阅读说明：本技术 一种具有保持投影光偏振状态的投影屏幕 (Projection screen capable of maintaining polarization state of projection light ) 是由 王勇竞 郑港 张喜玉 周永业 于 2020-06-24 设计创作，主要内容包括：本发明公开一种具有保持投影光偏振状态的投影屏幕,包括若干投影屏幕单元,每一所述投影屏幕单元包括至少两层的光学层状结构,每一光学层状结构的相位变化可以由其他层补偿。每一层所述光学层状结构的材质设置为光学介质膜和/或金属膜。本发明通过设置至少两层的光学层状结构,通过对构成每一层光学层状结构的介质的材质选择和厚度设计,可以起到相位补偿的作用,使得一层光学层状结构产生的相位和振幅的变化,可以被其它层光学层状结构补偿,从而可以保持出射光的偏振态与入射光的偏振态相一致,保偏率可以做到200：1到2000：1或以上,典型的保偏率为1000：1；如此,可以大大消除3D电影的重影,降低眩晕感,提高3D观影体验。(The invention discloses a projection screen capable of maintaining the polarization state of projection light, which comprises a plurality of projection screen units, wherein each projection screen unit comprises at least two layers of optical laminated structures, and the phase change of each optical laminated structure can be compensated by other layers. The material of each layer of the optical layered structure is set to be an optical dielectric film and/or a metal film. The invention can play a role of phase compensation by arranging at least two layers of optical layered structures and selecting materials and designing the thickness of a medium forming each layer of optical layered structure, so that the change of the phase and the amplitude generated by one layer of optical layered structure can be compensated by other layers of optical layered structures, thereby keeping the polarization state of emergent light consistent with the polarization state of incident light, and the polarization retention rate can be 200: 1 to 2000: 1 or more, typical polarization maintaining ratio is 1000: 1; therefore, double images of the 3D film can be greatly eliminated, the vertigo feeling is reduced, and the 3D film watching experience is improved.)

1. A projection screen having a polarization state maintaining means for projecting light, comprising a plurality of projection screen units, each of said projection screen units comprising at least two layers of optical layered structures, wherein the phase change of each optical layered structure is compensated by the other layers.

2. The projection screen of claim 1, wherein each layer of the optical layered structure is configured to include either or both of an optical dielectric film and a metal film.

3. The projection screen of claim 2 wherein each of said optical layered structures is provided as a multilayer optical film.

4. The projection screen of claim 2, wherein each of the optical layered structures is configured as a metal film; when the reflective film is disposed, the reflection angle of each metal film is set to be less than 45 degrees.

5. The projection screen of claim 2, wherein two films are provided for each optical layered structure, wherein a first film is provided as a metal film, a second film is provided as an all-transparent optical dielectric film, and wherein the all-transparent optical dielectric film is provided over the metal film.

6. The projection screen of claim 2 wherein two metal films are provided per optical layered structure to maintain the polarization state of the projected light.

7. The projection screen with preserved polarization state of the projected light of any of claims 2-6, wherein the optical axis direction of each layer of said optical layered structure is tilted with respect to its corresponding projection screen unit.

8. The projection screen of claim 7, wherein the optical axis of each layer of the optical layered structure is tilted relative to its corresponding projection screen unit by an angle of between +/-20 degrees and +/-45 degrees.

9. The projection screen of claim 7, wherein the setting of the tilt angle is selectively controlled by one or more of laser direct write, binary optical or diffractive optics, specific angular surface distribution.

10. The projection screen with preserved polarization state of the projected light of claim 7, wherein the optical axis direction of each layer of said optical layered structure is obliquely arranged with respect to its corresponding projection screen unit.

Technical Field

The invention relates to the technical field of 3D display, in particular to a projection screen capable of keeping the polarization state of projection light.

Background

3D movie theaters provide people with a more realistic viewing experience, which has become the mainstream of movie theaters in recent years. The 3D cinema is generally implemented by using one or two projectors, and adding a polarizer or a polarization conversion device to project pictures for the left eye and the right eye to view respectively. The image polarization states of the left eye and the right eye are different, the screen scatters and reflects light from the projector, and the audience distinguishes images of the left eye and the right eye by wearing polarized glasses, so that the left eye only sees a left eye image, the right eye only sees a right eye image, and the human brain continuously processes the images seen by the left eye and the right eye to generate stereoscopic vision to form 3D vision.

The 3D projection screen generally uses a metal screen, and a metal reflective layer, generally in the form of metal powder or metal flakes, is coated on a substrate, and has a certain angular distribution, so that the screen has a certain viewing angle range, and is visible to viewers at different angles, and the polarization state of reflected light can be ensured. However, when light is reflected at any interface, a certain depolarization effect is generated. This depolarization mainly results from several completely different physical mechanisms, as shown in fig. 1-3:

first, the phase is depolarized. When light is reflected, any medium is added with a phase, and the polarization of p-linear polarization light and s-linear polarization light is added with a different phase change delta no matter the medium is transparent or metal, as shown in fig. 1A and 1B. It is noted that for the reflection of the optical multilayer dielectric film, the phase change Δ is a constant π at less than a certain angle; for the metal coating, the phase change Δ is a variable, and the phase change changes the polarization state of the incident linearly polarized light, i.e., generates depolarization of the light.

Second, the amplitude is depolarized. When the light I is reflected on any surface, the surface has different reflectivities for P-linearly polarized light and S-linearly polarized light when the light I is reflected at other angles than the light which is normally incident, and the reflected light O becomes P 'and S' after the P-linearly polarized light and the S-linearly polarized light are reflected, as shown in FIG. 2. Although the phase of the reflected light is not changed, the amplitudes of the P-linear polarized light and the S-linear polarized light are changed, and P 'and S' finally converge into a light beam with a changed positive state, namely depolarization is generated.

And thirdly, geometric depolarization. When a light ray is reflected, although the polarization state of the light ray may not change with respect to a linear coordinate system, the polarization state of the light ray may actually change with respect to an absolute coordinate system, and such a change in the polarization state may change into a change in the polarization direction of the light in the case of multiple reflections. Fig. 3 shows an extreme case where the polarization state is rotated by 90 degrees after three reflections, although each reflection is an ideal reflection without any additional phase change and amplitude change.

The existing 3D projection screen has a certain back-off to the reflected light, especially in the case of large angles: for example, the image projected by the projector for the left eye has a specific polarization direction, such as left-handed light, when the image is projected on a 3D projection screen, based on half-wave retardation, most of the reflected light is right-handed circularly polarized light, and a small part of the reflected light is left-handed circularly polarized light due to depolarization, so that the polarization state of the projected light changes on the screen, the right eye not only sees the image of the right eye, but also sees a small part of the image of the left eye, and ghost images are generated on the screen, so that viewers easily feel dizzy, and the viewing experience of the 3D cinema is greatly reduced. Currently, the polarization retention rate of a general 3D projection screen is only 100: 1, i.e. 1% of the polarized light of the left eye image becomes another polarization and is seen by the right eye, so that the user experience is not good. The polarization maintaining rate of a few high-end screens can be close to 800: 1. there is an urgent need in the market for a 3D projection screen that can maintain the polarization state of projection light without generating ghost images.

Accordingly, the prior art is deficient and needs improvement.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a projection light polarization maintaining device which can maintain the polarization maintaining rate to be 200: 1 to 2000: 1 or more, can eliminate the ghost image of 3D film greatly, reduce dizzy sense, improve the projection screen that 3D viewed the shadow experience.

In order to achieve the purpose, the invention is realized by the following technical scheme: the invention provides a projection screen capable of maintaining the polarization state of projection light, which comprises a plurality of projection screen units, wherein each projection screen unit comprises at least two layers of optical laminated structures, and the phase change of each optical laminated structure is compensated by other layers.

In the projection screen with the function of maintaining the polarization state of the projected light, the material of each layer of the optical layered structure is set to include an optical dielectric film or a metal film.

In the projection screen with the function of maintaining the polarization state of the projected light, each optical layered structure is configured as a multilayer optical film.

The projection screen with the function of maintaining the polarization state of the projected light is applied to each technical scheme, and each optical layered structure is arranged into a metal film; when the reflective film is disposed, the reflection angle of each metal film is set to be less than 45 degrees.

The projection screen capable of maintaining the polarization state of the projection light is applied to each technical scheme, each optical layered structure is provided with two layers of films, wherein the first layer of film is a metal film, the second layer of film is a fully transparent optical dielectric film, and the fully transparent optical dielectric film is arranged above the metal film.

The projection screen with the function of maintaining the polarization state of the projected light is applied to each technical scheme, and each optical layered structure is provided with two layers of metal films.

The projection screen with the function of maintaining the polarization state of the projection light is applied to each technical scheme, and the optical axis direction of each layer of the optical layered structure is obliquely arranged relative to the corresponding projection screen unit.

In the projection screen capable of maintaining the polarization state of the projection light, the inclination angle of the optical axis direction of each layer of the optical layered structure, which is obliquely arranged relative to the corresponding projection screen unit, is +/-20 degrees to +/-45 degrees.

The projection screen with the function of maintaining the polarization state of the projection light is applied to each technical scheme, and the arrangement of the inclination angle is controlled by selecting one or more modes of laser direct writing, binary optics or diffraction optics and specific angle surface distribution.

The optical layered structure is applied to each technical scheme, for example, a nano-imprinting mode is adopted, a specific surface shape is formed on a mold through computer control, a projection angle is increased, and the optical axis direction of each layer of the optical layered structure is obliquely arranged relative to the corresponding projection screen unit.

By adopting the scheme, the invention has the advantages that at least two layers of optical layered structures are arranged, and the selection and thickness design of the medium forming each layer of optical layered structure can play a role in phase compensation, so that the phase and amplitude changes generated by one layer of optical layered structure can be compensated by other layers of optical layered structures, the polarization state of emergent light can be kept consistent with the polarization state of incident light, and the polarization retention rate can be 200: 1 to 2000: 1 or more, wherein, most preferably, the typical polarization maintaining rate is 1000: 1; therefore, double images of the 3D film can be greatly eliminated, the vertigo feeling is reduced, and the 3D film watching experience is improved.

Drawings

Fig. 1A is a schematic diagram of p-linearly polarized light depolarization during phase depolarization in the prior art.

Fig. 1B is a schematic diagram of s-linear polarized light depolarization in phase depolarization in the prior art.

Fig. 2 is a diagram illustrating amplitude de-warping in the prior art.

FIG. 3 is a schematic diagram of geometric depolarization in the prior art.

Fig. 4 is a schematic structural diagram of a projection screen according to an embodiment of the invention.

Fig. 5 is a schematic structural diagram of a projection screen according to another embodiment of the invention.

Detailed Description

The invention is described in detail below with reference to the figures and the specific embodiments.

The present embodiment provides a projection screen with a polarization state of projected light maintained, as shown in fig. 4, which includes a plurality of projection screen units, for example, including a projection screen unit 401, a projection screen unit 402, a projection screen unit 403, a projection screen unit 404, and the like.

Each projection screen unit comprises at least two layers of optical laminated structures, wherein each projection screen unit can comprise two layers of optical laminated structures, or three layers of optical laminated structures, or more layers of optical laminated structures; in the projection screen units, the number of layers of the optical layered structure generally included between the projection screen units is the same.

The optical layered structure of each layer is configured to include, but not limited to, any one or two of an optical dielectric film and a metal film, so that the phase compensation function can be performed by selecting the material and designing the thickness of the medium constituting each layer of optical layered structure, so that the phase and amplitude changes generated by one layer of optical layered structure can be compensated by the other layer of optical layered structure.

Because each projection screen unit comprises at least two layers of optical laminated structures, each projection screen unit has more than one layer of dielectric films or/and metal films, and can form a field strong reflection function, so that light from the direction of the projector is reflected to the eyes of audiences by certain angle distribution.

For example, a first embodiment of the present invention is: each projection screen unit comprises at least two layers of optical laminated structures, and each optical laminated structure is arranged into a multilayer optical medium film; in this way, each optical layered structure is provided as a multilayer optical dielectric film, and when reflection occurs, the added phase changes to 180 degrees for both directions of polarized light, so the reflected light does not change the direction of polarization. Also, the optical layered structure is provided as a multilayer optical dielectric film designed to have the same reflectance for p-light and s-light upon reflection, so that the reflected light does not change the direction of polarization.

As another example, a second embodiment of the present invention is: each projection screen unit comprises at least two layers of optical laminated structures, and each optical laminated structure is arranged into a metal film; when the reflective film is disposed, the reflection angle of each metal film is set to be less than 45 degrees. When reflection occurs in this way, the phase change imparted by the material to the polarized light in different directions is sufficiently small that the phase of the reflected light is not altered in combination.

For another example, the third embodiment of the present invention is: each projection screen unit comprises at least two optical layered structures, as shown in fig. 4, each optical layered structure is provided with a first layer film 411 and a second layer film 412, wherein the first layer film 411 is provided as a metal film, the second layer film 412 is provided as a fully transparent optical dielectric film, and the fully transparent optical dielectric film 412 is provided above the metal film 411; thus, the two layers of films play two roles, when light is reflected on the fully transparent optical dielectric film, the reflection generated on the surface of the metal film and the phase change generated on the transparent dielectric film are mutually offset, so that the polarization is kept, and the polarization direction of the reflected light is not changed.

Finally, a fourth embodiment of the invention is: each screen unit comprises at least two layers of optical layered structures, and each optical layered structure is provided with two metal films; in this way, the phase changes that occur in the two metal surfaces that reflect cancel each other out, which causes polarization to be preserved so that the reflected light does not change the direction of polarization.

In the above embodiment, in order to obtain a certain angular distribution of the reflected light of the projection screen, the two or more layers of the optical layered structure of each projection screen unit need to reflect the light with a single angular distribution.

Wherein these angular distributions are achievable with different distributions of optical layered structures versus diffraction and scattering to different angles. Alternatively, these different angular distributions may be determined with each projection screen unit having a different shape of the surface and optical axis.

When each projection screen unit is determined to have different surface shapes and optical axes, the optical axis direction of each layer of the optical layered structure can be obliquely arranged relative to the corresponding projection screen unit, and the inclination angle and the distribution thereof are designed according to the viewing angle requirement of the projection screen and are generally within +/-20 degrees to +/-45 degrees. For example, as shown in fig. 5, the first layer optical layered structure 511 and the second layer optical layered structure 512 are obliquely disposed with respect to their corresponding projection screen units, respectively.

Wherein the setting of the tilt angle can be controlled by one or more of laser direct writing, binary or diffractive optics, and specific angular surface distribution.

For example, by using a laser direct writing method, on a surface with a specific inclination, the inclination angles of different units are distributed within a certain angle, so that light from one direction is dispersed to different directions, and thus, a projector projects the picture on a screen and has a certain visual angle distribution.

For another example, a binary optical or diffractive optical mode is adopted, so that different diffraction angles are formed for the optics in the projector direction, and the optics are diffracted to different directions to form a certain visual angle distribution; specifically, a specific diffraction pattern is formed on a mold. Different diffraction angles are formed for the optics in the projector direction, and the optics diffract to different directions to form certain visual angle distribution.

For another example, the pattern of the specific angular surface distribution, such as a specific sand blasting process, a specific etching process. Or a nano-imprinting mode can be used, a specific surface shape is formed by computer control, and the effect of increasing the projection angle is achieved, wherein a specific sand blasting process, a specific corrosion process and a friction process are specifically adopted to manufacture the mold.

Or, a nano-imprinting mode can be adopted, a specific surface shape is formed on the mold through computer control, the effect of increasing the projection angle is achieved, and the optical axis direction of each layer of the optical layered structure can be obliquely arranged relative to the corresponding projection screen unit.

Therefore, the inclination angle and the spatial distribution of each projection screen unit can minimize the geometric depolarization effect for most light rays, thereby achieving the effect of polarization maintaining.

Through the above embodiment, the polarization state of the emergent light can be kept consistent with that of the incident light, and the polarization maintaining rate can be 200: 1 to 2000: 1 or more, wherein, most preferably, the typical polarization maintaining rate is 1000: 1; therefore, double images of the 3D film can be greatly eliminated, the vertigo feeling is reduced, and the 3D film watching experience is improved.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.