US 2009/0244672 A1Published application

Two-Element F-Theta Lens Used For Micro-Electro Mechanical System (MEMS) Laser Scanning Unit

AssigneeE-Pin Optical Industry Co., Ltd.

InventorsBo-Yuan Shih, Shon-Woei Shyu

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Abstract

A two-element f-θ lens used for a micro-electro mechanical system (MEMS) laser scanning unit includes a first lens and a second lens, both in a meniscus shape having a concave surface facing the side of the MEMS reflecting mirror. The two-element f-θ lens comprising a first lens with a first optical surface and a second optical surface and a second lens with a third optical surface and a fourth optical surface, both in a meniscus shape and having a concave surface on the side of the MEMS reflecting mirror; at least one optical surface is aspherical surface in both main scanning direction and sub scanning direction, and satisfies specifical optical conditions. The two-element f-θ lens corrects the nonlinear relationship between scanned angle and the time into the linear relationship between the image spot distances and the time. Meanwhile, the two-element f-θ lens focuses the scan light to the target in the main scanning and sun scanning directions, such that the purpose of the scanning linearity effect and the high resolution scanning can be achieved.

Claims5

Dependent claims

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 meniscus shape, and having a concave surface toward said MEMS reflecting mirror;
and
a second lens, in a meniscus shape, and having a concave 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.

3 more elements

Dependencies are inferred from the claim text.