U.S. patent application number 12/656314 was filed with the patent office on 2010-07-29 for mirror unit and image capturing apparatus.
This patent application is currently assigned to NIKON CORPORATION. Invention is credited to Toshiaki Kurahashi.
Application Number | 20100189428 12/656314 |
Document ID | / |
Family ID | 42354225 |
Filed Date | 2010-07-29 |
United States Patent
Application |
20100189428 |
Kind Code |
A1 |
Kurahashi; Toshiaki |
July 29, 2010 |
Mirror unit and image capturing apparatus
Abstract
Goal: Providing a mirror unit that can decrease the wait time
before distance measurement. Means: A mirror unit comprising a
first mirror; a second mirror; a first mirror holder that holds the
first mirror, is rotatable on a rotational axis arranged above an
optical path of the incident light, is lowered to a first
mirror-down position, and is raised to a first mirror-up position;
and a second mirror holder that includes an auxiliary component and
a mirror holding component holding the second mirror, is lowered to
a second mirror-down position, and is raised to a second mirror-up
position, wherein the auxiliary component is provided below the
first mirror holder in the direction of the lowering, is rotatable
on a rotational axis that is the same as or parallel to the
rotational axis of the first mirror holder, and can be lowered
independently of the first mirror holder, and the mirror holding
component is engaged with the auxiliary component to be relatively
rotatable around a rotational axis that is parallel to the
rotational axis of the auxiliary component.
Inventors: |
Kurahashi; Toshiaki;
(US) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700, 1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
NIKON CORPORATION
Tokyo
JP
|
Family ID: |
42354225 |
Appl. No.: |
12/656314 |
Filed: |
January 25, 2010 |
Current U.S.
Class: |
396/111 ;
359/872 |
Current CPC
Class: |
G03B 13/00 20130101 |
Class at
Publication: |
396/111 ;
359/872 |
International
Class: |
G03B 13/00 20060101
G03B013/00; G02B 7/182 20060101 G02B007/182 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 26, 2009 |
JP |
2009-014052 |
Claims
1. A mirror unit comprising: a first mirror that reflects and
passes incident light from a subject side; a second mirror that
reflects the incident light passed by the first mirror; a first
mirror holder that holds the first mirror, is rotatable on a
rotational axis arranged above an optical path of the incident
light, is lowered to a first mirror-down position in which the
first mirror is inserted into the optical path of the incident
light, and is raised to a first mirror-up position in which the
first mirror is removed from the optical path of the incident
light; and a second mirror holder that includes an auxiliary
component and a mirror holding component holding the second mirror,
is lowered to a second mirror-down position in which the second
mirror is inserted into the optical path of the incident light, and
is raised to a second mirror-up position in which the second mirror
is removed from the optical path of the incident light, wherein the
auxiliary component is provided below the first mirror holder in
the direction of the lowering, is rotatable on a rotational axis
that is the same as or parallel to the rotational axis of the first
mirror holder, and can be lowered independently of the first mirror
holder, and the mirror holding component is engaged with the
auxiliary component to be relatively rotatable around a rotational
axis that is parallel to the rotational axis of the auxiliary
component.
2. The mirror unit according to claim 1, wherein the auxiliary
component and the first mirror holder are rotatable on the same
axis.
3. The mirror unit according to claim 1, wherein the second mirror
holder is lowered from the second mirror-up position to the second
mirror-down position prior to the first mirror holder being lowered
from the first mirror-up position to the first mirror-down
position.
4. The mirror unit according to claim 1, further comprising: a
first contact member provided on the first mirror holder; a second
contact member provided on the auxiliary component; and a pushing
component that contacts the first contact member and the second
contact member to be moved upward by the first contact member and
the second contact member, thereby pushing the first mirror holder
to the first mirror-up position and pushing the second mirror
holder to the second mirror-up position.
5. The mirror unit according to claim 1, wherein a rotational
radius of the auxiliary component is less than a rotational radius
of the first mirror holder.
6. The mirror unit according to claim 1, comprising: a first
biasing member that biases the first mirror holder in a direction
of the lowering; and a second biasing member that biases the
auxiliary component in the direction of the lowering to lower the
auxiliary component more quickly than the first mirror holder.
7. An image capturing apparatus comprising: for unit according to
claim 1; an image capturing unit that is arranged in the optical
path of the incident light; and a distance measuring sensor that
receives the incident light reflected by the second mirror.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present application claims priority from a Japanese
Patent Application No. 2009-014052 filed on Jan. 26, 2009, the
contents of which are incorporated herein by reference.
[0003] The present invention relates to a mirror unit and an image
capturing apparatus.
[0004] 2. Related Art
[0005] A known mirror unit for a single lens reflex camera includes
a main mirror, which is a half mirror, and a sub-mirror that
reflects the light passed by the main mirror downward to a distance
measuring sensor, and these mirrors are lowered into the optical
path or raised above the optical path, as shown in Japanese Patent
Application Publications No. 62-78536 and No. 63-95430. In such a
mirror unit, a sub-frame holding the sub-mirror hangs down to be
rotatable relative to a main frame holding the main mirror.
[0006] To achieve accurate distance measurement, it is desirable
that measurement be started after vibration of the lowered
sub-mirror has stopped. However, in this mirror unit, the vibration
of the sub-mirror does not stop until the vibration of the lowered
main frame has stopped. In other words, initiation of distance
measurement is delayed because of the vibration of the main
frame.
SUMMARY
[0007] To solve this problem, a first aspect of the present
invention provides a mirror unit comprising a first mirror (102)
that reflects and passes incident light from a subject side; a
second mirror (104) that reflects the incident light passed by the
first mirror; a first mirror holder (110) that holds the first
mirror, is rotatable on a rotational axis arranged above an optical
path of the incident light, is lowered to a first mirror-down
position in which the first mirror is inserted into the optical
path of the incident light, and is raised to a first mirror-up
position in which the first mirror is removed from the optical path
of the incident light; and a second mirror holder that includes an
auxiliary component (114) and a mirror holding component (112)
holding the second mirror, is lowered to a second mirror-down
position in which the second mirror is inserted into the optical
path of the incident light, and is raised to a second mirror-up
position in which the second mirror is removed from the optical
path of the incident light, wherein the auxiliary component is
provided below the first mirror holder in the direction of the
lowering, is rotatable on a rotational axis that is the same as or
parallel to the rotational axis of the first mirror holder, and can
be lowered independently of the first mirror holder, and the mirror
holding component is engaged with the auxiliary component to be
relatively rotatable around a rotational axis that is parallel to
the rotational axis of the auxiliary component.
[0008] The summary clause does not necessarily describe all
necessary features of the embodiments of the present invention. The
present invention may also be a sub-combination of the features
described above. The above and other features and advantages of the
present invention will become more apparent from the following
description of the embodiments taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic cross-sectional side view of a single
lens reflex digital camera 101 provided with a mirror unit 100
according to an embodiment of the present invention.
[0010] FIG. 2 is a schematic view as seen from the right side of a
photographer of the mirror unit 100 in a mirror-down state
[0011] FIG. 3 is a schematic view as seen from the left side of a
photographer of the mirror unit 100 in a mirror-down state.
[0012] FIG. 4A is a schematic view as seen from the right side of a
photographer of the auxiliary frame 114 and the sub-frame 112 in a
mirror-down state.
[0013] FIG. 4B is a schematic view as seen from the left side of a
photographer of the auxiliary frame 114 and the sub-frame 112 in a
mirror-down state.
[0014] FIG. 5 is a plan view seen from below of the mirror unit 100
in a mirror-up state.
[0015] FIG. 6A is a side view as seen from the right side of a
photographer of the mirror unit 100 in a mirror-down state.
[0016] FIG. 6B is a side view as seen from the left side of a
photographer of the mirror unit 100 in a mirror-down state.
[0017] FIG. 7A is a side view as seen from the right side of a
photographer of the mirror unit 100 when a mirror-up operation is
performed.
[0018] FIG. 7B is a side view as seen from the left side of a
photographer of the mirror unit 100 when a mirror-up operation is
performed.
[0019] FIG. 8A is a side view as seen from the right side of a
photographer of the mirror unit 100 in the mirror-up state.
[0020] FIG. 8B is a side view as seen from the left side of a
photographer of the mirror unit 100 in the mirror-up state.
[0021] FIG. 9A is a side view as seen from the right side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed.
[0022] FIG. 9B is a side view as seen from the left side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed.
[0023] FIG. 10A is a side view as seen from the right side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed.
[0024] FIG. 10B is a side view as seen from the left side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed.
[0025] FIG. 11A is a side view as seen from the right side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed.
[0026] FIG. 11B is a side view as seen from the left side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed.
[0027] FIG. 12A is a side view as seen from the right side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed.
[0028] FIG. 12B is a side view as seen from the left side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0029] Hereinafter, some embodiments of the present invention will
be described. The embodiments do not limit the invention according
to the claims, and all the combinations of the features described
in the embodiments are not necessarily essential to means provided
by aspects of the invention.
[0030] FIG. 1 is a schematic cross-sectional side view of a single
lens reflex digital camera 101 provided with a mirror unit 100
according to an embodiment of the present invention. As shown in
FIG. 1, the digital camera 101 is provided with an optical
component 420, a lens barrel 430, an image capturing unit 500 such
as a CCD, and a control section 550. The lens barrel 430 houses the
optical component 420. The image capturing unit 500 captures an
image of a subject that is focused by the optical component 420.
The control section 550 controls the image capturing unit 500.
[0031] The digital camera 101 includes a lens unit 410, which
contains the optical component 420 and the lens barrel 430, and a
body 460. The lens unit 410 is detachably mounted on the body 460
via a mount 450.
[0032] The optical component 420 contains, in order from an
incident end that is the left side of FIG. 1, a front lens 422, a
compensator lens 424, a focusing lens 426, and a main lens 428. An
iris unit 440 is arranged between the focusing lens 426 and the
main lens 428.
[0033] The body 460 houses an optical component that includes the
mirror unit 100, a pentaprism 470, and an eyepiece system 490. The
mirror unit 100 includes a main mirror 102, which is a half mirror
for reflecting and passing incident light passed through the lens
unit 410. The main mirror 102 moves between (i) a down position in
which the main mirror 102 is arranged diagonally in the optical
path of the incident light and (ii) an up position, shown by a
dotted line in FIG. 1, in which the main mirror 102 is raised out
of the optical path of the incident light.
[0034] When in the down position, the main mirror 102 guides a
majority of the incident light to the pentaprism 470. The
pentaprism 470 projects the reflection of the incident light toward
the eyepiece system 490, and therefore the image of the focusing
screen can be seen as a real image from the eyepiece system 490.
The remaining incident light is guided to the light measuring unit
480 by the pentaprism 470. The light measuring unit 480 measures
the intensity of the incident light, and a distribution or the like
of this intensity.
[0035] A half mirror 492 is arranged between the pentaprism 470 and
the eyepiece system 490 to superimpose a display image formed by a
finder liquid crystal 494 onto the image of the focusing screen.
The display image is displayed overlapping the image projected from
the pentaprism 470.
[0036] The mirror unit 100 includes a sub-mirror 104 on a back side
of the main mirror 102, which is the side of the main mirror 102
not facing the incident light. The sub-mirror 104 moves between (i)
a down position in which the sub-mirror 104 is arranged diagonally
in the optical path of the incident light and (ii) an up position,
shown by the dotted line in FIG. 1, in which the sub-mirror 104 is
raised out of the optical path of the incident light.
[0037] When in the down position, the sub-mirror 104 guides the
incident light passed by the main mirror 102 to a distance
measuring unit 530 arranged below the sub-mirror 104. In other
words, when the main mirror 102 and the sub-mirror 104 are in the
down position, the distance measuring unit 530 measures the
distance to the subject. When the main mirror 102 is moved to the
up position, the sub-mirror 104 also moves to the up position.
[0038] A focal plane shutter 540, a low-pass filter 510, and an
image capturing unit 500 are arranged in the stated order behind
the main mirror 102 in the direction of the incident light. When
the focal plane shutter 540 is opened, the main mirror 102 and the
sub-mirror 104 positioned immediately in front of the focal plane
shutter 540 are moved to the up position, and so the incident light
can enter directly into the image capturing unit 500. In this way,
the image formed by the incident light is converted into an
electric signal. As a result, the image capturing unit 500 can
capture the image focused by the lens unit 410.
[0039] FIG. 2 is a schematic view as seen from the right side of a
photographer of the mirror unit 100 in a mirror-down state. In FIG.
2, a direction to the right of the camera is represented by the
arrow X, a direction upward from the camera is represented by the
arrow Y, and the direction in which the incident light proceeds is
represented by the arrow Z.
[0040] The mirror unit 100 is provided with a main frame 110 that
holds the main mirror 102, a sub-frame 112 that holds the
sub-mirror 104, and an auxiliary frame 114 that holds the sub-frame
112. The main frame 110 is provided with a rectangular base part
116 on which the main mirror 102 is mounted and side parts 118 and
120 that are provided on the left and right sides of the base part
116 and extend at substantially right angles therefrom to curve
toward a subject side. The base part 116 has a rectangular aperture
122 that passes the incident light passed through the main mirror
102.
[0041] Circular holes are formed on the tips of the side parts 118
and 120 and shafts 124 and 126 are inserted into these holes to be
relatively rotatable. The shafts 124 and 126 are arranged along an
axis that runs crosswise in the camera and that is positioned above
the optical path of the incident light, and are fixed on a unit
frame 111. Therefore, the main frame 110 is supported in a manner
to be rotatable on an axis positioned above the optical path of the
incident light and extending crosswise in the camera.
[0042] The shaft 126 is inserted into a torsion coil spring 140
serving as a biasing member. The ends of the torsion coil spring
140 are locked respectively by an upper portion of the side part
120 and a locking part 103 formed on the unit frame 111. The ends
of the torsion coil spring 140 can be elastically deformed in a
direction to draw near each other, and the restorative force biases
the side part 120 downward around the shaft 126. Accordingly, the
main frame 110 is biased by the torsion coil spring 140 downward
around the shafts 124 and 126.
[0043] The auxiliary frame 114 includes a rectangular base part 128
that is arranged lower than the base part 116 and has a length
extending crosswise in the camera, and side parts 130 and 132 that
are provided on the left and right sides of the base part 128 and
extend at substantially right angles in a curving manner. The side
parts 130 and 132 have lengths that extend along the width of the
base part 128. One longitudinal end of the side part 130 has a
circular hole into which the shaft 124 is inserted to be relatively
rotatable, and one longitudinal end of the side part 132 has a
circular hole into which the shaft 126 is inserted to be relatively
rotatable. As a result, the auxiliary frame 114 can be supported in
a manner to be rotatable relative to the unit frame 111 on an axis
positioned above the optical path of the incident light and
extending crosswise in the camera. Furthermore, the auxiliary frame
114 is supported to be rotatable with respect to the unit frame 111
on the same axis as the main frame 110.
[0044] The shaft 124 is inserted into a torsion coil spring 142
serving as a biasing member. The ends of the torsion coil spring
142 are locked respectively by an upper portion of the side part
130 and a locking part 105 formed on the unit frame 111. The ends
of the torsion coil spring 142 can be elastically deformed in a
direction to draw near each other, and the restorative force biases
the side part 130 downward around the shaft 124. Accordingly, the
auxiliary frame 114 is biased by the torsion coil spring 142
downward around the shafts 124 and 126.
[0045] The sub-frame 112 includes a rectangular base part 134 that
has a length extending crosswise in the camera and on which is
mounted the sub-mirror 104, and side parts 136 and 138 that are
provided on the left and right sides of the base part 134 and
extend at substantially right angles in to curve toward a subject
side. The side parts 136 and 138 have lengths that extend along the
width of the base part 134. One longitudinal end of the side part
136 is engaged with the side part 130 of the auxiliary frame 114
via a coupling axle 137 in a manner to be relatively rotatable, and
one longitudinal end of the side part 138 is engaged with the side
part 132 of the auxiliary frame 114 via the coupling axle 137 in a
manner to be relatively rotatable.
[0046] One longitudinal end of the side part 136 has a boss 144
protruding towards the center of the camera in the crosswise
direction. A longitudinal central portion of the side part 130 of
the auxiliary frame 114 has a boss 146 that protrudes outward in
the crosswise direction. The base end of the boss 146 is inserted
into a toggle spring 148 serving as a biasing member. One end of
the toggle spring 148 is locked by the side part 130, and the other
end of the toggle spring 148 is locked by the boss 144. The ends of
the toggle spring 148 can be elastically deformed in a direction to
draw near each other, and the restorative force biases the side
part 136 in the rotational direction of the coupling axle 137. The
operation of the toggle spring 148 is described further below.
[0047] The side part 118 of the main frame 110 has a cam 150
mounted via an axle 152. The axle 152 is arranged in line with the
boss 146 in the direction of rotation. The cam 150 is an
elliptically shaped component, and one longitudinal end of the cam
150 is engaged with the axle 152. The other longitudinal end of the
cam 150 is arranged to oppose the end surface of the boss 146.
[0048] A mirror-up lever 154 is arranged below the cam 150 and the
boss 146. The mirror-up lever 154 pivots on a pivotal axis arranged
toward the subject side and the bottom thereof to push up the cam
150 and the boss 146. A detailed description of this operation is
described further below.
[0049] A positioning pin 156 is provided beneath the shaft 126 and
below the auxiliary frame 114 in a direction in which the auxiliary
frame 114 is lowered. The positioning pin 156 contacts the base
part 128 when the auxiliary frame 114 is lowered. The down position
of the auxiliary frame 114 is determined by the positioning pin 156
exerting pressure on the torsion coil spring 142.
[0050] A positioning pin 158 is arranged directly below the shaft
126. The other longitudinal end of the side part 138 of the
sub-frame 112, i.e. the end on the outside of the rotational radial
direction, has a U-shaped groove 160, and the positioning pin 158
engages with this U-shaped groove 160. The down position of the
sub-frame 112 is determined by toggle spring 148 applying pressure
to the positioning pin 158.
[0051] Here, the length of the auxiliary frame 114 from the shafts
124 and 126 to the outer end in the rotational radial direction is
less than the length of the main frame 110 from the shafts 124 and
126 to the outer end in the rotational radial direction. In
particular, in the mirror unit 100 of the present embodiment, the
length of the auxiliary frame 114 from the shafts 124 and 126 to
the outer end in the rotational radial direction is less than half
of the length of the main frame 110 from the shafts 124 and 126 to
the outer end in the rotational radial direction. As a result, the
moment of inertia of the auxiliary frame 114 is less than the
moment of inertia of the main frame 110.
[0052] The spring constants of the torsion coil springs 140 and 142
are set according to the difference in moment of inertia between
the auxiliary frame 114 and the main frame 110, such that the
auxiliary frame 114 is lowered faster than the main frame 110. For
example, in the present embodiment, the moment of inertia of the
main frame 110 is greater than that of the auxiliary frame 114, and
so the spring constants of the torsion coil springs 140 and 142 are
set to be the same, or are set such that the spring constant of the
torsion coil spring 142 biasing the auxiliary frame 114 is greater
than the spring constant of the torsion coil spring 140 biasing the
main frame 110. Furthermore, the spring constant of the torsion
coil spring 140 may be set greater than the spring constant of the
torsion coil spring 142 as long as the lowering speed of the main
frame 110 does not exceed the lowering speed of the auxiliary frame
114.
[0053] FIG. 3 is a schematic view as seen from the left side of a
photographer of the mirror unit 100 in a mirror-down state. As
shown in FIG. 3, a positioning pin 162 is arranged beneath the
shaft 124 and below the main frame 110 in the direction in which
the main frame 110 is lowered. The positioning pin 162 contacts the
base part 116 of the lowered main frame 110. The down position of
the main frame 110 is determined by the torsion coil spring 140
exerting pressure on the positioning pin 162.
[0054] A cam 164 is provided on an upper end of the side part 138
of the sub-frame 112. A cam groove 166 is formed in the cam 164.
The unit frame 111 has a cam pin 168 that protrudes to be inserted
into the cam groove 166. The operation of the cam 164 and the cam
pin 168 is explained in detail further below.
[0055] FIG. 4A is a schematic view as seen from the right side of a
photographer of the auxiliary frame 114 and the sub-frame 112 in a
mirror-down state. As shown in FIG. 4A, the auxiliary frame 114 is
suspended from the shafts 124 and 126 in a diagonal orientation
relative to the subject side. The sub-frame 112 is suspended from
the coupling axle 137 in a diagonal orientation relative to the
imaging side.
[0056] Here, the auxiliary frame 114 is not engaged with the main
frame 110, and the base part 128 of the auxiliary frame 114 is
arranged below the base part 116 of the main frame 110. Therefore,
when the auxiliary frame 114 is lowered to the down position, there
is no interference with the main frame 110. Accordingly, the
auxiliary frame 114 can be lowered to the down position
independently from the main frame 110.
[0057] FIG. 4B is a schematic view as seen from the left side of a
photographer of the auxiliary frame 114 and the sub-frame 112 in a
mirror-down state. As shown in FIG. 4B, the cam groove 166 of the
cam 164 is formed on a free curve. The wall of the cam groove 166
contacts the cam pin 168 when the sub-frame 112 is raised from the
down position to the up position, but the direction of the weight
between the cam groove 166 and the cam pin 168 changes according to
the angular position of the sub-frame 112.
[0058] FIG. 5 is a plan view seen from below of the mirror unit 100
in a mirror-up state. As shown in FIG. 5, the aperture 122 formed
in the base part 116 of the main frame 110 is blocked by the main
mirror 102. However, a passing portion 1021 with an area smaller
than that of the aperture 122 is formed in a region where the main
mirror 102 overlaps the aperture 122. The periphery of the passing
portion 1021 of the main mirror 102 is a light blocking region
covered with an opaque material.
[0059] Here, the base part 134 of the sub-frame 112 has a greater
area than the passing portion 1021, and the base part 134 overlaps
with the entire area of the passing portion 1021 when viewed in an
up and down direction.
[0060] As a result, with the main mirror 102 and the sub-mirror 104
in the up position, light is blocked from reaching the passing
portion 1021 of the main mirror 102 by the sub-mirror 104 and the
base part 134 of the sub-frame 112. Accordingly, the inverse
incident light from the finder is prevented from leaking into the
mirror box.
[0061] The following describes the operation of the mirror unit
100. In the following description, the rotation of the main frame
110, the sub-frame 112, and the auxiliary frame 114 from the down
position to the up position is referred to as the "up direction"
and the rotation of the main frame 110, the sub-frame 112, and the
auxiliary frame 114 from the up position to the down position is
referred to as the "down direction."
[0062] FIG. 6A is a side view as seen from the right side of a
photographer of the mirror unit 100 in a mirror-down state, and
FIG. 6B is a side view as seen from the left side of a photographer
of the mirror unit 100 in a mirror-down state. As shown in FIGS. 6A
and 6B, by pressing a release switch, a drive motor of the mirror
unit 100 is driven to pivot the mirror-up lever 154. The mirror-up
lever 154 pivots around a pivot point 155 that is arranged downward
and toward the subject side from the mirror-up lever 154. The
mirror-up lever 154 pivots upward and toward the subject side
around the pivot point 155.
[0063] With the main frame 110 and the auxiliary frame 114 in the
down position, the mirror-up lever 154 does not contact the boss
146 or the cam 150. Furthermore, the wall of the cam groove 166
does not contact the cam pin 168.
[0064] FIG. 7A is a side view as seen from the right side of a
photographer of the mirror unit 100 when a mirror-up operation is
performed, and FIG. 7B is a side view as seen from the left side of
a photographer of the mirror unit 100 when a mirror-up operation is
performed. As shown in FIGS. 7A and 7B, when the mirror-up
operation is begun for the mirror unit 100, the mirror-up lever 154
contacts the boss 146. The auxiliary frame 114 responds to the bias
of the torsion coil spring 142 to rotate on the shafts 124 and 126
in the up direction. Next, the mirror-up lever 154 contacts the cam
150. The main frame 110 responds to the bias of the torsion coil
spring 140 to rotate on the shafts 124 and 126 in the up
direction.
[0065] At this time, the sub-frame 112 follows the auxiliary frame
114 to rotate on the shafts 124 and 126 in the up direction. In
this state, the bias of the toggle spring 148 is exerted against
the sub-frame 112 in the down direction around the coupling axle
137. Furthermore, the wall of the cam groove 166 contacts the cam
pin 168, and the cam pin 168 exerts a counter force on the cam
groove 166. This counter force is exerted on the cam 164 in the up
direction around the coupling axle 137. Due to this counter force,
the sub-frame 112 responds to the bias of the toggle spring 148 to
rotate in the up direction on the coupling axle 137.
[0066] When the auxiliary frame 114 is raised further, the cam
groove 166 and the cam pin 168 cause the sub-frame 112 to rotate in
the up direction on the coupling axle 137. The bias direction of
the toggle spring 148 changes to the up direction on the coupling
axle 137. Therefore, the sub-frame 112 responds to the bias of the
toggle spring 148 to rotate in the up direction on the coupling
axle 137.
[0067] FIG. 8A is a side view as seen from the right side of a
photographer of the mirror unit 100 in the mirror-up state, and
FIG. 8B is a side view as seen from the left side of a photographer
of the mirror unit 100 in the mirror-up state. As shown in FIGS. 8A
and 8B, in this state, the bias of the torsion coil spring 142
causes the boss 146 of the auxiliary frame 114 to exert pressure on
the top surface of the mirror-up lever 154. Furthermore, the bias
of the torsion coil spring 140 causes the cam 150 of the main frame
110 to exert pressure on the top surface of the mirror-up lever
154. As a result, the main frame 110 and the auxiliary frame 114
are stopped in a state of vertically overlapping each other.
[0068] The bias of the toggle spring 148 causes the base part 134
of the sub-frame 112 to exert pressure on the base part 116 of the
main frame 110. As a result, the main frame 110 and the sub-frame
112 are stopped in a state of vertically overlapping each
other.
[0069] FIG. 9A is a side view as seen from the right side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed, and FIG. 9B is a side view as seen from the left side of
a photographer of the mirror unit 100 when a mirror-down operation
is performed. As shown in FIGS. 9A and 9B, when the mirror-down
operation is begun for the mirror unit 100, the mirror-up lever 154
is lowered. Next, the auxiliary frame 114 and the main frame 110
are lowered by the bias of the torsion coil springs 142 and 140
exerting pressure on the mirror-up lever 154. Furthermore, the cam
groove 166 and the cam pin 168 cause the auxiliary frame 114 to
rotate in the down direction on the coupling axle 137. The bias
direction of the toggle spring 148 then changes to the down
direction on the coupling axle 137.
[0070] FIG. 10A is a side view as seen from the right side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed, and FIG. 10B is a side view as seen from the left side
of a photographer of the mirror unit 100 when a mirror-down
operation is performed. As shown in FIGS. 10A and 10B, in this
state, the auxiliary frame 114 rotates in the down direction, i.e.
the auxiliary frame 114 is lowered, due to its own weight, the
weight of the sub-frame 112, and the bias of the torsion coil
spring 142. The sub-frame 112 rotates in the down direction due to
its own weight and the bias of the toggle spring 148. The main
frame 110 rotates in the down direction, i.e. the main frame 110 is
lowered, by its own weight and the bias of the torsion coil spring
140.
[0071] Here, the length of the auxiliary frame 114 from the shafts
124 and 126 to the outer end in the rotational radial direction is
less than the length of the main frame 110 from the shafts 124 and
126 to the outer end in the rotational radial direction. As a
result, the moment of inertia of the auxiliary frame 114 is less
than the moment of inertia of the main frame 110. The spring
constants of the torsion coil springs 140 and 142 are set such that
the rotational speed of the auxiliary frame 114 in the down
direction is greater than the rotational speed of the main frame
110 in the down direction. Accordingly, when the mirror-down
operation is performed for the mirror unit 100, the auxiliary frame
114 begins rotating in the down direction earlier than the main
frame 110.
[0072] FIG. 11A is a side view as seen from the right side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed, and FIG. 11B is a side view as seen from the left side
of a photographer of the mirror unit 100 when a mirror-down
operation is performed. As shown in FIGS. 11A and 11B, the
positioning pin 158 is engaged with the U-shaped groove 160 of the
sub-frame 112 prior to the auxiliary frame 114 contacting the
positioning pin 156.
[0073] FIG. 12A is a side view as seen from the right side of a
photographer of the mirror unit 100 when a mirror-down operation is
performed, and FIG. 12B is a side view as seen from the left side
of a photographer of the mirror unit 100 when a mirror-down
operation is performed. As shown in FIGS. 12A and 12B, the
auxiliary frame 114 rotates in the down direction due to its own
weight, the weight of the sub-frame 112, and the bias of the
torsion coil spring 142. As a result, the auxiliary frame 114 comes
into contact with the positioning pin 156, and the positioning pin
158 enters deeply into the U-shaped groove 160. In this state, the
bias of the torsion coil spring 142 causes the auxiliary frame 114
to exert pressure on the positioning pin 156, and the bias of the
toggle spring 148 causes the sub-frame 112 to exert pressure on the
positioning pin 158. As a result, the auxiliary frame 114 and the
sub-frame 112 are stopped in the down position.
[0074] On the other hand, the main frame 110 rotates in the down
direction, due to its own weight and the bias of the torsion coil
spring 140, later than the auxiliary frame 114. The main frame 110
then contacts the positioning pin 162. In this state, the bias of
the torsion coil spring 140 causes the main frame 110 to exert
pressure on the positioning pin 162. As a result, the main frame
110 stops in the down position.
[0075] After the main frame 110, the sub-frame 112, and the
auxiliary frame 114 reach the down position, vibrate vibration is
caused by elastic vibration of the torsion coil springs 140 and 142
and the toggle spring 148. In other words, the main frame 110, the
sub-frame 112, and the auxiliary frame 114 bounce upon reaching the
down position.
[0076] Here, the sub-mirror 104 held by the sub-frame 112 guides
the incident light to the distance measuring sensor disposed
therebelow, but when the sub-mirror 104 bounces, the length of the
optical path and direction of the optical axis of the incident
light directed toward the distance measuring sensor changes,
thereby preventing accurate distance measurement. Therefore, it is
necessary to wait for the sub-mirror 104 to stop bouncing before
beginning the distance measurement.
[0077] If the time from when the mirror-down operation begins to
when the sub-mirror 104 stops bouncing can be shortened so that the
distance measurement can begin earlier, the number of images that
can be captured per unit time during continuous image capturing can
be increased.
[0078] In the mirror unit 100 of the present embodiment, the
auxiliary frame 114 and the sub-frame 112 are lowered to the down
position independently from the main frame 110, and therefore the
bouncing of the main frame 110 does not affect the sub-mirror 104.
Accordingly, the distance measurement can be begun without waiting
for the bouncing of the main frame 110 to stop.
[0079] In particular, since the rotational radius of the auxiliary
frame 114 in the mirror unit 100 of the present embodiment is less
than the rotational radius of the main frame 110, the moment of
inertia of the auxiliary frame 114 is less than the moment of
inertia of the main frame 110. Furthermore, the spring forces of
the torsion coil springs 140 and 142 are set such that the
rotational speed of the main frame 110 in the down direction does
not exceed the rotational speed of the auxiliary frame 114 in the
down direction. Yet further, the auxiliary frame 114 is arranged
further downward in the direction of the lowering than the main
frame 110, and so the auxiliary frame 114 can rotate in the down
direction independently from the main frame 110.
[0080] Since the auxiliary frame 114 and the sub-frame 112 move to
the down position prior to the main frame 110, as described above,
the time from when the mirror-down operation begins to when the
sub-mirror 104 stops bouncing is shortened. Accordingly, the
distance measurement can be begun earlier and the number of images
that can be captured per unit time during continuous image
capturing can be increased.
[0081] With the mirror unit 100 of the present embodiment, the
mirror-up lever 154 contacts the boss 146 that is provided on the
auxiliary frame 114 and the cam 150 provided on the main frame 110.
As a result, the main mirror 102 and the sub-mirror 104, which move
independently from each other during the mirror-up and mirror-down
operations, can be driven by a shared mirror driving mechanism.
Accordingly, an increase in the cost of the mirror driving
mechanism is prevented.
[0082] While the embodiments of the present invention have been
described, the technical scope of the invention is not limited to
the above described embodiments. It is apparent to persons skilled
in the art that various alterations and improvements can be added
to the above-described embodiments. It is also apparent from the
scope of the claims that the embodiments added with such
alterations or improvements can be included in the technical scope
of the invention. For example, the embodiments described the main
frame 110 and the auxiliary frame 114 as being rotatable on the
same axis, but the main frame 110 and the auxiliary frame 114 may
instead be arranged to be rotatable on separate rotational axes
that are parallel to each other.
[0083] The operations, procedures, steps, and stages of each
process performed by an apparatus, system, program, and method
shown in the claims, embodiments, or diagrams can be performed in
any order as long as the order is not indicated by "prior to,"
"before," or the like and as long as the output from a previous
process is not used in a later process. Even if the process flow is
described using phrases such as "first" or "next" in the claims,
embodiments, or diagrams, it does not necessarily mean that the
process must be performed in this order.
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