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Touch sensor with force-actuated switched capacitor

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Title: Touch sensor with force-actuated switched capacitor.
Abstract: This disclosure provides apparatus, systems and methods of fabricating force-sensitive switches. In some implementations, an array of force-sensitive switches and local capacitors of a combined sensor device may be used to connect the local capacitor into associated projected capacitive touch (PCT) detection circuitry. In some implementations, each capacitor may be formed with a thin dielectric layer to achieve a high capacitance increase when the force-sensitive switch is closed, e.g., by the pressing of a stylus or finger. In some implementations, the same PCT detection circuitry can be used to detect changes in mutual capacitance when touched with a finger (touch mode) and changes in sensel capacitance when the force-sensitive switch is depressed (stylus or fingerprint mode). ...


Qualcomm Mems Technologies, Inc. - Browse recent Qualcomm patents - San Diego, CA, US
Inventor: Russel Allyn Martin
USPTO Applicaton #: #20120092279 - Class: 345173 (USPTO) - 04/19/12 - Class 345 


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The Patent Description & Claims data below is from USPTO Patent Application 20120092279, Touch sensor with force-actuated switched capacitor.

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CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 61/394,054, entitled “COMBINATION TOUCH, HANDWRITING AND FINGERPRINT SENSOR” (Attorney Docket No. QUALP045P/102908P1) and filed on Oct. 18, 2010, which is hereby incorporated by reference and for all purposes. This application is related to U.S. patent application Ser. No. ______, entitled “COMBINATION TOUCH, HANDWRITING AND FINGERPRINT SENSOR” (Attorney Docket No. QUALP045A/102908U1) and filed on Oct. 11, 2011, to U.S. patent application Ser. No. ______, entitled “FABRICATION OF TOUCH, HANDWRITING AND FINGERPRINT SENSOR” (Attorney Docket No. QUALP045B/102908U2) and filed on Oct. 11, 2011, to U.S. patent application Ser. No. ______, entitled “TOUCH, HANDWRITING AND FINGERPRINT SENSOR WITH ELASTOMERIC SPACER LAYER” (Attorney Docket No. QUALP045C/102908U3) and filed on Oct. 11, 2011, to U.S. patent application Ser. No. ______, entitled “WRAPAROUND ASSEMBLY FOR COMBINATION TOUCH, HANDWRITING AND FINGERPRINT SENSOR” (Attorney Docket No. QUALP045E/102908U5) and filed on Oct. 11, 2011, to U.S. patent application Ser. No. ______, entitled “MULTIFUNCTIONAL INPUT DEVICE FOR AUTHENTICATION AND SECURITY APPLICATIONS” (Attorney Docket No. QUALP045F/102908U6) and filed on Oct. 11, 2011, to U.S. patent application Ser. No. ______, entitled “CONTROLLER ARCHITECTURE FOR COMBINATION TOUCH, HANDWRITING AND FINGERPRINT SENSOR” (Attorney Docket No. QUALP045G/102908U7) and filed on Oct. 11, 2011, all of which are hereby incorporated by reference and for all purposes.

TECHNICAL FIELD

This disclosure relates to display devices, including but not limited to display devices that incorporate multifunctional touch screens.

DESCRIPTION OF THE RELATED TECHNOLOGY

Electromechanical systems (EMS) include devices having electrical and mechanical elements, actuators, transducers, sensors, optical components (including mirrors) and electronics. Electromechanical systems can be manufactured at a variety of scales including, but not limited to, microscales and nanoscales. For example, microelectromechanical systems (MEMS) devices can include structures having sizes ranging from about a micron to hundreds of microns or more. Nanoelectromechanical systems (NEMS) devices can include structures having sizes smaller than a micron including, for example, sizes smaller than several hundred nanometers. Electromechanical elements may be created using deposition, etching, lithography, and/or other micromachining processes that etch away parts of substrates and/or deposited material layers, or that add layers to form electrical and electromechanical devices.

One type of EMS device is called an interferometric modulator (IMOD). As used herein, the term interferometric modulator or interferometric light modulator refers to a device that selectively absorbs and/or reflects light using the principles of optical interference. In some implementations, an interferometric modulator may include a pair of conductive plates, one or both of which may be transparent and/or reflective, wholly or in part, and capable of relative motion upon application of an appropriate electrical signal. In an implementation, one plate may include a stationary layer deposited on a substrate and the other plate may include a reflective membrane separated from the stationary layer by an air gap. The position of one plate in relation to another can change the optical interference of light incident on the interferometric modulator. Interferometric modulator devices have a wide range of applications, and are anticipated to be used in improving existing products and creating new products, especially those with display capabilities.

The increased use of touch screens in handheld devices causes increased complexity and cost for modules that now include the display, the touch panel and a cover glass. Each layer in the device adds thickness and requires costly glass-to-glass bonding solutions for attachment to the neighboring substrates. These problems can be further exacerbated for reflective displays when a frontlight also needs to be integrated, adding to the thickness and cost of the module.

SUMMARY

The systems, methods and devices of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein. Some implementations described herein provide a combined sensor device that combines aspects of capacitive and resistive technologies for touch sensing, handwriting input and fingerprint imaging. Some such implementations provide a touch sensor that combines capacitive and resistive technologies to enable a multi-feature user input sensor overlaid on a display.

In some such implementations, a cover glass apparatus of a consumer device such as a cell phone, an e-reader, or a tablet computer serves additionally as part of a combined sensor device having a single or multi-touch sensor, a handwriting or stylus input device, and/or a fingerprint sensor. The cover glass apparatus may include 2, 3 or more layers. The substrates used to form a cover glass apparatus may be formed of various suitable substantially transparent materials, such as actual glass, plastic, polymer, etc. Such a cover glass apparatus with touch, handwriting and/or fingerprint detection capability may, for example, be overlaid on a display.

One innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus that includes a first substantially transparent substrate having first rows of substantially transparent conductor formed thereon. A first substantially transparent insulator may be formed on the first rows of conductor. A second substantially transparent conductor may be formed in discontinuous areas of second rows on the first insulator.

The apparatus may include a second substantially transparent and flexible substrate having a third substantially transparent conductor formed in columns thereon. In some implementations, the columns may be substantially orthogonal to the rows. The apparatus may include a substantially transparent elastomeric material formed in second portions of the discontinuous areas of the second conductor. The elastomeric material may extend from the discontinuous areas to the second substrate between the columns on the second substrate. The apparatus may include force-sensitive resistor material disposed between the rows and the columns.

The apparatus may include substantially transparent resistors formed in first portions of the discontinuous areas. The columns may overlap the resistors. The second conductor, the resistors and the third conductor may form switches that can be closed when sufficient force and/or pressure is applied to the second substrate. The apparatus may include an analog-to-digital converter and/or a leakage resistor.

The first conductor, the first insulator and the second conductor may form a first capacitor. The apparatus may include a second capacitor configured in parallel with the first capacitor. The second conductor, a resistor and the third conductor may form a switch that can be closed when sufficient force and/or pressure is applied to the second substrate. The switch may be configured in series with the second capacitor. A capacitance of the first capacitor may be modulated when a conducting object is near the second substrate.

The apparatus may include a sensor controller that is configured for communication with the first conductor, the second conductor and the third conductor. The sensor controller may include a touch sensor controller, a handwriting sensor controller and/or a fingerprint sensor controller. The apparatus may include a display and a processor that is configured to communicate with the display and with the sensor controller. The processor may be configured to process image data.

The apparatus may include a memory device that is configured to communicate with the processor. The apparatus may include a driver circuit configured to send at least one signal to the display and a controller configured to send at least a portion of the image data to the driver circuit. The apparatus may include an image source module configured to send the image data to the processor. The image source module may include at least one of a receiver, transceiver, and transmitter. The apparatus may include an input device configured to receive input data and to communicate the input data to the processor.

Another innovative aspect of the subject matter described in this disclosure can be implemented in a method that involves forming first rows of substantially transparent conductor material on a first substantially transparent substrate, forming a first substantially transparent insulator on the first rows of conductor material and forming second substantially transparent conductor material in discontinuous areas of second rows on the first insulator.

A method of this type may involve forming third substantially transparent conductor material in columns on a second substantially transparent and flexible substrate. The columns may be substantially orthogonal to the rows. The method may involve forming substantially transparent elastomeric material in second portions of the discontinuous areas of the second conductor. The elastomeric material may extend from the discontinuous areas to the second substrate between the columns on the second substrate.

The method may involve forming substantially transparent resistors in first portions of the discontinuous areas. The second conductor material, the resistors and the third conductor material may be formed into a switch that can be closed when sufficient force and/or pressure is applied to the second substrate. The switch may be configured in series with the second capacitor. The first conductor material, the first insulator and the second conductor material may form a capacitor. The method may involve forming force-sensitive resistor material between the rows and the columns.

The method may involve configuring a sensor controller for communication with the first conductor, the second conductor and the third conductor. The method may involve configuring the sensor controller to function as a touch sensor controller and/or as a handwriting sensor controller.

The method may involve attaching the apparatus to a display. The method also may involve configuring the sensor controller for communication with a processor that is configured for controlling the display.

Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Although the examples provided in this summary are primarily described in terms of MEMS-based displays, the concepts provided herein may apply to other types of displays, such as liquid crystal displays, organic light-emitting diode (“OLED”) displays and field emission displays. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of an isometric view depicting two adjacent pixels in a series of pixels of an interferometric modulator (IMOD) display device.

FIG. 2 shows an example of a system block diagram illustrating an electronic device incorporating a 3×3 interferometric modulator display.

FIG. 3 shows an example of a diagram illustrating movable reflective layer position versus applied voltage for the interferometric modulator of FIG. 1.

FIG. 4 shows an example of a table illustrating various states of an interferometric modulator when various common and segment voltages are applied.

FIG. 5A shows an example of a diagram illustrating a frame of display data in the 3×3 interferometric modulator display of FIG. 2.

FIG. 5B shows an example of a timing diagram for common and segment signals that may be used to write the frame of display data illustrated in FIG. 5A.

FIG. 6A shows an example of a partial cross-section of the interferometric modulator display of FIG. 1.

FIGS. 6B-6E show examples of cross-sections of varying implementations of interferometric modulators.

FIG. 7 shows an example of a flow diagram illustrating a manufacturing process for an interferometric modulator.

FIGS. 8A-8E show examples of cross-sectional schematic illustrations of various stages in a method of making an interferometric modulator.

FIG. 9A shows an example of sensor electrodes formed on a cover glass.

FIG. 9B shows an alternative example of sensor electrodes formed on a cover glass.

FIG. 10A shows an example of a cross-sectional view of a combined sensor device.

FIGS. 10B-10D show examples of cross-sectional views of alternative combined sensor devices.

FIGS. 11A-11D show examples of cross-sectional views of combined sensor devices having high-modulus and low-modulus compressible layers.

FIG. 12 shows an example of a device that includes a cover glass with a combination touch, handwriting and fingerprint sensor.

FIG. 13 shows an example of a top view of a force-sensitive switch implementation.

FIG. 14 shows an example of a cross-section through a row of the force-sensitive switch implementation shown in FIG. 13.

FIG. 15A shows an example of a circuit diagram that represents components of the implementation shown in FIGS. 13 and 14.

FIG. 15B shows an example of a circuit diagram that represents components of an alternative implementation related to FIGS. 13 and 14.

FIG. 16 shows an example of a flow diagram illustrating a manufacturing process for a combined sensor device.

FIGS. 17A-17D show examples of partially formed combined sensor devices during various stages of the manufacturing process of FIG. 16.

FIG. 18A shows an example of a block diagram that illustrates a high-level architecture of a combined sensor device.

FIG. 18B shows an example of a block diagram that illustrates a control system for a combined sensor device.

FIG. 18C shows an example representation of physical components and their electrical equivalents for a sensel in a combined sensor device.

FIG. 18D shows an example of an alternative sensel of a combined sensor device.

FIG. 18E shows an example of a schematic diagram representing equivalent circuit components of a sensel in a combined sensor device.

FIG. 18F shows an example of an operational amplifier circuit for a combined sensor device that may be configured for handwriting or stylus mode sensing.

FIG. 18G shows an example of the operational amplifier circuit of FIG. 18F configured for touch mode sensing.

FIG. 18H shows an example of an operational amplifier circuit for a combined sensor device that includes a clamp circuit.

FIG. 18I shows examples of clamp circuit transfer functions.

FIG. 18J shows an example of a circuit diagram for a clamp circuit.

FIG. 19 shows an example of a cross-section of a portion of an alternative combined sensor device.

FIG. 20 shows an example of a top view of routing for a combined sensor device.

FIG. 21A shows an example of a cross-sectional view through the combined sensor device shown in FIG. 20.

FIG. 21B shows an example of a cross-sectional view of a wrap-around implementation.

FIG. 22 shows an example of a flow diagram illustrating a fingerprint-based user authentication process.

FIG. 23A shows an example of a mobile device that may be configured for making secure commercial transactions.

FIG. 23B shows an example of using a fingerprint-secured mobile device for physical access applications.

FIG. 24A shows an example of a secure tablet device.

FIG. 24B shows an example of an alternative secure tablet device.

FIGS. 25A and 25B show examples of system block diagrams illustrating a display device that includes a combined sensor device.

Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

The following description is directed to certain implementations for the purposes of describing the innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations may be implemented in any device or system that can be configured to display an image, whether in motion (e.g., video) or stationary (e.g., still image), and whether textual, graphical or pictorial. More particularly, it is contemplated that the described implementations may be included in or associated with a variety of electronic devices such as, but not limited to: mobile telephones, multimedia Internet enabled cellular telephones, mobile television receivers, wireless devices, smartphones, Bluetooth® devices, personal data assistants (PDAs), wireless electronic mail receivers, hand-held or portable computers, netbooks, notebooks, smartbooks, tablets, printers, copiers, scanners, facsimile devices, GPS receivers/navigators, cameras, MP3 players, camcorders, game consoles, wrist watches, clocks, calculators, television monitors, flat panel displays, electronic reading devices (i.e., e-readers), computer monitors, auto displays (including odometer and speedometer displays, etc.), cockpit controls and/or displays, camera view displays (such as the display of a rear view camera in a vehicle), electronic photographs, electronic billboards or signs, projectors, architectural structures, microwaves, refrigerators, stereo systems, cassette recorders or players, DVD players, CD players, VCRs, radios, portable memory chips, washers, dryers, washer/dryers, parking meters, packaging (such as in electromechanical systems, microelectromechanical systems, and non-MEMS applications), aesthetic structures (e.g., display of images on a piece of jewelry) and a variety of EMS devices. The teachings herein also can be used in non-display applications such as, but not limited to, electronic switching devices, radio frequency filters, sensors, accelerometers, gyroscopes, motion-sensing devices, magnetometers, inertial components for consumer electronics, parts of consumer electronics products, varactors, liquid crystal devices, electrophoretic devices, drive schemes, manufacturing processes and electronic test equipment. Thus, the teachings are not intended to be limited to the implementations depicted solely in the Figures, but instead have wide applicability as will be readily apparent to one having ordinary skill in the art.

Some implementations described herein combine novel aspects of capacitive and resistive technologies for touch sensing, stylus detection for handwriting input, and fingerprint imaging. Some such implementations provide a combined sensor device, at least part of which is incorporated in a cover glass apparatus that may be overlaid on or otherwise combined with a display. The cover glass apparatus may have 2, 3 or more layers. In some implementations, the cover glass apparatus includes a substantially transparent and flexible upper substrate and a substantially transparent and relatively more rigid lower substrate. In some such implementations, the lower substrate of the cover glass apparatus may be overlaid on a display substrate. In alternative implementations, the lower substrate of the cover glass apparatus may be a display substrate. For example, the lower substrate of the cover glass apparatus may be the same transparent substrate on which IMOD devices are fabricated, as described below.

Various implementations of such sensor devices are described herein. In some implementations, the cover glass of a display device serves as a single or multi-touch sensor, as a handwriting (or note capture) input device, and as a fingerprint sensor. Sensor functionality and resolution can be tailored to specific locations on the cover glass. In some such implementations, the area in which the fingerprint sensing elements are located may provide not only fingerprint detection, but also handwriting and touch functionality. In some other implementations, the fingerprint sensor may be segregated in a separate, high-resolution zone that only provides fingerprint functionality. In some implementations, the sensor device serves as a combination touch and stylus input device. Various methods of fabrication are described herein, as well as methods for using a device that includes a combined sensor device.

Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. Some implementations described herein combine aspects of capacitive and resistive technologies for touch sensing, handwriting input and in some cases fingerprint imaging. Some such implementations provide a touch sensor that combines capacitive and resistive technologies to enable a multi-functional user input sensor that can be overlaid on a display. Some implementations of the combined sensor device eliminate a middle touch sensor layer that is disposed between the cover glass and the display glass in some conventional projected capacitive touch (PCT)-based devices. Accordingly, some such implementations can mitigate or eliminate at least some drawbacks of PCT and resistive technologies.

A hybrid PCT and digital resistive touch (DRT) implementation allows, for example, detection of a narrow stylus tip pressing onto the display with the DRT aspect while also allowing the detection of very light brushing or close hovering over the display with a finger using the PCT aspect. The sensor device can accept any form of stylus or pen input, regardless of whether it is conducting or non-conducting. Transparent or effectively transparent force-sensitive resistors may be included within some or all of the sensels to improve optical and electrical performance.

According to some implementations, the combination sensor may include two or more patterned layers, some of which may be on a different substrate. The upper (or outer) substrate may, for example, be formed of a plastic such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide, or a similar material. The upper substrate also may be substantially transparent and have a substantially transparent conductor such as indium-tin-oxide (ITO) patterned on its underside. The lower substrate may be formed of a substantially transparent substrate material, such as glass, with another suitable material. The top surface of the substantially transparent substrate can be a patterned layer of substantially transparent conductor material such as ITO. In some implementations, the conductors on the underside of the upper substrate and the upper side of the lower substrate may be patterned into diamond-shaped electrodes, connected as rows or columns on each of the two different layers

Some such implementations include a wrap-around configuration wherein a flexible upper substrate of the sensor device has patterned metallization on an extended portion to allow routing of signal lines, electrical ground, and power. This flexible upper substrate may be wrapped around an edge of a relatively more rigid lower substrate of the cover glass apparatus. One or more ICs or passive components including connecting sockets may be mounted onto the flexible layer to reduce cost and complexity. Signal lines that address sensor electrodes on the lower substrate may be routed and connected to corresponding patterns on the underside of the flexible upper substrate. Such implementations have the potential advantage of eliminating the need for a flex cable for electrically connecting signal lines of the upper layer to integrated circuits and/or other devices. The approach allows a bezel-less configuration for some versions of the final cover glass apparatus.

Fabrication methods include predominantly transparent substrates and materials to increase the optical performance of underlying displays. The fabrication processes may utilize flexible substrates for at least a portion of the sensor device, and lend themselves to roll-to-roll processing for low cost.

Use of a compliant, elastomeric layer between upper and lower portions of the combination sensor can increase the sensitivity to applied pressure or force from a stylus, while increasing the lateral resolution for a given sensel pitch. The elastomeric material may include open regions for the inclusion of force-sensitive resistors. With careful selection of the elastomeric and FSR materials, the loss of transmissivity that can accompany air gaps is minimized.

An array of force-sensitive switches and local capacitors may be used to connect the local capacitor into associated PCT detection circuitry, where each capacitor is formed with a thin dielectric layer to achieve a high capacitance increase when the force-sensitive switch is closed by the pressing of a stylus or finger. The same PCT detection circuitry can therefore be used to detect changes in mutual capacitance when touched with a finger (touch mode) and changes in sensel capacitance when the force-sensitive switch is depressed (stylus or fingerprint mode).

The combined, multi-functional sensor device enables a single touchscreen to perform additional functions such as handwriting input and fingerprint recognition. In some implementations, these multiple features allow increased security through user authentication, and allow better capture of handwriting and a more interactive approach to user interfaces. A handheld mobile device such as a cell phone with the sensor device enables an array of applications, including using the mobile device as a gateway for user authentication to enable transactions and physical access; using the handwriting input function for signature recognition and transmittal for transaction applications; and using the handwriting input feature to automatically capture notes and other documents of students in an academic setting or employees in a corporate setting.

In some such implementations, a separate controller may be configured for the sensor device, or the controller may be included as part of an applications processor. Software for handwriting, touch and fingerprint detection may be included on one or more controllers or the applications processor. Low, medium and high resolution can be obtained with a single sensor device by scanning a subset of the sensels, or by aggregating lines or columns. Power consumption may be reduced by aggregating sensor pixels (or rows or columns) electrically using the controller, so that they perform as a low power small array until higher resolution with a larger array is needed. Power consumption may be reduced by turning off portions or all of the sensor device, turning off parts of the controller, or employing first-level screening at a reduced frame rate. In some such implementations, a combination PCT sensor and digital resistive touch (DRT) sensor has a passive array of capacitors (PCT) and a passive array of resistive switches (DRT). While the touch sensor and stylus sensor systems generally use different sensing techniques, a holistic approach with a common structure saves on PCB part count, reduces area in an ASIC implementation, reduces power, and eliminates the need for isolation between touch and stylus subsystems.

An example of a suitable EMS or MEMS device, to which the described implementations may apply, is a reflective display device. Reflective display devices can incorporate interferometric modulators (IMODs) to selectively absorb and/or reflect light incident thereon using principles of optical interference. IMODs can include an absorber, a reflector that is movable with respect to the absorber, and an optical resonant cavity defined between the absorber and the reflector. The reflector can be moved to two or more different positions, which can change the size of the optical resonant cavity and thereby affect the reflectance of the interferometric modulator. The reflectance spectrums of IMODs can create fairly broad spectral bands which can be shifted across the visible wavelengths to generate different colors. The position of the spectral band can be adjusted by changing the thickness of the optical resonant cavity. One way of changing the optical resonant cavity is by changing the position of the reflector.

FIG. 1 shows an example of an isometric view depicting two adjacent pixels in a series of pixels of an interferometric modulator (IMOD) display device. The IMOD display device includes one or more interferometric MEMS display elements. In these devices, the pixels of the MEMS display elements can be in either a bright or dark state. In the bright (“relaxed,” “open” or “on”) state, the display element reflects a large portion of incident visible light, e.g., to a user. Conversely, in the dark (“actuated,” “closed” or “off”) state, the display element reflects little incident visible light. In some implementations, the light reflectance properties of the on and off states may be reversed. MEMS pixels can be configured to reflect predominantly at particular wavelengths allowing for a color display in addition to black and white.

The IMOD display device can include a row/column array of IMODs. Each IMOD can include a pair of reflective layers, i.e., a movable reflective layer and a fixed partially reflective layer, positioned at a variable and controllable distance from each other to form an air gap (also referred to as an optical gap or cavity). The movable reflective layer may be moved between at least two positions. In a first position, i.e., a relaxed position, the movable reflective layer can be positioned at a relatively large distance from the fixed partially reflective layer. In a second position, i.e., an actuated position, the movable reflective layer can be positioned more closely to the partially reflective layer. Incident light that reflects from the two layers can interfere constructively or destructively depending on the position of the movable reflective layer, producing either an overall reflective or non-reflective state for each pixel. In some implementations, the IMOD may be in a reflective state when unactuated, reflecting light within the visible spectrum, and may be in a dark state when unactuated, absorbing and/or destructively interfering light within the visible range. In some other implementations, however, an IMOD may be in a dark state when unactuated, and in a reflective state when actuated. In some implementations, the introduction of an applied voltage can drive the pixels to change states. In some other implementations, an applied charge can drive the pixels to change states.

The depicted portion of the pixel array in FIG. 1 includes two adjacent interferometric modulators 12 (i.e., IMOD pixels). In the IMOD 12 on the left (as illustrated), a movable reflective layer 14 is illustrated in a relaxed position at a distance (which may be predetermined based on design parameters) from an optical stack 16, which includes a partially reflective layer. The voltage V0 applied across the IMOD 12 on the left is insufficient to cause actuation of the movable reflective layer 14. In the IMOD 12 on the right, the movable reflective layer 14 is illustrated in an actuated position near, adjacent or touching the optical stack 16. The voltage Vbias applied across the IMOD 12 on the right is sufficient to move and can maintain the movable reflective layer 14 in the actuated position.

In FIG. 1, the reflective properties of pixels 12 are generally illustrated with arrows 13 indicating light incident upon the pixels 12, and light 15 reflecting from the pixel 12 on the left. A person having ordinary skill in the art will readily recognize that most of the light 13 incident upon the pixels 12 may be transmitted through the transparent substrate 20, toward the optical stack 16. A portion of the light incident upon the optical stack 16 may be transmitted through the partially reflective layer of the optical stack 16, and a portion will be reflected back through the transparent substrate 20. The portion of light 13 that is transmitted through the optical stack 16 may be reflected at the movable reflective layer 14, back toward (and through) the transparent substrate 20. Interference (constructive or destructive) between the light reflected from the partially reflective layer of the optical stack 16 and the light reflected from the movable reflective layer 14 will determine the wavelength(s) of light 15 reflected from the pixel 12.

The optical stack 16 can include a single layer or several layers. The layer(s) can include one or more of an electrode layer, a partially reflective and partially transmissive layer and a transparent dielectric layer. In some implementations, the optical stack 16 is electrically conductive, partially transparent and partially reflective, and may be fabricated, for example, by depositing one or more of the above layers onto a transparent substrate 20. The electrode layer can be formed from a variety of materials, such as various metals, for example indium tin oxide (ITO). The partially reflective layer can be formed from a variety of materials that are partially reflective, such as various metals, such as chromium (Cr), semiconductors, and dielectrics. The partially reflective layer can be formed of one or more layers of materials, and each of the layers can be formed of a single material or a combination of materials. In some implementations, the optical stack 16 can include a single semi-transparent thickness of metal or semiconductor which serves as both an optical absorber and electrical conductor, while different, more electrically conductive layers or portions (e.g., of the optical stack 16 or of other structures of the IMOD) can serve to bus signals between IMOD pixels. The optical stack 16 also can include one or more insulating or dielectric layers covering one or more conductive layers or an electrically conductive/optically absorptive layer.

In some implementations, the layer(s) of the optical stack 16 can be patterned into parallel strips, and may form row electrodes in a display device as described further below. As will be understood by one having ordinary skill in the art, the term “patterned” is used herein to refer to masking as well as etching processes. In some implementations, a highly conductive and reflective material, such as aluminum (Al), may be used for the movable reflective layer 14, and these strips may form column electrodes in a display device. The movable reflective layer 14 may be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes of the optical stack 16) to form columns deposited on top of posts 18 and an intervening sacrificial material deposited between the posts 18. When the sacrificial material is etched away, a defined gap 19, or optical cavity, can be formed between the movable reflective layer 14 and the optical stack 16. In some implementations, the spacing between posts 18 may be approximately 1-1000 um, while the gap 19 may be approximately less than 10,000 Angstroms (Å).

In some implementations, each pixel of the IMOD, whether in the actuated or relaxed state, is essentially a capacitor formed by the fixed and moving reflective layers. When no voltage is applied, the movable reflective layer 14 remains in a mechanically relaxed state, as illustrated by the pixel 12 on the left in FIG. 1, with the gap 19 between the movable reflective layer 14 and optical stack 16. However, when a potential difference, e.g., voltage, is applied to at least one of a selected row and column, the capacitor formed at the intersection of the row and column electrodes at the corresponding pixel becomes charged, and electrostatic forces pull the electrodes together. If the applied voltage exceeds a threshold, the movable reflective layer 14 can deform and move near or against the optical stack 16. A dielectric layer (not shown) within the optical stack 16 may prevent shorting and control the separation distance between the layers 14 and 16, as illustrated by the actuated pixel 12 on the right in FIG. 1. The behavior is the same regardless of the polarity of the applied potential difference. Though a series of pixels in an array may be referred to in some instances as “rows” or “columns,” a person having ordinary skill in the art will readily understand that referring to one direction as a “row” and another as a “column” is arbitrary. Restated, in some orientations, the rows can be considered columns, and the columns considered to be rows. Furthermore, the display elements may be evenly arranged in orthogonal rows and columns (an “array”), or arranged in non-linear configurations, for example, having certain positional offsets with respect to one another (a “mosaic”). The terms “array” and “mosaic” may refer to either configuration. Thus, although the display is referred to as including an “array” or “mosaic,” the elements themselves need not be arranged orthogonally to one another, or disposed in an even distribution, in any instance, but may include arrangements having asymmetric shapes and unevenly distributed elements.

FIG. 2 shows an example of a system block diagram illustrating an electronic device incorporating a 3×3 interferometric modulator display. The electronic device includes a processor 21 that may be configured to execute one or more software modules. In addition to executing an operating system, the processor 21 may be configured to execute one or more software applications, including a web browser, a telephone application, an email program, or any other software application.

The processor 21 can be configured to communicate with an array driver 22. The array driver 22 can include a row driver circuit 24 and a column driver circuit 26 that provide signals to, e.g., a display array or panel 30. The cross section of the IMOD display device illustrated in FIG. 1 is shown by the lines 1-1 in FIG. 2. Although FIG. 2 illustrates a 3×3 array of IMODs for the sake of clarity, the display array 30 may contain a very large number of IMODs, and may have a different number of IMODs in rows than in columns, and vice versa.



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stats Patent Info
Application #
US 20120092279 A1
Publish Date
04/19/2012
Document #
13271063
File Date
10/11/2011
USPTO Class
345173
Other USPTO Classes
361749, 29829
International Class
/
Drawings
36


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Qualcomm Mems Technologies, Inc.

Qualcomm Mems Technologies, Inc. - Browse recent Qualcomm patents