KR100747576B1 - Method and apparatus for controlling exposure level for camera - Google Patents

Abstract

The present invention relates to an apparatus for controlling exposure of a camera and a method thereof, and more particularly, to remove noise caused by an excessive amount of light, a lens module, an image sensor for receiving an image through the lens module, and The front end module digitizes the signal output from the image sensor and outputs the signal output from the front end module. The luminance component of each horizontal synchronization signal of the image sensor is compared to detect whether there is an excessive amount of light. And a data capture unit and a controller configured to determine and control an iris opening degree according to whether the amount of light is excessive. The iris control effectively removes noise generated by an excess of light when the camera is photographed. In addition to regular still cameras, portable devices such as mobile phones and laptop computers It can be applied to the camera module installed in.

Camera, Iris, Portable, Luminance, Capture.

Description

Camera exposure control device and method thereof {Method and apparatus for controlling exposure level for camera}

1 is a screen diagram showing an example of a conventional camera exposure control method

2 is a block diagram showing an embodiment of an exposure control apparatus of the present invention;

3 is a schematic view showing an example of an image sensor of the exposure control device of the present invention;

4 is a schematic diagram showing an example of a readout of an image sensor of the exposure control device of the present invention;

5 is a schematic view showing an embodiment of an iris opening state of the exposure control apparatus of the present invention;

6 is a flow chart showing an embodiment of the exposure control method of the present invention.

<Brief description of the main parts of the drawing>

10 lens module 20 image sensor

30: front end module 40: data capture unit

50: control unit 60: motor control unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera exposure control apparatus and method thereof, and more particularly, to a camera exposure control apparatus and method for removing noise caused by excessive amount of light.

The camera's Auto Exposure or Auto Iris is a function to optimize the light entering the CCD (Charge-coupled devices).

That is, the exposure of the camera is controlled by setting an optimum aperture value according to the amount of incident light.

Such automatic exposure control is a phenomenon in which a strong light incident above the amount of saturation light enters a signal charge, and excess charge is mixed in the surrounding pixels, thereby brightening the part where the light is not illuminated. Phenomena of bright streaks in the vertical direction are also provided to remove or prevent a phenomenon such as smear caused by incomplete shading of the CCD vertical transfer unit.

However, in order to capture dark subjects in the dark state and bright subjects in the bright state, the dynamic range of the CCD must be wide enough, but the saturation output of the high resolution (more than 3 million pixels) CCD It is limited to 200mV ~ 500mV, and the SN ratio (signal-to-noise ratio) cannot be increased, so it is not able to cope with the above blooming and smear completely.

In particular, when the subject's face is not darkened in the backlight, and the image is taken clearly while looking directly at the lighting, the noise may appear even when the car can be photographed even when the headlight is turned on at night.

Under such conditions, the exposure control using the average amount of light simply integrating the luminance information of the entire screen cannot obtain a great effect.

In order to prevent the above phenomenon, the prior art uses a screen averaging method and a screen split averaging method in which specific gravity is given to each screen as shown in FIG. 1.

The screen averaging method is a technique of controlling the iris by comparing the average value of the luminance levels of the entire screen or a part of the screen, and the screen split averaging method is a photographing screen using luminance information obtained for each area by splitting an image signal as shown in FIG. Points to a technique for detecting and automatically correcting light and dark distributions.

However, the above method is also not an effective solution to the noise (Smear, Blooming), in particular, when applied to a mobile device camera, such as a mobile phone or notebook computer iris due to the spatial constraints of the camera module However, it is very difficult to apply ND (Neutral Density) filter.

In addition, the limited partition window size causes a large number of errors in detecting a light source having a high luminance in a small area, which causes smears, and has a problem of eliminating side effects.

The present invention is to solve the problems as described above, to effectively remove the noise caused by the excess of the light beam when shooting the camera through the iris control, in particular, not only a general still camera, but also a mobile phone, notebook computer An object of the present invention is to provide an exposure control apparatus and method of a camera that can be applied to a camera module installed in a portable device such as a computer.

In order to achieve the object of the present invention as described above, the present invention, a lens module, an image sensor for receiving an image through the lens module, a front end module for digitizing and outputting the signal output from the image sensor, and A data capture unit for capturing a signal output from the front end module and comparing luminance components of each horizontal synchronous signal of the image sensor to detect whether there is excess light, and determining an iris opening degree according to whether the light amount is excessive. It is achieved by including a control unit to control by.

The data capture unit detects an excessive amount of light when the luminance of neighboring horizontal transmission lines is two or more times.

The degree of the iris opening of the controller according to the excess amount of light can be controlled by two stages of opening and closing. However, in order to improve the optical characteristics while improving the noise control effect, the iris opening degree can be controlled in three or more stages. desirable.

The controller may control the function of the shutter by controlling the opening speed together with the opening degree of the iris.

The method of claim 1, wherein the data capture unit compares the luminance component for each pixel in the horizontal synchronization signal, wherein the luminance component is selected from all pixels, even pixels, odd pixels, and specific multiple pixels according to the performance of the processing speed. To compare.

The frame for detecting the amount of light may detect whether the amount of light is excessive according to the entire frame or the selected frame, and in this case, the frame to be considered may be selected according to the performance of the processing speed.

On the other hand, in some cases, instead of controlling the iris opening degree according to whether the light amount is excessive, the effect of the present invention can be achieved by lowering the gain value of the R, G, and B levels of the signal.

In the exposure control method of the camera as described above, the first step of comparing the luminance component for each pixel in the horizontal synchronization signal output from the image sensor, and if the amount of light is determined to be excessive by comparing the luminance component to increase the flag value A second step, a third step of increasing the count when the flag value exceeds an overflow value, and performing the first to third steps over the entire horizontal synchronization signal, and opening the iris according to the count value. It comprises a fourth step of determining the degree.

Thus, the iris opening step is performed in two or more steps according to the count value.

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

2 shows the overall configuration of the present invention, the lens module 10, an image sensor 20 for receiving and processing light received through the lens module 10, and is output from the image sensor 20 A front end module (AFE) 30 for digitizing and outputting a signal, a data capture unit 40 for detecting whether the amount of light is excessive, and an iris opening degree are determined and controlled according to whether the amount of light is excessive. The control unit 50 is shown.

The lens module 10 includes a focus lens and an iris, and in some cases, a zoom lens may be included.

The front end module (AFE) 30 is generally configured in detail including a sampling part, an amplifier, an AD converter, a vertical horizontal driver, and the like to process and digitize an analog signal output from the image sensor 20. Perform.

The data capture unit 40 performs an interpolation and downscale process after buffering the RGB Bayer format of the image sensor 20 and captures image information.

The data capture unit 40 may be generally included in a digital signal processor (DSP) or an image signal processor (ISP) module.

The control unit 50 detects a light source (backlight, headlight and direct illumination) that causes noise such as smear and judges the iris adjustment according to the detected light source degree, and thus the iris closing degree and speed Determine.

Instead of the control unit 50 according to the detection result, it may be provided with a separate motor control unit 60 to control.

FIG. 3 shows an example of a readout of a charge coupled device (CCD) sensor as an example of the image sensor 20. As shown, the total number of pixels of the CCD is determined according to the number of vertical and horizontal pixels. Fig. 3 shows a CCD having a number of pixels of 5.2M by (1970 pixels vertical × 2668 pixels horizontal).

In addition to the CCD as described above, an image sensor 20 such as CMOS may also be used.

In addition, as shown in Figure 4, the CCD analog output output to the horizontal transmission line has a RG G B type Bayer (BAYER), this type is repeated four horizontally.

That is, the CCD readout method in the form of R G G B is determined according to the CCD analog output outputted to the horizontal transmission line. The readout method is divided into 4/8 lines, 2/8 lines, and 4/16 lines.

4 shows a 4/8 line readout as an example, which extracts four values of eight vertical pixels. The data evicted in this manner is interpolated with the downscale by the data capture unit 40 and then displayed according to the resolution for each.

At this time, the data capture unit 40 detects (compares luminance) a subject that causes noise such as smear, and accordingly, the controller 50 adjusts the iris opening state.

That is, as shown in FIG. 5, the iris is controlled to the state of the iris according to the luminance detection value.

Hereinafter, the exposure control method of the present invention will be described in detail with reference to FIGS. 5 and 6.

First, a step (S1) of comparing the luminance components for each pixel in the horizontal synchronization signal output from the image sensor 20 is performed.

This compares the luminance components Y (n) and Y (n + 1) of neighboring pixels to increase the flag when the luminance of the neighboring pixels is more than twice (S2).

The comparison of the luminance is performed on all pixels of one horizontal synchronization signal until the flag reaches a specific value K (S5).

The specific value K is a value that can be determined to be an excessive amount of light, and is set to a value such that smear or other noise may occur.

Such a value may vary depending on the type of the image sensor 20 or other hardware.

As described above, when it is determined that the value comparing the luminance components exceeds a specific value and the light amount is excessive, the count is increased (S4).

Thereafter, the process proceeds to the next horizontal synchronizing signal (S6). Then, the luminance components in the horizontal synchronizing signal are compared, and the processes of S1 to S5 are repeated.

When this process is completed over the entire resolution, the iris opening state is controlled as shown in FIG. 5 according to the range of the count value.

The above-described luminance component comparison process may be performed only for the first frame of the image, or the comparison process may be performed for the entire frame (for example, when 60 frames are input in one second).

On the other hand, the comparison process may be performed only on the even-numbered frame, the odd-numbered frame, or a frame corresponding to a specific multiple.

Controlling the iris according to the result of the comparison process as described above is as follows.

That is, when there are few elements that generate noise due to the excessive amount of light, for example, when the count value of the range corresponding to count1 (count1) of FIG. 5 is calculated, the shutter is opened by opening all the irises (F3.5). To shoot. The F value may vary depending on the type of lens.

At this time, the operation of the shutter can achieve the same effect as the operation of the mechanical shutter by advancing the iris to the state F43.1 of step 5 after a specific exposure time.

When the excess amount of light occurs in a range corresponding to count 2 (count 2), the shutter is operated after opening the iris F3.69 by step 1.

Similarly, noise can be actively reduced by controlling the iris opening state according to the calculated count value, such as count 3, count 4, count 5, and the like.

In addition, in order to simplify the operation quickly, the generation of noise may be reduced by reducing the gain of the R, G, and B levels of the image sensor signal according to the count value without controlling the opening degree of the iris.

The above embodiment is an example for explaining the technical idea of the present invention in detail, and the present invention is not limited to the above embodiment, various modifications are possible, and various embodiments of the technical idea are all protected by the present invention. It belongs to the scope.

The present invention as described above can effectively remove the noise caused by the excess of the light when shooting the camera through the iris control, in particular, a camera installed in a portable device such as a mobile phone, a notebook computer as well as a general still camera There is an effect that can be applied to modules.

Claims (20)

A lens module; An image sensor for receiving an image through the lens module; A front end module for digitizing and outputting a signal output from the image sensor; A data capture unit which captures a signal output from the front end module, compares luminance components of each horizontal synchronization signal of the image sensor, and detects whether the amount of light is excessive; And a controller configured to determine and control an iris opening degree according to whether the amount of light is excessive. The exposure control apparatus of claim 1, wherein the data capture unit detects an excessive amount of light when the luminance of a neighboring horizontal transmission line is two or more times. The exposure control apparatus of a camera according to claim 1, wherein the step of opening the iris of the control unit is two steps of opening and closing. The exposure control apparatus of a camera according to claim 1, wherein the degree of the iris opening of the control unit is three or more steps. The apparatus of claim 1, wherein the controller controls the iris opening speed together. The exposure control apparatus of claim 1, wherein the data capture unit compares luminance components for each pixel in each horizontal synchronization signal. The exposure control apparatus of claim 6, wherein the luminance component comparison comprises comparing a luminance component by selecting among all pixels, an even pixel, an odd pixel, and a specific multiple of pixels. The exposure control apparatus of claim 1, wherein the data capture unit detects an excessive amount of light according to the entire frame or the selected frame. The exposure control apparatus of claim 8, wherein the selected frame is any one of an even frame, an odd frame, and a specific multiple frame. A lens module; An image sensor for receiving an image through the lens module; A front end module for digitizing and outputting a signal output from the image sensor; A data capture unit which captures a signal output from the front end module, compares luminance components of each horizontal synchronization signal of the image sensor, and detects whether the amount of light is excessive; And a control unit configured to determine and control whether or not the R, G, B gain values are reduced according to whether the amount of light is excessive. The exposure control apparatus of a camera according to claim 1 or 10, wherein the exposure control apparatus is installed in a camera module of a portable device. In the exposure control method of a camera having an image sensor, A first step of determining whether the amount of light is excessive by comparing luminance components for each pixel in the horizontal synchronization signal output from the image sensor; And a second step of determining the iris opening degree according to the determination value by performing the first step over the entire horizontal synchronization signal. The method of claim 12, wherein the luminance component comparison of each pixel of the first step comprises selecting a pixel from among all pixels, an even pixel, an odd pixel, and a specific multiple of the pixels to compare the luminance components. The method of claim 12, wherein the step of opening the iris of the second step is two steps of opening and closing. 13. The method of claim 12, wherein the degree of the iris opening of the second step is three or more steps. 13. The method of claim 12, wherein the step of opening the iris of the second step comprises six steps including maximum opening and closing. The method of claim 12, wherein the determination of the excess in the first step determines that the luminance of the neighboring pixel is two or more times as an excess of light. 13. The exposure of the camera according to claim 12, wherein the determination of excess of the first step accumulates the case where the luminance of the neighboring pixel is 2 times or more, and determines that the case where the cumulative value is greater than or equal to a specific value is an excess of light. Control method. In the exposure control method of a camera having an image sensor, A first step of comparing luminance components for each pixel in the horizontal synchronization signal output from the image sensor; Comparing the luminance components and increasing a flag value when it is determined that the amount of light is excessive; Increasing a count when the flag value exceeds an overflow value; Performing the first to third steps over the entire horizontal synchronization signal, and determining whether to decrease the R, G, and B gain values according to the count value, and including the fourth step. Exposure control method of the camera characterized in that. In the exposure control method of a camera having an image sensor, A first step of comparing luminance components for each pixel in the horizontal synchronization signal output from the image sensor; Comparing the luminance components and increasing a flag value when it is determined that the amount of light is excessive; A third step of incrementing a count when the flag value exceeds an overflow value; And a fourth step of performing the first to third steps over the entire horizontal synchronization signal to determine the iris opening degree according to the count value.

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