KR20100095824A - Method of controlling the intensity of radiaton of flash in digital imaging processing device - Google Patents

Abstract

PURPOSE: A method for controlling intensity of flash in a digital image processing device is provided to control intensity of flash based on a multi line light emitting method, thereby preventing ununiformity of brightness of an image. CONSTITUTION: A digital signal processing unit sets an optimum light emitting time based on flash emitting time of a digital image signal processing device and light exposure time of each line of a rolling shutter. A multi line light emitting unit periodically emits line light every optimum light emitting time. The digital image signal processing device includes at least one of a charging capacitor or a hardware flash for emitting a multi line light.

Description

{Method of controlling the intensity of radiaton of flash in digital imaging processing device}

The present invention relates to a method of controlling the amount of flash light in a digital image signal processing apparatus. More specifically, the present invention relates to a method of controlling the amount of flash light using a multi-line emission method in a digital image signal processing apparatus using a CIS.

Currently, a digital image signal processing apparatus uses a flash to correct an amount of light of a subject when the image sensor is exposed to a dark environment. Luminescence correction by the flash is controlled through the firing time. If the light emission time is long, the subject is taken brightly, and if it is short, the subject taken dark.

There are two main methods of controlling the light emission time: dimming method and pre-emission method.

The dimming method has the disadvantage of adding a dimmer sensor price and adjusting the dimming sensor in the production process, and difficulty in correcting when the subject is locally saturated.

1 shows a method of controlling the light emission time by the pre-emission method. The pre-emission method is generally used in a digital image signal processing apparatus using a CCD. However, when the brightness of the image is measured locally as shown in FIG. 3 during the preliminary emission, there is a problem in that the brightness of the normal emission cannot be calculated normally.

In addition, like the CCD type, the digital image signal processing apparatus using the global shutter method can use both the dimming method and the pre-luminous method, but the CIS (CMOS image sensor) using the rolling shutter In the case of not using the dimming method, there is a problem that the brightness difference occurs in the top and bottom of the image.

The present invention solves the problem that the brightness of an image is not uniform by controlling the amount of flash light based on a multi-beam emission method in consideration of the characteristics of a rolling shutter in a digital image signal processing apparatus using a CIS having a rolling shutter function.

The digital image signal processing apparatus using the rolling shutter of the present invention comprises: a digital signal processor configured to set an optimal emission time based on an exposure time and a flash emission time in each line of the rolling shutter; And a multi-beam light emitting unit which performs preliminary light emission periodically at the optimum light emission time.

A method of controlling the amount of flash light in a digital image signal processing apparatus using a rolling shutter of the present invention includes an optimal light emission time based on an exposure time in each line of the rolling shutter and a flash emission time of the digital image signal processing apparatus in a digital signal processing unit. Setting up; And periodically performing pre-emission at every optimal emission time, wherein the digital image signal processing apparatus includes at least one of a plurality of charging capacitors or hardware flashes to perform the multi-emission.

The present invention can solve the problem that the brightness difference occurs in the top and bottom of the image when the dimming method is not used in the CIS using the rolling shutter.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following description and the annexed drawings are for understanding the operation according to the present invention, and a part that can be easily implemented by those skilled in the art may be omitted.

In addition, the specification and drawings are not provided to limit the invention, the scope of the invention should be defined by the claims. Terms used in the present specification should be interpreted as meanings and concepts corresponding to the technical spirit of the present invention so as to best express the present invention.

2 to 4 illustrate the characteristics of the rolling shutter used in the present invention, the characteristics of the light emission timing of the flash during the preliminary light emission operation, and the problems occurring during image capturing using these two characteristics.

5 to 8 describe how to use the multiple pre-emission method for controlling the amount of flash light in the digital image signal processing apparatus using the CIS in the present invention in consideration of the characteristics described in FIGS. 9 shows an exemplary structure of a digital image signal processing apparatus of the present invention.

2 (a) to 2 (b) show the characteristics of the rolling shutter. As shown in FIGS. 2 (a) to 2 (b), the rolling shutter has a different exposure time for each horizontal line. The reason is that in the rolling shutter, since horizontal lines of one frame are sequentially exposed, a difference in brightness occurs due to a time difference caused by exposure between the horizontal lines.

3 shows the light emission timing of the flash in the conventional pre-emission operation.

Reference numeral 310 denotes a portion to which pre-emission is applied, and 320 denotes a portion to which main emission is applied. In this case, the image brightness is measured locally and the brightness of the normal emission cannot be calculated. Therefore, there is a need for a light emission control method in consideration of the rolling shutter of the CIS.

4 illustrates an example of an image photographed at the time of preliminary light emission in the rolling shutter mode. In Still Mode, the entire screen is exposed for a certain period of time using a shutter (Mechnical Shutter), and the shutter is read after the shutter is closed. Therefore, even when a rolling shutter is used, there is little effect of the flash.

However, the image photographed using the rolling shutter and the flash without using the shutter is as shown in FIG. 4. The brightness of the flash is reduced before one frame is transmitted by the rolling shutter, so that the portion where the flash is emitted 410 and the portion where the flash is not emitted 420 appear.

In the still mode, the conventional Xenon tube requires a strong light quantity, but a large amount of light cannot be used for the preliminary light emission operation for the light quantity measurement. It is difficult to get the right picture from the processing unit.

5 shows one characteristic of the pre-luminous method used in the present invention.

CIS is also capable of high-frame rate output, typically over 1000fps. Currently available CIS is capable of 1200fps and is expected to enable higher speeds in the future. Using the characteristics of the CIS, it is possible to increase the frame rate at the time of pre-emission of FIG. 5 (510). As a result, even when the rolling shutter is used in the flash, it is possible to read out the amount of light emitted at the same brightness in all the lie.

FIG. 6 is an embodiment of the present invention, and shows an example of enlarging the light emitting application portion in FIG. 5. For example, Xenon Flash can continuously emit light for a short time as shown in FIG. 6. In this case, the light emission time of Xenon Flash can be shortened by synchronizing with the exposure time instead of the VD cycle. However, if the exposure time of the sensor is shortened, a sufficient light source cannot be obtained from the photodiode and the image becomes dark. Therefore, without using ISO gain or digital gain, sufficient brightness for light quantity calculation cannot be obtained.

7 (a) to 7 (c) show a conceptual diagram of a rolling shutter transmission method used in the present invention. Fig. 7A shows the initialization, exposure and transmission of the rolling shutter.

Fig. 7 (b) shows the operation state for each part of the individual lines in the rolling shutter transmission. The individual lines are divided into detailed operations such as initialization 710, exposure 720 and transmission 730, respectively. Of these, the most significant influence on the frame rate is the exposure 720 time.

In the case of CIS, there is no limit to raising the frame rate in theory, but as the frame rate increases, the time required for the exposure 720 is relatively reduced. Calculation is required.

The present invention provides a method for detecting the amount of flash light of the pre-emitting method using the characteristics of the rolling shutter in order to use the pre-emitting method in a digital image signal processing apparatus using a CIS having a rolling shutter function.

To this end, the digital image signal processing apparatus of the present invention includes a separate light emitting capacitor for pre-luminescence in hardware and includes a separate flash for main light.

As shown in (c) of FIG. 7, the presence of the exposure time difference in each line (Line 1, Line 2, Line 3, ...) of the rolling shutter means that the transmission time tn (740, 741, 742, 743 ...). In order to optimize the function of the rolling shutter, it is required to shorten the transmission time tn of each line. However, since it is difficult to physically reduce tn, it may be considered to emit light in consideration of the emission time of each transmission time t1, t2, t3, ... tn and flash.

8 shows a light emitting method in the CMOS image sensor proposed in the present invention.

The digital image signal processing apparatus of the present invention includes a separate light emitting flash capacitor for pre-emission in hardware and includes a separate flash for the main light emission. That is, in order to implement the light emitting function proposed by the present invention, an implementation of the light emitting function of the improved flash is required, unlike the existing invention. To this end, for example, a camera includes a plurality of Xenon Lamp charging capacitors, and it is assumed that hardware for detecting the charge is implemented.

In consideration of the light emission time of the flash of the digital image signal processing apparatus and the exposure time in each line of the rolling shutter, an optimal light emission time (T) 810 is set. Then, during the optimum light emission time T, the number of horizontal lines which can complete exposure and transmission is grasped. After performing n-th order pre-emission, image data for light quantity calculation is grasped.

For example, when the same amount of light can be irradiated to three horizontal lines during the optimal emission time T during the first linear emission, light quantity data is obtained from three lines. After that, light quantity data is obtained from three lines through the second preliminary emission. In this manner, when the nth order of preliminary light emission is completed, an image of the same brightness can be obtained for one VD (frame).

9 shows an exemplary structure of a digital image signal processing apparatus using the multi-line emission type flash emission control of the present invention.

The digital video signal processing apparatus of the present invention includes a mobile phone, a handheld device, a PMP, a PDP, a camcorder, a notebook, and the like. And, as mentioned in Figure 8, the digital image signal processing apparatus of the present invention includes a separate light emitting capacitor for the pre-luminescence in hardware, and includes a separate flash for the present light emission. Examples of flash modes include auto flash, forced flash, flash off, red-eye reduction, slow synchro, and the like. In addition, the digital image signal processing apparatus of the present invention may include an auxiliary light. The auxiliary light supplies light to the subject so that the digital image processing device can focus quickly and accurately when the amount of light is insufficient or at night.

The digital photographing apparatus 900 embodying the present invention includes an optical unit 910, an optical driver 911, an imaging device 915, an imaging device controller 916, an operation unit 920, a program storage unit 930, The buffer storage unit 940, the data storage unit 950, the touch screen display 960, and the digital signal processor DSP may be included.

The optical signal transmitted through the optical unit 910 reaches the light receiving surface of the imaging device 915 to form an image of the subject. The imaging device 115 may use a Charge Coupled Device (CCD) or a Complementary Metal Oxide Semiconductor Image Sensor (CIS) that converts an optical signal into an electrical signal. However, as mentioned above, in the case of the CCD type, both the dimming method and the preliminary light emitting method may be used. However, in the CIS, when the preliminary light emitting method is used, there is a problem in that brightness difference occurs in the upper and lower parts of the image. It may be implemented more suitably in the case.

Such an image pickup device 915 may be controlled by the image pickup device controller 916 such as sensitivity. The imaging device controller 916 may control the imaging device 915 according to a control signal automatically generated by an image signal input in real time or a control signal manually input by a user's operation.

The operation unit 920 is a place that can input a control signal from the outside such as a user. The operation unit 920 may include a shutter release button for inputting a shutter release signal for taking a picture by exposing the imaging device 915 to light for a predetermined time, a power release button for supplying power, and an angle of view according to the input. There are a wide-angle zoom button and a tele-zoom button to widen or narrow the angle of view, and various function buttons such as selecting a text input or shooting mode, a playback mode, selecting a white balance setting function, and selecting an exposure setting function. The operation unit 920 may have a variety of buttons as described above, but is not limited thereto. The operation unit 920 may be implemented in any form that a user can input, such as a keyboard, a touch pad, a touch screen, a remote controller, and the like.

The present invention has been described above with reference to preferred embodiments. Those skilled in the art will understand that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the above-described embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and the inventions claimed by the claims and the inventions equivalent to the claimed invention are to be construed as being included in the present invention.

1 shows a method of controlling the light emission time by the pre-emission method.

2 (a) to 2 (b) show the characteristics of the rolling shutter.

3 shows the light emission timing of the flash in the conventional pre-emission operation.

4 illustrates an example of an image photographed at the time of preliminary light emission in the rolling shutter mode.

5 shows one characteristic of the pre-luminous method used in the present invention.

FIG. 6 is an embodiment of the present invention, and shows an example of enlarging the light emitting application portion in FIG. 5.

7 (a) to 7 (c) show a conceptual diagram of a rolling shutter transmission method used in the present invention.

8 shows a light emitting method in the CMOS image sensor proposed in the present invention.

9 shows an exemplary structure of a digital image signal processing apparatus using the multi-line emission type flash emission control of the present invention.

Claims (7)

A digital video signal processing apparatus using a rolling shutter, A digital signal processor configured to set an optimal light emission time based on an exposure time and a flash emission time of the digital image signal processing apparatus in each line of the rolling shutter; And And a multi-line light emitting unit for performing pre-emission periodically at every optimum light emitting time. The apparatus of claim 1, wherein the digital image signal processing apparatus A digital video signal processing apparatus using a CMOS image sensor. The apparatus of claim 1, wherein the digital image signal processing apparatus And at least one of a plurality of charging capacitors or a hardware flash to perform the multi-emission. The method of claim 1, And setting the number of pre-emissions performed by the multi-line light emitting unit based on the number of horizontal lines that can be exposed and transmitted during the optimum light emitting time in the rolling shutter. The method of claim 3, wherein the plurality of charging capacitors Digital image signal processing device, characterized in that the plurality of Xenon Lamp charging capacitors. The method of claim 1, wherein the optimal light emission time And a time at which the brightness of the image photographed by the digital image signal processing device can be set uniformly. A method of controlling the amount of flash light in a digital image signal processing apparatus using a rolling shutter, Setting an optimum light emitting time in the digital signal processor based on an exposure time in each line of the rolling shutter and a flash light emitting time of the digital image signal processing apparatus; And And periodically performing pre-emission at every optimum emission time, wherein the digital image signal processing apparatus includes at least one of a plurality of charging capacitors or hardware flashes to perform the multi-emission. A method of controlling the amount of flash light used.

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