Abstract:
An exemplary digital display device includes a light source, a converging member, a micro-electrical-mechanical system (MEMS) chip, and a projection member. The converging member is for converging the light emitted from the light source onto the MEMS chip. The MEMS chip is for selectively reflecting light transmitted from the converging member to form an alphanumeric character to the projection member. The projection member is for projecting the alphanumeric character onto a projection screen.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a digital display device and, particularly, to a micro-electrical-mechanical system (MEMS) digital display device. 
         [0003]    2. Description of Related Art 
         [0004]    Recently, seven-segment displays are widely used in digital clocks, electronic meters, and other electronic devices for displaying alphanumeric information. 
         [0005]    In a typical digital display device, light emitting diode (LED) based seven-segment displays are commonly used. However, each LED requires packaging before application, thus it makes the digital display device large and heavy, which is not suitable for the miniaturized handheld devices for displaying alphanumeric information. 
         [0006]    Therefore, a new digital display device is desired to overcome the above mentioned problems. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  is a schematic, perspective view of a digital display device in accordance with a first embodiment of the present invention. 
           [0009]      FIG. 2  is a schematic, top plan view of a reflective member group of  FIG. 1 . 
           [0010]      FIG. 3  is a schematic, perspective view of a reflective member of  FIG. 2 . 
           [0011]      FIG. 4  is a schematic, perspective view of a moving mirror in the reflective member of  FIG. 3 . 
           [0012]      FIG. 5  is a schematic, top plan view of a reflective member group in accordance with a second embodiment of the present invention. 
           [0013]      FIG. 6  is a schematic, top plan view of a reflective member group in accordance with a third embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Embodiments will now be described in detail below with reference to the drawings. 
         [0015]    Referring to  FIG. 1 , a digital display device  100  includes a light source  10 , a converging member  20 , a MEMS chip  30 , and a projection member  40 . 
         [0016]    The light source  10  can be one of a laser source and a light emitting diode (LED) source. 
         [0017]    The converging member  20  includes two converging lenses  22 ,  24  for converging light emitted from the light source  10  onto the MEMS chip  30 . 
         [0018]    The MEMS chip  30  reflects the light transmitted from the converging member  20  to form an alphanumeric character. The alphanumeric character can be ten Arabic numerals, Latin letters, Cyrillic, Greek alphabets or mathematical symbols. 
         [0019]    The projection member  40  includes two projection lenses  42 ,  44 . The projection member  40  projects the alphanumeric character onto a projection screen  50 . 
         [0020]    The MEMS chip  30  is fabricated using MEMS and complementary metal oxide semiconductor (CMOS) techniques. The MEMS chip  30  includes a substrate  32 , a light absorption layer  34  formed on the substrate  32 , and a plurality of reflective member groups  36  formed on the light absorption layer  34 , and a controller  38 . The substrate  32  can be a silicon substrate, for example. In one embodiment, the light absorption layer  34  can be made of chromium. Because the light absorption layer  34  not covered by the reflective member groups  36  can absorb light, the projection screen  50  appears dark corresponding to the light absorption layer  34  not covered by the reflective member groups  36 . Each reflective member group  36  consists of a plurality of reflective members arranged in a predetermined pattern being configured for displaying one of the alphanumeric characters. In the present embodiment, four reflective member groups  36  are adopted. It can be understood that the number of the reflective member groups  36  depends on the application and requirements. The controller  38  can be a pulse-width modulation (PWM) controller. 
         [0021]    Referring to  FIGS. 2-3 , each reflective member group  36  consists of seven reflective members  362  arranged in a seven-segment pattern. Each reflective member  362  includes a mirror  3622 , two torsion beams  3624 , two support posts  3626 , a first electrode  3627 , a second electrode  3628 , and two insulation pads  3629 . In the seven-segment pattern, seven mirrors  3622  are arranged as a rectangle of two vertical mirrors  3622  on each side with one horizontal mirror  3622  on the top and bottom, respectively. Additionally, the seventh mirror  3622  bisects the rectangle horizontally. 
         [0022]    The mirror  3622  suspends above the light absorption layer  34 . The mirror  3622  is strip shaped. The mirror  3622  includes a first side edge  3622   a , a second side edge  3622   b , and two opposite ends  3622   c ,  3622   d . The mirror  3622  is made of polysilicon. The mirror  3622  can further have a metal layer (not shown), such as gold or copper layer formed thereon to enhance the reflective effect thereof. 
         [0023]    The two torsion beams  3624  extend from opposite ends  3622   c ,  3622   d  of the mirror  3622  respectively. The two torsion beams  3624  are fixed to the mirror  3622  by an adhesive or solder. It can be understood that the torsion beams  3624  can also be integrally formed with the mirror  3622 . Each of the torsion beams  3624  is made of elastic polysilicon and is deformable. 
         [0024]    The two support posts  3626  connect the two torsion beams  3624 , respectively, in order to support the two torsion beams  3624  and the mirror  3622 . 
         [0025]    Each of the insulation pads  3629  is disposed between each of the support posts  3626  and the light absorption layer  34 . Each of the insulation pads  3629  is made of silicon nitride or silicon dioxide. 
         [0026]    The first electrodes  3627  and the second electrodes  3628  are disposed on the light absorption layer  34  below the first and the second side edges  3622   a ,  3622   b  of the mirror  3622 , respectively. 
         [0027]    Referring to  FIG. 4 , when a voltage is applied to the first electrode  3627  and the mirror  3622 , the mirror  3622  moves relative to the light absorption layer  34  with the first side edge  3622   a  towards the first electrode  3627  due to an electrostatic attraction between the first electrode  3627  and the mirror  3622 . The mirror  3622  can return to its original position when the voltage is withdrawn. Likewise, when a voltage is applied to the second electrode  3628 , the mirror  3622  moves relative to the light absorption layer  34  with the second side edge  3622   b  towards the second electrode  3628 . The controller  38  of the MEMS chip  30  can control the voltage applied to the first electrode  3627  or the second electrode  3628 . In the present embodiment, the reflective member  362  is in the first position when the mirror  3622  moves towards the first electrode  3627 , while the reflective member  362  is in the second position when the mirror  3622  moves towards the second electrode  3628 . When the mirror  3622  is in the first position, light from the converging member  20  is reflected onto the projection screen  50 . When the mirror  3622  is in the second position, light is directed elsewhere, usually onto a heatsink (not shown) for example. The mirrors  3622  in the first positions cooperatively form an alphanumeric character. It can be understood that the reflective member  362  can be in the first position when the mirror  3622  moves towards the second electrode  3628 , which can be controlled by adjusting the optical path. Therefore, to reposition each mirror  3622  of each reflective member  36 , light incident upon the MEMS chip  30  can be selectively reflected into the projection member  40 , thus resulting in the corresponding alphanumeric character being displayed on the projection screen  50 . Each of the moving angles between the first electrode  3627  and second electrode  3628  and the mirror  3622  are the same. The moving angles can be a predetermined value, for example 10-12 degrees. 
         [0028]    Referring to  FIG. 5 , a reflective member group  60  according to a second embodiment is shown. The reflective member group  60  consists of fourteen reflective members  362  arranged in a fourteen-segment pattern. It is an extension of the above described reflective member group  36  in the first embodiment, but adding four diagonal mirrors  3622  and two vertical mirrors  3622  and with two middle horizontal mirrors  3622  other than one. 
         [0029]    Referring to  FIG. 6 , a reflective member group  70  according to a third embodiment is shown. The reflective member group  70  consists of sixteen reflective members  362  arranged in a sixteen-segment pattern. It is an extension of the above described reflective member group  60  in the second embodiment, but with two horizontal mirrors  3622  on the top and bottom, respectively. 
         [0030]    It can be understood that the layout and the number of the mirrors in each reflective member group are not limited to the above described embodiments, which can be set according to the alphanumeric character being displayed. 
         [0031]    The digital display device  100  is fabricated using MEMS and CMOS techniques, thus the digital display device  100  is compact, light-weight, low cost, and very suitable for the miniaturized handheld device, for example, mp3, cell phone, for displaying the alphanumeric information. 
         [0032]    While certain embodiments have been described and exemplified above, various other embodiments from the foregoing disclosure will be apparent to those skilled in the art. The present invention is not limited to the particular embodiments described and exemplified but is capable of considerable variation and modification without departure from the scope and spirit of the appended claims.