CN113639967A - Laser beam quality real-time measuring method based on special-shaped prism - Google Patents
Laser beam quality real-time measuring method based on special-shaped prism Download PDFInfo
- Publication number
- CN113639967A CN113639967A CN202110906386.2A CN202110906386A CN113639967A CN 113639967 A CN113639967 A CN 113639967A CN 202110906386 A CN202110906386 A CN 202110906386A CN 113639967 A CN113639967 A CN 113639967A
- Authority
- CN
- China
- Prior art keywords
- special
- focusing lens
- light
- shaped prism
- laser
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
Abstract
The invention discloses a method for measuring the quality of a laser beam in real time based on a special-shaped prism, which comprises the steps of enabling the laser to be measured to enter a second focusing lens through a first focusing lens for beam shrinkage, enabling the beam after beam shrinkage to enter the special-shaped prism, dividing an axial beam in a laser transmission direction into two beams through the special-shaped prism, imaging the two beams onto a CCD (charge coupled device) simultaneously, obtaining light spot light intensity information of two axial positions in the laser transmission direction, obtaining an optical path difference between the two light spots through the refractive index of a prism medium, and obtaining a beam quality factor M through solving an iterative GS (generalized engineering) or TIE (generalized equation) equation2. The measuring device is simple, the measuring speed is high, the real-time measurement can be realized, no measuring device needing to be moved is needed in the measuring process, and the light intensity distribution of two light spots with known optical path difference can be obtained by only shooting the light intensity distribution diagram of one laser transmission direction, so that the laser beam quality M is obtained2The factor is simpler and quicker than the prior art.
Description
Technical Field
The invention belongs to the technical field of lasers, and particularly relates to a method for measuring the quality of a laser beam in real time based on a special-shaped prism.
Background
Since the advent of laser, laser has been widely used in the fields of industry, medical treatment, military affairs, and the like because of its excellent directivity, monochromaticity, and high brightness. With the combination of laser and computer numerical control system, the laser processing technology has become a key technology for industrial automatic production in the industrial links of cutting, welding, punching, etching and the like. In medical treatment, various laser medical machines, laser physical therapy machines and laser intracavity therapeutic machines appear, so that a plurality of complicated medical problems become simple, and a plurality of difficult and complicated diseases have the possibility of curing. In military affairs, laser blinding weapons, laser guided bombs and other laser weapons appear, so that the laser can be expected to be more widely applied in military affairs in the future.
The beam quality is a core parameter for measuring the quality of a laser. For different laser applications, various evaluation parameters have historically been proposed by scientific techniques, such as: stelmor ratio, diffraction limit factor beta, beam quality factor (M)2) And the like. The quality factor of the light beam covers the near field and far field characteristics of the laser, and the light beam M passes through an ideal optical system2The factor is unchanged. In contrast to other definitions, M2The factor can better reflect the essence of the beam quality, and is adopted and popularized by the ISO international standardization organization.
For laser beam quality factor M2There are many methods such as CCD multi-position measurement, knife edge method, liquid lens method, etc. which require a certain measurement time, and many dynamic measurement methods such as wavefront analysis, pattern decomposition method, etc. The methods have the defects of complex measuring structure, low measuring speed and the like.
Disclosure of Invention
The invention aims to provide a method for measuring the quality of a laser beam in real time based on a special-shaped prism, which has high measuring speed and simple structure.
The technical solution for realizing the purpose of the invention is as follows: a real-time laser beam quality measuring method based on a special-shaped prism comprises the following steps:
firstly, building a laser beam quality measuring device: the laser beam quality device comprises a beam-shrinking system, a special-shaped prism and a Charge Coupled Device (CCD), wherein the beam-shrinking system comprises a first focusing lens and a second focusing lens;
secondly, the laser to be measured is imaged on a CCD (charge coupled device) of a CCD (charge coupled device) through a special-shaped prism after passing through a first focusing lens and a second focusing lens to obtain two light intensity distributions of the laser at the moment, and the diameter of a laser spot passing through the second focusing lens meets the light splitting requirement of the special-shaped prism;
thirdly, calculating the complex amplitude of a specific position through the light intensity of the light spots at two positions with known optical path difference, and calculating M by using a transmission algorithm and a hyperbolic fitting algorithm2A factor.
Preferably, the first focusing lens is an achromatic double cemented lens, the surface of the first focusing lens with the larger curvature radius is an incident surface of the light beam, and the surface of the first focusing lens with the smaller curvature radius is an emergent surface of the light beam.
Preferably, the second focusing lens is an achromatic double-cemented lens, the surface of the second focusing lens with the smaller curvature radius is an incident surface of the light beam, and the surface of the second focusing lens with the larger curvature radius is an emergent surface of the light beam.
Preferably, a neutral density filter is placed in front of the first focusing lens and the second focusing lens.
Preferably, the special-shaped prism comprises three anti-reflection films, a semi-transparent semi-reflection film and a reflection film, the three anti-reflection films are perpendicular to the incidence direction of the laser beam, the semi-transparent semi-reflection film and the incidence direction of the laser beam form 45 degrees, the reflection film and the original transmission direction of the laser beam form 45 degrees, the incident light is divided into light in the horizontal axial direction and light in the vertical direction through the semi-transparent semi-reflection film, the light in the vertical direction is refracted again through the reflection film, and the light in the horizontal axial direction form two beams of light which are located in the same horizontal line and are parallel to each other.
Preferably, the intensity of the light spot incident on the camera CCD is above the threshold of the CCD and below the saturation of the camera.
Preferably, the object-image relationship in the beam-shrinking system satisfies:
in the formula (f)1、f2The focal lengths of the first focusing lens and the second focusing lens, omega1、ω2The radius of the light beam before the first focusing lens and the radius of the light beam from the second focusing lens to the special-shaped prism are respectively.
Compared with the prior art, the invention has the remarkable advantages that: (1) the invention has simple measuring structure and no device needing to move; (2) the invention uses a special-shaped prism, only needs to collect a laser transmission elevation map, can obtain the light intensity distribution of light spots at two axial positions, and has simple measuring method; (3) the invention has high measuring speed and can realize real-time measurement.
Drawings
FIG. 1 is a schematic structural diagram of a laser beam quality measuring device according to the present invention.
Fig. 2 is a schematic diagram of a profiled prism structure.
Detailed Description
The invention is further described with reference to the following figures and detailed description.
A laser beam quality real-time measurement method based on a special-shaped prism enables laser to be measured to enter a second focusing lens through a first focusing lens for beam shrinkage, the beam shrunk light enters the special-shaped prism, an axial light beam in a laser transmission direction is divided into two parts through the special-shaped prism and simultaneously imaged on a CCD (charge coupled device), so that light spot light intensity information of two axial positions in the laser transmission direction is obtained, meanwhile, an optical path difference between two light spots can be obtained through the refractive index of a prism medium, a beam quality factor M2 is obtained through GS iteration or TIE equation solving, and the method specifically comprises the following steps:
the method comprises the following steps of firstly, building a laser beam quality measuring device, wherein the laser beam quality measuring device comprises a beam reduction system, a special-shaped prism 3 and a charge coupled device camera CCD4, and the beam reduction system comprises a first focusing lens 1 and a second focusing lens 2. The focal points of a first focusing lens 1 and a second focusing lens 2 of the beam-shrinking system are positioned on the same horizontal line and share the same optical axis with emergent light of the laser. The special-shaped prism 3 is positioned at the focus of the second focusing lens 2, and the optical axis of the light beam passing through the second focusing lens 2 is vertical to the incident plane of the special-shaped prism 3. The incidence plane of the special-shaped prism 3 is parallel to the two emergence planes of the special-shaped prism 3 and is parallel to the target plane of the CCD4 of the CCD camera. The CCD4 target surface is enough to accommodate two light spots formed by the beam splitting of the special-shaped prism 3.
In a further embodiment, the first focusing lens 1 is an achromatic double cemented lens, the surface of the first focusing lens 1 with the larger curvature radius is an incident surface of the light beam, and the surface with the smaller curvature radius is an exit surface of the light beam.
In a further embodiment, the second focusing lens 2 is an achromatic double-cemented lens, a surface of the second focusing lens 2 with a smaller curvature radius is an incident surface of the light beam, and a surface with a larger curvature radius is an exit surface of the light beam.
In a further embodiment, a neutral density filter is placed in front of the first focusing lens 1 and the second focusing lens 2.
In a further embodiment, the semi-transparent and semi-reflective film of the special-shaped prism 3 is perpendicular to the laser transmission direction by 45 degrees, and divides incident light into light in the horizontal axis direction and light in the horizontal direction, the light in the horizontal direction is refracted again through the reflective film perpendicular to the original laser transmission direction by 45 degrees, and forms two parallel light beams in the same horizontal line with the light in the horizontal axis direction.
Secondly, the laser to be measured sequentially passes through the first focusing lens 1 and the second focusing lens 2, the diameter of a light spot passing through the second focusing lens 2 meets the light splitting requirement of the special-shaped prism 3, and the laser is imaged on a CCD4 of a charge coupled device camera through the special-shaped prism 3 to obtain two light intensity distributions of the laser at the moment;
in a further embodiment, the intensity of the light spot incident on camera CCD4 is above the threshold of CCD4 and below the saturation of the camera, and can be controlled by adjusting a neutral density filter.
In a further embodiment, the object-image relationship in the beam-shrinking system satisfies:
in the formula (f)1、f2The focal lengths of the first focusing lens 1 and the second focusing lens 2 are respectively. Omega1、ω2The radius of the light beam before the first focusing lens 1 and the radius of the light beam from the second focusing lens 2 to the special-shaped prism 3 are respectively. All in oneTime, omega1Is the laser beam waist radius before beam-shrinking, i.e. the laser exit beam radius, omega2Is the radius of the beam after passing through the beam-shrinking system.
Thirdly, calculating the complex amplitude of a specific position through the light intensity of the light spots at two positions with known optical path difference, and calculating M by using a transmission algorithm and a hyperbolic fitting algorithm2A factor.
In a further embodiment, the complex amplitude calculation satisfies:
wherein k is a wave number,
r is the lateral position coordinate (x, y), I (r) is the light intensity distribution at one of the positions,
for the hamiltonian acting on the r-plane,
is the phase.
The light split by the special-shaped prism (3) and the position in z perpendicular to the optical axis direction can be measured by a charge coupled device camera CCD (4)0And z0Light intensity in + dz plane according to the formula [ I (x, y, z)0+dz)-I(x,y,z0)]The axial differential of the light intensity is obtained by the/dz. Further, the following are used:
solving the quantitative phase information of the light wave to be measured
The light field information may be derived from the complex amplitude, i.e. z, obtained as described above0Light intensity, phase, angle of passage of positionThe spectrum diffraction transmission yields the complex amplitude at each position:
in the formula, Gd(x,y,z0+ d) is the distance z0A light field U of a position dd(x,y,z0+ d) Fourier transform, Gz(x,y,z0) Is z0Positional light field Uz(x,y,z0) Fourier transform of (i.e. pair)
And performing Fourier transform, and converting the Fourier transform into a frequency domain for solving. k is the number of waves,
d is a distance z0λ is the wavelength, fx、fyIs the coordinate of the frequency domain in which the fourier transform is performed.
Through Gd(x,y,z0+ d) inverse Fourier transform to obtain Ud(x,y,z0+ d) to obtain Id(x,y,z0+ d). From the light intensity distribution Id(x,y,z0+ d) z is obtained from the second moment0Waist ω at + d positiond。
In a further embodiment, the beam waist at ten or more positions is obtained according to the above method, and according to a multi-point fitting rule, a hyperbolic fitting formula of the beam width is:
ω2＝Az2+Bz+C
obtaining coefficients A, B, C from a multi-point fit, M2The factor satisfies:
by adopting the method, the laser beam quality measuring device is set up according to the figure 1, and all measuring modules are erected on the optical anti-seismic platform. The laser to be measured is clamped by a clamper and can be adjusted left and right, the laser to be measured is fixed on a platform by a bracket and can be adjusted up and down, the laser is firstly turned on to preheat to ensure the stability of the emergent light beam, then the height inclination and pitching of the laser are adjusted to ensure the collimation and light emitting of the laser, the collimated laser to be measured is focused into a focusing lens 2 through the focusing lens 1 to be condensed, a neutral density filter is adjusted to ensure that the light intensity incident to a CCD is higher than the threshold value of the CCD camera and lower than the saturation concentration of the CCD camera, the incident light is imaged into a CCD camera 4 arranged on an imaging plane by a special-shaped prism 3, the special-shaped prism consists of three antireflection films, a semi-transparent and semi-reflective film and a reflective film according to the figure 2, the antireflection film is ensured to be vertical to the transmission direction of the laser beam, the antireflection film is inclined at 45 degrees with the transmission direction of the laser beam and the transmission direction of the laser beam, and the reflective film is also inclined with the transmission direction of the laser beam, Are inclined at 45 degrees perpendicular to the transmission direction of the laser beam. And finally, recording the axial light intensity distribution of two known optical path difference positions in the transmission direction of the laser to be measured by the CCD.
After the device obtains the light intensity distribution of two known optical path difference positions in the laser transmission direction, the beam width in the transmission direction is determined by using a diffraction transmission algorithm and a second moment method, and the laser beam quality M is calculated by hyperbolic curve fitting2A factor.
Claims (7)
1. A real-time laser beam quality measuring method based on a special-shaped prism is characterized by comprising the following steps:
firstly, building a laser beam quality measuring device: the laser beam quality device comprises a beam reduction system, a special-shaped prism (3) and a charge coupled device camera CCD (4), wherein the beam reduction system comprises a first focusing lens (1) and a second focusing lens (2);
secondly, the laser to be measured is imaged on a CCD (4) of a charge coupled device camera through a first focusing lens (1) and a second focusing lens (2) through a special-shaped prism (3) to obtain two light intensity distributions of the laser at the moment, and the diameter of a laser spot passing through the second focusing lens (2) meets the light splitting requirement of the special-shaped prism (3);
thirdly, calculating the light intensity of the light spots at two positions with known optical path differenceThe complex amplitude of the fixed position is calculated by using a transmission algorithm and a hyperbolic curve fitting algorithm2A factor.
2. The method for measuring the quality of the laser beam based on the special-shaped prism in real time as claimed in claim 1, wherein the first focusing lens (1) is an achromatic double cemented lens, the surface of the first focusing lens (1) with the larger curvature radius is an incident surface of the beam, and the surface with the smaller curvature radius is an emergent surface of the beam.
3. The method for real-time measurement of the quality of the laser beam based on the special-shaped prism as claimed in claim 1, wherein the second focusing lens (2) is an achromatic double cemented lens, the side of the second focusing lens (2) with the smaller curvature radius is an incident surface of the beam, and the side with the larger curvature radius is an emergent surface of the beam.
4. The method for measuring the quality of the laser beam based on the special-shaped prism in real time as claimed in claim 1, wherein neutral density filters are placed in front of the first focusing lens (1) and the second focusing lens (2).
5. The method for measuring the quality of the laser beam based on the special-shaped prism in real time as claimed in claim 1, wherein the special-shaped prism (3) comprises three anti-reflection films, a semi-transparent and semi-reflective film and a reflective film, the three anti-reflection films are perpendicular to the incident direction of the laser beam, the semi-transparent and semi-reflective film and the incident direction of the laser beam form 45 degrees, the reflective film and the original transmission direction of the laser beam form 45 degrees, the incident light is divided into light in the horizontal axial direction and light in the vertical direction through the semi-transparent and semi-reflective film, the light in the vertical direction is refracted again through the reflective film, and the light in the horizontal axial direction form two beams of light which are located in the same horizontal line and are parallel to each other.
6. The method for measuring the quality of the laser beam based on the special-shaped prism in real time as claimed in claim 1, wherein the light intensity of the light spot incident to the camera CCD (4) is higher than the threshold value of the CCD camera CCD (4) and lower than the saturation of the camera.
7. The method for measuring the quality of the laser beam based on the special-shaped prism in real time as claimed in claim 1, wherein the object-image relationship in the beam-shrinking system satisfies the following conditions:
in the formula (f)1、f2The focal length, omega, of the first focusing lens (1) and the second focusing lens (2) respectively1、ω2The radius of the light beam emitted by the laser and the radius of the light beam from the second focusing lens (2) to the special-shaped prism (3) are respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110906386.2A CN113639967A (en) | 2021-08-09 | 2021-08-09 | Laser beam quality real-time measuring method based on special-shaped prism |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110906386.2A CN113639967A (en) | 2021-08-09 | 2021-08-09 | Laser beam quality real-time measuring method based on special-shaped prism |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN113639967A true CN113639967A (en) | 2021-11-12 |
Family
ID=78420091
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110906386.2A Pending CN113639967A (en) | 2021-08-09 | 2021-08-09 | Laser beam quality real-time measuring method based on special-shaped prism |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113639967A (en) |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140111798A1 (en) * | 2012-10-22 | 2014-04-24 | Haas Laser Technologies, Inc. | Apparatus for focus beam analysis of high power lasers |
| CN104198054A (en) * | 2014-08-27 | 2014-12-10 | 中国科学院上海光学精密机械研究所 | Movable high-power laser beam wavefront measuring device and measuring method thereof |
| CN105222901A (en) * | 2015-09-24 | 2016-01-06 | 程灏波 | Based on the real-time quantitative phase detection device of light intensity transmission equation |
| CN107607195A (en) * | 2017-08-07 | 2018-01-19 | 南京理工大学 | A kind of beam quality measuring method obtained in real time based on complex amplitude |
| CN109798847A (en) * | 2018-11-27 | 2019-05-24 | 中国科学院国家天文台南京天文光学技术研究所 | The measuring device and its test method of the measuring beam angle of divergence and the laser-quality factor |
| CN113091898A (en) * | 2021-03-04 | 2021-07-09 | 南京理工大学 | Laser beam quality measuring method based on scattered light imaging method |
| CN113155279A (en) * | 2020-10-30 | 2021-07-23 | 长春理工大学 | Single-point measurement method for laser beam quality |
-
2021
- 2021-08-09 CN CN202110906386.2A patent/CN113639967A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140111798A1 (en) * | 2012-10-22 | 2014-04-24 | Haas Laser Technologies, Inc. | Apparatus for focus beam analysis of high power lasers |
| CN104198054A (en) * | 2014-08-27 | 2014-12-10 | 中国科学院上海光学精密机械研究所 | Movable high-power laser beam wavefront measuring device and measuring method thereof |
| CN105222901A (en) * | 2015-09-24 | 2016-01-06 | 程灏波 | Based on the real-time quantitative phase detection device of light intensity transmission equation |
| CN107607195A (en) * | 2017-08-07 | 2018-01-19 | 南京理工大学 | A kind of beam quality measuring method obtained in real time based on complex amplitude |
| CN109798847A (en) * | 2018-11-27 | 2019-05-24 | 中国科学院国家天文台南京天文光学技术研究所 | The measuring device and its test method of the measuring beam angle of divergence and the laser-quality factor |
| CN113155279A (en) * | 2020-10-30 | 2021-07-23 | 长春理工大学 | Single-point measurement method for laser beam quality |
| CN113091898A (en) * | 2021-03-04 | 2021-07-09 | 南京理工大学 | Laser beam quality measuring method based on scattered light imaging method |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110470245B (en) | Phase recovery detection device and phase recovery method based on Fresnel zone plate diffraction information fusion | |
| US10627222B2 (en) | Method and apparatus for detecting cylinder and cylindrical converging lens | |
| CN107607195B (en) | A kind of beam quality measurement method obtained in real time based on complex amplitude | |
| CN113568153B (en) | Microscopic imaging equipment and nanoscale three-dimensional shape measurement system | |
| CN110907415A (en) | Three-dimensional sub-ten nanometer positioning method and device based on parallel detection | |
| US20190219388A1 (en) | Method and apparatus for detecting concave cylinder and cylindrical diverging lens | |
| CN114216659A (en) | System and method for measuring parallelism of large-caliber long-focus optical axis | |
| CN113504717B (en) | Uniform holographic two-photon microscope system based on space-time focusing | |
| CN105758381A (en) | Method for detecting inclination of camera die set based on frequency spectrum analysis | |
| CN105676423B (en) | A kind of lens subassembly and the method for obtaining Beams | |
| WO2013009550A9 (en) | Beam shaping and control apparatus | |
| CN114688963A (en) | Light path beam combination quality detection and calibration method and system for multi-wavelength point diffraction interferometer | |
| CN108563027B (en) | Automatic adjustment method for expanded collimated light beam | |
| Zhao et al. | An approximate analytical propagation formula for Gaussian beams through a cat-eye optical lens under large incidence angle condition | |
| CN113639967A (en) | Laser beam quality real-time measuring method based on special-shaped prism | |
| CN107966279B (en) | Multi-view-field wavefront measuring device and method for telescope system | |
| CN111061063B (en) | Pupil filtering far-field super-resolution imaging system and pupil filter design method | |
| CN113933277B (en) | High-density three-dimensional single-molecule positioning super-resolution microscopic imaging system and method | |
| CN113091898A (en) | Laser beam quality measuring method based on scattered light imaging method | |
| Eckmann et al. | Imaging in reflecting spheres | |
| CN113552094A (en) | Measuring device and measuring method for ICF target pellet ice layer refractive index three-dimensional reconstruction | |
| JPS63273806A (en) | Objective for laser beam machining | |
| CN112859359B (en) | Focal spot control method | |
| CN117575901B (en) | X-ray phase contrast micro-splicing method and system based on multilayer film Laue lens | |
| CN216284938U (en) | High-density three-dimensional single-molecule positioning super-resolution microscopic imaging system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |