Patent ID: 8748820

Claim:
A projection type display system having a position detection function which projects an image from an image projection device and optically detects a position of a target object between a surface on which the image is projected and the image projection device, comprising: the image projection device; a position detection light source unit disposed on the image projection device to emit position detection light toward a detection area in which the position of the target object is detected, the position detection light having intensity; a light detector which detects reflection intensity of reflected position detection light reflected by the target object in the detection area that is defined by a first side and a second side opposite to the first side; and a position detection unit which detects the position of the target object based on the reflection intensity detected by the light detector, wherein an intensity distribution of the position detection light in the detection area is produced in a manner in which the intensity monotonously decreases from the first side to the second side during a first period and in which the intensity monotonously increases from the first side to the second side during a second period that is different from the first period, and the light detector detects the reflection intensity of the reflected position detection light without detecting an image of the target object.