| 摘要 |
A thin hologram optical element being high in light transmittance and excellent to handle, and a surface light source device using it. A hologram optical element which has a small wavelength dependency by a bending angle, and prevents the spectral separation of a white light incident from an oblique direction to allow the light to exit after bent in a vertical direction. A hologram optical element, wherein when lights having three wavelengths, lambda1, lambda2, lambda3, are incident at an angle Thetai in a transmitting diffraction lattice - where lambda1, lambda2, lambda3 are respectively in the ranges, 0.46<=lambda1<=0.50 mum (blue light), 0. 53<=lambda2<=0.57 mum (green light), 0.60<=lambda 3<=0.64 mum (red light), a diffraction angle that maximizes the diffraction efficiency of each wavelength falls within a range, - 5° to +5°.
|
