Patent ID: 7852566

Claim:
A single fθ lens used for a micro-electro mechanical system (MEMS) laser scanning unit, applied in a MEMS laser scanning unit, which the MEMS laser scanning unit comprising a light source for emitting laser beam, a MEMS reflecting mirror for reflecting laser beam emitted by a light source into a scanning light by resonant oscillation, and a target provided for sensing light; wherein, the single fθ lens being a lens in a meniscus shape and having a concave surface on the side of the MEMS reflecting minor, comprising a first optical surface and a second optical surface, at least one optical surface is aspherical surface in both main scanning direction and sub scanning direction; said the single fθ lens converting the non-linear relation of reflecting angle with time into a linear relation between the distance of the scan spot with time and focusing the scanning light to form an image at the target; wherein the main scanning direction satisfies the condition of 0 < d 3 f Y < 0.6 ; wherein, f y is the focal length of the single fθ lens in the main scanning direction, and d 3 is the distance from the second optical surface to the target side on the optical axis Z.