| 摘要 |
PURPOSE: To provide a light beam scanning optical system capable of making a spherical mirror small while assuring good scanning performance. CONSTITUTION: This light beam scanning optical system has a polygon mirror K which deflects a light beam at an equal angular speed, the spherical mirror M of which the surface shape in a main scanning direction is a spherical face directing its concave face toward the polygon mirror K and which reflects the light beam to condense the light beam onto the plane N to be scanned and a positive meniscus lens L of which the shape in the main scanning direction directs its concave face toward the polygon mirror K. The optical system satisfies the condition equations: 0.15<2.d13 /-|CRM|<0.45, 0.05<d11 /|CRM|<0.1, 0.1<d11 )/d2 <0.2 (CRM: the radius of curvature in the main scanning direction of the spherical mirror, d11 : the distance from the deflection point of a deflector to the front face of the lens, d13 : the distance from the rear face of the lens to the spherical mirror, d2 : the distance from the spherical mirror to the plane to be scanned). |
