An imaging method. A light beam passes through a first lens set, a second lens set, an imaging device and a projection lens set. The light beam is focused in a first position. The focused light beam converges in a first relay position via the first lens set and in a second relay position via the second lens set. The optical path from the first position to the principal plane of the first lens set is defined as a first optical path, and the principal plane of the second lens set to the second relay position as the fourth optical path. The length of the first optical path is longer than twice the focal length of the first lens set, and the length of the fourth optical path is longer than twice the focal length of the second lens set.

An illumination optical system comprises a light source lamp (1), a light mixing element (3) for mixing light emitted from the light source lamp (1), a DMD element (5) having a plurality of pixels, a transmission optical system (4) for bringing a light-exit surface (3a) of the light mixing element (3) into optical conjugation with a to-be-illuminated surface (5S) of the DMD element (5), and a field lens (6) located in front of the DMD element (5). The focal length of the field lens (6) can be changed so that an illuminance distribution that varies according to the application of the illumination optical system can be achieved on the to-be-illuminated surface (5S).

The invention includes a color projection system. System includes a light source, a first relay lens, disposed on a first optical path, optically coupled to the light source. System also includes a second relay lens, disposed in a second optical path, optically coupled to the first lens, the second optical path being of a predetermined vertical distance above the first optical path. The color projection system also includes a light management device, having a light entrance surface and a light exit surface, the light entrance surface optically coupled to the second lens along the second optical path, the light exit surface located on a third optical path, and the third optical path being substantially parallel to the first and second optical paths and being a predetermined distance below the second optical path. A projection lens may be optically coupled to the light exit surface of the light management device.

A projection type display apparatus is composed of a light source (101), an illumination optical system (102) for forming illumination light, a reflection type light valve (106) for reflecting the illumination light to form an optical image, a projection optical system (107) for projecting the optical image, and a lens (105) with a positive power. An optical axis (115) of the reflection type light valve, an optical axis (113) of the projection optical system, and an optical axis (114) of the lens with a positive power are matched with each other. The illumination optical system (102) is placed so that the illumination light passes through the lens (105) with a positive power and is reflected from the reflection type light valve (106). An output pupil (108) of the illumination optical system (102) and an entrance pupil (109) of the projection optical system (107) are placed so as to have a conjugate relationship with respect to the lens (105) with a positive power.

According to one exemplary embodiment discussed herein, an active color wheel is provided. The active color wheel according to one exemplary embodiment includes a plurality of light sources configured to be moved through a period of motion. Further, the plurality of light sources are configured to be activated over a range of the period of motion.