JPH11275446A - Camera-shake detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a camera-shake detection circuit that provides information denoting whether or not a motion vector is accurate and senses accurately whether or not a camera-shake takes place. SOLUTION: An image pickup element 11 picks up an image of an object at a shutter speed controlled by a control circuit 12 and generates sequentially a plurality of frame images, the images are stored in a memory circuit 15 via a signal processing circuit 13 and given to a motion vector detection circuit 14, where a motion vector is detected. Then a memory circuit 18 stores the motion vector and the shutter speed in pairs, an output control circuit 16 detects whether or not a camera shake takes place based on the pairs and corrects the camera-shake and an interpolation circuit 17 interpolates the result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera shake detection circuit for detecting a camera shake of a video camera or the like.

[0002]

2. Description of the Related Art Conventionally, a camera shake detection circuit which is incorporated in an image pickup apparatus such as a video camera and detects a camera shake of the apparatus has been 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 for detecting camera shake and correcting 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 includes an image sensor 11
Controls the operation in generating a plurality of frame images. The signal processing circuit 13 converts a plurality of frame images output from the image sensor 11 into digital image data. The motion vector detection circuit 14 sequentially detects motion vectors 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 the motion vectors detected over a plurality of frames, and when the magnitude or direction of the motion vector changes at random, detects that the motion is a camera shake, and according to the motion vector, A cutout signal indicating which image area in the image represented by the image data stored in the memory circuit 15 is to be cut out is generated, and image blur is corrected by reading out image data from the memory circuit 15 with the cutout signal.

[0005] The interpolation circuit 17 generates an image signal to be displayed on a monitor screen by interpolating image data subjected to camera shake correction. The above-mentioned prior art seeks a motion vector and detects and corrects camera shake based on the motion vector. The premise is that the motion vector is accurately obtained.

Incidentally, there are various techniques for detecting and correcting camera shake by obtaining a motion vector, in addition to the above-mentioned conventional techniques. For example, Japanese Patent Application Laid-Open No. Hei 5-22645 discloses a technique in which a central motion vector is detected based on central image data likely to include the motion of a subject, and based on peripheral image data unlikely including motion of the subject. Detect the peripheral motion vector, exclude the motion of the subject by the central motion vector, determine the motion of the entire screen by the peripheral motion vector, detect whether or not the camera shake, and correct the camera shake when it is detected as the camera shake. A technique has been proposed to do so.

Further, Japanese Patent Laid-Open No. 5-75913 discloses that it is determined whether or not a motion vector obtained from each area 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 whether or not camera shake is detected is determined by determination, and camera shake correction is performed when camera shake is detected.

[0008]

However, the technique proposed in the above-mentioned Japanese Patent Application Laid-Open Nos. 5-22645 and 5-75913 describes how the camera shake and the motion of the subject are determined from the motion vector once obtained. This is a proposal for discriminating the motion vector, and there is no proposal for accurately obtaining a motion vector based on the presumption. For example, there is a high possibility that an incorrect motion vector is obtained when the subject is moving at high speed or when an image is flowing due to extremely large camera shake. If the obtained motion vector is incorrect, no camera shake can be accurately detected and corrected after all using any algorithm based on the incorrect motion vector.

The present invention has been made in view of the above circumstances, and has as its object to provide a camera shake detection circuit which can provide information as to whether or not a motion vector is accurate and can accurately detect whether or not a camera shake has occurred.

[0010]

To achieve the above object, the present invention provides a camera shake detection circuit comprising: (1) an image sensor for sequentially generating a plurality of frame images by imaging (2) a plurality of frames obtained by the image sensor; A motion vector detecting section for sequentially detecting a motion vector between frame images based on the image (3) a control section for controlling a shutter speed for photographing by the image sensor based on the motion vector detected by the motion vector detecting section; 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; and (5) a camera shake detection unit for detecting whether or not a camera shake has occurred based on the pair over a plurality of frames. It is characterized by having.

The camera shake detection circuit of the present invention controls a shutter speed based on a motion vector, and detects whether or not there is a camera shake based on a pair of the motion vector and the shutter speed. For example, the motion vector detected based on an unclear image captured when the subject is moving at high speed or when the image is flowing due to large camera shake is unreliable. 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 camera shake occurs.

In this case, it is effective to provide a camera shake correction section for correcting camera shake on a frame image obtained by the image pickup device when camera shake is detected by the camera shake detection section. If such a camera shake correction unit is provided, camera shake correction will be performed based on accurately detected camera shake, and the accuracy of camera shake correction can be increased.

[0013]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram of a camera shake detection circuit according to one embodiment of the present invention. Note that the same components as those of the above-described camera shake detection circuit 20 shown in FIG. 2 are denoted by the same reference numerals, and redundant description will be omitted.

The camera shake detection circuit 10 shown in FIG. 1 is different from the camera shake detection circuit 20 shown in FIG. 2 in that a control circuit 22 and an output control circuit 26 are replaced by a control circuit 12 and an output control circuit 16 which will be described later. The difference is that a memory circuit 18 is added. The control circuit 12 controls a shutter speed for photographing by the image sensor 11 based on the motion vector detected by the motion vector detection circuit 14.

The memory circuit 18 stores the motion vector detected by the motion vector detecting circuit 14 and the control circuit 12.
And stores the shutter speed controlled as a pair. The output control circuit 16 includes, in addition to the pair of the motion vector and the shutter speed obtained from the memory circuit 18 obtained in the past, the currently obtained motion vector from the motion vector detection circuit 14 and the shutter obtained from the control circuit 12. A pair with the speed is input. The output control circuit 16 has a camera shake detection unit, and detects whether or not there is a camera shake as described later based on a pair of a motion vector and a shutter speed obtained in the past over a plurality of frames. Based on the pair of the obtained motion vector and shutter speed, it is also detected whether or not the camera shake is the latest. Further, this output control circuit 16
The image sensor 11 is used when the camera shake is detected by the camera shake detection unit.
To perform image stabilization on the frame image obtained in
A cutout signal indicating which image area in the image represented by the image data stored in the memory circuit 15 is to be cut out is generated, and the image data is read out from the memory circuit 15 by this cutout signal to perform camera shake correction. The image data corrected for camera shake is interpolated by the interpolation circuit 17 to generate an image signal to be displayed on a monitor screen.

In the camera shake detecting circuit 10 according to the present embodiment, the shutter speed is controlled in four steps. The detection of camera shake is performed by executing the steps described below. 1) First, in the first step, it is assumed that shooting is performed at the slowest shutter speed among the shutter speeds controlled in four stages. It is determined whether a motion vector obtained based on an image captured at the shutter speed has exceeded a predetermined threshold. If it is determined that the value does not exceed the predetermined threshold, the first step is looped. On the other hand, when it is determined that the value exceeds the predetermined threshold, the process proceeds to the second step. The pair of the shutter speed and the motion vector in the first step is stored in the memory circuit 18.

2) In the second step, it is determined whether or not a motion vector obtained based on an image photographed at a shutter speed higher than the shutter speed in the first step has exceeded a predetermined threshold value. You. If it is determined that the difference does not exceed the predetermined threshold, the shutter speed is reduced and the process returns to the first step. On the other hand, if it is determined that the threshold value has been exceeded, the process proceeds to the third step. The pair of the shutter speed and the motion vector in the second step is stored in the memory circuit 18.

3) In the third step, it is determined whether or not a motion vector obtained based on an image photographed at a shutter speed higher than the shutter speed in the second step has exceeded a predetermined threshold value. You. If it is determined that the difference does not exceed the predetermined threshold, the process returns to the second step. On the other hand, when it is determined that the value exceeds the predetermined threshold, the process proceeds to the fourth step. The pair of the shutter speed and the motion vector in the third step is stored in the memory circuit 1
8 is stored.

4) In the fourth step, it is determined whether or not a motion vector obtained based on an image photographed at a shutter speed higher than the shutter speed in the third step has exceeded a predetermined threshold value. You. When it is determined that the difference does not exceed the predetermined threshold, the process returns to the third step. On the other hand, if it is determined that the value exceeds the predetermined threshold, the fourth step is looped. The pair of the shutter speed and the motion vector in the fourth step is stored in the memory circuit 18.

Thus, based on the pair of the shutter speed and the motion vector in each step stored in the memory circuit 18, it is determined whether or not the camera shake is performed as described below. First, when the direction of the motion vector corresponding to the fastest shutter speed in the fourth step is random, it is determined that a camera shake has occurred. on the other hand,
If the direction of the motion vector is constant, it is highly likely that the subject and the camera are changing at the same speed, so that it is determined that the camera is not shaken.

If the shutter speed changes randomly over each step, it is highly likely that the subject is moving or the motion vector is not accurate, so it is determined that there is no camera shake. Furthermore, even when the shutter speed is low, if the direction of the motion vector is random, it is determined that the camera shake is occurring.

In this embodiment, since the shutter speed is used to determine whether or not the motion vector is accurate, camera shake can be detected accurately. The motion vector that controls the shutter speed may be detected for each region when the image is divided into a plurality of regions, or may be detected for the entire image. , An accurate motion vector can be detected.

[0023]

As described above, according to the present invention,
Even when the subject is moving at high speed or when there is extremely large camera shake, an accurate motion vector can be obtained, and whether or not camera shake is detected based on the accurate motion vector. Therefore, it is possible to accurately detect whether or not camera shake occurs.

[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 sensor 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)

[Claims] An image sensor that sequentially generates a plurality of frame images by imaging; a 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; A control unit that controls a shutter speed for photographing by the image sensor based on the motion vector detected by the motion vector detection unit; and a control unit that controls 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 memory unit for storing a pair; and a camera shake detection unit for detecting whether or not a camera shake has occurred based on the pair over a plurality of frames. 2. The camera shake detection circuit according to claim 1, further comprising: a camera shake correction unit that performs a camera shake correction on a frame image obtained by the image pickup device when the camera shake detection unit detects the camera shake. .