System and method for detecting the temperature of an electrophoretic display device

An apparatus includes a temperature detector coupled to a conductive layer of an electrophoretic display device. The temperature detector is operable to measure a leakage current that is responsive to a temperature associated with the electrophoretic device and determine the temperature associated with the electrophoretic device based at least in part on the measured leakage current.

TECHNICAL FIELD OF THE INVENTION

This invention relates to electronics and, more specifically, to electrophoretic display devices.

BACKGROUND OF THE INVENTION

Facets of the electronics industry benefit from various information that is displayed on electronic display devices. Accordingly, electrophoretic display devices have been developed to display information. These electrophoretic display devices, however, have proven inadequate in various respects.

SUMMARY OF THE DISCLOSURE

In accordance with the teachings of the present disclosure, disadvantages and problems associated with previous electrophoretic display devices can be reduced or eliminated by providing a system and method that detects the temperature of an electrophoretic display device.

According to one embodiment of the present disclosure, an apparatus includes a temperature detector coupled to a conductive layer of an electrophoretic display device. The temperature detector is operable to measure a leakage current that is responsive to a temperature associated with the electrophoretic device and to determine the temperature associated with the electrophoretic device based at least in part on the measured leakage current.

According to another embodiment of the present disclosure, a method includes measuring a leakage current that is responsive to a temperature associated with the electrophoretic device using a temperature detector coupled to a conductive layer of an electrophoretic display device and determining the temperature associated with the electrophoretic device based at least in part on the measured leakage current using the temperature detector.

Certain embodiments of the present disclosure may provide one or more technical advantages. A technical advantage of one embodiment includes detecting the temperature of an electrophoretic display device. The temperature may be measured by converting a measured leakage current associated with the electrophoretic display device to temperature. This may provide a more accurate estimate of the temperature than may be obtained by measuring the ambient air temperature surrounding the electrophoretic display device. Another technical advantage may include using a detected temperature of an electrophoretic display device to more accurately attain a desired reflective state. Another technical advantage may be that compensating for temperature variations may allow for more bits to be displayed in a grayscale and/or may allow for operation over a greater temperature range than conventional electrophoretic display devices.

Certain embodiments of the present disclosure may include none, some, or all of the above technical advantages. One or more other technical advantages may be readily apparent to one skilled in the art in view of the figures, descriptions, and claims of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention and its advantages are best understood by referring toFIGS. 1 through 4, wherein like numerals refer to like and corresponding parts of the various drawings.

FIG. 1is a block diagram illustrating an example embodiment of a system100for detecting the temperature of an electrophoretic display device102. System100includes an electrophoretic display device102, a temperature detector104, a pulse generation unit106, and a display input108, coupled as shown. Electrophoretic display device102includes a viewing surface103, a transparent layer120, a conductive layer122, an adhesive layer124, a grounding layer126, a backsheet128, ink capsules130, and pigment particles132, arranged as shown. Electrophoretic display device102may include one or more zones, as shown.

In general, system100uses temperature detector104to detect the temperature of electrophoretic display device102. For example, temperature detector104may be coupled to conductive layer122and/or grounding layer126, such that temperature detector104may measure leakage current110. Leakage current110is generally responsive to temperature variations associated with electrophoretic display device102. Based on the measured leakage current110, temperature detector104may determine a temperature of electrophoretic display device102and generate temperature information105. System100may then use pulse generation unit106to display information on electrophoretic display device102. Pulse generation unit106may display information based in part on detected temperature information105, which may thereby compensate for temperature variations of electrophoretic display device102. Displayed information may represent one or more combinations of various desired reflective states of viewing surface103, including any number and/or shades of colors, such as a grayscale.

Electrophoretic display devices, such as electrophoretic device102, are generally capable displaying various reflective states at a viewing surface. These devices operate by applying pulses of various amplitudes and/or wavelengths to ink capsules that include electrically charged pigment particles. The pigment particles may be various colors with different electrical charges, such as positively charged white pigment particles and/or negatively charged black pigment particles. When a pulse is applied, particles of one color may be attracted to the viewing surface and particles of another color may be repelled from the viewing surface. The resulting concentration of pigment particles at the viewing surface produces a net change in optical reflectivity of the display device. Accordingly, waveforms of various amplitudes and wavelengths may be applied to yield various shades between color pigments. For example, an electrophoretic display device may be capable of displaying two or more bits of a grayscale. After a pulse drives the display device to a given shade of reflectivity, the pigment particles generally remain suspended in place until the next pulse is applied.

Generally, the viscosity and electrodynamics of electrophoretic display devices are highly temperature dependent. Accordingly, the pulse and/or waveform required to achieve a particular desired reflective state may be dependent on the temperature of the electrophoretic device. A pulse operable to achieve a desired reflective state at one temperature may result in an undesired reflective state at a different temperature. Humidity similarly affects electrophoretic displays. For these and similar reasons, certain known electrophoretic display devices may not be capable of accurately displaying information and/or reflective states across a wide temperature range. In addition, temperature variations may limit the number of bits in a grayscale that can be accurately displayed. Accordingly, system100that detects the temperature of electrophoretic display device102may substantially reduce and/or eliminate these limitations and problems.

Electrophoretic display device102represents any combination of structure, materials, hardware, software, and/or controlling logic operable to display information at viewing surface103. Electrophoretic display device102may be operable to display images, video, text, and other information. While depicted as including various elements, it should be understood that the illustrated embodiment of electrophoretic display device102is provided by way of example only and may include any number and configuration of elements and other materials operable to form a viewing surface103of an appropriate area and resolution.

Electrophoretic display device102may include one or more temperature zones, each zone associated with a temperature detector104operable to detect the temperature associated with that zone. The illustrated portion of electrophoretic display device102comprises one temperature zone and one temperature detector104. It should be understood, however, that in various embodiments, electrophoretic display device102includes multiple zones, each with one or more temperature detectors, as described in greater detail with respect toFIGS. 4aand4b.

Temperature detector104represents any combination of structure, materials, hardware, software and/or controlling logic operable to detect the temperature of electrophoretic display device102. Temperature detector104may include circuit elements operable to measure leakage current110and determine the temperature associated with electrophoretic display device102based on the measured leakage current110. Temperature detector104may transmit temperature information105, which may include the determined temperature, to pulse generation unit106. An example of temperature detector104is described in greater detail with respect toFIG. 2below. Measuring and converting leakage current110to temperature may provide a more accurate estimate of temperature than other temperature measurement techniques. For example, a thermistor placed in proximity to an electrophoretic display device may heat and cool at different rates than the electrophoretic display itself due to sunlight, shade, air currents, and other environmental factors. As a result, temperatures detected by a thermistor in proximity to an electrophoretic display device may not be accurate. Converting a measured leakage current110to temperature, however, may accurately measure temperature of electrophoretic display device102even when exposed to radiative, convective, and conductive heating and cooling from external sources.

Pulse generation unit106represents any combination of structure, materials, hardware, software, and/or controlling logic operable to control the reflectivity of viewing surface103. Pulse generation unit106may receive display information109from display input108. In addition, pulse generation unit106may receive temperature information105from temperature detector104. Based on display information109and temperature information105, pulse generation unit106may generate and/or apply pulse107of various amplitudes and/or wavelengths to attain a desired reflective state of viewing surface103. For example, pulse generation unit106may apply a pulse to conducting electrode122and grounding electrode126. Pulse generation unit106may determine one or more desired reflective states based on display information109. Accordingly, pulse generation unit106may be capable of driving the reflective states of various ink capsules103with various pulses107such that the image, video, text, or other information is displayed at viewing surface103. An example of pulse generation unit106is described in greater detail with respect toFIG. 2below.

Display input108represents any combination of hardware, software, and controlling logic operable to form an interface capable of receiving display information. For example, display input108may receive display information109from a camera, personal computer, personal digital assistant, or other source of display information. In some embodiments, display information109received from display input108includes information that represents an image, video, text, or other information. Alternatively or in addition, display information109may include one or more desired reflective states of ink capsules130.

Electrophoretic display device102may include various elements. Transparent layer120represents any dimension of transparent material, such as plastic or glass, operable to allow pigment particles132to be viewed at viewing surface103. Conductive layer122and grounding layer126represent electrical nodes, or electrodes, operable to apply a pulse across ink capsule130. For example, conductive layer122may form a positive electrode and grounding layer126may form a negative and/or grounding electrode. Adhesive layer124represents any combination of structure and materials necessary to adhere ink capsules130to grounding electrode126. Back sheet128represents any combination of structure and materials operable to form a foundation and/or backing layer of electrophoretic display device102.

Ink capsules130represent any appropriate configuration of conductive material operable to encapsulate pigment particles132. Ink capsules130may be generally capable of allowing migration of pigment particles132while a pulse is applied. In various embodiments, ink capsules130may be arranged in a grid or other suitable pattern. In addition or in the alternative, ink capsules130may be generally capable of suspending pigment particles132in place when a pulse is not being applied. In some embodiments, each ink capsule130may represent a pixel or other color unit of electrophoretic display device102. Accordingly, the number of ink capsules130in an embodiment of electrophoretic display device102may represent the resolution of the electrophoretic display device102.

Pigment particles132represent multi-colored particles that may be positively or negatively charged. For example, pigment particles132may include negatively charged white particles and positively charged black particles. Pigment particles132are generally operable to migrate towards and away from viewing surface103in response to pulses107applied to ink capsules130through electrodes122and126.

Leakage current110represents a current associated with electrophoretic device102. Leakage current110may represent a waste current and/or otherwise undesirable current that may be created as a byproduct of the electrical characteristics of electrophoretic display device102. Leakage current110may represent a current that migrates from conductive layer122to grounding layer126. For example, leakage current110may migrate through and/or around ink capsule130, as illustrated. In various embodiments, leakage current110may be relatively minor as compared to currents that are associated with pulse107. In many embodiments, the amount of leakage current110is responsive to the temperature of electrophoretic display device102. The dependency of leakage current110on temperature may be caused by the relationship of voltage, current, and resistance to temperature. As the temperature of electrophoretic display device102changes, the resistivity of ink capsules130changes accordingly. Thus, the amount of leakage current110associated with electrophoretic display device102may be measured and used to determine the temperature of electrophoretic display device102. For example, in an exemplary embodiment of electrophoretic display device102, leakage current110may vary based on temperature variations of elements of electrophoretic display device102such as electrodes122and126, ink capsules130, and/or pigment particles132. Leakage current110may depend on the size of the display and other environmental factors. In some embodiments, leakage current110may be measured in microamperes.

In operation, system100uses temperature detector104determine temperature information105associated with electrophoretic display device102. For example, temperature detector104may measure leakage current110and convert the measured leakage current110to temperature information105. Pulse generation unit106may receive display information109and temperature information105. Based on display information109and temperature information105, pulse generation unit106may generate one or more pulses107to change the reflective state of viewing surface103. The details of these operations will be discussed in more detail with respect toFIG. 2below.

FIG. 2is a block diagram illustrating another example embodiment of system100for detecting the temperature of an electrophoretic display device102. As previously described, system100includes electrophoretic display device102, temperature detector104, pulse generation unit106, and display input108. While it should be understood that any combination of hardware, software, and/or controlling logic may be appropriate, examples of embodiments of temperature detector104and pulse generation unit106are described as illustrated.

Temperature detector104includes a current detecting unit204, an analog-to-digital (A/D) converter210, a temperature determiner214, and a humidity sensor218. Pulse generation unit106includes a pulse length determiner230, a controller pulse modulator240, and a calibration unit246.

Current detecting unit204represents any combination of hardware, software, and/or controlling logic operable to detect and/or measure a leakage current110that is associated with electrophoretic display device102. Current detecting unit204includes any appropriate resistor208, a transimpedance operational amplifier (op-amp)206, and a switch212operable to measure leakage current110. In an exemplary embodiment, resistor208and op-amp206may form a current-to-voltage converter, where the size of the resistor may determine an output voltage.

The various elements of current detecting unit204may be arranged in any suitable manner operable to measure leakage current110. For example, current detecting unit204may include leads coupled to conductor layer122and grounding layer126of electrophoretic display device102. Conductive layer122may be coupled to the negative input of op-amp206and to one end of resistor208. Grounding layer126may be coupled to the positive input of op-amp206and to ground. The output of op-amp206may be coupled to the opposite end of resistor208and/or may be coupled to an analog input of an appropriate A/D converter210. In some embodiments, switch212is coupled to the positive and negative inputs of op-amp206.

Switch212may be any suitable switch operable to cease measuring the leakage current when electrophoretic display device102is undergoing a change of a reflective state and/or when a pulse107is being applied. For example, switch212may be closed at the start of pulse107, thereby preventing current detecting unit204from measuring leakage current110for the duration of pulse107. Accordingly, when pulse107ceases, switch107may be opened, thereby allowing current detecting unit204to measure leakage current110after the duration of pulse107.

A/D converter210represents any suitable analog-to-digital converter of a suitable bit size and precision to digitize measured leakage current205. For example, A/D converter may be suitable to accurately digitize a measured leakage current205that corresponds to a leakage current110that may be in the microampere range.

Temperature determiner214includes any suitable combination of hardware, software, and/or controlling logic operable to convert measured leakage current205to temperature information105. For example, temperature determiner214may include one or more memory units, processors, and/or interfaces. In some embodiments, temperature determiner214includes a memory216operable to store a temperature lookup table217that correlates measured leakage current205to temperature information105. Temperature lookup table217may store a temperature profile that includes measured leakage currents at each of various temperatures in a temperature range. Accordingly, temperature determiner214may look up the temperature information105in the table that corresponds to a given measured leakage current205. In some embodiments, temperature lookup table217may store one or more temperature profiles that correlate humidity values and leakage current values to temperature. For example, each temperature profile can correlate current with temperature for a particular humidity value. Temperature determiner214may determine the humidity, then use the temperature profile for that humidity.

Humidity sensor218represents any suitable sensor operable to sense an ambient humidity associated with electrophoretic device102. Humidity sensor218may transmit a measured humidity219to temperature determiner214. In some embodiments, humidity sensor218may be encapsulated with similar materials as are used to encapsulate materials in electrophoretic display device102such that the measured humidity219may track with the humidity within electrophoretic display device102.

Pulse length determiner230includes any suitable combination of hardware, software, and/or controlling logic operable to determine pulse length information234based on temperature information105and one or more desired reflective states included in display information109. For example, pulse length determiner230may include one or more memory units, processors, and/or interfaces. In some embodiments, pulse length determiner230includes a memory232operable to store temperature profile data233. Temperature profile data233may include an interpolated2D lookup table. For example, temperature profile data233may store information that correlates actual reflective states achieved at various temperatures based on various pulse lengths applied at those temperatures. In other words, pulse length determiner230may look up a pulse length calculated to achieve a desired reflective state at a given temperature based on the previously determined actual reflective state at that temperature. Thus, various pulse length durations are each a function of one or more of many desired reflective states at one or more of many given temperatures. In some embodiments, temperature profile data233may include information similar to the information illustrated byFIG. 3, described in greater detail below.

Controller pulse modulator240includes any suitable combination of hardware, software, and/or condoning logic operable to generate one or more pulses107to change the reflective state to one or more desired reflective states included in display information109. Controller pulse modulator240may include one or more memory units, processors, and/or interfaces. Pulse modulator240may be capable of applying multiple pulses in sequence or in parallel such that information109may be displayed at viewing surface103, as previously described.

Calibration unit246includes any suitable combination of hardware, software, and/or controlling logic operable to calibrate electrophoretic display device102by storing temperature information in temperature lookup table217and/or temperature profile data233. For example, calibration unit246may be capable of storing a number of measured leakage currents at various temperatures in temperature lookup table217. In various embodiments, calibration unit246may use an alternative temperature measurement device, such as a thermistor, to measure the various temperatures used in the calibration process. As another example, calibration unit246may be capable of storing a number of achieved reflective states that correspond to various temperatures, humidity levels, and/or pulse length durations in temperature profile data233.

Calibration unit246may generate and/or store temperature lookup table217and/or temperature profile data233during a testing phase of electrophoretic display device102. In addition or in the alternative, calibration unit246may include an interface operable to receive information such as temperature lookup table217and/or temperature profile data233. In some embodiments, such information may be loaded and/or stored based on predetermined electromechanical characteristics of electrophoretic display device102. In some embodiments, calibration unit246may be capable of initiating a calibration process in which a user or other person may be prompted to provide feedback regarding reflective states and/or to set ambient temperatures and/or humidity such that calibration unit246may collect temperature, humidity, and/or reflective state information.

In operation, temperature detector104may determine a temperature associated with electrophoretic display device102. Current detecting unit204of temperature detector104may measure leakage current110associated with electrophoretic display device102. Measured leakage current205may be digitized by A/D converter210and/or may be transmitted to temperature determiner214. In some embodiments, humidity sensor218measures ambient humidity and submits measured humidity219to temperature determiner216. Based on measured leakage current205and/or measured humidity219, temperature determiner216may look up temperature information105in temperature lookup table217to determine the temperature. Temperature determiner216may then transmit temperature information105to pulse generation unit106. In some embodiments, temperature detector104uses switch212to cease measuring leakage current110when a pulse107is being applied to change the reflective state of electrophoretic display device102. In addition or in the alternative, temperature detector104may determine temperature intermittently and/or at a predetermined sampling rate.

Pulse generation unit106may attain a desired reflective state by applying a pulse107the electrophoretic display device102. Pulse generation unit may compensate for temperature of electrophoretic display device102using temperature information105. Pulse length determiner230may receive temperature information105and display information109. Pulse length determiner230may determine the duration and/or waveform of pulses107based on one or more desired reflective states included in display information109received from display input108and temperature information105. Pulse length determiner230may correlate one or more desired reflective states and the temperature information105to determine pulse length information234. For example, pulse length determiner230may look up an appropriate pulse length duration and/or waveform in temperature profile data232stored in memory233. Once pulse length information234is determined from temperature profile data233, pulse length determiner230may transmit pulse length information234to controller pulse modulator240. Based on the pulse length information234, controller pulse modulator240generates one or more pulses107of appropriate waveforms and durations to attain the desired reflective states at viewing surface103. Pulses107may be applied to conductive layer122and grounding layer126of electrophoretic display device102. In some embodiments, calibration unit246may calibrate temperature detector104and pulse generation106such that the temperature associated with measured leakage current and desired reflective states can be adjusted in order to more accurately measure temperature and/or achieve desired reflective estates.

FIG. 3is a chart illustrating exemplary temperature profile data233that may be used in temperature compensated electrophoretic display device102. The X axis represents various pulse lengths, and the Y axis represents a scale of achieved reflectivity. Each line of the graph represents the reflectivity achieved by applying pulses of various wavelengths at each of a number of discrete temperatures. While a number of discrete temperatures are shown, it should be understood that any number of temperatures and corresponding pulse lengths/achieved reflective states may be stored in temperature profile data233. Accordingly, a range of temperatures may be stored such that a gray scale of up to six and/or more bits may be achieved over the range of temperatures.

According to the teachings of the present disclosure, pulse link determiner230may use the correlation between achieved reflective state, temperature, and pulse length, as demonstrated by this chart and/or stored in temperature profile data233, to determine a pulse length calculated to achieve one or more desired reflective states at any of various temperatures. It should be understood that this graph is merely a representation of exemplary data that may be stored and is provided to aid the reader's understanding of the present disclosure.

FIGS. 4A and 4Billustrate exemplary systems for detecting temperatures of electrophoretic display devices that include temperature zones. Temperatures across the screen of an electrophoretic display device may not be uniform. For example, temperatures across a viewing surface may vary according to the manner in which an electrophoretic display device is mounted, the ambient surroundings of the device, and/or other various electromechanical characteristic. Accordingly, electrophoretic display devices400and410may comprise various temperature zones. Each zone402,404,412,414, and/or416may include one or more temperature detectors that detect the measured leakage current associated with that zone. The temperature detectors associated with each zone may thereby determine the temperature associated with that zone. Thus, pulses applied to various areas of the viewing surface103may take into account the regional temperature of the electrophoretic display device. The use of zones may allow temperature compensated pulse107to more accurately achieve desired reflective states that display information109.

The geometries of various zones may be determined based on predetermined temperature gradients across viewing surface103. For example, zones402and404may be appropriate for an electrophoretic display device400that may be subject to environmental conditions that cause regions near to the perimeter of display surface103to be exposed to higher and/or lower temperatures than the inner regions. As another example, zones412,414, and416may be appropriate for an electrophoretic display device410that may be subject to environmental conditions that cause regions along two sides of viewing surface103to be exposed to higher and/or lower temperatures. In some embodiments, zones may be customized by a user based on particular temperature gradients being experienced by a given electrophoretic display device. It should be understood that while specific configurations of zones are illustrated, any number of zones may be utilized in order to account for a temperature gradient across a electrophoretic display device.

Modifications, additions, or omissions may be made to the systems and apparatuses disclosed herein without departing from the scope of the invention. The components of the systems and apparatuses may be integrated or separated. For example, temperature detector104and pulse generation unit106may be integrated onto a single integrated circuit board. Alternatively, various elements of temperature detector104may be included as elements of pulse generation unit106, and vice versa. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. For example, temperature lookup table217and temperature profile data233may be integrated into a single memory unit and/or included in a single database and/or may be accessible by a user and/or calibration unit246. In addition or the alternative, temperature detector104may convert measured leakage current110to temperature using a predetermined formula based on the known and/or estimated resistivity of ink capsules130and/or other components of electrophoretic display device102. As another example, the operations of controller pulse modulator240may be performed by more than one component. Additionally, operations of the systems and apparatuses may be performed using any suitable logic comprising software, hardware, and/or other logic. As used in this document, “each” refers to each member of a set or each member of a subset of a set.

Modifications, additions, or omissions may be made to the methods disclosed herein without departing from the scope of the invention. The methods may include more, fewer, or other steps. For example, new temperature105information may not necessarily be transmitted each time a desired reflective state included in display information109is transmitted. Alternatively, pulse generation unit106may be operable to request new temperature information105from temperature detector104based on any number of appropriate conditions. Additionally, steps may be performed in any suitable order. For example, display input108may be capable of transmitting multiple sets of display information109that each include various desired reflective states and/or pulse generation unit106may store such information and/or display data in a buffer before, during, or while pulses107are being generated.

A component of the systems and apparatuses disclosed herein may include an interface, logic, memory, and/or other suitable element. An interface receives input, sends output, processes the input and/or output, and/or performs other suitable operation. An interface may comprise hardware and/or software.

Logic performs the operations of the component, for example, executes instructions to generate output from input. Logic may include hardware, software, and/or other logic. Logic may be encoded in one or more tangible media and may perform operations when executed by a computer. Certain logic, such as a processor, may manage the operation of a component. Examples of a processor include one or more computers, one or more microprocessors, one or more applications, and/or other logic.

In particular embodiments, the operations of the embodiments may be performed by one or more computer readable media encoded with a computer program, software, computer executable instructions, and/or instructions capable of being executed by a computer. In particular embodiments, the operations of the embodiments may be performed by one or more computer readable media storing, embodied with, and/or encoded with a computer program and/or having a stored and/or an encoded computer program.

A memory stores information. A memory may comprise one or more non-transitory, tangible, computer-readable, and/or computer-executable storage media. Examples of memory include computer memory (for example, Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (for example, a hard disk), removable storage media (for example, a Compact Disk (CD) or a Digital Video Disk (DVD)), database and/or network storage (for example, a server), and/or other computer-readable medium.

Components of the systems and apparatuses may be coupled by any suitable communication network. A communication network may comprise all or a portion of one or more of the following: a public switched telephone network (PSTN), a public or private data network, a local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), a local, regional, or global communication or computer network such as the Internet, a wireline or wireless network, an enterprise intranet, other suitable communication link, or any combination of any of the preceding.