Digital Camera Patent Abstract
A lens unit structure for an SLR digital camera is provided with
a photographing lens block and a finder block. The photographing
lens block includes a lens barrel having a pair of guide shafts
extending in parallel with an optical axis. Ends of the guide shafts
are secured to the lens barrel. A focusing lens and a zoom lens
are slidably supported by the guide shaft so as to move in a direction
of the optical axis, but prevents the lenses from moving in a direction
perpendicular to the optical axis. The finder block includes a casing
that accommodates a finder optical system, a CCD, and a beam splitter.
The beam splitter splits the light from the photographing lens block
into components directed to the finder optical system and the image
capturing element. The casing has a plurality of holes respectively
receiving the pair of guide shaft members. Digital Camera Patent Claims
What is claimed is:
1. A lens unit structure for a single lens reflex digital camera,
comprising a photographing lens block and a finder block, wherein
said photographing lens block includes: a lens barrel having a plurality
of guide shaft members extending in parallel with an optical axis
of said photographing lens block, proximal ends of said plurality
of guide shaft members being secured to said lens barrel and distal
ends of said plurality of guide shaft members projecting out of
said photographing lens block; and at least one lens group accommodated
in said lens barrel, said at least one lens group being slidably
supported in the direction of said optical axis by said plurality
of guide shaft members, said plurality of guide shaft members preventing
said at least one lens group from moving in a direction perpendicular
to the optical axis of said photographing lens block; wherein said
photographing lens block comprises an integrally formed unit that
is separable from said finder block; and wherein said finder block
includes a casing that accommodates a finder optical system, an
image capturing element, and a beam splitter, an image receiving
surface of said image capturing element being perpendicular to an
optical axis of said beam splitter, said beam splitter splitting
the light passed through said photographing lens block into light
directed to said finder optical system and light directed to said
image capturing element, said casing having a plurality of holes
respectively receiving said distal ends of said plurality of guide
shaft members provided on said lens barrel; wherein said plurality
of guide shaft members regulate a positional relationship of an
optical axis of said photographing lens block with respect to an
optical axis of said finder block.
2. A lens unit structure for a single lens reflex digital camera,
comprising an photographing lens block and a finder block, wherein
said photographing lens block includes: a lens barrel having a first
lens group and a plurality of guide shaft members extending in parallel
with an optical axis of said first lens group, distal ends of said
plurality of guide shaft members projecting out of said photographing
lens block; and at least one lens group accommodated in said lens
barrel, said at least one lens group being supported by said plurality
of guide shaft members, said at least one lens group being movable
only in a direction parallel to said optical axis, wherein said
photographing lens block comprises an integrally formed unit that
is separable from said finder block; wherein said finder block includes
a casing that accommodates a finder optical system, an image capturing
element, and a beam splitter, an image receiving surface of said
image capturing element being perpendicular to an optical axis of
said beam splitter, said beam splitter splitting the light passed
through said photographing lens block into light directed to said
finder optical system and light directed to said image capturing
element, said casing having a plurality of holes respectively receiving
said distal ends of said plurality of guide shaft members provided
on said lens barrel; wherein an optical alignment of said photographing
lens block and said finder block are regulated by inserting said
distal ends of said plurality of guide shaft members in said plurality
of holes, respectively.
3. The lens unit structure according to claim 2, wherein said plurality
of guide shaft members regulate a position of said at least one
lens group so that an optical axis of said at least one lens group
coincides with the optical axis of said first lens group.
4. The lens unit structure according to claim 2, wherein said at
least one lens group accommodated in said lens barrel includes a
focusing lens.
5. The lens unit structure according to claim 4, wherein said focusing
lens being held by a focusing lens frame, a plurality of through
holes in which said plurality of guide shaft members are slidably
inserted are formed on said focusing lens frame.
6. The lens unit structure according to claim 4, wherein said at
least one lens group accommodated in said lens barrel includes a
zoom lens.
7. The lens unit structure according to claim 6, wherein said zoom
lens being held by a zoom lens frame, a plurality of through holes
in which said plurality of guide shaft members are slidably inserted
are formed on said zoom lens frame.
8. The lens unit structure according to claim 2, wherein said plurality
of guide shaft members consists of a pair of shaft members.
9. The lens unit structure according to claim 8, wherein said pair
of shaft members are arranged opposite to each other with respect
to the optical axis of said first lens group.
10. The lens unit structure according to claim 2, wherein said
first lens group is an objective lens group.
Digital Camera Patent Description
BACKGROUND OF THE INVENTION
The present invention relates to a lens unit structure adopted
for use in an SLR (single lens reflex) type digital camera.
Recently, SLR type digital cameras (hereinafter, referred to as
SLR digital cameras) have become widely used. An example of an SLR
digital camera is constructed as follows.
The light from an object is incident on a photographing lens system
including a plurality of lens groups. The light passed through the
photographing lens system is incident on a beam splitter, which
splits the incident light into light directed toward a finder optical
system, and light directed to an image capturing element such as
a CCD (Charge Coupled Device). In particular, in the SLR digital
camera which is not a lens-exchangeable one, the photographing lens
system and the finder optical system as well as the beam splitter
are integrally formed as a lens unit.
In general, the plurality of lens groups are held by respective
frame members, which are mounted one by one with the optical axes
thereof being made coincide with each other.
In order to assemble the frame members with holding the positional
relationship therebetween, a plurality of bosses and corresponding
holes for accepting the bosses are formed onto the opponent surfaces
of the frame members.
In such a structure, however, position and surface errors of the
bosses and holes may easily be accumulated, and the optical axes
of the optical elements respectively held by the frame members may
not be aligned accurately. Further, assembling of such a lens unit
is an exacting work, which requires concentration and is time consuming.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an
improved lens unit structure for an SLR digital camera, with which
the lens unit including the photographing optical system and the
finder optical system can be assembled relatively easily at a high
positioning accuracy.
For the above object, according to this invention, there is provided
a lens unit structure for a single lens reflex digital camera, which
is provided with a photographing lens block and a finder block.
The photographing lens block includes a lens barrel having a plurality
of guide shaft members extending in parallel with an optical axis
of the photographing lens block, ends of the plurality of guide
shafts being secured to the lens barrel, and at least one lens group
accommodated in the lens barrel, the at least one lens group being
slidably supported by the plurality of guide shaft members, the
plurality of guide shaft members preventing the at least one lens
group from moving in a direction perpendicular to the optical axis
of the photographing lens block. The finder block includes a casing
that accommodates a finder optical system, an image capturing element,
and a beam splitter, an image receiving surface of the image capturing
element being perpendicular to an optical axis of the beam splitter,
the beam splitter splitting the light passed through the photographing
lens block into light directed to the finder optical system and
light directed to the image capturing element, the casing having
a plurality of holes respectively receiving the plurality of guide
shaft members provided to the lens barrel.
With this structure, the photographing lens block and the finder
block can be separately assembled, and then both blocks are easily
assembled at high accuracy.
It is preferable that, a positional relationship of an optical
axis of the photographing lens block with respect to an optical
axis of the finder block is regulated only by the plurality of guide
shaft members.
According to another aspect of the invention, there is provided
a lens unit structure for a single lens reflex digital camera, comprising
an photographing lens block and a finder block. The photographing
lens block includes a lens barrel having a first lens group and
a plurality of guide shaft members extending in parallel with an
optical axis of the first lens group, and at least one lens group
accommodated in the lens barrel, the at least one lens group being
supported by the plurality of guide shaft members, the at least
one lens group being movable only in a direction parallel to the
optical axis. Further, the finder block includes a casing that accommodates
a finder optical system, an image capturing element, and a beam
splitter, an image receiving surface of the image capturing element
being perpendicular to an optical axis of the beam splitter, the
beam splitter splitting the light passed through the photographing
lens block into light directed to the finder optical system and
light directed to the image capturing element, the casing having
a plurality of holes respectively receiving the plurality of guide
shaft members provided to the lens barrel.
With the above structure, the lens unit including the photographing
optical system and the finder optical system can be assembled relatively
easily at a high positioning accuracy.
Optionally, a position of the at least one lens group so that an
optical axis of the at least one lens coincides with the optical
axis of the first lens group may be regulated only by the plurality
of guide shaft members.
In particular, an optical alignment of the photographing lens block
and the finder block is regulated by inserting the plurality of
guide shaft members in the plurality of holes, respectively.
Further optionally, the at least one lens group accommodated in
the lens barrel includes a focusing lens.
In a particular case, the focusing lens may be held by a focusing
lens frame, and a plurality of through holes, in which the plurality
of guide shaft members are slidably inserted, are formed on the
focusing lens frame.
Still optionally, at least one lens group accommodated in the lens
barrel may further include a zoom lens.
In this case, the focusing lens may be held by a zoom lens frame,
and a plurality of through holes, in which the plurality of guide
shaft members are slidably inserted, are formed on the focusing
lens frame.
In a particular case, the plurality of guide shaft members consists
of a pair of shaft members.
In this case, the pair of shaft members may be arranged opposite
to each other with respect to the optical axis of the first lens
group.
Still optionally, the first lens group may be an objective lens
group of the photographing lens.
DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG. 1 is an exploded perspective view of a lens unit, which includes
a photographing lens block and a finder block, for a single lens
reflex camera according to an embodiment of the invention;
FIG. 2 shows an arrangement of optical elements of a finder optical
system;
FIG. 3 is a plan view of a coupling member formed on a focusing
lens frame; and
FIG. 4 is a perspective rear view of the photographing lens block.
DESCRIPTION OF THE EMBODIMENT
Referring to the accompanying drawings, an SLR digital camera according
to an embodiment of the invention will be described.
FIG. 1 is an exploded perspective view of a lens unit 1 for a single
lens reflex camera according to an embodiment of the invention.
As shown in FIG. 1, the lens unit 1 includes a photographing lens
block 18 and a finder block 11. The photographing lens block 18
and the finder block 11 are separately assembled, and then both
blocks 11 and 18 are assembled into the lens unit 1.
The photographing lens block 18 includes an objective lens 13 attached
to a lens barrel 15, a focusing lens 2 and a zoom lens 6, which
are movably supported inside the lens barrel 15.
The objective lens 13 receives the light from an object and converges
the same. The light passed through the objective lens 13 further
passes through, along an optical axis 14, the focusing lens 2 and
the zoom lens 6, and is emerged from a window 9c formed on a lens
barrel cover 9. Then, the light emerged from the window 9c is incident
on a beam splitter 10, which is accommodated in the finder block
11.
FIG. 2 shows an arrangement of optical elements accommodated in
the finder block 11. The finder block 11 has a casing 11c which
accommodates the above-mentioned beam splitter 10 which splits the
incident light into two components: a first component directed to
a finder optical system 20; and a second component directed to an
imaging device 12.
As shown in FIG. 2, the first component split by the beam splitter
10 forms an image on a focusing glass 21. The light from the focusing
glass 21 is collected by a collective lens 22, and is directed to
a mirror 23. The light reflected by the mirror 23 passes through
a relaying lens 24, reflected by mirrors 25 and 26, and forms an
erected image on a second image plane 27. The erected image is viewed
through an eyepiece lens 16 in a magnified fashion.
As shown in FIG. 1, the lens barrel 15 is formed with a pair of
inner holes 13a and 13b oppositely arranged about and extended along
the optical axis 14. In the inner holes 13a and 13b, one ends of
a pair of guide shafts 3 and 4 are fitted, respectively.
The focusing lens 2 is held by a ring-shaped frame 2a (which will
be referred to as a focusing lens frame). A coupling member 5, which
is elongated in a direction parallel with the optical axis 14, is
integrally formed on the outer circumferential surface of the focusing
lens frame 2a.
FIG. 3 shows a plan view of the coupling member 5. The coupling
member 5 is provided with a pair of guide holes 5c and 5d arranged
to be spaced apart in the direction parallel to the optical axis
14. The guide shaft 4 is slidably fitted in guide holes 5c and 5d.
It should be noted that the pair of guide holes 5c and 5d may be
replaced with a through hole extending in a direction parallel to
the optical axis 14.
The focusing lens frame 2a is further provided with a boss member
17 on the outer-circumferential surface thereof, at a position opposing
to the coupling member 5 with respect to the optical axis 14. The
boss member 17 is formed with a guide hole 17a, to which the guide
shaft 3 is slidably inserted.
In order to allow manufacturing errors, the guide hole 17a may
be formed as a rounded-rectangular shape, which is elongated along
a line connecting the optical axis 14 and the center of the guide
hole 17a. In this case, arc portions are located at both ends of
the rectangular shape, a radius of curvature of each arc portion
is substantially the same as the radius of the guide shaft 3, and
a width (i.e., a distance between the longer sides) of the rectangular
shape is substantially the same as the diameter of the guide shaft
3.
Further, the coupling member 5 is provided with a pair of lug members
5a and 5b (see FIG. 3), between which an operating member of a focusing
lens driving mechanism (not shown) is engaged. By moving the operating
member in a direction parallel to the optical axis 14, the focusing
lens 2 is reciprocally moved along the optical axis 14 with guided
by the guide shafts 3 and 4.
Since the guide shafts 3 and 4 are secured to the lens barrel 15,
and the frame 2a is movable only in the direction of the optical
axis 14, the positional relationship of the frame 2a with respect
to the lens barrel 15 in a direction perpendicular to the optical
axis of the lens barrel 15 is fixed. It should be noted that the
holes 5c, 5d and 17a should be formed such that, when the focusing
lens frame 2a is supported by the guide shafts 3 and 4, the optical
axis of the focusing lens 2 coincides with the optical axis of the
objective lens 13.
Similarly, the zoom lens 6 is held by a ring-shaped frame 61 (which
will be referred to as zoom lens frame), which is formed with a
coupling member 7 on the outer circumferential surface thereof.
The coupling member 7 is formed with a through hole (guide hole)
7a, to which the guide shaft 3 is slidably inserted. It should be
noted that the coupling member 7 is located on the guide shaft 3
side in order to avoid the conflict thereof with respect to the
coupling member 5 when the focusing lens frame 2a and the zoom lens
frame 61 approach.
The zoom lens frame 61 is further formed with a boss member 8 on
the outer-circumferential surface thereof, at the position opposite
to the coupling member 7 with respect to the optical axis of the
zoom lens 6. A through hole (guide hole) 8a is formed on the boss
member 8. The guide shaft 4 is slidably inserted in the guide hole
8a.
In order to allow manufacturing errors, the guide hole 8a may be
formed as a rounded-rectangular shape, which is elongated along
a line connecting the optical axis 14 and the center of the guide
hole 8a. In this case, arc portions are located at both ends of
the rectangular shape, a radius of curvature of each arc portion
is substantially the same as the radius of the guide shaft 4, and
a width (i.e., a distance between the longer sides) of the rectangular
shape is substantially the same as the diameter of the guide shaft
4.
The coupling member 7 is engaged with an operating member of a
zoom lens driving mechanism (not shown) so that the zoom lens frame
61 is reciprocally movable along the optical axis 14 with guided
by the guide shafts 3 and 4.
Since the guide shafts 3 and 4 are secured to the lens barrel 15,
and the frame 61 is movable only in the direction of the optical
axis 14, the positional relationship of the frame 61 with respect
to the lens barrel 15 in a direction perpendicular to the optical
axis of the lens barrel 15 is fixed. It should be noted that the
through holes 7a and 8a should be formed such that, when the frame
61 is supported by the guide shafts 3 and 4, the optical axis of
the zoom lens 6 coincides with the optical axis of the objective
lens 13.
The lens barrel cover 9 is provided with a pair of through-holes
9a and 9b, through which the guide shafts 4 and 3 are inserted.
The photographing lens block 18 is assembled as follows.
Firstly, the pair of guide shafts 3 and 4 are inserted through
the guide hole 17a, and the pair of guide holes 5c and 5d of the
focusing lens frame 2a, respectively. The ends of the guide shafts
3 and 4, which are protruded from the focusing lens frame 2a, are
fitted into the inner holes 13a and 13b. Then, the focusing lens
frame 2a is accommodated inside the lens barrel 15.
Thereafter, the zoom lens frame 61 is accommodated in the lens
barrel 15 by inserting the guide shafts 3 and 4 through the guide
holes 7a and 8a, respectively. Then, the guide shafts 3 and 4 inserted
through the holes 9b and 9a of the lens barrel cover 9, respectively,
and the lens barrel cover 9 is attached and secured to the lens
barrel 15 by means of screws (not shown).
FIG. 4 is a perspective rear view of the photographing lens block
18 as assembled. As shown in FIG. 4, when the lens barrel cover
9 has been attached to the lens barrel 15, the guide shafts 3 and
4 are slightly protruded from the lens barrel cover 9 through the
holes 9b and 9a, respectively.
Since the positions of the lens barrel 15, the focusing lens frame
2a, the zoom lens frame 61 and the lens barrel cover 9 are regulated
by the common guide shafts 3 and 4, which extend in the direction
parallel to the optical axis 14, the photographing lens block 18
can be assembled at a high positional accuracy, and the objective
lens 13, the focusing lens 2 and the zoom lens 6 can be precisely
aligned to have the common optical axis 14.
Next, assembling of the photographing lens block 18 and the finder
block 11 will be described.
The imaging device 12 is secured to the predetermined position
of the finder block 11, on a rear side of the beam splitter 10 such
that the image receiving surface of the imaging device 12 is perpendicular
to the optical axis of the beam splitter 10 (see FIGS. 1 and 2),
by screws or the like.
The finder block 11 is provided with a pair of protruding members
110 and 111, which are protruded in a direction perpendicular to
the optical axis 14. The protruding members 110 and 111 respectively
having through-holes 110a and 111a, which extend in a direction
parallel to the optical axis 14, at the positions corresponding
to the through-holes 9b and 9a of the lens barrel cover 9, or the
positions corresponding to the guide shafts 4 and 3 protruded from
the lens barrel cover 9, respectively.
When the finder block 11 is coupled to the photographing lens block
18, the guide shafts 4 and 3 protruded out of the photographing
lens block 18 (see FIG. 4) are inserted through the through-holes
110a and 111a of the finder block 11. By inserting the guide shafts
4 and 3 through the through-holes 110a and 111a, the positional
relationship between the finder block 11 and the photographing lens
block 18 in the direction perpendicular to the optical axis 14 is
fixed. Then, the finder block 11 is abutted against the photographing
lens block 18 and secured to the lens barrel cover 9 thereof by
means of screws (not shown) which are inserted in screw holes 111b,
121b, 131b (see FIG. 1) and 141b, 151b and 161b (see FIG. 4). Thereby,
the finder block 11 is securely coupled to the photographing lens
block 18.
As described above, according to the lens unit 1 described above,
the pair of guide shafts 3 and 4 are used for adjusting the positional
relationship of the focusing lens 2 and the zoom lens 6 with respect
to the optical axis 14, and for guiding the reciprocal movements
(i.e., focusing and zooming) of the focusing lens and the zoom lens.
Further, the guide shafts 3 and 4 are used for adjusting the positional
relationship, in the direction perpendicular to the optical axis
14, between the separately assembled photographing lens block 18
and the finder block 11.
In the above-described embodiments, the photographing lens block
is described to include both the focusing lens and the zoom lens.
The invention is not limited to this structure, and even if the
photographing lens includes only one movable lens (i.e., focusing
lens), the invention can be applied. Further, even in a case where
the photographing lens includes more than two lenses which are to
be guided by and movable along the guide shafts, the invention can
be applied.
The present disclosure relates to the subject matter contained
in Japanese Patent Application No. 2000-021183, filed on Jan. 31,
2000, which is expressly incorporated herein by reference in its
entirety.
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