A lens assembly includes a first lens, a second lens, a third lens, and a fourth lens, wherein the first lens, the second lens, the third lens, and the fourth lens are arranged in order from an object side to an image side along an optical axis. The first lens is with positive refractive power and includes a convex surface facing the object side. The second lens is with negative refractive power and includes a concave surface facing the image side. The third lens is with refractive power and includes a convex surface facing the image side. The fourth lens is with refractive power. The lens assembly satisfies: FOV?56?, wherein FOV is a field of view of the lens assembly.

A lens assembly includes a first lens, a second lens, a third lens, and a fourth lens, wherein the first lens, the second lens, the third lens, and the fourth lens are arranged in order from an object side to an image side along an optical axis. The first lens is with positive refractive power and includes a convex surface facing the object side. The second lens is with negative refractive power and includes a concave surface facing the image side. The third lens is with refractive power and includes a convex surface facing the image side. The fourth lens is with refractive power. The lens assembly satisfies: FOV?56?, wherein FOV is a field of view of the lens assembly.

A projector including an image beam generator and a projecting lens is disclosed. The image beam generator is adapted to generate an image beam. The projecting lens includes a relay system and a projection system. The relay system is adapted to receive the image beam. The projection system includes a first lens and a second lens. A reflective coating is formed on a surface of the first lens. Whereby, the image beam generated by the image beam generator is transmitted through the second lens to the first lens, and reflected by the reflective coating of the first lens. Then, the image beam reflected by the first lens is transmitted through the second lens again and projected on an image plane.

A lens assembly for portable devices comprises: an aperture stop, a plastic first lens element with positive refractive power having a convex object-side surface; a plastic second lens element with negative refractive power having a concave image-side surface and an object-side surface being concave in a peripheral region; a plastic third lens element with negative refractive power having a concave object-side surface and a convex image-side surface; a plastic fourth lens element with positive refractive power having an image-side surface being concave in a paraxial region and convex in a peripheral region; and an IR-cut filter (infrared-cut filter); wherein the RI.sub.min represents the minimum RI (relative illumination) of effective field and it satisfies the following relation: 0.36<RI.sub.min<0.65.

A lens assembly for portable devices comprises: an aperture stop, a plastic first lens element with positive refractive power having a convex object-side surface; a plastic second lens element with negative refractive power having a concave image-side surface and an object-side surface being concave in a peripheral region; a plastic third lens element with negative refractive power having a concave object-side surface and a convex image-side surface; a plastic fourth lens element with positive refractive power having an image-side surface being concave in a paraxial region and convex in a peripheral region; and an IR-cut filter (infrared-cut filter); wherein the RI.sub.min represents the minimum RI (relative illumination) of effective field and it satisfies the following relation: 0.36<RI.sub.min<0.65.

A lens assembly for portable devices comprises: an aperture stop, a plastic first lens element with positive refractive power having a convex object-side surface; a plastic second lens element with negative refractive power having a concave image-side surface and an object-side surface being concave in a peripheral region; a plastic third lens element with negative refractive power having a concave object-side surface and a convex image-side surface; a plastic fourth lens element with positive refractive power having an image-side surface being concave in a paraxial region and convex in a peripheral region; and an IR-cut filter(infrared-cut filter);wherein the RI.sub.min represents the minimum RI(relative illumination) of effective field and it satisfies the following relation: 0.36<RI.sub.min<0.65.

A lens assembly for portable devices comprises: an aperture stop, a plastic first lens element with positive refractive power having a convex object-side surface; a plastic second lens element with negative refractive power having a concave image-side surface and an object-side surface being concave in a peripheral region; a plastic third lens element with negative refractive power having a concave object-side surface and a convex image-side surface; a plastic fourth lens element with positive refractive power having an image-side surface being concave in a paraxial region and convex in a peripheral region; and an IR-cut filter(infrared-cut filter);wherein the RI.sub.min represents the minimum RI(relative illumination) of effective field and it satisfies the following relation: 0.36<RI.sub.min<0.65.

An optical imaging system includes a first lens, a second lens, a third lens, and a fourth lens sequentially disposed from an object side toward an image side on an optical axis, and a reflecting member disposed closer to the object side, as compared to the first lens, and having a reflecting surface configured to change a path of light to be incident to the first to fourth lenses. The first to fourth lenses are disposed to be spaced apart from each other by a preset distance along the optical axis, and 1.3<TTL/BFL<3.5, where TTL is a distance from an object-side surface of the first lens to an imaging plane of an image sensor, and BFL is a distance from an image-side surface of the fourth lens to the imaging plane of the image sensor.

An optical imaging system includes a first lens, a second lens, a third lens, and a fourth lens sequentially disposed from an object side toward an image side on an optical axis, and a reflecting member disposed closer to the object side, as compared to the first lens, and having a reflecting surface configured to change a path of light to be incident to the first to fourth lenses. The first to fourth lenses are disposed to be spaced apart from each other by a preset distance along the optical axis, and 1.3<TTL/BFL<3.5, where TTL is a distance from an object-side surface of the first lens to an imaging plane of an image sensor, and BFL is a distance from an image-side surface of the fourth lens to the imaging plane of the image sensor.

An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens, sequentially disposed from an object side, wherein the first to fifth lenses are spaced apart from each other by predetermined distances along an optical axis in a paraxial region, the first lens and the second lens each have a non-circular shape when viewed in an optical axis direction, and the optical imaging system satisfies 0.62398<ZS1/ZS2<1.36318, where ZS1 is a ratio of an area of an object-side surface of the first lens to a distance from the object-side surface of the first lens to an imaging plane of an image sensor, and ZS2 is a ratio of an area of an object-side surface of the second lens to a distance from the object-side surface of the second lens to the imaging plane of the image sensor.