TWI546610B - Projection device and fabrication method of a polarization grating - Google Patents

Description

Projection device and method of manufacturing polarization grating

The present invention relates to a display device and a method of fabricating the same, and more particularly to a projection device and a method of fabricating the polarization grating.

In the field of display technology, when a large display screen is required, the flat panel display needs to have a commensurate size. However, a projection device having a smaller size can form a large display on the screen. Therefore, in the case where many people watch a display screen together (for example, a conference, a briefing, or watching a movie), the projection apparatus has an advantage. Therefore, projection devices have an irreplaceable position in the field of display technology.

In a conventional liquid-crystal-on-silicon (LCOS) projector, the unpolarized beam is polarized and the beam then travels to the upper liquid crystal panel. The upper liquid crystal panel reflects the polarized light beam and modulates the polarization state of the polarized light beam. The polarizing beam splitter then blocks a portion of the polarized beam from the upper liquid crystal panel that has a polarization direction and allows another portion of the polarized beam having another vertical polarization direction to travel to the projection lens. When the non-polarized beam is polarized and the beam passes through a polarizing beam splitter, the optical efficiency of the liquid crystal projector is significantly reduced. For routine The color filter is a liquid crystal projector with an optical efficiency of about 3% to 4%.

The present invention provides a projection apparatus having higher optical efficiency.

The present invention provides a method of manufacturing a polarization grating which can produce a polarization grating having excellent quality.

In accordance with an embodiment of the present invention, a projection apparatus is provided that includes a light source, a reflective spatial polarization modulator, a polarization grating, and a projection lens. The light source is used to provide a light beam. A reflective spatial polarization modulator is disposed on the path of the beam and is used to reflect the beam and modulate the polarization state of the beam. A polarization grating is disposed on the path of the beam between the source and the reflective spatial polarization modulator, wherein the reflective spatial polarization modulator reflects the beam from the polarization grating back to the polarization grating. The projection lens is disposed on the path of the light beam from the reflective spatial polarization modulator, wherein the polarization grating is disposed on the path of the light beam between the reflective spatial polarization modulator and the projection lens.

According to an embodiment of the present invention, a method of fabricating a polarization grating is provided. The method includes: providing a polarization-sensitive material; and scanning the polarization-sensitive material with light that orthogonalizes the two polarization states to each other and on the polarization-sensitive material.

In view of the above, a projection apparatus according to an embodiment of the present invention employs a polarization grating to diffract a light beam from a light source, and light energy transmitted to the projection lens can be concentrated on a light beam having a certain diffraction order. Therefore, the optical efficiency of the projection device is excellent, so that the projection device can provide an image picture with high brightness. In addition, in the manufacturing method of the polarization grating, the polarization-sensitive material is processed by light instead of The polarization sensitive material is processed by contacting the polarization sensitive material with an alignment layer. Therefore, the problem of contact with the alignment layer can be prevented. Therefore, the manufacturing method of the polarization grating is simple and a polarizing grating having excellent quality can be manufactured.

The above described features and advantages of the invention will be apparent from the following description.

50‧‧‧Polarization sensitive materials

60‧‧‧Original light

62‧‧‧Lights whose polarization states are orthogonal to each other

64‧‧‧Lights whose polarization states are orthogonal to each other

70‧‧‧Laser source

80‧‧‧Polarizing beam splitter

92‧‧‧Scan mirror

94‧‧‧Scan mirror

100‧‧‧Projection device

100b‧‧‧projector

105‧‧‧ screen

110‧‧‧Light source

112‧‧‧ Beam

120‧‧‧Reflective spatial polarization modulator

130‧‧‧Polarization grating

130a‧‧‧Density grating

131‧‧‧ slow axis

132‧‧‧First phase delay strip

133‧‧‧ slow axis

134‧‧‧Second phase delay strip

135a‧‧‧ slow axis

140‧‧‧Projection lens

150‧‧‧ Total internal reflection稜鏡

150c‧‧‧ reflector

152‧‧‧稜鏡

154‧‧‧稜鏡

156‧‧‧ Total internal reflection surface

160‧‧‧Light cover parts

170‧‧‧ lens

210‧‧‧矽 substrate

212‧‧‧Optoelectronics

222‧‧‧ pixel electrodes

240‧‧‧Alignment layer

250‧‧‧Liquid layer

260‧‧‧Alignment layer

270‧‧‧Transparent conductive layer

280‧‧‧Color Filter Array

282‧‧‧Red filter

284‧‧‧Green Filter

286‧‧‧Blue filter

290‧‧‧Transparent substrate

D1‧‧‧ first direction

D2‧‧‧ second direction

D3‧‧‧ third direction

L‧‧‧Injection position

P0‧‧‧polarization direction

P1‧‧‧polarization direction

P2‧‧‧polarization direction

S1‧‧‧ first side diffracted beam

S2‧‧‧second side diffracted beam

SC‧‧‧Central diffracted beam

Φ‧‧‧ angle

FIG. 1A is a schematic diagram of a projection apparatus in accordance with an embodiment of the present invention.

1B is a schematic cross-sectional view of the reflective spatial polarization modulator of FIG. 1A.

1C is a schematic plan view of the polarization grating of FIG. 1A.

2 is a schematic top plan view of a polarization grating in accordance with another embodiment of the present invention.

3 is a schematic diagram of a projection apparatus in accordance with another embodiment of the present invention.

4A is a schematic view illustrating a method of manufacturing a polarization grating.

Figure 4B is a schematic diagram showing the coordinates and position of the light of Figure 4A illuminated on the polarization sensitive material of Figure 4A.

4C is a schematic diagram showing the combined polarization states of the two beams of light when the two beams of FIG. 4A meet on the polarization sensitive material of FIG. 4A.

5A and 5B are other variants of Figs. 4B and 4C, respectively, in another embodiment of the present invention.

1A is a schematic diagram of a projection apparatus in accordance with an embodiment of the present invention; FIG. 1B is a schematic cross-sectional view of the reflective spatial polarization modulator of FIG. 1A; and FIG. 1C is a schematic top view of the polarization grating of FIG. 1A. Referring to FIGS. 1A through 1C, the projection apparatus 100 in this embodiment includes a light source 110, a reflective spatial polarization modulator 120, a polarization grating 130, and a projection lens 140. Light source 110 is used to provide beam 112. In this embodiment, the beam 112 is a white beam, and the source 110 includes at least one white-light emitting diode (LED) that emits a white beam. However, in other embodiments, light source 110 can be an ultra-high-pressure (UHP) lamp that emits a white light beam. Alternatively, beam 112 may comprise a plurality of sub-beams of different colors, and these different colors are mixed to form a white color. For example, beam 112 can include red, green, and blue sub-beams, and the three sub-beams mix to form a white beam. In addition, light source 110 can include a plurality of LEDs of different colors, and sub-beams of different colors can be emitted from LEDs of different colors, respectively. In one embodiment, sub-beams of different colors are simultaneously emitted from light source 110. However, in another embodiment, sub-beams of different colors are alternately emitted from the light source 110. In another embodiment, light source 110 can include at least one laser emitter, such as at least one laser diode.

A reflective spatial polarization modulator 120 is disposed on the path of the beam 112 and is used to reflect the beam 112 and modulate the polarization state of the beam 112. The reflective spatial polarization modulator 120 can be a liquid crystal on the surface (LCOS) panel. In this embodiment, reflective The spatial polarization modulator 120 is a color filter and a liquid crystal panel. Specifically, in this embodiment, the color filter on-chip liquid crystal panel includes a germanium substrate 210, a plurality of pixel electrodes 222, an insulating layer 230, an alignment layer 240, a liquid crystal layer 250, an alignment layer 260, and a transparent conductive layer 270. The color filter array 280 and the transparent substrate 290. A plurality of transistors 212 are arrayed on the ruthenium substrate 210. The transistor 212 can be electrically coupled to a plurality of scan lines and a plurality of data lines on the germanium substrate 210. The pixel electrodes 222 are electrically coupled to the transistor 212 and cover the transistor 212, respectively. The pixel electrode 222 is made of a metal such as aluminum. The insulating layer 230 separates the pixel electrode 222. The alignment layer 240 covers the pixel electrode 222. The color filter array 280 is disposed on the transparent substrate 290. The transparent substrate 290 can be made of glass or any other suitable transparent material. The color filter array 280 includes a plurality of color filters having different colors. For example, color filter array 280 includes a plurality of red filters 282, a plurality of green filters 284, and a plurality of blue filters 286 arranged in an array. The transparent conductive layer 270 covers the color filter array 280, and the alignment layer 260 covers the transparent conductive layer 270. The transparent conductive layer 270 is made of, for example, indium tin oxide (ITO). The liquid crystal layer 250 is filled between the alignment layer 240 and the alignment layer 260.

In this embodiment, the color filter array 280 is disposed between the alignment layer 260 and the transparent substrate 290, but the invention is not limited thereto. In other embodiments, color filter array 280 is disposed between pixel electrode 222 and alignment layer 240 or may be disposed at any other suitable location.

In another embodiment, the color filter array 280 may not be employed; that is, there is no color filter array 280 between the transparent conductive layer 270 and the transparent substrate 290.

Polarization grating 130 is disposed on the path of beam 112 between source 110 and reflective spatial polarization modulator 120, and reflective spatial polarization modulator 120 reflects beam 112 from polarization grating 130 back to polarization grating 130. The projection lens 140 is disposed on the path of the light beam 112 from the reflective spatial polarization modulator 120, and the polarization grating 130 is disposed on the path of the light beam 112 between the reflective spatial polarization modulator 120 and the projection lens 140. The light beam 112 from the polarization grating 130 sequentially passes through the transparent substrate 290, the color filter array 280, the transparent conductive layer 270, the alignment layer 260, the liquid crystal layer 250, and the alignment layer 240 to reach the pixel electrode 222. The beam 112 is then reflected by the pixel electrode 222 and then sequentially passes through the alignment layer 240, the liquid crystal layer 250, the alignment layer 260, the transparent conductive layer 270, the color filter array 280, and the transparent substrate 290 to reach the projection lens 140.

In this embodiment, the polarization grating 130 includes a plurality of first phase retardation strips 132 and a plurality of second phase retardation strips 134 that are alternately arranged in the first direction D1. Each of the first phase delay bars 132 extends along a second direction D2, and each of the second phase delay bars 134 extends along a second direction D2. In this embodiment, the first direction D1 and the second direction D2 are perpendicular to the third direction D3, and the third direction D3 is parallel to the normal of the polarization grating 130, and the first direction D1 is perpendicular to the second direction D2. The slow axis 131 of the first phase delay strip 132 is perpendicular to the slow axis 133 of the second phase delay strip 134. The slow axis 131 of the first phase delay bar 132 and the slow axis 133 of the second phase delay bar 134 may be an extraordinary axis of the first phase delay bar 132 and the second phase delay bar 134, or may be a first phase The ordinary axis (ordinarv axis) of the delay strip 132 and the second phase delay strip 134. In this embodiment, the first phase delay The delay strip 132 and the second phase delay strip 134 are periodically arranged along the first direction D1.

In this embodiment, the beam 112 emitted from the source 110 is an unpolarized beam before traveling to the polarization grating 130. The beam 112 is primarily diffracted by the polarization grating 130 into a +1 diffraction order sub-beam and a -1 diffraction order sub-beam. When the polarization grating 130 is well designed, the intensity of the 0-diffraction order sub-beam is much smaller than the intensity of the +1 diffraction-order sub-beam and much less than the intensity of the -1 diffraction-order sub-beam. Therefore, the zero-order sub-beam can be ignored.

First, the condition in which the light beam 112 is perpendicularly incident on the polarization grating 130 will be described as follows. The +1 diffraction order sub-beam may be a clockwise circularly polarized sub-beam and have a diffraction angle + θ with respect to the normal to the polarization grating 130. The -1 diffraction step sub-beam may be a counterclockwise circularly polarized sub-beam and have a diffraction angle -θ with respect to the normal to the polarization grating 130. When any pixel of the reflective spatial polarization modulator 120 is in a state similar to a mirror plus transparent layer (ie, a 0 wavelength phase retarder), the +1 diffraction order sub-beam is pixel-wise along the polarization grating 130 The normal is tilted in the direction of the angle + θ and maintains a clockwise circular polarization. Next, the +1 diffraction step sub-beam is diffracted by the polarization grating 130 in a direction inclined by an angle +2 θ with respect to the normal to the polarization grating 130 and maintains a clockwise circular polarization, and is hereinafter referred to as "the first side". The sub-beam S1" is diffracted. In addition, the -1 diffraction-order sub-beam is reflected by the pixel in a direction inclined by an angle -θ with respect to the normal line of the polarization grating 130 and maintains a counterclockwise circular polarization. Next, the -1 diffraction order sub-beam is diffracted by the polarization grating 130 in a direction inclined by an angle -2 θ with respect to the normal to the polarization grating 130 and maintained counterclockwise circularly polarized, and is hereinafter referred to as "the second side" The sub-beam S2" is diffracted. On the other hand, when any pixel of the reflective spatial polarization modulator 120 is at Similar to the state of the mirror plus quarter wave plate, the +1 diffraction order sub-beam is reflected by the pixel in a direction inclined by an angle +θ with respect to the normal line of the polarization grating 130 and has a change to a counterclockwise circular polarization. The polarization state, and the -1 diffraction order sub-beam is reflected by the pixel in a direction inclined by an angle -θ with respect to the normal to the polarization grating 130 and has a polarization state changed to a clockwise circular polarization. Next, the +1 diffraction order sub-beam and the -1 diffraction order sub-beam are diffracted by the polarization grating 130 along the normal of the polarization and combined into a central diffracted beam SC.

In this embodiment, the light beam 112 is obliquely incident on the polarization grating 130 such that the first side diffracted beam S1, the second side diffracted beam S2, and the central diffracted sub-beam SC are respectively relative to the first of the above conditions. The one side diffracted sub-beam S1, the second side diffracted sub-beam S2, and the central diffracted sub-beam S are tilted. Further, in this embodiment, the central diffracted sub-beam SC acts as an image beam and enters the projection lens 140, but the first side diffracted sub-beam S1 and the second side sub-sub-beam S2 do not travel to the projection lens 140. Projection lens 140 projects a central diffracted sub-beam SC (i.e., image beam) onto a screen to form an image frame on the screen.

In this embodiment, the projection apparatus 100 further includes a total internal reflection (TIR) 稜鏡 150 disposed on the path of the light beam 112 between the light source 110 and the polarization grating 130 and the polarization grating 130 and the projection lens 140. Between the paths of the beam 112. The total internal reflection 稜鏡150 can include two turns 152 and 154. The crucible 152 rests against the crucible 154 and has a total internal reflection surface (TIR surface) 156 facing the crucible 154. The TIR surface 156 totally reflects the beam 112 from the source 110 to the polarization grating 130 and allows the central diffract beam SC to pass and then travel To the projection lens 140. In this embodiment, the projection device 100 can further include at least one lens 170 disposed on the path of the light beam 112 between the crucible 152 and the light source 110 to concentrate the light beam 112.

In this embodiment, projection device 100 further includes a light mask 160 disposed on the path of beam 112 that is reflected from reflective spatial polarization modulator 120 and that is diffracted by polarization grating 130. The light masking member 160 is configured to block the diffracted beam 112 (eg, the first side divergence beam S1 and the second side divergence beam S2) having a partial diffraction order to travel to the projection lens 140, and allow another A portion of the diffracted diffracted beam 112 (eg, central diffracted beam SC) travels to projection lens 140.

In another embodiment, the light mask member 160 may not be used, and the projection lens 140 has an aperture stop having a smaller aperture such that the central diffracted beam SC can pass through the projection lens 140, but the first side is diffracted. The sub-beam S1 and the second side diffracted beam S2 cannot pass. Alternatively, in another embodiment, the first side diffracted beam S1 may be totally reflected by the TIR surface 156 and thus cannot travel to the projection lens 140, and the second side of the diffracted beam S2 is between the normal to the polarization grating 130 The angle is sufficiently large that the second side diffracted beam S2 is offset from the projection lens 140.

In this embodiment, the projection device 100 employs a polarization grating 130 to circulate the light beam 112 from the light source 110, and the light energy transmitted to the projection lens 140 can be concentrated on the light beam 112 having a certain diffraction order (eg, central winding) On the beam of the beam). Therefore, a polarizing beam splitter (PBS) that reduces optical efficiency may not be employed. Therefore, the optical efficiency of the projection apparatus 100 is excellent, so that the projection apparatus 100 can provide an image picture with high brightness.

2 is a schematic top plan view of a polarization grating in accordance with another embodiment of the present invention. Referring to Fig. 2, a polarization grating 130a in this embodiment can be substituted for the polarization grating 130 of Fig. 1A to form another embodiment of the projection device. In this embodiment, the polarization grating 130 has a slow axis 135a that periodically changes rotationally along the first direction D1 and does not change along the second direction D2.

3 is a schematic diagram of a projection apparatus in accordance with another embodiment of the present invention. Referring to Fig. 3, the projection apparatus 100b in this embodiment is similar to the projection apparatus 100 in Fig. 1A, and the difference between the two is as follows. In the projection device 100b, a reflector 150c is employed instead of the total internal reflection cymbal 150. The reflector 150c is disposed on the path of the light beam 112 between the light source 110 and the polarization grating 130. The reflector 150c blocks the diffracted beam 112 (eg, the central diffracted beam SC) having a partial diffraction order to travel to the projection lens 140. In this embodiment, the reflector 150c reflects the central diffracted beam SC such that the central diffracted beam SC does not travel to the projection lens 140. Furthermore, the reflector 150c allows the diffracted beam 112 (eg, the first side divergence beam S1 and the second side divergence beam S2) having another portion of the diffraction order to travel to the projection lens 140. This is because the first side diffracted beam S1 and the second side diffracted beam S2 from the polarization grating 130 are not blocked by the reflector 150c. In this embodiment, the reflector 150c is mirrored. However, in other embodiments, the reflector 150c can be a reflective ridge. Next, the first side diffracted beam S1 and the second side diffracted beam S2 are projected onto the screen 105.

4A is a schematic view illustrating a method of fabricating a polarization grating, and FIG. 4B is a view showing coordinates and positions of light in FIG. 4A irradiated on the polarization sensitive material of FIG. 4A. Schematic, and Figure 4C is a schematic diagram showing the combined polarization states of the two beams of light when the two beams of Figure 4A meet on the polarization sensitive material of Figure 4A. Referring to Figures 4A through 4C, a method of fabricating a polarization grating in this embodiment can be used to fabricate the above-described polarization grating 130. The method of fabrication includes providing a polarization sensitive material 50. In this embodiment, the polarization sensitive material 50 is a liquid crystal material. Next, the fabrication method includes scanning the polarization sensitive material 50 with light 62 and 64 that orthogonalize the two polarization states to each other and on the polarization sensitive material 50.

In this embodiment, the method of fabrication further includes emitting the original light 60 and splitting the original light 60 into light 62 and 64 that are orthogonal to each other in two polarization states. The original light 60 is, for example, laser light. In this embodiment, laser source 70 can be used to emit raw light 60. Moreover, in this embodiment, a polarizing beam splitter (PBS) 80 is disposed on the path of the original light 60 to split the original light 60 into light 62 and 64 whose two polarization states are orthogonal to each other. In this embodiment, the original light 60, light 62, and light 64 are linearly polarized light. The polarization direction P1 of the light 62 is perpendicular to the polarization direction P2 of the light 64. The polarization direction P0 of the original light 60 and the polarization direction P1 of the light 62 form an angle of 45°. The polarization direction P0 of the original light 60 and the polarization direction P2 of the light 64 form an angle of 45°. Two scanning mirrors 92 and 94 are employed to reflect the two beams 62 and 64, respectively, such that the two beams 62 and 64 meet on the polarization sensitive material 50. In this embodiment, the angle φ is formed between the lights 62 and 64 of the two polarization states orthogonal to each other and the incident positions L of the lights 62 and 64 orthogonal to each other on the polarization sensitive material 50. At the office.

When the two scanning mirrors 92 and 94 are rotated, the two beams 62 and 64 scan the polarization sensitive material 50 in one direction (e.g., the x direction). At this point, two beams of light 62 and The difference in optical path length between 64 changes such that the combined polarization states of the two beams 62 and 64 on the polarization sensitive material 50 change. In Figure 4C, the combined polarization states of the two beams 62 and 64 vary along the x-direction. The particular axis of the liquid crystal molecules of the polarization sensitive material 50 is rotated to a direction perpendicular to the combined polarization direction. Therefore, the slow axis of the polarization sensitive material 50 periodically changes along the x direction but does not change along the y direction. After the two beams 62 and 64 scan the polarization sensitive material 50, the polarization sensitive material 50 is cured to form the polarization grating 130 of FIG. 1C, wherein the x direction in FIG. 4A corresponds to the first direction D1 in FIG. 1C, FIG. 4A The y direction in the middle corresponds to the second direction D2 in FIG. 1C, and the z direction is perpendicular to the x direction and the y direction. In FIG. 4C, there is a circular polarization state and an elliptical polarization state between two adjacent orthogonal linear polarization states such that the boundary between the adjacent first phase delay bar 132 and the second phase delay bar 134 is substantially blurred. .

In another embodiment, referring to Figures 5A and 5B, two quarter-wave plates may be disposed on the paths of light 62 and 64 between PBS 80 and polarization sensitive material 50, respectively, such that the two beams are orthogonal. The circularly polarized light meets on the polarization sensitive material 50. For example, light 62 is converted to counterclockwise circularly polarized light before reaching polarization sensitive material 50, and light 64 is converted to clockwise circularly polarized light before reaching polarization sensitive material 50. In this case, when the lights 62 and 64 scan the polarization sensitive material 50, the combined polarization states of the lights 62 and 64 are always linear, and the linear polarization direction of the combined polarization state periodically varies rotationally along the x direction and along The y direction does not change. Therefore, after the polarization sensitive material 50 is scanned and cured, the polarization grating 130a is formed. In yet another embodiment, lights 62 and 64 can be two beams of orthogonal elliptically polarized light.

In the method of fabricating the polarization grating in this embodiment, the polarization sensitive material 50 is processed by light, rather than by contacting the polarization sensitive material with the alignment layer. Therefore, problems of contact with the alignment layer (for example, contamination) can be prevented. Therefore, the manufacturing method of the polarization grating is simple and a polarizing grating having excellent quality can be manufactured. Furthermore, the optical path lengths of the lights 62 and 64 are easily adjusted, so that the spatial period of the polarization grating can be freely designed. Furthermore, the spatial period of the polarization grating can be smaller than the space period achievable by conventional photolithography. That is to say, the manufacturing method of the polarization grating can produce a polarization grating having a small spatial period.

In summary, a projection apparatus according to an embodiment of the present invention employs a polarization grating to diffract a light beam from a light source, and light energy transmitted to the projection lens can be concentrated on a light beam having a certain diffraction order. Therefore, the optical efficiency of the projection device is excellent, so that the projection device can provide an image picture with high brightness. In addition, in the method of fabricating a polarizing grating, the polarization-sensitive material is processed by light, rather than by contacting the polarization-sensitive material with the alignment layer. Therefore, the problem of contact with the alignment layer can be prevented. Therefore, the manufacturing method of the polarization grating is simple and a polarizing grating having excellent quality can be manufactured.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧Projection device

110‧‧‧Light source

112‧‧‧ Beam

120‧‧‧Reflective spatial polarization modulator

130‧‧‧Polarization grating

132‧‧‧First phase delay strip

134‧‧‧Second phase delay strip

140‧‧‧Projection lens

150‧‧‧ Total internal reflection稜鏡

152‧‧‧稜鏡

154‧‧‧稜鏡

156‧‧‧ Total internal reflection surface

160‧‧‧Light cover parts

170‧‧‧ lens

D1‧‧‧ first direction

D2‧‧‧ second direction

D3‧‧‧ third direction

S1‧‧‧ first side diffracted beam

S2‧‧‧second side diffracted beam

SC‧‧‧Central diffracted beam

Claims (13)

A projection apparatus comprising: a light source for providing a light beam; a reflective spatial polarization modulator disposed on a path of the light beam for reflecting the light beam and modulating a polarization state of the light beam; and a polarization grating disposed at The path of the light beam between the light source and the reflective spatial polarization modulator, wherein the reflective spatial polarization modulator reflects the light beam from the polarization grating back to the polarization grating; And a projection lens disposed on the path of the light beam from the reflective spatial polarization modulator, wherein the polarization grating is disposed between the reflective spatial polarization modulator and the projection lens The path of the beam of light, wherein the beam is diffracted by the polarization grating into a diffracted beam having a plurality of diffraction orders. The projection device of claim 1, wherein the reflective spatial polarization modulator is an upper liquid crystal panel. The projection device of claim 2, wherein the liquid crystal panel is a color filter and a liquid crystal panel. The projection device of claim 3, wherein the light beam is a white light beam. The projection apparatus of claim 3, wherein the light beam comprises a plurality of sub-beams of different colors, and the different colors are mixed to form a white color. The projection device of claim 5, wherein the difference is The sub-beams of color are simultaneously emitted from the light source. The projection device of claim 5, wherein the sub-beams of different colors are alternately emitted from the light source. The projection device of claim 1, further comprising a light masking member disposed on the light beam reflected from the reflective spatial polarization modulator and diffracted by the polarization grating And on the path, the light mask is configured to block the diffracted beam having a partial diffraction order from traveling to the projection lens, and to allow the diffraction of the diffraction order having another portion The beam travels to the projection lens. The projection device of claim 1, further comprising a total internal reflection 稜鏡 disposed on the path of the light beam between the light source and the polarization grating The path of the light beam between the polarization grating and the projection lens. The projection device of claim 1, further comprising a reflector disposed on the path of the light beam between the light source and the polarization grating, wherein the reflector blocks The light beam diffracted by the polarization grating having a partial diffraction order travels to the projection lens and allows the diffracted beam having another portion of the diffraction order to travel to the projection lens. The projection apparatus of claim 1, wherein the light beam emitted from the light source is an unpolarized light beam before traveling to the polarization grating. The projection apparatus of claim 1, wherein the polarization grating comprises a plurality of first phase retardation strips and a plurality of first alternating rows arranged in a first direction a two-phase delay strip, each of the first phase delay strips extending along a second direction, each of the second phase delay strips extending along the second direction, and the first The slow axis of the phase delay strip is perpendicular to the slow axis of the second phase delay strip. The projection apparatus of claim 1, wherein the polarization grating has a slow axis that periodically rotates in a first direction and does not change along a second direction.