CN101929848B

CN101929848B - Product confocal-scanning detection method with high spatial resolution

Info

Publication number: CN101929848B
Application number: CN2010102135113A
Authority: CN
Inventors: 赵维谦; 邱丽荣; 刘超; 刘大礼
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2010-06-30
Filing date: 2010-06-30
Publication date: 2012-04-25
Anticipated expiration: 2030-06-30
Also published as: CN101929848A

Abstract

The invention relates to a product confocal-scanning detection method with high spatial resolution, belonging to the technical field of detection of surface minuteness structure and biologic microscopic imaging, wherein the method comprises the steps of: multiplying the defocusing signals of a double biased detector in a differential confocal double receiving optical path to get product confocal signals; detecting and imaging the detected sample; improving the vertical and transverse resolution of a product confocal microscopical detection method by the product of the two biased signals thereby achieving the product confocal detection with high spatial resolution. The method can also improve the spatial resolution by combining with an optical super-resolution confocal detection method; meets the requirements of high spatial resolution and high precision of detection and imaging; and is applicable for the detection of surface three-dimensional minuteness structure, micro-step, line width and surface appearance, and the detection of biologic imaging with high precision.

Description

Product confocal scanning detection method with high spatial resolution

Technical Field

The invention belongs to the technical field of microscopic imaging and microscopic measurement, and particularly provides a method for detecting surface three-dimensional fine structures, micro steps, integrated circuit line widths and surface morphologies and high-resolution microscopic imaging in the biomedical field.

Background

Confocal microscopy is widely applied to the fields of high-resolution imaging and detection due to the unique three-dimensional tomography capability, but the further improvement of the resolution is restricted due to the principle limitation of diffraction effect. In order to break through the diffraction limit fundamentally and improve the resolution capability of the confocal microscopy method, scholars at home and abroad make many researches and put forward a plurality of non-traditional confocal microscopy imaging principles and super-resolution methods.

To improve the axial resolution of confocal microscopy, C-H.Lee et al, Taiwan university, proposed the theory of non-interfering differential confocal microscopy (Optics common.1997, 35: 232-; the differential confocal nanoscale light focusing detection method is proposed by the TuBin, Wangfengsheng and Zhao Wei of the great university of Harbin industry, and the axial resolution of the method reaches 2nm (proceedings of the third research on the two sides of the strait and the scientific and technological academic seminars, Lanzhou, 2000: 59-63); the Chinese patent 'differential confocal scanning detection method with high spatial resolution' (patent number: ZL 200410006359.6) realizes axial nano-scale and transverse submicron-scale detection by utilizing a response curve linear interval; the chinese patent "confocal microscope" (application No. 01122439.8, publication No. CN 1395127a) proposes a method for improving axial resolution by introducing an interference method into the conventional confocal microscopic imaging technique; chinese patent 'double-frequency confocal step height microscopic measurement device' (application number: 02120884.0, publication number: CN 1384334A) proposes a double-frequency confocal step interference microscopic measurement method; chinese patent "confocal interference microscope with high spatial resolution imaging ability (application No. 200410096338.8, publication No. CN 1614457)", etc.; in 1998, the american scholars Tasso r.m.sales et al designed two-zone pure phase pupil filters to improve the Axial resolution of the optical system (Axial super resolution with phase-only phase filters. optics communications.1998, 156: 227-.

However, the above mentioned results are limited to improving and increasing the axial resolution of the confocal microscope system, and cannot increase the lateral resolution, which is the key to increase the spatial resolution.

At present, methods and techniques for improving the lateral resolution of confocal microscopy mainly include spatial frequency limiting, pupil filtering, and 4PI confocal methods. The adoption of the three-dimensional super-resolution pupil filter is a main means for improving the spatial resolution of the optical detection method, but the three-dimensional super-resolution pupil filter has both axial resolution and transverse resolution, and the three-dimensional super-resolution effect is not obvious.

Disclosure of Invention

The present invention aims to overcome the defects of the prior art, and provides an optical detection method with high spatial resolution, which realizes high spatial resolution optical detection and microscopic imaging detection on three-dimensional fine structures, micro steps, integrated circuit line widths, object surface morphologies and biomedical fields.

The invention adopts the double receiving light path arrangement and the double detection of the differential confocal microscopyThe product detection of a detector is used for scanning and measuring a measured sample, an incident beam enters the measured sample through a polarizing beam splitter, an 1/4 wave plate and a measuring objective, is reflected by the measured sample, then enters the polarizing beam splitter after passing through the measuring objective and an 1/4 wave plate again, the light beam reflected by the polarizing beam splitter is divided into two paths by the beam splitter, one path is focused by a condenser, a pinhole is positioned at a distance M in front of the focus of the condenser, a detector is positioned behind the pinhole and measures an intensity curve I reflecting the convex-concave change of the measured sample₁(v，u，u_M) The other path is focused by a condenser, the other pinhole is positioned at a distance M behind the other condenser, the other detector is positioned behind the other pinhole and measures an intensity curve I reflecting the convex-concave change of the measured sample₂(v，u-u_M) Wherein, the normalized axial distance corresponding to M is u_MU is an axial normalized optical coordinate, v is a transverse normalized optical coordinate, u_MFor normalizing the axial distance, the method is characterized in that:

(1) will I₁(v，u，u_M) And I₂(v，u，-u_M) Multiplying and normalizing to obtain an intensity curve I corresponding to the convex-concave change of the sample to be measured_MCM(v，u，u_M)；

(2) According to curve I_MCM(v，u，u_M) Magnitude of intensity in linear interval, or according to curve I_MCM(v，u，u_M) And reconstructing the surface appearance and the micro scale of the measured sample according to the position of the maximum intensity.

Wherein the distance u between a pinhole and its corresponding condenser focus is optimized_MCan reduce the half-height width of the product confocal response curve and improve the spatial resolution of the confocal microscopy technology_MThe full width at half maximum of the confocal axial response curve and the focal point response intensity are jointly determined by the product.

According to the 'correlation' idea, the two detected axial offset signals are multiplied, so that the axial resolution and the transverse resolution of the system can be improved simultaneously, and the aim of improving the spatial resolution is fulfilled.

Another aspect of the inventionThe detection method adopts the double receiving light path arrangement of differential confocal microscopy and the product detection of double detectors to scan and measure a measured sample, an incident beam enters the measured sample through an optical super-resolution device, a polarizing beam splitter, 1/4 wave plates and a measuring objective, is reflected by the measured sample, then enters the polarizing beam splitter after passing through the measuring objective and 1/4 wave plates again, the light beam reflected by the polarizing beam splitter is divided into two paths by the beam splitter, one path is focused by a condenser, a pinhole is positioned at a distance M in front of the focus of the condenser, a detector is positioned behind the pinhole and measures an intensity curve I reflecting the convex-concave change of the measured sample₁(v，u，u_M) The other path is focused by another condenser, another pinhole is positioned at a distance M behind the other condenser, another detector is positioned behind the other pinhole and measures an intensity curve I reflecting the convex-concave change of the measured sample₂(v，u，-u_M) Wherein, the normalized axial distance corresponding to M is u_MU is an axial normalized optical coordinate, v is a transverse normalized optical coordinate, u_MFor normalizing the axial distance, the method is characterized in that:

(2) Optimizing the parameters of optical super-resolution device to meet super-resolution parameters G_rAnd S, sharpening the main valve of airy disk of the product confocal microscope system, and further improving the transverse resolution of the product confocal microscope, wherein G_rThe ratio of the half-height width of a transverse response curve without an optical super-resolution device, and S is the ratio of the focal strength without the optical super-resolution device;

(3) according to curve I_MCM(v，u，u_M) The magnitude of the intensity in a linear interval, or according to curve I_MCM(v，u，u_M) And reconstructing the surface appearance and the micro scale of the measured sample according to the position of the maximum intensity.

Wherein, when the optical super-resolution device is adopted to carry out transverse super-resolutionOptimizing the distance u between a pinhole and its corresponding condenser focus_MCan reduce the half-height width of the product confocal response curve and improve the spatial resolution of the confocal microscopy technology_MThe full width at half maximum of the confocal axial response curve and the focal point response intensity are jointly determined by the product.

The optical super-resolution confocal detection method for improving the transverse resolution and the product confocal detection method for improving the spatial resolution are fused to form the optical super-resolution product confocal detection method. The improvement of the spatial resolution can be realized by the differential confocal light path arrangement and the product detection; the mask of the differential confocal microscope system is corrected by adopting a specially designed optical super-resolution device, so that the wavefront is changed, the main valve of the Airy spot is sharpened, the transverse resolution of the product confocal microscope system is further improved, and finally the spatial resolution of the product confocal microscope system is improved. The optical super-resolution device may be a pupil filter including an amplitude type filter, a phase type filter, and a complex amplitude type filter, and may be a shaping binary optical device that generates ring light.

The detection technology of the invention has the following characteristics and good effects:

1. compared with the prior confocal technology, the space imaging detection capability of the confocal microscopy technology is obviously improved;

2. by utilizing the 'correlation' concept and adopting the product processing of the offset detection signals, the defect that the existing three-dimensional super-resolution technology cannot give consideration to both axial resolution and transverse resolution is avoided, and the axial resolution and the transverse resolution can be improved obviously;

3. and an optical super-resolution technology is also fused, so that the transverse resolution of confocal microscopy is further improved, and the effect of improving the spatial resolution is more remarkable.

Drawings

FIG. 1 is a schematic diagram of a high spatial resolution product confocal scanning detection method;

FIG. 2 is a normalized response curve I_MCM(v，u，u_M)；

FIG. 3 is a schematic diagram of a high spatial resolution confocal scanning method;

FIG. 4 is a diagram of the sensing principle of the high spatial resolution product confocal scanning detection method;

FIG. 5 shows the detector offset u_MA relationship to a lateral response signal;

FIG. 6 shows the detector offset u_MThe relation curve with the axial response signal (a) an axial intensity normalization curve (b) an axial intensity curve;

FIG. 7 is a schematic diagram of a high spatial resolution product confocal scanning detection method using a shaped annular illumination mode;

FIG. 8 shows u_MThe relationship of epsilon to the transverse normalized response curve when 6;

FIG. 9 shows u_MRelationship of ∈ to axial response curve at 6 ═ a) axial intensity curve (b) axial normalized intensity curve;

mu when ε is 0.50 in FIG. 10_MRelationship to axial response curve (a) axial intensity curve (b) axial normalized intensity curve;

FIG. 11 shows the offset μ_MWhen the axial response curve is 5.21, the confocal scanning detection method has a product with high spatial resolution;

FIG. 12 is a comparison chart of step transverse scanning;

the device comprises an optical super-resolution device, a 2-polarizing beam splitter, a 3-1/4 wave plate, a 4-measuring objective, a 5-measured sample, a 6-beam splitter, a 7, 8-condenser, a 9, 10-pinhole, a 11, 12-detector, a 13-product confocal double-receiving light path, a 14-light source, a 15-collimation beam expander, a 16-spatial filtering pinhole, a 17-micro-displacement workbench, an 18-multiplier, a 19-displacement sensor, a 20-piezoelectric ceramic driver, a 21-driving power supply, a 22-amplification processing circuit, a 23-microcomputer processing system, a 24-shaping binary optical device and 25-incident light beams.

Detailed Description

The invention is further illustrated by the following figures and examples.

The basic idea of the invention is to multiply and normalize the intensity curve measured by the detector, and can simultaneously improve the axial resolution and the transverse resolution of the system, thereby achieving the purpose of improving the spatial resolution.

As shown in fig. 1, the virtual frame portion is a product confocal dual-receiving optical path 13, and the incident light beam is transmitted by the polarizing beam splitter 2 and the 1/4 wave plate 3, and then focused on the surface of the sample 5 to be measured by the measurement objective 4. The measuring light reflected by the surface of the measured sample 5 is reflected by the polarizing beam splitter 2 through the 1/4 wave plate 3 again, then is divided into two beams by the beam splitter 6, and is focused by the two

same condensers

7 and 8 respectively. The pinhole 9 and the detector 11 are arranged at the focal back distance M of the focal plane of the condenser 7, the pinhole 10 and the detector 12 are arranged at the focal front distance M of the focal plane of the condenser 8, and the optical normalization displacement corresponding to the distance M is u_M。

Let the axial normalized optical coordinate be u and the transverse normalized optical coordinate be v. When the tested sample 5 is scanned axially and transversely, the detector 12 measures the scanning response curve I₁(v，u，u_M) The detector 11 measures the scanning response curve I₂(v，u，-u_M). Will respond to curve I₁(v，u，u_M) And I₂(v，u，-u_M) The product is multiplied and normalized to obtain the normalized response curve I shown in FIG. 2 of the measurement method_MCM(v，u，u_M) I.e. by

When the axial resolution characteristic is considered, v is a constant and is set as c, and the above equation can be simplified as follows:

as shown in fig. 1, when the product confocal system works in a defocusing area, the sample 5 to be measured is measured by using a hypotenuse linear segment, and it can be seen from the figure that the sensitivity of the hypotenuse of the s curve is higher than that of the confocal characteristic curve d, that is, the axial resolution is improved; when the product confocal system works at the focus, the maximum value is adopted to measure the tested sample 5, and the half-height of the half-height-width ratio confocal characteristic curve d of the s curve can be seen from the graphThe width, namely the axial resolution is improved. As shown in FIG. 1, the product confocal system response curve I_MCM(v，c，u_M) The half-height-width ratio confocal system response curve I_cmThe full width at half maximum of (v, c, 0) is narrow, i.e., the lateral resolution is improved. Thus, when the sample is scanned using a product confocal system, the response curve I_MCM(v，u，u_M) The light intensity in the linear section of the bevel edge or the position of the maximum light intensity reflects the concave-convex change of the measured sample 5, the surface appearance and the microscale of the measured sample 5 can be reconstructed by utilizing the value, the axial resolution and the transverse resolution are improved, namely the spatial resolution is improved.

Example 1

The following embodiment of the present invention is to use the product confocal microscopy method to improve the spatial resolution, and further describe the product confocal microscopy method with high spatial resolution as follows:

as shown in fig. 4, a light source 14 emits a laser beam with a wavelength λ of 633nm, the laser beam is expanded into a gaussian beam with a wavelength Φ of 4mm by a collimating beam expander 15, the gaussian beam passes through a spatial filtering pinhole 16 to become a point light source, the expanded parallel light is transmitted and reflected by a polarizing beam splitter 2, wherein the p light transmitted by the polarizing beam splitter 2 is converged on the surface of a sample 5 to be measured by an 1/4 wave plate 3 and a measuring objective 4, the light reflected by the sample 5 to be measured returns along the original path, passes through a 1/4 wave plate 3 again to become s light and is reflected by the polarizing beam splitter 2, the reflected light is divided into two reflected beams and two beams with equal intensity by a beam splitter 6 and is focused by a condenser 7 and a condenser 8 respectively, a transmission pinhole 9 and a pinhole 10 are respectively placed before and after the focus of the condenser 7 and the condenser 8 and are respectively received by a detector 11 and a detector 12, the light intensity signals detected by the detector 11 and the detector 12 are multiplied by the multiplier 18 and amplified by the amplification processing circuit 22 to obtain a focus error signal of the confocal sensor near the focus, wherein the focus error signal corresponds to the distance between the detected sample 5 and the focus position. In order to expand the range of the sensor, the measuring objective 4 is fixed on an objective Z-direction tracking scanning system which is composed of a piezoelectric ceramic driver 20 and a displacement sensor 19, the range of the objective Z-direction tracking scanning system reaches 350 μm, and the scanning frequency is 150 Hz. The microcomputer processing system 23 controls the output of the driving power supply 21 according to the feedback signal of the displacement sensor 19, so that the piezoelectric ceramic driver 20 makes axial displacement, when the measured sample 5 passes through the focal plane of the measuring objective 4, the detected product light intensity signal passes through the vicinity of the maximum value and is used as an aiming trigger signal, and the sum of the signal measured by the displacement sensor 19 and the signal in the vicinity of the maximum value during the aiming trigger can reflect the change of the axial position of the measured sample 5.

The resolution characteristic of the high spatial resolution tracking confocal sensor measuring method of the embodiment is calculated according to the following theory.

Light intensity response function I (v, u) of reflective confocal microscope with detector offset_M) Comprises the following steps:

<math> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <mi>v</mi> <mo>,</mo> <mi>u</mi> <mo>,</mo> <msub> <mi>u</mi> <mi>M</mi> </msub> <mo>)</mo> </mrow> <mo>=</mo> <msup> <mrow> <mo>|</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mn>1</mn> </msubsup> <mi>P</mi> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>iu</mi> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>·</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mn>1</mn> </msubsup> <mi>P</mi> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>i</mi> <mrow> <mo>(</mo> <mi>u</mi> <mo>+</mo> <msub> <mi>u</mi> <mi>M</mi> </msub> <mo>)</mo> </mrow> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow> </math>

wherein,

z is the axial displacement distance, r is the radial coordinate, u_MAxial offset of the pinhole, α₀Is the objective lens numerical aperture angle.

Normalized pupil function of

The transverse resolution characteristic of the measuring method is as follows:

when the measured object is in the defocused state, the two-point detector respectively shifts + u in the axial direction_MAnd-u_MThen, from equation (3), the transverse intensity distribution characteristic is:

<math> <mrow> <msup> <mrow> <mo>=</mo> <mrow> <mo>|</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mn>1</mn> </msubsup> <mi>P</mi> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>iu</mi> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>·</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mn>1</mn> </msubsup> <mi>P</mi> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>i</mi> <mrow> <mo>(</mo> <mi>u</mi> <mo>+</mo> <msub> <mi>u</mi> <mi>M</mi> </msub> <mo>)</mo> </mrow> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>|</mo> </mrow> </mrow> <mn>2</mn> </msup> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>6</mn> <mo>)</mo> </mrow> </mrow> </math>

<math> <mrow> <mo>×</mo> <msup> <mrow> <mo>|</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mn>1</mn> </msubsup> <mi>P</mi> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>iu</mi> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>·</mo> <msubsup> <mo>&Integral;</mo> <mn>0</mn> <mn>1</mn> </msubsup> <mi>P</mi> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>i</mi> <mrow> <mo>(</mo> <mi>u</mi> <mo>-</mo> <msub> <mi>u</mi> <mi>M</mi> </msub> <mo>)</mo> </mrow> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> </math>

when the measured sample 5 is in the focal plane, namely u is 0, the transverse resolution characteristic is along with the axial offset u of the pinhole_MThe change rule of (2) is shown in fig. 5. As can be seen in FIG. 5, u_MWhen the intensity is less than 10, the full width at half maximum of the light intensity hardly follows u_MVariation, i.e. lateral resolution and pinhole axial offset u_MIs irrelevant.

The axial resolution characteristic of the measuring method is as follows:

the focus error signal is obtained from equation (3):

the corresponding relation between the focus error signal and the detection distance u is shown in formula (7), and a relation curve s between the focus error signal and the detection distance z is obtained from formula (4).

In the product confocal sensing technology, the axial offset u of a detector_MWill directly affect the axial resolution characteristic of the sensor, and figure 6 shows the axial resolution characteristic and the offset u_MThe relationship of (1). As can be seen in FIG. 6, u_MThe increase and the decrease of the axial full width at half maximum, namely the improvement of the axial resolving power, but the response intensity is reduced, and the side lobe is increased, which is unfavorable for the imaging detection, but the pinhole of the confocal method can inhibit the influence.

By adopting the method, the detector has better performance by comprehensively considering the axial resolution and the energy loss.

Example 2

The following uses the shaping annular optical product confocal microscopy method to improve the spatial resolution as the second embodiment of the present invention, and further describes the product confocal microscopy method with high spatial resolution as follows:

as shown in fig. 7, the dashed frame portion is a product confocal microscopy double-receive optical path arrangement 13, and the optical super-resolution device is a shaping binary optical device 24. Light intensity response function I (v, u) of a reflective confocal microscope with pupil function P (ρ) under monochromatic light illumination_M) Comprises the following steps:

<math> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <mi>v</mi> <mo>,</mo> <mi>u</mi> <mo>,</mo> <msub> <mi>u</mi> <mi>M</mi> </msub> <mo>)</mo> </mrow> <mo>=</mo> <msup> <mrow> <mo>|</mo> <msubsup> <mo>&Integral;</mo> <mi>ϵ</mi> <mn>1</mn> </msubsup> <mi>P</mi> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>iu</mi> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>·</mo> <msubsup> <mo>&Integral;</mo> <mi>ϵ</mi> <mn>1</mn> </msubsup> <mi>P</mi> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>i</mi> <mrow> <mo>(</mo> <mi>u</mi> <mo>+</mo> <msub> <mi>u</mi> <mi>M</mi> </msub> <mo>)</mo> </mrow> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mtext>8</mtext> <mo>)</mo> </mrow> </mrow> </math>

wherein,

z is the axial displacement distance, r is the radial coordinate, epsilon is the normalized radius of the laser beam, u_MAxial offset of the pinhole, α₀Is the objective lens numerical aperture angle.

Normalized pupil function of

When the binary optical device is used for shaping annular light, the light in the central part is transferred to the outer ring, the system has no energy loss in the energy transfer process, and assuming that the amplitude on the ring is A, the intensity distribution of the shaped light beam can be represented as follows:

according to the law of conservation of energy

The transverse resolution characteristic of the measuring method is as follows:

when the detected sample 5 is in a defocusing state, the two-point detector respectively deviates + u in the axial direction_MAnd-u_MThen, from equation (8), the transverse intensity distribution characteristic is:

<math> <mrow> <mo>=</mo> <msup> <mrow> <mo>|</mo> <msubsup> <mo>&Integral;</mo> <mi>ϵ</mi> <mn>1</mn> </msubsup> <msub> <mi>P</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>iu</mi> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>·</mo> <msubsup> <mo>&Integral;</mo> <mi>ϵ</mi> <mn>1</mn> </msubsup> <msub> <mi>P</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>i</mi> <mrow> <mo>(</mo> <mi>u</mi> <mo>+</mo> <msub> <mi>u</mi> <mi>M</mi> </msub> <mo>)</mo> </mrow> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mtext>13</mtext> <mo>)</mo> </mrow> </mrow> </math>

<math> <msup> <mrow> <mo>×</mo> <mrow> <mo>|</mo> <msubsup> <mo>&Integral;</mo> <mi>ϵ</mi> <mn>1</mn> </msubsup> <msub> <mi>P</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>iu</mi> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>·</mo> <msubsup> <mo>&Integral;</mo> <mi>ϵ</mi> <mn>1</mn> </msubsup> <msub> <mi>P</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>ρ</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mfrac> <mrow> <mi>i</mi> <mrow> <mo>(</mo> <mi>u</mi> <mo>-</mo> <msub> <mi>u</mi> <mi>M</mi> </msub> <mo>)</mo> </mrow> <msup> <mi>ρ</mi> <mn>2</mn> </msup> </mrow> <mn>2</mn> </mfrac> </msup> <msub> <mi>J</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>ρv</mi> <mo>)</mo> </mrow> <mi>ρdρ</mi> <mo>|</mo> </mrow> </mrow> <mn>2</mn> </msup> </math>

when the measured sample 5 is in the focal plane, i.e., u is 0, the change rule of the lateral resolution characteristic with epsilon is shown in fig. 8. As can be seen from fig. 8, epsilon increases, and the smaller the full width at half maximum of the light intensity, the higher the lateral resolution.

The axial resolution characteristic of the measuring method is as follows:

the focus error signal is obtained from equation (8):

the corresponding relation between the focus error signal and the detection distance u is shown in the formula (14), and a relation curve s between the focus error signal and the detection distance z is obtained by the formula (9).

In the annular optical product confocal sensing technology, the axial offset u of a detector_MThe resolution of the response curve of the annular light product confocal detection method is determined by the offset u of two pinholes_MThe normalized radius epsilon of the annular light and the numerical aperture of the objective lens.

FIG. 9 shows u_MThe axial resolution curves for 6, 0.25, 0.50 and 0.75, and fig. 10 shows 0.5, u_MVersus axial resolution characteristic. As can be seen from fig. 9 and 10, epsilon increases, the axial full width at half maximum, i.e. the axial resolving power decreases, but the response intensity increases; u. of_MIncrease ofThe axial half-width is reduced, that is, the axial resolution is improved, but the response intensity is reduced, and the side lobe suppression caused by defocus is more obvious.

By adopting the method, the detector should comprehensively consider the axial resolution, the transverse resolution and the energy loss, so that the performance of the detector is optimal.

The experimental verification system with the high spatial resolution product confocal scanning detection method has the following main device models and parameters:

as shown in FIG. 4, the measurement objective 4 in the experiment is preferably a 10X 0.25, 40X 0.65 and 60X 0.85 plano-achromatic microscope objective, respectively; the photodetectors 11 and 12 preferably employ a 2001 photoelectric receiver, manufactured by NEWFOCUS, USA, with a saturation power of 10mW and a maximum adjustable gain of 10⁴Minimum noise equivalent power of

The response at a wavelength of 632.8nm was 0.42A/W; the pinholes 9 and 10 are preferably PH-10 pinholes of NEWPORT, USA, which is made of ultra-thin molybdenum material, with pore size of 10 μm and thickness of 15.24 μm; the driver of the micro-displacement workbench 17 preferably adopts a large-range and high-stability Picoottor micro-displacement driver produced by NEWFOCUS company in America, and is matched with a flexible hinge workbench with the reduction ratio of 5: 1 to form a nano-scale micro-motion calibration system, and each driving pulse of the Picoottor micro-displacement driver can enable the micro-displacement workbench 17 to obtain the feeding of 2 nm; the axial tracking and positioning of the measuring objective 4 preferably adopts a fiber objective micro-positioning device produced by German PI company, which comprises a piezoelectric ceramic driver 20, a displacement sensor 19, an axial driving mechanism and the like, the driving resolution is 10nm, the measuring range is 300 mu m, and the loading frequency response is 100 Hz.

The initial test result of the super-resolution performance of the high spatial resolution product confocal sensor measuring device based on the method of the invention is as follows:

the resolution characteristics of the system can be assessed by the standard steps associated with the Dimension3100 model atomic force microscope, DI, USA. The measured sample 5 is a standard step with the height of 100nm, the measuring objective 4 is an objective with the height of 60 multiplied by 0.85, the step is arranged on an objective table, the step is adjusted along the axial direction by a fine adjustment mechanism, so that an optical needle is focused on the surface of the step, the step is moved along the transverse direction vertical to the optical needle, the resolution of a micro-displacement workbench 17 is 2nm, the moving range is 12 mu m, the HP5528A dual-frequency laser interferometer is used for detecting the moving amount of the step, the resolution is 0.01 mu m, and a driving system is used for micro-moving the step by the feeding amount with the resolution of 0.01 mu m.

FIG. 11 shows the offset u_MThe confocal axial response curve is 5.21.

Fig. 12 shows the confocal step scan curve and the product confocal step scan curve, and the slope change of the jump region of the product confocal step scan curve is relatively large.

The embodiments and simulation effects of the present invention are described above with reference to the drawings, but the description should not be construed as limiting the scope of the present invention, which is defined by the appended claims, and any modifications made on the basis of the claims are intended to be within the scope of the present invention.

Claims

1. A high-spatial resolution product confocal scanning detection method for scanning and measuring the sample to be measured by using the product detection of double receiving light paths and double detectors of differential confocal microscopy includes such steps as passing the incident light beam through polarizing beam splitter, 1/4 wave plate, measuring objective lens to the sample to be measured, reflecting it by the sample to be measured, passing the light beam through measuring objective lens and 1/4 wave plate, polarizing beam splitter, dividing the reflected light beam into two paths, focusing one path by condenser lens, locating pinhole at the position in front of the condenser lens by M distance, locating detector behind the pinhole and measuring the convex-concave variation of the sample to be measuredNormalized intensity Curve I₁(v，u，u_M) The other path is focused by another condenser, another pinhole is positioned at the position of distance M behind the focal point of another condenser, another detector is positioned behind another pinhole and measures an intensity curve I reflecting the convex-concave change of the measured sample₂(v，u，-u_M) Wherein, the normalized axial distance corresponding to M is u_MU is an axial normalized optical coordinate, v is a transverse normalized optical coordinate, u_MFor normalizing the axial distance, the method is characterized in that:

(2) According to curve I_MCM(v，u，u_M) The magnitude of the intensity in a linear interval, or according to curve I_MCM(v，u，u_M) And reconstructing the surface appearance and the micro scale of the measured sample according to the position of the maximum intensity.

2. The confocal scanning detection method with high spatial resolution product according to claim 1, characterized in that: optimizing the distance u between a pinhole and its corresponding condenser focus_MCan reduce the half-height width of the product confocal axial response curve and improve the spatial resolution of the confocal microscopy technology_MThe full width at half maximum of the confocal axial response curve of the product and the focal point response intensity are jointly determined;

3. a high-spatial resolution product confocal scanning detection method for scanning and measuring the sample to be measured by using the product detection of double receiving light paths and double detectors of differential confocal microscopy includes such steps as using the incident light beam to pass through optical super-resolution device, polarizing spectroscope, 1/4 wave plate and measuring objective lens, incident it on the sample to be measured, reflecting it by the sample, passing through the measuring objective lens and 1/4 wave plate, incident it on the polarizing spectroscope, dividing the light beam reflected by the polarizing spectroscope into two paths, focusing one path by condenser lens, locating pinhole at the position of M distance before the condenser lens, locating detector at positionAfter the pinhole, the intensity curve I reflecting the convex-concave change of the sample to be measured is measured₁(v，u，u_M) The other path is focused by another condenser, another pinhole is positioned at the position of distance M behind the focal point of another condenser, another detector is positioned behind another pinhole and measures an intensity curve I reflecting the convex-concave change of the measured sample₂(v，u，-u_M) Wherein u is an axial normalized optical coordinate, v is a transverse normalized optical coordinate, u_MFor normalized axial distance, M corresponds to a normalized axial distance of u_MThe method is characterized in that:

(3) according to curve I_MCM(v，u，u_M) Magnitude of intensity in linear interval, or according to curve I_MCM(v，u，u_M) And reconstructing the surface appearance and the micro scale of the measured sample according to the position of the maximum intensity.

4. The confocal scanning detection method with high spatial resolution product according to claim 3, characterized in that: optimizing the distance u between the pinhole and the focus of the corresponding condenser lens when the optical super-resolution device is used for transverse super-resolution_MCan reduce the half-height width of the product confocal axial response curve and improve the spatial resolution of the confocal microscopy technology_MThe full width at half maximum of the confocal axial response curve of the product and the focal point response intensity are jointly determined;

5. the confocal scanning detection method with high spatial resolution product according to claim 3, characterized in that: the optical super-resolution device may be a phase type filter, an amplitude and phase hybrid filter, or a ring light shaping optical device.