Note: Descriptions are shown in the official language in which they were submitted.
TITLE OF TIIE INVENTION
E'ROJECTION TYPE DISPLAY APPARATUS
BACKGROUND OF THE INVENTION
F:ield of the Invention
Tne present invention rela-tes to a projection -type
display apparatus which projeets image l.ight from a eatnode-
ray tube (hereinafter abbrevia-te(l as CRT) through a projee-
tion lens for p:rojectlorl Or an enlarged :imag~e onto a screen,
and more partic;ularly to automatie adjustment o-f -the eharac-
teristics of the CRT.
Description of Rela-ted Ar-t
Adjustments speeially required -for the eharacteristics
of -the CRTs used in projeetion type display apparatuses
generally inelude -focus adjustments for effec-ting proper-
foeusing on the screen, eonvergenee adjus-tments for correct-
ing the separa-tion of eolors on the sereen, raster dis-tor-
tion adjustments for eorree-ting raster distor-tions eaused
when an eleetron beam is not eorreetly deflected for ras-ter
seanning due to nonlinearity of deflection circuitry, ete.,
eu-toff adjustments for adjusting the euto-ff voltage at whicn
lumineseent spots become invisible, and white balanee ad-
justments for p:reventing blaek-and-white pietures -to be
uniformly tinted.
Fig. 1 is a schemat;ic diagra~l of a prior art projec-
tion -type disp1ay apparatus disclosed, for example, in
Japanese Paten-t Applicatio~ Laicl Open No. 59-23684, relating
to focus adjustment. In Fig. 1, the reference nllmeral l
designa-tes a CRT having a phosphor screen 10. In front of
the CRT 1 is a projec-tion lens 2 with A lens cover 21 fit
over i-t. The Lens cover 21 i5 provided at i-ts center with a
PIN pho-tocliode ~1 serving as a pho-tocletector for detecting
the brightness of the phosphor screen 10 of -the CRT 1.
Next, the opera-tion of the above dispLay appara-tus wlll
be described below. When using the projection -type display
apparatus, the lens cover 21 is removed and image light from
the CRT 1 is projected through the projec-tion lens 2 onto a
screen (not shown) on which the resultin~ image is focused.
When making focus adjustments, a beam spot is emitted -to
illuminate the cen-ter of the phosphor screen and the beam
spot is detected by the PIN photodiode 41. Then, the focus
vol-tage is adjus-ted by a focus adjusting circui-t (not shown~
with reference to the output of -the PIN photodiode 41 so
tha-t the detec-ted brightness of the beam spot is reduced to
the minimum level.
In the prior ar-t projection -type display apparatus,
potentiometers for adjus-ting the cutoff and whi-te balance
characteris-tics are provided -for each CRT. When adjusting
the cu-to-ff and white balance charac-teristics, these potenti-
~8~3~3
ometers are marlually adjus-ted, which are used -in combination
wi-th special tes-t equipment respectively, so lhat proper
values are obtained.
Furthermore, in the pl'iOI` ar-t projection -type d:isplay
apparatus, convergence and raster distortion adjllstlllerlts are
also made manua]]y as in the above adjustments.
Since the prior art projection -type display apparatus
is constructed as describecl above, focus adjustment requires
-the WOI'k to fit a ]ens cover, ancl the adjustment is possible
only in the manufacturing process of the apparatus. The
resultirlg problem is -tha-t~ even if the adjustment has been
once made, devia-tion from the proper value may occur because
o-f deterioration of the CRT characterist:ics with time, e-tc.
Another problem is that adjusting the cu-to-ff and whi-te
balance characteristics requires special equipment built for
the respective purposes, taking a lot of trouble for adjus-t-
ment. Fur-thermore, the adjustment can only be made in the
manufacturing process of the apparatus, and the problem here
is also that, even if the adjus-tment has been once made,
deviation from the proper value ma~ occur af-ter manufactur-
ing because of various factors such as the de-terioration of
the CRT phosphors, the temperature charac-teristics of compo-
nents, etc.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a
projection type d-isplay apparatus in which the various
adjustments specially required fo.r the characteris-tics of
the CRT can be made automatically w.itll the display apparatu6
in an assembled state.
It is another objec-t of the :inven-tion to provide a
projection ty~pe display apparatus capable of being automa-ti-
cally adjusted w:ithout requiring the use of special equip-
ment.
The projec-tion -type display apparatus of the present
invention includes a pattern forming means for forming an
adjusting pattern on a CRT, a de-tecting means for de-tecting
the projected image of the adjusting pattern, and an adjust-
ing means for adius-ting the characteristics of the CRT on
-the basis of the results of detection by the detecting
means. Using the pattern forming means, an ad~justing pat-
tern is formed on the screen of the CRT, and this adjusting
pat-tern is projec-ted on-to the detecting means, based on -the
output of which the characteristics of the CRT are au-toma-ti-
cally adjusted with -the adjusting pattern being adjusted to
optimum level.
To describe specifi.cally, focus adjustments, conver-
gence adjustments, ras-ter distortion correc-tions, cutoff
characteristic adjustments, white balance characteris-tic
adjus-tmen-ts, etc. are automatically made. When -the detect-
ing mearls is installecl ou-tside tlle effective image area of
the screen, the characteris-tics Oe the CRT can be adjusted
wi-thout inter-fering wi-th the normal imag~e clisplay.
The above and further objects and features of the
invention will more flllly be apparent from -the following
detailed description with accompanying drawings.
BRIEF DESCRIPTION OF TIIE DR~WINGS
Fig. 1 is a schema-tic cliagram showing the construc-
tion of a pI' i O I' art projection type display appara-tus.
Fig. 2 is a schematic sectional -view showing the
construction of a projection type display apparatus accord-
ing to -the invention.
Fig. 3 is a diagram showing images, such as focus
adjusting pa-t-terns, formed on a CRT screen.
Fig. ~ is a diagram showing the locations of photode-
tectors.
Fig. 5 is a schema-tic diagram showing a feedback
system for focus adjllstment, convergence adjustment, and
ras-ter distortion correction.
Fig. 6 is a schematic sectional view showing -the
construction of a projection type display appara-tus accord-
ing to another embodimen-t of -the invention.
Fig. 7 is a diagram showing images, such as cutoff
and white balance adjus-ting pa-tterns, formed on a CRT
~ ~ 8 ~
screen.
Fig. 3 is a diagram showing the loca-tions of photode-
tect~rs.
Fig. 9 is a schematic diagram showing a feedback
sys-tem for cutof~ and whi-te balance adjustments.
Fig. 10 is a schematic sec-tional v:iew show:ing the
construction of a projection type display apparatus accord-
ing to a further embodiment of the inven-tion.
DESCRIPTION OF THE PRRFERRED FMBODIMENTS
The preferred embodiments o~ the presen-t invention will
now be described below with reference to -the accompanying
drawings.
(Embodiment 1)
Fig. 2 is a schematic sectional view showing a pro-
jection type display appara-tus according to one embodimen-t
of the present inven-tion. A projec-tion lens 2 is mounted in
front of the screen of a CRT 1~ and a screen 3 is installed
at a dis-tance in fron-t of the projection lens 2. The screen
3 is supported at i-ts periphery by a screen frame 31. Pho-
todetectors ~ having CCDs, etc. are moun-ted on -the surface
of the screen frame on the same side as -the projected side
of the screen 3.
In the projection type display apparatus of -the above
?3 ~ i~
construction, an imagSe formecl on the screen of the CRT l is
enlarged through the projection lens 2 and beamed in the
form of projection 1.igh-t 110 onto -the screen 3 for viewing.
The diverging angle of the projecti.on l;.ght 110 is made
wider than -the angle that just matches the screerl sir~e, so
tha-t -the photodetectors 4 mounted outside the periphery o~
-the screen 3 can also be illumi.nated.
Fig. 3 shows the condiLion of an image eorme(l on the
phosphor screen 10 of the CRT 1. An area 13 on the phosphor
screen 10, wh:ich is projec-ted on-to -the screen 3, is smaller
-than an image area 12, the ac-tual image area formed by
ras-ter scanning on -the phosphor screen 10. In practice,
this image area 12 is beamed toward the screen 3. This
means -that part of the area on the phosphor screen 10 which
is raster-scanned by an electron beam does no-t appear on the
screen 3.
Outside ~he image area 12 on which an image is formed,
a cross-shaped focus adj~s-ting pat-tern 1'l (hereinafter
referred -to as the pattern 14) is formed, for example, by
applying an outpllt of a character genera-tor to the CRT 1.
In Fig. 3, the pattern 14 is cen-tered on each side of the
rectangular image area 12, tha-t is, a total of four patterns
14 are formecl.
Fig. 4 shows the screen 3 viewed from -the projecting
side. As shown, on the screen frame 31 supporting the
~8~8~
screen 3 a,t the periphery thereof, four photo-letec-tors 'I are
mounted correspondirlg in position and number -to the pat-terns
l'l .
Fig. 5 shows a t`eeclback sys-tem for the projec-tion -type
display apparatus wi-th regard -to one embodilllen-t of' the
invention, except the por-tions indicclted by dot and dash
type lines. In the figure, the numeral 7 indicates a t'OCllS
adjus-ting circuit f`or adj~lsting eOcus, ancl 6 is a microcom-
pu-ter for controlling -the foc~ls adjusting~ circuit 7 on the
basis of outputs fed from -the photode-tectors ~.
The pa-tterns l~ formed cn the phosphor screen lO of t~le
CRT 1 are beamed through -t,he projection lens 2 and projected
beamed in the'Porm of pro,jec-tion light 110 onto the pho-tode-
-tectors ~ moun-ted on the screen frame 31. ~ased on the
outputs of the pho-todetectors ~1, the n~icrocomputer 6 con-
-trols the focus adjusting circuit 7 so as to mini~li2e the
line width of each projec-ted pattern 14~ Wi-th this con-trol,
a focus voltage for proper focusing is set in the fOCllS
adjusting circui-t 7, and -this focus voltage is applied -to
the CRT 1.
In the illustrated e~ample, four focus adjusting pat-
-terns 1~ are used, but i-t will be appreciated that a single
pattern may serve the purpose. Also, the number of patterns
1~ is made equal to -the number of photode-tec-tors ~, but the
pho-todetectors ~ may be made fewer in number than the pat-
terns l~1.
(Embodiment 2)
~ ig. 6 is a schemat:ic sec-tional view showing a pro-
jection type display apparat11s using, for exampLe, three
separate CRTs for red~ green, and blue colors, accorc~ing to
ano-ther embodiment of the invention. In Fig. 6, -the same
reference numerals as those in Fig. 2 desigrlate the same
parts. Projection lenses 2a, 2b, and 2c are mounted in
front of the screerls of -the three CRTs la, Ib, and Ic,
respectively.
In this pr~ojection type display appara-tus, one of the
-three primary color images, for example, formed on the CRT
la, is beamed through -the projec-tion lens 2a, where the
enlarged image is projected in -the ~orm of projection light
ll0a on-to -the screen 3. Obviously, the same applies to -the
other CRTs lb, lc, projection lenses 2b, 2c, and projection
light llOb, llOc. Thus, a full-color image is formed on the
screen 3.
The feedback system for the above projection -type
display apparatus is fundamentally the same as the one shown
by solid lineæ in Fig~ 5. Tha-t is, in the configuration
of Fig. 5, -the CRTs la, lb, and lc are generally repre-
sented by the CRT l, and the focus adjusting circui-t 7 for
adjus-ting focus is designed to ou-tput a separate adjusting
signal for each of the CRTs la, lb, and lc.
Focu5 adjus-tment in such a -three--tube proJection type
display appara-tus is performed separately ~or each of the
CRTs ta, lb, and 1c, but clescrip-tion o~ the eOcus adjus-tment
is omi-tted herein as it is in operation the same as thal;
described in connection wi-th the f`:irst embodiment.
(Embodiment 3)
The third embocliment hereina-fter described concerrls a
three-tube projection type displ&y apparatus wherein conver-
gence adjustmen-ts are made au-toma-tically. The outline of
the -feedback system used for this purpose is indica-ted by a
one-dot and dash -type line in Fig. 5. O-therwise, -the con-
struc-tion o-f -the apparatus is the same as tha-t shown in Fig.
6.
~ eferring primarily to Figs. 5 and 6, we will de-
scribe how convergence adjustments are made. The same
patterns 14 as shown in Fig. 3 are formed ho-th on the CRT
lb and on -the CRT la (or lc), and -these patterns 1~ are
simul-taneously projected onto the pho-todetectors 4. Based
on the ou-tpu-ts of the photode-tec-tors 4, the microcompu-ter 6
detects any misalignment between -the projected images of the
pat-terns 1'1 on each photodetec-tor 4 and controls the gain of
a convergence adjus-ting circui-t 8 -to correc-t the misalign-
ment. The convergence adjus-ting circuit 8 OUtplltS conver-
f~
gence acljusting signals -to the CRTs lb and la (or lc) to
correct the separation of col.ors. Correc-ti.ng color separa-
-tion between the CRTs lb an(l la and between the CRTs lb and
lc -resul$s in correcting misconvergence of all -the CRTs la,
lb, and lc, and -thus, proper convergence adJustment is matle
-~or the projec-tion type display apparatus.
(Embodiment ~)
The fourth embodlment hereinafter described concerns a
three-tube projection type d.isplay apparat-us wherein ras-ter
distort:ion correc-tions are made automatical.ly, The outli.ne
of -the feedback system used ~or this purpose is indicated by
a two-dot and dash -type line in Fig. 5. O-therwise, the
construction o~ -the ap-paratus is the same as tha-t shown in
Fig. 6. Raster distortion corrections are made separately
and sequentially ror each o-~ the CRTs la, lb, and lc. As in
~ocus ad,justment, the pat-terns 14 as shown in Fig. 3 are
beamed onto the photodetectors ~. Based on -the outputs o:t'
the photodeteotors ~1 the microcompu-ter 6 detects how much
the projected images on the photode-tectors ~ are deviated
from the required proper position, and controls the gain o~
a raster dis-tortion correc-ting circui-t 9 -to correct the
deviations. The raster distortion correcting circui-t 9
outputs a raster distortion correction signal to any CRTs
la, lb, or lc on which ras-ter dis-tortion has been detec-ted.
.
Raster distortiorl i.s -thus correcl;ed.
It will be :recognized tha-t automatic raster correc-tion
can be appl;.ed not only to three--tube sys-tems but also to
one-tube systems and -that raster correc-t:ion carl be made
along with foc~ls adjustmen-t.
In the firs-t to t,he ~ourth ernbodiments, patterns 1~ of
cross sh~pe are used, but i-t wil]. be appreciated that -t;he
shape of the pa-ttern may be o~` spo-t or s-traight line.
In the case of a p:rojection type display apparatus
using a mul-tiple CRTs, the configura-tions o-f the second and
third embodiments may be combined to produce a system where-
in both the focus and convergence adjustments are au-tomati-
cally made wi-th the microcomputer 6 con-trolling the focus
adjusting circuit 7 and the convergence adjusting circuit 8.
Furthermore, the configuration of -the -fourth embodiment may
also be incorporated -to add -the raster dis-tor-tion correc-tion
function.
(Embodiment 5)
The fifth embodiment o-f -the invention hereinaf-ter
described concerns a projection -type display appara-tus
wherein whi-te balance and cutoff characteristics are auto-
ma-tically adjusted. The ou-tline of the cons-truc-tion of the
apparatus is the same as that shown in Fig. 6.
Fig. 7 shows the condi-tion of an image formed on the
1~
~3~
phosphor screen 10 of each of the CRTs la, lb, and Ic. An
area 13 on the phosphor screen, which is projected on-to the
screen 3, is smaller than an image area 12, -the ima~e area
actually formed by raster scanning on the phosphor screen
10. Therefore, some part of the area scanned by an electron
beam on the phosphor screen lO does not appear on the screen
3.
In this marginal area, cutoff/white balance adjus-ting
patterns 15 (hereinafter referred to as the pat-terns 15) are
formed at the same positions as the patterns 1~ of Fig. 3
by using, for example, a charac-ter generator. Each pa-t-tern
15 consists of two vertical lines, for example, a black line
and a color line of one of the three primary colors (for
example, red for the CRT la, blue for the CRT lb, and green
for the CRT lc). A total of four patterns 15 are formed on
the phosphor screen 10 of each of the CRTs la, lb, and lc.
Fig. 8 is a diagram showing the screen 3 viewed from
the projecting side. Four pho-todetectors ~ are moun-ted on
the screen frame 31 in positions and in number corresponding
~o -the pat-terns 15 shown in Fig. 7.
~ ig. 9 shows a feedback system for the projection
display apparatus according to the fifth embodiment. In
Fig. 9, the same parts as those shown in Figs. 5 and 6
are designated by the same numerals. The microcompu-ter 6
compu-tes the amount of con-trol, based on -the outputs of the
pho-tocletectors ~I, to op-timize the cutoff and white balance
charac-teristics. '['he numeral 16 designates a cutof'f' adjust-
ing circuit for outputl;ing cu-toff signa:Ls respec-tively to
adjust the cu-to-ff cha-racteristics of the CRTs la, Ib, and Ic
under -the control o:f the microcompu-ter 6, and the numeral 'L7
shows a white balance adjusting circu:it, also unde:r the
control of the m:icrocomputer G, ~or ou-tputtin~ wh:ite balance
adjus-ting s:ignals respectivel.y -to adjust the white ba]ance
character:istics of the CRTs la, Ib, ancl lc.
The pat-terns 15 formed on the CRT la are beamed through
-the projection lens 2a and projec-ted in the fortn o-f projec-
tion ligh-t llOa on-to the photodetec-tors ~. The patterns 15
-formed on the'CRTs lb and lc are also projected on the
photodetec-tors ~ in the same manner. The projected images
of the pat-terns 15 from -the respective CRTs la, lb, and lc
are superimposed one on top of another on each photodetec-tor
~; -these superimposed images are combined -to form an image
of black and whi-te vertical lines when cutoff and white
balance are proPerly adjusted.
Based on -the outputs of the pho-tode-tectors ~ on which
the projected images of -the patterns 15 are superimposed as
described above, the microcomputer 6 recognizes informa-tion
about cutoff and white balance deviations -from -the proper
values, and con-trols -the cu-toff adjusting circui-t 16 and -the
white balance adjusting circuit 17 so as to correc-t -the
1~
3 ~ '~
deviations, i.e. so tha-t the projected pa-t-terns on each
pho-todetector ~ I`orm an image of blaclc and white lines.
Under -the cont.rol of the miclocompllte:r 6; the correc-
-tion vol-tages applied to the cutoff adjus-ting circuit :16 and
the white balance adjusting circuit 17 are ~ar:ied. Accord-
ingly, the cu-toff adjust:ing circuit 16 outputs cu-to-rf ad-
jUSti.llg s:ignals to the CRTs .La, Ib, and lc to op-tim:ize thei.-r
cu-toff charncteristics, and the white balance adjus-ting
circui-t 17 ou-tputs white balance adjusting signa~s -to the
CRTs la, lb, and lc to optimize their white balance charac-
teris-tics. With such a feedback loop, the correction volt-
ages are se-t. 60 as to optimize -the respect;ive values.
In -the i.llus-tra-ted example, four patterns 15 are used,
but it will be appreciated -that a single pat-tern may serve
the purpose. Also, each pa-ttern 15 has two vertical lines,
bu-t o-ther appropria-te forms may be used. Further, the
number o:f pat-terns 15 per CRT is made equal -to -the number of
photodetectors, but the photodetectors may be made ~ewer i~
number than the patterns L5.
(Embodiment 6)
Fig. 10 is a schematic sectional view of a reflec-
tion-type projection display apparatus which projects a CRT
image onto a projection screen by using a reflec-tion mirror.
A mirror 18 is mounted in -the path of the projection ligh-t
6 ~ ~
1l0 to reflec-t the proJection l:ight llO. Otherwise, -the
construction is the same as -that of the direct pl~ojec-tion
type display apparatus; the same parts as those in ~i~s. 2
and 6 are designated by the same numerals, and description
of such parts ls omitted herein. I-t wiL1 be appreclated
that each of the above embodiments can also be applied to
the reflection--type projection display ap-paratus of Fig.
10, in which case the same erfects as described above can
also be obtained.
In each of the above embodimen-ts, the photodetectors
are ins-talled outside -the ef~ective image area of -the pro-
jection screen, bu-t i-t will be apprecia-ted -that the same
effec-ts as described in each of the above embodimen-ts can be
obtained if the photodetectors are installed inside -the
effective image area of the projection screen, for example,
on the periphery of -the screen.
Any of the above-described projection type display
apparatuses do no-t require special CRT adjustments in the
manufac-turing process) and the adjus-tments are automatically
made any time after -the apparatus is ins-talled in place.
As described above, according to the projection type
display apparatus of the invention, adjusting pa-tterns are
formed on the CRT screen, and -the projected images of these
pa-tterns are detected by pho-tode-tectors, based on the out-
puts of which -the CRT characteris-tics are adjusted. This
16
~6~3
enables foclls:irlg or ot,her charact:,eri.sti.c,s such as cutoff and
white balance to be adjustecl autolllatica:LIy, the effect be:ing
tha-t the per-formance o~ the projection apparatus is not
a~fec-ted by environmental conditions or de-teriorat:ion with
time .
As -thi.s invention may be emboclied in seve:ral :f`orllls
withollt cleparting ~rom -the spirit of essential characteris-
tics thereof, the presen-t embodimen-t is -therefore i.l.lustra-
tive and not restrictive, since the scope of the :inven-t.ion
is defined by the appended claims ra-ther -than by tlle de-
scription preceding -them, and all changes that fall within
metes and bounds of -the claims, or equivalence of sllch metes
and bounds thereof are therefore in-tended to be embraced by
the claims.
