DE4210304A1 - Birefringence determn. esp. by on=line process - by measuring intensities of several light beams of different polarisation directions and calculating light propagation retardation in sample from measured data etc. - Google Patents

Abstract

A birefringence determn. process comprises either (A) measuring the intensities of several light beams of different polarisation directions, after transmission through a sample of known refraction direction, and calculating the light propagation retardation in the sample from the measured data; or (b) measuring the intensities of three beams of different polarisation directions, after transmission through a sample and then calculating the retardation and the main refraction direction of the sample from the measured data. Birefringence measurement appts. comprises a detection system for measuring, after transmission through a sample, the intensities of three or more light beams of different polarisation directions and an operating system for calculating retardation and the main refraction direction from the output of the detection system. USE/ADVANTAGE - The processes are used for determining birefringence e.g. of a high polymer film or plate such as a phase contrast film for a LCD. They allow esp. on-line measurement of retardation variation along the material travel direction in a short time without requiring rotation of the material or the detection system.

Description

The present invention relates to a method and a device for determining the birefringence z. B. a method and apparatus for determining the Slowing down and the direction in which the refractionin dex is greatest (hereinafter referred to as "main break direction ") of a film or a plate ei nes high-polimer material such. B. a Phasenkon Trastfilms for a liquid crystal display and in particular a method such as a device for determining the Birefringence, which are suitable in a manufacture process of films or plates.  

The determination of birefringence is often considered simple Method for measuring an optical anisotropy of a transparent or translucent material used.

So far, the method that normally exists for Determination of the birefringence of a plate-shaped Ma terials is used, from the following steps: Pla decorate a sample between a polarizer and a Analyzer operating in a predetermined polarization are arranged directional relationship to each other (in parallel or vertical NICOL'S relationship), causing the Sample a relative rotation with respect to the polarizer and the analyzer and the incident optical axis describes and determining the deceleration of the curve, the main direction of refraction and the like. In this method however, it was a limiting factor in shortening the Measuring time to determine the intensity of the transmit light, that they are executed for a full turn had to become. Also, the adjustment and maintenance the moving parts of the rotating mechanism be had to be used, needed and this created additional Expenditure. For these reasons, it was felt that the On-line measurements on the production line difficult would be.

The object of the present invention is a method and a device for determining the change in the Slowdown and the like to create in a movie or in a plate-like material along its Progress direction takes place, the primary for it is meant to be a measurement during the production pro on a movie or a plate that's made of high polymärmaterial are made to make.  

It is needless to say that it is not just for on-line Measurements are suitable, but also for efficient Off-line measurements in front of, inter alia, slowdown, the is taken with a sample cut across to or along the progression direction of the sample.

In the apparatus of the present invention Proposed means consisting of two or more pairs of Polarizers and analyzers exist in parallel Eler or vertical NICOL'S arrangement with the Polari direction of each pair individually variable and a means for determining the intensity the light that passed through the analyzer when the Sample is lit and that between the polarizer and wanders through the analyzer, the polarisa tor is illuminated with a luminous flux, the unit in wavelength, and means for calculating and determining the slowing of the sample or both the slowing down and the main direction of refraction of the Sample from the direction of polarization and the determinate th intensity of each transmitted light.

The deceleration value at a certain point in the Sample can be obtained by arranging the individual elements of the Transmitted means for determining the intensities Light that through a variety of polarizers different in polarization direction along the off direction of the sample has passed and testing the determined expenses of the individual elements in such a way that the elements are the same Point on the sample to be determined.

The deceleration value at every two-dimensional point On the sample, by arranging a plurality of An regulations of the abovementioned means of determination transverse to  Progressing direction of the sample can be obtained by the sample widthwise and relative to a set of Is scanned or by placing a Variety of units of means of determination in one Matrix arrangement has arranged.

As an embodiment of this invention, the below to be described in detail with reference to an off example with three or more sets of polari and analyzers that are different in their pola direction and which are in a parallel NICOL'S Arrangement are arranged to be described.

In this case, the intensity of the light, the is transmitted through the analyzer, I (πi), through the following formula represents:

I (R i) = A 2 {1 + (1/2) * (C-1) sin 2 2 (R i -φ)} (1)

C ≡ cos (2 π R / λ). (2)

in which
R is the slowing down value of the sample,
A is the amplitude of the linearly polarized wave falling on the sample,
λ the wavelength,
Ri the azimuth angle of the polarizer and the analyzer against the reference direction of the sample (MD direction),
Φ is the azimuth angle of the main refraction direction to the sample reference direction (MD direction), and
i is the serial number of the set of polarizer and analyzer, where i is 1 to n,
indicates.

Generally, the distribution of I (Ri) is as shown in FIG. 1, where Ri is collectively described by R.

The result of partial differentiation on both Pages of Equations (1) to A and C are as follows:

∂ I / ∂ A = 2 A {1 + 1/2 * (C-1) sin 2 2 (R i - Φ) (3)

∂ I / ∂ C = 1/2 · A² sin² (R i - Φ) (4)

If in the following matrix B of functions

set the correct input values to P = (A0 + C0) become,

e = - (B ^t B) ^-1 B ^t S (6)

can be calculated, where S is a matrix of the left over lasting differences. Then in the following formula

P = P + e (7)

the same calculation with (P + e) repeated with one new input value performed until a convergence condition is met. Although in the formula (1) the value Is still unknown at this time, the Value Φ treated as a known value in cases A and C. and determined as the convergence value.

Specifically, if the values A and C are out of the first certain data I (Ri) are calculated, the above cal with the value Φ, in each case by a 1 ° between 0 ° to 90 ° varied, performed to the values A and C to determine each 1 ° value of R, and the values Φ0 of Φ become minimal if the sum of squares stays differences between the given values and taken from the calculated values, and is considered to be opti taken.

Therefore, the value of R is the value obtained by using the value C corresponding to the value Φ0 when using the formula (2) is determined, the desired slowing of the sample.

If the values Φ and R from the specific data I (Ri) to be determined for the second time and further, is the Time needed for the calculation, shorter if the values Φ and R are determined in the same way with the range of Φ being in a range of ± 5 ° is varied, where Φ0 from the previously determined Test data is determined as the center and also the Varia  tion of the values Φ and R in a manufacturing process for Movies or records with the passage of time become more and more accurate be true.

With the target values of R = 100 nm and Φ = -10 ° and the Number of dates 3, 4, 5, 6 and 9, became a simulation carried out, with 180 ° were divided equally and the Polarization directions of the polarizer of the analyzer were determined accordingly. The result is in table (1) shown.

As can be seen from the tabulated data was the result is abnormal if the number of dates was 4, but since even in this case the result is the same as in the other cases, except when the division angle was 45 °, is only a number of more than 3 dates necessary. It can certainly be said that enough Exactly can be obtained if the number of dates is 5 or more.

Table 1

Since the result of the measurement by means of birefringence method can be obtained on-line, the received Result back to the high polymorph film production line  be guided to control the speed of extension to process control such. B. the control of Birefringence properties of the film.

Other features and advantages of the invention will become apparent from the following description of a preferred Embodiment of the invention, with reference to the lying drawing is explained in more detail. Showing:

Fig. 1 shows an exemplary angular distribution of the intensity of a light which has passed through an analyzer, when the polarization direction of the crystallizer Analy rotates a full circle in parallel NICOL'S arrangement for explaining the operation of the direction before the present invention,

FIG. 2 is a perspective view of a first embodiment of the present invention; FIG.

Fig. 3 is a system diagram which a monitoring device for measuring the Prior Doppelbre according to a second example of the present exporting approximately OF INVENTION dung shows

Fig. 4 is a view showing the arrangement of the individual components of the photometric part of the apparatus shown in Fig. 3,

Fig. 4 is a view showing the arrangement of the individual components of the photometric part of the apparatus of Fig. 3,

Fig. 5 is an illustrative representation of an arrangement, the polarizers and Analy of the apparatus of Fig. 3 catalysts,

Fig. 6 is another illustrative view illustrating the arrangement of polarizers and analyzers in the apparatus of Fig. 3;

Fig. 7 is a view showing the constructive Kon tion of the filter in the Vorrich processing of FIG. 3,

Fig. 8 is a view showing an example of use of the photometric part of the apparatus of Fig. 3,

Fig. 9 is a view in the. 3 moves the mechanism of the photometric part Before direction of FIG.

Fig. 10 is a schematic structural view of a device as a third exemplary implementation of the present invention from,

FIG. 11 is a detailed view of polarizers and analyzers shown in FIG. 10; FIG.

FIG. 12 is a measurement chart showing an example of the result of measurement of doping refraction when using a device according to FIG. 10.

Fig. 2 is a schematic diagram showing an on direction according to a first embodiment of the prior invention. Reference numerals 1 , 2 and 3 denote polarizer pairs (a polarizer and an analyzer), the lower polarizers and the upper analyzers. Both are elongated and the longer side is dimensioned a little larger than the width of the band 4th Reference numerals 5 , 6 and 7 denote strip-shaped light sources placed below each pair of polarizers. On each analyzer, capacitors 15 are arranged at fixed intervals and each of them has attached thereto the end of an optical fiber 8 and the other ends of the individual optical fibers attached to each pair of polarizers become in a row in the same order as summarized on the analyzer. The images of the ends of this series of optical fibers are printed on a linear photosensor, such as a photo sensor. B. a CCD 9 , 10 and 11 are formed. The reference numeral 12 denotes a computer for controlling the apparatus and data processing of the detected result of the measurement, the reference numeral 13 is a memory.

The computer of the construction described above serves the following control functions. With a center-to-center distance between two adjacent polarizers such as D and a propagation velocity of the trajectory such as V, the time taken for a given point of the trajectory to travel from one polarizer A to the next is T = D / V. One output from the CCD 9 is read, and another output from the CCD 10 is read a time T times later, and yet another output from the CCD 11 is read a different time T later, and these read data are read in the Memory 13 stored. Thereby, pieces of data due to the intensity of the transmitted light I (R ₁ ), I (R ₂ ), I (R ₃ ) are obtained from a plurality of points on a transverse line on the track. With these data pieces, a main refraction direction Φ and a deceleration R at a point on a transverse line on the trajectory can be calculated by taking the above expression from the data I (R ₁ ), I (R ₂ ), I (R ₃ ), which is obtained for the same point with mutually corresponding longitudinal length of the Polarisato renpaare 1 , 2 , 3 (web width), and the procedure is repeated at a plurality of points on a transverse line on the track and the result stored in the memory 13 . As the trajectory moves a little while this process is being performed, the procedure described above is repeated, and values relating to the distribution of anisotropy along the width of the trajectory are taken at a particular fixed longitudinal interval.

Since neither the pair of polarizers, nor the web in This arrangement must be rotated is the mechanism the device is very simple. Since no rotation to Measurement of birefringence at one point is needed and the measurement takes place with a single measurement procedure can, the measurement can be done efficiently and It is possible to take continuous measurements at specified times Intervals on a long track with high speed ability to take off. It is also possible, Measurements in a short period of time with a variety of The webs of an automatic Probenzuführmechanis mus be taken.  

Fig. 3 is a schematic diagram of the system construction of a birefringence measuring apparatus as a second embodiment of the present invention, and Fig. 4 is a diagram showing an arrangement of the photometric portion of the apparatus of Fig. 3.

In Figs. 3 and 4, numeral 101 denotes a photometric part, 103 a filter part, 104 a polarization part, 105 a sample part, 106 an analyzer part, and 107 an optical detection part, all of which are formed as lattice panels.

The light source part 102 is made up of minute light sources and a condenser lens for each of them arrayed in the X and Y directions. The minute light sources are implemented as a surface light source masked by slits, as minute point light sources, or as one or more light sources that are divided by optical fibers or slits.

The reference numeral 102 designates a light source control part for controlling the light emission intensity and the light emission period of the light source part 102 . Continuous emitting light is sufficient if the object (web) to be measured is stationary when checking for outputs from photometric parts, when the intermittently moving web is stopped or when the speed of the web is relatively slow ( less than 1 m / sec.), but if the speed of the web is more than a few m / sec. It is preferable to perform checking synchronously with an intermittent light emitting system. The period of a cycle of light emission and its interruption may be decided depending on the moving speed of the web which can be measured and the spatial measuring precision required and the like. For this control, a light source control program 113 d is stored in the data processing program memory 113 .

A single filter 103 transmitting light of a given wavelength will suffice if the light to be measured is at a single wavelength, but if the light to be measured includes a plurality of wavelengths, it is possible Lich to provide a filter having separate zones, each with a transmission wavelength as shown in Fig. 7 (A) or (B), z. B. for selective Be use according to the wavelength of the light to be measured ge. It is also possible to keep more than one photometric output stored according to the different wavelengths in order to store it for the purpose of determining the slowdown required during data handling.

The polarizer 104 and the analyzer 106 are divided into small zones in matrix-wise X- and Y-direction and each zone has in this arranged Polarisationselemen te K, L or M have different polarization directions. For example, the polarization element K has the polarization direction + 20 °, L the + 45 ° and M the + 70 ° counterclockwise from the X axis or from the main direction of refraction accordingly. Needless to say that it is advisable to increase the number of polarisati onselemente z. B. more than 3 (K, L, M, N. ..), In order to divide the polarization directions finer thereby, to magnify the accuracy of the measurement ßern.

Fig. 5 shows examples of the arrangement of polarizers and analyzers. In the example (A), the elements are arranged in the direction of polarization in the X direction, and in the Y direction, the polarization direction of the ordered elements changes periodically, in the example (B), elements are arranged in polarization direction in the Y direction and X direction changes the polarization direction of the arranged elements periodically and in the example (C), the polarization direction of the arranged elements changes periodically in both X and Y directions, and many other types of arrangement are conceivable.

In Fig. 6 examples of the arrangement of elements of polarizer 104 and analyzer 106 are shown in different polarization directions in which sets of Po larisatoren and analyzers (K, L, M, N) are arranged in a matrix in the X and Y directions. In (A) of Fig. 6, the polarizer plates and the analyzer plates have their faces formed of a polarizing material and parceled for each polarization direction into rectangles and in (B) polarizers K, L, M, N are formed as circles and in X and Y directions arranged in pairs of K, L, M, N. In both (A) and (B), in play, each adjacent two longitudinal and lateral rows are rectangularly parceled according to the polarization directions and as can be seen from the rectangles highlighted above, pairs of K, L, M, N educated. In (C) circles are well arranged in X and Y directions and equally divided into four, each pair representing K, L, M, N.

In any case, the polarizer 104 and the analyzer 106 are identical in their construction and the corresponding pitches are formed by elements identical in polarization direction.

Referring again to Figs. 3 and 4, the sample S passes between the polarizer 104 and the analyzer 106 , but the sample portion 105 is provided with a corresponding sample guiding mechanism so as to maintain an appropriate distance between the sample and the polarizer or analyzer remains if the surface of the train should fluctuate.

The optical detection part 107 is divided into matrices in X and Y directions and consists of two-dimensional fields of photodiodes or two-dimensional CCD photosensors.

Reference numeral 108 represents an input data processing part in which the signals detected by the optical detecting part are read in at an appropriate time interval and input to the data processing part after conversion into digital signals. Reference numeral 109 denotes a sample position indicating signal apparatus which generates a pulse signal at each time point at which the disk makes a slight movement equivalent to one element or a set of three elements (K, L, M, N) in the Y direction. The sample position indication signal is generated by processing the pulse signal when the web is formed on the web feed roller on the production line of the plate so as to measure movements around a predetermined distance.

Reference numeral 111 denotes a bus data the data processing part, 112 a CPU, 113 a program memory, which has a system program 113a stored therein for controlling the apparatus as a whole, a Probenzuführprogramm 113 b, and the like. 114 is an information memory, the memory having an input buffer 114 a for temporarily storing the measured data taken from the input data processing part, has a task buffer 114 b for storing the data already processed for display and / or for storing and data memory 114 c for storing various forms and basic data, which are needed for the calculation. 115 denotes an image display such. B. a CRT and 116 a recording device such. For example, a printer or an XY recorder.

Fig. 7 shows an example of a construction of a wavelength selection filter which is used when performing birefringence measurements by means of a plurality of wavelengths for a sample, or when the same is done by switching the wavelength according to the type of sample: (A) a case in which narrow filters in the Y direction along the X direction correspond to their transmitted wavelengths λ ₁ , λ ₂ ,. , , are angeord net, while (B) is a case in which filters are arranged narrow in the X direction in the Y direction according to their runaway wavelength. In both cases, the width of a parcel is chosen according to the polarizer and analyzer, namely W1 and W2. If W1 = W2, both can be used by simply changing the direction.

Fig. 8 shows an example in which the above-mentioned ele ments 102 to 107 are integrated. The light source 102 , the filter 103 and the polarizer 104 are integrated as a unit using the shelves 117 , 118 , etc., while the analyzer 106 and the optical detection unit 107 are integrated as another unit and both units are in mutually corresponding positional relationship , In order to prevent both units from being contaminated by the sample, each unit may preferably be provided in a protective box or with transparent protective covers 90 on the sides facing the sample.

Each unit of light source 102 , filter 103 , Polarisa tor 104 and analyzer 106 is connected to z. B. the following individual, keitlichkeitsgleichiegenden means provided. The sensitivity of each optical sensing element corresponding to each unit must be adjusted to equalize the output of the analyzer for detecting the intensity of the transmitted light in the case of the absence of a sample, and a detection output I0i is stored.

When the lamp has been changed as a light source or after being used for measurement for a predetermined period of time, the transmitted light intensity of the analyzer in each unit must be detected, and the ratio of the then detected output Ii to the initially detected and stored detection output I0i,
Ki = 0i / Ii
must be stored as a calibration factor for use if the unit is later used to compensate for the sensitivity. This calibration factor Ki must be determined again each time the light source lamp has been replaced or if deemed necessary.

Fig. 9 shows an embodiment for cases in which it is considered necessary to make the photometric unit movable in width so as to cope with plates which are to be measured and have grown in width by several meters wherein (A) is a plan view, (B) is a frontal view, and (C) is a side view along the side AB. Reference numeral 120 denotes a unit above the plate to be measured (unit 1), and reference numeral 121 denotes another unit below it (unit 2), these units are mounted on frames 122 and 123, respectively. Reference numerals 124 and 125 denote the supports on which the unit 1 slides, while reference numerals 126 and 127 denote the supports on which the unit 2 slides; these supports are measured by support units 128 , 129 on both sides and outside the sample should be, stand, support. In order to move the photometric unit 120 along the width of the sample to be measured, each of the frames 122 , 123 must be provided with a drive, or the support units 128 , 129 must be provided with a drive which together with straps and Roles represents a driving mechanism. In this case, the seitwärtige positional relationship between the unit 1 and the unit 2 must be maintained when they are moved and for this purpose the drive motors must be operated for both phase-locked or it must be used a pulse motor. It is also possible to use one of the moving beams 124 , 125 and one of the other pair of movable beams 126 , 127 , each provided with a gear drive mechanism, and to use a single motor to synchronize these gears.

.. The embodiments of the invention described above with reference to Figures 3 to 9, have the following advantages:

• 1. Data at any point of the sample measured It should be possible to genom at any time be men.
• 2. It can efficiently ge a profile along the width be measured.
• 3. The measurements can be done efficiently along the cross direction as well as along the longitudinal direction of the sample be carried out and two-dimensional measurements (transverse and longitudinal) are also possible.
• 4. Multi-channel positioning (adaptation to several opti Axis) is feasible.
• 5. The local relationships to the measurement can be more accurate be true.
• 6. Optical detection and reading can simul tan be carried out. Optical detection of the Intensi of the transmitted light, checking and storing of data in the memory are together with the reading of stored data and processing (calculation the slowing down and the main direction of refraction, sign NEN of the intensity of the transmitted light in one Distribution curve and broad profiles of demands samung etc.), image representation, etc. possible.
• 7. There is the possibility of a random selection of intervals between adjacent test positions in Units of interval intervals.  
• 8. The arrangement of the photometric parts is unified and with greater efficiency.
• 9. The data used to determine a two-dimensional len distribution may be required by testing effi be earned.
• 10. Reducing the size and weight saving of photomotor part.
• 11. Good maneuverability and durability.
• 12. Serviceability, Easy Repair and Er settability of parts.
• 13. Improvement of productivity, cost benefits ratio and upgradeability through unification chung.

Fig. 10 is a schematic view showing a device for measuring the birefringence as a drit th embodiment of the present invention, which contains a sample portion 201 through which the sample S passes, a light source 202, a Fil terteil 203, a Polarisierteil 204 an analyzing part 205 , an optical detector 206 for photoelectrically converting the intensity of the light passing through the analyzer step.

The light source 202 includes a retaining plate 220 , which in itself a plurality of z. B. 5 to 6 small light sources 221 , 222nd , , with their centers on the same circumference at approximately equal angular intervals.

As shown in plan plan view of Fig. 11 (A), the parallel light quantities L 1 , L 2 . , , L 6 identical in intensity and cross-sectional shape and are radiated downward in Fig. 10. Instead of using separate light sources, it is possible to use dish-shaped or annular light sources, and by the additional use of converging systems, such as converging lenses (or mirrors) and converging holes (or slits), a large number of parallel light beams can be taken out. It is also possible to use a converging system to converge the light from a single light source and split it into light beams of a proper diameter and then take out the required number of parallel light beams by means of a proper number of optical fibers.

The filter part 203 may be a simple filter plate or formed by embodying filter elements in a holding plate at positions corresponding to the respective individual light beams.

The polarizing part 204 and the analyzing part 205 have, as shown in plan views, Figs. 11 (B), (C) respectively, in holding plates 240 , 250 polarizers 241 , 242,. , , and analyzers 251 , 252,. , , at positions corresponding to the individual optical axes already in itself and the polarization directions of the polarizers of the polarizing member 304 are each 30 ° from each other. For example, when the polarization direction of the polarizer 241 is 0 °, the polarization directions of the polarizers 242 are . , , 246 + 30 °, + 60 °, + 120 °, and 150 ° counterclockwise. Each polarizer of the analyzing part 205 has the direction of polarization determined such that the polarizers on the same optical axis are in a given relation with respect to the polarization direction, e.g. In parallel NICOL'S relationship.

The sample part 201 (not particularly shown) is provided as a measuring space having a narrow gap through which the web continuously passes from the production conveyor belt. If the width of the web to be measured is small, this measuring space may be closed at both lateral ends, but it is preferable to keep a lateral end open, which facilitates the setting of the photometric part relative to the web the photometric part can be gescho ben to a random transverse position of the web during the transverse scanning of the photometric part or the like .. Therefore, in a case where the photometric part is integrally molded, it is preferable to provide the cantilever type holding mechanism in which the elements from the light source part to the polarizer part (A) and the analyzer part and the detecting part (B) are provided. be held on each end of the track.

It is possible to have a marking mechanism in the sample part of an ink jet type or the like for printing Measuring position identification marks at positions with the measuring points of the web to be measured, kor respond (eg at the longitudinal ends of the web or at the points at which is measured) in given Abstän or time intervals or according to a Zeitge testing the data to be measured. It is also possible, identification codes according to these printed markings on the web to the detected Signal checking data to give the data processing enable. This will be the tabulation of the measured  Enable data, taking out and processing or the like. Of the desired data from those measured and were stored, the repeated checking of ge measured data and the like.

In the detection part 206 , detection elements 261 , 262 are arranged on a support plate 260 corresponding to the respective optical axes. As detection elements z. B. photoelectric conversion elements such as solar cells len, photodiodes and CCD elements used.

A photometric part for detecting a variety of Amounts of light, the above light source part, the Filter part, a polarized part, a sample part, an ana lysing part and a detection part contains, as a individual unit are formed, with a space for through management of the railway. It is possible to shrink the photometric part as a whole, the possibility of standardizing the design and the production of elements from which the photometric Part is as well as the composition of the Ju bullet and checking etc. of the photometric part. An improvement in precision and productivity takes place likewise. Also, the unification allows ment the treatment of the photometric part as a Individual detection option and this allows an In stallation of this in a production plant, esp the instrumentation and the scanning of Meßpunk th, which are arranged across the web, (eg Scanning the photometric part), further protect one DE jacket against the temperature, atmosphere, etc. in the factory environment, improving efficiency the installation work, especially the installation the scanning unit for measuring the points across are arranged over the web.  

The size of this photometric unit (size of pola irradiated light rays in all necessary directions) can be up to 10mm in diameter or square but continuous for approximate on-line measurements it may be 2 to 3 cm (in Diameter or square).

The following are data processing and control party le, whose main parts separate from the factory floor environment can be installed and, if this is the case, the transfer of ge measure data, control commands, etc. to and from that photometric part made by wires or wireless electrical signals can happen, or by opti shear communication by optical fibers or the like.

Reference numeral 207 denotes an input processing part which amplifies each detected output from a detector 206 and outputs it after A / D conversion. These elements and the transmitting part may possibly be attached to suitable detection ends corresponding to the system structure of the measuring device as a whole. Reference numeral 280 is a data bus line of a data processing and control part, and reference numeral 208 denotes a CPU.

A program storage section 209 having a fixed (or semi-fixed) memory such as ROM or EPROM for storing various control and arithmetic programs includes a storage area 209 a for a control program for controlling the device as a whole. In spite of an overall control program of the storage area 209a may be programs for things such as placing an Meßpositions- identification mark on the web and for Filterau stausch and the like with separate Pro. Be provided. The Programmspei cherteil 209 further includes a memory area 209 for a test program that teaches the testing of the data from the detected output, a memory region 209 c for an arithmetic program for performing the necessary ver various calculations from the measured data stored in the memory 210, the bottom will be described as shown and a memory area 209 d for an output program for outputting the processed data to a CRT 211 , a printer 212 or the like.

As the test program, as described above, such methods may be used in which to check the data from a continuous web coming out of production in a predetermined length or time, or to check a method in the data at a predetermined point on the web (eg where it is marked, irrespective of whether the lane is stopped or moving), and in these cases outputs from the capture elements are checked by an input processing part 207 and the checked data is stored in memory 210 along with the related information such as number of the detection element (eg, the polarization direction) and position of the web, where the measurement was made ge stored.

The above-mentioned arithmetic program is used for various necessary calculations, among others, the calculation of the deceleration, the base data, and the measured data stored in the memory 210 .

The above-mentioned output program is generally used for processing for CRT display, printout, and output control, is checked for displaying the angular distribution of the polarized transmitted light intensity at the time of the output from the detection part, and is stored in the memory 210 for on-screen display. Line continuous display of the variation of the birefringence properties along the flow direction of the web, etc.

The memory 210 is a memory of a memory content of the variable type of the RAMs includes, and areas such as an input buffer memory 210 a for temporarily storing measured data, etc. that are input from a Eingabeverar beitungsteil 207, contains a SpeI cherregion 210 b for calculated data storing the processed data and the like., a Basisdatenspeicherre gion 210 c for storing basic data that are necessary for Because tenverarbeitung and equations and the like., and an output buffer memory 210 d for storing data for the CRT display, the print output and the like Reference numeral 213 is a keyboard input.

embodiment

Measurements were made on a polypropylene sheet (60 μm thick) using the apparatus of the present invention as shown in Figs. 10 and 11 at a web speed of 30 m / min. The test interval was 2 sec, the results are shown in FIG . The test was based on the intensity of the transmitted polarized light in six directions of polarization every 2 seconds. carried out, ie the web moved each 1 m, the deceleration value at the point of measurement was calculated for each test. The se was continued for 20 min (599 samples, track length 600 m) and the result was recorded as a diagram and it was thus possible to measure on-line the changes of the slowing along the direction of travel of the web. The respective representative values determined on the basis of the experimentally obtained data are the following:

Minimum value of deceleration Rmin = 1079.2 Maximum value of deceleration Rmax = 1143.6 Mean of the slowdown rave = 1117.5 standard deviation = 10.5 nm

The main direction of refraction was approximately constant (about 87 °) as shown in the upper half of FIG .

When taking measurements on a stationary orbit from the material was the standard deviation 0.3 nm. The result of the slowdown measurement with the method of the present invention has been achieved showed that the result of the on-line measurements, the currency The movement was sufficiently reliable is. It is possible the interval between the Meßpunk to make 1 to 2 places smaller on the web.

The advantages of the embodiments shown in Figs. 10 and 11 are as follows:

• 1. The measured data used to calculate the Ver slowing down can be ongoing to everyone Date to be obtained. This allows on-line Measurements of birefringence. That's why it's on a pro production line for films or the like possible, the editions ments in the properties of the railway along its river direction.  
• 2. The method and the device according to the invention allow a simultaneous determination of the slowdown and the main direction of refraction.
• 3. With the method according to the invention and the Vor direction, it is possible to store the storage space chern the required amount of plates within prakti to keep their limits without unnecessarily reducing the precision of measurement give up.
• 4. Since the angular distribution of the intensity of the polari transmitted and transmitted light continuously may be the extent of anisothropia Track can be determined as necessary and visually by continuous display of the above distribution be be observed.

The invention can ver in other embodiments ver be wirklicht, without departing from the spirit or spirit essential characteristics to deviate. The present The embodiments are therefore in all respects considered as illustrative rather than limiting, and the protection of the invention will be apparent from the attached Claims for protection instead of the description, and all deviations into the equivalence range of the sayings are expressly included.

The in the above description, the claims, As well as in the drawings disclosed features of the inventions can be used individually as well as in any combination For the realization of the invention in its various embodiments be essential.

Claims (14)

A method of determining birefringence, characterized in that the intensities of a plurality of lights each having different polarization directions and transmitted through a sample of a known direction of refraction are measured, and slowing the propagation velocity (retardation) in the sample calculated as the result of the measured data. 2. Method for Determining Birefringence characterized in that the intensity of three Rays, each with different polarization directions own and are transmitted through a sample, ge measure and the slowing down of the spread speed (retardation) and the main refractive index  calculation of the sample as a result of the measured data net becomes. 3. Device for measuring the birefringence marked characterized by

• Detection means for measuring the intensity of three or more lights, each having different directions of polarization when transmitted through the sample, and
• - means for calculating the deceleration of the propagation velocity (retardation) and the main direction of refraction based on the output of the detection means.

4. A device for measuring birefringence according to claim 3, characterized by

• - means for checking the detected output according to a predetermined program, and
• - Storage means for storing the checked data, wherein the resources with the stored data of the storage means count.

5. Device for measuring the birefringence after egg Nem of claims 3 or 4, characterized by means for on-line display of the angular distribution of the transmit light intensity, deceleration value or the distribution of this.   6. Device for measuring birefringence after egg nem of claims 3, 4 or 5, characterized by a photometric part, which is a light source part, a butt larisatorteil, an analyzer part and a detection part contains, which are formed as a unit. 7. Device for measuring the birefringence according to An Award 3, characterized in that individual elements the detection means along the sample progress are arranged direction. 8. Device for measuring the birefringence according to An claim 7, characterized in that the device for timed review of the issue of each Elements of the detection means depending on the Progression of the sample is arranged so that an Er of expenditure of the same items on the Sample is possible. 9. Device for measuring birefringence after egg nem of claims 3 to 6, characterized in that the detection means arranged transversely relative to the sample are. 10. Device for measuring birefringence after egg Nem of claims 3 to 6, characterized by scanning de means for scanning a photometric part, the the detection means in the direction across the sample lock in.   11. Device for measuring birefringence after egg nem of claims 3 to 6, characterized in that the detection means matrix-like in the locomotion direction and in the direction transverse thereto. 12. Device for measuring the birefringence according to An claim 3, characterized by sensitivity compensation means for each detection element. 13. Device for measuring the birefringence according to An claim 3, characterized in that a plurality of Detecting means in close proximity to each other ordered, and sensing elements of this frontward are provided with wavelength selection means, each because they are different in wavelength, or that some detection means parallel or variable are arranged to each other. 14. Device for measuring the birefringence according to An claim 3, characterized in that a plurality of Detecting means propeller-like as parts of a common seed circle are arranged, wherein the detection Mitmit Tel, which are arranged in the same circle, with Po larisatorelementen are equipped, each vonei have different polarization directions.