US Patent 7303289 Projection type display apparatus

A projection type display apparatus includes a projection portion for projecting an image onto a surface to be projected, a light receiving portion disposed apart from the projection portion by a base line length and used for detecting a reference image projected onto the surface to be projected, and a scanning portion for scanning the reference image on the surface to be projected in a direction of the base line length, in which the projection portion is focused based on information about a scanning position of the reference image upon predetermined detection with the light receiving portion. With the projection type display apparatus, a system can be configured with a simple processing circuit, and cost reduction can be realized.