Optical apparatus with cam cylinder having concave and convex cams

An optical apparatus according to the present invention includes a cylindrical holding barrel, a plurality of moving lens frames which are held in the holding barrel such that the moving lens frames are moved back and forth in an optical axis direction, and a cam cylinder fitted on an outer surface of the holding barrel so as to move the moving lens frames. The cam cylinder slides and rotates on the outer surface of the holding barrel, and includes a first cam cylinder and a second cam cylinder each having a cam section on an inner surface thereof, and one end face of the first cam cylinder and one end face of the second cam cylinder are coupled to each other such that the first and second cam cylinders are rotated together.

BACKGROUND OF THE INVENTION 
The present invention relates to an optical apparatus such as a camera, 
which is so constituted that an optical element can be adjusted optically 
by rotating a cylindrical cam element. 
In general, most of optical apparatuses such as cameras include an 
adjustment mechanism which is so constituted that a specific optical 
element such as a zoom lens is moved back and forth in the optical axis 
direction by rotating a cylindrical cam element to perform an optical 
adjustment such as a change in magnification of images. 
The optical apparatus described above is increased in costs since a mold 
structure for molding the cam element is very complicated. To resolve this 
problem, it can be thought to mold a cylindrical cam element from a mold 
which is split into two in the optical axis direction. However, in this 
case, a parting line is formed in a predetermined position of the molded 
cam element or a position corresponding to a junction of the two-way split 
mold, and a recess for avoiding a burr is formed in a cam groove portion 
crossing the parting line. Therefore, another problem will occur in which 
a cam follower (e.g., pin) is easy to fall into the recess to prevent the 
cam follower from moving smoothly. 
Jpn. Pat. Appln. KOKAI Publication No. 6-51178 discloses a mechanism for 
countering the latter problem. According to this mechanism, the cross 
section of a cam follower is elliptical to prevent the cam follower from 
falling into a recess for avoiding a burr. 
It is to be wished that the optical apparatus as described in the above 
Publication is excellent in various points in which not only the 
cylindrical cam element is easily fabricated and the cam follower is 
smoothly moved but also the cam element is rugged, easy to insure 
accuracy, and compact in size because of a low parts count. However, the 
Publication does not refer to any technical means for satisfying these 
points. 
BRIEF SUMMARY OF THE INVENTION 
It is accordingly an object of the present invention to provide an optical 
apparatus such as a camera including a cylindrical cam element having the 
advantages of being rugged, easy to insure accuracy, and compact in size 
because of a low parts count. 
In order to attain the above object, the optical apparatus of the present 
invention has the following feature in constitution. The other features of 
the present invention will be clarified in the Description of the 
Embodiment. 
An optical apparatus comprises a cylindrical holding barrel, a plurality of 
moving lens frames which are held in the holding barrel such that the 
moving lens frames are moved back and forth in an optical axis direction, 
and a cam cylinder fitted on an outer surface of the holding barrel so as 
to move the moving lens frames, 
wherein the cam cylinder slides and rotates on the outer surface of the 
holding barrel, and includes a first cam cylinder and a second cam 
cylinder each having a cam section on an inner surface thereof, and one 
end face of the first cam cylinder and one end face of the second cam 
cylinder are coupled to each other such that the first and second cam 
cylinders are rotated together.

DETAILED DESCRIPTION OF THE INVENTION 
(Embodiment) 
In FIGS. 1 and 2, reference numeral 1 indicates a camera body; 2, an 
optical system (including optical components such as a zoom lens); 3, a 
finder; 4, an LCD unit for monitoring; 5, a stroboscope; 6, a release 
button; and 7, a power switch. Hereinafter a lens barrel unit including 
the optical system 2, which is the main part of the present invention, 
will be described in detail. 
A cylindrical case as illustrated in the center of FIG. 3 is a holding 
barrel 21 both ends of which are opened. A front lens barrel 22 is fixed 
to the front open end of the holding barrel 21, which is shown on the left 
side of FIG. 3, by a fixing means such as a screw, while a mounting 
substrate 23 is fixed to the rear open end of the holding barrel 21, which 
is shown on the right side of FIG. 3, by the fixing means. 
One end of each of paired guide shafts 24a and 24b is inserted into a hole 
of the mounting substrate 23 and adhesively fixed thereto, and the other 
end thereof is fitted to and supported by the rim portion of the front 
lens barrel 22. These paired guide shafts 24a and 24b are arranged in the 
holding barrel 21 in parallel to the optical axis. A moving lens frame 
group 25 (12G, 13G, 14G, etc.) is guided by the guide shafts 24a and 24b 
and moved slidably in the optical axis direction in the holding barrel 21. 
As will be clearly described later, the moving lens frame 14G moves along 
the guide shafts 24a and 24b, together with the moving lens frames 12G and 
13G, while it is mounted on a moving frame 14K. For convenience of 
description, in this embodiment, an optical component with a lens is 
denoted by G and that without a lens is represented by K. The components 
12G and 13G are used chiefly for zooming (ZOOM) and the components 14G and 
14K are for autofocus (AF), though they are not necessarily differentiated 
definitely. The components 14G and 14K are driven so as to be relatively 
brought close to and separated from each other by means of an AF motor 14m 
provided on the moving frame 14K, thereby adjusting the focus 
automatically. 
A plurality of ribs 21x, 21y and 21z (three ribs in this embodiment) are 
provided on the inner surface of the holding barrel 21 in parallel to the 
optical axis. These ribs extend from the front open end of the holding 
barrel 21 to the inner position thereof, which is beyond a light quantity 
adjusting unit 27 or an aperture shutter unit for adjusting a quantity of 
light passing therethrough. The ribs 21x, 21y and 21z therefore function 
as guide rails for the unit 27. The light quantity adjusting unit 27 is 
shaped like a disk and has notched portions 27x, 27y and 27z on its 
periphery. If the notched portions 27x, 27y and 27z are engaged with the 
ribs 21x, 21y and 21z, respectively to slide the light quantity adjusting 
unit 27 using the ribs as guides, the unit 27 can easily be inserted 
inwardly from the front open end of the holding barrel 21. 
The ribs 21x, 21y and 21z are provided at one end with screw holes 21a, 21b 
and 21c for screwing the front lens barrel 22. 
The front lens barrel 22 has mounting threads 22d formed on the inner 
surface thereof to detachably mount optical components such as an adapter 
lens and a filter from outside. The front lens barrel 22 also has screw 
inserting holes 22a to 22c corresponding to the screw holes 21a to 21c of 
the ribs 2lx to 21z. 
A cam cylinder 26, which is the principal element constituting a lens 
moving mechanism DR, is fitted on the outer surface of the holding barrel 
21 such that it can slidably contact and rotate thereon. The cam cylinder 
26 is designed to move the moving lens frame group 25 back and forth in 
the optical axis direction, and includes a first cam cylinder 26a having a 
convex cam M on its inner surface and a second cam cylinder 26b having a 
concave cam N thereon which are coupled to each other. The cam cylinder 26 
is rotated by power transmitted from a driving source, which is 
constituted of a zooming motor 23a and a reduction mechanism 23b and fixed 
on the mounting substrate 23, by means of a power transmission mechanism. 
As is clearly shown in FIG. 4, a convex portion V is formed on the coupling 
end face of the first cam cylinder 26a, and a concave portion W is 
provided in its corresponding portion of the coupling end face of the 
second cam cylinder 26b. These portions V and W can be engaged with each 
other. Thus, the two cam cylinders 26a and 26b are coupled to each other, 
without any special components, in such a manner that they cannot rotate 
in the circumferential direction relatively to each other. 
As illustrated in FIG. 5, the convex cam M of the first cam cylinder 26a 
has different cam faces Ma and Mb on both sides thereof. Cam followers 13a 
and 14a of the moving lens frame 13G and moving frame 14K are placed into 
contact with the cam faces Ma and Mb, respectively at a predetermined 
pressure. In other words, the moving lens frame 13G and moving frame 14K 
are displaced by a spring (not shown) in which direction they are brought 
close to each other, and pressed on the cam faces Ma and Mb, respectively. 
Thus, the moving lens frame 13G and moving frame 14K are moved in the 
optical axis direction by the different cam faces Ma and Mb by rotation of 
the cam cylinder 26. 
As shown in FIG. 6, a recess R is formed in a position of the outer surface 
of the first cam cylinder 26a, which corresponds to that of the convex 
cam. For this reason, the cam cylinder 26 is formed so as to have a 
uniform thickness. 
As illustrated in FIG. 7, the concave cam N of the second cam cylinder 26b 
is fitted to a cam follower pin (not shown) provided on the moving lens 
frame 12G. The frame 12G thus moves in the optical axis direction by 
rotation of the second cam cylinder 26b. The concave cam N has an open end 
Na which is closed by part of the front lens barrel 22 attached to the 
front end portion of the holding barrel 21. 
Returning to FIG. 3, the cam cylinder 26 is fitted rotatably on the outer 
surface of the holding barrel 21, and not moved in the optical axis 
direction but rotated by the power transmitted from the driving source, 
which is constituted of the zooming motor 23a and reduction mechanism 23b, 
by means of a power transmission. Thus, the moving lens frame group 25 
(12G, 13G, 14G, etc.) are moved in their own fashion in the optical axis 
direction. 
The light quantity adjusting unit 27 has a pair of driving sources or 
solenoid plungers 27a and 27b for driving an aperture member and a shutter 
member, respectively. 
The zooming motor 23a and reduction mechanism 23b, which serve as driving 
sources of the lens moving mechanism DR, and the solenoid plungers 27a and 
27b, which serve as those of the light quantity adjusting unit 27, are 
held in the holding barrel 21 without protruding therefrom, as is a 
flexible printed board (not shown), which connects the driving sources of 
the mechanisms DR and 27 and the electric circuits provided outside the 
holding barrel 21. 
It is needless to say that the present invention is not limited to the 
above embodiment and various changes and modifications can be applied 
thereto. 
(Features of the Embodiment) 
[1] In an optical apparatus according to the embodiment of the present 
invention, which comprises a cylindrical holding barrel 21, a plurality of 
moving lens frames 12G, 13G and 14G which are held in the holding barrel 
21 such that the moving lens frames are moved back and forth in an optical 
axis direction, and a cam cylinder 26 fitted on an outer surface of the 
holding barrel 21 so as to move the moving lens frames, the cam cylinder 
26 slides and rotates on the outer surface of the holding barrel 21, and 
includes a first cam cylinder 26a and a second cam cylinder 26b each 
having a cam section on an inner surface thereof, and one end face of the 
first cam cylinder 26a and that of the second cam cylinder 26b are coupled 
to each other such that they can be rotated together. 
In the optical apparatus described above, all the cam sections are formed 
on the inner surface of the cam cylinder 26, and no slit-like portions 
penetrate the cam cylinder 26. Therefore, the mechanical strength of the 
cam cylinder 26 is high, and it is unlikely that dust will intrude 
thereinto from outside. It is unnecessary to take a parting line into 
consideration at all. Since, furthermore, the cam cylinder 26 can be 
divided into the first and second cam cylinders 26a and 26b, their molding 
structures can be simplified. Consequently, the molding costs are low and 
the accuracy of required components is easy to insure. 
[2] In the optical apparatus as described in above item [1], a convex 
portion V is formed on the one end face of the first cam cylinder 26a, and 
a concave portion W is formed in a position of the one end face of the 
second cam cylinder 26b, which corresponds to the convex portion V, the 
convex portion V and the concave portion W being engaged with each other. 
In the foregoing optical apparatus, the convex and concave portions are 
engaged with each other like the teeth of a comb; therefore, the two cam 
cylinders 26a and 26b are coupled integrally as one component, without any 
special components, in such a manner that they cannot rotate relatively to 
each other. Consequently, the components can easily be assembled and the 
cam cylinder 26 is not likely to increase in whole length. 
[3] In the optical apparatus as described in above item [1] or [2], the 
first cam cylinder 26a has a convex cam M formed on the inner surface 
thereof, and the convex cam M has different cam faces Ma and Mb on both 
sides thereof. 
In the above-described optical apparatus, the cam faces Ma and Mb can be 
made correspondent with the moving lens frame 13G and the moving frame 
14K, respectively. The first cam cylinder 26a having such a constitution 
can be formed by a "sliding cutting type" mold with a simple structure, 
with the result that the molding costs can be reduced and the molded 
product can be increased in precision. 
[4] In the optical apparatus as described in above item [3], a recess is 
formed in a position of the outer surface of the first cam cylinder 26a 
which corresponds to that of the convex cam M. 
Since, in the above optical apparatus, the first cam cylinder 26a is formed 
to have a uniform thickness, a so-called mold distortion does not occur at 
the time of molding; therefore, a predetermined level of dimension 
precision of the cam section can be maintained. 
[5] In the optical apparatus as described in any one of above items [1] to 
[4], the second cam cylinder 26b has a concave cam N formed on the inner 
surface thereof, and the concave cam N has an open one end which is closed 
by part of the front lens barrel 22 attached to the front end portion of 
the holding barrel 21. 
Since, in the foregoing optical apparatus, one end of the concave cam N is 
opened, the second cam cylinder 26b can be formed by a "revolving cutting 
type" mold with a simple structure, and thus the molding costs are low. 
Since, furthermore, part of the front lens barrel 22 is used as a stopper 
of the cam follower of the moving lens frame group 25, any additional 
components are not required. In this respect, too, the apparatus can be 
manufactured at low costs and can be assembled easily.