A method and device for testing phase delay of wave plate

Abstract

The present invention discloses a method and device for testing the phase delay of a wave plate. The method comprises the following steps: step 1, arranging a light source, a polarizer, a wave plate to be tested, an analyzer, and an optical power meter in sequence along an optical path, wherein the optical axis of the wave plate to be tested is at a 45° angle to the X-axis, and the light transmission axis of the analyzer is parallel to the X-axis; step 2, turning on the light source and recording a first optical power P1; step 3, rotating the analyzer 90° and recording a second optical power P2; and step 4, calculating the phase delay of the wave plate to be tested according to the Jones matrix of the wave plate to be tested. During the test process, the present invention only needs to rotate the analyzer once, and no operation is required on the polarizer or the wave plate to be tested. This avoids the accumulation of operational errors that may be caused by multiple operations of multiple devices, thereby leading to a problem of large errors in the test results, thereby ensuring test accuracy. At the same time, due to the simplification of the test process, the test efficiency is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of wave plate parameter testing, and in particular to a method and device for testing wave plate phase delay. Background Art

[0002] Wave plates are commonly used optical components in the field of polarization optics. They are polarization optical devices based on the birefringence of crystals and are also called phase retarders. They can alter the polarization state of light by generating an additional optical path difference (or phase difference) that couples to the two perpendicular components of polarized light, thereby altering the polarization state of the light. This optical path difference is called the wave plate's phase retardation. Commonly used wave plates include quarter-wave plates and half-wave plates. The phase retardation properties of wave plates not only alter the polarization state of light but also have broad applications in fiber optic communications, photoelasticity, polarization state testing of light waves, and various polarization-related technologies.

[0003] In order to detect the delay accuracy and effect of the wave plate, it is necessary to measure the phase delay of the wave plate. On December 31, 2019, the Chinese patent with publication number CN110631806A disclosed a device and method for quickly measuring the phase delay of a wide-band wave plate. The method uses the Stokes vector method to derive the correspondence between the phase delay of the wave plate to be measured and the output energy, thereby calibrating the phase delay of the wave plate to be measured by measuring the output energy. This method uses the Mueller matrix for calculation, involves many parameters, and the calculation is relatively complicated. In addition, its polarizer, wave plate to be measured, and analyzer all need to have a rotating structure, which requires multiple rotations during the test process, resulting in an overly complicated test process.

[0004] The present invention utilizes the principle of polarized light interference to achieve the conversion of phase delay and interference light energy, and can be used to test the phase delay of wave plate products. Summary of the Invention

[0005] In order to overcome the above-mentioned deficiencies in the prior art, the present invention provides a method and apparatus for testing the phase delay of a wave plate, so as to solve at least one of the above-mentioned technical problems.

[0006] In one aspect, the present invention provides a method for testing the phase delay of a wave plate, comprising:

[0007] Step 1: Place a light source, a polarizer, a wave plate to be measured, an analyzer, and an optical power meter in sequence along the optical path, with the optical axis of the wave plate to be measured forming a 45° angle with the X-axis, and the transmittance axis of the analyzer parallel to the X-axis.

[0008] Step 2: Turn on the light source and record the first light power P1;

[0009] Step 3, rotate the analyzer 90° and record the second optical power P2;

[0010] Step 4: Calculate the phase delay of the wave plate to be measured according to the Jones matrix of the wave plate to be measured.

[0011] The above technical solution utilizes the principle of polarized light interference. After linearly polarized light passes through the wave plate, the elliptically polarized light obtained has different components in the X-axis and Y-axis directions, but it has an accurate mathematical relationship with the phase delay of the o-light and e-light. By measuring the light intensity on the X and Y axes, the phase delay caused by the wave plate can be obtained.

[0012] During the test process, the above technical solution only needs to rotate the polarizer once, and no operation is required on the polarizer or the wave plate to be tested. This avoids the accumulation of operational errors that may be caused by multiple operations of multiple devices, which in turn leads to large errors in the test results, thereby ensuring test accuracy. At the same time, due to the simplification of the test process, the test efficiency is greatly improved.

[0013] As a further technical solution, when the optical axis of the wave plate to be measured is at an angle of 45° to the X axis, the complex amplitude of the transmitted light after passing through the wave plate is The Jones vector is

[0014] ,

[0015] Complex amplitude of light transmitted through the wave plate The ratio of the components on the X and Y axes is ,in is the phase delay of the wave plate to be measured.

[0016] As a further technical solution, according to the fact that the ratio of optical powers is equal to the ratio of optical intensities, and the ratio of optical intensities is equal to the square of the ratio of complex amplitudes, the phase delay of the wave plate to be measured is calculated as

[0017] .

[0018] As a further technical solution, the cross section of the light beam remains unchanged before and after the polarizer is rotated.

[0019] On one hand, the present invention provides a device for testing the phase delay of a wave plate, which is used to implement the method described above. The device comprises a light source, a polarizer, a wave plate to be tested, an analyzer and an optical power meter arranged in sequence along an optical path. The optical axis of the wave plate to be tested is placed at a 45° angle to the X-axis, and the transmission axis of the analyzer is parallel to the X-axis.

[0020] The above technical solution has a simple structure and is easy to operate. During the test, no other devices need to be operated. Only one rotation of the polarizer is required to obtain two optical power values. These two optical power values can be combined with the Jones matrix to calculate the phase delay of the wave plate to be tested, which greatly improves the test efficiency.

[0021] Compared with existing devices, the above technical solution simplifies the test device, eliminates the need to operate the wave plate and / or polarizer to be tested, simplifies the test process, and only requires one rotation of the polarizer to complete the test. This not only improves the test efficiency, but also avoids the problem of repeated operation of multiple devices leading to the accumulation of operational errors, which in turn affects the test accuracy.

[0022] As a further technical solution, the polarizer is provided with a rotating structure for realizing a 90° rotation of the polarizer.

[0023] As a further technical solution, the light emitted by the light source passes through the polarizer, the wave plate to be measured, and the analyzer in sequence, enters the optical power meter and records the first light power P1, then rotates the analyzer 90° and records the second light power P2, and calculates the phase delay of the wave plate to be measured based on P1, P2 and the Jones matrix.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention utilizes the principle of polarized light interference. The components of the elliptically polarized light obtained after the linearly polarized light passes through the wave plate are different in the X-axis and Y-axis directions, but they have an accurate mathematical relationship with the phase delay of the o-light and e-light. The phase delay caused by the wave plate can be obtained by measuring the light intensity on the X and Y axes.

[0026] (2) During the test process, the present invention only needs to rotate the analyzer once, and no operation is required on the polarizer or the wave plate to be tested. This avoids the accumulation of operational errors that may be caused by multiple operations on multiple devices, which in turn leads to large errors in the test results, thereby ensuring the test accuracy. At the same time, due to the simplification of the test process, the test efficiency is greatly improved.

[0027] (3) The present invention has a simple structure, is easy to operate, requires little computation, and is suitable for large-scale engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the optical path for testing the phase delay of a wave plate according to an embodiment of the present invention.

[0029] Figure 2 Schematic diagram of a device for testing the phase delay of a wave plate according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions of various embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include one or more of the specified features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0032] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections, or mutual communication; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0033] On the one hand, the present invention provides a method for testing the phase delay of a wave plate. The method utilizes the principle of polarized light interference to realize the conversion of phase delay and interference light energy, and can be used to test the phase delay of a wave plate product.

[0034] Light intensity is proportional to the square of the complex amplitude modulus, and the complex amplitude varies with the phase. However, the optical vibration period is too short and the frequency is high. Existing detectors cannot measure the exact light intensity at a given moment, and can only measure the average energy density over a period of time. The present invention utilizes the principle of polarized light interference. The components of elliptically polarized light obtained after linearly polarized light passes through a wave plate are different in the X-axis and Y-axis directions, but they have an accurate mathematical relationship with the phase delay of the O-light and E-light. By measuring the light intensity on the X and Y axes, the phase delay produced by the wave plate can be obtained. Although the exact light intensity at any moment cannot be measured, the ratio of the intensities in two orthogonal directions at any moment is a constant. The detector receives the average energy, and the ratio of the average energy in the two directions remains an accurate value.

[0035] In one aspect, the present invention provides a method for testing the phase delay of a wave plate, comprising:

[0036] Step 1: Set up the light source, polarizer, wave plate to be measured, analyzer and optical power meter in sequence along the optical path, and the optical axis of the wave plate to be measured is at a 45° angle to the X-axis, and the transmittance axis of the analyzer is parallel to the X-axis. Figure 1 shown.

[0037] Alternatively, the light source may be a laser.

[0038] The light emitted by the laser is converted into horizontally polarized light after passing through a horizontally transparent polarizer. The horizontally polarized light is incident vertically on the wave plate to be measured and the surface of the analyzer in turn, and then enters the optical power meter, where the optical power is read and recorded.

[0039] Step 2: Turn on the light source and record the first optical power P1.

[0040] Step 3: Rotate the analyzer 90° and record the second optical power P2.

[0041] Step 4: Calculate the phase delay of the wave plate to be measured according to the Jones matrix of the wave plate to be measured.

[0042] Optionally, let the horizontal polarization amplitude be , the wave plate optical axis is perpendicular to the X axis Angle, the Jones vector of the complex amplitude of the transmitted light after passing through the wave plate is The following operations are performed using the Jones matrix of the wave plate:

[0043]

[0044] Substituting into the 45° angle, we can calculate:

[0045] =45°

[0046]

[0047] Complex amplitude of light transmitted by visible wave plate The ratio of the components on the X and Y axes is , the ratio of light intensities is the square of the ratio of complex amplitudes, and the beam cross section remains unchanged before and after the analyzer is rotated, so the ratio of light powers is the ratio of light intensities, that is,

[0048]

[0049] .

[0050] The above equation gives an accurate expression for the relationship between phase delay and optical power at any given moment. (In actual calculations, the positive direction of the X-axis is opposite to that in the diagram, and the observation direction is toward the beam propagation, that is, from right to left.)

[0051] During the test process, the method of the present invention only needs to rotate the polarizer once, and no operation is required on the polarizer and the wave plate to be tested. This avoids the accumulation of operational errors that may be caused by multiple operations on multiple devices, which in turn leads to large errors in the test results, thereby ensuring test accuracy. At the same time, due to the simplification of the test process, the test efficiency is greatly improved.

[0052] On the one hand, the present invention provides a device for testing the phase delay of a wave plate, which is used to implement the method described, as follows: Figure 2As shown, it includes a laser, a polarizer, a wave plate to be measured, an analyzer and an optical power meter arranged in sequence along the optical path. The optical axis of the wave plate to be measured is placed at a 45° angle to the X-axis, and the transmission axis of the analyzer is parallel to the X-axis.

[0053] When testing the device provided by the present invention, the light emitted by the light source passes through the polarizer, the wave plate to be tested, and the analyzer in sequence, enters the optical power meter and records the first optical power P1, then rotates the analyzer 90° and records the second optical power P2. The phase delay of the wave plate to be tested is calculated based on P1 and P2 in combination with the Jones matrix. The calculation formula is: .

[0054] Optionally, the analyzer is provided with a rotating structure for rotating the analyzer by 90°. The rotating structure can be manual or electric, and the present invention does not impose any limitation thereto.

[0055] The device described in the present invention has a simple structure and is easy to operate. During the test process, no other devices need to be operated. Only one rotation of the polarizer is required to obtain two optical power values. The phase delay of the wave plate to be tested can be calculated by combining these two optical power values with the Jones matrix, which greatly improves the test efficiency.

[0056] Compared with existing devices, the present invention simplifies the test device, eliminates the need to operate the wave plate and / or polarizer to be tested, simplifies the test process, and can complete the test by rotating the polarizer once. This not only improves the test efficiency, but also avoids the problem of repeated operation of multiple devices leading to the accumulation of operational errors, which in turn affects the test accuracy.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for testing the phase delay of a wave plate, characterized in that: include: Step 1: Place a light source, a polarizer, a wave plate to be measured, an analyzer, and an optical power meter along the optical path in sequence, with the optical axis of the wave plate to be measured forming a 45° angle with the X-axis, and the transmittance axis of the analyzer parallel to the X-axis. Step 2: Turn on the light source and record the first light power P1; Step 3, rotate the analyzer 90° and record the second optical power P2; Step 4: Calculate the phase delay of the wave plate to be tested according to the Jones matrix of the wave plate to be tested. Including: Assume that the amplitude of horizontal polarized light is , the optical axis of the wave plate to be measured is perpendicular to the X axis Angle, the Jones vector of the complex amplitude of the transmitted light after passing through the wave plate is , use the Jones matrix of the wave plate to be measured to perform the following operation: , ; Substitute the 45° angle and calculate: , ; Complex amplitude of light transmitted through the wave plate The ratio of the components on the X and Y axes is , the ratio of light intensity is the square of the ratio of complex amplitudes, and the ratio of light power is equal to the ratio of light intensity, that is, , the phase delay of the wave plate to be measured .

2. A method for testing the phase delay of a wave plate according to claim 1, characterized in that: The cross section of the beam remains unchanged before and after the analyzer is rotated.

3. A device for testing the phase delay of a wave plate, used to implement the method according to any one of claims 1 to 2, characterized in that: The optical system comprises a light source, a polarizer, a wave plate to be measured, an analyzer and an optical power meter arranged in sequence along the optical path. The optical axis of the wave plate to be measured is placed at a 45° angle to the X-axis, and the transmission axis of the analyzer is parallel to the X-axis.

4. The device for testing the phase delay of a wave plate according to claim 3, characterized in that: The polarizer is equipped with a rotating structure for rotating the polarizer by 90 degrees.

5. The device for testing the phase delay of a wave plate according to claim 3, characterized in that: The light emitted by the light source passes through the polarizer, the wave plate to be measured, and the analyzer in sequence, enters the optical power meter and records the first optical power P1, then rotates the analyzer 90° and records the second optical power P2, and calculates the phase delay of the wave plate to be measured based on P1, P2 and the Jones matrix.

Images