Projection optical system and projection apparatus

Abstract

The application relates to a projection optical system, which comprises a light source assembly, a diffractive optical assembly, a polarization light splitting element, a reflective modulation element, a first polarization element, a second polarization element and a lens, the second polarization element unifies the outgoing light of the light source assembly into first polarization state light rays to the diffractive optical assembly. The diffractive optical assembly is arranged on the light outgoing side of the light source assembly, the polarization light splitting element receives the light rays emitted by the diffractive optical assembly, the polarization light splitting element can reflect the first polarization state light rays and transmit second polarization state light rays, the reflective modulation element receives the light rays reflected by the polarization light splitting element, and the first polarization element is arranged between the polarization light splitting element and the reflective modulation element, wherein the first polarization state light rays reflected by the polarization light splitting element are reflected by the first polarization element and the reflective modulation element to be converted into second polarization state light rays. The application is favorable for reducing the probability of high-order diffraction light rays participating in projection imaging and improving the projection picture contrast of the projection optical system.

Description

Technical Field

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

[0002] In related technologies, projection optical systems typically require several lenses, compound lenses, or light bars to shape and homogenize the laser. To further simplify these systems, projection optical systems employing diffractive optical elements (DOEs) for shaping have emerged. Diffractive optical systems can replace compound lenses and other optical elements in related technologies, facilitating miniaturization. However, in projection optical systems using diffractive optical elements, some higher-order diffracted light is prone to reflection and refraction within the system, leading to increased black level brightness and affecting contrast. Summary of the Invention

[0003] Therefore, it is necessary to provide a projection optical system and projection device to address the problem that some higher-order diffraction light generated by diffractive optical elements can easily affect the contrast of the projection optical system.

[0004] A projection optical system, comprising:

[0005] Light source assembly for emitting linearly polarized light;

[0006] A diffractive optical component is disposed on the light-emitting side of the light source component;

[0007] A polarization beam splitter is used to receive light emitted from the diffractive optical component, and the polarization beam splitter is configured to reflect light of a first polarization state and transmit light of a second polarization state.

[0008] A reflective modulation element for receiving light reflected from the polarization beam splitter; and,

[0009] A first polarization element is disposed between the polarization beam splitter and the reflective modulation element, wherein light rays of the first polarization state reflected by the polarization beam splitter travel back and forth to the first polarization element and are converted into light rays of the second polarization state after being reflected by the reflective modulation element;

[0010] A second polarizing element is disposed on the light-emitting side of the light source assembly. The second polarizing element is used to convert the polarization state of at least a portion of the emitted light from the light source assembly, so that the polarization state of the emitted light from the light source assembly is unified into a first polarization state light that strikes the diffractive optical assembly; and,

[0011] A lens for receiving light reflected by the reflective modulation element and transmitted through the polarizing beam splitter.

[0012] In the aforementioned projection optical system, the first polarized light emitted by the light source assembly is diffracted by the diffractive optical assembly. The effective imaging light, which is also in the first polarized state, is reflected by the polarization beam splitter onto the first polarization element. This light then travels through the first polarization element to the reflective modulation element, is reflected again by the reflective modulation element, and is converted back into second polarized light by the first polarization element before exiting through the polarization beam splitter. Higher-order diffracted light, which is in the first polarization state and has a diffraction order higher than the effective imaging light, is reflected by the polarization beam splitter and travels outside the range of the first polarization element. It cannot be converted back into second polarized light and therefore cannot exit from the polarization beam splitter. This reduces the probability of higher-order diffracted light participating in the projection image, thus improving the contrast of the projected image. Furthermore, using a diffractive optical assembly to shape the light eliminates the need for compound eye lenses and other optical components, facilitating the miniaturization of the projection optical system.

[0013] A projection device includes a projection optical system as described in any of the above embodiments. By employing the above-described projection optical system in the projection device, higher-order diffraction light in the projection optical system can be effectively reduced, and the size of the projection optical system can be reduced, thereby improving the projection imaging quality of the projection device and facilitating its miniaturization. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of a projection optical system in related technologies.

[0015] Figure 2 for Figure 1 The diagram shows a schematic of the projection optics system using DOE elements.

[0016] Figure 3 for Figure 2 The diagram shows the structure of the DOE element.

[0017] Figure 4 For the light in the related technology Figure 3 The diagram shows the structure of the target diffraction image and the higher-order diffraction image behind the DOE element.

[0018] Figure 5 For light to pass through Figure 2 The diagram shows the structural schematic of the propagation paths of the target diffracted light and the higher-order diffracted light in the projection optics system of the related technology.

[0019] Figure 6 This is a schematic diagram of the structure of a projection optical system that changes the polarization state of the emitted light from a third laser in one embodiment of this application.

[0020] Figure 7This is a schematic diagram showing the change in the polarization state of the light rays after passing through the projection optical system when the outgoing light after passing through the second polarization element 14 is S-polarized light in one embodiment of this application.

[0021] Figure 8 This is a schematic diagram showing the change in the polarization state of the light rays after passing through the projection optics system when the outgoing light after passing through the second polarization element 14 is P-polarized light in one embodiment of this application.

[0022] Figure 9 This is a schematic diagram of the structure of the target diffraction light image and the higher order diffraction light image in one embodiment of this application.

[0023] Figure 10 This is a schematic diagram of the projection optical system using liquid crystal on silicon (LCOS) and a compensation sheet in one embodiment of this application.

[0024] Figure 11 This is a schematic diagram of the structure of a projection optical system that changes the polarization state of the emitted light from the first laser and the second laser in one embodiment of this application.

[0025] Figure 12 This is a schematic diagram of the structure of a light source assembly in which lasers in each row are arranged adjacent to each other in one embodiment of this application.

[0026] Figure 13 For light to pass through Figure 12 The diagram shows the structure of the light source assembly.

[0027] Figure 14 This is a schematic diagram of a structure in one embodiment of the present application in which the first laser, green laser, and blue laser are located on different substrates.

[0028] Figure 15 This is a schematic diagram of the structure of a projection device according to an embodiment of this application.

[0029] Explanation of reference numerals in the attached figures:

[0030] 100. Projection optical system;

[0031] 10. Light source assembly; 1. Laser; 11. First laser; 111. First laser chip; 12. Second laser; 121. Second laser chip; 13. Third laser; 131. Third laser chip; 14. Second polarization element; 15. Substrate; 16. First housing; 17. Second housing; 18. Third housing; 20. Diffractive optical element; 21. First diffractive optical element; 22. Second diffractive optical element; 23. Third diffractive optical element; 30. Polarization beam splitter; 31. Polarization combining surface; 40. Reflector 41. Fiber optic modulation element; 42. Compensation plate; 43. Effective region; 44. Ineffective region; 50. First polarizing element; 51. Liquid crystal on silicon; 61. First dichroic filter; 62. Second dichroic filter; 63. Third dichroic filter; 70. Lens; 80. Focusing lens; 91. First polarized ray; 92. Second polarized ray; 93. Third polarized ray; 94. Fourth polarized ray; 101. Target diffraction image; 102. Higher order diffraction image; 110. Housing; F1. First direction; F2. Second direction;

[0032] L, Optical mechanism; L1, First shaping lens; L2, Second shaping lens; L3, Third shaping lens; L4, Fourth shaping lens; L5, Fifth shaping lens; L6, Reflective modulation element; L7, Total internal reflection lens; L8, Lens; L9, Diffractive optical element. Detailed Implementation

[0033] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0034] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0035] A projection optics system is an optical system that magnifies and projects the optical image of an object onto a screen. It mainly consists of three parts: a light source, an imaging system, and a projection lens. The contrast ratio of the projected image is one of the most important indicators of projector image quality, directly determining the image's depth, clarity, and detail. Contrast ratio refers to the ratio of the brightest white to the deepest black in an image. A higher contrast ratio indicates stronger contrast between light and dark areas, deeper blacks, richer details in dark areas, and a stronger sense of depth. For example, in shadow areas, high contrast can clearly delineate details, making the entire image look more three-dimensional, realistic, and with superior image quality. Conversely, if the contrast ratio is low, blacks will appear grayish, and the image will easily appear flat and lack impact. Therefore, improving the contrast ratio of the projected image in a projection optics system is crucial.

[0036] In related technologies, projection optics systems typically require the sequential placement of several lenses, compound eyes, or light bars on the light-emitting side of the optical engine to shape and homogenize the laser emitted from the engine. (See also...) Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of a projection optical system according to an embodiment of the related technology. Figure 1 In the illustrated embodiment, the related technology employs a first shaping lens L1, a second shaping lens L2, a third shaping lens L3, a fourth shaping lens L4, and a fifth shaping lens L5 sequentially positioned on the light-emitting side of the optical engine L to shape and homogenize the laser emitted from the optical engine L. The first shaping lens L1 and the second shaping lens L2 can be a combination of a convex lens and a concave lens, primarily used to correct phase aberrations, converge light to improve light utilization, and reduce stray light and light scattering in the optical path by designing the combination of convex and concave lenses, thereby improving the contrast of the projected image. The third shaping lens L3 can be an optical device such as a compound eye or a light bar. Figure 1The third shaping lens L3 is a compound eye lens, which splits the light beam into multiple smaller beams and superimposes them to achieve uniform light energy distribution, thus realizing high light energy utilization and large-area uniform illumination. The fourth shaping lens L4 and the fifth shaping lens L5 then smoothly propagate and converge the light beam. The beam optimized by the first shaping lens L1, second shaping lens L2, third shaping lens L3, fourth shaping lens L4, and fifth shaping lens L5 is then modulated by a reflective modulation element L6 and a total internal reflection lens L7. The total internal reflection lens L7 deflects and propagates the light path, while the reflective modulation element L6 modulates the light. The beam then exits from the total internal reflection lens L7 and enters the lens L8, from where it exits and is projected to form an image. The reflective modulation element L6 can be a digital micromirror device (DMD), and the total internal reflection lens L7 can be a TIR device. It is evident that projection optical systems in related technologies typically incorporate multiple lenses to optimize the quality of the laser emitted from the optomechanical system, thereby achieving higher contrast in the projected image. However, combined with... Figure 1 The aforementioned design in related technologies usually results in a large size of the projection optical system, making it difficult to miniaturize the projection optical system.

[0037] To further simplify optical systems, a single diffractive optical element (DOE) can replace some or more lenses. A DOE integrates multiple optical functions into a single element, reducing the number of required optical components and thus simplifying optical path design. For example, a DOE can simultaneously perform beam shaping, beam splitting, and focusing, avoiding the use of multiple traditional optical elements and making the projection optical system more compact. Furthermore, the flat and thin nature of DOEs makes them a preferred solution for projection optical systems that prioritize compactness. Compared to traditional refractive optical elements, DOEs are significantly smaller and lighter, contributing to the lightweighting and miniaturization of projection optical systems. Figure 2 and Figure 3 As shown, Figure 2 for Figure 1 The diagram shows a schematic of the projection optics system using DOE elements. Figure 3 for Figure 2 The diagram shows the structure of a DOE element. It is evident that by replacing some lenses with diffractive optical elements (DOEs), the size of the projection optical system is significantly reduced.

[0038] DOEs possess multiple stepped microstructures of varying heights. When laser light is irradiated onto a DOE, in addition to generating the desired target diffraction pattern, the microstructures on the DOE surface also produce higher-order diffraction patterns. (See also...) Figure 4 and Figure 5 As shown, Figure 4 For the light of the related technology Figure 3The diagram shows the structure of the target diffraction image and the higher-order diffraction image behind the DOE element. Figure 5 For light to pass through Figure 2 The diagram illustrates the propagation paths of the target diffracted light and higher-order diffracted light in a projection optics system of the related technology. These higher-order diffracted lights undergo uncontrolled refraction and reflection within the system, such as... Figure 5 The long dashed line in the middle represents the target diffracted light, and the short dashed lines around it represent higher-order diffracted light. It can be seen that the higher-order diffracted light, because its propagation direction is peripheral to the target diffracted light, is more diffuse, causing it to be repeatedly reflected by the total internal reflection lens L7 and undergo uncontrollable refraction and reflection within the system before finally entering the lens. As explained above, a higher contrast ratio indicates a stronger contrast between light and dark areas of the image. Therefore, it is understandable that the uncontrolled refraction and reflection of higher-order diffracted light within the system and its entry into the lens will obviously affect the brightness of the projected black level, thus affecting the contrast of the projected image.

[0039] Based on this, this application provides a projection optical system and projection device that can reduce the probability of higher-order diffraction rays participating in projection imaging, thereby improving the contrast of the projected image of the projection optical system.

[0040] See Figure 6 As shown, Figure 6 This is a schematic diagram of the structure of a projection optical system 100 that changes the polarization state of the emitted light from the third laser 13 in one embodiment of this application.

[0041] The projection optical system 100 provided in this application includes a light source assembly 10, a diffractive optical assembly, a polarizing beam splitter 30, a reflective modulation element 40, a first polarizing element 50, a second polarizing element 14, and a lens 70. The light source assembly 10 emits linearly polarized light. The second polarizing element 14 is disposed on the light-emitting side of the light source assembly 10 and is used to convert the polarization state of at least a portion of the emitted light from the light source assembly 10, so that the polarization state of the emitted light from the light source assembly 10 is unified into a first polarized state ray that is incident on the diffractive optical assembly. In some embodiments, the first polarized state ray 91 can be S-polarized light or P-polarized light, where the electric field vibration direction of S-polarized light is perpendicular to the incident plane, and the electric field vibration direction of P-polarized light is parallel to the incident plane.

[0042] The diffractive optical component is located on the light-emitting side of the light source assembly 10. By designing the diffractive optical component, it is possible to simultaneously perform beam shaping, beam splitting, and focusing functions on the light emitted from the light source assembly 10. Specifically, the diffractive optical component can be designed to perform beam shaping, beam splitting, or focusing, or it can be designed to perform at least two of these multiple functions. The specific functions that the diffractive optical component needs to perform on the light emitted from the light source assembly 10 can be designed according to specific requirements, and will not be elaborated further here.

[0043] The polarization beam splitter 30 is used to receive light emitted from the diffraction optical component, and the polarization beam splitter 30 is configured to reflect the first polarized light 91 and transmit the second polarized light 92. In some embodiments, the second polarized light 92 is either S-polarized light or P-polarized light, which is different from the first polarized light 91. When the first polarized light 91 is S-polarized light, the second polarized light 92 is P-polarized light; when the first polarized light 91 is P-polarized light, the second polarized light 92 is S-polarized light.

[0044] The reflective modulation element 40 is used to receive light reflected from the polarization beam splitter 30, primarily for spatial modulation of the light to form an image. In some embodiments, the reflective modulation element 40 can be configured as a digital micromirror device (DMD). The DMD receives digital signals from a computer or other device to control the deflection state of each micromirror. The deflection state of each micromirror determines the direction of light reflection, thereby affecting the light intensity. This enables spatial modulation of the light to form an image. Furthermore, by controlling the deflection time of the micromirrors, i.e., the frequency at which the micromirrors switch between on and off states, different grayscale levels of light intensity modulation can be achieved. In other words, time modulation technology enables the DMD to generate high-resolution images. Specifically, light passing through the on-state micromirrors is reflected into the projection light path, forming bright pixels, while light passing through the off-state micromirrors is reflected into the non-projection light path, forming dark pixels.

[0045] The first polarization element 50 is disposed between the polarization beam splitter 30 and the reflective modulation element 40. The first polarized light 91, reflected by the polarization beam splitter 30, travels back and forth to the first polarization element 50 and is then reflected by the reflective modulation element 40, converting into a second polarized light 92. The lens is used to receive the light reflected by the reflective modulation element 40 and transmitted through the polarization beam splitter 30.

[0046] After passing through the second polarization element 14, the first polarized light ray 91 is spatially modulated by the diffraction optical component and then incident on the polarization beam splitter 30. The polarization beam splitter 30 reflects the received first polarized light ray 91 back to the first polarization element 50. The first polarization element 50 converts the first polarized light ray 91 into a third polarized light ray 93, which then propagates to the reflective modulation element 40. The third polarized light ray 93, after passing through the reflective modulation element 40, is converted into a fourth polarized light ray 94 and reflected back to the first polarization element 50. The fourth polarized light ray 94, after passing through the first polarization element 50, is converted into a second polarized light ray 92. Thus, the first polarized light ray 91 travels back and forth between the first polarization element 50 and is reflected by the reflective modulation element 40, converting into a second polarized light ray 92. The second polarized light ray 92 is reflected and propagates to the polarization beam splitter 30, passes through the polarization beam splitter 30, and finally propagates to the lens 70, from which it is projected onto the screen to form a projected image.

[0047] It is understandable that when the first polarized ray 91 is S-polarized light, the second polarized ray 92 is P-polarized light, the third polarized ray 93 is either left-handed or right-handed polarized light, and the fourth polarized ray 94 is either right-handed or left-handed polarized light, different from the polarization state of the third polarized ray 93. The specific polarization states of the third polarized ray 93 and the fourth polarized ray 94 can be adjusted by the type and specific structure of the first polarizing element 50, which will not be elaborated here. (See reference...) Figure 6 and in conjunction with reference Figure 7 As shown, Figure 7 This diagram illustrates the polarization state change of light rays passing through the projection optical system 100 when the outgoing light after passing through the second polarization element 14 is S-polarized light, according to one embodiment of this application. The S-polarized light, after passing through the second polarization element 14, is incident on the polarization beam splitter 30 after passing through the diffraction optical component. The polarization beam splitter 30 reflects the received S-polarized light to the first polarization element 50, which converts the S-polarized light into left-handed polarized light. The left-handed polarized light is then reflected by the reflective modulation element 40 and converted into right-handed polarized light. Alternatively, the first polarization element 50 converts the S-polarized light into right-handed polarized light, and the left-handed polarized light is reflected by the reflective modulation element 40 and converted into left-handed polarized light. The light then passes through the first polarization element 50 and is converted into P-polarized light. Thus, the S-polarized light travels back and forth between the first polarization element 50 and is reflected by the reflective modulation element 40, converting it into P-polarized light. The P-polarized light is reflected and propagates to the polarization beam splitter 30, passes through the polarization beam splitter 30, and finally propagates to the lens 70, from which it is projected onto the screen to form a projected image.

[0048] When the first polarized ray 91 is P-polarized, the second polarized ray 92 is S-polarized, and the third polarized ray 93 is either left-handed or right-handed polarized. The third polarized ray 93 is either right-handed or left-handed polarized, with a polarization state different from that of the fourth polarized ray 94. (See also...) Figure 6 Combined with reference Figure 8 As shown, Figure 8 This is a schematic diagram illustrating the polarization state change of P-polarized light emitted after passing through the second polarization element 14 in one embodiment of this application, as it passes through the projection optical system 100. The P-polarized light emitted after passing through the second polarization element 14 is incident on the polarization beam splitter 30 after passing through the diffraction optical component. The polarization beam splitter 30 reflects the received P-polarized light to the first polarization element 50. The first polarization element 50 converts the P-polarized light into a third polarization state ray 93, which is left-handedly polarized. This left-handedly polarized light is then reflected by the reflective modulation element 40 and converted into a fourth polarization state ray 94, which is right-handedly polarized. Alternatively, the first polarization element 50 converts the P-polarized light into a third polarization state ray 93, which is right-handedly polarized, and then reflects by the reflective modulation element 40 and converted into a fourth polarization state ray 94, which is left-handedly polarized. In other words, the third polarization state ray 93 and the fourth polarization state ray 94 are not limited to specific left-handed or right-handedly polarized light, but are specifically determined by the design of the first polarization element 50. Subsequently, the fourth polarized light 94 is converted into S-polarized light after passing through the first polarization element 50. Thus, the P-polarized light travels back and forth to the first polarization element 50 and is reflected by the reflective modulation element 40, converting into S-polarized light. The S-polarized light is reflected and propagates to the polarization beam splitter 30, passes through the polarization beam splitter 30, and finally propagates to the lens 70, from which it is emitted onto the screen to form a projected image.

[0049] The projection optical system 100 of this application, after passing through the second polarization element 14, emits a first polarized light 91, which is then diffracted by a diffraction optical component. The effective imaging light ray of the first polarized light 91 can be reflected by the polarization beam splitter 30 onto the first polarization element 50, then onto the reflective modulation element 40, and after being reflected by the reflective modulation element 40, it is converted into a second polarized light 92 by the first polarization element 50 and emitted through the polarization beam splitter 30. (See also...) Figure 9 As shown, Figure 9This is a schematic diagram of the target diffracted light image 101 and the higher-order diffracted light image 102 in one embodiment of this application. The higher-order diffracted light, which is a first-polarized light 91 and has a diffraction order higher than the effective imaging light, is reflected by the polarization beam splitter 30 and ends up outside the range of the first polarization element 50. Therefore, this portion of light cannot be converted into a second-polarized light 92, and thus cannot exit from the polarization beam splitter 30 into the lens 70. It can be understood that in the above design of this application, the light that ultimately enters the lens 70 is the modulated light transmitted through the polarization beam splitter 30. Because the higher-order diffracted light is in the first polarization state, it cannot enter the lens 70, and therefore will not affect the imaging effect of the light emitted from the lens 70, especially the impact on image contrast. That is, this application helps to reduce the probability of higher-order diffracted light participating in projection imaging, and helps to improve the contrast of the projected image of the projection optical system 100. At the same time, using diffractive optical components to shape the light also eliminates the need for compound eye lenses and other optical components, which is beneficial to the miniaturization of the projection optical system 100.

[0050] In some embodiments, the first polarizing element 50 may be a quarter-wave plate. In this case, whether the third polarized ray 93 is left-handed or right-handed polarized can be adjusted by changing the fast axis direction of the quarter-wave plate and the rotation angle of the quarter-wave plate, thereby changing the angle between the polarization direction of the incident light and the fast axis of the wave plate. When the angle is +45° (clockwise), the emitted third polarized ray 93 is left-handed circularly polarized. When the angle is -45° (counterclockwise), the emitted third polarized ray 93 is right-handed circularly polarized.

[0051] In some embodiments, the first polarization element 50 may also employ a liquid crystal on silicon (LCOS) 51 instead of a quarter-wave plate to achieve the function of converting the polarization state of light. LCOS can dynamically change the polarization state of light through changes in the arrangement of liquid crystal molecules, thereby enabling the conversion of light from a first polarization state to a second polarization state. Compared to the traditional optical elements that change the polarization state of light, LCOS is a reflective imaging technology with high light utilization efficiency, reaching over 40%, while traditional optical elements have lower light utilization efficiency. Furthermore, the transistors and driving circuits of LCOS are located within the silicon substrate, not occupying surface area, thus resulting in higher resolution and aperture ratio, achieving higher image quality than traditional optical elements. Simultaneously, LCOS can not only change the polarization state of light but also achieve phase and amplitude modulation of light through the arrangement of liquid crystal molecules, providing richer optical modulation functions.

[0052] When using an LCOS to change the polarization state of light, a compensation plate 41 can be used in conjunction with the LCOS to adjust the polarization state of the light. The compensation plate 41 is used to compensate for the phase of the light, thus solving the phase difference problem that may occur during the polarization state conversion process of the LCOS. Through the compensation plate 41, the polarization state of the light can be optimized, making the polarization state of the emitted light more stable and consistent. Therefore, by working together with the LCOS and the compensation plate 41, the utilization rate of light can be improved while ensuring that the polarization state of the emitted light meets the requirements.

[0053] See Figure 10 As shown, Figure 10 This is a schematic diagram of the projection optical system 100 in one embodiment of this application, employing a liquid crystal on silicon (LCOS) 51 and a compensation plate 41. The first polarized light 91, emitted after passing through the second polarization element 14, such as P-polarized light, is spatially modulated by the diffraction optical component and then incident on the polarization beam splitter 30. The polarization beam splitter 30 reflects the received first polarized light 91 to the compensation plate 41. The compensation plate 41 converts the first polarized light 91 into a third polarized light 93, which then propagates to the LCOS. The third polarized light 93, after passing through the LCOS, is converted into a fourth polarized light 94 and reflected back to the compensation plate 41. The fourth polarized light 94, after passing through the compensation plate 41, is converted into a second polarized light 92. Thus, the first polarized light 91 travels back and forth between the compensation plate 41 and is reflected by the LCOS, converting into the second polarized light 92. The second polarized light 92 is reflected and propagates to the polarization beam splitter 30, passes through the polarization beam splitter 30, and finally propagates to the lens 70, from which it is emitted onto the screen to form a projected image.

[0054] For example, if the LCOS can only function as an 8 / 1 wave plate, then the compensator 41 can also function as an 8 / 1 wave plate. Thus, the LCOS is a reflective design, allowing it to function as a half-wave plate in conjunction with the compensator 41. As light travels back and forth between the LCOS and the compensator 41, the first polarization state can be converted to the second polarization state. For example, when the first polarization state ray 91 is P-polarized, the second polarization state ray 92 is S-polarized, and the phase difference between them is π. The P-polarized light emitted after passing through the second polarization element 14 is incident on the polarization beam splitter 30 after passing through the diffraction optical component. The polarization beam splitter 30 reflects the received P-polarized light to the first polarization element 50. The first polarization element 50 converts the P-polarized light into a third polarization state ray 93. The third polarization state ray 93 is delayed in phase by π / 4 compared to the first polarization state ray 91. The third polarization state ray 93 is reflected by the reflective modulation element 40 and converted into a fourth polarization state ray 94. The fourth polarization state ray 94 is delayed in phase by π / 2 compared to the third polarization state ray 93. The fourth polarization state ray 94 is converted into a second polarization state ray 92 by the first polarization element 50. The second polarization state ray 92 is delayed in phase by π compared to the fourth polarization state ray 94. Thus, the second polarization state ray 92 is delayed in phase by π compared to the first polarization state ray. The conversion of the first polarization state ray 91 into the second polarization state ray 92 is achieved by LCOS and compensation plate 41.

[0055] In some embodiments, multiple lasers 1 emitting different colors of laser light can be used. These laser sources have advantages such as good monochromaticity, high brightness, and long lifespan. Furthermore, the polarization state of the light emitted by each laser 1 can be set to be the same. Alternatively, different lasers 1 can be set to emit light with different polarization states, and the polarization state of the laser light emitted by the lasers 1 can be adjusted by a component capable of adjusting the polarization state of the light, such as a second polarization element 14, so that multiple lasers 1 emit light with the same polarization state.

[0056] In some embodiments, the diffractive optical component includes a diffractive optical element 20 (DOE) that spatially modulates the first polarized light 91 emitted after passing through the second polarization element 14. Based on parameters such as the wavelength and intensity distribution of the light emitted from the light source component 10, and parameters such as the shape, size, and uniformity of the target light spot or projected image, the phase distribution of the DOE can be calculated using methods such as the Gerchberg-Saxton algorithm (GS algorithm) and the Yang-Gu algorithm (YG algorithm). Due to the periodicity of the phase, the phase of the DOE can be compressed to the range of [0, 2π]. The phase distribution of the DOE is then transformed into step-like microstructures with different heights, and these are processed to form the corresponding DOE. The diffractive optical element 20 (DOE) integrates multiple optical functions, avoiding the use of multiple traditional optical elements. This helps to reduce the size of the projection optical system 100, making it more compact and contributing to the lightweighting and miniaturization of the projection optical system 100.

[0057] In some embodiments, see Figure 6 and in conjunction with reference Figure 7 , Figure 8 and Figure 10 As shown, the polarization beam splitter 30 has a polarization combining surface 31, which is configured to reflect a first polarized ray 91 and transmit a second polarized ray 92. When the first polarized ray 91 is S-polarized light and the second polarized ray 92 is P-polarized light, the polarization combining surface 31 is configured to reflect S-polarized light and transmit P-polarized light. Correspondingly, when the first polarized ray 91 is P-polarized light and the second polarized ray 92 is S-polarized light, the polarization combining surface 31 is configured to reflect P-polarized light and transmit S-polarized light.

[0058] The orthographic projections of the reflective modulation element 40 and the first polarization element 50 onto the polarization combining surface 31 both fall on the polarization combining surface 31. The receiving surfaces of the reflective modulation element 40 and the first polarization element 50 are relatively small compared to the polarization combining surface 31, allowing for more precise reception and reflection of the target diffracted light reflected by the polarization combining surface 31. This also reduces scattering and loss of the target diffracted light, thereby improving its utilization rate. Simultaneously, the smaller receiving surface helps reduce stray light generation, especially reducing the reception of higher-order diffracted light around the target diffracted light. This allows more of the higher-order diffracted light in the first polarization state reflected by the polarization combining surface 31 to propagate to the periphery of the reflective modulation element 40 and the first polarization element 50, preventing it from converting back and forth between the first polarization element 50 and the reflective modulation element 40 into a second polarization state. It is understood that the higher-order diffracted light incident on the periphery of the reflective modulation element 40 and the first polarization element 50 is still in the first polarization state and cannot pass through the polarization beam splitter 30 to enter the lens 70. This can effectively reduce the amount of higher-order diffracted light entering the lens 70, which is beneficial to improving the contrast and image quality of the generated image.

[0059] In some embodiments, a coating process can be used to deposit a multilayer dielectric film on the lens, which can reflect light of the first polarization state 91 and transmit light of the second polarization state 92. By utilizing the alternating superposition of high-refractive-index and low-refractive-index materials, combined with the characteristics of interference effect and Brewster angle, light of a specific polarization state can be selectively reflected or transmitted, so that the coated polarization beam splitter 30 can effectively separate S-polarized light and P-polarized light. Using a coating process to deposit film layers to separate light of different polarization states can achieve a high extinction ratio, improve the separation accuracy of light of different polarization states, optimize the transmittance and reflectance of light of different polarization states, reduce light loss during beam splitting, and improve light energy utilization.

[0060] In some embodiments, continue reading Figure 6 and in conjunction with reference Figure 7 , Figure 8 and Figure 10As shown, the orthographic projection of the first polarizing element 50 onto the reflective modulation element 40 falls within the outline of the reflective modulation element 40. This design facilitates the effective and comprehensive reception and reflection of the target diffracted light incident on the reflective modulation element 40 after passing through the first polarizing element 50, thereby improving the utilization rate of the target diffracted light and enhancing the quality of the projected image. Furthermore, the relatively smaller radial dimension of the first polarizing element 50 compared to the reflective modulation element 40 further facilitates the filtering of higher-order diffracted light surrounding the target diffracted light. It can be understood that even if higher-order diffracted light in a first polarization state is reflected by the polarizing beam splitter 30 and propagates towards the first polarizing element 50 and the reflective modulation element 40, due to the relatively small radial dimension of the first polarizing element 50, some of the higher-order diffracted light will directly incident on the reflective modulation element 40 without passing through the first polarizing element 50. In this case, the higher-order diffracted light remains in a first polarization state and cannot pass through the polarizing beam splitter 30 to be projected into the lens 70. This clearly facilitates further filtering of stray light, especially higher-order diffracted light. That is, setting the radial dimension of the first polarization element 50 to be smaller than the radial dimension of the reflective modulation element 40 is beneficial to make full use of the target diffracted light, improve the quality of the projected image, and further filter out higher-order diffracted light, thereby further improving the contrast of the projected image.

[0061] In some embodiments, see Figure 6 and Figure 11 As shown, the orthographic projection of the first polarizing element 50 onto the reflective modulation element 40 is spaced apart from the outline of the reflective modulation element 40, and the orthographic projection of the reflective modulation element 40 onto the polarization combining surface 31 is spaced apart from the outline of the polarization combining surface 31. It should be noted that this refers to the orthographic projection of the first polarizing element 50 onto the reflective modulation element 40 being spaced apart from the outline of the effective region 42 of the reflective modulation element 40; specifically, it means that the radial dimension of the effective region 42 is larger than the radial dimension of the first polarizing element 50. Through this spacing, most of the higher-order diffracted light can be filtered out successively, improving the purity of the target diffracted light incident on the lens 70, which is beneficial for improving the contrast of the projected image.

[0062] After the first polarized light 91 emitted from the second polarizing element 14 is spatially modulated by the diffractive optical component, both the target diffracted light and some higher-order diffracted light are in the first polarization state. Both the target diffracted light and some higher-order diffracted light in the first polarization state are incident on the polarizing beam splitter 30. The polarizing beam splitter 30 reflects the received first polarized light 91 towards the first polarizing element 50. The first polarizing element 50 converts the target diffracted light in the first polarization state into a third polarization state light 93, which then propagates to the reflective modulation element 40. The portion of the higher-order diffracted light in the first polarization state that is farther from the target diffracted light in the middle cannot be incident on the first polarizing element 50 and the reflective modulation element 40. This portion of higher-order diffracted light cannot be reflected by the reflective modulation element 40 to the polarizing beam splitter 30 and cannot enter the lens 70. Furthermore, since this portion of higher-order diffracted light is in the first polarization state, even if it is repeatedly reflected within the optical system, it still cannot pass through the polarizing beam splitter 30 to enter the lens 70, thus not affecting the contrast of the projected image. The portion of the target diffracted light that is relatively close to the center of the higher-order diffracted light in the first polarization state is incident on the reflective modulation element 40, but cannot be incident on the first polarization element 50. Even if this portion of the higher-order diffracted light is reflected by the reflective modulation element 40, it is still in the first polarization state, so it still cannot pass through the polarization beam splitter 30 into the lens 70, and therefore will not affect the contrast of the projected image.

[0063] The first polarizing element 50 converts the target diffracted light in the first polarization state into a third polarization state ray 93, which then propagates to the reflective modulation element 40. The third polarization state ray 93, after passing through the reflective modulation element 40, is converted into a fourth polarization state ray 94 and reflected back to the first polarizing element 50. The fourth polarization state ray 94, after passing through the first polarizing element 50, is converted into a second polarization state ray 92. Thus, the first polarization state ray 91 travels back and forth between the first polarizing element 50 and the reflective modulation element 40, and is then converted into a second polarization state ray 92. The second polarization state ray 92 passes through the polarizing beam splitter 30 and finally propagates to the lens 70, from which it exits onto the screen to form a projected image. Therefore, the arrangement of the first polarizing element 50, the reflective modulation element 40, and the polarizing beam splitter 30 in this application can successively filter out most of the higher-order diffracted light, improving the purity of the target diffracted light incident on the lens 70, reducing the amount of higher-order diffracted light entering the lens 70, and reducing the impact on the brightness contrast of the target diffracted light within the lens 70, thereby effectively improving the contrast of the projected image.

[0064] In some embodiments, see Figure 6 and Figure 11As shown, the reflective modulation element 40 includes an effective region 42 and an ineffective region 43. The effective region 42 is used for spatial modulation of the received target diffracted light, and the ineffective region 43 is disposed around the effective region 42 to perform functions such as protecting the effective region 42. In some embodiments, the ineffective region 43 can be subjected to an extinction process, which includes, but is not limited to, operations such as blackening or frosting. This ensures that most of the higher-order diffracted light incident on the ineffective region 43 is absorbed by the ineffective region 43 and cannot undergo uncontrolled reflection within the projection optical system 100, thereby helping to reduce stray light generation, improve the brightness contrast of the target diffracted light, and improve the contrast of the projected image of the target diffracted light.

[0065] In some embodiments, the projection optical system 100 further includes a baffle disposed on the periphery of the reflective modulation element 40, for absorbing the higher-order diffracted light in the first polarization state reflected by the polarization beam splitter 30 to the periphery of the reflective modulation element 40, reducing the back-and-forth reflection of this portion of the higher-order diffracted light within the projection optical system 100, weakening its influence on the target diffracted light, and thereby improving the contrast of the target diffracted light projection image.

[0066] In some embodiments, see Figure 6 As shown, the light source assembly 10 includes at least two lasers 1 arranged side by side, wherein at least one laser 1 is used to emit light with a first polarization state 91, and the other at least one laser 1 is used to emit light with a second polarization state 92. This application uses lasers 1 to emit a laser light source, taking advantage of the advantages of laser light sources such as good monochromaticity, high brightness, and long lifespan. Furthermore, with the increase in the power of lasers 1, lasers 1 are gradually replacing conventional light sources. In projection equipment, lasers 1 are used as projection light sources, gradually replacing mercury lamp illumination. The application of lasers 1 is relatively mature and stable, providing a stable light source. Compared to LED light sources, lasers 1 also have the advantages of small optical spread and high brightness. Using different lasers 1 can emit light with different polarization states, allowing for flexible selection of lasers 1 by considering factors such as lifespan and luminous intensity, thus improving the flexibility of laser 1 usage.

[0067] The second polarization element 14 is disposed on the light-emitting side of the laser 1 used to emit light rays 92 in the second polarization state, and is configured to convert the light rays 92 in the second polarization state into light rays 91 in the first polarization state. In this way, even if different lasers 1 emit lasers with different polarization states, the light rays emitted by the laser 1 can be converted into light rays of the same polarization state by the second polarization element 14, so that the target diffracted light rays are all converted into light rays in the first polarization state 91, and then enter the lens 70 after passing through the polarization beam splitter 30, the first polarization element 50 and the reflective modulation element 40, and are emitted from the lens 70 to form a projected image.

[0068] It is understandable that the different polarization states of lasers of different colors typically affect the quality of light during propagation. For example, the blue and green lasers emitted by the blue and green semiconductor laser 1 are S-polarized light, with their polarization direction perpendicular to the incident plane. This polarization state can reduce reflection loss and improve light utilization efficiency in optical systems. Red light is typically P-polarized light, with its polarization direction parallel to the incident plane. This polarization state of red light allows for better coordination with optical components, such as polarization beam splitters, to achieve efficient light transmission and modulation. Therefore, to obtain higher quality red, green, and blue light, the polarization states of the lasers emitted by the three lasers 1 are usually different. Thus, this application provides a second polarization element 14 to adjust the laser emitted by the corresponding color laser 1, making its polarization state the same as that of the lasers emitted by other colors laser 1. This helps to maintain the original advantages of the laser 1 while obtaining light with the same polarization state, resulting in a light source with higher utilization and transmission efficiency.

[0069] In some embodiments, multiple lasers 1 can be configured to emit lasers with the same polarization state to meet actual design requirements and achieve better light utilization and contrast. No further limitations are imposed here.

[0070] In some embodiments, the specific polarization states of the first polarized ray 91 and the second polarized ray 92 are not limited, as long as the polarization planes of the first polarized ray 91 and the second polarized ray 92 are perpendicular to each other, and the corresponding second polarization element 14 is a half-wave plate and the first polarization element 50 is a quarter-wave plate.

[0071] The second polarized light 92 emitted from the laser 1, used to emit the second polarized light beam 92, is converted into a first polarized light beam 91 after a phase delay of π / 2 by the second polarization element 14. This first polarized light beam 91 is then reflected by the polarization beam splitter 30 to the first polarization element 50, and after a phase delay of π / 4 by the first polarization element 50, it is incident on the reflective modulation element 40. The reflective modulation element 40 reflects the light back to the first polarization element 50, where the phase is again delayed by π / 4, converting it into the second polarized light beam 92. This light then passes through the polarization beam splitter 30 and exits through the lens 70 for projection imaging. Thus, the polarization conversion of the light emitted from the laser 1 can be achieved through the combination of a half-wave plate and a quarter-wave plate. This method is simple in structure, low in cost, and the polarization conversion of the half-wave plate and quarter-wave plate is highly stable, which helps improve the stability of the projected light and the quality of the projected image.

[0072] In some embodiments, continue reading Figure 6 As shown, and in conjunction with reference Figure 11 As shown, Figure 11This is a schematic diagram of the structure of a projection optical system 100 that changes the polarization state of the emitted light from the first laser 11 and the second laser 12 in one embodiment of this application. The light source assembly 10 includes a first laser 11, a second laser 12, and a third laser 13. The first laser 11 is a red laser for emitting P-polarized light. When the P-polarized red light is used in conjunction with the polarization beam splitter 30 and the reflective modulation element 40, it can effectively reduce red light glare during propagation. At the same time, red light itself has high brightness and penetrability. Combined with the characteristics of P-polarized light, it can provide higher brightness, thereby significantly improving light utilization and projection image quality.

[0073] The second laser 12 is a blue laser that emits S-polarized light, and the third laser 13 is a green laser that emits S-polarized light. Thus, both S-polarized blue and S-polarized green light help reduce glare during propagation, improve image clarity, and enrich details in both bright and dark areas, thereby enhancing image contrast.

[0074] Furthermore, blue light has a shorter wavelength and is easily absorbed and scattered. Using S-polarized blue light is beneficial to further enhance the filtering effect of blue light. It can be understood that if there is a position opposite to blue light in the dark part of the projected image, the filtering effect of S-polarized blue light is better, which can make the dark part opposite to blue light in the projected image darker, thereby further improving the contrast of the image.

[0075] In some embodiments, see Figure 6As shown, the first polarized light 91 can be S-polarized light. In this case, the second polarization element 14 is a half-wave plate located on the output side of the first laser 11. The polarization beam splitter 30 reflects the S-polarized light and transmits the P-polarized light. When the first polarized light 91 is S-polarized light, the second polarized light 92 is P-polarized light. The P-polarized red light emitted from the first laser 11 is converted into S-polarized red light by the second polarization element 14, making the red light have the same polarization state as the blue and green light, all of which are S-polarized. Then, the S-polarized red, blue, and green mixed light is incident on the polarization beam splitter 30. The polarization beam splitter 30 reflects the received S-polarized red, blue, and green mixed light to the first polarization element 50. The first polarization element 50 converts the S-polarized red, blue, and green mixed light into a third polarization state. The red, blue, and green mixed light of the third polarization state propagates to the reflective modulation element 40. After passing through the reflective modulation element 40, the red, blue, and green mixed light of the fourth polarization state is converted into red, blue, and green mixed light of the fourth polarization state and reflected back to the first polarization element 50. After passing through the first polarization element 50, the red, blue, and green mixed light of the fourth polarization state is converted into red, blue, and green mixed light of the P polarization state. The P polarization state red, blue, and green mixed light is reflected and propagated to the polarization beam splitter 30, and after passing through the polarization beam splitter 30, it finally propagates to the lens 70 and is emitted from the lens 70 onto the screen to form a projected image. Among them, the red, blue, and green mixed light of the third polarization state is left-handed or right-handed polarized light with a phase delay of π / 4 relative to the red, blue, and green mixed light of the S polarization state. The red, blue, and green mixed light of the fourth polarization state is polarized light with a phase difference of π from the red, blue, and green mixed light of the third polarization state. For example, if the mixed light of red, blue and green in the third polarization state is left-handed polarized, then the mixed light of red, blue and green in the fourth polarization state is right-handed polarized. If the mixed light of red, blue and green in the third polarization state is right-handed polarized, then the mixed light of red, blue and green in the fourth polarization state is left-handed polarized.

[0076] In some embodiments, see Figure 11As shown, the first polarized light 91 can be P-polarized light. In this case, the second polarization element 14 is a half-wave plate located on the output side of the second laser 12 and the third laser 13. The polarization beam splitter 30 reflects the P-polarized light and transmits the S-polarized light. When the first polarized light 91 is P-polarized light, the second polarized light 92 is S-polarized light. The S-polarized blue and green light emitted from the second laser 12 and the third laser 13 are converted into P-polarized blue and green light by the second polarization element 14, so that the blue and green light have the same polarization state as the red light, which is P-polarized. Then, the P-polarized red, blue and green mixed light is incident on the polarization beam splitter 30. The polarization beam splitter 30 reflects the received P-polarized red, blue and green mixed light to the first polarization element 50. The first polarization element 50 converts the P-polarized red, blue and green mixed light into P-polarized light. The red, blue, and green mixed light in the third polarization state is converted to a fourth polarization state and propagates to the reflective modulation element 40. After passing through the reflective modulation element 40, the third polarization state red, blue, and green mixed light is converted to a fourth polarization state red, blue, and green mixed light and reflected back to the first polarization element 50. The fourth polarization state red, blue, and green mixed light then passes through the first polarization element 50 and is converted to an S-polarization state red, blue, and green mixed light. This S-polarization state red, blue, and green mixed light is reflected and propagates to the polarization beam splitter 30, passes through the polarization beam splitter 30, and finally propagates to the lens 70, from which it is projected onto the screen to form a projected image. The third polarization state red, blue, and green mixed light is left- or right-handed polarized light with a phase delay of π / 4 relative to the P-polarization state red, blue, and green mixed light. The fourth polarization state red, blue, and green mixed light is polarized light with a phase difference of π from the third polarization state red, blue, and green mixed light. For example, if the mixed light of red, blue and green in the third polarization state is left-handed polarized, then the mixed light of red, blue and green in the fourth polarization state is right-handed polarized. If the mixed light of red, blue and green in the third polarization state is right-handed polarized, then the mixed light of red, blue and green in the fourth polarization state is left-handed polarized.

[0077] In some embodiments, see Figure 6 and Figure 11 As shown, the light source assembly 10 includes at least two lasers 1 arranged side by side, and the diffractive optical assembly includes at least two diffractive optical elements 20 (DOEs). The at least two diffractive optical elements 20 are correspondingly disposed on the light-emitting side of the at least two lasers 1. Each diffractive optical element 20 can independently shape the laser emitted from its corresponding laser 1, which helps to ensure good uniformity of each laser beam, thereby improving the beam quality of the entire projection optical system 100. Furthermore, equipping each laser 1 with an independent diffractive optical element 20 allows for customization based on the characteristics of different lasers 1 and application requirements. This enables more precise adjustment of the direction of each laser beam, allowing them to converge or propagate in parallel better in the subsequent optical path, improving the beam pointing accuracy and stability.

[0078] In some embodiments, the method is not limited to setting up a diffractive optical element 20 and a laser 1. Depending on the actual application requirements, the same diffractive optical element 20 can be set up for two or more lasers 1 to use together. No further restrictions are imposed here.

[0079] In some embodiments, in conjunction with reference Figure 4 , Figure 5 , Figure 6 , Figure 9 and Figure 11 As shown, the light emitted by the diffractive optical component includes a first diffracted ray and a second diffracted ray. The diffraction order of the second diffracted ray is higher than that of the first diffracted ray. On a plane perpendicular to the light path, the second diffracted ray is positioned around the first diffracted ray, and the position of the first polarizing element 50 corresponds to the first diffracted ray. It can be understood that the first diffracted ray is the target diffracted light required to form the target diffracted light image 101, and the second diffracted ray is the higher-order diffracted light required to form the higher-order diffracted light image 102.

[0080] like Figure 4 and Figure 9 As shown, the higher-order second diffracted light is more diffused around the first diffracted light. The second diffracted light is repeatedly reflected within the projection optical system 100, and uncontrollable refraction and reflection inevitably occur. If this part of the second diffracted light that has undergone uncontrollable refraction and reflection enters the lens 70, it will affect the brightness of the projected black field, and will inevitably affect the contrast of the projected image of the first diffracted light within the lens 70.

[0081] See also Figure 5 It is evident that optical systems used for projection in related technologies often struggle to filter out higher-order diffraction light. Furthermore, higher-order diffraction light is easily reflected repeatedly by the total internal reflection lens L7 and undergoes uncontrollable refraction and reflection within the system, eventually entering the lens 70 and affecting the brightness of the projected black field, thereby affecting the contrast of the projected image.

[0082] In this application, the position of the first polarizing element 50 corresponds to the first diffracted ray, see reference. Figure 6As shown, the first diffracted light in the first polarization state smoothly enters the first polarization element 50 and undergoes polarization conversion, ultimately converting into second polarization state light 92. This allows it to smoothly pass through the polarization beam splitter 30 and be projected onto the image through the lens 70. The second diffracted light of a higher diffraction order propagates around the first diffracted light and reaches the periphery of the first polarization element 50, but most of it cannot enter the first polarization element 50 for polarization conversion. Therefore, the second diffracted light of a higher diffraction order is still mostly in the first polarization state 91 and cannot pass through the polarization beam splitter 30 and be projected onto the image through the lens 70. Thus, this application effectively filters out the second diffracted light of a higher diffraction order, significantly reducing the impact of high-diffraction-order light on the brightness of the projected black field, thereby improving the contrast of the projected image.

[0083] In some embodiments, the first diffracted ray, or target diffracted ray, is the positive and negative first-order diffracted ray after passing through the diffractive optical element 20. The positive and negative first-order diffracted ray typically has high diffraction efficiency and can be effectively collected and utilized by the optical elements of the projection optical system 100, thereby forming a clear image during the projection process. The second diffracted ray, or higher-order diffracted ray, is the diffracted ray with a higher diffraction order than the positive and negative first-order diffracted ray after passing through the diffractive optical element 20, such as positive and negative second-order and positive and negative third-order diffracted ray. These higher-order diffracted ray typically has lower diffraction efficiency and may produce unwanted halos or interference in the projection optical system 100. This application can effectively filter out most of these rays, improve the clarity of the projected image, and enhance image contrast.

[0084] It should be noted that the target diffracted light is not limited to only the positive and negative first-order diffracted light, and the higher-order diffracted light is the diffracted light with a higher diffraction order than the positive and negative first-order diffracted light. Specifically, the diffractive optical element 20, the corresponding reflective modulation element 40, and the first polarization element 50 can be adjusted according to the needs of projection imaging. For example, at least one of the positive and negative second-order and positive and negative third-order diffracted light can be utilized in the same way. No further restrictions are imposed here.

[0085] In some embodiments, see Figure 6 and Figure 11 As shown, the projection optical system 100 also includes a beam combining component, which is located on the light-emitting side of the diffractive optical components and is used to combine the light rays emitted from at least two diffractive optical elements 20 and project them onto the polarization beam splitter 30. Combining multiple beams facilitates high light integration, simplifies the optical path, and enables miniaturization of the projection optical system 100. Furthermore, the beam combining component effectively combines beams, reduces light energy loss, enhances beam intensity, and improves the system's light energy utilization efficiency. It also facilitates the realization of optical functions after beam combining, such as spatial modulation of the light rays through a reflective modulation element 40 to form an image.

[0086] In some embodiments, the beam combiner can employ a beam-splitting prism. When light from different directions is incident on the beam-splitting prism, the prism's beam-splitting film reflects and transmits the light, thereby combining the light incident from different directions into a single beam. The beam combiner can also utilize the diffraction effect, designing a diffractive optical element 20 to combine multiple beams into one, while simultaneously achieving beam shaping and energy distribution. The beam combiner can also employ other lenses, dichroic filters, or fiber optic couplers, etc., to combine the light rays emitted from at least two diffractive optical elements 20 and then project them onto the polarizing beam-splitting element 30. No further limitations are imposed here.

[0087] In some embodiments, see Figure 6 and Figure 11 As shown, the light source assembly 10 includes a first laser 11, a second laser 12, and a third laser 13 that emit different colors. The diffraction optical assembly includes a first diffraction optical element 21 opposite to the first laser 11, a second diffraction optical element 22 opposite to the second laser 12, and a third diffraction optical element 23 opposite to the third laser 13. By having the three diffraction optical elements 20 correspondingly positioned on the light-emitting side of the three lasers, the laser light emitted from each laser 1 can be shaped, ensuring good uniformity in each laser beam, thereby improving the beam quality of the entire projection optical system 100.

[0088] In some embodiments, a first laser 11 may emit red light, a second laser 12 may emit blue light, and a third laser 13 may emit green light. A first diffractive optical element 21, a second diffractive optical element 22, and a third diffractive optical element 23 may correspond to the first laser 11, the second laser 12, and the third laser 13, respectively. The first diffractive optical element 21 is constructed by calculating its phase distribution using methods such as the Gerchberg-Saxton algorithm (GS algorithm) and the Yang-Gu algorithm (YG algorithm) based on parameters such as the wavelength and intensity distribution of the light emitted by the first laser 11, as well as parameters such as the shape, size, and uniformity of the target light spot or projected image. The phase of the first diffractive optical element 21 is compressed to the range [0, 2π], and then its phase distribution is transformed into a stepped microstructure with different heights, thus forming the corresponding first diffractive optical element 21.

[0089] Correspondingly, the second diffractive optical element 22 is calculated based on parameters such as the wavelength and intensity distribution of the light emitted by the second laser 12, as well as parameters such as the shape, size, and uniformity of the target light spot or projected image. The phase distribution of the second diffractive optical element 22 can be calculated using methods such as the Gerchberg-Saxton algorithm (GS algorithm) and the Yang-Gu algorithm (YG algorithm). The phase of the second diffractive optical element 22 is compressed to the range of [0, 2π], and then the phase distribution of the second diffractive optical element 22 is transformed into a stepped microstructure with different heights, and the corresponding second diffractive optical element 22 is formed.

[0090] Correspondingly, the third diffractive optical element 23 is calculated based on parameters such as the wavelength and intensity distribution of the light emitted by the third laser 13, as well as parameters such as the shape, size, and uniformity of the target light spot or projected image. The phase distribution of the third diffractive optical element 23 can be calculated using methods such as the Gerchberg-Saxton algorithm (GS algorithm) and the Yang-Gu algorithm (YG algorithm). The phase of the third diffractive optical element 23 is compressed to the range of [0, 2π], and then the phase distribution of the third diffractive optical element 23 is transformed into a stepped microstructure with different heights, and the corresponding third diffractive optical element 23 is formed.

[0091] Continue reading Figure 6 and Figure 11 As shown, the light combining assembly includes a first dichroic filter 61, a second dichroic filter 62, and a third dichroic filter 63. By using these three dichroic filters for light combining, the light emitted from the first diffractive optical element 21, the second diffractive optical element 22, and the third diffractive optical element 23 is combined into a single beam. The dichroic filters can precisely and selectively reflect or transmit light of specific wavelengths according to their wavelength, thereby achieving efficient light combining of different wavelengths while filtering out stray light of unnecessary wavelengths, which helps improve beam quality. Compared to traditional filters, dichroic filters reflect unwanted wavelengths instead of absorbing them, which reduces energy loss and allows the desired wavelengths of light to be combined more brightly and efficiently, resulting in a clearer and brighter projected image and improved contrast.

[0092] The third dichroic filter 63 is used to reflect the light emitted from the third diffractive optical element 23 toward the second dichroic filter 62. The third dichroic filter 63 can be disposed on the light-emitting side of the third diffractive optical element 23 and tilted relative to the light-emitting direction of the third diffractive optical element 23. In this way, the third dichroic filter 63 faces the third diffractive optical element 23 and the second dichroic filter 62, thereby reflecting the light emitted from the third diffractive optical element 23 to the second dichroic filter 62.

[0093] The second dichroic filter 62 is used to reflect the light emitted from the second diffractive optical element 22 toward the first dichroic filter 61 and to transmit the light emitted from the third diffractive optical element 23. The second dichroic filter 62 is located on the light-emitting side of the second diffractive optical element 22, and the light-emitting direction of its reflected light is the same as the light-emitting direction of its transmitted light. In this way, the light emitted from the transmitted third diffractive optical element 23 and the light emitted from the reflected second diffractive optical element 22 can be combined into a single beam of light.

[0094] The first dichroic filter 61 is used to reflect the light emitted from the first diffractive optical element 21 toward the polarizing beam splitter 30, while allowing the light emitted from the second diffractive optical element 22 and the third diffractive optical element 23 to pass through. Correspondingly, the first dichroic filter 61 is disposed on the light-emitting side of the first diffractive optical element 21, and the light-emitting direction of its reflected light is the same as the light-emitting direction of its transmitted light. In this way, the light emitted from the first diffractive optical element 21 and the light emitted from the second diffractive optical element 22 and the third diffractive optical element 23 can be combined into a single beam of light.

[0095] In some embodiments, the dichroic filter includes a transmissive and reflective side, which can be formed by applying a transmissive and reflective film layer to the dichroic filter using a coating technology. This allows the dichroic filter to transmit light of a corresponding wavelength and reflect light of the wavelength that needs to be reflected. The use of a robust coating technology and the use of durable materials give the dichroic filter superior resistance to damage and fading, and it is less susceptible to environmental factors such as humidity and temperature fluctuations, thereby improving the long-term operational stability of the light combining component.

[0096] In some embodiments, for example, the transmissive and reflective surfaces of the third dichroic filter 63 can be arranged to face the third diffractive optical element 23 and the second dichroic filter 62, and the transmissive and reflective surfaces of the third dichroic filter 63 are at a 45° angle to the direction of the light emitted from the third diffractive optical element 23. The transmissive and reflective surfaces of the second dichroic filter 62 are arranged to face the second diffractive optical element 22 and the first dichroic filter 61, and the transmissive and reflective surfaces of the second dichroic filter 62 are at a 45° angle to the direction of the light emitted from the second diffractive optical element 22. The transmissive and reflective surfaces of the first dichroic filter 61 are arranged to face the first diffractive optical element 21 and the polarizing beam splitter 30, and the transmissive and reflective surfaces of the first dichroic filter 61 are at a 45° angle to the direction of the light emitted from the second diffractive optical element 22. This achieves light combining and satisfies the above-mentioned angles, allowing for installation according to the angles without repeated adjustments of the dichroic filters, thus improving installation convenience.

[0097] In some embodiments, see Figure 12 and Figure 13 As shown, Figure 12 This is a schematic diagram of the structure of the light source assembly 10 with each row of lasers 1 arranged adjacent to each other in one embodiment of this application. Figure 13 For light to pass through Figure 12The diagram shows the structure of the light source assembly 10. The first laser 11 includes multiple first laser chips 111, the second laser 12 includes multiple second laser chips 121, and the third laser 13 includes multiple third laser chips 131. The light combining assembly combines the lasers emitted from the three lasers.

[0098] In some embodiments, the brightness ratio of the laser emitted by the corresponding laser 1 can be changed by altering the number of laser chips in the corresponding laser 1, thereby making the brightness of lasers of different colors more balanced. For example, if the first laser chip 111 emits red light, the second laser chip 121 emits blue light, and the third laser chip 131 emits green light, then increasing the number of the first laser chip 111 will increase the brightness and proportion of red light.

[0099] In some embodiments, a first laser 11, a second laser 12, and a third laser 13 may be arranged side-by-side along a first direction, and multiple corresponding laser chips of the laser 1 may be arranged sequentially along a second direction. Figure 12 The substrate 15 shown is arranged in an array to form the light source. At this time, multiple first lasers 11, multiple second lasers 12 and multiple third lasers 13 are all arranged in an array.

[0100] At this point, the number of the first laser 11 is increased, such as... Figure 12 and 13 As shown, the method of adding a column of first laser chips 111 can be adopted. The first laser 11 is equipped with two columns of first laser chips 111, which increases the brightness of the light emitted by the first laser 11.

[0101] In some embodiments, see Figure 14 As shown, Figure 14 This is a schematic diagram of a structure in one embodiment of the present application in which the first laser 11, the second laser 12, and the third laser 13 are located on different substrates 15. Two first lasers 11 can be disposed on the same substrate 15, while an adjacent second laser 12 and a third laser 13 can be disposed on another substrate 15. This allows for flexible arrangement and combination of the first laser 11 with the other two lasers.

[0102] Alternatively, the first laser 11, the second laser 12, and the third laser 13 can be located on different substrates 15, that is, different lasers 1 can be located on different substrates 15, which can effectively improve the flexibility of the arrangement and combination of different lasers 1. Alternatively, the first laser 11 can be located on the same substrate 15 as one of the second laser 12 and the third laser 13, while the other is located on a separate substrate 15. It should be noted that all of the above-mentioned possible embodiments require arranging and combining multiple substrates 15 to form the entire light source.

[0103] In some embodiments, such as Figure 14 As shown, the multiple first laser chips 111 of the first laser 11 are packaged through the first housing 16, the multiple second laser chips 121 of the second laser 12 are packaged through the second housing 17, and the multiple third laser chips 131 of the third laser 13 are packaged through the third housing 18. The design can be customized according to actual needs, and no further restrictions are imposed here.

[0104] It should be noted that in some embodiments, multiple substrates 15 are arranged to form the entire light source. If lasers 1 of different colors are independently packaged in a row, such as... Figure 14 As shown, lasers 1 of the same color need to be arranged sequentially along the second direction so that the dichroic color filter can combine lasers of different colors.

[0105] In some embodiments, see Figure 6 As shown, the projection optical system also includes a focusing lens 80, which is disposed between the third dichroic filter 63 and the polarizing beam splitter 30. The focusing lens 80 is used to focus the mixed light after it has been combined by the beam combining component, control the shape and divergence angle of the beam, and thus optimize the distribution of the beam in the target area.

[0106] In some embodiments, other optical elements may be added between the third dichroic filter 63 and the polarizing beam splitter 30 to modulate light, and the focusing lens 80 may be replaced with other optical elements as needed, without further restrictions.

[0107] In some embodiments, continue reading Figure 6 and Figure 11 As shown, the light source assembly 10 and the reflective modulation element 40 are oriented in the same direction. The first dichroic color filter 61, the second dichroic color filter 62 and the third dichroic color filter 63 are parallel to each other and all inclined to the light emission direction of the light source assembly 10. The multiple dichroic color filters are parallel to each other and inclined to the light emission direction of the light source assembly 10, which makes the optical path more compact and helps to reduce the size and weight of the optical system.

[0108] like Figure 6 and Figure 11 The reflective modulation element 40 is located on the side of the polarization beam splitter 30 facing the light source assembly 10. By utilizing the reflection function of the reflective modulation element 40 and the reflection function of the polarization beam splitter 30, the polarization conversion of light is achieved, which helps to make the optical path more compact, reduces the size and weight of the optical system, and facilitates the miniaturization of the projection optical system 100.

[0109] The polarization combining surface 31 of the polarization beam splitter 30 is inclined to the first polarization element 50. In the direction from the light source assembly 10 to the reflective modulation element 40, the polarization combining surface 31 is opposite to the first dichroic filter 61. Thus, the beam combined by the first dichroic filter 61 smoothly enters the polarization beam splitter 30 and is incident on the polarization combining surface 31. Furthermore, the relative arrangement of the polarization beam splitter 30 and the first dichroic filter 61 can reduce the scattering and reflection of the beam when passing through these elements, thereby improving the stability and efficiency of the beam.

[0110] See Figure 15 As shown, Figure 15 This is a schematic diagram of the structure of a projection device according to one embodiment of this application. This application also provides a projection device including the projection optical system 100 described in any of the above embodiments. The projection device further includes a housing 110, within which the projection optical system 100 is housed. The projection device employing the above-described projection optical system 100 has the following advantages: higher-order diffracted light in the projection optical system 100 can be effectively reduced, which helps to improve the contrast of the projected image and enhance the quality of the projected image. The projection optical system 100 uses diffractive optical elements 20 and optimizes the optical path design, making the optical elements in the projection optical system 100 more compact, thus reducing the size of the projection device.

[0111] The projection optical system 100 and projection device of this application achieve polarization conversion of the light emitted from the light source assembly 10 through diffractive optical components, polarization beam splitting element 30, reflective modulation element 40, and first polarization element 50. This polarization conversion filters out most of the higher-order diffracted light, reducing the amount of higher-order diffracted light entering the lens 70, thereby improving the contrast of the image projected through the lens 70, reducing the impact on the brightness of the dark field, and thus improving the contrast of the projected image. Simultaneously, this application optimizes the optical path design through the positional design of the dichroic filter, reflective modulation element 40, and polarization beam splitting element 30. While utilizing the reflection functions of the reflective modulation element 40 and the polarization beam splitting element 30 to achieve polarization conversion of light, it also facilitates a more compact optical path, reducing the size and weight of the optical system and contributing to the miniaturization of the projection optical system 100. The projection optical system 100 and projection device of this application also have advantages such as better light utilization, higher light transmission efficiency, and higher light transmission stability. They also have the advantages of reducing light glare during propagation, improving image clarity, and making the bright and dark details of the image richer. Therefore, the projection optical system 100 and projection device of this application have high projection quality.

[0112] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0113] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A projection optical system, characterized in that, include: Light source assembly for emitting linearly polarized light; A diffractive optical component is disposed on the light-emitting side of the light source component; A polarization beam splitter is used to receive light emitted from the diffractive optical component, and the polarization beam splitter is configured to reflect light of a first polarization state and transmit light of a second polarization state. A reflective modulation element is used to receive the light reflected by the polarization beam splitter; A first polarization element is disposed between the polarization beam splitter and the reflective modulation element, wherein light rays of the first polarization state reflected by the polarization beam splitter travel back and forth to the first polarization element and are converted into light rays of the second polarization state after being reflected by the reflective modulation element; A second polarizing element is disposed on the light-emitting side of the light source assembly. The second polarizing element is used to convert the polarization state of at least a portion of the emitted light from the light source assembly, so that the polarization state of the emitted light from the light source assembly is unified into a first polarization state light that strikes the diffractive optical assembly; and, A lens for receiving light reflected by the reflective modulation element and transmitted through the polarizing beam splitter.

2. The projection optical system according to claim 1, characterized in that, The polarization beam splitter has a polarization combining surface, which is configured to reflect light of a first polarization state and transmit light of a second polarization state. The orthogonal projections of the reflective modulation element and the first polarization element onto the polarization combining surface both fall on the polarization combining surface.

3. The projection optical system according to claim 2, characterized in that, The orthographic projection of the first polarizing element onto the reflective modulation element falls within the outline of the reflective modulation element.

4. The projection optical system according to claim 3, characterized in that, The orthographic projection of the first polarizing element onto the reflective modulation element is spaced apart from the outline of the reflective modulation element, and the orthographic projection of the reflective modulation element onto the polarization combining surface is spaced apart from the outline of the polarization combining surface.

5. The projection optical system according to claim 1, characterized in that, The light source assembly includes at least two lasers arranged side by side, wherein at least one laser is used to emit light in a first polarization state and the other at least one laser is used to emit light in a second polarization state. The second polarization element is disposed on the light-emitting side of the laser used to emit light in the second polarization state and is configured to convert the light in the second polarization state into light in the first polarization state.

6. The projection optical system according to claim 5, characterized in that, The polarization planes of the first polarized ray and the second polarized ray are perpendicular to each other; the second polarization element is a half-wave plate, and the first polarization element is a quarter-wave plate; and / or, The light source assembly includes a first laser, a second laser, and a third laser. The first laser is a red laser that emits P-polarized light, the second laser is a blue laser that emits S-polarized light, and the third laser is a green laser that emits S-polarized light. The first polarized light is S-polarized light, and the second polarization element is a half-wave plate disposed on the light-emitting side of the first laser; or, The first polarized light is P-polarized light, and the second polarization element is a half-wave plate disposed on the light-emitting side of the second laser and the third laser.

7. The projection optical system according to claim 1, characterized in that, The light source assembly includes at least two lasers arranged side by side, and the diffractive optical assembly includes at least two diffractive optical elements, with each of the at least two diffractive optical elements corresponding to the light-emitting side of the at least two lasers.

8. The projection optical system according to claim 7, characterized in that, The light emitted by the diffractive optical component includes a first diffractive ray and a second diffractive ray. The diffraction order of the second diffractive ray is higher than that of the first diffractive ray. On a plane perpendicular to the light path, the second diffractive ray is arranged around the first diffractive ray. The position of the first polarizing element corresponds to the first diffractive ray.

9. The projection optical system according to claim 7, characterized in that, The projection optical system further includes a light combining component, which is located on the light-emitting side of the diffractive optical component and is used to combine the light rays emitted from at least two of the diffractive optical elements and project them onto the polarization beam splitter.

10. The projection optical system according to claim 9, characterized in that, The light source assembly includes a first laser, a second laser, and a third laser that emit different colors. The diffractive optical assembly includes a first diffractive optical element opposite to the first laser, a second diffractive optical element opposite to the second laser, and a third diffractive optical element opposite to the third laser. The light combining assembly includes a first dichroic filter, a second dichroic filter, and a third dichroic filter. The third dichroic filter reflects the light emitted from the third diffractive optical element toward the second dichroic filter. The second dichroic filter reflects the light emitted from the second diffractive optical element toward the first dichroic filter and allows the light emitted from the third diffractive optical element to pass through. The first dichroic filter reflects the light emitted from the first diffractive optical element toward the polarizing beam splitter and allows the light emitted from the second diffractive optical element and the third diffractive optical element to pass through.

11. A projection device, characterized in that, Includes the projection optical system as described in any one of claims 1-10.

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