KR0135950B1 - How to adjust the autofocus of your camcorder - Google Patents

Abstract

The present invention relates to a focus control of a camcorder, and in particular, by subdividing a focus evaluation value region and controlling the focus lens with reference thereto, the malfunction of the auto focus operation is prevented by preventing the focus motor from stopping at a vertex having a small shape of the focus evaluation value. The automatic focusing method of the camcorder to be solved.

The present invention determines the focus motor driving direction according to the focus evaluation value values for the first and second regions, and then drives the focus motor in the forward focus direction, and the current focus evaluation values for the first and second regions. And determining whether the focus motor is driven by comparing the past focus evaluation value with the past focus evaluation value, and when the focus motor is driven, the current focus evaluation value of the third station corresponding to the difference between the first area and the second area is past. Comparing with the focus evaluation value and stopping the driving of the focus motor and completing the focus adjustment operation when the current focus evaluation value of the third region is smaller than the past focus evaluation value.

Description

How to adjust the autofocus of your camcorder

1 is a block diagram of the automatic focusing apparatus of a conventional camcorder.

(A) to (d) of FIG. 2 are explanatory diagrams of a focus evaluation value extraction region.

3 is a graph of focus evaluation values according to focus lens positions.

4 is a graph of focus evaluation values according to focus lens positions for explaining the present invention.

5 is an autofocus signal flow diagram of a camcorder of the present invention.

* Description of the symbols for the main parts of the drawings *

105: high pass filter 106: analog / digital conversion unit

108: microcomputer 109: focus motor drive unit

The present invention relates to focus control in an integrated camera VR (hereinafter referred to as a camcorder). In particular, the focus motor is stopped at a vertex having a small peak evaluation value by controlling the focus lens by subdividing the focus evaluation value region and referring to this. The present invention relates to an automatic focus control method of a camcorder, which attempts to solve a malfunction of the automatic focus operation by preventing the error.

FIG. 1 is a block diagram of an automatic focusing apparatus of a general camcorder. As shown therein, a zoom lens 101 for inputting an image of a subject while moving forward and backward in the optical axis direction, and an optical signal of the subject through the zoom lens 101 Is converted into a captured image signal according to an externally generated screen region division control signal, and a color signal and a luminance signal are outputted from the captured image signal of each screen region inputted from the image capture tube 102. A sampling and gain control unit 103 for detecting, sampling, gain controlling, and outputting the video signal processing unit for encoding a color signal and a luminance signal obtained from the sampling and gain control unit 103 into a composite video signal and outputting the composite video signal as a video image signal. And a high pass filter 105 for high pass filtering the luminance signal of the video signal for each screen separated by the sampling and gain control unit 103. An analog / digital converter 106 for converting a luminance signal of a high frequency component for each region of the screen filtered by the high pass filter 015 into a digital signal, and the digital signal through the analog / digital converter 106. Divide the luminance signal of the subject for the area of the screen obtained by conversion into the horizontal / vertical register, and divide the luminance signal for the area of the divided screen according to the horizontal / vertical synchronization, and the luminance of the area of the divided screen. A focus lens control signal is generated in accordance with the area division and addition unit 107 for integrating the signal for one field and obtaining the sum signal, and the sum signal of the screen obtained by the area division and addition unit 107 to generate the entire lens of the camcorder. A microcomputer 108 for controlling a system operation, and a focus motor driver 109 for adjusting a focus lens by driving in accordance with a focus lens control signal output from the microcomputer 108. Consists of.

Referring to FIGS. 2 and 3 of the accompanying drawings, operations of the autofocus control device of the general camcorder configured as described above will be described in detail as follows.

First, when the image is input to the image capturing tube 102 through the zoom lens 101 of the subject, the image capturing tube 102 converts the image of the input subject into a captured image signal according to a screen area division control signal input from the outside, thereby sampling and gaining the image. The control unit 103 is input.

The sampling and gain control unit 103 samples and gain-controls the captured image signal of the input screen area and outputs the color signal and the luminance signal separately.

In this case, the color signal and the luminance signal are input to the high pass filter 015 and the video image processor 104 according to the movement amount of the zoom lens 101.

The video image processing unit 104 converts the input color signal and the luminance signal into a TV signal and outputs the video image signal.

Meanwhile, the high pass filter unit 50 extracts a high pass component of the luminance signal input in one horizontal retrace period of the corresponding area of the screen, and inputs the high pass component to the analog / digital converter 106, wherein the high pass filtered The value will be larger than if it is in focus or not (if it is not).

The analog / digital conversion unit 106 is one field unit 262.5H for each area of the screen sequentially input through the high pass filter unit 105 to convert the high frequency component of the luminance signal into a digital signal and divide the area. It is input to the adder 107.

Accordingly, the area dividing and adding unit 107 adds and outputs the high frequency component of the digital luminance signal for each field input from the analog / digital converter 106 for one field.

The luminance value output from the area divider and adder 107 is input to the microcomputer 108.

Accordingly, the microcomputer 108 automatically adjusts the focus by adjusting the focus motor to the maximum evaluation value according to the input luminance value.

At this time, to extract a specific area of the screen, it has a focus evaluation value extraction area as in the second degree (area A), and the high frequency component value of this area is maximized so as to focus.

Referring to FIG. 2, when the screen with the subjects (a) and (b) is grabbed, the focus evaluation value extraction region for focusing is selected in a predetermined region of the screen as shown in FIG.

When the focus lens driving motor is driven to an infinity position in order to calculate the focus evaluation values according to the subjects (a) and (b), the focus evaluation values as shown in (b) of FIG. 2 appear.

The main subject we are going to shoot is. However, when focusing by the subject (b) is detected at the focus lens b position, the camera focuses on the b position, that is, the subject (b).

Therefore, focusing is not performed on the subject.

Accordingly, this problem can be improved by selecting the focus evaluation value extraction region as shown in FIG.

As described above, in order to determine whether another subject appears in one focal region, four (i.e., four B regions) of left, right, up and down around the subject (a) are identified. The focus evaluation value detection area is set, and the focus lens driving motor is driven to an infinite magnification in each focus evaluation value detection area to detect the focus evaluation value.

In this case, only one vertex value is detected in ① focus evaluation value detection area ① of FIG. 2 (C) and two values are detected in area ②.

Area ③ has no detection, and area ④ also has one vertex value detected, so it can be seen that there are two subjects in the focus evaluation value detection area. Therefore, focusing can be performed precisely on the object to be focused. .

However, as the lens is in a high magnification state, the focus evaluation value of a small area becomes very small, making it difficult to focus.

Therefore, the focus evaluation region is usually extracted with the focus evaluation values for the vertical and horizontal 1 / 4V and 1 / 4H time domains.

When the focus lens is moved in infinity from this state to infinity, a mountain-like focus evaluation value of the third degree is extracted.

This mountain shape is influenced by how the subject exists in the focus value extraction area.

However, the automatic focus control device of such a camcorder has a mountain shape as shown in FIG. 3 when the subject exists in the focus evaluation value extraction area and the plane exists in the three-dimensional manner. There was a problem that the autofocus control malfunctioned because the focus motor stopped at the peak of the small mountain shape of the focus evaluation value.

Therefore, an object of the present invention is to subdivide the focus evaluation value area and to control the focus lens with reference thereto, thereby preventing the focus motor from stopping at the peak of the small mountain shape of the focus evaluation value so as to solve the malfunction of the auto focus operation. It is provided in the focus control method.

The object of the present invention is to determine the focus motor driving direction according to the focus evaluation values for the first and second areas, and then move in the forward focus direction, the current focus evaluation value and the past focus evaluation value of the first area. Determining whether the focus motor is driven by comparing the first and second comparisons, and if the current focus evaluation value of the first area is less than the previous focus evaluation value, comparing the current focus evaluation value and the previous focus evaluation value of the second area; Obtaining a focus evaluation value of the third area obtained by subtracting the second area from the first area when the current focus evaluation value of the second area is smaller than the past focus evaluation value as a result of the recomparison, and the current focus evaluation value of the third area; By comparing the previous and previous focus evaluation values and stopping the focus motor and completing the focus adjustment operation when the current focus value is smaller than the previous focus evaluation value. To be sex, hereinafter will be described in detail based on the accompanying drawings, the present invention. The apparatus for adjusting the autofocus of the camcorder applied to the present invention is the same as that of FIG. 1 and the accompanying drawings. Hereinafter, the method of adjusting the autofocus of the camcorder of the present invention will be described in detail with reference to FIGS. 4 and 5.

5 is an automatic focusing signal flow diagram of a camcorder according to the present invention. As shown in FIG. 5, when the focusing operation is started, a focus evaluation value for each region (A, B region) is input (S1), and the received A Determining a focus motor driving direction with the focus evaluation value of the region B and driving the focus motor in the constant focus direction (S2), and comparing the current focus evaluation value and the past focus evaluation value for the region A (S3). ) And comparing the present focus evaluation value for the area B with the past focus evaluation value (area B) when the current focus evaluation value of the area A is less than the past focus evaluation value (area A). (S4) and when the current focus evaluation value of the area B is smaller than the past focus evaluation value (area B) as a result of the comparison in step S4, the focus evaluation value of another area (area C) is extracted from the area A-B. Step S5 and the extracted region C (region A-B zero) (S6) comparing the current focus evaluation value and the previous focus evaluation value (C region) of the step S), and the current focus evaluation value of the C region is larger than the past focus evaluation value (C region) as a result of the comparison in the step (S6). If the focus control operation is completed, if the current focus evaluation value of the region C is smaller than the previous focus evaluation value (region C), the focus motor is stopped (S7), and the focus adjustment operation is completed.

Hereinafter, the operation and effects of the present invention will be described in detail.

First, in order to illustrate the concept of the present invention, when quoting a problem in the automatic focusing of a general camcorder, when the focus motor is moved from the proximal position to the infinity position, the image is first matched to the subject in front of the vertex as shown in FIG. 4. A is generated, and if the focus motor is continuously moved to infinity, vertex B is generated.

When the focus evaluation values corresponding to the vertex A and the vertex B generated in this way are summed, the mountain-shaped focus evaluation values of the third degree are extracted. By stopping, there was a problem that the autofocus control became unstable and malfunctioned.

Therefore, in the present invention, one area (area A) and the surrounding area (area B) are provided, and the autofocus is adjusted using the focus evaluation values of the areas A and B to calculate the focus evaluation value even when the subject is three-dimensional. This is to prevent the focus motor from stopping at the small shape vertex.

That is, when the automatic focus adjustment operation is started, the focus evaluation values of the set area A and area B are received.

Thereafter, the focus motor driving direction is determined according to the focus evaluation values of the input A and B regions, and the focus motor is driven in the focal direction according to the determined result (S2).

Then, the current focus evaluation value for the area A (see FIG. 2) and the past focus evaluation value (area A) are compared (S3).

In this case, the current focus evaluation value is smaller than the previous focus evaluation value, and if the current focus evaluation value is larger than the previous focus evaluation value, the automatic focus control operation is finished, whereas the current focus evaluation value is the past focus value. If it is smaller than the evaluation value, the current focus evaluation value and the past focus evaluation value of the area B (see FIG. 2) installed around the area A to prevent the motor from stopping at the peak where the mountain shape of the focus evaluation value is small. Area B) (S4).

If the current focus evaluation value for the area B is larger than the previous focus evaluation value, the automatic focus control operation is finished. In contrast, if the current focus evaluation value for the area B is smaller than the previous focus evaluation value, the area corresponding to the area A-B area is completed. The focus evaluation value of the C region (see FIG. 2) is calculated (S5).

After that, the present focus evaluation value of the area C is compared with the past focus evaluation value (area C) (S6) and the focus control operation is finished when the current focus evaluation value of the area C is larger than the previous focus evaluation value.

If the current focus evaluation value of the region is smaller than the previous focus evaluation value, the focus motor is stopped (S7) and all focus adjustment operations are completed.

As described in detail above, the present invention provides a new focus evaluation value area around the central focus evaluation value area as a reference area, and the current focus evaluation value and the previous focus value of the central focus evaluation value area and the reference area. By controlling the focus motor in comparison with the evaluation value, there is an effect that the focus motor can be prevented from stopping at a peak where the peak shape of the focus evaluation value is small.

Claims (2)

Determining the focus motor driving direction according to the focus evaluation value values for the first and second areas, and then driving the focus motor in the forward focus direction, and present focus evaluation values for the first and second areas and corresponding past focus points. Comparing the evaluation value with the evaluation value to determine whether the focus motor is driven; and if it is determined that the focus motor is driven, the current focus evaluation value of the third area corresponding to the difference between the first area and the second area is compared with the past focus evaluation value. Comparing the step of stopping the driving of the focus motor and completing the focus adjustment operation when the current focus evaluation value of the third region is smaller than the previous focus evaluation value. The method of claim 1, wherein the determining whether the focus motor is driven comprises: comparing a current focus evaluation value and a past focus evaluation value of the first area, and wherein the current focus evaluation value of the first area is greater than the past focus evaluation value. If it is larger, the focus adjustment operation is completed, and if it is small, the automatic focus control method of the camcorder comprises comparing the current focus evaluation value and the previous focus evaluation value of the second area to determine whether the focus motor is driven. .