JP3725690B2 - Camera shake detection circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a camera shake detection circuit that detects camera shake in a video camera or the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a camera shake detection circuit that is incorporated in an imaging apparatus such as a video camera and detects camera shake of the apparatus is known.
FIG. 2 is a block diagram of a conventional camera shake detection circuit.
The camera shake detection circuit 20 shown in FIG. 2 includes a circuit portion that detects camera shake and corrects the detected camera shake. The image sensor 11 constituting the camera shake detection circuit 20 sequentially generates a plurality of frame images by imaging.
[0003]
The control circuit 22 controls the operation of the image sensor 11 in generating a plurality of frame images.
The signal processing circuit 13 converts the plurality of frame images output from the image sensor 11 into digital image data.
The motion vector detection circuit 14 sequentially detects a motion vector between frame images based on the image data output from the signal processing circuit 13.
[0004]
The memory circuit 15 stores the image data from the signal processing circuit 13.
The output control circuit 26 compares motion vectors detected over a plurality of frames, and detects that the motion vector is moving when the magnitude or direction of the motion vector changes randomly, and according to the motion vector, A cut-out signal indicating which image region in the image represented by the image data stored in the memory circuit 15 is cut out is generated, and image data is read out from the memory circuit 15 using the cut-out signal to correct camera shake.
[0005]
The interpolation circuit 17 interpolates the image data that has undergone camera shake correction and generates an image signal for display on the monitor screen.
The above prior art is to obtain a motion vector and detect and correct camera shake based on the motion vector. The premise is that the motion vector is accurately obtained.
[0006]
By the way, there are various techniques other than the above-described conventional techniques for detecting and correcting camera shake by obtaining a motion vector. For example, Japanese Patent Laid-Open No. 5-22645 discloses that a central motion vector is detected based on central image data that is likely to include subject motion, and is based on peripheral image data that is unlikely to include subject motion. Detects peripheral motion vector, excludes motion of the subject by the central motion vector, and determines whether the camera shake is caused by determining the motion of the whole screen by the peripheral motion vector. The technique of doing is proposed.
[0007]
Further, in Japanese Patent Laid-Open No. 5-75913, it is determined whether or not a motion vector obtained from each region is necessary, and the motion of the entire screen is determined based on the motion vector determined to be necessary. A technique has been proposed in which it is detected whether or not the camera shake is detected, and the camera shake correction is performed when the camera shake is detected.
[0008]
[Problems to be solved by the invention]
However, the technique proposed in the above-mentioned Japanese Patent Laid-Open Nos. 5-22645 and 5-75913 proposes how to distinguish a camera shake from a motion of a subject from a motion vector once obtained. No point has been proposed for accurately obtaining a motion vector as a premise thereof. For example, there is a high possibility that an inaccurate motion vector is required when an object is moving at high speed or when an image is flowing due to extremely large camera shake. If the obtained motion vector is inaccurate, camera shake cannot be accurately detected and corrected by using any algorithm based on the inaccurate motion vector.
[0009]
In view of the above circumstances, an object of the present invention is to provide a camera shake detection circuit that can provide information on whether or not a motion vector is accurate and can accurately detect whether or not a camera shake has occurred.
[0010]
[Means for Solving the Problems]
The camera shake detection circuit of the present invention that achieves the above-described object provides:
(1) Image sensor that sequentially generates a plurality of frame images by imaging (2) Motion vector detection unit that sequentially detects a motion vector between frame images based on the plurality of frame images obtained by the image sensor (3) A control unit for controlling the shutter speed of photographing by the image sensor based on the motion vector detected by the motion vector detection unit. (4) The motion vector detected by the motion vector detection unit and the shutter speed controlled by the control unit. (5) A camera shake detection unit for detecting whether or not there is a camera shake based on the pair over a plurality of frames.
[0011]
The camera shake detection circuit of the present invention controls the shutter speed based on the motion vector, and detects whether the camera shake is based on the pair of the motion vector and the shutter speed. For example, if the subject is moving at high speed or if there is a large amount of camera shake and the image is flowing, the motion vector detected based on the unclear image taken is low in reliability. By obtaining a clear image and obtaining an accurate motion vector based on the clear image, it is possible to accurately detect whether or not there is a camera shake.
[0012]
Here, it is effective to include a camera shake correction unit that performs camera shake correction on the frame image obtained by the imaging device when camera shake is detected by the camera shake detection unit.
When such a camera shake correction unit is provided, camera shake correction is performed based on accurately detected camera shake, and the accuracy of camera shake correction can be increased.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a block diagram of a camera shake detection circuit according to an embodiment of the present invention.
Note that the same components as those of the above-described camera shake detection circuit 20 shown in FIG.
[0014]
Compared with the camera shake detection circuit 20 shown in FIG. 2, the camera shake detection circuit 10 shown in FIG. 1 has a control circuit 22 and an output control circuit 26 replaced with a control circuit 12 and an output control circuit 16 described later, and a memory circuit 18. The point that is added is different.
The control circuit 12 controls the shutter speed of shooting by the image sensor 11 based on the motion vector detected by the motion vector detection circuit 14.
[0015]
The memory circuit 18 stores a pair of the motion vector detected by the motion vector detection circuit 14 and the shutter speed controlled by the control circuit 12.
In addition to the previously obtained pair of the motion vector from the memory circuit 18 and the shutter speed, the output control circuit 16 includes the motion vector from the motion vector detection circuit 14 and the shutter from the control circuit 12 obtained in the past. A pair with speed is entered. The output control circuit 16 has a camera shake detection unit, detects whether or not there is a camera shake as described later, based on a pair of motion vectors and shutter speeds obtained in the past over a plurality of frames, Whether the camera shake is the latest or not is detected based on the pair of the motion vector and the shutter speed. In addition, the output control circuit 16 is configured to display the image data stored in the memory circuit 15 for correcting the camera shake on the frame image obtained by the image sensor 11 when the camera shake is detected by the camera shake detection unit. A cut-out signal indicating which image area of the image to be cut out is generated, and image data is read out from the memory circuit 15 by this cut-out signal to perform camera shake correction. The image data subjected to camera shake correction is interpolated by the interpolation circuit 17 and is generated into an image signal to be displayed on the monitor screen.
[0016]
In the camera shake detection circuit 10 of the present embodiment configured as described above, the shutter speed is controlled in four stages. The detection of whether or not there is a camera shake is performed by executing the steps described below.
1) First, in the first step, shooting is performed at the slowest shutter speed among shutter speeds controlled in four stages. It is determined whether or not the motion vector obtained based on the image captured at the shutter speed exceeds a predetermined threshold value. When it is determined that the predetermined threshold value is not exceeded, the first step is looped. On the other hand, when it is determined that the predetermined threshold value is exceeded, the process proceeds to the second step. The pair of shutter speed and motion vector in the first step is stored in the memory circuit 18.
[0017]
2) In the second step, it is determined whether or not a motion vector obtained based on an image shot at a shutter speed faster than the shutter speed in the first step exceeds a predetermined threshold value. If it is determined that the predetermined threshold value is not exceeded, the shutter speed is decreased and the process returns to the first step. On the other hand, if it is determined that the predetermined threshold value has been exceeded, the process proceeds to the third step. The pair of shutter speed and motion vector in the second step is stored in the memory circuit 18.
[0018]
3) In the third step, it is determined whether or not the motion vector obtained based on the image captured at a shutter speed faster than the shutter speed in the second step exceeds a predetermined threshold value. If it is determined that the predetermined threshold is not exceeded, the process returns to the second step. On the other hand, if it is determined that the predetermined threshold value has been exceeded, the process proceeds to the fourth step. The pair of shutter speed and motion vector in the third step is stored in the memory circuit 18.
[0019]
4) In the fourth step, it is determined whether or not the motion vector obtained based on the image shot at a shutter speed faster than the shutter speed in the third step exceeds a predetermined threshold value. If it is determined that the predetermined threshold is not exceeded, the process returns to the third step. On the other hand, if it is determined that the predetermined threshold value has been exceeded, the fourth step is looped. The pair of shutter speed and motion vector in the fourth step is stored in the memory circuit 18.
[0020]
Thus, based on the pair of shutter speed and motion vector in each step stored in the memory circuit 18, it is determined whether or not there is a camera shake as described below.
First, if the direction of the motion vector corresponding to the fastest shutter speed in the fourth step is random, it is determined that the camera shake is occurring. On the other hand, when the direction of the motion vector is constant, there is a high possibility that the subject and the camera are changing at the same speed, so it is determined that there is no camera shake.
[0021]
Also, if the shutter speed changes randomly throughout each step, it is determined that there is no camera shake because there is a high possibility that the subject is moving or the motion vector is not accurate.
Furthermore, even when the shutter speed is slow, if the direction of the motion vector is random, it is determined that there is a camera shake.
[0022]
In this embodiment, since the shutter speed is used to determine whether or not the motion vector is accurate as described above, camera shake can be detected accurately.
Note that the motion vector that controls the shutter speed may be detected for each area when the image is divided into a plurality of areas, or may be detected for the entire image. It is possible to detect a motion vector with high accuracy.
[0023]
【The invention's effect】
As described above, according to the present invention, an accurate motion vector can be obtained even when the subject is moving at high speed or there is an extremely large camera shake, and whether or not the camera shake is based on this accurate motion vector. Is detected. Therefore, it is possible to accurately detect whether or not there is a camera shake.
[Brief description of the drawings]
FIG. 1 is a block diagram of a camera shake detection circuit according to an embodiment of the present invention.
FIG. 2 is a block diagram of a conventional camera shake detection circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Camera shake detection circuit 11 Image pick-up element 12 Control circuit 13 Signal processing circuit 14 Motion vector detection circuit 15, 18 Memory circuit 16 Output control circuit 17 Interpolation circuit

Claims (2)

An image sensor that sequentially generates a plurality of frame images by imaging;
A motion vector detector that sequentially detects a motion vector between frame images based on a plurality of frame images obtained by the imaging device;
A control unit for controlling the shutter speed of photographing by the image sensor based on the motion vector detected by the motion vector detection unit;
A memory unit for storing a pair of a motion vector detected by the motion vector detection unit and a shutter speed controlled by the control unit;
A camera shake detection circuit comprising: a camera shake detection unit that detects whether or not the camera shake is based on the pair over a plurality of frames. The camera shake detection circuit according to claim 1, further comprising a camera shake correction unit that performs camera shake correction on a frame image obtained by the imaging device when camera shake is detected by the camera shake detection unit.

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