U.S. patent application number 09/792242 was filed with the patent office on 2001-07-26 for optical element, optical system using optical element, and optical device with optical element.
Invention is credited to Iida, Seiji, Kawano, Kenji, Sekita, Makoto, Uehara, Tsukasa.
Application Number | 20010009477 09/792242 |
Document ID | / |
Family ID | 27530027 |
Filed Date | 2001-07-26 |
United States Patent
Application |
20010009477 |
Kind Code |
A1 |
Uehara, Tsukasa ; et
al. |
July 26, 2001 |
Optical element, optical system using optical element, and optical
device with optical element
Abstract
In an optical element (B1) prepared by integrally forming, on
surfaces of a transparent member, a refracting surface (R2) for
receiving a light beam, a plurality of reflecting surfaces (R3, R4,
R5) with curvatures, and a refracting surface (R6) for outputting
the light beam reflected by the plurality of reflecting surfaces, a
reference portion (7) for defining the position of the optical
element in a predetermined direction with respect to a Y'-Z' plane
including an incident reference axis (5) and an exit reference axis
(5) of at least one reflecting surface of the optical element (B1)
is formed on the optical element.
Inventors: |
Uehara, Tsukasa;
(Kawasaki-shi, JP) ; Sekita, Makoto;
(Yokohama-shi, JP) ; Kawano, Kenji; (Tokyo,
JP) ; Iida, Seiji; (Tokyo, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
345 Park Avenue
New York
NY
10154-0053
US
|
Family ID: |
27530027 |
Appl. No.: |
09/792242 |
Filed: |
February 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09792242 |
Feb 23, 2001 |
|
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08915044 |
Aug 20, 1997 |
|
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6243208 |
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Current U.S.
Class: |
359/627 ;
359/631 |
Current CPC
Class: |
G02B 17/0896 20130101;
G02B 17/0848 20130101; G02B 17/086 20130101 |
Class at
Publication: |
359/627 ;
359/631 |
International
Class: |
G02B 027/10; G02B
027/14 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 22, 1996 |
JP |
8-239840 |
Oct 31, 1996 |
JP |
8-290047 |
Oct 31, 1996 |
JP |
8-290048 |
Oct 31, 1996 |
JP |
8-290049 |
Oct 31, 1996 |
JP |
8-290050 |
Claims
What is claimed is:
1. An optical element prepared by integrally forming, on surfaces
of a transparent member, a refracting surface for receiving a light
beam, a plurality of reflecting surfaces with curvatures, and a
refracting surface for outputting the light beam reflected by the
plurality of reflecting surfaces, comprising: a reference portion
for defining a position of said optical element in a predetermined
direction with respect to a plane including an incident and exit
reference axes of at least one reflecting surface of said optical
element.
2. An optical element prepared by integrally forming, on surfaces
of a transparent member, a refracting surface for receiving a light
beam, a plurality of reflecting surfaces with curvatures, and a
refracting surface for outputting the light beam reflected by the
plurality of reflecting surfaces, comprising: a reference portion
for defining a position of said optical element in a predetermined
direction with respect to a plane perpendicular to a reference axis
of said optical element at an intersection between the incident
refracting surface or exit refracting surface and the reference
axis of said optical element.
3. The element according to claim 1, wherein the predetermined
direction is a direction parallel and/or perpendicular to the plane
including the reference axes.
4. The element according to claim 2, wherein the predetermined
direction is a direction parallel and/or perpendicular to the plane
perpendicular to the reference axis.
5. The element according to claim 1, wherein a center of gravity of
said optical element is present within a region included in a
projection of said reference portion onto said optical element in a
direction perpendicular to the plane including the reference axis
of said optical element.
6. The element according to claim 2, wherein a center of gravity of
said optical element is present within a region included in a
projection of said reference portion onto said optical element in a
direction perpendicular to the plane including the reference axis
of said optical element.
7. The element according to claim 1, wherein said reference portion
is formed on a region other than a light ray effective portion of
said optical element.
8. The element according to claim 2, wherein said reference portion
is formed on a region other than a light ray effective portion of
said optical element.
9. The element according to claim 1, wherein said reference portion
is made up of a plurality of flat surfaces.
10. The element according to claim 2, wherein said reference
portion is made up of a plurality of flat surfaces.
11. The element according to claim 3, wherein said reference
portion has a flat surface parallel to the plane including the
reference axis of said optical element and at least two flat
surfaces perpendicular to the plane.
12. The element according to claim 4, wherein said reference
portion has a flat surface parallel to the plane including the
reference axis of said optical element and at least two flat
surfaces perpendicular to the plane.
13. The element according to claim 1, wherein said reference
portion is a hole portion or projected portion formed on said
optical element.
14. The element according to claim 2, wherein said reference
portion is a hole portion or projected portion formed on said
optical element.
15. The element according to claim 13, wherein the hole portion or
the projected portion has a cylindrical surface having a central
axis perpendicular to the plane including the reference axis of
said optical element.
16. The element according to claim 14, wherein the hole portion or
the projected portion has a cylindrical surface having a central
axis perpendicular to the plane including the reference axis of
said optical element.
17. The element according to claim 1, wherein an auxiliary portion
for assisting in determining the position of said optical element
is formed on said optical element.
18. The element according to claim 2, wherein an auxiliary portion
for assisting in determining the position of said optical element
is formed on said optical element.
19. The element according to claim 17, wherein said auxiliary
portion is set to be parallel and/or perpendicular to said
reference portion.
20. The element according to claim 18, wherein said auxiliary
portion is set to be parallel and/or perpendicular to said
reference portion.
21. The element according to claim 19, wherein a plurality of
auxiliary portions equivalent to said auxiliary portions are
formed, and at least one of the auxiliary portions faces said
reference portion.
22. The element according to claim 20, wherein a plurality of
auxiliary portions equivalent to said auxiliary portions are
formed, and at least one of the auxiliary portions faces said
reference portion.
23. The element according to claim 21, wherein a center of gravity
of said optical element is present in a region sandwiched between
said reference portion and the auxiliary portion facing said
reference portion.
24. The element according to claim 22, wherein a center of gravity
of said optical element is present in a region sandwiched between
said reference portion and the auxiliary portion facing said
reference portion.
25. The element according to claim 17, wherein said reference
portion and said auxiliary portion are formed on a region other
than a light ray effective portion of said optical element.
26. The element according to claim 18, wherein said reference
portion and said auxiliary portion are formed on a region other
than a light ray effective portion of said optical element.
27. The element according to claim 25, wherein said auxiliary
portion is made up of a plurality of flat surfaces.
28. The element according to claim 26, wherein said auxiliary
portion is made up of a plurality of flat surfaces.
29. The element according to claim 27, wherein said auxiliary
portion has a flat surface parallel to the plane including the
reference axis of said optical element and at least one flat
surface perpendicular to the plane.
30. The element according to claim 28, wherein said auxiliary
portion has a flat surface parallel to the plane including the
reference axis of said optical element and at least one flat
surface perpendicular to the plane.
31. The element according to claim 25, wherein said auxiliary
portion is a hole portion formed on said optical element.
32. The element according to claim 26, wherein said auxiliary
portion is a hole portion formed on said optical element.
33. The element according to claim 31, wherein the hole portion or
the projected portion has a cylindrical surface having a central
axis perpendicular to the plane including the reference axis of
said optical element.
34. The element according to claim 32, wherein the hole portion or
the projected portion has a cylindrical surface having a central
axis perpendicular to the plane including the reference axis of
said optical element.
35. The element according to claim 31, wherein the hole portion or
the projected portion has an elliptic cylindrical surface having a
central axis perpendicular to the plane including the reference
axis of said optical element.
36. The element according to claim 32, wherein the hole portion or
the projected portion has an elliptic cylindrical surface having a
central axis perpendicular to the plane including the reference
axis of said optical element.
37. An optical system formed by stationarily or movably holding
said optical element of claim 1 via a holding member, which has a
coupling portion fitted or coupled to said reference portion.
38. An optical system formed by stationarily or movably holding
said optical element of claim 2 via a holding member, which has a
coupling portion fitted or coupled to said reference portion.
39. An optical system formed by stationarily or movably holding
said optical element of claim 17 via a holding member, which has a
coupling portion fitted or coupled to said reference portion.
40. An optical system formed by stationarily or movably holding
said optical element of claim 18 via a holding member, which has a
coupling portion fitted or coupled to said reference portion.
41. The system according to claim 37, wherein a predetermined air
layer is formed between said holding member and said optical
element except for said coupling portion of said holding
member.
42. The system according to claim 38, wherein a predetermined air
layer is formed between said holding member and said optical
element except for said coupling portion of said holding
member.
43. The system according to claim 39, wherein a predetermined air
layer is formed between said holding member and said optical
element except for said coupling portion of said holding
member.
44. The system according to claim 40, wherein a predetermined air
layer is formed between said holding member and said optical
element except for said coupling portion of said holding
member.
45. An optical system comprising an optical element prepared by
integrally forming, on surfaces of a transparent member, a
refracting surface for receiving a light beam, a plurality of
reflecting surfaces with curvatures, and a refracting surface for
outputting the light beam reflected by the plurality of reflecting
surfaces, said optical element having a fitting portion formed
integrally therewith, said fitting portion being fitted on guide
means for defining a moving direction of said optical element, and
said optical element being arranged to be movable in the defined
direction.
46. The system according to claim 45, wherein a central axis of
said fitting portion is set to be parallel to a plane including an
incident and exit reference axes of at least one reflecting surface
of said optical element.
47. The system according to claim 45, wherein a central axis of
said fitting portion is in a plane including an incident and exit
reference axes of at least one reflecting surface of said optical
element.
48. An optical device comprising an optical element in which a
light beam enters said optical element via one refracting surface,
is repetitively reflected by a plurality of reflecting surfaces,
and leaves said optical element from another refracting surface,
said optical element being fixed to a support member at one end
portion thereof.
49. An optical device comprising a zoom optical system having a
plurality of optical elements in each of which a light beam enters
said optical element via one refracting surface, is repetitively
reflected by a plurality of reflecting surfaces, and leaves said
optical element from another refracting surface, at least one
optical element being fixed to a support member at one end portion
thereof.
50. The device according to claim 48, wherein said optical element
comprises a projection at a position separated from the refracting
and reflecting surfaces of the light beam, and said projection is
fixed to said support member.
51. The device according to claim 49, wherein said optical element
comprises a projection at a position separated from the refracting
and reflecting surfaces of the light beam, and said projection is
fixed to said support member.
52. The device according to claim 50, wherein said projection of
said optical element projects in a direction perpendicular to a
longitudinal direction of said optical element.
53. The device according to claim 51, wherein said projection of
said optical element projects in a direction perpendicular to a
longitudinal direction of said optical element.
54. The device according to claim 52, wherein a slit portion or a
groove portion is formed on said projection of said optical element
so as not to adversely influence refraction or reflection of the
light beam when said optical element is fixed to said support
member.
55. The device according to claim 53, wherein a slit portion or a
groove portion is formed on said projection of said optical element
so as not to adversely influence refraction or reflection of the
light beam when said optical element is fixed to said support
member.
56. The device according to claim 50, wherein said optical element
has a gate used upon forming said optical element at a fixing
portion side thereof.
57. The device according to claim 51, wherein said optical element
has a gate used upon forming said optical element at a fixing
portion side thereof.
58. An optical device comprising a zoom optical system having a
plurality of optical elements in each of which a light beam enters
said optical element via one refracting surface, is repetitively
reflected by a plurality of reflecting surfaces, and leaves said
optical element from another refracting surface, wherein at least
one optical element of said zoom optical system is fixed to a
support member at one end portion thereof, has a plurality of
projections in a longitudinal direction thereof, and is placed on
an extended portion of said support member via said plurality of
projections.
59. The device according to claim 58, wherein said plurality of
projections of said optical element are formed to be separated in
the longitudinal direction and a widthwise direction of said
optical element.
60. An optical device comprising an optical element in which a
light beam enters said optical element via one refracting surface,
is repetitively reflected by a plurality of reflecting surfaces,
and leaves said optical element from another refracting surface,
wherein said optical element has a plurality of projections in a
longitudinal direction thereof, is arranged on a support member via
said plurality of projections, and is fixed to said support member
by adhering one of said plurality of projections to said support
member.
61. The device according to claim 58, wherein said support member
comprises a butt portion for receiving said plurality of
projections of said optical element so as to attain high-precision
positioning.
62. The device according to claim 60, wherein said support member
comprises a butt portion for receiving said plurality of
projections of said optical element so as to attain high-precision
positioning.
63. An optical device comprising a zoom optical system having a
plurality of optical elements in each of which a light beam enters
said optical element via one refracting surface, is repetitively
reflected by a plurality of reflecting surfaces, and leaves said
optical element from another refracting surface, and driving means
for driving said zoom optical system to attain zooming, wherein the
zooming is done by moving first and second movable bases along a
guide member in an optical axis direction in which light leaving
one optical element mounted on said first movable base of said
plurality of optical elements of said zoom optical system enters
another optical element mounted on said second movable base, and
said one optical element and said other optical element are
respectively attached to said first and second movable bases at
one-end portions thereof.
64. An optical device comprising a zoom optical system having a
plurality of optical elements in each of which a light beam enters
said optical element via one refracting surface, is repetitively
reflected by a plurality of reflecting surfaces, and leaves said
optical element from another refracting surface, and driving means
for driving said zoom optical system to attain zooming, wherein the
zooming is done by moving first and second movable bases along a
guide member in an optical axis direction in which light leaving
one optical element mounted on said first movable base of said
plurality of optical elements of said zoom optical system enters
another optical element mounted on said second movable base, and an
attachment position of said one optical element to said first
movable base and an attachment position of said other optical
element to said second movable base are present on the optical axis
side of the individual optical elements.
65. An optical device comprising a zoom optical system having a
plurality of optical elements in each of which a light beam enters
said optical element via one refracting surface, is repetitively
reflected by a plurality of reflecting surfaces, and leaves said
optical element from another refracting surface, and driving means
for driving said zoom optical system to attain zooming, wherein the
zooming is done by moving first and second movable bases along a
guide member in an optical axis direction in which light leaving
one optical element mounted on said first movable base of said
plurality of optical elements of said zoom optical system enters
another optical element mounted on said second movable base, and an
attachment position of said one optical element to said first
movable base and an attachment position of said other optical
element to said second movable base are symmetrical positions with
respect to said guide member.
66. The device according to claim 63, wherein said guide member is
arranged in the vicinity of the optical axis to be parallel to the
optical axis.
67. The device according to claim 64, wherein said guide member is
arranged in the vicinity of the optical axis to be parallel to the
optical axis.
68. The device according to claim 65, wherein said guide member is
arranged in the vicinity of the optical axis to be parallel to the
optical axis.
69. The device according to claim 63, wherein said first and second
movable bases use a common guide member.
70. The device according to claim 64, wherein said first and second
movable bases use a common guide member.
71. The device according to claim 65, wherein said first and second
movable bases use a common guide member.
72. The device according to claim 69, wherein said one optical
element is arranged to extend from one side to the other side of
said guide member with a longitudinal direction thereof being
perpendicular to said guide member and is fixed to said first
movable base at the other side thereof, and said other optical
element is arranged to extend from one side to the other side of
said guide member with a longitudinal direction thereof being
perpendicular to said guide member and is fixed to said second
movable base at one side thereof.
73. The device according to claim 70, wherein said one optical
element is arranged to extend from one side to the other side of
said guide member with a longitudinal direction thereof being
perpendicular to said guide member and is fixed to said first
movable base at the other side thereof, and said other optical
element is arranged to extend from one side to the other side of
said guide member with a longitudinal direction thereof being
perpendicular to said guide member and is fixed to said second
movable base at one side thereof.
74. The device according to claim 71, wherein said one optical
element is arranged to extend from one side to the other side of
said guide member with a longitudinal direction thereof being
perpendicular to said guide member and is fixed to said first
movable base at the other side thereof, and said other optical
element is arranged to extend from one side to the other side of
said guide member with a longitudinal direction thereof being
perpendicular to said guide member and is fixed to said second
movable base at one side thereof.
75. An optical device comprising a zoom optical system having a
plurality of optical elements in each of which a light beam enters
said optical element via one refracting surface, is repetitively
reflected by a plurality of reflecting surfaces, and leaves said
optical element from another refracting surface, and driving means
for driving said zoom optical system to attain zooming, wherein a
fixing position of a first optical element to a base of said zoom
optical system, a fixing position of a second optical element to a
first movable base, and a fixing position of a third optical
element to a second movable base are located on a side of a guide
member common to said first and second movable bases in a
longitudinal direction of the optical elements.
76. The device according to claim 63, wherein said guide member
comprises a guide rail which fits into holes formed on said first
and second movable bases.
77. The device according to claim 64, wherein said guide member
comprises a guide rail which fits into holes formed on said first
and second movable bases.
78. The device according to claim 65, wherein said guide member
comprises a guide rail which fits into holes formed on said first
and second movable bases.
79. The device according to claim 75, wherein said guide member
comprises a guide rail which fits into holes formed on said first
and second movable bases.
80. An optical device comprising a zoom optical system having a
plurality of optical elements in each of which a light beam enters
said optical element via one refracting surface, is repetitively
reflected by a plurality of reflecting surfaces, and leaves said
optical element from another refracting surface, and driving means
for driving said zoom optical system to attain zooming, wherein a
first driving source of said driving means is arranged among first,
second, and third optical elements of said zoom optical system, and
a second driving source of said driving means is arranged between
the second and third optical elements.
81. The device according to claim 80, wherein said second driving
source of said driving means is arranged between the second and
third optical elements.
82. The device according to claim 81, wherein said first and second
driving sources comprise motors.
83. The device according to claim 82, wherein shafts of the motors
are arranged to be parallel to a moving plane of the optical
elements for attaining the zooming.
84. The device according to claim 83, wherein a power transmission
mechanism between the shafts of the motors and the optical elements
is a gear mechanism or a cam mechanism or a mechanism in which a
screw and a rack mesh with each other.
85. The device according to claim 82, wherein shafts of the motors
are arranged to be perpendicular to a moving plane of the optical
elements for attaining the zooming.
86. The device according to claim 85, wherein a circuit board is
arranged between the motors and a base for supporting the motors
and the optical elements.
87. An optical device comprising a zoom optical system having a
plurality of optical elements in each of which a light beam enters
said optical element via one refracting surface, is repetitively
reflected by a plurality of reflecting surfaces, and leaves said
optical element from another refracting surface, and driving means
for driving said zoom optical system to attain zooming, wherein the
zooming is done by moving first and second movable bases along a
guide member in an optical axis direction in which light leaving
one optical element of said plurality of optical elements of said
zoom optical system enters another optical element, and said guide
member is arranged in the vicinity of the optical axis.
88. The device according to claim 87, wherein said one and other
optical elements use a common guide member.
89. The device according to claim 87, wherein said driving means
transmits a driving force to said one and other optical elements at
a position in the vicinity of said guide member.
90. The device according to claim 87, wherein said guide member
comprises a guide rail that fits into holes formed on support
members for supporting the optical elements.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an optical element and an
optical system using the same and, more particularly, to an optical
system element suitable for, e.g., a video camera, still video
camera, copying machine, and the like, and an optical system using
the same.
[0003] The present invention also relates to an optical device
which is used in, e.g., a silver halide camera, video camera,
electronic still camera, or the like, and comprises an optical
element formed integrally with a plurality of refracting surfaces
and a plurality of reflecting surfaces.
[0004] 2. Description of Related Art
[0005] Conventionally, as a photographing optical system, some
components of which are built by reflecting surfaces, a so-called
mirror optical system (reflection optical system), as shown in FIG.
12, is known.
[0006] FIG. 12 is schematic view showing principal part of a mirror
optical system made up of one concave mirror and one convex mirror.
In the mirror optical system shown in FIG. 12, an object light beam
104 coming from an object is reflected by a concave mirror 101, and
propagates as a converging beam toward the object side. The light
beam is reflected by a convex mirror 102, and thereafter, is
refracted by a lens 110, thus forming an image on an image surface
103.
[0007] This mirror optical system is based on an arrangement of a
so-called Cassegrainian reflecting telescope, and aims at
shortening the total length of the optical system by folding the
optical path of a telescope lens system with a large total lens
length made up of a refraction lens using two reflecting
mirrors.
[0008] In an objective lens system, such a telescope system, a
large number of methods for shortening the total lengths of optical
systems using a plurality of reflecting mirrors are known in
addition to the Cassegrainian type for the same purpose as
above.
[0009] In this manner, a compact mirror optical system is
conventionally obtained by efficiently folding the optical path
using a reflecting mirror in place of a lens of a photographing
lens with a large total lens length.
[0010] However, in general, mirror optical systems such as a
Cassegrainian reflecting telescope and the like suffer a problem
that some object light rays are eclipsed by the convex mirror 102.
This problem is caused by the presence of the convex mirror 102 in
the passage region of the object light beam 104.
[0011] In order to solve this problem, there has also been proposed
a mirror optical system that uses a decentered reflecting mirror to
avoid the passage region of the object light beam 104 from being
shielded by other portions of the optical system, i.e., to separate
main rays of the light beam from an optical axis 105.
[0012] FIG. 13 is a schematic view showing principal part of a
mirror optical system disclosed in U.S. Pat. No. 3,674,334. This
optical solves the problem of eclipse using portions of reflecting
mirrors which are rotationally symmetrical about the optical
axis.
[0013] The mirror optical system shown in FIG. 13 includes a
concave mirror 111, a convex mirror 113, and a concave mirror 112
in the passage order of a light beam, and these mirrors are
originally rotationally symmetrical about an optical axis 114, as
indicated by two dashed chain lines in FIG. 13. Of these mirrors,
only the upper side of the concave mirror 111, the lower side of
the convex mirror 113, and the lower side of the concave mirror 112
with respect to the optical axis 114 on the plane of the drawing
are used, thus constituting an optical system that separates main
rays 116 of an object light beam 115 from the optical axis 114 and
avoids the object light beam 115 from being eclipsed.
[0014] FIG. 14 is a schematic view showing principal part of a
mirror optical system disclosed in U.S. Pat. No. 5,063,586. The
mirror optical system shown in FIG. 14 solves the above problem by
decentering the central axis itself of each reflecting mirror. In
FIG. 14, if an axis perpendicular to an object surface 121 is
defined to be an optical axis 127, central coordinates and central
axes (an axis that connects the center of the reflecting surface
and the center of curvature of that surface) 122a, 123a, 124a, and
125a of a convex mirror 122, a concave mirror 123, a convex mirror
124, and a concave mirror 125 in the passage order of a light beam
are decentered from the optical axis 127. In this mirror optical
system, by appropriately setting the decentering amounts and the
radii of curvature of the individual surfaces at that time, an
object light beam 128 can be prevented from being eclipsed by these
reflecting mirrors, and an object image is efficiently formed on an
imaging surface 126.
[0015] Also, U.S. Pat. Nos. 4,737,021 and 4,265,510 disclose an
arrangement for avoiding eclipse using portions of reflecting
mirrors which are rotationally symmetrical about the optical axis,
and an arrangement for avoiding eclipse by decentering the central
axis itself of each reflecting mirror from the optical axis.
[0016] As described above, by decentering the reflecting mirrors
that build the mirror optical system, an object light beam can be
avoided from being eclipsed. However, since the individual
reflecting mirrors must be set to have different decentering
amounts, a structure that attaches these reflecting mirrors is
complicated, and it becomes very difficult to assure high
alingnment precision.
[0017] As one method of solving this problem, for example, a mirror
system may be formed as a block to avoid assembly errors of optical
parts upon assembly.
[0018] As conventional blocks having a large number of reflecting
surfaces, for example, optical prisms such as a pentagonal roof
prism, a Porro prism, and the like, which are used in a finder
system or the like, a color separation prism that separates a light
beam coming from a photographing lens into three, i.e., red, green,
and blue color light beams and forms object images based on the
individual color light beams on the surfaces of corresponding image
sensing elements, and the like are known.
[0019] In these prisms, since a plurality of reflecting surfaces
are integrally formed, the relative positional relationship among
the reflecting surfaces is accurately determined, and the positions
of the reflecting surfaces need not be adjusted.
[0020] However, the principal function of such prisms is to reverse
an image by changing the traveling directions of light rays, and
each reflecting surface is defined by a plane.
[0021] In contrast to this, an optical system in which reflecting
surfaces of a prism have curvatures is also known.
[0022] FIG. 15 is a schematic view showing principal part of an
observation optical system disclosed in U.S. Pat. No. 4,775,217.
This observation optical system allows an observer to observe the
landscape of the outer field and also to observe an image displayed
on an information display member overlapping the landscape.
[0023] In this observation optical system, a display light beam 145
originating from an image displayed on an information display
member 141 is reflected by a surface 142, and propagates toward the
object side. The light beam is then incident on a half mirror
surface 143 defined by a concave surface. The light beam is
reflected by the half mirror surface 143, and becomes a nearly
collimated light beam by the refractive power of the concave
surface 143. After the light beam is refracted by and transmitted
through a surface 142, it forms an enlarged virtual image of the
displayed image and enters the pupil 144 of the observer, thus
making the observer to see the displayed image.
[0024] On the other hand, an object light beam 146 from an object
is incident on and refracted by a surface 147 which is nearly
parallel to the reflecting surface 142, and reaches the half mirror
surface 143 as the concave surface. Since a semi-transparent film
is deposited on the concave surface 143, some light components of
the object light beam 146 are transmitted through the concave
surface 142, are refracted by and transmitted through the surface
142, and then enter the pupil 144 of the observer. With these light
components, the observer visually observes the displayed image
overlapping the landscape of the outer field.
[0025] FIG. 16 is a schematic view showing principal part of an
observation optical system disclosed in Japanese Patent Laid-Open
Patent No. 2-297516. This observation optical system also allows
the observer to observe the landscape of an outer field, and to
observe an image displayed on an information display member
overlapping the landscape.
[0026] In this observation optical system, a display light beam 154
originating from an information display member 150 is transmitted
through a flat surface 157, that builds a prism Pa, to enter the
prism Pa, and then strikes a parabolic reflecting surface 151. The
display light beam 154 is reflected by the reflecting surface 151
to be converted into a converging light beam, and forms an image on
a focal plane 156. At this time, the display light beam 154
reflected by the reflecting surface 151 reaches the focal plane 156
while being totally reflected by two parallel flat surfaces 157 and
158 that build the prism Pa, thus achieving a low-profile optical
system as a whole.
[0027] The display light beam 154 that leaves the focal plane 156
as a diverging light beam is incident on a half mirror 152 defined
by a parabolic surface while being totally reflected between the
flat surfaces 157 and 158, and is reflected by the half mirror
surface 152. At the same time, the light beam 154 forms an enlarged
virtual image of the displayed image by the refractive power of the
half mirror surface 152, and becomes a nearly collimated light
beam. The light beam is transmitted through the surface 157 and
enters a pupil 153 of the observer, thus making the observer to
recognize the displayed image.
[0028] On the other hand, an object light beam 155 coming from an
outer field is transmitted through a surface 158b that builds a
prism Pb, is transmitted through the half mirror 152 defined by the
parabolic surface, and is transmitted through the surface 157 to
enter the pupil 153 of the observer. The observer visually observes
the displayed image that overlaps the landscape of the outer
field.
[0029] In this reference as well, the displayed image is observed
and an object image can also be recognized by the arrangement
similar to that in U.S. Pat. No. 4,775,217.
[0030] Furthermore, Japanese Patent Application Nos. 7-65109 and
7-123256 disclose a zoom optical system which has a plurality of
transparent optical elements, each of which is formed integrally
with a plurality of refracting surfaces and a plurality of
reflecting surfaces, so that a light beam enters the transparent
optical element from one refracting surface, and leaves externally
from another refracting surface after it is repetitively reflected
by the plurality of reflecting surfaces. Also, an image sensing
device which forms an image on a solid-state image sensing element
using such an optical system is disclosed in Japanese Patent
Application Nos. 7-65104, 7-65106, 7-65107, 7-65108, and
7-65111.
SUMMARY OF THE INVENTION
[0031] As a conventional optical prism with reflecting surfaces
having curvatures normally suffers larger variations in optical
performance due to decentering errors of the reflecting surfaces
than an optical prism made up of only flat surfaces, the allowable
positional precision of each reflecting surface is very strict, and
such optical prism is not easy to manufacture.
[0032] When such optical prism is moved for focusing or zooming,
the optical prism and a holding member for holding it must be
precisely coupled to each other. However, in U.S. Pat. No.
4,775,217, Japanese Patent Laid-Open No. 2-297516, and the like
disclose the arrangements of such optical prisms alone, but do not
mention any methods of guaranteeing the positional precision of the
reflecting surfaces and the optical prism itself, any holding
method of the holding member, and the like.
[0033] In a conventional coaxial optical system, the optical system
can be inspected with reference to its optical axis in the
manufacture, measurements, assembly, and the like. However, in such
optical prism which has decentered reflecting surfaces without any
optical axis, a method of setting a reference portion that serves
as a reference upon inspecting the optical system in the
manufacture, measurements, assembly, and the like of such optical
system is indispensable.
[0034] It is an object of the present invention to provide an
optical element and an optical system using the same, which can
improve precision in the manufacture, assembly, and measurements of
an optical element, and can prevent optical performance from
deteriorating.
[0035] Also, the present invention has the following objects:
[0036] i) to make a reference portion in the optical element easy
to use by limiting a specific direction to a parallel direction
and/or a perpendicular direction;
[0037] ii) to accurately and securely hold the optical element on a
holding member or the like by forming an auxiliary portion for
assisting position determination of the optical element in addition
to the reference portion to be parallel or perpendicular to the
reference portion, and arranging at least one auxiliary portion to
oppose the reference portion;
[0038] iii) to satisfactorily hold the holding member and the
optical element upon holding the optical element by setting the
reference and auxiliary portions so that the position of the center
of gravity of a region sandwiched between the reference and
auxiliary portions substantially matches that of the optical
element;
[0039] iv) to obtain an optical element which suffers less ghost,
can prevent the reference portion and/or the auxiliary portion from
shielding effective light rays, and can reduce harmful light rays
that may be produced by the reference portion and/or the auxiliary
portion, by forming the reference portion and/or the auxiliary
portion on a region other than the light ray effective portion of
the optical element;
[0040] v) to satisfactorily hold and fix an optical element in
correspondence with every situations by defining the reference
portion and/or the auxiliary portion by a plurality of flat
surfaces, hole portions, or projections;
[0041] vi) to arrange a holding member that holds the optical
element to move or fix the optical element, and to precisely
position the holding member and the optical element by forming, on
the holding member, portions that fit or join the reference portion
and/or the auxiliary portion formed on the optical member;
[0042] vii) to obtain an optical element suffering less ghost,
which can eliminate harmful light rays entering the optical element
from the holding member as much as possible by forming a
predetermined air gap between the holding member and the optical
element in a region other than the fitting or joining portions when
the optical element and the holding member for the optical element
are fitted or joined to each other;
[0043] viii) to obtain a high degree of parallelism between the
central axis of a fitting hole and a plane including a reference
axis by integrally forming the fitting hole for receiving a guide
bar for moving the optical element in the optical element;
[0044] ix) to set the central axis of the fitting hole to be
parallel to the incident reference axis of the optical element by
forming the fitting hole for receiving the guide bar for moving the
optical element in the optical element, and to eliminate changes in
posture upon movement of the optical element as much as possible
when an optical system is built using the optical element; and
[0045] x) to further eliminate changes in posture upon movement of
the optical element when an optical system is built using the
optical element, by setting the central axis of the fitting hole to
be parallel to the incident reference axis of the optical element
in a plane including the reference axis of the optical element.
[0046] On the other hand, none of the above-mentioned prior arts
touch upon any method of attaching an optical element.
[0047] The present invention has been made in consideration of such
situation, and has as its object to prevent deterioration of
optical performance due to the way of attaching an optical element
in an optical device which comprises an optical element which is
arranged so that a light beam enters the optical element from one
refracting surface, and leaves externally from another refracting
surface after it is repetitively reflected by a plurality of
reflecting surfaces.
[0048] None of the above-mentioned prior arts mention any structure
of an optical device that takes changes in temperature into
consideration.
[0049] The present invention has been made in consideration of such
situation, and has as its object to prevent an image from
deteriorating due to expansion and shrinkage of an optical element
due to changes in temperature, changes in refractive index due to
such expansion or shrinkage, and the like, in an optical device
comprising a zoom optical system having a plurality of optical
elements each of which is arranged so that a light beam enters the
optical element from one refracting surface, and leaves externally
from another refracting surface after it is repetitively reflected
by a plurality of reflecting surfaces, and a driving means for
zoom-driving the zoom optical system.
[0050] Furthermore, Japanese Patent Application Nos. 7-65109 and
7-123256 do not mention size reduction of such optical device. On
the other hand, Japanese Patent Application Nos. 7-65104, 7-65106,
7-65107, 7-65108, and 7-65111 propose a low-profile structure of
such optical device, but apply it to a driving source different
from a general driving motor.
[0051] The present invention has been made in consideration of such
situation, and has as its object to attain a size reduction of an
optical device comprising a zoom optical system having a plurality
of optical elements each of which is arranged so that light beam
enters the optical element from one refracting surface, and leaves
externally from another refracting surface after it is repetitively
reflected by a plurality of reflecting surfaces, and a driving
means for zoom-driving the zoom optical system.
[0052] None of the above-mentioned prior arts mention in detail a
structure for driving an optical element with high precision.
[0053] The present invention has been made in consideration of such
situation, and has as its object to realize high-precision zoom
driving in an optical device comprising a zoom optical system
having a plurality of optical elements each of which is arranged so
that light beam enters the optical element from one refracting
surface, and leaves externally from another refracting surface
after it is repetitively reflected by a plurality of reflecting
surfaces, and a driving means for zoom-driving the zoom optical
system.
[0054] Other features and advantages of the present invention will
be apparent from the following description taken in conjunction
with the accompanying drawings, in which like reference characters
designate the same or similar parts throughout the figures
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] FIG. 1 is a sectional view of an optical system according to
an embodiment of the present invention;
[0056] FIG. 2 is a perspective view of an optical element according
to the first embodiment of the present invention;
[0057] FIG. 3 is an explanatory view showing a case wherein the
optical element of the first embodiment is held by a holding
member;
[0058] FIG. 4 is a front view showing a case wherein an optical
element is improperly coupled to a holding member to form an
optical system;
[0059] FIG. 5 is a front view showing a case wherein the optical
element of the first embodiment is coupled to the holding member to
form an optical system;
[0060] FIG. 6 is a perspective view of an optical element according
to the second embodiment of the present invention;
[0061] FIG. 7 is a perspective view of an optical element according
to the third embodiment of the present invention;
[0062] FIG. 8 is a perspective view of an optical element according
to the fourth embodiment of the present invention, and an optical
system using the same;
[0063] FIG. 9 is a perspective view of an optical element according
to the fifth embodiment of the present invention;
[0064] FIG. 10 is a perspective view of an optical element
according to the sixth embodiment of the present invention;
[0065] FIG. 11 is an explanatory view of a coordinate system that
defines configuration data of the optical system of the present
invention;
[0066] FIG. 12 is a schematic view showing principal part of a
conventional reflecting optical system;
[0067] FIG. 13 is a schematic view showing principal part of a
conventional reflecting optical system;
[0068] FIG. 14 is a schematic view showing principal part of a
conventional reflecting optical system;
[0069] FIG. 15 is a schematic view showing principal part of a
conventional observation optical system;
[0070] FIG. 16 is a schematic view showing principal part of a
conventional observation optical system;
[0071] FIG. 17 is a perspective view of an image sensing device
according to the seventh embodiment of the present invention;
[0072] FIG. 18 is a plan view of FIG. 17;
[0073] FIG. 19 is a side view of FIG. 17;
[0074] FIG. 20 is a perspective view of the image sensing device
excluding first, second, and third optical elements;
[0075] FIG. 21 is a view for explaining the optical axes of
incident light and reflected light;
[0076] FIG. 22 is a view showing the optical paths of incident
light and reflected light;
[0077] FIG. 23 is a perspective view of an image sensing device
according to the eighth embodiment of the present invention;
[0078] FIG. 24 is a side view of FIG. 23; and
[0079] FIG. 25 is a view showing the shape of an optical element
according to the ninth embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0080] An optical element of the present invention and an optical
system using the same do not have any symmetrical axis like an
optical axis in a normal optical system. Hence, in the optical
system of the present invention, a "reference axis" corresponding
to the optical axis in the coaxial system is set, and the
arrangement of individual elements in the optical system will be
described on the basis of the reference axis.
[0081] Definition of the reference axis will be given below. In
general, the optical path of a certain light ray of a reference
wavelength that leaves an object surface and reaches an image
surface, and serves as a reference is defined as the "reference
axis" in that optical system. However, since this definition alone
cannot define a light ray that serves as a reference, the reference
axis light ray is normally set according to one of the two
following rules:
[0082] Rule 1: When an axis in which an optical system has
symmetry, albeit partially is present, and an aberration correction
can be symmetrically made about this axis, a light ray that
propagates along the symmetry axis is defined as the reference axis
light ray.
[0083] Rule 2: When no symmetry axis is generally present in an
optical system, or when an aberration correction cannot be
symmetrically made about a symmetrical axis even if such
symmetrical axis is partially present, a light ray that leaves the
center of the object surface (the center of the range to be
photographed or observed), passes through an optical system in the
order of designated surfaces of the optical system, and passes
through the center of a stop in the optical system, or a light ray
that passes through the center of the stop in the optical system
and reaches the center of the final image surface, is set as the
reference axis light ray, and its optical path is defined to be the
reference axis.
[0084] The reference axis defined in this manner normally has a
folded shape. In each surface, the intersection between the surface
and the reference axis light ray is defined to be a reference
point, the reference axis light ray on the object side of each
surface is defined as an incident reference axis, and the reference
axis light ray on the image side of each surface is defined as an
exit reference axis. Furthermore, the reference axis has a
direction, which is assumed to be a direction in which the
reference axis light ray propagates upon forming an image. Hence,
an incident reference axis direction and an exit reference axis
direction are respectively present on the incident and exit sides.
In this manner, the reference axis finally reaches the image
surface while changing its direction in accordance with the
refraction or reflection rule in the order of surfaces which is set
in advance. In an optical-element (optical system) made up of a
plurality of surfaces, the reference axis light ray that enters a
surface closest to the object side is defined to be an incident
reference axis of that optical element (optical system), and the
reference axis light ray that leaves from a surface closest to the
image side is defined to be an exit reference axis of that optical
element (optical system). The definitions of the directions of
these incident and exit reference axes are the same as those of the
surfaces.
[0085] Prior to a description of the embodiments, the method of
expressing configuration data of the embodiments, and common
factors throughout the embodiments will be explained below.
[0086] FIG. 11 is an explanatory view of a coordinate system that
defines configuration data of the optical system of the present
invention. In an embodiment of the invention, a surface at an i-th
position along one light ray (indicated by a dotted line in FIG. 11
and to be referred to as a reference axis light ray hereinafter)
that travels from the object side toward the image side will be
referred to as an i-th surface hereinafter.
[0087] In FIG. 11, a first surface R1 is a stop (an aperture), a
second surface R2 is a refracting surface coaxial with the first
surface, a third surface R3 is a reflecting surface which is tilted
with respect to the second surface R2, fourth and fifth surfaces R4
and R5 are reflecting surfaces which are respectively shifted and
tilted with respect to their previous surfaces, and a sixth surface
R6 is a refracting surface which is shifted and tilted with respect
to the fifth surface R5. The second to sixth surfaces R2 to R6 are
formed on a single optical element made from a medium such as
glass, plastic, or the like, and this optical element is referred
to as an optical element B1 in FIG. 11.
[0088] Hence, in the arrangement in FIG. 11, the medium from an
object surface (not shown) to the second surface R2 is air, the
media between adjacent ones of the second to sixth surfaces R2 to
R6 are a certain common medium, and the media between the sixth
surface R6 and a seventh surface R7 (not shown) is air.
[0089] Since the optical system of the present invention is a
decentered optical system, the individual surfaces that build the
optical system do not have any common optical axis. In this
embodiment, an "absolute coordinate system of the optical system"
having, as an origin, the center of the light ray effective
diameter of the first surface serving as the stop is set. In the
present invention, the individual axes of the absolute coordinate
system of the optical system are set as follows.
[0090] Z-axis: the reference axis that passes through the origin
and extends toward the second surface R2
[0091] Y-axis: a straight line that passes through the origin and
90.degree. counterclockwise with the Z-axis within a tilt plane
(within the plane of the drawing of FIG. 11)
[0092] X-axis: a straight line that passes through the origin and
is perpendicular to the Z- and Y-axes (a straight line
perpendicular to the plane of the drawing of FIG. 11)
[0093] Since the surface shape of the i-th surface that builds the
optical system is preferably expressed by setting a local
coordinate system which has, as a reference point, the intersection
between the reference axis and the i-th surface so as to allow
easier understanding than that expressed by the absolute coordinate
system upon recognizing the shape, numerical value data of each
embodiment of the present invention express the surface shape of
the i-th surface by the local coordinate system.
[0094] The tilt angle of the i-th surface in the Y-Z plane is
expressed by an angle .theta.i (unit: .degree.) which has a
positive value in the counterclockwise direction with respect to
the Z-axis of the absolute coordinate system of the optical system.
Hence, in this embodiment, the origin of the local coordinate
system of each surface is present on the Y-Z plane in FIG. 11.
Neither tilt nor shift take place in the X-Z and X-Y planes.
Furthermore, the y- and z-axes of the local coordinate system (x,
y, z) of the i-th surface are tilted by the angle .theta.i in the
Y-Z plane with respect to the absolute coordinate system (X, Y, Z)
of the optical system, and are set as follows:
[0095] z-axis: a straight line that passes through the origin of
the local coordinate system, and makes the angle .theta.i
counterclockwise in the Y-Z plane with the Z-direction of the
absolute coordinate system of the optical system
[0096] y-axis: a straight line that passes through the origin of
the local coordinate system and 90.degree. counterclockwise in the
Y-Z plane with the z-direction x-axis: a straight line that passes
through the origin of the local coordinate system, and is
perpendicular to the Y-Z plane
[0097] Also, Di is the scalar quantity that represents the interval
between the origins of the local coordinate systems of the i-th and
(i+1)-th surfaces, and Ndi and vdi are respectively the refractive
index and Abbe's number of the medium between the i-th and (i+1)-th
surfaces. Note that the stop and the final imaging surface are
displayed as independent flat surfaces.
[0098] Each embodiment of the present invention has a spherical
surface and an aspherical surface with rotational asymmetry. Of
these surfaces, a spherical surface portion is assumed to have a
spherical shape and is described with its radius Ri of curvature.
Assume that the radius Ri of curvature has a positive sign when the
center of curvature points in the plus direction of the z-axis of
the local coordinate system, and has a minus sign when the center
points in the minus direction of the z-axis.
[0099] The spherical surface has a shape expressed by the following
equation (1): 1 z = ( x 2 + y 2 ) / R i 1 + { 1 - ( x 2 + y 2 ) / R
i 2 } 1 / 2 ( 1 )
[0100] The optical system of the present invention has at least one
rotation-asymmetric aspherical surface, whose shape is expressed by
the following equation (2):
[0101]
z=A/B+C.sub.02y.sup.2+C.sub.11xy+C.sub.20x.sup.2+C.sub.03y.sup.3+C-
.sub.12xy.sup.2+C.sub.21x.sup.2y+C.sub.30x.sup.3+C.sub.04y.sup.4+C.sub.13x-
y.sup.3+C.sub.22x.sup.2y.sup.2+C.sub.31x.sup.3y+C.sub.40x.sup.4+. .
. (2)
[0102]
[0103] for
A=(a+b).multidot.(y.sup.2.multidot.cos.sup.2t+.sub.x.sup.2)
B=2a.multidot.b.multidot.cos t[1+{(b-a).multidot.y.multidot.sin
t/(2a.multidot.b)} +[1+{(b-a).multidot.y.multidot.sin
t/(a.multidot.b)}-{y.sup.2/(a.multidot.b)}
-{4a.multidot.b.multidot..sub.-
cos.sup.2t+(a+b).sup.2.sub.sin.sup.2t}.sub.x.sup.2/4.sub.a.sup.2.sub.b.sup-
.2cos.sup.2t)].sup.1/2]
[0104] Note that the shape of each rotation-asymmetrical surface in
the present invention is set to have a shape symmetrical about the
y-z plane by using only even-numbered order terms associated with x
and setting odd-numbered order terms at "0" in the above equation
that represents the curved surface.
[0105] When the condition given by equation (3) below is satisfied,
the surface has a shape symmetrical about the x-z plane:
C.sub.03=C.sub.21=t=0 (3)
[0106] Furthermore, when the condition given by equation (4) below
is satisfied, that surface has a shape with rotation symmetry:
[0107] C.sub.02=C.sub.20=C.sub.04=C.sub.40=C.sub.22/2 (4)
[0108]
[0109] If neither conditions are satisfied, the surface has a shape
with rotation asymmetry.
[0110] In the numerical value data, a horizontal half field angle
uY is the maximum field angle of a light beam which is incident on
the first surface R1 in the Y-Z plane in FIG. 11, and a vertical
half field angle uX is the maximum field angle of a light beam
which is incident on the first surface R1 in the X-Z plane.
[0111] As data that represents the brightness of the optical
system, the diameter of a stop (aperture)(entrance pupil)
represents the stop (aperture) diameter. Also, an image size is the
effective image range on the image surface. The image size is
expressed by a rectangular region defined by "horizontal"
indicating the size in the y-direction and "vertical" indicating
the size in the x-direction both of the local coordinate
system.
[0112] FIG. 1 is a sectional view of an optical system according to
one embodiment of the present invention, and shows an optical path.
Reference numeral B1 denotes an optical element formed integrally
with a plurality of reflecting surfaces with curvatures. The
optical element B1 is prepared by forming on the surfaces of a
transparent member, an incident refracting surface R2, five
reflecting surfaces, i.e., a concave mirror R3, a convex mirror R4,
a concave mirror R5, a convex mirror R6, and a concave mirror R7,
and an exit refracting surface R8 along the reference axis light
ray in the order from the object side. These refracting surfaces
and reflecting surfaces are symmetrical about the plane of the
drawing (Y-Z plane), and hence, all the reference axes are included
in the Y-Z plane. The direction of the incident and exit reference
axes of the optical element B1 are antiparallel to each other. Note
that a reflecting film is formed on each reflecting surface.
Furthermore, the optical element B1 has two side surfaces parallel
to the plane of the drawing.
[0113] Reference numeral 2 denotes an optical correction plate such
as a quartz low-pass filter, an infrared cut filter, or the like;
and 3, a final imaging surface, where the image sensing surface of
an image sensing element such as a CCD or the like is located.
Reference numeral 4 denotes a stop arranged on the object side of
the optical element B1; and 5, a reference axis of the optical
system.
[0114] The imaging process in this embodiment will be explained
below. The amount of an incident light beam 6 coming from an object
is limited by the stop 4, and the light beam 6 is incident on the
incident refracting surface R2 of the optical element B1. The light
beam 6 is refracted by the surface R2, and reaches the concave
mirror R3.
[0115] The concave mirror R3 reflects the object light beam 6
toward the convex mirror R4, and forms a primary object image on an
intermediate imaging surface N1 by the power of the concave
mirror.
[0116] In this manner, since the object image is formed in the
optical element B1 in an early stage, an increase in light ray
effective diameter of the surfaces arranged on the image side due
to the stop 4 is suppressed.
[0117] The object light beam 6 that formed the primary image on the
intermediate imaging surface N1 is reflected in turn by the convex
mirror R4, concave mirror R5, convex mirror R6, and concave mirror
R7, and reaches the exit refracting surface R8 while being
influenced by the powers of these reflecting mirrors. The light
beam 6 is refracted by the surface R8, and leaves the optical
element B1. The object light beam 6 is then transmitted through the
optical correction plate 2, and forms an image on the final image
surface 3.
[0118] In this manner, the optical element B1 serves as a lens unit
which has desired optical performance while repeating reflections
by the plurality of reflecting mirrors with curvatures, has an
imaging effect as a whole, and has a very low profile in the
X-direction.
[0119] In this optical system, focusing is attained by moving the
optical element B1 in a direction parallel to its incident
reference axis.
[0120] FIG. 1 shows an example of the optical system of the present
invention. As another optical system of the present invention, a
zooming optical system which has a plurality of optical elements
each of which is integrally formed with a plurality of reflecting
surfaces with curvatures, and moves these optical elements to
attain zooming is also available.
[0121] Since the optical system of the present invention is used
while being built in a video camera, still video camera, copying
machine, or the like, the image sensing element, the optical
correction plate, and the like are fixed to the main body (not
shown), and the optical element B1 of this embodiment is coupled to
a holding member and is attached to be movable with respect to the
main body, thus building the optical system.
[0122] The XYZ coordinate system shown in FIG. 1 is the absolute
coordinate system of the optical system, and is assumed to be set
on the main body.
[0123] [First Embodiment]
[0124] FIG. 2 is a perspective view of an optical element according
to the first embodiment of the present invention. The same
reference numerals in FIG. 2 denote the same parts as in FIG. 1.
Note that an X'Y'Z' coordinate system shown in FIG. 2 is an
"absolute coordinate system of an optical element", and the
individual axes are set as follows to have, as the origin, a
reference point (a reference point of an incident refracting
surface R2 in this embodiment) of a certain surface present on a
plane (its definition will be described later) including the
reference axis of the optical element:
[0125] Z'-axis: the incident reference axis to the reference
point
[0126] Y'-axis: a straight line that passes through the origin in
the plane including the reference axis of the optical element, and
90.degree. counterclockwise with the Z-axis
[0127] X'-axis: a straight line that passes through the origin and
is perpendicular to the Z'- and Y'-axes.
[0128] In all the optical elements of the individual embodiments to
be described below, the X'Y'Z' coordinate system is the one
described above.
[0129] In FIG. 2, reference numeral 7 denotes a reference portion,
which is formed by three surfaces 7a, 7b, and 7c, and another
surface on a side surface (to be referred to as a forming surface
in the sense of forming the reference portion) of an optical
element B1, and defines the position of the optical element B1 in a
specific direction.
[0130] Of the surfaces that form the reference portion 7, the
surface 7a is parallel to a plane (Y'-Z' plane) including a
reference axis 5, and defines the position of the optical element
B1 on the Y'-Z' plane. On the other hand, the surfaces 7b and 7c
are perpendicular to the plane (Y'-Z' plane) including the
reference axis 5. The surface 7b defines the position of the
optical element B1 on the Z'-X' plane, and the surface 7c defines
the position of the optical element B1 on the X'-Y' plane.
[0131] The reference portion 7 defines the position of the optical
element B1 in a specific direction with respect to a plane that
includes an incident and exit reference axes of at least one
reflecting surface of the optical element B1.
[0132] In this manner, since the position of the optical element B1
is defined using the reference portion 7, the relative positional
relationship among the individual surfaces that define the optical
element B1 and the reference portion 7 can be expressed to allow
easy understanding.
[0133] In a conventional coaxial optical system, a single axis
common to lenses that build that optical system is present as its
name implies, and the characteristics of the individual lenses can
be two-dimensionally expressed with reference to this axis.
[0134] However, in an optical element that allows a free
three-dimensional layout of the individual surfaces as in this
embodiment, an axis that serves as a reference in design may be
set, but it is hard to set an axis that serves as a reference from
its outer appearance.
[0135] For this reason, in this embodiment, a reference portion is
set on the optical element, so that a coordinate system normally
set on a virtual space can be set on the optical element in a
visible form. With this coordinate system, when the optical element
of this embodiment is formed by molding, the individual surfaces
can be worked with reference to the reference portion 7 upon
working molds used in formation by molding. Also, when the
positional relationship among the individual surfaces of a molded
product is measured with reference to the reference portion 7, the
mold working data and the measurement data of the molded product
can be made common. Even when errors have occurred during working,
the working data can be easily corrected based on the measurement
data, and the optical element can be worked with high
precision.
[0136] In this embodiment, an auxiliary portion 8 is formed on the
optical element B1 in addition to the reference portion 7 to
improve the holding precision of the optical element. The reference
portion 7 is formed on one side surface of the optical element, and
the auxiliary portion 8 is formed at a position facing the
reference portion 7 on another side surface (forming surface) to
have a shape similar to that of the reference portion 7. That is,
the auxiliary portion 7 has surfaces, which respectively correspond
to the surfaces 7a, 7b, and 7c that define the reference portion 7,
and are parallel to these surfaces 7a, 7b, and 7c. The auxiliary
portion 8 helps define the position of the optical element B1 by
the reference portion 7.
[0137] At this time, when the reference and auxiliary portions 7
and 8 are formed to face each other, so that the position of the
center of gravity of the optical element B1 is located within the
region sandwiched between the reference and auxiliary portions 7
and 8, the optical element B1 can be held on the holding member
with good balance when it is held by the holding member via the
reference and auxiliary portions 7 and 8.
[0138] The reference and auxiliary portions 7 and 8 are formed in
consideration of an effective light ray transmission region inside
the optical element B1, and of course, they are formed on portions
that do not shield the light ray effective portion of the optical
element B1.
[0139] In this embodiment, the reference portion 7 is defined by
the surfaces 7a, 7b, and 7c which are parallel or perpendicular to
the plane (Y'-Z' plane) including the reference axis 5.
Alternatively, the reference portion 7 may be defined with respect
to a plane perpendicular to the reference axis 5 at an intersection
A between the reference axis 5 and the incident refracting surface
R2 or an intersection B between the reference axis 5 and the exit
refracting surface R8.
[0140] Furthermore, in this embodiment, the surfaces that form the
reference portion 7 are set to be parallel or perpendicular to the
plane (Y'-Z' plane) including the reference axis 5 to help
understand the relationship between the plane including the
reference axis and the reference portion. Of course, the reference
portion may be set to tilt a predetermined-angle with respect to
the plane (Y'-Z' plane) including the reference axis of the optical
element.
[0141] FIG. 3 is an explanatory showing a case wherein the optical
element B1 is held by holding members 9 and 11 using the reference
portions 7 and the auxiliary portion 8 of the first embodiment. In
FIG. 3, reference numeral 9 denotes a holding member which has a
rectangular projection (coupling portion) 10 to be coupled to the
reference portion 7 thereon. The holding member 9 is movably
coupled to the main body (not shown) via a moving surface. Also,
reference numeral 11 denotes another holding member, which has a
projection (coupling portion) 12 to be coupled to the auxiliary
portion 8 thereon.
[0142] A method of coupling the optical element B1 to the holding
members will be explained below. The surfaces 7a, 7b, and 7c that
define the reference portion 7 of the optical element B1 are joined
to surfaces 10a, 10b, and 10c that define the projection 10 of the
holding member 9 to define the positions of the X'-, Y'-, and
Z'-axes of the optical elements B1 with respect to the holding
member 9.
[0143] Subsequently, a surface 8c that forms the auxiliary portion
8 of the optical element B1 is joined to a surface 12c that forms
the projection 12 of the holding member 11, and thereafter, the
holding member 11 is coupled to the holding member 9. In this
manner, the optical element B1 can be clamped by the two holding
members and, hence, the optical element B1 is accurately and
reliably held on the holding member 9 by a uniform force with
respect to the holding direction, i.e., the X'-direction.
[0144] Furthermore, since the surface 10a of the projection 10 of
the holding member 9 is formed to be parallel to the moving surface
of the holding member 9, the plane (Y'-Z' plane) including the
reference axis 5, the surface 7a of the reference portion 7, and
the moving surface of the holding member 9 become parallel to each
other. With this arrangement, when the optical element B1 is moved
together with the holding member 9 upon focusing or zooming, a high
degree of parallelism between the moving surface of the holding
member 9 and the optical element B1 can be guaranteed, and the
influences of, e.g., decentering of the reference axis that is
likely to occur upon movement of the optical element B1, can be
eliminated, thus preventing deterioration of the optical
performance.
[0145] Also, in this embodiment, by modifying the holding method of
the optical element B1 and the holding members, an optical system
that produces less harmful light rays can be built. This state will
be explained below with reference to FIGS. 4 and 5.
[0146] FIG. 4 is a front view showing a case wherein the optical
element B1 is improperly coupled to the holding members 9 and 11 to
build the optical system. In this case, the reference portion 7 of
the optical element B1 is joined to the projection 10 of the
holding member 9, the auxiliary portion 8 is joined to the
projection 12 of the holding member 11, and the holding members 9
and 11 and the optical element B1 are held in tight contact with
each other.
[0147] At this time, harmful light rays 13 produced in the optical
element B1 are bound to pass through a side surface 14 of the
optical element B1 to leave it. However, since the optical element
B1 is in tight contact with the holding member 9, the light rays 13
are immediately reflected by the holding member 9 and return to the
optical element B1. As a consequence, the harmful light rays 13 may
reach the image sensing surface.
[0148] FIG. 5 is a front view showing a case wherein the optical
element of the first embodiment is coupled to the holding members 9
and 11 to form an optical system. In FIG. 5, the holding members
and the optical element B1 are separated at a predetermined
interval except for the joint portions between the reference
portion 7 and the projection 10 of the holding member 9, and
between the auxiliary portion 8 and the projection 12 of the
holding member 11. More specifically, the height (the height in the
X-direction in FIG. 5) of the projection 10 is determined to form a
predetermined air gap between the optical element B1 and the
holding member 9. When the optical element B1 is held to form an
optical system in this manner, the harmful light rays 13 produced
inside the optical element B1 pass through the side surface 14 of
the optical element 13 and leave the optical element B1, thus
preventing the light rays 13 from being reflected by the holding
member 9 and re-entering the optical element B1.
[0149] [Second Embodiment]
[0150] FIG. 6 is a perspective view of an optical element according
to the second embodiment of the present invention. In the first
embodiment, the optical element is held by one reference portion
and one auxiliary portion, while in the second embodiment, a
plurality of auxiliary portions are formed, and an optical element
can be reliably held with higher precision than in the first
embodiment.
[0151] As shown in FIG. 6, an optical element B2 of the second
embodiment has a reference portion 7 and an auxiliary portion 8 on
its two side surfaces as in the first embodiment, and also has four
auxiliary portions 15, 16, 17, and 18 at positions separated from
the reference and auxiliary portions 7 and 8 on the two side
surfaces (forming surfaces).
[0152] More specifically, the auxiliary portions 17 and 18 are
formed on the formation side of the reference portion 7 of the
optical element B2, and the auxiliary portions 15 and 16 are formed
on the formation side of the auxiliary portion 8. Furthermore, as
in the relationship between the reference and auxiliary portions 7
and 8, the auxiliary portions 15 and 17, and the auxiliary portions
16 and 18 are formed to face each other. With this arrangement,
even when the optical element B2 has a complex shape that cannot be
held by a pair of reference and auxiliary portions with good
balance, the holding area for holding the optical element is
increased by the plurality of auxiliary portions, and the optical
element B2 can be more securely held with high precision. The
plurality of auxiliary portions of the second embodiment strongly
assist the position determination of the optical element by the
reference portion.
[0153] As for other arrangements, the same reference numerals
denote the same parts as in the first embodiment, and a detailed
description thereof will be omitted.
[0154] [Third Embodiment]
[0155] FIG. 7 is a perspective view of an optical element according
to the third embodiment of the present invention. In an optical
element B3 of the third embodiment, the reference and auxiliary
portions made up of a plurality of surfaces in the above embodiment
are made up of round holes or elliptic holes, i.e., hole
portions.
[0156] In FIG. 7, reference numeral 19 denotes a reference portion
formed on the optical element B3, which is a round hole (a hole
portion) defined by a flat surface (bottom surface) 19a parallel to
the plane (Y'-Z' plane) including the reference axis and a
cylindrical surface, a central axis 22 of which is perpendicular to
the Y'-Z' plane. Reference numeral 20 denotes an auxiliary portion
formed on the optical element B3, which is an elliptic hole (a hole
portion) defined by a flat surface 20a parallel to the Y'-Z' plane,
and an elliptic cylindrical surface, the central axis of which is
perpendicular to the Y'-Z' plane and the major axis direction of
which agrees with the Y'-direction.
[0157] Reference numeral 23 denotes a holding member which
comprises a projection (coupling portion) 24 to be coupled to the
reference portion 19, and a projection (coupling portion) 25 to be
coupled to the auxiliary portion 20 thereon.
[0158] The round hole of the reference portion 19 defines the
position of the optical element B3 by defining the X'-axis by the
central axis 22 and defining the Y'-Z' plane by the flat surface
19a.
[0159] In a method of connecting the optical element B3 of the
third embodiment to the holding member 23, the optical element B3
is held on the holding member 23 by fitting or adhering the
projection 24 of the holding member 23 and the reference portion
19, and the projection 25 of the holding member 23 and the
auxiliary portion 20 to each other.
[0160] However, since rotation of the optical element B3 about the
X'-axis cannot be restrained by fitting the reference portion 19
onto the projection 24 of the holding member 23 alone, the
auxiliary portion 20 is defined by an elliptic hole in the third
embodiment, so that the auxiliary portion 20 is fitted on the
projection 25 of the holding member 23 to restrain movement in the
Z'-direction, thus restraining rotation of the optical element B3
about the X'-axis and coupling the holding member 23 and the
optical element B3 more securely.
[0161] The reason why the auxiliary portion 20 is defined by an
elliptic hole, the major axis direction of which agrees with the
Y'-direction is as follows. That is, even when the interval between
the reference portion 19 and the auxiliary portion 20 of the
optical element B3 in the Y'-direction varies, if the auxiliary
portion 20 is defined by the above-mentioned elliptic hole, the
optical element B3 can be coupled to the holding member 23 without
being deformed while restraining rotation of the optical element B3
about the X'-axis, although the positional relationship between the
projection 24 and the auxiliary portion 20 in the Y'-direction
shifts.
[0162] In the third embodiment, the reference and auxiliary
portions are formed on only one side surface of the optical element
B3. If the optical element B3 can be securely coupled to the
holding member by only one side, no auxiliary portion need be
formed on the side surface opposing the reference portion of the
optical element B3.
[0163] As for other arrangements, the same reference numerals
denote the same parts as in the first embodiment, and a detailed
description thereof will be omitted.
[0164] [Fourth Embodiment]
[0165] FIG. 8 is a perspective view showing an optical element
according to the fourth embodiment of the present invention, and an
optical system using the same. An optical element B4 of the fourth
embodiment is held by guide bars 31 and 32 fixed to a main body
(not shown), and is movable for attaining focusing or zooming using
these guide bars 31 and 32 to build an optical system. Note that
the guide bar 31 and the like constitute a guide means.
[0166] In the optical element B4 of the fourth embodiment, a hole
portion 28 serving as a reference portion is formed on a sleeve 27
formed on a portion of the element B4, and a guide portion 30
serving as an auxiliary portion is formed on a sleeve 35. A central
axis 29 of the hole portion 28 is set to be parallel to the plane
(Y'-Z' plane) including the reference axis, and the hole portion 28
is movably fitted onto the guide bar 31, thereby defining the
Z'-axis position of the optical element B4.
[0167] Since rotation of the optical element B4 about the Z'-axis
cannot be restrained by fitting of the hole portion 28 and the
guide bar 31 alone, the guide portion 30 of the optical element B4
is movably fitted on the guide bar 32 parallel to the guide bar 31,
thereby restraining rotation of the optical element B4 about the
Z'-axis and also defining its position on the Y'-Z' plane.
[0168] Note that the guide bars 31 and 32 are fixed to be parallel
to the Y-Z plane of the absolute coordinate system of the optical
system set on the main body, and the Y'-Z' plane matches the Y-Z
plane when the optical element B4 is attached to the two guide
bars.
[0169] The sleeves 27 and 35 may be attached as independent members
to the optical element B4 after the optical element B4 is formed.
However, in order to obtain a high degree of parallelism between
the central axis 29 of the hole portion 28 and the Z'-axis, the
sleeves 27 and 35, the reference portion 28, and the auxiliary
portion 30 are preferably integrally formed on the optical element
B4 in the manufacture of the optical element B4.
[0170] With this arrangement, when the optical element B4 is moved
for the purpose of focusing or zooming, the parallelism between the
guide bar 31 and the optical element B4 can be maintained
satisfactorily high.
[0171] Furthermore, in the fourth embodiment, since the central
axis 29 of the hole portion 28 is set in the Y'-Z' plane, changes
in posture upon movement of the optical element B4, especially,
changes in posture upon rotation of the optical element B4 about
the Y'- and Z'-axes, can be further eliminated.
[0172] As for other arrangements, the same reference numerals
denote the same parts as in the first embodiment, and a detailed
description thereof will be omitted.
[0173] [Fifth Embodiment]
[0174] FIG. 9 is a perspective view of an optical element according
to the fifth embodiment of the present invention. In an optical
element B5 of the fifth embodiment, the reference and auxiliary
portions of the optical element B1 of the first embodiment are
formed by shapes projecting from the side surface (forming
surface). In FIG. 9, reference numeral 33 denotes a reference
portion, which is a column defined by a cylindrical surface with a
central axis perpendicular to the Y'-Z' plane, and a surface
parallel to the Y'-Z' plane, and which projects unlike the third
embodiment. The reference portion 33 defines the position of the
optical element B5.
[0175] Reference numeral 34 denotes an auxiliary portion, which is
defined by a flat surface 34a parallel to the plane (Y'-Z' plane)
including the reference axis 5 of the optical element B5, a flat
surface 34b parallel to the X'-Y' plane, a flat surface 34c
parallel to the Z'-X' plane, and two more surfaces, and projects
from the side surface (forming surface).
[0176] Reference numeral 36 denotes a holding member, on which a
hole portion (coupling portion) 37 to be coupled to the reference
portion 33, and a hole portion (coupling portion) 38 to be coupled
to the auxiliary portion 34 are formed.
[0177] In a method of connecting the optical element B5 of the
fifth embodiment to the holding member 36, the optical element B5
is held on the holding member 36 by fitting or adhering the hole
portion 37 of the holding member 36 onto the reference portion 33
contrary to the third embodiment.
[0178] However, since rotation of the optical element B5 about the
X'-axis cannot be restrained by fitting of the hole portion and the
projection alone, in the fifth embodiment, the flat surface 34b of
the auxiliary portion 34 is joined to a flat surface 38b of the
hole portion 38 formed on the holding member 36, thereby
restraining rotation of the optical element B5 about the
X'-axis.
[0179] Contrary to the above-mentioned embodiment, when the
reference portion has a rectangular shape projecting from the side
surface (forming surface), the position determination and rotation
restrain of the optical element B5 can be attained by only the
reference portion without forming any auxiliary portion.
[0180] At this time, the reference portion is formed so that the
position of the center of gravity of the optical element is located
within a region included in a projection of the reference portion
in a direction perpendicular to the plane including the reference
axis of the optical element. In this manner, the optical element
can be held on the holding member with good balance.
[0181] As for other arrangements, the same reference numerals
denote the same parts as in the first embodiment, and a detailed
description thereof will be omitted.
[0182] [Sixth Embodiment]
[0183] FIG. 10 is a perspective view of an optical element
according to the sixth embodiment of the present invention. In an
optical element B6 of the sixth embodiment, the reference and
auxiliary portions of the optical element B1 of the first
embodiment are formed as a combination of a hole portion and a
projection. More specifically, reference numeral 40 denotes a
reference portion formed as a projection; and 41, an auxiliary
portion formed as a hole portion. In this manner, the shapes the
reference and auxiliary portions can be appropriately selected in
correspondence with situations.
[0184] As for other arrangements, the same reference numerals
denote the same parts as in the first embodiment, and a detailed
description thereof will be omitted.
[0185] The numerical value data of the optical system of this
embodiment shown in FIG. 1 will be listed below.
[0186] [Numerical Value Data]
[0187] Horizontal half field angle=31.7
[0188] Vertical half field angle=24.8
[0189] Stop (aperture) Diameter=2.0
[0190] Image size=horizontal 4 mm.times.vertical 3 mm
1 i Yi Zi .theta.i Di Ndi .nu.di 1 0.00 0.00 0.00 1.82 1 stop
Optical Element B1 2 0.00 1.82 0.00 7.49 1.58310 30.20 refracting
surface 3 0.00 9.30 18.49 9.86 1.58310 30.20 reflecting surface 4
-5.93 1.43 3.23 9.30 1.58310 30.20 reflecting surface 5 -10.65 9.44
-12.55 8.90 1.58310 30.20 reflecting surface 6 -11.50 0.58 -22.91
9.39 1.58310 30.20 reflecting surface 7 -18.82 6.46 -25.63 8.02
1.58310 30.20 reflecting surface 8 -18.82 -1.56 0.01 3.68 1
refracting surface 9 -18.82 -5.24 0.01 0.00 1 image surface
[0191] Spherical Surface Shape
[0192] R1 surface R.sub.1=.infin.
[0193] R2 surface R.sub.2=-7.648
[0194] R8 surface R.sub.8=10.757
[0195] R9 surface R.sub.9=.infin.
2 R3 surface a = -1.09716e + 01 b = -1.25390e + 01 t = 2.15145e +
01 C.sub.02 = 0 C.sub.20 = 0 C.sub.03 = 6.87152e - 05 C.sub.21 =
-1.21962e - 04 C.sub.04 = 3.59209e - 05 C.sub.22 = 1.02173e - 04
C.sub.40 = 4.95588e - 05 R4 surface a = -2.34468e + 00 b = 4.88786e
+ 00 t = -3.56094e + 01 C.sub.02 = 0 C.sub.20 = 0 C.sub.03 =
-4.48049e - 03 C.sub.21 = -7.45433e - 03 C.sub.04 = 1.81003e - 03
C.sub.22 = 2.09229e - 03 C.sub.40 = -8.28024e - 04 R5 surface a =
-6.11985e + 00 b = 1.70396e + 01 t = -2.17033e + 01 C.sub.02 = 0
C.sub.20 = 0 C.sub.03 = -3.23467e - 04 C.sub.21 = -1.07985e - 03
C.sub.04 = -3.70249e - 05 C.sub.22 = -1.74689e - 04 C.sub.40 =
-1.21908e - 04 R6 surface a = .infin. b = .infin. t = 0 C.sub.02 =
0 C.sub.20 = 0 C.sub.03 = 1.10097e - 03 C.sub.21 = -3.73963e - 04
C.sub.04 = -1.59596e - 04 C.sub.22 = -3.22152e - 04 C.sub.40 =
-1.74291e - 04 R7 surface a = -2.11332e + 01 b = -1.31315e + 03 t =
1.70335e + 00 C.sub.02 = 0 C.sub.20 = 0 C.sub.03 = 8.29145e - 05
C.sub.21 = -1.11374e - 03 C.sub.04 = -2.50522e - 05 C.sub.22 =
-5.28330e - 05 C.sub.40 = -2.91711e - 05
[0196] With the above-mentioned arrangement according to the
present invention, a planar, low-profile optical element prepared
by integrally forming a refracting surface for receiving a light
beam, a plurality of reflecting surfaces with curvatures, and a
refracting surface for outputting the light beam reflected by the
plurality of reflecting surfaces on surfaces of a transparent
member, is formed with a reference portion for defining the
position of the optical element in a specific direction with
respect to a plane including an incident and exit reference axes of
at least one reflecting surface of the optical element, or a
reference portion for defining the position of the optical element
in a specific direction with respect to a plane perpendicular to a
reference axis at an intersection between the incident refracting
surface or exit refracting surface of the optical element, and the
reference axis of the optical element. With this arrangement, an
optical element which can define the relative positional
relationship among the refracting surfaces and the decentered
reflecting surfaces with respect to the reference portions, can
improve precision in the manufacture, assembly, and measurements of
the optical element, and can prevent deterioration of optical
performance, and an optical system using the optical element, can
be achieved.
[0197] In addition, the present invention has the following
effects.
[0198] The reference portion of the optical element is made easy to
use by limiting the specific direction to a parallel direction
and/or a perpendicular direction with respect to the plane.
[0199] The optical element is accurately and securely held on the
holding member or the like by forming an auxiliary portion for
assisting the position determination of the optical element in
addition to the reference portion to be parallel or perpendicular
to the reference portion, and arranging at least one auxiliary
portion to oppose the reference portion.
[0200] The holding member and the optical element are
satisfactorily held upon holding the optical element by setting the
reference and auxiliary portions so that the position of the center
of gravity of region sandwiched between the reference and auxiliary
portions substantially matches that of the optical element.
[0201] The reference portion and/or the auxiliary portion are/is
formed on a region other than the light ray effective portion of
the optical element, so as to obtain an optical element which
suffers less ghost, can prevent the reference portion and/or the
auxiliary portion from shielding effective light rays, and can
reduce harmful light rays that may be produced by the reference
portion and/or the auxiliary portion.
[0202] The reference portion and/or the auxiliary portion are/is
formed by a plurality of flat surfaces, hole portions, or
projections so as to satisfactorily hold and fix the optical
element in correspondence with every situations.
[0203] A holding member that holds the optical element is designed
to move or fix the optical element, and the holding member and the
optical element are precisely positioned by forming, on the holding
member, portions that fit or join the reference portion and/or the
auxiliary portion formed on the optical member.
[0204] When the optical element and the holding member for the
optical element are fitted or joined to each other, a predetermined
air gap is formed between the holding member and the optical
element in a region other than the fitting or joining portions, so
as to obtain an optical element which suffers less ghost, and can
eliminate harmful light rays entering the optical element from the
holding member as much as possible.
[0205] By integrally forming, on the optical element, a fitting
hole for receiving a guide bar for moving the optical element, a
high degree of parallelism between the central axis of the fitting
hole and the plane including the reference axis can be assured.
[0206] By forming, on the optical element, a fitting hole for
receiving the guide bar for moving the optical element, and setting
the central axis of the fitting hole to be parallel to the incident
reference axis of the optical element, changes in posture upon
movement of the optical element can be eliminated as much as
possible when an optical system is built using the optical
element.
[0207] By setting the central axis of the fitting hole to be
parallel to the incident reference axis of the optical element in
the plane including the reference axis of the optical element,
changes in posture upon movement of the optical element can be
further eliminated when an optical system is built using the
optical element.
[0208] An embodiment in which the optical device of the present
invention is applied to an image sensing device will be explained
below. Note that the present invention is not limited to an optical
device having a solid-state image sensing device (e.g., a CCD) like
in the embodiments, but may be similarly applied to, e.g., a silver
halide camera and the like.
[0209] [Seventh Embodiment]
[0210] FIG. 17 is a perspective view showing an image sensing
device which uses first, second, and third optical elements
according to the seventh embodiment of the present invention. FIG.
18 is a plan view of the device when viewed from a direction A in
FIG. 17. FIG. 19 is a side view of the device when viewed from a
direction B in FIG. 17. FIG. 20 is a perspective view showing the
state wherein the first, second, and third optical elements are
removed from the image sensing device shown in FIG. 17, i.e., an
explanatory view of various members other than the first, second,
and third optical elements mounted on the image sensing device.
FIG. 21 is an explanatory view of the reference optical axes of
incident light and reflected light. FIG. 22 shows the optical paths
of incident light and reflected light.
[0211] In FIGS. 17 to 22, reference numeral 201 denotes a first
optical element (corresponding to the function of a front lens unit
in a conventional lens) which consists of plastic, glass, or the
like, and is formed integrally with two refracting surfaces (an
incident light surface 201a and an exit light surface 201f in FIG.
21), and four reflecting surfaces (surfaces 201b, 201c, 201d, and
201e in FIG. 21). One end portion 201h of the first optical element
201 is fixed to an attachment portion 216 (see FIG. 20) of a base
209 by attachment screws 217. The first optical element 201 is
fixed to the base 209 at its one end portion 201h to absorb
expansion and shrinkage due to changes in temperature especially
when the element 201 is plastic. As will be described later, second
and third optical elements 202 and 203 are fixed to the base at
their one-end portions to be free to expand or shrink in their
longitudinal directions (nearly the directions of arrows C and D)
according to the same idea as the first optical element 201. Since
the one-end portions of the first, second, and third optical
elements are fixed by screws, stresses produced by fastening the
screws do not adversely influence portions (the optical path
extending from the incident light surface 201a to the reflecting
surface 201b) requiring optical performance. Furthermore, when each
optical element of this embodiment is plastic, a gate (an injection
port of a molten plastic material upon injection molding) is formed
on the side of an end face 201i of its one end portion 201h so as
not to adversely influence the portion that requires high optical
performance.
[0212] Reference numeral 202 denotes a second optical element
(corresponding to a variator in the conventional lens) which
consists of plastic, glass, or the like, and is formed integrally
with two refracting surfaces (an incident light surface 202a and an
exit light surface 202g in FIG. 21), and five reflecting surfaces
(surfaces 202b, 202c, 202d, 202e, and 202f in FIG. 21). Reference
numeral 203 denotes a third optical element (corresponding to a
compensator in the conventional lens) which consists of plastic,
glass, or the like, and is formed integrally with two refracting
surfaces (an incident light surface 203a and an exit light surface
203g in FIG. 21), and four reflecting surfaces (surfaces 203b,
203c, 203d, 203e, and 203f in FIG. 21). Reference numeral 204
denotes a stop mechanism (details are not shown). Reference numeral
205 denotes a first movable base, which has a plurality of fitting
holes 205a on its one end portion, and has a U-groove 205b on the
other end portion. These fitting holes 205a are fitted on a first
guide rail 215 fixed to first guide rail fixing portions 211 of the
base 209 by screws 213 without any cluttering, and the U-groove
205b is fitted on a second guide rail 214 attached to second guide
rail fixing portions 210 by screws 213 so as to have a certain gap
(in the directions of the arrows C and D in FIG. 18). The first
movable base 205 is smoothly slidably in the direction of the arrow
B and a direction opposite thereto along and with reference to the
guide rail 215 by a driving force of a stepping motor 206 (to be
described later). The first movable base 205 also has an adhesion
portion 205d (see FIG. 20), to which the second optical element 202
is fixed by adhesion, on a portion roughly immediately above the
fitting holes 205a (in the direction point out of the page of FIG.
18 or the direction of an arrow E in FIG. 19). The adhesion portion
205d can hold one end portion (exit light side) of the second
optical element 202 by adhesion. As shown in FIG. 19, the second
optical element 202 and the first movable base 205 are in tight
contact with each other on the adhesion portion 205d but a surface
205e (see FIG. 20) other than the adhesion portion 205d has a
predetermined step with respect to the adhesion portion 205d. For
this reason, a gap m is formed between the optical element 202 and
the surface 205e, as shown in FIG. 19. This is to allow the optical
element 202 to be free to expand or shrink in the directions of the
arrows C and D with reference to the adhesion portion 205d when
environmental changes (e.g., changes in temperature R) have taken
place, as described above. In this embodiment, the gap m is formed.
Alternatively, the adhesion portion 205d may be flush with the
surface 205e without forming any gap m, and the optical element 202
may be fixed by adhesion by only the adhesion portion 205d. The
first movable base 205 further has a rack portion 205c (see FIGS.
18 and 20), which meshes with a screw shaft 207 of the first
stepping motor 206. When the stepping motor 206 is driven by a
driving control circuit (not shown), the first movable base 205 and
the second optical element 202 fixed thereto by adhesion are fed
along the guide rail 215 by the rack portion 205c and the screw
shaft 207. Note that the first stepping motor 206 is attached to a
first angle 208, which is fixed to the base 209.
[0213] In this embodiment, a stepping motor is used as the driving
source. However, the present invention is not limited to this, and
any other driving sources such as a DC motor, an ultrasonic wave
motor, a voice coil driving device, and the like may be used as
long as they can drive the first movable base 205 and the second
optical element 202.
[0214] Reference numeral 218 denotes a second movable base, the
structure of which is substantially the same as that of the first
movable base 205. The second movable base 218 has fitting holes
218a on its one end portion, and a U-groove 218b similar to the
groove 205b (see FIG. 20) on the other end portion. The fitting
holes 218a are fitted on the first guide rail 215 attached to the
first guide rail fixing portions 211 of the base 209 without any
cluttering, and the U-groove 218b is fitted on a third guide rail
222 attached to third guide rail fixing portions 212 of the base
209 by screws 213, so as to have a certain gap in the directions of
the arrows C and D in FIG. 18. As in the first movable base 205,
the second movable base 218 can smoothly move along and with
reference to the first guide rail 215.
[0215] The common guide rail 215 is used to serve as a reference
since the following merits and are expected as compared to using
independent guide rails 215.
[0216] The second and third optical elements 202 and 203 move in
the direction of the arrow B in FIG. 18 and a direction opposite
thereto so as to attain zooming. In this case, a high-performance
zoom mechanism requires that the exit optical axis from the second
optical element 202 and the incident optical axis to the third
optical element 203 (an optical axis of the reflecting surface 202f
to the reflecting surface 203b shown in FIG. 21 to be described
later) always agree with each other during movement of the optical
elements 202 and 203 and at a stop position after movement. If
independent guide rails 215 are used, the optical axes may not
agree with each other due to assembly precision errors, parts
variations, and the like, thus adversely influencing the
performance. If a common guide rail 215 is used, such problem can
be solved.
[0217] A cost reduction can be attained by reducing the number of
parts, the number of assembly steps, and the like.
[0218] The second movable base 218 has an adhesion portion 218d for
fixing the third optical element 203 by adhesion on a portion
roughly immediately above the fitting holes 218a, and the adhesion
portion 218d can hold one end portion (incident light side) of the
third optical element 203 by adhesion. Note that as in the first
movable base 205, a predetermined step is formed between the
adhesion portion 218d and a surface 218e other than the adhesion
portion 218d. This step also serves to absorb environmental changes
(e.g., changes in temperature). Furthermore, the second movable
base 218 has a rack portion 218c (see FIGS. 18 and 20) as in the
first movable base 205, which portion meshes with a screw shaft 220
of a second stepping motor 219. When the second stepping motor 219
is driven by a driving control circuit (not shown), the second
movable base 218 and the third optical element 203 adhered thereto
are fed along the guide rail 215 by the second stepping motor 219
and the screw shaft 220. Note that the second stepping motor 219 is
attached to a second angle 221, which is fixed to the base 209.
[0219] Reference numeral 223 denotes an optical low-pass filter;
224, an IR (infrared ray) blocking filter; and 225, a CCD
(solid-state image sensing device), which are known means required
for converting optical information into an electrical signal, and
are used for converting optical information which has passed
through the first, second, and third optical elements 201, 202, and
203 into an electrical signal, as shown in FIG. 21. Note that the
optical low-pass filter 223, IR blocking filter 224, and CCD 225
normally have a predetermined structure, and are integrally coupled
and attached. However, this structure is not shown. Also, the CCD
225 is normally connected to a signal processing circuit, but this
portion is not shown, either. Reference numeral 226 denotes a CCD
attachment plate to which the CCD 225 is attached; 227, an angle
for attaching these members to the base 209; and 232, a projection
(see FIG. 18; it seems recessed in the direction of the arrow B in
FIG. 17) formed by drawing the angle 227 in the direction of the
arrow B in FIG. 17. The CCD attachment plate 226 is coupled to the
angle 227 to abut against the projection 232 by screws 230 and a
screw 228 via a spring washer 229. This structure is used to adjust
the tilt angle of the CCD 225 so that light can enter the CCD 225
at a predetermined incident angle, when light leaving the exit
surface 203g of the third optical element 203 cannot enter the CCD
225 in a direction perpendicular to the surface of the CCD 225 due
to parts precision errors, assembly errors, and the like. That is,
the screws 228 and 230 are appropriately fastened or loosened to
determine the position of the CCD 225 about the projection 232 as a
fulcrum.
[0220] The reason why the second optical element 202 is fixed by
adhesion to a position roughly immediately above the fitting hole
205a of the first movable base 205 (roughly immediately below the
exit optical axis from the second optical element 202; each optical
axis extends along one plane in FIG. 21, and a first guide rail 215
is present in or in the vicinity of a plane which crosses that
plane at a position of the optical axis of the reflecting surface
202f to the reflecting surface 203b, and is perpendicular to that
plane, and is nearly parallel to the optical axis of the reflecting
surface 202f to the reflecting surface 203b), and the third optical
element 203 is fixed by adhesion to a position roughly immediately
above the fitting hole of the second movable base 218 (roughly
immediately below the incident optical axis of the third optical
element 203) will be explained below.
[0221] As described above, both the movable bases 205 and 218 that
respectively hold the second and third optical elements 202 and 203
are fitted on the first guide rail 215, and are movable along
it.
[0222] When ambient temperature changes, the optical element 202
expands or shrinks. Since the exit optical axis (light rays leaving
the reflected surface 202f in FIG. 21) side of the optical element
202 is adhered to the adhesion portion 205d of the first movable
base 205 roughly immediately above the fitting holes 205a, it
expands in the direction of the arrow C or shrinks in the direction
of the arrow D in FIG. 18 with reference to that adhered portion.
On the other hand, since the incident optical axis (light rays
entering the surface 203a in FIG. 21) of the third optical element
203 is adhered to the adhesion portion 218d of the first movable
base 205 roughly immediately above the fitting holes 218a, it
expands in the direction of the arrow D or shrinks in the direction
of the arrow C in FIG. 18 with reference to that adhered portion.
That is, the two optical elements can expand or shrink in opposite
directions with reference to the first guide rail 215. Since the
exit optical axis from the second optical element 202 and the
incident optical axis to the third optical element (the optical
axis extending from the surface 202f to the surface 203b in FIG.
21) is present roughly immediately above the guide rail 215, these
two optical elements 202 and 203 expand or shrink in opposite
directions with reference to the exit optical axis from the second
optical element 202 and the incident optical axis to the third
optical element 203. As a consequence, light leaving the second
optical element 202 can always be launched on an identical position
of the incident light surface 203a (see FIG. 21) without being
influenced by changes in temperature.
[0223] On the other hand, since the first optical element 201 is
fixed to the attachment portion 216 from the base 209 at its one
end portion 201h close to the first guide rail 215, it expands in
nearly the direction of the arrow C or shrinks in the direction of
the arrow D with reference to its one end portion 201h. Such
expansion and shrinkage take place in the same directions as those
of the second optical element 202. Also, in the first optical
element, the length in the direction of the arrow C from the
position of the attachment screw 217 to the exit light surface 201f
is about 40 mm, while in the second optical element 202, the size
in the direction of the arrow C from the adhered portion (the
position of the exit optical axis from the surface 202f) to the
incident light surface 202a is about 45 mm, i.e., the difference
between these sizes is small. Hence, the two optical elements have
substantially equal expansion/shrinkage amounts due to changes in
temperature. With this structure, light leaving the exit light
surface 201f strikes a substantially identical position on the
incident light surface 202a of the second optical element 202
without being influenced by changes in temperature. That is, the
above-mentioned structure can prevent optical performance from
deteriorating due to changes in temperature.
[0224] Note that the position of light leaving the third optical
element 203 (i.e., light rays coming from the surface 203f) shifts
in the direction of the arrow C or D in FIG. 18 due to changes in
temperature. However, no serious problem is posed since these light
rays enter the CCD 225 which does not particularly require high
attachment precision in the directions of the arrows C and D with
respect to the third optical element 203 (the precision can be
low).
[0225] The layout of the stepping motors 206 and 219 will be
explained below.
[0226] In FIG. 18, the first stepping motor 206 is arranged at a
position surrounded by the first, second, and third optical
elements 201, 202, and 203. On the other hand, the second stepping
motor 219 is arranged at a position surrounded by the second and
third optical elements 202 and 203, and the CCD 225. These places
correspond to dead spaces in the layout of the optical elements,
and when stepping motors are installed at these places, the overall
space factor can be improved, thus contributing to a size reduction
of the device. Furthermore, these positions correspond to the
vicinities of the first guide rail 215 serving as a reference upon
movement of the first and second movable bases 205 and 218, and can
minimize twisting or the like produced upon movement of the
individual movable bases. Hence, the optical elements can be moved
with high precision.
[0227] Since the first guide rail 215 serving as a reference is
arranged in the vicinity of light that leaves the second optical
element 202 and light that enters the third optical element 203 (an
identical optical axis, i.e., the optical axis of the surface 202f
to the surface 203b), the adverse influences of cluttering or the
like upon zoom movement on the optical axis of the surface 202f to
the surface 203b can be minimized. Note that a common guide rail
may be arranged in the vicinity of the optical axis of the surface
201e to the surface 202b in FIG. 21, but is preferably arranged in
the vicinity of the optical axis of the surface 202f to the surface
203b for the following reason.
[0228] That is, the first optical element 201 is fixed in position;
it does not move. On the contrary, the second and third optical
elements 202 and 203 always move upon zooming. More specifically,
when the guide rail 215 serving as a reference is arranged in the
vicinity of the optical axis of the surface 202f to the surface
203b that suffers many variation factors due to cluttering and the
like, the variation factors can be suppressed, and a zoom mechanism
with higher precision can be realized.
[0229] The operation for fetching an image by the CCD 225 in the
above-mentioned arrangement will be described below with reference
to FIG. 21. Note that FIG. 21 illustrates only the optical path of
chief light rays, the behavior of the entire light beam is
disclosed in, e.g., Japanese Patent Application Nos. 7-65109 and
7-123256, and a detailed description thereof will be omitted.
[0230] In FIG. 21, image information of an object 231 is incident
on the incident light surface 201a of the first optical element
201. Since the first optical element 201 consists of plastic,
glass, or the like, as described above, the image information is
refracted by the refracting power of the incident light surface
201a upon incidence. In this case, a driving control circuit (not
shown) drives the stop mechanism 204 on the basis of brightness
information from a light amount detection mechanism (not shown) to
adjust the incident light amount to be a predetermined value. The
light entering the incident light surface 201a is reflected in turn
by the reflecting surfaces 201b, 201c, 201d, and 201e, and leaves
the first optical element 201 after it is similarly refracted by
the refracting power of the exit light surface 201f. The light then
becomes incident on the incident light surface 202a of the second
optical element 202. In this case, the light is refracted by the
refracting power of the surface 202a. The light is reflected in
turn by the reflecting surfaces 202b, 202c, 202d, 202e, and 202f of
the second optical element 202, and leaves the second optical
element 202 after it is refracted by the refracting power of the
exit light surface 202g. This light enters the third optical
element 203 after it becomes refracted light by the incident light
surface 203a of the third optical element 203, is reflected in turn
by the surfaces 203b, 203c, 203d, 203e, and 203f, and leaves the
third optical element 203 from the exit light surface 203g as
refracted light. The light from the exit light surface 203g passes
through the low-pass filter 223 and the IR blocking filter 224, and
forms an image on the CCD 225. The image information from the CCD
225 is processed by a signal processing circuit or the like (not
shown), and is finally displayed on a display device (not shown).
The operator who observes the displayed image operates an operation
device (not shown) to adjust the object image to a desired field
angle. This operation corresponds to that of a zoom switch toward
the telephoto or wide-angle side in a conventional video camera or
electronic still camera. In general, auto-focusing is done after
zooming, but its control method is a state-of-the-art technique.
Furthermore, during this interval, a control unit (not shown)
controls the stop mechanism 204 to obtain desired lightness.
[0231] The control of the second and third optical elements 202 and
203 upon operation of the zoom switch by the operator will be
explained below.
[0232] When the operator operates the zoom switch toward the
telephoto side, the stepping motors 206 and 219 (see FIG. 18)
rotate in a predetermined direction in accordance with a control
signal from a control unit (not shown). At the same time, the screw
shafts 207 and 220 are rotated. Since the screw shafts 207 and 220
respectively mesh (threadably fit) with the rack portion 205c of
the first movable base 205 and the rack portion 218c of the second
movable base 218, the second and third optical elements 202 and 203
move by a predetermined amount in the direction of the arrow B in
FIGS. 17, 18, and 21. When the operator stops the operation at an
appropriate position, the first or second movable base 205 or 218
is controlled to move by a very small amount in the direction of
the arrow B or a direction opposite thereto, thus bringing a focal
point on the CCD 225. Note that the state illustrated in FIGS. 18
and 21 is close to the wide-angle side. When the zoom switch is
operated from this state toward the wide-angle side, the second and
third optical elements 202 and 203 move in the direction opposite
to the direction of the arrow B, but their moving amount is smaller
than that when they move toward the telephoto side. FIG. 22 is an
optical path diagram of light rays by the optical elements of this
embodiment, and illustrates, as an example, the propagation state
of light rays while forming images inside the optical elements.
Note that the behavior of a light beam upon movement of a plurality
of optical elements each having a plurality of refracting surfaces
and a plurality of reflecting surfaces by the telephoto/wide-angle
operation is described in, e.g., Japanese Patent Application Nos.
7-65109 and 7-123256, and a detailed description thereof will be
omitted.
[0233] Note that the stop mechanism 204 is subjected to
predetermined control by a predetermined control signal during such
zoom operations, needless to say. Furthermore, when the image
sensing device is an electronic still camera, since a shutter is
required, the stop mechanism 204 may be provided with a shutter
function, a CCD with a shutter function may be mounted, or a
shutter may be added.
[0234] As described above, according to this embodiment, in an
optical device having an optical element in which a light beam is
incident from one refracting surface, is reflected by a plurality
of reflecting surfaces, and departs from the element from another
refracting surface, the optical performance can be prevented from
deteriorating due to stress upon fixing the optical element and
changes in temperature.
[0235] Also, according to this embodiment, in an optical device
which comprises a zoom optical system having a plurality of optical
elements in each of which a light beam is incident from one
refracting surface, is reflected by a plurality of reflecting
surfaces, and leaves the element from another refracting surface,
and a driving means for driving the zoom optical system to attain
zooming, the following effects i to iv can be obtained.
[0236] i. The individual optical elements are fixed to the
corresponding movable bases on the side of an optical axis where
light leaving one optical element enters the other optical element,
and a common reference guide rail is used for the movable bases and
is arranged in the vicinity of the optical axis.
[0237] As a result, the adverse influences of expansion/shrinkage
of the optical elements arising from changes in temperature and
resulting changes in refracting power on image quality can be
removed.
[0238] ii. Since the individual optical elements are fixed to the
corresponding movable bases at their one-end side and at the side
of the optical axis, adverse influences on image quality can be
similarly removed.
[0239] iii. When the thermal expansion coefficient of the optical
elements assumes a value close to that of the movable bases to
which the optical elements are attached, the attachment position of
one optical element to the first movable base, and that of the
other optical element to the second movable base are determined to
be symmetrical about the common reference guide, thereby similarly
removing adverse influences on image quality.
[0240] iv. The fixing position of the stationary first optical
element to the base, and the fixing positions of the movable second
and third optical elements to the first and second movable bases
are set on the reference guide rail side, thereby similarly
removing adverse influences on image quality.
[0241] According to this embodiment, dead spaces can be effectively
used to achieve a size reduction of an image sensing device that
comprises a zoom optical system in which a light beam is incident
from one refracting surface, is reflected by a plurality of
reflecting surfaces, and leaves the element from another refracting
surface, and a driving means for driving the zoom optical system to
attain zooming.
[0242] Furthermore, according to this embodiment, the following
effects v and vi can be obtained.
[0243] v. In the arrangement that attains zooming by moving two
optical elements in an identical optical axis direction in which
the exit optical axis from one element integrally formed with a
plurality of refracting surfaces and a plurality of reflecting
surfaces becomes the incident optical axis of the other similar
optical element, a common guide rail for moving these elements is
arranged in the vicinity of the identical optical axis, thus
enabling high-precision zoom driving.
[0244] vi. Since the optical elements are driven in the vicinity of
a guide rail, twisting or the like can be suppressed from being
produced, and high-precision feeding can be realized.
[0245] [Eighth Embodiment]
[0246] FIG. 23 is a plan view of an image sensing device according
to the eighth embodiment of the present invention. FIG. 24 is a
side view of FIG. 23. FIGS. 23 and 24 respectively correspond to
FIGS. 18 and 19 of the seventh embodiment. In the seventh
embodiment, the second and third optical elements 202 and 203 are
moved using the stepping motors 206 and 219 and the screw shafts
207 and 220. However, in this embodiment, a cam feed mechanism is
adopted, and the layout of the stepping motors is changed. Such
modifications are made to improve the space factor as compared to
the seventh embodiment and, more specifically, to decrease the
thickness of the mechanical structure. Furthermore, the attachment
methods of the second and third optical elements 202 and 203 are
changed. Note that the same reference numerals in FIGS. 23 and 24
denote the same parts as in the seventh embodiment, and a detailed
description thereof will be omitted.
[0247] Reference numeral 301 denotes a first optical element
(corresponding to reference numeral 201 in FIG. 17); and 302, a
second optical element (corresponding to reference numeral 202 in
FIG. 17). The difference from the seventh embodiment is that an
attachment portion 302h is formed on one end portion of the second
optical element 302. As described above, this structure is
exploited to prevent stress produced upon fastening the screws from
adversely influencing the optical performance. In this embodiment,
the shape is improved, and the attachment portion 302h is formed on
the second optical element 302 to sandwich slits 302i therebetween
(see FIG. 24). This attachment portion 302h is fixed to an upright
portion 305f of a first movable base 305 (corresponding to
reference numeral 205 in FIG. 17) by screws 350.
[0248] As another attachment shape that does not adversely
influence the portion requiring high optical performance, an
example shown in FIG. 25 is also available. In FIG. 25, reference
numeral 402 denotes a second optical element according to the ninth
embodiment. Reference numeral 402h denotes an attachment portion
formed on one end portion of the second optical element 402 like
the attachment portion 302h. In this embodiment, however, groove
portions 402i are formed as fastening stress relief portions in
place of the slits 302i. Note that the shape shown in FIG. 25
allows mold release in the directions of arrows F and G. That is,
the shape of this embodiment takes the mold structure into
consideration. The first, second, and third optical elements 201,
202, and 203 also take the mold structure into consideration. In
this embodiment, the attachment portion is formed by protruding one
end portion of the optical element in its longitudinal direction.
In order to prevent fastening stress from adversely influencing the
optical performance, the attachment portion may protrude from a
position separate from the refracting or reflecting surface of the
optical element and perpendicular to these surfaces, more
particularly, in a direction pointing out of or into the page, and
may be attached to a fixing member, thus obtaining the same effect
as in the above embodiments.
[0249] Referring back to FIG. 23, reference numeral 303 denotes a
third optical element (corresponding to reference numeral 203 in
FIG. 17), which is formed with an attachment portion 303h and slits
303i (not shown) as in the second optical element 302. The third
optical element 303 is fixed to an upright portion 318f of a second
movable base 318 by screws 351. Note that the attachment portions
of the second and third optical elements 302 and 303 are formed on
the side of a first guide rail 215 serving as a reference. This
structure is used in consideration of expansion and shrinkage with
temperature as in the seventh embodiment.
[0250] Furthermore, in this embodiment, the fixing position of the
second optical element 302 to the first movable base 305 by the
screws is nearly symmetrical to that of the third optical element
303 to the second movable base 318 by the screws to sandwich the
first guide rail 215 therebetween in FIG. 23 (the distances from
the guide rail 215 to these elements are also nearly equal to each
other). When both the optical elements and movable bases consist of
materials having nearly equal thermal expansion coefficients, e.g.,
when they consist of plastic materials, such layout can also
prevent expansion/shrinkage due to changes in temperature from
adversely influencing the optical performance. The advantage of
such layout will be explained in detail below taking the second
optical element 302 as an example.
[0251] For example, when the temperature rises, an attachment
portion 305f of the first movable base 305 shifts in the direction
of an arrow D due to expansion with reference to the first guide
rail 215. However, the second optical element 302 shifts in the
direction of an arrow C (opposite to the direction of the arrow D)
by expansion with reference to its attachment portion 302h. That
is, since these elements expand in directions to cancel each other,
an optical axis of a surface 202f to a surface 203b (exit light
from the second optical element 302, incident light to the third
optical element 303) maintains a position roughly immediately above
the first guide rail 215. Even when these elements shrink after the
temperature drops, they shrink in directions to cancel each other,
and the optical axis of the surface 202f.fwdarw.the surface 203b
can keep its position roughly immediately above the first guide
rail 215. The same applies to the relationship between the third
optical element 303 and the second movable base 318. With this
arrangement, the exit optical axis from the second optical element
303 always guides an incident light beam onto a predetermined
position of the third optical element 303, and the optical
performance never deteriorates.
[0252] Projections (bulges pointing into the page in FIG. 23) 302g
and 303g are formed on both the second and third optical elements
302 and 303 in FIG. 23.
[0253] These projections are formed for the following reason.
[0254] In the seventh embodiment, the optical element is fixed to
the movable base by an adhesive. In the manufacture, it is assumed
that the optical element is three-dimensionally positioned using a
jig, and is fixed by an adhesive. In this embodiment, for example,
as for the second optical element 302 (the same applies to the
third optical element 303), the projections 302g are formed with
high precision, and are used as a reference upon attachment. With
this arrangement, after the optical element is placed on the
movable base, it can be fixed to the movable base by only fastening
the screws 350.
[0255] Note that a total of three projections must be formed at
positions separated by largest possible distances in the
longitudinal direction (the directions of the arrows C and D) and
at a position separated by a largest possible distance in the
widthwise direction (a direction perpendicular to the directions of
the arrows C and D), so that the optical element can be stably
placed on the first movable base 305. Also, butt surfaces may be
formed on the first movable base 305 as needed with high precision
to attain high-precision positioning.
[0256] If the optical element consists of glass, the second optical
element 302, for example, may have no attachment portion 302h (the
same shape as that of the second optical element 202 of the seventh
embodiment), and at least one of the projections 302g may be fixed
by an adhesive. In this case, since the positioning portion is
fixed by an adhesive, the optical element can be positioned and
fixed with high precision.
[0257] Reference numeral 306 denotes a first driving motor for
moving the first movable base 305 along the first guide rail 215.
The first driving motor 306 has a tongue-like cam portion 306c with
an elongated hole portion 306a, which cam portion is coupled to a
shaft portion 320 (see FIG. 24). Note that the elongated hole
portion 306a engages with an engaging pin 305g formed on the first
movable base 305. In FIG. 23, when the first driving motor 306
rotates from a chain line P to a chain line Q, the first movable
base 305 and the second optical element 302 fixed thereto move in
the direction of the arrow B. Note that FIG. 23 illustrates the
positions of the cam portion 306c by two-dashed chain lines when
the driving motor 306 has rotated a predetermined angle.
[0258] The second movable base 318 and the third optical element
303 fixed thereto move by a second driving motor 319 in the
direction of the arrow B or in a direction opposite thereto. As in
the first driving motor 306, the second driving motor 319 has a
tongue-like cam portion 319c with an elongated hole portion 319a,
which cam portion is coupled to a shaft portion (not shown), and
the elongated hole portion 319a engages with an engaging pin 318g
formed on the second movable base 318. With this structure, the
second movable base 318 and the third optical element 303 can move
in the direction of the arrow B or in a direction opposite thereto.
Note that the positions of the cam portion 319c upon rotation of
the second driving motor 319 by a predetermined angle are indicated
by two-dashed chain lines.
[0259] The layout of the driving motors 306 and 319 in this
embodiment will be described below.
[0260] In FIG. 23, the first driving motor 306 is arranged among
the second and third optical elements 302 and 303, and a CCD 225,
and the second driving motor 319 is arranged among the first,
second, and third optical elements 301, 302, and 303. This layout
is the same as that in the seventh embodiment to attain space
savings and a size reduction of the device. However, in the seventh
embodiment, the stepping motors 206 and 219 are merely arranged on
dead spaces in the plan view (see FIG. 18). By contrast, in this
embodiment, the driving motors 306 and 319 are arranged so that
their motor shaft directions are perpendicular to the page of FIG.
23 (in the seventh embodiment, the shaft directions are parallel to
the page). Furthermore, the moving mechanism adopts a cam
mechanism. For this reason, as compared to the seventh embodiment,
the driving motors 306 and 319 can shift in the direction of the
arrow E in FIG. 24. As a result, the spaces where the stepping
motors 206 and 219 in the seventh embodiment are arranged can be
used as those for arranging a printed circuit board, and the like,
and the space factor of the whole device can be improved, thus more
contributing to a size reduction. In this embodiment, the cam
mechanism is adopted. Alternatively, a gear train such as a spur
gear, helical gear, and the like may be used to realize a
low-profile structure, thus obtaining the same effect as in the
above embodiment.
[0261] As described above, according to this embodiment, the same
effect as in the seventh embodiment can be obtained.
[0262] Also, according to this embodiment, the same effect as in
the seventh embodiment can be obtained, and since slits or grooves
are formed on the projection of each optical element, the influence
on the optical performance due to fixing stress can be further
reduced.
[0263] Furthermore, according to this embodiment, a compact,
low-profile image sensing device can be realized as in the seventh
embodiment.
[0264] As described above, according to the present invention,
deterioration of the optical performance of the optical element
owing to the way of fixing the optical element can be
prevented.
[0265] According to the present invention, in an optical device
which comprises a zoom optical system having a plurality of optical
elements in each of which a light beam is incident from one
refracting surface, is reflected by a plurality of reflecting
surfaces, and leaves the element from another refracting surface,
and a driving means for driving the zoom optical system to attain
zooming, deterioration of images caused by expansion/shrinkage of
the optical elements due to changes in temperature, and changes in
refracting power due to the expansion/shrinkage can be
prevented.
[0266] Also, according to the present invention, a size reduction
of an optical device that comprises a zoom optical system in which
a light beam is incident from one refracting surface, is reflected
by a plurality of reflecting surfaces, and leaves the element from
another refracting surface, and a driving means for driving the
zoom optical system to attain zooming can be attained.
[0267] Furthermore, according to the present invention, in an
optical device which comprises a zoom optical system having a
plurality of optical elements in each of which a light beam is
incident from one refracting surface, is reflected by a plurality
of reflecting surfaces, and leaves the element from another
refracting surface, and a driving means for driving the zoom
optical system to attain zooming, the zoom driving can be done with
high precision.
[0268] As many apparently widely different embodiments of the
present invention can be made without departing from the spirit and
scope thereof, it is to be understood that the invention is not
limited to the specific embodiments thereof except as defined in
the appended claims.
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