CN112731750B - Laser light source and laser display system - Google Patents

Abstract

The invention relates to the technical field of laser display, and provides a laser light source and a laser display system, wherein the laser light source comprises: the laser module comprises a laser and an optical fiber outlet end, and light beams of the laser are emitted through the optical fiber outlet end; the conical surface of the conical lens is opposite to the plane of the conical lens, the plane of the conical lens faces the outlet end of the optical fiber, and the optical axis of the laser beam is superposed with the central axis of the conical lens; the diffusion sheet is provided with a micro lens array which is randomly arranged. The invention effectively improves the problem of beam hollowing by arranging the conical lens and the scattering sheet on the light-emitting path of the laser module with the optical fiber outlet end, so that the distribution of the hollow beam is more uniform, the beam is diffused by the micro-lens array of the scattering sheet, the probability of beam interference is further reduced, speckles with alternate light and shade are avoided, and the problem of uneven image illumination is improved.

Description

Laser light source and laser display system

Technical Field

The invention relates to the technical field of laser display, in particular to a laser light source and a laser display system.

Background

Laser light has been used in the field of projection display technology as a light source in recent years because of its advantages such as high brightness, high directivity, and good monochromaticity. The laser projection display technology (LDT) is also called as laser projection technology or laser display technology, and is a display technology which takes red, green and blue tricolor laser as a light source, can more truly reproduce rich and gorgeous colors of an objective world, and has better expressive force.

Laser generated by the existing laser is emitted from an optical fiber outlet end after being shaped and combined, the optical field distribution of the laser is hollow, namely, the energy of a light beam close to the center of a light beam ring is weaker, and the energy of the light beam ring positioned at the outer layer is stronger, so that the image illumination is uneven, the laser projection quality is deteriorated, and the watching experience of a user is poor.

Disclosure of Invention

The invention aims to provide a laser light source and a laser display system, and aims to solve the technical problem of uneven screen illumination caused by hollow light beams of the laser light source in the prior art.

In order to achieve the purpose, the invention adopts the technical scheme that:

in one aspect, the present invention provides a laser light source, including:

the laser module comprises a laser and an optical fiber outlet end, and light beams of the laser are emitted through the optical fiber outlet end;

the conical surface of the conical lens is opposite to the plane of the conical lens, the plane of the conical lens faces the outlet end of the optical fiber, and the optical axis of the laser beam is superposed with the central axis of the conical lens;

the diffusion sheet is provided with a micro lens array which is randomly arranged.

In one embodiment, the axicon lens includes a cylindrical end and a conical end, the plane of the cylindrical end faces the fiber exit end, and the conical surface of the conical end faces the diffuser plate.

In one embodiment, the thickness of the cylindrical end of the conical lens is 4-7 mm, the distance between the vertex of the conical end and the bottom surface of the conical end is 2-4 mm, and the vertex angle of the conical end is 15-40 degrees.

In one embodiment, the diffuser has a divergence angle of 15 to 30 °.

In one embodiment, the exit angle of the exit beam of the laser light source is 25-35 °.

In one embodiment, the radius of curvature of each microlens in the diffuser is 100 to 480 microns, the height of each microlens is 10 to 33 microns, and the thickness of each microlens is 100 to 140 microns.

In one embodiment, the thickness of the scattering sheet is 0.5-2 mm, the length of the scattering sheet is 10-20 mm, and the width of the scattering sheet is 10-20 mm.

In one embodiment, the laser light source further comprises:

the light homogenizing rod is arranged on the light emitting path of the scattering sheet.

In one embodiment, the laser light source is a monochromatic laser light source, the laser module comprises a laser, and the laser is a red laser, a green laser or a blue laser;

or, the laser light source is a multicolor laser light source, the laser module comprises a plurality of lasers, and light beams of the plurality of lasers are emitted out through the optical fiber outlet end after being combined.

In another aspect, the present invention further provides a laser display system, including the above laser light source.

The laser light source provided by the invention has the beneficial effects that: according to the invention, the conical lens and the scattering sheet are arranged on the light-emitting path of the laser module with the optical fiber outlet end, the technical bias that the conical lens is only used for reducing the central energy distribution of the light beam in a Gaussian light beam is overcome, the conical lens is creatively used for hollowing the light beam, the problem of hollowing the light beam is effectively improved, the distribution of the hollow light beam is more uniform, the probability of interference of the light beam can be reduced, the light beam is diffused through the micro lens array of the scattering sheet, the divergence degree and the random spatial phase of the light beam are greatly increased, the probability of interference of the light beam is further reduced, speckles with alternate light and shade are avoided, the problem of uneven illumination of a picture is improved, the laser projection quality is improved, and the viewing experience of a user is improved.

Drawings

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

Fig. 1 is a schematic view of light spot distribution of a light beam of a laser module in a laser light source according to an embodiment of the present invention;

fig. 2 is a first schematic diagram of an optical path structure of a laser light source according to an embodiment of the present invention;

fig. 3 is a schematic view of a light path structure of a laser light source according to an embodiment of the present invention.

Wherein, in the figures, the various reference numbers:

10	laser module
		11	Laser device
12	Fiber exit end
		20	Cone lens
201	Plane surface
		202	Conical surface
203	Vertex point
		21	Cylindrical end
22	Conical end
		30	Scattering sheet
31	Microlens array
		40	Light-homogenizing rod

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly or indirectly disposed on the other element. When an element is referred to as being "connected to" another element, it can be directly or indirectly connected to the other element. The terms "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positions based on the orientations or positions shown in the drawings, and are for convenience of description only and not to be construed as limiting the technical solution. The terms "first", "second" and "first" are used merely for descriptive purposes and are not to be construed as indicating or implying relative importance or to implicitly indicate a number of technical features. The meaning of "plurality" is two or more unless specifically limited otherwise.

In laser displays, the quality of the laser light source has a very important influence on the effectiveness of the laser projection. The laser has the advantages of high brightness, strong directivity and good monochromaticity, but also has a plurality of defects, for example, the laser has high coherence, so that when the laser generated by the laser irradiates the projection surface, because the wavelength of the laser is the same and the phase is constant, the light scattered by the projection surface generates interference in space, so that the interference in a partial area is long, the interference in the partial area is destructive, speckles such as dark spots, color spots and color blocks appear on the projection surface, and the display effect is greatly reduced. For another example, for a common laser, when a beam generated by the common laser directly exits, the energy distribution is generally gaussian, that is, the central energy density of the beam is large, and the farther away from the center, the lower the energy density is, so that the central energy of the beam is too concentrated and the uniformity is poor. In order to make the energy distribution of the laser beam more uniform, an optical fiber is connected at the outlet end of the laser, the energy distribution of the beam is changed after the laser is emitted through the optical fiber and is not concentrated in the center of the beam, but hollowing occurs, i.e., the energy of the center of the beam is lower, while the energy of the outer layer of the beam is stronger, and the hollowing of the beam of blue light is relatively more obvious (as shown in fig. 1 (a)), the hollowing of the beam of green light is less (as shown in fig. 1 (b)), the hollowing of the beam of red light is relatively better (as shown in fig. 1 (c)), and the uniformity of the energy distribution of the beam needs to be further improved.

The axicon lens is an optical element capable of changing the energy distribution of a light beam, and comprises a conical surface and a flat surface, wherein the light beam enters the axicon lens from the flat surface and exits from the conical surface. When parallel light beams enter from one side of the plane of the conical lens and exit from the conical surface, the conical surface refraction has the function of focusing and converging, so that the light beams exiting from the conical surface can be focused; the vertex of the conical surface has a divergence effect on the light beam, so that the light beam emitted from the vertex of the conical surface diverges towards a plurality of directions, thereby dispersing the energy of the light beam. Therefore, for a Gaussian beam generated by a common laser, the cone lens can disperse the beam at the center of which the energy density is concentrated, so that the energy density at the center of the beam is reduced, and the energy distribution of the laser beam is more uniform. For the light beams with uniform energy distribution, the cone lens can disperse the central light beam, so that the energy density of the center of the light beam is weakened, a plurality of annular light beams can be formed after passing through the cone lens, the light beam energy of the concentric annular light beams close to the center of the light beam ring is weaker, the light beam ring energy of the concentric annular light beams positioned on the outer layer is stronger, and a hollow annular structure is formed. Therefore, the cone lens can effectively reduce the energy density of the center of the light beam and easily form a hollow annular structure no matter the light beam is a Gaussian light beam or a light beam with uniform energy distribution. For the laser beam having the hollow ring structure, it is generally considered that the use of the axicon further enhances the hollowing of the laser beam, and the problem of using the axicon to improve the uneven energy distribution of the beam is not considered.

In the research of the application, the characteristics that the cone lens focuses the conical surface emergent light and diverges the conical surface vertex emergent light are found, according to the reversibility of light, the light beam with the excessively high central energy can be hollowed after passing through the cone lens, and the hollowed light beam can be condensed after passing through the inverted cone lens, so that the problem that the hollow laser beam is uneven in energy distribution can be solved.

Referring to fig. 2, the present embodiment provides a laser light source, which includes a laser module 10, a cone lens 20, and a scattering sheet 30 sequentially disposed along a light path. The laser module 10 includes a laser 11 and an optical fiber exit end 12, and a light beam of the laser 11 exits through the optical fiber exit end 12. The tapered surface 202 of the axicon lens 20 is opposite to the flat surface 201 of the axicon lens 20, the flat surface 201 of the axicon lens 20 faces the fiber exit end 12, and the optical axis of the beam of the laser 11 coincides with the central axis of the axicon lens 20. The scattering sheet 30 is provided with a microlens array 31 which is randomly arranged, and parameters such as curvature radius, diameter and thickness of each microlens in the microlens array 31 are randomly arranged, so that each microlens is not completely the same, and the randomness and the divergence degree of the emergent angle of the light beam can be increased.

In the laser module in this embodiment, a light beam generated by the laser 11 is emitted to the axicon 20 through the optical fiber outlet end 12, and the light beam is emitted to the scattering sheet 30 through the conical surface of the axicon 20 and is emitted after being scattered by the scattering sheet 30.

On one hand, since the light beam generated by the laser 11 exits through the fiber exit end 12, the light field distribution of the light beam entering the axicon lens 20 is a hollow ring structure, the central energy of the light beam is low, and at this time, the energy of the light beam exiting through the conical surface 202 of the axicon lens 20 is much larger than the energy of the light beam exiting through the vertex 203 of the axicon lens 20. The light beam emitted from the conical surface 202 converges toward the center of the light beam, so that the light intensity at the center of the light beam is increased, and since the energy of the light beam incident to the conical lens 20 is low and the light beam at the center is emitted through the vertex 203 of the conical lens 20, the light beam energy diffused through the vertex 203 of the conical lens 20 is small, so that the diffusion effect at the center of the light beam is weakened as a whole, the light intensity at the center of the hollow light beam is increased after the hollow light beam passes through the conical lens 20, and the light beam energy at the outer layer is weakened, so that the light beam distribution is more uniform.

On the other hand, after the light beam of the laser 11 enters the conical lens 20 through the plane 201 of the conical lens 20, an annular light beam with a diameter increased with the distance but a consistent annular thickness is generated, and due to different optical paths of the light beam with different distances from the optical axis reaching the conical surface 202, the optical path difference and the phase difference of different annular light beams in the transmission process are large, and the coherent length is exceeded, so that the probability of interference among a plurality of light beam rings is greatly reduced, and speckles with alternate light and dark colors are avoided.

Furthermore, the diffuser 30 is located on the light exit path of the axicon 20, and is used for diffusing the light beam, so as to enhance the effect of eliminating interference. Because the scattering sheet 30 is provided with the microlens arrays 31 which are randomly arranged, and the parameters of the curvature radius, the diameter, the thickness and the like of each microlens in the microlens arrays 31 are randomly set, the random diffusivity of the scattering sheet 30 is greatly increased, and the random redistribution can be carried out on the divergence angle, so that the homogenization of the light beam near the optical axis is enhanced, the energy of the light beam with the large-angle divergence angle is reduced, and the uniformity degree of the whole light beam is improved. Therefore, the divergence degree of the light beams emitted by the micro lenses in the micro lens array 31 is greatly increased, the phases or phase differences are completely randomly distributed, the random space phase of the light beams is increased, the divergence is more uniform, and the probability of interference of the light beams is greatly reduced.

The laser light source provided by the embodiment has the beneficial effects that: this embodiment sets up cone lens 20 and scattering piece 30 through set up on the light-emitting path of laser module 10 that is equipped with fiber outlet end 12, the technical bias that cone lens 20 only is used for reducing the central energy distribution of light beam in the gaussian beam has been overcome, creatively is used for cone lens 20 in the hollow light beam, the problem of light beam hollowing has effectively been improved, make the distribution of hollow light beam more even, and can reduce the probability that the light beam takes place to interfere, and spread the light beam through the microlens array 31 of scattering piece 30, greatly increased the divergence degree and the random space phase of light beam, the probability that the light beam takes place to interfere has further been reduced, avoid appearing light and shade alternate speckle, improve the inhomogeneous problem of picture illuminance, promote laser projection quality, improve user's the experience of watching.

Referring to fig. 3, in order to make the light beam distribution more uniform, a light-homogenizing rod 40 (also called an integrating rod) is further disposed on the light path of the diffuser 30, and the light beam emitted from the diffuser 30 enters the light-homogenizing rod 40 for further homogenization and then is emitted to the imaging system. The light beam reaches the emergent section after undergoing multiple total internal reflections in the light-homogenizing rod 40, the light beam is reflected once and is equivalent to the illumination of a mirror image virtual light source, and finally a uniform light spot surface is formed on the tail end surface of the light-homogenizing rod 40. It will be appreciated that the integrator rod 40 has a range of incident angles, and light beams having divergence angles exceeding the range of incident angles will not enter the integrator rod 40, and will tend to cause loss of light energy.

Further, the axicon lens 20 includes an integrated cylindrical end 21 and a conical end 22, a plane 201 of the cylindrical end 21 faces the fiber exit end 12, which is an incident end of the beam of the laser 11; the conical surface 202 of the conical end 22 faces the diffuser sheet 30, which serves as the exit end for the light beam. The cylindrical end 21 can increase the optical path of the light beam entering the axicon 20, thereby increasing the optical path difference and phase difference of the light beam in the transmission process and further reducing the probability of light beam interference.

In the embodiment, the thickness d1 of the cylindrical end 21 of the axicon lens 20 is 4 to 7 mm, the distance d2 between the vertex 203 of the conical end 22 and the bottom surface of the conical end 22 is 2 to 4 mm, and the distance between the vertex 203 of the conical end 22 and the plane 201 of the cylindrical end 21 is 6 to 11 mm, so that large optical path difference and phase difference of different annular light beams can be ensured in the transmission process, and the probability of interference among a plurality of light beam rings can be effectively reduced.

In consideration of the hollow center of the light beam, it is desirable that the light beam with smaller energy in the hollow center region of the light beam is emitted through the vertex 203 of the cone end 22 as much as possible, and the light beam at the outer layer of the light beam is emitted through the cone surface 202. In this embodiment, the vertex 203 of the cone end is 15 to 40 °, for example, 15 °, 20 °, 25 °, 30 °, 35 °, 40 °, and the like, so that the light beam emitted through the cone 202 can be better converged toward the center of the light beam, and the light beam emitted through the vertex 203 is less, so that the light intensity at the center of the light beam is increased, the light beam energy at the outer layer is weakened, and the light beam distribution is more uniform. It will be appreciated that as the size of the region of hollowing in the beam exiting through the fiber exit end 12 varies, the apex 203 can be adjusted accordingly.

Further, in order to diffuse all the light beams emitted through the axicon 20, the length and the width of the diffusion sheet 30 are both 10 to 20 mm, and one side surface of the diffusion sheet 30 is covered with a micro lens array. In order to ensure the diffuser 30 to reasonably diffuse the light beam, the radius of curvature of each microlens in the diffuser 30 is 100-480 micrometers, the height of the microlens (the distance between the highest point and the lowest point of the curved surface of the microlens) is 10-33 micrometers, the thickness of the microlens is 100-140 micrometers, and the divergence angle of the diffuser 30 is 15-30 °. The curvature radius of the micro lens is randomly set within the range of 100-480 microns, the diameter of the micro lens is randomly set within the range of 10-33 microns, and the thickness of the micro lens is randomly set within the range of 100-140 microns, so that the light beam is randomly diffused after passing through the micro lens, the divergence degree of the light beam and the randomness of phase or phase difference distribution are increased, the divergence is more uniform, and the probability of interference of the light beam is reduced. Meanwhile, after the parameters such as the thickness, the diameter, the curvature radius and the like of the micro lens are determined, the diffusion angle of the micro lens is also determined, so that the parameters such as the thickness, the diameter, the curvature radius and the like of the micro lens are adjusted, the diffusion angle of the micro lens can also be adjusted, the divergence angle of the scattering sheet 30 is 15-30 degrees, the requirement of the incidence angle of the dodging rod 40 with different specifications can be met, the light beam can be ensured to be effectively incident into the dodging rod 40, and the light loss is reduced.

In this embodiment, the laser light source may be a monochromatic laser light source, or may also be a two-color laser light source or a three-color laser light source. When laser light source is monochromatic laser light source, laser module 10 includes a laser 11, and laser 11 can be red laser, green laser or blue laser. It can be understood that, because the hollowing degree of the laser beams generated by the red laser, the green laser and the blue laser after being emitted through the fiber outlet end 12 is different, various parameters of the axicon lens 20 can be adjusted accordingly. When the laser light source is a bicolor laser light source, the laser module 10 includes two lasers 11, and the two lasers 11 are two of a red laser, a green laser or a blue laser. When laser source is three-colour laser source, laser module 10 includes three laser instrument 11, and three laser instrument 11 is red laser instrument, green laser instrument or blue laser instrument respectively, and the laser beam that three laser instrument produced is closed the back and is exported through the optic fibre exit end. It is understood that a beam combiner can be disposed in the laser module 10 to combine the multiple laser beams into one beam and then exit through the fiber exit end 12.

The present embodiment is also directed to a laser display system, which includes the laser light source. A light guide (e.g., a dodging rod) of a laser light source is coupled into the imaging system. The laser display system provided by the embodiment adopts the laser light source, so that the illumination uniformity of the picture is effectively improved, and the generation of speckles such as dark spots, color spots and color blocks is reduced, thereby improving the shimming problem.

The above description is intended to be illustrative of the preferred embodiment of the present invention and should not be taken as limiting the invention, but rather, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Claims (10)

1. A laser light source comprising, disposed along an optical path:

the laser module comprises a laser and an optical fiber outlet end, light beams of the laser are emitted through the optical fiber outlet end, and the light field distribution of the light beams emitted through the optical fiber outlet end is a hollow annular structure;

the conical surface of the conical lens is opposite to the plane of the conical lens, the plane of the conical lens faces the optical fiber outlet end, and the optical axis of the laser beam is superposed with the central axis of the conical lens;

the scattering sheet is provided with a micro lens array which is randomly arranged;

and light beams generated by the laser are emitted to the conical lens through the optical fiber outlet end, are emitted to the scattering sheet through the conical surface of the conical lens and are emitted after being scattered by the scattering sheet.

2. The laser light source of claim 1, wherein the axicon lens comprises a cylindrical end and a conical end, the plane of the cylindrical end facing the fiber exit end, the conical surface of the conical end facing the diffuser.

3. The laser light source according to claim 2, wherein the thickness of the cylindrical end of the axicon is 4 to 7 mm, the distance between the vertex of the conical end and the bottom surface of the conical end is 2 to 4 mm, and the vertex angle of the conical end is 15 to 40 °.

4. The laser light source according to claim 3, wherein the diffusion sheet has a divergence angle of 15 to 30 °.

5. The laser light source according to claim 4, wherein an exit angle of an exit beam of the laser light source is 25 to 35 °.

6. The laser light source according to claim 1, wherein each of the microlenses in the diffuser has a radius of curvature of 100 to 480 micrometers, a height of 10 to 33 micrometers, and a thickness of 100 to 140 micrometers.

7. The laser light source according to claim 1, wherein the thickness of the diffuser is 0.5 to 2 mm, the length of the diffuser is 10 to 20 mm, and the width of the diffuser is 10 to 20 mm.

8. The laser light source of claim 1, further comprising:

the light homogenizing rod is arranged on the light emitting path of the scattering sheet.

9. The laser light source according to any one of claims 1 to 8, wherein the laser light source is a monochromatic laser light source, the laser module comprises a laser, and the laser is a red laser, a green laser or a blue laser;

or, the laser light source is a multicolor laser light source, the laser module comprises a plurality of lasers, and light beams of the plurality of lasers are emitted out through the optical fiber outlet end after being combined.

10. A laser display system comprising the laser light source according to any one of claims 1 to 9.

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