Laser processing method for carrying out three-dimensional point carving inside ice block

Abstract

The invention discloses a laser processing method for carrying out three-dimensional point carving inside an ice block. According to the method, an ice blank is fixed in a sample clamp in a low-temperature constant-temperature cavity, and after a short-pulse laser is adjusted by an energy modulator, the ice blank is guided by a galvanometer / scanning unit according to a preset path and is accurately focused to a specified point in the ice blank by a low-temperature compatible focusing objective lens, so that micro-bubbles or microstructures are locally generated to realize three-dimensional point carving. The on-line monitoring camera and the acoustic / temperature sensor collect the inscribing effect and the ice blank state in real time, and the control system carries out closed-loop adjustment on laser energy, a scanning track and a focusing position based on feedback signals so as to improve the inscribing precision and reduce the risk of cracks and thermal damage. According to the invention, high-resolution and low-heat-influence three-dimensional point carving processing can be realized in the ice block, and the method is suitable for decoration, identification, functional microstructure preparation and other applications.

Description

Technical Field

[0001] This invention belongs to the field of laser processing and low-temperature micromachining technology, specifically relating to a laser processing method and control strategy for three-dimensional dot engraving inside ice blocks. Background Technology

[0002] Micromachining within transparent bodies using short-pulse lasers is a well-known technique. Through effects such as nonlinear absorption or localized vaporization, microbubbles, microcracks, or refractive index changes can be created within a volume, achieving three-dimensional microstructures. Extending this method to the interior of transparent ice blanks can be used for decorative engraving, marking, or the fabrication of functional microstructures. However, the low-temperature sensitivity, susceptibility to cracking, and thermal conductivity of ice pose challenges to processing stability and precision. Therefore, it is necessary to design low-temperature compatible optical systems, energy control methods, and real-time closed-loop monitoring and protection strategies to achieve high-precision, low-damage three-dimensional point engraving within ice blanks. Summary of the Invention

[0003] Purpose of the invention: To provide a laser processing method for three-dimensional dot engraving inside ice blocks. By controlling short-pulse laser energy, precisely scanning the optical path, maintaining a low-temperature constant temperature environment, and implementing real-time monitoring closed-loop control, reliable, repeatable, and high-resolution three-dimensional dot engraving processing inside ice can be achieved, reducing the risk of cracks and thermal damage.

[0004] Technical Solution Summary: This method includes the following main steps: The ice block is fixed in a sample fixture within a cryogenic constant-temperature chamber, maintaining the required low temperature for processing; the control system sends control commands to the short-pulse laser, energy modulator, and galvanometer / scanning unit based on a preset three-dimensional path plan; the laser outputs a short-pulse laser beam, and the energy modulator adjusts the output energy at the pulse or packet level as set; the galvanometer / scanning unit controls the optical path according to the path, and a cryogenically compatible focusing objective focuses the laser onto a designated point inside the ice to form microbubbles / microstructures; an online monitoring camera (transmission / scattering mode) and acoustic / temperature sensors collect the marking effect and ice block status in real time and transmit the data back to the control system; the control system performs closed-loop adjustments to the laser energy, pulse number, scanning trajectory, and focusing depth based on the monitoring data, pausing or correcting the processing as necessary to protect the integrity of the workpiece.

[0005] Clamping and temperature control: Place the ice block (size as required by the application, such as diameter or square sample) on the sample holder, which is installed on the cooling worktable inside the cryogenic constant temperature chamber; set and maintain the sample working temperature Twork (e.g. -10 °C to -30 °C, which can be optimized according to the transparency and mechanical stability of the ice), and monitor the sample temperature in real time through a temperature sensor (thermocouple or RTD).

[0006] Path planning: Load the three-dimensional point matrix / path data (layered or point-by-point coordinates) to be inscribed into the control system. The control system decomposes the three-dimensional path into scanning instructions for each layer / point and determines the number of pulses, single pulse energy and focusing depth for each inscription point.

[0007] Laser parameters and output: A short-pulse laser (femtosecond or picosecond) is used. Typical parameter examples: pulse width 100 fs–20 ps (implementation options include 100 fs–10 ps or 1 ps–10 ps); repetition frequency selectable from 1 kHz to 1 MHz; single-pulse energy range can be set from tens of nJ to several μJ, with appropriate energy selected for different processing depths / target point sizes. The laser outputs a laser beam after receiving on / off and energy setting commands from the control system.

[0008] Energy modulation: The output energy of the laser beam is adjusted by an energy modulator (which can be an acousto-optic modulator AOM, an electro-optic modulator EOM, or a variable attenuator) at the pulse level or packet level, thereby achieving fine control of the energy accumulation at a single point (e.g., accumulating 10–1000 pulses per point, or processing in batches as needed).

[0009] Scanning and Focusing: After the laser beam is oriented by a galvanometer / scanning unit (Galvo or mirror scanning), it is focused onto a specified depth inside the ice body by a cryogenic compatible or immersion focusing objective (numerical aperture NA range, e.g., 0.4–1.2; for immersion types, cryogenic medium matching must also be considered), forming a localized high-intensity region, generating microbubbles or localized structural changes, thus completing single-point writing. The focusing depth is achieved by adjusting the focusing objective in the Z-axis or moving the sample stage in the Z-axis.

[0010] Online monitoring and closed-loop control: The system is equipped with an online monitoring camera (transmission / scattering imaging) to detect the scattering brightness, shape, and location of the marking points. Simultaneously, acoustic sensors (piezoelectric elements) and temperature sensors monitor acoustic emission and local temperature changes. Monitoring data is transmitted back to the control system in real time. The control system adjusts the energy modulator output, changes the pulse count, or pauses processing based on preset thresholds and algorithms to prevent cracking or overheating. All processing parameters and monitoring data are logged for traceability and optimization.

[0011] Layered or point-by-point strategy: For complex three-dimensional structures, a layer-by-layer or point-by-point hierarchical accumulation strategy is adopted. The basic structure is first formed with low energy / few pulses, and the energy or repeated pulses are gradually increased to achieve the target size and shape, reducing the risk of cracks caused by excessive energy at one time. Attached Figure Description

[0012] Figure 1 This is a flowchart illustrating the method of the present invention. Example

[0013] During processing, when the acoustic emission amplitude or frequency characteristics detected by the acoustic sensor exceed the preset threshold, or when the temperature sensor detects that the local temperature rise exceeds the allowable range, the control system executes a protection procedure: immediately reduces the output energy of the energy modulator, suspends subsequent scanning actions, and performs a small number of probe pulses in low energy or safe mode to verify whether the writing point is stable; if the abnormality is eliminated, normal parameters are restored and processing continues; if the abnormality persists, an alarm is triggered and processing is terminated, prompting the operator to check sample fixation, temperature control, or adjust the path / parameters.

[0014] Laser type: Optional 800 nm femtosecond laser (pulse width ~100 fs, repetition rate 100 kHz–1 MHz) or 1030 nm picosecond laser (pulse width 1–10 ps, ​​repetition rate 10 kHz–500 kHz).

[0015] Single pulse energy and accumulation: Single pulse energy 0.05 μJ–5 μJ, single point pulse count 10–2000 times, adjusted according to the size and depth of the writing point.

[0016] Focusing numerical aperture: NA 0.6–1.0 (a higher NA can be used for immersion objectives to achieve a smaller focal point). The numerical aperture and depth of focus together determine the single-point size.

[0017] Temperature control: The operating temperature can be set from -5 °C to -30 °C (optimized according to transparency and stress testing), and anti-frost / anti-condensation measures are arranged at the edge of the sample.

[0018] Scanning speed: The galvo scan line speed or inter-point movement speed is set according to the repetition frequency and inter-point interval. The typical inter-point movement speed ranges from 0.1 mm / s to 100 mm / s (the point-to-point movement is the main method of point-to-point engraving strategy).

[0019] This invention combines short-pulse laser, energy modulation, precise scanning, and a low-temperature isothermal environment, and introduces closed-loop control with online imaging and acoustic temperature monitoring to achieve high-precision, low-thermal-affected three-dimensional dot engraving inside ice blanks. This method significantly reduces the risk of cracking due to heat accumulation or localized overheating, improves engraving repeatability and yield, and is suitable for decorative engraving, personalized marking, and functional processing scenarios with special microstructure requirements.

[0020] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. It should be understood that, for the technical solutions of the present invention, equivalent substitutions or appropriate improvements can be made to the laser type, pulse parameters, sensor configuration, control algorithm, sample fixture, and temperature control strategy without departing from the concept of the present invention, and all such substitutions or appropriate improvements are within the scope of protection of the present invention.

[0021] In summary, this invention provides a stable, controllable, and industrially achievable laser processing method for three-dimensional dot engraving inside ice blocks, which has high processing accuracy, good processing stability, and broad application prospects.

Claims

1. A laser processing method for three-dimensional dot engraving inside an ice block, characterized in that, Includes the following steps: Ice is placed in a cryogenic constant-temperature chamber and fixed by a sample clamp. The required low-temperature working conditions for processing are set and maintained. The control system sends control commands to the short-pulse laser, energy modulator, and galvanometer / scanning unit according to a preset three-dimensional path plan. The laser outputs a short-pulse laser beam, which is distributed according to the set energy by the energy modulator. The galvanometer / scanning unit controls the laser beam direction according to the path, and the focusing objective focuses the laser energy onto a designated internal point on the ice to generate microbubbles or microstructure points. An online monitoring camera and acoustic / temperature sensor collect the engraving effect and ice state in real time and transmit the monitoring data back to the control system. The control system performs closed-loop adjustments to the laser energy, pulse number, scanning trajectory, and focusing position based on the monitoring data until the predetermined three-dimensional engraved structure is completed.

2. The method according to item 1, wherein the short-pulse laser is a femtosecond laser or a picosecond laser.

3. The method according to item 1, wherein the energy modulator adjusts the single pulse energy at the pulse level or packet level to regulate the size and morphology of the internal microstructure by controlling the number of single-point pulses and the single pulse energy.

4. The method according to item 1, wherein the galvanometer / scanning unit is a galvo galvanometer or a reflector scanning unit, used to achieve high-speed scanning and precise optical path pointing control.

5. The method according to claim 1, wherein the focusing objective is a cryogenic or immersion objective to achieve high numerical aperture focusing in cryogenic or immersion environments.

6. According to the method described in item 1, wherein the online monitoring camera uses transmission imaging or scattering imaging mode to detect the scattering intensity, shape and position of the inscribed point, and transmits the detection results back to the control system in real time.

7. The method according to item 1, wherein the acoustic / temperature sensor is used to detect acoustic emission signals and local temperature changes to determine whether cracks or thermal anomalies occur, and to send an alarm message to the control system when an anomaly exceeding a preset threshold is detected.

8. The method according to item 1, wherein the control system performs closed-loop control based on the monitoring data, including automatically adjusting the output of the energy modulator, adjusting the scanning speed and path, adjusting the focusing depth, or pausing processing to ensure the integrity of the ice block and the writing accuracy.

9. The method according to item 1, wherein the step further includes layer-by-layer or point-by-point hierarchical multiple pulse processing to progressively form the desired three-dimensional lattice structure or complex microstructure.

10. According to the method in item 1, when the acoustic / temperature sensor detects an abnormality threshold exceeding a preset threshold, the control system automatically reduces the output energy of the energy modulator and pauses or adjusts the scanning trajectory, and resumes processing after the monitored parameters return to the allowable range.

11. The method according to claim 1, wherein the cryogenic constant temperature chamber includes a cooling stage and is equipped with a precisely positionable sample stage, wherein the focal point is precisely positioned in the depth direction by moving the sample stage or moving the Z-axis position of the focusing objective.

12. According to the method described in item 1, wherein the control system records real-time monitoring data and laser parameters for each inscription point and generates a processing log for subsequent quality assessment and parameter optimization.

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