CN113092070B - Beam quality factor M 2 Quick measuring device and method - Google Patents
Beam quality factor M 2 Quick measuring device and method Download PDFInfo
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Abstract
The invention belongs to a beam quality factor M 2 The technical field of measurement, and particularly discloses a beam quality factor M 2 A rapid measurement device and method. The device comprises a device to be sampled, a zooming device, a light spot measuring device and a data processing device, wherein the light beam quality factor M of the laser source to be measured is calculated according to the focal length of the zooming device and the light spot size of the light spot measuring device which is acquired and measured by the zooming device in real time under different focal lengths 2 . The method comprises the following steps: the laser source to be measured emits laser and attenuates the laser; focusing the attenuated laser, collecting and measuring the laser spot size at the focus in real time in the continuous zooming process, and calculating the beam quality factor M of the laser source to be measured 2 . The invention overcomes the defects of the prior M 2 The measuring equipment has the defects of low measuring speed caused by the requirement of driving the reflecting mirror group to carry out large-stroke displacement, has the advantages of clear principle, high adjusting speed, simple and convenient operation and the like, and can greatly improve the beam quality factor M 2 Is provided.
Description
Technical Field
The invention belongs to a beam quality factor M 2 The field of measurement, more specifically, to a beam quality factor M 2 A rapid measurement device and method.
Background
Beam quality has received widespread attention from researchers and users as a core index for lasers. In order to accurately evaluate the quality of the laser beam, the laser is used at home and abroadResearchers have proposed a variety of beam quality assessment factors, most commonly beam quality factor M, from theoretical and practical perspectives 2 A diffraction limit multiplier factor beta, a Power In Barrel (PIB), a power in barrel ratio (BQ), a Stell Ratio (SR), and so on. For uniform evaluation of the quality of the laser output beam, the International organization for standardization (ISO) proposes M 2 The proposal of the factor representation beam quality is widely accepted at home and abroad.
M according to ISO 11146-1:2005 standard 2 The factor is defined as:
wherein:
d 0 -beam waist width or beam waist diameter;
θ—far field beam divergence angle.
Due to M 2 The factor is the beam cross-sectional diameter calculated using a second moment method. Based on beam width measurement M 2 Many researches are carried out on the factor method, and specifically, a focusing two-point method, a three-point method, a multi-point fitting method and the like are carried out. In principle, M can be calculated using the beam width at three different positions 2 The factor, more measurements of the location, are used to check against each other to reduce the error. Measuring beam width d of light beam at different positions along propagation axis z, determining transmission profile of light beam by hyperbola fitting, and finally determining M 2 Factors. According to the ISO standards concerned, at least 10 measurements must be made, at least 5 times, within the rayleigh length of the beam in order to guarantee measurement accuracy. The fitting formula of the beam width is as follows:
d 2 ＝A+B·z+C·z 2
after coefficients A, B and C of the hyperbola are obtained by using knowledge of mathematical statistics, the beam waist position z can be obtained 0 And diameter d 0 Far field divergence angle θ and M 2 A factor, as shown in the following equation:
common M 2 The working principle of the factor measuring equipment is shown in figure 4, and the high-power light source to be measured enters M after passing through the reflector, the sampling device and the attenuation sheet 2 In the analyzer, a control system scans near the beam waist by controlling a servo motor connected with a movable guide rail, so that the beam width d of the light beam at different positions along the propagation axis z can be obtained, the transmission profile of the light beam is determined after hyperbola fitting processing, and finally M is determined 2 Factors. According to the ISO standard, at least 10 measurements must be made, at least 5 times, within the rayleigh length of the beam, in order to guarantee measurement accuracy. Existing M 2 The test equipment, the movement of the measuring position is the mechanical displacement of the distance adjusting structure through electric control, more than 10 times of displacement-measurement-fitting-displacement processes are needed, and the measuring time is about 1min-2min. The working time of the high-power laser is generally shorter, and the long-time operation of the laser and the optical components can lead to the degradation of the quality of the light beam, so that M is measured for a long time 2 The value does not truly reflect the beam quality of the laser beam, but rather is an average value over a period of time.
Disclosure of Invention
In response to the above-identified deficiencies or improvements in the prior art, the present invention provides a beam quality factor M 2 Fast measuring device and method, wherein a beam quality factor M is combined 2 The characteristics of the self and the characteristics of the measuring and calculating methods thereof correspondingly design a beam quality factor M 2 Quick measuring device and method, and key components such as to be measuredThe structures of the sampling device, the zooming device, the electric control adjusting device and the data processing device and the specific setting modes thereof are researched and designed, and the traditional M can be correspondingly and effectively solved 2 The measuring equipment needs to drive the reflecting mirror group to carry out large-stroke displacement to cause the problem of low measuring speed, has the advantages of clear principle, high adjusting speed, simple and convenient operation and the like, and can greatly improve the beam quality factor M 2 Is provided.
To achieve the above object, according to one aspect of the present invention, there is provided a beam quality factor M 2 A rapid measurement apparatus comprising:
the device to be sampled is used for inputting the collimated laser emitted by the laser source to be tested and attenuating the collimated laser;
the zoom device is used for changing the focal length of the collimated laser under the control of the electric control adjusting device and focusing the attenuated collimated laser under different focal lengths;
the light spot measuring device is used for collecting and measuring the light spot size of the collimated laser focused by the zooming device in real time;
the data processing device is used for calculating the beam quality factor M of the laser source to be measured according to the focal length of the zooming device and the spot size acquired and measured by the spot measuring device in real time under different focal lengths of the zooming device 2 。
As a further preferred feature, the apparatus further comprises an optical path folding means provided between the zoom means and the spot measuring means for folding the optical path between the zoom means and the spot measuring means.
As a further preferred option, the zoom device is a variable focus lens, a variable focus mirror or a variable focus multi-lens group of a combination of lenses and mirrors driven by a micro-electromechanical system, the focal length of the zoom device typically ranging from 1 mm to 1000 mm. .
As a further preferred aspect, the electronic control adjusting device is connected with the zooming device through an electronic control interface, and the electronic control adjusting device drives the movable unit or the acousto-optic characteristic or the electromagnetic characteristic in the zooming device by changing the current or voltage signal input into the zooming device so as to control the change of the focal length of the zooming device.
As a further preferable mode, the built-in detector of the light spot measuring device is a CCD camera or a CMOS, the response wavelength range of the detector covers the center wavelength of the light source to be measured, and the distance between the light spot measuring device and the zooming device is fixed to be the median of the focal length variation range of the zooming device.
As a further preferred aspect, the data processing device calculates the beam quality factor M of the laser source under test by constructing a spot radius calculation model at the spot measuring device 2 ；
The light spot radius calculation model is as follows:
wherein,for the beam waist radius of the collimated laser beam after focusing by the zoom device with focal length f, +.>For the rayleigh length of the collimated laser beam after focusing by a zoom device with a focal length f, z f The distance between the beam waist of the collimated laser beam focused by the zooming device with the focal length f and the detection surface of the facula measuring device;
since the zoom device and the light spot measuring device are kept unchanged, z f ＝f-f 0 The spot radius calculation model is expressed as:
wherein,B＝ω 2 ，C＝-2ω 2 f 0 ，D＝ω 2 f 0 2 thereby deriving a beam quality factor M for calculating the laser source to be measured 2 The calculation model of (2) is as follows:
wherein f is the focal length of the zoom device, pi and lambda are constants, M 2 Is the beam quality factor of the laser source to be measured, omega is the beam waist radius of the laser source to be measured, f 0 Is an initial focal length value (default is the median of the focusing range) of the zoom apparatus (2).
According to another aspect of the invention, the invention also provides a beam quality factor M 2 The rapid measurement method comprises the following steps:
(11) The laser source to be measured emits collimated laser and attenuates the collimated laser;
(12) Performing primary focusing on the attenuated collimated laser, and collecting and measuring the size of a collimated laser spot at a focus of primary focusing of the laser;
(13) Changing the focal length of the collimation laser focusing, and collecting and measuring the size of the collimation laser spot at the primary focusing focal point in real time in the continuous zooming process;
(14) Calculating a beam quality factor M of the laser source to be measured according to the size of the collimated laser spot obtained by primary focusing measurement, the focal length of primary focusing and the size of the collimated laser spot at the focal point of primary focusing under different focal lengths 2 。
As a further preferable mode, in the step (12) and the step (13), when focusing the laser, the optical path folding device is also used for folding the optical path in the focusing process.
As a further preferred option, the focal length of the collimated laser focus is changed by a zoom device, and the spot size of the collimated laser at the primary focused focal point is collected and measured in real time by a spot measurement device, wherein the distance between the zoom device and the spot measurement device is kept unchanged.
As a further preferred, step (14) specifically comprises the steps of:
(141) Constructing a calculation model of the laser spot size at the primary focusing focal point:
wherein,for the beam waist radius of the collimated laser beam after focusing by the zoom device with focal length f, +.>For the rayleigh length of the collimated laser beam after focusing by a zoom device with a focal length f, z f The distance between the beam waist of the collimated laser beam focused by the zooming device with the focal length f and the detection surface of the facula measuring device;
(142) Since the zoom device and the light spot measuring device are kept unchanged, z f ＝f-f 0 The spot radius calculation model is expressed as:
wherein,B＝ω 2 ，C＝-2ω 2 f 0 ，D＝ω 2 f 0 2 ，
(143) Deriving a beam quality factor M for calculating the laser source under test according to step (142) 2 The calculation model of (2) is as follows:
wherein f is the focal length of the zoom device, and pi and lambda are bothConstant, M 2 Is the beam quality factor of the laser source to be measured, omega is the beam waist radius of the laser source to be measured, f 0 Is an initial focal length value (default is the median of the focusing range) of the zoom apparatus (2).
In general, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:
1. the invention combines the beam quality factor M 2 The characteristics of the device and the measuring and calculating method thereof, and the structure and the specific setting mode of key components such as the device to be sampled, the zooming device, the electric control adjusting device and the data processing device are researched and designed, thus correspondingly and effectively solving the problem of traditional M 2 The measuring equipment needs to drive the reflecting mirror group to carry out large-stroke displacement to cause the problem of low measuring speed, has the advantages of clear principle, high adjusting speed, simple and convenient operation and the like, and can greatly improve the beam quality factor M 2 Is provided.
2. According to the invention, the focal length of the zooming device is changed through the electric control adjusting device, and the spot measuring device keeps the axial position unchanged, so that the spot size under different focal lengths can be obtained. Due to the spot size and the beam quality factor M of the beam to be measured 2 The initial spot size, the system focal length and the like are closely related, and the beam quality factor M of the beam to be measured can be obtained through theoretical derivation and data fitting 2 。
3. The light path folding device adopts the reflection light path to fold the light path between the zooming device and the light spot measuring device so as to reduce the size of the whole device.
4. The focal length of the zoom lens is extremely fast in change speed, and the bottleneck of measurement is the frame frequency of the CCD camera and the data processing speed. The CCD camera takes about 50ms to acquire a single frame image, and the radius of a calculated light spot is smaller than 1ms, so that the time for completing 11 times of measurement is smaller than 600ms, the data fitting can be controlled within 50ms, the whole measurement process can be completed within 700ms, and the method is far higher than the traditional M 2 Testing speed.
5. The invention adopts a zooming device to replace the traditional fixed focus lens or liquid crystal spatial light modulator, and the detector is fixedly arrangedWithout electric adjustment, the new fitting equation is adopted to obtain M of the light source to be measured 2 Under the restraint of collimated light, the system derives the corresponding relation between the radius and the focal length of the light spot, and M can be obtained by fitting a function in a specific form by only 2 coefficients 2 Is a numerical value of (2).
Drawings
FIG. 1 is a schematic view of a beam quality factor rapid measurement apparatus according to a preferred embodiment of the present invention;
FIG. 2 is a schematic view of a beam quality factor rapid measurement apparatus according to another preferred embodiment of the present invention;
fig. 3 shows a beam quality factor M calculated by a beam quality factor rapid measuring apparatus according to fig. 2 2 Results of (2);
FIG. 4 is a conventional beam quality factor M 2 Is a schematic diagram of the structure of the measuring device.
Like reference numerals denote like technical features throughout the drawings, in particular: the device comprises a 1-device to be sampled, a 2-zooming device, a 3-electric control adjusting device, a 4-light path folding device, a 5-light spot measuring device, a 6-data processing device, a 7-light source to be tested, an 8-first reflecting mirror, a 9-wedge mirror, a 10-electric attenuation piece, a 11-variable focus lens, a 12-controller, a 13-second reflecting mirror and a 15-silicon-based CCD camera.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
As shown in FIG. 1, the present invention provides a beam quality factor M 2 The device comprises a sampling device, a zooming device, an electric control adjusting device, a light path folding device, a light spot measuring device and a data processing device, wherein the zooming device and the light spot measuring deviceThe measuring device is coaxial, and the light spot measuring device is positioned at the initial focal plane of the zooming device. The laser beam to be measured is incident along the optical axis direction of the system, and the light spot size of the focal plane is obtained through the light spot measuring device. The focal length of the zooming device is changed through the electric control adjusting device, and the light spot measuring device keeps the axial position unchanged, so that the light spot size under different focal lengths can be obtained. Due to the spot size and the beam quality factor M of the beam to be measured 2 The initial spot size, the system focal length and the like are closely related, and the beam quality factor M of the beam to be measured can be obtained through theoretical derivation and data fitting 2 。
Specifically, the invention provides a beam quality factor M 2 The rapid measurement apparatus includes: the device 1 to be sampled is used for inputting collimated laser emitted by a laser source to be tested, the Rayleigh length of the collimated laser is far longer than the distance from the light source to the zooming device 2, and the laser is attenuated. The zoom device 2 is used for changing the focal length under the control of the electric control adjusting device 3 and focusing the attenuated collimated laser under different focal lengths; the spot measuring device 5 is used for collecting and measuring the spot size of the laser focused by the zooming device 2 in real time; a data processing device 6 for calculating a beam quality factor M of the laser source to be measured according to the focal length of the zoom device 2 and the spot size acquired and measured by the spot measuring device 5 under different focal lengths of the zoom device 2 in real time 2 . Wherein, the collimated laser emitted by the laser source to be measured is input into the sampling device 1 to be attenuated into weak light, and then focused by the zooming device 2 and then input into the spot measuring device 4, the spot measuring device 4 is used for collecting and measuring the spot size of the collimated laser focused by the zooming device 2 in real time, and the data processing device 6 is used for calculating the beam quality factor M of the laser source to be measured according to the focal length of the zooming device 2 and the spot sizes collected and measured by the spot measuring device 5 under different focal lengths of the zooming device 2 in real time 2 。
In the present invention, the device further comprises an optical path folding device 4, and the optical path folding device 4 is arranged between the zooming device 2 and the light spot measuring device 5 and is used for folding the optical path between the zooming device 2 and the light spot measuring device 5. The optical path folding device 4 folds the optical path between the zoom device 2 and the spot measuring device 5 by adopting a reflection type optical path so as to reduce the size of the whole device.
In the invention, the laser source to be measured can enter the subsequent measuring device only after being greatly attenuated into weak light without distortion by the sampling device 1.
In the present invention, the zoom device 2 is a zoom lens driven by a mems, a zoom mirror, or a zoom multi-lens type lens group composed of a lens and a mirror, the focal length of the zoom device 2 is varied independently of the characteristics of the light source to be measured, and the focal length is typically in the range of 1 mm to 1000 mm. The focal length of the zoom device 2 may be rapidly changing in real time, and may be of a transmissive or reflective construction, such as a variable focus lens/mirror or a multi-lens group, with a focal length typically ranging from tens of millimeters to hundreds of millimeters.
In the invention, the electric control adjusting device 3 is connected with the zooming device 2 through an electric control interface, and the electric control adjusting device 3 drives a movable unit or acousto-optic characteristic or electromagnetic characteristic in the zooming device 2 by changing a current or voltage signal input into the zooming device 2 so as to control the change of the focal length of the zooming device 2.
In the present invention, the built-in detector of the spot measurement device 5 is a CCD camera or a CMOS, and the response wavelength range of the detector covers the center wavelength of the light source to be measured, and the distance (calculated by the actual optical path) from the zoom device is fixed as the median of the focal length variation range of the zoom device. The light spot measuring device 5 is located at a focal plane of the zoom device 2, the built-in detector is a photoelectric device such as a CCD camera and a CMOS, the response wavelength range covers the center wavelength of the light source to be measured, and the light spot measuring device can respond to the light spot which is normally incident to the detection plane.
The data processing device 6 communicates with the electronic control adjusting device 3 and the light spot measuring device 5 through a universal data interface to obtain the current focal length of the zooming device 3 and the current measured light spot size of the light spot measuring device 5. When the focal length of the zooming device 3 is changed, multiple groups of focal lengths and spot sizes are recorded, and the data are processed through a built-in algorithm to obtain a beam quality factor M of the laser to be measured 2 And other relevant measurements.
In the present invention, the data processing device 6 calculates the beam quality factor M of the laser source to be measured by constructing a spot radius calculation model at the spot measuring device 5 2 。
The light spot radius calculation model is as follows:
wherein,for the beam waist radius of the collimated laser beam after focusing by the zoom device 2 with focal length f, +.>Z is the rayleigh length of the beam focused by the focal length f zoom device 2 f The distance between the beam waist of the light beam focused by the zooming device 2 with the focal length f and the detection surface of the facula measuring device 5;
since the zoom device 2 and the spot measuring device 5 remain unchanged, z f ＝f-f 0 The spot radius calculation model is expressed as:
wherein,B＝ω 2 ，C＝-2ω 2 f 0 ，D＝ω 2 f 0 2 thereby deriving a beam quality factor M for calculating the laser source to be measured 2 The calculation model of (2) is as follows:
where f is the focal length of the zoom device 2, pi and lambda are constants, M 2 Is the beam quality factor of the laser source to be measured, omega is the beam waist radius of the laser source to be measured, f 0 Is an initial focal length value of the zoom apparatus (2) (default is a focal length median value of the zoom apparatus 2).
The invention overcomes the defects of the prior M 2 The measuring equipment has the defects of low measuring speed caused by the requirement of driving the reflecting mirror group to carry out large-stroke displacement, has the advantages of clear principle, high adjusting speed, simple and convenient operation and the like, and can greatly improve the beam quality factor M 2 Is provided.
According to another aspect of the present invention, there is also provided a beam quality factor M 2 The rapid measurement method comprises the following steps:
(11) The laser source to be measured emits collimated laser and attenuates the collimated laser.
(12) And (3) carrying out primary focusing on the attenuated collimated laser, and collecting and measuring the size of a collimated laser spot at a focus of primary focusing of the collimated laser.
(13) The focal length of laser focusing is changed, and the size of a collimated laser spot at the primary focusing focal point is collected and measured in real time in the continuous zooming process.
In the step (12) and the step (13), when the alignment laser is focused, the light path folding device 4 is also required to fold the light path in the focusing process. The focal length of the collimated laser is changed by adopting the zooming device 2, and the size of a collimated laser spot at the primary focused focal point is acquired and measured in real time by adopting the spot measuring device 5, wherein the distance between the zooming device 2 and the spot measuring device 5 is kept unchanged.
(14) Calculating a beam quality factor M of the laser source to be measured according to the size of the collimated laser spot obtained by primary focusing measurement, the focal length of primary focusing and the size of the collimated laser spot at the focal point of primary focusing under different focal lengths 2 。
The step (14) specifically comprises the following steps:
(141) Constructing a calculation model of the size of a collimated laser spot at a focus of primary focusing:
wherein,for the beam waist radius of the beam after focusing by the zoom device 2 with focal length f,z is the rayleigh length of the beam focused by the focal length f zoom device 2 f The distance between the beam waist of the light beam focused by the zooming device 2 with the focal length f and the detection surface of the facula measuring device 5;
(142) Since the zoom device 2 and the spot measuring device 5 remain unchanged, z f ＝f-f 0 The spot radius calculation model is expressed as:
wherein,B＝ω 2 ，C＝-2ω 2 f 0 ，D＝ω 2 f 0 2 ；
(143) Deriving a beam quality factor M for calculating the laser source under test according to step (142) 2 The calculation model of (2) is as follows:
wherein f is the focal length of the zoom device (2), pi and lambda are constants, M 2 Is the beam quality factor of the laser source to be measured, omega is the beam waist radius of the laser source to be measured, f 0 Is an initial focal length value of the zoom device (2).
In the invention, a zooming device is adopted,instead of the traditional fixed focus lens or liquid crystal spatial light modulator, the zoom device is a zoom lens driven by a micro-electromechanical system, a zoom reflector or a zoom multi-lens type lens group formed by combining the lens and the reflector, the focal length change of the zoom device is independent of the characteristic of a light source to be measured, and the typical value range of the focal length is between 1 mm and 1000 mm. In the specific implementation aspect, the type of the detector is CCD camera or CMOS, more importantly, the distance between the detector and the zooming device is specifically designed, namely, the median of the focusing range of the zooming device is limited, so that the device is more definite and more operable to implement, and meanwhile, the problem of inaccurate spot measurement caused by mismatching of the position of the detector and the focal length of the zooming device is avoided. Furthermore, the new fitting equation adopted in the invention obtains M of the light source to be measured 2 . The traditional measurement method is that after hyperbolic fitting is carried out on the diameter and the position, M is obtained through 3 coefficients 2 Is a numerical value of (2). The invention derives the corresponding relation between the light spot radius and the focal length by the system under the restraint of the collimated light, and M can be obtained by the function fitting of a specific form and only 2 coefficients 2 Is a numerical value of (2).
FIGS. 2 and 3 show the laser beam quality factor M 2 A fast measurement device and an example of the device measurement result. The device comprises a device to be sampled 1, a zooming device 2, an electric control adjusting device 3, a light path folding device 4, a light spot measuring device 5 and a data processing device 6, wherein the device to be sampled 1 comprises a light source 7 to be tested, a first reflecting mirror 8, a wedge mirror 9 and an electric attenuation sheet 10. The laser to be measured is output from the light source 7 to be measured, and the output laser sequentially passes through the first reflecting mirror 8, the wedge mirror 9 and the electric attenuation sheet 10, and enters the zoom device 2 after being attenuated in the electric attenuation sheet 10. The zoom device 2 is a variable focus lens 11 for changing the focus of the attenuated laser light. The electronically controlled adjustment means 3 is a controller for changing the focus of the variable focus lens 11. The optical path folding device 4 is two second reflecting mirrors 13 correspondingly arranged, and is used for changing the line of the laser focused by the variable focus lens 11 so as to fold the laser line. The flare measuring device 5 isA silicon-based CCD camera. A beam of Gaussian-like collimated laser with output power of 1kW and peak wavelength of 1064nm and beam radius of 5mm is sampled by a piece of film plating wedge mirror, the wedge mirror is plated with a high-transmittance film, the residual reflectivity is less than 2 per mill, and then the laser enters a beam quality tester by an electric attenuation sheet group. The zoom device of the light beam quality tester adopts an ultrafast acousto-optic variable focal length lens, the focal length variation range of the variable focal length lens is 300mm-400mm, and the focal length variation speed reaches the sub microsecond magnitude. The two second reflectors which are arranged at 45 degrees fold the light path after passing through the lenses, the horizontal distance between the second reflectors and the zoom lenses is 150mm, the vertical distance between the second reflectors is 50mm, the light spot measuring device 5 adopts a silicon-based CCD camera, the response wavelength range of the silicon-based CCD camera is 400nm-1100nm, the caliber is 5.12mm multiplied by 5.12mm,1024 multiplied by 1024 pixels, the size of a single pixel is 5 mu m multiplied by 5 mu m, the frame frequency of the light spot measuring device 5 is 20Hz, and the light path length between the light spot measuring device 5 and the zoom lenses is 350mm.
In the light emitting process, the focal length of the zoom lens is increased from 340mm to 360mm, and the step length is 2mm. Since the focal length of the zoom lens varies extremely fast, the bottleneck of measurement is the frame rate of the CCD camera and the speed of data processing. The CCD camera takes about 50ms to acquire a single frame image, and the radius of a calculated light spot is smaller than 1ms, so that the time for completing 11 times of measurement is smaller than 600ms, the data fitting can be controlled within 50ms, the whole measurement process can be completed within 700ms, and the method is far higher than the traditional M 2 Testing speed. Table 1 gives the simulated test results and fitting conditions.
Table 1 input parameters and simulation results
Thus, there are:
substantially coincident with the simulation input.
This example shows that the present invention can effectively, correctly and rapidly adjust the beam quality factor M 2 Testing was performed.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (8)
1. Beam quality factor M 2 A rapid measurement device, comprising:
the device to be sampled (1) is used for inputting the collimated laser emitted by the laser source to be tested and attenuating the collimated laser;
the zoom device (2) is used for changing the focal length under the control of the electric control adjusting device (3) and focusing the attenuated collimated laser under different focal lengths;
the spot measuring device (5) is used for collecting and measuring the spot size of the collimated laser focused by the zooming device (2) in real time;
the data processing device (6) is used for calculating the beam quality factor M of the laser source to be measured according to the focal length of the zooming device (2) and the spot size acquired and measured by the spot measuring device (5) under different focal lengths of the zooming device (2) in real time 2 ；
The data processing device (6) calculates the beam quality factor M of the laser source to be measured by constructing a spot radius calculation model at the spot measuring device (5) 2 ；
The light spot radius calculation model is as follows:
wherein,for the beam waist radius of the collimated laser beam after focusing by the zoom device (2) with focal length f, +.>For the Rayleigh length, z, of the collimated laser beam after focusing by a zoom device (2) with a focal length f f The distance between the beam waist of the collimated laser beam focused by the zooming device (2) with the focal length f and the detection surface of the facula measuring device (5);
since the zoom device (2) and the flare measuring device (5) are kept unchanged, z f ＝f-f 0 The spot radius calculation model is expressed as:
wherein,B＝ω 2 ，C＝-2ω 2 f 0 ，/>thereby constructing a beam quality factor M for calculating the laser source to be measured 2 Is a computational model of (a):
wherein f is the focal length of the zoom device (2), pi and lambda are constants, M 2 Is the beam quality factor of the laser source to be measured, omega is the beam waist radius of the laser source to be measured, f 0 Is an initial focal length value of the zoom device (2);
wherein the position distance between the zooming device (2) and the light spot measuring device (5) is kept unchanged.
2. A beam quality factor M according to claim 1 2 The rapid measuring device is characterized by further comprising an optical path folding device (4), wherein the optical path folding device (4) is arranged between the zooming device (2) and the light spot measuring device (5) and is used for folding an optical path between the zooming device (2) and the light spot measuring device (5).
3. A beam quality factor M according to claim 1 2 The rapid measuring device is characterized in that the zooming device (2) is a zooming lens driven by a micro-electromechanical system, a zooming reflecting mirror or a zooming multi-lens type lens group formed by combining the lens and the reflecting mirror, and the typical value range of the focal length of the zooming device (2) is between 1 millimeter and 1000 millimeters.
4. A beam quality factor M according to claim 1 2 The rapid measuring device is characterized in that the electric control adjusting device (3) is connected with the zooming device (2) through an electric control interface, and the electric control adjusting device (3) drives a movable unit or acousto-optic characteristic or electromagnetic characteristic in the zooming device (2) through changing a current or voltage signal input into the zooming device (2) so as to control the change of the focal length of the zooming device (2).
5. A beam quality factor M according to claim 1 2 The rapid measuring device is characterized in that a detector arranged in the facula measuring device (5) is a CCD camera or a CMOS, the response wavelength range of the detector covers the central wavelength of a light source to be measured, and the distance between the facula measuring device (5) and the zooming device (2) is fixed to be the median of the focal length change range of the zooming device (2).
6. Beam quality factor M 2 A rapid measurement method, implemented with a device according to any one of claims 1-5, comprising the steps of:
(11) The laser source to be measured emits collimated laser and attenuates the collimated laser;
(12) Performing primary focusing on the attenuated collimated laser, and collecting and measuring the size of a collimated laser spot at a focus of primary focusing of the collimated laser;
(13) Changing the focal length of the collimation laser focusing, and collecting and measuring the size of the collimation laser spot at the primary focusing focal point in real time in the continuous zooming process;
(14) Calculating a beam quality factor M of the laser source to be measured according to the size of the collimated laser spot obtained by primary focusing measurement, the focal length of primary focusing and the size of the collimated laser spot at the focal point of primary focusing under different focal lengths 2 ；
The step (14) specifically comprises the following steps:
(141) Constructing a calculation model of the size of a collimated laser spot at a focus of primary focusing:
wherein,for the beam waist radius of the collimated laser beam after focusing by the zoom device (2) with focal length f, +.>For the Rayleigh length, z, of the collimated laser beam after focusing by a zoom device (2) with a focal length f f The distance between the beam waist of the collimated laser beam focused by the zooming device (2) with the focal length f and the detection surface of the facula measuring device (5);
(142) Since the zoom device (2) and the flare measuring device (5) are kept unchanged, z f ＝f-f 0 The spot radius calculation model is expressed as:
wherein,B＝ω 2 ，C＝-2ω 2 f 0 ，/>
(143) Deriving a beam quality factor M for calculating the laser source under test according to step (142) 2 The calculation model of (2) is as follows:
wherein f is the focal length of the zoom device (2), pi and lambda are constants, M 2 Is the beam quality factor of the laser source to be measured, omega is the beam waist radius of the laser source to be measured, f 0 Is an initial focal length value of the zoom device (2).
7. A beam quality factor M according to claim 6 2 The rapid measurement method is characterized in that in the step (12) and the step (13), when the alignment laser is focused, an optical path folding device (4) is also required to fold an optical path in the focusing process.
8. A beam quality factor M according to claim 6 2 The rapid measurement method is characterized in that a zoom device (2) is adopted to change the focal length of the collimated laser focus, a spot measurement device (5) is adopted to collect and measure the size of a collimated laser spot at the focus of primary focusing in real time, and the distance between the zoom device (2) and the spot measurement device (5) is kept unchanged.
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