Patent ID: 11931004
Assignee: OLYMPUS CORPORATION
Field: Optics (Instruments)
Classification: CPC A  G | IPC A  G

Claim 2:
3. The objective optical system according to claim 1, wherein a surface on the opposite side of the second optical medium from the object is a flat surface perpendicular to the optical axis; and
the following conditional expression (2) is satisfied:

1≤(R1+R2)*[{1/cos(2θ2−θ1)}−1]/L  (2)

where
R1 indicates a radius of the first spherical lens,
R2 indicates a radius of the second spherical lens,
L indicates the interval on the optical axis between a surface on the opposite side of the first spherical lens from the object and the surface on the object side of the second spherical lens,
n2 indicates a refractive index of the second spherical lens,
n4 indicates a refractive index of the second optical medium,
θ1=sin−1(1/n4), and
θ2=sin−1(1/n2).