BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to an optical area, and more particularly to a lens.

Description of the Related Art

Many electronic devices (e.g. mobile phone or tablet) are currently provided with front camera lens.FIG. 1is a schematic diagram of a prior lens assembly100.FIG. 2is a partially sectional view of the prior lens assembly100. As shown inFIGS. 1-2, the lens assembly100includes a lens body101and a plurality of lenses disposed in the lens body101, wherein the lens closest to an object side of the lens assembly100is a first lens102. The first lens102is entirely surrounded by the lens body101. The lens body101has an end surface directed at the object side, and the first lens102has an effective-diameter region in which a top point is lower than the end surface of the lens body101directed at the object side. In the lens assembly100, the first lens102occupies much space in the lens body101and has a limited view angle, and the lens device100is somewhat thick because the first lens102is entirely surrounded by the lens body101.

BRIEF SUMMARY OF THE INVENTION

The invention provides a lens assembly to solve the above problems. The lens assembly of the invention is provided with characteristics of a decreased total lens length, a decreased volume, a decreased thickness, and an increased view angle, and still has a good optical performance.

A lens assembly in accordance with an embodiment of the invention includes a lens body and a plurality of lenses. The lens body includes a lens barrel. The plurality of lenses includes a first lens, a second lens, a third lens and a fourth lens, wherein the first lens is closest to the object side. The first lens, the second lens, the third lens and the fourth lens are fixed in the lens body in order from the object side to an image side along an optical axis. The first lens includes an object side surface and an image side surface, the object side surface is protruded along the optical axis, the first lens in a cross section is higher at a middle than at both sides so that the first lens is protruded at the middle towards the object side to form a pillar. The first lens further includes a first portion close to the object side and a second portion close to the image side, and a diameter of the first portion is smaller than a diameter of the second portion so that a step is formed between the first portion and the second portion. The lens assembly further includes a lens minor diameter portion close to the object side and a lens major diameter portion close to the image side, the lens minor diameter portion is different to the lens major diameter portion in diameter, and the lens assembly satisfies: 0<A/B<0.3, where A is a maximal outer diameter of the first portion of the first lens, and B is a maximal outer diameter of the lens major diameter portion of the lens assembly.

In another embodiment, the first lens further includes an optical effective diameter portion and an edge portion for the first lens to be supported and fixed, and the lens assembly satisfies: 0.19≤A/B≤0.28, where A is the maximal outer diameter of the first portion of the first lens, and B is the maximal outer diameter of the lens major diameter portion of the lens assembly.

In yet another embodiment, the lens barrel includes a major diameter portion close to the image side and a minor diameter portion close to the object side, a stepped surface is formed between the major diameter portion and the minor diameter portion, the lens minor diameter portion is formed by the minor diameter portion of the lens barrel, and the lens major diameter portion is formed by the major diameter portion of the lens barrel.

In another embodiment, the edge portion of the first lens is fixed in the major diameter portion of the lens barrel, and the optical effective diameter portion is inside the minor diameter portion of the lens barrel.

In yet another embodiment, the lens assembly further includes a cover connected to an object end of the lens barrel, wherein the cover has an opening and forms a stop structure in front of the object side surface of the first lens.

In another embodiment, the object side surface of the first lens is flushed or is lower than an object side surface of the cover, the lens barrel and the cover are integrally formed as a continuous-unity piece, and the opening of the cover is in a shape of circle, polygon, non-circle, polygon with sides arranged symmetrically to the optical axis, bottle or oak barrel.

In yet another embodiment, the lens barrel includes an end surface facing the object side, the end surface is provided with a first lens fixing hole, the edge portion is fixed in the lens barrel, and a part of the optical effective diameter portion is projected from the first lens fixing hole.

In another embodiment, the lens minor diameter portion is formed by the part of the optical effective diameter portion of the first lens, the lens major diameter portion is formed by the lens barrel, and an edge of the object side surface of the first lens is provided with a stop structure of the lens assembly.

In yet another embodiment, the lens assembly further satisfies at least one of following conditions: 0<A≤2.2 mm; h≥0.8 mm; 0.8>h/H≥0.22; and 0<S1/S2<0.25, where h is a thickness of the lens minor diameter portion along the optical axis, H is a thickness of the lens assembly along the optical axis, S1is an area of a cross section of the lens minor diameter portion, and S2is an area of a cross section of the lens major diameter portion.

In another embodiment, the lens minor diameter portion is in a shape of circle, polygon, non-circle, polygon with sides arranged symmetrically to the optical axis, bottle or oak barrel. The lens major diameter portion is in a shape of circle, polygon, non-circle, polygon with sides arranged symmetrically to the optical axis, bottle or oak barrel.

In yet another embodiment, the object side surface of the first lens is convex surface, f1is a focal length of the first lens, L1D is an optical effective diameter of the object side surface of the first lens, L1T is a distance from the object side surface of the first lens to the image side surface of the first lens along the optical axis, EFL is an effective focal length of the lens assembly, TTL is a distance from the object side surface of the first lens to an imaging plane along the optical axis, ALT is a sum of thicknesses of the lenses along the optical axis, C is a maximal outer diameter of the lens minor diameter portion, and the lens assembly further satisfies at least one of the following conditions: 0<f1/L1T<5; 0.8<L1D/L1T<1.7; 1<EFL/L1T<4; 1.9<EFL/L1D<2.6; 2 mm<(L1D+L1T)<5 mm; 3<(EFL+TTL)/L1T<9; 1.5<ALT/L1T<3.5; 0<C/B≤0.38.

In another embodiment, the lens assembly further includes a fifth lens with positive refractive power, wherein the fifth lens is disposed between the first lens and the second lens, the object side surface of the first lens is convex surface, the second lens includes an object side surface and an image side surface, the fifth lens includes an object side surface and an image side surface, the image side surface of the fifth lens is convex surface.

In yet another embodiment, the lens assembly further satisfies: 0.29 mm<L1T−L5T−L2T<0.89 mm, wherein L1T is a distance from the object side surface of the first lens to the image side surface of the first lens along the optical axis, L2T is a distance from the object side surface of the second lens to the image side surface of the second lens along the optical axis, L5T is a distance from the object side surface of the fifth lens to the image side surface of the fifth lens along the optical axis.

In another embodiment, the object side surface of the first lens is convex surface, the third lens includes an object side surface and an image side surface, the fourth lens includes an object side surface and an image side surface, the third lens is with positive refractive power, the image side surface of the third lens is convex surface, and the image side surface of the fourth lens is concave surface.

In yet another embodiment, the lens assembly includes a lens body and a plurality of lenses. The lens body includes a lens barrel. The plurality of lenses includes a first lens, a second lens, a third lens and a fourth lens, all of which are fixed in the lens body in order from an object side to an image side along an optical axis. The first lens is with positive refractive power and includes an object side surface and an image side surface. The second lens is with negative refractive power. The third lens is with refractive power. The fourth lens is with negative refractive power. The lens assembly satisfies: 2.5 mm2<G1×f1<8 mm2, where f1is a focal length of the first lens, and G1is a distance along the optical axis from a central point of the object side surface of the first lens to an edge of an effective diameter of the image side surface of the first lens. The lens assembly further includes a lens minor diameter portion close to the object side and a lens major diameter portion close to the image side, and the lens minor diameter portion is different to the lens major diameter portion in diameter.

A detailed description is given in the following embodiments with reference to the accompanying drawings.

