A backlighting unit for a liquid crystal display device includes a light guide plate and an optical member, one of which is provided with a random dot disposition pattern so that luminance of the backlighting unit is uniform over the surface thereof while suppressing moire and dot visibility. A dot pattern of concave or convex portions effective for reflection, scattering, refraction, diffraction, absorption, transmission, polarization or deflection of light rays or portions exhibiting different optical characteristics or portions imparted with optical activity is formed in a surface of the light guide plate or optical member. The dot pattern is determined to exhibit randomness by using random numbers so as to meet predetermined conditions concerning radial distribution function. In the random dot pattern superposed onto a regular color filter pattern, occurrence of moire is suppressed. A dot overlap suppressing processing is performed for preventing inter-dot overlap and abnormal proximity between the adjacent dots.
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