CN109388014B

CN109388014B - Projection screen and projection system

Info

Publication number: CN109388014B
Application number: CN201710663024.9A
Authority: CN
Inventors: 王霖; 胡飞; 李屹
Original assignee: Appotronics Corp Ltd
Current assignee: Shenzhen Appotronics Corp Ltd
Priority date: 2017-08-04
Filing date: 2017-08-04
Publication date: 2021-07-06
Anticipated expiration: 2037-08-04
Also published as: CN109388014A; WO2019024366A1

Abstract

The invention discloses a projection screen, which can reflect projection light rays to the field range of a viewer, the projection screen comprises a light diffusion layer, a total reflection layer and a light absorption layer which are sequentially arranged from the incident side of the projection light rays, the light absorption layer can absorb the incident light rays, the light diffusion layer is used for increasing the divergence angle of the emergent light rays, the total reflection layer at least comprises a microstructure layer positioned on the light diffusion layer side and an inner layer positioned on the light absorption layer side, the refractive index of the microstructure layer is greater than that of the inner layer, a plurality of microstructure units are arranged on the microstructure layer, the microstructure units continuously extend in the plane of the projection screen and are rotationally symmetrical, and the projection light rays from an ultra-short-focus projector and the projection light rays from a long-focus projector can be continuously reflected twice in the microstructure to be emergent by skillfully arranging the microstructure of the total reflection layer, so that one screen can be used for both an ultra-short-focus projector and a long-focus projector.

Description

Projection screen and projection system

Technical Field

The invention relates to a projection screen and a projection system. In particular, the present invention relates to a projection screen for a multi-focal segment that is resistant to ambient light and can be suitably used for a long-focus projector and an ultra-short-focus projector, and a projection system using the same.

Background

In recent years, with the increasing brightness of projectors, the advantages of projection display systems in large-size home theater applications have come to be realized. Compared with an LCD television and an OLED television, the projection display system is small in size, convenient to install, capable of easily realizing a display picture larger than 100 inches, and relatively low in price.

A conventional projector is called a long focus projector, and such a projector usually requires a distance of 3 meters or more to project a picture of 80 inches on a screen, and a transmitted light is incident on the screen at a small incident angle, and thus is also called a direct projection projector. Because the indoor space is limited, the long-focus projector is difficult to transmit a large projection picture indoors, and thus the short-focus and even ultra-short-focus projector is produced. The ultra-short-focus projector on the market can transmit more than 80 inches of pictures within 1 meter. Because the long-focus projector and the ultra-short-focus projector are different in placement distance and position relative to the screen, screens with different optical structures are needed, so that one screen cannot be shared by the long-focus projector and the ultra-short-focus projector, the use cost of a user is increased, and the space utilization rate is reduced.

In addition, in a home application environment, projection display systems are often installed in a living room. The living room usually has good natural lighting conditions and bright lighting sources, and thus there is a lot of ambient veiling glare. A typical projector screen can reflect both projector light and ambient light. In such an environment, the contrast of the picture formed by the light reflected by the projection screen is much lower than the contrast of the projector itself, due to the influence of the ambient light. In order to improve the screen contrast under the condition of the existence of ambient light, the current projection screen resisting the ambient light is realized by adopting an array microstructure and a light reflecting layer or a light absorbing layer.

For example, as shown in a and b of fig. 1, a circularly symmetric fresnel optical screen structure for an ultra-short focus projector is proposed in chinese patent application publication No. CN 105408777A. The screen adopts the technical scheme that the array microstructure is added with the light absorption layer. The array microstructure of the screen consists of a lenticular surface 32 and a non-lenticular surface 33. The included angle between the lens surface 32 and the screen plane is smaller than that between the non-lens surface 33 and the screen plane, and the incident light of the projector is only incident on the lens surface 32 with a small included angle. Light incident on the lens surface 32 is reflected to the viewer side by the reflection layer 20 composed of a plurality of metal thin films 25 laminated on the surface thereof. Although the screen can reflect the incident light of the projector to the eyes of the viewer, the specular reflection layer 20 inevitably reflects the incident light from other directions, such as the stray light in the environment, so that the contrast of the projection screen cannot be greatly improved. To improve contrast, a colored layer 42 is also added to the viewer side of the array microstructure. The colored layer 42 absorbs stray light but also absorbs part of the projected light. Thus, although the contrast of the screen is improved, the optical efficiency of the entire projection system is reduced, which amounts to a compromise between contrast and optical efficiency. The screen gain which can be realized by the projection screen adopting the structure in mass production in the current market is only about 0.9-1.1.

A reflective screen for an ultra short-focus projector having a microstructure as shown in a of fig. 2 is disclosed in chinese patent application publication No. CN 1670618A. The unit of the microstructure is composed of two slopes, a slope 3 formed of white reflective resin facing the projector for reflecting light from the projector, and a black light absorbing layer 4 coated on the surface of the slope facing upward for absorbing ambient light incident from above the screen. The screen disclosed in chinese patent application publication No. CN1693989A is also for an ultra short-focus projector and has a similar structure, and as shown in b of fig. 2, the base material constituting the microstructure is a light-absorbing material, and a white resin layer 6 is coated on the surface of the downward slope to reflect light from the projector. In addition, chinese patent application publication No. CN1954260A proposes a reflective screen for a tele projector. As shown in c of fig. 2, the light absorbing portion 14 and the reflective layer 13 form a microstructure having an isosceles trapezoid cross section, the ambient light is absorbed by the light absorbing portion 14, the projected light is totally reflected on the surface of the light absorbing portion 14, and is reflected by the reflective layer 13 on the bottom surface of the narrow side of the trapezoid.

In order to achieve an improvement in contrast, an optically functional layer for absorbing and/or reflecting light is provided in each of the microstructures of the screen. However, since the size of the microstructure is very small, the pitch is generally in the range of 25 to 250 μm, the process of selectively coating the optical functional layer on the surface of the microstructure is very complicated, the yield is low, and the optical efficiency is not high.

Disclosure of Invention

In view of the above problems, it is desirable to provide a projection screen and a projection system that can be shared by a long-focus projector and an ultra-short-focus projector, are resistant to ambient light, and have a simple process.

According to an embodiment of the present invention, there is disclosed a projection screen capable of reflecting projection light rays to a field of view of a viewer, the projection screen including a light diffusion layer, a total reflection layer, and a light absorption layer arranged in this order from an incident side of the projection light rays, the light absorption layer being capable of absorbing the incident light rays, the light diffusion layer being for increasing a divergence angle of the outgoing light rays,

the total reflection layer at least comprises a microstructure layer positioned on the light diffusion layer side and an inner layer positioned on the light absorption layer side, the refractive index of the microstructure layer is greater than that of the inner layer, a plurality of microstructure units are arranged on the microstructure layer, the microstructure units continuously extend in the plane of the projection screen and are rotationally symmetrical,

wherein: each microstructure unit includes a first plane, a second plane, a third plane, and a fourth plane, the first plane and the second plane being different in inclination direction with respect to a plane parallel to the projection screen, the third plane and the fourth plane being different in inclination direction with respect to a plane parallel to the projection screen, the inclination angles of the first plane, the second plane, the third plane, and the fourth plane with respect to the plane parallel to the projection screen being set such that:

the projection light rays incident at an incident angle within a first angle range are continuously totally reflected at the first plane and the second plane, and the projection light rays incident at an incident angle within a second angle range are continuously totally reflected at the third plane and the fourth plane.

The invention also discloses a projection system which comprises the projection screen and the projector.

As described above, the projection screen and the projection system according to the present invention have at least the following advantages:

(1) by skillfully arranging the microstructure of the total reflection layer, the projection light from the ultra-short-focus projector and the projection light from the long-focus projector can be emitted out through two continuous total reflections in the microstructure, so that one screen can be used for the ultra-short-focus projector and the long-focus projector.

(2) The light absorption layer for absorbing ambient stray light is integrally arranged on the back of the microstructure, and a metal reflection film or the light absorption layer does not need to be coated in the microstructure, so that the cost is reduced, and the yield is improved.

(3) The microstructure utilizes the angle selection characteristic of total reflection to reflect projection light from a projector while substantially not reflecting ambient stray light toward a viewing area of a viewer. Most of the ambient stray light from the top passes through the total reflection microstructures, is absorbed by the light absorption layer on the back, and is reflected to the outside of the viewing area of a viewer in a small part, so that the contrast of a projected image is improved, and the optical efficiency is improved.

It is to be understood that the advantageous effects of the present invention are not limited to the above-described effects, but may be any of the advantageous effects described herein.

Drawings

Fig. 1 is a schematic diagram showing an example of a projection screen in the related art.

Fig. 2 is a schematic diagram showing other examples of projection screens in the prior art.

Fig. 3 is a schematic structural diagram illustrating a projection system according to an embodiment of the present invention.

Fig. 4 is a schematic view illustrating a rotational symmetric structure of a total reflection layer of a projection screen according to an embodiment of the present invention.

Fig. 5 is a schematic view showing a main sectional structure of a microstructure unit of a total reflection layer of a projection screen according to an embodiment of the present invention.

Fig. 6 is a schematic diagram showing a main sectional structure of a microstructure unit of a projection screen and an optical path when used in an ultra-short focus projector according to an embodiment of the present invention.

Fig. 7 is a schematic diagram showing a main sectional structure of a microstructure unit of a projection screen according to an embodiment of the present invention and an optical path when used in a telephoto projector.

Fig. 8 is a schematic diagram illustrating an optical path when ambient stray light is irradiated on a projection screen according to an embodiment of the present invention.

Fig. 9 is a schematic diagram showing a main sectional structure of a microstructure unit of a projection screen according to another embodiment of the present invention and light paths when used for an ultra-short focus projector and a long focus projector.

FIG. 10 is a schematic diagram illustrating a scattering film layer of a projection screen according to an embodiment of the present invention.

Detailed Description

Hereinafter, specific embodiments according to the present invention will be described in detail with reference to the accompanying drawings. It is emphasized that all dimensions in the figures are merely schematic and not necessarily to scale, thus not limiting. For example, it should be understood that the thickness, thickness ratio, and angles of the layers in the various layer structures in the projection screen are not shown in actual size and ratio, but are for convenience of illustration only.

Overview of a full reflection projection System

Fig. 3 is a schematic structural diagram illustrating a projection system according to an embodiment of the present invention. As shown in fig. 3, the projection system includes a projection screen 10 and a projector 20. Note that fig. 3 shows an example in which the projector 20 is an ultra short-focus projector, but the projection screen 10 may be used for a long-focus projector as described below. The projection screen 10 includes a surface microstructure layer 14, a diffusion layer 13, a total reflection layer 12, and a light absorption layer 11, which are sequentially stacked from the incident side of the projection light of the projector. The projection light from the projector 20 is transmitted through the surface microstructure layer 14 and the diffusion layer 13 and enters the total reflection layer 12. Hereinafter, the incident side of the projection light of the projection screen 10 is also referred to as the outer side of the screen (i.e., the side facing the viewer), and the light absorbing layer side is referred to as the inner side of the screen (i.e., the side facing away from the viewer). The total reflection layer 12 is formed with a microstructure unit array. Each microstructure unit includes an optical structure (described in detail below) that is designed so that the projected light from either the long-focus projector or the ultra-short-focus projector can be totally reflected in the microstructure unit and finally reflected to the field of view of the viewer, while the ambient stray light from above the projection screen 10 cannot satisfy the condition of total reflection in the microstructure unit, and is absorbed by the light absorption layer 11 through the total reflection layer 12. The light absorbing layer 11 is black, for example.

As shown in fig. 4, the microstructure units of the total reflection layer 12 have a rotationally symmetric array arrangement on the screen plane. The axis of the center of rotation (optical center) of the rotationally symmetric array arrangement is perpendicular to the plane of the screen and below the screen. Preferably, the projector 20 is arranged on the central axis of rotation.

A diffusion layer 13 and a surface microstructure layer 14 are sequentially disposed outside the total reflection layer 12. The diffusion layer 13 and the surface microstructure layer 14 may be collectively referred to as a light diffusion layer, and both serve to diffuse the collimated light beam reflected from the total reflection layer 12 to make the projection screen 10 have a larger viewing angle. It should be understood that, although an example in which both the diffusion layer 13 and the surface microstructure layer 14 are provided is illustrated in fig. 3, the projection screen 10 may be provided with only the diffusion layer 13 or the surface microstructure layer 14. In addition, a protective layer may be added on the outer side of the surface microstructure layer 14 to prevent scratching or chemical corrosion. Of course, other auxiliary functional layers may be provided according to design requirements.

Fig. 5 shows a schematic cross-sectional structure diagram of the microstructure unit of the total reflection layer 12 of the projection screen according to the embodiment of the present invention. As shown in fig. 5, the total reflection layer 12 includes a transparent substrate 120, a microstructure layer 121, and an inner layer 122. The transparent substrate 120 is located on the side of the total reflection layer 12 closest to the light diffusion layer and is in contact with the light diffusion layer, wherein the transparent substrate 120 comprises a transparent material such as PET, PC or PMMA. The micro-structure layer 121 is disposed on the opposite side of the transparent substrate 120 from the side in contact with the light diffusion layer. The microstructure layer 121 is made of a resin material, and the resin is usually an epoxy resin adhesive system, an acrylate adhesive system, a polyester adhesive system, a polyurethane adhesive system, or a polyimide adhesive system. The transparent substrate 120 and the microstructure layer 121 are integrated by a UV coating apparatus or a thermal forming apparatus. The inner layer 122 is formed on the side of the microstructure layer 121 close to the light absorbing layer and is in contact with the light absorbing layer 11. The refractive index of the material forming the inner layer 122 is lower than the refractive index of the material forming the microstructure layer 121. The surface of the microstructure layer 121 adjacent to the inner layer 122 is provided with a plurality of microstructure units. Here, in each microstructure unit of the total reflection layer 12, the microstructure layer 121 is formed as a total reflection prism. Fig. 5 shows a main cross-sectional view of the prismatic structure of the microstructure layer 121 in two microstructure units. The sides of each prism structure are made up of 4

intersecting planes

1241, 1243, 1244 and 1242. In the main sectional view shown in fig. 5, these 4 intersecting planes are illustrated as 4 line segments 1241 to 1244 connected in sequence having different inclination angles with respect to a plane parallel to the projection screen (hereinafter simply referred to as "screen plane"). The

planes

1241 and 1243 and the

planes

1242 and 1244 are not inclined to the screen. In other words, in each microstructure unit of the total reflection layer 12, the microstructure layer 121 is a row of rotationally symmetric prisms formed on the surface of the transparent substrate 120, and the

planes

1241, 1243, 1244 and 1244 are interfaces between two different material layers, namely the microstructure layer 121 and the inner layer 122, wherein the microstructure layer 121 is a first material layer and the inner layer 122 is a second material layer. For example, such prisms are fabricated by applying a resin to the roll and a UV or thermal curing process. In fig. 5, only two microstructure units are shown for clarity of illustration. As will be described in detail below, since the incident angle range (the first angle range, for example, 30 degrees to 80 degrees) in which the projection light of the ultra-short-focus projector is incident on the projection screen and the incident angle range (the second angle range, for example, 0 degrees to 30 degrees) in which the projection light of the long-focus projector is incident on the projection screen are greatly different, by skillfully setting the inclination directions and the inclination angles of the

planes

1241, 1243, 1244, and 1244, the incident light 123 (as shown in fig. 5) from the ultra-short-focus projector can be reflected twice in succession at the two

planes

1241 and 1242, and finally reflected into the field of view of the viewer, and the incident light 123 (not shown in fig. 5, see fig. 7) from the long-focus projector can be totally reflected at the two

planes

1243 and 1244, respectively, and finally reflected into the field of view of the viewer. That is, in the microstructure layer 121, the interface between the microstructure layer 121 and the inner layer 122 includes two sets of planes, one set (1241 and 1242) is used to make the incident light from the ultra-short-focus projector totally reflected and enter the field of view of the viewer, and the other set (1243 and 1244) is used to make the incident light from the long-focus projector totally reflected and enter the field of view of the viewer.

Furthermore, the ambient veiling glare 127 comes primarily from ceiling lights in the room. In most cases, the dome lamp is remote from the axis of rotation of the rotationally symmetrical structure of the microstructure elements of the screen. Thus, the incident angle of the ambient veiling glare 127 is smaller than the incident angle of the projected light from the ultra-short-focus projector, but much larger than the incident angle of the projected light from the long-focus projector. Therefore, the ambient stray light 127 cannot satisfy the condition that total reflection occurs twice in succession on the plane 1241 and the plane 1242 or on the

planes

1243 and 1244, and most of the ambient stray light passes through the microstructure unit and is absorbed by the light absorbing layer 11.

As described above, the projection screen 10 according to the embodiment of the present invention utilizes the angle-selective reflection characteristic of the total reflection layer 12, so that the screen can reflect the projection light from the ultra-short-focus projector into the field of view of the viewer, and can reflect the projection light from the long-focus projector into the field of view of the viewer. Meanwhile, the projection screen 10 can also automatically distinguish projection light from ambient light, and the light absorbing layer 11 for absorbing ambient stray light is integrally disposed inside the total reflection layer 12, thereby achieving high contrast and simplifying the processing process, reducing the cost, and improving the yield.

Second, optical principle and angle selection of total reflection microstructure unit

Hereinafter, the optical principle of the total reflection microstructure unit of the projection screen 10 according to an embodiment of the present invention will be described in detail with reference to fig. 6 to 8. Among them, fig. 6 shows an example of an optical path when the projection screen 10 is used for an ultra-short focus projector, fig. 7 shows an example of an optical path when the projection screen 10 is used for a long focus projector, and fig. 8 shows an example of an optical path when ambient stray light is incident to the projection screen 10.

As shown in FIG. 6, the refractive index of the microstructure layer 121 is n₁And the refractive index of the inner layer 122 is n₂Inclination of the 4

inclined intersecting planes

1241, 1242, 1243 and 1244 of the microstructure elements with respect to the screen planeAngles are each theta₁、θ₂、θ₃And theta₄(the unit is degree, the same below). The angles between the incident and reflected light rays and the horizontal direction are α and β (in degrees, the same applies hereinafter), respectively. Wherein, when the reflected light is emitted horizontally, β is obviously 0 degree, and the following are set: beta is negative when the reflected ray is below the horizon (i.e., toward the ground) and positive when the reflected ray is above the horizon (i.e., toward the ceiling).

In order to make the incident light 123 from the ultra-short-focus projector 20 emit to the eye of the viewer after undergoing total reflection twice on the

inclined planes

1241 and 1242, the following equations (1) to (3) must be satisfied according to the geometrical optical principle and the optical total reflection condition:

θ cannot be completely determined based on the above equations (1) to (3)₁And theta₂Still leave certain design freedom. Let γ be an angle between an intermediate ray between an incident ray and an outgoing ray and a plane of a screen (i.e., a vertical direction), and let γ be a positive value when the intermediate ray is deflected toward a viewer side and a negative value when the intermediate ray is deflected toward the viewer side. Then according to the geometrical optics principle and the optical total reflection condition, the following can be calculated:

as can be seen from equations (4) and (5), as long as the optical paths of the incident light, the emergent light, and the intermediate light are determined (i.e., α, β, and γ are determined), the tilt angle θ of the two intersecting

planes

1241 and 1242 of the microstructure can be completely determined₁And theta₂。

In addition, as can be seen from the formulas (4) and (5), even when the optical paths of the incident light and the emergent light are determined, the optical path of the intermediate light (i.e., the value of γ) can be adjusted within a certain range according to different application requirements₁And theta₂Is selected. For example, in ultra-short-focus projection applications, the projector is located below the screen, so α>0 is always true; and the eyes of the viewer are positioned above the projector, so as to ensure the emergent light to be incident to the eyes of the viewer, the alpha + beta>0 is also always true; in this case, it can be obtained from equation (1):

θ₁+θ₂＜90 (6)

as can be seen from equation (6), in the application of ultra-short focus projection, the included angle formed by the two

inclined planes

1241 and 1242 of the microstructure unit of the projection screen according to the present invention must be an obtuse angle.

In addition, as can be seen from the above analysis, it is preferable that the intermediate light beam after the incident light beam 123 from the ultra-short focus projector is totally reflected by the inclined plane 1241 of the microstructure unit travels in the direction parallel to the screen plane in the microstructure layer 121.

In this case, γ is 0 degree, β is 0 degree, and θ is equal to₂When β is 0 degrees, which is the angle of 45 degrees, the outgoing light ray is emitted perpendicularly to the screen, and θ can be known from the above equation (6)₁<45 degrees, i.e. theta₁<θ₂。

Since the set of

inclined planes

1241 and 1242 of the microstructure unit has the optical structure as described above, as shown in fig. 6, a part of the incident light 123 from the ultra-short-focus projector 20 undergoes two total reflections at the set of

inclined planes

1241 and 1242 of the microstructure unit and is reflected into the field of view of the viewer; and another part of the incident light 123 from the ultra-short-focus projector 20 irradiates on another set of

inclined planes

1243 and 1244 of the microstructure unit, and since the

inclined planes

1243 and 1244 do not have the above optical structure, the incident light 123 from the ultra-short-focus projector 20 does not satisfy the total reflection condition at least one of the

inclined planes

1243 and 1244, and then the part of the light passes through the total reflection layer and is absorbed by the inner light absorption layer 11.

Fig. 7 illustrates an example of an optical path when the projection screen 10 is used for a telephoto projector. When the projection screen 10 is used in a tele projector, as shown in fig. 7, a portion of the incident light 123 is totally reflected twice at a set of

inclined planes

1243 and 1244 of the micro-structure unit and reflected into the field of view of the viewer. Since the incident light of a tele projector can be considered to be incident at an angle approximately to the normal screen plane, in order to reflect the incident light into the field of view of the viewer, the tilt angles of the tilted

planes

1243 and 1244 with respect to the screen plane need to satisfy the following relation:

θ₃+θ₄＝90 (7)

in addition, another part of the incident light 123 is irradiated on another set of

inclined planes

1241 and 1242 of the microstructure unit, and since the inclination angles of the

inclined planes

1241 and 1242 do not satisfy the relation (6), the incident light 123 from the telephoto projector does not satisfy the total reflection condition at least one of the

inclined planes

1241 and 1242, and thus the part of the light is transmitted through the total reflection layer and absorbed by the inner light absorption layer 11.

In the microstructure unit, in addition to the inclination angle with respect to the screen plane, the relationship of the extended lengths of the two sets of

planes

1241 and 1242 for totally reflecting the projection light from the ultra-short-focus projector and the

planes

1243 and 1244 for totally reflecting the projection light from the long-focus projector also has a large influence on the optical performance of the screen. It can be found through experiments that when the ratio of the extended length of the

planes

1243 and 1244 to the extended total length of the

planes

1241, 1242, 1243 and 1244 (i.e., the ratio of the sum of the lengths of the line segment 1243 and the line segment 1244 to the total length of the line segment 1241, the line segment 1242, the line segment 1243 and the line segment 1244 in the main cross-sectional views of fig. 6 to 8) should be greater than 0.2 and less than 0.8.

In contrast to the above, fig. 8 illustrates an example of the optical path when ambient stray light is incident to the projection screen 10. In the actual use environment of a projection system, ambient stray light generally originates mainly from light fixtures above the ceiling or walls. Thus, the incident angle of the ambient stray light on the projection screen is much smaller than the incident angle of the projection light emitted from the ultra-short-focus projector located at a short distance below the screen. Therefore, when the ambient stray light 127 is incident on the projection screen from the ceiling side, the ambient stray light cannot satisfy the condition that total reflection occurs twice in succession on the

planes

1241 and 1242 or on the

planes

1243 and 1244, but is completely absorbed by the light absorbing layer 11 inside through the total reflection layer.

In the above description, the case where 1241, 1243, 1244, and 1242 are provided in this order from the bottom in the main sectional view is taken as an example for explanation. However, as is clear from the above analysis, the arrangement order of the four planes is not limited thereto. For example, as shown in fig. 9, a set of planes (i.e., 1243 and 1244) for total reflection of the projection light from the tele projector may also be provided on the outer side, in other words, the four planes are arranged in the order of 1243, 1241, 1242, and 1244 from bottom to top. As mentioned above, the included angle between the plane 1243 and the plane 1244 is 90 degrees, and the included angle between the plane 1241 and the plane 1241 is an obtuse angle.

In addition, as described above, the projection screen 10 according to the present invention has a rotationally symmetric structure and includes a plurality of microstructure units. Thus, the angular design of each microstructure element may be the same or different. For example, since the outgoing light beam always horizontally travels toward the viewer, β is 0 degrees and θ₂This is always true at 45 degrees. According to the simulation result, the theta of the microstructure unit is known₁Gradually decreases as approaching the upper side of the screen, and theta₁<θ₂Thus, the above formula (6) is satisfied. Alternatively, on the premise that the above formulas (1) to (6) are satisfied, θ of the microstructure unit of the projection screen may be projected in a direction from the center of the screen to the edge of the screen₁Is constantly decreasing and theta₂The value of (a) is increasing.

Refractive index selection of total reflection microstructure unit

Except for theta₁To theta₄Besides the value of (a), the total reflection microstructure unit satisfying the two total reflections is also subjected to the refractive index n of the microstructure layer 121 according to the optical total reflection formula₁And refractive index n of inner layer 122₂The influence of (c). The microstructure layer 121 of the projection screen according to the present invention is generally made of a transparent resin material, and has a refractive index in the range of 1.3 to 1.7. Alternatively, the microstructure layer 121 may be made of other materials having similar refractive indexes. In addition, the material for forming the microstructure layer 121 may be doped with scattering ions or an absorbing material. Therefore, in order to satisfy the condition of total reflection, it is necessary to consider the refractive index n of the inner layer 122₂Selection of (2). The incident ray V can be expressed as (V)_x,V_y,V_z) With the z-axis perpendicular to the screen and the X, Y-axes parallel to the screen. It is clear that the total reflection area of an incident ray depends on V_xAnd V_yThe value range of (a). V_zSatisfies the following conditions:

assuming that the emergent ray is directed toward the eye of the viewer and the refractive index n of the microstructure layer 121₁1.6, the component (V) of the incident light satisfying the total reflection condition can be obtained according to the above equations (2) and (3)_x,V_y) Is in a range that depends on the refractive index n of the inner layer 122₂The trend of change of (c). With n₂The area of the incident light rays which are subjected to total reflection at the two inclined planes of the microstructure unit is continuously reduced. In other words, with n₂The probability that the light emitted from the projector cannot be totally reflected twice on the two inclined planes of the microstructure unit is increased. Therefore, in order to ensure a certain screen reflection efficiency, n is required to be used₁And n₂Satisfies the following conditions:

n₂<n₁-0.2 (9)

it should be understood that the inside layer 122 may be an air layer in the case where the above conditions are satisfied. In this case, the tips of the reflective prisms of the micro-structure layer 121 may be directly adhered to the light absorbing layer 11.

Selection of light diffusion layer

As described above, after the projection light is reflected by the total reflection layer 12, the divergence angle of the outgoing light is generally small, and in order to increase the visible range of the projection screen, a light diffusion layer may be disposed outside the total reflection layer 12. In the example shown in fig. 3, a diffusion layer 13 and a surface microstructure layer 14 are provided in this order as a light diffusion layer on the outer side of the total reflection layer 12. However, only one light diffusion layer may be provided. Fig. 10 a to c respectively show 3 commercial optical scattering film structures that can be used as a light diffusion layer: a bulk scattering film, an irregular surface scattering film and a regular surface microlens array film. These scattering film materials can be used to increase the viewing area of the screen and can be used alone or in stacks as desired. For example, the diffusion layer 13 and the surface microstructure layer 14 in fig. 3 may be formed by using a bulk scattering film and a regular surface microlens array film in superposition. The number and kind of the stacks are not limited thereto.

In the case of using an optical diffusion film as the light diffusion layer, the total reflection layer and the light diffusion layer are formed separately, and then optically bonded. Alternatively, the light-scattering layer and the total-reflection layer may be formed separately by subjecting both surfaces of the same substrate (for example, PET) to different surface processing.

Although the projection screen and the projection system according to the present invention have been described above with reference to the accompanying drawings, the present invention is not limited thereto, and those skilled in the art will appreciate that various changes, combinations, sub-combinations, and modifications may be made without departing from the spirit or scope of the invention as defined in the appended claims.

Claims

1. A projection screen capable of reflecting projection light rays into a field of view of a viewer,

the projection screen includes a light diffusion layer, a total reflection layer, and a light absorption layer, which are sequentially arranged from an incident side of the projection light, the light absorption layer being capable of absorbing the incident light, the light diffusion layer increasing a divergence angle of the outgoing light,

the total reflection layer at least comprises a microstructure layer positioned on the light diffusion layer side and an inner layer positioned on the light absorption layer side, the refractive index of the microstructure layer is greater than that of the inner layer, the microstructure layer is a first material layer, the inner layer is a second material layer, a plurality of microstructure units are arranged on the microstructure layer, the microstructure units continuously extend in the plane of the projection screen and are rotationally symmetrical,

2. The projection screen of claim 1 wherein the fully reflective layer further comprises a transparent substrate layer, and the microstructure units are cured on the transparent substrate layer by coating with a resin and UV curing or thermoforming.

3. The projection screen of claim 1 wherein the first material layer of each microstructure unit is configured as a rotationally symmetric total reflection prism, the first, second, third, and fourth planes having an inclination angle with respect to a plane parallel to the projection screenAre each theta₁、θ₂、θ₃And theta₄Wherein, in the step (A),

θ₁and theta₂Satisfies the relationship: theta₁+θ₂Is < 90, and

θ₃and theta₄Satisfies the relationship: theta₃+θ₄＝90。

4. The projection screen of claim 3 wherein θ is the number of microstructure units₂Are all 45 degrees.

5. The projection screen of claim 3 wherein θ is the number of microstructure units₁Is different, said theta₂Is different, said theta₃Is different, and said theta₄As well as different.

6. The projection screen of claim 1 wherein the refractive index n of the first layer of material₁And the refractive index n of the second material layer₂Satisfies the relationship: n is₂<n₁-0.2。

7. The projection screen of claim 1 wherein the first, second, third and fourth planes each have a first length L in a main cross-section of the total reflective layer orthogonal to a plane parallel to the projection screen along a perpendicular direction₁A second length L₂A third length L₃And a fourth length L₄Said L is₁The said L₂The said L₃And said L₄The following relationship is satisfied:

8. the projection screen of any one of claims 1 to 6 wherein the light diffusing layer is formed from one of a bulk scattering film, an irregular surface scattering film, and a regular surface microlens array film; or

The light diffusion layer is formed by laminating at least one of a scattering film, an irregular surface scattering film, and a regular surface microlens array film.

9. The projection screen of claim 8 wherein the second layer of material is a layer of air.

10. The projection screen of claim 8 wherein the first and second planes are arranged such that the projection light rays travel in a direction parallel to the projection screen after a first total reflection at one of the two.

11. The projection screen of claim 8 wherein the center axes of rotation of the rotationally symmetric microstructure elements are perpendicular to a plane parallel to the projection screen and below the projection screen.

12. The projection screen of any one of claims 1-7 wherein the second layer of material is a layer of air.

13. The projection screen of any one of claims 1-7 wherein the first and second planes are arranged such that the projection light rays travel in a direction parallel to the projection screen after a first total reflection at one of the two.

14. The projection screen of any one of claims 1-7 wherein the center axes of rotation of the rotationally symmetric microstructure elements are perpendicular to a plane parallel to the projection screen and below the projection screen.

15. A projection system comprising a projection screen as claimed in any one of claims 1 to 14 and a projector.

16. The projection system of claim 15, wherein the projector is an ultra-short-focus projector located below the projection screen, the projected light rays from the projector being incident on the projection screen at angles of incidence within the first range of angles.

17. The projection system of claim 15, wherein the projector is a tele projector, the projected light from the projector being incident on the projection screen at an incident angle within the second range of angles.