Projection equipment and projection system

Abstract

A projection device and a projection system, the projection device comprising at least one laser (10) and at least one diffractive optical element (20), one diffractive optical element (20) corresponding to one laser (10), the diffractive optical element (20) being located at a light emitting side of the corresponding laser (10); wherein the phase distribution of the diffractive optical element (20) is determined according to an initial parameter of an incident laser beam and an output parameter of the incident laser beam after passing through the diffractive optical element (20); a laser beam emitted by the laser (10) passes through the diffractive optical element (20) and then forms a rectangular light spot with uniform energy distribution at a set position.

Description

Projection equipment and projection systems

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on November 15, 2022, with application number 202211428648.X and application name “A laser projection system”, the entire contents of which are incorporated by reference into this application; this application claims priority to the Chinese patent application filed with the China Patent Office on November 15, 2022, with application number 202211428153.7 and application name “A projection device and projection system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of laser projection, and in particular to a projection device and a projection system. Background Art

[0004] Laser projection display technology, also known as laser projection or laser display technology, uses lasers as a light source for projection display. Laser projection can cover over 90% of the color space perceptible by the human eye, more than double the color gamut coverage of traditional displays. It can realistically reproduce the rich, vibrant colors of the real world, providing even more striking expressiveness.

[0005] Currently, laser projection systems typically use optical components such as light pipes and fly-eye lenses on the light output side of the laser light source to shape and homogenize the beam. This process can easily lead to energy loss during beam propagation through these optical components, resulting in a very long optical system and preventing the need for a smaller design.

[0006] Summary of the Invention

[0007] According to a first aspect of an embodiment of the present application, a projection device is provided, comprising:

[0008] At least one laser; the laser comprises a plurality of laser chips arranged in an array;

[0009] At least one diffractive optical element, one diffractive optical element corresponding to one laser, the diffractive optical element being located on the light-emitting side of the corresponding laser; the diffractive optical element comprising a plurality of diffraction regions, one diffraction region corresponding to one laser chip; the size of the diffraction region being larger than the size of the laser spot formed when the laser beam emitted by the corresponding laser chip enters the diffraction region; the laser spots of the laser beams emitted by adjacent laser chips do not overlap when entering the corresponding diffraction regions, and adjacent diffraction regions do not overlap;

[0010] In which, the phase distribution of each diffraction area in the diffraction optical element is determined according to the initial parameters of the incident laser beam and the output parameters after passing through the diffraction area; the laser beam emitted by the laser forms a rectangular light spot with uniform energy distribution at a set position after passing through the diffraction optical element.

[0011] According to a second aspect of an embodiment of the present application, a projection system is provided, comprising any one of the above-mentioned projection devices and a projection screen located on the light-emitting side of the projection device. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings introduced below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0013] FIG1 is a schematic diagram of an intensity distribution curve of a laser beam provided in an embodiment of the present application;

[0014] FIG2 is a schematic diagram of a structure of a projection device according to an embodiment of the present application;

[0015] FIG3 is a schematic diagram of a top view of the structure of a laser provided in an embodiment of the present application;

[0016] FIG4 is a schematic diagram of a cross-sectional structure of a laser according to an embodiment of the present application;

[0017] FIG5 is a schematic diagram showing the correspondence between the laser chip and the diffraction region provided in an embodiment of the present application;

[0018] FIG6 is a schematic structural diagram of a diffractive optical element provided in an embodiment of the present application;

[0019] FIG7 is a second schematic diagram of the cross-sectional structure of a laser provided in an embodiment of the present application;

[0020] FIG8 is a third schematic diagram of the cross-sectional structure of a laser provided in an embodiment of the present application;

[0021] FIG9 is a schematic diagram of the light spot of a laser beam before and after passing through a diffraction element according to an embodiment of the present application;

[0022] FIG10 is a schematic diagram of the arrangement structure of the laser chips provided in an embodiment of the present application;

[0023] FIG11 is a schematic diagram of a laser spot emitted by the laser shown in FIG10 ;

[0024] FIG12 is a schematic diagram of a light spot of a laser beam after passing through a diffractive optical element according to an embodiment of the present application;

[0025] FIG13 is a second schematic diagram of a light spot of a laser beam after passing through a diffractive optical element according to an embodiment of the present application;

[0026] FIG14 is a second structural diagram of a projection device provided in an embodiment of the present application;

[0027] FIG15 is a third structural diagram of a projection device provided in an embodiment of the present application;

[0028] FIG16 is a fourth structural diagram of a projection device provided in an embodiment of the present application;

[0029] FIG17 is a fifth structural diagram of a projection device provided in an embodiment of the present application;

[0030] FIG18 is a schematic diagram of the structure of a light combining assembly according to an embodiment of the present application;

[0031] FIG19 is a second structural diagram of a light combining assembly provided in an embodiment of the present application;

[0032] FIG20 is a third structural diagram of a light combining assembly according to an embodiment of the present application;

[0033] FIG21 is a fourth structural diagram of a light combining assembly provided in an embodiment of the present application;

[0034] FIG22 is a fifth structural diagram of a light combining assembly provided in an embodiment of the present application;

[0035] FIG23 is a sixth structural diagram of a projection device provided in an embodiment of the present application;

[0036] FIG24 is a flowchart of a method for designing a diffractive optical element according to an embodiment of the present application;

[0037] FIG25 is a second flowchart of the method for designing a diffractive optical element provided in an embodiment of the present application;

[0038] FIG26 is a schematic diagram showing the distribution of the initial field intensity of the light spot provided in an embodiment of the present application;

[0039] FIG27 is a schematic diagram showing the distribution of the output field intensity of the light spot provided in an embodiment of the present application;

[0040] FIG28 is a schematic diagram of the phase distribution of the diffraction region provided in an embodiment of the present application;

[0041] FIG29 is a schematic diagram of a laser spot incident on a diffractive optical element according to an embodiment of the present application;

[0042] Figure 30 is a schematic diagram of a laser spot emitted from a diffraction optical element provided in an embodiment of the present application. DETAILED DESCRIPTION

[0043] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application will be further described below with reference to the accompanying drawings and examples. However, the example embodiments can be implemented in various forms and should not be understood as being limited to the embodiments set forth herein; on the contrary, these embodiments are provided to make the present application more comprehensive and complete, and to fully convey the concepts of the example embodiments to those skilled in the art. The same figure marks in the figures represent the same or similar structures, and their repeated descriptions will be omitted. The words expressing position and direction described in this application are all explained using the accompanying drawings as examples, but changes can be made as needed, and all changes are included in the scope of protection of this application. The drawings in this application are only used to illustrate relative position relationships and do not represent true proportions.

[0044] Projection technology is widely used in various aspects of life and production. Common projection technologies include liquid crystal display (LCD), digital light processor (DLP), and liquid crystal on silicon (LCS). DLP-based projection devices offer advantages such as low cost, compact size, high brightness, and strong resistance to light interference, enabling clear, bright, and vibrant images. Currently, lasers are commonly used as the projection light source for DLP projection devices. Lasers can cover over 90% of the color space perceptible by the human eye, more than double the color gamut coverage of traditional displays. Therefore, using lasers as projection light sources maximizes the reproduction of real-world colors, providing even more striking visual impact. DLP projection devices utilize a digital micromirror device (DMD) as their core component. Light from the projection light source strikes the DMD, generating an image. The resulting image is then directed to the projection lens, where it is formed and ultimately received by the projection screen.

[0045] FIG1 is a schematic diagram of an intensity distribution curve of a laser beam provided in an embodiment of the present application.

[0046] Currently, the energy distribution of a single laser beam emitted by a laser is a Gaussian distribution, as shown in (a) in Figure 1. The Gaussian distribution shows a trend in which the light intensity at the center is higher and the light intensity at the edge decreases sharply, which cannot meet the requirements of uniform illumination.

[0047] The display surface of a DMD is typically rectangular. Therefore, to achieve uniform illumination, the laser beam emitted by the laser must be adjusted to form a rectangular spot with uniform intensity distribution, as shown in Figure 1(b). This rectangular spot provides uniform light intensity at all locations, meeting the illumination requirements of projection systems.

[0048] To homogenize the laser beam's intensity, a diffuser can be placed on the laser's light-emitting side. However, in practice, using a diffuser to homogenize the beam results in a pattern of high brightness at the center and low brightness at the edges, as shown in Figure 1(c). To achieve even more uniform intensity, the diffusion angle needs to be increased, which results in a significant loss of edge energy.

[0049] Furthermore, the projection system requires light-homogenizing components such as light pipes to homogenize the light. However, injecting the laser beam into a narrow light pipe results in significant energy loss. To achieve a certain uniformity, the light pipe needs to be relatively long, typically over 30mm. This results in a very long optical engine, preventing a smaller footprint.

[0050] In view of this, an embodiment of the present application provides a projection device that can effectively homogenize the intensity distribution of a laser beam and omit the use of light-homogenizing components such as light pipes, thereby achieving a small-volume design of the projection system.

[0051] FIG2 is one of the structural schematic diagrams of the projection device provided in an embodiment of the present application.

[0052] As shown in FIG. 2 , the projection device may include: at least one laser 10 , at least one diffractive optical element 20 , a light modulation component 30 and a projection lens 40 .

[0053] One laser 10 is correspondingly provided with one diffractive optical element 20 , and the diffractive optical element 20 is located at the light-emitting side of the corresponding laser 10 .

[0054] FIG3 is a schematic diagram of a top view of the structure of a laser provided in an embodiment of the present application, and FIG4 is one of the schematic diagrams of a cross-sectional structure of a laser provided in an embodiment of the present application.

[0055] As shown in Figures 3 and 4, the laser may include a packaging structure 102 and multiple laser chips 101 arranged in an array within the packaging structure 102. The packaging structure 102 comprises a base plate d, a housing g, and a cover plate f. The housing g surrounds the base plate, forming a space for accommodating each laser chip 101. The cover plate f is located on the side of the housing g facing away from the base plate d. The cover plate f is sealed to the housing g around the periphery, forming a sealed space for encapsulating the laser chips 101.

[0056] In the embodiment of the present application, the light modulation component 30 can adopt DMD, which is composed of thousands of micro-lenses, each of which is a precise, miniature reflector. Each micro-lens can be driven by the rotating device below it under the control of a digital drive signal, and its angle and direction can be adjusted at a very fast speed, tilting to an open or closed state. The light incident on the surface of the micro-lens in the open state can be reflected by it to the projection lens 40, and the light incident on the surface of the micro-lens in the closed state is reflected to the light receiving device.

[0057] The projection lens 40 is located in the outgoing light path of the light modulation component 30 and can be used to project the light modulated by the light modulation component 30 to form an image, thereby projecting an image onto a projection screen or a set position. Viewers viewing the projection screen can see the displayed image. In a specific implementation, the projection lens 40 may include at least one lens. For example, the projection lens 40 may include a convex lens, a concave-convex lens, or a combination thereof. Specifically, it may be at least one of a spherical lens, an aspherical lens, or a free-form surface lens, although this is not limited here. The optical design of the projection lens 40 is based on the specific usage scenario and requirements to achieve the desired display effect. The specific structure of the projection lens is not limited here.

[0058] As shown in FIG2 , in an embodiment of the application, the diffraction optical element 20 includes a plurality of diffraction regions 201 , each of which can be arranged in an array corresponding to each laser chip 101 in the laser, with each laser chip 101 corresponding to a diffraction region 201 . Each diffraction region 201 is used to shape and homogenize the laser beam emitted by its corresponding laser chip 101 , ultimately forming a rectangular light spot with uniform energy distribution and a size that matches the incident DMD after passing through the diffraction optical element 20 . Since each laser chip 101 is located at a different position in the laser, its diffraction angle and phase distribution after passing through the corresponding diffraction region 201 are different from those of other laser chips 101 . Therefore, in an embodiment of the application, a diffraction region 201 is individually designed for each laser chip 101 to correspond thereto, thereby improving the diffraction efficiency of the diffraction optical element.

[0059] FIG5 is a schematic diagram showing the correspondence between the laser chip and the diffraction region provided in an embodiment of the present application.

[0060] As shown in FIG5 , the laser light beam emitted by the laser chip 101 forms a laser spot s when it enters the corresponding diffraction region 201 after propagating a certain distance. In order to ensure the diffraction efficiency of the diffraction region, the size of the diffraction region 201 needs to be slightly larger than the size of the laser spot when the laser light beam emitted by the corresponding chip enters the diffraction region.

[0061] The laser used in the embodiment of the present application can be a semiconductor laser. Semiconductor lasers have advantages such as high conversion efficiency, small size, and long life, but the laser beam emitted by the laser is not a plane light wave or a spherical light wave, but an elliptical Gaussian beam, and has a fast axis and a slow axis, and the divergence angle of the emitted laser on the fast axis and the slow axis is different. Then the longer the propagation distance of the laser beam emitted by the laser chip 101, the larger the laser spot generated due to the existence of the laser beam divergence angle. If the two laser spots overlap, interference will occur, affecting the diffraction efficiency. Therefore, in the embodiment of the present application, it is necessary to set the diffraction optical element 20 in a suitable position so that the laser spots s of the laser beams emitted by adjacent laser chips 101 do not overlap when they are incident on the corresponding diffraction areas 201, and each diffraction area 201 in the diffraction optical element 20 will be arranged according to the arrangement rule of its corresponding laser chip 101 and the distance between it and the laser chip 101, and adjacent diffraction areas 201 do not overlap. In a specific implementation, adjacent diffraction regions 201 may be spaced a certain distance apart, or the edges of adjacent diffraction regions 201 may coincide with each other. The arrangement needs to be determined according to the size of the incident laser spot s and the overall size of the diffraction optical element.

[0062] As mentioned above, the DMD requires the incident light spot to be a rectangular spot of appropriate size and uniform energy distribution. Each diffraction region 201 in the diffractive optical element 20 can shape and homogenize the laser beam emitted by the corresponding laser chip 101, so that the laser light emitted by the laser forms a rectangular light spot with uniform energy distribution at a set position after passing through the diffractive optical element. This rectangular light spot can directly meet the lighting requirements of the light modulation component 30. The light modulation component 30 receives the incident laser beam, modulates the incident laser beam, and then emits it to the projection lens 40, where it forms an image.

[0063] By providing a diffraction optical element corresponding to the laser in the projection device, light-homogenizing components such as light pipes can be omitted, thereby avoiding energy loss caused by light-homogenizing components such as light pipes and realizing a miniaturized design of the projection device.

[0064] FIG6 is a schematic structural diagram of a diffractive optical element provided in an embodiment of the present application.

[0065] As shown in Figure 6 , each diffractive region in a diffractive optical element (DOE) 20 includes multiple diffractive structures 200, arranged in a two-dimensional matrix. The diffractive structures 200 may be stepped or sawtooth structures, as shown in Figure 6 . Alternatively, the diffractive structures 200 may be at least one of a variety of diffractive microstructures, such as trapezoidal structures and tilted rectangular structures. The thickness of a DOE is generally less than 1 mm to ensure high transmittance while being lightweight and thin. This also provides the DOE with suitable rigidity for easy attachment to the projection device.

[0066] In the embodiments of the present application, the phase distribution of each diffraction region in the diffractive optical element is determined using an iterative Fourier transform algorithm based on the initial parameters of the laser beam emitted by the corresponding laser chip before it enters the diffraction region and the output parameters after passing through the diffraction region. Specifically, the initial parameters of the laser beam include: the wavelength, beam quality, and beam waist radius of the laser beam before it enters the diffractive optical element; the output parameters of the laser beam include: the size of the laser spot emitted from the diffractive optical element, the emission distance, and the diffraction order.

[0067] Each diffraction area in the diffraction optical element is designed specifically according to the initial parameters and output parameters of the incident laser beam, so that the diffraction structure of each diffraction area in the diffraction optical element has a specific morphology, size, refractive index, etc., thereby making the laser beam emitted by the laser diffract when passing through the corresponding diffraction optical element and generate interference at a certain distance, forming a specific light intensity distribution, and realizing fine control of the laser wavefront phase distribution.

[0068] In actual applications, due to the differences in the application scenarios of the projection system, the projection brightness and distance, the parameters of the laser light source, the type, size and configuration of the light modulation components, etc. are not the same. Therefore, for different application scenarios, the optical path structure of the projection equipment during design varies greatly. The embodiments of the present application can simplify the above optical path structure through the design of the diffractive optical element. For different application scenarios, the size of the diffractive optical element is different, the incident laser has different wavelengths and the optical etendue of the DMD is different, and the requirements of different F# require the reasonable setting of the size of the diffractive structure in the diffractive optical element and the working distance of the diffractive optical element.

[0069] The projection system in the embodiments of the present application is an etendue-limited system, and its etendue is limited by the DMD. Therefore, when designing a diffractive optical element, the diffraction angle can be constrained based on the etendue of the DMD. This allows the optical distance between the diffractive optical element and the DMD, i.e., the working distance, to be determined based on the required illumination size of the DMD.

[0070] The maximum period of the diffraction structure 200 satisfies: d×sinθ=λ;

[0071] Here, d represents the maximum period of the diffractive structure, θ represents the diffraction angle of the diffractive structure, and λ represents the wavelength of the incident laser light. A smaller maximum period of the diffractive structure indicates a smaller size when forming the diffractive structure. However, smaller diffractive structures require higher precision in the manufacturing process. Therefore, when designing diffractive optical elements, it is necessary to consider the trade-off between process precision and the maximum period of the diffractive structure.

[0072] The diffractive optical element can be placed in different locations depending on the laser's packaging structure. In some embodiments, as shown in Figure 4 , the laser includes a packaging structure that encapsulates multiple laser chips 101 arranged in an array. The package structure's tube shell (g) is sealed around the cover plate (f). The diffractive optical element 20 can be placed on the laser's cover plate (f).

[0073] Directly placing the diffractive optical element 20 on the cover plate f of the laser can, on the one hand, simplify the installation of the diffractive optical element 20. Since the thickness of the diffractive optical element 20 is very thin, placing the diffractive optical element 20 on the cover plate f can increase the strength of the diffractive optical element and reduce the possibility of damage to the diffractive optical element during installation and use. On the other hand, since the laser light emitted by the laser has divergence angles in both the fast axis and slow axis directions, and the divergence angle in the fast axis direction is greater than the divergence angle in the slow axis direction, for example, the divergence angle in the fast axis direction of some lasers is three times the divergence angle in the slow axis direction. The longer the propagation distance of the laser light, the more likely it is to interfere. Therefore, it is necessary to place the diffractive optical element 20 closer to the laser chip. Without changing the packaging structure of the laser, placing the diffractive optical element on the cover plate can ensure that the diffraction optical element has a higher diffraction efficiency. In a specific implementation, the diffractive optical element can also be placed in the packaging structure of the laser. For example, each diffraction area can be directly placed on the corresponding laser chip, which is not limited here.

[0074] Taking the example of some lasers with a divergence angle of 40° in the fast axis direction and a divergence angle of 10° in the slow axis direction, when the light emission size of the laser chip in the fast axis direction is 1μm, if the spacing between adjacent laser chips along the fast axis direction is 6mm, based on the trigonometric relationship, it can be calculated that when the light emission distance of the laser chip reaches 7.15mm, the size of the laser spot along the fast axis direction has reached 6mm, and as the light emission distance increases, the laser spot size will also increase. According to the current process, the distance between the laser chip and the laser surface (such as the cover plate f) is approximately 5-7mm. Therefore, when the diffraction optical element is set on the cover plate, it can be avoided that the lasers emitted by adjacent laser chips at this position will interfere with each other and affect the diffraction efficiency.

[0075] In addition, the placement of the diffractive optical element also needs to take into account the issue of etendue. Assuming that the projection system is an ideal optical system, the etendue is conserved, and the formula for etendue is:

[0076] Where A represents the illumination area on the DOE, π×NA 2 Represents the solid angle of radiation emitted by the DOE. According to the conservation of etendue, a larger illumination area can result in a smaller beam divergence angle. However, a larger illumination area also means a longer distance between the laser and the DOE, which can lead to laser interference and affect the DOE's diffraction efficiency. Therefore, the DOE's position must be properly set during optical design.

[0077] FIG7 is a second schematic diagram of the cross-sectional structure of the laser provided in an embodiment of the present application; FIG8 is a third schematic diagram of the cross-sectional structure of the laser provided in an embodiment of the present application.

[0078] As shown in Figures 7 and 8, the laser packaging structure may further include multiple collimating lenses 103 located on the cover plate f. One collimating lens 103 is provided for each laser chip 101, and the collimating lens 103 is used to collimate the laser beam emitted by the laser chip 101. Each diffraction region in the diffractive optical element may be provided in a one-to-one correspondence with each collimating lens 103, and the laser light received by each diffraction region is the laser light collimated by the collimating lens.

[0079] In some embodiments, as shown in FIG7 , the diffractive optical element 20 can be disposed on each collimating lens 103 so that each diffraction region corresponds to the corresponding collimating lens. In a specific implementation, the diffractive optical element 20 can be bonded to each collimating lens 103 so that each diffraction region corresponds to the corresponding collimating lens 103.

[0080] In some embodiments, as shown in FIG8 , the diffractive optical element 20 can be installed at a certain distance from each collimating lens 103. This prevents the packaging structure of the laser from being changed when the diffractive optical element 20 is installed, and avoids damage to the collimating lens when the diffractive optical element 20 is installed.

[0081] When the diffractive optical element 20 is positioned on the light-emitting side of the collimating lens 103, the light beam received by each diffraction region of the diffractive optical element can be a collimated laser beam, thereby avoiding the limitation of the laser divergence angle on the placement of the diffractive optical element 20. In an ideal state, if the collimation degree of the collimating lens 103 is very high, the laser beam emitted by the laser chip 101 is parallel light after being collimated by the collimating lens 103. Then, the placement of the diffractive optical element 20 is no longer restricted, and the system design can be flexibly carried out according to actual needs.

[0082] However, in practical applications, due to the existence of a fast axis and a slow axis in the laser, if the collimating lens has the same focal length along the fast axis and the slow axis, it will cause there to still be a divergence angle in at least one direction in the fast axis and the slow axis. In response to this problem, the embodiment of the present application can improve the optical design of the collimating lens 103 so that the collimating lens has different focal lengths along the fast axis and the slow axis direction. However, due to the problem of optical etendue, a trade-off is also required between the size and collimation of the light beam of the collimating lens. Therefore, it is still necessary to arrange the diffraction optical element in a reasonable position in the system to ensure the diffraction efficiency of the diffraction optical element.

[0083] Simulation results of the optical architecture provided in the embodiments of this application indicate that the area of ​​the diffractive optical element 20 increases as the distance between the diffractive optical element 20 and the light modulating component 30 increases. It is worth noting that the distance between the diffractive optical element 20 and the light modulating component 30 in the embodiments of this application refers to the optical distance of the principal light rays between them. Based on this simulation result, the size of the diffractive optical element can be adjusted by adjusting the distance between the diffractive optical element 20 and the light modulating component 30, thereby reducing the manufacturing difficulty.

[0084] At the same time, through the simulation of diffractive optical elements, it is found that the distance from DOE to DMD (i.e., the focal length of DOE) has a certain impact on the optical performance of the system. The specific impact is shown in the following table:

[0085] The simulation results in the table above show that increasing the DOE's design focal length increases its overall size, improving diffraction efficiency and reducing stray light intensity. Therefore, appropriately increasing the distance between the DOE and the DMD can improve the DOE's diffraction efficiency. In practice, this distance can be increased by placing a reflector between the DOE and the DMD to deflect the optical path. The DOE can be designed with a specific focal length to homogenize and shape the incident light beam while simultaneously focusing it on the DMD. After the laser beam is collimated, although the spatial locations of the laser chip 101 vary, the angle of incidence into the corresponding diffraction region remains the same. For example, the laser beam emitted by the laser chip can be collimated to enter the diffraction optical element perpendicularly. The shaped laser beam will enter the DMD at different angles. Based on information such as the laser's position, wavelength, and angle, the shaped light spot can be confocalized onto the DMD.

[0086] It should be noted that the larger the distance between the DOE and the DMD, the larger the volume of the optical system needs to be. Therefore, when setting the position of the DOE, a balance needs to be struck between the diffraction efficiency of the DOE and the overall volume of the optical system.

[0087] In an embodiment of the present application, the laser beam after passing through the diffraction optical element can be merged into a rectangular light spot with uniform energy distribution at a set position, such as on the DMD, thereby achieving the effect of shaping and homogenizing the laser beam and meeting the lighting requirements of the light modulation components in the projection equipment.

[0088] FIG9 is a schematic diagram of the light spot of the laser beam before and after passing through the diffraction element provided in an embodiment of the present application.

[0089] As shown in Figure 9, by specifically designing the phase distribution of the DOE, the laser beam can be made into a rectangular spot after passing through the DOE. The rectangular spot has more uniform energy distribution and can meet the lighting requirements of the optical modulation component.

[0090] In some embodiments, as shown in FIG. 2 , the projection device may include a laser 10 and a diffractive optical element 20 .

[0091] Laser 10 includes multiple laser chips, of at least two types. Different laser chips emit lasers of different wavelengths, and the laser chips are arranged in an array to form a laser chip array. In a specific implementation, laser 10 may include red, green, and blue laser chips to achieve full-color display. The red, green, and blue laser chips are arranged to form a laser chip array based on design requirements. This embodiment of the application does not limit the color, number, or specific location of the laser chips in the array.

[0092] The following embodiments are all described in detail by taking as an example the case where the laser 10 includes 8 red laser chips, 4 green laser chips, and 4 blue laser chips, and the laser chips form a 4×4 laser chip array.

[0093] FIG10 is a schematic diagram of the arrangement structure of the laser chips provided in an embodiment of the present application.

[0094] As shown in FIG10 , the laser may include a red laser chip 101r, a green laser chip 101g, and a blue laser chip 101b. The red laser chip 101r forms a 2×4 red laser chip array, the green laser chip 101g forms a 1×4 green laser chip array, and the blue laser chip 101b forms a 1×4 blue laser chip array. Every four laser chips of the same color are arranged along a first direction X, and the red laser chip array, green laser chip array, and blue laser chip array are arranged along a second direction Y, thereby forming a 4×4 laser chip array.

[0095] FIG11 is a schematic diagram of a laser spot emitted by the laser shown in FIG10 .

[0096] As shown in Figure 11, the lasers emitted by each laser chip are all elliptical Gaussian beams. Each laser beam has a certain waist radius and divergence angle. After propagating a certain distance, the lasers emitted from each laser chip form an elliptical red laser spot a1, an elliptical green laser spot b1, and an elliptical blue laser spot c1 of a certain size. Laser spots of different colors can be superimposed in subsequent optical components to achieve light combination.

[0097] In an embodiment of the present application, a diffraction optical element 20 is provided on the light-emitting side of the laser 10. For ease of installation, the diffraction optical element 20 can be provided close to the light-emitting surface of the laser 10. The diffraction optical element 20 includes a plurality of diffraction regions, one of which corresponds to one laser chip, and each diffraction region forms an integral diffraction optical element through a semiconductor processing technique. Each diffraction region in the diffraction optical element 20 has a specific morphology, size, refractive index, etc. corresponding to the laser beam emitted by its laser chip. Each diffraction region can finely control the wavefront phase distribution of the laser beam incident therein, thereby achieving shaping and homogenization of the laser beam emitted by the corresponding laser chip.

[0098] Each diffraction area in the diffraction optical element 20 is individually designed for the laser light beam emitted by its corresponding laser chip, so that the laser light beam emitted by each laser chip is diffracted when passing through its corresponding diffraction area, and interferes at a certain distance to form a specific light intensity distribution. In this way, the laser light beams emitted by each laser chip can be merged into a rectangular light spot with uniform energy distribution at a set position after passing through the diffraction optical element, thereby achieving the effect of shaping and homogenizing the laser light beam to meet the lighting requirements of the light modulation component.

[0099] FIG12 is one of schematic diagrams of the light spot of the laser beam after passing through the diffraction optical element according to an embodiment of the present application; FIG13 is a second schematic diagram of the light spot of the laser beam after passing through the diffraction optical element according to an embodiment of the present application.

[0100] As shown in Figures 12 and 13, for the laser shown in Figure 10, the diffraction optical element 20 in the embodiment of the present application may include 16 diffraction regions, specifically including 8 first diffraction regions 201r, 4 second diffraction regions 201g and 4 third diffraction regions 201b, one first diffraction region 201r corresponds to a red laser chip 101r, one second diffraction region 201g corresponds to a green laser chip 101g, and one third diffraction region 201b corresponds to a blue laser chip 101b. Each first diffraction region 201r is located at the light-emitting side of the corresponding red laser chip 101r, each second diffraction region 201g is located at the light-emitting side of the corresponding green laser chip 101g, and each third diffraction region 201b is located at the light-emitting side of the corresponding blue laser chip 101b.

[0101] The red laser beam emitted by each red laser chip 101r can be shaped into a rectangular red laser spot a2 after passing through the corresponding first diffraction area 201r. The green laser beam emitted by each green laser chip 101g can be shaped into a rectangular green laser spot b2 after passing through the corresponding second diffraction area 201g. The blue laser light emitted by each blue laser chip 101b can be shaped into a rectangular blue laser spot c2 after passing through the corresponding third diffraction area 201b. The rectangular laser spots of red, green, and blue are respectively projected by the corresponding diffraction areas at the same set position to form a rectangular white spot H. The intensity distribution of the formed rectangular white spot H has good uniformity.

[0102] In specific implementations, the arrangement of laser chips in the laser can take various forms. For example, in some embodiments, the laser includes laser chips arranged in a 4-row × 7-column array, wherein the green laser chips are arranged in one row, the blue laser chips are arranged in one row, and the red laser chips are arranged in two rows. The center wavelengths of the laser chips emitting lasers of the same color can be the same or different. For example, the center wavelength of the laser emitted by the green laser chip can be 525 nm, the center wavelength of the laser emitted by the blue laser chip can be 465 nm, and the center wavelength of the laser emitted by the red laser chip includes 643 nm, 647 nm, and 639 nm. In some embodiments, the laser includes laser chips arranged in two rows, wherein the red laser chip is arranged in one row, and the green laser chip and the blue laser chip are arranged in one row. The number of red laser chips is 4, and the sum of the number of green laser chips and blue laser chips is 5. The central wavelengths of laser light emitted by red laser chips include 643nm, 647nm, and 639nm. The central wavelength of laser light emitted by green laser chips can be 525nm. The central wavelength of laser light emitted by blue laser chips can be 465nm. The embodiments of this application illustrate only the arrangement of the laser chips in the aforementioned lasers and do not limit other arrangements of laser chips.

[0103] FIG14 is a second schematic diagram of the structure of the projection device provided in an embodiment of the present application.

[0104] In some embodiments, as shown in FIG14 , the projection device may further include a reflective assembly 50, which is located between the diffractive optical element 20 and the light modulation component 30. The reflective assembly 50 may be used to reflect the output light of the diffractive optical element 20 toward the light modulation component 30 at a set angle. When a DMD is used as the light modulation component 30, it is necessary to make the light enter the DMD at a specific angle. Therefore, the reflective assembly 50 may be provided before the optical path of the DMD, so that the rectangular light spot after shaping and homogenization is incident on the DMD at a suitable angle. In a specific implementation, the reflective assembly 50 may be a reflector or a total reflection prism, etc. FIG9 illustrates an example of a reflective assembly 50 using a total reflection prism. The embodiments of the present application do not limit the specific structure of the reflective assembly.

[0105] FIG15 is a third structural schematic diagram of the projection device provided in an embodiment of the present application.

[0106] In some embodiments, as shown in FIG15 , the projection device may further include an aperture 60, which is located between the diffraction optical element 20 and the light modulation component 30. In a specific implementation, the aperture 60 may be rectangular in shape, and the aperture 60 may be set at the position where the light spot formed by shaping and homogenizing the diffraction optical element 20 is located, so that the aperture 60 can limit the range of the light spot and filter out excess stray light.

[0107] The collimating and focusing lens assembly 70 is located between the aperture 60 and the light modulation component 30 and can be used to collimate and converge the shaped light spot. In a specific implementation, the collimating and focusing lens assembly 70 may include a first lens 701 and a second lens 702. The first lens 701 is located in the output light path of the aperture 60, and the distance from the aperture 60 is equal to the focal length of the first lens 701. The first lens 701 can be used to collimate the light emitted from the aperture 60. The second lens 702 is located between the first lens 701 and the light modulation component 30 and can be used to converge the collimated light emitted by the first lens 701 into a light spot incident on the reflective assembly 50.

[0108] The optical path propagation process of the projection device shown in Figure 15 is as follows: the light emitted from the laser 10 is incident on the diffraction optical element 20, and the laser light beams emitted by each laser chip in the laser 10 are shaped and homogenized by the corresponding diffraction area to form a light spot with uniform intensity distribution at a set position. The light spot is filtered by the aperture 60 for filtering the edge stray light and is incident on the collimating focusing lens group 70 to be converged, and then is incident on the reflection component 50, and is then reflected by the reflection component 50 at a certain angle to the light modulation component 30. The light modulation component 30 modulates the light spot and emits it to the projection lens 40 through the reflection component 50, and the projection lens 40 projects the modulated light spot for imaging.

[0109] FIG16 is a fourth structural schematic diagram of the projection device provided in an embodiment of the present application.

[0110] In some embodiments, as shown in FIG. 16 , the projection device may include a plurality of lasers 10 and a plurality of diffractive optical elements 20 , and the projection device further includes a light combining component 80 .

[0111] Each laser 10 is configured to emit laser light of a specific color. Each laser 10 emits laser light of a different wavelength, enabling full-color display. In a specific implementation, the laser 10 may be a bank laser. Other types of lasers may also be used, without limitation.

[0112] The multiple diffractive optical elements 20 correspond one-to-one to the multiple lasers 10, and each diffractive optical element 20 is located on the light-emitting side of the corresponding laser 10. The diffractive optical element 20 is used to homogenize and shape the laser beam emitted by the corresponding laser 10 into a rectangular spot with uniform intensity distribution.

[0113] The light combining assembly 80 is located on a side of each diffractive optical element 20 away from the laser 10. The light combining assembly 80 is used to combine the laser beams homogenized and shaped by each diffractive optical element 20.

[0114] Among them, the phase distribution of each diffraction optical element 20 is determined according to the initial parameters of the laser light beam emitted by the corresponding laser 10 and the output parameters after passing through the diffraction optical element 20, so that the laser light beam emitted by each laser 10 is merged into a rectangular light spot with the same size and uniform intensity distribution at the same position after passing through the diffraction optical element 20 and the light combining component 80.

[0115] By carrying out targeted design of the diffraction optical element 20 corresponding to each laser 10, the laser light beams emitted by each laser 10 can be combined into rectangular light spots of the same size and uniform intensity distribution at the same position after being homogenized and shaped by the corresponding diffraction optical element 20 and combined by the light combining component 80 to meet the lighting requirements of the light modulation component 30, thereby omitting the need for light guides and other light-uniform components in the projection equipment, thereby avoiding energy loss caused by light guides and other light-uniform components, and at the same time realizing a miniaturized design of the projection equipment.

[0116] Since the micro-mirrors on the DMD surface are usually set to be deflected to a set angle for use, such as +12°, 0°, and -12°, the output light beam of the light combining component 80 needs to enter the light modulation component 30 at a specific angle. Therefore, in a specific implementation, a reflective component 50 can be provided in the projection device.

[0117] FIG17 is a fifth structural diagram of the projection device provided in an embodiment of the present application.

[0118] In some embodiments, as shown in FIG17 , the projection device may further include a reflective component 50. The reflective component 50 is located on the light-emitting side of the light-combining component 80. The function of the reflective component 50 is to reflect the outgoing light beam of the light-combining component 80 toward the light modulation component 30 at a set angle. By adjusting the light path of the light before it enters the DMD and after it is reflected by the DMD through the reflective component 50, the light-combining component 80 and the projection lens 40 are no longer limited by the deflection angle of the tiny reflectors on the surface of the DMD when setting them, so that the optical axis of the outgoing light of the light-combining component 80 can be set perpendicular to the optical axis of the incident light of the projection lens 40, or can be set at other angles to meet more usage scenarios.

[0119] Taking FIG17 as an example, the reflective assembly 50 may include two total reflection prisms arranged opposite each other. When a laser beam is incident on one of the total reflection prisms at a set angle, the incident angle satisfies the total reflection condition of the total reflection prism, and the total reflection prism can reflect all the light toward the light modulation component 30. After being modulated by the light modulation component 30, the light is emitted again toward the total reflection prism. At this time, the light no longer meets the total reflection condition and can be emitted smoothly. After being refracted by the other total reflection prism, the modulated light is incident on the projection lens 40.

[0120] Alternatively, the reflective assembly 50 may be a mirror. After the laser beam is incident on the reflective mirror at a set angle, the reflective mirror reflects the light back to the light modulator 30 in a direction that satisfies the incident angle of the light modulator 30. The light modulator 30 modulates the light before emitting it toward the projection lens. Alternatively, the reflective assembly 50 may be other optical elements with a reflective function, which are not limited herein.

[0121] In some embodiments, as shown in Figures 16 and 17, multiple lasers 10 are divided into a first laser 110, a second laser 120, and a third laser 130. The first laser 110 is used to emit red laser light, the second laser 120 is used to emit green laser light, and the third laser 130 is used to emit blue laser light, thereby achieving full-color display. Specifically, the wavelength of the red laser light emitted by the first laser 110 can be 625nm, the wavelength of the green laser light emitted by the second laser 120 can be 550nm, and the wavelength of the blue laser light emitted by the third laser 130 can be 450nm. According to actual needs, the emitted laser light of the first laser 110, the second laser 120, and the third laser 130 can also be other wavelengths, which are not limited here.

[0122] The multiple diffractive optical elements 20 are divided into a first diffractive optical element 210, a second diffractive optical element 220, and a third diffractive optical element 230. The first diffractive optical element 210 is located on the light-emitting side of the first laser 110, the second diffractive optical element 220 is located on the light-emitting side of the second laser 120, and the third diffractive optical element 230 is located on the light-emitting side of the third laser 130.

[0123] FIG18 is one of the structural schematic diagrams of the light combining assembly provided in an embodiment of the present application.

[0124] In some embodiments, as shown in FIG18 , the light-combining assembly 80 is a light-combining prism. The light-combining prism has a rectangular parallelepiped structure and includes a first light-incident surface S1, a second light-incident surface S2, a third light-incident surface S3, and a light-exiting surface S4. The first light-incident surface S1 is disposed opposite the third light-incident surface S3, and the second light-incident surface S2 is disposed opposite the light-exiting surface S4. The first diffractive optical element 210 is disposed opposite the first light-incident surface S1, the second diffractive optical element 220 is disposed opposite the second light-incident surface S2, and the third diffractive optical element 230 is disposed opposite the third light-incident surface S3.

[0125] Among them, the output lasers of the first laser 110, the second laser 120 and the third laser 130 are respectively homogenized and shaped by the first diffraction optical element 210, the second diffraction optical element 220 and the third diffraction optical element 230, and the homogenized and shaped laser beams are respectively relatively vertically incident on the first light incident surface S1, the second light incident surface S2 and the third light incident surface S3 into the light combining prism. After being combined by the light combining prism, the combined light beam is relatively vertically emitted from the light exiting surface. After being emitted through the light combining prism, the output lasers of each laser are combined at the same position into rectangular light spots with the same size and uniform intensity distribution.

[0126] As shown in FIG18 , the light-combining prism includes a first transflective layer 810 and a second transflective layer 820 arranged along the diagonal surfaces of the rectangular parallelepiped. The first transflective layer 810 and the second transflective layer 820 intersect with each other, wherein the first transflective layer 810 is used to receive the laser light emitted by the first laser 110, reflect it toward the light-emitting surface S4, and transmit the laser light emitted by the second laser 120 and the third laser 130; the second transflective layer 820 is used to receive the laser light emitted by the third laser 130, reflect it toward the light-emitting surface S4, and transmit the laser light emitted by the first laser 110 and the second laser 120.

[0127] In a specific implementation, the first transflective layer 810 may be a low-pass, high-reflection transflective layer, and the second transflective layer 820 may be a high-pass, low-reflection transflective layer. The high-pass, low-reflection transflective layer can pass laser light with a wavelength greater than a cutoff wavelength and reflect laser light with a wavelength less than the cutoff wavelength; the low-pass, high-reflection transflective layer can pass laser light with a wavelength less than the cutoff wavelength and reflect laser light with a wavelength greater than the cutoff wavelength. The cutoff wavelength of the first transflective layer 810 is smaller than the wavelength of the laser light emitted by the first laser 110, but larger than the wavelengths of the laser light emitted by the second laser 120 and the third laser 130. The cutoff wavelength of the second transflective layer 820 is smaller than the wavelengths of the laser light emitted by the first laser 110 and the second laser 120, but larger than the wavelength of the laser light emitted by the third laser 130. As a result, the first transflective layer 810 can reflect the laser light emitted by the first laser 110, and the second transflective layer 820 can reflect the laser light emitted by the third laser 130. At the same time, both the first transflective layer 810 and the second transflective layer 820 can transmit the laser light emitted by the second laser 120, thereby combining the laser light beams emitted by the three lasers, simplifying the structure, and improving the utilization rate of light.

[0128] FIG19 is a second structural diagram of the light combining assembly provided in an embodiment of the present application.

[0129] In some embodiments, as shown in FIG19 , the light-combining prism (light-combining component 80 ) may also adopt a cube structure. In order to reduce the volume of the projection device, each diffraction optical element 20 may be fitted with each light-incident surface of the light-combining prism (light-combining component 80 ).

[0130] FIG20 is a third structural schematic diagram of the light combining component provided in an embodiment of the present application.

[0131] In some embodiments, as shown in FIG20 , the projection device further includes a focusing lens 90. The focusing lens 90 is located on the light-emitting side of the light-combining assembly 80. The focusing lens 90 is used to adjust the size of the rectangular light spot after the light-combining assembly 80 combines the light. Thus, for DMDs of different sizes or different projection systems, the size of the combined rectangular light spot can be adjusted by using focusing lenses 90 of different focal lengths without changing other structures. This allows the adjusted size of the rectangular light spot to be compatible with the size of the DMD, thereby expanding its range of applications.

[0132] In a specific implementation, the focusing lens 90 can be a plano-convex lens, and the plane of the plano-convex lens is aligned with the light-emitting surface S4 of the light-combining prism, thereby reducing the difficulty of installing the focusing lens and making the structure of the projection device more compact.

[0133] In addition, the focusing lens 90 may also be a lens group, which can be used to enlarge or reduce the size of the light spot, and is not limited here.

[0134] FIG21 is a fourth schematic diagram of the structure of the light combining assembly provided in an embodiment of the present application; FIG22 is a fifth schematic diagram of the structure of the light combining assembly provided in an embodiment of the present application.

[0135] In some embodiments, as shown in Figures 21 and 22, the first laser 110, the second laser 120, and the third laser 130 are arranged side by side, with the second laser 120 located between the first laser 110 and the third laser 130. The light combining assembly 80 includes a reflector 801, a first light combining mirror 802, and a second light combining mirror 803. The first light combining mirror 802 and the second light combining mirror 803 are both dichroic mirrors.

[0136] In a specific implementation, as shown in FIG21 , the reflector 801 is located on the side of the third diffractive optical element 230 facing away from the third laser 130, the first light-combining mirror 802 is located at the intersection of the reflected light from the reflector 801 and the laser light emitted from the second diffractive optical element 220, and the second light-combining mirror 803 is located at the intersection of the laser light emitted from the first light-combining mirror 802 and the laser light emitted from the first diffractive optical element 210. The reflector 801 is used to receive the laser light emitted from the third laser 130 and reflect it toward the first light-combining mirror 802; the first light-combining mirror 802 is used to transmit the laser light emitted from the third laser 130 and reflect the laser light emitted from the second laser 120; and the second light-combining mirror 803 is used to transmit the laser light emitted from the third laser 130 and the laser light emitted from the second laser 120 and reflect the laser light emitted from the first laser 110.

[0137] Alternatively, as shown in FIG22 , the reflector 801 is located on the side of the first diffractive optical element 210 facing away from the first laser 110, the first light-combining mirror 802 is located at the intersection of the reflected light from the reflector 801 and the laser light emitted from the second diffractive optical element 220, and the second light-combining mirror 803 is located at the intersection of the laser light emitted from the first light-combining mirror 802 and the laser light emitted from the third diffractive optical element 230. The reflector 801 is configured to receive the laser light emitted from the first laser 110 and reflect it toward the first light-combining mirror 802; the first light-combining mirror 802 is configured to transmit the laser light emitted from the first laser 110 and reflect the laser light emitted from the second laser 120; and the second light-combining mirror 803 is configured to transmit the laser light emitted from the first laser 110 and the laser light emitted from the second laser 120 and reflect the laser light emitted from the third laser 130.

[0138] Furthermore, a focusing lens or a lens group can be provided on the light-emitting side of the light-combining component 80 to adjust the size of the combined rectangular light spot and expand the scope of use, which is not limited here.

[0139] In the embodiment of the present application, the laser beams emitted by the first laser 110, the second laser 120, and the third laser 130 are homogenized and shaped by the corresponding diffractive optical element 20, and are combined by the light combining assembly 80. The propagation paths and distances of the light beams are different, which affects the overlap of the rectangular light spots emitted by each diffractive optical element 20 after the light is combined by the light combining assembly 80. Therefore, it is also necessary to determine the distance between each diffractive optical element 20 and the corresponding laser 10, as well as the distance between each diffractive optical element 20 and the corresponding light incident surface, based on the phase distribution of each diffractive optical element 20. Alternatively, when designing the diffractive optical element 20, the phase distribution of the diffractive optical element 20 is determined based on the distance between each diffractive optical element 20 and the corresponding laser 10, as well as the distance between each diffractive optical element 20 and the corresponding light incident surface. This ensures that the rectangular light spots have a high overlap after the light is combined by the light combining assembly 80, while making the structure of each element more compact and reducing the volume of the projection device.

[0140] FIG23 is a sixth structural diagram of the projection device provided in an embodiment of the present application.

[0141] In some embodiments, as shown in FIG23 , the projection device may further include a moving diffuser 100. The moving diffuser 100 is located on the light-emitting side of the light-combining assembly 80 and can rotate about the optical axis of the outgoing laser beam from the light-combining assembly to reduce the coherence of the incident laser beam.

[0142] In a specific implementation, the moving diffuser 100 can be made of a birefringent material, a material with a microcrystalline structure or a rough surface on the outside or inside, such as fused quartz, frosted glass, opal glass, etc., which is not limited here.

[0143] Another aspect of the embodiments of the present application further provides a method for designing a diffractive optical element. For the projection device shown in Figure 2, Figure 14 or Figure 15, the method for designing a diffractive optical element specifically refers to a method for designing each diffraction area corresponding to each laser chip in the diffractive optical element.

[0144] FIG24 is one of the flow charts of the design method of the diffractive optical element provided in an embodiment of the present application.

[0145] As shown in FIG24 , the design method of the diffractive optical element includes:

[0146] S1. Determine the initial parameters of the laser beam emitted by each laser chip when it enters the corresponding diffraction area and the output parameters when it emerges from the diffraction area;

[0147] S2. determining the phase distribution of each diffraction region by an iterative Fourier transform algorithm according to the initial parameters and the output parameters;

[0148] S3. Determine the morphology of each diffraction region according to the phase distribution of each diffraction region and process it to form a diffraction optical element.

[0149] Because each diffraction region of a diffractive optical element can only produce a specific light intensity distribution within a certain depth of field, certain parameter restrictions are imposed on the design and fabrication of diffraction optical elements. Specifically, the initial parameters in step S1 must include the wavelength, beam quality, and beam waist radius of the laser beam emitted by each laser chip before it enters the corresponding diffraction region; the output parameters include the size, emission distance, and diffraction order of the laser spot emitted from each diffraction region.

[0150] FIG25 is a second flowchart of the method for designing a diffractive optical element provided in an embodiment of the present application.

[0151] After determining the various initial parameters and output parameters in step S1, the phase distribution of each diffraction region can be determined by an iterative Fourier transform algorithm. Step S2 specifically includes:

[0152] S201, determining the initial field intensity distribution of the laser beam emitted by each laser chip before it enters the corresponding diffraction area according to the initial parameters;

[0153] S202, performing Fourier transform on the initial field intensity distribution to determine the output field intensity distribution of the laser spot emitted from each diffraction area;

[0154] S203, using a first constraint function to constrain the output field intensity distribution;

[0155] S204, performing an inverse Fourier transform on the constrained output field intensity distribution to obtain a new spatial distribution, using a second constraint function to constrain the phase in the spatial domain, and repeatedly using the second constraint function to constrain the constrained phase until the output condition is met, ending the iteration and obtaining an output result;

[0156] S205, performing phase compression on the phase of the output result using a set compression function;

[0157] S206 , using a set quantization function to quantize the compressed phase into steps, and determining the phase distribution of the diffraction area.

[0158] Specifically, the initial field intensity distribution in step S201 can be a Gaussian distribution function Where A1(X1, Y1) and They are the amplitude distribution and initial phase of the laser beam emitted by the laser chip before it enters the corresponding diffraction area, and the initial phase Can be a random value between [0,2π].

[0159] In step S202 and step S203, the output phase distribution function of the laser spot emitted from each diffraction area is Here, it is necessary to make appropriate constraints on the output field intensity distribution in the frequency domain, and amplitude constraints or support domain constraints can be used. The embodiment of the present application uses the first constraint function to perform amplitude constraints on the output field intensity distribution and keep the phase unchanged, and replaces the amplitude in the frequency domain with the known diffraction spot intensity distribution A2 (X2, Y2). In specific implementation, the first constraint function can adopt a super-Gaussian amplitude distribution.

[0160] In step S204, the output field intensity distribution after constraint is The second constraint function can be the same as the first constraint function or different, and needs to be determined according to the specific situation. The output condition can be the number of iterations or the amplitude error, etc. In the embodiment of the present application, the output condition is satisfied when the amplitude error is less than a specific value. The specific expression is Where SEA represents the amplitude error, and ε represents a specific value.

[0161] The compression function used in step S205 can be Where q is the blaze coefficient. When the blaze is accurate, q = 1. When q ≠ 1, it indicates errors such as processing and wavelength. The compression function can be used to achieve 2π phase compression.

[0162] The quantization function used in step S206 can be

[0163] Figure 26 is a schematic diagram of the distribution of the initial field intensity of the light spot provided in an embodiment of the present application; Figure 27 is a schematic diagram of the distribution of the output field intensity of the light spot provided in an embodiment of the present application; Figure 28 is a schematic diagram of the phase distribution of the diffraction area provided in an embodiment of the present application.

[0164] Figures 26 to 28 are illustrated using one of the diffraction areas of the diffraction optical element as an example. Specifically, Figure 26 shows the initial field intensity distribution of the elliptical light spot before the laser beam emitted from the laser chip corresponding to the diffraction area is incident on the diffraction area. Figure 27 shows the output field intensity distribution of the rectangular light spot emitted after the light spot is homogenized and shaped by the diffraction area. Figure 28 shows the phase distribution of the diffraction area calculated based on the initial field intensity distribution and output field intensity distribution of the light spot using the method for manufacturing the diffraction optical element provided in an embodiment of the present application.

[0165] By using the method for manufacturing a diffractive optical element provided in an embodiment of the present application, the phase distribution of each diffraction region can be obtained, based on the determination of the initial field intensity distribution of the laser beam emitted by each laser chip before it enters the corresponding diffraction region and the output field intensity distribution of the laser spot emitted from each diffraction region. The method for manufacturing a diffractive optical element provided in an embodiment of the present application is based on an improved Gerchberg-Saxton phase retrieval algorithm. The improved algorithm has high optimization efficiency and local optimization rate, and can break free from the limitations of local extreme points. The diffraction efficiency of the diffractive optical element manufactured using the method for manufacturing a diffractive optical element provided in an embodiment of the present application can reach over 95%, and the signal-to-noise ratio can reach over 50%. Compared with the results in related technologies, higher diffraction efficiency and signal-to-noise ratio can be achieved.

[0166] For the projection device shown in FIG14 , the design method of the diffractive optical element specifically refers to a design method for each diffractive optical element specifically for each laser.

[0167] FIG29 is a schematic diagram of a laser spot incident on a diffractive optical element provided in an embodiment of the present application.

[0168] The incident laser of the diffractive optical element has a wavelength of 450nm and a beam quality of M 2 For example, a blue laser beam with a wavelength of 1 is used. The incident laser beam is a Gaussian beam with a waist radius of 250μm and 500μm, respectively. As shown in Figure 29, the incident spot is elliptical. The divergence angles of the laser are 0.032828° and 0.016414°, respectively, and the Rayleigh lengths are 436.33mm and 1.7453m, respectively.

[0169] In a specific implementation, the shape of the light-combining prism can be a 20mm×20mm×20mm cube. In this case, the propagation distance of the laser beam in the light-combining prism is 20mm. To reduce the volume of the laser projection system, each diffractive optical element 20 can be placed in contact with the light incident surface of the light-combining prism. The output distance of the diffractive optical element 20 is 20mm. In this way, the laser beams emitted by the diffractive optical elements can be incident on the light incident surface of the light-combining prism and then combined at the light exit surface.

[0170] Figure 30 is a schematic diagram of a laser spot emitted from a diffraction optical element provided in an embodiment of the present application.

[0171] To ensure the overlap of the combined light spots after the light-combining prism, it is necessary to ensure that the rectangular light spots emitted by each diffractive optical element 20 are of the same size when combined. In practice, the size of the laser light spot emitted by each diffractive optical element can be set to 5.1mm×2.9mm. The diffraction order is set according to actual conditions.

[0172] After determining the initial parameters of the outgoing laser of the above-mentioned laser and the output parameters after passing through the diffraction optical element, the relevant parameters are input into the Zemax software for refined optical simulation to obtain the initial phase distribution of the diffraction optical element. Then, the optimization design is performed using the iterative Fourier transform method using Matlab software. The number of iterations for phase optimization is at least 100, and the number of iterations for signal-to-noise ratio optimization is at least 50. The specific simulation and optimization process can refer to the existing technology, and finally the target phase of the diffraction optical element obtained is used to generate a processable phase file for the processing and manufacture of the diffraction optical element. The diffraction optical element can be made of infrared materials such as quartz, glass, gemstone, plastic and resin, ZnSe, etc., and can be coated with an anti-reflection film, which is not limited here.

[0173] The diffractive optical elements corresponding to the lasers emitting red laser and green laser can be designed and manufactured using the same method, so that the size and emission distance of the laser spots emitted by each diffractive optical element are ultimately the same.

[0174] Since the light-combining prism is a cube, the size and emission distance of the laser spots emitted by each diffractive optical element are the same. When installing the laser projection system, each diffractive optical element is aligned with the corresponding light incident surface. At this time, it is only necessary to set the laser in the center of the corresponding diffractive optical element to ensure that the diffraction spots have a high degree of overlap.

[0175] In specific implementation, the laser may be allowed to have a certain offset relative to the center of the corresponding diffractive optical element. The setting of the offset is different for lasers of different wavelengths, and the diffractive optical element needs to be designed accordingly.

[0176] When adjusting the relative position between the laser and the corresponding diffractive optical element, the diffractive optical element can be placed at the corresponding laser beam waist radius position, where the laser energy is more concentrated and the diffraction effect is optimal. In addition, the planar dimensions of the diffractive optical element (the diameter of a circle or the length and width of a rectangle) can be greater than twice the beam waist radius to ensure high diffraction efficiency and reduce laser energy loss.

[0177] Since the incident laser spot does not cover the entire diffractive optical element, and the laser spot emitted by the diffractive optical element will continue to diverge, the optical path distance from the diffractive optical element to the light-emitting surface can be the depth of field. The light spot near the depth of field position has the best light intensity distribution, and the fluctuation of the light spot intensity distribution obtained by moving back and forth at this position is small, which is conducive to reducing tolerance.

[0178] In specific implementation, the design and installation position of the diffractive optical element for projection equipment of different structures can refer to the above process. The size of the light-combining prism needs to be designed according to the output distance of the diffractive optical element, the size of the output light spot, etc., to ensure that all light is incident on the light-combining prism and combined into a rectangular light spot on the light-emitting surface. The light-combining prism can also be a rectangular parallelepiped, which is not limited here.

[0179] In addition, the light incident surface of the diffractive optical element and the corresponding light-combining prism may not be in contact with each other, and the laser spots emitted by each diffractive optical element may also be combined into a rectangular spot at other positions on the output light path, which is not limited here.

[0180] For the projection devices shown in Figures 21 and 22, when the light combining assembly 80 includes a reflector 801, a first light combining mirror 802, and a second light combining mirror 803, the diffractive optical element can also be designed in the manner described above for the light combining prism. However, because the emission distances of the laser spots emitted by each diffractive optical element before merging into a single spot are different, the emission distances of the laser spots emitted by each diffractive optical element need to be individually designed when designing the diffractive optical element.

[0181] Based on the same inventive concept, an embodiment of the present application also provides a projection system, comprising a projection screen and any of the above-mentioned projection devices, wherein the projection screen is located on the light-emitting side of the projection device. In the projection device, a diffraction optical element is provided on the light-emitting side of the laser, and the diffraction optical element is designed and manufactured according to the various parameters of the incident laser beam and the outgoing laser beam, so that the laser beam emitted from the laser is shaped into a rectangular light spot after passing through the diffraction optical element and is projected to the same set position. The rectangular light spots of different colors have a high degree of overlap, and the intensity distribution of the synthesized white rectangular light spot is uniform. Thus, components such as the light-uniformity component and the shaping lens group are omitted, which is conducive to the miniaturization of the projection system and has a good projection display effect. After the projection light beam emitted by the projection device is incident on the projection screen, it is transmitted or reflected by the projection screen to the human eye, so that the viewer can see the projected image.

Claims

1. A projection device, comprising: At least one laser; the laser comprises a plurality of laser chips arranged in an array; At least one diffractive optical element, one diffractive optical element corresponding to one laser, the diffractive optical element being located on the light-emitting side of the corresponding laser; the diffractive optical element comprising a plurality of diffraction regions, one diffraction region corresponding to one laser chip; the size of the diffraction region being larger than the size of the laser spot formed when the laser beam emitted by the corresponding laser chip enters the diffraction region; the laser spots of the laser beams emitted by adjacent laser chips do not overlap when entering the corresponding diffraction regions, and adjacent diffraction regions do not overlap; In which, the phase distribution of each diffraction area in the diffraction optical element is determined according to the initial parameters of the incident laser beam and the output parameters after passing through the diffraction area; the laser beam emitted by the laser forms a rectangular light spot with uniform energy distribution at a set position after passing through the diffraction optical element.

2. The projection device according to claim 1, wherein: The initial parameters include: wavelength, beam quality and beam waist radius of the laser beam; The output parameters include: the size, emission distance and diffraction order of the laser spot emitted from the diffractive optical element.

3. The projection device according to claim 1, wherein: Each of the diffraction regions in the diffraction optical element includes a plurality of diffraction structures, and each of the diffraction structures is distributed in two dimensions; the diffraction structure includes at least one of a sawtooth structure, a trapezoidal structure, an inclined rectangular structure or a stepped structure.

4. The projection device according to claim 3, wherein: The thickness of the diffractive optical element is less than 1 mm.

5. The projection device according to claim 3, wherein: The maximum period of the diffraction structure satisfies: d×sinθ=λ; Wherein, d represents the maximum period of the diffraction structure, θ represents the diffraction angle of the diffraction structure, and λ represents the wavelength of the incident laser.

6. The projection device according to any one of claims 1 to 5, wherein: The laser further comprises: a packaging structure for packaging each of the laser chips; the packaging structure comprises: base plate; A tube shell is arranged around the four sides of the base plate; the base plate and the tube shell form a receiving space for receiving each laser chip; a cover plate, located on a side of the tube shell facing away from the bottom plate, and the four sides of the cover plate are sealed with the tube shell; The diffractive optical element is located on the cover plate of the corresponding laser.

7. The projection device according to any one of claims 1 to 5, wherein: The laser further comprises: a packaging structure for packaging each of the laser chips; the packaging structure comprises: base plate; A tube shell is arranged around the four sides of the base plate; the base plate and the tube shell form a receiving space for receiving each laser chip; a cover plate, located on a side of the tube shell facing away from the bottom plate, and the four sides of the cover plate are sealed with the tube shell; A plurality of collimating lenses are located on the cover plate; one collimating lens is provided corresponding to one laser chip; The diffraction regions in the diffraction optical element are arranged in one-to-one correspondence with the collimating lenses; the diffraction regions are located on the corresponding collimating lenses; or, the diffraction optical element and the multiple collimating lenses are separated by a set distance.

8. The projection device according to any one of claims 1 to 7, further comprising: a light modulation component, located on an outgoing light path of the diffractive optical element; The outgoing light of the diffractive optical element is incident on the light modulation component at a set angle; The light modulation component is used to modulate the incident light and then emit it; The projection lens is located on the outgoing light path of the light modulation component; the projection lens is used to project the light modulated by the light modulation component into an image.

9. The projection device according to claim 8, wherein: The area of ​​the diffractive optical element increases as the distance between the diffractive optical element and the light modulation component increases.

10. The projection device according to claim 8, further comprising: A reflective component is located between the diffractive optical element and the light modulation component; the reflective component is used to The outgoing light is reflected toward the light modulation component at a set angle; The reflection component is a reflector or a total reflection prism.

11. The projection device according to any one of claims 1 to 10, wherein: The projection device includes a laser and a diffractive optical element; The phase distribution of each diffraction region is determined by using an iterative algorithm of Fourier transform according to the initial parameters of the laser beam emitted by the corresponding laser chip and the output parameters after passing through the diffractive optical element.

12. The projection device according to claim 11, further comprising: an aperture, located on the light-emitting side of the diffractive optical element; The aperture is rectangular in shape and is used to filter out excess stray light; The collimating and focusing lens group is located on the side of the aperture away from the diffractive optical element.

13. The projection device according to claim 11 or 12, wherein: The lasers include: a red laser chip, a green laser chip, and a blue laser chip; The diffraction areas are divided into: a first diffraction area, a second diffraction area, and a third diffraction area; one first diffraction area corresponds to one red laser chip, one second diffraction area corresponds to one green laser chip, and one third diffraction area corresponds to one blue laser chip; each first diffraction area is located on the light-emitting side of the corresponding red laser chip, each second diffraction area is located on the light-emitting side of the corresponding green laser chip, and each third diffraction area is located on the light-emitting side of the corresponding blue laser chip.

14. The projection device according to any one of claims 1 to 10, wherein: The projection device includes a plurality of the lasers and a plurality of the diffractive optical elements; The projection device further comprises: a light combining assembly, located on a side of each diffractive optical element away from the corresponding laser, for combining the light homogenized and shaped by each diffractive optical element; The laser beams emitted by each laser pass through the corresponding diffraction optical element and the light combining component and are then combined at the same set position to form rectangular light spots with the same size and uniform intensity distribution.

15. The projection device according to claim 14, wherein: The plurality of lasers include: a first laser, a second laser and a third laser; the first laser is used to emit red laser light, the second laser is used to emit green laser light, and the third laser is used to emit blue laser light; The multiple diffractive optical elements include: a first diffractive optical element located on the light exit side of the first laser, a second diffractive optical element located on the light exit side of the second laser, and a third diffractive optical element located on the light exit side of the third laser.

16. The projection device according to claim 15, wherein: The light combining component is a light combining prism; The light-combining prism is a rectangular parallelepiped structure; the light-combining prism includes a first light incident surface, a second light incident surface, a third light incident surface, and a light exit surface; the first light incident surface is arranged opposite to the third light incident surface, and the second light incident surface is arranged opposite to the light exit surface; the first diffractive optical element is arranged opposite to the first light incident surface, the second diffractive optical element is arranged opposite to the second light incident surface, and the third diffractive optical element is arranged opposite to the third light incident surface; The light-combining prism includes a first transflective layer and a second transflective layer arranged along the diagonal surfaces of the rectangular parallelepiped; the first transflective layer and the second transflective layer intersect with each other; the first transflective layer is used to receive the laser light emitted by the first laser, reflect it toward the light-emitting surface, and transmit the laser light emitted by the second laser and the third laser; the second transflective layer is used to receive the laser light emitted by the third laser, reflect it toward the light-emitting surface, and transmit the laser light emitted by the first laser and the second laser.

17. The projection device according to claim 16, further comprising: A focusing lens, located on the light-emitting side of the light-combining prism; The focusing lens is a plano-convex lens; the plane of the plano-convex lens is in contact with the light-emitting surface of the light-combining prism.

18. The projection device according to claim 15, wherein: The light combining assembly includes a reflector, a first light combining mirror, and a second light combining mirror; the first light combining mirror and the second light combining mirror are both dichroic mirrors; The first laser, the second laser and the third laser are arranged side by side, and the second laser is located between the first laser and the third laser; The reflecting mirror is located on the side of the third diffractive optical element away from the third laser, and the first light combining mirror is located on the reflecting mirror. The second light combining mirror is located at the intersection of the reflected light of the mirror and the output laser of the second diffractive optical element, and the second light combining mirror is located at the intersection of the output laser of the first light combining mirror and the output laser of the first diffractive optical element; the reflector is used to receive the output laser of the third laser and reflect it to the first light combining mirror; the first light combining mirror is used to transmit the output laser of the third laser and reflect the output laser of the second laser; the second light combining mirror is used to transmit the output laser of the third laser and the output laser of the second laser, and reflect the output laser of the first laser; Alternatively, the reflector is located on the side of the first diffraction optical element away from the first laser, the first light combining mirror is located at the intersection of the reflected light of the reflector and the output laser of the second diffraction optical element, and the second light combining mirror is located at the intersection of the output laser of the first light combining mirror and the output laser of the third diffraction optical element; the reflector is used to receive the output laser of the first laser and reflect it to the first light combining mirror; the first light combining mirror is used to transmit the output laser of the first laser and reflect the output laser of the second laser; the second light combining mirror is used to transmit the output laser of the first laser and the output laser of the second laser, and reflect the output laser of the third laser.

19. The projection device according to any one of claims 14 to 18, further comprising: The moving diffuser is located on the light-emitting side of the light-combining component; the moving diffuser rotates around the optical axis of the outgoing laser of the light-combining component to reduce the coherence of the incident laser.

20. A projection system comprising the projection device according to any one of claims 1 to 19 and a projection screen located on a light-emitting side of the projection device.

Images