KR101990642B1 - Optical property measuring method and apparatus - Google Patents

Abstract

The transparent portion 12 irradiates the optical film 11 with circularly polarized light as measuring light. The light receiving section 13 has a plurality of types of wavelength plates arranged in the X direction and a plurality of unit light receiving areas which are units for obtaining one measurement value in a region corresponding to each wavelength plate are arranged, And the transmitted measurement light is received for each unit light receiving area in plural kinds of polarization states. While the optical film 11 is transported in the X direction, the measurement light is received in a plurality of unit light receiving areas for each unit measurement area. The Mueller matrix calculator 19a calculates a Mueller matrix of the unit measurement area from a plurality of measured values obtained for the same unit measurement area. The optical characteristic calculator 19b calculates the optical characteristics using the elements of the Muller matrix.

Description

[0001] OPTICAL PROPERTY MEASURING METHOD AND APPARATUS [0002]

The present invention relates to a method and an apparatus for measuring optical characteristics of a transparent film.

2. Description of the Related Art In recent years, display devices using liquid crystal (hereinafter referred to as liquid crystal display devices) have been used as monitors for televisions and PCs. A functional plastic resin film (hereinafter referred to as an optical film) having various optical characteristics such as a polarizing plate, a viewing angle compensation film, and an antireflection film is adhered (adhered) to a liquid crystal panel. Since the liquid crystal display device obtains contrast using the birefringence characteristics of the liquid crystal, the display characteristics of the liquid crystal display device depend on the birefringence characteristics of various optical films to be used. For example, when the birefringence characteristic of the optical film is not uniform over the entire surface of the display screen of the liquid crystal panel, unevenness occurs in the display image. For this reason, the optical film used in the liquid crystal display device is inspected for whether or not it has a predetermined optical characteristic (in particular, birefringence characteristics).

Measurement of optical characteristics such as birefringence characteristics can be performed by, for example, a light source for irradiating a predetermined measurement light to the optical film, a light receiver such as a CCD camera for receiving measurement light transmitted through the optical film, a wavelength plate, Is used. In order to measure the birefringence characteristic at a certain point on the optical film, it is necessary to measure the same point a plurality of times by using measurement light having a different polarization state.

As an apparatus for measuring the birefringence characteristic of such an optical film, for example, a wave plate capable of freely rotating between a light source and a CCD camera is formed, and by rotating the wave plate, an image of the optical film in various polarization states An optical characteristic measuring device for calculating a birefringence characteristic for each pixel on the basis of a change in luminance value of each image of the obtained image group is known (JP-A-2009-229279). It is also possible to form a fine wavelength plate having different phase axes in advance in each pixel of the image pickup device and successively photographing the optical film while moving the optical film in a constant direction so that any measurement point of the optical film is irradiated by using a measurement light having a different polarization state An optical property measuring device capable of obtaining data measured a plurality of times is known (Japanese Unexamined Patent Application Publication No. 2007-263593).

In recent years, along with the increase in the size of a liquid crystal display device, optical films used therefor are required to have large-sized and uniform optical characteristics. For example, a liquid crystal display device of 20 inches requires an optical film of about A3 size. For this reason, a measurement device capable of measuring a large-area optical film is required. When an optical film is picked up and optical characteristics are measured, a telecentric lens is used as an image pickup lens in order to obtain high measurement accuracy. This is because the effect of deformation of the image due to the shift of the focus and the parallax is suppressed to be small. However, since the field of view of the square of the telecentric lens is about 5 cm at most, it is difficult to inspect a large-area optical film such as the A3 size with one field of view. For this reason, in an apparatus for measuring optical characteristics of an optical film, it is necessary to carry out studies for measuring optical characteristics without fail and with high accuracy while moving a measurement position.

In the case of measuring the optical characteristics of a certain measurement position while changing the polarization state of the measurement light by rotating the wavelength plate as in the optical property measurement apparatus of Japanese Patent Application Laid-Open No. 2009-229279, the optical film and the measurement system (light source, It is necessary to capture the measurement position a plurality of times while rotating the wavelength plate. Therefore, in order to move the measurement position, movement and stop of the optical film (or the measurement system) must be repeated to measure the optical characteristics of the large-area optical film, which requires a large amount of time.

On the other hand, the optical characteristic measuring apparatus of Japanese Patent Application Laid-Open No. 2007-263593 can measure the optical characteristic of the optical film while moving the optical film (or the measuring system). However, since a wave plate having different fast axis directions is formed for each pixel, the measurement is performed in units of one pixel. Therefore, the random noise per pixel such as the readout output noise and the dark current noise is directly included in the measured value (pixel value) as an error. This makes it difficult to measure high-precision optical characteristics and deteriorates the reproducibility of measured values. In order to eliminate the influence of the noise and improve the measurement accuracy, it is necessary to measure the same point a plurality of times and average it. Thus, like the optical characteristic measuring apparatus of Patent Document 1, Measurement of characteristics requires a great deal of time.

An object of the present invention is to measure optical characteristics with high precision while relatively moving the optical film and the measurement system without stopping.

The optical characteristic measuring apparatus of the present invention comprises a transparent portion, a light receiving portion, a carrying portion, a Mueller matrix calculating portion, and an optical characteristic calculating portion. The light-transmitting portion irradiates the transparent optical film with light in a predetermined polarization state as measurement light. The light receiving unit has a plurality of kinds of wavelength plates arranged in a predetermined direction, and a plurality of unit light receiving areas, each of which is a unit for obtaining one measurement value, are arranged in a predetermined direction so as to correspond to each of a plurality of kinds of wavelength plates. Each unit light receiving area receives measurement light transmitted through the optical film in a plurality of kinds of polarization states determined by a wave plate. The transfer section moves the unit measurement area in a predetermined direction by relatively moving the light receiving section and the optical film along a predetermined direction when the area corresponding to the unit light receiving area on the optical film is set as the unit measurement area. During this movement, the plurality of unit light receiving areas measure the measurement light transmitted through the unit measurement area. The Mueller matrix calculator calculates a Mueller matrix of the unit measurement area based on a plurality of measured values obtained for the same unit measurement area. The optical characteristic calculator calculates the optical characteristics of the unit measurement area using the elements of the Mueller matrix of the unit measurement area.

The Stokes parameter of the measurement light incident on the unit measurement area is previously measured for each unit light emitting area and the Stokes parameter of the measurement light after passing through the unit measurement area is set as a unit light emission area, It is preferable that the polarization transfer matrix for correlating the parameter to the measured value is previously measured for each unit light receiving area. The Muller matrix calculator calculates in advance a sample measurement matrix in which a plurality of measured values corresponding to the same unit measurement area are associated with the elements of the Muller matrix based on the Stokes parameter and the polarization transfer matrix of the measurement light incident on the unit measurement area , And when the measured values are obtained, calculate the elements of the Muller matrix using the sample measurement matrix.

The light transmittance portion is formed so as to be freely movable along a predetermined direction and the Stokes parameter of the measurement light incident on the unit measurement area is measured by receiving the measurement light at the light receiving portion while moving the light transmitting portion in the predetermined direction in the state where there is no optical film .

It is preferable that the light transmitting portion irradiates the measurement light in a range approximately the same size as the visual field of the light receiving portion. It is preferable that the light transmitting portion irradiate circularly polarized light to the optical film as measurement light.

The light-transmitting portion includes a planar light source that emits light in a non-polarized state from a plane light-emitting surface, a polarizer that adjusts the light incident from the planar light source to linearly polarized light, and a polarizer that converts linearly polarized light incident from the polarizer into circularly polarized light, It is preferable to provide a 1/4 wavelength plate for irradiation. It is preferable that the 1/4 wavelength plate is formed so as to be freely rotatable around the irradiation optical axis of the measurement light.

The light-receiving unit includes a lens for imaging measurement light transmitted through a plurality of kinds of wavelength plates onto an image pickup device, and the lens is an object-side telecentric lens that can consider the optical axis and the principal ray parallel to the object side desirable. The lens may be a bilateral telecentric lens that can regard the optical axis and the principal ray parallel to each other on the object side and the image side. It is preferable that the light-receiving unit is provided with four or more and 40 or less types of wave plates as a plurality of types of wave plates.

It is preferable that the plurality of types of wave plates provided in the light receiving unit are arranged so that the directions of the main axes are different from each other in the predetermined direction. It is preferable that the plurality of kinds of wave plates provided in the light receiving unit have a ground phase amount of 70 degrees or more and 170 degrees or less or 190 degrees or more and 290 degrees or less.

The unit light receiving area is preferably a combined pixel which is composed of a plurality of adjacent pixels and whose average value of the output values of the plurality of pixels belonging thereto is taken as one measurement value. It is preferable that the number of pixels constituting the combined pixel is a square of 2 or more natural numbers and the same number of pixels in the vertical and horizontal directions.

It is preferable that a plurality of sets of the transparent portion and the light receiving portion are provided in a direction perpendicular to the predetermined direction. It is preferable to measure the entire surface of the optical film by moving the set of the light-projecting portion and the light-receiving portion formed in the vertical direction.

The optical characteristic measuring method of the present invention comprises a measuring step, a Mueller matrix calculating step, and an optical characteristic calculating step. The measuring step is a step of irradiating the transparent optical film with light in a predetermined polarization state from the light transmitting portion as measurement light and measuring the transmitted light transmitted through the optical film in a plurality of types of polarization states for each unit light receiving area as a unit for obtaining one measurement value And a measurement value is obtained for each unit measurement area on the optical film corresponding to the unit light receiving area. At this time, a plurality of measurement values measured in a plurality of kinds of polarization states are obtained for one unit measurement area by receiving light while relatively moving the optical film and the light receiving unit. The Mueller matrix calculating step calculates the Mueller matrix of the unit measurement area for each unit measurement area based on the plurality of measurement values obtained in the measurement step. The optical characteristic calculating step calculates an optical characteristic of the unit measurement area using the elements of the Müller matrix.

The Muller matrix calculation step calculates a Muller matrix from measurement values using a sample measurement matrix in which a plurality of the measured values are associated with the elements of the Muller matrix. The sample measurement matrix is a matrix for associating a Stokes parameter of measurement light after passing through a unit measurement area with a measurement value. The matrix includes a polarization transfer matrix preliminarily measured for each unit light emitting area and a unit light transmitting area on the light emitting part corresponding to the unit light receiving area Are calculated in advance using the Stokes parameters that have been measured in advance.

According to the present invention, it is possible to measure the optical characteristics of the optical film with high precision while relatively moving the optical film and the measurement system without stopping.

1 is a perspective view schematically showing an optical characteristic measuring apparatus.
2 is an explanatory view showing a light-transmitting portion.
3 is an explanatory diagram showing a light receiving section;
4 is an explanatory view showing the axial directions of the respective wave plates and the polarizing plate of the divided wave plate;
5 is an explanatory diagram showing an aspect of a coupling pixel CP;
6 is an explanatory view showing an aspect of a unit measurement area (E);
Fig. 7 is an explanatory view showing an aspect of a unit light emitting area F. Fig.
8 is a flowchart showing an aspect of obtaining a polarization characteristic by an optical characteristic measuring apparatus.
Fig. 9 is an explanatory view showing an aspect of calibration of a light receiving portion. Fig.
10 is an explanatory view showing an aspect of the calibration of the transparent portion.
11 is an explanatory view showing an aspect in which each unit light-emitting area F is measured by calibration.
Fig. 12 is an explanatory view showing aspects of a storage area secured for each unit measurement area E; Fig.
13 is an explanatory diagram showing an aspect in which a polarization characteristic of an optical film is measured;
14 is a graph showing the relationship between the ground level of the wave plate and the calculation error.
15 is a data table showing the relationship between the ground level of the wave plate and the calculation error;
16 is an explanatory diagram showing another configuration of the light receiving section;
17 is a graph showing the deviation between the number of coupled outputs and the output value.
Fig. 18 is an explanatory view showing an example in which a plurality of sets of the light-transmitting portion and the light-receiving portion are formed in the width direction of the optical film;
19 is an explanatory view showing an example of sweeping one set of the light-projecting portion and the light-receiving portion in the width direction of the optical film;
20 is an explanatory view showing a light-projecting portion in which a quarter-wave plate rotates;
21 is an explanatory view showing a measurement mode of polarization characteristics in the case of time-modulating measurement light;
Fig. 22 is an explanatory view showing a light-projecting portion when the measurement light is subjected to spatial modulation; Fig.
23 is an explanatory diagram showing an aspect of increasing the number of times of measurement.
Fig. 24 is an explanatory view showing a method of handling measured values when the characteristic of a unit measurement area is measured over two coupled pixels. Fig.

As shown in Fig. 1, the optical characteristic measuring apparatus 10 is characterized in that, as optical characteristics of the optical film 11, an optical characteristic (for example, a phase difference) Hereinafter, referred to as polarization characteristics). The optical characteristic apparatus 10 includes a transparent portion 12, a light receiving portion 13, a conveying roller 14 (conveying portion), a control device 16, and the like.

The optical film 11 is made of a transparent resin. The optical film 11 is formed by stretching or the like, and if it is normally formed, it has a certain polarization characteristic in the plane. As described later, the polarization characteristic of the optical film 11 is determined by the fact that the measurement light of circularly polarized light is incident on the transparent portion 12 and the transmitted light is measured by the light receiving portion 13, See Fig. 6). The optical film 11 has a constant width in the Y direction and continues in the X direction perpendicular to the Y direction and is conveyed while being kept flat in the X direction by the plurality of conveying rollers 14. [ Measurement of the polarization characteristics of the optical film 11 by the optical characteristic measuring apparatus 10 is carried out while continuously conveying the optical film 11 continuously. After the polarization property is measured by the optical property measurement device 10, the optical film 11 is cut into sheets in a predetermined width in the X direction and the Y direction, and is used for a liquid crystal display device or the like. The conveying roller 14 constitutes a conveying portion of the optical film 11. Further, the optical film 11 may be nipped and conveyed by the conveying roller and the conveying roller.

The light projecting unit 12 is a planar light source that irradiates at least light of a certain constant condition as measurement light in at least the field of view 13a of the light receiving unit 13. The light projecting face 12a is parallel to the optical film 11, Is formed below the optical film (11) so as to oppose the optical film (13). The measurement light irradiated to the optical film 11 by the transparent portion 12 is monochromatic light of a predetermined wavelength and light having substantially constant intensity and polarization state in the visual field 13a. The polarization state of the specific measurement light is circularly polarized light.

The transparent portion 12 is disposed on the light source moving portion 12b. The light source moving section 12b keeps the transparent portion 12 movable by a predetermined distance along the X direction. The light source moving section 12b moves the light projecting section 12 at the time of calibration of the light projecting section 12 and measures the polarization characteristics of the optical film 11 as described later. The transparent portion 12 is held at a predetermined position opposite to the transparent portion 12a.

The light receiving section 13 is formed above the optical film 11 so as to face the light transmitting section 12 so that the light projecting section 12 irradiates the optical film 11 to measure a change in the polarization state thereof . The measurement value measured by the light receiving unit 13 is input to the control unit 16. [ The light receiving section 13 is mounted on the arm 17 and the arm 17 is mounted on a support 18 formed to extend over the optical film 11 and the light receiving section 13 is mounted on the optical film 11 So that it can freely move in the vertical direction. Therefore, the light receiving portion 13 moves in the Z direction while facing the transparent portion 12. The movement of the light receiving portion 13 by the arm 17 is controlled by the control device 16 and the control device 16 moves the light receiving portion 13 in the Z direction for adjusting the focus. The movement of the light receiving portion 13 can be realized by forming a feed screw on the arm 17 or forming an endless belt.

The control device 16 is a control device for controlling each part of the optical characteristic measuring device 10 in a general manner and includes an input / output device (not shown) such as a control computer 16a, a monitor 16b, Respectively. The control device 16 controls the conveying roller 14 at a predetermined rotational speed to convey the optical film 11 at a constant speed in the X direction. At this time, the amount of movement of the optical film 11 and the position of the field of view 13a in the optical film 11 are detected by counting the driving pulse of the conveying roller 14 by a pulse counter (not shown). Further, the control device 16 controls the measurement timing by the light receiving section 13. [ Specifically, the amount of conveyance and the timing of conveyance of the optical film 11 and the measurement by the light receiving section 13 are performed in synchronization with each other. The control device 16 controls the movement of the transparent portion 12 by the light source moving portion 12b and the measurement of the measurement light by the light receiving portion 13 during the calibration of the transparent portion 12.

The control computer 16a has a Mueller matrix calculating section 19a and an optical characteristic calculating section 19b for calculating the polarization characteristic of the optical film 11 based on the data measured by the light receiving section 13 Function. The polarization characteristic of the optical film 11 is calculated for each unit measurement area E described later.

2, the transparent portion 12 includes a planar light source 21, a polarizing plate 22, and a quarter-wave plate 23. The planar light source 21 has a planar light emitting surface 21a and a parallel light in a nonpolarized state (hereinafter referred to as unpolarized light L1) from the light emitting surface 21a is emitted from the light emitting surface 21a in a substantially constant It strikes with strength. The polarizing plate 22 adjusts the non-polarized light L1 emitted by the surface light source 21 to be a linearly polarized light L2 and enters the 1/4 wave plate 23. The 1/4 wave plate 23 is disposed on the optical film 11 side of the polarizing plate 22 so that the slow axis (forward speed axis) is at an angle of 45 degrees with respect to the polarization direction of the linearly polarized light L2. Therefore, the 1/4 wave plate 23 adjusts the linearly polarized light L 2 incident from the polarizing plate 22 to circularly polarized light L 3 and emits it. Therefore, the transparent portion 12 projects the circularly polarized light L3 onto the optical film 11 as measurement light (hereinafter referred to as measurement light L3).

The range in which the transparent portion 12 irradiates the measurement light L3 substantially coincides with the visual field 13a of the light receiving portion 13. [ The irradiation range of the measurement light L3 by the transparent portion 12 may be larger than the visual field 13a of the light receiving portion 13 as long as it covers at least the entire range of the visual field 13a.

3, the light receiving section 13 includes a divided wave plate 31, a polarizing plate 32, a telecentric lens 33, and an image pickup device 34.

The divided wave plate 31 has four kinds of wave plates such as a first wave plate 31a, a second wave plate 31b, a third wave plate 31c and a fourth wave plate 31d. Each of the wave plates 31a to 31d constituting the divided wave plate 31 is arranged on the most front side (optical film 11 side) of the light receiving unit 13 in the conveying direction of the optical film 11 The first wave plate 31a, the second wave plate 31b, the third wave plate 31c, and the fourth wave plate 31d along the X direction in this order. The measurement light L3 emitted from the transparent portion 12 is transmitted through the optical film 11 to become the measurement light L4 carrying the polarization characteristic of the transmitted point and is incident on the divided wave plate 31, And is incident on the polarizing plate 32 through the first to fourth wave plates 31a to 31d according to the incident position.

The polarizing plate 32 makes the telecentric lens 33 enter the linearly polarized light component in a predetermined direction along the fast axis (or slow axis) of the measurement light L4 transmitted through the divided wave plate 31. [

The telecentric lens 33 causes the measurement light L4 that has been transmitted through the divided wave plate 31 and the polarizing plate 32 to become linearly polarized light to be incident on the imaging surface 34a of the imaging device 34. [ The telecentric lens 33 is an object-side telecentric lens that can regard the optical axis and the principal ray parallel to at least the object side (on the side of the optical film 11) It may be a bilateral telecentric lens which can regard the optical axis and the principal ray as parallel. The magnification of the telecentric lens 33 has a predetermined magnification (for example, about 1 to 1/3) for forming an image of the visual field 13a on the imaging surface 34a. As the telecentric lens 33, a telecentric lens for imaging an in-phase image may be used. Hereinafter, an image of the field of view 13a is assumed to be imaged on the image sensing surface 34a for simplicity. That is to say, the incident positions of the measurement light L4 transmitted through the first through fourth wave plates 31a through 31d, respectively, on the image pickup surface 34a by the telecentric lens 33 are respectively on the image pickup surface 34a The order of arrangement of the first to fourth wave plates 31a to 31d is the same as that of the upstream side (the X direction negative side) to the downstream side (the X direction positive side).

The image pickup device 34 is, for example, a CCD type image sensor, and picks up the optical film 11 by the measurement light L4. A plurality of pixels P are formed in a predetermined arrangement on the imaging surface 34a. Each pixel P generates a signal charge corresponding to the incident light amount by photoelectric conversion. The imaging device 34 treats a plurality of pixels P as one unit pixel (a unit light receiving area, hereinafter, referred to as a coupling pixel CP) as will be described later. That is, the imaging device 34 outputs a value obtained by averaging the signal charges generated in each pixel P to the control device 16 as the measured value D for each of the coupling pixels CP.

The light receiving section 13 is provided with a rotation mechanism (not shown) for alignment adjustment. The rotating mechanism is a mechanism for rotating the imaging device 34, the telecentric lens 33, the polarizing plate 32, and the divided wave plate 31 integrally around the optical axis. The rotating mechanism rotates the light receiving portion 13 so that the direction of the visual field 13a of the light receiving portion 13 is exactly aligned with the carrying direction X and the width direction Y of the optical film 11. [ Therefore, in the following description, the direction of the light receiving section 13 by the rotation mechanism allows the boundary lines of the wave plates 31a to 31d of the divided wave plate 31 to be aligned in the width direction Y of the optical film 11 to be transported, It is assumed that the sides of each pixel P (or the coupling pixel CP) exactly coincide with the conveying direction X and the width direction Y of the optical film 11.

4, the transmission axis of the polarizing plate 32 is arranged so as to be parallel (0 degrees) with respect to the transport direction X of the optical film 11. As shown in Fig. On the other hand, the principal axes (fast axis) orientations of the first to fourth wave plates 31a to 31d constituting the divided wave plate 31 are different from each other and the azimuths of the main axis of the second to fourth wave plates 31b to 31d Is rotated by about 36 degrees with respect to the main axis direction of the first wave plate 31a. The major axis direction of the first wave plate 31a is, for example, about 20 degrees with respect to the transport direction X of the optical film 11. In this case, the main axis direction of the second wave plate 31b is about 56 degrees with respect to the carrying direction X and the main axis direction of the third wave plate 31c is about 92 degrees with respect to the carrying direction X . The major axis direction of the fourth wave plate 31d is about 118 degrees with respect to the carrying direction X. [ The ground amounts of the first to fourth wave plates 31a to 31d are all 135 degrees.

In addition, the major axis directions of the first to fourth wave plates 31a to 31d need to be different from each other, and it is not necessarily the direction described above. This is because the polarization transfer matrix of the light receiving portion 13 is obtained for each coupling pixel CP by actual measurement at the time of calibration as will be described later and the main axis direction of each of the wave plates 31a to 31d Is reflected in the polarization transfer matrix.

5, the pixel P of the image pickup device 34 is sufficiently smaller than the first to fourth wave plates 31a to 31d, and the pixel P of the image pickup device 34 is sufficiently smaller than the first to fourth wave plates 31a to 31d. For example, Paying attention to the area A, a plurality of pixels P are arranged in the area A along the conveying direction X and the width direction Y of the optical film 11. The imaging device 34 treats 3 × 3 pixels as one unit of combined pixels CP and outputs a signal based on the signal charge of each pixel P in the combined pixel CP as shown by bold lines and hatching As a measurement value D as the entire combined pixel (CP). As shown in FIG. 5, when 3 × 3 pixels are used as one coupling pixel (CP), the average of all the nine pixels included in the three pixels is the measured value. Although one coupling pixel CP is adopted here by hatching, a plurality of coupling pixels CP are formed in the X direction and the Y direction.

As described above, since the image pickup device 34 outputs the measurement value in units of the coupling pixels CP, the polarization characteristic of the optical film 11 is measured in units of the coupling pixels CP. Therefore, the spatial resolution for measuring the polarization characteristics of the optical film 11 is generally determined by the size of the pixel P and the number of pixels (the size of the coupling pixel CP) handled as the coupling pixel CP. Hereinafter, it is assumed that the size of the pixel P and the size of the coupling pixel CP are determined within a range in which the spatial resolution necessary for measuring the polarization characteristics of the optical film 11 is obtained.

As described above, the optical characteristic measuring apparatus 10 measures the polarization characteristics of the optical film 11 in units of the coupling pixels CP, and therefore, as shown in Fig. 6, in the optical film 11, (Hereinafter, referred to as a unit measurement area) E corresponding to the coupling pixel CP. The optical characteristic measuring apparatus 10 is configured such that the optical film 11 in the visual field 13a is irradiated by the light receiving unit 13 every time the optical film 11 is transported in the X direction by the length of the unit measurement area E . Therefore, any one unit measurement area E is measured once by a plurality of coupling pixels CP arranged in the X direction, and after the optical film 11 enters the visual field 13a by the conveyance of the optical film 11, The number of times equivalent to the number of the coupling pixels CP arranged in the X direction is measured during the period from when the pixel 13a is exited. At this time, the unit measurement area E crosses each of the wave plates 31a to 31d of the divided wave plate 31, and a plurality of coupling pixels CP , So that any one unit measurement area E is measured plural times in each of the wave plates 31a to 31d.

7, the light projecting portion 12 can be divided into a region (hereinafter referred to as a unit light projection area) F having a size corresponding to the coupling pixel CP have. The unit light emitting area F corresponds to the coupling pixel CP on a one-to-one basis and the measurement light L3 emitted from a unit light emitting area F is transmitted through the optical film 11, The measurement light L4 carrying the characteristic is incident on the corresponding coupling pixel CP. As described later, the Stokes parameter (hereinafter referred to as S parameter) of the measurement light L3 irradiated to the optical film 11 by the transparent portion 12 is measured by the measurement of the transparent portion 12, Here, the S parameter measured here is calculated for each unit light emitting area (F).

Next, the measurement of the polarization characteristic of the optical film 11 by the optical characteristic measuring apparatus 10 will be described. As shown in Fig. 8, when measuring the polarization characteristics of the optical film 11 by the optical characteristic measuring apparatus 10, the polarization transfer matrix is measured in advance for each coupling pixel CP (step S01). The polarization transfer matrix is a matrix for mapping the S parameter of the incident light to the measured value D by the coupling pixel CP. That is, when the incident light to the coupling pixel CP is represented by ^T using S parameter (S0 ', S1', S2 ', S3'), the measured value D = (A1, A2, A3, A4) S0 ', S1', S2 ' , S3') a matrix a = (A1, A2, A3 , A4) is polarized transfer matrix satisfying ^T. The polarization transfer matrix A includes the photoelectric conversion characteristics of the pixels P constituting the coupling pixels CP and the polarization characteristics of the telecentric lens 33, the polarizing plate 32, the divided wave plates 31 (coupling pixels CP) The wavelength plate corresponding to the wavelength plate) is reflected.

In addition, S0 'is a light intensity, S1' is a horizontal linear polarization intensity, S2 'is a 45-degree linear polarization intensity, and S3' is a clockwise rotation polarization intensity. The polarization transfer matrix A corresponds to the element of the first row of the Muller matrix (element representing the change in the intensity of various polarization states) showing the polarization transfer characteristic of the light receiving unit 13, The value obtained as D is the value of light intensity S0 in terms of the S parameter.

The measurement of the polarization transfer matrix for each of the coupling pixels CP performed here corresponds to the calibration of the light receiving unit 13 and the optical characteristic measuring apparatus 10 can be used as long as the configuration of the light receiving unit 13 is not changed by repair or the like You only need to do it once when you use it for the first time. The measured polarization transfer matrix A is stored in the control device 16 and is used when calculating the polarization characteristic of the optical film 11 based on the measurement value by each coupling pixel CP.

Next, before measuring the polarization characteristic of the optical film 11, the S parameter of the measurement light L3 is measured for each unit light emitting area F (step S02). This is equivalent to the calibration of the transparent portion 12 and may be performed only once if there is no change in the characteristics of the transparent portion 12. However, at the start of use of the optical characteristic measuring device 10 ).

The polarization characteristic of the optical film 11 is measured by the calibration of the light receiving unit 13 and the light projecting unit 12 so that the polarization transfer matrix A for each coupling pixel CP is already known, F), the S parameter of the measurement light L3 is already known.

At this time, a vector (Stokes vector) S '= (S0', S1 ', S2', S3 ') consisting of S parameters of the measurement light L4 transmitted through a unit measurement area E of the optical film 11 Is calculated by using S parameter S = (S0, S1, S2, S3) of the measurement light L3 before transmission and Muller matrix (hereinafter referred to as M matrix) of the unit measurement area E, It is in the relationship of M · S. As described above, the measurement value D is D = A · S 'when the polarization transfer matrix A is used. Therefore, in the case of calculating the polarization characteristic of the unit measurement area E since D = A 占 S S and the Stokes vector S of the polarization transmission matrix A and the measurement light L3 is already known, ask the elements _{M ij (i, j = 1} ~ 4) of the M matrix from D, it is possible to calculate the polarization properties, such as the main axis direction α or retardation δ of the unit measuring the area (E) from the M matrix elements M _ij.

However, since the matrix M is a 4 × 4 matrix and all elements are 16, and D = M · S is the same as one equation, only this formula obtained by one measurement (one kind) M _ij can not be determined. To determine the total elements of the M matrix, we need 16 independent equations.

In this respect, the optical characteristic measuring apparatus 10 has a plurality of measurement values Dn = (D ₁ , D ₂ , ..., D (N times) _n, ... D _N) is referred to as a transformation matrix (hereinafter referred to as sample measurement matrix corresponding to each element M _ij of the matrix M) and calculates a T ⁺ advance (step S03). This sample measurement matrix T ⁺ is used to calculate the polarization transfer matrix A _n = (A1 _n , A2 _n , A3 _n , A4 _n ) of each coupling pixel CP (n) already known by calibration and the corresponding unit transmitting area F ) it is calculated using the Stokes vector _{S n = (S0 n, S1} n, S2 n, S3 n) T of the measuring light (L3) which is irradiated. In addition, since the correction at the time of the Stokes vector S _n of the measurement light (L3) is used in the apparatus disclosed as described above, the sample measurement matrix T ⁺ calculated back also to the use of the apparatus according to this disclosure.

When the sample measurement matrix T ⁺ is calculated in this manner, the measurement of the polarization characteristics of the optical film 11 is started. The measurement of the polarization characteristic of the optical film 11 is performed by irradiating the measurement light L3 from the light projecting unit 12 while the optical film 11 is conveyed in the X direction and irradiating the optical film 11 with the light receiving unit 13. [ (Step S04) by taking the image of the optical film 11 with the measurement light L4 transmitted through the optical film 11.

At this time, the control device 16 calculates an M matrix element M _ij for each unit measurement area E using the sample measurement matrix T ⁺ from the measurement value D _n obtained from each combination pixel CP (n) S05). Then, using the calculated M matrix elements M _ij , the principal axis direction? Or retardation? Is calculated as the polarization characteristic of the unit measurement area E (step S06).

Hereinafter, aspects of each step will be described in detail.

<Calibration of Light Receiving Portion>

As shown in Fig. 9, the reference light-projecting unit 41 is used for the calibration of the light-receiving unit 13 (step S01). The reference transparent portion 41 is a light source that emits the reference light 41a for which the S parameter is already known. The reference transparent portion 41 includes a surface light source 42, a 1/4 wave plate 43, and a polarizing plate 44. The reference transparent portion 41 is configured to be substantially the same as the transparent portion 12 and the reference light 41a is circularly polarized light and the quarter wave plate 43 is formed to rotate at a predetermined speed. The transmission axis direction? Of the polarizing plate 44 is constant, but the main axis (fast axis) direction? Of the 1/4 wave plate 43 changes with time. The transmission axis direction? Of the polarizing plate 44 and the main axis direction? Of the 1/4 wave plate are already known by the arrangement of the reference light-projecting portion 41 with respect to the light-

In the calibration of the light receiving unit 13, the reference light 41a is directly incident on the light receiving unit 13 without passing through the optical film 11, and the light receiving unit 13 receives the reference light 41a And outputs a value (measured value) D.

Assuming that the S parameters of the reference light 41a are P0, P1, P2 and P3 and the Stokes vector P of the reference light 41a is P = (P0, P1, P2, P3) ^T , P = A1 · P0 + A2 · P1 + A3 · P2 + A4 · P3 using the polarization transfer matrix A and the Stokes vector P.

On the other hand, the Stokes vector P of the reference light 41a is expressed by the following equation (1), using the main axis direction? Of the quarter wave plate 43 and the transmission axis direction? Of the polarizing plate 44. However, the light intensity K, C = cos 2?, S = sin 2? Of the reference light 41a. When this measured value D is expressed by using this, the following equation (2) is obtained. The predetermined coefficient K 'is a coefficient previously determined by the light intensity K of the reference light 41a and the sensitivity or gain of the image pickup device 34 or the like.

As described above, the main axis direction? Of the 1/4 wave plate rotates in a constant direction, so that the measured value D is obtained in a time series with respect to the rotating main axis direction?. Since the predetermined coefficient K is a known number obtained from the light intensity of the reference light 41a and the sensitivity and gain of the image pickup device 34, a value D / K 'obtained by normalizing the obtained measurement value D with a predetermined coefficient K' , by a discrete Fourier transform (DFT), for the major axis direction γ, a direct current (DC) component F _DC, F _cos4 cos4γ component _{γ, γ sin4} sin4γ component F, component F sin2γ _{sin2 γ} can be obtained, respectively.

As it can be seen from the formula of equation (2), each component F _DC, F _{cos4 γ,} F _{sin4 γ,} F _{sin2 γ} obtained by the DFT, using the elements and coefficient K of the polarization transfer matrix A, the following formula 3.

Since the transmission axis direction? Of the polarizing plate 44 is already known (for example, 0 degree), the polarization transfer matrix A = (A1, A2, A3, A4) can be calculated based on the formula (3).

Further, the noise due to the dark current of the image pickup device 34 is superimposed as the background BG in the direct current component F _DC . For this reason, the image pickup device 34, the light shielding by the image pickup by pre-placed to measure the background BG of the dark current noise, from F _DC obtained by the DFT, the F _DC obtained by subtracting the background BG of the true direct current component F _DC, polarized The transfer matrix A is calculated using this true DC component F _DC .

9 shows an example in which the reference light projecting unit 41 is provided with the surface light source 42 and the reference light 41a is incident on the entire light receiving unit 13. However, the present invention is not limited to this. The reference light-projecting unit 41 may be any one capable of causing a reference light for which an S parameter is already known to enter at least one coupling pixel CP.

&Lt; Calibration of light transmitting portion &

10, the calibration (step S02) of the transparent portion 12 is performed by irradiating the measuring light L3 from the transparent portion 12 and moving the light source moving portion 12b from the upstream side in the X- . This is performed without the optical film 11 between the transparent portion 12 and the light receiving portion 13 and the light receiving portion 13 measures the measurement light L3 emitted from the transparent portion 12.

As shown in Fig. 11, the CP (1), CP (2), ..., CP (1), CP (1), F (2), ..., CP (N) in the X direction in the light projecting unit 12 so as to correspond to each of these coupling pixels CP , F (N) are listed. Therefore, when the light projecting unit 12 is moved downward from the upstream side in the X direction by the light source moving unit 12b, the light projecting unit 12 starts to enter the lower side of the light receiving unit 13, The measurement light L3 (n) emitted from each unit light-emitting area F (n) from the bottom to the bottom of the entire unit pixel CP (1) to CP (N) is measured once.

For example, when paying attention to the unit light emitting area F (N) positioned on the most downstream side, the measurement light L3 (N) emitted from the unit light emitting area F (N) , ... , CP (N) are measured in each combination pixel CP (n) in this order. Let D ₁ , D ₂ , ..., D be measured values measured at each coupling pixel CP (n) at this time. And D _N , N measurement values are obtained for the measurement light L3 (N) emitted from one unit light-emitting area F (N).

Among the _N measured values D ₁ to D _N measured in this manner, among the divided wave plates 31, the measured values passed through the first wave plate 31a and the measured values measured through the second wave plate 31b A measurement value, a measurement value measured through the third wavelength plate 31c, and a measurement value measured through the fourth wavelength plate 31d.

Assuming that there are k coupling pixels CP in the area of each of the wave plates 31a to 31d among the N coupling pixels CP (n) along the X direction, N = 4k, and each of the wave plates 31a- K measurement values are obtained. Since the polarization transfer matrix A is different for each coupling pixel CP (n), they are different values.

Therefore, at the time of calibration of the transparent portion 12, all measured values D ₁ to D _N by the coupling pixels CP (1) to CP (N) arranged in the X direction are stored. 12, the number of wave plates (here, 4) included in the divided wave plate 31 and the number of coupled pixels CP arranged in the X direction in each wave plate (here, k Dimensional storage area 46 having an index as an index is secured. This two-dimensional storage area 46 is secured for one unit light emitting area F (n), for example, and a measured value D _n obtained in each of the combining pixels CP (n) n, and the wavelength plates 31a to 31d that have been passed.

Based on the measurement values D ₁ to D _N obtained as described above, the S parameter of the measurement light L 3 is calculated as follows. First, the total Da of the measured values obtained by the first wavelength plate 31a, the total Db of the measured values obtained by the second wavelength plate 31b, the sum Dc of the measured values obtained by the third wavelength plate 31c, And the sum Dd of the measured values obtained by the plate 31d is calculated. The sum Da to Dd of each measured value in each of the wave plates 31a to 31d is expressed by the following expression (4).

On the other hand, since the polarization transfer matrix A _n = (A1 _n , A2 _n , A3 _n , A4 _n ) of each coupling pixel CP ( _n ) is already known by the calibration of the light receiving section 13, When the Stokes vector S _j of the measurement light L3 (j) as S _j = (S0 _j, S1 _j, S2 _j, S3 _j) ^T emitted from _{j = 1 ~ n, D n} = a n · S j to be. When this is used, the above-described equation (4) is expressed by the following equation (5).

Since the coefficients of the S parameters S0 _j to S3 _j are all composed only of the elements of the known polarization transfer matrix A _n in Equation (5), the unit light emitting area F (j ) it is possible to determine the S parameters S0 ~ S3 _{j j} of measurement light L3 (j) emitted from. Here, a certain unit light emitting area F (j) is taken as an example, but the same applies to the other unit light emitting areas F. Although the unit light emitting area F in any row in the X direction is exemplified, the other rows are also the same. Therefore, the control device 16 determines the S parameter of the measurement light L3 emitted to all the unit light-projecting areas F of the light-projecting unit 12 by the above-described method.

&Lt; Measurement of optical film &

13, when the measurement of the polarization characteristic of the optical film 11 (step S04) is performed, the coupling pixels CP (1) to CP (1) arranged in the direction of the transport direction X of the optical film 11 The light projecting unit 12 and the light receiving unit 13 are disposed so as to face each other and the corresponding unit light emitting areas F (1) to F (N) face each other. That is, the measurement light L3 (n) emitted from the unit light emitting area F (n) is incident on the coupling pixel CP (n) after passing through the optical film 11.

The optical film 11 is arranged between the light-transmitting portion 12 and the light-receiving portion 13 in the X direction (X direction) in a state where the combining pixel CP (n) and the unit light- . At this time, the transparent portion 12 irradiates the measurement light L3 to the optical film 11, and the light receiving portion 13 receives the measurement light L4 transmitted through the optical film 11, The optical film 11 is picked up at a predetermined timing in synchronism with the conveyance amount of the optical film 11.

For example, when paying attention to a certain unit measurement area E on the optical film 11, at any point in time, the unit measurement area E is irradiated with the measurement light L3 (1) irradiated from the unit light- And the measurement light L4 (1) transmitted through the unit measurement area E is picked up by the coupling pixel CP (1). Thereafter, the optical film 11 is transported, and the unit measurement area E is moved to a position corresponding to the coupling pixel CP (2). At this time, the measurement light L3 (2) is irradiated from the unit light-projecting area F (2), and the light receiver 13 is irradiated with the measurement light L4 (2) transmitted through the unit measurement area E, The unit measurement area E is imaged.

Similarly, the optical film 11 is transported in the X direction at the stage corresponding to the coupling pixel CP, so that the optical film 11 sequentially passes through the corresponding unit light-emitting areas F (1), F (2), ... (2), ..., CP (1), CP (2), ..., CP As shown in FIG. Therefore, in each area corresponding to each of the wave plates 31a to 31d of the divided wave plate 31, a total of N (= 4k) times of imaging is performed k times.

For the sake of simplicity, the description has been given to a certain unit measurement area E, but since the light receiving unit 13 picks up the entire surface of the visual field 13a, a plurality of unit measurement areas E are simultaneously imaged. For example, N unit measurement areas located on the same row as the noted unit measurement area E are picked up by the combination pixels CP (1) to CP (N), respectively. Similarly, there are a plurality of rows in which the N coupling pixels CP are arranged in the width direction Y of the optical film 11 as well.

However, the optical characteristic measuring apparatus 10 secures the two-dimensional storage region 46 for one unit measurement area E (as in the case of the above-described calibration of the transparent portion 12) , And stores all the measured values D ₁ to D _N for N times in each unit measurement area (E).

The N measured values D ₁ to D _N for the unit measurement area E obtained as described above are stored in the unit measurement area E (E) using the pre-calculated sample measurement matrix T ⁺ _Gt ; M &lt; / RTI &gt; Thereafter, using the M matrix element M _ij of the unit measurement area E thus calculated, the control device 16 calculates the principal axis orientation? And the retardation? In the unit measurement area E as polarization characteristics .

<Sample Measurement Matrix>

Based on the measurement of the polarization characteristics of the optical film 11 as described above, the sample measurement matrix T ⁺ is calculated as follows (step S03). Let the Stokes vector of the measurement light L3 (n) irradiated from the unit light-projecting area F (n) be S _n , the M matrix of the unit measurement area E, and the measurement light L4 (n) after passing through the unit measurement area E (n) is S ' _n , S' _n = M · S _n . Specifically, the following equation (6) is used.

The measurement light L4 (n) after passing through the unit measurement area E is incident on the coupling pixel CP (n) at a position corresponding to the unit light projection area F (n). At this time, the measured value obtained by the combined pixel CP (n) D _n is, when the Stokes vector of the measuring light L4 (n) to S _'n, by using the polarization transfer matrix A _n of the combined pixel CP (n), D _n = A &_lt; _n &_gt; S &_lt; _n &_gt;, which is expressed by the following equation (7).

Then, substituting the above-mentioned equation (6) the expression of Equation (7), the measured value D _n is when the Stokes vector of the measurement light L3 (n) as S _n, by M matrix of unit measuring the area (E) , D _n = A _n · (M · S _n ), which can be expressed in the following equation (8).

The formula (8) described above is a measurement value D _n by the combination pixel CP (n) and the unit measurement area E is picked up by the combination pixels CP (1) to CP (N) The measured values D ₁ to D _N are obtained. This means that for one unit measurement area (E), N equations are obtained.

In the equation (8), the elements of the polarization transfer matrix A and the S parameters of the measurement light L3 are all known quantities by calibration, and an amount not yet known is the M matrix element M of the unit measurement area E _ij . Therefore, the above-mentioned equation of Equation 8 and listed in the order of the measurement value D ₁ ~ D _N, the measurement value D ₁ ~ measurement vector D arranged to D _N to D = (D _1, D _2, ... (M ₁₁ , ..., M ₁₄ , M ₂₁ , ..., M _N ), a rearranged vector M '(hereinafter referred to as an M element vector) of the M matrix elements M _ij of the unit measurement area _{M 24, M 31, ...,} M 34, M 41, ..., M 44) to the base material when a ^T organized in a matrix format, represented by D = T · M '. This can be described concretely by the following equation (9). The measurement vector D consists of N elements, and the M element vector M 'consists of 16 elements. The matrix T is a transformation matrix for mapping the M matrix elements M _ij to the measured values D ₁ to D _N , and is an N x 16 matrix.

As can be seen from the equation (9), the element of the transformation matrix T that maps the M element vector M 'to the measured value vector D is an element of the polarization transfer matrix A, which is already known, . Therefore, the control device 16 calculates the polarization transfer matrix A obtained for each coupling pixel CP and each unit light-emitting area F, and the polarization transfer matrix A obtained for each unit light-emitting area F at the stage where the calibration of the light- The transformation matrix T is calculated in advance using the S parameter of the light L3.

On the other hand, since the data obtained by the measurement is the measured values D ₁ to D _N (measured value vector D), contrary to the equation of the equation (9), the measured value vector D corresponds to the M element vector M ' And calculates the inverse matrix T ⁺ . The inverse matrix of the transformation matrix T thus calculated is the sample measurement matrix T ⁺ .

Since the transformation matrix T is an Nx16 matrix as described above and is not a square matrix depending on the number N of coupling pixels (CP) arranged in the X direction, precisely, the quasi-inverse matrix of the transformation matrix T is a sample measurement Is the matrix T ⁺ . In some cases, the inverse matrix (pseudo inverse matrix) of the transformation matrix T does not exist. However, this problem is avoided when the sample is limited to the linear birefringence sample and the M element to be specified is limited. Hereinafter, the optical characteristic measuring apparatus 10 is assumed to be capable of calculating the sample measurement matrix T ⁺ .

The control device 16 controls the polarization transfer matrix A and the measurement light L3 obtained by the calibration of the light receiving section 13 and the light projecting section 12 as described above before the start of measurement of the polarization characteristics of the optical film 11 The sample measurement matrix T ⁺ is calculated and maintained in advance from the S parameter. Although the combining pixels CP (1) to CP (N) and the unit light-emitting areas F (1) to F (N) arranged in any row in the X direction have been described above as an example, the same is true for the other rows. ^{+ Is} calculated in advance. Therefore, the controller 16, a unit measuring the area (E) is at the same time as measured by any combination pixel CP (1) ~ CP (N) arranged in the X direction, the measured value D ₁ ~ D _N, and sample measurements obtained Using the matrix T ⁺ , the M matrix element M _ij of the unit measurement area E is calculated.

<Calculation of Polarization Characteristics>

The polarization characteristic of the unit measurement area E is calculated as follows based on the M matrix element M _ij of the unit measurement area E calculated as described above (step S06). By completely specifying the M matrix elements M _ij of the unit measurement area E, it is possible to calculate the polarization characteristics such as linear birefringence, linear dichroism, circular birefringence, circular dichroism, and depolarization. Hereinafter, An example will be described in which the polarization property of the optical film 11 is regarded as a linear birefringence and the principal axis direction alpha and retardation delta of the linear birefringence are calculated.

When the polarization property of the optical film 11 can be regarded as a linear birefringence, the M matrix of the unit measurement area E is expressed by the following equation (10). Q ₁ to Q ₅ are quantities expressed by Equation (11) using the principal axis orientation? Of the unit measurement area (E) and the retardation?. However, K ₁ = cos ₂ ? And K ₂ = sin _{2 ?} .

Therefore, controller 16, using the M matrix elements M _ij of a unit measuring the area (E), for example, the main shaft bearing α tan2α = Q ₄ / by Q _5, a retardation δ sinδ = Q ₄ / Q ₂ .

As described above, the optical characteristic measuring apparatus 10 includes a light-receiving portion (light-receiving portion) 31a to 31d in which four kinds of wave plates 31a to 31d are arranged in the carrying direction X of the optical film 11 by the divided wave plate 31 13 picks up the optical film 11 and performs measurement in a plurality of polarization states necessary for calculation of the polarization characteristic. Therefore, the optical characteristic measuring apparatus 10 can quickly measure the polarization characteristic while always conveying the optical film 11 in the X direction without stopping the conveyance of the optical film 11. For example, in the case of measuring the optical film 11 of a predetermined size under the conditions of the spatial resolution of 1 mm and the axial direction measurement accuracy of 0.1 degrees, the optical film 11 is transported every time the light receiving section 13 is moved, It takes about 10 minutes to perform measurement while stopping. On the other hand, in the present invention, since the conveying of the optical film 11 is not stopped, the measurement of the polarization characteristics can be completed in about two and a half minutes.

The optical characteristic measuring device 10 may be configured not to use the data obtained from each pixel P of the image pickup device 34 as a measurement value but to use a combination pixel CP in which a plurality of pixels P are collectively arranged Since the measurement of the polarization characteristics of the optical film 11 is performed in units of a unit, the noise of the image pickup device 34 can be reduced and the polarization characteristics of high precision can be measured.

It should be noted that the combination pixel CP has pluralities for each of the wave plates 31a to 31d in the divided wave plate 31. Using the measured values D ₁ to D _N obtained from all these combined pixels CP, And the polarization characteristic of the optical film 11 is calculated. This is equivalent to performing a plurality of measurements and performing an average, and the S / N ratio can be improved as compared with the case where the measurement is performed once in one wavelength plate to calculate the polarization characteristic. Therefore, in the optical characteristic measuring apparatus 10, it is possible to measure the polarization characteristics with high accuracy.

In the optical property measuring apparatus 10, the polarization transfer matrixes A of the plurality of coupling pixels CP are obtained by the calibration of the light receiving unit 13, The S parameter of the measurement light L3 emitted from the unit light-projecting area F corresponding to the projection optical system CP is calculated. Based on the obtained S-parameters of the polarization transmission matrix A and the measurement light L3, the sample measurement matrix T ⁺ is calculated in advance before the measurement of the polarization characteristics of the optical film 11. When measuring the polarization characteristics of the optical film 11, the measurement values D ₁ to D _N obtained from the respective coupling pixels CP and the sample measurement matrix T ⁺ are used to determine the optical film 11 E)) calculate the matrix M elements M _ij of, and uses a matrix M elements M _ij calculated and calculates the polarization characteristics. Therefore, the optical characteristic measuring apparatus 10 can quickly and accurately calculate various polarization characteristics such as linear birefringence, linear dichroism, circular birefringence, circular dichroism, and depolarization.

As described above, the optical characteristic measuring apparatus 10 is provided with the light projecting unit 12 for irradiating the measurement light L3 so as to substantially coincide with the visual field 13a of the light receiving unit 13. Thereby, the optical characteristic measuring apparatus 10 can quickly perform the calibration of the transparent portion 12. For example, when a large-area light-transmitting portion for irradiating measurement light L3 outside the visual field 13a of the light-receiving portion 13 is used and the polarization characteristic of the optical film 11 is measured while moving the light-receiving portion 13 The measurement light L3 (light projecting surface 12a) of the entire irradiation range (light projecting surface 12a) of the measurement light L3 by the light projecting unit 12 is measured by calibration before the start of measurement of the polarization characteristic of the optical film 11 ) &Lt; / RTI &gt; Compared with this case, the optical characteristic measuring apparatus 10 has a small area required to determine the S parameter, so that the time required for the calibration is short. Since the size of the transparent portion 12 is also the minimum necessary, the cost for the transparent portion 12 is also small.

In the embodiment described above, the S parameter of the measurement light L3 irradiated by the light projecting unit 12 is different for each unit light emitting area F, but instead, the S parameter It is also possible to use the light projecting portion 12 for irradiating the measurement light L3 uniformly. In this case, the S parameters for every unit light emitting area F are all the same, and the Stokes vector S _n , which has been distinguished from the unit light emitting areas F (1) to F (N) in the above- = (S0, S1, S2, S3). Therefore, the measured value D _n of the coupling pixel CP (n) corresponding to the above-described expression (8) is expressed by the following equation (12) by removing the suffix n for distinguishing the unit light emitting area F (n) with respect to the S parameter.

Therefore, in the same manner as in Equation (9), the formulas of the measured values D ₁ to D _N are listed, and the measured value vector D and the M element vector M 'are used to correspond to the measured value vector D , The following equation (13) is obtained.

When the polarization property of the optical film 11 can be regarded as a linear birefringence, the M matrix of the unit measurement area E can be expressed by the above-described equation (10). Therefore, The following equation (14) can be written. If the row in which the M matrix element is 0 is deleted, the following equation (15) is obtained.

Therefore, in the expression (16), when a matrix composed of elements of the polarization transfer matrix A of each of the coupling pixels CP (1) to CP (N) is T 'and its inverse matrix is T' ⁺ , do. However,?,?, And? Are expressed by the following equation (18).

If the elements S0,?,?, And? Of the left side of the equation (18) can be calculated from the measured values D ₁ to D _N (measured value vector D), the principal axis orientation? Can be obtained by the following expression (19).

The control device 16 calculates the matrix T ' ⁺ as a sample measurement matrix and calculates the elements S0,?,?, And? Of the left side of the equation (18) from the measured values D ₁ to D _N , 19, the principal axis bearing? And the retardation? May be calculated.

In the embodiment described above, four kinds of wave plates of the first to fourth wave plates 31a to 31d are formed in the divided wave plate 31. For example, the polarizing properties are measured with good precision The kind (the type is determined by the major axis direction and the ground amount) of the wave plate formed on the divided wave plate 31 may be four or more. By increasing the kinds of the wave plates in the divided wave plate 31 as described above, it is possible to increase the cut-off frequency of the noise included in the measured value D of each coupling pixel CP, Can be measured.

However, if the kind of the wave plate in the divided wave plate 31 is merely excessively increased, the area of one wave plate becomes small, so that the above-described average effect becomes small and the reliability of the measured value lowers. Since the coupling pixel CP over the boundary of the wave plate in the divided wave plate 31 can not be used for measurement, the larger the number of types of wave plates in the divided wave plate 31, And the substantial light receiving area of the image pickup device 34 is reduced. This means a decrease in the S / N ratio. In view of this, it is preferable that the kind of the wave plate in the divided wave plate 31 is at least four kinds or more that are necessary for calculation of the polarization characteristic, and it is preferably at most 40 types.

In the above-described embodiment, the major axis directions of the first to fourth wave plates 31a to 31d are set to be rotated by 36 degrees with respect to the main axis direction of the first wave plate 31a. However, Is an angle that equally divides 180 degrees so that the principal axis directions of the first to fourth wave plates (31a to 31d) fall as far as possible. Therefore, when the divided wave plate 31 is constituted by N (four or more) wave plates, the major axis direction of the other wave plates is 180 / (N + 1) degrees with respect to the main axis direction of one wave plate It is preferable that it is in the rotated direction. However, as described above, since the polarization transfer matrix of the light receiving section 13 is obtained by measurement at the time of calibration, strictness is unnecessary and may be within a range of, for example, approximately +/- 0.5 degrees of the above described value.

In the above-described embodiment, the ground amounts of the first to fourth wave plates 31a to 31d are all 135 degrees. In this manner, the major axis directions of the wave plates 31a to 31d are arranged so as to be as far as possible from each other, and the ground level is about 135 degrees, so that the error is minimized when calculating the sample measurement matrix T ⁺ (and polarization characteristic) .

The above-mentioned ground level of each of the wave plates 31a to 31d is a value determined according to the result of the simulation. Specifically, as shown in Fig. 14 and Fig. 15, the calculation error when calculating the sample measurement matrix T ⁺ is calculated as follows, regardless of the number of types of wave plates (four types are shown in quadrants) It can be seen that the amount becomes the minimum in the case where the amount is approximately 120 to 140 degrees or 220 to 240 degrees. According to a more detailed simulation, it has been found that a calculation error is adopted when the ground amount is about 135 degrees or about 225 degrees. In this regard, the wavelength plate in the divided wave plate 31 may have a ground amount of 70 degrees or more and 170 degrees or less, or 190 degrees or more and 290 degrees or less (a range where the relative error is approximately 20 or less in FIG. 15) (The range in which the relative error falls within two digits in Fig. 15), and is preferably within the range of 120 deg. To 140 deg. Deg. More preferably not less than 220 degrees and not more than 240 degrees, and particularly preferably not more than 135 degrees or not more than 225 degrees.

In the above-described embodiment, the divided wave plate 31 and the polarizing plate 32 are disposed in front of the telecentric lens 33 (on the side of the optical film 11). For example, The divided wave plate 31 and the polarizing plate 32 may be disposed between the image pickup device 34 and the telecentric lens 33 as shown in Fig. In this case, the divided wave plate 31 and the polarizing plate 32 can be made smaller than in the case of forming the front side of the telecentric lens 33. Therefore, the divided wave plate 31 and the polarizing plate 32 Can be reduced. However, the error of the polarization transfer matrix A of the coupling pixel CP tends to be large.

17, the number of pixels constituting the coupling pixel CP (hereinafter, referred to as the coupling number) is set to be the number of pixels composing the coupling pixel CP. In this embodiment, The variation of the output value (measured value) for each coupling pixel CP becomes smaller. Unless the coupling number is measured to some extent, the number of measurement times (number of times of imaging) is increased for the same unit measurement area E, It is not possible to measure the polarization characteristics of the liquid crystal layer E with good precision. Therefore, as described in the above-described embodiment, it is preferable to use, as the unit of measurement, the combined pixel (CP) formed of at least two or more pixels instead of using the output value for each pixel P as the measurer. In particular, the number of pixels P constituting the combined pixel CP is 4 (2 in the vertical dimension 2 in the horizontal direction), 9 (3 in the vertical direction, 3 in the horizontal direction), 16 (4 in the vertical direction and 4 in the horizontal direction) (2 or more), and the number of pixels P in the vertical and horizontal directions is the same.

The graph of FIG. 17 shows a comparatively bright (white) image by using a 12-bit output CCD type imaging device (1 / 1.8 inch, 2 million pixels, pixel P having a size of 4.4 占 퐉) A value obtained by subtracting the minimum value from the maximum value among the total output values obtained by performing 256 measurements while changing the number (x) of incident lights is input as a deviation (y) Black circles). The approximate curve (broken line) obtained from each point is y = 171.68x ^{-0. 5006} , and is approximately proportional to the -1/2 power of the number of couplings (x), the noise superimposed on the output of the image pickup device 34 has the property of random noise.

In the embodiment described above, the polarizing characteristics are measured while the optical transparency 12 and the light receiving section 13 are not moved but the optical film 11 is conveyed in the X direction. However, The optical film 11 and the set of the light projecting unit 12 and the light receiving unit 13 and the optical film 11 may be moved relative to each other in a predetermined direction (X direction). For example, The polarization characteristic may be measured while integrally moving the transparent portion 12 and the light receiving portion 13. It is also possible to measure the polarization characteristics while relatively moving the optical film 11, the light projecting portion 12, and the light receiving portion 13 together.

In the embodiment described above, the field of view 13a of the light receiving unit 13 is a part of the width direction (Y direction) of the optical film 11, and the region in which the polarization characteristic of the optical film 11 is measured, (13a) in the transport direction (X) of the optical film (11). 18, a plurality of sets of light-projecting portions 12A to 12D (for example, a plurality of light-projecting portions 12A to 12D (see Fig. 18) are arranged in the width direction of the optical film 11, And the light receiving portions 13A to 13D are formed. In this case, each set of the light-projecting portion and the light-receiving portion need not be arranged in one line in the width direction, and when the optical film 11 is transported, the respective sets of the light- It is sufficient that the surface is measured without gaps.

18, a plurality of sets of light projecting portions 12A to 12D and light receiving portions 13A to 13D are formed in the width direction of the optical film 11. As shown in Fig. 19, one set of light projecting portions 12 and the light receiving portion 13 may be swept in the width direction so as to measure the entire surface of the optical film 11 without fail.

In the embodiment described above, the transparent portion 12 irradiates substantially uniform circularly polarized measurement light L3 in the field of view 13a, and the measurement light L3 irradiated by the transparent portion 12 Is completely constant in the field of view 13a, and there is no distinction in the S parameter in each unit light emitting area F. However, in addition to the fact that the measurement light L3 irradiated by the light projecting unit 12 is completely constant in the field of view 13a, the light receiving unit 13 is provided so as not to be distinguished from each of the engagement pixels CP in the light receiving unit 13 The sample measurement matrix T ⁺ can not be calculated in some cases.

This corresponds to the case where there is no distinction in the S parameter of the measurement light L3 for each unit light emitting area F and the polarization transmission matrix A does not have a distinction for each coupling pixel CP. Concretely, for example, there is no distinction by the suffix n of S0 _n to S3 _n and A1 _n to A4 _{n in} the above-mentioned equation (9). In this case, each of the measured values D ₁ to D _N also has four kinds of values depending on the number of the wave plates 31a to 31d. Therefore, the equation of Equation (9) is substantially the same as the four equations even though the unknowns are all 16 (M matrix elements M _ij ), so that the sample measurement matrix T ⁺ can not be calculated and the M matrix elements M _ij (Or the error is extremely large), the polarization characteristics can not be calculated.

Taking this fact into consideration, the measurement light L3 is temporally modulated so that the S parameter of the measurement light L3 is positively generated for each unit light emitting area F, and the above-described problem does not occur . In this case, the limit of the linear birefringence sample which has been carried out so far is released, and the pseudo inverse matrix in the equation (13) exists, and it becomes possible to measure all of the M elements of the sample.

20, the transparent portion 12 is composed of the surface light source 21, the polarizing plate 22, and the 1/4 wavelength plate 51 in order to modulate the measurement light L3 in terms of time, for example, as shown in Fig. 20 . The planar light source 21 and the polarizing plate 22 are schematically formed into a circle in conformity with the shape of the quarter wave plate 51. The planar light source 21, the polarizing plate 22, It is the same. On the other hand, the 1/4 wave plate 51 is formed so as to rotate around the irradiation optical axis 53 of the measurement light L3 by the motor 52. The rotation of the 1/4 wave plate 51 is controlled by the control device 16 and is synchronized with the conveyance amount of the optical film 11 and the imaging timing of the light receiving unit 13 in the clockwise or counterclockwise rotation And is rotated at a predetermined speed. As a result, the principal axis direction? Of the quarter-wave plate changes.

When the 1/4 wave plate 51 is rotated in this manner, as shown in Fig. 21, when attention is paid to a certain unit measurement area E, the first measurement is performed by the combination pixel CP (1) The measurement light L3 to be irradiated is the S-parameter measurement light corresponding to the principal axis direction? Of the 1/4 wave plate 51. Then, when the optical film 11 is conveyed only in the width of the coupling pixel CP and enters the position corresponding to the coupling pixel CP2, the second measurement is performed. In the second measurement, the direction of the principal axis direction? Changes since the 1/4 wave plate 51 rotates, and the S parameter of the measurement light L3 irradiated on the unit measurement area E is the sum of the S- 1) at the time of the first measurement. Therefore, even if there is no difference in the polarization transfer matrix A between the coupling pixel CP (1) and the coupling pixel CP (2), the measured values D1 and D2 obtained in the respective pixels are different from each other, and the expressions expressed by the above- . The same is true after the third measurement.

Therefore, as described above, by rotating the 1/4 wave plate of the transparent portion 12 and temporally modulating the measurement light L3, the N equations included in the above-mentioned Equation (9) are independent from each other do. Thus, the sample measurement matrix T ⁺ , the M matrix element M _ij , and various polarization characteristics can be stably calculated.

Further, when the 1/4 wave plate of the transparent portion 12 is rotated as described above, the S parameter of the measurement light L3 mainly changes according to the rotation angle. Therefore, once the correspondence between the rotation angle and the S parameter is obtained, the calibration of the light projecting unit 12 at the start of measurement is not necessarily required every time. Therefore, when the 1/4 wave plate or the polarizing plate of the transparent portion 12 is rotated to time-modulate the measurement light L3, the time required for the calibration of the transparent portion 12 can be shortened, It is possible to start the polarization measurement of the polarization beam splitter 11.

Further, instead of temporally modulating the measurement light L3, the measurement light L3 may be positively and spatially modulated. 22, the quarter-wave plate of the light-projecting unit 12 is divided into a plurality of kinds of quarter-wave plates in the X-direction, for example, as shown in Fig. The divided wave plate 61 may be used. It should be noted that the divided wave plate 61 of the transparent portion 12 has a smaller number of divisions than the divided wave plate 31 of the light receiving portion 13 so that at least the respective quarter wave plates 31a- It is preferable that the plates 61a, 61b, ... are included.

Each of the quarter wave plates 61a, 61b, ... forming the divided wave plate 61 of the transparent portion 12 is arbitrarily arranged in the main axis direction?, And is periodically changed so as to correspond to the example of time modulation Or it may be random.

In the embodiment described above, the amount of conveyance of the optical film 11 and the measurement timing by the light receiving section 13 are synchronized, and the unit measurement area E is divided into N However, in order to further improve the measurement accuracy, it is desirable to increase the number of times of measurement.

In this case, as shown in Fig. 23, the number of times of the optical film 11 is doubled, for example. When the optical film 11 is transported by a half of the length of the unit measurement area E after performing the 2n-2th measurement in the combined pixel CP (n - 1) for a unit measurement area E The light receiving unit 13 picks up the optical film 11. In the (2n-2) -th measurement, the data in the unit measurement area E is measured in the combination pixel CP (n - 1) and the combination pixel CP (n). After that, when the optical film 11 is transported by the half of the length of the unit measurement area E, the light receiving unit 13 captures the optical film 11.

In this way, the measurement values obtained in the 2n-2th, 2n-th, and 2n + 2th measurements shown in (a), (c) and (d) are the same as those obtained in the above- a large number of measured values can be obtained as much as the unit measurement area E is measured over the two coupling pixels CP as in the (2n-1) th and 2n + 1th measurements shown in FIGS.

The measurement value when the unit measurement area E is measured over two coupling pixels CP can be handled as follows. For example, as shown in Fig. 24, when the unit measurement area E is measured over the combination pixel CP (n - 1) and the combination pixel CP (n) The measured value D _{n -1} and the measured value D _n obtained from the combined pixel CP (n) are calculated according to the ratio of the unit measurement area E overlapping with both the joint pixels CP (n - 1) and CP (n) The mixed value is taken as the measured value of the unit measurement area (E) in this measurement interval. For example, in the case of Figure 24, the percentage of overlap, combined pixel CP - because it is in a half (n 1) 1/2, combined pixel CP (n) _{in, 1/2 · D n -1} + 1 / 2 · D _n can be used as the measured value of the unit measurement area (E) in this measurement. Therefore, when the unit measurement area E is measured when 3/10 of the coupling pixel CP (n-1) is located at 7/10 of the coupling pixel CP (n), 3/10 D _{n -1} + _7/10 · D _n is the measured value of the unit measurement area (E) in this measurement.

In the above-described embodiment, the sum of the measured values Da to Dd of the respective measured values of the wave plates 31a to 31d is calculated at the time of calibration of the light receiving unit 13, For example, when the representative coupling pixels CP are arbitrarily selected by the respective wave plates 31a to 31d, one for each of the wave plates 31a to 31d, and the D _{representative} = The expression of A _{representative} · S _j is obtained. Therefore, the Stokes vector S _j of the measurement light L3 may be calculated by subtracting these four equations. However, to calculate the Stokes vector S _j for each wave plate (31a ~ 31d) are, with high precision measurement light (L3) side using a total Da ~ Dd of the respective measured values of the in such as the above-described embodiment .

Further, in the above-described embodiment, a CCD type imaging device is used as the imaging device 34, and a CMOS type imaging device may be used. Also in this case, as in the case of the CCD described above, the coupling pixel CP is used as a unit of measurement. The method of determining the number of coupled pixels CP, etc. is the same as that of the CCD.

Further, in the above-described embodiment, the polarization characteristic of the optical film 11 having a substantially infinite length in the carrying direction X is measured as compared with the width direction Y. However, It is also possible to measure the polarization characteristics of the polarized light.

The optical film 11 also includes a plate having a certain thickness in addition to a sheet having flexibility. The surface may be subjected to processing such as unevenness.

In the above-described embodiment, the optical film 11 has a constant polarization characteristic. However, the present invention can also measure the polarization characteristic not constant. For example, even if the polarization characteristics are partially different, or the polarization characteristics are different periodically, the polarization characteristics can be preferably measured.

10 Optical property measuring device 11 Optical film
12 light projecting part 13 light receiving part
14 conveying roller 16 control device
19a Müller matrix calculating section 19b Optical characteristic calculating section

Claims (18)

A transparent portion for irradiating a transparent optical film with light having a predetermined polarization state as measurement light,
Wherein a plurality of unit light receiving areas are arranged along the predetermined direction so as to obtain one measurement value corresponding to each of the plurality of kinds of wavelength plates, A light receiving unit that receives the measurement light transmitted through the plurality of kinds of polarization states determined by the wave plate for each unit light receiving area,
The unit measurement area is moved in the predetermined direction by relatively moving the light receiving unit and the optical film along the predetermined direction when the area on the optical film having the size corresponding to the unit light receiving area is set as the unit measurement area A conveying section,
And the measurement light transmitted through the unit measurement area is received by the plurality of unit light receiving areas while moving the unit measurement area in the predetermined direction by the carry section, A Mueller matrix calculating unit for calculating a Mueller matrix of the unit measurement area,
And an optical characteristic calculator for calculating an optical characteristic of the unit measurement area using an element of a Mueller matrix of the unit measurement area. The method according to claim 1,
Wherein a Stokes parameter of the measurement light incident on the unit measurement area is previously measured for each unit light emitting area when an area on the transparent portion with a size corresponding to the unit light receiving area is set as a unit light emitting area, A polarization transfer matrix for correlating a Stokes parameter of the measurement light with the measured value is previously measured for each unit light receiving area,
Wherein the Muller matrix calculator calculates a Muller matrix based on a Stokes parameter of the measurement light incident on the unit measurement area and a plurality of measurement values obtained for the same unit measurement area on the basis of the polarization transfer matrix, And the elements of the Muller matrix are respectively calculated using the sample measurement matrix when the measurement values are obtained. 3. The method of claim 2,
The light-transmitting portion is formed to be freely movable along the predetermined direction,
Wherein a Stokes parameter of the measurement light incident on the unit measurement area is measured by receiving the measurement light at the light receiving unit while moving the light transmitting unit in the predetermined direction in a state in which the optical film is absent Measuring device. The method according to claim 1,
Wherein the light-transmitting portion irradiates the measurement light in a range of the same size as the visual field of the light-receiving portion. The method according to claim 1,
Wherein the light-transmitting portion irradiates circularly polarized light to the optical film as the measuring light. The method according to claim 1,
Wherein the light transmitting portion includes a planar light source that emits light in a non-polarized state from a planar light emitting surface, a polarizer that adjusts the light incident from the planar light source to linearly polarized light, And a 1/4 wavelength plate for irradiating the optical film. The method according to claim 6,
Wherein the 1/4 wavelength plate is formed so as to freely rotate around an irradiation optical axis of the measurement light. The method according to claim 1,
The light receiving unit includes a lens for imaging the measurement light transmitted through the plurality of kinds of wavelength plates onto an image pickup device,
Wherein the lens is an object-side telecentric lens which can regard the optical axis and the principal ray parallel to the object side. 9. The method of claim 8,
Wherein said lens is a bilateral telecentric lens capable of considering the optical axis and principal ray in parallel on the object side and the image side. 10. The method according to any one of claims 1 to 9,
Wherein the light-receiving unit is provided with at least 4 kinds of wavelength plates and at most 40 kinds of wavelength plates as the plural kinds of wavelength plates. 10. The method according to any one of claims 1 to 9,
Wherein the plurality of kinds of wave plates provided in the light receiving unit are arranged so that their main axis directions are different from each other in the predetermined direction. 10. The method according to any one of claims 1 to 9,
Wherein the plurality of kinds of wavelength plates provided in the light receiving section have a ground amount of 70 degrees or more and 170 degrees or less or 190 degrees or more and 290 degrees or less. 10. The method according to any one of claims 1 to 9,
Wherein the unit light receiving area is a combined pixel including a plurality of adjacent pixels and having a measured value obtained by averaging output values of a plurality of pixels belonging thereto. 14. The method of claim 13,
Wherein the number of pixels constituting the combined pixel is a square of 2 or more natural numbers and the same number of pixels in the vertical and horizontal directions. 10. The method according to any one of claims 1 to 9,
Wherein a plurality of sets of the transparent portion and the light receiving portion are provided in a direction perpendicular to the predetermined direction. 10. The method according to any one of claims 1 to 9,
And the entire surface of the optical film is measured by moving the set of the transparent portion and the light receiving portion in a direction perpendicular to the predetermined direction. Receiving a measurement light from the transparent portion of the transparent optical film as a measurement light in a predetermined polarization state and receiving the measurement light transmitted through the optical film in a plurality of types of polarization states for each unit light receiving area in the light receiving portion, And a light receiving unit that receives the light beam while relatively moving the optical film and the light receiving unit when a measured value is obtained for each unit measurement area on the optical film corresponding to the light beam, A measurement step of obtaining a measurement value,
A Mueller matrix calculating step of calculating a Mueller matrix of the unit measurement area based on the plurality of measurement values obtained in the measurement step for each unit measurement area;
And an optical characteristic calculating step of calculating an optical characteristic of the unit measurement area using the elements of the Muller matrix. 18. The method of claim 17,
Wherein the Muller matrix calculation step calculates the Muller matrix from the measured values using a sample measurement matrix in which a plurality of the measured values are associated with elements of the Muller matrix,
Wherein the sample measurement matrix is a matrix in which a Stokes parameter of the measurement light after passing through the unit measurement area is made to correspond to the measurement value, the polarization distribution matrix corresponding to the unit light reception area Wherein the calculation is performed in advance using a Stokes parameter previously measured for each unit light-emitting area on the light-transmitting portion.

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