CN105428966A - External optical path compensation adjusting device and laser device formed thereby - Google Patents

Abstract

The invention proposes an external optical path compensation adjustment device based on the adjustment of the turning mirror, which includes a turning mirror, a piezoelectric ceramic micro-displacement driver and a rotatable base. By changing the voltage applied to the micro-displacement driver, the turning mirror is driven to rotate to realize Automatic compensation of optical path. On this basis, the present invention proposes a laser based on an external optical path compensation and adjustment device, including a laser, an external optical path compensation and adjustment device, an optical path shaping module, a focusing spherical mirror and a feedback control module. The feedback control module detects the output laser, and through the optical path compensation adjustment system, adjusts the deflection angle of the turning mirror to adjust the offset beam to the standard position, which can ensure the stability of the laser output power and the stability of the laser mode under each duty cycle , Improve the overall stability of the laser, and then ensure the efficient and stable operation of the RF slab laser processing system, ensure the processing quality of the processed device, and improve the processing efficiency.

Description

An external optical path compensation adjustment device and a laser composed of it

technical field

The invention belongs to the field of laser technology, and designs and develops a compensation system for adjusting the optical path offset of the shaping system based on a turning mirror of a high-power radio frequency slab CO ₂ laser, which can compensate for the optical path offset of the shaping system caused by the thermal distortion of the cavity mirror of the radio frequency slab CO ₂ laser. Make compensation.

Background technique

High power slab _CO2 laser with high beam quality, very compact and small size, no gas heat exchanger required, low optical losses, very high thermal stability, low gas consumption, no gas flow, no contamination of resonator optics, beam The quality figure of merit ^M2 can reach 1.2, which represents the development direction of _CO2 lasers at present. The laser adopts the design structure of the unstable-waveguide hybrid cavity, and the resonant cavity is composed of an output mirror, a reflector and a discharge slab waveguide. The near-field output spot of the laser is approximately a straight line of uneven thickness in the direction parallel to the electrode plane; in the far field, the beam diverges greatly in the direction perpendicular to the electrode plane, and external optical path beam shaping is required to achieve industrial applications.

Thermal distortion of the cavity mirror in high power RF slab _CO2 lasers can lead to beam instability in beam shaping systems. The sidelobe of the initial output beam cannot be effectively eliminated by the spatial filter in the beam shaping system, and the output beam of the RF slab CO ₂ laser has sidelobes after shaping, and the output power stability is affected. At the same time, the shape of the spot is no longer an ideal Gaussian distribution of the near-circular fundamental mode, and the beam quality is not improved. The instability of the output power and the failure to improve the beam quality have seriously affected the quality of laser processing. In addition, the lateral misalignment of the spatial filter also means an increase in output power loss. If the spatial filter is severely laterally misaligned, the energy of the main peak in the center will also be eliminated. Since it is a Gaussian distribution, the larger the offset displacement, the greater the power loss will be.

The existing method of adjusting the cavity mirror is aimed at optical path imbalance. Heating wires are placed on the back of the cavity mirror to heat, and the deformation direction is the same as that of the reflective surface of the cavity mirror. Disadvantages of this compensation adjustment method: first: the reaction time of heating is long, and the advantage of real-time adjustment is not obvious; second: heating control is difficult, which will affect the effect of compensation adjustment. In the existing spatial filter method, by adjusting the position of the spatial filter, the focal line of the beam and the slit of the spatial filter are matched. This method has strong real-time performance, but the adjustment accuracy is not high. To obtain high-precision adjustment, it is necessary to redesign and select a new micro-displacement positioner and redesign the adjustment system. In addition, this method does not make any corrections to the shifted optical axis, and only adjusts the position of the spatial filter diaphragm to adapt to the misalignment of the optical path. The beam directivity will become poor, and the practicability is not strong.

Contents of the invention

In view of the above defects or improvement needs of the prior art, the present invention provides an external optical path compensation adjustment device based on the adjustment of the turning mirror, the purpose of which is to adjust the shifted beam to the standard position, so that the output mode and power of the laser are consistent with the optical path The level before the offset, thereby solving the technical problem that the thermal distortion of the cavity mirror of the high-power RF slab _CO2 laser causes the beam to be unstable in the beam shaping system.

To achieve the above object, according to one aspect of the present invention, an external optical path compensation adjustment device based on the adjustment of the turning mirror is provided. The rotation adjustment of the turning mirror around the central axis of the rotatable base is realized by a micro-displacement driver. When the turning mirror rotates, the projection position of the beam on the focusing spherical mirror will be changed, and the position of the beam's focal line after being reflected by the focusing spherical mirror will change. When the beam returns to the position of the filter aperture on the focal line, the output laser power of the laser reaches the maximum value, and the side lobes in the spot caused by the offset of the optical path are also filtered out by the spatial filter. To achieve the purpose of the output mode and power of the laser reaching the level before the offset from the optical path.

Technical scheme of the present invention is:

An external optical path compensation adjustment device, which includes a turning mirror, a micro-displacement driver and a rotatable base, is characterized in that:

The turning mirror is in the shape of a right-angled triangular prism, and is fixed on the rotatable base through a bottom surface of itself. The inclined surface of the triangular prism is a reflecting surface, which is used to turn the incident laser direction perpendicular to the fixed bottom surface by 90 degrees. Changed to be parallel to the direction of the fixed bottom surface; through the rotation of the rotatable base, the deflection angle of the turning mirror can be adjusted;

The micro-displacement driver is a piezoelectric ceramic type, one end of which is fixed, and the other end is movably connected by the first connecting rod through the connecting rod circular shaft and the second connecting rod; the other end of the second connecting rod is connected to the other bottom surface of the turning mirror , the middle part of the second connecting rod is fixed by rotating the fixed circular shaft; the horizontal movement of the first connecting rod can drive the rotation of the second connecting rod relative to the fixed circular shaft; by changing the voltage applied to the micro displacement driver, the first connecting rod can be changed The horizontal displacement of the rod drives the two ends of the second connecting rod to rotate around the circular axis, thereby driving the turning mirror fixedly connected at the other end to rotate.

Further, in the external optical path compensation adjustment device, the rotatable base includes a metal block, a spring set, a concave circular base and a matching external convex circular handle, and the metal block is used to fix the Turning mirror, one end of the outer convex circular handle is fixedly connected with the metal block, and the other end is opened with a circular through hole, through the circular shaft of the base, the outer convex circular surface and the inner concave circular surface of the inner concave circular base rotate tangentially, and the outer convex The circular handle can rotate relative to the concave circular base with the circular axis of the base as the axis.

Further, in the external optical path compensation adjustment device, the spring set is composed of three springs with the same structural size and mechanical parameters, arranged in a right triangle.

Based on the external optical path compensation adjustment device, the present invention proposes a laser, including a laser, an external optical path compensation adjustment device, an optical path shaping module, a focusing spherical mirror and a feedback control module, characterized in that:

The turning mirror of the external optical path compensation adjustment device is aligned with the light exit window of the laser, which is used to reflect the laser and incident it on the focusing spherical mirror;

The focusing spherical mirror and the turning mirror are located on the same optical path, and the focal point is the spatial filter of the optical path shaping module; the laser beam is focused on the unstable direction of the output beam by the focusing spherical mirror, and the waveguide direction of the output beam is collimated, and sent to Incoming optical path shaping module;

The optical path shaping module includes a spatial filter, a cylindrical mirror, and an output spherical mirror, and the three are on the same optical axis; wherein the cylindrical mirror is located before the output spherical mirror and after the spatial filter; for eliminating side lobes in the output beam, improving The beam quality of the output beam in the unstable direction;

The sensor of the feedback control module is installed on the output laser optical path, and its output terminal is connected with the external optical path compensation adjustment device to control the action of the turning mirror; the feedback control module detects the outgoing laser of the optical path shaping module through the sensor, and according to the detected output optical power Calculate the voltage that needs to be loaded on the micro-displacement driver, and then transmit the electrical signal to the external optical path compensation adjustment device to control the micro-displacement driver to generate a corresponding displacement, so that the deflection angle of the turning mirror can be adjusted automatically.

Generally speaking, compared with the prior art, the above technical solution conceived by the present invention only needs to adjust the deflection angle of the turning mirror, and does not change the positions of the key components of the beam shaping module, such as spherical mirrors, spatial filters, and cylindrical mirrors. , can achieve the following beneficial effects: 1. The external optical path compensation adjustment device proposed by the present invention can adjust the optical path offset problem of the shaping system caused by the thermal distortion of the cavity mirror during the working process of the radio frequency slab _CO2 laser with higher precision; 2. 1. Ensure the stability of the output power and mode distribution of the laser at each duty cycle, and improve the overall stability of the laser; 3. While realizing the offset compensation micro-movement, avoid the problem of beam directivity; 4. Ensure the stability of the processed device Improve processing quality and improve processing efficiency.

Description of drawings

Fig. 1 is a schematic diagram of an external optical path compensation adjustment device;

Fig. 2 is a schematic diagram of the laser principle based on the external optical path compensation adjustment device;

Fig. 3 is a schematic block diagram of the overall design of the laser based on the external optical path compensation adjustment device;

Fig. 4 is a side view without shifting of the optical path;

Fig. 5 is a top view without shifting of the optical path;

Fig. 6 is a side view of optical path offset misalignment;

Fig. 7 is a top view of optical path offset misalignment;

Fig. 8 is a side view of the optical path after the adjustment of the external optical path compensation device;

Fig. 9 is a top view of the optical path after the adjustment of the external optical path compensation device;

Figure 10 is a comparison chart of laser output power before and after adjustment;

Fig. 11 is a comparison diagram of the facula pattern before and after adjustment; (a) is a diagram of the facula pattern before adjustment; (b) is a diagram of the facula pattern after adjustment.

In the figure: 1-laser, 2-external optical path compensation device, 3-optical path shaping module, 4-focusing spherical mirror, 5-spatial filter, 6-cylindrical mirror, 7-output spherical mirror, 8-feedback control module, 9- Micro-displacement driver, 10-first connecting rod, 11-second connecting rod, 12-turning mirror, 13-rotatable base, 14-metal block, 15-spring group, 16-concave circular base, 17-convex Round handle, 18-base round shaft, 19-connecting rod round shaft, 20-fixed round shaft.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

As shown in FIG. 1 , the external optical path compensation adjustment device of this embodiment is mainly composed of a turning mirror 12 , a piezoelectric ceramic micro-displacement driver 9 and a rotatable base 13 . The rotatable base 13 includes a metal block 14, a spring group 15, a concave circular base 16 and a matching convex circular handle 17, one end of the convex circular handle 17 is fixedly connected with the metal block 14, and one end of the convex circular shape has a The round through hole is placed tangentially with the concave circular base 16 through the base circular axis 18, and the convex circular handle 17 can rotate relative to the concave circular base 16 with the base circular axis 18 as the axis. The springs are respectively fixed at the right angles of the square metal blocks, and the piezoelectric ceramics generate displacement, which drives the connecting rod, thereby driving the turning mirror to move. Through the action of the spring, the turning mirror produces an angle change, thereby changing the optical path and achieving the purpose of adjusting the optical path.

The schematic diagram of the system principle of the laser based on the external optical path compensation adjustment device is shown in Figure 2, and the schematic block diagram of the overall system design is shown in Figure 3;

Figure 4-9 shows the schematic diagram of optical path offset and compensation adjustment.

In Figures 4 and 5, the beam shaping module of the external optical path of the RF slab CO ₂ laser has no optical path offset. The light beam is reflected by the turning mirror and then transmitted to the spherical mirror. After being converged by the spherical mirror, it is focused at the spatial filter. The slit width of the spatial filter is equal to the width of the main lobe after the beam is focused. The main lobe can pass through completely, and the side lobe is filtered by the spatial filter. , after the beam shaping module, the laser can get better mode distribution, and the beam quality is improved. In Figures 6 and 7, the optical path will deviate from the standard position shown in Figures 4 and 5 after the thermal distortion of the unstable waveguide cavity mirror occurs. After the light beam is focused by the mirror spherical mirror, its focus position and the position of the spatial filter will no longer coincide. Part of the main lobe of the beam is blocked by the spatial filter, and at the same time, a part of the side lobe cannot be filtered by the spatial filter, and enters the post-stage beam shaping module. Because the main lobe is blocked and side lobes pass, the final output laser power of the laser will decrease, and the beam quality will be accompanied by side lobes. In Figures 8 and 9, the external optical path compensation adjustment device adjusts the deflection angle of the turning mirror to adjust the shifted beam to the standard position, and the main lobe of the beam will pass through the spatial filter again, while the side lobes will be re-filtered. The output mode and power of the laser reach the level before the offset from the optical path.

The function of the feedback control circuit is feedback adjustment. Its working process is to first judge whether the laser optical path is offset by detecting the optical power of the output beam; judge the offset of the optical path according to the reduction of the optical power, and calculate the amount that needs to be loaded on the piezoelectric The voltage value on the ceramic is applied to the piezoelectric ceramic through the control circuit, thereby changing the angle of the turning mirror and adjusting the optical path to the standard position. The control process is carried out in real time, and the automatic adjustment ensures that the optical path is always at the standard position, thereby ensuring the stability of the laser output power.

In order to verify the effect of the external optical path compensation adjustment device of the present invention, a verification experiment of the adjustment method of the turning mirror and an effect test of the adjustment method of the turning mirror were carried out.

1. Set the laser power and adjust the compensation voltage test. Under a specific laser power duty cycle, adjust the full range of the turning mirror, the adjustment voltage interval is 0.1V, and the total adjustment voltage is 1.12V. Observe and record the output power of the laser at each adjustment distance, and the corresponding duty cycle The standard power parameters of the laser are compared to judge the adjustment effect of the optical path compensation system. The adjustment distance of the external optical path compensation is linearly proportional to the duty cycle, so it is only necessary to measure whether the adjustment of the turning mirror can meet the adjustment requirements under the highest power.

When the piezoelectric ceramic control voltage reaches 0.9V, the maximum output power of the 2KW laser is 1843W, which is very close to the standard laser power of 1811W under the 90% duty cycle of the laser; when the voltage exceeds 0.9V, the output power of the laser It starts to decrease, which means that the adjustment distance exceeds the range that needs to be adjusted, so that the outer optical path re-shifts to the standard position. Therefore, the device of the present invention can meet the adjustment requirement of the laser when the duty cycle is 90%.

2. Set the compensation voltage and adjust the laser power duty cycle. A total of 8 experimental points of 5%, 15%, 25%, 35%, 45%, 55%, 65%, and 75% were selected, respectively, under the conditions of adding the cavity mirror misalignment non-adjustable system and not adding the external optical path compensation adjustment device Next test the output power of the laser. Figure 10 shows the comparison of the output power before and after. It can be seen that the contribution of the external optical path compensation and adjustment device to the output power of the laser is not obvious at low duty ratios. When the power exceeds 50%, the effect of the external optical path compensation and adjustment device becomes more and more Obviously, the maximum power difference is about 100W. Figure 11 is a comparison of the spot pattern before and after the external optical path compensation adjustment of the laser. The spot basically has no side lobes when the duty cycle is 15%, and there are side lobes when the duty cycle is 35%-75%, and the size of the side lobes Gradually become larger; after compensation and adjustment, there are no side lobes under each duty cycle, and the system satisfies the compensation for the spot mode very well.

Those skilled in the art can easily understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (4)

1. an outer optical path compensation adjusting device, it comprises turning mirror (12), micro-displacement driver (9) and rotatable pedestal (13), it is characterized in that:

Described turning mirror (12) is at right angles triangular prism shaped, be fixed on described rotatable pedestal (13) by the bottom surface of self, triangular prism shaped inclined-plane is reflecting surface, for by the incident laser direction perpendicular to fixing bottom surface, turn to 90 degree, change into and be parallel to direction, fixing bottom surface; By the rotation of described rotatable pedestal (13), the deflection angle of adjustable described turning mirror (12);

Described micro-displacement driver (9) is Piezoelectric, and its one end is fixed, and the other end is flexibly connected by connecting rod circular shaft (19) and second connecting rod (11) by first connecting rod (10); The other end of second connecting rod (11) is connected to another bottom surface of turning mirror (12), and second connecting rod (11) middle part rotates fixing by fixing circular shaft (20); First connecting rod (10) move horizontally the rotation that second connecting rod (11) can be driven relative to fixing circular shaft (20); By changing the size being added to the upper voltage of micro-displacement driver (9), change the horizontal displacement of first connecting rod (10), drive second connecting rod (11) two ends to rotate around circular shaft (20), thus the turning mirror (12) driving its other end to be fixedly connected with rotate.

2. outer optical path compensation adjusting device according to claim 1, it is characterized in that, described rotatable pedestal (13) comprises metal derby (14), groups of springs (15), indent cup dolly (17) and the outer convexity handle (16) matched with it, metal derby (14) is for fixing described turning mirror (12), outer convexity handle (16) one end is fixedly connected with metal derby (14), the other end has a round tube hole, by base circular shaft (18), evagination disc (16) is made to rotate tangent cooperation with the indent disc of indent cup dolly (17), outer convexity handle (16) can with base circular shaft (18) for axle center be rotated relative to indent cup dolly (17).

3. outer optical path compensation adjusting device according to claim 1 and 2, is characterized in that, the spring that described groups of springs (15) is laid by identical with mechanics parameter, the rectangular triangle of three root architecture sizes forms.

4. the laser based on outer optical path compensation adjusting device described in claim 1 or 2 or 3, comprise laser (1), outer optical path compensation adjusting device (2), light path Shaping Module (3), focus on spherical mirror (4) and feedback control module (8), it is characterized in that:

The turning mirror of outer optical path compensation adjusting device (2) is aimed at laser (1) and is gone out optical window, after being reflected by laser (1), incides and focuses on spherical mirror (4);

Described focusing spherical mirror (4) and turning mirror are positioned at same light path, and its focus place is the spatial filter (5) of light path Shaping Module; The non-steady direction of laser line focus spherical mirror (4) to output beam focuses on, and after collimating the wave guide direction of output beam, sends into light path Shaping Module (3);

Described light path Shaping Module (3) comprises spatial filter (5), cylindrical mirror (6), and export spherical mirror (7), three is on same optical axis; Before its central column face mirror (6) is positioned at and exports spherical mirror (7), after spatial filter (5); For eliminating the secondary lobe in output beam, improve the beam quality in the non-steady direction of output beam;

The transducer of feedback control module (8) is arranged in Output of laser light path, and its output is connected with outer optical path compensation adjusting device (2), for controlling turning mirror action; Feedback control module (8) detects the shoot laser of light path Shaping Module (3) by transducer, according to the change of the Output optical power detected, calculate and need to be carried in the voltage on micro-displacement driver (9), then outer optical path compensation adjusting device (2) is given by electrical signal transfer, control micro-displacement driver (9) and produce corresponding displacement, thus make turning mirror deflection angle, reach the object automatically regulated.