Optical system and image pickup apparatus
An optical system includes, in order from an object side to an image side, a first unit and a second unit. The first unit includes a first substrate, and a first lens having a negative refractive power and disposed on the image side of the first substrate. The second unit includes a second substrate, and a second lens having a positive refractive power and disposed on the image side of the second substrate. An absolute value of the refractive power on an optical axis of the second lens is larger than that of the first lens. A surface on the image side of the first lens is an aspheric surface. In the aspheric surface of the first lens, a refractive power at an outermost peripheral portion of an effective area is smaller than a refractive power on the optical axis.
1. An optical system comprising: a first unit,
a second unit disposed on an image side of the first unit, and
a diaphragm disposed on the image side of the first unit,
wherein the first unit includes a first substrate, and a first lens having a negative refractive power and disposed on the image side of the first substrate,
wherein the second unit includes a second substrate, and a second lens having a positive refractive power and disposed on the image side of the second substrate,
wherein an absolute value of the refractive power on an optical axis of the second lens is larger than that of the first lens,
wherein an image side surface of the first lens is an aspheric surface,
wherein in the aspheric surface of the first lens, a refractive power at an outermost peripheral portion in an effective area is smaller than a refractive power on the optical axis, and
wherein the following inequality is satisfied:
1.00< R 1 e/d 1<30.00
where R 1 e is a radius of a curvature of the outermost peripheral portion in the effective area of the first lens, and d1 is a distance on the optical axis from the image side surface of the first lens to the diaphragm.
2. The optical system according to claim 1 , wherein the following inequality is satisfied:
1.10<| P 2/ P 1|<8.00
where P 1 is the refractive power of the first lens on the optical axis, and P 2 is the refractive power of the second lens on the optical axis.
3. The optical system according to claim 1 , wherein the following inequality is satisfied:
1.50<| rp 1|<20.00
where rp1 is a refractive power ratio on the optical axis to the outermost peripheral portion in the effective area of the first lens.
4. The optical system according to claim 1 , wherein an image side surface of the second lens is an aspheric surface, and
wherein in the aspherical surface of the second lens, a refractive power at an outermost peripheral portion in an effective area is smaller than a refractive power on the optical axis.
5. The optical system according to claim 1 , wherein the following inequality is satisfied:
1.25<| rp 2|<10.00
where rp2 is a refractive power ratio on the optical axis to the outermost peripheral portion in the effective area of the second lens.
6. The optical system according to claim 1 , wherein the diaphragm is disposed on the second substrate.
7. The optical system according to claim 1 , wherein the following inequality is satisfied:
0.53< d 0/ R 1<5.00
where d0 is a distance on the optical axis from an object side surface of the first unit to the diaphragm, and R 1 is a radius of curvature on the optical axis of the first lens.
8. The optical system according to claim 1 , wherein the following inequality is satisfied:
1.40< N 1<1.65
where N 1 is a refractive index of the first lens for d-line.
9. The optical system according to claim 1 , wherein the following inequality is satisfied:
1.40< N 2<1.65
where N 2 is a refractive index of the second lens for d-line.
10. The optical system according to claim 1 , wherein the following inequality is satisfied:
40<ν1<80
where ν1 is an Abbe number of the first lens based on d-line.
11. The optical system according to claim 1 , wherein the following inequality is satisfied:
40<ν2<80
where ν2 is an Abbe number of the second lens based on d-line.
12. The optical system according to claim 1 , wherein refractive indexes of the first substrate and the first lens are different from each other.
13. The optical system according to claim 1 , wherein refractive indexes of the second substrate and the second lens are different from each other.
14. The optical system according to claim 1 , wherein the first substrate is a flat substrate, the first lens is a plano-concave lens, and the first lens is disposed in close contact with the first substrate, and
wherein the second substrate is a flat substrate, the second lens is a plano-convex lens, and the second lens is disposed in close contact with the second substrate.
15. An image pickup apparatus comprising:
an optical system according to claim 1 ; and
an image sensor configured to receive an image formed by the optical system,
wherein the optical system includes, in order from an object side to an image side, a first unit and a second unit.
16. An optical system comprising:
a first unit,
a second unit disposed on an image side of the first unit, and
diaphragm disposed on the image side of the first unit,
wherein the first unit includes a first substrate, and a first lens having a negative refractive power and disposed on the image side of the first substrate,
wherein the second unit includes a second substrate, and a second lens having a positive refractive power and disposed on the image side of the second substrate,
wherein an absolute value of the refractive power on an optical axis of the second lens is larger than that of the first lens,
wherein an image side surface of the first lens is an aspheric surface,
wherein in the aspheric surface of the first lens, a refractive power at an outermost peripheral portion in an effective area is smaller than a refractive power on the optical axis, and
wherein the following inequality is satisfied:
0.53< d 0/ R 1<5.00 (6)
where d0 is a distance on the optical axis from an object side surface of the first unit to the diaphragm, and R 1 is a radius of curvature on the optical axis of the first lens.
17. An image pickup apparatus comprising:
an optical system according to claim 16 ; and
an image sensor configured to receive an image formed by the optical system.