Patent ID: 7982938

Claim:
An optical mask which applies spatial intensity modulation to input light in a beam cross-section and outputs a light after being subjected to the modulation, wherein when regions A 0 to A p defined by circumferences with p radiuses r 1 to r p (p is an even number, r p >r p−1 > . . . >r 2 >r 1 , and r p −r p−1 >r p−1 −r p−2 > . . . >r 3 −r 2 >r 2 −r 1 ≧r 1 ) around a predetermined position are set in order from an inner side, a region A m (m is an even number not less than 0 and not more than p) is a light transmission region, and a region A n (n is an odd number not less than 0 and not more than p) is a light shielding region, wherein p>=2, p>=m>=2, p>n>=1, and m is not equal to 0.