Optical system for laser beam scanner

An optical system for a laser beam scanner, comprising:

• a light source for generating a laser beam,
• a rotary polyhedron for directing the laser beam from said light source to a compensating lens array,
• said compensating lens array including a concave lens for receiving the laser beam from said rotary polyhedron and a convex lens attached with a holographic optical element for compensating the laser beam reflected from the rotary polyhedron and scanning the compensated laser beam to a drum, and
• wherein said holographic optical element is manufactured using a first and a second cylindrical lens having powers which cross at right angles and the holographic element is attached to the convex lens so as to satisfy the equations ##EQU3## where, HF1 is a focus distance of the holographic optical element at the scanning plane, HF2 is a focus distance of the holographic optical element at a plane perpendicular to the scanning plane, N is a refractive index of the convex lens, F1 is a distance between the focus of the first cylindrical lens and the holographic optical element at the scanning plane, F2 is a distance between the focus of the second cylindrical lens and the holographic optical element at a plane perpendicular to the scanning plane, T is a thickness of the convex lens, R2 is a radius of curvature of the convex lens at the scanning plane, and R2' is a radius of curvature of the convex lens at a plane perpendicular to the scanning plane.