Patent Publication Number: US-2021173214-A1

Title: Projection apparatus and wearable display device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of China application (CN201911232752.X), filed on Dec. 5, 2019. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     FIELD OF THE INVENTION 
     The invention relates to a display device, and more particularly to a projection apparatus and a wearable display device. 
     BACKGROUND OF THE INVENTION 
     A head-mounted display (HMD) uses an optical projection system to project images and/or text messages on a display element into a user&#39;s eyes. With the development of micro displays in higher resolution, smaller size and lower power consumption and the development of cloud technology in which large amounts of information can be downloaded from the cloud at any time, the head-mounted display devices is developed as a wearable display device. In addition to the military field, the wearable display devices also grow and occupy an important position in other related fields such as industrial production, simulation training, 3D display, medical treatment, sports and video games. 
     In the mini-optical engine of the augmented reality (AR) device or the virtual reality (VR) device, due to the limitations of the body machine, the extension region of many mechanisms and even the optically effective region are sacrificed to obtain a thinner and lighter design. However, because of this, unexpected stray and structured light is generated, and therefore the quality of the image output is affected. 
     The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     The invention provides a projection apparatus and a wearable display device, which can effectively eliminate the structured light generated by the projection apparatus due to volume limitation. 
     Other advantages and objects of the invention can be further understood from the technical features disclosed by the invention. 
     In order to achieve one or a portion of or all of the objects or other objects, the projection apparatus provided by the invention includes an illumination component, a light valve and an imaging component. The illumination component includes a light source module, a diffuser and a prism module. The light source module provides an illumination beam, and the light source module has a light emitting side. The diffuser is disposed between the light source module and the prism module. The illumination beam passes through the diffuser to the prism module. The light valve has an active surface for converting the illumination beam into an image beam. The illumination beam passing through the diffuser is transmitted to the light valve by the prism module. The imaging component receives and projects the image beam. 
     In order to achieve one or a portion of or all of the objects or other objects, the wearable display device provided by the invention includes a projection apparatus and a waveguide element. The projection apparatus includes an illumination component, a light valve and an imaging component. The illumination component includes a light source module, a diffuser and a prism module. The light source module provides an illumination beam. The light source module has a light emitting side. The diffuser is disposed between the light source module and the prism module. The illumination beam passes through the diffuser to the prism module. The light valve has an active surface for converting the illumination beam into an image beam. The illumination beam passing through the diffuser is transmitted to the light valve by the prism module. The imaging component receives and projects the image beam. The waveguide element guides the image beam and projects the image beam to a projection target. 
     In the invention, the configuration in which the diffuser is disposed between the light source module and the prism module can eliminate the structured light caused by volume limitation of the projection apparatus, that is, reduce the distribution of uneven light. Further, the use of a diffuser with an opening or a top-hat type diffuser can effectively improve the geometric efficiency caused by a general diffuser. 
     Other objectives, features and advantages of The invention will be further understood from the further technological features disclosed by the embodiments of The invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a schematic view of a projection apparatus according to an embodiment of the invention; 
         FIG. 2  is a schematic structural view of a light uniform module according to an embodiment of the invention; 
         FIGS. 3 a  to 3 i    are respective schematic views of light spot images on a light valve when sub-illumination beams outputted by a micro lenses in different rows are directly transmitted to the light valve by a prism module; 
         FIG. 4 a    is a schematic view of a superimposed light spot on a light valve; 
         FIG. 4 b    is a schematic view of a superimposed light spot on a light valve according to an embodiment of the invention; 
         FIG. 5  is a schematic view of an arrangement in which a diffuser is disposed corresponding to a micro-lens array according to an embodiment of the invention; 
         FIG. 6  is a schematic view of an arrangement in which a diffuser is disposed corresponding to a micro-lens array according to another embodiment of the invention; 
         FIGS. 7 a  and 7 b    are schematic views of the diffusion angle and light intensity of a Gaussian type diffuser and a top-hat type diffuser, respectively; 
         FIGS. 8 a  and 8 b    are schematic views of the light spot on the light valve formed by a Gaussian type diffuser and a top-hat type diffuser, respectively; 
         FIG. 9  is a schematic view of a projection apparatus according to another embodiment of the invention; 
         FIG. 10  is a schematic view of a wearable display device according to an embodiment of the invention; and 
         FIG. 11  is a schematic application view of a wearable display device according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top”, “bottom”, “front”, “back”, etc., is used with reference to the orientation of the Figure(s) being described. The components of the invention can be positioned in a number of different orientations. As such, the directional terminology is used for purposes of illustration and is in no way limiting. On the other hand, the drawings are only schematic and the sizes of components may be exaggerated for clarity. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the invention. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including”, “comprising”, or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected”, “coupled”, and “mounted” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. Similarly, the terms “facing”, “faces”, and variations thereof herein are used broadly and encompass direct and indirect facing, and “adjacent to” and variations thereof herein are used broadly and encompass directly and indirectly “adjacent to”. Therefore, the description of “A” component facing “B” component herein may contain the situations that “A” component facing “B” component directly or one or more additional components is between “A” component and “B” component. Also, the description of “A” component “adjacent to” “B” component herein may contain the situations that “A” component is directly “adjacent to” “B” component or one or more additional components is between “A” component and “B” component. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. 
       FIG. 1  is a schematic view of a projection apparatus according to an embodiment of the invention. As shown in  FIG. 1 , the projection apparatus  10  includes an illumination component  12 , a light valve  14  and an imaging component  16 . The illumination component  12  is used to provide an illumination beam IL to the light valve  14 . The illumination component  12  includes a light source module  18 , a light uniform module  20 , a diffuser  22  and a prism module  24 . The light source module  18  provides the illumination beam IL. The illumination beam IL is transmitted to the light valve  14  through the light uniform module  20 , the diffuser  22  and the prism module  24 . In the embodiment, the light source module  18  is, for example, a laser diode light source module or a light emitting diode light source module. The light source module  18  has a light emitting side. The light uniform module  20  is disposed on the light emitting side of the light source module  18 . The diffuser  22  is disposed between the light uniform module  20  and the prism module  24 . The illumination beam IL passes through the light uniform module  20 , the diffuser  22  and the prism module  24 , and is transmitted to the light valve  14  through the prism module  24 . 
     Follow the above description. The light valve  14  is disposed on the transmission path of the illumination beam IL and has an active surface  141 . The active surface  141  is adapted to convert the illumination beam IL from the prism module  24  into an image beam ML. In one embodiment, the light valve  14  is, for example, a digital micro-mirror device (DMD). In another embodiment, the light valve  14  may be a liquid crystal-on-silicon (LCOS) panel. The light valve  14  reflects the image beam ML to the imaging component  16 . The imaging component  16  receives and projects the image beam ML. In one embodiment, the imaging component  16  may include one or more lenses. 
       FIG. 2  is a schematic structural view of a light uniform module according to an embodiment of the invention. As shown in  FIG. 2 , the light uniform module  20  includes a micro-lens array  26  composed of a plurality of micro lenses  261 . The micro lenses  261  are arranged in an array form having a plurality of rows and a plurality of columns of micro lenses  261 . To facilitate the following explanation, the micro-lens array  26  is defined to have the first lens row C 1 , the second lens row C 2 , the third lens row C 3 , the fourth lens row C 4 , the fifth lens row C 5 , the sixth lens row C 6 , the seventh lens row C 7 , the eighth lens row C 8  and the ninth lens row C 9  in a direction from the bottom to top of the micro-lens array  26  (in the opposite direction of the gravity direction). Please refer to  FIGS. 1 and 2  together. In one embodiment in which the light source module  18  is a laser diode light source module, the illumination beam IL provided by the light source module  18  is transmitted to the micro-lens array  26 , and then sub-illumination beams (not labeled) are respectively outputted by the micro lenses  261  when the illumination beam IL is received by the micro-lens array  26 .  FIGS. 3 a  to 3 i    are respective schematic views of light spot images on the light valve  14  when the sub-illumination beams outputted by the micro lenses  261  in different rows are directly transmitted to the light valve  14  by the prism module  24 . As shown in  FIGS. 3 a  and 3 i   , the sub-illumination beams outputted by the first lens row C 1  and the ninth lens row C 9  almost have no light spot  28  distributed on the active surface  141  of the light valve  14 . As shown in  FIGS. 3 b , 3 c  and 3 d   , the shapes of the light spots  28  on the active surface  141  of the light valve  14  respectively generated by the sub-illumination beams outputted by the second lens row C 2 , the third lens row C 3  and the fourth lens row C 4  are different. In addition to that the light spot  28  does not fill the entire active surface  141 , an obvious boundary light  30  is generated at the upper edge of the light spot  28 . Further, as shown in  FIG. 3 b   , in addition to that the light spot  28  has the boundary light  30 , the brightness of the light spot  28  is clearly divided into two regions  28   a  and  28   b , wherein the brightness of region  28   a  is higher than the brightness of region  28   b . On the other hand, as shown in  FIGS. 3 f , 3 g  and 3 h   , the shapes of the light spots  28  on the active surface  141  of the light valve  14  respectively generated by the sub-illumination beams outputted by the sixth lens row C 6 , the seventh lens row C 7  and the eighth lens row C 8  are different. In addition to that the light spot  28  does not fill the entire active surface  141 , an obvious boundary light  30 ′ is generated at the bottom edge of the light spot  28 . Further, as shown in  FIG. 3 h   , in addition to that the light spot  28  has the boundary light  30 ′, the brightness of the light spot  28  is clearly divided into two regions  28   a  and  28   b , wherein the brightness of region  28   a  is higher than the brightness of region  28   b .  FIG. 4 a    is a schematic view of a superimposed light spot on a light valve, in which the sub-illumination beams outputted by the micro-lens array  26  are directly transmitted to the light valve  14  through the prism module  24 . As shown in  FIG. 4 a   , when the light spot  28  of each micro lenses  261  (shown in  FIG. 2 ) is superimposed, the upper and lower edges of the active surface  141  respectively generate three structured lights  32  and  32 ′ due to the superposition of the boundary lights  30  and  30 ′. 
     Further, in other embodiments, the projection apparatus may need to meet different size requirements, so that structured light may also be generated in the left and right edge regions of the active surface  141  of the light valve  14 . That is, the superimposition of the light spots  28  generated by the micro lenses  261  located in the upper, bottom, left and/or right edge regions of the micro-lens array  26  may all generate structured lights. Further, in other embodiments in which the light source module  18  is a light emitting diode light source module, the electrodes included in the light emitting diode light source module may also generate striped structured light. In other words, the structured light may include any uneven or unexpected stray light generated on the light valve  14  due to the light source module  18  and/or the micro-lens array  26 , thereby affecting the quality of the projected image. 
     The image beam ML outputted by the light valve  14  has structural stripes (e.g., structured light  32 ,  32 ′) when the micro-lens array  26  having the micro lenses  261  with different arrangement positions is used as the light uniform module  20 , resulting in poor image output quality. Therefore, a diffuser  22  is provided between the micro-lens array  26  and the prism module  24  in the embodiment of the invention.  FIG. 5  is a schematic view of an arrangement in which a diffuser is disposed corresponding to a micro-lens array according to an embodiment of the invention. The diffuser  22  completely shields the micro-lens array  26 . The micro lenses  261  respectively output the sub-illumination beams when the micro-lens array  26  receives the illumination beam IL. Each sub-illumination beam is first uniformized by the diffuser  22  to eliminate the superimposed structured light  32 ,  32 ′ originally generated by the micro lenses  261  located in the edge region.  FIG. 4 b    is a schematic view of a superimposed light spot on a light valve, in which the sub-illumination beams outputted by the micro lenses  261  of the micro-lens array  26  are uniformized by the diffuser  22  according to an embodiment of the invention and transmitted to the light valve  14  through the prism module  24 . As shown in  FIG. 4 b   , the light spot  28  superimposed on the light valve  14  is evenly distributed on the entire active surface  141 , so that the brightness of the structured light  32 ,  32 ′ shown in  FIG. 4 a    is reduced, and the structured light  32 ,  32 ′ may even disappear. 
       FIG. 6  is a schematic view of a diffuser according to another embodiment of the invention. In the embodiment, the diffuser  22 A includes a light transmitting substrate  221  and a diffusion structure  224  formed on the light transmitting substrate  221 . As shown in  FIG. 6 , the diffuser  22 A has a light transmitting region  222  and a diffusion region  223 . The diffusion region  223  has the diffusion structure, and the light transmitting region  222  does not have the diffusion structure. In one embodiment, the light transmitting region  222  may be an opening on the light transmitting substrate  221 . When the diffuser  22 A is disposed corresponding to the micro-lens array  26 , the micro lenses  261  in the middle rows (e.g., the fourth lens row C 4 , the fifth lens row C 5 , and the sixth lens row C 6 ) are exposed through the light transmitting region  222  (i.e., the opening) of the diffuser  22 A. 
     Follow the above description. Among the sub-illumination beams outputted by the micro lenses  261 , a part of the sub-illumination beams (e.g., sub-illumination beams outputted by the micro lenses  261  in the fourth lens row C 4 , the fifth lens row C 5  and the sixth lens row C 6  in  FIG. 2 ) does not have the aforementioned problem of the boundary light  30 ; therefore, the sub-illumination beams outputted by the micro lenses  261  in the fourth lens row C 4 , the fifth lens row C 5  and the sixth lens row C 6  can be designed to pass through the diffuser  22 A to the prism module  24  through the light transmitting region  222 , and the other part of the sub-illumination beams can be designed to pass through the diffuser  22 A to the prism module  24  through the diffusion region  223 . In this way, the sub-illumination beams outputted by the micro lenses  261  located in the middle rows can be directly transmitted to the prism module  24  through the light transmitting region  222 , thereby achieving the effect of improving geometric efficiency. Those skilled in the art can know the definition of geometric efficiency, and no redundant detail is to be given herein. In the embodiment, the configuration in which the diffuser  22 A with an opening as the light transmitting region  222  is disposed between the micro-lens array  26  and the prism module  24  can improve the geometric efficiency by about 10%, compared to the configuration in which the diffuser  22  does not have the light transmitting region  222  and completely shields the micro-lens array  26 . In addition, the light transmitting region of the diffuser  22 A is not limited to correspond to the middle rows in the micro-lens array  26 , and the light transmitting region can be adjusted correspondingly according to the position where the structured light is not generated, for example, corresponding to the middle columns or central region of the intersection of the middle rows and the middle columns. In other words, the structured light is generated when the diffuser  22 A is not used, and then the position where the structured light is generated is known, and then the diffuser  22 A is provided to eliminate the structured light. In addition, the light transmitting region may be provided correspondingly at a position where the structured light is not generated. 
     In order to improve the geometric efficiency, a top-hat type diffuser may be used as the diffuser  22  in one embodiment. Compared with a general Gaussian type diffuser, the top-hat type diffuser can more effectively converge the light spot on the light valve, so that light is converged more uniform.  FIGS. 7 a  and 7 b    are schematic views of the diffusion angle and light intensity of a Gaussian type diffuser and a top-hat type diffuser, respectively.  FIGS. 8 a  and 8 b    are schematic views of the light spot on the light valve formed by a Gaussian type diffuser and a top-hat type diffuser, respectively, wherein it is shown that the light spot outputted by the Gaussian type diffuser is large and scattered. As shown in  FIG. 8 a   , in addition to being distributed on the active surface of the light valve  14 , the light spot  28  is also scattered around the light valve  14 , so that the geometrical efficiency decreases. As shown in  FIGS. 7 a  and 7 b   , the Gaussian type diffuser and the top-hat type diffuser both diffuse at 15 degrees at the same FWHM diffusion angle, but the top-hat type diffuser has more convergent light spot  28 . As shown in  FIG. 8 b   , the light spot  28  converges in the region of the light valve  14  but still has the effect of eliminating structured light, thereby effectively improving the geometric efficiency. Compared with the configuration in which a Gaussian type diffuser is disposed between the micro-lens array  26  and the prism module  24 , the configuration in which a top-hat type diffuser is disposed between the micro-lens array  26  and the prism module  24  can improve geometric efficiency by about 8%. 
     In the embodiment shown in  FIG. 1 , the prism module  24  includes a first prism  241 , a second prism  242  and a third prism  243 . The first prism  241  has a curved surface, and the curved surface has a reflective layer R. The reflective layer R is used to reflect the illumination beam IL from the diffuser  22  to the light valve  14 . In one embodiment, there is a slight air gap (not shown) between any two adjacent prisms of the first prism  241 , the second prism  242  and the third prism  243 . For example, the first gap is formed between the first prism  241  and the second prism  242 , and the second gap is formed between the second prism  242  and the third prism  243 . The illumination beam IL from the diffuser  22 / 22 A is transmitted to the active surface  141  of the light valve  14  sequentially through the first prism  241 , the reflective layer R of the curved surface, the first gap, the second prism  242 , the second gap and the third prism  243 . The light valve  14  then converts the illumination beam IL into the image beam ML and reflects the image beam ML to the third prism  243 . The third prism  243  reflects the image beam ML to the imaging component  16  in a total internal reflection (TIR) manner. 
       FIG. 9  is a schematic view of a projection apparatus according to another embodiment of the invention. As shown in  FIG. 9 , the projection apparatus  10  includes an illumination component  12 , a light valve  14  and an imaging component  16 . The embodiment of  FIG. 9  is different from the embodiment of  FIG. 1  in that the light source module  18  is a light emitting diode light source module and the illumination component  12  does not include the light uniform module  20 . The illumination component  12  is used to provide an illumination beam IL to the light valve  14 . The illumination component  12  includes a light source module  18 , a diffuser  22  and a prism module  24 . The light source module  18  provides an illumination beam IL. The illumination beam IL is transmitted to the light valve  14  through the diffuser  22  and the prism module  24 . In the embodiment, the light source module  18  has a light emitting side, and the diffuser  22  is disposed between the light source module  18  and the prism module  24 . The illumination beam IL passes through the diffuser  22  to the prism module  24  and is transmitted to the light valve  14  through the prism module  24 . In the embodiment in which the light source module  18  is a light emitting diode light source module, the electrodes included in the light emitting diode light source module may also generate the striped structured light, and the uneven or unexpected stray light may be generated on the active surface  141  of the light valve  14 , thereby affecting the quality of the projected image. 
       FIG. 10  is a schematic view of a wearable display device according to an embodiment of the invention. As shown in  FIG. 10 , the wearable display device  40  includes a projection apparatus  10  and a waveguide element  42 . The waveguide element  42  is, for example, a high light transmission element made of glass or plastic and used to transmit image beams. The projection apparatus  10  includes an illumination component  12 , a light valve  14  and an imaging component  16 . The waveguide element  42  is disposed on one side of the imaging component  16 ; specifically, the imaging component  16  is located between the light valve  14  and the waveguide element  42 . The illumination component  12  includes a light source module  18 , a light uniform module  20 , a diffuser  22  and a prism module  24 . The light source module  18  provides the illumination beam IL. The illumination beam IL is transmitted to the light valve  14  through the light uniform module  20 , the diffuser  22  and the prism module  24 . The light valve  14  converts the illumination beam IL into an image beam ML. The imaging component  16  receives and projects the image beam ML to the waveguide element  42 . The waveguide element  42  guides the image beam ML so that the image beam ML is projected to a projection target, such as human eyes. 
       FIG. 11  is a schematic application view of a wearable display device according to an embodiment of the invention. As shown in  FIG. 11 , the wearable display device  40  further includes a wearing frame  44 . In one embodiment, the wearing frame  44  can be worn on the user&#39;s head. The projection apparatus  10  is disposed in the wearing frame  44 . An imaging component  46  is disposed on the wearing frame  44 . The waveguide element  42  is, for example, disposed in the imaging component  46 . The quantity of the imaging components  46  is, for example, two, and the two imaging components  46  are respectively located corresponding to the eyes of the user when the user wears the wearing frame  44 , so that the eyes of the user can see the images provided by the two imaging components  46  respectively. The invention does not limit the specific structure of the wearing frame  44 , and the wearable display device  40  can be applied to augmented reality (AR) devices or virtual reality (VR) devices. 
     In summary, in the projection apparatus of the embodiment of the invention, the configuration in which the diffuser is disposed between the light uniform module and the prism module or the diffuser is disposed between the light source module and the prism module can eliminate the structured light caused by volume limitation of the projection apparatus, that is, reduce the distribution of uneven light. Further, the use of a diffuser with an opening or a top-hat type diffuser can effectively improve the geometric efficiency caused by a general diffuser. 
     The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiments disclosed. Accordingly, the foregoing description should be regarded as illustrative rather than restrictive. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. The embodiments are chosen and described in order to best explain the principles of the invention and its best mode practical application, thereby to enable persons skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated. Therefore, the term “the invention”, “The invention” or the like is not necessary limited the claim scope to a specific embodiment, and the reference to particularly preferred exemplary embodiments of the invention does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is limited only by the spirit and scope of the appended claims. Moreover, these claims may refer to use “first”, “second”, etc. following with noun or element. Such terms should be understood as a nomenclature and should not be construed as giving the limitation on the number of the elements modified by such nomenclature unless specific number has been given. The abstract of the disclosure is provided to comply with the rules requiring an abstract, which will allow a searcher to quickly ascertain the subject matter of the technical disclosure of any patent issued from this disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Any advantages and benefits described may not apply to all embodiments of the invention. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the invention as defined by the following claims. Moreover, no element and component in the disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the following claims. Furthermore, the terms such as the first prism and the second prism are only used for distinguishing various elements and do not limit the number of the elements.