Title: Lens apparatus, projection type optical apparatus and projection type image display apparatus
Abstract: An optical apparatus according to the present invention has a plurality of lens units which can move in the direction of an optical axis, each of the lens units has a cam follower, a guide member which guides the each lens unit in the direction of the optical axis, and a cam member which has cams engaging with the cam followers and drives the lens units in the direction of the optical axis by rotating. The cam followers of the lens units are disposed substantially straight in the direction of the optical axis.
Patent Number: 7,019,916 Issued on 03/28/2006 to Suzuki
| Inventors:
|
Suzuki; Shoji (Kanagawa, JP)
|
| Assignee:
|
Canon Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
200920 |
| Filed:
|
July 22, 2002 |
Foreign Application Priority Data
| Jul 24, 2001[JP] | 2001-223157 |
| Current U.S. Class: |
359/699; 359/700 |
| Current Intern'l Class: |
G02B 15/14 (20060101) |
| Field of Search: |
359/699-701,823,826,649
396/83,144,146
349/5
|
References Cited [Referenced By]
U.S. Patent Documents
| 4341459 | Jul., 1982 | Sugiura et al.
| |
| 4961635 | Oct., 1990 | Kondo et al.
| |
| 5634147 | May., 1997 | Machida.
| |
| 5654833 | Aug., 1997 | Fujike et al.
| |
| 5715482 | Feb., 1998 | Wakabayashi et al.
| |
| 5748390 | May., 1998 | Koiwai et al.
| |
| 5832317 | Nov., 1998 | Shimizu.
| |
| 5884106 | Mar., 1999 | Manabe.
| |
| 6147814 | Nov., 2000 | Kitazawa et al.
| |
| 6185375 | Feb., 2001 | Mikami.
| |
| 6400904 | Jun., 2002 | Kobayashi et al.
| |
| 6553185 | Apr., 2003 | Inaba et al.
| |
| 6639730 | Oct., 2003 | Muto et al.
| |
| 2001/0005288 | Jun., 2001 | Hayashi et al.
| |
| Foreign Patent Documents |
| 3-139623 | Jun., 1991 | JP.
| |
| LO H07-311326 | Nov., 1995 | JP.
| |
| LO H08-234282 | Sep., 1996 | JP.
| |
| LO H10-161193 | Jun., 1998 | JP.
| |
| LO H11-212144 | Aug., 1999 | JP.
| |
| LO 2001-59932 | Mar., 2001 | JP.
| |
Other References
English abstract of JPLO H08-234282.
English abstract of JPLO H07-311326.
English abstract of JPLO H10-161193.
English abstract of JPLO H11-212144.
English abstract of JPLO 2001-59932.
|
Primary Examiner: Mai; Huy
Attorney, Agent or Firm: Morgan & Finnegan.com
Claims
What is claimed is:
1. An optical apparatus comprising:
at least three lens units which can move in the direction of an optical axis,
each of said lens units having a sleeve,
two guides shafts which guide said lens units in the direction of the optical
axis, and
a guide portion which guides said at least three lens units in the direction
of the optical axis,
wherein said sleeves of said lens units engage with said two guide shafts alternately
in the direction of the optical axis.
2. The optical apparatus according to claim 1, further comprising:
cam followers which are provided in each of said lens units, and
a cam member which has cams engaging with said cam followers of said lens units
and drives said lens units in the direction of the optical axis by rotating,
wherein said cam member is a cylindrical cam and rotates about an axis substantially
parallel to the optical axis.
3. The optical apparatus according to claim 2, wherein said cylindrical cam is
made of resin.
4. A projector comprising:
an optical apparatus according to claim 1, and
an image forming device which forms an original image,
wherein said optical apparatus projects light, modulated by said image forming
device, on a projection surface.
5. An optical apparatus comprising:
at least three lens units which can move in the direction of an optical axis,
each of said lens units having a cam follower and a sleeve,
two guide shafts which guide said lens units in the direction of the optical
axis,
a guide portion which guides said at least three lens units in the direction
of the optical axis, and
a cam member which has cams engaging with said cam followers of said lens units
and drives said lens units in the direction of the optical axis by rotating,
wherein said cam member is a cylindrical cam and rotates about an axis substantially
parallel to the optical axis,
said sleeves of said lens units engage with said two guide shafts alternatley
in the direction of the optical axis, and
said cam followers of said lens units are arranged between said two guide shafts
and disposed substantially straight in the direction of the optical axis.
6. The optical apparatus according to claim 5, wherein said cylindrical cam is
made of resin.
7. A projector comprising:
an optical apparatus according to claim 5, and
an image forming device which forms an original image,
wherein said optical apparatus projects light, modulated by said image forming
device, on a projection surface.
8. An optical apparatus comprising:
a first lens unit, a second lens unit and a third lens unit which can move in
the direction of an optical axis, said first, second and third lens units being
orderly arranged in the optical axis,
a first guide portion which guides said first and third lens units,
a second guide portion which guides said second lens unit, and
a third guide portion which guides said first, second and third lens units in
the direction of the optical axis.
9. The optical apparatus according to claim 8, wherein said first guide portion
comprises a first shaft which engages with a first sleeve and a third sleeve respectively
provided on said first and third lens units,
said second guide portion comprises a second shaft which engages with a second
sleeve provided on said second lens unit, and
said third guide portion comprises an elongated groove portion which engages
with a first projection portion, a second projection portin and a third projection
portion respectively provided on said first, second and third lens units.
10. The optical apparatus according to claim 8, wherein the optical apparatus
is a projection optical system for a projector, which projects an image formed
by an image forming device on a projection surface.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical apparatus used for a projection type
image display apparatus or an image-taking apparatus.
2. Description of the Related Art
A projection lens barrel used for a projection type image display apparatus is
constituted so that zooming etc. may be performed by driving each moving lens unit
in the direction of an optical axis by arranging a cam ring so as to surround the
circumference of a lens barrel body, engaging a cam follower, which is provided
in each moving lens unit, with a cam groove section formed in the cam ring, and
rotating the cam ring.
FIG. 6 shows an example of a projection type image display apparatus in which
such a projection lens barrel is mounted.
Inside an apparatus housing
140, an optical box
150 where an
illumination optical system, a color separation system, an image display device,
a color synthesis system, etc. are incorporated, a projection lens barrel
120
which is mounted in a light emitting section of this optical box
150, a
power supply unit
130, and an electric circuit board
160 which controls
an image forming device, forming an original image, an illumination lamp, etc.
are contained.
In addition, the structure of the projection lens barrel
120 is shown
in
FIG.
5. Reference numeral
33 denotes a front fixed barrel and reference
numeral
39 denotes a rear fixed barrel. These front and rear fixed barrel
33 and
39 constitute a lens barrel body integrated into a piece.
A guide groove (not shown) for guiding a moving lens units, described later, in
the direction of the optical axis is formed in the inner circumference of the front
fixed barrel
33.
Reference numeral
31 denotes a zoom operation member provided in
the outer circumference of the front fixed barrel
33. Reference numeral
32 denotes a cam ring rotatably arranged around the optical axis in the
outer circumference of the front fixed barrel
33, and is combined with the
zoom operation member
31 with screws (not shown).
Inside the lens barrel body, a plurality of moving lens holding barrels
35,
36,
37, and
38 which supports second to fifth lenses II to
V for performing zooming and can move in the direction of the optical axis is contained.
In three locations in the circumferential direction of these respective moving
lens holding barrels
35 to
38, cam followers
40a (
40b,
40c),
41a (
41b,
41c),
42a
(
42b,
42c), and
43a (
43b,
43c) are mounted, and each cam follower engages with each of cam
groove sections
32a to
32d for each moving lens unit
which is formed in the cam ring
32.
Reference numeral
34 denotes a first lens holding barrel holding
a first lens I for focusing by moving in the direction of the optical axis, and
a male helicoid section
34a is formed in its outer circumference.
The first lens holding barrel
34 engages with a focus operation member
30
so as to rotate integrally with the focus operation member
30. Since engaging
with a female helicoid section
33a formed in the front inner circumference
in the front fixed barrel
33, the male helicoid section
34a can
move this first lens holding barrel
34 in the direction of the optical axis
by rotating the first lens holding barrel
34 by rotational operation of
the focus operation member
30, and can perform the focusing.
However, since the cam ring
32 is arranged so as to surround the
outer circumference of the lens barrel body in the lens barrel having the above-described
structure, the outer diameter of the lens barrel becomes large in the whole circumferential direction.
In addition, since it is necessary to mount the cam followers, engaged with the
cam groove sections
32a to
32d of the cam ring
32,
in three locations in the circumferential direction of respective moving lens holding
barrels
35 to
38, assembly operation is complicated, and in addition,
it also needs much labor to perform adjustment for removing each minute tilt of
the lenses II to V, which derives from dispersion in dimensional accuracy as parts
every three cam followers, to the optical axis.
Furthermore, in the above-described lens barrel, the cam ring
32
is formed as a metal part from a viewpoint of securing the positional accuracy
of the moving lens holding barrels
35 to
38.
However, this cam ring
32 which is a metal part receives noise generated
in the power supply unit
130 shown in FIG. 6 to become a factor of generating
noise in the electric circuit board
160 near the cam ring
32. This
may become a cause of a trouble at the time of driving the apparatus by noise arising
in the electric circuit board
160.
SUMMARY OF THE INVENTION
The present invention provides an optical apparatus (and projection type optical
apparatus), which can lessen the outer diameter of the optical apparatus, whose
assembly operation is easy, and which hardly has tilts of lenses to an optical
axis, and a projection type image display apparatus which use the projection type
optical apparatus.
The optical apparatus according to the present invention comprises: a plurality
of lens units which can move in the direction of an optical axis, each of the lens
units has a cam follower, a guide member which guides the each lens unit in the
direction of the optical axis, and a cam member which has cams engaging with the
cam followers and drives the lens units in the direction of the optical axis by
rotating. The cam followers of the lens units are disposed substantially straight
in the direction of the optical axis.
Therefore, since points of action, which are engaging points of the cam
member and the cam followers of the lens units, and guiding points, which are engaging
points of the lens units and the guide member, can be close, it is easy to obtain
the good positional accuracy of the lens units.
The optical apparatus according to the present invention comprises, at least
three lens units which can move in the direction of an optical axis, each of the
lens units has a cam follower and a sleeve, two guide shafts which guide the lens
units in the direction of the optical axis, and a cam member which has cams engaging
with the cam followers and drives the lens units in the direction of the optical
axis by rotating. The cam member is a cylindrical cam and rotates about an axis
substantially parallel to the optical axis. The sleeves engage with the two guide
shafts alternately in the direction of the optical axis. The cam followers are
arranged between the two guide shafts and disposed substantially straight in the
direction of the optical axis.
In this manner, by arranging the cam member, which is a cylindrical cam, on a
part of outer circumference of an apparatus, it becomes possible to lessen the
outer diameter of a portion, other than a portion in which the cam member is arranged,
in the optical apparatus in comparison with a case of arranging a cam ring over
whole apparatus circumference like a conventional way.
Further specifically, it is good to arrange each of the guide shafts within
a range of 45° with respect to the cam member (cylindrical cam) about the
optical axis. And more preferably, it is good to arrange each of the guide shafts
within a range of 30° with respect to the cam member (cylindrical cam) about
the optical axis.
In addition, by properly (alternately) assigning each guide shaft, with which
each sleeve of the lens units engages, between two guide shafts, it becomes possible
to take the long engagement length of each sleeve to the guide shaft, and hence,
it is possible to realize the optical apparatus where tilts of lens units to the
optical axis hardly arise.
Furthermore, in the optical apparatus (lens barrel), only one cam follower
engaging with the cam of the cam member may be mounted every one lens unit, and
hence, not only it is easy to perform assembly operation, but also it is easy to
remove a minute tilt resulting from dispersion in the part accuracy of the cam followers.
In addition, a projection type image display apparatus according to the present
invention projects light, modulated by an image forming device which forms an original
image, by the above-described optical apparatus on a projection surface. In this
projection type image display apparatus, in the case that an electric circuit board
is arranged substantially parallel to the optical axis of the optical apparatus,
it is good to make a cam member of resin, or to arrange the optical apparatus (lens
barrel) so that the cam member and the guide member (or guide shafts) are located
in the opposite side of the electric circuit board with sandwiching the optical axis.
Although the cam member may be made of metal, it is possible by making it
of resin to prevent the cam member from becoming a noise-generating factor in an
electric circuit board with receiving noise from a power supply unit. In addition,
by arranging two guide shafts, which are metal parts, in the opposite side of the
electric circuit board with sandwiching the optical axis, it becomes possible to
separate metal parts of the optical apparatus from the electric circuit board,
and hence, it becomes possible to further securely prevent the metal parts of the
optical apparatus from becoming a factor of generating noise in the electric circuit board.
A detailed configuration of the lens apparatus (or projection type optical apparatus),
and projection type image display apparatus of the invention will be apparent from
the embodiments, described below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a lens barrel which is an embodiment of the present invention;
FIG. 2 is an exploded perspective view of the lens barrel shown in FIG. 1;
FIG. 3 is a front sectional view of the lens barrel shown in FIG. 1 in view
of the direction of an optical axis;
FIG. 4 is a perspective view of a projection type image display apparatus where
the lens barrel shown in FIG. 1 is mounted;
FIG. 5 is a sectional view of a conventional lens barrel; and
FIG. 6 is a perspective view of a projection type image display apparatus where
the conventional lens barrel is mounted.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, preferred embodiments of the invention will be described
in detail with reference to the drawings.
FIGS. 1 and 2 show the structure of a projection lens barrel (optical apparatus
or projection type optical apparatus) which is an embodiment of the present invention.
In these figures, reference numeral
9 denotes a fixed barrel (lens barrel
body), and first to fifth holding barrels
1,
3 to
5,
7,
holding first to fifth lenses I to V are contained inside it.
While the first lens holding barrel
1 holds the first lens I for focusing,
it has a focal operation ring section, and a male helicoid section
1a
is formed in the rear section of its circumference. This male helicoid section
1a engages with a female helicoid section
9g formed
in the front section of inner circumference of the fixed barrel
9.
Reference numeral
2 is a zoom ring rotatably arranged in the front
section of outer circumference of the fixed barrel
9, and a gear section
2a is formed in the rear section of its outer circumference. In addition,
pass-through slot sections
2b shown in FIG. 2, which have predetermined
length are formed in the circumferential direction are formed in three locations
in the circumferential direction of this zoom ring
2, and thrust regulating
sections
9d formed in three locations of outer circumference of the
fixed barrel
9 are inserted in these pass-through slot sections
2b.
When the zoom ring
2 is rotated, further rotation of the zoom ring
2
is prevented since an end face provided in the inner circumference of the zoom
ring
2 contacts to a stopper
17 shown in FIG.
1.
The second lens holding barrel
3 holds the second lens II, and constitutes
a lens unit. A cam follower
14a is mounted in a location in the circumferential
direction of this second lens holding barrel
3, and a sleeve section
3a
is formed in a location near to this cam follower
14a in one
direction of the circumferential direction. Furthermore, a guide projection
3b
is formed in an opposite location of the cam follower
14a with
sandwiching a lens's optical axis L in the second lens holding barrel
3.
The third lens holding barrel
4 holds the third lens III, and constitutes
a lens unit. A cam follower
14b is mounted in a location in the circumferential
direction of the third lens holding barrel
4, and a sleeve section
4a
is formed in a location near to the cam follower
14b in the other
direction (the opposite side of the sleeve section
3a in the second
lens holding barrel
3) of the circumferential direction. Furthermore, a
guide projection
4b is formed in an opposite location of the cam
follower
14b with sandwiching the lens's optical axis L in the third
lens holding barrel
4.
The fourth lens holding barrel
5 holds the fourth lens holding frame
6
(holding the fourth lens IV) described later, and constitutes a lens unit. A cam
follower
14c is mounted in a location in the circumferential direction
of this fourth lens holding barrel
5, and a sleeve section
5a
is formed in a location near to the cam follower
14c in one direction
(the same side of the sleeve section
3a) of the circumferential direction.
Furthermore, a guide projection
5b is formed in an opposite location
of the cam follower
14c with sandwiching the lens's optical axis
L in the fourth lens holding barrel
5.
The fourth lens holding frame
6 is arranged in the inner circumference
of the fourth lens holding barrel
5, and is combined with the fourth lens
holding barrel
5 in three locations through the cam follower
15.
Eccentric cam followers are used in two out of three cam followers
15 for
optical axis adjustment of the fourth lens IV held by the fourth lens holding frame
6. Since the fourth lens holding frame
6 can rotate to a surface
orthogonal to the optical axis L of other lenses by rotating this eccentric cam
follower
15, an optical axis of the fourth lens IV can be aligned with the
optical axis L of other lenses.
The fifth lens holding barrel
7 holds the fifth lenses V, and constitutes
a lens unit. A cam follower
14d is mounted in a location in the circumferential
direction of this fifth lens holding barrel
7, and a sleeve section
7a
is formed in a location near to the cam follower
14d in the other
direction (the same side of the sleeve section
4a of the third lens
holding barrel
4) of the circumferential direction. Furthermore, a guide
projection
7b is formed in an opposite location of the cam follower
14d with sandwiching the lens's optical axis L in the fifth lens
holding barrel
7.
In addition, the second lens II and fourth lens IV are lenses for variable power,
and the third lens III and fifth lenses V are correction lenses for correcting
the movement of a focal plane at the time of zooming.
Reference numeral
11 denotes a mount plate, and on this mount plate
11, a rear end of the fixed barrel
9, and a front end section of
the sixth lens holding barrel
8 holding the sixth lens VI are screwed.
Reference numeral
8 denotes a sixth lens holding barrel holding
the sixth lens VI, and is fixed to a rear face of the mount plate
11 with
a screw
8a.
Reference numeral
10 denotes a cylindrical cam (cam member) and
is a molded part with resin. A shaft section of a gear shaft
12 in which
a gear section
12a is provided in its front end is inserted in the
inner circumference of the cylindrical cam
10. The gear shaft
12
and cylindrical cam
10 are assembled so that rotation in one piece can be
performed in key coupling.
Then, a front section and a rear section of the gear shaft
12 are supported
by bearing sections
9a and
9b, formed in front and
rear sections which are parts of outer circumference of the fixed barrel
9
in the circumferential direction so that it can be rotated about an axis substantially
parallel to the optical axis L. In addition, the gear shaft
12 is prevented
from disjoining (moving in the direction of the optical axis L) from the bearing
sections
9a and
9b by a stop ring
16.
A gear section
12a of the gear shaft
12 mounted on the fixed
barrel
9 in this manner engages with a gear section
2a formed
in the zoom ring
2. Therefore, by rotating (manually operating) the zoom
ring
2, the rotation is transferred from the gear section
2a to
the gear section
12a, the gear shaft
12 rotates, and the cylindrical
cam
10 rotates. In addition, it is also good to make such structure that
the cylindrical cam
10 is rotated by an electric rotation mechanism rotating
the gear section
12a with a motor (not shown).
Four cam groove sections
10a to
10d are formed in
the outer circumference of the cylindrical cam
10. The cam followers
14a
to
14d of above-described respective lens holing barrels
3,
4,
5, and
7 which penetrate the groove
9e formed
in the fixed barrel
9 engage with these cam grooves sections
10a
to
10d respectively. As is evident also from FIGS. 1 and 2, respective
cam followers
14a to
14d are engaged with cam groove
sections
10a to
10d of the cylindrical cam
10
in the state of being arranged in a substantially straight line in the direction
of the optical axis L.
Furthermore, it is also good to make such structure that the cam groove
sections
10a to
10d formed in the outer periphery of
the cylindrical cam
10 are made to be convex cam threads, and the cam followers
14a to
14d of respective lens holding barrels
3,
4,
5, and
7 are engaged with these convex cam threads.
In addition, the sleeve sections
3a and
5a of the
second lens holding barrel
3 and fourth lens holding barrel
5 engage
with a guide shaft
13a, and the sleeve sections
4a and
7a of the third lens holding barrel
4 and fifth lens holding
barrel
7 engage with a guide shaft
13b. These guide shafts
13a and
13b are supported in both sides of them by
supporting hole sections
9f and
11a formed in a rear
section of the inner circumference of the fixed barrel
9, and a front section
of the mount plate
11, and extend in substantially parallel to the optical axis.
Here, FIG. 3 schematically shows the cross-sectional structure when viewing
the above-described lens barrel from the front in the direction of the optical
axis. In addition, only the members required for explanation are shown in FIG.
3.
As shown in this figure, in view of the direction of the optical axis, two guide
shafts
13a and
13b adjoin nearly to the cylindrical
cam
10, namely, are arranged with adjoining nearly in an angle range θ
smaller than 30° in the circumferential direction of the lens's optical axis
L, respectively.
In addition, in this embodiment, although θ is made to be in a range smaller
than 30° to some extent, it is possible to obtain an effect equivalent to
the above if they are arranges in an angular range equal to or less than 30°,
and furthermore, it is possible to obtain an effect mostly equivalent to the above
even if they are arranged in an angular range of about 45°.
The sleeve sections
3a and
5a of the second lens
holding barrel
3 and fourth lens holding barrel
5 extend backward
from cylindrical body sections of the second lens holding barrel
3 and fourth
lens holding barrel
5, respectively. The sleeve sections
4a and
7a of the third lens holding barrel
4 and fifth lens holding
barrel
7 extend forward from cylindrical body sections of the third lens
holding barrel
4 and fifth lens holding barrel
7, respectively.
Thus, it is possible to secure the sufficient engagement length of these sleeve
sections
3a,
4a,
5a, and
7a
to the guide shafts
13a and
13b by alternately
assigning by turns the sleeve sections
3a,
4a,
5a,
and
7a, which engage with two guide shafts
13a and
13b, between the two guide shafts
13a and
13b.
For this reason, since it is possible to prevent tilts of the second lens holding
barrel
3 to fifth lens holding barrel
6 to the lens's optical axis
L, it is possible to obtain the stable optical performance of the lens barrel.
Moreover, between the guide shafts
13a and
13b, the
cam followers
14a to
14d of respective lens holding
barrels
3,
4,
5, and
7 are arranged in a substantially
straight line in the direction of the optical axis L, and respective cam followers
14a to
14d are engaged with the cam groove sections
10a to
10d of the cylindrical cam
10. Owing
to this, since a point of action, which is an engaging point of the cylindrical
cam
10 and cam follower of each lens holding barrel (lens unit), and a guiding
point, which is an engaging point of each lens holding barrel (lens unit) and guide
shaft, are close, it is possible to stably perform movement in the direction of
the optical axis with keeping positional accuracy of each lens holding barrel (lens unit).
In addition, the guide projections
3b to
7b provided
in the second lens holding barrel
3 to fifth lens holding barrel
6
engage with the guide groove section
9c formed in the fixed barrel
9. Owing to this, it is possible to prevent each lens holding barrel from
rotating about the guide shaft with which each sleeve section engaged.
Furthermore, among respective components described above, the guide
shafts
13a and
13b are metal parts, and all the other
ones are resin-molded parts.
Here, the assembly procedure of the above-described lens barrel
20 will
be described by using FIGS. 1 and 2. First, respective lenses are incorporated
into the first lens holding barrel
1, second lens holding barrel
3,
third lens holding barrel
4, fourth holding frame
6, fifth lens holding
barrel
7, and sixth lens holding barrel
8. Then, the fourth holding
frame
6 and fourth lens holding barrel
5 are combined with the cam
follower
15. Thereby, each lens unit is completed.
Next, the cam followers
14a to
14d are mounted
in the second lens holding barrel
3 to fifth lens holding barrel
7.
Then, with incorporating guide shafts
13a and
13b in
the fixed barrel
9 and engaging the sleeve sections
3a to
7a of the second lens holding barrel
3 to the fifth lens holding
barrel
7 with these guide shafts
13a and
13b,
the guide projections
3b to
7b are engaged with the
guide groove section
9c of the fixed barrel
9.
Then, after alignment of the mount plate
11 to the fixed barrel
9
with aligning the mount plate
11 with the guide shafts
13a and
13b, they are combined in the fixed barrel
9 with screws (not shown).
Next, the groove section
2b of the zoom ring
2 is fixed
to the fixed barrel
9 with aligning the groove section
2b with
a thrust regulating section
9d, the first lens holding barrel
1
is combined with the fixed barrel
9 in helicoid coupling, and the stopper
screw
18 for focusing is screwed.
Furthermore, with engaging respective cam groove sections
10a
to
10d of the cylindrical cam
10 with the cam followers
14a to
14d of respective lens holding barrels
3
to
7, the gear shaft
12 is passed through the bearing sections
9a
and
9b of the fixed barrel
9, and the cylindrical cam
10 from the front. At this time, the gear shaft
12 and cylindrical
cam
10 are combined in key coupling. Then, the stop ring
16 is mounted
in the rear end of the gear shaft
12.
Next, a WIDE end position of zoom is adjusted, the stopper
17 is fixed
with a screw
17a, then, with performing the balancing of zoom, flange
back adjustment is performed by the optical axis adjustment of the sixth lens holding
barrel
8 (sixth lens VI), and the assembly and adjustment of the projector
lens barrel
20 is completed.
In the lens barrel
20 constituted as described above, since the cylindrical
cam
10 is arranged in a part of outer circumference of the fixed barrel
9, it is possible to lessen the outer diameter of a portion, other than
a portion in which the cylindrical cam
10 is arranged, in a lens barrel
20 in comparison with a case of arranging a cam ring over the whole circumference
of a lens barrel like a conventional way.
In addition, since the guide shafts
13a and
13b are
arranged nearly in contact with the cylindrical cam
10 in the circumferential
direction of the lens barrel
20, points of action which are engaging points
of cam groove sections
10a to
10d of the cylindrical
cam
10 and cam followers
14a to
14d of respective
lens holding barrels, and guide points which are engaging points of the sleeve
sections
3a to
7a of respective lens holding barrels
and guide shafts
13a and
13b become close. Furthermore,
since the sleeve sections
3a to
7a of respective lens
holding barrels alternately engage with two guide shafts
13a and
13b, it is possible to lengthen the engaging length of each sleeve
section to the guide shaft. Hence, since it is easy to obtain the good positional
accuracy of each lens holding barrel, it is possible for the lens barrel
20
to be a lens barrel in which tilts of lens units to the optical axis L hardly arise.
Furthermore, since one of the cam followers
14a to
14d
which engage with the cylindrical cam
10 is mounted in each of the lens
holding barrels
3 to
7 in this embodiment, not only assembly operation
is easy, but also it is possible to easily remove a minute tilt even if the minute
tilt of respective lens holding barrels
3 to
7 resulting from dispersion
in the part accuracy of respective cam followers arises.
The projection lens barrel
20 constituted as described above is incorporated
in a projection type image display apparatus shown in FIG.
4. In addition,
FIG. 4 shows a state where a top cover in an apparatus housing of the projection
type image display apparatus is removed.
Inside an apparatus housing
40 of this projection type image display
apparatus, an optical box
50 where an illumination optical system, a color
separation system, an image forming device, a color synthesis system, etc. which
are not shown are incorporated, the above-described projection lens barrel
20
which is mounted in a light emitting section of this optical box
50, a power
supply unit
30 used as a power supply for this apparatus, and an electric
circuit board
60 which controls the image forming device, illumination lamp,
etc. are contained.
The electric circuit board
60 is arranged above the optical box
50
and projection lens barrel
20 closely.
Here, when mounting the mount plate
11 of the projection lens barrel
20 on the light emitting section of the optical box
50, the projection
lens barrel
20 is mounted in such a direction that the cylindrical cam
10
and guide shafts
13a and
13b are located downward,
that is, in the opposite side of the electric circuit board
60 with sandwiching
a lens's optical axis.
Thereby, the guide shafts
13a and
13b which
are metal parts can be arranged with being apart from the electric circuit board
60.
Therefore, in addition to the cylindrical cam
10 formed with resin,
it is possible to certainly avoid that a metal part of the lens barrel
20
becomes a noise-generating factor in the electric circuit board
60 by receiving
noise from the power supply unit
30.
In addition, although a lens barrel mounted in a projection type image display
apparatus is described in this embodiment, the lens barrel of the present invention
can be also mounted in other optical instruments such as an image-taking apparatus.
While preferred embodiments have been described, it is to be understood that
modification and variation of the present invention may be made without departing
from the sprit or scope of the following claims.
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