CN113126281A

CN113126281A - Wide spectral line high resolution optical system

Info

Publication number: CN113126281A
Application number: CN201911392559.2A
Authority: CN
Inventors: 刘鹏
Original assignee: Zhangjiagang Zhonghe Automation Technology Co ltd
Current assignee: Zhangjiagang Zhonghe Automation Technology Co ltd
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2021-07-16
Anticipated expiration: 2039-12-30
Also published as: CN113126281B

Abstract

The present invention provides a wide spectral line high resolution optical system, comprising: a light source unit, an illumination unit, an imaging unit; the light source unit includes: a light source and a condensing element, the illumination unit including: the first illumination lens, the light homogenizing part and the second illumination lens project light beams passing through the second illumination lens to a second illumination surface; the imaging unit includes: first imaging lens, it is including setting gradually: the imaging lens system comprises a first imaging lens group, a second imaging lens group and a third imaging lens group. The wide-spectrum high-resolution optical system is different from the prior art, when the detection field of view (FOV) is small, the Numerical Aperture (NA) is large and close to 1, and the resolution ratio is high; when the field of view (FOV) of the examination becomes larger, the Numerical Aperture (NA) will not decrease accordingly, but will remain substantially unchanged, as will the resolution. The (NA) and the (FOV) are increased in proportion with the increase of the (FOV), so that the effect of high resolution and large field of view is achieved, and finally high resolution rapid detection is achieved.

Description

Wide spectral line high resolution optical system

Technical Field

The invention relates to the technical field of optics, in particular to a wide-spectrum high-resolution optical system.

Background

In the semiconductor field of LDSI (large scale integrated circuit), the difficulty of microfabrication is the greatest in which photolithography is the core. In the development and manufacturing process of LDSI, it is necessary to perform a plurality of high-precision optical detections on high-precision fine line patterns made of various different characteristic materials, and there is a demand for high stability and high-speed detection in the manufacturing field. Because the information content of various optical detection is very large, optical detection systems with ultra-large visual field, high resolution and wide spectral lines including ultraviolet wave bands are in use, and the demand is increasing.

As the integration density of semiconductor chips and devices increases, optical inspection systems are required to have higher optical resolution. The main factors determining the optical resolution are the wavelength of light and the numerical aperture, so in order to improve the resolution of the optical detection system, the wavelength range of the illumination light source of the optical system is increasingly shortened, such as near ultraviolet light and even deep ultraviolet light; the numerical aperture of the detection objective lens is increasingly increased and approaches the limit. In the ultraviolet wavelength region, especially in the deep ultraviolet wavelength region of 200nm to 450nm, the absorption of general optical materials is very large, the light transmittance is very low, and applicable optical materials are very limited, so that the design and manufacture of optical systems of wide spectral lines including the ultraviolet band, large field of view, and high resolution become very difficult. Since the solutions to the above problems are very limited, practical solutions are urgently needed. When a detection field of view (FOV) is small, a common optical microscope has a large Numerical Aperture (NA) close to 1 and a high resolution ratio; when the field of view (FOV) of the examination becomes larger, the Numerical Aperture (NA) is correspondingly reduced, and the resolution is also reduced. (NA) × (FOV) remains substantially unchanged.

Meanwhile, a wide-spectrum light source including ultraviolet has a complex structure, is expensive, has limited output energy, and can further reduce the available energy particularly after selecting a wavelength region or using a pupil filter. Moreover, wide-spectrum image sensors, including ultraviolet, are also complex, expensive, and have limited sensitivity.

How to effectively utilize the energy of the light source for detection and illumination, how to design and manufacture an optical imaging system with high resolution and large field-of-view broad spectrum, and realize the coordination and unification of the two, is a major issue to be solved urgently in the industry. The present invention provides a solution thereto.

Disclosure of Invention

The invention aims to provide a wide-spectrum high-resolution optical system to overcome the defects in the prior art.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a broad-spectrum line high-resolution optical system, comprising: a light source unit, an illumination unit, an imaging unit;

the light source unit includes: the light source and the light condensing element, the light condensing element condenses the light beam emitted by the light source to the first illumination surface, the illumination unit receives the light beam from the light source unit, and the light condensing element comprises: the light source comprises a first illumination lens, a light homogenizing component and a second illumination lens, wherein light beams passing through the second illumination lens are projected to a second illumination surface;

any lighting lens all includes that set gradually: the device comprises a first illuminating lens group, an illuminating aperture diaphragm and a second illuminating lens group;

in the first illumination lens, a first illumination lens group, an illumination aperture diaphragm and a second illumination lens group satisfy the relation: d2< f22<5D2, wherein: d2 is the diameter of the first illumination lens illumination aperture stop, f22 is the combined focal length of the first illumination lens and the second illumination assembly;

the light beam from the light source unit is projected on an object plane through the first illumination lens, the light homogenizing part and the second illumination lens in sequence;

a lens group and an optical path separation element are also arranged between the illumination unit and the imaging unit;

light beams from the illumination unit sequentially pass through the lens group, the light path separation element, the second imaging lens group and the first imaging lens group to reach the object plane, and light beams reflected and scattered from the object plane sequentially pass through the first imaging lens group, the second imaging lens group, the light path separation element and the third imaging lens group to form a first image plane;

the imaging unit receives the light beam reflected and scattered from the object plane, and comprises: the first imaging lens is used for imaging the light beam from the object plane through the first imaging lens, and the first imaging lens comprises the following components in sequence: the imaging lens group comprises a first imaging lens group, a second imaging lens group and a third imaging lens group;

the first imaging lens group and the second imaging lens group satisfy the relation: f1/f2 is more than 0.35 and less than 1.5, and the second imaging mirror group and the third imaging mirror group satisfy the relation: f3/(f2 x beta) < 0.22 < 0.8;

wherein f2 is the combined focal length of the second imaging lens group, f3 is the combined focal length of the third imaging lens group, and β is the magnification of the first imaging lens;

different pupil filters are selectively inserted at the illumination aperture stop;

and a field diaphragm is arranged on the second illumination surface, and the clear aperture of the field diaphragm is arranged corresponding to the size of the object space field of view (FOV).

As an improvement of the wide-spectrum high-resolution optical system, in the first illumination lens, a front focus of the first illumination lens group is located at the first illumination surface, an inlet of the dodging component is arranged at a rear focus of the second illumination lens group, a light beam emitted by the light source is changed into parallel light or approximately parallel light through the first illumination lens group, and then the parallel light or approximately parallel light passes through the illumination aperture diaphragm and the second illumination lens group and is converged to a rear focus, and then enters the inlet of the dodging component.

As an improvement of the wide-spectrum high-resolution optical system, in the first illumination lens, the second illumination lens group can move back and forth along the optical axis direction, the dodging component comprises at least two types which can be switched with each other, the at least two types of dodging components have different geometric sizes, and adaptive illumination conditions can be obtained when the FOVs of object space fields of view of the corresponding optical system are different; when the light homogenizing component is switched, the position of the outlet is kept unchanged, and the position of the inlet of the light homogenizing component is changed due to different geometric dimensions; the second lighting lens group moves back and forth along the optical axis, and the back focus of the second lighting lens group and the entrance of the light homogenizing component are kept at the same position, so that light beams emitted by the second lighting lens group enter the light homogenizing component most effectively.

As an improvement of the wide-spectral-line high-resolution optical system of the present invention, the first imaging lens group includes, directed from the object plane side to the image plane side: the first lens, the second lens and the third reflector; the object plane side curved surface of the first compound lens comprises a reflecting surface, the central part of the object plane side curved surface of the first compound lens is a transmitting surface, and the peripheral part of the object plane side curved surface of the first compound lens is a reflecting surface facing to the image side; the object plane side curved surface of the third reflector is a concave reflecting surface, and the center of the third reflector is provided with a through hole which can allow light beams to pass through.

As an improvement of the wide-spectrum high-resolution optical system, light beams from the object plane form an intermediate image after passing through the first imaging lens group, and the intermediate image is formed near a central through hole of the third reflector;

the first imaging lens group satisfies the relation: i f 1/R2I is less than 0.35, I f 1/R3I is less than 0.8; wherein f1 is the combined focal length of the first imaging lens group, R2 is the radius of curvature of the image plane side curved surface of the object plane side first compound lens, and R3 is the radius of curvature of the object plane side curved surface of the object plane side second compound lens.

As an improvement of the wide-spectral-line high-resolution optical system of the present invention, the intermediate image satisfies the relation: and the I Ti/f 2I is less than 0.4, and Ti is the distance between the intermediate image and the first lens of the second imaging lens group in the object space.

As an improvement of the wide-spectrum high-resolution optical system, the second imaging lens group is a lens group suitable for forming parallel light or near-parallel light,

in the second imaging lens group, at least 2 positive lenses satisfy the relation: dop >0.7 XD 1, and the 2 positive lenses with the shortest focal length satisfy the relation: 0.7 < (1/fp1+1/fp2) × f 2< 1.9;

wherein, Dop is the clear aperture of the lens, D1 is the diameter of the aperture stop of the second lens group (G2) and the third lens group (G3), fp1 is the focal length of the shortest positive lens satisfying the relation of Dop >0.7 × D1, fp2 is the focal length of the second shortest positive lens satisfying the relation of Dop >0.7 × D1.

in the second imaging lens group, at least 2 negative lenses satisfy the relation: dop >0.7 XD 1, and the 2-piece negative lens in which the absolute value of the focal length is the shortest satisfies the relation: 0.45 < |1/fm1+1/fm2| × f 2< 1.4;

wherein, Dop is the clear aperture of the lens, D1 is the diameter of the aperture stop of the second lens group (G2) and the third lens group (G3), fm1 is the focal length of the shortest absolute value negative lens satisfying the relation Dop >0.7 × D1 focal length, fm1 is the focal length of the second shortest absolute value negative lens satisfying the relation Dop >0.7 × D1 focal length.

As an improvement of the wide-spectrum high-resolution optical system, the image sensor is arranged at the position of the first image surface, the object surface target is synchronously scanned in proportion according to the line transfer speed of the image sensor, and the object surface target is exposed for multiple times.

As an improvement of the wide-line high-resolution optical system of the present invention, the wide-line high-resolution optical system has an aberration coefficient NA²×FOV×λmax/(λmin)²>2；

Wherein NA is the object-side numerical aperture; FOV is object field of view, unit: millimeter; λ max is the longest wavelength of the spectrum for which the objective lens is suitable, in units: micron size; λ min is the shortest wavelength of the spectrum suitable for the objective lens, unit: and (3) micron.

Compared with the prior art, the invention has the beneficial effects that: the wide-spectrum high-resolution optical system is different from the prior art, when the detection field of view (FOV) is small, the Numerical Aperture (NA) is large and close to 1, and the resolution ratio is high; when the field of view (FOV) of the examination becomes larger, the Numerical Aperture (NA) will not decrease accordingly, but will remain substantially unchanged, as will the resolution. The (NA) and the (FOV) are increased in proportion with the increase of the (FOV), so that the effect of high resolution and large field of view is achieved, and finally high resolution rapid detection is achieved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of a broad-spectrum high-resolution optical system according to an embodiment of the present invention;

FIG. 2 is a schematic view of a first imaging lens group according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a wide-spectral-line high-resolution optical system with optical parameters of a first imaging lens;

fig. 4 is a graph of the transfer function MTF of the first imaging lens.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, the wide-spectral-line high-resolution optical system of the present embodiment includes: a light source unit 1, an illumination unit 2, and an imaging unit 3.

The light beam emitted by the light source unit 1 is projected on an object plane through the illumination unit 2 in sequence and is imaged with large resolution after passing through the imaging unit 3. In one embodiment, the light source unit 1 includes: a light source 11 and a light-gathering element 12 for gathering the light beam emitted by the light source 11. The light condensing element 12 condenses the light beam emitted from the light source 11 to the first illumination surface.

In this embodiment, the light source 11 is a laser-driven light source, and includes: the focusing lens and the inner space are filled with high-intensity plasma bulbs. Laser is converged into a bulb through a focusing lens to heat xenon plasma, and the plasma emits light when heated to a sufficient temperature, and can also provide ultrahigh light emitting brightness in a range from deep ultraviolet to visible light and a wider spectral range.

The light-collecting element 12 has an arc-shaped mirror structure, and the light source 11 is located at the focal point of the arc-shaped mirror. In this way, the light converging element 12 converges the light flux emitted from the light source 11 on the illumination surface S1, and forms a spatial image of the light source 11. In one embodiment, the light-collecting element 12 may be an ellipsoidal mirror, or other light-collecting lens, and when an ellipsoidal mirror is used, the light-emitting point is located near the first focal point of the ellipsoid, and the first illuminating surface S1 is located near the second focal point of the ellipsoid.

The illumination unit 2 receives the light beam from the light source unit 1 and projects it into the imaging unit 3. The lighting unit 2 comprises the following components arranged in sequence: a first illumination lens 21, a dodging component RD and a second illumination lens 23. The light beam passing through the second illumination lens 23 is projected to the second illumination surface. Therefore, the light beam from the light source unit 1 is projected onto an object plane through the first illumination lens 21, the dodging unit RD and the second illumination lens 23 in sequence to illuminate the object plane.

The first illumination lens 21 and the second illumination lens 23 have the same structure, wherein the first illumination lens 21 includes, in sequence: a first illumination lens group G21, an illumination aperture stop AS2 and a second illumination lens group G22. The first illumination lens 22 includes, in order: a first illumination lens group G31, an illumination aperture stop AS3 and a second illumination lens group G32.

In the first illumination lens 21, the front focus of the first illumination lens group G21 is located at the first illumination surface S1, the entrance of the dodging member RD is located at the rear focus of the second illumination lens group G32, and the light beam emitted by the light source 11 passes through the first illumination lens group G21 and becomes parallel light, and then passes through the second illumination lens group G32 and converges to the rear focus, and enters the entrance of the dodging member RD. The second group of illuminating lenses G32 moves back and forth along the optical axis with the entrance of the dodging unit RD, keeping the back focus of the second group of illuminating lenses G32 at the same position as the entrance of the dodging unit RD.

In the first illumination lens 21 and the second illumination lens group G22, the AS2 and AS3 at the illumination aperture stop can be inserted into a pupil filter, and the pupil filter can change the spatial distribution of a pupil function, thereby changing the corresponding diffraction spot distribution and realizing super-resolution. The pupil filter comprises an amplitude type pupil filter and a phase type pupil filter.

In the first illumination lens 21, the first illumination lens group G21, the illumination aperture stop AS3, and the second illumination lens G32 satisfy the following relation: d2< f22<5D 2; wherein: d2 is the diameter of the illumination aperture stop, and f22 is the combined focal length of the first illumination assembly. According to the relational expression, the light homogenizing component can reasonably and effectively achieve a good light homogenizing effect, and if the light homogenizing component exceeds the upper limit, the size of the light homogenizing component is too large, the manufacturing cost is increased, the installation is not facilitated, and the balance of the system is damaged; if the optical aberration of the related lens group is too large to compensate, the light beam overflows from the light homogenizing component, and the utilization rate of the light beam energy is reduced.

The entrance of the dodging component RD coincides with the aerial image of the light source 11, the light beams emitted by the light source 11 are split and overlapped at the dodging component RD, become a uniform illumination area at the exit of the dodging component RD, and are projected to the second illumination surface S2 through the second illumination lens 23, the second illumination surface S2 may be an object plane target to be illuminated, or other optical systems may project the uniform illumination area of the second illumination surface S2 to the object plane target to be illuminated again.

In one embodiment, the dodging part RD may be a prism rod or a fly-eye lens, the prism rod is a cylinder with a rectangular, square, regular hexagon, regular triangle, etc. cross section, and the edge line of the cylinder is perpendicular to the end surface. By arranging the dodging component RD, the light source 11 space image can be regularly divided into a plurality of parts, and then the parts are superposed together, and finally the illumination surface with uniform light intensity is obtained.

Further, the dodging unit RD may adopt two groups that can be replaced with each other, and are respectively suitable for different object space view field ranges and different imaging magnifications. As described above, the two sets of the light unifying units RD correspond to different illumination ranges, respectively, but the outlets of the light unifying units RD maintain the same position. Meanwhile, the maximum numerical apertures of the two groups of light homogenizing components RD corresponding to different illumination ranges are the same, and the arrangement has the advantages that the different illumination ranges can share the same pupil filter, the efficiency of the light source 11 is effectively utilized, and the imaging resolution of the optical system is improved to the maximum extent; the light source 11 does not need to move, and the structure is simple.

A field stop is provided at the second illumination plane S2, and an image sensor is provided at the first image plane S3. The size of the field diaphragm is adjusted corresponding to different illumination ranges of the dodging component RD, so that light beams which reach the object plane target to be illuminated and are out of the effective measurement range are shielded, useless stray light can be eliminated, and the contrast and the definition of an image are improved.

The image sensor selects a Time Delay Integration Charge Coupled Device (TDICCD), synchronously scans an object plane target according to the line transfer speed of the TDICCD in proportion, exposes the object plane target for multiple times, and accumulates signals of the object plane target.

In order to achieve the effects of shortening the length of the whole system and saving space, a reflector is further disposed between the illumination unit 2 and the imaging unit 3, and the reflector can change the exit angle of the light beam exiting from the illumination unit 2 and introduce the light beam into the imaging unit 3.

The imaging unit 3 receives the light beam reflected and scattered from the object plane, and realizes high-magnification imaging with a large field of view. Specifically, the imaging unit 3 includes: the first imaging lens 31, the light beam from the illumination unit 2 is imaged through the first imaging lens 31.

The first imaging lens 31 includes, in order: the first imaging lens group G1, the second imaging lens group G2 and the third imaging lens group G3.

Wherein the first imaging lens group G1 includes, from the object plane side to the image plane side: the lens comprises a first compound lens, a second lens and a third reflector.

The object side curved surface of the first compound lens forms one reflecting surface M2, the object side curved surface of the third lens forms the other reflecting surface M1, the third reflector is provided with a through hole at the center for allowing the light beam to pass through, the central part of the object side curved surface of the first compound lens is a transmission surface, and the peripheral part of the object side curved surface of the first compound lens is a reflecting surface facing the image side. Thus, the optical components with small quantity are adopted, the structure is simplified, and the effect of correcting various optical aberrations is achieved by effectively utilizing the optical components to the maximum extent.

As shown in fig. 2, the first imaging lens group satisfies the relation: i f 1/R2I is less than 0.35, I f 1/R3I is less than 0.8; wherein f1 is the combined focal length of the first imaging lens group, R2 is the radius of curvature of the image plane side curved surface of the object plane side first compound lens, and R3 is the radius of curvature of the object plane side curved surface of the object plane side second compound lens. If the above-described limits are exceeded, correction of high-order chromatic aberration and spherical aberration may be difficult.

The first imaging lens group G1 includes at least two reflecting surfaces and at least one refractive lens, and the middle area of the at least two reflecting surfaces is an area suitable for light beam transmission. The light beams from the object plane form an intermediate image after passing through the first imaging lens group G1, and the intermediate image is formed near the central through hole of the third reflector.

The intermediate image satisfies the relation: and the I Ti/f 2I is less than 0.4, and Ti is the distance between the intermediate image and the first compound lens of the second imaging lens group object space. Beyond the upper limit of the above relation, aberration correction may be difficult, especially primary and advanced aberration correction may be difficult, resulting in a complicated lens structure and an increase in manufacturing cost.

The second group of imaging lenses G2 is a lens group adapted to form parallel light or near-parallel light.

at least 2 negative lenses satisfy the relation: dop >0.7 XD 1, and the 2-piece negative lens in which the absolute value of the focal length is the shortest satisfies the relation: 0.45 < |1/fm1+1/fm2| × f 2< 1.4;

wherein, Dop is the clear aperture of the lens, D1 is the diameter of the aperture stop of the second lens group (G2) and the third lens group (G3), fp1 is the focal length of the shortest positive lens satisfying the relation Dop >0.7 × D1 focal length, fp2 is the focal length of the second shortest positive lens satisfying the relation Dop >0.7 × D1 focal length, fm1 is the focal length of the shortest absolute value negative lens satisfying the relation Dop >0.7 × D1 focal length, and fm1 is the focal length of the second shortest absolute value negative lens satisfying the relation Dop >0.7 × D1 focal length.

By providing the second imaging lens group satisfying the above-mentioned relational expression, it is possible to achieve an effect of correcting various aberrations in a balanced manner without generating excessive high-order aberrations.

wherein f2 is the combined focal length of the second imaging lens group, f3 is the combined focal length of the third imaging lens group, and β is the magnification of the first imaging lens group. When the limit of the relation between the first imaging lens group and the second imaging lens group is exceeded, the chromatic aberration and the field curvature aberration can be corrected difficultly; beyond the lower limit, spherical aberration correction in particular can be difficult. Further, when the limit of the relational expression between the second imaging lens group and the third imaging lens group is exceeded, it may be difficult to cause correction of high-order chromatic aberration and spherical aberration; it can also be difficult to direct the coaxial epi-illumination beam from the structure.

The third imaging lens group G3 includes: at least two positive lenses and at least one negative lens.

Therefore, the light emitted from the object plane passes through the first set of imaging lenses G1 to form an intermediate image, which is located near the reflective surface of the second set of imaging lenses G2. The intermediate image forms approximately parallel light after passing through the second imaging lens group G2 or the approximately parallel light passes through the third imaging lens group G3 and then is imaged on an image surface S3 at a finite distance.

Further, a mirror group G4 and an optical path separating element BS are provided between the illumination unit 2 and the first imaging lens 31. The light beam from the illumination unit 2 sequentially passes through the lens group G4, the optical path separating element BS, the second imaging lens group G2 and the first imaging lens group G1 to reach the object plane, and the light beam from the object plane sequentially passes through the first imaging lens group G1, the second imaging lens group G2, the optical path separating element BS and the third imaging lens group G3 to form the image plane S3.

Accordingly, the light converging element 12 converges the light beam emitted from the light source 11 to the illumination surface S1, forms a spatial image of the light source 11, and then projects the spatial image uniformly onto the illumination surface S2. The light beam emitted from the light source 11 is introduced into the first imaging lens 31 through the lens group G4 and the optical path splitting element BS, and is projected onto the object plane, so as to illuminate the object plane.

With reference to fig. 3, the optical parameters of the first imaging lens 31 are shown in table 1 below:

parameter values of the objective lens:

NA＝0.9；

object space field diameter: 1.2 mm;

wavelength: 260-450 nm.

NA is the numerical aperture of the object.

TABLE 1 where surface 1 is aspheric, expressed by the following equation

c＝1/R1＝0

k＝0

α1＝-0.002282233

α2＝0.001063988

α3＝-0.000641664

α4＝0.00020374

α5＝-2.62E-05

The characteristic parameters are shown in table 2.

TABLE 2

The calculated values of the relationships are shown in table 3:

(1)	f3/(f2×β)	0.50
			(2)	f1/f2	0.80
(3)	\|f1/R2\|	0.20
			(4)	\|f1/R3\|	0.46
(5)	(1/fp1+1/fp2)×f2	1.16
			(6)	\|1/fm1+1/fm2\|×f2	0.77
(7)	\|Ti/f2\|＜0.4	0.07
			(8)	NA2×FOV×λmax/(λmin)2	6.47

TABLE 3

Defining the aberration coefficient NA of the broad-spectrum high-resolution optical system of the present embodiment²×FOV×λmax/(λmin)²>2；

This patent introduces the concept of aberration coefficients to compare and evaluate the technical difficulty and complexity of optical lens systems.

The aberration coefficient can represent the technical difficulty of the optical system of the embodiment, and the aberration coefficient comprises the comprehensive influence of factors of the field size FOV, the resolution and the applicable wavelength range of the optical system. The larger the aberration coefficient is, the larger the field of view is, the higher the resolution is, the wider the spectral band is, these factors all directly increase the technical difficulty of the optical system, including many aspects such as design, applicable material, manufacturing, assembling and debugging, and detection operation, the difficulty and cost of the light source and image sensor adapted thereto, and other associated devices are also correspondingly increased.

The aberration coefficient of the conventional optical system is mostly 0.3-1, while the aberration coefficient of the optical system of the present embodiment is larger than 2, which can reach 6.47. The comprehensive technical difficulty of the optical system is several times higher than that of the existing optical system.

In addition, in the optical system of the embodiment, all the lens and mirror elements do not include aspheric surfaces, so that the difficulty and cost of processing, detection and installation and correction can be greatly reduced. Meanwhile, all the lenses are made of quartz or calcium fluoride crystal materials. In the ultraviolet wavelength region, especially the deep ultraviolet wavelength region of 200nm to 450nm, the absorption of the common optical material is very large, the light transmittance is very low, and the light transmittance of the optical system can be improved by using quartz glass or calcium fluoride crystals. Both materials are suitable for use, and correcting the various optical aberrations of the system can become difficult, especially as numerical apertures increase.

As shown in fig. 4, the MTF is a graph of the transfer function of the first imaging lens 31. Wherein the horizontal axis is resolution, the unit is line pair/millimeter (lp/mm), and the number of line pairs that can be resolved per millimeter is the value of resolution. The vertical axis represents the modulation Transfer function (mtf), which is a quantitative description of the resolution of the lens. The contrast is expressed by Modulation (Modulation). Assuming that the maximum luminance is Imax, the minimum luminance is Imin, and the modulation degree M is defined as: m ═ i (Imax-Imin)/(Imax + Imin). The modulation is between 0 and 1, with a greater modulation indicating a greater contrast. When the maximum brightness and the minimum brightness are completely equal, the contrast disappears completely, and the modulation degree is equal to 0.

For a sine wave with an original modulation degree of M, if the modulation degree of an image reaching an image plane through a lens is M', the MTF function value is as follows: the MTF value is M 'or M'.

It can be seen that the MTF value must be between 0 and 1, and the closer to 1, the better the performance of the lens. If the MTF value of the lens is equal to 1, the modulation degree of the lens output completely reflects the contrast of the input sine wave; whereas if the modulation degree of the input sine wave is 1, the modulation degree of the output image is exactly equal to the MTF value. The MTF function therefore represents the contrast of the lens at a certain spatial frequency.

Further, as can be seen from the curves in fig. 4, the MTF values for the representative 0 field, 0.5 field and maximum field are already very close to the diffraction limit values. The diffraction limit means that when an ideal object point is imaged by an optical system, due to the limitation of diffraction of light of physical optics, an ideal image point cannot be obtained, but a fraunhofer diffraction image is obtained, and the diffraction image is the diffraction limit, namely the maximum value, of the physical optics.

It can be seen that the invention can approach the diffraction limit of physical optics over a wide spectrum range of 260-450 nm over the entire field of view. The result of analysis shows that the wave aberration WFE (RMS) of the whole field is less than 0.05 wavelength in the spectrum range of 260-450 nm.

In summary, the wide-spectrum high-resolution optical system of the present invention is different from the prior art, and when the detection field of view (FOV) is small, the Numerical Aperture (NA) is large, close to 1, and the resolution is high; when the field of view (FOV) of the examination becomes larger, the Numerical Aperture (NA) will not decrease accordingly, but will remain substantially unchanged, as will the resolution. The (NA) and the (FOV) are increased in proportion with the increase of the (FOV), so that the effect of high resolution and large field of view is achieved, and finally high resolution rapid detection is achieved.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. A broad line high resolution optical system, comprising: a light source unit, an illumination unit, an imaging unit;

2. The wide-spectrum high-resolution optical system according to claim 1, wherein in the first illumination lens, a front focus of the first illumination lens group is located at the first illumination surface, an inlet of the dodging component is located at a rear focus of the second illumination lens group, and a light beam emitted by the light source is changed into parallel light or approximately parallel light by the first illumination lens group, passes through the illumination aperture stop and the second illumination lens group, converges to a rear focus, and enters the inlet of the dodging component.

3. The wide-spectrum high-resolution optical system according to claim 1, wherein in the first illumination lens, the second illumination lens group can move back and forth along the optical axis direction, the dodging component comprises at least two types which can be switched with each other, at least two types of dodging components have different geometric dimensions, and adaptive illumination conditions can be obtained when the object field FOV of view of the corresponding optical system is different; when the light homogenizing component is switched, the position of the outlet is kept unchanged, and the position of the inlet of the light homogenizing component is changed due to different geometric dimensions; the second lighting lens group moves back and forth along the optical axis, and the back focus of the second lighting lens group and the entrance of the light homogenizing component are kept at the same position, so that light beams emitted by the second lighting lens group enter the light homogenizing component most effectively.

4. The broad line high resolution optical system of claim 1 wherein said first set of imaging mirrors comprises, pointing from the object plane side to the image plane side: the first lens, the second lens and the third reflector; the object plane side curved surface of the first compound lens comprises a reflecting surface, the central part of the object plane side curved surface of the first compound lens is a transmitting surface, and the peripheral part of the object plane side curved surface of the first compound lens is a reflecting surface facing to the image side; the object plane side curved surface of the third reflector is a concave reflecting surface, and the center of the third reflector is provided with a through hole which can allow light beams to pass through.

5. The wide-spectrum high-resolution optical system according to claim 4, wherein the light beam from the object plane passes through the first imaging mirror group to form an intermediate image, and the intermediate image is formed near a central through hole of the third reflector;

6. The broad line high resolution optical system of claim 5 wherein said intermediate image satisfies the relationship: and the I Ti/f 2I is less than 0.4, and Ti is the distance between the intermediate image and the first lens of the second imaging lens group in the object space.

7. The broad line high resolution optical system of claim 1 wherein said second set of imaging mirrors is a set of mirrors adapted to form parallel or near parallel light,

8. The broad line high resolution optical system according to claim 1 or 7 wherein said second set of imaging mirrors is a set of mirrors adapted to form parallel light or near parallel light,

9. The wide-line large-field objective system of claim 1, wherein an image sensor is disposed at the first image plane position, and the object plane target is scanned synchronously in proportion to the line transfer speed of the image sensor, and multiple exposures are performed on the object plane target.

10. The broad line high resolution optical system of claim 1 wherein the aberration coefficient of the broad line high resolution optical system is NA²×FOV×λmax/(λmin)²>2；