Patent Publication Number: US-2009236971-A1

Title: See-through Display apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a transparent display apparatus and in particular to a display apparatus having see-through characteristics and display functions. 
     2. Description of Prior Art 
     Resulting from the improvement of internet and wireless technology, mobile devices such as laptop computers, cellar phones, digital cameras, and personal digital assistants (PDA) are widely used in modern life. Since liquid crystal displays (LCD) have narrow dimensions, low mass and low power-consumption, their application in mobile products is increasing fast. 
     Small and medium-sized FPD (Flat Panel Display) panels for mobile products are improved to great-sized panel industry. The manufacturing processes of the great-size FPD are developed and the FPD has characteristics of high brightness, high contract, high response rate and lower energy-consuming than cathode ray tubes (CRT). FPD products have displaced CRTs in display applications, mainly because of the bulkiness of CRTs and the increasing popularity of low depth of display screen. 
     However, traditional displays including CRT, LCD and PDP are not transparent, i.e., a person can not see an object behind the display. When the traditional display is assembled on the shop window, objects behind the display will not be seen by observers. In other words, people can not see the information on display and the exhibit inside the shop window at the same time. Some developments produce a see-though display via a transparent substrate, transparent electrodes, and transparent fluorescence powders. However, the fluorescence powders are not 100% transparent and the light is scattered because of the shape of the powders so that the display color is gray. Furthermore, the field-emitting materials are coated on the substrate by adhesive materials and metal conductive materials. Therefore, the see-though ratio of the above-mentioned display is very low and observers can barely recognize an image through the display. 
     Therefore, the inventor proposes the present invention to overcome the above problems based on his expert experience and deliberate research. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is provided for a see-through display apparatus. The see-through display apparatus has sub-pixels and the adjacent sub-pixels are separated by a transparent area so that an observer can see through the display apparatus. 
     In order to achieve the above object, the present invention provides a see-through display apparatus, comprising: a substrate having a plurality of first electrodes on its top surface; an second substrate disposed on the substrate, wherein the second substrate has a plurality of second electrodes on its bottom surface, the first electrodes and the second electrodes are arranged to form a plurality of crossing areas, each crossing area defining a pixel area; and at least one electro-luminescent area disposed on each of the crossing areas; wherein a see-through ratio of each pixel area is in a predetermined range, the see-through ratio of the pixel area is determined by formula: T=(PA−EA)/PA*100%, where T is the see-through ratio of each pixel area, PA is the area of each pixel area, EA is the area of at least one electro-luminescent area on each crossing area. 
     Depending on the present invention, the objects behind the display apparatus can be seen by an observer in front of the display apparatus. Moreover, the observer still can see the image displayed by the display apparatus. In order to better understand the characteristics and technical contents of the present invention, a detailed description thereof will be made with reference to the accompanying drawings. However, it should be understood that the drawings and the description are illustrative but not used to limit the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view showing the see-through display apparatus according to the present invention. 
         FIG. 2  shows pixel areas defined in the see-through display apparatus according to the present invention. 
         FIG. 3  shows the first embodiment of electro-luminescent areas and transparent areas of the see-through display apparatus according to the present invention. 
         FIG. 3A  shows the second embodiment of electro-luminescent areas and transparent areas of the see-through display apparatus according to the present invention. 
         FIG. 3B  shows the third embodiment of electro-luminescent areas and transparent areas of the see-through display apparatus according to the present invention. 
         FIG. 3C  shows the fourth embodiment of electro-luminescent areas and transparent areas of the see-through display apparatus according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Please refer to  FIGS. 1-3 , the invention discloses a see-through display apparatus  1  and each of the pixels of the see-through display apparatus  1  are separated into sub-pixels so that a person can see images or subjects behind the see-through display apparatus  1 . In other words, when the see-through display apparatus  1  is not powered on, people can see through the see-through display apparatus  1  and alternatively, when the see-through display apparatus  1  is powered on in order to present some images thereon, people still can recognize the subjects behind the see-through display apparatus  1 . The see-through display apparatus  1  comprises a first substrate  10 , a second substrate  20  and at least one electro-luminescent area  311 . The first substrate  10  has a plurality of first electrodes  11  on its top surface and the second substrate  20  has a plurality of second electrodes  21  on its bottom surface. The first substrate  10  and the first electrodes  11  are constructed as a first electrode-plate. Similarly the second substrate  20  and the second electrodes are constructed as a second electrode-plate. The first electrodes  11  and the second electrodes  21  are arranged to form a plurality of crossing areas  30 . In the embodiment, the first electrodes  11  are longitudinally disposed on the top of the first substrate  10  as negative electrodes and the second electrodes  21  are transversely disposed at the bottom of the second substrate  20  as positive electrodes so that crossing areas  30  can be formed by the first electrodes  11  and the second electrodes  21 . Each crossing areas  30  defines a pixel area  31  by human, in other words, a “real” crossing areas  30  defines a “non-real” pixel area  31 . Please note crossing area  30  is not shown in  FIGS. 3-3C  for simplicity. The electro-luminescent area  311  is disposed on each of the crossing areas  30 , i.e., the pixel area  31 . In the invention, the see-through ratio of each pixel area  31  is calculated and ranged in a predetermined range so that the light behind the see-through display apparatus  1  is not blocked and can transmit through the see-through display apparatus  1 . The see-through ratio of the pixel area  31  is determined by formula: T=(PA−EA)/PA*100%, where T is the see-through ratio of each pixel area  31 , and PA is the area of each pixel area  31 , and EA is the area of at least one electro-luminescent area  311  on each crossing area  30 . 
     The electro-luminescent area  311  of each pixel area  31  is coated by a plurality of phosphor powders so that the electro-luminescent area  311  will illuminate to display information when the see-through display apparatus  1  is powered on. However, because the phosphor powders are non-transparent powers, the electro-luminescent area  311  are non-transparent areas. In other words, each pixel area  31  has transparent area  312  and non-transparent area (electro-luminescent area  311 ) and the transparent area  312  has greater area than the non-transparent area. By arranging the transparent areas  312  and non-transparent areas (electro-luminescent areas  311 ) in an interval manner, diffraction occurs when light waves encounter see-through display apparatus  1  in their propagating paths, and its effect is that a person in front of see-through display apparatus  1  can see through the display apparatus  1  to see things behind the see-through display apparatus  1 . Moreover, the electro-luminescent areas  311  of the each pixel area  31  perform as sub-pixel areas and people can see through the display apparatus  1  by arranging the sub-pixel areas of the each pixel area  31 . 
     Basically, resolution quantifies how close a pair of lines or points can be to each other and still be visibly resolved. Image resolution describes the detail an image holds. The term is calculated in spatial formula, and higher resolution means more image detail and higher image quality. Discussing about spatial frequency, the resolution of human eyes is decreasing extremely in high space frequency according to the MTF (modulation transfer function) defined as a ration of image contract (Mi) divided object contract (Mo). Accordingly, each pixel area  31  is classified into transparent areas  312  and non-transparent areas (electro-luminescent areas  311 ) and the transparent areas  312  alter with the non-transparent electro-luminescent areas  311  for arranging the two areas  311  and  312  in a high spatial frequency. Therefore, when the see-through display apparatus  1  is not powered on, an observer can not resolve the two areas  311  and  312  of the each pixel area  31  so that light waves transmitted through the greater transparent areas  312  are observed and the light waves encounter the non-see-through electro-luminescent areas  311  is overlooked. The effect makes a phenomenon that the observer feels seeing the image behind the see-through display apparatus  1 . Depending on research on MTF and regular spatial frequency, if the spatial frequency is higher, the resolution of the human eyes to observer the detail is lower. Therefore, if the transparent areas  312  and the non-transparent areas is arranged in manner of higher frequency, the obstacles (non-transparent electro-luminescent areas  311 ) on the light paths is not detectable for human eyes and in other words, the display apparatus  1  is transparent and can be see-through for human eyes. On the contrary, when the electro-luminescent areas  311  project light, the lighting sub-pixels can combine together to human eyes because the distances between the sub-pixels are small. Therefore, the sub-pixels perform information which is seen by a person because the spatial frequency is lower in the lighting condition. On the other hand, because the brightness of electro-luminescent areas  311  is much higher than the background light projected from the object behind the display apparatus  1  and the contract is higher, the information displayed by the electro-luminescent areas  311  can be seen by the observer. 
     Diffraction refers to various phenomena associated with the bending of waves when they interact with obstacles in their path. It occurs with any type of wave, including sound waves, water waves, and electromagnetic waves such as visible light, x-rays and radio waves. According to the Rayleigh Criterion invented by Lord Rayleigh and minimum resolvable distance, two images overlapped than the limitation of Rayleigh results in a blurring image. Therefore, when light behind the display apparatus  1  transmits thought the transparent area  312  and blocked by the electro-luminescent areas  311 , only the transmitted light can be observed by human eyes on physical. However, the total image is diffracted to be a blurring image so that human eyes can resolve the transmitted portion (transparent area  312 ) and the blocked portion (electro-luminescent areas  311 ). Thus, the observer feels that he can see though the display apparatus  1 . In other words, the present invention arranges the transparent area  312  and the electro-luminescent areas  311  in an alternative manner to produce a blurring image so that the observer can not resolve the transparent area  312  and the electro-luminescent areas  311  and the display apparatus  1  is see-through for the observer. 
     Furthermore, the first substrate  10  and second substrate  20  can be a transparent plate, for example a glass substrate. The electrodes  11  and  21  can be made from ITO (Indium Tin Oxides) or IZO (Indium Zinc Oxides), i.e., a transparent electrode. 
     Please refer to  FIGS. 3 to 3C , the electro-luminescent areas  311  of the pixel area  31  (sub-pixel area) has different arrangements. The pixel area  31  has only a rectangular electro-luminescent area  311  and the remaining portion of the pixel area  31  is transparent areas  312  in the first embodiment of  FIG. 3 . Calculating by the preceding formula, see-through ratio of each pixel area  31  (T) is about 75%.  FIG. 3A  shows the second embodiment of the present invention. The pixel area  31  has a plurality of rectangular electro-luminescent areas  311  and there is a transparent area  312  between each two adjacent electro-luminescent areas  311 . The see-through ratio of each pixel area  31  (T) is about 70% in the second embodiment.  FIG. 3B  shows the third embodiment of the present invention. The pixel area  31  has a plurality of circular electro-luminescent areas  311  and there is a transparent area  312  between each two adjacent electro-luminescent areas  311 . The see-through ratio of each pixel area  31  (T) is about 80% in the third embodiment.  FIG. 3C  shows the fourth embodiment of the present invention. The pixel area  31  has a plurality of circular electro-luminescent areas  311  in concentric arrangement and there is a transparent area  312  between each two adjacent electro-luminescent areas  311 . The see-through ratio of each pixel area  31  (T) is about 90% in the fourth embodiment. Accordingly, the each see-through ratio of each pixel area  31  (T) of the display apparatus  1  is preferably between 70% to 90% and the electro-luminescent areas  311  has display function between the above range. Therefore the display apparatus  1  can be seen-through and has a common display function for presenting images. 
     However, the pitch (d) between adjacent pixel areas  31  is a predetermined width and can be adjusted in the present. The width of pitch (d), for example, can be lengthened so that the MTF and regular spatial frequency is increasing and the observer can see the objects behind the display apparatus  1  more easily. For example, the width of pitch (d) is 5 mm in condition that the distance between observer and display apparatus  1  is 1 m. In other words, the width of pitch (d) can changed in order to increase the regular spatial frequency so that the display apparatus  1  performs a see-through display apparatus  1  for human eyes. 
     Accordingly, the display apparatus  1  is a multi-function display apparatus. The pixel areas  31  has electro-luminescent areas  311  and transparent area  312  spaced apart from one another and the see-through ratio of each pixel area  31  (T) is between 70% to 90% so that the observer can not notice the electro-luminescent areas  311  when the see-through display apparatus  1  is not powered on. On the contrary, when electro-luminescent areas  311  luminesce, observer not only can see the information displayed by the electro-luminescent areas  311  but also see the objects behind the display apparatus  1 . 
     To sum up, the present invention has the following advantages:
     1. The display apparatus  1  provides a better displaying performance. Because the electro-luminescent areas  311  and transparent area  312  space apart from one another and the see-through ratio of each pixel area  31  (T) is between 70% to 90%, human eyes will ignore the electro-luminescent areas  311  physically so that the observer feels that he can see through the display apparatus  1 .   2. The display apparatus  1  is a multi-function display apparatus and includes see-through property and a common displaying function.   3. The see-through display apparatus  1  can be used for demo window or production display.   

     Although the present invention has been described with reference to the foregoing preferred embodiment, it will be understood that the invention is not limited to the details thereof. Various equivalent variations and modifications may occur to those skilled in this art in view of the teachings of the present invention. Thus, all such variations and equivalent modifications are also embraced within the scope of the invention as defined in the appended claims.