KR20060113375A - Method and apparatus for compensating defect of camera module - Google Patents

Abstract

A method and an apparatus for compensating the deviation of a camera module are provided to store a setting value in a memory and call the setting value from the memory when entering a camera mode. A camera module(301) includes a lens for receiving the light and an image sensor for converting the light into an electric signal. An ISP(Image Signal Processor)(303) converts an analog video signal obtained from the camera module into the digital data and displays the digital data on a screen. A tuning terminal(305) detects a dead pixel and a lens shading deviation and finds a setting value for compensating the detected value. The found setting value is stored in a memory(307). The memory is mounted to the camera module and provides the setting value to the ISP.

Description

Method and apparatus for compensating for deviation of camera module {Method and apparatus for compensating defect of camera module}

1 is a view showing the structure of a deviation compensation system of a camera module according to the prior art.

2 is a flow chart showing a deviation compensation method of a camera module according to the prior art.

3 is a view showing the structure of the deviation compensation system of the camera module according to an embodiment of the present invention.

4 is a flowchart illustrating a setting value setting process in a debugging mode according to an exemplary embodiment of the present invention.

5 is a flowchart illustrating an image deviation compensation process in an operation mode according to an exemplary embodiment of the present invention.

Figure 6 is an illustration of a tuning program for setting a setting value according to an embodiment of the present invention.

Description of the main parts of the drawing

101, 301: camera module

103, 303: Image signal processor (ISP)

105, 305: tuning terminal

307: memory

The present invention relates to a method and apparatus for compensating for dead pixel and lens shading deviation of a camera module.

Dead pixels are those in which the image sensor itself in the camera module does not properly represent the color of a particular pixel. Lens shading refers to a phenomenon in which the central axis of the lens assembly is slightly distorted for each module, and the color becomes darker from the center to the outside. These dead pixel and lens shading deviations can be improved not only by hardware methods such as improving the image sensor when manufacturing the camera module or by using a multifocal lens, but also software characteristics of the image sensor and lens in the assembled camera module. It is also possible to improve by the method of compensating, but the present invention belongs to the latter area.

The deviation compensation method of the camera module according to the prior art will be described with reference to FIGS. 1 and 2 as follows.

1 is a view showing the structure of a dead pixel and lens shading deviation compensation system of a camera module according to the prior art.

Referring to FIG. 1, the apparatus for compensating dead pixels and lens shading deviations of the camera module according to the related art includes a camera module 101, an image signal processor (ISP) 103, and a tuning terminal 105. .

The camera module 101 includes a lens for receiving light and an image sensor for converting light into an electrical signal. In this case, the lens mounted on each camera module 101 to be mass produced has a dead pixel that is slightly shifted from the center axis of each camera module 101 to cause a lens shading phenomenon or a dead pixel that does not properly express a specific pixel color for each image sensor. It is included.

The image signal processor 103 is a device that converts an analog image signal obtained from an image sensor into digital data and then displays the image on a screen through an image processing process. The dead pixel and lens shading deviations of the camera module 101 according to the related art are uniformly compensated by changing parameter values of one firmware program mounted in the image signal processor 103.

The tuning terminal 105 is a device that detects dead pixels and lens shading deviations while looking at the preview image displayed on the screen via the image signal processor 103 and finds a setting value to compensate for this. In general, the tuning terminal 105 may be equipped with a program that can detect a location where such a dead pixel occurs and store it at a specific address, and find a correct setting value by changing the error of the lens or the degree of shading little by little. have.

The camera module 101 compensated for the dead pixel and lens shading deviation is mounted on an internal circuit board 110 of a product capable of capturing an image of a mobile phone or a digital camera, and functions as a photographing module.

2 is a flowchart illustrating a dead pixel and lens shading deviation compensation method of a camera module according to the related art.

Referring to FIG. 2, compensation of the dead pixel and lens shading deviation of the camera module is performed using a method of finding a compensation value while looking at the preview screen output to the tuning terminal and reflecting the compensation value to the firmware program of the image signal processor.

First, an image is previewed to compensate for the characteristics of the camera module (step 201). The image signal obtained through the camera module is processed by the image signal processor and then displayed on the tuning terminal. The operator detects the position of the dead pixel and the lens shading deviation while viewing the image displayed on the tuning terminal (step 203). When the dead pixel and lens shading deviations are detected, a setting value for compensating for the dead pixel and lens shading deviations is obtained using a program or the like installed in the tuning terminal (step 205).

The operator changes the source of the firmware program for image signal processing mounted on the image signal processor using the setting value obtained through the above process (step 207). The modified program is then compiled (step 209) to create a binary file of the firmware program. The compiled program is again downloaded to the image signal processor (step 211), and the image is repreviewed using this (step 213).

Finally, after determining whether the image compensation for the camera module is completed through the re-previewed image (step 215), if the compensation is determined to be completed, the compensation operation is completed, and dead pixel or lens shading deviation is also included in the re-previewed image. If found, image review (step 213) is repeated in dead pixel detection and lens shading deviation detection (step 203).

As described above, the dead pixel and lens shading deviation compensation method according to the related art compensates the characteristics of different camera modules using only one firmware program installed in the image signal processor, and thus it takes too long to compensate the characteristics of each module. There is this. That is, since the dead pixel and lens shading deviation compensation method according to the prior art cannot directly reflect the data obtained while previewing the image, the program source must be changed so that the acquired data can be set back to the parameter value on the program. . In addition, the conventional method should perform a process of generating a binary file of the changed program so that it can be mounted in the image signal processor, and downloading the generated binary file to the image signal processor. This method has no problem when testing with only a few camera modules, but when it is mass produced, there is a problem that takes too much time and effort. In practice, most camera module companies recognize the need to compensate for these dead pixel and lens shading deviations, but abandon accurate settings due to the problem of too much debugging time in mass production.

However, when the performance of a camera module in a camera phone goes to the mega level, dead pixels and lens shading have a greater effect on image quality, so it is difficult to obtain good image quality if it is ignored. Of course, depending on the product, there may be few dead pixels or a small lens shading error. In this case, some image quality may be expected due to the characteristics of the module. It is a fact that can affect.

In addition, the conventional image signal processor has a register for compensating the dead pixel and lens shading to compensate for the image signal, and by setting a specific value in this register compensates the average dead pixel and lens shading characteristics. However, this method has a disadvantage of not fully satisfying the dead pixels, which are different from sensor to module characteristics and sensors, which have a large influence on the image due to the slight lens difference.

An object of the present invention is to store a setting value for compensating the dead pixels and lens shading deviation of each module in the memory for each camera module, and call the setting value from the memory when entering the camera mode to compensate the video signal of the camera module It is an object of the present invention to provide a method and apparatus.

Another object of the present invention is to provide a method and system for compensating for dead pixel and lens shading deviation of a camera module, which has a small error, thereby improving product reliability.

According to another aspect of the present invention to achieve the above object, in the deviation compensation method of the camera module performed in the image signal processor coupled to the camera module, the tuning terminal and the memory, for generating a setting value from the camera module A first step of receiving a first image signal; A second step of signal processing the first image signal to generate first image data; A third step of transmitting the first image data to the tuning terminal, wherein the tuning terminal outputs the first image data to a screen and at least one key from an operator based on the first image data output to the screen; Receiving an input, generating a setting value for compensating at least one of a dead pixel and lens shading of the camera module, and transmitting the setting value to the memory; Receiving a second image signal for operating the camera module from the camera module; Extracting the setting value from the memory to compensate for the second image; And a sixth step of performing signal processing to compensate for the second image based on the setting value.

In a preferred embodiment, the first to third steps are procedures performed in a debugging mode, and the fourth to sixth steps are procedures performed in an operation mode. The setting value for the dead pixel may include a parameter indicating a position of a dead pixel and a parameter for a brightness value that the dead pixel should represent. In addition, the setting value for the lens shading is characterized in that it comprises a parameter indicating the correction position, a parameter for distinguishing the channel to be compensated, and a correction value to be multiplied for correction.

According to another aspect of the invention, the camera module for obtaining the image signal and transmitting to the image signal processor; An image signal processor configured to signal-process the image signal to generate image data, and to transmit the generated image data to a tuning terminal; A tuning terminal for generating a setting value for compensating at least one of dead pixels and lens shading of the camera module, and transmitting the setting value to a memory; And a memory configured to store setting values from the tuning terminal and to transmit the setting values to the image signal processor when the camera module and the image signal processor operate the camera. .

Hereinafter, a method and a system for compensating for a deviation of a camera module according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a view showing the structure of the deviation compensation system of the camera module according to an embodiment of the present invention.

Referring to FIG. 3, a deviation compensation system of a camera module according to an exemplary embodiment of the present invention includes a camera module 301, an image signal processor 303, a tuning terminal 305, and a memory 307.

The camera module 301 includes a lens for receiving light and an image sensor for converting light into an electrical signal. As described above, the lens mounted on each camera module 301 to be mass produced is slightly shifted in the central axis of each camera module 301 so that lens shading may occur or the color of a specific pixel may not be properly expressed for each image sensor. Contains dead pixels that can't.

An image signal processor (ISP) is a device that converts an analog image signal obtained by the camera module 301 into digital data and displays the image on a screen through an image processing process. The video signal processor 303 is equipped with a video signal processing program. By the image signal processing program, the image signal processor 301 processes the image signal with reference to the initial setting value in a debugging mode which will be described later, displays the image signal on the tuning terminal 305, finds an appropriate setting value, and stores it in the memory 307. Perform the function. In addition, the image signal processor 303 functions to compensate for dead pixel and lens shading deviations by calling a setting stored in the memory 307 in an operation mode, that is, when the user operates the camera module 301 for shooting. Do this.

The tuning terminal 305 detects dead pixels and lens shading deviations while looking at the preview image displayed on the screen via the image signal processor 303, and finds a setting value to compensate for this. The tuning terminal 305 may detect a location where such a dead pixel occurs and store it at a specific address, and may be equipped with a program that can find an accurate setting value by changing the error of the lens or the degree of shading little by little. In addition, the setting value obtained through this process may be stored in the memory 307 which is combined with the image signal processor 303.

The memory 307 stores settings that the tuning terminal finds to compensate for dead pixel and lens shading deviations. The memory 307 may be mounted in the camera module 301 to provide a setting value to the image signal processor in an operation mode which will be described later.

4 is a flowchart illustrating a setting value setting process in a debugging mode according to an exemplary embodiment of the present invention.

Referring to FIG. 4, a method for compensating for dead pixel and lens shading deviation of a camera module according to an exemplary embodiment of the present invention is performed by dividing into a debugging mode and an operation mode. . Debugging mode refers to a process of determining a setting value for compensation of a corresponding camera module by an operator and storing it in a memory. In operation mode, when a user operates a camera, an image signal processor is stored in the memory through the debugging mode. The process of compensating for an image signal input through a camera module by calling a setting value.

First, in the debugging mode, the operator previews the image to compensate for the characteristics of the camera module (step 401). The image signal obtained through the camera module is processed by the image signal processor and then displayed on the tuning terminal. The image signal processor includes an image signal processing program as described above. The image signal processing program generates image data that can be displayed on the screen by processing the image signal acquired through the camera module with reference to the initialized setting value.

The operator detects the position of the dead pixel and the lens shading deviation while viewing the image displayed on the tuning terminal (step 403). In this case, the dead pixel refers to a pixel that does not represent normal image data due to a defective sensor condenser. Dead pixels are divided into white dead pixels that are too bright than peripheral pixels and black dead pixels that are too dark. Such dead pixels may be detected by scanning the pixel values of the entire image and finding a difference in brightness values of neighboring pixels exceeding a specific threshold. On the other hand, the lens shading deviation may be detected by analyzing the distribution of R, G, and B components on the horizontal axis of the lens after photographing the gray components.

The operator acquires a setting value for compensating for dead pixel and lens shading errors through a tuning program mounted in the tuning terminal (step 405). The tuning terminal can detect the location where the dead pixel has occurred and store it at a specific address, and the program can be equipped with a program that can find the correct setting by changing the error of the lens or the degree of shading little by little, thereby making it easy for the operator. For example, a setting value for compensating for dead pixel and lens shading errors may be obtained. In this case, the setting value includes at least one of a setting value for compensating for the dead pixel and a setting value for compensating for lens shading. The setting value for compensating the dead pixel includes a parameter indicating the position of the dead pixel and a parameter for the brightness value that the dead pixel should represent. The setting value for compensating lens shading also includes a parameter indicating a correction position, a parameter identifying a channel to be compensated for, and a parameter indicating a correction value to be multiplied for correction. The determination of this setting value is performed based on the position of the pixel which is currently recognized as the dead pixel due to the difference in brightness from the surrounding pixel. That is, the setting value is determined so that the dead pixel has an average brightness of the surroundings. On the other hand, the lens shading error is determined based on the horizontal axis of the lens so that the R, G, and B distributions have the same shape. If the specific distribution is wrong, find out how much the gain should be multiplied to match the other channel, and set this as the setting value.

Thereafter, the image that compensates for the characteristics of each camera module by the image signal processor based on the setting value is re-previewed to the tuning terminal (step 407).

The operator determines whether image compensation through the camera module has been optimally performed through the repreviewed image (step 409). If the setting value for the image compensation is not determined optimally, steps 403 to 407 are repeated to determine the setting value for the optimal compensation. In this case, the steps 407 and 409 correspond to a procedure for determining a setting value so that an optimal compensation can be made when necessary.

If the setting value is determined to be optimal, the determined setting value is stored in a memory associated with the tuning terminal and the image signal processor (step 411). Debugging mode is terminated when the settings for compensation are stored in memory.

5 is a flowchart illustrating an image deviation compensation process in an operation mode according to an exemplary embodiment of the present invention.

Referring to FIG. 5, a method of compensating for dead pixel and lens shading deviation of a camera module according to an exemplary embodiment of the present invention is performed by dividing into a debugging mode and an operation mode. . The camera module and video signal processor whose settings are stored in memory through the debugging mode can be mounted on an internal circuit board of a product capable of capturing an image such as a mobile phone or a digital camera to perform a camera function. At this time, the process of performing the camera function corresponds to the operation mode.

When a user of an imaging device such as a mobile phone or a digital camera equipped with the camera module and the image signal processor operates the camera module for shooting, the deviation compensation device of the camera module according to the present invention enters an operation mode (step 501). ).

The video signal processor in charge of signal processing of the image acquired through the camera module recalls the stored setting value from the memory in the debugging mode (step 503).

The image signal processor compensates for the image signal input from the camera module based on the called setting value (step 505). That is, when a dead pixel or lens shading deviation exists in the input image signal, the image signal processor may compensate for the image signal by using the corresponding setting value.

6 is an exemplary diagram of a tuning program for setting a setting value according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the tuning program 600 may be displayed in the form of a window program on the tuning terminal, and the image acquired through the camera module may be adjusted by changing each parameter value on the program. The tuning program 600 is programmed to tune the compensation value and store the tuning result data in the memory in order to compensate for the dead pixel and lens shading deviation in the debugging mode.

While scanning the entire image through the tuning program 600, the operator may detect a pixel having a threshold value below or above the threshold pixel as a dead pixel, and setting the dead pixel value through the average brightness value of the surrounding pixel. Can be determined. In addition, the operator may photograph the gray component of the image through the tuning program 600 and then analyze the distribution of the R, G, and B components of the lens horizontal axis to find the lens shading deviation to determine the setting value. The determined setting value may be stored in a memory and then used to compensate for an image signal input by the image signal processor in operation mode.

According to the present invention, there is no need to perform a step of recording a setting value by tuning and reflecting it on a program and compiling and downloading a program, thereby reducing the time and effort required to compensate for dead pixel and lens shading deviations. have.

In addition, according to the present invention by providing an environment that can individually compensate for the characteristics of each camera module, it is possible to improve the production yield of the camera module and the reliability of the product.

Claims (5)

In the deviation compensation method of the camera module performed in the image signal processor coupled to the camera module, the tuning terminal and the memory, A first step of receiving a first image signal for generating a setting value from the camera module; A second step of signal processing the first image signal to generate first image data; A third step of transmitting the first image data to the tuning terminal, wherein the tuning terminal outputs the first image data to a screen and at least one key from an operator based on the first image data output to the screen; Receiving an input, generating a setting value for compensating at least one of a dead pixel and lens shading of the camera module, and transmitting the setting value to the memory; Receiving a second image signal for operating the camera module from the camera module; Extracting the setting value from the memory to compensate for the second image; And A sixth step of performing signal processing to compensate for the second image based on the setting value Deviation compensation method of the camera module comprising a. The method of claim 1, Wherein the first to third steps are procedures performed in a debugging mode, and the fourth to sixth steps are procedures performed in an operation mode. Deviation compensation method of the camera module, characterized in that. The method of claim 1, The setting value for the dead pixel includes a parameter indicating a position of the dead pixel and a parameter for a brightness value that the dead pixel should represent. Deviation compensation method of the camera module, characterized in that. The method of claim 1, The setting value for the lens shading includes a parameter indicating a correction position, a parameter identifying a channel to be compensated for, and a parameter indicating a correction value to be multiplied for correction. Deviation compensation method of the camera module, characterized in that. A camera module for obtaining an image signal and transmitting the image signal to an image signal processor; An image signal processor configured to signal-process the image signal to generate image data, and to transmit the generated image data to a tuning terminal; A tuning terminal for generating a setting value for compensating at least one of dead pixels and lens shading of the camera module, and transmitting the setting value to a memory; And A memory configured to store setting values from the tuning terminal and to transmit the setting values to the image signal processor when the camera module and the image signal processor operate the camera. Deviation compensation device of the camera module comprising a.

Images