CN1256609C - Precise rotation biprism optical beam scanner and control method thereof - Google Patents

Abstract

The present invention relates to a precise rotation biprism optical beam scanner for the spatial scan of a laser beam and a control method thereof The precise rotation biprism optical beam scanner comprises a driving circuit, two motors, a transmission mechanism and a double circular prism. The precise rotation biprism optical beam scanner is characterized in that a computer and a PID controller are arranged in front of the driving circuit; a specific data base is arranged in the computer; the data base stores corresponding numerical values of rotation angles (thet 1 and thet 2) of the double circular prism and a pitching angle and an azimuth angle (delta and phi) of a transmission light beam. The output end of the transmission mechanism corresponding to the double circular prism is provided with two angular transducers, and the output end of the transmission mechanism is connected with a computer. The precise rotation biprism optical beam scanner and the control method thereof of the present invention have the advantages that the precision of the pitching angle delta and the azimuth angle phi of the transmission light beam achieve a milliradian magnitude order, and a scanning range of the scanner is enlarged.

Description

Accurate rotation double prism beam scanner and control method thereof

Technical field

The spacescan of the present invention and laser beam and catch relevant, particularly a kind of accurate rotation double prism beam scanner and control method thereof.

Background technology

The spacescan of laser beam and catch be always space optical communication and laser radar technique give priority to one of research direction.Space optical communication and laser radar must scan and catch target to effective space exploration with laser beam, reach the purpose in accurate realization communication and measurement target distance and orientation.For reach this purpose formerly technology [1] (referring to Optics Guide 5, Chapter 10, Page12.) and formerly technology [2] is (referring to patents such as Zu Jifeng, application number: 03129234.8, in June, 2003 applying date) mention and utilize rotation biprism device to realize the two-dimensional scan of laser beam in particular range.Its ultimate principle is to drive two prism rotations respectively with two motors, when a certain laser beam after the turning axle direction incident of prism, through light beam after two prismatic refractions can be in a specific circular cone deflection and produce certain angle of pitch and position angle (target of catching or scanning is in the above-mentioned greatest circle cone angle that can obtain) in the process of calculating light beam deflection angle after by rotation biprism system continuously, formerly technology all is that the very little and light beam vertical irradiation of drift angle at the hypothesis prism is on prism and obtain the approximate formula of deflection angle

$\mathrm{\δ}=2(n-1)\mathrm{\α}\cos \left(\frac{{\mathrm{\θ}}_1-{\mathrm{\θ}}_2}{2}\right)---\left(1\right)$

And position angle

$\mathrm{\Φ}=\frac{{\mathrm{\θ}}_1+{\mathrm{\θ}}_2}{2}---\left(2\right)$

Its control procedure is to derive θ according to (1) (2) ₁=f ₁(δ, Φ), θ ₂=f ₂(δ Φ) realizes (accompanying drawing 1) 1 data converting circuit by means of data converting circuit then; 2 servo control circuits; 3 driving circuits; 4,5 motors; 6 gear trains; 7,8 circular prisms.Because formula (1) is approximate obtaining under the very little situation of the drift angle of prism, so its precision and sweep limit are subjected to certain restriction.

Summary of the invention

The technical problem to be solved in the present invention be to overcome above-mentioned technology formerly deficiency, provide light beam after by rotation biprism system deflection angle δ and the exact formulas of position angle Φ, and a kind of accurate rotation double prism beam scanner and control method thereof have been proposed according to this formula, reach the milliradian magnitude and enlarge sweep limit with the precision that improves biprism.

Design philosophy of the present invention can be described below:

The principal section of two circular prisms is all in the XY face when supposing beginning, the direction of rib is along the direction of Z, the unit vector of incident beam is A=(sin cos θ in XYZ coordinate system, sin sin θ, cos ), can derive the deflection angle δ of light beam after two prisms and the rotation angle θ of position angle Φ and two prisms ₁, θ ₂Between the pass be:

(sin ² ₂sin ²(θ ₂₂+δ ₂)≠1)

Φ＝0，(sin ² ₂sin ²(θ ₂₂+δ ₂)＝1) (4)

(3) in (4) two formulas: ₂=cos ^-1{ sin[cos ^-1(sin cos θ sin θ ₁+ cos θ ₁Cos )] cos (θ ₁₁+ δ ₁) sin (θ ₂-θ ₁)+cos (θ ₂-θ ₁) cos ₁}

(5)

(5) in (6) formula

₁＝cos ^-1(sincosθsinθ ₁+cosθ ₁cos)

(7) in the formula

(8) in the formula

As can be known after the direction of incident beam is determined, just can draw different rotational angle theta according to The above results ₁, θ ₂The deflection angle δ and the position angle Φ of corresponding light beam.

But the control procedure of scanner is how (δ Φ) determines the anglec of rotation (θ of two prisms by given parameter ₁, θ ₂)? can not draw analytic expression θ by (3) (4) ₁=f ₁(δ, Φ), θ ₂=f ₂Therefore (δ, Φ), formerly the control method in the technology is inapplicable to this device, but can draw (θ by formula (3) (4) ₁, θ ₂) and (δ, Φ) between value corresponding separate.For this reason, be that the matlab program is write on the basis with formula (3) (4), to the apex angle of prism, the refractive index n initialize of material, make θ according to actual conditions ₁, θ ₂In [0 2 π],, can draw a series of and (θ respectively with certain step-length value ₁, θ ₂) corresponding (δ, Φ), all (θ of maintenance ₁, θ ₂) and (δ, Φ) corresponding relation between and deposit a database in.The precision of this database is by θ ₁, θ ₂Step-length determine, such as being when step-length $(\frac{2\mathrm{\π}}{1500}\≈0.004)$ Can be as accurate as the milliradian magnitude, can also shorten step-length according to accuracy requirement certainly, but its precision can not surpass diffraction limit

(δ can find out after Φ) satisfied in this database when given $\mathrm{\Δ}=\sqrt{{(\mathrm{\δ}-{\mathrm{\δ}}_n)}^2+{(\mathrm{\Φ}-{\mathrm{\Φ}}_n)}^2}$ (δ for minimum value _n, Φ _n), then in the database with (δ _n, Φ _n) corresponding (θ _1n, θ _2n) be the angle of two circular each spinnings of prism.

Technical solution of the present invention is as follows:

A kind of precision rotation double prism beam scanner that is used for laser beam space scanning, comprise that driving circuit, motor, gear train, Double Circle prism, driving circuit receive instruction and make the rotation of Double Circle prism by this instruction drive motor respectively by gear train, it is characterized in that before driving circuit, also having computing machine and PID controller, be provided with private database in this computing machine, this database has the anglec of rotation (θ of Double Circle prism ₁, θ ₂) and the transmitted light beam angle of pitch and position angle (δ _n, Φ _n) corresponding numerical value, also be provided with angular transducer at the output terminal of gear train, its output termination computing machine.

The control method of described accurate rotation double prism beam scanner is characterized in that comprising the following steps:

1. according to the apex angle of Double Circle prism, the refractive index n of material, make θ ₁, θ ₂Between (0～2 π),, press following formula respectively by selected step-length value:

(3)

(sin ² ₂sin ²(θ ₂₂+δ ₂)≠1)

Φ＝0，(sin ² ₂sin ²(θ ₂₂+δ ₂)＝1) (4)

(3) in (4) two formulas:

₂＝cos ^-1{sin[cos ^-1(sincosθsinθ ₁+cosθ ₁cos)]cos(θ ₁₁+δ ₁)sin(θ ₂-θ ₁)+cos(θ ₂-θ ₁)cos ₁}

(5)

(5) in (6) formula

₁＝cos ^-1(sincosθsinθ ₁+cosθ ₁cos)

(7) in the formula

(8) in the formula

Utilize computing machine (1) to obtain a series of and (θ ₁, θ ₂) corresponding to target location (δ _n, φ _n) numerical solution, and deposit in the private database of computing machine (1);

2. with target position information (δ _x, φ _x) input computing machine after, computing machine is promptly found out satisfied at private database $\mathrm{\Δ}=\sqrt{{({\mathrm{\δ}}_x-{\mathrm{\δ}}_n)}^2+{({\mathrm{\Φ}}_x-{\mathrm{\Φ}}_n)}^2}$ (δ for minimum value _n, Φ _n), computing machine finds (δ _n, Φ _n) after, in private database, choose corresponding with it (θ again _1n, θ _2n);

3. with (θ _1n, θ _2n) and actual angle (the θ ＇ that measures of angular transducer _1n, θ ＇ _2n) compare, resulting difference is input to the PID controller, and this PID controller generation control signal corresponding drives bi-motor respectively by driving circuit and rotates to reposition by kinematic train drive Double Circle prism;

4. at this moment, two angular transducers again can with the new angle of each self-inductance measurement Double Circle prism (θ " _1n, θ " _2n) send into computing machine, computing machine is again with (θ _1n, θ _2n) with (θ " _1n, θ " _2n) compare, and difference is input to the PID controller, this controller generation control signal corresponding drives two motors respectively by driving circuit and rotates to reposition by kinematic train drive Double Circle prism;

5. so circulation makes the deflection angle of light beam and position angle satisfy target position information (δ at last _x, Φ _x).

Described anglec of rotation θ ₁, θ ₂Step-length elect as

Described private database (9) Datebase1.00 is divided into four word banks: azimuthal scope is (0 among the Datebase1.01, pi/2), among the Datebase1.02 azimuthal scope be (π/, π), azimuthal scope is (π among the Datebase1.03,3 pi/2s), azimuthal scope is (3 pi/2s, 2 π) among the Datebase1.04.

Technique effect of the present invention:

The present invention and the difference of technology [1] [2] formerly are to replace data converting circuit in the technology formerly with the database that has in computing machine and the computing machine, have also increased by two angular transducers in addition and have improved the precision that prism rotates.Formerly the data converting circuit in the technology changes servo-control signal into control signal according to approximate formula (1) (2), and the database among the present invention is the exact solution that draws according to formula (3) (4), therefore according to given (δ _x, Φ _x) control signal (θ that in the storehouse, finds _1n, θ _2n) be more accurate, with (θ _1n, θ _2n) and corner angle actual angle (the θ ＇ that records of angular transducer _1n, ＇ θ ＇ _2n) difference input PID controller, controller produces control signal and drives the prism rotation by driving circuit and makes transmitted light beam deflect into (δ ＇ _x, Φ ＇ _x), Theoretical Calculation shows works as θ ₁, θ ₂Step-length be

The time, (δ ＇ _x, Φ ＇ _x) and actual target position signal (δ _x, Φ _x) error can be controlled in the milliradian magnitude, the precision of this invention is at least than the high order of magnitude of precision of technology formerly.The derivation of formula (1) (2) also is subjected to the restriction of the condition of light beam vertical incidence on prism in addition, and formula (3) (4) draw the restriction that is not subjected to this condition, so this invention can realize the control to arbitrarily angled incident light.

Description of drawings:

Fig. 1 is the structured flowchart of technology formerly, among the figure: 1 °-data converting circuit; 2 °-servo control circuit;

The 3-driving circuit; 4,5-motor; The 6-gear train; 7, the circular prism of 8-.

Fig. 2 is a structured flowchart of the present invention, among the figure: the 1-computing machine; The 2-PID controller; The 3-driving circuit;

4,5-motor; The 6-gear train; 7, the circular prism of 8-; The 9-database; 10, the 11-angle passes

Sensor

Fig. 3 is the sectional view of circular prism, and the drift angle of prism is α=15 °, diameter of phi=250mm.

Fig. 4 be the expression light beam after through two circle prisms deflection angle δ and the definition of position angle Φ.

Fig. 5 is the schematic perspective view of rotation biprism.

The schematic flow sheet of Fig. 6 control method of the present invention.

Embodiment:

See also Fig. 3 earlier, Fig. 3 is the right structured flowchart of the present invention's accurate rotation double prism beam scanner, as seen from the figure, the accurate rotation of the present invention double prism beam scanner, comprise driving circuit 3, two motors 4,5, gear train 6, Double Circle prism 7,8, this driving circuit 3 receive instruction and drive two motors 4 by this instruction, 5 make Double Circle prism 7 respectively by gear train 6,8 rotations is characterized in that also having computing machine 1 and PID controller 2 before driving circuit 3, are provided with private database 9 in this computing machine 1, output terminal at gear train 6 also is provided with two angular transducers 10,11, the output termination computing machine 1 of this two angular transducer 10,11.

The control method of described accurate rotation double prism beam scanner comprises the following steps:

1. according to the apex angle of Double Circle prism 7,8, the refractive index n of material, make θ ₁, θ ₂Between (0～2 π),, press following formula respectively by selected step-length value:

(sin ² ₂sin ²(θ ₂₂+δ ₂)≠1)

Φ＝0，(sin ² ₂sin ²(θ ₂₂+δ ₂)＝1) (4)

(3) in (4) two formulas:

₂＝cos ^-1{sin[cos ^-1(sincosθsinθ ₁+cosθ ₁?cos)]cos(θ ₁₁+δ ₁)sin(θ ₂-θ ₁)+cos(θ ₂-θ ₁)cos ₁}

(5)

(5) in (6) formula

₁＝cos ^-1(sincosθsinθ ₁+cosθ ₁cos)

(7) in the formula

(8) in the formula

Utilize computing machine 1 to obtain a series of and (θ ₁, θ ₂) corresponding to target location (δ _n, Φ _n) numerical solution, and deposit in the database 9 of computing machine 1;

2. work as target position information (δ _x, Φ _x) input computing machine 1 after, computing machine 1 is promptly found out satisfied at private database 9 $\mathrm{\Δ}=\sqrt{{({\mathrm{\δ}}_x-{\mathrm{\δ}}_n)}^2+{({\mathrm{\Φ}}_x-{\mathrm{\Φ}}_n)}^2}$ Be (δ n, the Φ n) of minimum value, after computing machine 1 finds (δ n, Φ n), in private database 9, choose corresponding with it (θ again _1n, θ _2n), with (θ _1n, θ _2n) and actual angle (the θ ＇ that measures of angular transducer 10,11 _1n, θ ＇ _2n) compare, resulting difference is input to PID controller 2, and the control signal that this controller 2 produces drives two motors 4,5 respectively by driving circuit 3 and rotates to reposition by kinematic train 6 drive Double Circle prisms 7,8:

3. at this moment, angular transducer 10,11 again can with the new angle of the circular prism 7,8 of sensing (θ " _1n, θ " _2n) send into computing machine 1, computing machine 1 is again with (θ _1n, θ _2n) with (θ " _1n, θ " _2n) compare, and difference is input to PID controller 2, the control signal that this controller 2 produces by driving circuit 3 respectively drive motor 4,5 drive circular prism 7,8 by kinematic train 6 and rotate to reposition, so circulation makes the deflection angle of light beam and position angle satisfy target position information (δ at last _x, Φ _x).

Described anglec of rotation θ ₁, θ ₂Step-length elect as

Described database (9) Datebase1.00 is divided into four word banks: azimuthal scope is (0 among the Datebase1.01, pi/2), azimuthal scope is (a pi/2 among the Datebase1.02, π), azimuthal scope is (π among the Datebase1.03,3 pi/2s), azimuthal scope is (3 pi/2s, 2 π) among the Datebase1.04.

The material of circular prism 7,8 is a K9 glass, and diameter of phi is 250mm, and as shown in Figure 2, wavelength is the turning axle incident of the incident light of 632.8nm along prism, requires its sweep limit at ± 15 °, and scanning accuracy is the milliradian magnitude.

Can get refractive index n=1.51467 according to given condition, the incident vector is (0,1,0); By the derivation of formula (3) (4), learn rotation angle θ when two circular prisms 7,8 ₁=θ ₂=0 o'clock, light beam had maximum deflection angle, and substitution formula (3) (4) can be obtained when the apex angle of prism is 14.375 ° respectively, and the maximum deflection angle of light beam can reach 15 °.For guaranteeing the sweep limit of its regulation, the apex angle that we make two prisms is 15 °, the anglec of rotation θ of two prisms ₁, θ ₂Step-length be

The precision of this system can reach the milliradian magnitude, also can further shorten step-length, but the control accuracy of this method be subjected to the influence of actual light physical construction according to the different requirements of precision, and ultimate precision should be After computing machine 1 operation, can obtain database 9-Datebase1.00 according to formula (3)/(4), for response time of shortening whole process scope according to position angle Φ is divided into Datebase1.00 four word banks and deposits computing machine 1 in, azimuthal scope is (0, pi/2) among the Datebase1.01, azimuthal scope is (a pi/2 among the Datebase1.02, π), azimuthal scope is (π, 3 pi/2s) among the Datebase1.03, azimuthal scope is (3 pi/2s, 2 π) among the Datebase1.04.

When system receives target position information (δ _x, Φ _x), computing machine 1 can be controlled according to the flow process of Fig. 6: according to Φ _xValue judge (δ _x, Φ _x) in which word bank, and in this word bank, search satisfied $\mathrm{\Δ}=\sqrt{{({\mathrm{\δ}}_x-{\mathrm{\δ}}_n)}^2+{({\mathrm{\Φ}}_x-{\mathrm{\Φ}}_n)}^2}$ (δ for minimum value _n, Φ _n), call then and (δ _n, Φ _n) corresponding (θ _1n, θ _2n), with (θ _1n, θ _2n) and actual angle (the θ ＇ that measures of angular transducer 10,11 _1n, θ ＇ _2n) compare, resulting difference is input to PID controller 2.The control signal that this controller produces is rotated corresponding angle by driving circuit 3 drive motor 4,5, drive Double Circle prisms 7,8 by gear train 6 and rotate to corresponding position, transmitted light beam deflect into (δ ' _x, Φ ' _x), this moment and target location (δ _x, Φ _x) the error control precision in the milliradian magnitude.

Claims (4)

1, a kind of precision rotation double prism beam scanner that is used for laser beam space scanning, comprise driving circuit (3), two motors (4,5), gear train (6), Double Circle prism (7,8), the output terminal that it is characterized in that a computing machine (1) connects driving circuit (3) through PID controller (2), be provided with private database (9) in this computing machine (1), this database (9) has the anglec of rotation θ of Double Circle prism (7,8) ₁, θ ₂With transmitted light beam angle of pitch δ _nWith position angle Φ _nCorresponding numerical value, at corresponding two angular transducers (10,11) that are provided with of the output terminal and the Double Circle prism (7,8) of gear train (6), the output terminal of these two angular transducers (10,11) connects computing machine (1).

2, the control method of the described accurate rotation double prism beam scanner of claim 1 is characterized in that comprising the following steps:

1. according to the apex angle of Double Circle prism (7,8), the refractive index n of material, make θ ₁, θ ₂Between (0～2 π),, press following formula respectively by selected step-length value:

Φ＝0，(sin ² ₂sin ²(θ ₂₂+δ ₂)＝1) (4)

(3) in (4) two formulas:

₂＝cos ^-1{sin[cos ^-1(sincosθsinθ ₁+cosθ ₁cos)]cos(θ ₁₁+δ ₁)sin(θ ₂-θ ₁)+cos(θ ₂-θ ₁)cos ₁}

(5)

(5) in (6) formula

₁＝cos ^-1(sincosθsinθ ₁+cosθ ₁cos)

(7) in the formula

(8) in the formula

Utilize computing machine (1) to obtain a series of and (θ ₁, θ ₂) corresponding to target location (δ, numerical solution Φ), and depositing in the private database (9) of computing machine (1);

2. with target position information (δ _x, φ _x) after input computing machine (1), computing machine (1) is promptly found out satisfied at private database (9) $\mathrm{\Δ}=\sqrt{{({\mathrm{\δ}}_x-{\mathrm{\δ}}_n)}^2+{({\mathrm{\Φ}}_x-{\mathrm{\Φ}}_n)}^2}$ (δ for minimum value _n, Φ _n), computing machine (1) finds (δ _n, Φ _n) after, in private database (9), choose corresponding with it (θ again _1n, θ _2n);

3. with (θ _1n, θ _2n) and the actual angle that measures of angular transducer (10,11) (θ ' _1n, θ ' _2n) compare, resulting difference is input to PID controller (2), and the control signal that this controller (2) produces drives circular prism (7,8) by driving circuit (3) difference drive motor (4,5) by kinematic train (6) and rotates to reposition;

4. at this moment, angular transducer (10,11) again can with the new angle of sensing Double Circle prism (7,8) (θ " _1n, θ " _2n) send into computing machine (1), computing machine (1) is again with (θ _1n, θ _2n) with (θ " _1n, θ " _2n) compare, and difference is input to PID controller (2), the control signal that this controller (2) produces drives Double Circle prism (7,8) by driving circuit (3) difference drive motor (4,5) by kinematic train (6) and rotates to reposition;

5. so circulation makes the deflection angle of light beam and position angle satisfy target position information (δ at last _x, Φ _x).

3, control method according to claim 2 is characterized in that described anglec of rotation θ ₁And θ ₂Step-length elect as

4, control method according to claim 2, it is characterized in that described private database (9)-Datebase1.00 is divided into four word banks: azimuthal scope is (0 among the Datebase1.01, pi/2), azimuthal scope is (a pi/2 among the Datebase1.02, π), azimuthal scope is (π, 3 pi/2s) among the Datebase1.03, azimuthal scope is (3 pi/2s, 2 π) among the Datebase1.04.

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