Speckle reduction device, projection optical system and projection apparatus

Abstract

The present application relates to the technical field of projection optical systems. Disclosed is a speckle reduction device, which is arranged in a projection optical system and comprises a polarization conversion element and a vibration mechanism. The polarization conversion element is provided with at least two sub-regions, wherein at least one sub-region can convert a polarization state of a first light beam incident thereon, such that the polarization conversion element outputs the first light beam having at least two different polarization states. The vibration mechanism is connected to the polarization conversion element, and is configured to drive the polarization conversion element to vibrate. The present application can reduce a speckle effect in projected images, thereby enhancing the viewing experience of a user. Further disclosed in the present application are the projection optical system and a projection apparatus.

Description

Speckle elimination device, projection optical system and projection equipment

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on January 2, 2024, with application number 202410007298.2 and application name “Speckle Elimination Device, Projection Optical System and Projection Equipment”. The entire contents of the above application are incorporated into this application by reference. Technical Field

[0002] The present application relates to the field of laser display technology, and in particular to a speckle elimination device, a projection optical system, and a projection device. Background Art

[0003] Currently, image display devices are widely used in people's daily lives and work, such as projection equipment, VR, AR, and projection modules for 3D printing devices. Many existing projection devices use laser light sources. Laser light sources are coherent light sources. When scattered by rough surfaces, laser light interferes with each other, resulting in "noise" in the projected image. This phenomenon is called laser speckle.

[0004] In the existing technology, laser speckle is the biggest pain point of laser display devices. The presence of speckle will lead to a decrease in the clarity of the projected image, and at the same time, the human eye will be more easily fatigued when watching, which seriously affects the user's viewing experience.

[0005] Summary of the Invention

[0006] The present application provides a speckle elimination device, a projection optical system, and a projection device, which can reduce laser speckle on the projection screen and enhance the user experience.

[0007] In a first aspect, the present application provides a speckle reduction device, which is arranged in a projection optical system. A first light beam in the projection optical system is incident on the speckle reduction device along 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.

[0008] The speckle reduction device provided herein includes a polarization conversion element and a vibration mechanism. The polarization conversion element is provided with at least two subregions, at least one of which is capable of converting the polarization state of a first light beam incident thereon, so that the polarization conversion element outputs a first light beam having at least two different polarization states. The vibration mechanism is connected to the polarization conversion element and is configured to vibrate the polarization conversion element. Exemplarily, the vibration frequency of the polarization conversion element is 30-240 Hz.

[0009] When a first light beam passes through the polarization conversion element, because at least one subregion of the polarization conversion element is capable of converting the polarization state of the incident first light beam, the polarization conversion element can output the first light beam with at least two different polarization states, that is, output at least two polarized lights with different polarization states. Because the polarization states of each polarized light beam are different, the speckle patterns produced by each polarized light beam are independent or have low correlation. The superposition of these independent or low-correlated speckle patterns on the screen can reduce speckle contrast, thereby achieving a speckle reduction effect and enhancing the user experience. Furthermore, the present application introduces additional polarization diversity by providing a vibration mechanism to drive the polarization conversion element to vibrate back and forth. When the polarization conversion element is in different positions during vibration, the speckle patterns produced by each polarized light beam output by the polarization conversion element differ. The superposition of these different speckle patterns within a human eye integration period further enhances the speckle reduction effect.

[0010] In some implementations of the present application, the vibration mechanism includes a reed and an electromagnetic induction mechanism. The reed is provided with an opening, 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.

[0011] In some implementations of the present application, the outer contour of the reed is rectangular, and the vibration mechanism can drive the polarization conversion element to vibrate translationally on the plane where the polarization conversion element is located, or to swing and vibrate around a rotation axis perpendicular to the incident direction of the first light beam, or to swing and vibrate around multiple rotation axes at the same time.

[0012] When the polarization conversion element vibrates in translation, the vibration direction of the polarization conversion element is the length direction, width direction or diagonal direction of the reed.

[0013] When the polarization conversion element oscillates, 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.

[0014] 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 mutually orthogonal polarization directions, with the energy ratio of the two polarized lights being 4:6 to 6:4. Preferably, the energy ratio of the two polarized lights is 1:1. The inventors have discovered that when the light incident on any point on the screen is composed of two beams of equal energy and mutually orthogonal polarization directions superimposed, the speckle reduction effect can be enhanced. Therefore, the above technical solution can further enhance the speckle reduction effect.

[0015] In some implementations of the present application, a 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 mutually orthogonal, and the sum of the areas of the first sub-regions is equal to the sum of the areas of the second sub-regions. For example, 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 after passing through the second sub-region is mutually orthogonal to that before the incident.

[0016] In some implementations of the present application, the number of the first sub-region and the number of the second sub-region are both one, and the areas of the first sub-region and the second sub-region are equal.

[0017] 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 sequentially along a first direction. Along the first direction, the crystal axis direction of each sub-region gradually rotates along a first rotation direction, or the phase delay of each sub-region gradually increases or decreases. By configuring the crystal axis direction or phase delay of each sub-region to continuously change with spatial distribution, this continuous change can avoid light diffraction effects caused by excessively large gradients in crystal axis direction or phase change, thereby avoiding problems such as excessive light loss and the introduction of stray light.

[0018] In a second aspect, the present application provides a projection optical system comprising the speckle reduction device of the first aspect, further comprising a light-emitting unit and a lens assembly arranged sequentially along the propagation direction of a first light beam. The light-emitting unit is configured to emit a first light beam carrying image information. The lens assembly is configured to amplify the first light beam. The speckle reduction device is disposed on the light-entering side of the lens assembly or within the lens assembly. The first light beam output by the speckle reduction device is amplified by the lens assembly before being emitted. The amplified first light beam is used to display an image corresponding to the image information.

[0019] In some implementations of the present application, the speckle reduction device is disposed between the light-emitting unit's output end and the lens assembly's incident end. The vibration mechanism is a pixel dither disposed between the light-emitting unit's output end and the lens assembly's incident end. The pixel dither includes a reed capable of generating vibrations, and the polarization conversion element covers the opening of the reed. By integrating the polarization conversion element with the pixel dither, the present application simplifies the device structure, reduces the device size, and saves costs.

[0020] In some implementations of the present application, an aperture stop is provided within the lens assembly, and the speckle reduction device is positioned on the light entrance side or the light exit side of the aperture stop. Exemplarily, the spacing between the polarization conversion element and the aperture stop is less than or equal to 10 mm. The applicant has discovered that when the first light beam passes through the aperture stop, the light energy is more evenly distributed, and the contribution of light passing through any spatial position on the aperture stop to any point on the screen is equally weighted. Therefore, by positioning the polarization conversion element near the aperture stop, the present application ensures that the light at any point on the screen is a superposition of the various polarizations output by the polarization conversion element, thereby further enhancing the speckle reduction effect.

[0021] Furthermore, the polarization conversion element, located on the light entrance or exit side of the aperture stop, is equipped 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 and second sub-regions are orthogonal, 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 ensures that the light incident on any point on the screen is the superposition of two beams of equal energy and orthogonal polarization directions that have passed through the first and second sub-regions, thereby achieving optimal speckle reduction.

[0022] In some implementations of the present application, the light-emitting unit includes a laser light source and a display device. The laser light source is configured to emit a laser beam. The display device is configured to load image information onto the laser beam to form a first light beam.

[0023] In some implementations 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 direct the homogenized and shaped laser beam to the display device. A diffuser is provided on the illumination shaping optical path. The diffuser is capable of translational vibration in the plane in which the diffuser is located or rotation around an axis perpendicular to the plane in which the diffuser is located. The diffuser is used to reduce the coherence of the laser beam in the spatial distribution of the incident surface of the polarization conversion element. Exemplarily, the diffuser can be a diffuser wheel or a dither diffuser. The diffuser wheel can include an annular diffuser and a motor. The motor is located in the middle of the annular diffuser and can drive the annular diffuser to rotate around its own axis. The dither diffuser can include a ditherer and a rectangular diffuser. The rectangular diffuser is located on the ditherer, and the ditherer can drive the rectangular diffuser to vibrate back and forth. Specifically, the surface of the diffuser has irregular irregularities. When the first light beam passes through the diffuser, it is scattered by the diffuser. The light emitted from the diffuser has random angles and phases. Light with different angles and phases introduces different speckle patterns. These different speckle patterns are superimposed on the screen, effectively reducing speckle. Furthermore, by rotating or shaking the diffuser, the present application can also produce different speckle patterns for the light output when the diffuser is in different positions, further enhancing the speckle reduction effect.

[0024] In some implementations of the present application, when the diffuser vibrates in translation on the plane where the diffuser is located, the vibration amplitude of the diffuser is greater than or equal to 0.1 mm within a human eye integration period.

[0025] In a third aspect, the present application provides a projection device, comprising the projection optical system according to the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 shows a schematic diagram of the optical system of a single-chip LCOS projector;

[0027] FIG2 shows a schematic diagram of the optical system of a three-chip LCOS projector;

[0028] FIG3 shows a schematic diagram of the optical system of a single-chip DLP projector;

[0029] FIG4 shows a schematic diagram of the optical system of a three-chip LCD projector;

[0030] FIG5( a ) shows a schematic diagram 1 of a speckle reduction device in some embodiments of the present application;

[0031] FIG5( b ) shows a second schematic diagram of a speckle reduction device in some embodiments of the present application;

[0032] FIG6 shows a schematic diagram of a vibration mechanism in some embodiments of the present application;

[0033] FIG7( a ) shows a first schematic diagram of a polarization conversion element performing translational vibration in some embodiments of the present application;

[0034] FIG7( b ) shows a second schematic diagram of a polarization conversion element performing translational vibration in some embodiments of the present application;

[0035] FIG7( c ) shows a third schematic diagram of a polarization conversion element performing translational vibration in some embodiments of the present application;

[0036] FIG7( d ) shows a fourth schematic diagram of a polarization conversion element performing translational vibration in some embodiments of the present application;

[0037] FIG8( a ) shows a first schematic diagram of a polarization conversion element performing oscillatory vibration in some embodiments of the present application;

[0038] FIG8( b ) shows a second schematic diagram of a polarization conversion element performing oscillatory vibration in some embodiments of the present application;

[0039] FIG8( c ) shows a third schematic diagram of a polarization conversion element performing oscillatory vibration in some embodiments of the present application;

[0040] FIG8( d ) shows a fourth schematic diagram of a polarization conversion element performing oscillatory vibration in some embodiments of the present application;

[0041] FIG9 shows a first schematic diagram of a polarization conversion element in some embodiments of the present application;

[0042] FIG10 shows a second schematic diagram of a polarization conversion element in some embodiments of the present application;

[0043] FIG11 shows a third schematic diagram of a polarization conversion element in some embodiments of the present application;

[0044] FIG12 shows a fourth schematic diagram of a polarization conversion element in some embodiments of the present application;

[0045] FIG13 is a schematic diagram showing a polarization conversion element disposed on the light incident side of a lens assembly in some embodiments of the present application;

[0046] FIG14 is a schematic diagram showing a polarization conversion element disposed on the light incident side of an aperture stop in some embodiments of the present application;

[0047] FIG15 is a schematic diagram showing a polarization conversion element disposed on the light exit side of an aperture stop in some embodiments of the present application;

[0048] FIG16 is a schematic diagram showing the position of a diffuser in some embodiments of the present application;

[0049] FIG17 shows a structural block diagram of a projection device in some embodiments of the present application;

[0050] FIG18( a ) shows a schematic diagram of an application scenario 1 of a projection device in some embodiments of the present application;

[0051] FIG18( b ) shows a second schematic diagram of an application scenario of a projection device in some embodiments of the present application;

[0052] FIG18( c ) shows a third schematic diagram of an application scenario of a projection device in some embodiments of the present application;

[0053] FIG19 is a schematic diagram showing the position of a speckle reduction device in a three-chip projection device in some embodiments of the present application.

[0054] Description of reference numerals:

[0055] 1-light-emitting unit; 11-laser light source; 12-display device; 121-LCOS display device; 122-DMD display device; 123-LCD display device; 13-polarization beam splitter; 14-total internal reflection prism; 15-light-combining prism; 16-illumination shaping optical path; 17-polarizer;

[0056] 2-lens assembly; 21-aperture diaphragm;

[0057] 3-Screen;

[0058] 4-polarization conversion element; 41-subregion; 42-first subregion; 43-second subregion;

[0059] 5-vibration mechanism; 51-reed; 52-opening;

[0060] 6-diffuser; 61-diffuser;

[0061] 7- Image processing unit;

[0062] 8-Drive unit;

[0063] 9- target surface;

[0064] 10-first polarized light;

[0065] 20-second polarized light;

[0066] 100-speckle removal device;

[0067] 200-Projection equipment. DETAILED DESCRIPTION

[0068] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0069] The present invention provides a speckle reduction device that is installed within a projection optical system. A projection optical system is an optical system that projects images and videos onto a screen or target surface. The performance of a projection optical system is primarily determined by the light source technology it employs. Laser light sources are the latest generation of light source technology for projection optical systems. This technology utilizes red, green, and blue lasers directly as the light source for the projection optical system. Compared to previous-generation LED and light bulb lighting sources, laser light sources offer advantages such as high brightness, a wide color gamut, and high light efficiency.

[0070] In this application, the projection optical system can be applied to projection equipment, VR, AR, and HUD (head-up display), and can also be applied to the projection module of 3D printing equipment and 3D scanning equipment, which is not limited in this application. The following will be described using the application of the projection optical system to the projection equipment as an example.

[0071] Figures 1 to 4 show exemplary schematic diagrams of the projection optical system provided in the embodiments of the present 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, and Figure 4 is a schematic diagram of the optical system of a three-chip LCD (liquid crystal display) projector. Each of the above-mentioned projection devices includes a light-emitting unit 1 and a lens assembly 2. Among them, the working mechanism of the optical system is different, and the internal structure of the light-emitting unit 1 is different. However, the light-emitting unit 1 is used to emit a light beam outward. Because the light beam carries image information for displaying an image or video, in this scenario we call such a light beam image light.

[0072] 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, and RGB time-sequential lighting is used to achieve a color image. 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 display RGB images respectively, and the color image is synthesized by 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. RGB time-sequential lighting is used to achieve a color image. 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 display RGB images respectively, and the color image is synthesized by the light-combining prism 15.

[0073] The lens assembly 2 is used to amplify the image light and project it onto the screen 3. The lens assembly 2 can be a lens group commonly found in an optical system, such as a projection lens.

[0074] During use, these projection devices may produce laser speckle in the projected image. This is because the light sources used in these projection devices are lasers, which are coherent light sources. When scattered by the rough surface of the screen, the lasers interfere with each other, forming speckle. The presence of speckle reduces the clarity of the projected image and increases eye fatigue, seriously affecting the user's viewing experience.

[0075] The present application provides a speckle reduction device, as shown in Figures 5(a) and 5(b), comprising a polarization conversion element 4 and a vibration mechanism 5. The plane on which 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 indicated by the arrow in Figure 5(a)). The polarization conversion element 4 is provided with at least two sub-regions 41 (as shown in Figure 5(b)), at least one of which is capable of converting the polarization state of the first light beam incident thereon, so that the polarization conversion element 4 outputs a first light beam having at least two different polarization states. The vibration mechanism 5 is connected to the polarization conversion element 4 and is used to drive the polarization conversion element 4 to vibrate.

[0076] When the first light beam passes through the polarization conversion element 4, because at least one subregion 41 on the polarization conversion element 4 is capable of converting the polarization state of the incident first light beam, the polarization conversion element 4 can output the first light beam having at least two different polarization states. This means that at least two polarized lights having different polarization states are output, such as the first polarized light, the second polarized light, and the Nth polarized light shown in Figure 5(b). Because the polarization states of each polarized light are different, the speckle patterns generated by each polarized light are independent or have low correlation. The superposition of these independent or low-correlated speckle patterns on the screen can reduce speckle contrast, thereby achieving a speckle elimination effect and enhancing the user experience.

[0077] Furthermore, the present application introduces additional polarization perturbations by providing a vibration mechanism 5 to drive the polarization conversion element 4 to vibrate back and forth. When the polarization conversion element 4 vibrates, the polarization state of the first light beam emitted from the same spatial location changes over time, resulting in different speckle patterns produced by the polarizations output by the polarization conversion element 4. These different speckle patterns are superimposed within the human eye integration period, further enhancing the speckle reduction effect.

[0078] In some implementations of the present application, referring to Figures 5(a) and 6, the vibration mechanism 5 includes a reed 51 and an electromagnetic induction mechanism (not shown in the figures). The reed 51 is provided with an opening 52, 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. For example, the reed 51 includes an outer frame and an inner frame (not shown in the figures), 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 via 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, the coil and the magnet interact to generate an electromagnetic force, which can drive the inner frame to vibrate, thereby causing the polarization conversion element 4 to vibrate. Since the coil is energized as 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 may be 30-240 Hz, such as 30 Hz, 60 Hz, 120 Hz, 180 Hz or 240 Hz.

[0079] In some implementations 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 vibrate translationally on the plane where the polarization conversion element 4 is located (as shown in Figures 7(a) to 7(d)), or to swing and vibrate around a rotation axis perpendicular to the incident direction of the first light beam (as shown in Figures 8(a) to 8(d)), or to swing and vibrate around multiple swing axes at the same time.

[0080] This application does not limit the vibration direction of the polarization conversion element 4. When the polarization conversion element 4 vibrates in translation, the vibration direction of the polarization conversion element 4 is the length direction of the reed 51 (as shown in the X1 direction in Figure 7(a)), the width direction (as shown in the X2 direction in Figure 7(b)), the diagonal direction (as shown in the X3 direction in Figure 7(c)), or the direction rotated at a certain angle relative to the diagonal direction (as shown in the X4 direction in Figure 7(d)). When the polarization conversion element 4 vibrates in a swinging manner, the rotation axis extends along the length direction of the reed 51, and the polarization conversion element 4 rotates along the R1 direction in Figure 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 Figure 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 Figure 8(c); or the extension direction of the rotation axis forms a certain angle with the diagonal line of the reed 51, and the polarization conversion element 4 rotates along the R4 direction in Figure 8(d). When the polarization conversion element 4 swings and vibrates, the polarization conversion element 4 rotates a certain angle around a rotation axis perpendicular to the incident direction of the first light beam. At this time, the first light beam passing through the polarization conversion element 4 will produce a displacement perpendicular to the incident direction of the first light beam due to the refraction effect. By synchronizing the image signal with the timing of the polarization conversion element 4, the image resolution can be improved.

[0081] In some implementations of the present application, the vibration mechanism 5 may be provided with a single set of coils to cause the reed 51 and the polarization conversion element 4 to vibrate translationally in a single vibration direction, or to vibrate in an oscillatory manner about a single rotation axis. The vibration mechanism 5 may also be provided with multiple sets of coils to cause the reed 51 and the polarization conversion element 4 to vibrate translationally in multiple vibration directions simultaneously, or to vibrate in an oscillatory manner about multiple rotation axes simultaneously.

[0082] 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 mutually orthogonal polarization directions, with the energy ratio of the two polarized lights being 4:6 to 6:4. Preferably, the energy ratio of the two polarized lights is 1:1. The inventors have discovered that when the light incident on any point on the screen 3 is composed of two beams of equal energy and mutually orthogonal polarization directions superimposed, the speckle reduction effect can be enhanced. Therefore, the above technical solution can further enhance the speckle reduction effect.

[0083] In order to enable those skilled in the art to better understand the structure of the polarization conversion element 4 , the polarization conversion element 4 is described in detail below through two embodiments.

[0084] Example 1

[0085] In some implementations of the present application, referring to FIG9 , the polarization conversion element 4 is provided with at least one first sub-region 42 and at least one second sub-region 43. 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. For example, the first sub-region 42 is made of a transparent glass sheet. After passing through the first sub-region 42, the polarization direction of the first light beam incident on the first sub-region 42 remains unchanged, forming first polarized light 10. The second sub-region 43 has a half-wave phase delay that can change the polarization direction of light. After passing through the second sub-region 43, the polarization direction of the first light beam incident on the second sub-region 43 is changed, forming second polarized light 20. The polarization directions of the second polarized light 20 and the first polarized light 10 are orthogonal to each other.

[0086] Furthermore, 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. For example, referring to Figure 10, the number of the first sub-region 42 and the second sub-region 43 is 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 made 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, wherein the first sub-region 42 does not have phase delay, and the second sub-region 43 can be made to produce a half-wave phase delay by coating, film bonding or coating.

[0087] Example 2

[0088] In some implementations of the present application, referring to Figures 11 and 12 , the polarization conversion element 4 can be rectangular, with each sub-region 41 arranged in sequence along the length of the rectangle and having equal widths. The number of sub-regions 41 is greater than or equal to three, and each sub-region 41 is arranged in sequence along a first direction. Along the first direction, the crystal axis of each sub-region 41 gradually rotates along a first rotation direction (as shown in Figure 11 ), or the phase delay of each sub-region 41 gradually increases or decreases (as shown in Figure 12 ).

[0089] Figure 11 is a schematic diagram of an embodiment in which the crystal axis orientation of each sub-region 41 is gradually rotated along a first rotation direction. In Figure 11 , the crystal axis orientations of each sub-region 41 are different, 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 enters the polarization conversion element 4, the incident light passing through different sub-regions 41 is converted into linearly polarized light with different polarization directions. The speckle patterns generated by the linearly polarized light with different polarization directions are superimposed on the screen 3, effectively eliminating speckle.

[0090] FIG12 is a schematic diagram of an embodiment in which the phase delay of each sub-region 41 gradually increases or decreases. In FIG12 , each sub-region 41 has a different phase delay. When the first light beam enters the polarization conversion element 4, the incident light passing through different sub-regions 41 is converted into polarized light with different polarization states, including linear polarization, left-handed circular polarization, right-handed circular polarization, left-handed elliptically polarized light, and right-handed elliptically polarized light. The speckle patterns generated by the polarized light with different polarization states are superimposed on the screen 3, thereby eliminating speckle.

[0091] The present application sets the crystal axis direction or phase delay of each sub-region 41 to change continuously with the spatial distribution. This continuous change can avoid the light diffraction effect caused by excessive gradient of crystal axis direction change or excessive gradient of phase change, thereby avoiding problems such as excessive light loss and introduction of stray light.

[0092] The applicant has experimentally demonstrated that both of the above-mentioned embodiments can achieve speckle reduction. Table 1 below shows the measured speckle reduction effects of the speckle reduction device. The speckle contrast of the projection optical system without the speckle reduction device is 9.1%, the speckle contrast of the projection optical system using the speckle reduction device of Example 1 is 7.9%, and the speckle contrast of the projection optical system using the speckle reduction device of Example 2 is 7.2%. This indicates that the speckle contrast is significantly reduced after using the speckle reduction device provided by this application.

[0093] Table 1: Measured speckle reduction effect of polarization conversion elements

[0094] In a second aspect, the present application provides a projection optical system, comprising any of the speckle reduction devices described in conjunction with Figures 1-12 in the aforementioned embodiments. The projection optical system provided by the present application further comprises a light-emitting unit 1 and a lens assembly 2, arranged sequentially along the propagation direction of a first light beam, as shown in Figures 13 to 15 . The light-emitting unit 1 is configured to emit a first light beam, which carries image information and propagates from left to right in Figures 13 , 14 , and 15 . The lens assembly 2 is configured to amplify the first light beam. The speckle reduction device 100 is disposed on the light incident side of the lens assembly 2 (as shown in Figure 13 ) or within the lens assembly 2 (as shown in Figures 14 and 15 ). The first light beam output by the speckle reduction device 100 is amplified by the lens assembly 2 and then emitted. The amplified first light beam is used to display an image corresponding to the image information.

[0095] In some other embodiments, the polarization conversion element 4 is disposed within 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 within the light-emitting unit 1 of the LCOS system and the LCD system, the polarization characteristics of the incident light will be destroyed, 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 within the light-emitting unit 1 can only be applied to the DLP system that does not have requirements for the polarization state of the incident light, and cannot be applied to the LCOS system and the LCD system. The present application disposes the polarization conversion element 4 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 field of the embodiments of the present application is wider and more versatile. 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 this application are also applicable to other projection products that use laser as a light source, including: rear-projection TVs, laser light source PGU modules in car HUDs, projection exposure modules in 3D printers, and image projection modules in structured light 3D scanning devices.

[0096] In some implementations of the present application, referring to FIG13 , the polarization conversion element 4 is disposed between the output end of the light-emitting unit 1 and the incident end of the lens assembly 2. In order 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 into a device with vibration performance in the projection optical system. Exemplarily, the polarization conversion element 4 can be provided on a pixel dither between the output end of the light-emitting unit 1 and the incident end of the lens assembly 2, that is, the pixel dither is used as the vibration mechanism 5. Specifically, referring to FIG6 , the pixel dither 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 into the pixel dither, the transparent glass sheet installed on the pixel dither can be removed, and then the polarization conversion element 4 can be covered on the opening 52. The reed 51 is used to drive the polarization conversion element 4 to vibrate, thereby realizing the integration of the polarization conversion element 4 and the pixel dither, thereby simplifying the device structure, reducing the device volume, and saving costs.

[0097] In some implementations of the present application, the thickness of the polarization conversion element 4 provided between the output end of the light-emitting unit 1 and the incident end of the lens assembly 2 in the propagation direction of the first light beam is less than or equal to 10 mm. This design effectively compresses the optical path length and can have the effect of compressing the back focal length of the lens, thereby miniaturizing the projection optical system and reducing costs.

[0098] In some implementations of the present application, referring to Figures 14 and 15 , an aperture stop 21 is provided within the lens assembly 2, and the speckle reduction device 100 is positioned on the light entrance side of the aperture stop 21 (as shown in Figure 14 ) or on the light exit side of the aperture stop 21 (as shown in Figure 15 ). For example, the distance between the polarization conversion element 4 and the aperture stop 21 (as indicated by dimension L in Figures 14 and 15 ) is less than or equal to 10 mm. The applicant has discovered that when the first light beam passes through the aperture stop 21, the light energy is more evenly distributed, and the light from any spatial position on the aperture stop 21 contributes equally to any point on the screen 3. Therefore, by positioning the polarization conversion element 4 near the aperture stop 21, the light at any point on the screen 3 is composed of the sum of the polarized light beams output by the polarization conversion element 4, and the contributions of the polarized light beams output by the polarization conversion element 4 to any point on the screen 3 are equally weighted, thereby further enhancing the speckle reduction effect.

[0099] Furthermore, referring to Figures 9, 14, and 15, the polarization conversion element 4, located on the light entrance or exit side of the aperture stop 21, is provided with at least one first sub-region 42 and at least one second sub-region 43. The polarization directions of the first light beams output by the first sub-region 42 and the second sub-region 43 are mutually orthogonal, and the sum of the areas of the first sub-regions 42 and the sum of the areas of the second sub-regions 43 are equal. This design ensures that the light incident on any point on the screen 3 is composed of the superposition of two beams of equal energy and mutually orthogonal polarization directions that have passed through the first sub-region 42 and the second sub-region 43, thereby achieving optimal despeckle effect on the image on the screen 3.

[0100] In some implementations of the present application, referring to FIG16 , the light-emitting unit 1 includes a laser light source 11 and a display device 12 . The laser light source 11 is configured to emit a laser beam. The display device 12 is configured to load image information onto the laser beam, forming a first light beam. An illumination shaping optical path 16 is provided between the laser light source 11 and the display device 12 . The illumination shaping optical path 16 is configured to homogenize and shape the laser beam emitted by the laser light source 11 and direct the homogenized and shaped laser beam to the display device 12 .

[0101] In some implementations of the present application, referring to FIG16 , a diffuser 6 is provided on the illumination shaping optical path 16 . The diffuser 6 is capable of translating and vibrating in the plane in which the diffuser 6 resides or rotating about an axis perpendicular to the plane in which the diffuser 6 resides (as indicated by the dashed line L in FIG16 ). 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 translating and vibrating in the plane in which the diffuser 6 resides, the vibration amplitude of the diffuser 6 is greater than or equal to 0.1 mm within a human eye integration period. Exemplarily, when the diffuser 6 rotates about an axis perpendicular to the plane in which the diffuser 6 resides, the diffuser 6 may be a diffusion wheel. The diffusion wheel may include an annular diffuser 61 and a motor. The motor is located in the middle of the diffuser 61 and is capable of driving the diffuser 61 to rotate about its own axis. Specifically, the surface of the diffuser 61 has irregular irregularities. When the first light beam passes through the diffuser 61, it is scattered by the diffuser 61. The light emitted from the diffuser 61 has random angles and phases. Light with different angles and phases introduces different speckle patterns. These different speckle patterns are superimposed on the screen 3, effectively reducing speckle. Furthermore, by rotating the diffuser 61, the present application can also produce different speckle patterns for the light output when the diffuser 61 is in different positions. When the diffuser 61 rotates at high speed, the human eye sees multiple speckle patterns superimposed within the integration period. This superposition produces an averaging effect, which reduces the perceived laser speckle, further enhancing the speckle reduction effect.

[0102] In a third aspect, the present application provides a projection device, comprising any of the projection optical systems described in conjunction with Figures 13 to 16 in the aforementioned embodiments, and further comprising an image processing unit 7 and a drive unit 8. The image processing unit 7 is used to process an input image or video source. The drive unit 8 is used to receive information output by the image processing unit 7 and drive the projection optical system. For example, with reference to Figure 17 , the projection device 200 comprises an image processing unit 7, a drive unit 8, a light-emitting unit 1, a speckle removal device 100, and a lens assembly 2. The projection device 200 is capable of projecting images or videos onto a screen 3 or a target surface 9, as shown in Figures 18(a) to 18(c).

[0103] The projection device provided herein can be either a single-chip or multi-chip projection device. For example, FIG19 is a schematic diagram of the optical system of a three-chip LCOS projector. In FIG19 , a laser light source 11 emits a laser beam, which is homogenized and shaped by an illumination shaping optical path 16 before entering a light splitting and combining system. In the light splitting and combining system, the laser beam is sequentially split into red, green, and blue beams. Each beam passes through a polarization beam splitter 13 and is incident on three different LCOS display devices 121. The beams emitted by the LCOS display devices 121 are split by the polarization beam splitter 13 before being combined into a single beam, namely, a first beam, by an analyzer 17 and a light combining prism 15. The first beam propagates from left to right in FIG19 , is magnified by a lens assembly 2, and is projected onto a screen 3. When the display device provided herein is applied to the three-chip projector shown in FIG19 , a speckle reduction device 100 can be positioned at position A, position B, or position C in FIG19 to achieve the speckle reduction effect.

[0104] The above describes the implementation methods of the present application by means of specific specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Although the description of the present application will be introduced in conjunction with some embodiments, this does not mean that the features of this application are limited to the implementation methods. On the contrary, the purpose of introducing the application in conjunction with the implementation methods is to cover other options or modifications that may be extended 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 blurring the focus of the present application, some specific details are omitted in the description. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other unless there is a conflict.

[0105] In the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0106] In the embodiments of this application, "and / or" is simply a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this document generally indicates that the related objects are in an "or" relationship.

[0107] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium.

[0108] In the description of this application, it should be noted that the terms "upper", "lower", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application.

[0109] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "dispose," "install," "connect," and "fit" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0110] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is 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 used 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, wherein 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.

4. The speckle reduction device according to claim 3, wherein 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; 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.

5. The speckle dissipation device according to claim 1, characterized in that, 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, and 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, characterized in that, The vibration frequency of the polarization conversion element is 30 - 240 HZ.

9. A projection optical system, characterized in that, Comprising the speckle reduction 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 reduction device is arranged on the incident light side outside the lens assembly or inside the lens assembly, and the first light beam output by the speckle reduction 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, characterized in that, The speckle reduction 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, and the pixel ditherer includes a reed provided with an opening, and the polarization conversion element covers the opening of the reed.

11. The projection optical system according to claim 9, wherein An aperture stop is provided inside the lens assembly, and the speckle dissipation device is provided on the light incident side or the light exit 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 the spatial distribution.

15. The projection optical system according to claim 14, wherein, 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.

Images