Optical element, optical system, and method of manufacturing optical element

1. An optical system, comprising:

a plurality of optical elements arranged in an optical axis direction; and

an optical surface and a non-optical surface, the optical surface and the non-optical surface containing optical glass as a base material,

wherein the optical glass has a Knoop hardness of 600 N/mm 2 or more,

wherein the non-optical surface has a coating film layer formed thereon, the coating film layer containing a pigment as a color material and having a refractive index of 1.65 or more, and

wherein the optical system satisfies any one of the following conditions:

A m <A k ; where 1< m<N and for any k satisfying 1≦ k≦m− 1;

A m <A k ; where 1< m<N and for any k satisfying m+ 1≦ k≦N;

m= 1; or

m=N,

where N represents a number of the plurality of optical elements, m represents an order from an object side of an optical element having the non-optical surface among the plurality of optical elements and A i (i=1, . . . , N) represents a smallest diameter of the optical surface of the i-th optical element from the object side.

2. An optical system according to claim 1 ,

wherein the optical surface comprises first and second optical surfaces, and

wherein a third region overlaps with a first region, whereas the third region does not overlap with a second region, the first, second, and third regions being orthogonal projection regions obtained by orthogonally projecting the first and second optical surfaces and the non-optical surface in an optical axis direction, respectively.

3. An optical system according to claim 1 ,

wherein the optical surface comprises a first optical surface, and a second optical surface that is decentered with respect to the first optical surface and has, as an orthogonal projection region, a second region having the same area as a first region obtained by orthogonally projecting the first optical surface in an optical axis direction, and

wherein the non-optical surface has, as an orthogonal projection region, a third region inside the first region and outside the second region that is decentered with respect to the first region.

4. An optical system according to claim 1 , wherein an area ratio of an orthogonal projection of the non-optical surface in an optical axis direction to an orthogonal projection of the optical surface in the optical axis direction is 30% or more.

5. An optical system according to claim 1 , wherein the coating film layer contains particles of 500 nm or larger in a weight ratio of 5% or more.