Patent Application
20060139295
1. Technical Field of the Invention
This invention relates to control of cholersteric and other temperature sensitive displays.
2. Background Art
The emergence of Cholesteric Liquid Crystal Displays (ChLCD) provides a revolutionary breakthrough in LCD display technology by providing display technology that consumes no power to maintain an image, while providing a clear, sharp image view, from most viewing angles.
Given their “no power” attribute, ChLCD display technology is well suited for store shelf advertising, electronic price tags, and many other low power display applications where device costs must also be kept to a minimum.
Unlike Super Twisted Nematic LCD displays (STN-LCD displays) and other common display technology, ChLCD displays are updated via more sophisticated methods that define, as is illustrated in
The time-voltage sequences and the need to adjust these to account for temperature and parasitic effects, increases the physical size and cost of the driver circuitry needed to update a ChLCD display.
The general solution to these variances is to use a temperature sensor to indicate to the display controller to modify the programming characteristics based on temperature. Referring to
Disadvantages of the general solution include the circuit area required on the cholesteric display driver 100 for a temperature sensor 110, the development costs, and for low power applications, the electrical current required. Additionally, voltage requirements unique to temperature sensor 110 impose additional requirements back at the power supply 108.
There is a need in the art for a solution that eliminates the need for a temperature sensor, costs associated with the sensor, including those of development time and power. To reduce the application cost of ChLCD technology a new method is needed to reduce the size and complexity of the circuitry on cholesteric display driver 106, thereby lowering its overall cost.
A system, method, and program storage device for controlling a cholesteric display provides for storing display image data and temperature data in a database; providing the image data and temperature data to a display controller; and operating the display controller to convert the image data and temperature data to a voltage-time sequence for driving the cholesteric display.
Other features and advantages of this invention will become apparent from the following detailed description of the presently preferred embodiment of the invention, taken in conjunction with the accompanying drawings.
In accordance with the preferred embodiment of the invention, a cholesteric display is provided with a database of information to be displayed with an entry in the database used to indicate the temperature range of the display's environment. This entry is sent to the display controller to program the display based on a subset of the full operating temperature range of the display.
Further in accordance with the preferred embodiment of the invention, a method is provided for ChLCD display update whereby the need for a temperature sensor integrated with the driver circuitry and/or the display itself is eliminated, especially useful where the display's temperature is within a known range, or can be measured by a remote temperature sensing device. Such a sensing device could also, for example, be shared by multiple displays and other electronic systems.
Referring to
Referring to
ChLCD display's driver electronics 120 (likely an ASIC) is communicated as is represented by line 142 via wire or wirelessly from Central Control System (CCS) 140. CCS 140 stores all imagery to be displayed on ChLCD displays 122, 162, 166, and initiates the update of one or more displays, when appropriate, with new imagery to display. Each display 122, 162, 166 is uniquely addressable by CCS 140 with one or more of these displays located in an environment 150 of varied, but known temperature. Temperature is known based on the area 150 in which display 122 resides, i.e. heating/cooling system preset temperature, or can be monitored via a temperature probe 152, 154 that communicates to the CCS the temperature of the monitored area 150, 151.
When CCS 140 determines that a specific, addressable ChLCD display 122 requires update, CCS 140 accesses its database 144 to obtain the image data to be displayed at the given display 122 address, and also queries its database 144 to obtain the temperature of target display 122. The temperature obtained by the CCS 140 may be delivered from a database 144 record pre-assigned to the display address that stores a temperature representing temperature of the environment 150 where display 126 resides, or it may be delivered from a remote temperature sensor 152 monitoring the same area 150 as display 122. A given ChLCD display's database 144 records indicate whether a pre-recorded temperature should be used, stored as a record in the database, or if a temperature probe 152 co-located within the same area as the display should be read and conveyed, as is represented by line 158 to central control system 140.
When CCS 140 has obtained the image and temperature data of the addressed display 122 from database 144, these are communicated to the display driver 120 where, in accordance with an exemplary embodiment, they are stored to database 124, or fed directly to display controller 126 (this path is not shown). Once received by the display's driver circuitry 120 from CCS, the image and temperature data are translated by controller 126 to the necessary voltage-time sequence required to update display 122.
Referring to
In step 170, Central Control System (CCS) 140 enters the ChLCD display task.
In step 172, CCS 140 queries database 144 for a list of ChLCD displays 122, 162, 166 to be updated.
In step 174, a list of ChLCD display addresses returned to CCS 140 from database 144.
In step 176, CCS 140 indexes to the first display address in the display update list.
In step 178, using the display address, CCS 140 reads database 144 to obtain the content of image data needed to update the display.
In step 179, CCS 140 queries database 144 for the display temperature.
In step 180, the display temperature is either returned from the database 144 record (if the temperature has been pre-set), or CCS 140 retrieves temperature data from a temperature probe 152 located at the address provided by database 144.
In step 182, CCS 140 conveys temperature and image data to the addressed ChLCD display driver 120 either directly or via database 124 records 128, 132.
In step 184, ChLCD display driver 120 receives image and temperature data and translates this to the voltage-time sequence required to update display 122.
In step 186, CCS 140 increments to next display address in the display list and returns to step 178, or if none exist, in step 188 CCS 140 terminates the ChLCD display task In accordance with a further exemplary embodiment of the invention, for a cholesteric display system that uses a database 144 for information to be displayed, an entry in the database is associated with an individual display 122 and is used to indicate the temperature range of the display's environment 150. This entry is sent to display driver 120 to program display controller 126 on a subset of the full operating temperature range of display 122.
The power savings and resulting battery 108 extension by removing temperature sensor 110 are illustrated by the following example. Consider a cost sensitive, power consumptive sensitive cholesteric display multi-chip system with a typical application of supermarket price tag.
Suppose that the battery specified is a 55 mah lithium/manganese dioxide battery with a ten year shelf life. On an exemplary technology, power measurements on a temperature sensor show the sensor consumes 2.6 ma of current. The chip in which the temperature sensor resides has a current budget of 5.3 ma. The temperature sensor therefore consumes 50% of the total current budget for the chip. Based on the battery specified, the maximum current draw for this system is 6.5 ma, 40% of which is consumed by the temperature sensor. Removing the temperature sensor will give back 2.6 ma of current to the remaining logic of the system.
The cell savings for removing the temperature are as follows. The cell area for the sensor in 0.18 um technology is 0.0905 sq mm. This area includes the diode, A/D converter and digital counters in the temperature sensor design. The target die size for this chip in the display system is 2 sq mm. The temperature sensor constitutes 4.5% of the total chip area. This may not be significant by itself but may save enough space to retain the current die size or even reduce it.
Referring again to
Consider a super market price tag example. The temperature ranges in which the price tags are used can be divided into three categories, including freezer 200, cooler 202, and room temperature and above 204. These three ranges may be superimposed on a cholesteric update response time curve 206 of
In this example, database 144 includes fields for item, price of item, and one of these three temperature categories (or regions). When display 122 is updated, information in database 144 is sent to display controller 126, which translates the temperature range into programming control for display 122 based on one of three categories (or regions), 200, 202, or 204 within which the display resides.
In order to update a display 122 operating in the cooler region 202, assuming the actual temperature is 5 degrees C. and the most favorable display is produced by worst case temperature, database 144 indicates (is preset to show) this item is in the cooler region 202 which is within a range from −2 degrees C. to 18 degrees C. When display 122 is programmed by controller 126, the temperature selected is −2 degrees C. Since the temperature pre-set and selected is colder but within the proper operating range, the display programs correctly.
It is an advantage of the present invention that here is provided a system and method for controlling a cholesteric display that does not require a display controller with a temperature sensor.
It will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without departing from the spirit and scope of the invention. Referring to
Further, each step of the method may be executed on any general computer, such as IBM Systems designated as zSeries, iSeries, xSeries, and pSeries, or the like and pursuant to one or more, or a part of one or more, program elements, modules or objects generated from any programming language, such as C++, Java, Pl/1, Fortran or the like. And still further, each said step, or a file or object or the like implementing each said step, may be executed by special purpose hardware or a circuit module designed for that purpose.
Accordingly, the scope of protection of this invention is limited only by the following claims and their equivalents.
