US Patent 9304379 Projection display intensity equalization

In some examples, the intensity of an image projected onto a surface at an oblique angle may be controlled to equalize the intensity, and thereby to eliminate from the image perceptible variations in brightness. For instance, a first distance to a closer portion of the image and a second distance to a farther portion of the image may be used to determine an amount of change to be made to the intensity of at least one portion of the image. In some implementations, a filter may be used to control changes to the intensity of the image. In other implementations, the image information may be modified, such as on a pixel level, to control the intensity of the image.