Thermal lens effect testing system and method

Abstract

The present invention relates to the field of optical technology, and discloses a thermal lens effect testing system and method to improve compatibility and ensure measurement accuracy. The system includes: first and second branches inputting a second PBS; a third PBS located between the second output beam of the second PBS and a third beam expander; a first beam quality analyzer is provided on the first output beam of the second PBS to assist in calibrating the light spots of the two input branches; wherein the output beam of the third beam expander enters the second beam quality analyzer disposed on a second electric displacement platform via a 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 second electric displacement platform is used to reposition the focus of the beam with the assistance of the second beam quality analyzer after the thermal lens effect of the sample to be tested 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.

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 laser processing, the laser energy is high, and a photothermal effect commonly found in lens systems occurs—the thermal lens effect. The essence of the thermal lens effect is that when light energy is converted into heat energy, the uneven distribution of heat energy in the irradiated material causes different densities in different parts of the crystal. When light passes through the dividing lines of these different densities, it refracts to varying degrees, causing a change in the refractive index. At this point, the irradiated material can be roughly regarded as a lens. The thermal lens effect can cause the laser beam quality to deteriorate and the focus to drift, thereby affecting the quality of laser processing. In laser processing systems, in order to select high-quality optical components, it is necessary to test their thermal lens effect. The thermal lens effect is a characteristic of the material itself. Optical systems made of different materials have different thermal lens effects. In order to select suitable optical materials, it is necessary to measure the thermal lens effects produced by different optical materials.

[0003] There are two main testing methods currently available in the industry. The first method is to tilt the processing surface, mark it on the tilted 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 a period of operation. The second method is to use a high-power beam quality analyzer for online observation, and reflect the magnitude 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 a period of operation.

[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 in the light spot in real time, it is difficult to find the focus and it cannot feedback the changes in 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 component. Summary of the Invention

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

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

[0011] The first branch of the input second PBS is provided with a first laser, a first half-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 of the second PBS is provided with a second laser, a second half-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] a second PBS, configured 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, configured to reflect the S light in the first output light beam of the second PBS to a third beam expander;

[0015] The outgoing beam of the third beam expander enters the second beam quality analyzer deployed 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] The third beam expander is used for adjusting and determining 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 the 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 further discloses a thermal lens effect testing method, comprising the following steps:

[0022] Step S1, deploying the system according to any one of claims 1 to 3;

[0023] Step S2: Turn on the first laser and the second laser, and debug 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 placed 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 on the focal plane of the focusing lens, thereby obtaining 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 at 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 size 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. In essence, the low-power laser is used to effectively monitor the thermal lens effect generated by the high-power laser. In this way, the consistency of the spot size of each step in the test process can be monitored, effectively avoiding the adverse effects of inconsistent spot sizes 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 results.

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

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

[0034] 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:

[0035] Figure 1 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. However, 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 is 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 pass through and enter the beam expander 1, and most of the S light and a small part of the P light are 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 passes through and enters the beam quality analyzer 1, and the S light is reflected and enters the sample to be measured. 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 measured is reflected by the PBS3 and enters the beam expander 3 and the focusing lens, and then is focused on the beam quality analyzer 2.

[0041] In this embodiment, the criterion 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, the power is low; otherwise, the power is high.

[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, and the light spots of the two optical paths on the beam quality analyzer 1 coincide 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 motorized displacement stage 2 so that the beam focus 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 motorized displacement stage 2 cannot be adjusted to place the beam focus 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 subsequent steps are terminated.

[0045] 3. Move the motorized displacement stage 1, remove the sample to be measured, and turn on the high-power laser. Once the thermal lensing effect stabilizes, adjust the beam expander 3 so that the beam focus is located on the focal plane of the focusing lens. This step compensates for the system's thermal lensing effect and determines the initial focal position. The criterion for determining whether the thermal lensing effect is stable can be based on the spot size observed by the second beam quality analyzer. If the observed spot size and / or focal position no longer change, the beam is considered stable.

[0046] 4. Move motorized displacement stage 1 to insert the sample to be measured. Observe and record the changes in the beam spot of beam profiler 2. This step can record the changes in the thermal lensing effect over time. Similarly, during this process, the stability of the thermal lensing effect can be determined by observing and recording the changes in the beam spot of the second beam profiler.

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

[0048] In summary, it is obvious to those skilled in the art 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 following will not be described in detail), the first PBS (equivalent to Figure 1 PBS1 in the following will not be described in detail) 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 generated 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 beam separated from the first branch and the partial 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 the figure (which will not be described in detail later) is a second output light beam.

[0052] The third PBS is used to reflect the S light in the first output 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 the 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: Turn on the first laser and the second laser, and debug 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 stabilized so that the focus of the light beam is located on 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: Place the sample to be tested on the first electric displacement platform, and observe and record the changes in 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 at 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 systems and methods 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 size 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. In essence, the low-power laser is used to effectively monitor the thermal lens effect generated by the high-power laser. In this way, the consistency of the spot size of each step in the test process can be monitored, effectively avoiding the adverse effects of inconsistent spot sizes 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 results.

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

[0072] 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. A thermal lens effect testing system, characterized in that: include: The first branch of the input second PBS is provided with a first laser, a first half-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 of the second PBS is provided with a second laser, a second half-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; a second PBS, configured to combine the S light in the partial light beam separated from the first branch with the P light separated from the second branch to emit a first output light beam to the first beam quality analyzer, and to combine the P light in the partial light beam separated from the first branch with the S light separated from the second branch to emit a second output light beam to the third PBS; a third PBS, configured to reflect the S light in the second output beam of the second PBS to a third beam expander; The outgoing beam of the third beam expander enters the second beam quality analyzer deployed 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; The third beam expander is used for adjusting and determining 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 to obtain a relocated focus 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, and the distance between the relocated focus and the initial focus is determined as the focal shift; wherein, when the sample to be measured 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 so that the focus of the light beam is located in the focal plane of the focusing mirror to obtain the initial focus.

2. The system according to claim 1, wherein: 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 third PBS.

4. A thermal lens effect testing method, characterized in that: The following steps are involved: Step S1, deploying the system according to any one of claims 1 to 3; Step S2: Turn on the first laser and the second laser, and debug 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 placed 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 on the focal plane of the focusing lens, thereby obtaining 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 at 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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