JP3239051B2 - Video camera with image stabilization device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera having a camera shake correction device, and more particularly to a video camera having a camera shake correction device used as, for example, a consumer-use camera-integrated VTR.

[0002]

2. Description of the Related Art As an example of a method for detecting a camera shake component of an image pickup apparatus, a motion vector obtained from a representative point matching method described in Japanese Patent Application Laid-Open No. 61-201381 is used. One that detects a camera shake component is known. That is, a plurality of detection areas are arranged in a screen, and a motion vector is detected for each detection area. The camera shake correction is performed by calculating an entire motion vector (overall motion vector) based on a plurality of partial motion vectors, and moving a part of the image according to the entire motion vector.

[0003]

However, in such a method, if there is a detection area where a partial motion vector not caused by camera shake is detected, such as when an object passes through the screen, the detection area is affected by the detection area. As a result, there is a problem that the camera shake cannot be accurately corrected.

[0004] Therefore, a main object of the present invention is to provide a video camera having a camera shake correction device capable of accurately correcting camera shake.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a video camera having a camera shake correction device for correcting a camera shake based on motion vectors in a plurality of detection areas formed in a screen. And a high-frequency component detecting means for detecting a high-frequency component change amount of the video signal from another area, wherein the camera shake is not corrected when the change amount is equal to or more than a predetermined amount, Is a video camera.

[0006]

The brightness data of the current field and the brightness data of the previous field stored in the storage memory are input to a correlation value calculation circuit, and the brightness data between the two fields is subtracted to obtain a correlation value. Can be This correlation value is input to the average value detection circuit and the correlation accumulation addition memory, and the average value detection circuit outputs the average value of the correlation values to the microcomputer. Subsequently, in the correlation accumulative addition memory, the correlation values are accumulatively added by the number of the representative points, the result is input to the minimum value detection circuit, and the minimum value and the position data of the minimum value are input to the microcomputer. The overall motion vector is calculated based on the average value, the minimum value, and the position data of the minimum value thus obtained, and the camera shake is corrected according to the overall motion vector. At this time, when the value of (average value) / (minimum value) exceeds a predetermined threshold, the detection area may be determined to be valid.

For example, a gate control circuit sets a sampling area different from a detection area for detecting a partial motion vector at the center of the screen, and only a video signal from this sampling area, that is, a luminance signal is input to an integrating circuit. You. In this integrating circuit, the luminance signal is integrated for each field, and the integrated amount of the current field and the integrated amount of the previous field are compared to calculate the amount of change in the high frequency component between the fields. For example, in a microcomputer, when the change amount is equal to or more than a predetermined value, it is determined that there is a subject moving in the screen, and the camera shake correction operation is stopped.

[0008]

According to the present invention, the correction operation is stopped when an object passes through the detection area during the camera shake correction, so that it is possible to prevent the image from being disturbed due to the malfunction of the camera shake correction. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a video camera 10 having a camera shake correction apparatus according to this embodiment includes a solid-state imaging device 12 such as a CCD for converting a light signal from a subject input from a lens 14 into an electric signal. including. This solid-state imaging device 12
The level of the electric signal is adjusted by an AGC circuit (not shown), and a synchronization signal is added by a synchronization signal addition circuit (not shown). An analog video signal output from the solid-state imaging device 12 is converted into a digital video signal by an A / D converter 16 and is also applied to a high-frequency component detection circuit 18 to calculate a change amount of the high-frequency component. . The digitally converted video signal is supplied to the motion detection circuit 20.

Referring to FIG. 2, a motion detection circuit 20
An input terminal 24 for receiving a digital video signal from the / D converter 16 is provided. The video signal input from this terminal 24 is supplied to a representative point storage memory 28 and a correlation value calculation circuit 30 through a filter 26. Filter 26
Is a kind of digital low-pass filter, and the S / N ratio of the video signal is improved by this filter 26. The representative point storage memory 28 extracts, for example, 30 representative points for each of the four detection areas A, B, C, and D shown in FIG. 3, and stores the position data and the luminance data. The correlation value calculation circuit 30 subtracts the luminance data of the representative point one field before given from the representative point storage memory 28 and the luminance data of all the pixels in the current field given from the input terminal 24, and takes the absolute value. . That is,
The luminance difference between the luminance data of the current field and the luminance data of the previous field is obtained.

The calculated luminance difference is supplied to the correlation accumulation memory 32 and the average value detection circuit 34. In the correlation accumulation memory 32, pixels (representative points) at the same position in each detection area within the same detection area are detected. The obtained luminance differences are cumulatively added to output correlation value data. The correlation value data is given to the minimum value position detection circuit 36,
In 6, the minimum correlation value for each of the detection areas A to D and the position data of the pixel indicating the minimum correlation value are calculated. Similarly, in the average value detection circuit 34, each detection area A
The average correlation value for each −D is obtained, and the average correlation value, the minimum correlation value, and the position data thereof are output to the microcomputer 22 (see FIG. 1).

The position data of the minimum correlation value is detected as follows. As shown in FIG. 4, the luminance data A _n at the representative points of the previous field, the same horizontal i from the representative point position in the same detection area, the luminance data B _nij of the current field at the position in the vertical direction j, The luminance difference D _ij is obtained using the following equation.

[0013]

D _ij = Σ | A _n -B _nij | In this manner, the luminance difference D _ij is obtained, and the address (i, j) at which the luminance difference D _ij becomes the minimum is set as the position data of the minimum correlation value. Is calculated. The microcomputer 22 obtains a displacement of the pixel having the minimum correlation value with respect to the representative point based on the position data of the pixel having the minimum correlation value, and uses the displacement as a partial motion vector. Further, the microcomputer 22 detects whether or not a value obtained by dividing the average correlation value by the minimum correlation value is greater than a predetermined threshold value and whether or not the average correlation value is greater than or equal to a predetermined value for each of the detection areas AD. , It is determined whether or not each detection area AD is an effective area. That is, if the value obtained by dividing the average correlation value by the minimum correlation value is larger than a certain threshold value and the average correlation value is equal to or greater than a predetermined value, the detection area is determined to be an effective area.

Then, the microcomputer 22 calculates a motion vector (hereinafter simply referred to as an "entire motion vector") of the entire screen, that is, the image field 38 (see FIG. 3), based on the above-described position data and correlation value data. The data of the entire motion vector is stored in the memory control circuit 4
0, and the memory control circuit 40 determines a read start address and a write start address of the field memory 42. The video signal written in the field memory 42 is read according to the address. Since the read image needs to move in accordance with the entire motion vector calculated by the microcomputer 22, a part of the image is read. The read image is
The image is enlarged by the electronic zoom block 44, enlarged to a normal angle of view, analog-converted by the D / A converter 46, and output as a corrected image.

Referring to FIG. 5, high-frequency component detection circuit 18, which is a feature of this embodiment, includes a sync separation circuit 50, which converts an analog video signal input from input terminal 48 by the sync separation circuit 50. The vertical and horizontal synchronization signals are separated and input to the gate control circuit 52. The gate control circuit 52 supplies a gate opening / closing signal for setting a rectangular sampling area at the center of the screen to the gate circuit 54 based on the vertical synchronization signal, the horizontal synchronization signal, and the fixed oscillation pulse.

The analog video signal input from the input terminal 48 is input to a high-pass filter 56, and only the high-frequency component of the video signal, that is, the luminance component is detected.
8 is output. The video signal (luminance signal) subjected to amplitude detection in the detection circuit 58 is converted into a digital video signal (luminance signal data) in the A / D converter 60 and input to the gate circuit 54. Gate control circuit 52
According to the gate opening / closing signal from the gate circuit 54, only the luminance signal in the range restricted by the predetermined sampling area is input to the integrating circuit 62. In the integrating circuit 62, a luminance signal component in a predetermined range is integrated for each field. That is, the integrating circuit 62 calculates the amount of the high-frequency component of the video signal from the sampling area in the screen, and stores the amount of the high-frequency component in the memory 64. Thus, the high frequency component amount for each field is written in the memory 64.

On the other hand, the high-frequency component amount output from the integrating circuit 62 is directly input to the comparator 66 and
The high-frequency component amount four to one field before is supplied to the comparator 66. Then, the comparator 66 calculates the difference in the amount of the high frequency component between the two fields, that is, the amount of change in the high frequency component. The high-frequency component change amount is input to the microcomputer 22, and the microcomputer 22 determines whether there is a moving object (subject) in the screen according to the high-frequency component change amount.

More specifically, step S in FIG.
In 1, the microcomputer 22 determines that the high-frequency component change amount between the two fields calculated by the high-frequency component detection circuit 18 is
For example, it is determined whether the value is larger than a predetermined value determined by an experiment. If it is larger than the predetermined value, step S3
, The overall motion vector described above is set to “0”.

On the other hand, if the high-frequency component change amount is smaller than the predetermined value, it is determined in step S5 whether or not the partial motion vector detected for each detection area AD is valid. Specifically, as described above, when (average correlation value) / (minimum correlation value)> threshold, the detection area is determined to be valid. Then, in step S7, an overall motion vector is calculated according to the number of detection areas determined to be valid in step S5. Then, the camera shake is corrected using the entire motion vector.

In this embodiment, attention is paid to a high-frequency component of a video signal which greatly changes when there is a subject passing through the screen, and the entire motion vector is set to "0" based on the high-frequency component change amount. In addition, malfunctions due to camera shake correction are prevented. However, when the high frequency component change amount is larger than the predetermined value, the camera shake correction operation itself may be stopped.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of a motion detection circuit according to the embodiment in FIG. 1;

FIG. 3 is an illustrative view showing a principle of electronic zoom and showing a detection area in an image field;

FIG. 4 is an illustrative view showing a minimum correlation value and a method of detecting a pixel position having the minimum correlation value;

FIG. 5 is a block diagram illustrating an example of a high-frequency component detection circuit of the embodiment in FIG. 1;

FIG. 6 is a flowchart showing a part of the operation of the embodiment in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Video camera 18 ... High frequency component detection circuit 20 ... Motion detection circuit 22 ... Microcomputer 38 ... Image field 54 ... Gate circuit 56 ... High pass filter 62 ... Integration circuit 66 ... Comparison circuit

Claims (1)

(57) [Claims] 1. A video camera having a camera shake correction device for correcting camera shake based on motion vectors in a plurality of detection areas formed in a screen, wherein a different area from the detection area is set, and A video camera having a camera shake correction device, comprising: a high-frequency component detection unit configured to detect a high-frequency component change amount of a video signal from an area, wherein the camera shake is not corrected when the change amount is equal to or more than a predetermined value.