A method and system for detecting an optical axis angle of an optical film

Abstract

Embodiments of the present application provide a method and system for detecting an optical film optical axis angle. The method is applied to the system for detecting the optical film optical axis angle. The system comprises a light source assembly, a phase delay element, a polarizer and a detection module. In the case that the optical film to be detected is arranged in a rotating manner between the light source assembly and the phase delay element, the method comprises: controlling linearly polarized light of multiple fields of view to pass through different positions of the optical film, and then the light rays emitted from the optical film to pass through the phase delay element and the polarizer in turn and project onto the detection module; obtaining an azimuth angle of the light rays emitted from the optical film; obtaining a straight side angle of the optical film; establishing a relationship model according to the azimuth angle of the light rays emitted from the optical film and the straight side angle; and determining the optical axis angle of the optical film according to the relationship model.

Description

Technical Field

[0001] This application relates to the field of optical film detection technology, and more specifically, to a method and system for detecting the optical axis angle of an optical film. Background Technology

[0002] In the manufacturing process of displays, optical films need to be laminated onto optical components to achieve the display function of optical display devices. The lamination accuracy of the optical film is closely related to the display quality of the optical display device. Therefore, the detection of the optical axis angle of the optical film is particularly important.

[0003] Currently, the power method is a commonly used method for detecting the azimuth angle of the optical axis of optical films. However, when using the power method to detect optical films, it is generally necessary to rotate the film material around its entire radius to find the maximum or minimum power value, thereby determining the position of the optical axis. Moreover, the detection results of the power method are often affected by the excitation source and the detector. When the optical axis of the optical film changes by a small angle, the resolution of the detector is insufficient, making it difficult to accurately detect minute changes in light intensity.

[0004] Therefore, how to accurately detect the optical axis angle of the optical film is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this application is to provide a new technical solution for a method and system for detecting the optical axis angle of an optical film.

[0006] In a first aspect, this application provides a method for detecting the optical axis angle of an optical film. The method is applied to an optical film optical axis angle detection system, which includes: a light source assembly, a phase retardation element, a polarizer, and a detection module, wherein the phase retardation element rotates at an angular frequency ω; the optical film to be detected is placed between the light source assembly and the phase retardation element.

[0007] When the optical film to be tested is rotated between the light source assembly and the phase retardation element, the detection method includes:

[0008] After linearly polarized light with multiple fields of view passes through different positions of the optical film, the light emitted from the optical film passes sequentially through the phase delay element and the polarizer and is projected onto the detection module.

[0009] The azimuth angle of the light emitted from the optical film is obtained based on the intensity of the light emitted from the polarizer received by the detection module.

[0010] Obtain the straight edge angle of the optical film, wherein the straight edge angle is the angle between the straight edge of the optical film and the reference line, and the reference line is the vertical coordinate axis in the visual camera coordinate system;

[0011] A relationship model is established based on the azimuth angle of the light emitted from the optical film and the angle of the straight edge;

[0012] The optical axis angle of the optical film is determined based on the relationship model.

[0013] Optionally, obtaining the azimuth angle of the light emitted from the optical film based on the intensity of the polarizer-emitted light received by the detection module specifically includes:

[0014] The intensity of the light emitted from the polarizer is obtained when the angle between the fast axis of the phase delay element and the horizontal direction is α, where α = ωt, and t is the rotation time of the phase delay element;

[0015] Based on the intensity of the light emitted from the polarizer, the Stokes vector of the light emitted from the optical film is obtained;

[0016] The azimuth angle of the light emitted from the optical film is obtained based on the Stokes vector of the light emitted from the optical film.

[0017] Optionally, the phase delay element is a quarter-wave plate, and the polarizer is a horizontal linear polarizer.

[0018] Optionally, the optical film is one of a polarizing film, a reflective polarizing film, or a phase retardation film.

[0019] Optionally, the light source assembly includes a polarizer, and when the optical film is a phase retardation film, it further includes the following before the polarized light controlling multiple fields of view passes through different positions of the optical film:

[0020] The angle of the polarizer is controlled to be the ideal optical axis azimuth angle of the phase retardation film to be tested.

[0021] Optionally, obtaining the Stokes vector of the light emitted from the optical film based on the intensity of the light emitted from the polarizer specifically includes:

[0022] A model is established to determine the relationship between the intensity of the light emitted from the polarizer and the Stokes vector of the light emitted from the optical film.

[0023] Perform a Fourier transform on the relationship model and obtain the Fourier transform coefficients based on the intensity of the light emitted from the polarizer;

[0024] The Stokes vector of the light rays emitted from the optical film is obtained based on the Fourier transform coefficients.

[0025] Optionally, the model for obtaining the relationship between the intensity of the light emitted from the polarizer and the Stokes vector of the light emitted from the optical film specifically includes:

[0026] The Stokes vector of the light emitted from the optical film is defined as Sm;

[0027] Based on the Stokes vector Sm, obtain the Stokes vector S′ of the emitted light from the phase delay element;

[0028] Based on the Stokes vector S′, obtain the Stokes vector Sout of the polarizer-emitted light;

[0029] Based on the Stokes vector Sout, obtain the relationship expression between the intensity of the polarizer-emitted light and the Stokes vector of the optical film-emitted light.

[0030] Optionally, obtaining the Stokes vector S′ of the emitted light from the phase delay element based on the Stokes vector Sm specifically includes:

[0031] Based on the Stokes vector Sm and the Mueller matrix of the phase delay element with an angle α between the fast axis and the horizontal direction, the Stokes vector S′ of the emitted light from the phase delay element is obtained.

[0032] Optionally, obtaining the Stokes vector Sout of the polarizer-emitted ray based on the Stokes vector S′ specifically includes:

[0033] The Stokes vector Sout of the polarizer's outgoing light is obtained based on the Stokes vector S′ and the Mueller matrix of the polarizer.

[0034] Optionally, the phase delay element rotating at an angular frequency ω specifically includes:

[0035] The phase delay element is driven by a stepper motor to rotate at an angular frequency ω, where the number of steps of the stepper motor is n, the step size is aj, and α = ωt = n × aj.

[0036] Secondly, a detection system for the optical axis angle of an optical film is provided, the detection system comprising:

[0037] The light source assembly, phase delay element, polarizer, and detection module, wherein the phase delay element rotates at an angular frequency ω;

[0038] The light source assembly is used to emit polarized light with multiple fields of view;

[0039] When the optical film to be tested is placed between the light source assembly and the phase delay element, the optical film, the phase delay element, the polarizer, and the detection module are arranged sequentially along the same optical axis.

[0040] Optionally, the light source assembly includes: a light source, a fast reflector, a lens group, and a polarizer, wherein the lens group includes at least one lens;

[0041] The light emitted from the light source passes sequentially through the fast reflector, the lens group, and the polarizer before being projected onto the optical film to be tested.

[0042] Optionally, it also includes a stepper motor that drives the phase delay element to rotate at an angular frequency ω.

[0043] Optionally, the polarizer is a horizontal linear polarizer, and the phase delay element is a quarter-wave plate.

[0044] The technical solution provided in this application embodiment detects the azimuth angle of the light emitted from the optical film by combining a phase delay element rotating at an angular frequency ω with a polarizer and a detection module, and obtains the straight edge angle of the optical film through a vision camera. A relationship model is established based on the azimuth angle and straight edge angle of the emitted light from the optical film, and the optical axis angle of the optical film is obtained based on the relationship model. This application embodiment can obtain the optical axis angle of the optical film simply and quickly.

[0045] Other features and advantages of this specification will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0046] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of this specification and, together with their description, serve to explain the principles of this specification.

[0047] Figure 1 The diagram shown is a structural diagram of the optical film optical axis angle detection system provided in an embodiment of this application.

[0048] Figure 2 The figure shows the fitted curves of the azimuth angle of the light emitted from the optical film and the angle of the straight edge of the optical film.

[0049] Explanation of reference numerals in the attached figures:

[0050] 1. Light source assembly; 10. Light source; 11. Fast reflector; 12. First lens; 13. Second lens; 14. Polarizer;

[0051] 2. The optical film to be tested;

[0052] 3. Phase delay element;

[0053] 4. Polarizer;

[0054] 5. Detection module;

[0055] 6. Visual camera. Detailed Implementation

[0056] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0057] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0058] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0059] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0060] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0061] VR optical films generally include polarizing films (POL films), reflective polarizing films (RP films), and quarter-wave plates (QWP films). VR optical films, combined with lens groups, form optical modules with folded optical paths. The imaging quality of these modules is affected by the precision of the film bonding; even slight angular differences can severely impact image quality, as well as the user experience and eye comfort. Therefore, optical axis detection of the optical film is essential and plays a crucial role in controlling the incoming material quality, the bonding process, and the final yield of VR pancake lenses.

[0062] Currently, power detection methods are used to detect the optical axis of VR optical films. However, this method requires rotating the optical film a full circle to find the power maxima or minima, and then determining the optical axis position based on these values. Furthermore, power detection results are often affected by the excitation source and detector. When the optical axis of the film changes by a small angle, the detector resolution is insufficient, making it difficult to accurately detect minute changes in light intensity. Additionally, for the detection of single-wavelength quarter-wave plate (QWP) films, a laser source with the corresponding wavelength must be matched to the QWP film, resulting in insufficient versatility and increased testing costs.

[0063] To address the aforementioned technical issues, this application provides a novel method and system for detecting the optical axis angle of an optical film, enabling rapid and accurate detection of the optical axis angle. Specifically, the optical axis angle detection method provided in this application is applicable to the detection of the optical axis of a single optical film. For example, it can detect the transmission axis and absorption axis angles of a polarizing film (POL film), the transmission axis and reflection axis (reflective polarizing axis) angles of a reflective polarizing film (RP film), and the fast axis and slow axis angles of a quarter-wave plate (QWP film).

[0064] The method and system for detecting the optical axis angle of the optical film provided in this application will be described in detail below with reference to the accompanying drawings.

[0065] According to one embodiment of this application, a method for detecting the optical axis angle of an optical film is provided. Specifically, it is used to detect the polarization optical axis of an optical film in a VRPancake scheme. This method for detecting the optical axis angle of an optical film is applied to an optical film optical axis angle detection system. (Refer to...) Figure 1 The detection system includes: a light source assembly 1, a phase delay element 3, a polarizer 4, and a detection module 5, wherein the phase delay element 3 rotates at an angular frequency ω; the optical film to be tested is placed between the light source assembly 1 and the phase delay element 3. Specifically, the optical film to be tested is rotatably disposed between the light source assembly 1 and the phase delay element 3.

[0066] With the optical film to be tested rotatably disposed between the light source assembly 1 and the phase delay element 3, the detection system further includes a vision camera 6;

[0067] The detection method includes the following steps:

[0068] Step 1: After controlling the linearly polarized light from multiple fields of view to pass through different positions of the optical film, the light emitted from the optical film sequentially passes through the phase delay element and the polarizer and is projected onto the detection module;

[0069] Step 2: Based on the intensity of the polarizer-emitted light received by the detection module, obtain the azimuth angle of the light emitted from the optical film;

[0070] Step 3: Obtain the straight edge angle of the optical film, wherein the straight edge angle is the angle between the straight edge of the optical film and the reference line, and the reference line is the vertical coordinate axis in the visual camera 6-coordinate system;

[0071] Step 4: Establish a relationship model based on the azimuth angle of the light emitted from the optical film and the angle of the straight edge;

[0072] Step 5: Determine the optical axis angle of the optical film according to the relationship model.

[0073] According to the optical film optical axis angle detection method provided in this application embodiment, the optical film 2 to be tested is placed between the light source assembly 1 and the phase delay element 3, and the optical axis angle of the optical film is detected. For example, the transmission axis and absorption axis angle of a polarizing film (POL film) can be detected, the transmission axis and reflection axis (reflective polarizing axis) angle of a reflective polarizing film (RP film) can be calibrated, and the fast axis and slow axis angle of a quarter-wave plate (QWP film) can be detected.

[0074] Specifically, the azimuth angle of the light emitted from the optical film is detected by a combination of a phase delay element 3 rotating at an angular frequency ω, a polarizer 4, and a detection module 5, and the straight edge angle of the optical film is obtained by a vision camera 6. Based on the azimuth angle and straight edge angle of the light emitted from the optical film, the optical axis angle of the optical film can be detected in a low-cost, fast, and accurate manner.

[0075] In step 1, linearly polarized light with multiple fields of view is sequentially projected onto the detection module 5 through an optical film, a phase retardation element 3, and a polarizer 4. For example, the light source assembly 1 emits linearly polarized light with multiple fields of view, which sequentially passes through the optical film, the phase retardation element 3, and the polarizer 4, and is finally received by the detection module 5. For example, the detection module 5 can be a CCD camera.

[0076] In one specific embodiment, the optical film is a POL film or an RP film. A light source assembly generates linearly polarized light with multiple fields of view, which is then incident on the POL film or RP film under test. An electric rotary wheel rotates the POL film or RP film under test in increments of a certain size. After passing through the POL film or RP film, the linearly polarized light is aligned with the transmission axis of the film. This linearly polarized light then passes through a phase delay element 3 rotating at an angular frequency ω and a polarizer, and is finally received by a CCD.

[0077] In another specific embodiment, the optical film is a QWP film. A light source assembly generates linearly polarized light with multiple fields of view, which is then incident on the QWP film under test. An electric rotating wheel can rotate the QWP film in steps of a certain size. As the linearly polarized light passes through the QWP film, it exits as linearly polarized light when the incident linearly polarized light aligns with the fast axis of the QWP; otherwise, it exits as elliptically polarized light. The exiting light then passes through a phase delay element 3 rotating at angular frequency ω and a polarizer, and is finally received by a CCD.

[0078] It should be noted that the optical axis of a QWP film is wavelength-dependent. Currently, when detecting the optical axis of a QWP film using methods such as power analysis, a laser matching the wavelength of the QWP film needs to be purchased. This application, however, emits linearly polarized light from a light source assembly, eliminating the need to purchase a laser matching the wavelength of the QWP film. The optical axis angle detection method provided in this application can detect the optical axis angle of a QWP film at any wavelength. Specifically, the light source assembly emits linearly polarized light, and the QWP film has a fast axis and a slow axis. When the linearly polarized light transmitted to the QWP film is aligned with either the fast or slow axis, the QWP film transmits linearly polarized light. This application utilizes this feature, eliminating the need to limit the wavelength of the light source emitter in the light source assembly.

[0079] In step 2, the azimuth angle of the light emitted from the optical film is obtained based on the intensity of the polarizer-emitted light received by the detection module 5.

[0080] The azimuth angle of the light emitted from the optical film is the angle between the polarized light emitted from the optical film and the horizontal axis.

[0081] In this step, the azimuth angle of the polarizer-emitted light is obtained based on the Stokes vector and Mueller matrix by detecting the intensity of the polarizer-emitted light received by module 5. Since the optical film is rotatably mounted on the light source assembly and the phase delay element 3, and the phase delay element 3 rotates at an angular frequency ω, the azimuth angle of the polarizer-emitted light calculated by module 5 based on the Stokes vector and Mueller matrix also changes in real time. For example, based on the rotation of the optical film and the phase delay element 3, the azimuth angle of the polarized light emitted from the optical film can gradually decrease or increase in a regular manner, or it can change irregularly.

[0082] For example, when the detection module 5 detects that the fast axis of the phase delay element 3 makes an angle of α (α = ωt) with the horizontal direction, and considering the intensity of polarized light from multiple fields of view emitted by the polarizer 4, the azimuth angle of the polarized light emitted from the optical film is calculated based on the Stokes vector and the Mueller matrix, according to the intensity of the polarized light from the multiple fields of view emitted by the polarizer 4. For example, if the optical film is a POL film or an RP film, the azimuth angle of the linearly polarized light emitted from the optical film is calculated. For example, if the optical film is a QWP film, the azimuth angle of the polarized light emitted from the optical film is calculated, for example, the polarized light can be linearly polarized, circularly polarized, or elliptically polarized. When the polarized light is elliptically polarized, the azimuth angle of the major axis of the elliptically linearly polarized light is calculated.

[0083] Step 3: Obtain the straight edge angle of the optical film. The straight edge angle is the angle between the straight edge segment of the optical film and the reference line, where the reference line is the vertical coordinate axis in the visual camera's 6-coordinate system.

[0084] In this step, the angle between the straight edge of the optical film and the vertical coordinate axis determined by the visual camera 6 is obtained by the visual camera 6.

[0085] In one specific embodiment, a surface light source is provided to illuminate the side of the optical film. The vision camera 6 captures the straight edge of the optical film and obtains the angle between the straight edge segment of the optical film and the vertical coordinate axis determined by the vision camera 6 itself.

[0086] The vision camera 6 is fixedly positioned, while the optical film is rotatably positioned between the light source assembly and the phase delay element 3. During the rotation of the optical film, its straight edge rotates with the optical module, so the angle of the straight edge of the optical film acquired by the vision camera 6 also changes in real time. For example, based on the rotation of the light source film, the angle of the straight edge of the optical film can gradually decrease or gradually increase in a regular manner, or the angle of the straight edge of the optical film can change irregularly.

[0087] Upon arrival, the POL, RP, or QWP film has a straight edge segment. For example, the POL, RP, or QWP film includes an arc-shaped portion and a straight edge segment connected to the arc-shaped component. The straight edge segment can be formed by cutting, for example, by cutting a circular film to form an optical film with a straight edge segment.

[0088] In order to detect the optical axis angle of POL film, RP film or QWP film, since the optical axis is a virtual straight line and the optical axis angle cannot be directly measured by the device, this embodiment of the application sets a straight edge segment in POL film, RP film or QWP film, and indirectly characterizes the optical axis angle of the optical film by detecting the straight edge angle of POL film, RP film or QWP film.

[0089] In step 4, a relationship model is established based on the azimuth angle of the light emitted from the optical film and the angle of the straight edge.

[0090] Specifically, the acquisition of the straight edge angle of the optical film and the acquisition of the azimuth angle of the emitted light from the optical film are performed simultaneously, and within the same time period, there is a one-to-one correspondence between the acquired straight edge angle and the acquired azimuth angle of the emitted light from the optical film. By linearly fitting the azimuth angle of the emitted light from the optical film 2 under test with the straight edge angle of the optical film captured by the vision camera 6, a relationship model between the azimuth angle of the emitted light from the optical film and the straight edge angle can be obtained.

[0091] Since the optical film is rotatably positioned between the light source assembly and the phase delay element 3, in step 3, during the rotation of the optical film, the vision camera 6 acquires multiple different straight-edge angles. For example, the multiple different straight-edge angles acquired can be defined as a straight-edge angle group.

[0092] Since the optical film is rotatably positioned between the optical component and the phase delay element 3, and the phase delay element 3 is also rotatably positioned, in step 2, during the rotation of the optical film and the phase delay element 3, multiple different azimuth angles of the light rays emitted from the optical film will be acquired. For example, the multiple different azimuth angles of the light rays emitted from the optical film can be defined as an azimuth angle group.

[0093] A linear curve can be obtained by performing linear fitting on a one-to-one correspondence between the straight-side angle group and the azimuth angle group. For example, the relationship model between the straight-side angle and the azimuth angle is: y = kx + b, refer to... Figure 2 This is a fitted curve between the straight-side angle and the azimuth angle. (Refer to...) Figure 2 There is a positive correlation between the straight-side angle and the azimuth angle.

[0094] Where y is the azimuth angle of the optical axis of the polarized light emitted from the optical film 2 during its rotation, x is the angle of the straight edge of the optical film captured by the vision camera 6, k is the fitting coefficient, and b is a constant term.

[0095] In step 5, the optical axis angle of the optical film is determined according to the relationship model. Specifically, by inputting the azimuth angle of the ideal outgoing light of the optical film 2 under test, the straight edge angle of the optical film 2 under test can be obtained. The straight edge angle of the optical film can characterize the angle between the polarization axis and the horizontal axis of the optical film, that is, it can characterize the optical axis angle of the optical film.

[0096] For example, during the rotation of the optical film, its polarization axis also rotates, as does its straight edge segment. During this rotation, the vision camera 6 acquires the angle of the straight edge segment. For instance, if the ideal azimuth angle of the emitted light from the optical film 2 is 0°, inputting this 0° into the relational model corresponds to a straight edge angle, such as 1°. This means that when the azimuth angle of the emitted light from the optical film is 0°, the straight edge rotates by 1°. Therefore, it can be concluded that the polarization axis of the optical film rotates by 1° relative to the horizontal axis, i.e., the optical axis angle of the optical film is 1°.

[0097] Therefore, in this embodiment, the azimuth angle of the light emitted from the optical film is detected by combining the phase delay element 3 rotating at angular frequency ω with the polarizer 4 and the detection module 5, and the straight edge angle of the optical film is obtained by the vision camera 6. A relationship model is established based on the azimuth angle and straight edge angle of the emitted light from the optical film, and the optical axis angle of the optical film is obtained based on the relationship model. This embodiment can obtain the optical axis angle of the optical film simply and quickly. In addition, for the detection of QWP films with a single wavelength, there is no need to match a laser of the corresponding wavelength, which effectively saves the cost of the light source.

[0098] In an alternative embodiment, if only linearly polarized light is being measured, the phase retardation element rotating at angular frequency ω combined with the polarizer and CCD can be replaced by an expensive polarization camera. In an alternative embodiment, the CCD can be replaced by a CMOS sensor.

[0099] In one embodiment, obtaining the azimuth angle of the light emitted from the optical film based on the intensity of the polarizer-emitted light received by the detection module specifically includes the following steps:

[0100] Step 01: Obtain the intensity of the light emitted from the polarizer when the angle between the fast axis of the phase delay element and the horizontal direction is α, where α = ωt, and t is the rotation time of the phase delay element;

[0101] Step 02: Obtain the Stokes vector of the light emitted from the optical film based on the intensity of the light emitted from the polarizer;

[0102] Step 03: Obtain the optical axis azimuth angle of the optical film based on the Stokes vector of the light emitted from the optical film.

[0103] In this embodiment, the optical film under test is placed between the light source assembly 1 and the phase delay element 3, and the azimuth angle of the light emitted from the optical film is detected. Specifically, the azimuth angle of the optical film's emitted light box is detected by combining the phase delay element 3, which rotates at an angular frequency ω, with the polarizer 4 and the detection module 5. This method enables low-cost, fast, and accurate detection of the azimuth angle of the light emitted from the optical film.

[0104] In step 01, the intensity of the light emitted from the polarizer 4 is obtained when the angle between the fast axis of the phase delay element 3 and the horizontal direction is α, where α = ωt. Specifically, the polarized light from multiple fields of view emitted from the polarizer 4 is ultimately received by the detection module 5. After receiving the polarized light from multiple fields of view emitted from the polarizer 4, the intensity of the polarized light from multiple fields of view emitted from the polarizer 4 can be detected by the detection module 5. Since the phase delay element 3 is constantly rotating at an angular frequency ω, the detection module 5 can detect in real time the intensity of the polarized light from multiple fields of view emitted from the polarizer 4 when the angle between the fast axis of the phase delay element 3 and the horizontal direction is α.

[0105] In step 02, when the detection module 5 detects that the angle between the fast axis of the phase delay element 3 and the horizontal direction is α, and considering the intensity of the polarized light emitted from the polarizer 4 across multiple fields of view, the Stokes vector of the light emitted from the optical film can be obtained based on the intensity of the polarized light emitted from the polarizer 4 across multiple fields of view. The Stokes vector of the light emitted from the optical film characterizes the polarization state and intensity of the light beam.

[0106] For example, the Stokes vector for the light emitted from the optical film is Sm.

[0107]

[0108] Where S0 represents the total light intensity, S1 represents the light intensity difference between horizontally and vertically linearly polarized light, S2 represents the light intensity difference between 45-degree and -45-degree linearly polarized light, and S3 represents the light intensity difference between right-handed and left-handed circularly polarized light.

[0109] S0, S1, S2, and S3 can all be represented by the intensity of multiple field-of-view polarized lights emitted through polarizer 4.

[0110] In step 03, the azimuth angle of the emitted light from the optical film can be obtained based on the calculated Stokes vector Sm of the emitted light.

[0111] For example, the azimuth angle of the light rays emitted from the optical film is ψ.

[0112] The azimuth angle ψ of the light emitted from the optical film can be obtained by formula (2);

[0113]

[0114] Therefore, in this embodiment, based on the intensity of multiple field-of-view rays emitted by the polarizer 4 when the angle between the fast axis of the phase delay element 3 and the horizontal direction is α obtained by the detection module, the value of each element (S0, S1, S2 and S3) in formula (1) is calculated, where each element (S0, S1, S2 and S3) is also related to the angle α between the fast axis of the phase delay element 3 and the horizontal direction; then, based on the value of each element calculated in formula (1), the azimuth angle of the light emitted from the optical film is calculated according to formula (2).

[0115] In this embodiment, the azimuth angle of the light emitted from the optical film is detected by combining the phase delay element 3 rotating at an angular frequency ω with the polarizer 4 and the detection module 5. This method enables the rapid, accurate, and low-cost detection of the azimuth angle of the light emitted from the optical film.

[0116] In one example, the phase delay element is a quarter-wave plate, and the polarizer is a horizontal linear polarizer.

[0117] In this embodiment, the types of phase delay element 3 and polarizer 4 are limited. The Mueller matrix of the quarter-wave plate and the horizontal linear polarizer is relatively simple, which reduces the difficulty of obtaining the azimuth angle of the light emitted from the optical film. In addition, limiting the types of phase delay element 3 and polarizer 4 ensures that the polarized light emitted from the optical film, after passing through the quarter-wave plate and the horizontal linear polarizer, is still linearly polarized light emitted from the horizontal linear polarizer.

[0118] In one example, the light source assembly includes a polarizer, and in the case that the optical film is a phase retardation film, before controlling the polarized light of multiple fields of view to pass through different positions of the optical film, it further includes: controlling the angle of the polarizer to be the ideal optical axis angle of the phase retardation film to be tested.

[0119] Specifically, the angle of the polarizer is controlled to be the ideal optical axis angle of the phase retardation film under test. When the angle of the polarizer coincides with the optical axis angle of the phase retardation film, the polarized light emitted from the phase retardation film is linearly polarized. When the angle of the polarizer and the optical axis angle of the phase retardation film are offset, the polarized light emitted from the phase retardation film is elliptically polarized or circularly polarized. Therefore, to ensure that the polarized light emitted from the phase retardation film is linearly polarized, the angle of the polarizer is controlled to be the ideal optical axis angle of the phase retardation film under test. When the detected optical axis angle of the phase retardation film coincides with the angle of the polarizer, the polarized light emitted from the phase retardation film is linearly polarized.

[0120] In one example, obtaining the Stokes vector of the light emitted from the optical film based on the intensity of the light emitted from the polarizer 4 specifically includes the following steps:

[0121] S001: Obtain the relationship expression between the intensity of the light emitted from the polarizer 4 and the Stokes vector of the light emitted from the optical film;

[0122] S002: Perform a Fourier transform on the relational expression and obtain the Fourier transform coefficients based on the intensity of the light emitted from the polarizer 4;

[0123] S003: Obtain the Stokes vector of the light emitted from the optical film based on the Fourier transform coefficients.

[0124] In step S001, the intensity of the light emitted from the polarizer 4 is related to the Stokes vector of the light emitted from the optical film and the rotation angle of the phase delay element 3. For example, the angle between the fast axis of the phase delay element 3 and the horizontal direction is α, where α = ωt.

[0125] For example, if the phase delay element 3 is a quarter-wave plate and the polarizer 4 is a horizontal linear polarizer, the relationship between the intensity of the light emitted from the polarizer 4 and the Stokes vector of the light emitted from the optical film is expressed as follows:

[0126]

[0127] In formula (3), α is the angle between the fast axis of the phase delay element 3 and the horizontal direction, and S0, S1, S2 and S3 are all elements in the Stokes vector matrix of the light rays emitted from the optical film.

[0128] In step S002, a Fourier transform is performed on formula (3), and the Fourier transform coefficients are obtained based on the intensity of the light emitted from polarizer 4. Specifically, the relationship between the Fourier transform coefficients and the intensity of the detected light emitted from the polarizer can be obtained through the Fourier transform.

[0129] For example, formula (3) can be written in Fourier series form, where the Fourier series form corresponding to formula (3) is formula (4):

[0130]

[0131] Then, by applying a Fourier transform to formula (4), the relationship between the Fourier transform coefficients A, B, C, and D and the intensity of the detected polarizer 4 emitted light can be obtained. For example, formula (5) below shows the relationship between the Fourier transform coefficient A and the intensity of the detected polarizer emitted light; formula (6) shows the relationship between the Fourier transform coefficient B and the intensity of the detected polarizer emitted light; formula (7) shows the relationship between the Fourier transform coefficient C and the intensity of the detected polarizer emitted light; and formula (8) shows the relationship between the Fourier transform coefficient D and the intensity of the detected polarizer emitted light.

[0132]

[0133]

[0134]

[0135]

[0136] In step S003, the Stokes vector of the light rays emitted from the optical film is obtained based on the Fourier transform coefficients. Specifically, the parameters in the Stokes vector matrix of the light rays emitted from the optical film are obtained according to the above formulas (5)-(8).

[0137] Specifically, according to formulas (3) and (4), the relationship between the Fourier transform coefficients A, B, C, and D and the elements S0, S1, S2, and S3 in the Stokes vector matrix of the light rays emitted from the optical film can be obtained, where:

[0138]

[0139] B = S3 (10)

[0140]

[0141]

[0142] According to formulas (9) and (12), we can know that:

[0143] S0=AC (13)

[0144] S1=2C (14)

[0145] S2 = 2D (15)

[0146] S3=B (16)

[0147] Therefore, according to formulas (5)-(8) and (13)-(16), the parameters in the Stokes vector matrix of the optical film's emitted light can be obtained, thus obtaining the Stokes vector of the optical film's emitted light. Based on obtaining the Stokes vector of the optical film's emitted light, the azimuth angle of the optical film's emitted light can be calculated using formula (2).

[0148] In one example, obtaining the relationship between the intensity of the light emitted from the polarizer 4 and the Stokes vector of the light emitted from the optical film specifically includes the following steps:

[0149] S0001: Set the Stokes vector of the light emitted from the optical film to Sm;

[0150] S0002: Obtain the Stokes vector S′ of the emitted light from the phase delay element 3 based on the Stokes vector Sm;

[0151] S0003: Obtain the Stokes vector Sout of the emitted light from the polarizer 4 based on the Stokes vector S′;

[0152] S0004: Based on the Stokes vector Sout, obtain the relationship expression between the intensity of the light emitted from the polarizer 4 and the Stokes vector of the light emitted from the optical film.

[0153] Specifically, in step S0001, the Stokes vector of the light emitted from the optical film is first set to Sm.

[0154] For example, let the Stokes vector of the light rays emitted from the optical film be:

[0155] Where S0 represents the total light intensity, S1 represents the light intensity difference between horizontally and vertically linearly polarized light; S2 represents the light intensity difference between 45-degree and -45-degree linearly polarized light; and S3 represents the light intensity difference between right-handed and left-handed circularly polarized light.

[0156] In step S0002, the Stokes vector S′ of the emitted light from the phase delay element 3 is obtained according to the Stokes vector Sm. Specifically, based on the theory that the Stokes vector of the emitted light from a certain component is the product of the Mueller matrix of that component and the Stokes vector of the emitted light from the previous component, the Stokes vector of the emitted light from the phase delay element 3 is obtained.

[0157] For example, based on the Stokes vector Sm and the Mueller matrix of the phase delay element 3 with an angle α between the fast axis and the horizontal direction, the Stokes vector S′ of the emitted light from the phase delay element 3 can be obtained.

[0158] In a specific embodiment, the phase delay element 3 is a quarter-wave plate, and the Mueller matrix of the quarter-wave plate, which has an angle α between the fast axis and the horizontal direction, can be expressed as formula (17):

[0159]

[0160] The quarter-wave plate rotates at an angular velocity ω (α = ωt).

[0161] After the light emitted from the optical film passes through a rotating quarter-wave plate, the Stokes vector of the emitted light is given by formula (18):

[0162]

[0163] It should be noted that the phase delay element 3 can also be a half-wave plate. The half-wave plate allows the optical film to exit, and the light emitted from the half-wave plate is linearly polarized. After the light emitted from the optical film passes through the rotating half-wave plate, the Stokes vector of the emitted light is the product of the Mueller matrix of the half-wave plate and the Stokes vector of the light emitted from the optical film.

[0164] In step S0003, the Stokes vector S′ of the emitted light from the polarizer 4 is obtained based on the Stokes vector S′. out Specifically, the Stokes vector of the polarizer's output light is obtained based on the theory that the Stokes vector of the light emitted from a certain component is the product of the Mueller matrix of that component and the Stokes vector of the light emitted from the previous component.

[0165] For example, based on the Stokes vector S′ and the Mueller matrix of the polarizer 4, the Stokes vector S of the emitted light from the polarizer 4 can be obtained. out .

[0166] In one specific embodiment, polarizer 4 is a horizontal linear polarizer. The Mueller matrix of the horizontal linear polarizer (i.e., the Mueller matrix of the transmission axis of the horizontal linear polarizer in the horizontal direction) is expressed by formula (19):

[0167]

[0168] The relationship between the light emitted from the horizontal linear polarizer and the light emitted from the optical film is as follows:

[0169] S out =NMS VR (20)

[0170] The light emitted through a horizontal linear polarizer can be represented as follows: That is, the Stokes vector of the light emitted from a horizontal linear polarizer can be represented as follows:

[0171]

[0172] It should be noted that polarizer 4 can also be a circular polarizer. Based on the principle explained above, the Stokes vector of the light rays emitted after passing through the circular polarizer can be obtained.

[0173] In step S0004, according to the Stokes vector S out Obtain the relationship expression between the intensity of the light emitted from the polarizer 4 and the Stokes vector of the light emitted from the optical film.

[0174] Specifically, in the calculation, only the emitted light S out The first component, i.e., the total intensity, can be detected, S′0=I(α).

[0175]

[0176] Therefore, the above formula (3) shows the relationship between the intensity of the light emitted from the polarizer 4 and the Stokes vector of the light emitted from the optical film, where α is the angle between the fast axis of the phase delay element 3 and the horizontal direction, and S0, S1, S2 and S3 are all elements in the Stokes vector matrix of the light emitted from the optical film. Then, a Fourier transform is performed on formula (3) to obtain the Fourier transform coefficients based on the intensity of the light emitted from the polarizer 4. Specifically, the relationship between the Fourier transform coefficients and the intensity of the detected light emitted from the polarizer can be obtained through the Fourier transform. Then, by performing a Fourier transform on the above formula (4), the relationship between the Fourier transform coefficients A, B, C and D and the intensity of the detected light emitted from the polarizer 4 can be obtained. For example, formula (5) above shows the relationship between the Fourier transform coefficient A and the intensity of the detected polarizer-emitted light, formula (6) shows the relationship between the Fourier transform coefficient B and the intensity of the detected polarizer-emitted light, formula (7) shows the relationship between the Fourier transform coefficient C and the intensity of the detected polarizer-emitted light, and formula (8) shows the relationship between the Fourier transform coefficient D and the intensity of the detected polarizer-emitted light.

[0177] Therefore, based on the above formulas (5)-(8) and (13)-(16), the parameters in the Stokes vector matrix of the optical film's emitted light can be obtained, thus obtaining the Stokes vector of the optical film's emitted light. Based on obtaining the Stokes vector of the optical film's emitted light, the azimuth angle of the optical film's emitted light can be calculated using the above formula (2).

[0178] In one example, the rotation of the phase delay element 3 at an angular frequency ω specifically includes:

[0179] The phase delay element 3 is driven by a stepper motor to rotate at an angular frequency ω, wherein the number of steps of the stepper motor is n, the step size is aj, and α = ωt = n × aj.

[0180] In one specific embodiment, the phase delay element 3 is rotated by a stepper motor. For example, the quarter-wave plate is rotated by a stepper motor.

[0181] Specifically, a quarter-wave plate is placed on a fixed base and can be rotated in n steps by a stepper motor: ωt = nα j (α j (where α is the step size and N is the total number of steps). This is based on the formula α = ωt = nα. j By transforming formula (4), we can obtain formula (22).

[0182]

[0183] The Fourier transform can be used to obtain the relationship between the Fourier transform coefficients A, B, C and D and the intensity of the emitted light from the detected polarizer 4. Formulas (23)-(26) show the relationship between the Fourier transform coefficients A, B, C and D and the intensity of the emitted light from the detected polarizer 4.

[0184]

[0185]

[0186]

[0187]

[0188] Thus, in this embodiment, given the step size and number of steps of the stepper motor and the intensity of the emitted light from the polarizer 4, the Stokes vector of the emitted light from the optical film can be obtained. Then, the azimuth angle of the emitted light from the optical film is obtained based on the Stokes vector.

[0189] Secondly, embodiments of this application provide a system for detecting the optical axis angle of an optical film, referring to... Figure 1The detection system includes:

[0190] The light source assembly 1, phase delay element 3, polarizer 4 and detection module 5, wherein the phase delay element 3 rotates at an angular frequency ω;

[0191] The light source assembly 1 is used to emit linearly polarized light with multiple fields of view;

[0192] When the optical film 2 to be tested is placed between the light source assembly 1 and the phase delay element 3, the detection system further includes a vision camera 6, which is used to acquire the straight edge angle of the optical film.

[0193] When the optical film 2 to be tested is placed between the light source assembly 1 and the phase delay element 3, the optical film, the phase delay element 3, the polarizer 4 and the detection module 5 are arranged sequentially along the same optical axis.

[0194] In this embodiment, the azimuth angle of the light emitted from the optical film is detected by combining a phase delay element rotating at an angular frequency ω with a polarizer and a detection module. The straight edge angle of the optical film is obtained using a vision camera 6. A relationship model is established based on the azimuth angle and straight edge angle of the emitted light from the optical film, and the optical axis angle of the optical film is obtained based on the relationship model. This embodiment provides a simple and fast method for obtaining the optical axis angle of the optical film.

[0195] For example, detection module 5 can be an area CCD.

[0196] In an alternative embodiment, if only linearly polarized light is being measured, a quarter-wave plate rotating at angular frequency ω combined with a horizontal linear polarizer and a CCD can be replaced by an expensive polarization camera.

[0197] In one example, refer to Figure 1 The light source assembly 1 includes: a light source 10, a fast reflector 11, a lens group and a polarizer 14, wherein the lens group includes at least one lens;

[0198] The light emitted from the light source 10 passes sequentially through the fast reflector 11, the lens group, and the polarizer 14 and is projected onto the optical film 2 to be tested.

[0199] Specifically, the lens group includes a first lens 12 and a second lens 13. The light emitted from the laser passes through the fast-reflecting mirror 11, the first lens 12, and the second lens 13, wherein... Figure 1 In the image, F1 and F2 are the focal lengths of the first lens 12 and the second lens 13, respectively. After passing through the polarizer 14, they can generate linearly polarized light with multiple fields of view.

[0200] In one example, the detection system further includes a stepper motor that drives the phase delay element 3 to rotate at an angular frequency ω.

[0201] In this embodiment, the phase delay element 3 is driven by a stepper motor. Given the step size and number of steps of the stepper motor, and the intensity of the emitted light from the polarizer 4, the Stokes vector of the emitted light from the optical film can be obtained. Then, the polarization parameters of the optical film are obtained based on the Stokes vector of the emitted light.

[0202] In one example, refer to Figure 1 The polarizer 4 is a horizontal linear polarizer, and the phase delay element 3 is a quarter-wave plate.

[0203] In this embodiment, the types of phase delay element 3 and polarizer 4 are limited. The Mueller matrix of the quarter-wave plate and the horizontal linear polarizer is relatively simple, which reduces the difficulty of obtaining the azimuth angle of the light emitted from the optical film. In addition, limiting the types of phase delay element 3 and polarizer 4 ensures that the polarized light emitted from the optical film, after passing through the quarter-wave plate and the horizontal linear polarizer, is still linearly polarized light emitted from the horizontal linear polarizer.

[0204] The specific implementation of the optical film optical axis angle detection system of this application embodiment can refer to the various embodiments of the optical film polarization parameter detection method described above. Therefore, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0205] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0206] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A method for detecting the optical axis angle of an optical film, characterized in that, A detection system for the optical axis angle of an optical film is provided. The detection system includes: a light source assembly, a phase retardation element, a polarizer, and a detection module, wherein the phase retardation element rotates at an angular frequency ω; the optical film to be detected is placed between the light source assembly and the phase retardation element. When the optical film to be tested is rotated between the light source assembly and the phase retardation element, the detection method includes: After linearly polarized light with multiple fields of view passes through different positions of the optical film, the light emitted from the optical film passes sequentially through the phase delay element and the polarizer and is projected onto the detection module. The azimuth angle of the light emitted from the optical film is obtained based on the intensity of the light emitted from the polarizer received by the detection module. Obtain the straight edge angle of the optical film, wherein the straight edge angle is the angle between the straight edge of the optical film and the reference line, and the reference line is the vertical coordinate axis in the visual camera coordinate system; A relationship model is established based on the azimuth angle of the light emitted from the optical film and the angle of the straight edge; The optical axis angle of the optical film is determined based on the relationship model.

2. The detection method according to claim 1, characterized in that, Obtaining the azimuth angle of the light emitted from the optical film based on the intensity of the polarizer emitted by the detection module specifically includes: The intensity of the light emitted from the polarizer is obtained when the angle between the fast axis of the phase delay element and the horizontal direction is α, where α = ωt, and t is the rotation time of the phase delay element; Based on the intensity of the light emitted from the polarizer, the Stokes vector of the light emitted from the optical film is obtained; The azimuth angle of the light emitted from the optical film is obtained based on the Stokes vector of the light emitted from the optical film.

3. The detection method according to claim 1, characterized in that, The phase delay element is a quarter-wave plate, and the polarizer is a horizontal linear polarizer.

4. The detection method according to claim 1, characterized in that, The optical film is one of a polarizing film, a reflective polarizing film, or a phase delay film.

5. The detection method according to claim 1, characterized in that, The light source assembly includes a polarizer, and when the optical film is a phase retardation film, it further includes the following before the linearly polarized light controlling multiple fields of view passes through different positions of the optical film: The angle of the polarizer is controlled to be the ideal optical axis azimuth angle of the phase retardation film to be tested.

6. The detection method according to claim 2, characterized in that, Obtaining the Stokes vector of the light emitted from the optical film based on the intensity of the light emitted from the polarizer specifically includes: A model is established to determine the relationship between the intensity of the light emitted from the polarizer and the Stokes vector of the light emitted from the optical film. Perform a Fourier transform on the relationship model and obtain the Fourier transform coefficients based on the intensity of the light emitted from the polarizer; The Stokes vector of the light rays emitted from the optical film is obtained based on the Fourier transform coefficients.

7. The detection method according to claim 6, characterized in that, The model for obtaining the relationship between the intensity of the light emitted from the polarizer and the Stokes vector of the light emitted from the optical film specifically includes: The Stokes vector of the light emitted from the optical film is defined as Sm; Based on the Stokes vector Sm, obtain the Stokes vector of the emitted light from the phase delay element. ; According to the Stokes vector Obtain the Stokes vector Sout of the light emitted from the polarizer; Based on the Stokes vector Sout, obtain the relationship expression between the intensity of the polarizer-emitted light and the Stokes vector of the optical film-emitted light.

8. The detection method according to claim 7, characterized in that, Based on the Stokes vector Sm, obtain the Stokes vector of the emitted light from the phase delay element. Specifically, it includes: Based on the Stokes vector Sm and the Mueller matrix of the phase retardation element with an angle α between the fast axis and the horizontal direction, the Stokes vector of the emitted ray from the phase retardation element is obtained. .

9. The detection method according to claim 7, characterized in that, According to the Stokes vector Obtaining the Stokes vector Sout of the polarizer-emitted light specifically includes: According to the Stokes vector And the Mueller matrix of the polarizer, to obtain the Stokes vector Sout of the polarizer's outgoing light.

10. The detection method according to claim 1, characterized in that, The phase delay element rotates at an angular frequency ω, specifically including: The phase delay element is driven by a stepper motor to rotate at an angular frequency ω, where the number of steps of the stepper motor is n, the step size is aj, and α=ωt=n×aj.

11. A detection system for the optical axis angle of an optical film, the detection system performing the detection method for the optical axis angle of an optical film as described in any one of claims 1-10, the detection system comprising: The light source assembly, phase delay element, polarizer, and detection module, wherein the phase delay element rotates at an angular frequency ω; The light source assembly is used to emit linearly polarized light with multiple fields of view; When the optical film under test is placed between the light source assembly and the phase delay element, the optical film, the phase delay element, the polarizer, and the detection module are arranged sequentially along the transmission direction of the light received by the optical film.

12. The detection system according to claim 11, characterized in that, The light source assembly includes: a light source, a fast reflector, a lens group, and a polarizer, wherein the lens group includes at least one lens; The light emitted from the light source passes sequentially through the fast reflector, the lens group, and the polarizer before being projected onto the optical film to be tested.

13. The detection system according to claim 11, characterized in that, It also includes a stepper motor that drives the phase delay element to rotate at an angular frequency ω.

14. The detection system according to claim 11, characterized in that, The polarizer is a horizontal linear polarizer, and the phase delay element is a quarter-wave plate.

Images