CN101762878B

CN101762878B - Laser beam expanding system

Info

Publication number: CN101762878B
Application number: CN201010102500A
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: 2012-10-03
Anticipated expiration: 2030-01-25
Also published as: CN101762878A

Abstract

The invention relates to a location beam expanding system for ultraviolet laser, comprising a first lens and a second lens arranged in the light beam incidence direction; wherein the first lens is a crescent-shaped negative lens with back side thereof bent towards the incidence direction of light ray, the second lens is a plano-convex positive lens; the beam expanding system composed of the first lens and the second lens can expand diameter of incidence laser beam by 12 times and still eject the laser beam in the form of parallel light. As far as the beam expanding system of the invention is concerned, as the negative lens is short in focal length, thus not affecting aberration much; however, the positive lens is the main part which determines quality of outgoing beam from a beam expander. The beam expanding system enjoys a 12 times of beam expanding magnification, therefore a positive lens is enough to ensure quality of expanded outgoing beam; on the basis, not only shaping requirements are met, but also the best imaging quality is achieved; in addition, contour dimension is guaranteed to be the minimum, the imaging quality of the beam expanding system is very ideally balanced and volume of the whole lens is very small.

Description

Laser 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 through obtaining little focus point as far as possible.

Theoretical according to diffraction limit: the angle of divergence θ of laser and waist diameter d ₀Relation do

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 through certain focus focuses on, require the expanded light beam diameter to reduce angle of divergence θ, obtain bigger incident beam diameter simultaneously.

Suppose in laser instrument and focal length are the convergence optical system of f, to add a laser beam expanding system, 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 through 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 present invention provide a kind of can with the diameter of incoming laser beam expand bundle to 12 times, get very desirable Ultra-Violet Laser beam-expanding system to improve image quality and to expand bundle back picture element balance.

The technical scheme that the present invention adopted 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, said first lens are the negative lens of curved month type, its curved surface dorsad the incident direction of light crooked; Said second lens are the positive lens of planoconvex; After whole beam-expanding system can expand 12 times of bundles with the diameter of incoming laser beam, be still a branch of directional light and penetrate.

Wherein, said first lens and the spacing of second lens on optical axis are 89mm, and its margin tolerance is ± 5%.

Wherein, the largest beam diameter of said incoming laser beam is 2mm.

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

Wherein, the center thickness of said first lens on optical axis is 1mm, and its margin tolerance is ± 5%.

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

This laser beam expanding system, through two lens arranging in regular turn with " negative-just " are set, can the diameter of incoming laser beam be expanded 12 times of bundles after, still penetrate with directional light; Because it is 12 times that incoming laser beam expands the bundle multiplying power; So, need bear with a slice positive lens and expand bundle outgoing beam quality, like this; The needs of shaping had both been guaranteed; Can also make it reach best image quality, and the physical dimension that guarantees it also is minimum, the picture element of this beam-expanding system also balance to get very desirable whole camera lens volume also very little.

[description of drawings]

Below in conjunction with accompanying drawing and embodiment the present invention is further specified.

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 encircled energy 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 of along 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.

Visible by following formula, 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 through 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.

It is thus clear that D is more little for the entrance pupil diameter, 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, comprises that it is two lens that incident ray direction according to light sorts successively, respectively the first lens L1, the second lens L2; These two lens L1, L2 adopt " negative-just " combination; Wherein the focal length of negative lens is shorter, and is little to aberration effects, and positive lens is the main undertaker of decision beam expanding lens outgoing beam quality.The said first lens L1 is a meniscus lens, and curved surface dorsad the light incident direction crooked; 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:

Instance:

Φ _{Go into}=2mm β=12X λ=355nm

Wherein, Φ _{Go into}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 2mm; β is for expanding the bundle multiple, that is: this beam-expanding system is after the diameter expansion of incoming laser beam is restrainted 12 times, to remain a branch of directional light, 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	4.5	?1	1.46/68
2	2	?89
				3	0	?2	1.46/68
4	-47.5

The parameter area that this patent is implemented is following:

1)R1-R4 ΔR1-4≤±5％ (R1-R4)

2)d1-d3 Δd1-3≤±5％ (d1-d3)

3)Nd1/Vd1 ΔNd1/ΔVd1≤±5％ (Nd1/Vd1)

Through 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 2mm; At first light beam is become divergent beams, and then through after the second positive lens L2 shaping through the first negative lens L1, outgoing be parallel beam.The effect that whole beam-expanding system can reach is after the diameter expansion of incoming laser beam is restrainted 12 times, and still penetrates with parallel beam.Wherein the focal length of negative lens is shorter, and is little to aberration effects, and positive lens is the main undertaker of decision beam expanding lens outgoing beam quality.Because the expansion bundle multiple of this beam-expanding system is not big especially, so just can guarantee to expand the beam quality of restrainting the back laser beam 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 (spacings on optical axis of first lens and second lens) of this this beam-expanding system is adjustable, it is that mechanical adjustment through lens barrel realizes.

Through regulating the spacing of first, second lens on optical axis is the size of d2=89mm, 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 shows that for the encircled energy figure in the beam-expanding system preferred embodiment of the present invention encircled energy is very high; 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 characteristic of this system is very high, reaches perfect condition.

Claims

1. a laser 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, said first lens are the negative lens of curved month type, its concave curved surface dorsad the incident direction of light crooked; Said second lens are the positive lens of planoconvex; First lens are that two curved surface S1, the S2 of R1=4.5mm, R2=2mm constitute by radius-of-curvature respectively, and the center thickness d1=1mm on its optical axis, material are Nd1: Vd1=1.46/68; Second lens are that two curved surface S3, the S4 of R3=0, R4=-47.5mm constitute by radius-of-curvature respectively, and the center thickness d3=2mm on its optical axis, material are Nd2: Vd2=1.46/68; First lens and the spacing of second lens on optical axis are d2=89mm; And, radius of curvature R, material Nd: Vd, and the margin tolerance of center thickness d be ± 5%; After this beam-expanding system can expand 12 times of bundles with the diameter of incoming laser beam, be still a branch of directional light and penetrate.

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

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