CN111239155B - Axial differential dark field confocal microscopic measuring device and method thereof - Google Patents

Abstract

The invention discloses an axial differential dark field confocal microscopic measuring device and a method thereof, wherein the device comprises an annular light illumination module, an annular light scanning module and a differential confocal detection module; the three-dimensional distribution information of defects such as nano subsurface cracks, bubbles and the like is obtained by effectively separating a sample reflected signal and a scattering signal through illumination beam shaping and complementary aperture shielding detection; by differential confocal detection, the axial sensitivity, linearity and signal-to-noise ratio of the measurement system are improved, and common mode noise caused by environmental state difference, light source light intensity fluctuation, detector electrical drift and the like can be obviously restrained.

Description

Axial differential dark field confocal microscopic measurement device and method thereof

technical field

The invention relates to the technical field of optical precision measurement, and more specifically relates to an axial differential dark field confocal microscopic measurement device and a method thereof.

Background technique

High-performance optical components and micro-electromechanical components are the core components of modern high-end equipment. In order to ensure their processing quality and service reliability, it is necessary to perform surface topography measurement and sub-surface defect detection. At present, there is no equipment at home and abroad that can simultaneously achieve the above Function.

The existing non-destructive measurement technology of surface topography at home and abroad mainly includes: confocal microscopic measurement technology, white light interference microscopic measurement technology and zoom microscopic measurement technology. Compared with the other two techniques, the confocal microscopic measurement technology has the characteristics of wide applicability of measuring samples and the ability to measure complex sample structures, so it is widely used in the field of industrial testing. Non-destructive testing technologies for subsurface defects mainly include: laser modulation scattering technology, total internal reflection microscopy technology, optical coherence tomography technology, high-frequency scanning acoustic microscopy technology, and X-ray microscopic imaging technology. It generally has the disadvantages of low depth positioning accuracy, low signal-to-noise ratio, low detection efficiency, and limited detection samples.

Therefore, how to provide an axial differential dark-field confocal microscopic measurement device with high measurement accuracy and its method is an urgent problem to be solved by those skilled in the art.

Contents of the invention

In view of this, the present invention provides an axial differential dark-field confocal microscopic measurement device and its method, which can simultaneously obtain the three-dimensional distribution information of defects such as nanoscale surface scratches, wear and subsurface cracks, bubbles, etc. And the integrated detection function of subsurface defects, which solves the defects existing in various measurement technologies in the prior art.

In order to achieve the above object, the present invention adopts the following technical solutions:

An axial differential dark-field confocal microscopic measuring device, comprising: a ring light illumination module, a ring light scanning module and a differential confocal detection module;

According to the direction of light propagation, the ring light illumination module is as follows: a laser, a beam expander, a polarizer 1, a concave cone lens and a semi-reflective and semi-transparent film 1;

According to the light propagation direction, the ring-shaped light scanning module is: a two-dimensional scanning galvanometer, a scanning lens, a tube lens and an objective lens;

The differential confocal detection module includes: a semi-reflective and semi-permeable film 2 and a detection optical path; the detection optical path includes a transmission optical path unit and a reflection optical path unit;

The transmission optical path unit includes in order according to the direction of light propagation: a diaphragm 1, a polarizer 2, a focusing lens 1, a pinhole 1 and a camera 1;

The reflective optical path unit includes in sequence according to the direction of light propagation: a diaphragm 2, a polarizer 3, a focusing lens 2, a pinhole 2 and a camera 2;

Wherein the first semi-reflective and semi-permeable film is set correspondingly to the two-dimensional scanning vibrating mirror, and the first semi-reflective and semi-permeable film is set correspondingly to the second semi-reflective and semi-permeable film;

The beam transmitted through the first semi-reflective film reaches the two-dimensional scanning galvanometer, and the light beam reflected by the first semi-reflective film reaches the second semi-reflective film.

Preferably, the bottom angle α of the front and rear surfaces of the concave axicon is the same, and the outer diameter of the Gaussian beam shaped into a ring light matches the entrance pupil of the objective lens.

Preferably, the working surface of the scanning lens should be placed at the front focal plane of the tube lens.

Preferably, the sample to be measured is arranged in front of the objective lens, and the annular light is focused on the sample to be measured after incident on the objective lens.

Preferably, the apertures of the first stop and the second stop are complementary to the annular light aperture produced by the concave axicon, and the first stop and the second stop completely block the reflected beam from the sample to be measured, allowing only the sample to be tested to be carried The scattered light of the information enters the subsequent detection optical path.

Preferably, in the transmission optical path unit, the transmitted light beam is focused to a place close to the focal plane, passes through a pinhole and is collected by the camera;

In the reflective optical path unit, the reflected light beam is focused away from the focal plane, passed through the pinhole 2 and collected by the camera 2, and the device has an optical path layout of differential detection;

The near-focus plane is located between the focusing lens 1 and the pinhole 1, and the far-focus plane is located between the pinhole 2 and the camera 2.

A method for axial differential dark-field confocal microscopic measurement, specifically comprising the following steps:

S1. The parallel laser beam emitted by the laser, after being enlarged by the beam expander, becomes linearly polarized light after passing through the polarizer, and after passing through the concave axicon lens, the Gaussian beam is shaped into a ring beam; the linearly polarized ring beam transmits semi-reflective light The first transparent film is reflected by the two-dimensional scanning galvanometer and focused to the front focal plane of the tube mirror by the scanning lens. The circular parallel light beam is generated by the tube mirror and enters the objective lens to form a focused spot on the sample to be measured, so as to realize the The ring light illumination of the sample to be tested;

S2. Control the deflection of the two-dimensional scanning galvanometer so that the focused light spot performs two-dimensional scanning on the sample to be measured, and the scattered light and reflected light of the sample to be measured pass through the objective lens, the tube lens, and the The scanning lens and the two-dimensional scanning galvanometer are reflected by the semi-reflective and semi-transparent film to realize ring light scanning of the sample to be measured;

S3. The beam from the incident transflective film one to the transflective film two is divided into two detection beams:

In the transmission optical path, the light beam passes through the diaphragm 1, the direct reflection light of the sample to be measured is blocked and filtered, and the scattered light of the sample to be measured is focused to a place close to the focal plane through the polarizer 2 and the focusing lens 1 in turn, and passes through The pinhole is collected by the camera;

In the reflected light path, the light beam passes through the diaphragm 2, the direct reflected light of the sample to be measured is blocked and filtered, and the scattered light of the sample to be measured is focused to a place away from the focal plane through the polarizer 3 and the focusing lens 2 in sequence, and passes through The pinhole 2 is collected by the camera 2; the differential confocal detection of the sample to be tested is completed;

S4. Moving the sample to be tested in the vertical direction, performing horizontal two-dimensional scanning of different axial positions of the sample to be tested, and realizing stereomicroscopic measurement of the sample to be tested.

It can be seen from the above technical solutions that, compared with the prior art, the disclosure of the present invention provides an axial differential dark-field confocal microscopic measurement device, which has the following beneficial effects:

First, the present invention uses a concave axicon lens to shape the Gaussian beam into a ring beam, and utilizes ring light illumination with a suitable aperture and complementary aperture occlusion detection to effectively separate the sample reflection signal and scattering signal, overcoming the limitations of traditional confocal measurement of subsurface defects in samples Insufficient, to realize nanoscale high-precision detection of subsurface defects of high-performance optical components and micro-electromechanical components;

Second, the present invention utilizes the pre-focus and post-focus detection optical paths to scan the measured object, and performs differential detection for differential processing. The optical path layout and detection of differential confocal improve the axial sensitivity, linearity and signal-to-noise ratio of the measurement system, and can significantly suppress common-mode noise caused by environmental state differences, light intensity fluctuations of the light source, and electrical drift of the detector.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

FIG. 1 is a schematic structural diagram of an axial differential dark-field confocal microscopic measurement device provided by the present invention.

In the figure: 1 laser, 2 beam expander, 3 polarizer 1, 4 concave cone lens, 5 transflective film 1, 6 two-dimensional scanning galvanometer, 7 scanning lens, 8 tube mirror, 9 objective lens, 10 sample, 11 semi-reflective film 2, 12 aperture 1, 13 polarizer 2, 14 focus lens 1, 15 pinhole 1, 16 camera 1, 17 aperture 2, 18 polarizer 3, 19 focus lens 2, 20 pinhole Two, 21 cameras Two.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The embodiment of the present invention discloses an axial differential dark field confocal microscopic measurement device, comprising: a ring light illumination module, a ring light scanning module and a differential confocal detection module;

According to the direction of light propagation, the ring light illumination module is as follows: laser 1, beam expander 2, polarizer 3, concave cone lens 4 and transflective film 5;

According to the light propagation direction, the ring light scanning module is: two-dimensional scanning galvanometer 6, scanning lens 7, tube lens 8 and objective lens 9;

The differential confocal detection module includes: a semi-reflective and semi-permeable film 11 and a detection light path; the detection light path includes a transmission light path unit and a reflection light path unit;

The transmission optical path unit includes in order according to the direction of light propagation: a diaphragm one 12, a polarizer two 13, a focusing lens one 14, a pinhole one 15 and a camera one 16;

The reflective optical path unit includes in order according to the direction of light propagation: stop 2 17, polarizer 3 18, focusing lens 2 19, pinhole 2 20 and camera 2 21;

Wherein the semi-reflective and semi-permeable film one 5 and the two-dimensional scanning vibrating mirror 6 are correspondingly arranged, and the semi-reflective and semi-permeable film one 5 and the semi-reflective and semi-permeable film two 11 are correspondingly arranged;

The light beam transmitted through the first half-reflective film 5 reaches the two-dimensional scanning vibrating mirror 6 , and the light beam reflected by the first half-reflective film 5 reaches the second half-transparent film 11 .

In order to further implement the above-mentioned technical solution, the bottom angle α of the front and rear surfaces of the concave axicon 4 is the same, and the outer diameter of the Gaussian beam shaped into a ring light matches the entrance pupil of the objective lens 9 .

In order to further implement the above technical solution, the working surface of the scanning lens 7 should be placed at the front focal plane of the tube lens 8 .

In order to further implement the above technical solution, the sample 10 to be tested is arranged in front of the objective lens 9 , and the annular light is incident on the objective lens 9 and then focused on the sample 10 to be tested.

In order to further implement the above-mentioned technical scheme, the apertures of diaphragm one 12 and diaphragm two 17 are complementary to the annular light aperture produced by the concave axicon lens 4, and diaphragm one 12 and diaphragm two 17 completely block the reflected light beam from the sample 10 to be measured, Only the scattered light carrying the information of the sample 10 to be tested is allowed to enter the subsequent detection optical path, effectively separating the reflected signal and the scattered signal from the sample to be tested.

In order to further implement the above-mentioned technical solution, in the transmission optical path unit, the transmission light beam is focused to a place close to the focal plane, passes through the pinhole one 15 and is collected by the camera one 16;

In the reflective optical path unit, the reflected light beam is focused away from the focal plane, passes through the pinhole 20 and is collected by the camera 2 21, and the device has a differential detection optical path layout;

The close focal plane is located between the first focusing lens 14 and the first pinhole 15 , and the farther focal plane is located between the second pinhole 20 and the second camera 21 .

It should be noted:

Camera 1 16 is placed close to pinhole 1 15; camera 2 21 is placed close to pinhole 2 20; since it has two optical path units, the reflected optical path and the transmitted optical path, the device has an optical path layout for differential detection.

A method for axial differential dark-field confocal microscopic measurement, specifically comprising the following steps:

S1. The parallel laser beam emitted by the laser 1 is enlarged by the beam expander 2, and then becomes linearly polarized light after passing through the polarizer 1 3. After passing through the concave axicon lens 4, the Gaussian beam is shaped into a ring beam; the linearly polarized ring beam Transmitting semi-reflective and semi-permeable membrane-5, reflected by the two-dimensional scanning galvanometer 6, focusing on the front focal plane of the tube mirror 8 through the scanning lens 7, and generating a ring-shaped parallel beam incident on the objective lens 9 through the tube mirror 8, on the sample 10 to be tested Form a focused spot to realize the ring light illumination of the sample 10 to be tested;

S2. Control the deflection of the two-dimensional scanning galvanometer 6 so that the focused spot is scanned two-dimensionally on the sample 10 to be measured, and the scattered light and reflected light of the sample 10 to be measured pass through the objective lens 9, the tube mirror 8, the scanning lens 7 and the two-dimensional scanning in sequence The vibrating mirror 6 is reflected by the semi-reflective and semi-transparent membrane-5 to realize ring light scanning of the sample 10 to be tested;

S3. The light beam incident on semi-reflective and semi-permeable film 1 5 and incident on semi-reflective and semi-permeable film 2 11 is divided into two detection beams:

In the transmission optical path, the light beam passes through the diaphragm one 12, the direct reflection light of the sample 10 to be tested is blocked and filtered, and the scattered light of the sample 10 to be tested is focused to a place close to the focal plane through the polarizer two 13 and the focusing lens one 14 in turn, Collected by camera 16 through pinhole 15;

In the reflected optical path, the light beam passes through the aperture two 17, the direct reflection light of the sample 10 to be tested is blocked and filtered, and the scattered light of the sample 10 to be tested is focused to a place away from the focal plane through the polarizer three 18 and the focusing lens two 19 in turn, Collected by camera 2 21 through pinhole 2 20; complete differential confocal detection of sample 10 to be tested;

S4. Move the sample 10 to be tested in the vertical direction, and perform horizontal two-dimensional scanning of different axial positions of the sample 10 to be tested, so as to realize stereomicroscopic measurement of the sample 10 to be tested.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other. As for the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and for relevant details, please refer to the description of the method part.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (5)

1. An axial differential dark-field confocal microscopic measurement device, comprising: a ring light illumination module, a ring light scanning module and a differential confocal detection module; According to the light propagation direction, the ring light illumination module is as follows: laser (1), beam expander (2), polarizer one (3), concave axicon lens (4) and transflective film one (5); The ring-shaped light scanning module is sequentially arranged according to the direction of light propagation: a two-dimensional scanning galvanometer (6), a scanning lens (7), a tube lens (8) and an objective lens (9); The differential confocal detection module includes: a semi-reflective and semi-permeable membrane two (11) and a detection optical path; the detection optical path includes a transmission optical path unit and a reflection optical path unit; The transmission optical path unit includes in order according to the light propagation direction: diaphragm one (12), polarizer two (13), focusing lens one (14), pinhole one (15) and camera one (16), and the transmitted light beam is focused To the place close to the focal plane, pass through the pinhole one (15) and be collected by the camera one (16); The reflective optical path unit includes in order according to the light propagation direction: diaphragm two (17), polarizer three (18), focusing lens two (19), pinhole two (20) and camera two (21), the reflected light beam is focused To a place away from the focal plane, through the second pinhole (20) and collected by the second camera (21), the device has an optical path layout for differential detection; Wherein said transflective membrane one (5) and said two-dimensional scanning vibrating mirror (6) are arranged correspondingly, said transflective membrane one (5) and said transflective membrane two (11) correspond set up; The light beam transmitted through the transflective membrane one (5) reaches the two-dimensional scanning vibrating mirror (6), and the light beam reflected by the transflective membrane one (5) reaches the semireflective membrane two (11); The apertures of diaphragm one (12) and diaphragm two (17) are complementary to the annular light aperture produced by the concave axicon lens (4), and diaphragm one (12) and diaphragm two (17) completely block light from the sample to be measured (10 ), only allow the scattered light carrying the information of the sample to be measured (10) to enter the subsequent detection optical path; The close focus plane is located between the focusing lens one (14) and the pinhole one (15), and the far focus plane is located between the pinhole two (20) and the camera two (21) between. 2. A kind of axial differential dark field confocal microscopic measuring device according to claim 1, is characterized in that, the base angle α of the front and rear surfaces of the concave aconic lens (4) is the same, and the Gaussian beam is shaped into a ring light. The outer diameter matches the entrance pupil of the objective lens (9). 3. An axial differential dark-field confocal microscopic measurement device according to claim 1, characterized in that the working surface of the scanning lens (7) should be placed at the front focal plane of the tube lens (8). 4. A kind of axial differential dark field confocal microscopic measurement device according to claim 1, characterized in that, the sample to be measured (10) is arranged in front of the objective lens (9), and the annular light is incident on the objective lens (9) and focus on the sample to be tested (10). 5. An axial differential dark-field confocal microscopic measurement method, based on the axial differential dark-field confocal microscopic measurement device according to any one of claims 1 to 4, characterized in that it specifically comprises the following steps: S1. The parallel laser beam emitted by the laser (1), after the beam diameter is enlarged by the beam expander (2), becomes linearly polarized light through the polarizer (3), and the Gaussian beam is shaped after passing through the concave axicon lens (4). It is an annular light beam; the linearly polarized annular light beam is transmitted through the semi-reflective and semi-transparent film one (5), reflected by the two-dimensional scanning galvanometer (6), focused to the front focal plane of the tube mirror (8) by the scanning lens (7), and passed through the The tube mirror (8) produces an annular parallel light beam incident on the objective lens (9), forming a focused spot on the sample to be measured (10), realizing ring light illumination of the sample to be measured (10); S2. Control the deflection of the two-dimensional scanning galvanometer (6) so that the focused spot performs two-dimensional scanning on the sample to be tested (10), and the scattered light and reflected light of the sample to be tested (10) pass through the The objective lens (9), the tube mirror (8), the scanning lens (7) and the two-dimensional scanning vibrating mirror (6) are reflected by the semi-reflective and semi-permeable film one (5), realizing the Ring light scanning of the sample to be tested (10); S3. The light beam incident on the semi-reflective and semi-permeable film two (11) from the semi-reflective and semi-permeable film one (5) is divided into two detection beams: In the transmitted light path, the light beam passes through the diaphragm one (12), the direct reflection light of the sample to be measured (10) is blocked and filtered, and the scattered light of the sample to be measured (10) passes through the polarizer two (13) and Focusing lens one (14) is focused to a place close to the focal plane, and is collected by camera one (16) through pinhole one (15); In the reflected optical path, the light beam passes through the aperture two (17), the direct reflected light of the sample to be measured (10) is blocked and filtered, and the scattered light of the sample to be measured (10) passes through the polarizer three (18) and The second focusing lens (19) is focused away from the focal plane, and is collected by the second camera (21) through the second pinhole (20); the differential confocal detection of the sample to be measured (10) is completed; S4. Move the sample to be tested (10) in the vertical direction, perform horizontal two-dimensional scanning of different axial positions of the sample to be tested (10), and realize stereoscopic microscopic measurement of the sample to be tested (10) .

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