JPH08110265A - Retardation measuring device - Google Patents

Abstract

PURPOSE: To provide the retardation measuring device, which can set the accurate measuring position and can measure the quantity of retardation highly accurately. CONSTITUTION: Beneath the lower side of a stage 214, on which a sample 216 is mounted, a light source 202 for emitting the measuring light, a condenser lens 204, an interference filter 206, a polarizer 208, which transmits only the specified polarized component, a 1/4 wave plate 210 and a contact lens 212 are arranged sequentially from the lower side. Furthermore, on the upper side of the stage 14, an objective lens 218, an analyzer 220, which transmits only the specified polarized component, an image forming lens 225, a beam splitter 222 and a photometric device 224, which measures the intensity of the incident light are arranged. Furthermore, an eyepiece lens 226, which receives the reflected light from the beam splitter 222, is provided. The polarizer 208, the 1/4 wave plate 210 and the analyzer 220 are rotatably supported independently or in synchronization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the retardation amount of a sample having birefringence.

[0002]

2. Description of the Related Art As an apparatus for measuring the retardation amount of a sample having birefringence, there is, for example, a polarization microscope using Senarmont phase compensating means. This device
As shown in FIG. 8, a lamp light source 109 and a bandpass filter 10 that selectively transmits only light in a specific wavelength range.
0, a polarizer 101, and a condenser lens 1 that collects the light that has passed through the polarizer 101 onto a sample 104.
08 and the objective lens 1 for receiving the light transmitted through the sample 104
07, a quarter-wave plate 103 whose optical axis is aligned with the polarization direction of the polarizer 101, an analyzer 102 rotatable about the optical axis, and a photometric device 105 for examining the intensity of light passing through the analyzer 102. It has and. These optical elements are connected from the lamp light source 109 to the photometric device 105.
Are arranged linearly in order along the optical path leading to. Further, the apparatus has a stage 106 that rotatably holds the sample 104 between the polarizer 101 and the quarter-wave plate 103. The selected wavelength of the bandpass filter 100 matches the specified wavelength of the quarter wave plate 103.

The measurement is performed in the following procedure. First, the analyzer 102 is rotated with no sample on the stage so that the output of the photometric device 105 is adjusted to the minimum direction.
It is the origin of the analyzer 102. Next, the sample 104 is placed on the stage 106, and the stage 106 is rotated this time so that the output of the photometric device 105 is minimized again. The rotation angle of the stage 106 is further rotated by 45 degrees from here to set the rotation origin, and the measurement preparation is completed. In this state, the output of the photometric device 105 is generally not the minimum because of the birefringence of the sample.

The retardation is measured by the analyzer 1
02 is rotated so that the output of the photometric device 105 is minimized. Rotation angle φ from the origin of analyzer 102 at this time
Read. When the wavelength of light is λ, the retardation amount R of the sample 104 is calculated by the following equation.

R = λ (2φ + 2nπ) / 2π where n is the phase angle order and is an integer. If n is known, more accurate retardation amount is required.

[0006]

In the above apparatus, the sample 104 is rotated so that the output of the photometric device 105 is minimized, and then the sample 104 is further rotated by 45 degrees.
Therefore, if the center of rotation of the stage and the optical axis of the optical system do not coincide, the position on the sample through which the measurement light is transmitted is different between the preparation for measurement and the measurement. In order to solve this problem, it has been proposed to provide an xy stage on the rotary stage and correct the positional displacement due to rotation using the xy stage, but the correction work is troublesome and the device is expensive. It becomes a thing.

Further, in order to measure the retardation amount in an arbitrary region of a large sample, a very large rotary stage capable of rotating the sample while being mounted is required. However, since the size of the rotary stage that can be practically used is limited due to various circumstances, there is a drawback that a large sample such as an LCD substrate cannot be measured. The purpose of the present invention is to
An object of the present invention is to provide a device that can measure the retardation amount with accurate measurement position and high precision.

[0008]

A retardation amount measuring device of the present invention comprises a polarizer placed on the light source side or the photometric side centering on a sample placed on a stage, a compensator such as Senarmont on the photometric side or the light source side, and an analyzer. In the retardation measuring device for a birefringent object, wherein the polarizer, the analyzer, and the compensator are independently rotatable about the optical axis or synchronized with each other, the rotation angle can be read so that they can be read. Moreover, the compensating plate can be freely inserted into and removed from the optical axis.

In a preferred embodiment of the present invention, an objective lens disposed on the photometric side of the sample, which is disposed immediately after the sample, and a beam splitter which is disposed behind the objective lens and can be inserted and removed on the optical axis. And an imaging lens divided by the beam splitter in a direction perpendicular to the observation side, so that a fine area on the surface of the sample can be observed.

In a preferred embodiment of the present invention, the light source is a laser, and after passing the laser light source through the polarizer or the compensator and the analyzer,
It has a means for collecting light on the specimen.

[0011]

Before the sample and the compensator are placed in the optical path, either the polarizer or the analyzer is rotated to make the polarization directions orthogonal to each other. Next, the compensator is inserted into the optical path and rotated so that the optical axis of the compensator coincides with the polarization direction of the polarizer. Next, the sample is placed, and the polarizer, compensator, and analyzer are synchronously rotated so that the optical axis of the sample also coincides with the direction. From here, the polarizer, compensator, and analyzer are synchronously rotated by 45 degrees. This is the origin angle of the analyzer. Finally, rotate the analyzer until the output of the photometer is minimized. Assuming that the angle from the origin is φ and the wavelength of light is λ, the retardation amount R of the sample is calculated by the following equation. R = λ (2φ + 2nπ)
/ 2π where n is the phase angle order.

[0012]

【Example】

[First Embodiment] A first embodiment of the retardation measuring apparatus according to the present invention will be described with reference to FIGS. 1 and 2.
Like the conventional example, the present example is also a Senarmont type device using a quarter-wave plate as a compensating plate.

In FIG. 1, a light source 202 for emitting measurement light, a condenser lens 204, an interference filter 206, and a specific polarization component are transmitted below the stage 214 on which the sample 216 is placed. A polarizer 208, a quarter-wave plate 210, and a collector lens 212 are arranged.

On the upper side of the stage 214, in order from the bottom, an objective lens 218, an analyzer 220 that transmits only a specific polarization component, an imaging lens 225, and a beam splitter 222 that separates incident light into transmitted light and reflected light. A photometric device 224 for measuring the intensity of incident light is arranged.
Further, an eyepiece lens 226 for receiving the reflected light of the beam splitter 222 is provided, and the objective lens 218,
Together with the imaging lens 225, an observation optical system is configured. The imaging lens 225 may be arranged anywhere between the objective lens 218 and the eyepiece lens 226, and depending on the type of the objective lens 218, the imaging lens 225 may not be necessary. The polarizer 208 may be arranged anywhere between the objective lens 218 and the photometric device 224.

As shown in FIG. 2, the polarizers 208, 1
The quarter-wave plate 210 and the analyzer 220 have rotating members 230a, 230b, and 230c on the periphery, respectively.
Timing belts 232a, 232b, 232, respectively
c is hung. Timing belt 232a, 23
2b and 232c are pulse motors 236a and 236a, respectively.
Pulley 234 rotated by 236b, 236c
a, 234b, 234c. As a result, the polarizer 208, the quarter-wave plate 210, and the analyzer 220 are respectively connected to the pulse motors 236a and 236.
It is designed to be rotated by b and 236c.

Pulse motors 236a, 236b, 23
The rotation of 6c is controlled by the pulse motor driver 23.
8a, 238b, 238c and the pulse motor controller 240 by the computer 244,
It is possible to control each independently or in synchronization. The measurement data of the light amount by the photometric device 224 is loaded into the computer 244 through the photometric device controller 242.

The quarter wave plate 210 and the beam splitter 222 can be removed from the optical path by a control mechanism (not shown). The measurement of retardation is performed as follows. First, in a state where the sample 216 and the quarter-wave plate 210 are not on the optical path, either the polarizer 208 or the analyzer 220 is rotated to make the polarization directions orthogonal to each other. Next, the quarter-wave plate 210 is placed in the optical path and rotated so that the optical axis is aligned with the polarization direction of the polarizer 208. Up to this point, it is desirable that the beam splitter 222 is not in the optical path for the reason described later.

Here, the beam splitter 222 is returned to the optical path, the sample 216 is placed on the stage 214, and the location where the retardation is to be measured is adjusted to the photometric range within the observation visual field. Here, the beam splitter 222 is removed again, and the polarizer 208, the quarter-wave plate 210, and the analyzer 220 are synchronously rotated so that the optical axis of the quarter-wave plate 210 and the optical axis of the sample 216 coincide with each other. It goes without saying that all the rotation control up to this point is performed so that the output of the photometric device is minimized.

After that, the polarizer 208, the quarter-wave plate 210, and the analyzer 220 are synchronously rotated by 45 degrees, and the preparation for measurement is completed. Finally, photometry is performed while rotating the polarizer 208, and the rotation angle φ of the polarizer 208 when the photometric data becomes the minimum is searched for. The rotation angle φ is substituted into the above formula R = λ (2φ + 2nπ) / 2π to calculate the retardation R.

According to this embodiment, the polarizers 208, 1
Since the / 4 wave plate 210 and the analyzer 220 can be rotated independently or in synchronization, it is not necessary to rotate the sample, and therefore the alignment accompanying the rotation is also unnecessary,
Reliable retardation measurement can be performed. Therefore, it is also effective for measuring the retardation of a large sample that is difficult to rotate at any place. Further, since the magnified observation is performed, the retardation of a fine area of the sample can be accurately measured. Further, since the beam splitter necessary for observing the sample can be removed from the optical path, there is an advantage that more accurate measurement can be performed in a state where the adverse effect of the thin film forming the beam splitter on polarization is completely removed.

As the deflecting means, a simple mirror may be used instead of the beam splitter. In this case, the observation with the observation optical system and the measurement of the light amount by the photometric device cannot be performed at the same time, but the mirror may be removed after first confirming the measurement position with the observation optical system. By using a mirror, the cost can be reduced compared to a beam splitter.

In the present embodiment, unlike the conventional example, the arrangement order of the polarizer, the sample, the quarter-wave plate, and the analyzer is reversed with respect to the light source and the photometric device. However, this may be either, and it suffices that the polarizing plate to be rotated to finally measure the amount of retardation be located just outside the quarter-wave plate. [Second Embodiment] A second embodiment of the retardation measuring device according to the present invention will be described with reference to FIG. In the drawing, the same members as those in the first embodiment are designated by the same reference numerals.

The arrangement of the optical members is the same as in the conventional example. That is, the light source 250, the polarizer 208, the sample 216,
Quarter wave plate 210, analyzer 220, photometric device 26
They are arranged in the order of 4.

A polarizer 208, a quarter wave plate 210,
Similar to the first embodiment, the analyzer 220 can rotate independently or in synchronization. Further, the beam splitter 254 and the quarter-wave plate 210 which form the observation system can be taken out from the optical path by a mechanism (not shown) as in the first embodiment.

In this embodiment, the light source 250 is a laser having high spectral purity. The laser light emitted from the light source 250 is converted by the beam expander 252 into a parallel light beam having a diameter that sufficiently fills the pupil of the first objective lens 256,
The light is focused on the surface of the sample 216 by the objective lens 256. The light transmitted through the sample 216 is efficiently received by the second objective lens 258 placed below the sample 216, and
After passing through the four-wave plate 210 and the analyzer 220, an image is formed on the pinhole plate 262 by the imaging lens 260. A photometric device 264 is placed below the pinhole plate 262.

In the first embodiment, the light source for measurement and the light source for observing the sample can be shared, but in this embodiment, the laser light is focused on an extremely fine area of the sample surface.
It does not become observation light. Therefore, the observation optical system 266 is added. The illumination light from the lamp house 268 passes through the first objective lens 256 and constitutes an epi-illumination Koehler illumination system for the sample 256. The reflected light from the sample 216 is transferred to the CCD by the objective lens 256 and the imaging lens 270.
An image is formed on the camera 272, and the image is formed on the computer 2
It is displayed on the monitor 276 by 74, and the sample surface can be observed.

In this embodiment, since the laser light is used as the light source 250, the wavelength width is extremely narrow, and the quarter wavelength plate 2 is used.
It becomes the best light source for 10 specified wavelengths, and more accurate retardation measurement is possible. Further, since the measurement area on the sample can be narrowed to the utmost limit by narrowing down the laser light by the first objective lens 256 and the pinhole, it is possible to perform measurement with good position resolution.

A modified example of this embodiment is shown in FIG. In the device of FIG. 3, the laser 250 was assumed to be randomly polarized. That is, it is necessary to ensure that the transmitted light amount is constant regardless of the polarization direction of the polarizer 208.

However, it is generally said that the randomly polarized laser is inferior in the temporal stability of the light quantity to the linearly polarized laser. Therefore, in this modification, a linearly polarized laser 278 is used as the light source.

The light emitted from the laser 278 is expanded to a predetermined beam diameter by the beam expander 252,
It passes through a polarizer 280, which is placed with its polarization direction aligned with the polarization direction of the laser, and is circularly polarized by a quarter-wave plate 282. If the laser light is perfectly circularly polarized, the measurement light of constant intensity can always be obtained regardless of the rotation direction of the measuring polarizer 208.

The polarizer 280 is necessary because the linearity (ellipticity) of the linearly polarized laser 278 may not always be sufficient. As described above, in this modification, the measurement light intensity during measurement is further stabilized, and the reliability of measurement is improved. [Other Embodiments] In all of the above-described embodiments, the case of the Senarmont type using the quarter-wave plate as the compensator has been described. The present invention is not limited to this, and other compensation plates may be used. Berek on the compensator
The configuration of an example using a compensator is schematically shown in FIG. Further, FIG. 6 schematically shows the configuration of an example in which a Babinet Soleil compensator is used as the compensator. In either configuration, the polarizer 302 and the analyzer 306 are independently rotatable about the optical axis 300.

The Berek compensator 310 is shown in FIG.
As shown in, a parallel-plane plate of calcite cut perpendicularly to the optical axis is made rotatable about an axis of rotation included in the plane. In the figure, the rotation axis is set to the axis 312 orthogonal to the optical axis 300. The Berek compensator 310 is rotatably provided between the polarizer 302 and the analyzer 306 as the axis of the optical axis 300.

The measurement is performed according to the following procedure. (A) Polarizer 302 and analyzer 30 with sample 304 and Berek compensator 310 removed from the optical path
One of 6 is rotated so that the polarization directions of both are orthogonal.
(B) Insert the Berek compensator 310 between the polarizer 302 and the analyzer 306. (C) The Berek compensator 310 is rotated about the optical axis 300 so that the transmitted light becomes the darkest position. (D) A sample 304 is inserted between the Berek compensator 310 and the polarizer 302. (E) The polarizer 302, the Berek compensator 310, and the analyzer 306 are synchronously rotated while maintaining the positional relationship so that the transmitted light becomes the darkest position. (F) Only the polarizer 302 and the analyzer 306 are further rotated by 45 degrees. (G) The Berek compensator, that is, the crystal plate 310 is attached to the rotary shaft 31.
Rotate around 2 and find the angle where the transmitted light is the darkest.
(H) In this state, the specimen 304 and the compensator 31
Since the retardations of 0 cancel each other out, the retardation of the sample 304 can be found by obtaining the retardation of the compensator from the rotation angle of the crystal plate 310.

On the other hand, Babinerireille compensator 3
As shown in FIG. 6, reference numeral 00 designates two wedge-shaped crystal plates 324 and 32 which are superposed with their optical axes parallel to each other.
6 and a crystal plate 322 stacked on these crystal plates 324 and 326 with their optical axes orthogonal to each other. Crystal plate 3
26 is slidable in the direction of arrow 328,
This makes the retardation value of the three crystal plates variable. This Babi Neri Reuil Compensator 3
20 is between the polarizer 302 and the analyzer 306,
The three crystal plates 322, 324, 326 are rotatably provided around the optical axis 300 without changing the positional relationship.

The measurement procedure is very similar to that of the Berek compensator described above, and from (a) to (f) is exactly the same except that the Berek compensator replaces the Babinet Soleil compensator. (G ')
The crystal plate 326 is moved in the direction of the arrow 328, and the position where the transmitted light becomes darkest is searched for. (H ′) In this state, the retardations of the sample 304 and the compensator 320 cancel each other out, so the retardation of the sample 304 can be found by obtaining the retardation of the compensator 320 from the movement amount of the crystal plate 326.

As the compensating plate, in addition to the above-mentioned Berek compensator and Babinet Soleil compensator,
You can also use the Aering House Compensator or the Reversed Babyne Compensator. The usage of the Aering House Compensator is the same as that of the Berek Compensator, and the usage of the Reversed Babyne Compensator is the same as that of the Babinet Soleil Compensator.

Further, although all of the above-described embodiments were apparatus for making a microscope, the present invention is not necessarily applied only to a microscope, and in an extreme case, as shown in FIG. It also includes measurements.

[0038]

According to the present invention, in the retardation measurement of a sample having birefringence, it is not necessary to rotate the sample during the measurement, so that the inaccuracy due to the misalignment of the rotation axis can be eliminated and a large size can be eliminated. It is also possible to measure the sample. Also,
The accuracy of measurement is improved by pulling out an optical member that adversely affects the polarization component in the observation optical path from the optical path during measurement. Furthermore, using a laser as the light source further improves the measurement accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing an arrangement of optical elements in a first embodiment of a retardation measuring device according to the present invention.

FIG. 2 is a diagram schematically showing a drive mechanism and other configurations connected to the optical element of FIG.

FIG. 3 is a diagram showing a configuration of a second embodiment of the retardation measuring device according to the present invention.

FIG. 4 is a diagram showing a configuration of a modified example of the measurement light irradiation system of FIG.

FIG. 5 is a diagram schematically showing a configuration of a retardation measuring device of the present invention using a Berek compensator for a compensating plate.

FIG. 6 is a diagram schematically showing a configuration of a retardation measuring device of the present invention using a Babinet Soleil compensator for a compensating plate.

FIG. 7 is a diagram of a retardation measuring device consisting only of basic components naturally included in the present invention.

FIG. 8 is a diagram showing a configuration of a conventional retardation measuring device.

[Explanation of symbols]

208 ... Polarizer, 210 ... Quarter wave plate, 220 ...
analyzer

Claims (3)

[Claims] 1. A retardation measuring device for a birefringent object, comprising a polarizer placed on the light source side or the photometric side around a sample placed on a stage, and a compensator and an analyzer on the photometric side or the light source side. The polarizer, the analyzer, and the compensator can rotate independently of each other about the optical axis or in synchronization with each other, and the compensator can be inserted into and removed from the optical axis. Retardation measuring device. 2. The objective lens according to claim 1, wherein the objective lens is disposed on the photometric side of the sample, the deflecting means is insertable / removable with respect to the optical path disposed behind the objective lens, and is deflected by the deflecting means. And an observation optical system arranged on the optical axis, which makes it possible to observe a fine region on the surface of the sample. 3. The light source according to claim 1, wherein the light source is a laser, and means for condensing the laser light source on the sample after passing through the polarizer or the compensator and the analyzer. Retardation measuring device.