CN2723958Y - Broadband white light interferometer with wave zone plate structure - Google Patents

Broadband white light interferometer with wave zone plate structure Download PDF

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Publication number
CN2723958Y
CN2723958Y CN 200420090066 CN200420090066U CN2723958Y CN 2723958 Y CN2723958 Y CN 2723958Y CN 200420090066 CN200420090066 CN 200420090066 CN 200420090066 U CN200420090066 U CN 200420090066U CN 2723958 Y CN2723958 Y CN 2723958Y
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China
Prior art keywords
zone plate
interferometer
detector
white light
plate structure
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Expired - Fee Related
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CN 200420090066
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Chinese (zh)
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陈建文
高鸿奕
朱化凤
李儒新
徐至展
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Shanghai Institute of Optics and Fine Mechanics of CAS
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Shanghai Institute of Optics and Fine Mechanics of CAS
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Abstract

A broadband white light interferometer with a wave zone plate structure comprises a parallel light source and is characterized in that a wave zone plate, a pinhole diaphragm, an object to be detected, a detector and a computer are sequentially arranged along the advancing direction of a light beam, the wave zone plate is a Fresnel wave zone plate, and the position of the object to be detected meets the relation formula: z is a radical of0 (p+f)=p2In the formula: z0-the distance of the object to be measured to the detector; the distance from the p-pinhole diaphragm to the detector; the focal length of the f-Fresnel zone plate is long. The utility model discloses broadband white light interferometer of zone plate structure is particularly suitable for the relatively poor X ray of coherence, neutron, atomic beam and far ultraviolet wave band, is a high performance interferometer who is worth promoting very much.

Description

The wideband white light interferometer of zone plate structure
Technical field:
The relevant interferometer of the utility model, particularly a kind of wideband white light interferometer of zone plate structure.So-called wideband is meant from infrared, visible, ultraviolet, X ray even hard X ray wave band, as long as change the white light interferometer that the structural parameters of zone plate all are suitable for, its principle also is applicable to electron beam, atomic beam, neutron, ion etc., and all electromagnetic wave or matter waves with diffraction characteristic are all suitable.
Background technology:
Interference of light is meant when two light waves or a plurality of light wave meet, produce a kind of phenomenon of stable bright dark fringe owing to the stack of ripple, be not that any two light waves meet and can both produce interference, when having only two or more light waves to be coherent light, the light beam that promptly has certain room and time coherence can be observed this bright dark fringe.In this bright dark fringe, contain phase information.
Interferometer can be divided into two types, and a kind of long-wave band that is operated in comprises near infrared, visible or near ultraviolet band; Another kind is operated in short-wave band, comprises vacuum ultraviolet, X ray wave band, also is applicable to electron beam, atomic beam, neutron, ion etc., and all electromagnetic wave or matter waves with diffraction characteristic are all suitable.
After nineteen sixty, laser occurred, for the long-wave band interferometer provides a comparatively ideal coherent light source, development at full speed has appearred in interference technique, and successfully be applied to every field, become accurate the detection and the indispensable a kind of instrument of delicate metering (particularly mutually or the detection on corrugated), various interference techniques have been produced therefrom, and make some ancient interferometers obtain to use widely, such as mach-zehnder interferometer, Fabry-Paro interferometer, not help interferometer (Fizean), michelson interferometer, rayleigh interferometer (Rayleigh) or the like.
Common shortcoming of these interferometers is, the temporal coherence of light source or light beam is had certain requirement, and they only are suitable for use near infrared, visible or near ultraviolet band, and vacuum ultraviolet, X ray wave band or far infrared all are not suitable for.
In recent years fork-like farm tool used in ancient China, because the development of synchrotron radiation source and x-ray laser, the X ray interferometer has obtained progress Ulrich Bonse and Michael Hart[referring to technology formerly: U.Bonse and M.Hart, Appl.Phys.Lett.6,155-156 (1965)] designed the X ray interferometer, Atshushi Momose and Tohoru Takeda use it for the phase contrast imaging aspect.Three nearly perfectly parallel placements of crystal form an X ray interferometer.First crystal will be through the X ray light beam beam splitting after the monochromator; Middle crystal effect is that two-beam is closed bundle; The 3rd crystal is then as analyzing crystal.The thing sample is placed in the light path of a branch of light wherein, is closing between Shu Jingti and the analyzing crystal, and is introducing phase change thus.Interfere with reference light, and produce interference fringe.Striped is very responsive through the phase shift that produces after the thing sample for detecting light beam.
Because its sensitivity is very high, the X ray interferometer requires to have the perfect cystal collimation and the mechanical stability of height.On a monocrystalline, be made into this interferometer and can obtain splendid experiment effect.But the size of crystal is limited, has also limited the size of analyte sample.
Summary of the invention:
The utility model is at the shortcoming in the above-mentioned technology formerly, a kind of wideband white light interferometer of zone plate structure is provided, this interferometer requires very low to the temporal coherence and the mechanical stability of light source or light beam, and to all electromagnetic waves or matter wave, all ripples with diffraction characteristic all are fit to.
Technical solution of the present utility model is:
A kind of wideband white light interferometer of zone plate structure, comprise a source of parallel light, it is characterized in that also having zone plate, pinhole diaphragm, object under test, detector and computing machine successively along the direction that light beam advances, described zone plate is a Fresnel zone plate, described object under test) the position satisfy relational expression:
z 0(p+f)=p 2
In the formula: Z 0-object under test is to the distance of detector;
The p-pinhole diaphragm is to the distance of detector;
The focal length of f-Fresnel zone plate is long.
The foundation of our design concept can be described below:
Zone plate is a kind of diffraction optical element of special shape, can regard a circular grating as, and its line density radially increases progressively.Utilize the higher first-order diffraction of its efficient, almost can be to the radiant image of all wavelengths.The most basic zone plate is the Fresnel zone plate, and it is made up of a series of chequered with black and white endless belt.Position phase zone plate is that full impregnated is bright, but introduces the π phase shift on adjacent endless belt, and its theoretical efficiency is 4 times of Fresnel zone plate.
In fact, the proposition of Fresnel zone plate apart from the present by more than 100 years, it does not obtain due attention for a long time.Its reason: 1, its efficient is too low, and the energy that incides on the endless belt plate has only 1/ π 2(~10%) accumulates on the one-level focus; 2, imaging background is too strong, or signal to noise ratio (S/N ratio) is too low.There is 1/4 incident light not diffracted, and on the picture plane, produces a continuous background; 3, has very strong chromatic dispersion (f ∝ 1/ λ); 4, the difficulty on the manufacture craft.
As far back as 1888, Rayleigh just proposed the imagination of position phase zone plate.After 10 years, Wood has proved the superiority of this zone plate again.The result shows that the theoretical efficiency of position phase zone plate is 40%, is four times of Fresnel zone plate.Nineteen ninety, Hisao Fujisaki proposes the imagination of graded index position phase zone plate again, this zone plate same with on point to the focus aplanatism, the path difference between the different band is 2m π, m is an integer.As if we can think like this that similar with ordinary lens, this zone plate is equally applicable to Fermat principle, and its theoretical efficiency reaches 100%.Even consider absorption, its efficient also can reach 34%, is 1.4 times of the position phase zone plate made of same material.
Except imaging, convergent beam, also can utilize the diffusing monochromatic light that obtains of rich shade of zone plate.The light of certain bandwidth is injected on the zone plate, and different its focal positions of wavelength are also different.The diaphragm that the aperture is suitable places the place, focal plane of zone plate, changes the position of diaphragm on axle, can select the light of required wavelength.
According to the FKESNEL CIRCULAR APEKTUKE DIFFRACTION theory, if by formula r n = nfλ Circular hole is divided into half-wave zone one by one continuously, and odd number or even number half-wave zone covered, just can obtain the focusing phenomenon of similar lens in diffractional field, the zone plate of making according to this principle can be used as lens to limited big thing imaging, and follows following imaging relations.
1/p+1/q=1/f
P: object distance q: image distance:
The wideband white light interference instrument apparatus of zone plate structure of the present utility model from the first-order diffraction ripple of zone plate to the light path on the interferogram is as shown in Figure 1:
L 1 = ( p 2 + R 2 ) 1 / 2 ( f + p ) / p = ( f + p ) ( 1 + R 2 / p 2 ) 1 / 2
With binomial theorem it is launched and can be write as:
L 1 ≈ ( f + p ) ( 1 + R 2 2 p 2 - R 4 8 p 4 ) - - - ( 1 )
= f + p + ( f + p ) R 2 2 p 2 - ( f + p ) R 4 8 p 4
The light path that arrives on the interferogram from zone plate classical prescription diffraction by aperture is:
L 2 = f + ( p - z 0 ) + ( z 2 + R 2 ) 1 / 2 ≈ f + p + R 2 2 z 0 - R 4 8 z 0 3 - - - ( 2 )
So, L 1And L 2Between optical path difference be:
ΔL = | L 1 - L 2 | = | ( f + p ) R 2 2 p 2 - ( f + p ) R 4 8 p 4 - R 2 2 z 0 + R 4 8 z 0 3 | - - - ( 3 )
≈ | [ z 0 ( p + f ) - p 2 ] R 2 2 z 0 p 2 - [ ( p + f ) p 4 - z 0 - 3 ] R 4 8 |
If equation (3) satisfies following relationship:
z 0(p+f)=p 2 (4)
Optical path difference will be so
ΔL = | [ z 0 - 3 - ( p + f ) p 4 ] R 4 8 | - - - ( 5 )
= | p 2 - z 0 2 | R 4 8 z 0 3 p 2
Suppose that matter-element radius to be differentiated in the interference field is r, then the radius of maximum interference face is:
R=0.61z 0λ/r (6)
(6) formula substitution (5) formula is got:
ΔL = ( p 2 - z 0 2 ) ( 0.61 z 0 λ / r ) 4 8 z 3 p 2 - - - ( 7 )
= z 0 ( p 2 - z 0 2 ) ( 0.61 λ / r ) 8 p 2
And the radius r of zone plate zWith its focal spot radius r fSatisfy following relation:
r z=0.61fλ/r f (8)
And matter-element radius r and focal spot radius r fSatisfy following relation:
r=(z 0/p)r f
Therefore:
r z=0.61λz 0/rp (9)
Go in the above substitution reality as a result, if the above-mentioned interference instrument is applied in the X ray wave band: supposition λ=3.3nm, matter-element radius r=60nm, f=1.25mm, z 0=4mm can try to achieve: p=5mm, r z=33.55 μ m, and path difference Δ L=0.23nm, and path difference is so little, can ignore fully.
More than our the wideband white light interferometer that proved the utility model zone plate structure be an aplanatism accurate aplanatism interferometer in other words conj.or perhaps.
The wideband white light interference instrument apparatus of zone plate structure of the present utility model as shown in Figure 1, it is made up of six parts: light source 1, zone plate 2, pinhole diaphragm 3, object under test 4, detector 5 and computing machine 6.
Said light source 1 is a synchrotron radiation source, and radiation wavelength is chosen as 3.3nm through monochromator, and said zone plate 2 is that a radius is 34 μ m, and focal length length is the Fresnel zone plate of 1.25mm.
Said pinhole diaphragm 3 is the diaphragms that diameter is 30 μ m.
Said object under test 4 is biological samples, and the position that it is placed is extremely important, must satisfy equation z 0(p+f)=p 2Requirement.
Said detector 5 is CCD devices.
Said computing machine 6, the conoscope image that it can record CCD shows.
After X ray 1 passes through zone plate 2, produce diffraction, have only first-order diffraction ripple w fWith part zero order wave w 2Could pass through pinhole diaphragm 3, the zero order wave that sees through pinhole diaphragm 3 is used for shining testing sample 4, after the testing sample diffraction, again with first-order diffraction ripple w fOn detector 5, meet and produce interference, contain the phase information of testing sample 4 on this conoscope image.
The wideband white light interferometer of zone plate structure of the present utility model, compare with technology formerly, it requires very low to the temporal coherence of light source, be a kind of accurate aplanatism interferometer, the optical path difference of being allowed reaches atomic scale, and all have the diffraction characteristic electromagnetic wave or matter wave can both adopt this interferometer.
Description of drawings:
Fig. 1 is the wideband white light interferometer structural representation of the utility model zone plate structure.
Embodiment
Now as an example, set forth its embodiment with the grenz ray light source.As shown in Figure 1, the utility model wideband white light interferometer of the zone plate structure of grenz ray light source.It is made up of six parts: grenz ray synchrotron radiation source 1, zone plate 2, pinhole diaphragm 3, testing sample 4, detector 5 and computing machine 6.
Said light source 1 is a synchrotron radiation source, and radiation wavelength is chosen as 3.3nm through monochromator, and said zone plate 2 is that a radius is 34 μ m, and focal length length is the Fresnel zone plate of 1.25mm.
Said pinhole diaphragm 3 is the diaphragms that the aperture is 30 μ m.
Said object under test 4 is biological samples, and the position that it is placed is extremely important, must satisfy the requirement of equation 4.
Said detector 5 is CCD devices.
Said computing machine 6, the conoscope image that it can record CCD shows.
The grenz ray 1 that comes from synchrotron radiation source, inciding radius is 34 μ m, and focal length length is the zone plate 2 of 1.25mm, produces chromatic dispersion, and having only wavelength is the first-order diffraction w of 3.3nm fWith part zero level w zX ray can pass through pinhole diaphragm 3, and irradiation testing sample 4, and testing sample 4 is (p-z apart from aperture stop size 0), zero order wave w zIrradiation testing sample 4 also produces diffraction and first-order diffraction ripple w f, on detector C CD5, meeting, and produce the conoscope image that contains testing sample 4 phase informations, this conoscope image shows on computing machine 6.
The wideband white light interferometer of this zone plate structure is particularly suitable for the relatively poor X ray of coherence, neutron, atomic beam and extreme ultraviolet region, is a kind of high-performance interferometer that very is worthy to be popularized.

Claims (2)

1, a kind of wideband white light interferometer of zone plate structure, comprise a source of parallel light (1), it is characterized in that also having zone plate (2), pinhole diaphragm (3), object under test (4), detector (5) and computing machine (6) successively along the direction that light beam advances, described zone plate (2) is a Fresnel zone plate, and relational expression is satisfied in the position of described object under test (4):
z 0(p+f)=p 2
In the formula: Z 0-object under test (4) is to the distance of detector (5);
P-pinhole diaphragm (3) is to the distance of detector (5);
The focal length of f-Fresnel zone plate is long.
2, the wideband white light interferometer of zone plate structure according to claim 1, it is characterized in that said light source (1) is a synchrotron radiation source, radiation wavelength is chosen as 3.3nm through monochromator, said zone plate (2) is that a radius is 34 μ m, and focal length length is the Fresnel zone plate of 1.25mm; Said pinhole diaphragm (3) is a diaphragm that the aperture is 30 μ m, and said detector (5) is a CCD device, and said computing machine (6) is used for the conoscope image that CCD records is shown.
CN 200420090066 2004-09-15 2004-09-15 Broadband white light interferometer with wave zone plate structure Expired - Fee Related CN2723958Y (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102499648A (en) * 2011-11-16 2012-06-20 清华大学 Spectral-domain optical coherence tomography imaging system based on Fresnel spectrometer

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102499648A (en) * 2011-11-16 2012-06-20 清华大学 Spectral-domain optical coherence tomography imaging system based on Fresnel spectrometer
CN102499648B (en) * 2011-11-16 2013-11-06 清华大学 Spectral-domain optical coherence tomography imaging system based on Fresnel spectrometer

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