Projection apparatus and projection system

Abstract

Disclosed in the present application are a projection apparatus and a projection system. The projection apparatus comprises: a laser light source, and diffractive optical elements, a magnification lens and a display element which are arranged in sequence along a light emission path of the laser light source. The laser light source comprises three types of light emission areas and three diffractive optical elements arranged corresponding to the three types of light emission areas, wherein laser wavelengths emitted from the three types of light emission areas are different; a laser beam emitted from each light emission area, after being diffracted by the diffractive optical element and incident onto the display element, forms a rectangular light spot, which matches an effective area of the display element, the long-side direction of the rectangular light spot being parallel to the slow-axis direction of the laser beam emitted from said light emission area.

Description

Projection equipment and projection system

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410939717.6, filed on July 12, 2024, entitled "A Projection Device," the entire contents of which are incorporated herein by reference; and to Chinese Patent Application No. 202421874983.7, filed on August 5, 2024, entitled "A Projection Device and Projection System," the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of projection technology, and more particularly to a projection device and projection system. Background Technology

[0004] Laser projection display technology, also known as laser projection technology or laser display technology, is a technology that uses lasers as a light source for projection display. Laser projection can realistically reproduce the rich and vibrant colors of the objective world, providing a more stunning expressive effect. Its color gamut coverage can reach more than 90% of the color space that the human eye can perceive, which is more than twice the color gamut coverage of traditional displays.

[0005] Currently, laser projection systems typically incorporate an illumination system on the light-emitting side of the laser source for shaping and homogenization. This illumination system usually includes a light guide or compound eye to homogenize the light, followed by a relay system to reshape the light spot. The complex structure of the illumination system results in a large overall optical engine size, failing to meet the requirements for miniaturization. Furthermore, the complexity of the optical system also leads to low luminous efficiency. Summary of the Invention

[0006] This application provides a projection device, including:

[0007] A laser source for emitting three-color lasers; the laser source includes: three types of light-emitting regions and three diffractive optical elements corresponding one-to-one with the three types of light-emitting regions, wherein the lasers emitted from the three types of light-emitting regions have different wavelengths;

[0008] A magnification lens, located on the light-emitting side of the diffractive optical element, is used to change the size of the laser spot; and

[0009] A total internal reflection prism is located between the magnification lens and the display element; the total internal reflection prism is used to reflect the light emitted from the magnification lens to the display element and transmit the light emitted from the display element.

[0010] Wherein, the laser beam emitted from the light-emitting region forms a rectangular spot when it is diffracted by the diffractive optical element and then incident on the display element. The long side of the rectangular spot is parallel to the slow axis direction of the laser beam emitted from the light-emitting region.

[0011] This application also provides a projection system, including:

[0012] A projection device, wherein the projection device is the aforementioned projection device;

[0013] The projection screen is located on the light-emitting side of the projection device. Attached Figure Description

[0014] Figure 1 is a schematic diagram of the overall architecture of the projection device provided in the embodiment of this application;

[0015] Figure 2 is a schematic diagram of one of the projection devices provided in the embodiments of this application;

[0016] Figure 3 is one of the schematic diagrams showing the arrangement of the laser chip provided in the embodiments of this application;

[0017] Figure 4 is a second schematic diagram of the arrangement of the laser chip provided in the embodiment of this application;

[0018] Figure 5 is a schematic diagram of the laser spot emitted by the laser chip provided in the embodiment of this application;

[0019] Figure 6 is a schematic diagram of the laser spot emitted by the laser provided in the embodiment of this application;

[0020] Figure 7 is a schematic diagram of the laser spot emitted from the light-emitting region provided in the embodiment of this application;

[0021] Figure 8 is one of the schematic diagrams showing the correspondence between the light-emitting region and the diffractive optical element provided in the embodiments of this application;

[0022] Figure 9 is one of the schematic diagrams of light spot changes provided in the embodiments of this application;

[0023] Figure 10 is one of the schematic diagrams showing the positional correspondence between the display element and the rectangular light spot provided in the embodiment of this application;

[0024] Figure 11 is a second schematic diagram showing the positional correspondence between the display element and the rectangular light spot provided in the embodiment of this application;

[0025] Figure 12 is a third schematic diagram showing the positional correspondence between the display element and the rectangular light spot provided in the embodiment of this application;

[0026] Figure 13 is a second schematic diagram of the light spot change provided in the embodiment of this application;

[0027] Figure 14 is a second schematic diagram showing the correspondence between the light-emitting region and the diffractive optical element provided in the embodiments of this application;

[0028] Figure 15 is a third schematic diagram showing the correspondence between the light-emitting region and the diffractive optical element provided in the embodiments of this application;

[0029] Figure 16 is one of the schematic diagrams of the imaging principle provided in the embodiments of this application;

[0030] Figure 17 is a second schematic diagram of the structure of the projection device provided in the embodiment of this application;

[0031] Figure 18 is a second schematic diagram of the imaging principle provided in the embodiment of this application;

[0032] Figure 19 is a third schematic diagram of the projection device provided in the embodiment of this application;

[0033] Figure 20 is a third schematic diagram of the imaging principle provided in the embodiment of this application;

[0034] Figure 21 is a schematic diagram of the total internal reflection optical path principle provided in the embodiment of this application;

[0035] Figure 22 is a fourth structural schematic diagram of the projection device provided in the embodiment of this application;

[0036] Figure 23 is a schematic diagram of the projection system provided in an embodiment of this application. Detailed Implementation

[0037] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the application will be further described below in conjunction with the accompanying drawings and embodiments. However, the exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the figures denote the same or similar structures, and therefore repeated descriptions of them will be omitted. Terms describing position and direction described in this application are illustrative based on the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this application. The accompanying drawings of this application are for illustrating relative positional relationships only and do not represent actual scale.

[0038] Projection display is a method or device that uses a planar image information to control a light source, and utilizes an optical system and projection space to magnify and display the image on a projection screen. With the development of projection display technology, projection displays are gradually being applied to business activities, conferences and exhibitions, scientific education, military command, traffic management, centralized monitoring, and advertising and entertainment. Its advantages, such as large display size and clear display, are also suitable for the requirements of large-screen displays.

[0039] Projection devices can be based on a digital light processing (DLP) architecture, with a digital micromirror device (DMD) as the core component. The light emitted from the projection light source is incident on the DMD to generate an image, and then the image light generated by the DMD is incident on the projection lens, which then forms an image, which is finally received by the projection screen.

[0040] Figure 1 is a schematic diagram of the overall architecture of the projection device provided in the embodiment of this application.

[0041] As shown in Figure 1, the projection device may include: a projection light source 10, an illumination system 20, and a projection lens 30. The projection light source 10, the illumination system 20, and the projection lens 30 may also be collectively referred to as an optical engine.

[0042] The projection light source 10 is used to provide illumination, and the color gamut, overall brightness, and other characteristics of the projected image are all affected by the projection light source 10. In specific implementations, the projection light source 10 can be a mercury lamp, a light-emitting diode (LED), or a laser light source.

[0043] The lighting system 20 is located on the light-emitting side of the projection light source 10 and is used to shape and homogenize the light beam emitted from the projection light source 10. In addition, as shown in FIG1, the lighting system 20 includes a display element 201, which can be the DMD described above, and can modulate the incident light beam to form a display image.

[0044] The projection lens 30 is located on the light-emitting side of the lighting system 20, specifically on the light-emitting side of the display element 201, and is used to project the image formed by the display element 201 onto the projection surface to form an image of a size suitable for human eye viewing.

[0045] When the display element 201 uses a DMD, there are special requirements for the size and incident angle of the incident beam. Therefore, it is necessary to perform shaping and homogenization operations on the beam emitted from the projection light source 10 before it is incident on the display element 201. As shown in Figure 1, in order to achieve beam shaping and homogenization operations, it is necessary to set up a beam adjustment lens group 103, a homogenizing element 202, a focusing lens group 203, etc.

[0046] The beam adjustment lens group 103 can be a telescope lens group, which can perform beam reduction processing on the incident beam; the beam homogenizing element 202 can be a light guide or a compound eye lens group. In Figure 1, the beam homogenizing element 202 using a compound eye lens group is used as an example to illustrate the beam homogenizing element 202. The beam homogenizing element 202 is used to homogenize the incident beam. In order to meet the spot size and incident angle of the incident display element 201, a focusing lens group 203 is also required to focus the beam. After focusing, the projected beam can be incident on the display element 201 for modulation.

[0047] As shown in Figure 1, in order to meet the requirements of the incident light spot of the DMD in the projection device, multiple sets of lenses and light-diffusing elements need to be set in the optical path, which results in a large size of the entire optical engine, which cannot meet the requirements of miniaturization of the optical system.

[0048] In view of this, the embodiments of this application provide a diffractive optical element in the projection device. By utilizing the small size and high efficiency of the diffractive optical element, the multiple sets of lenses and light-diffusing elements set in the optical path can be omitted, thereby reducing the size of the projection device.

[0049] Specifically, as shown in Figure 2, the projection device includes: a laser light source, a magnification lens 203', a light-diffusing element 205, a total reflection prism 204, a display element 201, and a projection lens 30.

[0050] Laser light sources possess advantages such as good monochromaticity, high brightness, and long lifespan, making them ideal light sources. With the increasing power of lasers to meet the requirements of industrial applications, lasers are increasingly being used as lighting sources. In projection equipment, lasers are being used as projection light sources, gradually replacing mercury lamps. Furthermore, compared to LED light sources, lasers are widely used due to their smaller optical spread and higher brightness.

[0051] In this embodiment of the application, a diffractive optical element 104 is used in the laser source. Since the diffractive optical element 104 is sensitive to the wavelength and incident angle of the incident light, and the laser has a narrow half-peak width and high collimation, it is more suitable for use in the laser source.

[0052] As shown in Figure 2, the laser source can emit three-color lasers, specifically divided into three emission regions 101: the first emission region 101-1, the second emission region 101-2, and the third emission region 101-3. These three emission regions are used to emit lasers of different wavelengths. The three emission regions 101 can be different areas within a single laser capable of emitting three colors, or they can be three lasers emitting different colors; the specific distinction is not limited here.

[0053] The laser source also includes three diffractive optical elements 104, disposed on the light-emitting side of the three types of light-emitting regions 101, corresponding one-to-one with each of the three types of light-emitting regions 101. A diffractive optical element (DOE) is an optical element capable of altering the propagation characteristics of light. The diffractive optical element 104 has a relatively thin thickness and microstructures on at least one surface. The size of these microstructures is typically on the order of micrometers. These microstructures can change the phase of the incident light, thereby altering the light propagation path at a microscale, achieving beam shaping and homogenization.

[0054] The beam shaping principle of the diffractive optical element 104 is mainly based on the phenomena of light diffraction and interference. When a beam passes through the diffractive optical element 104, the microstructure of the element causes a change in the direction of light propagation. When different light waves meet in space, they interfere with each other. By precisely designing the microstructure of the diffractive optical element 104, the effects of diffraction and interference can be controlled, thereby achieving beam shaping.

[0055] Because a diffractive optical element 104 is provided on the light-emitting side of the laser source's emission region, the incident laser beam can be shaped and homogenized. Therefore, it is not necessary to set up more optical elements in the projection device for shaping and homogenizing the laser beam. As shown in Figure 2, the laser beams emitted from the three emission regions 101 of the laser source are combined after being diffracted by the diffractive optical element 104. The combined beam only needs to be focused onto the display element 201 by the magnification lens 203'. The projection lens projects the display image modulated by the display element 201 to obtain a larger-sized projected image.

[0056] As shown in Figure 2, by setting a diffractive optical element 104 in the laser source, lasers of different wavelengths are diffracted and shaped before light combining. After light combining, only the size of the combined beam needs to be adjusted to meet the illumination requirements of the display element. The optical path of the optical engine can omit multiple sets of lenses and light-diffusing elements, reducing the overall size of the optical engine and making the optical path simpler, which can meet the miniaturization design of projection devices.

[0057] This application uses a laser source capable of emitting three-color lasers as an example for illustration. As shown in Figures 3 and 4, the laser source may include multiple laser chips arranged in an array, divided into multiple first laser chips a1, multiple second laser chips a2, and multiple third laser chips a3; wherein, the first laser chip a1 is located in the first light-emitting region 101-1, the second laser chip a2 is located in the second light-emitting region 101-2, and the third laser chip a3 is located in the third light-emitting region 101-3.

[0058] In some embodiments, as shown in FIG3, the laser source can be an MCL laser, and the first laser chip a1, the second laser chip a2, and the third laser chip a3 are arranged in a 4×7 matrix along the first direction x and the second direction y. The number of the first laser chip a1 and the second laser chip a2 is less than the number of the third laser chip a3. The first laser chip a1 is arranged in one row along the first direction x, the second laser chip a2 is arranged in one row along the first direction, and the third laser chip a3 is arranged in two rows along the first direction.

[0059] In some embodiments, as shown in FIG4, the laser source can be a NUBB laser or a NUMB laser, and the first laser chip a1, the second laser chip a2, and the third laser chip a3 are arranged in an array along the first direction x and the second direction y. The number of the first laser chip a1 and the second laser chip a2 is less than the number of the third laser chip a3. The first laser chip a1 and the second laser chip a2 are arranged in a row along the first direction x, and the third laser chip a3 is arranged in a row along the first direction.

[0060] The lasers mentioned above are all semiconductor lasers. Due to issues such as materials and efficiency, a larger number of red laser chips are usually required. Therefore, the third laser chip a3 can be a red laser chip, the second laser chip a2 can be a green laser chip, and the first laser chip a1 can be a blue laser chip.

[0061] It is worth noting that the arrangement of laser chips shown in Figures 3 and 4 is only for illustrative purposes. In practical applications, there are no restrictions on the types of laser chips included in the laser, the wavelength of the laser emitted by each type of laser chip, the number of each type of laser chip, or their arrangement.

[0062] As shown in Figure 5, laser chip a can be composed of multiple stacked semiconductor layers. The laser beam emitted from it has different divergence angles in different directions, resulting in an elliptical laser spot B in the far field. The major axis of the ellipse corresponds to a plane parallel to the stacked structure of the laser chip (i.e., the plane formed by the first direction x and the second direction y), and the minor axis corresponds to the stacking direction of the laser chip (i.e., the third direction z in Figure 5). The divergence angle of the laser emitted from laser chip a along the plane parallel to the stacked structure is greater than the divergence angle along the stacking direction. Therefore, the major axis of the ellipse can be called the fast axis direction k1 of the laser, and the minor axis direction can be called the slow axis direction k2 of the laser.

[0063] As shown in Figure 6, the laser does not emit laser light directly from the laser chip a. Instead, a reflecting prism f is placed on the emitting side of the laser chip a. The laser light emitted from the laser chip a is incident on the reflecting prism f and reflected back to the laser's output port. Furthermore, the laser also has multiple collimating lenses t, each corresponding to a laser chip a, at the output port. These collimating lenses t are used to collimate the laser beam reflected by the reflecting prism f. Since the laser has a larger divergence angle in the fast axis direction k1, the collimating lenses t are typically designed to accommodate this divergence angle. This results in the laser beam having a smaller divergence angle in the fast axis direction k1 than in the slow axis direction k2 after passing through the collimating lenses t.

[0064] As shown in Figures 3 and 4, the same type of laser chips are usually arranged along the first direction x. Therefore, the slow axis of the laser emitted from the laser output port is parallel to the first direction x, and the fast axis is parallel to the second direction y.

[0065] Taking the laser shown in Figure 3 as an example, the laser beams emitted from the three types of emission regions can form a laser spot array as shown in Figure 7 at the emission port. Specifically, the laser beam emitted from the first laser chip a1 forms the first laser spot B1 at the emission port, the laser beam emitted from the second laser chip a2 forms the second laser spot B2 at the emission port, and the laser beam emitted from the third laser chip a3 forms the third laser spot B3 at the emission port. Considering each emission region as a whole, the laser beam emitted from the first emission region 101-1 forms the first laser spot array BL1 at the emission port, the laser beam emitted from the second emission region 101-2 forms the second laser spot array BL2 at the emission port, and the laser beam emitted from the third emission region 101-3 forms the third laser spot array BL3 at the emission port. Each laser spot array can be considered as a larger spot. Since each laser spot has a larger divergence angle along the slow axis (i.e., the first direction x) and a smaller divergence angle along the fast axis (i.e., the second direction y), the laser spot array (the overall spot) formed at the laser's output port has a larger divergence angle along the first direction x than along the second direction y. Furthermore, the size of the spot formed by the entire laser spot array along the first direction x is also larger than the size along the second direction y.

[0066] Optical spread is related to beam area and beam solid angle. A larger beam solid angle means a larger beam divergence angle; a larger beam area means a larger spot size. For the laser used in the embodiments of this application, the overall spot formed by the laser emitted from each emission region has not only a larger divergence angle along the first direction x compared to the second direction y, but also a larger spot size. Therefore, the optical spread of the laser beam emitted from the laser along the first direction x is greater than the optical spread along the second direction y.

[0067] As shown in Figure 8, the three diffractive optical elements corresponding to the three types of light-emitting regions 101 are a first diffractive optical element 104-1, a second diffractive optical element 104-2, and a third diffractive optical element 104-3. Specifically, the first diffractive optical element 104-1 corresponds to the first light-emitting region 101-1, the second diffractive optical element 104-2 corresponds to the second light-emitting region 101-2, and the third diffractive optical element 104-3 corresponds to the second light-emitting region 101-3. The laser beam emitted from each light-emitting region still has a certain divergence angle. As the optical path increases, the divergence of the laser beam increases, and the size of the resulting spot also increases. Therefore, in this embodiment, the diffractive optical elements can be positioned close to their corresponding light-emitting regions to control the size of the diffractive optical elements from becoming excessively large.

[0068] As shown in Figure 9, for each light-emitting region 101, the diffractive optical element 104 can shape the laser beam emitted from its corresponding light-emitting region and image the emitted spot onto the display element 201. The spot formed by the light emitted from the diffractive optical element 104 and imaged onto the display element is referred to as the imaging spot of the diffractive optical element. The imaging spot of the diffractive optical element 104 has the same shape as the effective area of ​​the display element 201. When the display element 201 uses a DMD, the imaging spot of the diffractive optical element 104 is a rectangular spot CB with an aspect ratio of 16:9. The rectangular shape of the imaging spot of the diffractive optical element 104 means that the optical spread along the long side of the rectangular spot CB is greater than the optical spread along the short side of the rectangular spot CB. To better match the optical spread of the laser, diffractive optical element, and display element, the microstructure of the diffractive optical element can be designed so that the long side of the rectangular spot CB imaged at the display element 201 is parallel to the slow axis of the laser beam emitted from the light-emitting region 101, and the short side of the rectangular spot CB is parallel to the fast axis of the laser beam emitted from the light-emitting region 101. This not only improves the diffraction efficiency of the diffractive optical element but also enhances the optical efficiency of the entire optical system.

[0069] As shown in Figure 2, the laser beams emitted from the three types of light-emitting regions 101 of the laser source pass through their corresponding diffractive optical elements 104 and are then incident on the light-combining component 102 for light combining.

[0070] Taking the laser shown in Figure 3 as an example, when combining the laser light shown in Figure 3, the light combining component 102 may include a first light combining element 102-1, a second light combining element 102-2, and a third light combining element 102-3. The first light combining element 102-1 corresponds to the first light-emitting region 101-1, the second light combining element 102-2 corresponds to the second light-emitting region 101-2, and the third light combining element 102-3 corresponds to the third light-emitting region 101-3. The first beam combiner 102-1 reflects the laser emitted from the first light-emitting region 101-1 toward the second beam combiner 102-2. The second beam combiner 102-2 combines the laser emitted from the first light-emitting region 101-1 and the laser emitted from the second light-emitting region 101-2, and then emits them toward the third beam combiner 102-3. Finally, the third beam combiner 102-3 combines the laser emitted from the first light-emitting region 101-1, the second light-emitting region 101-2, and the third light-emitting region 101-3. In specific implementations, the first beam combiner 102-1 can be a reflector, and the second and third beam combiners 102-2 and 102-3 can be dichroic mirrors; no limitation is made here.

[0071] Before the laser beam emitted from each light-emitting region 101 of the laser source is incident on the beam combining component 102, it is shaped by the corresponding diffractive optical element 104. Therefore, the laser spots incident on the beam combining component 102 are all rectangular spots, and the long sides of the three rectangular spots are parallel to each other, and the short sides of the three rectangular spots are parallel to each other. The beam combining component 102 combines the three-color lasers along the second direction y. The three rectangular spots after beam combining overlap, and the centers of the three rectangular spots coincide.

[0072] As shown in Figure 2, the combined tri-color laser beam passes through magnification lens 203' and is focused onto the display element 201. A light-diffusing element 205 and a total reflection prism 204 are also disposed between magnification lens 203' and display element 201.

[0073] The magnification lens 203' is used to adjust the size of the combined light spot to better suit the size of the effective area of ​​the display element 201. Depending on the specifications of different display elements 201, the magnification lens 203' can be a convex lens or a concave lens, and no limitation is made here.

[0074] In some embodiments, the homogenizing element 205 can be at least one of a diffuser, a compound eye lens, a diffuser wheel, or a moving diffuser, located between the magnification lens 203' and the total internal reflection prism 204. The diffuser is used to homogenize the incident laser beam. The diffuser is located near the total internal reflection prism 204 and can be stationary or moving. The diffuser can be a flat plate with dispersed diffraction particles or frosted glass, which itself has a scattering effect on the incident light. Combined with its high-frequency movement, it can make the polarization direction of the emitted laser disordered, thereby improving the laser speckle problem. The diffuser can move along the long side of the rectangular diffraction spot or flip along the diagonal direction, which is not limited here. Alternatively, the homogenizing element 205 can also be a diffuser wheel, which is connected to a driving device and can rotate, thereby diversifying the polarization direction of the laser to improve the laser speckle problem.

[0075] The total internal reflection prism 204 can separate the illumination beam and the imaging beam. The total internal reflection prism 204 reflects the light emitted from the magnification lens 203' to the display element 201 and transmits the light emitted from the display element 201 after modulation to the projection lens 30 for projection imaging.

[0076] Both the diffractive optical element 104 and the magnification lens 203' have the function of imaging. When designing the diffractive optical element 104, ideally, the laser beam emitted from each light-emitting area 101 of the laser source can be fully homogenized after being diffracted by the diffractive optical element 104, forming a clear rectangular spot at the position of the display element 201 that completely coincides with the effective area of ​​the display element 201.

[0077] However, in practical applications, the diffraction efficiency of the diffraction optical element 104 cannot reach 100%. The laser beam after passing through the diffraction optical element still has a certain divergence angle. Considering the tolerance and other issues in the optical path, in the embodiment of this application, when designing three diffraction optical elements 104, the emitted beams of the three types of light-emitting regions 101 can be arranged so that the imaging light spots at the position of the display element 201 after passing through the three diffraction optical elements 104 are all rectangular light spots, and the size of the three rectangular light spots can be slightly larger than the effective area of ​​the display element 201.

[0078] In some embodiments, as shown in FIG10, the area of ​​the imaging spot (rectangular spot CB) of the diffractive optical element can be 10% to 20% larger than the area of ​​the effective region 201a of the display element. At the same time, the centers of the imaging spots of the three diffractive optical elements coincide and have overlapping regions, which can cover the effective region of the display element 201 to ensure uniform energy distribution and color distribution of the three-color laser beam incident on the display element 201.

[0079] For semiconductor red laser chips, the emitted laser beam has two light-emitting points. After being diffracted by the corresponding diffractive optical element 104, it will form two light spots CB1 and CB2 as shown in Figure 11 when it is incident on the display element. The two light spots are different in size, which makes the light intensity distribution in the effective area 201a of the display element uneven, which will affect the display effect.

[0080] To overcome this problem, as shown in Figure 12, the diffractive optical element 104 corresponding to the red laser chip can be specially designed to change the distribution of its microstructure, thereby changing the phase distribution of the incident laser and increasing the diffraction angle of the diffracted beam parallel to the long side of the rectangular spot. This increases the length of the long side of the rectangular spot formed by the red laser beam output by the diffractive optical element and thus increases the length of the long side of the spot CB1 and CB2 formed by the dual light-emitting points. The length of the overlapping area of ​​the two spots increases, so that the overlapping area can cover the effective area 201a of the display element, thus overcoming the problem of uneven energy distribution of the red laser spot incident on the effective area 201a of the display element.

[0081] The combined three-color laser beam still has a certain divergence angle. As the optical path increases, it cannot achieve the clearest image when incident on the display element 201. Therefore, a magnification lens 203' is placed between the beam combining assembly 102 and the display element 201. The display element 201 can be located within 5mm before and after the focal plane of the magnification lens 203'. After passing through the magnification lens 203', the image incident on the display element 201 is a rectangular spot with clear boundaries and uniform energy distribution. The diffuser can be located within the focal length range of the magnification lens 203' to further homogenize the combined laser beam before it is incident on the display element 201.

[0082] The following, in conjunction with Figure 13, will specifically explain the changes in the divergence, size, and shape of the laser beam emitted from the laser source after passing through the optical combining element in the optical path of the optical engine shown in Figure 2. Figure 10 takes the optical path of a type of light-emitting region 101 of the laser source as an example. The optical paths of other light-emitting regions are similar and can be referred to each other.

[0083] When the laser shown in Figure 3 is used, as shown in Figure 13, the laser emitted from the light-emitting region 101 will form 1×7 elliptical spots at position (1) before the incident diffractive optical element 104. Each elliptical spot is a spot formed by the laser beam emitted from a laser chip at the laser's exit port. The emitted light from the light-emitting region 101 can be regarded as a laser beam with a certain width. Then, the emitted light from each laser chip in the light-emitting region 101 can be regarded as a sub-beam. The sub-beams emitted from the light-emitting region 101 are separated from each other, and the divergence angle along the slow axis direction k2 is greater than the divergence angle along the fast axis direction k1. The energy distribution of the sub-beams is Gaussian.

[0084] When the 1×7 sub-beams emitted from the light-emitting region 101 are incident on the diffractive optical element 104 and after being diffracted by the diffractive optical element 104, the energy distribution of each sub-beam is homogenized, and the principal optical axes of each sub-beam emitted from the diffractive optical element 104 are parallel to each other. At the emission position (2) of the diffractive optical element 104, 1×7 mutually separated rectangular light spots are formed. After diffraction by the diffractive optical element 104, the divergence angles of each sub-beam emitted along the fast axis direction k1 and the slow axis direction k2 are reduced. However, after a certain optical path of propagation, the size of the rectangular light spot formed at position (2) is larger than the size of the elliptical light spot formed at position (1).

[0085] After the sub-beams emitted from the diffractive optical element 104 are combined by the beam combining component 102, 1×7 separate rectangular light spots are formed at position (3) between the beam combining component 102 and the beam combining lens 203' before the incident magnification lens 203'. After the beam combining, the principal optical axes of each sub-beam remain parallel to each other and the divergence angle remains unchanged, but the size of the rectangular light spots increases after a certain optical path.

[0086] When the combined sub-beams are incident on the magnification lens 203', they will be focused by the magnification lens 203'. The principal optical axes of the sub-beams are no longer parallel. During the process of propagating through the magnification lens 203' to the display element 201, the sub-beams converge or diverge and gradually approach each other. Finally, they merge into a rectangular light spot with a clear outline at the position (4) corresponding to the incident light surface of the display element 201. The energy distribution of the rectangular light spot is uniform and satisfies the flat-top distribution.

[0087] Finally, the display element 201 modulates the incident beam to form a display image and emits the modulated light towards the projection lens 30. At the far field position (5), the previously merged sub-beams gradually separate as the propagation distance increases, causing the outline of the light spot to gradually become blurred and the sharpness to deteriorate. At this time, it is also necessary to cooperate with the reasonable optical design of the projection lens to obtain a clear projection image on the projection surface.

[0088] The aforementioned changes in beam and spot size apply only to one type of light-emitting region 101; the changes in beam and spot size for the other two types of light-emitting regions are similar. It is worth noting that because the divergence angles and spot sizes of the red, green, and blue lasers are not the same, a clear and uniformly distributed three-color rectangular spot can be obtained on the incident surface of the display element 201. However, the sizes of the three rectangular spots are not the same; typically, the red spot is larger than the green spot, and the green spot is larger than the blue spot. As long as the centers of the three rectangular spots coincide and all cover the effective area of ​​the display element, a color-shift-free image display can be obtained.

[0089] In this embodiment, when the three emission regions of the laser source can be different regions of the same laser, a single diffractive optical element can be used, with each emission region designed separately. When the three emission regions of the laser source are three lasers emitting different wavelengths, three diffractive optical elements can be applied.

[0090] The microstructure on the surface of the diffractive optical element 104 is fabricated using semiconductor processing technology. The morphology, size, and refractive index of the surface of the diffractive optical element 104 all affect the phase of the light rays. In order to obtain an image with uniform energy distribution and clear contours at the location of the display element 201, the phase of the diffractive optical element needs to be precisely designed according to the input parameters of the incident beam and the output parameters of the outgoing beam.

[0091] The input parameters of the incident beam may include: the wavelength, beam quality, beam waist radius, and intensity distribution of the laser beam emitted from each laser chip when it is incident on the corresponding region of the corresponding diffractive optical element; the input parameters of the outgoing beam may include: the size of the laser spot when it is incident on the display element, the outgoing distance, the diffraction order, and the intensity distribution.

[0092] The design of diffractive optical elements can employ algorithms such as GS and YG to calculate the phase of the diffractive optical element. Due to the periodicity of the phase, the phase of the diffractive optical element can be compressed to [0, 2π]. However, limited by current processing capabilities, it is impossible to fabricate microstructures with continuous phases. Therefore, continuous phases can be subdivided into stepped microstructures with different heights.

[0093] The following is a detailed introduction to the design concept of phase distribution for diffractive optical elements using the GS algorithm. When the amplitude distributions of the input field (incident laser beam) and the target field (laser beam displaying the element's position) are known, and the initial phase can be chosen as random, a Fourier transform is performed on the initial phase and the input field amplitude to obtain the complex amplitude in the frequency domain. The phase is extracted from the frequency domain complex amplitude and added to it along with the target field amplitude. An inverse Fourier transform is then performed on the resulting complex amplitude to obtain the spatial domain complex amplitude. The phase is extracted from this complex amplitude and added to it along with the input field amplitude to obtain a new complex amplitude. A Fourier transform is then performed on this new complex amplitude to obtain the frequency domain complex amplitude. This process of iterating through the Fourier transforms yields the phase of the finally extracted spatial domain complex amplitude, which is the phase of the diffractive optical element.

[0094] In addition, other algorithms can be used to design the phase of diffractive optical elements. This application only uses the GS algorithm as an example. In practical applications, a reasonable method can be selected to design diffractive optical elements according to the requirements.

[0095] Since the projection device uses a laser light source, and lasers have strong coherence, laser speckle is prone to occur. In this embodiment, a diffractive optical element is set in the laser light source. The diffractive optical element can modulate the phase of the light. Therefore, the diffractive optical element can be designed to have an additional phase adjustment function in addition to the above-mentioned modulation function of the incident beam, thereby improving the problem of laser speckle.

[0096] In some embodiments, as shown in FIG14, the diffractive optical element includes a first region 104a and a second region 104b. The laser emitted from the light-emitting region 101 is out of phase by an odd multiple of π after passing through the first region 104a and the second region 104b of the corresponding diffractive optical element.

[0097] Laser light emitted from a laser source is typically polarized light. For example, red laser chips emit p-polarized light, while green and blue laser chips emit s-polarized light. Lasers emitted from the same type of laser chip have the same polarization direction and phase, resulting in strong coherence and a tendency to produce laser speckle during projection displays. To mitigate this issue, the diffractive optical element can be designed by dividing it into two regions. The phase distribution of the diffractive optical element must not only shape the incident laser beam into a rectangular spot of a set size with uniform energy distribution, but also ensure that the phase difference between the emitted light from the two regions is an odd multiple of π. This allows the polarization direction of the laser emitted from the first region to be perpendicular to that of the laser emitted from the second region. If the areas of the first and second regions are equal, then the polarization direction of half of the emitted light from the diffractive optical element can be made perpendicular to that of the other half, thus minimizing laser coherence and improving laser speckle formation.

[0098] In some embodiments, as shown in FIG15, the diffractive optical element includes a first region 104a and two second regions 104b, the two second regions 104b being located on both sides of the first region 104a along the first direction x (the direction of the long side of the rectangular spot). By dividing the second region 104b into two parts and designing them symmetrically on both sides of the first region 104a, the phase adjustment of the emitted laser can be symmetrically distributed, thereby better improving the laser speckle problem.

[0099] In some embodiments, a driving device can also be provided in the projection device. The driving device is connected to the diffractive optical element, and the driving device can drive the diffractive optical element 104 to vibrate along the first direction x (the direction of the long side of the rectangular light spot). For example, the diffractive optical element can perform reciprocating motion at a high frequency along the first direction x. Then, each time the outgoing light passes through the diffractive optical element, it can form an imaging light spot. The effect of superimposing the imaging light spots after multiple vibrations can be regarded as homogenizing the light spot. This can also make the phase distribution of the outgoing light in space more uniform, thereby improving the problem of laser speckle.

[0100] In some embodiments, the diffractive optical element can be designed such that the polarization direction of the laser emitted from the light-emitting region 101 is disordered after passing through the corresponding diffractive optical element 104. That is, after the phase distribution of the diffractive optical element satisfies a specific shaping and homogenization effect, a random phase is added to the diffractive optical element, thereby making the polarization direction of the emitted light disordered, destroying the strong coherence of the laser, and thus achieving the purpose of eliminating speckle.

[0101] In some embodiments, the magnification lens 203' may be a focusing lens. Figure 16 is a schematic diagram of the imaging principle provided in the embodiment of this application. In order to highlight the imaging principle of the beam, some optical elements in the projection device are omitted.

[0102] As shown in Figure 16, for each light-emitting region, the emitted laser beam yb is incident on the diffractive optical element 104. The diffractive optical element can shape and image the beam. After shaping and imaging, the beam is focused on the position of the display element by a focusing lens (magnification lens 203'), and finally a diffraction spot CB is formed at the position of the display element. The diffraction spot CB is a rectangular spot with uniform energy distribution. The display element is usually also rectangular, and the long side of the rectangular spot is parallel to the long side of the display element, and the short side of the rectangular spot is parallel to the short side of the display element. The rectangular spot will cover the effective area of ​​the display element, so that the display element modulates the incident light to form a display image.

[0103] Meanwhile, as shown in Figure 16, due to the manufacturing limitations of the diffractive optical element 104, the phase of its surface microstructure changes nearly continuously, but not ideally continuously. Therefore, some light rays, after passing through the diffractive optical element 104, are not diffracted and instead pass directly through the focusing lens (magnification lens 203') for imaging, forming a bright spot at the center of the diffractive spot CB, called the zero-order spot OB. To distinguish between the light rays forming the diffractive spot CB and the zero-order spot OB, the light rays forming the diffractive spot CB are called diffracted light, and the light rays forming the zero-order spot OB are called zero-order light. The zero-order spot OB affects the uniformity of energy distribution within the effective area of ​​the display element, thereby reducing image quality.

[0104] To overcome the above problems, in this embodiment, the diffractive optical element 104 can be designed with an angular phase shift, so that the diffracted light after the laser beam passes through the diffractive optical element 104 and the zero-order light have a certain angle, so that when illuminating the display element, the diffracted spot CB and the zero-order spot OB are separated from each other, the diffracted spot CB covers the effective area of ​​the display element, and the zero-order spot OB does not overlap with the effective area of ​​the display element, thereby avoiding the adverse effects of the zero-order spot OB on the image.

[0105] Specifically, as shown in Figure 17, the laser beams emitted from the three types of light-emitting regions 101 of the laser source pass through their corresponding diffractive optical elements 104 and are then incident on the light-combining component 102 for light combining.

[0106] Before the laser beams emitted from the three types of light-emitting regions 101 are incident on the light-combining component 102, they are all shaped by the corresponding diffractive optical element 104. After diffraction by the diffractive optical element 104, the center of the emitted diffracted light beam is offset by a set angle θ relative to the center of the zero-order light beam.

[0107] Because lasers have different divergence angles in different directions, the laser emitted by each laser chip forms an elliptical spot in the far field. The light-emitting region 101 includes multiple laser chips, and the laser emitted by each chip can be considered as a sub-beam. Therefore, the multiple sub-beams emitted from the light-emitting region 101 form multiple elliptical spots when incident on the diffractive optical element 104. After diffraction by the diffraction optical element 104, the diffracted light exits from the diffraction optical element 104 as multiple rectangular spots. The edges of each rectangular spot are relatively blurred, and the beam centers of the sub-beams are parallel to each other. During incident on the focusing lens (magnification lens 203'), the sub-beams gradually diverge. After being focused by the focusing lens (magnification lens 203'), the beam centers of the diffracted light sub-beams are no longer parallel and converge. When incident on the display element, they become a larger rectangular spot with sharper edges. At the same time, the zero-order light emitted from the diffractive optical element 104 also has multiple sub-beams, and similarly, the sub-beams of the zero-order light will converge into a clear zero-order light spot near the display element.

[0108] Due to a special phase design of the diffractive optical elements, the diffractive optical elements are offset at a set angle to the diffracted light. This causes the diffracted light from the three types of light-emitting regions 101, after passing through the corresponding diffractive optical elements 104, to be focused by the focusing lens (magnification lens 203') onto the display element 201, forming three diffractive spots. Each of the three diffractive spots is a rectangle and a different color, with their long sides and short sides parallel to each other. The three color rectangles overlap, and their centers coincide. The overlapping area of ​​the three color rectangles covers the effective area of ​​the display element. The zero-order light from the three types of light-emitting regions 101, after passing through the corresponding diffractive optical elements 104, is focused by the focusing lens (magnification lens 203') to a position outside the display element 201, thus preventing the formation of a zero-order spot within the effective area of ​​the display element.

[0109] As shown in Figure 17, the light combiner (light combiner assembly 102) is inclined relative to the light emitting surface (the plane formed by the first direction x and the second direction y) of the light emitting region 101, so that the incident angles of the diffracted light and the zero-order light emitted from the diffracting optical element 104 when they enter the light combiner are different. As shown in Figure 18, there is also a set angle θ between the beam center of the diffracted light reflected by the light combiner and the beam center of the zero-order light. This set angle satisfies: θ=arctan(d / f);

[0110] Where θ represents the set angle between the center of the diffracted light beam and the center of the zeroth-order light beam, d represents the distance between the center of the diffracted spot and the center of the zeroth-order spot, and f represents the focal length of the focusing lens.

[0111] The aforementioned included angle θ is a theoretical design value. Due to issues such as lens aberrations and structural tolerances, in practical applications, the offset angle of the diffracted light is within a range, which can be in the range of [0.9θ~1.1θ].

[0112] In some embodiments, as shown in FIG17, the angle between the light combiner (light combiner assembly 102) and the light emitting surface (the plane formed by the first direction x and the second direction y) of the light emitting region 101 is 45°. Therefore, the incident angle of the zero-order light incident on the light combiner is 45°, while the incident angle of the diffracted light incident on the light combiner is... As shown in Figure 18, the center of the zero-order light beam reflected by the beam combiner coincides with the first direction x, while the angle between the center of the diffracted light beam and the first direction x is θ. At this time, as shown in Figure 17, it is necessary to rotate the focusing lens (magnification lens 203') and the optical elements behind it as a whole by an angle θ so that the optical axis of the optical system coincides with the center of the diffracted light beam.

[0113] In some embodiments, as shown in FIG19, the angle between the light combining member (light combining assembly 102) and the light emitting surface (the plane formed by the first direction x and the second direction y) of the light emitting region 101 is . The incident angle of the diffracted light incident on the beam combiner is 45°, while the incident angle of the zero-order light incident on the beam combiner is... As shown in Figure 20, the center of the diffracted light beam reflected by the beam combiner coincides with the first direction x, while the angle between the center of the zero-order light beam and the first direction x is θ. At this point, as shown in Figure 19, due to the pre-rotation of the beam combiner angle, the optical axes of the focusing lens (magnification lens 203') and subsequent optical elements are all parallel to the first direction x. This is more conducive to the design and aesthetics of the optical system, reduces the difficulty of structural design, and facilitates the miniaturization of the optical engine.

[0114] As shown in Figures 21 and 22, a light-blocking plate p is typically disposed around the display element 201. The light-blocking plate p can absorb stray light and prevent stray light from being reflected into the optical system and affecting the image display. In the embodiment of this application, it is necessary to ensure that both diffracted light and zero-order light are reflected by the total internal reflection prism after incident on it. The diffracted light is totally reflected to the display element, while the zero-order light is totally reflected to the light-blocking plate p around the display element, thereby preventing the zero-order light from being reflected into the optical system and affecting the image display.

[0115] Specifically, as shown in Figure 21, the total internal reflection prism 204 includes an incident light surface 204a and a total internal reflection surface 204b; the light emitted from the focusing lens is incident on the total internal reflection prism from the incident light surface 204a, and after total internal reflection at the total internal reflection surface 204b, it is emitted towards the display element 201.

[0116] To ensure that both diffracted and zero-order light can be totally reflected at the total internal reflection surface 204b of the total internal reflection prism, the critical angle of the prism needs to be considered. If the refractive index of the total internal reflection prism 204 is n, then the critical angle at which total internal reflection occurs at the total internal reflection surface of the prism is... If both diffracted light and zeroth-order light undergo total internal reflection at the total internal reflection surface, then the following condition must be met: α⁴ - θ ≥ α⁰;

[0117] Since the sum of the interior angles of a triangle is 180°, we can deduce that α₄ = α₂ + α₃. If the F-number of the optical system is F, then... From this, we can deduce that:

[0118] According to the law of refraction, sinα1 = nsinα3. Substituting this into the above equation, we get:

[0119] Where α1 represents the incident angle of the diffracted light onto the incident surface of the total internal reflection prism, α2 represents the angle between the incident surface and the total internal reflection surface of the prism, n represents the refractive index of the total internal reflection prism, and F represents the F-number of the optical system.

[0120] By designing diffractive optical elements and total internal reflection prisms to satisfy the above formula, it can be ensured that both the diffracted light and the zero-order light emitted from the diffractive optical elements can undergo total internal reflection at the total internal reflection surface of the total internal reflection prism, and that the diffracted light can be incident on the display element, while the zero-order light is incident on the light-blocking plates around the display element.

[0121] Based on the same inventive concept, this application also provides a projection system, as shown in FIG23, which includes a projection device 1 and a projection screen 2.

[0122] The projection screen 2 is located on the light-emitting side of the projection device 1, and the audience faces the projection screen 2. The projection device 1 emits projection light, which enters the projection screen 2, passes through the projection screen 2, and exits towards the audience, thus allowing the audience to view the projected image.

[0123] When the projection device 1 and the audience are located on the same side of the projection screen 2, this projection system is called a front projection system. When the projection device 1 and the audience are located on opposite sides of the projection screen 2, this projection system is called a rear projection system. In a front projection system, the projection device 1 emits projection light onto the projection screen 2, and the projection screen 2 reflects the projection light back to the audience, allowing the audience to view the projected image. In a rear projection system, the projection device 1 emits projection light onto the projection screen 2, and the projection light passes through the projection screen 2 and exits towards the audience, allowing the audience to view the projected image.

[0124] Projection device 1 can be any of the above-mentioned projection devices, which includes a laser light source, an illumination system, and a projection lens. The laser light source includes three light-emitting regions and three diffractive optical elements, with the emitted laser wavelengths differing among the three regions. The illumination system includes a magnification lens, a homogenizing element, a total internal reflection prism, and a display element. The display element modulates the incident laser to form a display image, which is then projected onto the projection lens for image formation.

[0125] The laser emitted from each light-emitting region of the laser source has a different wavelength. After being diffracted by the diffractive optical element, the laser beam emitted from each region forms a rectangular spot when it enters the display element. This rectangular spot matches the effective area of ​​the display element, and the long side of the rectangular spot is parallel to the slow axis of the laser beam emitted from the light-emitting region. This allows for a better match between the optical spread of the laser, the diffractive optical element, and the display element, improving not only the diffraction efficiency of the diffractive optical element but also the luminous efficiency of the optical system.

[0126] The laser emitted from each light-emitting region of the laser source has a different wavelength. When designing the diffractive optical element, a phase shift of the diffracted light is added so that when the laser beam emitted from each light-emitting region is diffracted by the diffractive optical element, the diffracted light is shifted by a set angle relative to the zero-order light. This allows the diffracted spot and the zero-order spot formed on the display element after the emitted light from the diffractive optical element passes through the focusing lens to be separated. The diffracted spot covers the effective area of ​​the display element, while the zero-order spot does not overlap with the display element, thus avoiding the adverse effects of the zero-order spot on the projected image.

[0127] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0128] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A projection device, comprising: Laser source, used to emit three-color lasers; The laser source includes: three types of light-emitting regions and three diffractive optical elements corresponding one-to-one with the three types of light-emitting regions, wherein the wavelengths of the laser emitted from the three types of light-emitting regions are different; A magnification lens, located on the light-emitting side of the diffractive optical element, is used to change the size of the laser spot; and The display element is located on the side of the homogenizing element away from the magnification lens, and is used to modulate the incident laser beam to form a display image; Wherein, the laser beam emitted from the light-emitting region forms a rectangular spot when it is diffracted by the diffractive optical element and then incident on the display element. The long side of the rectangular spot is parallel to the slow axis direction of the laser beam emitted from the light-emitting region.

2. The projection device as described in claim 1, wherein, The laser beams output from the three diffractive optical elements form three rectangular spots when incident on the display element; The centers of the three rectangular light spots coincide and there is an overlapping area, which covers the effective area of ​​the display element.

3. The projection device as described in claim 2, wherein, The area of ​​the rectangular spot formed by the laser beam output by the diffractive optical element when it is incident on the display element exceeds 10% to 20% of the area of ​​the effective region of the display element.

4. The projection device as described in claim 1, wherein, The magnification lens is a focusing lens or a diverging lens; The distance between the display element and the focal plane of the magnification lens is less than or equal to ±5mm.

5. The projection device as described in any one of claims 1 to 4, wherein, The diffractive optical element includes a first region and a second region. The laser emitted from the light-emitting region is out of phase by an odd multiple of π after passing through the first and second regions of the corresponding diffractive optical element.

6. The projection device as described in claim 5, wherein, The diffractive optical element includes a first region and two second regions, with the two second regions located on either side of the first region along the slow axis of the laser beam.

7. The projection device as described in claim 6, wherein, The diffractive optical element is connected to a driving device, which drives the diffractive optical element to vibrate along the long side of the rectangular light spot.

8. The projection device according to any one of claims 1 to 4, wherein, The laser emitted from the light-emitting region becomes disordered in polarization direction after passing through the corresponding diffractive optical element.

9. The projection device as described in any one of claims 1 to 4, wherein, The magnification lens is a focusing lens; The laser beam emitted from the light-emitting region passes through the diffractive optical element and the focusing lens and forms a diffraction spot and a zero-order spot when it is incident on the display element. The diffraction spot covers the effective area of ​​the display element, and the zero-order spot is separate from the diffraction spot.

10. The projection device according to any one of claims 1 to 9, further comprising: The beam combining component is located on the side of the three diffractive optical elements away from the three types of light-emitting regions, and is used to combine laser beams of three wavelengths.

11. The projection device as claimed in claim 10, wherein, The light combining component includes: three parallel light combining elements that correspond one-to-one with the three types of light emitting regions; the light combining elements are inclined relative to the light emitting surface of the corresponding light emitting region.

12. The projection device as claimed in claim 11, wherein, The diffracted light after passing through the diffractive optical element and the focusing lens forms the diffractive spot, and the zero-order light after passing through the diffractive optical element and the focusing lens forms the zero-order spot light; The center of the diffracted light beam and the center of the zeroth-order light beam form a predetermined angle, which satisfies the following: θ = arctan(d / f); Wherein, θ represents the set angle between the center of the diffracted light beam and the center of the zeroth-order light beam, d represents the distance between the center of the diffracted spot and the center of the zeroth-order spot, and f represents the focal length of the focusing lens.

13. The projection device as claimed in claim 12, wherein, The angle between the light combining element and the light emitting surface of the corresponding light emitting region is 45°; The beam center of the zeroth-order light coincides with the first direction, and the angle between the beam center of the diffracted light and the first direction is θ; the first direction is parallel to the light-emitting surface of the light-emitting region and forms a 45° angle with the light-combining element.

14. The projection device as claimed in claim 12, wherein, The angle between the light combining element and the light emitting surface of the corresponding light emitting region is: The center of the diffracted light beam coincides with the first direction, and the angle between the center of the zero-order light beam and the first direction is θ; the first direction is parallel to the light-emitting surface of the light-emitting region and is perpendicular to the light-combining element. Angle.

15. The projection device according to any one of claims 1 to 14, further comprising: A total internal reflection prism is located between the magnification lens and the display element; The total internal reflection prism is used to reflect the light emitted from the magnification lens to the display element and transmit the light emitted from the display element.

16. The projection device as claimed in claim 15, wherein, The incident angle of the diffracted light onto the incident surface of the total internal reflection prism satisfies: Wherein, α1 represents the incident angle of the diffracted light incident on the incident surface of the total internal reflection prism, α2 represents the angle between the incident surface and the total internal reflection surface of the total internal reflection prism, n represents the refractive index of the total internal reflection prism, and F represents the F-number of the optical system.

17. The projection device as claimed in claim 16, wherein, The display element is surrounded by light-blocking sheets; The diffracted light is incident on the display element, and the zero-order light is incident on the light-blocking plate.

18. The projection device according to any one of claims 1 to 17, further comprising: A beam homogenizing element, located between the magnification lens and the total reflection prism, is used to homogenize the laser beam; The light-diffusing element is at least one of a diffuser, a compound eye lens, a diffuser wheel, or a moving diffuser.

19. The projection device as claimed in claim 18, wherein, The light-diffusing element is a diffuser sheet; The diffuser is stationary; or the diffuser moves along the long side of the rectangular light spot.

20. A projection system, comprising: A projection device, wherein the projection device is the projection device according to any one of claims 1 to 19; The projection screen is located on the light-emitting side of the projection device.

Images