JPH0682365A - Double refraction measuring device - Google Patents

Abstract

PURPOSE:To accurately measure retardation by arranging respective polarizing elements different in azimuth angle around a center part in a fan-shaped radial state and irradiating the periphery of the center part with common measuring beam. CONSTITUTION:The center of a polarizer 11 and that of an analyser 14 are present on the axis of measuring beam and the mutually corresponding small polarizing elements of both of them are constituted in the relation of parallel Nicol. The measuring beam emitted from the side of the polarizer 12 passes through the polarizer 12 and a sample 4 and further passes through the analyser 14 to be taken in an area sensor 15 and the output corresponding to the intensity of transmitted beam is detected. Since it is known which places of the sensor 15 the intensities of transmitted beam calculated from the small polarizing elements of the polarizer 12 and the analyser 14 correspond to, the part where data must be obtained of measuring beam can be selected at the time of the reading of detection output. The reading place of the sensor 15 can be arbitrarily indicated and, when the number of pixels to be used and the centers thereof are selected, the range of a reading place can be determined and, therefore, the respective intensities of transmitted beam are instantaneously calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a birefringence measuring device, and more particularly to miniaturization of measuring points.

[0002]

2. Description of the Related Art Materials are anisotropy due to internal strain, stretching, etc., and birefringence occurs. On the contrary, by measuring the birefringence, the internal strain of the material and the degree of stretching of the material can be examined. The birefringence is measured by making linearly polarized light incident on the sample and detecting the phase difference of the orthogonal two-component polarized light at the time of sample transmission.

As a birefringence measuring device for continuously measuring lengthwise sheets in a lengthwise direction, a plurality of small polarizing elements are arranged collectively on one plane while changing their azimuth angles little by little. As an element, in the same configuration, the analyzers are arranged so that the orientation of the polarizing element of the portion corresponding to each polarizing element of the polarizer is parallel to the polarizing element of the polarizer, and the sample is placed between them. From the azimuth angle of each polarization element of the analyzer, calculate the relational expression between the transmitted light intensity of the three elements of the polarizer, the sample, and the analyzer and the azimuth angle of the polarization element. , There is a method in which the minimum is detected to obtain the retardation of the sample (Japanese Patent Laid-Open No. 4-89553).

Here, in order to measure the intensity of each transmitted light, a light receiving element is provided for each polarizer and combination of the polarizers. Therefore, a plurality of light receiving elements are required,
Measurement at the same location is difficult. Therefore, for samples with a small area and non-uniform thickness, or samples with non-uniform retardation, sandwich the sample between conventional polarizers and analyzers, rotate the sample, and then adjust the transmitted light intensity and rotation angle. Since the measurement position is different from that for obtaining the foundation, there are problems such as different numerical values.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to enable measurement at the same place as much as possible by selecting the transmitted light intensity of a minute area and to calculate a more accurate value.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a plurality of small polarizing elements are arranged in a plane by changing their azimuth angles little by little to form one polarizer. The orientation of the polarizing element of the part corresponding to the polarizer is arranged opposite to that of the polarizing element of the polarizer, the sample is placed between them, and the measuring light is radiated from the polarizer side. The output obtained from each polarizing element is detected by the area sensor, and the relational expression with the azimuth angle of the polarizing element is calculated as the intensity of the transmitted light of the polarizer, sample, and analyzer from the azimuth angle of the corresponding polarizing element. However, the birefringence measuring device is characterized by comprising a data processing device for determining the retardation of the sample, in which the polarizing elements having different azimuth angles are arranged in a fan-shaped radial pattern around the central part, and Common measurement (coaxial with the center) It is characterized in that it has configured to illuminate a bundle.

[0007]

In the past, since the light receiving area of each sensor was large, a certain area was required on the measurement surface (measurement point) of the retardation. When the retardation varied depending on the measurement site on the sample, the accuracy was lower than that in the offline case.

In the present invention, an area sensor is used as a light receiving element instead of providing a plurality of light receiving elements. The area sensor has approximately 200,000 light receiving element elements in one element, and by using this, it is possible to measure the transmitted light intensity in a very small area. Utilizing this, multiple small polarizing elements are arranged collectively on one plane with slightly different azimuth angles, and as a single polarizer, a portion corresponding to each polarizing element of the polarizer with the same configuration. Of the polarizing element of the polarizer is arranged in parallel with the polarizing element of the polarizer, and the sample is placed between them, and the output from each polarizing element of the analyzer is received, and the sensor The transmitted light intensity is obtained from each part, and the retardation is obtained. Therefore, according to the present invention, each measurement can be performed at a distance closer to that in the related art, and thus more accurate retardation measurement can be performed.

[0009]

FIG. 1 is a schematic configuration diagram of a birefringence measuring apparatus according to an embodiment of the present invention, and FIG. 2 shows a configuration example of a polarizer / analyzer in the apparatus of FIG. In FIG. 1, (1) is a data processing device, which controls the measurement operation and processes the data of the detection result of the sensor unit. (2) is an illuminating device (light source side) that irradiates a sample with a measurement light beam in a measurement head that performs photometry of detection data of birefringence measurement, and forms a parallel light beam with a required cross-sectional area from a white light source The optical system (condensing lens or mirror, collimator, light beam diaphragm), wavelength selection filter, and the like.

(3) is the detection side of the measuring head, which is composed of an analyzer, a sensor for detecting the transmitted light intensity, and the like.
The wavelength selection means may be provided on the detection side instead of the light source side, for example, in the middle of the analyzer and the sensor. Reference numeral (4) is a measurement sample, for example, a sheet that is running online in a production line of polymer flume or the like, but may be a sheet that is cut into an appropriate size from an original sheet.

Reference numeral (5) is a guide table for scanning the measuring head in the width direction of the measuring sheet, and although not shown, the light source side (2) and the detecting side (3) are in a fixed relationship. It is equipped with a drive mechanism and the like for keeping the above-mentioned and reciprocating in the width direction. (6) is a monitor display device for displaying measurement results. 2 is a configuration diagram of a main part of the present invention forming a part of the apparatus shown in FIG. 1. (11) is an optical element (glass fiber bundle or collimator lens or the like) of a projection unit of irradiation light, and (12) is Polarizer, (4) is a measurement sample, (13)
Is an optical element on the detection side, (14) is an analyzer, (1
5) is an area sensor, for example, a two-dimensional CCD sensor).

The polarizer (12) and the analyzer (14) respectively form or dispose small polarizing elements having mutually different polarization directions in a plurality of fan-shaped regions formed by equally dividing a circle into a plurality of circles. Composed of a polarizer (12)
And the center (O) of the analyzer (14) is on the axis (L) of the measurement light beam, and the small polarizing elements that correspond to each other are arranged in a parallel Nicol relationship. (In the figure, the polarizer (12),
The diagonal direction of the small polarization element of the analyzer (14) indicates the polarization direction of the element. ) The measurement luminous flux is as shown in Fig. 2.
The polarizer (12) and the analyzer (14) are irradiated coaxially with the center of the polarizer (12) from the side of the polarizer (12) and the sample (4).
The light that has passed through the
It is taken into 5). The area sensor (15) produces a detection output according to the taken transmitted light intensity.

In this embodiment, the area sensor (15) is
For example, a CCD camera is used, but other types of 2
It may be a dimension sensor. The detection output of the sensor (15) can read the output of an arbitrary two-dimensional position, and the read output is A / D converted at fixed time intervals, taken into the memory of the data processing device, and incorporated in the data processing device. According to the program, the retardation value is calculated, displayed, printed out and other processes are performed. An image memory is used as a memory for capturing and processing.

Since it is known to which part of the sensor the transmitted light intensity obtained from the small polarization elements of the respective polarizers and analyzers corresponds, which portion of the measurement light beam (that is, each small polarization light) when the detection output is read out. You can choose which part of the device) you want to get information about. The read-out location of the sensor can be arbitrarily specified, and the range of the read-out location can be determined by selecting the number of pixels to be used and the center of these pixels (see FIG. 3). Strength is instantly required. Since the storage position of the data of each pixel is known even after the reading into the image memory, it is possible to select the data to be used for the measurement within the range of the fetched data.

If the transmitted light intensity for each small polarization element at the center of the sensor centering on the optical axis is obtained, the smallest retardation can be obtained. For example, in the past, the sensor area was, for example, about 5 mm × 5 mm, so it was difficult to measure a measurement area of 5 mm × 5 mm or less. On the other hand, in the present invention, even if the same area is captured, one pixel Has a resolution of, for example, about 10 μm × 10 μm, and it is possible to measure the retardation in this minute range.

[0016]

According to the present invention, 1) By using a two-dimensional sensor as a light receiving element,
It is possible to measure the transmitted light intensity in a very small area and to measure the retardation more accurately. 2) Since the data for an arbitrary location can be selected from the outputs of the two-dimensional sensor, the size of the measurement point on the sample can be easily set and changed. 3) Since only one measuring light beam is required for a plurality of small polarization elements, the configuration of the optical system can be simplified.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a birefringence measuring apparatus according to an embodiment of the present invention.

2 is a main part configuration diagram of the apparatus of FIG. 1. FIG.

FIG. 3 is an explanatory diagram of a detection operation of a sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU 2 Illumination device 3 Detection part 4 Sample 5 Table 6 Monitor display device 11 Projection optical element 12 Polarizer 13 Light receiving optical element 14 Analyzer 15 Area sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kura Tomita 4-3-1 Jōkoji, Amagasaki City, Hyogo Prefecture Kanzaki Paper Mill Kanzaki Mill

Claims (2)

[Claims] 1. A plurality of small polarizing elements whose azimuth angles are gradually changed from each other are collectively arranged on one plane to form one polarizer.
In the same configuration, the analyzer is arranged so that the orientation of the polarization element of the part corresponding to each polarizer of the polarizer is parallel to the polarization element of the polarizer, the sample is placed between them, and from the polarizer side The area sensor senses the output obtained from each polarization element of the analyzer by irradiating the measurement light, and determines the polarization direction of the polarizer, sample, and analyzer from the azimuth angle of the corresponding polarization element. A birefringence measuring device, comprising a data processing device for calculating a relational expression with respect to an azimuth angle of the sample and obtaining a retardation of the sample. 2. Polarizing elements having different azimuth angles are fan-shaped radially arranged around a central portion, and a common measuring light flux is irradiated around the central portion (coaxial with the central portion). The birefringence measuring apparatus according to claim 1, which is characterized in that.