CN103941403A - Annular light beam generation device - Google Patents

Abstract

The invention discloses an annular light beam generation device which is composed of a constant-time beam expanding lens set, a DOE phase plate, a double telecentric zoom lens set, a polarizer lens set, a reflecting conical lens set and an observation positioning system. The annular light beam generation device is high in flexibility, even annular light beams with variable thicknesses and inner radiuses can be obtained for different types of input light beams, and an aberration does not exist.

Description

Annular beam generation device

Technical field

The present invention relates to beam shaping, especially a kind of annular beam generation device, can be shaped as the super-Gaussian partially coherent light of input thickness and the adjustable annular beam of inside radius that even intensity distributes.

Background technology

In recent years, laser is universal use in actual life, as the field such as laser hologram, Materialbearbeitung mit Laserlicht, particularly at medical field, laser is a kind of new type light source, has the features such as monochromaticity is good, coherence is good, high directivity, is widely used in therapeutic treatment.At present myopia therapeutic mainly adopts excimer laser to perform the operation (being designated hereinafter simply as LASIK), carries out phototropism cutting, the corneal curvature of reduction lesser ring of Merkel, thereby myopia correction with hypothallus under excimer laser corneal lobe.In lasik surgery, excimer laser output coherent light, carries out cornea ablation among a small circle continuously, has certain operating time, although there is in the meantime calibration system real-time follow-up, but still has certain danger.More safely carry out laser surgey for more convenient, excimer pulsed laser beam is shaped as to annular beam, disposable cutting cornea, reduces operation risk.The spacing shaping method of light beam is a lot, utilizes non-spherical lens group, diffraction optical element (being designated hereinafter simply as DOE), microlens array shaping, LCD space light modulator etc. all super-Gaussian partially coherent light can be shaped as to uniform annular beam.But comparatively speaking, partially coherent light is shaped as to annular beam, adopts DOE shaping methods simple in structure, shaping effect is good, easily realizes.

Summary of the invention

The object of the present invention is to provide a kind of annular beam generation device, this device is not only applicable in lasik surgery, also be applicable to the device of other demand annular beams, the thickness of annular beam and inside radius can regulate, and the aberration that the shaping of DOE phase board brings is compensated by two heart zoom mirror groups far away.

For achieving the above object, the present invention has taked following technical scheme:

A kind of annular beam generation device, its feature is: this device is made up of determine power beam expansion lens group, DOE phase board, two heart zoom mirror group far away, polaroid mirror group, reflection conical mirror group and observation positioning system successively;

Described determines power beam expansion lens group for Kepler's type beam expanding lens, is made up of the first plano-concave mirror and the first planoconvex lens;

Described DOE phase board is diffraction optical element, and super-Gaussian partially coherent light is shaped as to uniform circular light beam;

Described heart zoom mirror group two far away is made up of variable focus lens package, diaphragm and offset lens group successively;

Described polaroid mirror group is made up of the polarizer, polaroid and λ/4 wave plate;

Described reflection conical mirror group is made up of external reflection conical mirror, Inner reflection taper type lens barrel;

Described observation positioning system is made up of camera CCD and computer.

Described DOE phase board is to adopt conjugate gradient algorithm optimal design, the phase board that then process mask and photoetching obtain.

Excimer laser output is seven rank super-Gaussian partially coherent lights, and its mutual intensity is:

$J_0(r_1,r_2,0)=\exp {(-\frac{{r_1}^2+{r_2}^2}{w_0^2})}^7\×\exp {(-\frac{{(r_1-r_2)}^2}{{2\mathrm{\σ}}_0^2})}^7---\left(1\right)$

Along x, phase board is equidistantly divided respectively 2m by y direction, and 2n is interval, when

When m, n →+∞, can be by the light intensity on the film viewing screen of far field:

$I(r,z)=\frac{1}{{\mathrm{\λ}}_0^2{z}^2}\underset{-\∞}{\overset{+\∞}{\∫}}\underset{-\∞}{\overset{+\∞}{\∫}}\underset{-\∞}{\overset{+\∞}{\∫}}\underset{-\∞}{\overset{+\∞}{\∫}}J(r_1,r_2,0)\×\exp \{-\frac{i2\mathrm{\π}}{{\mathrm{\λ}}_{0}z}[x(x_1-x_2)+y(y_1-y_2)\left]\right\}---\left(2\right)$

Be reduced to:

$\begin{array}{c}I(r,z)=\frac{1}{{\mathrm{\λ}}_0^2{z}^2}\underset{i_1=-m}{\overset{m}{\mathrm{\Σ}}}\underset{i_2=-m}{\overset{m}{\mathrm{\Σ}}}\underset{j_1=-n}{\overset{n}{\mathrm{\Σ}}}\underset{j_2=-n}{\overset{n}{\mathrm{\Σ}}}\exp [-\frac{i2\mathrm{\π}(n_0-1)}{{\mathrm{\λ}}_0}(h_{i_1{j}_1}-h_{i_2{j}_2})]{\left(\mathrm{\Δx}\right)}^2{\left(\mathrm{\Δy}\right)}^2\\ \×J_0(i_1\mathrm{\Δx},j_1\mathrm{\Δy};i_2\mathrm{\Δx},j_2\mathrm{\Δy};0)\exp \{-\frac{i2\mathrm{\π}}{{\mathrm{\λ}}_{0}z}[x(i_1-i_2)\mathrm{\Δx}+y(j_1-j_2)\mathrm{\Δy}\}\end{array}---\left(3\right)$

Wherein, λ is wavelength, n ₀for phase board refractive index, hi _jrepresent the geometric thickness of phase board at x direction i circle point, y direction j circle point, Δ x, Δ y represent to be respectively x, the step-length of y direction.

Conjugate gradient algorithm are the improvement algorithms to steepest descent algorithm, in search procedure, the direction of search have been carried out to certain correction, thereby have improved optimizing ability:

Objective function: find optimum h _ij, make the homogenising degree of output intensity I (r, z) the highest.

Phase delay is distributed as:

The direction of search is:

Wherein, β _k-1for conjugate factor:

Shown in the process flow diagram 2 of employing conjugate gradient algorithm design DOE.

In described heart zoom mirror group two far away, fix the second plano-concave mirror, the distance d of the second plano-convex lens and the second plano-concave mirror ₁₂, the second plano-concave mirror and the first planoconvex lens distance d ₂₃, the amount of movement of the second planoconvex lens, the first planoconvex lens is:

${\mathrm{\Δd}}_{12}=-\frac{{f_2}^2}{{\mathrm{Mf}}_1}+d_{12}-f_1-f_2---\left(7\right)$

${\mathrm{\Δd}}_{23}=-\frac{1-(d_{12}-\mathrm{\Δ}{d}_{12})f_2}{f_1+f_2-(d_{12}-\mathrm{\Δ}{d}_{23})}+(f_3-d_{23})---\left(8\right)$

Δ d ₁₂represent the displacement of the second planoconvex lens, Δ d ₂₃represent the displacement of the first planoconvex lens, amount of movement Δ d ₁₂for on the occasion of time represent near the second plano-concave mirror, when negative value, represent away from; Amount of movement Δ d ₂₃for on the occasion of time represent that the first planoconvex lens, away from the second plano-concave mirror, represents close when negative value;

F ₁be the focal length of the second planoconvex lens, f ₂be the focal length of the second plano-concave mirror, f ₃it is the focal length of the first planoconvex lens; M is for selecting to expand multiple.

In described polaroid mirror group, utilize λ/4 wave plate that the light beam that eyes send is reflexed in CCD from polaroid, application image treatment technology is observed and locates uniform ring shaped light beam;

In described reflection conical mirror group, Inner reflection taper type lens barrel is fixed, and external reflection conical mirror can move forward and backward, and Inner reflection taper type lens barrel equates with the inclination angle of external reflection conical mirror, the distance d between Inner reflection taper type lens barrel and external reflection conical mirror _aBfor:

$d_{\mathrm{AB}}=\frac{r_1}{\sin (2*\mathrm{\θ})}---\left(9\right)$

D _aBrepresent the distance of Inner reflection taper type lens barrel and external reflection conical mirror;

θ represents the angle of external reflection conical mirror and optical axis direction, is also the inclination angle of external reflection conical mirror; r ₁for the annular beam inside radius of selecting.

Beneficial effect of the present invention is as follows:

1, the present invention is compared with excimer laser in LASIK, and this device can be exported uniform annular laser beam;

2, the inside radius of annular beam of the present invention and thickness can regulate by reflection conical mirror group and two heart zoom mirror group far away respectively;

3, the present invention not only can be shaped as equally distributed annular beam by the super-Gaussian partially coherent light of excimer laser, for myopia therapeutic operation, is also used in other devices, and annular beam can produce with this device, and inside radius and thickness adjustable.

Brief description of the drawings

Fig. 1 is annular beam generation device index path of the present invention;

Fig. 2 is the DOE design flow diagram based on conjugate gradient algorithm;

Fig. 3 is two heart zoom mirror group zoom schematic diagram far away;

Fig. 4 is the geometric graph of reflection conical mirror group regulating ring shaped light beam inside radius;

Fig. 5 is the optimum phase board PHASE DISTRIBUTION figure that conjugate gradient algorithm are obtained;

Fig. 6 is the output map that phase board is shaped as 20*20mm partially coherent light circular light beam r=8mm;

Fig. 7 is the beam uniformity schematic diagram of circular light beam r=8mm central cross-section;

Fig. 8 adjusts the r1=10mm that zoom and conical mirror obtain, the output beam of h=2mm;

Fig. 9 adjusts the r1=10mm that zoom and conical mirror obtain, the output beam of h=1.5mm;

Figure 10 adjusts the r1=12mm that zoom and conical mirror obtain, the output beam of h=2mm;

Embodiment

Below in conjunction with drawings and Examples, the present invention is further illustrated:

Embodiment 1:

As shown in Figure 1: annular beam generation device of the present invention is made up of determine power beam expansion lens group 1, DOE phase board 2, two heart zoom mirror group 3 far away, polaroid mirror group 4, reflection conical mirror group 5 and observation positioning system 6 successively;

Described determines power beam expansion lens group 1 for Kepler's type beam expanding lens, is made up of the first plano-concave mirror 101 and the first planoconvex lens 102;

Described DOE phase board 201 is diffraction optical element, and super-Gaussian partially coherent light is shaped as to Homogeneous Circular light beam;

Described heart zoom mirror group 3 two far away is made up of three parts, and variable focus lens package 301, diaphragm 302, offset lens group 303 form successively;

Described polaroid mirror group 4 is made up of the polarizer 401, polaroid 402, λ/4 wave plate 403;

Described reflection conical mirror group 5 is made up of external reflection conical mirror 502, Inner reflection taper type lens barrel 501;

Described observation positioning system 6 is made up of camera CCD601 and computer PC602.

Fig. 1 is annular beam generation device index path of the present invention.The partially coherent light of excimer laser is inputted by left side, first with determining power beam expansion lens group, partially coherent light is expanded to 20*20mm, after DOE phase board, obtain the Homogeneous Circular light beam of r=8mm, fixed lens 301-2, according to formula (7) and mobile the second plano-convex lens 301-1 of formula (8) and the first plano-convex lens 303, make light beam contracting bundle obtain the circular light spot of r0=2mm, after polaroid mirror group, adjust the distance d between Inner reflection taper type lens barrel 501 and external reflection conical mirror 502 according to formula (9) _aB, move forward and backward external reflection conical mirror 502, make internal diameter r1=10mm, obtain r=10mm, the annular beam of h=r0=2mm, as shown in Figure 8, eye reflections light is after λ/4 wave plate 403, from polarization

Sheet 402 is transmitted into CCD, just can obtain the position of annular beam at eyes by image processing techniques.

Embodiment 2:

Adjust two heart zoom mirror groups far away, obtain the circular light beam of contracting bundle r0=1.5mm, external reflection conical mirror 502 is adjusted in front and back, makes inside radius r1=10mm, finally obtains r=10mm, the annular beam of h=r0=1.5mm, and as shown in Figure 9, other methods of operating are with embodiment 1.

Embodiment 3:

Adjust two heart zoom mirror groups far away, obtain the circular light beam of contracting bundle r0=2mm, external reflection conical mirror 502 is adjusted in front and back, makes inside radius r1=12mm, finally obtains r=12mm, the annular beam of h=r0=2mm, and as shown in figure 10, other methods of operating are with embodiment 1.

Claims (4)

1. an annular beam generation device, is characterized in that: this device comprises to be determined power beam expansion lens group (1), DOE phase board (201), two heart zoom mirror groups far away (3), polaroid mirror group (4), reflection conical mirror group (5) and observe positioning system (6) to form:

Described determines power beam expansion lens group (1) for Kepler's type beam expanding lens, is made up of the first plano-concave mirror (101) and the first planoconvex lens (102);

Described DOE phase board (201) is diffraction optical element, and super-Gaussian partially coherent light is shaped as to uniform circular light beam;

Described heart zoom mirror group (3) two far away is made up of variable focus lens package (301), diaphragm (302) and offset lens group (303) successively, and described variable focus lens package (301) is made up of the second planoconvex lens (301-1) and the second plano-concave mirror (301-2);

Described polaroid mirror group (4) is made up of the polarizer (401), polaroid (402), λ/4 wave plate (403);

Described reflection conical mirror group (5) is made up of external reflection conical mirror (502) and internal reflection taper type lens barrel (501);

The first plano-concave mirror (101) of same optical axis successively along incident beam direction, the first planoconvex lens (102), DOE phase board (201), the second planoconvex lens (301-1), the second plano-concave mirror (301-2), diaphragm (302), offset lens group (303), the polarizer (401), polaroid (402), λ/4 wave plate (403), external reflection conical mirror (502) and internal reflection taper type lens barrel (501), described polaroid (402) is at 45 ° with optical axis, described observation positioning system (6) is made up of CCD camera (601) and computer (602), described CCD camera (601) is positioned at the reflected light outbound course of described polaroid (402), the input end of the computer (602) described in the output termination of described CCD camera (601).

2. annular beam generation device according to claim 1, is characterized in that: described DOE phase board is the phase board that adopts conjugate gradient algorithm optimal design, the phase board that then process mask and photoetching obtain.

3. annular beam generation device according to claim 1, it is characterized in that: described variable focus lens package (301) is made up of the second planoconvex lens (301-1) and the second plano-concave mirror (301-2), described the second planoconvex lens (301-1) is d with the distance of the second plano-concave mirror (301-2) ₁₂, the second described plano-concave mirror (301-2) is d with the distance of the first planoconvex lens (303) ₂₃, the amount of movement of the second planoconvex lens (301-1), the displacement of the first planoconvex lens (303) are respectively:

Δ d ₁₂represent the displacement of the second planoconvex lens (301-1), Δ d ₂₃represent the displacement of the first planoconvex lens (303), amount of movement Δ d ₁₂for on the occasion of time represent near the second plano-concave mirror (301-2), when negative value, to represent away from the second plano-concave mirror (301-2), amount of movement Δ d ₂₃for on the occasion of time represent that the first planoconvex lens (303) is away from the second plano-concave mirror (301-2), when negative value, represent near the second plano-concave mirror (301-2); f ₁be the focal length of the second planoconvex lens (301-1), f ₂be the focal length of the second plano-concave mirror (301-2), f ₃it is the focal length of the first planoconvex lens (303); M is for selecting to expand multiple.

4. annular beam generation device claimed in claim 1, it is characterized in that: in described reflection conical mirror group, described Inner reflection taper type lens barrel (501) is fixing, external reflection conical mirror (502) can move forward and backward, Inner reflection taper type lens barrel (501) equates with the inclination angle of external reflection conical mirror (502), the distance d of Inner reflection taper type lens barrel (501) and external reflection conical mirror (502) _aBfor:

Wherein, θ represents the angle of external reflection conical mirror (502) and optical axis direction, is also the inclination angle of external reflection conical mirror (502); r ₁for the inside radius of annular beam of selecting.