CN111239153A - Axial differential dark field confocal microscopic measurement device and method thereof - Google Patents

Abstract

The invention discloses an axial differential dark field confocal microscope measurement device and a method thereof. The device comprises an annular light illumination module, an annular light scanning module and a differential confocal detection module; Effectively separate the reflected signal and scattered signal of the sample, and obtain the three-dimensional distribution information of nano-scale subsurface cracks, bubbles and other defects; through differential confocal detection, the sensitivity, linearity and signal-to-noise ratio of the measurement system in the axial direction are improved, which can significantly suppress the environment Common mode noise caused by state differences, fluctuations in light intensity of the light source, and electrical drift of the detector.

Description

Axial differential dark field confocal microscope measurement device and method

technical field

The invention relates to the technical field of optical precision measurement, in particular 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, surface topography measurement and sub-surface defect detection are required. At present, there is no equipment at home and abroad that can simultaneously achieve the above. Function.

Existing surface topography non-destructive measurement technologies at home and abroad mainly include: confocal microscopic measurement technology, white light interference microscopic measurement technology and zoom microscopic measurement technology. Among them, confocal microscopy measurement technology has the characteristics of wide applicability to measure samples and can measure complex sample structures compared with the other two technologies, so it is widely used in the field of industrial inspection. The 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 microscopy imaging technology. It generally has shortcomings such as 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 microscope measurement device with high measurement accuracy and a method thereof are problems that those skilled in the art need to solve urgently.

SUMMARY OF THE INVENTION

In view of this, the present invention provides an axial differential dark field confocal microscope measurement device and method thereof, which can simultaneously obtain the three-dimensional distribution information of nano-scale surface scratches, wear, sub-surface cracks, bubbles and other defects, and has both surface And the integrated detection function of sub-surface defects solves the defects of 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 microscope measurement device, comprising: a ring light illumination module, a ring light scanning module and a differential confocal detection module;

The annular light illumination module includes, in order according to the light propagation direction: a laser, a beam expander, a polarizer, a polarizing beam splitter, a quarter-wave plate, a conical lens and a plane reflector;

The annular light scanning module includes, in order according to the light propagation direction: a semi-reflective and semi-transparent film one, two-dimensional scanning galvanometer, a scanning lens, a tube lens and an objective lens;

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

The transmission light path unit includes in sequence according to the light propagation direction: diaphragm 1, polarizer 2, focusing lens 1, pinhole 1 and camera 1; the reflection light path unit includes in sequence according to the light propagation direction: diaphragm 2, polarizer 3 , focusing lens 2, pinhole 2 and camera 2;

Wherein, the polarizing beam splitting film is arranged correspondingly to the semi-reflective and semi-transparent film 1, and the semi-reflective and semi-transparent film 1 is arranged correspondingly to the transflective and semi-transparent film 2;

The light beam reflected from the polarizing beam splitting film is reflected and transmitted through the first semi-reflective film; the light beam transmitted through the first semi-reflective film is reflected and transmitted through the second semi-reflective film again.

Preferably, the combination of the axicon lens and the plane reflector shapes the Gaussian beam into a ring light with adjustable inner and outer diameters, and the beam expander placed at the front end of the optical path of the axicon lens is used to adjust the inner diameter of the ring light, The larger the output spot diameter of the beam expander, the larger the thickness of the annular light, and the smaller the inner diameter; the outer diameter of the annular light depends on the distance between the axicon and the plane reflector, and the longer the relative distance, the larger the outer diameter. ; The outer diameter of the Gaussian beam after being shaped into a ring light matches the entrance pupil of the objective lens.

Preferably, the working surface of the scanning lens is arranged at the front focal plane of the tube lens.

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

Preferably, the apertures of the apertures 1 and 2 are complementary to the inner diameter of the annular light, and the apertures 1 and 2 completely block the reflected light beam from the sample to be tested, and are only allowed to carry all The scattered light of the sample information to be tested enters the detection light path.

Preferably, in the transmission light path unit, the transmission light beam is focused away from the focal plane, passes through the pinhole, and is collected by the camera;

In the reflected light path unit, the reflected light beam is focused to a position close to the defocused plane, and is collected by the second camera through the second pinhole;

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

An axial differential dark field confocal microscopy measurement method, which specifically includes the following steps:

S1. The parallel laser beam emitted by the laser, after the beam diameter is enlarged by the beam expander, becomes linearly polarized light after passing through the polarizer, passes through the polarizing beam splitter, quarter-wave plate and conical lens in turn, and is reflected by the plane mirror ; The reflected beam is shaped into a ring beam after passing through the axicon again, and after passing through the quarter-wave plate again, the polarization direction changes by 90°, and is reflected by the polarizing beam splitter to the semi-reflective and semi-transparent film one; The light beam is reflected by the one- and two-dimensional scanning galvanometers of the semi-reflective and semi-transparent film, and is focused to the front focal plane of the tube mirror by the scanning lens. Ring light illumination for the sample to be tested;

S2. Control the deflection of the two-dimensional scanning galvanometer so that the focused spot is two-dimensionally scanned on the sample, and the directly reflected light and scattered light in the surface and sub-surface of the sample to be tested pass through the objective lens, the tube mirror, After the scanning lens and the two-dimensional scanning galvanometer, transmit the semi-reflective and semi-transparent film 1 to realize annular light scanning of the sample to be tested;

S3. The light beam incident from the transflective film 1 to the transflective film 2 is divided into two detection beams:

In the transmission light path, the light beam passes through the aperture 1, and the directly reflected light of the sample to be tested is blocked and filtered out, and the scattered light of the sample to be tested is sequentially focused to the place away from the focal plane through the polarizer 2 and the focusing lens 1, and passes through the Once the pinhole is collected by the camera;

In the reflected light path, the light beam passes through the second diaphragm, and the directly reflected light of the sample to be tested is blocked and filtered out, and the scattered light of the sample to be tested is sequentially focused by the third polarizer and the second focusing lens to a place close to the defocused plane, and passes through the The second pinhole is collected by the second camera; the differential confocal detection of the sample to be tested is completed;

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

As can be seen from the above technical solutions, compared with the prior art, the present invention provides an axial differential dark field confocal microscope measurement device, which has the following beneficial effects:

First, the device in the present invention uses the combination of an axicon lens and a flat reflector to shape the Gaussian beam into a ring beam with adjustable inner and outer diameters, and uses a ring light with a suitable aperture to illuminate and a complementary aperture to block detection to effectively separate the reflected signal from the sample. The scattering signal overcomes the deficiencies of the subsurface defects of the traditional confocal measurement samples, and realizes the nanoscale high-precision detection of the subsurface defects of high-performance optical components and MEMS components;

Second, the present invention scans the object to be measured by using the pre-focus and post-focus detection optical paths, and performs differential processing to carry out differential detection; the optical path layout and detection of differential confocal improves the axial sensitivity of the measurement system, Linearity and signal-to-noise ratio can significantly suppress common-mode noise caused by environmental state differences, fluctuations in light intensity of light sources, and electrical drift of detectors.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying 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. For those of ordinary skill in the art, other drawings can also be obtained according to the provided drawings without creative work.

1 is a schematic structural diagram of an axial differential dark field confocal microscope measurement device provided by the present invention;

In the picture: 1 laser, 2 beam expanders, 3 polarizers, 4 polarizing beam splitters, 5 quarter-wave plates, 6 cone lenses, 7 plane mirrors, 8 semi-reflective and semi-transparent films, 1 and 9 two-dimensional scanning Galvanometer, 10 Scanning Lenses, 11 Tube Lenses, 12 Objective Lenses, 13 Samples, 14 Transflective Films 2, 15 Apertures 1, 16 Polarizers 2, 17 Focusing Lenses 1, 18 Pinholes 1, 19 Cameras 1, 20 Aperture two, 21 polarizer three, 22 focusing lens two, 23 pinhole two, 24 camera two.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

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

The ring light illumination module includes, in order according to the light propagation direction: a laser 1, a beam expander 2, a polarizer 3, a polarizing beam splitter 4, a quarter wave plate 5, a conical lens 6 and a plane reflector 7;

The annular light scanning module sequentially includes: a semi-reflective and semi-transparent film 8, a two-dimensional scanning galvanometer 9, a scanning lens 10, a tube mirror 11 and an objective lens 12 according to the light propagation direction;

The differential confocal detection module includes: a semi-reflective and semi-transparent film II 14 and a detection optical path; the detection optical path includes a transmission optical path unit and a reflection optical path unit;

The transmission light path unit includes: diaphragm one 15, polarizer two 16, focusing lens one 17, pinhole one 18 and camera one 19 in sequence according to the light propagation direction; the reflection light path unit sequentially includes: diaphragm two 20, polarized light path unit according to the light propagation direction Film three 21, focusing lens two 22, pinhole two 23 and camera two 24;

Wherein the polarizing beam splitting film 4 is correspondingly arranged with the semi-reflective and semi-transparent film one 8, and the semi-reflective and semi-transparent film one 8 and the semi-reflective and semi-transparent film two 14 are correspondingly arranged;

The light beam reflected from the polarizing beam splitting film 4 is reflected and transmitted through the semi-reflective and semi-transparent film 1 8;

In order to further implement the above-mentioned technical scheme, the combination of the axicon lens 6 and the plane reflector 7 shapes the Gaussian beam into an annular light with adjustable inner and outer diameters, and the beam expander 2 placed at the front end of the optical path of the axicon lens 6 is used to adjust the inner diameter of the annular light, The larger the output spot diameter of the beam expander 2, the larger the thickness of the ring light, and the smaller the inner diameter; the outer diameter of the ring light depends on the distance between the axicon 6 and the plane mirror 7, the longer the relative distance, the larger the outer diameter; the Gaussian beam The outer diameter after shaping into a ring light matches the entrance pupil of the objective lens 12 to meet the observation requirements of the sample.

In order to further implement the above technical solution, the working surface of the scanning lens 10 is arranged at the front focal plane of the tube lens 11 .

In order to further implement the above technical solution, the sample to be tested 13 is disposed in front of the objective lens 12 , and the annular light is incident on the objective lens 12 and then focused on the sample to be tested 13 .

In order to further implement the above technical solution, the apertures of diaphragm one 15 and diaphragm two 20 are complementary to the inner diameter of the annular light, diaphragm one 15 and diaphragm two 20 completely block the reflected light beam from the sample 13 to be tested, and only the sample 13 to be tested is allowed to be carried The scattered light of the information enters the detection optical path, effectively separating the reflected signal and the scattered signal from the sample.

In order to further implement the above technical solution, in the transmission light path unit, the transmission light beam is focused away from the focal plane, and is collected by the camera one 19 through the pinhole one 18;

In the reflected light path unit, the reflected light beam is focused to a position close to the defocused plane, and is collected by the second camera 24 through the second pinhole 23;

The distance from the focal plane is located between the pinhole 1 18 and the camera 1 19 , and the close-to-focus plane is located between the focusing lens 22 and the pinhole 2 23 .

It should be noted:

The camera one 19 is placed close to the pinhole one 18; the camera two 22 is placed close to the pinhole two 23; due to the two optical path units of the reflection optical path and the transmission optical path, the device has an optical path layout of differential detection.

An axial differential dark field confocal microscopy measurement method, which specifically includes 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 1 3, and passes through the polarizing beam splitter 4, the quarter-wave plate 5 and the cone lens 6 in turn. , is reflected by the plane mirror 7; the reflected beam is shaped into a ring beam after passing through the cone lens 6 again, and after passing through the quarter-wave plate 5 again, the polarization direction changes by 90°, and is reflected by the polarizing beam splitting film 4 to the semi-reflective and semi-transparent Film one 8; the annular beam is reflected by the semi-reflective and semi-transparent film one 8 and the two-dimensional scanning galvanometer 9, and is focused by the scanning lens 10 to the front focal plane of the tube mirror 11, and the tube mirror 11 generates a ring-shaped parallel beam incident on the objective lens 12. A focused light spot is formed on the sample to be tested 13 to realize ring light illumination of the sample to be tested 13;

S2. Control the deflection of the two-dimensional scanning galvanometer 9 so that the focused spot is two-dimensionally scanned on the sample 13, and the directly reflected light and scattered light in the surface and sub-surface of the sample 13 to be tested pass through the objective lens 12, the tube mirror 11, and the scanning lens 10 in sequence After being connected with the two-dimensional scanning galvanometer 9, the semi-reflective and semi-permeable membrane-8 is transmitted to realize the annular light scanning of the sample to be tested 13;

S3. The light beam incident from the transflective film 1 8 to the transflective film 2 14 is divided into two detection beams:

In the transmission light path, the light beam passes through the aperture one 15, the direct reflection light of the sample to be tested 13 is blocked and filtered, and the scattered light of the sample to be tested 13 is successively focused to the place away from the focal plane through the polarizer two 16 and the focusing lens one 17, Collected by camera-19 through pinhole-18;

In the reflected light path, the light beam passes through the second diaphragm 20, the direct reflected light of the sample to be tested 13 is blocked and filtered, and the scattered light of the sample to be tested 13 is sequentially focused to the place close to the focal plane through the third polarizer 21 and the second focusing lens 22, It is collected by the camera two 24 through the pinhole two 23; the differential confocal detection of the sample to be tested 13 is completed;

S4. Move the sample to be tested 13 in the vertical direction, and perform lateral two-dimensional scanning of different axial positions of the sample to be tested 13 , so as to realize stereoscopic microscopic measurement of the sample to be tested 13 .

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments 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 the relevant part can be referred to the description of the method.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to 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 (7)

1. An axial differential dark field confocal microscopy device, comprising: the device comprises an annular light illumination module, an annular light scanning module and a differential confocal detection module;

the annular light illuminating module sequentially comprises the following components in the light propagation direction: the device comprises a laser (1), a beam expander (2), a polarizer I (3), a polarization splitting film (4), a quarter-wave plate (5), a cone lens (6) and a plane reflector (7);

the annular light scanning module sequentially comprises according to the light propagation direction: the device comprises a half-reflecting half-transparent film I (8), a two-dimensional scanning galvanometer (9), a scanning lens (10), a tube mirror (11) and an objective lens (12);

the differential confocal detection module comprises: a semi-reflecting and semi-permeable membrane II (14) and a detection light path; the detection light path comprises a transmission light path unit and a reflection light path unit;

the transmission light path unit sequentially comprises the following components according to the light propagation direction: the device comprises a diaphragm I (15), a polaroid II (16), a focusing lens I (17), a pinhole I (18) and a camera I (19);

the reflection light path unit sequentially comprises the following components according to the light propagation direction: a diaphragm II (20), a polarizing plate III (21), a focusing lens II (22), a pinhole II (23) and a camera II (24);

the polarization light splitting film (4) and the semi-reflecting and semi-permeable film I (8) are arranged correspondingly, and the semi-reflecting and semi-permeable film I (8) and the semi-reflecting and semi-permeable film II (14) are arranged correspondingly;

the light beam reflected from the polarization splitting film (4) is reflected and transmitted through the semi-reflecting and semi-transmitting film I (8); the light beams transmitted by the first transflective film (8) are reflected and transmitted by the second transflective film (14) again.

2. The axial differential dark-field confocal microscopy device according to claim 1, characterized in that the combination of the axicon lens (6) and the plane reflector (7) shapes the Gaussian beam into annular light with adjustable inner and outer diameters, the beam expander (2) placed at the front end of the optical path of the axicon lens (6) is used for adjusting the inner diameter of the annular light, the larger the diameter of the output light spot of the beam expander (2), the larger the thickness of the annular light, and the smaller the inner diameter; the size of the outer diameter of the annular light depends on the distance between the conical lens (6) and the plane reflector (7), and the outer diameter is larger when the relative distance is longer; the outer diameter of the Gaussian beam after being shaped into annular light is matched with the entrance pupil of the objective lens (12).

3. The axial differential dark-field confocal microscopy measurement device according to claim 1, characterized in that the scanning lens (10) working surface is arranged at the front focal plane of the tube lens (11).

4. An axial differential dark-field confocal microscopy apparatus as claimed in claim 1, characterized in that the sample (13) to be measured is arranged in front of the objective (12), and the ring light is focused on the sample (13) to be measured after entering the objective (12).

5. An axial differential dark-field confocal microscopy measurement device according to claim 4, characterized in that the aperture of the first diaphragm (15) and the second diaphragm (20) is complementarily matched to the inner diameter of the ring light, the first diaphragm (15) and the second diaphragm (20) completely block the reflected light beam from the sample (13) to be measured, and only the scattered light carrying the information of the sample (13) to be measured is allowed to enter the detection light path.

6. The axial differential dark-field confocal microscopy device according to claim 1,

in the transmission light path unit, the transmission light beam is focused to a position far away from a focal plane, passes through a pinhole I (18) and is collected by a camera I (19);

in the reflection light path unit, the reflected light beam is focused to a near defocusing plane and passes through a second pinhole (23) to be collected by a second camera (24);

the far focal plane is located between the first pinhole (18) and the first camera (19), and the near defocusing plane is located between the second focusing lens (22) and the second pinhole (23).

7. An axial differential dark-field confocal microscopy method based on the axial differential dark-field confocal microscopy device as claimed in any one of claims 1 to 6 is characterized by comprising the following steps:

s1, parallel laser beams emitted by a laser (1) are amplified through a beam expander (2), then are changed into linearly polarized light through a polarizer I (3), and are reflected by a plane reflector (7) after passing through a polarization splitting film (4), a quarter-wave plate (5) and a cone lens (6) in sequence; the reflected light beam is shaped into an annular light beam after passing through the conical lens (6) again, the polarization direction changes by 90 degrees after passing through the quarter-wave plate (5) again, and the annular light beam is reflected to a semi-reflecting and semi-transmitting film I (8) by the polarization splitting film (4); the annular light beam is reflected by the semi-reflecting and semi-permeable film I (8) and the two-dimensional scanning galvanometer (9), is focused to the front focal plane of the tube lens (11) through the scanning lens (10), and generates an annular parallel light beam through the tube lens (11) to enter the objective lens (12) to form a focusing light spot on the sample (13) to be measured, so that the annular light illumination of the sample (13) to be measured is realized;

s2, controlling the deflection of the two-dimensional scanning galvanometer (9) to enable a focusing light spot to perform two-dimensional scanning on a sample (13), wherein directly reflected light and scattered light in the surface and the subsurface of the sample (13) to be detected sequentially pass through the objective lens (12), the tube lens (11), the scanning lens (10) and the two-dimensional scanning galvanometer (9) and then transmit the semi-reflecting and semi-transmitting film I (8), so that annular light scanning of the sample (13) to be detected is realized;

s3, dividing the light beam incident to the semi-reflective and semi-transparent film II (14) from the semi-reflective and semi-transparent film I (8) into two detection light beams:

in a transmission light path, light beams pass through a first diaphragm (15), direct reflected light of the sample (13) to be detected is shielded and filtered, scattered light of the sample (13) to be detected is focused to a position far away from a focal plane through a second polarizing film (16) and a first focusing lens (17) in sequence, and is collected by a first camera (19) through a first pinhole (18);

in a reflection light path, a light beam passes through a second diaphragm (20), directly reflected light of the sample (13) to be detected is shielded and filtered, scattered light of the sample (13) to be detected is focused to a near defocusing plane through a third polarizing film (21) and a second focusing lens (22) in sequence, and is collected by a second camera (24) through a second pinhole (23); completing differential confocal detection of the sample (13) to be detected;

and S4, moving the sample (13) to be measured in the vertical direction, and performing transverse two-dimensional scanning on different axial positions of the sample (13) to be measured to realize the three-dimensional microscopic measurement of the sample (13) to be measured.

Images