CA1099547A - Video image projection apparatus - Google Patents
Video image projection apparatusInfo
- Publication number
- CA1099547A CA1099547A CA302,615A CA302615A CA1099547A CA 1099547 A CA1099547 A CA 1099547A CA 302615 A CA302615 A CA 302615A CA 1099547 A CA1099547 A CA 1099547A
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- Canada
- Prior art keywords
- screen
- image
- lenses
- cathode ray
- intercepting
- Prior art date
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/12—Picture reproducers
- H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
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- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Video Image Reproduction Devices For Color Tv Systems (AREA)
- Transforming Electric Information Into Light Information (AREA)
- Projection Apparatus (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A projecting apparatus provides at least two video sources and two lenses. Video images by the video sources are projected through the respective lenses, and are compounded on a screen. The principal axes of the two lenses are parallel with each other, and moreover to the normal of the screen in the horizontal direction or in the vertical direction, the normal passing through the center of the screen. Further, each of principal axes of respective lenses is deflected from the normal of the screen in the horizontal direction or the vertical direction of the screen. Furthermore, two video sources are deflected from respective principal axes of two lenses to compound respective video images coincidentally on the screen. By further providing a intercepting plate or two intercepting plates respective to lenses, the distributions of the brightness or each projected reflection are substantially uniform in the horizontal direction or the vertical direction of the screen.
A projecting apparatus provides at least two video sources and two lenses. Video images by the video sources are projected through the respective lenses, and are compounded on a screen. The principal axes of the two lenses are parallel with each other, and moreover to the normal of the screen in the horizontal direction or in the vertical direction, the normal passing through the center of the screen. Further, each of principal axes of respective lenses is deflected from the normal of the screen in the horizontal direction or the vertical direction of the screen. Furthermore, two video sources are deflected from respective principal axes of two lenses to compound respective video images coincidentally on the screen. By further providing a intercepting plate or two intercepting plates respective to lenses, the distributions of the brightness or each projected reflection are substantially uniform in the horizontal direction or the vertical direction of the screen.
Description
Field of the lnvention This invention relates to a projecting apparatus wherein video images by at least two video sources are projected through respective focusing means and are co~pounced on a scre~n.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 ~ Fig. 3 relate to a conventional color video projector.
Fig. 1 is a plan view of the conventional color video projector.
Fig. 2 is a perspective view of the video projector showing the arrangement of the three vi~eo sources or the ca.hode _ay tubes and two lenses.
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Fig. 3A and Fig. 3B are the front views of the projected red image and the green image on the screen respectively.
Fig. 4 ~ Fig. 16 relate to video projectors according to this invention.
Fig. 4 is a plan view of a color video projector according tc the first embodiment of this invention.
Fig. S is a perspective view of the color video projector of the irst e~odiment showing the arrangement of the video sources or three cathode ray tubes and two lenses.
Fig. 6A and Fig. 6B are the front views of the projected red image and the green image on the screen, respectively.
Fig. 7 is a front view of the compounded image, when the central axes of the cathode ray tubes 11 and 12 are not deflected from the principal axes of the lenses 16 and 17 respectively.
' Fig-8 is a sidevie~l ofa modified color video projector, ¦ 20 wherein the video sources are arranged in front of the screen~
but under the normal of the screen.
Fig. 9A and Fig. 9B are the front views of the red projected image and the green projected image according to the projector shwon in Fig. 8.
~` 25 Fig. 10 is a graph which shows the distri~utions of the brightness of the red projected image and the green projected image along the width o the screen.
Fig. 11 is a plan view of a video projector which is the second embodiment of this invention.
Fig. 12 is a graph which shows the distributions ~q~9~S47 briahtness of the of ~ ~ected image and the green projected image along the width of the screen according to the projector shown in Fig. 11.
~ ig. 13 is a plan view o~ a video projector according to the third embodiment of this invention.
~ Fig. 14 is a side view of the video projector shown in Fig. 13.
Fig. 15A, Fig. 15B and Fig. 15C are the front views of the projected red image, green image and-blue image respectively, according to an apparatus in which three lenses and respective three cathode ray tubes are arranged in the conventional manner.
Fig. 16A, Fig. 16B and Fig. 16C are the front views of the projected red image, green image and blue image respectively, according to the apparatus shown in Fig. 13 and Fig. 14.
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Description of the Prior Art A so called color video projector is provided with three cathode ray tubes, each of which forms red video image, green video image and blue video image as video sources.
These images are projected through the respective focusing means or lenses and are ~ounded and mixed on a screen.
A conventional color video projector is arranged as shown in Fig. 1 and Fig. 2. That is, a cathode ray tube 1 for red image and a cathode ray tube 2 for green image are faced on a screen 4. On the other hand, a cathode ray tube 3 for blue image is arranged in such a manner that the axis of the tube 3 is vertical. The light beam of the red video image by the tube 1 is transmitted through a half mirror 5 and is refracted by the lens 6. Whereby the red video source is imaged on the screen 4 The light beam of the green video source by the tube 2 is refracted by the lens 7 .
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and imaged on the screen 4. Further, the light beam of the blue video source by the tube 3 is reflected by the half mirror S and is refracted by the lens 6, whereby the blue video source is also imaged on the screen 4. Accordingly projected three images are c ~ ounded and mixed on the screen, and hence a color image is formed.
In this apparatus, the principal axis 8 of the lens 6 and the principal axis 9 of the lens 7 intersect with the normal 10 of the screen 4 at the center of the screen 4 with the angle " w", as shown in Fig. 1. Further, the principal axis 8 of the lens 6 and the principal axis 9 of the lens 7 are symmetrical each other relative to the normal 1 of the screen 4. Accordingly, the red image on the screen 4 is deformed in the shape of trapezoid, as shown in Fig A 3~. Cn the other hand, the green image on the screen is deformed as shown in Fig. 3B. The blue image on the screen 4 is deformed as shown in Fig. ~ because the blue video source is projected through the lens 6. The trape70id shown in Fig. 3A and the trape~oid shown in Fig. 3B are symmetrical to each other relative to the vertical center line of the screen 4.
When these projected images are compounded to form a compounded or composite color image, the respective images do not coincide with each other speciall~ in the both side of the screen 4. That is, the red image and the green image do not coincide each other, and the blue image and the green image do not coincide, although the red image and the bule image are coincident with each other.
To rectify this problem, the conventional cathode ray tubes 1, 2 and 3 of the video projector are provided with correcting means which form the reversely deformed video sources to cancell the projected optical deformations.
These three deformed video sources are projected on the screen 4, and a-compounded color image is formed on the _4_ .~ ~ ~
s~7 screen 4. But by this method, the cathode ray tube becomes e~pensive because of the correcting means, and further it is not easy to form the reversely deformed reflection taking account of the optical deformation.
O ECTS AND SU~RY OF THE INVENTION
One of the objects of this invention i5 to provide improved means for compounding projected plural images on a screen fronl respective video sources without any preliminary correction.
Other object of this invention is to compound projected plural images on a screen from respective video sources in such a manner that the distribution of the lightness of each projected images is uniform along the width of the screen.
The structure of this invention includes at least a pair of focusing means or lenses, each of which projects the respective images by a video source on a screen. The principal axes of the levses are parallel to the normal of the screen which is passing through the center of the screen, and the principal axes of the lenses are deflected relative to said normal in the horizontal direction or in the vertical direction of the screen. Further, the video sources are deflected relative to the respective principal axes of the lenses. Whereby, the projected plural images ~ are compounded on the screen without any discrepancy.
¦ Unequality between the distributions of the ¦ brightness of the image projected by the first lens and that of the second lens owing to the deflections of the first and ¦ second lenses relative to the central normal of the screen j 30 can be rectified by a intercepting plate which intercepts partly before the light beams and refracted by the first lens and the second lens in both ends, respectively. Alter-natively, a plural intercepting plates can be used to intercept partly the light beam reflected by the respective lenses~
, ~ -5-More particularly, there is provided:
A projecting apparatus for projecting a compound image onto a screen; comprlsing a plurality of image souxces each providing a respective plane image with each o~ the image sources having a central axis normal to the plane of the image thereof; plural focusing means for projecting said images in respective optical paths onto said screen to ~orm said compound image, said focusing means having respective principal axes which are arranged substantially parallel to one another, at lD least one of said focusing means being arranged with the princi-pal axis thereof epaxially displaced with respect to the central axis of a respective one of said plurality of image sources so that the projected images are made to coincide with each other on said screen; and intercepting means interposed in at least one of said optical paths between said image sources and said screen to intercept a portion of the light emitted by at least one of said image sources so as to compensate for unevenness of distribution of brightness in the projected images.
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The above, and other objects, features and advantages - 20 of this invention will be apparant from the following detailed description of illustrative embodiment thereof which is to ~e~ ccor~n-e ~ o~ 4r~ s.
S~7 DETAILED DESCRIPTION OE' PREFERRED EMBODIMENT
Now below, it will be described color video projectors which are the embodiments of this invention, with reference to the drawings.
S Fig 4 and Fig.5 show the first embodiment of this invention~ According to this embodiment, a cathode ray tube 11 which forms the red Yideo images and a cathode ray tube 12 Which forms the green video images are arranged in such a manner that the front rurfaces of the tubes 11 and 12 are faced on a screen 14 whereon the projected images are mixed or compounded, On the other hand, the cathode ray tube 13 which forms the blue video image is arranged in such a manner that the axis oE the tube 13 is vertical. The light beam of the red image by the tube ~1 is transmitted through a half mirror 15 and is refracted by the lens 16. Whereby the image of the red video source is projected on the screen 14, The light beam of the green image by the tube 12 is refracted by the lens 17 and is projected on the screen 14. Further-/
the li~ht beam of the blue image by the tube 13 is reflected by the half mirror 15 and is refracted by the lens 16, whereby the image o~ the blue ~ideo source is projected on the screen 14, ~ccordingly, projected three color images are mixed and compounded on the screen 14 and hence a color imaye is formed.
Further, according to this apparatus, the principal axis 18 of the lens 16 and the principal axis 19 of the lens 17 are parallel to a normal 20 of the screen 14, the normal 20 passing through the center of the screen 14. Furthermore, the principal axis 18 and the principal axis 19 are symmet-rical each other relative to the normal 20, and the axis 18 and 19 are deflected from the normal 20 by predetermined ~9547 distance "d" respectively.
By this arrangement, the projected images are prevented from trapezoidal deforming at least in the vertical direction of the screen 14, because the principal axes 18 and 19 of the lenses 16 and 17 are parallel to the normal 20. That is, the projected image 21 by the red video source and the projected image by the blue video sourcd are developed in -the shape of rectangle as shown in Fig 6A, and the projected image 22 by the green video source are developed also in the shape of rectangle as shwon in Fig.6B, so far as the lenses 16 and 17 are arranged in such a manner that the principal axes 18 and 19 are horizontal. Therefore, the respective images coincide with each other in the vertical direction of the screen 14, when the projected images are compounded and mixed on the screen to form a mixed~color image. Thereby the mixed color image is prevented from color shifting in the vertical direction of the screen 14.
But, in fact, the projected red image 21 and the projected green image 22 do not coincide with each other by the distance "2d" in the horizontal direction on the screen as shown in Fig.7, because the principal axis 18 of the lens 16 is separated from the principal axis 19 of the lens 17 by "2d". That is, the horizontal shift between the red image 21 and the green image 22 occurs on the screen 1~.
In this case, the blue projected image is coincident with the red projected image 21 on the screen~
To rectify the above mentioned horizontal shift,the cathode ray tubes 11,12 and 13 are deflected from respective lenses 16 and 17 in this apparatus. That is, the central axes 23 and 2~ of the cathode ray tubes11 and 12 are parallel with and are deflected outside from the principal axes 18 and 19 of the lenses 16 and 17 respecti~ely by the distance "e" as shown in Fig.4. The central axis o:E the cathode ray tube 13 is also deflected rightside form the principal axis 18 of the lens 16 by the distance "e", whereby the central light beam of the blue image by the cathode ray tube 13 coincides with the central light beam of the red image when the blue light beam is reflected by the half mirror 15~
As discribed above, in this apparatus, the vartical shift between the plural projected images is rectified by the deflected arrangement of the lenses 16 and 17 relative to the normal 20, and the horizontal shift between the plural projected images lS rectified by the deflected arrangement of the cathode ray tubes 11, 12 and 13 relative to the principal axes of the lenses 16 and 17 respectively. Whereby the red, green and blue images are mixed and compounded on the screen 14 without any deformation or shifting of colors in the vertical direction and horizontal direction~
The light beams emitted from the center of the front surfaces of the cathode ray tubes 11, 12 and 13 must be focused on the center of the screen 14 by the lenses 16 and 17, Especially, the light beams which are emitted at the center of the front surfaces of the tubes 11, 12 and 13 and passing through the center of the lenses 16 and 17 must be landed on the center of the screen 14 without beiny refracted by the lenses 16 and 17. Therefore, -the ralation between ~a~ and "e" is given by the following equation:
e a (1) Where,"a"is the distance between the front surfaces of the cathode ray tubes 11, 12 and 13 and the lenses 16 and 17, i47 and"b"is the distance between the lenses 16 and 17 and the surface of the screen 14 as shwon in Fig.~. Further, as well known, the relation between "a" and "b" is given by the following equation:
1 ~ 1 = 1 (2) Where,"f"is a focal length of the lenses 16 and 17.
Accordingly the relation between "d" and "e" is also given by following equations:
d b - f or e = a - f (~) The ahove description relates to the apparatus in which the principal axes 18 and 19 of the lenses 16 and 17 are parallel to the normal 20 of the screen 14 both in the vertical direction and in horizontal direction. But this invention may be applied to an apparatus in which the principal axes 18 and 19 of the lenses 16 and 17 are parallel to the normal 20 of the screen 14 at least in the vertical direction~or in horizontal direction. For example, such a modification can be obtained as shwon in Fig.8. That is, the lenses 16 and 17 are arranged in such a manner that the principal axes 18 and 19 of the lenses 16 and 17 intersects with the normal 20 of the screen 14 b~ the angle "~" in the vertical direction or on viewing from the side of the apparatus. According to this apparatus, the projected red image 21 and the pro~ected green image 22 are not rectangular but are trapezoid as shown in Fig.9A and Fig.9B, respectively, which show the deformations in the horizontal direction.
But as these two trapezoids are congruent with each other, ~10-the color slipping never occurs, even if these trapezoid images are compounded. Accordingly, it is no use to correct the images preliminarily when the crossing angle " a" oE -the principal axes 18 and 19 and the normal 20 is small.
Alternatively, the cathode ray tubes 11, 12 and 13 may be provided with correcting means to correct the video sources preliminaril~ taking account of the optical deforma-tions, whereby the rectangular compounded images are displa~ed on the screen.
Next, it will be described the second embodiment of this invention, As described above, the first embodiment shown in Fig.4 rectifies the vertical optical deformation o~
the compounded images by arranging the lenses 16 and 17 in such a manner that the principal axes 18 and 19 of the lenses 16 and 17 are parallel to and deflected from the normal 20 of the screen 14. Further, the first embodiment rectifies the horizontal shift between plural images by arranging the cathode ray tubes 11, 12 and 13 in such a manner that the central axes of the tubes are deflected from the principal axes 18 and 19 of the lenses 16 and 17. ~ccording to this arrangement, the dislributions of the brightress of plural images along the with of the screen 14 are asymmetrical relative to the center of the screen 14, because the principal axes 18 and 19 are deflected from the normal 20 of the screen 14.
That is, the distributions of the brightness of the red image and the blue image projected by the lens 16 are sho~7n in the curve-line 25 in Fig.10. The distribution of the brightness of the green image projected by the :Lens 17 is shown in the curve-line 26 in Fig.10. In Fig.10, "L" is the ~9~
width of the screen 14. ThereEore, the red color and the blue color are emphasized on the right side of the screen 14, and the blue color is emphasized on the left side of the screen 14. Accordingly, the color tone varies along the width of the screen 14, and it is difficult to obtain the uniformity of the color tone all over the screen 14.
To overcome this problems, an lntercepting plate 27 is provided in front of the lenses 16 and 17 as shown in Fig. 11 . The plate 27 intercepts the ligh-t beams from the red video sources and the blue video sources partly with the right ride of the plate 27 and also intercepts the light beams from the blue video sources partly with the left side of the plate 27. According to this arrangement, the dis-tributions of the brightness of the red image and the blue image along the width of the screen 14 are almost symmetrical relative to the center of the screen 14, as shown in curve-line 28 in Fig.12, Further~ the distribution of the brightness of the green image along the width of the screen 1~ is also almost symmetrical relative to the center of the screen 14, as shown in curve-line 29 in Fig.12~ Therefore, the uniform color tone is obtained all over the screen 1 a, when the red image, green image and the blue image are com~ounuedon the screen through thé apparatus shwon in Fig.11.
Alternatively~ a pair of intercepting plates 30 arranged between the lenses 16 and 17 and the screen 14, may be used to intercept the light beams, as shown by the dot-dash line in Fig.11. In this modification, the right inter-cepting plate 30 intercepts the red light beam and blue light beam partly, and the left intercepting plate 30 intercept the green light beam partly.
~12-Next, it will be described the third embodiment of this invention with reference to Fig.13 and Fig.14. In this embodiment, the hal~ mirror is not used, and the red video source, the green video source and the blue video source, formed on the front surfaces of the cathode ray tubes 31, 32 and 33 respectively, are projected on the screen 37 through the respective lenses 34, 35 and 36. The cathode ray tubes 31, 32 and 33 are arranged in such a manner that they are at the three vertexes of a isosceles triangle respectively.
That is, in plan view, the central axis of the cathode ray tube 32 coincides with a normal which is passing through the center of the screen 37, and the cathode ray tubes 31 and 33 are deflected from the tube 32 right and left in Fig.13.
Further, in side view, the central axises of the cathode ray tubes 31 and 33 concide with the central normal of the screen 37, and the cathode ray tube 32 is deflected from the tube 31 and 32 dounward, as shown in Fig.14.
In this apparatus, when the lenses 34, 35 and 36 and the cathode ray tubes 31, 32 and 33 are arranged in such a manner thàt the principal axes of the lenses 34,35 and 36 and the central axes of the cathode ray tubes 31, 32 and 33 are passing through the center of the screen 37, in the same manner as conventional video projector, the projected red - image, green image and blue images are in such shapes as shwon in Fig.15A, Fig.15B and Fig.15C. When these three images are compounded on the screen 37, the color shif-ting wi.ll occur both in the vertical and in the horizontal direction.
Hence, in the horizontal direction, the lenses 34 and 36 are arranged in such a manner that the principal axes of the lenses 34 and 36 are parallel to the central normal of the screen 37, and are diflected from the normal by the distance "d".~ Further the cathode ray tubes 31 and 33 are arranged in such a manner that the central axes of the tubes 31 and 33 are deflected from the respective principle axes of the lenses 34 and 36 by the distance "e" as shown in Fig.
13. In the vertical direction, the lens 35 is arranged in such a manner that the principal axis of the lens 35 is parallel to the central normal of the screen 37 and is diflect- .
ed from the normal by the distance "d"'. Further, the cathode ray tube 32 is arranged in such a manner that the central axis of the tube 32 is deflected from the principle axis of the lens 35 by the distance "e"', as shown in Fig.14.
Accordingly, the projected red image, green image and blue image are all rectangular and are congruent with ~5 each other as shown in Fig.16A, Fig.16B and Fig.16C. The compounded image of the three images on the screen are prevented from color shifting both in the vertical cirection and in the horizontal direction of the screen. Further, the three immages are compouned with complete coincidence.
While this invention is illuslrated with specific embodiments, it will be recognized by those skilled in the art that modifications may be made therein without departing from the true scope of the invention as defined by the followlng claims, ~14-
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 ~ Fig. 3 relate to a conventional color video projector.
Fig. 1 is a plan view of the conventional color video projector.
Fig. 2 is a perspective view of the video projector showing the arrangement of the three vi~eo sources or the ca.hode _ay tubes and two lenses.
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Fig. 3A and Fig. 3B are the front views of the projected red image and the green image on the screen respectively.
Fig. 4 ~ Fig. 16 relate to video projectors according to this invention.
Fig. 4 is a plan view of a color video projector according tc the first embodiment of this invention.
Fig. S is a perspective view of the color video projector of the irst e~odiment showing the arrangement of the video sources or three cathode ray tubes and two lenses.
Fig. 6A and Fig. 6B are the front views of the projected red image and the green image on the screen, respectively.
Fig. 7 is a front view of the compounded image, when the central axes of the cathode ray tubes 11 and 12 are not deflected from the principal axes of the lenses 16 and 17 respectively.
' Fig-8 is a sidevie~l ofa modified color video projector, ¦ 20 wherein the video sources are arranged in front of the screen~
but under the normal of the screen.
Fig. 9A and Fig. 9B are the front views of the red projected image and the green projected image according to the projector shwon in Fig. 8.
~` 25 Fig. 10 is a graph which shows the distri~utions of the brightness of the red projected image and the green projected image along the width o the screen.
Fig. 11 is a plan view of a video projector which is the second embodiment of this invention.
Fig. 12 is a graph which shows the distributions ~q~9~S47 briahtness of the of ~ ~ected image and the green projected image along the width of the screen according to the projector shown in Fig. 11.
~ ig. 13 is a plan view o~ a video projector according to the third embodiment of this invention.
~ Fig. 14 is a side view of the video projector shown in Fig. 13.
Fig. 15A, Fig. 15B and Fig. 15C are the front views of the projected red image, green image and-blue image respectively, according to an apparatus in which three lenses and respective three cathode ray tubes are arranged in the conventional manner.
Fig. 16A, Fig. 16B and Fig. 16C are the front views of the projected red image, green image and blue image respectively, according to the apparatus shown in Fig. 13 and Fig. 14.
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Description of the Prior Art A so called color video projector is provided with three cathode ray tubes, each of which forms red video image, green video image and blue video image as video sources.
These images are projected through the respective focusing means or lenses and are ~ounded and mixed on a screen.
A conventional color video projector is arranged as shown in Fig. 1 and Fig. 2. That is, a cathode ray tube 1 for red image and a cathode ray tube 2 for green image are faced on a screen 4. On the other hand, a cathode ray tube 3 for blue image is arranged in such a manner that the axis of the tube 3 is vertical. The light beam of the red video image by the tube 1 is transmitted through a half mirror 5 and is refracted by the lens 6. Whereby the red video source is imaged on the screen 4 The light beam of the green video source by the tube 2 is refracted by the lens 7 .
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and imaged on the screen 4. Further, the light beam of the blue video source by the tube 3 is reflected by the half mirror S and is refracted by the lens 6, whereby the blue video source is also imaged on the screen 4. Accordingly projected three images are c ~ ounded and mixed on the screen, and hence a color image is formed.
In this apparatus, the principal axis 8 of the lens 6 and the principal axis 9 of the lens 7 intersect with the normal 10 of the screen 4 at the center of the screen 4 with the angle " w", as shown in Fig. 1. Further, the principal axis 8 of the lens 6 and the principal axis 9 of the lens 7 are symmetrical each other relative to the normal 1 of the screen 4. Accordingly, the red image on the screen 4 is deformed in the shape of trapezoid, as shown in Fig A 3~. Cn the other hand, the green image on the screen is deformed as shown in Fig. 3B. The blue image on the screen 4 is deformed as shown in Fig. ~ because the blue video source is projected through the lens 6. The trape70id shown in Fig. 3A and the trape~oid shown in Fig. 3B are symmetrical to each other relative to the vertical center line of the screen 4.
When these projected images are compounded to form a compounded or composite color image, the respective images do not coincide with each other speciall~ in the both side of the screen 4. That is, the red image and the green image do not coincide each other, and the blue image and the green image do not coincide, although the red image and the bule image are coincident with each other.
To rectify this problem, the conventional cathode ray tubes 1, 2 and 3 of the video projector are provided with correcting means which form the reversely deformed video sources to cancell the projected optical deformations.
These three deformed video sources are projected on the screen 4, and a-compounded color image is formed on the _4_ .~ ~ ~
s~7 screen 4. But by this method, the cathode ray tube becomes e~pensive because of the correcting means, and further it is not easy to form the reversely deformed reflection taking account of the optical deformation.
O ECTS AND SU~RY OF THE INVENTION
One of the objects of this invention i5 to provide improved means for compounding projected plural images on a screen fronl respective video sources without any preliminary correction.
Other object of this invention is to compound projected plural images on a screen from respective video sources in such a manner that the distribution of the lightness of each projected images is uniform along the width of the screen.
The structure of this invention includes at least a pair of focusing means or lenses, each of which projects the respective images by a video source on a screen. The principal axes of the levses are parallel to the normal of the screen which is passing through the center of the screen, and the principal axes of the lenses are deflected relative to said normal in the horizontal direction or in the vertical direction of the screen. Further, the video sources are deflected relative to the respective principal axes of the lenses. Whereby, the projected plural images ~ are compounded on the screen without any discrepancy.
¦ Unequality between the distributions of the ¦ brightness of the image projected by the first lens and that of the second lens owing to the deflections of the first and ¦ second lenses relative to the central normal of the screen j 30 can be rectified by a intercepting plate which intercepts partly before the light beams and refracted by the first lens and the second lens in both ends, respectively. Alter-natively, a plural intercepting plates can be used to intercept partly the light beam reflected by the respective lenses~
, ~ -5-More particularly, there is provided:
A projecting apparatus for projecting a compound image onto a screen; comprlsing a plurality of image souxces each providing a respective plane image with each o~ the image sources having a central axis normal to the plane of the image thereof; plural focusing means for projecting said images in respective optical paths onto said screen to ~orm said compound image, said focusing means having respective principal axes which are arranged substantially parallel to one another, at lD least one of said focusing means being arranged with the princi-pal axis thereof epaxially displaced with respect to the central axis of a respective one of said plurality of image sources so that the projected images are made to coincide with each other on said screen; and intercepting means interposed in at least one of said optical paths between said image sources and said screen to intercept a portion of the light emitted by at least one of said image sources so as to compensate for unevenness of distribution of brightness in the projected images.
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The above, and other objects, features and advantages - 20 of this invention will be apparant from the following detailed description of illustrative embodiment thereof which is to ~e~ ccor~n-e ~ o~ 4r~ s.
S~7 DETAILED DESCRIPTION OE' PREFERRED EMBODIMENT
Now below, it will be described color video projectors which are the embodiments of this invention, with reference to the drawings.
S Fig 4 and Fig.5 show the first embodiment of this invention~ According to this embodiment, a cathode ray tube 11 which forms the red Yideo images and a cathode ray tube 12 Which forms the green video images are arranged in such a manner that the front rurfaces of the tubes 11 and 12 are faced on a screen 14 whereon the projected images are mixed or compounded, On the other hand, the cathode ray tube 13 which forms the blue video image is arranged in such a manner that the axis oE the tube 13 is vertical. The light beam of the red image by the tube ~1 is transmitted through a half mirror 15 and is refracted by the lens 16. Whereby the image of the red video source is projected on the screen 14, The light beam of the green image by the tube 12 is refracted by the lens 17 and is projected on the screen 14. Further-/
the li~ht beam of the blue image by the tube 13 is reflected by the half mirror 15 and is refracted by the lens 16, whereby the image o~ the blue ~ideo source is projected on the screen 14, ~ccordingly, projected three color images are mixed and compounded on the screen 14 and hence a color imaye is formed.
Further, according to this apparatus, the principal axis 18 of the lens 16 and the principal axis 19 of the lens 17 are parallel to a normal 20 of the screen 14, the normal 20 passing through the center of the screen 14. Furthermore, the principal axis 18 and the principal axis 19 are symmet-rical each other relative to the normal 20, and the axis 18 and 19 are deflected from the normal 20 by predetermined ~9547 distance "d" respectively.
By this arrangement, the projected images are prevented from trapezoidal deforming at least in the vertical direction of the screen 14, because the principal axes 18 and 19 of the lenses 16 and 17 are parallel to the normal 20. That is, the projected image 21 by the red video source and the projected image by the blue video sourcd are developed in -the shape of rectangle as shown in Fig 6A, and the projected image 22 by the green video source are developed also in the shape of rectangle as shwon in Fig.6B, so far as the lenses 16 and 17 are arranged in such a manner that the principal axes 18 and 19 are horizontal. Therefore, the respective images coincide with each other in the vertical direction of the screen 14, when the projected images are compounded and mixed on the screen to form a mixed~color image. Thereby the mixed color image is prevented from color shifting in the vertical direction of the screen 14.
But, in fact, the projected red image 21 and the projected green image 22 do not coincide with each other by the distance "2d" in the horizontal direction on the screen as shown in Fig.7, because the principal axis 18 of the lens 16 is separated from the principal axis 19 of the lens 17 by "2d". That is, the horizontal shift between the red image 21 and the green image 22 occurs on the screen 1~.
In this case, the blue projected image is coincident with the red projected image 21 on the screen~
To rectify the above mentioned horizontal shift,the cathode ray tubes 11,12 and 13 are deflected from respective lenses 16 and 17 in this apparatus. That is, the central axes 23 and 2~ of the cathode ray tubes11 and 12 are parallel with and are deflected outside from the principal axes 18 and 19 of the lenses 16 and 17 respecti~ely by the distance "e" as shown in Fig.4. The central axis o:E the cathode ray tube 13 is also deflected rightside form the principal axis 18 of the lens 16 by the distance "e", whereby the central light beam of the blue image by the cathode ray tube 13 coincides with the central light beam of the red image when the blue light beam is reflected by the half mirror 15~
As discribed above, in this apparatus, the vartical shift between the plural projected images is rectified by the deflected arrangement of the lenses 16 and 17 relative to the normal 20, and the horizontal shift between the plural projected images lS rectified by the deflected arrangement of the cathode ray tubes 11, 12 and 13 relative to the principal axes of the lenses 16 and 17 respectively. Whereby the red, green and blue images are mixed and compounded on the screen 14 without any deformation or shifting of colors in the vertical direction and horizontal direction~
The light beams emitted from the center of the front surfaces of the cathode ray tubes 11, 12 and 13 must be focused on the center of the screen 14 by the lenses 16 and 17, Especially, the light beams which are emitted at the center of the front surfaces of the tubes 11, 12 and 13 and passing through the center of the lenses 16 and 17 must be landed on the center of the screen 14 without beiny refracted by the lenses 16 and 17. Therefore, -the ralation between ~a~ and "e" is given by the following equation:
e a (1) Where,"a"is the distance between the front surfaces of the cathode ray tubes 11, 12 and 13 and the lenses 16 and 17, i47 and"b"is the distance between the lenses 16 and 17 and the surface of the screen 14 as shwon in Fig.~. Further, as well known, the relation between "a" and "b" is given by the following equation:
1 ~ 1 = 1 (2) Where,"f"is a focal length of the lenses 16 and 17.
Accordingly the relation between "d" and "e" is also given by following equations:
d b - f or e = a - f (~) The ahove description relates to the apparatus in which the principal axes 18 and 19 of the lenses 16 and 17 are parallel to the normal 20 of the screen 14 both in the vertical direction and in horizontal direction. But this invention may be applied to an apparatus in which the principal axes 18 and 19 of the lenses 16 and 17 are parallel to the normal 20 of the screen 14 at least in the vertical direction~or in horizontal direction. For example, such a modification can be obtained as shwon in Fig.8. That is, the lenses 16 and 17 are arranged in such a manner that the principal axes 18 and 19 of the lenses 16 and 17 intersects with the normal 20 of the screen 14 b~ the angle "~" in the vertical direction or on viewing from the side of the apparatus. According to this apparatus, the projected red image 21 and the pro~ected green image 22 are not rectangular but are trapezoid as shown in Fig.9A and Fig.9B, respectively, which show the deformations in the horizontal direction.
But as these two trapezoids are congruent with each other, ~10-the color slipping never occurs, even if these trapezoid images are compounded. Accordingly, it is no use to correct the images preliminarily when the crossing angle " a" oE -the principal axes 18 and 19 and the normal 20 is small.
Alternatively, the cathode ray tubes 11, 12 and 13 may be provided with correcting means to correct the video sources preliminaril~ taking account of the optical deforma-tions, whereby the rectangular compounded images are displa~ed on the screen.
Next, it will be described the second embodiment of this invention, As described above, the first embodiment shown in Fig.4 rectifies the vertical optical deformation o~
the compounded images by arranging the lenses 16 and 17 in such a manner that the principal axes 18 and 19 of the lenses 16 and 17 are parallel to and deflected from the normal 20 of the screen 14. Further, the first embodiment rectifies the horizontal shift between plural images by arranging the cathode ray tubes 11, 12 and 13 in such a manner that the central axes of the tubes are deflected from the principal axes 18 and 19 of the lenses 16 and 17. ~ccording to this arrangement, the dislributions of the brightress of plural images along the with of the screen 14 are asymmetrical relative to the center of the screen 14, because the principal axes 18 and 19 are deflected from the normal 20 of the screen 14.
That is, the distributions of the brightness of the red image and the blue image projected by the lens 16 are sho~7n in the curve-line 25 in Fig.10. The distribution of the brightness of the green image projected by the :Lens 17 is shown in the curve-line 26 in Fig.10. In Fig.10, "L" is the ~9~
width of the screen 14. ThereEore, the red color and the blue color are emphasized on the right side of the screen 14, and the blue color is emphasized on the left side of the screen 14. Accordingly, the color tone varies along the width of the screen 14, and it is difficult to obtain the uniformity of the color tone all over the screen 14.
To overcome this problems, an lntercepting plate 27 is provided in front of the lenses 16 and 17 as shown in Fig. 11 . The plate 27 intercepts the ligh-t beams from the red video sources and the blue video sources partly with the right ride of the plate 27 and also intercepts the light beams from the blue video sources partly with the left side of the plate 27. According to this arrangement, the dis-tributions of the brightness of the red image and the blue image along the width of the screen 14 are almost symmetrical relative to the center of the screen 14, as shown in curve-line 28 in Fig.12, Further~ the distribution of the brightness of the green image along the width of the screen 1~ is also almost symmetrical relative to the center of the screen 14, as shown in curve-line 29 in Fig.12~ Therefore, the uniform color tone is obtained all over the screen 1 a, when the red image, green image and the blue image are com~ounuedon the screen through thé apparatus shwon in Fig.11.
Alternatively~ a pair of intercepting plates 30 arranged between the lenses 16 and 17 and the screen 14, may be used to intercept the light beams, as shown by the dot-dash line in Fig.11. In this modification, the right inter-cepting plate 30 intercepts the red light beam and blue light beam partly, and the left intercepting plate 30 intercept the green light beam partly.
~12-Next, it will be described the third embodiment of this invention with reference to Fig.13 and Fig.14. In this embodiment, the hal~ mirror is not used, and the red video source, the green video source and the blue video source, formed on the front surfaces of the cathode ray tubes 31, 32 and 33 respectively, are projected on the screen 37 through the respective lenses 34, 35 and 36. The cathode ray tubes 31, 32 and 33 are arranged in such a manner that they are at the three vertexes of a isosceles triangle respectively.
That is, in plan view, the central axis of the cathode ray tube 32 coincides with a normal which is passing through the center of the screen 37, and the cathode ray tubes 31 and 33 are deflected from the tube 32 right and left in Fig.13.
Further, in side view, the central axises of the cathode ray tubes 31 and 33 concide with the central normal of the screen 37, and the cathode ray tube 32 is deflected from the tube 31 and 32 dounward, as shown in Fig.14.
In this apparatus, when the lenses 34, 35 and 36 and the cathode ray tubes 31, 32 and 33 are arranged in such a manner thàt the principal axes of the lenses 34,35 and 36 and the central axes of the cathode ray tubes 31, 32 and 33 are passing through the center of the screen 37, in the same manner as conventional video projector, the projected red - image, green image and blue images are in such shapes as shwon in Fig.15A, Fig.15B and Fig.15C. When these three images are compounded on the screen 37, the color shif-ting wi.ll occur both in the vertical and in the horizontal direction.
Hence, in the horizontal direction, the lenses 34 and 36 are arranged in such a manner that the principal axes of the lenses 34 and 36 are parallel to the central normal of the screen 37, and are diflected from the normal by the distance "d".~ Further the cathode ray tubes 31 and 33 are arranged in such a manner that the central axes of the tubes 31 and 33 are deflected from the respective principle axes of the lenses 34 and 36 by the distance "e" as shown in Fig.
13. In the vertical direction, the lens 35 is arranged in such a manner that the principal axis of the lens 35 is parallel to the central normal of the screen 37 and is diflect- .
ed from the normal by the distance "d"'. Further, the cathode ray tube 32 is arranged in such a manner that the central axis of the tube 32 is deflected from the principle axis of the lens 35 by the distance "e"', as shown in Fig.14.
Accordingly, the projected red image, green image and blue image are all rectangular and are congruent with ~5 each other as shown in Fig.16A, Fig.16B and Fig.16C. The compounded image of the three images on the screen are prevented from color shifting both in the vertical cirection and in the horizontal direction of the screen. Further, the three immages are compouned with complete coincidence.
While this invention is illuslrated with specific embodiments, it will be recognized by those skilled in the art that modifications may be made therein without departing from the true scope of the invention as defined by the followlng claims, ~14-
Claims (10)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A projecting apparatus for projecting a compound image onto a screen; comprising a plurality of image sources each providing a respective plane image with each of the image sources having a central axis normal to the plane of the image thereof; plural focusing means for projecting said images in respective optical paths onto said screen to form said compound image, said focusing means having respective principal axes which are arranged substantially parallel to one another, at least one of said focusing means being arranged with the princi-pal axis thereof epaxially displaced with respect to the central axis of a respective one of said plurality of image sources so that the projected images are made to coincide with each other on said screen; and intercepting means interposed in at least one of said optical paths between said image sources and said screen to intercept a portion of the light emitted by at least one of said image sources so as to compensate for unevenness of distribution of brightness in the projected images.
2. A projecting apparatus according to claim 1; wherein each of said intercepting plates is of a substantially flat rectangular configuration, and is opaque.
3. A projecting apparatus according to claim 1; wherein said intercepting means includes plural intercepting plates, each arranged between a respective one of said focusing means and said screen, to intercept a portion of the light transmitted through said respective focusing means.
4. A projecting apparatus according to claim 1; wherein said intercepting means includes an intercepting plate interposed between at least one of said image sources and a respective one of said focusing means.
5. A projecting apparatus according to claim 1; wherein said plurality of image sources includes a plurality of cathode ray tubes forming respective color images of respective different primary colors, and said plurality of focusing means includes a plurality of projecting lenses for focusing respective color images on said screen whereon the color images are mixed and compounded.
6. A projecting apparatus according to claim 5; further comprising a half-reflecting mirror; and wherein said plurality of image sources includes first, second and third cathode ray tubes forming red, green and blue color images, respectively, and said plurality of projecting lenses includes two lenses, the image of the first cathode ray being transmitted through said half-reflecting mirror and through a first one of said lenses, the image of said second cathode ray tube being trans-mitted through a second one of said lenses, and the image of said third cathode ray tube being reflected by said half-reflect-ing mirror and transmitted through said first lens.
7. A projecting apparatus according to claim 6; wherein said principal axes of the first and second lenses are contained in a plane which is inclined, in the vertical direction, with respect to a line normal to the screen and passing through the center thereof, so as to intersect such line on the screen at a predetermined angle.
8. A projecting apparatus according to claim 6; wherein said intercepting means includes an intercepting plate disposed in the path between said cathode ray tubes and said projecting lenses so as to intercept a portion of the light emitted from said cathode ray tubes.
9. A projecting apparatus according to claim 5;
wherein said plurality of image sources includes first, second and third cathode ray tubes forming red, green and blue color images respectively, and arranged in a delta configuration, and said plurality of projecting lenses includes three lenses, respectively corresponding to said cathode ray tubes.
wherein said plurality of image sources includes first, second and third cathode ray tubes forming red, green and blue color images respectively, and arranged in a delta configuration, and said plurality of projecting lenses includes three lenses, respectively corresponding to said cathode ray tubes.
10. A projecting apparatus according to claim 9, wherein said intercepting means includes three intercepting plates, each plate being interposed between a respective cathode ray tube and its respective projecting lens for intercepting a portion of the light emanating from said respective cathode ray tube.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5288377A JPS53138326A (en) | 1977-05-09 | 1977-05-09 | Projector |
| JP52883/77 | 1977-05-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1099547A true CA1099547A (en) | 1981-04-21 |
Family
ID=12927269
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA302,615A Expired CA1099547A (en) | 1977-05-09 | 1978-05-04 | Video image projection apparatus |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS53138326A (en) |
| AU (1) | AU525507B2 (en) |
| CA (1) | CA1099547A (en) |
| DE (1) | DE2820175A1 (en) |
| FR (1) | FR2390870A1 (en) |
| GB (1) | GB1595610A (en) |
| NL (1) | NL7804924A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57162588A (en) * | 1981-03-30 | 1982-10-06 | Masaharu Nishiyama | Stereoscopic x-ray television device |
| JPS62160437A (en) * | 1986-01-08 | 1987-07-16 | Kawasaki Heavy Ind Ltd | Superposing method for projection image |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1235344A (en) * | 1968-12-10 | 1971-06-09 | Harries Electronic Corp | Improvements relating to optical correction systems |
| JPS604635B2 (en) * | 1975-03-12 | 1985-02-05 | ソニー株式会社 | color projector |
| JPS5271944A (en) * | 1975-12-11 | 1977-06-15 | Sanyo Electric Co Ltd | Projection-type color tv unit |
-
1977
- 1977-05-09 JP JP5288377A patent/JPS53138326A/en active Pending
-
1978
- 1978-05-02 AU AU35670/78A patent/AU525507B2/en not_active Expired
- 1978-05-03 GB GB1743978A patent/GB1595610A/en not_active Expired
- 1978-05-04 CA CA302,615A patent/CA1099547A/en not_active Expired
- 1978-05-08 NL NL7804924A patent/NL7804924A/en not_active Application Discontinuation
- 1978-05-09 DE DE19782820175 patent/DE2820175A1/en active Granted
- 1978-05-09 FR FR7813721A patent/FR2390870A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS53138326A (en) | 1978-12-02 |
| GB1595610A (en) | 1981-08-12 |
| FR2390870B1 (en) | 1983-11-18 |
| NL7804924A (en) | 1978-11-13 |
| DE2820175A1 (en) | 1978-11-23 |
| FR2390870A1 (en) | 1978-12-08 |
| AU3567078A (en) | 1979-11-08 |
| DE2820175C2 (en) | 1987-12-03 |
| AU525507B2 (en) | 1982-11-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |