Aspherical surface ftheta mirror and optical scanner

PURPOSE: To realize an aspherical surface fθ mirror with excellent image surface curvature correction and fθ characteristic correction. CONSTITUTION: This mirror is used in an optical scanner making luminous flux from a light source 1 a converged luminous flux and deflecting it in constant angular velocity by a deflection device 3 and reflecting the deflected luminous flux by a mirror 4 having an fθ characteristic and converging it on a scanned surface as a light spot and executing optical scanning. The aspherical surface fθ mirror 4 whose reflection surface shape is a coaxial aspherical surface and whose section shape containing an X axis when a symmetry axis is made the X axis is displayed as the relation Y 2 =2RX-EX 2 substantially by E within the range of 1≤E≤15 where a contact circle radius is R, a distance from the X axis is Y, a conical constant is E. COPYRIGHT: (C)1993,JPO&Japio