Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-06-12
2004-06-29
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
Switch
C385S018000, C385S019000
Reexamination Certificate
active
06757455
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a micromachine, such as an optical switching element for use in an image display device, and to a manufacturing method therefor.
2. Description of Related Art
An optical switching element using liquid crystals has been known as that enabled to control the switching-on and switching-off of light.
FIG. 13
schematically shows the configuration thereof. This optical switching element
900
may consist of polarizing plates
901
and
908
, glass plates
902
and
903
, transparent electrodes
904
and
905
, and liquid crystals
906
and
907
. The direction of alignment of liquid crystal molecules is changed by controlling a voltage applied between the transparent electrodes
904
and
905
. Thus, the plane of polarization thereof is turned thereby to perform optical switching. Consequently, an image display device can be constituted as a liquid crystal panel by arranging such optical switching elements (namely, liquid crystal cells) in a two-dimensional form.
However, this optical switching element using liquid crystals is poor in high-speed response, and operates at a response speed of as low as about several millimeters per second. It is, therefore, difficult to use a spatial light modulator, which employs liquid crystals, in optical communication, optical computing, an optical storage device such as a hologram memory, and an optical printer, which require a high response speed. Further, the spatial light modulator employing liquid crystals has a drawback in that efficiency in using light is degraded by the polarizing plates.
This enables higher-speed switching. Thus, optical switching elements, whose efficiency in using light is high, are demanded. One such optical switching element is a spatial light modulator enabled to achieve high-speed modulation by mechanically moving an optical element that can control light. An example of the spatial light modulator made to be highly practical is a micromirror device. This device is adapted so that a mirror serving as an optical element is turnably supported by a yoke, and that incident light is modulated by changing the angle of the mirror, and then outputted therefrom.
Alternatively, incident light can be modulated by moving the position of a planar optical element having a reflection function or a transmission function. Thus, a spatial light modulator adapted to mechanically move such an optical element may be employed. Applicant of the present application assiduously develops one such spatial light modulator adapted to extract evanescent light from a total reflection surface of a light guiding portion, which can transmit light by performing total reflection thereof, by bringing a switching portion, which has an extraction surface adapted to transmit light, (in an on-state) into contact with the total reflection surface. This switching portion is turned off by being detached from the total reflection surface by a minute distance of about one wavelength or less. This spatial light modulator can switch on and off light by moving the switching portion, which functions as an optical element, by a minute distance. Thus, this spatial light modulator is an optical switching element that can modulate and control light at a high speed. Electrostatic force generated by applying a voltage to the electrodes is mainly used as means for driving the switching portion.
In the case of using this spatial light modulator, it is necessary to move the switching portion with good accuracy by a distance on the order of the wavelength, for example, about one-tenth of several microns, namely, a distance of submicron order. Therefore, to manufacture the switching portion and a drive portion, a manufacturing method, by which such portions are manufactured with a sufficient precision of one micron, is demanded. Especially, the switching portion is an optical element, so that accuracy, which is commensurate with or less than the movement distance of submicron order, is demanded as the surface finish accuracy thereof. Furthermore, when a two-dimensional image is actually generated by the spatial light modulator, it is necessary to arrange a plurality of switching elements in an array. Thus, there is the necessity for manufacturing a large number of switching elements of the same constitution with precision of one micron or less in such a way so as to adjoin one another.
SUMMARY OF THE INVENTION
Techniques of manufacturing such elements with precision of one micron have currently been being developed. Such techniques are, for instance, photolithography techniques having progressed as techniques for manufacturing semiconductors. According to present design rules, necessary precision is about one-tenth of several microns. When the design rules are met, the precision needed for manufacturing the aforementioned spatial light modulator can be obtained. In addition, there has been developed a manufacturing method of manufacturing a structure with precision of one micron by utilizing manufacturing techniques, such as an oxide film formation technique, a crystal growth technique, a CMP planarization technique, a laser processing technique, a sol-gel forming technique, a sintering technique, and a machine cutting technique. Thus, a machine, which is called a micromachine and has structure of the size represented in units of microns, is manufactured by these techniques.
However, the tolerance of products produced by these manufacturing methods is one-tenth of several microns. Thus, although a structure constituted by a micromachine is produced by these manufacturing methods, the necessary surface accuracy of a microstructure, which is less than the tolerance thereof, cannot be necessarily ensured. Moreover, it is difficult to assure the positional relationship among a plurality of switching elements with precision of one-tenth of several microns or less. Furthermore, the photolithography techniques are the most advanced techniques of processing microstructures, and those for processing silicon employed as a material. Thus, even in the case of using the photolithography techniques, it is difficult to process other materials, for example, a transmissive resin material suitable for an optical element.
Similar problems occur in other micromachines, such as an optical micro-switch for switching on and off signals transmitted between optical fibers, and a microvalve for allowing fluids to flow therethrough and shutting off the fluids. Thus, it becomes necessary to develop a micromachine, which can ensure the surface accuracy of microstructures and establish the positional relationship between adjoining ones thereof and provide a gap or a step therebetween with high accuracy, and a manufacturing method therefor.
Accordingly, an object of the present invention is to provide a micromachine, which can highly accurately manufacture a machine, whose size is in the order of a micron or less, for driving a microstructure, such as a switching portion, and a manufacturing method therefor. Particularly, an object of the present invention is to provide a micromachine suitable for a spatial light modulator having a device operative to modulate light by moving and controlling a microswitch portion, such as the optical switching portion utilizing evanescent light, which has a planar component, that is, a micromachine in which a high-accuracy surface is formed and in which a drive system for microstructures, and to provide a manufacturing method therefor.
Further, another object of the present invention is to provide a configuration, by which a micromachine having a drive system can be manufactured, and to provide a manufacturing method therefor.
Moreover, another object of the present invention is to realize a structure of a micromachine efficiently providing a configuration, in which a plurality of units each having a high-accuracy surface of a microstructure and a drive system for the microstructure are arranged in a array, with high precision, and to provide a manufacturing method therefor.
Therefore,
Kamijima Shunji
Nishikawa Takao
Takeda Takashi
Yonekubo Masatoshi
Bovernick Rodney
Kang Juliana
Oliff & Berridg,e PLC
Seiko Epson Corporation
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