CN1786662A - Double hole type measural apparatus for scattering angle of laser beam - Google Patents

Abstract

The invention relates to two-hole type laser beam spread angle testing device. It solves the problem that the measuring precision of laser beam spread angle is low. It is made up optical antenna, two-hole diaphragm, long focus collimator, CCD detector, and computer with image collection card. Dish shaped plate body surface is set two circular holes. And the two holes are at the two side of the two-hole diaphragm axis. The former four are set with the same axis center. The imaging surface of the CCD detector is set at the focal plane of the long focus collimator. The signal input end of the CCD detector and the computer are connected. The invention adopts CCD detector to detect facula, and calculates its center position by image treating system. And its detecting precision error is less than 1 micron. And the detecting precision of laser shot beam spread angle can reach 0.1 micro rad. The invention has the advantages of reasonable design, reliable working, and large popularizing value.

Description

Double hole type measural apparatus for scattering angle of laser beam

Technical field

The present invention relates to a kind of beam divergence angle proving installation of laser.

Background technology

The beam divergence angle of Laser emission is the important parameter of existing laser beam emitting device, to its accurately measure be the development of high-precision laser emitter with use in major issue.Current measuring methods is many determines the scattered laser beam angle by the exploring laser light energy distribution, but this method only limits the use of in the beam divergence angle of measurement Gaussian laser beam, inaccurate when being used for other type.Because laser beam emitting device is increasingly sophisticated at present, and semiconductor laser output laser energy distributes comparatively complicated, the measuring accuracy of prior art is subjected to very big restriction, when the emission beam divergence angle is only surveyed for the quasi-parallel light of tens of μ rad, can not accurately record the numerical value at scattered laser beam angle, be difficult to satisfy test request.

Summary of the invention

The purpose of this invention is to provide a kind of double hole type measural apparatus for scattering angle of laser beam, measure the low defective of beam divergence angle degree of accuracy of quasi-parallel laser to overcome existing measurement mechanism.The present invention is by optical antenna 1, diplopore diaphragm 2, long burnt parallel light tube 3, ccd detector 4 is formed with the computing machine 5 that has image pick-up card, have two circular hole 2-1 on the disc surfaces of discoid diplopore diaphragm 2, two circular hole 2-1 are symmetricly set on the both sides of diplopore diaphragm 2 axial lines, optical antenna 1, diplopore diaphragm 2, long burnt parallel light tube 3 and ccd detector 4 preface concentric successively are provided with, the imaging surface of ccd detector 4 is positioned on the focal plane of long burnt parallel light tube 3, and the signal output part of ccd detector 4 connects the signal input part of the computing machine 5 that has image pick-up card.When using device of the present invention and carrying out the scattered laser beam angular measurement, by tested optical system emission laser beam, laser beam is from optical antenna 1 incident, pass two circular hole 2-1 and long burnt parallel light tube 3, on ccd detector 4, become two points as hot spot, ccd detector 4 has its image information that collects the computing machine of image pick-up card by the data cable input, computing machine calculates two spot center respectively, utilizes two points just can calculate the beam divergence angle of laser beam as the focal length of the distance of hot spot and the known burnt parallel light tube 3 of length.Rotate diplopore diaphragm 2 around axis in addition, can obtain the beam divergence angle data of many group laser beams, the mean value of getting multi-group data can remove the accidental error of testing process, makes measurement more accurate.The invention provides a kind of measurement mechanism of brand-new laser transmitting system beam divergence angle.Adopt CCD to survey hot spot, and by image processing system the spot center position is accurately calculated, resolution can reach 0.1 pixel.For existing C CD manufacturing accuracy, utilize this device hot spot detecting for spaces trueness error less than 1 μ m.Cooperate long burnt parallel light tube, the measuring accuracy of Laser emission beam divergence angle can reach the order of magnitude of 0.1 μ rad, thereby satisfies the demand of high precision measurement.Reasonable in design, the reliable operation of device of the present invention has bigger promotional value.

Description of drawings

Fig. 1 is a structural representation of the present invention, and Fig. 2 is the geometric relationship synoptic diagram that the present invention calculates beam divergence angle, and Fig. 3 is the structural representation of diplopore diaphragm 2 in the embodiment two.

Embodiment

Embodiment one: specify present embodiment below in conjunction with Fig. 1 and Fig. 2.Present embodiment is by optical antenna 1, diplopore diaphragm 2, long burnt parallel light tube 3, ccd detector 4 is formed with the computing machine 5 that has image pick-up card, have two circular hole 2-1 on the disc surfaces of discoid diplopore diaphragm 2, two circular hole 2-1 are symmetricly set on the both sides of diplopore diaphragm 2 axial lines, optical antenna 1, diplopore diaphragm 2, long burnt parallel light tube 3 and ccd detector 4 preface concentric successively are provided with, the imaging surface of ccd detector 4 is positioned on the focal plane of long burnt parallel light tube 3, and the signal output part of ccd detector 4 connects the signal input part of the computing machine 5 that has image pick-up card.

Diplopore diaphragm 2 is made by aluminium sheet in the present embodiment, determines the spacing of outside diameter and two circular hole 2-1 of diplopore diaphragm 2 according to the diameter of optical antenna 1.The MTV-1801 planar array type ccd video camera that ccd detector 4 selects for use Taiwan Min Tong company to produce, its major parameter is as follows: spectral response range 400nm～1100nm; Several 795 (H) * 596 (V) of pixel; Pixel dimension 10 μ rad; Line frequency 15625Hz; Field frequency 50Hz; Resolution 600TVL; Detection sensitivity 0.02lx; Signal to noise ratio (S/N ratio) is greater than 46dB; Working temperature-10 ℃～50 ℃; Power supply DC12V (2W).The beam deflection scope of correspondence ± 1mrad, effective pixel number of getting CCD is 500 (H) * 500 (V), utilizes this CCD hot spot detecting for spaces precision can reach 1 μ m.Long burnt parallel light tube 3 adopts focal length greater than the burnt parallel light tube of the length of 10m, adopts the burnt parallel light tube of this length to utilize this device beam divergence angle detection accuracy can reach 0.1 μ rad.Have the video capture card that adopts in the computing machine 5 of image pick-up card based on 1394 agreements, image information is imported computing machine.Computing machine passing threshold determining method reads the hot spot gray-scale value that incides ccd detector 4.Asking for each hot spot centre of form Coordinate Calculation formula is:

$X_c=\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(g_i-B)u(g_i-B)x_i}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(g_i-B)u(g_i-B)}---\left(2\right)$

$Y_c=\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(g_i-B)u(g_i-B)y_i}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(g_i-B)u(g_i-B)}---\left(3\right)$

Wherein, n is the number of pixel in the sample window, g _iBe the gray-scale value of pixel, B is a sampling threshold, and u (x) is a unit-step function, (x _i, y _i) be the coordinate of pixel.Choosing of sampling threshold by the intrinsic noise of system and sensor and the situation decision of bias light interference.Pixel gray-scale value to the sample window edge averages, and can estimate sampling threshold

$B=\frac{\underset{i=1}{\overset{2(W+H)-4}{\mathrm{\Σ}}}{g}_i}{2(W+H)-4}---\left(4\right)$

W wherein and H are respectively with the horizontal and vertical number of pixels of sample window.

Utilize above-mentioned algorithm to calculate the center X of hot spot respectively _C1, Y _C1, X _C2, Y _C2, then hot spot spacing d is

$d=\sqrt{{(X_{C1}-X_{C2})}^2+{(Y_{C1}-Y_{C2})}^2}---\left(5\right)$

As shown in Figure 2, the diplopore diaphragm 2 among Fig. 2, long burnt parallel light tube 3 and ccd detector 4 have all adopted the equivalent easy technique of painting, are convenient to geometric analysis, and by geometric relationship as can be known, this is apart from there being following relation between d and system under test (SUT) light beam beam divergence angle θ:

$\mathrm{tg}\frac{\mathrm{\θ}}{2}=\frac{d}{2f^{\′}}---\left(1\right)$

F ' is the focal length of long burnt parallel light tube 3, utilizes formula (1) can calculate system under test (SUT) scattered laser beam angle θ thus.

Embodiment two: specify present embodiment below in conjunction with Fig. 3.The difference of present embodiment and embodiment one is: the diameter phi of the circular hole 2-1 of diplopore diaphragm 2 and two circular hole 2-1 pitch of holes D sums equal the bore of optical antenna 1.Other composition is identical with embodiment one with annexation.So be provided with, two circular hole 2-1 pitch of holes D are maximal value basically, thereby make hot spot distance that two circular hole 2-1 are become on ccd detector 4 farthest, are convenient to accurate measurement.

Claims (2)

1, double hole type measural apparatus for scattering angle of laser beam, it is characterized in that it is by optical antenna (1), diplopore diaphragm (2), long burnt parallel light tube (3), ccd detector (4) and the computing machine (5) that has an image pick-up card are formed, have two circular holes (2-1) on the disc surfaces of discoid diplopore diaphragm (2), two circular holes (2-1) are symmetricly set on the both sides of diplopore diaphragm (2) axial line, optical antenna (1), diplopore diaphragm (2), long burnt parallel light tube (3) and ccd detector (4) preface concentric successively are provided with, the imaging surface of ccd detector (4) is positioned on the focal plane of long burnt parallel light tube (3), and the signal output part of ccd detector (4) connects the signal input part of the computing machine (5) that has image pick-up card.

2, double hole type measural apparatus for scattering angle of laser beam according to claim 1 is characterized in that diameter (φ) and two circular holes (2-1) pitchs of holes (D) sum of the circular hole (2-1) of diplopore diaphragm (2) equal the bore of optical antenna (1).

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