| 摘要 |
An optical device includes a scanning means, a first image-formation optical system, and a second image-formation optical system. A system for a device, such as the one in which images are formed by scanning with this optical device. The scanning means scans a light beam emitted from a light source. The first image-formation optical system forms the light beam, scanned by the scanning means, into an image in a first spot diameter with respect to the scanning direction, on a surface to be scanned. The second image-formation optical system utilizes the first image-formation optical system and at least part of an optical system for forming the light beam scanned, by the scanning means, into an image in a second spot diameter which is different from the first spot diameter, with respect to the scanning direction, on the surface to be scanned. The first image-formation optical system scans the surface to be scanned within a first scanning range, whereas the second image-formation optical system scans the surface to be scanned within a second scanning range which is different from the first scanning range.
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