Method of manufacturing imaging optical elements and optical scanning apparatus using imaging optical elements manufactured by the method

A method of manufacturing imaging optical elements which have the same optical performance and are to be used in an optical scanning apparatus,

• the optical scanning apparatus comprising:
• a plurality of light source units;
• an incident optical system for causing a plurality of light, beams emitted from the plurality of light source units to enter the same deflection surface of a deflection unit from an oblique direction with respect to a sub scanning direction;
• and
• a plurality of imaging optical systems for guiding the plurality of light beams deflected by the same deflection surface of the deflection unit to respective surfaces to be scanned which correspond to the plurality of light beams,
• in the plurality of imaging optical systems, such imaging optical elements that are arranged optically at the same position and have the same optical performance being configured to have different light beam passing states in the sub scanning direction, depending on the plurality of light beams corresponding to the respective surfaces to be scanned,
• the method of manufacturing imaging optical elements, comprising:
• measuring, with respect to the imaging optical elements having the same optical performance, the optical performance at each of a plurality of positions of the different light beam passing states;
• calculating a correction shape of an optical functional surface of the imaging optical element based on a deviation amount from a design value of the optical functional surface of the imaging optical element, the deviation amount being determined based on a plurality of pieces of measurement data obtained in the measurement of the optical performance;
• performing correction processing on a shape of a mirror-finish insert of a mold for molding, which corresponds to the optical functional surface of the imaging optical element, based on the correction shape of the optical functional surface obtained in the calculation of the correction shape;
• and
• performing molding by using the mirror-finish insert subjected to the correction processing.