CN1163814A

CN1163814A - Laser beam diameter cutter

Info

Publication number: CN1163814A
Application number: CN 97104165
Authority: CN
Inventors: 王慰平; 孙之旭
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-04-29
Filing date: 1997-04-29
Publication date: 1997-11-05

Abstract

A laser beam cutter for directly measuring the diameter and divergence angle of high-power laser beam features that part of laser beam is passed through slit of cutter and radiates after diverged in diffusion chamber onto a probe installed in the diffusion chamber to obtain detecting signals. Said cutter can move vertically to the optical axis to cut laser beam through the drive of step motor to provide initial and stop signals. The diameter and divergence angle of laser beam can be measured according to the displacement of cutter. Its advantages are high measuring accuracy, safe and reliable operation.

Description

Laser beam diameter cutter

The present invention relates to the field of high power laser beam diameter, beam divergence angle measuring instrument.

Beam divergence angle is the important parameter of Laser Processing, and is little as beam divergence angle, and focal beam spot is just little, focuses on easily, and power density is also high.Therefore add the high efficiency in man-hour, processing technology is good.So when design processing resonator, beam divergence angle is the geometric parameter that must consider.Simultaneously, with laser beam propagation factor K, times diffraction limit factor M ²There is functional relation, just can calculates K and M by functional relation as long as measure beam divergence angle ²Come.The key of measuring beam divergence angle is that correct measurement goes out beam diameter, with a tight waist, or artificial (focusing) is with a tight waist.The laser beam power of processing usefulness is very high, directly measures beam diameter, the very big difficulty of existence with a tight waist with focusing.Its high power density has hindered the realization of accurate measurement.Current methods is reference measure, be absolutely unsafe (as the over) that has, recommend in the world to distribute with measurement pattern, measure beam divergence angle by the second moment statistical method, this is a kind of very inadequate method, because the pattern of high power density light beam is measured the same problem that has accurate measurement, and high power low-mode laser device uses the light hurdle as the modeling means more, or resonator mirror is not single curvature, so the use limitation of this method is very big.

The purpose of this invention is to provide and a kind ofly can bear high power density, realize directly measurement high power laser beam diameter, quick, easy, safe, the instrument accurately of beam divergence angle.

Technical scheme of the present invention is based on following laser rule: scattered laser beam angle θ _σWith the focal beam spot diameter d _OfOr waist footpath d _{σ 0}, light beam wavelength λ ₀, focal distance f concerns just like minor function,

θ _σ=4 λ ₀/ π d _OfOr θ _σ=K ' d _Of/ f (K ' be focusing system aberration correction value) beam divergence angle θ _σPropagation factor K and times diffraction limit factor M with laser beam ²There is following functional relation:

K＝4λ ₀/π·n·d _σ0·θ _σ

M ²=π nd _{σ 0}θ _σ/ λ ₀N is the focus lamp ratio of refraction in the formula, d _{σ 0}Be the beam waist footpath.

Find out from above laser rule, as long as measure beam diameter, with a tight waist or focal beam spot diameter, other Several Parameters can both be calculated.The present invention realizes that high power laser beam spreading angle directly measures, and finishes by the horizontal perpendicular cuts light beam of light beam cutter.

This cutter is by the 0.01mm slit on the cutting head, when the perpendicular cuts light beam, the light at light beam one end edge enters slit, probe sends the initial communication signal immediately, along with moving continuously of cutter, probe sends response signal continuously, after the cutting head slit shifts out light beam other end edge, light beam disappears in slit, and the sonde response signal just stops.According to signal send and stop between the distance that moves of cutting head just can record the size of beam diameter or waist footpath, focal beam spot diameter.

The instrument resolution capability that the present invention uses is the beam diameter cutting head of 0.01mm, long-focus focus lamp and small-power fast-response detector, there is ready-made instrument in portion, and the damped system that bears high-power cutter head and introduce light beam from slit is a core technology of the present invention.

Cutting head is a material by the anaerobic red copper.The slit both sides is subjected to the reflection of light face to electroplate 0.1mm thick ( 13) proof gold, makes it only bear the light beam power of ∠ about 2%.Be subjected to the light reflection surface bottom that the high speed water-cooled is all arranged.The heat of accepting is shifted fast, the heat stagnation of sensitive surface is strolled less than destroying thresholding, the power density＞20kW/cm that can bear ²Do not enter the light of slit, or from the cutting head both sides by the back absorbed by optical gate, or by be subjected to light reflection surface reflex to its top the absorption cell bucket in be absorbed.Be subjected to the slit angle of light reflection surface and parallel optical axis to be slightly less than 90 °, be edge of a knife shape.The size of angle is decided by the scope of institute's photometry spot size.Little as angle, two absorb to receive the groove bucketss pitch from drawing back, but just photometry spot diameter scope increases, and the angle too small edge of a knife easily burns.

Enter the light of slit, the diffracted power density that makes is evacuated in slit, the diffraction of slit obtains the first step of decay power density, the light that appears from slit sidewall diffraction particularly, after being lowered, power density enters diffuser casing further by locular wall attenuation by absorption, reach the decay of second step, diffuser casing can adopt different absorbing surfaces according to different wave length laser.Fan She the veiling glare reception of being popped one's head at last, and can set up attenuator by probe the place ahead and regulate the power range of receiving that is fit to probe.To light beam is the laser probe available silicon photoelectric tube of 0.3-1.6 mum wavelength.Can be with acquisition sensors such as pyrolysis probes to the wavelength of 0.3-25 μ m.Vertically inject the light of slit, reflex to black absorption of arc by the gold-plated triangle reflection tooth bar that is faced behind the slit and survey on the wall its heat water that also is cooled and take away, avoid directly reflexing on the laser window eyeglass again.

Cutter of the present invention moving on the optical axis vertical plane can steadily be driven by stepper motor.Product by time between initialize signal and termination signal and translational speed directly shows footpath value (range finding).Also available manual operation records the footpath value by the vernier graduation chi.By aforementioned principles formula θ _σ, K, M ²All can determine.

Accompanying drawing 1 of the present invention is the structural representation of laser beam diameter cutter.

(1) is laser beam in the accompanying drawing 1, and (2) are slit, and (3) are absorbing surface, and (4) are triangle reflection tooth bar, and (5) are reflecting surface, and (6) are the absorption cell bucket, and (7) are and the attaching parts of stepper motor, and (8) are latasuture.

Embodiments of the invention are as follows: cutter is made with oxygen-free copper, and a proof gold electrodeposited coating is arranged on the slit both sides reflectings surface (5), and thickness of coating is 0.1mm, and fineness is at more than 13, available alcohol swab wiping and can not damage reflecting surface.Slit (2) width is 0.01mm, and the formed angle of slit wall and reflecting surface is slightly less than 90 °.Absorption cell bucket (6) is in the top of both sides reflecting surface respectively, absorbs the laser that reflects, and the absorption cell bucket can be followed cutter and be moved together.Stepper motor drives leading screw and connects cutter perpendicular cuts light beam by (7).When laser beam (1) by slit (2) perpendicular cuts, the light beam that enters slit becomes diffraction light, overflow from other end latasuture (8), enter the diffuser casing diffusion, part light is mapped on the detecting head, detecting head provides signal, and shows with pyroelectric electric device on display and make detecting head, can measure the laser beam of 0.3-25 mum wavelength.The light that enters the slit remainder is then reflexed to black wall by gold-plated triangle reflection tooth bar and absorbs, do not enter the light of slit, absorbed by optical gate by the back in the cutter both sides, or the reflecting surface (5) that is cut on the device reflexes to absorption in the absorption cell bucket of following the tracks of the location (6).Cutter is by mechanical movement, provides initialize signal when beginning to cut laser beam, provides end signal and end when finishing cutting laser, and the shift length of reading cutter from the vernier graduation chi then obtains beam diameter or focus spot diameter.Too high as focal beam spot place power density, when being difficult for directly measuring spot diameter, then can behind focus lamp, avoid the diverse location cutting light beam of focus, measure the beamwidth of diverse location, find out waist footpath (focal beam spot diameter) with the hyperbolic fit method, still draw parameters such as beam divergence angle with aforementioned formula.

Characteristics of the present invention can directly be measured beam diameter, beam divergence angle propagation factor and the diffraction coefficient of high power laser for (1); (2) Measure quick, easy; (3) handling safety; (4) measurement result accuracy height.

Claims

1, laser beam diameter cutter, it is characterized in that cutter cuts light beam with gold-plated water-cooled, on cutter top one slit is arranged, also obtain the first step of decay power density with the diffraction of slit with slit cutting high power density light beam, the sidewall of slit connects second step effect that an airtight diffuser casing reaches decay, detector probe is placed in appropriate location at diffuser casing, is the absorbing surface of black around the diffuser casing.Be the attaching parts of stepper motor below the cutter, the upper face electrogilding layer of cutter and slit formation are slightly less than 90 ° and are edge of a knife shape, and both sides have two absorption cell buckets of avoiding reflecting harm respectively above cutter.

2, laser beam diameter cutter according to claim 1 is characterized in that cutter made by anaerobic red copper or aluminium, and the proof gold electrodeposited coating is arranged on the reflecting surface of top, and there is water-cooled to reach to bear the ability of high power density the inside, position that cutter intussusception luminous power is high.

3, laser beam diameter cutter according to claim 1 and 2 is characterized in that detector probe is to be made by silicon photocell, photocell, fast-response pyroelectricity or photoconduction type device.