CN102213839B - Laser speckle eliminating device with dodging function - Google Patents

Abstract

The invention discloses a laser speckle eliminating device with the dodging function. The device comprises a laser light source, a transmission medium and a vibration module, wherein the vibration module is fixedly connected with the transmission medium; a scattering body is arranged in the transmission medium; the scattering body is formed by distributing the material which is different from the transmission medium with uniform density in the transmission medium; the vibration module is vibrated under the action of a power supply, thereby driving the transmission medium and the scattering body to vibrate together; and the input power of the vibration module is adjusted to adjust the vibration amplitude of the transmission medium and the scattering body until the optimal speckle eliminating effect is obtained.

Description

A laser speckle elimination device with uniform light function

technical field

The invention relates to a laser speckle elimination device with uniform light function, belonging to the technical field of laser imaging. the

Background technique

Laser has the characteristics of good directionality, high brightness, good monochromaticity, and good coherence. It is these characteristics that make lasers used in various fields. However, due to the particularly good coherence of the laser, speckle noise will be formed during imaging, which affects the imaging quality, and speckle needs to be controlled. In the typical hollow rectangular strong laser beam output by the laser, the intensity distribution of the beam is non-uniform along the direction of the flow field. The inhomogeneity of the light intensity distribution will lead to non-uniform thermal deformation of the numerous reflective mirrors in the laser transmission channel, which will distort the wavefront distribution of the final output beam of the laser system, resulting in a decrease in the quality of the output beam. So it is necessary to homogenize the laser beam. Therefore, it is a problem to make the emitted light beam uniform while eliminating the speckle. the

In high-power laser systems and applications, it is hoped that the output laser beam has a large fill factor and a uniform and smooth intensity distribution. In the amplifier, the inhomogeneity of the input beam will lead to nonlinear effects, which will deteriorate the quality of the output beam and even damage the laser working object. In practical applications, it is affected by the system. The light intensity of the beam is not only modulated by the amplitude, but also has a Gaussian distribution and a phase. Distortion, so dodging is required. The so-called laser beam homogenization technology refers to changing the intensity distribution of the incident laser beam to the required intensity distribution, and at the same time adjusting the phase splitting of the beam to control the propagation path. the

Figure 1 shows a schematic diagram of laser speckle formation. The concept of laser speckle: when a beam of light is irradiated on a rough surface with diffuse reflection characteristics, you can always see some light in the reflected light space with the observation screen. Speckle, this is the phenomenon of laser speckle. The reason is that after the electromagnetic wave or particle beam undergoes random scattering by the medium, it will form a scattered field with random distribution. When a signal is summed by a large number of complex components with independent phases, the signal will appear speckle. These components can have random lengths and random directions, or known lengths and random directions in the complex plane. When these components add up, they constitute what is known as a "random walk". The resulting sum can be larger or smaller, depending on the relative phases of the components of the summation, and in particular whether constructive or destructive interference is dominant. As shown in the figure, when the laser 102 irradiates the rough material surface 101, the two beams interfere at point A in front of the screen after the similar beams are diffusely reflected by the rough surface. If constructive interference occurs, point A appears as a bright spot, and if destructive interference occurs, point A appears as a dark spot. Therefore, when the laser is directly imaged on the object without processing, speckle noise with random distribution will be displayed on the screen. the

The patent publication with the publication number CN101425656A adopts the method of rapidly changing the laser cavity length or the optical path experienced by the laser by using piezoelectric effect, electro-optic effect, acousto-optic effect and etalon to make the laser output wavelength change rapidly or produce a jump to reduce the laser speckle effect. The disadvantage of this method is that the structure of the laser itself needs to be changed, and at the same time, the beam inhomogeneity of the laser beam itself has not been improved. the

In view of this, it is necessary to provide a device that can eliminate laser speckle and uniform light without changing the structure of the laser itself. the

Contents of the invention

The invention provides a laser speckle elimination device with uniform light function aiming at the deficiencies of the prior art. The technical scheme is as follows:

A laser speckle elimination device with uniform light function, comprising a laser light source, a transmission medium, a vibration module, the vibration module is fixedly connected to the transmission medium, there is a scatterer in the transmission medium, and the scatterer is made of a different The material of the transmission medium is formed in the transmission medium with a uniform density distribution; the vibration module vibrates under the action of the power supply, and then drives the transmission medium and the scatterer to vibrate together, and the input power of the vibration module is adjusted to adjust The vibration amplitude of the transmission medium and scatterers is obtained until the best speckle reduction effect is obtained. the

In the laser speckle elimination device with uniform light function, polymethyl methacrylate can be used as the transmission medium, and 4 μm SiO ₂ scattering particles with a mass fraction of 0.3 wt % can be used as the scatterer.

In the laser speckle elimination device with uniform light function, the vibration frequency of the vibration module is higher than 80 Hz. the

Advantages and positive effects:

This method can combine speckle elimination and laser beam homogenization to achieve the advantage of solving two problems at the same time. In the transmission process, because the transmission medium with scatterers is used, the scatterers refer to objects that can make the light soft and have no obvious projection, so the scatterers can make the transmitted laser beam uniform. The vibration scatterer and the transmission medium are meant to destroy the coherence of the laser in transmission, and the strong coherence of the laser is the main cause of speckle. Among them, the vibration adopts the vibration module, and the corresponding voltage is given to the vibration module to make the transmission medium and the scattering body vibrate together. Different voltages have different vibration frequencies, and the effect of eliminating speckle is also different. The voltage can be adjusted conveniently to obtain the imaging image with the best speckle elimination effect. The present invention adopts the above technical solution, and discloses a method that can effectively eliminate speckle and uniform light. At the same time, compared with other speckle elimination methods, this method does not need to change the structure of the laser itself, and the structure is simple. It also has great advantages in the field of laser imaging. big advantage.

Description of drawings

Figure 1 is a schematic diagram of the principle of speckle formation by laser;

Fig. 2 is a frame diagram of the present invention;

Fig. 3 is the structural representation of the embodiment of the present invention;

Description of symbols of main components: rough plane 101 , laser light source 102 , laser beam 301 , scatterer 302 , transmission medium 303 , vibration module 304 , power supply 305 . the

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. the

Fig. 2 is a schematic structural diagram of a laser speckle elimination device with uniform light function of the present invention, including a laser light source, a transmission medium, a vibration module, and the vibration module is fixedly connected to the transmission medium. the

Fig. 3 has shown the internal structure diagram and optical path schematic diagram of the present invention, wherein the laser beam 301 that laser light source sends is transmitted by the transmission medium 303 that has scatterer 302 in it, and scatterer 302 is by the material that is different from transmission medium 303 with uniform The density is distributed in the transmission medium. Generally, the transmission medium 303 can be made of polymethyl methacrylate, while the scattering body 302 mostly uses 4 μm SiO ₂ scattering particles with a mass fraction of 0.3 wt%. A vibration module 304 is added outside the transmission medium. The vibration module vibrates under the action of the power supply 305, and then drives the transmission medium 303 and the scatterer 302 to vibrate together. Adjust the input power of the vibration module to adjust the vibration of the transmission medium 303 and the scatterer 302. Vibrate the amplitude until the best speckle reduction effect is obtained. The vibration frequency is generally required to be greater than the critical flicker frequency of the human eye. When the frequency is higher than 80Hz, the relative energy amplitude is very close to 0, and the human eye can hardly feel the flicker, so the vibration frequency should be higher than 80Hz. The laser light is transmitted through the vibrating transmission medium and then projected on the imaging object 306 .

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should belong to the protection scope of the appended claims of the present invention. the

Claims (2)

1. A laser speckle elimination device with uniform light function, characterized in that it includes a laser light source, a transmission medium, a vibration module, the vibration module is fixedly connected to the transmission medium, and there is a scatterer in the transmission medium. The scatterer is formed by a material different from the transmission medium and distributed in the transmission medium with a uniform density; the vibration module vibrates under the action of the power supply, and then drives the transmission medium and the scatterer to vibrate together, and the vibration module is adjusted The input power is used to adjust the vibration amplitude of the transmission medium and the scatterer until the best speckle elimination effect is obtained; the transmission medium uses polymethyl methacrylate, and the scatterer uses polymethyl methacrylate with a mass fraction of 0.3wt%. 4 μm _SiO2 scattering particles. 2 . The laser speckle removal device with uniform light function according to claim 1 , wherein the vibration frequency of the vibration module is higher than 80 Hz.

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