Patent Publication Number: US-2022214553-A1

Title: Optical engine system and display apparatus

Description:
TECHNICAL FIELD 
     The present disclosure relates to the technical field of display, and to an optical engine system and a display apparatus. 
     BACKGROUND AND SUMMARY 
     This background is intended to provide a background or context for the detailed embodiments of the present disclosure as claimed in the claims. The description herein shall not be regarded as prior art just because it is described in this section of the specification. 
     A traditional movie projector usually uses an optical engine system with a large-size three-chip spatial light modulator. The optical engine system with the three-chip spatial light modulator usually uses a Phillips prism for color separation and color combination. As shown in  FIG. 1 , a light combining prism P 1  in the optical engine system  10  includes a first prism S 11  and a second prism S 12 . Illumination light transmits through coated layers respectively located between the first prism S 11  and air, and between the second prism S 12  and air for color separation, and then transmits through the coated layer for color combination after being modulated by the spatial light modulators N 1 , N 2  and N 3 . Since the incident illumination light and emitted projection beam of the spatial light modulators N 1 , N 2 , N 3  have a certain divergence angle, usually at +/−12 degrees, the transmittance curve for transmitting through the coated layer at different angles may be different (deviation), and the deviation amount of the transmittance curve will increase along with an incident angle. As shown in  FIG. 2  and  FIG. 3 , since the incident angle of the illumination light on the coated layer is relatively small, the transmittance curve for the coated layer is sharp, a transition area is relatively narrow, and the deviation amount of a spectral line with the incident angle is relatively small. Therefore, the light combining prism P 1  has high light separating and light combining efficiencies. 
     However, a manufacturing tolerance may be introduced in a process for manufacturing the coated layer, that is, there is a difference between the transmittance curve of the coated layer and an ideal transmittance curve, and the transmittance curve of the coated layer has an increased deviation amount as the incident angle of the incident illumination light increases, therefore, the coated layer causes great loss of light energy in a process of light combining and light separating at a large angle. 
     According to a first aspect of the present disclosure, an optical engine system is provided, including: a first modulation device configured to modulate first linearly polarized light in a first optical path to obtain first modulated light; a second modulation device configured to modulate second linearly polarized light in a second optical path to obtain second modulated light, the first linearly polarized light and the second linearly polarized light having a same polarization state; and a light combining prism configured to guide the first modulated light and the second modulated light to transmit along a same optical path and obtain projection light. The optical paths of the first modulated light, the second modulated light, and the projection light are located in a same plane. 
     According to a second aspect of the present disclosure, a display apparatus is provided, and the display apparatus includes the above-mentioned optical engine system. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       In order to explain the technical solutions in embodiments of the present disclosure more clearly, the drawings used in the description of embodiments will be briefly described below. Apparently, the drawings as described below are only some embodiments of the present disclosure. Those skilled in the art, without creative effort, may obtain other drawings based on these drawings, in which: 
         FIG. 1  is a schematic structure diagram of an optical engine system applied to a three-chip spatial light modulator; 
         FIG. 2  is a light transmittance curve of a coated layer of a light combining prism in the optical engine system shown in  FIG. 1 ; 
         FIG. 3  is a light transmittance curve of another coated layer of the light combining prism in the optical engine system shown in  FIG. 1 ; 
         FIG. 4  is a schematic structure diagram of a display apparatus according to the first embodiment of the present disclosure; 
         FIG. 5  is a schematic structure side view of the light combining prism shown in  FIG. 4 ; 
         FIG. 6  is a light transmittance curve of a light combining coated layer in the light combining prism shown in  FIG. 4 ; 
         FIG. 7  is a schematic structure diagram of a display apparatus according to a second embodiment of the present disclosure; and 
         FIG. 8  is a schematic structure diagram of a display apparatus according to a third embodiment of the present disclosure. 
     
    
    
     Reference signs of the main elements are described as follows: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Optical engine system 
                 10, 120, 220, 320 
               
               
                   
                 Light combining prism 
                 P1, P 
               
               
                   
                 Light combining coated layer 
                 G 
               
               
                   
                 Glue layer 
                 H 
               
               
                   
                 First prism 
                 S11, S1 
               
               
                   
                 Second prism 
                 S12, S2 
               
               
                   
                 Spatial light modulator 
                 N1, N2, N3 
               
               
                   
                 Normal 
                 n 
               
               
                   
                 Incident angle 
                 x1, x2, x 
               
               
                   
                 display apparatus 
                 100, 200, 300 
               
               
                   
                 light source 
                 110 
               
               
                   
                 Linearly polarized light converter 
                 123, 223, 323 
               
               
                   
                 First modulation device 
                 M1 
               
               
                   
                 Second modulation device 
                 M2 
               
               
                   
                 Illumination light 
                 a 
               
               
                   
                 Linearly polarized light 
                 b 
               
               
                   
                 First linearly polarized light 
                 c1 
               
               
                   
                 Second linearly polarized light 
                 c2 
               
               
                   
                 First modulated light 
                 d1 
               
               
                   
                 Second modulated light 
                 d2 
               
               
                   
                 Guiding element 
                 126, 226 
               
               
                   
                 First total internal reflection prism 
                 T1 
               
               
                   
                 Second total internal reflection prism 
                 T2 
               
               
                   
                 Double fly-eye lens 
                 122, 222 
               
               
                   
                 Optical integrator rod 
                 322 
               
               
                   
                 Relay lens 
                 121, 124 
               
               
                   
                 Reflection element 
                 225, 325 
               
               
                   
                   
               
            
           
         
       
     
     The present disclosure will be further described in the following embodiments in combination of the above figures. 
     DETAILED DESCRIPTION 
     In order to better illustrate the above objectives, and features and advantages of the present disclosure, the present disclosure will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments and the features in the embodiments can be combined with each other if there is no conflict. 
     In the following description, various specific details are set forth in order to better illustrate the present disclosure, and the described embodiments are merely some embodiments rather than all embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those ordinary skilled in the art without creative work shall fall within the protection scope of the present disclosure. 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. The terms used in the description of the present disclosure herein are only for a purpose of describing the detailed embodiments, but are not intended to limit the present disclosure. 
     As shown in  FIG. 1 , a surface of the first prism S 11  and a surface of the second prism S 12  are each coated with a dichroic medium film. When light is incidence on the first prism S 11  and the second prism S 12 , color separation and color combination are achieved. An incident angle x 1  is formed between the light incident onto the first prism S 11  and a normal line n of the first prism S 11 ; an incident angle x 2  is formed between the light incident onto the second prism S 12  and a normal line n of the second prism S 12 , where the x 1  and x 2  are relatively small. The incident angle x 1  is generally 30 degrees, and the angle x 2  is generally about 10 degrees, which are both less than a critical angle of a base material (glass material) of the prism. Therefore, an air gap between the first prism S 11  and the second prism S 12  can achieve color separation and color combination; since a difference between refractive indexes of the media of the first and second prisms S 11 , S 12  and air is large, the design of the coated layer is less difficult, and the transmittance of the coated layer slightly varies with the incident angle, therefore, color separation and color combination when illumination light of natural light transmits through the Phillips prism have relatively high efficiencies. Therefore, the Phillips prism has been widely applied for color combination commonly in 3-chip spatial light modulators, and is suitable for cinema projectors. 
     The disclosure provides an efficient optical engine system and a display apparatus including the optical engine system. The display apparatus can be a cinema projector, an engineering machine or a high-end home theater. The optical engine system according to the present disclosure can not only realize the compactness and miniaturization of a product, but also achieve a higher brightness, so that the product has a higher cost performance. 
     Referring to  FIG. 4 , a display apparatus  100  in this embodiment includes a light source  110  and an optical engine system  120 . The light source  110  is configured to provide the optical engine system  120  with illumination light a, and the illumination light a is unpolarized light, that is, the illumination light a is light having multiple polarization states. The optical engine system  120  is configured to modulate the illumination light a according to image data, to obtain projection light for projection. 
     Further, the light source  110  is configured to emit the illumination light a. In this embodiment, the illumination light a changes color in timing sequence. For example, the illumination light a includes red light, green light, and blue light emitted in timing sequence, and includes at least one of laser and fluorescent. In an embodiment, the illumination light a includes yellow light and blue light emitted in timing sequence. In an embodiment, the illumination light a includes red right, green light, yellow light or orange light and blue light emitted in timing sequence. In an embodiment, the illumination light a is white light. 
     Specifically, the light source  110  includes an excitation light source and a wavelength conversion element. The excitation light source is configured to emit excitation light, which may be blue laser. The wavelength conversion element is provided with a wavelength conversion material, which generates red fluorescence and green fluorescence in the illumination light a under an excitation of the excitation light, and the excitation light including the laser is scattered and is then emitted from the light source  110  as blue-primary-color light in the illumination light a. 
     In this embodiment, the light source  110  further includes a supplementary light source, and the supplementary light source is configured to emit at least one of red laser and green laser to be combined with the red fluorescent light and the green fluorescent light as red-primary-color light and the red-primary-color light in the illumination light a, increasing a display brightness of the display apparatus  100  and expanding a color gamut of the display apparatus  100 . 
     Referring to  FIG. 4  and  FIG. 5 , the optical engine system  120  includes a linearly polarized light converter (PCS)  123 , a first modulation device M 1 , a second modulation device M 2 , and a light combining prism P. The PCS 123  is configured to convert the illumination light a emitted by the light source  110  into linearly polarized light b having a single linear polarization state. The first modulation device M 1  is configured to modulate first linearly polarized light c 1  that is obtained from the linearly polarized light b and transmitted along a first optical path, to obtain first modulated light d 1 , and a transmission direction of the first optical path is a direction from bottom to top in  FIG. 4 , that is, a positive direction of Y-axis. The second modulation device M 2  is configured to modulate second linearly polarized light c 2  that is obtained from the linearly polarized light b and transmitted along a second optical path, to obtain second modulated light d 2 , and a transmission direction of the second optical path is a direction from left to right in  FIG. 4 , that is, a positive direction of Z-axis. The light combining prism P includes two prisms, namely a first prism S 1  and a second prism S 2 , and a glue layer H is provided between the first prism S 1  and the second prism S 2 . The glue layer H includes glue to bond the first prism S 1  and the second prism S 2 . As shown in  FIG. 6 , a surface of the second prism S 2  bonded to the glue layer H is provided with a light combining coated layer G. In other embodiments, a surface of the first prism S 1  and/or the second prism S 2  bonded to the glue layer H is provided with a light combining coated layer G. The first modulated light d 1  and the second modulated light d 2  are guided by the light combing coated layer G to be transmitted along a same optical path, to obtain projection light for projection. 
     In a propagation direction of the linearly polarized light b, a light vector vibrates only in a constant direction, thus a track of an end of the light vector is a straight line. The linearly polarized light b may be p light or s light. Since linear polarization states of the first linearly polarized light c 1  and the second linearly polarized light c 2  are the same, for example, they both are p light or s light, the first linearly polarized light c 1  may be linearly polarized light b of one color, and the second linearly polarized light c 2  may be other light in the linearly polarized light b, for example, the first linearly polarized light c 1  includes red light in the linearly polarized light b, and the second linearly polarized light c 2  includes blue light and green light in the linearly polarized light b. Alternatively, the first linearly polarized light c 1  includes red light and blue light in the linearly polarized light b, and the second linearly polarized light c 2  includes green light in the linearly polarized light b. Alternatively, the first linearly polarized light c 1  includes red light and part of blue light in the linearly polarized light b, and the second linearly polarized light c 2  includes green light and the remaining part of blue light in the linearly polarized light b. 
     As shown in  FIG. 4 , the first modulated light d 1  and the second modulated light d 2  are combined at the light combining coated layer G, and the light combining coated layer G is actually a light combining surface of the light combining prism P. Incident angles x at which the first modulated light d 1  and the second modulated light d 2  are incident onto the light combining coated layer G are both 45 degrees, and the two prisms of the light combining prism P are made of glass, and the incident angle x is greater than a total reflection angle of light from the glass to air. In other words, after the first modulated light d 1  is incident on the first prism S 1 , it will not be emitted from an interface between the first prism S 1  and air, but rather a total internal reflection occurs at the interface between the first prism S 1  and air, and thus the first modulated light d 1  is confined inside the first prism S 1 . 
     The total reflection angle is related to refractive indexes of the two media through which light passes. To avoid a total reflection of the first modulated light d 1  at the light combining prism P, surfaces of the first prism S 1  and the second prism S 2  that the first modulated light d 1  is expected to pass through are glued to each other by the glue layer H, so that the first modulated light d 1  exits from the first prism S 1 , passes through the glue layer H and the light combining coated layer G, and is then incident to the second prism S 2 . 
     Since the glue layer H and the light combining coated layer G adjacent to each other are provided between the first prism S 1  and the second prism S 2 , the first modulated light d 1  passes through the glue layer H and the light combining coated layer G successively, and is then combined with the second modulated light d 2 . Designing and manufacturing of the combining light coated layer G are difficult, and since the incident angles of the first modulated light d 1  and the second modulated light d 2  are relatively large, the transmittance curve has a greater deviation amount for different incident angles, reducing the light combining efficiency of the optical prism P. Especially for natural light, since layer-coating curves of the two polarization states of s light and p light will be separated from each other, and a separation amount of the two layer-coating curves is greater when the light incident angle changes, the optical engine system for natural light as the illumination light will have a serious light efficiency loss if such a 45-degree combining light method is adopted, and thus it will be difficult to achieve high-lumen product specifications. However, the 45-degree light combining method for the prism can achieve a shorter light combining optical path, and thus it is easier to achieve a compact and miniaturized product structure, which is beneficial to design and decreased cost of the lens. 
     The light combining coated layer G in the light combining prism P is configured to adjust a transmission direction of the light according to a wavelength range of the incident light. Specifically, the light combining coated layer G is a dichroic light separating film, to guide the first modulated light d 1  and the second modulated light d 2  to be transmitted along a same optical path. Specifically, in this embodiment, the dichroic light separating film is configured to transmit red light and reflect green light and blue light. It can be understood that the dichroic light separating film can be flexibly configured as required. In one embodiment, the dichroic light separating film in the light combining prism P is configured to transmit red light and part of blue light, and reflect green light and part of blue light. Accordingly, the first modulation device M 1  is configured to modulate red light and blue light in timing sequence, and the second modulation device M 2  is configured to modulate green light and blue light in timing sequence. 
     Referring to  FIG. 6 , which illustrates a transmittance curve of the dichroic light separating film of the light-combining coated layer G in the light-combining prism P, and in which different line types indicate the transmittance and wavelength curve of a light having a single linear polarization and the transmittance and wavelength curve of natural light (s light+p light). It can be seen from the figure that a transition area of the transmittance curve of natural light is wider, and a deviation amount of the curve is greater with the incident angle; while the transmittance curve of the light having a single linear polarization is sharper and compact, and a deviation amount of the curve is smaller with the incident angle. Therefore, after illumination light a is converted into linearly polarized light b, the color combination efficiency at the light combining prism P is higher, and it is less affected by the incident angle. 
     In addition, since the optical engine system  120  of the present disclosure has a high polarization-preserving efficiency for polarized light, that is, after the linearly polarized light incident to the optical engine system is transmitted, reflected, and modulated, a polarization state of the modulated light that exits is substantially the same as a polarization state of the linearly polarized light when being incident, when being used for 3D display, the luminous flux does not change as compared to being used in the 2D mode, thereby achieving a higher 3D efficiency. 
     In this embodiment, the first modulation device M 1  and the second modulation device M 2  are both digital micro-mirror devices (DMD). In one embodiment, the first modulation device M 1  and the second modulation device M 2  may also be liquid crystal or liquid crystal on silicon light modulation devices. 
     As shown in  FIG. 4 , the optical engine system  120  further includes a guiding element  126 , which is configured to separate the linearly polarized light b into first linearly polarized light c 1  transmitted along a first optical path and second linearly polarized light c 2  transmitted along a second optical path according to a wavelength range. Further, the guiding element  126  is configured to reflect part of light in the linearly polarized light b to obtain the first linearly polarized light c 1 , and to transmit the remaining part of light in the linearly polarized light b to obtain the second linearly polarized light c 2 . Specifically, the guiding element  126  may be a dichroic plate for reflecting red light and transmitting green light and blue light, without changing a linear polarization state of the incident polarized light b. The first linearly polarized light c 1  on the first optical path is incident onto the first modulation device M 1 , and the second linearly polarized light c 2  on the second optical path is incident onto the second modulation device M 2 . 
     The optical engine system  120  further includes a first total internal reflection (TIR) prism T 1  and a second total internal reflection (TIR) prism T 2 . The first TIR prism T 1  is configured to guide the first linearly polarized light c 1  emitted from the guiding element  126  to be incident to the first modulation device M 1 , and to guide the first modulated light d 1  emitted from the first modulation device M 1  to be incident to the light combining coated layer G, and the second TIR prism T 2  is configured to guide the second linearly polarized light c 2  emitted from the guiding element  126  to be incident to the second modulation device M 2 , and to guide the second modulated light d 2  emitted from the second modulation device M 2  to be incident to the light combining coated layer G. 
     As shown in  FIG. 4 , a paper plane is a yoz plane, and the optical paths of the first modulated light d 1 , the second modulated light d 2 , and the projection light (the light emitted from the light combining prism P) are located in a same plane, i.e., the yoz plane. Therefore, the linear polarization state of the linearly polarized light b has a higher maintenance during a color combining process of the light combining prism P. Just because of excellent polarization preserving of the optical engine system  120 , the transmittance curve of the linearly polarized light b for color combination at the light combining prism P can maintain a small deviation amount, which is beneficial to increase of light combining efficiency of the light combining prism P. In an embodiment, the light combining prism P further includes other incident light, and the optical paths of the incident light and the exit light of the light combining prism P are located in a same plane, thereby increasing the light combining efficiency of the light combining prism P. 
     Further, the optical paths of the first linearly polarized light c 1 , the second linearly polarized light c 2 , the first modulated light d 1 , the second modulated light d 2 , and the projection light emitted from the light combining prism P are located in a same plane, i.e., the yoz plane. Therefore, the linear polarization state of the linearly polarized light b has a higher maintenance during the processes of color separation at the guiding element  126 , the first modulation device M 1  modulating the light, the second modulation device M 2  modulating the light, and color combination of the light combining prism P. Just because of excellent polarization reserving of the optical engine system  120 , the transmittance curves of color separation and color combination of the linearly polarized light b at the guiding element  126  and the light combining prism P can be maintained at a small deviation amount, and cut-off wavelengths of color separation and color combination are kept consistent, which is beneficial to increase of the light combining efficiency of the optical engine system  120 . In an embodiment, the guiding element  126  further includes other incident light and exit light, and optical paths of the incident light and the exit light of the guiding element  126  are located in a same plane, thereby increasing the light separating efficiency of the guiding element  126 . 
     Specifically, positions and light exit angles of the guiding element  126 , the first TIR prism T 1 , the second TIR prism T 2 , the first modulation device M 1 , the second modulation device M 2 , and the light combining prism P can be adjusted such that the optical paths of the first modulated light d 1 , the second modulated light d 2  and the projection light emitted from the light combining prism P are located in a same plane, or the optical paths of the first linearly polarized light c 1 , the second linearly polarized light c 2 , the first modulated light d 1 , the second modulated light d 2 , and the projection light emitted from the light combining prism P are all located in a same plane. It can be understood that in other embodiments, the optical paths of the first modulated light d 1 , the second modulated light d 2 , and the projection light emitted from the light combining prism P are all located in a plane different from the yoz plane, or the first linearly polarized light c 1 , the second linearly polarized light c 2 , the first modulated light d 1 , the second modulated light d 2 , and the projection light emitted from the light combining prism P are all located in a plane different from the yoz plane. 
     As shown in  FIG. 4 , the optical engine system  120  further includes a light homogenizing device. In this embodiment, the light homogenizing device is a double fly-eye lens  122 . The illumination light a is incident to the linearly polarized light converter  123  through the double fly-eye lens  122 , which is configured to homogenize the illumination light a and also shape the illumination light a, for example expand a divergence angle of the illumination light a, so that the illumination light a has a larger spot area formed on the linearly polarized light converter  123 . 
     The optical engine system  120  further includes a relay lens  121  and a relay lens  124 . The illumination light a emitted by the light source  110  passes through the relay lens  121 , the double fly-eye lens  122 , the linearly polarized light converter  123 , and the relay lens  124  successively, and is then incident to the guiding element  126 . It can be understood that the optical engine system  120  may further include other necessary optical elements. 
     In one embodiment, the illumination light emitted by the light source  110  has a single linear polarization state, and the illumination light emitted by the light source  110  is linearly polarized light, and the linearly polarized light converter  123  is omitted in the optical engine system  120 . 
     The optical engine system  120  in this embodiment uses illumination light a (linearly polarized light b) having a single linear polarization state on the basis of maintaining that the first modulated light d 1  and the second modulated light d 2  are incident to the light combining coated layer G at 45 degrees at the light combining prism P, and in designing of the optical path of the optical engine system  120 , the linearly polarized light b is color separated and color combined in the two-dimensional plane yoz, so that the linearly polarized light b is maintained in a relatively good linear polarization state during transmission, thereby improving a light combining efficiency of the light combining prism P. In addition, if there is a lot of loss when the fluorescence in the illumination light a is separated at the guiding element  126  and is combined at the light combining prism P, the color coordinates of red light and green light separated from the fluorescence itself are better. In order to achieve a color gamut standard of DCI-P 3 , an amount of laser supplemented in the illumination light a will be quite small. Since the loss of the fluorescence is relatively large, and the supplemented laser is relatively small, it is difficult to achieve a brightness index of the whole machine. The optical engine system  120  in this embodiment ensures that the illumination light a has a higher efficiency in light separating and combining in the optical path, and therefore it is beneficial to increase of the brightness of the projection light emitted from the display apparatus  100 . When being used for 3D display, the luminous flux does not change as compared with being used in the 2D mode, and a higher 3D efficiency can be achieved. 
     Referring to  FIG. 7 , in a second embodiment, the optical engine system  220  of the display apparatus  200  further includes a reflection element  225 . Specifically, the linearly polarized light b emitted from the linearly polarized light converter  223  is reflected by the reflection element  225 , and is then incident to the guiding element  226 . The reflection element  225  may include a mirror of high-reflection dielectric film or a mirror of metal film, so that the optical path of the linearly polarized light b is reflected and folded in the yoz plane. When the linearly polarized light b is reflected at the reflection element  225 , the polarization direction of the linearly polarized light b can be parallel or perpendicular to a reflection surface of the reflection element  225 . After being reflected, the linear polarization state of the linearly polarized light b can remain unchanged, thereby ensuring the efficiencies in following color separating and color combining. Therefore, while ensuring a condition of the linear polarization of the transmitted light in the optical engine system  220 , the addition of the reflection element  225  can enable a volume and a size of the optical engine system  220  to be flexibly changed, and an angle at which the first linearly polarized light c 1  and the second linearly polarized light c 2  enters the first modulation device M 1  and the second modulation device M 2 , as well as the light spot thereof, can be adjusted and corrected. In this embodiment, both of the optical paths of incident light and exit light of the reflection element  225  are provided with relay lenses. 
     Since an incident surface of the linearly polarized light b received by the guiding element  226  is different from the guiding element  126 , in this embodiment, the guiding element  226  is configured to transmit part of the linearly polarized light b to obtain the first linearly polarized light c 1 , and to reflect part of the linearly polarized light b to obtain the second linearly polarized light c 2 . Specifically, the guiding element  226  is configured to transmit red light and to reflect green light and blue light. The optical engine system  220  with a high efficiency in this embodiment can not only achieve compactness and miniaturization of the product, but also achieve a higher brightness. 
     Referring to  FIG. 8 , as compared with the display apparatus  200  in the second embodiment, in the optical engine system  320  of the display apparatus  300  in a third embodiment, an optical integrator rod  322  is used to replace the double fly-eye lens  222  in the optical engine system  220 . Specifically, the illumination light a passes through the linear polarized light converter  323  to obtain the linearly polarized light b, and the linearly polarized light b passes through the optical integrator rod  322  and is then incident to the reflection element  325 . The optical integrator rod  322  homogenizes the linearly polarized light b while maintaining the linear polarization of linearly polarized light b. 
     The light combining prism in the optical engine system and the display apparatus according to the present disclosure guides the first modulated light and the second modulated light to combine colors in a same plane, and a plane in which light is emitted from the first modulator and the second modulator is the same as a light combining plane of the light combining prism, so that the original linear polarization state of the first modulated light and the second modulated light during the color combination process is better maintained, and a color combination efficiency thereof is higher, enabling to achieve higher 3D display brightness and efficiency. 
     It should be noted that, within a scope of the features of the present disclosure, various specific solutions in various embodiments can be applied to each other, and in order to save space and to avoid repetition, no further details are described herein. 
     For those skilled in the art, it is obvious that the present disclosure is not limited to the details of the above exemplary embodiments, and the present disclosure can be implemented in other specific forms without departing from the essential features of the present disclosure. Therefore, from any point of view, all embodiments shall be considered exemplary and non-limiting. The scope of the present disclosure is defined by the appended claims rather than the above description, and therefore all modifications falling within the meaning and scope of the equivalent elements of the claims are included in the present disclosure. Any reference sign in the claims shall not be regarded as limiting the claims involved. In addition, it is obvious that the term “including/comprising” does not exclude other elements or steps, and the singular does not exclude the plural. Multiple devices stated in the device claims may also be implemented by one device or system by means of a software or hardware. Terms such as “first” and “second” are used to denote names, rather than denoting any specific order. 
     Finally, it should be noted that the above embodiments are merely used to illustrate the technical solutions of the present disclosure, but not to limit thereto. Although the present disclosure has been described in detail with reference to the embodiments, those skilled in the art should understand that the technical solutions of the present disclosure may be modified or equivalently replaced without departing from the scope of the technical solutions of the present disclosure.