Camera and interchangeable lens

A camera which performs data communication with a mounted interchangeable lens includes a command generating circuit for generating a command which is not directly related to the data communication; and a control circuit for discontinuing the data communication with the mounted interchangeable lens when the command is generated while the data communication is being performed with the mounted interchangeable lens.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a camera system. More particularly, the 
present invention relates to a camera system which is suitable for 
communicating a variety of photographic information between a camera body 
and interchangeable lenses which are attached in such a way that they can 
be removed from the camera body or between a camera body and accessories 
mounted to the camera body, and which is suitable for performing 
photographic operations on the basis of the communicated information. 
2. Description of the Related Art 
Hitherto, as an information exchange communication method between a camera 
body used in a camera system in which interchangeable lenses or 
accessories can be removed from the camera body, and interchangeable 
lenses or accessories, often a serial communication method using a 
communication line, such as a clock line for synchronization, a data line 
for transmission, or a data line for reception, has been used. 
More specifically, a command is transmitted from the camera body to the 
interchangeable lenses or the accessories. Based on this, the 
interchangeable lenses or the accessories recognize the command, and in 
response, data is transmitted from the interchangeable lenses or the 
accessories to the camera body. As described above, the conventional 
communication method between the camera body and the interchangeable 
lenses or the accessories is a one-way method. Such a camera system is 
disclosed in Japanese Patent Laid-Open No. 6-3582. 
SUMMARY OF THE INVENTION 
According to the present invention, in a camera which performs data 
communication with mounted interchangeable lenses, even while data 
communication is being performed with the mounted interchangeable lenses, 
when a command which is not directly related to data communication is 
generated, the data communication with the interchangeable lenses is 
discontinued. Therefore, a command which is not directly related to data 
communication can be accepted even during data communication.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a block diagram illustrating the essential portion of a camera 
system according to a first embodiment of the present invention. Reference 
numeral 1 denotes a camera body. Incorporated within the camera body 1 is 
an intra-body electrical system 3 comprising a photometering section 4 for 
photometering a light beam which passes through a photographic lens, a 
range-finding section 5 for measuring the distance to a subject, a shutter 
6 for providing an appropriate exposure time, a transport charge system 7 
for winding and rewinding a film, and a microcomputer (intra-camera CPU) 8 
on the camera side for controlling the starting, stopping, or the like, of 
these operations, and performing an exposure computation, an AF 
computation, and communications with lenses. Power is also supplied to the 
intra-body electrical system 3 from an intra-body power supply 10. 
Reference numeral 9 denotes communication means provided on the camera body 
side, which comprises photographic lenses, for example, a 
single-focal-length lens and a zoom lens. Reference numeral 11 denotes a 
focusing lens which forms a part of the photographic lenses. Reference 
numeral 12 denotes an aperture provided within the photographic lens. 
Reference numeral 13 denotes an AF/MF switch for switching between 
auto-focus and manual focus. Reference numeral 14 denotes an electrical 
circuit section of an interchangeable lens 2. 
Incorporated within the electrical circuit section 14 are an AF/MF switch 
detection section 15 for detecting the state of the AF/MF switch 13, 
communication means 16 for performing serial communications with the 
camera body 1, a microcomputer (intra-lens CPU) 17 on the lens side for 
performing control of the inside of the interchangeable lens 2, a lens 
driving control section 18 for performing driving control of the focusing 
lens 11, a lens driving motor 19 for driving the focusing lens 11, an 
aperture control section 20 for performing driving control of the aperture 
12, an aperture driving motor 21 for driving the aperture 12, and others. 
The intra-lens microcomputer 17 receiving a command through the 
communication means 9 and 16 from the microcomputer 8 within the camera 
body 1 causes the lens driving control section 18 and the aperture control 
section 20 to operate according to the command. Further, the intra-lens 
microcomputer 17 transmits the states (zoom position, focus position, 
aperture value, and so on) within the interchangeable lens 2, and 
information (the open aperture value, the focal distance, range-finding 
computation data, and so on) about the interchangeable lens to the 
intra-camera microcomputer 8 through the communication means 9 and 16. In 
this embodiment, communications are performed by serial communications of 
an 8-bit data synchronizing clock method. 
The intra-camera microcomputer 8 transmits a command requesting the state 
and the information of the interchangeable lens 2 to the intra-lens 
microcomputer 17. In response, the intra-lens microcomputer 17 transmits 
the requested state and the information of the interchangeable lens 2 to 
the intra-lens microcomputer 17. The communication between the 
intra-camera microcomputer 8 and the intra-lens microcomputer 17 is the 
same as conventional communication. 
Here, when the camera body has a new auto-focus function different from the 
conventional one, the intra-camera microcomputer 8 determines whether or 
not the mounted interchangeable lens is an interchangeable lens which 
corresponds to the new auto-focus function on the basis of the state and 
the information of the interchangeable lens 2 received from the intra-lens 
microcomputer 17. At this time, when the mounted interchangeable lens is 
an interchangeable lens which corresponds to the new auto-focus function, 
the intra-camera microcomputer 8 requests special data corresponding to 
the new auto-focus function from the intra-lens microcomputer 17. On the 
other hand, when the mounted interchangeable lens is not an 
interchangeable lens which corresponds to the new auto-focus function, the 
intra-camera microcomputer 8 does not request special data and performs 
conventional communication. 
Further, when the camera body is a camera body which does not have the new 
auto-focus function, conventional communication is performed because it 
cannot be determined whether or not the mounted interchangeable lens is an 
interchangeable lens which corresponds to the new auto-focus function. 
As a result of adopting the above-described communication method, a lens 
body to which a new auto-focus function is added and a conventional lens 
body to which a new auto-focus function is not added can be used while 
maintaining compatibility. 
In this embodiment, an extension command for requesting special data is 
divided into three steps of extension commands 1, 2, and 3 described 
below. The extension command 1 is a command for requesting the total 
amount of special data. The interchangeable lens receiving this command 
transmits the total amount of special data in the current state to the 
camera body. The extension command 2 is a command for requesting the 
starting of the transmission of special data. The interchangeable lens 
receiving this command outputs data corresponding to the first unit of one 
data-length of the special data between the camera body and the 
interchangeable lens. 
The extension command 3 is a command for requesting the continuation of the 
communication of the special data. The interchangeable lens receiving this 
command transmits special data in units of one data length in accordance 
with the predetermined sequence. When the communication of the amount of 
data transmitted with respect to the extension command 1 is terminated, 
output is made starting again with the first unit of one data-length. 
The interchangeable lens does not need to continuously transmit extension 
data with respect to the extension command 2 or 3 and can receive another 
command during mid-processing. 
Next, the operation of this embodiment will be described with reference to 
the flowchart of FIG. 2, including FIGS. 2A and 2B. 
[Step 1] 
The interchangeable lens 2 is attached to the camera body 1, and the 
process of the flow starts. 
[Step 2] 
The camera body 1 and the interchangeable lens 2 start 8-bit serial 
communication via the communication means 9 and 16. A serial clock (not 
shown) is supplied from the camera body 1. A command is transmitted from 
the camera body 1 to the interchangeable lens 2 in synchronization with 
the serial clock. Data for the received command is transmitted from the 
interchangeable lens 2 to the camera body 1. 
Communication herein is performed by commands and data in the same manner 
as previous convention. When the interchangeable lens 2 is an 
interchangeable lens capable of handling the new auto-focus function, a 
signal indicating that there is special data is transmitted to the 
intra-camera microcomputer 8 of the camera body. For the signal indicating 
that there is special data, a bit which is not defined is used in the data 
that the interchangeable lens which does not correspond to the new 
auto-focus function transmits. As a result of the above, there is no 
problem with the combination of a camera body which does not correspond to 
the new auto-focus function and an interchangeable lens which corresponds 
to the new auto-focus function. Conversely, the combination of a camera 
body which corresponds to the new auto-focus function and an 
interchangeable lens which does not correspond to the new auto-focus 
function can be used without any problems. 
[Step 3] 
When the camera body 1 having the new auto-focus function recognizes that 
the interchangeable lens 2 has special data, the process proceeds to step 
5. When the camera body 1 recognizes that the interchangeable lens 2 does 
not have special data, the process proceeds to step 4. 
[Step 4] 
When the interchangeable lens 2 does not have special data, conventional 
communication is performed. 
[Step 5] 
When both the camera body 1 and the interchangeable lens 2 correspond to 
the new auto-focus function, one of the extension commands 1, 2, and 3 is 
transmitted from the camera body 1 to the interchangeable lens 2. The 
interchangeable lens 2 transmits data corresponding to the received 
extension command to the camera body 1. 
[Step 6] 
If the extension command transmitted from the camera body 1 to the 
interchangeable lens 2 is extension command 1 in step 5, the process 
proceeds to step 7. If it is not extension command 1, the process proceeds 
to step 8. 
The extension command 1 is a command for requesting the total amount of 
special data. The interchangeable lens 2 receiving this command transmits 
the total amount of special data to the camera body 1. 
[Step 7] 
The interchangeable lens 2 reads the position of the zoom lens, the 
position of the focusing lens along the optical axis, and the like, and 
sets the total amount of special data in the current state in a serial 
buffer, this data being transmitted to the camera body 1 at the next 
communication. 
[Step 8] 
If the extension command transmitted from the camera body 1 to the 
interchangeable lens 2 is extension command 2 in step 5, the process 
proceeds to step 9. If it is not extension command 2, the process proceeds 
to step 11. 
The extension command 2 is a command for requesting the start of the 
transmission of special data. The interchangeable lens 2 receiving this 
command outputs data corresponding to the first unit of one data-length of 
the special data to the camera body 1. 
[Step 9] 
The camera body 1 sets the data address for reading special data at the 
starting address. 
[Step 10] 
A data-length counter for determining whether or not the camera body 1 has 
received all the special data is reset. 
[Step 11] 
If the extension command transmitted from the camera body 1 to the 
interchangeable lens 2 is extension command 3 in step 5, the process 
proceeds to step 12. If it is not extension command 3, the process 
proceeds to step 15. 
The extension command 3 is a command for requesting the continuation of the 
transmission of the special data. The interchangeable lens 2 receiving 
this command transmits special data in units of one data length in 
accordance with the predetermined sequence. 
[Step 12] 
In order to count the number of bytes of the special data received by the 
camera body 1, the data-length counter is incremented. 
[Step 13] 
The total amount of data returned in response to extension command 1 is 
compared with the value of the data-length counter. When the value of the 
data-length counter is greater, the process proceeds to step 9. When the 
value of the data-length counter is smaller, the process proceeds to step 
14. 
[Step 14] 
The camera body 1 increments the data address for reading the special data 
by 1 from the current value. 
[Step 15] 
When the command transmitted from the camera body 1 to the interchangeable 
lens 2 is none of the extension commands 1, 2, and 3, even if the special 
data is being transmitted, this is stopped, and a process corresponding to 
the received command is performed. 
When the process corresponding to the received command is terminated, the 
process returns to step 5 again where extension command 3 is received, and 
the transmission of the special data is continued. 
[Step 16] 
Data is read from the data address which is set at the starting address in 
step 9. The data is set in the serial buffer in order that the data is 
transmitted to the camera body 1 at the next communication. Then, the 
process returns to step 5 where the next communication is awaited. 
FIG. 3 is a block diagram illustrating the electrical construction of a 
camera system according to a second embodiment of the present invention. 
Reference numeral 101 denotes a lens (interchangeable lens) in the camera 
system. Reference numeral 102 denotes a camera (camera body). 
The construction of the lens 101 will be described first. Shown in FIG. 3 
are a focusing lens 103, an aperture 104, an auto-focus button 
(hereinafter referred to as an AF button) 105, an AF/MF switch 106, and an 
electrical circuit section 107 within the lens 101. Provided within the 
electrical circuit section 107 are an AF-button detection section 108 for 
detecting the state of the AF button 105, an AF/MF switch detection 
section 109 for detecting the state of the AF/MF switch 106, communication 
means 110 for performing serial communication with the camera 102, an 
intra-lens CPU 111 for performing various control of the inside of the 
lens 101, an aperture control section 112 for performing driving control 
of the aperture 104, a lens driving control section 113 for performing 
driving control of the focusing lens 103, an aperture driving motor 114 
for driving the aperture 104, and a lens driving motor 115 for driving the 
focusing lens 103. 
Next, the construction of the camera 102 will be described. Reference 
numeral 116 denotes an electrical circuit section within the camera 102. 
Provided within the electrical circuit section 116 are a photometering 
section 117 for photometering the amount of light which passes through the 
lens 101, a range-finding section 118 for measuring the distance from the 
film surface (not shown) to a subject, a shutter 119 for causing a film to 
be exposed for an appropriate length of time, a transport charge system 
120 for winding and rewinding a film, an intra-camera CPU 121 for 
performing various control of the inside of the camera, and communication 
means 122 for performing serial communication with the lens 101. Further, 
a power supply 123 required as a power source for the lens 101 is also 
provided inside the camera 102. 
Next, with reference to the flowchart of FIG. 4, a description will be 
given of the operation (here, the operation within the intra-lens CPU 111) 
of the essential portion of the camera system constructed as described 
above. 
[Step 101] 
The lens 101 is attached to the camera 102, and the power supply is 
switched on. Thereupon, the operation beginning with step 102 in FIG. 4 is 
started. 
[Step 102] 
A check is made to determine whether or not serial communication is being 
performed between the camera and the lens. When the serial communication 
is being performed, the process proceeds to step 106. When the serial 
communication is not being performed, the process proceeds to step 103. 
The case in which communication is not being performed refers to, for 
example, a case in which neither the camera 102 nor the lens 101 is being 
operated for a particular length of time and the camera system enters a 
power saving mode for preventing the consumption of the battery. 
Here, assuming that communication is not being performed, a description of 
step 103 and subsequent steps will be given first. 
[Step 103] 
The state of the AF/MF switch 106 provided within the lens 101 is detected. 
If in manual-focus state, the process returns to step 102. If in 
auto-focus state, the process proceeds to step 104. 
[Step 104] 
The state of the AF button 105 provided in the lens 101 is detected. If the 
AF button 105 is on, the process proceeds to step 105. If the AF button 
105 is off, the process returns to step 102. 
[Step 105] 
A communication request signal is output to the camera 102 so as to start 
communication. 
The camera 102, upon receiving the above communication request signal, 
recognizes that the state of the lens 101 is changed and starts 
communication. 
When it is determined in step 102 described above that communication is 
being performed, the process proceeds to step 106 in the above-described 
manner. 
[Step 106] 
The state of the AF/MF switch 106 provided within the lens 101 is detected. 
If in manual-focus state, the process proceeds to step 110. If in 
auto-focus state, the process proceeds to step 107. 
[Step 107] 
Here, since the AF/MF switch 106 is in the auto-focus state, the output of 
the manual-focus signal to the camera 102 is stopped. 
As a result, the camera 102 determines that the AF/MF switch 106 is set to 
auto-focus because the manual-focus signal is not output, and enters an 
auto-focus controllable state. 
[Step 108] 
The state of the AF button 105 provided in the lens 101 is detected. If the 
AF button 105 is on, the process proceeds to step 109. If the AF button 
105 is off, the process proceeds to step 111. 
[Step 109] 
The on signal of the AF button 105 is output to the camera. 
The camera 102 receiving the on signal of the AF button 105 recognizes that 
the AF button 105 of the lens 101 is being pressed and performs auto-focus 
control. 
[Step 110] 
Here, since the AF/MF switch 106 is in the manual-focus state, a 
manual-focus signal is output to the camera 102. 
As a result, receiving the manual-focus signal, the camera 102 determines 
that the AF/MF switch 106 is set to manual focus and does not perform 
auto-focus control. 
[Step 111] 
Here, since the AF button 105 is off, the output of the on signal of the AF 
button 105 to the camera 102 is stopped. 
As a result, the camera 102 recognizes that the AF button 105 of the lens 
101 is turned off and stops the auto-focus control. 
As described above, by operating the AF button 105 of the lens 101, the 
starting and stopping of auto-focus can be performed. Thus, a camera 
system with high ease of use can be realized. 
FIG. 5 is a block diagram illustrating the electrical construction of a 
camera system according to a third embodiment of the present invention. 
Reference numeral 124 denotes a lens in the camera system. Reference 
numeral 125 denotes a camera. 
The construction of the lens 124 will be described first. Reference numeral 
126 denotes a focusing lens. Reference numeral 127 denotes an aperture. 
Reference numerals 128, 129, and 130 each denotes an AF button. Reference 
numeral 131 denotes an AF/MF switch for switching between auto-focus and 
manual focus. Reference numeral 132 denotes an electrical circuit section 
within the lens 124. Provided within the electrical circuit section 132 
are AF-button detection sections 133 to 135 for detecting the state of the 
AF buttons 128 to 130, respectively, an AF/MF switch detection section 136 
for detecting the state of the AF/MF switch 131, communication means 137 
for performing serial communication with the camera 125, an intra-lens CPU 
138 for performing various control of the inside of the lens 124, an 
aperture control section 139 for performing driving control of the 
aperture 127, a lens driving control section 140 for performing driving 
control of the focusing lens 126, an aperture driving motor 114 for 
driving the aperture 104, and a lens driving motor 142 for driving the 
focusing lens 126. 
Next, the construction of the camera 125 will be described. Reference 
numeral 143 denotes an electrical circuit section within the camera 125. 
Provided within the electrical circuit section 143 are a photometering 
section 144 for photometering the amount of light which passes through the 
lens 124, a multipoint range-finding section 145 having a plurality of 
range-finding sections for measuring the distance from the film surface 
(not shown) to a subject, a shutter 146 for causing a film to be exposed 
for an appropriate length of time, a transport charge system 147 for 
winding and rewinding a film, an intra-camera CPU 149 for performing 
various control of the inside of the camera, and a communication means 148 
for performing serial communication with the lens 124. Further, a power 
supply 150 required as a power source for the lens 124 is also provided 
inside the camera 125. 
In this embodiment, a case in which three switches and three switch 
detection means corresponding to the three switches are provided in the 
lens 124, and in which there are three range-finding points of the camera 
125 will be described. 
The three switches are denoted as an AF button a (130 in FIG. 5), an AF 
button b (129 in FIG. 5), and an AF button c (128 in FIG. 5), 
respectively. The switch detection means corresponding to these buttons 
are denoted as an AF-button detection section a (135 in FIG. 5), an 
AF-button detection section b (134 in FIG. 5), and an AF-button detection 
section c (133 in FIG. 5), respectively. The three range-finding points 
(not shown) on the camera side are denoted as a range-finding point a, a 
range-finding point b, and a range-finding point c, respectively. 
Next, referring to the flowchart of FIG. 6, the operation (the operation by 
the CPU 138) of the essential portion of the camera system constructed as 
described above will be described. 
[Step 201] 
The lens 124 is attached to the camera 125, and the power supply is 
switched on. Thereupon, the operation beginning with step 202 in FIG. 6A 
is started. 
[Step 202] 
When serial communication between the camera and the lens is being 
performed, the process proceeds to step 206. When serial communication is 
not being performed, the process proceeds to step 203. The case in which 
communication is not being performed refers to, for example, a case in 
which neither the camera 125 nor the lens 124 is being operated for a 
particular length of time and the camera system enters a power saving mode 
for preventing the consumption of the battery. 
Here, assuming that communication is not being performed, a description of 
step 203 and subsequent steps will be given first. 
[Step 203] 
The state of the AF/MF switch 131 provided within the lens 124 is detected. 
If in manual-focus state, the process returns to step 202. If in 
auto-focus state, the process proceeds to step 204. 
[Step 204] 
The states of all the AF buttons provided in the lens 124 are detected. If 
any one of them is on, the process proceeds to step 205. If all the AF 
buttons are off, the process returns to step 202. 
[Step 205] 
A communication request signal is output to the camera 125 so as to start 
communication. 
The camera 125 receiving the above communication request signal recognizes 
that the state of the lens 124 is changed and starts communication. 
When it is determined in step 202 described above that communication is 
being performed, the process proceeds to step 206 in the above-described 
manner. 
[Step 206] 
The state of the AF/MF switch 131 provided within the lens 124 is detected. 
If in manual-focus state, the process proceeds to step 214. If in 
auto-focus state, the process proceeds to step 207. 
[Step 207] 
Here, since the AF/MF switch 131 is in the auto-focus state, the output of 
the manual-focus signal to the camera 125 is stopped. 
As a result, the camera 125 determines that the AF/MF switch 131 is set to 
auto-focus because the manual-focus signal is not output, and enters an 
auto-focus controllable state. 
[Step 208] 
The state of the AF button a provided in the lens 124 is detected. If the 
AF button a is on, the process proceeds to step 209. If the AF button a is 
off, the process proceeds to step 215. 
[Step 209] 
Here, since the AF button a is on, the on signal of the AF button a is 
output to the camera 125. 
The camera 125 receiving the on signal of the AF button a recognizes that 
the AF button a of the lens 124 is being pressed, selects a range-finding 
point a corresponding to the AF button a, and performs auto-focus control. 
[Step 210] 
The state of the AF button b provided in the lens 124 is detected. If the 
AF button b is on, the process proceeds to step 210. If the AF button b is 
off, the process proceeds to step 216. 
[Step 211] 
Here, since the AF button b is on, the on signal of the AF button b is 
output to the camera 125. 
The camera 125 receiving the on signal of the AF button b recognizes that 
the AF button b of the lens 124 is being pressed, selects a range-finding 
point b corresponding to the AF button b, and performs auto-focus control. 
[Step 212] 
The state of the AF button c provided in the lens 124 is detected. If the 
AF button c is on, the process proceeds to step 213. If the AF button c is 
off, the process proceeds to step 217. 
[Step 213] 
Here, since the AF button c is on, the on signal of the AF button c is 
output to the camera 125. 
The camera 125 receiving the on signal of the AF button c recognizes that 
the AF button c of the lens 124 is being pressed, selects a range-finding 
point c corresponding to the AF button c, and performs auto-focus control. 
[Step 214] 
Here, since the AF/MF switch 131 is in the manual-focus state, the 
manual-focus signal is output to the camera 125. 
As a result, the camera 125 receiving the manual-focus signal determines 
that the AF/MF switch 131 of the lens 124 is set to manual focus, and does 
not perform auto-focus control. 
[Step 215] 
Here, since the AF button a is off, the output of the on signal of the AF 
button a to the camera 125 is stopped. 
As a result, the camera 125 recognizes that the AF button a of the lens 124 
is turned off and stops the auto-focus control at the range-finding point 
a. 
[Step 216] 
Here, since the AF button b is off, the output of the on signal of the AF 
button b to the camera 125 is stopped. 
As a result, the camera 125 recognizes that the AF button b of the lens 124 
is turned off and stops the auto-focus control at the range-finding point 
b. 
[Step 217] 
Here, since the AF button c is off, the output of the on signal of the AF 
button c to the camera 125 is stopped. 
As a result, the camera 125 recognizes that the AF button c of the lens 124 
is turned off and stops the auto-focus control at the range-finding point 
c. 
Further, when the camera 125 receives the on signal of a plurality of AF 
buttons, the camera 125 automatically selects the most appropriate 
range-finding point from among the plurality of range-finding points 
corresponding to these signals and performs auto-focus control. 
As described above, in the combination with a multipoint range-finding 
camera, by operating the AF button corresponding to the range-finding 
point, the selection of a desired range-finding point can be made easily 
and reliably. 
According to each of the above-described embodiments, by turning on an AF 
button provided in the lens, the camera starts auto-focus. Therefore, even 
when a release button is set to only a release function, ease of use is 
improved. 
Further, when the release button is set to only a release function, since 
the auto-focus operates only when the AF button of the lens is on, 
focus-locked-like use is possible. 
Furthermore, as in the third embodiment, since a plurality of AF buttons 
are made to correspond to the range-finding points of the multipoint 
range-finding camera, a complex operation needs not to be performed, and a 
desired range-finding point can be selected quickly. 
In addition, when a plurality of AF buttons are being pressed 
simultaneously, the camera automatically selects the most appropriate 
range-finding point from among the plurality of selected range-finding 
points and performs auto-focus control. Therefore, quick and reliable 
auto-focus becomes possible in any case. 
[Modification] 
Although each of the above-described embodiments describes the case of an 
application to a single-lens reflex camera, the present invention is not 
limited to this case and can be applied to, for example, an 
interchangeable-lens-type video camera. 
Although in each of the above-described embodiments an example is described 
in which the camera comprises a range-finding section for measuring the 
distance from the film surface to a subject and drives a lens on the basis 
of the range-finding information obtained thereby, it is a matter of 
course that, in place of the range-finding section, a focal-point 
detection section (for example, the amount of defocus of the subject is 
detected at each of a plurality of focal-point detection points, and the 
amount of defocus is determined in accordance with a predetermined 
algorithm) may be provided so that the lens is driven on the basis of the 
obtained defocus. 
Further, although not particularly described in each of the above-described 
embodiments, the release button provided in the camera is assumed to have 
both an auto-focus function and a release function similar to a 
conventional single-lens reflex camera and can be changed by switching the 
mode so that the release button is made to have only the release function 
and the AF button 105 of FIG. 3 is made to have an auto-focus function as 
in each of the above-described embodiments. 
Furthermore, when the release button is switched to the mode in which it 
has both an auto-focus function and a release function, a switching 
function other than the auto-focus function is added to the AF button 105 
of the lens 101, making it possible to reduce the number of switching 
means on the lens side (a reduction in the cost) and to eliminate 
limitations on design. 
Many different embodiments of the present invention may be constructed 
without departing from the spirit and scope of the present invention. It 
should be understood that the present invention is not limited to the 
specific embodiments described in this specification. To the contrary, the 
present invention is intended to cover various modifications and 
equivalent arrangements included within the spirit and scope of the 
invention as hereafter claimed. The scope of the following claims is to be 
accorded the broadest interpretation so as to encompass all such 
modifications, equivalent structures and functions.