CN119035576B - A method for compensating for focal length thermal effects in laser 3D metal printing equipment - Google Patents
A method for compensating for focal length thermal effects in laser 3D metal printing equipmentInfo
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- CN119035576B CN119035576B CN202411042528.5A CN202411042528A CN119035576B CN 119035576 B CN119035576 B CN 119035576B CN 202411042528 A CN202411042528 A CN 202411042528A CN 119035576 B CN119035576 B CN 119035576B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/30—Process control
- B22F10/36—Process control of energy beam parameters
- B22F10/366—Scanning parameters, e.g. hatch distance or scanning strategy
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/80—Data acquisition or data processing
- B22F10/85—Data acquisition or data processing for controlling or regulating additive manufacturing processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y50/00—Data acquisition or data processing for additive manufacturing
- B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
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Abstract
本发明公开了一种激光3D金属打印设备的焦距热效应补偿方法，属于激光3D打印领域，该设备的光路系统包括沿着激光光路方向依次设置的调焦镜片、聚焦镜片和反射振镜，调焦镜片和聚焦镜片上均设有温度传感器，调焦镜片通过音圈电机驱动使之沿着光路方向移动；激光3D打印时进行焦距热效应补偿，具体包括以下步骤：S1.通过温度传感器实时监测调焦镜片和聚焦镜片的温度变化；S2.基于实时的调焦镜片和聚焦镜片的温度变化计算调焦镜片和聚焦镜片的间距，并通过音圈电机调整调焦镜片，使得调焦镜片和聚焦镜片的间距满足计算结果。该温度补偿方法能够解决温度变化导致光学镜片焦距发生改变而引起的成像焦点漂移的问题，结构简单，调整过程简单。
This invention discloses a method for compensating for the focal length thermal effect in a laser 3D metal printing device, belonging to the field of laser 3D printing. The optical path system of the device includes a focusing lens, a focusing lens, and a reflecting mirror arranged sequentially along the laser optical path. Temperature sensors are installed on both the focusing and focusing lenses. The focusing lens is driven by a voice coil motor to move along the optical path. Focal length thermal effect compensation during laser 3D printing specifically includes the following steps: S1. Real-time monitoring of the temperature changes of the focusing and focusing lenses using temperature sensors; S2. Calculation of the distance between the focusing and focusing lenses based on the real-time temperature changes, and adjustment of the focusing lens using the voice coil motor to ensure that the distance between the focusing and focusing lenses meets the calculated result. This temperature compensation method can solve the problem of image focus drift caused by changes in the focal length of optical lenses due to temperature changes. It has a simple structure and a simple adjustment process.
Description
Technical Field
The invention belongs to the technical field of laser 3D metal printing equipment, and particularly relates to a focal length thermal effect compensation method of laser 3D metal printing equipment.
Background
The laser 3D metal printing SLM generally uses hundreds of watts to several kilowatts of fiber lasers for scanning printing, an optical imaging system for laser 3D metal printing is disclosed in the patent publication No. CN215867306U, and the focusing device for the 3D printer comprises a light source, a focusing lens group and a beam adjusting lens group, wherein the light source, the focusing lens group and the beam adjusting lens group are sequentially arranged in a shell, the centers of the light source, the focusing lens group and the beam adjusting lens group are positioned on the same straight line, the light source, the focusing lens group and the beam adjusting lens group are fixed with the shell, and the focusing lens group is in sliding connection with the shell.
In the optical imaging system, the glass material of the optical device has a certain absorptivity to high-power laser, and when the laser passes through the optical devices such as the imaging lens, a small part of optical power is lost, and the lost laser leads to the heating temperature of the relevant lens on the optical path to rise. Any optical lens glass material has a refractive index temperature coefficient constant (Constants of dn/dt) that indicates that temperature changes can cause changes in the focal length of the optical lens, ultimately causing imaging focal point temperature drift.
Fused silica glass materials are the most commonly used glass materials for metal laser 3D metal printing due to their good physical properties, low light absorption, and very low coefficient of thermal expansion. Currently, either a biaxial galvanometer system using an F-Theta lens or a dynamic focusing triaxial galvanometer system uses fused silica as a lens material in an optical path. Fused silica has a refractive index temperature coefficient constant of 2.2370E-005, which in a typical triaxial galvanometer system has severely degraded print quality due to imaging focal point drift values of about 4mm caused by temperature variations in optical material characteristics at a focal length of 500mm and a temperature difference of 100 ℃.
In order to compensate the temperature drift of the imaging focus, the conventional processing mode is to strengthen the cooling capacity as much as possible, and the working temperature of the optical lens is limited as much as possible by means of air cooling and the like, 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 for different temperatures, and use a control program to change the print focal length according to temperature to compensate for temperature drift caused by temperature changes. For example, chinese patent with the publication number CN215747081U discloses a real-time automatic compensation stabilizing device and system for laser focus drift, where the device includes a focus compensation module, a driver electrically connected to the focus compensation module, a feedback control module electrically connected to the driver, and a temperature sensor electrically connected to the feedback control module, the focus compensation module includes a concave lens and a convex lens capable of moving relatively, and the feedback control module changes the distance between the concave lens and the convex lens according to temperature data fed back by the temperature sensor, so as to adjust the focus position of the outgoing laser. The compensation mode needs to control the temperature of the optical path system or set different focal length values for different temperatures, so that the optical path system is complex in structure, the whole printing equipment is increased in volume, the focal length values need to be calculated according to different temperatures in the focusing process, and the process is complex.
Disclosure of Invention
The invention provides a focal length thermal effect compensation method of laser 3D metal printing equipment, which aims to solve the problems that in the existing optical imaging system, the lens temperature change can cause imaging focus temperature drift, the optical path system structure is complex and the focusing process is complex for compensating the imaging focus drift.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
The invention relates to a focal length thermal effect compensation method of laser 3D metal printing equipment, wherein an optical path system of the laser 3D metal printing equipment comprises a focusing lens, a reflecting vibrating mirror and a printing working surface which are sequentially arranged along the laser optical path direction, temperature sensors are arranged on the focusing lens and the focusing lens, the focusing lens is driven by a voice coil motor to move along the optical path direction, and the focal length thermal effect compensation is carried out during laser 3D printing, and specifically comprises the following steps:
s1, monitoring temperature changes of a focusing lens and a focusing lens in real time through a temperature sensor;
S2, calculating the distance between the focusing lens and the focusing lens based on the temperature change of the focusing lens and the focusing lens in real time, and adjusting the focusing lens through the voice coil motor so that the distance between the focusing lens and the focusing lens meets the calculation result, wherein the calculation formula of the distance between the focusing lens and the focusing lens is as follows:
(1),
In the formula, deltaT 1 is the temperature variation of the focusing lens, deltaT 2 is the temperature variation of the focusing lens, D is the distance between the focusing lens and the focusing lens obtained by calculation, f1 is the focal length of the focusing lens, and f2 is the focal length of the focusing lens.
Preferably, the focusing lens is a concave lens, the focusing lens is a convex lens, and both the focusing lens and the focusing lens are fused quartz lenses.
Preferably, the focusing lens is mounted on the temperature control base, and when the distance between the focusing lens and the focusing lens is adjusted, the temperature of the focusing lens is adjusted in a fixed proportion through the temperature control base according to the temperature change of the focusing lens.
Preferably, the temperature control base is a semiconductor refrigerator or a water cooling base.
Preferably, the thicknesses of the focusing lens and the focusing lens satisfy the following conditions:
(4),
In the formula, H1 is the thickness of the focusing lens, H2 is the thickness of the focusing lens, and D0 is the distance between the focusing lens and the focusing lens.
Preferably, the focusing lens and the focusing lens are both installed on the heat dissipation base, and the heat conductivity of the heat dissipation base for installing the focusing lens and the focusing lens meets the following conditions:
(5),
In the formula, λ1 is the heat conductivity of the focusing lens, λ2 is the heat conductivity of the focusing lens, W1 is the light absorption power of the focusing lens, W2 is the light absorption power of the focusing lens, and D0 is the distance between the focusing lens and the focusing lens.
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
1. The invention relates to an optical path system of laser 3D metal printing equipment, which comprises a focusing lens, a reflecting vibrating mirror and a printing working surface, wherein the focusing lens, the reflecting vibrating mirror and the printing working surface are sequentially arranged along the optical path direction of laser, temperature sensors are arranged on the focusing lens and the focusing lens, the focusing lens is driven by a voice coil motor to move along the optical path direction, focal length thermal effect compensation is carried out during laser 3D printing, the temperature changes of the focusing lens and the focusing lens are monitored in real time through the temperature sensors, the distance between the focusing lens and the focusing lens is calculated based on the temperature changes of the real-time focusing lens and the focusing lens, and the distance between the focusing lens and the focusing lens is adjusted through the voice coil motor so that the calculated result is met.
2. The focal length thermal effect compensation method of the laser 3D metal printing equipment monitors temperature changes of the focusing lens and the focusing lens in real time through the temperature sensor, calculates the distance between the focusing lens and the focusing lens based on the temperature changes of the focusing lens and the focusing lens in real time, and adjusts the focusing lens through the voice coil motor so that the distance between the focusing lens and the focusing lens meets the calculation result. On the basis, the temperature of the focusing lens and the focusing lens can be adjusted by setting the thickness ratio of the focusing lens and the focusing lens made of the same materials or setting the heat conductivity of the radiating bases of the focusing lens and the focusing lens, so that the structure is not required to be provided with an extra temperature control base, the structure is further simplified, and a thermal compensation method is simplified.
Drawings
Fig. 1 is a block diagram of a laser 3D metal printing apparatus according to the present invention;
FIG. 2 is an equivalent schematic diagram of the optical path system of the laser 3D metal printing device according to the invention;
Fig. 3 is a detailed view of the structure of the optical path system according to embodiment 1.
The reference sign is 1-laser, 2-focusing lens, 3-focusing lens, 4-reflecting galvanometer, 5-printing working face, 6-temperature sensor, 7-temperature control base, 8-heat dissipation base.
Detailed Description
The invention will be further understood by reference to the following examples which are given to illustrate the invention but are not intended to limit the scope of the invention.
Example 1
The invention relates to a focal length thermal effect compensation method of laser 3D metal printing equipment, referring to figure 1, an optical path system of the laser 3D metal printing equipment comprises a focusing lens 2, a focusing lens 3, a reflecting vibrating mirror 4 and a printing working surface 5 which are sequentially arranged along the optical path direction of laser 1, wherein the focusing lens 2 is a concave lens, the focusing lens 3 is a convex lens, both the focusing lens 2 and the focusing lens 3 are fused quartz lenses, the refractive index temperature coefficient constant of fused quartz is 2.2370E-005, the optical path system has very high laser transmittance and very low laser absorptivity, and is the most commonly used glass material in a high-power laser optical system. As is known from the temperature coefficient of refractive index of fused silica, a convex lens having a positive focal length has a larger refractive index and a shorter focal length drifts when the temperature of the lens increases.
Referring to fig. 3, temperature sensors 6 are disposed on the focusing lens 2 and the focusing lens 3, the focusing lens 2 is driven by a voice coil motor (not shown in the drawing) to move along the optical path direction, the focusing lens 3 is in a static state, the focusing lens 2 and the focusing lens 3 are mounted on a heat dissipation base 8 to reduce the temperature rise, in this embodiment, the heat conductivity of the two heat dissipation bases 8 is the same, the thicknesses of the focusing lens 2 and the focusing lens 3 have no specific requirement, referring to fig. 3, a temperature control base 7 is disposed at the bottom of the heat dissipation base 8 of the focusing lens 3, and the temperature control base 7 is a semiconductor refrigerator or a water cooling base.
When the laser 3D metal printing equipment performs laser 3D printing, as the refractive index is increased when the temperature of the focusing lens 3 is increased, the focal length can drift to be shortened, so that focal length thermal effect compensation is required, and the method specifically comprises the following steps of:
S1, monitoring temperature changes of a focusing lens 2 and a focusing lens 3 in real time through a temperature sensor 6;
S2, calculating the distance between the focusing lens 2 and the focusing lens 3 based on the temperature change of the focusing lens 2 and the focusing lens 3 in real time, and adjusting the focusing lens 2 through a voice coil motor so that the distance between the focusing lens 2 and the focusing lens 3 meets the calculation result, wherein the focal length of the focusing lens 2 is f1 (f 1< 0), the focal length of the focusing lens 3 is f2, and the whole light path focuses an incident parallel light beam into a light spot at the printing working surface 5, so that the equivalent focal length of the whole light path is a positive focal length, and therefore, -f1> f2 exists, the equivalent distance between the focusing lens 2 and the focusing lens 3 is D, and the distance between the focusing lens 3 and the printing working surface 5 is L, so that the following formula is provided:
,
According to the definition of the refractive index temperature coefficient constant of fused silica, in a certain temperature range, the refractive index change of fused silica is proportional to the temperature change, that is, the focal length change of a lens is proportional to the temperature change, so it is assumed that the relationship between the temperature change value deltat and the focal length change value deltaf is as follows, wherein k is a constant coefficient:
,
when the temperature change value of the focusing lens 2 is Δt1 and the temperature change of the focusing lens 3 is Δt2, the following formula is given:
,
Since-f 1> f2, Δt1> Δt2;
The ratio of focal length drift caused by temperature change of any glass material is not high, and when the refractive index temperature coefficient constant of fused quartz with the numerical value as listed above is 2.2370E-005, namely the lens temperature change is 100 ℃, the focal length change rate is only 0.2237 percent, namely delta f < < f, so that the above formula can be simplified as follows:
(1),
Equation 1 is a calculation equation of a distance between the focusing lens 2 and the focusing lens 3, wherein Δt1 is a temperature variation of the focusing lens 2, Δt2 is a temperature variation of the focusing lens 3, D is a calculated distance between the focusing lens 2 and the focusing lens 3, f1 is a focal length of the focusing lens 2, and f2 is a focal length of the focusing lens 3.
During real-time dynamic focusing of the focusing lens 2 in the printing process, the distance D between the focusing lens 2 and the focusing lens 3 is in a changing state, and during 3D printing or laser processing, in order to match the working distance change of a scanning laser spot in real time, the frequency response of the focusing lens 2 is required to be very high, the focusing lens 2 can be quickly moved to a proper position to compensate the focal length, so that the moving stroke of the focusing lens 2 is recorded as delta D which cannot be too long, and in actual engineering, delta D is not more than 1mm in principle, namely, the distance between the focusing lens 2 and the focusing lens 3 is changed in D0 and D0 plus delta D, wherein D0 is the initial distance between the focusing lens 2 and the focusing lens 3.
According to the characteristic-f 1> f2 of the optical path system, the characteristic value range of D-f1> f2, f2 is typically 300-1000 mm, so Δd < < f2, when the focusing lens 2 moves to the other end, the formula of the temperature rise of the focusing lens 3 is as follows:
(2),
In the formula, deltaT 2' is the temperature change when the lens moves to the other end, D0 is the distance between the focusing lens 2 and the focusing lens 3, deltaD is the distance change amount between the focusing lens 2 and the focusing lens 3 before and after the focusing lens 2 is adjusted, and in an actual 3D printing light path, the value of D-f1 is usually hundreds times or thousands times of DeltaD, so DeltaD < < D-f1.
Thus, equation 2 can be expressed as:
(3),
Therefore, the temperature change Δt1 of the focusing lens 2 and the temperature change Δt2 of the focusing lens 3 can maintain a stable proportional relationship, and when the distance between the focusing lens 2 and the focusing lens 3 is adjusted, the temperature adjustment of the temperature control base 7 under the focusing lens 3 does not need to be frequently adjusted according to different printing focal lengths, and only the temperature of the focusing lens 3 needs to be adjusted in a fixed proportion by the temperature control base 7 according to the temperature change of the focusing lens 2.
Example 2
The invention relates to a focal length thermal effect compensation method of laser 3D metal printing equipment, referring to figure 1, an optical path system of the laser 3D metal printing equipment comprises a focusing lens 2, a focusing lens 3, a reflecting vibrating mirror 4 and a printing working surface 5 which are sequentially arranged along the optical path direction of laser 1, wherein the focusing lens 2 is a concave lens, the focusing lens 3 is a convex lens, both the focusing lens 2 and the focusing lens 3 are fused quartz lenses, the refractive index temperature coefficient constant of fused quartz is 2.2370E-005, the optical path system has very high laser transmittance and very low laser absorptivity, and is the most commonly used glass material in a high-power laser optical system. As is known from the temperature coefficient of refractive index of fused silica, a convex lens having a positive focal length has a larger refractive index and a shorter focal length drifts when the temperature of the lens increases.
Referring to fig. 2, the focusing lens 2 and the focusing lens 3 are provided with temperature sensors 6, the focusing lens 2 is driven by a voice coil motor (not shown) to move along the direction of the optical path, the focusing lens 3 is in a static state, and the focusing lens 2 and the focusing lens 3 are mounted on a heat dissipation base 8 to reduce the temperature rise.
When the laser 3D metal printing equipment performs laser 3D printing, as the refractive index is increased when the temperature of the focusing lens 3 is increased, the focal length can drift to be shortened, so that focal length thermal effect compensation is required, and the method specifically comprises the following steps of:
S1, monitoring temperature changes of a focusing lens 2 and a focusing lens 3 in real time through a temperature sensor 6;
S2, calculating the distance between the focusing lens 2 and the focusing lens 3 based on the temperature change of the focusing lens 2 and the focusing lens 3 in real time, and adjusting the focusing lens 2 through a voice coil motor so that the distance between the focusing lens 2 and the focusing lens 3 meets the calculation result, wherein the focal length of the focusing lens 2 is f1 (f 1< 0), the focal length of the focusing lens 3 is f2, and the whole light path focuses an incident parallel light beam into a light spot at the printing working surface 5, so that the equivalent focal length of the whole light path is a positive focal length, and therefore, -f1> f2 exists, the equivalent distance between the focusing lens 2 and the focusing lens 3 is D, and the distance between the focusing lens 3 and the printing working surface 5 is L, so that the following formula is provided:
,
According to the definition of the refractive index temperature coefficient constant of fused silica, in a certain temperature range, the refractive index change of fused silica is proportional to the temperature change, that is, the focal length change of a lens is proportional to the temperature change, so it is assumed that the relationship between the temperature change value deltat and the focal length change value deltaf is as follows, wherein k is a constant coefficient:
,
when the temperature change value of the focusing lens 2 is Δt1 and the temperature change of the focusing lens 3 is Δt2, the following formula is given:
,
Since-f 1> f2, Δt1> Δt2;
The ratio of focal length drift caused by temperature change of any glass material is not high, and when the refractive index temperature coefficient constant of fused quartz with the numerical value as listed above is 2.2370E-005, namely the lens temperature change is 100 ℃, the focal length change rate is only 0.2237 percent, namely delta f < < f, so that the above formula can be simplified as follows:
(1),
That is, equation 1 is a calculation equation for the distance between the focusing lens 2 and the focusing lens 3, where Δt1 is the temperature variation of the focusing lens 2, Δt2 is the temperature variation of the focusing lens 3, D is the calculated distance between the focusing lens 2 and the focusing lens 3, f1 is the focal length of the focusing lens 2, and f2 is the focal length of the focusing lens 3.
In this embodiment, the thermal conductivities of the two heat dissipation bases 8 are the same, the thermal conductivities of the two heat dissipation bases 8 are λ, no additional heat dissipation device is added, so that the external heat dissipation coefficients of the lens groups are the same, the equivalent thicknesses of the focusing lens 2 and the focusing lens 3 are H1 and H2 respectively, and the power of the laser is W, and then the following formula is provided:
the method comprises the following steps of:
(4),
in the formula, H1 is the thickness of the focusing lens 2, H2 is the thickness of the focusing lens 3, and D0 is the distance between the focusing lens 2 and the focusing lens 3;
when the thicknesses of the two groups of lenses meet the formula, different temperature rises are generated by the two groups of lenses when the same laser passes through, and finally, imaging focus can not drift.
Example 3
The invention relates to a focal length thermal effect compensation method of laser 3D metal printing equipment, referring to figure 1, an optical path system of the laser 3D metal printing equipment comprises a focusing lens 2, a focusing lens 3, a reflecting vibrating mirror 4 and a printing working surface 5 which are sequentially arranged along the optical path direction of laser 1, wherein the focusing lens 2 is a concave lens, the focusing lens 3 is a convex lens, both the focusing lens 2 and the focusing lens 3 are fused quartz lenses, the refractive index temperature coefficient constant of fused quartz is 2.2370E-005, the optical path system has very high laser 1 transmittance and very low laser absorptivity, and is the most commonly used glass material in a high-power laser optical system. As is known from the temperature coefficient of refractive index of fused silica, a convex lens having a positive focal length has a larger refractive index and a shorter focal length drifts when the temperature of the lens increases.
Referring to fig. 2, the focusing lens 2 and the focusing lens 3 are provided with temperature sensors 6, the focusing lens 2 is driven by a voice coil motor (not shown) to move along the direction of the optical path, the focusing lens 3 is in a static state, and the focusing lens 2 and the focusing lens 3 are mounted on a heat dissipation base 8 to reduce the temperature rise.
When the laser 3D metal printing equipment performs laser 3D printing, as the refractive index is increased when the temperature of the focusing lens 3 is increased, the focal length can drift to be shortened, so that focal length thermal effect compensation is required, and the method specifically comprises the following steps of:
S1, monitoring temperature changes of a focusing lens 2 and a focusing lens 3 in real time through a temperature sensor 6;
S2, calculating the distance between the focusing lens 2 and the focusing lens 3 based on the temperature change of the focusing lens 2 and the focusing lens 3 in real time, and adjusting the focusing lens 2 through a voice coil motor so that the distance between the focusing lens 2 and the focusing lens 3 meets the calculation result, wherein the focal length of the focusing lens 2 is f1 (f 1< 0), the focal length of the focusing lens 3 is f2, and the whole light path focuses an incident parallel light beam into a light spot at the printing working surface 5, so that the equivalent focal length of the whole light path is a positive focal length, and therefore, -f1> f2 exists, the equivalent distance between the focusing lens 2 and the focusing lens 3 is D, and the distance between the focusing lens 3 and the printing working surface 5 is L, so that the following formula is provided:
,
According to the definition of the refractive index temperature coefficient constant of fused silica, in a certain temperature range, the refractive index change of fused silica is proportional to the temperature change, that is, the focal length change of a lens is proportional to the temperature change, so it is assumed that the relationship between the temperature change value deltat and the focal length change value deltaf is as follows, wherein k is a constant coefficient:
,
when the temperature change value of the focusing lens 2 is Δt1 and the temperature change of the focusing lens 3 is Δt2, the following formula is given:
,
Since-f 1> f2, Δt1> Δt2;
The ratio of focal length drift caused by temperature change of any glass material is not high, and when the refractive index temperature coefficient constant of fused quartz with the numerical value as listed above is 2.2370E-005, namely the lens temperature change is 100 ℃, the focal length change rate is only 0.2237 percent, namely delta f < < f, so that the above formula can be simplified as follows:
(1),
That is, equation 1 is a calculation equation for the distance between the focusing lens 2 and the focusing lens 3, where Δt1 is the temperature variation of the focusing lens 2, Δt2 is the temperature variation of the focusing lens 3, D is the calculated distance between the focusing lens 2 and the focusing lens 3, f1 is the focal length of the focusing lens 2, and f2 is the focal length of the focusing lens 3.
In this embodiment, no additional heat dissipating device is added to both heat dissipating bases 8, but the heat conductivities of the two heat dissipating bases 8 are different, and the absorption power of the two sets of lenses to the laser light 1 is calculated from the power of the incident laser light 1, the total thickness of the lenses and the index related to the absorptivity of the glass material, assuming that the laser light 1 passes through the focusing lens 2 and the focusing lens 3, and the absorption powers of the two sets of lenses to the laser light 1 are respectively W1 and W2. Assuming that the thermal conductivity of the equivalent heat dissipation of the focusing lens 2 to the external environment is λ1 and the thermal conductivity of the equivalent heat dissipation of the focusing lens 3 to the external environment is λ2, the following formula is given:
,
,
according to this formula, when λ1 and λ2 satisfy the following relationship, laser 1 passes through the lens group, and the focal length of the final imaging position is not affected when the lens is temperature-rising:
(5),
in the formula, λ1 is the heat conductivity of the focusing lens 2, λ2 is the heat conductivity of the focusing lens 3, W1 is the light absorption power of the focusing lens 2, W2 is the light absorption power of the focusing lens 3, and D0 is the distance between the focusing lens 2 and the focusing lens 3.
According to the basic knowledge of the thermal conductivity, the thermal conductivity λ is inversely proportional to the heat dissipation area of the material and directly proportional to the equivalent thickness of the heat generation source and the outside, so when designing the heat dissipation bases 8 of the focusing lens 2 and the focusing lens 3, the area of the heat dissipation bases 8 of the two groups of lenses and the equivalent thickness of the heat dissipation bases relative to the outside environment can be designed according to the calculation result of the formula, or simulation software is used for simulation, so that the heat dissipation coefficients of the heat dissipation bases 8 of the two groups of lenses meet the requirement of the formula, which is the conventional knowledge of the design of the heat dissipation bases 8 is not repeated here.
The present invention has been described in detail with reference to the embodiments, but the description is only the preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. All equivalent changes and modifications within the scope of the present invention should be considered as falling within the scope of the present invention.
Claims (5)
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| CN106216847A (en) * | 2016-07-29 | 2016-12-14 | 广州创乐激光设备有限公司 | A kind of Z axis dynamic compensation marking device and method |
| CN117103684A (en) * | 2023-09-27 | 2023-11-24 | 爱司凯科技股份有限公司 | Scanning system for reducing inertia of vibrating mirror with long working distance |
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| CN106216847A (en) * | 2016-07-29 | 2016-12-14 | 广州创乐激光设备有限公司 | A kind of Z axis dynamic compensation marking device and method |
| CN117103684A (en) * | 2023-09-27 | 2023-11-24 | 爱司凯科技股份有限公司 | Scanning system for reducing inertia of vibrating mirror with long working distance |
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