A backlight source comprising: a base; a solid state light source array including a plurality of solid state light sources disposed on the base; a light transmitting unit disposed above the solid state light source array; a plurality of light adjusting units disposed between the solid state light source array and the light transmitting unit, wherein each light adjusting unit includes a filter plate or film which reflects incident lights having incident angles smaller than a threshold angle and transmits incident lights having incident angles larger than or equal to the threshold angle, wherein each light adjusting unit spatially corresponds to one solid state light source; and a low refractive index medium having a refractive index below 1.3 disposed between the filter plates or films and the solid state light sources, wherein a distance between each light adjusting unit and the corresponding solid state light source is less than 1/5 of a bounding circle diameter of a light emitting area of the solid state light source, wherein each light adjusting unit reflects small-angle emitted light from the solid state light source back to the solid state light source, and wherein the solid state light source reflects or scatters the light reflected from the light adjusting unit back to the light adjusting unit at various angles, whereby a spatial distribution of light intensity of the light from the solid state light sources to the light transmitting unit is adjusted by the light adjusting units, wherein each filter plate or film selectively transmits incident light within a predetermined wavelength range corresponding to a wavelength range of a corresponding light source. a base; a solid state light source array including a plurality of solid state light sources disposed on the base; a light transmitting unit disposed above the solid state light source array; a plurality of light adjusting units disposed between the solid state light source array and the light transmitting unit, wherein each light adjusting unit includes a filter plate or film which reflects incident lights having incident angles smaller than a threshold angle and transmits incident lights having incident angles larger than or equal to the threshold angle, wherein each light adjusting unit spatially corresponds to one solid state light source; and a low refractive index medium having a refractive index below 1.3 disposed between the filter plates or films and the solid state light sources, wherein a distance between each light adjusting unit and the corresponding solid state light source is less than 1/5 of a bounding circle diameter of a light emitting area of the solid state light source, wherein each light adjusting unit reflects small-angle emitted light from the solid state light source back to the solid state light source, and wherein the solid state light source reflects or scatters the light reflected from the light adjusting unit back to the light adjusting unit at various angles, whereby a spatial distribution of light intensity of the light from the solid state light sources to the light transmitting unit is adjusted by the light adjusting units, wherein each filter plate or film selectively transmits incident light within a predetermined wavelength range corresponding to a wavelength range of a corresponding light source.