Automatic focusing camera

An automatic shutter driving device releasable when the image of a subject is sharply focused comprises a mode selection switch, enable-signal generating means, logic circuit, and a shutter driving circuit. The mode selection switch is mounted on a camera body having an automatic focusing function and selects at least a single mode or another mode, such as a continuous servo mode or a manual mode. The enable-signal generating means generates an enable-signal when the mode selection switch selects the single mode after a photographic lens having no automatic focusing function has been mounted on the camera body. The logic circuit executes logic operations of the enable signal and a detection output signal derived from a decision means for deciding whether the image of a subject is sharply focused or out-of-focus, thereby delivering a shutter driving signal. The shutter driving circuit drives a shutter in response to the shutter driving signal derived from the logic circuit.

BACKGROUND OF THE INVENTION 
The present invention relates to an automatic shutter driving device 
adapted to be energized when the image of a subject or object is sharply 
focused (to be referred to as an "automatic shutter driving device" 
hereinafter for brevity) which is adapted to be mounted on equipment 
having the function of automatically focusing, such as an 
automaticfocusing camera (to be referred to as an "AF camera" and which 
automatically drives a shutter when a subject reaches or appears at a 
position at which the subject is focused sharply known as 
"snap-in-focusing". 
Recently, there have been devised and demonstrated various cameras capable 
of using a plurality of interchangeable lens and equipped with a function 
for automatically focusing a subject (to be referred to as an "AF 
function" hereinafter in this specification for brevity). 
A camera body for such AF camera (to be referred to as an "AF body" 
hereinafter is disclosed, for example, in U.S.A. patent application Ser. 
No. 103,311, filed on Oct. 1, 1987 by the same applicant. 
When a photographic lens having the ability of performing an automatic 
focusing (to be referred to as the "AF lens" is mounted on the AF body, it 
becomes possible not only to perform automatic exposure controlled 
photography (to be referred to as the "AE", but also automatic focusing 
photography. When a conventional photographic lens without the capability 
of performing automatic focusing (to be referred to as a "conventional 
photographic lens" is mounted on the AF body, it becomes possible to 
perform AE photography. 
To better understand of the present invention, the construction and mode of 
operation of the AF body mounted with an AF lens or a conventional 
photographic lens will be described briefly hereinafter. 
FIG. 1 is a block diagram of a camera consisting of an AF body and an AF 
lens mounted thereon and reference numeral 101 represents the AF body. 
AF body 101 comprises a control unit 105 for controlling the AF or AE 
function as well as other functions of a camera, an image unit 106 which 
serves to decide whether the image of a subject is sharply focused or out 
of focus and lens driving means 107 for shifting one or more lens elements 
within an AF photographic lens 71. In addition, the mount of the camera 
body 101 is provided with a plurality of electrical contacts 175a, 175b, 
175c, 177, 179a, 179b and 181 used for exchanging information between the 
camera body 101 and the photographic lens 71 which is electrically 
connected to predetermined contacts disposed in the control unit 105. 
An AF lens 71 which is adapted to be mounted on the above-mentioned AF body 
101 is disclosed, for instance, in U.S. patent application Ser. No. 
103,311 filed by the same applicant in which reference numeral 71 in FIG. 
1 represents the AF lens. 
With the camera having the above-described construction, light rays from a 
subject, part of which is transmitted through the AF lens 71, is focused 
at the image unit 106. In response to the information delivered from the 
image unit 106, control unit 105 obtains a degree of out-of-focus of the 
focused image and compares it with a reference value, thereby deciding 
whether the image of the subject is sharply focused or out of focus. In 
this case, the control unit 105 provides a focus-detection signal which is 
representative of whether the image is sharply focused or out of focus. In 
case of out-of-focus condition the control unit 105 obtains a distance 
over which one or more movable lens elements 87 must be shifted so that 
the image of the subject can be sharply focused. In response to the 
displacement thus determined, lens driving means 107 shifts one or more 
movable lens elements 87 to a position at which the image of the subject 
is sharply focused. In this case, the lens driving force of the driving 
means 107 is transmitted to one or more movable lens elements 87 through a 
driving force transmission means 89 incorporated in the AF lens 71. Other 
information required for AE and AF photography is exchanged between the 
body and the lens through predetermined electrical contacts, so that 
desired AE or AF photography can be accomplished. 
In FIG. 1, reference numeral 73 represents a lens ROM in which is stored 
information inherent to the AF lens 71; and switching or selection means 
83 which turns on or off the lens ROM depending upon whether the camera 
body has the AF function or not and which, in the case of an "OFF" state, 
delivers information, such as a F-number determined by transistors 
Tr.sub.1 -Tr.sub.3, as the inherent information of the photographic lens. 
Reference numeral 88 represents one or more lens elements in the 
photographic lens 71 which is different from the movable lens elements 87. 
FIG. 2 is a schematic block diagram of a camera consisting of the AF body 
101 and a conventional photographic lens mounted thereon. In FIG. 2, 
reference numeral 15 represents a conventional photographic lens. 
In the case of an AF camera with the above-mentioned construction, an 
electrical signal representative of the mounting of the conventional 
photographic lens 15 is generated by utilizing the fact that the 
electrical contact 177 on the side of the AF body 101 is made into direct 
contact with the conventional photographic lens mount so that it becomes 
possible to accomplish AE photography by using the conventional lens 15. 
In the above case consisting of the conventional photographic lens 15 
mounted on the AF body 101, it is possible to accomplish AE photography; 
but there is a problem in that the AF function of the AF body is not 
positively utilized except to provide a focus indication. 
If the camera shutter is driven or released in response to a decision 
signal representative of a sharply focused image of a subject (to be 
referred to as a "decision signal" even when the conventional photographic 
lens is mounted on the AF body, it is advantageous for camera users 
because not only macro-photography but also photography in coincidence 
coincident with a desired shutter release can be accomplished. 
SUMMARY OF THE INVENTION 
In view of the above, an object of the present invention is to provide an 
automatic shutter driving or releasing device which overcomes the above 
and other problems and can automatically drive the shutter, especially in 
the case of the snap-in-focus, even when a conventional photographic lens 
is mounted on the AF body. 
Another object of the present invention is to improve the performance of 
the automatic focusing device. 
In order to achieve the above and other objects, according to an present 
invention, the automatic shutter driving device 201 is characterized by 
comprising a mode selection switch which is mounted on a camera body 
having the AF function and is adapted to select at least a single mode or 
another mode, such as a manual mode or continuous servo mode; an enable 
signal generator for generating an enable signal when the single mode is 
selected by the mode selection switch after a conventional lens having no 
AF function has been mounted on the camera body; a logic circuit for 
carrying out a logic operation of the enable signal and a decision signal 
derived from a decision means for deciding whether the image of a subject 
is sharply focused or out-of-focus, thereby generating a shutter driving 
or releasing signal; and a shutter driving circuit for driving or 
releasing a shutter in response to the output signal delivered from the 
logic circuit. 
Therefore, when the image of a subject is sharply focused, the shutter is 
automatically driven or released so that a kind of AF photography becomes 
possible, even when a conventional photographic lens having no AF function 
is mounted on the AF body. 
The present invention will be more apparent from the following description 
of a preferred embodiment thereof taken in conjunction with the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The attached drawings schematically shows a preferred embodiment to permit 
the better understanding of the present invention. Dimensions, shapes and 
arrangements of various component parts are not limited to those shown. In 
addition, same reference numerals are used to designate similar parts 
through out the figures and the component parts which are substantially 
similar in construction to those described above and which are designated 
by the same reference numerals will not be described in detail. 
In the case of the AF camera comprising the AF body 101 and the AF lens 71 
mounted thereon which has been described in detail hereinbefore with 
reference to FIG. 1, in order to accomplish (1) single mode exposure, (2) 
servo mode exposure and (3) manual mode exposure to be described 
hereinafter, a program for accomplishing each photographic mode is stored 
in the control unit 105 of the AF body 101. In this case, in order to 
select a desired photographic mode, the AF body is provided with a mode 
selection switch 203. 
The single mode exposure exits when the image of a subject is sharply 
focused, and the shift of one or more photographic lens elements is 
stopped and the shutter is ready to be released. This is a focus-priority 
mode, in which the subject's distance is measured by depressing the 
shutter release button halfway. The lens is then driven to the in-focus 
position and the focus is locked. The shutter button can be released by 
depressing the shutter release button all the way down. It is designed 
this way so that the shutter can not be released unless the subject is 
in-focus, preventing out-of-focus images. 
The continuous servo mode referred to as the "servo mode" is where one or 
more movable lens elements are shifted to follow a subject in such a way 
that the image of the subject can be always kept sharply focused. This is 
a shutter-release-priority mode, in which focusing is continuously 
adjusted to the subject as long as the shutter release button is depressed 
halfway. Unlike the AF single mode, the shutter can be released at any 
time, making it ideal for use when pursuing a mobile or moving subject. 
The manual mode is where the image of a subject is sharply focused by a 
user by operating a focusing ring, an alarm signal is generated or an 
alarm mark is displayed so that the user can detect that the image of the 
subject is sharply referred to as a focused (focus indication). 
As described with reference to FIG. 2, the AF body 101 has the AF function, 
when a conventional photographic lens is mounted on the AF body, the 
operation of the lens driving means 107 is disabled. However, it is still 
possible to focus the image of a subject at the image unit 106 through the 
conventional photographic lens, 15 and, therefore by a detection means for 
detecting whether the image of a subject is sharply focused or out of 
focus, which is composed of the image unit 106 and part of the control 
unit 15 as described above, it becomes possible in a simple manner to 
obtain a degree of out-of-focus of a subject, decide that the image is 
sharply focused and generate a detection signal representative of whether 
the image of the subject is sharply focused or out-of-focus. 
When the camera has other additional functions, the above-mentioned mode 
selection switch can be used as a means for generating a signal for 
selecting a specific function, and the detection signal is used as a 
signal for enabling or disabling a selected function. The automatic 
shutter driving device in accordance with the present invention is so 
designed and constructed that the mode selection switch and the detection 
signal can be utilized. 
Referring now to FIG. 3A, the construction of the automatic shutter driving 
device 201 will be described. FIG. 3A is a circuit diagram illustrating 
one embodiment of the automatic shutter driving device in accordance with 
the present invention. 
In the automatic shutter driving device 201 of FIG. 3A, a mode selection 
switch 203 is disposed at a suitable portion of the AF body 101 and is 
manually operated by a photographer to select a desired exposure mode. It 
is preferable that the mode selection switch is manually caused to slide 
to select the single mode or the servo mode and, in the case of the 
selection of the manual mode, must be once pushed and then caused to slide 
so that the erroneous selection of the manual mode is avoided when the 
single or servo mode is selected. 
The mode selection switch 203 generates a two bit signal and consists of 
two series circuits, each of which consists of a resistor and a switching 
element and which are disposed in parallel with each other. The switching 
elements may be of the mechanical type, the electronic type or the optical 
type. The mode selection output signals are applied to the input terminals 
of a two-input OR gate 205. At least one output signal, for example, 
S.sub.1 generated in response to the manual operation of the mode 
selection switch 203, is also transmitted to the control unit 105 (see 
FIG. 3B) having the functions described above so that either the single 
mode, the servo mode or the manual mode is selected. In this embodiment, 
the combinations of the signal S.sub.1 applied to one input terminal 205a 
of the OR gate 205 and another signal S.sub.2 applied to the other input 
terminals 205b as shown in TABLE 1 select the single mode, the manual mode 
or the servo mode. 
In the present embodiment, the mode selection switch 203 and the OR gate 
205 constitute an enable-signal generating means of the automatic shutter 
device, but it is to be understood that the present invention is not 
limited thereto and that the mode selection switch 203 may be arranged 
independently of the enable-signal generating means 207. The output 
terminals of the enable-signal generating means 207 in an (that is the 
output terminal of the OR gate 205) is connected to a shutter driving 
circuit 211, to be described hereinafter. 
A NOR gate 209 is provided which performs logic operation of the enable 
signal and the detection signal from the decision circuit, thereby 
generating a shutter driving signal. One input terminal of the NOR gate 
209 is connected to the output terminal of the enable-signal generating 
means 207 while a second input terminal thereof is connected to a 
detection signal output terminal of the control unit 105. 
The shutter driving circuit 211 of the preferred embodiment comprises a 
release switch 211a mounted on the camera body, a NOR gate 211b, an 
electromagnetic relay 211c and a transistor 211d for driving the relay 
211c. A signal line from the release switch 211a is connected to one of 
the input terminals of the NOR gate 211b while the output terminal of the 
NOR gate 209 is connected to a second input terminal of the NOR gate 211b. 
In response to the output signal derived from the NOR gate 211b, 
transistor 211d is turned on or off so as to open or close the shutter. 
Conventional camera bodies have an exterior shutter release terminal and 
when the exterior shutter release terminal is connected to an exterior 
shutter release switch 211e, the latter becomes one of the component parts 
of the driving circuit 211. The exterior shutter release switch 211e is 
connected to the output terminal of the NOR gate 211b so that in response 
to the output signal derived from the exterior shutter release switch 
211e, the shutter is released or driven, instead of being driven by the 
output signal derived from the NOR gate 211b. 
FIG. 3B shows a schematic block diagram illustrating the AF body 101 which 
incorporates the automatic shutter driving device 201 of the type 
described above and on which is mounted a conventional photographic lens 
15. FIG. 3B shows the conventional construction of the AF body 101 in 
detail, in which the component parts 211b, 211c, 211d and 211e described 
above with reference to FIG. 3A are shown as a block 212 and the component 
parts 203 and 207 are not shown. 
The AF body 101 must be so designed and constructed that it can perform all 
AF functions or utilize only the function for deciding whether the image 
of a subject is sharply focused or out-of-focus (the decision function) 
while disabling the lens driving means 107, depending upon the combination 
of the type of photographic lens 15 and one of the exposure modes selected 
by the mode selection switch 203. 
One example of the constructions of the AF bodies will be described 
hereinafter with reference to FIG. 4. 
In FIG. 4, reference numeral 177 designates the electrical contact for 
detecting the type of a photographic lens mounted to the AF body 101, as 
described above. More particularly, when the potential at the contact 177 
is "1", it indicates that an AF photographic lens is mounted on the AF 
body, but when the potential is "0", it indicates that a conventional 
photographic lens is mounted. The electrical contact 177 is connected to 
one of the input terminals of a two-input AND gate 213 while one-bit 
information of the mode selection signal or the information delivered to 
one terminal 205a of the gate 205 is applied through a NOT gate 215 to the 
other input terminal of the AND gate 213. The AF function unit in the 
control unit 105 generally comprises a focus decision circuit 105a and a 
driving motor circuit 105b. 
The output signal derived from the AND gate 213 varies in response to the 
output signal S.sub.3 derived from the electrical contact 177 and one 
signal component S.sub.1 of the mode selection signal. 
In this case, in response to the output signal from the AND gate 213, the 
control unit 105 is switched to the AF function for obtaining a sharply 
focused image of a subject by moving one or more lens elements by the 
driving motor circuit 105b which is energized in response to the output 
signal derived from the decision circuit 105a or to the focus decision 
function for enabling only the decision circuit 105a while de-energizing 
the driving means 107. The control unit 105 is so designed and constructed 
to accomplish the function of deciding whether the image of a subject is 
sharply focused or out-of-focus in response to the voltage representative 
of the logic "0" at the output terminal of the AND gate 213. In the 
circuit as shown in FIG. 4, when an AF lens is mounted on the AF body, and 
only when the single or servo mode is selected, the voltage representative 
of the logic "1" appears at the output terminal of the AND gate 213 so 
that the camera is switched into the AF function mode. 
On the other hand, when a conventional photographic lens is mounted and 
when the single mode is selected, the voltage representative of the logic 
"0" appears at the output terminal of the AND gate 213, the detection 
signal representative of a sharply focused image is derived from the 
control unit. 
As described above, when a conventional photographic lens having no AF 
function is mounted, the electrical terminal 177 is grounded and delivers 
the voltage representative of the logic "0" so, that the contact 177 is a 
contact having a function to detect whether a conventional photographic 
lens is mounted or not. When a conventional photographic lens is mounted 
and when the single mode is selected, the combination circuit consisting 
of the electrical contact 177, the AND gate 213 and the NOT gate 215 
enables only the decision circuit 105a in the AF function unit. 
Referring next to FIG. 3B and FIG. 5, the mode of operation of the 
automatic shutter driving device 201 in accordance with the present 
invention will be described. FIG. 5 is a flowchart of the program stored 
in the control unit 105 of the AF body 101 in the case of the operation of 
the automatic shutter driving device 201. 
In general, in the case of an AF camera, when the shutter release switch on 
the camera body is pushed halfway, the photometric switch is turned on and 
the brightness of a subject is measured, and at the same time or after 
then, the focusing operation is accomplished. When the shutter release 
switch is completely depressed, the shutter is released regardless of 
whether an image of a subject is sharply focused or out-of-focus. However, 
in the case of the AF camera incorporating the automatic shutter driving 
device 201 in accordance with the present invention, even if the shutter 
release switch is completely depressed, but a photometric switch remains 
in the "ON" state, the shutter is not released until a sharply focussed 
image of a subject is obtained; that is, the shutter is released when and 
only when the image of a subject is sharply focused. 
Whether or not the photometric switch s turned on is detected (Step 300) 
and when it is detected that the photometric switch is turned on, a 
determination is made of whether or not the shutter release switch 211a is 
turned on (Step 301). In this case, it should be noted that the shutter 
release switch 211a is turned on when it makes contact with an earth 
terminal. 
When it is determined that the shutter releases switch is turned on, it is 
determined what exposure mode is selected (Step 302). In this case, the AF 
mode (single and servo modes) or the manual mode is detected (Step 302). 
When the mode detected in step 302 is the manual mode, the shutter release 
process is executed so that the shutter is released (Steps 302 and 320). 
Further, when the AF mode is detected, it is determined whether the single 
mode or servo mode is selected. In the case of the servo mode, the shutter 
release process is executed so that the shutter is released. In this mode, 
during the halfway depressed position of the shutter release button, 
focusing is continuously adjusted on the subject such, for example, a 
moving one, and accordingly the shutter can be released at any time 
without any readjusting of the focusing by re-depressing the shutter 
release button halfway (Steps 303 and 320). In the case of the single 
mode, whether an AF lens or a conventional photographic lens is mounted is 
detected (Step 304). When it is detected that an AF lens is mounted and 
when the image of a subject is sharply focused, the shutter release 
process is executed so that the shutter is released. In this mode, the 
focussing is not continuously adjusted to the subject during the halfway 
depressed position of the shutter release button. Therefore, to prevent 
out-of-focus images, the focusing should be readjusted to the subject by 
depressing the shutter release button halfway prior to every releasing of 
the shutter (Steps 304, 305 and 320). 
When it is detected in step 304 that a conventional photographic lens is 
mounted, the control unit 105 selects the function for determining whether 
the image of a subject is sharply focused or out-of-focus (Step 311) as 
has already been explained with referring to FIG. 4. 
Under these conditions, the automatic shutter driving device 201 remains in 
the state where it waits for the arrival of the detection signal 
representative of a sharply focused image and upon arrival of the 
detection signal, the shutter release process is executed so that the 
shutter is released (Steps 312 and 320). 
During such waiting period, light rays from a subject passed through a 
photographic lens is directed to a main mirror 109 (FIG. 3B) and 
redirected to pass through a focusing screen 111, a pentagonal prism 113 
and other optical elements so that the brightness of the subject is 
measured by a photosensor 115. Thus, part of the information required for 
the AE exposure is delivered to the control unit 105. Furthermore, part of 
the light rays transmitted through the photographic lens 15 is redirected 
by a sub-mirror 117 to the image unit 106. 
In this case, for example, one of the following operations is carried out: 
(a) A photographer rotates a focusing ring to sharply focus the image of a 
subject; 
(b) The camera is moved toward a subject while the focusing ring remains at 
a predetermined angular position; or 
(c) A subject is moved toward the camera whose focusing ring is held in the 
stationary state. 
During these operations, the image of a subject is sharply focused. Then 
the control unit 105 delivers the signal representing that the image of a 
subject is sharply focused to the arithmetic-logic circuit or NOR gate 209 
in the automatic shutter driving device 201 so that the shutter is 
released at the instant when the image of a subject is sharply focused, 
whereby a desired picture can be obtained. 
However, sometimes it is desired to use the exterior release switch 211e 
(see FIG. 3A) instead of the release switch 211a incorporated in the came 
a body to release the shutter. The exterior shutter release switch 211e is 
different from the above mentioned shutter release switch 211a and it is 
assumed that the exterior shutter release switch 211e has no function of 
turning on the photometric switch. In this case, the detection whether the 
image of a subject is sharply focused or out-of-focus for the sake of the 
snap-in-focusing is not needed. For instance, when the exterior shutter 
release switch 211e is connected to the camera body, the shutter release 
switch 211a is connected to a power supply so that shutter release process 
is executed by the exterior shutter release switch 211e prior to the 
snap-in-focusing. In this case, according to the flowchart shown in FIG. 
5, when it is detected that the photometric switch is not turned on (Step 
300), it is detected whether or not the shutter release switch is turned 
on (Step 306). When it is detected that the shutter release switch is 
turned on, the shutter release process is executed to release the shutter. 
As described above, according to the present invention, not only AF 
exposure but also a kind of AE exposure can be accomplished by using a 
camera consisting of a conventional photographic lens and the AF body. 
Next, some of the practical use of the automatic shutter driving device in 
accordance with the present invention will be described so that the 
present invention may be more apparently understood. 
In the case of macro-photography, the focusing ring is held in the 
stationary state while the camera is moved toward or away from a subject. 
In this case, when the image of the subject is sharply focused, the 
shutter is automatically released. Thus, according to the present 
invention, macro-photography is greatly facilitated. 
Furthermore, it is assumed that a subject appears at an expected position. 
In this case, the focusing ring is rotated so that the expected position 
is sharply focused. Then, when the subject appears at the expected 
position, its image is sharply focused and therefore the shutter is 
automatically released whereby a picture is coincidence with a desired 
shutter releasing chance can be obtained in a very simple manner. 
It is to be understood that the present invention is not limited to the 
above described preferred embodiment For instance, the construction of the 
shutter driving device is not limited to the one shown in FIG. 3A, and 
other hard and soft arrangements can be employed within the spirit and 
scope of the present invention. 
So far, the present invention has been described wherein the automatic 
shutter driving device is incorporated into a camera comprising an AF body 
and a conventional photographic lens, but it is apparent that the present 
invention maybe equally applied to AF cameras themselves. 
As is apparent from the above description, according to the automatic 
shutter driving device adapted to be energized when the image of a subject 
is sharply focused in accordance with the present invention, it becomes 
possible to automatically release the shutter as needed when the image of 
a subject is sharply focused, even when a conventional photographic lens 
is mounted on a body having the AF function. Therefore, in addition to the 
AE exposure function, the function of releasing the shutter when the image 
of a subject is sharply focused can be attained. 
While the invention has been particularly shown and describes with 
reference to preferred embodiments thereof, it will be understood by those 
skilled in the art that the foregoing and other changes in form and 
details can be made therein without departing from the spirit and scope of 
the invention.