Method and apparatus for preventing keystone distortion

A method of generating an image for projection from a projection system without significant keystone distortion, wherein an axis of projection of the projection system is aligned at a non-perpendicular angle with a viewing screen, the method comprising:

• receiving an original image having a set of dimensions;
• maintaining a set of parameters relating to a geometrical relationship between a display device of the projection system and a plane parallel to the viewing screen;
• defining a usable area of the display device in which a representation of said original image may be rendered;
• for one or more portions of said usable area, identifying a corresponding portion of said original image;
• rendering characteristics of said corresponding portions of said original image to generate a display image for projection by the projection system onto the viewing screen;
• and
• adjusting the intensity of said display image to provide for substantially equal luminance throughout said display image;
• wherein said display image may be projected without significant keystone distortion.

A method of transforming an input image to form an output image for projection from a projection system onto a screen, wherein the input image is deformed to offset keystone distortion, the method comprising:

• determining a vertical angle between the projection system and normal to the screen;
• determining a horizontal angle between the projection system and a normal to the screen;
• receiving an input image;
• if said vertical angle is greater than or less than zero, transforming said input image to correct for keystone distortion that may be caused by said vertical angle;
• and
• if said horizontal angle is greater than or less than zero, transforming said input image to correct for keystone distortion that may be caused by said horizontal angle.

An apparatus for projecting an image onto a viewing surface with minimal keystone distortion, comprising:

• a first memory configured to store an entire original image received from an image source;
• a deformation module configured to deform said original image, in accordance with one or more scaling factors derived from an angle formed between said projection axis and a line normal to the viewing surface, to form a display image;
• a second memory configured to store a set of parameters for facilitating said deformation of said original image, including said one or more scaling factors;
• a luminance module configured to substantially equalize the luminance of said display image;
• a display device configured to display said display image;
• and
• a light source configured to project said display image along a projection axis onto a viewing screen.

A projection system for projecting an image onto a viewing surface with minimal keystone distortion, comprising:

• a digitizer configured to receive an image from an image source, wherein said image is received having a size;
• a resizing module configured to alter said size of said image;
• a keystone module configured to deform a portion of said image to create a display image by offsetting keystone distortion that would occur from projecting said image;
• a display device configured to display said display image;
• a generator configured to forward said display image to said display device;
• a memory configured to store a set of parameters for facilitating one or more of said deformation of said portion of said image and said resizing of said image;
• and
• a light source configured to project said display image from said display device onto the viewing screen.

An apparatus for deforming an input image to offset keystone distortion, comprising:

• a projector configured to project a display image onto a screen to form a projection image;
• an angle acquisition module configured to determine an angle between said projector and a normal to the screen;
• and
• an image processing module configured to transform said input image into said display image, comprising:
• a first angle correction module configured to deform said input image in accordance with a vertical aspect of said angle;
• a second angle correction module configured to deform said input image in accordance with a horizontal aspect of said angle;
• and
• a re-scaling module configured to resize said input image.

A computer readable storage medium storing instructions that, when executed by a computer, cause the computer to perform a method of generating an image for projection from a projection system without significant keystone distortion, wherein an axis of projection of the projection system is aligned at a non-perpendicular angle with a viewing screen, the method comprising:

• receiving an original image having a set of dimensions;
• maintaining a set of parameters relating to a geometrical relationship between a display device of the projection system and a plane parallel to the viewing screen;
• defining a usable area of the display device in which a representation of said original image may be rendered;
• for one or more portions of said usable area, identifying a corresponding portion of said original image;
• and
• rendering characteristics of said corresponding portions of said original image to generate a display image for projection by the projection system onto the viewing screen;
• wherein said display image may be projected without significant keystone distortion.