Optical system and optical apparatus
An optical system includes a plurality of lenses, a diaphragm configured to adjust a light amount, and an optical element having a transmittance distribution. A transmittance of the optical element satisfies predetermined conditions. In addition, another predetermined condition is satisfied when the diaphragm is fully opened.
1. An optical system comprising:
a plurality of lenses;
a diaphragm configured to adjust a light amount; and
an optical element having a transmittance distribution,
wherein a transmittance of the optical element decreases as a distance increases from an optical axis of the optical element in a radial direction in a range of r 1 <r, and the following conditional expressions are satisfied in a range of
0.9≦ T ( r )/ T 0 ; and
0.5≦ r 1 /r a ,
where r is a distance in the radial direction from the optical axis, r 1 is a distance in the radial direction from the optical axis to a position at which the transmittance of the optical element has a value of 90% of a maximum value, T(r) is the transmittance at a position having the distance r, T 0 is the maximum value of the transmittance, and r a is an effective diameter of the optical element, and
wherein the following conditional expression is satisfied:
(OP2+OP3)/2 r a ≦r 2 /r a ≦OP1/ r a
where the diaphragm is fully opened, r 2 is a distance in the radial direction from the optical axis to a position at which the transmittance of the optical element has a value of 50% of the maximum value, P 1 is an end point in an incident area of a most off-axis light flux in the optical element, P 2 is a top end of the incident area, P 3 is a bottom end of the incident area, and OPi is a distance between the optical axis and a point corresponding to Pi (i=1, 2, 3) projected onto a plane perpendicular to the optical axis.
2. The optical system according to claim 1 , wherein in focusing on infinity, the following conditional expression is satisfied:
10 mm≦ f/F no≦70 mm
where f is a focal length of the optical system, and Fno is an open aperture value.
3. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
9°≦ω≦45° (5)
where ω is half an angle of view of the optical system.
4. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
{( T max− T min)/ T max}×100(%)≦20(%)
where Tmax is the maximum value of the transmittance and Tmin is a minimum value of the transmittance in a wavelength range from 430 nm to 700 nm.
5. The optical system according to claim 1 , wherein the optical element is disposed near the diaphragm.
6. The optical system according to claim 1 , wherein two optical elements are disposed before and after the diaphragm.
7. An optical apparatus comprising an optical system,
wherein the optical system includes:
a plurality of lenses;
a diaphragm configured to adjust a light amount; and
an optical element having a transmittance distribution,
wherein a transmittance of the optical element decreases as a distance increases from an optical axis of the optical element in a radial direction in a range of r 1 <r, and the following conditional expressions are satisfied in a range of
0.9≦ T ( r )/ T 0 ; and
0.5≦ r 1 /r a ,
where r is a distance in the radial direction from the optical axis, r 1 is a distance in the radial direction from the optical axis to a position at which the transmittance of the optical element has a value of 90% of a maximum value, T(r) is the transmittance at a position having the distance r, T 0 is the maximum value of the transmittance, and r a is an effective diameter of the optical element, and
wherein the following conditional expression is satisfied:
(OP2+OP3)/2 r a ≦r 2 /r a ≦OP1/ r a
where the diaphragm is fully opened, r 2 is a distance in the radial direction from the optical axis to a position at which the transmittance of the optical element has a value of 50% of the maximum value, P 1 is an end point in an incident area of a most off-axis light flux in the optical element, P 2 is a top end of the incident area, P 3 is a bottom end of the incident area, and OPi is a distance between the optical axis and a point corresponding to Pi (i=1, 2, 3) projected onto a plane perpendicular to the optical axis.