Projection screen and projection system

Abstract

The present application discloses a projection screen and a projection system. The projection screen comprises: a Fresnel lens layer and resonance layers located on the surfaces of lens units of the Fresnel lens layer. Each resonance layer uses a single-layer thin film, can selectively reflect projection light emitted by a projection device, and has a greatly reduced reflectivity to light in other bands, thereby significantly improving the contrast of a projection image. The manufacturing process of resonance layers using single-layer thin films is simpler, reducing production costs and improving production efficiency.

Description

Projection screen and projection system

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410804940.X, filed on June 20, 2024, entitled “A Projection Screen and Projection System”, the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] As display products continue to trend towards larger sizes, considering factors such as power consumption, weight, and size, the market for projection displays as a large-screen alternative to LCD and OLED televisions is rapidly expanding. Laser televisions, which utilize ultra-short-throw projection equipment, are experiencing rapid growth due to their high image quality and the convenience of a large screen.

[0005] Projection systems are typically used with projection screens. White frosted matte projection screens can evenly reflect light from the projector and are inexpensive. However, white frosted matte projection screens are easily affected by ambient light when viewed in strong light, making them unsuitable for watching movies or other images that frequently use dark scenes. To overcome this problem, some layers of the projection screen are colored to absorb ambient light. However, because colored projection screens also absorb the light emitted from the projector, this results in a loss of brightness in the projected light, leading to reduced image contrast. Summary of the Invention

[0006] This application provides a projection screen, including:

[0007] A Fresnel lens layer; the Fresnel lens layer includes multiple lens units, each lens unit including a lens surface and a non-lens surface; the lens surface is inclined relative to the plane of the projection screen; and

[0008] A resonant layer covers at least the lens surface of each of the lens units; the resonant layer is a single-layer thin film, and the resonant layer has a higher reflectivity for the projected light emitted from the projection device than for other wavelengths of light.

[0009] This application also provides a projection system, including:

[0010] Projection equipment, used to emit projection light; and

[0011] A projection screen is located on the light-emitting side of the projection device, and the projection screen is the aforementioned projection screen. Attached Figure Description

[0012] Figure 1 is a schematic diagram of the projection system provided in an embodiment of this application;

[0013] Figure 2 is one of the cross-sectional structural diagrams of the projection screen provided in the embodiments of this application;

[0014] Figure 3 is a schematic diagram of the planar structure of the Fresnel lens layer provided in an embodiment of this application;

[0015] Figure 4 is a second schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application;

[0016] Figure 5 is a schematic diagram of the resonance principle provided in an embodiment of this application;

[0017] Figure 6 shows one of the simulation results provided in the embodiments of this application;

[0018] Figure 7 shows a second simulation result provided by an embodiment of this application;

[0019] Figure 8 shows the reflectivity curve of the resonant layer provided in the embodiment of this application;

[0020] Figure 9 is a schematic diagram of one of the methods for fabricating the resonant layer provided in the embodiments of this application;

[0021] Figure 10 is a second schematic diagram of the method for fabricating the resonant layer provided in the embodiments of this application;

[0022] Figure 11 is a third schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application;

[0023] Figure 12 shows one of the reflectivity curves of the resonant layer and the transmittance curve of the wavelength-selective absorption layer provided in the embodiments of this application;

[0024] Figure 13 shows the second of the reflectivity curves of the resonant layer and the transmittance curves of the wavelength-selective absorption layer provided in the embodiments of this application.

[0025] Figure 14 is a fourth schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application;

[0026] Figure 15 is a fifth schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application;

[0027] Figure 16 is a sixth schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application;

[0028] Figure 17 is the seventh schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application;

[0029] Figure 18 is the eighth schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application;

[0030] Figure 19 is a schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application (nine).

[0031] Figure 20 is a cross-sectional structural schematic diagram of the projection screen provided in the embodiment of this application;

[0032] Figure 21 is an eleventh schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application;

[0033] Figure 22 is a schematic diagram of the projection device provided in an embodiment of this application. Detailed Implementation

[0034] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the application will be further described below in conjunction with the accompanying drawings and embodiments. However, the exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the figures denote the same or similar structures, and therefore repeated descriptions of them will be omitted. Terms describing position and direction described in this application are illustrative based on the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this application. The accompanying drawings of this application are for illustrating relative positional relationships only and do not represent actual scale.

[0035] With the increasing popularity of laser display products, the market for laser TVs, as a large-screen alternative to LCD and OLED TVs, is rapidly expanding. To achieve better brightness and display effects, projection devices are generally used in conjunction with projection screens.

[0036] Figure 1 is a schematic diagram of the projection system provided in an embodiment of this application.

[0037] As shown in Figure 1, the projection system includes: projection device 2 and projection screen 1.

[0038] The projection screen 1 is located on the light-emitting side of the projection device 2, and the audience faces the projection screen 1. The projection device 2 emits projection light, which enters the projection screen 1, passes through the projection screen 1, and exits towards the audience, thus allowing the audience to view the projected image.

[0039] When the projection device 2 and the audience are located on the same side of the projection screen 1, this projection system is called a front projection system. When the projection device 2 and the audience are located on opposite sides of the projection screen 1, this projection system is called a rear projection system. In a front projection system, the projection device 2 emits projection light onto the projection screen 1, and the projection screen 1 reflects the projection light back to the audience, allowing the audience to view the projected image. In a rear projection system, the projection device 2 emits projection light onto the projection screen 1, and the projection light passes through the projection screen 1 and exits towards the audience, allowing the audience to view the projected image.

[0040] This application uses an ultra-short-throw projection system as an example to specifically describe the structure of the projection screen. The projection screen 1 can be mounted on a wall or suspended high up, or it can be integrated with the projection device into a single display device. In use, the projection device 2 can be located below the projection screen 1, projecting light from below and diagonally upwards onto the projection screen 1; or, the projection device 2 can be located above the projection screen 1, projecting light from above and diagonally downwards onto the projection screen 1. Because the ultra-short-throw projection system has a small throw ratio, a larger projected image can be obtained while reducing the distance between the projection device 2 and the projection screen 1, making it very suitable for applications such as laser TVs.

[0041] As shown in Figure 1, the projection screen 1 is usually rectangular in shape. When in use, its bottom and top sides are usually parallel to the horizontal direction x, and the two sides are parallel to the vertical direction y. The horizontal direction x is the direction parallel to the horizontal plane, and the vertical direction y is the direction located in the plane of the projection screen and perpendicular to the horizontal direction. In this embodiment, the projection device 2 is set at the bottom side of the projection screen 1 as an example.

[0042] Figure 2 is one of the cross-sectional structural diagrams of the projection screen provided in the embodiments of this application.

[0043] Figure 2 shows a projection screen used in conjunction with a front projection system. As shown in Figure 2, the projection screen includes: a surface functional layer 11, a Fresnel lens layer 12, and a reflective layer 13.

[0044] The surface functional layer 11 can be located on the outermost surface of the projection screen. In some embodiments, the surface functional layer 11 is located on the side closest to the audience, which plays a role in protecting the projection screen. In addition, the surface functional layer 11 can be processed in various ways according to different needs to achieve effects such as expanding the viewing angle, resisting ambient light reflection, and resisting ceiling reflection.

[0045] Figure 3 is a schematic diagram of the planar structure of the Fresnel lens layer provided in the embodiment of this application.

[0046] As shown in Figures 2 and 3, the Fresnel lens layer 12 is located on the side of the surface functional layer 11 away from the viewer. The Fresnel lens layer 12 includes multiple lens units 121 arranged according to a predetermined rule. As shown in Figure 3, the multiple lens units 121 can form concentric circles that expand radially in sequence. When the projection screen is used in an ultra-short-throw projection system, the center O of the concentric lens units 121 is usually not located within the projection screen. When the projection device emits projection light from below the projection screen, the center O of each lens unit 121 is located below the bottom edge of the projection screen and on the extension line of the projection screen's axis of symmetry I-I'. Along the projection screen from bottom to top, the radius of the lens units 121 gradually increases, and the projection screen does not contain complete circular lenses, but only partially arc-shaped lenses.

[0047] As shown in Figure 2, each lens unit 121 includes an interconnected lens surface x1 and a non-lens surface x2. The lens surface x1 is tilted relative to the plane of the projection screen, and the tilt angle of the lens surface x1 is set according to the incident angle of the projected light, so that the light emitted from the projection device can be reflected towards the viewer when it hits the reflective layer 13 on the surface of the lens surface x1. The non-lens surface x2 is used to connect to the lens surface x1, and the non-lens surface x2 can be a plane or a curved surface.

[0048] The Fresnel lens layer 12 in the projection screen facilitates the reflection of projected light towards the front of the projection screen, thereby improving the gain of the projection screen. In some embodiments, the Fresnel lens layer 12 can also be replaced by a prism layer. The prism layer may include multiple prism units, which are different from the lens unit 121 described above. The prism unit can be a strip-shaped prism extending horizontally and arranged vertically. The cross-section of the prism unit is similar to a triangle. The prism unit may also include a lens surface and a non-lens surface. The lens surface is inclined relative to the plane of the projection screen. The inclination angle of the lens surface is set according to the incident angle of the projected light, so that the projected light emitted from the projection device can be reflected towards the viewer when it is incident on the reflective layer of the lens surface. The functional layers in the projection screen can be set according to the usage requirements. This application embodiment uses a projection screen including a Fresnel lens layer 12 as an example for description, and no limitation is made here.

[0049] The reflective layer 13 covers at least the lens surface x1 of each lens unit 121 of the Fresnel lens layer 12. Since the tilt angle of the lens surface x1 of each lens unit 121 is in the direction of reflecting the incident projection light toward the viewer, and the reflective layer 13 covers the lens surface x1 of the lens unit 121 and has the same tilt angle as the lens surface x1, the incident projection light can be reflected toward the viewer as originally designed.

[0050] Current projection screens can be white, matte-finish screens that uniformly reflect light from the projection device at a low cost. However, these screens are easily affected by ambient light in bright light conditions, making them unsuitable for viewing images that frequently use dark scenes, such as movies. To overcome this problem, some layers of the projection screen can be colored to absorb ambient light. However, because colored screens also absorb the light emitted from the projection device, this results in a loss of brightness in the projected light, leading to reduced image contrast.

[0051] In view of this, this application provides a projection screen, as shown in FIG4. The projection screen includes a surface functional layer 11, a Fresnel lens layer 12, and a resonant layer F. The resonant layer F utilizes the principle of resonant enhancement of light of a set wavelength to selectively enhance the reflection of the projection light emitted by the projection device, while absorbing light of other wavelengths. This makes the reflectivity of the resonant layer F for the projection light emitted by the projection device greater than its reflectivity for other wavelengths, thereby achieving a black appearance when the projection device is off and a bright display when the projection device is on, thus significantly improving the contrast of the projected image.

[0052] As shown in Figure 4, the projection light L emitted from the projection device enters the projection screen from one side of the surface functional layer 11. When it enters the resonant layer F on the surface of the lens unit 121, it is reflected by the resonant layer F and thus exits in the direction of the viewer. At the same time, ambient light C enters the projection screen from one side of the surface functional layer 11. When ambient light C enters the resonant layer F on the surface of the lens unit, since the resonant layer F has a high reflectivity only for projection light and a low reflectivity for ambient light of other wavelengths, the reflection of ambient light can be greatly reduced, thereby improving the contrast of the projection light.

[0053] Figure 5 is a schematic diagram of the resonance principle provided in an embodiment of this application. Referring to Figure 5, the principle that the resonance layer F can generate resonance enhancement for light of a set wavelength will be explained in detail.

[0054] As shown in Figure 5, when the resonant layer F is placed in an air environment, two interfaces are formed between the two surfaces of the resonant layer F and the air, referred to as the first interface f1 and the second interface f2. When two parallel light rays a1 and a2 are incident from the air onto the resonant layer F, the light rays undergo reflection and refraction at the first interface f1. Specifically, light ray a2 is reflected by the first interface f1, forming reflected ray a2'; light ray a1 is incident into the resonant layer F and reflected at the second interface f2, and the reflected ray then exits from the first interface f1, forming reflected ray a1'.

[0055] According to the principle of interference, when the optical path difference between reflected rays a1' and a2' is an integer multiple of the wavelength of the light, the two rays are coherent and constructive; when the optical path difference between reflected rays a1' and a2' is an odd multiple of half the wavelength of the light, the two rays are coherent and destructive.

[0056] If the refractive index of the resonant layer F is n and the thickness is d, then as shown in Figure 5, the optical path difference between the two light beams is ΔL = 2ndcosθ. When the light beam is incident perpendicularly on the resonant layer F, θ = 0, and ΔL = 2nd. However, the projection light emitted by the projection device used in this embodiment is a three-color laser, namely red, green, and blue lasers. Therefore, the resonant layer F needs to simultaneously enhance the red, green, and blue lasers. Assume the wavelengths of the three-color lasers are: λ(R) = 643nm; λ(G) = 525nm; λ(B) = 465nm;

[0057] The three-color lasers have different refractive indices in the resonant layer F, which are distinguished by n(λ(R)), n(λ(G)), and n(λ(B)). Therefore, the thickness d of the resonant layer F must simultaneously satisfy the following three equations to achieve resonant enhancement of the three-color lasers:

[0058] Where λ(R) represents the wavelength of the red laser, λ(G) represents the wavelength of the green laser, and λ(B) represents the wavelength of the blue laser; n(λ(R)) represents the refractive index of the red laser in the resonant layer, n(λ(G)) represents the refractive index of the green laser in the resonant layer, and n(λ(B)) represents the refractive index of the blue laser in the resonant layer. l, m, and n are all natural numbers.

[0059] After calculating the thickness of the resonant layer to resonate and enhance red, green, and blue lasers according to the above formula, the least common multiple of the three thickness values ​​is then determined. This allows the resonant layer to simultaneously resonate and enhance red, green, and blue lasers at this thickness, achieving selective reflection of three-color lasers by a single-layer thin film.

[0060] In this embodiment, the resonant layer F is a single-layer thin film, which can be made of semiconductor or semiconductor compound. Since semiconductor materials possess the characteristics of both metallic and dielectric materials, incident light can be reflected from its two surfaces. By adjusting the refractive index and thickness of the resonant layer, the reflected light from its two surfaces can produce a resonant enhancement effect. Using a single-layer semiconductor thin film allows for selective reflection of the projected light, simplifying the resonant structure and manufacturing process. After selecting a suitable refractive index material, only the thickness needs to be controlled, which helps reduce production costs and improve production efficiency.

[0061] The embodiments of this application also simulate the characteristics that the semiconductor material used in the resonant layer F needs to meet. Figures 6 and 7 show the simulation results provided by the embodiments of this application.

[0062] Without considering dispersion, if the extinction coefficient k of the resonant layer is fixed at 0, and the refractive index n of the resonant layer material is varied between 2.0 and 4.5, the reflectivity of the resonant layer can be simulated, as shown in Figure 6. In Figure 6, the horizontal axis represents wavelength in nm, and the vertical axis represents reflectivity in %. As can be seen from Figure 6, when a semiconductor material is used for the resonant layer, it exhibits wavelength-selective reflection characteristics. The reflectivity for the three-color laser (wavelengths 465nm, 525nm, and 643nm) is greater than that for other wavelengths, especially when the refractive index is higher. Based on the simulation results, when selecting a semiconductor material, its refractive index relative to the projected light (three-color laser) should be greater than or equal to 2.5.

[0063] If the refractive index n of the resonant layer is fixed at 4.5, and the extinction coefficient k of the resonant layer is varied between 0 and 0.3, the reflectivity of the resonant layer can be simulated to obtain the results shown in Figure 7. In Figure 7, the horizontal axis represents wavelength in nm, and the vertical axis represents reflectivity in %. As can be seen from Figure 7, when a semiconductor material is used for the resonant layer, it exhibits wavelength-selective reflection characteristics. The reflectivity for the three-color laser light (wavelengths 465nm, 525nm, and 643nm) is greater than that for other wavelength bands. This wavelength-selective reflection characteristic is particularly pronounced when the extinction coefficient k is smaller. Based on the simulation results, when selecting a semiconductor material, its extinction coefficient relative to the projected light (three-color laser light) should be less than or equal to 0.3.

[0064] Therefore, the range of characteristics that the semiconductor material used in the resonant layer needs to meet can be obtained.

[0065] In practical implementation, the material of the resonant layer F can be Si, Ge, Se, GaAs, SiC, InP or GaN.

[0066] Taking Si as an example, the refractive index of red laser (λ(R) = 643nm) in Si is n(λ(R)) = 4.52, the refractive index of green laser (λ(G) = 525nm) in Si is n(λ(G)) = 4.18, and the refractive index of blue laser (λ(B) = 465nm) in Si is n(λ(B)) = 3.86. If the projected light is incident perpendicularly on the resonant layer F, then according to the above formula, the thickness of the resonant layer F that produces resonance enhancement for red laser is d(R) = 71.1 × l, the thickness of the resonant layer F that produces resonance enhancement for green laser is d(G) = 125.6 × m, and the thickness of the resonant layer F that produces resonance enhancement for blue laser is d(B) = 180.7 × n. Therefore, it can be determined that the thickness d of the resonant layer is controlled within the range of 180nm to 250nm to achieve resonance enhancement for all three colors of laser. Through calculation, it can be concluded that the wavelength selective reflection effect is better when the thickness d of the resonant layer F is around 220nm.

[0067] It is worth noting that the above values ​​are calculated based on the case where the projected light is incident perpendicularly on the resonant layer F. In actual applications, the incident angle of the projected light on the resonant layer F can be in the range of 0 to 20°. Therefore, the incident angle must also be considered when calculating the thickness of the resonant layer F.

[0068] When the material of the resonant layer F is Si and the thickness is controlled at around 220nm, the reflectivity of the resonant layer for the visible light band can be seen in Figure 8. The positions shown by the dashed lines in Figure 8 correspond to wavelengths of 465nm, 525nm, and 643nm, which are the center wavelengths of the projection light (three-color laser) emitted by the projection device in this embodiment. As can be seen from Figure 8, when the resonant layer F is Si, the reflectivity for the three-color projection light is greater than the reflectivity for other bands. Therefore, the resonant layer F has the characteristic of selective reflection of the projection light. Applying the resonant layer F in the projection screen can improve the contrast of the projection light.

[0069] The resonant layer F can be fabricated using sputtering or vapor deposition. The following description uses sputtering as an example to illustrate the fabrication of the resonant layer F. Figure 9 is one schematic diagram of the fabrication method of the resonant layer provided in this application embodiment; Figure 10 is another schematic diagram of the fabrication method of the resonant layer provided in this application embodiment.

[0070] In some embodiments, the Fresnel lens layer 12 can be fabricated using a flexible material, and the completed Fresnel lens layer 12 is a sheet. As shown in FIG9, the sheet of the Fresnel lens layer 12 can be placed on the rotating device G, with each lens unit of the Fresnel lens layer 12 facing outward. The sputtering source Z is disposed adjacent to the rotating device G, and the sputtering material of the sputtering source Z is Si. While the rotating device G rotates, the sputtering material Si is formed on the surface of the lens unit of the Fresnel lens layer to form a resonant layer F.

[0071] In some embodiments, the Fresnel lens layer 12 can be made of a flexible material and can be manufactured using a roll-to-roll process, resulting in a rolled-up Fresnel lens layer 12. As shown in Figure 10, the Fresnel lens layer 12 can be mounted on a roll-to-roll transmission device C, with each lens unit of the Fresnel lens layer 12 facing outwards. The sputtering source Z is positioned adjacent to the transmission device C, and the sputtering material of the sputtering source Z is Si. While the transmission device C moves the Fresnel lens layer 12, the sputtering material Si is formed on the surface of the lens units of the Fresnel lens layer, forming a resonant layer F.

[0072] This application uses Si as the sputtering material for illustrative purposes only. In practical applications, other sputtering materials can also be used. Semiconductor materials can also be doped into the sputtering material to reduce resistance. When using a high-resistivity target, radio frequency sputtering can also be used for fabrication; this is not a limitation.

[0073] In addition, the resonant layer F can also be fabricated using chemical vapor deposition (CVD), plasma enhanced CVD (PECVD), or thermal chemical vapor deposition (TCVD).

[0074] For example, when fabricating the resonant layer F using PECVD, silane (SiH4) is used as the raw material. Silane gas is introduced into a vacuum chamber (a few Pa to tens of Pa), and a high-frequency voltage is applied. After the silane decomposes, it becomes a plasma state, and Si is deposited on the surface of the lens unit of the Fresnel lens layer.

[0075] When the resonant layer F is fabricated using thermochemical vapor deposition, silane (SiH4) is used as the raw material. Silane gas is introduced into a vacuum chamber and heated to over 500°C to decompose the silane, depositing Si on the surface of the lens unit of the Fresnel lens layer.

[0076] The resonant layer F can be fabricated using the CVD method, which can also be combined with the process shown in Figure 9 or 10, and will not be elaborated here.

[0077] Figure 11 is a third schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application.

[0078] To further improve the contrast of the projected image, avoid interference from ambient light, or meet specific white balance requirements, a wavelength-selective absorption layer X can be added to the projection screen, as shown in Figure 9. The wavelength-selective absorption layer X has a higher absorption rate for light within a set wavelength range than for other wavelengths, exhibiting wavelength-selective absorption characteristics for incident light.

[0079] In some embodiments, the wavelength-selective absorption layer X has a high absorption rate for all wavelengths other than the wavelength corresponding to the projected light, thereby achieving less absorption of the projected light and more absorption of ambient light other than the projected light. Combined with the wavelength-selective reflection characteristics of the resonant layer F, the contrast of the projected image can be further improved.

[0080] It is worth noting that the aforementioned projection light refers to the light emitted by the projection device. In this embodiment, a three-color laser light source is used, so the projection light consists of red, green, and blue lasers. Red, green, and blue lasers each have a center wavelength of 643nm, 525nm, and 465nm, respectively. However, the three-color lasers are not of a single wavelength but cover a certain wavelength band, with higher energy near the center wavelength. Correspondingly, the wavelength-selective absorption layer X cannot achieve a drastic change in absorption rate for a precise wavelength. Therefore, the wavelength-selective absorption layer X can be set to have a lower absorption rate for the center wavelength of the three-color lasers and a higher absorption rate for the light in other wavelength bands.

[0081] In some embodiments, the wavelength-selective absorption layer X can also be used to adjust the white balance of the projection screen or the ratio of the three-color laser.

[0082] Figure 12 shows one of the reflectivity curves of the resonant layer and the transmittance curve of the wavelength-selective absorption layer provided in the embodiments of this application.

[0083] As shown in Figure 12, the resonant layer F has high reflectivity for all three colors of laser light emitted from the projection device, but low reflectivity for light of other wavelengths, thus exhibiting wavelength-selective reflection. However, since the resonant layer F is a single film layer, its refractive index and thickness are compromise values ​​for the three colors of laser light, making it impossible to achieve the same level of reflectivity for all three colors. As can be seen from Figure 12, the resonant layer F has lower reflectivity for blue laser light than for red and green laser light. This will result in the ratio of the three colors of laser light in the final light reflected from the projection screen not achieving the required white balance.

[0084] A wavelength-selective absorption layer X is set in the projection screen. By utilizing the selective absorption property of the wavelength-selective absorption layer X to absorb light of a specific wavelength, the light ultimately reflected by the projection screen meets the white balance requirements.

[0085] Specifically, the white coordinates (Xw, Yw) of a projection screen are usually fixed values ​​that meet white balance requirements. (Xw, Yw) can be converted according to the following formulas: Xw=X / (X+Y+Z); Xy=Y / (X+Y+Z);

[0086] in:

[0087] X, Y, and Z are the tristimulus values ​​of the XYZ color space, calculated using the formula above. and L(λw) is the color matching function, and L(λw) is the light power distribution function of the projection screen when displaying a full white image.

[0088] L(λw) can be determined according to the following formula: L(λw)=l×L(R(λ))+m×L(G(λ))+n×L(B(λ));

[0089] Where L(R(λ)), L(G(λ)), and L(B(λ)) are the optical power distribution functions of the three-color lasers when a completely white image is displayed on the projection screen. l, m, and n are weighting coefficients.

[0090] The aforementioned weighting coefficients are influenced by the reflectivity of the resonant layer F and the transmittance of the wavelength-selective absorption layer X. The wavelength-selective absorption layer X is typically positioned before the resonant layer F. This means that after the projected light enters the projection screen, it must first pass through the wavelength-selective absorption layer X, then enter the resonant layer F, be reflected by F, and then pass through the wavelength-selective absorption layer X again before finally exiting the screen. This requires passing through the wavelength-selective absorption layer X twice. Therefore, we can obtain: R sw (λ R )×(T(λ R )) 2 =l; R sw (λ G )×(T(λ G )) 2 =m; R sw (λ B )×(T(λ B )) 2 =n;

[0091] R sw Let T be the reflectivity of the resonant layer and T be the transmittance of the wavelength-selective absorption layer.

[0092] So, after continuously adjusting R swT can adjust the weighting coefficients l, m, and n to ensure that the projection screen meets the required white balance.

[0093] As shown in Figure 12, in order to achieve the white balance required by the projection screen, the transmittance of the wavelength selective absorption layer X for blue laser can be greater than that for green laser, and the transmittance of the wavelength selective absorption layer X for green laser can be greater than that for red laser, thereby increasing the proportion of blue and green light.

[0094] Figure 13 shows the reflectivity curve of the resonant layer and the transmittance curve of the wavelength-selective absorption layer provided in the embodiments of this application.

[0095] In some embodiments, ambient light in the room is a major factor affecting the projection image display effect, and the peak wavelength of current lighting is typically around 550nm or 580nm. Therefore, increasing the absorption rate of the wavelength-selective absorption layer X for the lighting light band can reduce the impact of the lighting light on the projection display effect.

[0096] As shown in Figure 13, the wavelength selective absorption layer X has a high absorption rate for light in the 500nm to 680nm band, which makes the transmission rate of the projection screen low for light in this band. The projection screen can absorb the incident illumination light, and combined with the enhanced reflection of the three-color laser by the resonant layer, a better display effect can be achieved.

[0097] The wavelength-selective absorption layer X can be fabricated by mixing various light-absorbing materials. Different types of light-absorbing materials can absorb different wavelengths, thereby achieving wavelength-selective absorption. The light-absorbing materials can include pigments or dyes, which can be the same materials used to make color filters in display products (such as color resist materials), without specific limitations here.

[0098] In addition, these light-absorbing materials can be mixed in different film layers of the projection screen so that these film layers can also have the function of wavelength selective absorption, thereby reducing the number of film layers in the projection screen.

[0099] In some embodiments, as shown in FIG11, the projection screen further includes an adhesive layer 14, which is located between the surface functional layer 11 and the Fresnel lens layer 12, and is used to bond the surface functional layer 11 and the Fresnel lens layer 12 together. The adhesive layer 14 may be made of adhesive materials such as epoxy resin, acrylic resin, and silicone resin, and is not limited thereto.

[0100] The lens unit 121 of the Fresnel lens layer 12 is located on the side opposite to the adhesive layer 14. The surface of the Fresnel lens layer 12 opposite to the lens unit 121 is a plane. The adhesive layer 14 bonds the surface functional layer 11 and the plane of the Fresnel lens layer 12 together.

[0101] In some embodiments, as shown in FIG11, the light-absorbing material described above can be mixed into the adhesive layer 14 to reuse the adhesive layer 14 as a wavelength-selective absorption layer X. This film layer is used to fix the surface functional layer 11 and the Fresnel lens layer 12 to each other, and also has the property of selectively absorbing incident light.

[0102] Figure 14 is a fourth schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application, and Figure 15 is a fifth schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application.

[0103] In some embodiments, the projection system provided in this application uses a laser light source. Lasers have high collimation, resulting in a small divergence angle for the projected light. The high collimation of the light reflected from the projection screen also leads to a smaller viewing angle. In some embodiments, the surface functional layer 11 can diffuse the light, thereby increasing the diffusion angle of the projected light after passing through the surface functional layer 11, which is beneficial for expanding the visible range of the projection screen. In addition, the surface functional layer 11 also helps reduce laser speckle and optimize the projected image.

[0104] As shown in Figures 14 and 15, the surface functional layer 11 may include a first substrate 111 and a diffusion layer 112. The first substrate 111 serves as the substrate for the diffusion layer 112. The Fresnel lens layer 12 may include a second substrate 122 and a plurality of lens units 121 located on the second substrate 122. The second substrate 122 can serve as the substrate for fabricating the plurality of lens units 121. An adhesive layer 14 bonds the first substrate 111 and the second substrate 122 together.

[0105] The first substrate 111 and the second substrate can be made of the same material or different materials, and can be made of, but is not limited to, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polymethyl methacrylate (PMMA), triacetylcellulose (TAC), cycloolefin polymer (COP), thermoplastic polyurethane (TPU), polyvinyl chloride (PVC), polyimide (PI), polyamide (PA), polyethylene (PE), polypropylene (PP), etc.

[0106] The diffusion layer 112 can be made of resin material or inorganic material containing diffusion particles. The diffusion particles can be, but are not limited to, silicon dioxide particles, aluminum oxide particles, titanium oxide particles, cerium oxide particles, zirconium oxide particles, tantalum oxide particles, zinc oxide particles, magnesium fluoride particles, etc. The diffusion layer 112 can be made using various coating methods, and no limitation is made here.

[0107] The lens unit 121 can be formed by coating a mold having the same shape as the lens unit with UV-curable resin and then imprinting and UV-curing the UV-curable resin using a second substrate 122.

[0108] In some embodiments, the Fresnel lens layer 12 can also be a one-piece structure, with one surface of the Fresnel lens layer 12 serving as a lens unit 121, and the surface opposite to the lens unit 121 being a flat surface. Using a one-piece Fresnel lens layer eliminates the need for the process of combining the substrate with the lens unit, further simplifying the manufacturing process. The one-piece Fresnel lens layer 12 can be manufactured using thermoforming, and the Fresnel lens layer can be made of thermoplastic materials; no limitation is made here.

[0109] In some embodiments, as shown in FIG14, the wavelength selective absorption layer X may be located between the first substrate 111 and the adhesive layer 14. In some embodiments, as shown in FIG15, the wavelength selective absorption layer X may be located between the second substrate 122 and the adhesive layer 14.

[0110] The wavelength selective absorption layer X can be set separately. It can be formed by mixing light-absorbing materials into the resin material, and then coating the resin mixed with light-absorbing materials onto the surface of the first substrate 111 or the second substrate 122 and curing it.

[0111] It is worth noting that if the wavelength-selective absorption layer X is coated on the surface of the first substrate 111, the wavelength-selective absorption layer can be formed on the surface of the first substrate 111 before or after the diffusion layer 112 is coated. If the wavelength-selective absorption layer X is coated on the surface of the second substrate 122, since the second substrate 122 also needs to be used to fabricate a Fresnel lens, in order to avoid affecting the fabrication of the Fresnel lens, the wavelength-selective absorption layer X can be formed on the surface of the second substrate 122 before fabricating the Fresnel lens.

[0112] Figure 16 is a sixth schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application, and Figure 17 is a seventh schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application.

[0113] In some embodiments, as shown in FIG16, a light-absorbing material can be mixed into the material of the first substrate 111, so that the first substrate 111 serves as the substrate of the diffusion layer 112 while also having wavelength-selective absorption characteristics. Similarly, in some embodiments, as shown in FIG17, a light-absorbing material can be mixed into the second substrate 122, so that the second substrate 122 serves as the substrate of the lens unit 121 while also having wavelength-selective absorption characteristics.

[0114] Figure 18 is the eighth schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application.

[0115] In some embodiments, as shown in FIG18, light-absorbing materials and diffusion materials can be mixed into resin at the same time, and then the resin can be coated on the surface of the first substrate 111 to form a diffusion layer 112, so that the diffusion layer 112 has both diffusion and wavelength-selective absorption functions.

[0116] Figure 19 is a schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application.

[0117] In some embodiments, as shown in FIG19, the surface functional layer may consist only of a first substrate 111, which is in contact with the adhesive layer 14 and bonded to the Fresnel lens layer 12 via the adhesive layer 14. The material of the first substrate 111 contains both diffusing and light-absorbing materials. Therefore, when forming the first substrate 111, it can be made to have light diffusion capability and a certain degree of haze, thereby expanding the field of view and preventing light from forming a clear image on the ceiling. It also has the function of wavelength selective absorption, eliminating the need for a separate wavelength selective absorption layer.

[0118] In some embodiments, the surface functional layer may consist only of a first substrate 111. The material of the first substrate 111 includes a diffusing material and a light-absorbing material, and the surface of the first substrate 111 facing away from the adhesive layer 14 is an uneven surface. This uneven surface can be formed by sandblasting or alkaline treatment of the surface of the first substrate 111, and is not limited thereto. The uneven surface of the first substrate 111 can play a certain role in light diffusion and fogging, thereby expanding the viewing angle and reducing ceiling glare. At the same time, the first substrate 111 contains light-absorbing materials, thus also having the function of wavelength selective absorption.

[0119] Figure 20 is a schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application.

[0120] In some embodiments, as shown in FIG20, the lens unit 121 of the Fresnel lens layer 12 is located on the side facing the adhesive layer 14, and the resonant layer F is located on the surface of the lens unit 121 of the Fresnel lens layer 12. Therefore, the resonant layer F is buried in the adhesive layer 14, which provides a certain degree of protection for the resonant layer F.

[0121] Similarly, light-absorbing materials can be mixed into the adhesive layer 14 to give the adhesive layer 14 wavelength-selective absorption, thereby further improving the contrast of the projected image.

[0122] Figure 21 is an eleventh schematic diagram of the cross-sectional structure of the projection screen provided in the embodiment of this application.

[0123] In some embodiments, as shown in FIG21, the projection screen may also include only a Fresnel lens layer 12, a resonant layer F located on the surface of each lens unit 121 of the Fresnel lens layer 12, and a surface functional layer 11. The lens units 121 of the Fresnel lens layer 12 are arranged on the side facing the viewer, and the surface functional layer 11 is located on the resonant layer F. In this case, the surface functional layer 11 may use a diffusion material covering the resonant layer F, and the diffusion material may be impregnated with a light-absorbing material to form particles. The diffusion material is formed on the surface of the resonant layer F by means of coating, spraying, etc., so that it has both light diffusion and wavelength selective absorption functions. This projection screen structure has a small thickness.

[0124] As shown in Figures 20 and 21, the Fresnel lens layer is located on the back of the projection screen. No light enters the Fresnel lens layer during projection display. Therefore, the requirements for the light transmittance and damage of the Fresnel lens layer 12 are reduced. It is no longer necessary to use expensive optical materials to make the Fresnel lens layer 12. It can be made with cheaper industrial materials, thereby reducing production costs.

[0125] Based on the same inventive concept, this application also provides a projection system, as shown in FIG1. ​​The projection system includes: a projection device 2 and a projection screen 1 located on the light-emitting side of the projection device 2.

[0126] Figure 22 is a schematic diagram of the projection device provided in an embodiment of this application.

[0127] As shown in Figure 22, the projection device includes: a light source device 21, an illumination light path 22, a display element 23, and a lens 24. The illumination light path 22 is located on the light-emitting side of the light source device 21, the display element 23 is located on the light-emitting side of the illumination light path 22, and the lens 24 is located on the light-emitting side of the display element 23.

[0128] The light source device 21 can be a laser light source device. The laser light source device can be a monochromatic laser, a laser capable of emitting multiple colors of laser light, or multiple lasers emitting different colors of laser light. When the laser light source device uses a monochromatic laser, the laser display device also needs to include a color wheel for color conversion. The monochromatic laser, in conjunction with the color wheel, can achieve the purpose of emitting different primary colors of light in a sequential manner. When the laser light source device uses a laser capable of emitting multiple colors of laser light, it is necessary to control the laser light source to emit different colors of laser light as primary colors in a sequential manner.

[0129] In this embodiment, the light source device can be a three-color laser light source device, which can be a laser that emits three primary color lasers, such as an MCL laser; or it can include a red laser, a green laser, and a blue laser that emit three primary color lasers respectively. Using a three-color laser light source device is beneficial for improving the color gamut of the projected image, resulting in better color performance and accurate reproduction of the input image.

[0130] The illumination light path 22 is located on the light-emitting side of the light source device 21. The illumination light path 22 collimates the emitted light from the light source device 21 and allows the emitted light from the light source device 21 to enter the display element 23 at a suitable angle. The illumination light path 22 may include multiple lenses or lens groups, which are not limited here.

[0131] Display element 23 is used to modulate the incident light. In a specific implementation, display element 23 can be a digital micromirror device (DMD). After passing through illumination path 22, the light beam conforms to the illumination size and incident angle required by the DMD. The DMD surface includes a number of micromirrors, each of which can be individually driven to deflect. By controlling the deflection angle of the DMD, the brightness of the light incident on lens 24 is controlled.

[0132] Lens 24 is used to image the light emitted from display element 23, and the image is then projected.

[0133] In this embodiment, the projection device 2 can be an ultra-short-throw projection device, that is, the lens 24 in the projection device is an ultra-short-throw lens. Using an ultra-short-throw projection device can greatly shorten the distance between the projection device 2 and the projection screen 1, and can achieve large-size image display while shortening the projection distance.

[0134] The projection screen 1 is located on the light-emitting side of the lens in the projection device. The projection screen 1 includes a surface functional layer, a Fresnel lens layer, and a resonant layer on the surface of the lens unit of the Fresnel lens layer. The resonant layer is a single-layer thin film that can selectively reflect the projected light emitted from the projection device, while significantly reducing the reflectivity of other wavelengths of light, thereby significantly improving the contrast of the projected image. The manufacturing process of the single-layer thin film resonant layer is simpler, which helps to reduce production costs and improve production efficiency.

[0135] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0136] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A projection screen, comprising: a Fresnel lens layer; the Fresnel lens layer comprises a plurality of lens units, the lens units comprise a lens surface and a non-lens surface; the lens surface is arranged obliquely relative to a plane in which the projection screen is located; and a resonance layer, covering at least the lens surface of each of the lens units; the resonance layer is a single layer of film, and the resonance layer has a reflectivity greater than that of other wavelengths of light for projection light emitted by a projection device.

2. The projection screen of claim 1, wherein, The material of the resonance layer is a semiconductor or a semiconductor compound; The product of the refractive index and the thickness of the resonance layer satisfies a condition for resonance of the projection light emitted by the projection device.

3. The projection screen of claim 2, wherein, The refractive index of the resonance layer is greater than or equal to 2.

5.

4. The projection screen of claim 2, wherein, The extinction coefficient of the resonance layer is less than or equal to 0.

3.

5. The projection screen of claim 2, wherein, The thickness of the resonance layer is 180nm to 250nm.

6. The projection screen of claim 2, wherein, The material of the resonance layer is Si, Ge, Se, GaAs, SiC, InP or GaN. 7.The projection screen according to any one of claims 1 to 6, further comprising: a wavelength-selective absorption layer; the wavelength-selective absorption layer has an absorption rate greater than that of other wavelengths of light for light of a set wavelength range; wherein the wavelength of the projection light emitted by the projection device does not fall within the set wavelength range. 8.The projection screen according to any one of claims 1 to 6, further comprising: a wavelength-selective absorption layer; the wavelength-selective absorption layer has an absorption rate greater than that of other wavelengths of light for light of a set wavelength range; wherein the wavelength of the projection light emitted by the projection device is not identical to the set wavelength range.

9. The projection screen of claim 8, wherein, The product of the reflectivity of the resonance layer and the transmittance of the wavelength-selective absorption layer satisfies a condition for the color coordinates of the projection screen to satisfy a set white balance.

10. The projection screen of claim 9, wherein, The projection light emitted by the projection device comprises red laser light, green laser light and blue laser light; The transmittance of the wavelength-selective absorption layer for the blue laser light is greater than that for the green laser light; and the transmittance of the wavelength-selective absorption layer for the green laser light is greater than that for the red laser light.

11. The projection screen of claim 8, wherein, The set wavelength range is 430nm to 680nm. 12.The projection screen according to claim 7 or 8, further comprising: a surface functional layer, located on a side of the Fresnel lens layer facing an audience; the surface functional layer is used for diffusing emitted light; and an adhesive layer, located between the surface functional layer and the Fresnel lens layer; the adhesive layer is used for bonding the surface functional layer and the Fresnel lens layer to each other. The surface functional layer comprises a first substrate and a diffusion layer located on a surface of the first substrate; 13. The projection screen of claim 12, wherein, The Fresnel lens layer comprises a second substrate and a plurality of lens units located on a surface of the second substrate; The adhesive layer is located between the first substrate and the second substrate. The adhesive layer comprises a light-absorbing material, which is multiplexed as the wavelength-selective absorption layer; 14. The projection screen of claim 13, wherein, Alternatively, the wavelength-selective absorption layer is located between the adhesive layer and the first substrate; Alternatively, the wavelength-selective absorption layer is located between the adhesive layer and the second substrate; Alternatively, the first substrate comprises a light-absorbing material, which is multiplexed as the wavelength-selective absorption layer; ​ Or, the second substrate comprises light-absorbing material, multiplexed as the wavelength-selective absorption layer. Or, the diffusion layer comprises light-absorbing material, multiplexed as the wavelength-selective absorption layer.

15. A projection system, comprising: a projection device for emitting projection light; and a projection screen located on the light-emitting side of the projection device, the projection screen being the projection screen of any one of claims 1-14.

16. The projection system of claim 15, wherein, The projection device is an ultra-short-focus laser projection device; the projection device comprises: a three-color laser light source device for emitting three primary color lasers; a display element located on the light-emitting side of the three-color laser light source device to make the emitted laser into an image; and a lens located on the light-emitting side of the display element.

Images