Camera

A camera system permitting mounting of an optical accessory in addition to a camera body and an interchangeable lens comprises: a diaphragm disposed within the interchangeable lens; a detecting part for detecting aperture information on a stopped down aperture obtained when the aperture of the diaphragm is stopped down; and a correction part which is arranged to correct the aperture information obtained by the detecting part when the optical accessory is mounted and to supply the corrected aperture information to the camera body.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a camera arranged to permit an optical accessory 
to be mounted thereon. 
2. Description of the Related Art 
It has been practiced to design a camera system taking into consideration 
the use of such accessories as a telephoto conversion lens (hereinafter 
referred to as a tele-converter), etc. For example, the use of a 
tele-converter which increases the focal length of a photo-taking lens by 
two or 1.4 times is in great demand. A camera system, therefore, must be 
designed to permit data correction in anticipation of an extender to be 
mounted for that purpose. More specifically, in the case of a camera 
system of the kind performing automatic focusing (hereinafter referred to 
as AF) and automatic exposure control (hereinafter referred to as AE), 
information on the lens received by the camera body without the use of any 
extender must be adjusted and corrected when the extender is used. To meet 
this requirement, there have been proposed various lens information 
correcting methods. In one method, the lens information (about its focal 
length, its aperture value, etc.) is corrected within the extender. In 
another, the use of an extender is detected and the lens information is 
corrected as necessary within an interchangable lens. 
However, the conventional camera system is arranged to correct the lens 
information obtained with the tele-converter mounted on the camera system 
on the assumption that the AF and AE actions are to be performed at a 
maximum aperture. The conventional camera system, therefore, has presented 
a problem that accurate control is hardly possible in cases where a video 
camera system is arranged to perform the AF and AE actions with the 
aperture in a state of having been stopped down. 
SUMMARY OF THE INVENTION 
One aspect of this invention lies in the provision of a camera system 
wherein data converting means is arranged to correct lens information by 
taking a stopped-down state of aperture also into consideration when an 
optical accessory is mounted either between a camera body and an 
interchangeable lens or at the fore end of the interchangeable lens. 
The above and other aspects and features of the invention will become 
apparent from the following detailed description of embodiments thereof 
taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a camera system arranged according to this invention as an 
embodiment thereof. The illustration includes a camera body C; an 
interchangeable lens L; a tele-converter AC which is of a double 
magnifying power and employed as another optical accessory; a clock 
oscillator 2; and a power supply circuit 3 which is provided for power 
supply to each applicable circuit. 
A driving circuit 4 is arranged to drive an image sensor 5 such as a CCD. 
The image sensor 5 is arranged to serve also as a sensor for focusing. A 
processing circuit 6 is arranged to perform a signal processing action on 
the output of the image sensor 5. A recording device 7 is arranged to 
record a processed signal output from the processing circuit 6. A 
piezoelectric element 8 is arranged to vibrate the image sensor 5. A 
focusing circuit 9 is arranged to determine the lens to be in a near-focus 
state or in a far-focus state on the basis of image information obtained 
when the image sensor 5 is vibrated in the direction of an optical axis. 
In focusing the interchangeable lens C, information on the lens such as 
its focal length, its aperture value is necessary. A zoom operation part 
10 is arranged to generate a signal indicating a telephoto position or a 
wide-angle position of the lens resulting from a zooming operation, which 
is generally performed on an external operation switch. A system 
controller 11 is arranged to perform control over the whole camera system 
and includes a microcomputer. 
In the interchangeable lens L, a microcomputer 100 is arranged within the 
lens L to control the operation of various actuators, to communicate with 
the system controller 11 which is disposed within the camera body C in 
such a way as to send the intrinsic and variable data relative to the 
lens. A driving circuit 101 is arranged to drive a focus motor 102. The 
focus motor 102 is provided as a drive source for a focus driving 
mechanism and is arranged to shift the position of a focusing lens (not 
shown) in the direction of the optical axis. An encoder 103 is provided 
for detecting the position of the focusing lens. A driving circuit 104 is 
arranged to drive a zoom motor 105. The zoom motor 105 is a drive source 
for a zoom driving mechanism and is arranged to shift the position of a 
zooming lens (not shown) in the direction of the optical axis. An encoder 
106 is provided for detecting the position of the zooming lens. A driving 
circuit 107 is provided for driving a diaphragm motor 108. The diaphragm 
motor 108 (or a drive source called "meter") is of a type varying the 
aperture of the diaphragm by sliding two blades or of a type varying the 
aperture by rotating three or four blades. An encoder 109 is provided for 
detecting an aperture value and is arranged to produce an absolute data 
value of the aperture obtained by detecting the movement of a working 
member by means of a Hall element. 
The double magnifying tele-converter AC which is employed as an optical 
accessory includes information output means which consists of resistors R1 
and R2 and is arranged to provide the interchangeable lens L with 
information, in the form of a voltage, about the tele-converter's own 
optical characteristic indicating, for example, a changed (or adjusted) 
value of focal length and that of the aperture (F number). 
Mount contacts P1 to P5 are disposed on the side of the camera body C. The 
mount contact P1 is provided for the power supply (high potential). The 
mount contact P2 is for the ground. The mount contacts P3 to P5 are 
provided for communication. Mount contacts P17 to P22 are disposed on the 
side of the lens L. The mount contact P17 is provided for the power supply 
and the mount contact P18 for the ground. The mount contacts P19, P20 and 
P21 are provided for communication. Further, the mount contact P22 is 
provided only on the side of the lens L for detection of mounting of an 
accessory such as the tele-converter and the kind of the accessory 
mounted. On the side of the camera body C, there is provided no mount 
contact in a position corresponding to this mount contact P22. Therefore, 
when the interchangeable lens L is mounted directly on the camera body C, 
the mount contact P22 does not come into contact with any of the mount 
contacts of the camera body. 
The tele-converter AC is provided with mount contacts P6 to P10 which are 
arranged to come into contact with the mount contacts P1 to P5 of the 
camera body C and is also provided with mount contacts P11 to P16 which 
are arranged to come into contact with the mount contacts P17 to P22 of 
the lens. 
As apparent from FIG. 1, the mount contacts P1 and P2 are connected to the 
power supply 3. The mount contacts P3 and P4 are connected to the system 
controller 11. The mount contact P5 is connected to the clock oscillator 
2. The mount contacts P17 and P18 of the lens L come into contact with the 
mount contacts P1 and P2 of the camera body C upon completion of bayonet 
mounting of the interchangeable lens L on the camera body C. This allows 
the power to be supplied to electrical elements disposed within the lens 
L. In cases where the tele-converter AC which is employed as an accessory 
is interposed in between the lens L and the camera body C, the mount 
contacts P17 and P18 come into contact with the mount contacts P11 and 
P12. 
The mount contacts P19 to P21 of the lens L are connected to the 
microcomputer 100 and, upon completion of lens mounting, come into contact 
with the mount contacts P3 to P5 in such a way as to permit communication 
between the lens L and the camera body C. In a case where the 
tele-converter AC is interposed in between the lens L and the camera body 
C, the mount contacts P19 to P21 come into contact with the mount contacts 
P13 to P15. 
The mount contact P22 is connected to the microcomputer 100. This contact 
P22 has no corresponding mount contact on the side of the camera body C. 
Therefore, when the lens L is mounted directly on the camera body C, the 
mount contact P22 receives a ground level voltage to allow detection of 
the fact that no such accessory as the converter or the like is mounted on 
the camera body C. In a case where an accessory (or the tele-converter AC) 
is mounted and interposed in between the lens L and the camera body C, the 
mount contact P22 comes into contact with the mount contact P16 of the 
accessory to receive voltage information on the kind of the accessory 
mounted. 
Further, in the tele-converter AC, the mount contacts P6 to P10 are 
arranged to merely communicate with the mount contacts P11 to P16 
respectively. The mount contact P16 is connected to resistors R1 and R2. 
Next, the operation of the camera system is described below with reference 
to FIGS. 2(A) and 2(B) which are flow charts: 
FIG. 2(A) shows the flow of operation of the system controller 11 disposed 
within the camera body C. Referring to FIG. 2(A), a check is made at a 
step ST1 to find if the interchangeable lens L is mounted on the camera 
body C. If so, the flow proceeds to a step ST2. The lens-mounted state is 
detected in one of various methods including a simple method of using a 
mechanical switch; and another method in which the camera is arranged to 
periodically inquire as to whether the lens is mounted and to determine 
that the lens is mounted when a reply is received. 
At the step ST2: Initial data communication is conducted to obtain initial 
data for the interchangeable lens L from the microcomputer 100 of the lens 
L. For example, the initial data to be thus received includes focal length 
values obtained at the telephoto end position and at the wide-angle end 
position of the lens; the F-number of a maximum aperture; the kind of a 
diaphragm mechanism: and the kind of a focusing mechanism. At a step ST3: 
Information is obtained from the encoders 103, 106 and 109 to find the 
current conditions including the state of the focusing lens, that of the 
zooming lens and that of the diaphragm. 
At a step ST4: The focusing circuit 9 is caused to perform a focusing 
action. For this purpose, the system controller 11 controls the focusing 
action not merely on the basis of the current degree of defocus but also 
considers information on a focal length which is obtained from the encoder 
106 and information on an aperture value which is obtained from the 
encoder 109. Then, data relative to the rotating direction and speed of 
the focusing motor 102, etc. is sent to the microcomputer 100 of the lens 
L. At a step ST5: The focusing action is allowed to continue until an 
in-focus state is determined to have been attained. At a step ST6: The 
rotation of the focus motor 102 is brought to a stop as the in-focus state 
has been detected. 
Next, referring to FIG. 2(B), the flow of operation of the microcomputer 
100 disposed on the side of the lens L is described as follows: At a step 
ST10: A check is made for the presence or absence of an optical accessory 
such as the converter on the camera body. For this purpose, the 
microcomputer 100 checks voltage information obtained from the mount 
contact P22. If this voltage is found to be at a ground level, the 
accessory is determined to be absent and the flow comes to a step ST18. If 
the voltage information is found not at the ground level, the accessory is 
determined to be mounted on the camera body and the flow proceeds to a 
step ST11. 
At the step ST11: A check is made for the kind of the optical accessory 
mounted on the camera body C. If the accessory is found to be of a type 1, 
the flow comes to a step ST12. If it is found to be of a type 2, the flow 
comes to a step ST15. In this instance, the flow of operation is described 
on the assumption that the optical accessories that can be mounted on the 
camera body C are divided into the type 1 and the type 2. 
At the step ST12: A check is made to find if a request has been received 
from the system controller 11 of the camera body C for the initial data. 
If so, the flow comes to a step ST13. At the step ST13: The initial data 
which is changed according to their use of the optical accessory of the 
type 1 is sent to the system controller 11. Assuming that the type 1 is 
the tele-converter of a double magnifying power as in the case of FIG. 1, 
data indicating the changed value of focal length, that of the maximum 
aperture F-number, etc. is sent to the system controller 11 of the camera 
body C. Further, the initial data to be used with the optical accessories 
of the types 1 and 2 is stored beforehand in the memory ROM of the 
microcomputer 100 of the interchangeable lens L. 
At a step ST14: The encoder data which has been changed by the use of the 
type 1 optical accessory is sent to the camera body C. More specifically, 
the data values of the encoders 103, 106 and 109 are not simply sent to 
the camera body as they are. Their values are replaced with applicable 
values stored in the memory ROM before the data is sent to the system 
controller of the camera body. 
Assuming that the interchangeable lens L of FIG. 1 is a zoom lens having 
focal length values from 14 to 80 mm and the F-numbers from F 1.4 to F 11, 
the encoder data is replaced in the following manner: FIG. 3(A) shows the 
encoder data values to be obtained with no optical accessory mounted on 
the camera body. FIG. 3(B) shows the encoder data values applicable to a 
case where an optical accessory of the type 1 (the double magnifying 
tele-converter) is mounted on the camera body. As apparent from FIGS. 3(A) 
and 3(B) which show actual numerical data values, this embodiment is 
arranged to send to the camera body not only the data of the maximum 
aperture value but also data for stopped-down aperture values obtained by 
replacing the data values with adjusted values as the encoder data. 
Further, the aperture values which are shown as the encoder data in FIG. 
3(B) are obtained by simply multiplying the normal aperture values by 2 
for the use of a standard tele-converter of a double magnifying power. In 
cases where some close-up ring or a special converter is used, however, 
the aperture value varies in a complex manner. 
Steps ST15 to ST17: With the request for the initial data received from the 
camera body like in the case of the steps ST12 to ST14 mentioned above, 
the initial data is sent to the camera body with the type 2 optical 
accessory mounted on the camera body. Further, after that, the data of 
each encoder is replaced with applicable data stored by the memory ROM 
within the microcomputer 100 and the replacement data is also sent to the 
camera body. 
At a step ST18: A check is made to find if a request for the initial data 
is received from the system controller 11 of the camera body. If so, the 
flow comes to a step ST19. At the step ST19: Since no optical accessory is 
mounted on the camera body in this instance, the intrinsic initial data of 
the interchangeable lens L is read out from the memory ROM of the 
microcomputer 100 and is sent to the camera body. At a step ST20: The 
encoder data for the interchangeable lens L is sent to the camera body 
without replacing it with any other data as no optical accessory is 
mounted on the camera body. 
Step ST21: Control data is received from the system controller 11 of the 
camera body, the data indicating, for example, that the focusing lens is 
to be moved at a specific speed toward the nearest distance position 
thereof. Step ST22: In accordance with the control data, the motor 102, 
105 or 108 is driven accordingly. 
Referring to FIG. 4, another embodiment of the invention is described as 
follows: In this case, a microcomputer 200 is included in the optical 
accessory AC. The initial data for the use of the optical accessory AC and 
the encoder data are replaced with other data by this microcomputer 200. 
Hence, in this case, the interchangeable lens L has no mount contact for 
detecting mounting of an optical accessory and the kind of the accessory. 
The arrangement of the embodiments described in the foregoing enables a 
camera system of the kind permitting use of optical accessories such as a 
tele-converter, etc. to replace the aperture value data with data apposite 
to the optical accessory during the process of varying the aperture. The 
invented arrangement thus ensures accurate operations of the camera 
system.