Patent Publication Number: US-6335714-B1

Title: Display apparatus having a rotating display panel

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a display apparatus and, more particularly, to a display apparatus having a rotating display panel provided with a polarizer thereon so as to generate a three dimensional (3-D) image that can be viewed by a viewer wearing polarized glasses. 
     2. Description of Related Art 
     A conventional electronic display board is composed of a very large number of light emitting units, such as light emitting diodes (LEDs), fluorescent lamps, or liquid crystal displays (LCDs). For example, in the case of a 500×500 pixel display board, if the board operates in a monochromatic display mode, it will require a total amount of 250,000 LEDs. Further, if it displays three colors, the required number of LEDs will be tripled. Obviously, more LEDs will increase the costs of the display board and result in higher maintenance cost. 
     In order to overcome the aforementioned disadvantages, the same applicant disclosed a display apparatus having a rotating display panel as shown in FIG. 1, which was issued as U.S. Pat. No. 5,818,401 on Oct. 6, 1998. The entire content of that patent is incorporated herein by reference. 
     Referring to FIG. 1, a conventional display apparatus  100  comprises a pedestal  10 , a cylindrical display body  20  rotatably mounted on the pedestal  10  and multiple, vertical, light emitting arrays  11  are secured at equal distances on the wall of the cylindrical body  20 . Each of the light emitting arrays  11  is composed of multiple light emitting units such as LEDs. When the display body  20  rotates at a speed that a viewer&#39;s eyes cannot distinguish the individual light emitting arrays  11  and the LEDs are sequentially turned on, a viewer sees the corresponding information on the rotating body  20  due to the persistence of vision. In order to achieve a steady picture without flickering, the light emitting arrays  11  and the rotating speed of the display body  20  have to meet certain conditions. In a normal case, the minimum frame rate is 24 frames per second. For this display apparatus  100 , the frame rate is the product of the number of light emitting arrays and the rotating speed of the display body. Thus, if there were eight light emitting arrays, the rotational speed of the display body would have to be 3 revolutions or more per second. 
     Furthermore, as described in U.S. Pat. No. 5,818,401, the rotatable display body of the display apparatus may be configured differently. In a first variant, the light emitting arrays are equally spaced on the outside of a spherical display body, and thus a spherical display panel will be achieved when the display body rotates. In a second variant, the light emitting arrays are placed on a planar surface of a roller body, and each of the arrays is equally spaced radially such that a circular display panel is achieved when the display body rotates. 
     Although U.S. Pat. No. 5,818,401 provides an improved display apparatus having a rotating display panel so as to generate an image displayed on the rotating display body due to the persistence of vision, the displayed image is simply a plane image, i.e., a two dimensional (2-D) image. 
     In the past, a three dimensional (3-D) image such as a conventional 3-D movie could be generated on a planar display panel through a specific process based on known optical technologies. Conventionally, polarizers having different polarization directions are provided on the lens of two projectors, respectively. In this arrangement, the images for the left and right eyes of a viewer, differently polarized in two polarization directions, are projected on the screen and reflected to a viewer&#39;s eyes, such that the viewer can see the 3-D image through the polarized glasses. 
     In addition, an optical valve is utilized to synchronously view the left and right images so as to generate an improved 3-D visual effect. However, the glasses formed with the optical valve are expensive and less convenient to use. 
     SUMMARY OF THE INVENTION 
     Accordingly, one object of the present invention is to provide a display apparatus having a rotating display panel that can generate a 3-D image when viewed by a viewer wearing polarized glasses. 
     Another object of the present invention is to provide a display apparatus having a rotating display panel that can generate a colorful image. 
     A further object of the present invention is to provide a display apparatus having a rotating display panel that reduces the costs of the display panel and the resultant maintenance cost. 
     A display apparatus comprises a pedestal; a display body rotatably mounted on the pedestal; multiple light emitting arrays, each light emitting array further comprising multiple light emitting units and being equally spaced on a surface of the display body to display information when the display body rotates; and a polarizer on each of the light emitting arrays, the polarization directions of adjacent polarizers being perpendicular. 
     The polarizers on odd light emitting arrays are horizontally polarized, and the polarizers on even light emitting arrays are vertically polarized. 
     In accordance with one aspect of the present invention, the display body of the display apparatus is cylindrical, and the light emitting arrays are arranged axially and spaced equally on the wall of the cylindrical display body. 
     The display body of the display apparatus can be spherical with each of the light emitting arrays equally spaced on the surface of the spherical display body. 
     The display body of the display apparatus can be a roller body with each of the light emitting arrays equally spaced radially on a planar surface of the roller display body. 
     Other objects, advantages and features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a conventional display apparatus having a cylindrical rotating display panel; 
     FIG. 2 is a perspective view of a display apparatus having a rotating cylindrical display panel in accordance with the present invention; 
     FIG. 3 is a perspective view of a horizontally polarized light emitting array of the display apparatus in FIG. 2; and 
     FIG. 4 is a perspective view of a vertically polarized light emitting array of the display apparatus in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring to FIG. 2, a display apparatus  200  in accordance with the present invention comprises a pedestal  10 , a display body  20  rotatably mounted on the pedestal  10  and multiple light emitting arrays  21 - 22  each equally spaced on a surface of the display body  20 . Each of the light emitting arrays  21 - 22  is composed of multiple light emitting units, such as light emitting diodes. For simplicity, all the light emitting units are referred as LEDs hereinafter. 
     The rotatable display body of the display apparatus in accordance with the present invention may be configured in different forms. As shown in FIG. 2, for example, the display body  20  is cylindrical, and each of the light emitting arrays  21 - 22  is arranged axially and equally spaced on a wall of the cylindrical display body  20 . However, the display body may be spherical, in which case each of the light emitting arrays would intersect the poles and be equally separated longitudinally on the outside of the spherical display body. Further, the display body could be a roller body, in which case the light emitting arrays originate at the axis of rotation and are equally spaced radially on a planar surface of the roller display body. 
     In addition, a control circuit (not shown) is mounted in the display body  20  for controlling the rotation speed of the display body  20  and the information displayed on the display apparatus. Also, a power supply (not shown) having a positive electrode and a negative electrode is mounted within the pedestal  10  to provide the power required by the display apparatus. Since a circuit designer of ordinary skill in the art can easily build the circuits required in the present invention, a description related to both the control circuit and the power supply is omitted. 
     The operation of the polarizer provided on each of light emitting arrays  21 - 22  will be described in detail with reference to FIGS. 3 and 4. 
     As shown in FIG. 3, a horizontally polarized light emitting array  21  comprises three sets of LEDs  211 ,  212  and  213  mounted on a circuit board  210 , and each set of LEDs  211 ,  212  and  213  is composed of multiple LEDs of different colors, respectively. For example, the color of one set of LEDs  211  is red, the color of another set of LEDs  212  is green, and the color of the final set of LEDs  213  is blue. The brightness of the individual LEDs in the sets  211 ,  212  and  213  is controlled by the control circuit (not shown) utilizing pulse width modulation (PWM), and thus a combined colorful image will be generated and displayed on the rotating display body  20  due to the persistence of vision. More particularly, a first transparent polarizer  214  is provided on the horizontally polarized light emitting array  21 . In this embodiment, the polarization direction of the first polarizer  214  on the horizontally polarized light emitting array  21  is in the horizontal direction X. 
     Similarly, as shown in FIG. 4, a vertically polarized light emitting array  22  comprises three sets of LEDs  221 ,  222  and  223  mounted on a circuit board  220 , and each set of LEDs  221 ,  222  and  223  is composed of multiple LEDs of different colors, respectively. For example, the color of one set of LEDs  221  is red, the color of another set of LEDs  222  is green, and the color of the final set of LEDs  223  is blue. The brightness of the LEDs in each set  221 ,  222  and  223  is controlled by the control circuit (not shown) utilizing pulse width modulation (PWM), and thus a combined colorful image will be generated and displayed on the rotating display body  20  due to the persistence of vision. More particularly, a second transparent polarizer  224  is provided on the vertically polarized light emitting array  22 . In this embodiment, the polarization direction of the second polarizer  224  on the vertically polarized light emitting array  22  is in the vertical direction Y. 
     Comparing the horizontally polarized light emitting array  21  shown in FIG. 3 with the vertically polarized light emitting array  22  shown in FIG. 4, the only difference between the two is that the first polarizer  214  provided on the light emitting array  21  is horizontally polarized while the vertically polarized polarizer  224  provided on the light emitting array  22  is vertically polarized. That is, the polarization direction of the polarizer  214  provided on the horizontally polarized light emitting array  21  is perpendicular to the polarization direction of the polarizer  224  provided on the horizontally polarized light emitting array  22 . 
     In this manner, the polarization directions of the polarizers on adjacent light emitting arrays are different. More specifically, in this embodiment, each polarizer on an odd numbered light emitting arrays  21  is horizontally polarized, and each polarizer on an even numbered light emitting arrays  22  is vertically polarized. 
     As the polarization direction of the polarizer provided on each of the odd numbered light emitting arrays  21  is horizontal, the light emitted by each LED of the odd numbered light emitting arrays  21  will be horizontally polarized by the corresponding polarizer provided thereon. Similarly, as the polarization direction of the polarizer provided on each of the even numbered light emitting arrays  22  is vertically polarized, the light emitted by each LED of the even numbered light emitting arrays  22  will be vertically polarized by the corresponding polarizer provided thereon. 
     As a result, two different polarized images will be generated. More specifically, the odd numbered light emitting arrays  21  will generate horizontally polarized images while the even numbered light emitting arrays  22  will generate vertically polarized images. 
     If the two different polarized images are at an appropriately different viewing angles with respect to the left and right eyes, the viewer wearing a pair of polarized glasses with the corresponding polarization directions can view the separated left and right image. Thus, the display apparatus in accordance with the present invention can achieve a 3-D visual effect. 
     In addition, since the left and right images generated by the light emitting arrays  21  and  22  and respectively polarized in two different polarization directions are directly viewed by the viewer, instead of being indirectly reflected to the viewer&#39;s eyes, the display apparatus in accordance with the present invention can achieve an improved 3-D visual effect. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.