CN113189757A - Laser scanning micro-measuring device and method thereof - Google Patents
Laser scanning micro-measuring device and method thereof Download PDFInfo
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- CN113189757A CN113189757A CN202110599094.9A CN202110599094A CN113189757A CN 113189757 A CN113189757 A CN 113189757A CN 202110599094 A CN202110599094 A CN 202110599094A CN 113189757 A CN113189757 A CN 113189757A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B21/00—Microscopes
- G02B21/0004—Microscopes specially adapted for specific applications
- G02B21/002—Scanning microscopes
- G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
- G02B21/0036—Scanning details, e.g. scanning stages
- G02B21/0048—Scanning details, e.g. scanning stages scanning mirrors, e.g. rotating or galvanomirrors, MEMS mirrors
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B21/00—Microscopes
- G02B21/0004—Microscopes specially adapted for specific applications
- G02B21/002—Scanning microscopes
- G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
- G02B21/0032—Optical details of illumination, e.g. light-sources, pinholes, beam splitters, slits, fibers
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B21/00—Microscopes
- G02B21/0004—Microscopes specially adapted for specific applications
- G02B21/002—Scanning microscopes
- G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
- G02B21/008—Details of detection or image processing, including general computer control
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- G—PHYSICS
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B21/00—Microscopes
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B21/00—Microscopes
- G02B21/36—Microscopes arranged for photographic purposes or projection purposes or digital imaging or video purposes including associated control and data processing arrangements
- G02B21/362—Mechanical details, e.g. mountings for the camera or image sensor, housings
Abstract
The invention relates to a laser scanning microscopic measuring device and a method, wherein a semi-reflecting and semi-transmitting mirror is arranged on an output light path of a laser, a galvanometer and a scanning objective lens are sequentially arranged on a reflecting light path of the semi-reflecting and semi-transmitting mirror, and a detection module is arranged on a transmitting light path; the laser emits laser, the laser is incident into a vibrating mirror through a semi-reflecting and semi-transmitting mirror, the vibrating mirror controls the laser to deflect in two dimensions, the laser is focused on a sample on a three-dimensional displacement table after being scanned by an objective lens, the laser is reflected after being incident into the sample, returns to the scanning objective lens and the vibrating mirror, and then enters a detection module after passing through the semi-reflecting and semi-transmitting mirror; the detection module acquires images under different X-Y-Z coordinates, a single or a plurality of CCD elements are used as virtual pinholes, the light intensity of the virtual pinhole area with the maximum light intensity in each image is acquired, the light intensity values under different X-Y-Z coordinates are acquired, the Z coordinate corresponding to the maximum light intensity under any X-Y coordinate is acquired, the depth distribution of the X-Y plane is acquired, and the surface appearance information of scratches and roughness is measured.
Description
Technical Field
The invention relates to a laser scanning microscopic measuring device and a method thereof.
Background
The Handbook of Image and Video Processing (Second Edition) chapter 10, focal microscope page 1293, page 4 of laser scanning Confocal microscopy, and page 2 of laser scanning Confocal microscopy all disclose optical path diagrams of laser scanning Confocal microscopy; page 4 of the laser scanning confocal microscope technology summarizes that "in recent decades, the optical components of the optical microscope have not changed much"; the brief introduction of the instrument performance of each company in chapter 1, section 5 of the laser scanning confocal microscopy, the optical components of the laser scanning confocal microscope all include a photomultiplier tube, a detection pinhole, a laser and a light source pinhole. In order to improve the longitudinal resolution, the detection pinhole is small and easy to cause diffraction, and different object points of a sample have deviation on the image point of the detection surface of the photomultiplier tube, but the position of the detection pinhole is fixed, so that the object point on the axis and the object point on the paraxial axis have deviation.
The application adopts a high-frame-rate area array camera which is rapidly developed in recent years, combines a high-gain microchannel plate imaging detector to form a detection module, and replaces a photomultiplier tube with high sensitivity and quick response time; and a single or a plurality of CCD elements of the area array camera are used as virtual pinholes to replace detection pinholes, for example, the light intensity of the CCD element with the maximum light intensity on each frame image and the light intensity detected by a photomultiplier tube behind the pinhole are used to replace the light intensity detected by the photomultiplier tube behind the pinhole, thereby avoiding the deviation of paraxial and on-axis points and avoiding diffraction after the detection pinholes are cancelled. The light spot behind the light source pinhole is small, the energy utilization rate is low, and the light source pinhole is small and is easy to cause diffraction; the beam expander is adopted to replace a light source pinhole, no light source pinhole diffraction is avoided, the energy utilization rate of the laser is high, the size of a light spot focused behind the objective lens is reduced, the transverse precision is improved, and the highest precision after Gaussian light focusing is 0.64 lambda/NA, which is 1.22 lambda/NA higher than that of a common optical microscope. The precision of the improved light source is equivalent to the laser scanning Confocal transverse resolution of 0.56 lambda/NA in the literature (Handbook of Image and Video Processing, chapter 10, 9, focal micro scope, page 1293).
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a laser scanning micro-measurement device and a method thereof.
The purpose of the invention is realized by the following technical scheme:
the laser scanning micro-measuring device is characterized in that: the three-dimensional displacement platform comprises a laser, a semi-reflecting and semi-transmitting mirror, a vibrating mirror, a scanning objective lens, a three-dimensional displacement platform and a detection module, wherein the semi-reflecting and semi-transmitting mirror is arranged on an output light path of the laser, the vibrating mirror and the scanning objective lens are sequentially arranged on a reflection light path of the semi-reflecting and semi-transmitting mirror, and the detection module is arranged on a transmission light path; the laser emits laser, the laser is incident into the vibrating mirror through the semi-reflecting and semi-transparent mirror, the vibrating mirror controls the laser to deflect in two dimensions, the laser is focused on a sample on the three-dimensional displacement table after being scanned by the objective lens, the laser is reflected after being incident into the sample, returns to the scanning objective lens and the vibrating mirror, and enters the detection module after passing through the semi-reflecting and semi-transparent mirror.
Further, in the laser scanning micro-measurement apparatus, the three-dimensional displacement stage includes a two-dimensional displacement stage for two-dimensional movement of the X axis and the Y axis and a piezoelectric ceramic Z-axis unit connected thereto for up-and-down movement of the Z axis; the piezoelectric ceramic Z-axis unit moves a sample along the Z axis, the galvanometer controls the laser to scan the X-Y surface of the sample under each Z coordinate, the detection module acquires images under different X-Y-Z coordinates, a single or a plurality of CCD elements are used as virtual pinholes, the light intensity of the virtual pinhole area with the maximum light intensity in each image is acquired, the light intensity values under different X-Y-Z coordinates are acquired, the Z coordinate corresponding to the maximum light intensity under any X-Y coordinate is acquired, the depth distribution of the X-Y plane is acquired, and the surface morphology information of scratches and roughness is measured.
Further, foretell laser scanning micro-measuring device, wherein, the laser instrument is installed on the laser instrument mounting bracket, the laser instrument mounting bracket is fixed in on the vertical screw rod, install on first adapter plate on the vertical screw rod, the beam expanding mirror is installed on first adapter plate through the adapter ring, vertical screw rod is fixed on the second adapter plate, the second adapter plate is fixed on cage quadrature steering plate, cage quadrature steering plate is installed on horizontal screw rod, the half-reflecting half-transparent mirror is installed on horizontal screw rod, the one end of horizontal screw rod connects with the mirror that shakes soon, scanning objective connects with the mirror that shakes soon, the third adapter plate is installed to the other end of horizontal screw rod, it fixes on the third adapter plate to detect the module.
Further, in the laser scanning micro-measurement apparatus, the detection module includes a microchannel plate imaging detector for laser amplification, an optical fiber plate for transmitting the signal amplified by the microchannel plate imaging detector to the high frame rate area-array camera without offset, and the high frame rate area-array camera, which are sequentially arranged.
Further, the laser scanning micro-measuring device, wherein the high frame rate area array camera is fixed on the camera frame, the camera frame is fixed on the cage plate adapter through a screw, the cage plate adapter is provided with a cavity for accommodating the optical fiber plate, the microchannel plate imaging detector, the first snap ring, the protective lens and the second snap ring, the optical fiber plate is located between the high frame rate area array camera and the microchannel plate imaging detector and abuts against the optical fiber plate, the microchannel plate imaging detector is fixed by the first snap ring, the protective lens is placed in front of the first snap ring, and the protective lens is fixed by the second snap ring.
Further, in the above laser scanning micro-measurement device, the high frame rate area-array camera is an area-array camera with MHz frame rate, and the micro-channel plate imaging detector is a signal amplifier 106～107A microchannel plate imaging detector.
Furthermore, in the laser scanning micro-measurement device, the laser can output Gaussian distribution and has a wavelength of 350-650 nm.
Further, the laser scanning micro-measuring device is characterized in that a beam expanding lens is arranged on an output light path of the laser.
The invention relates to a laser scanning microscopic measuring method.A laser emits laser which is incident into a vibrating mirror through a semi-reflecting and semi-transmitting mirror, the vibrating mirror controls the two-dimensional deflection of the laser, the laser is focused on a sample on a three-dimensional displacement table after passing through a scanning objective, the laser is reflected after being incident into the sample, the laser returns to the scanning objective and the vibrating mirror in the original path, and enters a detection module after passing through the semi-reflecting and semi-transmitting mirror;
moving the sample along the Z axis, controlling the laser to scan the X-Y surface of the sample by the galvanometer under each Z coordinate, acquiring images under different X-Y-Z coordinates by the detection module, taking a single or a plurality of CCD elements as virtual pinholes, acquiring the light intensity of the virtual pinhole area with the maximum light intensity in each image, acquiring the light intensity values under different X-Y-Z coordinates, acquiring the Z coordinate corresponding to the maximum light intensity under any X-Y coordinate, obtaining the depth distribution of the X-Y surface, and measuring the surface morphology information of scratches and roughness.
Furthermore, in the above laser scanning micro-measurement method, the laser outputs laser with Gaussian distribution, and the beam waist radius w passes through the vibrating mirror and the scanning objective lens0Expressed as:
in the formula, lambda and w1Respectively representing the wavelength and the size of an incident light spot before the objective lens is scanned; rayleigh distance z0＝πw0 2Lambda,/lambda; radius of lumbar macula w at distance zzIs represented as follows:
wherein z is-zcCoordinate position of beam waist, coordinate z-axis along laser propagation direction, spot size w at beam waistzMinimum; the focal length of the scanning objective lens is f, the image distance is far larger than f by adopting the image distance of 200mm, and the object distance is approximately equal to f by utilizing a Gaussian imaging formula; magnification of the objective lens is MAThe size of a light spot on a high-frame-rate area-array camera of the detection module is approximate to M (200/f)Awz；
The size of a CCD element of the high frame rate area-array camera is S, and x and y represent coordinates on a camera surface; only moving the z-axis, the power measured by the image space is in direct proportion to the laser power of the object space, and the total power of the image space is P0(ii) a When the object coordinate is z, the peak light intensity is IzPower P incident on the center of the spot on the cameraS(z) is represented by:
when the virtual pinhole size S is sufficiently large, the power P detected on the cameraS(z) always equals the total power P of the image space0Independent of the coordinate z; when using single or multiple camera CCD elements, PS(z) as a function of the z-axis, w when the beam waist is at the sample surfacezMinimum, PS(z) maximum, height information of the point is detected.
Compared with the prior art, the invention has obvious advantages and beneficial effects, and is embodied in the following aspects:
the invention adopts single or multiple CCD element points of the area-array camera as virtual pinholes, thereby avoiding errors caused by pinhole edge diffraction.
Secondly, a scanning galvanometer is adopted, so that the measurement error caused by sample shaking when the platform moves is avoided; an area-array camera with a high frame rate is combined with a microchannel plate imaging detector to form a detection module, so that the measurement precision during galvanometer scanning is improved; adopting the light intensity of the single or a plurality of CCD elements with the maximum light intensity on each frame image as the light intensity corresponding to the corresponding object point; the virtual pinhole formed by a single or a plurality of CCD elements changes along with the change of the position of the object point, and the light intensity measured by the detector with the virtual pinhole is always the light intensity of the central area of the beam waist of the Gaussian beam;
the beam expander is adopted to replace a light source pinhole, diffraction of the light source pinhole is avoided, and the energy utilization rate of the laser is high.
Fourthly, the light source has small pinholes, the light behind the pinholes is approximately uniformly distributed, the light spot size before the detection module is changed but the light intensity is uniform under different longitudinal positions, and the relative light intensity behind the detection pinholes is equal to the ratio of the area of the detection pinholes to the area of the light spots; the laser with Gaussian distribution changes the size of a light spot in front of the detection module at different longitudinal positions, the light intensity is weak at the center and the edge of the light spot, and the relative light intensity behind the virtual detection pinhole is equal to the light intensity integral in the area of the pinhole divided by the light intensity integral in the area of the light spot; under the same pinhole area, the light intensity ratio behind the virtual detection pinhole is greater than the light intensity ratio behind the actual pinhole, therefore the signal intensity and the signal-to-noise ratio of module are surveyed to virtual pinhole are higher.
The micro-channel plate imaging detector, the optical fiber plate and the high frame rate area array camera form a detection module, so that a pinhole and a photomultiplier can be replaced, the cost is lower, and the stability is better; the microchannel plate imaging detector converts optical signals into electric signals, electrons form images on the fluorescent screen, and the optical fiber plate transmits the images on the fluorescent screen to the camera; the optical fiber optical plate has small image distortion and no vignetting.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1: the structure of the device is shown schematically;
FIG. 2 a: a schematic structural diagram of the detection module;
FIG. 2 b: FIG. 2a is a schematic sectional view A-A;
FIG. 3: the invention measures the surface appearance photo of the glass with scratches;
FIG. 4: normalizing laser power and relative axial position (axial position divided by Rayleigh distance z) for different virtual pinhole sizes0) Wherein: a-the virtual pinhole size is equal to the beam waist diameter multiplied by the magnification, b-the virtual pinhole size is equal to the beam waist diameter;
FIG. 5: and normalizing the relation graph of the laser power and the axial position under the scanning lenses with different focal lengths.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present invention, the directional terms and the sequence terms, etc. are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.
The invention adopts a high frame rate area array camera, combines a high gain micro-channel plate imaging detector and an optical fiber plate to form a detection module, and uses a single or a plurality of CCD elements of the area array camera as a virtual pinhole, for example, the light intensity of the CCD element with the maximum light intensity on each frame image is used to avoid the deviation of paraxial and on-axis points, and the diffraction after the detection of the pinhole is cancelled is avoided. The light spot behind the light source pinhole is small, the energy utilization rate is low, and the light source pinhole is small and is easy to cause diffraction; by adopting the beam expander, no light source pinhole diffraction can be avoided, the energy utilization rate of the laser is high, the size of a light spot focused behind the objective lens is reduced, the transverse precision is improved, and the highest precision of the focused Gaussian light is 0.64 lambda/NA, which is obviously superior to the precision of a common optical microscope by 1.22 lambda/NA.
As shown in fig. 1, the laser scanning micro-measuring device is characterized in that: the laser comprises a laser 201, a half-reflecting and half-transmitting mirror 205, a vibrating mirror 206, a scanning objective 207, a three-dimensional displacement table 208 and a detection module 210, wherein the laser 201 is a laser capable of outputting Gaussian distribution and with a wavelength of 350-650nm, a beam expander 212 and the half-reflecting and half-transmitting mirror 205 are sequentially arranged on an output light path of the laser 201, the vibrating mirror 206 and the scanning objective 207 are sequentially arranged on a reflection light path of the half-reflecting and half-transmitting mirror 205, and the detection module 210 is arranged on a transmission light path.
The three-dimensional displacement table 208 comprises a two-dimensional displacement table used for two-dimensional movement of an X axis and a Y axis and a piezoelectric ceramic Z-axis unit connected to the two-dimensional displacement table and used for up-and-down movement of a Z axis; the piezoelectric ceramic Z-axis unit moves a sample along the Z axis, the galvanometer 206 controls the X-Y surface of a laser scanning sample under each Z coordinate, the detection module 210 acquires images under different X-Y-Z coordinates, a single or a plurality of CCD elements are used as virtual pinholes, the light intensity of the virtual pinhole area with the maximum light intensity in each image is acquired, the light intensity values under different X-Y-Z coordinates are acquired, the Z coordinate corresponding to the maximum light intensity under any X-Y coordinate is acquired, the depth distribution of the X-Y plane is acquired, and the surface topography information of scratches and roughness is measured.
Laser 201 is installed on laser mounting bracket 200, laser mounting bracket 200 is fixed in on vertical screw 202, install on first adapter plate 211 on vertical screw 202, beam expander 212 is installed on first adapter plate 211 through the adapter ring, vertical screw 202 is fixed on second adapter plate 203, second adapter plate 203 is fixed on cage quadrature steering plate 204, cage quadrature steering plate 204 is installed on horizontal screw 213, half anti-half mirror 205 is installed on horizontal screw 213, horizontal screw 213's one end and the mirror 206 that shakes connect soon mutually, scanning objective 207 connects with the mirror 206 that shakes soon mutually, third adapter plate 209 is installed to horizontal screw 213's the other end, it fixes on third adapter plate 209 to detect module 210.
As shown in fig. 2a and 2b, the detection module 210 includes a microchannel plate imaging detector 311 for laser amplification, an optical fiber plate 312 for transmitting the signal amplified by the microchannel plate imaging detector to the high frame rate area-array camera without offset, and a high frame rate area-array camera 301, the high frame rate area-array camera 301 is an area-array camera with MHz frame rate, the microchannel plate imaging detector 311 is a signal amplification 106～107A multiple microchannel plate imaging detector; the high frame rate area-array camera 301 is fixed on the camera frame 303 through screws on the first screw hole 310 and the second screw hole 314The camera frame 303 is fixed on the cage plate adaptor 302 through a first screw 305, a second screw 306 and a third screw 307, the cage plate adaptor 302 is provided with a chamber for accommodating the fiber optic plate 312, the microchannel plate imaging detector 311, a first snap ring 308, a protection lens 309 and a second snap ring 304, the fiber optic plate 312 with zero working distance abuts against the high frame rate area array camera 301 and the microchannel plate imaging detector 311, the microchannel plate imaging detector 311 is fixed by the first snap ring 308, the protection lens 309 is placed in front of the first snap ring 308, and the protection lens 309 is fixed by the second snap ring 304 in front of the protection lens 309.
The laser 201 emits laser, the laser is incident into the vibrating mirror 206 through the half-reflecting half-transmitting mirror 205, the vibrating mirror 206 controls the two-dimensional deflection of the laser, the laser is focused on a sample on the three-dimensional displacement table 208 after passing through the scanning objective 207, the laser is reflected after being incident into the sample, the laser returns to the scanning objective 207 and the vibrating mirror 206 in the original path, and enters the detection module 210 after passing through the half-reflecting half-transmitting mirror 205; measuring to obtain 3D shape of the scratch, measuring roughness of the scratch area and periphery, and measuring maximum height value R of each point in the areapMinimum height values R of points of the regionvScratch peak to valley value equal to Rp–Rv；
Moving the sample along the Z axis, controlling the X-Y surface of the laser scanning sample by the galvanometer 206 under each Z coordinate, acquiring images under different X-Y-Z coordinates by the detection module 210, taking a single or a plurality of CCD elements as virtual pinholes, acquiring the light intensity of the virtual pinhole area with the maximum light intensity in each image, acquiring the light intensity values under different X-Y-Z coordinates, acquiring the Z coordinate corresponding to the maximum light intensity under any X-Y coordinate, namely the depth distribution of the X-Y plane, and measuring the surface appearance information of scratches and roughness;
the laser 201 outputs laser with Gaussian distribution, and the beam waist radius w passes through the vibrating mirror 206 and the scanning objective 2070Expressed as:
in the formula, lambda and w1Respectively representing the wavelength and the size of an incident light spot before the objective lens is scanned; rayleigh distance z0＝πw0 2Lambda,/lambda; radius of lumbar macula w at distance zzIs represented as follows:
wherein z is-zcCoordinate position of beam waist, coordinate z-axis along laser propagation direction, spot size w at beam waistzMinimum; the focal length of the scanning objective lens is f, the image distance is far larger than f by adopting the image distance of 200mm, and the object distance is approximately equal to f by utilizing a Gaussian imaging formula; magnification of the objective lens is MAThe size of the light spot on the high frame rate area-array camera of the detection module 210 is approximately M, which is 200/fAwz；
The size of a CCD element of the high frame rate area-array camera is S, and x and y represent coordinates on a camera surface; only moving the z-axis, the power measured by the image space is in direct proportion to the laser power of the object space, and the total power of the image space is P0(ii) a When the object coordinate is z, the peak light intensity is IzPower P incident on the center of the spot on the cameraS(z) is represented by:
when the virtual pinhole size S is sufficiently large, the power P detected on the cameraS(z) always equals the total power P of the image space0Independent of the coordinate z; when using single or multiple camera CCD elements, PS(z) as a function of the z-axis, w when the beam waist is at the sample surfacezMinimum, PS(z) maximum, detecting height information of the point; detected power ratio PS(z)/P0Decreases with decreasing virtual pinhole size S, which is equal to the beam waist diameter wzMultiplying by a magnification MAThen, the power behind the pinhole is equal to 98.2% of the total power; virtual pinhole size down to beam waist diameter wzTime to power ratio PS(z)/P0Decrease of power ratio PS(z)/P0Decreases with increasing magnification; when the magnification ratio M isAWhen the value is equal to 10, the value,power ratio PS(z)/P0The drop to 3.92%; when the magnification is equal to 20, the power ratio PS(z)/P0Down to 0.995%.
Laser scanning microscopy
Example 1
A405 nm laser 201 (Changchun new industry, photoelectric technology, Inc., model MDL-XS-405) with the maximum power of 200mW emits laser with the diameter of 1.2mm, the laser spot size is enlarged after passing through a beam expander 212 (Soranbo, model BE-02-05-A) with the variable magnification of 2-5 times, the laser is reflected into a vibrating mirror 206 through a semi-reflecting and semi-transmitting mirror 205, the vibrating mirror 206 controls the two-dimensional deflection of the laser, and the vibrating mirror with sensing measurement is adopted, so that the vibrating mirror reflector is allowed to work in a closed loop mode and can output vibrating mirror coordinates. After passing through the scanning objective 207, the sample is focused on a three-dimensional displacement table 208, the three-dimensional displacement table is composed of a two-dimensional displacement table and a piezoelectric ceramic Z-axis unit, the two-dimensional displacement table (Sorabo, model MLS203-1) realizes two-dimensional movement of an X axis and a Y axis, the piezoelectric ceramic Z-axis unit (Sorabo, model MZS500-E) realizes up-and-down movement of a Z axis, the maximum stroke is 500 mu m, and the resolution is 25 nm; the laser beam is reflected after being incident on the sample, returns to the scanning objective 207 and the galvanometer 206, and enters the detection module 210 after being transmitted through the half-reflecting and half-transmitting mirror 205.
The Image side laser is amplified by a microchannel plate imaging detector 311(dmphotonics, model number microchannel plate-IFP 25/2), and the fiber optic plate 312 (szphoson, model number FOP-DSP) transmits the signal amplified by the microchannel plate imaging detector to the High frame rate area-array camera 301 (model number ISIS, reference a 16Mfps 165kpixel background-amplified CCD, Evolution of High-Speed Image Sensors, a background-Illuminated Image Sensor with 200,000pixel Operating at 250,000frame per Second and An Image Sensor low frequency 100 background Frames at 1000000Frames _ s) without offset, and the High frame rate camera ISIS indexes are summarized as follows:
grayscale range, 10 bit;
wavelength range, 350-650 nm;
CCD element size 3.0 × 3.6 μm;
the size of the photosensitive chip is 15.6mm multiplied by 19.7mm, and the photosensitive chip is packaged in the component 301 by ceramic;
the frame rate can reach 16 MHz.
Laser scanning microscopic measurement, a two-dimensional galvanometer tests information such as three-dimensional appearance of a sample, and an incident light spot is smaller than the diameter of an entrance pupil of a scanning lens, for example, the incident light spot is half of the diameter of the entrance pupil, and the incident light is allowed to incline by half. The rotating speed of the galvanometer is high, and the measurement error caused by sample shaking in the moving process of the platform is avoided. The platform inertia is large, the acceleration and deceleration time is about 100ms, the light acceleration and deceleration time of the galvanometer is short, the scanning delay is usually less than 1ms, and the acceleration and deceleration time is reduced by adopting a galvanometer scanning mode.
Example 2: and measuring the scratch peak-valley value by laser scanning microscopy.
The piezoelectric ceramic moves by 20 μm in Z-axis displacement with a step size of 0.25 μm. And in each Z-axis coordinate, the surface of the glass sample is scanned by using a scanning objective lens with the focal length of 4mm, the single scanning breadth is 282.6 mu m multiplied by 210 mu m, and the scanning angles in the X-Y directions are respectively 4.0 degrees and 3.0 degrees. The photographs showing the surface topography of the scratch are shown in fig. 3, the maximum height value Rp of each point in the area is 2.65 μm, the minimum height value Rv of each point in the area is-2.72 μm, and the peak-to-valley value of the scratch is equal to Rp-Rv of 5.4 μm.
Example 3
According to P under different virtual pinhole sizesSThe normalized power versus axial position calculated by the (z) equation is shown in FIG. 4. The size of the virtual pinhole corresponding to the curve a and the curve b is respectively the magnification times of the scanning objective lens by the size of the beam waist and the size of the beam waist, and the half-height width of the curve a is larger than that of the curve b, so that the smaller the size of the virtual pinhole is, the higher the precision of the longitudinal Z axis is. However, the smaller the size, the lower the intensity, and the higher the amplification and the sufficient sensitivity of the detection module are required. The longitudinal precision is improved, and besides the size of the virtual pinhole is reduced, the longitudinal precision can also be realized by reducing the focal length of the scanning objective lens.
Example 4
Under different focal length scanning objective lens according to PSThe normalized power versus axial position calculated by the (z) equation is shown in FIG. 5. The galvanometer is fixed at an X-Y coordinate point, and the sample is moved through the piezoelectric ceramics to measure the laser power behind the virtual pinhole under different Z coordinates. The laser emits 1.2mm light spots which are expanded by 3 timesThe spot size after the beam mirror becomes 3.6 mm. The scanning objective lens multiple is increased from 50 times to 100 times, the focal length is reduced from 4mm to 2mm, and the half-height width is reduced from 1.3 μm to 0.31 μm. The resolution of an area-array camera with a 10bit gray scale is 1/1024-0.098%. When the size of a virtual pinhole of the 50-time objective lens is equal to the size of a single CCD element which is 3.0 mu m multiplied by 3.6 mu m, when the position is changed by 93nm, the normalized power is reduced to 98.0 percent, and the difference of 2.0 percent can be tested by an area array camera, so the longitudinal precision can reach 93 nm. When the size of a virtual pinhole of the 100-time objective lens is equal to the size of a single CCD element which is 3.0 mu m multiplied by 3.6 mu m, when the position is changed by 23nm, the normalized power is reduced to 98.0 percent, and therefore the longitudinal precision can reach 23 nm.
The invention adopts single or a plurality of CCD element points of the area-array camera as the virtual pinhole, thereby avoiding the error caused by the diffraction of the edge of the pinhole.
A scanning galvanometer is adopted, so that the measurement error caused by sample shaking when the platform moves is avoided; the area-array camera with high frame rate is combined with the micro-channel plate imaging detector to form a detection module, so that the measurement precision during scanning of the galvanometer is improved. Adopting the light intensity of the single or a plurality of CCD elements with the maximum light intensity on each frame image as the light intensity corresponding to the corresponding object point; the virtual pinhole formed by single or multiple CCD elements changes with the position of the object point, and the light intensity measured by the detector with the virtual pinhole is always the light intensity of the central area of the beam waist of the Gaussian beam.
The invention adopts the beam expander to replace a light source pinhole, avoids diffraction of the light source pinhole, and has high energy utilization rate of the laser.
The light source pinhole is small, the light behind the pinhole is approximately uniformly distributed, the light spot size before the detection module is changed but the light intensity is uniform under different longitudinal positions, and the relative light intensity behind the detection pinhole is equal to the ratio of the area of the detection pinhole to the area of the light spot; the laser with Gaussian distribution changes the size of a light spot in front of the detection module at different longitudinal positions, the light intensity is weak at the center and the edge of the light spot, and the relative light intensity behind the virtual detection pinhole is equal to the light intensity integral in the area of the pinhole divided by the light intensity integral in the area of the light spot; under the same pinhole area, the light intensity ratio behind the virtual detection pinhole is greater than the light intensity ratio behind the actual pinhole, therefore the signal intensity and the signal-to-noise ratio of module are surveyed to virtual pinhole are higher.
The micro-channel plate imaging detector, the optical fiber plate and the high-frame-rate area-array camera form a detection module, so that a pinhole and a photomultiplier can be replaced, the cost is lower, and the stability is better; the microchannel plate imaging detector converts optical signals into electric signals, electrons form images on the fluorescent screen, and the optical fiber plate transmits the images on the fluorescent screen to the camera; the image transmitted by the optical fiber optical plate has small distortion and no vignetting; compared with the lens, the overall image deflection transmitted by the optical fiber optical plate is small; the optical fiber plate is applied to an optical fingerprint module of a mobile phone, and accurately transmits a fingerprint image to a CMOS or CCD camera, so that the optical fiber plate is low in cost.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and shall be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Claims (10)
1. Laser scanning micro-measuring device, its characterized in that: the laser scanning device comprises a laser (201), a semi-reflecting and semi-transparent mirror (205), a galvanometer (206), a scanning objective (207), a three-dimensional displacement table (208) and a detection module (210), wherein the semi-reflecting and semi-transparent mirror (205) is arranged on an output light path of the laser (201), the galvanometer (206) and the scanning objective (207) are sequentially arranged on a reflection light path of the semi-reflecting and semi-transparent mirror (205), and the detection module (210) is arranged on a transmission light path; laser is emitted by a laser (201), the laser is incident into a vibrating mirror (206) through a semi-reflecting and semi-transparent mirror (205), the vibrating mirror (206) controls two-dimensional deflection of the laser, the laser is focused on a sample on a three-dimensional displacement table (208) after passing through a scanning objective lens (207), the laser is reflected after being incident into the sample, returns to the scanning objective lens (207) and the vibrating mirror (206), and enters a detection module (210) after passing through the semi-reflecting and semi-transparent mirror (205).
2. The laser scanning micro-measurement apparatus of claim 1, wherein: the three-dimensional displacement table (208) comprises a two-dimensional displacement table used for two-dimensional movement of an X axis and a Y axis and a piezoelectric ceramic Z-axis unit connected to the two-dimensional displacement table and used for up-and-down movement of a Z axis; the piezoelectric ceramic Z-axis unit moves a sample along the Z axis, the galvanometer (206) controls the laser to scan the X-Y surface of the sample under each Z coordinate, the detection module (210) acquires images under different X-Y-Z coordinates, a single or a plurality of CCD elements are used as virtual pinholes, the light intensity of the virtual pinhole area with the maximum light intensity in each image is acquired, the light intensity values under different X-Y-Z coordinates are acquired, the Z coordinate corresponding to the maximum light intensity under any X-Y coordinate is acquired, the depth distribution of the X-Y plane is acquired, and the surface appearance information of scratches and roughness is measured.
3. The laser scanning micro-measurement apparatus of claim 1, wherein: laser instrument (201) are installed on laser instrument mounting bracket (200), laser instrument mounting bracket (200) are fixed in on vertical screw rod (202), install on first keysets (211) on vertical screw rod (202), beam expanding mirror (212) are installed on first keysets (211) through the adapter ring, vertical screw rod (202) are fixed on second keysets (203), second keysets (203) are fixed on cage quadrature steering plate (204), cage quadrature steering plate (204) are installed on horizontal screw rod (213), half anti-semi-transparent mirror (205) are installed on horizontal screw rod (213), the one end and the mirror that shakes (206) of horizontal screw rod (213) connect soon, scanning objective (207) connect soon with shake mirror (206) mutually, third keysets (209) are installed to the other end of horizontal screw rod (213), it fixes on third keysets (209) to detect module (210).
4. The laser scanning micro-measurement device of claim 1 or 2, characterized in that: the detection module (210) comprises a microchannel plate imaging detector (311) for laser amplification, an optical fiber plate (312) for transmitting signals amplified by the microchannel plate imaging detector to the high-frame-rate area-array camera without deviation, and the high-frame-rate area-array camera (301) which are sequentially arranged.
5. The laser scanning micro-measurement device of claim 4, wherein: the high frame rate area array camera (301) is fixed on a camera frame (303), the camera frame (303) is fixed on a cage plate adapter (302) through a screw, the cage plate adapter (302) is provided with a cavity for accommodating an optical fiber plate (312), a microchannel plate imaging detector (311), a first snap ring (308), a protective lens (309) and a second snap ring (304), the optical fiber plate (312) is located between the high frame rate area array camera (301) and the microchannel plate imaging detector (311) and abuts against the optical fiber plate, the microchannel plate imaging detector (311) is fixed by the first snap ring (308), the protective lens (309) is placed in front of the first snap ring (308), and the protective lens (309) is fixed by the second snap ring (304).
6. The laser scanning micro-measurement device of claim 4 or 5, characterized in that: the high frame rate area-array camera (301) isAn area-array camera with MHz frame rate, a micro-channel plate imaging detector (311) for amplifying the signal 106～107A microchannel plate imaging detector.
7. The laser scanning micro-measurement device of claim 1 or 3, characterized in that: the laser (201) is a laser capable of outputting Gaussian distribution and having a wavelength of 350-650 nm.
8. The laser scanning micro-measurement device of claim 1 or 3, characterized in that: a beam expander (212) is arranged on an output optical path of the laser (201).
9. The laser scanning microscopic measurement method is characterized by comprising the following steps: the laser (201) emits laser, the laser is incident into a vibrating mirror (206) through a semi-reflecting and semi-transparent mirror (205), the vibrating mirror (206) controls the two-dimensional deflection of the laser, the laser is focused on a sample on a three-dimensional displacement platform (208) after passing through a scanning objective lens (207), the laser is incident into the sample and then reflected, the laser returns to the scanning objective lens (207) and the vibrating mirror (206) in the original path, and the laser enters a detection module (210) after passing through the semi-reflecting and semi-transparent mirror (205);
moving the sample along the Z axis, controlling the laser to scan the X-Y surface of the sample by a galvanometer (206) under each Z coordinate, acquiring images under different X-Y-Z coordinates by a detection module (210), acquiring the light intensity of a virtual pinhole area with the maximum light intensity in each image by taking a single or a plurality of CCD elements as virtual pinholes, acquiring the light intensity values under different X-Y-Z coordinates, acquiring the Z coordinate corresponding to the maximum light intensity under any X-Y coordinate, obtaining the depth distribution of an X-Y plane, and measuring the surface topography information of scratches and roughness.
10. The laser scanning microscopic measuring method according to claim 9, characterized in that:
the laser (201) outputs laser with Gaussian distribution, and the beam waist radius w passes through the vibrating mirror (206) and the scanning objective lens (207)0Expressed as:
in the formula, lambda and w1Respectively representing the wavelength and the size of an incident light spot before the objective lens is scanned; rayleigh distance z0＝πw0 2Lambda,/lambda; radius of lumbar macula w at distance zzIs represented as follows:
wherein z is-zcCoordinate position of beam waist, coordinate z-axis along laser propagation direction, spot size w at beam waistzMinimum; the focal length of the scanning objective lens is f, the image distance is far larger than f by adopting the image distance of 200mm, and the object distance is approximately equal to f by utilizing a Gaussian imaging formula; magnification of the objective lens is MAThe size of a light spot on a high frame rate area-array camera of the detection module (210) is approximately M & lt 200 & gt/fAwz；
The size of a CCD element of the high frame rate area-array camera is S, and x and y represent coordinates on a camera surface; only moving the z-axis, the power measured by the image space is in direct proportion to the laser power of the object space, and the total power of the image space is P0(ii) a When the object coordinate is z, the peak light intensity is IzPower P incident on the center of the spot on the cameraS(z) is represented by:
when the virtual pinhole size S is sufficiently large, the power P detected on the cameraS(z) always equals the total power P of the image space0Independent of the coordinate z; when using single or multiple camera CCD elements, PS(z) as a function of the z-axis, w when the beam waist is at the sample surfacezMinimum, PS(z) maximum, height information of the point is detected.
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| CN100410719C (en) * | 2006-10-11 | 2008-08-13 | 南开大学 | Confocal micro imaging system using dummy pinhole |
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