CN101762877B

CN101762877B - Beam-expanding system

Info

Publication number: CN101762877B
Application number: CN2010101024999A
Authority: CN
Inventors: 高云峰; 李家英; 周朝明
Original assignee: Shenzhen Hans Laser Technology Co Ltd
Current assignee: Han s Laser Technology Industry Group Co Ltd
Priority date: 2010-01-25
Filing date: 2010-01-25
Publication date: 2011-11-09
Anticipated expiration: 2030-01-25
Also published as: CN101762877A

Abstract

The invention provides a laser beam-expanding system, which comprises a first lens and a second lens which are positioned in the incident direction of a beam and are arranged in turn, wherein the first lens is a crescent-type negative lens; the curved surface of the first lens backs onto the incident direction of a ray and bends; the second lens is a plano-convex positive lens; and the whole beam-expanding system can perform bean expansion on the diameter of an incident laser beam by 5 times and then emit the beam as a parallel beam. Through the two lenses which have focal power assigned in a 'negative-positive' form and are arranged in turn, the laser beam-expanding system can perform bean expansion on the diameter of an incident laser beam by 5 times and then emit the beam still as a parallel ray. As the focal length of the negative first lens is short and hardly affects aberration, the bean expansion multiple of the beam-expanding system is not big, so one positive lens is enough to undertake the quality of expanded emitted beams. Therefore, the system ensures shaping need, achieves the best imaging quality, and also ensures minimum overall dimensions. The beam-expanding system has the advantages of balanced ideal image quality and small volume of the whole lens.

Description

A kind of beam-expanding system

[technical field]

The present invention relates to a kind of fixed times beam-expanding system that is applied to Ultra-Violet Laser.

[background technology]

In the laser processing procedure, usually require laser very concentrated at the energy of focus point, guarantee the energy density of laser processing procedure focus point, make laser work effectively, and improve the work efficiency of laser, but how when work, to improve the focus energy density of laser? generally be by obtaining little focus point as far as possible.

According to the diffraction limit theory: the angle of divergence θ of laser and waist diameter d ₀The pass be

Wherein for using certain laser instrument, Wavelength of Laser λ is certain, so, the angle of divergence θ of laser and waist diameter d ₀Product be constant.Generally less from the laser beam diameter of laser instrument output, before the convergence optical system by certain focal length focuses on, require the expanded light beam diameter to reduce angle of divergence θ, obtain bigger incident beam diameter simultaneously.

Suppose to add a laser beam expanding system in laser instrument and focal length are the convergence optical system of f, select suitable expansion bundle multiple β as requested for use, making laser beam enlarge to diameter is D=β d ₀, this moment laser angle of divergence θ _{Go into}Still satisfy the diffraction limit theoretical relationship

So,

Like this, desirable convergent laser hot spot

So, obtain suitable D value by selecting suitable multiple β for use, just can obtain desirable focal beam spot δ to improve the energy density at job spotlight place.

Fixed times beam-expanding system of the present invention, mainly be for the shaping that solves UV laser beam and expansion of laser light beam diameter to improve the needs of image quality.Though thisly decide power beam expansion lens design more relatively easily, very convenient effectively to the ability of laser beam reshaping.

[summary of the invention]

The invention provides a kind of the diameter of incoming laser beam can be expanded bundle to 5 times, get very desirable Ultra-Violet Laser beam-expanding system to improve image quality and to expand bundle back picture element balance.

The technical solution adopted in the present invention is a kind of laser beam expanding system, comprising: be positioned at first and second lens that the incident direction of light beam is arranged in regular turn, described first lens are the negative lens of curved month type, its curved surface dorsad the incident direction bending of light; Described second lens are the positive lens of planoconvex; This beam-expanding system the diameter of incoming laser beam can be expanded 5 times of bundles after, be still the ejaculation of a branch of directional light.

Wherein, described first lens and the spacing of second lens on optical axis are 100mm, and its margin tolerance is ± 5%.

Wherein, the largest beam diameter of described incoming laser beam is 4mm.

Wherein, described incident laser is that wavelength is the Ultra-Violet Laser of 355nm.

Wherein, the center thickness of described first lens on optical axis is 2mm, and its margin tolerance is ± 5%.

Wherein, the center thickness of described second lens on optical axis is 3.5mm, and its margin tolerance is ± 5%.

This laser beam expanding system, by two lens arranging in regular turn with " negative-just " are set, the diameter of incoming laser beam can be expanded 5 times of bundles after, still penetrate with directional light; Because the focal length of the first negative lens is shorter, and is little to aberration effects, and the expansion bundle multiple of this beam-expanding system is not very big, so, need bear that to expand bundle outgoing beam quality just enough with a slice positive lens.Like this, both guaranteed the needs of shaping, and can also make it reach best image quality, and guaranteed that its physical dimension also is minimum, the picture element of this beam-expanding system also balance gets very ideal, and whole camera lens volume is also very little.

[description of drawings]

The present invention is further described below in conjunction with drawings and Examples.

Fig. 1 is the optical system structure synoptic diagram of laser beam expanding system of the present invention;

Fig. 2 is the disc of confusion figure in the beam-expanding system preferred embodiment of the present invention;

Fig. 3 is the spherical aberration figure in the beam-expanding system preferred embodiment of the present invention;

Fig. 4 is the figure of the optical transfer function MTF in the beam-expanding system preferred embodiment of the present invention.

[embodiment]

Along with developing rapidly of Laser Processing, the optical beam-expanding mirror occupies considerable status in the Laser Processing optical system.Owing to be used for the laser beam of Laser Processing the angle of divergence is arranged, so will adjust the irregularity of laser beam with the optics beam expanding lens, can make laser focusing system obtain bigger picture side's aperture angle, the energy density at focus place when improving laser focusing, thereby the elaboration and the efficient of raising laser.

According to Laplace invariant (Lagrange) theorem: energy J=nD θ=n ' D ' θ ', wherein, and n and the refractive index of n ' expression optical system in medium, when medium is air, n=n '=1; The entrance pupil diameter and the exit pupil diameter of D and D ' expression optical system; The field angle of the incident light of θ and θ ' expression optical system and the field angle of emergent light when field angle is very little, can be represented with radian.

By following formula as seen, when the emitting laser bundle had the angle of divergence, when promptly θ was big, by D → D ', promptly enlargement factor β=D '/D doubly can make the angle of divergence of laser beam dwindle β doubly, thereby reach the purpose of shaping laser beam by beam expanding lens.

On the other hand, general laser beam bright dipping diameter all very little (about about Φ=1mm) for this reason, directly focus on so thin light beam, and its Rayleigh disk is just very big, according to the Rayleigh disk formula: Rayleigh disk diameter δ=2.44 λ f/D.

As seen, D is more little for the entrance pupil diameter, and diameter δ is just big more, will reduce the precision of amasthenic lens widely.

In view of above two basic demands, the optical system of Laser Processing is generally all wanted the adapted beam expanding lens.Remove in addition, the beam expanding lens that has can mate use with focus lamp or f-θ camera lens separately, and some also must link together with the optical system that is used and consider the balance of aberration, just can obtain ideal results.

Disclosed by the invention is exactly that a kind of Ultra-Violet Laser is used fixed times beam-expanding system.

As shown in Figure 1, Ultra-Violet Laser disclosed by the invention is used fixed times beam-expanding system, comprise that it is two lens that incident ray direction according to light sorts successively, the difference first lens L1, the second lens L2, it be the combination of " bear-just " that described lens L1, L2 adopt the focal power forms of distribution, wherein the first negative lens focal length is shorter, so little to aberration effects, second positive lens then is used for bearing expanding restraints the outgoing beam quality.

The described first lens L1 is a meniscus lens, and curved surface dorsad the bending of light incident direction; Lens L2 is a plane-convex lens.

Their concrete structure and parameter are: lens L1 is that two curved surface S1, the S2 of R1, R2 constitute by radius-of-curvature respectively, and the center thickness d1 on its optical axis, material are Nd1:Vd1; Lens L2 is that two curved surface S3, the S4 of R3, R4 constitute by radius-of-curvature respectively, and the center thickness d3 on its optical axis, material are Nd1:Vd1; Lens L1 and the spacing of lens L2 on optical axis are d2.

In conjunction with above parameter, we have designed a beam-expanding system, and its concrete data are as follows respectively:

Example:

Φ _{Go into}=4mm β=5X λ=355nm

Wherein, Φ _{Go into}Be the maximum light inlet diameter that this beam-expanding system allows, that is: the largest beam of the receivable incoming laser beam of this beam-expanding system directly is 4mm; β is for expanding the bundle multiple, that is: this beam-expanding system is after the diameter expansion of incoming laser beam is restrainted 5 times, to remain a branch of directional light and penetrate, and the shaping expansion of laser light beam diameter that can solve UV laser beam is to improve the demand of image quality; λ is a wavelength, that is: incident light is the Ultra-Violet Laser of wavelength 355nm.

Curved surface S	Curvature R (mm)	Face is d (mm) at interval	Material Nd/Vd
				1	62	?2	1.46/68
2	10	?100
				3	0	?3.5	1.46/68
4	-62

The parameter area that this patent is implemented is as follows:

1)R1-R4 ΔR1-4≤±5％ (R1-R4)

2)d1-d3 Δd1-3≤±5％ (d1-d3)

3)Nd1/Vd1 ΔNd1/ΔVd1≤±5％ (Nd1/Vd1)

By above-mentioned concrete experiment parameter, can probably conclude the process of this beam-expanding system: the largest beam diameter is the incoming laser beam of 4mm, behind first lens L1 that process is negative and the second positive lens L2, the diameter of incoming laser beam is expanded 5 times of bundles, and still penetrates with parallel beam; Because the focal length of the first negative lens is shorter, and is little to aberration effects, and the expansion bundle multiple of this beam-expanding system is not very big, so, need bear that to expand bundle outgoing beam quality just enough with a slice positive lens.Like this, both guaranteed the needs of shaping, and can also make it reach best image quality, and guaranteed that its physical dimension also was minimum.

Because the irregularity of laser beam, its angle of divergence is not the quantity of being scheduled to, and for the d2 (first lens and the spacing of second lens on optical axis) of this this beam-expanding system is adjustable, it is that mechanical adjustment by lens barrel realizes.

By regulating the spacing of first, second lens on optical axis is the size of d2=100mm, just can be easily carry out the shaping of directional light to the laser beam of input, and the picture element of this beam-expanding system also balance to get very desirable whole camera lens volume also very little.

Fig. 2 shows that for the disc of confusion figure in the beam-expanding system preferred embodiment of the present invention image quality is very high; Fig. 3 has been corrected to optimum condition for the spherical aberration figure in the beam-expanding system preferred embodiment of the present invention; Fig. 4 shows that for the figure of the optical transfer function MTF in the beam-expanding system preferred embodiment of the present invention the resolution of this beam-expanding system is high, has reached perfect condition.

Claims

1. a beam-expanding system is characterized in that, comprising: be positioned at first and second lens that the incident direction of light beam is arranged in regular turn, described first lens are the negative lens of curved month type, its curved surface dorsad the incident direction bending of light; Described second lens are the positive lens of planoconvex; And first lens are that R1 is that 62mm, R2 are that two curved surfaces of 10mm constitute by radius-of-curvature respectively, and the center thickness d1 on its optical axis is 2mm, and its margin tolerance is ± 5%, and material Nd:Vd is 1.46/68; Second lens respectively by radius-of-curvature be that R3 is 0, R4 constitutes for two curved surfaces of-62mm, the center thickness d3 on its optical axis is 3.5mm, and its margin tolerance is ± 5%, material Nd:Vd is 1.46/68; First lens and the spacing of second lens on optical axis are that d2 is 100mm, and its margin tolerance is ± 5%; After this beam-expanding system can be restrainted 5 times with the diameter expansion of incoming laser beam, still with a branch of directional light ejaculation.

2. beam-expanding system as claimed in claim 1 is characterized in that: the largest beam diameter of described incoming laser beam is 4mm.

3. beam-expanding system as claimed in claim 1 is characterized in that: described incident laser is that wavelength is the Ultra-Violet Laser of 355nm.