Optical scanner

An optical scanner in which a divergent light beam emitted from a laser diode light source is changed by an anamorphic optical system to a parallel or weak convergent light beam in a main scan-corresponding direction and a convergent light beam in a cross scan-corresponding direction, and a portion of the light beam is interrupted by an aperture and the light beam of a light emitting section of said laser diode light source is focused and formed as a linear image extending in the main scan-corresponding direction and is then deflected by a rotary polygon mirror, and the deflected light beam is converged by an image-forming optical system toward a scanned face to obtain a light spot on the scanned face and optically scan the scanned face by this light spot;

• said image-forming optical system approximately setting the position of a deflecting/reflecting face of the rotary polygon mirror and a position of the scanned face in a conjugate relation in geometrical optics in the cross scan-corresponding direction;
• said image-forming optical system having a function for converging said deflected light beam onto the scanned face in the main scan-corresponding direction;
• and
• an opening diameter and an arrangement position of the aperture, and a focal length and an arrangement position of the anamorphic optical system in the cross scan-corresponding direction being determined such that
• a real image of the aperture formed by an image-forming element arranged between said aperture and the scanned face is located on a side of the rotary polygon mirror with respect to the scanned face in an entire effective scanning range;
• the image of the light emitting section of the laser diode light source formed by the image-forming element between said laser diode light source and the scanned face is located on a side opposite to the real image of said aperture with respect to the scanned face in the entire effective scanning range;
• and
• a waist position of the deflected light beam is located between the image of the light emitting section and the real image of the aperture on the side of the rotary polygon mirror with respect to the scanned face.

An optical scanner in which a divergent light beam emitted from a laser diode light source is changed by an anamorphic optical system to a parallel or weak convergent light beam in a main scan-corresponding direction and a convergent light beam in a cross scan-corresponding direction, and a portion of the light beam is interrupted by an aperture and the light beam of a light emitting section of said laser diode light source is focused and formed as a linear image extending in the main scan-corresponding direction and is then deflected by a rotary polygon mirror, and the deflected light beam is converged by an image-forming optical system toward a scanned face to obtain a light spot on the scanned face and optically scan the scanned face by this light spot;

• said image-forming optical system approximately setting the position of a deflecting/reflecting face of the rotary polygon mirror and a position of the scanned face in a conjugate relation in geometrical optics in the cross scan-corresponding direction;
• said image-forming optical system having a function for converging said deflected light beam onto the scanned face in the main scan-corresponding direction;
• the optical scanner being constructed such that a real image of the aperture formed by an image-forming element arranged between said aperture and the scanned face is located on a side of the rotary polygon mirror with respect to the scanned face in an entire effective scanning range;
• and
• an opening diameter and an arrangement position of the aperture, and a focal length and an arrangement position of the anamorphic optical system in the cross scan-corresponding direction being determined such that the following condition, ##EQU5## is satisfied where .sqroot. [ ] means a square root of a value within the bracket [ ];
• R designates a distance between a position of said real image and a position of the image of the light emitting section of the laser diode light source formed by the image-forming element between said laser diode light source and the scanned face;
• D designates a diameter of an opening image in the cross scan-corresponding direction with respect to the real image of said aperture;
• and
• .lambda. designates a light emitting wavelength of the laser diode light source.