TW511066B - Adaptive gamma curve correcting device and method of liquid crystal display - Google Patents

Abstract

The invention provides an adaptive gamma curve correcting device and method of liquid crystal display having multiple display modes or different display states. More than one gamma curves are provided to the liquid crystal display for adapting to the display exhibitions of liquid crystal display with different display modes or states. Each prepared gamma curve corresponds to a suitable display mode or state, so as to optimize the liquid crystal display. When a display mode is in operating, the gamma curves are switched to select a suitable gamma curve.

Description

511066 V. Description of the invention α) [Field of invention] The present invention generally relates to a liquid crystal display (LCD), and more particularly, to a display having multiple display modes or different displays Apparatus and method for adaptive gamma curve correction of state liquid crystal display. [Background of Invention]

LCD monitors are conventionally divided into two types: reflective and transmissive. As shown in Figure 1A, in a reflective liquid crystal display, the ambient light 10 on the front of the liquid crystal display passes through the liquid crystal display 12, and is then reflected by the reflector 14 and passes through the liquid crystal display, the display 12, so that it becomes The display light received by the viewer is 16. When the ambient light is weak 10 or the environment is not bright enough for the viewer, a clear image cannot be obtained. In addition, the modulation rate in LCD monitors is not good. In order to obtain a clear image display, the requirements for ambient light intensity are more stringent. As shown in Figure 1B, the transmissive liquid crystal display can use the backlight 18 provided by the light source to overcome the disadvantage of low light intensity. In a transmissive liquid crystal display, the backlight 18 passes through the liquid crystal display 12 and becomes the display light 16 that the viewer accepts. However, providing the light source 10 of the backlight 18 consumes power, which is also a disadvantage for reducing the size and weight of the liquid crystal display device. Moreover, when the environment is bright, the transmissive liquid crystal display is still not as good as the reflective liquid crystal display, which can save the power required for the backlight. As a solution, a transflective liquid crystal display has been proposed, which is a combination of a transmissive liquid crystal display and a transmissive liquid crystal display. As shown in FIG. 1C, in a transflective liquid crystal display,

Page 4 511066 V. Description of the invention (2) The ambient light 10 is partially reflected by the penetrating reflector 20, which also allows the backlight 18 to pass through. The transflective liquid crystal display has two display modes: a reflective display mode and a transmissive display mode. When ambient light! 〇 When it is strong enough, it can save the power required by the backlight 18. On the contrary, when the environment is dark, the backlight is turned on. However, transflective liquid crystal displays pose a problem because reflective liquid crystal displays have different optical characteristics from transmissive liquid crystal displays. A typical display system is illustrated in FIG. 2, in which the controller 22 receiving video signals generates a display data signal D passed to the data driver 26 and a scan signal s passed to the scan driver 24, and The liquid crystal display panel 28 is driven. In order to correct the non-linearity of the transmittance / reflectance to the driving voltage of the LCD panel 28, the data driver 26 is provided with a gamma curve correction device to apply what is called gamma The correction data of line 30 relates to the liquid crystal display panel 28. Unfortunately, if these two types of liquid crystal displays are optimized, the gamma curve of the reflective liquid crystal display is different from that of the transmissive liquid crystal display. When transmissive, the optical efficiency or performance in a liquid crystal display is optimized, the gamma curve of the gray level of the image in the reflective display panel and the gamma curve of the ^ level in the transmissive display mode different. Therefore, the display quality of the transflective liquid crystal display is deteriorated. In addition, when the ambient temperature changes, the performance of the liquid with a preset gamma curve will be worse, because the optical characteristics of the liquid crystal are temperature-dependent. The gamma curve correction device of the known technology cannot Adapt to the environment

511066 V. Description of the invention (3) Therefore, an adaptive gamma curve correction device and method for a liquid crystal display with multiple display modes or different display states is desired. [Summary of the Invention] An object of the present invention is to provide adaptive correction of a gamma curve of a liquid crystal display having a plurality of display modes or different display states.

According to the present invention, in a liquid crystal display having a plurality of display modes or different display states, each of the display modes or states is provided with a gamma curve in advance, and when the display modes or states are switched, the liquid crystal display Corresponding gamma curve is provided.

In a hardware-implemented embodiment, two voltage dividers are used to generate an RV curve for reflective display mode and a T-V curve for transmissive display mode. These curves are obtained by The switch controlled by the mode signal is selected to provide an appropriate gamma curve. In a digitally implemented embodiment, a memory is used to digitally store an RV curve for a reflective display mode and a TV curve for a transmissive display mode; and an addresser mode The signal is controlled, and an appropriate gamma curve is read from the memory. In a software-implemented embodiment, a memory will store parameters corresponding to an RV curve for a reflective display mode and a TV curve for a transmissive display mode; and a gamma controlled by the mode signal. The gamma curve generator calculates a gamma curve based on appropriate parameters stored in the memory. In a temperature-adaptive embodiment, a thermal coupler is used to sense the ambient temperature, and therefore from a plurality of gamma curves prepared for different temperature conditions

Page 6 511066 5. Description of the invention (4) Select an appropriate gamma curve from the line. With a plurality of gamma curves prepared in advance for multiple display modes or states, the present invention can adapt the display performance of a liquid crystal display by switching between the gamma curves. [Detailed description of the invention] As a display system of the present invention, FIG. 3 shows a block diagram of a transflective liquid crystal display, which is similar to the display system of the conventional liquid crystal display shown in FIG. A controller 32 receives the video signal and generates a display data signal D and a scanning signal S. A data driver 26 receives the display data signal D from the controller 3 2 and generates a data voltage DV of the image gray level, and drives a source of a thin film transistor (TFT) array in the liquid crystal display panel 28. Pole (not shown). _ On the other hand, a scan driver 24 receives a scan signal S from the controller 32 and generates a scan voltage SV of a scan line to drive the gate of the TFT array in the LCD panel 28. A backlight 29 is configured to project on the liquid crystal display panel 28 in the transmissive display mode. To correct the non-linearity of the liquid crystal display panel 28, a gamma curve correction device 34 supplies a gamma curve 7 to the data driver 26. However, the gamma curve correction device 34 is provided with two gamma curves, which are the RV curve 36 for the reflective display mode and the TV curve 38 for the transmissive display mode, and the output 7 of the gamma curve correction device 34 Tie between RV curve 36 and 1'- ¥ curve 38. The selection of 1 ^-¥ curve 36 and 1'- ¥ curve 38 is controlled by the mode signal M from the controller 32. When the LCD panel 28 operates in a reflective display mode, the controller 3 2 uses a mode signal

Page 7 511066 V. Description of the invention (5) M selects the R-V curve 36 in the gamma curve correction device 34 and supplies it to the data driver 26. When the transmissive display mode is desired, the controller 32 will turn on the backlight 29 and switch the gamma curve 7 to the T-V curve 38 in the gamma curve correction device 34 by the mode signal M. In this embodiment, the mode signal M is also used to switch the backlight 29. Therefore, when the reflective display mode is switched to the transmissive display mode, the gamma curve correction device 34 is switched to the TV curve 38 and at the same time, Turn on the backlight 29.

In order to further enhance the automatic adaptation, an optical sensor 39 is used to monitor the ambient light intensity. The method is based on one or more preset thresholds, and the optical sensor 39 is used to enable the penetrating display mode. When the environment is dark, the signal sensed by the sensor 39 reaches a preset threshold value, so a lighting notification signal I is sent to switch to the transmissive display mode, that is, the backlight '29 is turned on, and the gamma The curve correction is switched to the TV curve 38. The light beep sensor 39 can directly turn on the backlight 39 and then trigger the mode signal M with another signal; or the optical sensor 39 can be activated. The controller 3 2 triggers the mode signal M while turning on the backlight 39 and switching成 TV 线 38。 TV curve 38. In addition, the threshold for switching the display mode can be planned in consideration of the ambient lighting and its changes in a timely manner.

For an exemplary implementation, FIG. 4 provides an R-V curve 36 and a T-V curve 38 measured in an actual transflective liquid crystal display to show the difference between the characteristics and the characteristics. As is well known in the art, for specific voltages in the transition region between the black and white display voltage levels, the reflectance is less than the transmittance. This difference between the R-V curve 36 and the T-V curve 38 will worsen the display performance unless the individual gamma curves are biased for different display modes. because

Page 8 511066 V. Description of the invention (6) Only one gamma curve on the right is used in the reflective display mode and the transmissive display mode, but the display performance cannot be improved. The hardware path of the gamma curve correction split 3 4 is taken as an example: · Two voltage dividers 40 and 42 described in the fifth mode are connected in parallel, and their two terminal nodes are connected to a high-voltage power supply Vh, respectively. And a low-voltage power source VI. In other embodiments, the high-voltage power source and the low-voltage power source of the voltage divider corresponding to different display modes may be different. In this embodiment, the voltage divider 4 of the reflective display mode Five resistors in series Rrl, Rr2, Rr3, Rr4 and 讦 5; and a voltage divider 42 in transmissive display mode is also composed of five resistors Rtl, Rt2, Rt3, Rt4 and Rt5 in series The voltage dividers 4 and 42 are both impedance-graded to provide the gamma curve voltage and are connected to switches M1, SW3, and SW4. Switches SW 1-4 are controlled by the mode signal to switch to voltage divider 4 at the same time 0 or voltage divider 4 2. Therefore, two separate gamma curves can be controlled to provide a reflective display mode and a transmissive display mode. Figure 6 is another embodiment of providing a digital gamma curve. R — v curve 4 6 and a TV curve 48 are stored in read-only format in digitized form In Read Only Memory (R0M) 44, the values of both the gamma curve and 38 are sampled and stored in ROM 44 in advance. A positioner 50 is controlled by a mode signal M to generate a Appropriate address Α))) to read the RV curve 46 or TV curve 48 data to be output. If necessary, the digital gamma curve 7 from R 0 Μ 4 4 can be converted by digital analog DAC (Digital to Analog Converter; DAC) 52 is further converted into an analog voltage. In this way, the gamma curve provided by a comparison table

511066 5. Search in the description of invention (7), which is suitable for all digital display system.

A software-implemented embodiment of the present invention is provided in FIG. In this way, only the basic parameters of the R-V curve 56 and the T-V curve 58 are stored in a ROM 54, which can reduce the storage capacity. A gamma curve generator 60 is controlled by a mode signal M, and an appropriate parameter P is obtained from the ROM 54. In the gamma curve generator 60, a program for calculating a gamma curve value is executed based on the obtained parameters. For different systems, the software in the gamma curve generator 60 can be updated. As is known in the art, the actual gamma curve can be approximated by the finite point method, so this parameter requires only partial point data and an equation, which will simplify the calculations performed by the gamma curve generator 60. This approximation curve can be obtained directly from the actual R-V curve and T-V. Curve, as shown in Figure 4.

Fig. 8 shows a block diagram of a display system with a temperature-adaptive liquid crystal display. In this system, with the assistance of a thermal coupler 74, a reflective liquid crystal display panel 62 is optimized with a gamma curve correction device 66, wherein the gamma curve correction device 66 is The controller 64 switches. The gamma curve correction device 66 includes three temperature-dependent gamma curves: a high-temperature (HT) gamma curve 68, a medium-temperature (MT) gamma curve 70, and a low-temperature (LT) gamma curve 72 for LCD panel 6 2 operating in different temperature ranges. The thermal coupler 74 monitors the ambient temperature and sends a temperature notification signal T to the controller 64, and selects an appropriate gamma curve among the gamma curves 68, 70, and 72 to supply to the data driver 26. In other embodiments, the gamma curve correction device 66 may directly perform switching using the thermal coupler 74, which uses the signal T as the mode signal M. The multiple gamma curves can obviously be applied to reflective liquid crystal displays.

Page 511066

Device, transmissive liquid crystal display, partial valence liquid crystal display, and transmissive liquid crystal display, twisted nematic (T w i s t e d N e m a t i c; n), reflective display, super twisted nematic (Super-Twisted Nematic;

Liquid crystal displays, as well as thin film transistor liquid crystal displays, thin film diode (TFD) liquid crystal displays, metal insulator metal (MIM) liquid crystal displays, and long-term operating temperatures. # I The above description of the preferred embodiment of the present invention is for the purpose of clarification, and is not intended to limit the present invention to exactly the disclosed form. Based on the above teaching or learning from the embodiment of the present invention, it is modified or Variations are possible. The embodiments are chosen and explained in order to explain the principles of the present invention and allow those skilled in the art to use the present invention in practical applications in various embodiments. The technical ideas of the invention are intended to be covered by the following patent applications. And its equivalence— / definite 0

511066 Schematic description For those skilled in the art, from the following detailed description and accompanying drawings, the present invention will be more clearly understood, its above and other objectives and advantages will become more apparent, Among them: FIG. 1 shows three different types of liquid crystal displays; FIG. 2 shows a block diagram of a typical liquid crystal display display system; and FIG. 3 shows a block diagram of a display system for a liquid crystal display with multiple display modes according to the present invention. Figure 4 shows the RV curve and TV curve of the gamma curve in the LCD display system according to the present invention; Figure 5 shows the circuit diagram of the gamma curve correction device according to the first embodiment of the present invention; Figure 6 FIG. 7 is a block diagram showing a gamma curve correction device according to a second embodiment of the present invention; FIG. 7 is a block diagram showing a gamma curve correction device according to a third embodiment of the present invention; and FIG. Block diagram of a liquid crystal display system with temperature adaptation not according to the present invention. The components are disrespectful to the ambient light line of the watch. 12 The liquid crystal shows disrespect. 14 The reflector 16 shows the light line. 18 The back light

Page 12 511066 Brief description of the drawing 20 Transmissive reflector 22 Controller 24 Cat driver 26 Data driver 28 LCD panel 29 Backlight 30, Gamma curve 32 Controller 34 Gamma curve correction device 36 R-V curve 38 τ -v curve 39 optical sensor 40 voltage divider 42 voltage divider 44 read-only memory 46 R-V curve 48 TV curve 50 positioner 56 R-V curve 58 TV curve 54 read-only memory 60 gamma curve generation 62 reflective LCD panel 64 controller

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511066

Simple description of the drawing 66 68 70 72 74 P Rr J Rr2 Rr3 Rr4 Rr5 Rt 1 Rt2 Rt3 Rt4 Rt5 SW1 SW2 SW3 SW4 D DV S SV Gamma '-t Gaga ^ \ j ^ \ 1 / \) / τ τ Τ i Η ML / (V / fv / ίν 玛 温温 温 器 合 # Tiger letter material pressure pressure device device device device device device device device telecommunications Electricity, resistance, resistance, resistance, resistance, resistance, off, off, off, indication, aim, reference, electricity, electricity, electricity, electricity, electricity

Page 14 511066 Brief description of the drawing 7 Gamma curve Μ mode signal I Illumination notification signal Τ Temperature notification signal

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Claims (1)

511066 6. Application for Patent Scope 1. An adaptive gamma curve correction device for a liquid crystal display, comprising: a liquid crystal display panel having multiple display modes or states; multiple voltage dividers corresponding to the multiple displays respectively A plurality of gamma curves of modes or states; and a switch function means, which is controlled by a mode signal, and switches between the plurality of voltage dividers to provide an adaptive gamma curve for the LCD panel and the panel . 2. The device according to item 1 of the patent application scope, wherein the liquid crystal display panel is selected from the group consisting of a reflective liquid crystal display, a transmissive liquid crystal display, a partially reflective liquid crystal display, and a transflective liquid crystal display. 3. The device according to the scope of patent application, wherein the LCD panel is selected from the group consisting of a twisted nematic liquid crystal display and a super-twisted nematic liquid crystal display. 4. The device according to the scope of patent application, wherein The liquid crystal display panel is selected from the group consisting of a thin film transistor liquid crystal display, a thin film diode liquid crystal display, and a metal insulator metal liquid crystal display. 5. The device according to item 1 of the scope of patent application, wherein the display mode includes a reflective display mode and a transmissive display mode. 6. The device according to item 1 of the patent application range, wherein the display state includes different temperature states. 7. For example, the device of claim 6 includes a thermal coupler for monitoring the ambient temperature, and automatically switches between the plurality of gamma curves corresponding to the different temperature states. Page 16 511066 6. Scope of patent application 8. The device in the scope of patent application item 1 further includes a backlight for projecting onto the LCD panel. 9. The device according to item 8 of the scope of patent application, further comprising an optical sensor for monitoring the ambient light intensity, and automatically turning on and off the backlight according to at least one threshold value corresponding to the ambient light intensity. 10. The device according to item 7 of the scope of patent application, wherein the mode signal is guided for self-use and is a switching signal for turning on and off the backlight. 1 1. An adaptive gamma curve correction device for a liquid crystal display, including: A liquid crystal display panel having multiple display modes or states; a memory function means for storing multiple gamma curves of the multiple display modes or states; and * a certain addresser controlled by a mode signal and controlled by the Read a digital gamma curve from multiple gamma curves. 1 2 · The device according to item 11 of the patent application scope, wherein the liquid crystal display panel is selected from the group consisting of a reflective liquid crystal display, a transmissive liquid crystal display, a partially reflective liquid crystal display, and a transflective liquid crystal display. 13. The device according to item 11 of the scope of patent application, wherein the liquid crystal display panel is selected from the group consisting of a twisted nematic liquid crystal display and a super twisted nematic liquid crystal display. 14. The device according to item 11 of the scope of patent application, wherein the liquid crystal display panel is selected from the group consisting of a thin film transistor liquid crystal display, a thin film diode liquid crystal display, and a metal insulator metal liquid crystal display. Page 17 511066 6. Scope of patent application 1 5. The device according to item 11 of the scope of patent application, wherein the display mode includes a reflective display mode and a transmissive display mode. 16. The device according to item 11 of the scope of patent application, wherein the display state includes different temperature states. 17. The device according to item 16 of the patent application scope further includes a thermal coupler for monitoring the ambient temperature, and automatically switches between the plurality of gamma curves corresponding to the different temperature states. 18. The device according to item 11 of the patent application scope further comprises a backlight for projecting onto the liquid crystal display panel. 19. The device according to item 18 of the scope of patent application, further comprising an optical sensor for monitoring the ambient light intensity, and automatically turning on and off the backlight according to at least one threshold value corresponding to the ambient light intensity. * 2 0. The device according to item 17 of the scope of patent application, wherein the mode signal is derived from a switching signal for switching the backlight on and off. 2 1. The device according to item 11 of the patent application scope further includes a digital analog converter for converting the digital gamma curve into an analog signal. 2 2. —An adaptive gamma curve correction device for liquid crystal displays, including: A liquid crystal display panel having a plurality of display modes or states; a memory function means for storing a plurality of gamma curve parameters of the plurality of display modes or states; and a gamma curve generator controlled by a mode signal,产生 Generate a gamma curve signal according to the plurality of gamma curve parameters. 2 3. The device according to item 22 of the patent application scope, wherein the liquid crystal display Page 18 511066 6. Scope of patent application Device panel is selected from the group consisting of reflective liquid crystal display, transmissive liquid crystal display, partially reflective liquid crystal display and transflective liquid crystal display. 2. The device according to item 22 of the scope of patent application, wherein the liquid crystal display panel is selected from the group consisting of a twisted nematic liquid crystal display and a super twisted nematic liquid crystal display. 25. The device according to item 22 of the scope of patent application, wherein the liquid crystal display panel is selected from the group consisting of a thin film transistor liquid crystal display, a thin film diode liquid crystal display, and a metal insulator metal liquid crystal display. 2 6. The device according to item 22 of the scope of patent application, wherein the display mode includes a reflective display mode and a transmissive display mode. 2 7. The device according to item 22 of the scope of patent application, wherein the display state 'includes different temperature states. 2 8. The device according to item 27 of the patent application scope further includes a thermal coupler for monitoring the ambient temperature, and automatically switches between the plurality of gamma curves corresponding to the different temperature states. 2 9. The device according to item 22 of the patent application scope further includes a backlight for projecting onto the liquid crystal display panel. 30. The device according to item 29 of the scope of patent application, further comprising an optical sensor for monitoring the ambient light intensity, and automatically turning the backlight on and off according to at least one threshold value corresponding to the ambient light intensity. 31. The device according to item 28 of the scope of patent application, wherein the mode signal is derived from a switching signal for switching the backlight on and off. 3 2. —An adaptive gamma curve correction method for LCDs, including Page 19, 511066 6. The scope of patent application: The following steps: preparing a liquid crystal display panel with multiple display modes or states; preparing multiple gamma curves for the multiple display modes or states; and Switch between curves to provide a gamma curve signal. 33: The method according to item 32 of the scope of patent application further includes monitoring the ambient temperature, and automatically switching between the plurality of gamma curves corresponding to different temperature states. 34. The method according to item 32 of the patent application scope, further comprising projecting a backlight onto the liquid crystal display panel. 35. The method according to item 34 of the scope of patent application, further comprising monitoring the ambient light intensity, and automatically turning the backlight on and off according to at least one threshold value corresponding to the ambient light intensity. 36. The method according to item 32 of the scope of patent application, further comprising storing the plurality of gamma curves and reading one gamma curve therefrom. 37 7. The method according to item 36 of the patent application scope, further comprising converting the one gamma curve into an analog gamma curve signal. 38. The method according to item 32 of the patent application scope, further comprising storing a plurality of gamma curve parameters and generating the gamma curve signal according to one of the plurality of gamma curve parameters. Page 20