KR20080000972A - Apparatus and method for removing noise of image - Google Patents

Abstract

An apparatus and a method for removing noise of an image are provided to remove noise from an image according to a noise removing level corresponding to an illumination level set in a noise filter, measure a brightness component of image data to change the illumination level, and then remove noise. An apparatus for removing noise of an image includes an image sensor, a noise filter(120) and an illumination adjusting processor(200). The image sensor takes an image and makes image data corresponding to the image. The noise filter(120) removes the noise of the image data according to the set illumination level. The illumination adjusting processor(200) analyzes the brightness of image data and adjusts the illumination level of the noise filter corresponding to the brightness. The noise filter removes noise from the image data according to the illumination level changed by the illumination adjusting processor(200).

Description

Apparatus and method for removing noise of image}

1 is a diagram illustrating a camera module including a conventional noise filter.

2 is a block diagram illustrating an apparatus for removing noise in an image according to an exemplary embodiment of the present invention.

3 is a flowchart of a method for removing noise in an image according to an exemplary embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100: camera module

110: image sensor

120: noise filter

200: illuminance adjustment processor

The present invention relates to an apparatus for removing noise of an image, and more particularly, to an apparatus for removing noise of an image, by which a noise filter is automatically adjusted to obtain an image of clear image quality regardless of a change in light quantity.

An image sensor is a device that converts an optical image into an electrical signal. Charge Coupled Device (CCD) type image sensor and Complement MOS (CMOS) type image sensor, depending on how the electron-hole forms a signal and is transmitted to the output part There is.

The CCD image sensor and the CMOS image sensor have a light receiving unit which commonly receives light and converts it into an electric signal. CCD-type image sensors transmit electrical signals through the CCD and convert them to voltage in the final stage. CMOS image sensors, on the other hand, convert the signal from each pixel to a voltage and pass it outside. That is, the CCD-type image sensor moves electrons generated by light to the output unit by using a gate pulse as it is, and the CMOS-type image sensor converts electrons generated by light into voltage within each pixel and then converts the electrons into light by the number of pixels Output through the switch.

In the image sensor, several pixels are arranged in a two-dimensional structure. Each pixel in the image sensor converts it into an electrical signal based on the brightness of the light. By measuring this electric signal, we can know the amount of light entering each pixel, and convert it to an electric signal to construct an image of each pixel. The electric signal corresponding to the amount of light can be expressed numerically. This is called the pixel value. Here, each pixel value may be expressed as a value between 0 and 255.

At this time, the pixel value includes noise due to internal or external factors of the image sensor, and when reproduced as an image using the pixel value including this noise, the pixel value may be different from the actual image. have. Therefore, the pixel value containing the noise must be corrected to remove the noise.

Recently, a camera module is mounted on a portable device (eg, a mobile communication terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), etc.), and thus an image sensor is widely used. The camera module generally used in such a portable device has a characteristic that noise is increased in an acquired image when the amount of light decreases. In this case, in order to obtain a clear image with noise removed, a noise filter is attached to the rear of the image sensor so that a lot of noise is removed at low illumination and the noise filter is not operated at high or normal illumination. .

The camera module's settings for shooting in low light may apply a lot of noise filters to reduce noise in the image signal, but also reduce the size of the image signal component itself, resulting in lower overall sharpness. Here, the image signal means a pixel value passed through the image sensor.

On the other hand, the setting of the camera module photographing at high illuminance keeps the image obtained by applying less noise filter as sharp as possible. However, when the illuminance of the external environment suddenly decreases in such a setting state, the noise component of the image signal is rapidly increased, thereby obtaining unclear image data. In the case of encoding such image data in a file format such as JPEG, a noise component causes a large file size. This is a major disadvantage for portable devices with small storage spaces.

1 is a diagram illustrating a camera module including a conventional noise filter. The camera module 100 includes a CCD image sensor or a CMOS image sensor 110 and a noise filter 120 for removing noise.

The noise filter 120 analyzes information included in the image signal output from the CCD / CMOS image sensor 110 and performs a noise removing operation within a predetermined variation range according to the illumination level of the image signal.

The noise filter 120 has a preset illumination level for manually removing noise by the user. For example, the illuminance level may be a solar mode, a fluorescent lamp mode, a night mode, or the like. At high illuminance levels, such as in solar mode, no noise canceling operation is required for clear images, and at low illuminance levels, such as night mode, a high level of noise cancellation is required.

When the image signal output from the CCD / CMOS image sensor 110 is transmitted within the illumination level set by the user, the noise filter 120 performs an appropriate noise removing operation.

However, when the illuminance level changes abruptly due to a sudden change in the external environment, that is, when the amount of light incident on the CCD / CMOS image sensor 110 changes abruptly, the noise filter 120 is set previously. According to the noise reduction. Therefore, the noise filter 120 may not perform the noise canceling operation suitable for the low illuminance level while suddenly changing to the lower illuminance level while the noise canceling operation is not performed under the high illuminance level, and the noise may not be clear by the noise. There is a problem of obtaining image data.

When shooting in an environment where the brightness is not constant, the illuminance may change rapidly depending on the movement of the terminal with the camera attached.In the case of the decrease in the application of the noise filter and the bright illuminance when the brightness changes from low to bright There is a need for a method that automatically adjusts the increase in noise filter application when changing to low illumination.

Therefore, the present invention primarily performs noise removal according to the level of the noise canceling function according to the illumination level set in the noise filter, measures the brightness component of the image data, and changes the illumination level applied to the noise filter to reduce the noise. It provides a noise canceling device and a method of removing an image to secondly reset the level of the canceling function to obtain clearer image data.

Other objects of the present invention will be readily understood through the following description.

In order to achieve the above object, according to an aspect of the present invention, the image sensor for taking an image to generate image data corresponding to the image; A noise filter for removing noise of the image data according to a set illumination level; And an illuminance adjustment processor for analyzing the brightness of the image data and adjusting the illuminance level of the noise filter to correspond to the brightness.

Preferably, the noise filter may remove noise of the image data according to the illumination level changed by the illumination adjustment processor.

In addition, the illuminance adjustment processor may analyze brightness from image data generated by the image sensor or image data noise-removed by the noise filter.

Here, the illuminance adjustment processor may generate and transmit a command signal for operating the noise filter while adjusting the illuminance level.

In addition, the noise filter may change a level of removing noise of the image data within a predetermined fluctuation range corresponding to the illuminance level.

In order to achieve the above objects, according to another aspect of the present invention, in the method for removing the noise of the image data generated by the image sensor, (a) to first remove the noise of the image data according to the set first illumination level Doing; (b) analyzing the brightness of the image data in the illuminance adjustment processor; (c) applying a second illuminance level to the noise filter corresponding to the analyzed brightness; And (d) secondly removing noise of the image data according to the second illuminance level.

Preferably, the step (b) may analyze the brightness from the image data generated by the image sensor or the image data noise removed by the noise filter in the illumination adjustment processor.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the noise removing device and method of removing the image according to the present invention. In describing the present invention, when it is determined that the detailed description of the related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Numbers (eg, first, second, etc.) used in the description of the present specification are merely identification symbols for sequentially distinguishing identical or similar entities.

2 is a block diagram illustrating an apparatus for removing noise in an image according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the apparatus for removing noise of an image includes a camera module 100 and an illumination adjustment processor 200.

The camera module 100 includes an image sensor 110 and a noise filter 120.

The image sensor 110 captures an image and generates image data corresponding to the image. The image data has pixel values (eg, values of 0 to 255) of the pixels constituting the pixel array of the image sensor 110. The image data may be RGB data having brightness values of red (R), green (G), and blue (B), or YCbCr data having luminance (Y) and color difference signals (Cb, Cr).

The noise filter 120 analyzes the information included in the image data output from the CCD / CMOS image sensor 110. The noise of the image data is removed according to the set illumination level.

The illuminance level refers to the degree of brightness of the subject to be photographed by the current user with the device including the camera module 100. In general, in a digital camera, the user manually sets the solar mode, the fluorescent mode, the incandescent mode, or the night mode.

In the present invention, the illumination level of the noise filter 120 may be manually changed by the user. And it can be changed automatically by the illumination adjustment processor 200 demonstrated later.

When the image filter 110 receives the image data from the CCD / CMOS image sensor 110, the noise filter 120 performs a noise removing operation of the image data according to a preset illuminance level. If the illuminance level is later adjusted to a level other than the level previously set by the illuminance adjustment processor 200, the noise is removed secondarily once again according to the newly adjusted illuminance level with respect to the image data which is primarily noise-removed. Perform the action. This operation may be performed by itself when receiving the second noise removing signal from the illumination adjustment processor 200 or when the noise filter 120 adjusts the illumination level.

The noise filter 120 may remove noise within a predetermined fluctuation range for each illuminance level. The noise removing level is not fixed to one value for each illumination level, but the noise removing level may be changed within a range of fluctuation according to the brightness of the image data received from the image sensor 110. However, since it is a width that is allowed under the already set illuminance level, it does not correspond to a sudden change in the amount of light from the highest illuminance level to the lowest illuminance level, so adjustment of the illuminance level is necessary as described above.

The illumination adjustment processor 200 receives image data from the camera module 100. The image data at this time is either image data from which noise is removed by the noise filter 120 or image data received from the image sensor 110 before noise is removed.

The brightness of the image data is measured by analyzing the information included in the received image data. The brightness of the image data can be measured in various ways. For example, a formula such as Equation 1 used when converting RGB data into YCbCr data according to an NTSC broadcasting scheme may be used.

<Equation 1>

Here, Y means luminance and Cb and Cr mean color difference signals.

The brightness of the image data can be measured using the value of Y. In addition, it is obvious that brightness measurement may be performed by other persons skilled in the art in other ways.

The illuminance adjustment processor 200 measures the brightness of the image data and then determines the illuminance level of the noise filter 120 corresponding thereto. The relationship between the brightness and illuminance level of the image data is preferably stored in the form of a lookup table in a memory (not shown) or a register (not shown). After determining the illuminance level corresponding to the brightness based on the reference table, the illuminance level of the noise filter 120 is adjusted.

In addition, the illuminance adjustment processor 200 adjusts the illuminance level of the noise filter 120 and generates a command signal instructing that the noise filter 120 will perform the noise removing operation of the image data once again by applying the adjusted illuminance level. Can be additionally delivered.

3 is a flowchart of a method for removing noise in an image according to an exemplary embodiment of the present invention.

Referring to FIG. 3, in operation S310, the image sensor 110 photographs an arbitrary subject to generate image data. In this case, it is assumed that the image data has a large amount of light from the image data photographed immediately before due to a sudden change in the external environment.

In operation S320, the noise filter 120 receives image data from the image sensor 110. Then, the noise removing operation of the image data is performed according to the first illuminance level that is set in advance. However, due to the sudden change in the amount of light, the noise removing operation by the preset first illuminance level may be insufficient.

In operation S330, the illumination adjustment processor 200 receives image data. In this case, the image data may be either raw image data from the image sensor 110 or image data obtained by removing the first noise by the noise filter 120.

In operation S340, the illumination adjustment processor 200 analyzes the brightness of the received image data. Since the brightness analysis method has been described in detail above, it is omitted here.

In operation S350, the illumination adjustment processor 200 determines a second illumination level to be applied to the noise filter 120 based on the analyzed brightness. The relationship between brightness and illuminance levels may be prefilled with a lookup table and stored in memory or registers.

In operation S360, the illumination adjustment processor 200 applies the second illumination level to the noise filter 120. In addition, the noise filter 120 may transmit a command signal for performing the second noise removing operation. Alternatively, when the noise filter 120 itself adjusts the illumination level, the noise filter 120 may perform the noise removal operation once.

In operation S370, the noise filter 120 performs a second noise removing operation according to the newly applied second illuminance level to generate image data from which the noise is removed, and transmits the image data to continue processing in the next stage. Here, the next stage may include a color interpolator, a color adjuster, a gamma converter, a format converter, and the like.

As described above, the apparatus for removing noise and removing the image according to the present invention may remove noise components of the image data due to a sudden change in the amount of light that cannot be corrected by a general camera module mounted on a portable device.

In addition, noise is first removed according to the level of the noise canceling function according to the illuminance level set in the noise filter, the brightness component of the image data is measured, and the illuminance level applied to the noise filter is changed. By resetting the level secondly, you can obtain clearer image data.

In addition, portable devices that use low-cost camera modules with poor noise rejection can obtain the best image day, thus reducing the cost of portable devices.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be appreciated that modifications and changes can be made.

Claims (7)

An image sensor for photographing an image and generating image data corresponding to the image; A noise filter for removing noise of the image data according to a set illumination level; And And an illuminance adjustment processor analyzing the brightness of the image data and adjusting the illuminance level of the noise filter to correspond to the brightness. The method of claim 1, And the noise filter removes noise of the image data according to the illumination level changed by the illumination adjustment processor. The method of claim 1, And the illuminance adjustment processor analyzes brightness from image data generated by the image sensor or image data noise-removed by the noise filter. The method according to claim 2 or 3, And the illuminance adjusting processor generates and transmits a command signal for operating the noise filter while adjusting the illuminance level. The method of claim 1, And the noise filter changes the level of removing the noise of the image data within a predetermined variation corresponding to the illuminance level. In the method for removing noise of the image data generated by the image sensor, (a) first removing noise of the image data according to the set first illuminance level; (b) analyzing the brightness of the image data in the illuminance adjustment processor; (c) applying a second illuminance level to the noise filter corresponding to the analyzed brightness; And and (d) secondly removing noise of the image data according to the second illuminance level. The method of claim 6, The step (b) is the noise reduction method of the image to analyze the brightness from the image data generated by the image sensor or the image data noise removed by the noise filter in the illuminance adjustment processor.

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