SCAN OPTICAL SYSTEM, LIGHT SCAN DEVICE, AND IMAGE FORMATION DEVICE

摘要

In order to minimize the device size and suppress lowering of the transmittance caused by pollution, a scan optical system includes: a light source device (1) which emits a light flux having a wavelength of 500 nm or below; a deflection optical system (5) which deflects the light flux from the light source device (1) and performs scan in the main scan direction y; and a scan image formation optical system (8) which forms an image on a plane H to be scanned, from the light flux deflected by the deflection optical system (5). The scan image formation optical system (8) has a first lens (6) which is arranged adjacent to the deflection optical system (5) and formed from a plastic based on a resin containing an alicyclic structure. When NA1 is the numerical aperture of the light flux coming into the deflection optical system (5) in the sub-scan direction z and t1 [mm] is the distance between the deflection optical system (5) and the first lens (6), the following relationship is satisfied: 0.05 = NA1 t1 = 1.5