Abstract: In a display unit which makes coherent light perform scanning on a screen to display an image, it is necessary to rotate a polygon mirror at ultrahigh speed for display of a high resolution image such as HDTV, and therefore, a high-performance polygon mirror must be employed, and further, noise and power consumption during rotation of the polygon mirror cause problems. Mirrors for multiple reflection (6a) and (6b) are inserted in a coherent light scanning optical system, whereby plural scanning lines can be obtained while one plane of the polygon mirror (5) scans one line of coherent light, leading to reduction in the rpm of the polygon mirror.

Abstract: A common photodetecting unit detects a plurality of beams scanned by a plurality of polyhedral reflection mirrors provided in a multiple stages with a common rotation axis, and generates a synchronization detection signal based on detected beams. The reflection mirrors make a predetermined angle ?1 in a direction of rotation of the reflection mirrors. When time between two consecutive synchronization detection signals on a time line generated by the common photodetecting unit is ti, where i is a positive integer equal to or smaller than number of split beams, at least one of ti is different from others.

Abstract: Disclosed herein is a raster scanning-type display device using a diffractive light modulator. The diffractive light modulator includes a plurality of light sources, the diffractive light modulator, a plurality of illumination optical units, a combining unit, a Schlieren optical unit, and a scanning optical unit.

Abstract: An optical scanning device acquires a displacement amount of each of scanning light beams in the main scanning direction, and corrects, based on the displacement amount, writing energy density at a write position such that a variation in image density due to a variation of the displacement amount is reduced. The light beams are used for scanning a target surface to write image data on the target surface. The writing energy density is an amount of light per unit surface area of the target surface.