HK1214001B - Wafer-level liquid-crystal-on-silicon projection assembly systems and methods - Google Patents

Abstract

The present invention relates to wafer-level liquid-crystal-on-silicon projection assembly, systems and methods. A wafer-level liquid-crystal-on-silicon (LCOS) projection assembly includes a LCOS display for spatially modulating light incident on the LCOS display and a polarizing beam-separating (PBS) layer for directing light to and from the LCOS display. A method for fabricating a LCOS projection system includes disposing a PBS wafer above an active-matrix wafer. The active-matrix wafer includes a plurality of active matrices for addressing liquid crystal display pixels. The method, further includes disposing a lens wafer above the PBS wafer. The lens wafer includes a plurality of lenses. Additionally, a method for fabricating a wafer-level polarizing beam includes bonding a PBS wafer and at least one other wafer to form a stacked wafer. The PBS wafer includes a PBS layer that contains a plurality of PBS film bands.

Description

Wafer-level liquid crystal on silicon projection assembly, system and method

Technical Field

The present invention relates to an image projector using a Liquid Crystal On Silicon (LCOS) display, and more particularly to an optical assembly of this type of image projector.

Background

Liquid crystal on silicon (lcos) image projectors are based on lcos displays, and are used in consumer electronics applications such as hand-held projectors and near-eye displays (near-eye displays). The liquid crystal on silicon display in the liquid crystal on silicon projector reflects light through a beam splitter (beam splitter) and a compound lens (compound). Herein, the LCOS, the beam splitter and the compound lens can be referred to as a projection module.

For LCOS image projectors, precise alignment of the components of the projection module is necessary to meet performance requirements. In the conventional LCOS image projector, the projection module is manually assembled. However, if the alignment is to be accurately achieved by manual assembly, the assembly time is long, and the yield is also reduced.

Disclosure of Invention

According to one embodiment, a wafer-level LCOS projection device includes a LCOS display and a polarization beam splitting layer. The liquid crystal display is used for spatially modulating light incident on the liquid crystal display. The polarization beam splitting layer is used for guiding the light rays to the silicon-based liquid crystal display or the light rays coming out of the silicon-based liquid crystal display.

According to another embodiment, a method for assembling a wafer-level LCOS projection system includes: a polarization splitting wafer is arranged on an active matrix wafer, and the active matrix wafer comprises a plurality of active matrixes to define a plurality of liquid crystal display pixels. The assembly method further comprises: and arranging a lens wafer on the polarization splitting wafer, wherein the lens wafer comprises a plurality of lenses.

According to another embodiment, a method for assembling a wafer-level polarization splitter includes: a polarization splitting wafer and at least one other wafer are jointed to form a stacked wafer, wherein the polarization splitting wafer comprises a polarization splitting layer, and the polarization splitting layer comprises a plurality of polarization splitting film strips.

Drawings

Fig. 1 shows a projection assembly included in a near-eye display and disposed on a pair of glasses.

FIG. 2 shows an optical assembly of a projection assembly according to an embodiment of the invention.

Fig. 3 shows an assembly method of a projection module according to an embodiment of the invention and a related schematic diagram.

FIG. 4 is a block diagram of a wafer level assembly of multiple components of a projection device according to an embodiment of the present invention.

FIG. 5 illustrates an assembly method of another aspect of the method of FIG. 4.

FIG. 6 is a cross-sectional view of a wafer-level LCOS projection device prior to singulation, in accordance with an embodiment of the present invention.

FIG. 7 is a cross-sectional view of a diced wafer-level LCOS projection device mounted on a PCB, in accordance with an embodiment of the present invention.

FIG. 8 is a schematic diagram of a method of assembling a wafer level PBS according to an embodiment of the invention.

Detailed Description

Fig. 1 shows a projection assembly 100 included in a near-eye display 102 and disposed on eyewear 104. The near-eye display 102 also includes a light source 106. In other embodiments, the projection assembly 100 may be disposed in a different imaging device, such as a handheld image projector.

Fig. 2 shows an optical assembly of a projection assembly 200, the projection assembly 200 being an embodiment of the projection assembly 100. Projection assembly 200 includes a wafer and liquid crystal on silicon (die)250, a polarization splitter 206, and a compound lens 210. The compound lens 210 includes a plurality of lenses 226, 228, 229. The wafer level liquid crystal on silicon die 250 includes an active matrix substrate 222, an alignment layer 243, liquid crystal 221, a conductive film 203, and cover glass (cover glass) 204. The active matrix substrate 222 is fixedly mounted on a Printed Circuit Board (PCB) 201.

The wafer level LCOS die 250 is a liquid crystal on silicon display. The polarization splitter 206 may reflect light from a light source (not shown in FIG. 2) to the LCOS die 250 to illuminate the LCOS display. Light emitted by the liquid crystal on silicon display is at least partially transmitted by the polarizing beam splitter 206 and projected by the compound lens 210 to form an image of the liquid crystal on silicon display.

In the projection assembly 200, all of the components are centered on the optical axis 299 and maintained within alignment errors in the assembly direction. Lateral and longitudinal alignment errors refer to alignment errors along the X-axis and Z-axis, respectively, of coordinate system 298.

Fig. 3 shows an assembly method 300 of the projection assembly 200 according to an embodiment of the invention and a related diagram 320. The diagram 320 is merely illustrative and not meant to limit the present invention. For example, the method 300 of assembling the LCOS die 250, unlike the manner in which the liquid crystal 211 is injected, bonds the remaining components of the projection assembly 200 to the LCOS die 250 at the wafer level and using non-wafer level methods.

In step 302, the assembly method 300 aligns a cover glass on an active matrix wafer. In one example of step 302, the assembly method 300 aligns a cover glass 324 over the active matrix wafer 322.

In step 304, the assembly method 300 bonds a cover glass to the active matrix wafer to form a stack. In one example of step 304, the assembly method 300 bonds the cover glass 324 and the active matrix wafer 322 to form a stack 330. Cover glass 324 and active matrix wafer are examples of cover glass 204 and active matrix 222, respectively, of fig. 2.

In step 306, the assembly method 300 divides (single) the stack along the dividing lines to obtain a plurality of display substrates. In one example of step 306, the assembly method 300 divides the stack 330 along the dividing lines 335 to obtain a plurality of display substrates 340.

In step 308, the assembly method 300 injects a liquid crystal between the glass layer and the active matrix layer of a display substrate to form a wafer level liquid crystal on silicon die 250 of a projection device. In one example of step 308, the assembly method 300 injects a liquid crystal 321 between the glass layer 334 and the active matrix layer 332 of the display substrate 340 to form, for example, the wafer-level LCOS die 250 of the projection assembly 200 of FIG. 2.

Before step 306, the assembly method 300 may include adding alignment layers on the active matrix wafer 322 and the cover glass 324, without departing from the scope of the invention. In step 310, assembly method 300 forms projection assembly 200 of fig. 2 by bonding printed circuit board 201, polarizing beamsplitter 206, and lenses 226, 228, 229 of projection assembly 200 (fig. 2) to lcos die 250.

In the projection assembly 200, only the display substrate 340 is assembled at the wafer level. FIG. 4 illustrates an assembly method 400 in which various components of the projection assembly are assembled at the wafer level, and a related diagram 420 is shown. The schematic diagram 420 shows an active matrix wafer 422, a polarizing beam-separating (PBS) wafer 424, and lens wafers 426, 428, 429. Each lens wafer 426, 428, 429 includes an array of lenses with the same array coordinates such that the lens wafers 426, 428, 429 can be stacked and aligned by known techniques to form wafer level compound lenses. The number of lens wafers included in the assembly method 400 may be other than 3 without departing from the invention.

In fig. 4, the parallel lines on the polarization splitting wafer 424 refer to the polarization splitting film strips (PBS film bands)460 within the polarization splitting wafer 424. In one embodiment, the pitch of the polarizing beamsplitter strips is equal to the pitch of the lens columns on the lens wafers 426, 428, 429, and equal to the pitch of the rows of the active matrix 442 on the active matrix wafer 422.

In one embodiment of the PBS wafer 424, the PBS strip 460 can be a conventional multi-layer thin film polarizer, such as a MacNeille polarizer. In other embodiments, the polarizing beamsplitter strip 460 may be based on a multilayer thin film structure, which is described by Li and Dobrowolski, appl.opt.vol.35, p.2221 (1996). In other embodiments, the PBS wafer 424 may use a different polarization mechanism, such as wire-grid (Wire-grid), without departing from the invention.

In one embodiment, the polarization beam splitter wafer 424 includes a transparent conductive film, such as Indium Tin Oxide (ITO), deposited on the side of the polarization beam splitter wafer 424 facing the active matrix wafer 422. In one embodiment, the PBS wafer 424 includes an alignment layer. Thus, the polarizing beam splitter wafer 424 functions as a beam splitter and a substrate with light transmissive conductive layers and/or alignment layers to form a liquid crystal on silicon display for projection devices. By the above-mentioned two functions of the polarization splitting wafer 424, an additional cover glass layer is not required to be disposed on the active matrix wafer 422, such as the cover glass 204 of the projection assembly 200 of fig. 2. In one embodiment, the polarization splitting wafer 424 includes an anti-reflection (AR) coating and a transparent conductive film, and the polarization splitting film is disposed therebetween.

In step 401, the assembly method 400 receives an active matrix wafer, a polarization beam splitter wafer 424, and a lens wafer. In one example of step 401, the assembly method receives an active matrix wafer 411, a polarization splitting wafer 424, and lens wafers 426, 428, 429. The dotted grid on the active matrix wafer 422 represents a barrier structure (dam structures) 423. Active matrix wafer 422 includes a plurality of active matrices 442, such as active matrix 442(1), that are located between barrier structures 423. For clarity, active matrix 442(1) is the only active matrix of active matrix wafer 422 shown on the figure. The active matrix wafer 422 may include any of a second alignment layer, a reflective layer, and an electrode, as is known in the art.

In step 402, the assembly method 400 deposits liquid crystal on an active matrix wafer. In one example of step 402, the assembly method 400 deposits a liquid crystal 421, which is designated by (-) on the active matrix wafer 422. The deposition locations on the active matrix wafer 422 correspond to respective active matrices 442 of the active matrix wafer 422.

In one example of step 402, the liquid crystal deposition may be an in-drop liquid crystal injection (ODF) process, in which liquid crystal is deposited on the active matrix wafer 422 at locations corresponding to the active matrix 442. Other liquid crystal deposition methods may also be applied to the assembly method 400 without departing from the invention. The barrier structures 423 include respective locations of the liquid crystals 421 to the active matrix wafer 422.

In step 403, the assembly method disposes the polarization splitting wafer on the active matrix wafer. In one example, the assembly method 400 disposes the polarization splitting wafer 424 on the active matrix wafer 422.

In step 404, the assembly method 400 disposes the lens wafer on the polarization splitting wafer, and in one example, the assembly method 400 disposes the lens wafers 426, 428, 429 on the polarization splitting wafer 424.

In step 406, the assembly method 400 aligns the polarization splitting wafer 424 and the lens wafer over the active matrix wafer 422. In one example, the assembly method 400 aligns the polarization splitting wafer 424 and the lens wafers 426, 428, 429 on the active matrix wafer 422. Polarizing beam splitting wafer 424 is aligned such that polarizing beam splitting film strip 460 is centered over each active matrix 442 column within active matrix wafer 422.

Wafers 422,426, 428, 429 are aligned such that, within a certain alignment error, the center of each lens of lens wafer 429 is collinear with a lens center of lens wafer 428, a lens center of lens wafer 426 and the center of an active matrix on wafer 422. The polarizing beam splitter wafer 424 is aligned such that the polarizing beam splitter film strip 460 is aligned with the lens rows of the lens wafers 426, 428, 429 and the active matrix 442 rows on the active matrix wafer 422 within a certain alignment error. Step 406 may use any known wafer level optical device alignment method.

In step 407, the assembly method 400 stacks the wafers, as described in the prior art.

In step 408, the assembly method 400 bonds the active matrix wafer, the polarization beam splitting wafer, and the lens wafer to form a wafer stack. In one example, the assembly method 400 joins the wafers 422, 424, 426, 428, 429 to form a wafer stack 430.

In step 410, the assembly method 400 segments the wafer stack along the singulation lines to produce a plurality of wafer-level LCOS projection devices. In one example of step 410, the assembly method 400 segments the wafer stack 430 along the singulation lines 435 to produce a plurality of wafer-level LCOS projection devices 450.

Fig. 5 shows another assembly method 500, which is similar to method 400 except that the liquid crystal is deposited after the segmentation step 410, rather than before it. Steps 501, 503, 504, 506, 507, 508, 510 are the same as steps 401, 403, 404, 406, 407, 408, 410 of method 400, respectively.

The bonding step 508 of the assembly method 500 results in a wafer stack 530 that is identical to the wafer stack 430 except for the bottom layer, the active matrix wafer 422, and the liquid crystal 421 that it does not include, the barrier structure 423 supports an air gap between the active matrix wafer 422 and the polarization splitting wafer 424 through which the liquid crystal can be deposited after singulation.

With respect to the method 400, step 410 results in a wafer-level liquid crystal on silicon projection assembly 450, instead, step 510 of the method 500 results in a plurality of projector dies (projector dies) 540. The projector die 540 is identical to the liquid crystal on silicon projection assembly 450 except that the former lacks the liquid crystal 421.

In step 512, the method 500 injects a liquid crystal 521 into the air gap between the substrate layers 532 and the film layers 434 of the projector die 540 to form a wafer-level LCOS projection device 450. In one embodiment of the method 500, the liquid crystal injection step 512 may be performed by a conventional method, such as a vacuum-siphon (vacuum-siphon) method or a side-injection (side-injection) method.

FIG. 6 shows a cross-section 630 of one embodiment of the wafer stack 430 of FIG. 4 and the individual wafer-level LCOS projection elements 650 resulting from the singulation of the singulation lines 635. The cross-section 630 includes a liquid crystal on silicon layer 660, a polarization splitting layer 624, and a composite wafer lens 610.

The LCOS 660 includes an active matrix wafer 422, a lower alignment layer 443, and a liquid crystal 621. The barrier structure 623 includes liquid crystal 621. In the embodiment of the wafer stack 430 shown in fig. 6, the lower alignment layer 443 is deposited on the active matrix wafer 422. An active matrix 442 (fig. 4) is located within the active matrix wafer 422.

The polarization splitting layer 624 corresponds to the polarization splitting wafer 424 of fig. 4. The polarization splitting layer 624 includes an optional anti-reflective coating 624(4), a polarization splitting layer 624(3), a light-transmissive conductive layer 624(2), and an upper alignment layer 624 (1). The polarization splitting layer 624(3) includes a polarization splitting film strip 460 (fig. 4) between a pair of split lines 635. The liquid crystal 621 is located between the upper alignment layer 624(1) and the lower alignment layer 443. In one embodiment, the polarizing beam splitter film strips 460 are oriented substantially at 45 degrees to the plane of the LCOS layer 660.

Without departing from the spirit of the present invention, liquid crystal may be omitted from section 630 such that section 630 shows a section of one embodiment of wafer stack 530 of FIG. 5. The liquid crystal 621 may be added after being split along the split line 635, according to step 512 of the method 500 (fig. 5) to form wafer level components 650 including the liquid crystal 621. Thus, the wafer-level LCOS projection device 650 may be assembled by the method 400 (FIG. 4) or the method 500 (FIG. 5).

FIG. 7 shows an embodiment of a wafer level LCOS projection system 700. The projection system 700 includes a wafer level projection assembly 650 (fig. 6). The wafer-level LCOS projection device 650 is an embodiment of the wafer-level LCOS projection device 450.

The wafer-level LCOS projection module 650 includes a liquid crystal segment 760, a polarization beam splitter 724, and a compound wafer-level lens 610. The silicon-based liquid crystal segment 760 includes the active matrix wafer 722, which includes an active matrix 442 (fig. 4) and a reflective film. The active matrix wafer 722 supports a liquid crystal 621 (fig. 6) between the upper alignment layer 724(1) and the lower alignment layer 743. The upper alignment layer 724(1) and the lower alignment layer 743 are portions of the upper alignment layers 624(1), 643 of fig. 6, respectively, and are formed by division along the division line 635 (fig. 6). The barrier structures 623 (fig. 6) include liquid crystal 621 (fig. 6).

The polarization beam splitter 724 is formed from the polarization beam splitter wafer 424 and includes an upper alignment layer 724(1), a transparent conductive film 724(2), a polarization beam splitter assembly 724(3), and an anti-reflective coating 724 (4). The transparent conductive film 724(2), the polarization splitting element 724(3), and the anti-reflective coating 724(4) are portions of the transparent conductive film 624(2), the polarization splitting layer 624(3), and the anti-reflective coating 624(4) in fig. 6, respectively, and are formed by dividing along the dividing line 635 (fig. 6). The composite wafer level lens 610 includes wafer level lenses 726, 728, 729. Wafer level lenses 726, 728, 729 are formed from lens wafers 426, 428, 429, respectively. The wafer-level LCOS projection module 750 is mounted on the PCB 701.

In FIG. 7, a wafer level LCOS projection module 700 is illuminated by a light source 106. The light source 106 may include an optional collimating optics assembly 108. The light source 106 may be any known light source. For example, the light source 106 may include at least one light emitting diode that emits light at the same, overlapping, or non-overlapping wavelengths.

In one embodiment of the light source 106 and the wafer-level LCOS projection module 750, the light source 106 emits s-polarized input illumination (s-polarized illumination)790, which is incident on the polarization splitting module 724 (3). In fig. 7, s-polarization and p-polarization refer to those in which the field components are perpendicular to the plane of the drawing and parallel to the plane of the drawing, respectively. The input illumination 790 is the s-polarized component, which may also include the p-polarized component, of the total illumination emitted by the light source 106.

The polarization beam splitter 460 of the polarization beam splitter 724(2) reflects the input illumination 790 through the liquid crystal 621, and the liquid crystal 621 spatially modulates the illumination 790. The active matrix wafer 722 reflects at least a portion of the input illumination 790 back through the liquid crystal 621. Individual pixels of the active matrix wafer 722 may be configured to change the polarization state of light transmitted through the sub-pixels of the associated liquid crystal 621. In the illuminated state of a pixel, the polarization state of the illumination 790 is reversed by two passes of the liquid crystal 721 to produce emitted light comprising at least a p-polarization state. The P-polarized component of the emitted light is transmitted through polarizing beamsplitter 724(2) and projected by composite wafer-level lens 710 to form output illumination 791.

The wafer-level LCOS projection module 650 is advantageous over the projection module 200 of FIG. 2 in at least two respects: alignment and sizing. Because the optical components of the wafer-level LCOS projection module 450 are aligned at the wafer level, lateral alignment errors are less likely, and instead, lateral alignment errors are more likely to occur in the projection module 200 because the optical components of the projection module 200 are manually aligned. The wafer-level LCOS projection device 450 is more space efficient than the projection device 200, which requires a cover glass 204 between the polarizing beam splitter 206 and the active matrix substrate 222.

FIG. 8 illustrates a wafer level method 800 and an associated diagram 820 for assembling optical systems including a polarizing beam splitter. In step 801, the method 800 forms a polarization splitting wafer including a polarization splitting layer including a plurality of polarization splitting bands. In one example of step 801, the method 800 forms a polarization splitting wafer 824, the polarization splitting wafer 824 including a polarization splitting layer, the polarization splitting layer including a plurality of polarization splitting bands 860.

In one embodiment, the polarization splitting wafer 824 includes a substrate, and the polarization splitting layer is disposed on the substrate. The substrate may function as an alignment layer of a LCOS device, as described in FIGS. 4-7.

In step 802, the method 800 bonds the PBS wafer to a wafer to form a stacked wafer. In one example, the method 800 bonds the PBS wafer 824 to the wafer 822 to form a stacked wafer 830.

In one embodiment, wafer 822 is a liquid crystal on silicon wafer, such as active matrix wafer 422 of FIG. 4. In another embodiment, wafer 822 is a lens wafer, such as lens wafer 424 of FIG. 4.

At optional step 804, the method 800 singulates the stacked wafer to form a plurality of optical systems including a polarizing beamsplitter. In one example, the method 800 singulates the stacked wafer 830.

It is noted that the above-mentioned method and system can be modified or changed without departing from the spirit and scope of the invention, and that these are given by way of illustration only and not limitation in the above description and drawings. The claims are intended to cover the generic and specific features described, and all statements of the scope of the present method and system, which, as a matter of language, might be said to fall there between.

Claims (21)

1. A wafer-level liquid crystal on silicon projection module, comprising:

a liquid crystal on silicon display for spatially modulating light incident on the liquid crystal on silicon display;

a polarization beam splitting layer for guiding the light to the liquid crystal on silicon display or the light from the liquid crystal on silicon display; and

and the light-transmitting conducting layer is in contact with the plurality of polarization beam splitting assemblies in the polarization beam splitting layer and is used as an electrode of the silicon-based liquid crystal display.

2. The wafer-level liquid crystal on silicon projection assembly of claim 1, wherein the polarization splitting layer reflects light toward the liquid crystal on silicon display and transmits at least a portion of the light received from the liquid crystal on silicon display.

3. The wafer-level liquid crystal on silicon projection assembly of claim 1, further comprising a lens layer to image the display.

4. The wafer-level liquid crystal on silicon projection assembly of claim 3, wherein the polarization splitting layer is disposed between the liquid crystal on silicon display and the lens layer such that the polarization splitting layer transmits at least a portion of light from the display to the lens layer.

5. The wafer-level liquid crystal on silicon projection assembly of claim 4, wherein the lens layer comprises a wafer-level compound lens.

6. The wafer-level liquid crystal on silicon projection module of claim 1 implemented as a near-eye projector.

7. A method for assembling a wafer-level liquid crystal on silicon projection system, comprising:

arranging a polarization splitting wafer on an active matrix wafer, wherein the active matrix wafer comprises a plurality of active matrixes to define a plurality of liquid crystal display pixels; and

and arranging a lens wafer on the polarization splitting wafer, wherein the lens wafer comprises a plurality of lenses.

8. The assembly method of claim 7, further comprising:

aligning the lens wafer, the polarization splitting wafer and the active matrix wafer; and

bonding the lens wafer, the polarization splitting wafer, and the active matrix wafer to form a stacked wafer.

9. The assembly method of claim 7, further comprising:

and cutting a stacked wafer which comprises the polarization splitting wafer, the active matrix substrate and the lens wafer to form a plurality of liquid crystal on silicon projection systems.

10. The assembly method of claim 7, further comprising:

and injecting liquid crystal between at least one part of the polarization splitting wafer and at least one part of the active matrix wafer to form a silicon-based liquid crystal display.

11. The assembly method of claim 8, wherein the aligning step includes aligning the lens with a plurality of polarizing beam splitting film strips of the polarizing beam splitting wafer, respectively.

12. The assembly method of claim 11, wherein the aligning step includes aligning the polarizing beamsplitter strip with a plurality of active matrices of the active matrix wafer, respectively.

13. The assembly method of claim 7, further comprising, prior to the step of disposing the polarization splitting wafer:

disposing a plurality of liquid crystals on the active matrix wafer and corresponding to the active matrix.

14. The assembly method of claim 8, further comprising:

dicing the stacked wafer to form a plurality of optical modules; and

a portion of liquid crystal is injected between the active matrix wafer and the polarization splitting wafer to form at least a portion of the optical module.

15. A method of assembling a wafer-level polarizing beamsplitter, comprising:

a polarization splitting wafer is jointed with at least another wafer to form a stacked wafer, wherein the polarization splitting wafer comprises a polarization splitting layer, and the polarization splitting layer comprises a plurality of polarization splitting film strips.

16. The assembly method of claim 15, further comprising:

and segmenting the stacked wafer to form a plurality of polarization splitting modules, wherein each polarization splitting module comprises at least one of the polarization splitting film strips.

17. The assembly method of claim 15, wherein the engaging step comprises:

bonding the polarization splitting wafer to an active matrix wafer.

18. The assembly method of claim 17, further comprising:

liquid crystals are disposed on the active matrix wafer to form a display wafer including a plurality of displays.

19. The assembling method according to claim 18, further comprising, before the step of disposing the liquid crystal:

a plurality of barrier structures are formed to at least partially include a plurality of liquid crystals within the display, respectively.

20. The assembly method of claim 15, further comprising forming the polarization-splitting layer, the forming the polarization-splitting layer comprising:

stacking a plurality of substrates and a plurality of polarization splitting dielectric films to form a stack; and

the stack is partitioned at an oblique angle to the plane of the polarization splitting dielectric film to form the polarization splitting layer.

21. The method of assembling of claim 20, wherein said step of splitting comprises splitting said stack at a direction substantially 45 degrees from said plane of said polarizing beam splitting dielectric film.