Design method of thermal compensation lens for D-shaped collimating lens
By placing a compensation lens behind the D-shaped collimating lens and adjusting the focal length and spacing, the problem of focal length drift in high-power lasers was solved, achieving a high-precision thermal compensation effect and avoiding material failure and process complexity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA NAT HEAVY MACHINERY RES INSTCO
- Filing Date
- 2026-02-06
- Publication Date
- 2026-05-15
AI Technical Summary
In high-power lasers or extreme environments, D-shaped collimating lenses suffer from focal length drift due to thermal effects. Existing compensation methods have problems such as insufficient accuracy, limited material selection, and structural failure.
A compensation lens is placed coaxially behind the main lens. The parameters are dynamically matched through a two-degree-of-freedom adjustment mechanism (focal length and spacing). The focal length formula of the combined optical system is used to eliminate the effect of thermal focal shift. The compensation lens is made of the same material as the main lens.
It achieves submicron level compensation accuracy, avoids thermal damage to materials, simplifies manufacturing processes, and improves beam quality and imaging accuracy.
Smart Images
Figure CN122043732A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of thermal effect compensation methods, and specifically relates to a design method for a thermal compensation lens for a D-shaped collimating lens. Background Technology
[0002] In fields such as laser processing, precision measurement, and semiconductor lithography, D-shaped collimating lenses serve as core optical components, undertaking the crucial task of collimating and efficiently transmitting high-power laser beams. However, when the laser power is high (e.g., above kilowatts) or operates in extreme environments, the lens material experiences a temperature rise due to the absorption of light energy and environmental thermal radiation, leading to a series of thermal effects: (1) Changes in material parameters: The refractive index drifts with increasing temperature (Δn=αΔT, where α is the temperature coefficient of refractive index), resulting in changes in optical power; (2) Distortion of geometric parameters: The lens thickness and radius of curvature deform due to thermal expansion, and ΔR is related to the coefficient of thermal expansion β and the temperature gradient, further exacerbating the focal length shift. These effects cause the system focal length to deviate from the design value, resulting in an increased beam divergence angle, uneven energy distribution, and even optical axis shift, severely affecting imaging accuracy or processing quality.
[0003] To address the thermal effect problem, existing technologies have proposed various compensation schemes, but all have significant limitations: existing compensation methods typically employ mechanical compensation, material / optical compensation, or traditional combined lens designs. Mechanical compensation achieves compensation by adjusting the lens position or focal length, but D-shaped collimating lenses have extremely short focal lengths, typically on the millimeter level. The resolution and travel of mechanical adjustment mechanisms are insufficient to meet the requirements for high-precision, wide-temperature-range compensation, and dynamic adjustment easily introduces vibration noise. Material / optical compensation relies on special materials, such as low-expansion-coefficient glass or thermo-optically controllable crystals, due to their thermal properties. However, high-power scenarios impose stringent requirements on the thermal damage threshold and chemical stability of materials, resulting in very few available materials. Furthermore, the refractive index-temperature curves of different materials are significantly nonlinear, limiting compensation accuracy. While traditional combined lens designs can compensate for thermal effects through matching the spacing and focal length of the two lenses, they fail to establish the coupling relationship between the thermal effect and the refractive index (Δn), radius of curvature (ΔR) of the main lens, and the parameters of the compensation lens. Adjusting only a single parameter, such as fixing the focal length or spacing of the compensation lens, leads to compensation failure. For example, neglecting the influence of thermal deformation of the main lens on the radius of curvature ΔR and the geometric relationship between the lens thickness d and the aperture L, or failing to consider the thermal mismatch between the compensation lens and the main lens materials, the inconsistency of the thermal expansion coefficient β and the refractive index temperature coefficient α of different materials will ultimately cause the system focal length drift. Summary of the Invention
[0004] To address the problem of system focal length drift caused by thermal effects in existing D-shaped collimating lenses, the present invention aims to provide a design method for a thermal compensation lens for D-shaped collimating lenses. The present invention places a compensation lens coaxially behind the main lens and establishes a two-degree-of-freedom adjustment mechanism, namely the focal length and spacing of the compensation lens. By dynamically matching parameters using the focal length formula of the combined optical system, the system focal length is always equal to the initial focal length of the main lens, thus completely eliminating the influence of thermally induced focal shift on beam quality.
[0005] The technical solution of the present invention is: a design method for a thermal compensation lens for a D-shaped collimating lens, comprising the following steps: S1: Based on the refractive index change Δ of the main lens due to thermal effect under the laser's operating power. n and the change in radius of curvature Δ R After determining the focal shift and focal length of the primary lens f 1′; S2: Set the combined back focal length of the primary lens and compensating lens. f The focal length is equal to the initial focal length of the primary lens. f 1; S3: Place a compensating lens coaxially behind the main lens, and adjust the focal length of the compensating lens. f 2 and its distance from the main lens d 1. Complete the design of the thermal compensation lens, wherein the radius of curvature of the compensation lens is... R 2 is set to the radius of curvature of the primary lens. R 1. Same as above, compensating lens thickness d The second is determined by the geometric relationship between its radius of curvature and aperture, as follows: ; In the formula, L2 is the aperture of the compensating lens, and R2 is the radius of curvature of the compensating lens.
[0006] In step S1, the refractive index change Δ caused by the thermal effect n Specifically: Δ n = α Δ T In the formula, α is the rate of change of the refractive index of the principal lens, and ΔT is the temperature rise.
[0007] In step S1, the change in radius of curvature ΔR caused by the thermal effect is specifically as follows: In the formula, β is the thermal expansion coefficient of the main lens, L is the aperture of the main lens, d is the thickness of the main lens, and ΔT is the temperature rise.
[0008] The method for calculating the temperature rise ΔT is as follows: ; In the formula, a is the rate of change of the refractive index of the main lens, P is the operating power of the laser, r is the reflectivity, m is the mass of the main lens, and c is the specific heat capacity.
[0009] The focal length f1′ after focus shift is specifically: ;
[0010] In the formula, n0 is the refractive index of the lens, R1 is the radius of curvature of the main lens, and ∆n and ∆R are the changes in refractive index and radius of curvature caused by thermal effects, respectively.
[0011] The focal length f2 of the compensation lens is specifically expressed as: In the formula, f1 is the focal length of the main lens before focal shift, f1′ is the focal length after focal shift, and d1 is the distance between the compensation lens and the main lens.
[0012] The distance d1 between the compensation lens and the main lens is specifically expressed as follows:
[0013] In the formula, f 1 is the focal length of the main lens before focal shift, f1′ is the focal length after focal shift, and ∆n and ∆R are the changes in refractive index and radius of curvature caused by thermal effects, respectively.
[0014] The combined focal length of the primary lens and the compensating lens f Specifically:
[0015] In the formula, f f1 is the focal length of the main lens before focal shift, f1′ is the focal length after focal shift, and f2 is the focal length of the compensating lens.
[0016] The technical advantages of this invention are as follows: 1. By placing a compensation lens coaxially behind the main lens and establishing a two-degree-of-freedom adjustment mechanism, namely the focal length and spacing of the compensation lens, and dynamically matching parameters using the focal length formula of the combined optical system, the system focal length is always equal to the initial focal length of the main lens, thus completely eliminating the influence of thermally induced focal shift on beam quality. 2. This invention, by adjusting the thermal refractive index change Δn and the radius of curvature change ΔR of the main lens in relation to the focal length of the compensation lens... f 2. Spacing d 1. Incorporate into a unified model and utilize formulas f 2−1= f 1′− d 1 f 1′ f 1−1 Dynamic matching compensation of lens focal length and spacing ensures that the focal length of the combined system strictly returns to the initial value of the primary lens. f1. This invention solves the problem of insufficient adjustment range caused by short focal length in mechanical compensation methods, improving compensation accuracy to the sub-micron level. 3. This invention uses the same material as the main lens to fabricate the compensation lens, i.e., β and α are consistent, eliminating internal stress caused by thermal expansion mismatch and avoiding lens failure caused by differences in material thermal damage thresholds in high-power scenarios. Simultaneously, the radius of curvature of the compensation lens... R 2= R 1. The design simplifies geometric symmetry, matching the asymmetric structure of the D-shaped lens, making thermal deformation distribution more controllable. 4. This invention derives the radius of curvature of the compensating lens under the influence of thermal effects based on the lens manufacturer's formula. R 2 and thickness d The explicit expression in equation 2 avoids the iterative trial-and-error process of traditional numerical simulations. Furthermore, the explicit inclusion of lens thickness d and aperture L directly guides micro / nano fabrication, reducing process tolerance requirements.
[0017] The following will provide further explanation in conjunction with the accompanying drawings. Attached Figure Description
[0018] Figure 1 This is a flowchart of a design method for a thermal compensation lens for a D-shaped collimating lens according to the present invention.
[0019] Figure 2 This is a schematic diagram illustrating the focal shift of the refractive index of the thermally collimating D lens of the present invention.
[0020] Figure 3 This is a schematic diagram of the focal shift of the collimating D lens that compensates for thermal effects according to the present invention. Detailed Implementation Example 1
[0021] like Figures 1-3 As shown, a design method for a thermal compensation lens for a D-shaped collimating lens includes the following steps: S1: Based on the refractive index change Δ of the main lens due to thermal effect under the laser's operating power. n and the change in radius of curvature Δ R After determining the focal shift and focal length of the primary lens f 1′; S2: Set the combined back focal length of the primary lens and compensating lens. f The focal length is equal to the initial focal length of the primary lens. f 1; S3: Place a compensating lens coaxially behind the main lens, and adjust the focal length of the compensating lens. f 2 and its distance from the main lens d 1. Complete the design of the thermal compensation lens, wherein the radius of curvature of the compensation lens is... R 2 is set to the radius of curvature of the primary lens. R 1. Same as above, compensating lens thicknessd The second is determined by the geometric relationship between its radius of curvature and aperture, as follows: ; In the formula, L2 is the aperture of the compensating lens, and R2 is the radius of curvature of the compensating lens.
[0022] Furthermore, in step S1, the refractive index change Δ caused by the thermal effect n Specifically: Δ n = α Δ T In the formula, α is the rate of change of the refractive index of the principal lens, and ΔT is the temperature rise.
[0023] Furthermore, in step S1, the change in radius of curvature ΔR caused by the thermal effect is specifically as follows: In the formula, β is the thermal expansion coefficient of the main lens, L is the aperture of the main lens, d is the thickness of the main lens, and ΔT is the temperature rise.
[0024] Furthermore, the method for calculating the temperature rise ΔT is as follows: ; In the formula, a is the rate of change of the refractive index of the main lens, P is the operating power of the laser, r is the reflectivity, m is the mass of the main lens, and c is the specific heat capacity.
[0025] Furthermore, the focal length f1′ after focus shift is specifically: ;;
[0026] In the formula, n0 is the refractive index of the lens, R1 is the radius of curvature of the main lens, and ∆n and ∆R are the changes in refractive index and radius of curvature caused by thermal effects, respectively.
[0027] Furthermore, the focal length f2 of the compensation lens is specifically expressed as follows: In the formula, f1 is the focal length of the main lens before focal shift, f1′ is the focal length after focal shift, and d1 is the distance between the compensation lens and the main lens.
[0028] Furthermore, the distance d1 between the compensation lens and the main lens is specifically expressed as follows:
[0029] In the formula, f 1 is the focal length of the main lens before focal shift, f1′ is the focal length after focal shift, and ∆n and ∆R are the changes in refractive index and radius of curvature caused by thermal effects, respectively.
[0030] Furthermore, due to the change in refractive index and thermal expansion of the collimating D lens (the primary lens) caused by thermal effects, a focal shift occurs in the optical lens. A compensating lens is designed to compensate for this focal shift. The compensating lens and the primary lens are made of the same material, such as... Figure 2 As shown. The compensating lens is placed behind the main lens, at a distance d2 from the main lens, as... Figure 3 As shown in the figure. R1 and R2 are the radii of curvature of the primary lens and the compensating lens, respectively, n0 is the refractive index of the lens, and L is the aperture of the lens. The combined focal length of the primary lens and the compensating lens is... f Specifically:
[0031] In the formula, f f1 is the focal length of the main lens before focal shift, f1′ is the focal length after focal shift, and f2 is the focal length of the compensating lens.
[0032] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A design method for a thermal compensation lens for a D-shaped collimating lens, characterized in that: Includes the following steps: S1: Based on the refractive index change Δ of the main lens due to thermal effect under the laser's operating power. n and the change in radius of curvature Δ R After determining the focal shift and focal length of the primary lens f 1′; S2: Set the combined back focal length of the primary lens and compensating lens. f The focal length is equal to the initial focal length of the primary lens. f 1; S3: Place a compensating lens coaxially behind the main lens, and adjust the focal length of the compensating lens. f 2 and its distance from the main lens d 1. Complete the design of the thermal compensation lens, wherein the radius of curvature of the compensation lens is... R 2 is set to the radius of curvature of the primary lens. R 1. Same as above, compensating lens thickness d The second is determined by the geometric relationship between its radius of curvature and aperture, as follows: ； In the formula, L2 is the aperture of the compensating lens, and R2 is the radius of curvature of the compensating lens.
2. The design method for a thermal compensation lens for a D-shaped collimating lens according to claim 1, characterized in that: In step S1, the refractive index change Δ caused by the thermal effect n Specifically: D n = α D T； In the formula, α is the rate of change of the refractive index of the principal lens, and ΔT is the temperature rise.
3. The design method for a thermal compensation lens for a D-shaped collimating lens according to claim 2, characterized in that: In step S1, the change in radius of curvature ΔR caused by the thermal effect is specifically as follows: ； In the formula, β is the thermal expansion coefficient of the main lens, L is the aperture of the main lens, d is the thickness of the main lens, and ΔT is the temperature rise.
4. The design method for a thermal compensation lens for a D-shaped collimating lens according to claim 3, characterized in that: The method for calculating the temperature rise ΔT is as follows: ； In the formula, a is the rate of change of the refractive index of the main lens, P is the operating power of the laser, r is the reflectivity, m is the mass of the main lens, and c is the specific heat capacity.
5. The design method for a thermal compensation lens for a D-shaped collimating lens according to claim 4, characterized in that: The focal length f1′ after focus shift is specifically: ； In the formula, n0 is the refractive index of the lens, R1 is the radius of curvature of the main lens, and ∆n and ∆R are the changes in refractive index and radius of curvature caused by thermal effects, respectively.
6. The design method for a thermal compensation lens for a D-shaped collimating lens according to claim 5, characterized in that: The focal length f2 of the compensation lens is specifically expressed as: ； In the formula, f1 is the focal length of the main lens before focal shift, f1′ is the focal length after focal shift, and d1 is the distance between the compensation lens and the main lens.
7. The design method for a thermal compensation lens for a D-shaped collimating lens according to claim 6, characterized in that: The distance d1 between the compensation lens and the main lens is specifically expressed as follows: ； In the formula, f 1 is the focal length of the main lens before focal shift, f1′ is the focal length after focal shift, and ∆n and ∆R are the changes in refractive index and radius of curvature caused by thermal effects, respectively.
8. The design method for a thermal compensation lens for a D-shaped collimating lens according to claim 7, characterized in that: The combined focal length of the primary lens and the compensating lens f Specifically: ； In the formula, f f1 is the focal length of the main lens before focal shift, f1′ is the focal length after focal shift, and f2 is the focal length of the compensating lens.