CN101144908A - Design method of multi-wavelength porous lens - Google Patents

Abstract

A design method of a multi-wavelength porous lens comprises the following steps: (1) the design of the porous lens is carried out by applying a Fresnel zone plate, wherein the k-th zone radius of the Fresnel zone plate is

Corresponding width w of the Fresnel ring_k＝ρ_k－ρ_k－1，

Is the radius of a first zone, where f is the focal length, λ is the wavelength of the incident light, the center position of the aperture of the multi-aperture lens, i.e. the distance from the center of the aperture to the center of the lens, is located at the center of the corresponding kth zone, and the radius of the center of the aperture is

Description

A kind of method for designing of multiple wavelength porous lens

Technical field

The present invention relates to a kind of method for designing of expanding the perforated lens bandwidth, especially relate to a kind of method for designing of multiple wavelength porous lens.

Background technology

1871, the fresnel's zone plate of being made by Rayleigh is an imaging diffraction element the earliest, this element is a kind of special diaphragm in fact, it can hide the half-wave zone of uncouple number sequence or odd number preface, and make the half-wave zone of another sequence pass through, the optical path difference that the subwave that the odd number preface of passing through (or even number preface) half-wave zone is sent separately arrives observation point is the integral multiple of wavelength, position of caused light vibration was mutually identical when each subwave arrived this, thereby strengthen mutually, so the effect of zone plate is exactly to make all subwaves of coordination phase carry out the amplitude stack at the focus place, thereby on focus, obtain bigger light intensity, but this fresnel's zone plate imaging space resolution is directly suitable with the outermost layer wavestrip width of device, and the minimum process live width has determined the aerial image resolution of device.In order to overcome the restriction of characteristic dimension to spatial resolution, calendar year 2001, Kipp etc. have proposed the special diffraction optical device of a class, be called perforated lens, it replaces corresponding wavestrip to form by a series of separation apertures that are distributed in accurate stochastic distribution on the zone plate, and spatial resolution no longer is subject to characteristic dimension.

It is to overcome traditional diffraction element imaging resolution come by the limit feature development that perforated lens is based on zone plate, it has a lot of advantages with respect to zone plate, broken through the restriction that the diffraction element spatial resolution is subjected to device minimum process size such as it, and because pore density radially reduces, thereby can suppressed sidelobes, improve image contrast.Aperture is accurate stochastic distribution on hoop, has broken periodically and symmetry, can suppress high order diffraction, with respect to zone plate a plurality of focuses is arranged on axle, and perforated lens is approximate can think to have only a real focus.

But its design only is directed to single wavelength, and numerical aperture is big more, and element characteristic is just responsive more to wavelength.

The lens of single wavelength design are worked under its all band input light situation, can cause aberration, are difficult to realize multi-wavelength's coloured light imaging.

Summary of the invention

The technical matters that the present invention solves: for perforated lens in the past just at single wavelength design, a kind of method for designing of expanding the perforated lens of bandwidth is proposed, thus can be so that perforated lens can have identical focal length and image quality under a plurality of wavelength illuminations.

Technical solution of the present invention: a kind of method for designing of multiple wavelength porous lens, its characteristics are that step is as follows:

(1) use Fresnel zone plate and carry out the design of perforated lens, its first girdle radius of Fresnel zone plate is

${\mathrm{\ρ}}_1=\sqrt{\mathrm{f\λ}},$ Wherein f is a focal length, and λ is the incident light wavelength, and the k girdle radius is ${\mathrm{\ρ}}_k=\sqrt{k}{\mathrm{\ρ}}_1,$ Corresponding Fresnel endless belt width w _k=ρ _k-ρ _k-1, be λ at design wavelength so, when focal length is the perforated lens of f, the center of aperture (the aperture center is to the distance of lens center) is positioned over the center of corresponding wavestrip (being assumed to be k wavestrip), and its center radius is $r_k=\sqrt{2\mathrm{kf\λ}+k^2{\mathrm{\λ}}^2},$ For focus place light intensity is strengthened, little pore radius is the Fresnel endless belt width w of this place _k3～4 times,

(2) for a certain particular focal length, adopt the method for step (1) respectively the light of M kind different wave length to be carried out the design of perforated lens, obtain M piece perforated lens;

(3) adopting the method for zoning design, is initial point with the center with blank disk, equal angles at interval be divided into N zone, N is some integral multiples of M, simultaneously M piece perforated lens also is divided into N regional; Be the design part of the cycle inserting M piece perforated lens correspondence in turn in blank plane then with M, combination obtains multiple wavelength porous lens.

Described perforated lens aperture is accurate stochastic distribution on hoop, thereby has broken periodicity and symmetry, can suppress the background influence that high order diffraction light causes.

Described wavelength kind is counted M more than or equal to 2 kinds.

The present invention's advantage compared with prior art is: the design of this perforated lens is based on zoning design, and lens of its Application Design just can focus at the light of a plurality of wavelength and imaging, and make it have identical focal length and image quality.This has broken the restriction that existing perforated lens only is aimed at single wavelength, has expanded the bandwidth of perforated lens imaging greatly, and further enlarges its range of application.

Description of drawings

Fig. 1 is a Fresnel zone plate synoptic diagram of the present invention, and white portion is a photic zone among the figure, and black part is divided into non-photic zone;

Fig. 2 uses Fresnel zone plate design perforated lens synoptic diagram for the present invention, and white portion is a photic zone among the figure, and black part is divided into non-photic zone;

Fig. 3 is at wavelength X ₁=488nm and perforated lens synoptic diagram that designing institute gets, white portion is a photic zone among the figure, black part is divided into non-photic zone;

Fig. 4 is at wavelength X ₂=532nm and perforated lens synoptic diagram that designing institute gets, white portion is a photic zone among the figure, black part is divided into non-photic zone;

Fig. 5 is at wavelength X ₃=633nm and perforated lens synoptic diagram that designing institute gets, white portion is a photic zone among the figure, black part is divided into non-photic zone;

Fig. 6 gets three kinds of wavelength designing institutes the multiple wavelength porous lens synoptic diagram of the gained after perforated lens inserts in turn then for the plane is divided into 36 parts, and among the figure: 1 is wavelength X ₁The pairing lens component of=488nm, 2 is wavelength X ₂The pairing lens component of=532nm, 3 is wavelength X ₃The pairing lens component of=633nm.

Embodiment

The present invention is described in detail below in conjunction with embodiment and accompanying drawing, but protection scope of the present invention is not limited in the following example, should comprise the full content in claims.And those skilled in the art can realize full content the claim from a following embodiment.

Provide a specific embodiment of the present invention below:, design a kind of at λ by this method ₁=488nm, λ ₂=532nm, λ ₃The perforated lens of three kinds of wavelength of=633nm.

Concrete implementation step of the present invention:

1, use Fresnel zone plate and carry out the design of perforated lens, its first girdle radius of Fresnel zone plate is ${\mathrm{\ρ}}_1=\sqrt{\mathrm{f\λ}},$ Wherein f is a focal length, and λ is the incident light wavelength, and the k girdle radius is ${\mathrm{\ρ}}_1=\sqrt{k}{\mathrm{\ρ}}_1,$ Corresponding Fresnel endless belt width is λ at design wavelength, when focal length is the perforated lens of f, the center of aperture (the aperture center is to the distance of lens center) is positioned over the center of corresponding wavestrip (being assumed to be k wavestrip), its w _k=ρ _k-ρ _K-I, the aperture center radius is $r_k=\sqrt{2\mathrm{kf\λ}+k^2+{\mathrm{\λ}}^2},$ For focus place light intensity is strengthened, the aperture center radius is the Fresnel endless belt width w of this place _k3.5 times, the perforated lens aperture is accurate stochastic distribution on hoop;

2, be 20mm for bore, focal distance f is the design object of 200mm, at three kinds of wavelength X ₁=488nm, λ ₂=532nm, λ ₃=633nm adopts the method for designing of step 1 to obtain three perforated lens, as Fig. 3, Fig. 4, shown in Figure 5;

3, three perforated lens with step 2 gained are the center with the center of circle, be divided into 36 equal angles subregion at interval, numbering is respectively 1 to 36, and the blank disk with bore 20mm is the center with the center of circle simultaneously, and equal angles is divided into 36 sub regions, numbering also is 1 to 36, when numbering n=3k+1, k=0,1,2 ..., use λ at 11 o'clock ₁The part of identical numbering is filled in=488nm the perforated lens; When numbering n=3k+2, k=0,1,2 ..., use λ at 11 o'clock ₂The part of identical numbering is filled in=532nm the perforated lens; When numbering n=3k, k=1,2 ..., use λ at 12 o'clock ₃The part of identical numbering is filled in=633nm the perforated lens, combines multiple wavelength porous lens, as shown in Figure 6.

Claims (4)

1. the method for designing of a multiple wavelength porous lens is characterized in that step is as follows:

(1) use Fresnel zone plate and carry out the design of perforated lens, the k girdle radius of Fresnel zone plate is ${\mathrm{\ρ}}_k=\sqrt{k}{\mathrm{\ρ}}_1,$ Corresponding Fresnel endless belt width w _k=ρ _k-ρ _K-1, wherein f is a focal length, λ is the incident light wavelength, ${\mathrm{\ρ}}_1=\sqrt{\mathrm{f\λ}}$ Be first girdle radius, the center of perforated lens aperture, promptly the aperture center is positioned over the center of k corresponding wavestrip to the distance of lens center, and the aperture center radius is $r_k=\sqrt{2\mathrm{kf\λ}+k^2{\mathrm{\λ}}^2};$

(2) for a certain particular focal length, adopt the method for step (1) respectively the light of M kind different wave length to be carried out the design of perforated lens, obtain M piece perforated lens;

(3) adopting the method for zoning design, is initial point with the center with blank disk, equal angles at interval be divided into N zone, N is the integral multiple of M, simultaneously M piece perforated lens also is divided into N regional; Be the design part of the cycle inserting M piece perforated lens correspondence in turn in blank plane then with M, combination obtains multiple wavelength porous lens.

2. the method for designing of the described multiple wavelength porous lens of claim 1 is characterized in that: described perforated lens aperture is accurate stochastic distribution on hoop, has broken periodically and symmetry, can suppress high order diffraction.

3. the method for designing of the described multiple wavelength porous lens of claim 1, it is characterized in that: described wavelength kind is counted M more than or equal to 2 kinds.

4. the method for designing of the described multiple wavelength porous lens of claim 1 is characterized in that: strengthen in order to make focus place light intensity, described aperture center radius is located Fresnel endless belt width w for this _k3～4 times.

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