An image display apparatus comprising: a directional backlight unit comprising: at least one light source configured to emit light; and a light guide plate configured to guide the light emitted by the at least one light source, wherein a plurality of grating pattern groups, each comprising a plurality of grating patterns are provided on an exit surface of the light guide plate, and wherein the plurality of grating patterns comprise a plurality of image generation grating patterns configured to direct the light to a plurality of different respective viewing zones, and a plurality of dummy grating patterns respectively disposed between adjacent image generation grating patterns from among the plurality of image generation grating patterns, and wherein an interval between adjacent grating patterns from among the plurality of grating patterns is less than 1/10 of a wavelength of the light emitted by the light source, and an interval between adjacent grating pattern groups from among the plurality of grating pattern groups is greater than 180/π times the wavelength of the light emitted by the light source; and a display panel configured to form an image by using the light guided by the light guide plate, wherein the plurality of dummy grating patterns are configured to prevent light that propagates from each dummy grating pattern from among the plurality of dummy grating patterns from being used to form the image. a directional backlight unit comprising: at least one light source configured to emit light; and a light guide plate configured to guide the light emitted by the at least one light source, wherein a plurality of grating pattern groups, each comprising a plurality of grating patterns are provided on an exit surface of the light guide plate, and wherein the plurality of grating patterns comprise a plurality of image generation grating patterns configured to direct the light to a plurality of different respective viewing zones, and a plurality of dummy grating patterns respectively disposed between adjacent image generation grating patterns from among the plurality of image generation grating patterns, and wherein an interval between adjacent grating patterns from among the plurality of grating patterns is less than 1/10 of a wavelength of the light emitted by the light source, and an interval between adjacent grating pattern groups from among the plurality of grating pattern groups is greater than 180/π times the wavelength of the light emitted by the light source; and at least one light source configured to emit light; and a light guide plate configured to guide the light emitted by the at least one light source, wherein a plurality of grating pattern groups, each comprising a plurality of grating patterns are provided on an exit surface of the light guide plate, and wherein the plurality of grating patterns comprise a plurality of image generation grating patterns configured to direct the light to a plurality of different respective viewing zones, and a plurality of dummy grating patterns respectively disposed between adjacent image generation grating patterns from among the plurality of image generation grating patterns, and wherein an interval between adjacent grating patterns from among the plurality of grating patterns is less than 1/10 of a wavelength of the light emitted by the light source, and an interval between adjacent grating pattern groups from among the plurality of grating pattern groups is greater than 180/π times the wavelength of the light emitted by the light source; and a display panel configured to form an image by using the light guided by the light guide plate, wherein the plurality of dummy grating patterns are configured to prevent light that propagates from each dummy grating pattern from among the plurality of dummy grating patterns from being used to form the image.