CN201110835Y - Laser Scattering Detection Device for Large Diameter Neodymium Glass Surface Defects - Google Patents

Abstract

A laser scattering detection device for large-caliber neodymium glass surface defects comprises an X-Y precision stepping platform on which an optical element to be tested is placed; in the normal direction of the X-Y precision stepping platform and above the optical element to be tested, a second plane reflector, a scattered light collecting aperture, a scattered light collecting objective lens, and an optical fiber group collector are sequentially arranged coaxially from bottom to top, and the multi-path scattered light signals collected by the optical fiber group collector are introduced into a photoelectric detector array through the optical fiber group and converted into multi-path electrical signals; a laser, a Faraday isolator, a beam expander lens, a collimating lens, a focusing lens, a beam splitter and a first plane reflector are sequentially arranged coaxially along the direction of the laser beam emitted by the laser, and a computer, the scattered light signals collected by the photoelectric detector array are converted into multi-path electrical signals, and are input into the computer through a high-speed data acquisition card after being shaped and filtered; the computer drives the X-Y precision stepping platform to move through a stepping motor.

Description

Laser Scattering Detection Device for Large Diameter Neodymium Glass Surface Defects

technical field

The utility model relates to an optical plane, in particular to a laser scattering detection device for large-diameter neodymium glass surface defects. The system uses the scattering of incident laser light by defects on the surface of the optical plane, and uses the principle of Mie scattering to collect scattered light in various directions of defects in multiple channels under dark field conditions, so as to realize the identification, positioning, classification and classification of defects.

Background technique

The so-called surface defect refers to the unusual structure on the surface of optical components. The surface defects of precision optical components are roughly divided into pits, scratches, open bubbles, broken points and broken edges, which are important indicators of optical processing quality. The impact of defects The main manifestations are:

① Beam quality declines;

②The local thermal effect generated by the damage point causes the damage of the optical element;

③Due to the diffraction of the beam at the damage point, damage to other optical components, etc.

For high-power laser devices, the impact of imperfections in optical components is particularly serious.

At present, the detection of damage to optical components mainly uses non-laser light source illumination and observation by human eyes. This method uses an optical magnifying glass in the case of dark field illumination, directly observes the surface with human eyes and judges the level of defects. Its disadvantages It is time-consuming, laborious and inefficient, and due to the influence of many factors such as human subjective factors and human eye fatigue, the judgment has greater uncertainty. With the development of modern optical technology, especially high-power laser technology, more stringent requirements are put forward for the processing and inspection of optical components. The method of visual inspection alone can no longer meet the requirements.

Defects on the surface of large-diameter precision optical components need to meet the national standard II standards. The detection of defects cannot be done by sampling and averaging like the inspection of surface roughness, but must find all possible defects within the effective aperture of the component. sick.

The surface defect will scatter the incident laser light, and the scattering signal contains very rich information such as the type and size of the defect. The scattered light of the defect is collected through the dark field, and the scattering signal at each azimuth angle is analyzed to realize the surface Defect location, classification, grading.

Contents of the invention

The purpose of the utility model is to overcome the deficiencies of the prior art, provide a laser scattering detection device for large-diameter neodymium glass surface defects, and realize the positioning, classification and classification of optical plane surface defects.

The concrete technical solution of the utility model is as follows:

A laser scattering detection device for large-diameter neodymium glass surface defects, including an X-Y precision stepping platform for placing the optical element to be tested, using two laser beams to focus and irradiate the plane surface of the optical element to be tested from vertical and oblique directions respectively , the scattered light generated is collected by multiple photodetectors at different azimuth angles, converted into electrical signals and input to the computer, and the computer drives the X-Y precision stepping platform through the stepping motor to drive the optical element to be tested for scanning measurement. The measured scattered light signal is compared with the scattered light signal of the standard defect on the optical plane surface known in the computer database, so as to realize the positioning, classification and grading of the optical plane surface defect.

A laser scattering detection device for large-diameter neodymium glass surface defects, characterized in that it includes:

An X-Y precision stepping platform for placing optical components to be tested;

In the normal direction of the X-Y precision stepping platform and above the optical element to be measured, a second plane reflector, a scattered light collection diaphragm, a scattered light collection objective lens, and an optical fiber group collection are sequentially arranged on the same optical axis from bottom to top. The optical fiber group collector is located on the rear focal plane of the scattered light collecting objective lens, and the multi-channel scattered light signals collected by the optical fiber group collector are introduced into the photodetector array through the optical fiber group and converted into multiple electrical signals. The second flat reflector is 45° to the normal direction;

A laser device, a Faraday isolator, a beam expander lens, a collimator lens, a focusing lens, a beam splitter and a first plane reflector are sequentially arranged on the same optical axis along the direction of the laser beam emitted by the laser device, and the beam splitter surface of the beam splitter At 45° to the laser beam, the laser beam is divided into a reflected beam and a transmitted beam by the beam splitter, and the transmitted beam is focused obliquely on the optical element to be tested after being reflected by the first plane mirror On the plane surface of the optical element to be tested, the reflected beam is vertically focused on the plane surface of the optical element to be tested after being reflected by the second plane mirror, and the two illuminating beams are confocal on the plane surface of the optical element to be tested spot;

A computer, the scattered light signal collected by the photodetector array is converted into a multi-channel electrical signal, which is input into the computer (18) by a high-speed data acquisition card after shaping and filtering; the control terminal of the computer is connected to a drive module, and the drive Under the control of the computer, the module drives the X-Y precision stepping platform to move through the stepping motor.

Light traps are arranged in the transmission direction and the reflection direction of the reflected light beam that irradiates the optical element to be measured obliquely after the reflection of the first plane mirror, and the reflection beam after the reflection of the second plane mirror is vertical Light traps are also provided in the transmission direction for illuminating the optical element to be tested.

The optical fiber group collector has a plurality of scattered light collection points, and the scattered light collection points are symmetrically distributed about the center.

The scattered light collecting diaphragm is a circular ring with a central hole, which is attached to the scattered light collecting objective lens, and divides the scattered light collecting objective lens into a peripheral wide channel and a middle narrow channel.

The X-Y precision stepping platform has a certain Z-direction adjustable ability, so that when inspecting optical elements with different thicknesses, the focal spot of the incident laser light is always located on the plane surface of the optical element to be tested.

The laser is a frequency-doubled laser pumped by a laser diode, and the output wavelength is λ=532nm and a stable laser with a power of 200mW.

Compared with the existing visual method technology, the utility model has the following technical characteristics:

1. Compared with the prior art, this invention adopts laser diode laser scanning illumination system, high-sensitivity photodetector (such as photomultiplier tube array), multi-channel dark field scattered light collection, reflected light and transmitted light light trap Methods and technologies such as absorption improve the signal-to-noise ratio of the signal, thereby improving the resolution and accuracy of the system, eliminating the influence of human subjective factors, and enabling the system to detect, classify, and classify surface defects more accurately and stably. The detection efficiency is improved and the cost is reduced.

2. Compared with the prior art, in addition to more accurate identification of surface defects, the utility model can also accurately locate and record surface defects, conduct more scientific evaluation of defect levels, and can count optical plane defects. The defect information on the surface is richer, and the surface defect information of each detected optical plane can be stored for subsequent analysis.

3. The utility model is particularly applicable to the detection of large-caliber precision optical plane defect information.

Description of drawings

Fig. 1 is a schematic diagram of the principle of a laser scattering detection device for large-diameter neodymium glass surface defects of the present invention.

Fig. 2 is a cross-sectional view of the fiber group arrangement structure of the scattered light collection mechanism of the present invention.

Fig. 3 is a schematic diagram of the objective lens diaphragm of the scattered light collecting mechanism of the present invention.

Fig. 4 is one of the signal processing block diagrams of the utility model system.

Fig. 5 is the second block diagram of the signal processing system of the utility model.

Detailed ways

Please refer to Fig. 1 first. Fig. 1 is a schematic diagram of the principle of the laser scattering detection device for large-diameter neodymium glass surface defects of the present invention. It is also a structural schematic diagram of the best embodiment of the utility model. It can be seen from the figure that the laser scattering detection device for large-diameter neodymium glass surface defects of the utility model comprises:

An X-Y precision stepping platform 12 for placing the optical element 9 to be tested;

In the normal direction of the X-Y precision stepping platform 12 and above the optical element 9 to be measured, a second plane reflector 8, a scattered light collecting diaphragm 14, and a scattered light collecting objective lens are sequentially arranged on the same optical axis from bottom to top 15. An optical fiber group collector 16, which is located at the rear focal plane of the scattered light collecting objective lens 15, and the multi-channel scattered light signals collected by the optical fiber group collector 16 are introduced into the photodetector through the optical fiber group 17 The array 19 is converted into multiple electrical signals, and the second plane reflector 8 is 45° to the normal direction;

A laser 1, a Faraday isolator 2, a beam expander lens 3, a collimating lens 4, a focusing lens 5, a beam splitter 6 and a first plane reflector 7 are arranged in sequence along the laser beam emitted by the laser along the optical axis. The beam-splitting surface of the beam splitter 6 is 45° to the laser beam, and the laser beam is divided into a reflected beam and a transmitted beam by the beam splitter 6, and the transmitted beam is reflected obliquely by the first plane reflector 7 Focusing on the plane surface of the optical element 9 to be measured, the reflected beam is vertically focused on the plane surface of the optical element 9 to be measured after being reflected by the second plane mirror 8, and the two illumination beams are placed on the plane surface of the optical element 9 to be measured. A confocal spot on the plane surface of the optical element 9 to be measured;

A computer 17, the scattered light signal collected by the photodetector array 19 is converted into a multi-channel electrical signal, which is input to the computer 18 by a high-speed data acquisition card 20 after shaping and filtering; the control terminal of the computer 18 is connected to the drive module 11 , the driving module 11 drives the X-Y precision stepping platform 12 to move through the stepping motor 10 under the control of the computer 18 .

In this embodiment, a light trap 13 is provided in the transmission direction and reflection direction of the reflected light beam obliquely irradiating the optical element 9 to be measured after reflection by the first plane mirror 7, and a light trap 13 is arranged on the second plane A light trap 13 is also provided in the transmission direction in which the reflected light beam reflected by the mirror 8 irradiates the optical element 9 to be tested vertically.

In this embodiment, the optical fiber group collector 16, as shown in FIG. and scattered light collection points 162 distributed in a ring shape, the more the number of scattered light collection points, the better for defect classification, but it will also increase the system cost and increase the difficulty of signal processing. The fiber group 17 can be properly selected according to actual needs. quantity.

The scattered light collecting aperture 14 is a circular ring with a central hole 141, attached to the scattered light collecting objective lens 15, and divides the scattered light collecting objective lens 15 into a peripheral wide channel and a middle narrow channel.

The X-Y precision stepping platform 12 has a certain Z-direction adjustable capability, so that when inspecting optical elements with different thicknesses, the focal spot of the incident laser light is always located on the plane surface of the optical element 9 to be tested.

The laser 1 is a frequency-doubled laser pumped by a laser diode, which outputs a stable laser with a wavelength of λ=532nm and a power of 200mW.

Laser diode pumped frequency-doubled laser 1 outputs a stable laser with a wavelength of λ=532nm and a power of 200mW through the Faraday isolator 2, through the beam expander lens 3, collimator lens 4, and focus lens 5 to realize beam expansion, collimation, and focusing of the beam. The beam splitter 6 is divided into a transmitted light beam and a reflected light beam, which are respectively incident and focused on the surface of the optical element 9 to be measured by the first plane mirror 7 and the second plane mirror 8 along the oblique and vertical directions; 10 is a stepping motor driven by Computer 18 controls the driving module 11 to realize driving; 12 is an X-Y precision stepping platform, which is used to drive the optical element 9 to be tested and make it have a certain Z-direction adjustable ability, so that when detecting optical elements of different thicknesses, the focus of the incident laser The spot is always located on the surface of the detection plane; 13 is the light trap of the system, which is used to absorb reflected light and transmitted light, and reduce its influence on the scattered signal of defects; 14 is the aperture of the scattered light collection system, which divides the collection objective lens into surrounding Wide channel and narrow channel in the middle, so that collect the signal of each different channel; 15 is a scattered light collecting objective lens with large numerical aperture; 16 is the optical fiber group collector, and the multi-channel scattered light signal that collects is introduced photodetector through optical fiber group 17 The array 19 is converted into multiple electrical signals, which are collected by the high-speed data acquisition card 20 and sent to the computer 18 for storage after shaping and filtering.

The signal processing block diagram of the system is shown in Figure 4 and Figure 5. The electrical signals output by multiple photodetector units are independently amplified, filtered, and shaped by the module, and then converted into digital signals by the high-speed data acquisition card 20 and sent to the computer 18 for storage. 18 At the same time, it receives and saves the position information from the stepping scanning platform, and these data will participate in subsequent calculation and analysis after scanning. After the scanning is completed, the system extracts the signal of each defect to be analyzed from the computer database, and compares them with the standard defect signals in the computer database to obtain the reliability value corresponding to each standard signal, and calculate the maximum reliability. It can be considered that the defect to be analyzed is the most consistent with the standard defect as an equivalence relationship, and the standard defect can better replace the analyzed defect.

The standard defect information is to use other precision instruments (interferometer, tunneling microscope, AFT, etc.) to make standard defect detection samples with complete control of size, depth, and distribution, scan the detection samples, and store the measured data into the computer database. The standard defect signal required for system comparison. The X-Y precision stepping platform 12 drives the neodymium glass sheet to be tested to perform X-Y stepping scanning movement, and the scanning resolution of the surface is up to 1 μm; the repeatability is up to 5 μm.

The trial results show that the utility model has the advantages of high resolution, high accuracy, high detection efficiency, and is not affected by human subjective factors and naked eye fatigue.

Claims (5)

1. the laser light scattering pick-up unit of a heavy caliber neodymium glass beauty defects is characterized in that comprising:

One for the accurate stepping platform (12) of the X-Y that puts optical element to be measured (9);

In the normal direction of the accurate stepping platform of described X-Y (12) and the top of optical element to be measured (9), from bottom to top with optical axis set gradually second plane mirror (8), scattered light is collected diaphragm (14), scattered light is collected object lens (15), optical fibre set gatherer (16), this optical fibre set gatherer (16) is positioned at the back focal plane that described scattered light is collected object lens (15), the collected multichannel scattered light signal of this optical fibre set gatherer (16) is introduced photodetector array (19) through optical fibre set (17) and is converted into multi-channel electric signal, and described second plane mirror (8) is 45 ° with described normal direction;

One laser instrument (1), the direction of the laser beam of sending along this laser instrument (1) with optical axis set gradually faraday isolator (2), extender lens (3), collimation lens (4), condenser lens (5), spectroscope (6) and first plane mirror (7), the light splitting surface and the described laser beam of described spectroscope (6) are at 45, described laser beam is divided into folded light beam and transmitted light beam by described spectroscope (6), this transmitted light beam tiltedly focuses on the plane surface of described optical element to be measured (9) through first plane mirror (7) reflection hypsokinesis, this folded light beam vertically focuses on the plane surface of described optical element to be measured (9) after second plane mirror (8) reflection, and this two illumination beam is confocal spot on the plane surface of described optical element to be measured (9);

A computing machine (17), the scattered light signal that described photodetector array (19) is collected is converted into multi-channel electric signal, imports this computing machine (18) through behind the shaping filter by high-speed data acquisition card (20); The control termination driver module (11) of this computing machine (18), this driver module (11) drive the accurate stepping platform of described X-Y (12) motion by step motor (10) under the control of this computing machine (18).

2. the laser light scattering pick-up unit of heavy caliber neodymium glass beauty defects according to claim 1, it is characterized in that the transmission direction and the reflection direction that reflect the described optical element to be measured of irradiation obliquely (9) of back reflection light beam at described first plane mirror (7) are provided with light trapping (13), the transmission direction that the folded light beam after described second plane mirror (8) reflection is vertically shone described optical element to be measured (9) also is provided with light trapping (13).

3. the laser light scattering pick-up unit of heavy caliber neodymium glass beauty defects according to claim 1, it is characterized in that described optical fibre set gatherer (16) has the scattered light bleeding point of a plurality of dispersions, the distribution that is centrosymmetric of the scattered light bleeding point of these a plurality of dispersions.

4. the laser light scattering pick-up unit of heavy caliber neodymium glass beauty defects according to claim 1, it is characterized in that it is one to have the annulus of center pit (141) that described scattered light is collected diaphragm (14), be sticked and collect on the object lens (15), scattered light is collected object lens (15) be divided into fat pipe and middle narrow passage on every side at described scattered light.

5. the laser light scattering pick-up unit of heavy caliber neodymium glass beauty defects according to claim 1 is characterized in that described laser instrument (1) is laser diode-pumped frequency double laser, and output wavelength is the stabilized lasers of λ=532nm power 200mW.

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