CN110376755A - Disappear laser speckle device and scanning projection device - Google Patents

Abstract

The invention provides a laser speckle elimination device and scanning projection equipment, which relate to the technical field of projection equipment. The laser speckle elimination device includes: a non-polarization beam splitter, a polarization state conversion mechanism, and a polarization beam combiner; The beam splitter is used to split the incident light in the first polarization state into a first sub-beam and a second sub-beam; the first sub-beam can enter the polarization beam combiner, and the second sub-beam can pass through the polarization state conversion mechanism and then shoot Incoming polarization beam combiner; the polarization beam combiner is used to combine the first sub-beam and the second sub-beam; the polarization state conversion mechanism includes a half-wave plate corresponding to the wavelength of the incident light, which is used to combine the second beam through the half-wave plate The sub-beam is converted from the first polarization state to the second polarization state, and the difference between the length of the path traveled by the second sub-beam and the length of the path traveled by the first sub-beam is greater than the coherence length of the incident light, eliminating the projection beam coherence, so the speckle intensity is greatly reduced after synthesis.

Description

Laser speckle elimination device and scanning projection equipment

technical field

The invention relates to the technical field of projection equipment, in particular to a laser speckle elimination device and scanning projection equipment.

Background technique

Laser Beam Scanning (LBS, Laser Beam Scanning) shows that the laser spot incident to the center of the scan mirror (MEMS mirror) scans the projection display line by line, due to high contrast, compact structure, high integration, non-focus display, portable , convenient power supply and other advantages, it has a bright application prospect in consumer optoelectronic fields such as AR (Augmented Reality), VR (Virtual Reality) and MR (Mixed Reality), smart home, and smart driving.

The laser scanning projection device includes a scanning spot generator and a scanning galvanometer. When a laser light source with excellent coherence illuminates an optically rough surface (screen), the screen surface can be divided into many surface units, and the light reflected by each unit will have a phase difference. , meeting in space will interfere, forming a speckle pattern with randomly distributed granular structures. The existence of speckle will lead to partial loss of image information content, and will reduce the resolution of the image.

Therefore, speckle is the main factor that reduces image quality and resolution, and is also one of the factors that restrict the development of projectors.

Contents of the invention

The object of the present invention is to provide a laser speckle elimination device and a scanning projection device, so as to alleviate the technical problem that the speckle generated by the existing projection device affects the image quality and resolution.

In the first aspect, an embodiment of the present invention provides a device for eliminating laser speckle. The device for eliminating laser speckle includes: a non-polarizing beam splitter, a polarization state conversion mechanism, and a polarization beam combiner; for splitting the incident light in the first polarization state into a first sub-beam and a second sub-beam; the first sub-beam can enter the polarization beam combiner, and the second sub-beam can pass through the After the polarization conversion mechanism is injected into the polarization beam combiner; the polarization beam combiner is used to combine the first sub-beam and the second sub-beam;

The polarization conversion mechanism includes a half-wave plate corresponding to the wavelength of the incident light, for converting the second sub-beam passing through the half-wave plate from a first polarization state to a second polarization state, and the first polarization state and the second polarization state, one of which is a p-polarized state and the other is an s-polarized state;

The difference between the length of the path traveled by the second sub-beam and the length of the path traveled by the first sub-beam is greater than the coherence length of the incident light.

Further, the polarization conversion mechanism includes: a first reflection structure and a second reflection structure;

The first reflective structure is located on the propagation path of the second sub-beam, and the first reflective structure faces the non-polarizing beam splitter and the second reflective structure, so that the second sub-beam is reflected toward the second reflective structure;

The second reflective structure faces the first reflective structure and the polarization beam combiner, so that the second sub-beam is reflected toward the polarization beam combiner;

The half-wave plate is located between the first reflective structure and the second reflective structure.

Further, the number of the polarization state conversion mechanisms is n, and n is an integer greater than or equal to 2, and the n polarization state conversion mechanisms are arranged at intervals one by one along the direction away from the non-polarizing beam splitter;

in a direction away from the non-polarizing beam splitter,

The numbers of the n first reflective structures are respectively m ₁ , m ₂ , m ₃ . . . m _n ;

The numbers of the n second reflective structures are k ₁ , k ₂ , k ₃ . . . k _n ;

The numbers of the n half-wave plates are respectively b ₁ , b ₂ , b ₃ ... b _n , and the lasers of different wavelengths corresponding to the half-wave plates numbered b ₁ , b ₂ ... b _n are respectively J ₁ , J ₂ , J ₃ ... J _n laser;

The first reflective structure numbered m ₁ and the second reflective structure numbered k ₁ can reflect J ₁ laser light and transmit J ₂ -J _n laser light;

The first reflective structure numbered _m2 and the _second reflective structure numbered k2 can reflect J2 laser light and transmit _{J3-Jn laser light} ;

and so on;

The first reflective structure numbered m _n-1 and the second reflective structure numbered k _n-1 can reflect J _n-1 laser light and transmit J _n laser light;

The first reflective structure numbered _mn and the second reflective structure numbered _kn can reflect _Jn laser light;

so that the second sub-beams containing J ₁ , J ₂ , J ₃ ... J _n lasers can pass through n first reflection structures in sequence, and J ₁ , J ₂ , J ₃ ... J _n lasers are reflected and separated one by one , n The second reflective structure can combine the separated J ₁ , J ₂ , J ₃ . . . J _n laser beams and reflect them into the polarization beam combiner.

Further, both the first reflective structure and the second reflective structure are sheet-like structures;

The first reflective structure numbered m ₁ is coated with an anti-reflection coating for J ₂ ~ J _n lasers on the side facing the non-polarizing beam splitter, and a high-reflection coating for J ₁ laser, and is facing away from the non-polarizing beam splitter One side of the device is coated with an anti-reflection coating for J ₂ ～J _n lasers; the side of the second reflection structure numbered k ₁ facing the polarization beam combiner is coated with an anti-reflection coating for J ₂ ～J _n lasers. J ₁ laser high-reflection film, and the side facing away from the polarization beam combiner is coated with an anti-reflection film for J ₂ ~ J _n laser;

The first reflective structure numbered m ₂ is coated with an anti-reflection coating for J ₃ ~J _n lasers on the side facing the non-polarizing beam splitter, and a high-reflection coating for J ₂ lasers, and is facing away from the non-polarizing beam splitter One side of the device is coated with an anti-reflection coating for J ₃ ~J _n lasers; the side of the second reflection structure numbered k ₂ facing the polarization beam combiner is coated with an anti-reflection coating for J ₃ ~J _n lasers. J ₂ laser high-reflection film, and the side facing away from the polarization beam combiner is coated with an anti-reflection film for J ₃ ~ J _n laser;

and so on;

The first reflective structure numbered m _n-1 is coated with an anti-reflection coating for J _n laser and a high reflection coating for J _n-1 laser facing the non-polarizing beam splitter, and is facing away from the non-polarizing beam splitter. One side of the beam combiner is coated with an anti-reflection coating for the J _n laser; the second reflection structure numbered k _n-1 is coated with an anti-reflection coating for the J _n laser on the side facing the polarization beam combiner, and the J _{n- 1} Laser high-reflection film, and the side facing away from the polarization beam combiner is coated with an anti-reflection film for _Jn laser;

The side of the first reflective structure numbered m _n facing the non-polarizing beam splitter is coated with a high reflection film for J _n laser; the second reflecting structure numbered k _n is coated on the side facing the polarizing beam combiner J _n laser high reflection film.

Further, the laser speckle elimination device includes a first prism and a second prism, the main sections of the first prism and the second prism are both parallelograms, and the internal angles of the parallelograms are 45° and 135° respectively;

The number of the first prism and the second prism is n, and the plurality of first prisms are arranged along the direction away from the non-polarizing beam splitter, and are connected in sequence; the plurality of second prisms are arranged along the direction away from the polarizing beam combiner, And sequentially connected;

in a direction away from the non-polarizing beam splitter,

The numbers of the n first prisms are respectively f ₁ , f ₂ , f ₃ ...f _n ;

The numbers of the n second prisms are g ₁ , g ₂ , g ₃ ... g _n ;

The side of the _first prism numbered f1 away from the non-polarizing beam splitter faces the non-polarizing beam splitter and the half _- wave plate numbered b1, and this side is close to the non _- polarizing beam splitter with the first prism numbered f2 One side of the beam combiner is connected, and the antireflection coating of J ₂ ~ J _n laser is coated between the two, and the J ₁ laser is highly reflective; the side of the second prism numbered g ₁ away from the polarization beam combiner faces the The polarization beam combiner and the half-wave plate numbered b ₁ , and this surface is connected to the side of the second prism numbered g ₂ close to the polarization beam combiner, and J ₂ ~ J _n laser amplifiers are plated between the two Transparent film, high reflection film for J1 laser; and the _first prism numbered f1 is connected to _one side _of the half-wave plate numbered b1, and the other side _of the half-wave plate numbered b1 Connect with the second prism numbered g ₁ ;

_The side of the first prism numbered f2 away from the non-polarizing beam splitter faces the non-polarizing beam splitter and the half _- wave plate numbered b2, and this side is close to the non-polarizing beam splitter with the first prism numbered _f3 One side of the beam combiner is connected, and the anti-reflection coating of J ₃ ~ J _n laser is coated between the two, and the J ₂ laser is highly reflective; the side of the second prism numbered g ₂ away from the polarization beam combiner faces the The polarization beam combiner and the half _- wave plate numbered b2, and this surface is connected to the side _of the second prism numbered g3 close to the polarization beam combiner, and the _J3 ~ _Jn laser amplifier is coated between the two Transparent film, high reflection film for J2 laser _; and the first prism numbered f2 is connected to one side of the _{half -} wave plate numbered b2, and the other side of the half _- wave plate numbered b2 Connect with the second prism numbered g ₂ ;

and so on;

The side of the first prism numbered f _n-1 away from the non-polarizing beam splitter faces the non-polarizing beam splitter and the half-wave plate numbered b _n-1 , and this face is in contact with the first prism numbered f _n The side close to the non-polarizing beam splitter is connected, and the anti-reflection coating of J _n laser is coated between the two, and the high reflection coating of J _n-1 laser is applied; the second prism numbered g _n-1 is far away from the polarizing beam combiner One side faces the polarization beam combiner and the half-wave plate numbered b _n-1 , and this side is connected to the side of the second prism numbered g _n close to the polarization beam combiner, and there is a J plated between the two Anti-reflection coating for _n laser, high reflection coating for J _n-1 laser; and the first prism numbered f _n-1 is connected to one side of the half-wave plate numbered b _n-1 , the number The other side of the half-wave plate b _n-1 is connected to the second prism numbered g _n-1 ;

The side of the first prism numbered f _n away from the non-polarizing beam splitter faces the non-polarizing beam splitter and the half-wave plate numbered b _n ; the side of the second prism numbered g _n away from the polarizing beam combiner faces The polarization beam combiner and the half _- wave plate numbered b2; and the first prism numbered f _n is connected to one side of the half-wave plate numbered b _n , and the half wave plate numbered b _n The other side of the wave plate is connected with the second prism numbered g _n .

Further, both the light-incoming surface and the light-emitting surface of the half-wave plate are coated with an anti-reflection film.

Further, the number of the polarization state conversion mechanisms is three, and the three half-wave plates in the three polarization state conversion mechanisms correspond to red light, green light and blue light respectively.

In the second aspect, a scanning projection device provided by an embodiment of the present invention includes the above-mentioned device for eliminating laser speckle.

Further, the scanning projection device includes a scanning spot generator, and the scanning spot generator includes a plurality of light source mechanisms and a beam combining component, and the beam combining component is used to combine the laser beams output by the multiple light source mechanisms;

The scanning light spot generator further includes a shaping structure for shaping the elliptical light spot emitted by the light source mechanism into a circular light spot.

Further, the shaping structure is located behind the beam combining assembly, and is used to shape the laser beams that have been combined.

Further, the number of the shaping structures is the same as the number of the light source mechanisms, and they are in one-to-one correspondence;

The shaping structure is located between the light source mechanism and the beam combination assembly, so that the light emitted by the light source mechanism is first shaped and then combined.

Further, the shaping structure is a prism group or a biconical lens.

Further, the scanning projection device includes a laser wavelength temperature drift detection mechanism, and the laser wavelength temperature drift detection mechanism is used to detect the drift amount of the laser wavelength emitted by each light source mechanism.

Further, the beam combining component includes a plurality of spaced beam combining sheets, or includes a plurality of beam combining prisms connected to each other.

Further, the scanning projection device includes a beam expander located behind the scanning galvanometer, and the beam expander is used to increase the viewing angle of projection.

The laser speckle elimination device provided by the embodiment of the present invention includes: a non-polarization beam splitter, a polarization state conversion mechanism, and a polarization beam combiner. The laser beam in the first polarization state enters the non-polarizing beam splitter, which can split the laser beam into a first sub-beam and a second sub-beam, both of which advance in different directions, and the first sub-beam can Enter the polarization beam combiner, the second sub-beam can pass through the polarization conversion mechanism and enter the polarization beam combiner; the polarization beam combiner is used to combine the first sub-beam and the second sub-beam Beam combining; the polarization conversion mechanism includes a half-wave plate corresponding to the wavelength of the incident light, and the second sub-beam passing through the half-wave plate can be converted from a first polarization state to a second polarization state, and the first In the polarization state and the second polarization state, one is the p polarization state, and the other is the s polarization state; the length of the path traveled by the second sub-beam is the same as the length of the path traveled by the first sub-beam The difference is greater than the coherence length of the incident light. Laser speckle is a phenomenon of coherent superposition of scattered light produced by coherent laser irradiation on a diffuse reflection surface. The optical path difference between the light beam and the second sub-beam is greater than the coherence length of the corresponding laser light, which eliminates the coherence of the projected light beam, so the combined speckle intensity is greatly reduced, which can effectively improve the imaging quality of the scanning projection.

In the second aspect, a scanning projection device provided by an embodiment of the present invention includes the above-mentioned device for eliminating laser speckle. Because the scanning projection device provided by the embodiment of the present invention refers to the above-mentioned device for eliminating laser speckle, the scanning projection device provided by the embodiment of the present invention also has the advantages of the device for eliminating laser speckle.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative work.

FIG. 1 is a schematic diagram of a laser speckle elimination device provided by an embodiment of the present invention;

Fig. 2 is a schematic diagram of another laser speckle elimination device provided by an embodiment of the present invention;

FIG. 3 is a schematic diagram of a scanning projection device provided by an embodiment of the present invention;

FIG. 4 is a schematic diagram of another scanning spot generator of a scanning projection device according to an embodiment of the present invention.

Icons: 110-non-polarizing beam splitter; 120-polarization conversion mechanism; 121-first reflection structure; 122-half-wave plate; 123-second reflection structure; 130-polarization beam combiner; 141-first sub-beam ; 142-second sub-beam; 151-first prism; 152-second prism; 210-laser diode; 220-collimator lens; 230-energy beam splitter; 240-biconic lens; 260-prism group; 300-scanning mirror; 400-beam expander.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

As shown in FIG. 1 , the laser speckle elimination device provided by the embodiment of the present invention includes: a non-polarization beam splitter 110 , a polarization state conversion mechanism 120 , and a polarization beam combiner 130 . The laser light in the first polarization state enters the non-polarizing beam splitter 110, which can split the laser light into a first sub-beam 141 and a second sub-beam 142, both of which advance in different directions, the first The sub-beam 141 can enter the polarization beam combiner 130, and the second sub-beam 142 can pass through the polarization state conversion mechanism 120 and then enter the polarization beam combiner 130; the polarization beam combiner 130 uses Combining the first sub-beam 141 and the second sub-beam 142; the polarization conversion mechanism 120 includes a half-wave plate 122 corresponding to the wavelength of the incident light, and the second sub-beam 142 passing through the half-wave plate 122 can be From the first polarization state to the second polarization state, one of the first polarization state and the second polarization state is the p polarization state, and the other is the s polarization state; the second sub-beam 142 passes through The difference between the length of the path and the length of the path traveled by the first sub-beam 141 is greater than the coherence length of the incident light. Laser speckle is a phenomenon of coherent superposition of scattered light produced by coherent laser irradiation on a diffuse reflection surface. It is essentially caused by the coherence of laser light. Since the vibration directions of the first sub-beam 141 and the second sub-beam 142 are perpendicular to each other, the second The optical path difference between the first sub-beam 141 and the second sub-beam 142 is greater than the coherence length of the corresponding laser light, which eliminates the coherence of the projected beams, so the combined speckle intensity is greatly reduced, which can effectively improve the imaging quality of scanning projection.

It should be noted that the "speckle reduction" mentioned in this article refers to laser speckle reduction.

For the convenience of description, in the following description, the laser light entering into the laser speckle elimination device is taken as an example in which the polarization state of the laser light is the p-polarized state. The present invention starts from the root cause of laser speckle formation, that is, the laser itself has coherence, and proposes to divide the projection beam into the first sub-beam 141 of the horizontal p-polarization state and the second sub-beam 142 of the vertical s-polarization state. combination, and make the optical path difference between the second sub-beam 142 in the vertical s-polarization state and the first sub-beam 141 in the horizontal p-polarization state be greater than the coherence length of the corresponding laser, eliminate the coherence of the projection beam, and reduce the projection image well. The speckle intensity of .

As shown in FIG. 1 , the rightward-propagating first sub-beam 141 is p-polarized light and the upward-propagating second sub-beam 142 is s-polarized light, combined by the polarization beam combiner 130 , and combined into one beam before exiting. The polarizing beam combiner 130 can be a sheet structure, and the side facing the non-polarizing beam splitter 110 is coated with p-polarized anti-reflection coatings for blue light, green light and red light, and the side facing away from the non-polarizing beam splitter 110 is coated with blue light , green light and red light s polarized high reflection film, so that the first sub-beam 141 and the second sub-beam 142 are combined.

The polarization beam combiner 130 can also be a beam-splitting prism structure. In this case, each light-passing surface needs to be coated with an anti-reflection film system to improve light energy transmission and reduce stray light.

Preferably, the beam splitting ratio of the non-polarizing beam splitter 110 may be 50:50, that is, the energy ratio of the split first sub-beam 141 and the second sub-beam 142 is 1:1. Other non-polarizing beam splitters 110 close to this ratio can also be applied in the laser speckle elimination device. The non-polarizing beam splitter 110 has a beam-splitting surface at an angle of 45 degrees to the incident laser light. The first sub-beam 141 is transmitted according to the traveling direction of the original laser light, and the second sub-beam 142 is reflected in the direction perpendicular to the original laser light. The non-polarizing beam splitter 110 is a conventional optical element.

The non-polarizing beam splitter 110 and the polarizing beam combiner 130 can both be on the extension line of the travel route of the original laser, and the polarization state conversion mechanism 120 includes: a first reflective structure 121 and a second reflective structure 123, the first reflective The structure 121 is located on the propagation path of the second sub-beam 142, the incident angle of the second sub-beam 142 may be 45°, and the first reflective structure 121 faces the non-polarizing beam splitter 110 and the second reflective structure 123, so that the second sub-beam 142 is reflected toward the second reflective structure 123; the second reflective structure 123 faces the first reflective structure 121 and the polarization beam combiner 130, and the incident angle of the second sub-beam 142 can be 45° °, so that the second sub-beam 142 is reflected to the polarization beam combiner 130; the half-wave plate is located between the first reflection structure 121 and the second reflection structure 123. The first sub-beam 141 directly enters the polarization beam combiner 130 from the non-polarizing beam splitter 110, and the second sub-beam 142 enters the polarization beam combiner 130 after being reflected on both sides, thereby prolonging the light of the second sub-beam 142 Procedure. By adjusting the distance between the first reflective structure 121 and the non-polarizing beam splitter 110 and the distance between the second reflective structure 123 and the polarizing beam combiner 130 , the optical path difference between the first sub-beam 141 and the second sub-beam 142 can be adjusted.

The number of polarization state conversion mechanisms 120 is n, and n is an integer greater than or equal to 2. The n polarization state conversion mechanisms 120 are arranged at intervals one by one along the direction away from the non-polarization beam splitter 110; In the direction of the detector 110, the numbers of the n first reflective structures 121 are respectively m ₁ , m ₂ , m ₃ ... m _n ; the numbers of the n second reflective structures 123 are respectively k ₁ , k ₂ , k ₃ ... _{k n} ; the numbers of the _n half _- wave plates ₁₂₂ are respectively b ₁ , b ₂ , b ₃ . The lasers are J ₁ , J ₂ , J ₃ ... J _n lasers; the first reflective structure 121 numbered m ₁ and the second reflective structure 123 numbered k ₁ can reflect J ₁ laser light and transmit J ₂ ~J _n laser light; the first reflective structure 121 numbered m ₂ and the second reflective structure 123 numbered k ₂ can reflect J ₂ laser light and transmit J ₃ ~J _n laser light; and so on, the number The first reflective structure 121 numbered m _n-1 and the second reflective structure 123 numbered k _n-1 can reflect J _n-1 laser light and transmit J _n laser light; the first reflective structure 121 numbered m _n and the second reflective structure 123 numbered k _n can reflect J _n laser light. _{The second sub-beam 142 including J 1 , J 2 , J 3 .} , n The second reflective structure 123 can combine the separated J ₁ , J ₂ , J ₃ . . . J _n laser beams and reflect them into the polarization beam combiner 130 .

In this embodiment, the number of polarization conversion mechanisms 120 may be three, wherein the lights corresponding to the three half-wave plates 122 are blue light, green light and red light respectively. When the second sub-beam 142 containing blue light, green light and red light irradiates the first first reflective structure 121 vertically, the blue light is reflected to the first half-wave plate 122, and the polarization state of the blue light is changed. into s-polarized light; green light and red light are transmitted through the first first reflective structure 121 and irradiated onto the second first reflective structure 121, and at this time, the green light is reflected by the second first reflective structure 121 to the second A half-wave plate 122, the green light also changes from p-polarized state to s-polarized state; red light is irradiated on the third first reflective structure 121 after passing through the second first reflective structure 121, and the red light is reflected to With the third half-wave plate 122, the red light is also transformed into s-polarized state. The blue light, the green light and the red light respectively irradiated on the three parallel second reflective structures 123 can be irradiated onto the polarization beam combiner 130 after being combined.

Specifically, the first reflective structure 121 and the second reflective structure 123 may both be sheet structures; the side of the first reflective structure 121 numbered m ₁ facing the non-polarizing beam splitter 110 is coated with pairs of J ₂ -J _n The anti-reflection coating of the laser is a high-reflection coating for the J ₁ laser, and the anti-reflection coating for the J ₂ ~ J _n laser is coated on the side facing away from the non-polarizing beam splitter 110; the second reflection structure numbered k ₁ 123 The side facing the polarization beam combiner 130 is coated with an anti-reflection coating for J ₂ ~ J _n lasers, a high reflection coating for J ₁ laser, and the side facing away from the polarization beam combiner 130 is coated with a coating for J ₂ Anti-reflection coating for ~J _n lasers; the first reflective structure 121 numbered m ₂ facing the non-polarizing beam splitter 110 is coated with anti-reflection coatings for J ₃ ~J _n lasers, which is highly reflective for J ₂ lasers film, and the side facing away from the non-polarizing beam splitter 110 is coated with an anti-reflection coating for J ₃ ~ J _n lasers; the second reflection structure 123 numbered k ₂ is coated on the side facing the polarizing beam combiner 130 There is an anti-reflection coating for J ₃ ~J _n lasers, a high-reflection coating for J ₂ lasers, and an anti-reflection coating for J ₃ ~J _n lasers is coated on the side facing away from the polarization beam combiner 130; the number is m The side of the first reflective structure 121 of _n-1 facing the non-polarizing beam splitter 110 is coated with an anti-reflection coating for the J _n laser, a high reflection coating for the J _n-1 laser, and facing away from the non-polarizing beam splitter One side of the device 110 is coated with an anti-reflection coating to the J _n laser; the second reflection structure 123 numbered k _n-1 is coated with an anti-reflection coating to the J _n laser on the side of the polarization beam combiner 130, and the J _n-1 laser high-reflection coating, and the side facing away from the polarization beam combiner 130 is coated with an anti-reflection coating for J _n lasers; the first reflection structure 121 numbered m _n faces the non-polarization beam splitter 110 The side of the second reflective structure 123 numbered k _n facing the polarization beam combiner 130 _{is coated with a high reflection film for J n laser} .

The number of polarization conversion mechanisms 120 may be three, wherein the lights corresponding to the three half-wave plates 122 are blue light, green light and red light respectively. When the laser beam containing blue light, green light and red light enters the laser speckle elimination device, it is divided into two parts with equal energy by the non-polarizing beam splitter 110, the first sub-beam 141 and the second sub-beam 142, the first The sub-beam 141 continues to propagate forward, and the second sub-beam 142 propagates downward. At this time, the polarization directions of the forward and downward propagating beams remain unchanged, and are still horizontally p-polarized.

The second sub-beam 142 traveling downward passes through the three first reflective structures 121 in sequence, and the corresponding three first reflective structures 121 are used to separate blue light, green light and red light in turn. Among them, the upper surface of the first first reflective structure 121 is coated with green and red light anti-reflection coatings, blue light high-reflection coatings, and the lower surface is coated with green and red light anti-reflection coatings. The upper surface of the second first reflective structure 121 is coated with a red light anti-reflection film, a green light high-reflection film, and the lower surface is coated with a red light anti-reflection film. The upper surface of the third first reflective structure 121 is coated with a red light high reflective film. The angle between the second sub-beam 142 and the first reflective structure 121 is 45°, or other angles can be selected according to actual needs.

After being color-separated by the first reflection structure 121 , the light of each color passes through the corresponding half-wave plate 122 vertically in turn to convert the horizontal p-polarized light into vertical s-polarized light. The front and rear surfaces of the half-wave plate 122 are coated with anti-reflection films to reduce ghost images and improve light energy utilization.

After polarization conversion, each color light passes through three second reflective structures 123 in sequence, and finally synthesizes blue light, green light and red light into white light. Wherein, the upper surface of the third second reflective structure 123 away from the polarization beam combiner 130 is coated with a red high-reflection film. The lower surface of the second second reflective structure 123 is coated with a red light anti-reflection film, and the upper surface is coated with a red light anti-reflection film and a green light high-reflection film. The lower surface of the first second reflective structure 123 is coated with anti-reflection coatings for green light and red light; the upper surface is coated with anti-reflection coatings for green light and red light, and a high-reflection coating for blue light. The included angle between the second sub-beam 142 passing through the half-wave plate 122 and the second reflective structure 123 is 45°, or other angles can be selected according to actual needs. Because the first reflective structure 121 and the second reflective structure 123 have distances from the non-polarizing beam splitter 110 and the polarizing beam combiner 130 respectively, the distance traveled by the twice-reflected second sub-beam 142 must be greater than that of the first sub-beam 141. Adjust the positions of the first reflective structure 121 and the second reflective structure 123 according to the coherence length of the color light to be corrected, so that the optical path difference between the second sub-beam 142 and the first sub-beam 141 is greater than the coherence length of the corresponding color light.

According to the laser principle, the coherence length L _c of the laser can be expressed as L _c =λ ² /Δλ, where λ and Δλ are the center wavelength of the laser and the linewidth of the laser, respectively. It can be seen from the above formula that when the optical path difference of the two laser beams is greater than the coherence length of the laser beams, the two laser beams are no longer coherent, and the two laser beams no longer interfere. Take Osram’s laser J as an example. Its output center wavelength is 638nm and the laser line width is 1nm. Theoretically, its coherence length is 0.407mm. In practice, as long as the optical path difference is greater than 1mm, the coherence of the two beams of light can be eliminated.

The superposition of two beams of equal intensity light waves, the superimposed intensity can be expressed as:

I _p ＝2I ₀ +2I ₀ cosδ _p

Among them, I ₀ represents the light intensity of a beam of light waves, and δ _p represents the phase difference of two columns of light waves. When the p-polarized light is divided into equal-intensity p-light and s-light, the superimposed intensity can be expressed as

I _p+s ＝2I ₀ +I ₀ cosδ _s +I ₀ cosδ _p

Among them, δ _p and δ _s represent the phase difference of the two columns of light waves of s light and p light respectively. Since the vibration directions of the horizontal p component light and the vertical s component light are perpendicular to each other, there is no correlation between δ _p and δ _s , so the speckle intensity is greatly reduced after synthesis, which can effectively improve the imaging quality of scanning projection.

As shown in FIG. 2 , the first reflective structure 121 and the second reflective structure 123 may be formed by a prism structure in addition to being formed by a beam splitter with a sheet structure. Specifically, the laser speckle elimination device includes a first prism 151 and a second prism 152, the main sections of the first prism 151 and the second prism 152 are parallelograms, and the internal angles of the parallelograms are respectively 45° and 135°; the number of the first prism 151 and the second prism 152 is n, and a plurality of first prisms 151 are arranged along a direction away from the non-polarizing beam splitter 110, and are connected in sequence; a plurality of second prisms 152 are arranged along the Arranged in a direction away from the polarizing beam combiner 130 and connected in sequence; along the direction away from the non-polarizing beam splitter 110, the numbers of the n first prisms 151 are f ₁ , f ₂ , f ₃ ... f _n ; The numbers _of the _n second prisms 152 are respectively g ₁ , g ₂ , g ₃ . and the half-wave plate 122 numbered b ₁ , and this surface is connected to the side of the first prism 151 numbered f ₂ close to the non-polarizing beam splitter 110, and J ₂ ~ J _n laser amplifiers are plated between the two Transparent film, high reflection film for J ₁ laser; the side of the second prism 152 numbered g ₁ away from the polarization beam combiner 130 faces the polarization beam combiner 130 and the half-wave plate 122 numbered b ₁ , and this side It is connected to the side of the second prism 152 numbered g ₂ close to the polarization beam combiner 130, and the anti-reflection coating for J ₂ ~ J _n laser is coated between the two, and the high reflection coating for J ₁ laser; and the number The _first prism 151 for f1 is connected to _one side of the half-wave plate 122 numbered b1, and the other side _of the half-wave plate 122 numbered b1 is connected to the second prism 152 numbered _g1 ; The side of the first prism 151 numbered f ₂ away from the non-polarizing beam splitter 110 faces the non-polarizing beam splitter 110 and the half-wave plate 122 numbered b ₂ , and this side is in contact with the first prism numbered f ₃ 151 is connected to the side close to the non-polarizing beam splitter 110, and the anti-reflection coating of J ₃ ~ J _n laser is coated between the two, and the J ₂ laser is highly reflective; the second prism 152 numbered g ₂ is far away from the polarization combining One side of the beam combiner 130 faces the polarization beam combiner 130 and the half _- wave plate 122 numbered b2, and this side is connected to the side _of the second prism 152 numbered g3 close to the polarization beam combiner 130, and the two Anti-reflection coatings for J ₃ ~ J _n lasers are coated between them, and high-reflection coatings for J ₂ lasers; and the first prism 151 numbered f ₂ is connected to one side of the half-wave plate 122 numbered b ₂ , the other side of the half-wave plate 122 numbered b2 is connected to the _second prism 152 numbered g2 _; and so on; the first prism 151 numbered fn _-1 is far away from the non-polarizing beam splitter 110 One side faces the non-polarizing beam splitter 110 and the half-wave plate 122 numbered b _n-1 , and this side is connected to the side of the first prism 151 numbered f _n close to the non-polarizing beam splitter 110, and The anti-reflection coating of J _n laser is coated between the two, and the high reflection coating of J _n-1 laser; the second prism 152 numbered g _n-1 is away from the polarization beam combiner 130 and faces the polarization beam combiner 130 and the half-wave plate 122 numbered b _n-1 , and this surface is connected to the side of the second prism 152 numbered g _n close to the polarization beam combiner 130, and the antireflection of J _n laser is coated between the two film, a high-reflection film for J _n-1 laser; and the first prism 151 numbered f _n-1 is connected to one side of the half-wave plate 122 numbered b _n-1 , and the number is b _n The other side of the half-wave plate 122 of _-1 is connected to the second prism 152 numbered g _n-1 ; the side of the first prism 151 numbered f _n away from the non-polarizing beam splitter 110 faces the non-polarizing beam splitter 110 and the half-wave plate 122 numbered b _n ; the side of the second prism 152 numbered g _n away from the polarization beam combiner 130 faces the polarization beam combiner 130 and the half _- wave plate 122 numbered b2; and the The first prism 151 numbered f _n is connected to one side of the half-wave plate 122 numbered b _n , and the other side of the half-wave plate 122 numbered b _n is connected to the second prism 152 numbered g _n connect.

In the above implementation manners, the package structure of the laser speckle elimination device is more compact, and each optical element can be connected by gluing. The second sub-beam 142 traveling downward passes through the three first prisms 151 sequentially, and the three first prisms 151 play the role of light splitting and sequentially separate blue light, green light and red light. Wherein, the lower surface of the first first prism 151 is connected with the upper surface of the second first prism 151, and the anti-reflection coating of green light and red light is coated between the two, and the blue light high-reflection film; The connecting surface of the first prism 151 and the third first prism 151 is plated with a red light anti-reflection film, and a green light high-reflection film; It is 45°, and no coating is required because it satisfies the conditions for total reflection to occur.

After being separated by the three first prisms 151 , the light of each color passes through the corresponding half-wave plate 122 sequentially to convert the horizontal p-polarized light into vertical s-polarized light. The front and rear surfaces of the half-wave plate 122 are coated with anti-reflection films to reduce ghost images and improve light energy utilization.

After polarization conversion, the light of each color passes through three second prisms 152 in sequence. The second prisms 152 and the first prism 151 are symmetrical with respect to the half-wave plate 122 . The blue light, green light and red light will finally synthesize white light. Wherein, the second prism 152 of the third second prism 152 farthest away from the polarization beam combiner 130 satisfies the occurrence condition of total reflection and does not need coating; Red light anti-reflection coating, green light high-reflection coating; the connecting surface of the first second prism 152 and the second first prism 151 is coated with green light and red light anti-reflection coating, and blue light high-reflection coating. Because the prism has a certain thickness, by adjusting the thickness of the prism, the optical path difference between the second sub-beam 142 and the first sub-beam 141 is greater than the correlation length of the corresponding color light.

Red, green, and blue light provide the three primary colors of red, green, and blue RGB for the entire projection light machine, and are combined to synthesize white light to achieve full-color display. When the laser light incident on the laser speckle elimination device contains non-imaging light, such as infrared detection laser, the infrared detection light source is provided for the entire projection light machine, and with the assistance of the electronic control module, human-computer interaction can be realized. According to requirements, the infrared detection laser anti-reflection coating or high reflection coating is coated on the first reflection structure 121 and the second reflection structure 123, so that the infrared detection laser can pass through a plurality of first reflection structures 121 and second reflection structures 123 to enter into inside the polarization beam combiner 130. The speckle elimination process of the laser speckle elimination device does not affect the propagation of the infrared detection laser. A possible emission wavelength combination of common RGB three primary colors and infrared detection laser is 635nm, 525nm, 450nm and 825nm. The first reflective structure 121 , the half-wave plate 122 and the second reflective structure 123 are rationally set according to the above wavelength combination.

Because the first reflective structure 121 and the second reflective structure 123 are formed by prisms, the non-polarizing beam splitter 110 and the polarizing beam combiner 130 can also be prism structures, and the inner angles of the two are 45°-90°-45°. The hypotenuse of the non-polarizing beam splitter 110 is connected to one side of the first first prism 151 , and the hypotenuse of the polarizing beam combiner 130 is connected to one side of the first second prism 152 . The device for eliminating laser speckle can be integrated.

As shown in FIG. 3 and FIG. 4 , a scanning projection device provided by an embodiment of the present invention includes the above-mentioned device for eliminating laser speckle. Because the scanning projection device provided by the embodiment of the present invention refers to the above-mentioned device for eliminating laser speckle, the scanning projection device provided by the embodiment of the present invention also has the advantages of the device for eliminating laser speckle.

The scanning projection device includes a scanning spot generator, and the scanning spot generator includes a plurality of light source mechanisms and a beam combining assembly 250, and the beam combining assembly 250 is used to combine laser beams output by a plurality of light source mechanisms; the scanning spot The generator also includes a shaping structure for shaping the elliptical light spot emitted by the light source mechanism into a circular light spot.

The light source mechanism includes a laser and a collimating lens 220 , the collimating lens 220 is used to collimate the light beam emitted by the laser, and the laser may be a laser diode 210 . In this embodiment, the laser diodes 210 in the multiple laser mechanisms may be red, green and blue laser diodes 210, and infrared laser diodes 210 for infrared detection. The red, green, and blue laser diodes 210 provide the three primary colors of red, green, and blue RGB for the entire projection light machine, and combine them to synthesize white light to realize full-color display. Infrared laser diode 210 provides infrared detection light source for the entire projection light machine. With the assistance of the electronic control module, human-computer interaction is realized. A possible combination of the common RGB three primary colors and infrared detection laser is 635nm, 525nm, 450nm. and 825nm. Other wavelength combinations can also be selected according to actual needs.

The collimating lens 220 may be an aspherical lens, and can collimate the light beams emitted by the laser diode 210 with a certain divergence angle in two orthogonal directions into an elliptical spot with no power and a divergence angle of 0. The front and rear surfaces of the collimating lens 220 are coated with anti-reflection film system to reduce ghost images and improve the utilization rate of light energy. Due to the structural design of the edge-emitting laser diode 210 itself, the light-emitting area is a nearly rectangular area. The beams emitted from the laser diode 210 have different divergence angles in two orthogonal directions, and the beams emitted from the long side of the rectangular area have a smaller divergence angle. , is called the direction of the slow axis; the beam emitted from the short side of the rectangular area has a larger divergence angle, and is called the direction of the fast axis. Taking a laser diode 210 of Osram as an example, the divergence angle of the laser output in the horizontal and vertical directions is θ _∥ xθ _⊥ = 6.3°x22.5°. Therefore, after propagating for a certain distance, the divergent light beam emitted from the laser diode 210 is collimated by the collimator lens 220 into an elliptical spot.

The collimating lens 220 may be an aspheric collimating lens 220 of molded plastic and molded glass. Among them, for molded plastics, the absolute value R _L of the curvature radius of the light-incident surface on the left surface satisfies: 2<R _L <10mm, the absolute value R _R of the curvature radius of the light-emitting surface on the right surface satisfies: 1<R _R <2.5mm, and the left surface The absolute value of the ratio of the radius of curvature to the radius of curvature of the right surface is 1.5<R _L /R _R <4.5. For molded glass, the absolute value R _L of the radius of curvature of the left surface satisfies: 2<R _L <20mm, the absolute value R _R of the radius of curvature of the right surface satisfies: 1<R _R <2.5mm, the radius of curvature of the left surface and the radius of curvature of the right surface The absolute value of the ratio 2<R _L /R _R <15.

The beam combining component 250 includes a plurality of spaced beam combining sheets, or a plurality of beam combining prisms connected to each other.

When the number of laser diodes 210 is four, they are infrared laser diodes 210 , red laser diodes 210 , green laser diodes 210 and blue laser diodes 210 from left to right. To simplify the description, in the following description, the red light is referred to as Red, the green light is referred to as Green, the blue light is referred to as Blue, the infrared light is referred to as IR, and the laser diode 210 is referred to as LD.

The four combining sheets corresponding to the four LDs are, from left to right, the first combining sheet, the second combining sheet, the third combining sheet and the fourth combining sheet. The side of the first beam combining sheet facing the IRLD is coated with an IR high reflection film. The side of the second beam combiner facing the first beam combiner is coated with an IR anti-reflection coating, and the side of the second beam combiner facing the RedLD is coated with an IR anti-reflection coating and a Red high-reflection coating. The side of the third combiner facing the second combiner is coated with IR and Red anti-reflection coatings, and the side of the third combiner facing GreenLD is coated with IR and Red anti-reflective coatings, and Green high-reflection coating. The side of the fourth combiner facing the third combiner is coated with IR, Red and Green anti-reflective coatings, the side of the fourth combiner facing BlueLD is coated with IR, Red and Green anti-reflective coatings, and Blue high-reflective coating.

In another embodiment, the beam combining component 250 includes a plurality of beam combining prisms connected to each other. The number of beam combining prisms may be four, and the acute angles of the first three beam combining prisms are all 45°, and the obtuse angles are all 135°. Each angle of the 4th composite prism is 45 °-90 °-45 °. The side of the beam-combining prism facing the corresponding laser diode 210 is coated with an anti-reflection film system to reduce ghost imaging and improve light energy utilization.

The four beam combining prisms from left to right are respectively a first beam combining prism, a second beam combining prism, a third beam combining prism and a fourth beam combining prism. The side of the first beam combining prism facing the IRLD will undergo total reflection during operation, and no coating is required; the connecting surface of the second beam combining prism facing the first beam combining prism faces the RedLD, and is coated with IR anti-reflection coating and Red high-reflection coating. The side of the second beam combining prism facing the first beam combining prism is coated with IR antireflection coating and Red high reflection coating, and this side faces RedLD; the side of the second beam combining prism facing the third beam combining prism is coated with IR and Red antireflection coating Membrane, Green high reflective membrane. The side of the third beam combining prism facing the second beam combining prism is coated with IR and Red anti-reflection coatings and Green high reflection coating, and this side faces GreenLD; the side of the third beam combining prism facing the fourth horizontal and vertical prisms is coated with IR and Red and Green antireflection coating, Blue high reflection coating. The side of the fourth beam combining prism facing the third beam combining prism is coated with IR and Red and Green anti-reflection coatings, Blue high reflection coating, and this side faces BlueLD; the exit surface of the fourth beam combining prism is coated with IR and Red and Green and Blue AR coating. A plurality of laser diodes 210 below the beam combining component 250 can respectively illuminate corresponding beam combining prisms, and the combining component combines multiple beams of light into a beam of white light.

The number of the shaping structure may be one, and the shaping structure is located behind the beam combining assembly 250, and is used for shaping the laser beams that have been combined. The shaping structure can be a prism group 260 or a biconical lens 240 . Taking the shaping structure as a prism group 260 as an example, the prism group 260 may include two first shaping prisms and a second shaping prism whose main cross-section is a quadrangle, and the incident beam of the combined laser beam is incident on the first shaping prism at a certain angle, And exit vertically; then enter the second shaping prism at a certain angle, and exit vertically. Both the light incident and light exit surfaces of the second shaping prism are coated with anti-reflection coatings to reduce ghost imaging and improve light energy utilization. If the actually used LD is collimated by the collimator lens 220, and the size in the horizontal direction is smaller than the vertical direction, then it is necessary to expand the beam in the horizontal direction. At this time, the incident light should obliquely enter the prism and exit vertically; After the LD is collimated, if the size of the horizontal direction is larger than that of the vertical direction, it is necessary to reduce the beam in the horizontal direction. At this time, the incident light should enter the prism vertically and exit obliquely at a certain angle.

The number of the shaping structures is the same as the number of the light source mechanisms, and they correspond one-to-one; the shaping structures are located between the light source mechanisms and the beam combining assembly 250, so that the light emitted by the light source mechanisms is first shaped and then combined. bundle.

In this embodiment, the number of shaping structures is the same as the number of light source mechanisms, because the divergence angle of each color light is different, so the size of the formed elliptical spot is also different, through one-to-one correspondence of multiple shaping structures, the The light emitted by each light source mechanism is shaped into a circular spot, and then multiple beams of light are combined so that the obtained beam is closer to a circular spot. In this embodiment, the shaping structure may be a biconical lens 240, which is an afocal optical element and is mainly used to shape the beam, that is, to shape the elliptical beam into a circular beam. The shaping biconical lens 240 only shrinks or expands the beam in a certain direction, and has no effect on the beam in another orthogonal direction. Both the light-incoming and light-outgoing surfaces of the shaped biconical lens 240 are coated with an anti-reflection film system to reduce ghost imaging and improve light energy utilization. Table 1 shows the structural parameters of a biconical shaping lens suitable for RGB color light with a beam reduction ratio of 0.67. Wherein, the curvature radius ratio of the biconical shaping lens satisfies 2/3<R _L /R _R <2.

Table 3 Parameters of biconical shaping lens

radius thickness Material conic constant Light incident surface 3.6 3.526 H-K9L -0.318 light emitting surface 2.4 / / /

The scanning projection device includes a laser wavelength temperature drift detection mechanism, and the laser wavelength temperature drift detection mechanism is used to detect the drift amount of the laser wavelength emitted by each light source mechanism. The laser wavelength temperature drift detection mechanism includes an energy beam splitter 230 and a detection photodiode. The energy beam splitter 230 can be a Schott N-BK7 or Chengdu Guangming CDGM H-K9L glass parallel plate placed at an inclination of 45°, and about 1 % of the energy enters the detection photodiode to monitor the drift of the emission wavelength of the LD of each color as the temperature changes. The front and rear surfaces of the glass parallel plate are polished with high precision. The light-incoming surface is not coated, and the light-emitting surface is coated with an anti-reflection film system to reduce the generation of ghost images and improve light energy utilization. Different beam splitting ratios can be achieved by adjusting the inclination angle of the glass plate, that is, the glass parallel plate can also be set at 40°, 35°, 30° and 25° as required.

The scanning projection device includes a scanning galvanometer 300, which modulates the light spot incident on the center of the galvanometer in horizontal and vertical directions, and scans and forms images in a progressive scanning working form.

The scanning projection device includes a beam expander 400 located behind the scanning galvanometer 300, and the beam expander 400 is used to increase the viewing angle of projection. After the scanning projection beam emitted by the scanning galvanometer 300 passes through the beam expander 400, the field of view angle of projection is increased, the projection ratio is reduced, and a larger projection image can be obtained at a smaller projection distance. The beam expander 400 is only a concave lens schematically drawn, and actually may be composed of a double-cemented free-form surface lens and a plurality of free-form surface lens groups.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting 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: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (15)

1. A device for eliminating laser speckle, characterized in that the device for eliminating laser speckle includes: a non-polarizing beam splitter (110), a polarization state conversion mechanism (120), and a polarization beam combiner (130); The non-polarizing beam splitter (110) is used to split the incident light in the first polarization state into a first sub-beam (141) and a second sub-beam (142); the first sub-beam (141) can enter The polarization beam combiner (130), the second sub-beam (142) can enter the polarization beam combiner (130) after passing through the polarization state conversion mechanism (120); the polarization beam combiner (130) for combining the first sub-beam (141) and the second sub-beam (142); The polarization state conversion mechanism (120) includes a half-wave plate (122) corresponding to the wavelength of the incident light, for converting the second sub-beam (142) passing through the half-wave plate (122) from the first polarization state is a second polarization state, one of the first polarization state and the second polarization state is a p polarization state, and the other is an s polarization state; The difference between the length of the path traveled by the second sub-beam (142) and the length of the path traveled by the first sub-beam (141) is greater than the coherence length of the incident light. 2. The laser speckle elimination device according to claim 1, characterized in that, the polarization state conversion mechanism (120) comprises: a first reflection structure (121) and a second reflection structure (123); The first reflective structure (121) is located on the propagation path of the second sub-beam (142), and the first reflective structure (121) faces the non-polarizing beam splitter (110) and the second reflective structure (123), so that the second sub-beam (142) is reflected towards the second reflective structure (123); The second reflective structure (123) faces the first reflective structure (121) and the polarization beam combiner (130), so that the second sub-beam (142) is reflected towards the polarization beam combiner (130); The half-wave plate is located between the first reflective structure (121) and the second reflective structure (123). 3. The laser speckle elimination device according to claim 2, characterized in that, the number of the polarization state conversion mechanisms (120) is n, n is an integer greater than or equal to 2, and the n polarization state conversion mechanisms (120 ) are arranged at intervals one by one along a direction away from the non-polarizing beam splitter (110); in a direction away from said non-polarizing beam splitter (110), The numbers of the n first reflective structures (121) are respectively m ₁ , m ₂ , m ₃ ... m _n ; The numbers of the n second reflective structures (123) are k ₁ , k ₂ , k ₃ ... k _n ; The numbers of the n half-wave plates (122) are respectively b ₁ , b ₂ , b ₃ ... b _n , and are respectively corresponding to different wavelengths of the half-wave plates (122) numbered b ₁ , b ₂ ... b _n The lasers are LD ₁ , LD ₂ , LD ₃ ... LD _n lasers; The first reflective structure (121) numbered m ₁ and the second reflective structure (123) numbered k ₁ can reflect LD ₁ laser light and transmit LD ₂ to LD _n laser light; The first reflective structure (121) numbered _m2 and the _second reflective structure (123) numbered k2 can reflect LD2 laser light and transmit _{LD3 - LDn} laser light; and so on; The first reflective structure (121) numbered m _n-1 and the second reflective structure (123) numbered k _n-1 can reflect LD _n-1 laser light and transmit LD _n laser light; The first reflective structure (121) numbered m _n and the second reflective structure (123) numbered k _n can reflect LD _n laser light; so that the _{second sub-beams (142) including LD 1 , LD 2 , LD 3 . . .} The _n lasers are reflected and separated one by one, and the n second reflective structure (123) can combine the separated LD ₁ , LD ₂ , LD ₃ . . . LD _n laser beams and reflect them into the polarization beam combiner (130). 4. The laser speckle elimination device according to claim 3, characterized in that, the first reflective structure (121) and the second reflective structure (123) are both sheet structures; The _first reflective structure (121) numbered m1 is coated with an anti-reflection coating for LD ₂ ~ LD _n lasers and a high-reflection coating for LD ₁ lasers on the side facing the non-polarizing beam splitter (110), and is facing away from One side of the non-polarizing beam splitter (110) is coated with an anti-reflection coating for LD ₂ to LD _n lasers; the second reflection structure (123) numbered k ₁ faces the side of the polarizing beam combiner (130) An anti-reflection coating for LD ₂ ~ LD _n lasers is coated, a high-reflection coating for LD ₁ lasers is coated, and an anti-reflection coating for LD ₂ ~ LD _n lasers is coated on the side facing away from the polarization beam combiner (130); _The first reflective structure (121) numbered m2 is coated with an anti-reflection coating for LD ₃ ~ LD _n lasers and a high-reflection coating for LD ₂ lasers on the side facing the non-polarizing beam splitter (110), and is facing away from One side of the non-polarizing beam splitter (110) is coated with an anti-reflection coating for LD ₃ -LD _n lasers; the second reflective structure (123) numbered k ₂ faces the side of the polarizing beam combiner (130) An anti-reflection film for LD ₃ ~ LD _n lasers is coated, a high-reflection film for LD ₂ lasers is coated, and an anti-reflection film for LD ₃ ~ LD _n lasers is coated on the side facing away from the polarization beam combiner (130); and so on; The first reflective structure (121) numbered m _n-1 is coated with an anti-reflection coating for LD _n laser and a high reflection coating for LD _n-1 laser on the side facing the non-polarizing beam splitter (110), and the back The anti-reflection coating to the LD _n laser is coated on the side of the non-polarizing beam splitter (110); the second reflection structure (123) numbered k _n-1 faces the side of the polarizing beam combiner (130) Coated with an anti-reflection film for LD _n lasers, a high-reflection film for LD _n-1 lasers, and the side facing away from the polarization beam combiner (130) is coated with an anti-reflection film for LD _n lasers; The side of the first reflective structure (121) numbered m _n towards the non-polarizing beam splitter (110) is coated with a high reflection film for LD _n laser; the second reflective structure (123) numbered k _n faces towards the One side of the polarization beam combiner (130) is coated with a high reflection film for LD _n laser. 5. The device for eliminating laser speckle according to claim 3, characterized in that, the device for eliminating laser speckle comprises a first prism (151) and a second prism (152), and the first prism (151) and The main sections of the second prism (152) are all parallelograms, and the internal angles of the parallelograms are respectively 45° and 135°; The number of the first prisms (151) and the second prisms (152) is n, a plurality of first prisms (151) are arranged along a direction away from the non-polarizing beam splitter (110), and are connected in sequence; The two prisms (152) are arranged along the direction away from the polarization beam combiner (130), and are connected in sequence; in a direction away from said non-polarizing beam splitter (110), The numbers of the n first prisms (151) are respectively f ₁ , f ₂ , f ₃ ...f _n ; The numbers of the n second prisms (152) are g ₁ , g ₂ , g ₃ ... g _n ; The side of the first prism (151) numbered f ₁ away from the non-polarizing beam splitter (110) faces the non-polarizing beam splitter (110) and the half-wave plate (122) numbered b ₁ , and the side is in contact with the non-polarizing beam splitter (110) and _The first prism (151) numbered f2 is connected to the side close to the non-polarizing beam splitter (110), and the anti-reflection coating for LD ₂ ~ LD _n laser is coated between the two, and the high reflection coating for LD ₁ laser; The side of the second prism (152) numbered g ₁ away from the polarization beam combiner (130) faces the polarization beam combiner (130) and the half-wave plate (122) numbered b ₁ , and the side of the second prism (152) with the number The second prism (152) of g ₂ is connected to one side close to the polarization beam combiner (130), and the anti-reflection coating of LD ₂ ~ LD _n laser is coated between the two, and the high reflection coating of LD ₁ laser; and the said The _first prism (151) numbered f1 is connected to one side of the half-wave plate (122) numbered b1, and the other side _of the half-wave plate (122) numbered b1 is connected to the other side _of the half-wave plate (122) numbered _g1 The second prism (152) is connected; _The side of the first prism (151) numbered f2 away from the non-polarizing beam splitter (110) is facing the non-polarizing beam splitter (110) and the half _- wave plate (122) numbered b2, and the side is in contact with the non-polarizing beam splitter (110) and The first prism (151) numbered _f3 is connected to the side close to the non-polarizing beam splitter (110), and the anti-reflection coating for LD ₃ ~ LD _n lasers is coated between the two, and the high-reflection coating for LD ₂ lasers; The side of the second prism (152) numbered g ₂ away from the polarization beam combiner (130) faces the polarization beam combiner (130) and the half-wave plate (122) numbered b ₂ , and the side of the second prism (152) with the number b The second prism (152) of g ₃ is connected to one side close to the polarization beam combiner (130), and the anti-reflection coating of LD ₃ ~ LD _n laser is coated between the two, and the high reflection coating of LD ₂ laser; and the said _The first prism (151) numbered f2 is connected to one side of the half-wave plate (122) numbered b2, and the other side of the _{half -} wave plate (122) numbered b2 is connected to the other side of the half _- wave plate (122) numbered g2 The second prism (152) is connected; and so on; The side of the first prism (151) numbered f _n-1 away from the non-polarizing beam splitter (110) faces the non-polarizing beam splitter (110) and the half-wave plate (122) numbered b _n-1 , And this face is connected with the face of the first prism (151) that is numbered f _n near the non-polarizing beam splitter (110), and the anti-reflection coating of LD _n laser is coated between the two, which is high to LD _n-1 laser Reflective film; the side of the second prism (152) numbered g _n-1 away from the polarization beam combiner (130) faces the polarization beam combiner (130) and the half-wave plate (122) numbered b _n-1 , and this face is connected to the face of the second prism (152) numbered g _n close to the polarizing beam combiner (130), and the anti-reflection coating of LD _n laser is coated between the two, which is high for LD _n-1 laser Reflective film; and the first prism (151) numbered f _n-1 is connected to one side of the half-wave plate (122) numbered b _n-1 , and the half-wave plate (122) numbered b _n-1 The other side of the sheet (122) is connected with the second prism (152) numbered g _n-1 ; The side of the first prism (151) numbered f _n away from the non-polarizing beam splitter (110) faces the non-polarizing beam splitter (110) and the half-wave plate (122) numbered b _n ; numbered g _n The side of the second prism (152) away from the polarization beam combiner (130) faces the polarization beam combiner (130) and the half _- wave plate (122) numbered b2; and the first numbered f _n The prism (151) is connected to one side of the half-wave plate (122) numbered b _n , and the other side of the half-wave plate (122) numbered b _n is connected to the second prism (152) numbered g _n connect. 6. The laser speckle elimination device according to claim 5, characterized in that, both the light-incoming surface and the light-emitting surface of the half-wave plate (122) are coated with an anti-reflection film. 7. The laser speckle elimination device according to claim 5, characterized in that, the number of the polarization state conversion mechanisms (120) is three, and three and a half of the three polarization state conversion mechanisms (120) The wave plates (122) correspond to red light, green light and blue light respectively. 8. A scanning projection device, characterized in that it comprises the device for eliminating laser speckle according to any one of claims 1-7. 9. The scanning projection device according to claim 8, characterized in that, the scanning projection device comprises a scanning spot generator, and the scanning spot generator comprises a plurality of light source mechanisms and a beam combining assembly (250), and the beam combining The component (250) is used to combine the laser beams output by multiple light source mechanisms; The scanning light spot generator further includes a shaping structure for shaping the elliptical light spot emitted by the light source mechanism into a circular light spot. 10. The scanning projection device according to claim 9, characterized in that, the shaping structure is located behind the beam combining assembly (250), and is used for shaping the combined laser beams. 11. The scanning projection device according to claim 9, characterized in that, the number of the shaping structures is the same as the number of the light source mechanisms, and there is a one-to-one correspondence; The shaping structure is located between the light source mechanism and the beam combination assembly (250), so that the light emitted by the light source mechanism is first shaped and then combined. 12. The scanning projection device according to claim 9, characterized in that, the shaping structure is a prism group (260) or a biconical lens (240). 13. The scanning projection device according to claim 9, characterized in that the scanning projection device comprises a laser wavelength temperature drift detection mechanism, and the laser wavelength temperature drift detection mechanism is used to detect the wavelength of the laser light emitted by each light source mechanism. Amount of drift. 14. The scanning projection device according to claim 9, characterized in that, the beam combining component (250) comprises a plurality of spaced apart beam combining sheets, or comprises a plurality of mutually connected beam combining prisms. 15. The scanning projection device according to claim 8, characterized in that, the scanning projection device comprises a beam expander (400) located behind the scanning galvanometer (300), and the beam expander (400) is used to increase The projected field of view.