second electrode portion including a single series of electrodes extended in the predetermined direction, a slider arranged at the intervals, having electrode portions at a side face opposed to the first electrodes and movable in the predetermined direction, an electrostatic capacitance detecting circuit configured to detect electrostatic capacitances between three series or more of electrodes of the first electrode portion and the electrode portions of the slider, and a driving circuit configured to drive the slider in the predetermined direction by applying voltages alternately between the three series or more of electrodes of the first electrode portion or the second electrode portion and the electrode portions of the slider, the three series or more of series of electrodes respectively selected based on a detected result of the electrostatic capacitance detecting circuit.
Further, according to another aspect of the embodiment of the invention, in an electrostatic actuator having first electrode portion and second electrode portion arranged at predetermined intervals, the first electrode portion and second electrode portion including a plurality of series of electrodes arranging successively in a predetermined direction, a slider arranged in the intervals, having electrode portions at side faces opposed to the first electrode portion and the second electrode portion and movable in the predetermined direction, an electrostatic capacitance detecting circuit configured to defect an electrostatic capacitance between one electrode of either of the first electrode portion or the
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tamai Karl
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