GB2425614A

GB2425614A - Open hole-based diffractive light modulator

Info

Publication number: GB2425614A
Application number: GB0600093A
Authority: GB
Inventors: Sang Kyeong Yun
Original assignee: Samsung Electro Mechanics Co Ltd
Current assignee: Samsung Electro Mechanics Co Ltd
Priority date: 2005-04-26
Filing date: 2006-01-05
Publication date: 2006-11-01
Anticipated expiration: 2026-01-05
Also published as: FR2884932B1; GB2425613A; GB0600093D0; GB0600087D0; FR2884932A1; GB2425614B; CN1854796A; CN100485443C; GB2425613B

Abstract

This invention relates to a diffractive light modulator, in particular to an open-hole based diffractive light modulator. The modulator comprises a plurality of lower reflective patterns (503c1-503c3) mounted on a base member (501c) and open holes (531c1-531c3) are formed through an upper micromirror (530a) raised from the base member (501c) so that one pixel is formed using one element (501c) having the ribbon-shaped upper micromirror. The element (510c) comprises a lower support (511c) and piezoelectric layers (520c) and (520c'). The base member (501c) comprises a silicon substrate (501c1), a silicon oxide insulating layer (501c2), and a sacrificial silicon layer (501c3) which is formed by implanting a high concentration of oxygen in the silicon substrate. That portion of the sacrificial silicon layer (501c3) that is positioned beneath the upper micromirror (530a) is etched so as to create an air space to allow vertical movement of the element (510c). In addition, those portions of the sacrificial layer (501c3) which are positioned beneath piezoelectric layers (520c, 520c') are partially etched.

Description

OPEN HOLE-BASED DIFFRACTIVE LIGHT MODULATOR

BACKGROUND OF THE INVENTION

S 1. Field of the Invention

The present invention relates, in general, to a diffractive light modulator and, more particularly, to an open-hole based diffractive light modulator, in which a lower reflective part is provided on a base member and open holes are formed through an upper micromirror raised from the base member so that one pixel is formed using one element having the upper micromirror.

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 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 silicon 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 the oxide spacer layer 12 by a nitride frame 20.

In order to modulate light having a single wavelength of X, the modulator is designed so that thicknesses of the ribbon 18 and oxide spacer 12 are each X0/4.

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 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 formed on a lower side of the substrate 16 to act as a second electrode).

In an undeformed state of the light modulator with no voltage application, the grating amplitude is ?/2 while a total round-trip path difference between light beams reflected from the ribbon and substrate is ?. Thus, a phase of reflected light is reinforced.

Accordingly, in the undeformed state, the modulator 10 acts as a plane mirror when it reflects incident light. In FIG. 2, the reference numeral 20 denotes the incident light reflected by the modulator 10 in the undeforrned state.

When proper voltage is applied between the ribbon 18 and substrate 16, the electrostatic force enables the ribbon 18 to move downward toward the surface of the substrate 16. At this time, the grating amplitude is changed to 2/4. 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 +1diffractive modes (D+1, D-1) in the deformed state, respectively.

However, the light modulator by Bloom adopts an electrostatic method to control the position of a micromirror, which is disadvantageous in that operation voltage is relatively high (usually 30 V or so) and the relationship between the applied voltage and displacement is not linear, thus resulting in poor reliability in the control of light.

The light modulator described in the patent of Bloom can be used as a device for displaying images. In this case, a minimum of two adjacent elements may form a single pixel. Of course, three elements may form a single pixel, or four or six elements may form a single pixel.

However, the light modulator described in the patent of Bloom has a limitation in achieving miniaturization. That is, the light modulator has a limitation in that the widths of the elements thereof cannot be formed to be below 3 im and the interval between elements cannot be formed to be below 0.5 Lull.

Furthermore, a minimum of two elements is required to constitute a diffraction pixel, thus having a limitation in the miniaturization of a device.

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 diffractive light modulator in which one pixel is formed using as few as one ribbon element, thereby miniaturizing goods.

According to the present invention, there is provided an open hole- based diffractive light modulator, comprising: a substrate; an insulating layer disposed on the substrate; at least one sacrificial layer which is disposed on the insulating layer; a reflective part disposed on the insulating layer, said reflective part positioned to reflect incident light; is a support which is provided on the at least one sacrificial layer and through which at least one first open hole is formed; a micromirror disposed on the support, said micromirror having a reflective surface to reflect the incident light, at least one second open hole formed in the micromirror to correspond to the or each first open holes to pass the incident light therethrough; and at least one actuating unit to move an intermediate portion of the support when voltage is applied thereto, thereby changing the intensity of the diffracted light which is formed by light reflected from the micromirror and the reflective part.

The above and other objects, features and 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. I illustrates a grating light modulator adopting an electrostatic method according to a conventional technology; FIG. 2 illustrates reflection of incident light by the grating light modulator adopting the electrostatic method according to the conventional technology in an undeformed state; FIG. 3 illustrates diffraction of incident light by the grating light modulator according to the conventional technology in a deformed state caused by an electrostatic force; FIG. 4a is a perspective view of an open hole-based diffractive light modulator, which is partially broken away; FIG. 4b is a perspective view of an open hole-based diffractive light modulator, which is partially broken away; FIG. 4c is a perspective view of an open hole- based diffractive light modulator, which is partially broken away, according to an embodiment of the present invention; FIG. 4d is a perspective view of an open hole-based diffractive light modulator, which is partially broken away; FIG. 4e is a perspective view of an open hole- based diffractive light modulator, which is partially broken away; FIG. 4f is a perspective view of an open hole-based diffractive light modulator, which is partially broken away; FIG. 4g is a perspective view of an open hole-based diffractive light modulator, which is partially broken away; FIG. 4h is a perspective view of an open hole-based diffractive light modulator, which is partially broken away; FIG. 4i is a perspective view of an open hole-based diffractive light modulator, which is partially broken away; FIG 4j is a perspective view of an open hole- based diffractive light modulator, which is partially broken away; FIG. 5 illustrates an element 1-D array structure of the open-hole based diffractive light modulator; FIG. 6 illustrates an element 2-D array structure of the open-hole based diffractive light modulator; FIG. 7 illustrates a display system using the open-hole based diffractive light modulator according to the embodiment of the present invention; and FIG. 8a is a perspective view of the open-hole based diffractive light modulator in which incident light obliquely irradiates the upper micromirror of an element 1-D array, and FIG. 8b is a perspective view of the open-hole based diffractive light modulator in which light is perpendicularly incident on an upper micromirror of an element 1-0 array.

FIG. 4a is a perspective view of an open hole-based diffractive light modulator. Referring to the drawing, the light modulator includes a silicon substrate 501a, an insulating layer 502a, a micromirror 503a, and an element 510a. Although the insulating layer and the micromirror are illustrated as constructed in separate layers in this arrangement, the insulating layer can be implemented to function as the lower micromirror if it has light-reflective characteristics. Furthermore, herein, the insulating layer 502a is shown as formed on a surface of the base member 501a, but the insulating layer is not essential, thus the reflective part 503a may be formed without forming the insulating layer 502a.

The silicon substrate 501 a includes a recess for providing a space for the element 510a, the insulating layer 502a is formed on the silicon substrate 501a, the lower micromirror 503a is deposited above the silicon substrate 501a, and the bottom of the element 510a is attached to or otherwise supported by both sides of the silicon substrate 501 a outside the recess. A material, such as Si, A1203, Zr02, Quartz and Si02, may be used to constitute the silicon substrate 501a, and the lower and upper layers of the silicon substrate 501a (divided by a dotted line) may be formed using different materials. Additionally, a glass substrate may be used as the base member 501a.

The lower micromirror 503a is located on an upper side of the base member 501a, and reflects incident light. A micromirror may be used as the lower reflective part 503a, and metal, such as Al, Pt, Cr or Ag, can be used to constitute the lower micromirror 503a.

The element 510a is illustrated as formed in an elongate, thin ribbon shape, however, the element can be formed in other shapes, such as rectangular, square, oval, etc. The element 510a includes a lower support 511a, the bottoms of both sides of which are attached to or otherwise supported by sides of the silicon substrate 501a outside the recess of the silicon substrate 501a so as to allow the center portion of the element 510a to be spaced apart from the recess. The term lower support' 511a is named because it is situated under piezoelectric layers 520a and 520a'.

The piezoelectrjc layers 52Qa and 520a' may be provided on both sides of the lower support 511a, respectively, and the actuating force of the element 510a is provided through the shrinkage and expansion of the provided piezoelectric layers 520a and 520a'.

Si oxide (e.g., Si02, etc.), Si nitride (e.g., Si3N4, etc.), a ceramic substrate (Si, Zr02 and Al203, etc.), or Si carbide can be used to constitute the lower support 511a. Such a lower support 5lla can be omitted according to necessity.

The left or right piezoelectric layer 520a or 520a' includes a lower electrode layer 521a or 521a' adapted to provide piezoelectric voltage, a piezoelectric material layer 522a or 522a' formed on the lower electrode layer 521a or 521a' and adapted to generate a vertical actuating force through shrinkage and expansion when voltage is applied to both sides thereof, and an upper electrode layer 523a or 423a' formed on the piezoelectric material layer 521a or 521a' and adapted to provide piezoelectric voltage to the piezoelectric material layer 521a or 521a'. When voltage is applied to the upper electrode layers 523a and 523a' and the lower electrode layer 52la and 521a', the piezoelectric material layers 521a and 521a' shrink and expand,

S

thus causing the lower support 511a to move vertically toward or away from the micromirror 503a.

Pt, Ta/Pt, Ni, Au, Al, Ti/Pt, 1r02 and Ru02 can be used as the materials of the electrodes 52la, 521a', 523a and 523a', and such materials are deposited to have a depth within a range from 0.01 to 3 an using a sputtering or evaporation method.

eanwhile, an upper micromirror 530a is deposited at the center portion of the lower support 511a. The upper micrornirror 530a includes a plurality of open holes 531a1 to 531a3. In this case, the open holes 531a1 to 531a3 are preferably formed in a rectangular shape, but may be formed in any closed shape such as a circle or an ellipse. Furthermore, the lower support 511a and the upper micromirror 530a may be called an upper reflective part 540a. If the lower support is made of a light-reflective material, a separate upper micromirror does not need to be deposited, and the lower support alone functions as the upper reflective part 540a.

Such open holes 531a1 to 531a3 allow light incident on the element 5lOa to pass therethrough so that the light is incident on the portions of the lower micromirror 503a corresponding to the open holes 531a1 to 53la3, thus enabling the lower and upper micromirrors 503a and 530a to form pixels.

That is, for example, a portion (A) of the upper micromirror 530a, in which the open holes 53la1 to 531a3 are formed, and a portion (B) of the lower micromirror 503a can form a single pixel.

In other words, since the upper micromirror 530a has a reflective surface, it reflects incident light to form reflected light while it allows the incident light to reach the lower reflective part 503a through the open holes. The lower reflective part 503a then reflects incident light to form reflected light, thus light reflected from the upper micromirror 530a and light, reflected from the lower reflective part 503a interfere with each other, thereby forming diffracted light. The intensity of diffracted light depends on the distance between the upper micromirror 530a and the lower reflective part 503a.

In this case, incident light passing through the open holes 531a1 to 531a3 of the upper micromirror 530a can be incident on the corresponding portions of the lower micromirror 503a, and the maximal diffracted light is generated when the height difference between the upper micromirror 530a and the lower micrornirror 503a is one of odd multiples of X/4. As well, herein, only one element 5lOa is illustrated, but the open-hole based diffractive light modulator may include a plurality of elements which are parallel to each other. In other words, the open-hole based diffractive light modulator may include element arrays, which case is shown in FIGS. 5 and 6.

When using the element arrays according to the present invention, it is possible to realize a display device having a desired pixel using fewer elements than the conventional technology.

For example, in a conventional technology, it is possible to form one pixel using at least two ribbon-shaped elements. In the conventional technology, when two ribbon-shaped elements constitute one pixel, diffraction efficiency is 50 % or less, thus four or six elements constitute one pixel so as to increase diffraction efficiency. When four or more elements constitute one pixel, diffraction efficiency is 70 % or more, thus it is possible to gain desired maximum efficiency through an increase in the number of elements. In the above-described arrangement, three open holes 531a1-531a3 are formed through the upper micromirror 530a constituting an upper part of one element 510a to pass incident light S therethrough to reach the lower reflective part 503a, thereby gaining the same diffraction efficiency as the conventional technology that uses six elements to form one pixel. That is to say, a mirror part adjacent to the first open hole 531a1 of the upper micromirror 530a reflects incident light to function as one ribbon element of the conventional technology. Furthermore, a portion of the lower reflective part 503a, which is positioned under the first open hole 531a1 so as to correspond in position to the first open hole, reflects incident light passing through the first open hole 531a1, thereby functioning as another ribbon element. Additionally, a mirror part adjacent to the second open hole 531a2 of the upper rnicromirror 530a reflects incident light to function as another ribbon element of the conventional technology, and the portion of the lower reflective part 503a that is positioned under the second open hole 531a2 so as to correspond in position to the second open hole reflects incident light passing through the second open hole 531a2, thereby functioning as another ribbon element. As well, a mirror part adjacent to the third open hole 531a3 of the upper micromirror 530a reflects incident light to function as another ribbon element of the conventional technology, and the portion of the lower reflective part 503a that is positioned under the third open hole 531a3 so as to correspond in position to the third open hole reflects incident light passing through the third open hole 531a3, thereby functioning as another ribbon element. As described above, if using an upper micromirror 530a having three open holes 531a1- 531a3 formed therethrough and the lower reflective part 503a, the same diffraction efficiency that is gained when one pixel is formed using six ribbon elements in the conventional technology can be gained using one ribbon element 510a.

If a digital TV ND format, which corresponds to 1080 X 1920, is realized using the above-mentioned diffractive light modulator, 1080 pixels are vertically arranged and each pixel is subjected to 1920 optical modulations, thereby forming one frame.

If one pixel is formed using four or six driving ribbons through the conventional technology, 1080 X 4 (or 6) driving ribbons are required to form 1080 pixels. On the other hand, when using a ribbon-shaped element having two or three open holes according to the present invention, it is possible to form 1080 pixels using only 1080 X 1 ribbon element. Thus, the fabrication is easily achieved, productivity increases, and it is possible to fabricate a device having a small size.

FIG. 4b is a perspective view of an open hole-based diffractive light modulator, which is partially broken away, showing a second arrangement.

Referring to the drawing, the open hole-based diffractive light modulator comprises a base member 501 b, a lower reflective part 503b and an element 510b.

Unlike the first arrangement, the lower reflective part 503b includes a plurality of lower reflective patterns 503bl-503b3, and the plurality of lower reflective patterns 503b1-503b3 is provided on the surface of an insulating layer 502a at intervals so that they correspond in position to open holes 531bl-531b3 of an upper micromirror 530b. The other constructions are the same as those of FIG. 4a.

FIG. 4c is a perspective view of an open hole-based diffractive light modulator, which is partially broken away, according to an embodiment of the present invention.

Referring to the drawing, the open hole-based diffractive light modulator according to the embodiment of the present invention comprises a base member 501c which includes a SIMOX 501 (separation by implanted oxygen silicon-on-insulator) substrate (hereinafter, referred to as "silicon-oninsulator substrate"), a lower reflective part 503c, and an element 510c.

The embodiment of the present invention is different from the arrangement shown in FIG. 4a in that a silicon-on-insulator substrate, rather than a silicon substrate, is used as the base member 501c. Its fabrication is well known, thus a detailed description of it is omitted herein.

The base member 501c of the silicon-on-insulator used in the present invention comprises a silicon substrate 501c1, a silicon oxide insulating layer 501c2 which is formed by implanting oxygen ions in the silicon substrate, and a sacrificial silicon layer 501c3 which is formed by implanting a high concentration of oxygen in the silicon substrate. The portion of the sacrificial silicon layer 501 c3 that is positioned under an upper micromirror 530c is etched so as to assure a movement space (air space) in which the element 510c is capable of vertically moving. Furthermore, the portion of the sacrificial silicon layer 501c3 that is positioned under piezoelectric layers 520c, 520c', is partially etched so that the upper micromirror 530c is actuated by the shrinkage and expansion of piezoelectric materials 522c, 522c' of the piezoelectric layers 520c, 520c'. As well, the silicon oxide insulating layer 501c2 may be considered an etching prevention layer for preventing the silicon substrate 501c1 from being etched when the silicon sacrificial layer 501c3 is etched.

Furthermore, the embodiment of the present invention is also different from the arrangement shown in Figure 4a in that the lower reflective part 503c includes a plurality of lower reflective patterns 503c1-503c3 which are spaced apart from each other. In this respect, it is the same as the arrangement shown in Figure 4b.

Additionally, the embodiment of the present invention is different from the arrangement shown in Figure 4a in that the sacrificial silicon layer 501c3 provides the movement space (air space) for the element 51 Oc. That is to say, in the embodiment of the present invention, it is unnecessary to provide a separate recess on the silicon substrate 501c1. In this respect, the sacrificial silicon layer 501c3 may be considered a supporting member for supporting the element 510c so as to provide movement space for the element 51 Oc. Other construction details, and the operation of the open-hole based diffractive light modulator according to the embodiment of the present invention are essentially the same as those described above with reference to Figures 4a and 4b.

Furthermore, it will be apparent that all of the arrangements described herein could also be modified by the features of the embodiment of the invention, as illustrated in Figure 4c, including the provision of arrays such as described with reference to Figures 5 and 6.

FIG. 4d is a perspective view of an open hole-based diffractive light modulator, which is partially broken away, in which the light modulator comprises a base member 501d including a silicon substrate, a lower reflective part 503d, and an element 510d.

The arrangement of FIG. 4d is different from that of FIG. 4a in that open holes 531d1-531d3 are not longitudinally arranged, but are transversely arranged. The other construction details are the same as those of FIG. 4a.

FIG. 4e is a perspective view of an open hole-based diffractive light modulator, which is partially broken away. This modulator is different from those described previously in that a lower support 511e of an element 510e is raised from a base member 501e of a silicon substrate so as to provide a space. As a result, the element 510e can move vertically.

That is, the element 510e has an upper micromirror 530e for reflecting the incident light, and can move vertically while being raised from the base member 5Ole. In this case, if the lower support has light-reflective characteristics, the lower support can be implemented to function as a micromirror without needing to form a separate micromirror.

The lower support 511e of the element 510e is raised to provide the air space to the element 510e, and both sides thereof are attached to the base member 501e.

Furthermore, an insulating layer 502e and a lower reflective part 503e are deposited on the base member 501e including the silicon substrate, and the lower reflective part 503e reflects incident light passing through open holes. In this case, if the insulating layer has light- reflective characteristics, the insulating layer can function as the lower reflective part without needing to form a separate lower reflective part.

The element 510e may be formed in a ribbon shape, the central portion thereof is positioned to be raised and spaced apart from the base member 501e, and the bottoms of both sides thereof are attached to the base member 501e.

Piezoelectrjc layers 520e and 520e' form the left and right sides of the upper portion of the element 510e, respectively.

The piezoelectric layer 520e or 520& includes a lower electrode layer 521e or 521e' adapted to provide piezoelectric voltage, a piezoelectric material layer 522e or 522e' formed on the lower electrode layer 52le or 521e' and adapted to generate a vertical actuating force through shrinkage and expansion when voltage is applied to both sides thereof, and an upper electrode layer 523e or 523e' formed on the piezoelectric material layer 522e or 522e1 and adapted to provide piezoelectric voltage to the piezoelectrjc material layer 522e or 522e'.

When voltage is applied to the upper electrode layers 523e and 523e' and the lower electrode layers 521e and 521e', the element 510e moves upward and reflects incident light to form reflected light.

An upper micrornirror 530e is disposed at the center portion of the element 510e in which the piezoelectric layers 520e and 520e' of the lower support 511e are removed, and open holes 531e1 to 531e3 are provided in the upper micromirror 530e. In this case, the open holes 531e1 to 531e3 are preferably formed in a rectangular shape, but can be formed in any closed shape such as a circle or an ellipse.

Such open holes 531e1-531e3 allow the portions of the lower micromirror 503e corresponding to the open holes 531e1 to 531e3, together with the portions of the upper micromirror 530e adjacent to the open holes 531e1 to 531e3 of the upper rnicromirror 530e, to form pixels.

That is, for example, a portion (A) of the upper micromirror 530e, in which the open holes 531e1 to 531e3 are formed, and a portion (B) of the lower micromirror 503e form a single pixel.

In this case, incident light passing through the open holes 531e1 to 531e3 of the upper micromirror 530e can be incident on the corresponding portions of the lower micromirror 503e, and it can be understood that the maximal diffracted light is generated when the height difference between the upper micromirror 530e and the lower micromirror 503e is one of odd multiples of A/4.

FIG. 4f is a perspective view of an open hole-based diffractive light modulator, which is partially broken away. This modulator is different from that described with reference to Figure 4e in that open holes are arranged in a transverse direction. The other construction details are the same as those of the open hole-based diffractive light modulator shown in FIG. 4e.

FIG. 4g is a perspective view of an open hole-based diffractive light modulator, which is partially broken away. This modulator includes a silicon substrate 501g, a lower reflective part 503g layered on the silicon substrate, and an upper micromirror 510g.

Not only is the lower reflective part 503g used as the lower electrode, but it also reflects light to form reflected light.

An upper micromirror 510g has open holes 511g1-511g3 provided therein. In this case, the open holes 511g1-511g3 are preferably formed in a rectangular shape, but can be formed in any closed shape such as a circle or an ellipse.

Such open holes 51 lgl-511g3 allow the portions of the lower micromirror 503g corresponding to the open holes 51 Iga -511g3, together with the portions of the upper micromirror 530e adjacent to the open holes 51 lgl-51 I g3 of the upper micromirror 510g, to form pixels.

That is, for example, a portion (A) of the upper micromirror 510g, in which the open holes are formed, and a portion (B) of the lower micromirror 503g form a single pixel.

In this case, incident light passing through the open holes 511g1- 51 1g3 of the upper micromirror 510g can be incident on the corresponding portions of the lower micromirror 503g, and it can be understood that the maximal diffracted light is generated when the height difference betweenthe upper micromirror 510g and the lower micromirror 503g is one of odd multiples of A14.

FIG. 4h is a perspective view of an open hole-based diffractive light modulator, which is partially broken away. This modulator is different from that described with reference to Figure 4g in that open holes are transversely arranged. The other construction details are the same as those of FIG. 4g.

Meanwhile, in the arrangements described above, including the embodiment of the present invention, a vertical actuating force is generated using the piezoelectric material layer, and, in the arrangements shown in FIGS. 4g and 4h, the vertical actuating force is generated using an electrostatic force.

Furthermore, the vertical actuating force may be generated using an electromagnetic force.

Meanwhile! in the arrangements of FIGS. 4d to 4h, one mirror layer constitutes the lower reflective part, but, as shown in the arrangements of FIG. 4b, the lower reflective part may include a plurality of lower reflective patterns at intervals. That is to say, the lower reflective part includes a plurality of lower reflective patterns, and the plurality of lower reflective patterns is provided on a surface of the insulating layer at intervals so that they correspond in position to the open holes of the upper micromirror.

FIG. 4i is a perspective view of an open hole-based diffractive light modulator, which is partially broken away. The modulator comprises a base member 501i including a silicon substrate, a lower reflective part 510i formed in the middle of the recess of the base member 501i, and an upper micromirror 520i adapted to span the uppermost surfaces of the base member 501i. The lower reflective part 510i not only reflects incident light to form reflected light, but is also used as the upper electrode.

A lower electrode layer 503i is formed on the bottom of the recess of the base member 501i. The lower electrode layer 403i, together with the lower reflective part 51 Oi (upper electrode) positioned in the middle of the recess, provides the lower reflective part 510i with a vertical actuating force that is caused by an electrostatic force.

That is, the lower electrode 503i and the lower reflective part 510i attract each other due to an electrostatic force and generate a downward actuating force if voltage is applied thereto, or they generate an upward actuating force by a restoring force if the voltage is not applied thereto.

Meanwhile, open holes 53111-53113 are provided in the upper micromirror 520i. The open holes 53111-5313 are preferably formed in a s rectangular shape, but may be formed in any closed shape such as a circle or an ellipse.

Such open holes 531I1-531i3 enable the portions of the lower reflective part 510i corresponding to the open holes 531i1-53113, together with the portions of the upper micromirror 520i adjacent to the open holes 53111-531i3, to form pixels.

That is, for example, a portion (A) of the upper micromirror 5201, in which the open holes 53111-53113 are formed, and a portion (B) of the lower reflective part form a single pixel.

In this case, incident light passing through the open holes of the upper micromirror 5201 can be incident on the corresponding portions of the lower reflective part 5101, and it can be understood that the maximal diffracted light is generated when the height difference between the upper micromirror 5201 and the lower reflective part 520i is one of odd multiples of A/4.

FIG. 4j illustrates an open hole-based light modulator, which is different from that shown in FIG. 4i in that open holes are transversely arranged.

Meanwhile, in the arrangements shown in FIGS. 4d, 4g, 4h, 41 and 4j, a silicon substrate is used as the base member. However, as shown in the embodiment of the invention described in FIG. 4c, a Silicon-on-insulator substrate could alternatively be used.

FIG. 5 is a perspective view showing an element 1-D array of an open-hole based diffractive light modulator which comprises a plurality of elements 610a-610n having an upper micromirror unidirectionally arranged parallel to each other, thus diffracting incident light. Although, only the element I -D array of the open-hole based diffractive light modulator shown in FIG. 4a is described herein, the element 1-D arrays of the open- hole based diffractive light modulators according to the embodiment of the invention shown in FIG. 4c may be identically realized.

FIG. 6 is a perspective view showing an element 2-D array of an open-hole based diffractive light modulator which comprises a plurality of elements 7lOal-7lOnn arranged in X- and Y-directions. Although only the element 20 array of the open-hole based diffractive light modulator shown in FIG. 4g is described herein, the element 2-D arrays according to the embodiment of the invention shown in FIG. 4c may be identically realized.

Meanwhile, although the case of a single piezoelectric material layer has been described in this specification, it is possible to implement a multitype piezoelectrjc material layer formed of a plurality of piezoelectrjc material layers.

FIG. 7 illustrates a display device using the open-hole based diffractive light modulator according to the embodiment of the present invention. As described above, an optical system such as that used in a display device can also be used in a printer, and, in this case, a drum is used instead of a screen 818 as described later. In the case in which the drum is used, since the drum rotates, a separate scanning optical part rotates as in the display device, thus it is not essentially required to use a scanning optical part.

Referring to FIG. 7, the display device employing the diffractive light modulator according to the embodiment of the present invention comprises a display optical system 802 and a display electronic system 804. The display optical system 802 comprises a light source 806, a light optical part 808 for converting light which is emitted from the light source 806 into linear light so as to irradiate an open-hole based diffractive light modulator 810 in the form of linear light, the open-hole based diffractive optical modulator 810 for modulating linear light which is formed by the light optical part 808 to form diffracted light, a filtering optical part 812 for separating orders of diffracted light beams which are modulated by the open- hole based diffractive light modulator 810 to pass the desired order of diffracted light beam of the various orders of diffracted light beams therethrough, a projection and scanning optical part 816 for condensing diffracted light beams which pass through the filtering optical part 812 to scan condensed point light in a 2-D image, and a display screen 818.

The display electronic system 804 is connected to the light Source 806, the open-hole based diffractive light modulator 810, and the projection and scanning optical part 816.

Furthermore, if linear light is incident from the light optical part 808 onto the open-hole based diffractive light modulator sia, the modulator modulates incident light through a control of the display electronic system 804 to generate diffracted light, thus emitting it.

FIG. 8a is a perspective view of an open-hole based diffractive light modulator in which linear light obliquely irradiates a Plurality of upper micromirrors 812a-811n of an element 8lla-811n l-D array. If the, plurality of upper micromirrors 812a-8l2n vertically moves, incident linear light is modulated due to a height difference between the upper micrornirrors 812a-812n and a lower reflective part 813, thereby creating diffracted light. In this case, diffracted light is obliquely emitted because light is obliquely incident.

FIG. Sb is a perspective view of the open-hole based diffractive light modulator in which linear light perpendicularly irradiates a plurality of upper micromirrors 812a-811n of an element 811a-811n l-D array. If the plurality of upper micrornirrors 812a-812n vertically moves, incident linear light is modulated due to a height difference between the upper micromirrors 812a-812n and a lower reflective part 813, thereby creating diffracted light. In this case, a 0 order diffracted light beam is perpendicularly emitted and 1 order diffracted light beams are obliquely emitted, left and right, because light is perpendicularly incident.

Meanwhile, the filtering optical system 812 separates the desired orders of diffracted light beams from various orders of the diffracted light beams when diffracted light beams are incident thereon. The filtering optical system 812 includes a Fourier lens (not shown) and a filter (not shown), and selectively passes 0 or 1 order diffracted light beams therethrough.

As well, the projection and scanning optical part 816 includes a condensing lens (not shown) and a scanning mirror (not shown), and scans diffracted light beams on the screen 818 while controlling the display electronic system 804.

The display electronic system 804 drives a scanning mirror (not shown) of the projection and scanning optical device 816.

The projection and scanning optical device 816 projects an image on the display screen 818 and scans it on the display screen 818 in order to form a 2-D image on the display screen 818.

Meanwhile, in FIGS. 7 to Sb, only the generation of a monochromic image has been described, but it is possible to generate a color image. it is possible to implement the generation of the color image by additionally applying two light sources, two diffractive light modulators, and a filter to the display optical system 802.

As described above, the present invention aims to form one pixel using one driving ribbon element.

Furthermore, the present invention aims to form a plurality of open holes through an upper micromirror of the ribbon element, thereby creating diffracted light with improved diffraction efficiency.

As well, the present invention aims to substitute one driving element for four or six conventional driving elements, thereby improving the yield in the fabrication process and reducing fabrication costs.

Claims

CLAIM

1. An open hole-based diffractive light modulator, comprising: a substrate; an insulating layer disposed on the substrate; at least one sacrificial layer which is disposed on the insulating layer; a reflective part disposed on the insulating layer, said reflective part positioned to reflect incident light; a support which is provided on the at least one sacrificial layer and through which at least one first open hole is formed; a micromirror disposed on the support, said micromirror having a reflective surface to reflect the incident light, at least one second open hole formed in the micromirror to correspond to the or each first open holes to is pass the incident light therethrough; and at least one actuating unit to move an intermediate portion of the support when voltage is applied thereto, thereby changing the intensity of the diffracted light which is formed by light reflected from the micromirror and the reflective part.