Laser scanning microscope

1. A laser scanning microscope comprising:

a stage configured to have a sample placed thereon;

an objective lens that is disposed below the stage and that is configured to focus laser light from a light source onto the sample;

a scanner that is configured to scan the laser light focused by the objective lens over the sample;

a condenser lens disposed opposite the objective lens with the stage interposed therebetween;

a transmission detector that detects observation light that is generated at a condenser lens side of the sample by radiating the laser light to the sample via the objective lens, the observation light being condensed by the condenser lens; and

a light blocking cover that is disposed in an optical path between the condenser lens and the stage and that blocks external light entering the condenser lens from above the sample via the stage, wherein the light blocking cover is attached to the condenser lens, and the light blocking cover has a light-transparent opening at a central portion thereof.

2. The laser scanning microscope according to claim 1 , wherein the light blocking cover is attached to the condenser lens in an attachable and detachable manner, and

wherein an attachment position of the light blocking cover to the condenser lens is changeable along an optical-axis direction of the condenser lens.

3. The laser scanning microscope according to claim 1 , wherein the light blocking cover includes a non-movable piece that is positioned above a sample placement position on the stage, and a movable piece that moves relative to the non-movable piece so as to form an open space above the sample.

4. The laser scanning microscope according to claim 1 , wherein the light blocking cover comprises a flange section extending in a direction that intersects an optical axis of the condenser lens, and

wherein the flange section has a width that satisfies the conditional expression below:

R≥r o +L o tan θ o

where R denotes half of the width of the flange section of the light blocking cover, r o denotes an aperture radius of the objective lens, L o denotes a distance between the objective lens and the light blocking cover in an optical-axis direction, and θ o denotes an aperture angle of the objective lens.

5. The laser scanning microscope according to claim 1 , wherein the light blocking cover comprises a flange section extending in a direction that intersects an optical axis of the condenser lens, and

wherein the flange section has a width that satisfies the conditional expression below:

R≥r c +2 L c tan θ c

where R denotes half of the width of the flange section of the light blocking cover, r c denotes an aperture radius of the condenser lens, L c denotes a distance between the stage and the light blocking cover in an optical-axis direction, and θ c denotes an aperture angle of the condenser lens.

6. The laser scanning microscope according to claim 1 , further comprising:

a light-blocking tubular member that has light blocking properties and has a tubular shape, the light-blocking tubular member being disposed opposite the stage with the condenser lens interposed between the light-blocking tubular member and the stage, and the light-blocking tubular member covering an area surrounding an optical axis of the condenser lens; and

a transmissive column that extends in a vertical direction to support the condenser lens, the light-blocking tubular member, and the transmission detector,

wherein the light-blocking tubular member covers a circumference of the optical path along the optical axis of the condenser lens in a space above the condenser lens.

7. The laser scanning microscope according to claim 6 , wherein the light-blocking tubular member is expandable and contractible along an optical-axis direction.