Illumination apparatus and microscope having the same
View Patent ↗An illumination apparatus includes a light source and a collimator optical system converting light emitted from the light source to approximately-parallel light. The collimator optical system includes, in an order of proximity to the light source, a first lens having a positive power and including an approximately-flat surface and an aspheric surface, and a second lens having a positive power.
1. An illumination apparatus comprising:
a light source; and
a collimator optical system which converts light emitted from the light source to approximately-parallel light,
wherein the collimator optical system consists of two lenses which are, in an order of proximity to the light source, a first lens having a positive power and a second lens having a positive power,
wherein the first lens comprises, in an order of proximity to the light source, an approximately-flat first surface and an aspheric second surface, and
wherein a following conditional expression is satisfied:
FL 1 <FL 2
where FL 1 is a focal length of the first lens, and FL 2 is a focal length of the second lens.
2. The illumination apparatus according to claim 1 , wherein the light source is a LED light source.
3. The illumination apparatus according to claim 1 , wherein at least one of the first lens and the second lens is formed with a resin material.
4. The illumination apparatus according to claim 1 , wherein the second lens comprises an aspheric surface.
5. The illumination apparatus according to claim 1 , wherein a following conditional expression is satisfied:
|( D 1/ D 2)−1|<0.5
where D 1 is a thickness of the first lens and D 2 is a thickness of the second lens.
6. The illumination apparatus according to claim 1 , further comprising, at an emitting side of the collimator optical system:
a field stop; and
a relay lens which makes the approximately-parallel light emitted from the collimator optical system form an image.
7. The illumination apparatus according to claim 6 , further comprising:
an aperture stop at a position at which the approximately-parallel light emitted from the collimator optical system forms an image; and
a condenser lens which illuminates a sample surface,
wherein a focal position of the condenser lens corresponds to the position of the aperture stop.
8. The illumination apparatus according to claim 1 , wherein a following conditional expression is satisfied:
( D 1 /DL )+| R 2 /R 1|<1
where D 1 is a thickness of the first lens, DL is a distance between the light source and the first lens, R 1 is a radius of curvature of the first surface of the first lens, and R 2 is a radius of curvature of the second surface of the first lens.
9. The illumination apparatus according to claim 1 , wherein the second lens comprises, in an order of proximity to the light source, a first convex spherical surface and a second convex aspheric surface.