Patent ID: 12189107

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, scanning optical systems and scanning-type confocal microscopes according to first to sixth embodiments are described. First, referring toFIG.1, the scanning-type confocal microscopes that comprise the scanning optical systems according to the first to sixth embodiments are described. The scanning-type confocal microscope1mainly comprises: a first collective optical system2that collects laser light for illumination from a light source unit6onto a sample SA; a scanning device3that deflects the laser light collected on the sample SA and scans the sample SA with the laser light; an optical detection device5that detects a light intensity signal from the sample SA; and a second collective optical system4that guides the light from the sample SA to the optical detection device5.

The first collective optical system2comprises: a collimator lens21that converts oscillated laser light (a light flux) from the light source unit6into parallel light; a dichroic mirror22that reflects the laser light from the collimator lens21toward the sample SA; and a second objective lens23and an objective lens24that collect the laser light reflected by the dichroic mirror22onto the sample SA. The second objective lens23is arranged in a lens barrel11of a microscope main body10, and the collimator lens21and the dichroic mirror22are arranged in a microscope housing12provided above the lens barrel11. Note that the light source unit6and the microscope housing12are connected to each other by an optical fiber69using connectors C3and C4.

The scanning device3comprises a scanning mechanism (scanner)31that includes, for example, a galvanometer mirror (not shown) or a resonant mirror (not shown), and a scanning optical system32, and is arranged between the dichroic mirror22in the microscope housing12and the second objective lens23. The scanning mechanism (scanner)31deflects incident laser light. That is, the scanning mechanism (scanner)31deflects the laser light collected on the sample SA and scans the sample SA with the laser light. The scanning optical system32is an optical system provided between the objective lens24and the scanning mechanism (scanner)31. The scanning optical system32is an optical system whose focal position is disposed on an image surface I conjugate with the sample SA (a scanning surface of the sample SA).

The second collective optical system4comprises: the objective lens24and the second objective lens23; a total reflection mirror42that reflects fluorescent light from the sample SA; and a first collective lens41that collects the fluorescent light reflected by the total reflection mirror42onto a shielding plate52that is of the optical detection device5and includes a pinhole51. The total reflection mirror42and the first collective lens41are arranged above the dichroic mirror22and the collimator lens21in the microscope housing12.

The optical detection device5comprises: the shielding plate52having the pinhole51(aperture); an optical fiber53that allows light (fluorescent light) having passed through the pinhole51to be incident thereon; and a detection unit55that detects the light (fluorescent light) having passed through the pinhole51and the optical fiber53. The shielding plate52is arranged in the microscope housing12. The optical fiber53is connected to the microscope housing12and the detection unit55using respective connectors C1and C2. A processing unit57is electrically connected to the detection unit55via a cable56. Image processing (of the sample SA) based on a detection signal detected by the detection unit55is performed, and an observation image of the sample SA obtained through the image processing by the processing unit57is displayed on a monitor, not shown. Note that, in the configuration, illumination light emitted from the scanning device3is collected on an imaging surface (primary image surface)13, and is then collected on the sample SA by the second objective lens23and the objective lens24. A scanning surface of the sample SA, the imaging surface13, and the pinhole51have a conjugate relationship.

An after-mentioned scanning optical system SL according to each embodiment can be used as the scanning optical system32. First, a first embodiment of the scanning optical system SL is described. As with a scanning optical system SL(1) shown inFIG.2, the scanning optical system SL according to the first embodiment comprises, for example: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the scanning mechanism31(pupil conjugate surface P). By arranging the first lens group G1and the third lens group G3that have the negative refractive powers before and after the second lens group G2having the positive refractive power, the Petzval sum can be reduced close to zero, and the field curves can be favorably corrected.

The scanning optical system SL according to the first embodiment may be a scanning optical system SL(2) shown inFIG.4, a scanning optical system SL(3) shown inFIG.6, or a scanning optical system SL(4) shown inFIG.8. The scanning optical system SL according to the first embodiment may be a scanning optical system SL(5) shown inFIG.10, a scanning optical system SL(6) shown inFIG.12, or a scanning optical system SL(7) shown inFIG.14.

In the scanning optical system SL according to the first embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a positive refractive power, and satisfies the following conditional expression (1),
νd1>80  (1)
where νd1: an Abbe number with reference to d-line of the lens having the positive refractive power, defined by the following expression,
νd1=(nd1−1)/(nF1−nC1),wherein a refractive index of the lens having the positive refractive power for d-line is nd1, a refractive index of the lens having the positive refractive power for F-line is nF1, and a refractive index of the lens having the positive refractive power for C-line is nC1.

The conditional expression (1) defines the Abbe number of the material of the lens having the positive refractive power. The lens having the positive refractive power satisfies the conditional expression (1), which reduces the dispersion of light in the lens having the positive refractive power. Accordingly, the chromatic aberration of magnification can be favorably corrected.

If the corresponding value of the conditional expression (1) falls below the lower limit value, the dispersion of light in the lens having the positive refractive power increases. Accordingly, it is difficult to correct the chromatic aberration of magnification. By setting the lower limit value of the conditional expression (1) to 90, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the first embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a negative refractive power, and satisfies the following conditional expression (2),
νd2<50  (2)
where νd2: an Abbe number with reference to d-line of the lens having the negative refractive power, defined by the following expression,
νd1=(nd1−1)/(nF1−nC1),wherein a refractive index of the lens having the negative refractive power for d-line is nd2, a refractive index of the lens having the negative refractive power for F-line is nF2, and a refractive index of the lens having the negative refractive power for C-line is nC2.
νd2=(nd2−1)/(nF2−nC2).

The conditional expression (2) defines the Abbe number of the material of the lens having the negative refractive power. The lens having the negative refractive power satisfies the conditional expression (2), and the lens having the strong negative refractive power with the large dispersion of light is combined with the lenses having the positive refractive powers with the small dispersion of light. Accordingly, the chromatic aberration of magnification can be favorably corrected.

If the corresponding value of the conditional expression (2) exceeds an upper limit value, the dispersion of light of the lens having the negative refractive power decreases. Accordingly, it is difficult to correct the chromatic aberration of magnification through combination with the lens having the positive refractive power (with a small dispersion of light). By setting the upper limit value of the conditional expression (2) to 40, the advantageous effects of this embodiment can be more secured.

The scanning optical system SL according to the first embodiment satisfies the following conditional expression (3).
hmax≥18.0 [mm]  (3)
where h max: a maximum distance between an optical axis and a principal ray defining a maximum image height among principal rays passing through a back focus of the objective lens24.

The conditional expression (3) defines a maximum distance between an optical axis and a principal ray defining a maximum image height among principal rays passing through a back focus of the objective lens24. The conditional expression (3) is satisfied, which increases the maximum image height, and increases the maximum number of fields of view of the scanning optical system SL accordingly, thereby allowing the field of view to be increased. According to the first embodiment, the conditional expressions (1) to (3) are satisfied, which can reduce the chromatic aberration of magnification, and increase the field of view.

Note that the principal ray is a ray passing through the center of the aperture stop. Typically, an objective lens of a microscope is assumed to be telecentric. The back focus position of the objective lens is the position of the exit pupil (aperture stop) of the objective lens. Accordingly, the principal ray of the scanning optical system SL of the scanning-type confocal microscope1passes through the back focus of the objective lens24. At a position closer to the scanning mechanism31than the scanning optical system SL, the pupil conjugate surface P conjugate with the exit pupil of the objective lens24. The scanning mechanism31is arranged at a neighborhood of the pupil conjugate surface P. In each embodiment, the maximum number of fields of view of the scanning optical system SL indicates the diameter of the image surface I conjugate with the sample SA (the scanning surface of the sample SA), that is, the diameter of the imaging surface13(primary image surface) by the second objective lens23.

If the corresponding value of the conditional expression (3) falls below the lower limit value, the maximum image height decreases, and the maximum number of fields of view of the scanning optical system SL decreases accordingly. It is difficult to increase the field of view. By setting the lower limit value of the conditional expression (3) to 18.3 [mm], the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the first embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (4).
θgF1−(−0.00168×νd1)−0.644>0.03  (4)
where θgF1: a partial dispersion ratio of the lens having the positive refractive power, defined by the following expression,
θgF1=(ng1−nF1)/(nF1−nC1),wherein a refractive index of the lens having the positive refractive power for g-line is ng1, a refractive index of the lens having the positive refractive power for F-line is nF1, and a refractive index of the lens having the positive refractive power for C-line is nC1.

The conditional expression (4) defines the relationship between the partial dispersion ratio and the Abbe number of the material of the lens having the positive refractive power. The lens having the positive refractive power satisfies the conditional expression (4), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, using the anomalous dispersion characteristics of the material of the lens having the positive refractive power.

If the corresponding value of the conditional expression (4) falls below the lower limit value, the effect of the anomalous dispersion characteristics becomes insufficient. Accordingly, it is difficult to correct the chromatic aberration of magnification. By setting the lower limit value of the conditional expression (4) to 0.04, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the first embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (5).
θgF2−(−0.00168×νd2)−0.644<−0.002  (5)
where θgF2: a partial dispersion ratio of the lens having the negative refractive power, defined by the following expression,
θgF2=(ng2−nF2)/(nF2−nC2),wherein a refractive index of the lens having the negative refractive power for g-line is ng2, a refractive index of the lens having the negative refractive power for F-line is nF2, and a refractive index of the lens having the negative refractive power for C-line is nC2.

The conditional expression (5) defines the relationship between the partial dispersion ratio and the Abbe number of the material of the lens having the negative refractive power. The lens having the negative refractive power satisfies the conditional expression (5), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, using the anomalous dispersion characteristics of the material of the lens having the negative refractive power.

If the corresponding value of the conditional expression (5) exceeds the upper limit value, the effect of the anomalous dispersion characteristics becomes insufficient. Accordingly, it is difficult to correct the chromatic aberration of magnification. By setting the upper limit value of the conditional expression (5) to −0.004, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the first embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (6).
θgF1<0.55  (6)

The conditional expression (6) defines the partial dispersion ratio of the material of the lens having the positive refractive power. The lens having the positive refractive power satisfies the conditional expression (6), which can make the anomalous dispersion characteristics of the material of the lens having the positive refractive power appropriate, and favorably correct the chromatic aberration of magnification in the wavelength region of visible light.

If the corresponding value of the conditional expression (6) exceeds the upper limit value, the anomalous dispersion characteristics of the material of the lens having the positive refractive power become excessive. Accordingly, it is difficult to correct the chromatic aberration of magnification. By setting the upper limit value of the conditional expression (6) to 0.535, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the first embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (7)
θgF2>0.56  (7)

The conditional expression (7) defines the partial dispersion ratio of the material of the lens having the negative refractive power. The lens having the negative refractive power satisfies the conditional expression (7), which can make the anomalous dispersion characteristics of the material of the lens having the negative refractive power appropriate, and favorably correct the chromatic aberration of magnification in the wavelength region of visible light.

If the corresponding value of the conditional expression (7) falls below the lower limit value, the anomalous dispersion characteristics of the material of the lens having the negative refractive power become excessive. Accordingly, it is difficult to correct the chromatic aberration of magnification. By setting the lower limit value of the conditional expression (7) to 0.58, the advantageous effects of this embodiment can be more secured.

Next, a second embodiment of the scanning optical system is described. The scanning optical system according to the second embodiment has a configuration similar to that of the scanning optical system SL according to the first embodiment. Accordingly, the same symbols as those in the first embodiment are assigned and description is made. As with a scanning optical system SL(1) shown inFIG.2, the scanning optical system SL according to the second embodiment comprises, for example: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the scanning mechanism31(pupil conjugate surface P). By arranging the first lens group G1and the third lens group G3that have the negative refractive powers before and after the second lens group G2having the positive refractive power, the Petzval sum can be reduced close to zero, and the field curves can be favorably corrected.

The scanning optical system SL according to the second embodiment may be a scanning optical system SL(2) shown inFIG.4, a scanning optical system SL(3) shown inFIG.6, or a scanning optical system SL(4) shown inFIG.8. The scanning optical system SL according to the second embodiment may be a scanning optical system SL(5) shown inFIG.10, a scanning optical system SL(6) shown inFIG.12, or a scanning optical system SL(7) shown inFIG.14.

In the scanning optical system SL according to the second embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a positive refractive power, and satisfies the following conditional expression (4) described above,
θgF1−(−0.00168×νd1)−0.644>0.03  (4)

The lens having the positive refractive power satisfies the conditional expression (4), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (4) to 0.04, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the second embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a negative refractive power, and satisfies the following conditional expression (5) described above.
θgF2−(−0.00168×νd2)−0.644<−0.002  (5)

The lens having the negative refractive power satisfies the conditional expression (5), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (5) to −0.004, the advantageous effects of this embodiment can be more secured.

The scanning optical system SL according to the second embodiment satisfies the following conditional expression (3) described above.
hmax≥18.0 [mm]  (3)

By satisfying the conditional expression (3), the field of view can be increased, as with the first embodiment. According to the second embodiment, the conditional expressions (3) and (4)-(5) are satisfied, which can reduce the chromatic aberration of magnification, and increase the field of view. Note that by setting the lower limit value of the conditional expression (3) to 18.3 [mm], the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the second embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (1) described above.
νd1>80  (1)

The lens having the positive refractive power satisfies the conditional expression (1), which can favorably correct the chromatic aberration of magnification, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (1) to 90, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the second embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (2) described above.
νd2<50  (2)

The lens having the negative refractive power satisfies the conditional expression (2), which can favorably correct the chromatic aberration of magnification, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (2) to 40, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the second embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (6) described above.
θgF1<0.55  (6)

The lens having the positive refractive power satisfies the conditional expression (6), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (6) to 0.535, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the second embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (7) described above.
θgF2>0.56  (7)

The lens having the negative refractive power satisfies the conditional expression (7), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (7) to 0.58, the advantageous effects of this embodiment can be more secured.

Next, a third embodiment of the scanning optical system SL is described. The scanning optical system according to the third embodiment has a configuration similar to that of the scanning optical system SL according to the first embodiment. Accordingly, the same symbols as those in the first embodiment are assigned and description is made. As with a scanning optical system SL(1) shown inFIG.2, the scanning optical system SL according to the third embodiment comprises, for example: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the scanning mechanism31(pupil conjugate surface P). By arranging the first lens group G1and the third lens group G3that have the negative refractive powers before and after the second lens group G2having the positive refractive power, the Petzval sum can be reduced close to zero, and the field curves can be favorably corrected.

The scanning optical system SL according to the third embodiment may be a scanning optical system SL(2) shown inFIG.4, a scanning optical system SL(3) shown inFIG.6, or a scanning optical system SL(4) shown inFIG.8. The scanning optical system SL according to the third embodiment may be a scanning optical system SL(5) shown inFIG.10, a scanning optical system SL(6) shown inFIG.12, or a scanning optical system SL(7) shown inFIG.14.

In the scanning optical system SL according to the third embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a positive refractive power, and satisfies the following conditional expression (1) described above.
νd1>80  (1)

The lens having the positive refractive power satisfies the conditional expression (1), which can favorably correct the chromatic aberration of magnification, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (1) to 90, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the third embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a negative refractive power, and satisfies the following conditional expression (2) described above.
νd2<50  (2)

The lens having the negative refractive power satisfies the conditional expression (2), which can favorably correct the chromatic aberration of magnification, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (2) to 40, the advantageous effects of this embodiment can be more secured.

The scanning optical system SL according to the third embodiment satisfies the following conditional expression (8).
FOV≥23 [mm]  (8)
where FOV: the maximum number of fields of view of the scanning optical system SL.

The conditional expression (8) defines the maximum number of fields of view of the scanning optical system SL. The conditional expression (8) is satisfied, which increases the maximum number of fields of view of the scanning optical system SL, thereby allowing the field of view to be increased. According to the second embodiment, the conditional expressions (1), (2) and (8) are satisfied, which can reduce the chromatic aberration of magnification, and increase the field of view. As described above, the maximum number of fields of view of the scanning optical system SL indicates the diameter of the image surface I conjugate with the sample SA (the scanning surface of the sample SA), that is, the diameter of the imaging surface13(primary image surface) by the second objective lens23.

If the corresponding value of the conditional expression (8) falls below the lower limit value, the maximum number of fields of view of the scanning optical system SL decreases. Accordingly, it is difficult to increase the field of view. By setting the lower limit value of the conditional expression (8) to 24 [mm], the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the third embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (4) described above.
θgF1−(−0.00168×νd1)−0.644>0.03  (4)

The lens having the positive refractive power satisfies the conditional expression (4), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (4) to 0.04, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the third embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (5) described above.
θgF2−(−0.00168×νd2)−0.644<−0.002  (5)

The lens having the negative refractive power satisfies the conditional expression (5), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (5) to −0.004, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the third embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (6) described above.
θgF1<0.55  (6)

The lens having the positive refractive power satisfies the conditional expression (6), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (6) to 0.535, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the third embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (7) described above.
θgF2>0.56  (7)

The lens having the negative refractive power satisfies the conditional expression (7), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (7) to 0.58, the advantageous effects of this embodiment can be more secured.

Next, a fourth embodiment of the scanning optical system is described. The scanning optical system according to the fourth embodiment has a configuration similar to that of the scanning optical system SL according to the first embodiment. Accordingly, the same symbols as those in the first embodiment are assigned and description is made. As with a scanning optical system SL(1) shown inFIG.2, the scanning optical system SL according to the fourth embodiment comprises, for example: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the scanning mechanism31(pupil conjugate surface P). By arranging the first lens group G1and the third lens group G3that have the negative refractive powers before and after the second lens group G2having the positive refractive power, the Petzval sum can be reduced close to zero, and the field curves can be favorably corrected.

The scanning optical system SL according to the fourth embodiment may be a scanning optical system SL(2) shown inFIG.4, a scanning optical system SL(3) shown inFIG.6, or a scanning optical system SL(4) shown inFIG.8. The scanning optical system SL according to the fourth embodiment may be a scanning optical system SL(5) shown inFIG.10, a scanning optical system SL(6) shown inFIG.12, or a scanning optical system SL(7) shown inFIG.14.

In the scanning optical system SL according to the fourth embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a positive refractive power, and satisfies the following conditional expression (4) described above.
θgF1−(−0.00168×νd1)−0.644>0.03  (4)

The lens having the positive refractive power satisfies the conditional expression (4), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (4) to 0.04, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the fourth embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a negative refractive power, and satisfies the following conditional expression (5) described above.
θgF2−(−0.00168×νd2)−0.644<−0.002  (5)

The lens having the negative refractive power satisfies the conditional expression (5), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (5) to −0.004, the advantageous effects of this embodiment can be more secured.

The scanning optical system SL according to the fourth embodiment satisfies the following conditional expression (8) described above.
FOV≥23 [mm]  (8)

By satisfying the conditional expression (8), the field of view can be increased, as with the first embodiment. According to the fourth embodiment, the conditional expressions (4), (5) and (8) are satisfied, which can reduce the chromatic aberration of magnification, and increase the field of view. Note that by setting the lower limit value of the conditional expression (8) to [mm], the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the fourth embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (1) described above.
νd1>80  (1)

The lens having the positive refractive power satisfies the conditional expression (1), which can favorably correct the chromatic aberration of magnification, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (1) to 90, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the fourth embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (2) described above.
νd2<50  (2)

The lens having the negative refractive power satisfies the conditional expression (2), which can favorably correct the chromatic aberration of magnification, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (2) to 40, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the fourth embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (6) described above.
θgF1<0.55  (6)

The lens having the positive refractive power satisfies the conditional expression (6), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (6) to 0.535, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the fourth embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (7) described above.
θgF2>0.56  (7)

The lens having the negative refractive power satisfies the conditional expression (7), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (7) to 0.58, the advantageous effects of this embodiment can be more secured.

Next, a fifth embodiment of the scanning optical system is described. The scanning optical system according to the fifth embodiment has a configuration similar to that of the scanning optical system SL according to the first embodiment. Accordingly, the same symbols as those in the first embodiment are assigned and description is made. As with a scanning optical system SL(1) shown inFIG.2, the scanning optical system SL according to the fifth embodiment comprises, for example: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the scanning mechanism31(pupil conjugate surface P). By arranging the first lens group G1and the third lens group G3that have the negative refractive powers before and after the second lens group G2having the positive refractive power, the Petzval sum can be reduced close to zero, and the field curves can be favorably corrected.

The scanning optical system SL according to the fifth embodiment may be a scanning optical system SL(2) shown inFIG.4, a scanning optical system SL(3) shown inFIG.6, or a scanning optical system SL(4) shown inFIG.8. The scanning optical system SL according to the fifth embodiment may be a scanning optical system SL(5) shown inFIG.10, a scanning optical system SL(6) shown inFIG.12, or a scanning optical system SL(7) shown inFIG.14.

In the scanning optical system SL according to the fifth embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a positive refractive power, and satisfies the following conditional expression (1) described above.
νd1>80  (1)

The lens having the positive refractive power satisfies the conditional expression (1), which can favorably correct the chromatic aberration of magnification, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (1) to 90, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the fifth embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a negative refractive power, and satisfies the following conditional expression (2) described above.
νd2<50  (2)

The lens having the negative refractive power satisfies the conditional expression (2), which can favorably correct the chromatic aberration of magnification, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (2) to 40, the advantageous effects of this embodiment can be more secured.

The scanning optical system SL according to the fifth embodiment satisfies the following conditional expression (9).
Φ max≥48.0 [mm]  (9)
where Φ max: the maximum outer diameter of the scanning optical system SL.

The conditional expression (9) defines the maximum outer diameter of the scanning optical system SL. The conditional expression (9) is satisfied, which can increase the maximum outer diameter of the scanning optical system SL, and increase the maximum number of fields of view of the scanning optical system SL accordingly, thereby allowing the field of view to be increased. According to the fifth embodiment, the conditional expressions (1), (2) and (9) are satisfied, which can reduce the chromatic aberration of magnification, and increase the field of view.

If the corresponding value of the conditional expression (9) falls below the lower limit value, the maximum outer diameter of the scanning optical system SL decreases, and the maximum number of fields of view of the scanning optical system SL decreases accordingly. It is difficult to increase the field of view. By setting the lower limit value of the conditional expression (9) to 48.5 [mm], the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the fifth embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (4) described above.
θgF1−(−0.00168×νd1)−0.644>0.03  (4)

The lens having the positive refractive power satisfies the conditional expression (4), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (4) to 0.04, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the fifth embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (5) described above.
θgF2−(−0.00168×νd2)−0.644<−0.002  (5)

The lens having the negative refractive power satisfies the conditional expression (5), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (5) to −0.004, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the fifth embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (6) described above.
θgF1<0.55  (6)

The lens having the positive refractive power satisfies the conditional expression (6), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (6) to 0.535, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the fifth embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (7) described above.
θgF2>0.56  (7)

The lens having the negative refractive power satisfies the conditional expression (7), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (7) to 0.58, the advantageous effects of this embodiment can be more secured.

Next, a sixth embodiment of the scanning optical system is described. The scanning optical system according to the sixth embodiment has a configuration similar to that of the scanning optical system SL according to the first embodiment. Accordingly, the same symbols as those in the first embodiment are assigned and description is made. As with a scanning optical system SL(1) shown inFIG.2, the scanning optical system SL according to the sixth embodiment comprises, for example: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the scanning mechanism31(pupil conjugate surface P). By arranging the first lens group G1and the third lens group G3that have the negative refractive powers before and after the second lens group G2having the positive refractive power, the Petzval sum can be reduced close to zero, and the field curves can be favorably corrected.

The scanning optical system SL according to the sixth embodiment may be a scanning optical system SL(2) shown inFIG.4, a scanning optical system SL(3) shown inFIG.6, or a scanning optical system SL(4) shown inFIG.8. The scanning optical system SL according to the sixth embodiment may be a scanning optical system SL(5) shown inFIG.10, a scanning optical system SL(6) shown inFIG.12, or a scanning optical system SL(7) shown inFIG.14.

In the scanning optical system SL according to the sixth embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a positive refractive power, and satisfies the following conditional expression (4) described above.
θgF1−(−0.00168×νd1)−0.644>0.03  (4)

The lens having the positive refractive power satisfies the conditional expression (4), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (4) to 0.04, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the sixth embodiment, at least one lens included in any of the first lens group G1, the second lens group G2and the third lens group G3has a negative refractive power, and satisfies the following conditional expression (5) described above.
θgF2−(−0.00168×νd2)−0.644<−0.002  (5)

The lens having the negative refractive power satisfies the conditional expression (5), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (5) to −0.004, the advantageous effects of this embodiment can be more secured.

The scanning optical system SL according to the sixth embodiment satisfies the following conditional expression (9) described above.
Φ max≥48.0 [mm]  (9)

By satisfying the conditional expression (9), the field of view can be increased, as with the first embodiment. According to the sixth embodiment, the conditional expressions (4), (5) and (9) are satisfied, which can reduce the chromatic aberration of magnification, and increase the field of view. Note that by setting the lower limit value of the conditional expression (9) to 48.5 [mm], the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the sixth embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (1) described above.
νd1>80  (1)

The lens having the positive refractive power satisfies the conditional expression (1), which can favorably correct the chromatic aberration of magnification, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (1) to 90, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the sixth embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (2) described above.
νd2<50  (2)

The lens having the negative refractive power satisfies the conditional expression (2), which can favorably correct the chromatic aberration of magnification, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (2) to 40, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the sixth embodiment, at least one lens having the positive refractive power described above may satisfy the following conditional expression (6) described above.
θgF1<0.55  (6)

The lens having the positive refractive power satisfies the conditional expression (6), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the upper limit value of the conditional expression (6) to 0.535, the advantageous effects of this embodiment can be more secured.

In the scanning optical system SL according to the sixth embodiment, at least one lens having the negative refractive power described above may satisfy the following conditional expression (7) described above.
θgF2>0.56  (7)

The lens having the negative refractive power satisfies the conditional expression (7), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light, as with the first embodiment. Note that by setting the lower limit value of the conditional expression (7) to 0.58, the advantageous effects of this embodiment can be more secured.

The scanning optical systems SL according to the first to sixth embodiments may satisfy the following conditional expression (10).
0.35<FOV/Fh<0.55  (10)
where FOV: the maximum number of fields of view of the scanning optical system SL.Fh: the focal length of the scanning optical system SL.

The conditional expression (10) defines the relationship between the maximum number of fields of view of the scanning optical system SL and the focal length of the scanning optical system SL. By satisfying the conditional expression (10), the size of the scanning mechanism31is appropriately maintained, and the scanning speed is maintained while the maximum number of fields of view of the scanning optical system SL is increased, thereby allowing a wide field of view on the sample SA to be achieved.

If the corresponding value of the conditional expression (10) falls below the lower limit value, the focal length of the scanning optical system SL increases, and the numerical aperture of the scanning optical system SL decreases. As a result, in order to secure the luminance, the diameter of the pupil where the scanning mechanism31is arranged is required to increase, which in turn increases the size of the scanning mechanism31. By setting the lower limit value of the conditional expression (10) to 0.40, the advantageous effects of this embodiment can be more secured.

If the corresponding value of the conditional expression (10) exceeds the upper limit value, the focal length of the scanning optical system SL decreases, and the deflection angle of laser light by the scanning mechanism31is required to be large. As a result, the speed of scanning the sample SA with the laser light by the scanning mechanism31decreases. If the focal length of the scanning optical system SL decreases, the imaging performances, such as of field curves and chromatic aberration of magnification, decrease at the peripheral part of the field of view. By setting the upper limit value of the conditional expression (10) to 0.50, the advantageous effects of this embodiment can be more secured.

In each of the scanning optical systems SL according to the first to sixth embodiments, at least one lens having the positive refractive power described above may satisfy the following conditional expression (11).
θCt1−(0.0048×νd1)−0.542<−0.05  (11)
where θCt1: a partial dispersion ratio of the lens having the positive refractive power, defined by the following expression,
θCt1=(nC1−nt1)/(nF1−nC1),wherein a refractive index of the lens having the positive refractive power for C-line is nC1, a refractive index of the lens having the positive refractive power for t-line is nt1, and a refractive index of the lens having the positive refractive power for F-line is nF1.

The conditional expression (11) defines the relationship between the partial dispersion ratio and the Abbe number of the material of the lens having the positive refractive power. The lens having the positive refractive power satisfies the conditional expression (11), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light and a wavelength region of infrared light (for example, a wavelength region up to about 1000 nm), using the anomalous dispersion characteristics of the material of the lens having the positive refractive power. Accordingly, even in a scanning-type confocal microscope that uses excitation light in a wavelength region ranging from about 700 nm to 1000 nm and supports fluorescent observation with multiphoton excitation, the chromatic aberration of magnification can be favorably corrected.

If the corresponding value of the conditional expression (11) exceeds the upper limit value, the effect of the anomalous dispersion characteristics becomes insufficient. Accordingly, it is difficult to correct the chromatic aberration of magnification. By setting the upper limit value of the conditional expression (11) to −0.10, the advantageous effects of this embodiment can be more secured.

In each of the scanning optical systems SL according to the first to sixth embodiments, at least one lens having the negative refractive power described above may satisfy the following conditional expression (12).
θCt2−(0.0048×νd2)−0.542>0.01  (12)
where θCt2: a partial dispersion ratio of the lens having the negative refractive power, defined by the following expression,
θCt2=(nC2−nt2)/(nF2−nC2),wherein a refractive index of the lens having the negative refractive power for C-line is nC2, a refractive index of the lens having the negative refractive power for t-line is nt2, and a refractive index of the lens having the negative refractive power for F-line is nF2.

The conditional expression (12) defines the relationship between the partial dispersion ratio and the Abbe number of the material of the lens having the negative refractive power. The lens having the negative refractive power satisfies the conditional expression (12), which can favorably correct the chromatic aberration of magnification in the wavelength region of visible light and a wavelength region of infrared light (for example, a wavelength region up to about 1000 nm), using the anomalous dispersion characteristics of the material of the lens having the negative refractive power. Accordingly, even in a scanning-type confocal microscope that uses excitation light in a wavelength region ranging from about 700 nm to 1000 nm and supports fluorescent observation with multiphoton excitation, the chromatic aberration of magnification can be favorably corrected.

If the corresponding value of the conditional expression (12) falls below the lower limit value, the effect of the anomalous dispersion characteristics becomes insufficient. Accordingly, it is difficult to correct the chromatic aberration of magnification. By setting the lower limit value of the conditional expression (12) to 0.015, the advantageous effects of this embodiment can be more secured.

In each of the scanning optical systems SL according to the first to sixth embodiments, at least one lens having the positive refractive power described above may satisfy the following conditional expression (13).
θCt1>0.79  (13)

The conditional expression (13) defines the partial dispersion ratio of the material of the lens having the positive refractive power. The lens having the positive refractive power satisfies the conditional expression (13), which can make the anomalous dispersion characteristics of the material of the lens having the positive refractive power appropriate, and favorably correct the chromatic aberration of magnification in the wavelength region of visible light and a wavelength region of infrared light (for example, a wavelength region up to about 1000 nm).

If the corresponding value of the conditional expression (13) falls below the lower limit value, the anomalous dispersion characteristics of the material of the lens having the positive refractive power become excessive. Accordingly, it is difficult to correct the chromatic aberration of magnification. By setting the lower limit value of the conditional expression (13) to 0.82, the advantageous effects of this embodiment can be more secured.

In each of the scanning optical systems SL according to the first to sixth embodiments, at least one lens having the negative refractive power described above may satisfy the following conditional expression (14).
θCt2<0.8  (14)

The conditional expression (14) defines the partial dispersion ratio of the material of the lens having the negative refractive power. The lens having the negative refractive power satisfies the conditional expression (14), which can make the anomalous dispersion characteristics of the material of the lens having the negative refractive power appropriate, and favorably correct the chromatic aberration of magnification in the wavelength region of visible light and a wavelength region of infrared light (for example, a wavelength region up to about 1000 nm).

If the corresponding value of the conditional expression (14) exceeds the upper limit value, the anomalous dispersion characteristics of the material of the lens having the negative refractive power become excessive. Accordingly, it is difficult to correct the chromatic aberration of magnification. By setting the upper limit value of the conditional expression (14) to 0.75, the advantageous effects of this embodiment can be more secured.

The scanning optical systems SL according to the first to sixth embodiments may satisfy following conditional expressions (15) to (17).
1.5<(−Fh1)/Fh<5.0  (15)
0.6<Fh2/Fh<0.9  (16)
0.8<(−Fh3)/Fh<1.3  (17)
whereFh1: the focal length of the first lens group G1,Fh2: the focal length of the second lens group G2,Fh3: the focal length of the third lens group G3, andFh: the focal length of the scanning optical system SL.

The conditional expression (15) defines the power (refractive power) of the first lens group G1. The conditional expression (16) defines the power (refractive power) of the second lens group G2. The conditional expression (17) defines the power (refractive power) of the third lens group G3. By satisfying the conditional expressions (15) to (17), the distance between the scanning mechanism31and the scanning optical system SL, and the distance between the scanning optical system SL and the imaging surface13(primary image surface) by the second objective lens23can be maintained to be appropriate distances. The Petzval sum can be reduced close to zero, and the field curves can be favorably corrected accordingly.

If the corresponding value of the conditional expression (15) falls below the lower limit value, the negative power of the first lens group G1becomes excessive, and the Petzval sum becomes negatively strong accordingly. It is difficult to correct the field curves. By setting the lower limit value of the conditional expression (15) to 1.7, the advantageous effects of this embodiment can be more secured.

If the corresponding value of the conditional expression (15) exceeds the upper limit value, the negative power of the first lens group G1becomes insufficient, and the Petzval sum becomes positively large accordingly. It is difficult to correct the field curves. By setting the upper limit value of the conditional expression (15) to 4.6, the advantageous effects of this embodiment can be more secured.

If the corresponding value of the conditional expression (16) falls below the lower limit value, the positive power of the second lens group G2becomes excessive. Accordingly, it is difficult to correct off-axis aberrations, in particular, the coma aberration and the chromatic aberration of magnification. The Petzval sum becomes positively large, and it is difficult to correct the field curves. By setting the lower limit value of the conditional expression (16) to 0.65, the advantageous effects of this embodiment can be more secured.

If the corresponding value of the conditional expression (16) exceeds the upper limit value, the positive power of the second lens group G2becomes insufficient, and the Petzval sum becomes negatively strong accordingly. It is difficult to correct the field curves. By setting the upper limit value of the conditional expression (16) to 0.85, the advantageous effects of this embodiment can be more secured.

If the corresponding value of the conditional expression (17) falls below the lower limit value, the negative power of the third lens group G3becomes excessive, and the Petzval sum becomes negatively strong accordingly. It is difficult to correct the field curves. The distance (back focus) between the scanning optical system SL and the primary image surface13becomes small. Accordingly, an image of dust or the like on a lens surface on the primary image surface side tends to be taken. By setting the lower limit value of the conditional expression (17) to 0.85, the advantageous effects of this embodiment can be more secured.

If the corresponding value of the conditional expression (17) exceeds the upper limit value, the negative power of the third lens group G3becomes insufficient, and the Petzval sum becomes positively large accordingly. It is difficult to correct the field curves. By setting the upper limit value of the conditional expression (17) to 1.2, the advantageous effects of this embodiment can be more secured.

In each of the scanning optical systems SL according to the first to sixth embodiments, the lens surface that is closer to the scanning mechanism31and is of the lens of the first lens group G1arranged closest to the scanning mechanism31may be a concave surface, and the lens surface that is closer to the objective lens24and is of the lens of the third lens group G3arranged closest to the objective lens24may be a concave surface. Accordingly, the off-axis aberrations, in particular, field curves, can be favorably corrected.

In each of the scanning optical systems SL according to the first to sixth embodiments, the second lens group G2may include the lens having the positive refractive power described above. Accordingly, the longitudinal chromatic aberration and the chromatic aberration of magnification can be favorably corrected.

In each of the scanning optical systems SL according to the first to sixth embodiments, the second lens group G2may include at least one cemented lens. Accordingly, the longitudinal chromatic aberration and the chromatic aberration of magnification can be favorably corrected.

In each of the scanning optical systems SL according to the first to sixth embodiments, the cemented lens (of the second lens group G2) may include the lens having the positive refractive power described above. Accordingly, the longitudinal chromatic aberration and the chromatic aberration of magnification can be favorably corrected.

In each of the scanning optical systems SL according to the first to sixth embodiments, the third lens group G3may include a first cemented lens and a second cemented lens arranged sequentially from the side of the scanning mechanism31. Accordingly, the longitudinal chromatic aberration and the chromatic aberration of magnification can be favorably corrected.

The scanning optical systems SL according to the first to sixth embodiments may satisfy the following conditional expression (18).
νd3<νd4  (18)
where νd3: an Abbe number with reference to d-line of a positive lens included in the first cemented lens, defined by the following expression, assuming that a refractive index of the positive lens for d-line is nd3, a refractive index of the positive lens for F-line is nF3, and a refractive index of the positive lens for C-line is nC3,
νd3=(nd3−1)/(nF3−nC3)
where νd4: an Abbe number with reference to d-line of a negative lens included in the first cemented lens, defined by the following expression,
νd4=(nd4−1)/(nF4−nC4),wherein a refractive index of the negative lens for d-line is nd4, a refractive index of the negative lens for F-line is nF4, and a refractive index of the negative lens for C-line is nC4.

The conditional expression (18) defines the relationship between the Abbe number with reference to d-line of the positive lens included in the first cemented lens, and the Abbe number with reference to d-line of the negative lens included in the first cemented lens. By arranging the cemented lens intentionally causing chromatic aberrations at a predetermined position, the chromatic aberrations can be corrected over a wide wavelength region. In each of the scanning optical systems SL according to the first to sixth embodiments, chromatic aberrations can be intentionally caused at the first cemented lens between the two cemented lenses in the third lens group G3. The first cemented lens intentionally causing the chromatic aberrations satisfies the conditional expression (18), which allows correction of the chromatic aberrations over a wide wavelength region and, in particular, correction of the chromatic aberration of magnification, to be favorably performed.

In each of the scanning optical systems SL according to the first to sixth embodiments, the first lens group G1may include at least one cemented lens or a single lens. The third lens group G3may include two cemented lenses. Note that the second lens group G2may be arranged between the first lens group G1and the third lens group G3.

The scanning optical systems SL according to the first to sixth embodiments may satisfy the following conditional expression (19).
(FOV/Fh)×(NAob×Fob)>3.1 [mm]  (19)
where FOV: the maximum number of fields of view of the scanning optical system SL.Fh: the focal length of the scanning optical system SL.NAob: a numerical aperture of the objective lens24, andFob: a focal length of the objective lens24.

The conditional expression (19) defines the relationship between the maximum number of fields of view and the focal length of the scanning optical system SL, and the numerical aperture and the focal length of the objective lens24. When it is assumed that Wh=FOV/Fh and Pob=NAob×Fob, the conditional expression (19) can be represented as the following expression (19-1).
Wh×Pob>3.1 [mm]  (19-1)where it is assumed that the focal length of the lens is f, the maximum image height is y, the half angle of view is ω, the numerical aperture is NA, and the pupil diameter is ϕ. Typically, the relationship between the focal length f and the maximum image height y of the lens is y=f×tan ω. The relationship in a case where the lens (focal length f) is replaced with the scanning optical system SL (Focal length Fh), y=Fh×tan ω. The relationship between the maximum number of fields of view FOV and the maximum image height y is FOV=2×y. Consequently, Wh can be represented as the following expression (19-1A).

Wh=FOV/Fh=(2×y)/(y/tan⁢ω)=2×tan⁢ω(19-1⁢A)

As shown in the expression (19-1A), Wh substantially means the angle of view at the maximum number of fields of view of the scanning optical system SL. The relationship between the focal length f and the numerical aperture NA of the lens is ϕ=2×f×NA. The relationship described above in a case where the lens (the focal length f and the numerical aperture NA) is replaced with the objective lens24(the focal length Fob and the numerical aperture NAob) is ϕ=2×Fob×NAob. Consequently, Pob can be represented as the following expression (19-1B).

Pob=NAob×Fob=(2×Fob×NAob)/2=ϕ/2(19-1⁢B)

As shown in the expression (19-1B), Pob substantially means half a pupil diameter of the objective lens24. That is, in the conditional expression (19-1), Wh corresponds to the angle of view at the maximum number of fields of view of the scanning optical system SL, and Pob corresponds to the pupil diameter of the objective lens24. Accordingly, by satisfying the conditional expression (19-1), that is, the conditional expression (19), the pupil diameter of the objective lens24can be sufficiently secured with respect to the maximum number of fields of view of the scanning optical system SL, and a wide field of view and high resolution on the sample SA can be secured.

If the corresponding value of the conditional expression (19) falls below the lower limit value, the pupil diameter of the objective lens24cannot be sufficiently secured even with the maximum number of fields of view of the scanning optical system SL being increased to increase the field of view of the scanning optical system SL; it is difficult to observe the sample SA with a sufficient resolution. The focal length of the scanning optical system SL increases. Accordingly, the numerical aperture of the scanning optical system SL decreases. As a result, the diameter of the laser light (the beam diameter of excitation light) incident on the objective lens24decreases. It is difficult to observe the sample SA with a sufficient resolution. By setting the lower limit value of the conditional expression (19) to 4.0 [mm], the advantageous effects of this embodiment can be more secured.

The scanning optical systems SL according to the first to sixth embodiments may satisfy the following conditional expression (20).
Φb×θb>63 [mm×degrees]  (20)
where Φb: the diameter of laser light (the beam diameter of excitation light) incident from the scanning mechanism31onto the scanning optical system SL, andθb: a maximum angle between the optical axis and the laser light incident from the scanning mechanism31onto the scanning optical system SL.

The conditional expression (20) defines the relationship between the diameter of the laser light (e.g., the diameter of laser light reflected by a galvanometer mirror of the scanning mechanism31) incident on the scanning optical system SL from the scanning mechanism31, and the maximum angle (e.g., the maximum angle of laser light inclined from the optical axis by the galvanometer mirror of the scanning mechanism31) between the optical axis and the laser light incident on the scanning optical system SL from the scanning mechanism31. By satisfying the conditional expression (20), a high resolution for the sample SA can be secured even with the field of view being increased.

If the corresponding value of the conditional expression (20) falls below the lower limit value, a sufficient diameter of laser light (the beam diameter of excitation light) cannot be achieved even with the maximum number of fields of view of the scanning optical system SL being increased to increase the field of view of the scanning optical system SL, making it difficult to achieve a sufficient resolution for the sample SA. If a sufficient resolution for the sample SA is intended to be secured, it is difficult to increase the field of view. By setting the lower limit value of the conditional expression (20) to 70 [mm×degrees], the advantageous effects of this embodiment can be more secured.

EXAMPLES

Hereinafter, scanning optical systems SL according to examples of the first to sixth embodiments are described with reference to the drawings.FIGS.2,4,6,8,10,12and14are sectional views showing configurations and refractive power distributions of the scanning optical systems SL {SL(1) to SL(7)} according to first to seventh examples. In theseFIGS.2,4,6,8,10,12and14, each lens group is represented by a combinations of a symbol G and a numeral, and each lens is represented by a combination of a symbol L and a numeral. In this case, to prevent the types and numbers of symbols and numerals from being large and complicated, the lens groups and the like are represented using combinations of symbols and numerals independently in each of the examples. Accordingly, even if the same combinations of symbols and numerals are used among the examples, the usage does not mean the same configurations.

Hereinafter, Tables 1 to 7 are shown. Among them, Table 1 is a table showing each data item in the first example, Table 2 is that in the second example, Table 3 is that in the third example, Table 4 is that in the fourth example, Table 5 is that in the fifth example, Table 6 is that in the sixth example, and Table is that in the seventh example. In each example, d-line (wavelength λ=587.56 nm), g-line (wavelength λ=435.84 nm), and t-line (wavelength λ=1013.98 nm) are selected as calculation targets of aberration characteristics.

The table of [General Data], Fh indicates the focal length of the entire scanning optical system. FOV indicates the maximum number of fields of view of the scanning optical system. NAob indicates the numerical aperture of the objective lens. Fob indicates the focal length of the objective lens. Φb indicates the diameter of laser light incident from the scanning mechanism onto the scanning optical system. θb indicates the maximum angle between the optical axis and the laser light incident from the scanning mechanism onto the scanning optical system.

In the table of [Lens Data], the surface number indicates the order of optical surfaces from the side of the pupil conjugate surface (scanning mechanism) along the ray traveling direction. R indicates the radius of curvature of each optical surface (the surface where the center of curvature is positioned on the image surface side is assumed to have a positive value). D indicates the distance to the next optical surface on the optical axis; the distance is a distance from each optical surface to the next optical surface (or image surface). νd indicates the Abbe number with reference to d-line of the material of the optical member. nd indicates the refractive index of the material of the optical member for d-line. θgF and θCt indicate the partial dispersion ratios of the material of the optical member. The radius of curvature of “∞” indicates a plane or an aperture. The description of the refractive index nd=1.000000 of air is omitted.

The refractive index of the material of the optical member for C-line (wavelength λ=656.27 nm) is assumed as nC. The refractive index of the material of the optical member for d-line (wavelength λ=587.56 nm) is assumed as nd. The refractive index of the material of the optical member for F-line (wavelength λ=486.13 nm) is assumed as nF. The refractive index of the material of the optical member for g-line (wavelength λ=435.84 nm) is assumed as ng. The refractive index of the material of the optical member for t-line (wavelength λ=1013.98 nm) is assumed as nt.

Here, the Abbe number νd with reference to d-line of the material of the optical member is defined by the following expression (A).
νd=(nd−1)/(nF−nC)  (A)

Here, the partial dispersion ratio θgF of the material of the optical member is defined by the following expression (B).
θgF=(ng−nF)/(nF−nC)  (B)

Here, the partial dispersion ratio θCt of the material of the optical member is defined by the following expression (C).
θCt=(nC−nt)/(nF−nC)  (C)

The table of [Lens Group Data] shows the first surface (the surface closest to the scanning mechanism) of each lens group and the focal length.

The table of [Conditional Expression Corresponding Value] shows the value corresponding to each conditional expression.

Hereinafter, among all the data values, “mm” is generally used for the listed focal length Fh, radius of curvature R, distance D to the next lens surface, other lengths and the like if not otherwise specified. However, there is no limitation thereto, because the optical system can achieve equivalent optical performances even if being proportionally enlarged or reduced.

The description of the table so far is common to all the examples. Hereinafter, redundant description is omitted.

First Example

The first example is described with reference toFIGS.2and3and Table 1.FIG.2shows a lens configuration of a scanning optical system according to the first example of the first to sixth embodiments. A scanning optical system SL(1) according to the first example comprises: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the pupil conjugate surface P. Note that at a neighborhood of the pupil conjugate surface P, the scanning mechanism31(galvanometer mirror or the like) described above is arranged. The image surface I corresponds to the imaging surface13described above. A sign (+) or (−) assigned to each lens group symbol indicates the refractive power of each lens group. This also applies to all the examples described below.

The first lens group G1comprises a cemented lens of a negative meniscus lens L11with a concave surface facing the side of the pupil conjugate surface P, and a positive meniscus lens L12with a concave surface facing the side of the pupil conjugate surface P. The second lens group G2comprises: a positive meniscus lens L21with a concave surface facing the side of the pupil conjugate surface P; a biconvex positive lens L22; a cemented lens of a biconvex positive lens L23and a plano-concave negative lens L24; and a biconvex positive lens L25, the lenses being arranged sequentially from the side of the pupil conjugate surface P. The third lens group G3comprises: a first cemented lens of a positive meniscus lens L31with a convex surface facing the side of the pupil conjugate surface P, and a negative meniscus lens L32with a convex surface facing the side of the pupil conjugate surface P; and a second cemented lens of a biconvex positive lens L33, and a biconcave negative lens L34, the lenses being arranged sequentially from the side of the pupil conjugate surface P. An image surface I is arranged on the third lens group G3on the side toward the objective lens.

The following Table 1 lists values of data on the scanning optical system according to the first example.

TABLE 1[General Data]Fh = 60FOV = 25NAob = 1Fob = 10Φb = 6θb = 11.8[Lens Data]SurfaceNumberRDνdndθgFθCt1∞49.60002−24.993010.000064.141.5168000.53570.86473−139.937010.000082.571.4978200.53860.81754−48.43300.20005−133.20806.550070.311.4874900.52910.89826−63.12200.20007183.869010.000082.571.4978200.53860.81758−65.46402.70009162.003011.300091.361.4560000.53420.839910−53.81202.700034.701.7204670.58340.726711∞0.20001267.22108.150067.901.5931900.54400.796213−349.43700.20001449.86306.300022.801.8080950.63070.659615400.63803.250032.301.7380000.59000.71541625.83102.00001726.049013.650091.361.4560000.53420.839918−57.14002.250060.201.6400000.53770.85931931.799030.2711[Lens Group Data]FirstFocalGroupsurfacelengthG12−134.490G2547.642G314−71.221[Conditional Expression Corresponding Value]Conditional Expression (1)[positive meniscus lens L12] νd1 = 82.57[positive lensL22] νd1 = 82.57[positive lensL23] νd1 = 91.36[positive lensL33] νd1 = 91.36Conditional Expression (2)[negative lens L24] νd2 = 34.70Conditional Expression (3) hmax = 18.34Conditional Expression (4)[positive meniscus lens L12]θgF1-(−0.00168 × νd1) −0.644 = 0.0333[positive lensL22]θgF1-(−0.00168 × νd1) −0.644 = 0.0333[positive lens L23]θgF1-(−0.00168 × νd1) −0.644 = 0.0437[positive lens L33]θgF1-(−0.00168 × νd1) −0.644 = 0.0437Conditional Expression (5)[negative lens L24]θgF2-(−0.00168 × vd2) −0.644 = −0.0023Conditional Expression (6)[positive meniscus lens L12] egF1 = 0.5386[positive lens L22] θgF1 = 0.5386[positive lens L23] θgF1−0.5342[positive lens L33] θgF1 = 0.5342Conditional Expression (7)[negative lens L24] θgF2 = 0.5834Conditional Expression (8) FOV = 25Conditional Expression (9) Φmax = 50.0Conditional Expression (10) FOV/Fh = 0.4167Conditional Expression (11)[positive meniscus lens L12]θCt1-(0.0048 × νd1) −0.542 = −0.1208[positive lens L22]θct1-(0.0048 × νd1) −0.542 = −0.1208[positive lens L23]θCt1-(0.0048 × νd1) −0.542 = −0.1406[positive lens L33]θCt1-(0.0048 × νd1) −0.542 = −0.1406Conditional Expression (12)[negative lens L24]θCt2-(0.0048 × νd2) −0.542 = 0.0181Conditional Expression (13)[positive meniscus lens L12] θCt1 = 0.8175[positive lens L22] θCt1 = 0.8175[positive lens L23] θCt1−0.8399[positive lens L33] θCt1 = 0.8399Conditional Expression (14)[negative lens L24] θCt2−0.7267Conditional Expression (15) (−Fh1)/Fh = 2.241Conditional Expression (16) Fh2/Fh = 0.794Conditional Expression (17) (−Fh3)/Fh = 1.187Conditional Expression (18) νd3 = 22.80νd4 = 32.30Conditional Expression (19) (FOV/Fh) × (NAob × Fob) = 4.17Conditional Expression (20) Φb × θb = 70.8

FIG.3shows various aberration graphs of the scanning optical system according to the first example. In each aberration graph, FNO indicates the F-number, and Y indicates the image height. Note that the spherical aberration graph indicates the value of the F-number corresponding to the maximum diameter. The astigmatism graph and the distortion graph indicate the maximum value of the image height. The coma aberration graph indicates each image height. d indicates d-line (wavelength λ=587.56 nm), g indicates g-line (wavelength λ=435.84 nm), and t indicates t-line (wavelength λ=1013.98 nm). In the astigmatism graph, a solid line indicates a sagittal image surface, and a broken line indicates a meridional image surface. Note that also in the aberration graph in each example described below, symbols similar to those in this example are used, and redundant description is omitted.

Each aberration graph shows that in the scanning optical system according to the first example, various aberrations, such as the chromatic aberration of magnification, are favorably corrected in the wide wavelength region ranging from g-line to t-line, and the system has an excellent imaging performance.

Second Example

The second example is described with reference toFIGS.4and5and Table 2.FIG.4shows a lens configuration of a scanning optical system according to the second example of the first to sixth embodiments. A scanning optical system SL(2) according to the second example comprises: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the pupil conjugate surface P.

The first lens group G1comprises a cemented lens of a negative meniscus lens L11with a concave surface facing the side of the pupil conjugate surface P, and a positive meniscus lens L12with a concave surface facing the side of the pupil conjugate surface P. The second lens group G2comprises: a biconvex positive lens L21; a cemented lens of a biconvex positive lens L22and a plano-concave negative lens L23; and a positive meniscus lens L24with a convex surface facing the side of the pupil conjugate surface P, the lenses being arranged sequentially from the side of the pupil conjugate surface P. The third lens group G3comprises: a first cemented lens of a positive meniscus lens L31with a convex surface facing the side of the pupil conjugate surface P, and a negative meniscus lens L32with a convex surface facing the side of the pupil conjugate surface P; and a second cemented lens of a biconvex positive lens L33, and a biconcave negative lens L34, the lenses being arranged sequentially from the side of the pupil conjugate surface P. An image surface I is arranged on the third lens group G3on the side toward the objective lens.

The following Table 2 lists values of data on the scanning optical system according to the second example.

TABLE 2[General Data]Fh =60FOV =25NAob =1Fob =10Φb =6θb =11.8[Lens Data]SurfaceNumberRDνdndθgFθCt1∞53.55002−23.852912.000064.141.5168000.53570.86473−77.89088.000082.571.4978200.53860.81754−36.06763.50005141.39549.500082.571.4978200.53860.81756−65.66282.00007117.403710.500091.361.4560000.53420.83998−56.54722.500034.701.7204670.58340.72679∞0.20001053.44668.000067.901.5931900.54400.7962112062.15890.20001247.56766.500022.801.8080950.63070.659613213.56802.500032.301.7380000.59000.71541425.44522.50001528.156912.000091.361.4560000.53420.839916−51.36952.500060.201.6400000.53770.85931732.623730.3130[Lens Group Data]FirstFocalGroupsurfacelengthG12−275.012G2550.765G312−65.154[Conditional Expression Corresponding Value]Conditional Expression (1)[positive meniscus lens L12]νd1 = 82.57[positive lens L21]νd1 = 82.57[positive lens L22]νd1 = 91.36[positive lens L33]νd1 = 91.36Conditional Expression (2)[negative lens L23]νd2 = 34.70Conditional Expression (3)hmax = 18.79Conditional Expression (4)[positive meniscus lens L12]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0333[positive lens L21]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0023[positive lens L22]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437[positive lens L33]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437Conditional Expression (5)[negative lens L23]θgF2 − (−0.00168 × νd1) − 0.644 = −0.0023Conditional Expression (6)[positive meniscus lens L12]θgF1 = 0.5386[positive lens L21]θgF1 = 0.5386[positive lens L22]θgF1 = 0.5342[positive lens L33]θgF1 = 0.5342Conditional Expression (7)[negative lens L23]θgF2 = 0.5834Conditional Expression (8)FOV = 25Conditional Expression (9)Φmax = 49.5Conditional Expression (10)FOV/Fh = 0.4167Conditional Expression (11)[positive meniscus lens L12]θCt1 − (0.0048 × νd1) − 0.542 = −0.1208[positive lens L21]θCt1 − (0.0048 × νd1) − 0.542 = −0.1208[positive lens L22]θCt1 − (0.0048 × νd1) − 0.542 = −0.1406[positive lens L33]θCt1 − (0.0048 × νd1) − 0.542 = −0.1406Conditional Expression (12)[negative lens L23]θCt2 − (0.0048 × νd2) − 0.542 = 0.0181Conditional Expression (13)[positive meniscus lens L12]θCt1 = 0.8175[positive lens L21]θCt1 = 0.8175[positive lens L22]θCt1 = 0.8399[positive lens L33]θCt1 = 0.8399Conditional Expression (14)[negative lens L23]θCt2 = 0.7267Conditional Expression (15)(−Fh1)/Fh = 4.584Conditional Expression (16)Fh2/Fh = 0.846Conditional Expression (17)(−Fh3)/Fh = 1.086Conditional Expression (18)νd3 = 22.80νd4 = 32.30Conditional Expression (19)(FOV/Fh) × (NAob × Fob) = 4.17Conditional Expression (20)Φb × θb = 70.8

FIG.5shows various aberration graphs of the scanning optical system according to the second example. Each aberration graph shows that in the scanning optical system according to the second example, various aberrations, such as the chromatic aberration of magnification, are favorably corrected in the wide wavelength region ranging from g-line to t-line, and the system has an excellent imaging performance.

Third Example

The third example is described with reference toFIGS.6and7and Table 3.FIG.6shows a lens configuration of a scanning optical system according to the third example of the first to sixth embodiments. A scanning optical system SL(3) according to the third example comprises: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the pupil conjugate surface P.

The first lens group G1comprises a negative meniscus lens L11with a concave surface facing the side of the pupil conjugate surface P. The second lens group G2comprises: a positive meniscus lens L21with a concave surface facing the side of the pupil conjugate surface P; a cemented lens of a biconvex positive lens L22, and a negative meniscus lens L23with a concave surface facing the side of the pupil conjugate surface P; and a biconvex positive lens L24, the lenses being arranged sequentially from the side of the pupil conjugate surface P. The third lens group G3comprises: a first cemented lens of a positive meniscus lens L31with a convex surface facing the side of the pupil conjugate surface P, and a negative meniscus lens L32with a convex surface facing the side of the pupil conjugate surface P; and a second cemented lens of a biconvex positive lens L33, and a biconcave negative lens L34, the lenses being arranged sequentially from the side of the pupil conjugate surface P. An image surface I is arranged on the third lens group G3on the side toward the objective lens.

The following Table 3 lists values of data on the scanning optical system according to the third example.

TABLE 3[General Data]Fh =60FOV =25NAob =1Fob =10Φb =6θb =11.8[ Lens Data]SurfaceNumberRDνdndθgFθCt1∞53.35002−25.018210.000064.141.5168000.53570.86473−53.78788.50004−504.78169.000082.571.4978200.53860.81755−41.71260.50006224.310412.500082.571.4978200.53860.81757−41.02252.700034.701.7204670.58340.72678−116.37990.2000956.07839.000067.901.5931900.54400.796210−582.11350.20001145.72567.000022.801.8080950.63070.659612179.33733.000032.301.7380000.59000.71541321.65752.00001421.759214.500091.361.4560000.53420.839915−50.78472.500060.201.6400000.53770.85931630.269830.3911[Lens Group Data]FirstFocalGroupsurfacelengthG12−102.666G2441.948G311−65.054[Conditional Expression Corresponding Value]Conditional Expression (1)[positive meniscus lens L21]νd1 = 82.57[positive lens L22]νd1 = 82.57[positive lens L33]νd1 = 91.36Conditional Expression (2)[negative meniscus lens L23]νd2 = 34.70Conditional Expression (3)hmax = 19.56Conditional Expression (4)[positive meniscus lens L21]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0333[positive lens L22]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0333[positive lens L33]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437Conditional Expression (5)[negative meniscus lens L23]θgF2 − (−0.00168 × νd2) − 0.644 = −0.0023Conditional Expression (6)[positive meniscus lens L21]θgF1 = 0.5386[positive lens L22]θgF1 = 0.5386[positive lens L33]θgF1 = 0.5342Conditional Expression (7)[negative meniscus lens L23]θgF2 = 0.5834Conditional Expression (8)FOV = 25Conditional Expression (9)Φmax = 50.0Conditional Expression (10)FOV/Fh = 0.4167Conditional Expression (11)[positive meniscus lens L21]θCt1 − (0.0048 × νd1) − 0.542 = −0.1208[positive lens L22]θCt1 − (0.0048 × νd1) − 0.542 = −0.1208[positive lens L33]θCt1 − (0.0048 × νd1) − 0.542 = −0.1406Conditional Expression (12)[negative meniscus lens L23]θCt2 − (0.0048 × νd2) − 0.542 = 0.0181Conditional Expression (13)[positive meniscus lens L21]θCt1 = 0.8175[positive lens L22]θCt1 = 0.8175[positive lens L33]θCt1 = 0.8399Conditional Expression (14)[negative meniscus lens L23]θCt2 = 0.7267Conditional Expression (15)(−Fh1)/Fh = 1.711Conditional Expression (16)Fh2/Fh = 0.699Conditional Expression (17)(−Fh3)/Fh = 1.084Conditional Expression (18)νd3 = 22.80νd4 = 32.30Conditional Expression (19)(FOV/Fh) × (NAob × Fob) = 4.17Conditional Expression (20)Φb × θb = 70.8

FIG.7shows various aberration graphs of the scanning optical system according to the third example. Each aberration graph shows that in the scanning optical system according to the third example, various aberrations, such as the chromatic aberration of magnification, are favorably corrected in the wide wavelength region ranging from g-line to t-line, and the system has an excellent imaging performance.

Fourth Example

The fourth example is described with reference toFIGS.8and9and Table 4.FIG.8shows a lens configuration of a scanning optical system according to the fourth example of the first to sixth embodiments. A scanning optical system SL(4) according to the fourth example comprises: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the pupil conjugate surface P.

The first lens group G1comprises a negative meniscus lens L11with a concave surface facing the side of the pupil conjugate surface P. The second lens group G2comprises: a positive meniscus lens L21with a concave surface facing the side of the pupil conjugate surface P; a cemented lens of a biconvex positive lens L22, and a negative meniscus lens L23with a concave surface facing the side of the pupil conjugate surface P; and a biconvex positive lens L24, the lenses being arranged sequentially from the side of the pupil conjugate surface P. The third lens group G3comprises: a first cemented lens of a positive meniscus lens L31with a convex surface facing the side of the pupil conjugate surface P, and a negative meniscus lens L32with a convex surface facing the side of the pupil conjugate surface P; and a second cemented lens of a biconvex positive lens L33, and a biconcave negative lens L34, the lenses being arranged sequentially from the side of the pupil conjugate surface P. An image surface I is arranged on the third lens group G3on the side toward the objective lens.

The following Table 4 lists values of data on the scanning optical system according to the fourth example.

TABLE 4[General Data]Fh =60FOV =25NAob =1Fob =10Φb =6θb =11.8[Lens Data]SurfaceNumberRDνdndθgFθCt1∞53.40002−25.024212.500064.141.5168000.53570.86473−54.13696.00004−640.89069.500091.361.4560000.53420.83995−41.70850.50006178.215712.500082.571.4978200.53860.81757−42.40592.700034.701.7204670.58340.72678−108.87460.2000956.55988.500067.901.5931900.54400.796210−1309.38270.20001147.41107.500022.801.8080950.63070.659612240.81853.000032.301.7380000.59000.71541321.58612.00001421.773614.500091.361.4560000.53420.839915−57.14612.500058.571.6516000.54160.83411631.425330.5716[Lens Group Data]GroupFirst surfaceFocal lengthG12−105.472G2442.184G311−64.070[Conditional Expression Corresponding Value]Conditional Expression (1)[positive meniscus lens L21]νd1 = 91.36[positive lens L22]νd1 = 82.57[positive lens L33]νd1 = 91.36Conditional Expression (2)[negative meniscus lens L23]νd2=34.70Conditional Expression (3)hmax=19.51Conditional Expression (4)[positive meniscus lens L21]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437[positive lens L22]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0333[positive lens L33]θgF1 − (−0.00168 × νd1) − 0.644 =0.0437Conditional Expression (5)[negative meniscus lens L23]θgF2 − (−0.00168 × νd2) − 0.644 = −0.0023Conditional Expression (6)[positive meniscus lens L21]θgF1 = 0.5342[positive lens L22]θgF1 = 0.5386[positive lens L33]θgF1 = 0.5342Conditional Expression (7)[negative meniscus lens L23]θgF2 = 0.5834Conditional Expression (8)FOV = 25Conditional Expression (9)Φmax = 50.0Conditional Expression (10)FOV/Fh = 0.4167Conditional Expression (11)[positive meniscus lens L21]θCt1 − (0.0048 × νd1) − 0.542 = −0.1406[positive lens L22]θCt1 − (0.0048 × νd1) − 0.542 = −0.1208[positive lens L33]θCt1 − (0.0048 × νd1) − 0.542 = −0.1406Conditional Expression (12)[negative meniscus lens L23]θCt2 − (0.0048 × νd2) − 0.542 = 0.0181Conditional Expression (13)[positive meniscus lens L21]θCt1 = 0.8399[positive lens L22]θCt1 = 0.8175[positive lens L33]θCt1 = 0.8399Conditional Expression (14)[negative meniscus lens L23]θCt2 = 0.7267Conditional Expression (15)(−Fh1)/Fh = 1.758Conditional Expression (16)Fh2/Fh = 0.703Conditional Expression (17)(−Fh3)/Fh = 1.068Conditional (18)νd3 = 22.80νd4 = 32.30Conditional Expression (19)(FOV/Fh) × (NAob × Fob) = 4.17Conditional Expression (20)Φb x θb = 70.8

FIG.9shows various aberration graphs of the scanning optical system according to the fourth example. Each aberration graph shows that in the scanning optical system according to the fourth example, various aberrations, such as the chromatic aberration of magnification, are favorably corrected in the wide wavelength region ranging from g-line to t-line, and the system has an excellent imaging performance.

Fifth Example

The fifth example is described with reference toFIGS.10and11and Table 5.FIG.10shows a lens configuration of a scanning optical system according to the fifth example of the first to sixth embodiments. A scanning optical system SL(5) according to the fifth example comprises: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the pupil conjugate surface P.

The first lens group G1comprises a cemented lens of a negative meniscus lens L11with a concave surface facing the side of the pupil conjugate surface P, and a positive meniscus lens L12with a concave surface facing the side of the pupil conjugate surface P. The second lens group G2comprises: a positive meniscus lens L21with a concave surface facing the side of the pupil conjugate surface P; a biconvex positive lens L22; a cemented lens of a biconvex positive lens L23, and a biconcave negative lens L24; and a positive meniscus lens L25with a convex surface facing the side of the pupil conjugate surface P, the lenses being arranged sequentially from the side of the pupil conjugate surface P. The third lens group G3comprises: a first cemented lens of a negative meniscus lens L31with a convex surface facing the side of the pupil conjugate surface P, and a positive meniscus lens L32with a convex surface facing the side of the pupil conjugate surface P; and a second cemented lens of a biconvex positive lens L33, and a biconcave negative lens L34, the lenses being arranged sequentially from the side of the pupil conjugate surface P. An image surface I is arranged on the third lens group G3on the side toward the objective lens.

The following Table 5 lists values of data on the scanning optical system according to the fifth example.

TABLE 5[General Data]Fh =60FOV =25NAob =1Fob =10Φb =6θb =11.8[Lens Data]SurfaceNumberRDνdndθgFθCt1∞53.10002−23.37905.000064.141.5168000.53570.86473−521.07179.000091.361.4560000.53420.83994−36.56779.00005−186.56596.500082.571.4978200.53860.81756−55.97770.20007323.41238.000082.571.4978200.53860.81758−70.75780.2000975.93159.500091.361.4560000.53420.839910−109.12232.500034.701.7204670.58340.726711747.78800.20001246.46356.500082.571.4978200.53860.817513136.46440.20001460.27973.000032.301.7380000.59000.71541522.41386.000022.801.8080950.63070.65961628.18852.50001729.526911.000091.361.4560000.53420.839918−60.87912.500058.571.6516000.54160.83411931.848230.3736[Lens Group Data]FirstFocalGroupsurfacelengthG12−144.778G2542.055G314−53.948[Conditional Expression Corresponding Value]Conditional Expression (1)[positive meniscus lens L12]νd1 = 91.36[positive meniscus lens L21]νd1 = 82.57[positive lens L22]νd1 = 82.57[positive lens L23]νd1 = 91.36[positive meniscus lens L25]νd1 = 82.57[positive lens L33]νd1 = 91.36Conditional Expression (2)[negative lens L24]νd2 = 34.70Conditional Expression (3)hmax = 19.62Conditional Expression (4)[positive meniscus lens L12]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437[positive meniscus lens L21]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0333[positive lens L22]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0333[positive lens L23]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437[positive meniscus lens L25]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0333[positive lens L33]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437Conditional Expression (5)[negative lens L24]θgF2 − (−0.00168 × νd1) − 0.644 = −0.0023Conditional Expression (6)[positive meniscus lens L12]θgF1 = 0.5342[positive meniscus lens L21]θgF1 = 0.5386[positive lens L22]θgF1 = 0.5386[positive lens L23]θgF1 = 0.5342[positive meniscus lens L25]θgF1 = 0.5386[positive lens L33]θgF1 = 0.5342Conditional Expression (7)[negative lens L24]θgF2 = 0.5834Conditional Expression (8)FOV = 25Conditional Expression (9)Φmax = 51.0Conditional Expression (10)FOV/Fh = 0.4167Conditional Expression (11)[positive meniscus lens L12]θCt1 − (0.0048 × νd1) − 0.542 = −0.1406[positive meniscus lens L21]θCt1 − (0.0048 × νd1) − 0.542 = −0.1208[positive lens L22]θCt1 − (0.0048 × νd1) − 0.542 = −0.1208[positive lens L23]θCt1 − (0.0048 × νd1) − 0.542 = −0.1406[positive meniscus lens L25]θCt1 − (0.0048 × νd1) − 0.542 = −0.1208[positive lens L33]θCt1 − (0.0048 × νd1) − 0.542 = −0.1406Conditional Expression (12)[negative lens L24]θCt2 − (0.0048 × νd2) − 0.542 = 0.0181Conditional Expression (13)[positive meniscus lens L12]θCt1 = 0.8399[positive meniscus lens L21]θCt1 = 0.8175[positive lens L22]θCt1 = 0.8175[positive lens L23]θCt1 = 0.8399[positive meniscus lens L25]θCt1 = 0.8175[positive lens L33]θCt1 = 0.8399Conditional Expression (14)[negative lens L24]θCt2 = 0.7267Conditional Expression (15)(−Fh1)/Fh = 2.413Conditional Expression (16)Fh2/Fh = 0.701Conditional Expression (17)(−Fh3)/Fh = 0.899Conditional Expression (18)νd3 = 22.80νd4 = 32.30Conditional Expression (19)(FOV/Fh) × (NAob × Fob) = 4.17Conditional Expression (20)Φb × θb = 70.8

FIG.11shows various aberration graphs of the scanning optical system according to the fifth example. Each aberration graph shows that in the scanning optical system according to the fifth example, various aberrations, such as the chromatic aberration of magnification, are favorably corrected in the wide wavelength region ranging from g-line to t-line, and the system has an excellent imaging performance.

Sixth Example

The sixth example is described with reference toFIGS.12and13and Table 6.FIG.12shows a lens configuration of a scanning optical system according to the sixth example of the first to sixth embodiments. A scanning optical system SL(6) according to the sixth example comprises: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the pupil conjugate surface P.

The first lens group G1comprises a cemented lens of a negative meniscus lens L11with a concave surface facing the side of the pupil conjugate surface P, and a positive meniscus lens L12with a concave surface facing the side of the pupil conjugate surface P. The second lens group G2comprises: a positive meniscus lens L21with a concave surface facing the side of the pupil conjugate surface P; a cemented lens of a biconvex positive lens L22, and a negative meniscus lens L23with a concave surface facing the side of the pupil conjugate surface P; and a positive meniscus lens L24with a convex surface facing the side of the pupil conjugate surface P, the lenses being arranged sequentially from the side of the pupil conjugate surface P. The third lens group G3comprises: a first cemented lens of a positive meniscus lens L31with a convex surface facing the side of the pupil conjugate surface P, and a negative meniscus lens L32with a convex surface facing the side of the pupil conjugate surface P; and a second cemented lens of a biconvex positive lens L33, and a biconcave negative lens L34, the lenses being arranged sequentially from the side of the pupil conjugate surface P. An image surface I is arranged on the third lens group G3on the side toward the objective lens.

The following Table 6 lists values of data on the scanning optical system according to the sixth example.

TABLE 6[General Data]Fh =60FOV =25NAob =1Fob =10Φb =6θb =11.8[Lens Data]SurfaceNumberRDνdndθgFθCt1∞52.70002−23.31218.000067.851.4585040.52810.90623−83.91057.000082.571.4978200.53860.81754−38.11258.00005−416.30519.000091.361.4560000.53420.83996−45.35190.50007161.001711.000091.361.4560000.53420.83998−49.18792.500034.701.7204670.58340.72679−147.79980.50001048.88978.500067.901.5931900.54400.796211459.90260.50001248.27946.500022.801.8080950.63070.659613153.12022.500032.301.7380000.59000.71541424.63612.50001524.890012.500091.361.4560000.53420.839916−61.89892.500060.201.6400000.53770.85931728.870130.2538[Lens Group Data]GroupFirst surfaceFocal lengthG12−233.022G2547.089G312−61.973[Conditional Expression Corresponding Value]Conditional Expression (1)[positive meniscus lens L12]νd1 = 82.57[positive meniscus lens L21]νd1 = 91.36[positive lens L22]νd1 = 91.36[positive lens L33]νd1 = 91.36Conditional Expression (2)[negative meniscus lens L23]νd2 = 34.70Conditional Expression (3)hmax = 18.96Conditional Expression (4)[positive meniscus lens L12]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0333[positive meniscus lens L21]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437[positive lens L22]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437[positive lens L33]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437Conditional Expression (5)[negative meniscus lens L23]θgF2 − (−0.00168 × νd2) − 0.644 = −0.0023Conditional Expression (6)[positive meniscus lens L12]θgF1 = 0.5386[positive meniscus lens L21]θgF1 = 0.5342[positive lens L22]θgF1 = 0.5342[positive lens L33]θgF1 = 0.5342Conditional Expression (7)[negative meniscus lens L23]θgF2 = 0.5834Conditional Expression (8)FOV = 25Conditional Expression (9)Φmax = 49.0Conditional Expression (10)FOV/Fh = 0.4167Conditional Expression (11)[positive meniscus lens L12]θgF1 − (0.0048 × νd1) − 0.542 = −0.1208[positive meniscus lens L21]θgF1 − (0.0048 × νdl) − 0.542 = −0.1406[positive lens L22]θgF1 − (0.0048 × νdl) − 0.542 = −0.1406[positive lens L33]θgF1 − (0.0048 × νd1) − 0.542 = −0.1406Conditional Expression (12)[negative meniscus lens L23]@Ct2-(0.0048xνd2) -0.542=0.0181Conditional Expression (13)[positive meniscus lens L12]θCt1 = 0.8175[positive meniscus lens L21]θCt1 = 0.8399[positive lens L22]θCt1 = 0.8399[positive lens L33]θCt1 = 0.8399Conditional Expression (14)[negative meniscus lens L23]θCt2 = 0.7267Conditional Expression (15)(−Fh1)/Fh = 3.884Conditional Expression (16)Fh2/Fh = 0.785Conditional Expression (17)(−Fh3)/Fh = 1.033Conditional Expression (18)νd3 = 22.80νd4 = 32.30Conditional Expression (19)(FOV/Fh) × (NAob × Fob) = 4.17Conditional Expression (20)Φb × θb = 70.8

FIG.13shows various aberration graphs of the scanning optical system according to the sixth example. Each aberration graph shows that in the scanning optical system according to the sixth example, various aberrations, such as the chromatic aberration of magnification, are favorably corrected in the wide wavelength region ranging from g-line to t-line, and the system has an excellent imaging performance.

Seventh Example

The seventh example is described with reference toFIGS.14and15and Table 7.FIG.14shows a lens configuration of a scanning optical system according to the seventh example of the first to sixth embodiments. A scanning optical system SL(7) according to the seventh example comprises: a first lens group G1having a negative refractive power; a second lens group G2having a positive refractive power; and a third lens group G3having a negative refractive power, the lens groups being arranged sequentially from the side of the pupil conjugate surface P.

The first lens group G1comprises a cemented lens of a biconcave negative lens L11, and a biconvex positive lens L12. The second lens group G2comprises: a biconvex positive lens L21; a first cemented lens of a biconvex positive lens L22, and a negative meniscus lens L23with a concave surface facing the side of the pupil conjugate surface P; and a second cemented lens of a biconvex positive lens L24, and a biconcave negative lens L25, the lenses being arranged sequentially from the side of the pupil conjugate surface P. The third lens group G3comprises: a first cemented lens of a biconvex positive lens L31, and a biconcave negative lens L32; and a second cemented lens of a biconvex positive lens L33, and a biconcave negative lens L34, the lenses being arranged sequentially from the side of the pupil conjugate surface P. An image surface I is arranged on the third lens group G3on the side toward the objective lens.

The following Table 7 lists values of data on the scanning optical system according to the seventh example.

TABLE 7[General Data]Fh =60FOV =25NAob =1Fob =10Φb =6θb =11.8[Lens Data]SurfaceNumberRDνdndθgFθCt1∞40.55002−20.540610.000064.141.5168000.53570.864734483.993210.000082.571.4978200.53860.81754−33.22762.00005459.97678.000082.571.4978200.53860.81756−62.44930.500071234.92468.000091.361.4560000.53420.83998−59.87042.500044.271.6133970.56330.78259−106.50740.50001036.600713.000067.901.5931900.54400.796211−163.44012.500034.701.7204670.58340.726712171.56320.50001361.99957.000022.801.8080950.63070.659614−522.02532.500032.301.7380000.59000.71541521.64803.00001627.315814.000091.361.4560000.53420.839917−28.73382.500060.201.6400000.54160.83411869.809821.1140[Lens Group Data]GroupFirst surfaceFocal lengthG12−193.035G2541.909G313−55.895[Conditional Expression Corresponding Value]Conditional Expression (1)[positive lens L12]νd1 = 82.57[positive lens L21]νd1 = 82.57[positive lens L22]νd1 = 91.36[positive lens L33]νd1 = 91.36Conditional Expression (2)[negative meniscus lens L23]νd2 = 44.30[negative lens L25]νd2 = 34.70Conditional Expression (3)hmax = 19.25Conditional Expression (4)[positive lens L12]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0333[positive lens L21]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0333[positive lens L22]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437[positive lens L33]θgF1 − (−0.00168 × νd1) − 0.644 = 0.0437Conditional Expression (5)[negative meniscus lens L23]θgF2 − (−0.00168 × νd2) − 0.644 = −0.0063[negative lens L25]θgF2 − (−0.00168 × νd2) − 0.644 = −0.0023Conditional Expression (6)[positive lens L12]θgF1 = 0.5386[positive lens L21]θgF1 = 0.5386[positive lens L22]θgF1 = 0.5342[positive lens L33]θgF1 = 0.5342Conditional Expression (7)[negative meniscus lens L23]θgF2 = 0.5633[negative lens L25]θgF2 = 0.5834Conditional Expression (8)FOV = 25Conditional Expression (9)Φmax = 48.5Conditional Expression (10)FOV/Fh = 0.5000Conditional Expression (11)[positive lens L12]θCt1 − (0.0048 × νd1) − 0.542 = −0.1208[positive lens L21]θCt1 − (0.0048 × νd1) − 0.542 = −0.1208[positive lens L22]θCt1 − (0.0048 × νd1) − 0.542 = −0.1406[positive lens L33]θCt1 − (0.0048 × νd1) − 0.542 = −0.1406Conditional Expression (12)[negative meniscus lens L23]θCt2 − (0.0048 × νd2) − 0.542 = 0.0279[negative lens L25]θCt2 − (0.0048 × νd2) − 0.542 = 0.0181Conditional Expression (13)[positive lens L12]θCt1 = 0. 8175[positive lens L21]θCt1 = 0.8175[positive lens L22]θCt1 = 0.8399[positive lens L33]θCt1 = 0.8399Conditional Expression (14)[negative meniscus lens L23]θCt2 = 0.7825[negative lens L25]θCt2 = 0.7267Conditional Expression (15)(−Fh1)/Fh = 3.861Conditional Expression (16)Fh2/Fh = 0.838Conditional Expression (17)(−Fh3)/Fh = 1.118Conditional Expression (18)ν3d = 22.80ν4d = 32.30Conditional Expression (19)(FOV/Fh) × (NAob × Fob) = 5.00Conditional Expression (20)Φb × θb = 84.0

FIG.15shows various aberration graphs of the scanning optical system according to the seventh example. Each aberration graph shows that in the scanning optical system according to the seventh example, various aberrations, such as the chromatic aberration of magnification, are favorably corrected in the wide wavelength region ranging from g-line to t-line, and the system has an excellent imaging performance.

According to each example described above, the scanning optical system that can reduce the chromatic aberration of magnification, and increase the field of view, can be achieved.

Here, each example described above shows a specific example of the first to sixth embodiments. Each embodiment is not limited thereto.

Each of the microscopes including scanning optical systems according to the first to sixth embodiments is not limited to the scanning-type confocal microscope1shown inFIG.1, and may be a multiphoton excitation scanning-type confocal microscope that supports fluorescent observation through multiphoton excitation. Referring toFIG.16, a multiphoton excitation scanning-type confocal microscope101is described as a modified example of the scanning-type confocal microscope that comprises the scanning optical system according to the first to sixth embodiments. The multiphoton excitation scanning-type confocal microscope101mainly comprises: an excitation light guide102that guides laser light for illumination onto the sample SA; a scanning device3that deflects laser light to be collected on the sample SA and scans the sample SA; an optical detection device5that detects a light intensity signal from the sample SA; a second optical detection device108that detects a light intensity signal from the sample SA, the signal supporting multiphoton excitation; and a collective optical system104that guides light from the sample SA to the optical detection device5. The multiphoton excitation scanning-type confocal microscope101has a configuration obtained by partially changing that of the scanning-type confocal microscope1described above. Among components of the multiphoton excitation scanning-type confocal microscope101, components (e.g., the scanning device3, the optical detection device5, etc.) similar to those of the scanning-type confocal microscope1described above are assigned the same symbols as those in the case of the scanning-type confocal microscope1, and detailed description thereof is omitted.

The excitation light guide102comprises: a light source unit121that includes a laser light source, and a beam diameter adjusting mechanism; and a dichroic mirror122that reflects pulse laser light (light flux) oscillated by the light source unit121, toward the sample SA. The laser light reflected by the dichroic mirror122is collected on the sample SA by a second objective lens23and an objective lens24. Note that the second objective lens23is arranged in a lens barrel11of a microscope main body10, and the dichroic mirror122is arranged in a microscope housing12provided above the lens barrel11.

The scanning device3comprises a scanning mechanism (scanner)31, and a scanning optical system32. The scanning device3is arranged between the dichroic mirror122in the microscope housing12and the second objective lens23.

The collective optical system104comprises: the objective lens24and the second objective lens23; a total reflection mirror142that reflects fluorescent light from the sample SA; and a first collective lens141that collects the fluorescent light reflected by the total reflection mirror142onto a shielding plate52that is of the optical detection device5and includes a pinhole51. The total reflection mirror142and the first collective lens141are arranged above the dichroic mirror122in the microscope housing12.

The optical detection device5comprises the shielding plate52that has the pinhole51(aperture), an optical fiber53, and a detection unit55. The shielding plate52is arranged in the microscope housing12. The optical fiber53is connected to the microscope housing12and the detection unit55using respective connectors C1and C2. A processing unit57is electrically connected to the detection unit55through a cable56.

The second optical detection device108comprises a dichroic mirror181arranged between the objective lens24and the second objective lens23, relay lenses182and183, and a detection unit184. The processing unit57is electrically connected to the detection unit184via a cable185. Image processing (of the sample SA) based on a detection signal detected by the detection unit184is performed, and an observation image of the sample SA obtained through the image processing by the processing unit57is displayed on a monitor, not shown.

Note that the incident plane of the detection unit184in the second optical detection device108is arranged so as to be substantially conjugate with the pupil surface of the objective lens24. According to the configuration to collect light on the sample SA through the objective lens24, it is possible to allow fluorescent light passing through the objective lens24, which is part of fluorescent light emitted by multiphoton excitation, to completely reach the detection unit184. Accordingly, fluorescent light scattering in the sample SA can also be detected, which can obtain a brighter observation image (of the sample SA). In a case of a multiphoton excitation confocal microscope, a multiphoton excitation phenomenon occurs only in a minute region at a neighborhood of the focus of the objective lens24. Accordingly, similar to a typical confocal microscope, an image at a neighborhood of the focal plane can be obtained, even without using a pinhole.

G1 First lens groupG2 Second lens groupG3 Third lens groupP Pupil conjugate surfaceI Image surface