BEAM SHAPING OPTICAL SYSTEM AND OPTICAL SYSTEM OF LASER BEAM PRINTER

摘要

There is provided an axially asymmetric beam shaping optical system causing no astigmatism for variation in refractive index incident to an external cause, e.g. variation in wavelength of a light source or variation in ambient temperature. The system has a diffraction grating plane as follows. Assuming the optical axis is the z-axis and a plane perpendicular to the optical axis is the xy plane, the phase function in the x-axis direction and the y-axis direction of the diffraction grating plane is determined to minimize astigmatism by equalizing variation in distance from the light source to an image forming point or a virtual image point on the xz plane and variation in that distance on the yz plane. Furthermore, the system has a diffraction grating plane as follows. The phase function in the x-axis direction and the y-axis direction of the diffraction grating plane is determined to minimize astigmatism by equalizing variation in distance from the light source to the image forming point or the virtual image point on the xz plane and variation in that distance on the yz plane for temperature variation.