JP2787678B2 - Polarized light microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization measuring device and a polarization microscope using the same, and more particularly, to a microscopic rotation of a polarization plane when linearly polarized light is incident on a substance having optical rotation or birefringence. And a polarization microscope capable of enlarging and visualizing a polarization image of a minute region using the device.

[0002]

2. Description of the Related Art Polarization is one of the important properties of light as waves. There are various causes of polarized light, such as those related to light radiation, such as polarized light caused by heat radiation or stimulated radiation, and polarized light at the time of fluorescence. Also, those caused by the properties of the medium through which light propagates, such as crystals There are birefringence phenomena caused by a force or an electromagnetic field applied to the medium or medium, and bias in scattering caused by the presence of fine particles. In addition, there is polarization generated by boundary conditions for light propagation, for example, polarization generated by reflection or diffraction. Therefore, by measuring the nature and degree of polarized light, much knowledge about these causes and physical properties can be obtained.

For example, in a technique known as ellipsometry, when light is reflected on the surface of an object, the polarization state of the light changes before and after the reflection. Optical constants and surface properties can be analyzed. One of the polarization analysis methods is a method using linearly polarized light. When linearly polarized light is incident on a substance having optical rotation or birefringence, the linearly polarized light rotates during reflection, and information on the physical properties of the substance is obtained by detecting this rotation angle (rotation of the polarization plane). .

In the above method, if the rotation of the polarization plane is large during reflection, it is relatively easy to detect the rotation. However, for example, in the case of a minute rotation of about 1 °, no matter how precisely the high-precision rotation analyzer is rotated, the detection involves some difficulty, and even a minute rotation of the order of 0.1 ° is required. However, a normal detection system cannot detect it first, and special measures are required to detect it, or a special device specially designed must be used. Certainly, this type of polarization measuring device that detects minute rotation of the polarization plane has been known in the past, but requires an extremely high-performance polarizing element and an analyzing element, and is generally used for detection. Since the light reaching the vessel is weakened, a high-sensitivity, high-resolution detector is indispensable. In addition, the apparatus itself including the lamp light source system generally has a problem that it becomes a large-sized apparatus which can be used in a stationary state. Since the polarizing optical element is very expensive, there is a problem that the price of the apparatus itself is extremely expensive.

Specifically, a microscope equipped with a polarizing optical system will be described by exemplifying a magnetic domain observation polarizing microscope which visualizes magnetic domains of a magnetic substance, which has been studied recently. In recent years, high-performance magnetic recording devices have been used in many sites. Demands for higher densities and higher speeds are increasing along with the increase in the amount of information, and magnetic recording media and magnetic recording heads that can satisfy the demands are being developed. The magnetic recording medium used in such a high-performance magnetic recording device and the fine structure of the magnetic domains of the magnetic recording head directly affect the recording and reproducing characteristics. For this reason, the development of magnetic recording devices requires analysis of the fine structure of magnetic domains. Also, with the speeding up of the magnetic recording device, it is desired to know the dynamic characteristics of the magnetic domain structure of the head while operating at about 10 MHz to 100 MHz. In observing the microstructure of magnetic domains, an MFM (Magnetic Force Microscope) has been developed and put into practical use (for example, P. Grutter,
Th. Jung et.al., ”10-nm resolution by magnetic fo
rce microscopy on FeNdB ”J. Appl. Phys. 67 , pp. 1
437-1441 (1990)). This microscope has a high spatial resolution of over 10 nm. However, because the stylus contacts the sample and damages it, and because it is a scanning microscope, it takes a long time to obtain a single image, and dynamic observation of the magnetic domain structure can be performed. There is no problem. For dynamic observation of the magnetic domain structure, a method of detecting the rotation of the plane of polarization due to the magneto-optical effect is used (PV Koeppe and M. K.).
H. Kryder, "High-resolution magnetooptic imaging
of the high-frequency magnetic behavior of Ferrite
recording heads "IEEE Tran. Mag. 27 , pp.7
24-725 (1991)). In this method, since light is used, the sample is not in contact with the sample, and damage to the sample is extremely small. In addition, since pretreatment of the sample is unnecessary, it has a feature that it can be easily used anywhere. Further, stroboscopic time-resolved observation of the magnetic domain structure in the operating state of the magnetic head is possible by using a pulse laser or a flash lamp. However, this type of conventional magnetic domain observation microscope generally uses a mercury lamp or gas laser as a light source, and is not suitable for time-resolved measurement that needs to be synchronized with the operation of a magnetic head. The whole is also very large. Also, the use of extremely expensive Glan-Thompson prisms for polarizers and analyzers makes the equipment very expensive. That is, the Glan-Thompson prism is made of natural quartz or calcite, and two prisms of the same shape are cut out of these crystals and their slopes are joined to each other with a balsam. .06-
Since the extinction ratio is extremely small (0.6 °), the extinction ratio must be extremely high. If the extinction ratio of 10 ⁻⁶ to 10 ⁻⁵ is not realized, detection is almost impossible.

Another problem is that Glan-Thompson
When using prisms as polarizers and analyzers,
Since they are arranged in a crossed Nicols state, the throughput of light passing therethrough is extremely low, and the light reaching the photoelectric detector is weakened, so that a clear image or contrast may not be obtained.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel polarization measuring device for detecting minute rotation of a plane of polarization of transmitted or reflected light when linearly polarized light is incident on a substance having optical rotation or birefringence. Basic purpose. Another object of the present invention is to reduce the size of the device. Another object of the present invention is to provide a novel polarization microscope capable of detecting and visualizing minute rotation of the plane of polarization of transmitted or reflected light when linearly polarized light is incident on a substance having optical rotation or birefringence. It is in. Another object of the present invention is to provide a small and lightweight polarizing microscope suitable for field use. Still another object of the present invention is to provide a small and inexpensive polarizing microscope for magnetic observation that has high detection accuracy for minute rotation of linearly polarized light and is suitable for field use. Another object of the present invention is to provide a polarization microscope for magnetic observation that can dynamically observe the magnetic domain structure of a magnetic body.

[0008]

In order to achieve the above object, the present invention provides a linear polarizer provided between a light source and a subject, and an azimuth of the linear polarizer among linear polarized lights from the subject. Analysis means for suppressing a linearly polarized light component equal to the angle while transmitting a component orthogonal to the linearly polarized light component;
An analyzer for analyzing linearly polarized light from the analyzer, and a photoelectric converter for photoelectrically converting light from the analyzer, wherein the micro-rotation of the polarization plane of the linearly polarized light from the subject is performed by the analyzer. It is a basic feature that it is increased by.

[0009]

The linearly polarized light emitted from the linear polarizer is shown in FIG.
As shown in (A), the object is irradiated with the linearly polarized light 1 so that the polarization plane is rotated based on the properties of the object,
As shown in FIG. 3B, the azimuth of the linear polarizer is 2
Becomes a linearly polarized light 3 rotated by an angle θ. The linearly polarized light 3 is incident on the analyzing means, and as shown in FIG. 2, a linearly polarized light component equal to the azimuth angle 2 of the linearly polarized light is suppressed by an amount indicated by a vector 4, while this linearly polarized light is suppressed. The orthogonal components are transmitted as they are. As a result, the linearly polarized light emitted from the light detecting means becomes the linearly polarized light 5 having an angle θa larger than the angle θ. The analyzer detects the linearly polarized light 5. The detected light is converted into an electric signal by the photoelectric conversion means. As described above, since the rotation of the plane of polarization of linearly polarized light is represented as a vector sum of an incident polarized light component and a component orthogonal thereto, only the same polarized light component as the incident polarized light is reduced among these two components, and the rotation is performed. The basic principle is to increase the angle. In addition, the above-mentioned light detecting means can be simply described as an incident polarization plane.
It can be easily realized by an analyzer as an optical element having an azimuth orthogonal to (azimuth 2). In addition, since the intensity of the component orthogonal to the incident polarized light is usually as small as about 10 ⁻⁵ to 10 ⁻⁷ of the incident polarization direction component, the transmittance of the analyzer used for increasing the rotation angle may be considerably high. desirable.

[0010]

[Quantitative Evaluation of Rotation Angle Increase and Magnetic Domain Contrast] As an example, a case where a magnetic substance is applied to a subject will be described. The effect of the magnetic properties of matter on the polarization state of light,
Although there are the Faraday effect and the magnetic Kerr effect (magneto-optical effect in a narrow sense), the latter magnetic Kerr effect is shown.
The polar Kerr effect illustrated in FIGS. 3A, 3B, and 3C, respectively.
The vertical Kerr effect and the horizontal Kerr effect (the magnetization directions of the magnetic bodies 6, 7, and 8 are indicated by M, and the state of the incident and reflected polarization is indicated by solid lines 9 and 10 with arrows).
The reference numeral 11 indicates. ), The polar car effect (Fig. 3 (A))
Is described. Then, as shown in FIG. 4, the contrast is different between the different magnetic domains 61, perpendicularly magnetized in opposite directions.
Linear polarized light 91 is incident on 62, and as shown in FIG. 4B, the linearly polarized lights 93 and 94 of the reflected light 92 whose polarization planes are rotated in two different directions by the polar Kerr effect are targeted. I do. First, the extent to which the rotation angle of the polarization plane is increased by the above method will be verified by using a theoretical formula. The transmittances of two orthogonal polarization components are Tb and Tt, respectively.
When linearly polarized light tilted by θi with respect to an axis orthogonal to the azimuth of the element (referred to as the b-axis, and the direction of the azimuth is referred to as the t-axis) is incident on the analysis element in which (Tb≪Tt). (Direction 2 in FIG. 2 corresponds to the b-axis).

Assuming that the b-axis component and the t-axis component of the incident linearly polarized light at this time are Eib and Eit, the polarization components Eob and Eot immediately after the light detecting element are given by the following equations. Eob = √Tb · Eib (1) Eot = √Tt · Eit (2) where Eib and Eit are the electric fields Ei and θ of the incident linearly polarized light.
When expressed by i, the following equation is obtained. Eob = Ei · cos θi · √Tb (3) Eot = Ei · sin θi · √Tt (4) Assuming that the angle between the polarization plane immediately after the light analyzing element and the b axis is θo,
θo is expressed as follows: θo = tan ⁻¹ (Eot / Eob) = tan ⁻¹ (√ (Tt / Tb) · tan θi) (5) For example, Tt = 95%, Tb = 0.02
%, Θi = 1 mrad, θo = 68.8 mrad, and an increase rate of about 70 times can be obtained. Next, the magnetic domain contrast in this case will be verified. The reflected light intensity from two magnetic domains having antiparallel magnetization as shown in FIG. 4 is given by the following equation with respect to the incident linearly polarized light intensities Pt and Pb. _{I - = Pt · Ab + Pb} · At ...... (6) I + = Pt · At · sin (2θo) + Pt · Ab · cos (2θo) + Pb · At ... (7) where, Ab, At the 5 as illustrated, the linearly polarized light 93 of linearly polarized light (increased Kerr rotation angle theta _K after polarization rotation increases, the linear polarization of increased Kerr rotation angle - [theta] _K 9
4) is the extinction ratio (Ab≪At) of the analyzer 95 that detects the light, I ₋ represents the extinction component of the analyzer 95, and I ₊ represents the transmission component. The magnetic domain contrast V at this time _{is, V = (I + -I -} ) / (I + + I -) = [Pt · At · sin (2θo) + Pt · Ab · (cos (2θo) -1)] / [Pt · At · sin (2θo) + Pt · Ab · (cos (2θo) +1) + 2Pb · At] (8), for example, Pt = 95%, Pb = 0.02%, T
t = 95%, Tb = 0.02%, At: Ab = 100
Assuming that 0: 1 and θi = 1 mrad, from the above equations (5) and (8), V = 0.996, which indicates that a very high contrast can be obtained.

Based on the above analysis, a specific evaluation of the increase in the rotation of the polarization plane was calculated and found. 6 to 9 show the results.
Shown in In any case, the polarizer and the analyzing means for increasing the rotation angle are shared by a single polarizing beam splitter as in the embodiment described later. The specifications of the polarizing beam splitter to be evaluated include a transmittance of 95% for p-polarized light, a reflectance of 0.02%,
The transmittance of the s-polarized light was 0.02% and the reflectance was 95%. The analyzer at the final stage had an extinction ratio of 10 ^-4 .

FIG. 6 shows the rotation angle of the polarization plane immediately after the polarization beam splitter. The abscissa represents the Kerr rotation angle before the increase, in units of mrad (milliradian), and the ordinate represents the rotation angle after the increase, which is π times the scale, and the unit is rad (radian). FIG. 7 shows the ratio between the rotation angle on the vertical axis in FIG. 6 and the rotation angle of the polarization plane immediately before the polarization beam splitter (Kerr rotation angle shown on the horizontal axis in FIG. 6). An extremely high increase rate of 60 times or more is obtained in a wide range of 0.0 to 10.0 mrad. FIG. 8 shows a comparison of magnetic domain contrast between the method according to the present invention and the conventional method. In the conventional method, a Glan-Thompson prism having an extinction ratio of 10 ^-6 is used as a polarizer, and an extinction ratio of 10 ^-4 is used as an analyzer.
From FIG. 8, for example, when observing the magnetic domain of the thin film magnetic head, the Kerr rotation angle is 0.3 to 0.7 mrad, so that this method is very effective for obtaining this type of magnetic domain contrast. You can see that there is. FIG. 9 shows the magnetic domain contrast when the Kerr rotation angle on the horizontal axis is 0.0 to 10.0 μrad (microradian). According to this method, 10μ
It is understood that a clear magnetic domain contrast can be obtained to some extent even in a very small rotation of rad or less. By the way,
When converted to degrees, 5.0 μrad is 0.0000287.
°.

[0014]

FIG. 10 shows a polarization measuring device as an embodiment of the present invention. The subject 11 is a substance having a property of rotating the plane of polarization of the incident linearly polarized light when reflecting the incident linearly polarized light. The light source unit 12 includes a converging lens and a semiconductor laser or a high-brightness light emitting diode as a semiconductor light source. The convergent light 13 emitted from the light source unit 12 is reflected by the polarizing beam splitter 14 and the test light is given to the subject 11 via the lens 15.
The light reflected by the subject 11 passes through the lens 15, passes through the polarizing beam splitter 14, and further enters the photoelectric detector 17 through the polarizing plate 16 made of a polaroid plate or the like. The polarization beam splitter 14 has, for example, λ = 63
For light of 2.8 nm, p-polarized light transmittance is 98.0%, s-polarized light transmittance is 0.006%, p-polarized light reflectance is 99.0%, s-polarized light reflectance is 0.05%, and extinction ratio (H ₉₀ ) It has a characteristic of 2 × 10 ⁻⁵ . Therefore, when the convergent light 13 from the light source unit 12 is reflected by the polarization beam splitter 14, it is linearly polarized. Then, the light is condensed on the pupil plane of the lens 15, and the linearly polarized light is collimated by the lens 15 to illuminate the subject 11 uniformly. The reflected light from the subject 11 becomes a linearly polarized light having a plane of polarization that has been rotated with respect to the plane of polarization of the linearly polarized light that has entered. When the linearly polarized light enters the polarization beam splitter 14, a part of the light is reflected and returns to the light source unit 12, and the other part passes through the polarization beam splitter 14. When passing through, the linearly polarized light component that is equal to the azimuth that has been linearly polarized earlier is suppressed, and the component that is orthogonal to this linearly polarized light component is transmitted almost as it is. Has a rotation angle whose polarization plane is significantly increased as compared with the rotation angle of the polarization plane of the reflected linearly polarized light. The azimuth angle of the analyzer 16 is selected so as to analyze the linearly polarized light having the increased rotation angle.
Receives this analysis light and converts it to electronic intensity,
Output as an electric signal S. In the case where the analysis light is projected on a screen or the like and observed with the naked eye,
The photoelectric detector 17 can be omitted.

In the above embodiment, if the semiconductor light source of the light source unit 12 is a laser diode, the laser light emitted from the laser diode is originally linearly polarized, which is advantageous in relation to the extinction ratio of the polarization beam splitter 14. is there. That is, even if a polarizing beam splitter having an extinction ratio smaller by one or two digits is used, desired characteristics can be obtained. The polarization beam splitter herein refers to a prism formed by coating a dielectric reflective film on a slope of a right-angle prism to have a polarization characteristic and joining the right-angle prism having the same shape.
When a laser diode is used as a light source, there is a possibility that a problem of speckle noise may occur on the contrary to the above advantage.
In such a case, the semiconductor light source of the light source unit 12 is preferably a light emitting diode. High brightness, eg 10
It is preferable to use a light emitting diode having a luminance of 00 mcd or more.

The polarizing beam splitter 14 is a polarizer because it linearly polarizes incident light when reflecting light at the junction slope, and when transmitting rotating linearly polarized light from the subject 11, the polarizing beam splitter 14 has an orientation of the polarizer. Acts as an analyzer having an azimuth perpendicular to the angle, which increases the rotation angle of the rotating linearly polarized light. That is, the polarization beam splitter 14 suppresses a linearly polarized light component equal to the azimuthal angle of the linearly polarized light of the linearly polarized light from the linear polarizer and the subject, while transmitting a component orthogonal to the linearly polarized light component. Also serves as a means. Of course, it is needless to say that the linear polarizer and the analyzing means may be separated from each other in such a configuration. However, the use of the polarizing beam splitter has an advantage that the optical system can be made extremely compact. Also, the analyzer 16 is not a polarizing plate,
It is also possible to use a polarizing film. It may be provided separately from the polarization beam splitter 14 or may be attached to the light exit surface of the polarization beam splitter 14. As in the above embodiment, the polarization measurement device including the light source unit 12 including the semiconductor light source and the polarization beam splitter 14 has a compact and extremely miniaturized configuration as compared with a conventional device of this type. Of course, it is also possible to have a size that can be held by hand.

In the embodiment shown in FIG. 10, the linear polarizer and the analyzing means for increasing the rotation angle are used as a single polarizing beam splitter 14 for these functions. However, it is needless to say that the linear polarizer and the light detecting means may be constituted by independent members each performing a different function. FIG. 11 shows an optical path diagram of the optical system of the polarization measuring device having this configuration. 14p is a linear polarizer, 14h is a half mirror,
Reference numeral 14a denotes a first analyzer arranged in a crossed Nicols state with the linear polarizer 14p, and the analyzer 14a increases the rotation angle of the plane of polarization of linearly polarized light. In addition, the same reference numerals as those in FIG. 10 indicate the same or corresponding ones.

Further, in the embodiment shown in FIGS. 10 and 11, the case where the subject 11 is a light reflecting object is shown, but a configuration may be adopted in which the subject is a light transmitting type subject. FIG.
FIG. 1 shows an outline of an optical system and an optical path according to this embodiment. The linearly polarized light from the light transmitting material 11t is converted into the first analyzer 14a and the second analyzer 14a.
The image is formed on the photoelectric converter 17 by the condenser lens 19 through the analyzer 16 of FIG. This embodiment can be used for, for example, a polarimeter typified by a glucose meter or a polarimeter for measuring the Faraday effect.

Next, an embodiment in which the basic optical system according to the present invention is applied to an optical microscope will be described. FIG. 13 shows a partial sectional view of this embodiment. Reference numeral 20 denotes a sample table on which the sample 21 is placed, and reference numeral 22 denotes a light source unit that provides illumination light for illuminating the sample 21 through a hole opened in a lens barrel, and includes a semiconductor laser as a light source and a converging lens. Reference numeral 23 denotes an objective lens, 24 denotes a polarizing beam splitter that is installed at 45 ° to cross the optical axis of the microscope, 25 denotes an analyzer made of a polarizing plate, 26 denotes a relay lens, 27 denotes a teleconverter lens, 28 denotes a camera straight tube, and 29 denotes a camera. Is a CCD camera with an image intensifier. Reference numeral 30 denotes an eyepiece provided with an eyepiece 31. FIG. 14 illustrates the main optical system of the above embodiment and its optical path. FIG.
Those having the same reference numerals as those described above represent the same or corresponding ones. The light source unit 22 includes a semiconductor laser 221.
And collimator lens 222 and lenses 223 and 224
And an aperture stop 225 provided between the lens 223 and the lens 224. Here, the semiconductor laser 22
For 1, a visible semiconductor laser (manufactured by Nippon Kagaku Engineering Co., Ltd.) having an oscillation wavelength of 670 nm and a maximum output of 10 mW is used. The light emitted from the lens 224 is reflected by the joint slope of the polarizing beam splitter 24 and is reflected by the objective lens 2.
The light is condensed on the third pupil plane 23p. And
Since the converging angle is set to be small, the sample 21 can be efficiently illuminated by suppressing kicking of light in the lens barrel. It also helps to suppress coherent noise. As the polarization beam splitter 24, a 15 mm square one (manufactured by Nippon Kagaku Engineering Co., Ltd.) for a visible semiconductor laser is used. The characteristics are as follows: p-polarized light transmittance 95.0%, s-polarized light transmittance 0.0 for light having a wavelength of 670 nm.
2%, p-polarized light reflectance 95.0%, s-polarized light reflectance 0.02
%, And the extinction ratio (H ₉₀ ) is 2 × 10 ⁻⁵ . CCD camera 3
0 for CCD camera with image intensifier
(Model number DAS512G1 manufactured by Imagista Co., Ltd.) is used. Since this camera does not use an MCP (Microchannel Plate), it has features of high spatial resolution and small dark current. Furthermore, since S25 is used for the photocathode, it is highly sensitive to long wavelength light. Due to the high light use efficiency and high sensitivity of the image sensor described above, the relay lens 26 (2.5 times), the camera straight tube 28 and the teleconverter 27 (2 times) make the image forming system 5 times. Is obtained.

When a laser light source is used as the light source as in the configuration of this embodiment, it is inevitable that coherent noise such as interference fringes and speckle noise is generated. It becomes stronger due to reflection on the surface of the optical element. Therefore, in order to suppress the coherent noise, the collimator lens 2 of the semiconductor laser 221 is used.
The focal length of the optical system 22 is changed and selected, and the light is condensed on the pupil plane 23p of the objective lens 23 as an almost ideal point light source, whereby the configuration of the optical system is simplified and noise generated is reduced. I have to. In addition, by using a high-power laser at a low output, the spectrum width is widened and the coherent distance is shortened, thereby suppressing the generation of coherent noise. The output of the semiconductor laser actually used is 1 mW, and the spectrum width is 1.43 nm.
And the coherence length was 0.3 mm. This coherence length is approximately one-tenth of the coherence length when used at an output of 10 mW.

The operation of the microscope of the present embodiment when, for example, a magnetic thin film is set as the sample 21 on the sample table 20 will be described. When the laser light emitted from the light source unit 22 is incident on the joint slope of the polarization beam splitter 24, all of the p-polarized light and a part of the s-polarized light of the incident light are transmitted in the incident direction, but almost all of the s-polarized light is , And travels downward at a right angle toward the objective lens 23. The objective lens 23 collimates the linearly polarized s-polarized light,
Is illuminated uniformly. When the s-polarized light incident on the magnetic thin film 21 of the sample is reflected here, the plane of polarization of the linearly polarized light is rotated by the magnetic Kerr effect. The reflected light passes through the objective lens 23 and enters the polarization beam splitter 24.
At the junction slope of the polarization beam splitter 24, the s-polarized light component of the incident light is reflected and returns to the light source unit 22 side, while the remaining s-polarized light component and the p-polarized light component pass through here. Therefore, during this transmission, a large amount of the s-polarized light component is lost (due to reflection), so that the rotation of the plane of polarization of the linearly polarized light emitted from the polarization beam splitter 24 greatly increases as compared with the time of incidence. Analyzer 25
Is selected and set so that its azimuth angle is directed to the direction in which the transmitted p-polarized light component and the transmitted s-polarized light component are combined, so that only the combined linearly polarized light is detected.
The analysis light passes through a relay lens 26 and a teleconverter 27.
The image is formed on the photoelectric surface of the CCD camera 30 through CC
The D camera 30 outputs an image signal of an intensity in which only the area of the magnetic thin film 21 having a predetermined magnetic Kerr effect is brightened.

More specifically, FIG. 15 shows a polarization microscope system including the above-described image signal processing system, and also shows an example of observation to show the effectiveness of increasing the Kerr rotation angle. In FIG.
Reference numeral 22d denotes a semiconductor laser driving device that drives and controls the semiconductor laser of the light source unit 22, and 29d denotes a CCD driving device that drives and controls the CCD camera 29.
The image signal is taken into the frame grabber 35 via d and stored therein. The stored image signal is subjected to image processing such as integration processing and background removal processing by the computer device 37 by operating the terminal device 36. The processed image is displayed on the CRT monitor 38,
The image is output on a hard disk or, if necessary, by a video printer 39. In the microscope shown here, the analysis image can be directly observed with the naked eye via the eyepiece 30. Further, in order to record an image, a simple means such as mounting a camera loaded with a silver halide film in place of the CCD camera 29 and taking a picture without using the above-mentioned electronic system is simply adopted. You may do so.

FIGS. 16 and 17 show observation examples using the polarizing microscope according to the above embodiment. This is an image obtained by visualizing the structure of magnetic domains perpendicularly magnetized in an anti-parallel direction using a magneto-optical disk as the sample 21. As shown in FIG. 5, the analyzer 25 is one in which one of the linearly polarized lights is placed in a direction in which it is substantially non-transmitted, and is analyzed. FIG. 16 shows that the objective lens has a magnification of 20 times,
FIG. 15 shows an observation image of the magnetic domain structure when a metal objective lens having an NA of 0.4 is used. FIG. 15 shows a magnification of 50 times and an NA of 0.7.
Magneto-optical disk objective lens (manufactured by Nikon Corporation, model number M
It is an observation image when using Plan50PC). As is clear from both images, the shape of the magnetic domain of the magneto-optical disk is clearly detected with high contrast.

According to the polarizing microscope using the semiconductor laser light source according to the present invention, it has been found that the magnetic domain structure can be detected with high contrast despite a very simple and compact structure. As a result of measuring the increase rate of the Kerr rotation angle of this microscope, the increase rate of 30 times when using a 20 times objective lens and 10 times when using a 50 times objective lens is 35 times the theoretical value. Obtained. Due to the objective lens and the like, despite the fact that the polarization plane is distorted, an increase in the polarization plane rotation angle close to the theoretical value has been obtained, and shows how the polarization plane rotation angle increasing method according to the present invention is effective. is there.

In this polarization plane rotation angle increasing method, distortion of the polarization plane due to the objective lens also increases. The distortion of the polarization plane due to the objective lens increases as the NA of the objective lens increases. It is considered that this is why the increase rate when the 50 × objective lens is used is lower than that when the 20 × objective lens is used. However, this distortion of the polarization plane can be easily removed by using an objective lens with a rectifier.

Referring to the observation images of FIGS. 16 and 17,
Distortion appears in each image. In particular, in an image of 20 times, the groove of the magneto-optical disk is distorted. The manner of this distortion changes when the polarization beam splitters are exchanged, and it has been found that the distortion is unique to each polarization beam splitter. From this, it is considered that this distortion is partly due to the surface accuracy of the polarizing beam splitter used to obtain the observation image.

The suppression of coherent noise can be interpreted as being effective for a magneto-optical disk having a smooth surface. However, speckle noise appears on a sample with a considerably rough surface, so it is necessary to use a means of removing speckle noise, such as scanning a laser beam, on such a sample. is there.

Next, another embodiment of the polarization microscope according to the present invention will be described with reference to FIG. In FIG. 18, reference numeral 40 denotes a table on which a subject 41 is placed.
An objective lens 43 provided at a distance of 0 to form an enlarged real image of the surface of the subject 41; a light source unit 42 for supplying illumination light to the subject 41;
Linear polarizers 44a and 44b provided in an optical path between the light source 2 and the subject 41, and a linear polarization component equal to the azimuthal angle of the linear polarizer 44a among the linearly polarized light reflected by the subject 41, Analyzing means 44a and 44b for transmitting components orthogonal to the linearly polarized light component, an analyzer 45 for analyzing linearly polarized light from the analyzing means, and a visualizing means for visualizing light from the analyzer, for example. An image sensor 50 is provided, 46 is a relay lens, and 47 is a teleconverter lens. The light source unit 42 includes a high-intensity light emitting diode 421 as a light source and a collimator lens 4.
22, the converging lenses 423 and 424, and the aperture stop 4
25. The linear polarizers 44a and 44b and the analyzing means 44a and 44b are constituted by a single polarizing beam splitter 44 which also serves as both. The polarizing beam splitter 44 has a joint slope 45 ° with respect to each optical axis.
It is set to be a degree. The light from the high-brightness light emitting diode 421 is converged by the lenses 424, 422, and 423, is linearly polarized when reflected by the polarizing beam splitter 44, and is converted to a pupil plane 4 of the objective lens 43.
Light is condensed at a small light converging angle on 3p. This condensed light is collimated by the objective lens 43 and
Is illuminated uniformly. The reflected light from the subject 41 undergoes a rotation of the polarization plane, and the rotation of the polarization plane is increased when passing through the polarization beam splitter 44, is analyzed by the analyzer 45, and is reflected on the image sensor 50. It is imaged. Thereby, it is possible to observe an enlarged image of the subject 41 in which the incident linearly polarized light is rotated.

The polarization microscope shown in FIG. 18 shows a configuration in which the subject 41 is a light reflector, but the basic configuration is the same as that in FIG. 18 even when the subject is a light transmitting body. .

In the above embodiment, an advantage of using a high-intensity light emitting diode as a light source is that coherent noise does not appear as in a laser light source because the light source is incoherent. Further, the light emitting diode has a feature that power consumption is small due to high light conversion efficiency and heat generation is small, so that damage to the sample due to heat can be avoided. For example, it is particularly effective for biological samples and the like.

FIG. 19 shows an observation example according to this embodiment.
As the high-brightness light emitting diode light source 421, a model number TLRO180AP manufactured by Toshiba Corp., that is, a device having a luminance of 1000 mcd using InGaAlP and an oscillation wavelength of 620 nm is used, and a He- manufactured by HOYA Corp. is used as the polarization beam splitter 44.
Use a polarizing beam splitter for Ne (λ = 632.8nm)
(Note that this polarizing beam splitter has a p-polarized light transmittance of 98.0%, a s-polarized light transmittance of 0.006%, a p-polarized light reflectance of 99.0%, an s-polarized light reflectance of 0.05%, and an extinction ratio (H ₉₀ ) 2 of 632.8 nm light. × 10 ⁻⁵ , and an extinction ratio of 3 × 10 ⁻⁵ is guaranteed even at a wavelength of 620 nm), and a slow scan high sensitivity CCD camera (manufactured by FLOVEL, model number HCB14) is attached to the image sensor 50.
50 is an observed image of a magnetic domain structure on the surface of a magneto-optical disk when using (50). The objective lens has a magnification of 20 times and NA of 0.2.
65 fluorescent objective lenses were used. As can be seen from the observation image of this result, it can be seen that a spatial resolution of about 0.7 μm is obtained in comparison with the structure of a general magneto-optical disk.

In order to obtain a higher resolution image,
Use a type having a higher luminance (currently, a light emitting diode of 2000 mcd or more is also known), and a light emitting diode having a smaller light emitting area (a point light source is more suitable for the objective lens pupil surface 43p). Focus small and try to achieve perfect normal light incidence on the sample if the sample is to detect, for example, the polar Kerr effect),
For example, it is conceivable to match the wavelength of the polarizing beam splitter to be used with the wavelength of the light emitting diode.

In the above embodiment, when the object is a light reflector, that is, mainly a solid, it is preferable that the linearly polarized light to be incident on the object be incident on the object at an angle perpendicular to or nearly perpendicular to the object. Generally, when linearly polarized light is incident on a solid surface at an oblique incident angle, the reflected light becomes elliptically polarized light, and when considered as energy, a detection system that detects reflected linearly polarized light slightly reduces energy. Of course,
This does not prevent linearly polarized light from being incident at an oblique incident angle. Conversely, when linearly polarized light is incident obliquely, the reflected light becomes elliptically polarized light, and the direction of the principal axis rotates from the direction of polarization of the incident linearly polarized light. And the ellipticity, which is the ratio of the major axis to the minor axis of the ellipse, together with the increased rotation angle, can be used to determine the optical constants n and κ of the material, and to determine the thickness of the thin film, That is, the present method can be used for an ellipsometer.

FIG. 20 shows another embodiment, and is a schematic configuration diagram of a polarization microscope for optically scanning a sample surface. In FIG. 20, a sample 71 is placed on a sample stage 70. The semiconductor laser 72 as a light source is, for example, manufactured by Matsushita Electric Industrial Co., Ltd.
A GaAlAs semiconductor laser having an oscillation wavelength of 790 nm, a maximum output of 50 mW, and a maximum modulation frequency of 1 GHe or more is used. The semiconductor laser 72 illuminates the sample 71 with a minute spot light. Light from the semiconductor laser 72 is collimated by the lens 73. The collimated light is deflected by an acousto-optic device 74 (for example, model number EFLD250R, manufactured by Matsushita Electronics Co., Ltd.) as a light deflection device. Deflection angle is 2.8 degrees to 5.8 degrees, deflection frequency is 15k
Hz. The deflected light passes through the lens 75
Is condensed on the aperture stop 76. The condensed light is linearly polarized by the polarizer 77. It is not necessary to use a polarizer 77 having an extremely high performance such as an extinction ratio of 10 ^-6 , unlike a conventional polarizer, and a polarizer such as a commonly used polaroid plate of about 10 ^-4 may be used. In this example, this is used. The linearly polarized light that has been linearly polarized by the polarizer 77 passes through the field stop 79 via the lens 78, is reflected by the mirror 80, and is condensed on the pupil plane of the objective lens 81. Furthermore, the objective lens 8
1 illuminates the sample 71 obliquely. The angle of the oblique illumination is determined by the NA of the objective lens 81 and the focusing position of the laser light on the pupil plane.

Assuming that the sample 71 is, for example, a thin film magnetic head, the plane of polarization of reflected light from the surface of the thin film magnetic head is rotated by the vertical Kerr effect. The linearly polarized light whose polarization plane has been Kerr-rotated transmits through the objective lens 81, and the rotation angle due to Kerr rotation is increased by 20 to 30 times by the first analyzer 82 arranged in a state of orthogonal Nicols with the polarizer 77. . That is, the azimuthal component of the linearly polarized light transmitted through the polarizer 77 is suppressed,
The component orthogonal to this component is transmitted as it is, and although the light intensity is reduced, the rotation angle is significantly increased. The second analyzer 83 analyzes the linearly polarized light whose rotation angle has been increased. The light transmitted through the analyzer 83 is weakened, but is detected as an image by the imaging lens 84, for example, by the CCD camera 85 with an image intensifier. This image is subjected to integration processing and background removal processing by an image processing device 86 (for example, model number DVS-3000, manufactured by Hamamatsu Photonics Co., Ltd.) and displayed on a monitor 87. This polarization microscope for magnetic domain observation is capable of suppressing coherent noise such as interference fringes and speckle noise by suppressing laser light by scanning laser light over an aperture stop using an acousto-optic device. Have. Further, by using a high-output semiconductor laser as a light source, an optical system more compact than a conventional magnetic domain observation microscope is realized.

For example, the thin-film magnetic head 71 as a sample is operated, and the operation is synchronized with the driving circuit of the semiconductor laser driving device 88 so that the strobe of the magnetic domain structure in the operating state of the magnetic head is obtained. Scoping time-resolved observation can be easily performed. Knowing the dynamic characteristics of the magnetic domain structure of the magnetic head while operating at a high speed can be expected to realize a magnetic device with improved recording / reproducing characteristics. FIG. 21 is a schematic plan view of a head main body divided by magnetic domains of the thin-film magnetic head. FIG. 21A shows the structure of the magnetic domain, FIG. 21B shows the rotation of the plane of polarization of linearly polarized light by the magneto-optical effect based on the direction of magnetization indicated by the arrow in FIG. 21A, and FIG. The rotated linearly polarized light is detected, and the image of the magnetic domain contrast is represented by the magnitude of the contrast. With the polarizing microscope according to the present invention, such a magnetic domain contrast image can be clearly observed and recorded in a time-resolved manner.

In the above-mentioned polarization microscopes using the polarization plane rotation angle increasing method, as an example of the inspection object, the explanation has been made mainly on the observation of the magnetic domain based on the Kerr effect of the magnetic material. Because of its extremely high sensitivity, there are many applications and applications besides magnetic domain observation.

The method according to the present invention can be used, for example, in an inspection process in the technical field of a liquid crystal display. That is, for example, a rubbing step is a key process in the assembly of a TFT liquid crystal panel. The rubbing process is performed on both a glass substrate (TFT substrate) on which a TFT and a transparent pixel electrode are formed, and a glass substrate (color filter substrate) on which a color filter and a transparent electrode are formed.
The liquid crystal sealed during this time is arranged uniformly and twisted.
This is to form a polyimide alignment film to obtain a nematic structure.Currently, this polyimide alignment film is obtained by rubbing a polyimide film formed on a substrate in a certain direction with a buff cloth attached on a metal roll. Thereby aligning the polyimide molecules in that direction. However, in this rubbing treatment, if the substrate is rubbed too much and damaged, poor alignment is caused and light leakage occurs. Further, there is a problem that a point defect occurs when the TFT or the alignment film is destroyed by frictional charging, and this inspection is very important in terms of the yield of the product. The surface of the rubbed substrate has a fine groove structure with a width of about 10 nm, and its defect inspection is limited to existing methods. That is,
Since it has a fine groove structure with a width of about 10 nm, light interference cannot be used, and at present, SEM (Scanning Electron M
icroscope: Scanning electron microscope) and AFM (Atomic Forc)
e Microscope: Atomic force microscope).

However, if the polarization plane rotation angle increasing method disclosed herein is used, a fine groove structure with a width of about 10 nm on the substrate can be easily measured by using structural birefringence.

In consumer-use equipment, two types of rewritable optical disks are currently used for magneto-optical recording, except for the phase change type and the two-phase polymer type. (In both cases, signals are recorded with the direction of magnetization of the perpendicular magnetization film opposite to each other, and signal detection detects Kerr rotation of linearly polarized light.) This technique can be used. Since the rotation angle of the plane of polarization of linearly polarized light in reproducing a magneto-optical disk is generally less than 1 degree and as small as about 0.3 ■ 0.6 degrees, the signal-to-noise ratio (S
Consideration must be given to the N ratio) or the carrier-to-noise ratio (CN ratio). The performance of a magneto-optical disk as a memory can be known from the C / N (S / N at the recording / reproducing frequency) during reproduction. In theory, the reflectance of the recording film is R, the laser power is P, Assuming that the Kerr rotation angle is θ, it is approximately expressed by C / N to √ (RP) · θ. Therefore, C
In order to increase / N, the decrease in noise and the increase in the Kerr rotation angle θ have a more direct effect than the parameters in √.
In the magneto-optical disk, a method of increasing the rotation angle of the polarization plane by the magnetic Kerr effect has been proposed, and the rotation angle is increased by about three times by coating a sample surface with an SiO ₂ film or the like and performing multiple reflection. Is known to
(T. Niihara, N. Ohta, K. Kaneko, Y. Sugita and
S. Horigoe, "Kerrenhancement to SiO and AlN f
ilms spatterd on plastic substrate ", IEEE Tra
ns. Mag., MGA-22, 1215 (1986)). However, the method according to the present invention does not require any pretreatment of the sample,
A major feature of the detection system is that the rotation of the polarization plane is increased by 10 to 30 times. Therefore, speaking of the possibility of application only in the field of the magneto-optical disk, not only can it be applied to the current pickup device, but also there is a possibility that the recording density of the magneto-optical disk itself can be significantly increased.

[0041]

As described above, according to the polarization measuring device of the present invention, the rotation of the plane of polarization of linearly polarized light can be easily detected, and the rotation of the plane of polarization can be performed without using a high-performance polarizing element. It can be detected with high accuracy. According to the polarizing microscope of the present invention, the rotation of the plane of polarization of linearly polarized light can be easily detected, and the rotation of the plane of polarization can be detected with high accuracy without using a high-performance polarizing element. It is possible to visualize the region of the subject as a clear contrast image.

When a semiconductor light source and / or a polarizing beam splitter is used, the optical system is made compact and the whole device is extremely miniaturized, and can be used for field use. Can be significantly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of linearly polarized light linearly polarized by a polarizer and linearly polarized light whose polarization plane is rotated.

FIG. 2 is an explanatory diagram of the basic principle of the present invention showing only half of point symmetry.

FIG. 3 is an explanatory diagram of a magnetic Kerr effect.

FIG. 4 is an explanatory diagram of the polar Kerr effect when linearly polarized light is incident on a magnetic material perpendicularly magnetized in the opposite direction.

FIG. 5 is an explanatory diagram for obtaining magnetic domain contrast by detecting linearly polarized light having an increased Kerr rotation angle.

FIG. 6 is a graph showing a relationship between a car rotation angle and an increased rotation angle.

FIG. 7 is a graph showing an increase rate of a rotation angle with respect to a Kerr rotation angle.

FIG. 8 shows the visibility (Vi) with respect to a change in the car rotation angle.
7 is a graph showing the magnitude of contrast.

FIG. 9 is a graph showing the magnitude of contrast with respect to a change in the Kerr rotation angle with the horizontal axis taken to 10.0 microradians.

FIG. 10 is an optical path diagram of an optical system of the polarization measuring device according to one embodiment of the present invention.

FIG. 11 is an optical path diagram of an optical system of a polarization measuring device according to another embodiment of the present invention.

FIG. 12 is an optical path diagram of an optical system of a polarization measuring device according to still another embodiment of the present invention.

FIG. 13 is a partial sectional view of a polarization microscope according to one embodiment of the present invention.

14 is an optical path diagram of the optical system of the polarization microscope shown in FIG.

FIG. 15 is a schematic configuration diagram of a polarization microscope system according to one embodiment.

FIG. 16 is a drawing substitute photograph showing an observed image of a thin film on a magneto-optical disk, which is visually output using a polarizing microscope system.

FIG. 17 is a drawing substitute photograph showing an observed image of a thin film on a magneto-optical disk which is visually output using a polarizing microscope system when different objective lenses are used.

FIG. 18 is an optical path diagram of an optical system of a polarization microscope according to another embodiment of the present invention.

FIG. 19 is a drawing substitute photograph showing an observed image of a thin film on a magneto-optical disk that is visually output using the embodiment shown in FIG. 18;

FIG. 20 is a schematic configuration diagram of still another embodiment of the present invention.

FIG. 21 is a diagram for explaining magnetization visualization in which the magnetic domain and magnetization direction of a thin-film magnetic head, the rotation of linearly polarized light due to the Kerr effect, and the corresponding magnetic domain are represented by the magnitude of contrast.

[Explanation of symbols]

 Reference Signs List 1 Linear polarized light emitted from linear polarizer 2 Direction of azimuth angle of linear polarizer 3 Linear polarized light whose polarization plane is rotated 5 Linear polarized light whose rotation angle is increased 93,94 Linear polarized light rotated by polar Kerr effect 95 Analyzer 11 Subject 12 Light source unit 14 Polarizing beam splitter 15 Objective lens 16 Analyzer 17 Photoelectric converter 20, 40 Sample table 21, 41 Subject 22, 42 Light source unit 23, 43 Objective lens 24, 44 Polarizing beam splitter 25 , 45 analyzer 29, 50 CCD camera 221 semiconductor laser 421 high-brightness light-emitting diode 72 semiconductor laser 74 acoustic deflection element 77 linear polarizer 82 first analyzer 83 second analyzer 88 semiconductor laser drive controller 71 as subject Thin film magnetic head.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01J 4/04 G01N 21/21 G02B 21/00 G02B 27/28

Claims (3)

(57) [Claims] 1. An objective lens which is provided apart from a subject whose rotation of a polarization plane due to a magneto-optical effect is 1 ° or less and forms an enlarged real image of the subject, and a light source which supplies light to the subject And a linear polarizer provided in an optical path between the light source and the subject, and a linear polarization component equal to the azimuthal angle of the linear polarizer among the linearly polarized light from the subject, and It is characterized by comprising an analyzer for transmitting a component orthogonal to the polarization component, an analyzer for analyzing linearly polarized light from the analyzer, and a visualizer for visualizing light from the analyzer. Polarized light microscope. 2. The light source according to claim 1, wherein said light source is a semiconductor light source.
Polarized light microscope as described. 3. The polarization microscope according to claim 1, wherein said subject is a light reflector, and said linear polarizer and said analyzing means are a single polarizing beam splitter.