Raster scanning-type display device using diffractive light modulator

Disclosed herein is a raster scanning-type display device using a diffractive light modulator. The diffractive light modulator includes a plurality of light sources, the diffractive light modulator, a plurality of illumination optical units, a combining unit, a Schlieren optical unit, and a scanning optical unit.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2005-0133758, filed on Dec. 29, 2005, entitled “Raster Scanning Type Display Apparatus using the Diffraction Optical Modulation,” which is hereby incorporated by reference in its entirety into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a display device using a diffractive light modulator, and, more particularly, to a raster scanning-type display device using a diffractive light modulator, which causes each of a plurality of beams of light, emitted from a plurality of light sources, to be incident on one or more elements assigned to each wavelength, forms a plurality of beams of diffracted light for respective wavelengths, converts the plurality of beams of diffracted light for the respective wavelengths into a plurality of beams of spot light, combines the plurality of beams of spot light for the respective wavelengths together, and scans the combined spot light across a screen in a raster scanning fashion.

2. Description of the Related Art

With the development of microtechnology, Micro-Electro-Mechanical Systems (MEMS) devices and small-sized equipment, into which MEMS devices are incorporated, are attracting attention.

A MEMS device is formed on a substrate, such as a silicon substrate or a glass substrate, in microstructure form, and is a device into which an actuator for outputting mechanical actuating force and a semiconductor Integrated Circuit (IC) for controlling the actuator are electrically or mechanically combined. The fundamental feature of such a MEMS device is that an actuator having a mechanical structure is incorporated as part of the device. The actuator is electrically operated using Coulomb's force between electrodes.

Recently, light modulators using such MEMS devices have been developed. An example of such an optical device is a Grating Light Valve (GLV) that is disclosed in U.S. Pat. No. 5,311,360, issued to Bloom et al. In this patent, the GLV may be constructed to operate in reflective and diffractive modes.

In order to use the GLVs in display devices, the development of appropriate display devices is required.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a raster scanning-type display device using a diffractive light modulator, which causes each of a plurality of beams of light, emitted from a plurality of light sources, to be incident on one or more elements, assigned to each wavelength, forms a plurality of beams of diffracted light for respective wavelengths, converts the plurality of beams of diffracted light for the respective wavelengths into a plurality of beams of spot light, combines the plurality of beams of spot light for the respective wavelengths together, and scans the combined spot light across a screen in a raster scanning fashion.

In order to accomplish the above object, the present invention provides a raster scanning-type display device using a diffractive light modulator, including a plurality of light sources for emitting a plurality of beams of light having respective colors; the diffractive light modulator provided with a plurality of elements with colors respectively assigned to the elements, and configured to modulate incident light while vertically moving the elements according to external control signals and then to emit a plurality of beams of light having respective colors and each having a plurality of diffraction orders when the incident light having a plurality of colors is incident on corresponding elements; a plurality of illumination optical units for radiating the plurality of beams of light having respective colors, emitted from the light sources, onto the corresponding elements of the diffractive light modulator; a combining unit for combining the plurality of beams of light having respective colors and each having a plurality of diffraction orders, formed by the diffractive light modulator, together; a Schlieren optical unit for selecting diffracted light having one or more desired diffraction orders from the plurality of beams of light having respective colors and each having a plurality of diffraction orders, and passing the selected diffracted light therethrough; and a scanning optical unit for scanning the diffracted light, passed through the Schlieren optical unit, onto a screen in a raster scanning fashion.

In order to accomplish the above object, the present invention provides a raster scanning-type display device using a diffractive light modulator, including a plurality of light sources for emitting a plurality of beams of light having respective colors; the diffractive light modulator provided with a plurality of elements with the elements grouped into element groups and colors respectively assigned to the element groups, and configured to modulate incident light while vertically moving elements of a corresponding element group according to external control signals, and then to emit diffracted light having a plurality of diffraction orders when the incident light is incident on the elements of the corresponding element group; a plurality of illumination optical units for radiating the plurality of beams of light having respective colors, emitted from the light sources, onto corresponding element groups of the diffractive light modulator; a combining unit for combining the plurality of beams of light having respective colors and each having a plurality of diffraction orders, formed by the diffractive light modulator, together; a Schlieren optical unit for selecting diffracted light having one or more desired diffraction orders from the plurality of beams of light having respective colors and each having a plurality of diffraction orders, and passing the selected diffracted light therethrough; and a scanning optical unit for scanning the diffracted light, passed through the Schlieren optical unit, onto a screen in a raster scanning fashion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1Ais a section view of a recess-type diffractive light modulator using piezoelectric material, andFIGS. 1B and 1Care sectional views of an open hole-based diffractive light modulator using piezoelectric material.

Referring to the drawing, the recess-type diffractive light modulator includes a silicon substrate10and a plurality of elements12a˜12n.

The elements12a˜12nhave a uniform width and are regularly arranged. In the elements12a˜12n, beams of incident light are reflected by micromirrors (the micromirror17ain the case of the element12a) and adjacent beams of reflected light cause diffraction, thus forming diffracted light and a video image. That is, for example, light reflected from the micromirror17aof the element12aand light reflected from the micromirror of the element12bform diffracted light when the difference in vertical location between the micromirror17aof the element12aand the micromirror of the element12bis ¼ times wavelength λ (the difference can be produced through control because the elements12a˜12ncan be moved vertically), and a video image can be formed using the light intensity of the diffracted light.

The silicon substrate10has a recess so as to provide an air space for the element12a˜12n. An insulating layer11is disposed on the upper surface of the silicon substrate10, and the ends of the element12a˜12nare attached to the opposite sides of the recess.

Each of the elements12a˜12n(although only the element12ais described in detail here, the same description is applicable to the remaining elements12b˜12n) has a rod shape. The bottom surfaces of the ends of the element12aare attached to the opposite sides of the silicon substrate10so that the central portion of the element12aspans the recess of the silicon substrate10. The element12aincludes a lower support13a, a portion of which, which is located over the recess of the silicon substrate10, can move vertically.

Furthermore, the element12afurther includes a lower electrode layer14athat provides piezoelectric voltage, a piezoelectric material layer15athat is disposed on the lower electrode layer14aand generates vertical actuation force through expansion and contraction thereof when voltage is applied across both surfaces thereof, and an upper electrode layer16athat is disposed on the piezoelectric material layer15aand provides piezoelectric voltage to the piezoelectric material layer15a. These components are disposed at the left end of the lower support13a.

The element12afurther includes a lower electrode layer14a′ that provides piezoelectric voltage, a piezoelectric material layer15a′ that is disposed on the lower electrode layer14a′ and generates vertical actuation force through expansion and contraction thereof when voltage is applied to both surfaces thereof, and an upper electrode layer16a′ that is disposed on the piezoelectric material layer15a′ and provides piezoelectric voltage to the piezoelectric material layer15a′. These components are disposed at the right end of the lower support13a.

The element12afurther includes a micromirror17athat is placed on the central portion of the lower support13aand reflects incident light, thus forming diffracted light.

FIG. 1Bis a perspective view of an open hole-based diffractive light modulator. Referring toFIG. 1B, the open hole-based diffraction light modulator includes a silicon substrate21, an insulation layer22, a lower or proximal micromirror23and a plurality of elements30ato30n.

In this case, the lower micromirror23is deposited on the top of the silicon substrate21, and reflects incident light, thereby diffracting the incident light. The lower micromirror23may be made of metal, such as Al, Pt, Cr, or Ag.

The element30a(although only the element30ais described in detail here, the same description is applicable to the remaining elements) has a ribbon shape. The element30aincludes a lower support31a, the bottom surfaces of the ends of which are attached to the opposite sides of the silicon substrate21beside the recess of the silicon substrate21so that the central portion of the lower support31aspans the recess of the silicon substrate21.

Piezoelectric layers40aand40a′ are respectively formed on both sides of the lower support231a. The actuation force of the element30ais generated through the contraction and expansion of the piezoelectric layers40aand40a′.

The piezoelectric layers40aand40a′ include lower electrode layers41aand41a′ that provide piezoelectric voltage, piezoelectric material layers42aand42a′ that are respectively placed on the tops of the lower electrode layers41aand42a′ and contract and expand to thus generate vertical actuation force when voltage is applied to both surfaces of each of thereof, and upper electrode layers43aand43a′ that are respectively placed on the piezoelectric material layers42aand42a′ and provide piezoelectric voltage to the piezoelectric material layers42aand42a′. When voltage is applied to the upper electrode layers43aand43a′ and the lower electrode layers41aand42a′, the piezoelectric material layers42aand42a′ contract and expand, thus causing the vertical movement of the lower support31a.

Meanwhile, an upper or distal micromirror50ais deposited on the central portion of the lower support31a, and includes a plurality of open holes51a1to51a4. Although the shape of the open holes51a1to51a4is preferably rectangular, they may have any closed curve, such as a circle or an ellipse. When the lower support31ais made of optically reflective material, it is not necessary to deposit a separate upper mirror, and the lower support31amay function as the upper micromirror.

The open holes51a1to51a4allow light, which is incident on the element30a, to pass therethrough and be incident on the portions of the lower micromirror23corresponding to the locations of the open holes51a1to51a4, therefore the lower micromirror23and the upper micromirror50acan form a pixel.

As an example, each of portions (A) of the upper micromirror50abeside the open holes51a1to51a4and a corresponding portion (B) of the lower micromirror23can form a single pixel.

The incident light, which passes through the portions of the upper micromirror50ain which the open holes51a1to51a4are formed, can be incident on the corresponding portions of the lower micromirror23. When the distance between the upper micromirror50aand the lower micromirror23is an odd multiple of λ/4, maximally diffracted light can be generated.

Meanwhile,FIG. 1Billustrates an open hole-based light diffractive modulator characterized in that the open holes51a1to51a4are arranged in a direction identical to the longitudinal direction of the upper micromirror50a, whileFIG. 1Cillustrates an open hole-based light modulator in which a plurality of open holes51a1′ and51a2′ is arranged in a direction perpendicular to the longitudinal direction of the upper or distal micromirror50a.

With reference toFIGS. 2 to 5, a raster scanning-type display device using a diffractive light modulator is described.

FIG. 2is a view illustrating the construction of the raster scanning-type display device using the diffractive light modulator according to the embodiment of the present invention.

Referring toFIG. 2, the raster scanning-type display device using the diffractive light modulator according to the embodiment of the present invention includes a display optical system102and a display electronic system104.

The display optical system102includes red, green and blue light sources106R,106G and106B, and red, green and blue illustration optical units108R,108G and108B that respectively correspond to the light sources106R,106G and106B.

The display optical system102includes a diffractive light modulator110at least one element of which is assigned to each color and which forms diffracted light having a plurality of diffraction orders for each beam of incident light by modulating incident light having a corresponding color when the light having the corresponding color is incident on a corresponding assigned element from a corresponding illumination optical unit108R,108G or108B, and a combining unit112that combines a plurality of beams of diffracted light having respective wavelengths and each having a plurality of diffraction orders, emitted from the diffractive light modulator110, into a single beam of light.

The display optical system102includes a Schlieren optical unit114that divides the diffracted light having a plurality of diffraction orders, formed by the diffractive light modulator110, according to diffraction order and passes diffracted light having one or more desired diffraction orders, selected from the diffracted light having a plurality of diffraction orders, therethrough, a projection and scanning optical unit116that condenses the diffracted light passed through the Schlieren optical unit114and performs raster scanning on condensed spot light in a two-dimensional image form, and a display screen118.

The display electronic system104is electrically connected to the laser light sources106, the diffractive light modulator110, and the projection and scanning optical unit116.

With reference toFIGS. 2 to 5, the operation of the raster scanning-type display device using a diffractive light modulator according to the embodiment of the present invention is described in detail below.

The red, green and blue light sources106R,106G and106B of the display optical system102emit corresponding beams of light under the control of the display electronic system104.

The illumination optical unit108R,108G or108B corresponding to each color converts light, emitted from the light source106R,106G or106B, into circular spot light or elliptical light so as to radiate the circular spot light or elliptical light onto the upper and lower micromirrors of the corresponding assigned element of the diffractive light modulator110.

Each of the illumination optical units108R,108G and108B may include, for example, a convex lens (not shown) and a collimator lens (not shown).

The concave lens converts the incident light, emitted from a corresponding light source10R,106G or106B, into smaller circular spot light or elliptical light, a corresponding collimator lens converts the circular spot light or elliptical light into parallel light, and the resulting parallel light enters the diffractive light modulator110.

Meanwhile, in the diffractive light modulator110, at least one element is assigned to each color, and the micromirror of the element assigned to each color micromirror forms diffracted light having a plurality of diffraction orders by modulating the incident light.

As an example, as illustrated inFIG. 3, in the case where the diffractive light modulator110of the display optical system102includes three elements110a,110band110cand the three elements110a,110band110care respectively assigned to red, green and blue, the red illumination optical unit108R radiates elliptical light onto the micromirror of the element110aof the diffractive light modulator110that is assigned to red, the green illumination optical unit108G radiates elliptical light onto the micromirror of the element110bof the diffractive light modulator110that is assigned to green, and the blue illumination optical unit108B radiates elliptical light onto the micromirror of the element110cof the diffractive light modulator110that is assigned to blue. Thereafter, each of the elements110R,110G and110B forms diffracted light having a plurality of diffraction orders by modulating incident light having a corresponding wavelength.

That is, when each of the elements110R,110G and110B moves vertically in the case where elliptical light is incident on the upper micromirror of the element110R,110G or110B of the open hole-based diffractive light modulator110illustrated inFIG. 3, the incident light is reflected or diffracted due to the difference in vertical location between the upper micromirror and lower micromirror of the element110R,110G or110B, and thereby reflected light or diffracted light having a plurality of diffraction orders is generated.

Meanwhile, although the case where a single element is assigned to each color has been described, as illustrated inFIG. 3, the same implementation is applicable to the case where a plurality of elements is assigned to each color. The diffracted light that is generated for a single wavelength using the plurality of elements described above has light intensity selectivity higher than that of the diffracted light that is generated for a single wavelength using a single element. As an example, when diffracted light is generated using four elements, only one element may be caused to generate diffracted light, two elements may be caused to generate diffracted light, three elements may be caused to generate diffracted light, or all four elements may be caused to generate diffracted light. Since diffracted light having four different light intensities can be obtained at the time of generating diffracted light, the selectivity of light intensity is improved. Furthermore, although elliptical light has been described in conjunction withFIG. 3, the same description is applicable to circular spot light.

The combining unit112combines diffracted light having a plurality of wavelengths, generated by the diffractive light modulator110, into a single beam of light. For this purpose, the combining unit112includes, for example, two reflecting mirrors112R and112B, thereby combining diffracted light having a plurality of wavelengths.

The Schlieren optical unit114separates diffracted light having one or more diffraction orders from diffracted light having a plurality of diffraction orders when the diffracted light having a plurality of diffraction orders passes through the Schlieren optical unit114. The Schlieren optical unit114includes, for example, a Fourier lens (not shown) and a filter (not shown), and selectively passes 0th-order diffracted light or ±1-order diffracted light, selected from incident diffracted light, therethrough.

The projection and scanning optical unit116, as illustrated inFIG. 4, includes a condenser lens116a, a scanning mirror116b, and a projection lens116c, and projects incident diffracted light onto the screen118. That is, the projection and scanning optical unit116functions to form a spot by condensing a diffracted beam entering from the filter (not shown) onto the screen118.

The condenser lens116acondenses the diffracted beam, passed through the filter, onto the screen118. Of course, a concave lens (not shown) may be provided behind the condenser lens116a, and may change parallel light after condensing the diffracted beam passed through the filter, and project the changed parallel light onto the scanning mirror116b.

The scanning mirror116bincludes an X-scanning mirror116baand a Y-scanning mirror116bb, and the X-scanning mirror116bascans an incident spot across the screen118from the left to the right under the control of the display electronic system104, and the Y-scanning mirror116bavertically scans the incident spot across the screen118under the control of the display electronic system104.

A process in which the X-scanning mirror116baperforms horizontal scanning from the left to the right, the Y-scanning mirror116bbperforms vertical scanning to a subsequent line, the X-scanning mirror116baperform horizontal scanning from the left to the right again, the Y-scanning mirror116bbperforms vertical scanning to a subsequent line again, and so on is referred to as raster scanning. Although raster scanning has been described as being performed in such a way as to repeat a process of performing scanning from the left to the right, changing the line and then moving the spot to the left end of the screen, raster scan may be performed in such a way as to repeat a process of performing scanning from the left to the right, performing vertical scanning to the right end of a subsequent line, performing scanning from the right to the left, and then changing the line.

The display electronic system104actuates the scanning mirror116bof the projection and scanning optical unit116. The projection and scanning optical unit116projects an image onto the display screen118and scans a line image across the display screen118in a raster scanning fashion so as to form a two-dimensional image on the display screen118.

Meanwhile, although the method of displaying an image on the screen118using a single spot has been illustrated inFIGS. 2 to 4, it is possible to perform raster scanning using a plurality of spots.

As an example,FIG. 5is a plan view illustrating the case where elliptical light having a narrow and long line shape is radiated onto the four elements110R1˜110R4,110G1˜110G4, or110B1˜110B4of the open hole-based diffractive light modulator. When four elements are assigned to the formation of a single spot, the projection and scanning optical unit116can perform raster scanning across the screen118using a single spot.

InFIG. 5, when a plurality of elements independently moves vertically, elliptical light having a narrow and long line shape is reflected or diffracted due to the difference in vertical location between the upper micromirror and the lower micromirror of each of the elements110R1˜110R4,110G1˜110G4, and110B1˜110B4, thereby forming diffracted light in the same manner as inFIG. 3.

According to the present invention, a precise optical system, such as a line beam shaper required for a one-dimensional illumination system, is not necessary.

Furthermore, according to the present invention, there is an advantage in that a single spot or a small number of spots, instead of 1080 spots, is used, thereby simplifying the construction of an optical system.