Patent ID: 7710628

Claim:
A method of correcting output light-amounts of a spatial light modulator with diffraction grating structure comprising a plurality of light modulator elements, wherein each light modulator element of said plurality of light modulator elements comprises fixed reflective portions having strip-like fixed reflective surfaces parallel to a base surface and moving ribbons having strip-like moving reflective surfaces parallel to said base surface, and said fixed reflective portions and said moving ribbons are alternately arranged in a predetermined direction in said each light modulator element, said moving ribbons are sagged in accordance with a voltage inputted to said each light modulator element, to change a height of said moving reflective surfaces from said base surface, said each light modulator element changes between a state of emitting a zeroth order light beam and a state of first order diffracted light beams, and a height of said moving reflective surfaces from said base surface is different from that of said fixed reflective surfaces from said base surface in a state where said moving ribbons are not sagged in said each light modulator element, and said method of correcting output light-amounts of a spatial light modulator comprises the steps of: a) setting a light amount of an output light, which is a zeroth order light beam or first order diffracted light beams outputted from said each light modulator element in an ON state or an OFF state, as a target light-amount which is common to said plurality of light modulator elements; and b) obtaining a target voltage which is equal to an input voltage to said each light modulator element when an output light-amount of said each light modulator element first reaches said target light-amount in gradually increasing or decreasing said input voltage from a voltage corresponding to a light amount which is closer to said target light-amount out of the first minimum light-amount when a light amount of an output light first becomes minimum from when said moving ribbons start to sag in increasing said input voltage and the first maximum light-amount when a light amount of an output light first becomes maximum from when said moving ribbons start to sag in increasing said input voltage.