HK1110119A - Method of manufacturing a polymeric waveguide with a three-dimensional lens - Google Patents

Description

Method of fabricating a polymeric waveguide with a three-dimensional lens

Technical Field

The present invention relates generally to optical transmission devices, and more particularly to techniques for manufacturing optical transmission devices.

Background

User input devices for data processing systems may take many forms. Two suitable types are touch screens and pen-based screens. With a touch screen or pen-based input screen, a user may input data by touching the display screen with a finger or an input device such as a stylus or pen.

One conventional approach to providing a touch-based or pen-based input system is to overlay a resistive or capacitive film over the display screen. This approach has a number of problems. First, the film makes the display appear dim and obscures the view of the underlying (base) display. To compensate, the brightness of the display screen is typically increased. However, in the case of most portable devices, such as mobile phones, personal digital assistants, and laptop computers, high brightness screens are not typically provided. The increased brightness would require additional power if available, thereby reducing the life of the device's battery before recharging. These films are also susceptible to damage. In addition, the cost of the film scales dramatically with the size of the screen. The cost is therefore generally prohibitive if a large screen is utilized.

Another way to provide a touch-based or pen-based input system is to use an array of Light Emitting Diode (LED) sources along two adjacent X-Y sides of the input display and a reciprocal (reciprocal) array of corresponding photodiodes along the opposite two adjacent X-Y sides of the input display. Each LED generates a light beam directed to a reciprocal photodiode. When the user touches the display with a finger or pen, the interruptions in the light beams are detected by the respective X and Y photodiodes on the opposite side of the display. Thus, the data input is determined by calculating the coordinates of the interruption of the light beam detected by the X and Y photodiodes. However, this type of data entry display also has a number of problems. For typical data input displays, a large number of LEDs and photodiodes are required. The positions of the LED and the reciprocal photodiode also need to be aligned. The relatively large number of LEDs and photodiodes and the need for precise alignment make such displays complex, expensive and difficult to manufacture.

In view of the foregoing, there is a continuing effort to provide improved data input devices and methods that provide a continuous sheet or "lamina" of light in free space adjacent a touch screen and an optical position digitizer that detects data input by determining the location of a "shadow" in the lamina caused by an input device, such as a finger or stylus, interrupting the lamina when contacting the screen.

Disclosure of Invention

The present invention relates to light transmission techniques for efficient transmission of light rays in a desired plane above a work surface. These techniques particularly relate to optical transmission structures that include waveguides and optical lenses. An optical lens is formed on the working surface and has a thickness large enough to allow a curved front lens surface to be formed that collimates transmitted light rays to propagate in a plane coplanar with the working surface. The invention also relates to a technique for manufacturing a light-transmitting structure, which technique involves the use of a photo- (sensitive) polymer material. The optical transmission structure may be implemented in various systems such as systems for optical data input.

As a method, one embodiment of the present invention includes at least applying a layer of photopolymer material to a support substrate; providing a patterned gray scale mask that allows a pattern of light to pass through the mask with varying intensities; exposing the layer of photopolymer material to light directed through a grayscale mask such that selected portions of the photopolymer material are exposed to light of varying brightness; developing the layer of photopolymer material with a developing solution to remove portions of the layer of photopolymer material such that remaining portions of the photopolymer material form a waveguide that is integrated with the optical lens; and rinsing the layer of photopolymer material to wash away the removed portion of photopolymer material. In an alternative embodiment, the method further comprises forming the optical lens such that the optical lens has an in-plane collimating lens curve (curve) having an outline (outline) substantially defined in a plane perpendicular to at least the top surface of the support substrate, wherein the light rays transmitted from the waveguide are collimated by the optical lens such that the light rays are emitted through the in-plane collimating lens curve in a plane substantially coplanar with the top surface of the support substrate. In another alternative embodiment, the invention further comprises forming the optical lens such that the optical lens has a directionally collimating lens curve having a profile that is substantially defined within a plane that is at least coplanar with the top surface of the support substrate, wherein the light rays transmitted from the waveguide are collimated such that substantially all of the light rays emitted through the directionally collimating lens curve are parallel to each other and propagate in a single direction.

In another embodiment of the invention, the method includes at least applying at least a layer of photopolymer material to a support substrate; exposing the layer of photopolymer material to light directed through a patterned grayscale mask such that selected portions of the photopolymer material are exposed, wherein the grayscale mask allows the light pattern to pass through the mask with varying intensity; developing the layer of photopolymer material with a developing solution to remove portions of the layer of photopolymer material such that remaining portions of the photopolymer material form a waveguide in combination with an optical lens, wherein the optical lens has a height greater than a height of the waveguide and the optical lens has a sloped, curved front lens surface; and rinsing the layer of photopolymer material to wash away the removed portion of photopolymer material.

In another embodiment of the invention, the method includes at least applying a layer of photopolymer material to a support substrate; exposing the layer of photopolymer material to light directed through a patterned gray scale mask that allows a pattern of light to pass through the mask at varying intensities such that selected portions of the photopolymer material are exposed to the varying intensity light; developing the photopolymer material layer with a developing solution to remove portions of the photopolymer material layer such that remaining portions of the photopolymer material form a waveguide in combination with an optical lens, wherein the optical lens has a front lens surface with curvature defined in three dimensions, wherein light transmitted from the waveguide is collimated by the optical lens such that the light is emitted through the front lens surface in a plane substantially coplanar with the top surface of the support substrate; and rinsing the layer of photopolymer material to wash away the removed portion of photopolymer material.

Another aspect of the invention is a system for manufacturing an optical structure comprising at least a support substrate having a top surface, a photopolymer material layer applied to the top surface of the support substrate, a light source emitting light, and a patterned grayscale mask having a grayscale pattern that allows a desired pattern of light to be shined from the light source onto the photopolymer material layer, the grayscale pattern also allowing light to pass through the grayscale mask at different brightness levels, wherein a waveguide with an integrated optical lens can be formed in the photopolymer material layer by a photolithographic process.

These and other features and advantages of the present invention will be presented in more detail in the following specification of the invention and the accompanying figures which illustrate by way of example the principles of the invention.

Drawings

The invention, together with its advantages, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a touch screen display system according to one embodiment of the present invention.

Fig. 2 and 3 illustrate top and side views, respectively, of a light transport structure according to one embodiment of the present invention.

Fig. 4 and 5 illustrate top and side views, respectively, of an optical transmission structure according to an alternative embodiment of the present invention.

FIG. 6 illustrates a flow chart depicting a method for fabricating an optical structure according to one embodiment of the present invention.

Fig. 7 and 8 are top and side views, respectively, illustrating a layer of photopolymer material that has been applied to a support substrate wherein the layer of photopolymer material will be processed according to one embodiment of the present invention.

Detailed Description

The present invention will now be described in detail with reference to a few preferred embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are provided in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known operations have not been described in detail in order not to unnecessarily obscure the present invention.

The present invention relates to optical transmission techniques for efficiently transmitting light in a desired plane above a work surface. These techniques particularly relate to optical transmission structures that include waveguides and optical lenses. The optical lens is formed on the working surface and has a thickness large enough to allow the formation of a curved front lens surface that collimates the transmitted light rays so that they propagate in a plane coplanar with the working surface. The optical lens shape effectively collimates these light rays without the need for additional collimating lenses and manufacturing processes necessary to incorporate such additional lenses. The invention also relates to techniques for manufacturing light transport structures involving the use of photopolymer materials. The optical transmission structure may be implemented in various systems, for example in a system for optical data input.

The present specification will first describe an optical data input system that can utilize the optical transmission structure of the present invention. The present specification will then explore details regarding the optical transmission structure and the method for fabricating the optical transmission structure. Note that the optical transmission structure of the present invention may be used to transmit and/or receive optical signals, even though the term "transmission" may lead one to think that: this structure can only be used for transmitting signals. Thus, the term "transmission" does not functionally limit the optical structure to the transmission of signals.

Referring to FIG. 1, a touch screen display system according to one embodiment of the present invention is shown. The touchscreen display system 10 includes a continuous plane or "lamina" 12 of light generated in free space adjacent to a display screen 14 or just above the display screen 14. Lamina 12 is generated by X-axis input light source 16 and Y-axis input light source 18, each of X-axis input light source 16 and Y-axis input light source 18 being configured to propagate light in free space directly above the surface of display screen 14 in the X and Y directions, respectively. The free space is generally parallel to the surface of the display screen 14 and is positioned just in front of the display screen 14. Thus, the lamina 12 is interrupted when an input device (not shown) such as a user's finger or a hand-held stylus or pen is used to touch the display screen 14 during a data entry operation. An X-axis light receiving array 20 and a Y-axis light receiving array 22 are positioned on opposite sides of the display screen 14 opposite the X-axis and Y-axis light sources 16 and 18, respectively. The light receiving arrays 20 and 22 detect the X-axis and Y-axis coordinates of any breaks or "shadows" in the lamina 12 caused by an input device breaking (breaking) the lamina 12 in free space above the display screen 14 during a data entry operation. A processor 24 coupled to the X-axis and Y-axis arrays 20 and 22 is used to calculate the X-axis and Y-axis coordinates of the interrupt. Together, the X-axis and Y-axis arrays 20 and 22 and the processor 24 provide an optical position detection device for detecting the location of interruptions in the lamina 12. Based on the coordinates of the interrupt, the data input on the display screen 14 may be determined.

According to one embodiment of the invention, the light sheet 12 has a substantially uniform brightness. Thus, the dynamic range required by the photosensitive circuits in the receive X-axis and Y-axis arrays 20 and 22 is minimized and high interpolation accuracy is maintained. However, in alternative embodiments, non-uniform thin layers 12 may be used. In this case, the minimum brightness region of the lamina 12 will be above the photoexcitation threshold (effective limit) of the photodetecting elements used by the X-axis and Y-axis arrays 20 and 22.

The display 14 may be any type of data display according to various embodiments of the present invention. For example, the display screen 14 may be a display for: a personal computer, a workstation, a server, a mobile computer, a laptop computer, a point of sale terminal, a Personal Digital Assistant (PDA), a mobile phone, any combination thereof, or any type of device that receives and processes data input.

According to one embodiment of the invention, the X and Y input light sources 16 and 18 are each collimated beam sources. The collimated light can be generated in any of a number of different ways, for example, from a single light source mounted at the focal point of a collimating lens. Alternatively, collimated light beams may be generated from a plurality of point light sources and a collimator lens, respectively. In another embodiment, the X and Y input light sources 16 and 18 may be fabricated using fluorescent lamps and diffusers (diffusers). The one or more point light sources may be Light Emitting Diodes (LEDs) or Vertical Cavity Surface Emitting Lasers (VCSELs).

In another embodiment, the light source may be a light emitter with spaced facets fed with a vertical laser.

The wavelengths of light generated by the X and Y axis light sources 16 and 18 used to create the lamina 12 may also vary according to different embodiments of the present invention. For example, the light may be of a broadband type having an extended wavelength spectral range from 350nm to 1100nm, such as white light from an incandescent light source. Alternatively, the input light may be of a narrow band type with a limited spectrum in the range of 2 nm. The use of narrow band light enables filtering of broadband ambient noise light. The use of the narrow-band light also enables the light wavelength to substantially match the response profile (response profile) of the X-axis light-receiving array 20 and the Y-axis light-receiving array 22. In another embodiment, uniform, single wavelength light may be used. For example, infrared or IR light commonly used in wireless or remote data transfer communications may be used in such applications.

The light source, whatever the type, may also operate continuously or periodically, used on an on/off cycle. The on/off cycle conserves power, minimizes heat generated by the light source, and allows instantaneous filtering to reduce noise, such as lock-in detection. During the off cycle, the X-ray receiving array 20 and the Y-ray receiving array 22 measure passive or "dark" light (noise). The dark light measurement is then subtracted from the active light detected during the on cycle. Thus, the subtraction filters out the DC background (light) caused by ambient light. The passive light can also be calibrated during each off cycle, which allows the system to adapt to changing ambient light patterns.

In another embodiment, the X-axis and Y-axis light sources 16 and 18 may be cycled off and on intermittently. During the alternating cycle, when the X-axis light source 16 is on, the Y-axis light source 18 is off, and vice versa. This arrangement requires less peak power because only one light source is on at a time, while still allowing the subtractive filtering to occur during each X and Y on/off cycle, respectively.

To reduce power consumption, a "sleep" mode may also be used for the X-axis and Y-axis light sources 16 and 18. The brightness of the X-axis and Y-axis light sources 16 and 18 may be dimmed if no data is input for a predetermined period of time. The rate of sampling shadow interrupts may also be done at a low rate, for example, five times in a second. When a shadow break is detected, the brightness and sample rate of the X-axis and Y-axis light sources 16 and 18 are increased to a normal operating mode. If no shadow breaks are detected after a predetermined period of time, the X-axis and Y-axis light sources 16 and 18 are dimmed again and the sampling rate is reduced.

The X-axis and Y-axis arrays 20 and 22 each include an array of substrate waveguides and photosensitive elements. The photosensor is configured to convert the light signal into an electrical signal indicative of the brightness of the received light. Specifically, each substrate has a plurality of waveguides. Each waveguide has a free space end closest to the layer 12 and an output end closest to the photosensitive element. The photosensitive element is attached to or positioned adjacent to the output end of the waveguide, respectively. For a detailed explanation of the use and fabrication of waveguides, see U.S. patent No. 5,914,709 to David Graham et al, the inventor of the present application, and which is incorporated herein by reference for all purposes. The light sensitive elements may be implemented in a number of known ways, for example using a Charge Coupled Device (CCD) or a CMOS/photodiode array. Any type of imaging element may be implemented in many forms, including on an application specific integrated circuit such as an application specific integrated circuit, a programmable circuit, or any other type of integrated or discrete circuit that contains photosensitive regions or components. Again, additional details regarding the various types of photosensors that may be used with the present invention are discussed in the aforementioned patents. Whichever type of photosensor is used, the output electrical signals representing the received light intensity along the X and Y coordinates are provided to processor 24. The processor 24 determines the location of any shadows in the lamina 12 due to interruptions in the lamina during input operations based on the electrical signals.

Fig. 2 and 3 illustrate a top view and a side view, respectively, of a light transport structure 100 according to one embodiment of the present invention. Optical transmission structure 100 includes a waveguide 102 and an optical lens 104. The optical transmission structure 100 is formed on a bottom cladding layer (cladding layer)120, and the bottom cladding layer 120 is formed on the support structure 106. Top cladding layer 122 covers the top surface of waveguide 102. The dashed directional lines of fig. 2 and 3 generally illustrate the path of light through the optical structure 100. The directional arrows represent light rays transmitted out of optical structure 100, however, it should be understood that these light rays may also be received into optical structure 100 along substantially the same path represented by the dashed lines.

Waveguide 102 and optical lens 104 may be formed using any suitable material for transmitting light or optical signals through its medium, such as polymer-based materials, optical plastics, and epoxies. Waveguide 102 and optical lens 104 may be integrally or separately formed with each other and then attached to each other, or even formed in the closest position relative to each other. As shown in fig. 2 and 3, waveguides 102 and 104 are integrally formed with each other. The integrally formed waveguide 102 and optical lens 104 are easier to manufacture because alignment problems between these two components are avoided. Typically, the waveguide 102 and the optical lens 104 are formed using the same material. However, in some embodiments, waveguide 102 and optical lens 104 are formed separately, and these two components may be fabricated using different materials.

Top and bottom cladding layers 122 and 120, respectively, are used to improve the optical transmission quality of waveguide 102. Top and bottom cladding layers 122 and 120 are selected to have an index of refraction that complements the index of refraction of waveguide 102. These cladding layers also serve to physically protect waveguide 102, which can be made of a fragile material. Top cladding layer 122 covers waveguide 102 in fig. 3. However, in an alternative example of implementation, top cladding layer 122 also covers back surface 110 of optical lens 104. The top cladding layer 122 should not cover the surface of the optical lens 104 for light to travel in and out. In some embodiments, no top cladding layer is applied to the top surface of waveguide 102. In these embodiments, waveguide 102 is not protected physically and the surrounding air serves as a cladding layer. The refractive index of air may generally be optimal for light transmission purposes. Note that top cladding layer 122 is not shown in fig. 2 in order to more clearly illustrate the structure of waveguide 102.

Bottom cladding layer 120 extends below wave 102 and optical lens 104. In some embodiments, bottom cladding layer 120 is not used, as support substrate 106 may serve as a cladding layer. In these embodiments, the refractive index of the support substrate 106 should be appropriately selected.

Waveguide 102 is a lengthwise structure for transmitting light between two points. In the present invention, one end of waveguide 102 is connected to optical lens 104, while the opposite end is connected to a light source or light detection device. The optical transmission capacity of waveguide 102 may be varied by changing the dimensions of waveguide 102Cun should be adjusted. For example, the diameter or width and height of waveguide 102 may be sized appropriately. Height or thickness H of waveguide 102_wAs can be seen in fig. 3, and the width W of waveguide 102_wAs can be seen in fig. 2. The cross-sectional shape of waveguide 102 may be rectangular or circular.

The optical lens 104 has a height or thickness H_L，H_LGreater than H_w. Optical lens 104 rises in height from its interface with waveguide 102 to H of optical lens 104_LThe vertex 108 of (a). Back surface 110 defines the shape of optical lens 104 between waveguide 102 and apex 108. In this embodiment, back surface 110 has a substantially flat surface. The height of the optical lens 104 allows the front face of the optical lens 104 to have a curvature defined in two or three dimensions. The two-dimensional curvature of the optical lens 104 is a curve having a profile defined in a single plane (e.g., in the X-Y, X-Z, Y-Z plane). In other words, the curve is defined in two dimensions. The three-dimensional curvature is defined in three dimensions. For example, such a curve would have a profile shape defined in each of two planes (e.g., the X-Y and X-Z planes). As will be described, the optical lens 104 of fig. 2 and 3 has a three-dimensional curvature, wherein the curvature has a contoured shape defined in the X-Y and X-Z planes.

The front face of optical lens 104 slopes downward from apex 108 to the front edge of lens 104 that is in contact with support substrate 106. This slope can be seen in the side view of the optical structure 100 of fig. 3. FIG. 3 also illustrates a cross-sectional view of the optical structure 100 in the X-Z plane. The tilted plane is curved and forms an in-plane collimating lens curve 112. An in-plane collimating lens curve 112 is formed across the entire front face of optical lens 104 and collimates the outgoing light rays so that they are substantially parallel to the top surface of support substrate 106. The in-plane collimating lens curve 112 directs the light rays across the entire support substrate without allowing some of the light rays to exit away from the support substrate 106.

The contour of the in-plane collimating lens curve 112 is defined in a plane that is perpendicular to the top surface of the support substrate 106 and aligned with the direction of propagation of a particular light ray. Thus, the in-plane collimating lens curve 112 is visible from the side view of FIG. 3, which also represents the X-Z plane. Fig. 3 shows the in-plane collimating lens curve 112 for light rays propagating along the longitudinal axis 116 of the waveguide 102 as seen in the top view of fig. 2. The curvature of the in-plane collimating lens curve 112 depends on the height of the optical lens 104 and the distance of the front face of the optical lens 104 from the waveguide 102. The curvature of the in-plane collimating lens curve also depends on other factors such as the nature of the light rays and the refractive index of the lens material and the surrounding environment. For the data input system 10 of fig. 1, the in-plane collimating lens curve 112 of optical lens 104 allows the input light sources 16 and 18 to more efficiently form the lamina 12 of light because less light loss is experienced. Advantageously, this reduces the power requirements required to form the thin layer of light 12. Without the in-plane collimating lens curve 112, light rays from the optical structure 100 would diffract and a portion of the light rays would be directed away from the support substrate 106. To achieve the same function of the in-plane collimating lens curve 112, an additional optical lens would need to be positioned in front of the optical lens 104. This would be to manufacture a more complex optical system in terms of time, effort and resources. For example, the process of aligning the additional lens with the optical lens 104 would be time consuming and very susceptible to correction errors.

Note that the in-plane collimating lens curve 112 has a curve that forms a partial hemispherical arc. Thus, it is said that the optical lens 104 may form half of a full lens, wherein the missing half would be the specular reflection of the optical lens 104 along the X-axis. As will be described below, the shape of the optical lens 104 is easier to manufacture than if it had a full lens shape. Also, the "half-lens" shape of optical lens 104 allows for easier integration and alignment with waveguide 102. In particular, the "half-lens" shape of optical lens 104 makes the photolithographic manufacturing process ideal for manufacturing optical structure 100.

The in-plane collimating lens curve 112 as seen in the side view of fig. 3 is independent of the directional collimating lens curve, which can be seen from the top view of the optical lens of fig. 2. Note that fig. 2 illustrates a view of optical structure 100 in the X-Y plane. The contour shape (profile) of directionally collimating lens curve 114 is defined in a plane that is coplanar with the top surface of support substrate 106. The directionally collimating lens curve 114 collimates the exiting light rays to propagate parallel to each other in a single direction. In essence, directionally collimating lens curve 114 allows optical lens 104 to create a uniform beam of light. For the data input system 10 of fig. 1, the directionally collimating lens curve 114 allows each optical structure 100 to form a uniform beam of light that propagates across the display screen 14.

Optical lens 104 is shaped to allow light to propagate between front lens surface 112 and waveguide 102. To allow the maximum amount of light from waveguide 102 to be collimated with front lens surface 112, back surface 110 should have at leastThe angle of (c). Such an angle is referred to as the critical angle 118 of optical transmission 104. Note that n is₁Is the refractive index of the waveguide 102, n₂Is the larger of the refractive indices of the top cladding layer 120 or the bottom cladding layer 122, and n₃Is the refractive index of the optical lens 104. Note that when optical lens 104 and waveguide 102 are formed from the same material, n₁And n₃Will have the same value. Note that the maximum amount of light that can be collimated with the front lens surface 112 is inherently limited due to the shape of the optical lens 104. Since the optical lens 104 has a partial lens shape, where the full lens would have the shape of reflecting the optical lens 104 along the X-axis (specular), almost half of the light transmitted from the waveguide 102 is lost. Thus, optical structure 100 has approximately 3dB optical loss. In some embodiments, by allowing back surface 110 to have an angle less than the critical angle, slightly more light loss is sacrificed to achieve a lower H_LThe optical lens of (1) is suitable. In an alternative embodiment, back surface 110 of optical lens 104 may be raised above the planar surface defined by critical angle 118 (see fig. 4 and 5). Such an embodiment is also effective because the material above the critical angle 118 does not affect the light rays propagating through the rest of the optical lens 104.

As viewed from the top of FIG. 2As seen in the view, optical lens 104 has a conical shape, wherein optical lens 104 has a width W_LIncreasing as optical lens 104 extends away from waveguide 102. The conical shape of optical lens 104 allows the light rays from waveguide 102 to spread out over optical lens 104 until they are collimated into a uniform beam with directional lens curve 114. The taper-like proportions of the optical lens 104 depend in part on the optical performance requirements of each optical structure 100.

In alternative embodiments, optical lens 104 may have various sizes and shapes. For example, the optical lens 104 need not have a tapered shape as seen from the top view in fig. 2. Also, in the case where the light rays do not have to be emitted in a uniform beam, the optical lens 104 may have a flat front surface as seen from the top view of fig. 2. In one embodiment, the optical lens 104 can have a height H in the range of 50-200 um_LAnd a length in the range of about 0.8 to 1.2 mm. Sometimes, the size of optical lens 104 is limited by the size of the system in which it is used (e.g., the display screen shown in FIG. 1). The particular dimensions of the optical lens 104 are also determined by the relative refractive indices for the optical structure 100 and the surrounding environment. For example, the type of cladding surrounding the optical structure 100 is also a determining factor in the size of the optical lens 104.

The support structure 106 may be any surface through which light is intended to be directed across, for example, the display screen 14 shown in FIG. 1. Alternatively, the support structure 106 may be a structure separate from the display screen. For example, the support structure may be a separate mounting plane that supports each optical structure 100, where each optical structure 100 is then positioned proximate to a work surface such as a display screen. In these other embodiments, the support structure may be a layer of plastic, epoxy, or polymer. Support structure 106 may also be a cladding layer for protecting waveguide 102 from physical damage and for increasing the optical transmission efficiency of waveguide 102.

In one embodiment, the plurality of optical structures 100 are formed in a row such that a plurality of light beams are directed through a work surface, such as display screen 14 in FIG. 1. At the same time, another row of optical structures 100 is formed to receive each light beam. Two such sets of optical structures may then be formed to pass the light beam across the display screen 14 along two axes (e.g., the X-axis and the Y-axis).

Fig. 4 and 5 illustrate top and side views, respectively, of an optical transmission structure 200 according to an alternative embodiment of the present invention. The optical transmission structure 200 includes a waveguide 202 and an optical lens 204. The optical transmission structure 200 is formed on a support structure 206. The dashed directional lines of fig. 2 and 3 generally illustrate the path of light through the optical structure 100. These directional arrows represent light rays transmitted out of optical structure 100, however, it should be understood that light rays may also be received into optical structure 100 along substantially the same path as shown by the dashed lines.

Note that no top cladding layer is applied on top of the waveguide 202 and optical lens 204. Also, note that no bottom cladding layer supports the optical structure 200. However, the support substrate 206 may serve as a bottom cladding layer by selecting the material of the support substrate 206 to have an appropriate refractive index.

As described with respect to fig. 2 and 3, the optical lens 104 also has an in-plane collimating lens curve 212, which can be seen in fig. 5, and a directional lens curve 214, which can be seen in fig. 4. However, as can be seen in FIG. 5, optical lens 204 has a back surface 210 that extends beyond critical angle 118, as shown in FIG. 3. The back surface 210 has a substantially uniform height H_LUntil it quickly drops into engagement with the waveguide 202. Also, as can be seen from the top view of fig. 4, the optical lens 204 has an extension portion 208, the extension portion 208 having a uniform width W_L. In some cases, optical lens 104 of a particular size and proportion may be easily manufactured and may be more easily incorporated with other systems.

FIG. 6 illustrates a flow chart 300 describing a method for fabricating an optical structure according to one embodiment of the present invention. In some embodiments, the manufactured optical structure has a lens surface with a curvature defined in three dimensions. Fig. 7 and 8 will also be described in conjunction with fig. 6 to more fully illustrate the operation of flowchart 300. Fig. 7 and 8 illustrate top and side views of a photopolymer material layer 400 that has been applied to a support substrate 402 wherein the photopolymer material layer is to be processed according to an embodiment of the present invention.

In general, flow chart 300 describes the fabrication of optical structures using photopolymer, gray scale mask (reticle mask) and lithographic techniques. However, it should be understood that there are other techniques for fabricating the optical structures of the present invention. For example, micro molding techniques may be used to fabricate the lens structures at desired sizes and proportions. Also, the lens structures can be fabricated using three-dimensional gray scale photoresist (photoresist) structures, three-dimensional resist structures (resist structures) fabricated using "reflow" techniques followed by "dry" industrial etching processes (including reactive ion etching, ion milling), and other plasma-based compounds and methods, using glass, plastic, ceramic, and other materials.

Photopolymers are imaging compositions based on polymers, oligomers, or monomers, which can be selectively polymerized and/or crosslinked upon exposure to light radiation (e.g., ultraviolet light). Photopolymers are industrially regulated (leverage) into patternable systems, where light-induced chemical reactions in the polymer chemistry result in subtle changes in solubility between exposed and unexposed (masked) areas. Photopolymers can be made in different forms including films/sheets, liquids, solutions, etc., which can be used as photoresists in printing plates as well as in stereolithography and imaging. One conventional use of photopolymers is to form printing plates, wherein a photopolymer plate is exposed to a pattern of light to form the printing plate. The plate is then used for ink printing. Photopolymers are widely used in the electronics and microdevice industries as photoresists for the manufacture of complex patterns in microscopic circuits on semiconductor chips, printed circuit boards, and other products. Photopolymers are also used as uv adhesives for connecting optical fibers and for other industrial applications.

The photopolymer material can be exposed to light directed through a patterning mask. Such a patterning mask may be a gray scale mask. The grayscale mask has a designed pattern that, in addition to allowing light to pass through it in a desired pattern (the mask), also allows light to pass through the mask at a constantly changing brightness. Thus, the grayscale mask may allow the photopolymer layer to be exposed to a light pattern having a constantly changing luminance. In this way, portions of the photopolymer layer can be removed depending on the light intensity level of the received light. This means that the depth of photopolymer material removal can be controlled. For example, photopolymer material can be removed from the entire section or portions of photopolymer material can be removed to leave a remaining layer of photopolymer material with a varying thickness. Thus, the photopolymer can be formed into a specific structure having three dimensions of predetermined dimensions. In alternative embodiments of the present invention, masks that allow light to pass completely through or block light completely may also be used.

Flowchart 300 of fig. 6 begins at block 302 where a layer of photopolymer material 400 is applied to the top surface of a support substrate 402. Note that the reference numerals mentioned in the description of the flowchart 300 reflect the reference numerals shown in fig. 6, 7, and 8. Photopolymer material layer 400 typically has a relatively uniform thickness. Because some embodiments of the manufacturing process 300 will be used to manufacture the optical structures seen in fig. 2-5, the photopolymer material layer 400 should have a height H at least equal to the optical lens_LIs measured. The photopolymer material should be of a quality to efficiently transport light. For example, the photopolymer material can be of a very clear (transparent) quality. The photopolymer material can have a positive or negative tone for lithographic purposes.

Support substrate 402 has a top surface onto which photopolymer material layer 400 is applied. Support substrate 402 is typically a substrate that may be mounted within a lithography system so that photopolymer material layer 400 may be processed. Support substrate 402 may be formed from materials such as, but not limited to, plastics, polymers, ceramics, semiconductors, metals, and glass. The support substrate 402 may also be a cladding layer for surrounding a waveguide to be formed from a photopolymer material. Such a cladding layer protects the structure formed by the photopolymer layer 400 and its inherent refractive index facilitates the transmission of light through the photopolymer material. At the end of the manufacturing process, support structure 402 and the structure formed by photopolymer material layer 400 may be transported and then attached to a device (e.g., optical input device 10 as shown in FIG. 1).

In an alternative embodiment, a bottom cladding layer is applied to the support substrate 402, followed by application of a photopolymer material layer 400 on top of the bottom cladding layer. In the embodiments shown and described in fig. 6-8, support substrate 402 may be used as a bottom cladding layer, depending on the material selection. A bottom cladding layer may also be applied to the surface of support substrate 206 by photolithographic techniques.

At block 304 photopolymer material layer 400 is exposed to a light pattern created using a patterned grayscale mask 404. This is performed by shining a light source through the patterned grayscale mask 404 or by blocking light from passing through the mask. Grayscale mask 404 is patterned to create waveguides and optical lenses within photopolymer material layer 400. The waveguide and the optical lens may be integrally formed as shown in fig. 2-5. Using the same reference numbers as in fig. 2 and 3, the cross-hatching in fig. 7 and 8 represents waveguide 102 and optical lens 104 to be formed within photopolymer material layer 400. In other words, the cross-hatched areas represent the portions of the photopolymer layer 400 that will remain after the photolithography process is completed. The top view of fig. 7 shows that grayscale mask 404 allows light to expose areas of photopolymerizable material layer 400 outside of waveguide 102 and optical lens 104 and conversely protects photopolymer material 400 that will form waveguide 102 and optical lens 104 as a result of the light exposure.

Light irradiated through the gray scale mask 404 is indicated by directional lines and a dotted line 406 in fig. 8. The gray scale nature of mask 404 allows light to pass through at varying intensities and thus allows light to penetrate photopolymer material layer 400 to varying depths. The end points of each line 406 represent each ray passing throughThe depth of the light-transmissive polymer material layer 400. The material composition of the photopolymer layer 400 changes the exposure amount only with respect to the depth of light penetration and causes chemical changes in the photopolymer system created by this exposure gradient. The exposure gradient refers to the pattern of light generated by a grayscale mask, where the light rays passing through the mask have varying intensities. In this manner, three-dimensional (or "form") structures such as optical lens 104 may be formed using photopolymer material layer 400. Specifically, the front lens surface having the in-plane collimating lens curve 112 can be formed as seen in the side view of FIG. 8. As described above, the in-plane collimating lens curve has a profile that is defined in a plane that is perpendicular to the top surface of the support structure 106. Also, the front lens surface has a directionally collimating lens curve 114 as seen in the top view of FIG. 7. As described above, the directionally collimating lens curve has a profile that is defined within a plane that is coplanar with the top surface of support substrate 106. Also, optical lens 104 has a back surface 110 that is sloped and extends from waveguide 102 to the top of optical lens 104. The grayscale mask 404 may be patterned so that the back surface 110 may have any shape as long as it at least rises toAbove the critical angle 118 of (a), wherein n₁Is the refractive index of the waveguide 102, n₂Is the refractive index of the support substrate 402 (which serves as the bottom cladding layer), and n₃Is the refractive index of the optical lens 104.

In an alternative embodiment of block 304, photopolymer material layer 400 may be exposed to various patterns of light through a grayscale mask 404 to form various structures within photopolymer material layer 400. For example, various three-dimensional or two-dimensional structures may be formed. In particular, the optical lens 104 may have a lens surface that is either one of an in-plane collimating or a directionally collimating curve. The optical lens 104, which has only the directionally collimating lens curve 114, may have the same height as the waveguide 102, such that the optical structure has a flat top surface.

Waveguide 102 may be formed to have a rectangular or circular cross-sectional shape. In one embodiment, waveguide 102 may be formed to have a rectangular cross-sectional shape, each having a height and width of approximately 8-10 microns. The longitudinal dimension of waveguide 102 may extend along a straight or curved path for connection to a light source or light detector.

The use of photopolymer material layer 400 is beneficial because optical lens 104 and waveguide 102 can be easily formed integral with each other. This eliminates any laborious work of aligning the waveguide with the optical lens. The ability to form an optical lens with an in-plane collimating lens curve 112 also simplifies the manufacturing process of certain optical structures because a separate lens does not have to perform the function of the in-plane collimating lens curve 112. Such a separate lens would require additional resources for the lens itself and for positioning and alignment.

The same optical lens structure can be formed in a negative-tone (negative-tone) optical photopolymer by using a positive-tone mask with the negative-tone optical photopolymer or by using a negative-tone mask with the positive-tone optical photopolymer. Positive tone photopolymer material systems and negative tone photopolymer material systems can be used with gray scale mask technology to create exposure gradients resulting in three-dimensional polymeric structures after development. Furthermore, the structures formed from the photopolymer material form engineered structures such as waveguides or optical lenses.

In fig. 7 and 8, the portions of photopolymer material layer 400 that are exposed to light may be removed during a subsequent development process, positive tone. The length of each dashed line 406 in fig. 8 may represent the energy vector or amount of light energy per light ray impinging on photopolymer material layer 400.

In an alternative embodiment where the photopolymer material layer is a negative tone, the light causes the photopolymer material to crosslink into a more robust structure than is formed using a positive tone photopolymer system. The unexposed areas of the photopolymer material will be washed away. Where the length of each dashed line 406 of fig. 8 can be viewed as being proportional to the light energy of each light ray for a positive tone photopolymer material layer, the inverse amount of energy represented by each dashed line 406 is appropriate for a negative tone photopolymer material layer.

In some implementations of the manufacturing process 300, multiple optical structures formed by the waveguide 102 and the optical lens 104 may be formed. A plurality of optical structures can be formed such that an array of light beams is directed away from optical lens 104. Such an array of light beams may form a lamina of light 12 as shown in fig. 1.

In block 306, a developer solution is washed over photopolymer material layer 400 to develop photopolymer material layer 400. The developer may be an organic solvent or an aqueous solution. Exemplary developers include, but are not limited to, Methyl-Iso-Butyl-Ketone (MIBK), tetramethylammonium Hydroxide (TMAH), and Potassium Hydroxide (KOH). It is also possible to use dry development based on plasma treatment. The developer removes the exposed areas at a different rate than the unexposed areas (Differential solubility due to light induced chemical reactions in the photopolymer) resulting in a useful pattern after the development process. The portions of photopolymer material 400 not exposed to light remain intact and form the desired structures, such as waveguide 102 and optical lens 104.

In block 308, another aqueous solution, such as an organic solvent, is used to rinse away the developer solution and the portions of photopolymer material layer 400 that are dissolved.

Subsequently, in block 310, the support substrate 402 and the remaining optical structures formed using the photopolymer material layer 400 are subjected to a drying process. In this treatment, the aqueous rinse solution is dried off. The drying operation of block 310 may be performed in various ways, such as with heat, rotation, and/or air blowing.

Support substrate 402 and photopolymer material 400 can be formed in a size and shape suitable for installation in a lithography system, such as suitable for semiconductor manufacturing. In one embodiment, support substrate 402 and photopolymer material 400 can be formed on a wafer (such as a semiconductor wafer) that can be placed within a lithography system.

In some implementations of method 300, a top cladding layer may be applied over waveguide 102 and optical lens 104.

While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, and equivalents, which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.

Claims (23)

1. A method for fabricating an optical structure, comprising:

applying a layer of photopolymer material onto a bottom cladding layer formed on a support substrate;

providing a patterned gray scale mask that allows a particular pattern of light to pass through the mask with varying intensities; and

exposing the layer of photopolymer material to light directed through a grayscale mask such that selected portions of the photopolymer material are exposed to an exposure gradient of light having varying intensities of light;

developing the photopolymer material layer with a developing solution to remove portions of the photopolymer material layer such that remaining portions of the photopolymer material form a waveguide that is integrated with the optical lens; and

the layer of photopolymer material is rinsed to wash away the removed portions of the photopolymer material.

2. The method of claim 1, wherein the optical lens has a three-dimensional contoured shape.

3. The method of claim 1, wherein the developing operation further comprises:

the waveguide is formed such that it forms a lengthwise configuration having a first end coupled to the optical lens and a second end coupled to the light source or light detector.

4. The method of claim 1, wherein the developing operation further comprises:

the optical lens is formed such that the optical lens has a height greater than a height of the waveguide.

5. The method of claim 4, wherein the developing operation further comprises:

forming the optical lens such that the optical lens has an in-plane collimating lens curve having a profile that is substantially defined at least in a plane perpendicular to the top surface of the support substrate, wherein light rays transmitted from the waveguide are collimated by the optical lens so as to be emitted through the in-plane collimating lens curve in a plane that is substantially coplanar with the top surface of the support substrate.

6. The method of claim 5, wherein the in-plane collimating lens curve defines a front lens surface that extends from the support surface to a maximum height of the optical lens.

7. The method of claim 5, wherein the developing operation further comprises:

forming the optical lens such that the optical lens has a directionally collimating lens curve having a profile that is substantially defined at least in a plane that is coplanar with the top surface of the support surface, wherein the light rays transmitted from the waveguide are collimated such that substantially all of the light rays emitted through the directionally collimating lens curve are parallel to each other and propagate in a single direction.

8. The method of claim 5, wherein the developing operation further comprises:

an optical lens is formed such that the optical lens has a sloped back surface having a first edge joined to the waveguide and a second edge extending to a maximum height of the optical lens.

9. The method of claim 8, further comprising:

a top cladding layer is applied over the waveguide.

10. The method of claim 9, wherein the sloped back surface is substantially flat and at least equal toIs inclined by an angle of n₁Is the refractive index of the waveguide, n₂Is the greater of the top cladding layer or the bottom cladding layer, and n₃Is the refractive index of the optical lens.

11. The method of claim 5, wherein the developing operation further comprises:

the optical lens is formed such that the optical lens has a width that expands as the optical lens extends away from the waveguide.

12. A method of manufacturing an optical structure, comprising:

applying a layer of photopolymer material to a support substrate;

exposing the photopolymer material layer to an exposure gradient of light formed by directing light through a patterned grayscale mask that allows light to pass through the mask with varying intensities;

developing the photopolymer material layer with a developing solution to remove portions of the photopolymer material layer such that remaining portions of the photopolymer material form a waveguide in combination with an optical lens, wherein the optical lens has a height greater than a height of the waveguide and the optical lens has a sloped and curved front lens surface; and

the layer of photopolymer material is rinsed to wash away the removed portions of the photopolymer material.

13. The method of claim 12, wherein the exposing operation further comprises:

the photopolymer material is exposed to an exposure gradient of light such that a waveguide having an elongated shape is formed during the development operation having a first end coupled to an optical lens and a second end connected to a light source or light detector.

14. The method of claim 12, wherein the developing operation further comprises:

an optical lens is formed such that the optical lens has a directionally collimating lens curve having a profile that is substantially defined at least in a plane that is coplanar with the top surface of the support surface.

15. The method of claim 12, wherein the developing operation further comprises:

an optical lens is formed such that the optical lens has a sloped back surface having a first edge joined to the waveguide and a second edge extending to a maximum height of the optical lens.

16. The method of claim 12, further comprising:

the material forming the support substrate is selected such that its refractive index allows the support substrate to function as a bottom cladding layer.

17. A method of manufacturing an optical structure, comprising:

applying a layer of photopolymer material onto a bottom cladding layer formed on a support substrate;

exposing the layer of photopolymer material to light directed through a patterned gray scale mask that allows a particular pattern of light to pass through the mask at varying intensities such that selected portions of the photopolymer material are exposed to the varying intensities of light;

developing the photopolymer material layer with a developing solution to remove portions of the photopolymer material layer such that remaining portions of the photopolymer material form a waveguide in combination with an optical lens, wherein the optical lens has a front lens surface having a curvature defined in three dimensions, wherein light transmitted from the waveguide is collimated by the optical lens so as to be transmitted through the front lens surface in a plane substantially coplanar with the top surface of the support substrate; and

the layer of photopolymer material is rinsed to wash away the removed portions of the photopolymer material.

18. The method of claim 17, wherein the developing operation further comprises:

the optical lens is formed such that the optical lens has a height greater than a height of the waveguide.

19. The method of claim 17, wherein the developing operation further comprises:

forming the optical lens such that the optical lens has a directionally collimating lens curve having a profile that is substantially defined at least in a plane that is coplanar with the top surface of the support surface, wherein the light rays transmitted from the waveguide are collimated such that substantially all of the light rays emitted through the directionally collimating lens curve are parallel to each other and propagate in a single direction.

20. A system for fabricating an optical structure, comprising:

a support substrate having a top surface;

a bottom cladding layer formed on the top surface of the support substrate;

a layer of photopolymer material applied to the bottom cladding layer;

a light source that emits light; and

a patterned grayscale mask having a grayscale pattern that allows a desired pattern of light from a light source to be illuminated onto a layer of photopolymer material, the grayscale pattern also allowing light to pass through the grayscale mask at different brightness levels, wherein a waveguide with an incorporated optical lens can be formed in the layer of photopolymer material by a photolithographic process.

21. The system of claim 20, wherein the optical lens has a height greater than a height of the waveguide.

22. The system of claim 21, wherein the optical lens has a front lens surface having a curvature defined in three dimensions, wherein light rays transmitted from the waveguide are collimated by the optical lens so as to be emitted through the front lens surface in a plane substantially coplanar with the top surface of the support substrate.

23. The system of claim 22, wherein the front lens surface has a directionally collimating lens curve having a profile that is substantially defined at least in a plane that is coplanar with the top surface of the support surface, wherein the light rays transmitted from the waveguide are collimated such that substantially all of the light rays emitted through the directionally collimating lens curve are parallel to each other and propagate in a single direction.