Illumination system, lithography machine and illumination uniformity compensation method

The invention provides an illumination system, a photoetching machine and an illumination uniformity compensation method. The illumination unit is used for providing first illumination. The light uniformizing unit is used for uniformizing the first illumination and converting the first illumination into second illumination. And the compensation unit comprises at least one optical flat plate with various light transmittances. The compensation unit can move in the direction identical to or opposite to the light propagation direction of the second illumination. And the second illumination passes through the optical flat plate to correspondingly form third illumination. The illumination uniformity of the third illumination is greater than that of the second illumination. Therefore, the light uniformizing effect of the light uniformizing unit is compensated by arranging the compensation unit with various light transmittances, so that the second illumination is adjusted by the compensation unit with different light