Television – Camera – system and detail – Camera image stabilization
Reexamination Certificate
1997-02-27
2001-01-09
Ho, Tuan V. (Department: 2712)
Television
Camera, system and detail
Camera image stabilization
C348S240200, C348S352000
Reexamination Certificate
active
06172707
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image pickup device, and more particularly to an image pickup device provided with electronic zooming means and electronic image vibration compensating means, adapted for use in a video camera or the like.
2. Related Background Art
In an image pickup device for converting an optical image into an electrical signal, the image vibration or the object movement can be detected by a calculation between the frames of the image signal, and the image vibration can be reduced by means of the detected movement vector. The prevention of image vibration can be achieved by an optical configuration in which the vertical angle of a variable-angle prism is controlled according to the detected image vibration, thereby optically compensating the image vibration, or an electronic configuration in which a partial image compensating the image vibration is extracted from an image stored in an image memory and is released as an output in the normal size. The latter is also known as the electronic zooming function for electronically enlarging the taken image.
FIG. 1
is a block diagram of a video camera provided with a circuit for electronically preventing or compensating the image vibration. An image pickup device
12
converts an optical image, formed by a zoom lens
10
, into an electrical signal, and an A/D converter
14
converts the output of said image pickup device
12
into a digital signal. An image processing circuit
16
is functionally composed of a memory control circuit
20
for controlling an image memory
18
, a movement amount detection circuit
22
for detecting the image movement from the image signal, and an electronic zooming circuit
24
, and serves to reduce the image vibration by means of these circuits.
In the above-explained configuration, the image information entered through the zoom lens
10
and the image pickup device
12
is sampled with a predetermined sampling frequency, then converted into a digital signal by the A/D converter
14
and supplied to the image memory
18
through the image processing circuit
16
. Then amounts x, y of movement in the horizontal and vertical directions are determined by the correlation of said signal with the next field or frame, and a control circuit
4
reads the image information from the image memory
18
, with a reference point displaced according to said amounts of movement.
Referring to
FIG. 2
, an area W indicates the storage area of the image signal in the image memory
18
and is always constant. An area R
0
is the read-out area of the image signal from the image memory
18
when said amounts of movement are zero, while an area R
xy
is the read-out area of the image signal when said amounts of movement are X and Y respectively in the horizontal and vertical directions. The image signal thus read from the image memory is compensated for the vibration and provides a stabler image which is more comfortable to watch.
Within the entire image W stored in the image memory
18
, the image processing circuit
16
, when the image vibration compensating function is activated, reads a central portion R
0
from the image memory
18
and expands said portion to the size W by the electronic zooming circuit
24
, for supply to an interpolation circuit
26
.
When the movement amount detection circuit
22
detects a movement of the image, the area of extraction from the entire area W is moved in a direction compensating said movement, for example to an area R
xy
shown in
FIG. 2
, and the extracted image is expanded to the size of the area W by the electronic zooming circuit
24
and is subjected to interpolation between the lines or between the pixels in the interpolation circuit
26
.
Thus the interpolation circuit
26
replenishes the pixel data which have become deficient by the expansion in the electronic zooming circuit
24
, and a D/A converter
28
converts thus interpolated image data into an analog signal. Thus the output of the D/A converter
28
is a moving image signal with reduced image vibration. A video encoder
30
converts the output of the D/A converter
28
into a predetermined format, for example an NTSC video signal. The output of the D/A converter
28
is also supplied to an electronic view finder (EVF)
32
, for image display. The EVF
32
may also be given the output of the video encoder
30
.
The above-explained configuration is however unable to completely compensate the image vibration when it is large, so that the target object may vibrate significantly within the image frame or may disappear from the image frame and re-appear therein.
Also in the above-explained configuration, since the image signal already subjected to compensation of image vibration is displayed on the monitor, the photographer tends to misunderstand that the vibration caused by his hands is limited and depends on the image vibration compensating function even though he is in a situation capable of suppressing the vibration of the hands. For example in case of image recording with a camcorder, there is recorded an image with vibration which should have been avoided.
Also in the image vibration compensating device explained above, the read-out image is displaced in parallel manner corresponding to the vibration of the image, and the image has to be expanded in order to avoid the lack of image at an end portion, resulting from such image displacement. Stated differently, the image is expanded when the compensation for image vibration is in action.
If said compensation for image vibration is turned on and off, there will result deterioration of the image quality by a sudden change in the image angle, caused by the presence and absence of said image expansion.
SUMMARY OF THE INVENTION
In consideration of the foregoing, a first object of the present invention is to provide an image pickup device provided with electronic zooming and optical zooming functions, capable of eliminating discontinuity in the image angles of said electronic and optical zoomings, thereby enabling a natural zooming operation.
A second object of the present invention is to provide an image pickup device capable of controlling the optical zooming according to the function state of the electronic zooming, thereby achieving smooth switching between the electronic zooming and the optical zooming.
A third object of the present invention is to provide an image pickup device capable of compensating the change in image angle, when the electronic zooming is turned off, by controlling the optical zooming, thereby achieving a satisfactory zooming operation.
The above-mentioned objects can be attained, according to a preferred embodiment of the present invention, by an image pickup device provided with electronic image vibration compensating means, comprising electronic zooming means for electronically varying the image magnification of a designated portion of the taken image, a zoom lens constituting a phototaking lens, zoom detection means for detecting the zooming position of said zoom lens, drive means for zooming said zoom lens, and control means for linked control of said zoom lens and said electronic zooming means so as to maintain the image angle obtained by said zoom lens and said electronic zooming means at a designated value.
Also in another preferred embodiment of the present invention, there is provided an image pickup device provided with a zoom lens serving as a phototaking lens, image pickup means for converting an optical image formed by said zoom lens into an electrical signal and electronic zooming means for electronically varying the magnification of a designated portion of the image taken by said image pickup means, comprising control means for linked control of said zoom lens and said electronic zooming means so as to maintain the image angle, obtained by said zoom lens and said electronic zooming means, at a designated value.
Also in still another preferred embodiment of the present invention, there is provided an image pickup device provided with electronic zooming means f
Fujiwara Akihiro
Morofuji Tsuyoshi
Ouchi Toshimichi
Canon Kabushiki Kaisha
Ho Tuan V.
Robin Blecker & Daley
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