Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Reexamination Certificate
2000-01-24
2003-05-27
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
C396S072000
Reexamination Certificate
active
06570142
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens position control device and an optical apparatus having a full-time manual operating function whereby a lens can be moved in the direction of an optical axis through a mechanical cam or the like interlocked with a ring operation member and a focus preset function whereby the lens can be instantly driven and moved to a preset position.
2. Description of Related Art
It is known that some optical apparatuses have a focus preset (hereinafter abbreviated FP) function. For the FP function, an FP storing switch and an FP driving switch are provided on an interchangeable lens. With the FP storing switch operated at a desired focusing lens position beforehand, a focusing lens can be instantly moved to the desired position with a motor by just operating the FP driving switch, even after the focusing lens is driven with the motor by an automatic focusing (AF) action or by a manual focusing (MF) action performed according to the result of focus detection on the basis of an output of an AF sensor or according to the amount of operation on a manual operation ring. This FP function enables the user of the optical apparatus such as a camera, to carry out a photo-taking operation without delay in a case where shooting operation must be instantly be carried out.
Known optical apparatuses of the kind having the FP function include some of automatic focusing single-lens reflex cameras. The automatic focusing single-lens reflex cameras having the FP function must be arranged to electrically operate focusing lenses with motors.
FIG. 12
is a block diagram showing by way of example an interchangeable lens to be used by an automatic focusing single-lens reflex camera of the kind having the FP function. In
FIG. 12
, full lines indicate electrical connection and broken lines indicate mechanical connection.
Referring to
FIG. 12
, a lens microcomputer
102
is arranged at a lens body
101
to control various devices within the lens body
101
and to conduct communication with a camera body (not shown) through a contact part
103
.
An automatic/manual change-over (A/M) switch
104
is arranged to permit selection of an AF mode and an MF mode. In the AF mode, a result of focus detection made by a focusing detecting device (not shown) is transferred to the lens microcomputer
102
from the camera body. Then, in accordance with the result of focus detection, the lens microcomputer
102
causes a focus driving device
105
which is a drive source to act. The driving force of the focus driving device
105
is transmitted to a focus driving mechanism
106
which is a driving force transmission mechanism. The focus driving mechanism
106
then drives a focusing lens
107
accordingly.
An absolute value encoder
108
and a relative value encoder
109
are arranged to send their detection signals to the lens microcomputer
102
. The absolute value encoder
108
is disposed at a part of a transmission mechanism of the focus driving mechanism
106
and is formed, for example, to have a fixed Gray code pattern (not shown) and electric contacts (not shown) opposed to the Gray code pattern. The absolute value encoder
108
is thus arranged to detect the absolute position of the focusing lens
107
by detecting the state of the Gray code pattern through the electric contacts.
The relative value encoder
109
is disposed at a part of the transmission mechanism of the focus driving mechanism
106
and is formed, for example, with a fixed photo-interrupter (not shown) and a pulse plate which is arranged between the light-emitting and light-receiving parts of the photo-interrupter to transmit and block light. The relative value encoder
109
is thus arranged to detect the relative position of the focusing lens
107
by outputting a pulse signal which turns on and off accordingly as the focusing lens
107
moves and by counting the number of pulses of the pulse signal.
The resolution of the absolute value encoder
108
is obtained by dividing the maximum moving stroke of the focusing lens
107
, for example, into 32 parts (5 bits). The resolution of the absolute value encoder
108
is thus arranged to limit the movable range of the focusing lens
107
. The relative value encoder
109
is arranged to have a resolution which is at least equal to a degree of stopping precision required in bringing the focusing lens
107
to a stop and which satisfies a required rate of focusing accuracy determined according to the F-number and the focal length.
The lens microcomputer
102
controls the focus driving device
105
according to input of information. The lens microcomputer
102
stops the focus driving device
105
when a required amount of moving the focusing lens
107
decided according to the result of focus detection made by the focus detecting device (not shown) and an actual moving amount of the focusing lens
107
detected by the relative value encoder
109
eventually have coincided with each other.
In the MF mode, focus is not adjusted on the basis of the result of the above-stated focus detection. In the MF mode, focus is manually adjusted by operating the manual operation member
110
from outside. The manual operation member
110
is arranged to send, when it is operated, a signal to the lens microcomputer
102
according to the amount and speed of the operation.
Then, in accordance with the signal, the lens microcomputer
102
starts the focus driving device
105
while monitoring the output of the relative value encoder
109
, so as to cause the focus driving mechanism
106
to move the focusing lens
107
. Therefore, in the MF mode, the user of the camera can move the focusing lens
107
by operating the manual operation member
110
to an extent considered to be apposite to conditions under which the camera is operated.
A zone change-over switch
111
is arranged to permit selection and change-over of the movable range of the focusing lens
107
in the AF or MF mode by operating it from outside. More specifically, the normal movable range of the focusing lens
107
can be selected by turning the zone change-over switch
111
off, while a narrower limited range can be selected by turning the zone change-over switch
111
on. Information on the result of selection of the focusing lens movable range is sent from the zone change-over switch
111
to the lens microcomputer
102
. In accordance with the output of the zone change-over switch
111
, if the zone change-over switch
111
is turned on in the AF or MF mode, the lens microcomputer
102
controls the focus driving device
105
while monitoring the output of the absolute value encoder
108
, in such a way as to inhibit the focusing lens
107
from being driven to the outside of the selected range.
Switches
112
and
113
are provided for the focus preset (FP) function. Both the FP storing switch
112
and the FP driving switch
113
are arranged to be operable from outside and to send their outputs to the lens microcomputer
102
. The FP function is carried out as follows.
When the FP storing switch
112
is operated, the lens microcomputer
102
resets a first counter disposed therein to “0”. After that, when the focusing lens
107
is to be moved by the AF or MF action, the count value of the first counter is either incremented or decremented by one according to the moving direction of the focusing lens
107
, i.e., toward its nearest-distance-end position or toward its infinity-distance-end position according to changes taking place in the output of the relative value encoder
109
.
After that, when the FP driving switch
113
is operated, the lens microcomputer
102
causes the focus driving device
105
to drive the focusing lens
107
in the direction of causing the count value of the first counter to become “0”. When the count value of the first counter has become “0”, the lens microcomputer
102
stops the focus driving device
105
. The two FP switches
112
and
113
, therefore, enable the user to have the focusing lens
107
promptly moved to a desired posi
Kawanami Akihiro
Murakami Jun-ichi
Allen Stephone B.
Canon Kabushiki Kaisha
Robin Blecker & Daley
Spears Eric
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