Laser projection imaging apparatus

Abstract

A laser projection imaging apparatus, comprising: a light source chip (31), which comprises a driving circuit (311) and a light-emitting module (312), wherein the light-emitting module (312) comprises a plurality of light-emitting units made of a vertical-cavity surface-emitting laser device, and the driving circuit (311) is connected to the light-emitting units, and is configured to receive driving information of an image signal, and to drive, on the basis of a target operating current and a modulation pulse width, the light-emitting module (312) corresponding to a video signal, such that the light source chip (31) emits a target image; a micro-lens area array (32), which is located on a light-emergent side of the light source chip (31), and is configured to homogenize light spots of the light-emitting module (312); and an imaging lens (33), which is located on the side of the micro-lens area array (32) facing away from the light source chip (31) in a light beam propagation direction, and is configured to receive a light beam passing through the micro-lens area array (32) and to perform projection imaging on the light beam. The apparatus can reduce the volume of the apparatus and reduce the cost, while weakening speckles and improving the image quality.

Description

Laser projection imaging device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese application filed on August 15, 2023, with application number 202311026973.8; and filed on December 8, 2023, with application number 202311686660.5, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The embodiments of the present application relate to the field of projection imaging technology, and more particularly to a laser projection imaging device. Background Art

[0004] Compared to the LED (Light Emitting Diode) and blue laser-excited phosphor light sources used in traditional projection TVs, laser light sources are highly efficient, addressing the low electro-optical efficiency of LEDs, the low conversion efficiency of blue laser-excited phosphors, poor heat dissipation characteristics, and the difficulty in applying them to large-scale projections. Laser display technology, which supports laser light sources, offers advantages such as excellent monochromaticity, a wide color gamut, long life, high brightness, and low power consumption, leading to its widespread adoption.

[0005] Edge-emitting lasers (EELs), a widely used laser source on the market, often require a spatial light modulator called a digital micromirror device (DMD). The DMD's characteristics reduce the efficiency of the laser beam. EELs also suffer from low beam efficiency and require additional components to reduce speckle, resulting in a bulky optical path.

[0006] Summary of the Invention

[0007] An embodiment of the present application provides a laser projection imaging device, comprising: a light source chip, including a driving circuit and a light-emitting module; the light-emitting module includes a plurality of light-emitting units made of straight-cavity surface-emitting lasers; the light-emitting units include a first light-emitting unit for emitting red laser, a second light-emitting unit for emitting green laser, and a third light-emitting unit for emitting blue laser; the driving circuit is electrically connected to the light-emitting units and is configured to: receive driving information of an image signal; the driving information includes a target operating current representing the display brightness of the video signal, a target adjustment pulse width representing the display grayscale of the video signal, and a light-emitting module corresponding to the video signal; drive the light-emitting module corresponding to the video signal according to the target operating current and the modulated pulse width, so that the light source chip emits a target image; a microlens array, located on the light-emitting side of the light source chip, is configured to: homogenize the light spot of the light-emitting module; an imaging lens, located on the side of the microlens array away from the light source chip along the propagation direction of the light beam, is configured to receive the light beam after passing through the microlens array and project the light beam into an image.

[0008] In the laser projection imaging device provided by the embodiments of the present application, light-emitting units made of VCSELs (Vertical Cavity Surface Emitting Lasers) serve as the laser light source. This eliminates the need for a DMD, improves laser beam utilization, and reduces the cost of VCSELs, thereby reducing the overall cost of the laser projection imaging device. Compared to traditional EELs, the light beam emitted by the VCSEL light-emitting units is a circularly symmetrical Gaussian beam with higher beam quality, smaller divergence, easier beam shaping, and high coupling efficiency. The lateral beam size can reach several to tens of microns, making it easier to manufacture larger, high-density monolithic integrated light source chips. The number of arrays can be increased to increase power output and produce larger and brighter projected images. Furthermore, because the phase relationship between the light-emitting units in the VCSEL is not fixed and the coherence is relatively weak, monolithic light source chips with equal wavelength spacing can be manufactured. This helps reduce the device's beam coherence, mitigate speckle, and improve the quality of the projected image output. This eliminates the need for specialized speckle reduction components, thereby reducing the overall size of the laser projection imaging device. This reduces the size and cost of the laser projection imaging device while minimizing speckle and improving image quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the implementation methods in the embodiments of the present application or related technologies, the following is a brief introduction to the drawings required for use in the embodiments or related technology descriptions. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0010] FIG1 is a schematic diagram of imaging of a conventional laser projection imaging device according to one embodiment of the present application;

[0011] FIG2 is a schematic diagram of a three-color laser display optical path structure according to an embodiment of the present application;

[0012] FIG3 is a schematic diagram of the structure of an edge-emitting laser according to an embodiment of the present application;

[0013] FIG4 is a schematic structural diagram of a laser projection imaging device according to an embodiment of the present application;

[0014] FIG5 is a schematic diagram of a VCSEL structure provided according to an embodiment of the present application;

[0015] FIG6 is a schematic diagram of a driving circuit and a light-emitting unit structure according to an embodiment of the present application;

[0016] FIG7 is a schematic diagram of another driving circuit and light-emitting unit structure provided according to an embodiment of the present application;

[0017] FIG8 is a schematic diagram showing the relationship between luminous intensity and target operating current according to one embodiment of the present application;

[0018] FIG9 is a schematic diagram of a current pulse according to an embodiment of the present application;

[0019] FIG10 is a schematic diagram of another current pulse according to an embodiment of the present application;

[0020] FIG11 is a schematic diagram of a light emitting module arrangement according to an embodiment of the present application;

[0021] FIG12 is a schematic diagram of another arrangement of light-emitting modules according to an embodiment of the present application;

[0022] FIG13 is a schematic diagram of another arrangement of light-emitting modules according to an embodiment of the present application;

[0023] FIG14 is a schematic diagram of a light source chip structure according to an embodiment of the present application;

[0024] FIG15 is a schematic diagram of the structure of another light source chip provided according to an embodiment of the present application;

[0025] FIG16 is a schematic diagram of the structure of another light source chip provided according to an embodiment of the present application;

[0026] FIG17 is a schematic diagram of a light source chip structure provided according to one embodiment of the present application;

[0027] FIG18 is a schematic diagram of a microlens array structure provided according to an embodiment of the present application;

[0028] FIG19 is a schematic diagram of an application scenario of a microlens array according to an embodiment of the present application;

[0029] FIG20 is a schematic diagram of another application scenario of a microlens array according to an embodiment of the present application;

[0030] FIG21 is a schematic diagram of another application scenario of a microlens area array according to an embodiment of the present application;

[0031] FIG22 is a schematic diagram of a substrate structure provided according to one embodiment of the present application;

[0032] FIG23 is a schematic diagram of a computer controller connection method according to an embodiment of the present application;

[0033] FIG24 is a schematic structural diagram of another laser projection imaging device provided according to an embodiment of the present application;

[0034] FIG25 is a schematic diagram of a receiving screen structure provided according to an embodiment of the present application;

[0035] FIG26 is a schematic diagram of an application scenario of a laser projection imaging device according to an embodiment of the present application;

[0036] FIG27 is a top view of a laser chip provided according to one embodiment of the present application;

[0037] FIG28 is a side view of a laser chip provided according to one embodiment of the present application;

[0038] FIG29 is a partial cross-sectional view of a first laser unit according to one embodiment of the present application;

[0039] FIG30 is an energy level diagram before and after quantum well intercalation according to one embodiment of the present application;

[0040] FIG31 is a flow chart of a method for preparing a laser chip according to one embodiment of the present application;

[0041] FIG32 is a specific flow chart of preparing a dielectric film according to one embodiment of the present application;

[0042] FIG33 is a schematic structural diagram of a mask provided according to one embodiment of the present application;

[0043] FIG34 is a top view of another laser chip provided according to an embodiment of the present application;

[0044] FIG35 is a top view of another laser chip provided according to an embodiment of the present application;

[0045] FIG36 is a top view of another laser chip provided according to an embodiment of the present application;

[0046] FIG37 is a top view of another laser chip provided according to an embodiment of the present application;

[0047] FIG38 is a top view of a laser light source provided according to one embodiment of the present application;

[0048] FIG39 is a side view of a laser light source provided according to one embodiment of the present application;

[0049] Figure 40 is a side view of another laser light source provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0050] In order to make the purpose and implementation of this application clearer, the exemplary implementation of this application will be clearly and completely described below in conjunction with the drawings in the exemplary embodiments of this application. Obviously, the described exemplary embodiments are only part of the embodiments of this application, not all of the embodiments.

[0051] It should be noted that the brief descriptions of terms in this application are only for the purpose of facilitating the understanding of the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise specified, these terms should be understood according to their ordinary and usual meanings.

[0052] The terms "comprise," "include," and "have," and any variations thereof, are intended to cover but not exclude inclusion; for example, a product or device comprising a list of components is not necessarily limited to all the components expressly listed but may include other components not expressly listed or inherent to such product or device.

[0053] Figure 1 is a schematic diagram of a conventional laser projection imaging device commonly found on the market. The device primarily comprises a light source 10, a light modulation assembly 20, and a lens 30. As shown in Figure 1, the illumination beam emitted by light source 10 enters light modulation assembly 20. Light source 10 includes a laser assembly that emits blue laser light and a wavelength conversion device that receives the blue laser light and generates other primary colors besides blue, which together form the illumination beam.

[0054] The light modulation assembly 20 includes a first light homogenizing component 210, a reflector 220, a lens 230, and a prism assembly 250. The light valve 240 is configured to modulate the incident illumination beam into a projection beam based on the image signal and direct the projection beam toward the lens 30. The first light homogenizing component 210 can be a light pipe or a fly-eye lens.

[0055] Light valve 240 is a light modulation device, shown as a reflective light valve in the figure. Light valve 240 includes multiple reflective sheets, each corresponding to a pixel in the projection image. For example, depending on the image to be displayed, the reflective sheets of light valve 240 corresponding to the pixels to be illuminated can reflect a light beam toward lens 30. The light beam reflected toward lens 30 is called the projection beam. In this way, light valve 240 modulates the illumination beam to generate the projection beam, which is then used to display the image.

[0056] The light valve 240 in conventional laser projection imaging devices is often a digital micromirror device (DMD). A DMD includes multiple (e.g., tens of thousands) of individually driven, rotating micromirrors. These micromirrors can be arranged in an array. Each micromirror (e.g., each micromirror) corresponds to a pixel in the projected image to be displayed.

[0057] In the optical path architecture provided in Figure 1, the light source 10 and the light valve 240 are both driven and controlled by the display control component. The light source receives the brightness dimming signal and timing lighting control signal corresponding to the image signal to emit light, and the light valve DMD receives the driving control signal corresponding to the image signal, and flips the thousands of tiny mirrors on its surface at a positive or negative angle corresponding to the driving signal, forming the light beam from the light source that illuminates its surface into the image to be projected and reflected into the lens.

[0058] Next, based on FIG2 , the three-color laser display optical path structure in the conventional laser projection imaging device shown in FIG1 is explained. As shown in FIG2 , in the conventional three-color laser display solution, the laser light source of the laser display uses a multi-chip three-color laser to emit a green laser beam 100, a blue laser beam 200, and a red laser beam 300. The green laser beam 100 is reflected by the green light reflector 101 and projected through the blue dichroic plate 102 and the red dichroic plate 103. The blue laser beam 200 is reflected by the blue dichroic plate 102 and projected through the red dichroic plate 103. The red laser beam 300 is reflected by the red dichroic plate 103 and then reaches the diffuser 104. After being homogenized by the diffuser 104, the laser beam reaches the lens group 105. After being converged by the first lens group 105, the laser beam enters the light guide 106. After passing through the light guide 106, the laser beam reaches the second lens group 107. After being reflected and refracted by multiple second lens groups 107, the laser beam enters the TIR (Total Internal Reflection) The laser beam is totally reflected by the TIR prism 108, converged and focused onto the surface of the DMD 109. The laser beam reflected by the DMD 109 directly penetrates the TIR prism 108 and enters the lens 30, and is then magnified by the lens 30 and formed on the screen.

[0059] In this structure, DMD109, as a spatial light modulator, is the main display element of the digital light processing (DLP) display technology. It is generally composed of thousands of micro-high-reflection aluminum micromirror arrays made of semiconductor technology. Each reflective micromirror corresponds to a pixel point. Under the control of a digital signal, it realizes a ±12° deflection to reflect the incident laser beam to the lens 30. The laser beam that does not enter the lens 30 is absorbed, resulting in a decrease in the utilization rate of the laser beam. DMD 109 is monopolized by certain technology manufacturers and is expensive. Since the TIR prism 108 is very close to the DMD 109, it is easy to generate discrete light and affect the contrast of the picture. Furthermore, this structure needs to adopt an optical addressing method for projection imaging. The optical addressing process primarily involves first using a spatial light modulator (SLM), such as the DMD mentioned above, to convert the optical signal into a spatial charge distribution and refractive index distribution. This signal is then modulated and read out using various effects (electro-optical and birefringence). The corresponding structures can be liquid crystal light valves or cathode ray tube liquid crystal light valves. The need for devices like the SLM makes the overall structure of the laser display optical path complex and bulky, hindering miniaturization.

[0060] FIG3 is a schematic diagram of the structure of an edge-emitting laser provided according to an embodiment of the present application. Traditional laser projection imaging devices often use edge-emitting lasers to provide light sources. The conical diagram shown in FIG3 represents the laser beam. The laser light source of the edge-emitting laser is firstly EEL. Due to the good monochromaticity of the laser, its coherence is strong. The laser beam is highly coherent in time and space due to scattering from the rough surfaces of the optical elements in the laser display optical path structure and the influence of the subtle irregularities on the display screen surface. This will generate a large number of interference fringes and speckle noise, seriously affecting the image quality and viewer experience.

[0061] To reduce the effects of speckle, related art often incorporates rotating diffusers or diffusion wheels (e.g., diffuser 104) into the optical system. However, the addition of these diffusers reduces light energy utilization, resulting in poor display quality. Furthermore, they increase the overall system volume of the optical system, hindering miniaturization. Furthermore, the light spot corresponding to the beam emitted by the EEL is elliptical. Since this elliptical light spot needs to be shaped into a circular Gaussian spot, corresponding optical elements are required for beam shaping. The inclusion of these optical elements also complicates the overall structure of the optical system, increasing its volume and hindering miniaturization.

[0062] Based on the above problems, an embodiment of the present application provides a laser projection imaging device. Figure 4 is a schematic structural diagram of a laser projection imaging device provided according to an embodiment of the present application. As shown in Figure 4, the present application adopts micro-semiconductor laser panel (Micro Laser Diode Panel, MLDP) technology, uses a light source chip 31 as the laser light source of the laser projection imaging device, and at the same time, a micro-lens array 32 is set on the light-emitting side of the light source chip 31 to homogenize the light spot of the light-emitting module of the light source chip 31. In addition, an imaging lens 33 is set on the side of the micro-lens array 32 away from the light source chip 31 to receive the light beam after passing through the micro-lens array 32 and project it into an image.

[0063] Figure 5 is a schematic diagram of a VCSEL structure provided according to one embodiment of the present application. The conical shape in Figure 5 represents the laser beam. Compared to conventional EELs (Electroluminescent Light Emitting Diodes), the VCSEL's output beam is a circularly symmetrical Gaussian beam with a small beam divergence, excellent beam quality, ease of beam shaping, and high coupling efficiency. The lateral dimensions of the output beam can reach several to tens of microns. This small size facilitates the manufacture of larger, high-density, monolithically integrated two-dimensional light source chips. The number of chips in an array can also be increased, increasing power output and producing larger and brighter projected images. Furthermore, the integrated chip's active area is small, with low operating thresholds and energy consumption, effectively improving electro-optical conversion efficiency. Furthermore, the phase relationship between the light-emitting units in the light source chip can be flexible, resulting in weak coherence and the ability to manufacture monolithic light source chips with equal wavelength spacing. This helps reduce the device's beam coherence, mitigate speckle, and improve the quality of the projected image output. This eliminates the need for specialized components to reduce speckle, thereby reducing the overall size of the laser projection imaging device.

[0064] Taking a 0.47-inch DMD as an example, it may have 2.07 million micromirrors, which can project 1920*1080 pixels, and the size of each light-emitting module 312 is 5.4μm. The size of the light-emitting unit made of VCSEL can be reduced to less than 5μm. It can be seen that using VCSEL as the light-emitting unit of the Micro-LD Panel array can achieve higher resolution and further reduce the volume of the overall optical path system. By comparison with related solutions, the embodiment of the present application can reduce the use of multiple lens groups, greatly compress the volume of the optical path, and improve the utilization rate of light energy. Since the light source chip 31 integrates R, G, and B three-color light sources, it avoids the pixel alignment problem caused by multiple Micro Laser Diode Panel arrays and can simplify the system structure.

[0065] Continuing to refer to FIG. 4 , the light source chip 31 may include a driving circuit 311 and a light emitting module 312 .

[0066] The light-emitting module 312 includes a plurality of light-emitting units made of VCSEL, including a first light-emitting unit 3121, a second light-emitting unit 3122, and a third light-emitting unit 3123; the first light-emitting unit 3121 emits red laser light, the second light-emitting unit 3122 emits green laser light, and the third light-emitting unit 3123 emits blue laser light;

[0067] The driving circuit 311 is electrically connected to the first light-emitting unit 3121, the second light-emitting unit 3122 and the third light-emitting unit 3123, and is configured to: receive driving information of the image signal; the driving information includes a target operating current representing the display brightness of the video signal, a target adjustment pulse width representing the display grayscale of the video signal, and a light-emitting module corresponding to the video signal; drive the light-emitting module corresponding to the video signal with the target operating current and the modulated pulse width, so that the light source chip emits the target image.

[0068] In some embodiments, the light-emitting units can be driven using an electrical addressing method. This method typically uses a video signal or a computer level signal to control the complex transmittance of the spatial light modulator. This method applies the signal to the corresponding light-emitting unit by scanning the electrodes on the spatial light modulator. In the embodiments of the present application, the light-emitting units are driven using an electrical addressing method, which can control the light-emitting units to emit light of the target color and brightness, so that the light source chip 31 as a whole can emit the target image. This saves components corresponding to the optical addressing modulation, helps reduce the overall volume, and facilitates a miniaturized design.

[0069] In some embodiments, the driver circuit 311 may be a CMOS driver circuit 311. The driver circuit 311 can drive specific light-emitting units to emit light based on electrical addressing. For example, the light source chip 31 may include multiple light-emitting modules 312. For each light-emitting module 312, the color, brightness, and duration of the display can be controlled based on the desired image. Specifically, specific light-emitting units within each light-emitting module 312 can be controlled to emit light of a specific color, brightness, and duration. For example, the first light-emitting unit 3121 within a light-emitting module 312 can be controlled to emit red laser light of a specific brightness and duration, while the second and third light-emitting units 3122 and 3123 within the same light-emitting module 312 can be controlled to not emit light. After passing through the microlens array 32, the laser beam emitted by the light-emitting module 312 can be homogenized, forming a homogenized light spot. The homogenized light spot then passes through the imaging lens 33, which projects an image based on the received light spot, for example, onto the receiving screen 2401, allowing the user to view the corresponding image. The present application utilizes the CMOS driving circuit 311 to control and form an imaging image at the light source, which is projected onto the screen through the imaging lens 33, which is conducive to miniaturized system integration and can reduce costs and other advantages.

[0070] FIG6 is a schematic diagram of a drive circuit and light-emitting unit structure provided according to an embodiment of the present application; as shown in FIG6 , the number of drive circuits 311 for a single light-emitting module 312 can be multiple, for example, the number of drive circuits 311 can be equal to the number of light-emitting units in the light-emitting module 312, and each drive circuit 311 is electrically connected to a light-emitting unit, corresponding to controlling one light-emitting unit. For example, FIG6 illustrates the drive circuit as a first drive circuit 51. In this case, the first drive circuit 51 can be arranged in an array-like manner with the light-emitting units in the light-emitting module 312. When controlling the light-emitting units to emit a specific color laser, each first drive circuit 51 only controls one light-emitting unit to emit light. In this way, each drive circuit 311 can control one light-emitting unit, making the control of the light-emitting units more flexible.

[0071] FIG7 is a schematic diagram of another driving circuit and light-emitting unit structure provided according to an embodiment of the present application; as shown in FIG7 , the driving circuit 311 can realize multi-channel output. In FIG7 , the driving circuit is schematically shown as a second driving circuit 61. The second driving circuit 61 can be set in a one-to-one correspondence with the light-emitting module 312. The output end of a single second driving circuit 61 is respectively connected to the first light-emitting unit 3121, the second light-emitting unit 3122 and the third light-emitting unit 3123 corresponding to the same light-emitting module 312. At this time, the number of first driving circuits 51 can also be multiple, and can also be arranged in an array, and can be similar to the array arrangement of the light-emitting module 312, so as to facilitate the electrical connection between the driving circuit and the light-emitting unit in the corresponding light-emitting module, and simplify the circuit connection structure. In the embodiment of the present application, a single second driving circuit 61 can control the illumination of multiple light-emitting units in the corresponding light-emitting module 312, thereby reducing the number of driving circuits 311.

[0072] In some embodiments, in order to make the light-emitting unit emit a specific brightness and a specific color, the driving circuit 311 can apply a target operating current and / or a target modulation pulse width to the corresponding light-emitting unit; the target operating current can be used to control the brightness of the light-emitting unit, and the target modulation pulse width can be used to control the grayscale of the light-emitting unit.

[0073] Within the working range of the light source chip, the relationship between its luminous intensity and the target working current can be represented by the LI curve. Figure 8 is a schematic diagram of the relationship curve between the luminous intensity and the target working current provided according to an embodiment of the present application, wherein the horizontal axis I represents the current intensity and the vertical axis L represents the luminous intensity. Referring to Figure 8, as the injected current increases, the luminous intensity also increases. When the luminous intensity tends to saturation, its luminous intensity will no longer increase significantly with the increase of the injected current. The modulation characteristics of the light source chip can be achieved by applying different currents and different pulse widths to the light-emitting unit. The brightness of the light-emitting unit can be changed by adjusting the target working current and the driving time, thereby correspondingly presenting light and dark images of different brightness.

[0074] FIG9 is a schematic diagram of a current pulse provided according to an embodiment of the present application, wherein the horizontal axis represents time and the vertical axis represents current. For example, the current intensity in the T1-T2 time period is a, the current intensity in the T3-T4 time period is b, and a<b. When a light-emitting unit is controlled in this current pulse manner, the brightness of the light-emitting unit in the time period corresponding to T1-T2 is less than the brightness of the light-emitting unit in the time period corresponding to T3-T4. In this embodiment, only the same light-emitting unit is illustrated. The same principle applies to different light-emitting units. For example, current pulses of different current intensities can be input to different light-emitting units in the same time period, thereby making the brightness of different light-emitting units different. The pulse width can be divided into multiple levels, and different levels represent different grayscale information. By controlling the exposure duty cycle of each light-emitting unit pixel, each light-emitting unit can achieve a different grayscale level to achieve a modulation effect on the image grayscale.

[0075] Figure 10 is another current pulse schematic diagram provided according to an embodiment of the present application, wherein the horizontal axis represents time and the vertical axis represents current. The exposure duty cycle can be calculated as D = P / N, where D represents the exposure duty cycle, P represents the duration of non-zero current intensity within one or more time periods, N represents the duration of zero current intensity within one or more time periods, and P + N = 100. The relationship between grayscale and exposure duty cycle can satisfy G = P / (P + N) × 100%, where G represents grayscale. Further, P / N = G / (1-G). For example, the duration of the time period corresponding to T1-T2 is t1, the duration of the time period corresponding to T2-T3 is t2, the duration of the time period corresponding to T4-T5 is t3, and the duration of the time period corresponding to T5-T6 is t4, and t1>t3, (t1÷t2)≠(t3÷t4), that is, the current pulse width is different and the exposure duty cycle is also different. If a light-emitting unit is controlled in this current pulse manner, the grayscale in the time period corresponding to T1-T3 is different from the grayscale and brightness in the time period corresponding to T4-T6. For example, when displaying a pure white screen, the exposure duty cycle in one or more time periods can be 100 / 0. Conversely, when displaying a pure black screen, the exposure duty cycle in one or more time periods can be 0 / 100.

[0076] In some embodiments, the image displayed by each light-emitting module 312 is composed of the three primary colors of red (R), green (G), and blue (B). Within an image frame period, to achieve white balance, the RGB primary colors are displayed for different percentages. The sum of the percentages of the three primary colors is 100%. The grayscale of each light-emitting module 312 can be the sum of the percentages of the three primary colors of RGB, i.e., G = TR × GR + TG × GG + TB × GB, where TR represents the percentage of the red light display period within the image frame period to achieve white balance, TG represents the percentage of the green light display period within the image frame period to achieve white balance, and TB represents the percentage of the blue light display period within the image frame period to achieve white balance. GR represents the grayscale of red, GG represents the grayscale of green, and GB represents the grayscale of blue. To achieve a certain white balance requirement, within an image frame period, the red, green, and blue periods can each have a percentage of 50% for red, 20% for green, and 30% for blue.

[0077] In some embodiments, each light-emitting module 312 can be arranged by a 2×2 light-emitting unit array; in some implementations, the light-emitting efficiency of light-emitting units of different colors is different. In order to achieve ideal brightness effects, color saturation, color uniformity, etc., each light-emitting module 312 can be composed of two light-emitting units of the same color and two light-emitting units of different colors. Any light-emitting module may include two first light-emitting units, one second light-emitting unit, and one third light-emitting unit; or, one first light-emitting unit, two second light-emitting units, and one third light-emitting unit; or, one first light-emitting unit, one second light-emitting unit, and two third light-emitting units.

[0078] FIG11 is a schematic diagram of an arrangement of a light emitting module 312 according to an embodiment of the present application, FIG12 is a schematic diagram of another arrangement of a light emitting module 312 according to an embodiment of the present application, and FIG13 is a schematic diagram of another arrangement of a light emitting module 312 according to an embodiment of the present application. Referring to FIG11-FIG12, each light emitting module 312 may include a first light emitting unit 3121, a second light emitting unit 3122 and a third light emitting unit 3123. In FIG11, the number of the first light emitting units 3121 is two, and they are arranged in a diagonal manner, and the second light emitting unit 3122 and the third light emitting unit 3123 are each one, and The second light-emitting unit 3122 and the third light-emitting unit 3123 are also arranged diagonally. For another example, in FIG12 , there are two second light-emitting units 3122, which are arranged diagonally, and there are one first light-emitting unit 3121 and one third light-emitting unit 3123, and the first light-emitting unit 3121 and the third light-emitting unit 3123 are also arranged diagonally. For another example, in FIG13 , there are two third light-emitting units 3123, which are arranged diagonally, and there are one first light-emitting unit 3121 and one second light-emitting unit 3122, and the first light-emitting unit 3121 and the second light-emitting unit 3122 are also arranged diagonally. Thus, different light-emitting unit arrangements can be set based on different requirements to obtain brightness, color saturation, and color uniformity that meet the target projection display requirements.

[0079] In some embodiments, the light source chip 31 may include a plurality of light-emitting modules 312, and each light-emitting module 312 may include a plurality of light-emitting units. Figure 14 is a schematic diagram of the structure of a light source chip 31 provided according to an embodiment of the present application, Figure 15 is a schematic diagram of the structure of another light source chip 31 provided according to an embodiment of the present application, and Figure 16 is a schematic diagram of the structure of another light source chip 31 provided according to an embodiment of the present application. Referring to Figure 14, Figure 14 exemplarily shows a light source chip 31 composed of the light-emitting modules 312 in Figure 11 above, Figure 15 exemplarily shows a light source chip 31 composed of the light-emitting modules 312 in Figure 12 above, and Figure 16 exemplarily shows a light source chip 31 composed of the light-emitting modules 312 in Figure 13 above. In Figures 14-16, the light-emitting units in the light-emitting modules are arranged in an array along the first direction and the second direction, and the colors of the emitted lasers of two adjacent light-emitting units are different along the first direction and / or the second direction.

[0080] It should be noted that Figures 14 to 16 only illustrate the situation where the colors of the laser beams emitted by two adjacent light-emitting units in the first direction and the second direction are different. However, it is obvious that in the first direction or the second direction, there may be a situation where the laser beams emitted by two adjacent light-emitting units have the same color, which is not illustrated here. The first direction and the second direction can be simply understood as the horizontal direction and the vertical direction, that is, the first direction and the second direction can be perpendicular to each other, and a rectangular matrix is ​​formed between every four light-emitting units. It should be understood that this is only an exemplary explanation and does not limit the first direction and the second direction to be perpendicular to each other. For example, in some possible embodiments, the first direction and the second direction may only intersect and not be perpendicular to each other, and a rectangular matrix cannot be formed between every four light-emitting units, such as a parallelogram matrix.

[0081] Figure 17 is a schematic diagram of a light source chip structure provided according to an embodiment of the present application; in some embodiments, the first light-emitting unit 3121 may include a first light-emitting chip 1601 based on a gallium arsenide substrate, and the laser wavelength of the first light-emitting chip 1601 is within 630 nanometers to 650 nanometers; the emitted laser wavelengths of different first light-emitting chips 1601 are arranged at equal intervals; the second light-emitting unit 3122 may include a second light-emitting chip 1602 based on a gallium nitride substrate, and the laser wavelength of the second light-emitting chip 1602 is within 515 nanometers to 540 nanometers; the emitted laser wavelengths of different second light-emitting chips 1602 are arranged at equal intervals; the third light-emitting unit 3123 may include a third light-emitting chip 1603 based on a gallium nitride substrate, and the laser wavelength of the third light-emitting chip 1603 is within 440 nanometers to 480 nanometers; the emitted laser wavelengths of different third light-emitting chips 1603 are arranged at equal intervals.

[0082] Taking the first light-emitting unit 3121 as an example, the four first light-emitting units 3121 illustrated in Figure 17 all include a first light-emitting chip 1601. The first light-emitting chips 1601 can be 16011, 16012, 16013 and 16014 respectively. The wavelength of the red laser emitted by 16011 can be 630nm (nanometers), the wavelength of the red laser emitted by 16012 can be 635nm, the wavelength of the red laser emitted by 16013 can be 640nm, and the wavelength of the red laser emitted by 16014 can be 645nm. That is, the wavelengths of the emitted lasers of different first light-emitting chips 1601 are arranged at equal intervals. This arrangement can reduce the coherence of the laser beams emitted by different light-emitting chips, weaken speckle, and improve the final image quality.

[0083] In some embodiments, the wavelength interval between the wavelengths of the emitted lasers of different light-emitting chips can be between 3-5 nm. In some embodiments, the light source chip 31 may include multiple light-emitting chips (here referring to light-emitting chips of the same type, for example, the first light-emitting chip 1601), and different equal-interval arrangements may be set. For example, for the first light-emitting chip 1601 arranged in an array, the arrangement of the wavelength of the emitted laser along the first direction may be 630 nm, 635 nm, 640 nm, 645 nm, 640 nm, 635 nm, 630 nm, 635 nm, 640 nm..., or 630 nm, 635 nm, 640 nm, 645 nm, 630 nm, 635 nm, 640 nm, 645 nm... and so on. Continuing to refer to FIG4 , the laser projection imaging device in the embodiment of the present application may further include a microlens array 32. The main function of the microlens 1701 array has been briefly described in the above embodiment and will not be repeated here.

[0084] FIG18 is a schematic diagram of the structure of a microlens array 32 provided according to an embodiment of the present application. As shown in FIG18 , the microlens array 32 may include microlenses 1701 arranged in an array, each corresponding to a light-emitting unit. Continuing with FIG18 , there is a preset spacing between the microlens array 32 and the imaging lens 33. The light beam after passing through the microlens array 32 is irradiated onto the light receiving surface of the imaging lens 33. The laser beam emitted by the light source chip 31 is primarily a Gaussian spot, with its beam energy primarily concentrated in the center. To improve image quality, the microlenses 1701 need to adjust the divergence angle of the laser beam emitted by the corresponding light-emitting unit when homogenizing the laser beam emitted by the corresponding light-emitting unit, so that the emitted laser beam matches the optical etendue of the imaging lens, thereby ensuring that the microlens array 32 does not change the distribution of the target image emitted by the light source chip 31.

[0085] Different imaging lenses have different optical extensions. For different imaging lenses, the embodiment of the present application sets a preset angle range (10° to 12°) for judging whether the beam of the currently emitted laser is compatible with the imaging lens. For example, as shown in Figure 19, if the beam divergence angle of the emitted laser of the light-emitting unit is greater than the preset angle range, that is, >12°. The microlens array 32 can shrink the beam divergence angle of the emitted laser of the light-emitting unit to within the preset angle range. For another example, as shown in Figure 20, if the beam divergence angle of the emitted laser of the light-emitting unit is less than the preset angle range, that is, <10°. The microlens array 32 can expand the beam divergence angle of the emitted laser of the light-emitting unit to within the preset angle range. For another example, as shown in Figure 21, if the beam divergence angle of the emitted laser of the light-emitting unit is within the preset angle range, it means that the emitted laser of the light-emitting unit is compatible with the imaging lens, and there is no need to shrink or expand the emitted laser. At this time, the emitted laser of the light-emitting unit can be kept as a collimated beam.

[0086] Compared to EEL collimating lenses, the microlens array 32 is easy to manufacture and has a simple structure. Furthermore, because the output beam from the light source chip 31 is a Gaussian circular spot, the collimation effect is superior. Since the red, green, and blue light-emitting units are made of different materials and have different luminous properties, the surface curvature and structure of the microlenses 1701 can also be different for different light-emitting units. However, the function of the microlenses 1701 with different surface curvatures and structures is to homogenize and shape the light spots into the same size (same imaging aspect ratio). The microlenses 1701 can be made of one or more materials such as sapphire, glass, or resin, using techniques such as high-temperature reflow, self-assembly, molding / imprinting / stamping, grayscale mask lithography, or dry etching pattern transfer.

[0087] According to imaging optics theory, if the distance between the light source chip 31 and the imaging lens 33 is relatively large, an image beam reducer should be used near the light source chip 31 to ensure that the resulting image matches the imaging lens 33. Conversely, an image beam expander should be used. During design, the preset distance between the light source chip 31 and the imaging lens 33 should be appropriately designed based on the characteristics of the light source chip 31. This ensures that the image matches the imaging lens 33 as much as possible without the use of optical components, thereby avoiding the reduction in light energy utilization caused by the introduction of optical components.

[0088] FIG22 is a schematic diagram of the structure of a substrate 2101 provided according to an embodiment of the present application. In some embodiments, the laser projection imaging device may further include a substrate 2101, with a driving circuit 311 integrated on one side of the substrate 2101; and a light-emitting module 312 is located on the side of the driving circuit 311 facing away from the substrate 2101. Referring to FIG21 , the embodiment of the present application can utilize microfabrication (e.g., mass transfer, microtubing, etc.) technology to integrate the light-emitting module 312 in the above embodiment into the same substrate 2101. The substrate 2101 can be made of glass, silicon, sapphire, etc., and a set of electrodes (not shown) can be fabricated on the substrate using microfabrication technology to control the driving circuit 311. The present application can quickly and accurately transfer light-emitting units prepared on different epitaxial substrates to the substrate 2101 using mass transfer or microtubing technology, and form a good electrical connection and mechanical fixation between the light-emitting modules and the driving circuit 311. This method does not need to consider the lattice matching characteristics of the R / G / B epitaxial material and the base substrate 2101, which can greatly improve the stability and reliability of the light-emitting unit, extend the working life, and avoid the problem of affecting the output performance of the light-emitting unit due to the lattice constant mismatch between the epitaxial material and the base substrate 2101.

[0089] FIG23 is a schematic diagram illustrating a connection method for a computer controller 2201 according to one embodiment of the present application. In some embodiments, a computer controller 2201 may be provided to control a driver circuit 311 so that the light-emitting unit can emit a laser beam having parameters such as a specific color and brightness. The computer controller 2201 may be connected to the driver circuit 311. FIG22 does not illustrate the driver circuit 311, and thus only shows it as being electrically connected to the substrate 2101. However, it should be understood that the driver circuit 311 is provided on the substrate 2101 and that the computer controller 2201 is actually electrically connected to the driver circuit 311. The computer controller 2201 may transmit driving information of an image signal to the driver circuit 311 in response to the image to be projected.

[0090] In some embodiments, there is no fixed phase relationship between the light-emitting units, resulting in weak coherence, which is beneficial for improving speckle. To further reduce speckle, an optical element 2301 may be provided between the light source chip 31 and the imaging lens 33, with each optical element 2301 corresponding to each light-emitting unit. The optical element 2301 can be used to reduce imaging speckle. FIG24 is a schematic structural diagram of another laser projection imaging device provided according to an embodiment of the present application. The optical element 2301 may be at least one of a wave plate, a compound eye, and a diffractive optical element. For example, a wave plate may be provided between the light source chip 31 and the imaging lens. The wave plate changes the phase of the laser beam to reduce the coherence between different laser beams, thereby reducing speckle. In some embodiments, a corresponding wave plate and a specific wave plate axis direction may be set according to the polarization state of the laser beam. For linearly polarized light, for example, a quarter-wave plate or a half-wave plate may be provided. The phase delay differences in the linear polarization direction of the quarter-wave plate and the half-wave plate are π / 2 and π, respectively, and the corresponding phase propagation distances are λ / 4 and λ / 2, respectively. In some embodiments, the axis orientation of the quarter-wave plate or half-wave plate can be determined based on actual needs. For example, if the laser beam is linearly polarized and needs to remain linearly polarized after passing through the wave plate, the polarization direction of the linearly polarized light needs to be maintained along one of the axes of the quarter-wave plate or half-wave plate, so that the polarization direction does not change. If the polarization direction of the laser beam incident on the half-wave plate does not coincide with either axis, the polarization remains polarized, but the polarization direction is rotated. For example, if the angle between the linearly polarized light and the axis is 45°, the polarization direction is rotated 90°. If the angle between the linearly polarized light incident on the quarter-wave plate is 45°, the linearly polarized light will be converted to circularly polarized light after passing through the quarter-wave plate (conversely, circularly polarized light will be converted to linearly polarized light after passing through the quarter-wave plate). In some embodiments, the wave plate can be made of quartz crystal (SiO2), which has high transparency and high optical quality over a wide wavelength range. In some embodiments, it can also be made of materials such as calcite, magnesium fluoride, sapphire, mica, etc.

[0091] In order to enable the laser projection imaging device provided in the embodiments of the present application to be viewed by the user, the laser projection imaging device provided in the embodiments of the present application may further include a receiving screen 2401. FIG25 is a schematic structural diagram of the receiving screen 2401 provided in one or more embodiments of the present application. The receiving screen 2401 may be disposed on the light-emitting side of the imaging lens 33. The receiving screen 2401 may receive the light emitted by the imaging lens 33 to present a projected image corresponding to the target image. For example, the type of the receiving screen 2401 in the embodiments of the present application may be selected based on actual needs. Here, an example is provided in which the receiving screen 2401 may be a Fresnel projection screen. In some embodiments, the Fresnel projection screen may be composed of multiple film layers, such as a surface layer, a coloring layer, a diffusion layer, a Fresnel lens layer, and a reflective layer.

[0092] The laser projection imaging device in the embodiments of the present application can project light onto a Fresnel projection screen. The light enters the screen through refraction from the surface layer and passes through the coloring layer, diffusion layer, and so on before reaching the Fresnel lens layer. A reflective layer is provided on the back of the Fresnel lens layer. The light is reflected by the reflective layer and emitted from the screen, ultimately being received by the human eye. It should be noted that in some embodiments, the coloring layer, diffusion layer, and other film layers may be flexibly provided according to certain requirements. That is, the coloring layer, diffusion layer, and other film layers may not be separate film layers, but may be provided in the same layer as other film layers. Therefore, in some embodiments, the order in which light passes may differ from this example. However, it should be understood that this is merely an illustrative description and should not be construed as an improper description.

[0093] FIG26 is a schematic diagram of an application scenario of a laser projection imaging device provided according to an embodiment of the present application, in which 2501 represents a forming device composed of all laser projection imaging devices in the above embodiment except for the receiving screen 2401. During use, the computer controller 2201 can output a specific control signal to the driving circuit 311 based on the image to be output. The driving circuit 311 controls the specific light-emitting unit in each light-emitting module 312 to emit a specific laser beam based on the control signal. The laser beam can be homogenized, diverged, shrunk, collimated, etc. by the action of the microlens array 32. The laser beam passing through the microlens array 32 enters the imaging lens 33. The imaging lens 33 can project an image based on the received light spot (i.e., the laser beam), for example, projecting the projection light onto the receiving screen 2401, so that the user can view the corresponding image.

[0094] As mentioned earlier, the laser light sources widely distributed on the market are mainly edge-emitting lasers. Due to the good monochromaticity of lasers, their coherence is strong. Scattered by the rough optical surfaces of the projection system and affected by the subtle irregularities of the screen surface, the light beam becomes highly coherent in time and space, generating a large number of interference fringes and speckle noise, which seriously affects the image quality and viewer experience. Moreover, when the optical density of the laser cavity surface reaches the threshold, it absorbs photons and generates heat, causing the band gap here to shrink, making it easier to absorb photons, and the heat generated increases. This repeats, causing "thermal runaway" and eventually burning the laser cavity surface, that is, optical catastrophic damage occurs.

[0095] Considering that the generation and severity of speckle in laser projection display are related to multiple links and factors, it can be roughly divided into two processes:

[0096] (1) The speckle generated by the laser projection display machine itself is mainly related to the following factors: (a) the coherence of the laser light source used; the better the coherence, the more severe the speckle; (b) the surface roughness and aperture size of each component in the optical machine system. Laser light is easily scattered when passing through a rough surface. During the laser propagation process, it will also be scattered when it encounters the surface of the component and dust in the air. The interference of the scattered sub-waves will produce speckle.

[0097] (2) The speckle generated by the display screen is related to the surface condition of the display screen. The speckle generated by the above process or link is generally called primary speckle. The human eye is equivalent to an optical system, including structures such as the cornea, lens, vitreous body and retina. These structures are also rough for the wavelength of light, so new speckles will form on the retina. These speckles are called secondary scattered speckles. Different laser wavelengths will produce different speckle patterns. When the wavelength increases, the observed speckle pattern will expand in spatial scale, and when the wavelength decreases, the speckle pattern will shrink. The degree of scaling of the speckle pattern in spatial scale depends on the change in distance from the point on the observation plane after the laser mirror reflection to the speckle pattern. This is because, on the one hand, the diffraction angle is proportional to the illumination wavelength, and on the other hand, the change in laser wavelength will cause a change in random phase shift. The causes and influencing factors of speckle are that the size of speckle is closely related to multiple factors such as laser wavelength, light source angle and screen roughness. The relationship between speckle and laser wavelength and screen clarity is:

[0098] in, represents the average wavelength of the illumination; δλ represents the wavelength range; and σ represents the standard deviation of the scattering surface (screen). This formula confirms that speckle is inversely proportional to the laser spectral width and the square root of the screen roughness. Different laser wavelengths produce independent, uncorrelated speckle patterns, thereby reducing speckle contrast. By varying the laser wavelength to generate independent, uncorrelated speckle patterns, the coherence of the laser light source can be reduced, resulting in independent, uncorrelated speckle patterns. Furthermore, a larger spectral width and a rougher scattering surface result in reduced speckle contrast.

[0099] Based on the above analysis, an embodiment of the present application also provides a laser chip. By preparing laser units that emit lasers of different central wavelengths on the laser chip, the coherence of the laser emitted by the laser chip is reduced, the speckle contrast of the projected image is reduced, and the image quality of the picture is improved. Figure 27 is a top view of a laser chip provided according to an embodiment of the present application; Figure 28 is a side view of a laser chip provided according to an embodiment of the present application; Figure 29 is a partial cross-sectional view of the first laser unit provided according to an embodiment of the present application. As shown in Figures 27, 28 and 29, the laser chip includes:

[0100] a semiconductor substrate 10;

[0101] The epitaxial layer 20 is located on one side of the semiconductor substrate 10. The epitaxial layer 20 includes an active layer 21. The active layer 21 includes quantum wells and quantum barriers.

[0102] a first electrode layer 30 , the first electrode layer 30 being located on a side of the epitaxial layer 20 away from the semiconductor substrate 10 ;

[0103] a second electrode layer 40 , the second electrode layer 40 being located on a side of the semiconductor substrate 10 away from the epitaxial layer 20 ;

[0104] The laser chip includes at least two laser units 100 arranged along the width direction X of the laser chip and emitting laser light of the same color. The at least two laser units 100 include at least one first laser unit 101 and at least one second laser unit 102. The central wavelengths of the laser light emitted by the first laser unit 101 and the second laser unit 102 are different. The active layer of the first laser unit 101 includes a first non-absorption window 1011 and a non-doped region 1012 arranged along the cavity length direction Y. The first non-absorption window 1011 is adjacent to the light exit surface of the first laser unit 101. The active layer of the second laser unit 102 is a quantum well hybrid active layer.

[0105] It should be noted that it is difficult for each laser unit 100 to emit a laser with only one wavelength. The laser emitted by the laser unit 100 contains light of multiple wavelengths in a wavelength range. The central wavelength of the laser emitted by the laser unit 100 is the median of the multiple wavelengths, or the average of the minimum wavelength and the maximum wavelength of the laser. For example, if the laser unit 100 emits a laser with a central wavelength of 642 nanometers, then the laser unit 100 may actually emit lasers of different wavelengths in the range of 641 nanometers to 643 nanometers. Lasers with the same central wavelength have strong coherence. Lasers with different central wavelengths will have certain differences in color. In the embodiment of the present application, lasers of the same color refer to lasers whose wavelengths are all within the wavelength range corresponding to the same color. In the related art, the central wavelengths of the lasers emitted by the laser chips used to emit the same color in the same laser are all the same, so the coherence of the lasers of this color is strong, resulting in more serious speckle in the projected image. In the embodiments of the present application, multiple laser units 100 are fabricated on the same laser chip, and the laser light emitted from the same color is divided into at least two different central wavelengths. This reduces the amount of laser light with the same central wavelength while ensuring that the laser light from each laser unit 100 has the same color. This reduces the coherence of the laser light, thereby reducing the speckle contrast of the projected image and improving the image quality. Furthermore, speckle is related to wavelength, with longer wavelengths resulting in greater speckle. Therefore, red laser light has the greatest impact on speckle, and accordingly, the laser chip can be a red laser chip. In some embodiments, the laser units in a red laser chip emit laser light with a central wavelength ranging from 625nm to 650nm, which can enhance the user's visual experience.

[0106] It should also be noted that the figure only illustrates a laser chip with two different central wavelengths as one possible implementation, but the embodiments of the present application are not limited thereto. In other embodiments, the laser chip can also emit laser light with two or more different central wavelengths. In the above embodiment, the undoped region 1012 refers to the active layer in the corresponding region that is not doped with a doping material. Accordingly, the central wavelength of the laser light emitted by each first laser unit 101 is the same. The active layer of the second laser unit 102 is a quantum well intercalation active layer, that is, the active layer of the second laser unit 102 is doped using quantum well intercalation technology. When the doping material is the same, the blue shift of the central wavelength varies when the doping concentration is different. Therefore, by controlling the doping concentration of different second laser units 102, the central wavelength of the laser light emitted by different second laser units 102 can also be different. In this way, the laser chip can emit laser light with two or more different central wavelengths. It can be understood that quantum well intercalation is a process in which atoms from the quantum well and their corresponding quantum barriers diffuse into each other, thereby changing the quantized energy state. See Figure 30, where (a) is the energy level diagram before quantum well intercalation, and (b) is the energy level diagram after quantum well intercalation. By comparison, it can be seen that after quantum well intercalation, the band gap width is significantly widened, where the band gap width refers to the energy difference between the lowest energy level of the conduction band and the highest energy level of the valence band (i.e., the minimum energy difference between the conduction band and the valence band) Eg. Refer to the following photon energy formula,

[0107] According to this formula, as the bandgap increases, the central wavelength of the laser decreases, i.e., the central wavelength blueshifts. Therefore, quantum well intercalation technology can achieve this change in the central wavelength of the laser. This method also avoids multiple epitaxial growths of the epitaxial layer, reduces process complexity, and significantly reduces costs and production time. Furthermore, quantum well intercalation technology can precisely control the amount of blueshift in the central wavelength of the laser, enabling the fabrication of laser chips with a variety of different central wavelengths.

[0108] Furthermore, the second laser unit 102, which has a quantum well hybrid active layer, has an increased bandgap in its active layer material, thereby increasing the optical catastrophic damage threshold. This prevents the output power of the second laser unit 102 from reaching the optical catastrophic damage threshold, thereby reducing the occurrence of optical catastrophic damage in the second laser unit 102. Accordingly, the second laser unit 102 can withstand a higher output power. Simultaneously, the bandgap of the first laser unit 101 at the first non-absorption window 1011 widens, shortening the corresponding wavelength. This wavelength does not match the wavelength output by the first laser unit 101, and consequently, the first non-absorption window 1011 does not absorb the wavelength emitted by the first laser unit 101. Consequently, heat is not generated at the light output surface of the first laser unit 101, reducing the occurrence of optical catastrophic damage in the first laser unit 101.

[0109] In some embodiments, the material of the quantum well is GaInP, and the material of the quantum barrier is AlGaInP.

[0110] In some embodiments, the material of semiconductor substrate 10 includes silicon, gallium arsenide, or gallium nitride. In other embodiments, the material of semiconductor substrate 10 can also be other semiconductor materials, which are not limited in this application. For example, semiconductor substrate 10 can be an N-type gallium arsenide substrate.

[0111] In some embodiments, as shown in FIG28 , the epitaxial layer 20 may further include a lower confinement layer 22, a lower waveguide layer 23, an upper waveguide layer 24, an upper confinement layer 25, and an ohmic contact layer 26. In this case, the lower confinement layer 22, the lower waveguide layer 23, the active layer 21, the upper waveguide layer 24, the upper confinement layer 25, and the ohmic contact layer 26 are stacked in sequence. Accordingly, when preparing the epitaxial layer, the lower confinement layer 22, the lower waveguide layer 23, the active layer 21, the upper waveguide layer 24, the upper confinement layer 25, and the ohmic contact layer 26 may be sequentially deposited on the semiconductor substrate 10 using metal organic chemical vapor deposition (MOCVD). The lower confinement layer 22 and the upper confinement layer 25 are used to improve the carrier confinement capability of the semiconductor laser, thereby increasing carrier utilization. The lower waveguide layer 23 and the upper waveguide layer 24 are used to reduce the waveguide to expand the light spot and reduce the vertical divergence angle of the light beam. The materials and thicknesses of the lower confinement layer 22 , the lower waveguide layer 23 , the active layer 21 , the upper waveguide layer 24 , the upper confinement layer 25 and the ohmic contact layer 26 may be set according to actual requirements.

[0112] In some embodiments, the first electrode layer 30 may be a p-type ohmic contact electrode.

[0113] In some embodiments, Ti / Pt / Au can be sputtered on the surface of the ohmic contact layer 26 using magnetron sputtering equipment to improve ohmic contact conditions, and then annealed to form a p-type ohmic contact electrode. The second electrode layer 40 can be an n-type contact electrode.

[0114] FIG31 exemplarily shows a process for preparing the laser chip provided in an embodiment of the present application, as shown in FIG31 , including the following steps:

[0115] S110 , providing an epitaxial wafer including a semiconductor substrate and an epitaxial layer.

[0116] In some embodiments, the lasing wavelength of the epitaxial wafer may be 642 nanometers.

[0117] S120 , depositing a dielectric film on the surface of the epitaxial layer in a first non-absorption window region corresponding to the first laser unit and in a region corresponding to the second laser unit.

[0118] The laser chip includes at least two laser units arranged along the width direction of the laser chip and emitting laser light of the same color. The at least two laser units include at least one first laser unit and at least one second laser unit. The central wavelengths of the laser light emitted by the first laser unit and the second laser unit are different.

[0119] In this step, a dielectric film is deposited to form a shielding area, so that in the subsequent steps, the bandgap width of the active layer material corresponding to the non-shielding area changes, while the bandgap width of the active layer material corresponding to the shielding area remains unchanged, and the lasing wavelength of the corresponding laser unit remains unchanged, such as 642 nanometers mentioned above.

[0120] For implementation, refer to FIG32 . First, a photoresist is applied to the entire surface of the epitaxial layer (positive photoresist is used in the figure). The photoresist is exposed using the mask shown in FIG33 (the mask structure when using negative photoresist is complementary to the mask structure). Then, a developer is used to remove the exposed portion of the photoresist, leaving only the photoresist in the non-doped area of ​​the first laser unit. Then, a dielectric film (such as SiO2) is deposited on the entire surface using methods such as chemical vapor deposition (CVD) or physical vapor deposition (PVD). x 、Si x N y 、SiO x N y etc.), depositing a thickness of 100 to 200 nm; finally, immersing the epitaxial wafer with the dielectric film deposited on its entire surface in a photoresist stripping solution or a chemical stripper such as acetone, and heating it in an ultrasonic cleaner at 60 to 80° C. for 10 to 20 minutes to remove the photoresist and the dielectric film attached to the surface of the photoresist, thereby depositing a dielectric film in a first non-absorption window area corresponding to the first laser unit and in an area corresponding to the second laser unit on the surface of the epitaxial layer.

[0121] S130 , forming a first non-absorption window of the first laser unit and a quantum well hybrid active layer of the second laser unit.

[0122] In some embodiments, the product obtained in S120 and the diffusion source Zn3As2 or ZnO are placed in a quartz tube, fixed on both sides and evacuated to a high vacuum (<2*10 -3 The method comprises the following steps: first, preparing the sample by sealing the sample after being sintered in a diffusion furnace, an annealing furnace, or a vertical furnace; and finally, controlling the diffusion temperature at 400 to 650°C and the diffusion time at 5 to 60 minutes to determine the depth of Zn impurities diffused into the active layer; and finally, performing a wet etching process using hydrofluoric acid (HF), phosphoric acid (H3PO4), or other solutions to clean the dielectric film deposited on the sample surface. The sample is then annealed to eliminate defects such as lattice defects, impurities, and stress introduced during the preparation process, thereby improving the stability and reliability of the prepared laser chip.

[0123] The diffusion of Zn impurities will produce a large number of defects. Under the action of the defects, the Al atoms and Ga atoms in the quantum well and quantum barrier materials in the active area will be induced to diffuse with each other, thereby changing the band gap width of the area, thereby realizing the change of the laser output wavelength; while the part without Zn impurity diffusion has no change in its lasing wavelength.

[0124] Furthermore, by manipulating variables such as the type of impurity introduced (different materials, using Zn as an example in this application), its concentration, diffusion temperature, and diffusion time, the bandgap and lasing wavelength can be precisely controlled, thereby achieving a blue shift in wavelength. Theoretical calculations show that for the GaInP / AlGaInP material system, the wavelength blue shift is 0.8 to 82 nm.

[0125] S140 , forming a first electrode layer on a side of the epitaxial layer away from the semiconductor substrate.

[0126] S150 , forming a second electrode layer on a side of the semiconductor substrate away from the epitaxial layer.

[0127] In some embodiments, laser units emitting different central wavelengths may be periodically arranged along the width direction of the laser chip. For example, the laser chip includes a first laser unit and a second laser unit emitting two central wavelengths, and the first laser unit and the second laser unit are arranged alternately in the width direction of the laser chip. In this way, the phase distribution of the laser beam can be made more uniform, thereby reducing the appearance of dissipation speckle, and making the brightness of the display more uniform, reducing problems such as color difference. At the same time, the interlaced arrangement can also improve the reliability of the laser display device, because if a problem occurs with a laser unit of a certain wavelength, the laser units of other wavelengths can still work normally, thereby ensuring the stability and reliability of the device.

[0128] The laser chip provided in the embodiments of the present application utilizes at least two laser units capable of emitting laser light of the same color, formed on a single laser chip. The first and second laser units emit laser light of different central wavelengths. This allows the same laser chip to emit laser light of different central wavelengths, effectively reducing the coherence between the beams, thereby lowering the speckle contrast of the projected image and improving image quality. Quantum well intercalation technology is employed to dope the active layer of at least one laser unit, forming a second laser unit having a quantum well intercalation active layer. This increases the bandgap of the active layer material of the second laser unit, thereby altering the central wavelength of the laser light emitted therefrom. This increased bandgap improves the optical catastrophic damage threshold, thereby reducing the occurrence of optical catastrophic damage in the second laser unit. Moreover, for at least one laser unit that has not been doped throughout the active layer, a non-absorption window is formed on its light-exit cavity surface to obtain a first laser unit. Thus, without changing the central wavelength of the laser, the band gap of the active layer at the light-exit cavity surface is increased by using the non-absorption window, so that the band gap of the active layer at the light-exit cavity surface is greater than the energy of the laser photons, thereby reducing the light absorption at the cavity surface and reducing the occurrence of optical catastrophic damage to the first laser unit. In this way, the above process can not only reduce the coherence of the laser chip and improve the image quality, but also reduce the occurrence of optical catastrophic damage to the laser chip. In addition, in the related art, a single laser chip is cleaved from a bar array. The cleavage equipment is expensive and impurities are introduced during the cleavage process, causing the laser chip to be oxidized and damaged, affecting reliability.

[0129] This application prepares multiple laser units on the same laser chip, which can be obtained directly using bar strips, thus avoiding the use of cleavage equipment and reducing costs. In addition, because the bar strip has multiple light-emitting points (laser units), it is smaller in size compared to a multi-chip laser. For the same volume, it contains more laser units, making it easier to achieve high-power output of the laser. Similarly, to achieve the same output power as a multi-chip laser, the volume of the bar strip array will be smaller, which is more conducive to miniaturized packaging.

[0130] In some embodiments, the first non-absorption window and the active layer of the second laser unit have the same doping material and doping concentration.

[0131] In some embodiments, the laser chip may include a second laser unit that emits laser light of the same central wavelength, and the laser chip may also include multiple second laser units that emit laser light of different central wavelengths. When the doping materials and doping concentrations of the active layers of the first non-absorption window and the second laser unit are the same, the quantum well hybrid active layers of the first non-absorption window and the second laser unit can be prepared using the same process, that is, the preparation of the quantum well hybrid active layers of the first non-absorption window and the second laser unit can be achieved simultaneously, thereby saving process flow and reducing process costs.

[0132] In some embodiments, the width of the first non-absorption window along the cavity length direction is 30 microns to 70 microns.

[0133] In some embodiments, the inventors have found that when the width of the first non-absorbing window along the cavity length is less than 30 microns, the non-absorbing window is ineffective, effectively mitigating catastrophic optical damage. However, when the width of the first non-absorbing window along the cavity length is greater than 70 microns, the effective cavity length of the laser is reduced, impacting the laser's output performance (primarily output power and efficiency). Therefore, a first non-absorbing window width along the cavity length of 30 to 70 microns can effectively reduce catastrophic optical damage while maintaining laser output performance.

[0134] In some embodiments, the active layer of the first laser unit further includes a second non-absorption window, the non-doped region is located between the first non-absorption window and the second non-absorption window, and the second non-absorption window is adjacent to the non-light-exiting cavity surface of the first laser unit.

[0135] In some embodiments, the cavity surfaces at both ends of the laser unit can actually emit light. In order to meet product requirements and improve output performance, only one of the cavity surfaces needs to emit light, namely the light-emitting cavity surface, and the other cavity surface is the non-light-emitting cavity surface. In actual products, both ends of the laser unit need to be evaporated with a cavity mask. A high-reflection film will be evaporated on one of the cavity surfaces so that the cavity surface does not emit light, namely the non-light-emitting cavity surface; and an anti-reflection film will be evaporated on the other cavity surface, namely the light-emitting cavity surface. Considering that if the first non-absorption window is formed only on the light-emitting cavity surface, it is necessary to distinguish which is the light-emitting cavity surface and which is the non-light-emitting cavity surface when evaporating the cavity mask, which requires the front and back order of the laser chip to be correct after cleavage. However, once the order is reversed, the high-reflection film will be evaporated on the cavity surface with the first non-absorption window, resulting in the cavity surface that actually emits light having no non-absorption window, which in turn causes the corresponding first laser unit to suffer from optical catastrophic damage. To this end, the embodiment of the present application forms non-absorption windows on both cavity surfaces, that is, as shown in Figure 34, a first non-absorption window 1011 is formed on the light-output cavity surface, and a second non-absorption window 1013 is formed on the non-light-output cavity surface, so that there is no need to distinguish between the two cavity surfaces when evaporating the cavity mask, which can effectively prevent the problem of optical catastrophic damage to the first laser unit.

[0136] In some embodiments, the laser units are configured to emit red laser light, wherein the difference between adjacent center wavelengths of the red laser light emitted by each laser unit is 4 nanometers to 5 nanometers.

[0137] The inventors have discovered that when the difference between adjacent center wavelengths is less than 4 nanometers, the coherence between the corresponding lasers is strong, but the speckle problem remains severe. When the difference between adjacent center wavelengths is greater than 5 nanometers, the difficulty of growing red laser materials increases significantly, and the shorter-wavelength active layer material has a higher band gap, which makes carriers more likely to leak, affecting the laser's output efficiency. Therefore, in this embodiment of the present application, for red lasers, the difference between adjacent center wavelengths is set to 4 to 5 nanometers, effectively reducing speckle and making it easier to grow red laser materials, thereby ensuring laser output efficiency.

[0138] In some embodiments, the laser chip further includes at least one electrode welding portion, which is located on at least one of the side surfaces and the non-light-exiting cavity surface of the laser chip, and the first electrode layer is electrically connected to the electrode welding portion.

[0139] In some embodiments, the side refers to the side of the laser chip adjacent to the light-emitting cavity surface or the non-light-emitting cavity surface. As shown in Figure 35, the electrode welding portion 50 is located on the side of the laser chip, or as shown in Figure 36, the electrode welding portion 50 is located on the non-light-emitting cavity surface of the laser chip, or the side and non-light-emitting cavity surface of the laser chip are both provided with electrode welding portions 50. In this way, by providing the electrode welding portion 50 on the side and / or non-light-emitting cavity surface of the laser chip, the first electrode layer can be welded to the electrode welding portion 50 by gold wire, which can avoid the welding stress and laser chip damage caused by welding the gold wire to the light-emitting cavity surface, greatly improving the reliability of the laser chip during welding and improving the yield rate of the finished product. This embodiment does not limit the shape of the electrode welding portion 50, which can specifically be a triangle, a quadrilateral, a semicircle, a semi-ellipse or a polygon.

[0140] In some embodiments, the first electrode layer includes multiple independent first electrode blocks, and the first electrode blocks are arranged in a one-to-one correspondence with the laser units. The first electrode blocks of the laser units that emit lasers with the same central wavelength are electrically connected to the same electrode welding portion, and the first electrode blocks of the laser units that emit lasers with different central wavelengths are electrically connected to different electrode welding portions.

[0141] Since the characteristics of laser units of different wavelengths are different, when the same current is injected, the output power of each laser unit will be different, resulting in uneven light emission. In order to make the output power of each laser unit the same, the embodiment of the present application divides the first electrode layer into independent first electrode blocks, each electrode block is correspondingly arranged in a laser unit, so that each laser unit can be driven separately, and then the first electrode blocks of laser units with the same lasing wavelength are electrically connected to the same electrode welding part, and the first electrode blocks of laser units with different lasing wavelengths are electrically connected to different electrode welding parts. In this way, laser units with different lasing wavelengths can be driven separately, that is, laser units with different lasing wavelengths can be injected with different currents, so that the output power of each laser unit is the same, thereby improving the light emission uniformity of the laser chip. As shown in FIG37 , the laser chip includes multiple first laser units 101 and multiple second laser units 102. The first laser units 101 emit laser light having a first central wavelength, while the second laser units emit laser light having a second central wavelength. The first central wavelength and the second central wavelength are different. The electrode welding portion includes independent first electrode welding portions 51 and second electrode welding portions 52. The first electrode block of each first laser unit 101 is electrically connected to the first electrode welding portion 51, and the first electrode block of each second laser unit 102 is electrically connected to the second electrode welding portion 52. In this manner, all first laser units 101 can be driven by the first driving unit, and all second laser units 102 can be driven by the second driving unit, thereby ensuring that the output power of each first laser unit 101 and each second laser unit 102 is the same.

[0142] It should be noted that the laser chip provided in the embodiments of the present application can replace the light-emitting chip in the aforementioned light-emitting unit to provide a light source for the aforementioned light source chip. Furthermore, the laser chip provided in the embodiments of the present application can be used to manufacture a laser light source adapted for use in a conventional laser projection imaging device. For example, the manufactured laser light source can be used as light source 10 in the conventional laser projection imaging device shown in FIG1 , thereby reducing the speckle that may appear in the laser projection image and the optical catastrophic damage to the laser.

[0143] The laser light source made by the laser chip of the present application may include: a base plate, a tube wall, at least one laser chip provided by an embodiment of the present application, and a collimating lens group; the tube wall and at least one laser chip are both located on the base plate, and the tube wall is arranged around the laser chip, and the collimating lens group is used to collimate the laser emitted by each laser unit in at least one laser chip.

[0144] As shown in Figures 38 and 39, the laser light source can be a top-emitting laser light source, comprising: a base plate 1, a tube wall 2, at least one laser chip 3, at least one reflective prism 4, a heat sink 5, a transparent sealing glass 6, and a collimating lens assembly 7. The laser chip 3 is welded to the heat sink 5, the tube wall 2, the laser chip 3, and the reflective prism 4 are all fixed to the base plate 1, the laser chip 3 and the reflective prism 4 are surrounded by the tube wall 2, the transparent sealing glass 6 is sealed to the tube wall 2, and the collimating lens assembly 7 covers the transparent sealing glass 6. Laser light emitted by the laser chip 3 is reflected away from the base plate 1 by the reflective prism. The reflected laser light is then emitted perpendicularly to the base plate 1 by the collimating lens assembly 7. In this embodiment, the base plate 1 and tube wall 2 form a tube housing, which can be made of metal or ceramic. The collimating lens assembly 7 can include multiple collimating lenses, each corresponding to a laser unit, to collimate the laser light emitted by each laser unit.

[0145] In some embodiments, the laser light source further includes at least one reflective prism, which is disposed in a one-to-one correspondence with the laser chip, and is used to reflect the laser light emitted by the laser unit to the collimator lens group. Thus, by preparing multiple laser units with different lasing wavelengths on the same laser chip to form a laser array, a single laser chip can be used to replace multiple laser chips arranged side by side in the related art. Furthermore, the placement accuracy of each laser unit on the same laser chip is the same. Therefore, there is no need to provide a reflective prism for each laser unit. A single reflective prism can be used to reflect the laser light emitted by each laser unit on a laser chip to the collimator lens group without deviation.

[0146] As shown in FIG40 , the laser light source provided in the embodiment of the present application can also be a side-emitting laser light source, which does not require a reflective prism. It may include: a base plate 1, a tube wall 2, at least one laser chip 3, a heat sink 5, a collimating lens group 7, and a sealing cover 8. The laser chip 3 is welded to the heat sink 5, the tube wall 2 and the laser chip 3 are both fixed to the base plate 1, and the tube wall 2 is made of a transparent material. The laser chip 3 is surrounded by the tube wall 2, the sealing cover 8 is sealed to the tube wall 2, and the collimating lens group 7 is located on one side of the tube wall 2. The laser light emitted by the laser chip 3 directly passes through the tube wall 2 and is emitted parallel to the base plate 1 through the collimating lens group 7.

Claims

1. A laser projection imaging device, comprising: Light source chip, including driving circuit and light-emitting module; The light-emitting module comprises a plurality of light-emitting units made of straight-cavity surface-emitting lasers; the light-emitting units comprise a first light-emitting unit for emitting red laser light, a second light-emitting unit for emitting green laser light, and a third light-emitting unit for emitting blue laser light; The driving circuit is electrically connected to the light emitting unit and is configured to: receive driving information of an image signal; The driving information includes a target operating current representing the display brightness of the video signal, a target adjustment pulse width representing the display grayscale of the video signal, and a light-emitting module corresponding to the video signal; driving the light-emitting module corresponding to the video signal according to the target working current and the modulated pulse width, so that the light source chip emits a target image; A microlens array, located on the light-emitting side of the light source chip, is configured to: homogenize the light spot of the light-emitting module; The imaging lens is located on a side of the microlens array away from the light source chip along the light beam propagation direction, and is configured to receive the light beam after passing through the microlens array and project the light beam into an image.

2. The laser projection imaging device according to claim 1, wherein: The drive circuit array arrangement; The driving circuit is a first driving circuit with a single output, each first driving circuit corresponds to a unique light-emitting unit and is electrically connected to the corresponding light-emitting unit, and the first driving circuit is configured to drive the corresponding light-emitting unit; and / or, The driving circuit is a second driving circuit with multiple outputs, each second driving circuit corresponds to a unique light-emitting module, the output end of any second driving circuit is connected to the first light-emitting unit, the second light-emitting unit and the third light-emitting unit in the light-emitting module corresponding to the second driving circuit, and the second driving circuit is configured to drive the corresponding light-emitting module.

3. The laser projection imaging device according to claim 1, wherein: Any light-emitting module includes four light-emitting units, and the four light-emitting units are arranged in a 2×2 array.

4. The laser projection imaging device according to claim 3, wherein: The four light emitting units include two first light emitting units, one second light emitting unit, and one third light emitting unit; or, one first light emitting unit, two second light emitting units, and one third light emitting unit; or, one first light emitting unit, one second light emitting unit, and two third light emitting units.

5. The laser projection imaging device according to claim 3, wherein: The light emitting units in the array are arranged along a first direction and a second direction respectively; the first direction intersects the second direction; The light emitting units arranged in the first direction have different colors of emitted laser light; And / or, the light emitting units arranged in the second direction have different colors of emitted lasers.

6. The laser projection imaging device according to claim 1, wherein: The light emitting unit satisfies the following settings: The first light-emitting unit includes a first light-emitting chip based on a gallium arsenide substrate, the laser wavelength of the first light-emitting chip is within 630 nanometers to 650 nanometers; the laser wavelengths emitted by different first light-emitting chips are arranged at equal intervals; and / or, The second light-emitting unit includes a second light-emitting chip based on a gallium nitride substrate, the laser wavelength of the second light-emitting chip is within 515 nanometers to 540 nanometers; the laser wavelengths emitted by different second light-emitting chips are arranged at equal intervals; and / or, The third light-emitting unit includes a third light-emitting chip based on a gallium nitride substrate, and the laser wavelength of the third light-emitting chip is within a range of 440 nanometers to 480 nanometers; the laser wavelengths emitted by different third light-emitting chips are arranged at equal intervals.

7. The laser projection imaging device according to claim 6, wherein: The interval range of the laser wavelength is 3 to 5 nanometers.

8. The laser projection imaging device according to claim 1, wherein: The microlens array includes microlenses arranged in an array, and the microlenses are arranged in a one-to-one correspondence with the light-emitting units in the light-emitting module; The microlens is configured to homogenize the light beam emitted by the corresponding light emitting unit.

9. The laser projection imaging device according to claim 8, wherein: The microlens is made of at least one of sapphire, glass and resin.

10. The laser projection imaging device according to claim 8, wherein: There is a preset distance between the microlens array and the imaging lens; The microlens array is further configured to: adjust the divergence angle of the light beam emitted by the corresponding light emitting unit so that the homogenized light beam does not change the distribution of the target image; The light beam passing through the microlens array is irradiated onto the light receiving surface of the imaging lens.

11. The laser projection imaging device according to claim 8, wherein: The microlens array adjusts the divergence angle of the light beam emitted by the corresponding light emitting unit, and is specifically configured as follows: Determine the divergence angle of the light beam emitted by the corresponding light emitting unit; If the divergence angle is less than a first angle threshold, the light beam is expanded so that the divergence angle of the expanded light beam is between the first angle threshold and a second angle threshold; the second angle threshold is greater than the first angle threshold; If the divergence angle of the light beam is greater than the second angle threshold, the light speed is shrunk so that the divergence angle of the shrunk light beam is between the first angle threshold and the second angle threshold.

12. The laser projection imaging device according to claim 11, wherein: The first angle threshold is 10 degrees, and the second angle threshold is 12 degrees.

13. The laser projection imaging device according to any one of claims 1 to 12, further comprising: The base substrate, the driving circuit is integrated and arranged on one side of the base substrate, and the light-emitting module is located on a side of the driving circuit away from the base substrate.

14. The laser projection imaging device according to claim 13, wherein: The substrate is made of at least one of glass, silicon and sapphire.

15. The laser projection imaging device according to claim 13, wherein: The light emitting unit is integrated onto the substrate by mass transfer or micro-pipe technology.

16. The laser projection imaging device according to claim 13, wherein: Electrodes are also integrated on the substrate, and the electrodes are configured to drive the driving circuit.

17. The laser projection imaging device according to any one of claims 1 to 12, further comprising: An optical element, located between the light source chip and the imaging lens along the light beam propagation direction, and arranged in one-to-one correspondence with the light-emitting units; The optical element is configured to reduce imaging speckle.

18. The laser projection imaging device according to claim 17, wherein: The optical element includes at least one of a wave plate, a compound eye and a diffractive optical element.

19. The laser projection imaging device according to any one of claims 1 to 12, further comprising: A computer controller connected to the driving circuit; The computer controller is configured to: transmit driving information of an image signal to the driving circuit for an image to be projected; and / or, The receiving screen is located at the light emitting side of the imaging lens and is configured to receive the light emitted by the imaging lens to display the projection image of the target image.

20. The laser projection imaging device according to claim 19, wherein: The receiving screen is composed of a plurality of film layers, which include a surface layer, a coloring layer, a diffusion layer, a lens layer and a reflection layer.

Images