Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
PROJECTION APPARATUS
~ield of the Invention
~hi~ invention relates to optical instrument
building, to apparatuses ~or projecting the display
of yisual information, more specifically - to projec-
tion apparatus.
Description of the Prior Art
At the present time work i~ being conducted with
the aim of improving ~nown and creating ba~ically new
con~tructions of small-size projection apparatuses,
which would make it possible to obtain a high quality
reproduced image on medium-size and large screens,
The main requirement~ which such projection apparatu-
ses should ~ati~fy are high re~olution, contrast and
ll~m; n~nce of the image reproduced on the screen,
which image should be suitable for convenient obser-
vation under given ambient illumination conditions.
Furthermore, such projection apparatuses should sa-
tisfy a number of operational requirements, in parti-
- cular: the power consumed by the light source of the projection apparatus should be low, the apparatus
should operate in a normal electric and temperature
mode, the level o~ X-ray radiation should not e~ceed
permis~ible values (for projection apparatuse~ in
which a picture tube is used as the image source) etc.
Television projection systems, i.e. projection
apparatuses in ~hich a piGture tube is u~ed as the
source of the optical ima~e, are the most widely
u~ed ~ystem~, Such a televi~ion sy~tem (V.S. Babenko,
rrOptics of television apparatùses", 1982, Radio i
Svyaz, Moscow, p, 232-234) comprises a picture tube
and projection lens objective with the screen of
the picture tube positioned in the field of view
thereof. In such a televi~ion projection system the
illuminable image formed on the screen of the pic-
,,~
. .
-- 2 --ture tube i~ projected through the projection ob-
jective:onto a viewing screen
~ e luminou~ efficiency of ~uch a projection
~ystem, determin;n~ the llJm;nnnce, contra~t and co-
lor ~aturation of the projected image, i8 low. Thisi~ primarily due to the fact that when the project-
ion i~ made from an origi~al, the area of which i~
comparable with the area of the entrance pupil of
the projection objective, only up to 9% of the lu-
minous flu~, diffu~ively radiated by the original(picture tube screen), passe~ through the project-
ion lens objective to the viewing ~creen, thi~
being due to the low geomjetrical-lens aperture in
known projectors. An increase in the luminou~ eff-
ciency of the projection ~ystem obtained by increa-
~ing the area of the original without increa~ing
the area of the entrance pupil of the projection
len~ obàective i~ not e~fective because of the in-
crease in the vi~ible difference between the lumi-
nance in the center and at the edge~ of the project-
ion field on the viewing ~creen and becau~e of the
appearance of vi~ible geometrical aberration~. It i~
not ~easible to increase the luminous efficiency o~
the projection sy~tem by increa~ing the area of the
entrance pupil of the objective without increa~ing
the area of the original, either, since thi~ re-
sults in the necessity to increa~e the di~tance
between the objective and the original in order-to
1 prevent geometrical aberrations, which in turn
re~ult~ in a reduction of the useful luminous flux
in proportion to the square of the distance between
the objective and the original. ~urthermore, manu-
facturing projection objectives having a large ~ize
entrance pupil i~ a complex proces~ from the engi-
neering point of view~ The ll1min~nce of the projec-
ted image i~ u~ually increa~ed in televi~ion pro-
jection ~y~tem~ by operating the picture tube in
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forced electric and ~qevere temperature mode~. However,
thi~ re~qult~q in a ~harp reduction of the ~ervice life
of the picture tube, an increa~e in the X-ray radiat-
ion and a reduction of thb re~olving power o~ the
picture tube,
Mirror-len~ television projection sy~tems, so-ca-
lled Schmidt ~ystem~, are al~o known (V.S. ~abenko,
"Optic~ of televi~ion applaratu~es", 1982, Radio i
Svyaz, Mo~cow, p, 234-237). The~e ~y~tem~ comprise
a picture tube, a concave ~pherical mirror and a cor-
rection len~, all having a common optic axi~q, The
concave ~pherical mirror ,together with the correct-
ion len~ form~q a mirror-len~ projection objective,
The ~pherical mirror i9 mounted with it~ concave
~urface facing the screen of the picture tube, the
correction lens i~ di~posed behind the picture tube,
The diffu~ed luminou3 ~lux from the ~creen of the
picture tube, reflected ~rom the-mirror, iq focu~ed
by the correction len~ onto the viewing ~creen,
Such mirror-len~ televi~ion projection sy~tem~
have an optical tran~mission factor of up to 30%,
,which i~ higher than with the aforementioned projec-
tion ~y~tem with a len~ objective, ~hi~ is due to
the fact that a mirror-len~ objective ha~ a large
angle of view and high re~olving power,
The diameter of the ~pherical mirror i9 ~elec-
ted on the ba~i~ of more comple2 u~e of the lumi-
- nou~ flu~ radiated by the picture tube, in practice
the diameter of the ~pherical mirror is selected to
be from 3 to 4 time~ the-diameter of the picture
tube ~creen, The radiu~ of curvature of the mirror
~nd the diameter of the correction lens are ~elec-
ted on the ba~i~ of the conditions for obt~;n;n~
, the m~mum relative aperture and permiq~ible vig-
netting, Wherein, the radiu~ of curvature of themirror-i~ ~elected to be from 0,8 to 1,0 the dia-
'~ .
meter of the mirror, while the diameter of the cor-
rection len~ elected to be from 0.65 to 0.75 the
diameter of the mirror. These ratio~ ~how that for
small picture tube ~creen ~izes the mirror and correc-
tion lens are large. The use of picture tube~ having~mall ~creen sizes limits the luminou~ efficiency of
the projection ~y~tem ~or average and large viewing
~creen~; in other words, the attainment of high lu-
m~n~nce~ contrast and color ~aturation of the projec-
1b ted image on medium-size and large screen~ i~ not
po~sible with ~mall ~ize picture tube ~creen~. But
an increa~e in picture tube screen ~ize brings about
a ~ub~tantial increa~e in the dimen~ions o~ the ~phe-
rical mirror and correction lens, i.e. an increa~e
in the ~ize of the projection ~y~tem, which makes ma-
nufacturing and alignment of the projection sy~tem
more complex.
A projection apparatus i~ al~o known (US ~o.
3506782) compri~ing a fiber-optical plate, the ent-
rance face~ of the light guide~ of which coincidewith the plane of the original image, and a project-
ion objective, with the exit face~ of the light
guide~ of the ~iber-optical plate po~itioned in the
field of view of that objective. A picture tube
with ultraviolet diffu~ive light radiation i~ u~ed
in thi~ projection apparatu~ a~ the primary modula-
tor of the original image, a dichroic filter being
po~itioned on the screen thereof to reflect vi~ible
beam~ and pa~ ultraviolet ray~. ~he ~aid fiber-op-
3o tical plate is mounted on the dichroic filter, theplate having photochrome light guide~, the tran~pa-
rency o~ which change~ depending on the ll~m;n~nce
of the ultraviolet light. Thu~, the photochrome
light guide~ are a physically active optical medium,
~ub~tantially a ~econdar-~ spacellight modulator of
the original image, for the visible light pa~ing
-- 5 --
therethrough and forming the original image. ~urther-
more, the projection apparatus comprises a first op-
tical sy~tem, formed by a first mirror and collecti-
ve len~, for directing visible light from a point
source of light through the light guides of the
fiber-optical plate to the dichroic filter, and a se-
cond optical ~ystem, formed by the said collective
lens, a second mirror and a lens objective for mag-
nifying the image projected on the viewing screen,
for projecting the image reflected by the dichroic
filter.
During the sc~nn;ng of the~picture tube phosphor
~creen with the electron beam, the phosphor glows
with an ultraviolet light, v~hich passe~ through the
dichroic filter to the photochrome light guides,
the transparency of which decrea~es as the l~m;n~nce
of the ultraviolet light increases. ~herein, the
light rays from the poin-t ~ource o~ visible light,
directed by the firqt mirror and collective lens
along the optical axes of the light guide~? impinge
on the dichroic filter and reflecting therefrom pa~
along the optical axes of the light guides through
the said collective lens and second mirror into the
entrance pupil of the projection objective. By chan-
ging the l~m;n~nce of the ultraviolet light, ele-
ment-by-element of the p~imary image of the origi-
n&l on the picture tube screen, a change in the
tran~parency of the light guides takes place, as
a result of which a secondary image of the original
is fo~med element-by-element by the rays of visible
light within the space of the exit faces of the
light guide~, which secondary image i~ projected by
the objective to the viewing ~creen
~n advantage of this projection apparatus i~
increased contrast and a high optical transmission
factor of the projected images. This is due to the
;~
3 7 ~
-- 6 --
fact that the projected image of the original is
formed by a directed ligh~ source.
I However, it is generally known that photochrome
materials, from which the light guides of the fiber-
-optical plate are made, ensure the formation of
image~ with a thin linear range of half-tone grada-
tion~, which cau~es half-tone and color distortions
in the proaected image as compared with the origi-
nal image, Furthermore, due to their physical-che-
mical properties, photochrome material~ have a limi-
ted cyclicity, ,which lowers the operating service
life of the projection apparatus in the ca~e pf dy-
namic di~play of information. The ;dependence of the
speed and quality of the dynamic display of informat-
ion on the power of the modulating light (in thi~
case on the power of the ultraviolet light) limits
the frequency of image frame change of the original
on the screen of the display in the projection appa-
ratu~,
The use of light guides made of photochrome ma-
terial~limit~ the field of usage of such projection
apparatus, since photochrome light guides only chan-
ge their transparency due to the effect of ultravio-
let light; in other words such a projection appara-
tus i~ capable of projecting the image of originals
radiating ultraviolet light.
The presence of a fir~t optical ~ystem with an
e~ternal point source of visible light, the use of
photochrome light guide~ and dichroic filters make '
the con~truction of the projection apparatu~ more
' complex.
Furthermore, the use of an external source of
visible light re~ults in an increase in the power
con~umed by the projection apparatu~.
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Object~ and Summary o~ the Invention
~ he ob~ect of the invention i~ to create a pro-
jection apparatus in which the con~tructive realizat-
ion of the light guide~ of a fiber-optical plate
would en~ure high quality'of projected color and mono-
chrome image~ of the original during lengthy operat-
ion of the proje.ction apparatu~, ~implification of
it~ construction and reduction of the power con~ump-
tion.
This problem i~ ~olved in that in a projection
apparatu~ comprising a fiber-optical plate, the en-
trance faceq of the light guide~ of which coincide
with the plane of the original image, and a project-
ion len~j the e~it face~ of the light guide~ of the
fiber-optical plate being di~po~ed in the field of
view thereof, in accordance with the invention, an
optical syqtem is formed in each of the light guide~
of the fiber-optical plate in the path of propagat-
ion of the light beams to concentrate the light ray~
into a light beam and direct that light beam into
the entrance pupil of the projection objective. .
The optical ~yqtem formed in each of the light
guideq of the fiber-optical plate to concentrate .:
the light ray~ into a light beam and direct that
light beam into the entrance pupil of the objective
i~ physically pa~ive optical m.edium for light ray~ -
and only en~ure~ optical-geometrical tran~formation
of the primary image of the original u~ing optical
elements having con~tant light tran~mi~sion, refrac-
tion and reflection factor~. Thi~ in turn en~ure~the preservation of the width of the half-tone gra-
dation range, the color qaturation and color purity
in the projected image during lengthy ~ervice time
of the pro;ection apparatu~, independent of the fre-
quency and cyclicity of image frame change in the
.' ~, .
_ 8 --
- original. Concentration of, the luminous flu~, radia-
ted by the original, in the entrance pupil of the
projection objective ensure~ an increase in the lumi-
nance oflthe projected image on the viewing screen
without increasing the power consumed by the project-
ion apparatus. The realization of optical sy~tems in
the light guides of the fiber-optical plate ensures
simplification of the construction and size reduction.
~urthermore, such a projection apparatus is capable
of projecting any type of original image over the
whole band of the optical spectrum pa~sed by the
light guides of the fiber-optical plate.
Embodiments of the constructive realization of
optical systems for concentrating light rays into
a light beam and directing that light beam into the
entrance pupil of the objective are possible.,In the
case when the optical axes of the light guide~ are
parallel to the optical axis of the projection ob-
jective a~d do not pass through its entrance pupil,
then it is feasible that the optical system be for-
med by a focon, positive lens and refracting prism
positioned ~uccessively in the path of the light
rays in the light guide, ~Jhile the common optical
agis of the focon and positive lens be made to coin-
cide with the optical axis of the light guide. Theconstruction of the refracting prism and its orient-
ation in a separate light guide relative to the
entrance pupil of the objective ensuring the trans-
mission of a maximum luminous flu~ through the en-
trance pupil of the len~, is determined by wellknown calculations according to known methods.
In the case when the optical axes of the light
guides of the fiber-optical plate are directed to
the entrance pupil of the! len~, then it is feasible
that the optical system be formed by positioning
the focon and positive lens ~uccessively along the
,r
h .
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path of the light ray~ in the light guide, while the
common optical axi~ thereof wo~ld coincide with the
optical axi~ of the light guide and be directed to
the entrance pupil of the projection objective. In
that ca~e deflection of the light ray.~ i~ en~ured by
orientation of the light guides relative to the ent-
rance pupil of the projection objective.
,
Brief Description of the Drawing~
The advantages of the invention become easier
to under~tand from the following concrete e2ample~
- of realization thereof and drawing~ wherein:
Figure 1 ~how~ the ~chematic diagram of the
projection apparatu~ made in a televi~ion proaect-
ion sy~tem in accordance with the invention;
Figure 2 shows the out~ide element A in Figu-
re 1;
~ igure 3 ~how~ the schematic diagram of the pro-
jection apparatu~ made in a television projection
sy~tem in accordance with the invention, second em-
bodiment;
~ igure 4 ~how~ the out~ide element B in Figu-
re 3.
Description of the Preferred Embodiments
Consideration will be given to the fir~t embodi-
ment of a televi~ion apparatus made in accordance
with the invention and serving to project the image
of an original from the ~creen of a television pic-
ture tube. Thi~ projecti~n apparatu~ comprises
a fiber-optical plate 1 (Figure 1), the entrance
face~ 2 of the light guide~ 3 of which coincide
with plane a-a of the image of the original. In
other words, the fiber-optical plate 1 with entran-
ce face~ 2 of it~ light guides i~ positioned onthe ~creen 4 of a televi~ion picture tube 5. The
- 10 _
screen 4 of the picture tube 5 i8 formed by a phos-
phor layer 6 (~igure 2), applied to the entrance
faces 2 of the light guides 3 and covered with a
light reflecting film 7 made of aluminum. ~urther-
more, the projection apparatus comprises a project-
ion objective 8 (Figure 1), the exit faces 9 of
the light guides 3 being positioned in the field of
view thereof. The optical axes ~1-~1 of light quide~
3 are parallel to the optical axis ~2-~2 of the pro-
jection objective 8. An optical syqtem 10 (Figure 2)iq formed in each of the light guide~ 3 of the
fiber-optical plate 1 in the path of propagation
of the light rays, conditionally designated in the
drawing by arrows, to concentrate the light rays
into a light beam and direct that light beam to the
entrance pupil 11 (~igure 1) of the projection
objective 8. The optical system 10 is formed by
a focon ~2 (~igure 2), crescent-shaped positive
lens 13 and refracting prism 14, successively dispo-
sed along the path of the light rays in the lightguide. Wherein, the optical axes 03-03, 04-04 of
the facon 12 and crescent-shaped positive lens 13
concide with the optical axis ~1-~1 of the light
guide 3. Each of the light guides 3 is made in
a shell 15, the inner surfaces of vrhich are covered
with a light reflecting layer 16, in this case
a iayer of aluminum.
The described proje¢tion apparatus operates in
the following m~nner. During scanning of the screen
4 of the picture tube 5 with the electron ray,
element-by-element illumination of the phosphor
layer 6 takeq place with diffused light. ~he diffu-
sed light passes through the focon 12, the cre~cent-
shaped positive,lens 13 and refracting prism 14.
The focon 12 concentrates the diffused light in its
exit face. The crescent-shaped positive lens 13
i -1
transform~ the diverging wide light beam exiting
from the focon 12 into a diverging narrow light beam.
Concentration of the light rays into a light beam is
en~ured this way. After that the reflecting pri~m 14
deflects the light beam to the entrance pupil 11 of
the projection objective 8.
One more embodiment of the projection apparatus
will now be given consideration. The distinction
between this projection apparatus and the apparatus
described in the first embodiment is that the opti-
cal ~xes ~1-~1 (Figure 3) of the light guides 3 are
directed to the entrance pupil 11 of the projection
objective 8. This serve~ to simplify the construct-
ion of the optical system llO(Figure 4) for concent-
rating the light rays into a light beam and direct-
ing that light beam to the entrance pupil 11 of the
projection objective 8. This optical systemllO is
formed b~ positioning a focon 17 and crescent-shaped
positive lens 18 succes~ively along the path of the
light rayb in the light guide 3, the optical axes
~5~~5~ ~6-~6 of which coincide with the optical
agis ~1-~1 of the li~ht guide 3 and are directed to
the entrance pupil 11 of the projection objective 8.
This projection apparatu~ operates in a manner
similar to the projection apparatus described in the
first embodiment. The distinction is that the light
beam concentrated by the focon 17 and positive
crescent-shaped len~ 18 i~ directed to the entrance
pupil 11 of the projection objective 8 directly.
Industrial Use
The projection apparatuses made in accordance
with the invention are most effectively used in tele-
vision projection systems, projection displays, pro-
jection indicators and epidiascope~. These project-
ion apparatu~es ensure high luminouq efficiency,
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exceeding 50~0, with uniform ll~m;n~nce at the edges
and in the center of the field of the projected image~
~urthermore, such a projection apparatus makes it
possible to increase the l~m;n~nce of the projected
image for a constant size of the entrance pupil of
the projection objective due to the increase in the
size of the image of the original with a high lumi-
nous efficiency, which makes it possible to increase
the resolving power of the projection apparatus.
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