Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
1999-02-05
2001-01-23
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S697000, C359S696000
Reexamination Certificate
active
06178051
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens such as an inner-focus-type lens system, and more particularly to a control method for the position of the lens.
2. Description of Related Art
FIG. 11
shows the arrangement of an inner-focus-type lens system. Referring to
FIG. 11
, the inner-focus-type lens system is composed of a first lens group
1101
which is fixed, a second lens group
1102
for variation of magnification (hereinafter referred to as a variator lens), an iris
1103
, a third lens group
1104
which is fixed, a fourth lens group
1105
which has both a focus adjusting function and a so-called compensation function of compensating for the shift of a focal plane due to the variation of magnification (hereinafter referred to as a focusing lens), and an image pickup surface
1106
. As is well known, in the lens system arranged as shown in
FIG. 11
, since the focusing lens
1105
has both the focus adjusting function and the compensating function, the position of the focusing lens
1105
for focusing on the image pickup surface
1106
varies with object distances even if the focal length remains unchanged.
FIG. 12
is a diagram obtained by serially plotting positions of the focusing lens
1105
for focusing on the image pickup surface
1106
when the object distance is varied for various focal lengths. During zooming, one locus is selected from the loci shown in
FIG. 12
according to the object distance, and if the focusing lens
1105
is moved along the selected locus, a zooming operation without blur can be attained. Accordingly, it is general that information on a plurality of loci shown in
FIG. 12
is beforehand stored in a lens control microcomputer in some form, one locus is selected according to the positions of the focusing lens
1105
and the varaitor lens
1102
, and a zooming operation is performed tracing the selected locus.
However, such a locus tracing method requires the value of each lens position counter to be reset to a predetermined value. In other words, if the value of the lens position counter deviates from a correct value, it becomes impossible to correctly select cam locus information which indicates the relationship between the variator lens position and the focusing lens position stored in the microcomputer, so that a correct cam locus can not be accurately traced during a zooming operation.
Therefore, it is widely practiced that, before an ordinary operation is performed after the power supply is turned on, the variator lens
1102
and the focusing lens
1105
are moved to the respective predetermined reset positions and each of the lens position counters is reset. In this case, the reset positions are generally to be set to the respective mounting positions of photodiodes incorporated in a lens barrel. Then, the lens positions where output signals of the respective photodiodes change are made to be the respective lens reset positions, and the values of the respective lens position counters are set respectively to values decided by balance adjustment of an optical system. Further, during the lens resetting operation, a picked-up image is made not to be outputted because of having large blur, and after completion of the lens resetting operation, a picked-up image is outputted.
In addition, in another proposed method, while a picked-up image is inhibited from being outputted even after completion of the resetting operation of the lens position counters, the lenses are returned to the respective positions where the lens were located before the turning-on of a power supply, so that an angle of view or the like is prevented from being varied due to the lens resetting operation.
Further, it is general in recent years that a pulse motor is used as the motor for driving a lens. In the pulse motor, since a rotation angle relative to a step pulse number is constant, the position of the lens can be detected by incrementing the step pulse number as it is, so that no encoder for position detection is required.
In the above-mentioned example, a lens resetting operation is performed only at a point of time when a power supply is turned on. Therefore, in the case of a surveillance camera or the like operating 24 hours, if an out-of-step phenomenon has occurred due to a change of environment or a disturbance, such as mechanical impact, shut-off of the power supply, electrical noise or radio noise, the power supply must be again turned on (restarting of the power supply) and the lens must be reset.
However, there is a problem in the case of a surveillance camera or the like that if the power supply is made to be turned off, thereby making it impossible to view a picked-up image, the significance of the surveillance camera would be lost.
BRIEF SUMMARY OF THE INVENTION
It is an object of the invention to provide a lens control apparatus capable of always performing a highly accurate lens control irrespective of a change of environment.
Another object of the invention is to provide a lens control apparatus, a lens control method and a storage medium, each of which is capable of always accurately controlling the position of a desired lens without restarting a power supply.
To attain the above objects, in accordance with an aspect of the invention, there is provided a lens control apparatus, which comprises a lens, driving means for driving the lens, position detecting means for detecting that the lens is in a predetermined position, position indicating means for indicating a position of the lens, and rectifying means for rectifying the position indicated by the position indicating means to the predetermined position every time the lens passes the predetermined position.
These and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5276318 (1994-01-01), Hirasawa
patent: 5406069 (1995-04-01), Hirasawa
patent: 5406345 (1995-04-01), Hirasawa
patent: 5424776 (1995-06-01), Hirasawa
patent: 5786853 (1998-07-01), Ohkawara et al.
patent: 5890020 (1999-03-01), Hirasawa
patent: 5956528 (1999-09-01), Tanaka
patent: 6115552 (2000-09-01), Kanedsa
patent: 6118945 (2000-09-01), Tanaka
Canon Kabushiki Kaisha
Epps Georgia
Robin Blecker & Daley
Seyrafi Saeed
LandOfFree
Lens control apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lens control apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lens control apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2459272