Vibration compensator which corrects for vibration errors based on servocontrol unit errors

An imaging apparatus including an image sensing unit for converting light from an object into a video signal and outputting a video signal, and a vibration compensation unit for compensating picture vibrations of the video signal provided by the image sensing unit. Also included are a driving unit for driving a head relative to a recording medium, and a servocontrol unit for controlling a driving condition associated with the driving unit. A control unit is also included to control an output of the vibration compensation unit. The output is controlled on the basis of an error signal of the servocontrol unit.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a recording and/or reproducing apparatus, 
more particularly, to an imaging apparatus or a video camera system having 
a function of avoiding fluctuations or vibrations of pictures contained in 
video signals. 
2. Description of the Related Art 
In recent years, with video cameras integrated with a VTR coming into 
extensive use, their size and weight have been reduced and higher 
magnifications have been achieved. However, when such a video camera is 
used by being held by an operator's hands, vibrations of the camera may 
occur. Thus, it becomes necessary to compensate such vibrations. For this 
purpose, there have been proposed some techniques such as an inertial 
pendulum mechanism for preventing vibrations with a compensation optical 
system supported movably by a gimbals mechanism in which vibrations of 
pictures due to vibrations of operator's hands are compensated by the 
inertia of the compensation optical system; a vibration preventing system 
with a varying angle prism disposed in front of a front video lens wherein 
the apical angle of the prism is controlled in response to the output of a 
sensor which detects vibrations; and an electronic system for preventing 
vibrations wherein a video signal output from an image sensing device is 
stored in an image memory and picture vibrations are compensated by 
shifting the read-out addresses of the image memory depending on the 
amount of movement of the picture detected based on the information 
associated with the video signal stored in the image memory. 
Of these techniques, the electronic system for preventing vibrations has in 
particular received much attention in recent years because of its 
advantages in that it does not need any special mechanical parts for 
compensating picture vibrations, and in that it is possible to reduce the 
size, weight, and cost due to the fact that the rapid progress of 
semiconductor technology permits a very large scale electronic circuit to 
be contained in a very small package. 
FIG. 1 is a block diagram showing a configuration of a VTR incorporated 
with a video camera in a single device, which has a conventional 
electronic vibration compensation system. 
In this figure, a signal is provided by a camera image sensing device 100 
to a video camera signal processor 110, which performs AGC processing, 
gamma correction, matrix processing, and other required processing on the 
signal provided by the image sensing device 100. The resulting signal is 
output as a television image signal. This television image signal is 
applied to a picture vibration compensation circuit 120, which eliminates 
a picture vibration component included in the video signal. Then, after 
processing by a recording signal processor 130, the video signal is 
recorded on a recording tape via a recording head 140. 
However, in the above-mentioned conventional VTR incorporated with a video 
camera in a single device having a hand-vibration compensation system, 
picture vibration compensation is performed on the video signal provided 
by the camera signal processor 110, and then the video signal is recorded 
with the VTR. In such an arrangement, if accurate detection is not made 
whether picture movement is due to hand-vibrations or due to the 
operator's intentional movement such as panning and tilting, then the 
picture vibration compensation causes the video signal to become 
unnatural. In an electronic picture compensation system of this type in 
which picture vibration is compensated based on an input video signal, 
interpolation is usually performed by means of electronic zooming so as to 
recover the reduction in the angle of view. Due to the principle of this 
system, degradation of resolution of the video signal occurs. Therefore, 
if the picture vibration compensation processing is always in operation, 
then the resolution of the recorded video signal is degraded even in the 
case where hand-vibrations do not occur. 
Furthermore, the area associated with vibration compensation is 
automatically determined by an imaging sensing device, memory, picture 
quality, and the like. Therefore, if the compensation amount for 
vibrations exceeds the limitations, further compensation is impossible and 
thus the picture becomes ugly. 
Furthermore, because the magnitude of motions such as hand vibrations is 
detected from the video signal output from the image sensing device, it is 
essentially difficult to make an accurate decision whether the vibrations 
in the video signal are due to vibrations of the hands or due to movement 
of an object itself. To solve this problem, some known techniques include 
additional electrical or mechanical vibration vector detection means such 
as angular velocity detection means for detecting a vibration vector. In 
this technique, the vibration detection means is directly attached to the 
body of a camera itself, and thus it is possible to decide whether the 
camera itself is vibrating or whether an object is vibrating. However, 
such an arrangement causes an increase in the complexity of the circuits 
and an increase in cost. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to solve the problems described 
above. 
More specifically, it is an object of the present invention to provide an 
imaging apparatus which is capable of preventing picture vibration 
associated with both reproduced video signals and video signals provided 
by an image sensing device and which is capable of providing excellent 
quality of pictures. 
To achieve the objects described above, in one aspect of the present 
invention, an imaging apparatus is provided, comprising image sensing 
means for receiving light from an object, and for providing a video output 
signal; reproducing means for reproducing a video signal recorded on a 
recording medium; selection means for selectively outputting either a 
video signal provided by the image sensing means or a video signal 
provided by the reproducing means; and vibration compensation means for 
compensating picture vibrations of a video signal selected by the 
selection means. 
According to another aspect of the present invention, an imaging apparatus 
is provided comprising image sensing means for converting light from an 
object into a video signal, and for outputting the video signal. Vibration 
compensation means are provided for compensating picture vibrations of the 
video signal provided by said image sensing means. Driving means are also 
provided for driving a head relative to a recording medium. Servocontrol 
means are provided for controlling a driving condition associated with 
said driving means, and control means are also provided for controlling 
said vibration compensation means, based on an error signal of said 
servocontrol means. 
According to a further aspect of the present invention, an imaging 
apparatus is provided comprising image sensing means for converting light 
from an object into a video signal, and for outputting the video signal. 
Vibration compensation means are provided for compensating picture 
vibrations of the video signal provided by said image sensing means. In 
addition, there are provided driving means for driving a head relative to 
a recording medium, said driving means including motor means for moving 
the head. Moreover, there are included servocontrol means for controlling 
a driving condition associated with said driving means. The servocontrol 
means comprises phase comparison means for comparing the phase of pulses 
corresponding to a state of the head with the phase of a reference signal 
having a predetermined frequency so as to output a phase error signal. In 
addition, there are included control means for controlling said vibration 
compensation means, based on the phase error signal detected by said phase 
comparison means. 
According to still another aspect of the present invention, an imaging 
apparatus is provided comprising image sensing means for converting light 
from an object into a video signal, and for outputting the video signal. 
Vibration compensation means are provided for compensating picture 
vibrations of the video signal provided by said image sensing means. The 
vibration compensation means comprises motion vector detection means for 
detecting a motion vector associated with the video signal provided by 
said image sensing means. The vibration compensation means further 
comprises representative vector production means for producing a 
representative vector based on the motion vector detected by said motion 
vector detection means. In addition, there are provided driving means for 
driving a head relative to a recording medium, and servocontrol means for 
controlling a driving condition associated with said driving means. 
Control means are included for controlling said vibration compensation 
means, based on an error signal provided by said servocontrol means. The 
control means comprises setting means for setting the motion vector 
detected by said motion vector detection means to a predetermined value. 
According to yet another aspect of the present invention, an imaging 
apparatus is provided comprising image sensing means for converting light 
from an object into a video signal, and for outputting the video signal. 
There are also provided recording and reproducing means for recording and 
reproducing a video signal on/from a recording medium, said recording and 
reproducing means comprising a head. Driving means are included for 
driving said head relative to the recording medium, and servocontrol means 
are also provided for controlling a driving condition associated with said 
driving means. In addition, there are included selection means for 
selectively outputting either the video signal provided by said image 
sensing means or the video signal provided by said reproducing means. 
Vibration compensation means are also provided for compensating picture 
vibrations of the video signal, and control means are included for 
controlling said vibration compensation means, based on an error signal 
provided by said servocontrol means. The control means comprises vibration 
detection means for detecting picture vibration of the video signal, based 
on the error signal provided by said servocontrol means. 
Additional objects and features of the invention will be more readily 
apparent from the following detailed description of various aspects of the 
invention in conjunction with the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Embodiments of the present invention will now be described below with 
reference to the accompanying drawings. 
FIG. 2 is a block diagram showing the configuration of a VTR incorporated 
with a video camera in a single device in accordance with a first 
embodiment of the present invention. 
As seen in FIG. 2, light associated with an object passing through a lens 
(not shown) is converted to an electrical signal by an image sensing 
device 1 such as a CCD, and the obtained electrical signal is provided to 
a camera signal processor 2, where a video signal is produced based on 
this signal from the image sensing device 1. 
Reference numeral 3 denotes a reproduction head for reading out signals 
recorded on a tape in playback operation. The reproduction signal from the 
reproduction head 3 is provided to a VTR signal processor 4, where a video 
signal is produced based on this reproduction signal. The video signals 
from the camera signal processor 2 and from the VTR signal processor 4 are 
each provided to a switch 5 which selects either of these signals to 
provide it to a picture vibration compensation circuit 6. 
The video signal is compensated for picture vibrations as will be described 
later by the picture vibration compensation circuit 6, and then it is 
converted by a recording signal processor 7 into a signal in a form 
suitable for recording and displaying. This converted signal is recorded 
via a head 8 on a tape and is also output to external devices through an 
output terminal 10. A switch 9 is provided for on/off control of the 
picture vibration compensation circuit 6. An operator may set the switch 5 
so that output signals from the camera signal processor 2 are selected 
when he or she desires to record video signals from the image sensing 
device 1; while when he or she desires to watch pictures associated with 
reproduction signals from the reproduction head 3 displayed on external 
display means, he or she may set the switch 5 so that output signals from 
the VTR signal processor 4 are selected. 
Now, the control of the picture vibration compensation circuit 6 by means 
of the switch 9 will be described below. 
As described above, when an operator desires to record video signals 
obtained from the image sensing device 1, the switch 5 is set so that the 
output of the camera signal processor 2 is selected. In this situation, 
when a picture is taken by a video camera, the hand vibration component 
included in the video signal is compensated by the picture vibration 
compensation circuit 6 and thus a picture with no vibrations can be 
recorded on a tape. On the other hand, when he or she desires to watch 
pictures associated with reproduction signals from the reproduction head 3 
displayed on external display means (not shown), the switch 5 is set so 
that the output of the VTR signal processor 4 is selected. When this 
reproduction signal is selected, the operator may either switch on or 
switch off the switch 9 to perform desired control on the picture 
vibration compensation circuit 6. If he or she judges that effective 
compensation for picture vibration can be obtained, then the switch 9 is 
switched on so as to compensate picture vibrations included in the 
reproduction signal and so as to reproduce a picture with no vibrations. 
Referring to FIG. 3, the picture vibration compensation circuit 6 of the 
present embodiment will be described below in more detail. 
FIG. 3 is a block diagram showing a configuration of the picture vibration 
compensation circuit 6 shown in FIG. 2. 
In FIG. 3, a sync separator 122 separates a sync signal from an input video 
signal, and a clock generator 123 generates a clock signal based on this 
sync signal. Based on the sync signal and the clock signal, a write 
control circuit 125 produces an address signal used to write an input 
signal in a field memory 124. An A/D converter 121 converts the input 
signal into digital signals which are successively recorded in the field 
memory 124 designated by the writing address signals described above. The 
digital video signal from the A/D converter 121 is also input to field 
delay circuit 131. The field delay circuit 131 then gives one field delay 
to the input digital signal and outputs said digital signal to motion 
vector detector 127. 
The operation of reading out is carried out as follows: a motion vector 
between the input video signal and a one-field preceding video signal 
delayed by the field delay circuit is detected based on these video 
signals by a motion vector detector 127. Read-out addresses associated 
with the field memory 124 are controlled by the read-out control circuit 
126 so that the motion vector is minimized. In this way, picture 
vibrations can be compensated by means of control such that the motion 
vector may be minimized. Because the angle of view associated with the 
video signal read out from the field memory 124 is slightly reduced after 
the picture vibrations have been compensated, an electronic zooming 
processor 128 performs interpolation on each pixel associated with the 
video signal so that the angle of view may come to have a original value. 
Then, the video signal is output after it is converted into an analog 
signal by a D/A converter 129. 
In this embodiment, the clock signal applied to the read-out control 
circuit 126 of the picture vibration compensation circuit 6 may be a 
reference clock signal with no jitters generated by a crystal-controlled 
oscillator or the like so that the picture vibration compensation circuit 
6 may also be used as a TBC (time base corrector) so as to eliminate 
jitters included in reproduction video signals, in addition to its 
operation for picture vibration compensation in reproduction processing of 
the VTR. 
Referring to FIGS. 4 and 5, a second embodiment of the present invention 
will be described below. 
FIG. 4 and 5 are a block diagram schematically showing a configuration of a 
VTR incorporated with a video camera in a single device in accordance with 
the second embodiment of the invention. 
In FIG. 4, there is shown an optical lens system 11 for focusing incident 
light on to an image sensing device 12 comprising a 2-dimensional CCD 
which converts the light applied from the optical lens system 11 into 
electrical signals. There is also provided a camera signal processor 13 
which produces video signals from the electrical signals provided by the 
image sensing device 12. The output of the camera signal processor 13 is 
coupled to an image memory 14 capable of recording one field of video 
signal; a write control circuit 15 which controls writing operation of the 
image memory 14; and a motion vector detector 16 which detects a motion 
vector by comparing two video signals which are adjacent to each other in 
time sequence. There is also provided a compensation vector generator 17 
which produces a compensation vector by an operation using the motion 
vectors associated with the previous several fields of video signals which 
were detected by the motion vector detector 16. The output of the 
compensation vector generator 17 is connected to a read-out control 
circuit 18 which controls the read-out location of the image memory 14. 
An electronic zooming circuit 19 which electrically enlarges video signals 
is connected to the output of the image memory 14. The electronic zooming 
circuit 19 is supplied with output signals from an compensation area 
setting circuit 20 which provides signals used to set the areas in which 
picture vibrations are to be compensated. The output of the compensation 
area setting circuit 20 is also supplied to the compensation vector 
generator 17 and to a threshold generator 27 which will be described 
later. 
In FIG. 5, there is shown a rotating cylinder 21 of a VTR section. There is 
also provided a PG pulse generator 22 which generates PG pulses 
synchronized with the speed of rotation of the rotating cylinder 21. The 
output of the PG pulse generator 22 is connected to a phase comparator 23 
which outputs a signal representing the rotation error of the rotating 
cylinder 21 (hereinafter referred to simply as an error signal) by 
comparing the PG pulses with a reference signal with a predetermined 
frequency. Furthermore, there is provided a motor driving circuit 24 which 
controls the speed of rotation of a motor 21A coupled to the rotating 
cylinder 21, based on the error signal provided by the phase comparator 
23. Thus, the rotating cylinder 21, the PG pulse generator 22, the phase 
comparator 23, and the motor driving circuit 24 form a servo loop 40. The 
speed of rotation of the rotating cylinder 21 with recording and 
reproducing heads is maintained at a constant value by the servo loop 40. 
There are also provided an integrator 25 which integrates the error signals 
provided by the phase comparator 23; a comparator 26 which compares the 
output signal of the integrator 25 with the threshold produced by the 
threshold generator 27; and an encoder 28 which provides the magnification 
associated with the optical lens system 11, wherein the threshold value of 
the threshold generator 27 is produced based on both the encoded signal 
provided by the encoder 28 and the compensation area setting signal 
provided by the compensation area setting circuit 20. Furthermore, there 
is also provided an EVF driving circuit 29 which displays the output of 
the comparator 26 on an EVF 30. 
Now, operation of the system will be described below. 
After passing through the optical lens system 11, light from an object is 
focused onto the image sensing device 12, where the light is converted 
into electrical signals. The output signal of the image sensing device 12 
is provided to the camera signal processor 13 which performs AGC 
processing, gamma correction, separation of luminance signals and 
color-difference signals, and other required processing on the signal 
provided by the image sensing device 12. The resulting signal is output as 
a television image signal. This television image signal is stored in the 
image memory 14 comprising a field memory under the control of a control 
signal provided by the write control circuit 15, and the television image 
signal is also applied to the motion vector detector 16. The motion vector 
detector 16 detects a motion vector associated with the video signal of 
the current field by comparing the video signal of the current field with 
that of one-field previous. 
The motion vector output from the motion vector detector 16 is input into 
the compensation vector generator 17 which produces a compensation vector 
that moves the displayed picture in the opposite direction to that of the 
result of an operation using motion vectors associated with the latest 
several fields. Based on the output of the compensation vector generator 
17, the read-out control circuit 18 eliminates the picture vibrations by 
modifying the starting address of reading out the video signals stored in 
the image memory 14. 
After the vibration component is eliminated, the video signal is enlarged 
by a magnification value set in the electronic zooming circuit 19. In this 
operation, the magnification value is provided by the compensation area 
setting circuit 20 wherein the magnification value is generally set in 
proportion to the compensation area. When the compensation area is large, 
the magnification is set to a large value, and when the compensation area 
is small, the magnification is set to a small value so that degradation in 
picture quality may be minimized. 
Referring again to FIG. 5, the rotation of the rotating cylinder 21 in the 
VTR section for recording video signals is controlled in such a manner 
that comparison is made between the reference signal and the output signal 
of the PG pulse generator 22 which generates PG pulses synchronized with 
the speed of rotation of the rotating cylinder 21. An error signal is 
produced corresponding to the phase difference between these two signals, 
and the error signal is applied to the motor driving circuit 24, whereby a 
closed circuit is formed by these circuits. This permits the speed of 
rotation of the rotating cylinder 21 to be maintained always at a value 
corresponding to the reference signal. 
When the VTR incorporated with a video camera in a single device is fixed 
onto a tripod or the like, the fluctuation in the rotational speed of the 
rotating cylinder 21 is rather small because of the large inertial force 
of the rotating cylinder 21 itself. However, when the body of the VTR is 
vibrated, the rotating cylinder 21 receives force which disturbs its 
rotation. The error signal provided by the servo loop 40 is constant as 
long as the rotating cylinder 21 rotates at a constant speed in a stable 
situation. When external vibration is added to the stable rotation of the 
rotating cylinder 21, the error signal will change depending on the 
applied vibration. The integrator 25 integrates the error signals for a 
predetermined time period (for one field, for example), and the obtained 
summation is used to evaluate the vibration. 
The output of the encoder 28 representing the zooming magnification of the 
optical lens system 11 and the output signal of the compensation area 
setting circuit 20 are applied to the threshold generator 27. The 
threshold generator 27 modifies the threshold value in response to the 
magnification and the compensation area. That is, when the optical lens 
system 11 is in a wide angle mode, the threshold is set to a high value, 
and when the optical lens system 11 is in a telescope mode, the threshold 
is set to a low value. Furthermore, when the picture vibration 
compensation area is set to a large area, the threshold is set to a high 
value and vice versa. 
When the signal obtained by integrating the error signals is larger than 
the threshold value described above, the comparator 26 concludes that the 
vibration of the VTR itself is so large that there is a high possibility 
that a picture may vibrate beyond the picture vibration compensation area, 
and the comparator 26 indicates a warning sign superimposed on a picture 
on the EVF 30. 
As described above, in the present embodiment, if large vibrations occur 
which may exceed the (picture vibration compensation area, the vibrations 
are detected and a warning sign is indicated on an EVF or the like so as 
to give warning to an operator. Thus, it becomes possible to avoid taking 
a video picture including a large amount of vibrations. 
Referring to FIGS. 6 and 7, a third embodiment in accordance with the 
present invention will be described below. In these figures, elements 
having similar functions to those in the previous figures are denoted by 
the same corresponding reference numerals as those in the previous figures 
and detailed descriptions will not be repeated again. 
In FIG. 6, a compensation vector produced by a compensation vector 
generator 17 is applied to a switch 31. The other input terminal of the 
switch is supplied with a zero compensation vector, i.e., a signal 
indicating that there is no need for compensation. This switch 31 is 
switched based on the output of a comparator shown in FIG. 7. 
In FIG. 7, as in the case of the previous embodiment, an error signal is 
provided by an integrator 25 to the comparator 26. The comparator 26 
compares the integrated value of the error signals with a predetermined 
threshold value. If the integrated value of the error signals is larger 
than the threshold value, then it is concluded that the camera system 
itself is vibrating. In that case, the comparator 26 outputs a signal 
indicating that the switch 31 should be switched to select the output of 
the compensation vector generator 17 so that the operation of picture 
vibration compensation may be performed. On the other hand, if the 
integrated value of the error signals is smaller than the threshold value, 
then it is concluded that the camera system itself is not vibrating, and 
the comparator 26 outputs a signal indicating that the switch 31 should be 
switched to select the zero compensation vector. In that case, no 
operation occurs associated with picture vibration compensation. 
As described above, with a system in accordance with present embodiment, it 
is possible to make an easy decision without using an acceleration 
detector whether the change of a picture represents the change of the 
picture itself or whether it is due to the vibrations of the camera system 
itself, although a conventional electric circuit for picture vibration 
compensation of the type which detects a motion vector from the video 
signal does not have such good capability. As a result, it is possible to 
obtain an excellent quality of pictures without performing undesired and 
unnecessary picture vibration compensation. 
In the embodiment described above, depending on the output signal of the 
comparator 26, the output of the compensation vector is switched to obtain 
optimized control of the picture vibration compensation. However, the 
method of control is not limited to this. An alternative method may be 
that instead of the switch 31 shown in FIG. 6, a switch 31A may be 
provided between the motion vector detector 16 and the compensation vector 
generator 17 as shown in FIG. 8 so that when it is concluded that the 
camera system itself is not vibrating, the output of the comparator 26 may 
cause the switch 31A to be switched to impose the zero motion vector on 
the output of the motion vector detector 16. In this case, because the 
compensation vector generator 17 generates a compensation vector based on 
a value which is the result of an operation using motion vectors from the 
latest several fields, as described previously, the vibration compensation 
is not stopped suddenly when the error signal becomes less than the 
threshold value. Therefore, more natural pictures can be obtained. 
Referring to FIGS. 9 and 10, a fourth embodiment in accordance with the 
present invention will be described below. Elements having similar 
functions to those in the previous figures are again denoted by the same 
reference numerals as those in the previous figures. 
As in the case of the second embodiment described earlier, an encoder 28 
outputs a signal indicating a zooming magnification of an optical lens 
system 11. This signal indicating the magnification is input into a 
threshold generator 27 shown in FIG. 10. The threshold generator 27 
modifies a threshold value in response to the magnification and provides 
the threshold value to a comparator 26. When the magnification of the 
optical lens system 11 is in a wide angle mode, it can be understood that 
vibrations of the camera system do not cause significantly large 
vibrations of pictures, and thus the threshold is set to a high value. 
When the magnification of the optical lens system 11 is in a telescope 
mode, rather slight vibrations result in considerably large vibrations of 
pictures. Therefore, in this case, the threshold is set to a small value. 
As in the case of the previous embodiment, the comparator 26 compares the 
integrated value of error signals provided by an integrator 25 with the 
threshold value produced by the threshold generator 27 in such a way 
described above so as to output a signal indicating the switching of 
switch 31. In this embodiment, a motion vector associated with a picture 
is detected from a video signal, and this motion vector is used to control 
the reading-out location of the image memory which stores video signals so 
that the picture vibrations may be compensated. Similar control may also 
be achieved in the case where a varying angle prism is used. 
In this embodiment, as described above, the threshold value applied to the 
comparator 26 is modified depending on the magnification of the optical 
lens system 11 so as to make a more accurate decision as to whether the 
compensation for vibrations should be performed. 
Furthermore, in this embodiment, the control of the compensation operation 
for picture vibrations is performed based on the output of the comparator 
26. However, the method of control is not limited to this. As in the case 
of the third embodiment, instead of using the switch 31, a switch 31A may 
be provided between the motion vector detector 16 and the compensation 
vector generator 17 as shown in FIG. 11 so that based on the output of the 
comparator 26, the switch 31A may be switched to control the output of the 
motion vector to achieve optimum control of the picture vibration 
compensation. 
Except as otherwise disclosed herein, the various components shown in 
outline or in block form in the figures are individually well-known in 
their internal construction and operation and are not critical either to 
the making or using of this invention or to a description of the best mode 
of the invention. 
While the present invention has been described with respect to what is 
presently considered to be the preferred embodiments, it is to be 
understood that the invention is not limited to the disclosed embodiments. 
To the contrary, the invention is intended to cover various modifications 
and equivalent arrangements included within the spirit and scope of the 
appended claims. The scope of the following claims is to be accorded the 
broadest interpretation so as to encompass all such modifications and 
equivalent structures and functions.