Laser speckle suppression element and structure

Abstract

The invention discloses a laser speckle suppression element and structure, and belongs to the technical field of speckle suppression. The structure comprises a laser speckle suppression element, a beam expanding lens, a first lens and a convergent lens, incident light penetrates through the beam expanding lens, enters the optical splitter through the first lens, enters the convergent lens after being subjected to light splitting and is emitted out. A main light beam is split into a plurality of sub-light beams, then each sub-light beam can be processed (a reflecting surface with a random surface height structure is adopted), coherence of each sub-light beam is reduced, and the refractive index of a medium and the polarization characteristic of a material are controlled by utilizing multiple reflections, so that the coherence of each sub-light beam is reduced. According to the invention, a larger optical path difference and different polarization states can be generated between the sub-beams, so that speckles generated by different sub-beams are completely incoherent, speckle suppression is carried out from two aspects, and the speckle suppression effect is greatly improved. The structure adopts a reflective static element, so that an excellent speckle suppression effect and low light loss can be kept.

Description

Technical Field

[0001] The present invention relates to the technical field of speckle suppression, and particularly relates to a laser speckle suppression element and structure. Background Art

[0002] With the wide application of laser light sources in various fields, laser display and lighting have gradually become the mainstream technologies in the market. Among them, laser speckle is a key problem in laser display. It is an interference phenomenon caused by the high coherence of the laser, which will seriously affect the display quality of the picture and is likely to cause eye fatigue or even dizziness. Therefore, many speckle suppression methods and technologies have been proposed to suppress the speckle to an imperceptible level by the human eye, thereby solving the negative impact brought by the speckle. Speckle suppression means generally can be divided into generating polarization diversity, angular diversity, and wavelength diversity. And according to the characteristics of the human eye, multiple uncorrelated speckle patterns can be generated within the integration time of the human eye to achieve the purpose of speckle suppression.

[0003] In the prior art, there are various patents for suppressing speckle using diffuser sheets, moving diffuser plates, and galvanometric mirrors, such as "A Speckle-Eliminating Device (CN202220189373.8)", "Speckle-Eliminating Assembly and Optical System (CN202320593771.0)", "Speckle-Eliminating Device, Laser Light Source and Laser Projection System (CN201721364438.3)", "Speckle-Eliminating Assembly, Light Source Device and Control Method of Light Source Device (CN202110381875.0)", "Dynamic Diffuser Sheet Assembly and Control Method, Laser Speckle-Eliminating Device, Projector (CN202011613892.4)". These patents mainly suppress speckle by scattering of diffuser sheets or reducing the laser coherence by phase plates. Further, dynamic devices are used to generate multiple uncorrelated speckle patterns within the integration time of the human eye to improve the speckle suppression effect of the device. However, these devices have problems such as excessive light loss or low speckle suppression effect. At the same time, the dynamic elements will affect the overall structure volume and stability.

[0004] In addition, there is also a method of splitting the incident light and destroying the coherence between each sub-beam to achieve the effect of speckle suppression. Related patents include "Speckle Suppression Device and Projection Equipment (CN202210824640.9)", "Speckle Suppression Component and Optical System (CN202320593771.0)", "Time-domain and Spatial-domain Joint Speckle Suppression Device Based on Segmented Light Modulation and Manufacturing Method (CN202110686518.5)", "A Speckle Suppression Device Based on Frustrated Total Internal Reflection Spectroscopy (CN202111214491.6)", "A Speckle Suppression Device and Manufacturing Method (CN202111214493.5)", "A Method and Device for Equal-intensity Light Splitting and Speckle Suppression Based on Polarization State Modulation (CN201710526903.7)", "A Speckle Suppression and Depth of Focus Expansion Device Based on Angular Diversity (CN202011219164.5)", "A Laser Speckle Suppression Device and Method (CN202310136854.1)", "A Speckle Suppression Device, Laser Light Source and Projection Equipment (CN202011058809.1)", etc. Although the current patents can produce a light splitting effect and achieve a certain purpose of speckle suppression, the materials and processes used in these technologies are relatively complex, or the optical path difference between sub-beams is not sufficient to meet the requirements of decoherence, so the speckle suppression effect is not good.

[0005] For this reason, the present invention proposes a laser speckle suppression element and structure. Summary of the Invention

[0006] The present invention provides a laser speckle suppression element and structure, which can solve the technical problems of complex processes, high material requirements and unsatisfactory speckle suppression effect in the current technology of using light splitting means for speckle suppression.

[0007] In a first aspect, a laser speckle suppression element is provided, including a light splitter, and the light splitter includes a plurality of optical path channels for sub-beams to pass through and having the same width; the optical path channels include a light input port, a light output port and a reflectively inclined surface, and the reflectively inclined surfaces of each optical path channel are parallel to each other; the reflectively inclined surface is a total reflection surface;

[0008] The inclination angle of the reflectively inclined surface is α, the width of the optical path channel is h, the length of the optical path channel is L, and the distance between reflection positions along the length direction of the optical path channel is l; the relationship is satisfied: l = h·tanα.

[0009] Combined with the above first aspect, in a possible implementation manner, the light splitter composed of a plurality of optical path channels presents a parallelogram structure or a frustum structure.

[0010] Combined with the above first aspect, in a possible implementation manner, different refractive index filling materials are filled in a plurality of the optical path channels.

[0011] Combined with the above first aspect, in a possible implementation, wave plates for controlling polarization are placed at the light input port and the light output port of the optical path channel.

[0012] Combined with the above first aspect, in a possible implementation, the filling material further includes wave plates for controlling polarization.

[0013] Combined with the above first aspect, in a possible implementation, the reflecting surface is a reflecting surface with a random surface height structure.

[0014] Combined with the above first aspect, in a possible implementation, the reflecting surface is a reflecting mirror with a surface etching structure or a reflecting surface with a diffractive optical element attached thereto.

[0015] In a second aspect, a laser speckle suppression structure is provided, which includes a laser speckle suppression element and further includes:

[0016] a beam expander lens, a first lens, and a converging lens;

[0017] wherein, the incident light passes through the beam expander lens, is incident on the beam splitter through the first lens, and is split and then incident on the converging lens and exits.

[0018] Combined with the above second aspect, in a possible implementation, the beam expander lens is used to split the main beam into multiple sub-beams; the first lens is a frosted glass or a diffractive optical element.

[0019] Combined with the above second aspect, in a possible implementation, the first lens is used to increase the angular diversity of the light field incident on the beam splitter.

[0020] The laser speckle suppression structure provided by the present invention splits the main beam into multiple sub-beams, and then each sub-beam can be processed (using a reflecting surface with a random surface height structure) to reduce the coherence of each sub-beam. By using multiple reflections, controlling the refractive index of the medium and the polarization characteristics of the material, a larger optical path difference and different polarization states can be generated between each sub-beam, so that the speckles generated by different sub-beams are completely incoherent, and speckle suppression is performed from two aspects, greatly improving the speckle suppression effect. This structure uses a reflective static element, which can maintain excellent speckle suppression effect and low light loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the content of the embodiments of the present invention and these drawings.

[0022] Figure 1 A schematic diagram of a laser speckle suppression structure in Embodiment 3 provided by the present invention;

[0023] Figure 2 This is a schematic diagram of the optical path channel in the first embodiment provided by the present invention. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. In this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0025] Example 1

[0026] A laser speckle suppression element provided by an embodiment of the present invention includes a beam splitter, wherein the beam splitter includes a plurality of optical path channels; the plurality of optical path channels have equal widths; the beam splitter composed of the plurality of optical path channels presents a parallelogram structure; the beam splitter with a parallelogram structure has better structural stability and can more effectively disperse an incident light beam, thereby improving the speckle suppression effect.

[0027] The optical path channel is used for the passage of sub-light beams; the optical path channel includes a light inlet, a light outlet and an inclined reflective surface, and the reflective surfaces of each optical path channel are parallel to each other; the reflective surface is a total reflective surface; the reflective surfaces in each optical path channel are arranged parallel to each other, so that it can be ensured that the light emitted from different optical paths has the same propagation direction, which is beneficial to the design and use of subsequent optical systems;

[0028] In a specific embodiment, the sub-beam enters the optical path from the light inlet, and after multiple reflections on the reflective surface, is emitted from the light outlet;

[0029] After the incident light enters the optical path through the light inlet, the light will be reflected in the channel due to the inclined setting of the reflection surface. Since the reflection surface is a total reflection surface, the light will not produce energy loss during the reflection process, ensuring the transmission efficiency of the light.

[0030] like Figure 2As shown, the side of the optical path channel is a reflective surface. When the reflective surface is a total reflection surface, the reflective surfaces of each optical path channel are parallel to each other, with an inclination angle of α, and equal width, set to h (the height of the parallelogram), length set to L (the long side of the parallelogram), and the distance between the side reflection positions along the long side of the parallelogram is l. At this time, the relationship is satisfied: l = h·tanα, and the number of reflections can be approximated as L / l. The more the number of reflections, the longer the optical path that the light travels inside the optical path channel.

[0031] In a specific embodiment, the optical splitter specifically includes 8 parallel - arranged optical path channels. The width h of each optical path channel is 2 mm, and the length L is 20 mm. The inclination angle α of the reflective surface of the optical path channel is 45°, and the distance l between the reflection positions along the length direction of the optical path channel is 2 mm. According to the relationship l = h·tanα, it can be calculated that l = 2 mm·tan45° = 2 mm, which meets the design requirements.

[0032] It should be noted that different refractive - index filling materials are filled in several of the optical path channels to make the optical paths in different optical path channels inconsistent, so as to make the sub - beams decohere;

[0033] In a specific embodiment, the first optical path channel is filled with water with a refractive index of 1.33, the second optical path channel is filled with silicon dioxide with a refractive index of 1.46, the third optical path channel is filled with epoxy resin with a refractive index of 1.52, the fourth optical path channel is filled with polycarbonate with a refractive index of 1.58, the fifth optical path channel is filled with polysulfone with a refractive index of 1.65, the sixth optical path channel is filled with magnesium fluoride with a refractive index of 1.72, the seventh optical path channel is filled with zinc sulfide with a refractive index of 1.80, and the eighth optical path channel is filled with diamond with a refractive index of 1.90. The filling materials with different refractive indices make the light have different optical paths when propagating in different optical path channels, thus generating different phase differences, further enhancing the speckle suppression effect. At the same time, the filling materials can also protect the reflective surfaces in the optical path channels and extend the service life of the components.

[0034] In some implementation modes, wave plates for controlling polarization are added at the light - input port and light - output port of the optical path channel, so that the polarization states of the light emitted from the light - output port of each optical path channel are all different; a quarter - wave plate is placed at the light - input port of each optical path channel, and a half - wave plate is placed at the light - output port. The quarter - wave plate can convert linearly polarized light into circularly polarized light, and the half - wave plate can rotate the polarization direction by 90°. By placing wave plates for controlling polarization at the light - input port and light - output port of the optical path channel, the polarization state of the light can be changed, so that the emitted sub - beams have different polarization directions, thereby further reducing the coherence between the sub - beams and improving the speckle suppression effect.

[0035] Obviously, wave plates for controlling polarization can also be added to the filling material, all aiming to make the polarization states of the light emerging from the outlets of each optical path channel different from each other.

[0036] In this embodiment, the optical splitter includes 8 optical path channels, and wave plate particles for controlling polarization are mixed in the filling material in each optical path channel. Specifically, the wave plate particles are made of liquid crystal polymer material, with a particle size of 5 - 10 microns and a mass fraction of 0.5% - 2% in the filling material.

[0037] The wave plate particles are evenly distributed in the filling material and can continuously change the polarization state of the light during the propagation of the light, making the emerging sub - beams have a more complex polarization distribution, further reducing the coherence between the sub - beams and improving the speckle suppression effect.

[0038] In this application, the reflection surface can be a reflection surface with a random surface height structure. In a specific embodiment, the reflection surface can be a reflecting mirror with a surface etching structure or a reflection surface with a diffractive optical element attached to the surface. By using a reflecting mirror with a surface etching structure, the reflected light field can have more angular diversity, and multiple reflections can be equivalent to multiple sub - light sources. Therefore, for the sub - beams of each optical path channel, it undergoes a virtual beam splitting process again, which can further improve the speckle suppression effect.

[0039] Embodiment 2

[0040] A laser speckle suppression element provided by an embodiment of the present invention includes an optical splitter, where the optical splitter includes several optical path channels; the widths of several of the optical path channels are equal; the optical splitter composed of several optical path channels presents a frustum - of - cone structure; an annular channel around the frustum - of - cone is an optical path channel, and media with different refractive indices can be inserted into the optical path channel.

[0041] Specifically, it can be shown that the optical splitter is composed of 16 optical path channels, and these optical path channels are arranged in a frustum - of - cone structure. The optical splitter with a frustum - of - cone structure can disperse the incident light beam more evenly and further improve the speckle suppression effect.

[0042] The bottom diameter of the optical splitter with a frustum - of - cone structure is 32 mm, the top diameter is 16 mm, and the height is 20 mm. The width h of each optical path channel is 2 mm, the length L is 20 mm, the inclination angle α of the reflection surface is 45°, and the distance l between the reflection positions along the length direction of the optical path channel is 2 mm, satisfying the relationship l = h·tanα.

[0043] Embodiment 3

[0044] As Figure 1As shown in the figure, an embodiment of the present invention provides a laser speckle suppression structure, which includes the laser speckle suppression element described in Embodiment 1 or Embodiment 2, and further includes a beam expander lens, a first lens, and a converging lens;

[0045] Among them, they are arranged in sequence along the propagation path of the main beam. The incident light first passes through the beam expander lens, then passes through the first lens and is incident on the beam splitter, and after being split, it is incident on the converging lens and exits;

[0046] Among them, the beam expander lens is used to split the main beam into multiple sub-beams;

[0047] The sub-beams form a light field through the first lens and are incident on the beam splitter. The first lens can be a ground glass or a DOE (diffractive optical element), but it cannot be too thick and needs to maintain a high transmittance. Its function is to increase the angular diversity of the light field incident on the beam splitting device.

[0048] The converging lens is used to synthesize the sub-beams that have been subjected to speckle suppression by the beam splitter into an output light;

[0049] In this embodiment, the optical path arrangement of the laser speckle suppression structure is as follows: The incident light first passes through the beam expander lens, and the beam expander lens expands the incident light into a parallel beam with a diameter of 20 mm; then it passes through the first lens and is incident on the beam splitter. The first lens is a plano-convex lens with a focal length of 50 mm; the light is split into multiple sub-beams after passing through the beam splitter; finally, these sub-beams are incident on the converging lens and exit. The converging lens is a biconvex lens with a focal length of 100 mm.

[0050] The function of the beam expander lens is to expand the incident laser beam into a parallel beam with a larger diameter to make full use of the optical path channel of the beam splitter; the function of the first lens is to converge the parallel beam so that it is incident on the beam splitter at a certain angle, increasing the optical path difference of the light in the beam splitter; the function of the converging lens is to converge the multiple sub-beams exiting from the beam splitter to the same area to form a uniform light spot.

[0051] Through this optical structure design, the incident light is split into multiple sub-beams when passing through the beam splitter. These sub-beams have different optical path differences and phase relationships, and finally form a uniform light spot under the action of the converging lens, effectively suppressing the generation of laser speckles.

[0052] The laser speckle suppression structure proposed in this embodiment splits the main beam into multiple sub - beams, and then each sub - beam can be processed (using a reflecting surface with a random surface height structure) to reduce the coherence of each sub - beam. By using multiple reflections, controlling the refractive index of the medium, and the polarization characteristics of the material, a larger optical path difference and different polarization states can be generated between each sub - beam, making the speckles generated by different sub - beams completely incoherent. Speckle suppression is carried out from two aspects, greatly improving the speckle suppression effect. This structure uses a reflective static element, which can maintain excellent speckle suppression effect and low light loss.

[0053] It should be noted that Embodiment 1, Embodiment 2, and Embodiment 3 are all types of laser speckle suppression elements or laser speckle suppression structures.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the present invention. The above - disclosed are only several specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any changes that can be thought of by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A laser speckle suppression element, comprising a beam splitter, characterized in that, The optical splitter includes a number of optical path channels of equal width for sub-beams to pass through; the optical path channels include an incident light port, an exit light port, and a reflecting surface disposed obliquely, and the reflecting surfaces of each optical path channel are parallel to each other; the reflecting surface is a total reflection surface; The inclination angle of the reflecting surface is α, the width of the optical path channel is h, the length of the optical path channel is L, and the distance between the reflection positions along the length direction of the optical path channel is l; The relationship is satisfied: l = h·tanα.

2. The laser speckle suppression element according to claim 1, characterized in that, The optical splitter composed of a number of optical path channels presents a parallelogram structure or a frustum of a cone structure.

3. The laser speckle suppression element according to claim 1, characterized in that, A filling material with different refractive indexes is filled in a number of the optical path channels.

4. The laser speckle suppression element according to claim 1, characterized in that, Wave plates for controlling polarization are placed in the incident light port and the exit light port of the optical path channel.

5. The laser speckle suppression element according to claim 3, wherein Wave plates for controlling polarization are also mixed in the filling material.

6. The laser speckle suppression element according to claim 1, characterized in that, The reflecting surface is a reflecting surface with a random surface height structure.

7. The laser speckle suppression element according to claim 6, wherein The reflecting surface is a reflecting mirror with a surface etching structure or a reflecting surface with a diffractive optical element attached thereto.

8. A laser speckle suppression structure, comprising the laser speckle suppression element according to any one of claims 1-7, characterized in that, It further includes: A beam expander lens, a first lens, and a converging lens; Among them, the incident light passes through the beam expander lens, is incident on the optical splitter through the first lens, is split, and then is incident on the converging lens and exits.

9. The laser speckle suppression structure according to claim 8, wherein, The beam expander lens is used to split the main beam into multiple sub-beams; the first lens is a ground glass or a diffractive optical element.

10. A laser speckle suppression structure according to claim 8, characterized in that, The first lens is used to increase the angular diversity of the light field incident on the optical splitter.

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