A laser non-collimated beam expanding calibration method

Abstract

This invention discloses a laser beam collimation calibration method. The invention uses multiple cylindrical mirrors stacked together to correct the divergence angle as it gradually decreases, thus optimizing the collimation difficulty of a single cylindrical mirror when encountering a large divergence angle (≥70°). The design of stacking multiple cylindrical mirrors in this invention also optimizes the method of controlling the laser spot size, which originally required controlling the distance between the cylindrical mirrors, effectively reducing the size of the control equipment after collimation.

Description

Technical Field

[0001] This invention relates to the field of laser illumination calibration, and in particular to a method for calibrating an incollimated beam expansion laser. Background Technology

[0002] In laser illumination technology, for semiconductor lasers with different divergence angles on the fast and slow axes, a common method is to collimate the divergence angles of the fast and slow axes using two cylindrical mirrors with different focal lengths. This ensures that the fast and slow axis beams collimated by the cylindrical mirrors are parallel to each other. The parallel light is then expanded by a beam expander to change the angle of the outgoing light, thus achieving convergence or divergence. To ensure that the shaped beam spot is uniform and symmetrical, the focal length ratio of the two cylindrical mirrors needs to be approximately equal to the divergence angle ratio, and the distance between the two cylindrical mirrors and the light source needs to be controlled to be equal to their respective focal lengths. The collimation plus beam expansion method greatly simplifies the design process compared to designing irregularly shaped mirrors and aspherical mirrors separately, making it a popular design approach in the industry. However, this method has poor collimation performance when encountering large divergence angles, especially those exceeding 70 degrees. Controlling the uniformity and symmetry of the fast and slow axis beam spots and the overall size of the collimated device are more difficult compared to semiconductor lasers with small divergence angles. Summary of the Invention

[0003] This invention provides a method for calibrating inaccurate beam expansion of a laser, which can solve the problems pointed out in the background art.

[0004] A method for calibrating an inaccurate direct beam expansion of a laser includes the following steps:

[0005] Step 1: Obtain the actual lighting distance and the radius of the required lighting spot, and calculate the required divergence angle;

[0006] Step 2: Measure the laser's performance. place or The divergence angle at the point;

[0007] Step 3: Calculate the actual divergence angle of the beam through the first fast-axis cylindrical mirror in the fast-axis direction;

[0008] Step 4: If the actual divergence angle of the first fast-axis cylindrical mirror is not calibrated to the required divergence angle, add at least one more fast-axis cylindrical mirror so that the actual divergence angle of the beam in the fast-axis direction is calibrated to the required divergence angle by the added fast-axis cylindrical mirror. If the actual divergence angle of the first fast-axis cylindrical mirror is calibrated to the required divergence angle, proceed directly to the next step.

[0009] Step 5: Calculate the actual divergence angle of the beam through the first slow-axis cylindrical mirror in the slow-axis direction;

[0010] Step 6: If the actual divergence angle of the first slow-axis cylindrical mirror is not calibrated to the required divergence angle, add at least one more slow-axis cylindrical mirror so that the actual divergence angle of the beam in the fast-axis direction is calibrated to the required divergence angle by the added slow-axis cylindrical mirror. If the actual divergence angle of the first slow-axis cylindrical mirror is calibrated to the required divergence angle, proceed directly to the next step.

[0011] Step 7: Calculate the radius of curvature of all the fast-axis cylindrical mirrors and slow-axis cylindrical mirrors mentioned above;

[0012] Step 8: Based on the curvature radii of the multiple cylindrical mirrors calculated in Step 7, conduct a simulation experiment. If the collimation effect of the fast axis verification is unqualified, repeat Step 3, Step 4, and Step 7 to recalculate the required curvature radius of the fast axis cylindrical mirror and conduct the simulation experiment again. If the collimation effect of the slow axis verification is unqualified, repeat Step 5, Step 6, and Step 7 to recalculate the required curvature radius of the slow axis cylindrical mirror and conduct the simulation experiment again.

[0013] The formula for calculating the required divergence angle in step one is as follows:

[0014] ;

[0015] in, For lighting distance, Let be the radius of the illumination spot. The required divergence angle for the lens;

[0016] The method for calculating the actual divergence angle of the light beam through the first fast-axis cylindrical mirror in step three is as follows:

[0017] Assume the beam originates from the emission point. The projectile is launched, and its half-divergence angle is... The light beam is refracted at point M on the side of the first fast-axis cylindrical mirror, with a refraction angle of θ. When it passes through the elliptical arc of the cylindrical mirror, a second refraction occurs, with a refraction angle of θ. The angle between the normal at the secondary refraction point N and the x-axis is... The final divergence angle of the beam is ;

[0018] The actual divergence angle of the light beam through the first fast-axis cylindrical mirror in step three is calculated using the following formula:

[0019] Let the plane equation of the elliptical arc surface of the cylindrical mirror be:

[0020]

[0021] in, It is the semi-major axis of the ellipse. It is the semi-minor axis of the ellipse;

[0022] From the law of refraction:

[0023] ;

[0024] ;

[0025] in, Let be the sine of the angle between the incident ray and the normal to the first surface. Let be the refractive index of the lens. Let be the sine of the angle between the ray emitted from the first surface and the normal. Let be the sine of the angle between the ray emitted from the second surface and the normal. Let be the sine of the angle between the incident ray and the normal to the second surface;

[0026] Let the equation of the straight line MN of the light ray inside the cylindrical mirror be:

[0027]

[0028] in, It is the Y-coordinate of point N on the axis. These are the coordinates of point N on the X-axis. Let be the tangent of the angle between the ray emitted from the first face and the normal. It is the distance from the light source to the first surface of the cylindrical mirror. It is the semi-major axis of the ellipse. It is the distance between the first and second surfaces of the cylindrical mirror. It is the tangent of the beam's half-divergence angle;

[0029] Combining formulas and formula Find the coordinates of point N:

[0030] ;

[0031] ;

[0032] Simplifying the above two equations, we get:

[0033] ;

[0034] ;

[0035] Based on the slope of the normal at point N We can obtain:

[0036] ;

[0037] By inversely applying the formula for the law of refraction, we can obtain:

[0038] ;

[0039] ;

[0040] Finally, the divergence angle along the fast axis was calculated to be: .

[0041] The formulas for calculating the radii of curvature of the fast-axis cylindrical mirror and the slow-axis cylindrical mirror in step seven are as follows:

[0042]

[0043] in, a Let be the semi-major axis of the elliptical arc surface of the fast-axis or slow-axis cylindrical mirror. b Let be the semi-minor axis of the elliptical arc surface of the fast-axis cylindrical mirror or the slow-axis cylindrical mirror.

[0044] The method for calculating the actual divergence angle of the light beam through the first slow-axis cylindrical mirror in step five is as follows:

[0045] Using the calculation method for the actual divergence angle of the light beam through the first fast-axis cylindrical mirror in step three above, the following is used: Replace with By performing calculations, the actual divergence angle of the beam through the first slow-axis cylindrical mirror can be obtained;

[0046] ;

[0047] in, The inherent astigmatism of semiconductor lasers, This represents the total offset of parallel light rays passing through the fast-axis cylindrical mirror. For the thickness of the fast-axis cylindrical lens, The distance between the first fast-axis cylindrical mirror and the light source. This is the distance between the slow-axis cylindrical mirror and the last fast-axis cylindrical mirror.

[0048] The method for calculating the actual divergence angle of the light beam through the added fast-axis cylindrical mirror in step three is as follows:

[0049] Using the calculation method for the actual divergence angle of the light beam through the first fast-axis cylindrical mirror in step three above, the following is used: Replace with The actual divergence angle of the beam through the increased fast-axis cylindrical mirror can be calculated.

[0050] ;

[0051] Among them, The inherent astigmatism of semiconductor lasers, This represents the total offset of light rays passing through the cylindrical mirror in the perpendicular direction. For the thickness of the fast-axis cylindrical lens, The distance between the first fast-axis cylindrical mirror and the light source. This is the distance between the two cylindrical mirrors.

[0052] Compared with the prior art, the beneficial effects of the present invention are: the present invention uses multiple cylindrical mirrors stacked together to correct the divergence angle while gradually reducing the divergence angle, thus optimizing the original single cylindrical mirror's performance when encountering a large divergence angle. It is difficult to be accurate when )

[0053] The design of stacking multiple cylindrical mirrors in this invention also optimizes the method of controlling the laser spot size, which originally required controlling the distance between the cylindrical mirrors, and effectively reduces the size of the collimation control device. Attached Figure Description

[0054] Figure 1 Correcting the optical path diagram for a slow-axis cylindrical mirror;

[0055] Figure 2 Correcting the optical path diagram for the fast-axis cylindrical mirror;

[0056] Figure 3 Feature map of fast-axis cylindrical mirror;

[0057] Figure 4 Feature map of a slow-axis cylindrical mirror;

[0058] Figure 5 A simulation image of a combination of multiple cylindrical mirrors;

[0059] Figure 6 A diagram showing the calculated actual divergence angle of a single fast-axis cylindrical mirror;

[0060] Figure 7 The graph shows the calculated actual divergence angle after the two fast-axis cylindrical mirrors are stacked. Detailed Implementation

[0061] The following detailed description of a specific embodiment of the present invention is provided in conjunction with the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0062] like Figures 1 to 7 As shown in the figure, an embodiment of the present invention provides a laser incollimation beam expansion calibration method, which includes the following steps:

[0063] Step 1: Obtain the actual lighting distance and the radius of the required lighting spot, and calculate the required divergence angle;

[0064] Step 2: Measure the laser's performance. place or The divergence angle at the point;

[0065] Step 3: Calculate the actual divergence angle of the beam through the first fast-axis cylindrical mirror in the fast-axis direction;

[0066] Step 4: If the actual divergence angle of the first fast-axis cylindrical mirror is not calibrated to the required divergence angle, add at least one more fast-axis cylindrical mirror so that the actual divergence angle of the beam in the fast-axis direction is calibrated to the required divergence angle by the added fast-axis cylindrical mirror. If the actual divergence angle of the first fast-axis cylindrical mirror is calibrated to the required divergence angle, proceed directly to the next step.

[0067] Step 5: Calculate the actual divergence angle of the beam through the first slow-axis cylindrical mirror in the slow-axis direction;

[0068] Step 6: If the actual divergence angle of the first slow-axis cylindrical mirror is not calibrated to the required divergence angle, add at least one more slow-axis cylindrical mirror so that the actual divergence angle of the beam in the fast-axis direction is calibrated to the required divergence angle by the added slow-axis cylindrical mirror. If the actual divergence angle of the first slow-axis cylindrical mirror is calibrated to the required divergence angle, proceed directly to the next step.

[0069] Step 7: Calculate the radius of curvature of all the fast-axis cylindrical mirrors and slow-axis cylindrical mirrors mentioned above;

[0070] Step 8: Based on the curvature radii of the multiple cylindrical mirrors calculated in Step 7, conduct a simulation experiment. If the collimation effect of the fast axis verification is unqualified, repeat Step 3, Step 4, and Step 7 to recalculate the required curvature radius of the fast axis cylindrical mirror and conduct the simulation experiment again. If the collimation effect of the slow axis verification is unqualified, repeat Step 5, Step 6, and Step 7 to recalculate the required curvature radius of the slow axis cylindrical mirror and conduct the simulation experiment again.

[0071] The formula for calculating the required divergence angle in step one is as follows:

[0072] ;

[0073] in, For lighting distance, Let be the radius of the illumination spot. The required divergence angle for the lens;

[0074] The method for calculating the actual divergence angle of the light beam through the first fast-axis cylindrical mirror in step three is as follows:

[0075] Assume the beam originates from the emission point. The projectile is launched, and its half-divergence angle is... The light beam is refracted at point M on the side of the first fast-axis cylindrical mirror, with a refraction angle of θ. When it passes through the elliptical arc of the cylindrical mirror, a second refraction occurs, with a refraction angle of θ. The angle between the normal at the secondary refraction point N and the x-axis is... The final divergence angle of the beam is ;

[0076] The actual divergence angle of the light beam through the first fast-axis cylindrical mirror in step three is calculated using the following formula:

[0077] Let the plane equation of the elliptical arc surface of the cylindrical mirror be:

[0078]

[0079] in, For a fast-axis cylindrical mirror or a slow-axis cylindrical mirror, the semi-major axis of the elliptical arc surface is given. It is the semi-minor axis of the elliptical arc surface of a fast-axis cylindrical mirror or a slow-axis cylindrical mirror;

[0080] From the law of refraction:

[0081] ;

[0082] ;

[0083] in, Let be the sine of the angle between the incident ray and the normal to the first surface. Let be the refractive index of the lens. Let be the sine of the angle between the ray emitted from the first surface and the normal. Let be the sine of the angle between the ray emitted from the second surface and the normal. Let be the sine of the angle between the incident ray and the normal to the second surface;

[0084] Let the equation of the straight line MN of the light ray inside the cylindrical mirror be:

[0085]

[0086] in, It is the Y-coordinate of point N on the axis. These are the coordinates of point N on the X-axis. Let be the tangent of the angle between the ray emitted from the first face and the normal. It is the distance from the light source to the first surface of the cylindrical mirror. For a fast-axis cylindrical mirror or a slow-axis cylindrical mirror, the semi-major axis of the elliptical arc surface is given. It is the distance between the first and second surfaces of the cylindrical mirror. It is the tangent of the beam's half-divergence angle;

[0087] Combining formulas and formula Find the coordinates of point N:

[0088] ;

[0089] ;

[0090] Simplifying the above two equations, we get:

[0091] ;

[0092] ;

[0093] Based on the slope of the normal at point N We can obtain:

[0094] ;

[0095] By inversely applying the formula for the law of refraction, we can obtain:

[0096] ;

[0097] ;

[0098] Finally, the divergence angle along the fast axis was calculated to be: ;

[0099] and As an intermediate variable, The divergence angle is along the fast axis.

[0100] The formulas for calculating the radii of curvature of the fast-axis cylindrical mirror and the slow-axis cylindrical mirror in step seven are as follows:

[0101]

[0102] in, a Let be the semi-major axis of the elliptical arc surface of the fast-axis or slow-axis cylindrical mirror. b Let be the semi-minor axis of the elliptical arc surface of the fast-axis cylindrical mirror or the slow-axis cylindrical mirror;

[0103] Since the slow-axis divergence angle is generally small, only one slow-axis cylindrical mirror is usually needed to correct the divergence angle during beam expansion. Therefore, this embodiment takes the calculation of the actual divergence angle of the first slow-axis cylindrical mirror as an example. That is, the calculation method of the actual divergence angle of the beam passing through the first slow-axis cylindrical mirror in step five is as follows:

[0104] Using the calculation method for the actual divergence angle of the light beam through the first fast-axis cylindrical mirror in step three above, the following is used: Replace with By performing calculations, the actual divergence angle of the beam through the first slow-axis cylindrical mirror can be obtained;

[0105] ;

[0106] in, The inherent astigmatism of semiconductor lasers is approximately a few micrometers. This represents the total offset of parallel light rays passing through the fast-axis cylindrical mirror. For the thickness of the fast-axis cylindrical lens, The distance between the first fast-axis cylindrical mirror and the light source. This represents the distance between two fast-axis cylindrical mirrors, specifically the distance between the slow-axis cylindrical mirror and the last fast-axis cylindrical mirror.

[0107] During beam expansion, only two fast-axis cylindrical mirrors are generally needed to correct the divergence angle. Therefore, this embodiment takes the calculation of the actual divergence angle of two slow-axis cylindrical mirrors as an example. That is, the calculation method of the actual divergence angle of the beam passing through the added fast-axis cylindrical mirror in step three is as follows:

[0108] Using the calculation method for the actual divergence angle of the light beam through the first fast-axis cylindrical mirror in step four above, the method described above is used to... Replace with The actual divergence angle of the beam through the increased fast-axis cylindrical mirror can be calculated.

[0109] ;

[0110] Among them, The inherent astigmatism of semiconductor lasers, This represents the total offset of light rays passing through the cylindrical mirror in the perpendicular direction. For the thickness of the fast-axis cylindrical lens, The distance between the first fast-axis cylindrical mirror and the light source. This is the distance between the two fast-axis cylindrical mirrors.

[0111] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit and essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0112] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for calibrating an inaccurate direct beam expansion of a laser, characterized in that, Includes the following steps: Step 1: Obtain the actual lighting distance and the radius of the required lighting spot, and calculate the required divergence angle; Step 2: Measure the laser's performance. place or The angle of divergence at the point; Step 3: Calculate the actual divergence angle of the beam through the first fast-axis cylindrical mirror in the fast-axis direction; Step 4: If the actual divergence angle of the first fast-axis cylindrical mirror is not calibrated to the required divergence angle, add at least one more fast-axis cylindrical mirror so that the actual divergence angle of the beam in the fast-axis direction is calibrated to the required divergence angle by the added fast-axis cylindrical mirror. If the actual divergence angle of the first fast-axis cylindrical mirror is calibrated to the required divergence angle, proceed directly to the next step. Step 5: Calculate the actual divergence angle of the beam through the first slow-axis cylindrical mirror in the slow-axis direction; Step 6: If the actual divergence angle of the first slow-axis cylindrical mirror is not calibrated to the required divergence angle, add at least one more slow-axis cylindrical mirror so that the actual divergence angle of the beam in the fast-axis direction is calibrated to the required divergence angle by the added slow-axis cylindrical mirror. If the actual divergence angle of the first slow-axis cylindrical mirror is calibrated to the required divergence angle, proceed directly to the next step. Step 7: Calculate the radius of curvature of all the fast-axis cylindrical mirrors and slow-axis cylindrical mirrors mentioned above; Step 8: Based on the curvature radii of the multiple cylindrical mirrors calculated in Step 7, conduct a simulation experiment. If the collimation effect of the fast axis verification is unqualified, repeat Step 3, Step 4, and Step 7 to recalculate the required curvature radius of the fast axis cylindrical mirror and conduct the simulation experiment again. If the collimation effect of the slow axis verification is unqualified, repeat Step 5, Step 6, and Step 7 to recalculate the required curvature radius of the slow axis cylindrical mirror and conduct the simulation experiment again. The method for calculating the actual divergence angle of the light beam through the first fast-axis cylindrical mirror in step three is as follows: Assume the beam originates from the emission point. The projectile is launched, and its half-divergence angle is... The light beam is refracted at point M on the side of the first fast-axis cylindrical mirror, with a refraction angle of θ. When it passes through the elliptical arc of the cylindrical mirror, a second refraction occurs, with a refraction angle of θ. The angle between the normal at the secondary refraction point N and the x-axis is... The final divergence angle of the beam is ; The actual divergence angle of the light beam through the first fast-axis cylindrical mirror in step three is calculated using the following formula: Let the plane equation of the elliptical arc surface of the cylindrical mirror be: in, For a fast-axis cylindrical mirror or a slow-axis cylindrical mirror, the semi-major axis of the elliptical arc surface is given. It is the semi-minor axis of the elliptical arc surface of a fast-axis cylindrical mirror or a slow-axis cylindrical mirror; From the law of refraction: ； ； in, Let be the sine of the angle between the incident ray and the normal to the first surface. Let be the refractive index of the lens. Let be the sine of the angle between the ray emitted from the first surface and the normal. Let be the sine of the angle between the ray emitted from the second surface and the normal. Let be the sine of the angle between the incident ray and the normal to the second surface; Let the equation of the straight line MN of the light ray inside the cylindrical mirror be: in, It is the Y-coordinate of point N on the axis. These are the coordinates of point N on the X-axis. Let be the tangent of the angle between the ray emitted from the first face and the normal. It is the distance from the light source to the first surface of the cylindrical mirror. For a fast-axis cylindrical mirror or a slow-axis cylindrical mirror, the semi-major axis of the elliptical arc surface is given. It is the distance between the first and second surfaces of the cylindrical mirror. It is the tangent of the beam's half-divergence angle; Combining formulas and formula Find the coordinates of point N: ； ； Simplifying the above two equations, we get: ； ； Based on the slope of the normal at point N We can obtain: ； By inversely applying the formula for the law of refraction, we can obtain: ； ； Finally, the divergence angle along the fast axis was calculated to be: ; in, and As an intermediate variable, The divergence angle is in the direction of the fast axis.

2. The laser inaccurate beam expansion calibration method as described in claim 1, characterized in that, The formula for calculating the required divergence angle in step one is as follows: ； in, For lighting distance, Let be the radius of the illumination spot. This is the required divergence angle for the lens.

3. The laser inaccurate direct beam expansion calibration method as described in claim 1, characterized in that, The formulas for calculating the radii of curvature of the fast-axis cylindrical mirror and the slow-axis cylindrical mirror in step seven are as follows: in, a Let be the semi-major axis of the elliptical arc surface of the fast-axis or slow-axis cylindrical mirror. b Let be the semi-minor axis of the elliptical arc surface of the fast-axis cylindrical mirror or the slow-axis cylindrical mirror.

4. The laser inaccurate beam expansion calibration method as described in claim 1, characterized in that, The method for calculating the actual divergence angle of the light beam through the first slow-axis cylindrical mirror in step five is as follows: Using the method described in step three above for calculating the actual divergence angle of the light beam through the first fast-axis cylindrical mirror, the following steps are taken: Replace with By performing calculations, the actual divergence angle of the beam through the first slow-axis cylindrical mirror can be obtained; ； in, The inherent astigmatism of semiconductor lasers, This represents the total offset of parallel light rays passing through the fast-axis cylindrical mirror. For the thickness of the fast-axis cylindrical lens, The distance between the first fast-axis cylindrical mirror and the light source. This is the distance between the two cylindrical mirrors.

5. The laser inaccurate beam expansion calibration method as described in claim 1, characterized in that, The method for calculating the actual divergence angle of the light beam through the added fast-axis cylindrical mirror in step four is as follows: Using the calculation method for the actual divergence angle of the light beam through the first fast-axis cylindrical mirror in step three above, the following is used: Replace with The calculation is performed to determine the actual divergence angle of the beam through the added fast-axis cylindrical mirror; ； Among them, The inherent astigmatism of semiconductor lasers, This represents the total offset of light rays passing through the cylindrical mirror in the perpendicular direction. For the thickness of the fast-axis cylindrical lens, The distance between the first fast-axis cylindrical mirror and the light source. This is the distance between the two cylindrical mirrors.

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