Variable focusing lens barrel

A variable focus lens barrel in which a variable power drive frame has a plurality of cam grooves which each receive a cam pin provided on each of movable frames to which a lens group is each fixed, the variable power drive frame being driven by a motor to perform variable power drive, wherein a balanced groove is formed at each of both ends of a variable power drive range of each of the cam grooves formed in the variable power drive frame such that the balanced groove extends circumferentially of the variable power drive frame over a predetermined angular range from each end, and wherein each of the movable frames does not move in the direction of the optical axis in a rotational area of the variable power drive frame in which each of cam pins slides in the corresponding balanced groove.

This invention relates to a variable focusing lens barrel and more 
particularly to such barrel in which the movement of a variable power 
optical system along the optical axis between a shorter focal-distance end 
and a longer focal-distance end is performed by the torquefrom a variable 
power motor and the focusing drive is also performed by the torque from a 
focusing drive motor. 
Generally, when a plurality of lens groups constituting a zoom or a 
variable power optical system in a zoom lens barrel or a variable focusing 
lens barrel is individually driven selectively to perform a zoom or a 
variable power drive, a zoom or a variable power drive frame which rotates 
around the optical axis or directly moves along the optical axis is 
provided and driven manually. 
Recently, exposure, film feed, automatic focusing, etc., in a camera have 
electrically been performed automatically and the entire size of camera is 
greatly miniaturized. The present situation is that a type in which zoom 
or variable power drive is performed by applying the torque of a motor to 
the zoom or variable power drive frame also in the zoom lens barrel or 
variable focus lens barrel is employed and realized as a product. 
In that case, each of cam grooves provided to zoom drive a plurality of 
lens groups is formed such that it stops not only the zoom drive of a 
plurality of lens groups, but also the drive of the zoom drive frame in 
each of the shorter and longer focus side end areas of the zoom drive 
range. Therefore, there is the problem that when the zoom drive frame is 
driven by motor, the cam pin is strongly pushed against the end surface of 
the cam groove at the shorter and longer focus side ends of the zoom drive 
range, so that an overload acts on the motor. 
Especially, if a continuous cam groove is formed at the shorter focus side 
end of the zoom drive range for retraction of the lens barrel or a 
continuous cam groove is formed for macrodriving at the longer focus side 
end, the position accuracy of boundary portion (the accuracy with which an 
area where the zoom lens is located is ensured) is reduced to render mode 
switching uncertain. 
The position of such variable focusing lens once focused by changing the 
focal distance is likely to change compared to the zoom lens, so that it 
is necessary to perform a refocusing operation each time the focal 
distance is changed. However, it has the advantage that the entire lens 
optical system is miniaturized, so that it is often employed in a camera. 
In that case, the variable power drive frame provided for variable power 
drive of a plurality of lens groups is composed of at least one first and 
one second drive frame which are rotated integrally to move movable frames 
to which the corresponding lenses are individually fixed in the direction 
of the optical axis for variable power drive. In addition, a plurality of 
lens groups engaged in the second drive frame alone are driven for 
focusing by driving the second drive frame alone in the direction of the 
optical axis. 
The drive range of the second drive frame for focus drive is constant 
irrespective of where the focal distance in the variable power drive range 
is. Such drive range is set so as to have a range from the position of a 
maximum possible value, namely, infinity in the longest-focal distance 
side to a value corresponding to a predetermined nearest distance. 
A second drive frame driving range necessary for focus driving in the range 
from the position of infinity to a value corresponding to the 
predetermined nearest distance decreases as the focal distance decreases, 
of course. 
Therefore, the driven range set for the longest focal distance is focus 
driven to a further nearer position than the predetermined nearest 
position when the second drive frame is driven to the shorter focal 
distance side for variable power purposes. 
Thus, when the second drive frame is driven to the shorter focal distance 
side for variable power drive, it is focus driven to a near distance which 
does not satisfy the optical characteristic. 
Therefore, it is required to take some measures to prevent the focus 
driving to a near distance which does not satisfy the optical 
characteristic. 
In order to attain an automatically focused state in the variable focusing 
lens, it is possible to dispose a focusing sensor at a osition conjugate 
to the film surface to measure the distance normally on the basis of the 
output from the focusing sensor during variable power driving, and to 
drive the focusing lens by a focusing drive motor to achieve a focused 
state normally. However, it is impossible to sense a stop signal for the 
focusing drive motor at the nearest distance from the output of the 
focusing sensor. Therefore, it is required to take some measures also in 
that case to thereby prevent the focus driving to a near distance which 
does not satisfy the optical characteristic. 
This invention derives from the contemplation of the above situation. The 
object of this invention is to provide a variable focus lens barrel which 
when driven to each of the shorter and longer focal point side end areas 
of the variable power drive range for the variable focus lens barrel, 
exerts no overload on the motor and which is capable of realizing 
improvements to the accuracy of lens position at the respective end areas, 
namely, the focal-distance accuracyat the espective end areas without 
using an especial complicated structure. 
Another object of this invention is to provide a variable focusing lens 
barrel which prevents the focusing drive to a near distance which does not 
satisfy the optical characteristic. 
The first object of this invention is achieved by a variable focus lens 
barrel in which a variable power drive frame has a plurality of cam 
grooves which each receive a can pin provided on each of movable frames to 
which a lens group is each fixed, said variable power drive frame being 
driven by a motor to perform variable power drive, wherein a balanced 
groove is formed at each of both ends of a variable power drive range of 
each of the cam grooves formed in the variable power drive frame such that 
the balanced groove extends circumferentially of the variable power drive 
frame over a predetermined angular range from each of said both ends, and 
wherein each of movable frames does not move in the direction of the 
optical axis in the rotational area of the variable power drive frame in 
which each of cam pins slides in the corresponding balanced groove. 
The other object of this invention is achieved by a variable focus lens 
barrel in which a plurality of movable framesto which a lens group is each 
fixed are disposed slidable in the direction of the optical axis relative 
to a fixed lens barrel, a plurality of variable power drive frames each 
have cam grooves each receiving the corresponding cam pin provided on each 
of said movable frames and are rotatable relative to the fixed barrel, the 
variable power drive frames are rotated as a unit by a variable power 
drive motor to perform variable power drive of the plurality of lens 
groups, only a predetermined one of variable power drive frames is driven 
by a focusing drive motor to drive only the lens group engaged in the 
predetermined variable power drive frame in the direction of the optical 
axis to thereby perform a focusing drive, characterized by a stop pin 
fixed to said fixed barrel and a near-distance stop cam provided on the 
predetermined variable power drive frame such that said stop cam abuts on 
the stop pin at a position corresponding to the nearest-distance during 
variable-power driving. 
According to this invention, when the variable power frame is driven to 
each of the shorter and longer focus side end areas of a variable power 
drive range in the variable focus lens barrel, no overload acts on the 
drive motor, the accuracy of lens position in each end area, and hence the 
accuracy of focal distance in each end area are improved only by modifying 
a cam shape without using any special complicated structure. 
In an embodiment, barrier vanes can be closed at the end of the retracted 
barrel area, it is possible to pevent deposition of dust, finger prints, 
etc., on the lens surface and/or damage to the lens when the camera is in 
a non-photographing state. Provision of the lens barrier is optional. 
Since information corresponding to the position of the driven lens is 
extracted depending on the position where the variable power pattern base 
plate and a contact piece contact, each drive control, namely, variable 
power, macro, accommodation drive and control can be performed. 
In addition, since information on the photographing distance is extracted 
depending on the position where the focus pattern base plate and the 
contact piece contact, focus drive and control is upgraded. 
According to this invention, furthermore, the advantages of a variable 
focus lens that the lens system is miniaturized, lightened and 
manufactured inexpensively are utilized, while a deviation of the focusing 
position specific to the variable focus lens at the time of variable power 
and flucturations (indefiniteness) of the position where the near distance 
stopping is performed and occurring at the variable power position 
(changes in the focal distance) are eliminated surely. 
More particularly, a deviation of the focusing position when the power is 
varied can be eliminated adjustably by driving the focus drive motor on 
the basis of the output from an automatic focusing sensing circuit during 
or after the variable power. 
The positional restriction at the nearest-distance position occurring at 
the variable power position is achieved by forming, at the front end of 
the variable power drive frame, a near-distance stop cam surface 
corresponding to a quantity of extrusion of the lens corresponding to the 
focal distance and variable power drive angle, and fixing a stop pin to 
the fixed barrel so that the stop pin abuts on the near-distance stop cam 
surface at a predetermined position. Thus, even if the lens is at the 
nearest-distance position which satisfies the optical performance during 
telephoto photographing, the lens is prevented from being focused at the 
near-distance position which does not satisfy the optical performance 
during wide-angle photographing. 
Therefore, a deviation of an imaging position caused by the focusing 
operation and constituting a difficulty specific to the variable focus 
lens is automatically eliminated adjustably by the focusing drive motor. 
The near-distance stop positions at the respective focal distances vary, 
which is another difficulty; for example, the focus adjustment of the lens 
at a near-distance position which does not satisfy the optical performance 
in wide-angle photographing even if the lens is at a near-distance 
position satisfying the optical performance in telephoto photographing, is 
avoided by performing a positional restriction of the predetermined 
variable power drive frame by a near-distance stop provided on the 
predetermined variable power frame and a stop pin provided on the fixed 
barrel. Therefore, even if the photographing lens is in any focal 
distance, it is beforehand prevented from being used outside the 
near-distance limit where the optical performance is deteriorated.

FIG. 1 is a schematic cross-section view of a variable focus lens barrel 
showing a specific example of this invention. It shows an embodiment in 
which this invention is applied to a camera in which a variable focus lens 
barrel of the type in which a lens is driven electrically in three areas; 
a macro area, a variable power area and an accommodating area is fixed to 
the camera body, namely, a so-called multifocus compact camera. 
The specific example also shows that the variable power optical system is 
composed of five lens groups which are moved in a complex manner for 
variable power drive and that the rearmost lens group is moved for focus 
driving, namely, that the photographing lens is constituted by a so-called 
rear focus variable power lens. 
In FIGS. 1-5, a fixed cylindrical frame 1 is fixed integrally with the 
camera body (not shown). Provided around the outer periphery of the fixed 
frame is a variable power drive frame 2 which is prevented from moving 
along the optical axis P, but supported slidable circumferentially. 
Disposed within the frame 1 is a first cylindrical movable frame 3 such 
that it is slidable at its rear peripheral portion. A first group lens 4 
is fixed at the front end of the frame 3. A first outwardly protruding cam 
pin 5 is fixedly screwed into the rear end of the first movable frame 3. 
As shown in the exploded cam view of FIG. 2, the first cam pin 5 fits into 
a direct travel groove 1a provided in the frame 1 so as to be parallel to 
optical axis P and also into a first cam groove 2a provided in the drive 
frame 2 so as to traverse the optical axis P. The first cam groove 2a 
includes at its intermediate area a variable power curved portion 
corresponding to a variable power drive area (range) angle .theta..sub.1 
and a balanced area angle .theta..sub.4 formed so as to be orthogonal to 
the optical axis P so that the first cam pin 5 does not move in the 
direction of the optical axis P, the angle .theta..sub.4 continuing to the 
shorter-focus side end of the curved portion. A balanced area angle 
.theta..sub.5 similar to the balanced area angle .theta..sub.4 is formed 
such that it continues to the end of the longer focal distance side of the 
angle .theta..sub.1. In addition, a macro area angle .theta..sub.2 and an 
accommodating area angle .theta..sub.3 are formed so as to be continuous 
to the corresponding ends of the balanced area angles .theta..sub.5 and 
.theta..sub.4, respectively. 
Slidably provided within the fixed frame 1 is a second divided-type movable 
frame 6 which does not interfere with the first movable frame 3. A second 
group lens 7 is fixed to the second movable frame 6 and a second cam pin 8 
fixed to the periphery of the frame 6. 
The second cam pin 8 is arranged to be moved in the direction of variable 
power by means of a direct travel groove 1b and a second cam groove 2b 
similar to the corresponding ones mentioned above. The second cam groove 
2b also has angles .theta..sub.1 -.theta..sub.5 similar to the 
corresponding ones mentioned above. 
Slidably provided within the fixed frame 1 is a third movable frame 9 to 
which a third group lens 10 is fixed. A third cam pin 11 is fixed to the 
periphery of the frame 9. The third cam pin 11 is adapted to be moved in 
the direction of variable power by means of a direct travel groove 1c and 
a third cam groove 2c similar to the corresponding ones mentioned above. 
The third cam groove 2c includes in its intermediate area an angle 
.theta..sub.1 corresponding to the variable power driving range, a 
balanced ara formed at the shorter-focal distance end of the angle 
.theta..sub.1 so as to be orthogonal to the optical axis P so that the 
third cam pin 11 does not move in the direction of the optical axis P, and 
another balanced area similar to the above-mentioned balanced area formed 
at the longer-focal distance end of the angle .theta..sub.1. 
Slidably provided within the fixed frame 1 is a fourth movable frame 12 to 
which a fourth group lens 13 is fixed, and a fourth cam pin 14 is fixed to 
the periphery of the fourth movable frame 12. The fourth cam pin 14 is 
arranged to move in the direction of variable power by means of a direct 
travel groove 1d and a fourth cam groove 2d similar to the corresponding 
ones mentioned above. The fourth cam groove 2d includes at its 
intermediate area an angle .theta..sub.1 corresponding to the variable 
power driving range and similar to the shape of the third cam groove 
mentioned above, a balanced area formed at the shorter focal distance end 
of the angle .theta..sub.1 so as to be orthogonal to the optical axis P so 
that the fourth cam pin 14 does not move in the direction of the optical 
axis P, and another balanced area similar to the above-mentioned balanced 
area formed at the longer-focal distance end of the angle .theta..sub.1. 
Slidably provided within the fixed frame 1 is a fifth divided-type movable 
frame 15 which does not interfere with the fourth frame 12. The fifth 
frame 15 has in its inner periphery an internal thread 15a into which an 
external thread 16a formed around a small-diameter step in the stepped 
focus drive frame 16 is screwed. Teeth 16b of a spur gear are formed at 
the larger-diameter step of the focus drive frame 16. A fifth groiup lens 
17 is fixed to the fifth movable frame 15 with a fifth cam pin 18 being 
fixed to the periphery of the frame 15. 
The fifth cam pin 18 includes is arranged to move in the variable power 
direction by means of an extension of the direct travel 1c in which the 
third cam pin 11 is engaged and not interfering with the third cam pin 11, 
and a fifth cam groove 2e. The fifth cam groove 2e has in its intermediwte 
area an angle .theta..sub.1 corresponding to the variable power drive rage 
as in the third cam groove 2c and balanced areas, one at each of the 
shorter and longer focal-distance ends of .theta..sub.1, each balanced 
area being similar to the third cam groove 2c. 
The gear teeth 16b of the focus drive frame 16 mesh with an output gear 
wheel 20 formed at an end of the cylindrical focus drive motor 19 such 
that by rotation of the motor 19 the position of the focus drive frame 16 
relative to the fifth movable frame 15, namely, the position of the fifth 
group lens 17 relative to the fixed frame 1 and along the optical axis P 
is changed. Such change is arranged to cover a predetermined focus drive 
area when the frame 16 rotates through a certain angular area smaller than 
its complete rotation. 
Formed around the rear periphery of the variable power drive frame 2 are 
gear teeth 2' which mesh with an output gear wheel 22 formed at an end of 
a cylindrical variable power drive motor 21 such that by rotation of motor 
21, the frame 2 is rotated around the optical axis P. When the drive frame 
2 is rotated through a predetermined angular range smaller than one 
complete rotation, all the areas for the predetermined variable power 
driving, barrel retraction, macrodriving and balanced states are covered. 
On the other hand, fixed at a rear periphery of the frame 2 is a contact 
piece fixing plate 23 which supports one end of a contact piece 24. The 
other end of the contact piece 24 electrically contacts a variable power 
pattern base plate 25 fixed to the inner periphery of the rear 
large-diameter portion of the fixed frame 1. Thus an electrical signal 
corresponding to the angle of the frame 2 driven (for variable power) 
relative to the fixed frame 1 is obtained, for example, from the contact 
piece 24. 
Also, supported around the outer periphery of the focus drive frame 16 is a 
contact piece fixing plate 26 which supports at its end a contact piece 27 
movable in the direction of the optical axis P. The contact piece 27 is at 
its end in electrical contact with a focus pattern base plate 28 fixed to 
the outer periphery of the rear large-diameter portion of the fixed frame 
1. Thus an electrical signal corresponding to the rotational angle of the 
focus drive frame 16 driven for focusing relative to the fixed frame 1 is 
obtained, for example, from the contact piece 27. 
Similarly to the fixed frame 1, an outer housing 30 is provided integrally 
with the camera body and has a funnel-like open front end portion. An 
inwardly protruding support member 31 protruding at the front end of the 
intermediate portion of the housing 30 is fixed by caulking, so that 
barrier drive lever 32 is rotatably supported by the member 31. 
As shown in more detail in FIG. 4, the lever 32 is adapted to abut on or 
against the first cam pin 5 at a driven edge 32a formed on the side of one 
arm thereof, so that when the canm pin 5 is driven as the variable power 
frame 2 moves and corresponds to the barrel retraction range of the driven 
range x.sub.1, the barrier drive lever 32 is turned clockwise. 
A ring-like barrier drive disc 34 to which a barrier drive pin 33 
protruding backwardly is fixed is rotatably supported around the optical 
axis P within the front opening in the housing 30. The disc 34 has two 
slots in which correspoonding pins 35a are rotatably inserted, the pins 
35a being fixed to barrier vanes 35 and protruding backwardly from a pair 
of semi-circular barrier vanes 35 which form one disc when the vanes abut 
at their chords. Provided at the front surface of the vanes 35 are 
forwardly protruding pins 35b which are inserted rotatably into axial 
holes provided in a disc-like fixed plate 36. A front cover 37 is fixed 
before the fixed plate 36. The barrier drive pin 33 is engaged in the 
drive fork portion 32b of the lever 32. 
When the pin 33 is driven by the lever 32, the pair of barrier vanes 35 are 
opened and closed. 
The variable focus lens barrel of the embodiment constructed as described 
above operates as follows. 
Assume that focusing is performed in a state in which the variable power 
drive frame 2 is driven such that a desired focal distance is attained by 
the drive motor 21. When the focus drive motor 19 is rotated on the basis 
of the output from the automatic focus sensing circuit (not shown) 
provided in the camera body, the focus drive frame 16 is rotated via the 
output gear wheel 20 and the external thread portion 16 is subjected to 
the screwing action of the internal thread 15a of the fifth movable frame 
15, so that the focus drive frame 16 moves in the direction of the optical 
axis depending on the direction of rotation thereof. At that time, the 
movement of the fifth movable frame 15 in its rotative direction is 
restricted by the fifth pin 18 engaged in the direct travel groove 1c, so 
that only the focus drive frame 16 moves in the direction of the optical 
axis together with the fifth group lens 17 to thereby achieve a desired 
focused state. 
At the time, the position of the contact piece 27 in electrical contact 
with the focus pattern base plate 28 changes and the information on the 
focus pattern base plate 28 (the information on the focus position) is fed 
back to a control circuit (not shown) provided on the side of the camera 
body, so that the drive of the focus drive motor 19 is controlled 
appropriately in forward and reverse directions until the focused state is 
obtained. 
When the variable power drive motor 21 is powered by pressing a variable 
power button (not shown) in order to drive the power, the torque of motor 
21 is transmitted via the output gear wheel 22 to the teeth 2' to thereby 
rotate the drive frame 2. This causes the first-fifth cam pins 5, 8, 11, 
14 and 18 to move in the direction of the optical axis P in accordance 
with the respective shapes, of the first-fifth cam grooves 2a-2e in the 
state in which they are restricted from rotating around the optical axis P 
by the respective direct travel grooves 1a, 1b, 1c and 1d. As shown in 
FIG. 3, the first-fifth group lenses 4, 7, 10, 13 and 17 are moved by 
predetermined respective distances in the directionof the optical axis P 
to establish a variable focus photographing lens optical system. The range 
of such variable power drive is within the range of angle .theta..sub.1. 
By the rotation of the variable power drive frame 2, the position of 
contact piece 24 in electrical contact with the variable power pattern 
base plate 25 is changed, so that information on the current focal 
distance is sensed. This information is fed back to the control circuit 
provided in the camera body and processed in an appropriate manner. 
When the variable power drive motor 21 is powered in order to drive the 
lens to the variable power drive end, the drive frame 2 is rotated due to 
a delay in the stopping of the motor 21, etc., from the end of the angle 
.theta..sub.1 into the angle .theta..sub.4 in the balanced area or into 
the angle .theta..sub.5 (the cam pins 5, 8, 11, 14 and 18 slide on the 
balanced grooves provided over the angles .theta..sub.4, .theta..sub.5). 
Namely, the variable power drive frame 2 rotates in the state in which the 
movement of the first-fifth cam pins 5, 8, 11, 14 and 18 in the direction 
of the optical axis P is restricted (stopped), so that the first-fifth 
group lenses 4, 7, 10, 13 and 17 do not move in the direction of optical 
axis P and the focal distance corresponding to the end of the variable 
power range is maintained accurately even if the first-fifth lenses enter 
the balanced areas. 
On the other hand, when the variable power drive motor 21 is powered in 
order to perform mwacrophotographing, the first and second cam pins 5 and 
8 pass through the balanced area for angle .theta..sub.5 from the longer 
focus end of the angle .theta..sub.1 variable power area in a manner 
similar to that mentioned above and move in the direction of the optical 
axis P by quantities determined by the first and second cam grooves 2a and 
2b in the macroarea, so that the first movable frames 3 (first group lens 
4) and the second movable frame 6 (second group lens 7) each move also in 
the direction of the optical axis P. At that time, the third-fifth group 
lenses 10, 13 and 17 do not move in the direction of the optical axis P 
because the shape of the third-fifth cam grooves 2c, 2d and 2e are 
orthogonal to the optical axis P. 
In the above various cases, the first cam pin 5 does not abut on the driven 
portion 32a of the barrier drive lever 32, so that the barrier drive lever 
32 does not change in position and the barrier vanes 35 are open. 
When the drive motor 21 is powered in a nonphotographing state in order to 
retract the first and second movable frames 3 and 6, the variable power 
drive frame 2 rotates. Thus, similarly, the first and the second cam pins 
5 and 8 move from the shorter-focus end of the variable power area for the 
angle .theta..sub.1 to the balanced area for the angle .theta..sub.4 (the 
area where the balanced groove is formed) and restricted by the first and 
the second cam groove 2a and 2b in the accommodating area to thereby move 
in the direction of the optical axis P. At that time, the third-fifth 
group lenses 10, 13, 17 do not move in the direction of the optical axis P 
because the shape of the third-fifth cam grooves 2c, 2d and 2e are 
orthogonal to the optical axis P. 
When the motor 21 continues to rotate in the same direction as before, and 
the first and second cam pins 5 and 8 arrive at the end of the 
accommodating area for angle .theta..sub.3 while being subjected to the 
restriction of the first and second cam grooves 2a and 2b, both lenses 4 
and 7 (first and second movable frames 3 and 6) are accommodated into the 
lens barrel (outer housing 30), as shown in FIG. 5. 
In cooperation with such accommodating operation, the first cam pin 5 
pushes the driven portion 32a of the barrier drive lever 32 to move the 
barrier drive pin 33 by the fork portion 32b, so that the barrier drive 
plate 34 is rotated around the optical axis P. This causes the pin 35a of 
the barrier vane 35 which has the other pin 35b supported in the axial 
hole in the fixed plate 36 to rotate by means of the slot formed in the 
drive plate 34, so that the pair of barrier vanes 35 is closed. 
When variable power photographing is started in such retracted condition, 
the variable power drive motor 21 is powered such that the drive reverse 
to the above is performed to thereby move the lens into the variable power 
area or the macroarea in the operation reverse to that mentioned above. 
FIG. 6 is a schematic cross-section view showing the structure of another 
embodiment of a variable focus lens barrel according to this invention. 
This embodiment is a camera in which a variable focusing lens barrel of the 
type in which a lens is driven electrically between the shorter and longer 
focal distances is fixed to the camera body, a so-called multifocus 
compact camera, to which this invention is applied. This embodiment shows 
a photographing lens unit composed of a so-called front focus variable 
power lens, in which the variable power optical system is composed of five 
lens groups such that all the lens groups are moved complexly in the 
direction of the optical axis for variable power drive and the first and 
second group lenses alone are moved in the direction of the optical axis 
for focusing drive. 
In the examples of FIGS. 6-8, a cylindrical fixed lens barrel 51 is 
provided integrally with the camera body (not shown) and has a rear 
double-cylindrical portion, at the rear end of which a cylindrical 
connection member 52 is fixed at its rear end. Fixed to the front end of 
the connection member 52 is a fixed lens barrel 53 having a diameter 
smaller than the fixed lens barrel 51. 
Provided within the fixed barrel 51 is a variable power drive frame 54 
which is prevented from moving in the direction of the optical axis and 
supported slidable in the circumferential direction orthogonal to the 
optical axis. 
A first movable frame 56 to which a first group lens 55 is fixed is 
supported around the outer periphery of the fixed barrel 51 such that it 
is slidable within a restricted range. A first inwardly protruding cam pin 
57 is fixedly screwed into the first movable frame 56 and fitted slidably 
into the direct travel groove 51a formed in the fixed barrel 51 so as to 
be parallel to the optical axis, as shown in the view of an exploded cam 
in FIG. 7, and also fitted into the first cam groove 54a formed in the 
variable power drive frame 54 so as to intersect the optical axis. 
Slidably provided within the drive frame 54 is a second movable frame 59 to 
which the second group lens 58 is fixed. A second outwardly protruding cam 
pin 60 is fixedly screwed into a periphery of the second frame 59. The 
second cam pin 60 is arranged to move in the direction of variable power 
drive by means of direct travel groove 51b and second cam groove 54b 
similar to the corresponding ones mentioned above. 
Attached around the outer periphery of the fixed barrel 53 is a variable 
power drive frame 61 which is only allowed to rotate in a state in which 
the movement in the direction of the optical axis is prevented. The frame 
61 has teeth 61' around its outer rear periphery. Slidably provided within 
the frame 61 is a third movable frame 63 to which a third group lens 62 is 
fixed. A third cam pin 64 is fixed to the periphery of the frame 63. The 
third cam pin 64 is arranged to move in the direction of variable power 
drive by means of a direct travel groove 53a formed in the fixed barrel 53 
and a third cam groove 61a formed in the frame 61 in a manner similar to 
that mentioned above. 
Slidably provided within the fixed barrel 53 is a fourth movable frame 66 
to which a fourth group lens 65 is fixed. A fourth outwardly protruding 
cam pin 67 is fixed to the frame 66 and is arranged to move in the 
direction of variable power drive by means of a direct travel groove 53b 
formed in the fixed barrel 53 and a fourth cam groove 61b formed in the 
frame 61 in a manner similar to that mentioned above. 
Slidably provided within the fixed barrel 53 is a fifth movable frame 69 to 
which a fifth group lens 68 is fixed. The frame 69 does not interfere with 
the fourth movable frame 66. The fifth frame 69 has a fifth outwardly 
protruding cam pin 70 fixed thereto which is engaged in the direct travel 
groove 53c so as not to interfere with the fourth cam pin 67 and also 
engaged in the fifth cam groove 61c formed in the variable power drive 
frame 61 so as to move in the direction of variable power drive. The fifth 
cam pin 70, direct travel groove 53c, and fifth cam groove 61c are not 
shown in FIG. 7. 
The drive frame 61 has an outwardly protruding relay cam pin 71 fixed 
thereto. The pin 71 extends through an escape hole 52a provided in the 
surface of the link member 52 and is engaged at its end in a direct travel 
groove 61d formed in the variable power drive frame 54 so as to extend in 
the direction of the optical axis. 
Provided around the outer surface of an inner cylinder of the 
double-cylindrical fixed barrel 51 is a direct travel frame 73 into which 
an inwardly protruding relay cam pin 72 is fixedly screwed. The pin 72 
extends through escape hole 51c formed in the fixed barrel 51 and is 
engaged in cam groove 54c formed in the frame 54. 
Fixed to the frame 73 is an outwardly protruding relay cam pin 74 which 
stops the rotation of the travel frame 73 by means of a direct travel 
groove 51d formed in the fixed barrel 51 and which is engaged in a focus 
cam groove 75a formed in the focus drive frame 75. 
The focus drive frame 75 has a rear thicker portion, the outer periphery of 
which has gear teeth 75' which receive the torque from a cylindrical focus 
drive motor 77 via an output gear wheel 76. 
Gear teeth 61' on the outer rear portion of the drive frame 61 receive the 
torque of a cylindrical variable power drive motor 79 via an output gear 
wheel 78. 
As shown in FIG. 7, a near-distance stop cam surface 90 is formed at the 
front of the variable power drive frame 54 and is arrnged to abut on stop 
pin 81. 
The inclination of the cam surface 90 restricts the near-distance position 
for the focus drive range in the focusing optical system including the 
first and second group lenses 55 and 58. In more detail, as shown in FIG. 
8, the respective focus drive ranges on the telephoto and wide-angle sides 
for each of the first and second group lenses 55 and 58 are .DELTA..sub.XT 
on the telephoto side and .DELTA..sub.XW on the wide-angle side, so that 
the near-distance stop cam surface 90 is formed having such an inclination 
that the distance of the inclined cam surface has a distance covered until 
the cam surface 90 abuts the stop pin 81 corresponding to the respective 
nearest distances on the telephoto and wide-angle sides in variable power 
drive. 
The variable focus lens barrel according to the embodiment constructed as 
mentioned above operates as follows. 
Assume that focusing is performed under a condition in which the variable 
power drive frame 61 is rotated by the variable power drive motor 79 so as 
to provide a desired focal distance. When the focus drive motor 77 is 
rotated on the basis of the output from the automatic focusing sensing 
circuit (not shown) provided in the camera body, the torque is transmitted 
via output gear wheel 76 to the gear teeth 75' to thereby rotate the focus 
drive frame 75. 
This causes the relay cam pin 74 which is prevented from rotating by the 
direct travel groove 51d to be driven in the direction of the optical 
action by the focus cam groove 75a (driven to the maximum .DELTA..sub.XT), 
so that the direct travel frame 73 moves in the direction of the optical 
axis. By this operation, the relay cam pin 72 moves in the direction of 
the optical axis in escape hole 51c provided in the fixed barrel 51, the 
variable power drive frame 54 is pressed by relay cam pin 72 inserted into 
the cam groove 54c in the frame 54, so that the first and second cam pins 
57 and 60, which are prevented from rotating by the corresponding direct 
travel grooves 51a and 51b in the fixed barrel 51, are moved in the 
direction of the optical axis. 
Therefore, the first and second movable frames 56 and 59, combined with the 
first and second cam pins 57 and 60, are moved in the direction of the 
optical axis, so that the first and second group lenses 55 and 58 are 
moved in the direction of the optical axis to perform a focus adjustment. 
When the variable power drive frame 54 is moved in the direction of the 
optical action as the focus drive frame 75 rotates, the relay cam pin 71 
is not driven because of the presence of the travel groove 54d even if the 
frame 54 is moved, so that the frame 61 is kept stationary. Therefore, the 
third, fourth and fifth cam pins 64, 67 and 70 are kept stationary and the 
third, fourth and fifth group lenses 62, 65 and 68 are also kept 
stationary. 
On the other hand, a quantity of movement of the variable power drive frame 
54 in the direction of the optical axis occurring in the focus driving 
varies depending on where the variable power drive frame 54 is in the 
angular range .theta..sub.1 when the frame 54 rotates in accordance with 
the variable power drive, to be described in more detail later. Namely, as 
shown in FIG. 7, when the frame 54 is on the telephoto side, the movable 
distance .DELTA..sub.XT between the near-distance stop cam surface 90 and 
stop pin 81 is large, and when the frame 54 is on the wide-angle side, the 
distance .DELTA..sub.XW is smaller. The position of the drive frame 54 
corresponding to distance infinity is the rightmost retracted position, as 
shown in FIG. 6. As the drive frame54 is driven toward the near-distance 
side in accordance with the rotation of the focus drive motor 77, the 
drive frame 54 is moved forwardly. 
At that time, the forward movement of the frame 54 is limited depending on 
where the near-distance stop cam surface 90 is relative to stop pin 81. 
Namely, when the frame 54 is rotated deepest in the telephoto side, it has 
a maximum stroke .DELTA..sub.XT while when it is rotated deepest in the 
wide-angle side, it has a minimum stroke .DELTA..sub.XW. 
Therefore, when the frame 54 is rotated to the wide-angle side, it is 
prevented from being driven to the near-distance side in which the optical 
performance is deteriorated. 
When the variable power drive motor 79 is supplied in order to perform 
variable power drive, the variable power drive frame 61 is rotated via 
output gear wheel 78. This causes the third cam pin 64 engaged with the 
frame 61 to be moved in the direction of the optical axis by means of the 
third cam groove 61a under a condition in which the third cam pin 64 is 
prevented from rotating by the direct travel groove 53a in the fixed 
barrel 53. This causes the third movable frame 63 to move in the direction 
of the optical axis and the third group lens 62 moves in the direction of 
the optical axis. 
At the same time, the fourth and fifth group lenses 65 and 68 are moved in 
the direction of the optical axis by means of the fourth and fifth cam 
grooves 61b and 61c in a state in which the fourth and fifth cam pins 67 
and 70 are prevented from rotation by means of direct travel grooves 53b 
and 53c, respectively, as in the third cam pin 64. 
The relay cam pin 71 rotates in the circumferential direction orthogonal to 
the optical axis in accordance with the rotation of the variable power 
drive frame 61. This causes pin 71 to push the travel groove 54d to 
thereby rotate frame 54. The first cam pin 57 is moved in the direction of 
the optical axis by means of first cam groove 54a in a state in which it 
is prevented from rotation by means of travel groove 51a in the fixed 
barrel 51. This causes the first movable frame 56 to move in the direction 
of the optical axis to thereby move the first group lens 55 in the 
dirction of the optical axis. 
Simultaneously, similar to the first cam pin 57, the second cam pin 60 also 
is prevented from rotating by means of travel groove 51b and the second 
group lens 58 is moved in the direction of the optical axis by means of 
the second cam groove 54b. 
At the time of variable power drive in which the first, the second, the 
third, fourth and fifth group lenses 55, 58, 62, 65 and 68 are moved in 
this way, the variable power drive frame 54 is rotated by the relay cam 
pin 71, but is prevented from moving in the direction of the optical axis 
by the relay cam pin 72 provided on the direct travel frame 73 in a 
stationary state and the cam groove 54c extended circumferentially 
orthogonal to the optical axis and receiving the cam pin 72, so that the 
first and second group lenses 55 and 58 do not move for focus adjustment. 
However, there is a case in which the focus adjustment should be made even 
when the variable power drive motor 79 is being powered, namely, during 
the variable power drive. For example, when zooming is performed during 
photographing using a video camera in which the variable focus lens barrel 
according to this embodiment is built, the variable power drive of the 
first-fifth group lenses 55, 58, 62, 65 and 68 may be performed while the 
first and second group lenses 55 and 58 alone are moved additionally for 
focus adjustment by simultaneously powering the variable power drive and 
focus-drive motors 79 and 77. 
To this end, if the response of a focusing sensing mechanism (not shown) is 
speeded up, zooming equivalent to that by a conventional zoom lens is 
performed. 
In that case, assume that the near-distance stop cam surface 90 formed in 
the variable power drive frame 54 corresponding to the nearest distance on 
the telephoto side abuts on the stop pin 81. If the cam surface 90 is 
driven for variable power purposes toward the wide-angle side, the 
inclined surface of cam 90 pushes the stop pin 81, so that the frame 54 is 
moved compulsively in the direction of the optical axis. This compulsive 
movement is, however, performed in order to prevent the frame 54 from 
being moved into the deteriorated area of the optical performance 
corresponding to the focal distance during variable power driving, namely, 
into a distance shorter than the predetermined nearest distance. This 
increases the load on the drive motor 79 only slightly, so that there is 
no special problem occurring. 
This applies not only when variable power driving and focus adjustment are 
performed simultaneously, but also when the lenses are driven to the 
wide-angle side by the variable power driving in a state in which the 
lenses are moved to the nearest position by the focus drive motor 77 
during the telephoto photographing. 
Therefore, in summary, during the focus adjustment by the variable power 
drive frame 54, if the lens is driven to a distance less than the 
nearest-distance corresponding to the focal distance during variable power 
drive, the near-distance stop cam 90 surface hits on the stop pin 81 to 
prevent the movement of the drive frame 54 to thereby increase greatly the 
load current flowing through the motor 79. Therefore, by sensing the 
increase in the current, the focus driving can be stopped. 
This invention is not limited to the previous embodiments. For example, 
while the variable focus lens barrels in the embodiments have been 
described as being fixed to the camera body, it may be applicable to 
exchange lenses, of course. 
The lens structure is not limited to the specified embodiments. For 
example, this invention may be applicable to focusing systems such as a 
front focusing system, an inner focusing system and a rear focusing 
system.