JP2006242617A - Device and method for measuring axial azimuth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for accurately determining an axial azimuth of a sample such as a light polarizer and a phase piece. <P>SOLUTION: The axial azimuth measuring device 10 determines the permeation axial azimuth of a linear light polarizing element as a sample. The axial azimuth measuring device 10 comprises a light radiation means 12, a reference light polarizer 14 for converting the light from the light radiation means 12 into linearly polarized light and radiating it to the sample, a sample rotating means 18 for rotating the sample about the optical axis, a photo-detection means 20 for detecting light having permeated the sample, and an axial azimuth calculating means 26 for calculating the permeation axis azimuth of the sample based on the azimuthal angle of the sample of which permeation light intensity is minimum. The axial azimuth calculating means 26 calculates the permeation axis azimuth of the sample based on the front-side azimuthal angle θ<SB>+</SB>of the sample of which permeation light intensity is minimum when one surface of the sample is faced to one surface of the reference light polarizer 14 and the back-side azimuthal angle θ<SB>-</SB>at which permeation light intensity is minimum when the sample is turned over and the surface facing the reference light polarizer 14 is set as the other surface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus and method for measuring the axial orientation of a polarizing element such as a polarizer and a phase shifter.

A polarizing film (polarizer) and a retardation film (phase shifter) are functional materials that extract a specific polarization state or change the polarization state, and are used in liquid crystal displays and the like. These films are translucent and birefringent, and are characterized by light transmittance differences, refractive index differences, refractive index axial orientations, and the like. For example, a dichroic polarizing film extracts linearly polarized light in a predetermined direction using a difference in transmittance with respect to the polarization direction. Retardation films are characterized by how many times the wavelength of the light used is the product of the difference in refractive index and the thickness of the film. Has been.
The transmission axis direction of the polarizing film is determined by rotating the polarizing film with respect to the reference polarizer, and the direction in which the transmission axis of the reference polarizer and the transmission axis of the polarizing film are orthogonal, that is, the intensity of transmitted light is This is done by measuring the minimum orientation (extinction position). Then, from the transmitted light intensity at the extinction position and the transmitted light intensity when the 90 ° polarizing film is rotated from the extinction position (the direction in which the transmission axis of the polarizer and the transmission axis of the polarizing film are parallel), the polarizing film The degree of polarization or extinction rate of the light beam may be obtained (see Patent Document 1 for other examples).
Similarly, in the case of a retardation film, the axial direction (neutral axis) of intrinsic linearly polarized light is determined by placing two reference polarizers (polarizing plates) in a crossed Nicol state and placing a retardation film between them. Then, the retardation film is rotated to measure the direction in which the transmitted light intensity is minimized. When the neutral axis of the retardation film coincides with the transmission axis direction of the two polarizers, the transmitted light intensity is minimized. In other words, the transmission axis direction of each polarizer is two directions orthogonal to each other, but the neutral axis orientation of the retardation film is also two directions orthogonal to each other, and if these coincide with the polarization direction of each polarizer, Good.
JP-A-4-36631

However, for example, in the measurement for a polarizing film, the absolute direction of the transmission axis direction of the polarizing film is not accurately determined. In other words, it can be seen that the transmission axis direction of the polarizing film is orthogonal to the transmission axis direction of the reference polarizer, but there is no guarantee that the transmission axis direction of the reference polarizer itself is correctly determined. is there. In other words, in order to measure the absolute orientation, there is no doubt that a standard polarizer with a fixed axial orientation is necessary, but it is difficult in principle to prepare this, and as a result There was a definite lack of certainty in the extinction axis orientation that was found. Similarly, even in the case of a retardation film, the fact that two reference polarizers are in a crossed Nicol position means that the relative positional relationship between the two polarizers is orthogonal to each other. It is merely the direction, and the polarization direction of each polarizer is not absolutely determined, and another means is required to determine this. That is, in order to accurately determine the axial orientation of the polarizing film or retardation film as a sample, it is necessary to first obtain the absolute orientation of the transmission axis direction of the reference polarizer itself.
The present invention has been made in view of the above problems, and an object thereof is to provide a method and apparatus for accurately determining the axial orientation of a sample such as a polarizer or a phase shifter.

In order to achieve the above object, an axial azimuth measuring apparatus according to the present invention is an axial azimuth measuring apparatus that determines a transmission axis azimuth of a sample using a linearly polarizing element as a sample. A reference polarizer that irradiates a sample with light as linearly polarized light, a sample rotating means that rotates a sample placed opposite to the reference polarizer around the optical axis and changes the orientation of the sample, and the sample is transmitted. A light detecting means for detecting the transmitted light, and an axial azimuth calculating means for calculating the transmission axis direction of the sample based on the azimuth angle of the sample at which the transmitted light intensity is minimized when the sample is rotated by the sample rotating means. . Here, the axial azimuth calculating means has an azimuth angle θ ₊ that minimizes transmitted light intensity when one surface of the sample is opposed to the reference polarizer, and turns the sample over to serve as a reference polarizer of the sample. The transmission axis azimuth of the sample is calculated based on the azimuth angle θ ₋ that minimizes the transmitted light intensity when the opposite surface is the other surface.

In the axial azimuth measuring apparatus, the calculation means obtains the extinction axis azimuth of the reference polarizer as an intermediate position θ ₀ = (θ ₊ + θ ₋ ) / 2 between the azimuth angle θ ₊ and the azimuth angle θ ₋ It is preferable to determine the transmission axis direction of the sample based on the angle θ ₀ .
In the axial azimuth measuring apparatus described above, it is preferable to include a processing unit that rotates the sample by the sample rotating unit and obtains the direction of the sample that minimizes the transmitted light intensity. The processing means rotates the sample by the sample rotating means to determine a temporary orientation that determines the provisional orientation at which the transmitted light intensity is substantially minimized, and transmits the transmitted light intensity at a plurality of angular positions near the temporary orientation. A temporary azimuth vicinity measuring unit that measures and stores the measured transmitted light intensity in association with the angular position at that time, and fitting the stored transmitted light intensity with a quadratic function of the angular position, the vertex position of the quadratic function And a calculating unit for calculating. Then, the direction in which the transmitted light intensity is truly minimized is obtained from the vertex position calculated by the calculation unit.
In the axial azimuth measuring apparatus, the reference polarizer is a light detecting means so that a solid angle when the light receiving part of the light detecting means is viewed from the position of the reference polarizer is 1 × 10 ⁻² πsr or less. It is preferable that they are arranged away from each other.

Further, in the axial orientation measuring method of the present invention, a reference polarizer and a linearly polarizing element as a sample are opposed to each other, the orientation of the sample with respect to the reference polarizer is changed, and the reference polarizer and the sample are An axial orientation measurement method for determining a transmission axis orientation of a sample by measuring an orientation in which the intensity of transmitted light is minimum, wherein one surface of the sample is opposed to a reference polarizer, and the transmitted light intensity is A front-side measurement step for measuring the front-side azimuth angle θ ₊ that minimizes, and the back-side azimuth angle θ that minimizes the transmitted light intensity when the sample is turned over and the surface facing the reference polarizer of the sample is the other surface. _- and back measuring step of measuring, the front azimuth theta ₊ and the back azimuth theta _- characterized in that it comprises a and a calculation step of calculating the transmission axis azimuth of the sample on the basis of the.

An axial direction measuring apparatus of the present invention is an axial direction measuring apparatus that determines a neutral axis direction of a sample using a linear phase shift element as a sample, and the light irradiation unit and the light from the light irradiation unit are linearly converted. A first reference polarizer that is polarized and irradiates the sample; a second reference polarizer that is placed in a crossed Nicol state with respect to the first reference polarizer and that transmits transmitted light from the sample; and the first and second A sample rotating means capable of rotating a sample placed between the reference polarizers around the optical axis and changing the orientation of the sample; and a light detecting means for detecting light transmitted through the second reference polarizer; Axis azimuth calculating means for calculating the neutral axis azimuth of the sample based on the azimuth angle at which the transmitted light intensity is minimized when the sample is rotated by the sample rotating means. Then, the axial azimuth calculating means turns the sample over to the first azimuth angle θ _{+ at} which the transmitted light intensity is minimized when one surface of the sample is opposed to the first reference polarizer. The neutral axis azimuth of the sample is calculated based on the back side azimuth angle θ ₋ that minimizes the transmitted light intensity when the surface facing the reference polarizer is the other surface.

In the above-described axial azimuth measuring apparatus, the axial azimuth calculation means sets the extinction axis azimuth of the reference polarizer to an intermediate position θ ₀ = (θ ₊ + θ ₋ ) / 2 between the front side azimuth angle θ ₊ and the back side azimuth angle θ _−. It is preferable to obtain the neutral axis orientation of the sample based on the orientation θ ₀ .
In the axial azimuth measuring apparatus described above, it is preferable to include a processing unit that rotates the sample by the sample rotating unit and obtains the direction of the sample that minimizes the transmitted light intensity. Here, the processing means rotates the sample by the sample rotating means to determine a temporary orientation in which the transmitted light intensity is substantially minimum, and the transmitted light intensity at a plurality of angular positions near the temporary orientation. And measuring the transmitted light intensity in association with the angular position at that time, and storing the temporary azimuth vicinity measuring unit, and fitting the transmitted light intensity at a plurality of angular positions with a quadratic function of the angular position, A calculation unit that calculates the vertex position of the quadratic function, and obtains an orientation in which the transmitted light intensity is truly minimum from the vertex position calculated by the calculation unit.

In the axial azimuth measuring apparatus, the first reference polarizer is set so that a solid angle when the light receiving portion of the light detection means is viewed from the position of the first reference polarizer is 1 × 10 ⁻² πsr or less. Is preferably arranged apart from the light detection means.
In the axial direction measuring apparatus of the present invention, a linear phase shifter as a sample is installed between the first and second reference polarizers installed in crossed Nicols, and the sample is rotated about the optical axis. By changing the direction of the sample with respect to the first and second reference polarizers, the direction in which the intensity of light transmitted through the first reference polarizer, the sample, and the second reference polarizer is minimized is measured. Thus, the axial direction measuring method for determining the neutral axis direction of the sample, wherein one surface of the sample is opposed to the first reference polarizer, and the front side azimuth angle θ ₊ at which the transmitted light intensity is minimized is measured. A front side measuring step, and a back side measuring step for measuring the back side azimuth angle θ _{− at} which the transmitted light intensity is minimized when the sample is turned over and the surface facing the first reference polarizer of the sample is the other surface, the front azimuth theta ₊ and back azimuth theta _- and neutral axis of the sample on the basis of Characterized in that it comprises a calculation step of calculating a position, a.

In the above-described apparatus and method, it is not always necessary to use the same sample when measuring the axial orientation of the reference polarizer and measuring the axial orientation of the sample. In other words, when measuring the axial orientation of the reference polarizer, the axial orientation of the reference polarizer is determined in advance using a standard sample prepared for measuring the axial orientation of the reference polarizer. The axial orientation of the sample to be measured may be measured based on the axial orientation of the reference polarizer.
In addition, the light receiving portion of the light detection means refers to an incident opening of the integration sphere when the light detection means includes an integration sphere and a detector. Moreover, when comprised only with a detector, it points out the light-receiving surface of detector itself.

  According to the apparatus and method of the present invention, for the sample such as the linear polarization element and the linear phase shift element, the axial direction of the sample is determined based on the extinction direction obtained from both the front and back of the sample. With logical rigor, the axis orientation can be determined accurately.

Preferred embodiments of the present invention will be described below with reference to the drawings. First, the case where the axial direction of a polarizing film (linearly polarizing element) is measured as a sample will be described. FIG. 1 is a schematic configuration diagram of an axial orientation measuring apparatus according to an embodiment of the present invention. The axial azimuth measuring apparatus 10 has a light irradiating means 12 composed of a light source 28 and a spectroscope 30, a reference polarizer 14, a sample holder 16 holding a sample, and a sample holder 16 placed around the optical axis. A rotatable sample rotating means 18, a light detecting means 20 constituted by an integrating sphere 32 and a detector 34, and a computer 22 for controlling each means, processing data, and the like.
The light from the light irradiation means 12 passes through the reference polarizer 14 to be linearly polarized light, and is irradiated onto the sample held by the sample holder 16. The transmitted light from the sample is detected by the light detection means 20 and sent to the computer 22. Here, it is desirable that the light detection means 20 includes the integrating sphere 32 in order to remove the influence of the position unevenness on the light receiving surface of the detector 34 and the influence of polarization characteristics, but this is not essential.

The processing means 24 in the computer 22 controls the sample rotating means 18 to change the orientation of the sample with respect to the polarization direction of the reference polarizer 14 and obtain the angle at which the transmitted light intensity from the sample is minimized.
The axial direction calculation means 26 in the computer 22 calculates the transmission axis direction of the sample based on the azimuth angle of the sample that minimizes the transmitted light intensity. The most characteristic part in this embodiment is the part of the axial direction calculating means 26. In other words, the axial azimuth calculating means 26 turns the front side azimuth angle θ ₊ that minimizes the transmitted light intensity when one surface of the sample is opposed to the reference polarizer 14, and the sample to the reference polarizer 14 of the sample. The calculation is performed based on the back side azimuth angle θ ₋ that minimizes the transmitted light intensity when the opposite surface is the other surface. In this way, by using the measurement result when the sample or the reference polarizer 14 is turned over, the axial direction of the reference polarizer can be determined strictly as described later, and as a result, the transmission axis direction of the sample is also determined. It can be obtained accurately.

Further, the axial direction measuring method according to the present invention is a method of irradiating a linearly polarized light element as a sample with linearly polarized light from a reference polarizer, changing the direction of the sample with respect to the reference polarizer, and transmitting light through the sample. The axis direction of the measurement object is determined by measuring the direction in which the intensity of the object is minimized. Then, one surface of the sample is opposed to the reference polarizer, and a front-side measurement step of measuring the front-side azimuth angle θ ₊ at which the transmitted light intensity is minimized, and the sample is turned over to face the reference polarizer of the sample A back side measuring step for measuring the back side azimuth angle θ ₋ that minimizes the transmitted light intensity when the surface is the other side, and the reference polarizer and the reference polarizer based on the front side azimuth angle θ ₊ and the back side azimuth angle θ ₋ And / or a calculation step of calculating the axial direction of the sample.
The above is the schematic configuration of the axial orientation measuring apparatus and method of the present embodiment, which will be described in more detail below.

  First, as shown in FIGS. 2A and 2B, the sample holder 16 of the present embodiment includes a measurement light passage window for irradiating the sample with measurement light, and a sample spring for fixing the sample. Yes. The sample holder 16 is rotated by the sample rotating means about an axis that passes through the center of the measurement light passage window and is perpendicular to the sample. The sample holder 16 is provided with a reference line for defining the orientation (angular position) of the sample when the sample film is placed. This reference line is constituted by a completely flat abutting bar (FIG. 2A) or two pins (FIG. 2B). A reference side is also defined for the polarizing film as the sample, and the sample is placed on the holder so that this side coincides with the reference line of the sample holder (see FIGS. 3A and 3B). At this time, it is desirable that the transmission axis direction of the sample substantially coincides with the reference line of the sample holder 16, that is, the reference side of the polarizing film as the sample is substantially parallel to the transmission axis direction.

  After placing the sample film on the sample holder, the transmission axis direction of the sample film is determined according to the procedure described below. As shown in FIG. 4A, the angular position of the extinction axis (axis perpendicular to the transmission axis) direction of the reference polarizer is denoted by δ. The large circle in the figure shows the angle scale provided on the sample rotating means of the apparatus. Further, as shown in FIG. 4B, the angle of the transmission axis with respect to the reference side (reference line) of the sample is α. This angle α is an amount to be obtained. Further, as described in the section of the problem, since the angular position of the extinction axis of the reference polarizer (for example, the position measured by the angle scale provided in the apparatus) is not accurately known, the angular position δ is also unknown.

(1) Front-side measurement step With one surface of the sample facing the reference polarizer, an azimuth θ ₊ (an angular position of the reference line of the sample) that determines the minimum transmitted light intensity is determined. In this state, as shown in FIG. 5A, the extinction axis of the reference polarizer coincides with the transmission axis of the sample (the transmission axis of the reference polarizer and the transmission axis of the sample are orthogonal). The front-side azimuth angle θ ₊ , which is the azimuth of the reference line of the sample at this time, can be expressed as θ ₊ = δ−α using the angles δ and α described above.
(2) Back side measurement step Next, the sample is set upside down, and the surface opposite to the surface opposed in the surface measurement step is opposed to the reference polarizer, and the direction θ ₋ that minimizes the transmitted light intensity at that time Determine. That is, the measurement is performed with the surface on the light incident side of the sample opposite to that in the front side measurement step. As shown in FIG. 5B, the transmission axis of the sample when the sample is turned over is in a positional relationship symmetrical to the transmission axis at the front side with respect to the reference line of the sample holder. Therefore, the orientation (back side azimuth angle θ ₋ ) of the reference line when turned over can be expressed as θ ₋ = δ + α using the above angles δ and α.
(3) Axis orientation calculation step The intermediate position θ ₀ = (θ ₊ + θ ₋ ) / 2 between the front side orientation θ ₊ and the back side orientation θ ₋ is calculated. Since θ ₀ = δ from the above equation, the extinction axis direction of the reference polarizer can be determined by obtaining an intermediate position θ ₀ = (θ ₊ + θ ₋ ) / 2 between the direction θ ₊ and the direction θ _−. it can. _{Further, θ + -θ 0 = -α,} θ - -θ 0 = α because made, it is possible to obtain a transmission axis azimuth alpha of the sample as measured from the future reference line of the sample holder (reference edge of the sample).

In the above, the direction of the extinction axis of the reference polarizer was determined using the sample to be measured, but when measuring the axis direction of the reference polarizer, it was determined using the standard sample prepared for measuring the axis direction of the reference polarizer May be. The standard sample is configured by fixing a polarizer on a substrate whose one side is completely flat so that the side and the dislocation axis are almost parallel. This standard sample is prepared so that it can be used evenly even if it is turned over. Using this standard sample, the extinction axis direction of the reference polarizer is determined by the above process. That is, the front side measurement step and the back side measurement step are performed on the standard sample, and the extinction axis azimuth θ ₀ of the reference polarizer is obtained from the azimuth angles θ ₊ and θ ₋ obtained there. Next, a polarizing film as a sample is placed on the stage, an angular position where the transmitted light is minimized is obtained, and this is _defined as θ _obs . The transmission axis direction of the sample may be calculated as θ _obs −θ ₀ .
To calculate the degree of polarization or extinction rate of the sample, the transmission axis of the sample is determined as described above, and the transmitted light intensity at the extinction position is measured. Next, the sample is rotated exactly 90 °, the intensity of transmitted light at that time is measured, and the degree of polarization or the extinction ratio may be calculated from these two intensities by a conventional method.

In the apparatus shown in FIG. 1, the storage means 36 in the computer 22 stores the front side azimuth angle θ ₊ and the back side azimuth angle θ ₋ measured in the front side measurement step and the back side measurement step. Then, the azimuth angles θ ₊ and θ ₋ are read out from the storage means 36 by the axis azimuth calculating means 26 and the intermediate position θ ₀ = (θ ₊ + θ ₋ ) / 2 is calculated. The extinction axis direction θ ₀ of the reference polarizer thus obtained is stored in the storage means. Then, the transmission axis azimuth of the sample is obtained from the measured azimuth θ ₊ (or θ ₋ ). When the extinction axis direction of the reference polarizer is determined for the standard sample, the transmission axis direction θ _obs of the sample is newly measured, and the extinction axis direction θ ₀ of the stored reference polarizer is used to extinguish the sample. Calculate the axial direction.
As described above, the extinction axis direction of a sample (or a standard sample) can be determined with logical precision by a simple method of determining the extinction direction from both the front and back sides.

It explained suitable mechanism for determining the minimum position determination mechanism then the transmitted light intensity of the minimum transmission light intensity orientation.
When the axial direction of the polarizing film or retardation film is to be determined, the intensity of transmitted light is the cosine of the double angle 2θ of the angle θ between the axis of the reference polarizer on the apparatus side and the axis of the polarizing or retardation film ( The rate of change with respect to the angle is zero at the position of the extinction position (θ = 0) in proportion to 1−cos 2θ) / 2. For this reason, it is difficult to accurately determine this with the human eye, and the limit is 2/100 ° for the most skilled person and 1/10 ° for the ordinary person. In addition, even when a photodetector is used, it is difficult to determine a position where the transmitted light intensity is truly minimized. Therefore, the accuracy of measurement with respect to the polarization degree (or extinction degree) and axial orientation of the polarizing film and the axial orientation of the phase film is not sufficient.

  Therefore, in the embodiment of FIG. 1, the processing means 24 rotates the sample by the rotary stage 18, and determines a provisional orientation determining unit 38 that determines a provisional orientation in which the transmitted light intensity is generally the minimum, and a plurality of the vicinity of the provisional orientation. Measuring the transmitted light intensity at the angular position and storing the measured transmitted light intensity in association with the angular position at that time, and the transmitted light intensity at a plurality of angular positions. A calculation unit 42 that performs fitting with a quadratic function and calculates a vertex position of the quadratic function. The calculated vertex position is stored in the storage means 36. Thus, the direction in which the transmitted light intensity is minimum is obtained as the vertex position calculated by the calculation unit 42.

The temporary azimuth determining unit 38 controls the rotation stage to rotate the sample, monitors the detection signal from the light detection means, determines the azimuth at which the transmitted light intensity is approximately the minimum, and sets it as the temporary azimuth.
The temporary azimuth vicinity measuring unit 40 measures the intensity of transmitted light at a plurality of angular positions near the temporary azimuth position by rotating the sample, and associates the transmitted light intensity with the angular position of the sample at that time in the storage means 36. Remember. For example, the transmitted light intensity is measured at a plurality of angular positions at appropriate angular intervals (for example, intervals of 0.1 °) in the positive and negative directions (counterclockwise and clockwise) from the temporary orientation.
As shown in FIG. 6, the calculation unit fits the obtained transmitted light intensity at a plurality of angular positions as a quadratic function of the angular position by a method such as a least square method. FIG. 6 shows an example in which the transmitted light intensity is measured at 11 angular positions at intervals of 0.1 °. Here, the horizontal axis is the angular position, the vertical axis is the transmitted light intensity, and the temporary orientation is the 0 ° position. Vertex coordinates are obtained for the quadratic function thus obtained. This vertex coordinate is the exact angle of the extinction position (the azimuth angle at which the transmitted light intensity is minimized).

Also in the method of the present embodiment, it is preferable to determine the minimum position of transmitted light intensity by the method as described above. In other words, the angle at which the transmitted light intensity is substantially minimum is set as a temporary orientation, and the transmitted light intensity is measured at a plurality of angular positions near the temporary orientation. Next, the obtained transmitted light intensities at a plurality of angular positions are fitted as a quadratic function of the angular position, and vertex coordinates of the quadratic function are calculated. This vertex coordinate is an accurate position where the transmitted light intensity is minimum.
In this way, the vicinity of the minimum position of the transmitted light intensity is approximated by a quadratic function, and the position of the vertex of the quadratic function is calculated, so that transmission at an accuracy level of angular feed or higher A minimum position of light intensity can be determined.

Arrangement of Reference Polarizer There may be a case where a non-polarized component is included in the emitted light due to scattering due to dust or scratches attached to the reference polarizer. For this reason, it is preferable to prevent the scattered light including the non-polarized component from being detected by disposing the reference polarizer away from the light detection means. That is, as shown in FIGS. 7 (a) and 7 (b), the distance L when the reference polarizer is placed away from the light detection means is looked at from the position of the polarizer to the light receiving portion of the integrating sphere / detector. It is preferable that the solid angle is 1 × 10 ⁻² πsr or less. By separating the reference polarizer from the light detection means in this way, the scattered light is not detected. However, here, the light receiving portion refers to the incident aperture of the integrating sphere when the light detection means is composed of an integrating sphere and a detector. Moreover, when comprised only with a detector, it points out the light-receiving surface of detector itself.
At this time, the position of the sample is arranged close to the light detection means as shown in FIG. 7 (a) or close to the reference polarizer as shown in FIG. 7 (b). Also good. In FIG. 7A, the total transmitted light from the sample is evaluated, and in FIG. 7B, only the linear transmitted light from the sample is evaluated.

A method for measuring the axial direction of a phase difference element, an apparatus, and an embodiment in the case of measuring a phase difference film (linear phase shift element) as a sample will now be described. FIG. 8 is a schematic configuration diagram of an axial orientation measuring apparatus according to the second embodiment of the present invention. The axial azimuth measuring apparatus 110 includes a light irradiation means 112 including a light source 128 and a spectroscope 130, a first reference polarizer 114a, a sample holder 116 for holding a sample, and a sample centered on the optical axis. Sample rotating means 118a, second reference polarizer 114b, polarizer rotating means 118b for rotating the second reference polarizer 114b around the optical axis, integrating sphere 132 and detector 134. A light detection means 120 and a computer 122 for controlling each means, processing data, and the like.
The light from the light irradiation means 112 passes through the first reference polarizer 114 a to be linearly polarized light, and is irradiated onto the sample fixed to the sample holder 116. The sample holder 116 is installed between the first reference polarizer 114a and the second reference polarizer 114b, and the transmitted light from the sample passes through the second reference polarizer 114b and is detected by the light detection means 120. . Here, it is desirable that the light detection unit 120 includes the integrating sphere 132 in order to eliminate the influence of the position unevenness on the light receiving surface of the detector 134 and the influence of polarization characteristics, but this is not essential. In the present embodiment, the polarizer rotating means 118b is configured to rotate the second reference polarizer 114b. However, the first reference polarizer 114a may be rotated.

The sample holder 116 may be the same as that shown in FIGS. 2 (a) and 2 (b). Also, a reference side is defined on the sample film, and the sample is placed on the holder so that this side completely coincides with the reference line of the holder (see FIGS. 3A and 3B). The retardation film has two orthogonal neutral axes (fast axis and slow axis), and it is desirable to keep one of them substantially parallel to the reference side.
Prior to the measurement of the retardation film, the first reference polarizer 114a and the second reference polarizer 114b are set in a crossed Nicols state by the polarizer rotating means 118b. That is, it is installed so that the intensity of transmitted light is minimized when the sample is not installed.

Thereafter, the sample is placed between the first reference polarizer 114a and the second reference polarizer 114b, the sample orientation is changed by the sample rotating means 118a, and the direction at which the transmitted light intensity is minimized is measured. First, the azimuth angle that minimizes the transmitted light intensity when one surface of the sample is opposed to the first reference polarizer 114 a is measured, and this front side azimuth angle θ ₊ is stored in the storage means 136 in the computer 122. Keep it. Further, the sample is turned over, and the surface facing the first reference polarizer of the sample is set as the other surface, and the azimuth angle at which the transmitted light intensity is minimized is measured. This back side azimuth angle θ ₋ is also stored in the storage means 136. Then, the axial direction calculation means 126 in the computer 122 calculates the neutral axis direction of the sample based on the front side azimuth angle θ ₊ and the back side azimuth angle θ ₋ .

Moreover, the axial direction measuring method according to the present embodiment measures the axial direction of the sample using the above-described apparatus. That is, by installing a linear phase shifter as a sample between the first and second reference polarizers installed in crossed Nicols and rotating the sample around the optical axis, the first reference polarization The direction in which the intensity of the light transmitted through the optical element, the sample, and the second reference polarizer is minimized is measured, and the axial direction of the sample is determined from the result. Then, one surface of the sample is made to face the first reference polarizer, and the front side measurement step for measuring the azimuth angle θ ₊ at which the transmitted light intensity is minimized, and the sample is turned over to face the first reference polarizer of the sample and back measurement step of measuring an azimuth angle theta ₊ azimuth and theta _{- -} transmitted light intensity when the (opposite surface when the front side measuring step) and faces the other surface azimuthal theta becomes minimum And calculating a neutral axis orientation of the sample based on the above.
The above is the outline of the apparatus and method of the present embodiment, which will be described in more detail below.

(1) First, the first reference polarizer and the second reference polarizer are placed in a crossed Nicols state. The second reference polarizer may be rotated while the sample is not installed, and an angular position that minimizes the transmitted light intensity may be determined. At this time, as shown in FIG. 9A, the extinction axis of the first reference polarizer and the extinction axis of the second reference polarizer are orthogonal to each other. Here, the extinction axis direction of the first reference polarizer is δ. However, the extinction axis direction δ is unknown.
(2) Front-side measurement step As shown in FIG. 9 (b), the retardation film as a sample has axes that are orthogonal to the fast axis and the slow axis, which are collectively referred to as a neutral axis. The purpose of the measurement is to determine one side of the sample as a reference side and obtain the azimuth angle of the neutral axis with respect to the reference side. Here, an angle formed with the reference line of one of the two axes of the sample (here, the smaller angle formed with the reference line) is defined as α. This α is the amount to be obtained.
A retardation film as a sample is placed between the first reference polarizer and the second reference polarizer. If the neutral axis orientation of the retardation film and the polarization direction of the first (or second) polarizer do not completely match, the light is transmitted again through this system due to the retardation provided by the retardation film. . Therefore, by rotating the sample about the optical axis and obtaining the direction that minimizes the transmission axis intensity, the direction in which the neutral axis of the sample coincides with the extinction axes of the first and second reference polarizers (front side direction) Measure the angle θ ₊ ). The orientation of the sample is defined as the direction of the reference line (reference side). As shown in FIG. 10A, the azimuth θ ₊ can be expressed as θ ₊ = δ−α using the angles δ and α. Here, in FIG. 10, only one of the extinction axis of the first reference polarizer and the neutral axis of the sample is shown to avoid complexity.

(3) Back side measurement step Next, the sample is turned over and placed between the first and second reference polarizers, and the orientation θ _{− at} which the transmitted light intensity is minimized is determined. Then, the surface opposite to the reference polarizer of the sample is opposite to the front side measurement step. That is, the surface facing the first reference polarizer in the front-side measurement step faces the second reference polarizer in the back-side measurement step, and faces the second reference polarizer in the front-side measurement step. However, in the back side measurement configuration, it faces the first reference polarizer. In other words, the surface on the light incident side of the sample is measured by changing the front side measurement process and the back side measurement process. As shown in FIG. 10 (b), the axis of the sample when turned over samples, due to the front side of the transmission axis symmetrical positional relationship with respect to the reference line of the sample, back azimuth theta _- the above Using the angles δ and α, it can be expressed as θ ₋ = δ + α.
(4) Axial azimuth calculation step The intermediate position θ ₀ = (θ ₊ + θ ₋ ) / 2 between the front azimuth angle θ ₊ and the back azimuth angle θ ₋ is calculated. Since θ ₀ = δ from the above equation, the axial direction δ of the reference polarizer can be determined by obtaining an intermediate position θ ₀ = (θ ₊ + θ ₋ ) / 2 between the direction θ ₊ and the direction θ _−. it can. _{Further, θ + -θ 0 = -α,} θ - because - [theta] _{0 =} the alpha, can be determined axial orientation alpha samples measured therefrom from the reference line of the sample holder.

In the above description, the direction of the extinction axis of the reference polarizer is determined using the sample to be measured. However, when measuring the axis direction of the first (second) reference polarizer, the axis orientation of the reference polarizer is measured. You may determine using the standard sample prepared for. The standard sample is configured by fixing a retardation film to a substrate having one side completely flat, so that the neutral axis (one of the sides) substantially coincides with the side. This standard sample is prepared so that it can be used evenly even if it is turned over. This standard sample is set in the sample holder, and the extinction axis direction of the reference polarizer is determined by the above-described process. That is, the front side measurement process and the back side measurement process are performed on the standard sample, and the extinction axis azimuth θ ₀ (= δ) of the reference polarizer is obtained from the azimuth angles θ ₊ and θ ₋ obtained there. Next, with respect to the retardation film to be measured, the reference side of the sample is attached so as to be accurately aligned with the reference line of the holder, and the position (angle θ _obs ) at which the transmitted light intensity is minimized is obtained in the same manner. The angle θ formed between the axial direction of the measurement sample and the reference side is calculated as θ = θ _obs −θ ₀ .
As described above, the neutral axis direction of a sample (or standard sample) can be determined with logical precision by a simple method of determining the extinction direction from both the front and back sides.

Mechanism for Determining the Minimum Position of Transmitted Light Intensity Also in the embodiment of FIG. 8, it is preferable that the processing means 124 for determining the minimum position of the transmitted light intensity is provided as in the embodiment of FIG. That is, the processing unit 124 rotates the sample or the second reference polarizer 114b by the sample or polarizer rotating units 118a and 118b, and determines a temporary direction determining unit 138 that determines a temporary direction at which the transmitted light intensity is substantially minimum. The transmitted light intensity is measured at a plurality of angular positions near the temporary orientation, and the measured transmitted light intensity is stored in the storage unit 136 in association with the angular position at that time, and at the plurality of angular positions. Is fitted with a quadratic function of the angular position (see FIG. 6), and is calculated from a vertex position calculated by the calculation unit 142. The direction in which the light intensity is truly minimized is obtained.
That is, when the second reference polarizer 114b is rotated by the polarizer rotating means 118b to bring them into the crossed Nicols state, or the first and second reference polarizers are set in the crossed Nicols state, and the sample rotating means 118 is used for the sample. When the measurement is performed with the rotation, the minimum position of the transmitted light intensity is obtained by the processing means 124 described above.

Also in the method of the present embodiment, it is preferable to determine the minimum position of transmitted light intensity by the following method. First, an angle at which the intensity of transmitted light is substantially minimum is taken as a temporary orientation, and the transmitted light intensity is measured at a plurality of angular positions near the temporary orientation. Next, the transmitted light intensity at a plurality of angular positions obtained is fitted as a quadratic function of the angular position (see FIG. 6), and the vertex coordinates of the quadratic function are calculated. This vertex coordinate is an accurate position where the transmitted light intensity is minimum.
In this way, the vicinity of the minimum position of the transmitted light intensity is approximated by a quadratic function, and the position of the vertex of the quadratic function is calculated, so that transmission at an accuracy level of angular feed or higher A minimum position of light intensity can be determined.

Position of Reference Polarizer As shown in FIGS. 11A and 11B, it is preferable that the first reference polarizer is placed away from the light detection means in the second embodiment as well. Specifically, the distance L between the first reference polarizer 114a and the light detection means 120 is such that the solid angle when looking at the light receiving part of the light detection means 120 from the position of the first reference polarizer 114a is at least 1 × 10. it is preferable to take such a ^-2 Paisr less. By separating the first reference polarizer 114a from the light detection means 120 in this manner, light scattered by the scratches on the polarizer and attached dust is not detected. At this time, even if the second reference polarizer 114b is arranged close to the light detection means as shown in FIG. 11A, it is arranged close to the first reference polarizer 114b as shown in FIG. 11B. You may keep it. Further, the position of the sample is not particularly limited. However, here, the light receiving portion of the light detecting means refers to an incident aperture of the integrating sphere when the light detecting means includes an integrating sphere and a detector. Moreover, when comprised only with a detector, it points out the light-receiving surface of detector itself.

1 is a schematic configuration diagram of an axial orientation measuring apparatus according to a first embodiment of the present invention. Example of sample holder according to this embodiment Explanatory drawing when a sample is placed in the sample holder Diagram showing the extinction axis direction of the reference polarizer and the transmission axis direction of the sample relative to the reference side Explanatory drawing of the axial direction measuring method of 1st Embodiment concerning this invention. Explanatory drawing of the method for obtaining the minimum angular position of transmitted light intensity Explanatory drawing which shows the arrangement position of the reference | standard polarizer in 1st Embodiment. Schematic configuration diagram of an axial orientation measuring apparatus according to a second embodiment of the present invention The figure which shows the neutral-axis direction of the sample with respect to the extinction axis of the 1st (2nd) reference | standard polarizer in 2nd Embodiment, and a reference | standard edge | side Explanatory drawing of the axial direction measuring method concerning 2nd Embodiment Explanatory drawing which shows the arrangement position of the 1st (2nd) reference | standard polarizer in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Axis direction measuring apparatus 12 Light irradiation means 14 Reference | standard polarizer 16 Sample holder 18 Sample rotation means 20 Photodetection means 22 Computer 24 Processing means 26 Axial direction calculation means

Claims (10)

In an axial direction measuring apparatus that determines a transmission axis direction of a linearly polarizing element as a sample,
Light irradiation means;
A reference polarizer that irradiates the sample with light from the light irradiation means as linearly polarized light; and
A sample rotating means for rotating the sample placed opposite to the reference polarizer around the optical axis to change the direction of the sample;
A light detecting means for detecting light transmitted through the sample;
Axis direction calculating means for calculating the transmission axis direction of the sample based on the azimuth angle of the sample at which the transmitted light intensity is minimized when the sample is rotated by the sample rotating means,
The axial azimuth calculating means has an azimuth angle θ ₊ that minimizes the transmitted light intensity when one surface of the sample is opposed to the reference polarizer, and the sample is turned over to face the reference polarizer of the sample. An axial azimuth measuring apparatus that calculates the transmission axis azimuth of a sample based on an azimuth angle θ ₋ that minimizes the transmitted light intensity when the surface is the other surface. In the axial direction measuring apparatus according to claim 1,
The arithmetic means obtains the extinction axis azimuth of the reference polarizer as an intermediate position θ ₀ = (θ ₊ + θ ₋ ) / 2 between the azimuth angle θ ₊ and the azimuth angle θ ₋ , and based on the azimuth angle θ ₀ An axial orientation measuring apparatus for obtaining a transmission axis orientation. In the axial direction measuring apparatus according to claim 1 or 2,
A processing means for rotating the sample by the sample rotating means and obtaining the orientation of the sample that minimizes the transmitted light intensity, the processing means,
A temporary orientation determining unit that rotates the sample by the sample rotating means to determine a temporary orientation in which the transmitted light intensity is substantially minimized;
Measuring the transmitted light intensity at a plurality of angular positions near the temporary orientation, and storing the measured transmitted light intensity in association with the angular position at that time; and
Fitting the stored transmitted light intensity with a quadratic function of an angular position, and calculating a vertex position of the quadratic function,
An axial azimuth measuring apparatus characterized in that an azimuth in which transmitted light intensity is truly minimum is obtained from a vertex position calculated by the calculating unit. In the axial direction measuring apparatus according to claim 1,
The reference polarizer is arranged away from the light detection means so that the solid angle when looking into the light receiving part of the light detection means from the position of the reference polarizer is 1 × 10 ⁻² πsr or less. An axial bearing measuring device characterized by the above. A reference polarizer and a linear polarizing element as a sample are opposed to each other, and the orientation of the sample with respect to the reference polarizer is changed, so that the direction in which the intensity of light transmitted through the reference polarizer and the sample is minimized is obtained. In the axial direction measurement method for determining the transmission axis direction of the sample by measuring,
A front-side measurement step of measuring one front-side azimuth angle θ _{+ at} which one surface of the sample is opposed to a reference polarizer and the transmitted light intensity is minimized,
Flip the sample, and measure the back side azimuth angle θ ₋ that minimizes the transmitted light intensity when the surface facing the reference polarizer of the sample is the other side;
A calculation step of calculating a transmission axis direction of the sample based on the front side azimuth angle θ ₊ and the back side azimuth angle θ ₋ . In an axial direction measuring device that uses a linear phase shift element as a sample and determines the neutral axis direction of the sample,
Light irradiation means;
A first reference polarizer that irradiates the sample with light from the light irradiation means as linearly polarized light;
A second reference polarizer which is installed in a crossed Nicol state with respect to the first reference polarizer and transmits transmitted light from the sample;
A sample rotating means capable of rotating a sample placed between the first and second reference polarizers around an optical axis and changing the orientation of the sample;
Light detection means for detecting light transmitted through the second reference polarizer;
Axis direction calculating means for calculating the neutral axis direction of the sample based on the azimuth angle at which the transmitted light intensity is minimized when the sample is rotated by the sample rotating means,
The axial azimuth calculating means turns the sample into the first reference direction of the sample by turning the sample upside down and the front side azimuth angle θ ₊ that minimizes the transmitted light intensity when one surface of the sample is opposed to the first reference polarizer. An axial azimuth measuring apparatus for calculating a neutral axis azimuth of a sample based on a back side azimuth angle θ ₋ that minimizes transmitted light intensity when the surface facing the polarizer is the other surface. . In the axial direction measuring apparatus according to claim 6,
The axis azimuth calculating means obtains the extinction axis azimuth of the reference polarizer as an intermediate position θ ₀ = (θ ₊ + θ ₋ ) / 2 between the front side azimuth angle θ ₊ and the back side azimuth angle θ ₋ , and calculates the direction θ ₀ An axial orientation measuring device characterized in that the neutral axial orientation of a sample is obtained based on the basis. In the axial direction measuring apparatus according to claim 6 or 7,
A processing means for rotating the sample by the sample rotating means to obtain the orientation of the sample that minimizes the transmitted light intensity,
The processing means rotates the sample by the sample rotating means, and determines a temporary orientation determining unit that determines a temporary orientation at which the transmitted light intensity is substantially minimum;
Measuring the transmitted light intensity at a plurality of angular positions near the temporary orientation, and storing the measured transmitted light intensity in association with the angular position at that time; and
A transmission unit that fits the transmitted light intensity at a plurality of angular positions with a quadratic function of the angular position and calculates a vertex position of the quadratic function, and transmits transmitted light from the vertex position calculated by the calculation unit. An axial azimuth measuring apparatus characterized by obtaining an azimuth in which the intensity is truly minimum. In the axial direction measuring apparatus according to claim 6-8,
The first reference polarizer is separated from the light detection means so that the solid angle when looking into the light receiving part of the light detection means from the position of the first reference polarizer is 1 × 10 ⁻² πsr or less. An axial orientation measuring device characterized by being arranged. Between the first and second reference polarizers installed in the crossed Nicols, a linear phase shifter as a sample is installed, and the sample is rotated about the optical axis, whereby the first and second reference units are rotated. The orientation of the sample with respect to the polarizer is changed, and the neutral axis orientation of the sample is determined by measuring the orientation in which the intensity of light transmitted through the first reference polarizer, the sample, and the second reference polarizer is minimized. In the axial direction measuring method to
A front-side measurement step of measuring a front-side azimuth angle θ _{+ at} which one surface of the sample is opposed to the first reference polarizer and the transmitted light intensity is minimized;
A back side measuring step of measuring the back side azimuth angle θ _{− at} which the transmitted light intensity is minimized when the sample is turned over and the surface facing the first reference polarizer of the sample is the other side;
And a calculation step of calculating a neutral axis direction of the sample based on the front side azimuth angle θ ₊ and the back side azimuth angle θ ₋ .

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