JP4528023B2 - Laser focusing optical system - Google Patents

Description

  The present invention relates to a laser condensing optical system that condenses laser light at different portions in a medium.

  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. In addition, some LCD glasses have different thicknesses, and spherical aberration occurs even when observing through a substrate. Further, when the spherical aberration amount is different between different thicknesses (depths), there is a problem that the light condensing performance is 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 an infinite composite focal length (No Power Lens) in the optical axis direction is also known (for example, see Patent Document 2).
Furthermore, as shown in FIG. 11, a spherical aberration correction lens 52 is disposed 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, since the combined focal length is corrected with an infinite lens, the converging position does not change even when spherical aberration is corrected. When attempting to focus on different parts of the medium, the WD always changes, and aberration correction cannot be performed under 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, as shown in FIG. 11, the spherical aberration correction lens 52 can be corrected by moving the spherical aberration correction lens 52 in the optical axis direction. 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. 12, 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.

  The present invention has been made in consideration of such circumstances, and its object is to provide a laser focusing optical system that can easily perform spherical aberration correction without taking time and effort with a simple configuration. is there.

In order to achieve the above object, the present invention provides the following means.
The invention according to claim 1 is arranged between a laser light source that emits laser light and the laser light source and the medium, and condenses the laser light in the medium and recollects the light from the condensing point. A condensing optical system that emits light, a photodetector that detects the light re-condensed by the condensing optical system, a position of a laser divergence point of the laser light, and a position of the photodetector. A laser divergence point moving means capable of moving along the optical axis of the laser beam according to the refractive index of the medium to be collected and the distance from the surface of the medium to the position to be collected. An optical optical system is provided.

In the laser condensing optical system according to the present invention, the laser light emitted from the laser light source by the condensing optical system is condensed in the medium, and the light can be re-condensed from the condensing point, and re-condensed by the photodetector. The collected light can be detected. At this time, the laser light is incident on the condensing optical system in a divergent light state (non-parallel light beam state). That is, the light is emitted from the laser light source in a divergent light state, or is emitted from the laser light source in a parallel light flux state, and then converted into a divergent light state by an optical system such as various lenses, and enters the condensing optical system. Thus, the position (point) where the laser light is in the divergent light state is defined as the divergent point. Further, when condensing the laser light, the position of the laser divergence point and the position of the photodetector are adjusted by the laser divergence point moving means according to the refractive index of the medium to be condensed and the distance from the surface of the medium to the position to be condensed. Since the position is moved along the optical axis of the laser beam, even if the laser beam is condensed at a location where the depth in the medium is different, the generation amount of the spherical aberration can be suppressed as much as possible. Therefore, the laser beam can be efficiently condensed at the desired depth of the medium, and the condensing performance can be improved.
In addition, since the amount of spherical aberration generated can be suppressed as much as possible, an accurate observation image can be obtained by refocusing light with less aberration. Therefore, observation in the medium can be performed with high accuracy.

  In particular, since only the laser divergence point is moved, spherical aberration correction can be easily performed without taking time and effort as in the prior art. In addition, since it is not necessary to provide a special optical system unlike a conventional correction ring objective lens, the configuration can be simplified and the cost can be reduced. Furthermore, since it is only necessary to move the laser divergence point, it is easy to perform continuous variation and to cope with automation.

  According to a second aspect of the present invention, in the laser condensing optical system according to the first aspect, the laser condensing optical system includes a scanning unit capable of scanning the laser light in a direction orthogonal to the optical axis of the condensing optical system. A laser focusing optical system is provided.

  In the laser condensing optical system according to the present invention, since the laser beam can be scanned by the scanning means, the entire region of the medium can be observed without moving the medium side.

According to a third aspect of the present invention, in the laser condensing optical system according to the first or second aspect, the laser divergence point moving means further sets the position of the laser divergence point based on the NA of the condensing optical system. A laser focusing optical system is provided.

According to a fourth aspect of the present invention, in the laser condensing optical system according to any one of the first to third aspects, the laser divergence point moving means is configured to determine a laser divergence point based on wavefront data of the condensing optical system measured in advance. A laser focusing optical system for setting a position is provided.
In the laser condensing optical system according to the present invention, the laser divergence point moving means measures the wavefront data of the condensing optical system measured in advance, for example, the wavefront of the objective lens that is part of the condensing optical system Since the position of the laser divergence point is set in consideration of the data and the wavefront data of the whole condensing optical system, the condensing performance and observation performance of the laser light can be further improved.

According to a fifth aspect of the present invention, in the laser condensing optical system according to any one of the first to fourth aspects, the distance from the lower surface of the condensing optical system to the surface of the medium is provided in cooperation with the condensing optical system. Provided is a laser focusing optical system that includes an observation optical system that maintains a predetermined distance, and the observation optical system includes an autofocus detection unit or an autofocus mechanism.
In the laser condensing optical system according to the present invention, the distance from the lower surface of the condensing optical system to the surface of the medium can be maintained at a predetermined distance by the observation optical system. For example, the horizontal direction between the condensing optical system and the medium When the relative movement, i.e., scanning, is performed, the depth from the medium surface can be accurately controlled to a desired depth.

According to a sixth aspect of the present invention, in the laser condensing optical system according to any one of the first to fifth aspects, the relative distance in the optical axis direction between the condensing optical system and the surface of the medium is constant. A condensing optical system is provided.
  In the laser condensing optical system according to the present invention, the relative distance in the optical axis direction between the condensing optical system and the surface of the medium, that is, WD, even when the depth of the medium on which the laser light is to be collected changes. Since it is set to be constant, the apparatus configuration can be simplified and the observation speed can be increased.

The invention according to claim 7 is the laser focusing optical system according to claim 1,
The laser divergence point moving means moves the laser light source and the photodetector so that they are in a conjugate position with each other.
According to an eighth aspect of the present invention, in the laser focusing optical system according to the seventh aspect, the laser divergence point moving means includes a light source moving means for moving the laser light source along an optical axis direction, and the light source movement. And a photodetector moving means for moving the photodetector along the optical axis direction in synchronization with the means.
According to a ninth aspect of the present invention, in the laser focusing optical system according to the eighth aspect, the light source moving means and the light detector moving means move the laser light source and the light detector along the optical axis direction. And a laser condensing optical system characterized by being moved integrally.
  The invention according to claim 10 is the laser condensing optical system according to claim 7, wherein the laser divergence point moving means includes at least two mirrors provided in the condensing optical system, and the mirror as an optical axis. There is provided a laser condensing optical system comprising a mirror moving means that is moved along a direction.
According to an eleventh aspect of the present invention, in the laser focusing optical system according to the first aspect, a control means for controlling the laser divergence point moving means, an input means for inputting the refractive index and the distance, and the input There is provided a laser condensing optical system, comprising: calculating means for calculating a moving amount of the laser divergence point from the refractive index of the medium input from the means and the distance.

According to a twelfth aspect of the present invention, a laser light source that emits laser light and a laser light source that is disposed between the laser light source and the medium condense the laser light into the medium and recollect the light from the condensing point. A condensing optical system that emits light, scanning means that can scan the laser light in a direction orthogonal to the optical axis of the condensing optical system, and the light that is re-condensed by the condensing optical system. The photodetector to be detected, the position of the laser divergence point of the laser beam and the position of the photodetector are set to the refractive index of the medium on which the laser beam is to be collected and the distance from the surface of the medium to the position on which the beam is to be collected. Accordingly, there is provided a laser scanning microscope characterized by comprising laser divergence point moving means that can move along the optical axis of the laser light.

  According to the condensing optical system of the present invention, the laser divergence point is moved by the laser divergence point moving means according to the refractive index of the medium to be condensed and the distance from the surface of the medium to the position to be condensed. Since it is moved along the top, it is possible to suppress the generation amount of spherical aberration as much as possible at each position where the depth in the medium is different. Therefore, the laser beam can be efficiently condensed at the desired depth of the medium, and the condensing performance can be improved. In addition, since an accurate observation image can be obtained by refocusing light with less spherical aberration, observation in the medium can be performed with high accuracy. In particular, since only the laser divergence point is moved, it is possible to easily correct spherical aberration and eliminate the need for a special optical system without taking time and effort as in the prior art. This can be achieved and cost can be reduced.

A first embodiment of a laser focusing optical system according to the present invention will be described below with reference to FIGS.
As shown in FIG. 1, the laser condensing optical system 1 of the present embodiment includes a laser light source 2 that emits laser light L in a divergent light state (non-parallel light beam state), the laser light source 2, and a specimen (medium) 3. And a condensing optical system 4 for condensing the laser light L in the sample and re-condensing the light from the condensing point, and condensing at a position conjugate with the laser light source 2. The pinhole detector (light detector) 5 for detecting the light re-condensed by the optical system 4 and the position of the laser divergence point 6 of the laser light L, that is, the position of the laser light source 2 is focused on the laser light L. A laser divergence point moving means (not shown) that is movable along the optical axis of the laser light L in accordance with the refractive index of the specimen 3 to be desired and the distance from the specimen surface (surface of the specimen) 3a to the position to be collected; The Hall detector 5 is moved to a position conjugate with the moved laser divergence point 6. A pinhole detector moving means (not shown) for scanning, and a scanning means 7 capable of scanning the laser light L in a direction (horizontal direction, XY direction) orthogonal to the optical axis of the condensing optical system 4. Yes.
The specimen 3 is placed on a stage (not shown) that can move in the XY directions.

The laser divergence point moving means and the pinhole detector moving means are connected to a control unit (not shown), and the laser divergence point 6 can be moved by moving the laser light source 2 in response to a signal from the control unit. Has been. In addition, the control unit includes an input unit that can input predetermined information, and a calculation unit that calculates the movement amount of the laser light source 2 based on each input information (input data) input by the input unit. A signal is sent to the laser divergence point moving means according to the calculation result to move it.
In addition to the control of the laser divergence point moving means, the control unit simultaneously controls the laser light source 2 so that the laser light L is emitted after the movement of the laser divergence point 6 is completed.

  The condensing optical system 4 roughly reflects the laser light L emitted from the laser light source 2 to reflect the laser light L reflected by the half mirror 10 so that the direction of the optical axis is changed by 90 degrees. An imaging lens 11 for making parallel light, a first galvanometer mirror 12 for reflecting the laser beam L at different angles so that the laser beam L can be scanned in one direction (X direction) horizontal to the sample surface 3a, and the first galvanometer mirror 12 The first pupil relay optical system 13 that relays the reflected laser light L, and the laser light L that has passed through the first pupil relay optical system 13 can be scanned in the other direction (Y direction) horizontal to the sample surface 3a. The second galvanometer mirror 14 that reflects at a different angle, the second pupil relay optical system 15 that relays the laser light L reflected by the second galvanometer mirror 14, and the second pupil relay optical system 15 have passed. Les With focusing the laser light L to the specimen, an objective lens 16 for re-condensing the light from the condensing point.

The first galvanometer mirror 12 and the second galvanometer mirror 14 have rotation shafts 12a and 14a arranged at respective central positions so as to be orthogonal to each other, and the rotation shafts 12a and 14a It is configured to vibrate within a predetermined angle range around the axis. Due to this vibration, the laser beam L can be reflected at different angles as described above. Further, the combination of both galvanometer mirrors 12 and 14 enables scanning of the laser light L in a direction (XY direction) orthogonal to the optical axis direction of the condensing optical system 4. That is, both the galvanometer mirrors 12 and 14 function as the scanning means 7. The galvanometer mirrors 12 and 14 are controlled in vibration (operation) by the control unit.
The pinhole detector 5 is arranged on the rear side of the half mirror 10, and moves in the optical axis direction in synchronization with the movement of the laser light source 2 by the pinhole detector moving means controlled by the control unit. ing.

The case where the laser condensing optical system 1 configured as described above observes a position having a different depth from the sample surface 3a will be described. In the present embodiment, a case will be described in which, for example, positions of 50 μm, 75 μm, and 100 μm are observed from the sample surface 3a.
First, when observing a position at a depth of 50 μm from the sample surface 3a, as shown in FIG. 2, the refractive index of the sample 3, the distance from the sample surface 3a to the position where light is desired to be collected, as shown in FIG. That is, 50 μm and NA of the condensing optical system 4 are input (S1). Based on this input data, the calculation unit calculates the amount of movement of the laser divergence point 6, that is, the amount of movement of the laser light source 2, and calculates the distance between the focusing optical system 4 and the sample surface 3a, that is, the WD value. (S2). After completion of the calculation, the control unit controls the laser divergence point moving means to move in the direction of the optical axis of the laser light L based on the calculation result, thereby moving the position of the laser light source 2 to a predetermined position and collecting light. The distance (WD) between the optical system 4 and the sample surface 3a is changed (S3).

After the movement of the laser light source 2 and the change of the WD are completed, the control unit sends a signal to the laser light source 2 to emit the laser light L (S4). The emitted laser light L is reflected by the half mirror 10, is then made substantially parallel light by the imaging lens 11, and enters the first galvanometer mirror 12. Then, the first galvanometer mirror 12 reflects the sample surface 3a in the X direction at different angles. The reflected laser light L is reflected by the second galvanometer mirror 14 through the first pupil relay optical system 13 at different angles toward the Y direction of the sample surface 3a. The reflected laser light L is incident on the objective lens 16 via the second pupil relay optical system 15. And as shown to Fig.3 (a), it condenses by the objective lens 16 at the position of 50 micrometers from the sample surface 3a.
At this time, as described above, the position of the laser light source 2, that is, the position of the laser divergence point 6 is adjusted according to the depth of 50 μm, so that the generation amount of spherical aberration at the position of 50 μm depth can be suppressed as much as possible. 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 16 and detected by the pinhole detector 5 through the reverse optical path described above. That is, the light re-condensed by the objective lens 16 passes through the second pupil relay optical system 15, is reflected by the second galvanometer mirror 14, passes through the first pupil relay optical system 13, and the first galvanometer mirror. After the reflection by 12, the passage through the imaging lens 11, and the transmission through the half mirror 10, the detection is performed by the pinhole detector 5. The light refocused by the objective lens 16 is reflected by both galvanometer mirrors 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 light L is condensed at the condensing point (position of a depth of 50 μm from the sample surface) while suppressing the generation amount of spherical aberration as much as possible, the pinhole detector 5 makes an observation with little error. An image can be obtained. Therefore, highly accurate observation can be performed. In particular, since the pinhole detector 5 moves in the optical axis direction in synchronization with the movement of the laser light source 2, an observation image of a condensing point with good contrast can be obtained by the confocal effect.
In addition, since the laser light L is scanned in the horizontal direction (XY direction) of the sample surface 3a by both the galvanometer mirrors 12 and 14, a wide range of observation can be easily performed over the entire sample surface 3a. At this time, the entire specimen 3 can be scanned without moving the specimen 3 side (stage side).

Next, when observing a position having a depth of 75 μm or 100 μm from the sample surface 3a, as in the case described above, the refractive index of the sample surface 3a and the distance from the sample surface 3a to the position where the sample surface 3a is desired to be collected are input. (75 μm or 100 μm) and NA of the condensing optical system 4 are input. After the calculation by the calculation unit, the control unit controls the laser light source 2 to move in the optical axis direction of the laser light L based on the calculation result, and moves the position of the laser light source 2 to a predetermined position. Thereafter, the laser beam L is emitted, and the laser beam L is condensed at a position of 75 μm or 100 μm from the sample surface 3a by the condensing optical system 4, and the light from the condensing point is re-condensed to pinhole detector. 5 is detected.
At this time, as described above, since the position of the laser divergence point 6 is adjusted by moving the laser light source 2 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. 3B and 3C, 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.

  As described above, according to the laser condensing optical system 1 of the present embodiment, when the laser light L is condensed at different depths (50 μm, 75 μm, 100 μm) from the sample surface 3a, the refractive index of the sample 3 and Since the laser light source 2, that is, the laser divergence point 6 is moved along the optical axis by the laser divergence point moving means according to the distance from the sample surface 3 a to the position where light is desired to be collected, the generation amount of spherical aberration is suppressed as much as possible. Therefore, the laser beam L can be efficiently condensed in an optimum state at each depth. Therefore, even if the depth from the sample surface 3a is changed, an observation image with few errors can be obtained at each position, and the sample 3 can be observed with high accuracy. Moreover, since the pinhole detector 5 moves in the optical axis direction in synchronization with the movement of the laser light source 2, an observation image with good contrast can be obtained by the confocal effect.

  In addition, since the laser light source 2 is simply moved, spherical aberration correction can be easily performed without taking time and effort as in the prior art. In addition, since a special optical system such as a conventional correction ring objective lens is not required, the configuration can be simplified and the cost can be reduced. Furthermore, since only the laser light source 2 is moved, it is easy to perform continuous variation and to cope with automation.

In the first embodiment, the position of the laser light source 2 is determined by inputting the refractive index of the sample 3, the distance from the sample surface 3a to the position where light is to be collected, and the NA of the condensing optical system 4 to the input unit. Although the input data is not limited to that described above, for example, in addition to these input data, pre-measured wavefront data of the condensing optical system 4 may be further input to calculate the position of the laser light source 2. I do not care.
That is, as shown in FIG. 4, when various data are input to the input unit (S1 described above), the refractive index of the sample 3, the distance from the sample surface 3a to the position where light is desired to be collected, the NA of the condensing optical system 4 and The wavefront data of the condensing optical system 4 is input.
By so doing, spherical aberration correction can be performed with high accuracy, the condensing performance of the laser light L can be further improved, and an observation image with fewer errors can be obtained.
The wavefront data of the condensing optical system 4 may be, for example, the wavefront data of the objective lens 16 that is a part of the condensing optical system 4, or the wavefront data of the entire condensing optical system 4 is used. It doesn't matter.

Next, a second embodiment of the laser focusing 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 position of the laser divergence point 6 is adjusted by moving the laser light source 2 by the laser divergence point moving means. The laser condensing optical system 20 of the embodiment is configured such that the laser light source 2, the half mirror 10 and the pinhole detector 5 are integrally moved by the laser divergence point moving means to adjust the position of the laser divergence point. is there.
With this configuration, the position of the laser divergence point can be easily moved, and the pinhole detector 5 does not need to be synchronized with the movement of the laser light source 2. Therefore, the configuration can be simplified and the cost can be reduced.

The method of moving the laser divergence point is not limited to the first embodiment and the second embodiment, and for example, the laser divergence point 6 may be moved as in the laser focusing optical system 25 shown in FIG. . That is, the first mirror 26 and the second mirror 27 that reflect the laser light L transmitted through the half mirror 10 between the half mirror 10 and the imaging lens 11 so as to change the optical axis by 90 degrees respectively. Thus, both the mirrors 26 and 27 can change the emission direction of the laser light L by 180 degrees, and the laser divergence point moving means can move both the mirrors 26 and 27 integrally in the optical axis direction of the laser light L. You may comprise as follows.
With this configuration, the position of the laser divergence point 6 can be easily moved without changing the positions of the laser light source 2 and the pinhole detector 5, and the configuration can be further simplified.

The laser focusing optical system 25 includes a two-dimensional galvanometer mirror 28. The two-dimensional galvanometer mirror 28 has two rotation shafts 28a and 28b oriented in the same direction as the rotation shafts 12a and 14a of the first galvanometer mirror 12 and the second galvanometer mirror 14 of the first embodiment. Thus, it vibrates two-dimensionally within a range of a predetermined angle around the rotation shafts 28a and 28b. That is, the two-dimensional galvanometer mirror 28 functions as a scanning unit.
Thereby, since it is not necessary to provide two galvanometer mirrors and two pupil relay optical systems as in the first embodiment, the configuration can be further simplified and the cost can be reduced.

Next, a third embodiment of the laser focusing optical system of the present invention will be described with reference to FIGS. 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, scanning is performed regardless of the distance between the objective lens 16 and the specimen surface 3a, but in the third embodiment, the objective lens 16 is different from the second embodiment. This is a point where scanning is performed in a state where the distance from the sample surface 3a is kept constant.
That is, as shown in FIG. 7, the laser condensing optical system 30 of this embodiment is provided in cooperation with the condensing optical system 4, and the sample surface 3a from the condensing optical system 4, that is, the lower surface of the objective lens 16. Is provided with an observation optical system 31 that maintains a predetermined distance. The observation optical system 31 has an autofocus mechanism.

The observation optical system 31 includes a light source 32 for irradiating linearly polarized semiconductor laser light L ′, a first lens 33 for converting the semiconductor laser light L ′ irradiated from the light source 32 into parallel light, and the first lens 33. A polarization beam splitter 34 disposed adjacent to the second beam 35, a second lens 35 for converging and diverging the semiconductor laser light L ′ transmitted through the polarization beam splitter 34, and a semiconductor laser light L ′ diverged by the second lens 35. A third lens 36 for making the collimated light of the pupil diameter of the condensing optical system 16, a quarter-wave plate 37 for making the polarization of the semiconductor laser light L ′ transmitted through the third lens 36 circularly polarized, The dichroic mirror 38 for reflecting the semiconductor laser light L ′ transmitted through the quarter-wave plate 37 so as to change the direction of the optical axis by 90 degrees and entering the condensing optical system 16, and the quarter-wave plate 37 again. Transmitted and polarized The return light from the objective lens 16 is reflected by the beam splitter 34, a photodiode 41 disposed on the rear side of the fourth lens 40 and a cylindrical lens 39 to be incident on the cylindrical lens 39.
The dichroic mirror 38 is set so as to reflect the semiconductor laser light L ′ and transmit light of other wavelengths, for example, the laser light L emitted from the laser light source 2.

  The polarization beam splitter 34 transmits, for example, P component linearly polarized light, which is a vibration component parallel to the incident surface, of linearly polarized light, and reflects S component light, which is a vibration component perpendicular to the incident surface. It has a function to make it. Further, the control unit feedback-controls the stage based on a detection signal such as a focusing error signal received by the photodiode 41 to move the stage in the vertical direction (optical axis direction). That is, autofocus is performed. Thereby, the semiconductor laser light L ′ is adjusted so that the specimen surface 3 a is always in focus.

  When scanning is performed by the laser condensing optical system 30 configured as described above, the light source 32 emits linearly polarized semiconductor laser light L ′. The irradiated semiconductor laser light L ′ becomes parallel light by the first lens 33 and then enters the polarization beam splitter 34. Then, after the light becomes P-component linearly polarized light that is a vibration component parallel to the incident surface, the light is converged by the second lens 35 and then diverges. Then, the diverged light becomes parallel light again by the third lens 36 and enters the quarter-wave plate 37. At this time, the parallel light has a light flux width corresponding to the objective lens 16. The semiconductor laser light L ′ that has passed through the quarter-wave plate 37 and has become circularly polarized light is reflected by the dichroic mirror 38 and enters the objective lens 16. The light incident on the objective lens 16 is illuminated on the sample surface 3a.

  Next, the light reflected by the specimen surface 3a is collected by the objective lens 16, then reflected by the dichroic mirror 38 and incident on the quarter wavelength plate 37, and S component polarized light which is a vibration component perpendicular to the incident surface. It becomes. This light passes through the third lens 36 and the second lens 35, then enters the polarization beam splitter 34, and is reflected toward the fourth lens 40. Then, after being converged by the fourth lens 40, it passes through the cylindrical lens 39 and forms an image on the photodiode 41. The formed detection signal such as a focusing error signal is sent to the control unit (S5). The controller performs calculation based on the transmitted detection signal (S6), and moves the stage in the vertical direction (optical axis direction) so that the focus of the semiconductor laser light L ′ is aligned with the sample surface 3a (S7). ). That is, control is performed so that the autofocus is automatically performed and the specimen surface 3a is always imaged.

  Thus, scanning can be performed while the distance between the objective lens 16 and the sample surface 3a is always maintained at a constant distance. Therefore, even if the stage is slightly curved or there is some error in the movement of the stage, the laser beam L can be accurately condensed to a desired depth. Therefore, it is possible to perform scanning while controlling the condensing position from the sample surface 3a more accurately, and it is possible to observe the sample 3 with higher accuracy.

  Note that when changing the position at which the laser beam L is condensed when performing the above-described scanning, the scanning is performed after the autofocus offset amount calculation (S8) is performed in advance. For example, when scanning is performed with the light condensed to a depth of 100 μm and then performed with the light condensed to a depth of 50 μm, the WD value is changed to obtain an optimal state, that is, an optimal value. Must be set. As the WD value changes, it is necessary to offset the autofocus by a predetermined amount. In other words, the WD value can be corrected by calculating the autofocus offset amount. Then, after performing the offset, scanning at a different depth is performed in the same manner as described above.

Next, a fourth embodiment of the laser focusing optical system of the present invention will be described with reference to FIGS. In the fourth embodiment, the same components as those in the third embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The difference between the fourth embodiment and the third embodiment is that, in the third embodiment, the relative distance in the optical axis direction between the objective lens 16 and the specimen surface 3a, that is, the WD is not constant. In the fourth embodiment, the WD is constant.
In other words, after the positions of the stage and the objective lens 16 in the optical axis direction are set in advance, settings are made so that both positions are always maintained at the same position. That is, as shown in FIG. 9, when various data are input to the input unit (S1 described above), the data excluding the WD value, that is, the refractive index of the sample 3 and the distance from the sample surface 3a to the position to be collected. The NA data of the condensing optical system 4 is input.

  By doing this, as shown in FIG. 10, the laser divergence point moving means moves only the laser divergence point along the optical axis direction while keeping the WD constant, so that the autofocus offset amount is set to the initial value. After that, there is no need to calculate the offset amount again. Therefore, the time required for the offset can be shortened and the throughput can be improved. In addition, it is possible to reduce deterioration in autofocus accuracy caused by performing offset.

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, in each of the embodiments described above, the laser light is collected in the sample, but it is not limited to the sample, but may be collected in the medium. Further, the distance to be collected is set to 50 μm, 75 μm, and 100 μm from the sample surface, but is not limited to these distances and may be arbitrarily set. In addition, the stage is moved to change the relative distance between the objective lens and the sample surface in the optical axis direction. However, the present invention is not limited to this. For example, the objective lens can be moved using a piezo element or the like. The relative distance may be changed.
In addition, the control unit is configured to automatically control the laser divergence point moving means, but based on the calculation result by the control unit, the means operates the laser divergence point moving means to move the position of the laser divergence point. It doesn't matter.

  In addition, the observation optical system described in the third embodiment is an example. If the distance from the lower surface of the objective lens to the sample surface can be maintained at a predetermined distance, the optical system such as a lens may be combined. I do not care.

It is a block diagram which shows 1st Embodiment of the laser condensing optical system which concerns on this invention. It is an example of the flowchart in the case of irradiating a laser beam to the position from which a depth differs from a sample surface by the laser condensing optical system shown in FIG. FIGS. 2A and 2B are diagrams illustrating a state in which laser light is irradiated from the sample surface to a position having a different depth by the laser focusing optical system illustrated in FIG. 1, in which FIG. (C) is a diagram showing an irradiation at a position 100 μm from the sample surface. This is an example in which laser light is irradiated by the laser condensing optical system shown in FIG. 1 in consideration of the wavefront data of the condensing optical system. It is a block diagram which shows 2nd Embodiment of the laser condensing optical system which concerns on this invention. It is a block diagram which shows the other example of the laser condensing optical system which concerns on this invention. It is a block diagram which shows 3rd Embodiment of the laser condensing optical system which concerns on this invention. It is an example of the flowchart in the case of irradiating a laser beam to the position from which a depth differs from a sample surface with the laser condensing optical system shown in FIG. It is a figure which shows 4th Embodiment of the laser condensing optical system which concerns on this invention, Comprising: It is an example of the flowchart in the case of irradiating a laser beam to the position from which a depth differs from a sample surface. FIG. 9 is a diagram illustrating a state in which laser light is irradiated to a position having a different depth from the sample surface according to the flowchart illustrated in FIG. 9, where (a) is a position 50 μm from the sample surface, and (b) is a position 75 μm from the sample surface. (C) is the figure which has irradiated to the position of 100 micrometers from the sample surface. 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

L Laser light 1, 25, 30 Laser condensing optical system 2 Laser light source 3 Sample (medium)
4 Condensing optical system 5 Pinhole detector (photodetector)
6 Laser divergence point 7 Scanning means 28 Two-dimensional galvanometer mirror (scanning means)
31 Observation optical system

Claims (12)

A laser light source for emitting laser light;
A condensing optical system that is disposed between the laser light source and the medium, condenses the laser light in the medium, and re-condenses the light from the condensing point;
A photodetector for detecting the light re-condensed by the condensing optical system;
The position of the laser divergence point of the laser light and the position of the photodetector are determined according to the refractive index of the medium where the laser light is to be collected and the distance from the surface of the medium to the position where the laser light is to be collected. And a laser divergence point moving means movable along the optical axis. The laser focusing optical system according to claim 1,
A laser condensing optical system comprising scanning means capable of scanning the laser light in a direction perpendicular to the optical axis of the condensing optical system. In the laser condensing optical system according to claim 1 or 2,
The laser converging optical system is characterized in that the laser divergence point moving means further sets the position of the laser divergence point based on the NA of the condensing optical system. In the laser condensing optical system according to any one of claims 1 to 3,
The laser divergence point moving means sets the position of the laser divergence point based on the wavefront data of the condensing optical system measured in advance. In the laser condensing optical system according to claim 1 to 4,
An observation optical system provided in cooperation with the condensing optical system, and maintaining a distance from the lower surface of the condensing optical system to the surface of the medium at a predetermined distance;
A laser condensing optical system, wherein the observation optical system includes an autofocus detection means or an autofocus mechanism. In the laser condensing optical system according to any one of claims 1 to 5,
A laser condensing optical system characterized in that a relative distance between the condensing optical system and the surface of the medium in the optical axis direction is constant. The laser focusing optical system according to claim 1, wherein
The laser divergence point moving means moves the laser light source and the photodetector so that they are in a conjugate position with each other, The laser focusing optical system according to claim 7,
The laser divergence point moving means includes:
Light source moving means for moving the laser light source along the optical axis direction;
A laser condensing optical system comprising: a photodetector moving means for moving the photodetector along the optical axis direction in synchronization with the light source moving means. The laser focusing optical system according to claim 8,
The laser condensing optical system characterized in that the light source moving means and the light detector moving means move the laser light source and the light detector integrally along the optical axis direction. The laser focusing optical system according to claim 7,
The laser divergence point moving means includes:
At least two mirrors provided in the condensing optical system;
A mirror moving means for moving the mirror along the optical axis direction;
A laser condensing optical system. The laser focusing optical system according to claim 1, wherein
Control means for controlling the laser divergence point moving means;
Input means for inputting the refractive index and the distance;
Calculating means for calculating the amount of movement of the laser divergence point from the refractive index of the medium input from the input means and the distance;
A laser condensing optical system. A laser light source for emitting laser light;
A condensing optical system that is disposed between the laser light source and the medium, condenses the laser light in the medium, and re-condenses the light from the condensing point;
Scanning means capable of scanning the laser light in a direction perpendicular to the optical axis of the condensing optical system;
A photodetector for detecting the light re-condensed by the condensing optical system;
The position of the laser divergence point of the laser light and the position of the photodetector are determined according to the refractive index of the medium where the laser light is to be collected and the distance from the surface of the medium to the position where the laser light is to be collected. A laser scanning microscope characterized by comprising laser divergence point moving means movable along the optical axis.

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