Patent ID: 8031388
Filing Date: 2011-10-04
Classification: G02B

Abstract:
1. A two-element fθ lens used for a micro-electro mechanical system (MEMS) laser scanning unit, said MEMS laser scanning unit comprising a light source for emitting laser beam, a MEMS reflecting mirror for reflecting said laser beam emitted by said light source into a scanning light by resonant oscillation, and a target provided for sensing light, said two-element fθ lens being disposed between said target and said MEMS reflecting mirror, said two-element fθ lens comprising: a first lens, in a positive refraction meniscus shape, and having a convex surface toward said MEMS reflecting mirror; and a second lens, in a positive refraction meniscus shape, and having a convex surface toward said MEMS reflecting mirror, located between said first lens and said target; wherein, said first lens included a first optical surface and a second optical surface, at least one of said optical surfaces is an aspherical surface in both main scanning direction and sub scanning direction of said MEMS laser scanning unit; wherein, said second lens included a third optical surface and a fourth optical surface, at least one of said optical surfaces is an aspherical surface in both main scanning direction and sub scanning direction of said MEMS laser scanning unit; wherein, said two-element fθ lens converts the non-linear relation of reflecting angle with time of said scanning light into a linear relation between the distance of the scan spot with time and focusing the scanning light to form an image at said target.