KR19990002933A - Auto Exposure Control in Spot Light Mode - Google Patents

Abstract

end. FIELD OF THE INVENTION The present invention relates to a method for automatically controlling exposure of a photographing apparatus such as a camcorder.

I. SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic exposure control method capable of optimally photographing the brightness of a subject receiving a spot light in an imaging device such as a camcorder.

All. Summary of the Invention The present invention provides a photographing apparatus having an aperture for controlling an exposure amount when photographing a subject, and a digital signal processing unit for processing an encoded video signal with color and luminance data and outputting the same.

In spot light mode, exposure is automatically obtained by reading a group of luminance data having the highest level among the luminance data processed by the digital signal, calculating an average value thereof, and opening / closing the aperture so that the calculated average value matches a preset target value. It is characterized by a control box.

la. Important uses of the invention: It can be used in imaging equipment such as camcorders.

Description

Auto Exposure Control in Spot Light Mode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control method of a photographing apparatus such as a camcorder, and more particularly, to an automatic exposure control method for adjusting the brightness of a photographed subject to an optimal state in a spot light mode.

In general, a camcorder (CAMCORDER) is a video and audio signal processing apparatus capable of recording video and audio signals on a provided recording medium and reproducing the recorded signals. In other words, the camcorder not only has the functions of a general camera but also has a function of a recorder capable of recording a photographed subject. By using such a camcorder, a user can photograph and record a desired subject, and then check the photographed subject again. In general, camcorders are equipped with an automatic exposure control function. The automatic exposure control function takes an average value of luminance (brightness) data of an image to be imaged and controls the iris to match the target value (a luminance target value), and the average luminance data is If it is smaller than the target value, the aperture is opened and if it is larger, the aperture is closed to adjust the amount of light. However, in the spot light mode, the following problem occurs in automatically controlling the exposure of the subject in the same manner as described above.

First, FIG. 1 is a diagram illustrating an example of a screen when photographing a specific subject in the spot light mode, and FIG. 2 is a diagram illustrating a characteristic of luminance change in a 1V (Vertical) section of the subject photographed in FIG. 1. In FIG. 2, (a) shows a change in luminance when the exposure is not automatically controlled in the spot light mode, and (b) shows a change in luminance when the exposure is automatically controlled in the spot light mode. If only the human body portion A is stepped on by the spot light and the other portions are dark as shown in Fig. 1, the average value of the overall luminance data of the image to be captured is lowered. This is because there are many darker parts than bright parts of the entire screen to be imaged. Therefore, in the spot light mode, since the average luminance data is smaller than the target value, the aperture is opened to compensate for it. In this case, as shown in (b) of FIG. 2, since the luminance data of the human body portion A receiving the spot light is relatively larger than the target value, the object becomes a white clip and the object (ie, the human body portion) is not visible.

Accordingly, an object of the present invention is to provide an automatic exposure control method capable of capturing an optimal brightness of a subject receiving a spot light in a photographing apparatus such as a camcorder.

According to an aspect of the present invention, there is provided an imaging apparatus including an aperture controlling an exposure amount when photographing a subject, and a digital signal processing unit for processing the encoded image signal with color and luminance data and outputting the same.

In spot light mode, exposure is automatically obtained by reading a group of luminance data having the highest level among the luminance data processed by the digital signal, calculating an average value thereof, and opening / closing the aperture so that the calculated average value matches a preset target value. It is characterized by a control box.

1 is a screen example of photographing a specific subject in the spot light mode.

FIG. 2 is a diagram illustrating characteristics of luminance change in a 1V (Vertical) section of a subject photographed in FIG. 1; FIG.

3 is a schematic block diagram of a camcorder according to an embodiment of the present invention;

4 is a control flowchart illustrating an automatic exposure control process in the spot light mode according to an embodiment of the present invention.

FIG. 5 is a characteristic diagram of luminance change of a subject scratched by the automatic exposure control process of FIG. 4. FIG.

Hereinafter, an operation according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a schematic block diagram of a general camcorder. Referring to FIG. 3, the lens group 10 includes a focus lens 12b and a zoom lens 12a which enlarge and reduce a subject while receiving the image of the subject while moving forward and backward in the optical axis direction. The aperture 14 is opened / closed by a drive signal input from the aperture motor driver 28 to control the amount of light. The imaging tube 16 is operated according to horizontal and vertical imaging driving pulses generated by a timing generator (not shown) to enlarge and reduce the optical signal of the subject input through the lens group 10. And a solid state image pickup device (CCD) for converting the image data into a captured image signal. The correlation sampling and gain control unit 18 samples, gain-controls and outputs the video signal picked up from the imaging tube 16. The analog-to-digital (A / D) converting section 2 converts the gain-adjusted captured image signal for one field into a digital signal. The digital signal processor 22 encodes the digitized video signal for one field, processes it as a color or luminance signal in NTSC or PAL format, and outputs it to a VCR. The microcomputer 24 performs an overall control operation of the camcorder by embedding a memory in which a control program according to an exemplary embodiment of the present invention is stored. For example, the microcomputer 24 reads luminance data divided by 48 from the digital signal processor 22 for automatic exposure control. An aperture control signal for controlling the opening / closing amount of the aperture by reading a predetermined number of brightest luminance data among the read data (n in the embodiment of the present invention) and calculating an average value and comparing the calculated average value with a luminance target value. Outputs In this case, the aperture control signal is digitally converted by the D / A converter 26 and input to the aperture motor driver 28. Accordingly, the aperture motor driver 28 is a drive signal for opening / closing the aperture 14. The amount of light in the aperture 14 is controlled by outputting the. The luminance target value (hereinafter, referred to as a target value) indicates a preset value such that the photographed subject has an optimal brightness.

4 is a flow chart illustrating a process for automatically controlling exposure in a spot light mode according to an exemplary embodiment of the present invention, and FIG. 5 is a diagram illustrating characteristics of luminance change of an object scratched by the process of automatic exposure control of FIG. 4. It is shown.

Hereinafter, the automatic exposure control process in the spot light mode according to the embodiment of the present invention will be described with reference to FIGS. 3 to 5.

First, the microcomputer 24 determines whether it is in the spot light mode in step 30 of FIG. 4, and proceeds to step 32 in the spot light mode, and reads data divided by 48 from the digital signal processor 22. Thereafter, the microcomputer 24 reads n brightest luminance data among the data divided in step 34. In step 36, the average value of the read luminance data is calculated, and the target value is compared with the target value in step 38. If the average value of the calculated luminance data is equal to the target value, the microcomputer 24 proceeds to step 40 to maintain the aperture 14 in the current state. On the other hand, if the average value of the calculated luminance data is not the same as the target value, the microcomputer 24 proceeds to step 42 and determines whether the target value has a larger value than the average value. (14) is opened. As a result, as shown in FIG. 5, the luminance data of the subject receiving the spot light matches the target value, thereby achieving optimal brightness. On the other hand, if the average value of the luminance data is greater than the target value in step 42, the microcomputer 24 proceeds to step 46 to close the aperture 14 according to the degree of brightness. Therefore, the luminance data of the subject subjected to the spot light becomes optimal as shown in FIG. 5 by matching the target value.

As described above, the present invention calculates an average value by taking only luminance data of a subject receiving a spot light in the spot light mode, and compares the calculated average value with a preset target value to automatically control the exposure to obtain a brightness of the subject receiving the spot light. There is an advantage that can be maintained in an optimal state.

Claims (3)

A photographing apparatus having an aperture for controlling an exposure amount when photographing a subject and a digital signal processing unit for processing an encoded image signal with color and luminance data and outputting the same; In spot light mode, exposure is automatically obtained by reading a group of luminance data having the highest level among the luminance data processed by the digital signal, calculating an average value thereof, and opening / closing the aperture so that the calculated average value matches a preset target value. Automatic exposure control method characterized in that the control box. A camcorder having an aperture for controlling an exposure amount when photographing a subject, and a digital signal processor for processing an encoded video signal with color and luminance data and outputting the same; In the spot light mode, the luminance data of the subject receiving the spot light among the luminance data processed by the digital signal is calculated, and the exposure is automatically controlled by opening / closing the aperture so that the calculated average value matches a preset target value. Automatic exposure control method of a camcorder. The method of claim 2, wherein the average value is calculated by reading only a plurality of luminance data having the highest level among the luminance data of the subject receiving the spot light.