Real-time in-situ monitoring imaging method for pulse laser processing

Abstract

The invention relates to the technical field of laser micro-nano processing, and discloses a real-time in-situ monitoring imaging method for pulse laser processing, which comprises the following steps of: a, monitoring femtosecond laser processing in real time by using a high-speed holographic single-exposure compression imaging system and a high-speed video single-exposure compression imaging system; b, the laser is subjected to beam splitting through a beam splitter prism, and the laser is guided to the surface of the sample for three-dimensional shape micro-nano machining; and c, quickly coding the image information of the surface of the sample by using a digital micromirror device (DMD). According to the real-time in-situ monitoring imaging method for pulse laser processing, the high-speed two-dimensional image and the high-speed three-dimensional shape information of the processed material can be obtained at the same time, ultra-fast imaging is achieved in a low-cost mode, real-time imaging can be conducted on femtosecond laser processing, the sample is monitored in situ, and the real-time monitoring and imaging effect is achieved. The imaging system is independent and can reconstruct a low-frame-rate image into a high-frame-rate dynamic video, and the storage space is saved.

Description

Technical Field

[0001] The invention relates to the technical field of laser micro-nano processing, and in particular to a real-time in-situ monitoring imaging method for pulse laser processing. Background Art

[0002] In the industrial field, laser micro-nano processing has been widely used in the manufacture of electronic components, automobiles and aerospace. For example, in the electronics industry, laser micro-nano processing is used to manufacture printed circuit boards, packaging components and manufacture electronic devices. In the automotive industry, laser micro-nano processing is used to process various metal and non-metal materials; in the aerospace industry, laser micro-nano processing is used to produce lightweight and high-precision aerospace parts; in the medical field, laser micro-nano processing is widely used in minimally invasive surgery, such as cancer treatment, ophthalmic surgery and dental surgery. In scientific research, laser micro-nano processing is used to study the properties of materials and the interaction between lasers and matter, making significant contributions to the development of materials science and laser physics.

[0003] As the demand for high-precision laser micro-nano processing in various fields continues to increase, it has developed more and more rapidly. The high-precision monitoring method using imaging in laser micro-nano processing has also received widespread attention. In order to achieve high-precision processing, it is particularly important to accurately control the position and shape changes of the laser beam on the surface of the processed material. Since traditional laser micro-nano processing methods are often affected by external environmental factors and their own precision system factors, it is difficult to achieve the best processing results. Based on this, the industry urgently needs an auxiliary means of monitoring the laser processing process to achieve high-quality laser processing results.

[0004] However, the vision-assisted laser micro-nano processing monitoring technology currently only stays in the field of two-dimensional imaging technology. It can only obtain two-dimensional image information, that is, observe the pattern shape of the processed material, and cannot detect the depth of material processing. In laser micro-nano processing, the three-dimensional morphology monitoring of the material is crucial. The three-dimensional data can reflect the pros and cons of the current processing environment and the status of the laser engraving system, and feed back the real-time status of the processing to the laser precision system, which plays a decisive role in obtaining high-quality results of the processed materials.

[0005] Since the laser micro-nano processing process is extremely fast, ordinary camera imaging systems cannot capture every transient process of the processing, making it difficult to analyze and judge the problems in the processing process. The use of expensive ultrafast cameras has increased the cost of the entire processing system. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a real-time in-situ monitoring imaging method for pulse laser processing.

[0007] The real-time in-situ monitoring imaging method for pulsed laser processing provided by the present invention comprises the following steps:

[0008] a. Use high-speed holographic single-exposure compression imaging system and high-speed video single-exposure compression imaging system to monitor the processing femtosecond laser in real time;

[0009] b. Splitting the laser beam through a beam splitter prism and directing the laser beam to the sample surface for three-dimensional micro-nano processing;

[0010] c. Rapidly encode image information on the sample surface using a digital micromirror device (DMD);

[0011] d. Capturing the encoded image with a camera with a long exposure time to obtain a compressed image;

[0012] e. Sending the compressed image to a video single exposure compression imaging reconstruction algorithm for decoding and reconstruction to obtain a high-speed two-dimensional imaging process of femtosecond laser processing;

[0013] f. The compressed holographic image is sent to the video single exposure compression imaging reconstruction algorithm for decoding and reconstruction, and the three-dimensional morphology of the sample surface is reconstructed through the phase reconstruction algorithm and phase unwrapping algorithm.

[0014] Preferably, the working process of the high-speed video single-exposure compression imaging system includes processing femtosecond laser beam splitting, objective lens magnification, DMD encoding and camera capture.

[0015] Preferably, the working process of the high-speed holographic single-exposure compression imaging system includes the splitting of reference light and object light, objective lens magnification, interference, DMD encoding and camera capture.

[0016] Preferably, the video single-exposure compression imaging reconstruction algorithm can reconstruct a single-frame image into a dynamic video with n frames.

[0017] Preferably, the phase reconstruction algorithm and the phase unwrapping algorithm can reconstruct a single-frame compressed hologram into three-dimensional structural information of the sample surface at n moments.

[0018] Preferably, the method also includes using a deep learning image reconstruction algorithm to improve imaging quality and frame rate.

[0019] Preferably, the method further comprises the steps of hardware encoding and software decoding to achieve ultrafast imaging without using an expensive ultrafast camera.

[0020] Compared with the related art, the real-time in-situ monitoring imaging method of pulsed laser processing provided by the present invention has the following beneficial effects:

[0021] 1. The real-time in-situ monitoring imaging method for pulsed laser processing provided by the present invention can simultaneously obtain high-speed two-dimensional image information and high-speed three-dimensional morphological information of the processed material;

[0022] 2. The system uses hardware encoding and software decoding of low-speed cameras in conjunction with deep learning image reconstruction algorithms to achieve ultrafast imaging, replacing the previous cost problem of only being able to achieve ultrafast imaging by purchasing expensive ultrafast cameras;

[0023] 3. The system can perform real-time imaging of the femtosecond laser processing process;

[0024] 4. The system can realize in-situ monitoring of processed samples, that is, the sample position will not be moved, and the processing process of the sample will not be affected. The whole monitoring process can be completed in the original position of the sample on the processing table;

[0025] 5. The system is simple to install. The high-speed two-dimensional imaging system and the high-speed three-dimensional imaging system are independent of each other and can independently complete the required monitoring tasks;

[0026] 6. The low frame rate images obtained can be reconstructed into high frame rate laser micro-nano processing dynamic videos, and only occupy a small storage space. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a real-time in-situ monitoring device system for pulsed laser processing provided by the present invention. DETAILED DESCRIPTION

[0028] The scheme of the present invention is further described below in conjunction with the accompanying drawings and implementation modes.

[0029] The solution of the present invention is developed through the following ideas:

[0030] The Coded Aperture Compressive Temporal Imaging system is a technology that uses a high-speed rotating digital micromirror device to encode dynamic scenes at high speed, uses a low-speed camera to collect encoded images, and obtains high-frame-rate dynamic scene videos through a deep learning image reconstruction algorithm. In this system, there is no need to use expensive high-speed cameras, and the imaging effect of ordinary high-speed cameras can be achieved through hardware encoding and software decoding.

[0031] In the high-speed processing of femtosecond laser, ordinary cameras cannot capture such high-speed dynamic scenes. Applying the coded aperture time-domain compression imaging system to this high-speed processing monitoring can obtain detailed information of the high-speed processing process through optical path design, hardware construction, software calculation, etc., so as to better guide and analyze the problems in the laser processing process and intervene.

[0032] This paper proposes a real-time in-situ monitoring device system for pulsed laser processing. Figure 1 In this device, the imaging module is mainly divided into two parts, one is a high-speed holographic single-exposure compression imaging system, and the other is a high-speed video single-exposure compression imaging system.

[0033] For the high-speed video single-exposure compression imaging system, its working process is as follows: the processing femtosecond laser is reflected by the beam splitter prism 1 and then incident on the sample surface, performing three-dimensional micro-nano processing on the sample. At the same time, the laser emitted by the laser is reflected by the beam splitter prism 4 to the beam splitter prism 3, then reflected by the beam splitter prism 3, transmitted through the beam splitter prism 2, and then passed through the objective lens, and reached the sample surface through the beam splitter prism 1. Then, the light carrying the sample surface information is transmitted through the beam splitter prism 1, amplified by the objective lens, and then transmitted through the beam splitter prism 2 to the beam splitter prism 3. After further transmission here, it passes through the tube lens and is imaged on the surface of DMD1. The micromirror in DMD1 quickly encodes the image information of the sample surface after high-speed transformation. Then, the encoded image passes through the telecentric lens 1 and is incident on the surface of the photosensitive chip of the camera 1. The camera 1 obtains a compressed image of the sample encoded n times through a long exposure time.

[0034] For the high-speed holographic single-exposure compression imaging system, its working process is as follows: in the holographic optical path, the reference light part is the laser emitted by the laser, which passes through the beam splitter prism 4, is reflected by the reflector and passes through the beam splitter prism 2, and the tube lens 1 images the reference light at the interference surface position. The object light part is the processing femtosecond laser, which is reflected by the beam splitter prism 1 and then shot on the sample surface, and performs three-dimensional micro-nano processing on the sample. At the same time, the laser emitted by the laser is reflected by the beam splitter prism 4 to the beam splitter prism 3, and then reflected by the beam splitter prism 3, transmitted through the beam splitter prism 2, passes through the objective lens, and reaches the sample surface through the beam splitter prism 1. Next, the light carrying the sample surface information is transmitted through the dichroic prism 1, amplified by the objective lens, and then reflected by the dichroic prism 2 through the tube lens 1. The tube lens 1 interferes the object light information of the sample with the reference light at the interference surface to form a hologram. Next, the 4-F tube lens amplifies the hologram image and images it on the surface of DMD2. The micromirrors in DMD2 quickly encode the holographic image information after high-speed transformation. Next, the encoded hologram passes through the telecentric lens 2 and is incident on the surface of the photosensitive chip of the camera 2. The camera 2 obtains a holographic compressed image encoded n times through a long exposure time.

[0035] In this system, the compressed image obtained by the high-speed video single-exposure compression imaging system module needs to be sent to the video single-exposure compression imaging reconstruction algorithm for decoding and reconstruction. In the experiment, assuming that the compression ratio set in this module is n, then after reconstruction, a single-frame image will be reconstructed into a dynamic video with n frames. In this way, the collected multiple frames of compressed images are reconstructed separately to obtain the high-speed two-dimensional imaging process of femtosecond laser processing of samples.

[0036] In this system, the compressed holographic image obtained by the high-speed holographic single-exposure compression imaging system module needs to be sent to the video single-exposure compression imaging reconstruction algorithm for decoding and reconstruction to obtain a high-speed hologram with sample surface structure information during femtosecond laser high-speed processing. Then, the reconstructed hologram is sent to the phase reconstruction algorithm, and the three-dimensional morphology of the sample surface is reconstructed through the phase unwrapping algorithm. In the experiment, assuming that the compression ratio set in this module is n, then after reconstruction, a single-frame compressed hologram will be reconstructed into three-dimensional structure information of the sample surface at n moments.

[0037] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A real-time in-situ monitoring imaging method for pulsed laser processing, characterized in that: The following steps are involved: a. Use high-speed holographic single-exposure compression imaging system and high-speed video single-exposure compression imaging system to monitor the processing femtosecond laser in real time; b. Splitting the laser beam through a beam splitter prism and directing the laser beam to the sample surface for three-dimensional micro-nano processing; c. Use digital micromirror device (DMD) to quickly encode image information on the sample surface; d. Capturing the encoded image with a camera with a long exposure time to obtain a compressed image; e. Sending the compressed image to a video single exposure compression imaging reconstruction algorithm for decoding and reconstruction to obtain a high-speed two-dimensional imaging process of femtosecond laser processing; f. The compressed holographic image is sent to the video single exposure compression imaging reconstruction algorithm for decoding and reconstruction, and the three-dimensional morphology of the sample surface is reconstructed through the phase reconstruction algorithm and phase unwrapping algorithm.

2. The real-time in-situ monitoring imaging method for pulsed laser processing according to claim 1, characterized in that: The working process of the high-speed video single-exposure compression imaging system includes processing femtosecond laser light splitting, objective lens magnification, DMD encoding and camera capture.

3. The real-time in-situ monitoring imaging method for pulsed laser processing according to claim 1, characterized in that: The working process of the high-speed holographic single-exposure compression imaging system includes the splitting of reference light and object light, objective lens magnification, interference, DMD encoding and camera capture.

4. The real-time in-situ monitoring imaging method for pulsed laser processing according to claim 1, characterized in that: The video single-exposure compression imaging reconstruction algorithm can reconstruct a single-frame image into a dynamic video with n frames.

5. The real-time in-situ monitoring imaging method for pulsed laser processing according to claim 1, characterized in that: The phase reconstruction algorithm and phase unwrapping algorithm can reconstruct a single-frame compressed hologram into three-dimensional structural information of the sample surface at n moments.

6. The real-time in-situ monitoring imaging method for pulsed laser processing according to claim 1, characterized in that: The method also includes using a deep learning image reconstruction algorithm to improve imaging quality and frame rate.

7. The real-time in-situ monitoring imaging method for pulsed laser processing according to claim 1, characterized in that: The method also includes the steps of hardware encoding and software decoding to achieve ultrafast imaging without using an expensive ultrafast camera.

Images