Patent ID: 7399094

Claim:
A polygon mirror comprising: a reflective surface group having n number of reflective surfaces (M( 1 ), M( 2 ) , . . . , M(n)) formed individually as outer peripheral side faces; a flat portion which shuts one end portion of the reflective surface group; and n number of pin gate traces (L( 1 ), L( 2 ), , L(n)) which are provided on the flat portion and which correspond respectively to the n number of reflective surfaces, each of the pin gate traces being at a distance from an edge portion at which the reflective surface corresponding thereto crosses the flat portion, wherein the polygon mirror satisfies the following conditions: DM (1)> DL (1)/2 , DM (2)> DL (2)/2 , . . . , DM ( n )> DL ( n )/2; and DM (1)> DL ( n )/2 , DM (2)> DL (1)/2 , . . . , DM ( n )> DL ( n -1)/2, where DM( 1 ) is a shortest distance from the edge portion at which the reflective surface M( 1 ) and the flat portion cross each other to the pin gate trace L( 1 ), DM( 2 ) is a shortest distance from the edge portion at which the reflective surface M( 2 ) and the flat portion cross each other to the pin gate trace L( 2 ), . . . , and DM(n) is a shortest distance from the edge portion at which the reflective surface M(n) and the flat portion cross each other to the pin gate trace L(n), and where DL( 1 ) is a shortest distance between the pin gate trace L( 1 ) and the pin gate trace L( 2 ), DL( 2 ) is a shortest distance between the pin gate trace L( 2 ) and the pin gate trace L( 3 ), . . . , and DL(n) is a shortest distance between the pin gate trace L(n) and the pin gate trace L( 1 ).