Laser projection device

Abstract

The application relates to a laser projection device, and belongs to the technical field of projectors. The laser projection device has the technical problem that speckles appear in a projected picture. The laser projection device comprises, in sequence along a propagation light path, a laser light source, a rotary optical component, a light modulator and a projection lens. The laser light source is used for emitting a laser beam to the rotary optical component. The rotary optical component comprises a driving member and a rotary optical crystal located on the propagation light path of the laser beam. The driving member is connected to the rotary optical crystal and is used for driving the rotary optical crystal to rotate. The rotary optical crystal has a structure that alternately changes in thickness along a rotation direction. The rotary optical crystal is used for adjusting the polarization direction of the laser beam. The light modulator is used for adjusting the laser beam passing through the rotary optical crystal into an image beam. The projection lens is used for transmitting the image beam out of the laser projection device. The laser projection device can suppress speckles in the projected picture.

Description

Technical Field

[0001] This application belongs to the field of projector technology, and in particular relates to a laser projection device. Background Technology

[0002] With the increasing maturity of laser projection technology, the market for laser projection equipment is expanding rapidly. Laser projection boasts advantages such as high brightness, wide color gamut, long lifespan, and low energy consumption. However, due to the high coherence of laser light, laser projection suffers from a significant drawback: speckle. This speckle phenomenon severely affects image clarity and resolution, reducing display quality. The visual effect resembles a frosted film, with the human eye perceiving the image as having alternating bright and dark grainy spots. Prolonged viewing can easily cause discomfort such as eye strain and dizziness. Therefore, suppressing speckle in laser projection equipment is a pressing technical problem that needs to be solved. Summary of the Invention

[0003] This application provides a laser projection device to solve the technical problem of speckle in the projected image of existing laser projection devices.

[0004] This application provides a laser projection device, which includes a laser light source, a light rotator, a light modulator, and a projection lens arranged sequentially along the optical path.

[0005] The laser source is used to emit a laser beam to the optical rotation component;

[0006] The optical rotation component includes a driving element and an optical rotation crystal located in the propagation optical path of the laser beam. The driving element is connected to the optical rotation crystal and is used to drive the optical rotation crystal to rotate. The optical rotation crystal has a structure in which the thickness changes alternately along the rotation direction. The optical rotation crystal is used to adjust the polarization direction of the laser beam.

[0007] The optical modulator is used to adjust the laser beam passing through the optically rotating crystal into an image beam;

[0008] The projection lens is used to transmit the image beam out of the laser projection device.

[0009] Optionally, the thickness of the optically active crystal satisfies at least one of the following structures:

[0010] The thickness of the optically active crystal varies continuously along the radial direction;

[0011] The thickness of the optically active crystal increases or decreases continuously in the radial direction;

[0012] The thickness of the optically active crystal varies continuously along any direction parallel to the plane of rotation.

[0013] Optionally, the optical rotator crystal has a cylindrical or cylindrical structure and a rotationally symmetric structure. The optical rotator crystal rotates around a rotation axis under the action of the driving member. The rotation axis is parallel to the propagation optical path passing through the optical rotator crystal and passes through the center of gravity of the optical rotator crystal.

[0014] Optionally, in the rotation direction of the optically rotating crystal, the irradiation area of ​​the laser source on the optically rotating crystal covers adjacent regions of minimum and maximum thickness. And / or

[0015] In the radial direction of the optically active crystal, the irradiation area of ​​the laser source on the optically active crystal covers adjacent regions of minimum and maximum thickness.

[0016] Optionally, the optical axis of the optical rotator is parallel to the propagation optical path passing through the optical rotator.

[0017] Optionally, the optically active crystal includes a first surface and a second surface opposite to each other and through which the laser beam passes, both of which are curved surfaces; or, the first surface is curved and the second surface is planar.

[0018] Optionally, the optical rotator crystal includes a first surface and a second surface opposite to each other and through which the laser beam passes, both of which are curved surfaces; in the propagation optical path passing through the optical rotator crystal, the position of the maximum height of the first surface is opposite to the position of the maximum height of the second surface, and the position of the minimum height of the first surface is opposite to the position of the minimum height of the second surface.

[0019] Optionally, the optical rotation component further includes a transmission plate, which has isotropic optical properties. The transmission plate is attached to one side of the curved surface of the optical rotation crystal in the direction of the propagation optical path, and the side of the transmission plate opposite to the optical rotation crystal is a plane.

[0020] Optionally, the laser projection device further includes a reflector disposed on one side of the optical rotation component, the reflector being used to reflect the laser beam passing through the first region of the optical rotation crystal to the second region of the optical rotation crystal, the first region and the second region not overlapping each other.

[0021] Optionally, the location of the maximum thickness in the first region is projected along the propagation optical path to the location of the maximum thickness in the second region; the location of the minimum thickness in the first region is projected along the propagation optical path to the location of the minimum thickness in the second region.

[0022] Beneficial effects:

[0023] The laser projection device provided in this application includes a laser source, a light rotator, a light modulator, and a projection lens arranged sequentially along the propagation optical path. The laser source emits a laser beam to the light rotator. The light rotator includes a driving element and a light rotator crystal located on the propagation optical path of the laser beam. The driving element drives the light rotator crystal to rotate. The light rotator crystal has a structure with alternating thicknesses along the rotation direction and is used to adjust the polarization direction of the laser beam. The light modulator adjusts the laser beam passing through the light rotator crystal into an image beam. The projection lens transmits the image beam out of the laser projection device. In the above structure, after the laser beam emitted by the laser source passes through the light rotator crystal, the polarization angle of the laser beam changes. The amount of change in polarization angle is proportional to the thickness of the light rotator crystal. Therefore, by setting the thickness of the light rotator crystal to an alternating thickness structure, the polarization direction of the laser beam passing through different thickness regions can be controlled. The greater the difference in the polarization direction of the laser beam, the weaker the coherence, and the less likely it is to form speckle on the projected image, thereby achieving the technical effect of suppressing speckle. Meanwhile, due to the rotation of the optical crystal, the polarization angle of the laser beam can change continuously over time, and the difference in polarization angle between the sub-beams in the laser beam can also change continuously over time. Thus, the image seen by the human eye is a superposition of images formed by the laser beam passing through multiple regions of different thicknesses of the optical crystal. The intensity and size of speckle in these images also change over time. The speckle that the human eye can perceive is formed by the superposition of speckle in multiple images. The intensity and size of this constantly changing speckle can be averaged visually, thereby further reducing the human eye's perception of speckle and thus achieving the effect of suppressing speckle formation in laser projection equipment. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings. In the following description, the same reference numerals denote the same parts.

[0026] Figure 1 This is a schematic diagram of the structure of the laser projection device in the first embodiment of this application;

[0027] Figure 2 This is a schematic diagram of the structure of an optically active crystal in one embodiment of this application;

[0028] Figure 3 This is a waveform diagram showing the change in thickness of the optically active crystal along the rotation direction in one embodiment of this application;

[0029] Figure 4 This is a schematic diagram illustrating the function of the optical rotation component in a laser projection device according to one embodiment of this application;

[0030] Figure 5 This is a schematic diagram of the structure of a laser source in one embodiment of this application;

[0031] Figure 6 This is a schematic diagram of the structure of the laser projection device in the second embodiment of this application;

[0032] Figure 7 This is a three-dimensional structural diagram of an optically active crystal in one embodiment of this application;

[0033] Figure 8 This is a schematic diagram of the trajectory of any point on the optically active crystal when the optically active crystal rotates one revolution (360°) in one embodiment of this application;

[0034] Figure 9 This is a waveform diagram showing the change in the thickness of an optically active crystal along the rotation direction in one embodiment of this application;

[0035] Figure 10 for Figure 7 Enlarged schematic diagram of the middle surface F1-1;

[0036] Figure 11 This is a schematic diagram of the radial thickness variation waveform of an optically active crystal in one embodiment of this application;

[0037] Figure 12 This is a schematic diagram of the radial thickness variation waveform of an optically active crystal in one embodiment of this application;

[0038] Figure 13 This is a three-dimensional structural diagram of an optically active crystal in one embodiment of this application;

[0039] Figure 14 for Figure 13 A side view of a mesorotatory optical crystal;

[0040] Figure 15 This is a schematic diagram of the trajectory of any point on the optically active crystal when it rotates 360° in one embodiment of this application.

[0041] Figure 16 This is a schematic diagram of the thickness variation waveform of the optically active crystal along the D1 direction in one embodiment of this application;

[0042] Figure 17 This is a schematic diagram of the structure of an optically active crystal in one embodiment of this application;

[0043] Figure 18 This is a schematic diagram of the structure of an optically active crystal in one embodiment of this application;

[0044] Figure 19 for Figure 18 Schematic diagram of the structure of the central transmission plate T;

[0045] Figure 20 This is a schematic diagram of the structure of the laser projection device in the third embodiment of this application; Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0047] refer to Figure 1 This application provides a schematic diagram of the structure of a laser projection device, which may specifically be a laser cinema, a laser TV, or other laser projection instruments.

[0048] like Figure 1 As shown, the laser projection device includes a laser light source 110, a light-rotating component 120, a light modulator 130, and a projection lens 140. The light-rotating component 120 includes a light-rotating crystal 121 and a driving element 122.

[0049] The laser light source 110 can emit a laser beam 50. After being emitted from the laser light source 110, the laser beam 50 enters the optical rotator crystal 121. After exiting the optical rotator crystal 121, the laser beam 50 enters the optical modulator 130. After passing through the optical modulator 130, it enters the projection lens 140. Then, the laser beam 50 exits from the projection lens 140 and is projected onto an external display medium (such as a wall or screen) to form a projected image.

[0050] In this embodiment, the path that the laser beam 50 takes after being emitted from the laser source 110 is defined as the propagation optical path; that is, the laser source 110, the optical rotation component 120, the optical modulator 130 and the projection lens 140 are arranged sequentially along the propagation optical path.

[0051] The optical rotator crystal 121 possesses optical rotation properties and is used to adjust the polarization direction of the laser beam 50. Specifically, after the laser beam 50 passes through the optical rotator crystal 121, its polarization direction rotates, meaning the plane containing the polarization direction of the laser beam 50 rotates by a certain angle. The adjustment angle of the laser beam 50's polarization direction by the optical rotator crystal 121 is related to the optical rotation rate of the optical rotator crystal 121; the higher the optical rotation rate, the larger the adjustment angle. The adjustment angle is also proportional to the thickness of the optical rotator crystal 121. The optical rotation rate of the optical rotator crystal 121 used in this embodiment is unique. That is, in this embodiment, after the laser beam 50 passes through the optical rotator crystal 121, the rotation angle of the laser beam 50's polarization direction is only related to the thickness of the optical rotator crystal 121.

[0052] The outer surface of the optical rotator crystal 121 includes a first surface and a second surface opposite to each other. The distance between the first surface and the second surface is the thickness of the optical rotator crystal 121. However, the thickness of the optical rotator crystal 121 may not be the same at different positions. For example, during the rotation of the optical rotator crystal 121, the laser beam 50 always enters the first surface from one side of the optical rotator crystal 121. After passing through the optical rotator crystal 121, the laser beam 50 exits from the second surface and reaches the other side of the optical rotator crystal 121. During this process, the laser beam 50 forms a propagation optical path in the optical rotator crystal 121. In a preferred case, the rotation axis of the optical rotator crystal 121 is parallel to the propagation optical path. At this time, the thickness of the optical rotator crystal 121, that is, the distance between the first surface and the second surface, is equal to the path length of the laser beam 50 passing through the optical rotator crystal 121. Of course, the rotation axis of the optical rotator crystal 121 can also be at a certain angle to the propagation optical path. In a preferred embodiment, the propagation optical path is also parallel to the optical axis of the optical rotator crystal 121. The optical axis is a special direction in which light does not undergo birefringence when propagating within the optical rotator crystal 121 along this special direction. All straight lines parallel to this special direction constitute the optical axis of the optical rotator crystal 121. By making the laser beam 50 parallel to the optical axis of the optical rotator crystal 121, the laser beam 50 is linearly polarized both before and after passing through the optical rotator crystal 121.

[0053] In this embodiment, to improve the speckle elimination effect, the driving component 122 can drive the optically rotating crystal 121 to rotate around a rotation axis passing through itself, thereby achieving self-rotation. When the optically rotating crystal 121 rotates one revolution (360°), the trajectory formed by any point on the optically rotating crystal 121 is a planar circle, and the rotation axis of the optically rotating crystal 121 is perpendicular to this planar circle. Preferably, the rotation axis passes through the center of gravity of the optically rotating crystal 121, thereby achieving rotational stability. In this embodiment, the driving component 122 can be a motor. The driving component 122 connects to and fixes the optically rotating crystal 121. The fixed position can be located on the first surface or the second surface of the optically rotating crystal 121, or it can be located at the central hollow part of the optically rotating crystal 121 (when the optically rotating crystal 121 is cylindrical).

[0054] In this embodiment, since the change in polarization angle of the laser beam 50 is proportional to the thickness of the optical rotator crystal 121, in order to ensure that the path length of each laser beam 50 passing through the optical rotator crystal 121 is different as much as possible, the optical rotator crystal 121 has a structure in which the thickness changes alternately along the rotation direction, that is, the thickness value of the optical rotator crystal 121 changes alternately along the rotation direction of the optical rotator crystal 121. In this way, as the optical rotator crystal 121 rotates, the path length of the laser beam 50 passing through the optical rotator crystal 121 changes continuously, and the polarization direction of the laser beam 50 changes continuously over time. The difference in polarization direction between the sub-beams in the laser beam 50 also changes continuously over time. Thus, the image seen by the human eye is a superposition of images formed by the laser beam passing through multiple regions of different thicknesses of the optical rotator crystal. The intensity and size of speckle in these images also change over time. The speckle that the human eye can perceive is formed by the superposition of speckle in multiple images. The intensity and size of this constantly changing speckle can be averaged visually, thereby further reducing the human eye's perception of speckle and achieving the effect of suppressing speckle formation in laser projection equipment.

[0055] Specifically, Figure 2 This is a schematic diagram showing the shape of a square wave as the thickness of the optically active crystal 121 changes along the rotation direction. The optically active crystal 121 is generally cylindrical, but unlike a cylinder, one of its two opposing faces is replaced with the first surface F, while the other face remains circular (i.e.,...). Figure 3 The second surface F' is a planar circle; the thickness of the optical rotator crystal 121 is the distance between the first surface F and the second surface F'. Figure 2 Driven by a force (not shown in the diagram), the crystal rotates along direction r, with rotation axis A perpendicular to the second surface F' and passing through the centroid of the optical rotator crystal 121; it can be seen that the thickness of the optical rotator crystal 121 changes in a square wave shape along the rotation direction, as shown in the diagram. Figure 3 As shown, Figure 3 for Figure 2 The diagram shows the waveform of the thickness of the optically active crystal 121 changing along the rotation direction. The Y1 axis represents the thickness of the optically active crystal 121, and the X1 axis represents the rotation direction of the optically active crystal 121. It can be seen that the thickness of the optically active crystal 121 changes along the rotation direction in the shape of a square wave. Of course, the thickness of the optically active crystal 121 can also change along the rotation direction in other shapes, such as sawtooth, sine wave, and other undulating shapes.

[0056] In this embodiment of the application, the effect of the optically active crystal 121 is as follows: Figure 4 As shown, Figure 4 Figure B1 shows the polarization direction of the laser beam 50 without the optical rotation component 120 in the laser projection device. It can be seen that the polarization direction of the laser beam 50 is the same. Figure 4 Figure B2 shows the polarization direction of the laser beam 50 when the optical rotation component 120 is added to the laser projection device. It can be seen that the polarization direction of the laser beam 50 is not exactly the same under the action of the optical rotation component 120.

[0057] In a specific implementation, the laser source 110 may include a light source capable of emitting red, green and blue colors. When the laser beams 50 corresponding to the three light sources pass through the optical rotator crystal 121, the polarization direction of each sub-beam in the laser beam 50 will be changed accordingly.

[0058] As one embodiment, the laser source 110 can be composed of a red laser, a blue laser, and a color wheel. The red laser is used to emit red laser light, the blue laser is used to emit blue laser light, and the color wheel is provided with green phosphor, which can receive blue laser light as excitation light and perform wavelength conversion to emit green fluorescence. In this way, during use, part of the blue laser light is converted into green fluorescence, so as to emit red, green and blue light at the same time.

[0059] like Figure 5As shown, in another embodiment, the laser source 110 can also be directly composed of a red laser 110-1, a blue laser 110-2, and a green laser 110-3, which are used to emit lasers of red, green, and blue colors, respectively. That is, the laser source 110 is a pure laser source. The first dichroic mirror M1 and the second dichroic mirror M2 are used to converge the laser beams 50 emitted by the red laser 110-1, the blue laser 110-2, and the green laser 110-3 into one beam, which then enters the optical rotator 120. The polarization direction of the incoming laser beam 50 will be adjusted by 20. Of course, the optical rotation component 120 can also be located on the output side of the red laser 110-1, the blue laser 110-2 and the green laser 110-3 respectively. That is to say, before the three-color laser beams 50 converge, an optical rotation component 120 can be set separately for each color laser beam 50. After the polarization direction of each color laser beam 50 is adjusted, the three colors of laser beams 50 are converged into one path and then enter the next structure.

[0060] As another embodiment, the laser source 110 can also be a combination of a laser and an LED source. As can be seen from the above description, the laser source 110 can be implemented in multiple ways, and this application does not limit it.

[0061] The light modulator 130 is used to adjust the laser beam 50 passing through the optical crystal 121 into an image beam and output the image beam to the projection lens 140; the projection lens 140 is used to project the image beam out of the laser projection device and onto an external display medium (such as a wall or screen) to form a projected image.

[0062] The light modulator can be a Digital Micromirror Device (DMD) chip, which has millions of pixels. Each pixel has a mirror that can flip within a certain angle range under the drive of current to adjust the amount of light entering the lens, thereby making the image display different colors. The light modulator can also be a Liquid Crystal Display (LCD) panel or Liquid Crystal on Silicon (LCOS) display panel. The embodiments of this application do not limit this.

[0063] like Figure 6As shown, the laser projection device in this embodiment includes a laser light source 110, a light rotator 120, a light modulator 130, and a projection lens 140. It also includes a light shaping component 150. In the propagation optical path, the light shaping component can be located before or after the light rotator 120. This embodiment does not limit the location. The light shaping component 150 is mainly used to adjust the radial size and shape of the light beam. It can include a focusing lens, a compound eye lens, etc. This part belongs to the prior art and will not be described in detail here.

[0064] The laser projection device provided in this embodiment is equipped with a rotatable optical rotator crystal. The optical rotator crystal can adjust the polarization direction of the laser beam, and the adjustment angle is proportional to the thickness of the optical rotator crystal. By setting the optical rotator crystal to have an alternating thickness along the rotation direction, the polarization direction of the laser beam can change continuously over time. The difference in polarization direction between the sub-beams in the laser beam can also change continuously over time, thereby weakening the coherence of the laser beam, reducing or eliminating speckle effect in the projected image, improving the display quality of the projected image, and enhancing the user experience.

[0065] As one embodiment, the structure of the optically active crystal 121 in the laser projection device of this application can be as follows: Figures 7-12 As shown.

[0066] Figure 7 This is a three-dimensional structural diagram of the optical rotatory crystal 121. The optical rotatory crystal 121 has a rotationally symmetric structure; however, in other embodiments, the optical rotatory crystal 121 may not have a rotationally symmetric structure. In this embodiment, the optical rotatory crystal 121 is generally cylindrical. Unlike a cylindrical shape, one of the two opposite faces is replaced with the first surface F1, while the other face remains circular (i.e.,...). Figure 7 The second surface F2 is a planar circle; the thickness of the optically active crystal 121 is the distance between the first surface F1 and the second surface F2.

[0067] like Figure 7 As shown, the optical rotator crystal 121 is driven by the drive unit 122 ( Figure 7 Driven by a force (not shown in the diagram), the crystal rotates along direction r1. The rotation axis A1 passes through the center of gravity of the optical rotator crystal 121 (the center of gravity is located on a straight line passing through the center of the second surface F2 and perpendicular to the second surface F2). Figure 7(Not shown in the diagram). Of course, the rotation axis A1 may not pass through the center of gravity of the optical rotator crystal 121, for example, it may be offset from the center of gravity by a certain distance. The laser beam 50 enters from the first surface F1 on one side of the optical rotator crystal 121, passes through the optical rotator crystal 121, exits from the second surface F2, and reaches the other side of the optical rotator crystal 121, forming a propagation optical path. The rotation axis A1 is parallel to this propagation optical path. In other embodiments, the rotation axis A1 and the propagation optical path may not be parallel to each other. For example, the propagation optical path and the rotation axis A1 may form a certain angle.

[0068] Also refer to Figure 8 When the optical rotator crystal 121 rotates one full turn (360°), the trajectory formed by any point on the optical rotator crystal 121 is a planar circle P1. The rotation axis A1 of the optical rotator crystal 121 is perpendicular to this planar circle P1, and the planar circle P1 is parallel to the second surface F2 of the optical rotator crystal 121. Point T1 is the intersection of the planar circle P1 and the rotation axis A1, which is also the center of the planar circle P1. The direction of the line connecting the intersection point T1 to any point on the circumference of the planar circle P1 is the radial direction, for example, the radial direction R1. The circumferential direction of the planar circle P1 is the circumferential direction, which is shown as the circumferential direction C1 in the figure. The circumferential direction C1 and the rotation direction r1 of the optical rotator crystal 121 are in the same direction, and the optical rotator crystal 121 rotates around the circumferential direction C1.

[0069] Also refer to Figure 9 In this embodiment, the optically active crystal 121 exhibits an alternating thickness structure along the rotation direction r1 (i.e., circumferential C1). The Y2 axis represents the thickness of the optically active crystal 121, and the X2 axis represents the rotation direction r1. It can be seen that the thickness of the optically active crystal 121 changes in a square wave shape along the rotation direction r1, meaning that the optically active crystal 121 has an alternating thickness structure along the rotation direction r1. Of course, the thickness of the optically active crystal 121 can also exhibit other shapes along the rotation direction r1, such as sawtooth, sinusoidal, or other undulating shapes; this embodiment does not limit this. Figure 9 As shown, region N1 is the irradiation area of ​​the laser source 110 on the optical rotator crystal 121 along the rotation direction r1. This region N1 covers the adjacent minimum and maximum thickness regions of the optical rotator crystal 121 along the rotation direction r1. In other words, in the rotation direction of the optical rotator crystal 121, the irradiation area of ​​the laser source 50 on the optical rotator crystal 121 covers the adjacent minimum and maximum thickness regions.

[0070] Also refer to Figure 10 and Figure 11In this embodiment, the thickness of the optically active crystal 121 also varies continuously along the radial direction; the first surface F1 of the optically active crystal 121 is divided into 20 regions along the rotation direction r1. Of course, the number of regions divided by the first surface F1 along the rotation direction r1 can be changed as needed, such as dividing it into 30 or 60 regions. The division of the first surface F1 along the rotation direction r1 can also be unequal; this embodiment does not limit this. Figure 10 for Figure 7 An enlarged view of surface F1-1, one of the branches of the first surface F1 of the optically active crystal 121, shows that surface F1-1 has an undulating shape, and this undulation occurs radially. Since the second surface F2 of the optically active crystal 121 is planar, and the thickness of the optically active crystal 121 is the distance between the first surface F1 and the second surface F2, the thickness of the optically active crystal 121 varies radially. Figure 11 As shown, the Y3 axis represents the thickness of the optically active crystal 121, and the X3 axis represents the radial direction. It can be seen that the thickness of the optically active crystal 121 varies radially in the shape of a sine wave, meaning that the thickness of the optically active crystal 121 continuously fluctuates radially. Of course, the thickness of the optically active crystal 121 can also exhibit other shapes along the radial direction, such as sawtooth waves, square waves, or continuously increasing or decreasing shapes. This embodiment of the application does not limit this to such variations. Figure 11 As shown, region N2 is the irradiation area of ​​the laser source 110 on the optical rotator crystal 121 in the radial direction. Region N2 covers the adjacent minimum and maximum thickness regions of the optical rotator crystal 121 in the radial direction. In other words, in the radial direction of the optical rotator crystal 121, the irradiation area of ​​the laser source 50 on the optical rotator crystal covers the adjacent minimum and maximum thickness regions.

[0071] It should be noted that, in the radial direction of the optical rotator crystal 121 and in the rotation direction of the optical rotator crystal 121, the irradiation area of ​​the laser source 50 can simultaneously cover adjacent thickness minimum and thickness maximum regions, or it can only cover adjacent thickness minimum and thickness maximum regions in the radial direction of the optical rotator crystal 121, or only cover adjacent thickness minimum and thickness maximum regions in the rotation direction of the optical rotator crystal 121.

[0072] In this embodiment, the irradiation area of ​​the laser beam 50 in the radial direction and the rotation direction of the optical rotator crystal 121 covers the adjacent thickness maxima and minima. This is beneficial to increase the polarization direction difference of each sub-beam in the laser beam 50, so that the polarization direction difference of each sub-beam in the laser beam 50 is as close to 90° as possible. This more effectively eliminates the coherence of the laser beam 50 and is more conducive to suppressing speckle in the projected image of the laser projection device 110.

[0073] Also refer to Figure 12 As shown, the Y4 axis represents the thickness of the optically active crystal 121, and the X4 axis represents the radial direction. It can be seen that the thickness of the optically active crystal 121 changes in a continuously rising curve along the radial direction. In this case, the thickness of the optically active crystal 121 increases continuously along the radial direction. Of course, the thickness of the optically active crystal 121 can also decrease continuously along the radial direction. In this case, the curve shown in the figure will become a falling curve.

[0074] As can be seen from the above, optical rotator crystals not only have an alternating thickness structure along the rotation direction, but the thickness of optical rotator crystals also fluctuates continuously along the radial direction, or increases or decreases continuously along the radial direction. This structure allows optical rotator crystals to further increase the polarization direction difference of each sub-beam in the laser beam when rotating.

[0075] As another embodiment, the structure of the optically rotating crystal 121 in the laser projection device of this application can be as follows: Figure 13-14 As shown.

[0076] Figure 13 This is a schematic diagram of the three-dimensional structure of the optical rotatory crystal 121. The overall structure of the optical rotatory crystal 121 is cylindrical. However, unlike a cylinder, one of the two opposite faces is replaced with the first surface F1, while the other face remains circular (i.e.,...). Figure 13 The second surface F2 is a planar circle; the thickness of the optically active crystal 121 is the distance between the first surface F1 and the second surface F2.

[0077] like Figure 13 As shown, the optical rotator crystal 121 is driven by the drive unit 122 ( Figure 13 Driven by a force (not shown in the figure), the optical crystal 121 rotates along direction r2. The rotation axis A2 passes through the center of gravity of the optical crystal 121 (the center of gravity is located on a straight line passing through the center of the second surface F2 and perpendicular to the second surface F2, not shown in the figure). Of course, the rotation axis A2 may not pass through the center of gravity of the optical crystal 121, for example, it may be offset from the center of gravity by a certain distance. The laser beam 50 enters from the first surface F1 on one side of the optical crystal 121, passes through the optical crystal 121, exits from the second surface F2, and reaches the other side of the optical crystal 121, forming a propagation optical path. The rotation axis A2 is parallel to this propagation optical path. In other embodiments, the rotation axis A2 and the propagation optical path may not be parallel to each other. For example, the propagation optical path and the rotation axis A2 may form a certain angle.

[0078] Also refer to Figure 14 , Figure 14 for Figure 13 The schematic diagram of the optically active crystal 121 shown shows the first surface F1 and... Figure 13 The first surface F1 corresponds to the second surface F2 and Figure 13 The second surface F2 corresponds to the distance H, which is the thickness of the optically active crystal 121.

[0079] Also refer to Figure 15 When the optically active crystal 121 rotates one revolution (360°), the trajectory formed by any point on the optically active crystal 121 is a planar circle P2. The plane parallel to the planar circle P2 is defined as the rotation plane. The rotation axis A2 of the optically active crystal 121 is perpendicular to the planar circle P2, and the planar circle P2 is parallel to the second surface F2 of the optically active crystal 121. The circumferential direction of the planar circle P2 is the circumferential direction, shown as circumferential direction C2 in the diagram. The circumferential direction C2 and the rotation direction r2 of the optically active crystal 121 are in the same direction, and the optically active crystal 121 rotates around the circumferential direction C2. In this embodiment, the thickness of the optically active crystal 121 continuously varies along any direction parallel to the rotation plane. The direction parallel to the rotation plane is the same as the direction parallel to the planar circle P2. Therefore, any direction within the plane containing the planar circle P2 is parallel to the rotation plane. Figure 15 The direction is D1, and the line containing direction D1 passes through the center of the plane circle P2.

[0080] Also refer to Figure 16 , Figure 16 The diagram shows the thickness variation of the optically active crystal 121 along the D1 direction. The Y5 axis represents the thickness of the optically active crystal 121, and the X5 axis represents the direction D1. It can be seen that the thickness of the optically active crystal 121 along the D1 direction changes in a sinusoidal shape. Of course, the thickness variation of the optically active crystal 121 along the D1 direction can exhibit other shapes, such as sawtooth waves, square waves, or other continuously undulating shapes, or even irregular continuously undulating shapes. This embodiment of the application does not limit these variations. Due to this structure of the optically active crystal 121, the thickness variation along the rotation direction also exhibits an undulating shape; that is, the optically active crystal 121 has a structure with alternating thickness along the rotation direction.

[0081] It should be noted that, in the embodiments of this application, Figure 7 and Figure 13 The shape of the corresponding optically active crystal 121 can be other shapes, such as cylindrical, polygonal, etc., and this application embodiment does not limit this.

[0082] It should be noted that the embodiments of this application Figure 7 and Figure 13 The corresponding optically active crystal 121 has opposing first surfaces F1 and second surfaces F2 through which the laser beam 50 passes, which can both be curved surfaces, for example... Figure 7 The second surface F2 of the optical crystal 121 can have the same structure as the first surface F1, that is, both the first surface F1 and the second surface F2 are curved surfaces; Figure 13The second surface F2 of the mesorotatory optical crystal 121 can have the same structure as the first surface F1, that is, both the first surface F1 and the second surface F2 are curved surfaces; alternatively, it can be... Figure 7 The first surface F1 and Figure 13 The first surfaces F1 in the crystal are combined to form a new set of opposing surfaces, thereby obtaining a new optically active crystal structure. This application does not limit the specifics of this embodiment.

[0083] In the embodiments of this application, when the optical rotator crystal has a structure in which the first and second surfaces through which the laser beam passes are curved, the rotation of the optical rotator crystal will enhance the surrounding airflow, which will help the optical rotator crystal dissipate heat.

[0084] As one embodiment, reference Figure 17 The optically active crystal includes a first surface and a second surface opposite to each other through which a laser beam passes, and both the first surface and the second surface are curved surfaces.

[0085] like Figure 17 As shown, the optically active crystal 121 is cylindrical and includes a first surface F1 and a second surface F2. Both the first surface F1 and the second surface F2 are undulating curved surfaces. For example, the first surface F1 and the second surface F2 have the following characteristics: Figure 13 The optically active crystal 121 has the same structure as the first surface F1; the thickness of the optically active crystal 121 is the distance between the first surface F1 and the second surface F2, that is, the distance represented by height H1 or height H2. The laser beam 50 enters from the first surface F1 on one side of the optically active crystal 121, passes through the optically active crystal 121, exits from the second surface F2, and reaches the other side of the optically active crystal 121, forming a propagation optical path. The optically active crystal 121 rotates around the rotation axis A3, which is parallel to the aforementioned propagation optical path. Positions L1 and L2 represent height maxima on the first surface F1 and the second surface F2 of the optical rotator crystal 121, respectively. Positions L3 and L4 represent height minima on the first surface F1 and the second surface F2 of the optical rotator crystal 121, respectively. The line connecting positions L1 and L2 is parallel to the aforementioned propagation optical path, as is the line connecting positions L3 and L4. In other words, along the propagation optical path of the optical rotator crystal 121, the height maxima of the first surface F1 are opposite to the height maxima of the second surface F2, and the height minima of the first surface F1 are opposite to the height minima of the second surface F2. This structure maximizes the polarization direction difference between the sub-beams of the laser beam 50.

[0086] To reduce the noise generated by the optically active crystal 121 during rotation, embodiments of this application are provided. Figure 7 , Figure 13 and Figure 17 The corresponding optically active crystal 121 may also include a transmission sheet.

[0087] As one example, Figure 17 The optically active crystal 121 shown also includes a transmission plate T, configured as follows: Figure 18 The structure shown.

[0088] refer to Figure 17-19 The optical rotator crystal 121 also includes a transmission plate T, which allows the laser beam 50 to pass through. The transmission plate T has isotropic optical properties. The transmission plate T has a third surface F3 and a fourth surface F4. The third surface F3 is planar, and the fourth surface F4 is curved. The fourth surface F4 has the same structure as the first surface F1 or the second surface F2 of the optical rotator crystal 121. After the transmission plate T and the optical rotator crystal 121 are combined, the surface F4 of the transmission plate T is in contact with the surface F1 or the surface F2 of the optical rotator crystal 121, and the surface F3 of the transmission plate T is away from the optical rotator crystal 121. This structure makes the outer surface of the optical rotator crystal 121 no longer curved, but planar.

[0089] In this embodiment, the transmissive plate T is configured to have isotropic optical properties, so that the propagation of the laser beam 50 in the transmissive plate T is linear and does not affect the polarization direction of the laser beam 50. For example, the transmissive plate T can be glass.

[0090] In this embodiment, the optical rotator crystal includes a transmissive plate, which makes the outer surface of the optical rotator crystal planar. This helps to reduce the resistance and noise generated during the rotation of the optical rotator crystal. The number of transmissive plates can vary depending on whether the first and second surfaces of the optical rotator crystal are curved. For example, if both the first and second surfaces of the optical rotator crystal are curved, then there are two transmissive plates. If only one of the first and second surfaces of the optical rotator crystal is curved, then there can be only one transmissive plate.

[0091] In this embodiment of the application, the laser projection device further includes a reflector disposed on one side of the optical rotation component. The reflector is used to reflect the laser beam passing through the first region of the optical rotation crystal to the second region of the optical rotation crystal. The first region and the second region do not overlap.

[0092] refer to Figure 20 The laser projection device includes a laser light source 110, a light-rotating component 120, a reflector 160, a light modulator 130, and a projection lens 140. The light-rotating component 120 includes a light-rotating crystal 121 and a light-rotating component 122. Figure 20(Not shown in the drawing), the optical rotator crystal 121 includes a first surface F1 and a second surface F2. The thickness of the optical rotator crystal 121 is the distance between the first surface F1 and the second surface F2. The reflector 160 includes components 160-1 and 160-2. The reflector 160 is located on one side of the second surface F2 of the optical rotator crystal 121. The straight line E divides the optical rotator crystal 121 into two regions, namely the first region E1 and the second region E2. The first region E1 and the second region E2 do not overlap. The laser beam 50 emitted by the laser source 110 enters the optical rotator crystal 121 from the first surface F1 and passes through the optical rotator crystal 121. After exiting from the second surface F2 of the optical crystal 121, the laser beam 50 reaches component 160-1, which reflects it to component 160-2. Component 160-2 then reflects the laser beam 50 back to region E2 of the optical crystal 121. At this point, the laser beam 50 re-enters the optical crystal 121 from the second surface F2, passes through the optical crystal 121, and exits from the first surface F1. The laser beam 50 then enters the optical modulator 130 and, after passing through the optical modulator 130, is projected into the projection lens 140. During this process, the reflecting component 160 reflects the laser beam 50, which has passed through the first region E1 of the optical crystal, to the second region E2 of the optical crystal.

[0093] In a preferred embodiment, the location of the maximum thickness in the first region is projected along the propagation optical path to the location of the maximum thickness in the second region; the location of the minimum thickness in the first region is projected along the propagation optical path to the location of the minimum thickness in the second region.

[0094] Specifically, such as Figure 20 As shown, the first surface F1 of the optical rotator crystal 121 has positions L5 and L6, and the second surface F2 has positions L7 and L8. Positions L5 and L7 correspond to the maximum thickness of the optical rotator crystal 121, which is the thickest position. Positions L6 and L8 correspond to the minimum thickness of the optical rotator crystal 121, which is the thinnest position. The laser beam 50 emitted by the laser source 110 enters the optical rotator crystal 121 from position L5 (or L6) on the first surface F1. When the laser beam 50 is emitted from the optical rotator crystal 121, it will pass through the thickest (or thinnest) part of the first region E1 of the optical rotator crystal 121. After the laser beam 50 is reflected by the reflector 160, the laser beam 50 will enter the optical rotator crystal 121 from the L7 (or L8) position on the second surface F2 of the optical rotator crystal 121. At this time, the laser beam 50 will pass through the thickest (or thinnest) part of the second region E2 of the optical rotator crystal 121. Then the laser beam 50 enters the light modulator 130 and enters the projection lens 140 after passing through the light modulator 130.

[0095] In this embodiment, the reflector may be glass, a prism, or the like.

[0096] In this embodiment, under the action of the reflector, the laser beam passes through the optical rotator crystal twice. This structure can further increase the difference in polarization direction of each sub-beam in the laser beam, thereby more effectively suppressing the speckle of the laser projection device. Moreover, this structure of the laser beam passing through the optical rotator crystal twice is also conducive to reducing the thickness of the optical rotator crystal, thus achieving the effect of reducing costs overall. Furthermore, when the thickness maximum position in the first region is projected along the propagation optical path to the thickness maximum position in the second region, and the thickness minimum position in the first region is projected along the propagation optical path to the thickness minimum position in the second region, it is even more conducive to increasing the difference in polarization direction of each sub-beam in the laser beam, thereby further suppressing the speckle of the laser projection device.

[0097] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0098] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0099] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A laser projection device, characterized in that, The laser projection device includes a laser source, a light-rotating component, a light modulator, and a projection lens arranged sequentially along the optical path. The laser source is used to emit a laser beam to the optical rotation component; The optical rotation component includes a driving element and an optical rotation crystal located in the propagation optical path of the laser beam. The driving element is connected to the optical rotation crystal and is used to drive the optical rotation crystal to rotate. The optical rotation crystal has a structure in which the thickness changes alternately along the rotation direction. The optical rotation crystal is used to adjust the polarization direction of the laser beam. The optical modulator is used to adjust the laser beam passing through the optically rotating crystal into an image beam; The projection lens is used to project the image beam out of the laser projection device; The thickness of the optically active crystal varies continuously along the radial direction; In the rotation direction of the optically rotating crystal, the irradiation area of ​​the laser source on the optically rotating crystal covers adjacent regions of minimum and maximum thickness. In the radial direction of the optically rotating crystal, the irradiation area of ​​the laser source on the optically rotating crystal covers adjacent regions of minimum and maximum thickness.

2. The laser projection device according to claim 1, characterized in that, The optical rotator crystal has a cylindrical or cylindrical structure and a rotationally symmetric structure. The optical rotator crystal rotates around a rotation axis under the action of the driving member. The rotation axis is parallel to the propagation optical path passing through the optical rotator crystal and passes through the center of gravity of the optical rotator crystal.

3. The laser projection device according to claim 1, characterized in that, The optical axis of the optically active crystal is parallel to the propagation optical path passing through the optically active crystal.

4. The laser projection device according to claim 1, characterized in that, The optically active crystal includes a first surface and a second surface opposite to each other and through which the laser beam passes, wherein the first surface and the second surface are both curved surfaces; or, the first surface is curved and the second surface is planar.

5. The laser projection device according to claim 1, characterized in that, The optical rotator crystal includes a first surface and a second surface that are opposite to each other and through which the laser beam passes, both of which are curved surfaces; in the propagation optical path passing through the optical rotator crystal, the position of the maximum height of the first surface is opposite to the position of the maximum height of the second surface, and the position of the minimum height of the first surface is opposite to the position of the minimum height of the second surface.

6. The laser projection device according to claim 4 or 5, characterized in that, The optical rotation component also includes a transmission plate, which has isotropic optical properties. The transmission plate is attached to one side of the curved surface of the optical rotation crystal in the direction of the propagation optical path, and the side of the transmission plate opposite to the optical rotation crystal is a plane.

7. The laser projection device according to claim 1, characterized in that, The laser projection device further includes a reflector disposed on one side of the optical rotation component. The reflector is used to reflect the laser beam passing through the first region of the optical rotation crystal to the second region of the optical rotation crystal. The first region and the second region do not overlap.

8. The laser projection device according to claim 7, characterized in that, The location of the maximum thickness in the first region is projected along the propagation optical path to the location of the maximum thickness in the second region; the location of the minimum thickness in the first region is projected along the propagation optical path to the location of the minimum thickness in the second region.

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