CN2847219Y - Device for measuring laser beam parallelism - Google Patents

Abstract

The utility model provides a device for measuring laser beam parallelism, the utility model discloses a measuring device is constituteed to detected light beam, diaphragm, convergent lens, half-transparent half-reflecting mirror, two post lenses, two four-quadrant detectors and computer; the convergent objective lens, the half-transmitting and half-reflecting mirror, the two cylindrical lenses and the two four-quadrant detectors form a beam parallelism detector, and beam parallelism detection is carried out based on astigmatic focusing error detection. And (3) eliminating detection errors caused by off-axis incident light by adopting a differential method. The optical system can be designed to have any sensitivity and linear range; the device is particularly suitable for measuring the laser beams with high quality, small calibers and small divergence angles and with rotational symmetry.

Description

The device of measuring laser beam collimation

Technical field

The utility model belongs to laser technology, is a kind of device of measuring laser beam collimation.Be mainly used in the measurement of the angle of divergence of the detection of the laser beam divergent angle behind the collimation and small divergence angle, rotational symmetric laser beam.

Background technology

The laser collimator of the right alignment of measurement big machinery mesopore, axle system and the linearity on plane, flatness, the depth of parallelism, laser range finder, in laser atmospheric surveillance and the wireless light communication, all need the collimated laser light light beam, the collimation of laser beam has very big influence to the performance of surveying instrument, communication quality etc.Therefore, the detection range of application of collimation parallelity of laser beam is bigger.The collimated laser beam collimation is weighed by the far-field divergence angle of light beam.

Measuring the collimated laser beam collimation at present mainly realizes by interference technique.Tested light beam is divided into two-beam, produces in an appropriate location then and interferes, if incident beam is a directional light, then the interference fringe of Chan Shenging is the vertical bar line or does not have striped.This method accuracy of measurement is higher.But also there is following defective:

1) interferometer costs an arm and a leg;

2) volume of general interferometer is bigger, uses inconvenient;

3) vibrations are bigger to measuring influence;

4) angular range that can measure is less.

Summary of the invention

The technical problems to be solved in the utility model is to overcome the deficiency of above-mentioned technology formerly, and a kind of device of measuring laser beam collimation is provided, and it can be fast, measuring laser beam collimation easily.

Basic design of the present utility model is:

The utility model is based on the Astigmatism methord focusing error and surveys the measurement of carrying out parallel beam, constitutes the parallel beam detecting device by assembling object lens, semi-transparent semi-reflecting lens, two post lens and two 4 quadrant detectors.And adopt differential method to eliminate because the detecting error that incident light causes from axle.

Technical solution of the present utility model is as follows:

A kind of device of measuring laser beam collimation, its formation is: be provided with diaphragm, convergent lens, semi-transparent semi-reflecting lens, the first post lens, first 4 quadrant detector successively with optical axis ground, reflected light direction at described semi-transparent semi-reflecting lens, be the second post lens, second 4 quadrant detector successively promptly perpendicular to described optical axis direction, the described first post lens and the second post lens are symmetrical about the light splitting surface of described semi-transparent semi-reflecting lens, and the signal output part of described first 4 quadrant detector and second 4 quadrant detector links to each other with input end and computer.

The astigmatism direction of the branch slot of described first 4 quadrant detector and the described first post lens is at 45, the astigmatism direction of the branch slot of described second 4 quadrant detector and the described second post lens is at 45, hot spot is corresponding with the minor axis of hot spot on second 4 quadrant detector at the major axis on first 4 quadrant detector, and hot spot is corresponding with the major axis of hot spot on second 4 quadrant detector at the minor axis on first 4 quadrant detector.

Described convergent lens, the first post lens and the second post lens are achromat.

Utilize the method for the measurement device parallel beam of described measuring beam collimation, it is characterized in that comprising the following steps:

1. with the optical axis alignment of the utility model device light beam to be measured, make light beam to be measured along optical axis incident;

2. starter gear is measured automatically, by Computer Processing, obtains error signal

$H=\frac{(A_1+A_3)-({\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="Y20052004425200091.png"\; state="\{\{state\}\}">A</figure-callout>}}_2+A_4)}{\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{A}_i}+\frac{({\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="Y20052004425200091.png"\; state="\{\{state\}\}">B</figure-callout>}}_1+B_3)-({\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="Y20052004425200091.png"\; state="\{\{state\}\}">B</figure-callout>}}_2+B_4)}{\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{B}_i}$

In the formula: A ₁, A ₂, A ₃, A ₄Be respectively the area of the hot spot of four quadrants that impinge upon first 4 quadrant detector; B ₁, B ₂, B ₃, B ₄Be respectively the area of the hot spot of four quadrants that impinge upon second 4 quadrant detector;

In linear zone, the relation of H and angle of divergence θ can be expressed as the θ into H=K, and wherein, K is and the focal length of detector gain, convergent lens, the relevant coefficient of focal length of post lens.

The utility model has following advantage with respect to prior art:

1. cheap;

2. the instrument volume is little, measures quick, easy;

3. measuring accuracy depends primarily on the machining precision and the assembly precision of each optical element, and vibration influence is less;

4. can be by design optical system---the distance between focal length, convergent lens and the post lens of selection convergent lens and post lens, the position of 4 quadrant detector, to have any sensitivity and the range of linearity; Especially it is high-quality small-bore to be fit to measurement, the laser beam with rotational symmetry of small divergence angle.

5. convergent lens and post lens all can be made the achromat in the certain limit, promptly all can use when the incident of different wave length light beam and need not adjust light path.

Description of drawings

Fig. 1 is the structural representation of the utility model measuring laser beam collimation device embodiment.

Fig. 2 is the vertical view of second 4 quadrant detector 8 among Fig. 1.

Fig. 3 is the right side view that has of first 4 quadrant detector 7 among Fig. 1.

Embodiment

The utility model is described in further detail below in conjunction with drawings and Examples.

See also Fig. 1 earlier, Fig. 1 is the structural representation of the device embodiment of the utility model measuring laser beam collimation.As seen from the figure, the formation of the device of the utility model measuring laser beam collimation is: be provided with diaphragm 2 successively with optical axis ground, convergent lens 3, semi-transparent semi-reflecting lens 4, the first post lens 5, first 4 quadrant detector 7, reflected light direction at described semi-transparent semi-reflecting lens 4, be the second post lens 6 successively promptly perpendicular to described optical axis direction, second 4 quadrant detector 8, the described first post lens 5 and the second post lens 6 are symmetrical about the light splitting surface of described semi-transparent semi-reflecting lens 4, and the signal output part of described first 4 quadrant detector 7 and second 4 quadrant detector 8 links to each other with the input end of computing machine 9.The astigmatism direction of the branch slot of described first 4 quadrant detector 7 and the described first post lens 5 is at 45, the astigmatism direction of the branch slot of described second 4 quadrant detector 8 and the described second post lens 6 is at 45, hot spot is corresponding with the minor axis of hot spot on second 4 quadrant detector 8 at the major axis on first 4 quadrant detector 7, and hot spot is corresponding with the major axis of hot spot on second 4 quadrant detector 8 at the minor axis on first 4 quadrant detector 7.Described convergent lens 3, the first post lens 5 and the second post lens 6 are achromat.

Utilize the method for the measurement device parallel beam of the utility model measuring laser beam collimation, comprise the following steps:

1. with the optical axis alignment of the utility model device light beam to be measured, make light beam to be measured along optical axis incident;

2. starter gear is measured automatically, by Computer Processing, obtains error signal

$H=\frac{(A_1+A_3)-(A_2+A_4)}{\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{A}_i}+\frac{(B_1+B_3)-({\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="Y20052004425200091.png"\; state="\{\{state\}\}">B</figure-callout>}}_2+B_4)}{\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{B}_i}$

In the formula: A ₁, A ₂, A ₃, A ₄Be respectively the area of the hot spot of four quadrants 701,702,703,704 that impinge upon first 4 quadrant detector 7, referring to Fig. 3;

B ₁, B ₂, B ₃, B ₄Be respectively the area of the hot spot of four quadrants 801,802,803,804 that impinge upon second 4 quadrant detector 8, referring to Fig. 2;

The relation of H and angle of divergence θ can be expressed as the θ into H=K in linear zone, and wherein, K is and the focal length of detector gain, convergent lens, the relevant coefficient of focal length of post lens.

The course of work of the present utility model is as follows:

Tested light beam 1 makes incident beam become convergent beam through passing through convergent lens 3 behind the diaphragm 2 again; This convergent beam 50% through inciding after semi-transparent semi-reflecting lens 4 transmissions on the first post lens 5, on the astigmatism direction of the first post lens 5, produce astigmatism; Other 50% incides on the second post lens 6 after semi-transparent semi-reflecting lens 4 reflections, through producing astigmatism behind the second post lens 6 on the astigmatism direction of the second post lens 6.The optical axis coincidence of the optical axis of the first post lens 5 and convergent lens 3, the position of the first post lens 5, the second post lens 6 is about the light splitting surface symmetry of semi-transparent semi-reflecting lens 4.

The modes of emplacement of described post lens and 4 quadrant detector makes, the major axis of hot spot on corresponding second 4 quadrant detector 8 of the minor axis on first 4 quadrant detector 7, the minor axis of hot spot on corresponding second 4 quadrant detector 8 of the major axis on first 4 quadrant detector 7.So just can promptly eliminate the error of tested light beam when axle, can not influence the sensitivity of the error signal that obtains at last again, because respective quadrants is subtracted each other to angle.

First 4 quadrant detector 7, second 4 quadrant detector 8 that is placed on correct position receives the light beam that sees through the first post lens 5, the second post lens 6 respectively, and convert it to electric signal carry out the current-voltage conversion, through sending into the angle of divergence that can obtain incident beam 1 after computing machine 9 carries out a series of computings after the preposition amplification.Weigh the collimation of light beam with the angle of divergence of light beam.

The area of hot spot that impinges upon four quadrants 701,702,703,704 of first 4 quadrant detector 7 is respectively A ₁, A ₂, A ₃, A ₄, the area of hot spot that impinges upon four quadrants 801,802,803,804 of second 4 quadrant detector 8 is respectively B ₁, B ₂, B ₃, B ₄The error signal that the electric signal of first 4 quadrant detector 7,8 outputs of second 4 quadrant detector obtains after plus-minus, normalization computing:

$H=\frac{(A_1+A_3)-(A_2+A_4)}{\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{A}_i}+\frac{(B_1+B_3)-({\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="Y20052004425200091.png"\; state="\{\{state\}\}">B</figure-callout>}}_2+B_4)}{\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}{B}_i}$

The relation of H and angle of divergence θ can be expressed as the θ into H=K in linear zone

Wherein, K is and the focal length of detector gain, convergent lens, the relevant coefficients such as focal length of post lens.H is directly proportional with the angle of divergence of tested light beam in linear zone, for requiring more accurate measurement, can directly be drawn the angle of divergence of tested light beam again by the error signal that obtains by demarcating.

In the present embodiment, the aperture of diaphragm 2 is D=8mm; The focal length of convergent lens 3 is 20.2mm; The focal length of the first post lens 5, the second post lens 6 is 1000mm; Distance between the distance between first 4 quadrant detector 7 and the first post lens 5 and second 4 quadrant detector 8 and the second post lens 6 is 20mm; The length of side of first 4 quadrant detector 7, second 4 quadrant detector, 8 single quadrants is 0.08mm; Incident optical power is 5mW; The maximum angle of divergence that can survey is 2mrad.

H is directly proportional with incident optical power, and the gained error signal is carried out normalization: divided by incident optical power, get H0.

The corresponding relation of H0 value and angle of divergence θ such as following table.

The angle of divergence (rad)	0	0.000 2	0.000 4	0.000 6	0.000 8	0.001 0	0.001 2
								H0 after the normalization	0	0.031 7	0.062 8	0.092 7	0.121 1	0.147 6	0.172 0

Beam divergence angle (rad)	0	0.00002	0.00004	0.00006	0.00008
						H0 after the normalization	0	0.0032	0.0064	0.0095	0.0127

Claims (3)

1, a kind of device of measuring laser beam collimation, be characterised in that its formation is: be provided with diaphragm (2) successively with optical axis ground, convergent lens (3), semi-transparent semi-reflecting lens (4), the first post lens (5), first 4 quadrant detector (7), reflected light direction at described semi-transparent semi-reflecting lens (4), be the second post lens (6) successively promptly perpendicular to described optical axis direction, second 4 quadrant detector (8), the described first post lens (5) and the second post lens (6) are symmetrical about the light splitting surface of described semi-transparent semi-reflecting lens (4), and the signal output part of described first 4 quadrant detector (7) and second 4 quadrant detector (8) links to each other with the input end of computing machine (9).

2, the device of measuring laser beam collimation according to claim 1, the astigmatism direction that it is characterized in that the branch slot of described first 4 quadrant detector (7) and the described first post lens (5) is at 45, the astigmatism direction of the branch slot of described second 4 quadrant detector (8) and the described second post lens (6) is at 45, hot spot is corresponding with the minor axis of hot spot on second 4 quadrant detector (8) at the major axis on first 4 quadrant detector (7), and hot spot is corresponding with the major axis of hot spot on second 4 quadrant detector (8) at the minor axis on first 4 quadrant detector (7).

3, the device of measuring laser beam collimation according to claim 1 is characterized in that described convergent lens (3), the first post lens (5) and the second post lens (6) are achromat.

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