Patent ID: 9651722
Date: 2017-05-16
CPC Classifications: G02B,G03B

Claim:
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 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: 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.