Note: Descriptions are shown in the official language in which they were submitted.
103~10
- B~C~GROU~ OF THE INVE~TION
-
Field o~ the Invention
.. ..
This invention relates gerr~rally to the projection
of images on a viewing screen, and more particularly is
directed to improvements in image projection apparatus of the
type in which images, for example, in the form of letters,
indicia and/or patterns~ produced by an image reproducing
device, such as, a Bxaun or cathode ray tube, are projected
through a projection lens onto a viewing screen for providing
an enlargement ~f the reproduced image on the screen.
Descr ption of the Prior Art
It has been proposed to provide an apparatus in which
an image produced by a Braun or cathode ray tube or.other image
.
reproducing device is projected through a lens onto a viewing
screen so as to provide an enlarged reproduced image on such
screen. However, with such previously proposed apparatus,
there is inadequate contrast between the projected image and
the back~round or field or the vie~ing screen so that it is
difficult to distinguish the projected image from the background
or field, particularl~ when ambient ill~mlination falls on the
viewing screen. ~urther,il the reproduced irnages are to be
of various colors so that the image reproducing device is in
the form of a color cathode ray tube having a color phosphor
screen and an associated shadow mask, such shado~ mask
inherently red~ces the brightness oE the reproduced image, and
hence of the imaOe projected on the viewing screen, so that the
-2- '~
~4
: -
:
: . . -
~038Z~O
problem of distinguishing the projected ima~e from the background
or field of the viewino screen is aggravated.
OBJE TS A~D S~Y OF THE INVE~TION
Accordingly, it is an object of this invention to
provide an apparatus for projecting onto a viewing screen an
image produced by a Braun tu'oe or other image reproducing
device, and which is free of the above mentioned difficulties
encountered in the prior art.
~ lore particularly, it is an object of thls invention
to provide an image projecting apparatus, as aforesaid, in
whicl~ the enlarged image projected on the screen is clearly
distinguishable from the background or field of the viewing
screen.
Anothèr object is to provide an image projecting
apparatus, as aforesaid, in which the enlarged image projected
on the viewing screen is of increased brilliance.
A further object is to provide an i~!age projecting
apparatus, as aforesaid, in t~hich the visibility of the
projected image on the vie~ing screen, that is, the ability to
distinguis'n bet~ieen the projected image and the background or
field of tne viewing screen, is relatively less affected by
ambient illurnination.
In accordance ~ith an aspect of tllis invention, an
apparatus for projectino ima7es on a vie~ing scr~en compriscs
image reproducing means, projection lens ~ieans for projecting
onto the vie~in~ screen irnaOes produced ~y the image reproducin~
means, and colored light source means for superimposing colored
-3-
103~10
light therefrom on the images projected on the viewing screen,
with such superimposed colored light being preferably of a hue
or hues different from that o~ the projected image.
More particularly there is provided an apparatus for
projecting images cn a viewing screen comprising ima~e~reproducing
means having an image display panel and being operative to produce
on said display panel an image of at least one color, projection
lens means for projecting said image from said display panel onto
the viewing screen, and colored light source means for super-
imposing on the image projected onto said viewing screen coloredlight of a hue different from each said color of the image
produced by said image reproducing means.
The above, and other objects, features and advantages of
the invention, will be apparent in the following detailed descrip-
tion of illustrative embodiments which is to be read in connection
with the accompanying drawings.
BRIEF DESCRIPTION OF THE D:R:AWINGS
Fig. 1 is a schematic side elevational view, partly in
section, of an image projection system according to an embodiment
Of th s~inventilon;
Fig. 2 is a perspective view of the image projecting
apparatus included in the system shown on Fig. 1, with the cross-
hatching on such view representing the colors or hues of light
transmitted or passed by respective filters;
Figs.3 and 4 are diagrammatic front elevational views
of the viewing screen of the image projection system shown on Fig.
1, with the cross-hatching on such views representing respective
colors or hues; and
Fig. S is a schematic top plan view, partly in section,
of an image projection system according to another embodiment of
the invention.
B
,. . ..... . . . ~ :
.
103~0
DESC_PTION OF l~IE PRE~ER~I~D E~IBODI~ENTS
Referring to the drawings in detail, and initially
to Figs. 1 and 2 thereof, it ~ill be seen that an apparatus,~
according to this invention for projec~ing an image on a
viewing screen 2 may comprise a cabinet 1 which is spaced
substantially from the viewing screen and which contains an
image reproducing device 3. As shown, such image reproducing
device 3 may conveniently be in the form of a Braun or cathode
ray tube having a phosphor screen or panel 3a on which the
desired image is produced. The Bra~n or cathode ray t~ube 3 may
be mounted substantially verticaI~ within cabinet 1, as shown
on Fig. 1, so that the image reproduced on the uFwardly facing
phosphor screen or panel 3a is then reflected forwardly by
a mirror 4 through a projection lens 5 which is effective to
project an enlargement of the image on the remote viewing
screen 2.
- In accordance with this invention, the image projecting
apparatus further comprises light source means for superimposing
colored light therefrom on the enlarged image or images
projected on vie~ing screen 2, with the hue or hues of such
colored light being preferably different from that of the image
reproduced on t'ne phosphor screen or panel 3a of the image
rcproducing device. Ey way of example, in the embodiment of
the invention shown on Figs. 1 and 2, the image reproducing
device 3 may be a single color cathode ray tube having an
electron gun 6 emitting a single electron beam directed against
' ' .
103~32~0
the ~?hosphor screen 3a which is coated ~ith a phosphor emit~ing
green light when energized or excited by the electron beam
so that a green image will be reproduced. In such case, the
colored light source means provided in accordance with this
invention may comprise color filters 7 and 8 disposed in a.
front panel la of cabinet 1 at the opposite sides of an opening
in such front panel through which the image is projected by
lens 5, and which a~e effective to pass red color light
and blue color light, respectively, when lamps 9 and 10
disposed in back of filters 7 and 8, respectively, are energized .
or illuminated (Fig. 2). It will be apparent that, w~en lamp 9
is energized or illuminated, the red light passing through
filter 7 directly irradiates the entire area of viewing screen
2, as indicated by the broken lines 11 on Fi~. 1, so that such
. red light will be superimposed on the reproduced green image ~-
which is projected, by means of the mirror 4 and projection
lens 5, from phosphor screen 3a onto viewing screen 2.
Similarly, when the other lamp 10 is energized or illuminated,
the entire area of viewing scree~ 2 is irradiated with the blue
light passing through filter 8 and which is superimposed on
the projected green image. Further, as sho~n on Fig. 1, i~
desired, a suitable mechanism, indicated schematically at 12,
may be provided for adjustably supporting mirror 4 so that the
angle of the latter can b~ varied.
It ~ill be apparent that, ~hen both lc~nps 9 and 10
are deenergized, only the light of the image produced on
the phosphor screen 3a of tube 3 is projected onto vie~ing
-6-
.: .
1`03~ 0
screen 2. In the case where the phosphor screen 3a emits green
light and the image produced thereon is, for example, in the
form of the letters "A" and "B", the enlarged image of the
letters "A" and "B" projected on the viewing screen 2 is green,
while the background or field of the screen is black, as shown
on Fig. 3. However, when, for example, the lamp 9 is illuminated,
the red light passing through the respective filter 7 irradiates
the entire area of the viewing screen a~d is superimposed on
the enlarged projected image As a result, the background or
field of the screen is red while the enlarged projected image
o~ the letters "A" and ~'BI' appears to be yellow, as sho~rn on
Fig. 4. On the other hand, when the lamp 10 is ill~minated,
the blue light passing through the respective filter 8 irradiates
the entire area of the viewing screen and is superimposed on
the enlarged projected image, so that the background or field
of screen 2 becomes blue while the enlarged projected image
of the letters "A" and "B" appears to be cyan. In other words,
with either the lamp 9 or the lamp 10 illuminated, the
enlarged image of the letters "A" and "B" projected on the
viewing screen and the background or field of the viewing screen
have different or contrasting hues. By reason of such contrasting
hues, the projected image of the letters, indicia or the like
- can be readily and clearly distinguished from the background
or field oE the viewing screen. Furthermore, although the image
reproducing device 3 provides a reprocluced image in only a single
color, the imaOe pro3ecting apparatus according to this invention
-r.lakes it possible, by energizing the lamp 9 and/or the lamp 10,
-7-
1031~2~
to vary the color of the projected image on the viewing screen
2, and furt~ r provides color over the entire background or
field of the viewing screen as well as in the image projected
thereon so as to enhance the attractiveness of the viewing
screen.
It will be apparent that, if the colored light source
or sources are not provided in ~ccordance with this invention
or the lamps 9 and 10 are both deenergized, so that the image
projected on the viewing screen 2 is green against a black or
dark background or field of the screen, the impingement on the
screen of ambient illumination of relatively great intensity
will cause the background or field of the viewing screen to
become gray while the chroma of the projected green image on
the viewing screen is substantially reduced with the result
that the contrast between the projected image and the background
of the vie~ing screen deteriorates and distinguishing the
projected image becomes difficult. On the other hand, when
colored light is superimposed on the projected image on
viewing screen 2 in accordance ~ith the present invention, as
described above, the projected image is clearly distinguished
, from the back~round or field of the viewing screen by the hue
difference therebetween, and such hue difference continues to
exist for clearly distinguishing thc projected image even wllen
ambient light faLls on the viewing screen and thereby reduces
the brigh~ness contrast betwecn the projected image znd the
background. Furthermore, since liVht from the l~mp 9 or 10 is
.
--8--
~ f. ' '
', ' ' ' ', ' ' '
.' ~ " , ~ ' ' ' '
103&210
added to the light of the image projected on the viewing screen
2 from the image reproducing device 3, the brightness of the
viewin~ screen 2 is increased and, accordingly, the disturbing
effects of arnbient illumination, such as, due to the reflection
by the viewing screen of light from external sources, are
reduced.
Although it is possible to obtain a projected irnage
of one color on the viewing screen while the background or
field of the viewing screen is a different color by means of
a two-color cathode ray tube, that is, without the use of the
colored light ~ource or sources characteristic of the present
invention, such two-color cathode ray tube has to be provided
with a shadow mask for ensuring that the two different color
phosphors making up the phosphor screen of the tube will be
excited only by the the respective electron bearns. As is well
kno~n, such a shadow mask limits the energy of the electron
beams irnpinging on the respective color phosphors, and thereby
limits the brightness of the image produced on the phosphor
screen of the color picture tube. On the other hand in
accordance with the present invention, the projected ima8e and
back~round or field of the screen are provided with contrasting
colors or hues while using only a single-color cathode ray tube
in whi~ no shado~ mask is required so that the brightness of
the reproduced ima~e, tlla~is, the intensity of the light
elnitted from tl~ phosphor screen 3a on Fig. 1, is very substan-
tially increased for similarly increasi!~g tl~e brigh,ness of
the projected image on viewing screen 2.
_9_
-'' ' ' - ~
103~2~0
In the above described embodirnent of the invention,
the viewing screen 2 is directly irxadiated with the colored
light passing through filter 7 and/or f lter 8 upon the illum-
ination of the respective light sources 9 and 10. However, in
accordance with the present i~vention, the colored Light source
or sources may be disposed to irradiate the phosphor screen or
panel 3a of the image reproducing device 3 with the respective
colored light so that ~he projecting lens is then effective to
project onto the viewing screen both the colored reproduced
image and the colored background or field of the phosphor screen.
More specifically, as shown on Fig. 5 in which the co~ponents
or parts of an image projecti~n system corresponding to those
described above with reference to Figs. 1 and 2 are identified
by the same reference nurnerals, an image projecting apparatus
according to another embodiment of this invention rnay be
provided with lamps 13 and 14 which are respectively operative
to emit red color light ~nd blue color light and which are
disposed within cabinet 1 at opposite sides oE the green light- ;
emitting phosphor screen 3a of the single-color cathode ray
rube 3. Reflectors or light shielding members 15 and 16 are
associated with the lamps or colored light sources 13 and 14,
respectively, to direct the respective colored light over the
entire surface of panel or screen 3a and to prevent the passage
through lens 5 of colored light directly frorn larnps 13 and 14.
It will be apparent that, ~Jith the embod~r.ent of the
invention shown on Fig. S, when lamp 13 is ill~minated, red
.', ' . .
-10-
: ~ .
'
103~ 0
light therefrom is projected onto the entire front of outer sur-
face of the panel or phosphor screen 3a so as to be reflected
therefrom and projected through lens 5 onto the viewing screen 2
together with the light image produced by the tube 3. Similarly,
when lamp 14 is illuminated, blue color light emitted therefrom is
projected over the entire front or outer surface of the phosphor
screen or panel 3a and reflected therefrom so as to be projected
; by lens 5 onto viewing screen 2 together with the light image .
produced by the tube 3. Thus, in the case where phosphor screen
3a is composed of color phosphors which emit green light when
energized by the electron beam, the illumination of colored light
source 13 will cause the projected image on screen 2 to be colored
yellow while the background or field of the viewing screen is
colored red. On the other hand, the illumination of colored light
source 14 will cause the projected image on viewing screen 2 to be
colored cyan while the background or fieId of the viewing screen
will be colored blue.
In describing the operation o the embodiments of the
invention shown on Figs. 1 and 2 and on Fig. 5, specific
reference has been made above to the alternative illumination of
the lamps 9 and 10 and of the lamps 13 and 1~, respectively, so
that the background or field of the viewing screen 2 will be
colored either red or blue. However, if desired, both lamps 9
and 10, or both lamps 13 and 14, can be simultaneously illumin-
ated in which case, if the intensities of illumination from the
lamps 9 and 10, or 13 and 14 are suitably adjusted relative to
-
--11--
. . . .
-
103~2~0
each other, the color of the projected image on the viewing
screen 2 and also the color of the background or field of the
viewing screen can be varied.
Although the ernbodiments of the invention described
above with reference to Figs. 1 and 2 and Fig. 5, respectively,
employ a single-color cathode ray tube having a phosphor screen
emitting green light for reproducing the image in combination
with sources of red light and blue color light, it is to be
noted that, in accordance with this inven~on, the image
reproducing device may be a two-color cathode ray tube having,
for example, red and green light emitting phosphors making up
its phosp~rscreen, while the colored light source provided in
accordance with the invention is operative, for example, to
emit blue colored light. In this latter case, the image
reproduced on the phosphor screen of the two-color cathode ray
tube may be red or green or any mixture of such colors, while
the blue light is superimposed on such image as projected on
the viewing screen to provide the projected .image with still
another color which contrasts with the bLue background or ield
of the screen. Further, the color cathode ray tube constituting
the image reproducing device 3 may be of the three-color type,
in which case, still greater variation is possible in the color
of the image projected on the viewing screen and the contrast
of such color with the hue or color of the background of the
viewing screen resulting from the colored light superir.lposed
on the projected image in accordance with this invention. Since
two-color or three-color cathode ray tubes have to be provided
~12-
' - ~
" 103~0
with shadow masks which re~uce the intensity or brightness of
illumination of the reproduced images, as described above, the
described effects obtainable with such two color or three-color
cathode ray tubes in the image project;on apparatus according
to this invention can be more advantageously achieved by using,
as the image reproducing device, a plurality of single-color
cathode ray tubes having phosphor screens which respectively
emit different colors. When using a plurality of single-color
cathode ray tubes, identical images, but in different colors,
are reproduced on the phosphor screens of the plurality of
tubes, and the differently colored images are projectéd on the
viewing screen in registration with each other th~ ugh a common
projection lens, for example, by means of a dichroic or semi-
reflecting mirror. It will also be apparent that image repro-
ducing devices other than the specifically described cathode ray
tubes, such as for example, eidophors, can be employed in the
image projecting apparatus according to this invention.
In each of the embodiments illustrated on Figs. 1 and
2 and on Fig. 5, respectively, the viewing screen 2 has been
shown to be of the reflecting type, that is, is intended to
be viewed from the side thereof onto which the reproduced image
is projected However, it will be apparent that the image
projecting apparatus according to this invention can be used
with a viewing screen of the back-projection type, that is, one
in which the screen is viewed from the side thereof opposed to
that against which the reproduced image is projected.
-13-
.
~03~10
Advantageously, the viewing screen employed with the image
projecting apparatus according to this invention may be of a
so-called directional type so that light Erom overhead sources
of illumination will not be projected to the viewer's eyes
either by re1ection from, or transmission through the viewing
screen.
Although illustrative embodiments of this invention -
and various modifications thereof have been described in
detaîl herein, it is to be understood that the invention is
not limited to those precise embodiments or modifications, and
that various changes and further modifications may bé effected
therein by one skilled in the art without departing from the
scope or spirit of the invention as defined in the appended ~ :
claims.
-14-
