Illumination optical system and fluorescent microscope

1. An illumination optical system which irradiates a sample surface with light through an illuminating lens, comprising:

a light source;

a condensing optical system receiving the light emitted from the light source, wherein the condensing optical system is a collector lens; and

a lens array optical system including a first lens array surface and a second lens array surface each formed by a plurality of lens elements;

wherein:

the first lens array surface has a conjugate relation with a focal position of the illuminating lens;

the second lens array surface is placed at a back focal position of the lens array optical system and has a conjugate relation with a pupil position of the illuminating lens;

the light source and the condensing optical system are arranged to form an image of the light source on the first lens array surface; and

at least one of the light source and the collector lens functions as a switching unit for switching between a first illuminating state in which a plurality of images of the light source are formed on the second lens array surface and a second illuminating state in which an image of the light source is formed on the first lens array surface.

2. The system according to claim 1 , wherein the switching unit changes a distance between the light source and the collector lens.

3. The system according to claim 1 , wherein:

the collector lens includes a plurality of lenses; and

the switching unit moves a part of the plurality of lenses in a direction of an optical axis.

4. The system according to claim 1 , wherein:

the collector lens includes an attachable and detachable lens; and

the switching unit attaches the attachable and detachable lens to and detaches from an optical axis.

5. The system according to claim 1 , further comprising:

a relay optical system provided between the lens array optical system and the illuminating lens,

wherein a conditional expression of

0.1 ≦H L ·β CL ·β RL /Φ≦1.3

is satisfied where: H L indicates a light source height of the light source; Φ indicates a pupil diameter of the illuminating lens; β CL indicates a magnification of the collector lens in the second illuminating state; and β RL indicates a magnification of the relay optical system.

6. The system according to claim 1 , wherein when the second lens array surface matches the pupil position, a conditional expression of

0.1 ≦H L ·β CL /Φ≦1.3

is satisfied where: H L indicates a light source height of the light source; Φ indicates a pupil diameter of the illuminating lens; and β CL indicates a magnification of the collector lens in the second illuminating state.

7. An illumination optical system which irradiates a sample surface with light through an illuminating lens, comprising:

a light source;

a condensing optical system receiving the light emitted from the light source, the condensing optical system comprising a collector lens and a reflector reflecting the light emitted from the light source toward the collector lens; and

a lens array optical system including a first lens array surface and a second lens array surface each formed by a plurality of lens elements;

wherein:

the first lens array surface has a conjugate relation with a focal position of the illuminating lens;

the second lens array surface is placed at a back focal position of the lens array optical system and has a conjugate relation with a pupil position of the illuminating lens;

the light source and the condensing optical system are arranged to form an image of the light source on the first lens array surface; and

the reflector functions as a switching unit for switching between a third illuminating state in which the collector lens forms a plurality of images of the light source on the second lens array surface and a fourth illuminating state in which the collector lens forms an image of the light source on the first lens array surface and a plurality of images of the light source on the second lens array surface.

8. The system according to claim 7 , wherein in the fourth illuminating state, the collector lens converges:

direct light as illumination light which is emitted from the light source and directly enters the collector lens on the second lens array surface; and

indirect light as illumination light which is emitted from the light source and enters the collector lens after being reflected by the reflector on the first lens array surface.

9. The system according to claim 7 , wherein the switching unit changes a position of the image of the light source formed by the reflector.

10. An illumination optical system which irradiates a sample surface with light through an illuminating lens, comprising:

a light source;

a condensing optical system receiving the light emitted from the light source; and

a lens array optical system including a first lens array surface and a second lens array surface each formed by a plurality of lens elements;

wherein:

the first lens array surface has a conjugate relation with a focal position of the illuminating lens;

the second lens array surface is placed at a back focal position of the lens array optical system and has a conjugate relation with a pupil position of the illuminating lens;

the light source and the condensing optical system are arranged to form an image of the light source on the first lens array surface;

the illuminating lens includes a plurality of illuminating lenses having different optical specifications; and

the illumination optical system is used with the plurality of illuminating lenses one of which is selectively inserted into an optical axis of the illumination optical system.