JPH05196870A - Scanning type laser microscope - Google Patents

Abstract

PURPOSE:To efficiently observe a body by guiding deflected luminous flux, projected from an anisotropic Bragg diffraction acoustooptic light deflecting element, onto the body without any loss. CONSTITUTION:The anisotropic Bragg acoustooptic light deflecting element 3, a polarization beam splitter 6, and a galvanomirror 9 are arranged in the order of the travel of light from a light source 1 and the body S is scanned with the converged luminous flux in two dimensions; and the light scattered by the body S is passed through the galvanomirror 9 and directed by the polarization beam splitter 6 to the direction different from the direction to the light source and its intensity is detected by a detector 15. This scanning type laser microscope has a 1/4-wavelength plate 4 arranged between the anisotropic Bragg diffraction acoustooptic light deflecting element 3 and polarization beam splitter 6 and the deflected luminous flux which is elliptically polarized by the light deflecting element 3 is converted into linear polarized light which passes through the polarization beam splitter 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning laser microscope, and more particularly to a scanning laser microscope using an acousto-optic light deflection element.

[0002]

2. Description of the Related Art In a scanning laser microscope, a light beam from a laser light source is focused on a point on an object by an objective lens, and the scattered light is received by a photoelectric conversion device to obtain a signal representing the state of one point on the object. Which is a type of photoelectric microscope
By changing the relative positions of the object and the focused laser beam, it is possible to obtain information about the state of the surface of the object, and is expected to have a wide range of applications.

Conventionally, in this type of device, in order to change the relative position of the object and the laser beam, (1) the object is moved, or (2) a galvano mirror or a rotation is provided between the laser light source and the objective lens. Arranging a polyhedron or a quartz plate to change the focusing position of the light beam on the object, or (3) combining the optical deflecting element shown in (2) above with an acousto-optic optical deflecting element using anisotropic Bragg diffraction. Then, the method of changing the focusing position of the light flux on the object has been adopted.

[0004]

[Problems to be Solved by the Invention] However, (1)
In this method, the size of the scanning range can be arbitrarily selected, but since it is impossible to move the object at high speed, it takes a very long time to obtain a signal in a predetermined scanning region. there were. Also, in the method of (2),
The scanning speed is considerably high, but it is not sufficient. For example, there is a problem that an object image cannot be displayed in real time on a TV monitor screen.

Further, in the method (3), the above-mentioned acousto-optic light deflecting element is used for horizontal scanning (main scanning), and a galvano mirror or the like is used for vertical scanning (sub scanning), so that the scanning speed is set to display. This is sufficient to maintain real-time properties, but the anisotropy of the acousto-optic light deflection element causes the light emitted from this polarization element to be elliptically polarized, so the scattered light from the object is separated from the irradiation light path and the detection light path is separated. There is a problem in that the intensity of the focused light that reaches the object is reduced by a considerable amount of attenuation by the polarization beam splitter that leads to, and consequently the microscope becomes dark.

The present invention has been made in view of such a situation, and an object thereof is to combine a focused laser light flux on an object by combining an anisotropic Bragg diffractive acousto-optic light deflecting element and a light deflecting element such as a galvanometer mirror. In a scanning laser microscope which two-dimensionally scans with, the deflected light flux emitted from the anisotropic Bragg diffractive acousto-optic light deflecting element is guided onto the object without loss so that the object can be efficiently observed.

[0007]

A scanning laser microscope according to the present invention that achieves the above object has at least an anisotropic Bragg diffractive acousto-optical deflector, a beam splitter, and a second splitter in the order in which light from a light source travels. And a light deflecting element for scanning the focused light flux two-dimensionally on the object, and the light scattered from the object is directed to a direction different from the light source by the beam splitter via the second light deflecting element. In a scanning laser microscope that detects the intensity, a polarization beam splitter is used as a beam splitter, and a quarter wavelength plate is arranged between the anisotropic Bragg diffractive acousto-optic light deflector and the polarization beam splitter. To do.

[0008]

In the present invention, since the quarter-wave plate is arranged between the anisotropic Bragg diffractive acousto-optic light deflecting element and the polarization beam splitter, this quarter-wave plate allows the anisotropic Bragg diffractive acousto-optic device. The deflected light beam, which has become elliptically polarized by the light deflection element, can be converted into linearly polarized light that passes through the polarization beam splitter, and the deflected light beam emitted from the anisotropic Bragg diffractive acousto-optic light deflection element has almost no attenuation. Since the light passes through the splitter and reaches the sample, and the scattered light is detected by the detector, the amount of detected light is greatly increased and the observed image becomes bright.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The scanning laser microscope of the present invention will be described in detail below with reference to the illustrated embodiment. FIG. 1 is a diagram showing an optical system of one embodiment of the present invention, in which 1 is a laser light source,
A beam expander 2 expands the beam diameter by converting the light emitted from the laser light source 1 into a parallel light beam. Behind the beam expander 2, an anisotropic Bragg diffractive acousto-optic light deflection element (hereinafter referred to as AOD) which is a first light deflection element.
3 is arranged, and the emitted light is deflected at high speed within the plane of the drawing (main scanning). A quarter-wave plate 4 for converting the elliptically polarized light emitted from the AOD 3 into linearly polarized light is disposed behind it. Since the elliptically polarized state of the light emitted from the AOD 3 changes slightly according to the deflection angle, the quarter-wave plate 4 converts the elliptically polarized light into the linearly polarized light at the central deflection angle, for example.
At both ends of the deflection angle, the angles are set such that most of the polarization components are distributed in the linear polarization direction. A first positive lens 5 is disposed behind the AOD 3 with its deflecting surface aligned with the front focal point, and behind the AOD 3, a polarizing beam splitter 6 for discriminating between the light flux from the laser 1 and the scattered light from the object S.
Are arranged. Splitting the polarization beam splitter 6
Since the synthetic plane is set by adjusting the angle around the optical axis so that the light beam converted into the linearly polarized light by the quarter-wave plate 4 passes, it is not necessarily perpendicular to the paper surface. A second positive lens 7 is disposed confocal with the first positive lens 5 behind the polarization beam splitter 6, and the first positive lens 5 and the second positive lens 7 constitute a telecentric relay lens system. A galvanometer mirror 9 which is a second light deflecting element is arranged so as to match the rear focal point of the second positive lens 7, and the incident light beam is deflected perpendicularly to the paper surface (sub scanning). It should be noted that another linearly polarized light emitted from the polarization beam splitter 6 is converted into circularly polarized light, and the circularly polarized light returned from the object S is converted into linearly polarized light which is orthogonal to the linearly polarized light direction.
The quarter-wave plate 8 is arranged between the second positive lens 7 and the galvanometer mirror 9, but the arrangement position of the quarter-wave plate 8 is not necessarily limited to this position, and the polarization beam splitter is used. It may be any position between 6 and the object S. The light flux exiting the galvanometer mirror 9 and deflected in two directions perpendicular to the paper surface passes through a confocal third positive lens 10 and a fourth positive lens 11 which form a second telecentric relay lens system. The front focus of the third positive lens 10 is aligned with the rotation axis of the galvanometer mirror 9, and the rear focus of the fourth positive lens 11 is aligned with the entrance pupil of the objective lens 12. Has been done. The imaging lens 1 so as to focus the scattered light from the object S reflected by the splitting / combining surface of the polarization beam splitter 6.
3 is arranged, and a slit 14 for establishing a confocal property with the focused light on the object S is arranged at the image forming position with the slit direction oriented in the main scanning direction as shown in the figure,
A detector 15 that detects the light that has passed through the slit 14 is provided behind it.

Since the scanning laser microscope of the present invention is constructed as described above, the light beam emitted from the laser light source 1 is converted into a parallel light beam having a beam diameter enlarged by the beam expander 2, and the AOD 3 is provided on the paper surface. Is angularly deflected in the main scanning direction according to the wavelength of the applied ultrasonic wave. This deflected light flux is elliptically polarized light, but is converted into linearly polarized light in a predetermined direction or elliptically polarized light close to it by the quarter-wave plate 4. The parallel light flux is focused by the first positive lens 5 and is incident on the polarization beam splitter 6, but is ¼ so that its polarization state almost passes through the splitting / combining surface.
Since it is converted by the wave plate 4, it passes through the polarization beam splitter 6 with almost no attenuation and
It is converted into a parallel light flux by the positive lens 7. This linearly polarized light beam is incident on another quarter-wave plate 8 and converted into circularly polarized light. A galvano mirror 9 arranged at a position conjugate with the AOD 3 sub-scans the light perpendicular to the main scanning direction. It is deflected in the scanning direction. In this way, the luminous flux that is two-dimensionally deflected in the main scanning direction within the plane of the paper and the sub-scanning direction perpendicular to the plane of the paper is the third positive lens 10 and the fourth positive lens 10 constituting the second telecentric relay lens system. With the positive lens 11,
It is incident on the entrance pupil of the objective lens 12, and this entrance pupil is A
Since it is conjugated with OD3 and galvanometer mirror 9,
The light beam that enters the entrance pupil enters a fixed position that does not depend on the deflection angle. This light beam is transmitted to the object S by the objective lens 12.
It is focused on the surface as a converging point that is two-dimensionally scanned above. The scattered light flux including the information of the condensing point of the object S follows the optical path opposite to the above to the polarization beam splitter 6, but
Since the half-wave plate 8 converts the light beam that has passed through the polarization beam splitter 6 into a linearly polarized light which is orthogonal to the light beam, the scattered light beam from this object S is reflected by the splitting / combining surface of the polarization beam splitter 6 to form an imaging lens. The light enters the slit 13, is condensed on the slit 14, and its intensity is photoelectrically detected by the detector 15. Since only one of the light deflecting elements 9 passes through this return light beam, the condensing point moves in the other scanning direction, that is, the main scanning direction. Therefore, the side lobe (halo) of the detection light spot in the sub-scanning direction is removed via the slit 14 in which the slit is oriented in the main scanning direction at a position conjugate with the object S in front of the detection surface of the detector 15. Detected.

Here, as described above, as the first light deflection element 3, for example, from a single crystal of tellurium dioxide, <110.
An off <110> type anisotropic Bragg diffractive acousto-optic light deflector is used which propagates transverse ultrasonic waves in a direction tilted from the> axis and deflects a laser beam by an acousto-optic effect. Since the element 3 has a large deflection angle, it is possible to realize a scanning laser microscope having a practically sufficient scanning range and scanning speed. If the 1/4 wavelength plate 4 is not arranged, a large part of the light emitted from the AOD 3 by the polarization beam splitter 6 is reflected by the splitting / combining surface,
Since it does not reach the sample S, the amount of light detected by the detector 15 is greatly reduced, and the observed image becomes extremely dark. However, as described above, the quarter-wave plate 4 converts the elliptically polarized light emitted from the AOD 3 into the linearly polarized light that passes through the polarization beam splitter 6, so that the deflected light flux emitted from the AOD 3 is hardly attenuated. After passing through the polarization beam splitter 6 to reach the sample S and the scattered light is detected by the detector 15, the amount of detected light is greatly increased and the observed image becomes bright.

Next, the driving of each light deflection element and the processing of the detection signal will be briefly described. It is also effective to change the deflection angles of the AOD 3 and the galvano mirror 9 in a continuous and analog manner synchronously to obtain a surface image of the object S by raster scanning the converging point, but it is possible to specify the irradiation position. There is also a problem that it is difficult and it is difficult to associate the irradiation position with the information obtained from it. Therefore, the deflection angles of these optical deflection elements 3 and 9 are digitally changed at a predetermined interval in synchronization with each other, and the detection surface is divided into two directions orthogonal to each other at a predetermined interval in a grid pattern, and the position of each pixel is changed. The information of is detected as digital information. FIG. 1 also shows a configuration for this purpose. That is, the driver 21 of the AOD 3 and the driver 23 of the drive coil 22 of the galvanometer mirror 9 are the CPU
The AOD 3 is controlled so as to be deflected at regular intervals in the main scanning direction of the screen as shown by the deflection angle. Further, the galvano mirror 9 is controlled so that the deflection angle is increased by a constant interval in the sub-scanning direction every time the AOD 3 scans one side of the screen in the main scanning direction. The detection signal from the detector 15 is output by the A / D converter 24 to a predetermined number of gray levels, for example 25
It is converted into 6-tone (8-bit tone) digital density information and stored in the frame memory 25 through the CPU 20 in association with the address of each pixel. Then, the morphological information of the object S stored in the frame memory 25 or the information subjected to the predetermined image processing by the CPU 20 is displayed on the TV monitor 26.

As described above, the two-dimensional scanning of the scanning laser microscope is digitized at a predetermined interval, and the detection information is digitized in a predetermined number of gradations so that the visual field can be freely selected and the irradiation position of the laser beam can be selected. It is possible to easily deal with the information from there, and it becomes easy to measure the length and the product of the object, and it is possible to easily perform image processing on the obtained morphological information.

The scanning laser microscope of the present invention has been described above based on the embodiments, but the present invention is not limited to these embodiments and various modifications can be made.

[0015]

As is apparent from the above description, according to the scanning laser microscope of the present invention, the quarter wavelength plate is arranged between the anisotropic Bragg diffractive acousto-optic light deflecting element and the polarization beam splitter. With this quarter-wave plate, it is possible to convert the deflected light beam, which has been elliptically polarized by the anisotropic Bragg diffractive acousto-optic light deflection element, into linearly polarized light that passes through the polarization beam splitter. The deflected light flux emitted from the optical light deflector passes through the polarizing beam splitter with almost no attenuation and reaches the sample, and the scattered light is detected by the detector, so the detected light amount greatly increases and the observed image is bright. become.

By using an anisotropic black diffraction acousto-optic light deflection element, it is possible to take out a morphological image of the sample in real time, and a slit is used in front of the detector to enhance the confocal property. You can Therefore, the optical slicing of the sample can be performed very accurately. Further, since the sample is irradiated with the focused light, the depth of focus is shallow and an image of an arbitrary layer of the sample can be captured.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical system of one embodiment of a scanning laser microscope of the present invention.

[Explanation of symbols]

 S ... Object (sample) 1 ... Laser light source 2 ... Beam expander 3 ... Anisotropic Bragg diffraction acousto-optic light deflection element (AOD) 4 ... Quarter wave plate 5 ... First positive lens 6 ... Polarization beam splitter 7 ... 2 Positive lens 8 ... Quarter wave plate 9 ... Galvano mirror 10 ... Third positive lens 11 ... Fourth positive lens 12 ... Objective lens 13 ... Imaging lens 14 ... Slit 15 ... Detector 20 ... CPU 21 ... AOD driver 22 ... Drive coil 23 ... Galvano mirror driver 24 ... A / D converter 25 ... Frame memory 26 ... TV monitor

Claims (1)

[Claims] 1. A light source in the order of travel of light, at least:
An anisotropic Bragg diffractive acousto-optic light deflector, a beam splitter, and a second light deflector are arranged to two-dimensionally scan a focused light beam on the object, and the light scattered from the object is reflected by the second light deflector. In a scanning laser microscope that detects the intensity of a beam from a light source through a beam splitter through a beam deflector, a polarizing beam splitter is used as the beam splitter, and an anisotropic Bragg diffraction acousto-optic beam deflector and a polarized beam are used. A scanning laser microscope having a quarter-wave plate arranged between splitters.