Television – Camera – system and detail – Optics
Reexamination Certificate
1997-12-24
2002-01-08
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Optics
C348S240200, C348S347000, C348S229100
Reexamination Certificate
active
06337714
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an auto focusing control technique of a camera, and more particularly to a method for controlling auto focusing of a camera for variably selecting a wobbling width in accordance with the position of a zoom lens and opening of an iris.
2. Description of the Prior Art
A technique for controlling auto focusing of a camera is to detect a subject by using a luminance signal of the subject that is picked up via a camera lens, and driving an optical system to be fitted to the detected subject, thereby automatically adjusting its focus.
FIG. 1
schematically illustrates a circuit construction for controlling auto focusing of a camera.
Here, an optical system
10
includes an objective lens
10
a
, a zoom lens
10
a
, an iris
10
c
and a focusing lens
10
d
, and a photoelectric converting unit, i.e. CCD
20
, converts an image of a subject picked up via optical system
10
into an electric signal. Additionally, an automatic gain controlling (hereinafter simply referred to as “AGC”) circuit
30
carries out automatic gain controlling of a video signal converted by photoelectric converting unit
20
. A digital signal processing section
40
digitizes the AGC-processed video signal and separates it into a luminance signal and a chrominance signal to process the obtained signals, and an evaluation value detecting section
50
detects an evaluation value for the focusing controlling by using the luminance signal separated in digital signal processing section
40
. In addition to these, a controlling section
60
judges whether the subject is detected or not by means of the evaluation value detected in evaluation value detecting section
50
and provides a focusing area control signal and an optical system driving control signal in accordance with the result of the determination, and a focus motor driving section
70
a
receives the lens driving control signal from controlling section
60
to provide a focusing lens driving signal. A focus motor
80
a
drives focusing lens
10
d
in response to the focus motor driving signal, and an iris motor driving section
70
b
receives an iris driving control signal from controlling section
60
to provide an iris motor driving signal. Also included are an iris motor
80
b
for driving iris
10
c
in accordance with the iris motor driving signal, and a zoom motor driving section
70
c
for receiving a zoom driving control signal from controlling section
60
to provide a zoom motor driving signal. Further to these, a zoom motor
80
c
drives zoom lens
10
b
in accordance with the zoom motor driving signal, an exposure detecting section
90
detects the opening of iris
10
c
to supply it into controlling section
60
, and a zoom position detecting section
100
detects the position of zoom lens
10
b
to supply it to controlling section
60
.
The image picked up by optical system
10
is converted into the electric video signal in photoelectric converting unit
20
via objective lens
10
a
, zoom lens
10
b
, iris
10
c
and focusing lens
10
d
. Then, the obtained video signal is automatically gain-controlled by AGC circuit
30
to be supplied into digital signal processing section
40
.
Digital signal processing section
40
converts an input analog video signal into a digital signal, and separates the digital video signal into luminance signal Y and chrominance signal C. Thus, separated chrominance signal C is processed via a chrominance signal processor (not shown), and luminance signal Y is processed via a luminance signal processor (not shown), thereby providing a composite video signal CVS.
At this time, evaluation detecting section
50
receives the processed luminance signal to supply a luminance signal evaluation value of the subject image to controlling section
60
which in turn performs the control, such as auto focusing and auto exposure, based on the evaluation value supplied.
In the conventional auto focusing technique, however, the transferring speed and wobbling width of the focus lens are determined unrelated to a depth of focus.
Here, the depth of focus F
NO
is defined by an equation F
NO
=f/D (where f denotes a focal length by the zoom, and D denotes a diameter of the employed lens in accordance with the iris opening), which has a proportional relation to the iris opening.
That is, the larger the iris opening, the lower the depth of focus. Whereas, the smaller the iris opening, the larger the depth of focus.
But the wobbling width and lens transferring speed were heretofore controlled regardless of the depth of focus in the conventional auto focusing controlling technique.
More specifically, as shown in
FIG. 2
, focus motor
80
a
is controlled via focus motor driving section
70
a
by the wobbling width which is fixed to an optional focus position to drive focusing lens
10
d
, thereby deciding the auto focusing direction. Then, after focusing lens
10
d
is driven to be matched to the decided direction to track until reaching a peak point mode, the focus position is set at a peak point Zo at which the detected luminance signal evaluation value becomes decreased after being increased.
When the focusing operation is performed in the conventional auto focusing controlling technique, the focus lens speed is heretofore determined by the fixed wobbling width unrelated ti the depth of focus to thereby involve distinctive hunting phenomena in case of a low depth of focus.
SUMMARY OF THE INVENTION
The objects of the present invention are to overcome problems and disadvantages of the conventional method for controlling camera autofocusing
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
A first object of the present invention is to provide a method for controlling auto focusing of a camera, wherein an iris opening and a zoom position are detected to select a variable wobbling width in accordance with the result of the detection for preventing the hunting associative with a state of a depth of focus and enabling a quick auto focusing operation.
A second object of the present invention is to provide a method for controlling auto focusing of a camera, wherein an iris opening and a zoom position are detected to select a variable wobbling width in accordance with the result of the detection. An iris is controlled to allow the selected wobbling width to have a preset reference value prior to performing am auto focusing operation, thereby preventing the hunting and enabling a quick auto focusing operation.
A third object of the present invention is to provide a method for controlling auto focusing of a camera, wherein an iris opening is detected to have a preset reference value by controlling an iris. A variable wobbling width is selected in accordance with the result of the detection for performing an auto focusing operation, thereby preventing the hunting and enabling a quick auto focusing operation.
To achieve the first object of the present invention, the first embodiment of the present invention provides a method for controlling auto focusing of a camera, which is performed by detecting an opening of an iris and a zoom position of a zoom lens, and selecting a wobbling width based on the detected iris opening and zoom position. Thereafter, transferring a focus lens based on the selected wobbling width is carried out.
To achieve the second object of the present invention, a second embodiment of the present method detects an opening of an iris and a zoom position of a zoom lens and selects a first wobbling width based on the detected iris opening and zoom position. The selected first wobbling width is compared with a reference value, and the opening of the iris is controlled to a new opening in accordance with a result of the
Lee Seoung-Eog
Park Jin-Soo
Yeo Myung-Keun
Finnegan Henderson Farabow Garrett & Dunner LLP
Garber Wendy R.
L G Electronics Inc.
Tillery Rashann N.
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