A projection display system based on a conductive solution

Abstract

The application discloses a projection display system based on a conductive solution, which comprises a laser array, three-color laser beams emitted by the laser array are incident into an X-beam combiner prism, white laser beams emitted from the X-beam combiner prism are incident into a polarization converter, P-polarization state white light beams emitted from the polarization converter are dispersed into a plurality of sub-beams through a micromirror array, each sub-beam is incident into a corresponding speckle suppression unit, the sub-beams emitted from the speckle suppression unit enter an integrating rod, after the sub-beams are shaped and combined, the sub-beams are collimated by a collimating mirror and then enter a polarization beam splitter prism PBS, the PBS transmits the sub-beams to a color LCOS chip, the incident sub-beams are modulated, and the modulated S-polarization state light beams are returned to the PBS along the incident route, the S-polarization state light beams are reflected into a projection objective lens through the polarization beam splitter prism PBS and then are imaged, and the imaging is displayed through the projection objective lens. The projection display system based on the conductive solution effectively suppresses laser speckles and improves light energy utilization; the optical path structure is simple, the number of used components is small, and the volume is small.

Description

Technical Field

[0001] This invention belongs to the field of laser projection technology, and more specifically, this invention relates to a projection display system based on a conductive solution. Background Technology

[0002] Display technology is a primary means for humans to interact with the information world and has been applied in various fields of modern society, such as military, commercial entertainment, education, medicine, and industry. Display technology has fundamentally changed people's lifestyles, and people's daily lives and social activities are becoming increasingly inseparable from it. Currently, there are two main projection technologies: Liquid Crystal Display (LCD), Digital Light Processing (DLP), and Liquid Crystal on Silicon (LCOS).

[0003] LCOS projection systems have relatively low utilization of polarized light. This is mainly because they use ordinary light sources as illumination, emitting circularly polarized light. A polarization beam splitter (PBS) is used to change the polarization state of the light, requiring multiple polarization-polarization filters before it enters the LCOS chip. This method not only has low conversion efficiency but also wastes a significant amount of light. Therefore, increasing the output power of the illumination source is one way to improve the brightness of an LCOS projector, while simultaneously improving the overall light energy utilization of the projection optics system. In laser projection displays, when using highly coherent lasers as illumination sources, laser speckle is unavoidable, severely impacting the quality of the displayed image. Traditional speckle suppression methods for projection systems mainly include piezoelectric ceramics and scatterer pattern superposition. Piezoelectric ceramics are functional ceramic materials capable of converting mechanical energy and electrical energy. The working principle of piezoelectric ceramics dictates that speckle suppression relies primarily on the elastic stress of the ceramic. Stress easily leads to fatigue, which is the most significant drawback of piezoelectric materials. Furthermore, piezoelectric ceramics are relatively expensive. In the process of using a scatterer to suppress laser speckle patterns, the scatterer absorbs some energy, reducing the light energy utilization rate of the projection system and causing a decrease in the projector's brightness. At the same time, the scatterer also increases the overall size of the projection system. Summary of the Invention

[0004] This invention provides a projection display system based on a conductive solution, which aims to improve the above-mentioned problems.

[0005] This invention is implemented as follows: a projection display system based on a conductive solution, the system comprising:

[0006] The system includes a laser array, an X-beam combiner prism, a polarization converter, a micromirror array, a speckle suppressor, an integrating square bar, a collimating lens, a polarization beam splitter (PBS), a color LCOS chip, and a projection lens. The speckle suppressor is composed of several speckle suppression units.

[0007] Red, green, and blue laser beams emitted from the laser array enter an X-beam combiner prism. A white laser beam emitted from the X-beam combiner enters a polarization converter. The P-polarized white light beam emitted from the polarization converter is dispersed into multiple sub-beams by a micromirror array. Each sub-beam enters the incident end face of a corresponding speckle suppression unit. The sub-beams emitted from the speckle suppression unit enter an integrating square bar, which shapes and combines the individual sub-beams. The shaped and combined beam is collimated by a collimating lens and then enters a polarization beam splitter PBS. The polarization beam splitter PBS transmits the beam to a color LCOS chip. The color LCOS chip modulates the incident sub-beams and returns the modulated S-polarized beam along the incident path to the polarization beam splitter PBS. The S-polarized beam is reflected by the polarization beam splitter PBS and enters a projection lens for imaging. The image is displayed through the projection lens.

[0008] Furthermore, the speckle suppressor is an array of speckle suppression units. Each speckle suppression unit consists of two speckle suppression sub-units. Each speckle suppression sub-unit consists of a flexible, highly permeable hydrophobic layer, a driving electrode, a conductive solution, and a glass substrate. The glass substrate and the flexible, highly permeable hydrophobic layer are arranged opposite each other. Two driving electrodes are arranged at both ends of the glass substrate and the flexible, highly permeable hydrophobic layer. The space enclosed by the glass substrate, the flexible, highly permeable hydrophobic layer, and the driving electrodes is filled with a conductive liquid. The flexible, highly permeable hydrophobic layers of the two speckle suppression sub-units are arranged opposite each other, and an insulating solution is filled between the oppositely arranged flexible, highly permeable hydrophobic layers.

[0009] Furthermore, the micromirror array is composed of a series of focusing lenses, which converge the light beam onto the incident end face of the speckle suppression unit.

[0010] Furthermore, the polarization converter includes:

[0011] The first reflecting mirror and the second reflecting mirror are connected at their two ends to the incident end face and the exit end face, respectively. The first reflecting mirror forms a 135-degree angle with the incident light, and the second reflecting mirror forms a 45-degree angle with the incident light.

[0012] A first PBS prism and a second PBS prism are disposed within the incident end face and the exit end face, respectively. The first PBS prism and the second PBS prism are connected on the exit end face. The other ends of the first PBS prism and the second PBS prism are connected to the two ends of the incident end face and are respectively connected to the first reflector and the second reflector. A half-wave plate is disposed between the first PBS prism and the second PBS prism. The two ends of the half-wave plate are respectively connected to the center of the incident end face and the center of the exit end face, and the half-wave plate is set parallel to the incident light.

[0013] Furthermore, the laser array is composed of a number of lasers arranged together, with the number of broadband lasers ranging from 1 to 6.

[0014] Furthermore, there is a deviation in the center wavelength of each laser in the laser array.

[0015] Furthermore, the laser is a broadband laser.

[0016] Furthermore, the color LCOS chip is a monolithic color LCOS chip.

[0017] Furthermore, the laser array includes a red laser array, a green laser array, and a blue laser array, wherein the red laser has a spectral broadening of 635nm-650nm, the blue laser has a spectral broadening of 455nm-470nm, and the green laser has a spectral broadening of 535nm-550nm.

[0018] The projection display system based on conductive solution provided by this invention effectively suppresses laser speckle and improves light energy utilization; the optical path structure is simple, uses fewer components, and is small in size. Attached Figure Description

[0019] Figure 1 A schematic diagram of a projection display system based on a conductive solution provided in an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the polarization converter provided in an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the speckle suppressor provided in an embodiment of the present invention, wherein (a) is the initial state of the speckle suppressor and (b) is the state of the speckle suppressor after being energized;

[0022] Figure 4 This is a schematic diagram of the speckle suppression subunit provided in an embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of the power-on operation of the speckle suppression subunit provided in an embodiment of the present invention;

[0024] Figure 6 The beam channel composed of speckle suppression units provided in the embodiments of the present invention is shown in the following: (a) no voltage is applied at both ends, (b) the lower speckle suppression subunit is subjected to voltage, and the upper speckle suppression subunit is not subjected to voltage.

[0025] Figure 7 This is a schematic diagram of light propagation in a transmissive diffuser provided in an embodiment of the present invention, wherein (a) is the direction of light propagation when the diffuser is transmitted, and (b) is the vector direction. Detailed Implementation

[0026] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0027] Figure 1 This is a schematic diagram of a projection display system based on a conductive solution provided in an embodiment of the present invention. For ease of explanation, only the parts related to the embodiment of the present invention are shown. The system includes:

[0028] The system includes a laser array, an X-beam combiner prism, a polarization converter, a micromirror array, a speckle suppressor, an integrating square bar, a collimating lens, a polarization beam splitter (PBS), a color LCOS chip, and a projection lens. The speckle suppressor is composed of several speckle suppression units.

[0029] Red, green, and blue laser beams emitted from the laser array enter an X-beam combiner prism. A white laser beam emitted from the X-beam combiner enters a polarization converter. The P-polarized white light beam emitted from the polarization converter is dispersed into multiple sub-beams by a micromirror array. Each sub-beam enters the incident end face of a corresponding speckle suppression unit. The sub-beams emitted from the speckle suppression unit enter an integrating square bar, which shapes and combines the sub-beams. The shaped and combined beam is collimated by a collimating lens and enters a polarization beam splitter PBS. The PBS transmits to a color LCOS chip, which modulates the incident sub-beams and returns the modulated S-polarized beam along the incident path to the polarization beam splitter PBS. The S-polarized beam is reflected by the polarization beam splitter PBS and enters a projection lens for imaging. The image is displayed through the projection lens.

[0030] (1) Laser array;

[0031] The broadband laser array consists of three broadband laser arrays: a red broadband laser array, a green broadband laser array, and a blue broadband laser array. The midlines of the three broadband laser arrays intersect at the center of the X-beam combiner prism.

[0032] Lasers, as light sources, offer advantages such as wide color gamut, long lifespan, high brightness, and high image contrast. However, the high coherence of laser sources can lead to laser speckle, affecting image quality. Red lasers have a spectral broadening of 635 nm - 650 nm, blue lasers have a spectral broadening of 455 nm - 470 nm, and green lasers have a spectral broadening of 535 nm - 550 nm.

[0033] A broadband laser array consists of a number of broadband lasers, typically 1 to 6. Each monochromatic broadband laser produces a laser beam with a specific wavelength difference during normal operation, providing the system with multiple incident wavelengths with different center wavelengths. This gives the system a certain degree of speckle suppression capability. Therefore, choosing a laser array as the light source can reduce laser coherence, suppress laser speckle to some extent, and also improve the overall brightness of the projection display system. To further suppress laser speckle, the center wavelengths of each laser in the broadband laser array are slightly offset. Taking a red broadband laser array as an example, the red laser array consists of three broadband lasers, and the center wavelengths of these three broadband lasers have a deviation of 1 nm.

[0034] (2) Polarization converter;

[0035] Figure 2 This is a schematic diagram of the polarization converter provided in an embodiment of the present invention, combined with... Figure 2 The polarization converter is described below. It consists of a mirror, a PBS prism, and a half-wave plate.

[0036] The first reflecting mirror and the second reflecting mirror are connected at their two ends to the incident end face and the exit end face, respectively. The first reflecting mirror forms a 135-degree angle with the incident light, and the second reflecting mirror forms a 45-degree angle with the incident light.

[0037] A first PBS prism and a second PBS prism are disposed within the incident end face and the exit end face, respectively. The first PBS prism and the second PBS prism are connected to each other on the exit end face. The other ends of the first PBS prism and the second PBS prism are connected to the two ends of the incident end face and are respectively connected to the first reflector and the second reflector. A half-wave plate is disposed between the first PBS prism and the second PBS prism. The two ends of the half-wave plate are respectively connected to the center of the incident end face and the center of the exit end face, and the half-wave plate is set parallel to the incident light.

[0038] The first PBS prism splits the incident beam into two mutually perpendicular P-polarized and S-polarized beams. The P-polarized beam is transmitted through the first PBS prism and then enters the micromirror array. The S-polarized beam is modulated by the first PBS prism and then reflected. The reflected S-polarized beam passes through a half-wave plate, where the phase angle of the S-polarized beam is rotated by π / 2, thus modulating the S-polarized beam into P-polarized beam. The P-polarized beam continues to propagate along the original optical path and is transmitted through the second PBS prism. The transmitted P-polarized beam is reflected by the second mirror and then directly enters the micromirror array. The second PBS prism splits the incident beam into two mutually perpendicular P-polarized and S-polarized beams. The P-polarized beam is transmitted through the second PBS prism and then enters the micromirror array. The S-polarized beam is modulated by the second PBS prism and then reflected. The reflected S-polarized beam passes through a half-wave plate, where the phase angle of the S-polarized beam is rotated by π / 2, thus modulating the S-polarized beam into P-polarized beam. The P-polarized beam continues to propagate along the original optical path and is transmitted through the first PBS prism. The transmitted P-polarized beam is reflected by the first mirror and then directly enters the micromirror array. Both the first and second reflectors are coated with a high-reflectivity film. The design of the high-reflectivity film can greatly improve the utilization rate of the light beam and further improve the lighting brightness of the entire system.

[0039] (3) Micromirror array;

[0040] The micromirror array consists of n focusing lenses arranged in a row. When a beam of light passes through the focusing lens in the micromirror array, each focusing lens converges the light to a designated position, which is the incident end face of the speckle suppression unit.

[0041] (4) Speckle suppressor;

[0042] The speckle suppression unit array corresponds one-to-one with the micromirror array. The micromirror array consists of multiple focusing lenses. When the light beam passes through the micromirror array, each focusing lens converges the light and directly incident on the incident end face of the speckle suppression unit. If the micromirror array disperses the P-polarized white light beam into n sub-beams, then the speckle suppressor consists of n speckle suppression units. One speckle suppression unit corresponds to one sub-beam channel, and one speckle suppression unit consists of two speckle suppression sub-units. Each speckle suppression sub-unit consists of a flexible, highly permeable hydrophobic layer, driving electrodes, a conductive solution, and a glass substrate. The glass substrate and the flexible, highly permeable hydrophobic layer are positioned opposite each other. Two driving electrodes are positioned at both ends of the glass substrate and the flexible, highly permeable hydrophobic layer. The space enclosed by the glass substrate, the flexible, highly permeable hydrophobic layer, and the driving electrodes is filled with a conductive liquid. Figure 4 As shown, two flexible, highly permeable hydrophobic layers of speckle suppression subunits are arranged opposite each other, and an insulating solution is filled between the oppositely arranged flexible, highly permeable hydrophobic layers. Figure 3 As shown in (a), Figure 3 (b) shows the state of the speckle suppression unit under the same voltage.

[0043] When an electric current is applied to the conductive solution of the speckle suppression unit, the voltage causes undulations on the end face of the conductive solution. Different voltages correspond to different degrees of undulation, such as... Figure 5 As shown, the voltage applied to the conductive solution is controlled by the principle of electrowetting. Under the applied voltage, the surface tension of the liquid changes, causing a certain degree of change in the degree of bulging of the liquid surface, and a flexible hydrophobic layer covers the liquid surface.

[0044] like Figure 6 This diagram illustrates a beam path composed of two opposing speckle suppression sub-units. Different voltages are applied to each suppression unit simultaneously, with slight differences in voltage values. After passing through a micromirror array, the beam is split into multiple sub-beams, which can be considered coherent sub-beams. As these sub-beams propagate within their respective suppression units, they undergo volume scattering through particles in the liquid. When the time delay of the volume scattering change is equal to or greater than the coherence time of the light source, speckle can be suppressed. Due to the different voltages, the liquid level in the conductive solution varies, resulting in different propagation paths for the incident sub-beams. The undulations in the liquid level between the two opposing suppression sub-units can further alter the beam path, causing multi-angle scattering of the outgoing beam, thereby further suppressing speckle.

[0045] (5) Color LCOS chip:

[0046] This invention employs a monolithic LCOS projection display, using a color LCOS chip, also known as CF-LCOS (Color Filter LCOS). Compared to the CS-LCOS (Color Sequence LCOS) used in traditional three-chip LCOS projection display systems, it adds an extra color filter, enabling it to display a color image when white light is used as the light source to drive the optical path. The overall design utilizes a monolithic display chip, which greatly simplifies the optical path structure, thereby reducing the system size.

[0047] Compared to traditional time-series projection display technology, the color LCOS chip used in this invention avoids these drawbacks. Time-series projection display technology typically uses white light as the illumination source, which inevitably requires color separation devices such as color wheels, leading to an increase in components and a larger overall size. Furthermore, color wheels can cause problems such as heat dissipation difficulties for the entire system. The monochrome display chip mentioned in this solution effectively avoids these shortcomings. More importantly, the single-chip display significantly reduces the overall manufacturing cost of the optical system and simplifies the assembly and manufacturing process.

[0048] Speckle suppression principle and analysis; the final speckle contrast of the speckle suppressor in the optical path of the projection system of this invention is theoretically derived, assuming the use of The value representing speckle contrast is set to 1, with sufficient speckle development defined as the value. When N independent speckle images with equal average intensity are superimposed, the speckle contrast is reduced to:

[0049] (1)

[0050] Speckle suppressors utilize a combination of wavelength diversity and angular diversity to suppress laser speckle. Based on Joseph W. Goodman's summary and analysis of speckle phenomena in optics, it can be concluded that when lasers of the same color emit light with a wavelength difference of […], […]. The speckles formed during this process are independent of each other. The value is related to the center wavelength of the illumination source and the deformation diffuser in the optical path. It is related to the surface roughness of the surface.

[0051] When a beam of light with wavelength λ passes through the surface of a diffuser made of a transparent material with a refractive index of n in free space (refractive index 1), the k-vector of the illuminating light wave is expressed as: The plane positioning observation direction is z, which is a distance from the normal phase of the diffuse body. The k vector in this direction is The refracted wave k vector generated by the beam entering the diffuser is ,like Figure 7 As shown in (a) and (b). Let the diffuser be in... The surface height of the location point is The phase shift of the scattered field can be obtained. :

[0052] (2)

[0053] in, This represents the direction vector of the incident ray as it enters the diffuser and undergoes its first refraction. This represents the horizontal direction of the diffuse volume's cross-section. Define a scattering vector. :

[0054] (3)

[0055] lateral component of the scattering vector The z-axis component is:

[0056] (4)

[0057] (5)

[0058] in, , These represent the exit angle and the incident angle of the light beam, respectively.

[0059] The speckle suppressor uses wavelength diversity to suppress speckle. The wavelength of the monochromatic laser will change. Let the initial value be... The final quantity is You can get :

[0060] (6)

[0061] The characteristic function for path length fluctuations exhibiting Gaussian form for surface height fluctuations :

[0062] (7)

[0063] in, express The variance of the normalized power spectral density function. With the frequency difference of light waves The transformation, its autocoherence function It can be determined as follows:

[0064] (8)

[0065] For a surface exhibiting a Gaussian speckle pattern, its speckle contrast can be obtained from its height. :

[0066] (9)

[0067] in, Indicates 1 / e spectral width, A Gaussian spectrum with negative values ​​of the center frequency;

[0068] When the average phase shift generated on the surface is greater than or equal to 2π, a laser speckle pattern with independent and incoherent brightness can be formed, and the wavelength difference satisfies:

[0069] (10)

[0070] Because the center wavelength of a single laser wave drifts, The maximum center wavelength of the laser. The minimum center wavelength of the laser. The laser source is a laser diode whose center wavelength changes to some extent during operation. Combining it with a speckle suppression unit composed of a dynamic conductive liquid can further suppress laser speckle, mainly due to its wavelength diversity characteristic. The wavelength difference generated by the laser source during operation and the variance of the fluctuation height of each speckle suppression unit in the speckle suppressor are also factors. Once formula (10) is satisfied, the formation of independent speckle can be achieved. The superposition of independent speckle is also an important principle of this scheme to suppress speckle.

[0071] The present invention has been described by way of example. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A projection display system based on a conductive solution, characterized in that, The system includes: The system includes a laser array, an X-beam combiner prism, a polarization converter, a micromirror array, a speckle suppressor, an integrating square bar, a collimating lens, a polarization beam splitter (PBS), a color LCOS chip, and a projection lens. The speckle suppressor is composed of several speckle suppression units. Red, green, and blue laser beams emitted from the laser array are incident on an X-beam combiner prism. A white laser beam emitted from the X-beam combiner prism is incident on a polarization converter. The P-polarized white light beam emitted from the polarization converter is dispersed into multiple sub-beams by a micromirror array. Each sub-beam is incident on the incident end face of a corresponding speckle suppression unit. The sub-beams emitted from the speckle suppression unit enter an integrating square bar, which shapes and combines the sub-beams. The shaped and combined beam is collimated by a collimating lens and then enters a polarization beam splitter PBS. The polarization beam splitter PBS transmits the beam to a color LCOS chip. The color LCOS chip modulates the incident sub-beams and returns the modulated S-polarized beam along the incident path to the polarization beam splitter PBS. The S-polarized beam is reflected by the polarization beam splitter PBS and enters a projection lens for imaging. The image is displayed through the projection lens. The speckle suppressor is an array of speckle suppression units. One speckle suppression unit consists of two speckle suppression sub-units. Each speckle suppression sub-unit consists of a flexible, highly permeable hydrophobic layer, a driving electrode, a conductive solution, and a glass substrate. The glass substrate and the flexible, highly permeable hydrophobic layer are arranged opposite each other. Two driving electrodes are arranged at both ends of the glass substrate and the flexible, highly permeable hydrophobic layer. The space enclosed by the glass substrate, the flexible, highly permeable hydrophobic layer, and the driving electrodes is filled with a conductive liquid. The flexible, highly permeable hydrophobic layers of the two speckle suppression sub-units are arranged opposite each other. An insulating solution is filled between the oppositely arranged flexible, highly permeable hydrophobic layers. Polarization converters include: The first reflecting mirror and the second reflecting mirror are connected at their two ends to the incident end face and the exit end face, respectively. The first reflecting mirror forms a 135-degree angle with the incident light, and the second reflecting mirror forms a 45-degree angle with the incident light. A first PBS prism and a second PBS prism are disposed within the incident end face and the exit end face, respectively. The first PBS prism and the second PBS prism are connected on the exit end face. The other ends of the first PBS prism and the second PBS prism are connected to the two ends of the incident end face and are respectively connected to the first reflector and the second reflector. A half-wave plate is disposed between the first PBS prism and the second PBS prism. The two ends of the half-wave plate are respectively connected to the center of the incident end face and the center of the exit end face, and the half-wave plate is set parallel to the incident light.

2. The projection display system based on a conductive solution as described in claim 1, characterized in that, The micromirror array is composed of a series of focusing lenses, which converge the light beam onto the incident end face of the speckle suppression unit.

3. The projection display system based on a conductive solution as described in claim 1, characterized in that, A laser array consists of a number of lasers arranged together, with the number of broadband lasers ranging from 1 to 6.

4. The projection display system based on a conductive solution as described in claim 3, characterized in that, There is a deviation in the center wavelength of each laser in the laser array.

5. The projection display system based on a conductive solution as described in claim 3, characterized in that, The laser is a broadband laser.

6. The projection display system based on a conductive solution as described in claim 1, characterized in that, The color LCOS chip is a monolithic color LCOS chip.

7. The projection display system based on a conductive solution as described in claim 3 or 4, characterized in that, The laser arrays include: a red laser array, a green laser array, and a blue laser array. Among them, the red laser has a spectral broadening of 635nm-650nm, the blue laser has a spectral broadening of 455nm-470nm, and the green laser has a spectral broadening of 535nm-550nm.

Images