A dynamic beam quality measurement device based on a fast deflecting mirror and microlens group

Abstract

This invention provides a dynamic beam quality measurement device based on a fast deflecting mirror and a microlens group, comprising a first fast deflecting mirror, a second fast deflecting mirror, a microlens group, a focusing lens, and a charge-coupled device (CCD) camera arranged sequentially along the optical path. The first fast deflecting mirror reflects the laser beam to be measured onto the second fast deflecting mirror, and the second fast deflecting mirror reflects the laser beam modulated by the first fast deflecting mirror to the centers of different microlenses within the microlens group. The microlens group consists of multiple microlenses. The focusing lens is arranged in the transmission optical path of the microlens group, and the CCD camera is arranged at the focal point of the focusing lens in the transmission optical path of the focusing lens. In this invention, a single image acquired by the CCD camera can capture the distribution of four laser beam spots focused by lenses with different focal lengths. Combined with the high-speed deflection of the two fast reflecting mirrors, dynamic measurement of laser beam quality can be achieved while ensuring measurement accuracy.

Description

Technical Field

[0001] This invention belongs to the field of laser parameter measurement technology, and in particular relates to a dynamic beam quality measurement device based on a fast deflection mirror and a microlens group. Background Technology

[0002] Laser is one of the major inventions of the 20th century. Due to its high brightness, monochromaticity, directionality and coherence, it has been widely used in various fields such as industry, military, communications, medicine and scientific research, and has profoundly influenced the development and transformation of contemporary science, technology, economy and equipment.

[0003] Beam quality is a core parameter of lasers, playing a crucial role in their design, manufacturing, and application. In laser design and manufacturing, beam quality can assess the approximate ratio of low-order and high-order modes, thus enabling the suppression of high-order modes during laser design and manufacturing. In laser applications, beam quality directly determines the propagation and effectiveness of the laser. For example, in laser cutting, beam quality directly determines cutting efficiency; in laser welding, beam quality directly determines weld shape and strength; and in laser weapons, beam quality directly determines the laser's destructive effect on the target. The beam quality of a laser is primarily determined by its beam quality factor M. 2 In terms of evaluation, it can simultaneously cover the near-field and far-field characteristics of lasers.

[0004] For the laser beam quality factor M 2 To measure the quality factor M of a laser beam, scientists have successively proposed methods such as multi-point fitting, liquid lensing, spatial and spectral resolution, parallel plate method, defocusing grating method, scattered light imaging, computer-generated holography, spatial light modulator method, and complex amplitude reconstruction method. Some of these methods can achieve measurement of the laser beam quality factor M. 2 While accurate measurement is possible, it is time-consuming. Other methods, although capable of dynamic measurement of laser beam quality, suffer from inconsistent accuracy. Currently, the challenge lies in achieving dynamic and accurate measurement of the laser beam quality factor M. 2 It's a difficult problem. Summary of the Invention

[0005] The purpose of this invention is to provide a dynamic beam quality measurement device based on a fast deflection mirror and a microlens group, applicable to lasers in the visible and near-infrared bands, capable of measuring the laser beam quality factor M. 2 Enable dynamic measurement.

[0006] Therefore, the above-mentioned objectives of the present invention are achieved through the following technical solutions:

[0007] A dynamic beam quality measurement device based on a fast deflecting mirror and a microlens group is characterized in that: the dynamic beam quality measurement device based on a fast deflecting mirror and a microlens group includes a first fast deflecting mirror, a second fast deflecting mirror, a microlens group, a focusing lens, and a charge-coupled device (CCD) camera arranged sequentially along the optical path; the first fast deflecting mirror is used to reflect the laser to be measured onto the second fast deflecting mirror, the second fast deflecting mirror is used to reflect the laser modulated by the first fast deflecting mirror to the center of different microlenses in the microlens group, the microlens group is composed of multiple microlenses, the focusing lens is arranged in the transmission optical path of the microlens group, and the CCD camera is arranged at the focal point of the focusing lens in the transmission optical path of the focusing lens.

[0008] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0009] As a preferred technical solution of the present invention: the first fast deflection mirror and the second fast deflection mirror deflect the incident laser in the horizontal direction and the vertical direction, respectively.

[0010] As a preferred technical solution of the present invention: the driving signals of the first fast deflection mirror and the second fast deflection mirror are the same, which are two sets of square wave signals. The two sets of square wave signals control the deflection of the fast deflection mirror in the horizontal and vertical directions respectively. The two sets of square wave signals have the same intensity and frequency, but their phases differ by 90°.

[0011] As a preferred embodiment of the present invention, the microlens group preferably consists of four microlenses.

[0012] As a preferred embodiment of the present invention: the microlenses in the microlens group are all long focal length lenses, and the focal lengths of each microlens are different.

[0013] As a preferred technical solution of the present invention: the focusing lens is a long focal length lens, and the charge-coupled device camera is arranged at the focal point of the focusing lens in the transmission optical path of the focusing lens, thereby effectively avoiding the situation where the laser cannot be collected by the charge-coupled device camera due to the excessive divergence angle after being focused by the microlens or focusing lens.

[0014] As a preferred technical solution of the present invention: the sampling frequency of the charge-coupled device camera should be less than the square wave signal frequency of the first fast deflection mirror and the second fast deflection mirror, so as to ensure that the charge-coupled device camera can collect information on the laser after being modulated by the first fast deflection mirror and the second fast deflection mirror and passing through microlenses with different focal lengths on a single image.

[0015] As a preferred technical solution of the present invention, the charge-coupled device camera adopts a silicon substrate or an indium gallium arsenide substrate.

[0016] As a preferred technical solution of the present invention: if the beam quality of laser with a wavelength of 400-1100nm is measured, the charge-coupled device camera adopts a silicon substrate; if the beam quality of near-infrared laser with a wavelength greater than 1100nm is measured, the charge-coupled device camera adopts an indium gallium arsenide substrate.

[0017] As a preferred technical solution of the present invention: after the charge-coupled device camera acquires different light spots on a single image, it calculates the beam width of each light spot based on the definition of the second moment of light intensity. Finally, the calculated laser beam width and the corresponding focal length of the equivalent lens are substituted into the following equations, and the laser beam quality M can be calculated by solving the system of equations. 2 :

[0018]

[0019] In the formula: W is the calculated laser beam width, M 2 Let λ be the laser beam quality, a and b be proportionality coefficients, l be the distance from the charge-coupled device camera to the equivalent lens, λ be the wavelength of the laser to be measured, and f be the focal length of the equivalent lens; where the microlens and the focusing lens are considered as one equivalent lens.

[0020] Compared with the prior art, the beam quality dynamic measurement device based on a fast deflection mirror and a microlens group provided by the present invention has the following beneficial effects:

[0021] (1) A single image acquired by a charge-coupled device camera can capture the distribution of four laser spot focused by lenses with different focal lengths. Combined with the high-speed deflection of two fast reflectors, dynamic measurement of laser beam quality can be achieved while ensuring measurement accuracy.

[0022] (2) The device is compact and the system is not easily affected by external disturbances such as gravity and vibration.

[0023] (3) The combination of microlens array and focusing lens is adopted, which greatly reduces the size of the laser beam quality measurement device while ensuring measurement accuracy. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the dynamic beam quality measurement device based on a fast deflection mirror and a microlens group provided by the present invention.

[0025] Figure 2 This is a schematic diagram of the microlens assembly provided by the present invention.

[0026] Figure 3 This is the driving signal for the fast deflection mirror provided by the present invention. Detailed Implementation

[0027] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] Reference Figures 1 to 3 A dynamic beam quality measurement device based on a fast deflecting mirror and a microlens group includes a first fast deflecting mirror 1-1, a second fast deflecting mirror 1-2, a microlens group 2, a focusing lens 3, and a charge-coupled device (CCD) camera 4. The first fast deflecting mirror 1-1, the second fast deflecting mirror 1-2, the microlens group 2, the focusing lens 3, and the CCD camera 4 are placed sequentially along the optical path. The second fast deflecting mirror 1-2 is placed on the reflected light path of the first fast deflecting mirror 1-1; the microlens group 2, composed of four microlenses with different focal lengths, is placed on the reflected light path of the second fast deflecting mirror 1-2; the focusing lens 3 is placed on the transmitted light path of the microlens group 2; and the CCD camera 4 is placed at the focal point of the lens on the transmitted light path of the focusing lens 3.

[0029] The laser under test is first reflected by the first fast deflection mirror 1-1. After being modulated by the first fast deflection mirror 1-1, the laser is incident on the second fast deflection mirror 1-2. The second fast deflection mirror 1-2 further modulates the transmission path of the laser under test, so that the laser under test is incident on the center of different microlenses on the microlens group 2. After passing through the microlens group 2, the laser is incident on the focusing lens 3. After being focused by the focusing lens 3, it is collected by the charge-coupled device camera 4.

[0030] like Figure 2 As shown, the microlens group 2 consists of four microlenses with different focal lengths, which are arranged in a square arrangement relative to each other. The four microlenses in the microlens group 2 and the focusing lens 3 are all telephoto lenses, and the charge-coupled device camera 4 is placed at the focal point of the focusing lens 3, thereby enabling the simultaneous acquisition of light intensity information of the laser after passing through the four different microlenses and the focusing lens 3 on the charge-coupled device camera 4.

[0031] Figure 3 The driving signals for the two fast deflecting mirrors are S1-1 and S1-2, which are the horizontal and vertical driving signals for the first fast deflecting mirror, respectively, and S2-1 and S2-2, which are the horizontal and vertical driving signals for the second fast deflecting mirror, respectively. It can be seen that the signals driving the two fast deflecting mirrors are the same, which are two sets of square wave signals. The two sets of square wave signals control the deflection of the fast deflecting mirrors in the horizontal and vertical directions, respectively, and the two sets of square wave signals have the same intensity, the same frequency, and a phase difference of 90°.

[0032] The charge-coupled device (CCD) camera 4 uses a silicon substrate or an indium gallium arsenide (IGaAs) substrate. If measuring the beam quality of laser light with wavelengths between 400-1100 nm, a silicon substrate is used; if measuring the beam quality of near-infrared laser light with wavelengths greater than 1100 nm, an IGaAs substrate is used. The sampling frequency of the CCD camera 4 should be less than the frequency of the signals driving the first fast deflector 1-1 and the second fast deflector 1-2. After acquiring four different light spots, the CCD camera 4 calculates the beam width of each spot based on the definition of the second moment of light intensity. Finally, the calculated four sets of laser beam widths and the corresponding focal lengths of the equivalent lenses (the microlens and the focusing lens are considered as one equivalent lens) are substituted into the following equations, and the laser beam quality factor M is calculated by solving the equation system. 2 :

[0033]

[0034] In the formula: W is the calculated laser beam width, M 2 Let λ be the laser beam quality, a and b be proportionality coefficients, l be the distance from the charge-coupled device camera to the equivalent lens, λ be the wavelength of the laser to be measured, and f be the focal length of the equivalent lens; where the microlens and the focusing lens are considered as one equivalent lens.

[0035] Specifically, this is implemented through the following embodiments:

[0036] Reference Figure 1 A 1mW laser with a wavelength of 633nm is incident on a fast deflector 1-1 at a 45° angle. The laser is then reflected by the fast deflector 1-1 in four different directions at a frequency of 10Hz in both the horizontal and vertical directions. The first fast deflector 1-1 is a high-reflectivity mirror with a reflectivity of 99%. The reflected laser is then incident on a second fast deflector 1-2. After being modulated by the second fast deflector 1-2 at a frequency of 10Hz in both the horizontal and vertical directions, the laser light is incident on the center of each microlens in the microlens group 2. The second fast deflector 1-2 is also a high-reflectivity mirror with a reflectivity of 99%. Each lens in the microlens group 2 is coated with an anti-reflection film with a transmittance greater than 99%. The light transmitted through the microlens group is then focused by a focusing lens 3 coated with an anti-reflection film with a transmittance greater than 99%, and is collected by a charge-coupled device camera 4 at a frequency of 5Hz. Since the sampling frequency (5Hz) of the charge-coupled device (CCD) camera 4 is lower than the deflection frequency (10Hz) of the two fast deflection mirrors, the CCD camera 4 can simultaneously acquire information on four light spots after the laser under test passes through four microlenses with different focal lengths. The beam widths of the four different light spots are calculated based on the second-order moment algorithm of light intensity. The laser beam width and the distance between the corresponding equivalent lens and the CCD camera 4 are then substituted into equation (1) for calculation and solution, yielding the laser beam quality factor M.2 .

[0037] Based on the above parameters, the laser energy utilization rate R of this system can be determined by the following formula.

[0038] R=99%×99%×99%×99%≈96.06%

[0039] It is evident that this dynamic beam quality measurement device based on a fast deflection mirror and microlens group has good laser energy utilization.

[0040] As will be apparent from the foregoing description, certain aspects of the invention are not limited to the specific details of the examples shown herein, and thus, those skilled in the art will contemplate other modifications and applications or equivalents thereof. The terms “having,” “comprising,” and “including,” and similar terms as used in the foregoing description, are interpreted as “optional” or “may include” rather than “essential.” However, many changes, modifications, variations, and other uses and applications of the invention will be apparent to those skilled in the art upon consideration of the specification and drawings. All such changes, modifications, variations, and other uses and applications that do not depart from the scope and spirit of the invention are considered to be covered by the invention. It should be understood that the examples disclosed herein include any combination and all instances of the features described in any dependent claims.

Claims

1. A dynamic beam quality measurement device based on a fast deflecting mirror and a microlens group, characterized in that: The beam quality dynamic measurement device based on a fast deflecting mirror and a microlens group includes a first fast deflecting mirror, a second fast deflecting mirror, a microlens group, a focusing lens, and a charge-coupled device (CCD) camera arranged sequentially along the optical path. The first fast deflecting mirror is used to reflect the laser to be measured onto the second fast deflecting mirror, and the second fast deflecting mirror is used to reflect the laser modulated by the first fast deflecting mirror to the center of different microlenses in the microlens group. The microlens group is composed of multiple microlenses. The focusing lens is arranged in the transmission optical path of the microlens group, and the CCCD camera is arranged at the focal point of the focusing lens in the transmission optical path of the focusing lens. After acquiring different light spots on a single image, the charge-coupled device (CCD) camera calculates the beam width of each spot based on the definition of the second moment of light intensity. Finally, the calculated laser beam width and the corresponding equivalent lens focal length are substituted into the following equations, and the beam quality factor of the laser can be calculated by solving the system of equations. : Equation (1) In the formula: W is the calculated laser beam width, denoted as the beam quality factor of the laser, a and b are proportionality coefficients, l is the distance from the charge-coupled device camera to the equivalent lens, λ is the wavelength of the laser to be measured, and f is the focal length of the equivalent lens; where the microlens and the focusing lens are considered as one equivalent lens.

2. The beam quality dynamic measurement device based on a fast deflecting mirror and microlens group according to claim 1, characterized in that: The first fast deflection mirror and the second fast deflection mirror deflect the incident laser in the horizontal and vertical directions, respectively.

3. The dynamic beam quality measurement device based on a fast deflecting mirror and microlens group according to claim 1 or 2, characterized in that: The first and second fast deflection mirrors have the same driving signal, which is two sets of square wave signals. The two sets of square wave signals control the deflection of the fast deflection mirror in the horizontal and vertical directions, respectively. The two sets of square wave signals have the same intensity and frequency, but their phases differ by 90°.

4. The dynamic beam quality measurement device based on a fast deflecting mirror and microlens group according to claim 1, characterized in that: The microlens group consists of four microlenses.

5. The beam quality dynamic measurement device based on a fast deflecting mirror and microlens group according to claim 1, characterized in that: The microlenses in the microlens group are all long focal length lenses, and the focal lengths of each microlens are different.

6. The dynamic beam quality measurement device based on a fast deflecting mirror and microlens group according to claim 1, characterized in that: The focusing lens is a long focal length lens.

7. The dynamic beam quality measurement device based on a fast deflecting mirror and microlens group according to claim 1, characterized in that: The sampling frequency of the charge-coupled device camera should be lower than the square wave signal frequency of the first fast deflection mirror and the second fast deflection mirror.

8. The dynamic beam quality measurement device based on a fast deflecting mirror and microlens group according to claim 1, characterized in that: The charge-coupled device camera uses a silicon substrate or an indium gallium arsenide substrate.

9. The dynamic beam quality measurement device based on a fast deflecting mirror and microlens group according to claim 8, characterized in that: If the beam quality of laser with wavelengths of 400-1100 nm is to be measured, the charge-coupled device (CCD) camera uses a silicon substrate; if the beam quality of near-infrared laser with wavelengths greater than 1100 nm is to be measured, the CCD camera uses an indium gallium arsenide (IGaAs) substrate.

Images