Field lens enabling galvanometer laser scanning light to be uniform and field lens design method

Abstract

The invention discloses a field lens enabling galvanometer laser scanning light rays to be uniform and a field lens design method, and aims at overcoming the defects of most laser cleaning equipment using galvanometers at the present stage and making up for the defects of small machining equipment at the present stage, so that the field lens is labor-saving and convenient in practical application. The invention provides a field lens with uniform light and a design method thereof. The principle is that contours of the upper surface and the lower surface of the field lens are found out, so that incident fan-shaped light with non-uniform speed is changed into uniform parallel light with equal intensity. The structure is simple, and the condition of uneven light can be solved by only one lens. According to the invention, the laser scanning speed on the scanning surface can be directly changed. According to the invention, non-uniform light is directly changed into uniform parallel light with equal intensity, and the problem of overburning caused by too high light energy on part of scanning lines is solved.

Description

Technical Field

[0001] The invention belongs to the field of optomechanical and electrical engineering, and in particular relates to a field lens and a field lens design method for making galvanometer laser scanning light uniform. Background Art

[0002] Laser cleaning equipment is an emerging surface cleaning technology that uses the energy of laser beams to remove dirt, paint, rust or other unwanted coatings on the surface of materials. It has the advantages of avoiding pollution, strong cleaning ability, high efficiency and easy operation, and is being used in production and manufacturing.

[0003] However, currently, when the galvanometer is swinging, the laser projected on the galvanometer produces a linear scanning line. However, due to the uneven swinging speed of the galvanometer, the light at each point on the scanning line has different scanning speeds as the swinging angle changes. Different scanning speeds will cause the light energy received by each point on the scanning line to be different. Therefore, the laser cleaning equipment currently on the market will cause uneven cleaning or burnt ends during cleaning. Summary of the invention

[0004] Purpose of the invention: In order to solve the deficiencies of the prior art, the present invention provides a field lens and a field lens design method for making the galvanometer laser scanning light uniform.

[0005] Technical solution: A field lens and field lens design method for making the galvanometer laser scanning light uniform. Assume that the laser spot is a point, point A is the center point of the galvanometer swing, point B is the intersection of the laser and the upper surface of the field lens at time t, E and F are the galvanometer reflection surfaces, the intersection angle between the laser and the vertical coordinate axis y at time t is θ(t), the x-axis is the horizontal coordinate axis, and the origin is o, then:

[0006]

[0007] In the above formula, T is the oscillation period of the galvanometer, and a is the angular amplitude of the galvanometer. Since the field mirror is assumed to be symmetrical about the y-axis, only For the contour line F1(x) on the surface of the lens, the laser The x1 coordinate of the intersection point B with F1(x) can be calculated using the following formula:

[0008] x1=(h-F1(x1))sinθ(t) (1)

[0009] In the above formula, h and θ are known, and x and F1(x) are the values ​​to be set;

[0010] For the contour line F2(x) of the curved surface below the lens, the laser The x2 coordinate of the intersection point C with F2(x) can be calculated using the following formula:

[0011] x2=vt

[0012] v is the designed scanning speed of the laser on the scanning surface, which can be set as a constant or a time variable.

[0013] θ1=θ-tan -1 F1′(x1) (2)

[0014] θ1 is the laser The angle between F1(x) and the normal line. Then, from the law of refraction, we can get:

[0015]

[0016] θ2 is the laser The refraction angle at point B gives the laser The angle θ3 between the normal line at the intersection point C and the lower surface F2(x) is

[0017] θ3=tan -1 F2′(x2)-θ2-tan -1 F1′(x1) (4)

[0018] From the law of refraction we can get:

[0019]

[0020] θ4 is the refraction angle of θ3. is parallel to the y-axis, so

[0021] θ4=tan -1 F2′(x2) (6)

[0022] The geometric relationship between x1 and x2 can be obtained:

[0023] x1+F1(x1)F1′(x1)=x2-F2(x2)F2′(x2) (7)

[0024] The relationship between the slopes of the upper and lower surfaces and the curve is:

[0025]

[0026] There are 9 unknown parameters in the whole system, namely x1, θ1, θ2, θ3, θ4, F1(x1), F2(x2), F1′(x1) and F2′(x2). The above equations (1)-(9) have exactly 9 independent equations. Solving equations (1)-(9) can obtain all the unknown parameters. However, equations (1-7) are algebraic expressions and equations (8) and (9) are differential expressions. To solve them simultaneously, the differential expressions must be written as algebraic expressions. Here, the finite difference method can be used to solve them, and we get:

[0027]

[0028] When t = t i+1 When x1=x1 i+1 , when t = t i When x1=x1 i , Δx1=x1 i+1 -x1 i , here we will Divided into n small segments, that is, the time Δt of each segment is

[0029]

[0030] t i+1 =t i +Δt;

[0031] Using formula (1), we can get x1 at any time. Similarly,

[0032]

[0033] x2 i+1 =x2 i +Δx2=v(t i +Δt) (12)

[0034] Δx2 is t i+1 and t i Substitute equations (10) and (12) into equations (2), (4) and (7), and transform equations (1)-(7) into i+1 The algebraic expression for t can be directly solved i+1 By calculating i from 0 to n, we can get the unknown parameters at each time point, that is, the contours of the upper and lower surfaces of the lens.

[0035] For laser non-point light sources, multiple points are selected on the laser spot and the upper and lower contours of the field lens for each spot are determined according to the above method. Figure 3 As shown, the distance from the spot center to the point on the spot and the intersection of the y axis is hl secθ, and the projection point x2 = vt-l. These two equations are used to replace h and x2 in the above formula. The method of deriving the field lens profile equation of this point is the same as that of the spot center, so it will not be repeated here. After we divide the spot into several points, the field lens profile equation of each point is obtained, and the least squares method is used to find the approximate regression equation, and the lens is made with this equation as the field lens profile equation. If the spot is not large, this action can be omitted.

[0036] In addition, instead of dividing the light spot into many points, the optical software can be used to directly correct the contour equation obtained with the center point of the light spot to obtain the best result.

[0037] Beneficial effects: Aiming at the drawbacks of most small laser cleaning equipment at present, and making up for the shortcomings of small processing equipment at present, so as to save effort and be convenient in practical applications, the present invention provides a field lens with uniform light and a design method thereof, the basic principle of which is to find the contours of the upper and lower sides of the field lens so that the incident fan-shaped light with uneven speed can be transformed into uniform parallel light of equal intensity. The specific advantages of the present invention are as follows:

[0038] 1. The present invention has a simple structure and can solve the problem of uneven light with only one lens.

[0039] 2. The present invention can directly change the laser scanning speed on the scanning surface.

[0040] 3. The present invention directly converts uneven light into uniform parallel light of equal intensity, thereby solving the problem of overburning caused by excessive light energy received by some scanning lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the curved surface features of the upper surface or (and) the lower surface of the refractive surface of the collimating lens and the laser line of the present invention.

[0042] Figure 2 It is an enlarged view of the upper and lower sides of the laser light path of the refractive surface of the collimating lens of the present invention near BC;

[0043] Figure 3 It is the contour calculation of a certain point on different spots when the laser spot is not point-shaped;

[0044] Figure 4 is a diagram illustrating the light path of a specific embodiment 1 of the present invention;

[0045] Figure 5 It is a diagram illustrating the light path of specific embodiment 2 of the present invention. DETAILED DESCRIPTION

[0046] The following is a clear and complete description of the technical solutions in the embodiments of this patent in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of this patent, not all of them. Based on the embodiments in this patent, all other embodiments obtained by those skilled in the art or ordinary technicians without creative work are within the scope of protection of this patent.

[0047] Here, exemplary embodiments will be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are only examples of devices and products consistent with some aspects of the present disclosure as detailed in the attached claims.

[0048] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms of "a", "said" and "the" used in this disclosure and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0049] It should be understood that although the terms first, second, third, etc. may be used in the present disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0050] Field lens design method

[0051] A field lens and field lens design method for making the galvanometer laser scanning light uniform, assuming that the laser spot is a point (in reality, if the laser spot is not a point, the spot can be divided into many points for analysis, and the surface shape of each point is calculated, and these shapes are used as reference to find the best refraction mirror surface). Figure 1 Point A is the center point of the oscillation of the galvanometer, and point B is the intersection of the laser and the upper surface of the field mirror at time t. Therefore, the intersection angle between the laser and the vertical coordinate axis y at time t is θ(t), the x-axis is the horizontal coordinate axis, and the origin is o, then:

[0052]

[0053] In the above formula, T is the oscillation period of the galvanometer, and a is the angular amplitude of the galvanometer. Since the field mirror is assumed to be symmetrical about the y-axis, only For the contour line F1(x) on the surface of the lens, the laser The x1 coordinate of the intersection point B with F1(x) can be calculated using the following formula:

[0054] x1=(h-F1(x1))sinθ(t) (1)

[0055] In the above formula, h and θ are known, and x and F1(x) are the values ​​to be set. For the contour line F2(x) of the lower surface of the lens, the laser The x2 coordinate of the intersection point C with F2(x) can be calculated using the following formula:

[0056] x2=vt

[0057] v is the designed scanning speed of the laser on the scanning surface, which can be set as a constant or a time variable. Figure 2 available:

[0058] θ1=θ-tan -1 F1′(x1) (2)

[0059] θ1 is the laser The angle between F1(x) and the normal line. Then, from the law of refraction, we can get:

[0060]

[0061] θ2 is the laser The refraction angle at point B is given by Figure 2 Laser available The angle θ3 of the normal line at the intersection point C with the lower surface F2(x) is:

[0062] θ3=tan -1 F2′(x2)-θ2-tan -1 F1′(x1) (4)

[0063] From the law of refraction we can get:

[0064]

[0065] θ4 is the refraction angle of θ3. is parallel to the y-axis, so:

[0066] θ4=tan -1 F2′(x2) (6)

[0067] The geometric relationship between x1 and x2 can be obtained:

[0068] x1+F1(x1)F1′(x1)=x2-F2(x2)F2′(x2) (7)

[0069] The relationship between the slopes of the upper and lower surfaces and the curve is:

[0070]

[0071] There are 9 unknown parameters in the whole system, namely x1, θ1, θ2, θ3, θ4, F1(x1), F2(x2), F1′(x1) and F2′(x2). The above equations (1)-(9) have exactly 9 independent equations. Solving equations (1)-(9) can get all the unknown parameters. However, equations (1-7) are algebraic expressions and equations (8) and (9) are differential expressions. To solve them simultaneously, the differential expressions must be written as algebraic expressions. Here, the finite difference method can be used to solve them. For example:

[0072]

[0073] When t = t i+1 When x1=x1 i+1 , when t = t i When x1=x1 i , Δx1=x1 i+1 -x1 i , here we will Divided into n small segments, the time Δt of each segment is:

[0074]

[0075] t i+1 =t i +Δt

[0076] Using formula (1), we can get x1 at any time. Similarly,

[0077]

[0078] x2 i+1 =x2 i +Δx2=v(t i +Δt) (12)

[0079] Δx2 is t i+1 and t i Substitute equations (10) and (12) into equations (2), (4) and (7), and transform equations (1)-(7) into i+1 The algebraic expression for t can be directly solved i+1 If we count i from 0 to n, we can get F1(x1) and F2(x2) at each time point, and get the contour of the upper and lower surfaces of the lens. This contour can be used to manufacture the field lens.

[0080] For non-point laser sources, multiple points are selected on the laser spot to determine the upper and lower contours of the field lens for each spot according to the above method. Figure 3 As shown, the distance from the spot center to the point on the spot and the intersection of the y axis is hl secθ, and the projection point x2 = vt-l. These two equations are used to replace h and x2 in the above formula. The method of deriving the field lens profile equation of this point is the same as that of the spot center, so it will not be repeated here. After we divide the spot into several points, the field lens profile equation of each point is obtained, and the least squares method is used to find the approximate regression equation, and the lens is made with this equation as the field lens profile equation. If the spot is not large, this action can be omitted.

[0081] In addition, instead of dividing the light spot into many points, the optical software can be used to directly correct the contour equation obtained with the center point of the light spot to obtain the best result. Specific embodiment 1

[0083] like Figure 4 As shown, set F1(x1) = 0, F1′(x1 i+1 )=0, then equations (1)-(11) can be rewritten as: t=t i+1 :

[0084] x1 i+1 =hsinθ(t i+1 ) (1)

[0085] θ1 i+1 =θ(t i+1 ) (2)

[0086]

[0087] θ3 i+1 =tan -1 F2′(x2 i+1 )-θ2 i+1 (4)

[0088]

[0089] θ4 i+1 =tan -1 F2′(x2 i+1 ) (6)

[0090] x1 i+1 =x2 i+1 -F2(x2 i+1 )F2′(x2 i+1 ) (7)

[0091]

[0092] After sorting, we can get:

[0093]

[0094]

[0095] θ4 i+1 =θ3 i+1 +θ2 i+1 (15)

[0096] x1 i+1 =x2 i+1 -F2(x2 i+1 )θ4 i+1 (16)

[0097] From equations (13)-(16) and equation (5), we can get F2(x2i+1 ), we can get the F2(x2) points at t i The contour of F2(x2) is obtained by taking the position x2. Specific embodiment 2

[0099] like Figure 5 As shown, let F1(x1) be a circle with point A as its center. Then (1)-(11) can be rewritten as: i+1 :

[0100] F1(x1 i+1 )=h(1-cosθ(t) i+1 ),

[0101] x1 i+1 =hsinθ(t) i+1 (1)

[0102] Depend on Figure 4 available

[0103] θ1=θ2=0 (2)

[0104] θ3 i+1 =θ4 i+1 -θ(t) i+1 (4)

[0105] x1 i+1 +h(1-cosθ(t) i+1 )tanθ(t) i+1 =x2 i+1 -F2(x2 i+1 )F2′(x2 i+1 ) (7)

[0106]

[0107] From equations (4”) and (5), we can solve for θ3 i+1 and θ4 i+1 From formulas (1), (7) and (11), we can get F2(x2 i+1 ) and F2′(x2 i +1 ). Find i+1 Solve, and you can get the F2(x2) points at t i The contour of F2(x2) is obtained by taking the position x2.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0109] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A field lens and a field lens design method for making the galvanometer laser scanning light uniform, characterized in that: Assume that the laser spot is a point, point A is the center point of the oscillation of the galvanometer, point B is the intersection of the laser and the upper surface of the field mirror at time t, E and F are the reflection surfaces of the galvanometer, the intersection angle between the laser and the vertical coordinate axis y at time t is θ(t), the x-axis is the horizontal coordinate axis, and the origin is o, then: In the above formula, T is the oscillation period of the galvanometer, and a is the angular amplitude of the galvanometer. Since the field mirror is assumed to be symmetrical about the y-axis, only For the contour line F1(x) on the surface of the lens, the laser The x1 coordinate of the intersection point B with F1(x) can be calculated using the following formula: x1=(h-F1(x1))sinθ(t) (1) In the above formula, h and θ are known, and x and F1(x) are the values ​​to be set; For the contour line F2(x) of the curved surface below the lens, the laser The x2 coordinate of the intersection point C with F2(x) can be calculated using the following formula: x2=vt v is the designed scanning speed of the laser on the scanning surface, which can be set as a constant or a time variable. θ1=θ-tan -1 F1′(x1) (2) θ1 is the laser and the normal line of F1(x). Then, from the law of refraction, we can get: θ2 is the laser The refraction angle at point B gives the laser The angle θ3 between the normal line at the intersection point C and the lower surface F2(x) is <h2 style=";text-align:left;direction:ltr">θ3 = tan<h2 style=";text-align:left;direction:ltr"> -1 <h2 style=";text-align:left;direction:ltr"> F2′(x2)-θ2-tan<h2 style=";text-align:left;direction:ltr"> -1 <h2 style=";text-align:left;direction:ltr"> F1′(x1) (4) From the law of refraction we can get: θ4 is the refraction angle of θ3. is parallel to the y-axis, so <h2 style=";text-align:left;direction:ltr">θ4=tan<h2 style=";text-align:left;direction:ltr"> -1 <h2 style=";text-align:left;direction:ltr"> F2'(x2) (6) The geometric relationship between x1 and x2 can be obtained: x1+F1(x1)F1′(x1)=x2-F2(x2)F2′(x2) (7) The relationship between the slopes of the upper and lower surfaces and the curve is: There are 9 unknown parameters in the whole system, namely x1, θ1, θ2, θ3, θ4, F1(x1), F2(x2), F1′(x1) and F2′(x2). The above equations (1)-(9) have exactly 9 independent equations. Solving equations (1)-(9) can obtain all the unknown parameters. However, equations (1-7) are algebraic expressions and equations (8) and (9) are differential expressions. To solve them simultaneously, the differential expressions must be written as algebraic expressions. Here, the finite difference method can be used to solve them, and we get: When t = t i+1 When x1=x1 i+1 , when t = t i When x1=x1 i , Δx1=x1 i+1 -x1 i , here we will Divided into n small segments, that is, the time Δt of each segment is t i+1 =t i +Δt; Using formula (1), we can get x1 at any time. Similarly, x2 i+1 =x2 i +Δx2=v(t i +Δt) (12) Δx2 is t i+1 and t i Substitute equations (10) and (12) into equations (2), (4) and (7), and transform equations (1)-(7) into i+1 The algebraic expression for t can be directly solved i+1 By calculating i from 0 to n, we can get the F1(x1) and F2(x2) at each time point, that is, the contour of the upper and lower surfaces of the lens. The field lens is manufactured based on this contour.

2. The field lens and field lens design method for making the galvanometer laser scanning light uniform according to claim 1, characterized in that: For example, if the laser is not a point light source, select multiple points on the laser spot. The method of claim 1 is used to determine the upper and lower contours of the field lens for each light spot; at different points on the light spot at a distance l from the center of the light spot, h-lsecθ, and x2=vt-l are substituted for h and x2 in the formula of claim 1; the field lens contour equation of each point of the light spot is obtained, and then the least squares method is used to find the approximate regression equation, and the lens is manufactured using this equation as the field lens contour equation.

3. The field lens and field lens design method for making the galvanometer laser scanning light uniform according to claim 1, characterized in that: After obtaining the field lens profile obtained at the center point of the light spot, optical software is used to correct the profile equation to make the light more uniform.

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