Photography – Exposure control circuit – Diaphragm function only
Reexamination Certificate
2001-08-21
2003-10-28
Adams, Russell (Department: 2851)
Photography
Exposure control circuit
Diaphragm function only
C396S508000
Reexamination Certificate
active
06640056
ABSTRACT:
This application is based upon application No. 2000-252347 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device having a unit, which can be attached to or removed from a body of the device, such as a camera having an interchangeable lens, and relates to a method for controlling the unit from the body of the device. More specifically, the present invention relates to an equipment in the device for driving a driven member in the unit by means of a driving source provided in the body, and relates to the method for controlling the driven member from the equipment.
2. Description of the Related Arts
Conventionally, there have been proposed some camera systems, in which an aperture in a lens is driven by a camera.
For example, as for a camera provided with a motor, Japanese Non-examined Patent Publication No. 58-224336 discloses a technique that realizes non-provision of the urging means for resetting an aperture device in a lens, by making use of charging operation which makes the aperture device execute its resetting operation. It is disclosed therein that the aperture device is driven by a motor in a camera and stopped by a magnetic mechanism, and that a ring for driving the aperture device is urged in one direction in a connecting part between the camera body and the lens.
In U.S. Pat. No. 4,681,417, it discloses a technique that a small and low power motor only for actuating an aperture device in an interchangeable lens is equipped in a camera body. It is disclosed therein that a linear driving lever in the camera body and an aperture driving lever in the lens are provided for connecting parts between the body and the lens, and that its stopping position of the aperture device is detected by the lens.
In Japanese Non-examined Patent Publication No. 8-95145, it discloses a technique of lens changeable camera disposed at predetermined positions in a lens mount portion, in which an aperture driving mechanism and a focus driving mechanism are connected with two pairs of couplers, each having a key at a tip thereof. Engagement in a connecting portion is realized by at least one revolution (or rotation) of the couplers, and it is not necessary to align a mechanism of an interchangeable lens. Thus, the technique is suitable for an aperture driving system without urging springs, but retreating mechanism and the like are needed in order to disengage it from the connecting portion.
As for a driving mechanism driven and stopped by a motor, an overrun is necessarily occurred from a point of starting brake to a point of stopping. Main reasons of the overrun are stopping characteristics of the motor or a driving source, construction of the driving mechanism such as gear ratio and transfer property, load or inertia of driven members and so on.
As for control, the technique that driving operation started a little earlier (or ahead of time) in consideration of the delay of control system, is known.
For example, in U.S. Pat. No. 4,396,271, it is disclosed that calculating of moving distance of a movable aperture member, and starting to stop an aperture device when the aperture member arrives at calculated distance short of an object position (or target position) corresponding to aperture value, allow for precise aperture control.
In U.S. Pat. No. 4,538,893, a driving mechanism for changing the size of an aperture, driven through an aperture associated member by a motor, is disclosed. In the driving system, the displacement amount of the aperture associated member is detected; a position signal and a rate signal are produced; and the aperture associated member is controlled to stop at an object position, by means of correcting the position signal responding to the rate signal.
As for common methods for predicting overrun of a motor by velocity detected before braking, it is disclosed, for example, in U.S. Pat. No. 5,543,878, that a film feeding apparatus, comprising a decelerating controller for decelerating film feeding velocity, a reverse drive brake for stopping to feed a film by reversing the motor, a velocity detector for detecting the film feeding velocity, and a brake controller for controlling the decelerating controller and the reverse drive brake. In this apparatus, the fluctuation in the rate of reducing the speed, namely deceleration, depending on some conditions, causes errors.
In U.S. Pat. No. 4,745,425, it is disclosed that a lens barrel having a optical system adjusting to focus automatically responding to a signal detected by a focus detect means, is provided with a storing means for storing information about load torque in the optical system, such as data about load and inertia, in order to change the condition of adjusting the optical system during automatic focusing. In the lens barrel, it is difficult to employ a lens having no data, and to correspond to every lens with individual difference, including change in characteristics accompanying aging.
In Japanese Non-examined Patent Publication No. 7-181573, a method for controlling a motor in a camera is disclosed. According to this method, the motor is controlled responding to a signal, corresponding to a revolution of the motor, output by an encoder, and a film is stopped at an object position, by means of adjusting the velocity of the motor so as to follow a brake line indicating a function of operation start point, which is predetermined, and the velocity of the motor. This stopping control tasks a controller, and therefor the controller, is too busy to perform the other controlling operation at one time.
In an inexpensive camera system using an interchangeable lens provided with no motor, a motor built in a camera body drives an aperture device in the lens, and a long link mechanism from the motor to a driven member of the aperture device is needed. In that system, a spring for urging an aperture control member is needed in order to prevent play in the long link mechanism and stabilize stopping characteristics thereof. The spring can be provided in the camera body or in the interchangeable lens. In case that the spring is not provided in the interchangeable lens, connecting members, provided in the interchangeable lens, for connecting between the camera body and the interchangeable lens are unsteady, and therefor an engaging member provided in the camera body needs to dodge connecting members when attaching the lens to the camera body. On the contrary, in case that the spring is provided in the interchangeable lens, one-way urging mechanism can be provided in the camera body, and connecting mechanism between the camera body and the interchangeable lens can be simplified.
In case that a DC motor in a camera body drives a mechanism including spring urging mechanism in a interchangeable lens, it is possible to drive it in both directions by means of supplying the DC motor with electricity, but it is difficult to keep it stopping against urging of the spring without supplying the DC motor therewith. Specifically, the DC motor has a small static force, consisting of magnetic cocking and frictional force, and therefore, a reduction ratio of a transfer mechanism must be large enough to keep stopping against the spring force only by means of the static force.
In case that the DC motor having a small inertia is used in order to shorten aperture drive time, cocking torque diminishes and therefor, the reduction ratio needs to be enlarged much more.
In case that a stepping motor is provided in a camera body, it is possible to keep stopping against spring force by means of continuing to supply the same magnetic poles of the motor with electricity, but the reduction ratio needs also to be enlarged because the torque produced by the stepping motor is usually small.
High reduction ratio enough to keep stopping against the spring force only by means of stopping the motor causes a problem of prolonging stop down operation time, because revolutions of a output axis of the motor for stopping down in a set amount increases. St
Ito Atsutaka
Konishi Yoshito
Adams Russell
McDermott & Will & Emery
Minolta Co. , Ltd.
Smith Arthur A
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