KR20090126698A - Apparatus and method for controlling slow shutter speed of camera - Google Patents

Abstract

PURPOSE: An apparatus and a method for controlling slow shutter speed of a camera are provided to variably output a reset pulse of a photographing element to linearly perform switching from current shutter speed to target slow shutter speed, thereby naturally photographing a moving picture. CONSTITUTION: A microcomputer calculates the difference value between current shutter speed and target slow shutter speed(S12). When the target slow shutter speed is not reached, a linear slow shutter speed operation is performed while reducing the number of reset pulses applied to a CCD(Charge Coupled Device) by one(S16,S17).

Description

Apparatus and method for controlling slow shutter speed of camera}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slow shutter speed control apparatus and a method of a camera, and for example, a moving picture is captured using an imaging device such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). The present invention relates to a slow shutter speed control apparatus and a method of photographing a camera.

Generally, a photographing device such as a CDC or a CMOS is widely used in a camera for photographing a video. For example, in the camera, when photographing a subject having a high brightness level In order to reduce the amount of light incident on the imaging device, the amount of opening of the iris is automatically reduced, or the analog gain value for amplifying the output signal of the imaging device is automatically reduced.

In addition, in the camera, even when the iris opening amount and the analog gain value are automatically reduced as described above, when it is impossible to photograph a subject having an appropriate luminance level, the charges charged by the pixels of the image pickup device (Pixel) In order to reduce the amount of charge, the shutter speed of the imaging device is adjusted to a short shutter speed.

On the other hand, in the camera, when photographing a subject having a low brightness level, in order to increase the amount of light incident on the imaging device, the amount of opening of the iris is automatically increased or the output signal of the imaging device is amplified. This will automatically increase the analog gain value.

Also, in the camera, even when the iris opening amount and the analog gain value are automatically increased as described above, when it is impossible to photograph a subject having an appropriate luminance level, the charges charged by the pixels of the imaging element ( In order to increase the amount of charge, the shutter speed of the imaging device is adjusted to a long shutter speed, that is, a slow shutter speed.

Accordingly, in the camera, when capturing a subject having a high brightness level or capturing a subject having a low brightness level, the iris opening amount, the analog gain value, and the shutter speed are automatically adjusted to capture a subject at an appropriate level. Will be able to perform

However, in a general camera, when a low illuminance photographing mode for capturing a low luminance level subject is set as described above, for example, a shutter speed of one field period is set to a slow speed of two field periods or three field periods. 1, the shutter speed is adjusted. For example, as shown in FIG. There is a problem.

Therefore, the present invention was created in order to solve the above problems, for example, low luminance (Low Luminance) in a camera for shooting a video using an image pickup device such as CD (CCD) or CMOS (CMOS), etc. When shooting a subject, the Slow Shutter Speed control mode is automatically set, but the reset pulse of the image pickup device is variably outputted so that switching from the current shutter speed to the desired slow shutter speed can be performed. It is an object of the present invention to provide a slow shutter speed control apparatus and method for a camera to perform linearly.

The slow shutter speed control method of the camera according to the present invention for achieving the above object, a step of automatically setting the slow shutter speed control mode when shooting a low-light subject; And two steps of linearly performing a transition from the current shutter speed to the target slow shutter speed.

The second step may include: a lower first step of calculating a difference value between a current shutter speed and a target slow shutter speed when the slow shutter speed control mode is set; And calculating the number of charge reset pulses of the imaging device corresponding to the difference value, and outputting as many charge reset pulses as the number becomes smaller by one than the calculated number.

In addition, the number of charge reset pulses of the imaging device is characterized in that it is proportional to the difference between the current shutter speed and the target slow shutter speed,

In addition, the slow shutter speed control apparatus of the camera according to the present invention, the drive means for driving the imaging element; Detection means for detecting a low light subject photographing state; And controlling the driving means so that the slow shutter speed control mode is automatically set when the low-light subject is photographed, and the switching from the current shutter speed to the target slow shutter speed is performed linearly. Characterized in that it comprises a means,

Further, when the slow shutter speed control mode is set, the control unit calculates a difference value between the current shutter speed and the target slow shutter speed, and calculates the number of charge reset pulses of the imaging device corresponding to the difference value. After the calculation, characterized in that for controlling the drive means so that the number of the charge reset pulse is reduced by one less than the calculated number,

The number of charge reset pulses of the imaging device is characterized in that it is proportional to the difference between the current shutter speed and the target slow shutter speed.

The slow shutter speed control apparatus and method of the camera according to the present invention, for example, in a camera that shoots a video using an imaging device such as a CCD (CCD), CMOS (CMOS), when shooting a low-light subject, The shutter speed control mode is automatically set, but a variable output of the reset pulse of the imaging device is performed to linearly switch from the current shutter speed to the target slow shutter speed, thereby performing the slow shutter speed control operation. Even if it is possible to shoot video naturally.

Hereinafter, a preferred embodiment of an apparatus and method for controlling a slow shutter speed of a camera according to the present invention will be described in detail with reference to the accompanying drawings.

First, the slow shutter speed control apparatus and method according to the present invention, for example, a monitoring camera equipped with an imaging device such as a CD (CCD) or CMOS (CMOS) widely used for video shooting Applies to various types of cameras, such as.

2 illustrates a configuration of a camera to which the present invention is applied. For example, the camera includes a zoom lens 10, a focus lens 11, an iris 12, an imaging device 13, Analog Front End (AFE) 14, Digital Signal Processor 15, Driver 16, Timing Clock Generator 17, Low Light Detection 18, Memory 19, and Microcomputer 20. Etc. are comprised.

On the other hand, the microcomputer 20 operates the timing clock generator 17 to generate a timing clock Timing Cluck of a predetermined frequency, and the driver 16 uses the timing clock to generate the timing clock. The output timing of the charge charged by the pixels of the imaging device 13 is controlled.

In the analog front end 14, an automatic gain control (AGC) operation for amplifying the analog signal output from the imaging element 13 to a predetermined level, and the analog signal amplified to the predetermined level. The A / D conversion operation of converting the signal into a digital signal is performed.

In addition, the digital signal processor 15 amplifies the digital signal converted from the analog front end by applying a digital gain value, and then converts the digital signal into an automatic white balance (AWB). Perform digital signal processing operation.

Meanwhile, the low light detection unit 18 analyzes the video data signal-processed by the digital signal processing unit 15 to detect whether the low light level is in a low light level. Even if the iris opening is increased and the analog gain value is increased, if the average brightness of the subject image is not higher than the preset reference value, it is detected as a low luminance shooting state requiring adjustment of the shutter speed. Done.

The microcomputer 20 automatically sets a slow shutter speed control mode when the microcomputer 20 determines that the low light photographing state is in accordance with the detection signal output from the low light detection unit 18. The process of switching from the shutter speed to the target slow shutter speed can be performed linearly, which will be described in detail below.

3 is a flowchart illustrating a method of controlling a slow shutter speed of a camera according to the present invention. For example, in the microcomputer 20, a slow shutter speed control mode is set according to a user's request. Alternatively, when it is determined that the low light subject is photographed according to the detection signal output from the low light detection unit 18, the slow shutter speed control mode is automatically set (S10).

In addition, the microcomputer 20 checks the current shutter speed (S11), and calculates a difference value between the target slow shutter speed (S12). If the shutter speed is 1 field period and the target slow shutter speed is the shutter speed of 2 field periods, the difference value between the current shutter speed and the target slow shutter speed is calculated as one field.

Then, the maximum number of reset pulses of the imaging device corresponding to the one field is calculated (S13). For example, as shown in FIG. 4, the imaging device 13 is charged between one field. Assuming that the maximum number of reset pulses of the imaging device corresponding to the resolution required to gradually signal the charge is five, the microcomputer 20 operates and controls the driver 16, 1 In the first process of switching from the shutter speed of the field period to the shutter speed of the two field periods, four reset pulses are output.

That is, in the first process of switching from the shutter speed of one field period to the shutter speed of two field periods, four reset pulses are output to output the remaining 1/5 of the even field and the next odd field. Charged charge is output so that the shutter speed is 1.2 field periods.

In the second process, three reset pulses are output, so that the remaining 2/5 of the even field and the charged charges during the next odd field are output, so that the shutter speed is 1.4 field periods. In the third process, two reset pulses are output so that the remaining 3/5 of the even field and the charged charges during the next odd field are output, so that the shutter speed is 1.6 field periods.

Also, in the fourth process, one reset pulse is output so that the remaining 4/5 of the even field and the charged charge during the next odd field are output, so that the shutter speed is 1.8 field periods. In the fifth process, by not outputting the reset pulse, the linear slowing is performed so that the charged charges during the even field and the next field are output, resulting in a shutter speed of 2.0 field periods. The shutter speed operation is performed (S15).

And, while performing the above process, it is determined whether the target slow shutter speed is reached, for example, if the target slow shutter speed has not yet been reached (S16), as described above, While reducing the number of reset pulses applied to the scratch element by one (S17), the linear slow shutter speed operation is performed.

On the other hand, in the microcomputer 20, when the target slow shutter speed is reached, the reset pulse is no longer output to the imaging device and the slow shutter speed control mode is canceled (S18). Even if the shutter speed control operation is performed, the moving image can be naturally recorded.

Or more, preferred embodiments of the present invention described above, for the purpose of illustration, those skilled in the art, within the technical spirit and the technical scope of the present invention disclosed in the appended claims below, to further improve various other embodiments Changes, substitutions or additions will be possible.

FIG. 1 illustrates an embodiment of a slow shutter speed control process of a general camera.

2 illustrates a configuration of a camera to which the present invention is applied.

3 is a flowchart illustrating an operation of a slow shutter speed control method of a camera according to the present invention;

Figure 4 illustrates an embodiment of a slow shutter speed control process of the camera according to the present invention.

※ Explanation of code for main part of drawing

10: zoom lens 11: focus lens

12 Iris 13 Imaging Device

14: analog front end 15: digital signal processing unit

16 driver 17 timing clock generator

18: low light detection unit 19: memory

20: micom

Claims (6)

A step of automatically setting a slow shutter speed control mode when photographing a low-light subject; And A method of controlling a slow shutter speed of a camera, comprising: performing a linear change from a current shutter speed to a target slow shutter speed. The method of claim 1, The second step, A lower step of calculating a difference value between a current shutter speed and a target slow shutter speed when the slow shutter speed control mode is set; And Calculating the number of charge reset pulses of the image pickup device corresponding to the difference value, and outputting as many charge reset pulses as the number becomes smaller than the calculated number. Shutter speed control method. The method of claim 2, And the number of charge reset pulses of the imaging device is proportional to the difference between the current shutter speed and the target slow shutter speed. Driving means for driving an imaging device; Detection means for detecting a low light subject photographing state; And Control means for controlling the driving means so that the slow shutter speed control mode is automatically set when the low-light subject is photographed, and the switching from the current shutter speed to the target slow shutter speed is performed linearly. Slow shutter speed control device of the camera, characterized in that comprises a. The method of claim 4, wherein The control means, When the slow shutter speed control mode is set, the difference value between the current shutter speed and the target slow shutter speed is calculated, Calculating the number of charge reset pulses of the imaging device corresponding to the difference value, and controlling the driving means to output as many charge reset pulses as the number becomes smaller than the calculated number. Shutter speed control. The method of claim 5, And the number of charge reset pulses of the imaging device is proportional to the difference between the current shutter speed and the target slow shutter speed.

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