KR101373709B1 - The measurement device and the method of the principle axis and retardation of the 3-dimensional film - Google Patents

Abstract

In one direction of the two-dimensional detector, an enlarged or reduced image of the three-dimensional film is created, and in the other direction, an uneven optical system is produced so that an interference pattern of two orthogonal electric field components of light from each store's conjugate point is generated. The present invention relates to an apparatus capable of measuring a phase difference and a main axis without moving parts by forming an anamorphic optical system and a data processing method thereof.
The light from the sample passes through a spherical lens, a wedge-shaped birefringence wedge, an analyzer plate and a cylindrical lens and then enters a two-dimensional detector. The wedge-shaped birefringent prism serves as a function of continuously changing the phase difference of two orthogonal electric field components according to the position, and the analyzer plate combines the two orthogonal components of the electric field to interfere with each other. The cylindrical lens forms only the direction in which the curvature is present to produce the two-dimensional signal. The data processing process determines the one-dimensional distribution of the principal axis and phase difference of the three-dimensional film.

Description

Measuring device and measuring method of main axis and phase difference of three-dimensional film {THE MEASUREMENT DEVICE AND THE METHOD OF THE PRINCIPLE AXIS AND RETARDATION OF THE 3-DIMENSIONAL FILM}

The present invention relates to a main axis and a phase difference measuring apparatus and a measuring method of a three-dimensional film, and more particularly, light passing through the polarizing plate and the three-dimensional film passes through the birefringent prism and the inspection plate in order to form an interference fringe, interference pattern The apparatus and the measuring method of the principal axis and the phase difference of the three-dimensional film for calculating the phase axis and the phase difference of the three-dimensional film.

The phase difference is measured by using an ellipsometer which rotates the analyzer plate or the compensation plate at high speed or by using a phase stepping method. In this case, moving parts are required, so the measurement time is less than tens of milliseconds.

To overcome this problem, a technique for continuously changing phases without moving parts has been published (Suezou Nakadate, "High precision retardation measurement using phase detection of Young's fringes" Appl. Opt. 29, 242-246 (1990). )). In this paper, the phase difference is precisely determined from the interference fringes by continuously changing the phase difference of two orthogonal electric field components of light to be measured using a wedge birefringent prism. In this paper, the principal axis is pre-aligned and the measurement area is one of the samples of the 3D film.

1 is a schematic diagram of a common path interferometer for phase difference measurement showing the prior art.

As shown in FIG. 1, the light output from the laser is polarized light and is set to 45 ° with respect to the main axis of the phase plate (retarder of FIG. 1) whose polarization direction is a sample. The light passing through the sample is magnified by an objective lens and then incident on a wedge-shaped birefringent wedge. The optical axis (z-z ') of the wedge-shaped birefringent prism should be aligned with the direction of the major axis of the sample. The direction of the transmission axis of the polarizer behind the wedge birefringence prism is 45 ° to the optical axis of the birefringence prism. Afterwards, the interference fringe is measured using a one-dimensional detector.

The equation of the interference fringe when there is no sample is as follows.

χ is the spatial coordinate (distance from the reference point) in the one-dimensional detector direction, and f and φ ₀ are the phase difference between the two orthogonal electric field components at the spatial frequency and the detector reference point, respectively.

The equation of the interference fringe after the sample is mounted is as follows.

δφ is the phase difference of the sample and is calculated according to the following relationship.

, (i=1,2)

, (i = 1,2)

.

.

The spatial frequency f must be known in advance during the calibration process before full measurement is made. The advantage of being able to precisely measure the phase difference in one measurement is that the major axis of the sample must be precisely aligned with the major axis of the device. In addition, measurements are made at one point on the sample.

The present invention is a technique necessary for evaluating the principal axis and the phase difference in real time in the manufacturing process of the three-dimensional film, to provide a technique that can be measured in real time with the principal axis and the phase difference in the one-dimensional region of the film.

In order to solve the above problems, the measuring method of the main axis and the phase difference of the three-dimensional film according to the present invention comprises the steps of arranging a linear light source, a polarizing plate, a wedge-shaped birefringent prism, an analyzer; Allowing the light polarized by the polarizing plate to pass through the three-dimensional film while moving the three-dimensional film vertically between the polarizing plate and the wedge-shaped birefringent prism; Light passing through the three-dimensional film passes through the wedge-shaped birefringent prism and the spectrometer in order to form an interference fringe; And calculating and calculating a principal axis Θ and a phase difference Φ of the three-dimensional film from the interference fringes.

In addition, the present invention is characterized in that it comprises the step of adjusting the angle of the analyzer to meet the conditions of a predetermined three-dimensional film.

In addition, the present invention is characterized in that it comprises the step of correcting the main axis and the phase difference of the three-dimensional film by using the reference axis and the phase difference obtained from the interference fringe measured by placing the polarizing plate in the position of the three-dimensional film.

In addition, the measuring device for measuring the main axis and the phase difference of the three-dimensional film according to the present invention, in the measuring device for measuring the main axis and phase difference of the three-dimensional film, in the measuring device for measuring the main axis and phase difference of the three-dimensional film, A line light source that shines light on the three-dimensional film; A polarizing plate positioned in a path of light between the linear light source and the 3D film; A collimation optical system for paralleling light passing through the 3D film; A wedge-shaped birefringent prism which continuously changes the phase difference between two orthogonal electric field components of the light passing through the collimating optical system according to the position; An inspection plate which combines two orthogonal components of the electric field generated in the wedge birefringence prism so as to overlap and interfere with each other; A cylindrical lens for forming a two-dimensional signal by forming light passing through the detector plate; A two-dimensional detector measuring an interference fringe caused by light passing through the cylindrical lens; And a data analysis device for analyzing the interference fringe to obtain a retardation and a principal axis of the 3D film.

In addition, the present invention is characterized in that the wedge-shaped birefringent prism is added with a birefringent plate having the same thickness as the center of the wedge-shaped birefringent prism and having an optical axis that is orthogonal, and thus the net retardation of the center is zero.

In addition, an imaging optical system and a slit are provided between the collimating optical system and the three-dimensional film, and the imaging optical system makes an image of the sample in the slit, and the collimating optical system makes the light passing through the opening of the slit side by side. .

In addition, the band pass filter for adjusting the interference length of the light emitted from the light source is characterized in that it is further provided.

The present invention made as described above is a technique required to evaluate the main axis and the phase difference in real time in the manufacturing process of the three-dimensional film, it can provide a technology that can measure the main axis and phase difference in the real time in the one-dimensional region of the film together in real time have.

In addition, the main object of the present invention is to measure the retardation and the main axis of the three-dimensional film, but also includes the case where the measurement object is not limited to the three-dimensional film, but the main axis and the retardation of the general phase plate.

1 is a schematic diagram of a phase difference measuring method using a conventional wedge birefringent prism.
2 is a main axis and phase difference measuring apparatus according to an embodiment of the present invention.
3 is a main axis and phase difference measuring apparatus according to another embodiment of the present invention.
4A to 4B show the addition of a birefringent prism to a wedge-shaped birefringent prism according to the present invention.
5 is a measurement screen according to the present invention.
6a to 6b is a measurement result according to the present invention.

The present invention relates to a technique required for real-time evaluation of the principal axis and the phase difference in the manufacturing process of the three-dimensional film, and relates to a technology that can measure the principal axis and the phase difference in the real-time in the one-dimensional region of the film. The three-dimensional film is a film with a phase difference of 90 ° but a major axis alternates between + 45 ° and -45 ° at regular intervals.

<Measurement of spindle and phase difference>

The Jones vector after the light polarized by the polarizing plate whose azimuth angle of the transmission axis passes through the sample is as follows.

E ₀ is the normalized field amplitude so that | E _x | ² + | E _y | ² = 1. The amplitudes of the electric fields in the x- and y-axis directions are E ₀ | E _x | and E ₀ | E _y | and the phases are φ _x and φ _y, respectively. After passing through a wedge-shaped birefringent prism with an optical axis parallel to the x-axis, and a spectroscopic plate with an azimuth of A, the signal is as follows.

Here, φ _xy ≡ φ _x -φ _y , I _x ≡ | E _x | ² , I _y ≡ | E _y | ² , and I ₀ ≡ | E ₀ | ² . χ is the distance from the detector's reference point and κ is the phase difference of the x and y electric field components as it travels along the detector by the unit length, determined by the edge angle of the wedge-shaped birefringent prism and the wavelength of the light source. φ ₀ is the phase difference between two orthogonal electric field components at the detector reference point as in Equation 1. To rearrange Equation 5 is as follows.

,

,

,

,

,

,

,

,

.

.

If the measured interference fringe of the n-th pixel is set to I (n), the coefficient of Equation 6 can be obtained as follows.

Where Λ is the size of the pixel.

If s ₁ 'is defined as s ₁ ' ≡I _x '- ^' I _y 'as shown below, the following relationship is established.

^'I_y인 경우 검광판 투과축의 방위각 A를 45°보다 조금 작게 맞추면 된다. 본 발명에서는 3차원 필름과 같이 위상차가 거의 90° 근처에 있고 주축이 ±45° 근처에 있는 제한된 범위의 (선형)위상판의 주축과 위상차를 정밀하게 재는 것이 목적이므로 필름의 양산 조건에 맞게 검광판 투과축의 방위각 A를 조절하여 맞추면 s₁'이 항상 양수(또는 음수)가 되게 할 수 있다. 이 조건에서 벗어나는 경우 양산조건이 크게 훼손된 경우이고 또 그 경우에는 육안이나 기타 간단한 방식으로 불량을 쉽게 찾아낼 수 있으므로 그와 같은 경우는 본 발명의 관심 밖의 사항이다.In Equation 10, the azimuth angle A of the transmission plate transmission axis may be determined such that s ₁ ′ is always positive (or negative). If s ₁ 'is always positive, then I _x '>^' I _y ' should be I _x as defined in Equation 6.

^{In case of '} I _y , the azimuth angle A of the analyzer transmission axis is set to be slightly smaller than 45 °. In the present invention, the objective is to accurately measure the main axis and phase difference of the (linear) phase plate of the limited range where the phase difference is about 90 ° and the main axis is about ± 45 ° like the three-dimensional film. By adjusting the azimuth angle A of the plate transmission axis, it is possible to make s ₁ 'always positive (or negative). The deviation from this condition is a case in which the mass production condition is greatly impaired, and in this case, since the defect can be easily detected by the naked eye or other simple method, such a case is outside the interest of the present invention.

As defined in Equation ^{_{6 I x '+' I y}} '= 1 and, s _1' is always writing to the condition positive (or negative) I _x ^',' to obtain the I _y 'and φ _xy first I _x, ^When I _y is obtained, the polarization component of the Stokes parameter corresponding to the Jones vector of Equation 4 is obtained as follows.

가 회전변환

(

: 회전축, Ω: 회전각)에 의해 편광

가 된 경우의 회전변환 관계식은 다음과 같다.The Stokes vector of Equation 11 is the Stokes vector after the linearly polarized light having the polarization direction P passes through the sample (linear phase plate). Therefore, the phase plate as a sample serves to convert the incident polarization (cos (2P) sin (2P) 0) into the polarization of Equation 11. This transformation can be represented by a rotation transformation in the Poincare Sphere. Incident polarization

Rotation

(

: Polarized by rotation axis, Ω: rotation angle)

The relation of rotation transformation in case of is as follows.

Here, the rotation transformation is the rotation axis n = (cos (2Θ) sin (2Θ) 0) ^T when the principal axis of the sample is Θ and the rotation angle Ω is equal to the phase difference Φ of the sample. Summarizing according to Equation 12, the principal axis Θ and the phase difference Φ of the sample are obtained as follows.

In order to measure the principal axis and phase difference distribution of the one-dimensional region of the sample in real time, the present invention uses a two-dimensional detector to form a one-dimensional region of the sample in one direction of the detector and two orthogonal components of each conjugate point in the vertical direction thereof. To create an interference fringe. To do this, a cylindrical lens was placed in front of the detector, and the detector was placed on the hyperplane of the lens. The collimated light from the sample is imaged on the detector, but without interference in the orthogonal direction. This embodiment of the present invention is shown in FIG. The arrow marked on the upper part of the sample 20 of the 3D film of FIG. 2 indicates the moving direction of the sample 20.

2, a line light source 10 for shining light on the three-dimensional film; A polarizing plate 11 positioned in a path of light between the linear light source and the 3D film; A collimation optical system 14 for paralleling light passing through the 3D film; A wedge-shaped birefringent prism (15) which continuously changes the phase difference between two orthogonal electric field components of the light passing through the collimating optical system according to the position; An inspection plate (16) for combining two orthogonal components of the electric field generated in the wedge-shaped birefringent prism so as to overlap and interfere with each other; A cylindrical lens 17 for forming a two-dimensional signal by forming light passing through the detector plate; It consists of a two-dimensional detector (30) to measure the interference pattern caused by the light passing through the cylindrical lens.

Based on the result of the interference fringe obtained from the two-dimensional detector, the data analysis device calculates and obtains the principal axis and phase difference of the sample.

In the present invention, the linear light source should be used as a light source because one-dimensional measurement should be performed. Usually, a backlight made by combining several LEDs is used. LEDs have a shorter interference length than lasers. The shorter coherence length is advantageous for measurement due to less coherent noise, but the birefringence prism should be thinned so that the optical path difference between the abnormal light and the normal light is shorter than the coherence length of the light source. If the thickness is thin, the machining accuracy is poor, which is disadvantageous for the measurement. In the present invention, even if the birefringent plate having an orthogonal optical axis is added to the wedge birefringent prism, the optical path difference between the abnormal light and the normal light is not generated at the center. The thickness of the padded birefringent plate is equal to the thickness of the central portion of the wedge-shaped birefringent prism, and the optical axes are combined orthogonally to each other.

The contrast of the interference pattern measured by the interference distance of the light source, the misalignment of the light source, and the average by the finite size of the detector pixel is blunted, resulting in a low contrast. As a result, the actual measured interference fringes look like this:

Where γ is visibility. 1 is ideal, but usually less than 1. n _x and n _y are the pixel colors in the x and y directions, respectively. The calibration process requires knowing γ, κ, and φ ₀ to find the principal axis and azimuth. Device calibration was performed using a polarizer with no phase difference and having a thin and large area. The interference fringes measured by adjusting the transmission axis at 45 ° with the polarizing plate at the sample position are as follows.

The transmission axis A of the analyzer was assumed to be between 0 ° and 90 °. After the reference complex function E _ref is obtained from the measured interference fringes, the correction process is completed.

1. F (I (n)} is obtained by Fourier transforming I (n).

2. Divide the DC component of F {I (n)} by the number of data to get I ₀ '.

3. Divide F {I (n)} by I ₀ 'obtained in the previous step and replace the DC component of F {I (n)} with 0.

를 구한다.4. Inversely transform the result of step 3

.

를 힐버트(Hillbert) 변환하여

를 구한다.5.

To Hilbert transform

.

를 구한다.6. Complex function

.

를 구했으면 보정 과정이 마무리되었다. 측정은 수학식 14를 써서 앞의 과정에 따라 측정 복소함수 를 구하면 된다. Reference complex function

After the calibration has been completed, the calibration process is complete. For the measurement, use Equation 14 to obtain the measurement complex function according to the previous procedure.

Equation 16:

으로 나누고 sin(2A)으로 나눠 규격화된 복소함수

는 아래와 같다:Now refer to the measurement complex function E

Normalized complex function divided by and divided by sin (2A)

Is as follows:

Equation 17:

와,

은 각각 수학식 17의 실수부와 허수부이다. 이후 수학식 10, 11과 13에 따라 시료의 주축과 위상차를 구한다.Of equation (6)

Wow,

Are the real part and the imaginary part of Equation 17, respectively. Then, the main axis and phase difference of the sample are obtained according to Equations 10, 11, and 13.

Figure 2 is a device diagram specifically showing the operating principle of the present invention. The light from the light source is irradiated to the one-dimensional area of the sample using a cylindrical lens or the like, and the collimating lens paralleles the light passing through the sample. After that, it passes through the wedge-shaped birefringence prism and is divided into abnormal light and image light.The two-dimensional detector makes an interference pattern in the moving direction of the specimen by the analyzer plate and the cylindrical lens (front view), and forms an image in the vertical direction of the moving direction. Side view). The measured interference fringe is obtained through data processing to find the principal axis and phase difference. The resolution of the device is determined by the optics used and the pixel size of the detector. The resolution in the direction of movement of the sample is determined by the size of the light beam in the sample. If a high spatial resolution is required, an optical system with a large numerical aperture should be used. An optical system with a large numerical aperture is usually difficult to configure a device due to a short focal length.

3 shows another embodiment of the present invention which improves on this point. An arrow marked on the upper part of the sample 20 of the 3D film of FIG. 3 indicates a moving direction of the sample 20.

The measuring device of FIG. 3 was configured to measure light from the opening of the slit and to make the image of the sample into the slit. A band pass filter 12 was placed to adjust the interference length. The spatial resolution in the sample moving direction is adjusted by adjusting the magnification and the slit width of the optical system in front of the slit 13. The slit also serves to reduce the amount of ambient light entering the detector.

FIG. 5 is an interference fringed with a three-dimensional film in the device constructed according to the embodiment of FIG. 3. It can be seen that the position of the interference fringe is changed depending on the direction (or phase difference) of the optical axis. 6 shows a result of obtaining a phase axis and a phase difference through data processing. It can be seen that the phase difference is 90 degrees and the patterns in which the main axes are orthogonal to each other alternately appear.

The main object of the present invention is to measure the retardation with the main axis of the three-dimensional film, but also includes the case where the measurement object is not limited to the three-dimensional film, but also the retardation with the main axis of the general phase plate.

10: line light source 11: polarizing plate
12 band pass filter 13 slit
14 collimating optical system 15 wedge-shaped birefringent prism
16: detection plate 17: cylindrical lens
20: Sample of three-dimensional film 30: Two-dimensional detector

Claims (7)

In the measuring method for measuring the principal axis and the phase difference of the three-dimensional film,
Arranging a linear light source 10, a polarizing plate 11, a wedge-shaped birefringent prism 15, and an analyzer 16;
Allowing the light polarized by the polarizing plate to pass through the three-dimensional film while moving the three-dimensional film vertically between the polarizing plate and the wedge-shaped birefringent prism;
Light passing through the three-dimensional film passes through the wedge-shaped birefringent prism and the spectrometer in order to form an interference fringe; And
Calculating and obtaining a principal axis (Θ) and a phase difference (Φ) of the three-dimensional film from the interference fringe;
Method for measuring the principal axis and the phase difference of the three-dimensional film comprising a.
The method of claim 1, further comprising adjusting the angle of the analyzer to meet a predetermined condition of the 3D film. The method of claim 1, further comprising correcting the principal axis and the phase difference of the three-dimensional film by using the reference principal axis and the phase difference obtained from the interference fringe measured by placing the polarizing plate at the position of the three-dimensional film. Method for measuring the retardation and the principal axis of the film.
In the measuring device for measuring the principal axis and the phase difference of the three-dimensional film,
A line light source (10) for shining light on the three-dimensional film;
A polarizing plate 11 positioned in a path of light between the linear light source and the 3D film;
A collimation optical system 14 for paralleling light passing through the 3D film;
A wedge-shaped birefringent prism (15) which continuously changes the phase difference between two orthogonal electric field components of the light passing through the collimating optical system according to the position;
An inspection plate (16) for combining two orthogonal components of the electric field generated in the wedge-shaped birefringent prism so as to overlap and interfere with each other;
A cylindrical lens 17 for forming a two-dimensional signal by forming light passing through the detector plate;
A two-dimensional detector 30 measuring an interference pattern caused by light passing through the cylindrical lens;
A data analyzing apparatus for analyzing the interference fringes to obtain a phase difference between the principal axis of the 3D film;
Apparatus for measuring the main axis and the phase difference of the three-dimensional film comprising a.
5. The three-dimensional film of claim 4, wherein the wedge-shaped birefringent prism has a birefringent plate having a thickness equal to the center of the wedge-shaped birefringent prism and having an optical axis that is orthogonal, and thus the net retardation of the center is zero. Apparatus for measuring the phase difference between the main axis.
According to claim 4, Between the collimating optical system and the three-dimensional film is provided with an imaging optical system and a slit, the imaging optical system to make an image of the three-dimensional film in the slit and the collimating optical system to pass the light passing through the opening of the slit Apparatus for measuring the main axis and the phase difference of the three-dimensional film, characterized in that for making.
The apparatus of any one of claims 4 to 6, further comprising a bandpass filter for adjusting the coherence length of the light emitted from the line light source.

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