Ultrathin headlight with optical coupling element

Abstract

Embodiments of the present invention provide an ultra-thin headlight that includes an optical coupling element that receives light from a light source and directs the received light into a light guide that is thinner than a height of the light source. A height of the optical coupling element is approximately equal to or greater than a height of the light source, and a refractive index of the optical coupling element matches a refractive index of the light guide. The optical coupling element may be made of the same material as the light guide. The optical coupling element has several reflective surfaces, which may be polished, metallized, or with a dielectric mirror coating.

Description

Technical Field

[0001] The present disclosure generally relates to a front light applicable to various display devices such as digitizers or tablets. In particular, embodiments of the present invention relate to an ultra-thin front light in which a light source is separated from a light guide by an optical coupling element. Background Art

[0002] Mobile phones, tablets, PCs, automotive entertainment systems, white goods, and many other devices are typically equipped with interactive displays. These interactive displays combine a display screen (such as an LCD, oLED, plasma display, or electrophoretic display (EPD)) with an input system (such as a touch input system or a pen-stylus input system). The input system recognizes the presence of an input object (such as a touch or a pen-stylus near the display screen).

[0003] The display screens (such as EPDs) included in these devices are typically passive because they modulate light but do not generate light in the way of other types of displays (such as conventional cathode ray tube displays). Therefore, when a passive display (such as an EPD display) is placed in a dark environment, it may be difficult for a user to see the display. In a completely dark room, the user may not be able to see the display at all.

[0004] Therefore, passive display devices can be equipped with various lighting devices, such as a front light, which adds light to the display, enabling the user to see the display under low ambient light conditions. Figure 1 An illustration of a prior art front light is shown, which has a light guide 103, a filament of a transparent material (such as glass or plastic) that can transmit optical signals through successive internal reflections. The light guide 103 receives its light from a plurality of light sources (e.g., LEDs 105a to 105h) mounted on an LED circuit board 109, and then adds the light to an image emitted by a lower layer display (e.g., an EPD), which is not shown but is located below the light guide 103. The light sources 105a to 105h are located at different positions along the edge of the light guide 103. Figure 1

[0005] In a conventional design, light sources 105a through 105h are directly coupled to light guide 103. Light sources 105a through 105h tend to be much thicker than light guide 103. As requirements have grown to make devices (e.g., tablets) thinner, designers have implemented smaller light sources and thinner light guides. Using conventional equipment, designers may find that positioning a substantially thinner light guide (e.g., 50um) is slightly easier than positioning a substantially thinner light source (e.g., an LED with an emitter height of 300um). The height difference between light guide 103 and light sources 105a through 105h results in significant leakage of light from light sources 105a through 105h that does not reach light guide 103, thereby impairing the overall functional utility of the front light. Thus, conventional solutions for reduced screen brightness require an increase in the number of LEDs employed in the front light, which itself results in increased cost, increased power consumption, and other difficulties.

[0006] Although significant progress has been made in improving front lights on passive display devices in recent years, further improvements are still needed. Additionally, specific usage scenarios of passive display devices may require levels of precision and additional functionality that conventional devices cannot achieve. Summary of the Invention

[0007] Embodiments of the present invention provide a front light in a tablet computing device. The front light includes a light source, an optical coupling element that receives light from the light source, and a light guide that receives light from the light source that has passed through the optical coupling element, the light source having an emitter height greater than the thickness of the light guide.

[0008] In at least one embodiment of the present invention, light from the light source that initially misses the light guide when passing through the optical coupling element is reflected at a surface of the optical coupling element and enters the light guide after undergoing additional reflections within the optical coupling element.

[0009] In at least one embodiment of the present invention, the optical coupling element has a front surface adjacent to the light guide, the front surface having been mirror-coated, wherein light incident on the front surface from within the optical coupling element is reflected back into the optical coupling element; and a rear surface adjacent to the light source, the rear surface having been mirror-coated, wherein light incident on the rear surface from within the optical coupling element is reflected back into the optical coupling element.

[0010] In at least one embodiment of the present invention, the optical coupling element has a top surface and a bottom surface, wherein both the top surface and the bottom surface are optically polished, and wherein light having an incident angle with a critical angle lower than total internal reflection incident on at least one of the top surface and the bottom surface is reflected into the body of the optical coupling element. Brief Description of the Drawings

[0011] The disclosed embodiments have other advantages and features that will become more apparent from the specific embodiments, the appended claims, and the drawings. A brief introduction to the drawings is given below.

[0012] Figure 1 Shows a prior art headlamp with a light guide 103 having an array (e.g., LEDs 105a to 105h) directly coupled to a light source.

[0013] Figure 2 Shows the system architecture of an electronic paper tablet device for receiving input from an input mechanism such as a stylus.

[0014] Figure 3 Is a block diagram of the system architecture of an electronic paper tablet device according to an example embodiment.

[0015] Figure 4 Shows the hardware components of an example electrophoretic display (EPD) according to the disclosed embodiments.

[0016] Figure 5 Shows a representative display stack 500 composed of various display component layers.

[0017] Figure 6 Shows a headlamp 600 having a light guide 603 positioned at the top of a structure to which a light source (e.g., LEDs 606a to 606h) provides light.

[0018] Figure 7 Shows a component 700 in an embodiment of the present invention, which includes a light source (LED 705), an optical coupling element 702, and a circuit board 704.

[0019] Figure 8 Shows a headlamp 800 and other components in a display stack such as Figure 5 The display stack 500 shown.

[0020] Figure 9 Shows a display stack such as Figure 5 The display stack 500 shown, with a headlamp 900 among other components.

[0021] Figure 10 Illustrates an embodiment of an optical coupling element 1002 in cross-section.

[0022] Figures 11A to 11D Shows an embodiment of the present invention, which shows an optical coupling element 1101.

[0023] Figure 12FIG. 0 is a block diagram illustrating components of an example machine capable of reading instructions from a machine-readable medium and executing those instructions in a processor (or controller).

[0024] Figure 13 FIG. 4 illustrates a graph of coupling efficiency versus refractive index contrast in accordance with an embodiment of the present disclosure.

[0025] The drawings depict various embodiments of the invention for illustrative purposes only. Those skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods shown herein may be employed without departing from the principles described herein. DETAILED DESCRIPTION

[0026] The drawings and the following description relate only by way of illustration to preferred embodiments. It should be noted that alternative embodiments of the structures and methods disclosed herein will readily be recognized as viable alternatives that may be employed without departing from the principles of the claimed subject matter from the following discussion.

[0027] Reference will now be made in detail to several embodiments, examples of which are illustrated in the accompanying drawings. It is noted that wherever feasible, similar or like reference numerals may be used in the drawings and the following description, and similar or like reference numerals may indicate similar or like functions. The drawings depict embodiments of the disclosed system (or method) for illustrative purposes only. Those skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods shown herein may be employed without departing from the principles described herein.

[0028] OVERVIEW

[0029] Disclosed is an ultrathin front light that seeks to improve the efficiency of transferring light from a light source to a light guide. As discussed below, the ultrathin front light includes an optical coupling element that facilitates the transition of light from a significantly thicker light source to a significantly thinner light guide. Such an ultrathin front light is suitable for use with a variety of display devices, but is initially intended for use in a flat panel device having a passive display.

[0030] To provide context for implementing the ultrathin front light into various types of devices, an initial portion of the following disclosure describes a flat panel device into which the ultrathin front light may be incorporated. Those of ordinary skill in the art will recognize and understand that the disclosed ultrathin front light is readily combinable in several different devices, not just the described flat panel computing device.

[0031] EXAMPLE SYSTEM AND DEVICE CONFIGURATIONS

[0032] As Figure 2As shown, the electronic paper tablet device 210 receives input from an input mechanism 220. For example, when a user makes a certain gesture using the input mechanism 220, the input mechanism 220 makes physical contact with a contact-sensitive surface (e.g., a touch-sensitive screen) on the electronic paper tablet device 210. The input mechanism 220 can be a stylus or other device including the user's finger. The electronic paper tablet device 210 is referred to herein as an "electronic paper tablet", which is a device that mimics the appearance of ordinary ink on paper. Such devices are also referred to as "electronic paper" and "electronic ink". Although embodiments of the present invention are designed for electronic paper systems, embodiments of the present invention can also be applied to other forms of computing devices. Based on the nature of the contact, the electronic paper tablet device 210 generates and executes instructions for updating the content displayed on the contact-sensitive screen to reflect the gesture input. For example, in response to a gesture that translates an oral message (e.g., written text or drawing), the electronic paper tablet device 210 updates the contact-sensitive screen to display the translated message. As another example, in response to a gesture that selects a navigation option, the electronic paper tablet device 210 updates the screen to display a new page associated with the navigation option.

[0033] The input mechanism 220 can refer to any device or object compatible with the contact-sensitive screen of the electronic paper tablet device 210. In one embodiment, the input mechanism 220 can work in conjunction with an electronic ink (e.g., E-ink) contact-sensitive screen. For example, the input mechanism 220 can refer to any device or object that can make contact with the screen and from which the screen can detect the touch or contact of the input mechanism 220. Once the touch or contact is detected, the electronics associated with the screen generate a signal that the electronic paper tablet device 210 can process as a gesture that can be provided for display on the screen. When a gesture is detected by the input mechanism 220, the electronics within the contact-sensitive screen generate a signal that encodes instructions for displaying content or updating previously displayed content on the screen of the electronic paper tablet device 210 based on the movement of the detected gesture on the screen. For example, when processed by the electronic paper tablet device 210, the encoded signal can cause a representation of the detected gesture, such as a doodle, to be displayed on the screen of the electronic paper tablet device 210. As mentioned, the input mechanism 220 can be a stylus or other type of pointer device, including a part of the user's body, such as a finger.

[0034] In one embodiment, the input mechanism 220 is an enclosed magnetic coil. When close to the screen of the electronic paper tablet device 210, the magnetic coil helps generate a magnetic field that encodes signals for conveying instructions, which are processed by the electronic paper tablet device 210 to provide a representation of a gesture for display on the screen, e.g., displayed as a marker. The input mechanism 220 can be pressure-sensitive such that contact with the touch-sensitive display causes the magnetic coil to compress. Further, the interaction between the compressed coil and the touch-sensitive screen of the electronic paper tablet device 210 can generate different encoded signals for processing, e.g., in order to display a representation of a gesture with different characteristics on the screen, such as a thicker line marker. In an alternative embodiment, the input mechanism 220 includes a power source (e.g., a battery) that can generate an electric field using a touch-sensitive surface. It is noted that an encoded signal is a signal that is generated and can be conveyed. The encoded signal can have a signal pattern that can be used for further analog analysis or digital analysis (or interpretation).

[0035] In one embodiment, the touch-sensitive screen is a capacitive touch screen. The screen can be designed with a glass material coated with a conductive material. Electrodes or electrical components carrying an alternating current are arranged vertically along the glass coating of the screen to maintain a constant current level throughout the screen. A second set of electrodes is arranged horizontally. A matrix of vertically active electrodes and horizontally inactive electrodes creates an electrostatic field at each point on the screen. When an input mechanism 220 having conductive properties (e.g., an enclosed magnetic coil or a person's finger) contacts an area of the screen of the electronic paper tablet device 210, current will flow through the horizontally arranged electrodes, thereby disrupting the electrostatic field at the point of contact on the screen. The disruption of the electrostatic field at each point covered by the gesture can be measured, e.g., as a change in capacitance, and encoded into an analog signal or a digital signal.

[0036] In an alternative embodiment, the touch-sensitive screen is a resistive touch screen. A resistive touch screen includes two metal layers: a first metal layer in which stripe electrodes are located on a substrate (e.g., glass or plastic); and a second metal layer in which transparent electrodes are positioned. When contact from an input mechanism (e.g., a stylus, finger, or palm) is made on the surface of the touch screen, the two layers are pressed together. After contact, a voltage gradient is applied to the first layer and measured as a distance through the second layer to determine the horizontal coordinate of the contact point on the screen. Subsequently, a voltage gradient is applied to the second layer to determine the vertical coordinate of the contact point on the screen. The combination of the horizontal coordinate and the vertical coordinate records the exact position of the contact point on the touch-sensitive screen. Different from capacitive touch screens that rely on conductive input mechanisms, resistive touch screens are configured to sense contact from almost any input mechanism. Although some embodiments of the electronic paper tablet device are described herein with reference to capacitive touch screens, those skilled in the art will recognize that resistive touch screens can also be implemented.

[0037] In an alternative embodiment, the touch-sensitive screen is an inductive touch screen. The inductive touch screen includes a metal front layer configured to detect deflections when a contact is made on the screen by an input mechanism. Accordingly, the inductive touch screen is configured to sense contacts from almost any input mechanism. Although some embodiments of the electronic paper tablet device are described herein with reference to capacitive touch screens, those skilled in the art will recognize that alternative touch screen technologies can be implemented, such as inductive touch screens can also be implemented.

[0038] The cloud server 230 is configured to receive information from and / or convey instructions to the electronic paper tablet device 210. As Figure 2 shown, the cloud server 230 may include a cloud data processor 250 and a data storage device 260. Data recorded and stored by the electronic paper tablet device 210 can be conveyed via the network 240 to the cloud server 230 for storage in the data storage device 260. For example, the data storage device 260 may store documents, images, or other types of content generated or recorded by the user via the electronic paper tablet device 210. In some embodiments, the cloud data processor 250 monitors the activities and usage of the electronic paper tablet device 210 and conveys processing instructions to the electronic paper tablet device 210. For example, the cloud data processor 250 may adjust the synchronization protocol of the data stored in the data storage device 260 with the electronic paper tablet device 210.

[0039] The interaction between the electronic paper tablet device 210 and the cloud server 230 typically occurs via the network 240, which enables communication between the electronic paper tablet device 210 and the cloud server 230. In one embodiment, the network 240 uses standard communication technologies and / or protocols, which include but are not limited to links using technologies such as Ethernet, 802.11, Worldwide Interoperability for Microwave Access (WiMAX), 3G, 4G, LTE, Digital Subscriber Line (DSL), Asynchronous Transfer Mode (ATM), InfiniBand, and PCI Express Advanced Switching. The network 240 may also utilize dedicated, custom, or private communication links. The network 240 may include any combination of local area networks and / or wide area networks, using both wired communication systems and wireless communication systems.

[0040] Figure 3 is a block diagram of the system architecture of an electronic paper tablet device according to an example embodiment. In Figure 3 the illustrated embodiment, the electronic paper tablet device 210 includes an input detector module 310, an input digitizer 320, a display system 330, and a graphics generator 340.

[0041] The input detector module 310 can be configured to recognize that a gesture has been or is being made on the screen of the electronic paper tablet device 210. The input detector module 310 refers to the electronic devices integrated into the screen of the electronic paper tablet device 210, and these electronic devices are configured to interpret the encoded signals generated by the contact between the input mechanism 220 and the screen as recognizable gestures. To this end, the input detector module 310 can evaluate the attributes of the encoded signals to determine whether the signals represent gestures intentionally made by the user or gestures unintentionally made by the user.

[0042] The input digitizer 320 can be configured to convert the analog signals encoded by the contact between the input mechanism 220 and the screen into a digital instruction set. The converted digital instruction set can be processed by the electronic paper tablet device 210 to generate or update the user interface displayed on the screen to reflect the intentional gesture.

[0043] The display system 330 can include physical and firmware (or software) components to display (e.g., render) the user interface on the screen. The user interface can correspond to any type of visual representation that can be presented to or viewed by the user of the electronic paper tablet device 210.

[0044] Based on the digital signals generated by the input digitizer 320, the graphics generator 340 can be configured to generate or update the graphics of the user interface to be displayed on the screen of the electronic paper tablet device. The display system 330 can be configured to use the electronic devices integrated into the screen to present these graphics of the user interface for display to the user.

[0045] When the input mechanism 220 touches the touch-sensitive screen of the electronic paper tablet device 210, the input detector module 310 recognizes the gesture that has been made through the screen. The gesture can be recognized as part of the encoded signal generated by the compression of the coil in the input mechanism 220 and / or the corresponding electronic devices of the screen of the display system 330. The encoded signal is transmitted to the input detector module 310, and the input detector module evaluates the attributes of the encoded signal according to at least one gesture rule to determine whether the gesture is intentionally made by the user. If the input detector module 310 determines that the gesture is intentionally made, the input detector module 310 transmits the encoded signal to the digitizer output. The encoded signal is an analog representation of the gesture received by the sensor matrix embedded in the screen of the electronic paper tablet 210.

[0046] In an example embodiment, the input digitizer 320 converts physical points on the screen touched by the input mechanism 220 into a set of instructions for updating the content provided for display on the screen. For example, if the input detector module 310 detects an intentional gesture of swiping from a first page to a second page, the input digitizer 320 receives the analog signal generated by the input mechanism 220 as it performs the swiping gesture. The input digitizer 320 generates a digital signal for the swiping gesture that provides instructions to the display system 330 of the e-paper tablet device 210 to update the user interface of the screen to transition from, for example, the current page (or the first page) to the next page (or the second page, which may be before or after the first page).

[0047] In an example embodiment, the graphics generator 340 receives the digital instruction signal generated by the input digitizer 320 (e.g., a swiping gesture indicating a page transition such as flipping or turning a page). The graphics generator 340 generates graphics or updates to the previously displayed user interface graphics based on the received signal. The generated or updated user interface graphics are provided to be displayed by the display system 330 on the screen of the e-paper tablet device 210, for example, to show the user the transition from the current page to the next page. In Figure 3 the illustrated embodiment, the graphics generator 340 includes a rasterizer module 350 and a de-pixelizer module 360. Input gestures drawn by the user on the touch-sensitive surface are received as vector graphics and input into the rasterizer module 350. The rasterizer module 350 converts the input vector graphics into raster graphics that can be displayed (or provided for display) on the touch-sensitive surface. The de-pixelizer module 360 can apply image processing techniques to convert the displayed raster graphics back into vector graphics, for example, to improve the processing power of the e-paper tablet device 210 and save memory of the e-paper tablet device 210. In at least one implementation, when the content to be displayed on the screen is exported to a different format or to a different system, the de-pixelizer module 360 can convert the displayed raster graphics back into vector graphics.

[0048] More details regarding the structure and function of the e-paper tablet and its graphics display can be found in USP 11,158,097, entitled "Generating vector graphics by processing raster graphics", by Martin Sandsmark and Gunnar Sletta, and USP 10,824,274, entitled "Interactive displays", by Sondre Hoff Dyvik, Martin Sandsmark, and Magnus Haug Wanberg, both of which are incorporated herein by reference.

[0049] Figure 4 Illustrated are the hardware components of an example electrophoretic display (EPD) according to the disclosed embodiments. The EPD can be part of a display system 330 of an e-paper tablet device 210, as Figure 3 shown. The EPD includes a gate driver 309, a source driver 411, a shift register 423 having data and clock signal lines, a latch 425, a voltage selector 427, and rows that make up a display 405. The EPD industry has borrowed some components and concepts from the LCD industry; however, there are also some fundamental differences between the two devices. Of particular relevance here is the persistence of pixels in an EPD display. Unlike LCD displays, EPD displays do not require the frequent refreshing that LCD displays do. In an EPD display, for example, once a neutral voltage is set for a pixel, that pixel will not change and will remain that way for a long time, especially relative to LCD displays.

[0050] As mentioned, the electrophoretic display (EPD) 405 utilizes many aspects of the LCD production infrastructure and drive mechanism. The drive electronics typically consist of a gate driver (GD) 309 and a source driver (SD) 411. The display 405 has multiple rows of pixels. The pixel values ​​within a row may vary, for example, a logic high voltage may be a "black" pixel, while a logic low voltage or "ground" may be a colorless pixel. The function of the pixels in the EPD 405 is similar to a small capacitor that lasts for a long time interval. The EPD pixel contains a large number of charged particles suspended in a liquid. If a charge is applied, the particles will move to the surface, where they become visible. The white particles and the black particles carry opposite charges, so that the display of the pixel can be changed from white to black by applying opposite charges to the pixel. Therefore, the waveform applied to the EPD includes a long series of voltages to change from black to white or vice versa. It is also known that EPD technology can apply variable voltage levels that mix white particles and black particles to produce a variety of gray shades. The voltage levels in the pixels can also be layered between to provide shades (e.g., grayscale) between colorless and black. Groups of pixels surrounding each other may form a region that provides some visible characteristic to a user, such as an image on a screen, such as a screen of the display system 330 of the electronic paper tablet device 210 .

[0051] In order to change the pixel value in the area, the scanning of the display 405 usually starts from the top row (e.g., row 0 421), and a voltage is applied to update the pixels in a specific row, where the pixels need to be changed to correspond to the displayed image. In this example, the start pulse (GDSP) 103 can be used to reset the driver 411 to row 0 421. Row by row selection is performed by driving the driver gate 309 to select a row (e.g., active row 413). All pixels in a row are addressed simultaneously using the data transmitted to the display. The latch 425 receives the next set of voltages to be applied to the pixel row from the shift register 423. When the scanning of the active row is completed and the pixels are changed or updated when necessary, the clock pulse (GDCLK) 415 is sent down to the driver gate 309 to change to the next row 417 for scanning.

[0052] The source driver 411 is used to set the target voltage for each of the pixels / columns of the selected row. The source driver consists of a shift register 423 for holding voltage data, a latch circuit 425 for enabling pixel data transfer when the previous row was exposed, and a voltage selector (multiplexer) 427 for converting the latched voltage selection to the actual voltage. For all rows to be updated, all voltage values ​​must be shifted into the register 423 and latched so that the voltage is available.

[0053] Readers can understand that Figures 2 to 4The electronic paper tablet device 210 described in [[ ]] includes a reasonable amount of complexity. For example, embodiments of the display 330 typically include a stack formed by various components in the electronic paper tablet device 210.

[0054] Figure 5 FIG. illustrates a representative display stack 500 formed by various display component layers. From the bottom layer to the top layer, these layers include an EPD display 507, an optically clear adhesive layer 506, a light guide plate 504, an optically clear adhesive layer 505, a touch sensor 503, an optically clear adhesive layer 502, and a front panel 501. The EPD display 507 may include components similar to Figure 4 the display 405 described in [[ ]]. If there is a writing technology ( Figure 5 not shown in [[ ]], but if present, it may be below the EPD display 507), the writing technology may include elements similar to Figure 3 the graphics generator 340 disclosed in [[ ]]. The optically clear adhesive layers 506, 504, 502 are used to attach the components from other parts in the stack 500 together, but do so in a way that does not change or impede the transmission of light through the stack 500 to the user. The touch sensor 503 operates as part of a touch screen, which has been specifically described above in connection with Figure 2 . The stack 500 is typically covered by the front panel 501 that the user can touch during device operation. The front panel 501 is typically made of glass, but can also be made of other materials. For example, U.S. Patent Application No. 18 / 114,896 filed on February 27, 2023 and U.S. Provisional Application No. 63 / 314,500 filed on February 28, 2022, both named "Cover Lens for Consumer Electronics Device", describe one such front panel suitable for implementation in the stack 500.

[0055] The light guide plate 504 is described in Figure 5 as an ultra-thin light guide plate. As discussed above, consumer demands have forced display stacks (such as the display stack 500) to become thinner and thinner, so that the entire device (e.g., the electronic paper tablet device 210) itself can become thinner, and so that the parallax effect caused by the separation between the EPD and the writing surface can be reduced.

[0056] As discussed in the background art section, conventional solutions for providing a light guide in a display stack on a passive display device include directly coupling a light source (e.g., an LED) to the light guide in the display stack. However, as the display stack has been forced to become thinner, the height difference between the light source and the light guide has increased significantly. Thus, a large amount of light provided by the light source in such thin devices cannot enter the light guide, thereby impairing the overall function of the front light.

[0057] Example of an ultra-thin front light

[0058] Figures 6 to 1 1 depicts an embodiment of an ultra-thin front light having an optical coupling element that facilitates the efficient transition of light from a light source to a light guide. The inventors have provided a solution to the coupling efficiency problem in thin front lights (e.g., as Figure 1 described) by introducing additional optical coupling elements that increase the coupling efficiency. The resulting ultra-thin front light is suitable for implementation in a display stack (such as Figure 5 the display stack 500 shown) and ultimately suitable for integration into a device (such as an e-paper tablet device 210). Embodiments of the ultra-thin front light may include a light guide that is at least as thin as 50um for incorporation into Figure 2 the e-paper tablet 210 shown.

[0059] As described above, embodiments of the ultra-thin front light include an optical coupling element and additional optical elements designed to improve the coupling from a light source (e.g., an LED) to a light guide. The disclosed configuration differs from Figure 1 the conventional method shown, in which the light source is "directly coupled" to the light guide, due to the intervening presence of the optical coupling element. One of ordinary skill in the art will note that an ultra-thin light guide (e.g., 50um or thinner) is not necessarily a conventional "off-the-shelf" component, but is still well within the scope of conventional scientific and engineering understanding.

[0060] Embodiments of the present invention attempt to solve the coupling efficiency problem in thin front lights (e.g., as Figure 1 described) by introducing additional optical coupling elements that increase the coupling efficiency. The optical coupling element is used to accommodate the light diffusing out of the LED and to help couple more light from a thicker / higher light source into an elongated / thinner light guide. Thus, the inventors have provided a solution to the coupling efficiency problem in thin front lights through such optical coupling elements described herein.

[0061] In the absence of an additional optical coupling element, if the light from the source is both within the region of the source adjacent to the light guide and within the acceptance angle of the light guide, then the light from the source is only coupled into the light guide. (Light at higher angles may initially enter the light guide but will exit the light guide within a short distance.) Most of the light emitted by the source is outside the acceptance angle and / or region of the light guide and is thus wasted. The purpose of the additional optical coupling element is to cause such unused light to undergo multiple reflections that ultimately result in its entry into the light guide rather than being lost. The reflective surface of the optical coupling element is used to confine the light until it impinges on the light guide.

[0062] Figure 6 FIG. illustrates a headlight 600 having a light guide 603 positioned at the top of a structure to which light is provided from a light source (e.g., LEDs 606a to 606h). This structure, the optical coupling element 602, is placed near the light guide 603. The light source may be placed near the optical coupling element 602 or in a recess 601 in the optical coupling element, as Figure 6 shown. Thus, the optical coupling element 602 is located between the light guide 603 and the light source (e.g., LEDs 606a to 606h).

[0063] If present, the recess 601 may include small gaps 605a, 605b shown on either side of the LED 606h. The gaps 605a, 605b are not essential for the optical function of the headlight 600 but may be included to allow for manufacturing tolerances. The optical coupling element 602 has a height greater than or equal to the height of the light source (e.g., LEDs 606a to 606h). The optical coupling element 602 is typically made of the same material (e.g., polycarbonate) as the light guide 603. The optical coupling element 602 has the same refractive index as the light guide 603. The optical coupling element 602 does not have to exactly match the refractive index of the light guide 603; preferably, the optical coupling element 602 matches the refractive index of the light guide 603, otherwise the efficiency may be reduced. In the headlight 600, the light source (e.g., LEDs 606a to 606h) rests on a circuit board 604 (e.g., a flexible PCB) that also supports the optical coupling element 602. The light guide 603 is supported by other layers above or below the display stack, which are not Figure 6 shown in.

[0064] The optical coupling element 602 includes a solid transparent element having some reflective surfaces, which improves the coupling of light into the light guide (e.g., Figure 6The efficiency in the light guide 603 shown. The reflective surface can be achieved by total internal reflection due to the refractive index difference between the coupling element and the surrounding material, or by using a mirror coating, which can be a metal mirror or a dielectric mirror. The light rays from LEDs 606a to 606h that initially miss the light guide (e.g., Figure 6 the light guide 603 shown) are reflected at the surface of the optical coupling element 602 and enter the light guide 603 after undergoing these additional reflections. In manufacturing, any surface that is expected to have total internal reflection should preferably be polished, and it may also be beneficial to polish the surface on which the mirror coating is deposited. If a mirror coating is used, it should be deposited as evenly as possible and finished on the relevant surface so that the optical coupling element 602 functions as expected. The reflective surface does not have to be 100% reflective, but for higher reflectivity, the performance is improved. See Figures 11A to 11D for further discussion on the polishing and mirror coating of different surfaces on an embodiment of the optical coupling element 602.

[0065] In a representative embodiment of the present invention, instead of light being transmitted from the LED emission surface of about 300 microns and transmitted into the narrow surface (e.g., 50 microns) of the light guide 603, due to the intervening optical coupling element 602, most of the light now enters the lower part of the light guide 603. This connection may be particularly advantageous because the surface quality of the top and bottom parts of the light guide 603 is typically better than that of the edge parts of the light guide 603, and these edge parts are the parts that directly receive light (see, for example, Figure 1 ). It has been observed that the edge parts of the light guide tend to have more defects than the top and bottom parts.

[0066] The performance of the headlight 600 depends to a large extent on the specific materials selected for the light guide 603 and the optical coupling element 602. For the light guide, materials with a higher refractive index have a larger acceptance angle and will therefore be able to couple more light through the structure of the headlight 600. Thus, for example, a polycarbonate light guide has a larger acceptance angle than a guide made of polymethyl methacrylate (PMMA). Optical absorption characteristics are also important - for example, polyethylene terephthalate (PET) can be used, but it has a higher absorption of blue light and may cause a yellowing color shift, which may be undesirable for some applications, such as when a "cooler" tone is desired. The materials used for the optical coupling element 602 are basically the materials conventionally used in light guides, and for the optical coupling element 602, no unique material seems to be necessary.

[0067] The closer the refractive index of the optical coupling element 602 matches the refractive index of the light guide 603, the more effectively the optical coupling element performs its intended function. Optically, it is ideal for the optical coupling element 602 and the light guide 603 to appear as (and act as) a substantially single continuous piece with a uniform refractive index. The optical coupling element 602 and the light guide 603 may not be fabricated as a single piece because typically different processes are used to fabricate each component. However, if these components can be fabricated as an integral piece, such an assembly would also be suitable.

[0068] The optical coupling element 602 can have several overall shapes. Figure 6 A substantially rectangular optical coupling element 602 is illustrated, but the shape of the optical coupling element 602 can take other forms. For example, the walls of the optical coupling element 602 can be ramped or inclined in different directions without degrading performance. Figure 6 The illustrated rectangular shape may be easier to fabricate by some processes (e.g., molding) than a situation where the optical coupling element 602 has another shape. Thus, if different fabrication processes are more optimal for certain specific materials, the shape of the optical coupling element 602 can be adjusted without significantly degrading performance.

[0069] The height of the optical coupling element 602 should approximately match or exceed the height of the light source (e.g., LEDs 606a to 606h). Thus, the minimum size of the optical coupling element 602 is substantially limited (or governed) by the height of the LED emission surface. If the LEDs employed in the recesses 601 in the illustrated embodiments of the present invention are less than about 300 microns in LED emitter height, then the optical coupling element 602 will likewise be reduced. (The recess 601 can alternatively be referred to as a "slot" or a "hole".) Figure 6 If the LEDs employed in the recesses 601 in the illustrated embodiments of the present invention are less than about 300 microns in LED emitter height, then the optical coupling element 602 will likewise be reduced. (The recess 601 can alternatively be referred to as a "slot" or a "hole".)

[0070] The benefit of the optical coupling element 602 depends on the difference between the height of the light guide 603 and the height of the light source (LEDs 606a to 606h). As the difference increases (i.e., the light source becomes taller compared to the thickness of the light guide), the benefit of the optical coupling element 602 increases. As the difference decreases and the light source becomes comparable in height to the thickness of the light guide, the benefit of the optical coupling element 602 becomes negligible, and the coupling efficiency is similar to the coupling efficiency achievable in a direct coupling situation. In such embodiments where the height of the source is the same as the thickness of the light guide, the optical coupling element 602 may not be needed, unless other manufacturing or assembly considerations make such a configuration more advantageous. The mathematical form of the dependence of the efficiency improvement on the height ratio is not precisely defined and can depend on the coupling element geometry, but for some embodiments, this is considered to be a linear relationship that then asymptotically decreases as the height ratio approaches 1:1.

[0071] Table 1 shows the performance of one embodiment of the optical coupling element 602 based on simulated data. Table 1 shows the optically coupled efficiency simulated for the optical coupling element design with 50um and 150um light guides and approximately 300um LEDs, ignoring the effect of the adhesive. The optically coupled element efficiency plot in Table 1 assumes that the front face of the LED acts as a Lambertian reflector for any light reflected back onto it. Any absorption by the LED face will reduce the coupling efficiency with the optical coupling element from the values shown.

[0072]

[0073] Table 1

[0074] Table 2 shows the alignment sensitivity of the optical coupling element 602 of one embodiment of the present invention. The sensitivity of the coupling efficiency to different spatial misalignments between the LED and the optical coupling element 602 has been evaluated in the simulation. It is assumed that the LED emits light at the boundary of the package, and there is a nominal 5um air gap between the LED emission surface and the optical coupling element 602 when the two components are aligned.

[0075]

[0076] Table 2

[0077] The coupling efficiency does not seem to be very sensitive to tilt, but is strongly affected by displacements in the vertical and longitudinal directions. In at least one embodiment of the present invention, the displacement corresponding to a 0.8-fold reduction in efficiency is less than that in the case of direct coupling. However, the optical coupling element and the LED hole 601 can act as reference features, and the alignment tolerance may be easier to achieve (this assumes that the PCB 604 has some flexibility for slight changes in the LED position). To keep the efficiency within 80% of the maximum value, at least for one embodiment of the present invention, the displacement should preferably be kept within the limits shown in Table 2.

[0078] Figure 7 Illustrated is a component 700 in an embodiment of the present invention, which includes a light source (LED 705), an optical coupling element 702, and a circuit board 704. Figure 7 The components shown are similar to Figure 6 the components shown. A recess 706 is located between the LED 705 and the optical coupling element 702, which helps to improve the manufacturing tolerance of the component 700. The circuit board, the LED, and the coupling element should preferably be aligned with each other. The width of the recess can allow some wiggle room for the positioning of the LED relative to the recess. The tolerance of the light guide is typically not affected. For the purpose of illustration, Figure 7 the size of the recess 706 depicted in Figure 6The size of the recess 601 shown can be reduced as the manufacturing process improves, and the recess 706 in the production model will not be large enough to impair the performance of the headlight 700.

[0079] In operation, light leaves the LED 705 and enters a face on the optical coupling element 702. Once the light has entered the optical coupling element 702, from an optical perspective, the connection between the optical coupling element 702 and the light guide (e.g., Figure 6 the light guide 603 shown) is approximately optically continuous (with little or no refractive index change). Thus, some light travels diagonally straight up through the optical coupling element 702 and into the light guide (e.g., Figure 6 the light guide 603 shown).

[0080] Light that does not reach the light guide directly in this way instead hits one of the reflective surfaces of the optical coupling element 702 (see the discussion of the reflective surfaces shown in FIGS. 11a - 11d), and is reflected back into the optical coupling element. This light can then undergo multiple reflections within the optical coupling element before obtaining a trajectory to reach the light guide. Coupling this additional light into the light guide increases the overall coupling efficiency. Note that not all light reaches the guide - some light can escape or be absorbed from the optical coupling element.

[0081] Figure 8 Illustrated is the headlight 800 and other components in a display stack (such as Figure 5 the display stack 500 shown). The headlight 800 includes a light guide 812, an optical coupling element 802, and a plurality of light sources (LEDs 805a - 805g) disposed on a circuit board 804. Figure 8 Also illustrated are other components in the display stack, such as a front panel 811 and a light blocking film 810 attached to a portion of the light guide 812. Figure 8 In other respects similar to Figure 6 the embodiments of the present invention shown.

[0082] Figure 9 Illustrated is the headlight 900 among other components in a display stack (such as Figure 5 the display stack 500 shown). The headlight 900 includes an optical coupling element 902, an LED 905, and a light guide 903. The optical coupling element 902 and the LED are disposed on a circuit board 904. The light guide 903 is located on top of a lower layer (such as Figure 4 the lower layer shown) of the display stack 912.

[0083] The optical coupling element 902 is typically adhered to the light guide 903 using a refractive-index-matching optical adhesive or a solvent that creates a bond between these components. The optical adhesive can be easily used in manufacturing. Similarly, there may be an adhesive between the LED 905 and the optical coupling element 902. The adhesive will likely be pressed into place and then cured. Alternatively, there may be a small air gap between the light source and the optical coupling element 902.

[0084] The adhesive employed should have the same (or at least similar) refractive index as the materials (e.g., polycarbonate) used in the light guide 903 and the optical coupling element 902. The inventors have observed that conventional adhesives and manufacturing processes seem to be somewhat adjustable for a given material. In any case, the closer the refractive index of the adhesive employed matches the materials of the light guide 902 and the optical coupling element 902, the better the overall performance of the headlamp 900 will be.

[0085] Figure 10 An embodiment of the optical coupling element 1002 is illustrated in cross-section. The optical coupling element 1002 includes a region of approximately 750 microns into which a light guide (such as Figure 9 the light guide 903 shown) can be inserted. As mentioned, some embodiments of the ultra-thin headlamp are designed to work with a light guide having a thickness of approximately 50 microns. However, Figure 10 a region of approximately 75 microns in height for inserting the light guide is illustrated. The additional 25 microns is intended to compensate for the minimum thickness of the adhesive and machining tolerances.

[0086] Figures 11A to 11D An embodiment of the present invention is illustrated that shows the optical coupling element 1101. In this embodiment, the rear surface 1102 and the front surface 1103 are mirror-coated, and the top surface 1104 and the bottom surface 1105 are optically polished. Light incident on the surfaces 1102 and 1103 from within the optical coupling element is reflected back into the body of the optical coupling element. If the angle of incidence is below the critical angle for total internal reflection, light incident on the surfaces 1104 and 1105 from within the optical element is reflected back into the body of the optical coupling element. Total internal reflection reflects a smaller range of angles, but may be more desirable than a mirror coating due to lower losses.

[0087] Example computer machine architecture

[0088] Figure 12 is a block diagram illustrating the components of an example machine capable of reading instructions from a machine-readable medium and executing those instructions in a processor (or controller). Figure 12is an example of a processing system in which some or all of the described components of the processing system can be executed by the modules described herein.

[0089] In this example, Figure 12 a graphical representation of a machine in the example form of a computer system 1200 (e.g., Figure 3 the computing portion of the electronic paper tablet 210 shown) is illustrated, within which program code (e.g., software) can be executed to cause the machine to perform any one or more of the methods discussed herein. The electronic paper tablet device 210 may include some or all of the components of the computer system 1200. The program code may include instructions 1224 executable by one or more processors 1202. In the electronic paper tablet system 210, the instructions may correspond to Figures 2 to 4 the functional components described in

[0090] Although the embodiments described herein are in the context of the electronic paper tablet system 210, it should be noted that these principles can be applied to other touch-sensitive devices. In these contexts, Figure 12 the machine can be a server computer, a client computer, a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a cellular phone, a smart phone, a web device, a network router, an Internet of Things (IoT) device, a switch or bridge, or any machine capable of (sequentially or otherwise) executing the instructions 1224 specifying the actions to be taken by the machine. Further, although only a single machine is illustrated, the term "machine" should also be understood to include any collection of machines that individually or jointly execute the instructions 1224 to perform any one or more of the methods discussed herein.

[0091] The example computer system 1200 includes one or more processors 1202 (e.g., a central processing unit (CPU), one or more graphics processing units (GPUs), one or more digital signal processors (DSPs), one or more application specific integrated circuits (ASICs), one or more radio frequency integrated circuits (RFICs), or any combination thereof), main memory 1204, and static memory 1206, which are configured to communicate with each other via bus 1208. The computer system 1200 may further include a visual display interface 1210. The visual interface may include software drivers that enable a user interface to be displayed on a screen (or display). The visual interface may display the user interface directly (e.g., on a screen) or indirectly (e.g., via a visual projection unit) on a surface, window, etc. For ease of discussion, the visual interface may be described as a screen. The visual interface 1210 may include or interface with a touch-enabled screen such as an electronic paper tablet system 210, and may be associated with a display system 330. The computer system 1200 may also include an input device 1212 (e.g., a stylus, keyboard, or touchscreen keyboard), a cursor control device 1214 (e.g., a mouse, trackball, joystick, motion sensor, or other pointer instrument), a storage unit 1216, a signal generation device 1218 (e.g., a speaker), and a network interface device 1220, which are also configured to communicate via bus 1208.

[0092] The storage unit 1216 includes a machine-readable medium 1222 on which instructions 1224 (e.g., software) are stored (or encoded) that embody any one or more of the methods or functions described herein. The instructions 1224 (e.g., software) may also reside, at least partially, within the main memory 1204 or within the processor 1202 (e.g., in a cache memory of the processor) during execution by the computer system 1200, the main memory 1204, and the processor 1202, which also constitutes a machine-readable medium. The instructions 1224 (e.g., software) may be sent or received via the network interface device 1220 over a network 1226.

[0093] Although the machine-readable medium 1222 is shown as a single medium in the example embodiment, the term "machine-readable medium" should be considered to include a single medium or multiple media (e.g., a centralized or distributed database, or associated caches and servers) that are capable of storing instructions (e.g., instructions 1224). The term "machine-readable medium" should also be considered to include any medium that is capable of storing instructions (e.g., instructions 1224) executable by a machine and that cause the machine to perform any one or more of the methods disclosed herein. The term "machine-readable medium" includes, but is not limited to, data repositories in the form of solid-state memory, optical media, and magnetic media.

[0094] The computer system 1200 may also include one or more sensors 1225. Note also that a computing device may include only Figure 12 a subset of the components shown and described. For example, an IoT device may include only the processor 1202, the small storage unit 1216, the main memory 1204, the visual interface 1210, the network interface device 1220, and the sensor 1225.

[0095] Figure 13 A graph showing the coupling efficiency versus the refractive index contrast according to an embodiment of the present disclosure is illustrated. Refer to Figure 13 which shows how the coupling efficiency degrades with refractive index mismatch for adhesive thicknesses of 5um and 25um.

[0096] Additional Considerations

[0097] This disclosed configuration provides additional precision and options for a user when erasing portions of a drawing on an e - paper tablet. This should improve the efficiency of user interaction with the e - paper tablet while also endowing them with more precise functional capabilities.

[0098] It should be understood that the drawings and description of the present disclosure have been simplified to illustrate elements relevant to a clear understanding of the present disclosure, while eliminating many other elements that are present in a typical system for the sake of clarity. In implementing the present disclosure, those of ordinary skill in the art may recognize that other elements and / or steps are desirable and / or necessary. However, since such elements and steps are well known in the art and since they do not contribute to a better understanding of the present disclosure, a discussion of such elements and steps is not provided here. The present disclosure herein relates to all such variations and modifications of these elements and methods known to those of skill in the art.

[0099] Some of the above - described portions describe embodiments in terms of algorithms and symbolic representations of information operations. These algorithmic descriptions and representations are typically used by those skilled in the data - processing arts to effectively convey the substance of their work to other technicians in the field. These operations, while described functionally, computationally, or logically, should be understood to be implemented by a computer program or equivalent circuitry, microcode, etc. Additionally, it has sometimes proven convenient to refer to these operational arrangements as engines, without loss of generality. The described operations and their associated engines may be embodied in software, firmware, hardware, or any combination thereof.

[0100] As used herein, any reference to "an embodiment" or "embodiments" means that the particular elements, features, structures, or characteristics described in connection with the embodiment are included in at least one embodiment. In this specification, the phrase "in an embodiment" does not necessarily refer to the same embodiment each time it appears.

[0101] As used herein, the term "comprising," "having," or any other variation thereof is intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive or rather than an exclusive or. For example, condition A or B is satisfied in any of the following cases: A is true (or present) and B is false (or absent); A is false (or absent) and B is true (or present); and both A and B are true (or present).

[0102] Additionally, the articles "a" or "an" are used to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the invention. This description should be understood to include one or at least one, and the singular also includes the plural, unless clearly stated otherwise.

[0103] Although specific embodiments and applications have been illustrated and described, it should be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes, and variations that are obvious to one of ordinary skill in the art can be made to the arrangement, operation, and details of the methods and apparatuses disclosed herein without departing from the spirit and scope defined by the appended claims.

Claims

1. A front light in a tablet computing device, comprising: light source; an optical coupling element that receives light from the light source; as well as a light guide that receives light from the light source through the optical coupling element, Wherein, the light source has an emitter height that is greater than a thickness of the light guide.

2. The headlamp according to claim 1, wherein: The optical coupling element has a height equal to or greater than a height of the light source.

3. The headlamp according to claim 2, wherein: The optical coupling element has: a front surface adjacent to the light guide, the front surface being mirror-coated, wherein light incident on the front surface from within the optical coupling element is reflected back into the optical coupling element; and a rear surface adjacent to the light source, the rear surface being mirror-coated, wherein light incident on the rear surface from within the optical coupling element is reflected back into the optical coupling element.

4. The headlamp according to claim 3, wherein: The optical coupling element has a top surface and a bottom surface, wherein the top surface and the bottom surface are both optically polished, wherein light incident on at least one of the top surface and the bottom surface having an incident angle below a critical angle for total internal reflection is reflected into a body of the optical coupling element.

5. The headlamp according to claim 1, wherein: The light source includes a plurality of LEDs, wherein each LED of the plurality of LEDs is adjacent to the optical coupling element.

6. The headlamp according to claim 5, wherein: Each LED of at least a portion of the plurality of LEDs is located in a recess adjacent to the optical coupling element.

7. The headlamp according to claim 1, wherein: The light guide and the optical coupling element are composed of the same material.

8. The headlamp according to claim 7, wherein: The material is polycarbonate.

9. The headlamp according to claim 1, wherein: The optical coupling element has a refractive index matched to the light guide.

10. The headlamp of claim 1, wherein: The refractive index of the optical coupling element matches the refractive index of the light guide.

11. The headlamp of claim 1, wherein: The light guide includes a material with a higher refractive index that couples more light through the frontlight and into the display stack.

12. The headlamp of claim 1, wherein: The light source and the optical coupling element rest on a circuit board, and wherein the light guide is supported by a plurality of layers in a display stack.

13. The headlamp of claim 12, wherein: Two of the plurality of layers in the display stack include a front panel and a light blocking film attached to a portion of the light guide.

14. The headlamp of claim 1, wherein: The optical coupling element includes at least two mirror-coated surfaces and at least two uncoated optically polished surfaces.

15. The headlamp of claim 14, wherein: The at least two mirror-coated surfaces are one of a metallic mirror or a dielectric mirror.

16. The headlamp of claim 14, wherein: The optical coupling element comprises a solid transparent body, and wherein the at least two mirror-coated surfaces and the at least two uncoated optically polished surfaces provide a reflective surface on the optical coupling element, thereby providing total internal reflection through at least one of a refractive index difference between the optical coupling element and a material surrounding the optical coupling element in the tablet computing device and through the at least two mirror-coated surfaces.

17. The light guide of claim 16, wherein: Light originating from the light source that initially misses the light guide while passing through the optical coupling element is reflected at a surface on the optical coupling element and enters the light guide after undergoing additional reflections within the optical coupling element.

18. The light guide of claim 1, wherein: The optical coupling element comprises a rectangular shape.

19. The headlamp of claim 1, wherein: The light source comprises a plurality of LEDs, each LED having an emitter height of 300 microns, and wherein the light guide has a height of 50 microns.

20. The headlamp of claim 1, wherein: The optical coupling element includes a receiving area approximately 750 microns wide configured to receive the light guide, wherein the light guide has a thickness of approximately 50 microns, and wherein the receiving area has a depth of approximately 75 microns for insertion of the light guide.

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