Abstract:
The present invention provides a hybrid light modulator which includes a plurality of ribbons each having a plurality of protrusions to diffract incident light even at an early light receiving stage and to control a diffractive angle of the light beam using a microactuator, thereby realizing miniaturization of a device and assuring ease of digital operation.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to light modulators, and more particularly, to a hybrid light modulator which includes a plurality of ribbons each having a plurality of protrusions to diffract incident light from an early light receiving stage and to control a diffractive angle of the light beam using a microactuator, thereby realizing the miniaturization of a device and assuring the ease of digital operation, unlike conventional diffractive optical modulators in which incident light is reflected and diffracted by the operation of a plurality of micromirror actuators. 
   2. Description of the Related Art 
   Generally, an optical signal processing technology has advantages in that a great amount of data is quickly processed in a parallel manner unlike a conventional digital information processing technology in which it is impossible to process a great amount of data in real time. Studies have been conducted on the design and production of a binary phase only filter, an optical logic gate, a light amplifier, an image processing technique, an optical device, and a light modulator using a spatial light modulation theory. The spatial light modulator is applied to optical memory, optical display device, printer, optical interconnection, and hologram fields, and studies have been conducted to develop a display device employing it. 
   The spatial light modulator is embodied by a reflective deformable grating light modulator  10  as shown in  FIG. 1 . The modulator  10  is disclosed in U.S. Pat. No. 5,311,360 by Bloom et al. The modulator  10  includes a plurality of reflective deformable ribbons  18 , which have reflective surface parts, are suspended on an upper part of a substrate  16 , and are spaced apart from each other at regular intervals. An insulating layer  11  is deposited on the silicon substrate  16 . Subsequently, a sacrificial silicon dioxide film  12  and a low-stress silicon nitride film  14  are deposited. The nitride film  14  is patterned by the ribbons  18 , and a portion of the silicon dioxide film  12  is etched, thereby maintaining the ribbons  18  on an oxide spacer layer  12  by a nitride frame  20 . In order to modulate light having a single wavelength of λ o , the modulator is designed so that thicknesses of the ribbon  18  and oxide spacer  12  are each λ o /4. 
   Limited by a vertical distance (d) between a reflective surface  22  of each ribbon  18  and a reflective surface of the substrate  16 , a grating amplitude of the modulator  10  is controlled by applying a voltage between the ribbon  18  (the reflective surface  22  of the ribbon  18  acting as a first electrode) and the substrate  16  (a conductive layer  24  of a lower side of the substrate  16  acting as a second electrode). In its undeformed state, with no voltage application, the grating amplitude is λ o /2, and a total round-trip path difference between light beams reflected from the ribbon and substrate is one wavelength λ o , and thus, a phase of reflected light is reinforced. Accordingly, in its undeformed state, the modulator  10  acts as a plane mirror when it reflects light. In  FIG. 2 , reference numeral  20  denotes incident light and reflected light in its undeformed state. 
   When a proper voltage is applied between the ribbon  18  and substrate  16 , the electrostatic force enables the ribbon  18  to be moved downward toward a surface of the substrate  16 . At this time, the grating amplitude is changed to λ o /4. The total round-trip path difference is a half of a wavelength, and light reflected from the deformed ribbon  18  and light reflected from the substrate  16  are subjected to destructive interference. The modulator diffracts incident light  26  using the interference. In  FIG. 3 , reference numerals  28  and  30  denote light beams diffracted in a +/− diffractive mode (D+1, D−1) in a deformed state. 
   It has been proved that sticking between the ribbon  18  and substrate  16  is a gross problem of such a device during a wet process applied to form a space under the ribbon  18  and during operation of the modulator  10 . 
   In an effort to overcome the above-mentioned problems, a conventional improved technology is proposed in Korean Patent Application No. 10-2000-7014798, entitled “method and a device for modulating an incident light beam to form a 2-D image”, by Silicon Light Machines Inc. 
   In the “method and device for modulating the incident light beam to form the 2-D image”, the diffractive grating light valve includes a plurality of elongate elements each having a reflective surface. The elongate elements are arranged on an upper side of a substrate so that they are parallel to each other, have support ends, and their reflective surfaces lie in array (GLV array). The elongate elements form groups according to display elements. The groups alternately apply a voltage to the substrate, resulting in deformation of the elements. The almost planar center portion of each deformed elongate element is parallel to and spaced from the center portion of the undeformed element by a predetermined distance which is set to ⅓–¼ of the distance between the undeformed reflective surface and the substrate. Thus, the deformed elongate elements are prevented from coming into contact with the surface of the substrate. Sticking between the elongate elements and the substrate is prevented by preventing contact between the elements and substrate. Additionally, the predetermined distance between each deformed elongate element and the substrate is limited so as to prevent hysteresis causing deformation of the elongate elements. 
     FIG. 4  is a side sectional view of an elongate element  100  of a GLV in an undeformed state according to a conventional improved technology. In  FIG. 4 , the elongate element  100  is suspended above a surface of a substrate (including constitution layers) by ends thereof. In  FIG. 4 , reference numeral  102  denotes an air space. 
     FIG. 5  is a plan view of a portion of the GLV including six elongate elements  100 . The elongate elements  100  have the same width and are arranged parallel to each other. The elongate elements  100  are spaced close to each other, so that the elongate elements  100  can be deformed independently from other elements. 
     FIG. 6  is a front view of a display element  200  having undeformed elongate elements  100 .  FIG. 6  is a view taken in the direction of the arrows along the line A–A′ of  FIG. 5 . The undeformed state is selected by equalizing a bias on the elongate elements  100  to a conductive layer  106 . Since reflective surfaces of the elongate elements  100  are substantially co-planar, light incident on the elongate elements  100  is reflected. 
     FIG. 7  is a front view of the display element  200  in which the deformed elongate elements  100  are alternately arranged.  FIG. 7  is a view corresponding to  FIG. 6 , but showing the deformed elongate elements  100 . The elongate ribbons  100  which are not removed are maintained at desired positions by an applied bias voltage. Deformation of the moving elongate ribbons  100  is achieved by alternate applications of operation voltages through the conductive layer  106  to the elongate elements  100 . A vertical distance (d 1 ) is almost constant to the almost planar center part  102 , thereby limiting the grating amplitude of the GLV. The grating amplitude (d 1 ) may be controlled by adjusting an operation voltage on the operated elongate elements  100 . This results in precision tuning of the GLV in an optimum contrast ratio. 
   However, the light modulator which is manufactured by Silicon Light Machines Inc. and adopts an electrostatic method to control the position of a micromirror is disadvantageous in that an operation voltage is relatively high (usually 30 V or so) and a correlation between the applied voltage and displacement is nonlinear, and thus, reliability is poor in the course of controlling light. 
   Conventional light modulators disclosed in the patent filed by Bloom et al. have been used to form structures which display images. At this time, in each light modulator, two neighboring elements form one pixel. Of course, three neighboring elements may form one pixel. Alternatively, four neighboring elements may form one pixel. As a further alternative, six neighboring elements may form one pixel. In the case that a display device has an optical system which detects only diffracted light, when no voltage is applied to elements, such as ribbons, the ribbons are maintained in those original positions. At this time, pixels are dark, that is, are in a state of being turned off. Otherwise, when voltage is applied to the ribbons, the ribbons are warped downwards toward the silicon substrate. At this time, the pixels are bright, that is, attain a state of being turned on. A contrast ratio between a dark pixel and a bright pixel is a significant factor in forming the display system. In addition, an important matter in forming the display system is to accommodate the recent trend of miniaturization and high integration of electronic products. 
   However, the conventional light modulators disclosed in the patent filed by Bloom et al. have reached the limit in miniaturization. In other words, the conventional light modulators cannot be reduced under 3 μm in the width of the element. Furthermore, an interval between neighboring elements cannot be reduced under 0.5 μm. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a hybrid light modulator which includes ribbons having uneven upper surfaces, so that incident light is diffracted by the uneven upper surfaces of the ribbons from an early light receiving stage, but not by controlling the height difference between moving ribbons, thus realizing miniaturization and high integration of the hybrid light modulator. 
   In an aspect, the present invention provides a hybrid light modulator, including a substrate; and a light modulating element having a ribbon shape, attached at both ends thereof to the substrate while being spaced at an intermediate portion thereof from a bottom of the recess, and having a thin-film piezoelectric material layer, so that the intermediate portion of the light modulating element moves vertically when voltage is applied to both sides of the thin-film piezoelectric material layer. The light modulating element further has a plurality of protrusions on an upper surface thereof to diffract incident light using both each protrusion and a part of the upper surface of the light modulating element neighboring each protrusion. 
   In another aspect, the present invention provides a hybrid light modulator, including a substrate having a recess thereon to provide an air space to an intermediate portion of the substrate; and a lower supporter having a ribbon shape and attached at both ends thereof to the substrate along upper ends of sidewalls of the recess of the substrate while being spaced from a bottom of the recess at an intermediate portion thereof. The lower supporter is vertically movable at the intermediate portion thereof, which is spaced from the substrate. The hybrid light modulator further includes a light modulating element laminated on the lower supporter such that both ends of the light modulating element are placed above the recess of the substrate, and having a thin-film piezoelectric material layer, so that a predetermined portion of the light modulating element spaced from the bottom of the recess moves vertically when voltage is applied to both sides of the thin-film piezoelectric material layer. The light modulating element further has a plurality of protrusions on an upper surface thereof to diffract incident light using both each protrusion and a part of the upper surface of the light modulating element neighboring each protrusion. 
   In a further aspect, the present invention provides a hybrid light modulator, including a substrate having a recess thereon to provide an air space to an intermediate portion of the substrate; a lower supporter having a ribbon shape and attached at both ends thereof to the substrate along upper ends of sidewalls of the recess of the substrate while being spaced at an intermediate portion thereof from a bottom of the recess; and a first piezoelectric layer placed at a first end thereof on a first end of the lower supporter and placed at a second end thereof on a predetermined position of the lower supporter spaced to the first side from a center line of the recess. The first piezoelectric layer has a first thin-film piezoelectric material layer to generate a vertical actuating force by shrinking and expanding when a voltage is applied to the first thin-film piezoelectric material layer. The hybrid light modulator further includes a second piezoelectric layer placed at a second end thereof on a second end of the lower supporter and placed at a first end thereof on a predetermined position of the lower supporter spaced to the second side from the center line of the recess. The second piezoelectric layer has a second thin-film piezoelectric material layer to generate a vertical actuating force by shrinking and expanding when a voltage is applied to the second thin-film piezoelectric material layer. The hybrid light modulator further includes a mirror layer laminated on the intermediate portion of the lower supporter between the first and second piezoelectric layers. The mirror layer has a plurality of protrusions on an upper surface thereof to diffract incident light using both each protrusion and a part of the upper surface of the mirror layer neighboring each protrusion. 
   In yet another aspect, the present invention provides a hybrid light modulator, including a substrate having an insulating layer formed on an upper surface thereof; and a lower supporter having a ribbon shape and attached at both ends thereof to the substrate while being spaced at an intermediate portion thereof from the substrate by a predetermined distance. The lower supporter is vertically movable at the intermediate portion thereof, which is spaced from the substrate. The hybrid light modulator further includes a light modulating element laminated on the lower supporter, and having a thin-film piezoelectric material layer so that the light modulating element generates a vertical actuating force by shrinking and expanding when a voltage is applied to the piezoelectric material layer, thus being vertically moved at an intermediate portion of the light modulating element spaced from the substrate by a predetermined distance. The light modulating element further has a plurality of protrusions on an upper surface thereof to diffract incident light using both each protrusion and a part of the upper surface of the light modulating element neighboring each protrusion. 
   In still another aspect, the present invention provides a hybrid light modulator, including a substrate having an insulating layer formed on an upper surface thereof; and a lower supporter having a ribbon shape and attached at both ends thereof to the substrate while being spaced at an intermediate portion thereof from the substrate by a predetermined distance. The lower supporter is vertically movable at the intermediate portion thereof, which is spaced from the substrate. The hybrid light modulator further includes a first piezoelectric layer placed at a first end thereof on a first end of the lower supporter and placed at a second end thereof on a predetermined position of the lower supporter spaced to the first side from an intermediate line of the lower supporter. The first piezoelectric layer has a first thin-film piezoelectric material layer to generate a vertical actuating force by shrinking and expanding when a voltage is applied to the first thin-film piezoelectric material layer. The hybrid light modulator further includes a second piezoelectric layer placed at a second end thereof on a second end of the lower supporter and placed at a first end thereof on a predetermined position of the lower supporter spaced to the second side from the intermediate line of the lower supporter. The second piezoelectric layer has a second thin-film piezoelectric material layer to generate a vertical actuating force by shrinking and expanding when a voltage is applied to the second thin-film piezoelectric material layer. The hybrid light modulator further includes a mirror layer formed on the intermediate portion of the lower supporter between the first and second piezoelectric layers. The mirror layer has a plurality of protrusions on an upper surface thereof to diffract incident light using both each protrusion and a part of the upper surface of the mirror layer neighboring each protrusion. 
   In still another aspect, the present invention provides a hybrid light modulator, including a substrate having a recess thereon to provide an air space to an intermediate portion of the substrate; and a lower supporter having a ribbon shape and attached at both ends thereof to the substrate while being spaced at an intermediate portion thereof from a bottom of the recess of the substrate by a predetermined distance. The lower supporter is vertically movable at the intermediate portion thereof, which is spaced from the substrate. The hybrid light modulator further includes a piezoelectric mirror layer laminated on the lower supporter such that both ends of the piezoelectric mirror layer is placed above the recess, and having a thin-film piezoelectric material layer, so that a predetermined portion of the piezoelectric mirror layer spaced from the bottom of the recess moves vertically when voltage is applied to both sides of the thin-film piezoelectric material layer, thus reflecting or diffracting incident light; a first mirror layer laminated on a first end of the lower supporter while being stepped from the piezoelectric mirror layer, thus reflecting or diffracting incident light; and a second mirror layer laminated on a second end of the lower supporter while being stepped from the piezoelectric mirror layer, thus reflecting or diffracting incident light. 
   In still another aspect, the present invention provides a hybrid light modulator, including a substrate having a recess thereon to provide an air space to an intermediate portion of the substrate; a lower supporter having a ribbon shape and attached at both ends thereof to the substrate while being spaced at an intermediate portion thereof from a bottom of the recess of the substrate by a predetermined distance; and a first piezoelectric layer placed at a first end thereof on a first end of the lower supporter and placed at a second end thereof on a predetermined position of the lower supporter spaced to the first side from an intermediate line of the lower supporter. The first piezoelectric layer has a first thin-film piezoelectric material layer to generate a vertical actuating force by shrinking and expanding when a voltage is applied to the first thin-film piezoelectric material layer, thus reflecting or diffracting incident light. The hybrid light modulator further includes a second piezoelectric layer placed at a second end thereof on a second end of the lower supporter and placed at a first end thereof on a predetermined position of the lower supporter spaced to the second side from the intermediate line of the lower supporter. The second piezoelectric layer has a second thin-film piezoelectric material layer to generate a vertical actuating force by shrinking and expanding when a voltage is applied to both sides of the second thin-film piezoelectric material layer, thus reflecting or diffracting incident light. The hybrid light modulator further includes a mirror layer formed on the intermediate portion of the lower supporter between the first and second piezoelectric layers while being stepped from the first and second piezoelectric layers, thus reflecting or diffracting incident light. 
   In still another aspect, the present invention provides a hybrid light modulator, including a substrate having an insulating layer formed on an upper surface thereof; and a lower supporter having a ribbon shape and attached at both ends thereof to the substrate while being spaced at an intermediate portion thereof from the substrate by a predetermined distance. The lower supporter is vertically movable at the intermediate portion thereof, which is spaced from the substrate. The hybrid light modulator further includes a piezoelectric mirror layer laminated on the lower supporter such that both ends of the piezoelectric mirror layer are placed on the intermediate portion of the lower supporter spaced from the substrate, and having a thin-film piezoelectric material layer, so that a predetermined portion of the piezoelectric mirror layer spaced from the substrate moves vertically when voltage is applied to the thin-film piezoelectric material layer, thus reflecting or diffracting incident light; a first mirror layer laminated on a first end of the lower supporter while being stepped from the piezoelectric mirror layer, thus reflecting or diffracting incident light; and a second mirror layer laminated on a second end of the lower supporter while being stepped from the piezoelectric mirror layer, thus reflecting or diffracting incident light. 
   In still another aspect, the present invention provides a hybrid light modulator, including a substrate having an insulating layer formed on an upper surface thereof; a lower supporter having a ribbon shape and attached at both ends thereof to the substrate while being spaced at an intermediate portion thereof from the substrate by a predetermined distance; and a first piezoelectric layer placed at a first end thereof on a first end of the lower supporter and placed at a second end thereof on a predetermined position of the lower supporter spaced to the first side from an intermediate line of the lower supporter. The first piezoelectric layer has a first thin-film piezoelectric material layer to generate a vertical actuating force by shrinking and expanding when a voltage is applied to the first thin-film piezoelectric material layer, thus reflecting or diffracting incident light. The hybrid light modulator further includes a second piezoelectric layer placed at a second end thereof on a second end of the lower supporter and placed at a first end thereof on a predetermined position of the lower supporter spaced to the second side from the intermediate line of the lower supporter. The second piezoelectric layer has a second thin-film piezoelectric material layer to generate a vertical actuating force by shrinking and expanding when a voltage is applied to both sides of the second thin-film piezoelectric material layer, thus reflecting or diffracting incident light. The hybrid light modulator further includes a mirror layer formed on the intermediate portion of the lower supporter between the first and second piezoelectric layers while being stepped from the first and second piezoelectric layers, thus reflecting or diffracting incident light. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  illustrates an electrostatic-type grating light modulator according to a conventional technology; 
       FIG. 2  illustrates reflection of incident light by the electrostatic-type grating light modulator according to a conventional technology in an undeformed state; 
       FIG. 3  illustrates diffraction of incident light by the grating light modulator, in a deformed state due to an electrostatic force, according to a conventional technology; 
       FIGS. 8   a  through  8   f  are partial perspective views of hybrid light modulators having elements, according to first through sixth embodiment of the present invention, respectively; 
       FIGS. 9   a  through  9   f  are sectional views of the hybrid light modulators having the elements of  FIGS. 8   a  through  8   f  respectively; 
       FIG. 10  is a sectional view of a hybrid light modulator, according to a seventh embodiment of the present invention; 
       FIG. 11  is a sectional view of a hybrid light modulator, according to an eighth embodiment of the present invention; 
       FIG. 12  is a sectional view of a hybrid light modulator, according to a ninth embodiment of the present invention; and 
       FIGS. 13   a  through  13   c  are views showing operation of the hybrid light modulator, according to the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. 
   Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components. 
     FIGS. 8   a  through  8   f  are perspective views of hybrid light modulators having elements, according to first through sixth embodiments of the present invention, respectively. 
     FIG. 8   a  is a perspective view showing an element  1410   a  of a recess-type hybrid thin-film piezoelectric light modulator, according to a first embodiment of the present invention. Referring to  FIG. 8   a , the element  1410   a  includes a plurality of protrusions  1420   a   1 ,  1420   a   2 ,  1420   a   3 ,  1420   a   4  and  1420   a   5  which is placed on a micromirror layer  1415   a  of the element  1410   a  to reflect and diffract incident light. Each of the protrusions  1420   a   1 ,  1420   a   2 ,  1420   a   3 ,  1420   a   4  and  1420   a   5  has a rectangular column shape (ribbon shape). The protrusions  1420   a   1 ,  1420   a   2 ,  1420   a   3 ,  1420   a   4  and  1420   a   5  are arranged along a longitudinal axis of the element  1410   a , passing over the recess, to be spaced apart from each other at regular intervals (for example, each interval is the same as the width of the protrusion  1420   a   1 ,  1420   a   2 ,  1420   a   3 ,  1420   a   4 ,  1420   a   5 ). Each protrusion  1420   a   1 ,  1420   a   2 ,  1420   a   3 ,  1420   a   4 ,  1420   a   5  includes a support layer  1421   a   1 ,  1421   a   2 ,  1421   a   3 ,  1421   a   4 ,  1421   a   5  which is attached at a lower surface thereof to an upper surface of the micromirror layer  1415   a  of the element  1410   a . Each protrusion  1420   a   1 ,  1420   a   2 ,  1420   a   3 ,  1420   a   4 ,  1420   a   5  further includes a mirror layer  1422   a   1 ,  1422   a   2 ,  1422   a   3 ,  1422   a   4 ,  1422   a   5  which is layered on the support layer  1421   a   1 ,  1421   a   2 ,  1421   a   3 ,  1421   a   4 ,  1421   a   5  to reflect and diffract incident light. 
   At this time, one pixel is formed by both the mirror layer  1422   a   1 ,  1422   a   2 ,  1422   a   3 ,  1422   a   4 ,  1422   a   5  of one protrusion  1420   a   1 ,  1420   a   2 ,  1420   a   3 ,  1420   a   4 ,  1420   a   5  and one part of the micromirror layer  1415   a  of the element  1410   a  exposed from the protrusions  1420   a   1 ,  1420   a   2 ,  1420   a   3 ,  1420   a   4  and  1420   a   5 . Therefore, in the hybrid light modulator of  FIG. 8   a , two or more pixels are embodied in a single element  1410   a , thus realizing miniaturization and high integration of the hybrid light modulator.  FIG. 9   a  is a sectional view taken along the line A–A′ of  FIG. 8   a . With reference to  FIG. 9   a , the arrangement of the protrusions  1420   a   1 ,  1420   a   2 ,  1420   a   3 ,  1420   a   4  and  1420   a   5  along the longitudinal axis of the element  1410   a will be distinctly understood.    
   In the hybrid light modulator of  FIG. 8   a , a plurality of elements  1410   a  having regular widths are arranged at regular intervals to constitute the hybrid light modular. Alternatively, the elements  1410   a  having different widths may alternate to constitute the hybrid light modulator. As a further alternative, the elements  1410   a  may be spaced apart from each other at regular intervals (each interval is almost the same as the width of each element  1410   a ), in which a micromirror layer formed on an upper side of a silicon substrate  1401   a  reflects and diffracts incident light. 
   The silicon substrate  1401   a  has a recess to provide an air space to the elements  1410   a . An insulating layer  1402   a  is deposited on an upper surface of the silicon substrate  1401   a . Both ends of the elements  1410   a  are attached to upper sides of a wall of the recess. 
   The elements  1410   a  each have a ribbon shape. Lower sides of the both ends of the elements  1410   a  are attached to the remaining upper side of the silicon substrate  1401   a  except for the recess so that the centers of the elements  1410   a  are spaced from the recess of the silicon substrate  1401   a . The micromirror layer  1415   a  is formed on an upper side of each element  1410   a . Additionally, each element  1410   a  includes a lower supporter  1411   a  which has a vertically movable portion corresponding in position to the recess of the silicon substrate  1401   a.    
   Furthermore, the element  1410   a  includes a lower electrode layer  1412   a  which is laminated on the lower supporter  1411   a  to provide a piezoelectric voltage, and a piezoelectric material layer  1413   a  which is laminated on the lower electrode layer  1412   a  and shrinks and expands to generate a vertical actuating force when voltage is applied to upper and lower surfaces thereof. The element  1410   a  further includes an upper electrode layer  1414   a  which is laminated on the piezoelectric material layer  1413   a  and provides a piezoelectric voltage to the piezoelectric material layer  1413   a . The element  1410   a  further includes the micromirror layer  1415   a  which is laminated on the upper electrode layer  1414   a  to reflect and diffract incident light. 
     FIG. 8   b  is a perspective view showing an element  1410   b  of a recess-type hybrid thin-film piezoelectric light modulator, according to a second embodiment of the present invention. Referring to  FIG. 8   b , the element  1410   b  includes a plurality of protrusions  1420   b   1 ,  1420   b   2  and  1420   b   3  which is placed on a micromirror layer  1415   b  of the element  1410   b  that reflects and diffracts incident light. Each protrusion  1420   b   1 ,  1420   b   2 ,  1420   b   3  has a rectangular column shape (ribbon shape). When the longitudinal axis of the element  1410   b  is defined as the axis passing over the recess, the protrusions  1420   b   1 ,  1420   b   2  and  1420   b   3  are arranged along a latitudinal axis of the element  1410   b , unlike the element  1410   a  of  FIG. 8   a . The protrusions  1420   b   1 ,  1420   b   2  and  1420   b   3  are spaced apart from each other at regular intervals (for example, each interval is the same as the width of the protrusion  1420   b   1 ,  1420   b   2 ,  1420   b   3 ). Each protrusion  1420   b   1 ,  1420   b   2 ,  1420   b   3  includes a support layer  1421   b   1 ,  1421   b   2 ,  1421   b   3  which is attached at a lower surface thereof to an upper surface of the micromirror layer  1415   b  of the element  1410   b . Each protrusion  1420   b   1 ,  1420   b   2 ,  1420   b   3  further includes a mirror layer  1422   b   1 ,  1422   b   2 ,  1422   b   3  which is layered on the support layer  1421   b   1 ,  1421   b   2 ,  1421   b   3  to reflect and diffract incident light. 
   At this time, one pixel is formed by both the mirror layer  1422   b   1 ,  1422   b   2 ,  1422   b   3  of one protrusion  1420   b   1 ,  1420   b   2 ,  1420   b   3  and one part of the micromirror layer  1415   b  of the element  1410   b  exposed from the protrusions  1420   b   1 ,  1420   b   2  and  1420   b   3 . Therefore, in the hybrid light modulator of  FIG. 8   b , two or more pixels are embodied in a single element  1410   b , thus realizing miniaturization and high integration of the hybrid light modulator.  FIG. 9   b  is a sectional view taken along the line B–B′ of  FIG. 8   b . With reference to  FIG. 9   b , the arrangement of the protrusions  1420   b   1 ,  1420   b   2  and  1420   b   3  along the latitudinal axis of the element  1410   b  will be distinctly understood. Furthermore, the construction of the element  1410   b  of the second embodiment is the same as that of the element  1410   a  of the first embodiment, therefore further explanation is deemed unnecessary. 
     FIG. 8   c  is a perspective view showing an element  1410   c  of a recess-type hybrid thin-film piezoelectric light modulator, according to a third embodiment of the present invention. Referring to  FIG. 8   c , the element  1410   c  includes a plurality of protrusions  1420   c   1 ,  1420   c   2  and  1420   c   3  which is placed on a micromirror layer  1415   c  of the element  1410   c  that reflects and diffracts incident light. Each protrusion  1420   c   1 ,  1420   c   2 ,  1420   c   3  has a rectangular column shape (ribbon shape). The protrusions  1420   c   1 ,  1420   c   2  and  1420   c   3  are arranged along a longitudinal axis of the element  1410   c , passing over the recess, to be spaced apart from each other at regular intervals (for example, each interval is the same as the width of the protrusion  1420   c   1 ,  1420   c   2 ,  1420   c   3 ). Each protrusion  1420   c   1 ,  1420   c   2 ,  1420   c   3  includes a support layer  1421   c   1 ,  1421   c   2 ,  1421   c   3  which is attached at a lower surface thereof to an upper surface of the micromirror layer  1415   c  of the element  1410   c . The protrusion  1420   c   1 ,  1420   c   2 ,  1420   c   3  further includes a mirror layer  1422   c   1 ,  1422   c   2 ,  1422   c   3  which is layered on the support layer  1421   c   1 ,  1421   c   2 ,  1421   c   3  to reflect and diffract incident light. 
   At this time, one pixel is formed by both the mirror layer  1422   c   1 ,  1422   c   2 ,  1422   c   3  of one protrusion  1420   c   1 ,  1420   c   2 ,  1420   c   3  and one part of the micromirror layer  1415   c  of the element  1410   c  exposed from the protrusions  1420   c   1 ,  1420   c   2  and  1420   c   3 . Therefore, in the hybrid light modulator of  FIG. 8   c , two or more pixels are embodied in a single element  1410   c , thus realizing miniaturization and high integration of the hybrid light modulator.  FIG. 9   c  is a sectional view taken along the line C–C′ of  FIG. 8   c . With reference to  FIG. 9   c , the arrangement of the protrusions  1420   c   1 ,  1420   c   2  and  1420   c   3  along the longitudinal axis of the element  1410   c  will be distinctly understood. 
   In the hybrid light modulator of  FIG. 8   c , a plurality of elements  1410   c  having regular widths is arranged at regular intervals to constitute the hybrid light modular. Alternatively, elements  1410   c  having different widths may alternate to constitute the hybrid light modulator. As a further alternative, the elements  1410   c  may be spaced apart from each other at regular intervals (each interval is almost the same as the width of each element  1410   c ), in which a micromirror layer formed on an upper side of a silicon substrate  1401   c  reflects and diffracts incident light. 
   The silicon substrate  1401   c  has a recess to provide an air space to the elements  1410   c . An insulating layer  1402   c  is deposited on an upper surface of the silicon substrate  1401   c . Both ends of the elements  1410   c  are attached to upper sides of a wall of the recess. 
   The elements  1410   c  each have a ribbon shape. Lower sides of both ends of the elements  1410   c  are attached to the remaining upper side of the silicon substrate  1401   c  except for the recess so that the centers of the elements  1410   c  are spaced from the recess of the silicon substrate  1401   c . Additionally, each element  1410   c  includes a lower supporter  1411   c  which has a vertically movable portion corresponding in position to the recess of the silicon substrate  1401   c.    
   Furthermore, the element  1410   c  includes a first lower electrode layer  1412   c  which is laminated on a first end of the lower supporter  1411   c  to provide a piezoelectric voltage, and a first piezoelectric material layer  1413   c  which is laminated on the first lower electrode layer  1412   c  and shrinks and expands to generate a vertical actuating force when a voltage is applied to upper and lower surfaces thereof. The element  1410   c  further includes a first upper electrode layer  1414   c  which is laminated on the first piezoelectric material layer  1413   c  and provides a piezoelectric voltage to the first piezoelectric material layer  1413   c.    
   In addition, the element  1410   c  includes a second lower electrode layer  1412   c ′ which is laminated on a second end of the lower supporter  1411   c  to provide a piezoelectric voltage, and a second piezoelectric material layer  1413   c ′ which is laminated on the second lower electrode layer  1412   c ′ and shrinks and expands to generate a vertical actuating force when voltage is applied to upper and lower surfaces thereof. The element  1410   c  further includes a second upper electrode layer  1414   c ′ which is laminated on the second piezoelectric material layer  1413   c ′ and provides a piezoelectric voltage to the second piezoelectric material layer  1413   c′.    
     FIG. 8   b  is a perspective view showing an element  1410   b  of a recess-type hybrid thin-film piezoelectric light modulator, according to a fourth embodiment of the present invention. Referring to  FIG. 8   a , the element  1410   a  includes a plurality of protrusions  1420   d   1  and  1420   d   2  which is placed on a micromirror layer  1415   d  of the element  1410   d  that reflects and diffracts incident light. Each protrusion  1420   d   1 ,  1420   d   2  has a rectangular column shape (ribbon shape). When the longitudinal axis of the element  1410   d  is defined as the axis passing over the recess, the protrusions  1420   d   1  and  1420   d   2  are arranged along a latitudinal axis of the element  1410   d , unlike the element  1410   c  of  FIG. 8   c . The protrusions  1420   d   1  and  1420   d   2  are spaced apart from each other at regular intervals (for example, each interval is the same as the width of the protrusion  1420   d   1 ,  1420   d   2 ). Each protrusion  1420   d   1 ,  1420   d   2  includes a support layer  1421   d   1 ,  1421   d   2  which is attached at a lower surface thereof to an upper surface of the micromirror layer  1415   d  of the element  1410   d . The protrusion  1420   d   1 ,  1420   d   2  further includes a mirror layer  1422   d   1 ,  1422   d   2  which is layered on the support layer  1421   d   1 ,  1421   d   2  to reflect and diffract incident light. 
   At this time, one pixel is formed by both the mirror layer  1422   d   1 ,  1422   d   2  of one protrusion  1420   d   1 ,  1420   d   2  and one part of the micromirror layer  1415   d  of the element  1410   d  exposed from the protrusions  1420   d   1  and  1420   d   2 . Therefore, in the hybrid light modulator of  FIG. 8   d , two pixels are embodied in a the single element  1410   d , thus realizing miniaturization and high integration of the hybrid light modulator.  FIG. 9   d  is a sectional view taken along the line D–D′ of  FIG. 8   d . With reference to  FIG. 9   d , the arrangement of the protrusions  1420   d   1  and  1420   d   2  along the latitudinal axis of the element  1410   d  will be distinctly understood. Furthermore, the construction of the element  1410   d  of the fourth embodiment is the same as that of the element  1410   c  of the third embodiment, therefore further explanation is deemed unnecessary. 
     FIG. 8   e  is a perspective view showing an element  1410   e  of a recess-type hybrid thin-film piezoelectric light modulator, according to a fifth embodiment of the present invention. Referring to  FIG. 8   e , the element  1410   e  includes a plurality of protrusions  1420   e   1 ,  1420   e   2  and  1420   e   3  which is placed on a micromirror layer  1415   e  of the element  1410   e  that reflects and diffracts incident light. Each of the protrusions  1420   e   1 ,  1420   e   2  and  1420   e   3  has a rectangular column shape (ribbon shape). The protrusions  1420   e   1 ,  1420   e   2  and  1420   e   3  are arranged along a longitudinal axis of the element  1410   e , passing over the recess, to be spaced apart from each other at regular intervals (for example, each interval is the same as the width of the protrusion  1420   e   1 ,  1420   e   2 ,  1420   e   3 ). Each protrusion  1420   e   1 ,  1420   e   2 ,  1420   e   3  includes a support layer  1421   e   1 ,  1421   e   2 ,  1421   e   3  which is attached at a lower surface thereof to an upper surface of the micromirror layer  1415   e  of the element  1410   e . The protrusion  1420   e   1 ,  1420   e   2 ,  1420   e   3  further includes a mirror layer  1422   e   1 ,  1422   e   2 ,  1422   e   3  which is layered on the support layer  1421   e   1 ,  1421   e   2 ,  1421   e   3 , respectively, to reflect and diffract incident light. 
   At this time, one pixel is formed by both the mirror layer  1422   e   1 ,  1422   e   2 ,  1422   e   3  of one protrusion  1420   e   1 ,  1420   e   2 ,  1420   e   3  and one part of the micromirror layer  1415   e  of the element  1410   e  exposed from the protrusions  1420   e   1 ,  1420   e   2  and  1420   e   3 . Therefore, in the hybrid light modulator of  FIG. 8   e , two or more pixels are embodied in a single element  1410   e , thus realizing miniaturization and high integration of the hybrid light modulator.  FIG. 9   e  is a sectional view taken along the line E–E′ of  FIG. 8   e . With reference to  FIG. 9   e , the arrangement of the protrusions  1420   e   1 ,  1420   e   2  and  1420   e   3  along the longitudinal axis of the element  1410   e  will be understood. 
   In the hybrid light modulator of  FIG. 14   e , a plurality of elements  1410   e  having regular widths are arranged at regular intervals to constitute the hybrid light modulator. Alternatively, the elements  1410   e  having different widths may alternate to constitute the hybrid light modulator. As a further alternative, the elements  1410   e  may be spaced apart from each other at regular intervals (each interval is almost the same as the width of each element  1410   e ), in which a micromirror layer formed on an upper side of a silicon substrate  1401   e  reflects and diffracts incident light. 
   The silicon substrate  1401   e  has a recess to provide an air space to the elements  1410   e . An insulating layer  1402   e  is deposited on an upper surface of the silicon substrate  1401   e . Both ends of the elements  1410   e  are attached to upper sides of a wall of the recess. 
   The elements  1410   e  each have a ribbon shape. Lower sides of the both ends of the elements  1410   e  are attached to the remaining upper side of the silicon substrate  1401   e  except for the recess so that the centers of the elements  1410   e  are spaced from the recess of the silicon substrate  1401   e . The micromirror layer  1415   e  is formed on an upper side of each element  1410   e  above the recess of the silicon substrate  1401   e . That is, portions of the micromirror layer  1415   e , which are aligned with the remaining upper side of the silicon substrate  1401   e  other than the recess, are removed by an etching process. Additionally, each element  1410   e  includes a lower supporter  1411   e  which has a vertically movable portion corresponding in position to the recess of the silicon substrate  1401   e.    
   Furthermore, the element  1410   e  includes a lower electrode layer  1412   e  which is laminated on the lower supporter  1411   e  above the recess of the silicon substrate  1401   e  to provide a piezoelectric voltage. At this time, portions of the lower electrode layer  1412   e , which are aligned with the remaining upper side of the silicon substrate  1401   e  other than the recess, are removed by an etching process. The element  1410   e  further includes a piezoelectric material layer  1413   e  which is laminated on the lower electrode layer  1412   e  and shrinks and expands to generate a vertical actuating force when voltage is applied to upper and lower surfaces thereof. The element  1410   e  further includes an upper electrode layer  1414   e  which is laminated on the piezoelectric material layer  1413   e  and provides a piezoelectric voltage to the piezoelectric material layer  1413   e . The element  1410   e  further includes the micromirror layer  1415   e  which is laminated on the upper electrode layer  1414   e  to reflect and diffract incident light. 
     FIG. 8   f  is a perspective view showing an element  1410   f  of a recess-type hybrid thin-film piezoelectric light modulator, according to a sixth embodiment of the present invention. Referring to  FIG. 8   f , the element  1410   f  includes a plurality of protrusions  1420   f   1  and  1420   f   2  which is placed on a micromirror layer  1415   f  of the element  1410   f  that reflects and diffracts incident light. Each protrusion  1420   f   1 ,  1420   f   2  has a rectangular column shape (ribbon shape). When it is defined that the longitudinal axis of the element  1410   f  is aligned with the direction passing over the recess, the protrusions  1420   f   1  and  1420   f   2  are arranged along a latitudinal axis of the element  1410   f , unlike the element  1410   e  of  FIG. 8   e . The protrusions  1420   f   1  and  1420   f   2  are spaced apart from each other at regular intervals (for example, each interval is the same as the width of the protrusion  1420   f   1 ,  1420   f   2 ). Each protrusion  1420   f   1 ,  1420   f   2  includes a support layer  1421   f   1 ,  1421   f   2  which is attached at a lower surface thereof to an upper surface of the micromirror layer  1415   f  of the element  1410   f . The protrusion  1420   f   1 ,  1420   f   2  further includes a mirror layer  1422   f   1 ,  1422   f   2  which is layered on the support layer  1421   f   1 ,  1421   f   2  to reflect and diffract incident light. 
   At this time, one pixel is formed by both the mirror layer  1422   f   1 ,  1422   f   2  of one protrusion  1420   f   1 ,  1420   f   2  and one part of the micromirror layer  1415   f  of the element  1410   f  exposed from the protrusions  1420   f   1  and  1420   f   2 . Therefore, in the hybrid light modulator of  FIG. 8   f , two pixels are embodied in a single element  1410   f , thus realizing miniaturization and high integration of the hybrid light modulator.  FIG. 9   f  is a sectional view taken along the line F–F′ of  FIG. 8   f . Reference to  FIG. 9   f , the arrangement of the protrusions  1420   f   1  and  1420   f   2  along the latitudinal axis of the element  1410   f  will be distinctly understood. Furthermore, the construction of the element  1410   f  of the sixth embodiment is the same as that of the element  1410   e  of the fifth embodiment, therefore further explanation is deemed unnecessary. 
   In the meantime, the element  1410   a ,  1410   b ,  1410   c ,  1410   d ,  1410   e ,  1410   f  of each of the hybrid light modulators according to the first through sixth embodiments of  FIGS. 8   a  through  8   f  can be easily adapted to a protrusion-type diffractive thin-film piezoelectric light modulator disclosed in U.S. patent application Ser. No. 10/952,246, entitled “Diffractive Thin-Film Piezoelecric Light Modulator and a Method of Producing the Same,” incorporated herein by reference. 
     FIG. 10  is a sectional view of a hybrid light modulator, according to a seventh embodiment of the present invention. Referring to  FIG. 10 , an element  1610  of the hybrid light modulator according to the seventh embodiment is placed on a silicon substrate  1601  while being partially spaced from a bottom of a recess of the silicon substrate  1601 . The element  1610  includes a lower supporter  1611  which is attached at both ends thereof to the silicon substrate  1601  along upper ends of sidewalls of the recess. The element  1610  further includes a first lower electrode layer  1612   a  which is laminated on a first end of the lower supporter  1611  such that a first end of the first lower electrode layer  1612   a  is aligned with the first end of the lower supporter  1611  and a second end of the first lower electrode layer  1612   a  is placed on a predetermined position of the lower supporter  1611  spaced to the first side from the center line of the recess. The element  1610  further includes a first piezoelectric material layer  1613   a  which is laminated on the first lower electrode layer  1612   a  and generates a vertical actuating force when voltage is applied to the first lower electrode layer  1613   a . The element  1610  further includes a first upper electrode layer  1614   a  which is laminated on the first piezoelectric material layer  1613   a  and provides a piezoelectric voltage to the first piezoelectric material layer  1613   a . The element  1610  further includes the first micromirror layer  1615   a  which is laminated on the first upper electrode layer  1614   a  to reflect and diffract incident light. 
   The element  1610  further includes a third micromirror layer  1615   c  which is laminated on an intermediate portion of the lower supporter  1611  to reflect and diffract incident light. 
   The element  1610  further includes a second lower electrode layer  1612   b  which is laminated on a second end of the lower supporter  1611  such that a second end of the second lower electrode layer  1612   b  is aligned with the second end of the lower supporter  1611  and a first end of the second lower electrode layer  1612   b  is placed on a predetermined position of the lower supporter  1611  spaced to the second side from the center line of the recess. The element  1610  further includes a second piezoelectric material layer  1613   b  which is laminated on the second lower electrode layer  1612   b  and generates a vertical actuating force when a voltage is applied to the second lower electrode layer  1613   b . The element  1610  further includes a second upper electrode layer  1614   b  which is laminated on the second piezoelectric material layer  1613   b  and provides a piezoelectric voltage to the second piezoelectric material layer  1613   b . The element  1610  further includes the second micromirror layer  1615   b  which is laminated on the second upper electrode layer  1614   b  to reflect and diffract incident light. 
   In the hybrid light modulator of  FIG. 10 , one pixel is formed by both the first micromirror layer  1615   a  and a part of the third micromirror layer  1615   c  which is placed to the first side based on the line A–A′ of  FIG. 10 . The other pixel is formed by both the second micromirror layer  1615   b  and a part of the third micromirror layer  1615   c  which is placed to the second side based on the line A–A′ of  FIG. 16 . As a result, two pixels are embodied in a single element  1610 . 
     FIG. 11  is a sectional view of a hybrid light modulator, according to an eighth embodiment of the present invention. Referring to  FIG. 11 , in the hybrid light modulator according to the eighth embodiment, a plurality of protrusions  1620   a ,  1620   b  and  1620   c  are provided on a third micromirror layer  1615   c  of an element  1610  which has the same structure as that of the element  1610  of the seventh embodiment. At this time, the protrusions  1620   a ,  1620   b  and  1620   c  are arranged along a latitudinal axis of the element  1610 . The element  1610  of the eight embodiment includes first and second micromirror layers  1615   a  and  1615   b  which are laminated on first and second upper electrode layers  1614   a  and  1614   b , respectively, unlike the element  1410   c  of the third embodiment shown in  FIG. 8   c.    
   Each protrusion  1620   a ,  1620   b ,  1620   c  includes a support layer  1621   a ,  1621   b ,  1621   c  which is attached at a lower surface thereof to an upper surface of the third micromirror layer  1615   c , and a mirror layer  1622   a ,  1622   b ,  1622   c  which is layered on the support layer  1621   a ,  1621   b ,  1621   c.    
   In the hybrid light modulator of  FIG. 11 , one pixel is formed by both the first micromirror layer  1615   a  and a part of the third micromirror layer which is exposed between the first micromirror layer  1615   a  and the first protrusion  1620   a.    
   Another pixel is formed by both the first protrusion  1620   a  and a part of the third micromirror layer which is exposed between the first protrusion  1620   a  and the second protrusion  1620   b . In the same manner as above, a plurality of pixels can be embodied in a single element  1610 . The general construction of the element  1610  of the eighth embodiment, aside from the above-mentioned structure, remains the same as the seventh embodiment, therefore further explanation is deemed unnecessary. 
     FIG. 12  is a sectional view of a hybrid light modulator, according to a ninth embodiment of the present invention. 
   Referring to  FIG. 12 , an element  1810  of the hybrid light modulator according to the ninth embodiment includes first and third micromirror layers  1815   a  and  1815   c  which are provided on both ends of a lower supporter  1811 , unlike the element  1410   e  of the fifth embodiment shown in  FIG. 8   e . In the hybrid light modulator of  FIG. 12 , one pixel is formed by both the first micromirror layer  1815   a  and a part of the second micromirror layer  1815   b  which is on one side of line A–A′ of  FIG. 12 . The other one pixel is formed by both the third micromirror layer  1615   c  and a part of the second micromirror layer  1615   b  which is on the other side of the line A–A′ of  FIG. 12 . The general construction of the element  1810  of the ninth embodiment, aside from the above-mentioned structure, remains the same as the fifth embodiment of  FIG. 8   e , therefore further explanation is deemed unnecessary. 
     FIGS. 13   a  through  13   c  are views showing operation of the hybrid light modulator, according to the present invention. 
   Referring to  FIG. 13   a , the hybrid light modulator includes a plurality of protrusions  1920   a ,  1920   b  and  1920   c . As shown in  FIG. 13   b , if a lower supporter  1911  is rigid, the protrusions  1920   a ,  1920   b  and  1920   c  vertically move without being stepped. 
   However, as shown in  FIG. 13   c , if the lower supporter  1911  is flexible, the protrusions  1920   a ,  1920   b  and  1920   c  vertically move while forming a stepped structure. As a result, the direction of diffracted light is changed. 
   In other words, according to a degree of the rigidity of the lower supporter  1911 , the direction of diffracted light may be maintained or changed. Therefore, the hybrid light modulator of the present invention can diffract incident lights in a wide direction. 
   As described above, the present invention provides a hybrid light modulator which realizes miniaturization of products, thus reducing production costs. 
   Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.