Patent Description:
Projection display is increasingly used nowadays. The principle of the projection display is as follows: a projector projects image light onto a screen (known as a projection screen), the image light is reflected on the screen, and the reflected image light is received by human eyes. It seems to the human eyes as if the image light were emitted from the screen. In this way, an image is formed on the screen. Compared with the case where the projector projects image light directly onto a wall, the projection screen has a special surface microstructure design that directs the reflected image light to a viewer region. Therefore, the projection screen significantly improves the projection display effect.

Gain and uniformity are important design parameters for the projection screen. To ensure the viewing experience of the viewer, the projection screen needs to have both high gain and good brightness uniformity. The gain of the projection screen represents brightness levels in different viewing areas. Higher gain of the projection screen corresponds to better brightness experience. The uniformity is a measure of brightness differences at different viewing positions in a horizontal direction. Higher uniformity corresponds to better viewing experience.

Projection screens in the related art are wire grid structure screens. Due to the limitation of the optical structure of the screen, the uniformity of the projection screen is poor. To improve the uniformity, in the related art, scattering particles are usually added to a reflective layer of a wire grid microstructure, which leads to a lower reflectivity of the reflective layer; moreover, the scattering characteristics of the reflective layer will reduce the gain of the projection screen.

As a result, the projection screens in the related art cannot achieve both high gain and uniformity.

For instance, <CIT> Al discloses a retroreflective screen with a microstructure layer composed of corner cubes.

The present disclosure provides a projection screen with good uniformity and high gain.

A projection screen according to an embodiment of the present disclosure includes a microstructure layer, the microstructure layer including a matrix layer and a microstructure unit formed on a surface of the matrix layer. The microstructure unit includes triangular pyramid units arranged in an array. At least two of the triangular pyramid units that are arranged in a same row are identical to each other, and at least two triangular pyramid units of the triangular pyramid units that are arranged in a same column respectively have vertex angles that vary gradually, and each of the vertex angles forms between the surface of the matrix layer and an edge of one of the triangular pyramid units that has the vertex angle, wherein a projection of said edge on the surface of the matrix layer is coincident with a column direction.

In an embodiment, the vertex angles of the at least two triangular pyramid units arranged along the second direction satisfy: <MAT> where θ denotes an vertex angle of one triangular pyramid unit of the at least two triangular pyramid units, α1 denotes an incident angle of image light, α4 denotes an emergent angle of the image light, and n denotes a refractive index of the one triangular pyramid unit.

In an embodiment, a region between two adjacent triangular pyramid units of the triangular pyramid units that are arranged along the first direction is a light transmission region.

In an embodiment, an opaque structure is disposed between two adjacent triangular pyramid units of the triangular pyramid units that are arranged along the first direction.

In an embodiment, an optical coating layer is disposed between two adjacent triangular pyramid units of the triangular pyramid units that are arranged along the first direction, and the optical coating layer includes at least two of a reflective material, a light-absorbing material, or a light diffusion material.

In an embodiment, one of anti-structure prisms is disposed between two adjacent triangular pyramid units of the triangular pyramid units that are arranged along the first direction; wherein each of the triangular pyramid units is centrally symmetrical with one anti-structure prism of the anti-structure prisms that is adj acent to the triangular pyramid unit, a light output surface of the triangular pyramid unit and a light output surface of the one neighboring anti-structure prism face towards a same direction, and vertex angles of at least two of the anti-structure prisms arranged along a direction opposite to the second direction vary gradually.

In an embodiment, one of anti-structure prisms is disposed between two adjacent triangular pyramid units of the triangular pyramid units that are arranged along the first direction, and the anti-structure prisms have a same structure as the triangular pyramid units, wherein each of the triangular pyramid units is centrally symmetrical with one anti-structure prism of the anti-structure prisms that is adjacent to the triangular pyramid unit, and a light output surface of the triangular pyramid unit and a light output surface of the one anti-structure prism face towards a same direction.

In an embodiment, an angle between two surfaces that intersect each other to form the edge is within a value range of <NUM>°±<NUM>°.

In an embodiment, the projection screen further includes at least two of a diffusion layer, a reflective layer, or a protective layer. The microstructure unit is disposed on the diffusion layer, and a light output surface of one of the triangular pyramid units is attached to and fixed to the diffusion layer. The reflective layer covers the microstructure unit, and the protective layer covers an outermost side of the projection screen.

In an embodiment, the reflective layer is doped with scattering particles for scattering light.

In an embodiment, the diffusion layer is a layer structure with a uniform thickness, and the diffusion layer is the matrix layer of the projection screen.

In an embodiment, the thickness of the diffusion layer ranges from <NUM> to <NUM>.

The projection screen provided by the present disclosure includes multiple triangular pyramid units arranged in an array. Vertex angles of the triangular pyramid units vary gradually according to a predetermined relationship, so that image light transmitted from a projector is reflected by a microstructure layer having the triangular pyramid units and then converged in a range centered around human eyes, to reduce brightness differences at different viewing positions, thereby ensuring good uniformity and high gain of the projection screen.

The primary objective of the present disclosure is as follows: for a projection screen including multiple triangular pyramid units arranged in an array, vertex angles of the triangular pyramid units vary gradually in such a manner that image light transmitted from a projector is reflected by a microstructure layer having the triangular pyramid units and then converged in a range centered around human eyes, to reduce brightness differences at different viewing positions, thereby ensuring good brightness uniformity and high gain of the projection screen. In this way, both good brightness uniformity and high gain are achieved.

Based on the above objective, the following clearly and completely describes the technical solutions in the embodiments of the present disclosure with reference to the accompanying drawings in the embodiments of the present disclosure. It is understandable that the specific embodiments described herein are merely intended to explain the present disclosure, rather than to limit the present disclosure. The following embodiments and technical features in the embodiments can be combined with each other when there is no conflict therebetween. It should also be noted that, for convenience of description, only a partial structure related to the present disclosure rather than all the structure is shown in the accompany drawings. All other embodiments obtained by the person of ordinary skill in the art based on the embodiments of the present disclosure without creative efforts should fall within the protection scope of the present disclosure.

<FIG> is a top view of a partial structure of a microstructure layer of a projection screen according to a first embodiment of the present disclosure. <FIG> is a cross-sectional view of the projection screen in <FIG> taken along direction A-A. Referring to <FIG>, the microstructure layer of the projection screen <NUM> includes a matrix layer <NUM> and a microstructure unit formed on a surface of the matrix layer <NUM>, and the microstructure unit includes multiple triangular pyramid units <NUM> arranged in an array.

<FIG> is a perspective view of a triangular pyramid unit <NUM> shown in <FIG>. Referring to <FIG>, a single triangular pyramid unit <NUM> includes six straight edges: edge <NUM>, edge <NUM>, edge <NUM>, edge <NUM>, edge <NUM>, and edge <NUM>. The edge <NUM>, the edge <NUM>, and the edge <NUM> are connected end to end sequentially to form a triangular first surface <NUM>; the edge <NUM>, the edge <NUM>, and the edge <NUM> are connected end to end sequentially to form a triangular second surface <NUM>; the edge <NUM>, the edge <NUM>, and the edge <NUM> are connected end to end sequentially to form a triangular third surface <NUM>; the edge <NUM>, the edge <NUM>, and the edge <NUM> are connected end to end sequentially to form a triangular fourth surface <NUM>.

<FIG> is a view of the triangular pyramid unit <NUM> in <FIG> in a vertical viewing direction. Referring to <FIG>, an angle θ between the edge <NUM> and the first surface <NUM> is a vertex angle. <FIG> is a view of the triangular pyramid unit <NUM> in <FIG> in a horizontal viewing direction. Referring to <FIG> and <FIG>, an angle β between the third surface <NUM> and the fourth surface <NUM> is a span angle.

Referring to <FIG>, the first surfaces <NUM> of all triangular pyramid units <NUM> are located in a same plane, for example, located on a matrix layer <NUM> with a uniform thickness. The span angles β of all triangular pyramid units <NUM> face towards a same side. The vertex angles θ of all triangular pyramid units <NUM> in a row direction face towards a same direction, e.g., facing upwards; all triangular pyramid units <NUM> in a column direction are aligned one by one from top to bottom, and the vertex angles θ thereof also face towards a same direction. All triangular pyramid units <NUM> arranged along a first direction/a row direction D1 (e.g., a horizontal direction x shown in <FIG>) are identical, which indicates that structures and arrangement patterns thereof are identical. That is, the vertex angles θ of the triangular pyramid units <NUM> arranged along the first direction D1 are the same. The vertex angles θ of the triangular pyramid units <NUM> arranged along a second direction/a column direction D2 (e.g., a vertical direction y shown in <FIG>) are different.

In the present disclosure, referring to <FIG>, and <FIG>, after image light transmitted from a projector is incident on the projection screen <NUM>, the image light is refracted by the first surface <NUM> and then irradiated on the third surface <NUM> or the fourth surface <NUM>. A part of light reflected by the third surface <NUM> (a light component in the horizontal direction as shown in <FIG>) is irradiated to the fourth surface <NUM>, reflected by the fourth surface <NUM>, and transmitted by the first surface <NUM> to human eyes. Another part of light reflected by the third surface <NUM> (a light component in the vertical direction as shown in <FIG>) is irradiated to the first surface <NUM> and transmitted by the first surface <NUM> to the human eyes. Similarly, a part of light reflected by the fourth surface <NUM> (e.g., a light component in the horizontal direction) is irradiated to the third surface <NUM>, reflected by the third surface <NUM>, and transmitted by the first surface <NUM> to the human eyes; another part of light reflected by the fourth surface <NUM> (e.g., a light component in the vertical direction) is irradiated to the first surface <NUM> and transmitted by the first surface <NUM> to the human eyes. The first surface <NUM> not only serves as a light incident surface of the projection screen <NUM>, but also serves as a light output surface of the projection screen <NUM>. The image light is finally transmitted by the first surface <NUM> to the human eyes.

Based on this principle, in the projection screen <NUM>, provided that the vertex angles θ of the multiple triangular pyramid units <NUM> arranged along the second direction D2 satisfy a preset relationship, the image light transmitted from the projector can be reflected by the triangular pyramid units <NUM> and then converged in a range centered around the human eyes, to reduce brightness differences at different viewing positions, thereby ensuring good brightness uniformity and high gain of the projection screen. Specifically,.

In a horizontal direction, when the projector is located at a lower half part of the projection screen <NUM>, assuming that the human eyes are at a middle position of the projection screen <NUM>, the vertex angles θ gradually increase from bottom to top (with <FIG> and <FIG> as an example), so as to transmit as much image light to the position of the human eyes as possible.

In the horizontal direction, when the projector is located at an upper half part of the projection screen <NUM>, still assuming that the human eyes are at the middle position of the projection screen <NUM>, the vertex angles θ gradually increase from top to bottom (with <FIG> as an example), so as to transmit as much image light to the position of the human eyes as possible.

According to an image light transmission path shown in <FIG> (it should be understood that the image light transmission path shown in <FIG> is not an actual image light transmission path; sizes of incident angles and reflection angles of the image light at various interfaces are not in the relationship shown in <FIG> merely illustrates an angle variation trend of the vertex angles θ in the case of different incident angles and reflection angles), the triangular pyramid unit <NUM> satisfy the following relational expressions: <MAT> <MAT> and <MAT> where θ denotes the vertex angle of the triangular pyramid unit <NUM>, α1 denotes an incident angle of the image light when it is transmitted to the first surface <NUM> during incidence, α2 denotes a refraction angle of the image light after it is refracted by the first surface <NUM> during incidence, α3 denotes an incident angle of the image light when it is transmitted to the first surface <NUM> during emergence, α4 denotes an emergent angle of the image light, and n is a refractive index of the triangular pyramid unit <NUM>.

The following relational expression <NUM> can be derived from the above three relational expressions:
<MAT>.

In other words, provided that the vertex angles θ of the triangular pyramid units <NUM> arranged along the second direction D2 satisfy the relational expression <NUM> (namely, the above predetermined relationship), in the vertical direction y, the incident angles α1 and the emergent angles α4 change continuously between adjacent triangular pyramid units <NUM>, and working angles θ of adjacent triangular pyramid units <NUM> on the projection screen <NUM> also change continuously. That is, as shown in <FIG>, the vertex angles θ1, θ2 and θ3 of three adjacent triangular pyramid units <NUM> in the vertical direction change continuously according to the relational expression <NUM>.

When the projector is located in the lower half part of the projection screen <NUM>, assuming that the human eyes are at the middle position of the projection screen <NUM> and light beams emitted by the projector are cone-shaped, the triangular pyramid unit <NUM> at the lowermost of the projection screen <NUM> has a minimum incident angle α1 and a maximum emergent angle α4, and the triangular pyramid units <NUM> located at higher positions of the projection screen <NUM> have gradually increasing incident angles α1 and gradually decreasing emergent angles α4. The incident angle α1 and the emergent angle α4 vary within a range of <NUM>°-<NUM>°, that is: <MAT> increases gradually and <MAT> decreases gradually, so <MAT> increases gradually.

It can be seen that the vertex angles θ gradually increase from bottom to top of the projection screen <NUM>.

When the projector is located in the upper half part of the projection screen <NUM>, assuming that the human eyes are at the middle position of the projection screen <NUM> and light beams emitted by the projector are cone-shaped, the triangular pyramid unit <NUM> at the uppermost of the projection screen <NUM> has a minimum incident angle α1 and a maximum emergent angle α4, and the triangular pyramid units <NUM> located at lower positions of the projection screen <NUM> have gradually increasing incident angles α1 and gradually decreasing emergent angles α4. The incident angle α1 and the emergent angle α4 vary within a range of <NUM>°-<NUM>°, that is: <MAT> decreases gradually and <MAT> increases gradually, so <MAT> decreases gradually.

It can be seen that the vertex angle θ gradually decreases from bottom to top of the projection screen <NUM>.

It can be learned from the above that, in the vertical direction y of the projection screen <NUM>, by setting different working angles θ at different height positions, all the image light transmitted from the projector to different positions of the projection screen <NUM> can be converged within the range where the human eyes are located, as shown in <FIG>.

In an actual scenario, both the third surface <NUM> and the fourth surface <NUM> of the triangular pyramid unit <NUM> are treated with physical vapor deposition (PVD) to achieve a surface reflectivity of <NUM>%. With this implementation scenario as an example, as a viewer moves away from the central position of the projection screen <NUM> in the horizontal direction, i.e., as a horizontal viewing angle changes, variations of brightness uniformity of the projection screen <NUM> in this embodiment and an existing projection screen <NUM> are as shown in <FIG>. The brightness uniformity is also known as <NUM>-point uniformity. With reference to <FIG>, <FIG> points are uniformly distributed on half of the projection screen <NUM> (for example, the left half of the screen), the brightness being L (n, n = <NUM>, <NUM>. The brightness uniformity L0 is expressed as a ratio of minimum brightness min L(n) to central luminance L(<NUM>), that is, <MAT>.

It can be learned from <FIG> that, the brightness uniformity of the projection screen <NUM> is maintained at <NUM>% or above, which is much higher than a brightness uniformity of the projection screen <NUM> in the related art. In this case, the gain of the projection screen <NUM> is <NUM>, which is much greater than the gain of <NUM>, thus achieving high gain.

Referring to <FIG>, γ is an angle between the second surface <NUM> and the first surface <NUM>. A larger value of γ causes a larger area of the third surface <NUM> and a larger area of the fourth surface <NUM>, and in this case, the triangular pyramid unit <NUM> has higher reflection efficiency and higher energy utilization for the image light emitted from the projector. In practical application, considering the draftability of the triangular pyramid unit <NUM>, the value of γ ranges from <NUM>° to <NUM>°.

To improve the light reflection efficiency, the third surface <NUM> and the fourth surface <NUM> can be coated with a reflective material. The reflective coating can be a mixture of a metal reflective material (such as aluminum or silver) and other additives. The additives include a particular proportion of mixture of a leveling agent, a wetting agent, a defoaming agent and the like that are used to improve a coating effect, or a particular proportion of mixture of anhydrous acetone, anhydrous xylene, anhydrous cyclohexanone, anhydrous butanone, ethyl acetate and anhydrous butyl acetate, and the like. Depending on the actual application scenario, an appropriate diffusion material can also be added to the reflective coating to enhance the diffusion effect. The diffusion material includes, but not limited to, epoxy, acrylic or silicone organic resin particles, or other inorganic scattering materials. The second surface <NUM> is a non-working surface and can be painted black.

Referring to <FIG> again, in the horizontal direction x, the span angle β is an angle between the third surface <NUM> and the fourth surface <NUM>, and the value of β is in a range of <NUM>°±<NUM>°. When β=<NUM>°, after the image light transmitted from the projector is incident on the projection screen <NUM>, the image light is reflected by the third surface <NUM> and the fourth surface <NUM>, to be transmitted to the first surface <NUM>, and then refracted back to the projector in a direction the same as the incident direction. As shown in <FIG>, at different positions in the horizontal direction, the image light transmitted from the projector to different positions of the projection screen <NUM> all return back to the projector along the original paths. When β≠<NUM>°, the image light transmitted from the projector to different positions of the projection screen <NUM> cannot return to the projector along the original paths, but becomes a focal line in the horizontal direction of the observing plane. It is assumed that δ=<NUM>°-β, where a larger absolute value of δ corresponds to a longer focal line.

Referring to <FIG> again, the projection screen <NUM> can further include a diffusion layer <NUM>, a reflective layer <NUM>, and a protective layer <NUM>, and can include any combination thereof. The triangular pyramid units <NUM> arranged in an array forms an optical structure layer of the projection screen <NUM>. The optical structure layer can be prepared by heat embossing or UV glue transfer on a transparent substrate <NUM>. The transparent substrate <NUM> includes, but not limited to, organic materials such as polyethylene terephthalate (PET), polycarbonate (PC), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), etc. The substrate <NUM> can be formed by a diffusion layer <NUM> with a uniform thickness. The thickness of the diffusion layer <NUM> can be within a range from <NUM> to <NUM>, and the diffusion layer <NUM> can be made of epoxy, acrylic or silicone organic resin particles, or other inorganic scattering materials. The optical structure layer is attached and fixed to the diffusion layer <NUM>, and the first surfaces <NUM> of the triangular pyramid units <NUM> are attached and fixed to the diffusion layer <NUM>. The reflective layer <NUM> covers the optical structure layer. The reflective layer <NUM> can be doped with scattering particles for scattering light, to enhance the light scattering effect. The protective layer <NUM> covers an outermost side of the projection screen <NUM>. The protective layer <NUM> can be prepared by using a water and oxygen barrier material, to project the internal structure. The triangular pyramid units in the same row are identical to each other, and the triangular pyramid units in the same column respectively have vertex angles that vary gradually.

The diffusion layer <NUM>, the optical structure layer, the reflective layer <NUM>, and the protective layer <NUM> can be attached to and fixed to each other together through a glue, to jointly form the projection screen <NUM> with high gain and good uniformity.

Referring to <FIG> again, a region between two adjacent triangular pyramid units <NUM> that are arranged along the horizontal direction x is a light transmission region <NUM>. In other words, half region of the optical structure layer in an embodiment is provided with triangular pyramid microstructures, and the other half region is vacant. In this way, the projection screen <NUM> of this embodiment is applicable to scenarios where both a foreground image and background content need to be displayed.

<FIG> is a top view of a partial structure of a microstructure layer of a projection screen according to a second embodiment of the present disclosure. The present disclosure adopts the same reference numeral to represent identical elements. Referring to <FIG>, different from the foregoing embodiment, a black coating layer <NUM> is provided in a vacant region of the microstructure unit in an embodiment, that is, in a region between two adjacent triangular pyramid units <NUM> in a same row. The black coating layer <NUM> is configured to absorb light irradiated thereon. Therefore, light from the back of the projection screen <NUM> (which can be considered as ambient light) can be absorbed by the black coating layer <NUM>, so that the projection screen <NUM> provided by the embodiment has high resistance against the ambient light, and is applicable to scenarios where it is unnecessary to see the background.

The projection screen <NUM> can also be provided with other opaque structures in the region between two adjacent triangular pyramid units <NUM> in the same row. Light from the back of the projection screen <NUM> can be shielded by the opaque structure, so that the projection screen <NUM> of this embodiment has high resistance against ambient light, and is applicable to scenarios where it is unnecessary to see the background.

<FIG> is a top view of a partial structure of a microstructure layer of a projection screen according to a third embodiment of the present disclosure. As shown in <FIG>, different from the foregoing embodiment, an optical coating layer <NUM> is provided between two adjacent triangular pyramid units <NUM> in the same row. The optical coating layer <NUM> can include a metal reflective material, a black absorption material, other additives, and a diffusion material, and proportions of the materials of the reflective coating can be adjusted according to actual requirements, to adjust the light transmittance and light reflectivity of the optical coating layer <NUM>. The optical coating layer <NUM> not only has a light absorbing capability, but also has light reflection and light diffusion capabilities. Therefore, the projection screen <NUM> of the embodiment not only has high resistance against ambient light to be applicable to scenarios where it is unnecessary to see the background, but also has the light reflection and light diffusion capabilities to improve the intensity of light transmitted to human eyes, thus achieving high gain.

<FIG> is a top view of a partial structure of a microstructure layer of a projection screen according to a fourth embodiment of the present disclosure. As shown in <FIG>, different from the foregoing embodiment shown in <FIG>, an anti-structure prism <NUM> is provided between two adjacent triangular pyramid units <NUM> in the same row. The structure of the anti-structure prism <NUM> is substantially the same as a structure of the triangular pyramid unit <NUM>. In a direction of view perpendicular to the projection screen <NUM>, with reference to <FIG>, any one of the triangular pyramid units <NUM> is centrally symmetrical with its neighboring anti-structure prism <NUM>. The first surface <NUM> of the triangular pyramid unit <NUM> and a first surface of its neighboring anti-structure prism <NUM> face towards the same direction. The difference lies in that, the vertex angles of the triangular pyramid units <NUM> vary gradually in a direction opposite to a direction in which the vertex angles of the anti-structure prisms <NUM> gradually. For example, the vertex angles θ of the multiple triangular pyramid units <NUM> gradually increase from bottom to top along the projection screen <NUM>, while the vertex angles of the plurality of anti-structure prisms <NUM> gradually increase from top to bottom of the projection screen <NUM>. In this way, the vertex angles of the triangular pyramid units <NUM> and the vertex angles of the anti-structure prisms <NUM> face towards the same direction. For example, as shown in <FIG>, the vertex angles of the triangular pyramid units <NUM> face upwards, while the vertex angles of the anti-structure prisms <NUM> face downwards. The second surface <NUM> of the triangular pyramid unit <NUM> is in the shape of an obtuse triangle while the second surface <NUM> of the anti-structure prism <NUM> is in the shape of an acute triangle. Therefore, after the image light enters the interior of the anti-structure prism <NUM> through the first surface thereof (i.e., the light incident surface), the image light is reflected by the second surface of the anti-structure prism <NUM>, and then transmitted to the position of the human eyes through the first surface (i.e., the light output surface) of the anti-structure prism <NUM>.

When the first surfaces <NUM> of the triangular pyramid units <NUM> face towards the projector, the first surfaces of the anti-structure prisms <NUM> also face towards the projector. It should be understood that, the first surfaces <NUM> of all triangular pyramid units <NUM> are located in a same plane, for example, being located on a right side surface of the matrix layer <NUM> as shown in <FIG>; the first surfaces <NUM> of all anti-structure prisms <NUM> are also located in the same plane, for example, being located on the right side surface of the matrix layer <NUM> as shown in <FIG>. Based on the foregoing arrangement of the triangular pyramid units <NUM> and the anti-structure prisms <NUM>, the vertex angles of all the anti-structure prisms <NUM> satisfy the following relationship.

In the horizontal direction, when the projector faces towards the light incident surfaces (i.e., the first surfaces) of the anti-structure prisms <NUM> and is located at the lower half part of the projection screen <NUM>, assuming that the human eyes are at the middle position of the projection screen <NUM>, the vertex angles of the anti-structure prisms <NUM> increase gradually from bottom to top, and the vertex angles of the anti-structure prisms <NUM> from bottom to top also meet the foregoing relational expression <NUM>, so as to transmit as much image light to the position of the human eyes as possible.

In the horizontal direction, when the projector faces towards the light incident surfaces of the anti-structure prisms <NUM> and is located at the upper half part of the projection screen <NUM>, still assuming that the human eyes are at the middle position of the projection screen <NUM>, the vertex angles of the anti-structure prisms <NUM> increase gradually from top to bottom, and the vertex angles θ of the anti-structure prisms <NUM> from top to bottom also meet the foregoing relational expression <NUM>, so as to transmit as much image light to the position of the human eyes as possible.

The arrangement of the triangular pyramid units <NUM> can ensure good uniformity and high gain on one surface of the projection screen <NUM>. The arrangement of the anti-structure prisms <NUM> causes the image light transmitted from the projector to be also converged in the range centered around the human eyes after being reflected by the anti-structure prisms <NUM>, thereby ensuring the good uniformity and high gain of the projection screen <NUM>.

<FIG> is a top view of a partial structure of a microstructure layer of a projection screen according to a fifth embodiment of the present disclosure. As shown in <FIG>, different from the foregoing embodiment shown in <FIG>, an anti-structure prism <NUM> is also provided between two adjacent triangular pyramid units <NUM> in a same row. In a direction of view perpendicular to the projection screen <NUM>, with reference to <FIG>, although any one of the triangular pyramid units <NUM> is centrally symmetrical to its neighboring anti-structure prism <NUM>, the first surface <NUM> of the triangular pyramid unit <NUM> and the first surface of the anti-structure prism <NUM> face towards a same direction. In this way, the vertex angles of the triangular pyramid units <NUM> face towards an opposite direction to a direction in towards which the vertex angles of the anti-structure prisms <NUM> face. For example, as shown in <FIG>, the vertex angles of the triangular pyramid units <NUM> face upwards, while the vertex angles of the anti-structure prisms <NUM> face downwards.

That is, the first surfaces <NUM> of the triangular pyramid units <NUM> and the first surfaces of the anti-structure prism <NUM> all face towards the projector. In other words, in the same row, the triangular pyramid units <NUM> and the anti-structure prisms <NUM> are sequentially arranged in a staggered manner and are centrally symmetrical to each other. It should be understood that, the first surfaces <NUM> of all the triangular pyramid units <NUM> are located in the same plane, for example, located on a right side surface of the matrix layer <NUM> as shown in <FIG>. The first surfaces of all the anti-structure prisms <NUM> are also located in a same plane, for example, located on the right side surface of the matrix layer <NUM> as shown in <FIG>. Based on the foregoing configuration of the triangular pyramid units <NUM> and the anti-structure prisms <NUM>, the vertex angles of all anti-structure prisms <NUM> satisfy the following relationship.

In the horizontal direction, when the projector is located at the lower half part of the projection screen <NUM>, assuming that the human eyes are at the middle position of the projection screen <NUM>, the vertex angles θ of the triangular pyramid units <NUM> gradually increase from bottom to top (with <FIG> as an example), in order to transmit as much image light to the position of the human eyes as possible. As can be seen, when the projector is located at the lower part of the projection screen <NUM>, the image light is converged in a range centered around the human eyes after being reflected by the triangular pyramid units <NUM>, to reduce brightness differences at different viewing positions, thereby ensuring good uniformity and high gain of the projection screen <NUM>.

In the horizontal direction, when the projector is located at the upper half part of the projection screen <NUM>, still assuming that the human eyes are at the middle position of the projection screen <NUM>, the vertex angles of the anti-structure prisms <NUM> increase gradually from top to bottom, and the vertex angles of the anti-structure prisms <NUM> from top to bottom also satisfy the foregoing relational expression <NUM>, so as to transmit as much image light to the position of the human eyes as possible. As can be seen, when the projector is located above the projection screen <NUM>, the image light is converged in a range centered around the human eyes after being reflected by the anti-structure prisms <NUM>, to reduce brightness differences at different viewing positions, thereby also ensuring good uniformity and high gain of the projection screen <NUM>.

In the horizontal direction, when the projector is located at the lower half part of the projection screen <NUM>, assuming that the human eyes are at the middle position of the projection screen <NUM>, the vertex angles θ of the triangular pyramid units <NUM> gradually increase from bottom to top (with <FIG> as an example), in order to transmit as much image light to the position of the human eyes as possible. As can be seen, when the projector is located below the projection screen <NUM>, the image light is converged in a range centered around the human eyes after being reflected by the triangular pyramid units <NUM>, to reduce brightness differences at different viewing positions, thereby ensuring good uniformity and high gain of the projection screen <NUM>.

In conclusion, whether the projector is located above or below the projection screen <NUM>, the projection screen <NUM> can have good uniformity and high gain.

Claim 1:
A projection screen (<NUM>), comprising:
a microstructure layer, wherein the microstructure layer comprises a matrix layer (<NUM>) and a microstructure unit formed on a surface of the matrix layer (<NUM>);
wherein the microstructure unit comprises triangular pyramid units (<NUM>) arranged in an array, wherein at least two of the triangular pyramid units (<NUM>) that are arranged in a same row are identical to each other, and characterized in that at least two triangular pyramid units (<NUM>) of the triangular pyramid units (<NUM>) that are arranged in a same column respectively have vertex angles (θ) that vary gradually, and each of the vertex angles (θ) is formed between the surface of the matrix layer (<NUM>) and an edge (<NUM>) of one of the triangular pyramid units (<NUM>), wherein a projection of said edge (<NUM>) on the surface of the matrix layer (<NUM>) is coincident with a column direction (y).