Projection system having rotationally asymmetrical illumination unit for emitting light along optic axis

摘要

A projection system including an illumination unit, a polarization conversion unit, a light valve, a projection lens, and a polarizing beam split (PBS) element is provided. The polarization conversion unit includes a V-shaped PBS element, a wave plate, and two reflective surfaces. The V-shaped PBS element includes a first PBS portion and a second PBS portion. The first PBS portion is adapted to be passed through by a first partial beam with a first polarization direction and reflect a second partial beam with a second polarization direction. The second PBS portion is adapted to be passed through by a third partial beam with the first polarization direction and reflect a fourth partial beam with the second polarization direction. The wave plate is disposed in the transmission paths of the first partial beam and the third partial beam. The reflective surfaces are located at opposite sides of the V-shaped PBS element.

主权项

1. A projection system comprising:
an illumination unit for emitting a light beam, wherein the light beam emitted from the illumination unit is along an optic axis for the projection system, and the illumination unit comprises: an LED die; and a collimator lens comprising: a central part having a first light transmission surface and a second light transmission surface opposite to the first light transmission surface; and a peripheral part around the central part having an inner refraction wall coupled to the first light transmission surface to form a hollow for situating the LED die, an outer reflection wall opposite to the inner refraction wall, and a refraction surface connecting to the second light transmission surface and the outer reflection wall, wherein both the central part and the peripheral part of the collimator lens are rotationally asymmetrical corresponding to the optic axis; wherein the refraction surface comprises a first curved surface and a flat surface, an end of the first curved surface connects to the second light transmission surface and another end of the first curved surface connects to an end of the flat surface to form a vertex, and another end of the flat surface connects to the outer reflection wall where the flat surface without being curved is tilted relative to the optic axis, and a normal vector of the flat surface is not parallel to the optic axis; wherein the first curved surface protrudes from the peripheral part toward the optic axis; and wherein the first curved surface tilts relative to the optic axis, and an angle included between the first curved surface and the second light transmission surface and outside of the collimator lens is greater than 0 degree and less than 90 degrees; a polarization conversion unit disposed in the transmission path of the light beam and comprising: a V-shaped polarizing beam split (PBS) element comprising: a first PBS portion adapted to be passed through by a first partial beam of the light beam with a first polarization direction and reflect a second partial beam of the light beam with a second polarization direction; and a second PBS portion connected to the first PBS portion, wherein an angle greater than 0 degree and less than 180 degrees is included between the first PBS portion and the second PBS portion, the second PBS portion is adapted to be passed through by a third partial beam of the light beam with the first polarization direction and reflect a fourth partial beam of the light beam with the second polarization direction; a wave plate disposed in the transmission paths of the first partial beam from the first PBS portion and the third partial beam from the second PBS portion, wherein the wave plate is adapted to convert the first partial beam and the third partial beam with the first polarization direction into a fifth partial beam with the second polarization direction; and two reflective surfaces located at two opposite sides of the V-shaped PBS element and adapted to respectively reflect the second partial beam and the fourth partial beam from the V-shaped PBS element, wherein the second partial beam and the fourth partial beam from the reflective surfaces and the fifth partial beam from the wave plate are combined into an illumination beam with the second polarization direction; a light valve disposed in the transmission path of the illumination beam and adapted to convert the illumination beam into an image beam; a projection lens disposed in the transmission path of the image beam; and a PBS element disposed in the transmission paths of the illumination beam and the image beam and adapted to allow the illumination beam to be transmitted to the light valve and to allow the image beam to be transmitted to the projection lens.