Visual optical system
A visual optical system comprises a first optical system and a second optical system. The first optical system comprises a first lens having a positive refractive power, a reflective polarizing element, a quarter-wave plate, a second lens having a refractive power and a third lens having a positive refractive power. The second optical system comprises, sequentially along a second optical axis from the first side to the second side, first to sixth lens elements. An effective focal length f3′ of the third lens, a distance TD′ from a first-side surface of the first lens to a second-side surface of the third lens on the first optical axis, an effective focal length f1 of the first lens element and a distance TD from a first-side surface of the first lens element to a second-side surface of the sixth lens element on the second optical axis satisfy: 1.9<(f3′/TD′)/(|f1|/TD)<5.7.
1 . A visual optical system, comprising: a first optical system and a second optical system,
wherein the first optical system comprises, sequentially along a first optical axis from a first side to a second side, a first lens having a positive refractive power, a reflective polarizing element, a quarter-wave plate, a second lens having a refractive power, and a third lens having a positive refractive power, and
the second optical system comprises, sequentially along a second optical axis from the first side to the second side,
a first lens element having a refractive power;
a second lens element having a refractive power;
a third lens element having a refractive power;
a fourth lens element having a refractive power;
a fifth lens element having a positive refractive power; and
a sixth lens element having a refractive power,
wherein a number of lens elements in the second optical system is 6, and
an effective focal length f3′ of the third lens, a distance TD′ from a first-side surface of the first lens to a second-side surface of the third lens on the first optical axis, an effective focal length f1 of the first lens element, and a distance TD from a first-side surface of the first lens element to a second-side surface of the sixth lens element on the second optical axis satisfy: 1.9<(f3′/TD′)/(|f1/TD)<5.7.
2 . The visual optical system according to claim 1 , wherein the effective focal length f3′ of the third lens, a radius of curvature R6′ of the second-side surface of the third lens, the effective focal length f1 of the first lens element, and a radius of curvature R1 of the first-side surface of the first lens element satisfy: −0.8<(f3′/R6′)/(f1/R1)<−0.2.
3 . The visual optical system according to claim 1 , wherein a refractive index N3′ of the third lens, a refractive index N1 of the first lens element, and a total effective focal length f of the visual optical system satisfy: 1.1 mm<(N3′/N1)×f<1.8 mm.
4 . The visual optical system according to claim 1 , wherein an abbe number V3′ of the third lens, an abbe number V1 of the first lens element, and an abbe number V2 of the second lens element satisfy: 0.4<V3′/(V1+V2)<1.5.
5 . The visual optical system according to claim 1 , wherein an effective focal length f1′ of the first lens and a radius of curvature R2′ of a second-side surface of the first lens satisfy: −2.4<f1′/R2′<−0.6.
6 . The visual optical system according to claim 1 , wherein a radius of curvature R3′ of a first-side surface of the second lens and an effective focal length f2′ of the second lens satisfy: 0.4<R3′/f2′<0.8.
7 . The visual optical system according to claim 1 , a center thickness CT1′ of the first lens on the first optical axis, a center thickness CTR of the reflective polarizing element on the first optical axis, a center thickness CTQ of the quarter-wave plate on the first optical axis, and a total effective focal length f of the visual optical system satisfy: 2.1<(CT1′+CTR+CTQ)/f<3.8.
8 . The visual optical system according to claim 1 , wherein a center thickness CT2′ of the second lens on the first optical axis, a center thickness CT3′ of the third lens on the first optical axis, and a total effective focal length f of the visual optical system satisfy: 4.9<(CT2′+CT3′)/f<7.9.
9 . The visual optical system according to claim 1 , the distance TD′ from the first-side surface of the first lens to the second-side surface of the third lens on the first optical axis and a center thickness CT3′ of the third lens on the first optical axis satisfy: 1.5<TD′/CT3′<2.2.
10 . The visual optical system according to claim 1 , wherein an effective focal length f5 of the fifth lens element and a total effective focal length f of the visual optical system satisfy: 0.5<f5/f<1.4.
11 . The visual optical system according to claim 1 , wherein an effective focal length f4 of the fourth lens element and an effective focal length f2 of the second lens element satisfy: −1.7<f4/f2<−0.2.
12 . The visual optical system according to claim 1 , wherein a radius of curvature R1 of the first-side surface of the first lens element and a radius of curvature R2 of the second-side surface of the first lens element satisfy: 0.2<R1/R2<0.8.
13 . The visual optical system according to claim 1 , wherein a radius of curvature R5 of a first-side surface of the third lens element and a radius of curvature R4 of a second-side surface of the second lens element satisfy: 0.1<R5/R4<1.8.
14 . The visual optical system according to claim 1 , wherein a center thickness CT4 of the fourth lens element on the second optical axis, an abbe number V4 of the fourth lens element, a center thickness CT5 of the fifth lens element on the second optical axis, and an abbe number V5 of the fifth lens element satisfy: 0.1<(V4/V5)×(CT4/CT5)<1.7.
15 . The visual optical system according to claim 1 , wherein the distance TD from the first-side surface of the first lens element to the second-side surface of the sixth lens element on the second optical axis and a total effective focal length f of the visual optical system satisfy: 1.0<TD/f<2.1.
16 . The visual optical system according to claim 1 , wherein a radius of curvature R12 of the second-side surface of the sixth lens element and an effective focal length f6 of the sixth lens element satisfy: −0.8<R12/f6<−0.1.
17 . The visual optical system according to claim 1 , wherein a display screen is provided at a second side of the visual optical system, and the second optical system is positioned between the first optical system and the display screen.
18 . The visual optical system according to claim 1 , wherein an angle θ between the second optical axis and the first optical axis satisfies: 0°<θ<90°.