Micro-lens module
A micro-lens module including a first lens, a second lens, and an aperture stop is provided. The first lens is disposed between an object side and an image side, wherein a first surface of the first lens facing the object side is an aspheric surface, and the curvature radius of the aspheric surface is R 1 . The second lens is disposed between the first lens and the image side, wherein a second surface of the second lens facing the image side is an aspheric surface, and the curvature radius of the aspheric surface is R 2 . The aperture stop is disposed between the first lens and the second lens, wherein the distance from the first surface to the aperture stop is d 1 , and the distance from the second surface to the aperture stop is d 2 . The micro-lens module satisfies 6>d 2 /d 1 >2.5 and −2.5<R 1 /R 2 <1.5.
1. A lens module, comprising:
a first lens, disposed between an object side and an image side, wherein a first surface of the first lens facing the object side is an aspheric surface, and a curvature radius of the first surface is R 1 ;
a second lens, disposed between the first lens and the image side, wherein a second surface of the second lens facing the image side is an aspheric surface, and a curvature radius of the second surface is R 2 ;
a light transmissive device, wherein the first lens and the second lens are respectively leaned against two opposite sides of the light transmissive device; and
an aperture stop, disposed between the first lens and the second lens, wherein a distance from the first surface to the aperture stop is dl, and a distance from the second surface to the aperture stop is d 2 ,
wherein the lens module satisfies 6>d 2 /d 1 >2.5 and −2.5<R 1 /R 2 <1.5, an effective focal length (EFL) of the lens module is f, and the lens module satisfies 0.8<f<1.6, and a material refractive index of the first lens and the second lens is n d , and 1.62>n d >1.48,
wherein the first surface and the second surface are even aspheric surfaces, and which are respectively expressed as:
Z
=
cr
2
1
+
1
-
(
1
+
k
)
c
2
r
2
+
α
1
r
2
+
a
2
r
4
+
α
3
r
6
+
α
4
r
8
+
α
5
r
10
+
α
6
r
12
+
α
7
r
14
+
α
8
r
16
.
wherein α 1 to α 8 are aspheric coefficients, and the first surface and the second surface satisfy α 1 =0.
2. The lens module according to claim 1 , wherein the first surface is a convex surface, and the first lens is a plano-convex lens having the convex surface facing the object side.
3. The lens module according to claim 1 , wherein the second surface is a convex surface, and the second lens is a plano-convex lens having the convex surface facing the image side.
4. The lens module according to claim 1 , further comprising a optical detector, wherein the lens module is sequentially composed of the first lens, the aperture stop, the second lens, and the optical detector from the object side to the image side.