CN101299097A - Optical device provided with optical element formed of medium exhibiting negative refraction - Google Patents

Abstract

The invention relates to an optical device having an optical element composed of a medium exhibiting negative refraction. A lens includes an optical element composed of a material exhibiting a positive refraction index, and a medium which is formed on the optical element, having the optical element as a board, and exhibits negative refraction.

Description

Optical device having optical element formed of medium exhibiting negative refraction

The present application is a divisional application, filed as original application with application No. 200580029841.4, international application No. PCT/JP2005/016338, and application date 9/6/2005, entitled "optical device having an optical element formed of a medium exhibiting negative refraction".

Technical Field

The present invention relates to an optical device using an optical system such as an optical element, a microscope, a lithography optical system, and an optical disc optical system.

Background

In these optical systems, in order to improve the resolution, it has been proposed to improve the object side NA by a method such as water immersion, oil immersion, or solid immersion (see non-patent document 1 below). On the other hand, there are the following documents regarding a substance (for example, photonic crystal or the like) exhibiting refractive characteristics different from those of a general glass lens or the like (see non-patent documents 2 and 3 and patent documents 1, 2, 3, and 4).

Non-patent document 1: bridge みと stone game stone with optical system P73-77, P166-170 オプトロニクス, 2003-19 th month and 19 th journal

Non-patent document 2: J.B.Pendry Phys.Rev.Lett.Vol85, 18(2000)3966-

Non-patent document 3: m.notomi phy.rev.b.voll 62(2000)10696

Non-patent document 4: V.G.Veselago Sov.Phys.Usp.Vol.10, 509-514(1968)

Non-patent document 5: L.Liu and S.He Optics Express Vol.12No.204835-4840(2004)

Non-patent document 6: kombu chuang chuan オプトロニクス 2001 No. 7 month No. 197 ペ - ジ, オプトロニクス press

Patent document 1: US 2003/0227415a1

Patent document 2: US 2002/0175693a1

Patent document 3: japanese patent laid-open No. 2003-195002

Patent document 4: japanese patent laid-open No. 2004-133040

In the conventional method, the specimen surface, the optical disk surface, or the crystal surface is in contact with the lens, water, oil, and the mask, or is separated from the gap of about 30 nm, and the operation distance (hereinafter referred to as WD) is too short, and thus there is a problem that the specimen, the lens, and the like are actually damaged.

Disclosure of Invention

The present invention has been made in view of the above problems, and an object thereof is to provide an optical device and the like using various optical systems such as an observation optical system, an imaging optical system, and a projection optical system, which have a long WD or are not in contact with each other.

In order to achieve the above object, a first aspect of the present invention is a lens including: an optical element formed of a material having a positive refractive index; and a medium exhibiting negative refraction, the medium being formed on the optical element with the optical element as a substrate.

A second aspect of the present invention is an optical element including: an optical element formed of a material having a positive refractive index; and a medium exhibiting negative refraction, the medium being formed on the optical element with the optical element as a substrate.

A third aspect of the present invention is an optical element including: a transparent flat plate; and a medium exhibiting negative refraction, the medium being formed on the flat plate with the flat plate as a substrate.

A fourth aspect of the present invention is an optical system having an optical element formed of a medium exhibiting negative refraction.

A fifth aspect of the present invention is an optical system including an optical element formed of a medium exhibiting a negative refractive index, wherein high-precision imaging is realized by the optical element formed of a medium exhibiting a negative refractive index.

A sixth aspect of the present invention is an optical system including an optical element formed of a medium exhibiting negative refraction, wherein high-precision imaging is realized by utilizing a property of complete imaging of the optical element formed of the medium exhibiting negative refraction.

A seventh aspect of the present invention is an optical system including an optical element formed of a medium exhibiting negative refraction, in which a long operating distance is obtained by the optical element.

An eighth aspect of the present invention is an optical system including an optical element formed of a medium exhibiting negative refraction and an optical element other than the optical element.

A ninth aspect of the present invention is an optical system having an optical element formed of a medium exhibiting negative refraction and an optical element formed of a medium having positive refraction.

A tenth aspect of the present invention is an optical system including an optical element formed of a medium exhibiting negative refraction and an optical element formed of a medium exhibiting positive refraction, wherein a gap is provided between the optical element formed of a medium exhibiting positive refraction, which is closest to the optical element formed of a medium exhibiting negative refraction, and the optical element formed of a medium exhibiting negative refraction.

An eleventh aspect of the present invention is an optical system including an optical element formed of a medium exhibiting negative refraction and a plurality of optical elements other than the optical element.

A twelfth aspect of the present invention is an optical system in which an optical element formed of a medium exhibiting negative refraction and an imaging optical system are arranged in combination.

An optical system according to a thirteenth aspect of the present invention has an imaging relationship based on an optical element formed of a medium exhibiting negative refraction, and further has an optical element other than the optical element formed of the medium exhibiting negative refraction.

A fourteenth aspect of the present invention is an optical system including both an imaging relationship based on an optical element formed of a medium exhibiting negative refraction and an imaging relationship based on an imaging optical system.

A fifteenth aspect of the present invention is an optical system including an optical system having an optical element formed of a medium exhibiting negative refraction and an imaging optical system, wherein imaging is performed by the optical system, and the image is re-imaged by the imaging optical system.

A sixteenth aspect of the present invention is an optical system that images an image of an object through an imaging optical system and reimages the image through an optical system including an optical element formed of a medium exhibiting negative refraction.

A seventeenth aspect of the present invention is an optical system satisfying the following expression (8-5):

(8-5) formula | delta | < 100 λ

Wherein, Delta is WD + d-t

WD is the distance of the above-mentioned medium exhibiting negative refraction to the object or image plane,

d is the distance of the above-mentioned medium exhibiting negative refraction to the intermediate imaging point of the optical system,

t is the thickness of the above-described medium exhibiting negative refraction.

An eighteenth aspect of the present invention is an optical system in which an imaging optical system is disposed behind an optical element formed of a medium exhibiting negative refraction.

A nineteenth aspect of the present invention is an optical system in which an imaging optical system is disposed in front of an optical element formed of a medium exhibiting negative refraction.

A twentieth aspect of the present invention is an optical device including an optical system having an optical element formed of a medium exhibiting negative refraction.

A twenty-first aspect of the present invention is an optical device including an optical system including an optical element formed of a medium exhibiting negative refraction and another optical element.

A twenty-second aspect of the present invention is an optical device including an optical system having an optical element formed of a medium exhibiting negative refraction and an optical element formed of a medium having positive refraction.

A twenty-third aspect of the present invention is a signal processing device having an optical element formed of a medium exhibiting negative refraction.

A twenty-fourth aspect of the present invention is an optical disc device having an optical element formed of a medium exhibiting negative refraction.

A twenty-fifth mode of the present invention is a projection apparatus having an optical element formed of a medium exhibiting negative refraction.

A twenty-sixth mode of the present invention is an observation device having an optical element formed of a medium exhibiting negative refraction.

A twenty-seventh aspect of the present invention is an image pickup apparatus having an optical element formed of a medium exhibiting negative refraction.

A twenty-eighth aspect of the present invention is an optical device for performing imaging of the microstructure, including a light source, a member having the microstructure, and an optical element formed of a medium exhibiting negative refraction.

A twenty-ninth aspect of the present invention is an exposure apparatus for exposing a wafer, and arranging a light source, a photomask, and an optical element formed of a medium exhibiting negative refraction in this order.

A thirtieth aspect of the present invention is a lens that uses a photonic crystal as a medium exhibiting negative refraction and has an optical surface with a curved surface.

A thirty-first aspect of the present invention is an optical device including an optical element formed of a medium exhibiting negative refraction and an imaging optical system, wherein an absolute value of a distance from an intermediate imaging point of the imaging optical system to a surface of the optical element formed of the medium exhibiting negative refraction is 0.1 λ/a or more (where a is a numerical aperture of the imaging optical system at the intermediate imaging point).

A thirty-second aspect of the present invention is an optical device including an optical element formed of a medium exhibiting negative refraction and an imaging optical system, wherein an absolute value of a distance from an optical surface of the imaging optical system closest to the optical element formed of the medium exhibiting negative refraction to an intermediate imaging point of the imaging optical system is 0.1 λ/a or more (where a is a numerical aperture of the imaging optical system at the intermediate imaging point).

A thirteenth aspect of the present invention is an optical device including a light source, a member having a microstructure, and an optical element formed of a medium exhibiting negative refraction, wherein a distance between the member having a microstructure and a surface of the optical element formed of a medium exhibiting negative refraction is 0.1 λ or more.

A thirty-fourth aspect of the present invention is an optical device including an optical element formed of a medium exhibiting negative refraction and an imaging optical system, wherein a thickness t of the optical element formed of the medium exhibiting negative refraction satisfies any one of the following expressions (17), (18), (19), and (20).

T is more than or equal to 0.1mm and less than or equal to 300mm (17)

T is more than or equal to 0.01mm and less than or equal to 300mm (18)

T is more than or equal to 1100nm and less than or equal to 200mm (19)

T is more than or equal to 100nm and less than or equal to 50mm (20)

A thirty-fifth aspect of the present invention is an optical device including a light source, a member having a microstructure, and an optical element formed of a medium exhibiting negative refraction, wherein a thickness t of the optical element formed of the medium exhibiting negative refraction satisfies any one of the following expressions (17), (18), (19), and (20).

T is more than or equal to 0.1mm and less than or equal to 300mm (17)

T is more than or equal to 0.01mm and less than or equal to 300mm (18)

T is more than or equal to 1100nm and less than or equal to 200mm (19)

T is more than or equal to 100nm and less than or equal to 50mm (20)

A thirty-sixth aspect of the present invention is an optical device including an optical system including an optical element formed of a medium exhibiting negative refraction, the optical device further including an optical system using a photonic crystal as the medium exhibiting negative refraction, and an axis having a best rotational symmetry with the photonic crystal is oriented in an optical axis direction of the optical system.

A seventeenth aspect of the present invention is an optical device including an optical system including an optical element formed of a medium exhibiting negative refraction, wherein a length of the optical system measured along an optical axis of the optical system is 20m or less.

A thirty-eighth aspect of the present invention is a lens having a curved optical surface, wherein a photonic crystal having a negative refractive index is used as a negative refractive index medium.

A thirty-ninth mode of the present invention is a lens formed of a medium exhibiting negative refraction, one side of the lens being a flat surface.

A fortieth aspect of the present invention is a lens formed of a medium exhibiting negative refraction, the lens having an aspherical surface.

A fourth eleventh aspect of the present invention is a lens formed of a medium exhibiting negative refraction, the lens having a rotationally asymmetric surface.

A forty second aspect of the present invention is a lens formed of a medium exhibiting negative refraction, the lens having an expanded curved surface.

Drawings

Fig. 1 is a view showing an example of areflection microscope 302 using a negativerefractive index medium 301 according to an embodiment of the present invention.

Fig. 2 is a diagram showing an enlarged view of the vicinity of theobjective lens 306 in fig. 1.

Fig. 3 is a view showing atransmission microscope 315 using a negativerefractive index medium 301 according to another embodiment of the present invention.

Fig. 4 is a diagram showing an embodiment of anoptical system 320 for an optical disc.

Fig. 5 is a diagram showing an embodiment of an optical system of a projection exposure apparatus.

Fig. 6 is a diagram showing a conventional close contact type photolithography.

Fig. 7 is a diagram of a configuration in which parallel flat plates of negative index medium 301 are placed in close contact or close proximity on apolymer photomask 330 between asilicon wafer 326 and thepolymer photomask 330.

Fig. 8 is a diagram illustrating an embodiment of a lens 301-2 made of a negative refractive index medium.

Fig. 9 is a diagram showing an example of thephotonic crystal 340.

Fig. 10 is a diagram showing an example of thephotonic crystal 340.

Fig. 11 is a diagram of an example of areflection microscope 302 using a flat plate-shaped negativerefractive index medium 301 formed on aflat plate 450 formed of a material having a positive negative refractive index.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the drawings. Fig. 1 shows an example of areflection microscope 302 using a negativerefractive index medium 301, which is arranged in air, according to an embodiment of the present invention. Light emitted from a light source 303 (for example, a laser light source, a mercury lamp, or the like) is incident on anobjective lens 306 through anillumination lens 304 and ahalf mirror 305. The NA of the objective 306 is, for example, greater than 1, so that evanescent waves can be excited. Theobjective lens 306 includes optical elements formed of a medium having a positive refractive index, such as lenses 306-1, 306-2 made of glass.

Fig. 2 shows an enlarged view of the vicinity of theobjective lens 306 of fig. 1. Here, the surface closest to the object side of theobjective lens 306 is set as 311. The middle imaging point of the objective 306 is denoted by FF. The distance between the surface 311 and the intermediate image point FF is g.

A parallel flat plate-like negativerefractive index medium 301, for example, is disposed at a position away from the intermediate image forming point FF by distance d. d represents the distance between the intermediate imaging point FF and theupper surface 310 of the negative-index medium. The value of d is for example 50 μm. 312 is the object-side surface of negativerefractive index medium 301.

The light scattered by theobject 307 passes through the negativerefractive index medium 301, theobjective lens 306, thehalf mirror 305, and theeyepiece 308, and can be observed by theeye 309, a TV camera provided with animage pickup device 408, a refrigeration CCD camera, or the like. This is described in detail below.

Here, the negative-refractive-index medium 301 has a refractive index of-1 and a thickness t (e.g., 300 μm). WD is the distance between the negativerefractive index medium 301 and theobject 307 or an imaging means described later.

Details regarding WD are described later.

Since the negativerefractive index medium 301 has a refractive index of-1, the light scattered by theobject 307 is refracted differently from normal as shown by the arrow in fig. 2 (see non-patent document 2).

According to the refraction rule, if the incident angle is i and the emergent angle is r, the following formula is satisfied.

(0-3).

If the refractive index of the negativerefractive index medium 301 is n, the following expression is satisfied.

sin r ═ 1/n) sin i. (0-4).

According to non-patent document 2, when

(1) formula (WD + d)

The negative index medium 301 then images theobject 307 completely onto the intermediate imaging point FF. I.e. complete imaging is achieved. The term "complete imaging" as used herein means that all light as an electromagnetic field including radiation light and evanescent waves is imaged without being affected by the diffraction limit. Thus, it is equivalent to having an object at FF.

The value of g defined as the distance from FF to the face 311 satisfies the following formula,

0-g.lambda. (0),

the middle imaging point FF is very close to the face 311. This is a condition preferable for effectively utilizing the evanescent wave. From a practical viewpoint, the following equation may be used.

(0-1) formula (g is more than or equal to 0 and less than or equal to 10 lambda)

Further, λ is the wavelength of light used, and in the case of visible light, λ is 0.35 μm to 0.7 μm.

Thus, imaging with NA > 0.1, including evanescent waves, can be performed. Thus enabling a high resolution microscope.

Further, the following formula may be used depending on the application.

(0-1-0) formula (g is more than or equal to 0 and less than or equal to 1000 lambda)

In the expressions (0) to (0-1-0), when the lower limit of g is 0.1 λ/a, dust, damage, and the like on the lens surface 311 become blurred, and the adverse effect is reduced, which is also preferable. In addition, a is a Numerical Aperture (NA) in FF of theobjective lens 306.

In expressions (0) to (0-1-0), it is preferable that the lower limit of g is 0.6 λ/A because the influence of dust, damage, or the like on the lens surface 311 is further reduced.

In the expressions (0) to (0-1-0), it is preferable that the lower limit of g is 1.3 λ/A because the influence of dust, damage, or the like on the lens surface 311 is further greatly reduced.

Assuming that d is 50 μm, WD is 250 μm and WD is long according to formula (1), which is an advantage that has not been achieved so far, and if g is 0 to several tens nm, the imaging performance is substantially equivalent to that of a solid immersion lens in which theobjective lens 306 is almost in contact with theobject 307.

The key point of one embodiment of the present invention is to configure an optical element (301 or the like) formed of a negative refractive index medium and an imaging optical system (306 or the like) in combination. In the present embodiment, the imaging optical system is disposed on the image side of the negativerefractive index medium 301.

Further, an embodiment of the present invention is characterized in that an object image (intermediate image) imaged by the negativerefractive index 301 is re-imaged by theobjective lens 306. The intermediate image is a real image in the example of fig. 2, but may also be a virtual image depending on the use of the optical system. Also, in the example of fig. 2, there is a feature that the illumination light and the observation light transmit the negative refractive index medium 301 twice in the opposite direction.

In the above description, the case where g.gtoreq.0 is described, but the following formula is also possible.

(0-5) formula

The reason is that if d + g > 0(0-6), the imaging relationship can be maintained without the optical elements colliding with each other. By g < 0 is meant that FF enters the lens (e.g., 306-1). However, if g is too small, the condition for complete image formation is broken, and therefore the following formula is preferably satisfied.

(0-7) formula (I) t < g < 0

The following formula may be satisfied depending on the application.

(0-8) formula (I) -3t < g < 0

The following equation may be satisfied depending on the optical system.

(0-9) formula (I) 10t < g < 0

Further, d + g may be 0.

When the value of g is expressed as the actual length, the value of g is preferably as follows.

(0-10) formula (I) with-100 mm < g < 0

When the value of g is less than the lower limit of the formula (0-10), the production of the lens becomes difficult.

It is also good if the value of g satisfies the following formula.

(0-11) formula (I-10 mm < g < 0.)

In expressions (0-5) to (0-11), when the upper limit of g is (-0.1 λ)/a, it is preferable because evanescent waves can be reliably utilized, dust, damage, and the like on the lens surface 311 become blurred, and adverse effects are reduced. In the formulae (0-5) to (0-11), when the upper limit of g is (-0.6. lambda.)/A, the influence of dust, damage, or the like on the lens surface 311 is further reduced, which is preferable.

In the formulae (0-5) to (0-11), when the upper limit of g is (-1.3. lambda.)/A, the influence of dust, damage, or the like on the lens surface 311 is further greatly reduced, which is preferable.

The following equation (1) may not be strictly adhered to. This is because the image forming position by the negativerefractive index medium 301 may deviate from the expression (1) due to a manufacturing error of the refractive index of the negativerefractive index medium 301, an error of surface accuracy, or the like.

As long as the following formula is satisfied.

T is more than or equal to 0.8(WD + d) and less than or equal to 1.2(WD + d) (2)

The following formula is sometimes also permitted depending on the product.

T is more than or equal to 0.5(WD + d) and less than or equal to 1.5(WD + d) (3)

Depending on the use conditions of the product, the following formula may be satisfied.

T is more than or equal to 0.15(WD + d) and less than or equal to 4.0(WD + d) (4)

Alternatively, it is preferable to satisfy the following expression because a longer WD can be ensured.

t is less than or equal to 0.9(WD + d). (4-1)

The above-described idea is also applicable to other embodiments of the present application. Even in other embodiments, the refractive index of the negative-refractive-index medium 301 is, for example, -1.

Fig. 3 shows an example of atransmission microscope 315 using a negativerefractive index medium 301 according to another embodiment of the present invention. In fig. 3, only the vicinity of the illuminationoptical system 316 and theobjective lens 306 is shown enlarged. 315 are disposed in air.

The light from thelight source 303 is incident on theprism 317, and is incident on thesurface 318 of theprism 317 on thespecimen 314 side at an angle at which total reflection is performed. Whereby thespecimen 314 is illuminated by the evanescent waves. Scattered light from thespecimen 314 is refracted by thenegative index medium 301 and fully imaged near the intermediate imaging point FF. And is observed by re-imaging through theobjective lens 306.

The same applies to the formulae (0), (0-1-0), (0-3), (0-11), (1), (2), (3), (4), and (4-1) in this example.

In fig. 3, and fig. 4 and 5 described later, the case where the value of d is sufficiently small as compared with WD and the value of g is also close to 0 is described. The optical system of fig. 1 and 3 can also be applied to a scanning microscope.

Fig. 4 is an embodiment of anoptical system 320 for an optical disc. Light emitted from a semiconductor laser serving as alight source 321 passes through thehalf mirror 305, theobjective lens 322, and the negativerefractive index medium 301, and forms an image on theoptical disc 323, thereby performing writing. The NA of theobjective lens 322 is larger than 1, and writing with higher density including evanescent light is possible by passing a minute spot light so as not to contact theobjective lens 322. 320 are disposed in air.

The imaging relationship of the negative index medium 301 may be considered as light traveling in the opposite direction of the arrows in the embodiment of fig. 2. When a signal is read from theoptical disc 323, light emitted from thelight source 321 is scattered by theoptical disc 323, passes through the negativerefractive index medium 301 and theobjective lens 322, is reflected by thehalf mirror 305, and then enters thephotodetector 324. Readout can be performed in a non-contact manner with a high NA.

As shown in fig. 5, the configuration during writing is realized by disposing aphotomask 325 between thelight source 321 and theobjective lens 322, replacing theoptical disk 323 with asilicon wafer 326, and optically conjugating thephotomask 325 and thesilicon wafer 326, thereby realizing a projection exposure apparatus (such as a stepper) 349 for LSI production. Since the evanescent wave can be used with NA larger than 1, exposure can be performed with high resolution and in a non-contact manner, and the scene is good. In fig. 5, the optical system of the projection exposure apparatus is arranged in vacuum.

In the embodiments of fig. 4 and 5, the same applies to the equations (0), (0-1-0), (0-3),., (0-11), (1), (2), (3), (4), and (4-1).

In the examples of fig. 1 to 5, the negativerefractive index medium 301 and the lens closest to the negativerefractive index medium 301 are disposed with a gap therebetween.

Thus, for example, even when the negativerefractive index medium 301 is damaged by collision with an object, the function can be recovered by merely replacing the negativerefractive index medium 301, which is preferable. I.e. easy to repair.

Fig. 6 is a diagram showing a conventional close contact type photolithography. When thetransparent polymer photomask 330 having a line width of about 20nm is irradiated with illumination light from above, evanescent waves are generated below theconvex portions 331, and the photoresist on thesilicon wafer 326 is exposed to light. Then, LSI fabrication is performed. Thepolymer photomask 330 is a member having a fine structure. However, since thepolymer photomask 330 and thesilicon wafer 326 must be in close contact with each other, there are problems that thepolymer photomask 330 has a short life span and thepolymer photomask 330 is easily damaged during use. This problem arises even when a chrome photomask is used instead of a polymer photomask.

Therefore, in view of this, according to the present invention, by using the negativerefractive index medium 301, high-resolution lithography can be realized in a non-contact manner.

Fig. 7 is an explanatory view thereof, in which a parallel flat plate of the negativerefractive index medium 301 is disposed in close contact or in close proximity to thepolymer photomask 330 between thesilicon wafer 326 and thepolymer photomask 330. The optical system of fig. 7 is configured in vacuum or air.

Thus, the evanescent wave generated under theconvex portion 331 of thepolymer photomask 330 is completely imaged by the negativerefractive index medium 301, and the image of thephotomask 330 is formed on thesilicon wafer 326. The imaging magnification was 1 time. Thus, large WD and high resolution lithography can be realized.

If the distance between theconvex portion 331 and the negativerefractive index medium 301 is d, expressions (1) to (3), (4), and (4-1) are satisfied.

The NA of the object side, the optical disc side, or thesilicon wafer 326 side of the optical system of theobjective lens 306, theobjective lens 322, and theprojection lens 328 is preferably 0.1 or more, but may be less than 1.0. For example, 0.2 or more or less may be used. The reason is that the negativerefractive index medium 301 has an effect of extending WD.

When the NA of thelenses 306, 322, 328, etc. is 1.15 or more, high resolution can be achieved, which is preferable.

Further, it is also preferable that the NA is 1.3 or more because high resolution which cannot be achieved by the water immersion lens and/or the water immersion objective lens can be achieved.

When the NA is 1.5 or more, the objective lens can be immersed in oil and high resolution can be achieved, which is particularly preferable.

In the embodiment of fig. 1, 2, 3, 4, and 5, the shape of the negativerefractive index medium 301 may not be a parallel flat plate.

As shown in fig. 8, the negative refractive medium is formed of a negative refractive medium, and a lens 301-2 having a concave surface on the object side can also be used. An effect of correcting aberration can be obtained in addition to the effect of extending WD. In fig. 8, one side of the lens 301-2 formed of a negative refractive index medium is a flat surface, and the other side is a concave curved surface, but may have a shape of a biconvex lens, a planoconvex lens, a biconcave lens, a crescent convex lens, a crescent concave lens, or the like.

The curved surface shape of the lens 301-2 formed of a negative refractive index medium may be a spherical surface, an aspherical surface, or a free-form surface, and may be a rotationally asymmetric surface, an expanded curved surface, or the like.

The following describes the common aspects of the present invention. A photonic crystal is exemplified as a specific substance of the negativerefractive index medium 301. Fig. 9 shows a first specific example of thephotonic crystal 340, and fig. 10 shows a second specific example of thephotonic crystal 340. As shown in fig. 9 and 10, thephotonic crystal 340 is a substance having a structure with a period of about λ to several tens of λ, and is manufactured by photolithography or the like. The material used is a material containing SiO₂And a dielectric of synthetic resin such as acryl and polycarbonate, or GaAs. Here, λ is the wavelength of the light used. The values of the repetition periods Sx, Sy, Sz in the direction X, Y, Z in the figure have values of about λ to several tenths of λ. It is known that a negative refractive index can be achieved in the vicinity of the band end of a photonic crystal (see non-patent document 3). The z direction in the figure can be taken as the optical axis of the optical system.

The Z-axis is the direction of the axis of best rotational symmetry of the photonic crystal.

Sx, Sy, Sz preferably satisfy any one of the following formulae.

(5-1) formula of lambda/10 < Sx < lambda

(5-2) formula of λ/10 < Sy < λ

(5-3) formula of lambda/10 < Sz < lambda

The values of Sx, Sy, Sz exceed the upper limit or are less than the lower limit, and the function as a photonic crystal disappears.

Depending on the application, Sx, Sy, Sz may satisfy any one of the following formulae.

(5-4) formula of lambda/30 < Sx < 4 lambda

(5-5) formula of λ/30 < Sy < 4 λ

(5-6) formula of lambda/30 < Sz < 4 lambda

As for the negative refractive index medium, it is known that: when the dielectric constant epsilon of the medium is negative and the relative permeability mu of the medium is negative, the refractive index of the medium relative to vacuum is the following numerical expression 1.

<math> <mrow> <mo>-</mo> <msqrt> <mi>&epsiv;&mu;</mi> </msqrt> </mrow></math>(number formula 1)

As the negative refractive index medium, a substance exhibiting negative refraction or a substance approximately exhibiting negative refraction, for example, a thin film of silver, gold, copper, or the like can be used, and a substance exhibiting negative refractive index, a thin film of a substance having a dielectric constant ∈ of-1, or the like can be used for a specific polarization direction.

In addition, a negative-refractive-index medium is sometimes called a Left-handed material (Left handed material). In the present application, a thin film including all of these negative refractive index media, left-handed series materials, materials approximately showing negative refraction, materials showing negative refractive index with respect to a specific polarization direction, and materials having a dielectric constant ∈ of approximately-1, and the like are referred to as a medium showing negative refraction. Substances that represent a complete image are also included in the medium that exhibits negative refraction. In the case of a thin film formed of a material having a dielectric constant ∈ of substantially-1, the following expression may be satisfied.

(5-7) formula (E) -1.2 ≦ 0.8 ≦ E

The following formula may be used depending on the application.

1.6 < epsilon < -0.5. (5-8) formula

As the light wave of the light to be used, an example in which monochromatic light is mainly used has been described in the embodiment, but the present invention is not limited thereto, and the following light source may be used: a light source emitting a continuous spectrum, a white light source, a monochromatic light sum, or a low coherence light source such as a super-luminescent diode.

The wavelength may be a wavelength that can be transmitted even in air, and from the viewpoint of easy availability of a light source, a wavelength of 0.1 μm to 3 μm may be used. It is preferable to use the light having a visible wavelength because it is easier to use the light. It is also preferable that the wavelength is 0.6 μm or less because resolution is improved.

WD will be described in detail below.

The value of WD may be as follows.

WD is more than or equal to 100nm and less than or equal to 20mm (7) formula

If the lower limit of the expression (7) is exceeded, WD (operating distance) becomes too small to be handled easily. If the upper limit of the formula (7) is exceeded, the negative refractive index medium becomes too large, which is disadvantageous in terms of cost and processing. Further, the optical device also has a problem in that the size thereof becomes too large.

Depending on the product, the following formula may also be allowed.

WD is not less than 20nm and not more than 200mm

An optical device which can be used more easily can be obtained by the following formula.

WD is more than or equal to 1100nm and less than or equal to 200mm (8-0-1) formula

The following expression is preferable because it is easy to use and the mechanism for specifying the WD of the optical device is simple.

WD is more than or equal to 0.01mm and less than or equal to 200mm (8-0-2)

The following is preferable because it is easier to use and the mechanical accuracy of the optical device is further reduced.

WD is more than or equal to 0.1mm and less than or equal to 200mm (8-0-3) formula

In addition, WD preferably satisfies the following formula.

WD > d (8-1)

If t has the same value, WD increases as d decreases, as can be seen from equation (1).

The following formula (8-2) can also be allowed according to the product.

WD > 0.1 d. (8-2) formula

It is preferable because the size of the lenses of 306, 322, and 328, etc. can also be reduced by reducing the value of d.

In order to improve the resolution, it is preferable that the value of d satisfies the following expression (8-2-1),

d is more than or equal to 0. (8-2-1) formula

However, the value of d may be represented by the following formula (8-2-2) depending on the use.

(8-2-2) formula

In the formula (8-2-1), if the lower limit of d is 0.1 λ/A, FF is close to the side of the lens 306-1, so that evanescent waves are easily utilized, and dust, damage, and the like on thesurface 310 become blurred, and the adverse effect thereof is reduced, which is also preferable.

In the formula (8-2-1), when the lower limit of d is 0.6 λ/A, it is preferable to use evanescent waves more easily, thereby facilitating resolution enhancement and further reducing the influence of dust, damage, and the like.

In the formula (8-2-1), when the lower limit of d is 1.3. lambda./A, it becomes easier to make a large use of evanescent waves, and therefore, it is preferable because it is easier to improve resolution and also to further reduce the influence of dust, damage, and the like.

However, a is the numerical aperture at the point FF of the optical system, but in the optical system in which FF cannot be defined as shown in fig. 7, a is 1.

In the formula (8-2-1), if the lower limit of d is 0.005mm, the distance between the negativerefractive index medium 301 and the upper lens system is easily increased, and therefore, a frame structure for maintaining the distance between the negativerefractive index medium 301 and the upper lens system is simplified, which is preferable.

In the formula (8-2-2), when the upper limit of d is (-0.1. lambda.)/A, dust, damage, etc. on thesurface 310 become blurred, and the influence thereof is reduced, which is also preferable.

In the formula (8-2-2), it is preferable that the upper limit of d is (-0.6. lambda.)/A because the influence of dust, damage, etc. is further reduced.

In the formula (8-2-2), it is preferable that the upper limit of d is (-1.3. lambda.)/A because the influence of dust, damage, etc. is further greatly reduced.

Further, a is a Numerical Aperture (NA) of the imagingoptical systems 306, 322, and 328 and the like in the point FF.

Here, the effects of dust, damage, and the like on the optical surface on the imaging performance are summarized. As described above with the conditional expressions g and d, the larger the distance from the FF to the preceding or succeeding optical surface, the smaller the influence of dust, damage, and the like on the optical surface. The distance referred to herein is an optical length (air-converted length).

Further, the distance is preferably at least 0.1. lambda./A. Further, it is also preferable that the ratio is 0.6. lambda./A or 1.3. lambda./A or more. The optical surface further includes a surface of a negative refractive index medium.

Further, since the mechanical structure of the optical device and the like are studied, the value of WD is preferably variable. A stage of a microscope or the like is an example thereof.

Further, the negativerefractive index medium 301 and the surface of the lens closest to the negative refractive index medium 301 (surface 311 in fig. 2) may be joined. Alternatively, the negativerefractive index medium 301 may be formed as a substrate of a lens (i.e., the lens 306-1 in fig. 3). In these cases, the value of d is approximately 0 or 0.

Alternatively, the negativerefractive index medium 301 is formed on a transparent flat plate and arranged so that the transparent flat plate becomes a part of a lens for imaging. The position as the configuration may be the foremost part (the object side of the lens 306-1 in fig. 1) or the rearmost part (the wafer side of 328 in fig. 5) of the imaging lens system (theobjective lens 306 in fig. 1). A lens or a flat plate used as a substrate is preferably made of a material having a positive refractive index because it can be produced at low cost. Even in the case where the negativerefractive index medium 301 is provided on the substrate, the values of WD, d are measured from the surface of the negativerefractive index medium 301.

Fig. 11 is an example of areflection microscope 302 using a negativerefractive index medium 301 in a flat plate shape formed on aflat plate 450 formed of a material having a positive refractive index.

Such thatplate 450, lenses 306-1, and 306-2 together formobjective lens 306. The middle image point FF is slightly into theflat plate 450. Lens 306-1 andplate 450 are joined, but may be in intimate contact. The following expressions (12) and (13) are also applicable to the refractive index of theflat plate 450.

The optical system thus configured can be applied to the examples of fig. 3, 4, 5, and 7.

Further, the condition for complete imaging deviates from the expression (1), and in the case of the expression (8-3), the larger the value of | Δ | is, the worse the imaging state is.

(8-3) formula WD + d-t ═ Δ

If (8-4) is satisfied, a decrease in the imaging state to some extent can be suppressed.

(8-4) formula | Δ | < λ

In practical use, the following formula may be allowed depending on the product.

(8-4-1) formula | < 10 λ |

Depending on the conditions of use, the following formula may be allowed.

(8-5) formula | delta | < 100 λ

It is preferable to set the lower limit of | Δ | in expressions (8-4-1) to (8-5) to 0.1 λ/a because it is advantageous in some cases to ensure an increase in WD.

In addition, when the refractive index of the negativerefractive index medium 301 is n, n < 0. In the embodiments described so far, n is-1. In the case where the negative-refractive-index medium 301 is a parallel flat plate, it is desirable that n be-1. However, in practice, n may not be equal to-1 due to manufacturing errors of the negativerefractive index medium 301, shift of the wavelength used, and the like, and in this case, it is preferable to satisfy the following expression.

(9) 1.1 < n < -0.9 °

If the value of n is within the above range, complete imaging is not achieved, and the resolution is lowered. Depending on the product, the following formula is satisfied.

(10) n is more than-1.5 and less than-0.5

In applications where the WD is increased, the following equation may be satisfied.

-3 < n < -0.2 (11)

When the refractive index of the lens or optical element closest to the negative index medium (306-1, 322-1, and 328-1, respectively, for FIGS. 1, 4, and 5) is N, it is good because the resolution is higher the greater N is.

Satisfying the following formula can be used for a wide range of applications.

N is more than or equal to 1.3. (12) formula

It is also good to satisfy the following formula.

N is more than or equal to 1.7. (13) formula

In the formulae (12) and (13), when the upper limit of N is 1.82, the absorption (coloration) of the glass is reduced, which is preferable.

Satisfying the following expression is preferable because high resolution can be achieved although coloring is present.

N is more than or equal to 1.86 (13-1)

Further, it is considered that the negativerefractive index medium 301 is surrounded by air or vacuum, which can be said to be common in the embodiment of the present application.

Therefore, the refractive index n of the negativerefractive index medium 301 represents a relative refractive index with respect to air when the surroundings are air, and represents a refractive index with respect to vacuum when the surroundings are vacuum. When the surroundings are vacuum, vacuum ultraviolet light of short wavelength can be used without lowering resolution or the like due to fluctuation of air, thereby obtaining good imaging performance. If the ambient air is used, the optical device is easy to manufacture and easy to handle, which is preferable.

It is also possible that only the optical path around the negativerefractive index medium 301 is vacuum in the optical device, and the rest of the optical device is placed in air.

An optical device which is easy to handle and has good imaging performance can be obtained.

The negativerefractive index medium 301 has a refractive index nv with respect to vacuum and a refractive index nA with respect to air. At 1 atmosphere and 500nm wavelength, nA is 1.002818.

In the case where air is present around the optical device, the following equation is a necessary condition for performing ideal complete imaging.

(15) formula nv ═ -nA

In the case where the periphery of the optical device is vacuum, the following formula is a necessary condition for performing ideal complete imaging.

(16) formula (iv-1.0.)

In the examples of fig. 1, 2, 3, 4, 5, 7, 8, and 11, the portion d or WD may be filled with a liquid such as water or oil. In this case, nv may not have a value of-1, and the material of the negativerefractive index medium 301 may be easily selected. In this case, if the refractive index of the liquid such as water or oil is nL, the following formula is necessary for realizing complete image formation.

nv ═ nL (15-3) formula

When the relative refractive index of the negativerefractive index medium 301 with respect to the liquid is n, the equations (9), (10), and (11) can be applied similarly.

The value of t is described. In practice, the larger the WD, the better for the optical device to be used.

From (1), WD is a value equivalent to t. Therefore, it is preferable to satisfy the following equation. If the value of t exceeds the upper limit, the optical device becomes large and difficult to manufacture.

T is more than or equal to 0.1mm and less than or equal to 300mm (17)

Depending on the product, the following formula is also permissible.

T is more than or equal to 0.01mm and less than or equal to 300mm (18)

Depending on the application, the following formula (19) or formula (20) may be allowed to be satisfied.

(19) formula of t is more than or equal to 1100nm and less than or equal to 200mm

T is more than or equal to 100nm and less than or equal to 50mm (20)

Further, when the formula (17) or the formula (18) is satisfied, the mechanical strength of the negative refractive index medium as the optical element is increased, and therefore, handling at the time of assembling the optical device becomes easy, which is preferable. Alternatively, a substrate for supporting a negative refractive index medium may not be required, and thus is good.

In equations (19) and (20), if the upper limit value of t exceeds 0.01mm, a negative refractive index medium may be produced as a thin film by vapor deposition, sputtering, or the like, and thus is preferable.

For example, it is conceivable to produce a photonic crystal by a self-cloning (cloning) method (see non-patent document 6).

Further, it is also preferable that the length measured along the optical axis of the optical system including the negative refractive index medium is 20m or less, since the optical system and the optical apparatus are easy to manufacture.

As shown in the embodiments of fig. 1, 3, 4, and 5 of the present application, the distance between any one of the object point and the image point to the imaging optical system (306, 322, and 328, etc.) or the image point (real image before 308, image on FF, and 324, etc.) is limited.

In the present application, the term "complete imaging" is used, but the present application also encompasses a case where complete imaging of 100% is not performed, for example, a case where resolution is improved by 50%. That is, for example, the case where the resolution is improved to some extent from the normal diffraction limit is also included.

According to the present invention, it is possible to realize an optical device having various optical systems with a long WD or without contact while obtaining sufficient optical performance.

Finally, definitions of technical terms used in the present embodiment will be described.

By optical device is meant a device comprising an optical system or an optical element. The optical device alone may not function. I.e. may also be part of the device.

In an optical device comprising: an imaging device, an observation device, a display device, an illumination device, a signal processing device, an optical information processing device, a projection exposure device, and the like.

Examples of the imaging device include: a film camera, a digital camera for PDA, a robot eye, a lens-interchangeable digital single lens reflex camera, a television camera, a video recorder, an electronic video recorder, a camcorder, a VTR (tape recorder) camera, a digital camera for cellular phone, a television camera for cellular phone, an electronic endoscope, a capsule endoscope, a vehicle-mounted camera, a camera for satellite, a camera for planetary probe, a camera for cosmic probe, a camera for monitor device, various sensor eyes, a digital camera for recorder, an artificial vision, a laser scanning microscope, a projection exposure device, a step exposure device, an adjuster (aligner), a light probe type microscope, and the like. Any of a digital camera, a card-type digital camera, a television camera, a VTR camera, a video recording camera, a digital camera for a mobile phone, a television camera for a mobile phone, a vehicle-mounted camera, a camera for an artificial satellite, a camera for a planetary probe, a camera for a cosmic probe, a digital camera for a sound recording device, and the like is an example of the electronic image pickup device.

Examples of the observation device include: microscopes, telescopes, glasses, binoculars, loupes, fiber viewers, viewfinders (finders), view finders (view finders), contact lenses, artificial vision, and the like.

Examples of the display device include: a liquid crystal display, a viewfinder, a game machine (play station manufactured by sony corporation), a video projector, a liquid crystal projector, a Head Mounted Display (HMD), a PDA (portable information terminal), a cellular phone, an artificial vision, and the like.

A multimedia video projector, a liquid crystal projector, and the like are also projection devices.

Examples of the lighting device include: flash lamps for cameras, headlamps for automobiles, endoscope light sources, microscope light sources, and the like.

Examples of the signal processing device include: a mobile phone, a personal computer, a game machine, a reading/writing device for an optical disk, an arithmetic device for an optical calculator, an optical interconnection device, an optical information processing device, an optical LSI, an optical computer, a PDA, and the like.

The information transmission device is any one of the following devices capable of inputting and transmitting information: a remote controller for a mobile phone, a stationary phone, a game machine, a television, a radio recorder, a stereo set, and the like, a keyboard, a mouse, a touch panel, and the like of a personal computer and a personal computer.

The information transmission device further includes a television monitor attached to the image pickup device, a monitor of a personal computer, and a display.

The information transmitting apparatus is included in the signal processing apparatus.

The image pickup device is, for example, a CCD, a camera tube, a solid-state image pickup device, a photo film, or the like. Further, it is assumed that the parallel panel is one of the prisms included. The change in the observer includes a change in the angle of observation. The change of the subject includes: a change in distance of an object as a subject, movement of the object, vibration, wobbling of the object, and the like. An image pickup element, a wafer, an optical disk, a silver salt film, and the like are examples of the image forming member.

The definition of the expansion curve is as follows.

In addition to being spherical, planar, and rotationally symmetric aspherical, it is also possible to: an aspherical surface having a spherical surface, a planar surface, a rotationally symmetric aspherical surface, or a symmetric surface eccentric with respect to the optical axis; an aspherical surface having only one symmetrical surface; aspheric surfaces without a plane of symmetry; a free-form surface; and surfaces having any shape such as a point or a line which is not differentiable. The reflective surface and the refractive surface may be any surfaces that have some influence on light.

In the present invention, the above-described surfaces are collectively referred to as an expanding curved surface.

The imaging optical system includes an imaging optical system, an observation optical system, a projection exposure optical system, a display optical system, a signal processing optical system, and the like.

An example of the imaging optical system is an imaging lens of a digital camera.

Examples of the observation optical system include a microscope optical system and a telescope optical system.

Examples of the projection optical system include an optical system of a video projector, an optical system for lithography, an optical disk read/write optical system, and an optical system of an optical pickup.

An example of the projection exposure optical system is an optical system for lithography.

An example of the display optical system is an optical system of a viewfinder of a video camera.

Examples of the signal processing optical system include a reading/writing optical system of an optical disc and an optical system of an optical pickup.

The optical element includes an aspherical lens, a mirror, a prism, a free-form surface prism, a Diffractive Optical Element (DOE), a non-homogeneous lens, and the like. A parallel plate is also one type of optical element.

Industrial applicability of the invention

According to the present invention, it is possible to realize an optical device having various optical systems with a long WD or without contact while obtaining sufficient optical performance.

Claims (24)

1. An optical system having an optical element formed of a medium exhibiting negative refraction, characterized in that high-precision imaging is realized by the optical element formed of a medium exhibiting negative refraction.

2. The optical system according to claim 1, wherein high-precision imaging is achieved by utilizing a property of full imaging possessed by an optical element formed of a medium exhibiting a negative refractive index.

3. The optical system according to claim 1, wherein the optical element formed of a medium exhibiting negative refraction is a lens having a curved surface.

4. An optical device comprising a light source, a member having a microstructure, and the optical system of claim 1, the optical device being for performing imaging of the microstructure.

5. The optical device according to claim 4, wherein the optical device is used for exposing a wafer, and a light source, a photomask and an optical element formed of a medium exhibiting negative refraction are arranged in this order.

6. The optical device according to claim 4, wherein the refractive index n of the medium exhibiting negative refraction satisfies the following expression (11),

n is more than 3 and less than-0.2. (11).

7. The optical device according to claim 4, wherein the distance between the medium exhibiting negative refraction and the image plane satisfies the following expression (8),

WD is not less than 20nm and not more than 200mm

Where WD is the distance between the above-described medium exhibiting negative refraction and the object or image plane.

8. The optical device according to claim 4, wherein the optical system satisfies the following formula (8-2),

WD > 0.1 d. (8-2) formula

Wherein,

WD is the distance between the above-mentioned medium exhibiting negative refraction and the object or the image plane,

d is the distance between the above-mentioned medium exhibiting negative refraction and the intermediate imaging point of the optical system.

9. The optical system according to claim 1, characterized in that it uses a photonic crystal as the medium exhibiting negative refraction.

10. The optical system according to claim 1, characterized in that the optical system has an optical surface of a curved surface characterized by using a photonic crystal as a medium exhibiting negative refraction.

11. The optical device of claim 4, wherein the light used by the optical device is monochromatic.

12. The optical device according to claim 4, wherein the wavelength of light used in the optical device is 0.1 μm or more and 3 μm or less.

13. The optical device of claim 4, wherein the optical device uses evanescent waves for imaging.

14. An optical device according to claim 4, characterized in that the distance between the medium exhibiting negative refraction and the object or the imaging member or the member having fine structure can be varied.

15. An optical device according to claim 4, characterized in that the surroundings or a part of the surroundings of the medium exhibiting negative refraction are liquid.

16. The optical system according to claim 1, wherein the thickness t of the medium exhibiting negative refraction satisfies any one of the following formulae (17), (18), (19), and (20),

t is more than or equal to 0.1mm and less than or equal to 300mm (17)

T is more than or equal to 0.01mm and less than or equal to 300mm (18)

(19) formula of t is more than or equal to 1100nm and less than or equal to 200mm

T is more than or equal to 100nm and less than or equal to 50mm (20).

17. The optical device according to claim 4, wherein a distance between the component having the fine structure and the surface of the optical element formed of the medium exhibiting negative refraction is 0.1 λ or more.

18. The optical device according to claim 4, wherein the thickness t of the optical element formed of the medium exhibiting negative refraction satisfies any one of the following expressions (17), (18), (19), and (20),

t is more than or equal to 0.1mm and less than or equal to 300mm (17)

T is more than or equal to 0.01mm and less than or equal to 3000 mm. (18) formula

(19) formula of t is more than or equal to 1100nm and less than or equal to 200mm

T is more than or equal to 100nm and less than or equal to 50mm (20).

19. The optical system of claim 9, wherein the axis of best rotational symmetry with the photonic crystal is oriented in the direction of the optical axis of the optical system.

20. An optical system according to claim 1, characterized in that the length of the optical system, measured along the optical axis of the optical system, is less than or equal to 20 m.

21. An optical system as set forth in claim 1, characterized in that one side of the optical element formed by the medium exhibiting negative refraction is a plane.

22. The optical system according to claim 1, wherein the optical element formed of a medium exhibiting negative refraction has an aspherical surface.

23. An optical system as set forth in claim 1, characterized in that the optical element formed by a medium exhibiting negative refraction has rotationally asymmetric faces.

24. The optical system according to claim 1, wherein the optical element formed of a medium exhibiting negative refraction has an expanding curved surface.

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