CN116718551A - Optical element surface defect measuring device - Google Patents
Optical element surface defect measuring device Download PDFInfo
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- CN116718551A CN116718551A CN202310925058.6A CN202310925058A CN116718551A CN 116718551 A CN116718551 A CN 116718551A CN 202310925058 A CN202310925058 A CN 202310925058A CN 116718551 A CN116718551 A CN 116718551A
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8806—Specially adapted optical and illumination features
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
- G01N21/958—Inspecting transparent materials or objects, e.g. windscreens
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Abstract
The invention discloses a device for measuring surface defects of an optical element. The invention comprises an imaging unit, a scanning movement unit, a contour measuring unit, an automatic focusing unit, a sample clamping unit, a leveling and aligning unit and a main control unit. The imaging unit consists of a coarse measurement light path and a fine measurement light path; fitting by a contour measurement unit to generate a focusing topographic map; the automatic focusing unit adjusts the micro-motion up and down of the microscope objective to realize automatic focusing imaging; the sample clamping unit is used for fixing a sample to be tested; the aligning and leveling unit is an automatic device integrating leveling and aligning. The invention utilizes the low-magnification dark field scattering and high-magnification bright and dark field imaging mode to quickly find out the surface defects of the optical element and accurately measure the defect sizes; the invention ensures the efficiency and the precision of defect identification and classification.
Description
Technical Field
The invention relates to a precise detection technology, in particular to a device for measuring surface defects of an optical element. The invention can be used for quality detection of precision optical elements and is suitable for measuring surface defects of the optical elements.
Background
Along with the rapid development of modern industry, the precision optical element has wide application in various industrial fields, and the optical element is used as a carrier for realizing optical functions and plays a vital role in the development and use of various optical instruments. Therefore, in view of the scattering properties of the surface of the optical element, it has been proposed to detect the defects on the surface of the element better. The detection process of the optical element is very complicated and is full of uncertainty, and the optical element can be divided into a series of materials such as common optical glass, neodymium glass, fused silica optical glass, calcium fluoride (CaF 2) and the like according to the composition materials; the aperture of the optical element can be as large as a few meters or as small as two millimeters, and the difference can be thousands of times; the optical element can be divided into a flat plate, an aspheric target lens, a spherical lens, a cylindrical lens, a pyramid prism, a polarizer, a glass ball and the like according to the different appearance of the optical element. To accommodate the needs of the various optical elements of the above three aspects, measurement instruments, environments, equipment, techniques must be varied. In the face of such a wide variety of optical elements, which vary in function and shape, it is necessary to search for corresponding detection techniques.
The damage to the optical element surface defects on itself and the entire optical system is manifested in several aspects, namely a degradation of the quality of the light beam. The scattering effect of light can be generated at the surface defect of the element, so that the energy of the light beam is greatly consumed after the light beam passes through the defect, and the quality of the light beam is reduced; thermal effect phenomena of defects. Because the area where the surface defect is located is easy to absorb more energy than other areas, the generated thermal effect phenomenon can cause the component defect to generate local deformation, damage a film layer and the like, so that the whole optical system is endangered; damaging other optical elements in the system in which they are located. In a laser system, scattered light generated by defects on the surface of an element is absorbed by other optical elements in the system under the irradiation of a high-energy laser beam, so that the light receiving of the element is uneven, when the damage threshold value of an optical element material is reached, the quality of transmitted light is influenced, the optical element is damaged, and the optical system is more likely to be seriously damaged; defects can affect field cleaning. When there are too many defects on the optical element, microscopic attractiveness is affected, in addition, the defects can remain tiny dust, microorganisms, polishing powder and other impurities, which can cause corrosion, mildew and fog of the element and obviously affect the basic performance of the element. Therefore, it is important to develop surface defect researches of optical elements.
The invention discloses an optical element surface defect measuring device, which realizes automatic leveling and aligning of an optical element through a leveling and aligning device, adopts a low-magnification dark field scattering combined with high-magnification bright and dark field imaging mode, and adopts a low-magnification dark field scattering method to quickly find out surface defects, and adopts high-magnification bright and dark field imaging to accurately measure defect sizes so as to realize automatic detection of the optical element surface defects.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an optical element surface defect measuring device.
The technical scheme adopted for solving the technical problems is as follows:
the invention comprises an imaging unit (100), a scanning movement unit (200), a profile measuring unit (300), an automatic focusing unit (400), a sample clamping unit (500), a leveling and aligning unit (600) and a main control unit (800);
the imaging unit (100) consists of a coarse measuring light path and a fine measuring light path, and the coarse measuring light path and the fine measuring light path share one set of integrated optical module (102-2) and realize automatic switching of low-power and high-power objective lenses through a piezoelectric resonance micro turntable (102-1);
the scanning motion unit (200) comprises a five-axis cylindrical coordinate scanning measurement structure and a macro-micro two-stage driving structure; the five-axis cylindrical coordinate scanning measurement structure integrates three linear axes and two rotating shafts, and adopts an RTTTR structure form; the optical device is placed on a C shaft (205-5) rotating around a vertical axis in the leveling and aligning unit (600), the whole imaging unit (100) is placed on a P shaft (205-4) rotating around a horizontal axis, and the C shaft and the P shaft of the rotating shaft are connected with the base through a linear motion shaft; the C axis (205-5) is integrally arranged on the X axis (205-1), the P axis (205-4) is integrally arranged on the Z axis (205-3), the Z axis (205-3) is arranged on the Y axis (205-2), the Y axis (205-2) is arranged on the marble beam, and the X axis (205-1) is arranged on the marble table top; the macro-micro two-stage driving structure consists of a Z axis (205-3) and an F axis (205-6) of a focusing displacement table forming device in the five-axis cylindrical coordinate scanning measurement structure, and clear object images are realized through the macro-micro two-stage driving structure;
the profile measuring unit (300) measures the surface distance of a measured element by using a spectral confocal displacement sensor (306-1), drives a voice coil motor (306-2) to move through space transformation, swings a P-axis (205-4) to enable the spectral confocal displacement sensor (306-1) to be vertical to a horizontal plane, and drives a Z-axis (205-3) to enable the highest point and the lowest point of the measured element to be within the measuring range of the spectral confocal displacement sensor (306-1); fixing a Z axis (205-3), driving an X axis (205-1) and a Y axis (205-2) to perform raster scanning (306-3) on a measured element on an X-Y plane, obtaining a spectral confocal measurement value and an X-Y plane coordinate thereof, and fitting to generate a focusing topographic map (306-4);
the automatic focusing unit (400) performs micro-focusing by a PSD position converter (407-1), a motion controller (407-2), a semiconductor laser (407-4) and a voice coil motor (407-3) through a driving micro objective lens (103-12); the output of the PSD position converter (407-1) is used as a feedback input signal of the motion controller (407-2), the motion controller (407-2) controls the voice coil motor (407-3) according to the feedback input signal, so that the micro objective lens (103-12) is adjusted to jog up and down to realize automatic focusing imaging, and the semiconductor laser (407-4) is used for emitting laser;
the sample clamping unit (500) is used for fixing a sample to be tested and comprises a three-jaw elastic chuck and a radial locking device (508-1);
the aligning and leveling unit (600) is an automatic device integrating leveling and aligning.
The coarse measuring light path is used for carrying out dark field scanning imaging based on a low-magnification microscope objective lens and is used for quickly finding out surface defects of the element; the dark field light source is designed by annular epi-illumination (103-13), the dark field LED light source (103-1) enters the optical fiber harness (103-3) through the light guide column (103-2), and the light beam is annularly irradiated on the element through the annular lens, so that the annular epi-illumination (103-13) is formed; the diffuse reflection and diffraction light enters the first imaging lens group (103-6) through the 5 times of micro objective lens (103-12), then enters the second thin film spectroscope (103-7) behind the first imaging lens group (103-6), enters the area array camera (103-8) and the linear array camera (103-9) after being split by the second thin film spectroscope (103-7), and completes image acquisition.
The imaging unit (100) is also integrated with a bright field illumination module (103-14), and the bright field illumination module (103-14) comprises a bright field light source (103-11) and a second imaging lens group (103-10); when bright field observation is needed, a first thin film spectroscope (103-4) is moved between the objective lens (103-12) and the first imaging lens group (103-6); the bright-dark field switching is achieved by the light of the bright-field illumination modules (103-14).
The precise measurement light path has two working modes of a bright field and a dark field, under the dark field working mode, a thin film spectroscope (103-4) used for switching the bright field and the dark field in the light path is moved out, a camera switching thin film spectroscope (103-7) is also moved out, and is switched into a 20-time micro objective lens (104-1), and light reflected by a sample surface defect under the working mode enters an area array camera (103-8) to the greatest extent, so that the sensitivity of defect detection is ensured; in the bright field working mode, the light emitted by the fine measurement light path in the bright field LED light source is collimated and homogenized after passing through the bright field light source adaptive lens group, and the light is shared with an image plane of a 20-time micro objective lens (104-1); after the reflection effect of the film spectroscope (103-4), the light beam enters the 20 times micro objective (104-1) to irradiate on the surface of the sample, and the reflected light passes through the 20 times micro objective (104-1), the film spectroscope (103-4) and the imaging lens group (103-6) in sequence, is split by the second film spectroscope (103-7), and is finally captured and imaged by the area camera (103-8) and the linear camera (103-9).
The specific structure of the sample clamping unit (500) is as follows: the three-jaw elastic chuck comprises three groups of torsion springs (508-2), wherein the three groups of torsion springs (508-2) are fixed on an outer ring mounting ring of the chuck, and the three-jaw pretightening force is uniform; the radial locking devices (508-1) are distributed on the outer edge of the three-jaw elastic chuck, and the positions of the radial locking devices (508-1) are adjustable; the device is arranged in a reserved installation area (508-3) in the middle of the three-jaw elastic chuck when measuring small-size elements, and the head part of the ejector rod of the radial locking device (508-1) is provided with a replaceable attaching block (508-4).
The joint surface of the joint block (508-4) is designed to be a cylindrical surface structure; the contact head material of the three-jaw elastic chuck is preferably POM; the material of the attaching block is preferably nylon.
The aligning and leveling unit (600) is an automatic device integrating leveling and centering, the aligning and leveling unit (600) adopts a Kelvin hinge structure, three supporting balls (609-1) are used for precisely restraining the positions of the components, the three supporting balls (609-1) are in contact with three V-shaped grooves (609-2), and the central lines of the three V-shaped grooves (609-2) intersect at one point; wherein the upper surfaces of the two V-shaped grooves incline downwards from inside to outside; and the structure is symmetrically designed about the other V-shaped groove; the two leveling knobs (609-3) fine-tune the positions of the support balls in the two inclined V-shaped grooves through corresponding stepping servo motors 609-5 respectively.
The device is also provided with a cleaning control unit (700) which comprises a hundred-level laminar flow hood (7011-4), a low-noise fan (7011-1), a high-clean air filter (7011-2), a damping layer (7011-3) and a damping layer (7011-6); the main equipment of the whole device is arranged inside a clean control unit (700), namely an imaging unit (100), a scanning movement unit (200), a profile measurement unit (300), an automatic focusing unit (400), a sample clamping unit (500) and a leveling and aligning unit (600) are all arranged inside the clean control unit (700).
A hundred-level laminar flow hood (7011-4) is arranged above the cleaning control unit, ambient air passes through a high-efficiency air filter (7011-2) under stable wind pressure to generate clean air, the clean air is subjected to pressure equalization through a damping layer (7011-3) to form a uniform flow layer and is vertically and unidirectionally flowed to be sent into a detection area, and air in the detection area is discharged through a lower exhaust hole (7011-5).
The main control unit (800) comprises a motion control system, an illumination light source control system, an image acquisition control system and an automatic leveling control system;
the core motion control system adopts an 8-axis motion controller EC and two 4-axis motor drivers, the 8-axis motion controller is connected with a high-performance computer through Ethernet, and the 8-axis motion controller is connected with the 4-axis motor drivers through EtherCAT buses, so that the driving and the control of an X-axis linear displacement table, a Y-axis linear displacement table, a Z-axis linear displacement table, an F-axis focusing displacement table, a C-axis workpiece rotating table, a P-axis measuring head swinging table and a multiplying power switching table are realized;
in the illumination light source control system, a computer is connected with an LED driver through a USB port and controls the brightness and the opening and closing of a bright-field LED light source and a dark-field LED light source through a CDC virtual serial protocol;
the image acquisition control system controls the exposure and image acquisition of the linear array camera by the computer through the CameraLink acquisition card in a dark field mode; in the bright field mode, the computer is connected with the high-frame-rate area array camera through a USB3.0 interface, and the exposure and the drawing of the camera are controlled by external trigger;
the automatic leveling control system is mainly used for controlling the aligning leveling unit, and the computer is connected with the two stepping servo motors through an OpenCAN motion control card and controls the automatic leveling device to work through a CAN protocol; the spectral confocal sensor in the profile measuring unit is connected with the spectrometer and the high-performance computer, and the PSD signal processor in the automatic focusing unit is also connected with the AFProbe through the 8-axis motion controller.
Compared with the prior art, the invention has the beneficial effects that:
the invention utilizes a low-magnification dark field scattering combined with high-magnification bright and dark field imaging mode to rapidly find the surface defects of the optical element and accurately measure the defect sizes.
According to the invention, the self-leveling and aligning of the optical element are realized through the leveling and aligning device, a low-magnification dark field scattering combined with high-magnification bright and dark field imaging mode is adopted, the low-magnification dark field scattering method is used for rapidly finding out surface defects, and the high-magnification bright and dark field imaging is used for accurately measuring the defect sizes, so that the automatic detection of the surface defects of the optical element is realized. And the invention ensures the efficiency and precision of defect identification and classification.
The invention sets up the imaging unit and is made up of rough measuring light path and fine measuring light path, rough measuring light path and fine measuring light path share a set of integrated optical module, realize the automatic switching of the low-power and high-power objective through a piezoelectric resonance miniature rotary table, the low-power objective adopts the focusing design with high-power objective, after switching over the multiplying power, the focus position is basically identical. The coarse measurement light path is used for carrying out dark field scanning imaging based on a low-magnification microscope objective lens and is used for quickly finding out surface defects of elements, and the fine measurement light path has two working modes of a bright field and a dark field.
Drawings
FIG. 1 is a schematic diagram showing an apparatus for detecting surface defects of an optical element according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an integrated optical module for switching between coarse and fine measurement modes of an imaging unit according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a coarse measurement light path (fine measurement dark field light path) according to one embodiment of the present invention;
FIG. 4 is a schematic diagram of a precision measurement bright field optical path according to one embodiment of the present invention;
FIG. 5 is a schematic block diagram of the mechanical structure of a scan motion unit according to one embodiment of the invention;
FIG. 6 is a schematic diagram of a focal topography generation principle based on spectral confocal sensor ranging according to an embodiment of the invention;
FIG. 7 is a schematic diagram of an autofocus control principle of an embodiment of the present invention;
FIG. 8 is a schematic diagram of a clamping design for compatible sized samples in accordance with one embodiment of the present invention;
FIG. 9 is a schematic diagram of a Kelvin hinge-based self-leveling and aligning device of an embodiment of the present invention;
FIG. 10 is a schematic view of a hundred-grade cleaning apparatus according to one embodiment of the present invention;
FIG. 11 is a schematic diagram of the overall system control architecture of an embodiment of the present invention;
Detailed Description
The invention will now be described in detail with reference to the drawings and examples.
The embodiment of the invention relates to a device and a method for measuring surface defects of an optical element, which can be used for quality detection of a precise optical element. An embodiment according to the present invention is described below with reference to the accompanying drawings.
As shown in fig. 1, an embodiment of an apparatus for defect measurement according to the present invention includes an imaging unit 100, a scanning motion unit 200, a profile measurement unit 300, an auto-focusing unit 400, a sample clamping unit 500, a leveling and aligning unit 600, a cleaning control unit 700, and a main control unit 800.
In this embodiment, the imaging unit 100 is composed of a coarse measurement optical path and a fine measurement optical path, as shown in fig. 2, where the coarse measurement optical path and the fine measurement optical path share a set of integrated optical modules 102-2 (specific internal structure is shown in fig. 3), and automatic switching between low-power and high-power objective lenses is implemented by using a piezoelectric resonance micro turntable 102-1, and focal positions of the low-power objective lens and the high-power objective lens are substantially consistent after the magnification is switched.
In this embodiment, as shown in fig. 3, the coarse measurement light path is used for dark field scanning imaging based on a low-magnification microscope objective lens, so as to quickly find out the surface defects of the element. The dark field light source is designed by adopting annular epi-illumination 103-13, the dark field LED light source 103-1 enters the optical fiber harness 103-3 through the light guide column 103-2, and then the light beam is annularly irradiated on the element through the annular lens, so that the annular epi-illumination 103-13 is formed. The diffuse reflection and diffraction light enters the first imaging lens group 103-6 through the 5 times micro objective lens 103-12, then enters the second thin film spectroscope 103-7 (camera switching/movable) behind the first imaging lens group 103-6, enters the area array camera 103-8 and the linear array camera 103-9 after being split by the second thin film spectroscope 103-7, and completes image acquisition.
The imaging unit 100 of the present invention is further integrated with a bright field illumination module 103-14, the bright field illumination module 103-14 comprising a bright field light source 103-11 and a second imaging lens group 103-10. When bright field observation is needed, a first thin film spectroscope 103-4 is moved between the objective lens 103-12 and the first imaging lens group 103-6; the bright-dark field switching is achieved by the light of bright-field illumination module 103-14.
As shown in fig. 3 and 4, the precise measurement light path has two working modes of bright and dark fields, as shown in fig. 3, in the dark field working mode, the thin film spectroscope 103-4 for bright and dark field switching in the light path is moved out, the camera switching thin film spectroscope 103-7 is also moved out, and the light reflected by the surface defect of the sample is switched into the 20 times micro objective 104-1, in this way, the light reflected by the surface defect of the sample enters the area array camera 103-8 to the greatest extent, and the sensitivity of defect detection is ensured. As shown in fig. 4, in the bright field working mode, the light emitted by the bright field LED light source in the fine measurement light path is collimated and homogenized by the bright field light source adaptive lens group and is co-imaged with the 20-fold micro objective 104-1; after the reflection effect of the thin film spectroscope 103-4 (light-dark field switching/movable), the light beam enters the 20 times micro objective 104-1 to irradiate on the surface of the sample, and the reflected light passes through the 20 times micro objective 104-1, the thin film spectroscope 103-4 (light-dark field switching/movable) and the imaging lens group 103-6 in sequence, and then is split by the second thin film spectroscope 103-7 (camera switching/movable), and finally is captured and imaged by the area array camera 103-8 and the linear array camera 103-9.
In this embodiment, as shown in fig. 5, the scanning motion unit 200 includes a five-axis cylindrical coordinate scanning measurement structure and a macro-micro two-stage driving structure. The five-axis cylindrical coordinate scanning measurement structure integrates three linear axes and two rotating shafts, adopts a RTTTR (R represents the rotating shaft, T represents the linear axis) structure form, is arranged on a C axis 205-5 rotating around a vertical axis in a leveling and aligning unit 600, the whole imaging unit 100 is arranged on a P axis 205-4 rotating around a horizontal axis, and the C axis and the P axis of the rotating shafts are connected with a base through linear motion shafts. The C-axis 205-5 is integrally disposed on the X-axis 205-1, the P-axis 205-4 is integrally disposed on the Z-axis 205-3, the Z-axis 205-3 is disposed on the Y-axis 205-2, the Y-axis 205-2 is disposed on the marble cross-beam, and the X-axis 205-1 is mounted on the marble table. In the system, a X, Y linear moving shaft is driven by a linear motor, a Z-axis is driven by a servo motor with a band-type brake function by adopting a high-precision ball screw, and three shafts are supported by high-precision guide rails; C. the P rotating shaft is driven to rotate by a torque motor.
The macro-micro two-stage driving structure consists of a Z axis 205-3 in a five-axis cylindrical coordinate scanning measurement structure and an F axis 205-6 of a focusing displacement table forming device, and a clear object image is realized through the macro-micro two-stage driving structure.
In this embodiment, as shown in fig. 6, the contour measurement unit 300 measures the surface distance of the measured element by using the spectral confocal displacement sensor 306-1, drives the voice coil motor 306-2 to move through space transformation, swings the P-axis 205-4 to make the spectral confocal displacement sensor 306-1 perpendicular to the horizontal plane, and drives the Z-axis 205-3 to make the highest point and the lowest point of the measured element within the measurement range of the spectral confocal displacement sensor 306-1; the Z axis 205-3 is fixed, the X axis 205-1 and the Y axis 205-2 are driven to perform raster scanning 306-3 on the tested element on the X-Y plane, the spectral confocal measurement value and the X-Y plane coordinate thereof are obtained, and a focusing topographic map 306-4 is generated by fitting.
In this embodiment, as shown in fig. 7, the autofocus unit 400 performs micro-focusing by driving the micro-objective 103-12 through the PSD position converter 407-1, the motion controller 407-2, the semiconductor laser 407-4, and the voice coil motor 407-3. The output of the PSD position converter 407-1 is used as a feedback input signal of the motion controller 407-2, the motion controller 407-2 controls the voice coil motor 407-3 according to the feedback input signal, so as to adjust the micro objective 103-12 to jog up and down, realize automatic focusing imaging, and the semiconductor laser 407-4 is used for emitting laser.
In this embodiment, as shown in fig. 8, the sample clamping unit 500 includes a three-jaw elastic chuck and a radial locking device 508-1, the three-jaw elastic chuck includes three groups of torsion springs 508-2, the three groups of torsion springs 508-2 are fixed on an outer ring mounting ring of the chuck, and the three-jaw pretightening force is uniform; the radial locking devices 508-1 are distributed on the outer edge of the three-jaw elastic chuck, the positions of the radial locking devices 508-1 are adjustable, the radial locking devices are arranged in a reserved mounting area 508-3 in the middle of the three-jaw elastic chuck when small-size elements are measured, the head of a mandril of each radial locking device 508-1 is provided with a replaceable attaching block 508-4, and the attaching surface of each attaching block is designed to be a cylindrical surface structure; the contact head material of the three-jaw elastic chuck is preferably POM (race steel) material; the material of the attaching block is preferably nylon.
In this embodiment, as shown in fig. 9, the aligning and leveling unit 600 is an automatic device that integrates leveling and aligning, and has two modes, namely an automatic adjustment mode and a manual adjustment mode; the leveling device in the aligning and leveling unit 600 adopts a Kelvin hinge structure, uses three supporting balls 609-1 to precisely restrict the positions of components, and the three supporting balls 609-1 are contacted with three V-shaped grooves 609-2, and the central lines of the three V-shaped grooves 609-2 intersect at one point. Wherein the upper surfaces of the two V-shaped grooves incline downwards from inside to outside; and the leveling device structure is symmetrically designed about the other V-shaped groove. The two leveling knobs 609-3 respectively fine-tune the positions of the supporting balls in the two inclined V-shaped grooves through corresponding stepping servo motors 609-5;
specifically, the automatic leveling control system in the main control unit detects specific parameters of the spectral confocal sensor 306-1, and then the main control unit drives the stepping servo motor 609-5 to adjust through the parameters.
The centering procedure is similar to the leveling procedure, and is adjusted by two centering knobs 609-4. The two centering knobs 609-4 can fine-tune the position through corresponding stepping servo motors;
in this embodiment, as shown in fig. 10, the cleaning control unit 700 includes a hundred-stage laminar flow hood 7011-4, a low noise blower 7011-1, a high clean air filter 7011-2, a damping layer 7011-3, and a shock absorbing layer 7011-6. The main equipment of the whole device is arranged inside the cleaning control unit 700, namely, the imaging unit 100, the scanning motion unit 200, the profile measuring unit 300, the automatic focusing unit 400, the sample clamping unit 500 and the leveling and aligning unit 600 are all arranged inside the cleaning control unit 700.
A hundred-level laminar flow hood 7011-4 is arranged above the cleaning control unit, ambient air passes through a high-efficiency air filter 7011-2 under stable air pressure to generate clean air, the clean air is subjected to pressure equalization through a damping layer 7011-3 to form a uniform flow layer and is vertically and unidirectionally flowed to be sent into a detection area, and air in the detection area is discharged through a lower exhaust hole 7011-5;
in this embodiment, as shown in fig. 11, the main control unit 800 includes a motion control system 8012-27, an illumination source control system 8012-24, an image acquisition control system 8012-25, and an auto leveling control system 8012-26.
The core motion control system 8012-27 adopts an 8-axis motion controller EC8012-10 and two 4-axis motor drivers 8012-13 (supporting a linear motor, a voice coil motor and a rotary servo motor), the 8-axis motion controller 8012-10 is connected with a high-performance computer 8012-9 through Ethernet, and the 8-axis motion controller 8012-10 and the 4-axis motor drivers 8012-13 are connected through EtherCAT buses, so that the driving and the control of an X-axis linear displacement table 8012-16, a Y-axis linear displacement table 8012-17, a Z-axis linear displacement table 8012-18, an F-axis focusing displacement table 8012-19, a C-axis workpiece rotary table 8012-20, a P-axis measuring head swinging rotary table 8012-21 and a multiplying power switching table 8012-22 are realized.
In the illumination light source control system 8012-24, a computer is connected with the LED driver 8012-8 through a USB port, and controls the brightness and the opening and closing of the bright field LED light source 8012-1 and the dark field LED light source 8012-2 through a CDC virtual serial protocol.
The image acquisition control system 8012-25 controls the high-frequency line scanning camera 8012-4 (i.e. a linear array camera) to expose and acquire images by the computer through the CameraLink acquisition card 8012-7 in a dark field mode; in the bright field mode, the computer is connected with the high-frame-rate area array camera through the USB3.0 interface, and the exposure and the image acquisition of the camera are controlled by external triggering.
The automatic leveling control system 8012-26 is mainly used for controlling the aligning leveling unit, and a computer is connected with the two stepping servo motors 8012-6 through the OpenCAN motion control card 8012-23 and controls the automatic leveling device 8012-5 to work through a CAN protocol. The spectral confocal sensor 8012-15 in the profile measuring unit is connected with the spectrometer 8012 and the high-performance computer, and the PSD signal processor 8012-11 in the automatic focusing unit is also connected with the high-performance computer through the 8-axis motion controller.
The above embodiment is only a preferred embodiment of the present invention, but it is not intended to limit the present invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, all the technical schemes obtained by adopting the equivalent substitution or equivalent transformation are within the protection scope of the invention.
Claims (10)
1. The device for measuring the surface defects of the optical element is characterized by comprising an imaging unit (100), a scanning movement unit (200), a profile measuring unit (300), an automatic focusing unit (400), a sample clamping unit (500), a leveling and aligning unit (600) and a main control unit (800);
the imaging unit (100) consists of a coarse measuring light path and a fine measuring light path, and the coarse measuring light path and the fine measuring light path share one set of integrated optical module (102-2) and realize automatic switching of low-power and high-power objective lenses through a piezoelectric resonance micro turntable (102-1);
the scanning motion unit (200) comprises a five-axis cylindrical coordinate scanning measurement structure and a macro-micro two-stage driving structure; the five-axis cylindrical coordinate scanning measurement structure integrates three linear axes and two rotating shafts, and adopts an RTTTR structure form; the optical device is placed on a C shaft (205-5) rotating around a vertical axis in the leveling and aligning unit (600), the whole imaging unit (100) is placed on a P shaft (205-4) rotating around a horizontal axis, and the C shaft and the P shaft of the rotating shaft are connected with the base through a linear motion shaft; the C axis (205-5) is integrally arranged on the X axis (205-1), the P axis (205-4) is integrally arranged on the Z axis (205-3), the Z axis (205-3) is arranged on the Y axis (205-2), the Y axis (205-2) is arranged on the marble beam, and the X axis (205-1) is arranged on the marble table top; the macro-micro two-stage driving structure consists of a Z axis (205-3) and an F axis (205-6) of a focusing displacement table forming device in the five-axis cylindrical coordinate scanning measurement structure, and clear object images are realized through the macro-micro two-stage driving structure;
the profile measuring unit (300) measures the surface distance of a measured element by using a spectral confocal displacement sensor (306-1), drives a voice coil motor (306-2) to move through space transformation, swings a P-axis (205-4) to enable the spectral confocal displacement sensor (306-1) to be vertical to a horizontal plane, and drives a Z-axis (205-3) to enable the highest point and the lowest point of the measured element to be within the measuring range of the spectral confocal displacement sensor (306-1); fixing a Z axis (205-3), driving an X axis (205-1) and a Y axis (205-2) to perform raster scanning (306-3) on a measured element on an X-Y plane, obtaining a spectral confocal measurement value and an X-Y plane coordinate thereof, and fitting to generate a focusing topographic map (306-4);
the automatic focusing unit (400) performs micro-focusing by a PSD position converter (407-1), a motion controller (407-2), a semiconductor laser (407-4) and a voice coil motor (407-3) through a driving micro objective lens (103-12); the output of the PSD position converter (407-1) is used as a feedback input signal of the motion controller (407-2), the motion controller (407-2) controls the voice coil motor (407-3) according to the feedback input signal, so that the micro objective lens (103-12) is adjusted to jog up and down to realize automatic focusing imaging, and the semiconductor laser (407-4) is used for emitting laser;
the sample clamping unit (500) is used for fixing a sample to be tested and comprises a three-jaw elastic chuck and a radial locking device (508-1);
the aligning and leveling unit (600) is an automatic device integrating leveling and aligning.
2. An apparatus for measuring surface defects of an optical element according to claim 1,
the coarse measuring light path is used for carrying out dark field scanning imaging based on a low-magnification microscope objective lens and is used for quickly finding out surface defects of the element; the dark field light source is designed by annular epi-illumination (103-13), the dark field LED light source (103-1) enters the optical fiber harness (103-3) through the light guide column (103-2), and the light beam is annularly irradiated on the element through the annular lens, so that the annular epi-illumination (103-13) is formed; the diffuse reflection and diffraction light enters the first imaging lens group (103-6) through the 5 times of micro objective lens (103-12), then enters the second thin film spectroscope (103-7) behind the first imaging lens group (103-6), enters the area array camera (103-8) and the linear array camera (103-9) after being split by the second thin film spectroscope (103-7), and completes image acquisition.
3. An apparatus for measuring surface defects of an optical element as recited in claim 2, wherein
The imaging unit (100) is also integrated with a bright field illumination module (103-14), and the bright field illumination module (103-14) comprises a bright field light source (103-11) and a second imaging lens group (103-10); when bright field observation is needed, a first thin film spectroscope (103-4) is moved between the objective lens (103-12) and the first imaging lens group (103-6); the bright-dark field switching is achieved by the light of the bright-field illumination modules (103-14).
4. The device for measuring surface defects of optical elements according to claim 4, wherein the fine measuring light path has two working modes of bright and dark fields, in the dark field working mode, a thin film spectroscope (103-4) for bright and dark field switching in the light path is moved out, a camera switching thin film spectroscope (103-7) is also moved out, and the light reflected by the surface defects of the sample is switched into a 20-times micro objective lens (104-1), and the light reflected by the surface defects of the sample in the working mode enters an area camera (103-8) to the greatest extent, so that the sensitivity of defect detection is ensured; in the bright field working mode, the light emitted by the fine measurement light path in the bright field LED light source is collimated and homogenized after passing through the bright field light source adaptive lens group, and the light is shared with an image plane of a 20-time micro objective lens (104-1); after the reflection effect of the film spectroscope (103-4), the light beam enters the 20 times micro objective (104-1) to irradiate on the surface of the sample, and the reflected light passes through the 20 times micro objective (104-1), the film spectroscope (103-4) and the imaging lens group (103-6) in sequence, is split by the second film spectroscope (103-7), and is finally captured and imaged by the area camera (103-8) and the linear camera (103-9).
5. The device for measuring surface defects of optical elements according to claim 4, wherein the sample clamping unit (500) has the following specific structure: the three-jaw elastic chuck comprises three groups of torsion springs (508-2), wherein the three groups of torsion springs (508-2) are fixed on an outer ring mounting ring of the chuck, and the three-jaw pretightening force is uniform; the radial locking devices (508-1) are distributed on the outer edge of the three-jaw elastic chuck, and the positions of the radial locking devices (508-1) are adjustable; the device is arranged in a reserved installation area (508-3) in the middle of the three-jaw elastic chuck when measuring small-size elements, and the head part of the ejector rod of the radial locking device (508-1) is provided with a replaceable attaching block (508-4).
6. An apparatus for measuring surface defects of optical elements according to claim 5, wherein the bonding surface of said bonding block (508-4) is designed as a cylindrical surface structure; the contact head material of the three-jaw elastic chuck is preferably POM; the material of the attaching block is preferably nylon.
7. The device for measuring the surface defects of the optical element according to claim 1, wherein the aligning and leveling unit (600) is an automatic device integrating leveling and aligning, the aligning and leveling unit (600) adopts a kelvin hinge structure, the position of the component is precisely restrained by using three supporting balls (609-1), the three supporting balls (609-1) are in contact with three V-shaped grooves (609-2), and the central lines of the three V-shaped grooves (609-2) intersect at one point; wherein the upper surfaces of the two V-shaped grooves incline downwards from inside to outside; and the structure is symmetrically designed about the other V-shaped groove; the two leveling knobs (609-3) fine-tune the positions of the support balls in the two inclined V-shaped grooves through corresponding stepping servo motors 609-5 respectively.
8. The device for measuring the surface defects of the optical element according to claim 1, wherein the device is further provided with a cleaning control unit (700) comprising a hundred-level laminar flow hood (7011-4), a low-noise blower (7011-1), a high-clean air filter (7011-2), a damping layer (7011-3) and a shock absorption layer (7011-6); the main equipment of the whole device is arranged inside a clean control unit (700), namely an imaging unit (100), a scanning movement unit (200), a profile measurement unit (300), an automatic focusing unit (400), a sample clamping unit (500) and a leveling and aligning unit (600) are all arranged inside the clean control unit (700).
9. The device for measuring surface defects of optical elements according to claim 7, wherein a hundred-level laminar flow hood (7011-4) is arranged above the cleaning control unit, clean air is generated after ambient air passes through the high-efficiency air filter (7011-2) under stable wind pressure, the clean air forms a uniform flow layer after being subjected to pressure equalization through the damping layer (7011-3) and is sent into the detection area in a vertical unidirectional flow mode, and air in the detection area is discharged through the lower exhaust hole (7011-5).
10. The device for measuring surface defects of optical elements according to claim 1, wherein said main control unit (800) comprises a motion control system, an illumination light source control system, an image acquisition control system, an auto-leveling control system;
the core motion control system adopts an 8-axis motion controller EC and two 4-axis motor drivers, the 8-axis motion controller is connected with a high-performance computer through Ethernet, and the 8-axis motion controller is connected with the 4-axis motor drivers through EtherCAT buses, so that the driving and the control of an X-axis linear displacement table, a Y-axis linear displacement table, a Z-axis linear displacement table, an F-axis focusing displacement table, a C-axis workpiece rotating table, a P-axis measuring head swinging table and a multiplying power switching table are realized;
in the illumination light source control system, a computer is connected with an LED driver through a USB port and controls the brightness and the opening and closing of a bright-field LED light source and a dark-field LED light source through a CDC virtual serial protocol;
the image acquisition control system controls the exposure and image acquisition of the linear array camera by the computer through the CameraLink acquisition card in a dark field mode; in the bright field mode, the computer is connected with the high-frame-rate area array camera through a USB3.0 interface, and the exposure and the drawing of the camera are controlled by external trigger;
the automatic leveling control system is mainly used for controlling the aligning leveling unit, and the computer is connected with the two stepping servo motors through an OpenCAN motion control card and controls the automatic leveling device to work through a CAN protocol; the spectral confocal sensor in the profile measuring unit is connected with the spectrometer and the high-performance computer, and the PSD signal processor in the automatic focusing unit is also connected with the AFProbe through the 8-axis motion controller.
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| CN118151325A (en) * | 2024-05-08 | 2024-06-07 | 无锡星微科技有限公司杭州分公司 | Stroke-variable optical focusing system |
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