Projection system

Abstract

The present application discloses a projection system, comprising: a laser light source, a phase light modulator, a first lens group, a spatial filter, a second lens group, an amplitude light modulator, and a lens. The phase light modulator performs, on the basis of an image to be displayed, phase modulation on a laser light beam emitted by the laser light source, so as to form a modulated light beam matching a brightness distribution of the image to be displayed; the position where the modulated light beam propagates over a set distance is defined as an object plane of the first lens group; the first lens group focuses the incident light beam; the spatial filter capable of homogenizing a high-frequency component is arranged at a focusing position of the first lens group, so that the high-frequency component can be homogenized. The light beam passing through the spatial filter is imaged on a light receiving surface of the amplitude light modulator after passing through the second lens group again, and the amplitude light modulator performs amplitude modulation on the incident light on the basis of the image to be displayed, thereby effectively mitigating the speckle problem while enhancing the image contrast.

Description

Projection system

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202411524048.2, filed on October 29, 2024, and Chinese patent application No. 202411745806.3, filed on November 29, 2024, the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] Projection display technology is a technique that uses optical systems and projection space to magnify and display images. With the continuous development of projection technology, laser projection systems have been widely used in large-screen displays, laser TVs, digital cinemas, and portable projection displays. Laser projection displays can display more realistic and vibrant dynamic images on ultra-large screens. However, improving the image quality of laser projection systems remains a continuous pursuit within the industry. Summary of the Invention

[0005] Some embodiments of this application provide a projection system that can improve the image quality of a laser projection system. The projection system includes:

[0006] The laser source is configured to emit tri-color lasers;

[0007] A phase light modulator, located on the light-emitting side of the laser source, is configured to perform phase modulation on the laser emitted from the laser source according to the image to be displayed;

[0008] The first lens group, located on the light-emitting side of the phase light modulator, is configured to converge the phase-modulated light beam; the phase light modulator is located on the object plane of the first lens group or within a predetermined distance from the object plane of the first lens group.

[0009] The second lens group, located on the light-emitting side of the first lens group, is configured to convert the light beam from the first lens group into a light intensity distribution pattern and image it on the output surface; the image-side focal point of the first lens group and the object-side focal point of the second lens group are approximately coincident.

[0010] A spatial filter is located at the focal position of the first lens group or within a preset distance from the focal position of the first lens group; the spatial filter is configured to homogenize high-frequency noise; and

[0011] An amplitude light modulator, located on the image plane of the second lens group, is configured to modulate the amplitude of the incident light according to the image to be displayed, forming an image beam for projection imaging.

[0012] The projection system provided in some embodiments of this application includes: a laser source, a phase modulator, a first lens group, a spatial filter, a second lens group, an amplitude modulator, and a lens. The phase modulator modulates the phase of the laser beam emitted from the laser source according to the image to be displayed, forming a modulated beam that matches the brightness distribution of the image to be displayed. The position where the modulated beam propagates a set distance serves as the object plane of the first lens group. The first lens group focuses the incident beam, converting the modulated beam from the spatial domain to the frequency domain. At this time, the center of the spectrum is the origin, the area around the center is low-frequency, and the edges are high-frequency. Placing a spatial filter that homogenizes high-frequency components at or near the focusing position of the first lens group can homogenize the high-frequency components. High-frequency and low-frequency components refer to the spatial frequency. The size of the laser speckle distribution is on the order of micrometers, with a relatively high spatial frequency, belonging to the high-frequency component; while the size of the image with a specific amplitude distribution formed by the modulated beam emitted by the phase modulator is on the order of millimeters, belonging to the low-frequency component. Therefore, the spatial filter can effectively homogenize high-frequency noise without destroying the image with a specific amplitude distribution output by the phase modulator. After passing through the spatial filter, the light beam is converted from the frequency domain to the spatial domain after passing through the second lens group, and is imaged on the light-receiving surface of the amplitude light modulator. The amplitude light modulator modulates the amplitude of the incident light according to the image to be displayed, thereby enhancing the image contrast while effectively improving speckle problems and improving image quality.

[0013] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 is a schematic diagram of the projection system provided in some embodiments of this application;

[0016] Figure 2 is an architecture diagram of a projection system provided in some embodiments of this application;

[0017] Figure 3 is an architecture diagram of another projection system provided in some embodiments of this application;

[0018] Figure 4 is a schematic diagram of the structure of a laser provided in some embodiments of this application;

[0019] Figure 5 is a schematic diagram of another laser provided in some embodiments of this application;

[0020] Figure 6 is a schematic diagram of the structure of a laser source provided in some embodiments of this application;

[0021] Figure 7 is a schematic diagram of the structure of a phase light modulator provided in some embodiments of this application;

[0022] Figure 8 is another schematic diagram of the structure of a phase optical modulator provided in some embodiments of this application;

[0023] Figure 9 is another schematic diagram of the structure of a phase optical modulator provided in some embodiments of this application;

[0024] Figure 10 is an image of a specific amplitude distribution output by a phase light modulator provided in some embodiments of this application;

[0025] Figure 11 is a schematic diagram of the phase recovery algorithm of a phase optical modulator provided in some embodiments of this application;

[0026] Figure 12 is a schematic diagram of the filtering principle of a 4f filtering system provided in some embodiments of this application;

[0027] Figure 13 is a spectrum diagram provided by some embodiments of this application;

[0028] Figure 14 is a schematic diagram of the structure of a diffusion wheel provided in some embodiments of this application;

[0029] Figure 15 is a schematic diagram of the structure of a vibration diffuser provided in some embodiments of this application;

[0030] Figure 16 is a schematic diagram of the working principle of a tunable 4f filter system provided in some embodiments of this application;

[0031] Figure 17 is a schematic diagram of the working principle of a multi-stage 4f filter system provided in some embodiments of this application.

[0032] Figure 18 is a schematic diagram of the modulation effect of a phase light modulator in related technologies;

[0033] Figure 19 is a schematic diagram of the structure of the optical modulation system in some embodiments of this application;

[0034] Figure 20 is a schematic diagram comparing the display effects of the light intensity distribution patterns of the optical modulation system in some embodiments of this application;

[0035] Figure 21 is a schematic diagram comparing the display effects of the light intensity distribution pattern of the optical modulation system in some other embodiments of this application;

[0036] Figure 22 is a schematic diagram of the structure of the optical modulation system in some other embodiments of this application;

[0037] Figure 23 is a schematic diagram of the structure of the optical modulation system in some other embodiments of this application;

[0038] Figure 24 is a schematic diagram of the structure of the optical modulation system in some other embodiments of this application;

[0039] Figure 25 is a schematic diagram of the structure of the optical modulation system in some other embodiments of this application;

[0040] Figure 26 is a schematic diagram of the structure of the light-diffusing element in some embodiments of this application;

[0041] Figure 27 is a schematic diagram of the structure of the optical modulation system in some embodiments of this application;

[0042] Figure 28 is a schematic diagram of the structure of a laser projection device in some embodiments of this application;

[0043] Figure 29 is a schematic diagram of the structure of another laser projection device in some embodiments of this application;

[0044] Figure 30 is a schematic diagram of the structure of another laser projection device in some embodiments of this application;

[0045] Figure 31 is a comparison diagram of the display effect of the light intensity distribution pattern of the laser projection device in some embodiments of this application;

[0046] Figure 32 is a comparison diagram of the display effect of the light intensity distribution pattern of the laser projection device in some other embodiments of this application;

[0047] Figure 33 is a comparison diagram of the display effect of the light intensity distribution pattern of the laser projection device in some other embodiments of this application. Detailed Implementation

[0048] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the application will be further described below in conjunction with the accompanying drawings and embodiments. However, the exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the figures denote the same or similar structures, and therefore repeated descriptions of them will be omitted. Terms describing position and direction described in this application are illustrative based on the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this application. The accompanying drawings of this application are for illustrating relative positional relationships only and do not represent actual scale.

[0049] Projection systems can be divided into front projection systems and rear projection systems. In a front projection system, the projector and the viewer are located on the same side of the projection screen. The projector emits projection light onto the screen, and the light is reflected back to the viewer, allowing them to see the projected image. In a rear projection system, the projector and the viewer are located on opposite sides of the screen. The projector emits projection light onto the screen, and the screen transmits the light back to the viewer, allowing them to see the projected image.

[0050] Some embodiments of this application are illustrated using a front-projection system as an example. Figure 1 is a schematic diagram of the structure of a projection system provided in some embodiments of this application.

[0051] As shown in Figure 1, a front-projection system may include a projection device 10 and a projection screen 20.

[0052] The projection screen 20 is located on the light-emitting side of the projection device 10. The audience faces the projection screen 20. The projection device 10 emits projection light, which enters the projection screen 20 and is reflected back to the audience's location, so that the audience can see the projected image.

[0053] The projection device includes a projection light source, an illumination light path, and a lens. Its imaging principle is shown in Figure 2. The illumination light path is located on the light-emitting side of the projection light source, and the lens is located on the light-emitting side of the illumination light path. The projection light source emits a projection beam, and the illumination light path is configured to shape the projection beam. An amplitude modulator 13 is included in the illumination light path. The amplitude modulator 13 is a light modulation device that can modulate the amplitude of the incident light according to the image data of the image to be displayed, thereby forming an image beam for projection imaging. The image beam is finally projected through the lens 15 and viewed by the audience.

[0054] In some embodiments of this application, the projection light source may be a laser light source 11, which can emit three-color laser light as primary color light. Compared with other light sources, the laser light source has a higher color gamut, which can achieve better color performance and accurately reproduce the input image.

[0055] In related technologies, displays typically use liquid crystal displays (LCDs). LCDs are non-self-emissive displays and require light-emitting diodes (LEDs) or organic light-emitting diodes (OLEDs) as backlights. The backlight of an LCD can be divided into multiple zones, and the brightness of the light source in each zone can be controlled independently. This allows the light intensity of each backlight zone to be controlled according to the brightness distribution of the displayed image, thereby improving the contrast of the displayed image.

[0056] For laser projection systems, the laser light source always provides illumination according to a certain beam size and as a whole beam, so it cannot be divided into zones and cannot affect image contrast like an LCD monitor.

[0057] To enable the laser projection system to achieve a backlight zoning effect, as shown in Figure 2, a phase light modulator (PLM) 12 can be set in the projection system. The phase distribution of the laser beam is modulated by the diffraction of light, ultimately achieving the backlight zoning effect, which can significantly improve dynamic contrast.

[0058] However, due to the strong coherence of laser light, laser speckle can occur. Speckle arises when a laser beam is reflected or projected onto an inhomogeneous medium or surface, creating countless independent scattered wavelets. These wavelets coherently superimpose during propagation, resulting in uneven intensity distribution and alternating bright and dark spots. The size of the laser speckle distribution is approximately 1μm to 10μm, belonging to high-frequency changing signals. Speckle issues affect the image quality and visual effect of laser displays, reducing clarity and realism. Furthermore, the phase distribution inherent in PLM 12 is a computational hologram, and the calculation process involves random phase errors and high-frequency phase change signals. When superimposed on the laser speckle distribution, this exacerbates the speckle problem.

[0059] In view of this, some embodiments of this application provide a projection system that can effectively improve speckle problems and enhance image quality.

[0060] As shown in Figure 3, some embodiments of the projection system provided in this application include: a laser light source 11, a phase light modulator 12, an amplitude light modulator 13, a total internal reflection prism 14, and a lens 15.

[0061] The laser source 11 is configured to emit three-color laser light. In specific implementations, the laser source 11 may include one laser or multiple lasers. Each laser may be configured to emit three-color laser light, or different lasers may emit laser light of different wavelengths; this is not limited here.

[0062] Taking the example that each laser can emit three colors of laser light, the laser is usually packaged with multiple laser chips in a package structure and configured to emit lasers of different wavelengths.

[0063] As shown in Figures 4 and 5, the laser may include a first laser chip 111r, a second laser chip 111b, and a third laser chip 111g, wherein the lasers emitted by the first laser chip 111r, the second laser chip 111b, and the third laser chip 111g have different wavelengths.

[0064] In some embodiments, as shown in Figure 4, the number of first laser chips 111r is greater than the number of second laser chips 111b, and also greater than the number of third laser chips 111g. The first laser chips 111r are arranged in two rows, the second laser chips 111b are arranged in one row, and the third laser chips 111g are arranged in one row. The three types of laser chips are arranged in a 4×7 array.

[0065] In some embodiments, as shown in FIG5, the number of first laser chips 111r is greater than the number of second laser chips 111b, and also greater than the number of third laser chips 111g. Four first laser chips 111r are arranged in a row, and two second laser chips 111b and three third laser chips 111g are arranged in a row.

[0066] In some embodiments, the first laser chip 111r can be a red laser chip that emits red laser light; the second laser chip 111b can be a blue laser chip that emits blue laser light; and the third laser chip 111g can be a green laser chip that emits green laser light.

[0067] It is worth noting that the laser chip arrangement shown in Figures 4 and 5 is only for illustrative purposes. In practical applications, there are no restrictions on the types of laser chips included in the laser, the wavelength of the laser emitted by each type of laser chip, the number of each type of laser chip, or their arrangement.

[0068] The laser source 11 also includes a beam combining component, which is located on the light-emitting side of the laser and is configured to combine the three-color laser light emitted by the laser. Taking the laser source 11 as an example, which includes only one laser as shown in Figure 4 and emits three-color laser light, the structure of the beam combining component will be illustrated.

[0069] As shown in FIG6, in some embodiments, the light combining component 112 may include a first light combining element 112a, a second light combining element 112b, a third light combining element 112c, and a fourth light combining element 112d.

[0070] The first light combiner 112a and the second light combiner 112b are located on the light-emitting side of the two rows of first laser chips 111r, respectively. The third light combiner 112c is located on the light-emitting side of the second laser chip 111b, and the fourth light combiner 112d is located on the light-emitting side of the third laser chip 111g.

[0071] Among them, the first laser chip 111r emits red laser, the second laser chip 111b emits blue laser, and the third laser chip 111g emits green laser.

[0072] The first beam combiner 112a is configured to reflect the red laser emitted from the first row of first laser chips 111r towards the second beam combiner 112b. The second beam combiner 112b can combine the red lasers emitted from the two rows of first laser chips 111r and emit them towards the third beam combiner 112c. The second beam combiner 112b can be a polarization beam combiner. In this case, a phase delay element needs to be set on the light-emitting side of the second row of first laser chips 111r to convert the red laser emitted from the second row of first laser chips 111r from p-polarized light to s-polarized light. By utilizing the property of the polarization beam combiner to transmit p-polarized light and reflect s-polarized light, the red p-polarized light emitted from the first row of first laser chips 111r and the s-polarized light converted from the second row of first laser chips 111r can be combined.

[0073] The third light combiner 112c and the fourth light combiner 112d can be wavelength combining elements. In some embodiments, the third light combiner 112c and the fourth light combiner 112d can be dichroic filters or dichroic film layers. The third light combiner 112c can combine the red laser emitted from the first laser chip 111r with the blue laser emitted from the second laser chip 111b and output it to the fourth light combiner 112d. The fourth light combiner 112d can combine the red laser, the blue laser, and the green laser emitted from the third laser chip 111g.

[0074] In some embodiments, the phase-modulated light is configured to receive parallel incident light. The phase-modulated light achieves phase modulation through diffraction, and parallel incident light enables higher diffraction efficiency.

[0075] The laser emitted from a laser source typically has a certain divergence angle. To ensure that the laser beam incident on the phase light modulator is as close as possible to the parallel incident light, in some embodiments, as shown in Figure 6, a collimating lens group 113 is also provided in the laser source 11. The collimating lens group 113 is located on the light-emitting side of the light combining component and is configured to collimate the incident laser beam before it is emitted towards the phase light modulator. Collimating the laser emitted from the laser source 11 before it is incident on the phase light modulator helps to reduce the design difficulty of the phase light modulator and improve its efficiency.

[0076] As shown in Figure 3, the phase light modulator 12 is located on the light-emitting side of the laser source 11 and is configured to perform phase modulation on the laser emitted from the laser source 11 according to the image to be displayed. This makes the amplitude distribution of the modulated light on the light-receiving surface of the amplitude light modulator 13 match the brightness distribution of the image to be displayed. The area with higher brightness of the image to be displayed receives a greater light intensity from the corresponding area of ​​the amplitude light modulator, while the area with lower brightness of the image to be displayed receives a smaller light intensity from the corresponding area of ​​the amplitude light modulator. This can improve the brightness contrast of the displayed image.

[0077] In implementation, the phase modulator 12 can be a transmissive device or a reflective device. The reflective phase modulator can not only modulate the phase of the incident beam, but also fold the optical path and reduce the length of the projection system in the same direction.

[0078] Taking the PLM 12 using a reflective phase modulation device as an example, as shown in Figure 7, the PLM 12 may include: multiple dimming units u arranged in an array, as shown in Figure 8. Each dimming unit u includes: a driving component 121 and a reflector 122 mounted on the driving component; the driving component 121 is configured to drive the reflector 122 to move in a direction perpendicular to the reflective surface of the reflector to cause a phase change in the light.

[0079] In some embodiments, as shown in FIG9, the driving assembly 121 may include: a first substrate 1211 and a second substrate 1212 disposed opposite to each other, and a driving structure 1213 located between the first substrate 1211 and the second substrate 1212. A reflector 122 may be located on the side of the second substrate 1212 away from the first substrate 1211. The reflector 122 may be stacked on the second substrate 1212, with the reflective surface of the reflector 122 located on the side away from the second substrate 1212. The driving structure 1213 is configured to drive the second substrate 1212 to move in a direction perpendicular to the second substrate 1212, thereby causing the reflector 122 to move in a direction perpendicular to the reflector 122.

[0080] As shown in Figure 9, the driving structure 1213 may include: at least one first electrode 1213a located on the side of the first substrate 1211 near the second substrate 1212, a second electrode 1213b located on the side of the second substrate 1212 near the first substrate 1211, and a plurality of support members 1213c located between the first substrate 1211 and the second substrate 1212. One end of each support member 1213c may be fixedly connected to the first electrode 1213a, and the other end may be fixedly connected to the second electrode 1213b. The second electrode 1213b may be a planar electrode, and a fixed potential may always be applied to the second electrode 1213b. By applying the same voltage as the second electrode 1213b or a different voltage to at least one first electrode 1213a, the distance between the first substrate 1211 and the second substrate 1212 can be adjusted, thereby enabling the second substrate 1212 to drive the reflector 122 to adjust its position.

[0081] In some embodiments, when a voltage different from that of the second electrode 1213b is applied to the first electrode 1213a, a voltage difference is formed between the first electrode 1213a and the second electrode 1213b, which causes an electro-adsorption force to be generated between the first substrate 1211 and the second substrate 1212. Under the action of this electro-adsorption force, the second substrate 1212 can be moved in a direction perpendicular to the second substrate 1212 to adjust the distance between the first substrate 1211 and the second substrate 1212.

[0082] During the movement of the second substrate 1212 along a direction perpendicular to it, the multiple support members 1213c located between the first substrate 1211 and the second substrate 1212 need to be stretched or contracted. The magnitude of the electro-adhesive force generated between the first substrate 1211 and the second substrate 1212 is related to the area of ​​the first electrode 1213a. Therefore, by providing multiple first electrodes 1213a on the side of the first substrate 1211 closer to the second substrate 1212, various positional relationships between the first substrate 1211 and the second substrate 1212 can be controlled, allowing the reflector 122 on the side of the second substrate 1212 away from the first substrate 1211 to be located in various different positions, thereby effectively improving the modulation accuracy of the phase light modulator.

[0083] When the position of the reflector 122 on the drive assembly 121 changes, the incident light will be incident on the reflector 122 at different positions, and the optical path between the reflected light will be different, thereby creating a phase difference between the reflected light and achieving phase modulation of the light. Then the light intensity is redistributed when the modulated light shines on the light receiving surface of the amplitude light modulator 13.

[0084] In addition, the phase light modulator can also be replaced by a spatial light modulator (SLM) or a diffractive optical element (DOE) or other diffractive devices, which can also achieve the function of pre-distributing the intensity of the laser beam. No limitation is made here.

[0085] The amplitude light modulator 13 can be a transmissive light modulator or a reflective light modulator. The amplitude light modulator 13 shown in Figure 3 is a reflective light modulator, such as a liquid crystal on silicon (LCoS) or a digital micromirror device (DMD).

[0086] As shown in Figure 10, based on the brightness distribution of the image to be displayed, the phase light modulator 12 is used to adjust the light intensity distribution of the laser on the light-receiving surface of the incident amplitude light modulator 13 in advance. Combined with the amplitude modulation of the incident light by the amplitude light modulator 13, the brightness of the brighter areas in the displayed image can be increased, and the brightness of the less bright areas can be decreased, thereby improving the contrast between light and dark in the displayed image and enhancing the display effect.

[0087] Figure 10 takes the division of the image to be displayed into 3×3 partitions as an example. According to the overall brightness distribution of the image to be displayed, the phase light modulator 12 is driven to perform phase modulation on the incident laser beam, so that when the modulated light is on the light-receiving surface of the incident amplitude light modulator 13, the light intensity distribution can also be divided into 3×3 partitions, and the light intensity distribution of each partition matches the brightness distribution of the image to be displayed.

[0088] It should be noted that this embodiment of the application uses the division of the intensity distribution of the modulated light of the phase light modulator 12 into 9 partitions as an example for illustration. In actual application, the intensity distribution of the modulated light of the phase light modulator 12 is divided into hundreds or even more partitions, so that the intensity distribution of the modulated light of the incident amplitude light modulator 13 can be adjusted more finely.

[0089] If we call the beam emitted from the laser source 11 to the PLM 12 the laser beam, and the beam that, after phase modulation by the PLM 12, is incident on the light-receiving surface of the amplitude modulator 13 the illumination beam, then the amplitude distribution of the illumination beam on the light-receiving surface of the amplitude modulator 13 after phase modulation by the PLM 12 is the desired image. The complex amplitude distribution of the illumination beam on the light-receiving surface of the amplitude modulator 13 after phase modulation by the PLM 12 is:

[0090] Wherein, B(x,y) represents the amplitude distribution of the laser beam on the light-receiving surface of the amplitude modulator 13 after phase modulation by PLM 12; This represents the phase distribution of the laser beam on the light-receiving surface of the amplitude modulator 13 after phase modulation by PLM 12. The complex amplitude distribution g(x,y) is the desired distribution after phase modulation by PLM 12, therefore B(x,y) and Since all of these are known quantities, the complex amplitude g(x,y) is also a known quantity.

[0091] Once the structure of the laser source is determined, the amplitude and phase of the light rays at various positions in the laser beam provided by that source can be determined. In this case, the complex amplitude distribution of the laser beam provided by the laser source is as follows:

[0092] Where A(x,y) represents the amplitude distribution of the laser beam provided by the laser source; This represents the phase distribution of the laser beam before phase modulation by the PLM. Since A(x,y) and... Both can be obtained through measurement; therefore, the complex amplitude function f(x,y) is a known quantity. PLM alters the phase distribution of the laser beam through phase modulation, resulting in a new phase distribution of the illumination beam:

[0093] in, The value (x, y) represents the change in the phase distribution of the laser beam caused by the PLM; (x, y) represents the position of each mirror in the PLM. Phase superposition of the laser beam. The new complex amplitude distribution is then obtained as follows:

[0094] After the laser beam undergoes phase modulation by the PLM, the complex amplitude distribution g(x,y) and the complex amplitude distribution f ′ (x, y) satisfy the following conditions:

[0095] in, The expression represents the Fourier transform, which means that after performing a Fourier transform on the complex amplitude distribution f′(x,y), the complex amplitude distribution g(x,y) can be obtained. The inverse Fourier transform is represented by f′(x,y), which means that after performing the inverse Fourier transform on the complex amplitude distribution g(x,y), the complex amplitude distribution f′(x,y) can be obtained.

[0096] Therefore, the phase distribution that the PLM needs to adjust can be derived from the complex amplitude distribution g(x,y) and the complex amplitude distribution f′(x,y). Thus, based on the phase distribution that the PLM needs to adjust, the height of each mirror in the PLM on the reflecting surface perpendicular to the PLM can be determined.

[0097] Based on the complex amplitude distributions g(x,y) and f′(x,y), the phase distribution that the PLM needs to adjust can be determined using phase retrieval algorithms such as the Yang-Gu algorithm (YG algorithm), the Gerchberg-Saxton algorithm (GS algorithm), and the simulated annealing algorithm.

[0098] Taking the GS algorithm as an example, as shown in Figure 11, it includes the following steps:

[0099] S1. Initialize random phase The measured spatial domain amplitude A is combined to form a complex amplitude distribution.

[0100] S2. Perform a Fourier transform on the complex amplitude f to obtain... Preserve the obtained phase The complex amplitude is obtained by combining the desired amplitude B.

[0101] S3. Perform an inverse Fourier transform on the complex amplitude g to obtain... Preserve the obtained phase The measured spatial domain amplitude A is used to form a new complex amplitude distribution f for the next iteration;

[0102] Repeat steps S2 and S3 above until the maximum number of iterations is met, and finally obtain the phase. This allows us to obtain the phase distribution that the PLM needs to adjust.

[0103] In practice, the laser source 11 emits three primary color lights according to a set timing sequence. During image display, the image to be displayed is decomposed into red, green, and blue component images. The laser source 11 emits the red, green, and blue lasers sequentially to the amplitude modulator 13. The amplitude modulator 13 converts the component image signals into pixel driving signals, driving the pixels to accumulate the brightness of the primary color component images. After the three primary color component image frames are superimposed, a color image is formed by utilizing the persistence of vision effect of the human eye.

[0104] Accordingly, the phase modulator 12 can sequentially modulate the phase of the incident three-color laser according to the emission sequence of the laser source 11. The phase-modulated three-color lasers are then superimposed to form an image with a specific amplitude distribution, which matches the brightness distribution of the image to be displayed.

[0105] As can be seen from the above design process, the phase distribution loaded by the phase light modulator 12 is in the form of a calculated hologram. The calculation process involves random phase errors and high-frequency phase change signals, which will make the speckle problem more severe.

[0106] It is worth noting that both the laser speckle and the hologram loaded by the phase light modulator 12 are high-frequency signals, while the image with a specific amplitude distribution output by the phase light modulator 12 is a low-frequency signal. In this embodiment, "high frequency" and "low frequency" refer to the magnitude of the spatial frequency, which is the number of image variation cycles per unit size, and its unit can be lp / mm per line pair. For the laser speckle, its distribution size is on the order of micrometers, ranging from 1 μm to 10 μm, and its spatial frequency is between 0.0005 lp / mm and 0.005 lp / mm; for the image with a specific amplitude distribution output by the phase light modulator 12, its distribution size is on the order of millimeters, not less than 0.1 mm, and its spatial frequency is greater than 0.05 lp / mm. Therefore, the laser speckle belongs to the high-frequency component, while the image with a specific amplitude distribution output by the phase light modulator belongs to the low-frequency component.

[0107] To improve the speckle problem, the high-frequency components mentioned above need to be homogenized. As shown in Figure 3, some embodiments of the projection system provided in this application also include a first lens group 16a and a second lens group 16b.

[0108] The first lens group 16a is located on the light-emitting side of the phase modulator 12 and is configured to converge the light beam after phase modulation by the phase modulator 12. The second lens group 16b is disposed on the light-emitting side of the first lens group 16a and is configured to convert the light beam from the first lens group into a light intensity distribution pattern and image it on the output surface. The image-side focal point of the first lens group 16a and the object-side focal point of the second lens group 16b approximately coincide; exemplarily, the focal point position is position a in Figure 3.

[0109] A spatial filter 162 is provided at the focal position of the first lens group 16a or within a preset distance from the focal position, and the first optical system 16 is composed of the first lens group 16a, the spatial filter 162, and the second lens group 16b.

[0110] Wherein, the image-side focal point of the first lens group 16a may coincide with the object-side focal point of the second lens group 16b, or the distance error between the image-side focal point of the first lens group 16a and the object-side focal point of the second lens group 16b is within the range allowed by optical engineering.

[0111] The phase modulator 12 is positioned close to the object plane of the first lens group 16a. In other words, the phase modulator 12 is located at the object plane of the first lens group 16a, or within a preset distance range from the object plane of the first lens group 16a. Within this preset distance range, the imaging of the first lens group still meets the preset imaging requirements; for example, it can still generate a sufficiently clear image. After the phase-modulated beam emitted from the phase modulator 12 propagates a certain distance, it forms an image with a specific amplitude distribution in space, as shown in Figure 10. The location of this image can be the location of the object plane of the first lens group 16a. After being focused by the first lens group 16a, this beam is incident on the spatial filter 16 to homogenize high-frequency noise, and then imaged onto the light-receiving surface of the amplitude modulator 13 by the second lens group 16b.

[0112] The spatial filter 16 is configured to homogenize high-frequency noise. By homogenizing the high-frequency noise in the laser beam, the uniformity of the energy distribution of the laser spot can be improved, interference can be reduced, and thus speckle phenomena in the projected image can be effectively suppressed.

[0113] The aforementioned first optical system constitutes a 4f filtering system. Figure 12 is a schematic diagram of the filtering principle of the 4f filtering system. As shown in Figure 12, the 4f filtering system is an optical information processing system based on Fourier optics, utilizing the Fourier transform characteristics of lenses to achieve filtering of optical signals. In the 4f filtering system, the name "4f" comes from the system layout, which includes two lenses, each with a focal length f, and the distance between these two lenses is 2f, that is, the distance between the image-side focal plane of one lens and the object-side focal plane of the other lens.

[0114] The light rays first undergo a Fourier transform through the first lens, then pass through a spatial filter located between the two lenses. This spatial filter is configured to selectively block or allow certain frequency components. Next, the light rays pass through the second lens again, performing an inverse Fourier transform to recover the image in the spatial domain, but which has already been filtered.

[0115] Specifically, referring to Figure 3, in this embodiment, the first lens group 16a corresponds to the first lens in the 4f filter system, and the second lens group 16b corresponds to the second lens. The modulated light emitted from the phase modulator 12 propagates a certain distance to form an image with a specific amplitude distribution, and the position of this image is also the object plane of the first lens group 16a. The image-side focal point of the first lens group 16a and the object-side focal point of the second lens group 16b approximately coincide, and a spatial filter 162 is disposed near the image-side focal point of the first lens group 16a.

[0116] The modulated light emitted from the phase modulator 12 undergoes a Fourier transform after passing through the first lens group 16a, converting it from the spatial domain to the frequency domain. The spectrum is located at the image-side focal point of the first lens group 16a (position a in Figure 3), as shown in Figure 13. The center of the spectrum is the origin, representing the DC component or zero frequency, which is the part not modulated by the PLM. The area around the center of the spectrum represents low-frequency components, reflecting large-scale changes in the image, such as large-scale color or grayscale gradients. In some embodiments of this application, this is the image with a specific amplitude distribution output by the PLM. The edges of the spectrum represent high-frequency components, reflecting details and edges in the image, such as textures and boundaries. In some embodiments of this application, this is speckle noise. By placing a spatial filter 162 with the function of homogenizing high-frequency components at or near the focal position of the first lens group 16a, the high-frequency components in the frequency domain can be homogenized without affecting the low-frequency image with a specific amplitude distribution output by the PLM. The homogenized light then passes through the second lens group 16b and undergoes another Fourier transform, converting it from the frequency domain to the spatial domain. This transforms the light onto the light-receiving surface of the amplitude modulator 13, forming an image with a specific amplitude distribution. This amplitude distribution matches the brightness distribution of the image to be displayed. Therefore, high-frequency speckle noise can be effectively reduced without disrupting the image with the specific amplitude distribution output by the phase modulator 12.

[0117] In implementation, the spatial filter 162 can be positioned at or near position a. For example, the spatial filter 162 can be positioned between 0.7 and 1.3 times the focal length of the first lens group 16a, corresponding to interval b in Figure 3. That is, the spatial filter 162 can be positioned at the focal point of the first lens group 16a. The spatial filter 162 can also be positioned before the focal point of the first lens group 16a in the optical path. For example, the spatial filter 162 can be positioned at any position between 0.7 and 1.3 times the focal length of the first lens group 16a, so that the spatial filter 162 is in the optical path where the laser beam gradually converges. The spatial filter 162 can also be positioned after the focal point of the first lens group 16a in the optical path. For example, the spatial filter 162 can be positioned at any position between the focal point of the first lens group 16a and 1.3 times the focal length of the first lens group 16a, so that the spatial filter 162 is in the optical path where the laser beam gradually diverges after converging. However, in the above examples, it can be considered that the size of the light spot received by the spatial filter 162 is within a preset range. Alternatively, since the lens group is not an ideal lens, the spatial filter 162 is positioned as close as possible to the focal plane, which is beneficial for receiving laser beams with smaller light spot sizes.

[0118] In some embodiments, the spatial filter 162 may be one or more of a fixed diffuser, a moving diffuser, a random phase plate, a spatial light modulator (SLM), a diffractive optical element (DOE), or a metasurface.

[0119] Both fixed and moving diffusers consist of appropriately sized scattering particles mixed in a transparent medium, with particle sizes ranging from 3μm to 10μm. These scattering particles can scatter incident light, thereby increasing the random phase, disrupting the strong coherence of the laser, and balancing homogenization, scattering angle, and high transmittance. The scattering particles primarily affect high-frequency components; through their motion, they can further homogenize the speckle noise in these high-frequency parts, while having a relatively small impact on the low-frequency amplitude distribution in the central region.

[0120] A moving diffuser can include a diffuser wheel and a vibrating diffuser. Both the diffuser wheel and the vibrating diffuser can achieve dynamic light uniformity, and their uniformity effect is better than that of a fixed diffuser. The structure of the diffuser wheel is shown in Figure 14. The diffuser can be mounted on a rotating shaft, which is connected to a motor to drive the diffuser to rotate. The structure of the vibrating diffuser is shown in Figure 15. The diffuser is mounted on a drive assembly. The drive assembly has drive structures at its four corners. The drive structures can move up and down, thereby causing the diffuser to flip or vibrate along its side or diagonal.

[0121] Random phase plates can be categorized into those based on material surface treatment and those based on randomly distributed media. Random phase plates based on material surface treatment are typically achieved by performing specific surface treatments on a transparent substrate, such as etching, sandblasting, or depositing non-uniform thin films. These treatments create minute undulations on the material surface, resulting in random phase delays for transmitted or reflected light. Random phase plates based on randomly distributed media are achieved by passing light through a medium with a randomly distributed internal structure. For example, tiny particles can be suspended in a liquid or gel, or porous materials can be used, which can produce complex scattering and refraction of light, thereby achieving random phase modulation.

[0122] Spatial light modulators (SLMs) can be either liquid crystal-on-silicon (LCOS) or microelectromechanical system (MEMS) type. LCOS-type SLMs can employ either reflective liquid crystal on silicon (LCOS) or transmissive liquid crystal displays (LCDs). These SLMs can continuously load different random phase distributions, thereby dynamically altering the phase distribution of the light beam.

[0123] Diffractive optical elements (DOEs) can be used for beam shaping and homogenization. A DOE is an optical element that can change the propagation characteristics of light. DOEs have a relatively thin thickness and microstructures on at least one side of their surface. The size of the microstructures is typically on the order of micrometers. These microstructures can change the phase of the incident light, thereby changing the propagation path of the light at the microscale and achieving beam shaping and homogenization.

[0124] Metasurfaces have subwavelength microstructures, and random phase distributions can be generated by changing the size, height, and placement angle of the microstructures.

[0125] In implementation, any one or more of the above-mentioned spatial filters can be used depending on the application scenario. In addition, other devices that can generate phase can also be used, which are not limited here.

[0126] For example, the phase modulator 12 has large pixels and low diffraction efficiency. The light spot with a specific amplitude distribution output by the PLM itself may have poor uniformity. A moving diffuser can be set at the image-side focal point of the first lens group 16a, i.e., position a, and a fixed diffuser can be set in interval b, forming a combination of a fixed diffuser and a moving diffuser, which can further improve the uniformity of the projection system and suppress speckle noise.

[0127] In practice, the focal length of the first lens group 16a and the focal length of the second lens group 16b can be the same or different. The second lens group 16b can be set with a suitable focal length according to the position of the amplitude light modulator 13, so that the image of the specific amplitude distribution output by the phase light modulator 12 can be imaged on the light-receiving surface of the amplitude light modulator 13.

[0128] In some embodiments, as shown in FIG3, the first lens group 16a may include only one optical element 161, which has the function of focusing light rays. For example, a convex lens, a concave mirror, or a Fresnel lens may be used. In addition, other optical elements with focusing functions may be used, which are not limited here.

[0129] The second lens group 16b includes at least one convex lens.

[0130] In some embodiments, as shown in FIG3, the second lens group 16b may include a second lens 163, a third lens 164, and a fourth lens 165. The second lens 163 is located on the light-emitting side of the first lens group 16a; the third lens 164 is located on the side of the second lens 163 opposite to the first lens group 16a; and the fourth lens 165 is located on the side of the third lens 164 opposite to the second lens 162.

[0131] The second lens 163, third lens 164, and fourth lens 165 in the second lens group 16b can have different focal lengths and can be a combination of convex and concave lenses. Depending on the needs, they can also be spherical or aspherical surfaces, etc., which are not limited here.

[0132] As shown in Figure 3, the second lens group 16b may also be provided with a light path deflecting element 166, which is configured to deflect the light path, thereby reducing the length of the light path and adjusting the shape and volume of the projection system. The light path deflecting element 166 may be a plane mirror, a prism, or a mirror with imaging function, and there is no limitation here.

[0133] As shown in Figure 3, the projection system also includes a total reflection prism 14, located on the light-emitting side of the second lens group 16b, configured to totally reflect the emitted light from the second lens group 16b to the amplitude light modulator 13, and transmit the emitted light from the amplitude light modulator 13 to the lens 15.

[0134] The structures of the first and second lens groups described above are only used to explain the working principle of this application. In practical applications, the first and second lens groups may also contain other numbers and other structures of lenses.

[0135] In some embodiments, the first lens group 16a and / or the second lens group 16b may be a zoom lens group. In this case, the first optical system can constitute a tunable 4f filter system. The working principle of the tunable 4f filter system can be seen in Figure 16.

[0136] As shown in Figure 16, the first lens group 16a can be configured as a zoom lens group. The adjustable focal length of the first lens group performs a Fourier transform on the input light field, converting the spatial domain information to the frequency domain. By adjusting the focal length f1 of the first lens group 16a, the position and magnitude of the spatial spectrum of the input light field can be changed.

[0137] As shown in Figure 16, the second lens group 16b can be configured as a zoom lens group. The adjustable focal length of the second lens group performs another Fourier transform on the light field passing through the Fourier surface (i.e., the focal plane of the first lens group), converting the frequency domain information back to the spatial domain and forming the final image. Adjusting the focal length f2 of the second lens group 16b can affect the size and position of the output image.

[0138] Alternatively, both the first lens group 16a and the second lens group 16b can be configured as zoom lens groups. By dynamically adjusting the optical path length using adjustable focal length, the magnification and resolution of the system can be flexibly adjusted according to different application scenarios to adapt to different types of speckle processing requirements. Dynamically adjusting the optical path length may be applicable to smart projection, smart robots, or vehicle / aircraft projection systems, where the focal length of the lens group can be adjusted according to the application scenario or machine structure dimensions to adapt to application needs.

[0139] The aforementioned zoom lens group can be in the form of a concave lens paired with a convex lens, or it can be a liquid lens, a flexible lens, a tunable meta-lens, etc. Any device that can achieve focal length adjustment can be used, and there are no restrictions here.

[0140] In some embodiments, the projection system includes multiple cascaded first optical systems, with a phase modulator 12 positioned close to the object plane of the first optical system of the first stage, and an amplitude modulator 13 located on the image plane of the last stage of the first optical system. The image plane of the previous stage of the first optical system coincides with the object plane of the next stage of the first optical system.

[0141] The cascaded first optical systems can form a multi-stage 4f filtering system. The working principle of a multi-stage 4f filtering system can be seen in Figure 17, which illustrates two cascaded first optical systems 16 as an example. By employing a structure of multiple consecutive 4f filtering systems, each 4f filtering system's spectral plane can be configured with a spatial filter to enhance or refine the processing results of the preceding system. This approach allows for more precise control over speckle noise processing while maintaining high image quality.

[0142] For example, as shown in Figure 17, the modulated light output from the phase modulator propagates a certain distance to form an image with a specific amplitude distribution. This image is located at the object plane of the first optical system 16, i.e., object plane 1 in Figure 17. The amplitude modulator 13 is located at the image plane of the second optical system 16, i.e., image plane 2 in Figure 17. The image plane (image plane 1) of the first optical system 16 coincides with the object plane (object plane 2) of the second optical system 16.

[0143] A first spatial filter is positioned at the focal plane 1 of the first optical system 16; a second spatial filter is positioned at the focal plane 2 of the second optical system 16. Taking the example that both the first and second spatial filters use diffusers, the diffusers located at focal plane 1 and focal plane 2 can have different diffusion angles. For example, the diffusion angle of the diffuser located at focal plane 1 is 4°, and the diffusion angle of the diffuser located at focal plane 2 is 2°. This allows control over the scattering particles of the diffusers and the progressively decreasing diffusion angle to enhance or refine the processing results of the previous stage system.

[0144] In some embodiments, the spatial filter 162 may be a nonlinear optical crystal; or, a nonlinear optical crystal may be disposed between the phase light modulator 12 and the object plane of the first lens group 16a, and any of the above-mentioned spatial filters may still be disposed on the focal planes of the first lens group 16a and the second lens group 16b.

[0145] Nonlinear optical crystals generate new random frequency components in incident light through the nonlinear polarization response of their internal atoms or molecules. When a light field enters the crystal, the nonlinear polarization is determined by the second-order nonlinear polarizability and the square of the incident photoelectric field. This nonlinear polarization generates new electromagnetic waves, with common effects including frequency doubling (SHG), sum-frequency generation (SFG), difference-frequency generation (DFG), and optical parametric oscillation (OPO). To effectively output light waves of new frequencies, phase-matching conditions must be met to ensure no phase mismatch between the newly generated light wave and the incident light wave. By incorporating nonlinear optical crystals into projection systems, new frequency components can be generated under specific conditions, thereby achieving more complex speckle processing effects.

[0146] The nonlinear optical crystals may include: potassium titanium phosphate (KTP), barium borate (BBO), potassium dihydrogen phosphate (KDP), lithium niobate (LN), bismuth oxychloride (BIBO), rubidium titanium phosphate (RTP), potassium rubidium titanium phosphate (KTA), etc. Specific devices may employ thin film or bulk crystal materials incorporating the aforementioned nonlinear optical crystals.

[0147] Some embodiments of this application illustrate the modified structure of the first optical system. In practical applications, other modifications can be made to the part or the whole of the first optical system as needed. Any optical system that includes the first optical system and achieves the same filtering effect is within the protection scope of this application.

[0148] The projection system provided in some embodiments of this application includes: a laser light source, a phase light modulator, a first lens group, a spatial filter, a second lens group, an amplitude light modulator, and a lens. The phase light modulator modulates the phase of the laser beam emitted from the laser light source according to the image to be displayed, forming a modulated beam that matches the brightness distribution of the image to be displayed. The position where the modulated beam propagates a set distance serves as the object plane of the first lens group. The first lens group focuses the incident beam, converting the modulated beam from the spatial domain to the frequency domain. At this point, the center of the spectrum is the origin, the area around the center is low-frequency, and the edges are high-frequency. By placing a spatial filter with the function of homogenizing high-frequency components at the focusing position of the first lens group, the high-frequency components can be homogenized. High-frequency and low-frequency components refer to the spatial frequency. The size of the laser speckle distribution is on the order of micrometers, and its spatial frequency is relatively high, belonging to the high-frequency component. The size of the image with a specific amplitude distribution formed by the modulated beam emitted by the phase light modulator is on the order of millimeters, belonging to the low-frequency component. Therefore, the spatial filter can effectively homogenize high-frequency noise without destroying the image with a specific amplitude distribution output by the phase light modulator. After passing through the spatial filter, the light beam is converted from the frequency domain to the spatial domain after passing through the second lens group, and is imaged on the light-receiving surface of the amplitude light modulator. The amplitude light modulator modulates the amplitude of the incident light according to the image to be displayed, thereby effectively improving speckle problems while enhancing image contrast.

[0149] As mentioned earlier, intensity distribution modulation devices, such as phase light modulators, can be applied to optical systems such as laser projection to modulate the intensity distribution of light beams in order to enhance the display effect of laser projection, for example.

[0150] Figure 18 shows a schematic diagram of the modulation effect of an intensity distribution modulation device in the related art. In the related art, the intensity distribution modulation device can be a phase light modulator 12. The phase light modulator 12 can modulate the amplitude of the light beam from the light source based on phase modulation. By arranging a lens 120 on the light-emitting side of the phase light modulator 12, the image of the modulated light beam can be displayed on the imaging surface 130 at the focal length f of the lens 120. Here, z can indicate the light path direction from the phase light modulator 12 to the imaging surface 130, x1 and y1 can indicate the plane on which the phase light modulator 12 modulates the light beam, and x2 and y2 can indicate the plane on which the imaging surface 130 is located. The pixel size of the dimming mirror 110 (also known as a micromirror) on the phase light modulator 12 is about 10.8 micrometers. Since this size is larger than the wavelength of visible light, its phase modulation effect is not fine enough and the diffraction efficiency is low (when the pixel size reaches a scale close to the wavelength or subwavelength, for visible light, it is less than 2 micrometers or even hundreds of nanometers, the phase modulation of the incident light will be fine, and a high diffraction efficiency will be achieved). Therefore, a high proportion of the light beam is not modulated by the phase distribution loaded on the phase light modulator 12, and thus no specific phase information is loaded, becoming the unmodulated light beam in the phase light modulator 12, and a zero-order light spot 140 will exist on the imaging surface 130. Referring to Figure 7, the modulated light beam can form a light intensity distribution pattern 150 with a certain imaging range (the range of the image to be projected) in the imaging surface 130. The light intensity distribution pattern 150 may include the letter A (which can be designed according to the specific phase information loaded). Due to the pixel size limitation of the phase light modulator 12 mentioned above, there is still a zero-order light spot 140 in the light intensity distribution pattern 150 of the imaging surface 130. Therefore, even if specific phase information is loaded on the phase light modulator 12, due to the limitation of the phase light modulator 12 itself, there will still be a zero-order light spot 140 at, for example, the imaging surface 130, which will affect the display effect. The affected display effect is mainly manifested as a central bright spot appearing in the displayed image.

[0151] Therefore, in related technologies, when an optical device with intensity distribution modulation capability is used to modulate the intensity distribution of a light beam, zero-order diffraction will occur, resulting in a zero-order light spot in the modulated light beam. Without processing, this will cause a bright spot in the center of the projected image, such as a laser projection, affecting the display effect.

[0152] Therefore, some embodiments of this application also provide an optical modulation system and a laser projection device. In the optical modulation system, a localized homogenizing element can be set in the optical path between the intensity distribution modulator and the target imaging plane. This homogenizing area in the homogenizing element homogenizes the portion of the beam corresponding to the zero-order spot in the beam modulated by the intensity distribution modulator, thus homogenizing the zero-order spot onto the target imaging plane and reducing its impact on the display effect of the intensity distribution pattern of the target imaging area. Furthermore, the zero-order spot does not need to be eliminated, avoiding wasted light energy. In the application of a laser projection device, the impact of the zero-order spot on the display effect of the projected image can be reduced, and the zero-order spot does not need to be eliminated, avoiding wasted light energy.

[0153] The optical modulation system and laser projection device of this application will be described below in conjunction with the various embodiments and corresponding figures.

[0154] In some embodiments, as shown in FIG19, some embodiments of this application provide an optical modulation system. The optical modulation system may include a light intensity distribution modulator 100 and a light homogenizer 200. The light intensity distribution modulator 100 is an optical device with light intensity distribution modulation capability, such as the phase light modulator 12 (PLM) described in the foregoing embodiments. The light homogenizer 200 is an optical element with light homogenizing capability, such as a compound eye microlens array.

[0155] In some embodiments, the intensity distribution modulator 100 is configured to provide a modulated light beam to a target imaging plane P0, forming an intensity distribution pattern with a target imaging range at the target imaging plane P0. Specifically, the intensity distribution modulator 100 can modulate the amplitude of the light beam L1 from the light source based on phase modulation, providing a modulated light beam L2 to the target imaging plane P0. As described above, the intensity distribution modulator 100 can form an intensity distribution pattern with a target imaging range at the target imaging plane P0 by loading specific phase information. The target imaging range can be the area where the image needs to be projected at the target imaging plane P0, or it can be the planar area occupied by the intensity distribution pattern when projected onto the target imaging plane P0 (e.g., the area occupied by a circular pattern / square pattern).

[0156] In some embodiments, an optical path R1 is formed between the intensity distribution modulation device 100 and the target imaging plane P0, forming a modulated beam L2.

[0157] A homogenizing element 200 is disposed in the optical path R1 between the intensity distribution modulator 100 and the target imaging plane P0. It should be noted that the optical path R1 between the intensity distribution modulator 100 and the target imaging plane P0 may also contain other optical elements such as lenses, which are not specifically limited here. The homogenizing element 200 includes a homogenizing region 210. The homogenizing region 210 is the area of ​​the homogenizing element 200 that has the ability to homogenize the light beam; the homogenizing region 210 may be a part or all of the homogenizing element 200. The homogenizing region 210 is configured to homogenize the portion L20 of the modulated light beam L2 corresponding to the zero-order spot, so that the zero-order spot is homogenized within the target imaging plane P0 to the target imaging range. It should be noted that the zero-order spot is homogenized to the target imaging range on the target imaging plane P0. The purpose of homogenizing the beam portion L20 corresponding to the zero-order spot in the modulated beam L2 (i.e., a specific part of the modulated beam L2, not the entire beam) by the homogenizing area 210 of the homogenizing element 200 can spread outward to homogenize to the target imaging range where the light intensity distribution pattern exists. This ensures that there is no obvious central bright spot in the image projected on the target imaging plane P0. In this way, the influence of the zero-order spot can be reduced in the display of the light intensity distribution pattern, and the overall brightness and uniformity of the image projected on the target imaging plane P0 can be improved without eliminating the zero-order spot, thus avoiding the waste of light energy.

[0158] Figures 20 and 21 illustrate the display effect of the light intensity distribution pattern of this embodiment. Figures 20 and 21 show a comparison of the display effects of the two light intensity distribution patterns at, for example, the target imaging plane P0.

[0159] The light intensity distribution pattern shown in Figure 20 is a square with a certain gray level, and the target imaging range of this light intensity distribution pattern is indicated by F1. A51 in Figure 20 indicates the image projected at the target imaging plane P0 by the modulated light beam L2 provided by the light intensity distribution modulation device 100 in the related art. The image indicated by A51 will obviously contain the zero-order bright spot Z1 (corresponding to the zero-order light spot), so its image uniformity is poor. Moreover, since the light power ratio of the zero-order light spot is relatively high, the brightness of other positions in the image indicated by A51 will be relatively low, affecting its display effect. Figure 20, A52, illustrates the image projected onto the target imaging plane P0 after the beam portion L20 corresponding to the zero-order spot in the modulated beam L2 is homogenized by the homogenizing region 210 of the homogenizing element 200 in some embodiments of this application. A52 indicates that the image does not contain a zero-order bright spot Z1. This is because after the beam portion L20 corresponding to the zero-order spot is homogenized by the homogenizing region 210 of the aforementioned homogenizing element 200, the zero-order spot projected onto the target imaging plane P0 can diffuse outwards to be homogenized to the target imaging range F1 of the light intensity distribution pattern. This prevents the presence of a significant zero-order bright spot Z1 in the image projected onto the target imaging plane P0, reducing the impact of the zero-order spot on the display effect. Furthermore, the light power of the entire zero-order spot is homogenized to the entire projected image, resulting in improved overall brightness and uniformity.

[0160] The light intensity distribution pattern shown in Figure 21 is composed of multiple letters, and the target imaging range of this light intensity distribution pattern is also indicated by F1. Similarly, B51 in Figure 21 indicates the image projected onto the target imaging plane P0 by the modulated beam L2 provided by the light intensity distribution modulation device 100 in the related art. The image indicated by B51 also clearly contains a zero-order bright spot Z1, which significantly affects the expected intensity distribution of the image projected onto the target imaging plane P0. B52 in Figure 21 indicates the image projected onto the target imaging plane P0 by the modulated beam L2 after the beam portion L20 corresponding to the zero-order bright spot in the modulated beam L2 is homogenized by the homogenizing area 210 of the homogenizing element 200 in some embodiments of this application. The image indicated by B52 does not contain the zero-order bright spot Z1, as the zero-order bright spot has been homogenized to the entire projected image, thus reducing the impact of the zero-order bright spot on the display effect and improving the overall brightness and uniformity of the image.

[0161] In this embodiment, a localized homogenizing element 200 is provided in the optical path R1 between the intensity distribution modulator 100 and the target imaging plane P0. The homogenizing region 210 in the homogenizing element 200 homogenizes the portion L20 of the beam L2 modulated by the intensity distribution modulator that corresponds to the zero-order spot. This homogenizes the zero-order spot to the target imaging range on the target imaging plane P0, thereby reducing the impact of the zero-order spot on the display effect of the intensity distribution pattern of the target imaging range on the target imaging plane. Furthermore, there is no need to eliminate the zero-order spot, thus avoiding the waste of light energy.

[0162] For the homogenizing element 200, the homogenizing region 210 functions to homogenize the portion of the modulated beam L2 corresponding to the zero-order spot, while also avoiding affecting other portions of the modulated beam L2 besides the portion corresponding to the zero-order spot. Based on this, referring to FIG19, in some embodiments, the size of the homogenizing region 210 corresponds to the size of the zero-order spot illuminating the homogenizing element 200, so that the homogenizing region 210 homogenizes the portion of the beam L20 corresponding to the zero-order spot, avoids affecting other portions of the beam besides the portion corresponding to the zero-order spot, and allows the homogenizing element 200 with the homogenizing region 210 to be integrated into optical systems such as laser projection devices at the lowest possible cost.

[0163] In optical systems such as laser projection devices, the modulation, transmission, and projection of multi-wavelength beams may be involved. These multi-wavelength beams include beams of different wavelengths; for example, in some laser projection devices, the laser projection light source may include beams of three wavelengths (corresponding to red, blue, and green light, respectively). The homogenizing process of the homogenizing element on the portion of the modulated beam corresponding to the zero-order spot needs to consider the influence of the multi-wavelength beam. Based on this, referring to Figure 22, in some embodiments, the intensity distribution modulation device 100 is configured to provide a modulated multi-wavelength beam L3 to the target imaging plane P0; the size of the homogenizing region 210 corresponds to the spot size of the zero-order spot with the largest wavelength illuminating the homogenizing element 200, in order to homogenize the portion L30 of the modulated multi-wavelength beam L3 illuminating the homogenizing element 200 corresponding to the zero-order spots of each wavelength.

[0164] In this embodiment, the intensity distribution modulation device 100 modulates a multi-wavelength beam L1 into a modulated multi-wavelength beam L3, which is then transmitted to the target imaging plane P0 via an optical path R1. In this optical path R1, the beam portions L30 corresponding to the zero-order spots of each wavelength in the multi-wavelength beam L3 are homogenized by the homogenizing region 210 of the homogenizing element 200 located in the optical path R1. The multi-wavelength beam L1 can be composed of multiple beams of different wavelengths that have been combined and collimated before illuminating the intensity distribution modulation device 100. The homogenizing region 210 of the homogenizing element 200 can be randomly phase-modulated, without significant wavelength dependence. The beams of different wavelengths in the multi-wavelength beam L3 have been combined, and the zero-order spots of each wavelength have overlapped at the same position. Generally, when the multi-wavelength beam L3 illuminates the zero-order spots of each wavelength on the homogenizing element 200, the spot size corresponding to the larger wavelength zero-order spot is larger. For example, in some laser projection devices, the laser projection light source can include beams corresponding to three wavelengths: red, blue, and green light, respectively. Generally, the zero-order spot size of red light is the largest. Therefore, in order to homogenize the zero-order spots of each wavelength, the size of the homogenizing region 210 corresponds to the size of the zero-order spot with the largest wavelength illuminating the homogenizing element 200, so as to basically cover the zero-order spot with the largest wavelength. Thus, the homogenizing region 210 can homogenize the beam portion L30 of the modulated multi-wavelength beam L3 illuminating the homogenizing element 200 corresponding to the zero-order spots of each wavelength, and minimize the size of the homogenizing region 210, thereby reducing the influence of the homogenizing region 210 on the beam portion other than the beam portion L30.

[0165] As shown in FIG23, in some embodiments of the optical modulation system of this application, the optical modulation system may further include a multi-wavelength light source 300, which is configured to provide a combined multi-wavelength beam L1 to the intensity distribution modulator 100. In practical applications, the multi-wavelength light source 300 may include a three-color laser light source (e.g., the laser light source 11 in the aforementioned embodiments). The intensity distribution modulator 100 is configured to modulate the multi-wavelength beam L1 into a modulated multi-wavelength beam L3. In this embodiment, the multi-wavelength light source 300 is configured to generate multiple beams of different wavelengths, and to combine and collimate the multiple beams of different wavelengths to form a multi-wavelength beam L1, which is then provided to the intensity distribution modulator 100. This allows the zero-order spots of each wavelength in the modulated multi-wavelength beam L3 provided by the intensity distribution modulator 100 to overlap at the same position, facilitating homogenization by the homogenizing region 210 in the homogenizing element 200.

[0166] For the homogenizing element 200, the size of its homogenizing region 210 needs to correspond to the size of the zero-order light spot illuminating the homogenizing element 200. In some possible embodiments, the zero-order light spot illuminating the homogenizing element 200 may also have a specific shape, such as a circle, ellipse, or rectangle. The shape of the homogenizing region 210 of the homogenizing element 200 may also correspond to the shape of the zero-order light spot illuminating the homogenizing element 200. Regarding the size of the homogenizing region 210, since the homogenizing element 200 can be disposed on the optical path R1, and the optical path R1 may also have other optical elements, the size of the aforementioned zero-order light spot corresponding to different positions of the optical path R1 may have certain differences. In order to enable the homogenizing element 200 to homogenize the beam portion corresponding to the zero-order light spot more efficiently, more specifically, and at the lowest possible cost, and to avoid affecting the beam portion other than the beam portion corresponding to the zero-order light spot, the homogenizing element 200 needs to be placed at a suitable position in the optical path R1. Based on this, as shown in FIG24, in some embodiments, the optical modulation system may further include a coupling lens 400 of the intensity distribution modulator 100. The coupling lens 400 is disposed on the light-emitting side of the intensity distribution modulator 100 and is configured to provide a focusing plane P1 of the intensity distribution modulator 100 in the optical path R1. For this purpose, the homogenizing element 200 may be disposed at the focusing plane P21 of the zero-order spot between the focusing plane P1 of the intensity distribution modulator 100 and the coupling lens 400, or at the focusing plane P22 of the zero-order spot between the focusing plane P1 of the intensity distribution modulator 100 and the target imaging plane P0, and is configured to homogenize the beam portion corresponding to the zero-order spot at the focusing plane of the zero-order spot by the homogenizing region 210.

[0167] In one embodiment, the homogenizing element 200 can be disposed at the focusing plane P22 of the zero-order light spot and configured to homogenize the beam portion corresponding to the zero-order light spot at the focusing plane P22 by the homogenizing region 210 of the homogenizing element 200. In this embodiment, the focusing plane P1 of the intensity distribution modulator 100 can be formed by the coupling lens 400, and a homogenizing element 200 and its homogenizing region 210 are set at the focusing plane P22 of the zero-order spot between the focusing plane P1 and the target imaging plane P0 to homogenize the beam portion corresponding to the zero-order spot. Since the modulated beam L2 provided by the intensity distribution modulator 100 has the smallest beam range at its focusing plane P1, and the zero-order spot has a different focusing plane than the focusing plane P1 because it is not modulated by the intensity distribution modulator 100, the modulation effect on the convergence or divergence of the beam is different depending on the phase of the intensity distribution modulator 100 itself. The focusing plane of the zero-order spot may appear at the position between the focusing plane P1 and the target imaging plane P0 on the optical path R1, as shown in the position of the focusing plane P22 in Figure 24. Therefore, by setting the homogenizing element 200 at the focusing plane P22, the size of the homogenizing area 210 itself can be reduced as much as possible, and a portion of the modulated beam L2 can be homogenized with the smallest possible homogenizing area 210, avoiding affecting the display effect of the portion of the modulated beam L2 other than the portion corresponding to the zero-order spot. The cost of the homogenizing element 200 can also be minimized according to its size. Furthermore, there is usually a large available space at the focusing plane P22 to arrange the homogenizing element 200, making it relatively convenient to arrange the homogenizing element 200.

[0168] In another embodiment, the homogenizing element 200 can be disposed at the focusing plane P21 of the zero-order spot and configured to homogenize the beam portion corresponding to the zero-order spot at the focusing plane P21 by the homogenizing region 210 of the homogenizing element 200. In this embodiment, the focusing plane P1 of the intensity distribution modulator 100 can be formed by the coupling lens 400, and a homogenizing element 200 and its homogenizing region 210 are set at the focusing plane P21 of the zero-order spot between the focusing plane P1 and the coupling lens 400 to homogenize the beam portion corresponding to the zero-order spot. Since the modulated beam L2 provided by the intensity distribution modulator 100 has the smallest beam range at its focusing plane P1, and the zero-order spot has a different focusing plane than the focusing plane P1 because it is not modulated by the intensity distribution modulator 100, the modulation effect on the convergence or divergence of the beam is different depending on the phase of the intensity distribution modulator 100 itself. The focusing plane of the zero-order spot may also appear at the position between the focusing plane P1 and the coupling lens 400 on the optical path R1, that is, at the position of the focusing plane P21 in Figure 24. Therefore, by setting the homogenizing element 200 at the focusing plane P21, the size of the homogenizing area 210 itself can be reduced as much as possible, and a portion of the modulated beam L2 can be homogenized with the smallest possible homogenizing area 210, avoiding affecting the display effect of the portion of the modulated beam L2 other than the portion corresponding to the zero-order spot. The cost of the homogenizing element 200 can also be minimized according to its size. Furthermore, by arranging the homogenizing element 200 at the focusing plane P21 to homogenize the zero-order spot, it is convenient to verify at the focusing plane P1 of the light intensity distribution modulation device 100 whether the homogenizing effect of the homogenizing element 200 on the zero-order spot meets expectations. The homogenizing element 200 can be adjusted in a timely manner according to the verification results to ensure that the homogenizing effect meets expectations.

[0169] To ensure that the homogenizing region 210 of the homogenizing element 200 homogenizes the beam portion corresponding to the zero-order spot to the entire projected image, the diffusion angle of the homogenizing region 210 can be designed. As shown in Figure 24, in some embodiments, the diffusion angle of the homogenizing region 210 is constrained by the distance between the focusing plane P21 or P22 of the zero-order spot and the focusing plane P1 of the intensity distribution modulator 100, as well as the beam range formed by the modulated beam L2 on the focusing plane P1. That is, the diffusion angle of the homogenizing region 210 needs to be determined based on the distance between the focusing plane P21 or P22 of the zero-order spot and the focusing plane P1 of the intensity distribution modulator 100, and the beam range formed by the modulated beam L2 on the focusing plane P1. The beam range formed by the modulated beam L2 on the focusing plane P1 can be represented by the diagonal length X of the intensity distribution pattern projected by the modulated beam L2 on the focusing plane P1. The distance between the focusing plane P21 or P22 of the zero-order spot and the focusing plane P1 of the intensity distribution modulator 100 can be represented as d. Therefore, the diffusion angle θ of the uniform light region 210 can be represented as θ = atan(X / 2*d).

[0170] As described above, the homogenizing region 210 can be a part or all of the homogenizing element 200. As shown in FIG25, in some embodiments, the homogenizing element 200 may further include a light-transmitting region 220, which is configured to transmit the portion of the modulated beam L2 other than the beam portion L20 corresponding to the zero-order spot. In this embodiment, the homogenizing element 200 includes a homogenizing region 210 and a light-transmitting region 220. The region other than the homogenizing region 210 can be designed as the light-transmitting region 220. The light-transmitting region 220 can adopt a transmissive optical structure that is transparent to the modulated beam L2 (which may be visible light, etc.) and does not have other light modulation effects, thereby ensuring the transmission efficiency of the portion of the modulated beam L2 other than the beam portion L20 corresponding to the zero-order spot.

[0171] As shown in Figure 25, as an embodiment, for a light-diffusing element 200 including a light-diffusing region 210 and a light-transmitting region 220, the light-diffusing element 200 needs to have a size that at least covers the target beam range. This target beam range is the beam range formed by the modulated beam L2 illuminating the light-diffusing element 200. That is, in this embodiment, the light-diffusing element 200 needs to at least provide homogenization processing for the beam portion L20 corresponding to the zero-order spot in the modulated beam L2 through the light-diffusing region 210, and at least provide transmission processing for the beam portion of the modulated beam L2 excluding the beam portion L20 corresponding to the zero-order spot through the light-transmitting region 220, to avoid deficiencies in the homogenization or transmission processing of the modulated beam L2, which would affect the final image display effect. In some embodiments, the size of the light-diffusing element 200 including the light-diffusing region 210 and the light-transmitting region 220 can be the same as the beam range formed by the modulated beam L2 illuminating the light-diffusing element 200, in order to minimize the size of the light-diffusing element 200 and thus minimize cost.

[0172] As shown in FIG26, for a light-homogenizing element 200 comprising a light-homogenizing region 210 and a light-transmitting region 220, in some embodiments, the light-transmitting region 220 surrounds the light-homogenizing region 210, and there is a smooth transition between the light-homogenizing region 210 and the light-transmitting region 220. In this embodiment, the light-transmitting region 220 surrounding the light-homogenizing region 210 allows the light-transmitting region 220 to provide transmission processing for the portion of the modulated beam L2 excluding the beam portion L20 corresponding to the zero-order spot, and allows the light-homogenizing region 210 to provide homogenization processing for the beam portion L20 corresponding to the zero-order spot in the modulated beam L2. The smooth transition between the light-homogenizing region 210 and the light-transmitting region 220 is achieved by a smooth transition at the junction position 230 between the light-homogenizing region 210 and the light-transmitting region 220, thereby reducing diffraction effects and unnecessary light loss or shadows in the optical path. As an implementation, the junction position 230 between the light-homogenizing region 210 and the light-transmitting region 220 can be a continuously varying curved surface or slope to achieve a smooth transition.

[0173] In some embodiments, the light-diffusing region 210 can be directly fabricated on a single light-diffusing element 200 by means of nanoimprinting, molding, photolithography, sandblasting, etching, etc., or it can be formed by separately fabricating an independent homogenizing part and then bonding or attaching it to a blank optical glass sheet as the light-diffusing region 210 to form the light-diffusing element 200. In this embodiment, the region of the light-diffusing element 200 other than the light-diffusing region 210 belongs to the light-transmitting region 220.

[0174] For the homogenizing region 210, in practical applications, a random scattering structure, a compound eye microlens array, or a diffractive optical element (DOE) can be used. The random scattering structure can be a static or dynamic diffusion structure. As one implementation, a static diffusion structure can use a fixed diffuser sheet. The substrate of this diffuser sheet can be a material with high light transmittance. Traditional diffusers mainly incorporate chemical particles as scattering particles into the substrate, while some diffusers disperse these particles between resin layers. Therefore, when the light beam passes through the diffusion layer, it continuously passes through two media with different refractive indices, resulting in numerous refractions, reflections, and scattering phenomena, thus creating an optical diffusion effect. As another implementation, a dynamic diffusion structure can use a moving diffuser sheet (also called a diffusion wheel), which can be a rotating diffuser sheet. The diffusion wheel can diffuse a converging light beam, increasing the divergence angle and random phase. In practical applications, the homogenizing region 210 can occupy less than, for example, 20% of the total area of ​​the homogenizing element 200.

[0175] In some embodiments, the homogenizing region 210 can be made of a material with high transmittance and good scattering properties, such as microstructured glass or polymer scattering sheets, to achieve efficient zero-order beam homogenization. For example, the homogenizing region 210 can be formed using a random phase sheet based on a material surface treatment. Such phase sheets are typically achieved by performing specific surface treatments on a transparent substrate, such as etching, sandblasting, or depositing a non-uniform thin film. These treatments create minute undulations on the material surface, thereby producing random phase delays for the transmitted or reflected light. Alternatively, the homogenizing region 210 can be formed using a random phase sheet based on a randomly distributed medium. This type of phase sheet is achieved by passing light through a medium with a randomly distributed internal structure. Furthermore, the homogenizing region 210 can be formed by suspending tiny particles in a liquid or gel, or by using porous materials. These materials can produce complex scattering and refraction of light, thereby achieving random phase modulation. The light-transmitting region 220 can be made of a material with good light transmittance and low scattering effect, such as transparent optical glass or optical resin, to maintain the transmission efficiency of the non-zero-order beam.

[0176] As described above, the homogenizing region 210 of the homogenizing element 200 can homogenize the beam portion L20 corresponding to the zero-order spot in the modulated beam L2 provided by the intensity distribution modulator 100, so that the zero-order spot is homogenized to the target imaging range on the target imaging plane P0. After the homogenizing region 210 of the homogenizing element 200 homogenizes the beam portion L20 corresponding to the zero-order spot in the modulated beam L2, the beam portion L20 diffuses outward, reaching the target imaging range of the intensity distribution pattern. Therefore, for the zero-order spot, its size ratio in the modulated beam L2 changes before and after homogenization by the homogenizing region 210 of the homogenizing element 200. Based on this, as shown in FIG27, in some embodiments, the first size ratio of the zero-order spot in the modulated beam L2 at the first plane P3 is smaller than the second size ratio of the zero-order spot in the modulated beam L2 at the second plane P4. Wherein, the first plane P3 is the plane in front of the incident homogenizing element 200 where the modulated light beam L2 is incident (it can be a plane perpendicular to the light path R1), the second plane P4 is the plane after the exit of the homogenizing element 200 where the modulated light beam L2 is emitted (it can be a plane perpendicular to the light path R1), the first size ratio is the ratio of the size of the zero-order light spot to the size of the light intensity distribution pattern at the first plane P3, and the second size ratio is the ratio of the size of the zero-order light spot to the size of the light intensity distribution pattern at the second plane P4. In other words, in terms of optical phenomena, if the image projected by the modulated light beam L2 is captured at the first plane P3, the ratio of the size of the zero-order spot to the size of the light intensity distribution pattern can be recorded as the first size ratio. If the image projected by the modulated light beam L2 is captured at the second plane P4, the ratio of the size of the zero-order spot to the size of the light intensity distribution pattern can be recorded as the second size ratio. Because the homogenizing region 210 of the homogenizing element 200 homogenizes the portion L20 of the beam corresponding to the zero-order spot in the modulated light beam L2, the first size ratio will be smaller than the second size ratio.

[0177] In some embodiments, the intensity distribution modulation device of the optical modulation system may include a phase light modulator (PLM), and the target imaging plane may include the incident plane of an optical valve. The surface of the optical valve may have a size corresponding to the target imaging range, and the incident plane containing the surface of the optical valve may form a target imaging plane P0, configured to project an intensity distribution pattern with the target imaging range formed on the target imaging plane P0 onto a projection plane. In practical applications, the surface of the optical valve may have dimensions of 0.33 inches, 0.47 inches, or 0.65 inches.

[0178] Therefore, the optical modulation system of some embodiments of this application can be applied to laser projection devices that include a phase light modulator and a light valve, avoiding the appearance of zero-order bright spots in the light intensity distribution pattern provided by the phase light modulator to the light valve in related technologies, which affects the final projection display effect. As an implementation, the light valve can be a digital micromirror device (DMD). Thus, the optical modulation system provided in some embodiments of this application can be applied to laser projection devices that include a phase light modulator and a digital micromirror device, avoiding the appearance of zero-order bright spots in the light intensity distribution pattern provided by the phase light modulator to the digital micromirror device in related technologies, which affects the final projection display effect.

[0179] Based on the optical modulation system provided in the various embodiments of this application, in some embodiments, as shown in Figures 28 to 30, this application also provides a laser projection device including the optical modulation system.

[0180] The laser projection device of this embodiment, according to the laser beam propagation direction, may include a multi-wavelength light source 300, a phase light modulator 600, a coupling lens 400 of the phase light modulator 600, an illumination optical path 500 of the light valve 700, a total internal reflection prism (TIR prism) 900, and a laser projection lens 800. The multi-wavelength light source 300 may include a laser source for generating multiple laser beams of different wavelengths, which may be a laser diode array (LD array). The multi-wavelength light source 300 may also include optical elements for combining and collimating the multiple laser beams of different wavelengths to form a multi-wavelength laser beam that is provided to the phase light modulator 600. In practical applications, the multi-wavelength light source 300 may include a three-color laser source. Thus, the multi-wavelength light source 300 can illuminate the phase light modulator 600 with the combined and collimated multi-wavelength laser beam. The phase modulator 600 can perform phase recovery calculations to obtain a specific phase distribution based on the desired light intensity distribution pattern. The phase modulator 600 loads this phase distribution and outputs a modulated multi-wavelength laser beam to the coupling lens 400. The coupling lens 400 forms the focusing plane P1 of the phase modulator 600. Then, the illumination path 500 of the light valve 700 directs the modulated multi-wavelength laser beam exiting the coupling lens 400 through the total internal reflection prism 900 to illuminate the backlight onto the light valve 700, achieving zoned dynamic backlighting for the laser display. In practical applications, the light valve 700 can be a digital micromirror device (DMD). The beam processed by the light valve 700, after passing through the total internal reflection prism 900 and the laser projection lens 800, can project the corresponding display image onto the laser projection plane.

[0181] It should be noted that for laser projection devices with zoned backlighting that include a phase light modulator (PLM) and a digital micromirror device (DMD), the PLM uses the principle of light diffraction to adjust the intensity distribution of the illumination beam. However, due to the inherent characteristics of the PLM, zero-order diffraction will exist in the modulated beam, resulting in a central bright spot when it illuminates the DMD. Without processing, this central bright spot will appear on the projected image or other planes, severely affecting the display effect of the laser projection.

[0182] In laser projection equipment, the phase light modulator (PLM) adjusts the intensity distribution of the illumination beam based on phase modulation. The specific intensity distribution of the illumination beam output by the phase light modulator (PLM) is projected onto the digital micromirror device (DMD) through the imaging optical system to achieve zoned backlighting.

[0183] In the laser projection device of this embodiment, a light homogenizing element 200 with a light homogenizing region 210 (not specifically shown in Figures 28 to 30) is also included. The light homogenizing element 200 with the light homogenizing region 210 can be designed as a diffuser with a scattering structure or compound eye and a diffractive optical structure only in the center or a local area. Thus, spatial filtering can be achieved by the light homogenizing element 200. Diffusion and homogenization can be performed only on the zero-order spot area. The zero-order spot can be homogenized on the target imaging plane P0 (in this embodiment, the target imaging plane P0 can be the incident plane of the light valve 700) to the entire incident plane of the light valve 700, thereby reducing the influence of zero-order diffraction.

[0184] In this embodiment, according to the working principle of the laser projection device, the homogenizing element 200 needs to be placed in the optical path between the phase modulator 600 and the target imaging plane P0 to homogenize the portion of the beam corresponding to the zero-order spot in the modulated multi-wavelength laser beam provided by the phase modulator 600. As an implementation method, the homogenizing element 200 can be placed in the optical path between the phase modulator 600 and the coupling lens 400 (at the plane perpendicular to the optical path as shown by P5 in Figure 30), or in the optical path between the target imaging plane P0 and the focusing plane P1 of the phase modulator 600, or in the optical path between the focusing plane P1 and the coupling lens 400.

[0185] Referring to Figures 28 and 30, the homogenizing element 200 can be placed at the focal plane P21 or P22 of the zero-order spot near the focal plane P1. It is configured to homogenize the beam portion corresponding to the zero-order spot at the focal plane P21 or P22 by the homogenizing region 210. In this case, the modulated multi-wavelength laser beam provided by the phase modulator 600 converges at its focal plane P1 with the smallest beam range and the clearest image. Since the zero-order spot is not modulated by the intensity distribution modulator 100 and has a different focal plane than the focal plane P1, the modulation effect on the convergence or divergence of the multi-wavelength laser beam varies depending on the phase inherent in the phase modulator 600 itself. Therefore, the focal plane of the zero-order spot will appear at a position before or after the focal plane P1 in the optical path, i.e., the focal planes P21 or P22 shown in the figures. Therefore, the homogenizing element 200 can be disposed at the focal plane P21 or P22 of the zero-order spot near the focal plane P1, and configured to homogenize the beam portion corresponding to the zero-order spot at the focal plane P21 or P22 by the homogenizing region 210 of the homogenizing element 200. Thus, the homogenizing element 200 and its homogenizing region 210 can be disposed at the focal plane of the zero-order spot near the focal plane P1 to homogenize the beam portion corresponding to the zero-order spot. This can minimize the size of the homogenizing region 210 itself, and homogenize a portion of the modulated multi-wavelength laser beam with the smallest possible homogenizing region 210, avoiding affecting the display effect of the beam portion other than the beam portion corresponding to the zero-order spot in the modulated multi-wavelength laser beam. It can also minimize the cost of the homogenizing element 200 according to its size.

[0186] In this embodiment, to ensure that the homogenizing region 210 of the homogenizing element 200 homogenizes the beam portion corresponding to the zero-order spot to the entire projected image, the diffusion angle of the homogenizing region 210 can be designed. As shown in Figures 28 and 30, the diffusion angle of the homogenizing region 210 can be constrained by the distance d between the focusing plane P21 or P22 and the focusing plane P1, and the diagonal length X of the intensity distribution pattern of the modulated multi-wavelength laser beam projected onto the focusing plane P1. The diffusion angle θ of the homogenizing region 210 can be expressed as θ = atan(X / 2*d).

[0187] In this embodiment, the homogenizing element 200 may further include a light-transmitting region 220. All regions except the homogenizing region 210 can be designed as light-transmitting regions 220. The light-transmitting region 220 can employ a transmissive optical structure that is transparent to the modulated multi-wavelength laser beam and does not carry any other light modulation effects, thereby ensuring the transmission efficiency of the beam portion of the modulated multi-wavelength laser beam excluding the beam portion corresponding to the zero-order spot. The homogenizing element 200, including the homogenizing region 210 and the light-transmitting region 220, must have a size that at least covers the target beam range. This target beam range is the beam range formed by the modulated multi-wavelength laser beam illuminating the homogenizing element 200. Thus, the homogenizing element 200 can provide homogenization processing for the beam portion corresponding to the zero-order spot in the modulated multi-wavelength laser beam through the homogenizing region 210, and can provide transmission processing for the beam portion of the modulated multi-wavelength laser beam excluding the beam portion corresponding to the zero-order spot through the light-transmitting region 220, to avoid deficiencies in homogenization or transmission processing of the modulated multi-wavelength laser beam, which would affect the final image projection effect. The size of the homogenizing element 200, which includes a homogenizing region 210 and a transmitting region 220, can be the same as the beam range formed by the modulated multi-wavelength laser beam illuminating the homogenizing element 200, in order to minimize the size of the homogenizing element 200 and thus minimize cost. The transmitting region 220 can surround the homogenizing region 210, and the homogenizing region 210 and the transmitting region 220 have a smooth transition, thereby reducing diffraction effects and unnecessary light loss or shadows in the optical path. The junction between the homogenizing region 210 and the transmitting region 220 can use a continuously changing curved surface or slope to achieve a smooth transition.

[0188] In some embodiments, the optical modulation system can also be applied to the projection system shown in FIG3. For example, the light intensity distribution modulation device can be a phase light modulator 12, the coupling lens can be an optical element 161 in the first lens group 16a, the illumination light path can be a second lens group 106, and the light homogenizing element can be a spatial filter 162, that is, the light homogenizing area is disposed on the spatial filter 162.

[0189] The display effect of the light intensity distribution pattern of the laser projection device is explained with reference to Figures 31, 32, and 33. Among them, Figures 31, 32, and 33 show a comparison of the display effects of three light intensity distribution patterns at, for example, the target imaging plane P0.

[0190] The light intensity distribution pattern shown in Figure 31 is a nine-square holographic pattern. A131 in Figure 31 represents a light intensity distribution pattern projected onto, for example, the target imaging plane P0 in related technologies. This light intensity distribution pattern, represented by A131, clearly includes a zero-order bright spot, resulting in a central bright spot on the light valve and also appearing in the projected image, severely affecting the display effect of the laser projection. A132 in Figure 31 represents the light intensity distribution pattern projected onto, for example, the target imaging plane P0 after the zero-order bright spot has been homogenized by the homogenizing area 210 of the homogenizing element 200 in this embodiment. In this pattern, there is no zero-order bright spot, so a central bright spot will not form on the light valve, effectively improving the display effect of the laser projection. Furthermore, the light power of the entire zero-order bright spot is homogenized across the entire projected image, increasing the overall brightness and uniformity of the image.

[0191] The light intensity distribution pattern shown in Figure 32 is a triangular holographic pattern. B131 in Figure 32 represents the light intensity distribution pattern projected at, for example, the target imaging plane P0 in related technologies. B132 in Figure 32 represents the light intensity distribution pattern projected at, for example, the target imaging plane P0 after the zero-order light spot is homogenized by the homogenizing region 210 of the homogenizing element 200 in this embodiment. Therefore, it can be seen that the light intensity distribution pattern projected at, for example, the target imaging plane P0 in the laser projection device of this embodiment does not contain a zero-order bright spot, effectively improving the display effect of laser projection.

[0192] The light intensity distribution pattern shown in Figure 33 is a rectangular holographic pattern. C131 in Figure 33 represents the light intensity distribution pattern projected onto, for example, the target imaging plane P0 in related technologies. C132 in Figure 33 represents the light intensity distribution pattern projected onto, for example, the target imaging plane P0 after the zero-order light spot has been homogenized by the homogenizing region 210 of the homogenizing element 200 in this embodiment. Therefore, it can be seen that the laser projection device of this embodiment does not form a central bright spot on the light valve, effectively improving the display effect of laser projection and enhancing the overall brightness and uniformity of the projected image.

[0193] Based on the comparison of the effects of the three light intensity distribution patterns above, it can be seen that the laser projection device of this embodiment can effectively improve the display effect of laser projection and enhance the overall brightness and uniformity of the image under various light intensity distribution patterns.

[0194] Therefore, even though a zero-order spot may be generated after the phase light modulator modulates the illumination beam in a laser projection device containing a phase light modulator, the laser projection device of this embodiment can specifically homogenize and shape the zero-order spot through the homogenizing element 200 with the homogenizing region 210, thereby reducing the influence of the zero-order spot. This method can also avoid the waste of incident light energy caused by algorithms such as zero-order offset that may be used in related technologies, and can also avoid the problem of diffraction efficiency being affected by zero-order homogenization through algorithms, thereby effectively improving the picture effect of laser display.

[0195] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0196] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A projection system, comprising: The laser source is configured to emit tri-color lasers; A phase light modulator, located on the light-emitting side of the laser source, is configured to perform phase modulation on the laser emitted from the laser source according to the image to be displayed; The first lens group, located on the light-emitting side of the phase light modulator, is configured to converge the phase-modulated light beam; The phase light modulator is located on the object plane of the first lens group or within a preset distance from the object plane of the first lens group; The second lens group, located on the light-emitting side of the first lens group, is configured to convert the light beam from the first lens group into a light intensity distribution pattern and image it on the output surface; the image-side focal point of the first lens group and the object-side focal point of the second lens group are approximately coincident. A spatial filter is located at the focal position of the first lens group or within a preset distance from the focal position of the first lens group; the spatial filter is configured to homogenize high-frequency noise. and An amplitude light modulator, located on the image plane of the second lens group, is configured to modulate the amplitude of the incident light according to the image to be displayed, forming an image beam for projection imaging.

2. The projection system as claimed in claim 1, wherein, The focal length of the first lens group is the same as that of the second lens group.

3. The projection system as described in claim 1, wherein, The focal length of the first lens group is different from that of the second lens group.

4. The projection system as described in claim 2 or 3, wherein, The spatial filter is located between 0.7 times the focal length of the first lens group and the focusing position of the first lens group.

5. The projection system as described in claim 2 or 3, wherein, The spatial filter is located between the focal position of the first lens group and 1.3 times the focal length of the first lens group.

6. The projection system as claimed in claim 1, wherein, The spatial filter employs one or more of the following: fixed diffuser, moving diffuser, random phase plate, SLM, DOE, or metasurface.

7. The projection system as claimed in claim 1, wherein, The first lens group is selected from any of the following: Convex lens; Concave mirror; and Fresnel lens; The second lens group includes at least one convex lens.

8. The projection system according to claim 7, wherein, The second lens group includes: The second lens is located on the light-emitting side of the first lens group; The third lens is located on the side of the second lens that is opposite to the first lens group; and The fourth lens is located on the side of the third lens that is opposite to the second lens.

9. The projection system as claimed in claim 1, wherein, The first lens group and / or the second lens group are zoom lens groups; The size and position of the image are changed by adjusting the focal length of the zoom lens group.

10. The projection system of claim 1, wherein, The first lens group, the spatial filter, and the second lens group constitute a first optical system; The projection system includes at least one cascaded first optical system; the phase light modulator is positioned close to the object plane of the first optical system of the first stage, and the amplitude light modulator is located on the image plane of the first optical system of the last stage; the image plane of the first optical system of the previous stage coincides with the object plane of the first optical system of the next stage.

11. The projection system of claim 1, wherein, The space filter employs a nonlinear optical crystal; or The projection system further includes: a nonlinear optical crystal located between the phase light modulator and the object plane of the first lens group; The nonlinear optical crystal is configured to output light waves of random frequencies.

12. The projection system of claim 1, wherein, The phase light modulator is configured to receive parallel light incident.

13. The projection system of claim 1, further comprising: A light-uniform element is disposed in the optical path between the phase light modulator and the target imaging plane of the phase light modulator; wherein the phase light modulator provides a modulated light beam to the target imaging plane, forming a light intensity distribution pattern with a target imaging range at the target imaging plane. The light-diffusing element includes: The homogenizing region is configured to homogenize the portion of the modulated beam corresponding to the zero-order spot, such that the zero-order spot is homogenized to the target imaging range on the target imaging plane.

14. The projection system of claim 13, wherein, The size of the homogenizing region corresponds to the size of the zero-order spot with the largest wavelength illuminating the homogenizing element, so as to homogenize the portion of the light beam corresponding to the zero-order spot of each wavelength illuminating the homogenizing element.

15. The projection system of claim 13, wherein, The projection system also includes: A coupling lens is disposed on the light-emitting side of the phase light modulator and is configured to provide a focusing plane of the phase light modulator in the optical path; The homogenizing element is located at the focal plane of the zero-order spot between the focal plane of the phase modulator and the coupling lens, and is configured to homogenize the beam portion corresponding to the zero-order spot by the homogenizing region on the focal plane of the zero-order spot.

16. The projection system of claim 13, wherein, The projection system also includes: A coupling lens is disposed on the light-emitting side of the phase light modulator and is configured to provide a focusing plane of the phase light modulator in the optical path; The homogenizing element is located at the focal plane of the zero-order spot between the focal plane of the phase light modulator and the target imaging plane, and is configured to homogenize the beam portion corresponding to the zero-order spot through the homogenizing region on the focal plane of the zero-order spot.

17. The projection system as claimed in claim 15 or 16, wherein, The diffusion angle of the uniform light region is constrained by the distance between the focusing plane of the phase modulator and the focusing plane of the zero-order spot, and by the beam range formed by the modulated beam on the focusing plane of the phase modulator; wherein, the beam range is represented by the diagonal length of the light intensity distribution pattern projected by the modulated beam on the focusing plane of the phase modulator; the constraint relationship is expressed as: θ = atan(X / 2*d); where θ represents the diffusion angle of the uniform light region; X represents the diagonal length; and d represents the distance.

18. The projection system of claim 13, wherein, The light-diffusing element further includes: The light-transmitting region is configured to transmit a portion of the modulated light beam, excluding the portion corresponding to the zero-order spot. The light-transmitting area is arranged to surround the light-uniforming area; The light-uniform area and the light-transmitting area have a smooth transition; The homogenizing element has a size that at least covers the target beam range; the target beam range is the beam range formed by the modulated beam illuminating the homogenizing element.

19. The projection system of claim 13, wherein, The first size ratio of the zero-order spot of the modulated beam at the first plane is smaller than the second size ratio of the zero-order spot of the modulated beam at the second plane; the first plane is the plane in front of the modulated beam before it enters the homogenizing element; the second plane is the plane in which the modulated beam exits the homogenizing element; the first size ratio is the ratio of the size of the zero-order spot to the size of the intensity distribution pattern at the first plane; the second size ratio is the ratio of the size of the zero-order spot to the size of the intensity distribution pattern at the second plane.

20. The projection system of claim 13, wherein, The homogenizing region included in the homogenizing element accounts for less than 20% of the area of ​​the homogenizing element.

21. The projection system according to any one of claims 13, wherein, The homogenizing region of the homogenizing element is selected from any of the following structures: random scattering structure, compound eye microlens array, and diffractive optical element.

22. A laser projection device, comprising the projection system according to any one of claims 1 to 22.

23. The laser projection device of claim 22 further includes an optical valve; the surface of the optical valve has a size corresponding to the target imaging range, the incident plane on which the surface of the optical valve is located forms the target imaging plane, and the optical valve is configured to project a light intensity distribution pattern having the target imaging range formed on the target imaging plane onto a projection plane.

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