Thermal lens effect testing system and method

Abstract

The invention relates to the technical field of optics, and discloses a thermal lens effect testing system and method so as to improve compatibility and ensure measurement precision. The system comprises a first branch, a second branch and a third PBS, wherein the first branch and the second branch are input into a second PBS, the third PBS is positioned between a second output beam of the second PBS and a third beam expander, and a first beam quality analyzer for assisting in adjusting light spots of the two input branches is arranged on a first output beam of the second PBS; an emergent light beam of the third beam expanding lens enters a second light beam quality analyzer arranged on a second electric displacement platform through the focusing lens; a first electric displacement platform for placing a sample to be tested is arranged between the second PBS and the third PBS; and the second electric displacement platform is used for repositioning the focal point of the light beam under the assistance of the second light beam quality analyzer after the thermal lens effect of the sample to be detected on the first electric displacement platform is stable, so that the distance between the repositioned focal point and the initial focal point is determined as the focal shift amount.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a thermal lens effect testing system and method. Background Art

[0002] During the laser processing process, the laser energy is high, and a photothermal effect commonly found in lens systems will occur - the thermal lens effect. The essence of the thermal lens effect is that in the process of converting light energy into thermal energy, the thermal energy in the irradiated material is unevenly distributed, resulting in different densities in different parts of the crystal. When the light passes through the dividing line of these different densities, it will refract to different degrees, causing the refractive index to change. At this time, the irradiated material can be approximately regarded as a lens. The generation of the thermal lens effect will cause the beam quality of the laser beam to deteriorate and the focus to drift, thereby affecting the quality of laser processing. In the laser processing system, in order to select excellent optical components, it is necessary to test their thermal lens effect. The thermal lens effect is a characteristic of the material itself. The thermal lens effect of optical systems made of different materials is different. In order to select suitable optical materials, it is necessary to measure the thermal lens effect produced by different optical materials.

[0003] There are two main testing methods available in the industry. The first method is to tilt the processing surface, mark on the inclined processing surface, and calculate the focal shift by observing the offset of the mark line at the initial focus and the mark line at the focus after working for a period of time. The second method is to use a high-power beam quality analyzer for online observation, and reflect the size of the thermal lens effect by the change in the spot size at the focal position when the light is first emitted and the change in the spot size after working for a period of time.

[0004] The above two methods have the following problems:

[0005] 1. There are many optical modules in the laser processing system, and it is difficult to determine which module has a larger thermal lens effect.

[0006] 2. Method 1 cannot monitor the changes of the light spot in real time, it is troublesome to find the focus and it cannot feedback the changes of the thermal lens effect over time.

[0007] 3. Method 2 is prone to damage the beam quality analyzer at relatively high power.

[0008] Therefore, it is necessary to develop a better thermal lens effect testing system and method to test the thermal lens effect of an optical system or optical components. Summary of the invention

[0009] The present invention aims to disclose a thermal lens effect testing system and method to improve the compatibility with the tested samples and ensure the measurement accuracy.

[0010] To achieve the above-mentioned purpose, the thermal lens effect testing system disclosed in the present invention comprises:

[0011] The first branch inputting the second PBS is provided with a first laser, a first 1 / 2 wave plate, a first PBS and a first beam expander in sequence; the power of the light beam emitted by the first laser is higher than the power threshold of the thermal lens effect generated by the sample under test; the sample under test is an afocal optical device with parallel light input and parallel light output;

[0012] The second branch inputting the second PBS is provided with a second laser, a second 1 / 2 wave plate and a second beam expander in sequence; the power of the light beam emitted by the second laser is lower than the power threshold of the thermal lens effect generated by the sample under test;

[0013] The second PBS is used to synthesize the partial light beam separated from the first branch and the partial light beam separated from the second branch into a first output light beam directed to the first beam quality analyzer and a second output light beam directed to the third PBS;

[0014] A third PBS, used for reflecting the S light in the first output light beam of the second PBS to a third beam expander;

[0015] The outgoing light beam of the third beam expander enters the second beam quality analyzer disposed on the second electric displacement platform through the focusing lens;

[0016] A first electric displacement platform for placing a sample to be tested is disposed between the second PBS and the third PBS;

[0017] The first beam expander and the second beam expander are used for coordinated adjustment so that the two light spots presented in the first mass analyzer overlap;

[0018] A third beam expander, used for adjusting to determine the focal position of the light beam after passing through the focusing lens;

[0019] The second electric displacement platform is used to reposition the focus of the light beam with the assistance of a second beam quality analyzer after the thermal lens effect of the sample to be measured on the first electric displacement platform is stabilized, so that the distance between the repositioned focus and the initial focus is determined as the focal shift.

[0020] Preferably, a first light-collecting tube is disposed in the emission direction of the reflected light beam of the first PBS. Similarly, a second light-collecting tube may be disposed in the transmission direction of the reflected light beam of the third PBS.

[0021] To achieve the above object, the present invention also discloses a thermal lens effect testing method, comprising the following steps:

[0022] Step S1, deploying a system as described in any one of claims 1 to 3;

[0023] Step S2, turning on the first laser and the second laser, and debugging the system so that the two light spots from the first branch and the second branch on the first beam quality analyzer overlap and have equal sizes;

[0024] Step S4, when the sample to be tested is not deployed on the first electric displacement platform, the first laser is turned on, and after the thermal lens effect is stabilized, the third beam expander is adjusted to make the focus of the light beam located at the focal plane of the focusing lens to obtain the position of the initial focus; the sample to be tested is an afocal optical device with parallel light input and parallel light output;

[0025] Step S5, moving the sample to be tested onto the first electric displacement platform, observing and recording the change of the light spot of the second beam quality analyzer to determine whether the thermal lens effect is stable;

[0026] Step S6: after the thermal lens effect is stabilized, move the second electric displacement platform to find the repositioning focus after the thermal lens effect is stabilized, and use the moving distance of the second electric displacement platform between the repositioning focus and the initial focus as the focal shift caused by the thermal lens effect of the sample to be tested.

[0027] Preferably, between step S2 and step S4, the following steps are further included:

[0028] Step S3, turn off the first laser, add the sample to be tested, and determine whether the focus of the light beam can be located in the focal plane of the focusing lens by adjusting the third beam expander and the second electric displacement platform. If it is determined that the sample to be tested is an afocal optical device, go to step S4; otherwise, determine that the sample to be tested is unqualified and terminate the execution of subsequent steps.

[0029] The present invention has the following beneficial effects:

[0030] 1. The two spot sizes observed in the first beam quality analyzer can be regarded as the spot sizes incident on the sample to be tested, and the high-power optical path and the low-power optical path overlap after the second PBS and before the third PBS. The essence is to use low-power laser to effectively monitor the thermal lens effect generated by high-power laser; in this way, it can be monitored whether the spot size of each step in the test process is consistent, effectively avoiding the adverse effects of inconsistent spot size on the measurement results.

[0031] 2. During the measurement of the focal shift of the sample to be tested, the thermal lens effect of the second PBS and the third PBS in the test system is compensated, further ensuring the accuracy of the final measurement result.

[0032] 3. The test system of the present invention is suitable for various afocal optical devices and has strong compatibility. Moreover, it can detect whether the sample to be tested is an afocal optical device with parallel light input and parallel light output based on the low-power optical path, thereby making the logic between each step more rigorous and improving the test reliability.

[0033] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0035] Figure 1 It is a schematic diagram of the optical path of the thermal lens effect testing system disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0037] Example 1

[0038] This embodiment discloses a thermal lens effect testing system. Figure 1 As shown, including:

[0039] High-power optical path: The laser generated by the high-power laser will be adjusted by the 1 / 2 wave plate 1 and PBS1, so that most of the P light and a small part of the S light will pass through and enter the beam expander 1, and most of the S light and a small part of the P light will be reflected and enter the light collecting barrel 1; the beam expander 1 can adjust the spot size of the high-power laser beam. After the light beam emitted by the beam expander 1 enters PBS2, the S light is reflected and enters the beam quality analyzer 1, and the P light enters the sample to be tested; the light emitted by the sample to be tested passes through PBS3 and enters the light collecting barrel 2.

[0040] Low-power optical path: The laser generated by the low-power laser passes through the beam expander 2, 1 / 2 wave plate 2 and PBS2, the P light is transmitted into the beam quality analyzer 1, and the S light is reflected into the sample to be tested. The beam expander 2 can adjust the diameter of the low-power beam. By observing the light spot of the beam quality analyzer 1, the low-power spot and the high-power spot size can be made consistent. The 1 / 2 wave plate can adjust the energy ratio of the P light and the S light; the light beam emitted by the sample to be tested is reflected by PBS3 into the beam expander 3 and the focusing lens, and then focused on the beam quality analyzer 2.

[0041] In this embodiment, the standard for dividing the laser into high and low power is to determine whether a thermal lens effect is generated on the sample to be measured. If the emitted light beam does not generate a thermal lens effect on the sample to be measured, it is low power, otherwise, it is high power.

[0042] Preferably, basically Figure 1 The thermal lens effect test steps corresponding to the afocal optical system shown can be specifically as follows:

[0043] 1. System deployment and debugging, so that the low-power optical path and the high-power optical path coincide with each other, and the light spots of the two optical paths on the beam quality analyzer 1 coincide with each other and are equal in size.

[0044] 2. Turn off the high-power laser, turn on the low-power laser, add the sample to be tested, and adjust the beam expander 3 and the electric displacement platform 2 so that the focus of the light beam is located on the focal plane of the focusing lens. In this embodiment, the sample to be tested is an afocal optical device with parallel light input and parallel light output. If the beam expander 3 and the electric displacement platform 2 cannot be adjusted to make the focus of the light beam located on the focal plane of the focusing lens, it can be determined that the sample to be tested is not an afocal optical device and the execution of subsequent steps is terminated.

[0045] 3. Move the electric displacement platform 1, remove the sample to be tested, turn on the high-power laser, and adjust the beam expander 3 after the thermal lens effect is stable, so that the beam focus is located at the focal plane of the focusing lens. This step is used to compensate for the thermal lens effect of the system and obtain the position of the initial focus. Among them, the standard for judging whether the thermal lens effect is stable can be determined based on the spot size in the second beam quality analyzer. If the observed spot size and / or focal position no longer changes, it is considered stable.

[0046] 4. Move the electric displacement platform 1, move the sample to be tested, observe and record the spot changes of the beam quality analyzer 2. This step can record the changes of the thermal lens effect over time. Similarly, in this process, the thermal lens effect can be judged whether it is stable by observing and recording the spot changes of the second beam quality analyzer.

[0047] 5. After the thermal lens effect is stabilized, move the electric displacement platform 2 to find the focus after the thermal lens effect is stabilized. The distance moved by the electric displacement platform 2 is the focal shift caused by the thermal lens effect of the sample to be tested.

[0048] In summary, those skilled in the art can obviously conclude that the core of the thermal lens effect testing system disclosed in this embodiment mainly includes:

[0049] Enter the second PBS (equivalent to Figure 1 The first branch of PBS2 in the following will not be described in detail), is provided with a first laser (equivalent to Figure 1 The high-power laser in the following will not be described in detail), the first 1 / 2 wave plate (equivalent to Figure 1 The 1 / 2 wave plate 1 in the figure will not be described in detail later), the first PBS (equivalent to Figure 1 PBS1 in the following description) and the first beam expander (equivalent to Figure 1 The power of the light beam emitted by the first laser is higher than the power threshold of the thermal lens effect produced by the measured sample; the measured sample is an afocal optical device with parallel light input and parallel light output.

[0050] The second branch of the second PBS is provided with a second laser (equivalent to Figure 1 The low-power laser in the following will not be described in detail), the second 1 / 2 wave plate (equivalent to Figure 1 The 1 / 2 wave plate 2 in the figure will not be described in detail later) and the second beam expander (equivalent to Figure 1 The power of the light beam emitted by the second laser is lower than the power threshold of the thermal lens effect generated by the sample under test.

[0051] The second PBS is used to synthesize the partial light beam separated from the first branch and the partial light beam separated from the second branch and send them to the first beam quality analyzer (equivalent to Figure 1 The first output beam of the beam quality analyzer 1 in the figure (not described in detail later) and the first output beam directed to the third PBS (equivalent to Figure 1 The second output light beam of PBS3 in (which will not be described in detail later).

[0052] The third PBS is used to reflect the S light in the first output light beam of the second PBS to the third beam expander (equivalent to Figure 1 The beam expander 3 in the figure will not be described in detail later).

[0053] The output beam of the third beam expander enters the second electric displacement platform (equivalent to Figure 1 The second beam quality analyzer (equivalent to Figure 1 The beam quality analyzer 2 in the figure will not be described in detail later).

[0054] A first electric displacement platform (equivalent to Figure 1 The electric displacement platform 1 in the figure will not be described in detail later).

[0055] The first beam expander and the second beam expander are used for coordinated adjustment so that the two light spots presented in the first mass analyzer overlap.

[0056] The third beam expander is used for adjusting to determine the focal position of the light beam after passing through the focusing lens.

[0057] The second electric displacement platform is used to reposition the focus of the light beam with the assistance of a second beam quality analyzer after the thermal lens effect of the sample to be measured on the first electric displacement platform is stabilized, so that the distance between the repositioned focus and the initial focus is determined as the focal shift.

[0058] Preferably, a first light collecting tube (equivalent to Figure 1Similarly, a second light collecting tube (equivalent to Figure 1 The light collecting tube 2 in the figure will not be described in detail later).

[0059] Example 2

[0060] Corresponding to the above embodiment, this embodiment discloses a thermal lens effect testing method, comprising the following steps:

[0061] Step S1: deploy the system described in the above embodiment.

[0062] Step S2, turning on the first laser and the second laser, and debugging the system so that the two light spots on the first beam quality analyzer originating from the first branch and the second branch overlap and have equal sizes.

[0063] Step S4, when the sample to be tested is not deployed on the first electric displacement platform, turn on the first laser, and adjust the third beam expander after the thermal lens effect is stable, so that the focus of the light beam is located in the focal plane of the focusing mirror to obtain the position of the initial focus; the sample to be tested is an afocal optical device with parallel light input and parallel light output.

[0064] Step S5, moving the sample to be tested onto the first electric displacement platform, observing and recording the change of the light spot of the second beam quality analyzer to determine whether the thermal lens effect is stable.

[0065] Step S6: after the thermal lens effect is stabilized, move the second electric displacement platform to find the repositioning focus after the thermal lens effect is stabilized, and use the moving distance of the second electric displacement platform between the repositioning focus and the initial focus as the focal shift caused by the thermal lens effect of the sample to be tested.

[0066] Preferably, between step S2 and step S4, the following steps are further included:

[0067] Step S3, turn off the first laser, add the sample to be tested, and determine whether the focus of the light beam can be located in the focal plane of the focusing lens by adjusting the third beam expander and the second electric displacement platform. If it is determined that the sample to be tested is an afocal optical device, go to step S4; otherwise, determine that the sample to be tested is unqualified and terminate the execution of subsequent steps.

[0068] In summary, the test system and method disclosed in the embodiments of the present invention respectively have at least the following beneficial effects:

[0069] 1. The two spot sizes observed in the first beam quality analyzer can be regarded as the spot sizes incident on the sample to be tested, and the high-power optical path and the low-power optical path overlap after the second PBS and before the third PBS. The essence is to use low-power laser to effectively monitor the thermal lens effect generated by high-power laser; in this way, it can be monitored whether the spot size of each step in the test process is consistent, effectively avoiding the adverse effects of inconsistent spot size on the measurement results.

[0070] 2. During the measurement of the focal shift of the sample to be tested, the thermal lens effect of the second PBS and the third PBS in the test system is compensated, further ensuring the accuracy of the final measurement result.

[0071] 3. The test system of the present invention is suitable for various afocal optical devices and has strong compatibility. Moreover, it can detect whether the sample to be tested is an afocal optical device with parallel light input and parallel light output based on the low-power optical path, thereby making the logic between each step more rigorous and improving the test reliability.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A thermal lens effect testing system, characterized in that: include: The first branch inputting the second PBS is provided with a first laser, a first 1 / 2 wave plate, a first PBS and a first beam expander in sequence; the power of the light beam emitted by the first laser is higher than the power threshold of the thermal lens effect generated by the sample under test; the sample under test is an afocal optical device with parallel light input and parallel light output; The second branch inputting the second PBS is provided with a second laser, a second 1 / 2 wave plate and a second beam expander in sequence; the power of the light beam emitted by the second laser is lower than the power threshold of the thermal lens effect generated by the sample under test; The second PBS is used to synthesize the partial light beam separated from the first branch and the partial light beam separated from the second branch into a first output light beam directed to the first beam quality analyzer and a second output light beam directed to the third PBS; A third PBS, used for reflecting the S light in the first output light beam of the second PBS to a third beam expander; The outgoing light beam of the third beam expander enters the second beam quality analyzer disposed on the second electric displacement platform through the focusing lens; A first electric displacement platform for placing a sample to be tested is disposed between the second PBS and the third PBS; The first beam expander and the second beam expander are used for coordinated adjustment so that the two light spots presented in the first mass analyzer overlap; A third beam expander, used for adjusting to determine the focal position of the light beam after passing through the focusing lens; The second electric displacement platform is used to reposition the focus of the light beam with the assistance of a second beam quality analyzer after the thermal lens effect of the sample to be measured on the first electric displacement platform is stabilized, so that the distance between the repositioned focus and the initial focus is determined as the focal shift.

2. The system according to claim 1, characterized in that A first light-collecting tube is disposed in the emission direction of the reflected light beam of the first PBS.

3. The system according to claim 1 or 2, characterized in that: A second light-collecting tube is disposed in the transmission direction of the reflected light beam of the third PBS.

4. A thermal lens effect testing method, characterized in that: The following steps are involved: Step S1, deploying a system as described in any one of claims 1 to 3; Step S2, turning on the first laser and the second laser, and debugging the system so that the two light spots from the first branch and the second branch on the first beam quality analyzer overlap and have equal sizes; Step S4, when the sample to be tested is not deployed on the first electric displacement platform, the first laser is turned on, and after the thermal lens effect is stabilized, the third beam expander is adjusted to make the focus of the light beam located at the focal plane of the focusing lens to obtain the position of the initial focus; the sample to be tested is an afocal optical device with parallel light input and parallel light output; Step S5, moving the sample to be tested onto the first electric displacement platform, observing and recording the change of the light spot of the second beam quality analyzer to determine whether the thermal lens effect is stable; Step S6: after the thermal lens effect is stabilized, move the second electric displacement platform to find the repositioning focus after the thermal lens effect is stabilized, and use the moving distance of the second electric displacement platform between the repositioning focus and the initial focus as the focal shift caused by the thermal lens effect of the sample to be tested.

5. The thermal lens effect testing method according to claim 4, characterized in that: Also included between step S2 and step S4: Step S3, turn off the first laser, add the sample to be tested, and determine whether the focus of the light beam can be located in the focal plane of the focusing lens by adjusting the third beam expander and the second electric displacement platform. If it is determined that the sample to be tested is an afocal optical device, go to step S4; otherwise, determine that the sample to be tested is unqualified and terminate the execution of subsequent steps.

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