Silicon carbide substrate-based metasurface grating waveguide and augmented display system

Abstract

The application discloses a super surface grating waveguide based on a silicon carbide substrate and an enhanced display system, and belongs to the technical field of optoelectronic device manufacturing, and the technical scheme is characterized by comprising a tunable light source, a spatial light modulator, a super surface grating waveguide, an imaging device and a processing device, the spatial light modulator is used for receiving light emitted by the tunable light source, modulating the phase distribution of the light, and obtaining a light beam carrying image information; the processing device is used for adjusting the wavelength of the light emitted by the tunable light source and the length of an optical resonant cavity according to the current temperature, the optical resonant cavity is located in the tunable light source; the super surface grating waveguide comprises a silicon carbide substrate and is used for conducting the light beam emitted by a focusing lens to a pupil expander, so that the pupil expander outputs image information to a human eye, and the application can avoid mode jumping and solve the problem of uneven final imaging brightness by adjusting the length of an external cavity first, aligning the gain peak corresponding to the target wavelength of the longitudinal mode frequency, and then adjusting the current to make the wavelength reach the target wavelength.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic device manufacturing technology, and more specifically to a metasurface grating waveguide and enhanced display system based on a silicon carbide substrate. Background Technology

[0002] In the AR imaging technology system, optical waveguide technology, with its thin and light-sensitive characteristics and high light transmittance, precisely matches the miniaturization and lightweight trend of optoelectronic device manufacturing for consumer-grade AR glasses, becoming a core key optical solution. During the operation of AR glasses, the waveguide component manufactured by optoelectronic devices couples light into the substrate through precise optical path design, and completes the efficient transmission of light signals by means of the "total internal reflection" principle, ultimately releasing the light in front of the eye to achieve imaging. This process relies entirely on the high-precision manufacturing process of optoelectronic devices.

[0003] Among them, silicon carbide waveguides have emerged in the field of optoelectronic device manufacturing due to the ultra-high refractive index of silicon carbide material. Precise control of the material's refractive index in optoelectronic device manufacturing allows the full potential of silicon carbide to be realized. Compared to the complex solution in traditional optoelectronic device manufacturing that requires multiple layers of high-refractive-index glass to achieve full-color display, silicon carbide waveguides only require a single-layer structure to complete the task of wide-field-of-view full-color display. This not only simplifies the optoelectronic device manufacturing process but also significantly reduces lens weight, significantly optimizing the integration effect of optoelectronic devices in consumer-grade AR glasses.

[0004] However, due to technical bottlenecks in current optoelectronic device manufacturing processes, such as structural precision control and film deposition uniformity, images output through silicon carbide waveguides are prone to poor brightness uniformity. This also means that existing AR imaging technologies based on silicon carbide waveguides still have shortcomings in practical applications of optoelectronic device manufacturing. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a metasurface grating waveguide and enhanced display system based on a silicon carbide substrate, which solves the problem of uneven brightness in the final image by adjusting the external cavity length and wavelength, thereby avoiding mode jumps.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides an enhanced display system, comprising: a tunable light source, a spatial light modulator, a metasurface grating waveguide, an imaging device, and a processing device;

[0008] The spatial light modulator is used to receive light emitted by the tunable light source and modulate the phase distribution of the light emitted by the tunable light source to obtain a light beam carrying image information.

[0009] The processing device is used to adjust the wavelength of the light emitted by the tunable light source and the length of the optical resonant cavity according to the current temperature, wherein the optical resonant cavity is located in the tunable light source.

[0010] As a further improvement of the present invention, the processing device includes a wavelength adjustment unit, a cavity length adjustment unit, and a control unit;

[0011] The wavelength adjustment unit is used to obtain the target wavelength based on temperature and Bragg conditions;

[0012] The cavity length adjustment unit is used to obtain an updated cavity length value based on the target wavelength;

[0013] The control unit is used to first adjust the length of the optical resonant cavity according to the cavity length update value, and then adjust the wavelength of the light emitted by the tunable light source according to the target wavelength.

[0014] As a further improvement of the present invention, the wavelength adjustment unit includes a thermal expansion module, a thermo-optic module, and a matching module;

[0015] The thermal expansion module is used to obtain the period adjustment value of the grating based on the temperature and the coefficient of thermal expansion, and the grating is located in the metasurface grating waveguide;

[0016] The thermo-optic module is used to obtain the refractive index adjustment value of the grating based on the temperature and the thermo-optic coefficient;

[0017] The matching module is used to substitute the period adjustment value and the refractive index adjustment value into the Bragg condition to obtain the target wavelength.

[0018] As a further improvement of the present invention, the cavity length adjustment unit includes an adjustment module and a correction module;

[0019] The adjustment module is used to obtain a corrected cavity length value based on the target wavelength, the current wavelength, and the current cavity length value.

[0020] The correction module is used to obtain the cavity length update value based on the correction factor, the delay factor and the correction cavity length value, wherein the delay factor is determined according to the material of the grating and the correction factor is obtained according to the resonance condition.

[0021] As a further improvement of the present invention, the processing device further includes an image adjustment unit and a transmission unit, wherein the image adjustment unit includes an enhancement module and a correction module;

[0022] The enhancement module is used to adjust the contrast of the image to be displayed according to the fractal dimension of the image to be displayed, so as to obtain a first image;

[0023] The correction module is used to perform color calibration on the first image based on the pixel value of each pixel in the first image to obtain the second image;

[0024] The transmission unit is used to convert the second image into an electrical signal so that the spatial light modulator modulates the phase distribution of the light according to the electrical signal.

[0025] As a further improvement of the present invention, the enhancement module includes a calculation submodule and an adjustment submodule;

[0026] The calculation submodule is used to divide the image to be displayed into multiple sub-images and calculate the fractal dimension of each sub-image based on the box dimension.

[0027] The adjustment submodule is used to obtain adjustment coefficients based on the fractal dimension and the reference fractal dimension, obtain an iterative transformation function based on the adjustment coefficients, and adjust the contrast of the image to be displayed based on the iterative transformation function to obtain a first image.

[0028] As a further improvement of the present invention, the calculation submodule includes a counting function block and a fitting function block;

[0029] The counting function block is used to cover each sub-image with multiple preset grids and count the number of pixels in each preset grid whose pixel value is greater than a preset threshold.

[0030] The fitting function block is used to obtain a fitting equation based on the size and quantity of the preset grid, and to obtain the fractal dimension of each sub-image based on the fitting equation.

[0031] As a further improvement of the present invention, the correction module includes a first sub-module and a second sub-module;

[0032] The first submodule is used to obtain the correction coefficient based on the mean value of each channel in the first image;

[0033] The second submodule is used to obtain the second image based on the correction coefficient.

[0034] As a further improvement of the present invention, the imaging device includes a focusing lens and a pupil expander;

[0035] The focusing lens is located between the spatial light modulator and the metasurface grating waveguide. The focusing lens is used to convert the light beam output by the spatial light modulator into parallel light and then incident it onto the metasurface grating waveguide.

[0036] The pupil expander is used to replicate the light beam emitted from the metasurface grating waveguide into multiple exit pupils.

[0037] This invention provides a metasurface grating waveguide based on a silicon carbide substrate, applied to the aforementioned enhanced display system. The metasurface grating waveguide includes a silicon carbide substrate and is used to conduct the light beam incident from the focusing lens to a pupil expander, so that the pupil expander outputs image information to the human eye.

[0038] This invention addresses the problem of uneven brightness caused by temperature changes by adjusting the wavelength. Furthermore, before adjusting the wavelength, the target wavelength is used as a pre-tuning parameter for the mode jump suppression scheme to update the cavity length, aligning the longitudinal mode frequency with the gain peak corresponding to the target wavelength. This approach can solve the problem of uneven brightness in the final image while avoiding mode jumps. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the enhanced display system in this invention;

[0040] Figure 2 This is a schematic diagram of a metasurface grating structure;

[0041] Figure 3 This is a schematic diagram of the processing device;

[0042] Figure 4 This is a schematic diagram of the wavelength adjustment unit and the cavity length adjustment unit;

[0043] Figure 5 This is a schematic diagram of the image adjustment unit.

[0044] Figure 6 This is a schematic diagram showing the positions of the grid and sub-images. Detailed Implementation

[0045] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof.

[0046] Identical parts are indicated by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, while the terms "bottom surface," "top surface," "inner," and "outer" refer to directions toward or away from the geometric center of a specific part, respectively.

[0047] The term "and / or" in the following text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0048] like Figure 1 As shown, this application provides an enhanced display system, including: a tunable light source, a spatial light modulator, a metasurface grating waveguide, an imaging device, and a processing device;

[0049] A spatial light modulator is used to receive light emitted from a tunable light source and modulate the phase distribution of the light emitted from the tunable light source to obtain a beam carrying image information.

[0050] The processing device is used to adjust the wavelength of the light emitted by the tunable light source and the length of the optical resonant cavity, which is located in the tunable light source, according to the current temperature.

[0051] Among them, such as Figure 2 As shown, the metasurface grating waveguide includes a silicon carbide substrate, a waveguide layer, and a grating. The metasurface grating waveguide is used to conduct the light beam incident from the focusing lens to the pupil expander, so that the pupil expander outputs image information to the human eye. The imaging device includes a focusing lens and a pupil expander. The focusing lens is located between the spatial light modulator and the metasurface grating waveguide. The focusing lens is used to convert the light beam output from the spatial light modulator into parallel light and then incident it onto the metasurface grating waveguide. The pupil expander is used to replicate the light beam emitted from the metasurface grating waveguide into multiple exit pupils.

[0052] For example, the specific working principle of the enhanced display system is as follows: First, the processing device obtains the current temperature of the metasurface grating waveguide based on the temperature sensor, and calculates the updated values ​​of the target wavelength and the cavity length of the optical resonant cavity based on the temperature. The temperature sensor is located near the metasurface grating waveguide to obtain accurate real-time temperature values.

[0053] The processing device then sends signals to the current source and the piezoelectric ceramic element respectively. The signal received by the current source causes it to inject current into the tunable light source, thereby adjusting the wavelength. The signal received by the piezoelectric ceramic element causes it to deform, thereby adjusting the cavity length (length of the optical resonant cavity). Specifically, a tunable light source is a light source whose output wavelength (or frequency) can be dynamically adjusted within a certain range. It can be a fiber grating tunable laser or a tunable semiconductor laser. The tunable light source mainly includes a gain medium, an optical resonant cavity, and electrodes. The current source is connected to the electrodes to inject current. The piezoelectric ceramic element is connected to a mirror of the optical resonant cavity. When the piezoelectric ceramic element deforms due to the voltage signal, its deformation pushes the mirror to move, thereby changing the cavity length.

[0054] Then, light of the corresponding wavelength is emitted by the tunable light source and incident on the spatial light modulator, thereby loading image information onto the monochromatic light or laser emitted by the tunable light source. The image information is specifically an electrical signal converted from image data output by the processing device. The electrical signal acts on the pixel array in the spatial light modulator, so that the pixel array applies different phase delays to different positions of the incident light, thereby achieving the purpose of loading image information.

[0055] Next, the beam output from the spatial light modulator is converted into parallel light by a focusing lens and then incident on the metasurface grating waveguide to avoid divergence loss. The beam then undergoes multiple total internal reflections in the metasurface grating waveguide in the form of a guided mode, avoiding the energy loss of traditional prisms or multilayer film structures. Finally, the pupil expander replicates the beam emitted from the metasurface grating waveguide into multiple exit pupils to expand the observation range of the human eye and ensure that a complete image can be received from different viewing angles.

[0056] In the fabrication of silicon carbide waveguides, high-quality silicon carbide material can be used. Through methods such as chemical vapor deposition (CVD), the crystal growth of the substrate can be precisely controlled to ensure good optical uniformity and stability. The substrate surface is then finely polished to reduce surface roughness and minimize light scattering loss. Next, a metasurface grating structure with a specific period, shape, and depth is fabricated on the silicon carbide substrate surface using micro-nano fabrication techniques such as photolithography and etching. Finally, one or more layers of waveguide material are deposited on top of the metasurface grating using physical vapor deposition (PVD) or other suitable methods to form an integrated optical guide structure with the silicon carbide substrate and the metasurface grating. This embodiment applies silicon carbide substrates to the design of metasurface grating waveguides, utilizing the excellent optical, thermal, and mechanical properties of silicon carbide to improve the stability and light transmission efficiency of the optical guide structure, solving the problem of performance degradation of traditional substrates in complex environments. Furthermore, its unique crystal structure and high thermal conductivity can effectively reduce optical loss and improve the reliability and durability of the system.

[0057] This embodiment first pre-aligns the longitudinal mode with the gain peak. That is, by adjusting the cavity length in advance, the longitudinal mode corresponding to the target wavelength becomes the only mode that matches the gain peak. This avoids the longitudinal mode jumping across the interval between adjacent longitudinal modes during the tuning process. After that, the current only needs to be finely adjusted near the pre-aligned longitudinal mode. At this time, the tuning amount is much smaller than the longitudinal mode interval, thereby avoiding mode jumping while solving the problem of uneven brightness in the final image.

[0058] Among them, the longitudinal mode refers to the stable optical wave oscillation mode along the axis of the resonant cavity, which can be approximated as the frequency. Within the optical resonant cavity of the laser, light is continuously reflected between two mirrors, and only when specific conditions are met (the phase difference of the light wave during one round trip within the cavity is...)... Only frequencies that are integer multiples of each other can form stable standing waves. Each such allowed frequency value corresponds to a light field distribution along the longitudinal axis, i.e., a longitudinal mode. From a frequency perspective, the wavelengths of the longitudinal mode frequencies can form stable standing waves; these wavelengths correspond to the modes called longitudinal modes. A longitudinal mode jump refers to the phenomenon where the output longitudinal mode of a laser suddenly changes during operation. For example, if the output longitudinal mode originally outputs a certain frequency, due to external factors, the frequency changes significantly, jumping to another longitudinal mode frequency. The longitudinal mode spacing refers to the difference in center frequencies between two adjacent longitudinal modes, used to describe the spacing of different longitudinal mode frequency distributions within the resonant cavity. The gain peak refers to the peak corresponding to the wavelength with the highest gain within the wavelength range that the gain medium can provide.

[0059] Furthermore, such as Figure 3 As shown, this application provides a processing device, including a wavelength adjustment unit, a cavity length adjustment unit, and a control unit;

[0060] A wavelength adjustment unit is used to obtain the target wavelength based on temperature and Bragg conditions;

[0061] A cavity length adjustment unit is used to obtain an updated cavity length value based on the target wavelength;

[0062] The control unit is used to first adjust the length of the optical resonant cavity according to the cavity length update value, and then adjust the wavelength of the light emitted by the tunable light source according to the target wavelength.

[0063] This embodiment, based on the Bragg condition and the thermal expansion characteristics of waveguide materials, sets up a wavelength adjustment scheme to make the wavelength track the change of the grating period, maintain the Bragg condition, and solve the problem of uneven brightness caused by temperature changes.

[0064] It should be noted that the Bragg condition is a fundamental condition describing the coherent diffraction of waves (such as electromagnetic waves and light waves) in periodic structures (such as crystals and gratings). Its core idea is that strong diffraction occurs when the wavelength of the wave satisfies a specific geometric relationship with the periodic structure. For a one-dimensional grating (periodic structure), the Bragg condition can be expressed as:

[0065]

[0066] in, Indicates the wavelength of the incident light. Indicates the period of the grating. Let θ be the angle between the incident light and the grating normal. Uneven heating in different regions of the waveguide (such as concentrated heat near the light source) will cause localized expansion differences in the grating. Based on the thermal expansion characteristics of materials, it is known that as the temperature rises... As the wavelength increases, the original wavelength no longer satisfies the Bragg condition, leading to a decrease in the diffraction efficiency of the grating and a deterioration in brightness uniformity, such as localized brightness reduction or non-uniformity.

[0067] Specifically, in this embodiment, the relationship between the grating period and temperature can first be obtained based on the thermal expansion effect. :

[0068]

[0069] in, Indicates temperature. Reference temperature The grating period below, The coefficient of thermal expansion of the grating material needs to be determined based on the specific grating material used. Preferred coefficients are... .

[0070] Next, based on the thermo-optical effect, the relationship between the refractive index of the grating material and temperature can be obtained. :

[0071]

[0072] in, Reference temperature The refractive index of the grating below, The thermo-optic coefficient of the grating material needs to be determined based on the specific grating material used.

[0073] Substituting the above relationship into the Bragg condition, the target wavelength can be obtained. for:

[0074]

[0075] Next, the target wavelength is directly used as the pre-tuning parameter of the mode hopping suppression scheme to obtain the cavity length update value. ,in This is the initial cavity length value before updating. The initial wavelength value before adjustment, and the final adjusted cavity length value. , This is a correction factor.

[0076] Specifically, this embodiment sets the cavity length update value formula. The principle is as follows: First, according to the laser resonance condition, when light travels one round trip within the cavity, the propagation distance is... The corresponding phase difference change is ,in Wave number, representing the phase change per unit distance. This represents the cavity length. A necessary condition for laser generation is the formation of stable standing-wave interference within the cavity optical field, meaning the phase difference of the light traveling one round trip within the cavity is... Multiples of integers, mathematically expressed as: Substituting it into the above formula and simplifying, we get... Furthermore, in practical applications, if the refractive index of the medium is taken into account... Then the cavity length needs to be corrected to That is, the equivalent propagation distance of light in the medium, from which we obtain the formula. , This is the longitudinal module number.

[0077] Based on the above formula, we can conclude that in the initial state, ,Right now When the target wavelength is At that time, the cavity length needs to be adjusted to Assuming Without changing the wavelength and cavity length, we can obtain the requirements that need to be met. ,Will Substituting and simplifying, we get Since only a fine-tuning of the wavelength is needed at this point, the target wavelength should be approximately equal to the initial wavelength, meaning the difference between the target wavelength and the initial wavelength should be much smaller than the initial wavelength. At this point, the effect of wavelength change can be approximated as negligible, therefore It can be approximated as .

[0078] However, in the above analysis, this embodiment assumes... The formula remains unchanged. However, this embodiment found that due to the hysteresis effect of the longitudinal mode transition, directly using the above formula in practical applications will lead to over-adjustment, i.e., when the wavelength adjustment value... When approaching the longitudinal modulus interval, there is a high probability that the longitudinal modulus has already jumped, contrary to the assumption above. The error remains unchanged. Based on the aforementioned hysteresis effect, this embodiment further introduces a correction factor to achieve pre-compensation for the longitudinal mode jump. Specifically, after introducing the correction factor, the cavity length update value set in this embodiment can be obtained. If the wavelength adjustment value Approaching the longitudinal die interval, i.e. ,but ,because ,therefore This formula shows that when the wavelength adjustment value reaches the longitudinal mode spacing, the cavity length adjustment amount can be approximated as... This is consistent with the dimensions of the cavity length adjustment required when a longitudinal mold jump occurs; therefore, this approximate formula... The essence of setting the correction factor is to pre-compensate for possible jumps within a single longitudinal mode range, ensuring that the system can smoothly transition when approaching the jump threshold. The cavity length adjustment required when a longitudinal mode jump occurs can be derived from the resonance condition.

[0079] Furthermore, this embodiment also sets a delay factor so that the current The length of the cavity at any given time is based on Target wavelength at time Adjustments are made to avoid inaccurate cavity length updates caused by grating response delay. The final cavity length update value should be: ,in The delay factor is the time it takes for a temperature change to reach the grating and cause it to respond. It can be determined by factors such as the volume, thermal conductivity, and heat capacity of the grating.

[0080] Furthermore, in this embodiment, the cavity length is adjusted first, and then current is injected to adjust the wavelength. The principle behind this sequence is that if the wavelength is adjusted first and then the cavity length is adjusted, obvious multimode oscillation or longitudinal mode jump will occur, which contradicts the purpose of this embodiment to avoid longitudinal mode jump.

[0081] For example, suppose at the initial time Below, that is, the temperature has changed, and the temperature change causes the longitudinal mold wavelength and wavelength corresponding to the gain peak The wavelengths no longer overlap, resulting in uneven brightness. In this case, the wavelength and cavity length need to be adjusted to match the longitudinal modes. The wavelength and the wavelength corresponding to the gain peak are used to solve the problem of uneven brightness. If the current is adjusted first, assuming that... After adjusting the current, as the current increases, the temperature of the gain medium rises, causing the wavelength corresponding to the gain peak to shift towards longer wavelengths. This is called "redshift," denoted as from... Move to For longitudinal mold Adjusting the current will change the effective cavity length. A transient change (such as a change in current causing thermal expansion of some structures within the cavity, altering the optical path) results in a transient blue shift (movement towards shorter wavelengths) of the wavelength corresponding to the longitudinal mode. At this point, the longitudinal mode wavelength and the gain peak wavelength no longer coincide. Then... The cavity length is adjusted continuously, but because the mechanical movement is relatively slow (for example, adjusting the cavity length may be done by moving components such as mirrors through some mechanical structure), the effective cavity length has not changed significantly, so the longitudinal mold... Still close As for the gain peak, due to the ongoing effects of factors such as the thermal effect from the current, it continues to slowly redshift towards longer wavelengths. At time 1, the cavity length adjustment is complete, and the longitudinal mold... After adjustment, it has been... wavelength of the gain peak at time Align. However, in During this period, the longitudinal mode wavelength and the gain peak wavelength are always mismatched. This state makes the optical field in the laser cavity complex and will excite obvious multimode oscillation, that is, multiple longitudinal modes oscillate at the same time, or mode hopping phenomenon, that is, jumping from one longitudinal mode to another.

[0082] Conversely, if the cavity length is adjusted first and then the wavelength is adjusted, for example, at the initial moment... As mentioned above, in At this time, the cavity length is first adjusted, that is, the cavity length is slowly changed through a precision mechanical device (such as piezoelectric ceramic), at which point the longitudinal die... The corresponding wavelength gradually and slowly moves towards the target that coincides with the gain peak. During this process, because the current is not adjusted, the wavelength corresponding to the gain peak remains constant. The position remains unchanged, but with the longitudinal die The corresponding slow shift in wavelength gradually reduces the mismatch between the longitudinal mode and the gain peak. At that moment, the cavity length adjustment was completed, and the longitudinal mold... It is close to the target position, at which point the mismatch between the longitudinal mode and the gain peak is very small. The current is constantly adjusted to change the wavelength. At this point, the position of the longitudinal mode is relatively determined. Adjusting the current mainly changes the position of the gain peak to make it closer to the longitudinal mode. Since the cavity length adjustment has made the mismatch between the two small, and the current adjustment process is relatively gentle, it will not cause fierce competition between multiple modes, and it is not easy to cause mode jumping phenomenon. It can achieve the overlap of the longitudinal mode and the gain peak more smoothly.

[0083] This embodiment uses a method of adjusting the cavity length first. During the process of adjusting the cavity length, the adjustment of the longitudinal mode is a relatively slow and continuous process. When adjusting the cavity length, the gain peak remains basically stable, so that the mismatch time between the longitudinal mode and the gain peak is relatively short. Furthermore, by adjusting the cavity length first and then adjusting the wavelength, at least one of the longitudinal mode and the gain peak is relatively stable most of the time, and multiple longitudinal modes will not be easily excited to obtain gain at the same time. This effectively avoids the occurrence of multi-mode competition and thus avoids mode hopping.

[0084] like Figure 4 As shown, based on the above analysis, it can be summarized that the wavelength adjustment unit provided in this embodiment includes a thermal expansion module, a thermo-optic module, and a matching module, and the cavity length adjustment unit includes an adjustment module and a correction module;

[0085] A thermal expansion module is used to obtain the period adjustment value of the grating based on the temperature and the coefficient of thermal expansion. The grating is located in the metasurface grating waveguide.

[0086] Thermo-optic module, used to obtain the refractive index adjustment value of the grating based on temperature and thermo-optic coefficient;

[0087] The matching module is used to substitute the period adjustment value and the refractive index adjustment value into the Bragg condition to obtain the target wavelength;

[0088] The adjustment module is used to obtain a corrected cavity length value based on the target wavelength, the current wavelength, and the current cavity length value.

[0089] The correction module is used to obtain the cavity length update value based on the correction factor, the delay factor, and the correction cavity length value. The delay factor is determined according to the grating material, and the correction factor is obtained according to the resonance condition.

[0090] This embodiment addresses the brightness unevenness caused by temperature changes by adjusting the wavelength. To avoid longitudinal mode jumps during wavelength adjustment, the target wavelength value is used as a pre-tuning parameter for the mode jump suppression scheme to obtain the cavity length update value. The cavity length is then adjusted first, followed by the wavelength, effectively preventing jumps. Furthermore, considering that if the grating structure involves multiple layers of materials, such as a waveguide layer, temperature can affect the refractive index of the materials, indirectly altering the propagation characteristics of light in the grating and thus affecting the imaging brightness, and that the grating response has a delay, this embodiment further sets a correction factor and a delay factor to obtain the final cavity length update value.

[0091] Furthermore, such as Figure 5 As shown, the processing device provided in this embodiment further includes an image adjustment unit and a transmission unit, and the image adjustment unit includes an enhancement module and a correction module;

[0092] An enhancement module is used to adjust the contrast of the image to be displayed based on the fractal dimension of the image to be displayed, so as to obtain a first image;

[0093] The correction module is used to perform color calibration on the first image based on the pixel value of each pixel in the first image to obtain the second image;

[0094] The transmission unit is used to convert the second image into an electrical signal so that the spatial light modulator modulates the phase distribution of the light according to the electrical signal.

[0095] Specifically, the image to be displayed is first divided into multiple sub-images evenly. To reduce edge effects, there is an overlapping area between adjacent sub-images. Then, the pixel value of each pixel in each sub-image is normalized.

[0096] Next, for each sub-image, its fractal dimension is calculated using box-counting dimension. Specifically, an initial grid is first constructed, and then the grid side length is progressively increased in powers of 2 to obtain multiple preset grids. For example, such as... Figure 6 As shown, assuming the initial grid size is 1×1 pixels, the grid side length is gradually increased to obtain grids of sizes such as 2×2 pixels, 4×4 pixels, and 8×8 pixels, until the grid size can completely cover the sub-image, at which point grid generation stops.

[0097] Then, each grid is sequentially overlaid onto the sub-image, where the top-left corner of each grid should overlap the top-left corner of the sub-image, such as... Figure 6 As shown, the finer grid represents a sub-image, with each cell representing a pixel, and each coarser square represents a grid of a certain size. Figure 6 This is for illustrative purposes only and does not show all the grids. The number of pixels within each grid whose pixel value is greater than a preset threshold is then counted and denoted as... ,in This indicates the size of the grid, for example, for a 1×1 pixel grid. The preset threshold can be determined according to the actual situation, such as setting it to 0.1. After obtaining the number corresponding to each grid, the threshold can be set accordingly. As the x-axis, with Plot a scatter plot on the ordinate and perform a linear fit using the least squares method based on the scatter plot to obtain the fitted equation. The slope of the fitted equation is the fractal dimension corresponding to that sub-image. Repeat the above steps to obtain the fractal dimension corresponding to each sub-image. Then, use the mean of all fractal dimensions as the reference fractal dimension.

[0098] Then, based on the fractal dimension and the reference fractal dimension of each sub-image, the adjustment coefficient for each sub-image is obtained. ,in Let be the fractal dimension, and be Reference fractal dimension. This formula indicates that when the fractal dimension is greater than the reference fractal dimension, the sub-image has rich details, and the adjustment coefficient needs to be increased to highlight the details; conversely, when the fractal dimension is less than the reference fractal dimension, the adjustment coefficient needs to be decreased.

[0099] Then, for each sub-image, the corresponding iterative transformation function is obtained based on its corresponding adjustment coefficients:

[0100]

[0101] in, This represents the pixel value of any pixel within the sub-image. This indicates the adjusted pixel value. This represents the minimum pixel value among all pixels within the sub-image. This function enhances the contrast within the sub-image by stretching or compressing pixel values.

[0102] After adjusting the contrast of each pixel in each sub-image using an iterative transformation function, the sub-images are stitched together to obtain the output image. This process of division, fractal dimension calculation, and contrast adjustment is repeated for the output image until the average absolute error between two adjacent output images is less than a threshold (e.g., 0.01). At this point, the iteration stops, and the final output image is used as the first image. The average absolute error is calculated by summing the absolute values ​​of the differences between the pixel values ​​of all pixels in two adjacent output images to obtain the sum of the grayscale value changes of all pixels, and then dividing this sum by the total number of pixels in the output image.

[0103] Specifically, since there are overlapping areas between sub-images, a weighted fusion method needs to be used when merging pixels within the overlapping areas. For example, if a pixel belongs to both sub-image A and sub-image B, in sub-image A, the pixel value of that pixel is... In sub-image B, the pixel value of this pixel is After merging, the pixel value of that pixel will be... and The mean.

[0104] Based on the above analysis, it can be summarized that the enhancement module provided in this embodiment includes a calculation submodule and an adjustment submodule. The calculation submodule includes a counting function block and a fitting function block.

[0105] The calculation submodule is used to divide the image to be displayed into multiple sub-images and calculate the fractal dimension of each sub-image based on the box dimension.

[0106] The adjustment submodule is used to obtain adjustment coefficients based on the fractal dimension and the reference fractal dimension, obtain an iterative transformation function based on the adjustment coefficients, and adjust the contrast of the image to be displayed based on the iterative transformation function to obtain the first image;

[0107] The counting function block is used to cover each sub-image with multiple preset grids and count the number of pixels in each preset grid whose pixel value is greater than a preset threshold.

[0108] The fitting function block is used to obtain the fitting equation based on the size and number of preset grids, and to obtain the fractal dimension of each sub-image based on the fitting equation.

[0109] This embodiment designs an iterative transformation function based on the self-similarity of fractals and the principle of local detail magnification. Fractal self-similarity means that small-scale details and large-scale structures are similar. The iterative transformation function simulates the fractal interpolation process to magnify the fractal structures (such as edges and textures) at different scales in the image layer by layer, thereby enhancing the contrast of details at different scales in the image. Compared with traditional contrast enhancement methods, such as histogram equalization, which destroy the fractal self-similarity of the image and cause detail distortion, this embodiment simulates the generation law of natural fractals, which enhances the contrast while preserving the multi-scale self-similar structure of the image, making the processed image more consistent with the human eye's perception of natural scenes.

[0110] Furthermore, this embodiment provides a correction module, including a first submodule and a second submodule;

[0111] The first submodule is used to obtain the correction coefficients based on the mean value of each channel in the first image;

[0112] The second submodule is used to obtain the second image based on the correction coefficients.

[0113] Specifically, firstly, the global mean of the three channels R (red), G (green), and B (blue) in the first image is calculated, denoted as . , and And calculated to obtain , and geometric mean Then, the correction coefficients for each channel were obtained based on the geometric mean. , and Then, the R, G, and B channel values ​​of each pixel in the first image are multiplied by the corresponding correction coefficients to obtain the second image. Finally, the second image is converted into an electrical signal and applied to the spatial light modulator.

[0114] This application provides a metasurface grating waveguide and enhanced display system based on a silicon carbide substrate. The waveguide structure of the silicon carbide substrate is deeply integrated with processing devices, imaging devices, etc., to construct a complete enhanced display system. The system can adjust the wavelength and cavity length in a timely manner according to temperature changes, thus solving the problem of uneven imaging brightness caused by temperature changes.

[0115] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0116] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0117] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0118] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An enhanced display system, characterized in that, include: Tunable light source, spatial light modulator, metasurface grating waveguide, imaging device and processing device; The metasurface grating waveguide is fabricated using optoelectronic devices; The spatial light modulator is used to receive light emitted by the tunable light source and modulate the phase distribution of the light emitted by the tunable light source to obtain a light beam carrying image information. The imaging device includes a focusing lens and a pupil expander; The focusing lens is located between the spatial light modulator and the metasurface grating waveguide. The focusing lens is used to convert the light beam output by the spatial light modulator into parallel light and then incident it onto the metasurface grating waveguide. The pupil expander is used to replicate the light beam emitted from the metasurface grating waveguide into multiple exit pupils; The processing device is used to adjust the wavelength of the light emitted by the tunable light source and the length of the optical resonant cavity according to the current temperature of the metasurface grating waveguide, wherein the optical resonant cavity is located in the tunable light source; The processing device includes a wavelength adjustment unit, a cavity length adjustment unit, and a control unit; The wavelength adjustment unit is used to obtain the target wavelength based on temperature and Bragg conditions; The cavity length adjustment unit is used to obtain an updated cavity length value based on the target wavelength; The control unit is used to first adjust the length of the optical resonant cavity according to the cavity length update value, and then adjust the wavelength of the light emitted by the tunable light source according to the target wavelength. The wavelength adjustment unit includes a thermal expansion module, a thermo-optic module, and a matching module. The thermal expansion module is used to obtain the period adjustment value of the grating based on the temperature and the coefficient of thermal expansion, and the grating is located in the metasurface grating waveguide; The thermo-optic module is used to obtain the refractive index adjustment value of the grating based on the temperature and thermo-optic coefficient; The matching module is used to substitute the period adjustment value and the refractive index adjustment value into the Bragg condition to obtain the target wavelength; The cavity length adjustment unit includes an adjustment module and a correction module; The adjustment module is used to obtain a corrected cavity length value based on the target wavelength, the current wavelength, and the current cavity length value. The correction module is used to obtain the cavity length update value based on the correction factor, the delay factor, and the corrected cavity length value. ,in for The target wavelength at that moment, As a delay factor, As a correction factor, This is the initial cavity length value before updating. The initial wavelength value before adjustment. For the refractive index of the medium, At the current moment, the delay factor is determined based on the material of the grating, and the correction factor is obtained based on the resonance condition.

2. The enhanced display system according to claim 1, characterized in that, The processing device further includes an image adjustment unit and a transmission unit, wherein the image adjustment unit includes an enhancement module and a correction module; The enhancement module is used to adjust the contrast of the image to be displayed according to the fractal dimension of the image to be displayed, so as to obtain a first image; The correction module is used to perform color calibration on the first image based on the pixel value of each pixel in the first image to obtain the second image; The transmission unit is used to convert the second image into an electrical signal so that the spatial light modulator modulates the phase distribution of the light according to the electrical signal.

3. The enhanced display system according to claim 2, characterized in that, The enhancement module includes a calculation submodule and an adjustment submodule; The calculation submodule is used to divide the image to be displayed into multiple sub-images and calculate the fractal dimension of each sub-image based on the box dimension. The adjustment submodule is used to obtain adjustment coefficients based on the fractal dimension and the reference fractal dimension, obtain an iterative transformation function based on the adjustment coefficients, and adjust the contrast of the image to be displayed based on the iterative transformation function to obtain a first image.

4. The enhanced display system according to claim 3, characterized in that, The calculation submodule includes a counting function block and a fitting function block; The counting function block is used to cover each sub-image with multiple preset grids and count the number of pixels in each preset grid whose pixel value is greater than a preset threshold. The fitting function block is used to obtain a fitting equation based on the size and quantity of the preset grid, and to obtain the fractal dimension of each sub-image based on the fitting equation.

5. The enhanced display system according to claim 4, characterized in that, The correction module includes a first sub-module and a second sub-module; The first submodule is used to obtain the correction coefficient based on the mean value of each channel in the first image; The second submodule is used to obtain the second image based on the correction coefficient.

6. A metasurface grating waveguide based on a silicon carbide substrate, applied to the enhanced display system as described in any one of claims 1-5, characterized in that, The metasurface grating waveguide includes a silicon carbide substrate and is used to conduct a light beam incident from a focusing lens to a pupil expander, so that the pupil expander outputs image information to the human eye.

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