Information
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Patent Grant
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6590561
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Patent Number
6,590,561
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Date Filed
Saturday, May 26, 200123 years ago
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Date Issued
Tuesday, July 8, 200321 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
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CPC
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US Classifications
Field of Search
US
- 345 102
- 345 87
- 345 89
- 345 207
- 345 690
- 349 61
- 349 64
- 349 65
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International Classifications
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Abstract
A computer program, method, and device for controlling the brightness of a display (10) by proportionally varying the voltage delivered to each pixel in the display (10) after the back light (12) for the display (10) has been dimmed to its approximate lowest level. The display (10) includes a back light (12); a display module (16) having an array of pixels that may be individually controlled to selectively block or pass light from the back light (12) to create a desired image; a user interface (24) for selectively adjusting brightness of the back light (12) to vary the amount of light passing through the pixels to control the brightness of the image; and a controller (22) for proportionally adjusting the luminosity of the pixels to further control the amount of light passing through the pixels to control the brightness of the image.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to displays used in electronic devices such as laptop computers and avionics and marine equipment. More particularly, the invention relates to a computer program and method for controlling the brightness of a display by proportionally modifying the luminosity of each pixel in the display.
2. Description of the Prior Art
Thin-film transistor (TFT) liquid crystal displays (LCDs) and other types of displays are commonly used in a variety of electronic devices, including laptop computers, avionics and marine equipment, and global positioning satellite (GPS) receivers. Such displays typically have back lights that may be adjusted to brighten the displays when used in bright light and dim the displays when used in low light.
Adjusting the brightness of a back light to brighten or dim a display works well in most applications; however, back lights can only be dimmed so much before they effectively turn off entirely. Thus, once the lowest threshold of a back light has been reached, its display cannot be effectively dimmed any further. Those skilled in the art will appreciate that it is often desirable to dim a display beyond the lowest threshold of its back light in some environments such as in the cockpit of an aircraft or boat at night.
Accordingly, there is a need for an improved display and method of operation that overcomes the limitations of the prior art.
SUMMARY OF THE INVENTION
The present invention solves the above-described problems and provides a distinct advance in the art of display technology. More particularly, the present invention provides a computer program, method, and device for controlling the brightness of a display by proportionally varying the charge delivered to each pixel in the display after the back light for the display has been dimmed to its approximate lowest level.
One embodiment of the display of the present invention broadly includes a back light; a display module having an array of pixels that may be individually controlled to selectively block or pass light from the back light to create a desired image; a user interface for selectively adjusting the brightness of the back light to vary the amount of light passing through the pixels to control the brightness of the image; and a controller for proportionally adjusting the luminosity of the pixels to further control the amount of light passing through the pixels to control the brightness of the image. Thus, the controller and the user interface cooperate for dimming the display module in two ways: first by dimming the back light until it reaches its lowest threshold, and then by proportionally reducing the luminosity of the display module pixels to further limit the amount of light that passes through the pixels.
The preferred display also includes a color filter to render light passing through each of the pixels either red, green, or blue. These colors are combined and varied in intensity to create different color combinations. To dim the brightness of the display beyond the threshold of the back light, the controller proportionally lowers the values of the red, green, and blue components of all colors on the display. This dims the display while still maintaining the relative color gradations of the display.
By constructing a display as described herein, numerous advantages are realized. For example, by proportionally adjusting the luminosity of the pixels of the display, the brightness of the display can be further dimmed once the back light has been dimmed to its approximate lowest level. This allows the brightness of the display to be dimmed beyond the lowest threshold of the back light to accommodate for special operating environments such as in an aircraft or boat cockpit at night.
These and other important aspects of the present invention are described more fully in the detailed description below.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
A preferred embodiment of the present invention is described in detail below with reference to the attached drawing figures, wherein:
FIG. 1
is an exploded isometric view of the components of a display constructed in accordance with a preferred embodiment of the present invention.
FIG. 2
is a flow diagram depicting certain steps performed in a preferred embodiment of the present invention.
The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to
FIG. 1
, a display
10
constructed in accordance with a preferred embodiment of the invention is illustrated. The display
10
may be used in or with any electronic devices such as laptop computers, avionics and marine equipment, and GPS receivers. A preferred application for the display is in avionics and marine equipment manufactured and sold by Garmin International, Inc. of Olathe, Kans.
The display
10
broadly includes a back light
12
, a diffuser panel
14
, a display module
16
, a color filter
18
, an anti-reflective lens
20
, a brightness controller
22
, and a user interface
24
. The back light
12
, diffuser panel
14
, display module
16
, color filter
18
, and anti-reflective lens
20
are preferably sandwiched between a conventional mounting board
26
and a frame
28
. The controller
22
and user interface
24
may be integrally mounted with the other components of the display
10
or may be mounted in a separate enclosure attached to the other components of the display
10
.
The back light
12
is entirely conventional and is provided to direct light through the display module
16
to form images on the face thereof. The back light
12
may incorporate any conventional light source such as light-emitting diodes (LEDs) or high-intensity, cold-cathode flourescent tubes.
The diffuser panel
14
is positioned between the back light
12
and the display module
16
to diffuse and uniformly polarize light emitted from the back light
12
. This permits the light to be more effectively acted upon by the display module
16
.
The display module
16
is preferably a conventional thin-film transistor (TFT) liquid crystal display (LCD) display module having an array of pixels arranged on a glass substrate. The display module
16
preferably utilizes active matrix technology wherein each pixel is activated by a separate transistor. An image is created on the display module
16
by applying an electric charge to certain pixels to change the pixels' light absorption properties to vary the amount of light from the back light
12
that passes through the pixels.
The display module
16
may be formed with any number of pixels, and each pixel may be separately activated by various levels of voltage. For example, the display module
16
may include 128 rows and 240 columns of pixels with 256 levels of brightness per pixel. The display module
16
may employ several variations of liquid crystal technology, including super twisted nematics (STN), dual scan twisted nematics (DSTN), ferroelectric liquid crystal (FLC), and surface stabilized ferroelectric liquid crystal (SSFLC). Other display technologies, including metal-insulator-metal (MIM), may also be used.
The display
10
preferably displays color images and therefore includes a color filter
18
. The color filter
18
is positioned in front of or is formed on the front face of the display module
16
and is provided to color light passing through the pixels either red, green, or blue. The color filter
18
includes a glass substrate with individual pixel filter areas integrated thereon that block all wavelengths of light except those within the desired color range of a pixel. The areas in between the colored pixel filter areas are preferably printed black to increase contrast between the various colors. When the display
10
is used for avionics purposes, the choices of colors for symbols and graphics is guided by TSO C113 standards for EFIS displays. Color use on the display
10
may be varied or fixed. For example, if color use is fixed, land areas may always be displayed as black, water as blue, air space boundaries as green, labeling and some course lines as white, and the active course line as magenta.
The anti-reflective lens
20
is positioned in front of the display module
16
and the color filter
18
and is provided to polarize light passing through the color filter
18
to sharpen images and eliminate glare. The anti-reflective lens
20
is preferably a separate component, but it may also be integrally formed with the color filter
18
and/or the front face of the display module
16
.
The brightness controller
22
and user interface
24
are electrically coupled with the display module
16
and together control the brightness of the display module
16
. The controller
22
may be any conventional computing device such as a microprocessor or micro controller. The controller
22
may be part of a gate driver or data driver that drives the pixels of the display module
16
or may be a separate dedicated component. The user interface
24
may be any type of device that provides input to the controller
22
such as a touch-screen menu display having up/down arrows or a manually-activatable slider bar.
The controller
22
and user interface
24
may be operated to either brighten or dim images created on the display module
16
. Images may be brightened in a conventional manner. Specifically, an operator may press an up arrow or operate a slider bar on the user interface
24
to increase the intensity of the back light
12
.
The controller
22
and user interface
24
cooperate for dimming the display module
16
in two ways: first by dimming the back light
12
, then by proportionally reducing the luminosity of the pixels of the display module
16
. More specifically, the display module
16
is first dimmed by decreasing the brightness of the back light
12
in a conventional manner. Once the back light
12
has been dimmed to its lowest level before it turns off or to a selected threshold level, the display
10
may then be further dimmed by controlling the luminosity of each pixel of the display
10
to limit the amount of light that passes through the display module
16
. This may be accomplished via a variety of different means, depending on the display technology used. In the case of an active matrix display, the luminosity of the pixels may be reduced by proportionately reducing the voltage to each and every active pixel used to create an image. For example, if an image requires five pixels on the display module
16
to have brightness levels of 50, 100, 150, 200, and 250 (on a scale of 0-255), and it is desired to dim the display
10
, the voltage delivered to each of these pixels may be proportionally reduced to brightness levels of 25, 50, 75, 100, and 125 so that each active pixel is proportionally dimmed by 50%. When the display
10
includes a color filter
18
so as to display color images, the red, green, and blue subcomponents of each color presented by the display
10
are reduced in a proportional manner so as to dim the display
10
while maintaining relative color variations on the display
10
.
The flow chart of
FIG. 2
shows in more detail the functionality and operation of a preferred implementation of the controller
22
and user interface
24
to dim the display module
16
. Some of the blocks of the flow chart may represent a module segment or portion of code of the computer programs of the present invention which comprises one or more executable instructions for implementing the specified logical function or functions. In some alternative implementations, the functions noted in the various blocks may occur out of the order depicted in FIG.
2
. For example, two blocks shown in succession in
FIG. 2
may in fact be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order depending upon the functionality involved.
The dimming routine begins when the controller
22
senses a request to dim the display module
16
as depicted in step
200
of FIG.
2
. For example, an operator wishing to dim an image may press a down arrow or operate a slide bar on the user interface
24
. The controller
22
then determines if the lowest threshold of the back light
12
or a pre-selected threshold level has been reached as depicted in step
202
. The lowest threshold of the back light
12
is preselected and may be any percentage of the full brightness of the back light
12
. For example, through experimentation, it may be determined that the back light
12
ceases to emit appreciable light at a power level of 25%. This 25% level may then be preset as the lowest threshold for the back light
12
. If the lowest threshold of the back light
12
has not been reached, the program proceeds to step
204
where the controller
22
dims the back light
12
the amount requested by the user interface
24
to reduce the amount of light passing through the display module
16
. The routine then starts over to await further requests to dim the display module
16
.
If the controller
22
determines that the lowest or pre-selected threshold of the back light
12
has been reached in step
202
, the routine proceeds to step
206
where the controller
22
determines whether the lowest threshold of the pixels has been reached. The lowest threshold for the pixels may be preselected and may be any percentage of the normal voltage levels for the pixels. For example, it may be determined that the pixels fail to operate properly if their voltage level is reduced by more than 75%. If so, 25% of the pixels' normal operating voltage may be preset as the lowest threshold for the pixels. If the lowest threshold for the pixels has been reached, the routine ceases dimming the display module
16
.
If, however, the lowest threshold for the pixels has not been reached in step
206
, the routine proceeds to step
208
where the controller
22
proportionally adjusts the voltage level of all active pixels. The user interface
24
and the controller
22
may be configured to reduce the voltage levels delivered to the pixels in discrete steps or may provide an analog, infinite amount of reduction levels.
The steps described above can be implemented in hardware, software, firmware, or a combination thereof. In a preferred embodiment, however, the steps are preferably implemented with a computer program stored on or accessible by the controller.
The computer program preferably comprises an ordered listing of executable instructions for implementing logical functions in the controller
12
. The computer program can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device, and execute the instructions. In the context of this application, a “computer-readable medium” can be any means that can contain, store, communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable medium can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semi-conductor system, apparatus, device, or propagation medium. More specific, although not inclusive, examples of the computer-readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a random access memory (RAM), a read-only memory (ROM), an erasable, programmable, read-only memory (EPROM or Flash memory), an optical fiber, and a portable compact disk read-only memory (CDROM). The computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.
From the foregoing, it can be seen that the display
10
of the present invention provides advantages over prior art displays that merely provide dimming through adjustment of a back light. By proportionally adjusting the luminosity of the pixels of the display module
16
, the brightness of the display
10
can be further dimmed once the back light
12
has been dimmed to its approximate lowest level. This allows the brightness of the display
10
to be dimmed beyond the lowest threshold of the back light
12
to accommodate for special operating environments. Moreover, because the controller
22
proportionally reduces the voltage level to all active pixels, and therefore the red, green, and blue color components of a color when the display
10
is used to display color images, relative gray scale and color variations on the display
10
are maintained.
Although the invention has been described with reference to the preferred embodiment illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims. For example, although the preferred display includes a color filter
18
for displaying color images, the dimming routine of the present invention may be used with a monochrome display by proportionally varying the shades of gray of the display
10
.
Claims
- 1. A display comprising:a back light; a display module having an array of pixels that may be individually controlled to selectively block or pass light from the back light to create a desired image; and a controller for proportionally adjusting the luminosity of the pixels of the display module to control the amount of light passing through the pixels to control the brightness of the image, wherein the controller is coupled with the user interface and is operable to adjust the luminosity of the pixels after the brightness of the back light has been adjusted to its approximate lowest level.
- 2. The display as set forth in claim 1, further including a user interface for selectively adjusting brightness of the back light to vary the amount of light passing through the pixels of the display module to control the brightness of the image.
- 3. The display as set forth in claim 1, further including a color filter to render light passing through each of the pixels either red, green, or blue.
- 4. The display as set forth in claim 3, the controller being operable to proportionally adjust voltage delivered to each of the pixels to proportionally scale the red, green, and blue color light emitted through the color filter.
- 5. The display as set forth in claim 1, wherein the controller is coupled with the user interface and is operable to adjust the luminosity of the pixels after the brightness of the back light has been adjusted to a selected threshold level.
- 6. The display as set forth in claim 1, further including a diffuser panel for uniformly polarizing light emitted from the back light.
- 7. The display as set forth in claim 1, wherein the display module is a liquid crystal display module.
- 8. The display as set forth in claim 7, wherein the liquid crystal display module is a thin-film transistor device.
- 9. A method of controlling the brightness of a display, the display including a back light and a display module having an array of pixels that may be individually controlled to selectively block or pass light from the back light to create a desired image, the method comprising the steps of:adjusting the brightness of the back light to vary the amount of light passing through the pixels of the display module to control the brightness of the image; and when the back light has been dimmed to a pre-determined brightness level, proportionally adjusting the luminosity of the pixels to further reduce the amount of light passing through the pixels to reduce the brightness of the image.
- 10. The method as set forth in claim 9, wherein the proportionally adjusting the luminosity step is performed by proportionally adjusting the voltage delivered to each of the pixels to proportionally scale the amount of light passing through the pixels.
- 11. The method as set forth in claim 9, wherein the display includes a color filter to render light passing through each of the pixels either red, green, or blue.
- 12. The method as set forth in claim 9, wherein the pre-determined brightness level is an approximate lowest brightness level of the back light.
- 13. The method as set forth in claim 9, wherein the pre-determined brightness level is a selected threshold brightness level of the back light.
- 14. A display comprising:a back light; a display module having an array of pixels that may be individually controlled to selectively block or pass light from the back light to create a desired image; a color filter positioned adjacent the display module to render light passing through each of the pixels either red, green, or blue; a user interface for selectively adjusting brightness of the back light to vary the amount of light passing through the pixels of the display module to control the brightness of the image; and a controller for proportionally reducing the luminosity of the pixels of the display module to further control the amount of light passing through the pixels to control the brightness of the image.
- 15. The display as set forth in claim 14, the controller being operable to proportionally adjust voltage derived to each of the pixels to proportionally scale the red, green, and blue color light emitted through the color filter.
- 16. The display as set forth in claim 14, wherein the controller is coupled with the user interface and is operable to adjust the luminosity of the pixels after brightness of the back light has been adjusted to its approximate lowest level.
- 17. The display as set forth in claim 14, wherein the controller is coupled with the user interface and is operable to adjust the luminosity of the pixels after the brightness of the back light has been adjusted to a selected threshold level.
- 18. The display as set forth in claim 14, further including a diffuser pane for uniformly polarizing light emitted from the back light.
- 19. The display as set forth in claim 14, wherein the display module is a liquid crystal display module.
- 20. The display as set forth in claim 19, wherein the liquid crystal display module is a thin-film transistor device.
- 21. A computer program stored on computer-readable medium for controlling the brightness of a display, the display including a back light and a display module having an array of pixels that may be individually controlled to selectively block or pass light from the back light to create a desired image, the computer program including code segments for:adjusting the brightness of the back light to vary the amount of light passing through the pixels of the display module to control the brightness of the image; and when the back light has been dimmed to its approximate lowest brightness level, proportionally modifying luminosity of the pixels to further reduce the amount of light passing through the pixels to reduce the brightness of the image.
- 22. A display comprising:a back light; a display module having an array of pixels that may be individually controlled to selectively block or pass light from the back light to create a desired image; a controller for proportionally adjusting the luminosity of the pixels of the display module to control the amount of light passing through the pixels to control the brightness of the image, wherein the controller is coupled with the user interface and is operable to adjust the luminosity of the pixels after the brightness of the back light has been adjusted to a selected threshold level.
- 23. The display as set forth in claim 22, further including a user interface for selectively adjusting brightness of the back light to vary the amount of light passing through the pixels of the display module to control the brightness of the image.
- 24. The display as set forth in claim 22, further including a color filter to render light passing through each of the pixels either red, green, or blue.
- 25. The display as set forth in claim 24, the controller being operable to proportionally adjust voltage delivered to each of the pixels to proportionally scale the red, green, and blue color light emitted through the color filter.
- 26. The display as set forth in claim 22, further including a diffuser panel for uniformly polarizing light emitted from the back light.
- 27. The display as set forth in claim 22, wherein the display module is a liquid crystal display module.
- 28. The display as set forth in claim 27, wherein the liquid crystal display module is a thin-film transistor device.
US Referenced Citations (5)
Number |
Name |
Date |
Kind |
4958915 |
Okada et al. |
Sep 1990 |
A |
5019808 |
Prince et al. |
May 1991 |
A |
5406305 |
Shimomura et al. |
Apr 1995 |
A |
5933089 |
Katada |
Aug 1999 |
A |
6452582 |
Rolsto |
Sep 2002 |
B1 |