Multilayer film measuring device and measuring method

Abstract

The present application provides a measuring device and a measuring method for a multilayer film, wherein the measuring device includes: a measuring module, a multilayer film to be measured, and a circular polarization module. A light source unit and a receiving module are provided on the same side of the measuring module, and the light source unit can generate a laser beam. The circular polarization module is located between the measuring module and the multilayer film to be measured. When the laser beam passes through the circular polarization module to the multilayer film to be measured, the reflective polarizer in the multilayer film to be measured will totally reflect the laser beam to the receiving module, and the laser beam reflected by the surface of the first phase delay plate in the multilayer film to be measured will be absorbed by the second linear polarizer in the circular polarization module, so that the efficacy of the multilayer film to be measured can be accurately measured.

Description

Technical Field

[0001] The present application relates to a measuring device, and more particularly to a measuring device and a measuring method for a multilayer film that eliminates interference from reflected light signals of the multilayer film. Background Art

[0002] In virtual reality technology, a virtual world is constructed through computers or electronic devices, and special operating media are used to allow users to obtain various sensory simulations provided by the computers or electronic devices, thereby achieving the effect of entering the virtual world. The above-mentioned operating media include, for example, virtual reality glasses that provide visual information or virtual reality gloves that provide tactile information. Taking virtual reality glasses as an example, there are many types of virtual reality glasses on the market today. Among them, there is a type of virtual reality glasses that are used to combine with the display screen of a handheld electronic device (such as a mobile phone or tablet computer) to allow users to watch a virtual reality with visual effects in real time without being restricted by location. This type of virtual reality glasses does not require additional electronic circuits or chips. However, the virtual reality glasses currently available on the market are bulky and inconvenient to carry, which does not meet the needs of most consumers.

[0003] In ultra-short-throw pancake optical systems used in virtual reality (VR), polarizing films employ a multilayered structure, such as a three-layer stack consisting of a phase retarder (QWP), a reflective polarizer (RP), and a linear polarizer (LP). Laser interferometry is then used to test the surface topography of the reflective polarizer (RP) within the multilayer stack to ensure it is within optical specifications. Current measurement devices primarily measure surface topography by receiving reflected light signals from the reflective polarizer (RP).

[0004] like Figure 1 The following is a schematic diagram of the system architecture of a conventional measurement device. In a conventional measurement device, a laser transmitter 1 transmits a laser light source 10 to a multilayer stacked film 11. Because the multilayer stacked film 11 comprises a three-layer polarizing film structure: a phase retarder 111 (QWP), a reflective polarizer 112 (RP), and a linear polarizer 113 (LP), the receiver 2 receives two reflected light signals: a reflected light signal 101 from the reflective polarizer 112 (RP) and a reflected light signal 102 from the phase retarder 111 (QWP). However, the reflected light signal 102 from the phase retarder 111 (QWP) interferes with the reflected light signal 101 from the reflective polarizer 112 (RP), resulting in inaccurate surface topography measurements of the reflective polarizer 112 (RP). Therefore, improvements are necessary to address this issue. Summary of the Invention

[0005] The purpose of this application is to provide a multi-layer film measurement device and measurement method. By adding a circular polarization module between the measurement module and the multi-layer film to be measured, the interference of the reflected light signal of the multi-layer film on the measurement module is eliminated, so as to achieve the effect of accurately measuring the multi-layer stacked optical film.

[0006] To achieve the above objectives, the present application provides a multilayer film measurement device, comprising:

[0007] The measurement module has a projection port and a receiving port on one side, and the measurement module also includes:

[0008] a light source unit, located corresponding to the projection port, and capable of generating a laser beam;

[0009] a receiving module, located corresponding to the receiving port;

[0010] The multilayer film to be measured has a first phase retarder and a reflective polarizer, and the first phase retarder is adjacent to the measurement module;

[0011] a circular polarization module located between the measurement module and the multilayer film to be measured, the circular polarization module comprising a second phase retarder and a second linear polarizer, and the second linear polarizer being adjacent to the measurement module;

[0012] When the laser beam is projected from the projection port and passes through the circular polarization module to the multilayer film to be measured, the reflective polarizer uses total internal reflection to transmit the laser beam through the circular polarization module to the receiving port, and the laser beam reflected by the surface of the first phase delay plate will be absorbed by the second linear polarizer.

[0013] In one embodiment of the present application, the laser beam is defined as a cone shape rotating along a rotation axis as the center, the laser beam has a vertex, the vertex is located on an end face of the light source unit, and the light source unit is connected to the projection port along the extension direction of the rotation axis.

[0014] In one embodiment of the present application, the multilayer film to be tested is located on a supporting plane perpendicular to the rotation axis. The supporting plane is defined to extend along a first direction and a second direction. The first direction and the second direction are perpendicular to each other.

[0015] In one embodiment of the present application, the fast axis of the first phase retarder forms an angle of 45 degrees or 135 degrees with the transmission axis of the reflective polarizer, and the transmission axis of the reflective polarizer, the transmission axis of the first linear polarizer, and the first direction are parallel to each other.

[0016] In one embodiment of the present application, the second linear polarizer is the first direction linear polarizer, the second phase retarder is a phase retarder quarter wave plate, and the slow axis of the second phase retarder forms an angle of 45 degrees with the first direction.

[0017] In one embodiment of the present application, the multi-layer film to be tested further includes a first linear polarizer, and the reflective polarizer is located between the first phase retarder and the first linear polarizer.

[0018] To achieve the above-mentioned objectives, the present application provides a method for measuring a multilayer film, comprising:

[0019] Step (a): Providing a measurement module, a multilayer film to be measured, and a circular polarization module, wherein the measurement module has a light source unit and a receiving module, wherein the light source unit and the receiving module are located on the same side of the measurement module, and the light source unit can generate a laser beam, wherein the laser beam is defined as a cone shape rotating along a rotation axis as the center, the multilayer film to be measured has a first phase retarder, a reflective polarizer, and a first linear polarizer, wherein the reflective polarizer is located between the first phase retarder and the first linear polarizer, and the circular polarization module has a second phase retarder and a second linear polarizer;

[0020] Step (b): placing the multilayer film to be measured on a supporting plane perpendicular to the rotation axis, with the first phase retarder adjacent to the measurement module;

[0021] Step (c): placing the circular polarization module between the measurement module and the multilayer film to be measured, and placing the second linear polarizer adjacent to the measurement module;

[0022] Step (d): adjusting the circular polarization module and the supporting plane to be parallel to each other;

[0023] Step (e): Determining whether the circular polarization module is parallel to the supporting plane; when the circular polarization module is not parallel to the supporting plane, repeating step (d); when the circular polarization module is parallel to the supporting plane, adjusting the slow axis of the second phase retarder to form a 45-degree angle with the fast axis of the first phase retarder;

[0024] Step (f): generating the laser beam with the light source unit and transmitting the laser beam through the circular polarization module to the multilayer film to be tested;

[0025] Step (g): The reflective polarizer uses total internal reflection to transmit the laser beam through the circular polarization module to the receiving module, and the second linear polarizer blocks the laser beam reflected by the surface of the first phase retarder.

[0026] In one embodiment of the present application, step (a) further includes:

[0027] Step (a1): adjusting the transmission axis of the reflective polarizer and the transmission axis of the first linear polarizer to be parallel to each other;

[0028] Step (a2): Determining whether the transmission axis of the reflective polarizer is parallel to the transmission axis of the first linear polarizer; when the transmission axis of the reflective polarizer is not parallel to the transmission axis of the first linear polarizer, repeating step (a1); when the transmission axis of the reflective polarizer is parallel to the transmission axis of the first linear polarizer, executing step (a3);

[0029] Step (a3): adjusting the fast axis of the first phase retarder and the transmission axis of the reflective polarizer to form an angle of 45 degrees or 135 degrees;

[0030] Step (a4): Determine whether the fast axis of the first phase retarder is at an angle of 45 degrees or 135 degrees to the transmission axis of the reflective polarizer; when the fast axis of the first phase retarder is not at an angle of 45 degrees or 135 degrees to the transmission axis of the reflective polarizer, repeat step (a3); when the fast axis of the first phase retarder is at an angle of 45 degrees or 135 degrees to the transmission axis of the reflective polarizer, perform step (b).

[0031] In one embodiment of the present application, step (e) further includes:

[0032] Step (e1): Determine whether the slow axis of the second phase retarder forms a 45-degree angle with the fast axis of the first phase retarder; when the slow axis of the second phase retarder does not form a 45-degree angle with the fast axis of the first phase retarder, repeat step (e); when the slow axis of the second phase retarder forms a 45-degree angle with the fast axis of the first phase retarder, execute step (f). BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the system architecture of a traditional technology measurement device.

[0034] Figure 2 This is a schematic diagram of the system architecture of an embodiment of a multi-layer film measurement device of the present application.

[0035] Figure 3A This is a schematic diagram of an axial embodiment of the first phase retarder of the present application.

[0036] Figure 3B This is a schematic diagram of an axial embodiment of the reflective polarizer of the present application.

[0037] Figure 3C This is a schematic diagram of an axial embodiment of the first linear polarizer of the present application.

[0038] Figure 4A for Figure 1 Schematic diagram of surface measurement results with interfering reflected light signals in the system architecture.

[0039] Figure 4B for Figure 2 Schematic diagram of surface measurement results without interference from reflected light signals in the system architecture.

[0040] Figure 5A This is a schematic diagram of the architecture of the reflective polarizer reflected light signal analysis system of this application.

[0041] Figure 5B Schematic diagram of the receiving module of this application analyzing the reflected light signal of the reflective polarizer.

[0042] Figure 6A This is a schematic diagram of the architecture of the first phase delay plate reflected light signal analysis system of this application.

[0043] Figure 6B Schematic diagram of the receiving module of this application analyzing the light signal reflected by the first phase delay plate.

[0044] Figure 7A Schematic diagram of the system architecture for testing the reflected light signal of a single-layer reflective polarizer.

[0045] Figure 7B Schematic diagram of the surface profile test results of a single-layer reflective polarizer.

[0046] Figure 8A Schematic diagram of the system architecture for testing traditional multi-layer film reflected light signals.

[0047] Figure 8B Schematic diagram of the results of testing the surface profile of the reflective polarizer in a traditional multilayer film.

[0048] Figure 9A Schematic diagram of the architecture of the multilayer film reflected light signal system for testing this application.

[0049] Figure 9B A schematic diagram of the test results of the surface profile of the reflective polarizer in the multilayer film of this application.

[0050] Figure 10 This is a block diagram of an embodiment of the method for measuring a multilayer film of the present application.

[0051] Description of Figure Numbers:

[0052] 1. Laser transmitter 10. Laser light source

[0053] 101, 102: reflected light signal 11, multi-layer stacked film 111. Phase retarder 112. Reflective polarizer 113, Linear polarizer 2, Receiver

[0054] 3. Measuring module 30, side 31. Projection port 32. Receive port 33. Light source unit 331. End surface 34. Receiving module 35. Laser beam

[0055] 35a, circularly polarized light 35b, linearly polarized light

[0056] 35c, reflected light signal 35d, reflected light interference signal 350, rotation axis 351, vertex

[0057] 4. Multilayer film to be tested 41. First phase retarder 411, fast axis 412, slow axis

[0058] 42. Reflective polarizer 421. Transmission axis

[0059] 43. First linear polarizer 431. Transmission axis

[0060] 5. Circular polarization module 51, second phase retarder

[0061] 52. Second linear polarizer 6. Carrying plane

[0062] 61. First direction 62. Second direction

[0063] 7. Simulated detection surface 8. Lens

[0064] 80. Optical adhesive

[0065] 90, 901, 902, 903, 904, 91, 92, 93, 94, 940, 941, 95, 96, steps DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solutions and advantages of this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application, but are not intended to limit this application.

[0067] See also Figure 2 and Figure 3A 、 Figure 3B and Figure 3CSchematic diagrams of the system architecture of a multilayer film measurement device and axial embodiments of the multilayer film at one angle, another angle, and yet another angle are shown. The multilayer film measurement device of the present application includes a measurement module 3, a multilayer film to be measured 4, and a circular polarization module 5. The measurement module 3 is a frame structure having a projection port 31 and a receiving port 32 on a side surface 30. The measurement module 3 also includes a light source unit 33 and a receiving module 34. The light source unit 33 is located corresponding to the projection port 31 and can generate a laser beam 35. The receiving module 34 is located corresponding to the receiving port 32.

[0068] In the embodiment of the present application, laser beam 35 is defined as a cone that rotates about a rotation axis 350. Laser beam 35 has a vertex 351 located on an end surface 331 of light source unit 33. Light source unit 33 is connected to projection port 31 along the direction extending from rotation axis 350. Multilayer film 4 to be tested is located on support plane 6 perpendicular to rotation axis 350. Support plane 6 extends along a first direction 61 and a second direction 62, with first direction 61 and second direction 62 being perpendicular to each other.

[0069] The multilayer film 4 to be measured comprises a first phase retarder (QWP) 41, a reflective polarizer (RP) 42, and a first linear polarizer (LP) 43. The reflective polarizer 42 is positioned between the first phase retarder 41 and the first linear polarizer 43, with the first phase retarder 41 adjacent to the measurement module 3. In the present embodiment, the fast axis 411 of the first phase retarder 41 forms an angle of 45 degrees or 135 degrees with the transmission axis 421 of the reflective polarizer 42. Furthermore, the transmission axis 421 of the reflective polarizer 42, the transmission axis 431 of the first linear polarizer 43, and the first direction 61 are parallel to each other.

[0070] The circular polarization module 5 is located between the measurement module 3 and the multilayer film 4 to be measured. The circular polarization module 5 comprises a second phase retarder 51 and a second linear polarizer 52, with the second linear polarizer 52 positioned adjacent to the measurement module 3. In this embodiment, the second linear polarizer 52 is a linear polarizer in the first direction 61, while the second phase retarder 51 is a quarter-wave plate. The slow axis 412 of the second phase retarder 51 forms a 45-degree angle with the first direction 61.

[0071] When the light source unit 33 projects a laser beam 35 from the projection port 31, the laser beam 35 will pass through the circular polarization module 5 to the multilayer film 4 to be tested. After passing through the circular polarization module 5, the incident laser beam 35 will be converted into circularly polarized light 35a and incident on the multilayer film 4 to be tested in the multi-layer stack. The circularly polarized light 35a passes through the first phase delay plate 41 in the multilayer film 4 to be tested in the multi-layer stack and is converted into linearly polarized light 35b to be totally reflected on the surface of the reflective polarizer 42. The reflective polarizer 42 uses total reflection to transmit the first reflected light signal 35c through the circular polarization module 5 to the receiving port 32, and the surface shape of the reflective polarizer 42 is measured by the receiving module 34. The reflected light interference signal 35d reflected from the surface of the first phase delay plate 41 is absorbed by the second linear polarizer 52 and does not enter the receiving module 34. Please refer to Figure 4B As shown, Figure 2 Schematic diagram of surface measurement results without interference reflected light signal in the system architecture. Figure 4B The figure is only used as a schematic diagram. The different depths of grayscale in the figure are used to represent the micro-arc of the ripple measured by the system architecture. From the results shown in the figure, we can see that Figure 2 The ripple (Waviness) measured in the system architecture is 164 microradians (μrad), which is much smaller than Figure 4A shown Figure 1 The waviness measured in the system architecture is more accurate at 294 microradians (μrad) showing the surface shape of the reflective polarizer 42. Figure 4A The figure is only shown as a schematic diagram, and the grayscale colors of different depths in the figure are used to represent the micro-arcs of the ripples measured by the system architecture.

[0072] See also Figures 5A to 6B The figure shows the structure of the reflective polarizer and the first phase retarder reflection light signal analysis system of the present invention, and the receiving module analysis of the reflective polarizer and the first phase retarder reflection light signal. First, a simulation detection surface 7 is added between the measurement module 3 and the multilayer film 4 to be measured. The simulation detection surface 7 is a light reaction presented by the first direction 61 polarization. Figure 5A and Figure 5B The analysis of the light signal reflected from the reflective polarizer 42 shows that the light energy can directly penetrate the circular polarization module 5 and return to the simulation detection surface 7; Figure 6A and Figure 6B The figure shows the analysis of the light signal reflected from the surface of the first phase delay plate 41. The light signal reflected from the surface of the first phase delay plate 41 is absorbed by the second linear polarizer 52 in the circular polarization module 5 and does not enter the simulated detection surface 7. Figure 5B and Figure 6B These figures are only shown as schematic drawings, and the grayscale colors of different depths in the figures are used to represent different incoherent irradiances.

[0073] See also 7A to 9B The following is a schematic diagram of the system architecture for testing the reflected light signal of a single-layer reflective polarizer, a conventional multi-layer film, and the multi-layer film of the present invention, as well as a schematic diagram of the surface profile results of the single-layer reflective polarizer, the conventional multi-layer film, and the multi-layer film of the present invention. First, the lens 8 is set as a concave lens, and the surface of the lens 8 is connected to the object to be tested with OCA optical adhesive 80 (Optical Clear Adhesive). Figure 7A As shown in FIG, the waviness slope mean of the single-layer reflective polarizer 42 is 173.58 μrad, while Figure 8B As shown in the figure, the mean waviness slope of the multilayer film 4 is 294.52 μrad, while Figure 9B As shown in FIG, the multilayer film 4 with the circular polarization module 5 has a waviness slope mean of 164.30 μrad. In comparison, the multilayer film 4 with the circular polarization module 5 can better reflect the actual waviness slope of the single-layer reflective polarizer 42. Figure 7B 、 Figure 8B and Figure 9B These are only shown as schematic drawings, and the grayscale colors of different depths in the drawings are used to represent the micro-arcs of the ripples measured by the system architecture.

[0074] See also Figure 10 The following is a flow chart of an embodiment of the method for measuring a multilayer film of the present invention. The method for measuring a multilayer film of the present invention includes the following steps:

[0075] Step 90: Provide a measurement module, a multilayer film to be measured, and a circular polarization module, the measurement module having a light source unit and a receiving module, the light source unit and the receiving module being located on the same side of the measurement module, the light source unit being capable of generating a laser beam, the laser beam being defined as a cone shape rotating along a rotation axis as a center, the multilayer film to be measured having a first phase delay plate, a reflective polarizer, and a first linear polarizer, the reflective polarizer being located between the first phase delay plate and the first linear polarizer, the circular polarization module having a second phase delay plate and a second linear polarizer.

[0076] Step 901: Adjust the transmission axis of the reflective polarizer and the transmission axis of the first linear polarizer to be parallel to each other.

[0077] Step 902: Determine whether the transmission axis of the reflective polarizer is parallel to the transmission axis of the first linear polarizer. When the transmission axis of the reflective polarizer is not parallel to the transmission axis of the first linear polarizer, repeat step 901. When the transmission axis of the reflective polarizer is parallel to the transmission axis of the first linear polarizer, execute step 903.

[0078] Step 903: Adjust the fast axis of the first phase retarder and the transmission axis of the reflective polarizer to form an angle of 45 degrees or 135 degrees.

[0079] Step 904: Determine whether the fast axis of the first phase retarder forms an angle of 45 degrees or 135 degrees with the transmission axis of the reflective polarizer; when the fast axis of the first phase retarder does not form an angle of 45 degrees or 135 degrees with the transmission axis of the reflective polarizer, repeat step 903; when the fast axis of the first phase retarder forms an angle of 45 degrees or 135 degrees with the transmission axis of the reflective polarizer, execute step 91.

[0080] Step 91: Place the multilayer film to be measured on a supporting plane perpendicular to the rotation axis, with the first phase retarder adjacent to the measurement module.

[0081] Step 92: Place the circular polarization module between the measurement module and the multilayer film to be measured, and place the second linear polarizer adjacent to the measurement module.

[0082] Step 93: Adjust the circular polarization module and the supporting plane to be parallel to each other.

[0083] Step 94: Determine whether the circular polarization module is parallel to the supporting plane; when the circular polarization module is not parallel to the supporting plane, repeat step 93; when the circular polarization module is parallel to the supporting plane, execute step 940: adjust the slow axis of the second phase retarder to form a 45-degree angle with the fast axis of the first phase retarder.

[0084] Step 941: Determine whether the slow axis of the second phase retarder forms a 45-degree angle with the fast axis of the first phase retarder; when the slow axis of the second phase retarder does not form a 45-degree angle with the fast axis of the first phase retarder, repeat step 94; when the slow axis of the second phase retarder forms a 45-degree angle with the fast axis of the first phase retarder, execute step 95.

[0085] Step 95: Use a light source unit to generate a laser beam that passes through a circular polarization module to the multilayer film to be tested.

[0086] Step 96: The reflective polarizer uses total internal reflection to transmit the laser beam through the circular polarization module to the receiving module, and the second linear polarizer blocks the laser beam reflected by the surface of the first phase retarder.

[0087] The above detailed description is a specific description of the feasible embodiments of the present application, and the aforementioned embodiments are not intended to limit the patent scope of the present application. Any equivalent implementation or modification that does not deviate from the technical solution of the present application should be included in the patent scope of the present application.

Claims

1. A multilayer film measuring device, characterized in that: include: The measurement module has a projection port and a receiving port on one side, and the measurement module also includes: a light source unit, located corresponding to the projection port, and capable of generating a laser beam; a receiving module, located corresponding to the receiving port; The multilayer film to be measured has a first phase retarder and a reflective polarizer, and the first phase retarder is adjacent to the measurement module; a first linear polarizer, wherein the reflective polarizer is located between the first phase retarder and the first linear polarizer; a circular polarization module located between the measurement module and the multilayer film to be measured, the circular polarization module comprising a second phase retarder and a second linear polarizer, and the second linear polarizer being adjacent to the measurement module; When the laser beam is projected from the projection port and passes through the circular polarization module to the multilayer film to be measured, the reflective polarizer uses total internal reflection to transmit the laser beam through the circular polarization module to the receiving port, and the laser beam reflected by the surface of the first phase delay plate will be absorbed by the second linear polarizer.

2. The multilayer film measuring device according to claim 1, characterized in that: The laser beam is in a cone shape defined to rotate along a rotation axis as a center. The laser beam has a vertex located on an end surface of the light source unit. The light source unit is connected to the projection port along an extension direction of the rotation axis.

3. The multi-layer film measuring device according to claim 2, characterized in that: The multi-layer film to be tested is located on a supporting plane perpendicular to the rotation axis. The supporting plane is defined to extend along a first direction and a second direction. The first direction and the second direction are perpendicular to each other.

4. The multi-layer film measuring device according to claim 3, characterized in that: The fast axis of the first phase retarder forms an angle of 45 degrees or 135 degrees with the transmission axis of the reflective polarizer, and the transmission axis of the reflective polarizer, the transmission axis of the first linear polarizer, and the first direction are parallel to each other.

5. The multi-layer film measuring device according to claim 3, characterized in that: The second linear polarizer is the first direction linear polarizer, the second phase retarder is a phase retarder quarter wave plate, and the slow axis of the second phase retarder forms an angle of 45 degrees with the first direction.

6. A method for measuring a multilayer film, characterized in that: include: (a) providing a measurement module, a multilayer film to be measured, and a circular polarization module, wherein the measurement module comprises a light source unit and a receiving module, the light source unit and the receiving module being located on the same side of the measurement module, the light source unit being capable of generating a laser beam, the laser beam being in the shape of a cone defined to rotate along a rotation axis, the multilayer film to be measured comprising a first phase retarder, a reflective polarizer, and a first linear polarizer, the reflective polarizer being located between the first phase retarder and the first linear polarizer, and the circular polarization module comprising a second phase retarder and a second linear polarizer; (b) placing the multilayer film to be measured on a supporting plane perpendicular to the rotation axis, with the first phase retarder adjacent to the measurement module; (c) placing the circular polarization module between the measurement module and the multilayer film to be measured, and placing the second linear polarizer adjacent to the measurement module; (d) adjusting the circular polarization module and the supporting plane to be parallel to each other; (e) determining whether the circular polarization module is parallel to the supporting plane; when the circular polarization module is not parallel to the supporting plane, repeating step (d); when the circular polarization module is parallel to the supporting plane, adjusting the slow axis of the second phase retarder to form an angle of 45 degrees with the fast axis of the first phase retarder; (f) generating the laser beam with the light source unit and transmitting the laser beam through the circular polarization module to the multilayer film to be tested; (g) The reflective polarizer transmits the laser beam through the circular polarization module to the receiving module by total internal reflection, and the second linear polarizer blocks the laser beam reflected by the surface of the first phase retarder.

7. The method for measuring a multilayer film according to claim 6, wherein: After step (a), the method further comprises: (a1) adjusting the transmission axis of the reflective polarizer and the transmission axis of the first linear polarizer to be parallel to each other; (a2) determining whether the transmission axis of the reflective polarizer is parallel to the transmission axis of the first linear polarizer; when the transmission axis of the reflective polarizer is not parallel to the transmission axis of the first linear polarizer, repeating step (a1); when the transmission axis of the reflective polarizer is parallel to the transmission axis of the first linear polarizer, executing step (a3); (a3) adjusting the fast axis of the first phase retarder and the transmission axis of the reflective polarizer to form an angle of 45 degrees or 135 degrees; (a4) Determine whether the fast axis of the first phase retarder forms an angle of 45 degrees or 135 degrees with the transmission axis of the reflective polarizer; when the fast axis of the first phase retarder does not form an angle of 45 degrees or 135 degrees with the transmission axis of the reflective polarizer, repeat step (a3); when the fast axis of the first phase retarder forms an angle of 45 degrees or 135 degrees with the transmission axis of the reflective polarizer, perform step (b).

8. The method for measuring a multilayer film according to claim 7, wherein: After step (e), the method further comprises: (e1) Determine whether the slow axis of the second phase retarder forms an angle of 45 degrees with the fast axis of the first phase retarder; when the slow axis of the second phase retarder does not form an angle of 45 degrees with the fast axis of the first phase retarder, repeat step (e); when the slow axis of the second phase retarder forms an angle of 45 degrees with the fast axis of the first phase retarder, execute step (f).

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