KR101643773B1 - Apparatus and method for improving quality of preview image - Google Patents

Abstract

The present invention proposes a method for improving the image quality of a preview image. For this purpose, according to the present invention, when an image is input in units of frames, sub-sampling is performed to select a different pattern of a bait pattern having a different starting point of each sub-sampling for each frame to be input. Correlation between sub- And sequentially displays the generated preview images. By doing this, if the sampling rate is set high, it is possible to improve the aliasing phenomenon and the resolution deterioration occurring in the preview image.

Subsampling, preview

Description

[0001] APPARATUS AND METHOD FOR IMPROVING QUALITY OF PREVIEW IMAGE [0002]

The present invention relates to an image quality improving apparatus and method, and more particularly, to an apparatus and method for improving the quality of a preview image.

2. Description of the Related Art In general, an image sensor such as a camera, a camcorder, a webcam, etc. is equipped with an image sensor. The image sensor captures an image developed in the visual field, converts the image into an electrical signal, and converts the converted image signal into a digital signal. The image signal output through the image sensor is three color image data of red, green, and blue, and the image data is displayed through the display unit. An image sensor applied to such an image device can perform a sub-sampling mode operation for outputting a full frame image signal with a reduced resolution. This sub-sampling mode is performed for fast signal processing at a high-resolution display-free stage, such as a preview step for confirming the image before capturing the image.

In this sub-sampling mode, resolution is reduced by selecting only pixels of a specific row and column spaced apart at regular intervals for subsampling. For example, referring to FIG. 1, a frame image composed of a plurality of Bayer patterns 140 is illustrated in FIG. 1, and a subsampling method for generating a conventional preview image will be described.

As shown in FIG. 1, in the case of sampling at a resolution of 1/4 with respect to the horizontal and vertical directions in an n × m pixel, the image is divided into four sub windows 100, 110, 120 and 130, Bayer patterns 140, 150, 160, and 170 are selected. Such an image has a Bayer pattern in which two patterns of R (Red) and G (Green) are arranged in one row and two patterns of G (Green) and B I have. As described above, only one Bayer pattern that intersects in the horizontal direction and the vertical direction is selected, and the rest is removed to reduce the resolution, thereby reducing the amount of data to be processed. In the case of such a sub-sampling, only the same pixel data is always selected for all the frames. Accordingly, the spatial frequency sampled by the image sensor is always the same.

In the conventional sub-sampling mode, only pixels of a specific row and column are used for sub-sampling, and the amount of processed data can be reduced. However, since there are many unused pixels that are discarded, There is a significant aliasing problem that occurs. If the sampling rate is low, the spatial frequency becomes low, and the step phenomenon and resolution degradation become serious in the preview image. Accordingly, if a high sampling rate is required, there is a need for a method capable of improving a step phenomenon and a resolution degradation occurring in a preview image.

Accordingly, the present invention provides an apparatus and method for improving the quality of a preview image in a sub-sampling mode.

According to another aspect of the present invention, there is provided a method for improving the quality of a preview image in a video device, the method comprising: performing subsampling for selecting a basic Bayer pattern for each subwindow of an n-th frame of an input video; Sampling sub-sampling based on a sub-sampling start point shifted by a predetermined integer with respect to an (n + 1) th frame of the input image with respect to an initial sub-sampling starting point for each sub-window; And generating a preview image using each frame.

The present invention also provides a video apparatus for improving the quality of a preview image, comprising: a sub-sampling unit for performing sub-sampling for selecting a basic Bayer pattern for each sub window for an n-th frame of an input video, A sub-sampling unit for performing sub-sampling for each sub-window to select a basic Bayer pattern based on a sub-sampling starting point shifted by a predetermined integer on the basis of an initial sub-sampling starting point; And an image signal processor for generating an image.

According to the present invention, there is an advantage that the problem of aliasing is improved when a high sampling rate is required. Thereby, the image quality of the preview image can be improved.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The present invention proposes a method for improving the image quality of a preview image. To this end, according to the present invention, when an image is input on a frame basis, sub-sampling is performed to select a Bayer pattern having a different starting point of sub-sampling for each frame to be input, and a correlation between the sub- And sequentially displays the generated preview images. By doing this, if the sampling rate is set high, it is possible to improve the aliasing phenomenon and the resolution deterioration occurring in the preview image.

Referring to FIG. 2, a method for improving the quality of a preview image in a video apparatus having the above-described functions will be described. 2 is a block diagram of an internal block of a video apparatus for improving preview quality according to an embodiment of the present invention. Here, examples of the video device include a camera, a camcorder, a webcam, and the like.

First, when an image is input from a video device, an input image for displaying a preview image is transmitted to the sub-sampling unit 200 on a frame-by-frame basis. The subsampling unit 200 performs sub-sampling by selecting only necessary pixel data for the input image and deleting the remaining pixel data for the preview image.

According to the embodiment of the present invention, the sub-sampling unit 200 selects a basic Bayer pattern for each sub-window based on the positions of the rows a and b, i.e., (a, b) (a + k1, b + k2) shifted by k1 column and k2 row with respect to the (a, b) position in the (n + 1) th frame. At this time, k1 and k2 are integers and can be the same value.

Subsequently, the process of performing sub-sampling on the basis of the same position as that in the n-th frame and the (n + 1) -th frame may be repeated for the (n + 2) Alternatively, sub sampling may be performed by shifting the starting point constantly, for example, with reference to (a + k3, b + k4) in the (n + 2) th frame. In this way, the subsampling unit 200 performs subsampling with a predetermined sampling rate x. Here, the Bayer pattern refers to a pattern in which two patterns of R (Red) and G (Green) are arranged in one row and two patterns of G (Green) and B (Blue) are repeatedly arranged in another row. In this Bayer pattern, the basic Bayer pattern means four pixel data in which G and R pixels are arranged in a first row and B and G pixels are arranged in a second row.

The pixel value of each sub-sampled image includes noise due to an internal factor or an external factor, and when a preview image is generated using the pixel value including the noise, there may be a difference between the pixel value of the sub- Therefore, calibration should be done. Accordingly, the correlated double sampling (CDS) 210 removes noise from the sub-sampled image, i.e., the selected basic Bayer pattern. In this manner, it is possible to improve the flicker phenomenon through the noise reduction from the inter-frame relationship.

Each basic Bayer pattern of the noise-removed image is converted into digital data by an analog-to-digital converter (ADC) The data converted into digital data is input to the image signal processing unit 230. The image signal processing unit 230 generates a correlation between the frame and the pixel based on the initial sub sampling start point for each frame in which the sub sampling start point is shifted The preview image is created by fitting.

When the preview image correlated in this manner is input to the display unit 240, the preview image is displayed through the display unit 240. [ Accordingly, the preview viewer of the display unit 240 displays a preview image on a frame basis, and each frame has a parallax of 1 / frame ratio. However, since the preview image is generally displayed very quickly, the user can not feel the parallax due to the eye-sight phenomenon. However, unlike the subsampling method using only the pixel data at the fixed position, The stepped phenomenon and the resolution degradation phenomenon occurring in the preview image are improved. In addition, since the subsampling start point is shifted and sub-sampled, it is not necessary to temporarily store the sub-sampled frame in the buffer, so that it can be directly used for generating a preview image, thereby eliminating hardware changes.

The operation of the video apparatus having the above configuration will be described with reference to FIG. 3 is a flowchart illustrating an operation of a video apparatus according to an exemplary embodiment of the present invention. Hereinafter, FIG. 4 to FIG. 6 will be exemplified for better understanding of the embodiment of the present invention.

Referring to FIG. 3, when an image is input in units of frames in step 300, the video apparatus sets n, which indicates the number of frames, to 1 in step 305 and sets k, which indicates a shift integer for shifting the subsampling start point to row and column, And sets the sampling rate (x). Subsequently, in step 310, subsampling is performed from the position (a + k, b + k) of the n-th frame.

4, the first row has a pattern in which G and R pixels are alternately arranged, the second row has a pattern in which B and G pixels are alternately arranged, Thus, the odd performance illustrates one frame of an input image in which n × m pixels in the form of a two-dimensional matrix having a repetitive pattern of the first row and a repetitive pattern of the second row are arranged.

4, one frame is divided into a plurality of sub windows 445, 450, 455, 460, ... according to the horizontal 1/4 and vertical 1/4 subsampling in one frame of the input image, One basic Bayer pattern 400, 405, 410, 415, ... is selected for each of the sub windows 445, 450, 455, 460,. That is, the case of sub-sampling at 1/4 resolution is exemplified, and the sub-window is divided according to 1 / n resolution. In this way, in one frame, pixel data selection is performed in units of basic Bayer patterns as shown in FIG.

Sampling is performed to select one basic Beer pattern for each sub-window in the frame as shown in FIG. 4, and if the next frame is input in step 315, the number of frames is incremented by one in step 320 and n = n + 1 And sets k = k + y to shift the subsampling start point, where y is an integer. If k is not equal to or higher than the sampling rate x, the process returns to step 310. However, if k is equal to or greater than the sampling rate x, , K = 0 is initialized, and the process returns to step 310. If the next frame is not input in step 315, the flow advances to step 335 to generate and display a preview image using the selected basic Bayer pattern.

To describe this in more detail, referring to FIG. 5, if FIG. 4 exemplifies the n-th frame, FIG. 5 illustrates the (n + 1) th frame. the starting point of subsampling in the nth frame is the position of the basic Bayer pattern as indicated by 400, the starting point of the subsampling in the (n + 1) th frame is a basic Bayer pattern as indicated by 500 shifted by a predetermined integer. . Thus, as in 500, one basic Bayer pattern 500, 505, 510, and 515 is selected for each subwindow starting from the position of the basic Bayer pattern.

Therefore, if the subsampling start point changes twice as shown in FIGS. 4 and 5, the sub-sampling operation as in the n-th frame and the n + 1 Lt; th > frame are alternately repeated.

In contrast, in the case of a method in which the sub sampling start point is changed for each frame, the sub sampling start point is sequentially shifted by a predetermined integer. Accordingly, the shift constant k in step 320 is added by a predetermined constant y. In addition, although it has been described at step 310 that the same sub sampling start points (a, b) are shifted by k in the row and column directions, the integer k shifted in the row and column directions may be different from each other. At this time, the shift constant k is increased until it is not greater than the sampling rate x, and the sub sampling start point can be shifted by the shift integer. However, when the sampling rate x is greater than or equal to the sampling rate x, To zero so that the subsampling start point is again the initial subsampling starting point.

As described above, the sub-sampling operation in the n, n + 1, n + 2 th, etc. frames having different subsampling start points has been described with reference to FIG. 3. In each of the frames, The frame is as shown in FIG. 6 based on the time axis. 6, the position of the basic Bayer pattern indicated by 400 in the nth frame becomes the initial sub sampling start point, and the position of the basic Bayer pattern indicated by 500 in the (n + 1) And the position of the basic Bayer pattern indicated by 600 in the (n + 2) -th frame becomes a subsampling start point. FIG. 6 illustrates a spatial frequency viewed from a time axis according to an embodiment of the present invention.

As shown in FIG. 6, the video apparatus according to the embodiment of the present invention includes a sub-sampling operation for selecting a basic Bayer pattern for each sub-window based on a position shifted by a predetermined integer on the basis of an initial sub- . Then, for each frame that has been sub-sampled, a preview image is generated by performing an operation such as a correlation based on the initial sub-sampling start point and removing noise.

1 is a diagram illustrating a conventional sub-sampling method for generating a preview image,

FIG. 2 is an internal block diagram of a video apparatus for improving preview quality according to an exemplary embodiment of the present invention;

FIG. 3 is a flowchart illustrating an operation of a video apparatus according to an exemplary embodiment of the present invention,

FIGS. 4 to 6 are diagrams for explaining a sub-sampling method according to the present invention; FIG.

Claims (14)

A method for improving the quality of a preview image in a video device, Performing sub-sampling to select a basic Bayer pattern for each sub window for an n < th > frame of an input image, Sampling sub-sampling based on a sub-sampling starting point shifted by a predetermined integer with respect to an (n + 1) th frame of the input image with respect to an initial sub-sampling starting point for each sub-window; And generating a preview image by using a correlation between the first sub-sampling start point and each of the sub-sampling frames. 2. The apparatus according to claim 1, Wherein the pattern is a pattern of four pixel data in which pixel data of red and green colors are arranged in one row and pixel data of green and blue colors are arranged in another row. The method according to claim 1, Performing sub-sampling on the basis of the first sub-sampling start point for each frame input after the (n + 1) -th frame of the input image or performing sub-sampling on the basis of the shifted sub-sampling starting point Wherein the preview image includes a plurality of preview images. The method according to claim 1, Sampling the base Bayer pattern based on a sub-sampling starting point shifted by the predetermined integer with respect to a previous sub-sampling starting point each time a frame is input after the (n + 1) -th frame of the input image The method of claim 1, further comprising: The method of claim 4, further comprising the step of setting a sub-sampling start point at the time of inputting a next frame as an initial sub-sampling starting point when the shifted sub-sampling starting point is equal to or greater than a sampling rate. Lt; / RTI > The method of claim 1, wherein generating the preview image using each of the sub- Removing noise for a selected basic Bayer pattern of each of the sub-sampled frames; And converting the noise-removed basic Bayer pattern into a digital image to generate the preview image. The method according to claim 1, Further comprising the step of: correlating each of the subsampled frames based on the first subsampling start point. ≪ RTI ID = 0.0 > 8. < / RTI > A video apparatus for improving the quality of a preview image, Sub-sampling for selecting a basic Bayer pattern for each sub-window for the n-th frame of the input image, and shifting the sub-window by a predetermined integer with respect to the (n + 1) A sub-sampling unit for performing sub-sampling for selecting a basic Bayer pattern on the basis of a sub sampling start point, And a video signal processor for generating a preview image using the correlation with the first sub-sampling start point for each of the sub-sampled frames. The method according to claim 8, Wherein the image data is a pattern composed of four pixel data in which pixel data of red and green colors are arranged in one row and pixel data of green and blue color are arranged in another row. . 9. The apparatus of claim 8, wherein the sub- Sampling is performed with respect to each frame input after the (n + 1) -th frame of the input image on the basis of the first sub-sampling start point or sub-sampling is performed based on the shifted sub-sampling starting point A video device for improving the quality of a preview image. 9. The apparatus of claim 8, wherein the sub- Sampling is performed to select a basic Bayer pattern with respect to a sub-sampling starting point shifted by the predetermined integer with respect to a previous sub-sampling starting point whenever a frame is input after the (n + 1) -th frame of the input image To improve the quality of the preview image. 12. The apparatus of claim 11, wherein the sub- Wherein the sub sampling start point at the time of inputting the next frame is set as an initial sub sampling start point when the shifted sub sampling starting point is equal to or higher than the sampling rate. The apparatus of claim 8, wherein the image signal processor comprises: Wherein the preview image is generated by correlating each sub-sampled frame with respect to the initial sub-sampling start point. 9. The method of claim 8, A correlated double sampling unit for removing noise from the selected basic Bayer pattern of each of the subsampled frames, And an analog-to-digital (A / D) converter for digitally converting the noise-removed basic Bayer pattern.

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