Patent ID: 8462189
Filing Date: 2013-06-11
Classification: H04N

Abstract:
1. An optical scanner used for an image-forming device to form a color image, the image-forming device having a plurality of photosensitive drums for superimposing a developer image formed on each of the plurality of photosensitive drums, comprising: a casing; a plurality of light sources in a one-to-one correspondence with the plurality of photosensitive drums, each of the plurality of light sources emitting a laser beam; a single deflector provided in the casing that deflects all of the laser beams to respective ones of the plurality of photosensitive drums, the single deflector being a rotatable polygon mirror having a plurality of reflecting surfaces, at least two of the plurality of reflecting surfaces simultaneously deflecting and angularly moving the laser beam, respectively; an optical system provided in the casing for guiding the deflected laser beam to a corresponding one of the plurality of photosensitive drums to make the laser beam scan the corresponding one of the plurality of photosensitive drums, the optical system further comprises a scanning lens that makes the laser beam scan on the corresponding one of the plurality of photosensitive drums at a constant linear velocity; a storage device that stores a characteristic related to the laser beam scanning the corresponding one of the photosensitive drums; and a single optical sensor for detecting the laser beam deflected and scanned by the deflector at a reference position, wherein one of the plurality of reflecting surfaces has a first normal to deflect the laser beam emitted from one of the plurality of light sources to the single optical sensor, another of the plurality of reflecting surfaces has a second normal to deflect the laser beam emitted from another of the plurality of light sources toward an opposite side of the single optical sensor with respect to the rotatable polygon mirror, and an angle formed by the first normal and the second normal satisfies a following formula: where n is a number of the plurality of reflecting surfaces, m is a natural number within a range of 1≦m≦(n−1), and Δθ is a manufacture error angle (rad) of adjacent ones of the plurality of reflecting surfaces; and Δθ has an absolute value less than 25.4/(r×f), where f is a focal length (mm) of the scanning lens, and r is a resolution (dpi).