1. Field of the Invention
The present invention relates to a method and device of rapidly generating a gray-level versus brightness curve of a display.
2. Description of the Related Art
A gray-level versus brightness curve of a display is a curve of the relationship between different gray-level values and their corresponding brightness values. The gray-level value may be assigned to the x axis, while the brightness value may be assigned to the y axis; the resulting curve is called the “gray-level versus brightness curve”. As the gray-level versus brightness curve is approximately equal to the mathematical gamma curve (Y=X^r, γ curve, or gamma curve), the gray-level versus brightness curve may also be called a gamma curve.
Different displays have different gray-level versus brightness curves. As a result, to provide consistently high product qualities for displays, the gray-level versus brightness curve of each display must be measured. By obtaining the gray-level versus brightness curve of the display, the manufacturer learns of the characteristics of the display, which may be used to further adjust the color settings of the display.
In a prior art technology, entitled “SYSTEM AND METHOD FOR PANEL DISPLAY TELEVISION ADJUSTMENT” (JP patent No. 2005057543, U.S. Pat. No. 6,043,797, TW patent No. 00583624), a system to measure the brightness of a TV is used to perform γ compensation correction for the TV.
The measuring method of the system utilizes a computer (a PC) to consecutively send gray-level signals to the display, a light sensor obtains the brightness-related data from the panel display, and sends all of the data back to the computer for processing to obtain a voltage-brightness curve (voltage as a value suitably corresponds to brightness for the distribution curve) of the panel display. After a graphic generator sends graphic signals to the display, the light sensor measures and sends the data to the computer; this cycle requires one second. To obtain 8 bits of red, green and blue, the three primary colors, and gray values for a continuous gray-level versus brightness curve, which gray (or white) may be considered another primary color, requires 1 (sec)×256 (gray-level values)×4 (primary colors), which is about 17 minutes. Since each work station on the production line has a short period of time to work, if the y compensation correction procedure for the panel display is performed on the production line, a significant cost in terms of time will be imposed by the measurement, which is a reason why γ compensation correction for the panel displays is difficult to perform on the production line.
Therefore, it is desirable to provide a method and device of rapidly generating a gray-level versus brightness curve of a display to mitigate and/or obviate the aforementioned problems.
A main objective of the present invention is to provide a method of accelerating an image processing procedure for a digital image capturing device.
The method of the present invention obtains partial gray-level value and corresponding measured brightness value of the display and inputs them into the mathematic equation developed by the present invention to establish a gray-level versus brightness curve of the display. Since the present invention only needs partial gray-level value corresponding measured brightness value, the measuring time is reduced and is suitable for the production line.
The method of the present invention includes:
According to an embodiment of the present invention,
According to another embodiment of the present invention, the method further comprises a second mathematic formula:
The present invention further includes a device for searching gray-level versus brightness curve for a color display, the device includes:
According to another embodiment, a second mathematic formula is utilized:
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
Please refer to
According to the prior art technology, the signal generator 74 generates 0 to 255 gray-level image values for each color (red, green, blue and white), and the computer 73 needs only to record the information to obtain the gray-level versus brightness curve without any special operations.
But to rapidly obtain the gray-level versus brightness curve, the signal generator 74 of the present invention only generates a partial gray-level diagram (for example, 5 gray-level diagrams can be the gray-level diagrams for red, green, blue and white; the signal generator 74 may generate one gray-level diagram at once or a plurality of gray-level diagrams at once). The color analyzer 72 measures the corresponding brightness of these gray-level diagrams, and the computer 73 calculates the gray-level versus brightness curve of the color display 90 according to the 5 sets of gray-level values and brightness values.
A typical gamma-curve should be substantially identical to the gray-level versus brightness curve for the display shown in
But, if an S-curve is utilized, as shown in
However, the S-curve may not correctly represent the gray-level versus brightness curve at low level gray values.
Please refer to
Step 501:
The signal generator 74 only generates partial gray-level image diagrams to rapidly obtain the gray-level versus brightness curve. In the prior art technology, n is 256 (assuming the gray-level values may be represented as 8 bit values); in the present invention, n is at least 4; of course, the larger n is, the more accurate the curve may be. However, in order to rapidly obtain the gray-level versus brightness curve, the maximum value for n is preferably 30.
Step 502:
The n sets of (tj, Yj) values are input into the above-mentioned mathematical formula. Since the above-mentioned mathematical equations have many different variations, the following equation 2 is the general formula for the first mathematic equation.
According to a first embodiment, f(tj) is provided by the following Eqn. 3:
In other words, the first mathematic equation becomes equation 4:
wherein k=1, and b, cj are variables;
rj is a parameter; and
tmax is a maximum gray-level value (such as 255).
The first embodiment also employs a second mathematical formula,
which is shown in the following equation:
wherein M is a parameter, such as M=1.
For example, tmax=255, Lmax=255, n=5, M=1, if r1=1, r2=30, r3=0.18, r4=10, and 5 sets of measured corresponding brightness values of the gray-level values (tj, Yj, j=1˜5) are (40, 1), (140, 50), (190, 135), (220, 170), and (254, 254). These 5 sets of measured values are input into Eqn. 4 (a first mathematic formula) and Eqn. 5 (a second mathematic formula) to obtain the following 6 variable values: a=18.297, b=−0.095, c1=0.07826, c2=0.19338, c3=0.72836, c4=0.01995. As 5 sets of measured values input into Eqn. 4 can provide five conditions, and as Eqn. 5 is a condition itself, there are thus six conditions for six variable values.
A primary difference between the first embodiment and the second embodiment is that there is no need for Eqn. 5 in the second embodiment; therefore, there will reduce one condition, which results that the number of variable reduces one.
The first mathematic formula is then changed to Eqn. 6:
wherein k=2.
If n=5, only the variable C1˜C3 are needed, and not variable C4. Therefore, the number of variable reduces one.
A main difference between the first embodiment and the third embodiment is that f(tj) is changed to the following Eqn. 7:
wherein k=1.
Since there is no variable b, there is no need for Eqn. 5.
A main difference between the first embodiment and the fourth embodiment is that f(tj) is changed to the following Eqn. 8:
wherein k=0.
There is no variable b, but a new variable Cn is added, therefore, Eqn. 5 is still needed.
Step 503:
Obtaining the gray-level versus brightness curve from the calculation performed in step 502.
Since the computer 73 comprises a processor 731 and a memory 732, a software program stored in the memory 732 may perform the calculations needed to obtain a correct gray-level versus brightness curve.
Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.
Number | Date | Country | Kind |
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95147542 A | Dec 2006 | TW | national |
Number | Name | Date | Kind |
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6043797 | Clifton et al. | Mar 2000 | A |
Number | Date | Country | |
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20080143752 A1 | Jun 2008 | US |