CN114840104A

CN114840104A - Barrier layer and tactile surface features for optical touch detection devices

Info

Publication number: CN114840104A
Application number: CN202210531406.7A
Authority: CN
Inventors: R·库伯怀特; O·德拉姆
Original assignee: Beckett Co ltd
Current assignee: Beckett Co ltd
Priority date: 2018-08-21
Filing date: 2019-08-21
Publication date: 2022-08-02
Also published as: KR20210055711A; WO2020039255A1; KR102439724B1; CN113056722A

Abstract

The application is entitled barrier layer and tactile surface features for optical touch detection devices. An optical touch-sensitive device includes a touch-sensitive surface upon which touch events can be detected. The device also includes surface features on the surface that reduce touch object friction relative to an absence of the surface features. The emitters and detectors are arranged along the periphery of the touch-sensitive surface. The emitter may generate a light beam that travels through the touch-sensitive surface to the detector. A touch on the touch sensitive surface interferes with the optical beam, and the touch sensitive device determines a touch event based on the interfered optical beam. The surface features may also be arranged to reduce glare by diffusing light. In some embodiments, the antireflective layer is on top of the touch-sensitive surface and the surface features.

Description

Barrier layer and tactile surface features for optical touch detection devices

The present application is a divisional claim of chinese patent application 201980069325.6 entitled "barrier layer and tactile surface features for optical touch detection device" filed on 8/21 2019.

Cross Reference to Related Applications

This application claims the benefit of provisional application 62/720,585 filed on 21/8/2018, which is incorporated herein by reference.

Technical Field

The present disclosure relates generally to optical touch detection systems and, more particularly, to touch surfaces having tactile features.

Background

Touch sensitive displays for interacting with computing devices are becoming increasingly popular. Many techniques exist for implementing touch sensitive displays and other touch sensitive devices. Examples of such technologies include, for example, resistive touch screens, surface acoustic wave touch screens, capacitive touch screens, and certain types of optical touch screens.

The user experience of a touch sensitive display may be negatively affected by various factors. One such factor is friction between a touching object (e.g., a user's finger) and the touch-sensitive surface. For example, grease from the user's finger may interact with the surface, causing excessive friction, negatively affecting the user's haptic experience. Another problem that may arise is that light from the user's environment may reflect off of the touch-sensitive surface, distracting the user from the content being displayed. For example, a user may see reflections of their own face appear superimposed over a document they are processing, a video they are watching, and so on. Accordingly, there is a need for improved touch sensitive surfaces to provide improved haptic experience, to reduce the effects of reflected light, or both.

Disclosure of Invention

The optical touch-sensitive device has a surface that produces a haptic effect experienced by a user.

In one aspect, an optical touch-sensitive device includes a planar lightwave circuit structure having a top surface that includes tactile surface features (i.e., surface features that can be felt by a user). The apparatus also includes a plurality of emitters and detectors. The emitter and detector are arranged along the periphery of the waveguide structure. The light beam generated by the emitter propagates through the waveguide structure via Total Internal Reflection (TIR) to the detector. A touch on the top surface of the waveguide structure may interfere with the optical beams, and the touch sensitive device determines a touch event based on the interference.

In another aspect, a waveguide structure includes a planar waveguide having a planar featureless top surface and a tactile coating on the top surface. The tactile coating may have the same or different index of refraction as the planar waveguide. The tactile coating may include a printed material such as a printed graphic border, colored region, or blocking layer.

Other aspects include components, devices, systems, improvements, methods, processes, applications, computer-readable media, and other technologies relating to any of the above aspects.

Some embodiments relate to an optical touch-sensitive device that includes a touch-sensitive surface, surface features on the touch-sensitive surface, and emitters and detectors. A touch event may be detected on the touch-sensitive surface. The surface features reduce touch object friction relative to the absence of the surface features. The emitter may generate a light beam that travels through the touch-sensitive surface to the detector. A touch on the touch sensitive surface may disturb the light beam. The touch sensitive device determines a touch event based on the disturbed light beam. The emitters and detectors may be arranged along the periphery of the touch-sensitive surface. In some embodiments, the light beams are coupled to and from the touch-sensitive surface by a coupler such that the emitters and detectors are not arranged along the periphery (e.g., the emitters are below the touch-sensitive surface).

In some embodiments, the touch-sensitive surface is a top surface of the planar light guide. The light beams travel through the touch-sensitive surface via total internal reflection within the waveguide.

In some embodiments, the touch sensitive surface is insensitive to touch at the location of the surface features.

In some embodiments, the height of the surface features from the touch-sensitive surface is less than the evanescent field depth of the light beam.

In some embodiments, the surface feature is part of the waveguide and is defined by the shape of the waveguide.

In some embodiments, the surface features are formed from a material that is different from the material of the touch-sensitive surface.

In some embodiments, the refractive index of the surface features is less than the refractive index of the material of the touch-sensitive surface.

In some embodiments, the surface features include at least one of: fluorine or silicone.

In some embodiments, the lateral spacing between surface features is no less than the size of a typical human finger ridge.

In some embodiments, the surface features comprise a porous material or embedded microspheres.

In some embodiments, the touch-sensitive surface further comprises a filler material on the touch-sensitive surface and between at least some of the surface features.

In some embodiments, a portion of the surface features comprise a planar surface that is not parallel to the touch-sensitive surface. In some embodiments, a portion of the surface features comprises surface features that are at least one of triangular prisms, pyramids, or trapezoidal prisms.

In some embodiments, a portion of the surface feature comprises a rounded surface. In some embodiments, a portion of the surface features comprises surface features that are at least one of hemispheres or bumps.

In some embodiments, the touch sensitive device includes a barrier layer on the surface features and on portions of the touch sensitive surface between the surface features. The refractive index of the barrier layer is less than the refractive index of the material of the touch-sensitive surface. The thickness of the blocking layer is based on the depth of the evanescent field of the optical beam. In some embodiments, the thickness of the blocking layer is less than the depth of the evanescent field.

In some embodiments, the surface features are randomly arranged on the touch-sensitive surface.

In some embodiments, the surface features comprise a surface configured to scatter incident light.

In some embodiments, the touch sensitive device further comprises an antireflective layer over the surface features and over portions of the touch sensitive surface between the surface features. In some embodiments, the thickness of the anti-reflective layer on the portion of the touch-sensitive surface between the surface features is less than the evanescent field depth of the optical beam.

In some embodiments, at least one of the shape, height, or width of the surface features varies across the touch-sensitive surface.

Some embodiments relate to an optical touch-sensitive device that includes an optical waveguide, emitters and detectors, and a blocking layer. The optical waveguide has a touch-sensitive surface on which touch events can be detected. The emitter may generate a light beam that travels through the waveguide via total internal reflection to the detector. A touch on the touch sensitive surface may disturb the light beam. The touch sensitive device determines a touch event based on the disturbed light beam. The barrier layer is over the touch-sensitive surface. The refractive index of the barrier layer is less than the refractive index of the optical waveguide. The thickness of the blocking layer is less than the depth of the evanescent field of the optical beam. The emitters and detectors may be arranged along the periphery of the touch-sensitive surface. In some embodiments, the optical beams are coupled to and from the touch-sensitive surface by couplers such that the emitters and detectors are not arranged along the periphery (e.g., the emitters are below the touch-sensitive surface).

In some embodiments, the thickness of the blocking layer is varied such that a portion of the blocking layer has a thickness less than the evanescent field depth and another portion has a thickness greater than the evanescent field depth.

In some embodiments, the optical touch-sensitive device further comprises surface features on the touch-sensitive surface that reduce touch object friction relative to an absence of the surface features.

In some embodiments, the surface feature is part of the barrier layer and is defined by the shape of the barrier layer.

In some embodiments, the barrier layer comprises a porous material or embedded microspheres.

In some embodiments, a portion of the surface feature comprises a rounded surface. In some embodiments, a portion of the surface features comprise surface features that are at least one of hemispherical bumps or rounded bumps.

In some embodiments, the optical touch-sensitive device further comprises an anti-reflective layer on the barrier layer. In some embodiments, the combined thickness of the barrier layer and the antireflective layer is less than the evanescent field depth.

Drawings

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is an illustration of an optical touch-sensitive device according to one embodiment.

FIG. 2 is a flow diagram for determining a location of a touch event according to one embodiment.

Fig. 3A-3B illustrate frustrated TIR mechanisms for touch interaction with an optical beam in accordance with some embodiments.

FIG. 3C illustrates a touch interaction with beam enhanced transmission according to one embodiment.

Fig. 4A-4C are top views of differently shaped beam footprints (footprints) according to some embodiments.

Fig. 5A-5B are top views illustrating active area coverage of emitters and detectors according to some embodiments.

Fig. 6A is a cross-sectional view illustrating undulations in a top surface of a waveguide structure according to one embodiment.

Figure 6B is a cross-sectional view illustrating a stepped surface feature in a top surface of a waveguide structure according to one embodiment.

Figure 6C is a cross-sectional view illustrating a binary surface feature in a top surface of a waveguide structure, according to one embodiment.

Figure 6D is a cross-sectional view illustrating a segmented planar feature in a top surface of a waveguide structure according to one embodiment.

Fig. 7A-7H are top views of different types of binary surface features according to some embodiments.

FIG. 8 is a side view of an optical touch-sensitive device with a side-coupler, a waveguide structure with tactile surface features, and a blocking layer according to an embodiment.

FIG. 9 is a side view of an optical touch-sensitive device with an edge coupler, a waveguide structure with tactile surface features, and a blocking layer according to an embodiment.

Fig. 10A-10I are cross-sectional views illustrating surface features of a waveguide structure according to some embodiments.

Fig. 11 is a cross-sectional view illustrating a barrier layer on a waveguide according to an embodiment.

The figures depict various embodiments for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles described herein.

Detailed Description

I. Introduction to the design reside in

A. Overview of the device

FIG. 1 is an illustration of an optical touch-sensitive device 100 according to one embodiment. Optical touch-sensitive device 100 includes a controller 110, emitter/detector drive circuitry 120, and a touch-sensitive surface assembly 130. Surface assembly 130 includes a surface 131 on which touch events are to be detected. For convenience, region 131 may sometimes be referred to as an active touch region, touch sensitive surface, or active touch surface, even though the surface itself may be a completely passive structure (such as an optical waveguide). The assembly 130 also includes emitters and detectors arranged along the periphery of the active touch area 131 (although the emitters and detectors may be arranged along only a portion of the periphery, or not arranged along the periphery at all). In this example, there are J emitters labeled Ea-EJ and K detectors labeled D1-DK. The apparatus also includes a touch event processor 140, which may be implemented as part of the controller 110 or separately as shown in FIG. 1. The standardized API may be used to communicate with the touch event processor 140, such as between the touch event processor 140 and the controller 110, or between the touch event processor 140 and other devices connected to the touch event processor.

The emitter/detector drive circuit 120 serves as an interface between the controller 110 and the emitter Ej and the detector Dk. The emitter produces a "beam" of light that is received by the detector. Preferably, light generated by one emitter is received by more than one detector, and each detector receives light from more than one emitter. For convenience, "beam" will refer to light from one emitter to one detector, even though it may be part of a large fan of light reaching many detectors, rather than a single beam. The beam from emitter Ej to detector Dk will be referred to as beam jk. Fig. 1 explicitly labels beams a1, a2, a3, e1, and eK as examples. A touch within the active area 131 will interfere with certain light beams and thus alter the light beams received at the detector Dk. Data regarding these changes is passed to touch event processor 140, which analyzes the data to determine the location(s) (and time (s)) of the touch event on surface 131.

One advantage of the optical approach as shown in FIG. 1 is that the approach is comparable to conventional touch devices that cover the active touch area with sensors such as resistive and capacitive sensorsThe method scales well to larger screen sizes. Since the emitters and detectors are positioned around the periphery, the screen size increases linearly by a factor of N, which means N compared to a conventional touch device ² In contrast, the periphery is also extended by a factor of N.

These touch sensitive devices may be used in a variety of applications. Touch sensitive displays are one type of application. Such applications include displays for tablet computers, notebook computers, desktop computers, gaming consoles, smart phones, and other types of computing devices. Such applications also include displays for televisions, digital signage, public information, whiteboards, electronic readers, and other types of displays of superior resolution. However, these touch sensitive devices may also be used on smaller or lower resolution displays: simpler area phones, user controls (copier controls, printer controls, appliance controls, etc.). These touch sensitive devices may also be used in applications other than displays. The "surface" on which the touch is detected may be a passive element, such as a printed image or just some hard surface. The application may act as a user interface, similar to a trackball or mouse.

B. Summary of the procedures

FIG. 2 is a flow diagram for determining characteristics (e.g., location) of a touch event according to one embodiment. The apparatus of fig. 1 will be used to illustrate this process. The process 200 is broadly divided into two phases, which will be referred to as a physical phase 210 and a processing phase 220. Conceptually, the boundary between the two phases is a set of transmission coefficients Tjk.

The transmission coefficient Tjk is the transmittance of the beam from emitter j to detector k compared to the beam transmitted during a touch event without interaction with the beam. The use of this particular metric is merely an example. Other metrics may be used. In particular, since we are most interested in breaking the beam, an inverse metric such as (1-Tjk) may be used since the inverse metric is typically 0. Other examples include measurements of absorption, attenuation, reflection or scattering. In addition, although fig. 2 is explained using Tjk as the boundary between physical phase 210 and processing phase 220, Tjk need not be explicitly calculated. Nor does it require an explicit division between physical stage 210 and processing stage 220. Also note that Tjk may have a temporal aspect.

Returning to FIG. 2, physical phase 210 is a process that determines Tjk from the physical settings. Processing stage 220 determines a touch event from Tjk. The model shown in FIG. 2 is conceptually useful because it separates the physical setup and underlying physical mechanisms from subsequent processing to some extent.

For example, the physical phase 210 produces the transmission coefficient Tjk. Many different physical designs for the touch-sensitive surface assembly 130 are possible, and depending on the end application, different design tradeoffs will be considered. For example, the emitter and detector may be narrower or wider, various wavelengths, various powers, coherent or incoherent, and so forth. As another example, different types of multiplexing may be used to allow beams from multiple emitters to be received by each detector.

The inside of block 210 shows one possible implementation of process 210. In this example, the emitter emits (transmit)212 a beam of light to the plurality of detectors. Some of the light beams traveling through the touch-sensitive surface are disturbed by touch events. The detector receives 214 the light beams from the emitters in a multiplexed optical form. The received beams are demultiplexed 216 to distinguish the individual beams jk from each other. The transmission coefficient Tjk of each individual light beam jk is then determined 218.

The processing stage 220 may also be implemented in many different ways. Candidate touch points, line imaging, position interpolation, touch event templates, and multi-pass methods are all examples of techniques that may be used as part of processing stage 220.

Physical setup

The touch sensitive device 100 may be implemented in a number of different ways. The following are some examples of design changes.

A. Electronic device

With respect to the electronic aspects, it is noted that FIG. 1 is exemplary and functional in nature. The functions from the different blocks in fig. 1 may be implemented together in the same component.

B. Touch interaction

Different mechanisms for interacting with the touch of the optical beam may be used. One example is frustrated Total Internal Reflection (TIR). In frustrated TIR, the light beam is confined to the optical waveguide by total internal reflection, and touch interactions somehow interfere with total internal reflection. Fig. 3A-3B illustrate frustrated TIR mechanisms for touch interaction with an optical beam. In fig. 3A, a light beam, shown in dashed lines, travels from emitter E to detector D through optically transparent planar waveguide 302. The light beam is confined to the waveguide 302 by total internal reflection. The waveguide may be constructed of, for example, plastic or glass. In fig. 3B, an object 304 (such as a finger or stylus) in contact with transparent waveguide 302 has a higher refractive index than the air that typically surrounds the waveguide. Above the contact area, the increase in refractive index caused by the object disturbs the total internal reflection of the light beam within the waveguide. The interference of total internal reflection increases the light leakage from the waveguide, thereby attenuating any light beam passing through the contact region. Correspondingly, removal of the object 304 will stop attenuation of the light beam passing therethrough. The attenuation of the beam passing through the touch point will result in a power reduction at the detector, from which a reduced transmission coefficient Tjk can be calculated.

Note that in addition to the presence of a touch, some type of touch interaction may be used to measure contact pressure or touch velocity. Note also that some touch mechanisms may enhance transmission instead of or in addition to reducing transmission. FIG. 3C illustrates enhanced transmission of touch interaction with an optical beam. Fig. 3C is a top view. Emitter Ea typically produces a beam of light that is received by detector D1. When there is no touch interaction, Ta1 is 1 and Ta2 is 0. However, the touch interaction 304 blocks the light beam from reaching detector D1 and scatters some of the blocked light to detector D2. Thus, the detector D2 receives more light from the emitter Ea than usual. Thus, when there is a touch event 304, Ta1 decreases and Ta2 increases.

For convenience, touch interaction mechanisms may sometimes be classified as binary or analog. A binary interaction is an interaction that has essentially two possible responses as a function of touch. Examples include non-blocking and full blocking, or non-blocking and 10% + attenuating, or unsuppressed and frustrated TIR. Analog interaction is an interaction that has a "gray" response to touch: the non-occlusion crosses the partial occlusion to the gradual occlusion.

C. Emitter, detector and coupler

Each emitter emits light to a plurality of detectors. Typically, each emitter outputs light to more than one detector simultaneously. Similarly, each detector may receive light from a plurality of different emitters. The light beam may be visible, Infrared (IR) and/or Ultraviolet (UV). The term "light" is intended to include all such wavelengths, and terms such as "optical" should be construed accordingly.

Examples of light sources for emitters include Light Emitting Diodes (LEDs) and semiconductor lasers. IR sources may also be used. The modulation of the light beam may be external or internal. Examples of sensor elements for detectors include charge coupled devices, photodiodes, photoresistors, phototransistors, and nonlinear all-optical detectors.

The emitter and detector may comprise optics and/or electronics in addition to the primary light source, the sensor element. For example, the emitter and detector may be combined or attached to a lens to spread and/or collimate the emitted or incident light. In addition, one or more optical coupling components (couplers) of varying designs may be used for coupling the emitter and detector to the waveguide. The waveguide, coupler and any intervening optical elements have similar refractive indices that are higher than the refractive index of air to facilitate TIR throughout the optical path of each beam. These elements may be physically coupled together using an adhesive having a similar index of refraction as the waveguide and coupler. Alternatively, instead of adhesive, there may be air gaps between the components at various points along the optical path.

D. Light beam path

Another aspect of the touch sensitive system is the shape and position of the light beam and the light beam path. In fig. 1-2, the light beams are shown as lines. These lines should be interpreted as representing light beams, but the light beams themselves may be of different shapes and footprints. Fig. 4A to 4C are top views of light beam occupying regions of different shapes. In fig. 4A, a point emitter and point detector produce a narrow "pencil" beam with a linear footprint. In fig. 4B, a point emitter and a wide detector (or vice versa) produce a fan-shaped beam with a triangular footprint. In FIG. 4C, the wide emitter and wide detector produce a "rectangular" beam whose rectangular footprint width is fairly constant. Depending on the width of the footprint, the transmission coefficient Tjk behaves as a binary or analog quantity. A transmission coefficient is binary if it transitions rather abruptly from one extreme value to another as the touch point passes through the beam. For example, if the beam is very narrow, the beam will be completely blocked or not blocked at all. If the beam is wide, the beam may be partially blocked as the touch point passes through the beam, resulting in a more simulated behavior.

The beam may have a footprint in both the lateral (horizontal) direction as well as the vertical direction. The lateral footprint of the beam may be the same or different from the horizontal footprint of the beam.

The direction and spread of light emitted from the emitter and received by the detector may be different from the spread or angle of the beam footprint intended to cover the active area 131. To shape the beam to achieve the desired footprint, lenses may be attached to the emitter and detector. For example, point emitters and point detectors may be used in conjunction with lenses to spread the beam in horizontal or vertical directions.

Fig. 5A to 5B are top views showing coverage of the active areas of the emitter and the detector. As described above, the emitter and the detector are arranged along the periphery of the active area. All emitters may be arranged on both sides of the active area, e.g. on two adjacent vertical sides as shown in fig. 5A. Similarly, all detectors may be arranged on the other two sides of the active area. Alternatively, the emitters and detectors may be mixed or interleaved according to a pattern as shown in FIG. 5B. The pattern may be one emitter between each detector, or another more complex arrangement.

In most implementations, each emitter and each detector will support multiple beam paths, although there may be no beam from each emitter to each detector. The sum of the footprints of all beams from one emitter (or to one detector) will be referred to as the coverage area of that emitter (or detector). The coverage areas of all emitters (or detectors) can be aggregated to obtain the overall coverage of the system.

Different quantities can be used to describe the footprint of the individual beams: spatial extent (i.e., width), angular extent (i.e., radiation angle of the emitter, reception angle of the detector), and footprint shape. The individual beam paths from one emitter to one detector may be described by the width of the emitter, the width of the detector, and/or the angle and shape defining the beam path between the emitter and the detector. The coverage area of an emitter may be described by the width of the emitter, the sum width of the associated detectors, and/or the angle and shape that defines the sum of the beam paths from the emitter. Note that the individual footprints may overlap. The ratio of (sum of footprint of the emitters)/(coverage of the emitters) is a measure of the amount of overlap.

The total coverage area of all emitters should cover the entire active area 131. However, not all points within the active area 131 will be covered equally. Some points may be traversed by many beam paths while other points are traversed by much fewer beam paths. The distribution of the beam paths over the active area 131 can be characterized by counting the number of beam paths that traverse different (x, y) points within the active area. The orientation of the beam path is another aspect of the distribution. The (x, y) points resulting from three beam paths all extending in substantially the same direction are typically less distributed than the points traversed by three beam paths all extending at an angle of 60 degrees from each other.

The concepts described above for the emitter are also applicable to the detector. The footprint of the detector is the sum of all the footprints of the light beam received by the detector.

E. Multiplexing

Since multiple emitters emit multiple beams to multiple detectors, and since the behavior of individual beams is generally desired, multiplexing/demultiplexing schemes are used. For example, each detector typically outputs a single electrical signal indicative of the intensity of incident light, regardless of whether the light is from one beam produced by one emitter or many beams produced by many emitters. However, the transmittance Tjk is a characteristic of the individual light beam jk.

Different types of multiplexing may be used. Depending on the multiplexing scheme used, the transmission characteristics of the light beam (including its content and when it is transmitted) may vary. Thus, the selection of the multiplexing scheme may affect both the physical construction of the optical touch-sensitive device and its operation. Examples of multiplexing include code division multiplexing, frequency division multiplexing, time division multiplexing. Other multiplexing techniques commonly used with optical systems include wavelength division multiplexing, polarization multiplexing, spatial multiplexing, and angular multiplexing. Electronic modulation schemes (such as PSK, QAM and OFDM) may also be applied to distinguish the different beams. Several multiplexing techniques may also be used together.

Stage of treatment

In processing stage 220 of FIG. 2, the transmission coefficient Tjk is used to determine the location of the touch point. Different methods and techniques may be used, including candidate touch points, line imaging, position interpolation, touch event templates, multi-pass processing, and beam weighting.

Waveguide structure

A. Tactile surface features

The active area of the optical touch-sensitive device 100 may include an optical waveguide structure. The waveguide structure may be rigid or flexible. The top surface of the waveguide structure (also referred to as the touch-sensitive surface) includes tactile surface features that change the surface topography from a continuous plane to small (e.g., sub-millimeter) regions of different heights. As described further below, these regions may be steps (also referred to as binary features or flat lands), rounded bumps, or any other suitable shape. Alternatively, the waveguide may have a complex undulating surface. For example, the surface may have a random or pseudo-random height profile. The user may feel the tactile surface features directly as their finger moves across the surface, or the user may feel the tactile surface features indirectly (e.g., as a stylus moves across the surface). The surface features may enhance user interaction by reducing friction between a touching object (e.g., a finger or stylus) and the touch surface of the waveguide structure. The surface features may also give the user some feedback about the user's motion across the surface.

In some cases, a particular feature may mark a particular location on the surface, such as an edge or corner or center of the active area. The haptic feedback may then provide information to the user about their location on the surface.

Human fingers typically cannot reliably detect surface features less than about 10nm in height. In contrast, surfaces with features having a height greater than 100 μm are generally considered to be very rough. Thus, in various embodiments, the height of the strategic surface features is in a range between 10nm and 100 μm.

Fig. 6A-6D illustrate examples of waveguide structures having different types of tactile surface features. Fig. 6A is a cross-sectional view of a waveguide structure 600 having a contoured top surface 602. Because the undulations are discontinuous, the top surface 602 has a continuously varying height. The local relief may be characterized by various parameters, such as local gradient, local curvature, and local tilt angle (i.e., angle relative to the flat bottom surface). The undulating top surface may also be characterized by various parameters, including quantities based on local parameters. Examples include maximum statistics, mean statistics, and other statistics (e.g., standard deviation). Thus, the undulating top surface may be characterized by the maximum gradient or the mean and standard deviation of the gradient. The height difference 609 (maximum height variation) between the highest and lowest points is another parameter characterizing the surface.

Conversely, when designing the top surface 602, certain constraints may be placed on these quantities. The light beam travels through the waveguide structure 600 using TIR. That is, a beam that strikes the top or bottom surface at an angle greater than the critical angle will reflect off that surface. If the top and bottom surfaces are parallel, the beam will undergo TIR indefinitely (theoretically). However, the undulations 602 cause the top surface not always to be parallel to the bottom surface.

This results in a reduced TIR efficiency compared to a waveguide where the top and bottom surfaces are parallel. First, the top surface may cause more scattering, particularly depending on the configuration of the top surface 602. Second, local tilting of the top surface may cause the light beam to strike at an angle less than the critical angle, thus losing TIR, or to reflect at an angle that will subsequently lose TIR.

Third, the undulations can reduce the amount of contact between the object 604 and the waveguide structure 600. Touch events on the top surface are detected by frustrated TIR. That is, evanescent waves from TIR in the waveguide structure are disturbed by the contacting object. This frustrated TIR occurs even when the contacting object is slightly separated from the waveguide structure 600, but increasing the spacing will reduce the effect. For example, as shown in fig. 6A, when the finger 604 touches a local peak 606 of the top surface 602, this prevents the finger from contacting other adjacent points on the top surface 602. In this example, the maximum separation distance 608 is from the finger 604 to the partial slot. The distance 608 is preferably small enough so that the finger 604 is still within the evanescent field so that the finger 604 will still interfere with the light beam propagating in the waveguide structure 600.

Fig. 6B is a cross-sectional view of a waveguide structure 610 in which a top surface 612 has stepped surface features. The surface features are stepped because the step heights of the surface features vary discretely. In this example, the steps have many different heights, and these heights may even have some randomness element to their height, although in other designs the steps may have two, three, or another limited number of different heights. For this type of surface, quantities such as gradients and curvatures are less useful. Instead, useful parameters include step height (height difference between adjacent steps, such as 614) and maximum height variation 619. In fig. 6C, the top surface 622 is a binary surface, meaning that it is composed of two steps of different heights. For a binary surface, the step height and maximum height variation are the same 629.

Stepped surface features also lead to reduced TIR efficiency, but for different reasons. For example, the slope of the stepped surface does not change. The top surface is always piecewise parallel to the bottom surface. However, the vertical walls between the steps may cause vignetting or scattering, but also direct losses by causing light incident on the vertical surfaces to be refracted out of the waveguide and into the air. Inclined surfaces (rather than vertical surfaces) generally result in easier to clean surfaces because there are no steep side grooves to retain dirt, oil, etc.

Fig. 6D is a cross-sectional view of a waveguide structure 630, where the top surface 622 is piecewise planar. Other variations will be apparent, such as a top surface having a combination of the continuously varying features of fig. 6A-6D, stepped features, and segmented flat features.

Fig. 6A-6D illustrate different types of height variations (variations in the z-axis) for tactile surface features. The tactile surface features may also have different lateral designs (in the x, y plane). Fig. 7A to 7F are top views showing different types of lateral designs for binary surfaces. In these figures, the hatched area represents one step height, and the white area represents the other step height. Binary surfaces are used because it is easiest to illustrate, but these concepts can be extended to other types of surfaces.

In some embodiments, the tactile surface features are non-periodically spaced in the lateral direction on the top surface and may have some element of randomness to the spacing. In configurations where the touch-sensitive surface is part of a touch-sensitive display, the periodic pattern may cause unwanted interference effects on light generated by the display pixel matrix (which may be located below the waveguide and produce an image or other display element). For example, interactions between the surface feature pattern and light generated by the pixel matrix may cause undesirable interference. Non-periodic surface features can reduce such adverse interactions and can also provide antiglare functionality by dispersing reflected energy over a range of angles.

In fig. 7A and 7B, the transverse pattern has variations mainly in one direction. In fig. 7A, relatively narrow stripes are placed to produce a variation in the horizontal direction. Some randomness may be added by non-periodically placing the stripes, changing the width and/or shape of the stripes (or the middle white area), and/or tilting the stripes at slightly different angles. In fig. 7B, the stripe pattern also contains some information about the location on the surface. The frequency of the stripes is higher towards the center of the active area. In another variation, the duty cycle of the stripes may vary depending on the location on the surface. The percentage of the area covered by the hatched stripes towards the center of the surface may be higher, while the percentage of the area towards the edges is lower. Different directions of change are also possible. The change may occur from left to right across the touch sensitive surface or from top to bottom across the touch sensitive surface. Other directivities are also possible (e.g., bottom left to top right).

Fig. 7C to 7F show examples of two-dimensional patterns. Fig. 7C is based roughly on two intersecting one-dimensional patterns. Fig. 7D is the scattering of circular islands. The islands do not lie on a regular grid, but their size and spacing generally increases moving from the center to the edge of the active area. Fig. 7E is also a scattering of islands, but rectangular in shape and randomly varying in size and orientation. Fig. 7F is a combination of concepts. The basic pattern is similar to fig. 7D, but with long rectangular mark edges and a central square island mark the center.

Fig. 7G to 7H show examples based on radial coordinates. In fig. 7G, the surface features are approximately centered about a common center point. In fig. 7H, the surface features diverge generally radially from a common center point.

Patterns based on similar concepts may also be applied to non-binary surfaces. In some implementations, the manufacturing process can impart directionality to the surface features. Examples of manufacturing processes include hot stamping (particularly for polymer waveguides), molding, nanolithography, machining, and etching (glass waveguides can be processed in this manner). The transverse pattern can also be characterized by the following parameters: size (width, height, diameter), area, pitch, pattern frequency, percentage coverage, etc.

Because undulations or step changes in the top surface height may create locations for light traveling in the waveguide via TIR to impinge on the top surface of the waveguide at angles greater than the critical angle of the waveguide, changes in the top surface of the waveguide structure generally disfavor TIR. To reduce the effect of variations in the top surface of the waveguide, the height variations of the top surface are preferably large enough to be detected by human touch, but otherwise the height variations are relatively small. For example, if the top surface height is undulating, the rate of change of the surface angle is limited to within a threshold rate of change. Alternatively, if the top surface height is changed in discrete steps, the step change in height is limited to within a threshold step height. Both of which typically depend on the overall optical budget. In some embodiments, the loss from a waveguide structure with tactile surface features will preferably not be more than ten times the loss from a flat waveguide (without tactile surface features), and more preferably will not be more than four times this loss.

The amount of light loss caused by surface features is related to the height of the surface features (also referred to as the surface modulation depth). All other things being equal, increasing the height of the surface features generally results in a large amount of optical loss. Thus, a set of surface features (e.g., a binary surface) may be designed to be high enough to provide a desired haptic effect, but low enough so that a detector detects a sufficient amount of light (e.g., a touch event may be discernable despite some loss of light by the surface features).

When the height of the surface features is sufficiently small, the amount of optical loss can be reduced. Surface features having a height less than the wavelength of light propagating in the waveguide generally result in little or no optical loss relative to a planar waveguide surface. For example, surface features having a height less than half the wavelength of light have no substantial effect on propagation through the waveguide. High quality optical mirrors may have a surface flatness of λ/4 (where λ is the wavelength), so it is clear that this order of magnitude of surface height variation is consistent with low reflection losses. While there is no well-defined boundary height above which variations in surface height will strongly affect reflected light levels, it is generally believed that variations of λ/2 or less will not have a significant effect on specular reflection. Thus, light in the near Infrared (IR) range therein (having

1000nm wavelength), the surface features may have a height between 10nm and 500nm without causing an amount of light available for touch detectionAnd is significantly degraded. Note that, as previously mentioned, surface features having these heights are within a range perceptible to a human finger.

The amount of surface features on the surface also affects the amount of light leakage. Generally, increasing the number of surface features increases the total amount of optical loss. Thus, the surface features may be designed to cover enough of the waveguide to provide a tactile feel to the user, but not enough to keep the amount of light leakage caused by the surface features within an acceptable range. For example, discrete surface features are printed on the waveguide such that the cumulative surface area covered by the features is less than 5% of the total surface area. The percentage of cumulative surface area covered by the surface features may vary depending on the implementation and desired performance. Preferably, the contact area for touch is not reduced to less than half of the contact area with a flat waveguide (without tactile surface features). Note that if the spaces between surface features are large (e.g., hundreds of microns), the compliant nature of skin and many suitable pen materials may cause them to make contact with many of the surface areas between the touch-sensitive surface features.

As previously mentioned, the shape of the surface features may also affect the amount of light leakage. Shapes with defined angled edges (such as triangles and squares) may leak more light than shapes with soft edges or rounded surfaces (such as ramps and semi-circles). Because the angle at which light strikes the top surface can affect the TIR of the light beam, in some implementations, surface features with edges parallel to the bottom surface of the waveguide can be selected, while features with edges not parallel to the bottom surface are not. Features with gently sloping surfaces may reduce light leakage compared to features with perpendicular surfaces. Thus, in some implementations, features with beveled edges, which may be more preferred than edges, do not greatly change the elevation angle of light propagating in the waveguide.

In one embodiment, the threshold rate of change of the undulation and/or the threshold step height is less than the distance that the evanescent wave extends beyond the top surface so that the contacting object remains interacting with the evanescent wave. This distance is typically in the order of the wavelength of the light. For undulating surfaces, the threshold rate of change of the top surface may be selected such that the height difference between the peaks and valleys of any given undulation is within an order of magnitude of the wavelength of light. For a stepped surface, the threshold step height may be selected to be within an order of magnitude of the wavelength of the light, and more preferably less than the wavelength or less than half the wavelength. Thus, as previously mentioned, the features may have little or no effect on TIR of the propagating light because the features are too small to interact with the light. If the touch interaction is somewhat compliant, then greater surface feature heights can be accommodated because these features compress upon contact, thereby reducing their effective feature height.

With respect to the lateral pattern, the pitch of the lateral pattern (e.g., the lateral distance between peaks of the undulations or the lateral distance between steps) may be greater than the wavelength of light propagating in the waveguide by TIR. In various embodiments, the lateral spacing between tactile surface features is on the order of the size of a typical human finger. In some embodiments, the lateral spacing between tactile surface features is on the order of the size of a typical fingerprint ridge, which is typically in the range of 200 μm to 850 μm. In some embodiments, the spacing between features is no less than the size of a typical human finger ridge. However, the pitch is also small enough to produce the desired haptic effect. For example, the average lateral size of the tactile surface features may be less than the size of a typical human finger but greater than the wavelength of the light beam. If there is a display module underneath the waveguide structure (as shown in fig. 8 and 9), the lateral size of the tactile surface features may also depend on the pixel size of the display module. For large display modules, the tactile surface features may be significantly smaller (e.g., 10% or less) than the area of the display pixels, thereby reducing distortion of the displayed image. Typical pixel sizes on one side range from about 50 μm to about 500 μm.

10A-10F illustrate additional examples of waveguide structures having different types of tactile surface features according to some embodiments. The surface features may be protrusions 1002 or recesses 1022. The protrusions 1002 and recesses 1022 may be characterized by, among other properties, shape, height, width, and spacing. Although each of these characteristics is constant for each of the waveguides in fig. 10A-10F, these characteristics may vary across the waveguide surface. For example, the spacing between the protrusions 1002 or recesses 1022 may vary depending on the distance from the edge of the waveguide. As other examples, the shape, height, or width of the surface features may vary across the waveguide surface. Alternatively, the protrusions 1002 or recesses 1022 can be randomly or pseudo-randomly spaced (e.g., surface features designed as surfaces on a roller imparted with a film (e.g., waveguide) thereon).

The surface features may be part of the waveguide (e.g., as seen in fig. 10A) or placed on top of the waveguide surface (e.g., as seen in fig. 10B). For example, the protrusions 1002 may be printed on the surface of the waveguide. In another example, the surface feature is a portion of a thin film placed on the surface of the waveguide. The creation of a patterned surface can be accomplished in a number of ways, such as embossing, hot embossing, UV nanolithography, photolithography, etching (e.g., reactive ion etching), and selective deposition methods (such as inkjet printing and spraying).

Fig. 10A is a cross-sectional view of a waveguide structure 1000 having triangular protrusions 1002 (e.g., three-dimensional triangular prisms or pyramids). As previously discussed, the shapes of the protrusions 1002 may be different than those seen in fig. 10A. For example, the protrusions 1002 may be rectangular (e.g., a three-dimensional rectangular prism) or semi-circular (e.g., a three-dimensional hemispherical or circular bump). Fig. 10B is a cross-sectional view of a waveguide structure 1010 having protrusions 1002, the protrusions 1002 having been added to the top surface of the waveguide (e.g., via printing). Fig. 10C is a cross-sectional view of waveguide structure 1020 with recesses 1022. Fig. 10I is a cross-sectional view of a waveguide structure 1010 having a semicircular protrusion 1002.

In some embodiments, the surface features are made of a low refractive index material. Thus, sensing light propagating in the waveguide reflects off the boundary between the waveguide and the low index material (e.g., via TIR) such that there is little or no optical loss due to the surface features. A low index material is a material having a refractive index that is less than the refractive index of the waveguide, and typically significantly less than the refractive index of the waveguide. For example, the decrease in refractive index is sufficient to support TIR at any desired elevation (relative to the surface) of light sensed in the waveguide. For example, applying a UV-curable liquid with a refractive index of 1.36 to a glass substrate with a refractive index of 1.50 can support TIR with an elevation angle of up to 25 degrees (angle of incidence greater than 65 degrees).

For example, typical waveguides are made of glass (n ═ 1.5) or poly (methyl methacrylate) (PMMA) (n ═ 1.49). In this context, an example low index material is an aerogel (a porous material that is primarily air), or a material (e.g., a polymer) with air-filling and embedded microspheres that are much smaller than the wavelength of light in the waveguide (e.g., see material 1042 in fig. 10F). In both examples, the effective refractive index is a mixture of the refractive index of a solid material (e.g., n ═ 1.41 or higher) and the refractive index of air (n ═ 1.00003). Thus, the effective refractive index of these materials can be significantly lower than the refractive index of the waveguide. Another example of a low refractive index material includes a solid material having fluorine. These fluorine materials may have a sufficiently low index of refraction to induce TIR at the boundary with the waveguide. For example Polytetrafluoroethylene (PTFE) has a refractive index of 1.35. Other example low index materials include silicone (e.g., n ═ 1.4 to 1.46).

In one embodiment, the waveguide comprises 10 μm high rounded bumps of low refractive index material that cause friction reduction by lifting a finger a short distance from the waveguide surface. The low refractive index of the material causes the sensing light to reflect at the boundary with the waveguide via TIR, so little or no sensing light is lost by the bumps. For example, the bumps are formed by depositing a low refractive index material (e.g., a low refractive index liquid that is subsequently cured by exposure to ultraviolet light) by inkjet printing.

Because light propagating in the waveguide reflects off the boundary between the waveguide and the low-index material via TIR, the waveguide may be insensitive to touch events at the surface feature locations (e.g., if the height of the surface features is 2 μm or greater). However, this is not a problem if the cumulative surface area of the features is sufficiently small relative to the total surface area of the touch surface (e.g., if the spacing between the features is significantly larger than the size of the features). Assuming this is the case, the device can still detect touch events at the desired resolution. For example, 200 μm spaced surface features having square footprints with 20 μm sides cover only 1% of the total area of the touch surface. The effect of surface features on touch sensitivity may be further mitigated if the height of the surface features is less than the depth of the evanescent field of light propagating through the waveguide sensing the touch event. In this case, the sensed light is still affected by the touch on the surface feature because the touch object (e.g., finger) interferes with the evanescent field, resulting in a loss of optical energy. Typically, features having a thickness of 2 μm or more render the waveguide insensitive to touch, whereas if the thickness of the feature is less than 2 μm, a touch may be detected.

Fig. 10D is a cross-sectional view of a waveguide structure 1030 having a beveled protrusion 1002. As discussed above, because the beveled protrusions 1002 have sloped surfaces, they can reduce the amount of light leakage from the waveguide 1030 as compared to shapes with sharper edges (such as squares). An additional advantage of the inclined surface compared to a feature with a vertical surface is that the amount of oil and contaminants trapped on the surface can be reduced. They may also make the surface easier to clean. In some embodiments, the beveled protrusion 1002 has a width of 45 μm and/or a height of 10 μm to 20 μm.

Fig. 10E and 10F are cross-sectional views of a waveguide structure 1040 with a filler material 1042 between the protrusions 1002. A filler material 1042 may be placed between the protrusions 1002 (or in the recesses 1022) to create a surface that reduces glare from the waveguide. For example, the filler material 1042 in fig. 10F comprises microspheres, which can increase the surface roughness of the exposed surface of the filler material. The microspheres may be small voids in a gas (e.g., air) -filled filler material with a radius on the order of (or less than) the wavelength of visible light. Thus, the refractive index of the entire filled region may be somewhere between the refractive index of the filler material and the refractive index of the gas within the microsphere.

The fill material 1042 can be formed by the following example process. A curable liquid is applied to the molding surface and then treated to ensure that no liquid is present on top of the protrusions 1002 (or at least thinner thereon) (e.g., by passing the structured surface under a roller on a roll-to-roll process). The liquid is then exposed to a curing agent (such as UV light) to cure the filler material 1042. Some shrinkage will typically occur during curing and this facilitates the protrusion 1002 standing above the cured filler material 1042. Thereafter, an optional roughening process may be applied, such as etching using an agent that only erodes the cured fill material 1042 and does not erode the

substrate

1040 or 1050. Etching typically leaves a rough surface. If the fill material 1042 includes microspheres, the etching can partially expose the microspheres, which also increases surface roughness. The process of creating a roughened surface on the filler material 1042 is advantageous because the roughening process makes the surface a diffuse reflector of incident visible light without having a diffusing effect on the sensing light in the waveguide.

B. Multi-part waveguide structure

In some implementations, the waveguide structure is constructed from multiple portions. In one approach, the waveguide structure includes a planar waveguide having planar featureless top surfaces (i.e., planar parallel top and bottom surfaces) with a tactile coating on the top surface of the planar waveguide. The tactile coating may have an index of refraction matching the planar waveguide. In some embodiments, the tactile coating is a tactile film (e.g., an optically transparent film) having tactile surface features. The haptic coating can be fabricated using the methods described above (or suitable alternatives) and then attached to the flat featureless top surface of the waveguide structure. For example, the light transmissive film may be applied to the planar waveguide as a solid layer. Alternatively, it may be applied as a liquid which then cures into a layer having surface features. In some implementations, the tactile coating is applied as a separate layer around the periphery of the waveguide structure. The tactile coating may include a printed material, such as a printed graphic border, colored region, or blocking layer.

FIG. 8 is a side view of an optical touch-sensitive device 800 with a side coupler 802, and a waveguide structure 804 and a blocking layer 812. The waveguide structure 804 includes a planar waveguide 810 having a flat featureless top surface and also includes a tactile coating 814. In the example of fig. 8, a blocking layer 812 is interposed between the top surface of the planar waveguide 810 and the underside of the tactile coating 814. In other embodiments, the blocking layer 812 may be located on top of the tactile coating 814, rather than underneath it. Alternatively, the tactile coating 814 may be absent in this region, with the blocking layer 812 located directly on top of the planar waveguide 810.

The waveguide structure 804 is optically coupled to an emitter and detector 806 by an optical coupler assembly (or coupler) 802. The detector and emitter 806 are oriented to receive and emit light in directions parallel to the top and bottom surfaces of the waveguide 804, respectively, such that the light exits the emitter and enters the detector in a lateral direction substantially the same as the propagation direction within the waveguide 804. In fig. 8, coupler 802 is side-coupled to the bottom surface of waveguide structure 804. The optical touch-sensitive device 800 may also include a Printed Circuit Board (PCB)808 and a display module 816. In this example, both the waveguide 810 and the coating 814 extend beyond the active area of the touch-sensitive surface.

The blocking layer 812 blocks ambient light 830 from reaching the emitter/detector 806. The transition from the tactile coating 814 over the active area to the material over the blocking layer 812 is preferably horizontal so that the tactile boundary cannot be felt. The coating 814 on top of the blocking layer 812 may be smooth rather than intentionally tactile. In one implementation, the blocking layer 812 is opaque to both visible light and IR light beams. For example, the blocking layer 812 may be a reflective layer to reflect away ambient light 830. Alternatively, the blocking layer 812 may be an absorption layer that absorbs external light. The tactile coating 814 allows the blocking layer 812 to move to the top surface of the waveguide 810 without introducing tactile edges due to the blocking layer. This in turn allows greater design freedom in the detector, emitter and coupler.

FIG. 9 is a side view of an optical touch-sensitive device with an edge coupler 902 and a waveguide structure 804 and a blocking layer 912. In contrast to fig. 8, the detector and emitter 806 are oriented to receive and emit light in directions perpendicular to the top and bottom surfaces of the waveguide 810, respectively, such that the light exits the emitter in a direction rotated 90 degrees relative to the propagation direction in the waveguide structure 804. The coupler 902 is edge coupled to a side edge surface of the waveguide structure 804. In this example, the blocking layer 912 is located on top of the coating 814, rather than between the coating 814 and the waveguide 810 as shown in fig. 8.

C. Anti-glare surface features

As previously described, the tactile surface features may improve the user interaction experience by reducing friction and providing tactile feedback. The tactile surface features may also reduce glare of the touch-sensitive surface by diffusing or scattering light. In other words, the surface features may interfere with the spectral reflection of light on the surface.

To reduce glare, the surface features may have dimensions (e.g., height, width, length, surface area, size, etc.) on the order of the wavelength of visible light incident on the surface. In particular, since visible wavelengths are in the range of about 400nm to 700nm, the size of the surface features may be tens, hundreds, or thousands of nm long. For example, the glare-reducing surface features have a height modulation that may be 300nm to 200 μm. In some embodiments, the wavelength of the sensing light is longer than visible light (e.g., near infrared). Thus, surface features having a size on the order of the visible wavelength can advantageously interfere with the specular reflection of visible light while substantially maintaining the specular reflection at the longer sensing wavelengths.

The surface features may have various surface angles to scatter incident light in different directions. For example, referring to fig. 10B, the slope of the triangle may be different for each protrusion 1002 (or set of protrusions 1002). If the exact geometry of FIG. 10B is used, the result will be three substantially specular reflections (one from the top surface of the waveguide and one corresponding to each side of the triangular surface feature). The rounded bumps also inherently provide a variety of surface angles at which light can be scattered in different directions. The waveguide may include more than one surface feature shape (e.g., triangles, bumps, and bevels). To further reduce glare, surface features may be arranged in a random (or pseudo-random) order on the waveguide. For example, the etching process may form a rough surface with random features that scatter light in various directions.

D. Anti-reflection layer

The waveguide may have an anti-reflection layer to suppress light reflection. The antiglare feature diffuses light incident on the surface, while the antireflective layer reduces or eliminates the amount of light reflected from the surface via interference effects. The antireflective layer typically comprises a low index material (a material having a refractive index less than that of the waveguide). The anti-reflective layer may reduce the touch sensitivity of the waveguide because the touch object is not in direct contact with the waveguide, thereby reducing its effect on TIR. To address this problem, the thickness of the anti-reflection layer may be selected to be less than the evanescent field depth so that a touch event will still reduce the amount of light energy reflected within the waveguide. Additionally or alternatively, the thickness of the anti-reflective layer may vary (including being completely absent in some areas) such that regions of the touch surface are less affected by the anti-reflective layer than other regions. The tactile surface features may be partially or fully made of an anti-reflective material.

In some embodiments, the antireflective layer comprises one or more layers that reduce the amount of change in refractive index at the layer interface. For example, in order to reduce the refractive index change between air (n ═ 1.003) and the waveguide (e.g., n ═ 1.5), a material having n ═ 1.3 is disposed on the waveguide. This reduces the total amount of reflected light and may be referred to as index matching. Preferably, the refractive index of a given layer is the square root of the refractive index of the material below the given layer. For example, if the waveguide has n 1.5, the refractive index of the anti-reflection layer is

Adding material to the waveguide may increase the critical angle for TIR at the waveguide surface. Thus, the angular range over which the sensing light propagates in the waveguide via TIR is reduced. Thus, such approaches involve a tradeoff between reducing reflections from outside the waveguide and flexibility with respect to the angle used for sensing light within the waveguide.

In other embodiments, the anti-reflective layer is an interference coating that reduces reflections by forming reflected beams that are out of phase with each other. Fig. 10G and 10H are cross-sectional views of a waveguide structure 1060 with an anti-reflection layer according to some embodiments. Fig. 10G shows a beam 1064 reflected at the surface of the antireflective layer 1062 and the surface of the waveguide 1060. Due to the thickness of the anti-reflective layer 1062, the reflected beams are out of phase by half a wavelength and thus have destructive interference. Since visible light has a range of wavelengths: (

400nm to 700nm) the anti-reflective layer may have many layers with different refractive indices and thicknesses to produce destructive interference for multiple visible wavelengths (see, e.g., fig. 10H).

Although the tactile surface features, anti-glare surface features, and anti-reflective layers are described in separate sections, the waveguide may include any combination of these components. In embodiments having an antireflective layer, the antireflective layer is typically the outermost layer. As shown in fig. 10H, the waveguide 1060 may include protrusions 1002 (tactile surface features) and an anti-reflective layer 1072. Note that although the protrusions 1002 are covered by the antireflective layer 1072 in fig. 10H, the features are still present on the top surface sufficiently to reduce tactile friction. Further, although embodiments herein are described in the context of detecting touch events on a waveguide, a waveguide is not required. For example, the sensing light can travel over the touch surface (e.g., with surface features) to detect a touch object in contact with (or near) the touch surface, where the touch surface structure provides one or more of a haptic effect, an anti-glare behavior, or an anti-reflection behavior.

E. Application for thin waveguides

As previously described, tactile surface features, anti-glare surface features, and anti-reflective layers can reduce the touch sensitivity of the waveguide, meaning that a touching object attenuates the amount of light energy of the sensed light less than it reflects off the flat waveguide surface. In some cases, it may be advantageous to reduce touch sensitivity, especially for thin waveguides.

In some embodiments, it may be desirable to reduce the thickness of the waveguide (e.g., a reduction in cost, size, and weight). However, as the thickness of the waveguide is reduced, the waveguide may become more susceptible to surface contamination (even for normal and expected amounts of surface contamination). Other factors remain constant and as the thickness of the waveguide decreases, the amount of internal reflection of the sensing light in the waveguide will increase. Specifically, the light beam will reflect off the top surface every 2T/tan θ meters, where T is the waveguide thickness and θ is the elevation angle of the sensing light relative to the waveguide surface. For example, if the elevation angle is 16 ° and the waveguide is 3.2mm thick, the sensed light encounters the top surface every 22.32mm (44.8 reflections occur if the waveguide is 1m wide). However, if the waveguide is 0.4mm thick, the sensing light encounters the top surface every 2.79mm (358 reflections occur if the waveguide is 1m wide). Since the transmission through the waveguide is a composite transmission of each reflection, a large number of reflections may result in lower light transmission even though the loss per reflection is small. When contaminants (such as oil) are deposited on the surface, small losses may occur over a large area of the waveguide surface. For example, each reflection loss of 1% (e.g., caused by contamination), the total transmission is 0.99^44.8 ^ 63.7% for a 3.2mm waveguide, but only 0.99^358 ^ 2.7% for a 0.4mm waveguide. Thus, thinner waveguides are particularly susceptible to contamination.

A low index barrier layer (e.g., a layer including tactile surface features) may address this issue, thereby reducing the impact of contamination loss of the thin waveguide. Fig. 11 shows a cross-section of a waveguide 1104 with a barrier layer 1102. The sensing light beam 1108 propagates through the waveguide via TIR. As shown, the barrier layer 1102 is thinner than the evanescent field depth 1106 (also referred to as the evanescent field height). The blocking layer may have a thickness related to the depth of the evanescent field and be selected such that for any given reflection event, a desired proportion of the sensing light is available for touch detection. For example, if the blocking layer is slightly thinner than the evanescent field depth, only that portion of the evanescent field (e.g., 10% of the total light energy) will be affected by the object touching the waveguide. Similarly, only this proportion of light energy may be lost due to phantom touches caused by surface contamination. The thickness of the barrier layer may be continuous across the touch surface, or may be patterned to vary in thickness (e.g., for additional antiglare or tactile effects). Patterning in this manner provides another way of controlling the ultimate sensitivity of the waveguide.

To give a particular example, in an example waveguide of 5mm thickness, light propagating at an elevation angle of 30 degrees is reflected 100 times from the touch surface over a span of 1.73 meters. If the entire waveguide contact surface is covered with some contaminating material (e.g., finger oil), each reflection will result in a loss of optical energy. Even if the loss is assumed to be 1%, this is still significant because the loss is compounded by the number of reflections over the waveguide span. In practice, with 100 reflections, this corresponds to only 36.6% of the light energy traversing the entire 1.73 meter span. Although this is reasonable for a properly functioning touch sensor, if the waveguide thickness is instead only 0.5mm, the number of reflections will increase to 1,000 for the same 1.73m span. In this case, only 0.0043% of the light traverses the entire span, severely compromising the functionality of the touch sensor.

However, adding a barrier layer on the touch surface of a 0.5mm thick waveguide, such that only 10% of the evanescent energy is available on the touch surface, can reduce the contamination loss per reflection. For example, if the loss is reduced from 1% to 0.1%, 36.8% of the light traverses the entire span of the 0.5mm waveguide, similar to the results obtained for a 5mm waveguide (no barrier). In other words, the reduction in sensitivity caused by the barrier layer reduces losses caused by contamination, making the touch device less sensitive to contamination of the touch surface, which in turn enables the use of thinner waveguides. Additionally or alternatively, the number of touch insensitive tactile surface features on the surface may be increased to reduce the touch sensitivity of the waveguide and similarly reduce the effects of surface contamination. Surface features may be formed below or above the barrier layer. In some embodiments, the surface features are made of the same material as the barrier layer.

V. additional items

The figures depict embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.

Upon reading this disclosure, those skilled in the art will understand additional alternative structural and functional designs through the principles disclosed herein. Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes, and variations apparent to those skilled in the art may be made in the arrangement, operation, and details of the methods and apparatus disclosed herein without departing from the spirit and scope as defined in the appended claims.

Claims

1. An optical touch-sensitive device, comprising:

an optical waveguide having a touch-sensitive surface over which touch events can be detected;

an emitter and a detector, the emitter configured to generate an optical beam that travels through the waveguide via total internal reflection to the detector, wherein a touch on the touch-sensitive surface interferes with the optical beam, the touch-sensitive device determining a touch event based on the interfered optical beam; and

a blocking layer over the touch-sensitive surface, wherein a refractive index of the blocking layer is less than a refractive index of the optical waveguide, and wherein a portion of a thickness of the blocking layer is less than an evanescent field depth of the optical beam.

2. The optical touch-sensitive device of claim 1 wherein the thickness of the blocking layer varies such that the thickness of the portion of the blocking layer is less than the evanescent field depth and the thickness of another portion is greater than the evanescent field depth.

3. The optical touch-sensitive device of claim 1 wherein the optical touch-sensitive device further comprises surface features on the touch-sensitive surface configured to reduce touch object friction relative to an absence of surface features.

4. The optical touch-sensitive device of claim 3 wherein the surface feature is part of the blocking layer and is defined by a shape of the blocking layer.

5. The optical touch-sensitive device of claim 3 wherein the surface feature is part of the waveguide and is defined by a shape of the waveguide.

6. The optical touch-sensitive device of claim 3 wherein the height of the surface features from the touch-sensitive surface is less than the evanescent field depth of the optical beam.

7. The optical touch-sensitive device of claim 3 wherein the surface features are formed of a material that is different from a material of the touch-sensitive surface.

8. The optical touch-sensitive device of claim 3 wherein the surface features have an index of refraction that is less than an index of refraction of a material of the touch-sensitive surface.

9. The optical touch-sensitive device of claim 3 wherein the lateral spacing between surface features is no less than the size of a typical human finger ridge.

10. The optical touch-sensitive device of claim 3 wherein the surface features comprise at least one of fluorine or silicone.