Microscope system and method for microscope system

1. A microscope system comprising:

an electrically powered stage configured to have a specimen placed thereon, the stage being operable to adjust a position of the specimen;

a scanner configured to scan laser light to irradiate the specimen on the electrically powered stage;

a low-magnification objective lens configured to focus the laser light scanned by the scanner onto the specimen and a high-magnification objective lens having a higher magnification than the low-magnification objective lens;

a revolver that supports the low-magnification objective lens and the high-magnification objective lens so as to make it possible to selectively place the low-magnification objective lens or the high-magnification objective lens in an optical path of the laser light;

an image-acquisition portion configured to acquire an image of the specimen by detecting first return light that returns from the specimen due to the irradiation with the laser light; and

a controller configured to: (i) adjust a distance in an optical-axis direction between the revolver and the electrically powered stage based on a luminance of second return light, and detect focal positions of the low-magnification objective lens and the high-magnification objective lens, (ii) store in a memory one of the detected focal positions of the low-magnification objective lens as a reference position for the low-magnification objective lens, (iii) set the focal position at which the image is acquired by the image-acquisition portion with reference to the reference position for the low-magnification objective lens stored in the memory, (iv) set acquisition positions in a direction that intersects the optical axis for partial images of the specimen that are acquired by the image-acquisition portion in divided form based on predetermined viewing-field areas, and (v) when the partial images are acquired by the image-acquisition portion at the set focal position by moving the viewing-field areas to the acquisition positions by means of the electrically powered stage, generate a map image by arranging the acquired partial images in accordance with the acquisition positions,

wherein the controller detects the focal position of the high-magnification objective lens at an observation position set on the map image with reference to the reference position for the low-magnification objective lens stored in the memory.

2. The microscope system according to claim 1 , wherein, in a case in which the detected focal position of the high-magnification objective lens changes during time-lapse observation in which the image-acquisition portion acquires images at the observation position at a predetermined time interval, the controller corrects the focal position.

3. The microscope system according to claim 1 , wherein the controller detects the focal position of the high-magnification objective lens by taking into account a correction level for correcting a displacement between a parfocal distance of the low-magnification objective lens and a parfocal distance of the high-magnification objective lens.

4. The microscope system according to claim 1 , further comprising:

a thin, glass plate-like cover glass that covers the specimen placed on the electrically powered stage; and

a correction ring which is provided to the high-magnification objective lens and is operable to correct aberration in accordance with a thickness of the cover glass,

wherein the controller detects the focal position of the high-magnification objective lens by taking into account a correction level achieved by the correction ring in accordance with the thickness of the cover glass.

5. The microscope system according to claim 4 , wherein the cover glass is provided at a bottom surface of a container that accommodates the specimen, and covers the specimen from underneath.

6. The microscope system according to claim 1 , wherein the memory stores, individually as reference positions, three or more different focal positions for the low-magnification objective lens detected by the controller in directions that intersect the optical axis of the laser light, and the controller detects the focal position of the high-magnification objective lens based on the three or more reference positions for the low-magnification objective lens stored in the memory.

7. A method for a microscope system which comprises: (i) an electrically powered stage configured to have a specimen placed thereon, the stage being operable to adjust a position of the specimen; (ii) a scanner configured to scan laser light to irradiate the specimen on the electrically powered stage; (iii) a low-magnification objective lens configured to focus the laser light scanned by the scanner onto the specimen and a high-magnification objective lens having a higher magnification than the low-magnification objective lens; and (iv) a revolver that supports the low-magnification objective lens and the high-magnification objective lens so as to make it possible to selectively place the low-magnification objective lens or the high-magnification objective lens in an optical path of the laser light, wherein the method comprises:

acquiring an image of the specimen by detecting first return light that returns from the specimen due to the irradiation with the laser light;

adjusting a distance in an optical-axis direction between the revolver and the electrically powered stage based on a luminance of second return light, and detecting focal positions of the low-magnification objective lens and the high-magnification objective lens;

storing one of the detected focal positions of the low-magnification objective lens as a reference position for the low-magnification objective lens;

setting the focal position at which the image is acquired with reference to the stored reference position for the low-magnification objective lens, setting acquisition positions in a direction that intersects the optical axis for partial images of the specimen that are acquired in divided form based on predetermined viewing-field areas; and

when the partial images are acquired at the set focal position by moving the viewing-field areas to the acquisition positions by means of the electrically powered stage, generating a map image by arranging the acquired partial images in accordance with the acquisition positions,

wherein the focal position of the high-magnification objective lens is detected at an observation position set on the map image with reference to the stored reference position for the low-magnification objective lens.

8. The method according to claim 7 , wherein, in a case in which the detected focal position of the high-magnification objective lens changes during time-lapse observation in which images are acquired at the observation position at a predetermined time interval, the focal position is corrected.

9. The method according to claim 7 , wherein the focal position of the high-magnification objective lens is detected by taking into account a correction level for correcting a displacement between a parfocal distance of the low-magnification objective lens and a parfocal distance of the high-magnification objective lens.

10. The method according to claim 7 , wherein the microscope system further comprises a thin, glass plate-like cover glass that covers the specimen placed on the electrically powered stage,

wherein the high-magnification objective lens is provided with a correction ring which is operable to correct aberration in accordance with a thickness of the cover glass, and

wherein the focal position of the high-magnification objective lens is detected by taking into account a correction level achieved by the correction ring in accordance with the thickness of the cover glass.

11. The method according to claim 10 , wherein the cover glass is provided at a bottom surface of a container that accommodates the specimen, and covers the specimen from underneath.

12. The method according to claim 7 , further comprising storing, individually as reference positions, three or more different focal positions for the low-magnification objective lens detected in directions that intersect the optical axis of the laser light, and wherein the focal position of the high-magnification objective lens is detected based on the stored three or more reference positions for the low-magnification objective lens.