JP4544904B2 - Optical system - Google Patents

Description

  The present invention relates to an optical system capable of changing a light source position while keeping a light quantity and a light quantity distribution incident on a pupil plane of the optical system constant. In particular, the present invention relates to an optimal optical system capable of condensing light at different depths in a medium, or an optical system suitable for changing a light condensing position.

  Conventionally, there has been a demand for focusing at different depths in the medium, but in this case, spherical aberration is caused. For example, in the biological field, when preparing a microscopic specimen, in most cases, a specimen with a cover glass in which a sample is placed on a slide glass and a cover glass is placed on top of the specimen is generally used. Thus, the spherical aberration described above occurs when specimens with different cover glass thicknesses are observed. Further, for example, in the industrial field, there are glass having different thicknesses for LCD, and spherical aberration occurs even when observing through a substrate. When attempting to observe different thickness (depth) parts, the light condensing performance has changed (deteriorated).

Therefore, conventionally, various techniques have been employed in order to collect light on the portions having different thicknesses as described above while correcting the spherical aberration and suppressing the change in the light collecting performance.
As one of them, for example, one in which parallel plate glasses having different thicknesses are detachably disposed at the tip of a condensing optical system such as an objective lens is known.
Further, for example, an objective lens with a correction ring for a microscope is known in which various aberrations are satisfactorily corrected over a range of an ultra-wide field of view of about 40 × and NA of 0.93, and performance deterioration due to variations in cover glass thickness is small. For example, see Patent Document 1).
Furthermore, an optical system that corrects spherical aberration by moving a spherical aberration correction optical system having a combined focal length of infinity (No Power Lens) in the optical axis direction is also known (see, for example, Patent Document 2).
Furthermore, as shown in FIG. 22, a spherical aberration correction lens 52 is arranged between the objective lens 50 and the light source 51, and the spherical aberration is corrected by moving the spherical aberration correction lens 52 along the optical axis. A microscope apparatus is known (see, for example, Patent Document 3).
JP-A-5-119263 (FIG. 1 etc.) JP 2003-175497 A (FIG. 1 etc.) JP 2001-83428 A (FIG. 1 etc.)

By the way, among the spherical aberration corrections described above, those using parallel flat glass have a large performance deterioration due to the inclination of the parallel flat glass. Therefore, high accuracy is required for the frame that holds the parallel flat plate, and the fixing of the parallel flat plate to the frame also requires high accuracy, which is expensive. Moreover, it was necessary to perform replacement manually in a small WD, which was a very time-consuming operation. Furthermore, it was difficult to perform continuous variable.
In addition, the correction ring objective lens described in Patent Document 1 has high accuracy and is expensive and cannot be reduced in cost. Further, it is difficult to automatically adjust the spherical aberration amount according to the light collection position, and it is difficult to cope with automation.
Further, in the optical system described in Patent Document 2, the converging position does not change even when the spherical aberration is corrected because the combined focal length is corrected by a lens having an infinite distance. When attempting to focus on different parts of the medium, the WD always changes, and aberration correction cannot be performed under a constant WD. Further, since a spherical aberration correcting optical system is required in addition to the beam expander, the configuration is complicated, the number of parts is increased, and it is difficult to reduce the cost.

In the microscope apparatus described in Patent Document 3, spherical aberration can be corrected by moving the spherical aberration correction lens 52 in the optical axis direction as shown in FIG. With the movement of 52, the diameter of the light beam incident on the objective lens 50 changes. That is, the spread of the light flux changes. Therefore, as shown in FIG. 23, the amount of light changes, and the brightness on the sample surface changes. Here, when there is an image acquisition means, the brightness of the image is detected, and the power of the light source is changed according to the brightness. Although the brightness can be made constant by controlling the brightness on the image side, there is a problem that the device configuration is complicated.
Further, when there is a light amount distribution in the pupil plane, the light amount distribution may also change. There has been a problem that the light collecting performance changes due to such a change in the light amount distribution. Furthermore, since the spherical aberration correction lens is moved based on the electrical signal from the image acquisition means, it takes time.

On the other hand, when changing the focus position when observing, a configuration such as moving the stage on which the sample is placed in the optical axis direction or moving the optical system itself in the optical axis direction is generally adopted. Has been.
However, there is a large specimen such as a 12-inch wafer on the stage, and the apparatus has to be enlarged to move the position with high accuracy. Further, when moving the optical system itself, it is difficult to move it with high accuracy.

  The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide an optical system that can easily correct spherical aberration while keeping the light amount distribution constant with a simple structure and without any trouble. Is to provide. Furthermore, it is to provide an optical system that makes it possible to change the light collection position with a simple configuration.

In order to achieve the above object, the present invention provides the following means.
The invention according to claim 1 includes an exit unit that emits a light beam in a parallel light beam state, a condensing optical system that condenses the light beam, and the light beam between the exit unit and the condensing optical system. A first lens group that is arranged to be movable along the optical axis direction of the light beam and is configured by one or more lenses, and the light beam between the first lens group and the condensing optical system. A second lens group arranged in a fixed state and configured by one or more lenses, and a moving means for moving the first lens group according to a distance to a position where the light beam is to be collected. The second lens group provides an optical system in which a rear focal position is disposed at least in the vicinity of an entrance pupil position of the condensing optical system.

In the optical system according to the present invention, the light beams emitted in a parallel light beam state by the emitting means are refracted by the first lens group and the second lens group, respectively, and then enter the condensing optical system to be condensed. At this time, the light source position can be moved in the optical axis direction by moving the first lens group in the optical axis direction by the moving means. That is, by moving the first lens group, the light source position viewed from the second lens group can be changed, and further, the substantial light source position viewed from the condensing optical system can be changed.
Further, since the light beam incident on the first lens group is in a parallel light beam state, the light amount distribution in the pupil plane can be made constant. Therefore, it is possible to suppress a change in light collecting performance.

Here, it demonstrates more concretely with reference to FIG. As shown in FIG. 1, the first lens (first lens group) is arranged in a parallel light beam, and is incident on the first lens even when the first lens moves along the optical axis. If the distance (s) from the optical axis of the light beam to be transmitted is constant, the angle (q) of the light beam after passing through the first lens does not change (is parallel). The rays whose angles do not change (parallel) are condensed (be sure to pass) at one point on the rear focal plane of the second lens (second lens group). Since the rear focal position of the second lens and the entrance pupil position of the condensing optical system are arranged so as to coincide with each other, the parallel light beam incident on the first lens is independent of the position of the first lens. The light beam diameter is always the same at the entrance pupil position of the condensing optical system, and the light is collected without being lost by the condensing optical system.
That is, by moving the first lens group according to the distance to the position where light is to be collected, the light collection position by the light collection optical system can be moved in the optical axis direction. Further, since the diameter of the light beam incident on the condensing optical system is not changed by the second lens group, the change in the light amount at the condensing position or the change in the light amount distribution in the pupil plane as in the conventional case is substantially zero. Can be.

Also, in FIG. 1, the rear focal position of the second lens (second lens group) is made to coincide with the entrance pupil position of the condensing optical system, so that the amount of light at the condensing position changes or within the pupil plane. The change in the light quantity distribution of the second lens can be made substantially zero, but these two positions are positioned close to each other (that is, the rear focal position of the second lens is at least near the entrance pupil position of the condensing optical system). The same effect can be obtained. This will be described more specifically with reference to FIG.
As shown in FIG. 2, the amount of deviation between the rear focal position of the second lens (second lens group) and the entrance pupil position of the condensing optical system is d1, the focal length of the second lens is f2, and the first When the variation rate of the diameter of the light beam incident on the condensing optical system when the lens (the first lens group) moves (reference to the light beam diameter at the rear focal position of the second lens) is x%,
x = 100 × (d1 × d) / (f2 ² ).
That is, when this equation is rewritten, d1 = (f2 ² ) / d × (x / 100).
Here, when the rear focal position of the second lens coincides with the entrance pupil position of the condensing optical system, d1 = 0. That is, even when the first lens moves, the diameter of the light beam incident on the condensing optical system does not change (x = 0).
Although it is best to arrange in this state, by setting d1 ≦ 0.2 × f2 ² / d, the variation rate x ≦ 20 (± 10% or less) of the light beam diameter can be secured.
Furthermore, by setting d1 ≦ 0.1 × f2 ² / d, the variation rate of the beam diameter x ≦ 10 (± 5% or less) can be achieved.
More preferably, by satisfying d1 ≦ 0.06 × f2 ² / d, it is possible to ensure the variation rate x ≦ 6 (± 3% or less) of the beam diameter.

  Furthermore, since the position of the light source can be changed simply by moving the first lens group, there is no need to move the condensing optical system, the stage, etc. in the direction of the optical axis as in the prior art. Accordingly, the configuration can be simplified, and spherical aberration correction can be easily performed without taking time and effort. Further, since it is not necessary to provide a special optical system unlike a conventional correction ring objective lens or the like, the configuration can be simplified and the cost can be reduced.

  According to a second aspect of the present invention, in the optical system according to the first aspect, the condensing optical system condenses the light beam in a medium, and the moving means collects the refractive index and medium surface of the medium to be condensed. An optical system is provided that moves the first lens group according to the distance from the position to which the light is to be collected.

  In the optical system according to the present invention, the moving means moves the first lens group according to the refractive index of the medium to be collected and the distance from the medium surface to the position to be collected. The luminous flux can be condensed to a desired depth, and the amount of spherical aberration can be further suppressed. Therefore, the light collecting performance can be improved.

The invention according to claim 3 provides the optical system according to claim 1 or 2, wherein the emitting means includes a laser light source for emitting laser light.
According to a fourth aspect of the present invention, there is provided a laser light source that emits laser light, parallel light beam means for making the light beam of the laser light emitted from the laser light source a parallel light beam, and the laser light in the parallel light beam state in a medium. And a condensing optical system for condensing light from the condensing point and scanning that can scan the condensing point in the medium in a direction perpendicular to the optical axis direction of the laser light Means, a photodetector arranged at a position conjugate with the laser light source, for detecting the light re-condensed by the condensing optical system, and between the parallel beam means and the condensing optical system A first lens group configured to include one or more lenses disposed in the parallel light beam so as to be movable along an optical axis direction of the parallel light beam; the first lens group and the condensing optical system; Fixed in the parallel light flux between the A second lens group configured; and a moving unit that moves the first lens group according to a refractive index of the medium on which the laser beam is to be collected and a distance from the medium surface to a position on which the laser beam is to be collected; The second lens group provides an optical system in which a rear focal position is arranged at least in the vicinity of the entrance pupil position of the condensing optical system.

In the optical system according to the present invention, the laser light emitted from the laser light source is converted into a parallel light beam by the parallel light beam means and is incident on the first lens group, and the first lens group and the second lens group respectively. After being refracted, the light is condensed in a medium by a condensing optical system, re-condensed, and detected by a photodetector. At this time, the light source position can be moved in the optical axis direction by moving the first lens group in the optical axis direction by the moving means. That is, by moving the first lens group, the light source position seen from the second lens group can be changed, and further, the substantial light source position seen from the condensing optical system can be changed. Thereby, spherical aberration can be suppressed as much as possible according to the depth in the medium.
Further, since the light beam incident on the first lens group is in a parallel light beam state, even if the first lens group is moved in the optical axis direction and the light beam is refracted at each position, the light beam is emitted at the same refraction angle. .

Further, since the rear focal position of the second lens group is arranged at least near the entrance pupil position of the condensing optical system, the light incident on the second lens group is reliably condensed by the condensing optical system. Is done. Here, since the position incident on the second lens group can be changed by moving the first lens group according to the distance to the position where the light is to be condensed, the amount of spherical aberration generated at the desired condensing point can be reduced. It can be suppressed as much as possible. In addition, since the second lens group can reliably enter the condensing optical system without changing the luminous flux, it is possible to suppress the change in the light amount and the change in the light amount distribution in the pupil plane as in the past. it can. That is, the amount of light incident on the condensing optical system can be made constant, the light amount distribution in the pupil plane can be made constant, and changes in brightness and light collecting performance can be suppressed. Therefore, it is possible to suppress a change in light collecting performance.
In this way, the amount of spherical aberration generated can be suppressed as much as possible, so that an accurate observation image can be obtained by refocusing light with less aberration. Therefore, observation in the medium can be performed with high accuracy. Further, since the condensing point can be scanned by the scanning means, observation can be performed over the entire area of the medium.

  Furthermore, since the position of the light source can be changed simply by moving the first lens group, there is no need to move the condensing optical system, the stage, or the like as in the prior art. Therefore, the configuration can be simplified, and observation in the medium can be performed while correcting spherical aberration easily without taking time and effort. Further, since it is not necessary to provide a special optical system unlike a conventional correction ring objective lens or the like, the configuration can be simplified and the cost can be reduced.

According to the optical system of the present invention, the position of the light beam incident on the second lens group is changed by moving the first lens group in accordance with the distance to the position to be collected in the medium, that is, the light collecting point. Since the substantial change of the light source position as seen from the optical optical system can be performed, the generation amount of spherical aberration at the desired condensing point can be minimized. In addition, the second lens group whose rear focal position matches the entrance pupil position of the condensing optical system does not change the diameter of the light beam incident on the entrance pupil of the condensing optical system. It is possible to suppress a change or a change in the light amount distribution in the pupil plane. Therefore, it is possible to suppress a change in light collecting performance.
Furthermore, since the position of the light source can be changed simply by moving the first lens group, the configuration can be simplified, and the spherical aberration can be easily corrected without taking time and effort.

Hereinafter, a first embodiment of an optical system according to the present invention will be described with reference to FIGS.
As shown in FIG. 3, the optical system 1 of the present embodiment includes an emission unit (not shown) that emits a light beam L in a parallel light beam state, a condensing optical system 3 having an objective lens 2 that condenses the light beam L, and an emission. A first lens (first lens group) 4 movably disposed along the optical axis direction of the light beam L in the light beam between the means and the objective lens 2, and the first lens 4 and the objective lens 2 and the second lens (second lens group) 5 arranged in a fixed state in the light beam, and the first lens 4 is moved according to the distance to the position where the light beam L is to be collected. Moving means 6 to be moved.

The first lens 4 is a biconcave lens and is fixed to a lens frame (not shown). The moving means 6 is connected to the lens frame and can move the first lens 4 via the lens frame. Further, the moving means 6 is connected to a control unit (not shown) and operates in response to a signal from the control unit.
The control unit includes an input unit that can input predetermined information, and a calculation unit that calculates the movement amount of the first lens 4 based on each input information (input data) input by the input unit. Accordingly, the moving means 6 is moved by a predetermined amount according to the calculation result. In addition to the control of the moving means 6, the control unit simultaneously controls the emitting means so that the light beam L is emitted after the movement of the first lens 4 is completed.
The second lens 5 is a convex lens, the plane side faces the first lens 4 side, that is, the convex side faces the objective lens 2 side, and the rear focal position is incident on the objective lens 2. It is arranged at a position that is at least near the pupil position.

A case where the light beam L is collected by the optical system 1 configured as described above will be described.
First, as shown in FIG. 4, the amount of movement from the reference position to the condensing point where the light flux L is to be collected is input to the input unit of the control unit (S1). The calculator calculates the amount of movement of the moving means 6 based on this input data (S2). After completion of the calculation, the control unit controls the moving means 6 to move in the optical axis direction of the light beam L based on the calculation result, and moves the first lens 4 to a predetermined position (S3).

  After the movement of the first lens 4 is finished, the control unit sends a signal to the emitting means to emit the light beam L. The emitted light beam L is refracted by the first lens 4 in a parallel light beam state, becomes a divergent light state, and enters the second lens 5. That is, the position of the divergence point of the light beam L in the optical axis direction is changed by moving the first lens 4. The divergent light beam L is refracted again by the second lens 5, and then enters the objective lens 2 and is condensed at a desired position (S4).

  Next, when the light beam L is condensed at a position different from the above-described condensing point, the movement amount from the reference position to the new condensing point is input to the input unit in the same manner as described above. Based on the calculation result by the calculation unit, the control unit operates the moving unit 6 to move the first lens 4 along the optical axis direction. As a result, the light beam L emitted by the emission means is refracted at a position different from the position described above and enters the second lens 5 in a divergent light state. At this time, since the light beam L is incident on the first lens 4 in a parallel light beam state, the light beam L is always refracted at the same angle regardless of the position of the first lens 4 and is incident on the second lens 5. Therefore, the light beam L is collected by the objective lens 2 with the same light amount and light amount distribution in the pupil plane.

Thus, according to the optical system 1 of the present embodiment, by moving the first lens 4, the position of the divergence point of the light beam L can be changed, that is, the light source position can be substantially changed, and the pupil plane The condensing point (condensing point) can be changed to a desired position while keeping the light quantity and light quantity distribution in the inside constant, and the amount of spherical aberration generated at that position (each condensing point) is minimized. Can do.
Moreover, since it is the structure which only moves the 1st lens 4, it can comprise easily and can aim at cost reduction, and does not require an effort.

Here, FIG. 5 shows a more specific configuration example of the first lens and the second lens described in the first embodiment. Each lens is set as shown in Table 1.
In Table 1, R is the radius of curvature of the lens, d is the lens thickness or air spacing, and n is the refractive index.

Next, a second embodiment of the optical system of the present invention will be described with reference to FIG. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The difference between the second embodiment and the first embodiment is that, in the first embodiment, the first lens 4 is a biconcave lens , whereas the optical system of the second embodiment is the first lens 4. Is a convex lens, and the plane side faces the second lens 5 side.
In the present embodiment, similarly to the first embodiment, the light beam L incident in the parallel light beam state is always refracted at the same angle and is incident on the second lens 5 regardless of the position of the first lens 4. . Therefore, this embodiment has the same operational effects as the first embodiment.

Next, a third embodiment of the optical system of the present invention will be described with reference to FIG. In the third embodiment, the same components as those in the second embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The difference between the third embodiment and the second embodiment is that, in the second embodiment, the second lens group is composed of one convex lens, that is, the second lens 5, whereas the third lens group is the third embodiment. The second lens group 10 of the embodiment is configured by two lenses 11 and 12.
That is, as shown in FIG. 7, the second lens group 10 of the present embodiment includes a biconcave lens 11 disposed on the convex lens 4 side that is the first lens group, and a biconvex lens disposed adjacent to the biconcave lens 11. 12. The rear focal position of the entire second lens group 10 is positioned in the vicinity of the entrance pupil position of the objective lens 2.

  The optical system of the present embodiment can achieve the same effects as those of the second embodiment, and further, the distance (distance) between the second lens group 10 and the objective lens 2 can be increased. Other observation systems and the like can be arranged, and the degree of design freedom can be improved.

Here, FIG. 8 shows a more specific configuration example of the first lens and the second lens group described in the third embodiment. Each lens is set as shown in Table 2.
In Table 2, R is the radius of curvature of the lens, d is the lens thickness or air spacing, and n is the refractive index.

上記表２及び図８に示すように、第２のレンズ群を凹レンズ、凸レンズに構成することで、第２のレンズ群の焦点距離である４０ｍｍよりも第２のレンズ群最終面から第２のレンズ群の後側焦点位置までの距離を大きくすることができる。

As shown in Table 2 and FIG. 8, by configuring the second lens group to be a concave lens and a convex lens, the second lens group has a focal length of 40 mm which is the second lens group from the final surface of the second lens group. The distance to the rear focal position of the lens group can be increased.

Next, a fourth embodiment of the optical system of the present invention will be described with reference to FIG. In the fourth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The difference between the fourth embodiment and the first embodiment is that, in the first embodiment, the first lens group is composed of a single biconcave lens, that is, the first lens 4. The first lens group 15 of the fourth embodiment is configured by two lenses 16 and 17.
That is, as shown in FIG. 9, the first lens group 15 of the present embodiment includes a convex lens 16 having a convex portion directed toward the emitting means side and a biconcave lens 17 disposed adjacent to the convex lens 16. Has been. Further, the second lens group of the present embodiment is composed of a single biconvex lens 18.

In the present embodiment, similarly to the first embodiment, the light beam L incident in the parallel light beam state is always refracted at the same angle and incident on the second lens 18 regardless of the position of the first lens group 15. And there exists an effect similar to 1st Embodiment.
Further, if the combined focal length of the first lens group 15 by the two lenses 16 and 17 is f1, and the focal length of the biconvex lens 18 is f2, | f1 | = | f2 | The same effects as those of the first embodiment can be achieved while the diameter of the light beam incident on the second entrance pupil and the diameter of the light beam incident on the first lens group 15 remain the same.

Next, a fifth embodiment of the optical system of the present invention will be described with reference to FIGS. In the fifth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The difference between the fifth embodiment and the first embodiment is that, in the first embodiment, the light beam L is simply condensed at a desired position, whereas the optical system of the fifth embodiment uses the light beam L as a medium. It is the point which condenses to different depth from the surface of A.
That is, in the optical system of the present embodiment, the objective lens 2 collects the light beam L in the medium, and the moving means 6 has a refractive index of the medium A to be collected and a distance from the surface of the medium to a position to be collected. Accordingly, the first lens 4 (first lens group) is moved.

A case will be described in which the light beam L is condensed at a position having a different depth from the surface of the medium A by the optical system configured as described above.
First, as shown in FIG. 11, the refractive index of the medium A, the distance from the surface of the medium to the position where light is to be collected, for example, 50 μm and the NA of the condensing optical system 3 are input to the input unit of the control unit (S5 ). The calculation unit calculates the movement amount of the first lens 4 based on the input data (S6). After the calculation is completed, the control unit controls the moving unit 6 to move in the optical axis direction based on the calculation result, and moves the position of the first lens 4 to a predetermined position (S7).
After the movement of the first lens 4 is finished, the control unit emits the light beam L in a parallel light beam state from the emission unit. Thereby, the light beam L is condensed at a desired position from the surface of the medium A in a state where the amount of spherical aberration is suppressed as much as possible (S8).

  As described above, the first lens 4 is moved according to the distance input to the input unit to focus the light beam L, so that the generation amount of spherical aberration is further suppressed to the desired depth of the light beam L. It is possible to collect the light and improve the light collecting performance.

Here, FIG. 12 shows a more specific configuration example of the first lens group and the second lens described in the fifth embodiment. Each lens is set as shown in Table 3.
In Table 3, R is the radius of curvature of the lens, d is the lens thickness or air spacing, and n is the refractive index.

上記表３及び図１２に示すように、第１のレンズ群を凸レンズ、凹レンズの構成として、第１のレンズ群の合成焦点距離ｆ１＝−４０と、第２のレンズの合成焦点距離ｆ２＝４０との絶対値が等しくなるようにしている。このように構成することで、第１のレンズ群及び第２のレンズの近辺で光束を集光させることなく、第１のレンズ群への入射光束径と第２のレンズの後側焦点位置での光束径とを略同程度とすることができる。

As shown in Table 3 and FIG. 12, the first lens group is composed of a convex lens and a concave lens, and the combined focal length f1 = −40 of the first lens group and the combined focal length f2 = 40 of the second lens. So that the absolute values are equal. With this configuration, the incident light beam diameter to the first lens group and the rear focal position of the second lens are collected without condensing the light beam in the vicinity of the first lens group and the second lens. The beam diameter can be made approximately the same.

Next, a sixth embodiment of the optical system of the present invention will be described with reference to FIG. In addition, in this 6th Embodiment, the same code | symbol is attached | subjected about the part same as the component in 5th Embodiment, and the description is abbreviate | omitted.
The difference between the sixth embodiment and the fifth embodiment is that in the fifth embodiment, the light beam L is simply condensed at a position having a different depth from the surface of the medium A, whereas in the optical system of the sixth embodiment. The system is that the laser beam L ′ is condensed at different depths from the surface of the medium A and refocused for observation.

That is, the laser optical system (optical system) 20 of the present embodiment includes a laser light source 21 that emits laser light L ′ and an imaging lens that converts the light beam of the laser light L ′ emitted from the laser light source 21 into a parallel light beam. (Parallel light beam means) 22, a condensing optical system 23 that condenses the laser light L ′ in a parallel light flux state in the medium and re-condenses the light from the condensing point, and a laser at the condensing point in the medium The scanning means 24 capable of scanning in the direction perpendicular to the optical axis of the light L ′ (horizontal direction, XY direction) and the laser light source 21 are arranged at a conjugate position with the light converging optical system 23 to refocus the light. A pinhole detector (light detector) 25 for detecting light is provided.
The medium A is placed on a stage (not shown) that can move in the XY directions. In FIG. 13, the entire optical system is drawn in a two-dimensional plane, but in reality, the P portion (the broken line portion shown in the figure) is configured to be perpendicular to the paper surface.

  The condensing optical system 23 includes a half mirror 26 that reflects the laser light L ′ emitted from the laser light source 21 so as to change the direction of the optical axis by 90 degrees, and the laser light L ′ reflected by the half mirror 26. The imaging lens 22 that forms an image in a parallel light flux state, and a first galvanometer mirror that reflects the laser light L ′ at different angles so that the laser beam L ′ can be scanned in a horizontal direction (X direction) on the surface of the medium A 27, a first pupil relay optical system 28 that relays the laser light L ′ reflected by the first galvanometer mirror 27, and the laser light L ′ that has passed through the first pupil relay optical system 28 on the surface of the medium A A second galvanometer mirror 29 that reflects at different angles so that it can be scanned in the other horizontal direction (Y direction), and a second pupil relay that relays the laser light L ′ reflected by the second galvanometer mirror 29 light System 30, along with converging the laser beam L 'which has passed through the pupil relay optical system 30 of the second in the medium, an objective lens 2 to refocus light from the condensing point.

The first galvanometer mirror 27 and the second galvanometer mirror 29 have rotation shafts 27a and 29a arranged at the center positions so as to be orthogonal to each other, and the rotation shafts 27a and 29a It is configured to vibrate within a predetermined angle range around the axis. By this vibration, the laser beam L ′ can be reflected at different angles as described above. Further, the combination of both galvanometer mirrors 27 and 29 enables the laser beam L ′ to be scanned in a direction (XY direction) orthogonal to the optical axis direction of the condensing optical system 23. That is, both the galvanometer mirrors 27 and 29 function as the scanning means 24. The galvanometer mirrors 27 and 29 are controlled in vibration (operation) by the control unit.
The pinhole detector 25 is disposed on the rear side of the half mirror 26.

  Further, the first lens group of the present embodiment is composed of the first lens 4 which is a single biconvex lens, and is in the parallel light flux between the imaging lens 22 and the first galvanometer mirror 27. It is arranged to be movable along the optical axis direction. The second lens group is composed of a second lens 5 which is a single biconvex lens, and is in a parallel light flux between the first lens 4 and the first galvanometer mirror 27, The rear focal position is arranged in the vicinity of the entrance pupil position of the entire condensing optical system 23.

A case where the laser optical system 20 configured in this way observes positions at different depths from the surface of the medium A will be described. In the present embodiment, as shown in FIG. 14, a case will be described in which, for example, positions of 50 μm, 75 μm, and 100 μm are observed from the surface of the medium A.
First, as shown in FIG. 14A, when observing a position at a depth of 50 μm from the surface of the medium A, the refractive index of the medium A is desired to be collected from the surface of the medium A at the input unit of the control unit. The distance to the position, that is, 50 μm, the NA of the condensing optical system 23 and the distance between the objective lens 2 and the surface of the medium A, that is, the WD value are input. The calculation unit calculates the movement amount of the first lens 4 based on the input data. After the calculation is completed, the control unit controls the moving unit 6 to move in the optical axis direction based on the calculation result, and moves the position of the first lens 4 to a predetermined position.

After the movement of the first lens 4 is finished, the control unit sends a signal to the laser light source 21 to emit the laser light L ′. The emitted laser light L ′ is reflected by the half mirror 26, then becomes a parallel light flux state by the imaging lens 22, and enters the first lens 4 disposed at a predetermined position. Then, after being refracted by the first lens 4 to be in a convergent light state, it is refracted again by the second lens 5 and is incident on the first galvanometer mirror 27. Then, the light is reflected by the first galvanometer mirror 27 at different angles toward the X direction of the surface of the medium A. The reflected laser light L ′ is reflected at different angles toward the Y direction of the surface of the medium A by the second galvanometer mirror 29 via the first pupil relay optical system 28. The reflected laser beam L ′ is incident on the objective lens 2 via the second pupil relay optical system 30. Then, as shown in FIG. 14A, the light is condensed by the objective lens 2 at a position of 50 μm from the surface of the medium.
At this time, as described above, the position of the first lens 4, that is, the position of the substantial light source (position of the convergence point) is changed according to the depth of 50 μm, so that the spherical aberration at the position of 50 μm in depth. Can be suppressed as much as possible, and the laser beam L ′ can be efficiently condensed at this position.

  Further, the light from this condensing point is re-condensed by the objective lens 2 and detected by the pinhole detector 25 through the reverse optical path described above. That is, the light re-condensed by the objective lens 2 passes through the second pupil relay optical system 30, is reflected by the second galvanometer mirror 29, passes through the first pupil relay optical system 28, and the first galvanometer mirror. The light is detected by the pinhole detector 25 after sequentially passing through the second lens 5 and the first lens 4, passing through the imaging lens 22, and passing through the half mirror 26. The light refocused by the objective lens 2 is reflected by both galvanometer mirrors 27 and 29 so as to pass the same optical path as the optical path through which the laser light L ′ has passed.

As described above, since the laser beam L ′ is condensed at the condensing point (position at a depth of 50 μm from the surface of the medium) with the generation amount of spherical aberration suppressed as much as possible, the pinhole detector 25 causes an error. A few observation images can be obtained. Therefore, highly accurate observation can be performed.
In addition, since the laser light L ′ is scanned in the horizontal direction (XY direction) of the surface of the medium A by both the galvanometer mirrors 27 and 29, a wide range of observation is easily performed over the entire surface area of the medium A. be able to. At this time, the entire medium A can be scanned without moving the medium side (stage side).

Next, when observing the position at a depth of 75 μm or 100 μm from the surface of the medium A, as in the case described above, the refractive index of the medium A is input to the input unit to the position where the light is to be condensed from the surface of the medium A. The distance (75 μm or 100 μm) and the NA and WD values of the condensing optical system 23 are input. After the calculation by the calculation unit, the control unit controls the moving unit 6 to move in the optical axis direction based on the calculation result, and moves the position of the first lens 4 to a predetermined position. Thereafter, the laser light L ′ is emitted, and the condensing optical system 23 condenses the laser light L ′ at a position of 75 μm or 100 μm from the surface of the medium A, and condenses the light from the condensing point. Detection is performed by the pinhole detector 25.
At this time, as described above, since the position of the divergence point is adjusted by moving the first lens 4 in accordance with the depth of 75 μm or 100 μm, the generation amount of spherical aberration is suppressed as much as possible. As shown in FIGS. 14B and 14C, the laser beam L ′ can be efficiently condensed at a position of 75 μm or 100 μm. Therefore, a highly accurate observation image with few errors can be obtained.
When the WD value is changed, the control unit adjusts WD by controlling the stage to move in the optical axis direction, for example.

  As described above, according to the laser optical system 20 of the present embodiment, when the laser light L ′ is condensed at different depths (50 μm, 75 μm, 100 μm) from the surface of the medium A, the refractive index of the medium A and Since the first lens 4, that is, the divergence point is moved along the optical axis by the moving means 6 according to the distance from the surface of the medium A to the position where the light is to be collected, the generation amount of spherical aberration is suppressed as much as possible. Thus, the laser beam L ′ can be efficiently condensed in an optimum state at each depth. Therefore, even if the depth from the surface of the medium A is changed, an observation image with few errors can be obtained at each position, and the medium A can be observed with high accuracy.

In the sixth embodiment, the first galvanometer mirror 27 and the second galvanometer mirror 29 are employed as the scanning unit 24. However, the present invention is not limited to this. For example, as illustrated in FIG. A dimensional galvanometer mirror 35 may be adopted. The two-dimensional galvanometer mirror 35 has two rotation shafts 35a and 35b oriented in the same direction as the rotation shafts 27a and 29a of the first galvanometer mirror 27 and the second galvanometer mirror 29, and the rotation shaft 35a. , 35b is oscillated two-dimensionally within a predetermined angle range around the axis 35b.
Thereby, since it is not necessary to provide two galvanometer mirrors and two pupil relay optical systems as in the sixth embodiment, the configuration can be further simplified and the cost can be reduced.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the first lens group and the second lens group may be configured by a single lens as in the first embodiment, or one or more lenses as in the third and fourth embodiments. You may comprise by the lens of. Further, each lens is not limited to its type, for example, a convex lens, a concave lens, or a biconvex lens, and may be designed in any combination.

In particular, in each embodiment, the moving means may be set so as to move the first lens group so as to satisfy the following expression.
1 / | f | <0.01
Note that | f | is the combined focal length of the first lens group and the second lens group. By doing this, it is possible to have an afocal part.

In each of the above embodiments, the second lens group may be set so as to satisfy the following formula.
f2> 0
Note that f2 is the focal length of the second lens group.
The entrance pupil position of the condensing optical system is often in the condensing optical system, but the entrance pupil position of the condensing optical system is in the optical system by making the second lens group positive power (convex lens). Even if it exists, the rear focal position of the second lens group can be made coincident with the entrance pupil position of the condensing optical system.

In each of the above embodiments, the first lens group and the second lens group may be set so as to satisfy the following expression.
f1 <0
1 ≦ | f2 / f1 | ≦ 5
Note that f1 is a focal length of the first lens group, and f2 is a focal length of the second lens group.
By making the first lens group negative power (concave lens) and the second lens group positive power (convex lens), the configuration can be made compact. Further, since 1 ≦ f2 / f1, the first lens group can be configured easily. Therefore, not only can it be made inexpensive, but also performance degradation can be suppressed. Since | f2 / f1 | ≦ 5, the optical system can be configured compactly.

Further, as described above, the setting of the first lens group and the second lens group is not limited to f1 <0, 1 ≦ | f2 / f1 | ≦ 5. For example, in each of the above embodiments, the following expression is satisfied. You may set as follows.
f1> 0
0.5 ≦ | f1 / f2 | ≦ 2
By doing so, the focal lengths of both lens groups can be made positive, and relaying can be performed near the same magnification with a simple configuration.

In each of the above embodiments, the moving unit is automatically controlled by the control unit. However, based on the calculation result by the control unit, the moving unit is operated to move the position of the first lens group. It doesn't matter.
Further, the optical system of the present invention may be employed in an optical tweezer optical system as shown in FIG. In this case, since the generation amount of spherical aberration can be suppressed, for example, a minute object in water can be supplemented with higher accuracy.

Further, spherical aberration correction may be performed by an aberration correction optical system as shown in FIG. That is, the aberration correction optical system 40 is an optical system that condenses the light beam L from a light source (not shown), and a plurality of lenses 41, 42, and 43 that satisfy the following formula are exclusively arranged in the optical path so as to be removable. Yes.
2 (d ² + l × fl × d) NA = f × a
Here, d is the distance from the entrance pupil position of the condensing optical system 44 including the objective lens to the plurality of lenses 41, 42, 43, and l is the light source position from the entrance pupil position of the condensing optical system 44. Where f is the focal position of the plurality of lenses 41, 42, 43, NA is the NA of the light source (NA viewed from the condensing lens), and a is the condensing optics This is the entrance pupil diameter of the system 44. The light beam L is in a divergent light state, and the plurality of lenses 41, 42, 43 are convex lenses.
In the aberration correction optical system 40 configured as described above, in the case of a divergent light source, even when an attempt is made to observe (condensate) a portion having a different depth in the medium, the light amount is constant and the light amount distribution in the pupil plane is constant. Thus, it is possible to perform observation (condensation) while suppressing the generation amount of spherical aberration. Further, unlike the conventional case, there is no need to combine an expensive objective lens such as a correction ring objective lens, or to exchange glasses having different thicknesses.

In the aberration correction optical system 40 shown in FIG. 17 described above, a plurality of lenses 41, 42, and 43 that are convex lenses are arranged in the divergent light beam. However, as shown in FIG. , 42, 43 may be arranged. In this case, a plurality of lenses 41, 42, 43
Can be a concave lens.
Further, as shown in FIG. 19, a plurality of lenses 41, 42 and 43 which are concave lenses may be arranged in the parallel light flux.
Furthermore, as shown in FIG. 20, a plurality of lenses 41, 42, and 43 may be arranged after the parallel light beam is once converted into convergent light by the convex lens 45.

Furthermore, as shown in FIG. 21, the aberration correction optical system 40 may be used in combination with the laser optical system of the sixth embodiment. The plurality of lenses 41, 42, 43 are configured to be inserted / removed by the lens insertion / removal mechanism 46.
Even when configured in this manner, the same effects as those of the sixth embodiment can be obtained.

Further, the present invention includes the following.
[Additional Item 1]
An emission means for emitting a light beam in a parallel light beam state;
A condensing optical system for condensing the luminous flux;
A first lens group composed of one or more lenses arranged in the light beam between the emitting means and the condensing optical system so as to be movable along the optical axis direction of the light beam;
A second lens group which is arranged in a state of being fixed in the light beam between the first lens group and the condensing optical system and is configured by one or more lenses;
Moving means for moving the first lens group according to the distance to the position where the light beam is to be collected;
The optical system, wherein the second lens group has a rear focal position disposed at least in the vicinity of an entrance pupil position of the condensing optical system.
[Additional Item 2]
In the optical system according to appendix 1,
The condensing optical system condenses the luminous flux in a medium;
The optical system, wherein the moving means moves the first lens group according to a refractive index of the medium to be condensed and a distance from the medium surface to a position to be condensed.
[Additional Item 3]
In the optical system according to Additional Item 1 or 2,
An optical system, wherein the emission means includes a laser light source for emitting laser light.
[Additional Item 4]
A laser light source for emitting laser light;
Parallel light flux means for making the light flux of the laser light emitted from the laser light source a parallel light flux;
A condensing optical system that condenses the laser light in the parallel light beam state in a medium and re-condenses light from a condensing point;
A photodetector that is disposed at a position conjugate with the laser light source and detects the light re-condensed by the condensing optical system;
A first lens group composed of one or more lenses arranged in the parallel light beam between the parallel light beam means and the condensing optical system so as to be movable along the optical axis direction of the parallel light beam. When,
A second lens group configured by one or more lenses arranged in a fixed state in the parallel light flux between the first lens group and the condensing optical system;
A moving means for moving the first lens group according to the refractive index of the medium on which the laser beam is to be collected and the distance from the medium surface to the position on which the laser beam is to be collected;
The optical system, wherein the second lens group has a rear focal position disposed at least in the vicinity of an entrance pupil position of the condensing optical system.
[Additional Item 5]
A laser light source for emitting laser light;
Parallel light flux means for making the light flux L of the laser light emitted from the laser light source a parallel light flux;
A condensing optical system that condenses the laser light in the parallel light beam state in a medium and re-condenses light from a condensing point;
Scanning means capable of scanning a condensing point in the medium in a direction perpendicular to the optical axis direction of the laser beam;
A photodetector that is disposed at a position conjugate with the laser light source and detects the light re-condensed by the condensing optical system;
A first lens group composed of one or more lenses arranged in the parallel light beam between the parallel light beam means and the condensing optical system so as to be movable along the optical axis direction of the parallel light beam. When,
A second lens group configured by one or more lenses arranged in a fixed state in the parallel light flux between the first lens group and the condensing optical system;
A moving means for moving the first lens group according to the refractive index of the medium on which the laser beam is to be collected and the distance from the medium surface to the position on which the laser beam is to be collected;
The optical system, wherein the second lens group has a rear focal position disposed at least in the vicinity of an entrance pupil position of the condensing optical system.
[Additional Item 6]
In the optical system according to appendix 5,
The optical system, wherein the scanning means is a galvanometer mirror.
[Additional Item 7]
In the optical system according to any one of appendices 4 to 6,
An optical system, wherein the first lens group and the second lens group can be inserted and removed from an optical path.
[Additional Item 8]
In the optical system according to any one of appendices 4 to 7,
An optical system characterized in that a relative distance between the condensing optical system and the medium surface in the optical axis direction is constant.
[Additional Item 9]
An optical tweezer optical system comprising the optical system according to any one of additional items 1 to 3.
[Additional Item 10]
In the optical system according to any one of appendices 1 to 8,
The optical system, wherein the moving means moves the first lens group to a position satisfying the following formula.
1 / | f | <0.01
| F |; In-focus distance between the first lens group and the second lens group
[Additional Item 11]
In the optical system according to any one of appendices 1 to 8,
The optical system, wherein the second lens group satisfies the following formula.
f2> 0
f2: Focal length of the second lens group
[Additional Item 12]
In the optical system according to any one of appendices 1 to 8,
The optical system, wherein the first lens group and the second lens group satisfy the following expression.
f1 <0
1 ≦ | f2 / f1 | ≦ 5
f1; focal length of the first lens group f2; focal length of the second lens group
[Additional Item 13]
In the optical system according to any one of appendices 1 to 8,
The optical system, wherein the first lens group and the second lens group satisfy the following expression.
f1> 0
0.5 ≦ | f1 / f2 | ≦ 2
f1; focal length of the first lens group f2; focal length of the second lens group
[Additional Item 14]
An aberration correction optical system characterized in that, in an optical system for condensing a light beam from a light source, a plurality of lenses satisfying the following expression are exclusively inserted in and removed from the optical path.
2 (d ² + l × fl × d) NA = f × a
d: Distance from the entrance pupil position of the condensing optical system to the plurality of lenses l: Distance from the entrance pupil position of the condensing optical system to the light source position f: Focal position of the plurality of lenses NA: NA of the light source (condensing lens NA seen from)
a: Entrance pupil diameter of condensing optical system
[Additional Item 15]
A laser scanning optical system characterized in that a plurality of lenses satisfying the following formula are detachably arranged in an optical path in a converging / diverging optical system.
2 (d ² + l × fl × d) NA = f × a
d: Distance from the entrance pupil position of the condensing optical system to the plurality of lenses l: Distance from the entrance pupil position of the condensing optical system to the light source position f: Focal position of the plurality of lenses NA: NA of the light source (condensing lens NA seen from)
a: Entrance pupil diameter of condensing optical system
[Additional Item 16]
A laser scanning microscope comprising the laser scanning optical system according to appendix 15.
[Additional Item 17]
An optical tweezer optical system characterized in that a plurality of lenses satisfying the following formula are detachably arranged in the optical path in the converging / diverging optical system.
2 (d ² + l × fl × d) NA = f × a
d: Distance from the entrance pupil position of the condensing optical system to the plurality of lenses l: Distance from the entrance pupil position of the condensing optical system to the light source position f: Focal position of the plurality of lenses NA: NA of the light source (condensing lens NA seen from)
a: Entrance pupil diameter of condensing optical system
[Additional Item 18]
A light source that emits parallel luminous flux;
In a condensing optical system including an optical system that condenses parallel light beams,
An aberration correction optical system, wherein a plurality of lenses satisfying the following formula are exclusively inserted in and removed from the optical path.
b (f−d) / f = a
b: Diameter of a parallel light flux from the light source d: Distance from the entrance pupil position of the condensing optical system to the plurality of lenses f: Focal position of the plurality of lenses a: Entrance pupil diameter of the condensing optical system
[Additional Item 19]
A laser scanning optical system characterized in that a plurality of lenses satisfying the following formula are arranged in a parallel light beam so as to be detachable in the optical path.
b (f−d) / f = a
b: Diameter of a parallel light flux from the light source d: Distance from the entrance pupil position of the condensing optical system to the plurality of lenses f: Focal position of the plurality of lenses a: Entrance pupil diameter of the condensing optical system
[Additional Item 20]
An optical tweezer characterized in that a plurality of lenses satisfying the following formula are arranged in a parallel light flux so as to be detachable in the optical path.
b (f−d) / f = a
b: Diameter of a parallel light flux from the light source d: Distance from the entrance pupil position of the condensing optical system to the plurality of lenses f: Focal position of the plurality of lenses a: Entrance pupil diameter of the condensing optical system

It is a figure explaining the effect of the optical system which concerns on this invention, Comprising: It is a figure which shows the positional relationship of a 1st lens, a 2nd lens, and a condensing optical system. It is a figure which shows the relationship between the entrance pupil position of the condensing optical system in FIG. 1, and the back focal position of the 2nd lens. It is a block diagram which shows 1st Embodiment of the optical system which concerns on this invention. It is an example of the flowchart in the case of condensing a light beam to the desired position with the optical system shown in FIG. It is a specific block diagram of the 1st lens and 2nd lens which were demonstrated in 1st Embodiment of the optical system which concerns on this invention. It is a block diagram which shows 2nd Embodiment of the optical system which concerns on this invention. It is a block diagram which shows 3rd Embodiment of the optical system which concerns on this invention. It is a concrete block diagram of the 1st lens demonstrated in 3rd Embodiment of the optical system which concerns on this invention, and a 2nd lens. It is a block diagram which shows 4th Embodiment of the optical system which concerns on this invention. It is a block diagram which shows 5th Embodiment of the optical system which concerns on this invention. It is an example of the flowchart in the case of condensing a light beam to the desired position with the optical system shown in FIG. It is a specific block diagram of the 1st lens and 2nd lens which were demonstrated in 5th Embodiment of the optical system which concerns on this invention. It is a block diagram which shows 6th Embodiment of the optical system which concerns on this invention. It is a figure which shows the state which condensed the laser beam from the surface of a medium to the position where depth differs by the optical system shown in FIG. 13, Comprising: (a) is a position of 50 micrometers from the surface, (b) is from the surface. FIG. 7C is a diagram in which light is condensed at a position of 100 μm from the surface. It is a modification of the optical system shown in FIG. 13, and is a diagram showing an example of an optical system employing a two-dimensional galvanometer mirror. It is a figure which shows an example which employ | adopted the optical system which concerns on this invention for the optical tweezers optical system. It is a figure which shows the optical system which has arranged the several convex lens so that attachment or detachment is possible in a divergent light beam. It is a figure which shows the optical system which has arrange | positioned the several convex lens so that attachment or detachment is possible in a convergent light beam. It is a figure which shows the optical system which has arrange | positioned the several concave lens so that attachment or detachment is possible in a parallel light beam. It is a figure which shows the optical system which converted the parallel light beam into the convergent light with the convex lens, and arranged the several concave lens in the convergent light so that insertion or removal is possible. It is a figure which shows the optical system which combined the several concave lens with the optical system shown in FIG. 13 so that attachment or detachment is possible. It is a figure explaining the correction | amendment of the conventional spherical aberration, Comprising: It is a figure which shows an example of the optical system which can move a spherical aberration correction lens to an optical axis direction. It is the figure which showed the state from which the light quantity in an entrance pupil position changes with the optical system shown in FIG.

Explanation of symbols

A medium L light beam L ′ laser light 1 optical system 3 condensing optical system 4 first lens (first lens group)
5 Second lens (second lens group)
6 Moving means 10 Second lens group 15 First lens group 20 Laser optical system (optical system)
22 Imaging lens (parallel beam means)
23 Condensing optical system 24 Scanning means 25 Pin pole detector (photodetector)
35 Two-dimensional galvanometer mirror (scanning means)

Claims (4)

An emission means for emitting a light beam in a parallel light beam state;
A condensing optical system for condensing the luminous flux;
A first lens group composed of one or more lenses arranged in the light beam between the emitting means and the condensing optical system so as to be movable along the optical axis direction of the light beam;
A second lens group which is arranged in a state of being fixed in the light beam between the first lens group and the condensing optical system and is configured by one or more lenses;
Moving means for moving the first lens group according to the distance to the position where the light beam is to be collected;
The optical system, wherein the second lens group has a rear focal position disposed at least in the vicinity of an entrance pupil position of the condensing optical system. The optical system according to claim 1.
The condensing optical system condenses the luminous flux in a medium;
The optical system, wherein the moving means moves the first lens group according to a refractive index of the medium to be condensed and a distance from the medium surface to a position to be condensed.   The optical system according to claim 1 or 2,
  An optical system, wherein the emission means includes a laser light source for emitting laser light. A laser light source for emitting laser light;
Parallel light flux means for making the light flux of the laser light emitted from the laser light source a parallel light flux;
A condensing optical system that condenses the laser light in the parallel light beam state in a medium and re-condenses light from a condensing point;
Scanning means capable of scanning a condensing point in the medium in a direction perpendicular to the optical axis direction of the laser beam;
A photodetector that is disposed at a position conjugate with the laser light source and detects the light re-condensed by the condensing optical system;
A first lens group composed of one or more lenses arranged in the parallel light beam between the parallel light beam means and the condensing optical system so as to be movable along the optical axis direction of the parallel light beam. When,
A second lens group configured by one or more lenses arranged in a fixed state in the parallel light flux between the first lens group and the condensing optical system;
A moving means for moving the first lens group according to the refractive index of the medium on which the laser beam is to be collected and the distance from the medium surface to the position on which the laser beam is to be collected;
The optical system, wherein the second lens group has a rear focal position disposed at least in the vicinity of an entrance pupil position of the condensing optical system.

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