A projection display apparatus comprising: a light source configured to emit a first light; a reflective light modulator configured to modulate the first light to form a second light conveying a rendered image; a polarizer; a light guide plate having a light incidence surface through which the first light enters the light guide plate, a first outer surface through which a portion of the first light exits the light guide plate for traveling toward the light modulator, and a second outer surface opposite to the first outer surface through which a portion of the second light exits the light guide plate for traveling toward the polarizer; wherein the second outer surface of the light guide plate includes a plurality of optical elements (146, 346), each of the optical elements (146, 346) has a reference axis that is orthogonal to the second outer surface, and a first and a second sidewall (152, 352, 154, 354) that extend at two sides of the reference axis, the first sidewall (152, 352) facing toward the light incidence surface, the second sidewall (154, 354) facing toward a side of the light guide plate opposite to that of the first sidewall (152, 352), and a first angle defined between the first sidewall (152, 352) and the reference axis being smaller than a second angle defined between the second sidewall (154, 354) and the reference axis, the projection display apparatus being characterised in that it comprises a multilayer film coating comprised of dielectric or metal layers arranged on the first and second sidewalls of the optical elements (152, 352, 154, 354), the multilayer film coating promoting polarization selection when optical reflection occurs on the first and second sidewalls of the optical elements (152, 352, 154, 354) for the first light traveling through the light guide plate, and transmission through the first and second sidewalls of the optical elements (152, 352, 154, 354) for the second light from the light modulator; and in that it further comprises a focusing lens arranged between the light modulator and the light guide plate, the focusing lens being positioned to focus on the light modulator. a light source configured to emit a first light; a reflective light modulator configured to modulate the first light to form a second light conveying a rendered image; a polarizer; a light guide plate having a light incidence surface through which the first light enters the light guide plate, a first outer surface through which a portion of the first light exits the light guide plate for traveling toward the light modulator, and a second outer surface opposite to the first outer surface through which a portion of the second light exits the light guide plate for traveling toward the polarizer; wherein the second outer surface of the light guide plate includes a plurality of optical elements (146, 346), each of the optical elements (146, 346) has a reference axis that is orthogonal to the second outer surface, and a first and a second sidewall (152, 352, 154, 354) that extend at two sides of the reference axis, the first sidewall (152, 352) facing toward the light incidence surface, the second sidewall (154, 354) facing toward a side of the light guide plate opposite to that of the first sidewall (152, 352), and a first angle defined between the first sidewall (152, 352) and the reference axis being smaller than a second angle defined between the second sidewall (154, 354) and the reference axis, the projection display apparatus being characterised in that it comprises a multilayer film coating comprised of dielectric or metal layers arranged on the first and second sidewalls of the optical elements (152, 352, 154, 354), the multilayer film coating promoting polarization selection when optical reflection occurs on the first and second sidewalls of the optical elements (152, 352, 154, 354) for the first light traveling through the light guide plate, and transmission through the first and second sidewalls of the optical elements (152, 352, 154, 354) for the second light from the light modulator; and in that it further comprises a focusing lens arranged between the light modulator and the light guide plate, the focusing lens being positioned to focus on the light modulator.