Online lamination system and method for polarization direction rotator

Abstract

The present invention relates to the field of optical technology and discloses an online lamination system and method for a polarization direction rotator to improve the accuracy of lamination between an electrically controlled liquid crystal cell and a quarter-wave plate. The method comprises: using a goniometer and a polarimeter to, on the one hand, precisely determine the key angles of each step based on the change in ellipticity to meet extinction ratio requirements; on the other hand, calculate the parallelism between an electrically controlled variable phase retarder and the quarter-wave plate based on the change in the goniometer; during the lamination process, after the electrically controlled variable phase retarder is determined to have an ideal 45° angle between its two fast axes and the quarter-wave plate at the lowest point of ellipticity, the electrically controlled variable phase retarder is rotated within a range of plus or minus 0.5° so that the ellipticity of the output light beam at each test voltage, as observed by the polarimeter, is less than 1.8°. This balance strategy ensures that relatively ideal application performance is achieved at each test voltage and under no pressure.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to an online bonding system and method for a polarization direction rotator. Background Art

[0002] Polarization rotators are commonly used for polarization control in laser processing. They can quickly rotate the laser's polarization direction to process materials. Generally, the two most important parameters for a polarization rotator are the extinction ratio of the output linearly polarized light (typically >1000:1) and its response time, which is related to the modulation frequency.

[0003] Electro-optical crystals are currently commonly used for modulation, offering fast response times but prone to hysteresis, resulting in a low usable modulation frequency. Furthermore, to achieve an adjustable phase angle range of 0°-360°, the longer the wavelength, the longer or thicker the electro-optic crystal, increasing its cost. Furthermore, electro-optic crystals typically require high voltages exceeding kilovolts, requiring high-voltage amplifiers for conventional use, increasing both size and cost.

[0004] Compared with electro-optical crystals, if the polarization direction rotator adopts a solution that combines a phase retarder such as a liquid crystal box with a quarter wave plate, the cost and volume can be greatly reduced, and it can be used at low voltage, thereby improving the contrast of linearly polarized light. Thus: the liquid crystal polarization direction rotator is composed of a liquid crystal box and a zero-order quarter wave plate; the fast axes of the liquid crystal box and the wave plate are 45° to each other, and the linearly polarized light is incident on the polarization direction rotator from the side of the liquid crystal box. By adjusting the liquid crystal delay, the direction of the output polarized light can be rotated; wherein, the incident light must be linearly polarized, and the polarization direction must be aligned with one of the incident axes of the rotator (marked on the front of the shell). However, how to improve the accuracy of the bonding process between the two to avoid affecting the extinction ratio has become a technical problem that needs to be solved urgently. Among them, the main factors affecting the bonding accuracy are:

[0005] 1. The 1 / 4 wave plate is made of a large piece, and the 0° fast axis mark of the large piece has an error, which affects the pre-alignment.

[0006] 2. When the 1 / 4 wave plate is cut from a large piece, cutting errors will occur, affecting the pre-alignment.

[0007] 3. The fitting error between the electronically controlled liquid crystal box and the quarter wave plate. Summary of the Invention

[0008] The present invention aims to disclose an online lamination system and method for a polarization direction rotator, so as to improve the accuracy of lamination between an electrically controlled liquid crystal cell and a quarter wave plate.

[0009] To achieve the above-mentioned object, the present invention discloses an online laminating system for a polarization direction rotator, comprising at least: a laser generator, a first polarizer, a laminating platform, a polarimeter, and a goniometer; wherein the first polarizer is located between the laser generator and the laminating platform, and the laminating platform is located between the first polarizer and the polarimeter;

[0010] The upper portion of the lamination table is used to place a quarter-wave plate, and the lower portion is connected to positive and negative pressure-applying terminals connected to a voltage generator. The positive and negative pressure-applying terminals are used to detachably connect to the positive and negative pressure-receiving terminals of the electrically controlled variable phase retarder and are provided with a mechanism for rotating the electrically controlled variable phase retarder. The laser generator is deployed in a position such that the emitted laser first passes through the electrically controlled variable phase retarder and then passes through the quarter-wave plate.

[0011] The goniometer is used to measure the angle between the reflected light beam from the electrically controlled variable phase retarder and the reflected light beam from the quarter wave plate collected on the reticle, so as to determine the parallelism between the electrically controlled variable phase retarder and the quarter wave plate based on the angle;

[0012] The polarimeter is used to measure the polarization azimuth of the linearly polarized light of the collected light beam after it is placed in the electrically controlled variable phase retarder and before the quarter wave plate is placed, and the change in ellipticity after the quarter wave plate is placed as the quarter wave plate rotates at an angle and remains stationary for a certain period of time.

[0013] To achieve the above object, the present invention further discloses a bonding method applied to the above system, comprising:

[0014] Step S1, deploying an optical path;

[0015] Step S2: placing the electrically controlled variable phase retarder to be bonded into the bonding platform, and when the electrically controlled variable phase retarder is modulated to a polarization meter to observe linear polarized light with the lowest ellipticity, determining that the current fast axis direction of the electrically controlled variable phase retarder is parallel to the polarization direction of the first polarizer and the slow axis is perpendicular to the polarization direction of the first polarizer; then, rotating the electrically controlled variable phase retarder 45 degrees around the optical axis and fixing it;

[0016] Step S3: After dripping UV-curing adhesive onto the upper surface of the electrically controlled variable phase retarder, a quarter-wave plate to be bonded is placed onto the upper surface of the electrically controlled variable phase retarder. Pre-alignment is first performed using a trimmed edge, and then the quarter-wave plate is rotated until the polarimeter observes a change in elliptical polarization from elliptically polarized light to linearly polarized light, or until the ellipticity is minimized. The electrically controlled variable phase retarder is then sequentially voltaged to various test voltages and rotated within a range of plus or minus 0.5 degrees, such that the ellipticity of the outgoing light beam at each test voltage as observed by the polarimeter is less than 1.8°.

[0017] Step S4: Observe with a goniometer that the angle between the reflected light beam from the electrically controlled variable phase retarder and the reflected light beam from the quarter wave plate is the smallest during the static state, and then turn on the UV curing lamp to perform curing.

[0018] The present invention has the following beneficial effects:

[0019] 1. The structure and optical path deployment are simple and convenient.

[0020] 2. With the combined action of the goniometer and polarimeter, on the one hand, the key angles of each step can be precisely determined based on the changes in ellipticity to meet the extinction ratio requirements. On the other hand, the changes in the goniometer can be used to calculate the parallelism between the electrically controlled variable phase retarder and the 1 / 4 wave plate. Parallelism is very important in light transmission or optical coupling. Polarization devices often need to be rotated. Poor parallelism will cause the overall light spot to shift, affecting the transmission or coupling efficiency. Therefore, the static time can be accurately determined to ensure that the parallelism between the two bonded devices meets the requirements and improve the bonding efficiency.

[0021] 3. During the bonding process, after the electrically controlled variable phase retarder was positioned at an ideal 45° angle with the fast axes between the quarter-wave plates at the lowest point of ellipticity, it was then rotated within a range of ±0.5° to ensure that the ellipticity of the outgoing beam observed by the polarimeter was less than 1.8° at each test voltage. This ensured that the extinction ratio was greater than 1000:1 at each test voltage. This balancing strategy ensured ideal application performance at all test voltages and in the unstressed state.

[0022] The present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 Schematic diagram of the optical path of the online bonding system of the polarization direction rotator disclosed in an embodiment of the present invention.

[0025] Figure 2 It is a flow chart of an online bonding method of a polarization direction rotator disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0027] Example 1

[0028] This embodiment discloses an online lamination system for a polarization direction rotator, such as Figure 1 Shown, including:

[0029] Laser is the laser generator; L1 and L2 are lenses; Iris is the aperture; LP1 and LP2 are linear polarizers with parallel polarization directions; ARGlass is an anti-reflection film (used to be directly bonded to the LCVR to reduce the reflectivity of the final polarization direction rotator); LCVR is an electrically controlled variable phase retarder; QWP is a 1 / 4 wave plate corresponding to the laser wavelength; BS is a beamsplitter cube, used for splitting light, one beam enters P1 for monitoring the laser ellipticity and azimuth; the other beam enters A1 for monitoring parallelism; P1 is a polarimeter; A1 is a goniometer with its own light source; NF is a notch filter corresponding to the laser wavelength, used to block light from the laser generator; SPFC is a spatial filtering and collimation system, composed of L1, L2 and Iris, to reduce the spot size to meet the measurement aperture of the polarimeter; Controller is the controller of the liquid crystal box, which changes the delay amount and control speed of the liquid crystal box by adjusting the voltage and modulation frequency.

[0030] exist Figure 1 In this example, LP1 serves as an intensity modulator and LP2 as a polarizer. As a compromised implementation, either linear polarizer can be removed, with the undesirable consequence of reducing the extinction ratio of the bonded assembly (the combination of an electrically controlled variable phase retarder and a quarter-wave plate). In this embodiment, to maximize the extinction ratio of the bonded assembly, the extinction ratio of the incident light entering the bonded assembly must be maximized. In other words, the assistance of the two linear polarizers with parallel polarization directions effectively increases the extinction ratio of the incident light entering the bonded assembly, which can be referred to as the "initial extinction ratio" to distinguish it from the extinction ratio of the polarization rotator in the subsequent optical path.

[0031] The extinction ratio in polarization optical devices is a key parameter for measuring polarizer quality. Imagine two polarization elements, K1 and K2, positioned left and right, with K1 acting as the polarizer and K2 acting as the analyzer. The properties of polarization elements indicate that when natural light passes through K1, it becomes linearly polarized. If this linearly polarized light continues through K2, if the optical axes of K1 and K2 align, the light intensity passing through K2 is the highest. If the optical axes of K1 and K2 differ by 90 degrees, the light intensity is zero. However, in reality, polarization devices are not always ideal. Natural light passing through K1 may only produce partially polarized light. In this case, even if K1 and K2 are perpendicular to each other, the transmitted light intensity is not zero. Therefore, the ratio of the maximum transmitted light intensity to the minimum transmitted light intensity when analyzer K2 is rotated is called the extinction ratio.

[0032] Preferably, the delay accuracy of the 1 / 4 wave plate of this embodiment is <λ / 300, the variable phase retarder can be a liquid crystal box, and the adjustable phase angle range of the variable phase retarder is at least >360°. Preferably, in order to facilitate pre-alignment during the bonding process, the 1 / 4 wave plate can be rectangular and cut at 45 degrees to the two sides adjacent to the rectangle in the fast axis direction; correspondingly, the electrically controlled variable phase retarder also adopts a rectangular shape, and the fast axis direction extends along the direction of one side of the rectangle. Thereby, based on Figure 1 The structure shown in FIG. 1 , and the method for attaching the polarization direction rotator include the following steps:

[0033] 1. Attach the 1 / 4 wave plate + ARGlass and place them in the fixture.

[0034] 2. Rotate the fixture and adjust the 0° fast axis or slow axis of the 1 / 4 wave plate to be parallel or perpendicular to the transmission direction of LP2. P1 will display linear polarized light. When the ellipticity of P1 is the lowest, record the angle of the 1 / 4 wave plate at this time, and then rotate the fixture holding the 1 / 4 wave plate 45° or -45°.

[0035] Among them, ellipticity = (maximum outer diameter - minimum outer diameter) / nominal outer diameter * 100% = (major axis - minor axis) / major axis * 100%.

[0036] Preferably, the present invention uses an electrically controlled rotating device or fixture to ensure the accuracy of rotation, and the minimum angular rotation interval can be 0.1 degrees.

[0037] 3. Pour a drop of UV curing agent (the refractive index is consistent with that of the 1 / 4 wave plate and ARGlass to reduce reflectivity and stray light) on the upper surface of the 1 / 4 wave plate (the side not attached to ARGlass), place the electrically controlled liquid crystal cell on the upper surface of the 1 / 4 wave plate, first use the trimming to pre-align, then finely rotate the electrically controlled liquid crystal cell and observe P1. At this time, the ellipticity changes from elliptically polarized light to linearly polarized light until the ellipticity of the linearly polarized light drops to the minimum (<0.8°); at this time, apply voltage to the 1 / 4 wave plate for testing, adjust the output voltage from 0 to 10V, and make the ellipticity of the polarization meter under full voltage <1.8° ((tan1.8°) -2 ≈1000).

[0038] The conversion formula between ellipticity and extinction ratio is: ER = (tan(Ellipticity)) -2 , where Ellipticity is the ellipticity and ER is the extinction ratio.

[0039] 4. Let it sit for a few minutes. You'll see that the angular deviation in A1 is minimal, indicating optimal parallelism. (Parallelism is crucial in light transmission or coupling; polarizers often require rotation. Poor parallelism can cause the overall light spot to shift, affecting transmission or coupling efficiency.) Then, cure with a UV curing lamp. The purpose of this rest period is to improve the transmitted wavefront. A better transmitted wavefront also improves parallelism, thus resolving the current technical challenge of lacking a device to directly measure the transmitted wavefront.

[0040] In the system of this embodiment, in order to facilitate the above-mentioned operations, a bonding table can be set up, the upper part of which is used to place the 1 / 4 wave plate, and the lower part is connected to the positive and negative pressure-applying ends connected to the voltage generator. The positive and negative pressure-applying ends are used to be detachably connected to the positive and negative pressure-receiving ends of the electrically controlled variable phase retarder and are provided with a mechanism for rotating the electrically controlled variable phase retarder.

[0041] The goniometer in this embodiment is used to measure the angle between the reflected light beam from the electrically controlled variable phase retarder and the reflected light beam from the quarter-wave plate, as captured on a reticle. This angle is then used to determine the parallelism of the electrically controlled variable phase retarder and the quarter-wave plate. Generally, if the two reflected light beams overlap, the two components are strictly parallel. If the two light beams are separated by a certain distance and form an angle, the two components are not parallel, indicating a wedge angle.

[0042] The polarization meter of this embodiment is used to measure the polarization azimuth of the linearly polarized light of the collected light beam after it is placed in the electrically controlled variable phase retarder and before the 1 / 4 wave plate is placed, and the change in ellipticity that occurs with the rotation angle of the 1 / 4 wave plate and the static time after the 1 / 4 wave plate is placed.

[0043] Example 2

[0044] This embodiment discloses a method for laminating a polarization direction rotator in an online laminating system. Figure 2 Shown, including:

[0045] Step S1: deploying an optical path.

[0046] The specific optical path of this step can be referred to Figure 1The corresponding system structure includes at least: a laser generator, a first polarizer, a bonding stage, a polarimeter, and a goniometer; wherein the first polarizer is located between the laser generator and the bonding stage, and the bonding stage is located between the first polarizer and the polarimeter. The upper portion of the bonding stage is used to place the quarter-wave plate, and the lower portion is connected to positive and negative pressure-applying terminals connected to a voltage generator. The positive and negative pressure-applying terminals are used to detachably connect to the positive and negative pressure-receiving terminals of the electrically controlled variable phase retarder and are provided with a mechanism for rotating the electrically controlled variable phase retarder. The deployment position of the laser generator ensures that the emitted laser light first passes through the electrically controlled variable phase retarder and then through the quarter-wave plate. The goniometer is used to measure the angle between the reflected light beam from the electrically controlled variable phase retarder and the reflected light beam from the quarter-wave plate, collected on the graticule, to determine the parallelism of the electrically controlled variable phase retarder and the quarter-wave plate based on the angle. The polarimeter is used to measure the polarization azimuth of the linearly polarized light of the collected light beam after it is placed in the electrically controlled variable phase retarder and before the quarter wave plate is placed, as well as the change in ellipticity after the quarter wave plate is placed, which occurs with the rotation angle of the quarter wave plate and the static time.

[0047] Step S2: Place the electrically controlled variable phase retarder to be bonded on the bonding table. When the electrically controlled variable phase retarder is rotated until the polarization meter observes linear polarized light with the lowest ellipticity, determine that the current fast axis direction of the electrically controlled variable phase retarder is parallel to the polarization direction of the first polarizer and the slow axis is perpendicular to the polarization direction of the first polarizer. Then, rotate the electrically controlled variable phase retarder 45 degrees around the optical axis and fix it.

[0048] Step S3: After dripping UV-curing glue onto the upper surface of the electrically controlled variable phase retarder, a quarter-wave plate to be bonded is placed onto the upper surface of the electrically controlled variable phase retarder. After pre-alignment using trimming, the quarter-wave plate is rotated until the polarimeter observes that the ellipticity changes from elliptically polarized light to linearly polarized light, or until the ellipticity drops to a minimum. The electrically controlled variable phase retarder is then sequentially pressurized to various test voltages and rotated within a range of plus or minus 0.5 degrees, so that the ellipticity of the outgoing light beam at each test voltage as observed by the polarimeter is less than 1.8 degrees.

[0049] Step S4: Observe with a goniometer that the angle between the reflected light beam from the electrically controlled variable phase retarder and the reflected light beam from the quarter wave plate is the smallest during the static state, and then turn on the UV curing lamp to perform curing.

[0050] In summary, the online lamination system and method for a polarization direction rotator disclosed in the above embodiments of the present invention respectively have at least the following beneficial effects:

[0051] 1. The structure and optical path deployment are simple and convenient.

[0052] 2. With the combined action of the goniometer and polarimeter, on the one hand, the key angles of each step can be precisely determined based on the changes in ellipticity to meet the extinction ratio requirements. On the other hand, the changes in the goniometer can be used to calculate the parallelism between the electrically controlled variable phase retarder and the 1 / 4 wave plate. Parallelism is very important in light transmission or optical coupling. Polarization devices often need to be rotated. Poor parallelism will cause the overall light spot to shift, affecting the transmission or coupling efficiency. Therefore, the static time can be accurately determined to ensure that the parallelism between the two bonded devices meets the requirements and improve the bonding efficiency.

[0053] 3. During the bonding process, after the electrically controlled variable phase retarder was positioned at an ideal 45° angle with the fast axes between the quarter-wave plates at the lowest point of ellipticity, it was then rotated within a range of ±0.5° to ensure that the ellipticity of the outgoing beam observed by the polarimeter was less than 1.8° at each test voltage. This ensured that the extinction ratio was greater than 1000:1 at each test voltage. This balancing strategy ensured ideal application performance at all test voltages and in the unstressed state.

[0054] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An online lamination system for a polarization direction rotator, characterized in that: The device comprises at least: a laser generator, a first polarizer, a bonding platform, a polarimeter and a goniometer; wherein the first polarizer is located between the laser generator and the bonding platform, and the bonding platform is located between the first polarizer and the polarimeter; The upper portion of the lamination platform is used to place a quarter-wave plate, and the lower portion is connected to positive and negative pressure-applying terminals connected to a voltage generator. The positive and negative pressure-applying terminals are used to detachably connect to the positive and negative pressure-receiving terminals of the electrically controlled variable phase retarder and are provided with a mechanism for rotating the electrically controlled variable phase retarder. The laser generator is deployed in a position such that the emitted laser first passes through the electrically controlled variable phase retarder and then passes through the quarter-wave plate. The goniometer is used to measure the angle between the reflected light beam from the electrically controlled variable phase retarder and the reflected light beam from the quarter wave plate collected on the reticle, so as to determine the parallelism between the electrically controlled variable phase retarder and the quarter wave plate based on the angle; The polarimeter is used to measure the polarization azimuth of the linearly polarized light of the collected light beam after it is placed in the electrically controlled variable phase retarder and before the quarter wave plate is placed, and the change in ellipticity after the quarter wave plate is placed as the quarter wave plate rotates at an angle and remains stationary for a certain period of time.

2. The online lamination system for a polarization direction rotator according to claim 1, characterized in that: A second polarizer is further provided between the first polarizer and the laminating stage, and the polarization direction of the second polarizer is parallel to the polarization direction of the first polarizer.

3. The online laminating system for a polarization direction rotator according to claim 1 or 2, characterized in that: A beam splitter is provided between the bonding stage and the polarization measuring instrument, and the beam splitter is located between the bonding stage and the goniometer; A notch filter corresponding to the laser wavelength is provided between the beam splitter and the goniometer, and the reflected light source collected by the goniometer graticule is a self-provided light source.

4. The online lamination system for a polarization direction rotator according to claim 1 or 2, characterized in that: A component for filtering and collimating processing is provided between the laser and the first polarizer.

5. The online lamination system for a polarization direction rotator according to claim 4, characterized in that: The components used for filtering and collimating processing include: a first lens and a second lens located in front and back positions in the optical axis direction, and an aperture located between the first lens and the second lens.

6. The online lamination system for a polarization direction rotator according to claim 1 or 2, characterized in that: The quarter wave plate is rectangular and is cut with the fast axis at an angle of 45 degrees to the two adjacent sides of the rectangle. Correspondingly, the electrically controlled variable phase retarder is rectangular, and the fast axis direction extends along a side of the rectangle.

7. The online lamination system for a polarization direction rotator according to claim 1 or 2, characterized in that: An antireflection film is provided at the bottom of the electrically controlled variable phase retarder.

8. A bonding method for an online bonding system of a polarization direction rotator according to any one of claims 1 to 7, characterized in that: include: Step S1, deploying an optical path; Step S2: placing the electrically controlled variable phase retarder to be bonded into the bonding platform, rotating the electrically controlled variable phase retarder until the polarization meter observes linear polarized light and the ellipticity is at its lowest, determining that the current fast axis direction of the electrically controlled variable phase retarder is parallel to the polarization direction of the first polarizer and the slow axis is perpendicular to the polarization direction of the first polarizer; then rotating the electrically controlled variable phase retarder 45 degrees around the optical axis and fixing it; Step S3: After dripping UV-curing adhesive onto the upper surface of the electrically controlled variable phase retarder, a quarter-wave plate to be bonded is placed onto the upper surface of the electrically controlled variable phase retarder. After pre-alignment using trimming, the quarter-wave plate is rotated until the polarimeter observes a change in elliptical polarization to linear polarization, or until the ellipticity is minimized. The electrically controlled variable phase retarder is then sequentially voltaged to various test voltages and rotated within a range of plus or minus 0.5 degrees, such that the ellipticity of the outgoing light beam at each test voltage as observed by the polarimeter is less than 1.8°. Step S4: Observe with a goniometer that the angle between the reflected light beam from the electrically controlled variable phase retarder and the reflected light beam from the quarter wave plate is the smallest during the static state, and then turn on the UV curing lamp to perform curing.

Images