Thermal effect compensation optical imaging device

Abstract

The utility model discloses a thermal effect compensation optical imaging device, which belongs to the technical field of laser 3D (three-dimensional) metal printing equipment and comprises a laser used for emitting laser beams, a focusing lens driven by a voice coil motor and used for dynamically focusing the laser beams in real time and a focusing lens group used for accurately imaging the laser beams. And the focusing lens group comprises at least two lenses with different refractive index temperature coefficient constants. According to the utility model, the at least two lenses with different refractive index temperature coefficient constants are used to form the focusing lens group, so that the focus at different temperatures does not generate large drift any more, and the problem of focus drift is reduced or even perfectly solved; the optical imaging device does not need other mechanisms to specially control the temperature of the optical path system and set different focal length values for different temperatures any more, the equipment size is reduced, and focusing is convenient.

Description

Technical Field

[0001] The utility model belongs to the technical field of laser 3D metal printing equipment, and in particular relates to a thermal effect compensation optical imaging device. Background Art

[0002] Laser 3D metal printing SLM usually uses hundreds of watts to several kilowatts of fiber lasers for scanning and printing. The optical imaging system of laser 3D metal printing is a 3D printer focusing device disclosed in the utility model patent with authorization announcement number CN215867306U, which includes a light source, a focusing lens group, a focusing lens group and a beam adjustment lens group that adjusts the diffused light beam into a parallel beam or a focused beam, which are sequentially arranged inside the shell; the centers of the light source, the focusing lens group, the focusing lens group and the beam adjustment lens group are located on the same straight line; the light source, the focusing lens group and the beam adjustment lens group are all fixed to the shell, and the focusing lens group is slidably connected to the shell.

[0003] In the above optical imaging system, the glass material of the optical device has a certain absorption rate for high-power lasers. When the laser passes through the optical device such as the imaging lens, a small part of the optical power will be lost. The lost laser causes the temperature of the related lenses on the optical path to rise. Any optical lens glass material has a refractive index temperature coefficient constant (Constants of dn / dt). This coefficient constant indicates that temperature changes will cause the focal length of the optical lens to change, and ultimately cause the imaging focus temperature drift.

[0004] In order to compensate for the temperature drift of the imaging focus, the conventional approach is to increase the cooling capacity as much as possible, and use air cooling and other means to limit the rise in the operating temperature of the optical lens to the minimum possible, so as to reduce the focal length change of the optical system caused by the temperature change of the lens. A more accurate approach is to install a temperature sensor near the lens, test its true focal length at different temperatures, and use a control program to change the printing focal length according to the temperature to compensate for the temperature drift caused by the temperature change. The above compensation method requires controlling the temperature of the optical path system or setting different focal length values ​​for different temperatures, which results in a complex structure of the optical path system and an increase in the size of the entire printing device. The focusing process requires calculating the focal length value according to different temperatures, which is a cumbersome process. Utility Model Content

[0005] The utility model provides a thermal effect compensation optical imaging device to solve the problems of imaging focus temperature drift caused by lens temperature change in the existing optical imaging system, complex optical path system structure caused by compensation for image focus drift, and cumbersome focusing process.

[0006] In order to solve the above technical problems, the technical solution provided by the utility model is:

[0007] The utility model relates to a thermal effect compensation optical imaging device, which comprises a laser for emitting a laser beam, a focusing lens driven by a voice coil motor for real-time dynamic focusing of the laser beam, and a focusing lens group for accurately imaging the laser beam, wherein the focusing lens group comprises at least two lenses with different refractive index temperature coefficient constants.

[0008] Preferably, the focusing lens group includes two lenses with different refractive index temperature coefficient constants, one of which is a H-QK3L lens and the other is a fused silica lens.

[0009] Preferably, the H-QK3L lens is a convex lens, and the fused silica lens is a concave lens.

[0010] Preferably, the H-QK3L lens and the fused silica lens are arranged closely along the optical path direction of the laser beam.

[0011] Preferably, a pre-adjustment lens for pre-adjusting the focal length of the entire optical path system during installation is also provided between the focusing lens and the laser, and the pre-adjustment lens is a convex lens.

[0012] Compared with the prior art, the technical solution provided by the utility model has the following beneficial effects:

[0013] 1. The thermal effect compensation optical imaging device involved in the utility model uses at least two lenses with different refractive index temperature coefficient constants to form a focusing lens group, so that the focus at different temperatures will no longer drift greatly, thereby reducing or even perfectly solving the problem of focus drift. The optical imaging device no longer needs other mechanisms to specifically control the temperature of the optical path system and set different focal length values ​​for different temperatures. The device size is reduced and focusing is convenient.

[0014] 2. In the focusing lens group of the thermal effect compensation optical imaging device involved in the utility model, one lens is an H-QK3L lens and the other lens is a fused quartz lens. When the temperature changes, the focus drift directions of the H-QK3L lens and the fused quartz lens are opposite, so that the focus drifts can be accurately deducted from each other; and the H-QK3L lens has the lowest absorption rate for the metal laser 3D metal printing SLM laser wavelength, which further ensures the durability of the glass material and will not break due to excessive temperature changes in the working state. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a light path diagram of a thermal effect compensation optical imaging device;

[0016] Figure 2 It uses two imaging lenses made of the same fused quartz glass material, and the distribution of the imaging spot near the focus at 0℃, 50℃ and 100℃;

[0017] Figure 3 It uses two imaging lenses made of different glass materials (H-QK3L lens and fused silica lens), and the distribution of the imaging spot near the focus at 0℃, 50℃ and 100℃.

[0018] Reference numerals: 1 - laser, 2 - pre-adjustment lens, 3 - focusing lens, 4 - H-QK3L lens, 5 - fused silica lens. DETAILED DESCRIPTION

[0019] In order to further understand the content of the utility model, the utility model is described in detail in conjunction with embodiments. The following embodiments are used to illustrate the utility model but are not used to limit the scope of the utility model.

[0020] Refer to the attached Figure 1 As shown, the utility model relates to a thermal effect compensation optical imaging device comprising a laser 1 for emitting a laser beam, and a pre-adjustment lens 2 arranged in sequence according to the laser optical path for pre-adjusting the focal length of the entire optical path system during installation, a focusing lens 3 driven by a voice coil motor for real-time dynamic focusing of the laser beam, and a focusing lens group for accurately imaging the laser beam, wherein the focusing lens group comprises at least two lenses with different refractive index temperature coefficient constants.

[0021] Preferably, the focusing lens group includes two lenses with different refractive index temperature coefficient constants, one of which is an H-QK3L lens 4, and the other is a fused silica lens 5, and the H-QK3L lens 4 and the fused silica lens 5 are arranged closely along the optical path of the laser beam. The refractive index temperature coefficient constant of the H-QK3L lens 4 is -9.2600e-006, and the H-QK3L lens 4 is a convex lens; the refractive index temperature coefficient constant of the fused silica lens 5 is 2.2370e-005, and the fused silica lens 5 is a concave lens.

[0022] The pre-adjustment lens 2 and the focusing lens 3 are both convex lenses.

[0023] Parameters of the pre-adjustment lens 2, focusing lens 3, H-QK3L lens 4 and fused silica lens 5 are shown in Table 1.

[0024] Table 1. Parameters of pre-adjusted lenses, focus lenses, H-QK3L lenses, and fused silica lenses

[0025] Glass material diameter thickness Curvature radius 1 Curvature Radius 2 Pre-adjusted lenses 2 SILICA 25.4 3.8 flat 46 Focusing lens 3 SILICA 25.4 3 flat 85.1 H-QK3L lens 4 H-QK3L 25.4 5 58.84 247 Fused Silica Lens 5 SILICA 25.4 2 91.656 flat

[0026] Effect example

[0027] In this effect example, the H-QK3L lens 4 in Example 1 is replaced by a fused silica lens. When the temperature is increased from 0°C to 100°C, the drift of the imaging spot changes as shown in the following figure: Figure 2 As shown, the focus range shown in the figure is ±2000um.

[0028] When the temperature of the thermal effect compensation optical imaging device in Example 1 is increased from 0°C to 100°C, the drift change of the imaging spot is as follows: Figure 3 As shown, the focus range shown in the figure is ±2000um.

[0029] Combination Figure 2 and Figure 3 As shown in the figure, without thermal effect compensation, a temperature difference of 100°C can cause the focus drift to exceed 4mm. However, after using the thermal effect compensation design, the focus drift is less than 10um under the same temperature difference.

[0030] The above is a detailed description of the utility model in combination with the embodiments, but the contents described are only preferred embodiments of the utility model and cannot be considered to limit the scope of implementation of the utility model. All equivalent changes and improvements made within the scope of application of the utility model should still fall within the scope of the patent coverage of the utility model.

Claims

1. A thermal effect compensation optical imaging device, characterized in that: It includes a laser for emitting a laser beam, a focusing lens driven by a voice coil motor for real-time dynamic focusing of the laser beam, and a focusing lens group for accurately imaging the laser beam. The focusing lens group includes at least two lenses with different refractive index temperature coefficient constants.

2. The thermal effect compensation optical imaging device according to claim 1, characterized in that: The focusing lens group comprises two lenses with different refractive index temperature coefficient constants, one of which is an H-QK3L lens and the other is a fused quartz lens.

3. The thermal effect compensation optical imaging device according to claim 2, characterized in that: The H-QK3L lens is a convex lens, and the fused silica lens is a concave lens.

4. The thermal effect compensation optical imaging device according to claim 2, characterized in that: The H-QK3L lens and the fused silica lens are closely arranged along the optical path direction of the laser beam.

5. The thermal effect compensation optical imaging device according to claim 1, characterized in that: A pre-adjustment lens for pre-adjusting the focal length of the entire optical path system during installation is also arranged between the focusing lens and the laser, and the pre-adjustment lens is a convex lens.

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