JPH08226892A - Measuring equipment of birefringence - Google Patents

Abstract

PURPOSE: To enable high-speed and stable measurement of a value of birefringence of a material to be measured, by calculating values of birefringence in states of parallel and vertical nicols from a ratio between the quantities of measuring light and reference light and by determining the average value. CONSTITUTION: A light flux emitted from a halogen illumination device 10 is made a light of a single wavelength by a wavelength filter 40 and divided into lights of branch fiber parts 51-54 by a multi-branch fiber 50. The illumination light of the fiber part 54 is received 60 and amplified 70 and inputted as a reference light to an arithmetic device 80. The illumination lights of the fiber parts 51-53 are converged 91-93, passed through polarizers 101-103 and transmitted through a birefringent film A, parallel parts 111a-113a of polarizers 111-113 and vertical parts 111b-113b sequentially and the transmitted lights are received 121a-123a and 121b-123b and amplified 131a-133a and 131b-133b respectively and inputted as measuring lights to the arithmetic device 80. The arithmetic device 80 calculates a ratio between the quantities of the measuring light and the reference light, determines values of birefringence in states of parallel and vertical nicols from the relation between a ratio between set quantities of these lights and the values of birefringence and calculates the average value.

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 for measuring a birefringence value of a birefringent film, and particularly in a production line of a polymer film used for a liquid crystal display or the like, on-line where high speed measurement is required. The present invention relates to a birefringence measuring device suitable for measurement.

[0002]

2. Description of the Related Art Generally, when a polymer film is stretched, it has birefringence. By changing the stretch ratio of the polymer film, a polymer film having a desired birefringence value can be obtained. Such a birefringence value is obtained by inserting a polymer film between the polarizer and the analyzer arranged in parallel, changing the relative angular position of the polarizer and the analyzer with respect to the polymer film by a motor, and by illuminating means. It is obtained by irradiating light and measuring the ratio of the maximum value and the minimum value of the intensity of the light transmitted through the polymer film. Incidentally, such a technique is disclosed in, for example, Japanese Patent Laid-Open No. 4-218751.

[0003]

However, the present inventor has found that the above-described birefringence measuring device has the following problems. That is, since the relative angular positions of the polarizer and the analyzer with respect to the polymer film are gradually changed by the motor, it takes a lot of time for measurement. Therefore, online measurement, which requires high-speed measurement, cannot be performed. Further, when the illuminance of the illumination means changes, it affects the specification of the maximum and minimum values of transmitted light intensity,
Stable measurement will not be possible.

The object of the present invention is to solve the above-mentioned problems.
It is an object of the present invention to provide a birefringence measuring device capable of measuring a birefringence value at high speed and stably regardless of the change in the light quantity of the illumination means. The above and other objects and novel features of the present invention will be apparent from the description of the present specification and the accompanying drawings.

[0005]

The outline of the present invention will be briefly described as follows. The birefringence measuring apparatus of the present invention is divided into an illuminating unit that irradiates light, a light splitting unit that splits the light emitted from the illuminating unit, and a first light receiving element that directly receives the split spectrum. A first polarizer and a second polarizer that polarize the other spectrum, and a second light receiving element that receives the other spectrum that transmits the first polarizer and the second polarizer, And a calculation unit that calculates the amount of light transmitted through the first light receiving element and the second light receiving element, wherein the first polarizer and the second polarizer are parallel Nicols and vertical Nicols polarization directions. Have a relationship.

[0006]

[Operation] According to the above-mentioned means, the birefringence measuring device,
A first light-receiving element for directly receiving the light emitted from the illuminating means, a first for setting the polarization directions to parallel and vertical Nicols,
Since the second polarizer, the second light receiving element for receiving the light transmitted through the first and second polarizers, and the calculation means for calculating the amount of light transmitted through the first and second light receiving elements are provided, the calculation is performed. Means calculates a light quantity ratio between the measurement light received by the second light receiving element and the reference light received by the first light receiving element, and obtains a relationship between the light quantity ratio and a known birefringence value in advance to obtain a higher-order function. And approximate
It is set as a reference formula, and the birefringence value in parallel and vertical Nicols state is calculated from the light quantity ratio of the measurement light and the reference light to the unknown DUT by the calculation means, and the average value is calculated to calculate the measured value. The birefringence value of the object is obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. Here, FIG. 1 is a schematic configuration diagram of a birefringence measuring apparatus which is an embodiment of the present invention, FIG. 2 is a characteristic diagram of birefringence value and transmitted light intensity in a parallel Nicol state and a vertical Nicol state, and FIG. FIG. 4 shows a characteristic diagram of the light quantity ratio of the measurement light / reference light and the known birefringence value in the Nicol state, and FIG. 4 shows a characteristic chart of the light quantity ratio of the measurement light / reference light in the vertical Nicol state and the known birefringence value.

In FIG. 1, in the birefringence measuring apparatus, an optical fiber 2 is provided to an illuminating means such as a halogen illuminating device 10.
The relay lens 30 is disposed through the
A wavelength filter 40 for converting the light emitted from the halogen illuminating device 10 into the light of a single wavelength is disposed on the downstream side of the light having a very narrow pass band. Reference numeral 50 denotes an optical branching unit located downstream of the wavelength filter 40 for branching light, for example, a multi-branch optical fiber. The multi-branch optical fiber 50 includes branch optical fiber units 51, 52,
It consists of 53 and 54. A first light receiving element 60 such as a photodiode, a first amplifier 70, and an arithmetic device (arithmetic means) 80 are sequentially connected to the downstream end of the branched optical fiber portion 54.

The branch optical fiber parts 51, 52, 5
Condensing lenses 91, 92, 93 are provided at the downstream ends of 3 respectively.
Are individually arranged, and the first polarizers 101, 102 and 103 are individually arranged on the condenser lenses 91, 92 and 93. Furthermore, the first polarizers 101, 10
The second polarizers 111, 112, 11 on the second and third 103
3 are individually arranged, and the second polarizers 111 and 11 are provided.
Reference numerals 2 and 113 denote parallel portions 111a, 112a, 113a in a parallel state with the first polarizers 101, 102, 103 and vertical portions 111b, 112b, 113 in a vertical state.
Each is equally divided into b.

In addition, the second polarizers 111, 112, 11
The second light receiving elements 121a, 122a, 123a are arranged on the three parallel portions 111a, 112a, 113a, and the vertical portion 1 of the second polarizer 111, 112, 113 is arranged.
The third light-receiving element 12 is provided on 11b, 112b, 113b.
1b, 122b, 123b are arranged respectively.

Further, the second light receiving elements 121a and 122 are provided.
a and 123a have second amplifiers 131a, 132a, 1
33a is connected to the third light receiving elements 121b and 122.
b and 123b have third amplifiers 131b, 132b, 1
33b are respectively connected. And these second
And the third amplifiers 131a, 132a, 133a, 1
31b, 132b, 133b are connected to the arithmetic unit 80. In addition, A is the first polarizer 101, 102, 1
03 and the second polarizer 111, 112, 113 is a birefringent film of the object to be measured.

Next, a method for measuring a birefringence value by the birefringence measuring device having the above structure will be described. First, the luminous flux emitted from the halogen lighting device 10 over the entire visible range is applied to the wavelength filter 40 through the optical fiber 20 and the relay lens 30. Thereafter, the light beam is converted by the wavelength filter 40 into light having a desired single wavelength suitable for measuring the birefringence value. Here, the use of the optical fiber 20 is for cutting infrared rays generated from the halogen lighting device 10 to prevent generation of heat stress, and the halogen lighting device 10 is devised so as not to heat the wavelength filter 40. If so, the optical fiber 20 is unnecessary.

The single wavelength light is then split into a plurality of lights by a multi-branch optical fiber 50 having more branches than desired measurement points. The split lights are guided to the branch optical fiber units 51 to 54, respectively. The light emitted from the branch optical fiber unit 54 is the first light receiving element 60.
Is received, is amplified by the first amplifier 70, and is taken into the arithmetic unit 80 as reference light.

On the other hand, the light emitted from the branched optical fiber portions 51 to 53 is condensed by the condenser lenses 91 to 93 and guided to the first polarizers 101 to 103. Then the light
Birefringent film A, parallel parts 111a to 113a and vertical parts 111b to 113b of the second polarizers 111 to 113.
Sequentially transmitted. At this time, the parallel portions 111a to 113a
The light that has passed through is received by the second light receiving elements 121a to 123a, amplified by the second amplifiers 131a to 133a, and then taken into the arithmetic unit 80 as measurement light.

The light transmitted through the vertical portions 111b to 113b is received by the third light receiving elements 121b to 123b, amplified by the third amplifiers 131b to 133b, and then taken into the arithmetic unit 80 as measurement light. . Here, several kinds of samples whose birefringence values are already known are prepared. However, the birefringence values of these several types of samples shall be distributed in the range of unknown birefringence values to be measured. FIG. 2 shows the relationship between the birefringence value of the sample at a specific wavelength and the transmitted light intensity of the measuring device. According to FIG. 2, the measurement range B is a portion where the change in transmitted light intensity is large with respect to the birefringence value. Further, it is desirable that the samples are evenly distributed over the entire measurement range B.

Then, the sample is used as the first polarizer 101 to 10
3 and the second polarizers 111 to 113, the measurement light and the reference light are measured at the same time, and the arithmetic unit 80 calculates the light amount ratios of the measurement light / reference light for the parallel and vertical states, respectively. . As a result, as shown in FIGS. 3 and 4, the light amount ratio to the known birefringence value when the center wavelength of 500 nm is selected for the wavelength filter 40 in the parallel and vertical states is obtained.

From this, the birefringence value with respect to the light quantity ratio is approximated by a higher-order function to form a reference expression for actual measurement. That is,
In the parallel Nicol state, the following equation (1) is obtained. ^{R1 = 386.58 + 0.31352Lr + 0.0010811Lr 2} (1) Further, in the vertical Nicol state, the following equation (2). ^{R2 = 481.07-0.69440Lr + 0.00101Lr 2 (2} ) In addition, R1, R2 birefringence value, Lr denotes the light intensity ratio of the measurement light / reference light.

Thus, while the unknown birefringent film A is flown in the line, the light quantity ratio of the measurement light / reference light is calculated by the arithmetic unit 80, and the birefringent film A birefringence is calculated by the above equations (1) and (2). Refractive values R1 and R2 can be obtained. Then, the average value (R1 + R2) / 2 of these birefringence values R1 and R2 is output as the final birefringence value, and the birefringence value of the birefringence film A is obtained.

As described above, according to the present embodiment, the relationship between the light quantity ratio of the measurement light / reference light and the known birefringence value is measured in advance, approximated by a higher-order function, and set as a reference expression, Since the birefringence values in the parallel and vertical Nicols states are calculated from the light quantity ratio of the measurement light / reference light to the unknown birefringence film A, and the birefringence value is obtained by calculating the average value thereof, the measurement is speeded up. Online measurement becomes possible.

Further, since the ratio with respect to the reference light is always used as a calculation reference, even if the halogen lighting device 10 deteriorates for a long period of time and the light amount decreases, or if the light amount fluctuates in the short term due to disturbance or the like, the measurement is adversely affected. Never give. Therefore, stable measurement is possible. Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

[0021]

The effects obtained by the invention disclosed in the present application will be briefly described as follows.
According to the present invention, in the birefringence measuring device, the first light receiving element for directly receiving the light emitted from the illuminating means, the first and second polarizers whose polarization directions are parallel and vertical Nicols, and the first polarizer are provided. , The second light receiving element for receiving the light transmitted through the second polarizer and the calculation means for calculating the amount of light transmitted through the first and second light receiving elements are provided, so that the measurement is accelerated and the birefringence value is increased. Since it is possible to perform the on-line measurement, and to accurately perform the measurement while eliminating the error due to the influence of the change in the light amount of the illumination means, even when the illumination means is deteriorated for a long period of time and the light amount is reduced, The birefringence value can be stably measured without adversely affecting the measurement even when the light amount fluctuates in the short term due to disturbance or the like.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram of a birefringence value and a transmitted light intensity in a parallel Nicol state and a vertical Nicol state of a birefringence measuring apparatus that is an embodiment of the present invention.

FIG. 3 is a characteristic diagram of a light amount ratio of measurement light / reference light and a known birefringence value in a parallel Nicol state that is an embodiment of the present invention.

FIG. 4 is a characteristic diagram of a light amount ratio of measurement light / reference light and a known birefringence value in a vertical Nicol state of a birefringence measuring apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 10 ... Halogen illumination device 20 ... Optical fiber 30 ... Relay lens 40 ... Wavelength filter 50 ... Multi-branched optical fiber 51-54 ... Branch optical fiber part 60 ... First light receiving element 70 ... First amplifier 80 ... Arithmetic device 91-93 ... Collection Optical lens 101-103 ... 1st polarizer 111-113 ... 2nd polarizer 111a-113a ... Parallel part 111b-113b ... Vertical part 121a-123a ... 2nd light receiving element 121b-123b ... 3rd light receiving element 131a-133a ... 2nd amplifier 131b-133b ... 3rd amplifier A ... Birefringent film B ... Measuring range

Claims (1)

[Claims] 1. An illuminating means for irradiating light, a light branching means for dividing the light emitted from the illuminating means, a first light receiving element for directly receiving the divided spectrum, and another divided spectrum. A first polarizer and a second polarizer that polarize the light; a second light receiving element that receives the other spectroscopic light that passes through the first polarizer and the second polarizer; A light receiving element and a calculation means for calculating the amount of light transmitted through the second light receiving element, wherein the first polarizer and the second polarizer have a parallel Nicol and a vertical Nicol polarization direction relationship. A birefringence measuring device.