Method and apparatus for multi-beam optical scanning capable of effectively adjusting a scanning line pitch

摘要

An optical scanning apparatus includes light sources, an aperture having, and coupling lenses. Numbers of the light sources and the coupling lenses are equal to each other and the apparatus satisfies an inequality 12.7<(Dxbeta₀xm₀xdpi)/(2xNA)<38.1 and an equation beta₀=(beta₊-beta_-)/(n-1), wherein D represents a width of the slit of the aperture, beta₀ represents a beam open angle, mo represents a total lateral magnification ratio, dpi represents a number of dots per inch, NA represents a numerical aperture, beta₊ represents a positive open angle, beta_- represents a negative open angle, and n represents the number. Further, an image forming apparatus using this optical scanning apparatus and an image forming method are provided.