Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION
STEREO CAMERA
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a stereo camera.
More particularly, the invention relates to a stereo camera
which adjusts the distance between the optical axes of two
photographing lenses being interlocked to the operation for
adjusting the focal point.
Background of the Invention
In a stereo camera which takes two pieces of pictures
at one time through a pair of right and left photographing
lenses, the distance between the optical axes of the two
photographing lenses has generally been fixed. In the stereo
camera of this type in which the distance between the optical
axes is fixed as shown in Figs. 20(L) and 20(R) in an
exaggerated manner, there develop non-overlapped regions (a-b,
c-d) on the outer sides of the overlapped region (b-c) of the
right and left photographed pictures L and R due to parallax of
the two photographing lenses. As the distance to the subject
becomes closer, furthermore, the position of the image of the
subject in the right and left photographed pictures undergo a
displacement toward the directions to approach each other.
The non-overlapped regions (a-b, c-d) are the portions
where no stereo image is formed. When viewed by using a stereo
slide viewer, the picture frames of the slide mount are
overlapped on the boundaries of the non-overlapped regions as
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shown in Fig. 21, which is offensive to see. Besides, a stereo
image of the subject at a distance closer than a focal distance
appears in front of the stereo window (imaginary window in which
the right and left picture frames of the mount become in
agreement and appear as one picture when the stereo slide is
viewed in a three-dimensional manner), which is unnatural. The
stereo slides that have been proposed are accompanied by the
above-mentioned defects.
In order to correct these defects, therefore, it has
been attempted to mask the non-overlapped regions (a-b, c-d) of
the right and left pictures by using a stereo slide mount having
windows of a width narrower than the width of the pictures on
the films, and to correct the perspective feeling by adjusting
the pitch between the right and left films. The above method,
however, is accompanied by a difficulty for determining a proper
masking amount and for determining the positions of the films
relative to the windows of the mount in the transverse direction
and, besides, involves large loss of picture due to masking.
The above-mentioned problems caused by a difference in
the visual field between the right and left photographing lenses
can be solved by correcting the visual field by adjusting the
distance between the optical axes of the right and left
photographing lenses. As the devices for adjusting the distance
between the optical axes of the stereo camera, there have been
known the one of the manually adjusting type for adjusting the
distance between the optical axes irrespective of the focal
point-adjusting mechanism and the one of the automatically
adjusting type for adjusting the distance between the optical
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axes being interlocked to a mechanism for adjusting the focal
point. The device of the manually adjusting type is capable of
adjusting the distance between the optical axes of the lenses to
an optimum value depending upon a distance to the main subject
and upon a distance between the main subject and another
subject, but requires cumbersome operation for separately
adjusting the focal point and the distance between the optical
axes. Though scenery and still life can be photographed without
interruption, this method lacks performance for quickly shooting
pictures. Besides, the user may incorrectly set the distance
between the optical axes unless he is well accustomed to the
operation and function of the mechanism for adjusting the
distance between the optical axes, which is never easy to
handle. Accordingly, the automatic mechanism for adjusting the
distance between the optical axes is more suited for a stereo
camera used by general public than the manual mechanism for
adjusting the distance between the optical axes.
The conventional automatic mechanism for adjusting the
distance between the optical axes has been so constituted that
the vidual fields of the right and left photographing lenses are
brought into agreement at all times at a focal distance and that
the distance between the optical axes is automatically adjusted
being interlocked to the adjustment of the focal point to obtain
a constant effect for correcting the distance between the
optical axes.
If it is presumed that the lens is a thin lens and,
focal distance of the lens --- f
distance from the subject to a main
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point of the lens --- L
distance from the focal point of the
lens to the image-forming position --- d if
then,
~if = f2/(L - f) --- (1)
and the distance from the main point of the lens to the surface
of the film is given by f + p if.
Fig. 22 illustrates loci of motion of main points of
the photographing lenses at the focal distance for bringing into
agreement the visual fields of the right and left photographing
lenses. When the pitch between the right and left exposed
pictures of the stereo camera is denoted by P, the shifting
amount S1 of the right and left lenses for bringing into
agreement the visual fields of the right and left photographing
lenses at the focal distance is given by,
S1 = (P/2) x (f + ~if)/(L + f + ~if) --- (2)
A table of Fig. 23 illustrates relationships between
the delivering amounts D if of the lenses in the direction of
the optical axes and the shifting amounts S1 in the direction at
right angles with the optical axes based upon the above-
mentioned formula when a focal distance of the lenses is 36 mm
and the pitch P between the right and left exposed pictures is
66 mm. When the right and left photographing lenses are moved
toward the directions to approach each other by the shifting
amount S1 accompanying a decrease in the distance L to the
subject that is focused, the loci of motion of main points of
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the photographing lenses describe a loose curve, and the visual
fields of the right and left photographing lenses at the focal
distance are brought into agreement at all times.
The conventional mechanism for automatically adjusting
the distance between the optical axes is so constituted that the
main points of the photographing lenses move on loci given by
the above-mentioned formula by using a cam, a guide and the
like, and that the focal point is adjusted being interlocked to
the adjustment of the distance between the optical axes. In
practice, however, a satisfactory effect for correcting the
distance between the optical axes is not obtained in many cases.
This problem is caused by the fact that all subjects
in the picture seldom exist at a focal distance and, in many
cases, the subjects are existing at various distances. For
example, when a scenery is to be photographed by bringing the
focal point to infinity, some material bodies are in many cases
photographed in front of the subject at infinity. In taking a
picture from a close distance, e.g., in shooting flowers in a
flower garden from an upper tilted direction, the picture
includes flowers in front of the flowers at the central portion
of the picture to where the focal point is adjusted. When a
front portrait is to be shot by adjusting the focal point to the
eyes of a human model, the nose of the model is, then, located
in front of the focal distance.
In a stereo slide in which the subject that strongly
affects the matching of the right and left images exists at a
distance closer than the subject at the focal distance, the
stereo image of the subject at the closer distance is formed in
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front of the stereo windows and appears unnatural. To correct
this, it becomes necessary to mask the outer side edges of the
right and left pictures when the films are to be mounted in the
same manner as in the prior art and to correct the perspective
feeling by adjusting the pitch for mounting the right and left
films. Thus, the action of the conventional mechanism for
automatically adjusting the distance between the optical axes is
never perfect.
Therefore, a technical problem must be solved in order
to provide a stereo camera having a practicable function for
adjusting the distance between the optical axes so that stereo
pictures featuring an optimum stereo effect can be easily shot
by anybody. The object of the present invention is to solve
this problem.
SUMMARY OF THE INVENTION
The present invention is proposed in order to achieve
the above-mentioned object, and provides a stereo camera
provided with a mechanism for automatically adjusting the
distance between the optical axes, in which two photographing
lenses are mounted on independent lens boards, the distance
between the right and left lens boards is changed being
interlocked to the back-and-forth motion of the lens boards
accompanying the operation for adjusting the focal point, and
the distance between the optical axes of the two photographing
lenses is corrected depending upon the focal distance, wherein
the loci of motion of the two photographing lenses are right-
and-left symmetrical straight lines connecting the positions at
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where the distance between the optical axes of the two
photographing lenses at a position for adjusting the focal point
to infinity is narrower than a pitch between the right and left
exposed pictures or, preferably, connecting the positions within
a range of distance between the optical axes in which the visual
fields of the two photographing lenses are brought into
agreement at a distance of 2 to 3 meters in front of the main
points of the photographing lenses along the optical axes, to
the positions of the distance between the optical axes at where
the visual fields of the two photographing lenses at a position
for adjusting the shortest focal point are brought into
agreement at a focal distance, or to the positions in the
vicinities thereof.
The invention further provides a stereo camera in
which the loci of motion of the two photographing lenses are
right-and-left symmetrical arcs passing through the positions at
where the distance between the optical axes of the two
photographing lenses at a position for adjusting the focal point
to infinity is narrower than a pitch between the right and left
exposed pictures or, preferably, through the positions within a
range of distance between the optical axes in which the visual
fields of the two photographing lenses are brought into
agreement at a distance of 2 to 3 meters in front of the main
points of the photographing lenses along the optical axes, and
through the positions of the distance between the optical axes
at where the visual fields of the two photographing lenses at a
position for adjusting the shortest focal point are brought into
agreement at a focal distance or through the positions at where
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the distance between the optical axes is slightly narrower than
the distance between the optical axes with which the visual
fields are in agreement at the focal distance.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a graph illustrating a straight locus of
motion of a photographing lens according to an embodiment of the
present invention;
Fig. 2 is a graph illustrating a straight locus of
motion of the photographing lens according to the embodiment of
the present invention;
Fig. 3 is a graph illustrating a permissible range for
setting a straight locus of motion of the photographing lens
according to the embodiment of the present invention;
Fig. 4 is a graph illustrating an arcuate locus of
motion of the photographing lens according to the embodiment of
the present invention;
Fig. 5 is a graph illustrating a permissible range for
setting the arcuate locus of motion of the photographing lens
according to the embodiment of the present invention;
Fig. 6 is a graph illustrating the arcuate locus of
motion of the photographing lens according to the embodiment of
the present invention;
Fig. 7 is a diagram illustrating a calculation for
finding coordinates of any lens position on an arc;
Fig. 8 is a table expressing the arcuate locus of
motion of Fig. 6 using numerical figures;
Fig. 9 is a diagram illustrating, in a disassembled
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manner, a mechanism of the type of linear motion for
automatically adjusting the distance between the optical axes
according to the embodiment of. the present invention;
Fig. 10 is a sectional view of a stereo camera of the
type of linear motion;
Fig. 11 is a diagram illustrating the constitution of
a finder portion of the stereo camera of Fig. 10;
Fig. 12 is a diagram illustrating the constitution of
a mechanism for automatically adjusting the distance between the
optical axes in the stereo camera of Fig. 10;
Fig. 13 is a diagram illustrating the constitution of
the mechanism of the type of arcuate motion for automatically
adjusting the distance between the optical axes;
Fig. 14 is a vertical sectional view illustrating the
structure for coupling a lens board to the camera body of Fig.
13;
Fig. 15 is a sectional view of a stereo camera of the
type of arcuate motion;
Figs. 16(L) and 16(R) are diagrams illustrating the
constitutions of parallel linking mechanisms in the stereo
camera of Fig. 15;
Fig. 17 is a sectional view of the stereo camera of
the type of arcuate motion according to another embodiment;
Figs. 18(L) and 18(R) are diagrams illustrating the
constitutions of parallel linking mechanisms in the stereo
camera of Fig. 17;
Fig. 19 is a sectional view of the stereo camera of
the type of arcuate motion according to a further embodiment;
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Figs. 20(L) and 20(R) are diagrams illustrating films
photographed by using a conventional stereo camera;
Fig. 21 is a diagram illustrating losses of picture
using the conventional stereo camera;
Fig. 22 is a diagram illustrating curved loci of
motion of lenses when the visual fields of the right and left
lenses are brought into agreement at a focal distance; and
Fig. 23 is a table of numerical values representing
distances between the optical axes with which the visual fields
of the right and left photographing lenses are brought into
agreement at the focal distance.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will now be
described in detail. First, described below is a relationship
between a distance at which the right and left windows of a
stereo slide mount are brought into agreement to appear as a
single window and a distance at which a stereo image of a
subject can be seen in viewing a stereo slide by using a stereo
slide viewer.
In a stereo slide photographed by using a conventional
stereo camera of the type of automatically adjusting the
distance between the optical axes in which the visual fields of
the right and left lenses are brought into agreement at a focal
distance, the visual fields of the right and left lenses are in
agreement at the focal distance, and a stereo image of a subject
at the focal distance and the window of the stereo slide mount
appear at an equal distance.
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When, for example, a scenery at an infinity is
photographed as shown in Fig. 22, the shifting amount S1 of the
lens is zero. Accordingly, a pitch between the right and left
pictures is equal to a pitch of the same subject at infinity
between the right and left pictures, and the window of the
stereo slide mount is seen at infinity like the subject at
infinity and the subject which is not at infinity is seen being
located in front of the window of the stereo slide mount, which
is unnatural. It is therefore presumed that a good result can
be obtained if the photographing lenses are so shifted that the
visual fields of the right and left photographing lenses are
brought into agreement at a distance shorter than the focal
distance.
Therefore, considered below first is the shifting
amount of the photographing lenses of when the focal point is
adjusted to infinity.
When,
focal distance of the photographing
lens f = 36 mm,
pitch between the right and left
exposed pictures P = 66 mm, and
pitch between the subjects at the
focal distance = Pi,
which are the conditions same as those of the prior art, a
stereo image of the subject at a distance of, for example, one
meter and the window of the stereo slide mount can be seen at an
equal distance when the shifting amount S1 of the photographing
lenses is about 1.15 mm from the formula 2 when the focal point
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is adjusted to infinity. In this case, the images of the
subjects at infinity move equally to the shifting amount of the
photographing lenses on the exposed pictures of the films, i.e.,
respectively shifted by 1.15 mm in the directions in which they
approach each other and, hence, the pitch Pi decreases by 2.3 mm
between the images of the subjects at infinity on the right and
left films. The image of the exposed picture of the stereo
camera is an inverted image which is inverted right side left
and upside down. When the films photographed with the shifting
amount S1 of 1.15 mm are mounted in a state of erect images on
the stereo slide mount, the pitch Pi between the subjects at
infinity becomes larger by 2.3 mm than the pitch P (66 mm)
between the right and left pictures.
When the pitch Pi between the subjects at the focal
distance (infinity in this case) becomes very wider than the
pitch P between the right and left pictures, the images will
appear unnaturally as a matter of course. In order to examine
the permissible range of expansion, the inventor has observed a
variety of sample photographs varying the shifting amount of the
photographing lenses. As a result, it was evaluated that a
difference between the pitch of the right and left pictures and
the pitch of the images of the same subject of the right and
left pictures, should not generally be larger than about 1.2 mm.
That is, when the shifting amount S1 of the right and
left photographing lenses is not larger than 0.6 mm at the time
of photographing a subject at infinity under the above-mentioned
conditions, the difference between the pitch of the pictures and
the pitch of the images of the same subject at infinity of the
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right and left pictures becomes not larger than l.2 mm, and the
image at infinity does not appear unnaturally, and favorable
three-dimensional feeling is obtained despite there exists an
image of a subject at a short distance in the picture.
Though the shifting amount of the photographing lenses
in the case of infinity is set to be 0.6 mm, this value of 0.6
mm is nearly equal to the shifting amount S1 with which the
window of the stereo slide mount is seen at an equal distance as
the subject of about 2 meters as calculated from the formula 2.
Next, considered below is the shifting amount of the
photographing lenses in the case of the shortest focal distance.
Even in the case of the shortest focal distance, the condition
is applied in that the pitch between the images of the subject
at a focal ditance is wider by about 1.2 mm than the pitch
between the windows of the stereo slide mount like the case of
photographing a subject at infinity. That is, when the shortest
focal distance is L = 360 mm,
G if = f2/ (L - f ) = 362/ ( 360 - 36 ) = 4 mm
The moving amount Si of the image on either the right
or left picture is 1.2/2 = 0.6 mm. In this case, the shifting
amount S1 of the photographing lenses is given by,
S1 = (P - (L x Pi)/(L + f + D if))/2
- (P - (L x (P - 1.2))/(L + f + p if))/2
- (66 - (360 x (66 - 1.2))/(360 + 36 + 4))/2
- 3.84 mm
Furthermore, the distance Lw with which the visual
fields of the right and left photographing lenses are brought
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into agreement, i.e., the distance with which the right and left
windows of the stereo slide mount appears as a single window, is
given as follows:
Lw = (f + p if)(P - 2S1)/2S1
- (36 + 4)(66 - 2 x 3.84)/2 x 3.84 = 304 mm
Fig. 1 shows the locus of motion of the left
photographing lens only, which is described by coupling a
position of the lens at the time of shooting a subject at
infinity to a position of the lens at the shortest focal
distance. The windows of the stereo slide mount are set at a
distance of about 2 meters from the main points of the
photographing lenses when shooting the subject at infinity, and
are set at positions of 304 mm in the case of the shortest focal
distance of 360 mm.
In the above-mentioned example, the shifting amount
toward the inner side is larger than that of the locus L~F
represented by a broken line of the lenses of the conventional
stereo camera of the type which automatically adjusts the
distance between the optical axes over the whole range for
adjusting the focal point. Most of the photographed films can
be mounted on the stereo slide mount without correcting the
positions for mounting the films or without masking portions of
the pictures.
In Fig. 1, furthermore, the angle 8 of inclination of
the linear locus relative to the optical axis is given by,
8 - tan -1 ( 3. 84 - 0. 6 ) /4 = tan -10 . 81 = 39' 00'
and the shifting amount S1 of the lenses in the direction at
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right angles with the optical axis is given by,
S1 = 0 . 6 + ~ if x tan B ( B - 39' 00' )
Here, the shifting amount S1 of the photographing
lenses of when the focal point is brought to a distance of, for
example, one meter, is found to be,
Dif = fz/ (L - f ) = 362/ ( 1000 - 36 ) = 1. 344 mm
Sl = 0.6 + 1.344 x tan 39' 00' - 1.688 mm
The moving amount of the image at infinity on the
picture is equal to the shifting amount S1 of the photographing
lens. Therefore, when the background at infinity is
photographed on the picture in the case when the focal point is
adjusted to a distance of one meter, the pitch between the
images of the background at infinity on the right and left
pictures is increased by about 3.4 mm (= 2S1) compared to the
pitch between the pictures.
This is in excess of a recommended range (not larger
than about 1.2 mm) of the difference between the above-mentioned
pitch of pictures and the pitch of images of the subject. It is
therefore desired that the background at a distance does not
enter as much as possible into the picture when shooting a
subject from a close distance.
The above-mentioned locus of motion of the lens is
when importance is given to taking a picture from a close
distance. However, users in general shoot the subjects at
distances of not smaller than one meter. Besides, many cameras
have the shortest focal distance of about one meter. In these
cases, the shifting amount may be decreased as a whole compared
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to the amount of Fig. 1 (at a position of adjusting the focal
point to infinity as shown, for example, in Fig. 2, the window
of the stereo slide mount can ~e seen at 3 meters when the
shifting amount is S1 = 0.39 mm), or the angle of inclination of
the locus of motion may be decreased with respect to the optical
axis of the photographing lens, in order to suppress the problem
in that the pitch of image in the background becomes excessive
when the subject at a short distance and the background at a
distance are photographed on the same picture.
Referring to Fig. 2, the locus of motion of the
photographing lens intersects a conventional curved locus L~ at
a focal distance of about 700 mm (D if = 2.0 mm). Except when
shooting a subject from a close distance, most of the films do
not require correction at the time of mounting. Only the films
photographed from a close distance may be corrected for their
mounting positions or may be masked for their pictures as
required.
Therefore, the loci of photographing lenses can be set
within a range between the linear locus shown in Fig. 1 and the
linear locus shown in Fig. 2 depending upon whether importance
is given to shooting pictures from a close distance, importance
is given to shooting pictures from general distances, or upon
the conditions of the shortest focal distance of the
photographing lenses. When a locus is set in a range between
the two straight lines as shown in Fig. 3, there is obtained a
favorable effect for correcting the distance between the optical
axes better than that of the conventional stereo camera.
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Moreover, since the photographing lenses are linearly moved, the
structure of the mechanism for adjusting the distance between
the optical axes is simplified, and a high operation precision
is accomplished.
In the foregoing was described the case where the
photographing lenses were moved along the linear loci.
Operation maintaining a high precision can be further expected
by using a mechanism for adjusting the distance between the
optical axes by moving the photographing lenses along arcuate
loci by using parallel linking mechanisms made up of a
combination of a plurality of levers and links.
When the arcuate loci are employed, the radius is
equal to, or larger than, that of the conventional curved loci,
the photographing lenses are inwardly shifted at a position for
adjusting the focal point to infinity, the shifting amount is
decreased as the lenses are delivered, and the distance of the
window of the stereo slide mount is brought nearly in agreement
with a distance at which is seen a stereo image of the focused
subject at the shortest shooting distance. In this case,
however, the arc has a large radius and the links becomes long.
Therefore, the mechanism can be incorporated in a large camera
but cannot be incorporated in a small camera.
The radii of arcs can be decreased if, as shown in
Fig. 4, the photographing lenses are moved along the arcs having
centers of radii on the center sides between the right and left
photographing lenses contrary to that of the conventional curved
locus L~. The shifting amount may be set within a range of
from 0.39 to 0.6 mm so that the window of the stereo slide mount
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can be seen at a di~tance of about 2 to 3 meters at a
position for adjust:,ing the focal point to infinity.
Besides, at the shortest focal distance, the shifting
position may be set. within a relatively narrow
permissible range iz:~clusive of the shifting position of
the conventional ci.zrved locus LREF- However, the position
may be set depending upon the conditions such as desired
shifting character:i_stics, focal di:~tance of the lens,
shortest foca:l_ dis~a.nce, etc . , and no numerical
limitation is imposed thereon :like that of the linear
locus.
Therefore, a ~Ja.riety of arcs having different
centers of arcs and different radii of arcs can be set as
represented by arc;: A, B and C in Fig. 5. Like the range
of linear loci showzi in Fig. 3, however, the arcs are
limited within a rar~ge which is note much displaced from
the conventional cuwved locus LIEF. as a matter of course.
In Fig. 5, the arc A represents the locus of mction
of the lens o:E a st:e~reo camera wherein the arcuate loci
of motion of the two photographing lenses are right-and-
left symmetrical arcs passing through the positions
within a range of ~,t,,e distances between the optical axes
in which the visua::l_ fields of the two photographing
lenses at a position: for adjusting the focal point to
infinity are in agreement at a distance of 2 to 3 meters
in front of the maiz:~. points of the photographing lens
along the optical azxes, through the positions of the
distance between the optical axes at where the visual
fields of the two prActographing lenses at a position for
adj usting the foca::l_ point to a sub j ect at a distance of
about one meter arcs in agreement at, a focal distance, and
through the positic:>r:,s of the distance between the optical
axes at where the visual fields of the two photographing
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lenses at a position. for adjusting the shortest focal
point are brought :i_r~.to agreement at. a focal distance. The
window of the sterc::~c: slide mount appears at a distance of
about 2 meters where the focal point. is adjusted to
infinity, a stereo image of a subject at a focal distance
(e.g., 700 mm) appears at a distance equal to that of the
window of the stereo slide mount at. any intermediate
position within a range for adjusting i~he focal point,
and, on the side o:f: short distance:, the stereo image of
the subject at the focal distance appears again at a
distance equal to t~~.at of the window of the stereo slide
mount at the shortest focal distance though the shifting
amount becomes insi.if_ficient.
The arc E3 rep=resents the locu~~ of motion of the lens
of a stereo camera wherein the arcuate loci of motion of
the two photograph:ir~.g lenses are r_Lght-and-left
symmetrical arcs p<:~~sing through the positions within a
range of the distances between the optical axes in which
the visual fields of the two photographing lenses at a
position for adjusting the focal point to infinity are in
agreement at a dis~~ance of 2 to 3 rneters in front of the
main points of the photographing lens along the optical
axes, through the pc.~sitions of the distance between the
optical axes at where the visual fields of the two
photographing lense~~ at a position for adjusting the
focal point to a subject at a dirt<~nce of about one meter
are in agreement ate a focal distance, and through the
positions at where t=he distance between the optical axes
is slightly narrower than the distance between the
optical axes with which the visual fields of the twc
photographing lenses at a position for adjusting the
shortest focal pointy are brought into agreement at a
focal distance. Thc:e window of the :stereo slide mount
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appears at a distar-ice of about 2 meters when the focal
point is adjusted to infinity, a stereo image of a
subject at a focal distance appear~~ at a distance equal
to that of the window of the stereo slide mount at an
intermediate posit.on within a range for adjusting the
focal point, and, on the side of short distances, the
stereo image of thc: subject at the focal distance appears
at the back of the window of the st:ereo slide mount. The
arc B has a radius smaller than that of the arc A, and
makes it possible t:o shorten the length of the links.
The arc C represents the locu~~ of motion of the lens
of a stereo camera wherein the arcuate loci of motion of
the two photograph:i.ng lenses are right-and-left
symmetrical arcs parsing through the positions within a
range of the distances between the optical axes in which
the visual fields c:~f: the two photographing lenses at a
position for adjust:.ing the focal point to infinity are in
agreement at a distance of 2 to 3 meters in front of the
main points of the photographing lenses along the optical
axes, and through t:he positions of the distance between
the optical axes s_l.ightly narrower than the positions of
the distance between the optical axes at where the visual
fields of the two photographing lenses at a position for
adjusting the short:.est focal point are brought into
agreement at a focal distance, the distance between the
optical axes being r~.arrower than the distance between the
optical axes in which. the visual fields are in agreement
at the focal distaruce throughout the whole range of
adjusting the foca_1. point. The cent:er of radius of the
arc B is shifted inward (toward the right in Fig. 5) to
increase the shifting amount over t:he whole areas so will
not to come into contact with the conventional curved
locus LREF.
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Described below is a calculation for finding a locus
of an arc D shown Ln Fig. 6. When the focal distance of
the lens is 36 mm, the pitch Pl bet:ween the right and
left exposed pictu~:~es is 66 mm, the distance with which
the visual fields of the right and left, lenses come into
agreement is 2.5 meters when the focal point is adjusted
to infinity, and tlve position of the lens is O' like in
the above-mentioned example, then, from the formula 2,
the shifting amounts of the point O' is given by,
S1 - (66/2) x 36/ (2500 + 36) -- 0.468 mm
and the distance Xo" between the point 0 and the point O'
CA 02242173 2001-02-19
becomes about 0.47 mm. Then, a point where an arc which is the
locus of motion of the lens intersects the conventional curve
represented by a broken line is denoted by Q, a chord O'Q is
drawn between O' and Q of the arc and, similarly, a chord PQ is
drawn between P and Q of the arc. A perpendicular Axis drawn
from an intermediate point S of the chord O'Q, a perpendicular B~
is drawn from an intermediate point T of the chord PQ, and a
point where the perpendiculars A~ and B' meet together is found.
This intersecting point is a center V of the arc O'QP.
The coordinate position of the point O' is x = 0.47, y
- 0. If D if of the point Q is 2 mm which is an intermediate
point of the range of 4 mm in which the lens moves in the
direction of the optical axis, then, the x-coordinate of the
point Q is x - 1.7368 and the y-coordinate is y = 2 from the
table of Fig. 23. .
A difference in the x-value between the point O' and
the point Q is given by,
XQ - Xo' = 1.7368 - 0.47 = 1.2668
A difference in the y-value is,
YQ -Yo' - 2
The ratio of inclination of the chord O'Q relative to
the optical axis is 1.2668/2 = 0.6334.
The coordinate position of the point S is,
x = (0.47 + 1.7368)/2 =-1.1034 '
y = 2/2 = 1
The y-value on the perpendicular A~when x = 0 is,
y = 1 + 1.1034 x 0.6334 = 1.69889356
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21
<~nd the numerical formula representing the perpendicular A~ is
given by, y = -0.6334X + 1.69889356
Similarly, a difference in the y-value between the
point P and the point Q on the perpendicular B~is,
YQ - Yo' - 4 - 2 = 2
From Fig. 23, a difference in the x-value is,
XP - XQ = 3.30 - 1.7368 = 1.5632
The ratio of inclination of the chord PQ relative to
the optical axis is,
1.5632/2 = 0.7816
The coordinate position of the point T is,
x = (3.30 + 1.7368)/2 = 2.5184
y = (4 + 2)/2 = 3
The y-value on the perpendicular. B'when x = 0 is,
y = 3 + 2.5184 x 0.7816 = 4.96838144
and the perpendicular B~is expressed as,
y = -0.7816X + 4.96838144
The coordinates are in agreement at a point where the
perpendiculars A~ and B~ intersect and, hence,
-0.6334X + 1.69889356 = -0.7816X + 4.96838144
Upon transposition,
-0.6334X + 0.7816X = 4.96838144 - 1.69889356
By rearranging both sides,
0.1482X = 3.26948788
X = 22.06132173
Furthermore,
y = -0.7816 x 22.0613 + 4.9683 = -12.2748
CA 02242173 1998-06-30
22
Xv = 22.0613 mm
Yv = -12.2748 mm
Since the point O' is positioned on the arc D, the
radius Rv of the arc D is given by,
Rv = ,/~ ( ( Xv - Xo' ) 2 + Yv2 ) - .,~ ( ( 2 2 . 0 613 - 0 . 4 7 ) 2 +
12.27482) = 24.83656 mm
From the radius Rv of the arc and the center
coordinates Xv, Yv, furthermore, a lens position a on an arc
shown in Fig. 7 is,
/3 a = sin-1 ( ( D if - Yv) /Rv)
Xa = Xv - Rv cos (3 a
Table of Fig. 8 shows calculated values of D if of the
arc D, S1, a a and Xa.
In this example, the window of the stereo slide mount
is set to 2.5 meters when the focal point is adjusted to
infinity. When the focal point is adjusted to about 700 mm, the
window of the stereo slide mount appears at about 700 mm which
is equal to the focal distance. When the focal point is
adjusted to a distance shorter than about 700 mm, the window of
the stereo slide mount may appear slightly farther than the
focal distance. However, the difference is so small that the
offset needs be corrected by a very small amount at the time of
mounting. When the arc data shown in the table of Fig. 8 are
applied to a stereo camera of which the shortest focal distance
is larger than 700 mm, the optimum effect for correcting the
CA 02242173 1998-06-30
23
distance between the optical axes can be obtained under almost
all conditions.
Next, concretely described below is the structure of
the mechanism for automatically adjusting the distance between
the optical axes. Fig. 9 illustrates the mechanism for
automatically adjusting the distance between the optical axes by
linearly moving the lens boards, wherein reference numeral 1
denotes a slide base, and 2L and 2R denote sliders, the sliders
2L, 2R and lens boards 3L, 3R at the front portions thereof
being coupled together as unitary structures. Right-and-left
symmetrical linear tilted guide grooves 4L and 4R are formed in
the upper surface of the slide base secured to the bottom part
of the camera body, and ribs 5L and 5R are formed on the lower
surfaces of the sliders 2L and 2R so as to be opposed to the
guide grooves 4L and 4R.
Linear parallel grooves 6L and 6R are formed in the
inside portions of the right and left sliders 2R, 2L, i.e., in
the inner sides of the optical axes of the right and left
photographing lenses, the directions of the parallel grooves 6L
and 6R being at right angles with the directions of the ribs 5L,
5R.
The upper half of the inner portion of the left slider
2L in which the parallel groove 6L is formed, is cut away so as
to have a thickness one-half the thickness of the slider 2L.
The lower half of the inner portion of the right slider 2R is
cut away, too, so as to have a thickness one-half the thickness
of the slider 2R. In a state where the sliders 2L and 2R are
mounted on the slide base 1, the inner portions of the right and
CA 02242173 1998-06-30
24
left sliders 2R and 2L are superposed one upon the other.
A bearing 8 of cams for moving the lenses is mounted
on a central bearing-mounting hole la formed in the slide base
1. The cams 7L and 7R are mounted in upper and lower two stages
on an upper part of a shaft for adjusting the focal point, and a
pulley 9 is attached to a lower part of the shaft for adjusting
the focal point.
The left cam 7L and the right cam 7R are circular
eccentric cams of the same shape, have a diameter nearly equal
to the width of the parallel grooves 6L, 6R in the sliders 2L,
2R, and are mounted on the shaft for adjusting the focal point
maintaining a rotational angular difference equal to an angle
subtended by the right and left guide grooves 4R, 4L, the left
cam 7L engaging with the parallel groove 6L of the left slider
2L and the right cam 7R engaging with the parallel groove 6R of
the right slider 2R.
A knob 11 for adjusting the focal point is attached to
the head of a pulley shaft 10 supported by a camera body (not
shown), and a wire 13 or a belt is wrapped round a pulley 12
attached to a lower part of the pulley shaft 10 and a pulley 9
of the shaft for adjusting the focal point.
When the knob 11 for adjusting the focal point is
turned, the cams 7L and 7R are turned being interlocked to each
other, the right and left sliders 2R, 2L move aslant along the
guide grooves 4L, 4R in synchronism with each other, and the
distance between the optical axes is automatically adjusted
being interlocked to the adjustment of the focal point. As
described above, the directions of the parallel grooves 6L, 6R
CA 02242173 1998-06-30
are at right angles with the directions of the guide grooves 4L,
4R, and the directions in which the sliders 2L, 2R move are in
agreement with the directions ~n which the pushing forces of the
cams 7L, 7R act. Therefore, the sliders 2L, 2R slide smoothly.
If the wire 13 wrapped round the pulleys 9 and 12 is
secured at a point on the circumferences of the pulleys 9 and
12, though this pertains to a widely known means, the wire 13 is
prevented from slipping, and the pair of pulleys 9 and 12 can be
reliably rotated in synchronism.
Fig. 10 illustrates a three-lens type stereo camera 14
mounting a mechanism for linearly adjusting the distance between
the optical axes of Fig. 9, wherein a finder lens 16 is arranged
at the center on the front surface of a camera body 15, and a
pair of photographing lenses 17L, 17R are arranged on the right
and left sides thereof in line in the lateral direction, and the
optical axes of the three lenses 16, 17L and 17R are in parallel
and are positioned on the same plane. A focal plane shutter
(not shown) is arranged at the back of the photographing lenses
17L, 17R in just front of the exposed surfaces. Referring to
Fig. 11, a 45-degree reflex mirror 18 is secured at the back of
the finder lens 16. Light falling on the finder lens 16 passes
through the reflex mirror 18, focused on an upper focusing plate
19, and can be observed as an erect image through a penta prism
20 and an eyepiece 21 in the same manner as the general single-
lens reflex camera.
Fig. 12 illustrates sliders 22 for mounting a finder
lens board, and lens boards 3L, 3R for photographing lenses.
The sliders 22 are provided with a parallel groove 23 in the
CA 02242173 1998-06-30
26
right-and-left direction, and a circular eccentric cam 24 for
moving the finder lens is engaged with the parallel groove 23,
the circular eccentric cam 24 being provided on the shaft for
adjusting the focal point like the cams 7L, 7R for moving the
photographing lenses. Therefore, the three lenses 16, 17L and
17R move back and forth in synchronism being interlocked to the
turn of the shaft for adjusting the focal point, and the state
for adjusting the focal point can be judged depending upon the
state where the image is focused on the focusing plate 19.
The finder lens 16 may have a focal distance equal to
that of the photographing lenses 17L, 17R. However, use of the
finder lens having a focal distance shorter than that of the
photographing lenses makes it possible to decrease the space
occupied by the finder portion. In this case, the size of the
focusing plate 19 shown in Fig. 11 is decreased, the angle of
image on the focusing plate is brought into agreement with the
angle of images exposed through the photographing lenses 17L,
17R. Besides, the shape and size of the cam 24 for moving the
finder lens and the width of the parallel groove 23 in the
sliders 22, are so designed that the moving amount of the finder
lens satisfies the formula D if = f2/(L - f).
Fig. 13 illustrates a mechanism for adjusting the
distance between the optical axes being interlocked to the
adjustment of the focal point in the stereo camera in order to
move the photographing lenses along an arcuate loci. Two right
and left vertical shafts 32R and 32L are rotatably mounted on a
body frame (not shown) of the stereo camera 31, and
CA 02242173 1998-06-30
27
synchronizing gears 33L and 33R of the same shape are in mesh
with each other being mounted on the upper portions of the two
vertical shafts 32L and 32R. A pinion gear 35, a cam 36 for
moving a movable mirror of a range finder and a knob 37 for
adjusting the focal point, are attached to a shaft 34 for
adjusting the focal point disposed in front of the vertical
shafts 32L, 32R, and a pinion gear 35 is brought into mesh with
the one synchronizing gear 33R.
Bell crank-shaped levers 39 are secured to the upper
and lower portions of the vertical shafts 32L, 32R. Upper and
lower two bell crank-shaped levers 39 disposed on the outer
sides of the vertical shafts 32L, 32R are supported by the upper
and lower bearings of which the central shafts are provided on
the body frame (not shown). The front ends of these right and
left four levers 39 are pivoted near to the inner ends and the
outer ends on both the upper and lower surfaces of the right and
left lens boards 38R, 38L. Moreover, the rear ends of the
opposing two levers are coupled together by links 40 to
constitute parallel linking mechanisms.
The lever-pivoting points of the right and left lens
boards 38R, 38L are located on the outer sides of the vertical
shafts 32L, 32R. Upon turning the knob 37 for adjusting the
focal point, therefore, the right and left lens boards 38R, 38L
undergo a parallel motion on arcuate loci maintaining a right
angled relationship with respect to the optical axes of the
photographing lenses. Furthermore, the state of adjusting the
focal point can be viewed by turning the movable mirror of the
range finder due to the cam 36 for the range finder. The
CA 02242173 1998-06-30
28
structure of the range finder has been widely known and is not
described here.
Fig. 14 illustrates~the structure for mounting the
lens boards 38L, 38R on the camera body. The upper and lower
both ends of the lens boards slide in contact with the upper and
lower wall surfaces of the stereo camera 31 to interrupt light
coming from the outside, and correctly maintain the positions of
the lens boards 38L, 38R in the up-and-down direction. As means
for shielding the gaps between the side surfaces of the lens
boards and the camera body, furthermore, thin leaf springs that
will be described later are attached to the camera body and are
resiliently contacted to the side surfaces of the lens boards
thereby to shield the gaps between the lens boards and the
camera body.
The radii of arcuate loci along which the lens boards
38L, 38R move are determined by distances between the lever-
pivoting points of the lens boards 38L, 38R and the centers of
the vertical shafts 32L, 32R shown in Fig. 13. A variety of
arcuate loci as shown in Figs. 5 and 6 can be realized depending
upon the lengths of the levers and the central positions of the
vertical shafts 32L, 32R.
The links 40 coupling the levers 39 may be omitted.
When the links 40 are omitted, straight lines passing through
the two lever-pivoting points on both the right and left sides
of the lens boards 38L, 38R approach the vertical shafts 32L,
32R, and the operation may lose smoothness when the dead points
of the parallel linking mechanisms are approached. Upon
coupling the other ends of the bell prank-shaped levers 39 with
CA 02242173 1998-06-30
29
the links 40, however, the dead points can be eliminated, and
smooth operation is realized throughout the whole range of
motion.
Fig. 15 illustrates the stereo camera according to
another embodiment. In this stereo camera 41, the right and
left lens boards 42R and 42L are driven in a synchronized manner
through the cam 43, so that the photographing lenses 44L and 44R
move along arcuate loci. As shown in Figs. 16(L) and 16(R),
straight parallel grooves 45R and 45L are formed in the inner
portions of the right and left lens boards 42R, 42L in a
direction at right angles with the optical axes of the
photographing lenses 44R and 44L.
Like the lens boards 2L, 2R in Fig. 12, the upper half
is cut away from a portion forming a groove on the inner side of
the left lens board 42L so as to have a thickness one-half the
thickness of the lens board 42L. The upper half is cut away,
too, from a portion forming a groove of the right lens board 42R
so as to have a thickness one-half the thickness of the lens
board 42R. The cut-away portions of the right and left lens
boards 42R and 42L are superposed one upon the other, and are
coupled to the camera body 46 via two links 47 having an equal
length.
A circular eccentric cam 43 disposed at the center of
the base frame 46 is inserted in the parallel grooves 45R, 45L
of the right and left lens boards 42R, 42L. Upon turning the
shaft for adjusting the focal point on which the cam 43 is
mounted, the right and left lens boards 42R, 42L move
symmetrically along the arcuate loci.
CA 02242173 1998-06-30
The side surfaces of the lens boards 42R, 42L are
formed in an arcuate shape being curved in an opposing manner
relative to the loci of motion;, and the edges at the ends of the
leaf springs 48 attached to the camera body 46 are resiliently
contacted to the side surfaces of the lens boards 42R, 42L.
Therefore, no gap is formed between the leaf springs 48 and the
lens boards 42R, 42L irrespective of the positions of the lens
boards for adjusting the focal point, and the interior of the
camera body 46 is kept off from the infiltration of light, dust
or water droplets.
Figs. 17 and 18 illustrate another embodiment. In
this stereo camera 61, the links have a length shorter than that
of the stereo camera 41 of Fig. 14. The right and left two
links 62 are pivoted at their intermediate points, and the
central two links 62 are rotatably mounted on the shaft 64 for
adjusting the focal point.
A left lens board 65L is coupled to the front ends of
the two links 62 constituting a parallel linking mechanism of
the left side, a right lens board 65R is coupled to the front
ends of the two links 62 constituting a parallel linking
mechanism of the right side, and the other ends of the two sets
of links are coupled together by cam follower links 66L, 66R.
A circular eccentric cam 67 is engaged with parallel
grooves 68L, 68R of two pieces of cam follower links 66L, 66R
that are superposed one upon the other. When the cam 67 is
turned, the right and left lens boards 65R and 65L move
symmetrically describing arcs via the cam follower links 66L,
66R. The action is the same as that of Fig. 14. However, the
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31
radius of arcs is smaller since the levers are shorter than
those of Fig. 14.
In a stereo camera~71 shown in Fig. 19, the front
portions of the right and left two links 72 constituting a
parallel linking mechanism are pivoted to the camera body 73,
and the rear ends of the links 72 are pivoted to the rear
portions of the lens boards 74L, 74R. The centers of radii of
loci along which the right and left lens boards 74R and 74L move
are positioned on the outer sides of the optical axes; i.e., the
arcuate loci are approximate to the curved loci of the
conventional mechanism for automatically adjusting the distance
between the optical axes.
The applicant has proposed already a stereo camera for
synthesizing a finder picture by projecting, onto a focusing
plate, the inner one-halves of an inverted image (the left one-
half of the visual field of the left photographing lens and the
right one-half of the visual field of the right photographing
lens) that is incident through the two photographing lenses
relying upon the combination of a reflex mirror and one or a
plurality of prisms. In this stereo camera, the right and left
one-halves of the image in the finder are brought close to each
other or are separated away from each other making it possible
to judge the focusing state depending upon the distance for
adjusting the focal point of the photographing lenses.
In the stereo camera equipped with the mechanism for
adjusting the distance between the axes, the right and left one-
halves of the image in the finder are brought close to each
other or are separated away from each other even relying upon a
CA 02242173 1998-06-30
32
change in the distance between the optical axes of the
photographing lenses and, hence, the finder system must be
equipped with means for correcting the pitch between the right
and left one-halves of the image. To cope with this need, there
has been proposed a stereo camera equipped with a mechanism
which makes it possible to correctly adjust the focal point by
automatically correcting the visual fields of the right and left
finder systems by moving part or whole of the composite prism
back and forth being interlocked to a change in the distance
between the optical axes.
When the above-mentioned prism finder is mounted on
the stereo camera of the present invention, a cam for moving the
prism is mounted on the shaft for adjusting the focal point like
the circular eccentric cam 24 for moving the finder lens shown
in Fig. 12, and part or whole of the prism is moved back and
forth being interlocked to the adjustment of the focal
point/distance between the optical axes, in order to correct the
pitch between the right and left one-halves of the image of the
finder system and to highly precisely adjust the focal point.
As described above, the present invention deals with a
stereo camera in which the distance between the optical axes of
the photographing lenses is automatically adjusted depending
upon the distance of taking a picture, wherein the photographing
lenses are moved along the linear loci or arcuate loci corrected
by taking the human visual sense into consideration. Therefore,
the stereo camera is almost free from unnatural perspective
feeling that was often encountered with the conventional stereo
cameras. Thus, the stereo camera of the invention enables
CA 02242173 1998-06-30
33
everybody to easily shoot stereo pictures maintaining the
highest stereo effect, contributing to enhancing the
practicability of the stereo camera.
The present invention is in no way limited to the
above-mentioned embodiments only, but can be modified in a
variety of ways without departing from the technical scope of
the invention, and the invention encompasses such modifications
as a matter of course.
