Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2000-06-07
2001-07-31
Ben, Loha (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S698000, C396S077000, C396S091000, C396S104000, C348S064000, C348S352000, C250S201200
Reexamination Certificate
active
06268967
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a zoom lens used in TV cameras and the like.
2. Related Background Art
There are zoom lenses having the function of limiting a driving range of a zoom portion (which is so called the tracking function). With the zoom lenses developing their wider-angle tendency and higher-magnification tendency through the years, there are circumstances where a person or the like unwanted to take around a subject is present in the field with the zoom portion on the wide-angle side, whereas there are also circumstances where the subject is magnified so as to be too large to be settled in the field with the zoom portion at the telephoto extreme. Under such circumstances, a lens operator always has to finely adjust zoom stop positions on the wide-angle side and on the telephoto side by a zoom demand.
Thus the tracking function becomes useful for limiting the driving range of the zoom portion and permitting such photography of picture that only the subject desired to take is photographed at the wide-angle extreme and that the entire image of the subject is just fitted in the field at the telephoto extreme, without the need for the fine adjustment by the zoom demand.
There are also zoom lenses having the zoom preset function. In the case of news report programs, baseball relay broadcasting, etc., there are such occasions that a specific person is repeatedly taken many times in a specific size. The operator needed to set the zoom at the position for the photography in the specific size by manipulating the zoom demand every such occasion.
When the zoom preset function is used on such occasions, any given zoom position can be stored, and the zoom portion can be set at the stored zoom position by manipulating a switch as necessary, whereby the specific person can be photographed in the specific size.
FIG. 5
shows a control flowchart in a method of controlling the positions of lenses constituting the zoom portion and the focus portion in a zoom lens having the tracking function and the zoom preset function.
In this zoom lens, each of zoom preset data and tracking limit data from the zoom demand is converted into counter-equivalent position data (steps
103
to
106
); the position data after the conversion is compared with values of the counters and arithmetic operations are carried out (steps
107
to
110
); and a motor is driven to control the position of each lens (step
111
).
In the control using the position data of the lenses as described above, however, when the driving range of the zoom portion is limited by the tracking function, the angle of view at the tracking end varies depending upon the lens position of the focus portion, because the angle of view varies with driving of the focus portion.
In use of the zoom preset function, similarly, if the focus position upon storage of the lens position of the zoom portion is different from that upon setting of the zoom position by use of the preset function, the angle of view after the preset operation will be different from that upon the storage.
An object of the present invention is, therefore, to provide a zoom lens capable of keeping the angle of view constant under use of the tracking function and/or the zoom preset function, regardless of the focus driving.
SUMMARY OF THE INVENTION
One aspect of the application is to provide a control apparatus for a zoom lens, which drives and controls a zoom portion and a focus portion in accordance with input of zoom control information and focus control information, the control apparatus comprising an arithmetic circuit which obtains target angle-of-view information by comparison between a permissible angle of view indicating at least one (limit value) of a maximum and a minimum of angles of view and angle-of-view information resulting from conversion from the zoom control information to angle-of-view information by a converting circuit and which obtains zoom command information for achieving the target angle of view, based on the target angle of view and the focus control information.
One aspect of the application is to provide a control apparatus for a zoom lens, which drives and controls a zoom portion and a focus portion in accordance with input of zoom control information and focus control information, the control apparatus comprising an arithmetic circuit which obtains a commanded angle of view by comparison between a permissible angle-of-view range indicating a range of angles of view in which variation is permitted, and angle-of-view information resulting from conversion from the zoom control information to angle-of-view information by a converting circuit, and which obtains zoom command information for achieving the commanded angle of view, based on the commanded angle of view and the focus control information.
One aspect of the application is to provide a control apparatus for a zoom lens, which drives and controls a zoom portion and a focus portion in accordance with input of zoom control information and focus control information, wherein a permissible drive end of the zoom portion for achieving a permissible angle of view is calculated based on the permissible angle of view and the focus control information, and wherein the zoom portion is driven, based on comparison between the permissible drive end and the zoom control information.
One aspect of the application is to provide a zoom control apparatus comprising a manipulation member by which a zoom position is changed, a zoom position information forming circuit which forms zoom position information indicating the zoom position according to manipulation by the manipulation member, a converting circuit which converts the zoom position information to angle-of-view information, a limit information setting circuit which sets limit angle-of-view information, an arithmetic circuit which compares the limit angle-of-view information with the angle-of-view information obtained by the converting circuit and which calculates zoom position information for achieving the limit angle of view, based upon focus information indicating a focus position and upon the limit angle-of-view information, on the occasion of occurrence of such a situation that the angle-of-view information after the conversion exceeds the limit angle of view, and a control circuit which controls a zoom state in accordance with the zoom position information thus calculated.
One aspect of the application is to provide a zoom control apparatus comprising a zoom position information forming circuit which forms zoom position information indicating a target zoom position, a converting circuit which converts the zoom position information to target angle-of-view information, an arithmetic circuit which calculates zoom position information corresponding to the angle-of-view information, based upon focus information indicating a focus position and upon the angle-of-view information, and a control circuit which implements transfer into a zoom state according to the zoom position information thus calculated.
One aspect of the application is to provide a zoom control apparatus comprising a manipulation member by which a zoom position is changed, a zoom position information forming circuit which forms zoom position information indicating the zoom position according to manipulation by the manipulation member, a limit information setting circuit which sets limit angle-of-view information, an arithmetic circuit which calculates a limit position indicating a limit zoom position according to the limit angle of view, based upon the limit angle-of-view information and upon focus position information indicating a focus position, and a control circuit which compares the limit position with the zoom position information formed by the zoom position information forming circuit and which regulates a zoom state in which there occurs such a situation that the zoom position information exceeds the limit position, to the limit position.
The other objects of the present invention will become more apparent by embodiments which will
Ben Loha
Canon Kabushiki Kaisha
Morgan & Finnegan L.L.P.
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