Image display apparatus

1. An image display apparatus comprising:

at least one light source that emits coherent light;

a holographic optical element that diffracts the coherent light from the light source;

a Fourier lens that receives diffracted light from the holographic optical element to produce image light;

an optical mechanism that guides the image light from the Fourier lens, wherein the optical mechanism includes a slitter and a diffuser, the slitter disposed in an imaging position of the Fourier lens and having an opening through which most of the image light from the holographic optical element passes and a frame that partially blocks the image light from the holographic optical element, the slitter defining a display range of the image to be viewed by the viewer, and the diffuser disposed in an optical path behind the slitter;

at least one detection unit that detects intensity of the image light from the Fourier lens, the detection unit being disposed in the optical path after the holographic optical element; and

an adjustment unit that adjusts power of the light source based on a result of detection by the detection unit; and

wherein a display image, having a display image component, based on the image light is observable by a viewer and an image based on the image light incident to the detection unit are the same image, and wherein a change in brightness of the display image component depends on an area of the display image component.

2. The apparatus according to claim 1 ,

wherein the at least one light source comprises a plurality of light sources, and

wherein the at least one detection unit comprises a plurality of detection units corresponding to the plurality of light sources.