Speckle eliminating device, projection optical system and projection equipment

Abstract

The invention relates to the technical field of projection optical systems, and discloses a speckle eliminating device which is arranged in a projection optical system and comprises a polarization conversion element and a vibration mechanism. Wherein the polarization conversion element is provided with at least two sub-regions, and at least one sub-region can convert the polarization state of the first light beam incident on the sub-region, so that the polarization conversion element outputs the first light beam with at least two different polarization states. The vibration mechanism is connected with the polarization conversion element and used for driving the polarization conversion element to vibrate. The speckle effect of the projection picture can be reduced, and the watching experience of a user is enhanced. The invention further discloses a projection optical system and projection equipment.

Description

Technical Field

[0001] This application relates to the field of laser display technology, and particularly to a speckle reduction device, a projection optical system, and a projection device. Background Art

[0002] Currently, image display devices have been widely used in people's work and life, such as: projection modules of projection devices, VR, AR, and 3D printing devices. Many existing projection devices use laser light sources. A laser light source is a coherent light source. After laser is scattered by a rough surface, it will interfere with each other, resulting in "noise points" in the projected image, and this phenomenon is called laser speckle.

[0003] In the prior art, laser speckle is the biggest pain point of laser display devices. The existence of speckles will cause the clarity of the projected image to decrease, and at the same time, it is easier for the human eye to get fatigued when viewing, seriously affecting the user's viewing experience. Summary of the Invention

[0004] This application provides a speckle reduction device, a projection optical system, and a projection device, which can reduce the laser speckle of the projected image and enhance the user experience.

[0005] In a first aspect, this application provides a speckle reduction device. The speckle reduction device is disposed in a projection optical system, and a first light beam in the projection optical system is incident on the speckle reduction device in a direction perpendicular to the speckle reduction device. The speckle reduction device can reduce the speckle contrast of the first light beam to achieve a speckle reduction effect.

[0006] The speckle reduction device provided in this application includes a polarization conversion element and a vibration mechanism. Among them, at least two sub-regions are provided on the polarization conversion element, and at least one of the sub-regions can convert the polarization state of the first light beam incident on it, so that the polarization conversion element outputs a first light beam with at least two different polarization states. The vibration mechanism is connected to the polarization conversion element, and the vibration mechanism is used to drive the polarization conversion element to vibrate. Exemplarily, the vibration frequency of the polarization conversion element is 30 - 240 HZ.

[0007] When the first light beam passes through the polarization conversion element, since at least one sub-region on the polarization conversion element can convert the polarization state of the incident first light beam, the polarization conversion element can output a first light beam having at least two different polarization states, that is, output at least two kinds of polarized light having different polarization states. Since the polarization states of the polarized lights are different, the speckle patterns generated by the polarized lights are independent or have low correlation with each other. The independent or low-correlation speckle patterns are superimposed on the screen, which can reduce the speckle contrast, thereby achieving the speckle reduction effect and enhancing the user experience. In addition, in the present application, a vibration mechanism is provided to drive the polarization conversion element to vibrate reciprocally, which can introduce additional polarization diversity. When the polarization conversion element is in different positions during the vibration process, the speckle patterns generated by the polarized lights output by the polarization conversion element are different, and the different speckle patterns are superimposed on each other within one eye integration period, which will further enhance the speckle reduction effect.

[0008] In some implementation manners of the present application, the vibration mechanism includes a reed and an electromagnetic induction mechanism. Among them, an opening is provided on the reed, and the polarization conversion element covers the opening. The electromagnetic induction mechanism is used to drive the reed and the polarization conversion element to vibrate.

[0009] In some implementation manners of the present application, the outer contour of the reed is rectangular, and the vibration mechanism can drive the polarization conversion element to translate and vibrate on the plane where the polarization conversion element is located, or swing and vibrate around a rotation axis perpendicular to the incident direction of the first light beam, or swing and vibrate around multiple rotation axes simultaneously.

[0010] When the polarization conversion element translates and vibrates, the vibration direction of the polarization conversion element is the length direction, width direction or diagonal direction of the reed.

[0011] When the polarization conversion element swings and vibrates, the rotation axis extends along the length direction of the reed, or along the width direction of the reed, or along the diagonal direction of the reed.

[0012] In some embodiments of the present application, the first light beam output by the polarization conversion element can be decomposed into two polarized lights with orthogonal polarization directions, and the energy ratio of the two polarized lights is 4:6 - 6:4. Preferably, the energy ratio of the two polarized lights is 1:1. The inventors have discovered through exploration that when the light incident on any point on the screen is superimposed by two lights with equal energy and orthogonal polarization directions, the speckle reduction effect can be enhanced. Therefore, the above technical solution can further enhance the speckle reduction effect.

[0013] In some implementations of the present application, at least one first sub-region and at least one second sub-region are provided on the polarization conversion element. The polarization directions of the first light beams output from the first sub-region and the second sub-region are orthogonal to each other, and the sum of the areas of the first sub-regions is equal to the sum of the areas of the second sub-regions. Exemplarily, the first sub-region is made of a transparent glass sheet, and the polarization direction of the first light beam incident on the first sub-region remains unchanged after passing through the first sub-region. The second sub-region has a half-wave phase delay, and the polarization direction of the first light beam incident on the second sub-region is orthogonal to that before incidence after passing through the second sub-region.

[0014] In some implementations of the present application, the number of the first sub-region and the second sub-region is one each, and the areas of the first sub-region and the second sub-region are equal.

[0015] In some implementations of the present application, the number of sub-regions is greater than or equal to three, and the sub-regions are arranged in sequence along a first direction. Along the first direction, the crystal axis directions of the sub-regions gradually rotate along a first rotation direction, or the phase delay amounts of the sub-regions gradually increase or gradually decrease. By setting the crystal axis directions or phase delay amounts of the sub-regions to vary continuously with spatial distribution, such continuous variation can avoid problems such as light diffraction effects caused by too large a gradient of crystal axis direction change or too large a gradient of phase change, thereby avoiding problems such as excessive light loss and introduction of stray light.

[0016] In a second aspect, the present application provides a projection optical system, including a speckle eliminating device as in the first aspect, and further including a light emitting unit and a lens assembly arranged in sequence along the propagation direction of the first light beam. Among them, the light emitting unit is used for emitting a first light beam, and the first light beam carries image information. The lens assembly is used for magnifying the first light beam. The speckle eliminating device is arranged on the incident light side outside the lens assembly or inside the lens assembly. The first light beam output by the speckle eliminating device is magnified by the lens assembly and then emitted, and the magnified first light beam is used for displaying an image corresponding to the image information.

[0017] In some implementations of the present application, the speckle eliminating device is arranged between the output end of the light emitting unit and the incident end of the lens assembly, the vibration mechanism is a pixel ditherer arranged between the output end of the light emitting unit and the incident end of the lens assembly, the pixel ditherer includes a reed, the reed can generate vibration, and the polarization conversion element covers the opening of the reed. By integrating the polarization conversion element on the pixel ditherer, the present application can simplify the device structure, reduce the device volume, and save costs.

[0018] In some implementations of the present application, an aperture stop is provided inside the lens assembly, and the speckle elimination device is disposed on the light incident side or the light exiting side of the aperture stop. Exemplarily, the distance between the polarization conversion element and the aperture stop is less than or equal to 10 mm. The applicant has discovered through exploration that when the first light beam passes through the aperture stop, the energy of the light will be more evenly distributed, and the contribution of the light at any spatial position on the aperture stop to any point on the screen is of equal weight. Therefore, by disposing the polarization conversion element near the aperture stop in the present application, the light at any point on the screen can be formed by the superposition of the polarized lights output by the polarization conversion element, thereby further enhancing the speckle elimination effect.

[0019] Furthermore, at least one first sub-region and at least one second sub-region are provided on the polarization conversion element disposed on the light incident side or the light exiting side of the aperture stop. The polarization directions of the first light beams output by the first sub-region and the second sub-region are orthogonal to each other, and the sum of the areas of the first sub-regions is equal to the sum of the areas of the second sub-regions. This design can make the light incident on any point on the screen be the superposition of two light beams with equal energy and orthogonal polarization directions passing through the first sub-region and the second sub-region, thereby achieving the best speckle elimination effect.

[0020] In some implementations of the present application, the light emitting unit includes a laser light source and a display device. Among them, the laser light source is used to emit a laser beam. The display device is used to load image information onto the laser beam to form a first light beam.

[0021] In some implementation manners of the present application, an illumination shaping optical path is provided between the laser light source and the display device. The illumination shaping optical path is used to homogenize and shape the laser beam emitted by the laser light source, and guide the homogenized and shaped laser beam onto the display device. A diffuser is provided on the illumination shaping optical path. The diffuser can translate and vibrate on the plane where the diffuser is located or rotate around an axis perpendicular to the plane where the diffuser is located. The diffuser is used to reduce the coherence of the spatial distribution of the laser beam on the incident surface of the polarization conversion element. Exemplarily, the diffuser can be a diffuser wheel or a dither diffuser sheet. Among them, the diffuser wheel can include an annular diffuser sheet and a motor. The motor is provided in the middle of the annular diffuser sheet and can drive the annular diffuser sheet to rotate around its own axis. The dither diffuser sheet can include a dither and a rectangular diffuser sheet. The rectangular diffuser sheet is provided on the dither, and the dither can drive the rectangular diffuser sheet to vibrate reciprocally. Specifically, the surface of the diffuser sheet has irregular concavities and convexities. When the first light beam passes through the diffuser sheet, it will be scattered by the diffuser sheet. The light emitted from the diffuser sheet will have random angles and phases. The speckle patterns introduced by the light with different angles and phases are different. The different speckle patterns are superimposed on the screen, which can play a role in dissipating speckles. In addition, by rotating or dithering the diffuser sheet in the present application, the diffuser sheet can also produce different speckle patterns when it is in different positions, thereby further enhancing the effect of dissipating speckles.

[0022] In some implementation manners of the present application, when the diffuser translates and vibrates on the plane where the diffuser is located, within one human eye integration period, the vibration amplitude of the diffuser is greater than or equal to 0.1 mm.

[0023] In a third aspect, the present application provides a projection device, including the projection optical system as in the second aspect. Description of the Drawings

[0024] Figure 1 Shows a schematic diagram of the optical system of a single-chip LCOS projector;

[0025] Figure 2 Shows a schematic diagram of the optical system of a three-chip LCOS projector;

[0026] Figure 3 Shows a schematic diagram of the optical system of a single-chip DLP projector;

[0027] Figure 4 Shows a schematic diagram of the optical system of a three-chip LCD projector;

[0028] Figure 5(a) shows a schematic diagram of the speckle dissipation device in some embodiments of the present application Figure 1 ;

[0029] Figure 5(b) shows a schematic diagram of the speckle dissipation device in some embodiments of the present application Figure 2;

[0030] Figure 6 Shows a schematic diagram of a vibration mechanism in some embodiments of the present application;

[0031] Figure 7(a) shows a schematic diagram of the translational vibration of a polarization conversion element in some embodiments of the present application Figure 1 ;

[0032] Figure 7(b) shows a schematic diagram of the translational vibration of a polarization conversion element in some embodiments of the present application Figure 2 ;

[0033] Figure 7(c) shows a schematic diagram of the translational vibration of a polarization conversion element in some embodiments of the present application Figure 3 ;

[0034] Figure 7(d) shows a schematic diagram of the translational vibration of a polarization conversion element in some embodiments of the present application Figure 4 ;

[0035] Figure 8(a) shows a schematic diagram of the swinging vibration of a polarization conversion element in some embodiments of the present application Figure 1 ;

[0036] Figure 8(b) shows a schematic diagram of the swinging vibration of a polarization conversion element in some embodiments of the present application Figure 2 ;

[0037] Figure 8(c) shows a schematic diagram of the swinging vibration of a polarization conversion element in some embodiments of the present application Figure 3 ;

[0038] Figure 8(d) shows a schematic diagram of the swinging vibration of a polarization conversion element in some embodiments of the present application Figure 4 ;

[0039] Figure 9 Shows a schematic diagram of a polarization conversion element in some embodiments of the present application Figure 1 ;

[0040] Figure 10 Shows a schematic diagram of a polarization conversion element in some embodiments of the present application Figure 2 ;

[0041] Figure 11 Shows a schematic diagram of a polarization conversion element in some embodiments of the present application Figure 3 ;

[0042] Figure 12 Shows a schematic diagram of a polarization conversion element in some embodiments of the present application Figure 4 ;

[0043] Figure 13Shows a schematic diagram of a polarization conversion element disposed on the light incident side of a lens assembly in some embodiments of the present application;

[0044] Figure 14 Shows a schematic diagram of a polarization conversion element disposed on the light incident side of an aperture stop in some embodiments of the present application;

[0045] Figure 15 Shows a schematic diagram of a polarization conversion element disposed on the light exit side of an aperture stop in some embodiments of the present application;

[0046] Figure 16 Shows a schematic diagram of the position of a diffuser in some embodiments of the present application;

[0047] Figure 17 Shows a structural block diagram of a projection device in some embodiments of the present application;

[0048] Figure 18(a) shows a schematic diagram of an application scenario of a projection device in some embodiments of the present application Figure 1 ;

[0049] Figure 18(b) shows a schematic diagram of an application scenario of a projection device in some embodiments of the present application Figure 2 ;

[0050] Figure 18(c) shows a schematic diagram of an application scenario of a projection device in some embodiments of the present application Figure 3 ;

[0051] Figure 19 Shows a schematic diagram of the position where a speckle reduction device is disposed in a three - chip projection device in some embodiments of the present application.

[0052] Explanation of reference numerals:

[0053] 1 - Light emitting unit; 11 - Laser light source; 12 - Display device; 121 - LCOS display device; 122 - DMD display device; 123 - LCD display device; 13 - Polarizing beam splitter; 14 - Total internal reflection prism; 15 - Light combining prism; 16 - Illumination shaping optical path; 17 - Analyzer;

[0054] 2 - Lens assembly; 21 - Aperture stop;

[0055] 3 - Screen;

[0056] 4 - Polarization conversion element; 41 - Sub - region; 42 - First sub - region; 43 - Second sub - region;

[0057] 5 - Vibration mechanism; 51 - Reed; 52 - Opening;

[0058] 6 - Diffuser; 61 - Diffusion sheet;

[0059] 7 - Image processing unit;

[0060] 8 - Driving unit;

[0061] 9 - Target surface;

[0062] 10 - First polarized light;

[0063] 20 - Second polarized light;

[0064] 100 - Speckle reduction device;

[0065] 200 - Projection device. Detailed implementation manners

[0066] To make the objectives, technical solutions and advantages of this application clearer, the following will further describe the implementation manners of this application in detail with reference to the accompanying drawings.

[0067] An embodiment of this application provides a speckle reduction device, which is disposed in a projection optical system. A projection optical system is an optical system that can project images and videos onto a screen or a target surface. The quality of a projection optical system is mainly related to the light source technology it adopts. A laser light source is the latest generation of light source technology for projection optical systems. This technology directly uses red, green, and blue lasers as the light source of the projection optical system. Compared with the previous generation of LED and bulb illumination light sources, it has the advantages of high brightness, wide color gamut, and high luminous efficiency.

[0068] In this application, the projection optical system can be applied to projection devices, VR, AR, and HUD (head up display), and can also be applied to the projection modules of 3D printing devices and 3D scanning devices. This application does not make any limitations in this regard. Below, the projection optical system applied to a projection device will be used as an example for introduction.

[0069] Figures 1 to 4 Shows an exemplary schematic diagram of the projection optical system provided by an embodiment of this application. Among them, Figure 1 Is a schematic diagram of the optical system of a single-chip LCOS (liquid crystal on silicon) projector, Figure 2 Is a schematic diagram of the optical system of a three-chip LCOS projector, Figure 3 Is a schematic diagram of the optical system of a single-chip DLP (digital light processing) projector, Figure 4 Is a schematic diagram of the optical system of a three-chip LCD (liquid crystal display) projector. Each of the above projection devices includes a light-emitting unit 1 and a lens assembly 2. Among them, due to different working mechanisms of the optical systems, there are differences in the internal structures of the light-emitting units 1. However, the light-emitting unit 1 is all used to emit light beams outward. Since the light beams carry image information for displaying images or videos, in this scenario, we will call such light beams image light.

[0070] Further, referring to Figure 1 , the light-emitting unit 1 of a single-chip LCOS projector includes a laser light source 11, a polarization beam splitter (PBS) 13, and an LCOS display device 121. The RGB light is projected in a time-division manner to achieve a color picture. Referring to Figure 2 , the light-emitting unit 1 of a three-chip LCOS projector includes a laser light source 11, a polarization beam splitter (PBS) 13, three LCOS display devices 121, and a light-combining prism 15. The three LCOS display devices 121 respectively display RGB pictures, and the color picture is synthesized through the light-combining prism 15. Referring to Figure 3 , the light-emitting unit 1 of a single-chip DLP projector includes a laser light source 11, a total internal reflection prism (TIR) 14, and a DMD display device 122. The RGB light is projected in a time-division manner to achieve a color picture. Referring to Figure 4 , the light-emitting unit 1 of a three-chip LCD projector includes a laser light source 11, three LCD display devices 123, and a light-combining prism 15. The three LCD display devices 123 respectively display RGB pictures, and the color picture is synthesized through the light-combining prism 15.

[0071] The lens assembly 2 is used to magnify the image light and project it onto the screen 3. The lens assembly 2 can be a lens group commonly found in optical systems, such as a projection lens.

[0072] During the use of the above projection device, laser speckles will appear in the projected picture. This is because the light sources used in the above projection device are all laser light sources, and a laser light source is a coherent light source. After the laser is scattered by a screen with a rough surface, they will interfere with each other, thus forming speckles. The existence of speckles will cause the clarity of the projected picture to decrease, and at the same time, it is more likely to cause fatigue when viewed by the human eye, seriously affecting the user's viewing experience.

[0073] The present application provides a speckle dissipation device. Referring to FIGS. 5(a) and 5(b), it includes a polarization conversion element 4 and a vibration mechanism 5. Among them, the plane where the polarization conversion element 4 is located is perpendicular to the incident direction of the first light beam generated by the projection optical system (as shown by the arrow direction in FIG. 5(a)). At least two sub-regions 41 are provided on the polarization conversion element 4 (as shown in FIG. 5(b)), and at least one of the sub-regions 41 can convert the polarization state of the first light beam incident thereon, so that the polarization conversion element 4 outputs a first light beam with at least two different polarization states. The vibration mechanism 5 is connected to the polarization conversion element 4, and the vibration mechanism 5 is used to drive the polarization conversion element 4 to vibrate.

[0074] When the first light beam passes through the polarization conversion element 4, since at least one sub-region 41 on the polarization conversion element 4 can convert the polarization state of the incident first light beam, the polarization conversion element 4 can output a first light beam with at least two different polarization states, that is, output at least two kinds of polarized light with different polarization states, such as the first polarized light, the second polarized light, and the Nth polarized light shown in FIG. 5(b). Since the polarization states of the polarized lights are different, the speckle patterns generated by the polarized lights are independent or have low correlation with each other. The independent or low-correlation speckle patterns are superimposed on each other on the screen, which can reduce the speckle contrast, thereby achieving the speckle dissipation effect and enhancing the user experience.

[0075] In addition, in the present application, by setting the vibration mechanism 5 to drive the polarization conversion element 4 to vibrate reciprocally, additional polarization perturbations can be introduced. When the polarization conversion element 4 vibrates, the polarization state of the first light beam emitted from the same spatial position changes with time, so that the speckle patterns generated by the polarized lights output by the polarization conversion element 4 are different. The different speckle patterns are superimposed on each other within one eye integration period, which will further enhance the speckle dissipation effect.

[0076] In some implementation manners of the present application, referring to FIGS. 5(a) and Figure 6 , the vibration mechanism 5 includes a reed 51 and an electromagnetic induction mechanism (not shown in the figure). Among them, an opening 52 is provided on the reed 51, and the polarization conversion element 4 covers the opening 52. The electromagnetic induction mechanism can drive the reed 51 and the polarization conversion element 4 to vibrate. Exemplarily, the reed 51 includes an outer frame and an inner frame (not shown in the figure), and the polarization conversion element 4 covers the inner frame. An elastic connecting arm is provided between the outer frame and the inner frame, and the inner frame is connected to the outer frame through the elastic connecting arm, and the inner frame can vibrate relative to the outer frame. The electromagnetic induction mechanism includes a coil and a magnet, and the coil is connected to the inner frame. When the coil is energized, an electromagnetic force is generated by the interaction between the coil and the magnet, and the electromagnetic force can drive the inner frame to vibrate, so that the polarization conversion element 4 vibrates. Since the coil is powered by a periodic signal, the vibration of the polarization conversion element 4 has a certain frequency. Exemplarily, the vibration frequency of the polarization conversion element 4 can be 30 - 240 HZ, such as 30 Hz, 60 Hz, 120 Hz, 180 Hz, or 240 Hz.

[0077] In some implementation manners of the present application, the outer contour of the reed 51 is rectangular, and the vibration mechanism 5 can drive the polarization conversion element 4 to translate and vibrate (as Figures 7(a) to 7(d) shown) on the plane where the polarization conversion element 4 is located, or swing and vibrate around a rotation axis perpendicular to the incident direction of the first light beam (as Figures 8(a) to 8(d) shown), or swing and vibrate around multiple swing axes simultaneously.

[0078] The present application does not limit the vibration direction of the polarization conversion element 4. When the polarization conversion element 4 vibrates translationally, the vibration direction of the polarization conversion element 4 is the length direction of the reed 51 (shown as the X1 direction in Fig. 7(a)), the width direction (shown as the X2 direction in Fig. 7(b)), the diagonal direction (shown as the X3 direction in Fig. 7(c)), or a direction rotated by a certain angle relative to the diagonal direction (shown as the X4 direction in Fig. 7(d)). When the polarization conversion element 4 vibrates swingingly, the rotation axis extends along the length direction of the reed 51, and the polarization conversion element 4 rotates along the R1 direction in Fig. 8(a); or the rotation axis extends along the width direction of the reed 51, and the polarization conversion element 4 rotates along the R2 direction in Fig. 8(b); or the rotation axis extends along the diagonal direction of the reed 51, and the polarization conversion element 4 rotates along the R3 direction in Fig. 8(c); or the extension direction of the rotation axis forms a certain angle with the diagonal of the reed 51, and the polarization conversion element 4 rotates along the R4 direction in Fig. 8(d). When the polarization conversion element 4 vibrates swingingly, the polarization conversion element 4 will rotate by a certain angle around the rotation axis perpendicular to the incident direction of the first light beam. At this time, due to the refraction effect, the first light beam passing through the polarization conversion element 4 will generate a displacement perpendicular to the incident direction of the first light beam. By synchronously matching the image signal with the timing of the polarization conversion element 4, the effect of improving the image resolution can be achieved.

[0079] In some implementation manners of the present application, a set of coils may be provided on the vibration mechanism 5 to enable the reed 51 and the polarization conversion element 4 to vibrate translationally along one vibration direction, or swingingly rotate around one rotation axis. Multiple sets of coils may also be provided on the vibration mechanism 5 to enable the reed 51 and the polarization conversion element 4 to vibrate translationally along multiple vibration directions simultaneously, or swingingly rotate around multiple rotation axes simultaneously.

[0080] In some embodiments of the present application, the first light beam output by the polarization conversion element 4 can be decomposed into two polarized lights with orthogonal polarization directions, and the energy ratio of the two polarized lights is 4:6 - 6:4. Preferably, the energy ratio of the two polarized lights is 1:1. The inventor has discovered through exploration that when the light incident on any point on the screen 3 is the superposition of two lights with equal energy and orthogonal polarization directions, the speckle dissipation effect can be enhanced. Therefore, the above technical solution can further enhance the speckle dissipation effect.

[0081] To enable those skilled in the art to better understand the structure of the polarization conversion element 4, the polarization conversion element 4 will be described in detail through two embodiments below.

[0082] Embodiment 1

[0083] In some implementation manners of the present application, with reference to Figure 9, at least one first sub-region 42 and at least one second sub-region 43 are provided on the polarization conversion element 4, and the polarization directions of the first light beams output by the first sub-region 42 and the second sub-region 43 are orthogonal to each other. Exemplarily, the first sub-region 42 is made of a transparent glass sheet, and the polarization direction of the first light beam incident on the first sub-region 42 remains unchanged after passing through the first sub-region 42, forming a first polarized light 10. The second sub-region 43 has a half-wave phase delay and can change the polarization direction of light. The polarization direction of the first light beam incident on the second sub-region 43 changes after passing through the second sub-region 43, forming a second polarized light 20, and the polarization direction of the second polarized light 20 is orthogonal to that of the first polarized light 10.

[0084] Further, the ratio of the sum of the areas of the first sub-regions 42 to the sum of the areas of the second sub-regions 43 is 1:1. Exemplarily, referring to Figure 10 , the number of the first sub-region 42 and the second sub-region 43 is both one, and the areas of the first sub-region 42 and the second sub-region 43 are equal. The polarization conversion element 4 can be formed by splicing a half-wave plate and an ordinary transparent glass sheet. Among them, the first sub-region 42 is an ordinary transparent glass sheet, and the second sub-region 43 is a half-wave plate. The two elements can be bonded into a whole by glue or attached to the same substrate glass, or the first sub-region 42 and the second sub-region 43 can be divided on a glass substrate. The first sub-region 42 does not have a phase delay, and the second sub-region 43 can be made to have a half-wave phase delay by methods such as coating, laminating, or coating.

[0085] Embodiment 2

[0086] In some implementation manners of the present application, referring to Figure 11 and Figure 12 , the polarization conversion element 4 can be rectangular, and the sub-regions 41 are arranged in sequence along the length direction of the rectangle and the widths of the sub-regions 41 are equal. The number of the sub-regions 41 is greater than or equal to three, and the sub-regions 41 are arranged in sequence along the first direction. Along the first direction, the crystal axis directions of the sub-regions 41 gradually rotate along the first rotation direction (as shown in Figure 11 ), or the phase delay amounts of the sub-regions 41 gradually increase or gradually decrease (as shown in Figure 12 ).

[0087] Figure 11 is a schematic diagram of an embodiment in which the crystal axis directions of the sub-regions 41 gradually rotate along the first rotation direction, Figure 11The crystal axes of the sub-regions 41 therein are oriented differently, and the retardation of each sub-region 41 can be 0.5λ or close to 0.5λ, where λ is the wavelength of the first light beam. When the first light beam is incident on the polarization conversion element 4, the incident light passing through different sub-regions 41 is respectively converted into linearly polarized light with different polarization directions, and the speckle patterns generated by the linearly polarized lights with different polarization directions are superimposed on the screen 3, which can play a role in speckle elimination.

[0088] Figure 12 It is a schematic diagram of an embodiment in which the phase retardation of each sub-region 41 gradually increases or gradually decreases. Figure 12 The phase retardation of the sub-regions 41 therein is different. When the first light beam is incident on the polarization conversion element 4, the incident light passing through different sub-regions 41 is respectively converted into polarized light with different polarization states, which may include linearly polarized light, left-handed circularly polarized light, right-handed circularly polarized light, left-handed elliptically polarized light, right-handed elliptically polarized light, etc. The speckle patterns generated by the polarized lights with different polarization states are superimposed on the screen 3, which can play a role in speckle elimination.

[0089] In the present application, by setting the crystal axis direction or the phase retardation of each sub-region 41 to vary continuously with the spatial distribution, this continuous variation can avoid the light diffraction effect caused by too large a gradient of the crystal axis direction change or too large a gradient of the phase change, thereby avoiding problems such as excessive light loss and introduction of stray light.

[0090] The applicant has proved through experiments that both of the above two embodiments can play a role in speckle elimination. Table 1 below is a measured table of the speckle elimination effect of the speckle elimination device. Among them, the speckle contrast of the projection optical system without using the speckle elimination device is 9.1%, the speckle contrast of the projection optical system using the speckle elimination device in the first embodiment is 7.9%, and the speckle contrast of the projection optical system using the speckle elimination device in the second embodiment is 7.2%. It can be seen from this that after using the speckle elimination device provided by the present application, the speckle contrast has been significantly reduced.

[0091] Table 1: Measured table of the speckle elimination effect of the polarization conversion element

[0092] Speckle contrast Without using a speckle elimination device 9.1％ Example 1 7.9％ Example 2 7.2％

[0093] In a second aspect, the present application provides a projection optical system, including any one of the speckle elimination devices introduced in combination with the foregoing embodiments. The projection optical system provided by the present application further includes a light emitting unit 1 and a lens assembly 2 sequentially arranged along the propagation direction of the first light beam, as Figures 1-12 shown. Among them, the light emitting unit 1 is used to emit the first light beam, and image information is carried on the first light beam. The first light beam is composed of Figures 13 to 15 shown. Among them, the light emitting unit 1 is used to emit the first light beam, and image information is carried on the first light beam. The first light beam is composed of Figure 13 , Figure 14 and Figure 15propagates from the left side to the right side in []. The lens assembly 2 is used to magnify the first light beam. The speckle reducing device 100 is disposed on the light incident side outside the lens assembly 2 (as shown in Figure 13 ), or is disposed inside the lens assembly 2 (as shown in Figure 14 and Figure 15 ). The first light beam output by the speckle reducing device 100 is emitted after being magnified by the lens assembly 2, and the magnified first light beam is used to display an image corresponding to the image information.

[0094] In some other embodiments, the polarization conversion element 4 is disposed in the light emitting unit 1 to reduce laser speckle. However, since the LCOS system and the LCD system have high requirements for the polarization state of the incident light, if the polarization conversion element 4 is disposed in the light emitting unit 1 of the LCOS system and the LCD system, the polarization characteristics of the incident light will be damaged, thereby affecting the optical efficiency and contrast of the LCOS system and the LCD system. Therefore, the technical solution of disposing the polarization conversion element 4 in the light emitting unit 1 can only be applied to the DLP system that has no requirements for the polarization state of the incident light, and cannot be applied to the LCOS system and the LCD system. In the present application, the polarization conversion element 4 is disposed inside the lens assembly 2 or on the light incident side outside the lens assembly 2, which will not affect the optical efficiency and contrast of the LCOS system and the LCD system. Therefore, the application fields of the embodiments of the present application are more extensive and the versatility is stronger. From the perspective of display technology, the embodiments of the present application are applicable to various display technologies in the field of home projection, including single-chip LCOS, multi-chip LCOS, single-chip DLP, multi-chip DLP, single-chip LCD, and multi-chip LCD projectors. From the perspective of application scenarios, in addition to home projectors, the embodiments of the present application are also applicable to other projection products using lasers as light sources, including: rear projection TVs, laser light source PGU modules in vehicle-mounted HUDs, projection exposure modules in 3D printers, and image projection modules in structured light 3D scanning devices.

[0095] In some implementation manners of the present application, referring to Figure 13 , the polarization conversion element 4 is disposed between the light emitting end of the light emitting unit 1 and the light incident end of the lens assembly 2. To enable the polarization conversion element 4 to vibrate, a vibration mechanism 5 that cooperates with the polarization conversion element 4 can be separately provided, or the polarization conversion element 4 can be integrated on a device with vibration performance in the projection optical system. Exemplarily, the polarization conversion element 4 can be disposed on a pixel ditherer between the light emitting end of the light emitting unit 1 and the light incident end of the lens assembly 2, that is, the pixel ditherer is used as the vibration mechanism 5. Specifically, referring to Figure 6, the pixel ditherer includes a reed 51, and an opening 52 is provided on the reed 51. The opening 52 is covered with a transparent glass sheet. The reed 51 can drive the transparent glass sheet to generate high-frequency vibrations to improve the pixel resolution of the projected image. When the polarization conversion element 4 is integrated on the pixel ditherer, the transparent glass sheet installed on the pixel ditherer can be removed, and then the polarization conversion element 4 is covered on the opening 52. The reed 51 drives the polarization conversion element 4 to vibrate, thereby realizing the integration of the polarization conversion element 4 and the pixel ditherer, further simplifying the device structure, reducing the device volume, and saving costs.

[0096] In some implementation manners of the present application, the thickness of the polarization conversion element 4 provided between the light emitting end of the light emitting unit 1 and the incident end of the lens assembly 2 in the first light beam propagation direction is less than or equal to 10 mm. This design effectively compresses the optical path length, and can compress the back focal length of the lens, thereby miniaturizing the projection optical system and reducing costs.

[0097] In some implementation manners of the present application, refer to Figure 14 and Figure 15 , an aperture stop 21 is provided in the lens assembly 2, and the speckle dissipation device 100 is provided on the light incident side of the aperture stop 21 (as Figure 14 shown) or on the light output side of the aperture stop 21 (as Figure 15 shown). Exemplarily, the distance between the polarization conversion element 4 and the aperture stop 21 (such as the dimension L in Figure 14 and Figure 15 ) is less than or equal to 10 mm. The applicant has discovered through exploration that when the first light beam passes through the aperture stop 21, the energy of the light will be more evenly distributed, and the contribution of the light at any spatial position on the aperture stop 21 to any point on the screen 3 is of equal weight. Therefore, in the present application, by arranging the polarization conversion element 4 near the aperture stop 21, any point on the screen 3 can be composed of the superposition of the polarized lights output by the polarization conversion element 4, and the contribution of the polarized lights output by the polarization conversion element 4 to any point on the screen 3 is of equal weight, thereby being able to further enhance the speckle dissipation effect.

[0098] Further, refer to Figure 9 , Figure 14 and Figure 15, at least one first sub-region 42 and at least one second sub-region 43 are provided on the polarization conversion element 4 disposed on the light incident side or the light exiting side of the aperture stop 21. The polarization directions of the first light beams output by the first sub-region 42 and the second sub-region 43 are orthogonal to each other, and the sum of the areas of the first sub-regions 42 is equal to the sum of the areas of the second sub-regions 43. This design can make the light incident on any point of the screen 3 be composed of the superposition of two light beams with equal energy and orthogonal polarization directions passing through the first sub-region 42 and the second sub-region 43, so that the speckle reduction effect of the image on the screen 3 can reach the best.

[0099] In some implementation manners of the present application, refer to Figure 16 , the light-emitting unit 1 includes a laser light source 11 and a display device 12. Among them, the laser light source 11 is used to emit a laser beam. The display device 12 is used to load image information onto the laser beam to form a first light beam. An illumination shaping optical path 16 is provided between the laser light source 11 and the display device 12, and the illumination shaping optical path 16 is used to homogenize and shape the laser beam emitted by the laser light source 11 and introduce the homogenized and shaped laser beam onto the display device 12.

[0100] In some implementation manners of the present application, refer to Figure 16 , a diffuser 6 is provided on the illumination shaping optical path 16. The diffuser 6 can translate and vibrate in the plane where the diffuser 6 is located or rotate around an axis perpendicular to the plane where the diffuser 6 is located (as shown by the dashed line L in Figure 16 ). The diffuser 6 is used to reduce the coherence of the laser beam in the spatial distribution of the incident surface of the polarization conversion element 4. Exemplarily, when the diffuser 6 translates and vibrates in the plane where the diffuser 6 is located, within one human eye integration period, the vibration amplitude of the diffuser 6 is greater than or equal to 0.1 mm. Exemplarily, when the diffuser 6 rotates around an axis perpendicular to the plane where the diffuser 6 is located, the diffuser 6 can be a diffuser wheel. Among them, the diffuser wheel can include an annular diffuser sheet 61 and a motor. The motor is disposed in the middle of the diffuser sheet 61 and can drive the diffuser sheet 61 to rotate around its own axis. Specifically, the surface of the diffuser sheet 61 has different regular unevennesses. When the first light beam passes through the diffuser sheet 61, it will be scattered by the diffuser sheet 61, and the light emitted from the diffuser sheet 61 will have random angles and phases. The speckle patterns introduced by the light with different angles and phases are different, and the different speckle patterns are superimposed on the screen 3, which can play a role in reducing speckles. In addition, in the present application, by rotating the diffuser sheet 61, it is also possible to make the speckle patterns generated by the light output when the diffuser sheet 61 is in different positions different. When the diffuser sheet 61 rotates at a high speed, the human eye will see multiple speckle patterns superimposed on each other within the integration period time. After the speckle patterns are superimposed, an averaging effect will be generated, and the laser speckles seen by the human eye will be reduced, thereby further enhancing the speckle reduction effect.

[0101] In a third aspect, the present application provides a projection device, including any one of the projection optical systems introduced in combination with the foregoing embodiments, and further including an image processing unit 7 and a driving unit 8. Among them, the image processing unit 7 is used to process the input image or video source. The driving unit 8 is used to receive the information output by the image processing unit 7 and drive the projection optical system. Exemplarily, referring to Figures 13 to 16 FIG. Figures 13 to 16 , the projection device 200 includes an image processing unit 7, a driving unit 8, a light emitting unit 1, a speckle reducing device 100, and a lens assembly 2. The projection device 200 can project an image or video onto a screen 3 or a target surface 9, as Figure 17 shown. Figures 18(a) to 18(c)

[0102] The projection device provided by the present application can be either a single-chip projection device or a multi-chip projection device. Exemplarily, Figure 19 FIG. Figure 19 is a schematic diagram of the optical system of a three-chip LCOS projector. Figure 19 In FIG. Figure 19 , a laser light source 11 emits a laser beam. After being homogenized and shaped by an illumination shaping optical path 16, the laser beam enters a beam splitting and combining optical system. The laser beam is sequentially decomposed into red, green, and blue light beams in the beam splitting and combining optical system. After passing through a polarization beam splitter 13, each light beam is incident on three different LCOS display devices 121 respectively. After the light beam emitted from the LCOS display device 121 is split by the polarization beam splitter 13, it passes through an analyzer 17 and a combining prism 15 to be combined into a single light beam, that is, the first light beam. The first light beam propagates from the left to the right in Figure 19 FIG. Figure 19 , and after being magnified by the lens assembly 2, it is projected onto the screen 3. When the display device provided by the present application is applied to the three-chip projector shown in Figure 19 FIG. Figure 19 , the speckle reducing device 100 can be disposed at position A, position B, or position C in Figure 19 FIG. Figure 19 to achieve the effect of reducing speckles.

[0103] The above describes the embodiments of the present application by specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. Although the description of the present application will be introduced in combination with some embodiments, this does not mean that the features of this application are limited to this embodiment. On the contrary, the purpose of introducing the application in combination with the embodiment is to cover other alternatives or modifications that may extend based on the claims of the present application. The present application can also be implemented without using these details. In addition, in order to avoid confusion or obscuring the key points of the present application, some specific details are omitted in the description. It should be noted that, without conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0104] ​In the embodiments of the present application, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0105] In the embodiments of the present application, "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, the character " / " in this text generally represents an "or" relationship between the associated objects before and after.

[0106] In the description of the embodiments of the present application, it should be noted that unless otherwise clearly specified and defined, the terms "installation" and "connection" should be understood in a broad sense. For example, "connection" may be a detachable connection or a non-detachable connection; it may be a direct connection or an indirect connection through an intermediate medium.

[0107] In the description of the present application, it should be noted that the orientation or positional relationship indicated by terms such as "upper", "lower", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation on the present application.

[0108] In the description of the present application, it should be noted that unless otherwise clearly specified and defined, the terms "arrangement", "installation", "connection", and "fitting" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0109] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these modifications and variations.

Claims

1. A speckle dissipation device, characterized in that, Comprising: A polarization conversion element provided with at least two sub-regions, wherein at least one of the sub-regions is capable of converting the polarization state of a first light beam incident thereon, so that the polarization conversion element outputs the first light beam having at least two different polarization states; A vibration mechanism connected to the polarization conversion element, the vibration mechanism being configured to drive the polarization conversion element to vibrate.

2. The speckle dissipation device according to claim 1, characterized in that, The vibration mechanism includes: A reed provided with an opening, and the polarization conversion element covers the opening; An electromagnetic induction mechanism for driving the reed and the polarization conversion element to vibrate.

3. The speckle dissipation device according to claim 2, characterized in that, The outer contour of the reed is rectangular, and the vibration mechanism can drive the polarization conversion element to perform translational vibration on the plane where the polarization conversion element is located, or swing vibration around a rotation axis perpendicular to the incident direction of the first light beam, or swing vibration around multiple rotation axes simultaneously.

4. The speckle elimination device according to claim 3, wherein: When the polarization conversion element performs translational vibration, the vibration direction of the polarization conversion element is the length direction, width direction or diagonal direction of the reed; When the polarization conversion element performs swing vibration, the rotation axis extends along the length direction of the reed, or along the width direction of the reed, or along the diagonal direction of the reed.

5. The speckle dissipation device according to claim 1, wherein The first light beam output by the polarization conversion element can be decomposed into two polarized lights with orthogonal polarization directions, and the energy ratio of the two polarized lights is 4:6 - 6:

4.

6. The speckle dissipation device according to any one of claims 1 to 5, characterized in that, The polarization conversion element is provided with at least one first sub-region and at least one second sub-region, the polarization directions of the first light beams output by the first sub-region and the second sub-region are orthogonal to each other, and the sum of the areas of the first sub-regions is equal to the sum of the areas of the second sub-regions.

7. The speckle dissipation device according to any one of claims 1 to 5, characterized in that, The number of the sub-regions is greater than or equal to three, and the sub-regions are arranged in sequence along a first direction. Along the first direction, the crystal axis directions of the sub-regions gradually rotate in a first rotation direction, or the phase retardation amounts of the sub-regions gradually increase or gradually decrease.

8. The speckle dissipation device according to claim 1, wherein The vibration frequency of the polarization conversion element is 30 - 240 HZ.

9. A projection optical system, characterized in that, Comprising the speckle elimination device according to any one of claims 1 to 8, further comprising: A light emitting unit for emitting the first light beam, and the first light beam carries image information; A lens assembly for magnifying the first light beam; The speckle elimination device is arranged on the light incident side outside the lens assembly or inside the lens assembly, and the first light beam output by the speckle elimination device is magnified by the lens assembly and then emitted, and the magnified first light beam is used to display an image corresponding to the image information.

10. The projection optical system according to claim 9, wherein, The speckle elimination device is arranged between the light emitting end of the light emitting unit and the incident end of the lens assembly, the vibration mechanism is a pixel ditherer arranged between the light emitting end of the light emitting unit and the incident end of the lens assembly, the pixel ditherer includes a reed, and the reed is provided with an opening, and the polarization conversion element covers the opening of the reed.

11. The projection optical system according to claim 9, characterized in that, An aperture stop is provided inside the lens assembly, and the speckle dissipation device is provided on the light incident side or the light exiting side of the aperture stop.

12. The projection optical system according to claim 11, wherein, The distance between the polarization conversion element and the aperture stop is less than or equal to 10 mm.

13. The projection optical system according to claim 9, wherein, The light emitting unit includes: A laser light source for emitting a laser beam; A display device for loading image information onto the laser beam to form the first beam.

14. The projection optical system according to claim 13, characterized in that, An illumination shaping optical path is provided between the laser light source and the display device. The illumination shaping optical path is used to homogenize and shape the laser beam emitted by the laser light source and guide the homogenized and shaped laser beam onto the display device; a diffuser is provided on the illumination shaping optical path. The diffuser can translate and vibrate in the plane where the diffuser is located or rotate around an axis perpendicular to the plane where the diffuser is located. The diffuser is used to reduce the coherence of the laser beam in spatial distribution.

15. The projection optical system according to claim 14, characterized in that, When the diffuser translates and vibrates in the plane where the diffuser is located, within one human eye integration period, the vibration amplitude of the diffuser is greater than or equal to 0.1 mm.

16. A projection device, characterized in that, Including the projection optical system according to any one of claims 9 to 15, further comprising: An image processing unit for processing an input image or video source; A driving unit for receiving the information output by the image processing unit and driving the projection optical system.

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