KR20030018621A - Pin-cushion correction method of video display apparatus - Google Patents

Abstract

PURPOSE: A method for correcting pin cushion of a video display device is provided to correct pin cushion caused by characteristic of a display device to output images clearly, thereby improving quality of an LCD projector. CONSTITUTION: The equation of an oval is generated using a value for correcting pin cushion and image standard(400). A scaling value is calculated on the basis of the equation of an oval(402). A digital video signal is scaled according to the scaling value to be output(408). The scaling value is calculated for each line. When an image is output being dented according to the pin cushion, on the basis of the maximum value of the calculated scaling values, other lines are relatively reduced. The pin cushion correction value is input for each corner of an image, and the equation of an oval is generated for each corner.

Description

Pin-cushion correction method of video display device {PIN-CUSHION CORRECTION METHOD OF VIDEO DISPLAY APPARATUS}

The present invention relates to an image display device, and more particularly, to a pincushion correction method for an image display device.

An image processing procedure of a conventional LCD projector will be described with reference to FIG. The analog video signal input through the input signal selector 100 is input to an analog to digital converter (ADC) 102. The ADC 102 converts an analog video signal into a digital video signal and provides it to the digital video signal processor 104. The digital image signal processor 104 processes the digital image signal and provides the digital image signal to a digital to analog converter (DAC) 106 so that the image can be output in an optimal state. The DAC 106 converts a digital video signal into an analog video signal and provides the same to the display device 108. The display device 108 outputs an image according to the provided analog image signal.

However, the general LCD projector has a pincushion phenomenon in which the edge of the output image is distorted due to the optical characteristics of the display device LCD. That is, even when the analog image signal of the optimal state is provided to the display device of the LCD projector, the edge of the output image may be convex (or concave) as shown in FIG. 2.

Conventionally, such distortion is regarded as a characteristic of a display device, and it is accepted or, if the distortion is very severe, the display device has to be replaced.

Accordingly, in the related art, there has been a demand for the development of a technology that not only improves the quality of the LCD projector by correcting the pincushion phenomenon due to the characteristics of the display device, but also outputs the image clearly, and efficiently uses the display device.

Accordingly, an object of the present invention is to provide a pincushion correction method of an image display device capable of correcting a pincushion phenomenon due to the characteristics of a display device.

1 is a block diagram of a conventional image processing apparatus.

Fig. 2 is a diagram showing an example of image output according to the conventional method.

3 is a block diagram of an image processing apparatus according to a preferred embodiment of the present invention.

4 is a view showing an image output example according to a preferred embodiment of the present invention.

5 is an illustration of an ellipse for pincushion correction according to a preferred embodiment of the present invention.

6 is a flowchart of a method for generating an elliptic equation in accordance with a preferred embodiment of the present invention.

7 is a flowchart of a pincushion correction method according to a preferred embodiment of the present invention.

The present invention for achieving the above object is the step of generating an equation of the ellipse using the value and image specification for pincushion correction, calculating a scaling value based on the equation of the ellipse, and the digital image according to the scaling value And scaling and outputting the signal.

The present invention corrects the pincushion phenomenon caused by the display device by appropriately converting the video signal provided to the display device according to the characteristics of the display device.

An image processing apparatus according to a preferred embodiment of the present invention will be described with reference to the block diagram of FIG. 3. The analog video signal input through the input signal selector 200 is input to the ADC 202. The ADC 202 converts an analog video signal into a digital video signal and inputs it to the digital video signal processor 204. The digital image signal processor 204 processes the image to be output in an optimal state and provides the pincushion correction unit 206. The pincushion correction unit 206 corrects the pincushion by non-linear scaling of the digital image signal according to a preferred embodiment of the present invention and provides it to the DAC 208. The DAC 208 converts the nonlinear scaled digital video signal into an analog video signal and outputs the same through the display device 210.

The microcomputer 212 controls the image display device as a whole, and provides the pincushion correction unit 206 with a value for pincushion correction (hereinafter referred to as a pincushion correction value) input through the user interface 214. The memory 216 stores a processing program of the microcomputer 212, various information, and the like. The user interface 214 interfaces between the microcomputer 212 and the user.

An operation of the pincushion correction unit 206 will be schematically described with reference to FIGS. 4 and 5. Even if the digital image signal processor 204 outputs the digital image signal in an optimal state, the edge may be convex (or concave) due to the pincushion phenomenon due to the characteristics of the declave device 210. In this case, the pincushion correction unit 206 nonlinearly scales the digital image signal line by line to concave (or convex) the edges as shown in FIG. 4. As such, when the digital image signal with the nonlinear scaled edges concave (or convex) is output to the display device 210 to cancel the distortion caused by the pincushion phenomenon, the distortion of the output image is corrected.

As described above, the line-specific scaling value for scaling the concave edge of the image may be obtained based on an elliptic equation as shown in FIG. 5. This is because distortion due to the pincushion phenomenon can be approximated to an ellipse. These elliptic equations are generated from the values entered by the user for pincushion correction and the display specifications.

A method of obtaining an elliptic equation and a pincushion correction method will be described with reference to FIGS. 6 and 7. After selecting a pincushion correction mode, the user may input a pincushion correction value (step 300, 302). Here, when the user inputs a pincushion correction value, the user inputs a negative value when the edge of the image is convex, a positive value when the edge of the image is concave, and does not want to perform pincushion correction. Enter 0. The pincushion correction unit 206 searches whether the pincushion correction value is 0 (step 304). When the pincushion correction value is 0, the pincushion correction unit 206 determines that the user does not intend to perform the pincushion correction and does not perform an elliptic equation generation process. In contrast, when the pincushion correction value is not 0, the pincushion correction unit 206 generates an elliptic equation with reference to the pincushion correction value and the image standard. In addition, the pincushion correction unit 206 stores the sign of the pincushion correction value (step 306).

For example, if the image standard is a × b, and a convex pincushion phenomenon occurs on the right line of the screen, and the user inputs a -c value to correct by -c, the elliptic equation is represented by Equation 1.

As such, when the generation of the elliptic equation is completed, the pincushion correction unit 206 corrects the pincushion phenomenon by using the elliptic equation. That is, the pincushion correction unit 206 checks whether an ellipse equation is present whenever a digital image signal is input (step 400). In this case, if an elliptic equation exists, the pincushion correction unit 206 calculates a scaling value for each line according to the elliptic equation (step 402). For example, in the case where an elliptic equation such as Equation 1 exists, the scaling value of the n-line may be calculated as follows.

When the scaling values for all the lines are calculated in this manner, the pincushion correction unit 206 searches whether the sign of the pincushion correction value is positive (step 404). If the sign of the pincushion correction value is positive, the pincushion correction unit 206 readjusts the scaling value according to Equation 3 (step 406).

If the sign of the pincushion correction value is positive, the pixels must be increased to convex the edge of the output image, but the number of pixels of the digital image signal is fixed and cannot be increased. Therefore, in this case, the desired effect can be achieved by relatively decreasing the other lines based on the scaling value of the line to be maximized. The pincushion correction unit 206 nonlinearly scales and outputs the digital image signal for each line according to the readjusted scaling value.

On the other hand, if the sign of the pincushion correction value is negative, the pincushion correction unit 206 performs nonlinear scaling based on the scaling value calculated according to the elliptic equation without re-adjusting the scaling value.

In the above example, the input of one pincushion correction value is given as an example. However, by using different pincushion correction values for each corner of the image, an elliptic equation suitable for the distortion state of each corner is generated, and an equation of each ellipse is used. The distortion caused by the pincushion phenomenon can be corrected. In this case, pincushion correction for each corner is possible, which further improves the quality of the image display device.

In addition, in the above example, although the pincushion correction unit has been described as an example of an additional hardware, for example, an FPGA, etc., if the load of the microcomputer is not excessive, the microcushion correction unit may also serve as the pincushion correction unit.

As described above, the present invention improves the quality of the LCD projector by correcting the pincushion phenomenon due to the characteristics of the display device and clearly outputs the image, and has the advantage of enabling the display device to be used efficiently.

Claims (4)

In the pincushion correction method of the video display device, Generating an elliptic equation using values and image specifications for pincushion correction; Calculating a scaling value based on the elliptic equation, And outputting the digital video signal by scaling the digital video signal according to the scaling value. The method of claim 1, And the scaling value is calculated for each line. The method of claim 2, Inputting information for identifying whether the image is concave or convex by the pincushion; And reducing other lines relative to the maximum value among the calculated scaling values when the image is concavely output by the pincushion. The method of claim 1, The pincushion correction value is input to each corner of the image, the pincushion correction method of the image display device, characterized in that the equation of the ellipse for each corner is generated.