KR20080010752A - Mems-based light projection engine and associated method of manufacture - Google Patents

Abstract

An optical projection engine and a method for manufacturing the same are provided to simplify and downsize the optical projection engine and support several image formats. An optical projection engine comprises a light source(10), a first light scanner(30), and a second light scanner(40). The first light scanner scans one or more light beams transmitted from the light source in a first direction. The first light scanner includes a waveguide(31) movable in the first direction. The second light scanner scans one or more light beams transmitted from the first light scanner in a second direction, which is not parallel with the first direction.

Description

Optical projection engine based on micro-electromechanical systems and its manufacturing method {MEMS-BASED LIGHT PROJECTION ENGINE AND ASSOCIATED METHOD OF MANUFACTURE}

1 shows a plan view (a) and a side view (b) of an optical projection engine according to a first embodiment of the present invention.

FIG. 2 illustrates an exemplary light coupler that may be employed in the light projection engine of FIG. 1, in which light is coupled from the first and second inputs and the combined light is output.

3 is a perspective view (a) and a plan view (b) of a first optical scanner that can be employed in the light projection engine of FIG. 1.

FIG. 4 compares a conventional pixel-based display (a) in which resolution is limited by pixel size with analog light scanning (b) (c) using the light projection engine represented in FIG. 1.

5 is a plan view (a) and a cross-sectional view (b) of the light projection engine according to the second embodiment of the present invention.

6 is a detailed view of a micro lens that may be used in the light projection engine of FIG. 5.

7A-7N illustrate a method of manufacturing the first and second scanners for a light projection engine.

8 illustrates a completed structure according to an exemplary manufacturing method.

FIG. 9 illustrates an exemplary method for pretilting a vertical scan mirror using a plastic strain of silicon with a pushdown pin wafer.

* Explanation of symbols in the main part of the drawing *

10, 10 ': light source 11: solid state light source

20, 20 ': optical coupler 21: color optical coupler

30, 30 ': first optical scanner 31, 31': waveguide

32, 32 ', 42, 49, 81: comb structure 33: spring structure

34: anchor 40, 40 ': second optical scanner

41: mirror 46: micro lens

47: static etch mirror 48: silicon ring

50: transparent packaging cover 51: projection lens

60 control part 71: SOI substrate

71A: bottom silicon layer 71B: buried oxide layer

71C: upper silicon layer 72: trench

73, 75: silicon nitride 74, 77: silicon oxide

76: electrical contact area 78: opening area

79: wiring 80: fiber

82: moving comb element of the mirror 83: internal mirror

84: fixed comb element 85: outer frame

90: push-down pin wafer 91: fork

92, 93: push-down pin

The present invention and its various aspects generally relate to optical projection systems, and in particular, to methods for manufacturing micro-electromechanical systems (hereinafter referred to as MEMS) based optical projection engines, MEMS based optical projection engines and Related.

Current projection display technologies can be broadly divided into two categories: digital micro mirror devices (hereinafter, simply referred to as DMDs) and liquid crystal displays (hereinafter, referred to as LCDs). Both techniques use a light projection engine that includes a separate element for each of many image pixels. This device is typically illuminated by a high power white light lamp (eg a mercury lamp). The control unit modulates each individual pixel element to obtain the desired image brightness, contrast ratio and color. The projector may alternatively incorporate a color filter wheel to project red, green and blue images, or instead use three separate light projection engines to project each of these three primary colors.

DMD and LCD-based projectors have some disadvantages. First, if each image pixel is represented by a separate pixel element, the light projection engine is large, complex, and expensive to produce. XGA (Extended Graphics Array) digital optical technology (hereinafter referred to simply as DLP) devices correspond to, for example, 0.7 inches. Not only is there a small number of devices that can be produced per wafer, but the output of a fully operational device is low, so the cost of this device increases rapidly with the number of pixels. Second, DMD and LCD-based projectors are optimized for only one image format (i.e. number of horizontal and vertical pixels). Other image formats may be supported but will require extensive image processing (e.g. interpolation) and will show numerous image artifacts (e.g. aliasing). Third, because each image pixel comes from a separate pixel element, a closer look at this image shows that the pixels are separated by dark lines. Fourth, DMD and LCD-based projectors are inherently large and complex because many optical elements are required to illuminate them evenly. Fifth, in DMD and LCD-based projectors, the light source must always be completely on. Contrast ratios are created by modulating individual pixel elements to discard part of the light. The efficiency of discarding light determines the achievable contrast ratio. In particular, LCD-based projectors are not efficient and the contrast ratio is typically limited to about 500: 1.

Accordingly, an object of the present invention is to solve the above problems, and to provide an optical projection engine and a method of manufacturing the same that can be manufactured at low cost.

Another object of the present invention is to provide an optical projection engine capable of supporting various image formats and a method of manufacturing the same.

Another object of the present invention is to provide an optical projection engine and a method of manufacturing the same, in which pixels are not separated by dark lines even when the image is observed from close.

Another technical object of the present invention is to provide a small and simple light projection engine and a method of manufacturing the same.

Another object of the present invention is to provide a high contrast ratio light projection engine and a method of manufacturing the same.

One aspect of the invention provides a MEMS-based optical projection engine. The example light projection engine provided herein can be configured to support various resolution, color, frame rate, contrast ratio and luminance requirements.

In one example, the light engine includes a light source and two light scanners, the first light scanner including one or more steerable waveguides that scan one or more light beams along the first direction. The first optical scanner may comprise a plurality of waveguides, the plurality of waveguides being directly or indirectly to one another (for example by position feedback and dynamic control means) to provide synchronized movement of the plurality of scan beams. ) Can be spatially connected. The second optical scanner may comprise a moving mirror, lens or other suitable scanner for scanning along the second direction, wherein the first and second directions are not parallel, for example orthogonal. In one example, two scanners are monolithically manufactured on a single semiconductor wafer die and are electrostatically driven through interlacing comb structures. In one example, two optical scanners scan the light beam in orthogonal directions corresponding to the horizontal and vertical directions of the desired image.

The second optical scanner may include a scanning mirror configured monolithically integrated and / or mirror galvanometers. The second optical scanner may also include a scanning lens. The scanning lens may comprise glass, polysilicon, polymer or other suitable material. The first and / or second optical scanner may operate in resonant or non-resonant motion and may move magnetically, electrostatically, thermally and / or piezo-electrically. Additional optical elements known in the art, such as lenses, prisms, mirrors, polarizers, filters, gratings, etc., may additionally be included in any part of the system to set the direction and / or conditions of the light beam. .

The light source may comprise one or more monochromatic Light Emitting Diodes (hereinafter simply referred to as LEDs), Laser Diodes (hereinafter referred to simply as LDs) or other suitable light sources. The LEDs and / or LDs may be monolithically integrated in the optical projection engine or implemented separately and connected to one of the optical scanners, for example via optical fibers and / or waveguides. Additionally, light combiners may be included to align a plurality of color (eg red, green, blue) light sources to the first optical scanner or to increase the total intensity of the light. In one example, the optical coupler is monolithically integrated in the first optical scanner.

A control unit may additionally be included to control the operation of the light projection engine (e.g., operation of the first and second optical scanners to perform known raster scanning methods and light emission from the light source (s)). The controller also includes sinusoidal scan compensation, capacitive scan position feedback, stitching alignment feedback, and light source emission intensity feedback. The same technique can be used.

In another aspect, a method of manufacturing a MEMS-based light projection engine is provided. In one example, the method includes monolithically forming two optical scanners on a single semiconductor wafer die. In particular, conventional silicon-on-insulator (SOI) MEMS techniques and flip-chip bonding may be used to form two orthogonal optical scanners on a single chip. In another example, the light source (s) and / or optical element (s) may be further integrated on a single chip in addition to two optical scanners.

In another aspect, a method of operating a MEMS-based light projection engine having a first optical scanner for scanning along a first direction and a second optical scanner for scanning along a second direction is provided. Exemplary methods include controlling the scanner to produce the desired image. In one example, the first optical scanner is operative to project individual lines of the image, and the second optical scanner staggers individual lines to individual frames of the image. The scan rate may include, for example, approximately 30 kHz for the first optical scanner (horizontal scanner) and 30 Hz for the second optical scanner (vertical scanner). Additionally, various techniques such as sine scan compensation, (capacitive) scan position feedback, stitching alignment feedback, and light source emission intensity feedback can be used to control two optical scanners to produce the desired image.

The example devices described herein can be advantageously manufactured with low cost and low complexity to produce small, high resolution displays. For example, the exemplary light projection engine can be used in a variety of projection systems, such as portable projectors, small projectors (eg computer mouse size), front / rear projection televisions, and heads-up displays. The exemplary light projection engine is integrated into a small projector to communicate wirelessly with a laptop computer, personal digital assistant (PDA), etc., for example, projecting images up to four feet diagonally in UXGA resolution. In a new application, the exemplary light projection engine can be integrated for use in cell phones, digital cameras, PDAs, laptop computers, MP3 players, and the like.

The invention and its various embodiments can be better understood with reference to the following detailed description in conjunction with the accompanying drawings and claims. The following description is provided to enable any person skilled in the art to make or use the present invention. Descriptions of specific materials, techniques, and applications are provided by way of example only. Various modifications to the examples described herein will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the invention.

According to an example of the invention described herein, high speed and high resolution with, for example, 2000 or more resolvable spots, without digitizing the image by either a mirror or an electronic device (e.g. DLP or LCD). To form a line scan, steerable waveguides are used to deliver a light beam to a surface (eg, a screen or other suitable surface). The resolution of an exemplary light projection engine will increase compared to conventional systems (eg, DLP technology of 10 μm mirrors compared to the 1 μm waveguide aperture of this example). On-chip MEMS micro-optics, for example scan mirrors or microlenses, are used to provide stable frame refreshing. The original image is coded by direct modulation of the light source. Suitable light sources include LEDs, LDs, or other solid-state light sources that allow for reduced power consumption (eg, 100W white light lamps compared to 1W solid state light sources).

It should be noted that “horizontal” and “vertical” are used herein for illustrative purposes only to refer to the first and second scan directions. Those skilled in the art may contemplate other configurations of the first and second scanners for scanning in the first and second directions, and may include any non-parallel first and second directions.

1 shows a plan view (a) and a side view (b) of an optical projection engine according to a first embodiment of the present invention. Referring to the drawings, the light projection engine includes a first optical scanner 30 and a second optical scanner 40 integrated on a single chip.

The first optical scanner 30 includes one or more waveguides 31 that scan along a single plane (horizontal direction) parallel to the substrate. The plurality of waveguides 31 may be spatially fixed relative to each other. For example, the plurality of waveguides 31 may be stacked or electrically synchronized. The first optical scanner 30 represented in the figure comprises two waveguides 31 spatially fixed relative to one another for synchronized movement. The waveguide 31 of the first optical scanner 30 may operate in non-resonant or resonant motion and may move magnetically, electrostatically, thermally and / or piezoelectrically. The waveguide 31 of the first optical scanner 30 represented in the figure moves electrostatically. To this end, the first optical scanner 30 includes a comb structure 32 for horizontally operating the waveguide 31. The first optical scanner 30 delivers one or more light beams to the second optical scanner 40.

The second optical scanner 40 includes a pre-tilted moving scan mirror 41. In order to receive the light beam from the first optical scanner 30, the angle between the irradiated light beam and the plane of the mirror 41 must be greater than the maximum rotation angle of the mirror 41. However, the mirror 41 plane and the horizontal beam are parallel to the substrate after the initial process. Pre-tilting of the scan mirror 41 makes the initial angle between the horizontal scanning beam and the mirror 41 larger than the angle of rotation of the mirror 41, so that the first and second optical scanners 30, 40 are monolithic on a single chip. Enable to accumulate In addition, the pre-tilting of the mirror 41 directs the light beam back to the external projection lens 51 located on the mirror, which can be easily implemented in the transparent packaging cover 50. The scan mirror 41 rotates to vertically scan one or more light beams from the first optical scanner 30. This allows the first optical scanner 30 to quickly generate horizontal lines of the image, and the second optical scanner 40 quickly staggers these lines to project the desired image. In one example, an optical projection engine comprising two waveguides 31 and 32 is integrated on a single chip, and the transparent packaging cover 50 comprises a projection lens 51 or other optical element to produce the generated light beam. Set directions and / or conditions. In the second optical scanner 40, the mirror 41 is rotated by an electrostatically moving comb structure 42 connected thereto. Instead of the mirror 41, a second optical scanner using a moving lens or prism may be used.

Finally the scanned light is directed to the projection lens 51 to project on the screen. The projection lens 51 may be operable to autofocus.

The light projection engine may further comprise a light source 10 comprising one or more solid state light sources 11, for example LEDs or LDs. The light source 10 may comprise one or more sets of three primary colors, for example, and will be used to generate a full color image (eg RGB, CYM,...). The LEDs and / or LDs may be monolithically integrated in the light projection engine, or may be implemented separately and connected to the first optical scanner 30 via an optical fiber and / or waveguide.

The light projection engine may include a light combiner (also known as a light combiner, 20) to align the plurality of color light sources. The microfabricated color light combiner 21 combines the light from each set of light sources to form a complete color image. The light combiner 20 directs the combined light to the first light scanner 30. As shown, the optical coupler 20 can be monolithically directly to the first optical scanner 30.

The light projection engine may include a controller 60. The controller controls modulation of the light source 10 for image encoding, horizontal scanning of the first optical scanner 30, and vertical scanning of the second optical scanner 40.

The light source 10, the light coupler 20 and the first optical scanner 30 may be integrated on a single chip or may be separate elements combined with, for example, optical fibers, optical waveguides, or the like.

FIG. 2 illustrates an exemplary light coupler that may be employed in the light projection engine of FIG. 1, in which light is coupled from the first and second inputs and the combined light is output. For example, a passive waveguide light combiner combines light from a plurality of LEDs or LDs. Optical couplers are well known in the field of optical communications for raising power for laser pumping purposes. The waveguide light coupler may be formed of plastic, silica, silicon and / or other suitable material that traps and transmits light of the desired wavelength. The optical coupler can be formed using well known MEMS techniques or by printing or stamping a polymer onto a substrate, for example to form a waveguide. Because of the coherent nature of laser light, laser waveguides are typically carefully designed using well-known principles and algorithms to avoid interference between laser beams. However, in an example that includes an incoherent LED as a light source, the waveguide design is relatively simple. In addition, the use of MEMS process technology enables monolithic integration of optical couplers and optical scanners on a single chip, reducing optical losses and packaging costs.

3 is a perspective view (a) and a plan view (b) of a first optical scanner that can be employed in the light projection engine of FIG. 1. The electrostatically driven comb structure 32 'in the figure provides a force to move the waveguide 31' along the plane. The spring structure 33 is included to support the waveguide 31 'and to stabilize the horizontal movement of the waveguide 31'. 34 also serves as anchors for the moving structure.

The light projection engine described in FIG. 1 advantageously scans in an analog manner and is not limited by pixel size and position. FIG. 4 compares a conventional pixel-based display (a) in which resolution is limited by pixel size with analog light scanning (b) (c) using the light projection engine represented in FIG. 1. In general, as the scanning frequency is increased, the resolution of the light projection engine of FIG. 1 will be relatively increased than a conventional digital pixel based display as shown in FIG. The light projection engine of FIG. 1 quickly scans one or more light beams on the screen so that the pixels are projected in series rather than in parallel. This operation is similar to the way the CRT scans the electron beam on the fluorescent screen. Further, while the DLP and LCD devices use separate pixel elements for each of thousands to millions of pixels projected in parallel, the light projection engine of FIG. 1, in one example, only two moving elements (first and second light). Scanner).

In a first embodiment, the first optical scanner includes a plurality of waveguides to form a plurality of horizontal scanning beams. The light projection engine is controlled to scan a plurality of horizontal scanning beams vertically into a plurality of tiles (ie sections of a complete image). For example, two waveguides form two sets of parallel beams scanned by a mirror to form two tiles of the final rectangular image. In this way, the image can be refreshed with high speed and little movement. In one example, a microfabricated light projection engine comprising a plurality of waveguides fixed together in a steerable waveguide array transmitter (SWAT) is integrated with a polymer lens / mirror scanner capable of achieving 30 Hz vertical scanning. It can achieve fast horizontal scanning of 36 KHz. In another example, the light projection engine may provide scanning between 15 KHz and 120 KHz in the first direction and scanning between 15 Hz and 120 Hz in the second direction. It will be appreciated that other scanning speeds may also be considered.

5 is a plan view (a) and a cross-sectional view (b) of the light projection engine according to the second embodiment of the present invention. The light projection engine of FIG. 5 is similar to the light projection engine of FIG. 1, but microlenses 46 have been used in place of the moving micromirrors 41. In the figure a static etched mirror 47 deflects the light beam from the waveguide to the microlens 46. The micro lens 46 is controlled to operate in the plane of the first optical scanner, so as to scan the light beam vertically as desired.

In addition, the optical projection engine of FIG. 5 is similar to the optical projection engine of FIG. 1 but includes a steerable waveguide array transmitter (a kind of first optical scanner, SWAT, 30 '). The SWAT 30 'performs steering of eight horizontal beams directed to the etch mirror 47. The eight waveguides included in the SWAT 30 'are fixed relative to each other during movement such that beam steering is synchronized. Image encoding may be performed by the SWAT 30 '. SWAT 30 'is also coupled to light source 10' and light coupler 20 '.

6 is a detailed view of a micro lens that may be used in the light projection engine of FIG. 5. In one example, the microlenses include a lens 46 composed of a support and a UV cured polymer. Micro lens supports can be prepared using known SOI MEMS techniques. In particular, a released silicon ring 48 can be produced, after which the UV cured polymer 46 is inserted into the ring. The liquid UV cured polymer 46 will form an essentially round lens shape due to the surface tension at the edge of the ring. Translation can be accomplished through the electrostatic comb structure 49 shown or through other known MEMS devices.

Next, a summary of various aspects and features of an exemplary light projection engine that can be used alone or in combination will be described. However, this summary should not be construed as limited, and those skilled in the art will understand that various modifications and additions are possible.

1. Light beam:

The light projection engine may use one or more light beams.

The light beam may be monochromatic or polychromatic.

Any number of light beams can be turned on simultaneously or sequentially.

-Any number of light beams can be turned on during scanning from left to right, while scanning from left to right, during scanning from top to bottom or during scanning from bottom to top or both can be turned on.

Any number of light beams can scan in parallel, converge or diverge.

2. Optical coupler:

The optical coupler can be made of a polymer or standard semiconductor manufacturing material.

The color light coupler may be monolithically integrated in the first light scanner.

The plurality of color light couplers may be connected to the plurality of waveguides of the first optical scanner.

The optical coupler can combine any number of colors.

The optical coupler combines any number of similar or identical colors to increase the intensity of the output beam.

3. Horizontal and vertical scanning:

A waveguide scanner can be used as the first optical scanner.

In the case of a plurality of waveguides, the waveguides are tightly coupled to one another to enable their synchronized movement.

In the case of a plurality of waveguides, the waveguides can move apart from each other, but their movement is synchronized by the sensing means (eg capacitive sensing means) and the control mechanism.

A mirror and / or lens scanner can be used as the second optical scanner.

The vertical scanning mirror (s) may be composed of monolithically integrated and / or mirror galvanometers.

The vertical scanning lens (s) may be composed of glass, polysilicon, polymer or other suitable material (s).

The first and second optical scanners can operate in non-resonant or resonant motion.

The optical scanner can move magnetically and / or electrostatically and / or thermally and / or piezo-electrically.

The vertical scanning mirror (s) and / or the micro lens (s) may have an initial offset in the scan angle to direct the light beam to the projection lens located above the optical scanner.

One or more static mirrors or other optical elements can be used to increase the scan range.

Static mirrors can be integrated separately and / or monolithically.

The projection lens can be integrated separately and / or monolithically.

Projection lens can be included in the transparent packaging cover.

The projection lens may be operable to autofocus.

The light projection can be done in any combination of scan from left to right, scan from top to bottom, scan from right to left and scan from bottom to up.

For safety reasons, in order to turn off the light source in case of a scanning failure, the scanning can be monitored at the edge of the scan range (eg with a photodiode).

4. Light source:

The light source can be any combination of red, green and blue laser diodes and / or other light sources such as LEDs and / or lasers.

Multiple light sources can be used in any color to achieve the desired total light output.

The laser diode can operate at its own frequency or use a crystal or the like to achieve the desired output wavelength (eg 532 nm green light can be obtained by doubling 1064 nm infrared light).

The light source output can be monitored (eg using a photodiode), and the light source output can be image color, image brightness and ambient lighting to provide the desired image intensity and fidelity to the original image. It can be adjusted based on factors such as

The intensity of the light source can be modulated pixel by pixel to achieve the desired image contrast, brightness and color.

The light source can be separate from the light projection engine or can be monolithically integrated in the light projection engine.

The light source can be connected to the horizontal scanner by optical fibers and / or waveguides.

The optical fiber and / or waveguide may be separate or integrated monolithically.

In one preferred combination, the light projection engine comprises a chip having a first optical scanner and a second optical scanner integrated thereon (eg monolithically). The first and second optical scanners are connected with one or more light sources. The second optical scanner may comprise a moving mirror. The light projection engine may further include a separate or integrated waveguide light coupler and / or waveguide for connecting the light source to the light scanner. This example can reduce packaging complexity by monolithic integration and can reduce optical alignment complexity by the self-alignment of the waveguide of the first optical scanner and the mirror of the second optical scanner in the lithographic step (s). .

As another preferred combination, the light projection engine includes a light source and two light scanners integrated together on a single chip, wherein the first light scanner comprises one or more waveguides. The light source includes a plurality of integrated laser diodes formed with the chip. The scanner includes a plurality of waveguides for scanning along a first direction and a moving mirror for scanning along a second direction, the second direction being different (eg, orthogonal) to the first direction.

In another preferred combination, the light projection engine comprises two optical scanners, wherein the first optical scanner is a plurality of SOI waveguide scanners that scan the plurality of beams in a synchronized manner along the first direction. A plurality of SOI waveguide scanners can be used with the various projection engines described above, for example.

According to another aspect of the invention, various methods of manufacturing a MEMS based light projection engine will now be described. In one example, conventional SOI MEMS technology and flip-chip bonding will be used to fabricate optics, first and second optical scanners and light sources integrated on a single chip, which are both compact and cost effective MEMS two. Enables the photoluminescent scanner. In one example, a light projection engine may be included in a volume smaller than 5 mm x 2.5 mm x 2 mm. Thus, exemplary micromachine waveguides and microlens / microscanners enable miniaturization, mass production, and cost savings. In another example, more or fewer components are integrated in a single chip. For example, the first and second scanners can be coupled in a single chip and can be coupled to a light source and / or a light coupler.

7A-7N illustrate a method of manufacturing the first and second scanners for a light projection engine. 8 illustrates a completed structure according to an exemplary manufacturing method and will be referenced in conjunction with FIGS. 7A-7N. Here, the term “pattern” generally refers to a pattern definition by etching that is followed by photolithography to make an etching mask. Those skilled in the art will appreciate that the various materials and processes, such as etching, masking, deposition, etc., as well as the order in which the processes are described are merely exemplary. Various other processes and the order in which they are performed can be used to achieve similar results.

FIG. 7A: An exemplary process includes a silicon-on-insulator comprising a lower silicon layer 71A, an upper silicon layer 71C, and a buried oxide layer 71B interposed between the upper and lower silicon layers. ) Substrate (eg, can be 4 "to 8" in diameter, 71). The upper SOI silicon layer 71C is a device layer, and the relatively thick lower silicon layer 71A is a handle wafer. The buried oxide layer 71B functions as an etch stop layer for front and back etching, and prevents electrical leakage through the handle wafer 71A.

7B: Trench etching (eg, DRIE: Deep Reactive Ion Etching) to expose the oxide layer 71B is performed to insulate the electrical connection of the moving and stationary portions of the comb structure in the next step. Trench 72 is refilled with a dielectric material, such as silicon nitride, in the next step. The backfill material electrically insulates the two structures in the upper silicon layer from each other and at the same time makes it possible to mechanically connect the two structures. In this example, the two structures are moving and fixed protrusions in the comb structure of the mirror.

FIG. 7C: Low Pressure Chemical Vapor Deposition (LPCVD) of low stress Silicon Nitride (73) is used to refill the previously formed trench 72. The low stress silicon nitride 73 will also function as the lower cladding layer of the horizontally moving waveguide of the first optical scanner.

7D-7E: Pattern of waveguide core 74 using low pressure chemical vapor deposition (LPCVD) of silicon dioxide 74, for example using reactive ion etching (RIE). The refractive index of silicon dioxide 74 is smaller than silicon nitride and satisfies the waveguide core 74 and cladding 73 requirements.

FIG. 7F shows low pressure chemical vapor deposition (LPCVD) of silicon nitride 75 to cover waveguide core 74 region as side and top cladding 75.

7G: The electrical contact region 76 is patterned to the upper silicon layer 71C of the SOI wafer 71. This provides a wiring mating position for later electrical connection to the device.

FIG. 7H shows low pressure chemical vapor deposition (LPCVD) of silicon oxide 77 and patterns of first and second optical scanners (including areas for placing fibers or optical couplers). This step implements an oxide etch mask 77 for etching the front silicon structure in FIG. 7J.

Figure 7I: From the backside of the SOI wafer 71, i.e., the bottom silicon layer 71A, using the oxide layer 71B as an etch stop layer to form an opening region 78 that may correspond with a vertical scanning mirror region. Through, the DRIE etching is shown. This opening area 78 allows the mirror to be pre-tilted and twisted to drive as described above.

FIG. 7J: Etched from the front side of the wafer using the silicon dioxide etch mask 77 defined in FIG. 7H. After etching the silicon nitrides 73 and 75, the upper silicon layer 71C of the SOI wafer is continuously etched until it stops in the buried oxide layer 71B. This step forms the silicon microstructures of the first and second optical scanners.

7K: For example, the release of silicon microstructures by etching residual oxides 77, 71B in a hydro fluoride solution or vapor for a controlled time. Since silicon 71C is no longer bonded to the oxide layer 71B, it allows movement of the first and second optical scanners. This etching step should be timed to leave the buried oxide layer 71B under the anchor of the first and second optical scanners.

Figure 7L: Uses a two level fork wafer to align and apply vertical forces to the mirror and frame (see, for example, Figure 9.) Fork 91 is a pin (at two levels or a single level). 92, 93) but in a different location). This step creates pre-tilted mirrors and vertical actuators at different tilt angles. Thereafter, both wafers are heated at a high temperature up to the silicon glass transition temperature. The elastic silicon is fired and the mirror and frame can be held in a pre-tilted position after the wafer has cooled down.

7M: The electrical connection to the silicon actuator is then made by connecting the wiring 79 to pre-opened contact locations 76 using conventional wiring methods.

7N: Fibers 80 may then be placed in a predefined position for connection with the light source. In this example, this step is an alignment-free process, since grooves are defined in the silicon layer to position the fiber 80. The fiber is then connected to an RGB light source. In this exemplary manufacturing method, fiber 80 is used to connect a light source to the waveguide of the first optical scanner. However, in another example, the laser diode may be disposed at the end of the waveguide of the first optical scanner using mechanical mounting or self-assembly.

8 shows the potential difference during operation of the formed first and second optical scanners and the vertical scanner. That is, in the first and second optical scanners, the region having the first potential is hatched darkly, and the region having the second potential is lightly hatched. The first optical scanner includes an electrostatic comb structure 81, the operation of which is well known and will be understood by those skilled in the art. The vertical scanning mirror portion includes an inner mirror 83 having a moving comb element 82 and an outer frame 85 having a fixed comb element 84 electrically insulated, the anchor of the inner mirror being connected to the outer frame. It is mechanically connected. In order to achieve both this mechanical connection and electrical isolation simultaneously, nitride filled trenches 72 have been used as described in the exemplary method above. Similar insulation processes are described, for example, in published paper [1] [3].

FIG. 9 illustrates an exemplary method for pretilting a vertical scan mirror using a plastic strain of silicon with a pushdown pin wafer. Push down pins 81 can be fabricated on silicon wafers using standard DRIE processes. An exemplary pretilt process includes pressing the released portion of the scan mirror structure to a desired pretilt angle and heating to fix this angle using plastic deformation of the silicon torsion beam. It should be noted that the pushdown pin wafer 90 may be separated after cooling and reused in further wafer processing. A similar process is disclosed in [4], which makes a 10 degree tilt in a vertical comb drive but does not pretilt the mirror. In this example of the invention, this process is used to pretilt the vertical scan mirror and to implement a vertical comb drive. In this example, pushdown pins 92 and 93 are used to set the initial mirror angle (pre-tilting angle) and make a vertical comb drive.

In another example, the mirror and frame maintain different overlaps between the moving comb projection in the mirror and the fixed comb projection in the frame, while providing different preliminary angles to achieve a final mirror angle of approximately 45 degrees for the first optical scanner. It may have a tilting angle. 45 degree tilting is generally difficult because the moving comb of the mirror and the fixed comb of the frame will hardly be fully interlocked. In some instances, the uninterlocked comb will not generate enough force to drive the mirror. In this example, the outer frame is tilted approximately 30 degrees and the inner mirror is tilted approximately 15 degrees from the outer frame. This results in a total 45-degree absolute tilt of the internal mirror and comb linkage. (Note that overlapping and interlocking are possible in this example because the mirror is tilted 15 degrees relative to the frame). Using two different levels of pushdown pins or two different positions of pushdown pins in different positions (one pushdown pin pushes the mirror, the other pushdown pin pushes the frame), two different tilting This can be achieved at once. Although the two pushdown pins have the same height, the resulting pretilt angle will vary depending on the distance from the axis of rotation. In another example, two pushdown pins with different heights located at the same distance from the axis of rotation may be used.

The foregoing description is provided to explain exemplary embodiments and should not be construed as limiting. It will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the invention. For example, various support surface contours and slot widths can be used. In addition, numerous other materials and processes not expressly described herein may be used within the scope of exemplary methods and structures and will be understood by those skilled in the art. Accordingly, the invention is defined by the appended claims and should not be limited by the detailed description. In addition, specific examples have been discussed and how these examples are thought to address some drawbacks in the field. However, this discussion is not intended to limit the various examples of methods and / or systems that actually overcome or solve the shortcomings.

The following publications may be referenced for a more accurate understanding of the present description.

[1] H. Schenk, P. Durr, D. Kunze, H. Lakner, and H. Kuck, "A resonantly excited 2D-micro-scanning-mirror with large deflection," Sensors and Actuators A, vol 89, pp. 104-111, 2001.

[2] Sunghoon Kwon, Veljko Milanovic, Luke P. Lee, `` Vertical Microlens Actuator for 3D Imaging Applications, '' IEEE Photonics Technology Letters, vol. 14 (11), pp.1572-1574, 2002.

[3] Sunghoon Kwon, V. Milanovic, L. P. Lee, "A High Aspect Ratio 2D Gimbaled Microscanner with Large Static Rotation," IEEE / LEOS Optical MEMS 2002, Lugano, Switzerland, Aug. 2002

[4] J.B. Kim, H. Choo, L. Lin and R. S. Muller, "Microfabricated Torsional Actuator Using Self-Aligned Plastic Deformation," 12th Int. Conference on Solid State Sensors and Actuators, Transducers'03, Technical Digest, pp. 1015-1018, Boston, June 2003.

[5] Sunghoon Kwon and Luke P. Lee, "Micromachined transmissive scanning confocal microscope", OPTICS LETTERS, Vol. 29, No. 7, 2004

[6] Sunghoon Kwon and Luke P. Lee, "Stacked Two Dimensional Microlens Scanner for Micro Confocal Imaging Array," MEMS 2002, Las Vegas, U.S., 2002.

The light projection engine and its manufacturing method according to the present invention has the advantage that it can be manufactured at low cost.

The optical projection engine and its manufacturing method according to the present invention have the advantage of being able to simply support various image formats.

The light projection engine and the method of manufacturing the same according to the present invention have the advantage that the pixels are not separated by dark lines even when the image is observed close up.

The light projection engine and the method of manufacturing the same according to the present invention have an advantage of providing a small and simple light projection engine.

The light projection engine and its manufacturing method according to the present invention has an advantage that it is possible to provide a light projection engine having a high contrast ratio.

Claims (18)

Light source; A first optical scanner for scanning one or more light beams transmitted from the light source along a first direction, the first optical scanner including a waveguide movable along the first direction; And A second optical scanner for scanning the one or more light beams transmitted from the first optical scanner along a second direction that is not parallel to the first direction Light projection engine comprising a. The method of claim 1, And the first and second directions are perpendicular to each other. The method of claim 1, And the first optical scanner comprises two or more waveguides. The method of claim 1, And the second optical scanner comprises a moving mirror or lens. The method of claim 4, wherein The mirror or lens is pre-tilted light projection engine. The method of claim 1, And the first and second optical scanners are integrated into a single semiconductor substrate. The method of claim 1, And the light source and the first and second optical scanners are integrated into a single semiconductor chip or wafer. The method of claim 1, An optical coupler positioned between the light source and the first optical scanner and further including an optical coupler configured to combine the plurality of light beams output from the light source to form the one or more light beams and to transfer them to the first optical scanner engine The method of claim 1, The light source includes light emitting diodes (Light Emitting Diodes) or laser diodes (Laser Diodes). The method of claim 1, And a projection lens for projecting the one or more light beams transmitted from the second optical scanner onto a screen. The method of claim 10, And the projection lens is formed on a transparent packaging cover. In the manufacturing method of an optical projection engine, Forming first and second optical scanners on the substrate, The first optical scanner comprises one or more steerable waveguides for scanning the light beam along a first direction, The second optical scanner is configured to scan the light beam transmitted from the first optical scanner along a second direction that is not parallel to the first direction Method of manufacturing an optical projection engine. The method of claim 12, And the first and second optical scanners are monolithically integrated into the substrate. The method of claim 12, And a first direction and a second direction are orthogonal to each other. The method of claim 12, And the first optical scanner comprises two or more waveguides. The method of claim 12, And the second optical scanner comprises a moving mirror or lens. In the manufacturing method of an optical projection engine, Forming a moving mirror and a frame in the plane of the substrate, and Pretilting the mirror with respect to the plane of the substrate by tilting the frame by a first degree relative to the substrate and tilting the mirror by a second degree relative to the frame Method of manufacturing an optical projection engine comprising a. The method of claim 17, The pre-tilting step Pushing and tilting the mirror and the frame with two push down pins attached to an additional substrate Method of manufacturing an optical projection engine comprising a.

Images