CA1142376A - Method for correcting non-uniform illumination in oblique projection of slide transparencies - Google Patents
Method for correcting non-uniform illumination in oblique projection of slide transparenciesInfo
- Publication number
- CA1142376A CA1142376A CA000369698A CA369698A CA1142376A CA 1142376 A CA1142376 A CA 1142376A CA 000369698 A CA000369698 A CA 000369698A CA 369698 A CA369698 A CA 369698A CA 1142376 A CA1142376 A CA 1142376A
- Authority
- CA
- Canada
- Prior art keywords
- transparency
- light
- uniform illumination
- oblique projection
- slide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
ABSTRACT OF THE DISCLOSURE
Photography, particularly rear view projections systems.
The present method is directed towards correction of non-uniform illumination in oblique projection onto rear view screens. Traditionally, the oblique angle projection results in distortion known as the "Keystone effect" and in non-uniform illumination, namely that portion of the viewing screen nearest the lens receiving a greater portion of the light and that portion of the screen farthest from the lens receiving lesser light. The present method includes selective illumination of the slide transparency so as to direct more light through that portion of the image which is to be displayed farthest from the lens and less light upon that portion of the image which is to be displayed nearest the lens. As a result, there is achieved substantially uniform illumination of the obliquely projected image.
Photography, particularly rear view projections systems.
The present method is directed towards correction of non-uniform illumination in oblique projection onto rear view screens. Traditionally, the oblique angle projection results in distortion known as the "Keystone effect" and in non-uniform illumination, namely that portion of the viewing screen nearest the lens receiving a greater portion of the light and that portion of the screen farthest from the lens receiving lesser light. The present method includes selective illumination of the slide transparency so as to direct more light through that portion of the image which is to be displayed farthest from the lens and less light upon that portion of the image which is to be displayed nearest the lens. As a result, there is achieved substantially uniform illumination of the obliquely projected image.
Description
3'76 METHOD FOR CORRECTING NON-UNIFORM ILLUMINATION
IN OBL-[QUE PROJECTION OF SLIDE TRANSPARENCIES
CROSS REFERENCES TO RELATED APPLICATIONS:
Related to the co-pending METHOD OF MODIFYING SLIDE
TRANSPARENCIES SO AS TO PROVIDE UNIFORM ILLUMINATION IN ANGULAR
PROJECTION (Canadian Serial No. 369,699), filed January 30, 1981.
The present application is directed to a method for selectively illuminating the modified slide transparency so as to obtain uniform illumination of the image which is obliquely projected upon a viewing screen.
BACKGROUND OF THE INVENTION
Field of the Invention:
Photography, particularly the projection of images through a slide transparency and onto a viewing screen, which is obliquely moun-ted with respect to the optical path of projection.
Image distortions in oblique projection conven-tionally include the "Keystone effect" and non-uniform illumination. The "Key-stone effect" results in a trapezoid shaped projected image.
Non-uniform illumination results in a degrading of the pro-jected image quality, especially a lack of contrast and poor color rendition, since the por-tion of the obliquely supported viewing screen farthest from the projector receives less illumination and the portion nearest receives greater illumi-na-tion. These distortions will therefore create a projected ~5 image which is visually unattractive.
SUMMARY OF THE INVENTION:
In one broad aspect, the invention comprehends a method for correcting non-uniform illumination oblique projection of ~' ~L
':
- 1 - ~', 3'-~
slide transparencies which comprises supporting a slide trans-parency within a projection system, and selectively illumina-ting -the transparency such that a greater portion of light is pro-jected through the lower portion of the transparency and a lesser portion of light is projected -throug~ the upper portion of the transparency. The light projec-ted as an image is magnified through the transparency, and the image is displayed upon an angularly supported viewing screen, such -that the farthest portion of the viewing screen receives the greater portion of light and the nearest portion receives the lesser light.
In a further embodiment, the invention contemplates a method for correcting non-uniform illumination in oblique projection of slide transparencies which comprises supporting a slide transparency within a projection system, selectively illuminating the -transparency with an intensified light source by tilted condensing and collimating of light towards the transparency, such that the optical path is narrowed and its axis diverted towards the lower portion of the transparency, such that a greater portion of light is projected through the lower portion of -the transparency and a lesser portion of light is projected through the upper portion of the trans-parency. The light projec-ted is magnified as an image through the transparency, and the image is displayed upon an angularly supported viewing screen, such that the farthest portion of the viewing screen receives -the greater portion of light and the nearest portion receives the lesser light.
~ - 2 -As a result, the illumination of the image displayed upon -the obliquely supported screen .is nearly uniform.
The selective illumination of the transparency is accomplished by tilted condensing of collimated light, such that the optical pa-th of light is narrowed and its axis diverted towards the lower portion of the transparency.
The present method is especially a~apted to the use of rear view projection consoles wherein limited space is a critical factor. For example, a single central light source may be employed to project simultaneously, radially ~hrough a plurality of transparencies mounted upon an encircling carousel and the projected images in turn reflected upwardly on to a rear view screen. Conventionallyl the space allocated behind such rear view screens depends upon the focal length of the lens and the desired magni~ication ratio. Generally, a better image is produced when the lens used has a focal lengt~ at least equal to the diagonal of the projected image. This focal length requirement and the requirement for right angle projection onto the viewing screen often demands more space than is available~ When space limitations arise, mirrors are used to fold the optical projection path often requiring excess depth, as illustrated in the drawings. If folded properly, the projector can be placed in a more compact arrange-ment.
The present method is characterized by its extraordinarysaving in space, such that a plurality of images may be trans-3~7~
mitted simultaneously upon mul-tiple viewing screens.
DESCRIPTION OF THE DRAWINGS:
FIG. 1 is a schematic view, showing the employment of tilted condensers to selectively .illuminate the lower portion of a slide -transparency prior to its projection upon an obliquely supported viewing screen.
FIG. 2 is a transverse section, taken along section lines 2-2 of FIG. 1 and illustrating the trapezoidal negatiYe which is selectively illuminated.
FIG. 3 is a front elevation of the viewing screen anA
showing the selective illumination o-E the image being projected upon the viewing screen.
FIG. 4 is a schematic view of a system wherein a plurality of slide transparencies are suppor-ted in peripheral array with respect to a single central light source.
FIG. 5 is a side elevation, showing a proposed assembly for selective illumination of a slide transparency for oblique projection.
FIG. 6 is a side elevation of the tilted condensor
IN OBL-[QUE PROJECTION OF SLIDE TRANSPARENCIES
CROSS REFERENCES TO RELATED APPLICATIONS:
Related to the co-pending METHOD OF MODIFYING SLIDE
TRANSPARENCIES SO AS TO PROVIDE UNIFORM ILLUMINATION IN ANGULAR
PROJECTION (Canadian Serial No. 369,699), filed January 30, 1981.
The present application is directed to a method for selectively illuminating the modified slide transparency so as to obtain uniform illumination of the image which is obliquely projected upon a viewing screen.
BACKGROUND OF THE INVENTION
Field of the Invention:
Photography, particularly the projection of images through a slide transparency and onto a viewing screen, which is obliquely moun-ted with respect to the optical path of projection.
Image distortions in oblique projection conven-tionally include the "Keystone effect" and non-uniform illumination. The "Key-stone effect" results in a trapezoid shaped projected image.
Non-uniform illumination results in a degrading of the pro-jected image quality, especially a lack of contrast and poor color rendition, since the por-tion of the obliquely supported viewing screen farthest from the projector receives less illumination and the portion nearest receives greater illumi-na-tion. These distortions will therefore create a projected ~5 image which is visually unattractive.
SUMMARY OF THE INVENTION:
In one broad aspect, the invention comprehends a method for correcting non-uniform illumination oblique projection of ~' ~L
':
- 1 - ~', 3'-~
slide transparencies which comprises supporting a slide trans-parency within a projection system, and selectively illumina-ting -the transparency such that a greater portion of light is pro-jected through the lower portion of the transparency and a lesser portion of light is projected -throug~ the upper portion of the transparency. The light projec-ted as an image is magnified through the transparency, and the image is displayed upon an angularly supported viewing screen, such -that the farthest portion of the viewing screen receives the greater portion of light and the nearest portion receives the lesser light.
In a further embodiment, the invention contemplates a method for correcting non-uniform illumination in oblique projection of slide transparencies which comprises supporting a slide transparency within a projection system, selectively illuminating the -transparency with an intensified light source by tilted condensing and collimating of light towards the transparency, such that the optical path is narrowed and its axis diverted towards the lower portion of the transparency, such that a greater portion of light is projected through the lower portion of -the transparency and a lesser portion of light is projected through the upper portion of the trans-parency. The light projec-ted is magnified as an image through the transparency, and the image is displayed upon an angularly supported viewing screen, such that the farthest portion of the viewing screen receives -the greater portion of light and the nearest portion receives the lesser light.
~ - 2 -As a result, the illumination of the image displayed upon -the obliquely supported screen .is nearly uniform.
The selective illumination of the transparency is accomplished by tilted condensing of collimated light, such that the optical pa-th of light is narrowed and its axis diverted towards the lower portion of the transparency.
The present method is especially a~apted to the use of rear view projection consoles wherein limited space is a critical factor. For example, a single central light source may be employed to project simultaneously, radially ~hrough a plurality of transparencies mounted upon an encircling carousel and the projected images in turn reflected upwardly on to a rear view screen. Conventionallyl the space allocated behind such rear view screens depends upon the focal length of the lens and the desired magni~ication ratio. Generally, a better image is produced when the lens used has a focal lengt~ at least equal to the diagonal of the projected image. This focal length requirement and the requirement for right angle projection onto the viewing screen often demands more space than is available~ When space limitations arise, mirrors are used to fold the optical projection path often requiring excess depth, as illustrated in the drawings. If folded properly, the projector can be placed in a more compact arrange-ment.
The present method is characterized by its extraordinarysaving in space, such that a plurality of images may be trans-3~7~
mitted simultaneously upon mul-tiple viewing screens.
DESCRIPTION OF THE DRAWINGS:
FIG. 1 is a schematic view, showing the employment of tilted condensers to selectively .illuminate the lower portion of a slide -transparency prior to its projection upon an obliquely supported viewing screen.
FIG. 2 is a transverse section, taken along section lines 2-2 of FIG. 1 and illustrating the trapezoidal negatiYe which is selectively illuminated.
FIG. 3 is a front elevation of the viewing screen anA
showing the selective illumination o-E the image being projected upon the viewing screen.
FIG. 4 is a schematic view of a system wherein a plurality of slide transparencies are suppor-ted in peripheral array with respect to a single central light source.
FIG. 5 is a side elevation, showing a proposed assembly for selective illumination of a slide transparency for oblique projection.
FIG. 6 is a side elevation of the tilted condensor
2~ mounting.
FIG. 7 is a schematic view of the conventional single projection system wherein the projected image is twice "folded"
prior to display upon a rear view projection screen.
FIG. 8 is a schematic view of a dual conventional pro- -jection system, employing dual projectors and dual mirror systems for display upon a separate rear view screen.
FIG. 7 is a schematic view of the conventional single projection system wherein the projected image is twice "folded"
prior to display upon a rear view projection screen.
FIG. 8 is a schematic view of a dual conventional pro- -jection system, employing dual projectors and dual mirror systems for display upon a separate rear view screen.
3'7~
DESCRIPTION OF T~E DRAWINGS:
In FIG. 1 a central light source 20, such as a Xenon lamp is illustrated as positioned next -to aspheric lens 22 which collimates the light towards a pair of tilted condensers 24. The condensers 24 are tilted so as to divert the optical path toward the lo~er portion o~ slide transparency 31 posi-tioned in slide mount 28. The transparency image is then magnified by projection lens 26 and displayed upon viewing screen 30.
As illustrated in FIG. 2, the diverting of the optical path of light by the tilted condensers 24 directs more light towards the lower portion (Area B) of slide transparency 31 and less light towards the upper portion (Area A) of slide transparency 31. As a result, the image projected upon viewing screen 30, as illustrated in FIG. 3, receives more light in the upper portion (Area B) which is farthest from the light source (distance 11) and less light in the lower portion (Area A) which is nearest the light source (distance 12). This selective illumination of the transparency 31 achieves a uniform illuminati.on of the obliquely displayed image upon viewi.n~ screen 30.
In FIG. 4 the method is shown as adapted to a multi-image display reax view projection system, wherein a plurality of slide transpaxencies are supported in peripheral array with respect to an a~ial light source. The transparencies are selectively illuminated and simultaneously projected towards reflectin~ mirrors 32, 32', positioned within console 36 and, thence, displayed obliquely upon rear view screens 34, 34'.
~ /6 In FIG. 5 there is illustrated a proposed assembly for selective illumination of slide transparencies, including I Xenon light source 20, aspheric lens 22, tilted condensers ¦ 24, slide transparency 31, mounted in bracket 28, projector I lens 26 and a reflecting mirror 32 mounted upon back plate 38 supported in bracket 40 by means of an adjustment screw 42 or the like.
Aspheric collimating lens 22 may be supported in bracket 44, together with heat absorbing glass plate 46, serving to eliminate heat damage to the slide transparency 31. Bracket 44 may be mounted upon post 48 secured slidably upon transverse rods 50 and 52. The entire rod assembly may be supported ¦ upon posts 56 and 58 which extend to base 54. A pair of I tilted condensers 24 may be mounted within bracket 62 which 1l is supported upon adjustable base 60, such that the angle o~
¦l tilt may be varied readily.
The slide transparency bracket 28 may be mounted and turned upon carousel vertical post 76, extending from base plate 74. Base plate 74 is rotatably secured between roller assemblies 70, 72 mounted upon posts 66 and 68 extending to carousel sub-base 64. A suitable drive means (not illustrated) ¦ may be employed for rotating the carousel base.
¦ Stationary projector lens 26, in turn, may be supported upon post 80 which is slidably, adjustably mounted upon horizontal rods 50 and 52.
In FIGS. 7 and 8 there are illustrated the conventional "folding" techniques employed in rear view projection systems and requiring extensive cabinet structure for housing of the mirrors and projectors.
30 i In FIG. 7 a single projection source is used together I
2~7~i ~ith primary and secondary mirrors for display of the slide transparency upon a rear view projection screen.
In FIG. 8 a pair of projectors are used, each with primary l and secondary reflecting mirrors for l'folding" the projected ¦ image upon a rear view screen. ~s will be apparent, the space requirements for l'folding" of the image and projecting of the image at right angles, so as to avoid distortion, are prohibitive.
According to the present method a dramatic space reduction o ! is achieved in rear view oblique projection. The space inter-mediate the screens may be shared by multiple projection paths, since there is no intervening structure. According to ,, conventional oblique projection techniques, the image displayed !l upon the rear view projection screen is both distorted with ¦! the "Keystone effect" and non-uniformally illuminated~ With li respect to the non-uniform illumination, the lower portion of Il the image closest to the lens is brighter than the upper ¦, portion which i5 farthest from the lens. According to the I, present method of selective illumination of the transparency, ~ the oblique projection upon the viewing screen at an angle of less ~r more than 90 does not result in non-uniform illumi- !
¦ nation. As a result, there is enhanced resolution and color perception.
As will be apparent, the projection system may be superposed so as to be mounted above the rear view screens. Also, of ¦ course, the projection angles onto the viewing screens may be I varied selectively between each projection system and the ¦ selective illumination of the slide transparencies may be ! modified by changing the degree of tilting of the condensers.
¦1 Manifestly, the viewing screens may be mounted at a Il -- 7 --i` .
Il i ¦! .
~ 2~76 j diferell~ allqle ~r orn t:he ver~ical plane and tne entire unit ¦ may be ~100L- MOUnted Or ceiliny mountcd . Both 51 Lde tr:al~S
par-ellcies an~l motiorl pictures with or without sound effects may be e~llployed in black an(:l white or. in :~olor on an inter-miLt nt o~ COllt inuoL~. bas ! ~: .
.
,~, 1, .
DESCRIPTION OF T~E DRAWINGS:
In FIG. 1 a central light source 20, such as a Xenon lamp is illustrated as positioned next -to aspheric lens 22 which collimates the light towards a pair of tilted condensers 24. The condensers 24 are tilted so as to divert the optical path toward the lo~er portion o~ slide transparency 31 posi-tioned in slide mount 28. The transparency image is then magnified by projection lens 26 and displayed upon viewing screen 30.
As illustrated in FIG. 2, the diverting of the optical path of light by the tilted condensers 24 directs more light towards the lower portion (Area B) of slide transparency 31 and less light towards the upper portion (Area A) of slide transparency 31. As a result, the image projected upon viewing screen 30, as illustrated in FIG. 3, receives more light in the upper portion (Area B) which is farthest from the light source (distance 11) and less light in the lower portion (Area A) which is nearest the light source (distance 12). This selective illumination of the transparency 31 achieves a uniform illuminati.on of the obliquely displayed image upon viewi.n~ screen 30.
In FIG. 4 the method is shown as adapted to a multi-image display reax view projection system, wherein a plurality of slide transpaxencies are supported in peripheral array with respect to an a~ial light source. The transparencies are selectively illuminated and simultaneously projected towards reflectin~ mirrors 32, 32', positioned within console 36 and, thence, displayed obliquely upon rear view screens 34, 34'.
~ /6 In FIG. 5 there is illustrated a proposed assembly for selective illumination of slide transparencies, including I Xenon light source 20, aspheric lens 22, tilted condensers ¦ 24, slide transparency 31, mounted in bracket 28, projector I lens 26 and a reflecting mirror 32 mounted upon back plate 38 supported in bracket 40 by means of an adjustment screw 42 or the like.
Aspheric collimating lens 22 may be supported in bracket 44, together with heat absorbing glass plate 46, serving to eliminate heat damage to the slide transparency 31. Bracket 44 may be mounted upon post 48 secured slidably upon transverse rods 50 and 52. The entire rod assembly may be supported ¦ upon posts 56 and 58 which extend to base 54. A pair of I tilted condensers 24 may be mounted within bracket 62 which 1l is supported upon adjustable base 60, such that the angle o~
¦l tilt may be varied readily.
The slide transparency bracket 28 may be mounted and turned upon carousel vertical post 76, extending from base plate 74. Base plate 74 is rotatably secured between roller assemblies 70, 72 mounted upon posts 66 and 68 extending to carousel sub-base 64. A suitable drive means (not illustrated) ¦ may be employed for rotating the carousel base.
¦ Stationary projector lens 26, in turn, may be supported upon post 80 which is slidably, adjustably mounted upon horizontal rods 50 and 52.
In FIGS. 7 and 8 there are illustrated the conventional "folding" techniques employed in rear view projection systems and requiring extensive cabinet structure for housing of the mirrors and projectors.
30 i In FIG. 7 a single projection source is used together I
2~7~i ~ith primary and secondary mirrors for display of the slide transparency upon a rear view projection screen.
In FIG. 8 a pair of projectors are used, each with primary l and secondary reflecting mirrors for l'folding" the projected ¦ image upon a rear view screen. ~s will be apparent, the space requirements for l'folding" of the image and projecting of the image at right angles, so as to avoid distortion, are prohibitive.
According to the present method a dramatic space reduction o ! is achieved in rear view oblique projection. The space inter-mediate the screens may be shared by multiple projection paths, since there is no intervening structure. According to ,, conventional oblique projection techniques, the image displayed !l upon the rear view projection screen is both distorted with ¦! the "Keystone effect" and non-uniformally illuminated~ With li respect to the non-uniform illumination, the lower portion of Il the image closest to the lens is brighter than the upper ¦, portion which i5 farthest from the lens. According to the I, present method of selective illumination of the transparency, ~ the oblique projection upon the viewing screen at an angle of less ~r more than 90 does not result in non-uniform illumi- !
¦ nation. As a result, there is enhanced resolution and color perception.
As will be apparent, the projection system may be superposed so as to be mounted above the rear view screens. Also, of ¦ course, the projection angles onto the viewing screens may be I varied selectively between each projection system and the ¦ selective illumination of the slide transparencies may be ! modified by changing the degree of tilting of the condensers.
¦1 Manifestly, the viewing screens may be mounted at a Il -- 7 --i` .
Il i ¦! .
~ 2~76 j diferell~ allqle ~r orn t:he ver~ical plane and tne entire unit ¦ may be ~100L- MOUnted Or ceiliny mountcd . Both 51 Lde tr:al~S
par-ellcies an~l motiorl pictures with or without sound effects may be e~llployed in black an(:l white or. in :~olor on an inter-miLt nt o~ COllt inuoL~. bas ! ~: .
.
,~, 1, .
Claims (12)
1. Method for correcting non-uniform illumination in oblique projection of slide transparencies comprising:
A. Supporting a slide transparency within a projection system;
B. Selectively illuminating said transparency such that a greater portion of light is projected through the lower portion of the transparency and a lesser portion of light is projected through the upper portion of the transparency;
C. Magnifying the light projected as an image through said transparency; and D. Displaying the image upon an angularly supported viewing screen, such that the farthest portion of the viewing screen receives the greater portion of light and the nearest portion receives the lesser light.
A. Supporting a slide transparency within a projection system;
B. Selectively illuminating said transparency such that a greater portion of light is projected through the lower portion of the transparency and a lesser portion of light is projected through the upper portion of the transparency;
C. Magnifying the light projected as an image through said transparency; and D. Displaying the image upon an angularly supported viewing screen, such that the farthest portion of the viewing screen receives the greater portion of light and the nearest portion receives the lesser light.
2. Method for correcting non-uniform illumination in oblique projection of slide transparencies as in claim 1, wherein said illuminating includes collimating said light towards a selected portion of the transparency.
3. Method for correcting non-uniform illumination in oblique projection of slide transparencies as in claim 2, including tilted condensing of the collimated light, such that the optical path is narrowed and its axis diverted towards the lower portion of the transparency.
4. Method for correcting non-uniform illumination in oblique projection of slide transparencies as in claim 3, including angularly reflecting the projected light prior to said displaying of the image upon a viewing screen.
5. Method for correcting non-uniform illumination in oblique projection of slide transparencies as in claim 4, wherein said tilted condensing diverts the optical axis.
6. Method for correcting non-uniform illumination in oblique projection of slide transparencies as in claim 5, wherein said illuminating is by an intensified light source.
7. Method for correcting non-uniform illumination in oblique projection of slide transparencies, comprising:
A. supporting a slide transparency within a projection system;
B. selectively illuminating with an intensified light source by tilted condensing and collimating of light towards said transparency, such that -the optical path is narrowed and its axis diverted towards the lower portion of said transparency, such that a greater portion of light is projected through the lower portion of -the transparency and a lesser portion of light is projected through the upper portion of the transparency;
C. magnifying the light projected as an image through said transparency; and D. displaying the image upon an angularly supported viewing screen, such that the farthest portion of the viewing screen receives the greater portion or light and the nearest portion receives the lesser light.
A. supporting a slide transparency within a projection system;
B. selectively illuminating with an intensified light source by tilted condensing and collimating of light towards said transparency, such that -the optical path is narrowed and its axis diverted towards the lower portion of said transparency, such that a greater portion of light is projected through the lower portion of -the transparency and a lesser portion of light is projected through the upper portion of the transparency;
C. magnifying the light projected as an image through said transparency; and D. displaying the image upon an angularly supported viewing screen, such that the farthest portion of the viewing screen receives the greater portion or light and the nearest portion receives the lesser light.
8. Method for correcting non-uniform illumination in oblique projection of slide transparencies as in claim 6, including absorbing a portion of the heat of said illuminating, sequentially of aspherically collimating, so as to prevent heat damage to said transparency.
9. Method for correcting non-uniform illumination in oblique projection of slide transparencies as in claim 7, including absorbing a portion of the heat of said illuminating, sequentially of aspherically collimating, so as to prevent heat damage to said transparency.
10, Method for correcting non-uniform illumination in oblique projection of slide transparencies as in claim 8 or claim 9, including producing the transparency such that increased illumination is captured in the lower portion of the transparency and lesser illumination is captured in the upper portion of the transparency.
11. Method for correcting non-uniform illumination in oblique projection of slide transparencies as in claim 3, including supporting a plurality of slide transparencies in peripheral array and simultaneously illuminating, magnifying and displaying the images upon separate viewing screens.
12. Method for correcting non-uniform illumination in oblique projection of slide transparencies as in claim 3 or in claim 7, including varying the angle of said tilted con-densing relative to the angle of oblique projection.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US17325180A | 1980-07-29 | 1980-07-29 | |
| US173,251 | 1980-07-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1142376A true CA1142376A (en) | 1983-03-08 |
Family
ID=22631188
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000369698A Expired CA1142376A (en) | 1980-07-29 | 1981-01-30 | Method for correcting non-uniform illumination in oblique projection of slide transparencies |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1142376A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1811766A2 (en) * | 1998-10-02 | 2007-07-25 | Macronix International Co., Ltd. | Method and apparatus for preventing keystone distortion and equalizing luminance |
-
1981
- 1981-01-30 CA CA000369698A patent/CA1142376A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1811766A2 (en) * | 1998-10-02 | 2007-07-25 | Macronix International Co., Ltd. | Method and apparatus for preventing keystone distortion and equalizing luminance |
| EP1811766A3 (en) * | 1998-10-02 | 2008-11-05 | Magic Pixel, Inc. | Method and apparatus for preventing keystone distortion and equalizing luminance |
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