Patent ID: 7649625

Claim:
An optical apparatus comprising: a laser light source for emitting a beam of light; an integrator for dividing the beam of light into plural beams of light; a light focusing optical system for focusing the beams of light passed through the integrator; a stage on which the light concentrated by the light focusing optical system is irradiated and on which an object may be placed; and a projecting optical system for projecting the light transmitted through the object, wherein the projecting optical system has a visual field including an effective visual field, the integrator has a division number N corresponding to a predetermined direction in a predetermined effective visual field, a ghost image is formed in the effective visual field in the predetermined direction and has contrast γ, the light focusing optical system has numerical aperture NA 1 , the projecting optical system has numerical aperture NA 2 , (NA 1 /NA 2 ) defines a coherence factor σ, and the object has a light blocking portion with an amplitude transmittance T such that C is the ratio of the contrast γ to the amplitude transmittance T, whereby the following numerical formula (1) is satisfied N ≧ σ π ⁢ 8 π ⁢ ⁢ C 2 3 ⁢ ⁢ ( C = γ ⁢ / ⁢ T ) . ( 1 )