Collimator lens system
A collimator lens system includes a first lens, a second lens, a third lens and a diaphragm from an object side to an image side of the system in turn along an optical axis, in which the first lens is of a positive focal power, and an object side surface thereof is convex; the second lens is of a negative focal power; the third lens is of a positive focal power, and an image side surface thereof is convex; optical centers of all the lenses are arranged along a same straight line, the system meets following formulas: f12>f3; (dn/dt)1<−50×10 −6 /° C.; (dn/dt)2<−50×10 −6 /° C.; (dn/dt)3>−10×10 −6 /° C., where f12 represents a combined focal length of the first and second lenses, f3 represents a focal length of the third lens, and (dn/dt)1, (dn/dt)2, and (dn/dt)3 represent change rates of refractive indices of the first lens, the second lens and the third lens with temperature, respectively.
1. A collimator lens system, comprising a first lens, a second lens, a third lens and a diaphragm from an object side to an image side of the collimator lens system in turn along an optical axis of the collimator lens system, wherein
the first lens is of a positive focal power, an object side surface of the first lens is convex;
the second lens is of a negative focal power;
the third lens is of a positive focal power, an image side surface of the third lens is convex;
optical centers of the first lens, the second lens and the third lens are arranged along a same straight line,
the collimator lens system meets following formulas:
f 12> f 3;
(dn/dt)1<−50×10 −6 /° C.;
(dn/dt)2<−50×10 −6 /° C.;
(dn/dt)3>−10×10 −6 /° C.,
where f12 represents a combined focal length of the first lens and the second lens, f3 represents a focal length of the third lens, (dn/dt)1 represents a change rate of a refractive index of the first lens with temperature, (dn/dt)2 represents a change rate of a refractive index of the second lens with temperature, and (dn/dt)3 represents a change rate of a refractive index of the third lens with temperature.
2. The collimator lens system according to claim 1 , wherein the collimator lens system meets a following formula:
0< f 3/ f 1<3.5,
where f3 represents the focal length of the third lens, and f1 represents a focal length of the first lens.
3. The collimator lens system according to claim 2 , wherein object side surfaces and image side surfaces of the first lens, the second lens and the third lens are aspheric surfaces.
4. The collimator lens system according to claim 2 , wherein the first lens and the second lens comprise a plastic, and the third lens comprises glass.
5. The collimator lens system according to claim 1 , wherein the collimator lens system meets a following formula:
−5< f/r 6<0,
where f represents a focal length of the collimator lens system, and r 6 represents a curvature radius of the image side surface of the third lens.
6. The collimator lens system according to claim 5 , wherein object side surfaces and image side surfaces of the first lens, the second lens and the third lens are aspheric surfaces.
7. The collimator lens system according to claim 5 , wherein the first lens and the second lens comprise a plastic, and the third lens comprises glass.
8. The collimator lens system according to claim 1 , wherein the collimator lens system meets a following formula:
−5.5< r 1/ r 6<0,
where r1 represents a curvature radius of the object side surface of the first lens, and r 6 represents a curvature radius of the image side surface of the third lens.
9. The collimator lens system according to claim 8 , wherein object side surfaces and image side surfaces of the first lens, the second lens and the third lens are aspheric surfaces.
10. The collimator lens system according to claim 8 , wherein the first lens and the second lens comprise a plastic, and the third lens comprises glass.
11. The collimator lens system according to claim 1 , wherein the collimator lens system meets a following formula:
0.5<CT3/CT2<7.5,
where CT2 represents a central thickness of the second lens, and CT3 represents a central thickness of the third lens.
12. The collimator lens system according to claim 11 , wherein object side surfaces and image side surfaces of the first lens, the second lens and the third lens are aspheric surfaces.
13. The collimator lens system according to claim 11 , wherein the first lens and the second lens comprise a plastic, and the third lens comprises glass.
14. The collimator lens system according to claim 1 , wherein object side surfaces and image side surfaces of the first lens, the second lens and the third lens are aspheric surfaces.
15. The collimator lens system according to claim 14 , wherein each aspheric surface of the first lens, the second lens and the third lens in the collimator lens system meets a following formula:
z
=
ch
2
1
+
1
-
(
1
+
K
)
c
2
h
2
+
Bh
4
+
Ch
6
+
Dh
8
+
Eh
10
+
Fh
12
,
where z represents a distance between a surface and a tangent plane of a vertex of the surface in a direction of the optical axis, c represents a curvature of the vertex of the surface, K represents a 2 nd order correction coefficient, h represents a height from the surface to the optical axis, B, C, D, E and F represent 4 th , 6 th , 8 th , 10 th and 12 th order correction coefficients, respectively.
16. The collimator lens system according to claim 1 , wherein the first lens and the second lens comprise a plastic, and the third lens comprises glass.
17. The collimator lens system according to claim 1 , wherein the first lens, the second lens and the third lens are non-bonded and independent from each other.