Sheet illumination microscope system, image processing device and sheet illumination microscopy

1. A sheet illumination microscope system comprising:

a microscope apparatus configured to acquire a two-dimensional image of an observed object under a first illumination light amount distribution, the first illumination light amount distribution being formed by moving a condensing position of a light sheet in an illumination direction orthogonal to an observation direction, and the light sheet being emitted to the observed object from the illumination direction; and

an image processing device configured to perform a spatial frequency filtering process on image data of a three-dimensional image of the observed object in accordance with an optical transfer characteristic of the microscope apparatus, the spatial frequency filtering process being a process of changing a spatial frequency characteristic included in the three-dimensional image, and the three-dimensional image being constructed from a plurality of two-dimensional images acquired by the microscope apparatus,

wherein the image processing device performs the spatial frequency filtering process on the image data of the three-dimensional image on the basis of a first optical transfer characteristic of the microscope apparatus under the first illumination light amount distribution and a second optical transfer characteristic of the microscope apparatus under a second illumination light amount distribution, the second illumination light amount distribution being formed by keeping the condensing position of the light sheet at a fixed position, and

wherein the image processing device performs the spatial frequency filtering process on the image data of the three-dimensional image on the basis of a ratio between the first optical transfer characteristic and the second optical transfer characteristic.

2. The sheet illumination microscope system according to claim 1 , wherein

the spatial frequency filtering process is a Fourier filtering process in a spatial frequency domain for the image data of the three-dimensional image.

3. The sheet illumination microscope system according to claim 2 , wherein

the Fourier filtering process uses a second Fourier filter, the second Fourier filter being acquired by applying apodization for suppressing intensity of a spatial frequency component included in the image data of the three-dimensional image to a first Fourier filter, the spatial frequency component having a spatial frequency beyond a prescribed spatial frequency, and the first Fourier filter being calculated on the basis of the optical transfer characteristic of the microscope apparatus.

4. The sheet illumination microscope system according to claim 2 , wherein

the Fourier filtering process uses a second Fourier filter, the second Fourier filter being acquired by applying a spherical mask for improving isotropy to a first Fourier filter, and the first Fourier filter being calculated on the basis of the optical transfer characteristic of the microscope apparatus.

5. The sheet illumination microscope system according to claim 1 , wherein

the spatial frequency filtering process is a convolution filtering process in a space domain for the image data of the three-dimensional image.

6. The sheet illumination microscope system according to claim 5 , wherein

the convolution filtering process uses a one-dimensional convolution kernel that is parallel to an observation direction.

7. The sheet illumination microscope system according to claim 1 , wherein

the microscope apparatus includes:

an image pickup device configured to acquire a two-dimensional image of the observed object;

an observation optical system configured to project an image of the observed object onto the image pickup device; and

an illumination optical system configured to emit the light sheet to the observed object from the illumination direction, wherein

the illumination optical system includes a condensing position longitudinal movement device that moves the condensing position of the light sheet in the illumination direction.

8. The sheet illumination microscope system according to claim 7 , wherein

the microscope apparatus further includes an observed object movement device that moves the observed object in the observation direction.

9. The sheet illumination microscope system according to claim 7 , wherein

the illumination optical system further includes a deflector configured to deflect the light sheet.

10. An image processing device comprising:

a spatial frequency filtering process unit configured to perform a spatial frequency filtering process on image data of a three-dimensional image of an observed object in accordance with an optical transfer characteristic of a microscope apparatus, the spatial frequency filtering process being a process of changing a spatial frequency characteristic included in the three-dimensional image, the three-dimensional image being constructed from a plurality of two-dimensional images of the observed object acquired by the microscope apparatus under a first illumination light amount distribution, the first illumination light amount distribution being formed by moving a condensing position of a light sheet in an illumination direction orthogonal to an observation direction, and the light sheet being emitted to the observed object from the illumination direction,

wherein the spatial frequency filtering process performs the spatial frequency filtering process on the image data of the three-dimensional image on the basis of a first optical transfer characteristic of the microscope apparatus under the first illumination light amount distribution and a second optical transfer characteristic of the microscope apparatus under a second illumination light amount distribution, the second illumination light amount distribution being formed by keeping the condensing position of the light sheet at a fixed position, and

wherein the spatial frequency filtering process is performed on the image data of the three-dimensional image on the basis of a ratio between the first optical transfer characteristic and the second optical transfer characteristic.

11. A sheet illumination microscopy method comprising:

acquiring, by a microscope, a two-dimensional image of an observed object under a first illumination light amount distribution, the first illumination light amount distribution being formed by moving a condensing position of a light sheet in an illumination direction orthogonal to an observation direction, and the light sheet being emitted to the observed object from the illumination direction;

moving the condensing position of the light sheet based on the observed object in the observation direction;

constructing image data of a three-dimensional image of the observed object from a plurality of two-dimensional images, the plurality of two-dimensional images being acquired by repeating the acquisition of the two-dimensional image and the movement in the observation direction; and

performing a spatial frequency filtering process on the image data of the three-dimensional image in accordance with an optical transfer characteristic of the microscope apparatus, the spatial frequency filtering process being a process of changing a spatial frequency characteristic included in the three-dimensional image,

wherein the spatial frequency filtering process is a process of changing a spatial frequency characteristic included in the image data of the three-dimensional image on the basis of a first optical transfer characteristic of the microscope apparatus under the first illumination light amount distribution and a second optical transfer characteristic of the microscope apparatus under a second illumination light amount distribution, the second illumination light amount distribution being formed by keeping the condensing position of the light sheet at a fixed position, and

wherein the spatial frequency filtering process is performed on the image data of the three-dimensional image on the basis of a ratio between the first optical transfer characteristic and the second optical transfer characteristic.