CN203908683U - High-dynamic-range laser far field focal spot measuring apparatus - Google Patents

Abstract

The utility model relates to a high-dynamic-range laser far field focal spot measuring apparatus including a laser beam compressing/expanding system, an attenuation wedge plate, a spectroscope, a scientific-grade CCD detector, a microlens array, a CCD detector, and a control computer, the laser beam compressing/expanding system, the attenuation wedge plate, and the spectroscope are successively arranged on the same optical path, the spectroscope divides light incident to the spectroscope into transmitted light and reflected light, the scientific-grade CCD detector is arranged on an optical path where the reflected light via the spectroscope is, the microlens array and the CCD detector are successively arranged on the optical path where the refracted light via the spectroscope is, and the scientific-grade CCD detector and the CCD detector are connected with the control computer. The measuring device provided can realize the high-dynamic-range laser far field focal spot dynamic measurement and can better guarantee the measurement accuracy.

Description

High dynamic range laser far field focal spot measurement mechanism

Technical field

The utility model belongs to optical field, relates to a kind of high dynamic range laser far field focal spot measurement mechanism, relates in particular to a kind of laser far field focal spot reconstruct based on Fourier optics theory, realizes the device that high dynamic range laser far field focal spot is measured.

Background technology

Laser far field focal spot is the important indicator of describing large scale laser instrument output beam quality, is also in inertial confinement fusion system, to characterize the major parameter that laser beam is entered hole ability.Due to the main lobe of laser far field focal spot and the luminous energy density aberration of secondary lobe great disparity (more than 10000:1), not yet there is the detector of high dynamic range like this.Laser far field focal spot measuring method mainly contains at present: long-focus lens imaging method, array camera method of testing, Rattle Pair method of testing and schlieren method.

Long-focus lens imaging method is to utilize long-focus lens to focus on laser beam, then by imaging amplifying lens, focal spot is imaged on the test surface of CCD.Its shortcoming is: 1) ratio due to the main lobe of light laser and the secondary lobe portion of energy density at edge can reach several orders of magnitude, far beyond the dynamic range of CCD, therefore the main lobe that the laser focal spot image that adopts the method to test is actually light laser focal spot distributes, and the information of secondary lobe has been covered; 2) aberration of condenser lens is introduced focal spot distortion, and it affects the measuring accuracy of far-field focus.

Array camera method of testing is based on wedge principle, according to split the ration of division of plate and the linear dynamic range of recording medium can be from array figure the far-field distribution of reconstruct laser focal spot.Its shortcoming is: 1) be subject to the restriction of recording medium linear dynamic range, array figure can not reflect the secondary lobe information of laser far field focal spot completely; 2) array camera adopts off-axis reflection physical construction, although the adjustment of the system of giving brings convenience, the aberration of introducing is larger; 3) recording medium is that the resolving power of CCD is limited, introduces certain relative error, thereby affect the measuring accuracy of system during the focused spot diameter of the calculated column system of battle formations.

Rattle Pair method of testing is similar to array camera method of testing, and different is that it adopts coaxial light path, has reduced the off-axis aberration of system.Its shortcoming is: 1) system debug difficulty, and two pairs of wedges are cut apart the ratio difference of light beam, and focal spot reconstruct difficulty is large; 2) because the focal spot of a row or column is counted too much, be subject to the restriction of CCD target surface size, be difficult to all information of complete documentation focal plane row or column.

Schlieren method is to measure respectively main lobe and the secondary lobe of far-field focus, by Image Reconstruction, obtains complete far-field focus form.Its shortcoming is: 1) main lobe of laser far field focal spot and secondary lobe are that timesharing is measured, and are easily subject to noise in time domain, ambient windstream disturbance and the impact of laser instability on its reconstruct of detector; 2) it is little that the method requires the random drift of laser far field focal spot, increased the requirement to beam control system; 3) when the method is measured secondary lobe, main lobe need to be blocked, otherwise can cause the damage of detector, thus the device performance blocking is required higher, its tight, resistance to laser irradiation of must being in the light, and measurement result is not introduced to impact.

Utility model content

In order to solve the above-mentioned technical matters existing in background technology, the utility model provides a kind of and has realized the kinetic measurement of high dynamic range laser far field focal spot, and the measurement mechanism of fine assurance measuring accuracy.

Technical solution of the present utility model is: the utility model provides a kind of high dynamic range laser far field focal spot measurement mechanism, and its special character is: described high dynamic range laser far field focal spot measurement mechanism comprises laser contracting bundle/beam-expanding system, decay wedge, spectroscope, scientific grade CCD detector, microlens array, ccd detector and controls computing machine; Described laser contracting bundle/beam-expanding system, decay wedge and spectroscope are successively set in same light path; Described spectroscope will be incident to spectroscopical light and be divided into transmitted light and reflected light; Described scientific grade CCD detector is arranged in the reflected light place light path after spectroscope; Described microlens array and ccd detector are successively set in the refract light place light path after spectroscope; Described scientific grade CCD detector and ccd detector are connected with control computing machine respectively.

Above-mentioned microlens array equates apart from spectroscopical distance with the target surface of scientific grade CCD detector.

Above-mentioned laser contracting bundle/beam-expanding system comprises object lens and eyepiece; Described object lens, eyepiece, decay wedge and spectroscope are successively set in same light path.

The utility model has the advantages that:

The utility model provides a kind of high dynamic range laser far field focal spot measurement mechanism, this device is theoretical based on Fourier optics generalized pupil function, wavefront and the distribution of light intensity of by dynamic synchronization, measuring laser beam distribute, and utilize far-field focus reconstructing method to complete the reconstruct of laser far field focal spot, thereby realized the kinetic measurement to high dynamic range laser far field focal spot, and well guaranteed measuring accuracy.The utility model is not subject to the restriction of detector dynamic range, can realize the measurement of high dynamic range degree laser far field focal spot; The wavefront of kinetic measurement laser beam and distribution of light intensity distribute, and complete the reconstruct of laser far field focal spot, are not subject to the impact of external environment (air draught disturbance, vibration etc.); The wavefront of synchro measure laser beam and distribution of light intensity distribute, and complete the reconstruct of laser far field focal spot, the not instable impact of Stimulated Light; By to demarcating in advance before test macro transmitted wave, the not impact of tested person system aberration when laser far field focal spot is measured; Can realize the far-field focus of different caliber size laser beam is measured.Simple in structure, stability is high, reproducible, measurement result degree of confidence is high;

Accompanying drawing explanation

Fig. 1 is the structural representation of high dynamic range laser far field focal spot measurement mechanism provided by the utility model;

Wherein:

1-laser contracting bundle/beam-expanding system; The 2-wedge of decaying; 3-spectroscope; 4-scientific grade CCD detector; 5-microlens array; 6-CCD detector; 7-controls computing machine; 8-object lens; 9-eyepiece.

Embodiment

As shown in Figure 1, the utility model is comprised of laser contracting bundle/beam-expanding system 1, decay wedge 2, spectroscope 3, scientific grade CCD detector 4, microlens array 5, ccd detector 6, control computing machine 7.Laser contracting bundle/beam-expanding system 1 is comprised of object lens 8 and eyepiece 9, and it is Kepler's structure, adopts two telecentric beam paths, and carries out achromatism design, guarantees the wide spectrum work of test macro and eliminates the impact of detector position error on measurement result.According to measured laser bundle caliber size, choosing contracting restraints/expands than the laser contracting bundle/beam-expanding system 1 matching.According to measured laser beam energy size, choose the suitable decay wedge 2 of decay multiplying power, guarantee that scientific grade CCD detector 4 and ccd detector 6 are operated in linear response district.The target surface of microlens array 5 and scientific grade CCD detector 4 equates apart from the distance of spectroscope 3, and is placed in the exit pupil position of laser contracting bundle/beam-expanding system 1.In figure, black solid line is stationary installation, and dotted line is changing device.

The utility model specific works process is as follows: measured laser bundle is restrainted/expanded through 1 contracting of laser contracting bundle/beam-expanding system, then is decayed through decay wedge 2, then by spectroscope 3 part reflections, a part of transmission.The laser beam incident of reflection, to the target surface of scientific grade CCD detector 4, gathers measured laser bundle distribution of light intensity distributed image by scientific grade CCD detector 4.The laser beam incident of transmission simultaneously, to microlens array 5, obtains a period of time aperture light spot image on ccd detector 6 target surfaces, by ccd detector 6, gathers hot spot dot matrix image.By controlling computing machine 7, realizing synchronous acquisition and the data of scientific grade CCD detector 4 and ccd detector 6 stores.

The concrete steps of laser far field focal spot reconstruct are as follows:

Step1: collected the light field image of measured laser bundle by scientific grade CCD detector 4, obtain its distribution of light intensity distribution I (x, y).

Step2: collect dot matrix image by ccd detector 6, according to Shack-Hartmann wavefront test philosophy, calculate every distorted wavefront in sub-aperture and compare the facula mass center skew of reference wavefront, and calculate the average gradient of wavefront in the sub-pore diameter range cut apart by microlens array 5, then according to shouthwell model, try to achieve the distorted wavefront W (x, y) of measured laser bundle.

Step3: theoretical according to generalized pupil function, the light field complex amplitude P (x, y) that obtains measured laser bundle is:

$P(x,y)=\sqrt{I(x,y)}\exp \left[\mathrm{jkW}(x,y)\right]---\left(1\right)$

In formula, k=2 π/λ.

Step4: according to Fourier optics theory, the far-field focus of measured laser bundle is the Fourier spectrum of its light field complex amplitude, therefore the light field complex amplitude P (x to measured laser bundle, y) carry out two-dimensional fast fourier transform, and delivery square, obtaining laser far field focal spot intensity distribution U (ξ, η) is:

U(ξ,η)＝abs{FFT[P(x,y)]} ² (2)

In formula, FFT () is Fast Fourier Transform (FFT) operator, and abs () is delivery operator.

Step5: to (2) formula normalization, obtain standard laser far-field focus intensity distributions for:

$\stackrel{\‾}{U}(\mathrm{\ξ},\mathrm{\η})=\frac{U(\mathrm{\ξ},\mathrm{\η})}{\max \left(U(\mathrm{\ξ},\mathrm{\η})\right)}---\left(2\right)$

In formula, max () is for getting maximal operator.

According to (1)～(3) formula restructural, go out standard laser far field focal spot intensity distribution, thereby realized the high-acruracy survey of high dynamic range laser far field focal spot.

Claims (3)

1. a high dynamic range laser far field focal spot measurement mechanism, is characterized in that: described high dynamic range laser far field focal spot measurement mechanism comprises laser contracting bundle/beam-expanding system, decay wedge, spectroscope, scientific grade CCD detector, microlens array, ccd detector and controls computing machine; Described laser contracting bundle/beam-expanding system, decay wedge and spectroscope are successively set in same light path; Described spectroscope will be incident to spectroscopical light and be divided into transmitted light and reflected light; Described scientific grade CCD detector is arranged in the reflected light place light path after spectroscope; Described microlens array and ccd detector are successively set in the refract light place light path after spectroscope; Described scientific grade CCD detector and ccd detector are connected with control computing machine respectively.

2. high dynamic range laser far field focal spot measurement mechanism according to claim 1, is characterized in that: described microlens array equates apart from spectroscopical distance with the target surface of scientific grade CCD detector.

3. high dynamic range laser far field focal spot measurement mechanism according to claim 1 and 2, is characterized in that: described laser contracting bundle/beam-expanding system comprises object lens and eyepiece; Described object lens, eyepiece, decay wedge and spectroscope are successively set in same light path.