TWI904613B - Optical inspection method and optical inspection system - Google Patents

Abstract

An optical inspection method includes disposing a light-emitting unit array and an optical film set. The optical film set includes a diffuser, a lower polarizer, a standard film, and an upper polarizer stacked in sequence above the light-emitting unit array. The lower polarizer and the upper polarizer respectively have absorption axes being substantially parallel with each other. The method further includes disposing a film to be tested between the standard film and the upper polarizer. The film to be tested has a slow axis. An angle between the slow axis and the absorption axis of the upper polarizer is substantially 45 degrees. The method further includes driving the light-emitting unit array to emit light passing through the optical film set. The method further includes driving an image sensor to receive the light and obtain an image. The method further includes driving a processor to obtain a plurality of light intensity values based on the image and to obtain a plurality of retardation values associated with the film to be tested based on the light intensity values.

Description

Optical Detection Methods and Systems

This disclosure relates to an optical detection method and an optical detection system, and more particularly to an optical detection method and optical detection system for detecting optical compensation films.

Retardation films are widely used in display modules of electronic devices such as televisions, computers, and smartphones to control the polarization of light and improve image quality. The uniformity of the phase difference value possessed by the retardation film is a crucial factor for high-quality display. However, current systems for detecting its optical properties, such as phase difference value, have a limited detection range, resulting in time-consuming detection processes and hindering real-time inspection on production lines.

Therefore, how to propose an optical detection method and optical detection system that can solve the above problems is one of the problems that the industry is currently eager to invest research and development resources to solve.

In view of this, one purpose of this disclosure is to provide an optical detection method and optical detection system that can solve the above problems.

One aspect of this disclosure relates to an optical detection method comprising placing an array of light-emitting units and an optical film assembly above the array of light-emitting units. The optical film assembly includes a diffuser, a lower polarizer, a standard plate, and an upper polarizer. The diffuser, lower polarizer, standard plate, and upper polarizer are stacked sequentially along the light emission direction of the array of light-emitting units. The lower polarizer and the upper polarizer each have an absorption axis. The absorption axis of the lower polarizer and the absorption axis of the upper polarizer are substantially parallel to each other. The method further includes placing a film to be tested between the standard plate and the upper polarizer. The film to be tested has a slow axis. The slow axis forms a substantially 45-degree angle with the absorption axes of the lower and upper polarizers. The method further includes driving light emitted from the array of light-emitting units through the optical film assembly. The method further includes driving an image sensor to receive light passing through an optical film assembly and acquiring an image. The method also includes driving a processor to acquire multiple intensity values of the light based on the image. The processor is signal-connected to the image sensor. The image has multiple pixels corresponding to the intensity values. The method further includes driving the processor to acquire multiple phase difference values related to the film under test based on the intensity values.

Another aspect of this disclosure relates to an optical detection system comprising an array of light-emitting units, an optical film assembly, an image sensor, and a processor. The light-emitting unit array is configured to emit light. The optical film assembly is located above the light-emitting unit array. The optical film assembly includes a diffuser, a lower polarizer, a standard polarizer, and an upper polarizer. The diffuser, lower polarizer, standard polarizer, and upper polarizer are stacked sequentially along the light emission direction of the light-emitting unit array. The lower polarizer and the upper polarizer each have an absorption axis. The absorption axis of the lower polarizer and the absorption axis of the upper polarizer are substantially parallel to each other. The image sensor is configured to receive the light passing through the optical film assembly and acquire an image. The processor is signal-connected to the image sensor. The processor is configured to acquire multiple phase difference values based on the image. The image has multiple pixels corresponding to phase difference values.

In summary, in the optical inspection methods and systems disclosed herein, light emitted from an array of emitting units passes through an optical film assembly and the film under test, and an image sensor acquires the image. This allows for the simultaneous acquisition of two-dimensional phase difference information over a large area of the film under test, saving inspection and scanning time. Furthermore, the uniformity of the phase difference can be quickly analyzed using algorithms preset in the processor. Therefore, real-time inspection can be performed on the production line, allowing for continuous process adjustments. Additionally, the resolution of the inspection can be adjusted using an optical mirror assembly to improve the appearance of surface mura defects.

The preferred embodiments of this disclosure will become apparent from the following description of these and other aspects in conjunction with the diagrams, but variations and modifications may be made therein without departing from the spirit and scope of the novel concepts of this disclosure.

The following disclosure will be described more fully with reference to the accompanying drawings, some of which are exemplary embodiments. This disclosure may be implemented in various forms and should not be limited to the embodiments mentioned below. However, these embodiments are provided to aid in a more complete understanding of the contents of this disclosure and to fully convey the scope of this disclosure to those skilled in the art.

In the figures, the thicknesses of layers, films, panels, areas, etc., are enlarged for clarity. Throughout the specification, the same reference numerals refer to similar components. It should be understood that when a component such as a layer, film, area, or substrate is referred to as being "on" or "connected to" another component, it may be directly on or connected to the other component, or intermediate components may also be present. Conversely, when a component is referred to as being "directly on" or "directly connected to" another component, no intermediate components are present. As used in this disclosure, "connection" can refer to physical and/or electrical connections.

The terminology used herein is for the purpose of describing particular embodiments only and is not restrictive. As used in this disclosure, unless the content clearly indicates otherwise, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one.” “Or” means “and/or.” As used in this disclosure, the term “and/or” includes any and all combinations of one or more of the associated listed items. It should also be understood that, when used in this specification, the terms “comprising” and/or “including” specify the presence of the stated features, regions, integrals, steps, operations, elements, and/or components, but do not exclude the presence or addition of one or more other features, regions, integrals, steps, operations, elements, components, and/or combinations thereof.

Furthermore, relative terms such as "below" or "bottom" and "above" or "top" are used in this disclosure to describe the relationship between one element and another, as illustrated in the figures. It should be understood that relative terms are intended to include different orientations of the device beyond those shown in the figures. For example, if a device in a figure is flipped, an element described as being "below" of other elements will be oriented "above" of other elements. Thus, the exemplary term "below" can include both "below" and "above" orientations, depending on the specific orientation of the figure. Similarly, if a device in a figure is flipped, an element described as being "below" or "below" of other elements will be oriented "above" of other elements. Thus, the exemplary term "below" or "below" can include both "above" and "below" orientations.

As used in this disclosure, "about," "approximately," or "substantially" includes the value and the average of the values within an acceptable range of deviation from a particular value as determined by a person skilled in the art, taking into account the measurement under discussion and a specific number of errors associated with the measurement (i.e., limitations of the measurement system). For example, "about" may mean within one or more standard deviations of the value, or within ±30%, ±20%, ±10%, ±5%. Furthermore, as used in this disclosure, "about," "approximately," or "substantially" may be used to select a more acceptable range of deviations or standard deviations depending on the optical, etchable, or other properties, rather than applying a single standard deviation to all properties.

Unless otherwise defined, all terms used in this disclosure (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and this disclosure, and will not be interpreted as having an idealized or overly formal meaning unless expressly defined in this disclosure.

Please refer to Figure 1, which is a schematic diagram of an optical detection system 10 according to some embodiments of the present disclosure. As shown in Figure 1, the optical detection system 10 includes an array of light-emitting units 110, an optical film assembly 130, an image sensor 160, and a processor 170. The array of light-emitting units 110 is configured to emit light along direction D1, as indicated by the arrow in Figure 1. In some embodiments, the array of light-emitting units 110 may be an array of light-emitting diodes (LEDs) or mini LEDs. For example, as shown in Figure 1, the light-emitting unit array 110 includes periodically arranged sub-pixel units R, G, and B, which can be light-emitting units emitting light of the same or different wavelengths. In some embodiments, as shown in Figure 1, the optical detection system 10 also includes a controller 120. The controller 120 is signal-connected to the light-emitting unit array 110 and configured to control the light emission intensity of the light-emitting unit array 110.

As shown in Figure 1, the optical film assembly 130 is located above the light-emitting unit array 110. The optical film assembly 130 includes a diffuser 131, a lower polarizer 132, a standard polarizer 133, and an upper polarizer 134. The diffuser 131, lower polarizer 132, standard polarizer 133, and upper polarizer 134 are stacked sequentially along the light emission direction D1 of the light-emitting unit array 110. In other words, the diffuser 131 is located above the light-emitting unit array 110. The lower polarizer 132 is located above the diffuser 131. The standard polarizer 133 is located above the lower polarizer 132. The upper polarizer 134 is located above the standard polarizer 133.

A diffuser 131 is configured to improve the light emission uniformity of the light-emitting unit array 110. A lower polarizer 132 is configured to convert the homogenized unpolarized light source from the light-emitting unit array 110 into parallel linearly polarized light. In some embodiments, the absorption axes of the lower polarizer 132 and the upper polarizer 134 are substantially parallel to each other to absorb polarized light parallel to the absorption axis direction. A standard plate 133 is configured to change the polarization direction of the parallel linearly polarized light.

As shown in Figure 1, image sensor 160 is configured to receive light passing through optical film assembly 130 and acquire an image. In some embodiments, image sensor 160 may include a linear image sensor or other photosensitive element. For example, image sensor 160 is an industrial camera.

As shown in Figure 1, processor 170 is signal-connected to image sensor 160. In some embodiments, processor 170 includes a central processing unit (CPU), microprocessor, controller, microcontroller, or similar processing unit. For example, processor 170 is a computer configured to acquire 256 grayscale values for each wavelength of the image for analysis.

In some embodiments, the optical detection system 10 is configured to analyze the two-dimensional distribution of the phase difference of the optical film. Further, the film under test (S) can be an optical compensation film. During the detection process, the film under test (S) is positioned between the standard plate 133 and the upper polarizer 134, and the film under test (S) has a slow axis that forms a substantially 45-degree angle with the absorption axes of the lower polarizer 132 and the upper polarizer 134.

Depending on the approximate range of the phase difference value of the diaphragm S under test, the standard plate 133 included in the optical detection system 10 employs different phase difference waveplates and slow axis directions. In some embodiments, the possible range of phase difference values of the diaphragm S under test is divided into three regions, approximately one-quarter, one-half, and three-quarters of the wavelength to be analyzed. The corresponding standard plates 133 are a quarter-wave plate (QWP) with its slow axis direction substantially parallel to the slow axis direction of the diaphragm S under test, a zero-wave plate, and a quarter-wave plate with its slow axis direction substantially perpendicular to the slow axis direction of the diaphragm S under test. Accordingly, the components of the optical detection system 10 may have different parameter settings, which will be described in detail in later paragraphs.

When the possible phase difference range of the diaphragm S under test is approximately one-quarter of the wavelength to be analyzed, the standard plate 133 includes a quarter-wave plate. In some embodiments, the phase difference range is preset to be between 0 and... + Between. The wavelength to be analyzed. This is the known phase difference value (or reference phase difference value) for standard film 133. For example, the wavelength to be analyzed is selected. The standard wafer used is 133 reference phase difference value, which is 550 nanometers. If the phase difference is 142 nanometers, then when the possible phase difference of the membrane under test S falls between 0 nanometers and 200 nanometers, a quarter-wave plate is used as the standard plate 133.

In this embodiment, the slow axis of the standard plate 133 forms a substantial angle of +45 degrees with the absorption axis of the lower polarizer 132 and the absorption axis of the upper polarizer 134, and is substantially parallel to the slow axis of the film under test S. Furthermore, the slow axis of the standard plate 133 is also substantially +45 degrees. Thus, the light from the emitting unit array 110 sequentially passes through the diffuser 131 and the lower polarizer 132, becoming linearly polarized light substantially perpendicular to the absorption axis of the lower polarizer 132, and then passes through the standard plate 133, becoming circularly polarized light. The circularly polarized light then passes through the film under test S. Since the phase difference of the test film S is approximately one-quarter of the wavelength to be analyzed, circularly polarized light will be converted into linearly polarized light parallel to the absorption axis of the upper polarizer 134 after passing through the test film S. The light remaining after the upper polarizer 134 absorbs the linearly polarized light parallel to the absorption axis can be used as the basis for determining the phase difference between the test film S and the standard film 133. Next, the image sensor 160 receives the light and acquires an image, which is then transmitted to the processor 170. The processor 170 then obtains the phase difference value based on information from multiple pixels in the image.

Furthermore, these pixels include 256 gray levels of the light received by pixel unit P of image sensor 160, representing the intensity of the received light. A relationship between the light intensity and the phase difference for this phase difference range can be obtained through Jones matrix correction. In some embodiments, the relationship is defined as follows: . The phase difference value is the value of the film under test S at the corresponding pixel in the image. The light intensity value of the aforementioned pixel. To calibrate the constants of the intensity related to this interval, The phase shift calibration constants for systems related to this region are used. and This is based on calibration for the testing environment, which will be detailed in later paragraphs.

When the possible phase difference range of the diaphragm S under test is approximately half of the wavelength to be analyzed, the standard plate 133 includes a zero-phase-difference waveplate. In some embodiments, the phase difference range is preset to be within... + and In between. For example, selecting the wavelength to be analyzed. The phase difference is 550 nm. When the possible phase difference value of the test film S falls between 201 nm and 275 nm, the standard film 133 used is the reference phase difference value. It is a zero-phase waveplate with a diameter of 0 nanometers.

In this embodiment, since the phase difference between the lower polarizer 132 and the upper polarizer 134 is only set to a test film S with a phase difference range approximately half that of the wavelength to be analyzed, the light from the emitting unit array 110, after passing through the lower polarizer 132 and the test film S, will be converted into linearly polarized light whose angle between twice the slow axis and the absorption axis is substantially parallel to the absorption axis direction of the upper polarizer 134. In some embodiments, the relationship between the light intensity and the phase difference value within this phase difference range is defined as follows: Similarly, To calibrate the constants of the intensity related to this interval, The phase shift calibration constants for systems related to this region are used. and It is obtained by calibration according to the detection environment. It is worth noting that in some embodiments targeting this phase difference range, the standard sheet 133 may be omitted from the optical detection system 10. For the optical detection system 10 omitting the standard sheet 133, please refer to Figure 2, which is a schematic diagram of the light-emitting unit array 110, the optical film group 130, and the image sensor 160 of the optical detection system 10 according to other embodiments of this disclosure.

When the possible phase difference range of the diaphragm S under test is approximately three-quarters of the wavelength to be analyzed, the standard plate 133 includes a quarter-wave plate, and the slow axis direction of the standard plate 133 is substantially perpendicular to the slow axis direction of the diaphragm S under test. In some embodiments, the phase difference range is preset to be within... and In between. For example, selecting the wavelength to be analyzed. The standard wafer used is 133 reference phase difference value, which is 550 nanometers. If the phase difference is 142 nm, then when the possible phase difference of the test film S falls between 275 nm and 417 nm, a quarter-wave plate is used as the standard plate 133.

In this embodiment, the slow axis of the standard plate 133 forms an angle of -45 degrees with the absorption axis of the lower polarizer 132 and the absorption axis of the upper polarizer 134. More specifically, the angle between the slow axis of the standard plate 133 and the absorption axis of the lower polarizer 132 is 135 degrees. In some embodiments, the relationship between the light intensity and the phase difference value within this phase difference region is defined as follows: Similarly, To calibrate the constants of the intensity related to this interval, The phase shift calibration constants for systems related to this region are used. and It is obtained by calibration based on the testing environment.

It is worth noting that, in the same testing environment, , as well as They may have different values, at the same time , as well as They may have different values. In addition, in the same detection environment, the calibration constant does not need to be adjusted for every detection, but only needs to be calibrated periodically to prevent the system from deviating due to the attenuation of the luminous intensity of the luminous unit, loose component screws, or vibration and displacement of optical components.

In some embodiments, the processor 170 has an algorithm pre-written to analyze the phase difference values of the membrane under test. For example, parameters are defined. ,in The standard deviation of the phase difference value of the diaphragm under test within the detection area is denoted as . This is the average of the phase difference values. Parameter It can be used as an indicator of the uniformity of phase difference values within a measured area. Parameters The smaller the value, the higher the uniformity. For example, the parameter... A value less than 0.7 is considered a better process result.

Furthermore, the algorithm can also determine the distribution of liquid crystal alignment uniformity in the compensation film coating based on the normalized phase difference value. For example, the normalized phase difference value is defined as follows: The closer the normalized phase difference is to 1, the better the uniformity.

In some embodiments, as shown in Figure 1, the optical detection system 10 further includes an optical mirror assembly 150. The optical mirror assembly 150 is located between the image sensor 160 and the optical film assembly 130. More specifically, the optical mirror assembly 150 is located between the image sensor 160 and the upper polarizer 134. In some embodiments, the optical mirror assembly 150 includes at least one lens configured to narrow a large area of light to the receiving range of the image sensor 160. By selecting an appropriate lens, the detection resolution can be adjusted, which helps to improve mura defects caused by brightness and chromaticity inhomogeneities. In some embodiments, the optical mirror assembly 150 also includes an aperture configured to adjust the light throughput.

In some embodiments, as shown in Figure 1, the optical detection system 10 further includes a support 140 and a glass plate 142. The support 140 houses at least a portion of the light-emitting unit array 110 and the optical film assembly 130 within a space, allowing light to travel in a sufficiently dark space during detection, thereby improving detection accuracy. As shown in Figure 1, the glass plate 142 is connected to one side of the support 140 and positioned above the standard sheet 133, allowing the film under test S to be placed on the glass plate 142. In some embodiments, the film under test S is a roll, which facilitates its movement when placed on the glass plate 142. For example, the film under test S is configured to allow unfolding along its machine direction (MD), such as direction D2.

Please refer to Figure 3, which is a flowchart of an optical detection method 20 according to some embodiments of this disclosure. As shown in Figure 3, the optical detection method 20 includes steps S201 to S209. First, step S201 selects parameters based on the range of possible phase difference values that the film under test may have. As mentioned earlier, different detection system architectures and detection parameters are defined depending on the range of possible phase difference values of the film under test. The detection parameters may include the luminous intensity of the luminous unit array and the calibration constant of the relational expression. Generally, the theoretical value of the phase difference can be estimated based on the thickness of the film under test, or the phase difference value of a single point on the film under test can be measured using, for example, an AxoScan manufactured by Axometrics Corporation as a representative value.

Next, in step S202, an array of light-emitting units and an optical film assembly are arranged, wherein the optical film assembly is located in the light-emitting direction of the array of light-emitting units. As mentioned above, the optical film assembly may include a diffuser, a lower polarizer, a standard plate, and an upper polarizer, which are sequentially stacked above the array of light-emitting units along the light-emitting direction.

Next, in step S203, the film to be tested is placed in the optical film assembly. As mentioned earlier, the film to be tested may be a roll of material and is placed between the standard film and the upper polarizer in the optical film assembly.

Next, step S204 adjusts the luminous intensity of the luminous unit array and transmits the light through the optical film assembly to the image sensor. The luminous intensity is related to the phase difference range of the film under test.

Next, step S205 drives the image sensor to receive light and capture an image. In some embodiments, an optical mirror assembly is provided between the image sensor and the optical film assembly. After passing through the optical film assembly and the optical mirror assembly, the light is received by the image sensor to adjust the detection range and light flux.

Next, step S206 confirms whether the image acquired by the image sensor is overexposed or underexposed. In some embodiments, a processor signal is connected to the image sensor. The processor receives the image from the image sensor and determines whether the image is overexposed or underexposed based on the 256 grayscale values of each pixel in the image. For example, an overexposed image is defined as a grayscale value greater than or equal to 245, and an underexposed image is defined as a grayscale value less than or equal to 10.

If the processor determines that the image is overexposed or underexposed, it executes step S207 to adjust the light intensity of the light-emitting unit array until the processor determines that the image is not overexposed or underexposed, and corrects the calibration constants (such as the constants in the aforementioned relationship). , , , , as well as For example, the luminous intensity before adjustment was... The adjusted luminous intensity is Then correct the positive constants. Revised to And so on.

Once the processor determines that the image is neither overexposed nor underexposed, it executes step S208. In step S208, the processor acquires the light intensity value based on the image. In some embodiments, as described above, the processor acquires 256 grayscale values of the light received by each pixel unit in the image sensor as the light intensity value.

Next, step S209 obtains the phase difference value of each pixel based on the intensity value of the light and the relational expression. In this way, two-dimensional phase difference information of a large area of the film under test can be obtained at once, so that the processor can analyze the uniformity of the two-dimensional phase difference distribution.

In some implementations, the film under test can be replaced with a standard compensation film with a known phase difference distribution. Then, an luminous intensity that will not cause overexposure or underexposure of the image is selected, and steps S202 to S208 are executed. The obtained light intensity values are substituted into the relational formula. With the intensity values and phase difference values known, calibration constants related to the detection environment (such as the constants in the aforementioned relational formula) can be obtained. , , , , as well as ).

The detailed description of the specific embodiments disclosed above clearly shows that in some embodiments of the optical detection method and optical detection system disclosed herein, light emitted by an array of emitting units passes through an optical film assembly and the film under test, and an image sensor acquires the image. This allows for the acquisition of two-dimensional phase difference information of a large area of the film under test in a single operation, saving detection and scanning time. Furthermore, the uniformity of the phase difference can be quickly analyzed using algorithms preset in the processor. Therefore, real-time detection can be performed on the production line, allowing for process adjustments at any time. In addition, the detection resolution can be adjusted using an optical mirror assembly to improve the appearance of film surface defects.

The foregoing description is merely illustrative and descriptive of exemplary embodiments of this disclosure and is not intended to exhaustively illustrate or limit the precise form of the invention disclosed herein. The teachings above may be modified or varied.

The selected and illustrated embodiments are intended to explain the content of this disclosure and their practical application, thereby inspiring those skilled in the art to utilize this disclosure and the various embodiments, and to make various modifications to suit a particular intended use. Alternative embodiments will be obvious to those skilled in the art without departing from the spirit and scope of this disclosure. Therefore, the scope of this disclosure is determined by the scope of the appended invention claims, and not by the foregoing description and the exemplary embodiments described therein.

10: Optical Detection System 20: Optical Detection Method 110: Light Emitting Unit Array 120: Controller 130: Optical Film Assembly 131: Diffuser 132: Lower Polarizer 133: Standard Plate 134: Upper Polarizer 140: Support 142: Glass Plate 150: Optical Mirror Assembly 160: Image Sensor 170: Processor B, G, R: Subpixel Unit D1, D2: Orientation P: Pixel Unit S: Film Under Test S201, S202, S203, S204, S205, S206, S207, S208, S209: Steps

The figures illustrate one or more embodiments of this disclosure and, together with the written description, serve to explain the principles of this disclosure. Throughout the figures, the same stylistic reference numerals are used as much as possible to refer to similar or identical elements of the embodiments, wherein: Figure 1 is a schematic diagram of an optical detection system according to some embodiments of this disclosure. Figure 2 is a schematic diagram of an emitting unit array, an optical film assembly, and an image sensor of an optical detection system according to other embodiments of this disclosure. Figure 3 is a flowchart of an optical detection method according to some embodiments of this disclosure.

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20: Optical Detection Methods S201, S202, S203, S204, S205, S206, S207, S208, S209: Procedures

Claims (10)

An optical detection method includes: Disposing an array of light-emitting units and an optical film assembly above the array of light-emitting units, wherein the optical film assembly includes a diffuser, a lower polarizer, a standard plate, and an upper polarizer stacked sequentially along a light emission direction of the array of light-emitting units, and the lower polarizer and the upper polarizer each have an absorption axis, wherein the absorption axis of the lower polarizer and the absorption axis of the upper polarizer are substantially parallel to each other; Disposing a film to be tested between the standard plate and the upper polarizer, wherein the film to be tested has a slow axis, and the slow axis of the film to be tested forms a substantially 45-degree angle with the absorption axis of the upper polarizer; Driving the array of light-emitting units to emit a plurality of rays through the optical film assembly; An image sensor is driven to receive the light rays passing through the optical film assembly and acquire an image; A processor is driven to acquire a plurality of intensity values of the light rays based on the image, wherein the processor is signal-connected to the image sensor, and the image has a plurality of pixels corresponding to the intensity values; and The processor is driven to acquire a plurality of phase difference values related to the film under test based on the intensity values. The optical detection method as described in claim 1, wherein obtaining the phase difference values based on the intensity values includes obtaining the phase difference values using a relation based on a one-position phase difference value range of the film under test. The optical detection method as described in claim 2, wherein the standard plate has a slow axis and the slow axis of the standard plate forms a substantially +45-degree angle with the absorption axis of the upper polarizer. As described in claim 3, in the optical detection method, when the phase difference value range of the test film is approximately a quarter-wave plate, and the standard plate is a quarter-wave plate, the relationship is: ,in For the wavelength to be analyzed, The intensity value corresponding to one of those pixels in the image. This is a reference phase difference value for the standard film. and Let be a complex number of constants relating to the range of that phase difference value, and It is the one-bit phase difference value of that pixel among those pixels. As described in claim 2, in the optical detection method, when the phase difference value range of the test film is approximately equal to that of a half-wave plate, and the standard plate is a zero-phase-difference wave plate, the relationship is: ,in For the wavelength to be analyzed, The intensity value corresponding to one of those pixels in the image. and Let be a complex number of constants relating to the range of that phase difference value, and It is the one-bit phase difference value of that pixel among those pixels. The optical detection method as described in claim 2, wherein the standard plate has a slow axis and the slow axis of the standard plate forms an angle of substantially -45 degrees with the absorption axis of the upper polarizer. As described in claim 6, in the optical detection method, when the phase difference value of the test film is approximately within the range of a three-quarter wave plate, and the standard plate is a quarter wave plate, the relationship is: ,in For the wavelength to be analyzed, The intensity value corresponding to one of those pixels in the image. This is a reference phase difference value for the standard film. and Let be a complex number of constants relating to the range of that phase difference value, and It is the one-bit phase difference value of that pixel among those pixels. An optical detection system includes: an array of light-emitting units configured to emit a plurality of light rays; an optical film assembly positioned above the array of light-emitting units and comprising a diffuser, a lower polarizer, a standard plate, and an upper polarizer stacked sequentially along a light emission direction of the array of light-emitting units, wherein the lower polarizer and the upper polarizer each have an absorption axis, wherein the absorption axis of the lower polarizer and the absorption axis of the upper polarizer are substantially parallel to each other; an image sensor configured to receive the light rays passing through the optical film assembly and acquire an image; and a processor signal-connected to the image sensor and configured to acquire a plurality of phase difference values based on the image, wherein the image has a plurality of pixels corresponding to the phase difference values. The optical detection system as described in claim 8, wherein the standard plate has a slow axis and the slow axis forms a substantially +45-degree angle with the absorption axis of the upper polarizer. The optical detection system as described in claim 8, wherein the standard plate has a slow axis and the slow axis forms an angle of substantially -45 degrees with the absorption axis of the upper polarizer.