Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
OPAQUE PROJECTOR 2 01~ 3 7 ~
The pre~ent invention relates to an opaque projector
having a stage which transmits illumination light from a
light i~ource and on which an object to be projected can be
placed, a projecting mirror for reflecting light reflected by
the object to be projected, and a projecting lens for
converging reflected light from the projecting mirror and
imaging a projected image of the object on an external
projection plane.
An opaque projector of the type described above is an
apparatus arranged in such a manner that an original document
placed on the stage is illuminated by a strong illuminating
light ~ource and scattered light thuis generated i8 converged j. :
by a projecting lens having a large aperture 80 that the
original is projected on a screen. An.opaque projector must -
meet the following conditions: -~
~1) Since scattered light from the surface of an
original document is utilized, the efficiency of light i8 ~ .
inHufficient. In order to compensate the insufficient light .-
efficiency, a light source of, for example, 1000 to 1500W is
necessary in ordinary cases.
~2) In order to efficiently converge scattered
light
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reflected by the surface of the original document, the
following projecting lens having a large aperture and a great
f-number must be employed:
(Practical Level)
(illuminating light source : 1000 to 1500W)
Aperture : 100 to 140 ~
f : 300 to 350 mm
f-number : 1.4 to 3
(3) In order to use the above-described large aperture
lens, the depth of focus of the projecting lens is very small
as a result of a comparison made in terms of the OHP. For
example, the practical depth of focus is 20 to 40mm in terms
of the cost and the number of the lenses in the case where a
lens of f = 330, the aperture is 120 ~ and f-number is 2.9 is
used.
As described above, since the depth of focus is very
small in the conventional opaque projectors, the following
ad~ustments and the arrangements are necessary in order to
obtain a satisfactory projected image without any out of
focus.
(1.) The optical axis of the projecting lens and the
screen is vertically instersected each other and the
pro~ection optical paths are the same length in any
directlonæ on the screen at the same distance from the
optical axls (at least within the error of the depth of
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focus).
(2) The elevation angle of the projecting lens, that is,
the elevation angle of the opaque projector body must be
adjusted in accordance with the height of the body and the
desired height of the plane of projection. Furthermore, the
screen must be adjusted so as to be made vertical with
respect to the optical axis of the projecting lens, causing
an extremely difficult and complicated task to become
necessary.
(3) The quality of the projected image considerably
depends upon the structure of the screen whose angle can be
adjusted. However, the maximum angle of the inclination of
the screen is about 15 in consideration of the insufficient
quality of the image due to the inclination of the screen
lS caused from the size, the weight and the involved deflection
of the surface of the screen.
(4) When a projection of an image is performed with
making a certain elevation angle on a screen positioned
vertically (the screen is positioned vertically in major
cases), it is impossible to focus an object to be projected
on the entire surface of the plane of projection, causing
excessive inconvenience to occur.
An ob~ect of the present invention is to provide an
opaque pro~ector capable of easily and readily forming a
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projected image without out of focus on the screen
by adjusting the angle of the stage on which an original
document is placed even if the ~creen i~ not placed without
any correspondence to the elevation angle of the opaque
S projector body, that i~, the screen i~ not po~itioned
vertically with respect to the optical axis of the projecting
lens.
Other and further object~, feature~ and advantages of
the invention will be appear more fully from the following
drawing~, in which:
Fig. 1 is a perspective view which illustrate~ the
structure of an opaque projector according to the present
invention; and
Fig. 2 illustrates the operation of the opaque projector
according to the pre~ent invention.
According to the present invention, there is provided an
opaque projector having a stage which transmits illumination
light from a light source and on which an object to be
projected can be placed, a projecting mirror for reflecting
light reflected by the object to be projected, and a
projecting lens for converging reflected light from the
projecting mirror and imaging a projected image of the object
on an external projection plane, the opaque projector
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2 0 1 ~ 3 7
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comprising: a mechanism capable of changing the angle of
the stage on which the object to be projected can be
placed in such a manner that the object to be projected,
the optical axis of the projecting lens and the
projection place meet a Scheimpflug condition.
The preferred embodiment of the present invention
will now be described with reference to the drawings.
The "Scheimpflug condition" means a condition in
which the surface of the inclined object, the image
plane, and the principal planes of the lenses (or their
exten~ion planes) coincide with one another on a line.
As shown in the drawings, the opaque projector
according to the present invention comprises a projecting
lens having a focus-adjustment lever 2 on its front
surface, the opaque projector further having a stage 3 on
which an object to be projected ~omitted from
illustration) can be placed on the upper siurface thereof.
An end portion of the stage 3 is pivoted by a supporting
shaft 4 adjacent to the projecting lens 1 80 that angle Q
made from the upper surface of the opaque projector body
i8 adjusted. The opaque projector body includes a
reflecting mirror 8 for reflecting the original document
(an object to be projected) placed on the stage 3 at an
inclination angle of 45 with respect to the optical axis
13 of the len~ 1. As a result, light reflected by the
reflecting mirror B i~ converged by the projecting lens 1
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that the original document is proJected on screen S1. In
this case, the stage 3 and the optical axis 13 of the
projecting lens 1 run parallel to each other. A stage-angle
adjustment mechanism for moving the stage 3 with respect to
the supporting axis 4 comprises an eccentric cam 6 and a
stage-angle adjustment lever 5 each of which is disposed in
the opaque projector body in a place opposite to the
supporting shaft 4 for the stage 3. The stage 3 is always
pulled downwards by a spring 7 so as to be stabilized.
Furthermore, the stage 3 is provided with a focusing
indexes 10 and 11 at its two end portions including the
above-described end portion pivoted by the supporting shaft
4.
Only a half portion of an illuminating light source 16
for illuminating the original document with respect to the
stage 3 is illustrated in Fig. 1, and it is omitted from Fig.
2.
Then, the operation (adjustment means) of the opaque
projector according to the present invention will be
described with reference to Fig. 2.
As shown in Fig. 2, in the case where an ob~ect is
projected on the screen S1 positioned vertically with an
elevation angle (an elevation angle with respect to the
optical axis 13 of the proJecting lens 1) of the opaque
pro~ector according to the present invention arranged to be
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~2~ the object to be projected and placed on the stage 3 is
reflected by the reflecting mirror 8 80 as to be projected on
the ~creen Sl by the projecting lens 1. Then, the focusing
index 10 positioned above the supporting shaft 4 of the stage
3, whose back-foaus distance projected in the upper portion
of the screen Sl i8 not changed, is adjusted by the focus
adjustment lever 2. Then, the eccentric cam 6 is rotated by
the ~tage angle adjustment lever 5 connected to the eccentric
cam 6 of the ~ta~e angle adjustment mechanism 80 that the
rear portion of the ~tage 3 i8 moved upwardly. Thus, the
stage angle Q is changed ~o as to gradually incline the stage ---
3. As a result, a stage position 3' i~ achieved at which the
focus adjustment index 11 i~ focused on the screen Sl- Thu~
the focusing operation i8 ended.
The above-de cribed operations are performed with the
projecting mirror 8 disposed between the object to be
projected and the projecting lens 1. That i8, the above-
de~cribed operation~ are the operations in which ~tage
virtual images 3i and 3i' and focusing index virtual images
lOi and lli are being operated. In this case, the virtual
image of the object on the stage 3' and formed by the
projecting mirror 8 iff positioned on the stage Therefore,
each of the extension plane of the stage 3i', the image
surface of the screen Sl, and the principal plane of the
pro~ecting lens 12 coincide with one another on a line.
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As a result, the Scheimpflug condition i8 ~atisfied.
A screen S2 represent~ the inclination of the screen
when the opaque projector having no stage angle adjustment
mechanism i~ u~ed inclined by an angle of 92 to project the
object. In thi~ case, since the relationship 91 = ~2 must be
held, the adjustment of the ~creen S2 has been inconvenient.
Even if the inclination Q of the stage 3 i8 an optional
angle, the focusing can be ea~ily performed by aajusting the
stage 3 as described above. Therefore, the complicated
adjustment of the angle ~1 of the screens S2 can be ---
eliminated.
In the case where the object to be projected i8 placed
on the stage 3, the focusing can also be conducted by
observing the focused state of the object after the focu~ing
index il ha~ been focused.
Although the reflecting mirror 8 and the optical axis 13
make an angle of 45 according to this embodiment, the
pre~ent invention i8 not limited to this description.
As described above, it has been tedious to adjust the
angle of the screen ~ince the screen is very large and heavy.
Furthermore, ~ince the angle must be adjusted in accordance
with the elevation angle of the opaque projector body,
con~iderable skill has been necessary. However, according to
the pre~ent invention, lack of focus can be
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prevented and the adjustment of khe screen can be eliminated
only by adju~ting the angle of the stage.
Although the invention has been described in its
preferred form with a certain degree of particularly, it is
understood that the present disclosure of the preferred form
has been ~hanged in the details of construction and the
combination and arrangement of parts may be rei~orted to
without departing from the spirit and the Qcope of the
invention as hereinafter claimed.
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