Optical scanner and electrophotographic image forming apparatus

An electrophotographic image forming apparatus, comprising:

• an optical scanner, comprising:
• a light source, configured to emit a light beam;
• and
• an optical deflector, configured to deflect the light beam emitted from the light source;
• a first optical unit, arranged between the light source and the optical deflector, wherein the first optical unit includes a refraction unit and a diffraction unit, and wherein the light beam emitted from the light source sequentially passes through the refraction unit and the diffraction unit;
• and
• a second optical unit, arranged in a light exit direction of the optical deflector and configured to make the light beam deflected by the optical deflector form an image on a scanning target surface, wherein:
• a ratio of a refractive diopter Φr to a diffractive diopter Φd of the first optical unit in a main scanning direction is in a range of 0.3<Φr/Φd<0.5;
• and
• a ratio of a refractive diopter Φs to a diffractive diopter Φn of the first optical unit in a sub scanning direction is in a range of 0.7<Φs/Φn<1.0;
• and the electrophotographic image forming apparatus further comprising:
• a photosensitive unit capable of forming a latent image on a scanning target surface,
• a developing unit that develops the latent image on the photosensitive unit into a toner image,
• a transfer apparatus that transfers the toner image to a transfer medium, and
• a fixing apparatus that fixes the toner image on the transfer medium.