Cell observation apparatus and cell observation method

1. A method of optically observing a biological sample accommodated in a container, at least a bottom surface of the container being formed of a plastic raw material, the method comprising:

irradiating the biological sample with light having a near-infrared wavelength through an aperture plate and a condenser lens, the aperture plate having a rectangular aperture, wherein the rectangular aperture is arranged at a position distant from both a center portion thereof and an optical axis; and

forming an image of light from the biological sample on an image pickup device via the plastic raw material, an objective lens, a modulator, and an imaging lens, wherein

the modulator is arranged at a pupil position of the objective lens or a position conjugate with the pupil position of the objective lens, and wherein

the modulator has a region where transmittance changes stepwise.

2. The method according to claim 1 , wherein the near-infrared wavelength is 900 nm or more.

3. The method according to claim 1 , wherein the biological sample is a cell aggregate having an unstained three-dimensional structure.

4. An inverted microscope comprising:

a container configured to accommodate a biological sample, at least a bottom surface of the container being formed of a plastic raw material;

a stage on which the container is placed;

a near-infrared illuminating unit configured to illuminate the biological sample;

an aperture plate having a rectangular aperture, wherein the rectangular aperture is arranged at a position distant from both a center portion thereof and an optical axis; and

a condenser lens;

an objective lens;

a modulator having a region where transmittance changes stepwise;

an imaging lens; and

an image pickup device, wherein

the aperture plate and the modulator are arranged at a pupil position of the objective lens or a position conjugate with the pupil position of the objective lens, and wherein

the aperture plate is arranged on a side of the near-infrared illuminating unit than the biological sample, and

the modulator is arranged on a side of the image pickup device rather than the biological sample.

5. The inverted microscope according to claim 4 , wherein a near-infrared wavelength illuminated by the near-infrared illuminating unit is 900 nm or more.

6. The inverted microscope according to claim 4 , wherein the biological sample is a cell aggregate having an unstained three-dimensional structure.

7. The inverted microscope comprising according to claim 4 , wherein

the near-infrared illuminating unit comprises:

a light source and

a bandpass filter configured to extract a near-infrared wavelength from light illuminated by the light source.

8. The method according to claim 1 , wherein the aperture plate is arranged at a position conjugate with the pupil position of the objective lens.

9. The method according to claim 1 , wherein the modulator comprises a first region of a first transmittance, and a second region of a second transmittance that is different from the first transmittance, wherein the second region is offset from the first region in a direction parallel to a short side of the rectangular aperture of the aperture plate.

10. The method according to claim 9 , wherein the modulator further comprises a third region of a third transmittance, the third transmittance different from both the first transmittance and the second transmittance, the third region is offset from both the first region and the second region in the direction parallel to the short side of the rectangular aperture of the aperture place.

11. The method according to claim 9 , wherein the modulator is disk-shaped.

12. The method according to claim 11 , wherein the first region extends around a majority of a circumference of the disk-shaped modulator.

13. The inverted microscope according to claim 4 , wherein the modulator comprises a first region of a first transmittance, and a second region of a second transmittance that is different from the first transmittance, wherein the second region is offset from the first region in a direction parallel to a short side of the rectangular aperture of the aperture plate.

14. The inverted microscope according to claim 13 , wherein the modulator further comprises a third region of a third transmittance, the third transmittance different from both the first transmittance and the second transmittance, the third region is offset from both the first region and the second region in the direction parallel to the short side of the rectangular aperture of the aperture place.

15. The inverted microscope according to claim 13 , wherein the modulator is disk-shaped.

16. The inverted microscope according to claim 15 , wherein the first region extends around a majority of a circumference of the disk-shaped modulator.