1. Field of the Invention
The invention relates in general to a plasma display, and more particularly, to a brightness correction apparatus and method of a plasma display.
2. Description of Related Art
Generally, display apparatus can be classified into two major types. One is the display using the cathode ray tube (CRT), and the other is the flat panel display. Being lighter and thinner than the cathode ray tube display, and having a display image that is neither distorted nor interfered by a magnetic field, the flat panel display has gradually replaced the conventional cathode ray tube display to become the user favorite.
Commonly seen flat panel displays in the market include the liquid crystal display (LCD) and plasma display panel (PDP). The plasma display panel, which can be fabricated with a large display area, is specifically applicable for certain events and locations. In the discharge driving circuit of the plasma display, a field is typically divided into several sub-fields, while each sub-field has a specific number of sustain pulses. The display for different gray scale inputs is then achieved by a different allocation combination for each sub-field.
Referring to
However, due to factors such as discharging features or luminescence properties of fluorescent objects, a linear relationship between the actual display brightness and the sustain pulse number cannot exist. Normally, as shown in
The present invention provides brightness correction apparatus and method of a plasma display allowing an enhanced display effect between the gray scale and picture brightness of a plasma display.
In the brightness correction apparatus provided by the present invention, the brightness error between ideal display brightness and actual display brightness for each gray scale data of the plasma display has been established as a reference for the circuit thereof in advance. The brightness correction apparatus comprises an inverse y conversion lookup unit, an error diffusion unit and a gray scale allocation lookup unit. The inverse y conversion lookup table is used to receive an input signal and convert the input signal into a first gray scale data to be output according to the inverse y conversion rule. The error diffusion unit is coupled to the inverse y conversion lookup unit to receive the first gray scale data. Further, a second gray scale data is output by modifying the first gray scale data with consideration of the display brightness error of the neighboring pixel of the currently displaying pixel. The brightness error of the second gray scale data is looked up and recorded as the brightness error for the currently displaying pixel. The gray scale allocation lookup unit is coupled to the error diffusion unit to receive the integral portion of the second gray scale data, and to obtain the desired output gray scale allocation by looking up a gray scale allocation table.
In one embodiment of the present invention, the error diffusion unit of the brightness correction apparatus of the plasma display includes an adder, a brightness error lookup circuit, and a weighted error supply circuit. The adder is used to receive the first gray scale data, and to sum up the first gray scale data and the weighted display brightness error of the neighboring pixel of the currently displaying pixel as the second gray scale data to be output. The brightness error lookup circuit is coupled to the adder to receive the integral portion of the second gray scale data, and to look up the brightness error table to obtain the brightness error of the currently displaying pixel. The weighted error supply circuit is coupled to the adder and the brightness error lookup circuit to save the brightness error received from the brightness error lookup circuit as the display brightness error of the currently displaying pixel. The display brightness error of the neighboring pixel of the currently displaying pixel is weighted to obtain the weighted display brightness error required by the adder.
In another embodiment of the present invention, the error diffusion unit of the brightness correction apparatus of the plasma display comprises a first adder, a brightness error lookup circuit, a second adder, and a weighted error supply circuit. The first adder is used to receive the first gray scale data, and to sum up the first gray scale data and the weighted display brightness error of the neighboring pixel of the currently displaying pixel as the second gray scale data to be output. The brightness error lookup circuit is coupled to the first adder to receive the integral portion of the second gray scale data, and to look up the brightness error table to obtain the brightness error of the currently displaying pixel. The second adder is coupled to the first adder and the brightness error lookup circuit to receive the decimal portion of the second gray scale data and the brightness error of the currently displaying pixel, so as to sum up the decimal portion of the second gray scale data and the brightness error as the display brightness error of the currently displaying pixel to be output. The weighted error supply circuit is coupled to the first adder and the second adder to save the display brightness errors of the neighboring pixel and the currently displaying pixel. The display brightness error of the neighboring pixel of the currently displaying pixel is weighted to obtain the weighted display brightness error required by the first adder.
The present invention further provides a brightness correction apparatus for a plasma display of which ideal display brightness and actual display brightness for each gray scale has been established. The brightness correction apparatus comprises an inverse y conversion lookup unit, an error diffusion unit, an integer gray scale lookup unit and a gray scale allocation lookup unit. The inverse y conversion lookup unit is used to receive an input signal, and according to the inverse y conversion rule, to convert the input signal into a first gray scale data to be output. The error diffusion unit is coupled to the inverse y conversion unit to receive the first gray scale data, and to output a second gray scale data derived by modifying the first gray scale data with consideration of the display brightness error of the neighboring pixel of the currently displaying pixel. Further, the brightness error of the second gray scale data is looked up and recorded as the display brightness error of the currently displaying pixel after being modified. The integer gray scale lookup unit is coupled to the error diffusion unit to receive the integral portion of the second gray scale data, and to obtain a third gray scale data by looking up the integer gray scale table. The gray scale allocation unit is coupled to the integer gray scale lookup unit to receive the third gray scale data, and to look up the gray scale allocation table to obtain the sustain pulse number of the currently displaying pixel to be output.
In the third embodiment of the present invention, the error diffusion unit of the brightness correction apparatus of the plasma display includes a first adder, a brightness error lookup circuit, a subtractor, a second adder, and a weighted error supply circuit. The first adder is used to receive the first gray scale data, and to sum up the first gray scale data and the weighted display brightness error of the neighboring pixel of the currently displaying pixel as the second gray scale data to be output. The brightness error lookup circuit is coupled to the first adder to receive the integral portion of the second gray scale data, and to look up the brightness error table to obtain the brightness error of the currently displaying pixel. The subtractor is coupled to the first adder and the integer gray scale lookup unit to receive the second gray scale data and a third gray scale data, and to obtain a gray scale error by subtracting the second gray scale with the third gray scale data. The second adder is coupled to the subtractor and the brightness error lookup circuit to receive the gray scale error and the brightness error of the currently displaying pixel, so as to sum up the gray scale error and the brightness error into a display brightness error to be output. The weighted error supply circuit is coupled to the first adder and the second adder to save the display brightness errors of the neighboring pixel and the currently displaying pixel. The display brightness error of the neighboring pixel of the currently displaying pixel is weighted to obtain the weighted display brightness error required by the first adder.
In the above embodiments, the brightness error table includes a lookup table for integral portion G and brightness error E of the gray scale data. Assuming that the actual measured gray scale and brightness is represented by a function B0(G), and the ideal gray scale and brightness has the relationship of function B(G), preferably, the calculation formula for establishing the brightness error table is E=[(B(G)−B0(G))/B0(G)]*G. If the input signal is S, and the first gray scale data is G1, it is preferable that G1=(S/255)2.2*255 for the inverse y conversion rule with an NTSC input signal.
In addition, the present invention further provides a brightness correction method for a plasma display comprising the following steps. A brightness error between the ideal display brightness and the actual display brightness for each gray scale data is measured to establish a brightness table. When the first gray scale data of the currently displaying pixel is received, the first gray scale data is added with a value of the display brightness error of the neighboring pixel of the currently displayed pixel into a second gray scale data to be output. The brightness error table is looked up to obtain the brightness error of the second gray scale data. The brightness error of the second gray scale data is recorded as the display brightness error of the currently displaying pixel. Preferably, the recorded brightness error includes the decimal of the second gray scale data.
It is known from the above that the present invention provides a brightness correction apparatus and method for a plasma display. Because the brightness error diffusion has weighted and modified the display brightness error of the neighboring pixel of each of the currently displaying pixels, a spatial uniformity results, and a better picture brightness display effect is obtained.
These, as well as other features of the present invention, will become more apparent upon reference to the drawings wherein:
Referring to the relationship between sustain pulse and brightness as shown in
Assuming that the relationship is shown in
Referring to
The inverse γ conversion lookup unit 310 is used to receive an input signal S, and converts the input signal S into a first gray scale data G1 to be output according to inverse γ conversion rule. According to color display principle, the input signal S includes a red, green, or blue input signal. Using an NTSC signal as an example, the inverse γ conversion rule is G1=(S/255)2.2*255.
The adder 321 is used to receive the first gray scale data G1, and to obtain a second gray scale data by summing the first gray scale data G1 and a weighted display brightness error of a neighboring pixel of a currently displaying pixel. The objective of such calculation is to consider the display brightness error of the neighboring pixel of the currently displaying pixel, and to offset by brightness error diffusion, allowing a picture closer to the ideal value.
The brightness error lookup circuit 322 is coupled to the adder 321 to receive the integral portion of the second gray scale data, and to look up the brightness error table to obtain the brightness error of the currently displaying pixel. For example, in the brightness error table established above, the second gray scale data of the gray scale 4 is input, and the corresponding brightness error is ¾. The brightness error ¾ is input to a memory apparatus 324 of the weighted error supply circuit 323 to be stored as the display brightness error of the currently displaying pixel. According to the principle, the memory apparatus 324 will store the display brightness errors of the neighboring pixels of the previously sequentially displayed currently displaying pixels. The display brightness errors are weighted to obtain the weighted display brightness error required by the adder 321. For this embodiment, the display brightness error of the four neighboring pixels of the currently displaying pixel are weighted with weighting value a, b, c, d via the multipliers 326, 327, 328 and 329, respectively, where a+b+c+d is preferably equal to 1. The method to obtain the neighboring pixels is shown in
The gray scale allocation lookup unit 330 is coupled to the error diffusion unit 320 to receive the integral portion of the second gray scale data, and to look up a gray scale allocation table to obtain the sustain pulse number of the currently displaying pixel to be output.
Referring to
To comply with such circuit variation, the error diffusion unit 520 is modified to include a first adder 521, a brightness error lookup circuit 522, a subtractor 523, a second adder 524, and a weighted error supply circuit 525 which includes multipliers 527, 528, 529, 531 and a memory apparatus 526. The first adder 521, the brightness error lookup circuit 522, the multipliers 527, 528, 529, 531 and the memory apparatus 526 are similar to those described in the previous embodiments. To simultaneously consider the decimal error generated by the inverse γ conversion lookup unit 510 and the integer error generated by the integer gray scale lookup unit 530, the subtractor 523 is used to calculate the gray scale error between the decimal error and the integer error. Before saving brightness error into the memory apparatus 526, the gray scale error is included by the second adder 524 for calculating the display brightness error of the currently displaying pixel to be stored. In addition, the integer gray scale lookup unit 530 may be integrated into the gray scale allocation lookup unit 540. For example, when gray scales 45 and 46 are not to be output, the gray scales 45 and 46 are mapped to gray scale 44 in the gray scale allocation table in the gray scale allocation lookup unit 540. Meanwhile, the brightness error table of the brightness error lookup circuit 522 must also comply with the brightness errors for adjusting the gray scales 45 and 46. Apart from the different gray scale allocation table and the brightness table, the combined circuit structure is similar to the first or second embodiment.
Accordingly, a brightness correction method of a plasma display is shown in
According to the above, the present invention includes at least the following advantages:
1. As the brightness error between the ideal display brightness and the actual display brightness of the gray scale of the plasma display is considered and compensated by the brightness error diffusion, better picture quality and display effect are obtained.
2. The gray scales unwanted for output can be converted into other gray scales for output and compensated by brightness error diffusion.
Other embodiments of the invention will appear to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples are to be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
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