Television – Camera – system and detail – Optics
Reexamination Certificate
1997-12-12
2001-01-09
Garber, Wendy (Department: 2712)
Television
Camera, system and detail
Optics
C348S335000, C348S345000, C348S363000
Reexamination Certificate
active
06172709
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a detachable lens block attachable and detachable to and from a camera block including an image pickup device and a video (picture) signal processing circuit, and more particularly to a detachable lens block equipped with at least an autofocus control function and a video camera system based upon the same.
2. Description of the Related Art
In a video camera system having an integral construction of a camera block and a lens block, in general an autofocus control function is provided to automatically accomplish the in-focus condition with respect to a subject. Particularly, in the case of a monitoring type video camera system, this function is available.
Japanese Examined Patent Publication No. 39-5265 discloses one example of video camera systems having such an autofocus control function. Referring to a schematic block diagram of
FIG. 5
, a description will be made hereinbelow of the arrangement of this prior example.
In
FIG. 5
, a subject image coming through an optical lens
45
is incident on an image pickup device
40
to be converted into an electric signal serving as a video signal. This video signal is processed in a signal processing circuit
41
comprising a preamplifier and a process amplifier and then given to a video signal converting circuit
42
where, through processing such as the addition of a synchronizing signal and the synthesis of a color-difference signal, the video signal is converted into a composite video signal meeting the standard mode such as NTSC and PAL.
On the other hand, the video signal outputted from the signal processing circuit
41
is also fed to an AF (autofocus control) circuit
43
. This AF circuit
43
is composed of a differentiating circuit for detecting a rising edge of the video signal and a peak (maximum) point detecting circuit to produce a focus control signal indicative of the degree of the in-focus condition. This focus control signal is forwarded to a lens drive unit
44
which is for the purpose of moving the optical lens
45
in its optical-axis directions in accordance with the focus control signal (in Japanese Examined Patent Publication No. 39-5265, the image pickup device
40
is shifted in the optical-axis directions of the optical lens
45
), and which is made up of a mechanism section such as a motor and gears, a servo amplifier for creating a motor drive signal on the basis of the focus control signal, and others.
In this arrangement, the AF circuit
43
monitors the amplitude of the rising edge of a video signal and outputs, to the lens drive unit
44
, a focus control signal for the movement of the optical lens
45
in the direction that this amplitude increases. When the amplitude of the rising edge of the video signal reaches the peak point due to the movement of the optical lens
45
, a decision is made to the in-focus condition, thus stopping the optical lens
45
.
Furthermore, Japanese Examined Patent Publication No. 7-54969 discloses another example of video camera systems having an autofocus feature, where a focusing lens is oscillated in a narrow range in its optical-axis directions in accordance with a high-frequency reference signal so that the decision on the in-focus condition is made on the basis of the relation in phase between the component (oscillation component) due to the oscillation, included in a video signal outputted from an image pickup device, and the reference signal or a decision is made on the direction of moving an optical lens to assume the in-focus condition.
Accordingly, the aforesaid oscillation component is extracted from the video signal outputted from the image pickup device and processed in a preamplifier. The extracted oscillation signal is detected in synchronism with the aforesaid reference signal to detect the phase relation between the oscillation component and the reference signal, thereby deciding the direction of the movement of the optical lens for the in-focus condition. If the optical lens moves to pass through the in-focus point, the phase of the oscillation component is inverted, which allows the detection of the in-focus condition.
In the recent situation, in addition to the above-mentioned autofocus control function, the prior video camera systems have been equipped with an automatic iris control function which controls the iris in accordance with the fluctuation of brightness in the camera-using place so that a video signal with a constant intensity is always obtainable and further provided with a zoom control function, thereby achieving the easier-to-use of the system and providing higher-quality picture.
Furthermore, preferably the video camera systems has a structure which allows the interchange between optical lenses having different zooming magnifications. Particularly, in the case of an observational type video camera system, it is necessary to use an optical lens having a zooming magnification conforming with the environment (for example, the area of the monitoring space) in the camera-using place.
For meeting this requirement, it is considered that the video camera system is attachably and detachably divided into a block comprising a camera (which will be referred hereinafter to as a camera block) and a block including an optical lens (which will be referred hereinafter to as a lens block).
Referring again to
FIG. 5
, a brief description will be made hereinbelow of the division of this video camera system.
In
FIG. 5
, the camera block is a portion surrounded by a dotted line, including the image pickup device
40
, the signal processing circuit
41
, the video signal converting circuit
42
and the AF circuit
43
, whereas the lens block is the other portion including the optical lens
45
and the lens drive unit
44
. The camera block and the lens block are attachable and detachable, for example, through the use of a screw coupling construction (C mount or CS mount).
However, this division structure causes the following problems, which will be mentioned with reference to FIG.
5
.
First, a large number of connecting lines need to be placed between the camera block and the lens block.
That is, control lines
46
are necessary for sending a focus control signal from the AF circuit
43
to the lens drive unit
44
. As the control lines
46
, required are two lines: a transmission line for sending a control signal to move the optical lens in the infinitely far-end direction and a transmission line for feeding a control signal to shift it in the near-end direction. In addition, when the optical lens
45
reaches the infinitely far end or near end, there is a need to detect this fact and to forward an end detection signal to the AF circuit
43
for stopping the output of the focus control signal. For this reason, it is necessary to place two transmission lines for one of the infinitely far-end detection signal and the near-end detection signal, i.e., four in total (three when one is used in common), to send these end detection signals from the lens block to the AF circuit
43
. Further, one power supply line and one grounding line are necessary for supplying a power voltage from the camera block side to the lens drive unit
44
of the lens block. In consequence, the equipment of the autofocus control function requires at least 7 or 8 connecting lines
46
.
Moreover, if the camera system is additionally equipped with the iris control function and the zoom control function, the connecting lines further increases in number. In this case, although not shown in
FIG. 5
, an iris control circuit for producing an iris control signal is placed on the camera block side while an iris drive unit is located on the lens block side, and therefore, one transmission line becomes necessary for sending this iris control signal. In addition, it is necessary to detect that the iris takes the maximum and minimum open conditions and further to send maximum/minimum iris open detection signals, which stop the output of the iris control signal from the iris control circuit, to an iris control sy
Amano Makoto
Koizumi Mitsuyoshi
Tamura Akira
Yamano Shiro
Garber Wendy
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
White Mitchell
Yamamo Optical, Ltd.
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