阅读说明：本技术 一种用于激光投影抑制散斑的装置及其方法 (Device and method for inhibiting speckles in laser projection ) 是由 魏威 邹思源 董俊 林丰 贺银波 于 2021-10-18 设计创作，主要内容包括：本发明公开一种用于激光投影抑制散斑的装置及其方法,激光光源发出激光光束后,沿激光光束方向依次设有准直模块、均光器件、分光器件、周期型光程差器件、1/4玻片和探测面；激光光源置于准直模块的焦平面处,均光器件的有效孔径大于等于通过准直模块后的激光光束,分光器件的有效孔径大于等于通过均光器件后的激光光束；周期型光程差器件的有效孔径大于等于通过分光器件后的激光光束,周期型光程差器件配合设有可旋转的1/4玻片,可旋转的1/4玻片以激光光束光轴方向为旋转轴切向旋转,可旋转的1/4玻片的有效孔径大于通过周期型光程差器件的激光光束。本发明通过一个周期型光程差器件组合一个可沿光束传播方向呈中心旋转的1/4玻片实现对偏振态的破坏。(The invention discloses a device and a method for inhibiting speckles by laser projection.A collimation module, a light equalizing device, a light splitting device, a periodic optical path difference device, an 1/4 glass slide and a detection surface are sequentially arranged along the direction of a laser beam after the laser beam is emitted by a laser light source; the laser light source is arranged at the focal plane of the collimation module, the effective aperture of the light-equalizing device is larger than or equal to the laser beam passing through the collimation module, and the effective aperture of the light-splitting device is larger than or equal to the laser beam passing through the light-equalizing device; the effective aperture of the periodic optical path difference device is larger than or equal to the laser beam passing through the light splitting device, the periodic optical path difference device is matched with a rotatable 1/4 glass slide, the rotatable 1/4 glass slide rotates tangentially by taking the optical axis direction of the laser beam as a rotating shaft, and the effective aperture of the rotatable 1/4 glass slide is larger than the laser beam passing through the periodic optical path difference device. The present invention realizes the destruction of polarization state by combining a periodic optical path difference device with an 1/4 glass slide which can rotate along the propagation direction of light beams.)

1. The utility model provides a device for laser projection suppresses speckle, its constitution includes laser light source, collimation module, light equalizing device, beam splitter, periodic type optical path difference device, 1/4 slide and detection face, its characterized in that: after the laser light source emits laser beams, a collimation module, a light equalizing device, a light splitting device, a periodic optical path difference device, an 1/4 glass slide and a detection surface are sequentially arranged along the direction of the laser beams; the laser light source is arranged at the focal plane of the collimation module, the effective aperture of the light-equalizing device is larger than or equal to that of the laser beam passing through the collimation module, and the effective aperture of the light-splitting device is larger than or equal to that of the laser beam passing through the light-equalizing device; the effective aperture of the periodic optical path difference device is larger than or equal to the laser beam passing through the light splitting device, the periodic optical path difference device is matched with a rotatable 1/4 glass slide, the rotatable 1/4 glass slide rotates tangentially by taking the optical axis direction of the laser beam as a rotating shaft, and the effective aperture of the rotatable 1/4 glass slide is larger than the laser beam passing through the periodic optical path difference device.

2. The device of claim 1, wherein the beam splitter is one of a birefringent crystal and a polarizing beam splitter prism.

3. The device for suppressing speckle in laser projection according to claim 2, wherein the polarization direction of the laser light source is at an angle of 45 degrees or 135 degrees with respect to the crystal axis of the birefringent crystal or the polarization splitting axis of the polarization splitting prism.

4. The apparatus of claim 1, wherein the periodic optical path difference device is one of a one-dimensional periodic optical path difference device and a two-dimensional periodic optical path difference device.

5. A method for suppressing speckle in laser projection, namely using a periodic optical path difference device to combine an 1/4 glass slide which can rotate along the propagation direction of a light beam to realize the damage to the polarization state, and is characterized by comprising the following steps:

s1, positioning the laser light source at the focal plane of the collimation system, and integrating the light diverged by the laser light source into small-angle divergent light beams approximate to parallel light by the collimation system;

s2, positioning the light-equalizing device behind the light beam emitting direction of the collimation system, wherein the aperture of the light beam is continuously enlarged along with the increase of the working distance, the position of the light-equalizing device cannot be too far away from the collimation system, the effective aperture of the light-equalizing device is larger than or equal to that of the collimated light beam, and the light-equalizing device mainly has the effect of realizing that the light beam has an even light field in a far field;

s3, positioning the light splitting device behind the light homogenizing device along the light beam emitting direction, wherein the effective aperture of the light splitting device is larger than or equal to the laser light beam after light homogenizing, and the light splitting device mainly has the functions of splitting polarized light and preprocessing the polarized light beam to damage the consistency of the polarization state of the polarized light beam;

s4, positioning the periodic optical path difference device behind the birefringent crystal along the light beam emission direction, wherein the effective aperture of the periodic optical path difference device is larger than that of the laser light beam at the moment, and the periodic optical path difference device mainly has the function of realizing regional differentiation of the optical path of the polarized light beam, so that the polarization state of the light beam is divided according to regions, and the consistency of the polarization state of the polarized light beam is further destroyed;

s5, the rotatable 1/4 glass slide is located behind the periodic optical path difference device along the light beam emission direction, the effective aperture of the rotatable 1/4 glass slide is larger than that of the laser light beam at the moment, the rotatable 1/4 glass slide mainly has the effect that the polarization state of the light beam changes according to time, the consistency of the polarization state of the polarized light beam is further destroyed, the interference condition of the light beam falling on a detection surface (wall surface) is finally destroyed, and speckle suppression is further achieved.

6. The method of claim 5, wherein the beam splitter in S3 is any one of a birefringent crystal or a polarization beam splitter prism.

7. The method of claim 6, wherein the beam splitter is used to make the polarization direction of the laser source at an angle of 45 degrees or 135 degrees with respect to the birefringent crystal axis or polarization splitting axis.

Technical Field

The invention relates to the technical field of laser display, in particular to a device and a method for inhibiting speckles by laser projection.

Background

With the maturity of the technical level, projection devices are used in more and more fields, such as home video, advertisement projection, industrial projection detection, and the like. In spite of the recent development of laser display technology, laser display has many advantages such as wide color gamut, high brightness, large screen, and low power consumption, so that such schemes can be ascending in the rows and columns of the next generation display technology.

One problem that cannot be avoided with laser displays is the problem of speckle due to the high coherence of the laser light. This random distribution of light intensity in the form of particles can seriously affect picture quality. How to reduce the influence of speckle is an inevitable topic of research in the field of laser display.

The currently common mode for inhibiting laser speckles is to realize the superposition of independent speckles in a dynamic speckle elimination mode, a mechanical scanning mode, a vibration mode and the like. The method specifically comprises the following steps: scanning diffuse scatterers with random phase and motion screens. The above-mentioned methods are complicated to operate, expensive in components, and poor in suppression effect.

Accordingly, providing an apparatus for laser projection speckle suppression and a method thereof have been problems that need to be solved by those skilled in the art.

Disclosure of Invention

In view of this, the present invention provides a device for laser projection speckle suppression, which ultimately achieves suppression of laser projection speckle by making a light beam have polarization diversity, and meanwhile, the device has a simplified structure, is simple in device, and can achieve a better suppression effect.

In order to achieve the purpose, the invention provides the following technical scheme: the utility model provides a device for laser projection suppresses speckle, its constitution includes laser light source, collimation module, light equalizing device, beam splitter, periodic type optical path difference device, 1/4 slide and detection face, its characterized in that: after the laser light source emits laser beams, a collimation module, a light equalizing device, a light splitting device, a periodic optical path difference device, an 1/4 glass slide and a detection surface are sequentially arranged along the direction of the laser beams; the laser light source is arranged at the focal plane of the collimation module, the effective aperture of the light-equalizing device is larger than or equal to that of the laser beam passing through the collimation module, and the effective aperture of the light-splitting device is larger than or equal to that of the laser beam passing through the light-equalizing device; the effective aperture of the periodic optical path difference device is larger than or equal to the laser beam passing through the light splitting device, the periodic optical path difference device is matched with a rotatable 1/4 glass slide, the rotatable 1/4 glass slide rotates tangentially by taking the optical axis direction of the laser beam as a rotating shaft, and the effective aperture of the rotatable 1/4 glass slide is larger than the laser beam passing through the periodic optical path difference device.

Preferably, in the above apparatus for laser projection speckle suppression, the light splitting device is one of a birefringent crystal and a polarization beam splitter prism.

Preferably, in the above apparatus for suppressing speckle in laser projection, an angle between a polarization direction of the laser light source and a crystal axis of the birefringent crystal or a polarization splitting axis of the polarization splitting prism is 45 degrees or 135 degrees.

Preferably, in the above apparatus for suppressing speckle in laser projection, the periodic optical path difference device is one of a one-dimensional periodic optical path difference device and a two-dimensional periodic optical path difference device.

Through the technical scheme, compared with the prior art, the invention has the following advantages: the invention enables the interference condition of the light field to be destroyed by changing the included angle of the polarization direction of the laser beam, and further enables the speckle phenomenon to be inhibited, namely, an 1/4 glass sheet which can rotate along the transmission direction of the beam in the center is combined by using a periodic optical path difference device to realize the destruction of the polarization state.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic diagram of the present invention.

FIG. 2 is a schematic diagram of a one-dimensional periodic retardation device according to the present invention.

FIG. 3 is a schematic diagram of a two-dimensional periodic retardation device according to the present invention.

Fig. 4 is a schematic view of the present invention in an operating state.

FIG. 5 is a schematic diagram of the polarization distribution on the detection plane corresponding to FIG. 4.

In the figure: 1. a laser light source; 2. a collimation module; 3. a light equalizing device; 4. a light-splitting device; 5. a periodic optical path difference device; 6. 1/4 slide glass; 7. and detecting the surface.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-5, the device for suppressing speckle in laser projection disclosed by the present invention comprises a laser light source 1, a collimating module 2, a light equalizing device 3, a light splitting device 4, a periodic optical path difference device 5, an 1/4 slide 6, and a detection surface 7, and is characterized in that: after the laser light source 1 emits laser light beams, a collimation module 2, a light equalizing device 3, a light splitting device 4, a periodic optical path difference device 5, an 1/4 glass slide 6 and a detection surface 7 are sequentially arranged along the direction of the laser light beams; the laser light source 1 is arranged at the focal plane of the collimation module 2, the effective aperture of the light-homogenizing device 3 is larger than or equal to that of the laser beam passing through the collimation module 2, and the effective aperture of the light-splitting device 4 is larger than or equal to that of the laser beam passing through the light-homogenizing device 3; the effective aperture of the periodic optical path difference device 5 is larger than or equal to the laser beam passing through the light splitting device 4, the periodic optical path difference device 5 is provided with a rotatable 1/4 glass slide 6 in a matching manner, the rotatable 1/4 glass slide 6 rotates tangentially by taking the optical axis direction of the laser beam as a rotating shaft, and the effective aperture of the rotatable 1/4 glass slide 6 is larger than the laser beam passing through the periodic optical path difference device 5.

Preferably, in the above apparatus for suppressing speckle in laser projection, the light splitting device 4 is one of a birefringent crystal and a polarization beam splitter prism.

Preferably, in the above apparatus for suppressing speckle in laser projection, an angle between the polarization direction of the laser light source 1 and the crystal axis of the birefringent crystal or the polarization splitting axis of the polarization splitting prism is 45 degrees or 135 degrees.

Preferably, in the above apparatus for suppressing speckle in laser projection, the periodic optical path difference device 5 is one of a one-dimensional periodic optical path difference device and a two-dimensional periodic optical path difference device.

Principle description of the present device:

the laser light source 1 has three characteristics of good monochromaticity, good directivity and good coherence. In particular, a semiconductor laser light source used for laser projection has an extremely remarkable polarization characteristic, and Ts: Tp >99:1 is actually used.

Speckle phenomenon after the first laser in 1960 was discovered the peculiar phenomenon: when laser is irradiated on the surface of rough objects such as wall or paper, a plurality of granular patterns which are relatively uniform but have no specific distribution rule are generated. This random fluctuation in intensity is due to interference phenomena caused by the coherent light impinging on the "rough" surface.

This type of speckle phenomenon is actually an optical interference phenomenon. Only monochromatic wavelengths are considered for the moment, and the necessary conditions for light wave interference need to be met. If the two vibration directions form a plane wave with an included angle alpha.

The resultant vector of the two light waves is then:

since the interference refers to a stable intensity distribution of light intensity, the light intensity of the combined vibration needs to be considered, and actually, only an average value of a period of time can be observed, so that the formula can be expressed as follows:

wherein the content of the first and second substances,this is constant, the coherence term of the system is:

the included angle between the two vibration directions is alpha, when the two light waves are perpendicular to each other, the vibration directions are perpendicular to each othercos α is 0, and there is no interference.

The phase influencing factors that actually influence the interference state are:

if there is an interference condition, it is necessaryDoes not change with time, and the phase difference is constant and the frequency is the same.

The frequency is practically constant among the laser light sources 1 used.

Aiming at the principle situation, the interference condition of the light field is destroyed by changing the included angle of the polarization direction of the laser beam, and then the speckle phenomenon is inhibited.

In order to destroy the consistency of the polarization state of the laser beam, the invention provides a composite processing mechanism, namely, 1/4 glass which can rotate along the propagation direction of the beam in a central mode is combined by a periodic optical path difference device to realize the destruction of the polarization state.

There is a light splitting device (birefringent crystal) that splits a light beam into o light and e light after passing through; in practice, this is a kind of polarizing beam splitter. Polarized light can be distinguished into P-states and S-states. The vibration directions of the two types of polarized light in the space are mutually orthogonal. Such optical splitters include, but are not limited to, birefringent crystals or other optical splitters.

It is established that the laser beam passing through the collimation system and the light equalizing system is divided into two orthogonal polarized beams after passing through the light splitting device (birefringent crystal), and the polarization state is separated no matter whether the laser beam is completely divided into two separate beams or not after passing through the light splitting device.

When the light beam reaches the periodic optical path difference device 5, the light beam is divided into a plurality of sub light fields by the optical path difference device along with the change of the period, a certain optical path difference exists among the sub light fields, and the consistency of the polarization state of the laser light beam is damaged among the sub light fields due to the inconsistent optical path difference; when several sub-fields pass through 1/4 slides, their polarization states separate and become orthogonal, and the interference condition where the field falls on the screen has been destroyed. Because different screen materials have different depolarization responses to the polarization state of the incident beam, the speckle phenomenon is suppressed to a lower level no matter the depolarization degree.

The light splitting device includes, but is not limited to, a birefringent crystal, or a polarization splitting prism.

Due to the fact that the polarization characteristic of the laser light source is obvious, Ts: Tp is greater than 99: 1; when the optical splitting device is used, the angle between the polarization direction of the laser light source and the birefringent crystal axis or the polarization splitting axis needs to be 45 degrees or 135 degrees.

The arrangement mode of the device is mainly as follows:

the laser light source is positioned at the focal plane of the collimation system;

the collimation system integrates light emitted by the laser light source into small-angle divergent light beams approximate to parallel light;

the light-equalizing device is positioned behind the collimation system along the light beam emission direction, because the aperture of the light beam is continuously enlarged along with the increase of the working distance, the position of the light-equalizing device cannot be too far away from the collimation system, the effective aperture of the light-equalizing device is larger than or equal to that of the collimated light beam, and the light-equalizing device mainly has the function of realizing that the light beam has a uniform light field in a far field;

the birefringent crystal is positioned behind the light equalizing system along the light beam emitting direction, the effective aperture of the birefringent crystal is larger than or equal to the laser beam after light equalizing, and the birefringent crystal mainly has the functions of splitting the polarized light and preprocessing the polarized light beam so as to destroy the consistency of the polarization state of the polarized light beam;

the periodic optical path difference device is positioned behind the birefringent crystal along the light beam emission direction, the effective aperture of the periodic optical path difference device is larger than the laser light beam at the moment, and the periodic optical path difference device has the main function of realizing regional differentiation of the optical path of the polarized light beam, so that the polarization state of the light beam is divided according to the region, and the consistency of the polarization state of the polarized light beam is further destroyed;

the rotatable 1/4 slide is located behind the periodic optical path difference device along the beam emission direction, the effective aperture of the rotatable 1/4 slide is larger than the laser beam at the moment, the rotatable 1/4 slide mainly has the effect that the polarization state of the beam changes according to time, the consistency of the polarization state of the polarized beam is further destroyed, the interference condition falling on the detection surface (wall surface) is finally destroyed, and the speckle suppression is further realized.

The laser beam processed by the collimation and light equalization module in the light path is divided into a plurality of sub-beams by the periodic optical path difference device, and the optical paths of the sub-beams are different; wherein the more closely the periodic retardation device is within the effective beam aperture, the better the effect.

FIG. 4 is a graph showing the effect of the embodiment on polarization state in the operating state, wherein consider the change in polarization state of 1/4 slides falling on the screen from 0, rotated about the center of the optical axis with a 15 gap; if the change of the polarization state is severe, the conclusion that the consistency of the polarization state of the light field falling on the screen is damaged can be further obtained, and the effect that the speckles of laser projection are inhibited is achieved.

FIG. 5 (a) is the polarization distribution of the screen at 0 ° for 1/4 slides; (b) 1/4 the polarization distribution of the screen at 15 ° slide; (c) 1/4 the polarization state distribution of the screen at 30 ° slide; (d) 1/4 the polarization distribution of the screen at 45 ° slide; (e) 1/4 slide 60 ° screen polarization distribution; (f) 1/4 the polarization distribution of the screen at 75 ° slide; (g) 1/4 the polarization distribution of the screen at 90 deg.. In operation of such a system, it is clear that the polarization state of the light beam falling on the screen is constantly changing, which means that the interference phenomenon of the light field is attenuated, and the speckle phenomenon of the system is suppressed.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.