Patent Application
20090267968
This application is based upon and claims the benefit of priority from the prior Taiwanese Patent Application No. 097136364, filed Sep. 22, 2008, the entire contents of which are incorporated herein by reference.
1. Technical Field
The present invention relates to an image display technology, especially to a gamma curve compensating method, a gamma curve compensating circuit and an impulse-type driving display system using the same.
2. Description of the Related Art
At present, a typical method for eliminating or depressing motion blur phenomenon of liquid crystal displays (LCDs) is an impulse-type driving method, so call black insertion technology. However, in the impulse-type driving method, the black insertion technology can make the luminance of display screens of the LCDs decay, and cause an apparent flicker problem. In addition, a response time of the liquid crystal molecule of the LCD is not linear when a grey-scale applied thereto is increased from 0 to other level. If an original grey-scale applied thereto has a lower level, it needs to take more time for changing the original grey-scale to a destination grey-scale. Thus a ghost phenomenon is difficult to be eliminated.
In order to improve the above-described problems such as the luminance decay, flicker, or ghost phenomenon, a dynamic gray insertion technology is developed. The principle of the dynamic gray insertion technology is that a gray-scale to be inserted is determined according to different pictures.
However, in the process of inserting gray-scales, different gamma curves are achieved following insertion of different gray-scales. Thus, the situation of uneven brightness in a same picture, or even same color displaying different colors in different zones, is produced.
What is needed, therefore, is a gamma curve compensating method which is capable to overcome the above described problem.
In one aspect, an exemplary gamma curve compensating method is provided. The gamma curve compensating method is used in a displaying process of a display system for inserting a plurality of grey-scale images to adjust the displaying quality of the display system. A grey-scale luminance of each grey-scale image is one of the grey-scales. The grey-scale luminance of each grey-scale image is not completely same with each other. The gamma curve compensating method includes: providing a plurality of look-up tables (LUTs) corresponding to the different grey-scales; selecting a specific grey-scale from the grey-scales as a grey-scale luminance of one of the grey-scale images and accordingly selecting a specific LUT of the LUTs corresponding to the specific grey-scale; and performing a gamma-curve compensating based on the specific LUT to keep the gamma curve of the display system invariable in the displaying process.
In another aspect, an exemplary gamma curve compensating circuit used in a display system is provided. The gamma curve compensating circuit includes an image generating circuit, a grey-scale insertion determining circuit, a multiplexer, and a looking up and compensating circuit. The image generating circuit generates an original output image signal according to an input image signal received by the display system. The grey-scale insertion determining circuit determines a grey-scale luminance of a grey-scale image to be inserted according to the input image signal and output the grey-scale image. The multiplexer electrically couples to the grey-scale insertion determining circuit and the image generating circuit, and selects one of the grey-scale image and the original output image signal as an original display signal outputted therefrom. The looking up and compensating circuit electrically couples to the multiplexer for receiving the original display signal. The looking up and compensating circuit further provides a plurality of different LUTs, selects a specific LUT from the LUTs according to a grey-scale luminance of the grey-scale image, and performs a gamma-curve compensating on the original display signal based on the specific LUT.
Still in another aspect, an exemplary display system is provided. The display system includes a power supply, an image receiving terminal, a gamma curve compensating circuit, and a display screen. The power supply provides electric power to the display system for operating. The image receiving terminal receives an input image signal. The display screen displays a gamma-curve compensating result of the original output image signal generated by a gamma curve compensating circuit described as above.
Aforementioned embodiments of the present invention provide a plurality of LUTs according to the different grey-scales, select one specific grey-scale from the grey-scales to determine the luminance of one of the insertion grey-scale images in a displaying process, then select one specific LUT of the LUTs corresponding to the selected specific grey-scale, and perform gamma-curve compensating based on the specific LUT in order to adjust the gamma curve into a uniform standard gamma value, such as gamma 2.4. Therefore, the gamma curves of a display system can be kept to be invariable in the displaying process thereof, and then the display quality of the display system is improved.
Other objectives, features and advantages of the touch panel device will be further understood from the further technological features disclosed by the embodiments of display system wherein there are shown and described preferred embodiments of this touch panel device, simply by way of illustration of modes best suited to carry out the present invention.
These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which:
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
Referring to
The gamma curve compensating circuit 15 includes a grey-scale insertion determining circuit 150, an image generating circuit 152, a multiplexer 154, and a looking up and compensating circuit 156. The grey-scale insertion determining circuit 150 determines a grey-scale luminance of a grey-scale image to be inserted according to the received input image signal, and output the grey-scale image after the grey-scale luminance of the grey-scale image is determined. The image generating circuit 152 generates an original output image signal according to the received input image signals from the image receiving terminal 13. The multiplexer 154 electrically couples to the grey-scale insertion determining circuit 150 and the image generating circuit 152, selects the grey-scale image generated from the grey-scale insertion determining circuit 150 or the original output image signal generated from the image generating circuit 152 as an original display signal, and outputs the original display signal. The looking up and compensating circuit 156 electrically couples to the multiplexer 154 for receiving the original display signal. It is to be noticed that the looking up and compensating circuit 156 provides a plurality of different look-up tables (LUTs), selects a specific LUT from the different LUTs corresponding to grey-scale luminance of the inserted grey-scale image, and performs a gamma-curve compensating on the original display signal based on the specific LUT to keep the gamma curve of the display system 10 invariable in a displaying process. A gamma compensating result of the original output image signal by the looking up and compensating circuit 156 is displayed on the display screen 17.
Referring also to
In detail, the grey-scale image to be inserted depends on a division as a unit. A same division is inserted grey-scale images with a same grey-scale. One division can be a line, a segment, a frame or several frames. The analyzing module 1504 can employ histogram analyzing method or other typical analyzing methods, such as minimum grey insertion method or threshold method et al., to determine a pre-inserting grey-scale of each division and employs the outputted analyzing signals to denote the pre-inserting grey-scale. The grey-scale of an image is generally divided into 255 levels, that is grey-scales L0˜L255. In present embodiment, the grey-scale insertion limiting module 1506 can limit the range of the grey-scale to be inserted into a specific range, such as L0˜L30. Regarding two adjacent divisions, the grey-scale insertion limiting module 1506 may limit a varying range of the grey-scales to be inserted, that is, a difference between the two levels of the grey-scales to be respectively inserted into the two adjacent divisions is less than a predetermined value, such as 5 or 10, or smooth the two adjacent divisions. Thus, the grey-scale generating module 1508 can achieve the final grey-scale of the grey-scale image to be inserted, that is grey-scale luminance, according to the pre-inserting grey-scale determined by the analyzing module 1504 matching with the grey-scale limiting parameters stored in the grey-scale insertion limiting module 1506, and output the grey-scale image with the final grey-scale.
Referring to
A gamma curve compensating method of the above described display system 10 is described in following. The display system 10 can adjust the displaying quality thereof by inserting a plurality of grey-scale images in the displaying process. A grey-scale luminance of one grey-scale image is one of the grey-scales. The grey-scale luminance of each grey-scale image is not completely same with each other. The gamma curve compensating method may include the following steps.
Step 1: providing a plurality of look-up tables (LUTs) corresponding to the different grey-scales. The LUTs might be provided by the looking up and compensating circuit 156 of the gamma curve compensating circuit 15.
Step 2: selecting a specific grey-scale of the different grey-scales as a grey-scale luminance of one of the grey-scale images, and accordingly selecting a specific LUT of the LUTs corresponding to the specific grey-scale by the looking up and compensating circuit 156.
Step 3: performing a gamma-curve compensating based on the specific LUT to keep the gamma curve of the display system 10 invariable in the displaying process. For example, the gamma curve of the display system 10 can be adjusted into a uniform standard gamma value, such as gamma 2.4.
Referring to
The inserted grey-scale having a higher level corresponds to a narrower pulse width of the PWM signal. A PWM signal with an appropriate pulse width is used to maintain a grey-scale luminance curve of a grey-scale image with a higher inserted grey-scale, such as grey-scale L15, without sacrificing the maximum luminance and increasing power consumption. A PWM signal with a wider pulse width is used to map upward a grey-scale luminance curve of a grey-scale image with a lower inserted grey-scale, such as grey-scale L10 and L5, as the dotted arrow shown in the
In addition, in a displaying process of inserting a plurality of grey-scale images, following increase of the luminance of the maximum grey-scale, the luminance of the minimum grey-scale is also increased, which results in a bad contrast of a picture in the displaying process of the display system 10. Therefore, as showing in
To sum up, the above described embodiments of the present invention provide a plurality of LUTs corresponding to the different grey-scales, select one specific grey-scale from the grey-scales to determine the luminance of one of the insertion grey-scale images in a displaying process, then select one specific LUT from the LUTs corresponding to the selected specific grey-scale, and perform gamma-curve compensating based on the specific LUT in order to adjust the gamma curve into a uniform standard gamma value, such as gamma 2.4. Therefore, the gamma curves of a display system can be kept to be invariable in the displaying process thereof, and then the display quality of the display system is improved. In addition, due to controlling the light source, a luminance of an image is corrected and an increasing of luminance of a grey-scale image with lower grey-scale is depressed to increase the whole contrast of the image. Thus, the displaying quality of the display system 10 is better.
The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including configurations of the circuit and/or designs of the gamma curve compensating method. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 097115606 | Apr 2008 | TW | national |
| 097136364 | Sep 2008 | TW | national |
