Optics: image projectors – Distortion compensation
Reexamination Certificate
2000-08-21
2002-07-09
Dowling, William (Department: 2851)
Optics: image projectors
Distortion compensation
C353S070000
Reexamination Certificate
active
06416186
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a projection display unit that can project an image whose distortion is corrected.
DESCRIPTION OF THE RELATED ART
At a projection display unit, an image formed on such as a liquid crystal display (LCD) panel is taken out by transmitted through or reflected the LCD panel and the taken out image is projected on a screen surface. And when the image is projected on the screen surface, in order to make the zooming in/out rate of the image uniform in each part of the screen surface, the optical axis of the projection display unit must be perpendicularly intersected with the center of the screen surface. However, in case of a front projection display unit, the front projection display unit is disposed around the center position of a projection room in front of the screen surface, consequently the front projection display unit becomes an obstacle for observers to watch the screen surface. And at a rear projection display unit, there is a case that disposing the rear projection display unit at an ideal position becomes impossible caused by some limitation of the space of the projection room. Consequently, the projection display unit must be disposed in a state that the optical axis of the projection display unit is inclined for the screen surface, in this case, a distortions is generated in the projected image.
In order to solve this problem, Japanese Patent Application Laid-Open No. HEI 9-275538 discloses a liquid crystal projection display unit.
FIG. 1
is a diagram showing an image correction method of this conventional projection display unit. As shown in
FIG. 1
, at this conventional projection display unit, an original image (a) is vertically compressed and the vertically compressed image (b) is formed. And further a keystone distortion correction is applied to the vertically compressed image (b), and a keystone distortion corrected image (c) is formed. And this keystone distortion corrected image (c) is projected to a vertically disposed screen surface from an inclined upper direction, and a displaying image (d) whose distortion is corrected can be projected on the screen surface.
At the conventional projection display unit shown in
FIG. 1
, only the vertical compression and the keystone distortion correction are applied, therefore, the distortion caused by that the image is projected from an upward, downward, right, or left direction can be corrected. However, there is a problem that the distortion caused by that the image is projected from an inclined right upward, inclined right downward, inclined left upward, or inclined left downward direction can not be corrected. Further, it is difficult to solve the distortion caused by that the screen surface is not a regular surface such as an irregular surface or a free surface by only applying the vertical compression and the keystone distortion correction.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a projection display unit in which a distortion of an image is corrected even when the image is projected from an arbitrary direction, further which can correct a distortion caused by that an image is projected on a screen surface having an irregular surface or a free surface.
According to a first aspect of the present invention, for achieving the objects mentioned above, a projection display unit provides an image inputting means to which an original image is inputted, a screen surface obtaining means for obtaining a three dimensional shape of a screen surface by calculating an azimuth angle, a tilt angle, and a distance of the screen surface for the projection display unit by using the normal line vector of the screen surface, an image correcting means for executing an inclination correction and a zooming in/out correction for the original image corresponding to the three dimensional shape of the screen surface, and an image outputting means for outputting the corrected image as a projecting image.
According to a second aspect of the present invention, in the first aspect, the inclination correction makes the original image rotate corresponding to the inclination of the screen surface, and also makes the size of the original image change corresponding to the ratio between the distance of the screen surface and a focal distance of lens of the projection display unit, and makes the coordinate of the original image projected on a tentative reference surface change corresponding to the distance and the inclination of the screen surface, and the zooming in/out correction makes the coordinate of the original image change corresponding to the ratio between the distance from the center of the projection display unit to a reference surface and the distance from the center of the projection display unit to the tentative reference surface.
According to a third aspect of the present invention, in the first aspect, the projection display unit further provides a projection controlling means which calculates the focal distance of the lens of the projection display unit corresponding to the distance of the screen surface calculated at the screen surface obtaining means and controls the focus in the image outputting means.
According to a fourth aspect of the present invention, in the third aspect, the inclination correction is executed by the focal distance calculated at the projection controlling means.
According to a fifth aspect of the present invention, a projection display unit provides an image inputting means to which an original image is inputted, a screen surface obtaining means for obtaining a three dimensional shape of a screen surface by calculating an azimuth angle, a tilt angle, and a distance of the screen surface for the projection display unit by using the normal line vector of the screen surface, a virtual approximate screen surface generating means for generating a virtual approximate screen surface by using the three dimensional shape of the screen surface calculated at the screen surface obtaining means, a perspective projection means for calculating a corrected image by orthographic projection of a three dimensional image which is obtained by that a projection simulation is applied to the inputted original image on the virtual approximate screen surface by a perspective projection process, and an image outputting means for outputting the corrected image as a projecting image.
According to a sixth aspect of the present invention, in the fifth aspect, the virtual approximate screen surface is obtained by that the coordinate of the screen surface is rotated by the inclination of the screen surface, and a directional vector of the coordinate from the center of the projection display unit is obtained, and an angle between the directional vector and an optical axis of the projection display unit is obtained, and a process for calculating three dimensional coordinate of the position of the virtual approximate screen surface of the coordinate is applied to all coordinates, and a three dimensional polygon connected each coordinate of the virtual approximate screen surface is generated.
According to a seventh aspect of the present invention, a projection display unit provides an image inputting means to which an original image is inputted, an image outputting means which outputs an image that the original image is processed as a projecting image, a projection controlling means which changes over an image inputting to the image outputting means, a pattern image generating means which generates pattern images and outputs the pattern images, a screen surface obtaining means which obtains a shape of a screen surface by that by using the pattern images and images on the screen surface at the time when the pattern images are inputted to the image outputting means and are taken by a camera, and by obtaining three dimensional coordinates of the positions projected the pattern images by using a triangulation method with making the coordinate of the projection display unit correspond to the coordinate of camera images being the pattern images t
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