Photography – Exposure control circuit – Diaphragm function only
Reexamination Certificate
2001-11-02
2003-04-08
Perkey, W. B. (Department: 2851)
Photography
Exposure control circuit
Diaphragm function only
C396S429000, C396S529000, C348S064000, C348S363000, C348S375000
Reexamination Certificate
active
06546206
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical apparatus and, more particularly, to an optical apparatus including different types of image pickup apparatuses in different image taking forms, an interchangeable lens used for the image pickup apparatuses, and a driving scheme for the aperture stop of this interchangeable lens.
2. Related Background Art
As an image taking apparatus of the lens interchangeable type which consists of a lens detachably attached to a body of the image taking apparatus, a video camera, a single-lens reflex camera using a silver halide film, and the like are available. In an interchangeable lens camera system of this type, an interchangeable lens is comprised of an image taking lens for taking an image, a driving part for driving the image taking lens for zooming and focusing, an aperture stop, a stop driver part, a control part (CPU or the like) for controlling the respective driving parts and communicating information with a camera body, a mount part, and the like.
An interchangeable lens is mounted on a camera body by mechanically coupling the mount part of the interchangeable lens to the mount part of the camera body. Each mount part has electric contacts. When the mount parts are mounted on each other, they are electrically coupled to each other immediately to allow mutual communication of various kinds of information in a predetermined format between the interchangeable lens and the camera body. This makes it possible to perform various control operations for the camera and realize an interchangeable lens type camera system.
For a single-lens reflex camera, an interchangeable lens having unique characteristics based on a format unique to the single-lens reflex camera is prepared. In addition, for a video camera, an interchangeable lens having unique characteristics based on a format unique to the video camera is prepared. For this reason, an interchangeable lens for a single-lens reflex camera cannot be directly mounted on a video camera. Recently, however, an exchange adaptor has been available, which allows an interchangeable lens for a single-lens reflex camera to be used with a video camera by matching the respective mount parts, optical paths, communication formats, and various data.
Of the basic functional differences between the single-lens reflex camera and the video camera, the AE (Automatic Exposure) control schemes will be described below.
According to the AE control scheme in the single-lens reflex camera, the difference between the absolute value information of the current aperture stop and the absolute value information of a target aperture stop is converted on the camera side in accordance with a driving means on the lens side. The converted data is then sent to the lens side. On the lens side, light amount control is performed by driving the aperture stop by the designated amount, thereby performing control to finally achieve the aperture stop (light amount) intended by the user.
The stop driver part of an interchangeable lens for a single-lens reflex camera therefore uses a stepping motor as a driving source, with one step of the stepping motor being made to correspond to a predetermined number of stages of an aperture stop (e.g., 1/8 stage). A step count is received from the camera body at a predetermined timing by mutual communication based on the predetermined format, and the aperture stop is driven at the maximum speed determined by the characteristics of the driver part on the lens side. In the driving scheme for the stepping motor, rectangular wave driving is performed to realize high-speed driving.
According to the AE control scheme for the video camera, the difference value between a reference amount of light and the current amount of light is sent to the lens side, and the aperture stop is then driven on the basis of the difference value on the lens side to perform light amount control, thereby finally matching the actual amount of incident light with the reference amount of light. For example, Japanese Patent No. 2873877 discloses a matching means in this AE control scheme. In the above adaptor, the difference value between the reference amount of light and the current amount of light is received from the video camera side, and the difference value is converted into information of an absolute driving amount and sent to the lens side. With this operation, an interchangeable lens for a single-lens reflex camera can be used for a video camera.
Although no problem arises in terms of mechanical, electrical, and optical coupling between an interchangeable lens for a single-lens reflex camera and a video camera owing to the above adaptor, the following problem is posed due to the operation characteristics of an aperture stop because of the differences in basic function between the single-lens reflex camera and the video camera.
First of all, the single-lens reflex camera and video camera differ in their necessary aperture stop operation characteristics. The basic function of the video camera includes recording sounds as well as taking images. The operation of the aperture stop of the interchangeable lens for the video camera needs to be quiet.
If, however, the conventional interchangeable lens for the single-lens reflex camera is used for the video camera through the above adaptor, since the aperture stop is driven at the maximum speed by rectangular wave driving in the lens, quiet operation cannot be substantially performed. For this reason, sound produced in this operation is also recorded.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its object to provide an optical system including an interchangeable lens which can be effectively applied to a plurality of types of image pickup apparatuses and can always ensure a proper function and an image pickup apparatus on which the interchangeable lens is mounted.
In order to achieve the above object, the present invention comprises:
an actuator for driving an optical function member of an interchangeable lens;
a storage part storing a plurality of driving patterns for the actuator in advance; and
a controller for controlling the actuator to perform driving by using one of the plurality of driving patterns stored in the storage part,
wherein the controller selects one of the plurality of driving patterns from the storage part in accordance with a type of image pickup apparatus on which the interchangeable lens is mounted.
In addition, the present invention comprises:
an actuator for driving an optical function member;
a storage part storing a plurality of driving patterns for the actuator in advance; and
a controller for controlling the actuator to perform driving by using one of the plurality of driving patterns stored in the storage part,
wherein the controller selects one of the plurality of driving patterns from the storage part in accordance with a type of image pickup apparatus on which an interchangeable lens is mounted.
Furthermore, the present invention comprises:
an interchangeable lens having a mount with an electric contact for communication;
an image pickup apparatus having a mount which is detachably coupled to a mount of an interchangeable lens and has an electric contact connected to the electric contact of the interchangeable lens to perform communication;
an actuator for driving an optical function member of the interchangeable lens;
a storage part storing a plurality of driving patterns for the actuator in advance; and
a controller for obtaining predetermined information from the image pickup apparatus by the communication through the electric contacts and controlling the actuator to perform driving by using one of the plurality of driving patterns stored in the storage part,
wherein the controller selects one of the plurality of driving patterns from the storage part in accordance with the predetermined information obtained by the communication.
The above and other objects, features, and advantages of the present invention will be apparent from t
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Perkey W. B.
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