Optical scan apparatus, image formation apparatus, optical deflector manufacturing method, polygon mirror processing method, and polygon mirror processing apparatus

A manufacturing method for an optical deflector in which a mean width of profile elements of a cross section of a deflection surface in a sub scan direction is set to be smaller than a spacing of spots of the light beams which are formed adjacent to the deflection surface in the sub scan direction, the method comprising:

• a rough cutting step of forming a rough deflection surface on the optical deflector;
• and
• a finish cutting step of cutting the rough deflection surface by rotating a cutting member around a rotation axis while moving the optical deflector in a predetermined rotation axis direction at a predetermined speed, to form a deflection surface, the rotation axis being perpendicular to the predetermined rotation axis direction of the optical deflector, wherein
• a size of an illumination area of a light beam incident on the deflection surface in the sub scan direction is set to be smaller than a value which is obtained by dividing a moving distance of the optical deflector in the rotation axis direction per a predetermined time by a rotation speed of the cutting member per a predetermined time.

An image formation apparatus comprising:

• an optical deflector in which a mean width of profile elements of a cross section of a deflection surface in a sub scan direction is set to be smaller than a spacing of spots of light beams which are formed adjacent to the deflection surface in the sub scan direction;
• an optical scan apparatus which rotates the optical deflector around a predetermined rotation axis to scan a scanning plane with at least three or more light beams in a main scan direction, the at least three or more light beams being spaced in the sub scan direction;
• a photoreceptor on which an electrostatic latent image is formed on a scanned surface by the optical scan apparatus;
• a developer section which visualizes, as a toner image, the electrostatic latent image formed on the scanned surface of the photoreceptor;
• and
• a transfer section which fuses the toner image visualized by the developer section on a recording medium.