KR20110095556A - Image projection apparatus and image correcting method thereof - Google Patents

Abstract

PURPOSE: An image projection apparatus and a method for correcting an image are provided to implement high reproduction performance when projecting an image to a colored screen. CONSTITUTION: Gradation input signal by each color channel is outputted to a projected plane(202). Using a photographing apparatus, a gradation image by the outputted each channel is photographed. Each color channel value is extracted from the photographed image(204). The input signal is compensated using the extracted each channel value(212).

Description

Image projection apparatus and image correction method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device and an image correction method thereof, and more particularly to an image display device and an image correction method for correcting a color of an image to be projected when an image is projected to the outside through an image projection value.

Typically, image projection means a device that allows a user to project an image in any direction and location. Specifically, the image projecting device displays the image data stored in the memory or the image signal applied from the outside through the image input terminal at a place designated by the user. Here, the place where the image is projected may be a screen installed by the user, or a wall having a white color or any color or a plane having any color may be used as the screen. That is, the place where the image can be displayed can be anything the user wants.

As such, the image projecting device projects an image to the outside of the device, and has different characteristics from an internal display device (for example, an LCD display or a PDP display in a TV). That is, the internal display device can easily express the color of the image desired by the user by changing the setting value of the device. However, the external display device such as the image projection device can display the color of the image when the image is projected. , The brightness of the external light source, the color of the external light source, and the background color where the image is projected.

The environment in which an image is projected through such a projection projection generally has a detrimental effect on the image quality of the projected image. If the image is projected in the same manner as in the internal display device without correction for the projection environment, the projection is performed. The picture quality is degraded.

In particular, as the display of high-definition and large screens is preferred, the use of an image projector having the advantage of mobility is increased, and thus a color correction technology of the image projector is being developed considering the background color of the projected surface.

Conventional color correction techniques are based on background color correction techniques (e.g. Masato Tsukada, "Projector Color Reproduction Adapted to the Colored Wall Projection," CGIV 2004) and human Techniques for eliminating the effect of background color on any screen by applying visual color constancy techniques (eg, Son, "Color Correction of Images Projected on a Colored Screen for Mobile Beam Projector," Journal of Imaging Science and Technology, vol. 53, no. 3, 2008).

Tsukada's method corrects the effect of background color by introducing color adaptation model of human vision in CIEXYZ's color space, but due to the error of device characterization technology which derives the relationship between RGB output value and CIEXYZ value of color sensor Due to this, a large amount of error is involved in the background color correction, and in particular, the color correction technique in the CIEXYZ color space is difficult to implement in real time due to the large amount of computation in the gamut mapping process and the device characterization process.

In addition, Son's method is applied under the assumption that the influence of the chromaticity ratio of the background color is constant, and there is a problem that the accuracy of color correction on a screen having an arbitrary color decreases according to the chromaticity of the background color or the chromaticity of the background color.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image display device for performing color correction for a color screen and an image correction method thereof.

In the image correction method of the image projection apparatus according to an embodiment of the present invention, the step of outputting the gradation input signal for each color channel on the projection surface, the step of photographing the gradation image for each channel output on the projection surface by using the imaging device And extracting each color channel value from the photographed image, and correcting the input signal by using the extracted color channel value.

Here, the color channel value may be an RGB channel value.

The correcting of the input signal may include determining whether a background color exists on the projection surface by using the extracted RGB value, and correcting the input signal when the background color exists.

The method may further include generating a LUT for the white projection plane and the colored projection plane using the extracted RGB values, and using the generated LUT, the gray projection image for each channel may have the same RGB value in the white projection plane and the colored projection plane. Estimating an input signal value on a colored projection surface with respect to an input signal value of and generating a color correction matrix for correcting the gradation input using the estimated value.

Here, the imaging device may be built in the image projection device.

On the other hand, the image projection value according to an embodiment of the present invention, an output unit for outputting the gradation input signal for each color channel to the projection surface, an imaging unit for photographing the gradation image for each channel output to the projection surface, and the photographed And an image corrector for extracting each color channel value from the image and correcting the input signal using the extracted color channel values.

Here, the color channel value may be an RGB channel value.

The image corrector may determine whether a background color exists on the projection surface by using the extracted RGB value, and correct the input signal when the background color exists.

The image corrector may generate a LUT for the white projection plane and the color projection plane using the extracted RGB values, and the gray level image for each channel may have the same RGB value in the white projection plane and the color projection plane using the generated LUT. The input signal value on the colored projection surface can be estimated with respect to the input signal value on the white projection surface.

The image corrector may generate a color correction matrix for correcting the gray scale input using the estimated value.

Accordingly, high-quality color reproduction can be achieved even on a colored screen instead of the white screen.

1 is a block diagram illustrating a configuration of an image projection system according to an exemplary embodiment.
2 is a flowchart illustrating an image correction method of an image projection apparatus according to an exemplary embodiment.
3 is a detailed flowchart of a process of obtaining a projection image, according to an exemplary embodiment.
4 is a detailed operation flowchart of a color correction method according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the present invention.

1 is a block diagram illustrating a configuration of an image projection system according to an exemplary embodiment.

According to FIG. 1, an image projection system includes an image projection apparatus 100 and a display apparatus 200.

The imaging system is a system including a display device and an image projector capable of projecting an image onto the display device, and may be implemented in various forms. For example, the image system may be implemented as a projector screen device, a mobile communication terminal, or the like.

The image projection apparatus 100 includes an input unit 110, an image correction unit 120, an output unit 130, an imaging unit 140, and a controller 150.

The input unit 110 receives an image signal for projecting onto the display apparatus 200. Here, the input signal may be a gray scale input signal for each color channel. In addition, each color channel value may be an RGB channel value, and the gray level may be nine levels.

The image corrector 120 corrects an image signal input through the input unit 110. Specific functions of the image corrector 120 will be described later.

The output unit 130 functions to project the image output signal corrected by the image corrector 120 to be output to the external display device 200. The output unit 130 may include a light source, a transparent display device, a lens, and the like.

The imaging unit 140 performs a function of a general digital camera and converts a visual image signal input from an external subject into digital image data of an appropriate format.

In addition, the imaging unit 140 may capture the grayscale image for each channel output on the projection surface (or screen).

The controller 150 may collectively control the operations of the above-described functional units. For example, the controller 150 may control the image corrector 120 to correct the input signal by using the image photographed by the imaging unit 140.

The image corrector 120 may extract each color channel value from the image photographed by the imaging unit 140.

In addition, the image corrector 120 may correct the input signal using the extracted color channel values.

In detail, the image corrector 120 may determine whether the background color of the projection surface exists by using the extracted RGB value, and correct the input signal when there is a background color other than white (hereinafter, referred to as a colored projection surface).

In addition, the image correction unit 120 creates a LUT for the white projection plane and the color projection plane using the extracted RGB values, and the gray level image for each channel has the same RGB value in the white projection plane and the color projection plane using the created LUT. The input value for estimating the input signal value of the image projector on the colored projection surface with respect to the input value of the image projector on the white projection surface can be estimated.

In addition, the image corrector 120 may generate a color correction matrix for correcting the grayscale input using the estimated input signal value.

Meanwhile, in the present exemplary embodiment, the imaging unit 140 has been described as being included in the image projection apparatus 100. However, in some cases, an external imaging apparatus may transmit and receive data by wired or wireless communication with the image projection apparatus 100. It is also possible to implement.

In addition, the image projection apparatus 100 converts an input image signal into a display size, and includes a scaler unit (not shown) and various signals according to the type of display panel converting the image signal converted by the scaler unit (not shown). The apparatus may further include a display driver unit (not shown) for converting to a format.

The display apparatus 200 functions to display an image output signal projected by the image projection apparatus 100. The display apparatus 200 may be implemented as various types of display panels such as LCD, DLP, LCOS.

Meanwhile, in the present exemplary embodiment, the input unit 110, the image correcting unit 120, the output unit 130, the image capturing unit 140, and the control unit 150 are components of the image projector 100, and the display apparatus ( Although 200 has been described as a separate component, this is for convenience of description and each component may be combined or separated in a product implementation.

2 is a flowchart illustrating an image correction method of an image projection apparatus according to an exemplary embodiment.

According to the projection image color correction method of the image projector illustrated in FIG. 2, a patch indicating a gray level for each channel is output to the projection surface (S402). Here, each channel may be an RGB channel, and the gray level of each channel may be, for example, nine steps. This is an operation for determining the background color of the projection surface projecting the input signal.

Next, an image projected on the projection surface is photographed using a camera, and an average digital RGB value of the captured image is extracted (S204). Here, the camera may be a camera built in the image projection apparatus.

Thereafter, the chromaticity value of the extracted RGB is calculated to determine whether there is a colored background color other than white on the projection surface (S206).

As a result of the determination in step S206, when there is a background color other than white, the input signal is corrected to correct the present projected image color (S208).

Thereafter, the corrected input signal is output to the projection surface in real time (S212).

On the other hand, when the background color of the projection surface is almost white as a result of the determination in step S206, the original image may be output through the image projection value as it is, or the color image quality technology of the image projection apparatus itself may be applied (S210).

3 is a detailed flowchart of a process of obtaining a projection image, according to an exemplary embodiment.

According to FIG. 3, first, a gradation patch input for each channel is applied to the image projection apparatus and output to the projection surface (S302).

Specifically, before projecting the original image, a patch representing the gradation of nine levels for each channel of RGB may be output to the projection surface through the image projection value. For example, the gradation is (48,0,0), (68,0,0), (88,0,0), (108,0,0), (128,0,0), 9 steps of (148,0,0), (168,0,0), (188,0,0), (208,0,0).

Next, the gradation patch for each channel output on the projection surface is photographed by the camera (S304).

Thereafter, each RGB value of the RGB channel is extracted from the captured image (background color) (S306).

4 is a detailed operation flowchart of a color correction method according to an embodiment of the present invention.

Here, color correction may be appropriately employed in the image processing module included in the controller 140 shown in FIG. 1.

Referring to FIG. 4, RGB values of the gray level image of each channel photographed on the white and colored projection surfaces are extracted (S402). This may be performed by extracting an RGB value of each image by capturing an image projected through the image projection value with a camera as shown in FIG. 3.

Subsequently, LUTs for the white and colored projection surfaces are created (S404).

Subsequently, the input of the image projection apparatus is estimated on the colored projection surface relative to the input of the image projection apparatus on the white projection surface (S406).

Thereafter, a color correction matrix is obtained through the estimated input (S408), and an image corrected using the generated color correction matrix is obtained (S410).

Extracting the RGB value of the image projected in FIG. 4 (S402) is a step of extracting the RGB value of the gradation patch image for each channel photographed by the camera on the white projection surface and the colored projection surface.

According to an embodiment of the present invention, the LUT is created using the RGB values of the captured images of the gradation patches for each channel, and the input values of the image projection apparatus which have the RGB values of the same captured images on the white projection plane and the colored projection plane are used to estimate the color. This process is necessary because the calibration is performed.

Meanwhile, in the step of extracting the RGB values of the gray level patch images taken by the cameras, the average value of the region occupying 90% of the patch images taken by the camera may be estimated as the RGB values of the images in order to reduce the error.

In FIG. 4, the LUT creation step (S404) for the white and colored projection planes is performed by using the degree of change of the RGB value of the gray level patch image photographed on the screen having white and color of the gray level patch image photographed by the camera. It becomes a step. In detail, the degree of color change can be determined and an LUT can be prepared through the image of the projector output of the projector in the white and colored projection planes. This is necessary to estimate the input value of the image projection apparatus on the colored projection surface with respect to the input value of the image projection apparatus on the white projection surface in step S406.

In FIG. 4, the step of estimating the input of the image projection apparatus on the colored projection surface with respect to the input of the image projection apparatus on the white projection surface (S406) uses the LUT created in step S404 to capture the same gray level image of each channel on the white and colored projection surfaces. Estimate the input value of the image projector on the screen with the color for the white screen to have the RGB value of the image. This is estimated through Equation 1 below.

In Equation 1, R, G, and B are input values of gray level images input to the image projection apparatus on the white projection plane, and R ₁ , G ₁ , and B ₁ are each channel input to the image projection device on the colored projection plane. This is the input value of the gradation image.

In the obtaining of the color correction matrix (S408) in FIG. 4, a 3 × 3 color correction matrix is obtained through an input value of the image projection apparatus on the projection surface having the color of the input of the image projection apparatus on the white projection surface estimated in S406. to be. This is calculated through Equation 2 below.

In Equation 2, (R ₁ , R ₂ , ... R _n ) represents a channel input digital value of the image projection apparatus to be projected on the white projection surface, and (R ' ₁ , R' ₂ , ... R ' _n Denotes the channel input digital value of the image projection apparatus to be projected onto the colored projection surface that has the RGB value of the image photographed by the same camera as the white projection surface. N is the number of sample patches used, and a is the coefficient of the first order polynomial regression equation.

On the other hand, the color correction image acquisition step (S410) of Figure 4 is a step of obtaining a color-corrected image for the color screen by multiplying the 3x3 color correction matrix calculated in step S408 by the original image. This is calculated through the following equation (3).

In Equation 3, (R ₀ , G ₀ , B ₀ ) is a pixel value of the original image, and (Rc, Gc, Bc) is a result image of color correction.

In addition, a is a 3 × 3 color correction matrix calculated in step 408 of FIG. 4. Therefore, by outputting the corrected result image to the image projector, it is possible to reproduce the result image seen under the white screen from which the influence of the background color is removed.

As described above, according to the color correction method of the present invention, it is possible to achieve a high quality color reproduction by obtaining a resultant image similar to the image seen on the white screen even in a colored screen.

In addition, since the entire processor of the color correction method is simplified, and the amount of computation is small, real-time implementation is possible.

While the above has been shown and described with respect to preferred embodiments of the invention, the invention is not limited to the specific embodiments described above, it is usually in the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Various modifications can be made by those skilled in the art, and these modifications should not be understood from the technical idea or the prospect of the present invention.

110: input unit 120: image correction unit
130: output unit 140: imaging unit
150:

Claims (10)

In the image correction method of the image projection apparatus,
Outputting a gray scale input signal for each color channel to a projection surface;
Photographing a grayscale image for each channel output to the projection surface by using an imaging device;
Extracting each color channel value from the captured image; And,
And correcting the input signal by using the extracted color channel values. The method of claim 1,
The color channel value is,
Image correction method characterized in that the RGB channel value. The method of claim 2,
Correcting the input signal,
And determining the background color of the projection surface by using the extracted RGB value, and correcting the input signal when the background color exists. The method of claim 2,
Creating a LUT for a white projection plane and a colored projection plane using the extracted RGB values;
Estimating the input signal value on the colored projection surface to the input signal value on the white projection surface such that the gray level image for each channel has the same RGB value in the white projection surface and the colored projection surface using the prepared LUT; And
And generating a color correction matrix for correcting the gray level input by using the estimated value. The method of claim 1,
And the imaging device is built in the image projection device. An output unit for outputting a gray scale input signal for each color channel to a projection surface;
An imaging unit for capturing the grayscale image for each channel output on the projection surface; And
And an image corrector for extracting each color channel value from the photographed image and correcting the input signal using the extracted color channel value. The method of claim 6,
The color channel value is,
And an RGB channel value. The method of claim 7, wherein
The image correction unit,
And determining the background color of the projection surface by using the extracted RGB value, and correcting the input signal when the background color exists. The method of claim 7, wherein
The image correction unit,
Create a LUT for the white projection plane and the colored projection plane by using the extracted RGB values, and use the prepared LUT to input the gray level image for each channel in the white projection plane and the color projection plane to have the same RGB value. And an input signal value on a colored projection surface with respect to the value. 10. The method of claim 9,
The image correction unit,
And a color correction matrix for correcting the gradation input using the estimated value.

Images