Camera with an automatic focusing device

A distance detecting device for close-up photography applicable to a range finding device of the type wherein light emitted from a light source is projected onto an object through a projecting lens, and the light reflected from the object impinges upon one of a plurality of light receiving elements via a light receiving lens for detecting which one of a plurality of zones the object is located, depending on which one of the light receiving elements receives the light. The device in accordance with the present invention generates a single light pulse for ordinary photography and light pulses successively for close-up photography, indicating whether a camera-to-target-object distance matches a predetermined distance for close-up photography or deviates therefrom. The successive light pulses for close-up photography may be weaker in intensity than the single light pulse for ordinary photography.

DESCRIPTION 
1. Field of the Invention 
The present invention relates to a camera including an automatic focusing 
device which adjusts the focusing of a camera objective or picture taking 
lens in accordance with a range finding and particular to such apparatus 
wherein a light from a light source is projected onto a target object, the 
light reflected therefrom is selectively received by a plurality of light 
receiving elements, and the object distance is determined in dependence on 
which light receiving element has received the reflected light. 
2. Prior Art 
Heretofore, automatic focusing devices have been proposed, such as in U.S. 
Pat. No. 3,723,003, which devices adjust the focus of a camera objective 
in accordance with range finding wherein a light emitting element light 
source is caused to emit a pulse of light, the light pulse reflected from 
a target object is received by one of a plurality of light receiving 
elements arranged to respectively receive light from zones at different 
distances, and the distance to the target object is detected by which 
element received the light. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a camera including the 
above type of automatic focusing device which facilitates close-up 
photography as well. 
To attain the object, the camera according to the present invention is 
arranged such that a light emitting element light source is caused to emit 
a single light pulse for range finding in ordinary photography, thereby 
focusing a camera objective or picture taking system. At the same time, 
the camera is further arranged such that, in the case of close-up 
photography where the focusing of a picture taking optical system is fixed 
at a specific distance, the light emitting element is caused to 
successively emit light pulses for continuous range finding to indicate 
that the camera and a target object are in the positional relationship 
most suitable for close-up photography when the fixed distance being 
focused by the picture taking optical system matches the actual 
camera-to-target-object distance. According to the present invention, the 
automatic focusing of the picture taking optical system can be effected in 
ordinary photography, and at the same time, a continuous range finding 
operation is performed for close-up photography, the result thereof being 
indicated to allow easy determination of a relative distance between the 
camera and a target object with the camera-to-target object distance being 
changed while the indication of the indicating means is observed thereby 
enabling easy close-up photography. Additionally, as the light emitting 
element is caused to emit a light pulse only once for a range finding in 
ordinary photography, power consumption is saved than in the case when the 
light emitting element is always caused to succesively emit light pulses. 
Furthermore, according to an embodiment of the present invention, a single 
light emitting element is used for the range findings in both ordinary and 
close-up photography, resulting in an advantage in terms of space and 
cost. In addition, in view of the fact that, in close-up photography, it 
is possible to obtain sufficient accuracy in range finding even if the 
light from the light emitting element is slightly low in intensity, 
because a target object is located near the camera, the light for close-up 
photography is emitted at lower intensity than that for ordinary range 
finding, thereby saving power consumption, even if the light emitting 
element emits light successively. In addition, an indication means for the 
close up focusing is arranged to also indicate that a target object is 
outside the focusable distance range in ordinary photography by the 
picture taking optical system, thereby informing a photographer of the 
need for the changeover from ordinary photography to close-up photography.

BEST MODE OF CARRYING OUT THE INVENTION 
With reference to FIG. 1a, range finding unit 2 includes light projecting 
lens 4 and light receiving lens 6 spaced from each other by a 
predetermined distance. Light emitting element 8 is disposed behind light 
projecting lens 4. Light receiving elements 10a through 10e arranged 
behind light receiving lens 6 correspond to different distance zones, 
respectively. In more detail, with respect to light receiving lens 6 light 
receiving element 10a is located at a position conjugate with distance 
zone a, light receiving element 10b at a position conjugate with distance 
zone b, light receiving element 10c at a position conjugate with distance 
zone c, light receiving element 10d at a position conjugate with distance 
zone d, and light receiving element 10e at a position conjugate with 
distance zone e, respectively. Thus, the light emitted from light emitting 
element 8 is projected onto target object 12 through light projecting lens 
4, and which one of the light receiving elements receiving the light 
reflected from target object 12 is detected by circuitry to be described 
more fully hereinafter, whereby a distance zone at which target object 12 
is located is detected. It should be noted that the above embodiment is 
arranged such that one distance zone is identified even when the reflected 
light is received by two adjacent light receiving elements, as described 
later. This arrangement allows the division of the range distance of the 
scene to be photographed into more number of zones than that of the light 
receiving elements for range finding detection, resulting in increased 
accuracy of range finding. 
With reference to FIG. 1b showing the appearance of indication in the 
viewfinder, range finding mark 16 for a range finding area and distance 
mark 18 for camera-to-target-object distances are shown within view field 
14 of the viewfinder. Furthermore, seven light emitting elements 20a to 
20g for distance indications are arranged near distance mark 18 outside 
view field 14 of the viewfinder. Also arranged above light emitting 
element 20a are light emitting elements 22a and 22b for in-focus 
indication in close-up photography and for warning of too short distance 
in ordinary photography. With the arrangement, one of light emitting 
elements 20a to 20g is energized in ordinary photography, to indicate a 
camera-to-target-object distance. When a target object is located closer 
to the camera than at the shortest focusable distance of a picture taking 
lens, both light emitting elements 22a and 22b are energized to give a 
warning of a too short distance. Moreover, when a target object is located 
at a position suitable for close-up photography, light emitting elements 
22a and 22b blink during close-up photography. 
FIG. 2a is a perspective view of the essential part of a camera showing a 
mechanism for switching the picture taking optical system from ordinary 
photography to close-up photography or vice versa. With reference to FIG. 
2a, when focus ring 26 is rotated, picture taking lens 24 is displaced 
wholly or in part, thereby changing the focus distance continuously. Focus 
ring 26 is provided with projection 26a and gear teeth 26b formed thereon 
(see FIG. 2b). Projection 26a is adapted for keeping constant the focus 
distance of picture taking lens 24, i.e. the distance of an object being 
focused by the lens, for close-up photography and gear teeth 26b is for 
changing the focus distance of picture taking lens 24 for ordinary 
photography. 
Changeover member 28 for changing over between ordinary and close-up 
photography conditions is provided with close-up lens 28a and handle 28b, 
and is slidably guided by a guide mechanism (not shown) to move in the 
direction of arrow D, whereby the picture taking optical system is 
switchable between the ordinary photography condition where close-up lens 
28a is retracted from the front of picture taking lens 24 and the close-up 
photography condition where close-up lens 28a is positioned in front of 
picture taking lens 24. Setting lever 32 is connected to changeover member 
28 by connecting rods 30a and 30b, and is slidable integrally with 
changeover member 28. Index 32a is provided on top of setting lever 32 to 
point to mark "A" for ordinary photography and mark "CL" for close-up 
photography as shown in FIG. 2b. Bent portion 32b formed at one end of 
setting lever 32 is, in close-up photography, located at a predetermined 
position within the rotational path of projection 26a formed on focus ring 
26 such that projection 26a is engaged by bent portion 32b to prevent the 
rotation of focus ring 26 at a predetermined position, thereby fixing the 
focus distance of picture taking lens 24 to a given value. Changeover 
switch 34 changes over the electric circuitry between ordinary and 
close-up photography conditions. In ordinary photography condition, 
connecting rod 30b presses contact 34a to connect contact 34b while, in 
close up photography condition, contact 34 is released from the pressed 
condition to connect contact 34c. 
With the above arrangement, in the ordinary photography condition shown in 
FIG. 2a, close-up lens 28a is retracted from the front of picture taking 
lens 24, index 32a of setting lever 32 is registered with mark "A" and 
bent piece 32b of setting lever 32 is retracted outside the rotatable path 
of projection 26a of focus ring 26, whereby focus ring 26 can be rotated 
by a mechanism to be described later. A changeover from the condition 
shown in FIG. 2a to the close-up photography condition is effected by 
sliding movement of changeover member 28 to dispose close-up lens 28a in 
front of picture taking lens 24. Then index 32a on setting lever 32 is 
registered with mark "CL", with bent piece 32b being placed at a 
predetermined position within the rotatable path of projection 26a on 
focus ring 26 so that the rotation of focus ring 26 may be prevented at 
the predetermined position. Furthermore, contact 34a of changeover switch 
34 is connected to contact 34b for ordinary photography and is connected 
to contact 34c for close-up photography. 
FIG. 2b is a schematic diagram of the essential parts for the explanation 
of a focusing mechanism for picture taking lens 24 for ordinary 
photography, as well as a focus distance fixing mechanism for picture 
taking lens 24 for close-up photography. Referring to FIG. 2b, drive 
member 36 is provided with rack 36a which is in mesh with teeth 26b of 
focus ring 26. Drive member 36 is charged to and restrained at a 
predetermined position in conjunction with shutter setting or film wind-up 
operation. When released upon depression of a range finder button (not 
shown), drive member 36 is moved to the right under the action of a spring 
(not shown) or the like, thereby rotating focus ring 26 in the direction 
of arrow B to change the focusing or focus distance of picture taking lens 
24. For close-up photography, focus ring 26 is prevented from rotating 
under the action of drive member 36 when projection 26a abuts bent portion 
32b as shown in FIG. 2b and restrained thereat, while for ordinary 
photography, a stopping electromagnet described later is energized to stop 
drive member 36 selectively at several predetermined positions in a manner 
well known in the art. 
The following is a description of the electric circuitry which is switched 
by using changeover switch 34. With reference to FIG. 3, the circuitry 
includes power supply 38, power supply switch 40 and range finding switch 
42. Upon depression of a range finding button (not shown), power supply 
switch 40 is closed and then range finding switch 42 is opened. Switches 
35 and 37 adapted to be changed over by changeover switch 34 shown in FIG. 
2a are both connected to the side "A" in the ordinary photography 
condition, i.e., when contacts 34a and 34b of changeover switch 34 are in 
contact with each other, and are both changed over to the side "CL" for 
the close-up photography condition, i.e., when contacts 34a and 34c of 
changeover switch 34 are in contact with each other. Connected on either 
side of switch 35 are trigger circuit 44, monostable circuit 46 and 
oscillating circuit 48 in the manner as shown in FIG. 2b. When switch 35 
is connected to the side "A", transistor 54 is turned on once by an output 
from monostable circuit 46, and light emitting element 8 is energized by 
the charge stored in capacitor 56 to emit a light pulse only once. When 
switch 35 is connected to the side "CL" on the other hand, light emitting 
element 8 is supplied with successive periodic signals from oscillating 
circuit 48 to emit light pulses successively. Resistor 52 connected to the 
output terminal of oscillating circuit 48 has a larger resistance than 
that of resistor 50 connected to the output terminal of monostable circuit 
46. Therefore, in the close-up photography a current flowing to light 
emitting element 8 is smaller than that during ordinary photography so 
that the light emitted from light emitting element 8 is lower in 
intensity. This is to save power consumption during the successive light 
pulse emission, relying on the fact that a target object is located near a 
camera in close-up photography, and that it is possible to provide 
sufficient range finding accuracy even if the light emitted from light 
emitting element 8 is low in intensity. 
Buffer circuit 58 is adapted to synchronize the operational timing of 
amplifiers 60a through 60e for amplifying the outputs of light receiving 
elements 10a through 10e, with the timing of light emission from light 
emitting element 8. With the present embodiment, when a target object is 
located at a position corresponding to the shortest focusable distance 
zone of picture taking lens 24, the light pulse reflected from the target 
object is received by light receiving element 10b alone. When the target 
object is located at a position where the reflected pulse of light is 
received by light receiving element 10a disposed at a position 
corresponding to a distance zone closer than that to be detected by light 
receiving element 10b, it is judged that focusing is impossible in 
ordinary photography. Furthermore, when the target object is located in 
such a position that the light pulse reflected from the target object is 
received by both light receiving elements 10a and 10b, the picture taking 
optical system is to be exactly focused on the target object in close-up 
photography. 
AND circuit 62, OR circuit 64, flip-flop 66 and AND circuit 68 together 
constitute short distance warning circuit I for warning that the target 
object is positioned closer to a camera than the shortest focusable 
distance of the picture taking lens in ordinary photography. Short 
distance warning circuit I is actuated to turn on both light emitting 
elements 22a and 22b to be viewed in the viewfinder when a light pulse 
emitted from light emitting element 8 and reflected from the target object 
is received only by light receiving element 10a or by both light receiving 
elements 10a and 10b. 
AND circuits 70, 72 . . . 82, OR circuit 84 and inverter 86 together 
constitute distance zone discriminating circuit II for, in ordinary 
photography, discriminating the distance zone where a target object is 
located. When the reflected light pulse is received by two adjoining light 
receiving elements, one of the outputs of AND circuits 70, 72 and 74 
becomes a high level, while only one of the outputs of AND circuits 76, 
78, 80 and 82 becomes a high level when the reflected light pulse is 
received by a single light receiving element. Flip-flops 88a through 88g 
respectively receiving the outputs of AND circuits 70, 72 . . . 82 store 
the outputs of AND circuits 70, 72 . . . 82. The output of the particular 
flip-flop to which a high level output is applied becomes a high level, 
thereby presenting range information, the output being applied to 
indicating circuit 20, whereby either one of light emitting elements 20a 
through 20g commensurate with the flip-flop generating a high level output 
is energized. 
The range information provided from flip-flops 88a through 88g is also 
applied to comparator 90. Comparator 90 also receives an output from lens 
position signal circuit 92 which presents information of the focusing 
distance of the picture taking lens by converting the rotational position 
of the distance ring or the like into an electric signal. Comparator 90 
generates a high level output when the above two inputs are matched with 
each other. The high level output is applied to AND circuit 94, one input 
terminal of which is connected to power supply 38 through switch 37 which 
is closed during ordinary photography. AND circuit 94 generates a high 
level output when the output of comparator 90 becomes a high level in 
ordinary photography. As described earlier, stopping magnet 96 for 
stopping the displacement of drive member 36 shown in FIG. 2b, stops the 
movement of drive member 36 to stop the change of the focus distance of 
picture taking lens 24 when energized by AND circuit 94. At this time, the 
range information matches the focus distance information of the picture 
taking lens, as described earlier, whereby the focus of the picture taking 
lens is adjusted on a target object. Reset circuit 98 resets flip-flops 66 
and 88a through 88g when power supply switch 40 is closed. 
Inverter 100 and AND circuits 102 and 104 together constitute focus 
indicating circuit III for close-up photography. In close-up photography, 
both switches 35 and 37 are changed over to contact "CL" (i.e., switch 37 
is closed), whereby the output of inverter 100 is at a high level. 
Furthermore, in case a target object is located at a position suitable for 
close-up photography, when light emitting element 8 is driven to emit 
light pulses continuously with the frequency of oscillating circuit 48, 
the light pulses reflected from the target object are received by both 
light receiving elements 10a and 10b, whereby AND circuits 10 and 104 are 
both oscillated with the frequency of the reflected light pulses so that 
both light emitting elements 22a and 22b are turned on and off 
continuously with that frequency. Additionally, when a target object is 
positioned slightly displaced from the position suitable for close-up 
photography, either one of light emitting elements 22a and 22b is 
continuously turned on and off, thereby indicating that the distance from 
the camera to the target object to be focused is unsuitable for close-up 
photography, as well as indicating the direction of the displacement 
thereof. More specifically, when the distance from the camera to a target 
object to be focused is longer than the predetermined focus distance for 
close-up photography of a picture taking optical system, light emitting 
element 22b alone is continuously turned on and off, and when the distance 
is shorter, light emitting element 22a alone is continuously turned on and 
off. 
The operation of the present embodiment with the above construction will 
now be described. For ordinary photography, changeover member 28 and 
setting lever 32 are in the conditions shown in FIG. 2a, and index 32a on 
setting lever 32 is registered with mark "A". Close-up lens 28a is 
retracted from the front of picture taking lens 24. Bent portion 32b of 
setting lever 32 is also retracted from the rotational path of projection 
26a on distance ring 26. Both switches 35 and 37 are connected to contact 
"A". When a range finding button (not shown) is depressed, power supply 
switch 40 is closed and reset circuit 98 resets flip-flops 66 and 88a 
through 88g, followed by a opening of range finding switch 42. As the 
result, monostable circuit 46 actuates light emitting element 8 to emit a 
single light pulse. When a target object is located within the focusable 
distance range of picture taking lens 24, either a single one or adjoining 
two of light receiving elements 10b through 10e receives a light pulse 
reflected from the target object, and in response to the output of the 
light receiving element or elements thereof, either one of flip-flops 88a 
through 88g generates a high level output, and one of light emitting 
elements 20a through 20g associated with the corresponding the flip-flop 
is actuated to thereby indicate a camera-to-target-object distance in the 
viewfinder. Additionally, when drive member 36 released from its 
restrained condition upon depression of the range finding button is 
displaced under the action of a spring or the like (not shown), the focus 
distance i.e. the distance to be focused by picture taking lens 24 is 
changed, causing the information of the focus distance to be supplied to 
comparator 90 through lens position signaling circuit 92. Comparator 90 
compares the information of focus distance with the information of the 
found range from flip-flops 88a through 88g, and energizes stopping magnet 
96 through AND circuit 94 when both of the information are matched, 
thereby stopping the displacement of drive member 36, as well as stopping 
the change of the focus distance of picture taking lens 24. 
When a target object is located closer to a camera than the position within 
the focusable distance range of picture taking lens 24, the light pulse 
reflected from the target object is received by light receiving element 
10a alone or by both light receiving elements 10a and 10b. In either case, 
short distance warning circuit I is actuated to turned on both light 
emitting elements 22a and 22b, whereby a warning is indicated in the 
viewfinder. 
Next, in the case of close-up photography, changeover member 28 is slid to 
the right from the condition shown in FIG. 2a so that close-up lens 28a 
may be positioned in front of picture taking lens 24. This causes index 
32a of setting lever 32 to be registered with mark "CL" and at the same 
time bent portion 32a to be in a predetermined position within the 
rotational path of projection 26a on focus ring 26, whereby switches 35 
and 37 are both changed over to the side "CL". Upon depression of a range 
finding button (not shown), a drive member which has been restrained at 
its charged position is released, thereby causing distance ring 26 to be 
rotated. The rotation of focus ring 26 is, however, stopped by projection 
26a abuting upon bent portion 32b on setting lever 32, and the focus ring 
26 is maintained stopped. Accordingly, in close-up photography, the focus 
distance of picture taking lens 24 is fixed to a predetermined value, 
whereby the focus distance of the picture taking optical system consisting 
of picture taking lens 24 and close-up lens 28a is always maintained 
constant. 
Furthermore, upon depression of the range finding button, light emitting 
element 8 is driven to emit light pulses successively with the frequency 
of oscillating circuit 48, allowing the photographer to change the 
relative distance between the camera and the target object observing the 
indication in the viewfinder to obtain a relative distance most suitable 
for close-up photography. Specifically, when a camera-to-target-object 
distance is too short, light emitting element 22a alone is continuously 
turned on and off in the viewfinder, and when the distance is too long, 
light emitting element 22b alone is continuously turned on and off. 
Therefore, the photographer may change the position of the camera of the 
target object, or both, observing the indication of the viewfinder until 
both light emitting elements 22a and 22b are continuously turned on and 
off. With this latter condition, the picture taking optical system is 
adjusted to focus on the target object. 
FIG. 4 shows a modification of the optical system of the above embodiment, 
wherein the same reference numerals are used for the components or members 
corresponding to those of FIGS. 1 and 2, and a further description thereof 
is omitted. With reference to FIG. 4, viewfinder optical system 106 
consists of objective lens 106a and eyepiece 106b, with a light reflective 
material applied to the rear circumferential surface of objective lens 
106a. Light emitting element holder 108 fixed to range finding unit 2 
holds light emitting elements 20a through 20g and 22a and 22b for 
indication. With the above arrangement, the light emitted from light 
emitting elements 20a through 20g and 22a and 22b is reflected upon the 
reflective material on the rear surface of objective lens 106a for 
introduction into the viewfinder optical path. 
Changeover member 28 is provided with viewfinder correction prism 28c and 
range finding unit correction prism 28d in addition to close-up lens 28a. 
Moreover, in close-up photography changeover member 28 is positioned as 
shown by the solid lines in FIG. 4, with close-up lens 28a in front of 
picture taking lens 24, prism 28c in front of viewfinder optical system 
106 and prism 28d in front of light projecting lens 4 of range finding 
unit 2, respectively. For ordinary photography, changeover member 28 is 
shifted to the position shown by the dotted lines, whereby close-up lens 
28a, prism 28c and prism 28d are retracted from the front of picture 
taking lens 24, viewfinder optical system 106 and light projecting lens 4, 
respectively. Light receiving element 110 for close-up photography 
consists of two elements coupled to be a set which corresponds to close-up 
light receiving elements 10a and 10b of the above embodiment, and is 
provided in the present embodiment separately from light receiving element 
10 for ordinary photography. When a target object is located at a position 
suitable for close-up photography, light pulses emitted continuously from 
light emitting element 8 and reflected from the target object is received 
by the pair of elements constituting light receiving element 110. 
Thus, prisms 28c and 28d are positioned in front of viewfinder optical 
system 106 and light projecting lens 4 of range finding unit 2, 
respectively, for close-up photography, and the optical axes of the 
viewfinder optical system and range finding optical system are inclined 
towards the optical axis of picture taking lens 24, whereby the parallaxes 
of the viewfinder and the range finder can be eliminated for close-up 
photography. 
It should be noted that the present invention is not limited to the above 
embodiments. A picture taking optical system may be arranged, for example, 
such that a first optical system for ordinary photography is exchangeable 
for a second optical system for close-up photography and vice versa or 
that a picture taking lens or part thereof is shifted to a predetermined 
position and fixed thereat for close-up photography.