Patent ID: 8704143

Claim:
An image projection apparatus comprising: a projection lens configured to project an image onto a projection surface; a beam splitter configured to split light from a light source into first color light and second color light; a first reflective image display element configured to optically modulate the first color light; a second reflective image display element configured to optically modulate the second color light; a first parallel plate arranged between the beam splitter and the first reflective image display element; and a second parallel plate arranged between the beam splitter and the second reflective image display element, wherein the following expressions are satisfied: 5 ⁢ L ≥ ABS ⁢ { ( T 1 - T 2 ) + D 2 × ( 1 n 22 - 1 n 21 ) } ≥ L 2 5 ⁢ L ≥ ABS ⁢ { ( T 2 - T 1 ) + D 1 × ( 1 n 11 - 1 n 12 ) } ≥ L 2 ⁢ - 20 ⁢ ⁢ μ ⁢ m ≤ T 1 ≤ 20 ⁢ ⁢ μ ⁢ m ⁢ - 20 ⁢ ⁢ μ ⁢ m ≤ T 2 ≤ 20 ⁢ ⁢ μ ⁢ m , and where n 11 is a refractive index of the first parallel plate for a gravity center wavelength λ 1 of the first color light, n 12 is a refractive index of the first parallel plate for a gravity center wavelength λ 2 of the second color light, n 21 is a refractive index of the second parallel plate for a gravity center wavelength λ 1 of the first color light, n 22 is a refractive index of the second parallel plate for a gravity center wavelength λ 2 of the second color light, D 1 (μm) is a thickness of the first parallel plate in an optical axis direction, D 2 (μm) is a thickness of the second parallel plate in the optical axis direction, T 1 (μm) is a longitudinal chromatic aberration of the gravity center wavelength λ 1 of the first color light based on a gravity center wavelength λ 3 of third color light different from each of the first color light and the second color light, T 2 (μm) is a longitudinal chromatic aberration of the gravity center wavelength λ 2 of the second color light based on the gravity center wavelength λ 3 of third color light, and L (μm) is a coherent distance of the light source, and wherein the gravity center wavelength is a wavelength corresponding to a center of gravity calculated from a product between a spectrum of a light flux emitted from the image projection apparatus and a color matching function.