A design method for an optical system that generates uniform ring light

Abstract

The present invention discloses a method for designing an optical system that produces uniform annular light, and belongs to the field of optical design. Technical solution: The optical system involved is formed by a combination of a conical mirror and a cylindrical mirror. A beam of circular parallel light is incident on the conical mirror, and the light emitted from the conical mirror is reflected on the cylindrical mirror. The concave and convex areas on the cylindrical mirror divide the light beam, and then are stacked and converged at the focal plane at the same time to form a focused annular light of a certain width. The conical mirror is formed by a cone line rotating around the optical axis Z; the concave and convex areas on the cylindrical mirror are a curved surface formed by a plurality of parabolas with alternating concave and convex rotating around the optical axis Z; the focused annular light has a width of 6 mm and an energy uniformity of more than 89%. In the present invention, the more concave and convex areas there are on the cylindrical mirror, the higher the uniformity of the annular light on the focal plane.

Description

Technical Field

[0001] The invention belongs to the field of optical system design, and in particular relates to an optical system design method for generating uniform annular light. Background Art

[0002] The shaping and control of light beams are key technical issues in the development of the optical industry towards advancement, lightweighting, and high performance, and play an important role in fields such as optical fiber communications, laser cutting, and laser welding. Ring beams are usually used for welding industrial thin-walled pipes. Most of these ring lights are shaped by an optical system consisting of a conical lens and a focusing mirror. For example, the utility model patent CN201820983136.2 discloses "an annular focused beam system" or the invention patent CN202011544208.1 discloses "an annular light laser welding device." However, the technical methods involved do not solve problems such as uneven energy distribution of the focal plane ring light. For annular welds with larger welds, defocused welding is often used. Not only is the ring light energy seriously dissipated, but the weld also suffers from thermal deformation, and its application scenarios are limited. Summary of the Invention

[0003] The present invention aims to provide a method for designing a compact reflective optical system. By using a designed cylindrical surface integral mirror, a focused ring light of arbitrary size and uniform energy distribution can be generated. This method not only provides a high degree of design freedom but also exhibits high-power laser resistance, a compact structure, and ease of fabrication in practical applications. The technical solution for achieving this objective is that the optical system is designed to be formed by combining a conical mirror and a cylindrical surface integral mirror. The conical mirror is formed by a cone line rotating one revolution around the optical axis Z. The cone line equation L(x,z) in the XOZ plane is defined as follows:

[0004] Z= cot(θ / 2)·X+Z1 (1)

[0005] Z1 is the distance between the conical mirror vertex and the X axis, and θ is the conical mirror vertex angle.

[0006] The cylindrical surface integral mirror is a continuous concave-convex surface formed by rotating a plurality of concave-convex parabolas around the optical axis Z. The specific design steps of the cylindrical surface integral mirror are:

[0007] First calculate the initial conditions: according to the size of the focal plane ring light width CD, the incident light beam on the conical mirror is divided into 1, 2, 3.. areas, and the width of each area in the Z axis direction is Z 11 ,Z 12 ,Z 13 ..., now determine the specific coordinates of point C and point D, Z 11 ,Z 12 ,Z 13 ...are all known values.

[0008] Analyzing the optical path propagation process: the light from regions 1, 3, etc. is reflected by the concave surface of the integrator, converges at focal points F1 and F3 respectively, and then diverges to CD. The light from region 2 is reflected by the convex surface, diverges in the opposite direction to CD along the virtual focus F2, and the width of region 2 is smaller than the length of CD.

[0009] The final calculation parameters: When the conical mirror vertex angle is θ, F1(X F1 ,Z F1 ) is the concave parabola equation P n1 (X n1 ,Z n1 ) can be defined as follows:

[0010] (sinθ·(Z n1 -Z F1 )+cosθ·(X n1 -X F1 )) 2 =-4f n1 (sinθ·(X n1 -X F1 )-cosθ·(Z n1 -Z F1 )-f n1 ) (2)

[0011] Points A and B are located on the parabola, and F1 is the intersection of lines AD and BC; A(X A ,Z A )、C(X C ,Z C ) and D(X D ,Z D ) are known coordinates, point B(X B ,Z B )Z B =Z A +Z 11 , so the unknown parameter X B , focus F1 coordinates and focal length f n1 This can be solved by the following system of equations:

[0012]

[0013] Similarly, with F2(X F2 ,Z F2 ) is the convex parabola equation P n2 (X n2 ,Z n2 ) can be defined as follows:

[0014] (sinθ·(Z n2 -Z F2 )+cosθ·(X n2 -XF2 )) 2 =4f n2 (sinθ·(X n2 -X F2 )-cosθ·(Z n2 -Z F2 )+f n2 ) (4)

[0015] B(X B ,Z B )、C(X C ,Z C ) and D(X D ,Z D ) are known coordinates, point E(X E ,Z E )Z E =Z B +Z 12 , combined with equation group (3), the focus F2 coordinates and focal length f in equation (4) can be calculated n2 ; Calculate the parameters of other concave and convex parabolas according to the above method, and finally obtain the complete cylindrical area component mirror.

[0016] In the above technical solution, the energy of the Gaussian beam incident on regions 1-3 is distributed monotonically decreasingly. After being reflected from the concave surface above region 1 to CD, its energy gradually decreases from point D to point C. On the other hand, the energy of the light reflected from region 2 to CD gradually increases from point D to point C. Therefore, the light on the cone surface is reflected by multiple concave and convex surfaces and is superimposed at CD in a decreasing and increasing manner, which concentrates the light intensity while also increasing its uniformity.

[0017] The above description is only an overview of the method of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following specifically cites preferred embodiments and describes them in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of a method for designing an optical system for generating uniform annular light;

[0019] Figure 2 A schematic diagram of the optical system structure provided by an embodiment of the present invention;

[0020] Figure 3 A schematic diagram of an energy distribution curve provided by an embodiment of the present invention;

[0021] Figure 2 Marking explanation: S1, conical mirror; S2, cylindrical mirror; S3, focused annular light. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] If the incident parallel laser diameter is known to be 10mm, an optical system is required to be designed to produce a focused ring light with an outer diameter of 12mm, an inner diameter of 6mm, and a width of 6mm at a laser working distance Z1 = 150mm, with a uniformity of more than 85%. Figure 1 The entire system can be designed by combining a conical mirror and a cylindrical integral mirror. The selected conical mirror has an apex angle of 86°, and is formed by rotating its cone line around the optical axis Z. According to the above formula (1), the cone line equation L(x,z) defined in the XOZ plane is:

[0024] Z=1.0724·X-150(5)

[0025] Secondly, the ring light width CD is known to be 6mm. The incident light beam on the conical mirror is divided into 6 regions. The width of each region in the Z-axis direction is Z 11 =Z 12 =Z 13 ...=2mm. When the apex angle of the conical mirror is 86°, the concave parabola equation P in region 1 can be calculated by combining formula (2) and formula (3): n1 (X n1 ,Z n1 ) parameters: focus F1 = (23.525, -90.648) and focal length f n1 =33.878mm.

[0026] Similarly, the equation of the convex parabola in region 2 is P n2 (X n2 ,Z n2 ) parameters: focus F2 = (96.977, -415.039) and focal length f n2 =157.743mm. Calculate the other parameters of the concave-convex parabola using the above method, as follows:

[0027] Concave parabola P n3 (X n3 ,Z n3 ): Focus F3 = (25.283, -87.971) and focal length f n3 =34.024mm,

[0028] Convex parabola P n4 (X n4 ,Z n4 ): Focus F4 = (106.682, -409.323) and focal length f n4 =161.119mm,

[0029] Concave parabola P n5 (X n5 ,Z n5 ): focus F5 = (26.976, -85.279) and focal length f n5 =34.186mm,

[0030] Convex parabola P n6 (X n6 ,Z n6 ): Focus F6 = (116.626, -404.145) and focal length f n6 =165.022mm, and a complete cylindrical area mirror is obtained.

[0031] See attached Figure 2 The optical path structure of the entire optical system is as follows: a beam of circular parallel light is incident on the conical mirror, and the light emitted from the conical mirror is reflected on the cylindrical surface divider. The concave and convex areas on the cylindrical surface divider split the light beam, and then stack them together and converge at the focal plane to form a focused ring light of a certain width.

[0032] See attached Figure 3 , energy distribution curve of the focal plane annular light, the intensity average of the high energy point on the flat top of the curve I max It is 230.6, low energy mean I min is 205.3, so the uniformity P is:

[0033] P=(I min / I max )×100%=89.2%(6).

Claims

1. A method for designing an optical system for generating uniform annular light, characterized in that : The optical system is formed by combining a conical mirror and a cylindrical mirror. The specific design idea is to split the light beam incident on the conical mirror into 1, 2, 3... areas according to the size of the focal plane ring light width CD. The width of each area in the Z axis direction is Z 11 ,Z 12 ,Z 13 ...; Light from regions 1 and 3 is reflected by the concave surface of the integrator, converges at focal points F1 and F3, and then diverges to CD. Light from region 2 is reflected by the convex surface and diverges in the opposite direction to CD along the virtual focus F2. The width of region 2 is smaller than the length of CD. The conical mirror is formed by rotating the cone line around the optical axis Z. The cone line equation L(x,z) in the XOZ plane is defined as follows: Z=cot(θ / 2)·X+Z1 (1) Z1 is the distance between the conical mirror vertex and the X axis, θ is the conical mirror vertex angle; The cylindrical integral mirror is a concave-convex continuous curved surface formed by rotating a plurality of concave-convex parabolas around the optical axis Z. When the apex angle of the conical mirror is θ, the angle of F1(X F1 ,Z F1 ) is the concave parabola equation P n1 (X n1 ,Z n1 ) is defined as follows: (sinθ·(Z n1 -Z F1 )+cosθ·(X n1 -X F1 )) 2 =-4f n1 (sinθ·(X n1 -X F1 )-cosθ·(Z n1 -Z F1 )-f n1 )(2) Points A and B are located on the parabola, and F1 is the intersection of lines AD and BC; A(X A ,Z A )、C(X C ,Z C ) and D(X D ,Z D ) are known coordinates, point B(X B ,Z B )Z B =Z A +Z 11 , so the unknown parameter X B , focus F1 coordinates and focal length f n1 This can be solved by the following system of equations: Similarly, with F2(X F2 ,Z F2 ) is the convex parabola equation P n2 (X n2 ,Z n2 ) can be defined as follows: (sinθ·(Z n2 -Z F2 )+cosθ·(X n2 -XF2)) 2 =4f n2 (sinθ·(X n2 -X F2 )-cosθ·(Z n2 -Z F2 )+f n2 )(4) B(X B ,Z B )、C(X C ,Z C ) and D(X D ,Z D ) are known coordinates, point E(X E ,Z E )Z E =Z B +Z 12 , combined with equation group (3), the focus F2 coordinates and focal length f in equation (4) can be calculated n2 ; According to the above method, calculate the parameters of other concave and convex parabolas, and finally obtain the complete cylindrical area component mirror.

Images