CN1696661A - Method and device for laser speckle interferometry - Google Patents

Abstract

The present invention relates to a method and device for measuring nanoparticles by laser. A laser 1, a beam splitter 2, a spatial phase scanning plate 3, a measured sample 4, a phase scanning mirror 5, and a CCD camera 6 are placed on the Michelson laser interference optical path. , adjust the optical path of the Michelson laser interference, and use the spatial phase scanning plate and the phase scanning mirror to record the three-dimensional phase information of the surface of the measured sample in real time during the change of the surface shape of the measured sample, and form a transverse shearing laser beam in the CCD camera. The speckle interference image is stored in the computer through the image acquisition card. The image is then processed by statistical correlation theory and subdivision technology. The invention provides a laser speckle interferometry method and device capable of measuring three-dimensional phase information, expanding the amount of information, improving the accuracy of lateral measurement, and expanding the application range. It can not only be applied to the characterization of the dynamic behavior of nanoparticles, but also can be used as a detection method in the fields of microelectronics, micro-optical components and semiconductor manufacturing.

Description

Method and device for laser speckle interferometry

Technical Field: The present invention relates to a method and device for measuring nanoparticles with laser light.

Background technology: Laser speckle is a phenomenon in which the high coherence of laser light is coherent on the rough surface of a diffuse object. The speckle phenomenon is manifested as when the diffuse surface is illuminated by laser light, the image surface is granular, and the surface is covered by some small statistically distributed bright and dark spots. The reason is that when an object is irradiated by a laser, every point scatters light. Due to the high coherence of the laser light source, the light scattered by one object point interferes with the light scattered by other object points, forming a statistically regular and seemingly chaotic interference pattern.

The experimental device of the traditional laser speckle interferometry method is shown in Figure 1, including a laser 1, a beam splitter 2, a phase delay device 3, a measured sample 4, a reference sample 5, and a CCD camera 6. The light emitted by the laser 1 passes through the beam splitter 2 and shines on the measured sample 4 and the reference sample 5, and the reflected object light and reference light enter the CCD camera 6 through the beam splitter 2 again to form a speckle interference pattern. In this process, the reference light passes through the beam splitter 2 three times, and the object light passes through the beam splitter 2 once. In order to compensate the optical path difference between the two, a phase delay device 3 is usually added between the beam splitter 2 and the sample 4 to be measured. Through this method, the plane information of the tested sample is obtained.

Because the traditional laser speckle interferometry method and device can only obtain the phase information of the sample plane, the amount of information obtained by the measurement is not rich enough, so the measurement accuracy is not high. At present, the lateral measurement accuracy is only up to 10um. This limits the application field of the laser speckle interferometry method. For example, in nanotechnology, since the particle size is generally on the nanometer scale, in order to obtain the dynamic behavior process of the nanoparticle, it is required that the lateral measurement accuracy of the detection method should be below 1um. even smaller. This requires us to obtain more information during detection. Obviously, the existing laser speckle interferometry method cannot meet the requirements of measurement accuracy, and these fields have obvious advantages in detection by laser speckle interferometry. . That is to say, the main problems existing in the existing laser speckle interferometry method and its device are that the amount of information obtained is not rich enough, and the accuracy of lateral measurement is not high enough.

Details of the invention:

The technical problem to be solved in the present invention:

In view of the problems existing in the existing laser speckle interferometry method, the technical problem we want to solve is: to improve the existing laser speckle interferometry method and device that cannot measure the three-dimensional phase information, the amount of information is not rich enough, and the lateral measurement accuracy is not high enough Problem, for this reason, the present invention will provide a laser speckle interferometry method and device capable of measuring three-dimensional phase information, expanding the amount of information, improving the accuracy of lateral measurement, and expanding the scope of application.

The technical scheme of the device of the present invention is shown in Figure 2, and it comprises: laser device, spectroscopic plate, spatial phase scanning plate, measured sample, phase scanning mirror, CCD camera;

On one optical path of the Michelson interferometer, the laser, the spectroscopic plate, the spatial phase scanning plate and the measured sample are placed coaxially in sequence, and the spatial phase scanning plate is placed between the spectroscopic plate and the measured sample; the other optical path is in the The phase-scanning mirror and the CCD camera are respectively placed on both sides of the beam splitter, and the beam splitter, the phase-scanning mirror and the CCD camera are kept coaxial.

Method of the present invention: as can be seen from Fig. 2, the laser speckle interferometry steps are as follows:

First, a laser, a beam splitter, a spatial phase scanning plate and the measured sample are placed on one optical path of the Michelson interference device to form a laser beam splitting interference optical path, and a phase scanning mirror and a CCD camera are placed on the other optical path to form a Another laser beam splitting interference optical path, adjust the laser beam splitting interference optical path;

Then apply a driving signal to the measured sample, and simultaneously drive the spatial phase scanning plate and the phase scanning mirror to uniformly scan the surface of the measured sample, and transversely shear the surface of the measured sample to form an interference image; make the spatial phase scanning plate and the phase scanning mirror interact with each other Cooperate to obtain the three-dimensional phase information of the measured sample, and record the surface changes of the measured sample in real time; use the phase-locking and unlocking of the spatial phase scanning plate and the phase scanning mirror to form a speckle fringe image of spatial interference imaging relative to the measured sample, and Synchronously generate multiple shear and phase scanning interference images of the sample under test; store the speckle fringe image in the computer, display the laser speckle interference pattern on the display, and analyze the dynamic behavior of the particles on the sample surface driven by external signals;

The speckle fringe image is extracted from the background light, and then the observed laser speckle fringe image is subdivided, and the phase-locking technology is used to make the light reflected from different points of the sample under test form a fixed phase difference, thereby interfering with each other to form Periodic interference pattern, using image analysis software to analyze the interference pattern to obtain the surface information of a specific area of the measured sample, and complete the measurement of laser speckle interference.

Working process: The light emitted by the laser passes through the beam splitter and becomes two beams of light that shine on the measured sample and the reference mirror respectively, and the reflected object light and reference light pass through the beam splitter again and then enter the CCD camera to form speckle interference image.

Advantages of the present invention:

It can be seen from Fig. 2 that the research scheme of the present invention is different from the previous schemes in that a spatial phase scanning plate is added to the object optical path and a phase scanning mirror is added to the reference optical path. Background Art Only a phase delay device is placed on the object-side optical path to compensate the optical path to ensure interference between the two beams of light; or the phase-shift method is used to improve the object-side longitudinal (ranging) resolution, and the obtained plane information is still obtained. However, in the present invention, the spatial phase scanning plate and the phase scanning mirror are placed in the optical path at the same time, so that the surface of the sample to be tested can be scanned uniformly and in a large range, which not only has the interference imaging of transverse shearing, but also improves the longitudinal resolution, and obtains a three-dimensional phase information.

The notable advantages of the laser speckle interferometry method and device for dual-phase scanning of the present invention are: (1) It can measure three-dimensional phase information and expand the amount of information. (2) The measurement accuracy is high. Combined with the image subdivision method, the lateral measurement accuracy can be reduced from the current 10 μm to less than 1 μm, or even smaller. (3) It has a wide range of applications, not only can realize traditional laser speckle interferometry, but also can be applied to the dynamic behavior characterization of nanoparticles. The invention is a non-contact, non-destructive, real-time and dynamic measurement method, which is widely used in the measurement of surface roughness, displacement, deformation, stress and the like. It can not only be applied to the measurement of nanoparticles, but also can be used as a detection method in the fields of microelectronics, micro-optical components and semiconductor manufacturing.

Description of drawings:

Figure 1 is the laser speckle interferometry method and device in the background technology

Fig. 2 is the laser speckle interferometry method and device of dual-phase scanning of the present invention

Detailed ways:

The phase scanning laser speckle interferometry method of the invention has been applied in the detection of magnetic fluid optical display screens. With reference to Fig. 2, the application of the present invention is described. It includes: a laser 1 , a beam splitter 2 , a spatial phase scanning plate 3 , a measured sample 4 , a phase scanning mirror 5 , and a CCD camera 6 .

Laser 1 uses a 30mw He-Ne laser or other types of lasers; beam splitter 2 uses a general-purpose optical beam splitter; spatial phase scanning board 3 includes a synchronous motor and an oscillator mirror, and the oscillator mirror is driven by a synchronous motor, or the oscillator is driven by a sawtooth wave mirror, or other driving methods; the measured sample 4 uses a magnetic fluid display panel as the tested sample, and the size is selected as 10cm×10cm; the phase scanning mirror 5 includes a synchronous motor and a phase plate, and the phase plate is driven by a synchronous motor, or Other drive modes; CCD camera 6 adopts a CCD camera with 1 million pixels.

First, a He-Ne laser, an optical beam splitter, a spatial phase scanning panel and a magnetic fluid display panel are placed on one optical path of the Michelson interference device to form a laser beam splitting interference optical path, and a phase scanning reflector is placed on the other optical path The mirror and the 1 million pixel CCD camera form another laser beam splitting interference optical path, and adjust the laser beam splitting interference optical path;

Use a signal generator to apply a driving signal to the magnetic fluid display panel, and at the same time use a sawtooth wave to drive the vibrator mirror and a synchronous motor to drive the phase plate to uniformly scan the surface of the magnetic fluid display panel, and transversely shear the surface of the magnetic fluid display panel to make the magnetic fluid display The light reflected back from different points on the surface of the plate interferes with each other to form an interference image; make the vibrator mirror and the phase plate cooperate with each other and maintain a certain functional relationship to obtain the three-dimensional phase information of the magnetic fluid display panel, then in the process of changing the surface shape of the magnetic fluid display panel , to record the change of its surface morphology in real time; using the phase-locking and unlocking of the spatial phase scanning plate and the phase scanning mirror to form a speckle fringe image of spatial interference imaging on the surface of the magnetic fluid display panel, and synchronously generate multiple images on the surface of the magnetic fluid display panel. Interference images of shearing and phase scanning; the speckle fringe images are stored in the computer through the image acquisition card, and the laser speckle interference patterns are displayed on the monitor; the image analysis software is used to analyze the dynamic behavior of the particles on the sample surface driven by external signals ;

Using image processing technology and statistical correlation theory, the gray scale method can be used to extract the speckle fringe image from the background light, and then the laser speckle fringe image is thinned. It is divided into 10 parts to make the measurement accuracy from the current 10μm to 1μm; use the phase-locking technology to make the magnetic fluid display panel different; the reflected light forms a fixed phase difference, thereby interfering with each other to form a periodic interference pattern. The image analysis software compiled in language analyzes the interference pattern to obtain the surface particle information of the measured area of the magnetic fluid display panel sample, and completes the measurement of laser speckle interference.

Claims (2)

1. A laser speckle interferometry device, comprising: a laser (1), a spectroscopic plate (2), a sample to be measured (4), and a CCD camera (6); it is characterized in that it also includes: a spatial phase scanning plate (3), The phase scanning mirror (5) coaxially places the laser (1), the beam splitter (2), the spatial phase scanning plate (3) and the measured sample (4) sequentially on one optical path of the Michelson interferometer. A spatial phase scanning plate (3) is placed between the spectroscopic plate (2) and the measured sample (4); the phase scanning mirror (5) and a CCD camera ( 6), and keep the beam splitter 2, the phase scanning mirror (5) and the CCD camera (6) coaxial. 2. Laser speckle interferometry method, characterized in that: First, a laser, a beam splitter, a spatial phase scanning plate and the measured sample are placed on one optical path of the Michelson interference device to form a laser beam splitting interference optical path, and a phase scanning mirror and a CCD camera are placed on the other optical path to form a Another laser beam splitting interference optical path, adjust the laser beam splitting interference optical path; Then apply a driving signal to the measured sample, and simultaneously drive the spatial phase scanning plate and the phase scanning mirror to uniformly scan the surface of the measured sample, and transversely shear the surface of the measured sample to form an interference image; make the spatial phase scanning plate and the phase scanning mirror interact with each other Cooperate to obtain the three-dimensional phase information of the measured sample, and record the surface changes of the measured sample in real time; use the phase-locking and unlocking of the spatial phase scanning plate and the phase scanning mirror to form a speckle fringe image of spatial interference imaging relative to the measured sample, and Synchronously generate multiple shear and phase scanning interference images of the sample under test; store the speckle fringe image in the computer, display the laser speckle interference pattern on the display, and analyze the dynamic behavior of the particles on the sample surface driven by external signals; The speckle fringe image is extracted from the background light, and then the observed laser speckle fringe image is subdivided, and the phase-locking technology is used to make the light reflected from different points of the sample under test form a fixed phase difference, thereby interfering with each other to form Periodic interference pattern, using image analysis software to analyze the interference pattern to obtain the surface information of a specific area of the measured sample, and complete the measurement of laser speckle interference.